Structural,thermal, dielectric and ac conductivity properties of lithium fluoro-borate optical glasses

Transparent and stable glasses in the chemical composition of Li₂O–LiF–B₂O₃–MO (M = Zn and Cd) have been prepared by a conventional melt quenching method. For these glasses, absorption spectra, structural (XRD, FT-IR, and Raman spectra), thermal (TG–DTA and DSC), dielectric (?′, ?″, tan δ), ac conductivity (σ_ac), and electric modulus (M′ and M″) have been investigated. Amorphous nature of these glasses has been confirmed from their XRD profiles. The LFB glasses with the presence of ZnO or CdO an extended UV-transmission ability has been achieved. The measured FT-IR and Raman spectra have exhibited the vibrational bands of B–O from [BO₃] and [BO₄] units and Li–O. The dielectric properties (tan δ, dielectric constant (?′), dielectric loss (?″)), electrical modulus and electrical conductivity (σ_ac) of these glasses have also been studied from 100 Hz to 1 MHz at the room temperature. Based on the trends noticed in the ac conductivities, the present glasses could be found useful as battery cathode materials.     

非生物储存因素互作对储藏土耳其带壳榛子呼吸、干物质损失和黄曲霉毒素B1污染的影响（网络首发、推荐阅读）

榛子是一种具重要经济意义、世界各地广泛食用的坚果,易受黄曲霉感染和黄曲霉毒素的污染。以土耳其榛子为研究对象,旨在了解不同的温度和可利用水分下,自然存储的带壳榛子的量化呼吸速率、干物质损失（DML）和黄曲霉毒素B1（AFB1）的污染等情况,以及榛子储存前附加接种黄曲霉对干物质损失和AFB1污染的影响。榛子和相关菌群的最大呼吸作用发生在0.90~0.95水分活度（aw = 12.5%~18%水分含量）的潮湿条件下。这导致25和30 ℃下储存5 d后,榛子损失约10%的DML。储存的带壳榛子+接种黄曲霉在25~30 ℃和小于0.90 aw下产生类似的最佳呼吸模式。事实上,在测试的最大水分水平0.90 aw的AFB1 污染是最高的;这样的污染水平超过了欧盟对这些坚果污染AFB1的法定限制。两组研究中,DML与所有AFB1数据之间的相关性表明,由于干燥或≥ 0.6%不良储存引起非常小的DML变化,可导致AFB1 污染超过欧盟法定限制。因此,有效干燥和安全监控储存对于最大限度地降低这种重要经济商品中AFB1污染风险并避免消费者暴露于此类毒素是十分必要的。     

VISCOELASTICITY OF A SIMULATED POLYMER AND COMPARISON WITH CHICKPEA FLOUR DOUGHS

An integrated approach consisting of compression and stress relaxation is performed with a simulated model system of poly dimethyl siloxane (PDMS), a viscoelastic polymer material when the compressive strain, height of sample and crosshead speed were varied. The parameters derived are the forces at the end of compression and relaxation, energy for compression and the extent of elasticity of the sample based on the ratios of forces as well as the proposed energy values. The results were verified with food doughs undergoing large deformations that show a nonlinear behavior. The proposed extent of elasticity based on the ratios of energy stored and compression can be used as an index for the characterization of viscoelasticity. A nonlinear three‐parameter model had also been proposed to predict the stress decay characteristics as a function of time, which was found suitable for the PDMS system, and was better than the two‐parameter Peleg model as judged by lower variance values (0.0006–0.018 and 0.002–0.048, respectively). Further, an actual system of food doughs in the form of chickpea (Cicer arietinum L.) flour dough was used to verify the proposed model and viscoelastic index at different moisture contents (27–39%) subjected to compressive strains of 25–75%. The nonlinear relaxation characteristics of the food dough are sensitive to moisture content as well as to strain level.     

Effect of particle size on thermomechanical properties of particulate polymer composite

Particulate composite materials (PCM) consisting of a matrix reinforced by micro to nano-sized dispersed phase are receiving the attention of designers as a promising futuristic materials. This study unearths the thermal and mechanical behavior of maleic anhydride grafted polypropylene/silica (MA-g-PP/silica) composites for reinforcement ranging from micro- to nano-size. The monodisperse silica spherical particles were used in all the formulations of composites. Further the volume fraction was kept the same in all the compounded thermoplastic composites ranging from 100 nm to 130 μm in a co-rotating conical twin-screw micro-compounder. The micrographs were obtained from transmission electron microscopy (TEM) and the scanning electron microscopy (SEM). The SEM and TEM results revealed a good dispersion of the silica spheres within the MA-g-PP matrix. The compounded composite materials were injection molded to fabricate tensile test specimens (ASTM D638 type V) and tested for tensile properties. In order to investigate the effect of particle size on crystallite structure of the matrix, the composites were tested on differential scanning calorimeter and X-ray diffraction (WAXD). The thermal stability and degradation kinetics were studied via thermogravimetric analysis. The results show increase in crystallization rate, crystallinity percentage, Young’s modulus, strength and thermal stability of MA-g-PP by addition of the silica particles. Further it was observed that the small-sized dispersed phase had better overall thermal and mechanical behavior than its larger sized counterpart.     

Structural changes in S&T research in India

Before India became an independent country, its scientists and policy makers could foreseethe importance of science in its development, and accordingly a number of research anddevelopment (R&D) institutions were established. However during these five decades ofindependence, the choice between basic sciences and technology was always a subject of debate.It will be appropriate now to examine the changing patterns of Science and Technology (S&T)manpower growth to find out the ground truth reality. The present study pertains to the analysis ofS&T outturn data in various fields of scientific research that can provide a base for S&T planningand policy making. These S&T indicators will be helpful in estimating future requirements, whichin turn can be useful to a great extent in science and technology policy formulation. Theseestimates and future projections are based on mathematical modelling of the data pertaining to theoutturn of highly qualified Scientific and Technical (S&T) personnel in India from differentfaculties over the period 1990-1998. From the trend analysis it is evident that research is no moreperceived as an interesting career except in the field of engineering and medicine. The findingsfurther suggest that there is a noticeable shift from basic sciences to technology.     

Development of a 2D Vibration Stage for Vibration-assisted Micro-milling

Vibration-assisted machining (VAM) has the advantages of extending tool life, reducing cutting force and improving the surface finish. Implementation of vibration assistance with high frequency and amplitude is still a challenge, especially for a micro-milling process. In this paper, a new 2D vibration stage for vibration-assisted micro-milling is developed. The kinematics of the milling process with vibration assistance is modeled, and the effects of vibration parameters on the periodic tool-workpiece separation (TWS) is analyzed. The structure of the vibration stage is designed with flexure hinges, and two piezoelectric actuators are used to drive the stage in two directions. An amplifier is integrated into the vibration stage, and the dynamics of the whole vibration system are identified and analyzed. Micro-milling experiments are conducted to determine the effects of vibration assistance on cutting force and surface quality.     

Design of experiments and analysis of dual fluidized bed gasifier for syngas production: Cold flow studies

Biomass gasification is a thermo-chemical process widely accepted as a future technology for syngas production. Numerous types of gasification systems have been proposed and studied in the past. Recent developments have shown that Dual Fluidized Bed (DFB) gasifier are commercially more attractive for production of the hydrogen-rich syngas as compared to others. DFB gasification system is very complex in construction and operation. Hence, a detailed understanding of hydrodynamics in such systems is essential for optimum design and scale-up. Hydrodynamics of DFB gasifier mainly depends on the Solid Circulation Rate (SCR). SCR is governed by riser velocity, gasifier velocity, and loop seal velocities. In present work, Central Composite Rotatable Design (CCRD) based Response Surface Method (RSM) was employed to determine the effect of riser velocity, gasifier velocity, recycle chamber velocity, supply chamber velocity, and vertical supply chamber velocity and their interaction on the SCR. Adequacy of regression model developed from RSM was confirmed using ANOVA analysis. The value of coefficient of determination (R²) of the model was 0.9729, which confirms model represents the experimental results satisfactorily. Riser and recycle chamber velocity were found to be most significant parameters, plays an important role in SCR in DFB gasifier.     

Evolution of PAPR Reduction Techniques: A Wavelet Based OFDM Approach

Wireless Personal Communications - Orthogonal frequency division multiplexing (OFDM) is considered among the most suitable multiplexing technique for realizing high speed wireless communication in...     

A theoretical model for the flow behavior of commercial dual-phase steels containing metastable retained austenite: Part I. derivation of flow curve equations

A semi-mechanistic model for predicting the flow behavior of a typical commercial dual-phase steel containing 20 vol pct of ‘as quenched’ martensite and varying amounts of retained austenite has been developed in this paper. Assuming that up to 20 vol pct of austenite with different degrees of mechanical stability can be retained as a result of certain thermomechanical treatments in a steel of appropriate low carbon low alloy chemistry, expressions for composite flow stress and strain have been derived. The model takes into account the work hardening of the individual microconstituents(viz., ferrite-@#@ α, retained austenite- γ _r, and martensite -α′) and the extra hardening of ferrite caused by accommodation dislocations surrounding the ‘as quenched’ as well as the strain-induced(γ _r→ α′) martensite. Load transfer between the phases has been accounted for using an intermediate law of mixtures which also considers the relative hardness of the soft and the hard phases. From the derived expressions, the flow behavior of dual phase steels can be predicted if the properties of the individual microconstituents are known. Versatility of the model for application to other commercial steels containing a metastable phase is discussed.     

Atherosclerosis: are dairy products safe?

The role of lipids, particularly saturated fats, in the development of atherosclerosis and other heart diseases has been widely accepted. It is generally recommended that animal food products, namely, eggs, meat and dairy products, especially butter, butteroil, ghee, cheese, etc, which contain high levels of saturated fatty acids, should be minimized in the diet. The diet-heart issue and the role of fats in the development of atherosclerosis are reviewed with emphasis on the need to explore other factors which significantly affect the circulation of blood. It is concluded that it is not the type of fat but the balance of dietary components that contributes to the development of atherosclerosis.