摘要：Molten salt pebble bed reactor is one of the sixth-generation Ⅳ reactor types. To investigate the mechanical behavior of the fuel pebbles in the core, a visualization experiment facility of pebble bed(VEFPB) is designed. To obtain a uniform flow field of the core and analyze the influence of the flow field on the structure of the pebble bed, computational fluid dynamics software Fluent is used to simulate the flow field distribution of the core of VEFPB. The simulation results show that the disturbance at the bottom of the pebble bed is proportional to the flow velocity of the inlet pipe, and the flow velocity close to the inlet side is more significant than that in other parts; the design of the cylinder bottom plate with holes of different sizes can effectively reduce the flow velocity and the disturbance at the bottom of the pebble bed. In addition,according to the velocity contours of the core of VEFPB, it is observed that the flow field distribution of the core is considerably uniform except at the bottom of the pebble bed. This ensures the stability of the pebble bed and verifies the rationality of the design of VEFPB. This study provides the technical support and reference for the flow field analysis of the core of molten salt pebble bed reactor.

摘要：The fore claws of the nymph of Cryptotympana atrata have excellent ability to cut and dig soil. Inspired by this, we designed a biomimetic stubble cutter to reduce the cutting resistance. Reverse engineering and 3D print technology were applied to design the biomimetic stubble cutter. Two types of biomimetic corn stubble cutters with different tooth heights （5 mm and 2.5 mm） were designed. The cutting ability of biomimetic corn stubble cutters was compared to the conventional design by the quadratic regression orthogonal test. Tooth height, dip angle of cutting edge, and cutting velocity were chosen as orthogonal test factors. The biomimetic stubble cutters show lower cutting resistance than the conventional one. Cutting velocity exerts the least effect on cutting resistance, followed by tooth height and dip angle of cutting edge. Optimal combination with the least cutting resistance is tooth height of 2.5 mm and dip angle of cutting edge of 40° while the cutting resistance does not vary remarkably with cutting velocity. Test results indicate the serrated structure design as a principal factor for cutting resistance reduction. The biomimetic stubble cutter design, inspired by the soil-cutting mechanism of Cryptotympana atrata nymph, remarkably improves the performance of stubble cutter.

摘要：Brain-derived neurotrophic factor (BDNF) plays a crucial role in human obesity. Yet, the neural circuitry supporting the BDNF-mediated control of energy homeostasis remains largely undefined. To map key regions that might provide inputs to or receive inputs from the paraventricular nucleus (PVN) BDNF neurons, a key type of cells in regulating feeding and thermogenesis, we used rabies virus-based transsynaptic labeling and adeno-associated virus based anterograde tracing techniques to reveal their whole-brain distributions. We found that dozens of brain regions provide dense inputs to or receive dense inputs from PVN BDNF neurons, including several known weight control regions and several novel regions that might be functionally important for the BDNF-mediated regulation of energy ***, several regions show very dense reciprocal connections with PVN BDNF neurons, including the lateral septum, the preoptic area, the ventromedial hypothalamic nucleus, the paraventricular thalamic nucleus, the zona incerta, the lateral parabrachial nucleus, the subiculum, the raphe magnus nucleus, and the raphe pallidus nucleus. These strong anatomical connections might be indicative of important functional connections. Therefore, we provide an outline of potential neural circuitry mediated by PVN BDNF neurons, which might be helpful to resolve the complex obesity network.

摘要：提出了一种带预处理的离散系数滤波器设计方法。该方法基于离散系数滤波器设计问题的{-1,1}二次规划模型,利用{-1,1}二次规划的全局最优性条件,提出了一种最优解元素的判断准则,得到了一个规模较小的离散系数滤波器设计问题。结合随机扰动方法,得到了求解离散系数滤波器设计问题的一种带预处理的随机扰动算法。与随机扰动方法相比,带预处理的随机扰动方法得到的次优解的性能更好,需要的时间也大大减少。

摘要：根据动力学原理,对汽车在弯坡路段上的运行状态及行车安全性进行了分析。认为弯坡路段之所以成为车辆运行安全隐患的原因是由于设计速度与车辆实际运行速度不协调造成的,在弯坡路段的线形组合设计中应根据车辆的实际运行速度选用技术指标。利用Matlab绘制出在不同设计速度下,坡长、坡度与速度的关系图及“速度与半径的关系图”,为设计公路在弯坡路段的线形组合中合理选取技术指标提供了依据。

摘要：In order to suppress the effect of the temperature variation on the wavefront of the laser communication terminal, the secondary mirror support with flexure hinges is designed. The series-wound straight-circle flexure hinge is designed to achieve the maximal variation range of the flexibility or stiffness with the limit of flexure hinges' geometrical size. The position and quantity of the flexure hinges are determined to control the deformation direction of the secondary mirror. In order to search the direction in which the wavefront aberration is minimum, the flexure hinges' parameters are optimized with the system wavefront aberration as the optimization objective. The prototype of the laser communication terminal is constructed and the value of the wavefront aberration is measured under the condition of 20±2°C. Experimental results show that the value of the wavefront aberration root mean square(RMS) is reduced from 0.066λ to 0.042λ, meeting the requirement of RMS less than 1/20λ(λ=632.8 nm). The athermal design method presented in this paper provides a novel way for the athermal design of the small aperture mirror support in off-axis optical systems.

摘要：在非连续正交频分复用系统中,为了改善信道估计的性能并尽可能地降低计算复杂度,基于最小化最小二乘信道估计均方误差(Mean Square Error,MSE)的准则提出了一种次优导频设计方法.该方法利用凸映射解决了导频位置优化设计的非凸问题,求得符合三次函数关系的非均匀分布次优导频位置,并推导导频位置已知条件下的最优导频功率分布.仿真结果表明:所提次优导频设计方法与现存导频设计方法相比,能够获得较好的信道估计MSE性能,且具有计算简单的优势.

摘要：在高端工厂自动化应用中（如油气厂和电厂），常会要求多路采集通道与通道之间进行隔离，其中高耐压、小尺寸、低EMI、高可靠性和低成本等要求在通道间隔离设计中别具挑战性。现有成熟方案，标准模块实现的通道密度往往仅限于四个通道或八个通道，通道间隔离只能承受数百伏特耐压。本文将提出一种替代性的高密度、易于设计的通道间隔离模拟输入模块的完整解决方案。

摘要：薄钢板剪力墙依靠内填钢板屈曲后形成拉力带以抵抗水平荷载,是一种适用于高烈度地区的新型抗侧力结构.采用精细模型进行钢板剪力墙的计算和设计耗时长,为提高钢板墙结构设计的效率,基于拉力带简化模型,提出了交叉支撑-拉力带简化模型(CBSM)用于模拟交叉加劲钢板剪力墙的抗侧性能.推导了交叉加劲钢板墙的初始刚度和承载力计算公式,通过ABAQUS有限元软件建立精细模型和CBSM简化模型,与理论公式计算结果对比,验证简化模型的准确性.结果表明,在不同的跨度、内填板厚度和加劲肋刚度的情况下,精细模型、CBSM简化模型和理论公式3种方法预测的交叉加劲钢板剪力墙承载力有良好的一致性,说明CBSM简化模型能够较准确地预测交叉加劲钢板剪力墙的承载力,反映出加劲肋对钢板剪力墙结构抗侧能力的贡献.初始刚度理论计算公式与精细模型吻合得较好,CBSM简化模型预测刚度低于精细模型,是偏于安全的.

摘要：文章从设计符号学视角出发,探索将桂林地区的旅游体验与当地文化资源进行融合创新的方法,提升文化创意产品的文化价值与审美价值。从语义、语构、语境、语用等多个维度对桂林旅游文化进行了深入解读,并基于此进行设计实践。在造型设计方面,通过符号学方法提炼桂林自然景观和传统工艺的符号特征,进行再设计。在功能创新方面,引入智能家居理念,探索人与文化创意产品的新型交互方式。通过设计符号学解析桂林自然与人文符号,并应用于台灯、香薰的设计实践中。以期为促进桂林地区特色旅游文化的发展提供参考,提升桂林山水文化的内涵价值。