行星轮爬壁机构的运动仿真与有限元模态分析

基于UG平台,以行星轮爬壁机构为研究对象,根据设计要求完成了其所有零部件的结构设计、三维建模及虚拟装配;应用ADAM S对其进行运动仿真,得到位移—时间、角速度—时间的关系曲线,为行星轮爬壁机构的动力学分析提供了科学依据;应用AN SY S软件进行了有限元模态分析,得到了前6阶模态和振型图,使机构的固有频率避开了共振频率,减小了机构的振动。     

Surfactant cleaning of ultrafiltration membranes fouled by whey

A polyethersulphone ultrafiltration membrane was prepared for concentration of whey. The membrane was fouled by whey and the effect of different cleaning agents on flux recovery of the fouled membrane was studied. The optimum cleaning procedure for membrane regeneration was elucidated. The results showed that a combination of surfactants (anionic, cationic and nonionic) may be employed as the optimum cleaning agent for maximum flux recovery. The fluorescence studies revealed that the cationic surfactant interact with proteins by breaking the intra‐chain hydrophobic bonding and providing electrostatic repulsion. Changing the alkyl chain from dodecyl to hexadecyl increases the interaction of surfactant–protein. Dodecyltrimethylammonium bromide (DTAB) provided a weak interaction with whey proteins than to tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB). All data obtained in this study support a surfactant–protein interaction in which hydrophobic forces play a dominant role. The nonionic surfactants poly(oxyethylene) isooctyl phenyl ether (TX‐100) and anionic surfactants SDS interact with amino acids in the inner protein structure thus denaturate tertiary protein structure and reduce hydrophobic interaction of proteins by membrane surface.     

The characteristics of an inclined crack in anisotropic paperboard under biaxial loading

In this paper, a fracture mechanics method was applied for the evaluation of crack behaviour in anisotropic paperboard subjected to biaxial uniform loading. The experiment was performed to determine the crack propagation angle and the fracture strength of paperboard under biaxial loading with the cruciform specimen optimized by FEM simulation. The effects of biaxial loads on the critical stress ratio and crack propagation angle for various inclination angles were investigated. The experimental results were compared with theoretical results, which were calculated by using the Normal Stress Ratio Criteria. The experimental results for crack propagation angle and critical stress show good agreement with theoretical results.     

Role of Ion Beam Irradiation and Annealing Efect on the Deposition of AlON Nanolayers by Using Plasma Focus Device

AlON nanolayers are synthesized on Al substrate by the irradiation of energetic nitrogen ions using plasma focusing. Samples are exposed to multiple(5, 10, 15, 20 and 25) focus shots. Ion energy and ion number density range from 80 keV to 1.4 MeV and 5.6×1019m-3 to 1.3×1019m-3, respectively. Moreover, the efect of continuous annealing(473 K and 523 K) on an AlN surface layer synthesized with 25 focus shots is also examined. The main features of the X-ray difraction(XRD) patterns with increasing focus shots are:(i) variation in the crystallinity of AlN along(111),(200) and(311) planes,(ii) increasing average crystallite size of AlN(111) plane, and(iii) stress relaxation observed in AlN(111) and (200) planes. The crystallinity of AlN surface layer is comparatively better at 473 K annealing temperature. A broadened difraction peak related to an aluminium oxide phase showing weak crystallinity is observed for 15 focus shots while non-bounded oxides are present in all other deposited layers. Raman and Fourier transform infrared spectroscopy(FTIR) analysis confirm the presence of AlN and Al2O3 for the surface layer annealed at 473 K temperature. Raman analysis shows that the overlapping of AlN and Al2O3 results in the development of residual stresses. Scanning electron microscope(SEM) results demonstrate that the formation of rounded grains(range from 20 nm to 200 nm) and variations in their microstructures features depend on the increasing number of focus shots. Decomposition of larger clusters into smaller ones is observed.     

Negatively Buoyant Flow Along Vertical Cylinders at High Rayleigh Numbers

Conditions that must be satisfied before the launch of a Space Transportation System (STS) include combinations of ambient temperature and wind speed that are intended to prevent ice formation on the External Tank (ET) and a local air temperature around the STS of 33°F (0.56°C) or less. Nineteen effluent gases are purged or vented from the STS into the launch pad environment, the most significant of these being the cold and negatively buoyant boil-off gaseous oxygen (GOX) from the oxygen tank. Vented into the ambient, this GOX can be wind-carried toward the STS, where it will cool the launch pad environment. This article described a combined three-dimensional (3D) and two-dimensional (2D) computational fluid dynamics (CFD) analysis that investigated this cooling effect. The results of this analysis for a 6-knot (3.09 m/s) west wind and an ambient temperature of 38°F (3.33°C) indicate that the GOX could cool, relative to the ambient, the local air in the vicinity of the STS and the surface of the east Redesigned Solid Rocket Motor (RSRM) by as much as 28°F (15.56°C) and 5 to 6°F (2.78 to 3.33°C), respectively. The large lengths associated with the ET and the east RSRM resulted in Rayleigh numbers that were one to three orders of magnitude larger than those found in literature.     

ARTIFICIAL NEURAL NETWORK MODELING OF APPLE DRYING PROCESS

Artificial neural network (ANN) modeling and several mathematical models were applied to predict the moisture ratio in an apple drying process. Four drying mathematical models were fitted to the data obtained from eight drying runs and the most accurate model was selected. Two sets of ANN modeling were also performed. In the first set, the data obtained from each pilot were modeled individually to compare the ANN predictions with the best mathematical model. In the second set of ANN modeling, the simultaneous effect of all the four input parameters including air velocity, air temperature, the thickness of apple slices and drying time was investigated. The results showed that the ANN predictions were more accurate in comparison with the best fitted mathematical model. In addition, none of the mathematical models are able to predict the effect of the four input parameters simultaneously, while the presented ANN model predicts this effect with a good precision.

PRACTICAL APPLICATIONS

Today, modeling of chemical engineering processes is widespread in the process industries. An accurate modeling results in a precise prediction of the products of a process which could be very expensive or even unsafe to evaluate by experimental experiences. Because artificial neural network modeling is more or less proved to be one of the best modelings against mathematical ones, we suggest it to be considered for industrial processes such as drying in the food industry.     

Investigation of nonionic diazo dye-doped polymer dispersed liquid crystal film

Sudan black B (SBB) was used to investigate as the nonionic diazo dye-doped in polymer dispersed liquid crystal (PDLC) display, by polymerization-induced phase separation (PIPS) method. The maximum absorbance, contrast ratio, dichroic ratio and the order parameter of nonionic diazo dye in nemetic host (TL203) were investigated using UV?CVis polarized spectroscopy. The orientation of the dye molecules was controlled by electric field, which enabled the contrast ratio of the dye to be obtained by electrically switching. The change occurring on droplet morphologies and electro-optical properties of PDLC film with the change in contents of Sudan black dye and liquid crystals (LC) contents was investigated. We found an increase in LC droplet sizes with the increase of diazo dye and LC contents. Moreover the addition of small amount of nonionic diazo dye reduced the threshold voltage (V $_{\boldsymbol{\rm th}})$ , increased off-state transmittance, enhanced the contrast ratio and decreased the response time of dye-doped PDLC. Additionally the change in transition temperature of LC and changes in LC droplet morphologies with the addition of dye were also observed. Such changes were observed with the images taken by polarized optical microscope (POM). The detail discussions on such behaviours were also made.     

Buckling analysis of partially corroded steel plates with irregular surfaces

Corrosion is a long-term, inevitable process, lessens the thickness and load carrying capacity of structures. Old steel structures are more vulnerable to buckling, yielding and fracture due to corrosion. In lieu of a detailed analysis, average thickness assumption is employed for general type of corrosion. However, the estimation of load carrying capacity reduction of corroded structures typically need a much higher level of accuracy, since the actual corroded plates would have irregular surfaces. The objective of this article is to determine the effect of general corrosion on reduction of elastic buckling strength of both-sided partially corroded plates with irregular surfaces. Eigenvalue analysis using finite element method is employed for Euler stress calculation of corroded plates. The effects of different influential parameters are investigated and it is found that, aspect ratio of plate, location of corroded area, standard deviation of thickness diminution and concentration of corrosion have influence on reduction of elastic buckling strength. Reduction of elastic buckling strength is very sensitive to the amount of corrosion loss. The higher the amount of corrosion loss, the more reduction of elastic buckling strength.     

SENSORY ACCEPTABILITY OF A DEEP-FRIED CARROT CHIP PRODUCT AS EVALUATED BY AMERICAN AND SOUTHEAST ASIAN CONSUMER PANELS

Following development of deep‐fried carrot chips, a high provitamin A carotenoid‐snack, consumer acceptances for color, uniformity, overall appearance, odor, saltiness, sweetness, overall flavor, crispiness, oiliness, overall texture, and overall acceptability of the product were evaluated. Eighty‐nine consumer panelists consisting of Americans from the Plains states of the United States (n = 45) and Southeast Asians (n = 44), males and females,19–45 years, participated in this study. Color, uniformity, and odor were rated as good. Saltiness and sweetness were rated as nearly about right. Crispiness was rated as good, and oiliness as slightly oily. Generally, the product was acceptable to both types of consumer panelists, American and Southeast Asian, as shown by their ratings on overall appearance, overall flavor, overall texture, and overall acceptability. The differences in acceptance among country, gender, and country X gender groups were statistically not significant (P0.05).