Stability of Skutterudite Thermoelectric Materials

By multifilling with La, Ba, Ga, Ti, Yb, Ca, Al, and In, the dimensionless figure of merit ZT of filled skutterudites has been improved in this work. ZT reached 0.75 for p-type (La,Ba,Ga,Ti) _x (Fe,Co)₄Sb₁₂ (x = 0.8 to 1.0) and 1.0 for n-type (Yb,Ca,Al,Ga,In) _y (Co,Fe)₄Sb₁₂ (y = 0.7 to 0.9). After annealing at 873 K for 180 h, 300 h, 710 h, 1000 h, and 5000 h in vacuum, the Seebeck coefficient S and the electrical resistivity ρ of the samples increased while the thermal conductivity λ decreased with increasing annealing time. As a result, the ZT values of both p- and n-type skutterudites remained unchanged or were slightly improved, demonstrating the excellent thermal stability of these skutterudites.     

基于电磁矢量传感器的MIMO天线阵列系统研究

将电磁矢量传感器(EVS,electromagnetic vetor sensor)信号处理法与传统MIMO信号处理有机地结合,建立了基于EVS的多天线三维信道模型。采用多重信号分类(MUSIC,multiple signal classification)算法对MIMO的达波信号方向(DOA,direction of arrival)进行空间谱估计,导出基于EVS的三维空间信道解析式,阐明了EVS信号处理与MIMO多径信道相关性的关系。与传统标量传感器阵列(SSA,scalar sensor array)MIMO天线阵列比较,EVS阵列能获取达波信号的多维极化信息,同时具有空间域和极化信号处理能力。因此可缓解空间多径信道相关性,使空间极化分量的相关性趋于零值,而且使MIMO系统性能受空间结构的影响较小。理论分析和仿真结果表明在提高MIMO天线系统性能上,基于EVS阵列的系统比SSA系统具有更高的优越性。     

Raman fiber oscillator as optical amplifier

A Raman fiber oscillator used for optical amplification is demonstrated to have lower double Rayleigh scattering, transient spikes, cross-phase modulation, and higher saturation input threshold compared with a conventional discrete Raman amplifier at similar operating conditions. This could be a promising technology for deployment in practical systems.     

Coherent demodulation of optical multilevel phase-shift-keying signals using homodyne detection and digital signal processing

We demonstrate coherent demodulation of optical multilevel (M-ary) phase-shift-keying (PSK) signals. Since the carrier phase is estimated accurately through digital signal processing after phase-diversity homodyne detection, the system performance is highly tolerant to the carrier phase noise. By off-line bit-error-rate measurements using distributed feedback semiconductor lasers with linewidths of 150 kHz as a transmitter and a local oscillator, it is shown that binary PSK (M=2), quadrature PSK (M=4), and eight-PSK (M=8) signals are successfully demodulated at the symbol rate of 10 Gsymbol/s.     

Experimental evaluation of electrode conversion efficiency of alkali metal thermal to electric converter

The alkali metal thermal to electric converter (AMTEC) system which utilizes the sodium ion conductivity of a beta″‐alumina solid electrolyte (BASE) is expected to have high conversion efficiency above 30% including practical heat losses. However, the achieved experimental efficiencies have been around 15%. In this paper, current–voltage characteristics and heat and mass transfer processes on a single cell have been examined experimentally and thermal electrode conversion efficiency has been discussed. Measured electrode conversion efficiency without thermal losses showed that it was about 40% at a power density of 0.3 W/cm². A theoretical analysis on the thermal losses has also been conducted and these losses are estimated to be 0.3 W/cm² in a practical tube type cell, so that an actual cell system efficiency of 30% is expected. © 2001 Scripta Technica, Heat Trans Asian Res, 30(3): 234–244, 2001     

New polarisation-control scheme for optical heterodyne receiver using two Faraday rotators

A new state-of-polarisation (SOP) control scheme using two Faraday rotators is proposed. It features low optical insertion loss and quick response. Experiment shows that the receiver output is stable regardless of drastic SOP changes in the signal.     

Dependence of semiconductor laser linewidth on measurement time: evidence of predominance of 1/f noise

Linewidths of 1.3 ?m InGaAsP lasers were measured by using delayed self-heterodyne set-ups with two different delay-line lengths, i.e. with two equivalent measurement times. It has been found that in high-power operation the linewidth increases as the measurement time becomes longer, and that this dependence is explained well by a calculation assuming that the 1/f noise in the FM noise spectrum is the predominant cause of the spectral broadening. The significance of this fact in coherent optical communications is discussed.     

Attentional modulation of the mere exposure effect.

The mere exposure effect refers to the phenomenon where previous exposures to stimuli increase participants’ subsequent affective preference for those stimuli. This study explored the effect of selective attention on the mere exposure effect. The experiments manipulated the to-be-attended drawings in the exposure period (either red or green polygons in Experiments 1 and 2; both red and green polygons in Experiments 3 and 4) and black to-be-evaluated drawings in the affective judgment period (morphologically identical to the red or green polygons in Experiments 1 and 4; morphologically identical to the composite drawings in Experiments 2 and 3). The results showed a significant mere exposure effect only for the target shapes involved in attentional selection, even when the participants could recognize the nontarget shapes. This indicates that selective attention modulated the mere exposure effect. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Generalized warpage parameter

A warpage index (Δψ_m) was introduced for studying warpage characteristics of a plastic part injection molded from PA66 compounded with 30 wt% glass fiber. Δψ_m is defined as Δψ_m = (Δψ_m)_max – (Δψ_m)_min, where ψ_m = ψ(θ)_max, where ψ(θ) = (ε(θ) – α(θ)ΔT)/| α(θ)ΔT|, where ε is the total strain, α is the linear thermal expansion coefficient, ΔT is temperature difference, and θ is the angle along which ε and α are calculated. Finite element analysis was used for calculating flow field in injection, fiber orientation, material anisotropy and warpage. ψ_m is calculated in each finite element, and Δψ_m is calculated in a whole finite element model. Δψ_m is a measure of the ratio of actual shrinkage to the amount of shrinkage that would occur if an element freely shrank. The characteristics of Δψ_m were studied. It has been found that warpage is null if Δψ_m = 0, but that null warpage generally does not indicate Δψ_m = 0. It is shown that Δψ_m quantitatively represents the warped and unwarped state. Δψ_m distinguishes the null warpage state with possible buckling from the null warpage state without possible buckling. It has been shown that material anisotropy is possibly described with Δψ_m, and that the cause of warpage is self-restrictive deformation in an injection molded part. It has been deduced that it is generally not possible to eliminate warpage only by controlling material properties. Δψ_m is obtainable for a plastic part with complex geometry and complex fiber orientation state, and for arbitrary materials. Applications of Δψ_m are left for future study.     

Serum Amyloid A3 Promoter-Driven Luciferase Activity Enables Visualization of Diabetic Kidney Disease

The early detection of diabetic nephropathy (DN) in mice is necessary for the development of drugs and functional foods. The purpose of this study was to identify genes that are significantly upregulated in the early stage of DN progression and develop a novel model to non-invasively monitor disease progression within living animals using in vivo imaging technology. Streptozotocin (STZ) treatment has been widely used as a DN model; however, it also exhibits direct cytotoxicity to the kidneys. As it is important to distinguish between DN-related and STZ-induced nephropathy, in this study, we compared renal responses induced by the diabetic milieu with two types of STZ models: multiple low-dose STZ injections with a high-fat diet and two moderate-dose STZ injections to induce DN. We found 221 genes whose expression was significantly altered during DN development in both models and identified serum amyloid A3 (Saa3) as a candidate gene. Next, we applied the Saa3 promoter-driven luciferase reporter (Saa3-promoter luc mice) to these two STZ models and performed in vivo bioluminescent imaging to monitor the progression of renal pathology. In this study, to further exclude the possibility that the in vivo bioluminescence signal is related to renal cytotoxicity by STZ treatment, we injected insulin into Saa3-promoter luc mice and showed that insulin treatment could downregulate renal inflammatory responses with a decreased signal intensity of in vivo bioluminescence imaging. These results strongly suggest that Saa3 promoter activity is a potent non-invasive indicator that can be used to monitor DN progression and explore therapeutic agents and functional foods.