Abstract This paper presents the detailed design, key components, and technical verification of a vacuum chamber for space electric propulsion system environmental testing. The chamber features a horizontal configuration equipped with an oil-free pumping system, achieving a base pressure better than 5 × 10 −5 Pa and an operating pressure better than 2.0 × 10 −3 Pa at a xenon gas flow rate of 60 sccm. To mitigate the high-density plasma plume encountered in electric propulsion experiments, a sputtering protection system composed of titanium plates and stainless steel tubes is proposed, which effectively reduces contamination and sputtering damage to the vacuum vessel. For the xenon pump, comparative analyses of the temperature distribution between single-sided and double-sided pumping cold plates are conducted. Results indicate that the double-sided configuration provides superior temperature uniformity, while the single-sided design offers advantages in lighter weight and shorter cool-down time. Performance tests demonstrate that the xenon pump achieves a pumping speed of 17,500 – 18,500 L / s at cold plate temperatures below 35 K, and the system yields an effective pumping speed of approximately 61,700 L / s under on-load conditions. The completion of this vacuum chamber has effectively addressed the challenges posed by high-density plasma plumes, large gas flow rates, and severe thermal loads in ground-based vacuum tests, providing critical support for the research and development of electric propulsion systems.

In order to enhance the standard of educational delivery in open online educational offerings at higher education institutions social network analysis (SNA) is introduced to carry out an Investigation into the factors that impact educational instruction quality of open online educational offerings at higher education institutions. Firstly, the elements that influence the teaching standard of college open digital coursework are analysed, the relevant hypotheses are put forward, the conceptual model of the factors influencing educational excellence in college accessible online learning opportunities is constructed, and then the questionnaire is designed to demonstrate the hypotheses. The empirical results show that the rapport between educators and learners, network cohesive subgroups and network density have a significant impact on the teaching standard of college open online educational offerings at institutions of higher learning, namely colleges and universities can improve the teaching quality of online open courses by optimising the network structure, expanding the network scale, and promoting the interaction and communication among users.

The existing methods for evaluating the quality of blended learning lack unified standards and evaluation systems, resulting in low comparability of evaluation results. Therefore, a hybrid teaching quality evaluation method based on PSO-BP neural network was studied. Firstly, the selection of quality evaluation indicators for blended learning should follow the principles of scientificity, comprehensiveness, and testability. Then, the analytic hierarchy process (AHP) was used to construct a mixed teaching quality evaluation index system. Finally, the obtained evaluation indicators will be used as inputs for the PSO-BP neural network, and through the learning and optimisation capabilities of the neural network, hybrid teaching quality evaluation will be achieved. The experimental results indicate that, the R2 of the PSO-BP neural network model for evaluating the quality of blended learning is 0.985, indicating high fitting ability. The actual level is consistent with the evaluation level, with an evaluation error of less than 2%, indicating practicality.

In order to overcome the problems of unreasonable index weight distribution, poor quality evaluation results and low accuracy in the process of online education quality evaluation, this paper proposes a method of online education quality evaluation based on fuzzy rough set. Fuzzy rough set theory is introduced to eliminate redundant attributes of network. According to the regional characteristics of online education network, this paper constructs an evaluation index system, calculates the evaluation weight of education network, evaluates the importance of education network nodes, determines the level of education quality, and obtains the evaluation results of education quality. The experimental results show that the maximum value of evaluation index weight distribution rationality parameter can reach 29.45, and the quality evaluation result U = 90, which shows that the quality effect is excellent, and the accuracy rate reaches 90%. This method has good practicability and guidance.

The solar simulator is an important device for simulating solar irradiation in cold black and vacuum environments and has a wide range of application prospects. In this work, a method of thermal conductivity measurement by a double specimen protection thermal plate method under vacuum conditions was proposed, and the thermal conductivity of a new thermal insulation material under a cryogenic vacuum environment was studied. By designing a vacuum adjustment device and a multi-layer insulation structure with a low outgassing rate, it is possible to adjust the vacuum pressure from 10−4 Pa to atmospheric. A temperature control and thermal conductivity test can be realized from −160 °C to 280 °C by the joint temperature control of liquid nitrogen cooling and electric heating. Then, the measurement accuracy of the device was checked by the national standard sample, the thermal conductivity of the sample was measured under different vacuum and temperature conditions, the uncertainty analysis of the device was given, and, finally, the thermal conductivity of the new material was tested.

Solar–thermal conversion and migration characteristics of nanofluids have attracted intensive attention recently. Due to the strong absorption of solar energy, solar collectors with nanofluids have wide applications in many areas including desalination and power generation. Researchers have mainly focused on the macroscopic performance of nanofluids in solar collectors, but the nanoparticles’ migration characteristics with vapor during phase transformation have not been further investigated. Therefore, an experimental investigation on solar–thermal conversion characteristics of nanofluids and migration characteristics with vapor during phase transformation was conducted in this work, in order to verify the enhancement effect of nanoparticles on solar energy absorption and explore the nanoparticles’ migration behavior with vapor. It was found that part of Ag nanoparticles migrate out of the nanofluids with generated vapor by boiling nanofluids, and most of the nanoparticles remained in the nanofluids. In addition, more Ag nanoparticles migrated with vapor with the increased heating power. The concentration of migrated nanofluids was 20.58 ppm with a power of 16.2 W and 31.39 ppm with a power of 20 W. The investigation pointed out the potential danger of nanofluids in the process of utility and provided a reference for the standardized application of nanofluids.

在人员疏散中,撤离者之间的冲突行为复杂且对疏散的速率影响较大,为了模拟此过程,提出了一种将博弈论与元胞自动机相结合的模型.在该模型中设置了两种策略的人(叛逃者和合作者),并引入恐慌指数和惯性系数两个重要参数,来描述疏散过程中撤离者的恐慌和保持原策略的能力;每一次冲突即是一次博弈,发生冲突的撤离者之间通过收益矩阵来确定成功者;并且在博弈完成时采用费米函数进行策略更新.模型再现了"出口拱形"和"快即是慢"现象;同时发现在相同的恐慌下,叛逃者与合作者的比率总是倾向于一致状态.这些自组织现象支持了模型的正确性.该项工作也有助于理解惯性因素对于合作行为产生与存续的影响.

复合相变保温砂浆可作为内保温砂浆与日光温室墙体组成复合相变保温墙体,为温室生产提供热能.通过对日光温室相变墙体相变传热过程的数值模拟研究,可较好地掌握其蓄放热特性,为日光温室应用复合相变材料提供理论支持.该文利用ANSYS有限元分析软件模拟研究日光温室复合相变保温墙体的传热过程,数值模拟结果表明:50 mm复合相变保温砂浆与490 mm砖墙组成的复合相变保温墙体和30 mm复合相变保温砂浆与240 mm加气混凝土砌块墙组成的复合相变保温墙体都具有较强的蓄放热能力,两者的持续蓄热时间均为8h,持续放热时间分别为16和13h,这2种复合相变保温墙体均适合于冬季温室生产.

In order to meet the requirements of ground verification test at various stages of space station development, it is necessary to develop a comprehensive performance test verification platform for space station environmental control system. According to the test requirements, the ground comprehensive performance verification cabin must have a stable thermal environment. When the temperature difference between the inside and outside of the cabin is higher than 5 °C, the leakage heat of the cabin is not more than 300W. Taking the cargo spacecraft as an example, the cabin structure was modeled, and the computational fluid dynamics method was used to simulate the fluid-solid coupling heat transfer. The rationality of the design of the leak-proof thermal structure was verified, and the experiment was designed to test the temperature uniformity and heat leakage. The results show that both uniformity and heat leakage meet the requirements.

为真实地再现人员疏散场景,针对人员疏散过程中的逆流行为问题,提出一种基于社会力模型的人员逆流行为仿真模型,研究在场馆内人员疏散过程中的逆流行为及其对疏散结果的影响.根据社会力模型建立人员疏散模型,采用主从个体之间的吸引力对从个体行动方向的决策作用来描述逆流行为.在有逆流行为情形下的单出口和多出口场馆进行仿真,仿真结果表明,该模型有效且具有可行性,能够模拟出人员疏散过程中的逆流行为,随着逆流个体的增多疏散时间呈非线性增加,在相同情况下主原地等待行为比主不原地等待行为的影响更明显.

The optical characteristics of the space science detectors are very sensitive to the temperature fluctuation. In order to study the effect of it, a method to simulate the temperature fluctuation was put forward in this paper, and the feasibility of this method was verified numerically. A radiation disturbance was artificially applied at a certain distance from the test platform, so that the surface temperature of the platform changed periodically with the radiation heater. The results show that the radiation heat transfer disturbance could produce a temperature fluctuation on the test platform, which provides a reliable theoretical support for the time-varying temperature control system.

The temperature-adjustable system of the Space Environment Simulator was introduced, which can keep the thermal shield in the temperature range from 123 K to 423 K. Design method of the main equipments was supplied, and applied to KM2 space environment simulator. The main parameters such as the thermal load of the system, gaseous nitrogen's mass flow, etc. were calculated, and the fan, main spray equipment and heater were selected according to the calculation result, numerical simulation was also conducted. Test verification has been completed, during the test the cool-down rate is 1.03 K/min and the Uniformity of the thermal shield temperature is better than +/- 5 K, which match well with the technical index. So the design method can be applied in the development of the similar system.

The surface temperature uniformity of a test platform with an effective test area of 600 mm x 600mm was numerically studied. The conductive heat transfer model for the test platform and the device under test ( DUT) installed on the surface was established in the present work, as well as the radiation heat transfer model from the platform surface to the background temperature. The platform surface was divided into 5 or 9 regions where heated independently to make the surface temperature consistent. The temperature uniformity of these two partition designs was compared. The result shows that the 9 regions design has higher temperature uniformity at both target temperatures of -10 degrees C and +45 degrees C.

Extensive numerical study on the heat transfer performance of the gaseous nitrogen ( GN) thermoregulation shroud surface was conducted in this work. The average heat transfer coefficient was investigated under different shroud length and nitrogen parameters ( such as velocity, temperature and mass flow rate). The result shows that the heat transfer performance is affected less by shroud length but largely by mass flow rate. When the mass flow rate is constant, the inlet temperature increases heat transfer coefficient. Finally, dimensionless correlation of the average Nusselt number over shroud surface with Reynolds number and Prandtl number was obtained.

With the development and progress of space, the space environment simulation equipment market has entered the golden age of rapid development, environmental simulation enterprises in the fierce competition in the field environment, want to keep the lasting competitiveness must develop its own unique corporate culture, on the other hand, the competition between enterprises can be converted to talented person's competition, the enterprise only set up their own enterprise culture and improve the personnel training mode, to improve the staff's comprehensive strength. The development of enterprise culture is closely related to the cultivation of talents. Only by combining the two can the advantages of an enterprise be brought into full play.

In order to improve the design skills of space environment simulation equipment, KANO model was used to analyze customer needs, and then the quality function deployment method was employed to decompose customer needs step by step into detailed design and technical characteristics of products, and finally into the core requirements of process management.

The characteristics of scientific research projects determine that there are more uncertainties in project risks. In addition to common risks such as contracts, taxes and funds, more attention should be paid to the risks of time, technology, member change, coordination and target change, so that professional project managers can participate in project risk management as soon as possible.

Explosive decompression is the rapid decompression process of aircraft in the sky caused by the damage of cabin which challenges the safety of people and equipment. The explosive decompression tester usually uses negative pressure reserve cabin technology. Numerical study was conducted to analyse the influence of the throttling and negative pressure reserve cabin volume on the explosive decompression process. The results show that as the throttle opening, the explosive decompression time decreases and the fluctuation amplitude of the two chambers after the pressure balance is enhanced; the volume of the negative pressure reserve cabin has little effects on the rate of explosive decompression and has no obvious influence on the fluctuation.

In order to study the environment temperature control method in the low pressure chamber, the numerical simulation and tests were conducted. The heat transfer process in the low pressure chamber was simulated by Fluent, and the radiation and heat conduction were considered to research the effect of the shroud opening hole, then the forced-convection was added to the simulation to research the effect of the forced-convection fan. No-load and on-load tests in the low pressure chamber were completed to research the effect of the test pressure, and the test pieces and toolings. The results show that, the shroud opening hole could make the uniformity of environment temperature worse, and the forced-convection fan being rationally designed could improve the characteristic of environment temperature, and the test pressure, the test pieces and toolings could affect the environment temperature. The environment temperature control method in the low pressure chamber should take all these factors into account, and can be applied to the development of the near space environment simulation equipment.

To ensure the safety of the pilot, the design scheme of a ground experiment platform for testing the performance of oxygen supply system under rapid decompression was presented. Detail design process of the subsystems such as vacuum system, rapid decompression system and temperature control system was introduced. Numerical simulations were carried out for the latter two subsystems. The results show that, the requirements both for the temperature uniformity of the experiment cabin and for the rapid decompression time can be achieved, based on the design of the present work which is very valuable for constructing the rapid decompression test platform of oxygen supply system.