Hydrolytic Degradation Behaviors of Poly（p-dioxanone） in Ambient Environments

The effects of temperature and relative humidity on the hydrolytic degradation of poly（p-dioxanone）（PPDO） were investigated. The hydrolytic degradation behaviors were monitored by tracing the changes of water absorption, mechanical and crystalline properties, molecular weight and its distribution, surface morphologies, as well as infrared absorption peaks and hydrogen chemical shifts during the degradation. It is found that the water absorption increases whilst the intrinsic viscosity, tensile strength and elongation at break decrease as the temperature or relative humidity increases. With degradation time growing, the molecular weight drops and its distribution broadens. The crystallinity of PPDO has a tendency to increase at first and then to decrease, while the crystalline structure is not significantly changed. At the same time, some cracks are observed on the surface and keep growing and deepening. All results show that temperature plays more significant roles than relative humidity during the degradation. The analyses of Fourier transform infrared spectroscopy and hydrogen nuclear magnetic resonance spectroscopy reveal that the degradation of PPDO is a predominant hydrolysis of ester linkages.     

大相对孔径长波红外光学系统无热化设计

 针对目前许多军工仪器红外成像系统的结构简单、体积小、质量轻的无热化设计要求,采用光学被动式方法对8 μm~12 μm波段、相对孔径为1的红外光学系统进行了无热化设计。具体光学系统参数：F=1,f=60 mm,2ω=11.4°。设计结果：在-40℃~60℃工作范围内,该系统的调制传递函数（MTF）接近衍射极限,空间分辨率在20 lp/mm处,中心视场传函接近0.7,边缘视场传函大于0.6。其设计结果满足系统的无热化设计要求。     

机载卫星制导武器直接瞄准攻击研究

 介绍了卫星制导武器直接瞄准攻击方式在对地精确打击中占据的关键位置,阐述了卫星制导武器直接瞄准攻击方法的原理。由于卫星制导武器直接瞄准攻击对目标定位要求较高,采用常用定位手段已不能满足系统对目标定位的要求,分析了使用相对GPS制导成为卫星制导武器直接瞄准攻击的关键的原因。相对GPS制导误差主要包括采用载机和武器相对GPS定位误差以及传感器对目标的相对定位误差,分别对两者的定位精度进行了分析和推导。仿真结果表明：这两者的综合误差理论值小于7.5 m,满足卫星制导武器在直接瞄准攻击中对目标定位的需求。     

基于红外波段光谱吸收的小型化湿度探测系统

 探测系统的光源选择为垂直腔面发射激光器,选定水汽在1.854 μm的吸收峰。系统自动在直接测量法与谐波测量法之间切换,能够适应高低湿度环境。在低湿度环境检测中,利用二次谐波与一次谐波的比值来定标湿度,有效去除了光源不稳定对测量带来的影响;过采样的A/D转换结合数字锁相放大（DLIA）技术,提高了检测精度。系统通过以太网接口,可以实现远程数据采集。     

开尔文滴水起电机在潮湿环境下的实验研究

探讨了开尔文滴水起电机要求环境凉爽、干燥的原因,并对传统的开尔文滴水起电机进行了改进,通过改善传统滴水起电机的表面绝缘性,增大水溶液的离子浓度以及预加初始电荷等方法使其能在潮湿的环境下快速获得较大的高压静电,起电效果明显.     

A study on volunteer augmentation navigation technology

Navigation augmentation technology is one of the most common methods to increase the continuity,reliability and integrity of the global satellite navigation system.The concept of volunteer augmentation navigation (VNA) is proposed and the elements and topological structure of VNA are also analyzed in this paper.The study focuses on the neural network model that volunteers and ordinary users use modern communication information network to exchange self-organizing information.The neural cell model of Voluntee...     

水下航行器通气超空泡生成与维持实验研究

超高速水下航行器通气系统工作时需采用多级通气流量.为获得通气流量的设计依据,在西北工业大学高速水洞进行了超空泡生成和维持、通气流量突变对空泡形态影响的系列实验研究.实验结果表明:生成超空泡的通气流量与维持相应空泡形态的通气流量相差很大,就本次研究所选的模型而言,前者是后者的2.616倍左右;通气超空泡生成速度与航行器速...     

Variable-step variable-order 3-stage Hermite-Birkhoff-Obrechkoff DDE solver of order 4 to 14

This article presents a solver for delay differential equations (DDEs) called HBO414DDE based on a hybrid variable-step variable-order 3-stage Hermite-Birkhoff-Obrechkoff ODE solver of order 4 to 14. The current version of our method solves DDEs with state dependent, non-vanishing, small, vanishing and asymptotically vanishing delays, except neutral type and initial value DDEs. Delayed values are computed using Hermite interpolation, small delays are dealt with by extrapolation, and discontinuities are located by a bisection method. HBO414DDE was tested on several problems and results were compared with those of known solvers like SYSDEL and the recent Matlab DDE solver ddesd and statistics show that it gives, most of the time, a smaller relative error than the other solvers for the same number of function evaluations.     

紧耦合INS/视觉相对位姿测量方法

研究了一种紧耦合INS/视觉相对位姿测量方法在无人机自主空中加油中的应用。该方法直接将特征点的图像坐标作为滤波器输入,避免了求解复杂的非线性位姿方程,尤其是特征点提取不全时,该方法具有较强的鲁棒性。引入相对惯导误差建立了增广状态模型,根据杆臂效应详细推导了紧、松两种耦合模式的量测方程。采用扩展卡尔曼滤波算法估计误差状态,并校正惯导输出获取精确的相对位姿信息。仿真结果表明,与松耦合模式相比,紧耦合在提高系统实时性的同时可获得更高的测量精度,位置误差小于0.1 m,姿态角误差小于3'。     

A Hydrolytically Stable Vanadium(IV) Metal–Organic Framework with Photocatalytic Bacteriostatic Activity for Autonomous Indoor Humidity Control

Metal–organic frameworks (MOFs) with long‐term stability and reversible high water uptake properties can be ideal candidates for water harvesting and indoor humidity control. Now, a mesoporous and highly stable MOF, BIT‐66 is presented that has indoor humidity control capability and a photocatalytic bacteriostatic effect. BIT‐66 (V₃(O)₃(H₂O)(BTB)₂), possesses prominent moisture tunability in the range of 45–60 % RH and a water uptake and working capacity of 71 and 55 wt %, respectively, showing good recyclability and excellent performance in water adsorption–desorption cycles. Importantly, this MOF demonstrates a unique photocatalytic bacteriostatic behavior under visible light, which can effectively ameliorate the bacteria and/or mold breeding problem in water adsorbing materials.