Integrated VCO With Up/Down Converter for Si-Based 60 GHz WPAN Applications

This letter presents the design and implementation of the largest reported bandwidth of a 60 GHz up/down converter with an integrated voltage controlled oscillator (VCO) in a low-cost 0.18 mum silicon-germanium process. The up/down conversion is achieved using the 2X sub-harmonic passive mixing with anti-parallel diode pairs. A 30 GHz cross-coupled VCO is designed, optimized and integrated with the sub-harmonic mixer through a cascode amplifier to meet the local oscillator power requirements. The fully integrated chip takes only 1.5 mm² of silicon die area and consumes only 40 mW of dc power for a measured conversion loss of 12 dB at 61.5 GHz. The integrated up/down converter is measured to have greater than 9 GHz double-sided 3-dB RF bandwidth suitable for wideband high data-rate WPAN transceiver requirements. The VCO and VCO-amplifier test structures are separately fabricated and measured to have a phase noise as low as -105 dBc/Hz at 1 MHz offset with a tuning range of 2.3 GHz.     

Throughput and Fairness Guarantees Through Maximal Scheduling in Wireless Networks

The question of providing throughput guarantees through distributed scheduling, which has remained an open problem for some time, is addressed in this paper. It is shown that a simple distributed scheduling strategy, maximal scheduling, attains a guaranteed fraction of the maximum throughput region in arbitrary wireless networks. The guaranteed fraction depends on the ldquointerference degreerdquo of the network, which is the maximum number of transmitter-receiver pairs that interfere with any given transmitter-receiver pair in the network and do not interfere with each other. Depending on the nature of communication, the transmission powers and the propagation models, the guaranteed fraction can be lower-bounded by the maximum link degrees in the underlying topology, or even by constants that are independent of the topology. The guarantees are tight in that they cannot be improved any further with maximal scheduling. The results can be generalized to end-to-end multihop sessions. Finally, enhancements to maximal scheduling that can guarantee fairness of rate allocation among different sessions, are discussed.     

A Framework for Heterogeneous Resource Allocation in Sensor-Cloud Environment

Wireless Personal Communications - With the advent of sensor technologies, cloud applications are able to acquire sensed data from remotely located sensors which are geographically distributed....     

Minimum norm mutual coupling compensation with applications in direction of arrival estimation

This paper introduces a new mutual coupling compensation method based on the minimum norm solution to an underdetermined system of equations. The crucial advantage over previous techniques is that the formulation is valid independent of the type of antenna element and provides good results in situations where signal strengths vary considerably. In using the matrix pencil algorithm to estimate the directions of arrival, the examples show that the proposed method results in significantly lower bias than the traditional open circuit method. The analysis of mutual coupling is also applied in the context of a code division multiple access communication system.     

Studies of microstructural imperfections of powdered Zirconium-based alloys

Different model based approaches of X-ray diffraction line profile analysis have been applied on the heavily deformed zirconium-based alloys in the powdered form to characterize the microstructural parameters like domain size, microstrain and dislocation density. In characterizing the microstructure of the material, these methods are complimentary to each other. Though the parameters obtained by different techniques are differently defined and thus not necessarily comparable, the values of domain size and microstrain obtained from the different techniques show similar trends.     

Optimization of enzymatic process parameters for increased juice yield from carrot (Daucus carota L.) using response surface methodology

The effects of enzyme concentration (50–650 mg/kg grated carrot), pectolytic and cellulolytic enzyme ratio (3:7–7:3), incubation time (30–150 min) and temperature (25–65 °C) on juice recovery and viscosity from grated carrot were studied. A central composite rotatable design (CCRD) was used in designing the treatment combinations of four variables at five levels. The process involved in treating the blanched grated carrot with mixture of crude pectolytic enzyme from Aspergillus foetidus and crude cellulolytic enzyme from Trichoderma ressi, keeping the samples at the desired time, followed by extraction of juice. Enzyme-treated grated carrot sample showed increased juice recovery as compared to control. A second-order response surface model adequately fitted the data. All the variables affected juice recovery and viscosity significantly. Enzyme concentration, pectolytic and cellulolytic enzyme ratio, incubation time and temperature had total and combined effect at linear, square and interactive level on both responses. The optimum condition was enzyme concentration, 210.7 mg/kg of grated carrot; pectolytic and cellulolytic enzyme ratio, 3.84:6.16; incubation time, 130 min and incubation temperature 47 °C. Under the optimal conditions, juice extracted from enzyme-treated grated carrot was 74.3% having juice viscosity 1.07 cP, corresponding to the increase in yield by 13.95% and decrease in viscosity by 0.45 cP.     

In vitro model improves the prediction of soil arsenic bioavailability: worst-case scenario

There is a strong interest in developing an in vitro arsenic (As) model that satisfactorily estimates the variability in in vivo relative oral bioavailability (RBA) measurements. Several in vitro tests have been developed, but none is universally accepted due to their limited success in predicting soil As RBA. A suite of amorphous and crystalline solid As phases were chosen, utilizing a worst-case scenario (WCS) that simulated fasting children's gastric solution chemistry. The objectives of this study were to (i) determine the effects of residence time, pH, and solid-to-solution ratio on As bioaccessibility and speciation in the in vitro gastric test; (ii) provide the fundamental basis for an optimized in vitro model constrained by the WCS; and (iii) validate the optimized in vitro test with the in vivo RBA obtained with BALB/c mice. The gastric pH was the only significant (p < 0.05) factor influencing solid As bioaccessibility. Bioaccessible As retained the oxidation state after its release from the solid into the gastric solution. The optimized in vitro model adequately predicted RBA values for a suite of solid As phases typically encountered in soils, with the exception of aluminum-based solids. This study is an excellent starting point for developing an in vitro test applicable to different As-contaminated soils.     

Using nitrogen and carbon dioxide molecules to probe arsenic(V) bioaccessibility in soils

Highly specialized personnel and high cost are typically required for in vivo risk assessment of arsenic (As) exposure to humans in As-contaminated soils. Arsenic bioaccessibility in soils, as determined with the aid of in vitro tests, is quite variable, and its magnitude depends upon unidentified soil properties. Use of soil chemical properties is a common practice for construction of As(V) sorption and bioaccessibility models with relative success. We propose a novel As(V) bioaccessibility model, which was tested on 17 soils. The model includes only two parameters characterizing surface properties of soils that are readily determined from N2- and CO2-based specific surface areas (SSAs), and total organic carbon (OC) content. We found that N2 and CO2 molecules act as As(V) "surrogates", probing easily accessible and relatively difficult to access soil porosity, respectively. Three interrelated linear models were constructed using two terms (CO2/N2-based SSAs and OC) that were significant (p <0.001) in explaining 51 and 95% of the variability observed in As(V) sorption and bioaccessibility, respectively. The proposed models successfully predicted bioaccessible As concentrations for 4 out of the 5 soils that were not included in the bioaccessibility models, reaching RMSE values of < or =10%.     

Ni-Ti-Cu-V四元薄膜库中微观结构和相变的组合合成和高通量表征

过去70年来,基于Ni-Ti的形状记忆合金(shape memory alloy,SMA)已得到广泛使用,但是提高其功能稳定性仍然是实现更稳健和更高级应用的关键.SMA因其能够通过可逆的马氏体转变来保持加工后的形状而得名,它对成分的变化非常敏感.因此,用三元和四元元素合金化来微调SMA的晶格参数和热滞,成为材料研究中的...