采用温控和碘吸收池技术的发射激光稳频技术

多普勒测风激光雷达通过分析系统回波信号的多普勒频移反演出风速，为提高风场探测精度，从稳频技术方面展开研究。在稳频过程中，分别采取措施消除激光频率的长期漂移和短期抖动。针对激光频率的长期漂移，设计并研制了种子激光器温控箱，通过水浴的控温方式大大减小了激光频率的长期漂移，将激光频率稳定在±50 MHz以内；针对激光频率的短期抖动，采用以碘分子吸收池为核心器件的稳频系统，通过半导体控温方式对碘分子吸收池精确控温，控温精度达0.03 ℃，提高了稳频精度，将激光频率进一步稳定在±8 MHz以内，满足±10 MHz以内的设计精度要求。通过搭建多普勒测风激光雷达系统，对发射激光稳频装置进行系统验证，连续4组风场观测结果表明:系统探测高度为17 km，绝大部分方差在4 m/s以下，满足测风激光雷达测量指标的要求。     

Alterations in the Genomic Distribution of 5hmC in In Vivo Aged Human Skin Fibroblasts

5-Hydroxymethylcytosine (5hmC) is a functionally active epigenetic modification. We analyzed whether changes in DNA 5-hydroxymethylation are an element of age-related epigenetic drift. We tested primary fibroblast cultures originating from individuals aged 22–35 years and 74–94 years. Global quantities of methylation-related DNA modifications were estimated by the dot blot and colorimetric methods. Regions of the genome differentially hydroxymethylated with age (DHMRs) were identified by hMeDIP-seq and the MEDIPS and DiffBind algorithms. Global levels of DNA modifications were not associated with age. We identified numerous DHMRs that were enriched within introns and intergenic regions and most commonly associated with the H3K4me1 histone mark, promoter-flanking regions, and CCCTC-binding factor (CTCF) binding sites. However, only seven DHMRs were identified by both algorithms and all of their settings. Among them, hypo-hydroxymethylated DHMR in the intron of Rab Escort Protein 1 (CHM) coexisted with increased expression in old cells, while increased 5-hydroxymethylation in the bodies of Arginine and Serine Rich Protein 1 (RSRP1) and Mitochondrial Poly(A) Polymerase (MTPAP) did not change their expression. These age-related differences were not associated with changes in the expression of any of the ten-eleven translocation (TET) enzymes or their activity. In conclusion, the distribution of 5hmC in DNA of in vivo aged human fibroblasts underwent age-associated modifications. The identified DHMRs are, likely, marker changes.     

Scalable Clock Synchronization Analysis: A Symmetric Noncooperative Output Feedback Tubes-MPC Approach

In the cyber-physical environment, the clock synchronization algorithm is required to have better expansion for network scale. In this paper, a new measurement model of observability under the equivalent transformation of minimum mean square error (MMSE) is constructed based on basic measurement unit (BMU), which can realize the scaled expansion of MMSE measurement. Based on the state updating equation of absolute clock and the decoupled measurement model of MMSE-like equivalence, which is proposed to calculate the positive definite invariant set by using the theoretical-practical Luenberger observer as the synthetical observer, the local noncooperative optimal control problem is built, and the clock synchronization system driven by the ideal state of local clock can reach the exponential convergence for synchronization performance. Different from the problem of general linear system regulators, the state estimation error and state control error are analyzed in the established affine system based on the set-theory-in-control to achieve the quantification of state deviation caused by noise interference. Based on the BMU for isomorphic state map, the synchronization performance of clock states between multiple sets of representative nodes is evaluated, and the scale of evaluated system can be still expanded. After the synchronization is completed, the state of perturbation system remains in the maximum range of measurement accuracy, and the state of nominal system can be stabilized at the ideal state for local clock and realizes the exponential convergence of the clock synchronization system.      

Estimation of power density in IMPATT using different materials

ABSTRACT

The RF output power dissipated per unit area is calculated using Runge-Kutta method for the high-moderate-moderate-high (n⁺-n-p-p⁺) doping profile of double drift region (DDR)-based impact avalanche transit time (IMPATT) diode by taking different substrate at Ka band. Those substrates are silicon, gallium arsenide, germanium, wurtzite gallium nitride, indium phosphide and 4H-silicon carbide. A comparative study regarding power dissipation ability by the IMPATT using different material is being presented thereby modelling the DDR IMPATT diode in a one-dimensional structure. The IMPATT based on 4H-SiC element has highest power density in the order of 10¹⁰ Wm^?2 and the Si-based counterpart has lowest power density of order 10⁶ Wm^?2 throughout the Ka band. So, 4H-SiC-based IMPATT should be preferable over others for the power density preference based application. This result will be helpful to estimate the power density of the IMPATT for any doping profile and to select the proper element for the optimum design of the IMPATT as far as power density is concerned in the Ka band. Also, we have focused on variation of power density with different junction temperatures and modelled the heat sink with analysis of thermal resistances.     

大豆肽对果蝇睡眠的影响

研究大豆肽(soybean peptides,SBP)对果蝇睡眠的影响。通过大豆分离蛋白酶解,制得SBP,选择20日的雄性果蝇,分为4组,无添加的培养基作为空白组,SBP分为2、4、8 mg/mL额外添加到培养基作为3个实验模型组,通过VideoTrack动物行为分析系统监测果蝇睡眠时长,并检测SBP对果蝇脑部生物钟基因(per、tim、clk、cyc)与参与调控睡眠神经递质合成限速酶的基因(gad、tph、gdh、hdc)以及五羟色胺(5-hydroxytryptamine,5-HT)的影响。研究发现,在监测睡眠的第2日晚上,SBP对果蝇睡眠延长效果最好,并呈现剂量依赖性,又通过剥离取头,分析其生物钟基因(per、tim、clk、cyc)和神经递质合成限速酶基因(gad、tph、gdh、hdc),得到SBP是通过调节tim和tph的基因表达并提高5-HT在脑部的含量来延长果蝇的睡眠时长的结论。     

Preprocessed dynamic classifier ensemble selection for highly imbalanced drifted data streams

This work aims to connect two rarely combined research directions, i.e., non-stationary data stream classification and data analysis with skewed class distributions. We propose a novel framework employing stratified bagging for training base classifiers to integrate data preprocessing and dynamic ensemble selection methods for imbalanced data stream classification. The proposed approach has been evaluated based on computer experiments carried out on 135 artificially generated data streams with various imbalance ratios, label noise levels, and types of concept drift as well as on two selected real streams. Four preprocessing techniques and two dynamic selection methods, used on both bagging classifiers and base estimators levels, were considered. Experimentation results showed that, for highly imbalanced data streams, dynamic ensemble selection coupled with data preprocessing could outperform online and chunk-based state-of-art methods.     

Improved multi-recessed 4H–SiC MESFETs with double-recessed p-buffer layer

An improved multi-recessed 4H–SiC metal semiconductor field effect transistor (MRD-MESFET) with double-recessed p-buffer layer (DRB-MESFET) is proposed in this paper. By introducing a double-recessed p-buffer layer, the gate depletion layer is further modulated, and higher drain saturation current and DC transconductance are obtained compared with the MRD-MESFET. The simulations show that the drain saturation current of the DRB-MESFET is about 42.4% larger than that of the MRD-MESFET. The DC transconductance of the DRB-MESFET is almost 15% higher than that of the MRD-MESFET and very close to that of double-recessed structure (DR-MESFET) at the bias conditions of V_gs=0 V and V_ds=40 V. The proposed structure has an improvement of 26.1% and 74.2% in the output maximum power density compared with that of the MRD-MESFET and DR-MESFET, respectively. In the meanwhile, the proposed structure possesses smaller gate-source capacitance, which results in better RF characteristics.     

Optimum design for unbonded posttensioned precast split shear wall system using genetic algorithm

Precast concrete structures are increasingly being adopted by building designers in regions of high seismicity. An unbonded posttensioned (PT) precast split shear wall system (UPPSSW) was proposed by the Precast Seismic Structural Systems (PRESSS). The UPPSSW system is composed of two or more single precast concrete wall panels that are connected together with energy‐dissipating shear connectors and anchored to the foundation with unbonded PT tendons located at the panel center. In this paper, an optimum design program has been developed for designing this system. The objective of the optimum process is to find the optimum combination between PT tendons and shear connectors while keeping the moment capacity of the wall equal to the applied design moment and achieving zero residual drift simultaneously. In addition, MATLAB was employed to explore an optimization program using genetic algorithm. Compared with the existing design methods for the system, the optimum design program proposed in this research is accurate, efficient, and direct. Moreover, it can yield the optimum design automatically and quickly. As a result, the existing lengthy and manual design process of trial and error for the system can be avoided.     

汽车起重机起升机构动态研究

本文对汽车起重机起升机构的“二次下滑”现象进行了研究,并对垆或机构作了改进,对液压系统利用功率键合图和状态空间进行了动态特性分析。