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31.
This work presents a simplified modeling and simulation approach for energy systems engineering that is capable of providing quick and accurate responses during system design. For that, the laws of conservation are combined with available empirical and theoretical correlations to quantify the diverse types of flows that cross the system and produce a simplified tridimensional mathematical model, namely a volume element model (VEM). The physical domain of interest is discretized in space, thus producing a system of algebraic and ODEs with respect to time, whose solution delivers the project variables spatial distribution and dynamic response. In order to illustrate the application of the VEM in energy systems engineering, three example problems are considered: (i) a regenerative heat exchanger; (ii) a power electronic building block (PEBB); and (iii) a notional all‐electric ship. The same mathematical model was used to analyze problems (ii) and (iii), that is, the thermal management of heat‐generating equipment packaging. In the examples, the converged mesh had a total of 20, 2000, and 7725 volume elements. The third problem led to the largest simulation, which for steady‐state cases took between 5 and 10 min of computational time to reach convergence and for the ship dynamic response 50 min (i.e., 80,000 s of real time). The regenerative heat exchanger model demonstrated how VEM allowed for the coexistence of different phases (subsystems) within the same volume element. The thermal management model was adjusted and experimentally validated for the PEBB system, and it was possible to perform a parametric and dynamic analysis of the PEBB and of the notional all‐electric ship. Therefore, because of the observed combination of accuracy and low computational time, it is expected that the model could be used as an efficient tool for design, control, and optimization in energy systems engineering. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
32.
The contributions of mechanisms by which chelators influence metal translocation to plant shoot tissues are analyzed using a combination of numerical modelling and physical experiments. The model distinguishes between apoplastic and symplastic pathways of water and solute movement. It also includes the barrier effects of the endodermis and plasma membrane. Simulations are used to assess transport pathways for free and chelated metals, identifying mechanisms involved in chelate-enhanced phytoextraction. Hypothesized transport mechanisms and parameters specific to amendment treatments are estimated, with simulated results compared to experimental data. Parameter values for each amendment treatment are estimated based on literature and experimental values, and used for model calibration and simulation of amendment influences on solute transport pathways and mechanisms. Modeling indicates that chelation alters the pathways for Cu transport. For free ions, Cu transport to leaf tissue can be described using purely apoplastic or transcellular pathways. For strong chelators (ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA)), transport by the purely apoplastic pathway is insufficient to represent measured Cu transport to leaf tissue. Consistent with experimental observations, increased membrane permeability is required for simulating translocation in EDTA and DTPA treatments. Increasing the membrane permeability is key to enhancing phytoextraction efficiency. 相似文献
33.
This paper presents a direct traction boundary integral equation method (DTBIEM) for two-dimensional crack problems of materials. The traction boundary integral equation was collocated on both the external boundary and either side of the crack surfaces. The displacements and tractions were used as unknowns on the external boundary, while the relative crack opening displacement (RCOD) was chosen as unknowns on either side of crack surfaces to keep the single-domain merit. Only one side of the crack surfaces was concerned and needed to be discretized, thus the proposed method resulted in a smaller system of algebraic equations compared with the dual boundary element method (DBEM). A new set of crack-tip shape functions was constructed to represent the strain field singularity exactly, and the SIFs were evaluated by the extrapolation of the RCOD. Numerical examples for both straight and curved cracks are given to validate the accuracy and efficiency of the presented method. 相似文献
34.
超低渗油藏在线分流酸化增注技术研究与应用 总被引:1,自引:0,他引:1
酸化是超低渗油藏最有效的增注措施之一,但由于储层物性差、非均质性强等问题,造成目前常规酸化措施普遍具有施工周期长、有效率低、有效作用距离短等不足,且酸化过程中存在指进现象和储层二次伤害。针对这一问题,选取鄂尔多斯盆地环江油田三叠系超低渗油藏为研究对象,提出了在线分流酸化技术,并配套研制了一种多元缓速螯合酸COA-1S和一种新型的水溶性分流剂COA-1P。通过室内评价实验和在线分流酸化模拟实验,发现该技术在缓速性、配伍性、水溶性、螯合能力和暂堵功能等方面均显著优于常规酸化;现场先导性实验结果表明,酸化后剖面吸水均匀程度从28.5%上升至50.9%,视吸水指数增加2倍左右,降压增注效果显著;同时,该技术还具有“不停井、不泄压、不动管柱、不返排”的特点,简化了常规分流酸化工序、降低了安全环保风险,是一种能够很好地适应超低渗油藏特征的酸化增注技术。 相似文献
35.
为智能化地识别警戒作业人员出现的低觉醒、注意力下降的生理状态,本文介绍了一种基于FPGA和脑电信号处理的低觉醒状态检测与唤醒系统,系统通过传感器从大脑头皮采集脑电信号,转换为数字信号,经傅里叶变换获取了脑电信号的θ相对能量、α相对能量、重心频率、谱熵等4个特征量,由4个特征量表征低觉醒状态并运用支持向量机对低警戒状态进行识别,当识别出低觉醒状态时采用声音报警模块发出声音,唤醒警戒作业人员。设计系统能够较好地识别出低觉醒状态,识别率达90.8%,可为提高警戒作业工作绩效提供一种可穿戴的智能装备。 相似文献
36.
Dr. Aimee J. Marko Mykhaylo Dukh Dr. Nayan J. Patel Joseph R. Missert Prof. Dr. Tymish Ohulchanskyy Walter A. Tabaczynski Dr. Kei Ohkubo Prof. Dr. Shunichi Fukuzumi Prof. Dr. Rutao Yao Prof. Dr. Munawwar Sajjad Prof. Dr. Ravindra K. Pandey 《ChemMedChem》2019,14(16):1503-1513
Herein we report the synthesis, photophysical properties, positron emission tomography (PET) imaging and photodynamic therapy (PDT) efficacy of methyl 3-(1′-m-iodobenzyloxy)ethyl-3-devinyl-verdin 4 (with or without the 124I isotope). The PET imaging ability and ex vivo biodistribution of [124I] 4 were compared with the well-studied methyl [3-(1241′-m-iodobenzyloxy)ethyl]-3-devinyl-pyropheophorbide-a methyl ester (PET-ONCO or [124I] 2 ) and [18F]fluorodeoxyglucose ([18F]FDG) in BALB/c mice bearing colon-26 tumors. Whole-body PET images of [124I] 4 containing a fused methoxy cyclohexenone ring system showed excellent tumor contrast with time (72>48>24 h post-injection). Ex vivo biodistribution results indicate that relative to the current clinical standard [18F]FDG and [124I] 2 in 2 % ethanol formulation, [124I] 4 , at the same radioactive dose (25 μCi per mouse), showed higher tumor uptake at 24 h post-injection and longer tumor retention. In biological environments, compound 4 showed lower fluorescence and lower singlet oxygen yield than 2 , which is possibly due to higher aggregation caused by the presence of a fused cyclohexenone ring system, resulting in limited in vitro/in vivo PDT efficacy. Therefore, the chlorophyll-a analogue [124I] 4 provides easy access to a novel PET imaging agent (with no skin phototoxicity) to image cancer types—brain, renal carcinomas, pancreas—in which [18F]FDG shows limitations. 相似文献
37.
Manoj Kumar Nayak Vinay Shankar Pandey Dharmendra Tripathi Noreen Sher Akbar Oluwole D Makinde 《亚洲传热研究》2020,49(3):1256-1280
The present study aims to investigate the effects of thermal‐diffusion and diffusion‐thermo onan magnetohydrodynamic convective flow of viscous fluids over an exponentially stretching sheet. Thermal radiation effects are also considered in the study. This analysis is carried out in three dimensions and a similarity transformation is adopted to get a set of ordinary differential equations from a set of partial differential equations. And the Fourth‐order Runge‐Kutta method and shooting technique along with the secant method are employed to find out an iterative solution. We also analyze here the influence of the variable magnetic field, nonuniform permeability and variable chemical reaction on the fluid flow. The impact of various pertinent parameters of interest has extensively been explored through graphs and tables. The major findings of the present study are that resistive Lorentz force diminishes the fluid velocity and uplifts the thermal as well as concentration fields. Inclusion of porous matrix improves the viscous drag force which in turn augments wall shear stresses and peters out the heat and mass transfer rates from the sheet. In addition, the thermal expansion coefficient has an inverse relation with temperature. 相似文献
38.
39.
A non-destructive version of a standard test for concrete permeability has been demonstrated. The method is based on water penetration depth estimation from near-field microwave measurements using an open-ended rectangular waveguide. In particular, water penetration is determined from the differential measurement of reflection coefficient in the S-band before and after injection of water under pressure. Experimental results show a good correlation between the standard destructive test and the new method. Microwave measurements simplify the standard test avoiding the need of drilling out a sample from the structure and thus reducing both the cost and time needed in the analysis. 相似文献
40.
Anuj G. Agrawal Ashok Kumar Paraag S. Gide 《Drug development and industrial pharmacy》2015,41(4):594-604
Atorvastatin calcium (ATRC) is a poor water soluble drug used for treatment of hypercholesterolemia. This research is aimed to improve solubility and dissolution rate of ATRC by formulating into solid self-nanoemulsifying drug delivery system (S-SNEDDS) using N-methyl pyrrolidone (NMP) as cosolvent. Solubility of ATRC was determined in various vehicles. Ternary phase diagrams were constructed to identify stable nanoemulsion region. SNEDDS formulations were evaluated for robustness to dilution, thermodynamic stability study, % transmittance, self-emulsification time, globule size and transmission electron microscopy. The optimized liquid SNEDDS showed robust to all dilutions exhibiting no signs of phase separation or precipitation for 24?h. Liquid SNEDDS was transformed into S-SNEDDS using different adsorbents. Differential scanning calorimetry and scanning electron microscopy studies unravel the transformation of native crystalline state to amorphous state/solubilized state. In vitro dissolution study of S-SNEDDS was found to be significantly higher in comparison to that from plain drug, irrespective of pH (p?0.001). Furthermore, ex vivo permeation studies showed a 4.45-fold improvement in apparent permeability coefficient (Papp) from S-SNEDDS compared to plain drug. In conclusion, S-SNEDDS prepared using NMP as cosolvent provides an effective approach for improved oral delivery of ATRC. 相似文献