Formulation of fumed silica grease from waste transformer oil as base oil

This study aimed to formulate fumed silica (FS) grease using waste transformer oil (WTO) and to investigate the grease properties. Various unexplored application of the reused WTO due to its reusable characteristic. WTO and fresh transformer oil (ITO) were used as grease base fluid and the properties of oil and grease were evaluated using ASTM International standards and SKF’s Grease Test Kit. The oil and grease chemical compound were determined using Fourier Transform-Infrared Spectroscopy at wavenumber of 500–4000?cm^?1. It was found that WTO have high viscosity index of 96 and low moisture content of 0.05% after pre-treatment than ITO. FS greases with and without MoS₂ were classified as NLGI 2 greases when FS content was 8%. Grease formulated with MoS₂ shows better performances in term of corrosiveness, oil bleed within ?15% to +15%, oil separation less than 4%, and dropping point of >300?°C. FTIR results shows no significant different between ITO and WTO, and between all formulated greases. Based on the findings, it was concluded that WTO can be utilized as an alternative base oil in grease formulation due to the good properties exhibited by the formulated WTO-based FS grease blended with MoS₂.     

啤酒酵母和乳酸菌发酵棕榈粕渣饲料制备工艺的响应面优化

通过单因素实验和响应面法对啤酒酵母和乳酸菌发酵棕榈粕渣饲料制备工艺进行研究。结果表明:基料制备最佳发酵条件为发酵时间5 d、棕榈仁渣目数70目、菌料比1∶103、发酵温度30℃、含水量36%,该条件下基料中总菌落数为7.20×10~(10)个/g;发酵产物最佳发酵条件为发酵温度30℃、棕榈果渣与空果串配比1∶2、棕榈果渣及空果粉碎长度4 cm、配料比1∶10(基料与棕榈果渣和空果串质量比)、含水量35%、发酵时间36 d,该条件下发酵产物营养成分OD值为0.966。对发酵饲料主要成分进行分析,其粗蛋白、粗脂肪、粗纤维、粗灰分、钙、磷、含水量分别为7.20%、7.61%、26.20%、5.20%、0.38%、0.26%、16.20%,总菌落数为9.0×10~7个/g。该发酵方法工艺简单,具有良好的工业化生产前景。     

Experimental Study of RF-excited Diffusion Cooled Off-axis Unstable Resonator with High Frequency Modulation in a Waveguide CO2 Laser

The experimental study of the laser beam parameters of the pulse repetitive RF-excited diffusion cooled waveguide CO2 laser are presented. The measurements are carried out for the pumping pulse duration of 100 μs and pulse repetitive rates 5 - 14 kHz. The average power density delivered to the active medium is 76 W/cm^3. Three types of the pulses, namely the square, the sine and the triangular ones have been applied at the input as pumping pulses and their effects on the output power and the delay time have been studied. The output power of the radiation versus input power, pressure of the laser gas mixture and modulation frequency has been investigated. The results indicate that the output peak power for the three types of pulses increases with increase of the pressure of the laser gas mixture and with the input power where as it decreases with the repetition frequency. The delay time of the output pulse decreases with the increase of the repetition frequency and input power, where as it increases with the increase of the pressure of the laser gas mixture. The behavior of the output power and the delay time with duty cycle for square pulse has also been investigated.     

SIVA: A System for Coverage-Directed State Space Search

We introduce SImulation Verification with Augmentation (SIVA), a tool for coverage-directed state space search on digital hardware designs. SIVA tightly integrates simulation with symbolic techniques for efficient state space search. Specifically, the core algorithm uses a combination of ATPG and BDDs to generate directed input vectors, i.e., inputs which cover behavior not excited by simulation. We also present approaches to automatically generate lighthouses that guide the search towards hard-to-reach coverage goals. Experiments demonstrate that our approach is capable of achieving significantly greater coverage than either simulation or symbolic techniques in isolation.     

A modified rain attenuation prediction model for tropical V‐band satellite earth link

Radio wave propagation plays a very important part in the design and eventually dictates performance of space communication systems. Over time, the requirements of satellite communication have grown extensively where higher capacity communications systems are needed. Escalating demands of microwave and millimetre wave communications are causing frequency spectrum congestion. Hence, existing and future satellite system operators are planning to employ frequency bands well above 10 GHz. The challenge in operating at such high frequencies for communication purposes is that there exists stronger electromagnetic interaction between the radio signals and atmospheric hydrometeors. Such instances will degrade the performance of such high frequency satellite communication systems. The development of a revised model for a better‐improved rain fade prediction of signal propagations in tropical region is considered very important. Researchers and engineers can employ the model to accurately plan the future high frequencies satellite services. Copyright © 2014 John Wiley & Sons, Ltd.     

Single‐Phase Filamentary Cellular Breakdown Via Laser‐Induced Solute Segregation

Nanosecond melting and quenching of materials offers a pathway to novel structures with unusual properties. Impurity‐rich silicon processed using nanosecond‐pulsed‐laser‐melting is known to produce nanoscale features in a process referred to as “cellular breakdown” due to destabilization of the planar liquid/solid interface. Here, atom probe tomography combined with electron microscopy is applied to show that the morphology of cellular breakdown in these materials is significantly more complex than previously documented. Breakdown into a complex, branching filamentary structure topped by a few nm of a cell‐like layer is observed. Single‐phase diamond cubic silicon highly supersaturated with at least 10% atomic Co and no detectable silicides is reported within these filaments. In addition, the unprecedented spatio‐chemical accuracy of the atom probe allows to investigate nanosecond formation dynamics of this complex material. Previously reported properties of these materials can now be reconsidered in light of their true composition, and this class of inhomogeneous metastable alloys in silicon can be explored with confidence.     

A 0D Lead‐Free Hybrid Crystal with Ultralow Thermal Conductivity

Organic–inorganic hybrid materials are of significant interest owing to their diverse applications ranging from photovoltaics and electronics to catalysis. Control over the organic and inorganic components offers flexibility through tuning their chemical and physical properties. Herein, it is reported that a new organic–inorganic hybrid, [Mn(C₂H₆OS)₆]I₄, with linear tetraiodide anions exhibit an ultralow thermal conductivity of 0.15 ± 0.01 W m^?1 K^?1 at room temperature, which is among the lowest values reported for organic–inorganic hybrid materials. Interestingly, the hybrid compound has a unique 0D structure, which extends into 3D supramolecular frameworks through nonclassical hydrogen bonding. Phonon band structure calculations reveal that low group velocities and localization of vibrational energy underlie the observed ultralow thermal conductivity, which could serve as a general principle to design novel thermal management materials.     

Modification of Exciton Lifetime by the Metal Cathode in Phosphorescent OLEDs,and Implications on Device Efficiency and Efficiency Roll‐off Behavior

Time resolved photoluminescence and electroluminescence measurements are used to study changes in the emission characteristics of materials typically used in phosphorescent organic light emitting devices (PhOLEDs). Studies on archetypical PhOLEDs with phosphorescent material, fac‐tris(2‐phenylpyridine) iridium (Ir(ppy)₃), show that the lifetime of triplet exciton is modified when in close proximity to a metal layer. Interactions with a metal layer ～30–100 nm away, as is typically the case in PhOLEDs, result in an increase in the spontaneous emission decay rate of triplet excitons, and causes the exciton lifetime to become shorter as the distance between the phosphorescent material and the metal becomes smaller. The phenomenon, possibly the result of the confined radiation field by the metal, affects device efficiency and efficiency roll‐off behavior. The results shed the light on phenomena affecting the efficiency behavior of PhOLEDs, and provide new insights for device design that can help enhance efficiency performance.     

EETP-MAC: energy efficient traffic prioritization for medium access control in wireless body area networks

Wireless body area network (WBAN) has witnessed significant attentions in the healthcare domain using biomedical sensor-based monitoring of heterogeneous nature of vital signs of a patient’s body. The design of frequency band, MAC superframe structure, and slots allocation to the heterogeneous nature of the patient’s packets have become the challenging problems in WBAN due to the diverse QoS requirements. In this context, this paper proposes an Energy Efficient Traffic Prioritization for Medium Access Control (EETP-MAC) protocol, which provides sufficient slots with higher bandwidth and guard bands to avoid channels interference causing longer delay. Specifically, the design of EETP-MAC is broadly divided in to four folds. Firstly, patient data traffic prioritization is presented with broad categorization including Non-Constrained Data (NCD), Delay-Constrained Data (DCD), Reliability-Constrained Data (RCD) and Critical Data (CD). Secondly, a modified superframe structure design is proposed for effectively handling the traffic prioritization. Thirdly, threshold based slot allocation technique is developed to reduce contention by effectively quantifying criticality on patient data. Forth, an energy efficient frame design is presented focusing on beacon interval, superframe duration, and packet size and inactive period. Simulations are performed to comparatively evaluate the performance of the proposed EETP-MAC with the state-of-the-art MAC protocols. The comparative evaluation attests the benefit of EETP-MAC in terms of efficient slot allocation resulting in lower delay and energy consumption.

     

Filter-Bank Modulation Based Signal Design and Transmission Techniques for Intensity Modulated MIMO Visible Light Communication Systems

Wireless Personal Communications - Current research in wireless communication undoubtedly points towards the tremendous advantages of using visible light as a spectrum for significantly boosting...