境外毒源防治的有效措施——替代种植

作为毒源防治的重要举措之一,替代种植一直是禁毒工作的战略重心.自上世纪90年代我国发展境外替代种植以来,取得了卓越的成果.新时期,为进一步加强替代种植禁毒防艾工作,推动中缅、中老禁毒与经贸合作实现共赢,必须赋予替代种植新的內容,即走产业结构替代发展的道路.     

时间计量单位“年”的国际符号是什么?

正在英文文献中,时间计量单位"年"的常用符号为y、yrs(复数)。这种用法是不正确的。y和yrs是英文名词year、years的缩写,曾经作为计量单位年的符号。其实国际上早就对年的符号作出了以a替代y、yrs的规定。我国也采纳了符号a,在1984年2月27日国务院颁布的《关于在我国统一实行法定计量单位的命令》中,就有"周、月、年(年的符号为a),为一般常用时间单位"的备注。     

《世界国防科技工业概览》出版发行

《国防科技名词大典》是一部集系统性、权威性、实用性于一体的大型国防科技工具书。出版发行以来得到了科技出版界广泛的好评。前不久荣获第十一届全国优秀科技图书一等奖。 这部书是通过3700位专家的努力,在对国防科技工业200多个学科领域里的技术名词进行了搜集、整理,共收集国防科技名词近25000条,通过分析、研究,删除了一些现代已基本不用的旧词,     

军事科学名词审定工作第一次会议在军事科学院召开

根据中央军委批准的《军事科学名词审定工作实施纲要》和全国科学技术名词审定委员会的工作部署,军事科学名词审定工作第一次会议于2013年4月12日在军事科学院召开。会议的主要任务是全面启动军事科学15个分支学科的名     

《孙子》“形”义辨

该本对《孙子兵法》中“形”字的用法作了详尽的统计与研讨,归纳出了“形”在作名词时所表示的五种意义和作动词时所表示的二种意义,进而得出“形”字无论是作动词或名词,所表示的事物或现象均具有外显性、可变性两个特点.从而对“形”字的意义做出解释:“形”是指军事活动中的一切外在表现形式.既包括军事活动的主体——军队,如兵力的部署、军队的行动及作战形式等,也包括与军事活动有关的凡能通过观察而获取的各种有形的事物,如地形、工事等.     

大型敞开式汽车库性能化消防设计探讨

以某大型敞开式汽车库为例,对大型敞开式汽车库防火分区划分难以满足现行规范要求、利用防火隔离带替代防火墙等问题进行探讨.提出采用防火隔离带替代防火墙或防火卷帘可行,敞开式汽车库在满足一定的条件下,其防火分区可相应扩大.     

微元法应用中容易忽视的一个重要条件

分析了讲授定积分应用微元分析法中容易忽视的一个近似替代的前提条件,用具体实例阐明了这一条件的重要性,并对如何寻找未知量的微分进行了探讨.     

短波通信技术发展及分析

短波通信目前依然是不可替代的有效通信方式,其在灾区应急、航海远程通信、军事通信等领域有着广泛的应用.本文简要概述了短波通信的发展历程,并给出了存在的问题和未来发展方向的预测.     

九种化学元素获中文定名——海峡两岸将共同使用这些新元素名

全国科学技术名词审定委员会公布了101—109号元素的中文定名,并发布有关信息科学技术新词定名。     

高技术是个动态概念

“高技术”作为一个专用名词并不是科技界先提出来的,而是经济界首先采用了它.1983年正式收入到美国出版的《韦氏第三版国际辞典补充的九千个词》当中,作为一个正式名词定了下来.对这个词的理解应是动态的.它是在相对意义上的,而且是发展变化着的一个概念.不同的国家和地区,不同的时空领域,不同的角度和立场,对它的定义和理解各有侧重,解释也不尽相同.     

基于RBF网络的滑模变结构控制在无刷直流电机伺服系统中的应用

无刷直流电动机的参数强耦合、高度非线性特性增加了对其速度控制的难度，针对这一特点，设计了一种神经网络滑模变结构速度控制器。将无刷直流电机速度伺服系统分成名义模型和不确定模型，采用状态反馈方法对名义模型进行控制，以RBF神经网络为滑模动态补偿器对不确定系统进行控制。该方法不仪具有变结构控制的抗参数摄动、抗干扰以及速度快等优点，神经网络控制的加入还有效地减弱了单纯滑模变结构控制所带来的“抖振”现象。Matlab仿真结果表明，该控制器具有良好的控制性能和鲁棒性能。     

Effect of transverse compression on the residual tensile strength of ultrahigh molecular weight polyethylene (Dyneema® SK-76) yarns

Ballistic impact induces complex stress states on fiber-based armor systems. During impact fibers undergo multiaxial loading which includes axial tension, axial compression, transverse compression, and transverse shear. Transverse compression induced by the projectile leads to permanent deformation and fibrillation of fibers resulting in degradation of material tensile strength. Previous work (Sockalingam et al. Textile Res. J 2018) has shown a reduction of 20% in the tensile strength of Dyneema® SK76 single fibers subjected to 77% nominal transverse compressive strains. Experimental investigation of quasi-static transverse compression on Dyneema® SK-76 yarns, unconstrained in the lateral direction, indicate an average of 4% reduction in tensile strength of yarns compressed to 77% nominal strains. In this work we use finite element modeling techniques to understand the difference in residual tensile strength between single fibers and yarns observed in laterally unconstrained transverse compression experiments. Finite element study of the transverse compression response of single fibers and yarns indicate that local strains developed in fibers within the yarn are much lower than the local strains developed in single fibers subjected to a given nominal strain and may explain the less reduction in strength observed in yarns.     

临近空间拦截弹最优弹道跟踪制导律

针对拦截临近空间高超声速飞行器的弹道跟踪过程,基于线性二次型调节器理论和高斯伪谱法设计一种跟踪制导律。为了对标称弹道进行精确跟踪,考虑线性二次型跟踪问题,应用最优控制理论推导最优解的充要条件,得到带时变增益的线性状态反馈控制量的表达式;基于高斯伪谱法,在离散的勒让德-高斯点上利用标称弹道数据计算差分矩阵和系数矩阵,求得状态扰动反馈控制律。仿真结果表明,与基于求解矩阵黎卡提方程的方法相比,该方法选取较少的节点即可获得高精度的反馈控制量,且运算效率大幅提高,满足在线实施要求。     

A single period model for a multiproduct perishable inventory system with economic substitution

This paper develops a single period model for a specific class of multiproduct perishable inventory systems where demands are interdependent. This class of inventory systems has the property that there is economic substitution between products. It is shown that the optimal policy has the economic substitution property, and that the rate of substitution is age dependent. The model serves as a generalization of a theorem discovered by Ignall and Veinott.     

Country survey: military expenditure and defence policy in Norway 1970–2013

This article examines military expenditure and defence policy in Norway from 1970 to 2013. Until 1990 Norwegian military expenditure remained between 2.5 and 3.0 per cent of Gross Domestic Product (GDP). Despite constant GDP shares, the military expenditure could not sustain a large and properly armed mobilization army. The constant nominal defence budgets of the 1990s accentuated the Norwegian Armed Forces' underlying imbalance between tasks, structure and budget. Around year 2000, large organizational reforms were effectuated, in which costs, the number of man-years, and underlying imbalances between tasks, structure and budget were reduced. Military expenditure increased in nominal terms between 2003 and 2013, while real military expenditure remained practically constant.     

The impact of demand uncertainty on product line design under endogenous substitution

The existing product line design literature devotes little attention to the effect of demand uncertainty. Due to demand uncertainty, the supply‐demand mismatch is inevitable which leads to different degrees of lost sales depending on the configuration of product lines. In this article, we adopt a stylized two‐segment setup with uncertain market sizes and illustrate the interplay between two effects: risk pooling that mitigates the impact of demand uncertainty and market segmentation that facilitates consumer differentiation. Compared to downward substitution, inducing bidirectional substitution through product line decisions including quality levels and prices can yield greater risk pooling effects. However, we show that the additional benefit from the risk pooling effect cannot compensate for the reduced market segmentation effect. We demonstrate that the presence of demand uncertainty can reduce the benefit of market segmentation and therefore the length of product lines in terms of the difference between products. We also propose three heuristics that separate product line and production decisions; each of these heuristics corresponds to one particular form of demand substitution. Our numerical studies indicate that the best of the three heuristics yields performance that is close to optimality. © 2015 Wiley Periodicals, Inc. Naval Research Logistics 62: 143–157, 2015     

采用故障树的数据链系统故障模式

根据数据链系统的故障检测困难的特点,采用故障树分析法,建立了数据链系统的故障树;在详细分析数据链系统故障特点的基础上,提出了端口功能检测法、调制解调器替代法和电性能参数检测法3种故障定位方法。设计了端口功能检测法中数据测试仪、终端设备模拟器和自环测试监测仪的系统连接方法,设计了调制解调器替代法的系统连接方法和电性能参数检测法的常见电性能参数。综合使用故障检测定位方法,可快速定位数据链系统常见故障。     

近地一次环月两次交会的载人登月任务规划

针对近地一次环月两次交会的载人登月任务飞行阶段多、周期长、约束复杂,导致各阶段飞行窗口与轨道衔接匹配复杂的难题,提出分层分解、正逆向结合的全任务标称飞行窗口与轨道衔接设计策略。介绍近地一次环月两次交会的载人登月任务飞行模式特点和应用前景,假定任务基本需求与工程约束,仿真验证所提方法的有效性,可以快速规划出近地一次环月两次交会的载人登月任务飞行轨道与窗口。     

求解卷积公式的一种新方法

基于数形结合方法以及变量代换方法发现计算卷积公式存在某些不足之处,研究卷积公式的计算方法,给出一种新的确定积分限的方法.该方法直观明了、容易理解和掌握并且可操作性强,有效避免作图和分析图形的繁琐,并举例说明了该应用方法.     

Indirect robust control of agile missile via Theta-D technique

An agile missile with tail fins and pulse thrusters has continuous and discontinuous control inputs. This brings certain difficulty to the autopilot design and stability analysis. Indirect robust control via Theta-D technique is employed to handle this problem. An acceleration tracking system is formulated based on the nonlinear dynamics of agile missile. Considering the dynamics of actuators, there is an error between actual input and computed input. A robust control problem is formed by treating the error as input uncertainty. The robust control is equivalent to a nonlinear quadratic optimal control of the nominal system with a modified performance index including uncertainty bound. Theta-D technique is applied to solve the nonlinear optimal control problem to obtain the final control law. Numerical results show the effectiveness and robustness of the proposed strategy.