Comparison of TRMM multisatellite precipitation analysis (TMPA) products and daily-monthly gauge data over Bali

Research has been conducted to compare daily, monthly and seasonal rain rates derived from Tropical Rainfall Measuring Mission (TRMM) multisatellite precipitation analysis (TMPA) using rain gauge analysis from 1998 to 2002. Three rain gauges in the Bali islands were employed. Statistical analysis was used to analyse the relationship of the TMPA product with the rain gauge data. Resulting statistical measures consisted of the linear correlation coefficient (r), the mean bias error (MBE), the root mean square error (RMSE) and the mean absolute error (MAE). The results of these analyses indicate that satellite data have lower values than the gauge estimation values. The validation analysis showed a very good relationship with the gauge data on monthly timescales. However, a poor relationship was found between the gauge data and the daily data analysis from the TMPA. The 3B42 and 3B43 products showed the same levels of relationship during the wet season and dry season. The correlation in the dry season was better than during the wet season. Statistical error levels during the wet season were better than in the dry season. The 3B43 showed slight improvement in these values when compared with the 3B42 (both the random error measurement and the scatter of the estimates were reduced). In general, the data from TMPA are potentially usable to replace rain gauge data, especially to replace the monthly data, if inconsistencies and errors are taken into account.     

Occurrence of Aspergillus spp. and aflatoxin B1 in Malaysian foods used for human consumption

Malaysian population widely consumes the cereal-based foods, oilseeds, nuts, and spices in their daily diet. Mycotoxigenic fungi are well known to invade food products under storage conditions and produce mycotoxins that have threat to human and animal health. Therefore, determining toxigenic fungi and aflatoxin B(1) (AFB1) in foods used for human consumption is of prime importance to develop suitable management strategies and to minimize risk. Ninety-five food products marketed in Penang, Malaysia were randomly collected from different supermarkets and were analyzed for presence of Aspergillus spp. by agar plate assay and AFB1 by enzyme-linked immunosorbent assay (ELISA). A. flavus was the dominant fungi in all foods followed by A. niger. Fifty-five A. flavus strains were tested for their ability to produce aflatoxins on rice grain substrate. Thirty-six (65.4%) strains out of 55 produced AFB1 ranging from 1700 to 4400 μg/kg and 17 strains (31%) produced AFB2 ranging from 620 to 1670 μg/kg. Natural occurrence of AFB1 could be detected in 72.6% food products ranging from 0.54 to 15.33 μg/kg with a mean of 1.95 μg/kg. Maximum AFB1 levels were detected in peanut products ranging from 1.47 to 15.33 μg/kg. AFB1 levels detected in all food products were below the Malaysian permissible limits (<35 μg/kg). Aspergillus spp. and AFB1 was not detected in any cookies tested. Although this survey was not comprehensive, it provides valuable information on aflatoxin levels in foods marketed in Malaysia.     

基于剪切波域改进Gamma校正的医学图像增强算法

为了解决医学图像在采集和传输过程中引入噪 声和干扰导致图像质量恶化从而严重影响医学诊断的问题,提出 一种基于剪切波(shearlet)域改进Gamma校正的图像增强方法。首先,通过剪切波变换,把 图像分解成高频 部分和低频部分;其次,用改进的Gamma校正处理剪切波分解后的低频部分以调整图像的整 体对比 度,采用改进的自适应阈值函数对高频部分进行去噪;最后,把剪切波反变换的重构图 像进行模糊对比 增强,以突出图像的细节信息。实验结果表明,本文算法的峰值信噪比(PSNR )、结构相似度(SSIM)和 绝对均值差(MAE)优于其他对比算法,尤其是PSNR的提升更加明显。这些 客观指标说明,本 文算法不仅能有效地抑制噪声,而且能明显改善增强对比度。从主观方面观察,本文算法与 其他算法相比,能获得更好的视觉效果。     

Transmission Characteristics of Hybrid Modes in Corrugated Waveguides Above the Bragg Frequency

We studied the transmission characteristics of hybrid modes in a corrugated circular waveguide above the Bragg frequency to develop a broad-band transmission line for millimeter waves. Millimeter waves at 294 GHz were transmitted into a straight waveguide. From observed power profiles in waveguide cross-sections, a high attenuation rate of 0.13 dB/m was obtained. To match a theoretical attenuation constant with the experimental one, we introduced an ad hoc coefficient of conventional surface reactance in the waveguide wall. This was necessary because the wall began to look like the surface with a decreasing anisotropic reactance owing to the frequency above the Bragg frequency. Using nonlinear optimization for mode content analysis, the observed power profiles in the waveguide cross-section were matched with theoretical profiles. There was good agreement between the calculated and observed centers of power profiles and attenuation rate along the waveguide. The theoretical analysis showed that the magnetic field at the waveguide wall increases and the substantial attenuation takes place. Above the Bragg frequency coupling to backwards propagating modes is a point of consideration. A combination of the backwards propagating EH_1,26 and the forward propagating HE₁₁ modes satisfied the Bragg condition at 294.7 GHz which was the nearest frequency of operating frequency. A strong attenuation of the incoming HE₁₁ mode by Bragg resonance was not expected due to large difference of 0.7 GHz. It becomes clear that the observed high transmission loss outside of the Bragg resonance can be explained by a decrease in anisotropic surface reactance at the wall.     

A mechanical sensorless control system for salient-pole brushlessDC motor with autocalibration of estimated position angles

In this paper, a mechanical sensorless control system is reported for salient-pole brushless DC motor drives. Here, two new methods are proposed for obtaining the position angle, the accuracy of which affects the operation of the switching devices of the inverter that drives the motor. First, the method for estimating the position angle is proposed. Secondly, the correcting method for reducing the errors involved in the estimation of position angle is given. The experimental results show that the estimated position angles are calibrated automatically, and then the proposed sensorless control system can control the speed and the position angles of the motor precisely     

Sensitivity analyses for scenario reduction in flexible flow sheet design with a large number of uncertain parameters

A solution strategy for designing flexible process flow sheets with a large number of uncertain parameters is presented. The basic mathematical formulation is a two‐stage stochastic program transformed into its multi‐scenario deterministic equivalent. The main feature of the proposed approach is a tremendous reduction in scenarios to a smaller number of those critical ones. This reduction is achieved through simple sensitivity analyses that identify those uncertain parameters that are critical for feasibility and those that are involved in a stochastic approximation of the objective value. Through the application of this strategy, it is possible to solve the problems with several tens or even hundred uncertain parameters, assuming weak interactions between them. Feasible designs are obtained for a fixed degree of flexibility, while the expected objective function is approximated fairly well. The strategy is applied to two flow sheet examples. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2862–2871, 2013     

Amyloid beta-peptide and its fragments induce acetylcholine release in in vitro basal forebrain tissue slices of rat brain, but do not affect the choline uptake

OBJECTIVE: Although stressor uncontrollability has been shown to suppress immune responses in animals and for human subjects, the results have been inconsistent. We reanalyzed results of our previous study regarding stress-related immune deviation in man, to establish whether perceived uncontrollability of an acute stressor acts as a co-determinant in the observed changes in immunological parameters. METHOD: Three types of cognitive reactions to an acute interpersonal stressor were assessed: "motivation," "uncontrollability," and "guiltiness." Stress-induced changes in the number of several types of immune cells in peripheral blood and proliferative responses of lymphocytes to antigens and mitogens were assessed. RESULTS: In comparison with control subjects and with subjects perceiving high control over the experimental stress situation, the subject perceiving low control showed a stressor-induced decrease in the number of T helper cells. Reversely, subjects perceiving high control showed an increase in the number of B cells as opposed to the other two groups. The effects of perceived uncontrollability could not be accounted for by mood changes, but they were related to previously experienced life stress. CONCLUSIONS: Perceived uncontrollability of an acute stressor can have immuno-modulating effects over and above those of the stressor per se.     

Maximum power point tracking with estimation of the capacitance of the capacitor connected to photovoltaic array

This paper presents a new perturbation and observation method with a capacitance estimation technique for maximum power point tracking (MPPT) in a photovoltaic system. Usually, the maximum power point is tracked by increasing or decreasing the duty ratio of power switching devices. However, it is well known that actual capacitance of an electrolytic capacitor in parallel with a photovoltaic array has 50% tolerance of its nominal value and also that its capacitance value degrades as time passes. If the variation of the duty ratio is determined and fixed using the capacitor nominal value, the MPPT performance may be degraded. Therefore, we must use the actual capacitance in order to improve the MPPT performance. In our system, we applied the model reference adaptive system (MRAS), then obtained the accurate capacitance value and accordingly corrected the duty ratio variation. As a result, it was possible to obtain high MPPT performance. Experimental results show that the proposed method can stably track the maximum power point at widely changing capacitance values by using a newly developed buck‐boost chopper‐type power inverter. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(4): 75–85, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10150