Tool path generation for free form surfaces using Bézier curves/surfaces

Presented in this paper is a tool path generation method for multi-axis machining of free-form surfaces using Bézier curves and surfaces. The tool path generation includes two core steps. First is the forward-step function that determines the maximum distance, called forward step, between two cutter contact (CC) points with a given tolerance. The second component is the side step function which determines the maximum distance, called side step, between two adjacent tool paths with a given scallop height. Using the Bézier curves and surfaces, we generate cutter contact (CC) points for free-form surfaces and cutter location (CL) data files for post processing. Several parts are machined using a multi-axis milling machine. As part of the validation process, the tool paths generated from Bézier curves and surfaces are analyzed to compare the machined part and the desired part.     

Efficient and secure source authentication scheme for multicast user authentication

Multicast technology application has been widely utilized in broadband internet. Source authentication is one of the most needs for many multicast applications transferring real-time information such as stream video and online news. Because multicast current services provided to the group members are changed dynamically, data transferring by a group member is not used by the recipient. In order to verify the identity of the sender who sent the packet and to make sure that the data have not been tampered, an optimized source authentication scheme has been proposed to transfer the authentication information not to the next-door packet. The proposed method for multiple packets authenticates the source with a limited number of electronic signatures. The proposed method can reduce overhead compared to the method by adding a digital signature for every packet. In addition, by sending the generated electronic signature to the first packet and the last packet, it prevents the loss of consecutive packets, as well as a source authentication can be provided in real-time services.     

An approach to multi-criteria assembly sequence planning using genetic algorithms

This paper focuses on multi-criteria assembly sequence planning (ASP) known as a large-scale, time-consuming combinatorial problem. Although the ASP problem has been tackled via a variety of optimization techniques, these techniques are often inefficient when applied to larger-scale problems. Genetic algorithm (GA) is the most widely known type of evolutionary computation method, incorporating biological concepts into analytical studies of systems. In this research, an approach is proposed to optimize multi-criteria ASP based on GA. A precedence matrix is proposed to determine feasible assembly sequences that satisfy precedence constraints. A numerical example is presented to demonstrate the performance of the proposed algorithm. The results of comparison in the provided experiment show that the developed algorithm is an efficient approach to solve the ASP problem and can be suitably applied to any kind of ASP with large numbers of components and multi-objective functions.     

CHANGES IN MOLECULAR SPECIES COMPOSITIONS OF GLYCEROPHOSPHOLIPIDS IN THE ADDUCTOR MUSCLE OF THE GIANT EZO SCALLOP PATINOPECTEN YESSOENSIS DURING FROZEN STORAGE

Changes in lipid components, particularly glycerophospholipids, in the adducto; muscle of giant ezo scallop during storage at −20C were investigated. During storage, the contents of total lipids (TL) and polar lipids (PL) decreased, but that of nonpolar lipids increased. Thiobarbituric acid reactive substances and peroxide values of the TL increased with duration of storage. Glycerylphosphorylcholine (GPC) and glycerylphosphrylethanolamine (GPE) decomposed considerably during storage, and decreased by 50% and 15% of the initial content, while lyso-PC (LPC) and free fatty acids (FFA) increased, respectively. The percentages of polyunsaturated fatty acids (PUFAs) such as 20:5n-3 and 22:6n-3 in the TL and PL during storage decreased, however, those of the PUPAs in the NL increased. Diacylglycerylphosphorylcholine (diacyl-GPC) and diacylglycerylophosphorylethanolamine (diacyl-GPE), major components in the GPC and GPE subclasses, showed a marked decrease with duration of storage. Particularly, diacyl-GPC decreased by 68% of the initial contents of the PL. In the alkenylacyl-GPE and diacyl-GPC, the percentages of the molecular species having longer hydrocarbon chains on the sn-l positions of glycerol moieties decreased at     

Tocopherols, Retinol and Carotenes in Chicken Egg and Tissues as Influenced by Dietary Palm Oil

Incorporation of palm oil (PO) increased the α-and γ-tocotrienol content of eggs, liver, meat and adipose tissue. Total tocotrienols were higher in eggs, liver and adipose tissue of hens fed 1.5% PO than those fed 3.5% PO. An increase in retinol was observed in the eggs, liver and dark meat of hens fed PO diet. Feeding diets containing 1.5 or 3.5% PO increased the α-and β- carotenes in eggs and liver tissue. However, carotenoids were not detected in white meat, dark meat or adipose tissue. Dark meat incorporated higher levels of tocopherols and retinol than white meat. The diets had no effect on egg or yolk weight. Egg yolks from hens fed PO had higher yolk color than those without PO. Addition of tocopherol mix in the control diet increased total tocopherol content in all tissues.     

Fracture behaviors of nanowire-coated metal/polymer systems under mode-I loading condition

In previous works, two kinds of nanowires were formed on the surface of a copper-based leadframe by immersing them in two kinds of hot alkaline solutions. The nanowire-coated copper-based leadframe sheets were molded with epoxy molding compound (EMC), and the molded bodies were machined to form sandwiched double-cantilever beam specimens to measure the fracture toughness of the nanowire-coated leadframe (metal)/EMC (polymer) interfaces under quasi-mode-I loading condition. After the adhesion test, the fracture surfaces were analyzed to clarify the failure path by using various equipments. The present work attempted to correlate the failure path to adhesion strength by using a simple adhesion model.     

固体氧化物燃料电池离子- 电子混合传导性Ni/ScSZ 燃料极的制备以及性能分析

在薄膜固体氧化物燃料电池中,为增加发生电化学反应的三相界面面积,燃料极和空气极通常制备成离子-电子混合传导性质的多孔形态。该研究将燃料极电化学反应(氢氧化反应)的催化剂——镍(Ni)和氧离子传导性好的氧化钪稳定的氧化锆(ScSZ)混合制备成离子-电子混合传导燃料极。实验结果显示,与纯 Ni 燃料极相比,所制备的 Ni/ScSZ 燃料极因其三相界面面积的增加,可显著降低极化电阻,但同时欧姆电阻也显著增加,从而最终导致燃料电池单池性能总体下降。     

Strengthening and Toughening Mechanisms of Ceramic Nanocomposites

Crack-tip bridging by particles is considered to be one of the primary strengthening mechanisms of ceramic nanocomposites. Small, brittle particulate inclusions have been shown to cause crack-tip bridging at short distances behind the crack tip. This mechanism leads to modest toughness but a very steep R -curve, and it is the latter that produces the very high fracture strength of the ceramic nanocomposite. Localized high residual stress around the particles (particularly in the case of silicon carbide-alumina material) causes the strengthening mechanism to operate effectively, even at a small volume fraction of 5%. The present study predicts the magnitude of the toughness increase and the extent of R -curve behavior for the nanocomposite.