摘要：To accelerate the development and design of magnesium(Mg)alloys,the structural and mechanical properties of important precipitates in Mg−Zn alloys were studied by experiments and density functional *** nano-indentation tests revealed that the hardness of the precipitates initially increased and then decreased with increasing Zn content,and was significantly higher than that of pure Mg and *** calculation results revealed that the precipitates stability initially increased and then decreased with increasing Zn *** bulk moduli of the precipitates increased,whereas their shear and Young’s moduli initially increased and then decreased with increasing Zn *** decreasing order of ductility for these compounds is MgZn_(2)>Mg_(21)Zn_(25)>Mg_(2)Zn_(11)>Mg_(4)Zn_(7).The surface profiles of the compounds revealed that they are obvious *** the degree of covalency and bond length of covalent bonds initially increased and then decreased with increasing Zn content.

摘要：A plasma injection ion source has been de-veloped for the photoelectron velocity imag-ing studies of metal-containing *** source employs a pulse discharge nozzle for generating a plasma beam that perpendicu-larly crosses the master supersonic jet beam from a home-made pulsed piezo *** discharge nozzle is designed for high voltage gas discharge with efficient metal sputtering of the cathode,and thus plays a role in met-al atom and ion *** jet-cooled anions can be produced in the master gas jet via reactions of the plasma *** source is integrated into a photoelectron ve-locity imaging *** mass spectrometry experiments show that the ion source can efficiently produce transition metal containing anions,such as FeO_(m)^(-),CuO_(m)^(-),CuC_(n)^(-),CuC_(n)O_(m)^(-).The photoelectron imaging results by photodetachment of O-show that the pho-toelectron energy resolution of the whole instrument isΔE/E≈2.3%,and the results of FeO^(-)indicate that internal temperatures of anions from the source could be efficiently cooled down.

摘要：采用响应面法在摇瓶水平对重组巴斯德毕赤酵母合成内切几丁质酶的培养基组分进行优化,并探讨重组内切几丁质酶降解几丁质的最佳反应条件。首先对培养基中显著影响内切几丁质酶活力的关键组分通过Plackett-Burman试验设计进行筛选;然后通过Box-Behnken试验设计和响应面法确定关键组分的最佳浓度。结果筛选出3个具有显著效应的关键组分为酵母膏、油酸和吐温-80,最佳浓度分别为:2.45%、0.17%和0.62%。优化后的最佳培养基组成为:2.45%酵母膏、2.00%蛋白胨、0.50%酵母氮碱(YNB)、0.50%甲醇、0.17%油酸、0.62%吐温-80和0.40%PTM1。在该培养基中,重组巴斯德毕赤酵母在摇瓶水平(25m L/250m L)发酵生产内切几丁质酶的活力高达92.26U/m L。重组内切几丁质酶催化几丁质降解的最佳反应条件为:粉末几丁质浓度为4%,p H和温度分别为7.0和30℃,反应时间为10h。研究结果为后期在发酵罐中大规模生产内切几丁质酶和几丁寡糖提供了基础。

摘要：青海省引黄济宁工程隧洞全长74.4 km,隧洞穿越4条区域活动性断裂。保证隧洞穿越活动性断裂的安全是引黄济宁工程面临的关键问题之一。首先，提出了各活动性断裂的基本参数，为针对性设计提供了依据。其次，以青海南山北缘断裂（F2）为例，采用数值模拟的方法，建立了隧洞穿越活动性断裂的弹塑性分析模型，研究了不同错动量下整体系衬砌和铰接衬砌的响应特征。结果表明：整体式衬砌条件下，隧洞的变形量、衬砌应力及内力均随错动量的增加而增加，左右边墙变形量、衬砌最大拉应力、剪力最大值出现在断裂带的中心部位，拱顶底板变形量、衬砌弯矩最大值出现在断裂带交接部位；铰接式衬砌条件下，隧洞不同部位的纵向应力、等效轴力、弯矩和剪力在断裂带错动量超过30 cm后，最大应力和内力没有表现出随错动量增加而增加的趋势，变形主要发生在铰接缝，有效改善了衬砌在错动条件下的受力状态。最后，提出了引黄济宁工程隧洞穿越活动性断裂下一步的研究方向。

摘要：现有双稳态抓手通常只有单一的抓取、锁定和释放目标物体的工作模式,限制了其应用的灵活性。为此,本文提出了一种基于可调双稳态机构的刚柔耦合多模态抓手。抓手的夹持表面为弹性带,通过带的包裹可以被动适应不同外形的抓取物。支持夹持表面的手指骨架为刚性连杆组成的可调双稳态机构,其通过弹性圈进行储能。抓手还具有一根由离合器控制的主动绳索,可对弹性带进行能量调节。通过协调控制双稳态机构和主动绳索可调节抓手的能量,抓手具有触发跳变关闭、可控抓取和物体弹射等不同工作模态。建立了抓手触发力的解析模型,并通过动力学仿真和实验对设计参数进行分析,优化选取了弹性元件的刚度和自由长度。在不同工作模态下进行了样机实验,实验结果表明从初始状态切换到触发状态时触发力的调节范围为0.1~1.1 N,对直径30 mm、质量10 g的圆柱体的水平弹射距离可达3.35 m。

摘要：河流交汇区是河网系统中水、沙、污染物、生物等环境要素的突变点,也是河网行洪与污染物输移扩散的关键控制节点。从野外测量、室内试验与数值模拟方面,总结分析了河流交汇区水流结构与污染物输移的基本特征及其在不同交汇条件作用下的响应规律,以及复杂水流结构与生境对于河流交汇区水安全的重要影响。展望了未来研究重点,建议加强非恒定流条件下的交汇区水力学特性研究,进一步揭示交汇区污染物掺混输移特征与水动力条件之间的响应机制,研究通过工程布局与水力优化调控相结合的措施系统提升了交汇区防洪安全与水生态环境质量。

摘要：用多点激振单点拾振的脉冲激励试验模态测试方法 ,对某涡喷发动机中介机匣的振动特性进行了模态分析 ,对比了模型机中介机匣与改型机中介机匣的振动模态 ,试验结果表明模型机中介机匣在结构设计方面存在薄弱环节 ,其结果为某涡喷发动机结构设计、振动故障分析提供了依据。

摘要：大电流加速器束管中,当带电粒子流通过束管时,会在束管中激励起高频场,为了降低对束流的影响,束管中产生的高次模需要利用阻尼器将高频场能量转换成热量并通过冷却装置导走。介绍了某混合型高次模阻尼器的研制及主要性能。阻尼器采用的吸收材料为铁氧体和碳化硅,吸收材料通过金属化和钎焊实现与金属基板的焊接。通过CST和COMSOL软件分别开展了微波性能仿真和热仿真,对阻尼器的结构进行了优化设计。阻尼器的测试结果表明:该混合型阻尼器的吸收效率与计算结果在1.7 GHz以下频段相接近,在1.7 GHz以上高频段后,仿真吸收效率高于实测结果,相差较大;真空漏率、极限真空、水路耐压均满足超导高频腔设计需求。

摘要：Ultrathin planar absorbers hold promise in solar energy systems because they can reduce the material, fabrication, and system cost. Here, we present a general strategy of effective medium design to realize ultrathin planar broadband absorbers. The absorber consists of two ultrathin absorbing dielectrics to design an effective absorbing medium, a transparent layer, and metallic substrate. Compared with previous studies, this strategy provides another dimension of freedom to enhance optical absorption; therefore, destructive interference can be realized over a broad spectrum. To demonstrate the power and simplicity of this strategy, we both experimentally and theoretically characterized an absorber with 5-nm-thick Ge, 10-nm-thick Ti, and 50-nm-thick SiO2 films coated on an Ag substrate fabricated using simple deposition methods. Absorptivity higher than 80% was achieved in 15-nm-thick （1/50 of the center wavelength） Ge and Ti films from 400 nm to near 1 btm. As an application example, we experimentally demonstrated that the absorber exhibited a normal solar absorptivity of 0.8 with a normal emittance of 0.1 at 500 ~C, thus demonstrating its potential in solar thermal systems. The effective medium design strategy is general and allows material versatility, suggesting possible applications in real-time optical manipulation using dynamic materials.

摘要：针对混沌电力系统可能导致相角发散、电压崩溃,严重的甚至导致停电等问题,提出了一种基于混合脉冲控制的混沌双机互联电力系统有限时间稳定控制策略。在混沌双机互联电力系统中,给出其有限时间稳定的混合脉冲控制设计,用混合脉冲控制能使其在有限时间内进入稳定运行状态。最后,通过仿真实验验证了所用方法及所提控制策略的有效性与正确性。