a jabari | Kirkuk University (original) (raw)

Papers by a jabari

Standard software packages by default implement methods such as listwise deletion that simply dro... more Standard software packages by default implement methods such as listwise deletion that simply drops cases that have missing values. This study tested three techniques (multiple imputation, mean substitution, and listwise deletion) used to remedy problems associated with missing data. Data from the revised General Social Survey from 1993 were used in this study. Four variables were selected for inclusion in this study: age, education, socioeconomic status, and number of hours of TV viewing. A total of 30 samples (10 each with a sample size of 50, 100, and 200) were randomly selected from the 1,500 cases in this database using SPSS - Windows, ver. 12.0. From these samples, additional samples were generated with 10%, 30%, and 50% of values randomly deleted using a random number generator. These data manipulations produced 40 samples for each sample size. The compensatory techniques (listwise deletion, mean substitution, and multiple imputation) were applied to every sample, with summary statistics (e.g., means, standard deviations, medians, and minimum and maximum scores) generated for each sample. Regression analyses were completed for each of the samples, with number of TV hours used as the criterion variable, and age, education, and socioeconomic status used as predictor variables. Means and standard deviations of the R2s for each of the sample sizes and compensatory techniques were obtained to allow comparisons across the samples. ^ Mean ratios were computed for each missing value condition to determine the degree to which each technique effectively compensated for missing values. To determine the mean ratios for the mean scores, the mean of each sample was compared to the mean of its original sample. A similar method was used to compare the R2s for each of the missing value conditions with the R2 for the original sample. In addition, a 3 x 3 factorial analysis of variance was used to test for differences between the main effects of compensatory technique and percent of missing values. Mean substitution appeared to produce estimates that most nearly emulated that of the original sample. ^

Chemical Engineering Journal, Jan 1, 2011

All distributed drinking water receives some form of disinfection and a minimum disinfectant resi... more All distributed drinking water receives some form of disinfection and a minimum disinfectant residual should be maintained at the customer tap. The most popular disinfectant is chlorine. Chlorine reacts with compounds in water and hence decays. Description of chlorine decay is often difficult, due to a complex set of reactions and an initial fast reaction followed by a slower reaction. Before any attempt could be made to understand the decay characteristics in the distribution system, chlorine decay in bulk water has to be correctly described. The parallel second order reaction model was found to be one of the most suitable models for this purpose. However, widespread use of this model is hindered by its complexity, most importantly the non-existence of an analytical solution. In this paper, an analytical solution for this model was developed by initially assuming that the ratio (α) of slow and fast reaction rate coefficients is small. The estimated parameters and the chlorine residuals predicted by the numerical analysis and the proposed solution were compared for the chlorine decay data sets obtained from the literature as well as laboratory analysis. The results showed that the proposed analytical solution was very accurate for the prediction of chlorine decay behaviour in all samples.

Users sharing and authoring of Web contents via different Web sites is the main idea of the Web 2... more Users sharing and authoring of Web contents via different Web sites is the main idea of the Web 2.0. However, Web users belong to different communities and follow their own semantics (referred to as local contexts) to represent and interpret Web contents. Therefore, they encounter discrepancies when they have to interpret Web contents authored by different persons. This paper proposes a context-aware interaction approach that helps Web authors annotate Web contents with their local context information, so that it becomes possible for Web browsers to personalize these contents according to different users’ local contexts.

Molecular dynamics simulations are used to study relationships between material morphology, adhes... more Molecular dynamics simulations are used to study relationships between material morphology, adhesion, and sliding friction in carbon nanotube (CNT) coatings at the nanoscale. Two controlled quantities, CNT chirality and vacancy defects, are found to have significant effects on CNT coating adhesion to Si surfaces and sliding friction in turn. For example, using free energy calculations, a CNT of chirality (10,0) with a corresponding diameter of 7.777 Å was observed to have an adhesion energy-per-unit-length of approximately three-times that of a CNT with (5,5) chirality and corresponding diameter of 6.732 Å. Simulations of aligned carbon nanotube arrays containing various vacancy defect densities in sliding contact with Si substrates were also performed. Friction and wear were shown to increase with defect density. Similar studies are underway to investigate how other characteristics of CNTs in addition to chirality, such as CNT length distribution and defect concentration, affect adhesion and friction in CNT-Si coatings. Outcomes may shed light on fundamental principles governing, for example, sliding interfaces in micro- and nano-electro-mechanical and other tribological systems.

It is well known that half of the radiation received by humans is due to the presence of radon (2... more It is well known that half of the radiation received by humans is due to the presence of radon (222Rn) in the built environment. As part of a project measuring indoor radon in Hamadan, western Iran, a survey was undertaken of atmospheric radon in 28 wells in the region using a Sarad Doseman. Specific geological features of this settlement include highly permeable alluvial fan deposits which result in radon being released to the atmosphere. The observed radon concentrations in well shafts(between 1,000 Bq m3 and 36,600 Bq m3) show considerable variability both in space and time. One aspect of this study was to also assess whether there was a relationship between the depth of a well and the measured atmospheric radon concentration. The importance of such measurements in this region is highlighted by the fact that radon levels in homes in Hamadan are probably greatly influenced by the porous nature of this underlying geology and its use as a water reservoir / conduit through the application of qanat technology.

Sid Symposium Digest of Technical Papers, Jan 1, 2002

Various polymer substrates, including polyimide and polystyrene were bombarded with an Ar þ ion b... more Various polymer substrates, including polyimide and polystyrene were bombarded with an Ar þ ion beam in high vacuum at an oblique angle. The alignment direction of the liquid crystal 5CB on these polymer substrates is always parallel to the ion beam propagation direction regardless of the type of polymer used. The alignment mechanism is studied using surface sensitive techniques such as Polarized Attenuated Total Reflection Infrared Spectroscopy (ATR-IR), and X-ray Photoelectron Spectroscopy. We propose that selective destruction of the weakest bonds (p bonds) in the polymer by the Ar þ ion beam results in a net excess of the remaining p bonds. The anisotropy in these p bonds align liquid crystals parallel to the ion beam propagation direction.

The Clearing House, Jan 1, 1998

... (A California hip hop dance troupe called ... Yet, that stance also helps students to take mo... more ... (A California hip hop dance troupe called ... Yet, that stance also helps students to take more responsibil-ity for, and feel more ownership of, their learning. ... felt that a few of her students did not accept her attempts to bring the images, issues, and themes from hip hop culture into ...

International Orthopaedics, Jan 1, 2011

The purpose of this study was to compare the incidence of reinfection in patients who received or... more The purpose of this study was to compare the incidence of reinfection in patients who received oral antibiotic prophylaxis with those who did not following two-stage revision knee arthroplasty. Additional purposes included: (1) comparison of these findings to the infection rate in patients who underwent revision for aseptic reasons, and (2) characterisation of the organisms responsible for reinfection following revision procedures. Twenty-eight two-stage revision knee arthroplasty procedures were followed up by a mean of 33 days of oral antibiotics (range, 28-43 days), while the remaining 38 procedures received only 24-72 hours of in-patient antibiotics. The incidence of reinfection in each group within 12 months was compared. The reinfection rates were additionally compared to those of 237 patients who underwent revision for aseptic loosening over the same time period. Patients who were treated with postoperative antibiotic prophylaxis had a considerably lower reinfection rate, with one reinfection in the prophylaxis group (4%), compared to six reinfections in the no-prophylaxis group (16%). The reinfection rates remained higher compared to those found in patients who underwent revision knee arthroplasty for aseptic loosening (1 of 237 patients; 0.4%). Both high and low virulence organisms were identified in the patients who were subsequently reinfected. A minimum of 28 days of postoperative oral antibiotics appeared to decrease reinfection rates following two-stage revision knee arthroplasty. These results suggest that the use of oral antibiotic prophylaxis following re-implantation may be appropriate in all patients undergoing two-stage revision, even in the absence of any signs of active infection.

Chemical Engineering Journal, Jan 1, 2001

Deposition of carbon particles on plastic spheres was experimentally investigated. The effects of... more Deposition of carbon particles on plastic spheres was experimentally investigated. The effects of CaCl2 concentration, soap concentration and the mixing speed on the deposition rate and the equilibrium particle concentration were studied. The effect of the above parameters on the Langmuir model constants was also determined.In the absence of CaCl2, almost no deposition takes place. However, when CaCl2 was added, the deposition becomes very fast. A large equilibrium constant was obtained when the concentration of CaCl2 equals the stoichiometric amount necessary to react with the sodium stearate soap. On the other hand, when the concentration of CaCl2 was above the stoichiometric amount, both coagulation of carbon particles and deposition took place simultaneously. When the soap concentration was above the stoichiometric amount the deposition rate is slow. Further increase in the soap concentration has similar effect on the deposition rate.The effect of mixing speed on the deposition rate was examined. Mixing speeds of 100, 300 and 500 rpm were used. Results showed that the deposition rate increases as the mixing speed increases until a certain point is reached where it starts to decrease.

Talanta, Jan 1, 1988

A new spectrophotometric method for the determination of micro amounts of formaldehyde in aqueous... more A new spectrophotometric method for the determination of micro amounts of formaldehyde in aqueous and methanol solutions is based on the oxidation of formaldehyde by hydrous silver oxide at pH 11–12.5 and oxidation of the metallic silver produced, with iron(III) in the presence of Ferrozine. The absorbance of the resulting iron(II)—Ferrozine complex at 562 nm is proportional to the amount of formaldehyde and corresponds to an apparent molar absorptivity of 5.58 × 104 1.mole−1.cm−1.

Desalination and Water Treatment, Jan 1, 2011

The chlorine decay is usually described by the first order model (FOM) due to its easiness, altho... more The chlorine decay is usually described by the first order model (FOM) due to its easiness, although its weaknesses are well known. In this work, two better models, second order model (SOM) and parallel second order model (PSOM), are compared for their accuracy to predict chlorine residuals for a single dosing scenario. Results showed that SOM model provided a better prediction compared to FOM. However, SOM had two important shortcomings. Firstly, it overly predicted residuals in the lower end of chlorine decay curve, implying false sense of security in achieving secondary disinfection goals. Secondly, when higher initial dose was practiced, chlorine residual prediction was poorer. PSOM on the other hand provided the best fit for the experimental data in the initial as well as the later part of the decay curve for any doses. Compared to SOM which had two parameters, PSOM is more complex as it uses four parameters. Comparing to the advantages, complexity of PSOM is not an issue as EPANET-MSX can be used for full scale system simulation.

Journal of Separation Science, Jan 1, 2004

The dynamics of supercritical fluid extraction (SFE) of the metal content of wood fibers chelated... more The dynamics of supercritical fluid extraction (SFE) of the metal content of wood fibers chelated with lithium bis(trifluoroethyl) dithiocarbamate (FDDC) by supercritical (SF) CO2 was investigated experimentally by monitoring the spectra of the eluted metal complex as a function of time. The characteristic shape of the dynamic SFE curve was determined mainly by the flow conditions in the extraction vessel, the mass transfer resistance in the SF phase, and the solubility. High extraction yields of metal content were obtained in two-stage extraction including static (batch) and dynamic (semi-batch) stages. Increasing the length of the static stage increased the rate of dynamic elution of metal complex until it approached the dynamics of fluid displacement for a continuous stirred tank reactor (CSTR). In such cases, increasing the flow rate had no effect on the dynamic extraction curve when it was plotted using dimensionless time. Efficient chelation-SFE from wood fibers was obtained at a pressure of 20.3 MPa and with a static time of 30 min.

Human & Experimental Toxicology, Jan 1, 2008

Although aminoglycosides antibiotics are used in children and adult commonly, they have serious s... more Although aminoglycosides antibiotics are used in children and adult commonly, they have serious side effects such as nephrotoxicity and ototoxicity. In clinical practice, for renal function, the levels of serum creatinine and blood urea nitrogen routinely are measured. Since these parameters have limitations such as unreliability, insensitivity, and nonspecificity, the rapid assessment of renal function based on these patients is very important. Increase in N-acetyl-beta-D-glucosaminidase (NAG), a hydrolytic lysosomal enzyme, suggests proximal tubular cell damage. In this study, 32 children aged 2 months through 2 years, treated with gentamicin and amikacin for suspected infections at the pediatric ward of Alborz hospital from September 2006 to February 2007, were enrolled. Serum and fresh urine before and after drug infusion were obtained on the 1st, 3rd, and 5th days of antibiotic treatment. Serum urea and creatinine with urinary creatinine, albumin, NAG, lactate dehydrogenase (LDH) and alkaline phosphatase (AP) activity were then determined. A statistically significant increase in urinary NAG, LDH, and AP on 5th day was found compared with before gentamicin administration (P &amp;amp;amp;amp;amp;lt; 0.001, P &amp;amp;amp;amp;amp;lt; 0.01, P &amp;amp;amp;amp;amp;lt; 0.05, respectively). The urinary NAG activity may be a useful indicator of renal injury in children treated with aminoglycosides drugs compared with other routine clinical indicators.

Chemical Engineering Communications, Jan 1, 2002

Separation Science and Technology, Jan 1, 2002

Fullerenes Nanotubes and Carbon Nanostructures, Jan 1, 2010

... View all references) determination of optimal run; and (77. Jahanshahi, M., Raoof, J., Hajiza... more ... View all references) determination of optimal run; and (77. Jahanshahi, M., Raoof, J., Hajizadeh, S. and Jabari Seresht, R. Synthesis of ... ideal product will only respond to the operator&#x27;s signals and will be unaffected by random noise factors (eg, weather, temperature, humidity). ...

Talanta, Jan 1, 1987

Silver(I), copper(II) and nickel(II) can be reduced to the metallic state by formaldehyde at pH 1... more Silver(I), copper(II) and nickel(II) can be reduced to the metallic state by formaldehyde at pH 11, chromium(II) in 2.5M sulphuric acid, and borohydride at pH 5.5–6.0, respectively. Reoxidation of these metals with iron(III) in the presence of Ferrozine enables their determination at concentration below 1 μg/ml by measurement of the absorbance of the iron(II)—Ferrozine complex at 562 nm, with a precision better than 3%. The apparent molar absorptivities for silver, copper and nickel are 2.78 × 104, 5.56 × 104 and 5.58 × 104 l.mole−1.cm−1, respectively. The average thickness of silver films on glass surfaces can be determined in the way.

Journal of Separation Science, Jan 1, 2002

Journal of Experimental Nanoscience, Jan 1, 2009

Well graphitised nanocarbons including onion-like fullerenes and single- and multi-walled carbon ... more Well graphitised nanocarbons including onion-like fullerenes and single- and multi-walled carbon nanotubes (CNTs) were synthesised in high yield by automatic arc-discharge method in solution. This technique is considered a low-cost method since it does not require any expensive equipment. Herein, an arc discharge full automatic set-up was used for fabrication of CNTs which enables controlling of the gap between the

Advanced Materials, Jan 1, 2010

The user has requested enhancement of the downloaded file. Public reporting burden for this colle... more The user has requested enhancement of the downloaded file. Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. carbon nanotubes, polyaniline nanofibers or Si nanowires were irradiated using a photographic flash. [1-3]. In these studies, the high surface to volume ratio of the nanomaterials being flashed, coupled with the inability of the small structures to efficiently dissipate the absorbed energy, led to a rapid increase in temperature and subsequent ignition/welding of the materials. Although heating materials through the use of light energy is not a new phenomenon, achieving such a rapid and dramatic temperature change using only millisecond pulses of light demonstrates a tangible and technologically significant capability, unique to nanoscale materials.