Modeling of the Flow Dynamics through Incompressible Porous Media in Solid-Liquid Filtration

Solid-liquid filtration is a long-standing engineering practice and has been widely used in the chemical, process and mineral industries. Current models are semi-empirical in nature; thus, they require significant experimental and/or computational resources in order to determine the empirical quantities. In contrast, this dissertation provides a model to predict the dynamic behavior for both the liquid and solid phase of a filtration process without the requirement of empirical parameters. Instead, the model relies solely on the to-be-captured particle size distribution of contaminants as well as the pore size distribution of the filtration media. The new algorithm is capable of describing filtration based on both “steric” capture of contaminants as well as capture within dead-end pores in the material. This dissertation shows the performance of the model in modeling beds comprised of high void fraction materials (diatomaceous earth) that is used for the removal of multi-modal mixtures of contaminant. By formally accounting for the complex pore size distribution, the predict flow dynamics that are much closer to experimental results than the predictions of the traditional Kozeny-Carmen (K-C) model and show that this approach is viable for both statically formed and evolving (dynamic) beds. In an effort to understand the relationship between flow dynamics and pore size distribution more fully, a dynamic filter cake model is proposed that continuously modifies the pore size distribution as contaminants (polydispere spheres) are deposited. This dissertation also describes a simulation model capable of describing the capture of spherical particles within dead-end pores. A 3D discrete element method-lattice Boltzmann method (DEM-LBM) coupling approach is applied to investigate the particle capture under conditions of different particle size and pore structures. Both the pressure drop and the fluid density are examined to indicate this capture performance. The predicted flow dynamics of this new model match the dynamic experimental results remarkably well, setting the stage for a priori prediction of filtration times, flow-rates, particle capture, and pressure requirements from simple measurements of the size distribution of both the filter media pores as well as the contaminant particles/droplets

Professional self-identity in medical students and workplace range: a survey of Guangzhou Medical School

Background: Research finds that medical students in different schools have different professional identity. Therefore, it is necessary to explore professional identity of medical students. Objective: To explore the influencing factors of medical students’ professional identity and the relationship between professional cognition, emotion, commitment, expectation, behavior and values and professional identity. Methods: Literature Review, Questionnaire Survey, Structural Equation Model, Statistical Analysis Results: (1) The overall score of medical students' professional identity is 3.86 points (Full score of 5). (2) The factors that have a significant impact on professional identity of medical students include academic qualifications, school, first choice for college entrance examination, and reasons for studying medicine. (3) Six factors explaining medical students' professional identity are professional behavior, emotion, value, cognition, expectation, and commitment from high to low. Conclusion: The main factors that constitute the professional identity of medical students are professional cognition, professional emotion, professional behavior, professional commitment, professional expectation, and professional value. And the biggest influencing factor is professional behavior. To enhance professional identity of medical students, we propose countermeasures from the three perspectives of the Chinese government, medical schools and hospitals. The Chinese government should increase investment in working conditions of doctors and improve relevant laws and regulations. Medical schools need to pay attention to guidance and reform the medical curricula. Hospitals need to establish better medical environments and attach importance to the psychological state of medical students.Contexto: Força de reserva da equipa clínica, a identidade profissional dos estudantes de medicina afeta a qualidade do corpo clínico e o desenvolvimento médico futuro. Portanto, é necessário explorar a sua identidade profissional. Objetivo: Explorar os fatores de influência da identidade profissional dos estudantes de medicina e a relação entre cognição, emoção, compromisso, expectativa, comportamento, valores e a identidade profissional. Métodos: Revisão de Literatura, Pesquisa de Questionário, Modelo de Equação Estrutural, Análise Estatística. Resultados: (1) A pontuação geral da identidade profissional dos estudantes de medicina é 3,86 (pontuação máxima 5). (2) Os fatores que mais influenciam a identidade profissional dos estudantes de medicina incluem qualificações acadêmicas, escola, primeira escolha no exame nacional e motivação de estudo. (3) Os seis fatores de influência são, por ordem descendente, comportamento, emoção, valor, cognição, expectativa e compromisso profissionais. Conclusão: Os principais fatores que constituem a identidade profissional dos estudantes de medicina são cognição, emoção, comportamento, compromisso, expectativa e valor profissionais. O maior fator de influência é o comportamento profissional. Para reforçar a identidade profissional dos estudantes de medicina, propomos contramedidas a partir de perspetivas do governo chinês, dos institutos de medicina e dos hospitais. O governo chinês deve aumentar o investimento nas condições de trabalho dos médicos e aperfeiçoar os relativos leis e regulamentos. Os institutos de medicina devem aprimorar a orientação e reformar os currículos médicos. Os hospitais devem melhorar o ambiente médico e dar importância ao estado psicológico dos estudantes de medicina

Subsonic steady-states for bipolar hydrodynamic model for semiconductors

In this paper, we study the well-posedness, ill-posedness and uniqueness of the stationary 3-D radial solution to the bipolar isothermal hydrodynamic model for semiconductors. The density of electron is imposed with sonic boundary and interiorly subsonic case and the density of hole is fully subsonic case

Validity of Kozeny-Carman Equation in Constant-Pressure Cake Filtration

Filtrations in the separation of solid-liquid mixtures have been studied for 80 years. However, the lack of a generalized set of laws for filtration has increased the difficulty of incorporating equations from one model into another. This thesis is focused on the relationship between fluid properties and cake structure on the void distribution and ultimate pressure drop during a filtration process. By comparing experimental results to those predicted from the Kozeny-Carman model/equation, we assess the utility of this equation for application to systems that include poly-disperse particles at moderate fluid pressure. We find substantial agreement between model and experiment only for systems that result in well-ordered particle packing (i.e., those that have a tight distribution of void sizes). Dramatic disagreement is observed for particle beds that exhibit wide void size distributions. The cake structure is primarily influenced by the size ratio of the particles that compose the cake; specifically, particles with a size ratio in which Rs/l is larger than 0.5 do not typically form an ordered pore structure. We propose a modified Kozeny-Carman equation, based on a bimodal void distribution, by introducing two factors: the fraction of expanded voids (κ) and the ratio of void sizes (β). Discrete Element Method (DEM) simulations of the packing of poly-disperse spheres are used to analyze the cake structure for different size ratios of binary mixtures. Based on the simulation results, void size distributions of the simulated beds can be extracted by means of a radical Delaunay tessellation. The void structure is quantified in terms of probability density functions of pore and constriction sizes. By fitting the simulated void size distributions to a bimodal (two normal) distribution, the factors κ and β can be calculated based on different mean void sizes and probability density. The predicted flow dynamics from the modified equation with factors extracted from the simulation results are found to be much more similar to the experimental flow rates than those calculated using the unmodified Kozeny-Carman equation. Therefore, the modified equation is deemed reliable at predicting the flow behavior, provided that an approximate representation of the void size distribution is available

Three-dimensional single gyroid photonic crystals with a mid-infrared bandgap

A gyroid structure is a distinct morphology that is triply periodic and consists of minimal isosurfaces containing no straight lines. We have designed and synthesized amorphous silicon (a-Si) mid-infrared gyroid photonic crystals that exhibit a complete bandgap in infrared spectroscopy measurements. Photonic crystals were synthesized by deposition of a-Si/Al2O3 coatings onto a sacrificial polymer scaffold defined by two-photon lithography. We observed a 100% reflectance at 7.5 \mum for single gyroids with a unit cell size of 4.5 \mum, in agreement with the photonic bandgap position predicted from full-wave electromagnetic simulations, whereas the observed reflection peak shifted to 8 um for a 5.5 \mum unit cell size. This approach represents a simulation-fabrication-characterization platform to realize three-dimensional gyroid photonic crystals with well-defined dimensions in real space and tailored properties in momentum space

Nonlinear Robust Disturbance Attenuation Control Design for Static Var Compensator in Power System

The problem of designing an adaptive backstepping controller for nonlinear static var compensator (SVC) system is addressed adopting two perspectives. First, instead of artificially assuming an upper bound or inequality scaling, the minimax theory is used to treat the external unknown disturbances. The system is insensitive to effects of large disturbances due to taking into account the worst case disturbance. Second, a parameter projection mechanism is introduced in adaptive control to force the parameter estimate within a prior specified interval. The proposed controller handles the nonlinear parameterization without compromising control smoothness and at the same time the parameter estimate speed is improved and the robustness of system is strengthened. Considering the short-circuit ground fault and mechanical power perturbation, a simulation study is carried out. The results show the effectiveness of the proposed control method

Single-shot quantitative differential phase contrast imaging combined with programmable polarization multiplexing illumination

We propose a single-shot quantitative differential phase contrast (DPC) method with polarization multiplexing illumination. In the illumination module of our system, the programmable LED array is divided into four quadrants and covered with polarizing films of four different polarization angles. We use a polarization camera with polarizers before the pixels in the imaging module. By matching the polarization angle between the polarizing films over the custom LED array and the polarizers in the camera, two sets of asymmetric illumination acquisition images can be calculated from a single-shot acquisition image. Combined with the phase transfer function, we can calculate the quantitative phase of the sample. We present the design, implementation, and experimental image data demonstrating the ability of our method to obtain quantitative phase images of the phase resolution target, as well as Hela cells.Comment: 5 pages,4figure

Role of Cytokines and Chemokines in Alcohol-Induced Tumor Promotion

Excessive chronic alcohol consumption has become a worldwide health problem. The oncogenic effect of chronic alcohol consumption is one of the leading concerns. The mechanisms of alcohol-induced tumorigenesis and tumor progression are largely unknown, although many factors have been implicated in the process. This review discusses the recent progress in this research area with concentration on alcohol-induced dysregulation of cytokines and chemokines. Based on the available evidence, we propose that alcohol promotes tumor progression by the dysregulation of the cytokine/chemokine system. In addition, we discuss specific transcription factors and signaling pathways that are involved in the action of these cytokines/chemokines and the oncogenic effect of alcohol. This review provides novel insight into the mechanisms of alcohol-induced tumor promotion

Establishment and Evaluation of a Loop-Mediated Isothermal Amplification Assay for Detection of Raccoon Dog in Meat Mixtures

Raccoon dog (Nyctereutes procyonoides) is an economically important animal used for fur production, but consuming its meat is injurious to human health. Currently, no rapid and sensitive method for detecting raccoon dog meat in meat mixtures is available. In this study, we developed an easily applicable, rapid, and economically feasible method for identifying the presence of raccoon dog in meat mixtures based on loop-mediated isothermal amplification (LAMP). Four sets of LAMP primers were tested at different temperatures, and the primers that worked best at 62°C (set 2) were determined. In the LAMP assay, there was no cross-reactivity with the meat procured from other species of animals and the detection limit of DNA concentration was 0.1 pg·μL−1, slightly higher than TaqMan real-time PCR (0.01 pg·μL−1), but sensitivity of 0.1 pg·μL−1 complies with most requirements of routine analysis. Moreover, by the LAMP method, the meat mixtures containing more than 0.5% of the raccoon dog component were directly detected (without DNA extraction) in the supernatant isolated from the meat mixtures after performing repeated cycles of thawing and freezing of minced meat mixtures. Our results show that LAMP assay is a valuable, straightforward, and sensitive detection tool for identification of raccoon dog meat in mixtures