Spatial factors and muscle spindle input influence the generation of neuromuscular responses to stimulation of the human foot

Removal of the mechanical pressure gradient on the soles leads to physiological adaptations that ultimately result in neuromotor degradation during spaceflight. We propose that mechanical stimulation of the soles serves to partially restore the afference associated with bipedal loading and assists in attenuating the negative neuromotor consequences of spaceflight. A dynamic foot stimulus device was used to stimulate the soles in a variety of conditions with different stimulation locations, stimulation patterns and muscle spindle input. Surface electromyography revealed the lateral side of the sole elicited the greatest neuromuscular response in ankle musculature, followed by the medial side, then the heel. These responses were modified by preceding stimulation. Neuromuscular responses were also influenced by the level of muscle spindle input. These results provide important information that can be used to guide the development of a “passive” countermeasure that relies on sole stimulation and can supplement existing exercise protocols during spaceflight.     

Phasic-to-tonic shift in trunk muscle activity relative to walking during low-impact weight bearing exercise

The aim of this study was to investigate the influence of an exercise device, designed to improve the function of lumbopelvic muscles via low-impact weight-bearing exercise, on electromyographic (EMG) activity of lumbopelvic, including abdominal muscles. Surface EMG activity was collected from lumbar multifidus (LM), erector spinae (ES), internal oblique (IO), external oblique (EO) and rectus abdominis (RA) during overground walking (OW) and exercise device (EX) conditions. During walking, most muscles showed peaks in activity which were not seen during EX. Spinal extensors (LM, ES) were more active in EX. Internal oblique and RA were less active in EX. In EX, LM and ES were active for longer than during OW. Conversely, EO and RA were active for a shorter duration in EX than OW. The exercise device showed a phasic-to-tonic shift in activation of both local and global lumbopelvic muscles and promoted increased activation of spinal extensors in relation to walking. These features could make the exercise device a useful rehabilitative tool for populations with lumbopelvic muscle atrophy and dysfunction, including those recovering from deconditioning due to long-term bed rest and microgravity in astronauts.     

The ankle ergometer: a new tool for quantifying changes in mechanical properties of human muscle as a result of spaceflight

A mechanical device for studying changes in mechanical properties of human muscle as a result of spaceflight is presented. Its main capacities are to allow during a given experiment investigation of both contractile and visco-elastic properties of a musculo-articular complex using respectively isometric contractions, isokinetic movements, quick-release tests and sinusoidal perturbations. This device is a motor driven ergometer associated to an experimental protocol designed for pre- and post-flight experiments. As microgravity preferentially affects postural muscles, the apparatus was designed to test muscle groups crossing the ankle joint. Three subjects were tested during the Euromir '94 mission. Preliminary results obtained on the european astronaut are briefly reported. During the next two years the experiments will be performed during six missions.     

Bone loss during long term space flight is prevented by the application of a short term impulsive mechanical stimulus

In long term space flight, the mechanical forces applied to the skeleton are substantially reduced and are altered in character. This reduced skeletal loading results in a reduction in bone mass. Exercise techniques currently used in space can maintain muscle mass but the mechanical stimulus provided by this exercise does not prevent bone loss. By applying an external impulsive load for a short period each day, which is intended to mimic the heel strike transient, to the lower limb of an astronaut during a long term space flight (5 months), this study tests the hypothesis that the bone cells can be activated by an appropriate external mechanical stimulus to maintain bone mass throughout prolonged periods of weightlessness. A mechanical loading device was developed to produce a loading of the os-calcis similar to that observed during the heel strike transient. The device is activated by the astronaut to provide a transient load to the heel of one leg whilst providing an equivalent exercising load to the other leg. During the EUROMIR95 mission on the MIR space station, an astronaut used this device for a short period daily throughout the duration of the mission. Pre- and post-flight measurements of bone mineral density (BMD) of the os-calcis and femoral neck of the astronaut were made to determine the efficacy of the device in preventing loss of bone mineral during the mission. On the os-calcis which received the mechanical stimulus, BMD was maintained throughout the period of the flight, while it was reduced by up to 7% on the os-calcis which received no stimulus. Post-flight, BMD in both the stimulated and non-stimulated os-calcis reduces, the extent of this reduction however is less in the stimulated os-calcis. For the femoral neck, the mechanical stimulation does not produce a positive effect.     

Interface Familiarity Restores Active Advantage in a Virtual Exploration and Reconstruction Task in Children

Abstract

Active exploration is reportedly better than passive observation of spatial displacements in real environments, for the acquisition of relational spatial information, especially by children. However, a previous study using a virtual environment (VE) showed that children in a passive observation condition performed better than actives when asked to reconstruct in reality the environment explored virtually. Active children were unpractised in using the input device, which may have detracted from any active advantage, since input device operation may be regarded as a concurrent task, increasing cognitive load and spatial working memory demands. To examine this possibility, 7–8-year-old children in the present study were given 5 minutes of training with the joystick input device. When compared with passive participants for spatial learning, active participants gave a better performance than passives, placing objects significantly more accurately. The importance of interface training when using VEs for assessment and training was discussed.     

基于图像识别技术的火箭飞行时序判读

在运载火箭开展射前综合测试时,控制系统在预先指定的飞行时序向末端发送一系列指令,指示末端设备做出相应动作,以达成对应的目标。这些动作主要依赖火工品完成,这些动作变化会体现在火工品等效器指示灯上。当前控制系统无法检测到末端等效器的电流情况变化,因此无法对末端动作进行有效监测,测试缺乏可靠性、准确性与可追溯性的问题亟需改善。通过综合运用人工智能、数字图像处理与计算机视觉技术,经由特征匹配、指示灯定位、指示灯状态建模等步骤,可对末端火工品等效器状态变化实现精准监测,进而实现飞行时序自动判读。与标准判据比对后,本文提出的火箭飞行时序判读系统准确率可达98.89%。     

追踪星跟踪空间非合作目标的相对轨道设计

对空间非合作目标跟踪飞行可以执行观测或监视等任务。首先从一般性出发对追踪星与非合作目标之间的椭圆轨道相对运动方程进行分析,给出具有任意初始条件的相对运动方程解析表达式。其次,对追踪星沿航向跟踪目标并考虑约束条件时的相对轨道设计进行分析后,给出设计追踪星轨道的方法,该方法使得追踪星在保持对地定向的同时也满足测量敏感器的约束条件。最后通过数学仿真进行了验证。     

同心筒发射的集中参数模型及应用

导弹在同心筒结构中的发射涉及复杂的燃气流动和多种载荷共同作用。为了从理论上分析发射筒结构、发动机参数等设计变量与发射弹道特性之间的关联关系,对同心筒结构中的燃气流动特征进行了深入分析。在此基础上,结合燃气流动各区域的典型特征、气体流动基本方程、弹体动力学方程和水下气泡运动方程,建立可用于大气和水下环境的同心筒发射数值分析集中参数模型。利用该模型进行的示例分析表明,集中参数模型反映了同心筒发射过程中的燃气流动特性,能便捷方便地分析多种设计参数与发射弹道之间的相互关系,可为同心筒发射装置的方案设计和理论分析提供依据。     

Effect of unloading on muscle volume with and without resistance training

The present study aimed to investigate the effect of resistance training on the volume of four muscle groups and/or 17 individual muscles of the human lower limb during 20 days of $6^{\circ }$ head-down tilt bed rest. Twelve healthy men were divided into two groups: the resistance training group: BR-Tr $(n=6)$ and the control group: BR-Cont $(n=6)$. The volumes of the knee extensor, knee flexor, adductor, plantar flexor, and dorsiflexor muscle groups and their individual muscles were calculated. After the bed rest, the BR-Tr subjects showed no significant change in the volume in almost all tested muscles; in contrast, the volumes of the four muscle groups significantly decreased in the BR-Cont group ($-12$% to $-8$%). These results suggest that resistance training during bed rest can prevent the deteriorating of thigh muscles and calf muscles.     

Modeling the benefits of an artificial gravity countermeasure coupled with exercise and vibration

The current, system-specific countermeasures to space deconditioning have limited success with the musculoskeletal system in long duration missions. Artificial gravity (AG) that is produced by short radius centrifugation has been hypothesized as an effective countermeasure because it reintroduces an acceleration field in space; however, AG alone might not be enough stimuli to preserve the musculoskeletal system. A novel combination of AG coupled with one-legged squats on a vibrating platform may preserve muscle and bone in the lower limbs to a greater extent than the current exercise paradigm. The benefits of the proposed countermeasure have been analyzed through the development of a simulation platform. Ground reaction force data and motion data were collected using a motion capture system while performing one-legged and two-legged squats in 1-G. The motion was modeled in OpenSim, an open-source software, and inverse dynamics were applied in order to determine the muscle and reaction forces of lower limb joints. Vibration stimulus was modeled by adding a 20 Hz sinusoidal force of 0.5 body weight to the force plate data. From the numerical model in a 1-G acceleration field, muscle forces for quadriceps femoris, plantar flexors and glutei increased substantially for one-legged squats with vibration compared to one- or two-legged squats without vibration. Additionally, joint reaction forces for one-legged squats with vibration also increased significantly compared to two-legged squats with or without vibration. Higher muscle forces and joint reaction forces might help to stimulate muscle activation and bone modeling and thus might reduce musculoskeletal deconditioning. These results indicate that the proposed countermeasure might surpass the performance of the current space countermeasures and should be further studied as a method of mitigating musculoskeletal deconditioning.     

A harness for enhanced comfort and loading during treadmill exercise in space

IntroductionLocomotor and some resistance exercises in space require a gravity replacement force in order to allow 1g-like ground reaction forces to be generated. Currently bungee cords, or other loading devices, interface with the crew member through a harness with a waist belt and shoulder straps. Crew members often find the application of the required loads to be uncomfortable, particularly at the hips.MethodsAn experimental harness was built that differed from previous in-flight designs by having a wider, moldable waist belt and contoured shoulder straps with additional padding. Eight subjects ran at 100% body weight (BW) loading for a total duration of 30 min per day on 12 days over a 3-week period in simulated 0-g conditions using horizontal suspension. A 100 mm Visual Analog Scale (VAS)¹ was used to assess harness-related and lower extremity discomfort at the end of each run.ResultsThe overall rating of harness discomfort decreased from 27 mm on the 100 mm scale on day 1 to 10 mm on day 12, with significant decreases recorded for the back and hip regions as well as the overall harness.DiscussionThe experimental harness allows for repeated exposure to 30-minute bouts of 100% BW loaded simulated 0-g running with levels of discomfort less than 30 mm on a VAS scale of 0–100 mm. We believe that the use of such a harness during on-orbit exercise countermeasures may allow exercise to be performed at levels which are more effective in preventing bone and muscle loss.     

光敏电阻在火灾报警器中的应用

文章提出了一种大型密闭油库,密闭燃油机房等场所用到的火灾自动报警装置。这些场所在发生火灾时极易发生爆炸等危险情况,如果采用人工灭火安全隐患很大。为了降低安全隐患,文章提出了基于光敏电阻的火灾自动检测装置,使用可编程逻辑器件CPLD作为火灾信号的提取并产生灭火信号的部件。装置结构简单,工作可靠,具有一定实用价值。     

Changes in mood status and neurotic levels during a 20-day bed rest

This study evaluated changes of mood status and depressive and neurotic levels in nine young male subjects during a 20-day 6 degrees head-down tilting bed rest and examined whether exercise training modified these changes. Participants were asked to complete psychometrical inventories on before, during, and after the bed rest experiment. Depressive and neurotic levels were enhanced during bed rest period according to the Japanese version of Zung's Self-rating Depression Scale and the Japanese version of the General Health Questionnaire. Mood state "vigor" was impaired and "confusion" was increased during bed rest and recumbent control periods compared to pre-bed rest and ambulatory control periods according to the Japanese version of Profiles of Mood State, whereas the mood "tension-anxiety", "depression-dejection", "anger-hostility" and "fatigue" were relatively stable during experiment. Isometric exercise training did not modify these results. Microgravity, along with confinement to bed and isolation from familiar environments, induced impairment of mental status.     

Biomedical support of man in space

In its broadest sense, biomedical support of man in space must not be limited to assisting spacecraft crew during the mission; such support should also ensure that flight personnel be able to perform properly during landing and after leaving the craft. Man has developed mechanisms that allow him to cope with specific stresses in his normal habitat; there is indisputable evidence that, in some cases, the space environment, by relieving these stresses, has also allowed the adaptive mechanisms to lapse, causing serious problems after re-entry. Inflight biomedical support must therefore include means to simulate some of the normal stresses of the Earth environment. In the area of cardiovascular performance, we have come to rely heavily on complex feedback mechanisms to cope with two stresses, often combined: postural changes, which alter the body axis along which gravitational acceleration acts, and physical exercise, which increases the total load on the system. Unless the appropriate responses are reinforced continuously during flight, crew members may be incapacitated upon return. The first step in the support process must be a study of the way in which changes in g, even of short duration, affect these responses. In particular we should learn more about effects of g on the "on" and "off" dynamics, using a variety of approaches: increased acceleration on one hand at recumbency, immersion, lower body positive pressure, and other means of simulating some of the effects of low g, on the other. Once we understand this, we will have to determine the minimal exposure dose required to maintain the response mechanisms. Finally, we shall have to design stresses that simulate Earth environment and can be imposed in the space vehicle. Some of the information is already at hand; we know that several aspects of the response to exercise are affected by posture. Results from a current series of studies on the kinetics of tilt and on the dynamics of readjustment to exercise in different postures will be presented and discussed.     

SiC MOSFET器件单粒子烧毁仿真分析

应用于航天器的宽禁带半导体功率器件会受到空间带电粒子的影响而存在单粒子烧毁（SEB）风险。为研究单粒子烧毁的机理及防护措施，文章利用半导体工艺器件仿真（TCAD）对SiC MOSFET器件进行了SEB仿真分析，发现粒子入射最敏感位置时器件发生SEB的阈值电压在500 V。同时，通过仿真获得器件微观电参数分布特性，分析认为器件发生SEB的机理是寄生晶体管的正反馈作用导致缓冲层和基区的电场强度（5.4 MV/cm和4.2 MV/cm）超过SiC材料击穿场强（3 MV/cm）。此外，针对仿真揭示的器件SEB薄弱区域，提出将P+源区的深度向下延伸至Pbase基区底部的工艺加固思路，并通过仿真验证表明该措施使器件发生SEB的阈值电压提高到近550 V。以上模拟结果可为该类器件的抗SEB设计提供技术支持。     

一种浮动锁销式柔性气浮组件的承载特性测试及分析

为在空间机构产品集成与测试中合理使用气浮组件,采用刚度试验台模拟加载的方案对一种浮动锁销式柔性气浮组件的承载特性进行测试。试验结果表明:浮动锁销式柔性气浮组件在未预压缩状态下,承载特性近似为线性弹簧压缩模型;在预压缩状态下,初始承载特性近似为刚体,承载力超过气浮组件的保持力后承载特性近似为线性弹簧压缩模型。因此,为避免气浮组件在承载过程中表现出的作用力与位移变化等特性对空间机构产品的运动特性、系统性能造成显著的附加影响,气浮组件在使用前应根据产品重力调节弹簧预压缩量,并严格控制4组可调弹簧支撑组件的制造误差;同时,在产品重力完全被卸载之前需要借助压紧释放机构或刚性支撑工装对产品进行约束。     

Interplanetary travel and permanent injury to normal heart.

This hypothesis is that some crewmen on prolonged space flights may develop permanent myocardial injury despite the absence of coronary atherosclerosis and even without the hazards of radiation beyond orbit. This may resuIt from atrophy of skeletal muscle and bone resulting in magnesium ion deficiency predisposing to a vicious cycle with catecholamine elevations, with the latter aggravated by stress, dehydration-provoked angiotensin elevations, unremitting endurance exercise, and in turn a second vicious cycle with severe ischemia. Toxic free radicals can develop complicating ischemia and potential high radiation, with magnesium ion deficiency and high vascular catecholamines playing contributing roles. These free radicals may lead to inactivation of endothelium-derived relaxing factor (EDRF) causing coronary endothelial injury by a third vicious cycle, increased peripheral resistance and coronary vasospasm intensifying ischemia. Local and systemic thrombogenesis could contribute ultimately to focal fibrosis of the myocardium, if the ischemia is not recognized. Sufficient magnesium and time for repair are vital.     

柔索并联式导弹自动抓取装置动力学仿真

针对导弹质量大、作业环境复杂等形成的难以自动装填问题,融合钢丝绳柔性浮动对位原理,对柔索并联式导弹自动抓取装置进行动态特性分析。基于有限段离散建模方法,对该抓取装置钢丝绳进行柔性体建模,进而建立了该抓取装置的多体动力学模型。通过仿真计算,分析了抓取装置和导弹模块,在处于不同的对位姿态时,钢丝绳柔性和结构接触耦合作用下,抓取装置下放-抓弹-吊弹过程中的运动和受力特性,验证了引入钢丝绳柔性环节的抓取装置方案,针对对位时姿态偏差的自适应调整能力,为该导弹自动装填系统设计提供了参考。     

一种提升近地小行星防御中拦截效率的方法

利用核爆直接炸毁小行星或改变小行星的轨道以避免其与地球相撞,是近地小行星防御最主要的手段之一。文章基于美国爱荷华州立大学的超高速小行星拦截器(HAIV)概念,提出一种将原撞击引导器改为长杆撞击器的方案,采用自主研发的欧拉型冲击动力学仿真软件NTS模拟长杆撞击器对小行星连续开坑的过程,并在仿真中加入能量源以模拟核爆装置在不同深度爆炸对小行星产生的偏转与破坏效应。研究结果表明,采用长杆撞击器并合理控制撞击速度,能够引导核爆装置进入更深的地下爆炸,从而更加高效地耦合核爆能量,提升偏转小行星或直接摧毁小行星的能力。