Space station short-term mission planning using ontology modelling and time iteration

This paper studies the problem of the space station short-term mission planning, which aims to allocate the executing time of missions effectively, schedule the corresponding resources reasonably and arrange the time of the astronauts properly. A domain model is developed by using the ontology theory to describe the concepts, constraints and relations of the planning domain formally, abstractly and normatively. A method based on time iteration is adopted to solve the short-term planning problem. Meanwhile, the resolving strategies are proposed to resolve different kinds of conflicts induced by the constraints of power, heat, resource, astronaut and relationship. The proposed approach is evaluated in a test case with fifteen missions, thirteen resources and three astronauts. The results show that the developed domain ontology model is reasonable, and the time iteration method using the proposed resolving strategies can successfully obtain the plan satisfying all considered constraints.

A Brief Introduction to the International Lunar Research Station Program and the Interstellar Express Mission

China has planned and implemented a series of lunar and deep space exploration programs since the first lunar exploration satellite Chang’E-1 launched in 2007.In the future,China has initiated the international lunar research station program,which aims to build a shared platform on the Moon jointly with many other countries for long-term and continuous lunar exploration,lunar-based observations and experiments,as well as in-situ resource utilization.In addition,China has also proposed an interstellar express mission to unveil the mysteries of the outer heliosphere,nearby interstellar space,and their interactions.This paper gives a brief introduction to the International Lunar Research Station program and the Interstellar Express mission.

Overview of the Mars climate station for Tianwen-1 mission

The background and scientific objectives of the Mars Climate Station(MCS)for Tianwen-1 are introduced,accompanied by a comparative review of the status of related meteorological observation missions and of advanced sensing technologies.As one of the China Tianwen-1 Mission’s principal scientific payloads,the MCS contains four measurement sensors and one electronic processing unit that are specially designed to measure local temperature,pressure,wind,and sound on the Martian surface.The MCS’s measurement principles,technical schemes,ground calibration techniques,and adaptability evaluation to the Mars surface environment of MCS are introduced in details.The conclusion presents measurement performance specifications of the MCS,based on ground test results,that will provide guidance to future research based on data from the Tianwen-1 and later Mars missions.

带干扰项的ARZ交通流模型的时滞控制与ISS稳定性

针对线性化之后的ARZ交通流模型,已有文献通常基于如下假设:一是系统的平衡态恰好等于自由流的速度,二是进入上游路段的交通量恰好等于交通需求的数学期望,三是边界反馈不考虑时滞因素的影响.该文抛开各类限制条件,结合时滞边界控制策略,建立了具有模型漂移项和边界扰动项的PDE-PDE无穷维耦合闭环系统.具体地,采用算子半群理论,将闭环系统改写为抽象发展方程的形式;结合线性系统解与控制算子的允许性理论,证明了闭环系统的适定性;构造加权ISS-Lyapunov函数,证明了闭环系统的输入-状态稳定性(ISS),得到了反馈参数的耗散性条件.通过数值仿真实验,进一步验证本文设计的时滞控制器的有效性与参数条件的可行性.

Locating the Polar Cap Boundary of Postnoon Sector from Observations of 630.0 nm Auroral Emission at Zhongshan Station

We studied the ground observations of 630.0 nm auroral emission at Zhongshan Station to determine the polar cap boundary with the latitudinal profile of emission intensity. The open-closed field time boundary is assumed to lie at the boundary between polar rain and plasma sheet precipitation. We assume that nonprecipitation-dependent sources of 630.0 nm emission cause a spatially uniform luminosity in the polar cap and that auroral zone luminosity is also spatially uniform. Therefore we determine the location of the polar cap boundary of postnoon sector from the auroral emission data each time by finding the best fit of the observations to a step function in latitude and we produce a time series of the location of the polar cap boundary. The average error of the practice in the paper is less than 0.8 degree.

Rule Based Collector Station Selection Scheme for Lossless Data Transmission in Underground Sensor Networks

There are fundamentally two different communication media in wireless underground sensor networks. The first of these is a solid medium where the sensor nodes are buried underground and wirelessly transmit data from underground to aboveground. The second is an underground medium such as tunnel, cave etc. and the data is transmitted from underground to the aboveground through partially solid medium. The quality of communication is greatly influenced by the humidity of the soil in both environments. The placement of wireless underground sensor nodes at hard-to-reach locations makes energy efficient work compulsory. In this paper, rule based collector station selection scheme is proposed for lossless data transmission in underground sensor networks. In order for sensor nodes to transmit energy-efficient lossless data, rulebased selection operations are carried out with the help of fuzzy logic. The proposed wireless underground sensor network is simulated using Riverbed software, and fuzzy logic-based selection scheme is implemented utilizing Matlab software. In order to evaluate the performance of the sensor network;the parameters of delay, throughput and energy consumption are investigated. Examining performance evaluation results, it is seen that average delay and maximum throughput are accomplished in the proposed underground sensor network. Under these conditions, it has been shown that the most appropriate collector station selection decision is made with the aim of minimizing energy consumption.

On selecting transmission mode for D2D transmitter in underlay cellular network with a multi-antenna base station

The Device-to-Device(D2D)communication underlaying cellular networks is considered in this study.The D2D transmitter in the D2D mode can directly transmit messages to a receiver,but it may interfere with the transmission of another cellular user who shares the same uplink channel.The transmitter can also operate in a cellular mode in which no interference to another cellular user occurs.We propose a mode selection scheme that aims to minimize the transmission power of the D2D transmitter subject to constraints on the minimum required data rate and maximum interference to other cellular users.The proposed scheme is based on bounds for transmission power and is less complex than the optimal scheme.Furthermore,it requires only a few statistics and does not need a fading channel distribution.The performance of the scheme is close to optimum when the number of Base Station(BS)antennas is large,and the mean absolute deviation of the fading terms is small.We verify this with numerical results of the Rician and Rayleigh fading channels by assuming that the BS antennas are independent.The simulation results for the two correlated BS antennas are presented herein.

ISS特征融合NDT的点云配准研究

点云配准技术在三维重建、自动驾驶领域中起着重要作用。针对正态分布变换(NDT)算法点云配准数据量较大时,配准效率低和配准精度受到初始位姿影响较大的问题,提出一种内部形状描述子(ISS)特征点融合NDT的点云配准方法。首先利用ISS算法对点云进行特征点提取,然后计算特征点处的快速点特征直方图(FPFH)来描述特征点处的局部几何信息,再利用随机采样一致初始配准算法(SAC-IA)进行粗配准,在粗配准后目标点云与源点云获得一个初始变换位姿,最后将该初始变换提供给NDT算法进行精配准。通过对数据集进行不同算法下的对比实验,证明该算法可以有效地提高点云的配准精度和配准效率。

Study on Transmission Planning of Cascade Hydropower Stations along Lancang River Basin

Most of the hydropower projects in Southwest China and the adjacent foreign regions will be put into operation between 2015 and 2020, which will bring some difficulties for reasonable accommodation and delivery of electric energy. In this paper the author studies the development scale, development schedule, accommodation and transmission schemes of the cascade hydropower stations along the Lancang River basin, one of the five large basins in China, based on the load characteristics of grids at both the sending end and the receiving end, the strategy of complementary utilization of thermal power and hydropower, the advanced transmission technologies, and the optimal economic performance. The study results show that, the cascade hydropower stations on the upper reaches of the Lancang River in Yunnan should mainly serve Guangdong Province, with proper planning of partly serving Yunnan Province during dry seasons. The transmission schemes should adopt UHVDC, UHVAC, and single-tower double-circuited HVDC transmission scheme according to the transmission capacity and distance.

Models to Simulate Effective Coverage of Fire Station Based on Real-Time Travel Times

In recent years,frequent fire disasters have led to enormous damage in China.Effective firefighting rescues can minimize the losses caused by fires.During the rescue processes,the travel time of fire trucks can be severely affected by traffic conditions,changing the effective coverage of fire stations.However,it is still challenging to determine the effective coverage of fire stations considering dynamic traffic conditions.This paper addresses this issue by combining the traveling time calculationmodelwith the effective coverage simulationmodel.In addition,it proposes a new index of total effective coverage area(TECA)based on the time-weighted average of the effective coverage area(ECA)to evaluate the urban fire services.It also selects China as the case study to validate the feasibility of the models,a fire station(FS-JX)in Changsha.FS-JX station and its surrounding 9,117 fire risk points are selected as the fire service supply and demand points,respectively.A total of 196 simulation scenarios throughout a consecutiveweek are analyzed.Eventually,1,933,815 sets of valid sample data are obtained.The results showed that the TECA of FS-JX is 3.27 km^(2),which is far below the standard requirement of 7.00 km^(2) due to the traffic conditions.The visualization results showed that three rivers around FS-JX interrupt the continuity of its effective coverage.The proposed method can provide data support to optimize the locations of fire stations by accurately and dynamically determining the effective coverage of fire stations.

Comparative Study on Distributed Waste Pyrolysis Cold Emission Energy Station and Incineration Power Generation

The proper terminal disposal of organic solid waste such as domestic waste is a worldwide issue.Landfill covers a large area,with limited capacity,and a single landfill will be filled one day;incineration is costly to build and operate.These methods all need to transfer and centralized treatment,and secondary pollution is difficult to control,against the purification law of the nature."NIMBY effect"is very serious,and the social cost of treatment is increasing,becoming a heavy financial burden."The Distributed Waste Pyrolysis Cold Emission Energy Station"developed by Hunan Zhongzhou Energy-Saving Technology Co.,Ltd.overcomes these disadvantages and constructs a more appropriate environmental economic industrial chain for the treatment of organic solid waste such as urban and rural household waste.Based on its technical characteristics,this paper compares it with waste incineration power generation project in the aspects of secondary pollution control,treatment effect,energy utilization,investment and operation economy,etc.

High Reliability LM-2F Launch Vehicle for Space Station Mission

As China’s only manned launch vehicle,the LM-2 F Launch vehicle successfully launched the Shenzhou 12 manned spacecraft into its predetermined orbit on June 12,2021,signifying the successful completion of the first manned launch mission in the construction and key technology test stage of China Space Station(CSS).From the launch of the Shenzhou 11 manned spacecraft on October 12,2016 to the launch of Shenzhou 12 in 2021,over the past five years,the LM-2 F launch vehicle has been continuously improved in terms of product reliability through technological innovation and design improvement,and its flight reliability index has increased from 0.97 to 0.98.Based on the new launch mission requirements for the construction stage of CSS,this paper introduces the technological innovation and reliability improvement methods of the LM-2 F from the aspects of design improvement,research methods and process optimization.The LM-2 F launch vehicle will make greater contributions in supporting the construction of CSS with higher reliability and perfect launch success rate.

Evaluation of a Wireless Solar Powered Personal Weather Station

We are evaluating dryland cotton production in Martin County, Texas, measuring cotton lint yield per unit of rainfall. Our goal is to collect rainfall data per 250 - 400 ha. Upon selection of a rainfall gauge, we realized that the cost of using, for example, a tipping bucket-type rain gauge would be too expensive and thus searched for an alternative method. We selected an all-in-one commercially available weather station;hereafter, referred to as a Personal Weather Station (PWS) that is both wireless and solar powered. Our objective was to evaluate average measurements of rainfall obtained with the PWS and to compare these to measurements obtained with an automatic weather station (AWS). For this purpose, we installed four PWS deployed within 20 m of the Plant Stress and Water Conservation Meteorological Tower that was used as our AWS, located at USDA-ARS Cropping Systems Research Laboratory, Lubbock, TX. In addition, we measured and compared hourly average values of short-wave irradiance (Rg), air temperature (Tair) and relative humidity (RH), and wind speed (WS), and calculated values of dewpoint temperature (Tdew). This comparison was done over a 242-day period (1 October 2022-31 May 2023) and results indicated that there was no statistical difference in measurements of rainfall between the PWS and AWS. Hourly average values of Rg measured with the PWS and AWS agreed on clear days, but PWS measurements were higher on cloudy days. There was no statistical difference between PWS and AWS hourly average measurements of Tair, RH, and calculated Tdew. Hourly average measurements of Rg and WS were more variable. We concluded that the PWS we selected will provide adequate values of rainfall and other weather variables to meet our goal of evaluating dryland cotton lint yield per unit rainfall.

A guidance strategy for rendezvous and docking to the space station in the Earth-Moon NRHO orbit

With the development of space technology,it is possible to build a space station in Earth-Moon space as a transit for Earth-Moon round-trip and entering in the deep space.Rendezvous and docking is one of the key technologies for building an Earth-Moon space station.A guidance strategy for rendezvous and docking from the Earth orbit to the space station in the Earth-Moon NRHO orbit is proposed in this paper,which is suitable for engineering applications.Firstly,the rendezvous and docking process is divided into three sections,i.e.,the large-range orbit transfer section,far-range guidance section,and close-range approaching section.The suitable terminal of large-range orbit transfer is selected according to the eigenvalue of NRHO orbit state transition matrix.The two-impulse guidance method based on the relative motion equation in the three-body problem is adopted for the far-range guidance section.The impulse time and amplitude are solved with the optimization algorithm.The linear constant three-body relative motion equation is proposed for the close-range approaching section,and the rendezvous and docking is completed by a two-stage linear approximation.Finally,a simulation analysis is carried out,and the simulation results show that the adopted dynamics equations and the designed guidance law are effective,and the three flight phases are naturally connected to accomplish the rendezvous and docking mission from the Earth orbit to the space station on the Earth-Moon NRHO.

Strategic Placement of Charging Stations for Enhanced Electric Vehicle Adoption in San Diego, California

California mandated that 100% of vehicles sold must be electric by 2035. As electric vehicles (EVs) reach a higher penetration of the car sector, cities will need to provide publicly accessible charging stations to meet the charging demand of people who do not have access to a private charging spot like a personal garage. We have chosen to limit our scope to San Diego County due to its non-trivial size, well-defined shape, and dependence on personal vehicles;this project models 100% of current vehicles as electric, roughly 2.5 million. By planning for the future, our model becomes more useful as well as more equitable. We anticipate that our model will find locations that can service multiple population centers, while also maximizing distance to other stations. Sensitivity analysis and testing of our algorithms are conducted for Coronado Island, an island with 24,697 residents. Our formulation is then scaled to set the parameters for the whole county.

Simulation of Underground Reservoir Stability of Pumped Storage Power Station Based on Fluid-Structure Coupling

Based on global initiatives such as the clean energy transition and the development of renewable energy,the pumped storage power station has become a new and significant way of energy storage and regulation,and its construction environment is more complex than that of a traditional reservoir.In particular,the stability of the rock strata in the underground reservoirs is affected by the seepage pressure and rock stress,which presents some challenges in achieving engineering safety and stability.Using the advantages of the numerical simulation method in dealing deal with nonlinear problems in engineering stability,in this study,the stability of the underground reservoir of the Shidangshan(SDS)pumped storage power station was numerically calculated and quantitatively analyzed based on fluid-structure coupling theory,providing an important reference for the safe operation and management of the underground reservoir.First,using the COMSOL software,a suitablemechanicalmodel was created in accordance with the geological structure and project characteristics of the underground reservoir.Next,the characteristics of the stress field,displacement field,and seepage field after excavation of the underground reservoir were simulated in light of the seepage effect of groundwater on the nearby rock of the underground reservoir.Finally,based on the construction specifications and Molar-Coulomb criterion,a thorough evaluation of the stability of the underground reservoir was performed through simulation of the filling and discharge conditions and anti-seepage strengthening measures.The findings demonstrate that the numerical simulation results have a certain level of reliability and are in accordance with the stress measured in the project area.The underground reservoir excavation resulted in a maximum displacement value of the rock mass around the caverns of 3.56 mm in a typical section,and the safety coefficient of the parts,as determined using the Molar-Coulomb criterion,was higher than 1,indicating that the project as a whole is in a stable state.

A Multi-Objective Optimization for Locating Maintenance Stations and Operator Dispatching of Corrective Maintenance

In this study,we introduce a novel multi-objective optimization model tailored for modern manufacturing,aiming to mitigate the cost impacts of operational disruptions through optimized corrective maintenance.Central to our approach is the strategic placement of maintenance stations and the efficient allocation of personnel,addressing a crucial gap in the integration of maintenance personnel dispatching and station selection.Our model uniquely combines the spatial distribution of machinery with the expertise of operators to achieve a harmonious balance between maintenance efficiency and cost-effectiveness.The core of our methodology is the NSGA Ⅲ+Dispatch,an advanced adaptation of the Non-Dominated Sorting Genetic Algorithm Ⅲ(NSGA-Ⅲ),meticulously designed for the selection of maintenance stations and effective operator dispatching.This method integrates a comprehensive coding process,crossover operator,and mutation operator to efficiently manage multiple objectives.Rigorous empirical testing,including a detailed analysis from a taiwan region electronic equipment manufacturer,validated the effectiveness of our approach across various scenarios of machine failure frequencies and operator configurations.The findings reveal that the proposed model significantly outperforms current practices by reducing response times by up to 23%in low-frequency and 28.23%in high-frequency machine failure scenarios,leading to notable improvements in efficiency and cost reduction.Additionally,it demonstrates significant improvements in oper-ational efficiency,particularly in selective high-frequency failure contexts,while ensuring substantial manpower cost savings without compromising on operational effectiveness.This research significantly advances maintenance strategies in production environments,providing the manufacturing industry with practical,optimized solutions for diverse machine malfunction situations.Furthermore,the methodologies and principles developed in this study have potential applications in various other sectors,including healthcare,transportation,and energy,where maintenance efficiency and resource optimization are equally critical.

EV Charging Station Load Prediction in Coupled Urban Transportation and Distribution Networks

The increasingly large number of electric vehicles(EVs)has resulted in a growing concern for EV charging station load prediction for the purpose of comprehensively evaluating the influence of the charging load on distribution networks.To address this issue,an EV charging station load predictionmethod is proposed in coupled urban transportation and distribution networks.Firstly,a finer dynamic urban transportation network model is formulated considering both nodal and path resistance.Then,a finer EV power consumption model is proposed by considering the influence of traffic congestion and ambient temperature.Thirdly,the Monte Carlo method is applied to predict the distribution of EVcharging station load based on the proposed dynamic urban transportation network model and finer EV power consumption model.Moreover,a dynamic charging pricing scheme for EVs is devised based on the EV charging station load requirements and the maximum thresholds to ensure the security operation of distribution networks.Finally,the validity of the proposed dynamic urban transportation model was verified by accurately estimating five sets of test data on travel time by contrast with the BPR model.The five groups of travel time prediction results showed that the average absolute percentage errors could be improved from 32.87%to 37.21%compared to the BPR model.Additionally,the effectiveness of the proposed EV charging station load prediction method was demonstrated by four case studies in which the prediction of EV charging load was improved from27.2 to 31.49MWh by considering the influence of ambient temperature and speed on power energy consumption.