Monolithic Integration of GaAs-Based Resonant Tunneling Diode and High Electron Mobility Transistor

The resonant tunneling diode (RTD) is an ultra-highspeed and ultra-high frequency quantum-transport deviceaccompanied with negative differential resistance (NDR)I-Vcharacteristic originating fromresonant tunneling effect .The core structure of RTDis doubl…     

InP-based RTD/HEMT monolithic integration

Monolithic integration of resonant tunneling diodes (RTDs) and high electron mobility transistors (HEMTs) is an important development direction of ultra-high speed integrated circuit. A kind of top-RTD and bottom-HEMT material structure is epitaxied on InP substrate through molecular beam epitaxy. Based on wet chemical etching, metal lift-off and air bridge interconnection technology, RTD and HEMT are fabricated simultaneously. The peak-to-valley current ratio of RTD is 7.7 and the peak voltage is 0.33 V at room temperature. The pinch-off voltage is -0.5 V and the current gain cut-frequency is 30 GHz for a 1.0 μm gate length depletion mode HEMT. The two devices are conformable in current magnitude, which is suitable for the construction of various RTD/HEMT monolithic integration logic circuits.     

嵌入式行星螺杆挤出机内流场混沌行为研究

基于有限体积方法,对嵌入式行星螺杆挤出机内流场进行了三维等温数值模拟。通过简化的物理模型来模拟螺杆的几何结构,使用用户自定义程序设定了行星螺杆运动的边界条件。分析了挤出机螺槽内压力和速度的分布;使用粒子追踪技术观察了螺杆内流体运动轨迹和粒子分布规律;对粒子在螺杆内的停留时间分布进行了统计。结果表明行星螺杆对流体运动产生了周期性扰动。初始位置在一起的两个粒子,终点位置却相距很远。示踪粒子的具有对初始敏感的混沌特性,粒子的运动轨迹具有无序性,说明流体存在着混沌效应。     

气升式内环流反应器的液相流动混合模型

1Introduction Internalairliftloopreactor(AL)[1],originatedfrom bubblecolumn(BC)[2],isanefficientreactor.Itsspe cialsuperiorties,suchasthesimplicityofitsdesign andbettertransportrates,makeitveryattractivein fermentationengineering,wastewatertreatmentand cellsculture.Asisknown,themixinglevelofthe fluidisdirectlyaffectedbytheflowcharacteristicsof liquid.Thetwo phaseflowinreactorisverycomplex andincompletemixingbecauseofbackmixing,dead zone,bypassandtime lapse.Generally,theresearch isbasedontwoi…     

Hydraulic modeling of an anaerobic expanded bed reactor for municipal sewage treatment

Anaerobic expanded bed reactor （AEBR） is mostly used for the treatment of fairly low strength wastewaters. Since the performance of AEBR largely depends on its hydraulic characteristics, residence time distribution （RTD） method is commonly used for investigation of the hydraulic characteristics of AEBR under different ascending velocity of mixed liquor. In this paper, a pilot-scale AEBR reactor is investigated for treatment of municipal sewage in which lithium chloride is used as a tracer. The results show that the AEBR could be considered as the superimposition of several constant stirred tank reactors （CSTR） and the increase of hydraulic up-flow velocity could increase the number of the CSTR and decrease the volume rate of the dead zone. The optimal up-flow velocity of the investigated AEBR was approximately 1.9 rn/h in the municipal sewage treatment.     

计算主族元素Sm~的新方法

应用灰色理论中的等时空距灰色模型GM（1,1）研究了主族元素标准熵（Sm（?））和周期间的关系,所建模型对20种主族元素标准熵（Sm（?））的计算结果和文献报导值与实验测定结果进行了比较,新建模型求得Sm（?）值与实验测定结果之间的绝对平均差为1.807,标准偏差为1.736,明显优于已有文献报导结果（绝对平均值差和标准偏差分别为2.748和2.195）.利用所建模型预言了113号元素（ununtrium,Uut）、114号元素（Ununquadium,Uuq）、119号元素（ununennium,Uue）、120号元素（unbinilium,Ubn）以及阶和Ra的Sm（?）.它们分别是85.96,97.75,120.04,97.38,102.08,78.88 kj/mol.     

At Risk on the Border: Assessment of Student Learning at an Hispanic Serving Institution

Hispanics face multiple barriers to academic achievement. This study measured learning in an undergraduate criminal justice program at an Hispanic Serving Institution bordering Mexico. We estimated the average gains students achieved across core content areas using a technique that can be used by other faculty as part of program assessment. The majority of participants were Hispanic first-generation college students. An independent samples t-test was used to examine differences between freshman- and senior-level students, and the Lovett/Johnson model (2012) model was used to measure student gains using regression analysis. Results indicated that seniors showed meaningful gains at every level.     

Allocation of time in self-paced memory tasks: the role of practice, instructions, and individual differences in optimizing performance

Nelson & Narens (1990) proposed that the allocation of study time in self-paced memory tasks depends on the comparison between the norm of study (established before studying) and the level of learning reached. We explored the role of practice, instructions, and individual differences in determining the norm of study and optimizing performance. In Study 1, participants carried out various study trials involving different (but similar) lists of words. In Study 2, participants were instructed to attain either maximum recall or maximum speed. In Study 3, the study time spontaneously used by each participant was estimated. The effect of increasing or decreasing this time was observed. Memory span and speed of lexical processing were also measured. Finally, Study 4 estimated participants were able to adapt performance to objective criteria (e.g., instructions). However, the time that they spontaneously use tends to be the most efficient. Variations in these times lead to losses in efficiency. Differences in processing capacity or motivation seem not to determine the differences in study time.     

具有二阶非线性校正功能的铂电阻温度变送器

分析采用XTR103芯片的铂电阻温度变送器,给出其电路图,详细地探讨电路工作原理,并计算出详细测试数据．结果显示：采XTR103芯片设计的铂电阻温度变送器的电路具有二阶非线性校正功能且电路简洁;该变送器采用两线制与二次仪表连接,输出电流为4～20mA,与铂电阻之间采用三线制连接方式,工作电压范围为9-40V,在标准的24V供电时可配接≤750Q的二次仪表;实际测试显示在0～800℃温度范围内的非线性误差小于0．28％．     

Environmental impact prediction using remote sensing images

Environmental impact prediction is an important step in many environmental studies. A wide variety of methods have been developed in this concern. During this study, remote sensing images were used for environmental impact prediction in Robatkarim area, Iran, during the years of 2005-2007. It was assumed that environmental impact could be predicted using time series satellite imageries. Natural vegetation cover was chosen as a main environmental element and a case study. Environmental impacts of the regional development on natural vegetation of the area were investigated considering the changes occurred on the extent of natural vegetation cover and the amount of biomass. Vegetation data, land use and land cover classes （as activity factors） within several years were prepared using satellite images. The amount ofbiomass was measured by Soil-adjusted Vegetation Index （SAVI） and Normalized Difference Vegetation Index （NDVI） based on satellite images. The resulted biomass estimates were tested by the paired samples t-test method. No significant difference was observed between the average biomass of estimated and control samples at the 5% significance level. Finally, regression models were used for the environmental impacts prediction. All obtained regression models for prediction of impacts on natural vegetation cover show values over 0.9 for both correlation coefficient and R-squared. According to the resulted methodology, the prediction models of projects and plans impacts can also be developed for other environmental elements which may be derived using time series remote sensing images.     

Bioremediation potential of spirulina： toxicity and biosorption studies of lead

INTRODUCTION Environmental contamination by toxic metals isa serious problem worldwide due to their incrementalaccumulation in the food chain and continued per-sistence in the ecosystem. Conventional technologies,such as ion exchange or lime precipitation, are oftenineffective and/or expensive, particularly for the re-moval of heavy metal ions at low concentrations(below 50 mg/L). Furthermore, most of these tech-niques are based on physical displacement orchemical replacement, generating …     

Kinetic analysis of γ-glutamyltransferase reaction process for measuring activity via an integration strategy at low concentrations of γ-glutamyl p-nitroaniline

At 0.12 mmol/L γ-glutamyl p-nitroaniline (GGPNA), an improved integrated method was developed for kinetic analysis of γ-glutamyltransferase (GGT) reaction process and the integration with the classical initial rate method to measure serum GGT. For the improved integrated method, an integrated rate equation, which used the predictor variable of reaction time and considered inhibitions by both GGPNA and products, was nonlinearly fit to GGT reaction processes. For the integration strategy, classical initial rates were estimated when GGPNA consumption percentages were below 50%; otherwise, maximal reaction rates of GGT were estimated by the improved integrated method and converted into initial rates according to the differential rate equation at 0.11 mmol/L GGPNA. The integration strategy was validated using optimized GGT kinetic parameters and 10-s intervals to record reaction curves within 8.0 min. By the integration strategy, there was a linear response from 0.9 to 32.0 U/L GGT, coefficients of variation were below 3.5% for GGT from 8.0 to 32.0 U/L (n=5), and GGT activities in clinical sera responded linearly to their classical initial rates at 2.00 mmol/L GGPNA with an expected slope. Therefore, the integration strategy was successful in measuring GGT at 0.12 mmol/L GGPNA.     

Emotional support and adult depression in survivors of childhood sexual abuse

The goals of this study were to evaluate the effects of emotional support from friends and parents at two time points (adolescence and adulthood) on adult depression in a nationally representative sample of survivors of childhood sexual abuse (CSA), and examine whether the associations were moderated by the identity of the perpetrator (parent/caregiver vs. not). Data were taken from Waves I and IV of the National Longitudinal Study of Adolescent Health (Add Health). The study sample included 1,238 Add Health participants with a history of CSA and an equivalently sized comparison group of individuals with no history of CSA. Parental support was measured using four items from each wave that assessed the warmth of participants’ relationships with their parents and their satisfaction with those relationships. Friend support in adolescence was measured using participants’ perceptions of how much their friends cared about them and in adulthood using participants’ self-reported number of close friends. Depression was measured using a 10-item subscale of the CES-D. Logistic regressions showed that support from friends and parents in adulthood were significantly associated with lower odds of adult depression in CSA survivors who reported non-parent/caregiver abuse. Among survivors of parent/caregiver abuse, emotional support was not significantly associated with adult depression regardless of when or by whom it was provided. In conclusion, emotional support in adulthood from friends and parents is associated with reduced odds of adult depression in CSA survivors, but only in cases where the abuse was perpetrated by someone other than a parent or caregiver.     

Simulated moving bed separation of tocopherol homologues: simulation and experiments

Chromatograms of tocopherol homologues were obtained by a column of analytical size （inner diameter （ID） 0.46 cm cm×10 cm） packed with silica gel. Adsorption isotherms and film mass-transfer coefficient were estimated from the chromatograms by using a general rate model, which considers axial dispersion, external mass-transfer and intraparticle diffusion. Based on the obtained isotherms and mass-transfer coefficient, the separation process of tocopherol homologues on simulated moving bed （SMB） was simulated using the same model. According to the simulated results, a mixture of α-, γ-, δ-tocopherols and other impurities was separated on an SMB equipment. The SMB equipment was composed of 8 columns of ID 2 cm× 1 0 cm, with 2 columns in each section. The solid phase was silica gel, and the mobile phase was n-hexane/2-propanol （99/1 by volume）. γ- and δ-tocopherols of purity greater than 98% were obtained with recovery greater than 98%. The effects of operating conditions （flow rates and switching time） on the performance of SMB were studied by both simulation and experiments. It was found that all the simulation results were quite close to the experimental results. We conclude that process development and optimization of operating conditions of SMB by simulation are feasible.     

Do peer relationships mediate the association between children’s facial emotion recognition ability and their academic attainment? Findings from the ALSPAC study

We examined whether children’s facial emotion recognition ability predicted their academic attainment over time, and whether peer relationships mediated that association. A secondary aim was to test whether the putative causal pathways would be significantly different for boys and girls. The model was tested using data from The Avon Longitudinal Study of Parents and Children (ALSPAC), a prospective longitudinal cohort population. Facial emotion recognition ability was assessed using the Diagnostic Assessment of Non-Verbal Accuracy (DANVA) at age 8.5 years while academic attainment was measured using data on UK Key Stage 4 (General Certificate of Secondary Education) at 16 years (outcome). The teacher’s version of the Strengths and Difficulties Questionnaire was used to measure children’s peer relationship problems at 10–11 years (mediator). We adjusted for area-level socio-economic status and child’s early academic attainment, and examined whether mediation was moderated by sex. The results showed that low facial emotion recognition ability in childhood was associated with low academic attainment at age 16 years. There was evidence of mediation via peer problems, with an estimated 19% of the total effect mediated by errors in emotion recognition. Further analyses showed that there was no difference in mediation for boys versus girls. The findings suggest that children’s facial emotion recognition ability and peer relationships should be potential targets for programmes that aim to improve children’s educational attainment and their social and emotional competence.     

Does the choice of reference levels of education matter in the ORU earnings equation?

This paper examines whether the results of the earnings equation developed in the over-education/required education/under-education (ORU) literature are sensitive to whether the usual or reference levels of education are measured using the Realized Matches or Worker Self-Assessment methods. The analyses are conducted for all male native-born and immigrant workers in the US, by level of skill, and by occupation. While point estimates differ, particularly when earnings equations are estimated for the smaller samples of sub-groups of the workforce, the general findings are robust to this measurement issue. Thus, the answers provided to the typical research questions in the ORU literature on the productivity of schooling are independent of the measure of the usual or reference level of education used in the analyses.     

Knowing what it takes: The effect of information about returns to studying on study effort and achievement

We study the effect of providing students with information on the returns to study effort in a large introductory microeconomics course. To do so, we use historical time-use data from the course’s online homework module to estimate the association between study time and course performance. We measure the impact of providing students this information on subsequent study effort, class attendance, homework scores, and exam performance using a randomized research design. Results show that the information contained in our intervention increased time spent studying by approximately 7% throughout the entire course, though this effect is imprecisely measured. However, when examining shorter-run outcomes (prior to the next exam) we find larger and more precisely estimated treatment effects on time spent on homeworks (12%) and homework scores (14% of a standard deviation). Treatment effects on longer run outcomes in the course are negligible. We additionally estimate large, but somewhat imprecise, average treatment effects on class attendance and small positive and insignificant average treatment effects on exam performance throughout the course.     

陆英及其提取物乌索酸对小鼠出血和凝血时间的影响

目的：通过实验研究陆英及其提取物乌索酸对动物出血、凝血时间的影响。方法：分别灌胃给予小鼠陆英水煎剂、乌索酸（15、30、60mg/kg）、生理盐水,每天一次,共给药7天,采用断尾法测定小鼠的出血时间,玻片法测定小鼠的凝血时间。结果：与生理盐水组比较,陆英、乌索酸（15、30、60mg/kg）组均有显著性差异（p〈0.05）。结论：陆英和乌索酸均能明显延长小鼠出血时间和凝血时间,与其活血化瘀功效相符。     

Miscibility on blends of PVA and PFSA by viscometry

The intrinsic viscosity and viscometric interaction parameters of perfluorosulfonic acid(PFSA) and poly(vinyl alcohol)(PVA) were measured by dilute solution viscometry.The miscibility between PFSA and PVA was estimated by the criteria of △B and μ.The results indicated that PFSA and PVA were completely miscible for any weight fraction in aqueous solution.     

基于自适应无味卡尔曼滤波的机床选点温升快速辨识方法研究

研究目的：为了缩短机床温升试验时间,提出一种机床热特性快速辨识方法,利用较短时间的温度采样数据即可准确预测出完整的温升曲线,进而获得热平衡时间及稳态温度等热特性参数。创新要点：提出了基于自适应无味卡尔曼滤波的机床选点温升快速辨识方法,其中最短辨识时间判据可以有效解决如何寻找准确辨识热特性参数的最短采样时间问题,而自适应无味卡尔曼滤波则可以实时调整参数,防止外界因素对辨识的干扰。研究方法：由于无味卡尔曼滤波在非线性状态预测和参数辨识上具有优势,所以本文将无味卡尔曼滤波算法应用到机床选点温升辨识上。为了防止辨识过程中的发散退化等问题,将无味卡尔曼滤波发展为自适应无味卡尔曼滤波（图1）。在快速辨识方法上提出了最短辨识时间判据（图2）。文章中又将此算法应用到实际的立式加工中心温升辨识上,证明了该算法的可行性及有效性（图5和6）。最后又将带有自适应调整过程的无味卡尔曼滤波算法和不带调整过程的算法做了对比,显示了自适应调整过程对辨识算法的重要性（图6和11）。重要结论：基于自适应无味卡尔曼滤波的机床选点温升快速辨识方法可以准确快速地辨识出温升曲线,获取热特性参数,将原来394 min的热平衡试验时间缩短,只需28 min即可得到温升变化情况。