Improving electrical conductivity of poly methyl methacrylate by utilization of carbon nanotube and CO2 laser

In this work, the electrical surface conductivity enhancement of injection‐molded multiwalled carbon nanotube (MWCNT)/poly(methyl methacrylate) (PMMA) nanocomposite by using CO₂ laser processing was studied. Variable input factors are considered as MWCNT concentration (in three levels 0.5, 1, and 1.5 wt %), the laser feed angle with the flow direction (in five levels 0°, 30°, 45°, 75°, and 90°), and the cavity machining method that were produced by electrodischarge machining and computer numerical control milling with finishing process. The studies show that the irradiation of laser and utilization of covering gas could enhance the CNT–CNT contacts and the surface electrical conductivity. The morphology of laser‐irradiated surface by using scanning electron microscope certified that the conductive network generated from CNT–CNT contacts can transfer the electrical current. The findings clearly show that the laser feed angle with the flow direction influenced the electrical conductivity. The maximum conductivity (～ 5.310 × 10^?4 S) was observed at 75°. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42671.     

临近高压电气设备电缆局部放电脉冲的鉴别方法

On-line partial discharge(PD)diagnostics data are corrupted by various noise sources and this makes it more challenging to extract the PD signal contained in the raw data.Though the noise sources can be filtered out using signal processing techniques,PDs from neighboring cables and other high voltage equipment make the de-noising process more difficult due to the similar features of these signals with the PD signal of interest.Proposed in this paper is a double-ended partial discharge diagnostic system with dual sensors at each end which uses wireless time triggering using global time reference with the aid of global positioning system(GPS).Using the time of arrival method based on the velocity of propagation on the data,PD pulses originating from other sources can be discarded which reduces the volume of data to be stored and would eventually also reduce the hardware and software requirements of the denoising process thereby improving de-noising efficiency.System design,laboratory tests and on-site measurements are discussed.     

Effect of oxygen transfer rates on alcohols production by Candida guilliermondii cultivated on soybean hull hydrolysate

BACKGROUND: In this research the use of soybean hull hydrolysate (SHH) as substrate for xylitol and ethanol production using an osmotolerant strain of Candida guilliermondii was studied. The production of alcohols was investigated in batch cultivations in which the variable parameter was the volumetric oxygen mass transfer coefficient (k_La) obtained from three different conditions of air supply: anaerobic (150 rpm, no aeration); microaerobic (300 rpm, 1 vvm), and aerobic (600 rpm, 2 vvm), corresponding to k_La values of 0; 8; and 46 h^?1, respectively. RESULTS: SHH, although presenting a very high osmotic pressure (1413 mOsm kg^?1), was completely metabolized under aerobic conditions with high biomass productivities of 0.49 g cells (L h)^?1, with little formation of ethanol. Xylitol was produced under microaeration, with product yield of 0.22 g g^?1 xylose, with the formation of glycerol as a by‐product. No xylose was metabolized under anaerobic conditions, but ethanol was produced from hexoses with high product yields of 0.5 g g^?1. CONCLUSION: These results suggest that the hydrolysis of soybean hull and its conversion to ethanol and other alcohols could be an important use of this agro‐industrial waste, which could be used for biofuel, xylitol or biomass production, depending on the aeration conditions of the cultures. Copyright © 2008 Society of Chemical Industry     

Analytic solution for flow of a micropolar fluid

Summary The time-independent equations for the two dimensional incompressible micropolar fluid have been considered. Using group method the equations have been reduced to ordinary differential equations and then solved analytically. Finally the boundary value problem has been discussed, and the graphical results are in good agreement with the numerical solution.     

Optimization of soybean hull acid hydrolysis and its characterization as a potential substrate for bioprocessing

Present global soybean production generates about 20 Mt of lignocellulosic by-products that can be converted into bioethanol and other bioprocess molecules. In this work, the chemical composition and the kinetics of diluted acid hydrolysis of soybean hull were investigated. The chemical composition (mass fraction % on a dry basis) of soybean hull showed a content of approximately 40% of cellulose, 26% of xylose, 9% of lignin, and 13% of proteins. Hydrolyses were carried out under different conditions of temperature and acid concentrations following a 2² central composite design (CCD) to evaluate the release of fermentable sugars (glucose, xylose, and arabinose), and toxic compounds (furfural, hydroxymethilfurfural, acetic acid, and soluble lignin). An objective function was defined to estimate the best treatment for high sugar release and low toxic compounds generation. The kinetics of hydrolyses showed that the best condition for recovering sugars were 153 °C and mass fraction of 1.7% H₂SO₄ for 60 min with a hydrolysis efficiency of 87%. The objective function, considering a non-inhibiting concentration of toxic compounds (<4 g dm⁻³), was 118 °C and 2.7% H₂SO₄ (mass fraction) for 40 min with 59% of hydrolysis efficiency concerning the total sugar content of soybean hulls.     

Lipase‐catalyzed ethanolysis of soybean oil in a solvent‐free system using central composite design and response surface methodology

BACKGROUND: In this work we describe the synthesis of ethyl esters, commonly known as biodiesel, using refined soybean oil and ethanol in a solvent‐free system catalyzed by lipase from Thermomyces lanuginosus. Central composite design and response surface methodology (RSM) were employed to optimize the biodiesel synthesis parameters, which were: reaction time, temperature, substrate molar ratio, enzyme content, and added water, measured as percentage of yield conversion. RESULTS: The optimal conditions obtained were: temperature, 31.5 °C; reaction time, 7 h; substrate molar ratio, 7.5:1 ethanol:soybean oil; enzyme content, 15% (g enzyme g⁻¹ oil); added water, 4% (g water g⁻¹ oil). The experimental yield conversion obtained under these conditions was 96%, which is very close to the maximum predicted value of 94.4%. The reaction time‐course at the optimal values indicated that 5 h was necessary to obtain high yield conversions. CONCLUSION: A high yield conversion was obtained under the optimized conditions, with relative low enzyme content and short time. Comparison of predicted and experimental values showed good correspondence, implying that the empirical model derived from RSM can be used to adequately describe the relationship between the reaction parameters and the response (yield conversion) in lipase‐catalyzed biodiesel synthesis. Copyright © 2008 Society of Chemical Industry     

Dispersive behaviour of humid anisotropic media

The results of dielectric measurements on a humid system consisting of filter papers which show strongly anisotropic properties in the planes and normal to the planes of the sheets, are reported. Configurations were used in which the flow of current is, respectively, normal to and in the planes and these show distinctively different behaviour. Transport in the planes provides some of the best examples of LFD ever seen by us, extending over up to eight decades of frequency; transport across the planes is influenced by less dispersive behaviour which is ascribed to the fibre-fibre contacts.     

Message Drop Control Buffer Management Policy for DTN Routing Protocols

In delay tolerant network interruptions will occur continuously because there is no end-to-end path exists for the longer period of time from source to destination. In this context, delays can be immensely large due to its environment contrails e.g. wildlife tracking, sensor network, deep space and ocean networks. Furthermore, larger replication of messages put into the network is to increase delivery probability. Due to this high buffer occupancy storage space and replication result in a huge overhead on the network. Consequently, well-ordered intelligent message control buffer drop policies are necessary to operate on buffer that allows control on messages drop when the node buffers are near to overflow. In this paper, we propose an efficient buffer management policy which is called message drop control source relay (MDC-SR) for delay tolerant routing protocols. We also illustrate that conventional buffer management policy like Drop oldest, LIFO and MOFO be ineffective to consider all appropriate information in this framework. The proposed MDC-SR buffer policy controls the message drop while at the same time maximizes the delivery probability and buffer time average and reduces the message relay, drop and hop count in the reasonable amount. Using simulations support on an imitation mobility models Shortest Path Map Based Movement and Map Route Movements, we show that our drop buffer management MDC-SR with random message sizes performs better as compared to existing MOFO, LIFO and DOA.     

Diffraction of waves by an oscillating source and an oscillating half plane

In this paper we have studied the problem of diffraction of cylindrical acoustic waves (emanating from a harmonic time dependent source) by an oscillating half plane. An analytical solution, using spatial and temporal Fourier transforms, complex Fourier series, the Wiener-Hopf technique and the method of steepest descent, is constructed. Some graphs showing the effects of various parameters on the diffracted field are also presented.