A new microcellular injection molding process for polycarbonate using water as the physical blowing agent

This article presents a new process for producing microcellular injection molded plastic parts using water as the physical blowing agent and micro‐scaled particles as the cell nucleating agents. Distilled water with dissolved salt were fed through the hopper of an injection molding machine at a preset rate and mixed with polycarbonate (PC) in the machine barrel. Microcellular PC tensile bars were then injection molded with different shot volumes, water/salt solution feed rates, and salt concentrations. Tiny salt crystals of 10–20 μm recrystallized during molding acted as nucleating agents in the PC foamed parts. The surface roughness, mechanical properties, and microstructure of the solid and foamed parts were measured and compared with microcellular injection molded parts using supercritical fluid (SCF) nitrogen as the physical blowing agent. At a similar weight reduction of about 10%, the water foamed PC parts have a smooth surface comparable to that of solid injection molded parts. They also possess similar, if not better, mechanical properties compared to SCF nitrogen foamed PC parts. Without the nucleating agent, PC/water foamed parts exhibit much larger and fewer bubbles within the molded parts. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Study the effect of conductive fillers on a secondary Zn electrode based on ball-milled ZnO and Ca(OH)2 mixture powders

The active materials of the secondary Zn electrode containing a mixture powder of zinc oxide (ZnO) and calcium hydroxide (Ca(OH)₂) powders were prepared by a ball-milled method. The characteristic properties of active materials of ball-milled ZnO + Ca(OH)₂ mixture powders were examined by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) system, X-ray diffraction (XRD) analysis, and micro-Raman spectroscopy. The prepared Zn powder electrodes were by using the ball-milled active materials powder +2 wt.% highly electronic conductive fillers, i.e., nano-copper or carbon nanotubes (CNTs) powder. The electrochemical properties of the secondary Zn electrodes without and with the conductive fillers were studied by using cyclic voltammetry (CV) and galvanostatic charge/discharge tests. It was found that the charge/discharge properties of the secondary Zn electrode could be improved when the nano-sized conductive fillers were added into the electrode. In fact, it may be due to the formation of a better electronic conduction path in the electrode matrix. In particular, it was found that the best electrochemical properties were the secondary Zn electrode with 2 wt.% nano-copper fillers. According to the results, it is demonstrated here that the CV method is a quick technique to effectively evaluate the performance of a secondary Zn electrode.     

A genetic algorithm for sequential part assignment for PCB assembly

We present a genetic algorithm for printed circuit board (PCB) assembly, which simultaneously solves the feeder assignment and component sequencing problems. The algorithm uses a unique gene selection procedure that increases the convergence rate without degrading the solution quality. We have compared the performance of our algorithm with existing approaches and have demonstrated improved performance. We have also implemented the algorithm on a Quad IIIc insertion machine for surface mount components. The resulting suboptimal assembly times estimated by the algorithm have been found to be close to the actual optimal values.     

H2O2 Mediates VEGF- and Flow-Induced Dilations of Coronary Arterioles in Early Type 1 Diabetes: Role of Vascular Arginase and PI3K-Linked eNOS Uncoupling

In diabetes, the enzyme arginase is upregulated, which may compete with endothelial nitric oxide (NO) synthase (eNOS) for their common substrate L-arginine and compromise NO-mediated vasodilation. However, this eNOS uncoupling can lead to superoxide production and possibly vasodilator hydrogen peroxide (H₂O₂) formation to compensate for NO deficiency. This hypothesis was tested in coronary arterioles isolated from pigs with 2-week diabetes after streptozocin injection. The NO-mediated vasodilation induced by flow and VEGF was abolished by NOS inhibitor L-NAME and phosphoinositide 3-kinase (PI3K) inhibitor wortmannin but was not affected by arginase inhibitor N^ω-hydroxy-nor-L-arginine (nor-NOHA) or H₂O₂ scavenger catalase in control pigs. With diabetes, this vasodilation was partially blunted, and the remaining vasodilation was abolished by catalase and wortmannin. Administration of L-arginine or nor-NOHA restored flow-induced vasodilation in an L-NAME sensitive manner. Diabetes did not alter vascular superoxide dismutase 1, catalase, and glutathione peroxidase mRNA levels. This study demonstrates that endothelium-dependent NO-mediated coronary arteriolar dilation is partially compromised in early type 1 diabetes by reducing eNOS substrate L-arginine via arginase activation. It appears that upregulated arginase contributes to endothelial NO deficiency in early diabetes, but production of H₂O₂ during PI3K-linked eNOS uncoupling likely compensates for and masks this disturbance.     

Distributed architecture for real-time coordination of bus holding in transit networks

A distributed control approach based on multiagent negotiation is presented, wherein stops and buses act as agents that communicate in real-time to achieve dynamic coordination of bus dispatching at various stops. The negotiation between a Bus Agent and a Stop Agent is conducted based on marginal cost calculations. We present optimality conditions for the formulated problem, using a negotiation algorithm, which we derive, to coordinate bus holding at various stops. A comparison between the negotiation algorithm and other simple bus control strategies such as on-schedule and even-headway strategies made through simulations verifies the robustness and efficiency of our negotiation strategy to different transit environments, involving both stationary passenger arrivals as well as a variety of nonstationary passenger arrivals.     

Response of multilayered composite laminates to dynamic surface loads

A theoretical investigation of the response of multilayered composite laminates to concentrated and distributed dynamic surface loads is carried out. Each layer of the laminate is assumed to be transversely isotropic and dissipative with arbitrarily oriented symmetry axis. The dissipative property of the material is modeled approximately through the introduction of a frequency-dependent damping function. A multiple transform technique is used to calculate the spectra and time histories of the displacements and stresses produced by a variety of dynamic loads, and the quantitative features of the waves produced in the laminate are determined. The methodology developed in this work is expected to be useful in the prediction of the response of composite laminates to impact loads and also in the characterization of acoustic emission (AE) sources in these materials under static and dynamic loads.     

Rapid Single-Round Pool Testing of Infectious Disease Enabled by Multicolor Digital Melting PCR

Pooled nucleic acid amplification test is a promising strategy to reduce cost and resources for screening large populations for infectious disease. However, the benefit of pooled testing is reversed when disease prevalence is high, because of the need to retest each sample to identify infected individual when a pool is positive. Split, Amplify, and Melt analysis of Pooled Assay (SAMPA) is presented, a multicolor digital melting PCR assay in nanoliter chambers that simultaneously identify infected individuals and quantify their viral loads in a single round of pooled testing. This is achieved by early sample tagging with unique barcodes and pooling, followed by single molecule barcode identification in a digital PCR platform using a highly multiplexed melt curve analysis strategy. The feasibility is demonstrated of SAMPA for quantitative unmixing and variant identification from pools of eight synthetic DNA and RNA samples corresponding to the N1 gene, as well as from heat-inactivated SARS-CoV-2 virus. Single round pooled testing of barcoded samples with SAMPA can be a valuable tool for rapid and scalable population testing of infectious disease.     

移动通信的技术演变研究趋势之全景展现

＂Without an appropriate research setting, a study cannot be qualified as a reasonable piece＂, this notion is manifested in the methodological polices. In this research, we attempt to examine previous studies within the scope of technology evolution and market perception in telecommunication industry through extracting research structures, methodologies, corresponding variables, and processing methods. A general process of social scientific research is adopted to analyze eighty-four selected papers; and simultaneously, the framework for doing this analysis is established, as well. In this manner, we inspect the subjects and the issues in these papers according to product types, academic domains, and divisions of technological evolution （from 1G to 4G）. Then, their research designs are anatomized into the key dimensions of general research conventions. This research eventually provides an entire picture of a research scenario for mobile telecommunication industry; and apparently, this framewbrk can help scholars to establish specific tendencies for academic scenarios in future research plans. Also, we propose the main streams and emerging issues can be expected to engage in the future within both theacademic and the operational fields.     

Robust smart‐card‐based remote user password authentication scheme

Smart‐card‐based remote user password authentication schemes are commonly used for providing authorized users a secure method for remotely accessing resources over insecure networks. In 2009, Xu et al. proposed a smart‐card‐based password authentication scheme. They claimed their scheme can withstand attacks when the information stored on the smart card is disclosed. Recently, Sood et al. and Song discovered that the smart‐card‐based password authentication scheme of Xu et al. is vulnerable to impersonation and internal attacks. They then proposed their respective improved schemes. However, we found that there are still flaws in their schemes: the scheme of Sood et al. does not achieve mutual authentication and the secret key in the login phase of Song's scheme is permanent and thus vulnerable to stolen‐smart‐card and off‐line guessing attacks. In this paper, we will propose an improved and efficient smart‐card‐based password authentication and key agreement scheme. According to our analysis, the proposed scheme not only maintains the original secret requirement but also achieves mutual authentication and withstands the stolen‐smart‐card attack. Copyright © 2012 John Wiley & Sons, Ltd.     

Direct Conversion of Single‐Layer SnO Nanoplates to Multi‐Layer SnO2 Nanoplates with Enhanced Ethanol Sensing Properties

Direct conversion of single‐layer SnO nanoplates to multi‐layer SnO₂ nanoplates is achieved by annealing in an O₂ ambient at 700 °C. For 50 ppm ethanol, the sensitivities of the multi‐layer SnO₂ nanoplates are more than double that of single‐layer SnO₂ nanoplates, which are also formed from the single‐layer SnO. The higher sensitivity of the multi‐layer nanoplates is attributed to their larger surface/volume ratio. The facile fabrication of interconnected multi‐layer SnO₂ nanoplates at low temperature directly on a Si substrate and sensing chip without the aid of catalysts offers vast advantages over competing methods for the fabrication of high‐sensitivity SnO₂ sensors.