航天载荷应用软件可靠性参数的分析与确立

航天载荷应用软件可靠性研究是开展航天载荷系统可靠性工程的重要组成部分。而软件可靠性参数的分析与确立是进行软件可靠性研究的前提。首先定义并解释了航天载荷应用软件可靠性,其次对航天载荷系统中常用的软件可靠性参数进行了计算与分析,最后依据软件可靠性参数选取的原则提出了一个航天载荷应用软件可靠性参数集。该参数集在开展航天载荷软件可靠性工程中具有一定的参考价值,也是进行航天载荷软件可靠性设计与分析的前提。

航天载荷应用软件可靠性参数集的分析与研究

开展航天载荷软件可靠性参数的研究是进行航天载荷软件可靠性工程的基础.首先定义并解释了航天载荷应用软件可靠性,并依据软件可靠性参数选取的原则提出了一个航天载荷应用软件可靠性参数集,解释并分析了航天载荷系统中常用的软件可靠性参数.该参数集是进行航天载荷软件可靠性设计与分析的前提.

航天应用载荷的高精度时间同步与共用信息分发

应用载荷直接获取航天器平台的时间和公共测量信息,并不能完全满足载荷的高精度时间基准和共用信息使用需求。一些功能载荷具备向外输出高精度时间和状态测量信息的能力,但硬件接口资源有限。将功能载荷作为FC-AE-1553光纤网络的一个节点,在FC-AE-1553光纤网络中叠加IEEE 1588v2时间同步协议,功能载荷的高精度时钟源能同步给有需求的其他载荷。并在时间同步的前提下,将功能载荷的测量数据如定位数据、姿态数据和轨道数据等共用信息同步发送至网络上的其他载荷节点。通过时间同步与同步发送机制,解决了各载荷对高精度时间和共用信息的需求,弥补了专用信息硬件接口资源的不足。结果表明,与直接利用航天器平台的信息源相比较,当时钟源和共用信息来自功能载荷时,FC-AE-1553网络时间同步之后的时间基准精度和共用信息利用性能高出3个数量级,载荷获取的UTC时间精度达到百纳听语音聊科研与作者互动秒量级。

空间站工程空间应用载荷安全性认定技术研究

针对我国空间站工程大规模空间应用的安全性需求,提出了空间站工程空间应用载荷安全性认定的概念与内涵,明确了载荷上站安全性认定工作的关键技术要素,涉及基于多因素风险的载荷分类原则、有效载荷危险分级技术以及有效载荷安全性认定的技术要求体系等工程技术范畴,在此基础上,制定了空间应用载荷安全性认定的技术实施流程,为后续开展空间站大规模空间应用载荷上站安全性认定工作提供了参考。

汽车载荷谱的分析与应用

随着汽车自主品牌的发展,汽车企业越来越重视汽车标准的建立,开始进行载荷谱采集工作。除了建立试验标准载荷谱还有很多方面用途。本文将探讨汽车载荷谱的分析与应用。

中国空间站光学遥感载荷的发展研究

光学遥感载荷的空间站平台相比卫星平台具有很大的优势,吸引了包括俄罗斯、美国和欧空局在内的国际空间站成员国争相进行空间站光学遥感载荷的新技术实验验证和对地观测研究。文章介绍了国际空间站光学遥感载荷的观测方式和特点,结合国际空间站光学遥感载荷的应用情况,从新技术实验验证和对地观测两个方面分析了中国空间站光学遥感载荷发展应该注意的问题,为中国空间站光学遥感载荷的发展提出了几点建议。

纳型卫星研制关键技术

纳型卫星的低成本研制与长期可靠运行、微型化需求与现有器/部件水平,以及受限的资源与高性能有效载荷之间形成了3组矛盾。针对上述问题,文章从多学科优化和总体架构设计、微机电器/部件研制方法及高性能有效载荷空间应用方式3个层次开展研究,介绍了基于多学科优化的纳型卫星平台研制技术、星上高性能微机电器/部件技术,以及适用于纳型卫星平台搭载的有效载荷应用技术。研究成果已在我国多个商业卫星星群,以及探月工程、高分专项等任务中进行了批量化应用。

空间站工程空间激光安全工程技术研究

针对我国空间站工程空间激光器的危害问题,提出了完整的空间站工程激光安全的技术方案,涉及激光器安全等级的划分、激光器安全阈值要求、激光器危害的防护控制措施、以及激光器安全风险的评估等工程范畴。在此基础上,结合我国目前空间站空间应用的实际需求,提出了开展空间激光器安全防护的工程设计准则,为后续空间站工程空间应用系统激光器安全性设计提供了参考。

Evaluation of coal pillar loads during longwall extraction using the numerical method and its application

It is very difficult to reasonably evaluate the loads acting on coal pillars in longwall panels during the planning of a new pillar system. The application of empirical equations is a common practice in calculating coal pillar loads while designing a new pillar. This paper proposes numerical models for evaluating coal pillar loads. The key of building a successful numerical model for calculating coal pillar loads lies in the fact that the model should represent the redistribution of stress all over the longwall panels and the surrounding areas, and it is especially important to include the characteristics of the stress rebuilding process in the gob areas, which are crucial for the building process of coal pillar loads. Based on the geo-mechanical background of the Baoshan Coal Mine, this paper details the procedures of applying numerical models to the evaluation of coal pillar loads and their local practices. The study results show it is feasible and reasonable to use numerical models to evaluate coal pillar loads.

Effects of thermal treatment on physical and mechanical characteristics of coal rock

To study the physical and mechanical properties of coal rock after treatment at different temperatures under impact loading, dynamic compression experiments were conducted by using a split Hopkinson pressure bar(SHPB). The stress–strain curves of specimens under impact loading were obtained, and then four indexes affected by temperature were analyzed in the experiment: the longitudinal wave velocity, elastic modulus, peak stress and peak strain. Among these indexes, the elastic modulus was utilized to express the specimens' damage characteristics. The results show that the stress–strain curves under impact loading lack the stage of micro-fissure closure and the slope of the elastic deformation stage is higher than that under static loading. Due to the dynamic loading effect, the peak stress increases while peak strain decreases. The dynamic mechanical properties of coal rock show obvious temperature effects. The longitudinal wave velocity, elastic modulus and peak stress all decrease to different extents with increasing temperature, while the peak strain increases continuously. During the whole heating process, the thermal damage value continues to increase linearly, which indicates that the internal structure of coal rock is gradually damaged by high temperature.

Analytical solution to rock pressure acting on three shallow tunnels subjected to unsymmetrical loads

According to the interaction of three shallow tunnels with large section, the analytical solution to rock pressure has been derived and discussed. The load model is given when the bilateral tunnels are excavated. According to the model, the stresses of three tunnels and single tunnel are calculated and compared to analyze the distribution characteristics, where the stresses are influenced by controlling factors of clear distance, covering depth and inclination angle of ground surface. The results show that, in general, the bias distribution is more serious. Therefore, it is significant to settle down the load model of three shallow tunnels so as to determine the measure of reinforcement and design the structure of support. The model and results can be used as a theoretical basis in designation and further research of the three shallow tunnels.

Passive control of along-wind response of tall building

Most of modern tall buildings using lighter construction materials with high strength and less stiffness are more flexible, which occurs excessive wind-induced vibration, resulting in occupant discomfort and structural unsafety. It is necessary to predict wind-induced vibration response and find out a method to mitigate such an excessive wind-induced vibration at the preliminary design stage. Recently, many studies have been conducted in using actuator control force based on the linear quadratic optimum control algorithm. It was accepted as a common knowledge that the performance of passive tuned mass damper(TMD) could increase by incorporating a feedback active control force in the design of TMD, which is called active tuned mass damper(ATMD). However, the fact that ATMD is superior to TMD to reduce wind-induced vibration of a tall building is still a question. The effectiveness of TMD for mitigating the along-wind vibration of a tall building was investigated. Optimum parameters of tuning frequency and damping ratio for TMD under a random load which has a white noise spectra were used. Fluctuating along-wind load acting on a tall building treated as a stationary Gaussian random process was simulated numerically using the along-wind load spectra. And using this simulated along-wind load, along-wind responses of a tall building with and without TMD were calculated and the effectiveness of TMD in mitigating the along-wind response of a tall building was found out.

A Theoretical Analysis of the Bearing Performance of Vertically Loaded Large-Diameter Pipe Pile Groups

This paper aims to present a theoretical method to study the bearing performance of vertically loaded large-diameter pipe pile groups.The interactions between group piles result in different bearing performance of both a single pile and pile groups.Considering the pile group effect and the skin friction from both outer and inner soils,an analytical solution is developed to calculate the settlement and axial force in large-diameter pipe pile groups.The analytical solution was verified by centrifuge and field testing results.An extensive parametric analysis was performed to study the bearing performance of the pipe pile groups.The results reveal that the axial forces in group piles are not the same.The larger the distance from central pile,the larger the axial force.The axial force in the central pile is the smallest,while that in corner piles is the largest.The axial force on the top of the corner piles decreases while that in the central pile increases with increasing of pile spacing and decreasing of pile length.The axial force in side piles varies little with the variations of pile spacing,pile length,and shear modulus of the soil and is approximately equal to the average load shared by one pile.For a pile group,the larger the pile length is,the larger the influence radius is.As a result,the pile group effect is more apparent for a larger pile length.The settlement of pile groups decreases with increasing of the pile number in the group and the shear modulus of the underlying soil.

Study and application of a new type of foamed concrete wall in coal mines

A new type of airtight wall with the combination of foamed concrete and pier support was designed in this study. Based on the theories and models related to the foamed concrete and blasting shock load, using the numerical analysis method, this study obtains the new material＇s mechanical and destruction laws through analyzing its reaction to different conditions of load （mining and shock waves）, airtight wall thickness （1.2, 1.5, 1.8, 2.1 m） and steel pipe diameters （400, 450, 500 and 600 mm）. The results show that： ①foamed concrete can have very good suspension, and the pier column support is the main carrier of roof pressure; ② the damaged area of foamed concrete decreases as the foamed concrete thickness increases. Under impact loading, the thickness of the foamed concrete wall plays a more obvious role in retaining its integrity; ③under the same mining pressure, the damage area increases as the steel pipe diameter increases; ④ with additional mining stress increase, under whether static load or impact load, the stress on the foamed concrete and steel pipe will also increase gradually, therefore the actual airtight wall design will need to be based on specific circumstances in steel stress.

Three Dimension Finite Element Analysis of the Influence Factors of Stress Responses in the Roadbed and Ground under a Moving Load

Focusing on the vibration of the roadbed and ground induced by high-speed train load, a three dimensional finite element model which includes the roadbed and horizontal layered site is established to study how the site conditions, the load moving speed and the depth of the soil element influence the soil element stress response. Based on a track-subsoil analytical model in which the rail is simulated as an Euler-Bernoulli beam resting on Winkler foundation in the vertical plane, the reaction force between the sleeper and roadbed excited by a single axle is presented, and then that is exerted on relevant elements to simulate the moving load. The dynamic response in the roadbed and subsoil excited by a single axle moving load is computed based on the parallel computing platform of the ABAQUS finite element software, and the stress time-history, stress path and curves of the principal stress axes rotation of the soil element under the track are presented. The results show that： the soil element stress path is an apple-shaped curve in the horizontal shear stress τd versus the stress difference （σsh - σch ）/2 coordinate system; the principal stress axes rotate 180° for the soil element under the load moving line during the load running, and the stress state changes from the pure shear to triaxial shear and then back to the pure shear again. The element dynamic stress increases as the moving load speed increases, which increases sharply when the load speed approaches the Rayleigh wave velocity of soil layer; the site conditions and the soil element depth affect the soil element stress path significantly.

Permissible Stress Level of Brick Masonry under Compressive Cyclic Loading

Laboratory tests revealed that the behavior of brick masonry under compressive cyclic loading is characterized by three distinct stress-strain curves. These three curves are termed as envelope curve, common point curve and stability point curve. The envelope curve is obtained by superimposing the cyclic peaks on the monotonic stress-strain curve. The common point curve is the locus of intersection points of loading and unloading curves of the cycles. If for the same cycle, the loading and unloading are repeated several times, the intersection points of loading and unloading paths will stabilize at a lower bound. The locus of these stabilized points （lower bound points） of all cycles form the stability point curve. Therefore, the stability point curve can be used as a measure for the allowable stress for masonry under cyclic loadings. The proposed cyclic allowable stress level is associated with the accumulation of residual （plastic） strain levels as a result of cyclic loading history. The permissible stress level was found to be about two thirds of the cyclic peak stress of the specimen.

长方形多旋翼无人机设计与研究

针对普通的四旋翼无人机和六旋翼无人机存在作业面狭窄、负载小,不适合大面积作业和物流的缺点,设计了长方形多旋翼无人机,并分析了它的气动力布局、受力分析、运动方式等关键问题,同时也探索了长方形多旋翼无人机在消防应急救援、植保与喷涂、物流等领域的应用。

Safety analysis of building foundations over old goaf under additional stress from building load and seismic actions

Additional displacement of the building foundations over old goaf are prone to happen under the addi- tional loads induced by new buildings, weakening-rock mass by mining and seismic actions, which will cause serious damage to the buildings. In order to analyze the safety of the building foundations safety over the old goaf. the structure characteristics of the strata over the old goaf was investigated and the instability conditions of overhanging rocks upon old goaf were also analyzed in this paper. The results indicate that the stability of overhanging rocks is remarkably decreased by the interactions of mining fractures, earthquake force and building load, in addition, the settlement of the foundations over old goal is increased by the instability of overhanging rocks. According to the location of a new power plant in Yima Mine and its ambient conditions, we defined the influence scope of old goal via resistivity tomography. Based on the seismic parameters of the construction site, a numerical FLAC3d model of the building foundation under the seismic actions and building load was developed. The numerical results are obtained as follows： the foundation of the main power house meets the requirement of 6° seismic fortification intensity： however, under 7° seismic fortification intensity, the maximum differential settlement of foundation between the neighboring pillars is close to the maximum allowable value, while the seismic fortification intensity reaches 8°, but the safety requirements will not be satisfied.

Numerical Simulation of the Spreading Dynamic Responses of the Multibody System with a Floating Base

To simulate the dynamic responses of the multibody system with a floating base when the upper parts spread with a certain sequence and relative speed, the homogeneous matrix method is employed to model and simulate a four-body system with a floating base and the motions are analyzed when the upper parts are spread sequentially or synchronously. The rolling, swaying and heaving temporal variations are obtained when the multibody system is under the conditions of the static water along with the wave loads and the mean wind loads or the single pulse wind loads, respectively. The moment variations of each joint under the single pulse wind load are also gained. The numerical results showed that the swaying of the floating base is almost not influenced by the spreading time or form when the upper parts spread sequentially or synchronously, while the rolling and the heaving mainly depend on the spreading time and forms. The swaying and heaving motions are influenced significantly by the mean wind loads. The single pulse wind load also has influences on the dynamic responses. The torque of joint 3 and joint 4 in the single pulse wind environment may be twice that in the windless environment when the system spreads with 60 s duration.

A simplified model to predict blast response of CFST columns

In order to study the dynamic response of concrete-filled steel tube(CFST) columns against blast loads,a simplified model is established utilizing the equivalent single-degree-of-freedom(SDOF) method,which considers the non-uniform distribution of blast loads on real column and the axial load-bending moment(P-M) interaction of CFST columns.Results of the SDOF analysis compare well with the experimental data reported in open literature and the values from finite element modeling(FEM) using the program LS-DYNA.Further comparisons between the results of SDOF and FEM analysis show that the proposed model is effective to predict the dynamic response of CFST columns with different blast conditions and column details.Also,it is found that the maximum responses of the columns are overestimated when ignoring the non-uniformity of blast loads,and that neglecting the effect of P-M interaction underestimates the maximum response of the columns with large axial load ratio against close range blast.The proposed SDOF model can be used in the design of the blast-loaded CFST columns.