Digital control of a voltage-mode synchronous buck converter

A digital control algorithm capable of separately specifying the desired output voltage and transient response for a synchronous buck converter operating in voltage mode was developed. This algorithm is based on superimposing a small control signal onto a voltage reference at each switching cycle to cancel out the perturbations. A zero steady-state error in the output voltage can be obtained with the aid of additional dynamics to allow the controller to track a load change and update the reference to a new load state. The specifications of the control algorithm are achieved by pole placement using complete state feedback. The control algorithm was implemented on a digital signal processor (DSP)-controlled synchronous buck converter.     

Dynamic NBTI of p-MOS transistors and its impact on MOSFET scaling

For the first time, a dynamic negative bias temperature instability (DNBTI) effect in p-MOSFETs with ultrathin gate oxide (1.3 nm) has been studied. The interface traps generated under NBTI stressing corresponding to p-MOSFET operating condition of the "high" output state in a CMOS inverter, are subsequently passivated when the gate to drain voltage switches to positive corresponding to the p-MOSFET operating condition of the "low" output state in the CMOS inverter. Consequently, this DNBTI effect significantly prolongs the lifetime of p-MOSFETs operating in a digital circuit, and the conventional static NBTI (SNBTI) measurement underestimates the p-MOSFET lifetime. A physical model is presented to explain the DNBTI. This finding has significant impact on future scaling of CMOS devices.     

基于CNN与传统S盒结合的图像加密算法

目前人们针对不同场景设计和研究出各种基于混沌的图像加密算法并取得不俗的研究成果,但仍有一些图像加密算法存在不足之处,因而相关专家学者们不断研究新的图像加密方法并对传统的各种加密算法进行改进.针对目前低维混沌算法存在的明显缺点,提出一种基于CNN超混沌与S盒结合的图像加密算法,仿真实验表明,该算法能够有效地抵挡明文(密文...     

Synthesis of pyramidal,cubical and truncated octahedral magnetite nanocrystals by controlling reaction heating rate

Pyramidal, cubical and truncated octahedral magnetite nanocrystals have been synthesized by thermal de-composition of iron (III) acetylacetone (Fe(acac)₃) in the presence of oleic acid under various reaction rate controlled by heating rate. The magnetite nanocrystals were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). High-resolution transmission electron microscopy (HRTEM) was applied to reveal the structural information of single magnetite (Fe₃O₄) nanocrystals. Magnetization curves of the three types of magnetite nanocrystals show that the pyramidal crystals exhibit a slight hysteresis compared to the other two despite of the similar size range. The results suggest that in addition to the surfactant selective capping and varying reaction temperature, the reaction rate variation is also an effective means for controlling the morphology and functions of the magnetite nanocrystals.     

Antioxidant Activities and Polyphenolic Constituents of Bitter Bean Parkia Speciosa

Bitter bean (Parkia speciosa), also known as petai, is a popular non-timber forest product. Traditionally, its fruits are consumed as vegetables and herbal medicines in Malaysia. The present study aimed to evaluate the antioxidant activities of aqueous and ethanol extracts of P. speciosa empty pods using various antioxidant assays, as well as examining their polyphenolic constituent contents. Results showed that with the exception of superoxide radical scavenging activity, ethanol extracts possessed stronger DPPH and ABTS radical scavenging, anti-lipid peroxidation, metal chelating and reducing power activities than aqueous extracts. It was found to contain a higher level of total flavonoids and total phenols than aqueous extracts. The major polyphenolic constituents present in these extracts were gallic acid, catechin, ellagic acid, and quercetin. Although aqueous extracts contained a higher level in gallic acid, its catechin, ellagic acid, and quercetin contents were lower than ethanol extracts. Taken together, the higher amount of polyphenolic compounds present in ethanol extracts could have contributed to its stronger antioxidant activities than aqueous extracts; these results also provided the chemical basis for certain health benefits claimed of P. speciosa empty pods in folk medicine and as foods.     

基于挥发性成分分析的葡萄酒产地及品种鉴别研究进展

随着葡萄酒市场的日渐繁荣,消费者越来越注重对葡萄酒品质的追求。葡萄酒的原产地及品种是决定葡萄酒品质的重要因素,而挥发性成分在表征某一特定产地或某一品种葡萄酒中起着重要作用,因此,利用挥发性成分鉴别葡萄酒产地及品种有重要意义。本文介绍了葡萄酒挥发性成分分析方法的研究进展,总结了利用挥发性成分鉴别葡萄酒产地及品种的研究现状,以期促进对葡萄酒挥发性成分的深入研究,为保障葡萄酒的品质和真实性,以及建立更加完善的葡萄酒挥发性指纹图谱提供理论参考。     

基于非标记蛋白质组学技术研究白羽肉鸡不同部位肌肉的蛋白差异

蛋白质作为肉类组成的重要部分,其发生改变会引起肉品质的变化,不同部位肌肉的理化特性及蛋白质组成不同。通过非标记蛋白质组学定量技术和数据非依赖型扫描技术,对白羽肉鸡鸡腿肉和鸡胸肉进行蛋白质鉴定和定量分析,并对其进行生物信息学分析。结果表明：鸡腿肉和鸡胸肉中共鉴定出875 个蛋白质与16 855 条肽段,且筛选出98 个差异蛋白;对鸡腿肉中的上调差异蛋白进行基因本体论（gene ontology,GO）组分富集分析的结果显示,在生物学过程中,其主要参与酰基辅酶A脱氢酶的脂肪酸β-氧化、三羧酸循环等过程,在细胞组分中主要富集于线粒体内,在分子功能中主要具有氧化还原酶活性、脂肪酰基辅酶A结合、烟酰胺腺嘌呤二核苷酸结合、肌动活动、电子载体活性、黄素腺嘌呤二核苷酸结合和催化活性等功能;鸡胸肉中上调差异蛋白的GO组分富集分析结果显示,在生物学过程中,其主要富集在骨骼肌收缩过程,在细胞组分中富集于胞外外泌体中的蛋白质最多;鸡腿肉中的高表达蛋白均富集于运动相关功能,而鸡胸肉中的上调蛋白多富集于肌肉收缩功能。