Constant Time Delay Research Papers (original) (raw)

We study two simple yet general complexity classes, which provide a unifying framework for efficient query evaluation in areas like graph databases and information extraction, among others. We investigate the complexity of three fundamental algorithmic problems for these classes: enumeration, counting and uniform generation of solutions, and show that they have several desirable properties in this respect. Both complexity classes are defined in terms of non deterministic logarithmic-space transducers (NL transducers). For the first class, we consider the case of unambiguous NL transducers, and we prove constant delay enumeration, and both counting and uniform generation of solutions in polynomial time. For the second class, we consider unrestricted NL transducers, and we obtain polynomial delay enumeration, approximate counting in polynomial time, and polynomial-time randomized algorithms for uniform generation. More specifically, we show that each problem in this second class admits a fully polynomial-time randomized approximation scheme (FPRAS) and a polynomial-time Las Vegas algorithm (with preprocessing) for uniform generation. Remarkably , the key idea to prove these results is to show that the fundamental problem #NFA admits an FPRAS, where #NFA is the problem of counting the number of strings of length n (given in unary) accepted by a non-deterministic finite automaton (NFA). While this problem is known to be #P-complete and, more precisely, SpanL-complete, it was open whether this problem admits an FPRAS. In this work, we solve this open problem, and obtain as a welcome corollary that every function in SpanL admits an FPRAS.

- by
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- Approximation Algorithms, Graph Database, Databases, Constant Time Delay

State-resolved two-pulse correlation measurement is useful to study the time scale and mechanism of photo-induced desorption as well as electronic structures of admolecules before desorption. In photodesorption of nitric oxide molecules from Pt(1 1 1) at 250 K induced by 80 fs, 620 nm laser pulses, the yields and translational temperatures reached a maximum at zero delay time. In contrast, the rotational temperature of X ¼ 3=2 molecules reached a maximum at a delay time of AE1 ps, while that of X ¼ 1=2 molecules was enhanced at around zero delay. In addition, the ratio of total yields of X ¼ 1=2 molecules to that of X ¼ 3=2 molecules increased at short delay times. All of these results can be explained by the model of rotational heating, including spin-orbit (SO) coupling, where the difference in the correlation time was found to be due to the SO structure in the adsorbed phase. : S 0 0 3 9 -6 0 2 8 ( 0 2 ) 0 1 6 5 9 -X

- by Anders Hellman
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- Condensed Matter Physics, Quantum Physics, Surface Science, Time-Delay Systems

Steady-state fluorescence (SSF) technique was employed for studying swelling of polyacrylamide (PAAm) hydrogels. Disc-shaped gels were prepared by free-radical crosslinking copolymerization of acrylamide (AAm) with N, N¢-methylenebis (acrylamide) (BIS) as crosslinker in the presence of ammonium persulfate (APS) as an initiator. Pyranine was introduced as a fluorescence probe. Fluorescence intensity of pyranine was measured during in situ swelling process at various temperatures and it was observed that fluorescence intensity values decreased as swelling is proceeded. Li-Tanaka equation was used to determine the swelling time constants, s c and cooperative diffusion coefficients, D c from intensity, weight and volume variations during the swelling processes. It is observed that swelling time constants, s c decreased and diffusion coefficients, D c increased as the swelling temperature is increased. The swelling activation energies, DE were measured from the intensity, weight and volume variations and found to be 10.7, 32.2 and 64.1 kJ mol -1 , respectively.

- by Önder Pekcan and +1
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- Engineering, Materials Science, Free Radical, Activation Energy

Ahstract-In this paper, a software simulation model is developed for a two wheels driven mobile robot motion controller that can navigate the robot safely through an unknown environment. The work involves the design of a controller, which has four functions: motion control; obstacle avoidance; self-location; and path planning both global and local. The proposed controller is responsible for the mobile robot navigation after it generates a trajectory between start and goal points. Also it enables the robot to operate successfully in the presence of various obstacles present in any user built maps. The mobile robot is able to locate its position on any given map. The dynamic of the mobile robot is examined and the time constant of the two motors, which affects the direction of the mobile robot motion, is controlled. Obstacle avoidance is implemented with Fuzzy Logic Controller. The numerical experiments demonstrated that the indoor robot navigated successfully in tight corridors, avoided obstacles and dealt with a variety of world maps with various irregular wall shapes that were presented to it.

- by Siba Sharef
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- Fuzzy Logic, Motion control, Path planning, Fuzzy Control

Background: Thymol is widely used as a general antiseptic and antioxidant compound in the medical practice and industry, and also as a stabilizer to several therapeutic agents, including halothane. Thus intoxication with thymol may occur in case of ingestion or improper anesthesia. In the present study, therefore, concentration-dependent effects of thymol (30-600 micro-grams) were studied on calcium and potassium currents in enzymatically isolated rat skeletal muscle fibers using the double vaseline gap voltage clamp technique.

- by N. Szentandrássy and +4
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- Skeletal muscle biology, Kinetics, Patch-clamp and imaging techniques, Antioxidants

Moisture is one of the most deteriorating factors of buildings. The deteriorating effect of moisture occurs mainly during the drying phase, and not in the wetting phase. Appropriate parameters of the drying kinetics are required for the building materials. Environmental factors, such as air temperature, air humidity, and air velocity affect drying. An experimental air dryer of controlled drying air conditions was used to investigate the drying performance of 4 stone materials, 2 bricks and 7 plasters. Drying kinetics was examined at 4 air temperatures, 6 air humidities, and 3 air velocities. A first-order kinetics model was obtained, in which the drying time constant was a function of the drying conditions, and the equilibrium material moisture content was described by the Oswin equation. The parameters of the proposed model were found to be affected strongly by the material and the drying air conditions. The results obtained are very useful in selecting the appropriate plaster to protect existing historic buildings.

- by Maria Karoglou
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- Chemical Engineering, Drying Technology, Air Conditioning, First-Order Logic

Photoinduced electron transfer (ET) and excitation energy transfer (ENT) reactions in monomer and slippedcofacial dimer systems of a directly linked Zn porphyrin (Por)-Zn phthalocyanine (Pc) heterodyad, ZnPc-ZnPor, were investigated by means of the picosecond and femtosecond transient absorption spectroscopies. In the dimer dyad system of two heterodyads connected through the coordination bond between two imidazolylsubstituted ZnPor bearing ZnPc, ZnPc-ZnPor(D), the rapid ENT from the ZnPor to ZnPc in the subpicosecond time region was followed by photoinduced charge separation (CS) and charge recombination (CR) with time constants of 47 and 510 ps, respectively. On the other hand in the monomer dyad system, no clear chargeseparated state was observed although the CS with a time constant of 200 ps and CR with e70 ps were estimated. These results indicated that the dimer slipped-cofacial arrangement of pair porphyrins is advantageous for the effective production of the CS state. This advantage was discussed from the viewpoint of a decrease in the reorganization energy of the dimer relative to that of the monomer system. In addition, the electrochemical measurements indicated that the strong interaction between ZnPc and ZnPor moieties also contributed to the fast CS process despite the marginal driving force for the CS process. The dimer dyad of ZnPc-ZnPor provides full advantages in efficiencies of the light harvesting and the CS state production. SCHEME 1: Molecular Structure of ZnPc-ZnPor(D) and ZnPc-ZnPor(M) SCHEME 2: Molecular Structures of Reference Compounds Used Electron/Energy Transfer in ZnPor/ZnPc Composites

- by Sazzadur Rahman Khan
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- Zinc, The, Constant Time Delay, THEORETICAL AND COMPUTATIONAL CHEMISTRY

The simple free running multivibrator built around a single fractional capacitor is examined in this letter. Equations for the oscillation frequency of the multivibrator are derived taking into account the positive feedback factor around the multivibrator. We show that the use of the fractional capacitance allows the multivibrator to have very high frequencies of oscillation for reasonable time constants used. PSPICE simulation and experimental results demonstrate the analysis with an approximation to a fractional capacitor that yields a result, which is at least 1000 times in frequency compared to if a normal capacitor of the same value was employed.

- by Brent Maundy and +1
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- Oscillations, Oscillators, Positive Feedback, Fractional Calculus

Older adults have serious difficulty seeing under low illumination and at night, even in the absence of ocular disease. Optical changes in the aged eye, such as pupillary miosis and increased lens density, cannot account for the severity of this problem, and little is known about its neural basis. Dark adaptation functions were measured on 94 adults ranging in age from the 20s to the 80s to assess the rate of rod-mediated sensitivity recovery after exposure to a 98% bleach. Fundus photography and a grading scale were used to characterize macular health in subjects over age 49 in order to control for macular disease. Thresholds for each subject were corrected for lens density based on individual estimates, and pupil diameter was controlled. Results indicated that during human aging there is a dramatic slowing in rod-mediated dark adaptation that can be attributed to delayed rhodopsin regeneration. During the second component of the rod-mediated phase of dark adaptation, the rate of sensitivity recovery decreased 0.02 log unit/min per decade, and the time constant of rhodopsin regeneration increased 8.4 s/decade. The amount of time to reach within 0.3 log units of baseline scotopic sensitivity increased 2.76 min/decade. These aging-related changes in rod-mediated dark adaptation may contribute to night vision problems commonly experienced by the elderly.

- by Cynthia Owsley
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- Aging, Vision, Aged, Constant Time Delay

A simple apparatus for time-correla ted single photon counting (TCSPC) m easurements in the near-infrared (near-IR) region for scanning-type applications has been constructed and examined. The apparatus consisted of ® ve m ajor com ponents including a pulsed diode laser source (lasing wavelength 5 780 nm; rep etition rate 5 80 MHz; power 5 5 mW ; pulse width 5 150 ps), an integrated m icroscope, a large-photoactive-area avalanche photodiode (APD), a TCSPC PC-board including the electron ics, and a Windows-based software package for accu mulating the¯uorescen ce decay pro® les. The instrument response function (IRF) of this assembly was found to be 460 ps, which is adequate for measuring lifetim es with t f $ 500 ps. Due to the sm all size of the device, it also allowed implem entation into scanning experim ents where lifetimes were measured. To dem onstrate this capability, we scanned a three-well microscope slide containing a near-IR dye. The decay pro® le of the near-IR dye, aluminum 2,3-naphthalocyanine, was collected and analyzed to obtain its lifetime, which was found to be 2.73 ns, in close agreement with the literature value for this particular dye. In addition, a three-dim ensional plot showing the decay pro® les (tim e vs. photocounts) and scan position of aluminum 2,3-naphthalocyaninē uorescence was acquired by scanning the m icroscope head over this three-well glass slide. In the scanning m ode, the IRFs as well as the decays of the dyes were found to be very stable. The device dem onstrated a concentration detection sensitivity of 0.44 nM; however, the dynamic range was limited due to the slow tim e constant (passive quenching) associated with the APD.

- by Michael Wahl
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- Mechanical Engineering, Optics, Analytical Chemistry, Medical Imaging

Blood in the splanchnic vasculature can be transferred to the extremities. We quantified such blood shifts in normal subjects by measuring trunk volume by optoelectronic plethysmography, simultaneously with changes in body volume by whole body plethysmography during contractions of the diaphragm and abdominal muscles. Trunk volume changes with blood shifts, but body volume does not so that the blood volume shifted between trunk and extremities (Vbs) is the difference between changes in trunk and body volume. This is so because both trunk and body volume change identically with breathing and gas expansion or compression. During tidal breathing Vbs was 50-75 ml with an ejection fraction of 4-6% and an output of 750-1500 ml/min. Step increases in abdominal pressure resulted in rapid emptying presumably from the liver with a time constant of 0.6160.1SE sec. followed by slower flow from non-hepatic viscera. The filling time constant was 0.5760.09SE sec. Splanchnic emptying shifted up to 650 ml blood. With emptying, the increased hepatic vein flow increases the blood pressure at its entry into the inferior vena cava (IVC) and abolishes the pressure gradient producing flow between the femoral vein and the IVC inducing blood pooling in the legs. The findings are important for exercise because the larger the Vbs the greater the perfusion of locomotor muscles. During asystolic cardiac arrest we calculate that appropriate timing of abdominal compression could produce an output of 6 L/min. so that the abdominal circulatory pump might act as an auxiliary heart.

- by Andrea Aliverti
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- Multidisciplinary, Cardiac arrest, Blood Pressure, Exercise

We measured the kinetics of recombination of 11-cis-retinal with opsin in intact frog rod outer segment (ROS). The rhodopsin in ROS was bleached and allowed to decay to ''indicator yellow,'' a photoproduct where all-trans-retinal is partly free, and partly bound to non-specific amino groups of disk membranes. By briefly illuminating the ''indicator yellow'' by an intense 465 or 380nm flash, we then photoconverted all-trans-retinal to (mostly) the 11-cis-form thus introducing into ROS a certain amount of cis-chromophore. The recombination of cis-retinal with opsin and the formation of rhodopsin were followed by fast single-cell microspectrophotometry. Regeneration proceeded with a time constant of $3.5 min; up to 27% of bleached visual pigment was restored. The regenerated pigment consisted of 91% rhodopsin (11-cis-chromophore) and 9% of presumably isorhodopsin (9-cischromophore). The recombination of 11-cis-retinal with opsin inside the ROS proceeds substantially faster than rhodopsin regeneration in the intact eye and, hence, is not the rate-limiting step in the visual cycle.

- by Victor Govardovskii
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- Kinetics, Vision, Plant tissue Culture Techniques, Single Cell

The photodissociation dynamics of iodo-, bromo-and chlorobenzene upon excitation at 266 nm have been studied by femtosecond pump-probe spectroscopy combined with time-of-¯ight (TOF) mass spectrometric detection. The kinetics are characterized by a single time constant for chlorobenzene (1 ns) and bromobenzene (28 ps), and by two time constants for iodobenzene (700 and 350 fs). The time constant of 350 fs is due to direct dissociation. The increase of the other time constants with decreasing halogen mass supports the assignment of these constants to the decay of the initially excited p; p Ã states to the repulsive triplet n; r Ã state due to spin±orbit coupling. Ó

- by Jan Davidsson and +1
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- Technology, Kinetics, Time of Flight, Physical sciences

Photoinduced birefringence creation/decay dynamics in poly{1-[4-(3-carboxy-4-hydroxyphenylazo) benzenesulfonamido]-1,2-ethanediyl, sodium salt}cast films, has been characterized in the 5 to 100 mW writing laser power range at the wavelength of 514 nm. The maximum birefringence magnitude increased with laser beam power, being the largest value of 0.03, measured at 632.8 nm. Birefringence creation kinetics followed a biexponential behavior, where a slow process and a fast process could be clearly distinguished. The fast process accounted for more than 60% of birefringence. The time constants for both fast and slow processes decreased with increasing power of writing beam. Birefringence relaxation after removal of writing laser beam revealed to be independent of beam power and, was found to be ruled by two processes, described by a biexponential curve plus a constant term accounting for residual birefringence. A high residual birefringence signal of 85 ± 3% was attained, with the fast process contributing to 67% of decay from maximum value. The large values obtained for time constants for both birefringence creation and relaxation processes are believed to arise from stabilization of azo-group either by the formation of an ionic network, or by local short range interactions that are coming through as a result polyelectrolyte coiling due to its high degree of ionization.

- by Paulo Ribeiro
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- Engineering, Technology, Polyelectrolytes, Kinetics

Single-unit recordings of vestibular afferents from the semicircular canals of squirrel monkeys have shown that the cupular time constant (T c) is between 5 and 6 sec. Such recordings obviously cannot be performed in humans, and the corresponding values have thus been inferred to be somewhat longer based on their size and on the cupulaendolymph system. The ocular motor response of the rotational vestibulo-ocular reflex (rVOR) is characterized by longer time constants, typically between 15 and 20 sec, due to the so-called velocity storage mechanism (VSM), which prolongs the time constant of the afferents through central processing. Recent studies have attempted to determine the time constant of the cupula by fitting the slow phase velocity (SPV) of the response to postrotational stimuli using a mathematical model of the rVOR processing. To this goal they considered the processing of head velocity due to the peripheral vestibular organs and to the VSM. The resulting estimates of T c are lower than expected, averaging about 4 sec. These modeling approaches, though, neglect both the processing of the final common pathway and the adaptation shown by the discharge of primary vestibular afferents. Here we argue that such an approach may be bound to underestimate the duration of the rVOR time constants.

This study presents an optimal design for magnetorheological (MR) valves for minimizing the control energy to be applied to coils to control the pressure drop of the valves. The optimization problem identifies parameters such as applied current, coil wire size and geometric dimensions of the valves which satisfy the specified pressure drop and inductive time constant requirements. After describing the configuration of MR valves, their pressure drops are obtained on the basis of the Bingham model of MR fluid. Then, the control energy which is an objective function and the inductive time constant are derived. Subsequently, an optimization procedure using a golden-section algorithm and a local quadratic fitting technique is constructed via a commercial finite element method parametric design language. Using the optimization tool developed in this study, optimal MR valve configurations are identified, which are constrained to a specific cylindrical volume defined by its radius and height. In addition, optimization results for MR valves with different required pressure drops and different constrained volumes are obtained and presented.

- by Norman Wereley
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- Engineering, System Identification, Rheology, Finite element method

An investigation of the critical factors effecting the resolution of SR695 from efavirenz in the assay of efavirenz by reversed-phase HPLC was performed. This study was implemented to address the inability of a subset of the Zorbax SB-CN columns used in this method to adequately perform this separation, which were otherwise indistinguishable from columns of this type that could. In this study, column temperature, detector time-constant, pre-gradient isocratic hold-time, pre-column mixing volume, column, and HPLC type were considered. Experimental Design methods were employed to find the relative importance of these factors and to find parameters that would optimize the resolution of SR695 and efavirenz on any HPLC, with any column of this type, for both efavirenz oral liquid and capsule samples. It was also desired that this method change be minimal, so that extensive revalidation would not be required. The most important factors were the column temperature, with lower temperatures giving better resolution, and pre-column mixing volume of sample with mobile phase, with higher mixing volumes giving better resolution up to an asymptote reached at around 150 ml. Added pre-gradient isocratic hold time was found to result in a small improvement in resolution, but was insignificant compared with the other factors mentioned above. A possible explanation is given for the mechanism by which temperature and pre-column mixing have this effect on the resolution obtained in this assay.

- by Robert Weissburg
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- Chemistry, Analytical Chemistry, Experimental Design, Medicine

Field-oriented control methodology requires knowledge of the machine parameters and, in particular, the rotor time constant. The interest here is in tracking the value of T R as it changes due to ohmic heating so that an accurate value is available to estimate the rotor flux linkages for a field-oriented controller. The approach presented here uses a nonlinear least-squares approach using measurements of the stator currents and voltages along with the rotor speed. The nature of this technique lends itself directly to an online implementation and therefore can be used to track the rotor time constant. Experimental results are presented to demonstrate the validity of the approach.

- by Marc Bodson
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- Proceedings, Constant Time Delay, Induction machine

Experimental studies on preparation of thin films of ternary compositions of Mn 3 O 4 , NiO and CoO using ion beam sputtering technique and electrical properties characterization have been carried out. The compatibility of thin films deposited on thermally grown silicon oxide on Si wafer of <1 0 0> orientation to produce thin film thermistors on a thermal isolation structure (TIS) by wet chemical micro-machining process has also been investigated. It is observed from energy dispersive X-ray (EDAX) analysis that the chemical compositions of thin films have close proximity to the target composition, with minor deviations in the individual oxide contents. While the films whose manganese oxide content is higher and nickel oxide lower, have higher thermistor constant 3600 K, and sheet resistance 4×10 7 /sq, the films which have lower manganese oxide and higher nickel oxide are found to have medium thermistor constant 2186 K, and lower sheet resistance 5×10 5 /sq. The micro-machined TIS, analyzed by scanning electron microscope, is observed to have an isolated bridge structure. The voltage-current relationship of the sensor element deposited on the TIS is linear up to an applied bias of 10 V, and the thermal conductivity and the thermal mass of the entire bridge structure are respectively 2.6×10 −6 W K −1 and 1.3 × 10 −9 J K −1 . The responsivity, and detectivity of the infrared detector fabricated, using thin film thermistor sensor deposited on a micro-machined TIS together with a suitable infrared absorber coating, are respectively equal to 3000 V W −1 and 4.4×10 8 cm Hz 1/2 W −1 at 10 Hz operating frequency, and the time constant is 0.53 ms.

- by qiao hui
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- Materials Engineering, Mechanical Engineering, Thin Film, Experimental Study

Perceptual direction detection thresholds for yaw rotation about an earth-vertical axis were measured at seven frequencies (0.05, 0.1, 0.2, 0.5, 1, 2, and 5 Hz) in seven subjects in the dark. Motion stimuli consisted of single cycles of sinusoidal acceleration and were generated by a motion platform. An adaptive two-alternative categorical forced-choice procedure was used. The subjects had to indicate by button presses whether they perceived yaw rotation to the left or to the right. Thresholds were measured using a 3-down, 1-up staircase paradigm. Mean yaw rotation velocity thresholds were 2.8 deg s−1 for 0.05 Hz, 2.5 deg s−1 for 0.1 Hz, 1.7 deg s−1 for 0.2 Hz, 0.7 deg s−1 for 0.5 Hz, 0.6 deg s−1 for 1 Hz, 0.4 deg s−1 for 2 Hz, and 0.6 deg s−1 for 5 Hz. The results show that motion thresholds increase at 0.2 Hz and below and plateau at 0.5 Hz and above. Increasing velocity thresholds at lower frequencies qualitatively mimic the high-pass characteristics of the semicircular canals, since the increase at 0.2 Hz and below would be consistent with decreased gain/sensitivity observed in the VOR at lower frequencies. In fact, the measured dynamics are consistent with a high pass filter having a threshold plateau of 0.71 deg s-1 and a cut-off frequency of 0.23 Hz, which corresponds to a time constant of approximately 0.70 s. These findings provide no evidence for an influence of velocity storage on perceptual yaw rotation thresholds.

- by Fred W Mast and +1
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- Motion perception, Constant Time Delay, Rotation, Choice Behavior

From a comparison of the photoresponses and membrane properties of photoreceptors from 20 species of Diptera, we conclude that coding in the time domain is matched to the dictates of visual ecology. This matching involves the dynamics of phototransduction and the use of an appropriate mix of potassium conductances to tune the photoreceptor membrane. Rapidly flying, manoeuvrable diurnal Diptera from several families have fast photoreceptors, with corner frequencies (the frequency at which signal power falls by a half) of between 50 and 107 Hz. The ponderous and predominantly nocturnal tipulids have slow photoreceptors with fully light adapted corner frequencies of 16 to 19 Hz. Dark adapted fast photoreceptors have a lower gain (as indicated by lower noise levels), a lower sensitivity, and light adapt more rapidly than dark adapted slow photoreceptors. Fast cells also have much lower input resistances and shorter time constants. Fast photoreceptors rectify more strongly in the steady state because of a weakly inactivating delayed rectifier potassium conductance with fast and slow components of activation. Slow photoreceptors rectify less strongly in the steady state because their membrane properties are dominated by strongly inactivating outward currents with reversal potentials in the range — 80 to -90 mV. The differences between potassium conductances match the differing functional requirements of fast and slow photoreceptors. The non-inactivating delayed rectifier promotes the rapid response of fast cells by reducing the membrane time constant. This is an expensive strategy, involving large conductances and currents. Slowly flying nocturnal insects do not require a high speed of response. The potassium conductances in their slow photoreceptors inactivate to avoid costly and unnecessary ion fluxes. Both the dynamics of the photoresponse and photoreceptor membrane properties exhibit sexual dimorphism. Light adapted photoreceptors in the enlarged male dorsal eye of Bibio markii have a corner frequency of 42 Hz, compared with 27 Hz for cells in the smaller female eye. This difference in frequency response correlates with the male's higher spatial acuity and is accompanied by consistent differences in potassium conductance activation rate. We conclude that the divison between fast and slow cells is the product of cellular constraints, metabolic costs and the requirements of coding efficiency at different light levels and retinal image velocities.

- by Matti Weckstrom
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- Electrophysiology, Comparative Physiology, Sexual dimorphism, Biological Sciences

The time constant of applied temperature sensor and sensor location influence the sought model error most significantly. The proper choice of these technical parameters, in a way minimizing the model error is possible only as a result of optimization process. The simulation methods significantly raise the effectiveness of such the experiments. The results presented in paper have been achieved in Department of Applied Physics of Technical University Delft.

- by Janusz Gajda
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- Constant Time Delay, Temperature Sensor

This paper investigates typical behaviors like damped oscillations in fractional order (FO) dynamical systems. Such response occurs due to the presence of, what is conceived as, pseudo-damping and meta-damping in some special class of FO systems. Here, approximation of such damped oscillation in FO systems with the conventional notion of integer order damping and time constant has been carried out using Genetic Algorithm (GA). Next, a multilayer feed-forward Artificial Neural Network (ANN) has been trained using the GA based results to predict the optimal pseudo and meta-damping from knowledge of the maximum order or number of terms in the FO dynamical system.

- by Saptarshi Das
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- Information Systems, Engineering, Applied Mathematics, Economics

This paper considers the possible benefits of mitigation of climate change for coastal areas with a strong emphasis on sea-level rise, as this is one of the most certain consequences of human-induced global warming. There is a long-term 'commitment to sea-level rise' due to the long thermal lags of the ocean system and hence the response of sea-level rise to mitigation is slower than for other climate factors. Therefore, while climate stabilisation reduces coastal impacts during the 21st century, compared to unmitigated emissions, the largest benefits may occur in the 22nd century (and beyond). The results of the analysis suggest that a mixture of adaptation and mitigation policies need to be considered for coastal areas, as this will provide a more robust response to human-induced climate change than either policy in isolation. This requires the joint evaluation of mitigation and adaptation in coastal areas, ideally using a probabilistic risk-based methodology, which would be a departure from existing analyses. Because of the long time constants involved such assessments need to continue beyond 2100 to provide the full implications of the different policy choices. r

- by Dr. Suresh kumar
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- Climate Change, Global Environmental Change, Multidisciplinary, Global Warming

Abstract. Time series of ocean properties provide a measure of global ice volume and monitor key features of the wind-driven and Censity-driven circulations over the past 400,000 years. Cycles with periods near 23,000, 41,000, and 100,000 years dominate this climatic narrative. When the narrative is examined in a geographic array of time series, the phase of each climatic oscillation is seen to progress through the system in essentially the same geographic sequence in all three cycles. We argue that

- by Will Howard
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- Geology, Geochemistry, Oceanography, Paleoceanography

Bacteriorhodopsin (BR) was incorporated in solid supported lipid bilayers by fusion of reverse phase vesicles on chemisorbed monolayers of 1,2-dimyristoyl-sn-glycero-3-phosphothioethanol (DMPTE) on gold substrates. The passive electrical behavior of the artificial membranes was monitored by impedance spectroscopy in order to determine both the membrane resistances and capacitances and to guarantee reproducibility of the bilayer formation. Illumination of the BR containing solid supported lipid bilayers resulted in a transient photocurrent as expected from earlier experiments with black lipid membranes. The present preparation technique however is advantageous because of its long term stability up to 1 day without loss of BR activity and its easy handling. We investigated the dependence of the photocurrent on the BR content, lipid environment, pH, and a proton carrier using a common current amplifier. Maximum current densities were obtained in the presence of negatively charged lipids like 1,2-dimyristoyl-sn-glycero-3-phosphatidic acid (DMPA) or 1-palmitoyl-2-sn-glycero-3-phosphoglycerol (POPG) at a pH of 6.4. Moreover it could be shown that the pump activity of reconstituted BR is insignificantly influenced by the capacitance of the first self-assembled DMPTE-monolayer on the gold electrodes. This may be explained by an incomplete fusion of BR containing vesicles on the hydrophobic surface. Carbonylcyanid-4-trifluoromethoxy-phenylhydrazone (FCCP), a membrane soluble proton translocator, increases the membrane conductance as well as the capacitance of the lipid bilayer that was derived either from impedance spectroscopy or evaluation of the time constants of the transient photocurrents.

- by Claudia Steinem
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- Impedance Spectroscopy, Lipid Membranes, Physical sciences, Bacteriorhodopsin

Acquisition of TRM by a cooling assemblage of identical monodomain grains involves a transition from superparamagnetic to blocked behavior over a narrow but indefinite range of temperature. Blocking temperature may, nevertheless, be precisely defined by comparing the blocked magnetization, after cooling, with the curve of equilibrium magnetization against temperature. At the blocking temperature T B the relaxation time ß of the magnetization is of the same order as the cooling time constant which is the time required for T to increase by a factor e. An approximate analytic solution of the differential equation for magnetization in a cooling system gives for TB: C(TB)/kT = ln(1.78C0) where c is the activation energy for rotation of magnetic moments, k is Boltzmann's constant, and C is the frequency factor (~1010 Hz). Because c varies with temperature, the cooling time constant O is given by 1/O = (1/kTB)(dc/dT-C/TB)dT/dt. The 95% blocking interval is about 7.2•. For steady cooling it is reasonable to assume • to be constant through this interval; small deviations from constancy have a negligible effect upon T B. In small external fields the variable grain geometry to be found within a real assemblage can be incorporated in a parameter Co, which is the activation energy at OøC. Curves of against T B for magnetite and haematite, at cooling rates from 6øC per minute to 3øC per million years, show that (1) a change in c o by a factor of 2 corresponds to 12 orders of magnitude change in cooling rate and (2) for a broad distribution of grain sizes a large proportion of the size range will acquire their magnetization within 100øC-200øC of the Curie point. Using these curves, blocking temperature in cooling assemblages can be related to laboratory demagnetization temperatures; the differences are greater at slower cooling rates and lower temperatures and tend to zero as the Curie temperature is approached. Intensity of magnetization should increase by a few percent for each order of magnitude decrease in cooling rate. Magnetization acquired at temperatures near the Curie point should dominate in a chemically homogenous monodomain assemblage with a broad spread of grain sizes. Possible tests of the theory and its application to the determination of cooling history are discussed. cuts the time axis so that a o = O: provided t'he system starts in a superparamagnetic state, its ß >> 8. Figure 2 shows how, in the blocking range initial condition does not significantly affect which lasts for only a few time constants, its final state. ß •,e (4) ß We can now quickly derive a simple expression for blocking temperature by writing the usual expression for relaxation time T in the form

- by Elizabeth McClelland
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- Multidisciplinary, Cooling Rate, Activation Energy, Grain size

A novel methodology for the diagnosis of an operating proton exchange membrane fuel cell (PEMFC) is proposed in this manuscript. The cell impedance can be represented as the sum of two terms: the membrane resistance and a second-order transfer function. An experimental procedure and a method to estimate the parameters of this impedance model from the experimental data, by applying parameter identification techniques, are proposed. The experimental procedure consists in reading the dynamic response of the cell voltage and current after the occurrence of small changes in the load value. This experimental procedure, intended for application on operating cells, does not significantly interfere with the cell operation. It has been designed supposing that the frequency range of the relevant cell phenomena is 1 Hz to 5 kHz. The required experimental equipment is inexpensive and easily portable. Analytical relationships have been derived in order to calculate the following cell electrochemical parameters from the model parameters: the diffusion resistance, the charge transfer resistance, the diffusion-related time constant, the membrane resistance and the double layer capacitance.

- by Angel Urquia
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- Engineering, Impedance Spectroscopy, Parameter estimation, Identification

The paper proposes an ABCD modeling approach to model the crosstalk coupling noise on the victim interconnect due to single / multiple aggressor(s) in deep sub-micron (DSM) chips. After the order reduction the crosstalk model is utilized for the analysis of crosstalk coupling noise on the victim's far end signal. Various timing issues related to signal waveform such as, delay time, overshoot and undershoot occurrence time etc., that in effect help to ensure in prior the desired signal integrity (SI) and performance reliability of the SoCs, can be estimated analytically using the reduced order crosstalk model. It has been observed that the crosstalk coupling noise introduces the delay in the victim's far end signal which can be significant enough or even unacceptable if many aggressors simultaneously couple energy to the victim line, or the line spacing between the aggressor and victim is reduced due to manufacturing defect such as under-etching or even, length of the victim interconnect is increased due to improper layouts of / routings between cores and devices on chips. Influences of other interconnect parasitics on the victim´s far end signal can also be analyzed using the same model. Simulation results obtained with the proposed reduced order model is found to be quite comparable to the accuracy of the PSPICE simulation.

- by Juergen Schloeffel
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- Vlsi Design, Signal Integrity, VLSI, Model Order Reduction

Field orientation techniques without flux measurements depend on the parameters of the motor, particularly on the rotor resistance or rotor time constant (for rotor field orientation). Since these parameters change continuously as a function of temperature, it is important that the value of rotor resistance is continuously estimated online. A fourth-order sliding-mode flux observer is developed in this paper. Two sliding surfaces representing combinations of estimated flux and current errors are used to enforce the flux and current estimates to their real values. Switching functions are used to drive the sliding surfaces to zero. The equivalent values of the switching functions (low-frequency components) are proven to be the rotor resistance and the inverse of the rotor time constant. This property is used to simultaneously estimate the rotor resistance and the inverse of the time constant without prior knowledge of either the rotor resistance or the magnetizing inductance. Simulations and experimental results prove the validity of the proposed approach.

- by Ali Keyhani
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- Engineering, Low Frequency, Parameter estimation, Temperature

MRI systems often use magnetic field gradient and shim pulse-shaping networks (pre-emphasis) to correct for magnetic field distortions caused by eddy currents. A pre-emphasis system that uses up to 16 fixed resistor-capacitor (RC) time constants per channel with programmable amplitude coefficients is described. The magnetic fields induced by the pre-emphasis RC time constants serve as a set of basis functions for compensating eddy-current fields induced by the gradient set. The resultant time-varying magnetic field gradient accurately reflects the gradient specified by the pulse programmer. Reductions in eddy-current fields are demonstrated for actively shielded and unshielded gradient sets.

- by Arvind Caprihan
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- Biomedical Engineering, Magnetic Resonance Imaging, Software, Computer Systems

Long Valley Caldera is an active volcanic region in east central California. Surface deformation on the resurgent dome within the caldera was an order of magnitude higher for the ®ve-month period September 1997 through January 1998 compared to the previous three-year average. However, the location of the immediate (shallow) source of deformation remained essentially constant, 5±7 km beneath the dome, near the top of a region of probable magma accumulation de®ned by seismic data. Similarly, although the rate of seismic moment release increased dramatically, earthquake locations remained similar to earlier periods. The rate of deformation increased exponentially between April±May 1997 and late November 1997 with a time constant of ,55±65 days, after which it decreased exponentially with about the same time constant. We develop a model consistent with these observations and also consistent with independent constraints on sub-surface rheology from thermal, geochemical and laboratory data. Deformation at sites on the resurgent dome most sensitive to the shallow deformation source are well ®t by a model with a single pressure source at 6 km depth which experienced a pressure pulse that began in late 1996, peaked in November 1997, close to the time of major seismic moment release, and essentially ended in mid-1999. The pressure source in our model is surrounded by a 1 km thick ªshellº of Maxwell viscoelastic material (shell viscosity 10 16 Pa s) within an elastic half space, and has peak values that are much lower than corresponding purely elastic half space models. The shell viscosity is characteristic of a weak, deformable solid, e.g. quartz-bearing country rock surrounding the magma chamber at temperatures in the range 500±6008C, i.e. above the brittle±ductile transition, and/or largely crystallized rhyolite near its solidus temperature of ,6708C, material that probably exists near the top of the zoned magma chamber at Long Valley. q (T.H. Dixon). Fig. 4. Seismicity at Long Valley for November 1997. Inset shows all events in map view projected onto a west-east cross section. Note well-de®ned linear trend, which may indicate location of a dike or fault near the south moat.

- by Jacqueline Eaby Dixon
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- Geodesy, Geology, Geochemistry, Geophysics

We report the vibrational and orientational dynamics of water molecules in isotopically diluted NaOH and NaOD solutions using polarization-resolved femtosecond vibrational spectroscopy and terahertz time-domain dielectric relaxation measurements. We observe a speed-up of the vibrational relaxation of the O-D stretching vibration of HDO molecules outside the first hydration shell of OH − from 1.7 ± 0.2 ps for neat water to 1.0 ± 0.2 ps for a solution of 5 M NaOH in HDO:H 2 O. For the O-H vibration of HDO molecules outside the first hydration shell of OD − , we observe a similar speed-up from 750 ± 50 fs to 600 ± 50 fs for a solution of 6 M NaOD in HDO:D 2 O. The acceleration of the decay is assigned to fluctuations in the energy levels of the HDO molecules due to charge transfer events and charge fluctuations. The reorientation dynamics of water molecules outside the first hydration shell are observed to show the same time constant of 2.5 ± 0.2 ps as in bulk liquid water, indicating that there is no long range effect of the hydroxide ion on the hydrogen-bond structure of liquid water. The terahertz dielectric relaxation experiments show that the transfer of the hydroxide ion through liquid water involves the simultaneous motion of ∼7 surrounding water molecules, considerably less than previously reported for the proton.

- by Huib Bakker
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- Engineering, Thermodynamics, Water, Vibrational Spectroscopy
- by Roberto Ballarini
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- Biophysical Chemistry, Biological Sciences, Elasticity, Stress relaxation

Pr 3 + 0.2, 0.75, and 3 mol% doped YAP single crystalline scintillators were grown by using the micropulling down (m-PD) method. Pr 3 + 0.05 mol% doped YAP was also prepared by using the Czochralski method. In transmittance spectra, 4f-5d absorption line appeared at 230 nm. The m-PD grown crystals showed intense emission at 290 nm while the Czochralski grown one showed an emission peak at 245 nm in radio luminescence spectra under X-ray excitation. Among them, the Czochralski grown one exhibited the highest light yield under 137 Cs 662 keV excitation and the absolute light yield of this sample was estimated to be 20400 7 2000 ph/MeV. The decay time constants of these scintillators were around 10 ns due to Pr 3 + 5d-4f transition.

- by A. Krasnikov
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- Crystal Growth, X Rays, Constant Time Delay, Single Crystal

Abstruct-Optimal measurement and control procedures with adaptive algorithms based on dynamically evaluated output signals for operating a dew point hygrometer are discussed. The influence of dew condensation and evaporation time constants and the amplitude of mirror overheating and overcooling, as well as limits of the flow rate of the measured gas and the thickness of the dew layer upon dew point detection and the accuracy of the dynamically measured mirror temperature, are described. Flow diagrams for computer procedures and schematic diagrams of electronic measurement systems are included.

- by Ryszard Jachowicz
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- Optimal Control, Thermoelectricity, System Design, Temperature measurement

A simple physics-based analytical model for a non-self-aligned GaN MESFET suitable for microwave frequency applications is presented. The model includes the effect of parasitic source/drain resistances and the gate length modulation. The model is then extended to evaluate I± V and C±V characteristics, transconductance, cut-off frequency, transit time, RC time constant, optimum noise ®gure and maximum power density. The transconductance of about 21 mS/mm is obtained for GaN MESFET using the present theory in comparison to 23 mS/mm of the reported data. The cut-off frequency of more than 1 GHz, optimum noise ®gure of 6 dB and maximum output power density of more than 1 W/mm are predicted. q

- by Sandip Bose
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- Microelectronics, Constant Time Delay, Analytical Model, Analytical Modelling

The characteristic time constants of the relaxation dynamics of core-excited atoms have hitherto been inferred from the linewidths of electronic transitions measured by continuous-wave extreme ultraviolet or X-ray spectroscopy. Here we demonstrate that a laser-based sampling system, consisting of a few-femtosecond visible light pulse and a synchronized sub-femtosecond soft X-ray pulse, allows us to trace these dynamics directly in the time domain with attosecond resolution. We have measured a lifetime of 7:9 11:0 20:9 fs of M-shell vacancies of krypton in such a pump-probe experiment.

- by Matthias Uiberacker
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- Multidisciplinary, Nature, Time Resolved, Constant Time Delay

The experimental detection of capacitance variations with a resolution as low as few zeptoFarads (10 −21 F) is presented. This is achieved by means of a CMOS ultra-low-noise and wide-bandwidth current sensing circuit, coupled to a lock-in amplifier to perform capacitance and conductance measurements in a frequency range from DC to 1 MHz. The adoption of an integrated implementation, based on an original circuital topology, provides miniaturization and performance improvement. The mm-sized chip can be easily integrated in extremely compact sensing setups. Resolution limits are analyzed in detail and experimentally investigated by means of a mechanical fixture that converts micrometric linear displacement into sub-aF capacitance steps. The experimental results match the theoretical expectation down to a resolution of 5 zF rms (6 V at 100 kHz, with a 100 ms time constant). The achieved current resolution of 15 fA rms (at ∼ms time scale) and the tracking of 40 zF capacitance steps demonstrate how the proposed read-out circuit can serve as a versatile tool for the development of nanosensors.

We describe a neutron/gamma pulse shape discrimination (PSD) system that overcomes count rate limitations of previous methods for distinguishing neutrons from gammas in liquid scintillation detectors. Previous methods of PSD usually involve pulse shaping time constants that allow throughput of tens of thousands counts per second. Time correlated measurements require many millions of counts per second to accurately characterize nuclear material samples. To rapidly inspect many test articles, a high-throughput system is desired. To add neutron - gamma distinction to the analysis provides a much desired enhancement to the characterizations. However, if the PSD addition significantly slows down the inspection throughput, this PSD feature defeats any analysis advantage. Our goal for the fast PSD system is to provide sorted timing pulses to a fast, multi-channel, time-correlation processor at rates approaching several million counts per second enabling high throughput, enhanced inspection of nuclear materials.

This work deals with the design of an Adaptive Reference model Controller for (MRAC) for parameters adaptation apply to an indirect field oriented controller for induction motor control. The parameters behavior was analyzed using three different reference models. The considered reference models were: direct (d) axis voltage, the quadrature (q) axis voltage and the reactive power. For each reference model the adaptation error was analyzed. Using these equations the parameters convergence was analyzed and discussed under several motor conditions. The results were presented and the simulation for all the reference models considered, illustrating the parameters behavior under several motor operating conditions. The analysis and simulation results show the superiority of the dynamic reference models using quadrature (q) axis voltage and reactive power model.

- by Aldo Garcia
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- Reactive Power, Reference model, Constant Time Delay, Operant Conditioning

Modern applications, such as wireless communication systems or hybrid electric vehicles operate at high power fluctuations. For some applications, where the power frequencies are high (above some 10 or 100 Hz) it is possible to filter the high frequencies using passive components; yet this results in additional costs. In other applications, where the dynamic time constants are in the range up to some seconds, filtering cannot be done. Batteries are hence operated with the dynamic loads. But what happens under these dynamic operation conditions?

- by Andreas Jossen
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- Engineering, Mass Transfer, Performance, High Frequency
- by Hermann Schumacher
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- Signal Analysis, Dispersion, Frequency-domain analysis, Mmic

The b Ti-29Nb-13Ta-4.6Zr (TNTZ) has been recently developed as a new implant material. TNTZ alloy is composed of non toxic elements and has a low modulus of elasticity than the other titanium alloys. However, its electrochemical behaviour has not yet been studied. Hence in the present work, the influence of potential on electrochemical behaviour of TNTZ alloy under simulated physiological condition was investigated by electrochemical impedance spectroscopy (EIS). The experimental results were compared with those obtained for titanium (Cp-Ti). All measurements were obtained in aerated Hank's solution at 37°C and at different potentials E corr , 0 mV (SCE), 500 mV (SCE) and 1000 mV (SCE). The EIS behaviour of the TNTZ alloy is unique in nature compared to Cp-Ti, exhibiting two-time constants indicating the formation two layers only at higher potentials.

- by Rahul Bhola
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- Engineering, Chemical Engineering, Materials Science, Kinetics

A sequential algorithm is presented for computing the exact Euclidean distance transform (DT) of a k-dimensional binary image in time linear in the total number of voxels N. The algorithm, which is based on dimensionality reduction and partial Voronoi diagram construction, can be used for computing the DT for a wide class of distance functions, including the L p and chamfer metrics. At each dimension level, the DT is computed by constructing the intersection of the Voronoi diagram whose sites are the feature voxels with each row of the image. This construction is performed efficiently by using the DT in the next lower dimension. The correctness and linear time complexity are demonstrated analytically and verified experimentally. The algorithm may be of practical value since it is relatively simple and easy to implement and it is relatively fast (not only does it run in OðNÞ time but the time constant is small). A simple modification of the algorithm computes the weighted Euclidean DT, which is useful for images with anisotropic voxel dimensions. A parallel version of the algorithm runs in OðN=pÞ time with p processors.

We present a MEMS affinity sensor that can potentially allow long-term continuous monitoring of glucose in subcutaneous tissue for diabetes management. The sensing principle is based on detection of viscosity changes due to affinity binding between glucose and poly(acrylamide-ran-3-acrylamidophenylboronic acid) (PAA-ran-PAAPBA), a biocompatible, glucose-specific polymer. The device uses a magnetically driven vibrating microcantilever as a sensing element, which is fabricated from Parylene and situated in a microchamber. A solution of PAA-ran-PAAPBA fills the microchamber, which is separated from the surroundings by a semi-permeable membrane. Glucose permeates through the membrane and binds reversibly to the phenylboronic acid moiety of the polymer. This results in a viscosity change of the sensing solution, which is obtained by measuring the damped cantilever vibration using an optical lever setup, allowing determination of the glucose concentration. Experimental results demonstrate that the device is capable of detecting glucose at physiologically relevant concentrations from 27 mg/dL to 324 mg/dL. The glucose response time constant of the sensor is approximately 3 min, which can be further improved with device design optimization. Excellent reversibility and stability are observed in sensor responses, as highly desired for long-term, stable continuous glucose monitoring.

The stabilization of fluid catalytic cracking reactors is tackled in this paper. A robust PID control law is developed in order to control the outlet reactor temperature. The suggested control is based on a reduced order model of the reactor given by a system of ordinary differential equations. The controller is synthesized using an input/output linearizing control law coupled to a proportional-derivative reduced order observer to infer on-line the unknown heat of reaction. The proposed control algorithm leads to a classical PID structure. New tuning rules are given, based on the system structure, estimations and closed-loop time constants. This control strategy turns out to be robust against model uncertainties, noisy temperature measurements and set point changes. The performance of the reaction temperature in a tubular riser reactor is numerically compared when the proposed control scheme and standard PID controllers are applied. #

- by Rafael Maya-Yescas
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- Chemical Engineering, Process Control, Process, Fluid Catalytic Cracking

The current-voltage (I-V) characteristics of metal/insulator/metal (MIM) diodes illuminated at optical frequencies are modeled using a semiclassical approach that accounts for the photon energy of the radiation. Instead of classical small-signal rectification, in which a continuous span of the dc I-V curve is sampled during rectification, at optical frequencies, the radiation samples the dc I-V curve at discrete voltage steps separated by the photon energy (divided by the electronic charge). As a result, the diode resistance and responsivity differ from their classical values. At optical frequencies, a diode with even a moderate forward-to-reverse current asymmetry exhibits high quantum efficiency. An analysis is carried out to determine the requirements imposed by the operating frequency on the circuit parameters of antenna-coupled diode rectifiers, which are also called rectennas. Diodes with low resistance and capacitance are required for the RC time constant of the rectenna to be smaller than the reciprocal of the operating frequency and to couple energy efficiently from the antenna. Existing MIM diodes do not meet the requirements to operate efficiently at visible-to-near-infrared wavelengths.

- by Garret Moddel
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- Solar Cell, Near Infrared, Mott metal-insulator transition, Resistance

The transfer function of a moving coil electromagnetic geophone requires up to six constants: the suspended mass, the natural resonant frequency, the mechanical and the electrical damping factors, the inductive time constant of the coil-damping resistance circuit, and the coil transductance. If the mass is known, the remaining constants may be satisfactorily determined by displacing the mass with a known

- by Michael Asten
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- Damping, Calibration, Electromagnetic Induction, Transfer Function