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141.
This note describes a method for producing cubic curves made up from Bézier functions on an oscilloscope screen using simple analogue techniques. Ruled surface patches are illustrated in a simple extension of the method. It also indicates how generalized Bézier patches could be produced. 相似文献
142.
Seyed Taghi Akhavan Niaki Mohammad Javad Ershadi Mahdi Malaki 《The International Journal of Advanced Manufacturing Technology》2010,48(1-4):283-296
Economic design of multivariate exponentially weighted moving average (MEWMA) control charts for monitoring the process mean vector involves determining economically the optimum values of the three control parameters: the sample size, the sampling interval between successive samples, and the control limits or the critical region of the chart. In the economic-statistical design, constraints (including the requirements of type I error probability and power) are added such that the statistical property of the chart is satisfied. In this paper, using the multivariate Taguchi loss approach, the Lorenzen–Vance (Technometrics 28:3-10, 1) cost function of implementing the control chart is extended to include intangible external costs along with the in-control average run length (ARL0) and out-of-control average run length (ARL1) as statistical constraints. A Markov chain model is then developed to estimate the ARLs and a genetic algorithm whose parameters are optimally obtained by design of experiments is used to solve the model and estimate the optimum values of the control chart parameters. A numerical example and a sensitivity analysis are provided to illustrate the solution procedure and to investigate the effects of cost parameters on the optimal designs. The results show that the proposed economic-statistical design of the chart has better statistical properties in comparison to the economic design while the difference between the costs is negligible. 相似文献
143.
Three Polyvinylidene fluoride (PVDF) different in molecular structure were used to produce nanocomposities films by cast extrusion with a particular emphasis on maximizing the β crystal phase content. The PVDF/clay compounding followed by cast film production was carried out through melt extrusion using a twin screw extruder equipped with a slit die. X‐ray diffraction (XRD) results showed that clay melt intercalation is almost similar for all three PVDFs. The XRD results also revealed that nanocomposite films from PVDF with branched chain structure (PVDFB) generated the greatest amount of β phase. FTIR spectroscopy measurements confirmed the XRD results but also revealed that significant stretching of the melt films at the die or rapid cooling would adversely affect the formation of β phase. The amount of β phase obtained based on nanoclay compounding was compared with that obtained from conventional method: stretching of molded PVDF film with initial α phase. Stretching of PVDF film at 60°C yielded pure β phase that means complete transformation of α to β. From mechanical properties, tensile tests were carried out on PVDF nanocomposite films to evaluate mechanical strength. PVDF with low molecular weight exhibited a very low strain at break while branched PVDF and high molecular weight PVDF could sustain more strain. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers 相似文献
144.
Neda Hashemipour Javad Karimi-Sabet Kazem Motahari Saeed Mahruz Monfared Younes Amini Mohammad Ali Moosavian 《中国化学工程学报》2019,27(8):1745-1755
In this article,numerical simulations are performed to investigate the performance of the thermal diffusion column for the separation of n-heptane/benzene mixture.The present work tried to optimize column by analyzing significant parameters such as feed flow rate,temperature and cut.In order to obtain the hydrodynamic and temperature and mass distribution inside thermal diffusion column,computational fluid dynamic(CFD) method is applied to solve the Navier-Stocks equations.Numerical simulations are conducted to study the main parameters in both stationary and time-dependent conditions.By using the separation work unit as a function of cut,the optimal cut for maximum SWU occurs within a limited range of 0.47-0.5 for feed rate between 0.5 and 4 g min-1.Our findings reveal that the optimum feed rate in the range of optimum cut is about 1 g min~(-1).In transient study,results show that the best cut for reaching to steady-state condition is θ=0.5. 相似文献
145.
146.
During rough rice drying, gradients of moisture content and glass transition temperature cause thermal and mechanical stresses inside the kernel. These stresses eventuate to kernel fissuring during the milling process. In this study, convective drying of Hashemi (long grain) rough rice was applied to investigate the effect of continuous and stepwise changes in air temperature on stress cracking index and process duration. Toward this objective, the concepts of glass transition and analysis of moisture contents distributions within the rice kernel were determined through a numerical modeling of mass transfer. For stepwise temperature change, the drying experiments were conducted at temperatures above the glass transition temperature. Results indicated that the stress cracking index under stepwise temperature change conditions (i.e., within the rubbery state) was reduced compared to the continuous mode probably due to a drip in the moisture content gradients created inside the kernels during the drying process. Moreover, the drying duration significantly was shortened when the kernel was dried within the rubbery state due to faster diffusion moisture within the kernel. 相似文献
147.
Acrylamide in Foods: Chemistry and Analysis. A Review 总被引:1,自引:0,他引:1
Javad Keramat Alain LeBail Carole Prost Nafiseh Soltanizadeh 《Food and Bioprocess Technology》2011,4(3):340-363
Acrylamide is a potential cause of a wide spectrum of toxic effects and is classified as probably “carcinogenic in humans”.
The discovery of acrylamide in human foods has given rise to extensive studies exploring its formation mechanisms and levels
of exposure and has spurred search into suitable analytical procedures for its determination in foodstuffs. However, the exact
chemical mechanisms governing acrylamide formation are not yet known and cheap, convenient, and rapid screening methods are
still to be developed. Acrylamide in food is produced by heat-induced reactions between the amino group of asparagine and
the carbonyl group of reducing sugars along with thermal treatment of early Maillard reaction products (N-glycosides). Similarly, the decarboxylated Schiff base and decarboxylated Amadori compounds of asparagine as well as the
Strecker aldehyde have been proposed as direct precursors and intermediates of acrylamide. Corresponding chromatographic methods
are used to determine various structural groups present in Maillard reaction model systems. Gas chromatography-mass spectrometry
and liquid chromatography with tandem mass spectrometry analysis are both acknowledged as the main, useful, and authoritative
methods for acrylamide determination. This review is an attempt to summarize the state-of-the-art knowledge of acrylamide
chemistry, formation mechanisms, and analytical methods. Special attention is given to comparison of different chromatographic
techniques, particularly the novel, simple, and low-cost methods of its determination. 相似文献
148.
A new, sensitive, and low cost solid-phase extraction method using pyridine-functionalized MCM-48 mesoporous silica for the extraction, pre-concentration, and electrothermal atomic absorption spectrometric determination of nickel and lead in food samples at ng mL−1 levels is described herein. The levels of nickel and lead in different types of vegetables grow in Shiraz–Iran and Rafsanjan–Iran were determined by electrothermal atomic absorption spectrometry. The use of two standard reference materials and also comparing the results to a standard reference procedure ensured the accuracy of this method. Factors, such as flow rate of extraction, and the type, pH, concentration, and volume of eluent, were appraised. The effect of various ions on recovery was also investigated. Detection limits of 0.11 and 0.14 ng mL−1 were obtained for lead and nickel, respectively. 相似文献
149.
Maryan Mohammad Moradinezhad Azhari Seyed Javad Amini-Valashani Majid 《Analog Integrated Circuits and Signal Processing》2022,110(3):569-581
Analog Integrated Circuits and Signal Processing - A new circuit-level methodology called input controlled leakage restrainer transistor (ICLRT) compatible with single threshold CMOS technology is... 相似文献
150.
This article deals with the evaluation of pressure drop and consumption of energy for a steady-state solvent extraction in a horizontal pulsed sieve-plate column, which are important for the design and optimization of the periodic-flow processes for industrial applications. In this study, the pressure drop and the position of loading points are investigated. Moreover, a mathematical evaluation on the energy consumption in the case of a pulsed flow is conducted, and besides the influence of pulsation intensity, the effect of geometrical parameters including the plate spacing and plate-free area is investigated as well. The results of this study are helpful for optimization of column geometry targeted to higher performance and lower energy consumption. 相似文献