深井高温对钻柱横向振动固有频率影响研究

钻柱共振是引起深井钻具失效的主要原因。钻柱在深井段处在一个高温的环境下,温度的升高必然使钻柱的固有频率发生变化。为此,分析了井下高温对钻柱横向振动固有频率的影响,推导出井下任意温度时在轴向力作用下钻柱横向振动固有频率的计算公式。通过实际算例,分析了考虑轴向力因素时井下高温对钻柱横向振动固有频率的影响。计算结果表明随着温度的升高,钻柱横向振动的固有频率逐渐降低,其降低的幅度随着轴向压力的增大而增大;轴向压力较大时,温度对钻柱横向振动一阶固有频率的影响远大于对二阶固有频率的影响;轴向压力对钻柱一阶固有频率随温度变化的影响程度远大于轴向拉力的影响程度。     

可机动弹道导弹三维飞行状态建模与仿真研究

为提供接近实际的弹道导弹飞行状态数据,根据弹道导弹气动特性和飞行控制原理,在实际飞行环境下,建立了可进行气动力及质心侧向力控制的多级助推弹道导弹三维飞行状态模型,并分别对单级、双级、三级助推的弹道导弹在气动力及质心侧向力控制下的飞行状态进行仿真。仿真结果表明:该模型能真实模拟质心侧向力及气动力控制的弹道导弹飞行规律,为弹道导弹拦截、突防、攻防对抗仿真等研究提供实时飞行的位置、速度等仿真数据。     

静力弹塑性分析方法中不同加载模式的对比研究

Pushover分析方法是一种逐渐得到广泛研究与应用的评估结构抗震性能的简化方法,已经被我国现行建筑结构抗震设计规范采用.侧向加栽模式的选取是Pushover分析方法中的一个关键问题,不同结构的高阶振型对Pushover分析结果的影响程度不同.本文通过拟合规范的反应谱曲线,对三个钢筋混凝土结构分别选取了适用Ⅱ类场地的2条地震动记录和1条人工波,对比了典型地震动下非线性时程分析和采用5种不同侧向力分布模式的Pushover分析的层间位移角,以及推覆分析各工况下的结构推覆曲线、等效周期和等效阻尼比.通过振型质量参与系数体现高阶振型对结构反应的贡献.研究发现,随着结构层数的增加,高阶振型的影响变大,侧向加载模式的选取变得很重要.     

Integrated tilt with active lateral secondary suspension control for high speed railway vehicles

This paper presents a novel active suspension control configuration for high speed tilting railway vehicles which integrates tilt with active lateral secondary suspension. The use of the active lateral secondary suspension is to attenuate the vehicle body lateral vibration on straight track, while complementing tilt action during curving. Various control strategies are proposed to accommodate both tilt and active lateral suspension multiple design requirements, whilst considering the strong interaction between vehicle body roll and lateral modes. Compared with the commercial solutions for tilt control, the proposed integration strategy improves the tilting control performance both on curved and straight track as illustrated by simulation tests and control assessments based on given track profiles.     

肌萎缩侧索硬化的临床分型、分期及病情评估

肌萎缩侧索硬化(amyotrophic lateral sclerosis,ALS)是一种进展性神经系统变性疾病。其起病隐袭,进展缓慢,因呼吸衰竭死亡,目前尚无治愈方法。近年来研究表明多种措施可延长患者存活期,提高患者生活质量。为了科学合理地治疗ALS,本文就其临床分型、分期、治疗模式及对ALS病情进展的评估和随访方法进行介绍。     

Optimal orientation in flows: providing a benchmark for animal movement strategies

Animal movements in air and water can be strongly affected by experienced flow. While various flow-orientation strategies have been proposed and observed, their performance in variable flow conditions remains unclear. We apply control theory to establish a benchmark for time-minimizing (optimal) orientation. We then define optimal orientation for movement in steady flow patterns and, using dynamic wind data, for short-distance mass movements of thrushes (Turdus sp.) and 6000 km non-stop migratory flights by great snipes, Gallinago media. Relative to the optimal benchmark, we assess the efficiency (travel speed) and reliability (success rate) of three generic orientation strategies: full compensation for lateral drift, vector orientation (single-heading movement) and goal orientation (continually heading towards the goal). Optimal orientation is characterized by detours to regions of high flow support, especially when flow speeds approach and exceed the animal''s self-propelled speed. In strong predictable flow (short distance thrush flights), vector orientation adjusted to flow on departure is nearly optimal, whereas for unpredictable flow (inter-continental snipe flights), only goal orientation was near-optimally reliable and efficient. Optimal orientation provides a benchmark for assessing efficiency of responses to complex flow conditions, thereby offering insight into adaptive flow-orientation across taxa in the light of flow strength, predictability and navigation capacity.     

III–Vs on Si for photonic applications—A monolithic approach

Epitaxial lateral overgrowth (ELOG) technology is demonstrated as a viable technology to realize monolithic integration of III-Vs on silicon. As an alternative to wafer-to-wafer bonding and die-to-wafer bonding, ELOG provides an attractive platform for fabricating discrete and integrated components in high volume at low cost. A possible route for monolithic integration of III–Vs on silicon for silicon photonics is exemplified by the case of a monolithic evanescently coupled silicon laser (MECSL) by combining InP on Si/SiO₂ through ELOG. Passive waveguide in MECSL also acts as the defect filtering mask in ELOG. The structural design of a monolithic evanescently coupled silicon laser (MECSL) and its thermal resistivity are established through simulations. Material studies to realize the above laser through ELOG are undertaken by studying appropriate ELOG pattern designs to achieve InP on narrow regions of silicon. We show that defect-free InP can be obtained on SiO₂ as the first step which paves the way for realizing active photonic devices on Si/SiO₂ waveguides, e.g. an MECSL.     

Combined Inverse Kinematic and Static Analysis and Optimal Design of a Cable-Driven Mechanism with a Spring Spine

Abstract

A special humanoid neck with low motion noise requirements yields a cable-driven parallel mechanism to imitate the rotational motion of a human neck. The fixed base and moving platform of the mechanism are connected by four cables and a column compression spring. The four cables are actuated separately, while the spring can support weight on the moving platform. Although similar mechanisms exist in the literature, the analysis of them is scarce because a flexible spring instead of a rigid kinematic chain is used as the spine. With the spring’s lateral buckling motion, a new approach must be adopted to solve the kinematics. In this paper, we propose a method that combines the kinematics with the statics to solve them simultaneously. The configuration of the moving platform is parameterized with four parameters, one of which is considered as parasitic motion. Using the spring’s lateral buckling equation, we can obtain the parasitic motion and solve the inverse position problem. The optimal design for cable placements is then performed to minimize the actuation force. The method in this paper provides a novel way to analyze parallel mechanisms with a spring spine and it can be applied to other mechanisms with flexible spines.     

Vibratory sources as compound stimuli for the octavolateralis systems: Dissection of specific stimulation channels using multiple behavioral approaches.

Underwater vibratory sources simultaneously present acoustic and hydrodynamic disturbances. Because vibratory dipole sources are poor sonic projectors, most researchers have assumed that such sources are of greatest relevance to the lateral line system. Both hydroacoustic principles and empirical studies have shown that dipole sources are also a potent stimulus to the inner ear. Responses to vibratory sources in mottled sculpin (Cottus bairdi) were assessed using unconditioned orienting, differential and nondifferential conditioning. Orienting responses are dominated by lateral line inputs and eliminated by lateral line inactivation. Simple conditioning depends on inputs from other systems and was not affected by lateral line inactivation. Differential conditioning alters behavioral control, and sculpin could be conditioned to ignore substrate-borne vibrations and respond only to hydroacoustic stimulation of the ear. The lateral line and inner ear of mottled sculpin do not necessarily exhibit range fractionation, as both systems operate over a similar distance (within 1.5 body lengths) and respond to many of the same sources. Vibratory dipole sources generate compound stimuli that simultaneously activate multiple octavolateralis systems, and sculpin make use of the channels differentially under different behavioral tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intra- and inter-laboratory validation of a dipstick immunoassay for the detection of tropane alkaloids hyoscyamine and scopolamine in animal feed

Tropane alkaloids (TAs) are toxic secondary metabolites produced by plants of, inter alia, the genera Datura (thorn apple) and Atropa (deadly nightshade). The most relevant TAs are (–)-L-hyoscyamine and (–)-L-scopolamine, which act as antagonists of acetylcholine muscarinic receptors and can induce a variety of distinct toxic syndromes in mammals (anti-cholinergic poisoning). The European Union has regulated the presence of seeds of Datura sp. in animal feeds, specifying that the content should not exceed 1000 mg kg^–1 (Directive 2002/32/EC). For materials that have not been ground, visual screening methods are often used to comply with these regulations, but these cannot be used for ground materials and compound feeds. Immunological assays, preferably in dipstick format, can be a simple and cost-effective approach to monitor feedstuffs in an HACCP setting in control laboratories. So far no reports have been published on immunoassays that are capable of detecting both hyoscyamine and scopolamine with equal sensitivity and that can be used, preferably in dipstick format, for application as a fast screening tool in feed analysis. This study presents the results obtained for the in-house and inter-laboratory validation of a dipstick immunoassay for the detection of hyoscyamine and scopolamine in animal feed. The target level was set at 800 µg kg^–1 for the sum of both alkaloids. By using a representative set of compound feeds during validation and a robust study design, a reliable impression of the relevant characteristics of the assay could be obtained. The dipstick test displayed similar sensitivity towards the two alkaloids and it could be concluded that the test has a very low probability of producing a false-positive result at blank level or a false-negative result at target level. The assay can be used for monitoring of TAs in feedstuffs, but has also potential as a quick screening tool in food- or feed-related poisonings.