Characterization and modeling of in-building power lines for high-speed data transmission

This paper analyzes the characteristics of power lines in Singapore residential network in order to develop a channel model suitable to simulate its behavior for high-speed data transmission. The channel model, which describes the transfer function and noise characteristics of typical in-building power line channels in a frequency band from 1 to 10 MHz, is developed and tested through software simulation and hardware implementation. The transfer function is described by an echo model and the noise spectrum is derived statistically from measurements on actual power lines. Some measurement results on power line impedance, noise and attenuation are presented. The results are based on measurements between line and neutral conductors in a 230-V power line network. From the results obtained so far, the impedance, noise and attenuation of power lines exhibit variations with frequency, time and location.     

Characteristic analysis of biaxially stretched PVDF thin films

By use of biaxial stretching process of poly(vinylidene fluoride) fabrication to gain high piezoelectricity is the focus in this article. The influence of different stretch ratio and temperature are investigated and compared to uniaxial stretching process. The Fourier transform infrared spectroscopy and X‐ray diffraction are used to observe the β‐phase fraction and the degree of crystallinity. The piezoelectric coefficients (d₃₃, d₃₁) and the sensitivity are also measured. All the above characteristic examinations show the same consequences that equi‐biaxial stretching process employed with same stretch ratio in both axial directions of poly(vinylidene fluoride) fabrication is the focus in this article. And heating temperature would have adequate piezoelectricity approximate to uniaxial stretching. In observation of surface morphology by using scanning electron microscopy, uniformity in biaxial direction is gained. However, biaxial stretching with higher stretch ratio of R = 4 × 4 would produce porosity and crack. Via atomic force microscopy, biaxial stretching with higher stretch ratio attains better surface chain orientation and smoothness. To sum up, the biaxial stretching approach has the advantage of low stretch ratio requirement to preserve good fabrication quality. Set up with stretch ratio in‐between R = 3 × 3 and R = 4 × 4 at 80 °C is suggested to use in biaxial stretching. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46677.     

Effect of modulation index on design of asymmetric coded FPM

The design of asymmetric coded frequency/phase modulation (FPM) is discussed. Designs for optimum asymmetric 2FSK/4PSK, 2FSK/8PSK and 2FSK/16PSK modulation schemes are derived and the effect of modulation index is studied. It is shown that an additional gain of 1.2-2.6 dB can be achieved by using optimised asymmetric modulation over that of a symmetric scheme     

A Protocol for Multimedia CDMA Personal Communication Networks

In this paper, a joint CDMA/TDMA protocol has been proposed for integratedvideo-phone/voice/data traffic in personal communication networks (PCN). Thevideophone service is implemented according to H.261 standard. The concept ofdynamic boundary is adopted in both code and time domains to meet thedifferent requirements for videophone, voice and data traffic.Two mathematical analysis methods are adopted to evaluate the systemperformance. One is the traditional Markov analysis (TDMA), which is used tocalculate the average videophone and voice call blocking probabilities. Theother is Transient Fluid Analysis (TFA), which is adopted to evaluate the datadelay and channel utilization performance. Results show that two dynamicboundaries can be adjusted to achieve the optimal system performance, andsuggestions of how to adjust these boundaries are also given.     

Controlled synthesis of Pt-decorated Au nanostructure and its promoted activity toward formic acid electro-oxidation

Highly active Pt-decorated Au nanoparticles on carbon support with Pt:Au mole ratio ranging from 1:10 to 1:2 was successfully synthesized based on successive reduction strategy. The successful formation of this structure was suggested by transmission electron microscopy, UV-vis and voltammetry analyses. The electrocatalytic activity of this decorated structure toward formic acid oxidation surprisingly increases despite the low amount of Pt being used. At 0.1 V, the specific activity of PtAu/C with Pt/Au mole ratio 1:8 was more than one order of magnitude higher than the conventional Pt/C. The enhancement was attributed to the less Pt ensemble sites that the decorated structure possesses (ensemble effect) and the increase in the Pt atom reactivity on Au nanocrystal. The formic acid oxidation mechanism on this decorated structure was also elucidated using electrochemical impedance spectroscopy technique. It is proposed that besides the dehydrogenation reaction pathway happening on clean Pt sites, the reactive intermediate i.e. formate species could also be oxidized by the adsorbed water species on Pt at higher potential.     

Power control supported dynamic channel assignment in cellular radio systems

Transmitter power control is an effective technique to reduce co-channel interference and increase system capacity for cellular radio networks. Dynamic channel assignment can also be used to improve spectrum efficiency and thus increases the system capacity. This paper investigates channel assignment algorithms which combine dynamic channel assignment with signal-to-interference ratio balanced power control and proposes a new algorithm. Simulation results show that this new scheme can greatly reduce the channel reassignment rate and still maintain satisfactory performance. It may thus be used as an effective channel assignment scheme in cellular mobile systems. © 1997 by John Wiley & Sons, Ltd.     

Noncoherent delay-lock tracking loop for chip-interleaving DS SSsystem

A noncoherent delay-lock loop (DLL) is proposed for code tracking in chip-interleaving (CI) direct sequence (DS) spread spectrum (SS) systems. Analyses show that the proposed loop achieves the same code-tracking performance as the traditional noncoherent DLL does for conventional DS SS systems     

Performance of chip-interleaving DS SS system with nonlinearity under pulsed interference

Analytical bit error rate (BER) results of a chip-interleaving direct sequence (DS) spread spectrum (SS) system using nonlinearity in the presence of pulsed interference are presented. Several simple nonlinearities, such as hole puncher, soft clipper, and hard limiter nonlinearities, are studied. The BERs of a conventional DS SS system employing the same nonlinearities are also given. The proposed system is compared with the conventional DS SS system using numerical examples.     

Accuracy improvement in nanographite powder-suspended dielectric fluid for micro-electrical discharge machining processes

Micro-electric discharge machining (??-EDM) is an important manufacturing process that is able to produce components and tools with micro-features. Improvement to this process has resulted in the use of powder mixed dielectric (PMD), which results in better surface quality and faster machining time. However, the presence of conductive powder in the dielectric fluid negatively affects the accuracy of the machining depth. This paper presents a novel method of suspending nanographite powder in dielectric fluid, using ultrasonic vibration of dielectric fluid, and using the number of discharge pulses in order to improve the accuracy of the PMD-??-EDM process. As a result, machining time has been significantly reduced up to 35%, accuracy increased, and the appearance of micro-cracks on the workpiece surface has been reduced.     

Purification and identification of rice bran oil fatty acid steryl and wax esters

Fatty acid steryl esters (FASE) and wax esters (WE) of rice bran oil (RBO) have potential applications in cosmetic, nutraceutical, and pharmaceutical formulations. FASE and WE were extracted from RBO by a modified Soxhlet extraction using hexane as the solvent. FASE and WE were then separated by storage in acetone at 10°C for 24 h. The FASE fraction was further purified by silica, gel column chromatography. The contents and compositions of FASE and WE, as well as their saponified products, were identified by GC and GC-MS. The identification of FASE and WE was carried out by comparing the retention time of GC peaks and mass spectral analysis with standards synthesized in our laboratory. FASE and WE accounted for ca. 4.0% of crude RBO, of which 2.8–3.2% and 1.2–1.4% are FASE and WE, respectively. GC-MS of FASE showed five major peaks. Major FA in the FASE fraction were linoleic acid and oleic acid, which were esterified with 4-desmethyl, 4-monomethyl, and 4,4-dimethyl sterols. The contents of 4-desmethylsterol, 4-monomethylsterol, and 4,4-dimethylsterol esters in crude RBO were 76.1, 8.7, and 15.1%, respectively. WE of RBO consisted of both even and odd carbon numbers ranging from C₄₄ to C₆₄. The major constituents were, saturated esters of C₂₂ and C₂₄ FA and C₂₄ to C₄₀ aliphatic alcohols, with C₂₄ and C₃₀ being the predominant FA and fatty alcohol, respectively. The advantages of using a modified Soxhlet extraction over column chromatography are less solvent usage and larger sample size per batch with shorter operation time.