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排序方式: 共有993条查询结果,搜索用时 15 毫秒
41.
Asymptotic solutions to countercurrent moving-bed exchange equations are discussed considering the effect of axial dispersion and interphase mass transfer. Existence conditions are derived by using perturbation theory in a properly defined moving coordinate system. The flow are ratio turns out to be a very important parameter and its effect on the exchange performance is carefully examined. In particular, the effect of interphase mass transfer disappears when the exchange zone becomes stationary. Applications are illustrated by using the Langmuir adsorption isotherm. Numerical solutions of the transient equations show that the asymptotic solution may be useful. 相似文献
42.
Kee-Youn?Yoo Jiwen?HeEmail author Neal?R.?Amundson 《Korean Journal of Chemical Engineering》2004,21(2):303-307
We describe a canonical form of electrolyte solution systems for the mathematical interpretation of solidliquid equilibrium.
The canonical form is obtained from the analysis of the algebraic structure of electrolyte solution systems and the Karush-Kuhn-Tucker
(KKT) conditions for the minimization of the total Gibbs free energy. As a result, the mathematical role of solid species
in the solid-liquid equilibrium problem is explained as a Lagrange multiplier of a sort of the linearly constrained optimization
problem. This finding will add to the development of an efficient numerical algorithm for the simulation of electrolyte solution
systems.
This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University. 相似文献
43.
44.
Investigated the nature of the relationship between life satisfaction and job satisfaction using both 2-stage least squares and the analysis of linear structural equations by LISREL. Both techniques provided the possibility of evaluating causal relationships that are bidirectional. 873 civil service workers were administered a battery of tests, including the Job Diagnostic Survey, the short form of the Minnesota Satisfaction Questionnaire, and the Rosenberg Self-Esteem Scale. Results are consistent with a model that hypothesizes a reciprocal relationship between job and life domains. Estimates of structural parameters were consistent across analysis techniques. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
45.
Capacitive micromachined ultrasonic transducers with diffraction-based integrated optical displacement detection 总被引:1,自引:0,他引:1
Hall NA Lee W Degertekin FL 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2003,50(11):1570-1580
Capacitive detection limits the performance of capacitive micromachined ultrasonic transducers (CMUTs) by providing poor sensitivity below megahertz frequencies and limiting acoustic power output by imposing constraints on the membrane-substrate gap height. In this paper, an integrated optical interferometric detection method for CMUTs, which provides high displacement sensitivity independent of operation frequency and device capacitance, is reported. The method also enables optoelectronics integration in a small volume and provides optoelectronic isolation between transmit and receive electronics. Implementation of the method involves fabricating CMUTs on transparent substrates and shaping the electrode under each individual CMUT membrane in the form of an optical diffraction grating. Each CMUT membrane thus forms a phase-sensitive optical diffraction grating structure that is used to measure membrane displacements down to 2/spl times/10/sup -4/ /spl Aring///spl radic/Hz level in the dc to 2-MHz range. Test devices are fabricated on quartz substrates, and ultrasonic array imaging in air is performed using a single 4-mm square CMUT consisting of 19/spl times/19 array of membranes operating at 750 kHz. 相似文献
46.
Investigation of corrosion and container integrity in metal food containers using scanning electron microscopy-X-ray microanalysis 总被引:1,自引:0,他引:1
Charbonneau JE 《Scanning》2001,23(3):198-203
Scanning electron microscopy and x-ray microanalysis were used to investigate microleakage, two incidences of loss of coating integrity, filiform corrosion, and sulfide black corrosion in enamel-lined metal food containers. Microleakage developed in a canned cheese sauce at the side seam weld and was traced to a hot weld and a cold weld defect. An enamel-blistering problem developed in an aseptically processed milk-based product when the tinplate was heated above its melting point; the tin melted under the enamel coating, causing the blistering. An enamel-blistering problem, due to silicon contamination of the metal surface prior to enameling, developed on the bottom of a two-piece can that contained a chicken-based product. A sulfide black problem developed in canned clams, caused by scratches in the coating that were introduced during can manufacturing. A filiform corrosion problem developed on the outside of the easy score line of enameled tinplate lids with a light tin coating 0.08 microns thick. 相似文献
47.
Schmitt Neal; Oswald Frederick L.; Kim Brian H.; Imus Anna; Merritt Stephanie; Friede Alyssa; Shivpuri Smriti 《Canadian Metallurgical Quarterly》2007,92(1):165
To determine whether profiles of predictor variables provide incremental prediction of college student outcomes, the authors 1st applied an empirical clustering method to profiles based on the scores of 2,771 entering college students on a battery of biographical data and situational judgment measures, along with SAT and American College Test scores and high school grade point average, which resulted in 5 student groups. Performance of the students in these clusters was meaningfully different on a set of external variables, including college grade point average, self-rated performance, class absenteeism, organizational citizenship behavior, intent to quit their university, and satisfaction with college. The 14 variables in the profile were all significantly correlated with 1 or more of the outcome measures; however, nonlinear prediction of these outcomes on the basis of cluster membership did not add incrementally to a linear-regression-based combination of these 14 variables as predictors. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
48.
Spring Bonnie; Doran Neal; Pagoto Sherry; McChargue Dennis; Cook Jessica Werth; Bailey Katherine; Crayton John; Hedeker Donald 《Canadian Metallurgical Quarterly》2007,75(1):85
The study was a randomized placebo-controlled trial testing whether fluoxetine selectively enhances cessation for smokers with a history of depression. Euthymic smokers with (H+, n = 109) or without (H-, n = 138) a history of major depression received 60 mg fluoxetine or placebo plus group behavioral quit-smoking treatment for 12 weeks. Fluoxetine initially enhanced cessation for H+ smokers (p = .02) but subsequently impaired cessation regardless of depressive history. Six months after quit date, fluoxetine-treated participants were 3.3 times more likely to be smoking (p = .02). Further research is warranted to determine why high-dose fluoxetine produces continuing effects that oppose tobacco abstinence. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
49.
The purpose of this study was to see whether 3 types of social support (enacted support, negative interaction, and anticipated support) are associated with change in meaning in life. Data from a nationwide longitudinal survey of older people suggested that greater anticipated support (i.e., the belief that others will provide assistance in the future if needed) is associated with a deeper sense of meaning over time. The same was true with respect to emotional support received from family members and close friends. In contrast, the findings revealed that, at least initially, negative interaction lowers an older person's sense of meaning in life. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
50.
Vishwa Priya Podduturi Isidro B. Magaña D. Patrick O’Neal Pedro A. Derosa 《Computer methods and programs in biomedicine》2013
Determining the factors that influence the delivery of sub-micron particles to tumors and understanding the relative importance of each of these factors is fundamental to the optimization of the particle delivery process. In this paper, a model that combines random walk with the pressure driven movement of nanoparticles in a tumor vasculature is presented. Nanoparticle movement in a cylindrical tube with dimensions similar to the tumor's blood capillary with a single pore is simulated. Nanoparticle velocities are calculated as a pressure driven flow over imposed to Brownian motion. The number and percentage of nanoparticles leaving the blood vessel through a single pore is obtained as a function of pore size, nanoparticle size and concentration, interstitial pressure, and blood pressure. The model presented here is able to determine the importance of these controllable parameters and thus it can be used to understand the process and predict the best conditions for nanoparticle-based treatment. The results indicate that the nanoparticle delivery gradually increases with pore size and decreases with nanoparticle size for tumors with high interstitial fluid pressure (in this work we found this behavior for head and neck carcinoma and for metastatic melanoma with interstitial pressures of 18 mmHg and 19 mmHg, respectively). For tumors with lower interstitial fluid pressure (rectal carcinoma with 15.3 mmHg) however, delivery is observed to have little sensitivity to particle size for almost the entire nanoparticle size range. Though an increase in nanoparticle concentration increases the number of nanoparticles being delivered, the efficiency of the delivery (percentage of nanoparticles delivered) is found to remain closely unaffected. 相似文献