采用交变脉冲电源单元的隔离型多输入直流变换器

多输入直流变换器(MIC)实现多种能源输入,可同时或分时向负载提供能量,具有优先利用能源、简化系统结构及降低系统成本等优点,因此适用于新能源联合供电系统。本文针对输入输出隔离场合,提出采用交变脉冲电源单元构建隔离型MIC的方法:根据交变脉冲电源单元组合规则推导出基本隔离型MIC,利用最大功率传输原则确定MIC的控制策略,通过分析开关管的开关时序对基本隔离型MIC进行简化,进而得到多种不同类型的简化隔离型MIC拓扑。本文将详细给出通过交变脉冲电源单元构建隔离型MIC的方法,并以将半桥三电平单元与全桥单元组合而成的双输入变换器为例,采用有效的能量管理策略实现两输入源的功率分配,最后通过一个1kW的原理样机验证理论分析的正确性。     

A modified hypervolume based expected improvement for multi-objective efficient global optimization method

The hypervolume indicator has been proved as an outstanding metric for the distribution of Pareto points, and the derived hypervolume based expected improvement (HVEI) has received a particular attention in the multi-objective efficient global optimization (EGO) method. However, the high computational cost has become the bottle neck which limits the application of HVEI on many objective optimization. Aiming at this problem, a modified version of HVEI (MHVEI) is proposed in this paper, which is easier to implement, maintains all the desired properties, and has a much lower computational cost. The theoretical study shows that the new criterion can be considered as a weighted integral form of HVEI, and it prefers the new point with a higher uncertainty compared with HVEI. The numerical tests show that the MHVEI performs similar as HVEI on the lower dimensional problem, and the advantage of MHVEI becomes more obvious as the dimension grows.     

In vitro degradation performance and biological response of a Mg-Zn-Zr alloy

The feasibility of a Mg-Zn-Zr alloy for biomedical applications was studied through microstructure characterization, corrosion tests in different biological media, and cell proliferation, differentiation and adhesion tests. Corrosion tests showed that the ZK60 alloy in the as-extruded state with finer grain sizes exhibited slower corrosion rates than the same alloy in the as-cast state. The tests in different biological fluids showed that the corrosion rates of the as-cast and as-extruded ZK60 alloy in DMEM + FBS were the highest, while those in Hank's solution were the lowest. The corrosion rate of the as-extruded ZK60 alloy was similar to the corrosion rates of other commercial magnesium alloys, namely the die-cast AZ91D, die-cast AM50, extruded AZ31 and extruded WE43 alloys. The results obtained from the indirect cytotoxicity evaluation showed that the 100% concentrated cast and extruded ZK60 alloy extracts resulted in significantly reduced cell numbers and total protein amounts, as compared to the negative control. The cell number and total protein amount increased with the gradual dilution of the extracts, but the protein normalized ALP activity showed an opposite trend. For the direct assay, L-929 and MG63 cells exhibited good adhesion with spread pseudopod on the surface of extruded ZK60 alloy samples after 24 h culture. In short, the as-extruded ZK60 alloy could be a good candidate material for biodegradable implants.     

Element differential method and its application in thermal‐mechanical problems

In this paper, a new numerical method, element differential method (EDM), is proposed for solving general thermal‐mechanical problems. The key point of the method is the direct differentiation of the shape functions of Lagrange isoparametric elements used to characterize the geometry and physical variables. A set of analytical expressions for computing the first‐ and second‐order partial derivatives of the shape functions with respect to global coordinates are derived. Based on these expressions, a new collocation method is proposed for establishing the system of equations, in which the equilibrium equations are collocated at nodes inside elements, and the traction equilibrium equations are collocated at interface nodes between elements and outer surface nodes of the problem. Attributed to the use of the Lagrange elements that can guarantee the variation of physical variables consistent through all elemental nodes, EDM has higher stability than the traditional collocation method. The other main features of EDM are that no mathematical or mechanical principles are required to set up the system of equations and no integrals are involved to form the coefficients of the system. A number of numerical examples of 2‐ and 3‐dimensional problems are given to demonstrate the correctness and efficiency of the proposed method.     

次高斯情形下随机三角级数的几个重要结论

利用重要不等式的研究方法，在∑n=0^∞xn^2〈∞这个条件下，对随机三角级数∑n=0^∞ξnxncos（nt＋Фn）（其中ξn是次正态随机变量序列）进行研究，得到了∑n=0^∞ξnxncos（nt＋Фn）几乎处处几乎必然收敛且此级数属于∩0〈p〈∞L^pa.s.的重要结论．     

Biocompatibility evaluation in vitro. Part III: Cytotoxicity expression of human and animal osteoblasts on the biomaterials

Ｂｉｏｃｏｍｐａｔｉｂｉｌｉｔｙａｓｓｅｓｓｍｅｎｔｏｆｉｍｐｌａｎｔｍａｔｅ ｒｉａｌｓｉｓｂａｓｅｄｏｎｉｎｖｉｔｒｏａｎｄｉｎｖｉｖｏａｐｐｒｏａｃｈ ｅｓ[1,2 ] .Ｄｉｓｓｏｌｕｔｉｏｎａｎｄｄｅｇｒａｄａｔｉｏｎｏｆｉｍｐｌａｎｔｍａｔｅｒｉａｌｓｉｎｂｏｄｙｆｌｕｉｄｓｍａｙｌｅａｄｔｏｌｏｃａｌｉｎｆｌａｍ ｍａｔｉｏｎ ,ｓｙｓｔｅｍｔｏｘｉｃｉｔｙ ,ｏｒａｌｌｅｒｇｉｃｒｅａｃｔｉｏｎ .Ｉｔｉｓｉｍｐｏｒｔａｎｔｔｈｅｒｅｆｏｒｅｔｏｅｖａｌｕａｔｅｔｈｅｔｏｘｉ ｃｉｔｙｏｆｔｈｅｉ…     

Implementation of Adaptive Fuzzy Control for a Real-Time Control Demo-Model

From 1995–1999 a R&D project on fuzzy control applications to the Belgian Reactor 1 (BR1) was conducted at the Belgian Nuclear Research Centre (SCK·CEN). Due to the safety regulations of the nuclear reactor, it is not realistic to perform many experiments at BR1. In this situation, part of the pre-processing experiments had to be carried outside the reactor (e.g., comparisons of different methods and the preliminary choices of the parameters). Therefore a water-level control system, referred to as a real-time control demo-model, was designed and constructed. In this paper, the construction of the demo-model and related hardware aspects is firstly outlined, then the results of a fuzzy control (Mamdani-type) and an adaptive fuzzy control are presented. The adaptive fuzzy control is a fuzzy control with an adaptive function that can self-regulate the fuzzy control rules. Finally, an implementation of a computer simulation is introduced with an adaptive fuzzy control for this real-time control demo-model.     

In vitro and in vivo studies on Ti-based bulk metallic glass as potential dental implant material

In this study, a high glass forming system, Ti41.5Zr2.5Hf5Cu37.5Ni7.5Si1Sn5 (TZHCNSS) bulk metallic glass (BMG), is studied in terms of microstructure, surface analysis, mechanical properties, corrosion resistance, in vitro cytotoxicity and in vivo biocompatibility. It is found that the as-prepared TZHCNSS samples are fully amorphous by XRD and TEM observations, as well as DSC curve. Comparing with pure Ti, TZHCNSS BMG shows superior mechanical properties with higher hardness and better wear resistance. Due to the oxide film formed on its surface, TZHCNSS BMG shows great corrosion resistance close to pure Ti in electrochemical measurements. The pitting corrosion potential in artificial saliva solution is much higher than that in SBF solution. The indirect and direct cytotoxicity results show that TZHCNSS extracts had obvious low cell viability on both L929 and NIH3T3 cells. However, the in vivo testing results proved that TZHCNSS BMG could integrate with bone tissue, showing excellent osseointegration.     

回路管道的缺陷分析

在意大利引进的回路组装过程中，发现一条回路试验段出口处管道的内壁有微裂纹，该回路在意大利已运行过７０００小时。为弄清裂纹的性能及来源而进行本试验。试验通过宏观、微观检测，化学成分分析，夹杂物性质分析，力学性能复验等，提示出初始缺陷形成于材料成型中，在使用中逐渐扩展成裂纹。     

型钢混凝土粘结性能试验研究

根据对型钢(角钢)埋入混凝土试件中进行的一系列抗拔破坏试验,研究了在轴拉荷载作用下角钢与混凝土之间的粘结应力分布情况,分析了角钢与混凝土之间的粘结性能,得出了辅助锚固对角钢的抗拔承载力的影响,给出了可供参考的角钢最小锚固长度的计算公式.