Journal articles on the topic 'Conditions de charge variables'
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Wisawapipat, W., I. Kheoruenromne, A. Suddhiprakarn, and R. J. Gilkes. "Surface charge characteristics of variable charge soils in Thailand." Soil Research 48, no. 4 (2010): 337. http://dx.doi.org/10.1071/sr09151.
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Surface charge characteristics were investigated using a charge fingerprinting procedure for 90 samples from 32 profiles of highly weathered Oxisols and Ultisols derived from shale/limestone, basalt, granite, local alluvium, sedimentary, and metasedimentary rocks under tropical savanna and tropical monsoonal climates in Thailand. The charge fingerprints of 5 whole soils, after removal of organic matter and of kaolin and ion oxides from these soils, were also measured to clarify factors contributing to the variable charge behaviour. Phosphate sorption was determined and related to charge properties. Kaolin was the dominant mineral of the clay fraction with moderate amounts of goethite and hematite. Gibbsite was present in Oxisols formed on limestone and basalt under more humid conditions. All soils exhibited variable charge behaviour but the magnitude and rate of change in variable charge with pH varied greatly between Oxisols and Ultisols. Oxisols had higher amounts of variable charge than Ultisols, reflecting the differences in amounts of clay and extractable Fe and Al. Oxisols formed on basalt and limestone under more humid conditions had high values of anion exchange capacity (AEC) due to the contributions of goethite, gibbsite, and boehmite. The relationships of base cation exchange capacity (CECB) and AEC with pH were linear. Rates of change with pH of both negative and positive variable charge (Ac, Aa) were closely related to CEC, specific surface area (SSA), pH(NaF), and various forms of extractable Fe, Al, and Mn. The charge fingerprints of soil after removal of organic matter indicated that organic matter exerted a strong influence on both the magnitude of negative charge and rate of change with pH. Kaolin had permanent and variable charge, with SSA and crystal size (MCD001) being highly predictive of the rate of change in variable negative charge with pH. Iron oxide concentrates exhibited strongly pH-dependent charge and the mean coherently diffracting length (MCD110) of hematite was highly predictive of both the magnitude and rate of change in variable positive charge with pH. Charge coefficients (Ac, Ba) had highly significant (P = 0.005) positive relationships with Langmuir and Freundlich phosphate sorption maximum coefficients (Xm, k), indicating that the surfaces of amorphous, poorly ordered, and crystalline Fe and Al oxides are prime sites for both P sorption and variable charge.
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Juban, Rusty, and Lara Gardner. "To File or Not to File? How EEOC Claims Change with the Economy." Labor Studies Journal 45, no. 3 (January 6, 2020): 296–318. http://dx.doi.org/10.1177/0160449x19897403.
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Discrimination and sexual harassment are pervasive problems in today’s organizations. Traditionally, individual variables such as justice and power are used to study an employee’s response to discrimination or sexual harassment. In this study, we propose the use of economic variables (unemployment and economic health) to explain when an individual is more likely to make a discrimination or sexual harassment charge. Using monthly data from the U.S. Equal Employment Opportunity Commission on discrimination charges, we find there is strong evidence that U.S. economic conditions play an important role in the number and types of complaints filed.
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Shingne, Prasad S., Jeff Sterniak, Dennis N. Assanis, Claus Borgnakke, and Jason B. Martz. "Thermodynamic model for homogeneous charge compression ignition combustion with recompression valve events and direct injection: Part II—Combustion model and evaluation against transient experiments." International Journal of Engine Research 18, no. 7 (August 26, 2016): 677–700. http://dx.doi.org/10.1177/1468087416665052.
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This two-part article presents a combustion model for boosted and moderately stratified homogeneous charge compression ignition combustion for use in thermodynamic engine cycle simulations. The model consists of two parts: one an ignition model for the prediction of auto-ignition onset and the other an empirical combustion rate model. This article focuses on the development of the combustion model which is algebraic in form and is based on the key physical variables affecting the combustion process. The model is fit with experimental data collected from 290 discrete automotive homogeneous charge compression ignition operating conditions with moderate stratification resulting from both the direct injection and negative valve overlap valve events. Both the ignition model from part 1 and the combustion model from this article are implemented in GT-Power and validated against experimental homogeneous charge compression ignition data under steady-state and transient conditions. The ignition and combustion model are then exercised to identify the dominant variables affecting the homogeneous charge compression ignition and combustion processes. Sensitivity analysis reveals that ignition timing is primarily a function of the charge temperature, and that combustion duration is largely a function of ignition timing.
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Wohaib, Ameer Zuhair, and Nidhal Khazaal Maraie. "Variables affecting sulfasalazine - ion exchange resin complexation." Al Mustansiriyah Journal of Pharmaceutical Sciences 19, no. 4 (December 1, 2019): 140–50. http://dx.doi.org/10.32947/ajps.v19i4.645.
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The aim of this work is studying the effect of different variables on the loading of sulfasalazine on DEAE sephadex A 25 ion exchange resin as a carrier for systemic action. Different drug: resin complexes (resinate) of different ratios (2:1, 1:1, 1:2, 1:4, 1:6) were prepared, dionized distilled
water used to prepare sulfasalazine solution, and their entrapment efficiency was estimated through changing variable conditions including temperature of stirring, stirring time, stirring speed, pH. The best complex was formed using 1:6 drug: resin ratio prepared at 50 ºC, stirring speed 400 rpm for 120 minutes in deionized water (pH 7). The prepared complex gave 77.8% drug release within 15 minute and continued up to 97.613% within 75 minute upon exchanging the drug with ions of similar charge in the dissolution medium (phosphate buffer pH 7.4).
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Edström, K., and S. T. Glad. "Algorithmic, physically based mode initialization when simulating hybrid systems." Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering 216, no. 1 (February 1, 2002): 65–72. http://dx.doi.org/10.1243/0959651021541435.
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In the simulation of hybrid systems, discontinuities can appear at mode changes. An algorithm is presented that gives initial values for the continuous state variables in a new mode. The algorithm is based on a switched bond graph representation of the system, and it handles discontinuities introduced by a changed number of state variables at a mode change. The algorithm is obtained by integrating the bond graph relations over the mode change and assuming that the physical variables are bounded. This gives a relation between the variables before and after the mode change. It is proved here that the equations for the new initial conditions are solvable. The algorithm is related to a singular perturbation theory by replacing the discontinuity by a fast continuous change. The action is considered of a single switch and the corresponding continuous change, tuned by a single parameter. By letting this parameter tend to zero, the same initial state values are achieved as those derived by the presented algorithm. The algorithm is also related to physical principles such as charge conservation.
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Marchi, Giuliano, Cesar Crispim Vilar, George O’Connor, and Marx Leandro Naves Silva. "Surface Complexation Modeling in Variable Charge Soils: Charge Characterization by Potentiometric Titration." Revista Brasileira de Ciência do Solo 39, no. 5 (October 2015): 1387–94. http://dx.doi.org/10.1590/01000683rbcs20140528.
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ABSTRACT Intrinsic equilibrium constants of 17 representative Brazilian Oxisols were estimated from potentiometric titration measuring the adsorption of H+ and OH− on amphoteric surfaces in suspensions of varying ionic strength. Equilibrium constants were fitted to two surface complexation models: diffuse layer and constant capacitance. The former was fitted by calculating total site concentration from curve fitting estimates and pH-extrapolation of the intrinsic equilibrium constants to the PZNPC (hand calculation), considering one and two reactive sites, and by the FITEQL software. The latter was fitted only by FITEQL, with one reactive site. Soil chemical and physical properties were correlated to the intrinsic equilibrium constants. Both surface complexation models satisfactorily fit our experimental data, but for results at low ionic strength, optimization did not converge in FITEQL. Data were incorporated in Visual MINTEQ and they provide a modeling system that can predict protonation-dissociation reactions in the soil surface under changing environmental conditions.
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Liu, Wei, Zhirun Yuan, Changbin Mao, Qingxi Hou, and Kecheng Li. "Removal of hemicelluloses by NaOH pre-extraction from aspen chips prior to mechanical pulping." BioResources 6, no. 3 (July 28, 2011): 3469–80. http://dx.doi.org/10.15376/biores.6.3.3469-3480.
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chips prior to mechanical pulping, which would offer new feedstocks for the production of chemicals and fuels. The aim of this study was to evaluate pre-extraction to maximize pre-extraction yield, while minimizing negative impacts on wood chips. The effects of three independent process variables (NaOH charge, pre-extraction temperature, and time) on three dependent variables (pre-extraction yield, xylan extraction yield, and cellulose content based on original wood) were studied using a Box-Behnken experimental design. The mathematical models were obtained and validated well. It was found that NaOH charge, time, interaction between NaOH charge and time, and interaction between temperature and time have significant effects on xylan extraction yield. The xylan extraction yield was 22.55%; i.e., about 37.3 kg of xylan could be extracted from one ton of oven-dried aspen chips under the conditions of 5.68% NaOH charge, 100 °C, and 35 min.
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Robertson, Kevin, Raynald Gauvin, and James Finch. "Charge Contrast Imaging of Gibbsite Using the Variable Pressure SEM." Microscopy and Microanalysis 10, no. 6 (December 2004): 721–32. http://dx.doi.org/10.1017/s1431927604040590.
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The variable pressure scanning electron microscope (VP-SEM) allows imaging of insulators without the need for a conductive coating, due to charge neutralization at the surface from recombination of positive ions and surface electrons. Varying certain parameters such as pressure, bias, and working distance creates incomplete neutralization, and localized charging develops called charge contrast. Although the exact mechanism creating charge contrast imaging (CCI) is unknown, it is agreed that it is related to an optimum charge compensation. The behavior of the CCI is still vague, which presents a problem for determining the mechanisms. This article provides user-friendly methods of finding the optimum levels of charge contrast in the VP-SEM. We show that the CCI is obtained at optimum operating conditions where the specimen current is between 2.5 nA and 3.5 nA. The specimen current is a function of secondary electrons (SE) emission and ionization potential, producing an ion flux. Therefore an optimum specimen current represents the balanced conditions of SE emission and ion flux. Controlling the pressure, working distance, bias, scan rate, and beam current allows the microscopist to set the specimen current at this optimum level for charge contrast imaging. All the work was performed on gibbsite using the S3000N VP-SEM from Hitachi.
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Suárez-Carreño, Franyelit, and Luis Rosales-Romero. "Anisotropy Induced by Electric Charge: A Computational Analytical Approach." Physics 6, no. 2 (May 16, 2024): 780–92. http://dx.doi.org/10.3390/physics6020048.
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This paper presents a novel class of interior solutions for anisotropic stars under the imposition of a self-similar symmetry. This means proposing exact solutions to the Einstein field equations to describe charged matter distribution with radiation flow. The Einstein–Maxwell system by employing specific choices of mass function is formulated to describe the gravitational collapse of charged, anisotropic, spherically symmetric distributions using the Schwarzschild metric. Two ordinary differential equations governing the dynamics are derived by matching a straightforward solution of the symmetry equations to the charged exterior (Reissner–Nordström–Vaidya). Models with satisfactory physical behavior are constructed by extensively exploring self-similar solutions for a set of parameters and initial conditions. Finally, the paper presents the evolution of physical variables and the collapsing radius, demonstrating the inevitable collapse of the matter distribution.
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Osmolovskii, Nikolai P., Meizhi Qian, and Jan Sokołowski. "Network optimality conditions." Control and Cybernetics 52, no. 2 (June 1, 2023): 129–80. http://dx.doi.org/10.2478/candc-2023-0035.
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Abstract Optimality conditions for optimal control problems arising in network modeling are discussed. We confine ourselves to the steady state network models. Therefore, we consider only control systems described by ordinary differential equations. First, we derive optimality conditions for the nonlinear problem for a single beam. These conditions are formulated in terms of the local Pontryagin maximum principle and the matrix Riccati equation. Then, the optimality conditions for the control problem for networks posed on an arbitrary planar graph are discussed. This problem has a set of independent variables x i varying within their intervals [0, l i], associated with the corresponding beams at network edges. The lengths l i of intervals are not specified and must be determined. So, the optimization problem is non-standard, it is a combination of control and design of networks. However, using a linear change of the independent variables, it can be reduced to a standard one, and we show this. Two simple numerical examples for the single-beam problem are considered.
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Feng, X. H., P. L. Dubin, H. W. Zhang, G. F. Kirton, P. Bahadur, and J. Parotte. "Critical Conditions for Binding of Dimethyldodecylamine Oxide Micelles to Polyanions of Variable Charge Density." Macromolecules 34, no. 18 (August 2001): 6373–79. http://dx.doi.org/10.1021/ma010304l.
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Liutsko, Liudmila, Jose Maria Tous, and Sergi Segura. "The Effects of dual task (fine motor precision + cognitive charge) on proprioception." Journal of Education Culture and Society 5, no. 1 (January 6, 2020): 79–86. http://dx.doi.org/10.15503/jecs20141.79.86.
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The aim of the given preliminary study was to check whether any changes in fi ne motor behaviour exist in switching from single to double task (with cognition charge) in proprioceptive sensory graphomotor test conditions. Ten students (fi ve males and fi ve females), aged from 20 to 30 years old, took part in the experiment - precision of tracking of the models in both experimental test conditions: without and with cognitive task (counting numbers back). The variables for assessment were obtained with use of the digitalized proprioceptive diagnostics (Tous, 2008; Tous, J.M., Muiños, Tous, O., & Tous J, 2012) of Mira y Lopez laboratory (University of Barcelona) that transformed the measurements of drawn lines on a touch screen from pixels into millimetres. As results showed, in the proprioceptive test condition, the changes in deviations related to spatial (lineograms) or line length variability (parallels) did not reach any statistical signifi cance; while the changes in line length performance (lineograms) were found signifi cant (that corresponds to inhibition- -excitatory balance of nervous system).
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Liu, Shan Shan, Gui Gan Fang, Yong Jun Deng, and Qiang Wang. "Sulfonated Chemi-Mechanical Pulp of Cotton Stalk and Bleaching." Advanced Materials Research 291-294 (July 2011): 1887–91. http://dx.doi.org/10.4028/www.scientific.net/amr.291-294.1887.
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The influence of operational variables in the Sulfonated Chemi-mechanical pulp (SCMP) of cotton stalk was studied, and the hydrogen peroxide bleaching sequence was carried out. The major factors, such as sulfite sodium charge (calculated as Na2SO33%, 6%, 9%or 12%on oven-dry cotton stalk), active alkali charge (calculated as NaOH 2%, 4%, 6%or 8%on oven-dry cotton stalk) and the maximum temperature (110°C, 130°C or 150°C) was investigated. The result shows that: the pulp physical property was influenced significantly by sulfite sodium and active alkali charge, at an increasing tendency with above factors. The optimal chemical treatment cooking conditions could be proposed as follows: sulfite sodium charge 9%, active alkali charge 2%, maximum temperature 130°C and liquor ratio 4:1. What’s more, the single H2O2bleaching sequence was employed, which can provide pulps with brightness 58.0%ISO.
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Li, Zilong, Yaoyuan Zhang, Guan Huang, Wenbin Zhao, Zhuoyao He, Yong Qian, and Xingcai Lu. "Control of intake boundary conditions for enabling clean combustion in variable engine conditions under intelligent charge compression ignition (ICCI) mode." Applied Energy 274 (September 2020): 115297. http://dx.doi.org/10.1016/j.apenergy.2020.115297.
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Trubitsyn, K. V., T. E. Gavrilova, E. V. Kotova, K. V. Kolotilkina, S. V. Zaitsev, and V. A. Kudinov. "Additional boundary conditions in heat conduction problems with coordinate variable initial condition." Vestnik IGEU, no. 6 (December 28, 2023): 88–94. http://dx.doi.org/10.17588/2072-2672.2023.6.088-094.
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It is exceedingly difficult to obtain mathematically accurate analytical solutions of heat conduction problems with a variable initial condition. Known solutions of these problems are expressed by cumbersome functional series that converge poorly in the range of small values of time and space variables. Thus, to obtain simpler and more effective solutions of these problems is an urgent issue. The authors have used an additional required function and additional boundary conditions to obtain solutions of the problem. Application of the additional required function allows us to reduce the original partial differential equation to the integration of an ordinary differential equation. Additional boundary conditions are in such a form that their fulfillment using the resulting solution is equivalent to the fulfillment of the equation at the boundary points. The authors have developed a technique to obtain an analytical solution of the heat conduction problem under a linear change of the initial condition, based on an additional required function and additional boundary conditions. Solution of an ordinary differential equation with respect to the additional required function determines the eigenvalues. In classical methods these eigenvalues are found in the solution of the Sturm–Liouville boundary value problem. The authors have proposed another, simpler solution to determine eigenvalues. An accurate analytical solution of the heat conduction problem for an unbounded plate with a coordinate-variable initial condition is obtained. The scientific and practical value of the proposed analytical solution is the development of an innovative approach to determine eigenvalues, as well as elimination of complex integrals when we solve the equation and initial conditions of the boundary value problem. It makes possible to simplify the use of the solution obtained in engineering applications.
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Miličević, Ante. "Estimating flavonoid oxidation potentials: mechanisms and charge-related regression models." Archives of Industrial Hygiene and Toxicology 74, no. 2 (June 1, 2023): 99–105. http://dx.doi.org/10.2478/aiht-2023-74-3721.
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Abstract In this paper, I tested our quadratic regression models for the estimation of flavonoid oxidation potentials based on spin populations, the differences in the net atomic charges between a cation and a neutral flavonoid, between a radical and an anion of a flavonoid, and between a radical and a neutral flavonoid on a larger set of flavonoids (N = 35). By including six new flavonoids (5,6,7-trihydroxyflavone, 3,3’,4’,7-tetrahydroxyflavone, 3,7-dihydroxyflavone, 4’,7-dihydroxyflavone, 4’,5,7-trihydroxyisoflavone, and 6-hydroxyflavone), we created a respectable calibration set of 35 flavonoids with their oxidation potentials all measured at the same conditions by the same experimentalist. The best model was based on the mean values of the three variables using differences in the net atomic charges (R 2 = 0.970, S.E. = 0.043), which are connected with the three different mechanisms of electrochemical oxidation, SET-PT, SPLET, and HAT.
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Mahmoud, Tariq Y., Sarmad B. Dikran, and Alaa K. Mohammed. "Spectrophotometric Determination of Sulfamethoxazole Based on Charge-Transfer Complexation with Sodium Nitroprusside." Ibn AL- Haitham Journal For Pure and Applied Science 30, no. 3 (December 28, 2017): 102. http://dx.doi.org/10.30526/30.3.1606.
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A simple, accurate and precise spectrophotometric method has been developed for the analysis of sulfamethoxazole (SMZ) in pure form and pharmaceutical preparation. The method involves a direct charge transfer complexation of sulfamethoxazole (SMZ) with sodium nitroprusside (SNP) in alkaline medium and the presence of hydroxyl amine hydrochloride. Variables affecting the formation of the formed orange colored complex were optimized following two approaches univariate and central composite experimental design (CCD) multivariate. Under optimum recommended conditions, the formed complex exhibits λmax at 512 nm and the method conforms Beer's law for SMZ concentration in the range of 5.0-150.0 (µg.mL-1) with molar absorptivity 1.139×103 L.mol-1.cm-1, and r = 0.9997. Analysis of SMZ pharmaceutical dosages shows a good agreement with the real amounts.
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Zarnoch, S. J., W. A. Bechtold, and K. W. Stolte. "Using crown condition variables as indicators of forest health." Canadian Journal of Forest Research 34, no. 5 (May 1, 2004): 1057–70. http://dx.doi.org/10.1139/x03-277.
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Indicators of forest health used in previous studies have focused on crown variables analyzed individually at the tree level by summarizing over all species. This approach has the virtue of simplicity but does not account for the three-dimensional attributes of a tree crown, the multivariate nature of the crown variables, or variability among species. To alleviate these difficulties, we define composite crown indicators based on geometric principles to better quantify the entire tree crown. These include crown volume, crown surface area, and crown production efficiency. These indicators were then standardized to a mean of 0 and variance of 1 to enable direct comparison among species. Residualized indicators, which can also be standardized, were defined as the deviation from a regression model that adjusted for tree and plot conditions. Distributional properties were examined for the three composite crown indicators and their standardized-residualized counterparts for 6167 trees from 250 permanent plots distributed across Virginia, Georgia, and Alabama. Comparisons between the composite crown indicators and their associated standardized residual indicators revealed that only two or three plots were jointly classified as poor by both when thresholds were set at the lower 5 percentiles of statistical distributions. In contrast, 19-21 other plots were classified differently, emphasizing that different aspects of crown condition are being summarized when the raw values are adjusted and standardized. Generally, crown volume and crown surface area behaved similarly, while crown production efficiency was substantially different.
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Donnelly, Thomas W. "High-Energy Lepton Scattering and Nuclear Structure Issues." Universe 9, no. 4 (April 20, 2023): 196. http://dx.doi.org/10.3390/universe9040196.
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High-energy lepton scattering constitutes the focus of this study. Developments are provided to motivate the basic choices of kinematic variables for the particular case of semi-inclusive electron scattering where these variables are devised to match well with the underlying dynamics to be expected for the general “nuclear landscape”. Various nuclear structure issues and other issues related to the nature of the electroweak currents at high energies are then discussed, as are some of the issues related to the different conditions occurring for electron scattering versus what is typically the case for charge-changing neutrino reactions.
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Sahoo, Satyabrata, and M. Ramgopal. "Theoretical performance of an adsorbed natural gas storage system subjected to variable charge–discharge conditions." International Journal of Ambient Energy 37, no. 4 (November 14, 2014): 372–83. http://dx.doi.org/10.1080/01430750.2014.977495.
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Gomes, Tânia P., Vera L. D. Costa, Álvaro F. C. Vaz, and Rogério M. S. Simões. "Fractionation of broom (Cytisus striatus) biomass components via mild sulfite pretreatment and enzymatic hydrolysis." BioResources 16, no. 1 (November 9, 2020): 118–40. http://dx.doi.org/10.15376/biores.16.1.118-140.
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The potential of broom biomass to produce oligo- and monosaccharides was investigated using mild sulfite pretreatment conditions followed by enzymatic hydrolysis. Both treatments were analyzed via response surface methodology using an experimental central composite rotatable design 24 + star, which explored the following variables: sulfuric acid charge (0% to 3%), sodium sulfite charge (0% to 4%, maximum temperature (150 °C to 190 °C), and time at maximum temperature (0 min to 30 min). Oligo- and monosaccharides in the pretreatment hydrolysates were determined using high performance liquid chromatography. The amount of total extracted xylose, mannose, and galactose ranged from 3.5% to 15.8% of the initial biomass, while the model estimated optimal reaction conditions enabled the extraction of practically all hemicellulose in the raw material. However, the mildest pretreatment reaction conditions, with low temperature and low sulfuric acid charges, provided a hydrolysate where a major part of the extracted polysaccharides remained in oligomer form, enabling their separation by filtration. The cellulose-rich solid residue was submitted to enzymatic hydrolysis using a Novozymes® enzymatic cocktail. The enzymatic hydrolysis was successful, but some polysaccharides remained in the solid residue, mainly composed of lignin. An enzymatic yield of 60% was attained with no added sulfite in the pretreatment at 190 °C, despite the confirmed positive role of sulfur content in the solid residues.
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Bukala, Julia, Prabhusrinivas Yavvari, Jacek Walkowiak, Matthias Ballauff, and Marie Weinhart. "Interaction of Linear Polyelectrolytes with Proteins: Role of Specific Charge–Charge Interaction and Ionic Strength." Biomolecules 11, no. 9 (September 17, 2021): 1377. http://dx.doi.org/10.3390/biom11091377.
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We present a thermodynamic study of the interaction of synthetic, linear polyelectrolytes with bovine serum albumin (BSA). All polyelectrolytes are based on poly(allyl glycidyl ether) which has been modified by polymer-analogous reaction with anionic (-SO3Na), cationic (-NH3Cl or -NHMe2Cl) or zwitterionic groups (-NMe2(CH2)3SO3). While the anionic polymer shows a very weak interaction, the zwitterionic polymer exhibits no interaction with BSA (pI = 4.7) under the applied pH = 7.4, ionic strength (I = 23–80 mM) and temperature conditions (T = 20–37 °C). A strong binding, however, was observed for the polycations bearing primary amino or tertiary dimethyl amino groups, which could be analysed in detail by isothermal titration calorimetry (ITC). The analysis was done using an expression which describes the free energy of binding, ΔGb, as the function of the two decisive variables, temperature, T, and salt concentration, cs. The underlying model splits ΔGb into a term related to counterion release and a term related to water release. While the number of released counter ions is similar for both systems, the release of bound water is more important for the primary amine compared to the tertiary N,N-dimethyl amine presenting polymer. This finding is further traced back to a closer contact of the polymers’ protonated primary amino groups in the complex with oppositely charged moieties of BSA as compared to the bulkier protonated tertiary amine groups. We thus present an investigation that quantifies both driving forces for electrostatic binding, namely counterion release and change of hydration, which contribute to a deeper understanding with direct impact on future advancements in the biomedical field.
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Mahmoud, Basant Salah, and Christopher McConville. "Box–Behnken Design of Experiments of Polycaprolactone Nanoparticles Loaded with Irinotecan Hydrochloride." Pharmaceutics 15, no. 4 (April 18, 2023): 1271. http://dx.doi.org/10.3390/pharmaceutics15041271.
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Background: The Box–Behnken design of experiments (BBD) is a statistical modelling technique that allows the determination of the significant factors in developing nanoparticles (NPs) using a limited number of runs. It also allows the prediction of the best levels of variables to obtain the desired characteristics (size, charge, and encapsulation efficiency) of the NPs. The aim of this study was to examine the effect of the independent variables (amount of polymer and drug, and surfactant concentration) and their interaction on the characteristics of the irinotecan hydrochloride (IRH)-loaded polycaprolactone (PCL) NPs and to determine the most optimum conditions for producing the desired NPs. Methods: The development of the NPs was carried out by a double emulsion solvent evaporation technique with yield enhancement. The NPs data were fitted in Minitab software to obtain the best fit model. Results: By using BBD, the most optimum conditions for producing the smallest size, highest magnitude of charge, and highest EE% of PCL NPs were predicted to be achieved by using 61.02 mg PCL, 9 mg IRH, and 4.82% PVA, which would yield 203.01 nm, −15.81 mV, and 82.35% EE. Conclusion: The analysis by BBD highlighted that the model was a good fit to the data, confirming the suitability of the design of the experiments.
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Iumsrivun, Chonthicha, Kazuki Matsuda, Shunsaku Ohkubo, and Yuya Ishii. "Variable Direct Electromechanical Properties of As-Electrospun Polystyrene Microfiber Mats with Different Electrospinning Conditions." Polymers 14, no. 9 (April 29, 2022): 1840. http://dx.doi.org/10.3390/polym14091840.
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As-electrospun microfiber mats comprising atactic polystyrene (aPS), a low-cost commodity polymer, have demonstrated beneficial electromechanical properties. However, the variability of the electromechanical properties of fiber mats produced using different electrospinning conditions has not been investigated. Therefore, herein, the direct electromechanical properties of aPS fiber mats produced using different deposition times (tdep) and electrospinning voltages (VES) are investigated. The resulting apparent piezoelectric d constant (dapp) of the fiber mats demonstrates a specific peak value for tdep as high as ~1600 pC N−1 under 1-kPa pressure application after ~0.2-kPa pre-pressure application, although the dapp of the fiber mats produced with some conditions is nearly zero pC·N−1. Furthermore, the peak position of dapp with tdep is fundamentally determined with σEff0/YD(h-hpre) [σEff0: effective surface charge density, YD(h-hpre): secant modulus of elasticity]. Charge distribution models for fiber mats with different tdep are established. The models explain the characteristics of the significant changes in YD(h-hpre) and σEff0 with tdep. These findings provide significant directions for the production of fiber mats with improved direct electromechanical properties.
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Salem, Hesham. "Analytical Study for the Charge-Transfer Complexes of Pregabalin." E-Journal of Chemistry 6, no. 2 (2009): 332–40. http://dx.doi.org/10.1155/2009/194653.
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Studies were carried out, for the first time, to investigate the charge-transfer reactions of Pregabalin (PRE) asn-electron donor with various π-acceptors: 7,7,8,8-tetracyanoquinodimethane (TCNQ), 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (chloranilic acid,pCA), tetracyanoethylene (TCNE) and 2,3,5,6-tetrachloro-1,4-benzoquinone (chloranil). Different colored charge-transfer complexes and radical anions were obtained. Different variables affecting the reactions were studied and optimized. The formations of the colored complexes were utilized in the development of simple, rapid and accurate spectrophotometric methods for the analysis of PRE in pure form as well as in its pharmaceutical preparation. Under the optimum reaction conditions, linear relationships with good correlation coefficients (0.9995-0.9999) were found between the absorbance and the concentrations of PRE in the range of 8-400 µg mL-1. The limits of assays detection ranged from 0.60 to 8.11 µg mL-1. No interference could be observed from the additives commonly present in the capsules. The methods were successfully applied to the analysis of capsules that contain PRE, with good accuracy and precision; the recovery percentages ranged from 100.19±0.83 to 100.50±0.53. The results were compared favorably with the reported method.
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Valencia, Fausto, and Hugo Arcos. "Method of Images for a Charge inside a Three-Layer Medium and Implementation of a Dirichlet Border Condition." Revista Politécnica 44, no. 2 (January 31, 2020): 7–14. http://dx.doi.org/10.33333/rp.vol44n2.01.
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A process to apply the method of images for a charge located in a three-layer medium is presented. The images are found according to the boundary conditions between the layers for the electric field. The characteristics of the electric potential are also considered, thus the number of unknown variables becomesa guide to set the image charges needed to solve the problem. The results are compared with finite element simulations through the use of the software FEMM 4.2, showing good agreement. The found limitations of the process are also noted, mainly in regards to the dependence of the images on the coordinates where the field is to be calculated. The model obtained was applied to different cases, where it was seen that it was not limited to three material media only. Finally, the null potential boundary condition was applied, showing how the method of images could be applied to this type of problems.
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Bodian, Ansoumana, Lamine Diop, Geremy Panthou, Honoré Dacosta, Abdoulaye Deme, Alain Dezetter, Pape Malick Ndiaye, Ibrahima Diouf, and Théo Vischel. "Recent Trend in Hydroclimatic Conditions in the Senegal River Basin." Water 12, no. 2 (February 6, 2020): 436. http://dx.doi.org/10.3390/w12020436.
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Analyzing trends of annual rainfall and assessing the impacts of these trends on the hydrological regime are crucial in the context of climate change and increasing water use. This research investigates the recent trend of hydroclimatic variables in the Senegal River basin based on 36 rain gauge stations and three hydrometric stations not influenced by hydraulic structures. The Man Kendall and Pettitt’s tests were applied for the annual rainfall time series from 1940 to 2013 to detect the shift and the general trend of the annual rainfall. In addition, trends of average annual flow rate (AAFR), maximum daily flow (MADF), and low flow rate (LFR) were evaluated before and after annual rainfall shift. The results show that the first shift is situated on average at 1969 whereas the second one is at 1994. While the first shift is very consistent between stations (between 1966 and 1972), there is a significant dispersion of the second change-point between 1984 and 2002. After the second shift (1994), an increase of annual rainfall is noticed compared to the previous period (1969–1994) which indicates a not significant, partial rainfall recovery at the basin level. The relative changes of hydrologic variables differ based on the variables and the sub-basin. Relative changes before and after first change-point are significantly negative for all variables. The highest relative changes are observed for the AAFR. Considering the periods before and second shifts, the relative changes are mainly significantly positive except for the LFR.
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Ayoub, Bassam M., Ramzia I. El-Bagary, and Ehab F. Elkady. "Spectrophotometric Methods Based on Charge Transfer ComplexationReactions for the Determination of Saxagliptin in Bulk and Pharmaceutical Preparation." International Journal of Biomedical Science 8, no. 3 (September 15, 2012): 204–8. http://dx.doi.org/10.59566/ijbs.2012.8204.
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Simple, accurate and precise spectrophotometric methods have been developed for the determination of saxagliptin in bulk and dosage forms.The proposed methods are based on the charge transfer complexes of saxagliptin with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and7,7,8,8-tetracyanoquinodimethane (TCNQ). All the variables were studied to optimize the reactions' conditions. Beer's law was obeyed in the concentration ranges of 50-300 μg/ml and 10- 110 μg/ml with DDQ and TCNQ, respectively.The developed methods werevalidated and proved to be precise and accurate for the quality control of the saxagliptinin its pharmaceutical dosage form.
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Lozito, Gabriele Maria, Valentina Lucaferri, Francesco Riganti Fulginei, and Alessandro Salvini. "Improvement of an Equivalent Circuit Model for Li-Ion Batteries Operating at Variable Discharge Conditions." Electronics 9, no. 1 (January 1, 2020): 78. http://dx.doi.org/10.3390/electronics9010078.
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A real time simulation of battery conditions is an essential step in the development of energy harvesting devices. Since it is not possible to have a direct measurement, the battery information, such as the remaining charge, need to be estimated by means of model-based estimation algorithms. Most of the existing models describing battery behaviour, are suitable only for a constant discharge current. This paper proposes a study of the dependence of the equivalent circuit model parameters on different discharge conditions. The model presented provides a powerful tool to represent the batteries’ behaviour in energy harvesting systems, involving continuous charge and discharge cycles. The extraction of parameters was performed, starting from a set of reference curves generated in Matlab Simulink environment, referring to Li-ion technology batteries. The parameters were extracted by means of a cascade of global and local search identification algorithms. Finally, the relations describing parameters’ behaviours as functions of the discharge current are presented.
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Sparks, Darrell. "A Climatic Model for Pecan Production under Humid Conditions." Journal of the American Society for Horticultural Science 121, no. 5 (September 1996): 908–14. http://dx.doi.org/10.21273/jashs.121.5.908.
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A multiple regression model was developed from historical data, 1945-92, to predict pecan [Carya illinoensis (Wangenh.) C. Koch] production in a humid climate. Variables were production trend (year of production), previous year's production, and climatic indices for the previous and current year. Production trend was used to measure change in production with time. Previous year's production was the index of alternate bearing. Variables for previous year's climate were heating degree-days for April-October and cumulative rainfall during May-July and 1-15 Sept. Variables for current year's climate were cumulative rainfall during April-August and 1-15 Sept. The indicator used for scab [Cladosporium caryigenum (Ell. & Langl.) Gottwald] infection was the highest cumulative sum of 2 or more days of consecutive rain occurring in May, June, or 1-15 July. The R2 for the model was 0.908. Production trend was the most important factor influencing production during the 1945-92 study period. Importance of the other variables in decreasing order were previous year's rainfall in May-July, consecutive rainy days, previous year's production, current year's 1-15 Sept. rainfall, previous year's heating degree-days, previous year's rainfall for 1-15 Sept., and current year's rainfall during April-August. Previous year's conditions had a greater effect on production than current year's. The recent decline in pecan production in the southeastern United States is due to an unfavorable change in climate.
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Satrapová, J., T. Hyvönen, V. Venclová, and J. Soukup. "Growth and reproductive characteristics of C4 weeds under climatic conditions of the Czech Republic ." Plant, Soil and Environment 59, No. 7 (June 26, 2013): 309–15. http://dx.doi.org/10.17221/77/2013-pse.
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Climate change could promote the altitudinal spread of C4 weed species since they can benefit from warmer climate. The effects of altitude and climatic conditions (the sum of temperatures above 5°C and precipitation) on the biomass and seed production of two annual C4 weeds – Amaranthus retroflexus L. and Echinochloa crus-galli (L.) P.<br />Beauv. – were studied in the Czech Republic. We included both temperature and precipitation variables in the study since they both serve as basic indicators of climate change and thus they have the greatest impact on plant development. The experiment was carried out by sowing both weed species on m<sup>2</sup> area with four replicates in seven localities differing in altitude in 2010 and 2011. We found no significant impacts due to altitude on any variables measured. However, climatic factors explained 44.5% of the variation in plant dry biomass and 41.4% of the seed number produced by A. retroflexus. The same variables did not significantly contribute to the variation in above-ground biomass or seed number of E. crus-galli. These results show the impact of climate conditions to vary between species and not to limit reproduction at high altitudes.
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Gilbert, Yan, Yann Le Bihan, Gerardo Buelna, and Paul Lessard. "Application de la respirométrie pour le suivi de l'activité de la biomasse d'un biofiltre sur lit organique traitant du lisier de porc." Water Quality Research Journal 40, no. 2 (May 1, 2005): 155–63. http://dx.doi.org/10.2166/wqrj.2005.018.
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Abstract L'opération de systèmes de biofiltration à support organique nécessite le développement de méthodes de suivi simples et rapides La respirométrie de type LSS a donc été adaptée afin d'évaluer l'activité potentielle des organismes hétérotrophes présents dans le biofiltre. Des essais respirométriques ont été réalisés à différentes concentrations de milieu filtrant afin d'adapter la méthode à cette biomasse, fixée sur le support. Des colonnes de biofiltration de laboratoire ont été montées et alimentées à des charges hydrauliques et massiques variables et à des durées de fonctionnement différentes afin d'évaluer l'activité hétérotrophe à divers degrés de colonisation. Même après 60 jours d'opération des biofiltres, pour différentes conditions d'opération, la colonisation du milieu filtrant est toujours en accroissement et le suivi respirométrique reflète une colonisation du milieu filtrant lente dans le temps. L'activité des microorganismes a pu être mise en relation avec la quantité de matière organique cumulée dans le biofiltre. Les relations obtenues démontrent que la charge organique et la charge hydraulique ont une influence importante sur l'activité de la biomasse.
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Lozano Avilés, Ana Belén, Francisco del Cerro Velázquez, and Mercedes Llorens Pascual del Riquelme. "Methodology for Energy Optimization in Wastewater Treatment Plants. Phase I: Control of the Best Operating Conditions." Sustainability 11, no. 14 (July 18, 2019): 3919. http://dx.doi.org/10.3390/su11143919.
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Most purification systems work correctly from the point of view of water quality; purification, like any industrial process, must also be carried out efficiently with a minimization of costs. The overall project examined the potential benefits of using a recommended methodology for process evaluation and energy optimization in the aeration stage of activated sludge in the biological reactor at wastewater treatment plants (WWTP), which accounts for more than 44% of total operating costs. This energy control methodology encompasses the process, the installation and the control system. These three phases are examined in separate articles to make it easier to guide the user in the arduous task of optimizing energy efficiency of the WWTP from start to finish. This article focuses on Phase I of the methodology, the stage in charge of selecting the correct variables to control the best process conditions in the activated sludge system of the WWTP. Operating conditions that are a function of the recommended sludge age are influenced by exogenous factors such as temperature. The implementation of a real-time control system of the selected process variables, adapted to the needs, achieves reductions in the overall energy consumption of the installation, in this phase alone, of more than 15%, by reducing the oxygen requirements of the system and the recirculation ratios.
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Hambrouck, Micheline, Georges Thinès, and Michel Michiels. "Modal Completion: Critical Variables in Apparent Transparency." Perception 16, no. 6 (December 1987): 719–30. http://dx.doi.org/10.1068/p160719.
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Conditions for perceptual modal completion are investigated using a stimulation pattern consisting of a figure moving behind a black opaque strip. This configuration leads, depending on conditions, either to the amodal Michotte tunnel effect, or to modal completion, ie the apparent transparency phenomenon. Four experiments are reported in which an attempt was made to define the critical variables of this latter effect. The results show that modal completion is not typically related to luminance interactions, ie to assimilation, but depends on the figural dominance of the filled-in object, this being determined by structural factors such as figure–ground relationship and stimulation change. The effect also depends strongly on the complexity of the spatiotemporal integration needed to maintain phenomenal identity of the object. No significant effect was found for the two other variables investigated, ie formal complexity of the figure and depth between the figure and the strip. The data are discussed in relation to those on moving visual phantoms.
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Marchi, Giuliano, Cesar Crispim Vilar, George O’Connor, Letuzia Maria de Oliveira, Adriana Reatto, and Thomaz Adolph Rein. "Surface Complexation Modeling in Variable Charge Soils: Prediction of Cadmium Adsorption." Revista Brasileira de Ciência do Solo 39, no. 5 (October 2015): 1395–405. http://dx.doi.org/10.1590/01000683rbcs20140529.
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ABSTRACT Intrinsic equilibrium constants for 22 representative Brazilian Oxisols were estimated from a cadmium adsorption experiment. Equilibrium constants were fitted to two surface complexation models: diffuse layer and constant capacitance. Intrinsic equilibrium constants were optimized by FITEQL and by hand calculation using Visual MINTEQ in sweep mode, and Excel spreadsheets. Data from both models were incorporated into Visual MINTEQ. Constants estimated by FITEQL and incorporated in Visual MINTEQ software failed to predict observed data accurately. However, FITEQL raw output data rendered good results when predicted values were directly compared with observed values, instead of incorporating the estimated constants into Visual MINTEQ. Intrinsic equilibrium constants optimized by hand calculation and incorporated in Visual MINTEQ reliably predicted Cd adsorption reactions on soil surfaces under changing environmental conditions.
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Hu, Chunsheng, Fangjuan Cheng, Liang Ma, and Bohao Li. "State of Charge Estimation for Lithium-Ion Batteries Based on TCN-LSTM Neural Networks." Journal of The Electrochemical Society 169, no. 3 (March 1, 2022): 030544. http://dx.doi.org/10.1149/1945-7111/ac5cf2.
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Accurately estimating the state of charge (SOC) of lithium-ion batteries is critical for developing more reliable and efficient operation of electric vehicles. However, the commonly used models cannot simultaneously extract effective spatial and temporal features from the original data, leading to an inefficient SOC estimation. This paper proposes a novel neural network method for accurate and robust battery SOC estimation, which incorporates the temporal convolutional network (TCN) and the long short-term memory (LSTM), namely TCN-LSTM model. Specifically, the TCN is employed to extract more advanced spatial features among multivariate variables, and the LSTM captures long-term dependencies from time-series data and maps battery temporal information into current SOC and historical inputs. The proposed model performs well in various estimation conditions. The average value of mean absolute error, root mean square error, and maximum error of SOC estimation achieve 0.48%, 0.60%, and 2.3% at multiple temperature conditions, respectively, and reach 0.70%, 0.81%, and 2.7% for a different battery, respectively. In addition, the proposed method has better accuracy than the LSTM or TCN used independently and the CNN-LSTM network. The computational burden with varying length of input is also investigated. In summary, experiment results show that the proposed method has excellent generalization and robustness.
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Abella, Scott R., and Charles W. Denton. "Spatial variation in reference conditions: historical tree density and pattern on a Pinus ponderosa landscape." Canadian Journal of Forest Research 39, no. 12 (December 2009): 2391–403. http://dx.doi.org/10.1139/x09-146.
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The reference conditions of historical tree density and pattern underpin ecological restoration and management of Pinus ponderosa Douglas ex Lawson & C.Lawson forests in western North America, yet the potential spatial variation in these variables across the landscape remains unclear. We reconstructed historical (1880) tree density and spatial pattern on 1 ha plots at 53 sites within a 110 000 ha P. ponderosa landscape in northern Arizona, compared these variables among US Forest Service ecosystem classification units, and modeled spatial variation with environmental variables. Mean tree density differed 19-fold among nine ecosystem types, and regression trees using four soil or climatic variables explained 62%–74% of the variation in density. Although density was more sensitive to environmental variation than was pattern, we did not find the clumped pattern widely described for P. ponderosa forests to be universal across ecosystems. Results suggest that (i) multivariate combinations of soil and climatic properties influenced historical forest structure, (ii) as much variation exists in reference conditions within the study landscape as between P. ponderosa regions, (iii) ecosystem classification is a useful framework for quantifying spatial variation in reference conditions, and (iv) determining spatial variation in reference conditions can assist resource managers in prioritizing areas for management and in developing ecosystem-specific management strategies within landscapes.
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Trencia, J. "Identification de descripteurs morphométriques sensibles aux conditions générales de croissance des semis de chêne rouge [Quercusrubra) en milieu naturel." Canadian Journal of Forest Research 25, no. 1 (January 1, 1995): 157–65. http://dx.doi.org/10.1139/x95-018.
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Red oak (Quertusrubra L.) seedlings measuring less than 1 m in height were collected from seven sites in the Québec City region. The sites were grouped according to pedology, dendrometry, and phytosociology. The object of this study was to select morphometric characteristics that are most sensitive to global differences in growth conditions. Most of the variables studied are frequently used to assess seedling performance in greenhouse or laboratory experiments. The characteristics measured included total stem height; mean annual increment of the biomass; number, mass, and length of the roots; shoot/root dry mass ratio; specific root length. Two topologic variables were also measured: the total external pathlength and the diameter of the root system, as defined by Fitter. The topologic variables and number of roots differentiated well the various groups of sites. Among the variables chosen, it is possible to estimate the value of the ones that are most difficult to assess, from less time-consuming variables.
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Shurygin, Vladimir A. "Nonlinear Problems of Equilibrium Charge State Transport in Hot Plasmas." Symmetry 13, no. 2 (February 16, 2021): 324. http://dx.doi.org/10.3390/sym13020324.
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The general coupling between particle transport and ionization-recombination processes in hot plasma is considered on the key concept of equilibrium charge state (CS) transport. A theoretical interpretation of particle and CS transport is gained in terms of a two-dimensional (2D) Markovian stochastic (random) processes, a discrete 2D Fokker-Plank-Kolmogorov equation (in charge and space variables) and generalized 2D coronal equilibrium between atomic processes and particle transport. The basic tool for analysis of CS equilibrium and transport is the equilibrium cell (EC) (two states on charge and two on space), which presents simultaneously a unit phase volume, the characteristic scales (in space and time) of local equilibrium, and a comprehensive solution for the simplest nonlinear relations between transport and atomic processes. The space-time relationships between the equilibrium constant, transport rates, density distributions, and impurity confinement time are found. The subsequent direct calculation of the total and partial density profiles and the transport coefficients of argon impurity showed a strong dependence of the 2D CS equilibrium and transport on the atomic structure of ions. A model for recovering the recombination rate profiles of carbon impurity was developed basing on the CS equilibrium conditions, the derived relationships, the data about density profiles, plasma parameters and ionization rates.
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Kumar, Nilesh, Zhiqiang Liu, Carol Flinchbaugh, Md Yahin Hossain, and Md Nahin Hossain. "Impact of emotional labour on taking charge to predict employee’s creative and task performance: The moderation of performance-based pay from the lens of self-determination theory." PLOS ONE 17, no. 10 (October 6, 2022): e0269196. http://dx.doi.org/10.1371/journal.pone.0269196.
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The importance of emotional labouring and performance of frontline service employees, who in their boundary-spanning positions significantly affect service-rendering organisations’ efficiency by their direct communications with customers, continues to increase. However, it is still important to ascertain an efficient understanding of the comprehensive process including behavioural mechanism and a common perception of the rewards’ impacts on motivation and creativity. Therefore, guided by self-determination theory, this study examined the mechanism and boundary conditions between emotional labour and job performance (creative and task)–specifically, taking charge has been considered as a mediator and performance-based pay as a moderator in between relationships. The authors selected a time-lagged cross-sectional design to investigate interrelations amongst study variables at two different time points and surveyed 417 team members and 186 team leaders in Pakistan’s commercial banks. Findings were consistent with the assumed conceptual framework. For instance, deep-acting affected taking charge positively, surface-acting demonstrated a positive link with task performance and taking charge partially mediated the relationships between deep-acting and performances under boundary conditions of low performance-based pay. By summing up, the study adds to the literature and recommends managerial implications with a more affluent view of nomothetic linkage among frontline employees’ emotional labor, HR practices, and the service sector.
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Rothman, Laura, Robert Miller, Richard Wang, Tim Baechle, Steve Silverman, and Douglas Cooper. "SEMATECH Minienvironment Benchmarking Project." Journal of the IEST 38, no. 3 (May 31, 1995): 36–41. http://dx.doi.org/10.17764/jiet.2.38.3.f727t147k603p560.
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A thin films fabrication facility using minienvironments and product-handling automation was benchmarked to determine the extent to which isolating products from the cleanroom avoids contamination. Data were collected from tests that simulated production conditions while controlling random variables. The study found that isolation factors of at least 1000 were demonstrated by settling wafer data, and 10,000 by aerosol data. In general, lowered room airflow did not significantly degrade minienvironment cleanliness. In addition, the study investigated reliability, electrostatic charge and electromagnetic interference issues, and materials outgassing.
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KARLTUN, E. "Modelling SO42- surface complexation on variable charge minerals: I. H+ and SO42- exchange under different solution conditions." European Journal of Soil Science 48, no. 3 (September 1997): 483–91. http://dx.doi.org/10.1046/j.1365-2389.1997.00091.x.
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Seregina, E. V., M. A. Stepovich, and M. N. Filippov. "On a Mathematical Model of the Diffusion of Excitons in a Semiconductor Taking into Account Their Variable Lifetime." Поверхность. Рентгеновские, синхротронные и нейтронные исследования, no. 3 (March 1, 2023): 74–78. http://dx.doi.org/10.31857/s1028096023030159.
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The time dependence of the concentration of nonequilibrium minority charge carriers generated in a homogeneous semiconductor material by a sharply focused electron beam, an electron probe, after the target irradiation is described. A mathematical model is constructed for the nonstationary diffusion of charged particles generated by a low-energy electron probe in a semiconductor target in the presence of two independent recombination channels of generated charge carriers in the target material. The use of a low-energy electron probe made it possible to use a two-dimensional mathematical model of diffusion in the simulation. As an initial condition in this model, the distribution of the concentration of nonequilibrium minority charge carriers under quasi-equilibrium conditions, before turning off the electron irradiation, is used. In the presence of two independent recombination channels, the profile of the decline in the concentration of nonequilibrium minority charge carriers in the target after the electron irradiation is turned off is described by the sum of two time-dependent exponents. This approach made it possible to obtain a solution to the differential equation for two-dimensional diffusion of charge carriers, taking into account their variable effective lifetime. The practical application of the developed mathematical model is implemented for the method of time-of-flight cathodoluminescence in describing the diffusion of excitons in single-crystal gallium nitride, taking into account the dependence of the concentration of generated excitons on time.
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Bonatesta, F., and P. J. Shayler. "Factors influencing the burn rate characteristics of a spark ignition engine with variable valve timing." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 222, no. 11 (November 1, 2008): 2147–58. http://dx.doi.org/10.1243/09544070jauto873.
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The charge burn characteristics of a four-cylinder port-fuel-injected spark ignition engine fitted with a dual independent variable-valve-timing system have been investigated experimentally. The influence of valve timings on the flame development angle and the rapid burn angle is primarily associated with valve overlap values and internal gas recirculation. Conditions examined cover light to medium loads and engine speeds up to 3500r/min. As engine loads and speeds exceeded about 6bar net indicated mean effective pressure and 3000r/min respectively, combustion duration was virtually independent of the valve timing setting. At lower speeds and work output conditions, valve timing influenced burn angles through changes in dilution mass fraction, charge density, and charge temperature. Of these, changes in dilution mass fraction had the greatest influence. Increasing the dilution by increasing the valve overlap produced an increase in both burn angles. The effects of mean piston speed and spark timing have also been examined, and empirical expressions for the flame development and the rapid burn angles are presented.
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Antun, Jozinović, Ačkar Đurđica, Jokić Stela, Babić Jurislav, Balentić Jelena Panak, Banožić Marija, and Šubarić Drago. "Optimisation of extrusion variables for the production of corn snack products enriched with defatted hemp cake." Czech Journal of Food Sciences 35, No. 6 (December 20, 2017): 507–16. http://dx.doi.org/10.17221/83/2017-cjfs.
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The effects of defatted hemp cake added to corn grits (at ratios of 0, 5, and 10% DM), the moisture content of the mixtures (15, 20, and 25%) and the temperature in the extruder ejection zone (150, 165, and 180°C) on the physical properties of extruded products have been investigated. Statistical optimization of investigated extrusion conditions using the response surface methodology was performed. The hemp cake was completely defatted by means of a supercritical CO2 extraction. The extrusion was performed on a laboratory single screw extruder and regulated by the following parameters: temperature in the dosing and compression zone (120 and 150°C), screw compression ratio (4 : 1), round die (4 mm). The change of extrusion process conditions significantly affected the physical properties of produced snacks. The expansion ratio ranged between 1.38 and 3.11, bulk density between 0.14 and 0.49 g/cm3, hardness between 18.15 and 70.62 N, fracturability from 3.65 to 10.38 mm, and the total colour change between 3.25 and 24.73.
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Harning, David J., Áslaug Geirsdóttir, and Gifford H. Miller. "Punctuated Holocene climate of Vestfirðir, Iceland, linked to internal/external variables and oceanographic conditions." Quaternary Science Reviews 189 (June 2018): 31–42. http://dx.doi.org/10.1016/j.quascirev.2018.04.009.
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Li, Kai, Feng Yuan, Yinghui Hu, Yongbin Du, Wei Chen, and Chunyun Lan. "Least-Square-Method-Based Optimal Laser Spots Acquisition and Position in Cooperative Target Measurement." Sensors 22, no. 14 (July 7, 2022): 5110. http://dx.doi.org/10.3390/s22145110.
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The relative positioning precisions of coordinate points is an important indicator that affects the final accuracy in the visual measurement system of space cooperative targets. Many factors, such as measurement methods, environmental conditions, data processing principles and equipment parameters, are supposed to influence the cooperative target’s acquisition and determine the precision of the cooperative target’s position in a ground simulation experiment with laser projected spots on parallel screens. To overcome the precision insufficiencies of cooperative target measurement, the factors of the laser diode supply current and charge couple device (CCD) camera exposure time are studied in this article. On the hypothesis of the optimal experimental conditions, the state equations under the image coordinates’ system that describe the laser spot position’s variation are established. The novel optimizing method is proposed by taking laser spot position as state variables, diode supply current and exposure time as controllable variables, calculating the optimal controllable variables through intersecting the focal spot centroid line and the 3-D surface, and avoiding the inconvenience of solving nonlinear equations. The experiment based on the new algorithm shows that the optimal solution can guarantee the focal spot’s variation range in 5–10 pixels under image coordinates’ system equivalent to the space with a 3 m distance and 0.6–1.2 mm positioning accuracy.
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Marques, N. C. S., L. Rattis, and F. Nomura. "Local environmental conditions affecting anuran tadpoles' microhabitat choice and morphological adaptation." Marine and Freshwater Research 70, no. 3 (2019): 395. http://dx.doi.org/10.1071/mf18106.
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In this study, we investigated the environmental variables that best explained tadpole occurrence, as well as associations between environmental variables and the morphological traits of tadpoles. We modelled the occurrence of tadpoles to evaluate the significance of trait–environment relationships by sampling in 86 ponds, measuring a set of environmental descriptors of these ponds, determining the tadpoles’ external-morphology changes and using a generalised linear mixed model approach. The best fitting model predicting tadpole occurrence included all the environmental variables measured (pond dimensions, pond margin type, pond bottom substrate, vegetation type inside the pond, vegetation type in the pond margins, landscape descriptors) and seven morphology–environment interactions. Tadpoles are capable of fine-tuning their morphology according to the environmental traits of the pond and land use changes around the pond. Vegetation heterogeneity of ponds interacts with tadpole morphology primarily on tail size and deviations in the mean position of the eye, nostril and mouth. Moreover, there are increases in body size and tail length in smaller ponds, as well as in ponds surrounded vegetation changes from forest to pasture or short crops. Changes in environmental variables as a result of land use change can affect the dispersion of adult frogs and, consequently, the occurrence of and morphological variations in tadpoles. Local environmental variables play important roles driving tadpoles’ microhabitat choice; once tadpoles cannot select the site of their developmental, they need to compensate for any mismatching by induced morphological adaptations.
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Wang, Xin, Wenke Wang, and Bing Yan. "Tropical Cyclone Intensity Change Prediction Based on Surrounding Environmental Conditions with Deep Learning." Water 12, no. 10 (September 25, 2020): 2685. http://dx.doi.org/10.3390/w12102685.
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Tropical cyclone (TC) motion has an important impact on both human lives and infrastructure. Predicting TC intensity is crucial, especially within the 24 h warning time. TC intensity change prediction can be regarded as a problem of both regression and classification. Statistical forecasting methods based on empirical relationships and traditional numerical prediction methods based on dynamical equations still have difficulty in accurately predicting TC intensity. In this study, a prediction algorithm for TC intensity changes based on deep learning is proposed by exploring the joint spatial features of three-dimensional (3D) environmental conditions that contain the basic variables of the atmosphere and ocean. These features can also be interpreted as fused characteristics of the distributions and interactions of these 3D environmental variables. We adopt a 3D convolutional neural network (3D-CNN) for learning the implicit correlations between the spatial distribution features and TC intensity changes. Image processing technology is also used to enhance the data from a small number of TC samples to generate the training set. Considering the instantaneous 3D status of a TC, we extract deep hybrid features from TC image patterns to predict 24 h intensity changes. Compared to previous studies, the experimental results show that the mean absolute error (MAE) of TC intensity change predictions and the accuracy of the classification as either intensifying or weakening are both significantly improved. The results of combining features of high and low spatial layers confirm that considering the distributions and interactions of 3D environmental variables is conducive to predicting TC intensity changes, thus providing insight into the process of TC evolution.
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Sarafanov, G. F., and A. A. Utkin. "MODEL OF FORMATION AND PROPAGATION OF SLIP BANDS IN METALS." Problems of Strength and Plasticity 85, no. 1 (2023): 5–13. http://dx.doi.org/10.32326/1814-9146-2023-85-1-5-13.
Full textAbstract:
A theoretical study of the processes of localization of plastic deformation in metals has been carried out. Within the framework of the system of evolutionary equations for dislocation density, taking into account the multiplication and annihilation of dislocations, the possibility of a running solution for the slip strip is established. It is shown that the initial system has two equilibrium states. For the total dislocation density and dislocation charge normalized to a stationary homogeneous solution for dislocation density, these are the states (0,0) and (1,0) on the phase plane of the above variables in dimensionless form. From the analysis of singular points, it follows that the point (0,0) is a stable node, and the equilibrium state (1,0) is a saddle. In this case, the desired solution of the initial system of evolutionary equations is a separatrix going from point (0,0) to point (1,0), which corresponds to solutions in the form of a drop wave for the dislocation density forming the slip band and a momentum for the dislocation charge. It is shown that the dislocation charge propagates in the front of the slip band, which moves at a velocity u = kV (V is the drift velocity of dislocations due to external load, the proportionality coefficient k satisfies the condition 0 < k < 1). After analyzing the existence of self-similar solutions, it follows that non-homogeneous wave solutions occur only at A = t1/t2 > 1, where t1 and t2 are, respectively, relaxation times of the total dislocation density and dislocation charge to a homogeneous state. Estimates show that for a given dislocation kinetics (dislocation generation and annihilation processes) A > 1, i.e. satisfy the conditions for the formation of a slip strip of a given type. The stability of the obtained wave stationary self-similar solutions is considered. Assuming that deviations from stationary solutions for the dislocation density and dislocation charge are limited to a given domain, and considering the deviations small, we obtain the Sturm – Liouville problem for own functions and eigenvalues with zero boundary conditions at the boundary of this domain. The appropriate transformation reduces the problem to an equation of the Schrodinger equation type. It is shown that under certain conditions the spectrum of the Schrodinger operator is in the left half-plane, i.e. deviations of dislocation density and dislocation charge decay exponentially over time and the desired stationary solutions are asymptotically stable. The issue related to the determination of the steady-state velocity of wave propagation is considered. Linearization of the initial system of equations for dislocation density and dislocation charge allowed us to obtain a linear sine-Gordon equation, from the solution of which the steady-state wave velocity is determined. It is shown that for the initial system of the system of equations for A > 1, arbitrary initial distributions of the desired variables acquire the form of self-similar solutions over time and move at the lowest possible speed u = 2VA1/2/(1 + A).