Adaptation of a 2-D Clinostat for Simulated Microgravity Experiments with Adherent Cells

The fast-rotating 2-D clinostat, a ground-based facility for investigations in simulated microgravity, is mainly used for experiments with cell suspensions. Here, we describe the adaptation of a 2-D clinostat for adherent cell investigations using commercially available slide flasks. As a gradient of residual accelerations is present in the slide flasks during clinorotation, the range of maximal g-values has to be adjusted to the investigated cells and type of analysis. For gene expression analysis, a harvesting slide chamber was constructed, allowing collection of cells exposed to defined g-values. Using this slide chamber, human 1F6 melanoma cell line, exposed in the ranges of ≤0.012 g, ≤0.024 g, or ≤0.036 g for 24 h, was harvested and the respective mRNA levels of guanylyl cyclase A (GC-A), an enzyme catalyzing cyclic GMP synthesis, were determined by real-time quantitative PCR analysis. Our results show that the down-regulation of GC-A mRNA levels in 1F6 melanoma cells depends on the residual acceleration values with a maximal reduction at ≤0.012 g. We further used the slide flasks by the clinorotation of murine RAW 264.7 macrophage cell line for f-actin analysis. The laser scanning microscopy images of cells exposed to g-values of ≤0.006 g for 1 h show an increase in the cell size of clinorotated cells, but no rearrangement in the f-actin filament system compared to static 1-g controls. Thus, 2-D clinostats equipped with slide flasks can be used for adherent cell experiments, however, the maximal g-values have to be carefully considered.     

The Bonn Criteria: Minimal Experimental Parameter Reporting for Clinostat and Random Positioning Machine Experiments with Cells and Tissues

Published reports on studies in clinostats and random positioning machines frequently do not include adequate operational data on physical parameters of the culture device or cell culture conditions. This failure to report minimum physical and chemical data on how experiments are performed makes it impossible to determine specific hardware utilization or to calculate forces delivered. This makes experimental comparisons difficult and isolation of critical methodological differences between investigational results impossible. A minimum set of parameters to be reported in clinostat or random positioning machines is proposed to be known as the Bonn criteria. For random positioning machine experiments, the minimum experimental parameters to be reported should include angular velocity of rotation, highest angular acceleration, operating mode (random, centrifuge, or clinostat in rpm or freely programmable mode). For both clinostat and random positioning machines, experimental reporting should include the properties of the culture vessel, culture media and carrier beads. These should also include dimensions and rotation speed of vessel, chemical consistency including density and viscosity of media, size, density, and porosity of beads, size, density, and porosity of cells, whether cells are motile or non-motile, density of beads with cells attached, as well as time of rotation, nature of controls, operating temperature, and gas content.     

Experimental Investigation to Optimize Tool Life and Surface Roughness in Inconel 718 Machining

In addition to the cutting conditions, the surface quality is also affected significantly by a worn tool in machining processes. Identification of the desirable tool life so that the surface quality is maintained within a desirable level is an essential task, especially in the machining of hard materials. In this paper, an optimal tool life and surface quality were identified in the turning operation of Inconel 718 Superalloy by means of experimental investigations and intelligent methods. First, the effect of machining time (MT) at the different cutting parameters was widely investigated on the surface roughness using the neural network model. Then, the modified Non-dominated Sorting Genetic Algorithm (NSGA) was implemented to optimize tool life and surface roughness. For this purpose, a new approach was implemented and the MT was taken into account as the input and output parameters during the optimization. Finally, the results of optimization were classified and the suitable states of the machining outputs were found. The results indicate that the implemented strategy in this paper provides an efficient approach to determine a desirable criterion for tool life estimation in machining processes.     

工科院校愉快式双语教学方法探微

文章讨论了工科类院校运用愉快双语教学的最佳方法和手段,并就如何创造最佳的环境来激发学生,使他们既掌握专业知识又能培养学习英语的兴趣作了有益的尝试.     

An Analytical Approach to Optimize NC Tool Path Planning for Face Milling Flat Convex Polygonal Surfaces

CAD/CAM systems currently generate the tool cutter path for many NC operations. However no mathematical model is available for computing an optimal tool cutter path for face milling. By utilizing such a model, the minimum length of cut can be identified for face milling flat surfaces. In this paper, the authors present an analytical procedure from which the optimal cutting path may be derived.     

浅谈现代教育技术与大学物理实验整合

文章首先对大学物理的设计性实验提出了一些构想和改革建议;然后就现代教育技术与大学物理实验整合提出了一些改革措施,一方面要丰富网络资源,另一方面对开发和开设部分仿真性实验提出一些建议;最后对大学物理实验的考试提出了一些建议.     

A Genetic-Algorithms-Based Multiobjective Approach for a Three-Dimensional Guillotine Cutting Problem

A novel method based upon multiobjective genetic algorithms is presented for simultaneously minimizing the amount of scrap and the number of turns in a three-dimensional guillotine cutting. The concept of best orientation between two cuboids has been used to improve the efficiency of the minimization process. Two different evolutionary algorithms have been used and also compared for effectiveness.     

改进试验设计法优化电动汽车按时间租赁利润

针对电动汽车租赁服务系统,结合顾客到达率瓶颈、顾客依据感知价值选择服务的特征及电动汽车特性,构建了按时间收费利润模型。以利润最大化为目标,采用改进试验设计法求解模型。先采用传统试验设计法求出最佳利润及因素取值组合,确定利润函数在最佳因素取值组合处的单调性,进而更精确地判断可取得最优利润的因素水平取值区间,根据精确化后的取值区间并保持各因素水平数不变,采用试验设计法再次优化利润。实例分析比较了试验设计法改进前后所得利润优化结果,显示改进后方法得出的利润显著更优,验证了模型的有效性和实用性。     

Bayesian Approach to Assessing Uncertainty and Calculating a Reference Value in Key Comparison Experiments

International experiments called Key Comparisons pose an interesting statistical problem, the estimation of a quantity called a Reference Value. There are many possible forms that this estimator can take. Recently, this topic has received much international attention. In this paper, it is argued that a fully Bayesian approach to this problem is compatible with the current practice of metrology, and can easily be used to create statistical models which satisfy the varied properties and assumptions of these experiments.     

三维动态八结点有限单元的建立及理论推导

本文为扩大动态有限单元法的应用范围,在 J.S.Przemieniecki 和 K.K.Gupta 等人的研究基础上建立了一种新的三维动态八结点单元,并对其进行了理论推导。通过算例验证了本文理论结果的正确性。     

Bayesian Inference for a New Class of Distributions on Equivalence Classes of Three-Dimensional Orientations With Applications to Materials Science

Experiments in materials science investigating cubic crystalline structures often collect data which are in truth equivalence classes of crystallographically symmetric orientations. These intend to represent how lattice structures of particles are orientated relative to a reference coordinate system. Motivated by a materials science application, we formulate parametric probability models for “unlabeled orientation data.” This amounts to developing models on equivalence classes of three-dimensional rotations. We use a flexible existing model class for random rotations (called uniform-axis-random-spin models) to induce probability distributions on the equivalence classes of rotations. We develop one-sample Bayesian inference for the parameters in these models, and compare this methodology to some likelihood-based approaches. We also contrast the new parametric analysis of unlabeled orientation data with other analyses that proceed as if the data have been preprocessed into honest orientation data. Supplementary materials for this article are available online.     

Use of X-Y Plots and Simple DOE Approach to Optimize Settings on Automated Test Equipment

Statistical designed experiments can be used to verify that test equipment is performing optimally. This case dealt with the calibration of a pressure decay leak test for plastic poppets used in anti-lock breaking systems. Calibration of most equipment requires several setup parameters. These parameters can be optimized by running trials at various setup levels. Choosing a response variable that measures either repeatability or accuracy may help testers ensure that acceptable parts are being passed and rejects are being failed, which can have a significant effect on the bottom line. Final setups can be verified by measuring against known standards.     

Three-Dimensional Static and Dynamic Analysis of a Composite Cruciform Structure Subjected to Biaxial Loading: A Discontinuum Approach

A three-dimensional structural integrity analysis using the eXtended Finite Element Method (XFEM) is considered for simulating the crack behaviour of a chopped fibre-glass-reinforced polyester (CGRP) cruciform specimen subjected to a quasi-static tensile biaxial loading. This is the first time this problem is accomplished for computing the stress intensity factors (SIFs) produced in the biaxially loaded area of the cruciform specimen. A static crack analysis for the calculation of the mixed-mode SIFs is carried out. SIFs are calculated for infinite plates under biaxial loading as well as for the CGRP cruciform specimens in order to review the possible edge effects. A ratio relating the side of the central zone of the cruciform and the crack length is proposed. Additionally, the initiation and evolution of a three-dimensional crack are successfully simulated. Specific challenges such as the 3D crack initiation, based on a principal stress criterion, and its front propagation, in perpendicular to the principal stress direction, are conveniently addressed. No initial crack location is pre-defined and an unique crack is developed. Finally, computational outputs are compared with theoretical and experimental results validating the analysis.     

经络科学对生命调节现象的理论概括及数学表达

总结50年实验，证明人体经络通路现象具有生物学客观真实性，可能有助于进一步总结中华传统医药学宝贵经验；概括经络科学对人体生命调节现象的理论性概念，对与生命共存的人体经络循行给出数学表述。     

A Statistical Experimental Approach to Cosolvent Formulation of a Water-Insoluble Drug

19-Nor-1α,25-dihydroxyvitamin D₂, an analog of vitamin D₂, is a nonpolar compound with limited solubility in water. An injectable solution was formulated using a cosolvent system consisting of water, ethanol, and propylene glycol. A statistical response surface approach was used to evaluate the effect of these three solvents on the solubility of the drug (25°C) in the ternary cosolvent system. The data generated from five selected formulations were used to develop a multiple linear regression model that quantitatively defines the solubility of the drug as a function of the cosolvent composition. Close agreement was found between the experimental data and data calculated using the model. The capability of this model to predict drug solubility in cosolvent systems with various combinations of the three solvents was also verified.     

An Experimental and Computational Approach to the Development of ZnO Nanoparticles that are Safe by Design

Zinc oxide nanoparticles have found wide application due to their unique optoelectronic and photocatalytic characteristics. However, their safety aspects remain of critical concern, prompting the use of physicochemical modifications of pristine ZnO to reduce any potential toxicity. However, the relationships between these modifications and their effects on biology are complex and still relatively unexplored. To address this knowledge gap, a library of 45 types of ZnO nanoparticles with varying particle size, aspect ratio, doping type, doping concentration, and surface coating is synthesized, and their biological effects measured. Three biological assays measuring cell damage or stress are used to study the responses of human umbilical vein endothelial cells (HUVECs) or human hepatocellular liver carcinoma cells (HepG2) to the nanoparticles. These experimental data are used to develop quantitative and predictive computational models linking nanoparticle properties to cell viability, membrane integrity, and oxidative stress. It is found that the concentration of nanoparticles the cells are exposed to, the type of surface coating, the nature and extent of doping, and the aspect ratio of the particles make significant contributions to the cell toxicity of the nanoparticles tested. Our study shows that it is feasible to generate models that could be used to design or optimize nanoparticles with commercially useful properties that are also safe to humans and the environment.     

Developing a Systems Approach to Engineering Problem Solving and Design of Experiments in a Racecar‐Based Laboratory Course

A capstone mechanical engineering laboratory course is being implemented at the University of South Carolina that develops the student's abilities to analyze complex mechanical and thermal systems, to design experiments, and to develop their professional skills. The course is based upon an integrated sequence of laboratory experiments on a Legends‐class racecar. This vehicle is chosen as the system of study because it provides opportunities for the students to apply the spectrum of their mechanical engineering knowledge. It's also exciting to the students. As the students progress through the series of experiments, they are increasingly involved in experimental design (selecting sensors, sensor locations and experimental operating conditions). The course culminates in a truly open‐ended design of an experiment of their choosing. This course development project is supported by the National Science Foundation's Instrumentation and Laboratory Improvement Program, the NSF's Course, Curriculum and Laboratory Improvement Program, and the University of South Carolina. This paper describes the work in progress.     

An Algorithm for a Class of Three-Dimensional Assignment Problems Arising in Scheduling Applications

A scheduling problem often arising in trade shows and conventions is modeled as a planar three-dimensional assignment problem having a special cost structure. A polynomial-time algorithm for solving this case of the planar assignment problem is presented. The algorithm can also be used to solve heuristically a variation of the m-traveling salesman problem which arises as a secondary problem in the original scheduling application. Computational experience with data from a tourism industry convention scheduling problem is given.