计及时间相关性的微能源网鲁棒规划方法

微能源网以能源的梯级利用为原则,可实现风、光等多种新能源的高比例消纳,满足区域内电、热、冷等多种能源需求。微能源网中存在新能源出力与冷、热、电负荷的多重不确定性。为增强系统规划结果的鲁棒性,常采用不确定集表述新能源出力与多种用能需求的不确定性,实现针对微能源网的鲁棒规划设计,往往使系统规划结果过于保守,降低系统经济性。为克服以上问题,规避实际运行中不可能发生的场景,降低系统规划结果的保守性,文章提出一种考虑时间相关性的微能源网鲁棒规划模型。该模型在计及多重源荷不确定性的基础上,进一步考虑新能源出力与冷、热、电负荷的时间相关性。通过算例对传统不确定集与所提出的改进不确定集进行对比分析,验证了所提模型及方法的优越性和有效性。     

Cutting parameter optimization for one-step shaft excavation technique based on parallel cutting method

The outcome of the cutting blasting in a one-step shaft excavation is heavily related to the cutting parameters used for parallel cutting method. In this study, the relationships between the cutting parameters (such as the hole spacing L and the empty hole diameter D) and damage zones were investigated by numerical simulation. A damage state index γ was introduced and used to characterize the crushing and crack damage zones through a user-defined subroutine. Two indices, i.e., η₁ and η₂ that can reflect the cutting performance, were also introduced. The simulation results indicate that an optimal value of L can be obtained so that the η₁ and η₂ can reach their optimal states for the best cutting performance. A larger D results in better cutting performance when the L value maintains its best. In addition, the influences of the loading rate and the in-situ stress on the cutting performance were investigated. It is found that an explosive with a high loading rate is suit for cutting blasting. The propagation direction and the length of the tensile cracks are affected by the direction and the magnitude of the maximum principal stress.     

LTE室分高倒流小区解决方案的研究

LTE室分高倒流直接影响室内4G用户的感知，同时较大程度拉低LTE网络驻留率指标。由于室内无线环境的封闭性，室分小区之间的覆盖独立性，仅仅通过参数调整的手段达到降低高倒流的效果非常不明显，因此本文针对目前影响室内用户感知的高倒流问题，从高倒流小区的标准出发，对室分高倒流小区的发现手段，产生原因及解决方案进行详尽地阐述，并针对各类型的高倒流情形提出解决方法，最终提供读者发现、分析及解决室分高倒流小区的有效方案，从而作为研究方法提供给LTE室内小区高倒流问题解决的指导意见     

Turbulent times: tourists’ attitudes towards wind turbines in the Southern Highlands in Iceland

As a response to the threat of climate change, many nations are increasing their use of renewable energy, including wind energy. Large wind farms often conflict with other land uses, particularly tourism, which is a growing industry worldwide. In Iceland, tourism has recently become the largest export sector, with majority of tourists travelling to the country to experience its nature. This paper examines tourists’ opinions and perceptions of wind power development in the Southern Highlands of Iceland and compares how number, size and proximity of wind turbines, and the landscape in which they are situated, influence tourists’ perceptions. The study is based on an on-site questionnaire survey conducted in 2015. The results indicate that one-third of the travellers would be less likely to visit the Southern Highlands if a proposed wind farm were built, and two-thirds think that wind turbines would decrease the area’s attractiveness.     

Structural optimization with an automatic mode identification method for tracking the local vibration mode

Traditional optimization methods, which take a specific order of modal frequency as the design constraint, could fail to obtain the desired solution because of modal substitution. An improved optimization model with continuous sizing variables is established to solve this problem, in which the minimum weight and a given local modal frequency are considered as the objective and the constraint. To capture accurately the expected mode of vibration, a local mode identification technique is proposed based on the strain energy ratio between the local area and the whole structure. With that scheme, an optimization system is developed, in which the local mode can be effectively identified and the constraint can be updated with it in the iteration process. Two numerical examples, of a reinforced plate and a satellite structure, are applied to illustrate the effectiveness and efficacy of the proposed method.     

阳泉矿区煤样不同应力状态下声发射特性分析

为探索原煤煤样的力学性能和不同应力状态下的声发射活动特性,对阳泉矿区新景矿、平舒矿主采煤层的煤样进行了单轴、三轴压缩和巴西劈裂的声发射试验,分析了2种煤样力学性能及不同加载过程的声发射活动规律。证明通过监测声发射(微震)活动分析煤样或煤岩体内部破坏状态是一种方便有效的手段。     

A spectrally selective surface structure for combined photothermic conversion and radiative sky cooling

The sun and outer space are the ultimate heat and cold sources for the earth, respectively. They have significant potential for renewable energy harvesting. In this paper, a spectrally selective surface structure that has a planar polydimethylsiloxane layer covering a solar absorber is conceptually proposed and optically designed for the combination of photothermic conversion (PT) and nighttime radiative sky cooling (RC). An optical simulation is conducted whose result shows that the designed surface structure (i.e., PT-RC surface structure) has a strong solar absorption coefficient of 0.92 and simultaneously emits as a mid-infrared spectral-selective emitter with an average emissivity of 0.84 within the atmospheric window. A thermal analysis prediction reveals that the designed PT-RC surface structure can be heated to 79.1°C higher than the ambient temperature in the daytime and passively cooled below the ambient temperature of approximately 10°C in the nighttime, indicating that the designed PT-RC surface structure has the potential for integrated PT conversion and nighttime RC utilization.     

CFD modeling of thermal contact resistance between solid contacting surfaces

Heat transfer has considerable applications in different industries such as designing of heat exchanger, nuclear reactor cooling, control system for spacecraft, and designing of microelectronics cooling. As the surfaces of two metals contact each other, this issue becomes so crucial. Thermal contact resistance (TCR) is one of the key physical parameters in heat transfer of mentioned surfaces. Measuring the experimental value of TCR in laboratory is highly expensive and difficult. As an alternative, numerical modeling methods could be engaged. In this study, inverse problem method solution is utilized as a proper method for estimation of TCR value. In this order, three different configurations (flat-flat, flat-cylinder, and cylinder-cylinder) were utilized in two steady and unsteady state conditions to predict the value of TCR. A comparison between the measured values and obtained values from the simulation show the errors for flat-flat, flat-cylinder, and cylinder-cylinder configuration after 10 min from starting the experiment are 4.6074%, 0.1662%, and 0.5622%, respectively. And in steady-state condition, the corresponding errors are 6.06e-3%, 1.506%, and 0.846%, respectively. In conclusion, the final results establish the fact that the inverse problem method solution can predict TCR values between contacting surfaces.     

超临界蒸汽参数对燃气蒸汽联合循环性能影响研究

为进一步提高联合循环效率,参考现有燃气蒸汽联合循环12.5 MPa/568℃亚临界蒸汽参数,提出27 MPa/585℃超临界蒸汽参数,根据燃气蒸汽联合循环计算模型,以397 MW燃气轮机联合循环机组为例,计算了超临界蒸汽参数与两种亚临界蒸汽参数的底循环效率和联合循环效率,并分析对比了3种蒸汽参数的底循环效率对联合循环效率的贡献。研究表明:对于同一燃气轮机,超临界和亚临界中低压蒸汽参数不同时,超临界蒸汽参数的底循环效率比亚临界提高了4.3%,蒸汽底循环输出功率占联合循环机组输出功率的百分比由30.21%增加到32.62%,联合循环净效率增加了2.21%,联合循环机组的输出功率增加了20.38 MW;中低压蒸汽参数相同时,超临界蒸汽参数的底循环效率比亚临界提高了2.87%,蒸汽底循环输出功率占联合循环机组输出功率的百分比由31.16%增加到32.62%,联合循环净效率增加了1.44%,联合循环机组的输出功率增加12.5 MW。