Abrasive wear in ceramic laminated composites

Laminated ceramic structures in the system Al₂O₃/Al₂O₃ + 3Y-TZP (A/AZ) were prepared using a tape casting technique in order to obtain ceramic layers with different compositions and thicknesses. Piezo-spectroscopy was used to evaluate the residual stresses arisen from a calibrated mismatch in thermal expansion coefficients of the layers during the sintering process of the composite. The dependence of the residual stresses in the A and AZ layers on their thickness ratio was established. A microscale ball cratering method was used to investigate the influence that the surface compressive stress can play on the abrasive wear resistance of the composite structures. The results were compared with those obtained with an unstressed reference material prepared either by lamination of pure alumina green-sheets or by cold isostatic pressing of alumina powder. The experimental results have shown that the abrasive wear resistance is higher for samples with compressive residual stresses within the surface regions.     

Annealing behaviors of vacancy in varied neutron irradiated Czochralski silicon

The difference of annealing behaviors of vacancy-oxygen complex (VO) in varied dose neutron irradiated Czochralski silicon: (S1 5×10¹⁷ n/cm³ and S2 1.07×10¹⁹ n/cm³) were studied. The results show that the VO is one of the main defects formed in neutron irradiated Czochralski silicon (CZ-Si). In this defect, oxygen atom shares a vacancy, it is bonded to two silicon neighbors. Annealed at 200 °C, divacancies are trapped by interstitial oxygen(O_i) to form V₂O (840 cm⁻¹). With the decrease of the 829 cm⁻¹ (VO) three infrared absorption bands at 825 cm⁻¹ (V₂O₂), 834 cm⁻¹ (V₂O₃) and 840 cm⁻¹ (V₂O) will rise after annealed at temperature range of 200–500 °C. After annealed at 450–500 °C the main absorption bands in S1 sample are 834 cm⁻¹, 825 cm⁻¹ and 889 cm⁻¹ (VO₂), in S2 is 825 cm⁻¹. Annealing of A-center in varied neutron irradiated CZ-Si is suggested to consist of two processes. The first is due to trapping of VO by O_i in low dose neutron irradiated CZ-Si (S1) and the second is due to capture the wandering vacancy by VO, etc, in high dose neutron irradiated CZ-Si (S2), the VO₂ plays an important role in the annealing of A-center. With the increase of the irradiation dose, the annealing behavior of A-center is changed.     

Design and realization of low profile dual-wideband monopole antenna incorporating a novel ohm (Ω) shaped DMS and semi-circular DGS for wireless applications

In this paper, a compact microstrip line fed dual-wideband printed monopole antenna (PMA) for wireless communication applications is presented. The proposed antenna consists of an asymmetric rectangular patch via a microstrip-fed line, an ohm (Ω) shaped DMS loaded at the rectangular patch, and dual semi-circular shaped DGS embedded in the partial rectangular ground plane. The combination of an ohm shaped DMS and two semi-circular DGS is used to broaden the bandwidth of the two bands and improve the return loss for the desired antenna. The measured 10 dB bandwidth for return loss are achieved to be 21.52% (3.40–4.22 GHz) and 47.32% (5–8.1 GHz) in the lower and upper band, respectively which covers the bandwidth requirements of 5.2/5.8 GHz WLAN and 3.5/5.5 GHz Wi-MAX application bands. Furthermore, the proposed antenna has a very simple planar structure and occupies a small area of only 621 mm² (23 mm × 27 mm). The proposed antenna has a desirable VSWR level, radiation pattern, radiation efficiency and gain characteristics which are suitable for wireless communication applications.     

基于IEEE1588的分布式柔性测压带系统设计

为了研发一套分布式翼面柔性测压带系统,实现以表面贴附的方式测量飞机翼面压力,同时满足大规模分散式的传感器节点数据的同步采集、实时传输和本地存储等功能,提出系统总体设计方案,提供了硬件设计方法和软件设计流程。测试了系统的各项性能,并进行系统性能评估。测试结果表明:该系统达到了预期的技术指标,符合测试平台的要求;该系统是通用的,可以将压力传感器换成其他类型的传感器,尤其对于需要大量传感器的测试环境,其提供了一种安装方便、扩展灵活、数据传输可靠的解决方案。     

Energy-efficient control in serial production lines: Modeling,analysis and improvement⋆

Control of production operations is one of the most cost-effective methods to improve energy efficiency in production lines. Although many research efforts have been devoted to utilizing production control to boost production energy efficiency, it is not clear how production dynamics change in reaction to the energy saving operations, which is important to capture energy saving opportunities. In this paper, an optimal energy saving control method based on N-policy is introduced to reduce the system energy consumption while only slightly decreasing productivity. A Markov chain model is established to interpret the dynamics of serial production lines with N-policy. The analytical formulas of production rate and energy consumption are derived. Then, an energy-efficient control model is formulated to balance the productivity and energy consumption. For two-machine production lines, the monotonicity property of the model is proved, and the analytical N-policy is derived. For longer production lines, an adaptive genetic algorithm is utilized to solve the energy-efficient control model. Case studies validate the effectiveness of the proposed optimal energy saving control method.     

The shortest period of coal spontaneous combustion on the basis of oxidative heat release intensity

It’s necessary to forecast the shortest spontaneous combustion period for preventing and controlling the coal spontaneous combustion. During the experimental process, a calculating model of the SSCP is established on the basis of the oxidative heat release intensity and thermal capacity at different temperatures. According to the basic parameters of spontaneous combustion, heat of water evaporation and gas desorption, the SSCPs of different coals are further predicted. Finally, this study analyzed the relationships of the SSCP and the judging indexes of the self-ignite tendency. The result shows that the SSCP non-linearly increases with the decrease of dynamic oxygen adsorption and increase of activation energy. Compared with the practical fire situation of mine, this reliable method can meet the actual requirement of mine production.     

园林铺地纹饰对空间文化氛围的强化

装饰图案是中国传统园林文化的精华,是独特的民俗文化符号,为能更全面的进行解读,以园林铺地纹饰为研究对象,在分析纹饰形制的基础上,对其与空间主题和文化氛围的关系进行了简析.认为他是园林构成元素中一个重要的研究对象,无论在样式和内涵上都具有独特的意义：他是造园设计中衬托、突出园景主题的重要手段,是对园林文化内涵的补充;同时也生动的反映了中国古人自然观和社会文化观的完美融合.     

基于因子分析法的中小制造企业成长性研究

研究中小制造企业成长性评价体系并分析各种影响因素的作用大小,对提升中小企业成长性及完善行业发展政策具有重要意义.文中以2011年前上市的30家中小制造型企业为例,运用因子分析法对企业成长进行了评价,并验证了这种评价方法对中小企业成长性的基本适用性.结果表明,该评价方法以广泛的财务指标为评价基础,具有较强的操作性,且能科学反映出我国中小企业的成长能力.文中最后根据对中小制造企业的实证研究结果对其成长性评价作了简单总结,并对现阶段我国中小制造企业的成长提出了建议措施.     

DPillar: Dual-port server interconnection network for large scale data centers

To meet the huge demands of computation power and storage space, a future data center may have to include up to millions of servers. The conventional hierarchical tree-based data center network architecture faces several challenges in scaling a data center to that size. Previous research effort has shown that a server-centric architecture, where servers are not only computation and storage workstations but also intermediate nodes relaying traffic for other servers, performs well in scaling a data center to a huge number of servers. This paper presents a server-centric data center network called DPillar, whose topology is inspired by the classic butterfly network. DPillar provides several nice properties and achieves the balance between topological scalability, network performance, and cost efficiency, which make it suitable for building large scale future data centers. Using only commodity hardware, a DPillar network can easily accommodate millions of servers. The structure of a DPillar network is symmetric so that any network bottleneck is eliminated at the architectural level. With each server having only two ports, DPillar is able to provide the bandwidth to support communication intensive distributed applications. This paper studies the interconnection features of DPillar, how to compute routes in DPillar, and how to forward packets in DPillar. Extensive simulation experiments have been performed to evaluate the performance of DPillar. The results show that DPillar performs well even in the presence of a large number of server and switch failures.     

不完备CBR系统中属性权值计算方法研究

对于特征属性值存在缺失的CBR(Case-Based Reasoning)信息系统,使用经典粗糙集理论无法进行权值计算;同时,在CBR系统的实际应用中,计算属性的权值应避免出现结果为0的情况;首先分析了容差关系模型下使用条件熵进行权值计算的方法,然后根据属性值是否缺失分析各属性对整个系统的重要度,综合两种方法的优点,提出了一种新的权值计算方法,提高了权值计算的精确性和严谨性;将该权值计算方法应用于飞机故障诊断专家系统中,取得了满意的结果,验证了其可行性。