liqun Ma - Academia.edu (original) (raw)

Papers by liqun Ma

2014 IEEE Topical Conference on Power Amplifiers for Wireless and Radio Applications (PAWR), 2014

ABSTRACT The theory of class-J power amplifiers is reviewed. Based on the theory, a new output ma... more ABSTRACT The theory of class-J power amplifiers is reviewed. Based on the theory, a new output match method is proposed. Instead of the restricted impedance condition, we design the different fundamental and 2nd harmonic output impedances based on the variation tendency of termination impedance according to the different frequencies. Therefore, the PA can work efficiently in the band. A 10W GaN transistor device (CGH40010) is applied in the simulation. And the results show this method can enhance the PAE over 60% across a bandwidth of 1.6-2.5 GHz.

In this paper, we propose a new non-local population model of logistic type equation on a bounded... more In this paper, we propose a new non-local population model of logistic type equation on a bounded Lipschitz domain in the whole Euclidean space. This model preserves the L 2 norm, which is called mass, of the solution on the domain. We show that this model has the global existence, stability and asymptotic behavior at time infinity.

Wireless communication between devices can be lossy in the sense that packet transmissions via a ... more Wireless communication between devices can be lossy in the sense that packet transmissions via a wireless link may fail (so that the packet is lost) due to a number of factors-channel fading, interference or mobility of devices. In some scenarios, the lossy characteristic of wireless communication can be random, and thus better characterised from a stochastic perspective. This thesis investigates lossy wireless networks, which are wireless communication networks consisting of lossy wireless links, where the packet transmission via a lossy wireless link is successful with a certain value of probability. iii Statement of originality iv Related publications v Table of contents vi List of figures x List of tables xi List of symbols xiii List of abbreviations xv List of figures

Journal of Inorganic Materials, 2015

Spinel LiMn 1-x Ni x TiO 4 (x=0, 0.1, 0.2, 0.3) cathode materials were prepared by Sol-Gel method... more Spinel LiMn 1-x Ni x TiO 4 (x=0, 0.1, 0.2, 0.3) cathode materials were prepared by Sol-Gel method. The surface morphology and phase structure of LiMn 1-x Ni x TiO 4 (x=0, 0.1, 0.2, 0.3) were characterized by FESEM and XRD. FESEM analysis indicated all the samples consisted of irregular particles and XRD patterns showed that all the materials had impurity TiO 2 , but there were no impurities related to Ni element. Electrochemical studies of doped and undoped spinels were carried out by cyclic voltammetry (CV) and constant current charge-discharge. CV results showed that LiMnTiO 4 had two couples of sharp redox peaks corresponding to Mn 3+ /Mn 4+ , Mn 2+ /Mn 3+ redox reactions. However, after Ni substitution, there appeared the third redox coupled, which was related to the Ni 3+ /Ni 4+ redox reaction. LiMn 1-x Ni x TiO 4 (x=0.1, 0.2, 0.3) exhibited improved electrochemical properties compared with LiMnTiO 4. When the Ni substitution was 0.1, the first discharge capacity of LiMn 0.9 Ni 0.1 TiO 4 was 171.6 mAh/g at current density of 30 mA/g, and after 48 charge-discharge cycles, the discharge capacity was 162.8 mAh/g, with the capacity retention of 82.7%. The Ex XRD pattern of LiMn 0.9 Ni 0.1 TiO 4 showed that the material structure had no changes after the first cycle, and there was no transition between cubic phase and tetragonal phase.

Asian Journal of Chemistry, 2015

Employing the newly developed PM7 method,we have computationally investigated endohedral hydrogen... more Employing the newly developed PM7 method,we have computationally investigated endohedral hydrogen storage capacities of boronnitride based nanocages, BmNm (m = 12, 24, 36, 48 and 96). The calculation results revealed that the smallest two boron-nitride nanocages, B12N12 and B24N24, (their gravimetric density of hydrogen storages are 1.35 and 3.05 wt. %) are not suitable for hydrogen doping due to their rather small endohedral cavities. B36N36, whose hydrogen storage density is 4.96 wt. %, may not be very efficient although it has better storage capacity than the smallest two. On the other hand, the gravimetric densities of hydrogen storage inside the B48N48 and B96N96 nanocages are predicted to be 6.6 and 10.6 wt. %, respectively. This high weight percentage of hydrogen storage indicates that B48N48 and B96N96 can be considered as promising hydrogen storage materials.

2013 IEEE Global Communications Conference (GLOBECOM), 2013

Wireless communication is notoriously lossy due to channel fading, interference and multi-path ef... more Wireless communication is notoriously lossy due to channel fading, interference and multi-path effects. This work investigates the reliability of all-to-all broadcast in lossy wireless networks where the reliability is measured by the probability that every node in the network receives or decodes the native packet of every other node. To improve the reliability, a novel network coding scheme, namely random neighbour network coding (RNNC) scheme is proposed, which is capable of adaptively generating encoding packets according to the packets received from lossy wireless channels. The network reliability is analysed theoretically and the optimal RNNC scheme that maximises the reliability of a given network is obtained. The theoretical analysis is validated using simulations and it is shown that RNNC can improve the network reliability significantly.

China Journal of Chinese Materia Medica, 2011

To establish a method for determination of 7 alkaloid in Herba Sophorae Alopecuroidis by HPLC. X-... more To establish a method for determination of 7 alkaloid in Herba Sophorae Alopecuroidis by HPLC. X-Brige C18 (4.6 mm x 200 mm, 5 microm) column was used with acetonitriles-0.05 mol x L(-1) KH2PO4 solution (2.0 mL x L(-1) triethylamine) with gradient elution as the mobile phase and 1.0 mL x min(-1) as the flow rate. The detection wavelength was 205 nm. Aloperin curve was linear in the range from 20.66 to 103.32 microg (r = 0.998 8) and the average recovery was 97.12% (RSD 7. 3%); sophoridine curve was linear in the range from 22.82 to 114.12 microg (r = 0.999 7) and the average recovery was 97.47% (RSD 3.0%); oxymatrine curve was linear in the range from 25.10 to 125.52 microg (r = 0.999 1) and the average recovery was 96.21% (RSD 4.5%); oxysophocarpine curve was linear in the range from 23.88 to 119.40 microg (r = 0.997 5) and the average recovery was 94. 64% (RSD 5.2%); matrine curve was linear in the range from 5.00 to 24.99 microg (r = 0.998 6) and the average recovery was 98.04% (RSD 5.4%); sophocarping curve was linear in the range from 4.69 to 23.46 microg (r = 0.999 6) and the average recovery was 96.24 (RSD 5.8%); lehmannine curve was linear in the range from 4.60 to 23.01 microg (r = 0.997 8) and the average recovery was 101.31% (RSD 4.3%). The method is accurate, simple and feasible. It can be used as a quality evaluation in Herba S. Alopecuroidis.

Physics in Medicine and Biology, 2005

Dedicated linac-based radiosurgery has been reported for trigeminal neuralgia treatments. In this... more Dedicated linac-based radiosurgery has been reported for trigeminal neuralgia treatments. In this study, we investigated the dose fall-off characteristics and setup error tolerance of linac-based radiosurgery as compared with standard Gamma Knife radiosurgery. In order to minimize the errors from different treatment planning calculations, consistent imaging registration, dose calculation and dose volume analysis methods were developed and implemented for both Gamma Knife and linac-based treatments. Intra-arc setup errors were incorporated into the treatment planning process of linac-based deliveries. The effects of intra-arc setup errors with increasing number of arcs were studied and benchmarked against Gamma Knife deliveries with and without plugging patterns. Our studies found equivalent dose fall-off properties between Gamma Knife and linac-based radiosurgery given a sufficient number of arcs (>7) and small intra-arc errors (<0.5 mm) were satisfied for linac-based deliveries. Increasing the number of arcs significantly decreased the variations in the dose fall-off curve at the low isodose region (e.g. from 40% to 10%) and also improved dose uniformity at the high isodose region (e.g. from 70% to 90%). As the number of arcs increased, the effects of intra-arc setup errors on the dose fall-off curves decreased. Increasing the number of arcs also reduced the integral dose to the distal normal brain tissues. In conclusion, linac-based radiosurgery produces equivalent dose fall-off characteristics to Gamma Knife radiosurgery with a high number of arcs. However, one must note the increased treatment time for a large number of arcs and isocentre accuracies.

Journal of Materials Science Letters, 1995

Journal of Chromatographic Science, 2002

Reversed-phase high-performance liquid chromatography is widely used in the analysis of drug subs... more Reversed-phase high-performance liquid chromatography is widely used in the analysis of drug substances and their metabolites. The interaction of quinolones with residual silanol in a silica-based C 18 stationary phase causes peak broadening and bad peak shapes and makes it hard to resolve the peak separations. This unusual interaction is studied and finally can be removed by masking the residual silanol of a silica-based C 18 stationary phase, then good peak separation is achieved. We have chosen four new quinolones and ciprofloxacin and improved the peak shapes by optimizing the pH of the eluent and the quantity of the additive (N,N-dimethyloctylamine, approximately 0-40mM) in the monomeric C 18 stationary phase. The elution behavior of quinolones in the polymeric C 18 stationary phase is compared with that in the monomeric C 18 stationary phase under the same eluent condition. Good peak symmetry and a high plate number are achieved by this technique, which are hardly obtained with the conventional silica-based C 18 stationary phase. Based on these results, we present data of the influence of the eluent composition such as pH, buffer, and additive concentration on the peak shape.

Integrated Ferroelectrics, 1997

Abstract Ruthenium dioxide thin films were deposited on SiO2/Si substrate at low temperatures by ... more Abstract Ruthenium dioxide thin films were deposited on SiO2/Si substrate at low temperatures by hot-wall metalorganic chemical vapor deposition using the ruthenocene and oxygen gas mixtures. The RuO2 films annealed at 700°C in 1 atm. oxygen ambient showed a dense and improved microstructure. However, above 750°C evaporation of RuO2 was observed at the interface between RuO2 and SiO2/Si substrates as well as the surface of RuO2 films. RuO2 annealed at vacuum ambient(about 1.0 × 10−5 torr) of 500°C were partially reduced to Ru and completely Ru at 700°C. Films annealed at vacuum ambient showed the most low resistivity because RuO2 was reduced to the Ru metal with increasing annealing temperatures. Films annealed in oxygen atmosphere of 600°C after vacuum annealing showed an uniform RuOx grain size but a little porous structure.

$Research paper thumbnail of Exponential <math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow><msub><mi>H</mi><mi mathvariant="normal">∞</mi></msub></mrow><annotation encoding="application/x-tex">H_{\infty}</annotation></semantics></math>H∞ Filter Design for Discrete Time-Delay Stochastic Systems With Markovian Jump Parameters and Missing Measurements$

IEEE Transactions on Circuits and Systems I: Regular Papers, 2011

In this paper, the exponential filtering problem is studied for discrete time-delay stochastic sy... more In this paper, the exponential filtering problem is studied for discrete time-delay stochastic systems with Markovian jump parameters and missing measurements. The measurement missing phenomenon, which is related to the modes of subsystems, is described in the form of random matrix function and the missing probability of each sensor at every mode is governed by an individual random variable taking values in the interval [0 1]. This description of missing measurements is more general than the existing ones, where the missing probability is described by a Bernoulli distribution white sequence or a certain diagonal matrix. By using Lyapunov method and the properties of conditional mathematical expectation, we propose a novel approach to achieve the delay-dependent exponential stability criterion such that the filtering error system is mean-square exponentially stable and satisfies a prescribed performance level. Moreover, there is no equation restriction on decay rate. Then, based on the obtained sufficient criterion, the filter matrices can be directly characterized by solving a set of linear matrix inequalities (LMIs). Finally, a numerical example is provided to show the validity of the main result. Index Terms-Discrete-time, Markovian jump parameters, missing measurements, stochastic system, time-delay. I. INTRODUCTION I N MOST of the literature concerning output feedback control and filtering problems, it is implicitly assumed that the system measurements always entirely contain consecutive useful signals. However, in many practical applications, such an assumption does not hold. As described in [1], taking the target tracking control for example, due to the high maneuverability of the tracked target, there may be a nonzero probability that Manuscript

Corrosion Science, 2006

Surface treatment of the MmNi 3.8 Co 0.75 Mn 0.4 Al 0.2 (Mm = Ce-rich mischmetal) hydrogen storag... more Surface treatment of the MmNi 3.8 Co 0.75 Mn 0.4 Al 0.2 (Mm = Ce-rich mischmetal) hydrogen storage alloy is carried out by using the solution of HF and KF with a little addition of KBH 4. The electrochemical properties of the original and the treated hydrogen storage alloys are investigated. The discharge properties such as discharge capacity, potential plateau, and high rate dischargeability (HRD) are improved after the treatment. At a current rate of 900 mA/g, the HRD of the treated alloy still remains a high value of 80.2% while the original one cannot discharge. The result of the linear polarization measurement shows that the exchange current density increases from 80.99 to 124.98 mA/g and the polarization resistance decreases from 371.1 to 205.5 m g after the treatment. The result of the electrochemical impedance spectroscopy (EIS) also demonstrates the same consequence. The hydrogen diffusion coefficient studied by potential-step measurement increases from 1.79 × 10 −9 to 3.29 × 10 −9 cm 2 /s after the treatment.

Catalysis Today, 2000

Promotional effects of chromia on the structure and activity of skeletal copper catalysts for met... more Promotional effects of chromia on the structure and activity of skeletal copper catalysts for methanol steam reforming and water gas shift have been studied. Catalysts were prepared by leaching CuAl 2 alloy particles in aqueous NaOH solutions containing sodium chromate at various concentrations. XPS spectra showed that the surface of the resulting catalysts mainly consisted of Cr 3+ compounds and Cu 0. Cu + and/or Cu 2+ were not observed by XPS. Increasing the concentration of chromate in the leach liquor resulted in decreases in pore diameter and copper crystallite size but significant enhancement of BET surface area was observed while the total pore volume was maintained. The addition of small amounts of chromate to the leach liquor significantly enhanced the Cu surface area. However, higher concentrations of chromate in the leach liquor decreased the Cu surface areas although the total surface areas increased. The activities of Cr 2 O 3 promoted skeletal copper catalysts for both methanol steam reforming and water gas shift reactions were determined separately. The results indicated that deposition of Cr 2 O 3 on skeletal copper catalysts significantly improved the specific activities for these reactions. Chromia is found to act as a structural and catalytic promoter for these reactions.

Asian Journal of Chemistry, 2013

Nowadays, developing new type hydrogen storage alloy which has large hydrogen storage capacity, e... more Nowadays, developing new type hydrogen storage alloy which has large hydrogen storage capacity, excellent discharge dynamics performance, low cost and pollution-free to substitute for the traditional LaNi5 base hydrogen storage alloy has become the focus of study. RM3 (R = rare earth elements, Ca, Mg and 3, 4 group element, M = Ni, Fe, Cu, Co, Zn, etc.) hydrogen storage alloy which has PuNi3 type structure has aroused widespread concern of scholars globally owing to its special structure, large hydrogen storage capacity and excellent alloy electrode dynamic performance advantages 1-3. Especially AB3-type hydrogen storage alloy containing Mg, its maximum discharge capacity can reach 400 mAh/g above which is 1.3 times as large as AB3-type alloy, thus, it has been received wide concern. Kadir et al. 4 synthesized many new type ternary magnesium base alloys through mixed reaction of MgNi2 and intermetallic compound RNi5 (R = La, Ce, Pr, Nd, Sm and Gd) or direct combination according to the atomic ratio R:Mg:Ni = 1:2:9. Kohno et al. 5 studied new type La-Mg-Ni alloy: La2MgNi9, La5Mg2Ni23 and La3MgNi14 systems with hydrogen storage properties, La0.67Mg0.33Ni2.5Co0.5, La0.7Mg0.3Ni2.8Co0.5, La0.75Mg0.25Ni3.0Co0.5 alloys were produced by the method of induction smelting in argon gas, then the sucking/putting hydrogen characteristics of these alloys were studied. The

Journal of Electronic Materials

Sixth Symposium on Novel Optoelectronic Detection Technology and Applications, 2020

Minimal distance between engine assembled pipes is an important parameter for evaluating the asse... more Minimal distance between engine assembled pipes is an important parameter for evaluating the assembling quality. Feeler gauge is a traditional method, which is time-consuming and low accuracy. In this article, a new approach is proposed which employs an accurate 3D scanner to obtain the surface cloud points of pipes, then extracting the pipe center lines to calculate the minimal distance of two pipes. Firstly, points belonging to the same pipe were picked up. Then equal-interval grids were built along a coordinate direction in which the pipe stretched longest. Point cloud was divided into grid according to its coordinates. Center points of all grids constituted rough tendency points of a pipe. Then, a vertical plane was built on each tendency point passing through it. Then point cloud of the pipe was projected onto the nearest plane. And on each plane, the projected points were fitted into a circle. The center points of all circles constituted center-line points of a pipe. Then traversing method was used to calculate rough minimal-distance (RMD) between two center lines. Then a searching process is conducted around the minimal-point-pair to further calculate minimal distance of two center lines. And minimal-distance of two pipe surfaces was calculated by subtracting radii of two pipes from the minimal-distance of center-line points. Four groups of pipes were examined to verify the proposed strategy. The results showed that the deviations of minimal-distance of two pipe surfaces were within -0.35mm~0.46mm. And the deviations of pipe radius were within-0.1mm~0.29mm.

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National Medical Journal of China, Jun 8, 2005

Proceedings of the 2021 Conference on Empirical Methods in Natural Language Processing, 2021

Dialogue summarization has drawn much attention recently. Especially in the customer service doma... more Dialogue summarization has drawn much attention recently. Especially in the customer service domain, agents could use dialogue summaries to help boost their works by quickly knowing customer's issues and service progress. These applications require summaries to contain the perspective of a single speaker and have a clear topic flow structure, while neither are available in existing datasets. Therefore, in this paper, we introduce a novel Chinese dataset for Customer Service Dialogue Summarization (CSDS). CSDS improves the abstractive summaries in two aspects: (1) In addition to the overall summary for the whole dialogue, role-oriented summaries are also provided to acquire different speakers' viewpoints. (2) All the summaries sum up each topic separately, thus containing the topic-level structure of the dialogue. We define tasks in CSDS as generating the overall summary and different role-oriented summaries for a given dialogue. Next, we compare various summarization methods on CSDS, and experiment results show that existing methods are prone to generate redundant and incoherent summaries. Besides, the performance becomes much worse when analyzing the performance on role-oriented summaries and topic structures. We hope that this study could benchmark Chinese dialogue summarization and benefit further studies.

2014 9th International Conference on Computer Science & Education, 2014

Along with the more and more application of big data mining based on cloud computing in economic ... more Along with the more and more application of big data mining based on cloud computing in economic life worldwidely, it has also brought revolution to securities industry. This paper firstly reviews the relevant studies on big data, cloud computing and their applications in securities industry, then with the SWOT analysis method, illustrates the strength of big data mining along with the chances it has brought to securities industry, as well as its inherent weakness and challenges facing with securities industry. Then it investigates the status quo and puts forward the related countermeasures for domestic securities industry to develop big data mining. Finally it summarizes the research and proposes outlooks.