A Novel Energy Efficient Key Distribution Scheme for Mobile WiMAX Networks

Wireless Personal Communications - In Mobile WiMAX, a Base Station (BS) delivers security keys to Mobile Stations (MSs) through a key distribution scheme to guarantee security and access control....     

Modulation of Gut Microbiota in the Management of Metabolic Disorders: The Prospects and Challenges

The gut microbiota plays a number of important roles including digestion, metabolism, extraction of nutrients, synthesis of vitamins, prevention against pathogen colonization, and modulation of the immune system. Alterations or changes in composition and biodiversity of the gut microbiota have been associated with many gastrointestinal tract (GIT) disorders such as inflammatory bowel disease and colon cancer. Recent evidence suggests that altered composition and diversity of gut microbiota may play a role in the increased prevalence of metabolic diseases. This review article has two main objectives. First, it underscores approaches (such as probiotics, prebiotics, antimicrobial agents, bariatric surgery, and weight loss strategies) and their prospects in modulating the gut microbiota in the management of metabolic diseases. Second, it highlights some of the current challenges and discusses areas of future research as it relates to the gut microbiota and metabolic diseases. The prospect of modulating the gut microbiota seems promising. However, considering that research investigating the role of gut microbiota in metabolic diseases is still in its infancy, more rigorous and well-designed in vitro, animal and clinical studies are needed.     

Fermentative hydrogen production from indigenous mesophilic strain Bacillus anthracis PUNAJAN 1 newly isolated from palm oil mill effluent

In the present study, a new mesophilic bacterial strain, identified as Bacillus anthracis strain PUNAJAN 1 was isolated from palm oil mill effluent (POME) sludge, and tested for its hydrogen production ability. Effect of physico-chemical factors such as temperature, initial pH, nitrogen source and carbon sources were investigated in order to determine the optimal conditions for hydrogen production. The maximum hydrogen yield of 2.42 mol H₂/mol mannose was obtained at 35 °C and initial pH of 6.5. Yeast and mannose were used as the main carbon and nitrogen sources respectively in the course of the hydrogen production. Apart from synthetic substrate, specific hydrogen production potentials of the strain using POME was calculated and found to be 236 ml H₂/g chemical oxygen demand (COD). The findings of this study demonstrate that the indigenous strain PUNAJAN 1 could be a potential candidate for hydrogen using POME as substrate.     

Genetic Programming to Predict Bridge Pier Scour

Bridge-pier scour is a significant problem for the safety of bridges. Extensive laboratory and field studies have been conducted examining the effect of relevant variables. This note presents an alternative to the conventional regression-based equations (HEC-18 and regression equation developed by the writers), in the form of artificial neural networks (ANNs) and genetic programming (GP). There had been 398 data sets of field measurements that were collected from published literature and were used to train the network or evolve the program. The developed network and evolved programs were validated by using the observations that were not involved in the training. The performance of GP was found more effective when compared to regression equations and ANNs in predicting the scour depth at bridge piers.     

Development of monitoring system for FTTH‐PON using combined ACS and SANTAD

This paper proposes a design of Access Control System (ACS) for fiber‐to‐the‐home passive optical network (FTTH‐PON). Our design works on a standard local area network using a specially designed hardware interfaced with a microcontroller integrated Ethernet to monitor the status of optical signals flow and provides the restoration against fiber failures/faults in FTTH‐PON. We also introduce the centralized troubleshooting system by means of Smart Access Network Testing, Analyzing, and Database (SANTAD). ACS is the subsystem that controls the troubleshooting mechanism carried out by SANTAD. This design will be implemented together with optical line terminal (OLT) at central office (CO) to centralized monitoring and for controlling each optical fiber line's status as well as detecting any failure that occurs in the network system downwardly from CO toward multiple optical network units at different customer residential locations. The scope of this discussion highlighted only the monitoring and controlling instead of the restoration scheme offered. Copyright © 2009 John Wiley & Sons, Ltd.     

Effect of Fiber Esterification on Fundamental Properties of Oil Palm Empty Fruit Bunch Fiber/Poly(butylene adipate-co-terephthalate) Biocomposites

A new class of biocomposites based on oil palm empty fruit bunch fiber and poly(butylene adipate-co-terephthalate) (PBAT), which is a biodegradable aliphatic aromatic co-polyester, were prepared using melt blending technique. The composites were prepared at various fiber contents of 10, 20, 30, 40 and 50 wt% and characterized. Chemical treatment of oil palm empty fruit bunch (EFB) fiber was successfully done by grafting succinic anhydride (SAH) onto the EFB fiber surface, and the modified fibers were obtained in two levels of grafting (low and high weight percentage gain, WPG) after 5 and 6 h of grafting. The FTIR characterization showed evidence of successful fiber esterification. The results showed that 40 wt% of fiber loading improved the tensile properties of the biocomposite. The effects of EFB fiber chemical treatments and various organic initiators content on mechanical and thermal properties and water absorption of PBAT/EFB 60/40 wt% biocomposites were also examined. The SAH-g-EFB fiber at low WPG in presence of 1 wt% of dicumyl peroxide (DCP) initiator was found to significantly enhance the tensile and flexural properties as well as water resistance of biocomposite (up to 24%) compared with those of untreated fiber reinforced composites. The thermal behavior of the composites was evaluated from thermogravimetric analysis (TGA)/differential thermogravimetric (DTG) thermograms. It was observed that, the chemical treatment has marginally improved the biocomposites' thermal stability in presence of 1 wt% of dicumyl peroxide at the low WPG level of grafting. The improved fiber-matrix surface enhancement in the chemically treated biocomposite was confirmed by SEM analysis of the tensile fractured specimens.     

无铅钎焊--机遇和挑战

环境法规和利益相关方对环境意识的增强要求电子设备中不应含有铅。许多电子制造商将在2006年前从传统的锡铅合金钎焊工艺改变为无铅合金的钎焊工艺。虽然试验证明从技术上可以有多种锡铅的替代物，但在高技术制造上实施新工艺仍然存在一系列的挑战。中国目前尚处于替代技术规划期，因此，许多生产者持旁观态度，而一些装配商感到了来自替代要求的威胁。本文在总结全球相关的法规后，对无铅钎焊工艺进行了评述，并提出了如何应对挑战的建议。     

Effects of compatibilizer,compounding method,extrusion parameters,and nanofiller loading in clay‐reinforced recycled HDPE/PET nanocomposites

Nanocomposites based on recycled high density polyethylene (rHDPE), recycled polyethylene terephthalate (rPET), and organoclay (C10A) were made using twin screw extruder followed by hot pressing. The independent effects of polymer/clay compatibility, preparation method, extrusion parameters, and clay loadings were investigated. Ethylene‐glycidyl methacrylate could effectively improve the compatibilization of immiscible rHDPE/rPET blend with clay, which confirmed by the good polymers‐clay adherence and domain size reduction obtained in scanning electron microscopy images. Although intercalated structures were observed in the composites made by one‐step compounding, in the composites prepared by two‐step extrusion method, enhanced dispersion of clay in polymer blend was found from X‐ray diffraction results. Higher extrusion temperature and intermediate speed of rotation (90 rpm) appeared to increase the mechanical properties due to improvement of nanofiller dispersion in matrix. Results showed that the stiffness increased whereas tensile and impact strength decreased with clay content. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42287.