Influence of alcohol pre‐infusion on the quality of VARTM composites

In the vacuum assisted resin transfer molding (VARTM) process, part‐to‐part variations such as the uncertainty in the permeability and race tracking phenomenon make it difficult to achieve consistent mold filling and ensure part quality of composites. Alcohol pre‐infusion was presented in this study as a novel real‐time monitoring and control approach for the flow process in the VARTM process, alcohol test fluid is infused before the actual resin infusion to locate the potential dry spots without using the large quantity of sensors. Then corresponding process control strategy is designed, such as opening the auxiliary gate at specific moment on those predicted dry spot locations to compensate flow defects. Moreover, alcohol can be easily removed by heat without changing the local permeability. The influence of alcohol pre‐infusion on the quality of VARTM composites were investigated in this study. The mechanical tests were conducted to verify that the alcohol pre‐infusion approach has no significant effect on composite properties because alcohol can be removed from fiber by heat and air flow. Specifically, DMA, TGA, and FTIR spectrum proved that negligible difference existed on the resin–fiber interface between the composites with or without alcohol pre‐infusion. Finally, the microscopy results revealed a similar failure path in a resin matrix. TMA results also demonstrated similar dimension stability. This alcohol pre‐infusion approach was effective when compared with computer simulation and could eliminate the occurrence of dry spots and voids without using sensors or data‐acquisition system. The control schemes were shown in a case study to be capable of compensating the flow defects and achieving desired fill patterns in the face of permeability uncertainty. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Processing,characterization, and modeling of carbon nanotube-reinforced multiscale composites

Carbon fiber-reinforced epoxy composites modified with carbon nanotubes (CNTs) were fabricated and characterized. High-energy sonication was used to disperse CNTs in the resin, followed by infiltration of fiber preform with the resin/CNT mixture. The effects of sonication time on the mechanical properties of “multiscale” composites, which contain reinforcements at varying scales, were studied. A low CNT loading of 0.3 wt% in resin had little influence on tensile properties, while it improved the flexural modulus, strength, and percent strain to break by 11.6%, 18.0%, and 11.4%, respectively, as compared to the control carbon fiber/epoxy composite. While sonication is an effective method to disperse CNTs in a resin, duration, intensity, and temperature need to be controlled to prevent damages imposed on CNTs and premature resin curing. A combination of Halpin–Tsai equations and woven fiber micromechanics was used in hierarchy to predict the mechanical properties of multiscale composites, and the discrepancies between the predicted and experimental values are explained.     

Managing the full ERP life-cycle: Considerations of maintenance and support requirements and IT governance practice as integral elements of the formula for successful ERP adoption

Companies adopting enterprise resource planning (ERP) systems have often focused primarily on implementation-related factors while neglecting those of post-implementation. As a result, the usefulness and operation of the ERP systems, once installed, are compromised. This research adopted a case study approach to demonstrate that ERP adoption efforts that fail to pay attention to post-implementation requirements (especially those relevant to maintenance and support (M&S)) from an early stage in the project lifecycle will face dire consequences. It points out that poor planning and management of M&S services can imperil the normal operations of an ERP system and the daily activities of a business. With the life span of ERP systems getting shorter, sound M&S practices can extend their life and create a stable system platform to support efficient and effective business operations. M&S issues deserve to be considered as integral elements among the critical success factors (CSF) of ERP adoption projects. In other words, ERP success requires a full lifecycle perspective to be taken by adopting companies. With lessons having been learned from the mistakes in the first project, the company in this case study revamped its ERP implementation second time out, with due consideration being given to M&S strategies and practices from project initiation onward in order to realize a stable, usable, and maintainable system. The case study explores and identifies the critical success factors (CSF) of ERP adoption, and shows that M&S must be included as a key element from the outset and throughout the system lifecycle. Our findings capture a great deal of experience for any ERP adopting companies to follow in order to avoid learning costly lessons both in implementation and subsequent M&S throughout the lifespan of the system. A set of propositions is also presented for academic researcher to consider in future ERP research endeavors.     

Reinforcing polymer composites with epoxide-grafted carbon nanotubes

An in situ functionalization method was used to graft epoxide onto single-walled carbon nanotubes (SWNTs) and improve the integration of SWNTs into epoxy polymer. The characterization results of Raman, FT-IR and transmission electron microscopy (TEM) validated the successful functionalization with epoxide. These functionalized SWNTs were used to fabricate nanocomposites, resulting in uniform dispersion and strong interfacial bonding. The mechanical test demonstrated that, with only 1?wt% loading of functionalized SWNTs, the tensile strength of nanocomposites was improved by 40%, and Young's modulus by 60%.These results suggested that efficient load transfer has been achieved through epoxide-grafting. This investigation provided an efficient way to improve the interfacial bonding of multifunctional high-performance nanocomposites for lightweight structure material applications.     

Mechanical and electrical properties of polycarbonate nanotube buckypaper composite sheets

The thermogravimetric, mechanical, and electrical properties of composite sheets produced by infiltrating single-wall carbon nanotube films (also known as 'buckypapers') with polycarbonate solution were characterized. The composite sheets showed improved stiffness and toughness, while the electrical conductivity decreased, as compared to a neat buckypaper. In addition, polycarbonate/buckypaper composite sheets showed higher resistance to handling and processing damages. Experimental results suggest the viability of the infiltration process as a means to toughen buckypapers and to fabricate polymer/carbon nanotube composites having high nanotube concentration and controlled nanotube structure.     

Software-Based Video/Audio Processing for Cellular Phones

Nowadays, most cellular phones are used beyond voice communication. Although the processing power of cellular phones is sufficient for most data applications, it is difficult to play video and audio contents in software because of their computational complexity and lack of basic tools for multimedia processing, so software-based multimedia processing on cellular phones is a challenging issue. Several transcoding methods are introduced to address this issue, but they are mainly of the DCT-domain conversion. Hence, they are only applicable to high-end cellular phones. To develop a solution for low-end and mid-tier cellular phones, we begin this paper by analyzing the complexity of existing video standards to see if it is possible to play them on cellular phones by software. Next, various coding profiles as combinations of subalgorithms are studied, and we select a profile that adapts its complexity to the processing power of cellular phones. Also, an efficient dithering algorithm called out-of-order dithering is developed. We implement the profile with out-of-order dithering in an actual cellular phone software environment and present the performance results. The performance results show that software based video/audio processing is indeed possible on low-end cellular phones.     

A novel hybrid combination optimization algorithm based on search area segmentation and fast Fourier transform

A novel hybrid optimization algorithm combining search area segmentation technique and the fast Fourier transform (HSAS/FFT) is presented to solve the numerical optimization problems. Firstly, the spectrum of each dimension of the objective function can be acquired by the FFT. The search space is segmented by using the spectrum to ensure that each subspace is unimodal. Secondly, the population of subspaces is produced and the optimal individual can be obtained by gradient descent algorithm. Finally, the local optimal solution in the optimal subspace is generated by the binary search algorithm. Make the optimal individual the new search space and repeat the process until meeting the termination condition. The proposed HSAS/FFT was tested on the CEC2017 benchmark, which evaluates the performance of the proposed algorithm on solving global optimization problems. Results obtained show that HSAS/FFT has an excellent performance and better convergence speed in comparison with some of the state-of-the-art algorithms.     

Impact of protocol overheads on network throughput over high-speed interconnects: measurement,analysis, and improvement

Although extremely high-speed interconnects are available today, the traditional protocol stacks such as TCP/IP and UDP/IP are not able to utilize the maximum network bandwidth due to inherent overheads in the protocol stacks. Such overheads are a big obstacle for high-performance computing applications to exploit high-speed interconnects in cluster environments. To address this issue, many researchers have been presenting analyses of protocol overheads and suggesting a number of optimization approaches to harness the TCP/IP suite over high-speed interconnects. However, to the best of our knowledge, there is no study that analyzes and optimizes the protocol overheads thoroughly in an integrated manner. In this paper, we exploit a set of protocol optimization mechanisms in an integrated manner while dealing with the full spectrum of the protocol layers from the transport layer to the physical layer. To evaluate the impact of each protocol overhead, we apply the optimization mechanisms one by one and perform detailed analyses at each step. The thorough overhead measurements and analyses reveal the dependencies between protocol overheads. With our comprehensive optimizations, we show that UDP/IP can utilize more than 95% of the maximum network throughput a Myrinet-based experimental system can provide.

Quantitation of Human Whole‐Body Synthesis‐Secretion Rates of Docosahexaenoic Acid and Eicosapentaenoate Acid from Circulating Unesterified α‐Linolenic Acid at Steady State

The rate at which dietary α‐linolenic acid (ALA) is desaturated and elongated to its longer‐chain n‐3 polyunsaturated fatty acid (PUFA) in humans is not agreed upon. In this study, we applied a methodology developed using rodents to investigate the whole‐body, presumably hepatic, synthesis‐secretion rates of esterified n‐3 PUFA from circulating unesterified ALA in 2 healthy overweight women after 10 weeks of low‐linoleate diet exposure. During continuous iv infusion of d5‐ALA, 17 arterial blood samples were collected from each subject at ?10, 0, 10, 20, 40, 60, 80, 100, 120, 150, 180, and 210 min, and at 4, 5, 6, 7, and 8 h after beginning infusion. Plasma esterified d5‐n‐3 PUFA concentrations were plotted against the infusion time and fit to a sigmoidal curve using nonlinear regression. These curves were used to estimate kinetic parameters using a kinetic analysis developed using rodents. Calculated synthesis‐secretion rates of esterified eicosapentaenoate, n‐3 docosapentaenoate, docosahexaenoic acid, tetracosapentaenate, and tetracosahexaenoate from circulating unesterified ALA were 2.1 and 2.7; 1.7 and 5.3; 0.47 and 0.27; 0.30 and 0.30; and 0.32 and 0.27 mg/day for subjects S01 and S02, respectively. This study provides new estimates of whole‐body synthesis‐secretion rates of esterified longer‐chain n‐3 PUFA from circulating unesterified ALA in human subjects. This method now can be extended to study factors that regulate human whole‐body PUFA synthesis‐secretion in health and disease.     

Performance impact of JobTracker failure in Hadoop

In this paper, we analyze the performance impact of JobTracker failure in Hadoop. A JobTracker failure is a serious problem that affects the overall job processing performance. We describe the cause of failure and the system behaviors because of failed job processing in the Hadoop. On the basis of the analysis, we build a job completion time model that reflects failure effects. Our model is based on a stochastic process with a node crash probability. With our model, we run simulation of performance impact with very credible failure data available from USENIX called computer failure data repository that have been collected for past 9 years. The results show that the performance impact is very severe in that the job completion time increases about four times typically, and in a worst case, it increases up to 68 times. Copyright © 2014 John Wiley & Sons, Ltd.