Study on Hydrogen Storage Properties,Anti-Oxide Ability and Rate Limiting Step of ZrCr-Based Alloy after Introducing Cobalt as Additive

In this work,the microstructure,hydrogen storage properties,anti-oxide ability and rate limiting step of Zr(Cr_(1−x)Co_(x))_(2)(x=0,0.2,0.4 and 0.6)alloys have been investigated.After studying the crystal structure,we found that all alloy samples could show C14-type phase but the alloy sample x=0 could also show a small amount of Cr phase.Rietveld fitting showed that lattice parameter and unit cell volume of C14-type phase decreased with increasing x.After further research,it was clear that the first hydrogen absorption capacity decreased with increasing x.But introducing more Co content had a positive influence on the effective hydrogen storage capacity and cyclic hydrogen absorption and desorption properties of the alloy sample.We also found that adding Co to ZrCr_(2)alloy could improve its anti-oxide ability.In addition to this,the rate limiting step model was also studied.

Capillary flow rate limitation in asymmetry open channel

Abstract This paper focuses on the stability of capillary forced flow. In space, open capillary channels are widely used as the liquid and gas separation devices to manage liquid positioning and transportation. Surface collapse happens when the flow rate exceeds the critical value, leading to a failure of propellant management. Knowledge of flow rate limitation is of great significance in design and optimization of propellant management devices （PMDs）. However, the capillary flow rate limitation in an asymmetry channel has not been studied yet in the literature. In this paper, by introducing an equivalent angle to convert the asymmetry corner to a symmetry one, the one-dimensional theoretical model is developed. The flow rate limitation can then be investigated as a function of the channel geometry as well as liquid property based on the model. Comparisons between the asymmetry and symmetry channels bring forth the characteristics of the two kinds of channels, and demonstrate good accordance between the new advanced model and the existing one in the literature. This theoretical model can provide valuable reference for PMD designers.

Flow rate limitation in open wedge channel under microgravity

A study of flow rate limitation in an open wedge channel is reported in this paper. Under microgravity condition, the flow is controlled by the convection and the viscosity in the channel as well as the curvature of the liquid free surface. A maximum flow rate is achieved when the curvature cannot balance the pressure difference leading to a collapse of the free surface. A 1-dimensional theoretical model is used to predict the critical flow rate and calculate the shape of the free surface. Computa- tional Fluid Dynamics tool is also used to simulate the phenomenon. Results show that the 1-dimensional model overestimates the critical flow rate because extra pressure loss is not included in the governing equation. Good agreement is found in 3-dim- ensional simulation results. Parametric study with different wedge angles and channel lengths show that the critical flow rate increases with increasing the cross section area; and decreases with increasing the channel length. The work in this paper can help understand the surface collapsing without gravity and for the design in propellant management devices in satellite tanks.

Passive Q-Switching of a Yb:LuVO_4 Laser with Cr^(4+):YAG:Approaching the Intrinsic Upper Limit of Repetition Rate

We demonstrate a diode pumped Yb：LuVO4 laser that can be passively Q-switched by a Cr^（4＋）：YAG saturable absorber having an initial transmission as high as 99.3%.A maximum pulsed output power of 2.35 W is generated at a repetition rate of 285.7 kHz,approaching or very near the intrinsic upper limit imposed by the recovery time of the Cr^（4＋）：YAG saturable absorber,and the resulting pulse energy,duration and peak power are,respectively,8.2μJ,39.2ns and 0.209kW.

A NOTE ON EXACT CONVERGENCE RATE IN THE LOCAL LIMIT THEOREM FOR A LATTICE BRANCHING RANDOM WALK

Consider a branching random walk, where the underlying branching mechanism is governed by a Galton-Watson process and the moving law of particles by a discrete random variable on the integer lattice Z. Denote by Zn（z） the number of particles in the n-th generation in the model for each z ∈ Z. We derive the exact convergence rate in the local limit theorem for Zn（z） assuming a condition like ＂EN（logN）1＋λ 〈 ∞＂ for the offspring distribution and a finite moment condition on the motion law. This complements the known results for the strongly non-lattice branching random walk on the real line and for the simple symmetric branching random walk on the integer lattice.

Nonlinear instability suppression of closed-loop pilot-vehicle system with rate-limiting actuator based on anti-windup compensation

To solve the flight safety problem caused by nonlinear instabilities（category II pilot induced oscillations, PIOs） of the closed-loop pilot-vehicle system with rate-limiting actuator, the antiwindup（AW） compensation method to avoid category II PIOs is investigated. Firstly, the AW compensation method originally used for controlling input magnitude limited system is introduced, then this method is extended for controlling input rate-limiting system through a circle criterion theorem. Secondly, the establishment of the AW compensator is transformed into the solving of linear matrix inequalities. Finally, an AW compensator establishment algorithm for the closed-loop pilot-vehicle system with the rate-limiting actuator is obtained. The effectiveness of the AW compensation method to avoid category II PIOs is validated by time-domain simulations,and compared with rate-limited feedback（RLF） command rate compensation method. The results show that the AW compensation method can effectively suppress category II PIOs and maintain the nominal performance when the closed-loop pilot-vehicle system is normal. Unlike the command rate compensator which works upon system uninterruptedly, the AW compensation method affects the closed-loop pilot-vehicle system only when the rate-limiting of actuator is activated, so it is a novel PIO avoidance method.

RATE OF CONVERGENCE AND EXPANSION OF RNYI ENTROPIC CENTRAL LIMIT THEOREM

We obtain the expansion of Renyi divergence of order α （0 〈 α 〈 1） between the normalized sum of IID continuous random variables and the Caussian limit under minimal moment conditions via Edgeworth-type expansion. The rate is faster than that of Shannon case, which can be used to improve the rate of convergence in total variance norm.

ON THE RATES OF CONVERGENCE IN THE CENTRAL LIMIT THEOREM FOR TWO－PARAMETER MARTINGALE DIFFERENCES

In this paper we obtain the uniform bounds on the rate of convergence in the central limit theorem (CLT) for a class of two-parameter martingale difference sequences under certain conditions.

A STUDY OF HIGH FRAME RATE ULTRASONIC IMAGING WITH LIMITED DIFFRACTION BEAMS

Objective To investigate a new class of solutions to the isotropic/homogeneous scalar wave equation, which termed limited diffraction beams and realize ultrasonic 3D imaging. Methods Limited diffraction beams were derived. We performed the study of 3D pulse echo imaging with limited diffraction array beam. To obtain high frame rate images, a single plane wave pulse (broadband) was transmitted with the arrays. Echoes received with the same arrays were processed with Fourier method to construct 3D images. Results Compared with traditional pulse echo imaging, this method has a larger depth of field, high frame rate, and high signal to noise ratio. Conclusion The new method has prospect of high frame rate 3D imaging. In addition, the imaging system based this method is easily implemented and has high quality image.

高应变率下不同初始相变温度NiTi合金的力学响应

为获得高应变率下不同初始相变温度NiTi合金的屈服应力等基本物理特性和力学响应规律,采用10^(−3)s^(−1)应变率下准静态压缩与拉伸、10^(5)s^(−1)应变率下准等熵压缩及10^(7)s^(−1)应变率下冲击加载实现跨量级的不同应变率加载,高应变率加载实验中通过控制样品初始温度实现不同初始相态NiTi合金的力学响应测量。结果显示,初始马氏体相和初始奥氏体相NiTi合金的准静态加载应力-应变曲线中均出现2次模量变化,初始马氏体相中的模量变化由晶体重定向和马氏体相塑性变形引起,初始奥氏体相中的模量变化由马氏体相变和相变后塑性变形引起。准等熵加载下,初始马氏体相NiTi合金的Lagrangian声速随粒子速度增大而增大,未观察到间断等非线性变化;而初始奥氏体相中声速曲线存在间断,声速由初始横波值间断减小至体波声速后再随粒子速度线性增大。冲击实验中,初始马氏体相NiTi合金后自由面速度约34 m/s处出现双波结构,而将样品初始温度升至402 K后再冲击加载,则在约100 m/s处出现双波结构,二者速度曲线拐点分别由马氏体相弹塑性屈服和奥氏体相塑性屈服引起;在初始奥氏体相NiTi合金冲击实验中,在样品后自由面速度达到220~260 m/s时才出现显著的奥氏体相弹塑性转变。随着应变率从约105 s^(−1)升高至10^(7) s^(−1),相同组分奥氏体相NiTi合金的弹性极限由约2 GPa增大至约4 GPa,10^(7) s^(−1)应变率下,随着初始样品温度升至402 K,弹性极限降至1.7 GPa,表明NiTi合金的弹性极限存在显著的温度和应变率效应。

考虑填充墙的RC框架结构性能指标限值确定方法

填充墙钢筋混凝土(RC)框架结构是我国应用最为广泛的结构形式之一,而我国规范中给出的此类结构性能指标限值并未充分考虑填充墙对整体结构破坏状态的影响。遵循我国规范中对结构破坏状态的定义原则,提出基于构件破坏率的填充墙RC框架结构性能指标限值确定方法,为此类结构破坏状态与工程需求参数对应关系的研究提供新的思路。以典型结构为例建立数值分析模型,采用该文方法计算考虑填充墙的RC框架结构性能指标限值,并与不考虑填充墙的“纯框架”限值进行了对比分析。相较于“纯框架指标”,该文指标完好、轻微破坏、中等破坏和严重破坏四个破坏状态的层间位移角上限值均更小,其中,完好状态的上限值为1/832,远小于规范中规定的弹性层间位移角限值1/550,说明判定填充墙RC框架结构的破坏状态时,直接应用规范限值会低估结构的破坏程度。

城镇化水平对投资率的影响研究

我国城镇化进入了减速期,未来城镇化水平提升空间有限,在城镇化与投资互为因果的情况下,如何维持合理的城镇化水平和投资率具有重要研究意义。建立城镇化率与投资率的理论模型,选择42个国家1980—2022年的面板数据,并引入杠杆率作为调节变量,研究城镇化率与投资率的关系,结果发现:(1)城镇化率与投资率之间存在显著的倒U型关系,在老龄化国家更为显著;(2)杠杆率是影响城镇化率与投资率之间倒U型关系的调节变量,在低杠杆和高杠杆、政府部门和非金融企业部门都十分显著。进一步提出中国城镇化率的上限在80%左右、投资率的下限在20%左右的政策建议,同时发挥杠杆率的调节作用,推进以人为核心的新型城镇化。

白藜芦醇可调控运动性疲劳大鼠的糖异生

背景:白藜芦醇是从植物中提取而来的天然抗氧化剂,其改善运动性疲劳的机制主要集中在氧化应激和炎症反应的保护作用上,此次研究主要从糖异生角度探讨其对运动性疲劳的保护机制。目的:探讨白藜芦醇对运动性疲劳大鼠糖异生的影响。方法:SD雄性大鼠适应性训练1周后随机分为4组,即空白对照组、白藜芦醇组、运动组、白藜芦醇+运动组,每组12只。空白对照组和白藜芦醇组正常饲养,不进行游泳训练;白藜芦醇+运动组和运动组采用负重游泳训练模拟长时间中高强度运动,每天负重5%游泳1 h后,分别灌胃50 mg/kg的白藜芦醇溶液或等体积的二甲基亚砜溶剂,每周6 d,共6周。末次运动后24 h取材,试剂盒检测尿素氮、肌酸激酶、血糖、肝糖原以及肝脏组织中乳酸、丙酮酸水平;微量法检测磷酸烯醇式丙酮酸羧激酶活性,酶联免疫吸附法检测葡萄糖-6-磷酸酶活性;RT-PCR检测SIRT1、CREB和PGC-1α的基因表达水平。结果与结论:①运动组大鼠血浆尿素氮和肌酸激酶水平明显升高(均P<0.05),肝脏乳酸、丙酮酸水平和乳酸/丙酮酸比值明显升高(均P<0.01),血糖和肝糖原水平明显降低(均P<0.01);补充白藜芦醇可有效改善以上情况;②运动使大鼠肝脏组织糖异生关键酶磷酸烯醇式丙酮酸羧激酶和葡萄糖-6-磷酸酶的活性明显降低(P<0.01,P<0.05),补充白藜芦醇可明显提高磷酸烯醇式丙酮酸羧激酶活性(P<0.01);③运动组肝脏组织SIRT1、CREB和PGC-1α的mRNA表达水平明显降低(均P<0.01),补充白藜芦醇可使该通路基因表达水平明显升高;④提示白藜芦醇能缓解长时间中高强度运动导致的运动性疲劳,其机制可能与上调糖异生调控通路、提高限速酶活性、促进肝脏糖异生、升高血糖和肝糖原水平有关。

某医院2019—2022年麻醉药品使用情况分析

目的对某医院2019—2022年麻醉药品使用情况进行分析,以期加强麻醉药品的规范管理,保障麻醉药品在临床中合理使用。方法调取该医院信息系统中2019—2022年麻醉药品的使用数据,包括药品的名称、规格、数量、使用金额,计算各品规销售金额占比、用药频率(DDDs)、限定日费用(DDC)、使用金额排序与DDDs的排序比(B/A)。并对2019—2022年该医院麻醉药品的处方点评结果进行汇总分析。结果4年间,该院麻醉药品共使用18个品规;使用金额总体呈增长趋势,且每种麻醉药品的使用金额每年排序相对稳定;DDDs稳居前三位的是吗啡缓释片(30 mg)、芬太尼贴剂(8.4 mg)和芬太尼贴剂(4.2 mg);DDC相对稳定,前3名分别是羟考酮注射液、注射用瑞芬太尼(1 mg)和注射用瑞芬太尼(2 mg);所有麻醉药品的B/A处于0.1~3.5之间。该院麻醉药品处方医嘱点评合格率在97%以上。结论该院麻醉药品的临床使用基本合理,用药符合医院学科特色,能够全面、认真地贯彻并落实麻醉药品相关法律法规,符合麻醉药品的安全性、有效性、经济性和适宜性原则。

产鲨烯重组大肠杆菌的构建及发酵研究

鲨烯是一种在食品、医药等行业有着广泛应用的三萜类化合物。大肠杆菌被认为是非常有潜力的合成鲨烯的底盘细胞。为提高大肠杆菌内鲨烯的合成水平,以三个诱导型启动子p3-lac、p6-lac、p10-lac强度为水平,以dxs、idi、ispA三个4-磷酸甲基赤藓糖醇途径(methylerythritol 4-phosphate pathway,MEP)的限速酶基因作为因素,进行正交设计,同时引入鲨烯合酶基因,构建了9株重组菌株进行鲨烯发酵实验。通过绿色荧光蛋白表达水平确定了p3-lac启动子强度相对最强,p10-lac相对最弱。通过分析正交发酵实验数据的极差,发现dxs是影响鲨烯产量最主要的因素,其次是ispA,最后是idi,且三个因素最佳水平组合所对应的菌株为1063/DE3,产量达到了450 mg/L。最终获得了一株鲨烯产量相较于出发菌株提高了681倍的产鲨烯重组大肠杆菌菌株,并为提高大肠杆菌内鲨烯产量提供了新的策略。

水库黄土岸坡塌岸预测模型及参数敏感性研究

塌岸宽度预测是水电工程重要研究问题之一。现有的经验图解法基于塌岸最终稳定坡形进行塌岸宽度预测,难以反映塌岸的过程、特征,且对岸坡岩土体的物理力学性质考虑也较少。基于此,研究提出了基于极限平衡理论的黄土岸坡塌岸宽度预测模型,确定了模型关键参数取值,并对参数敏感性进行了分析。结果显示,基于极限平衡理论进行预测塌岸宽度时应选取合理的水下堆积系数,水下堆积系数随岸坡高度和水深的增加而增加。而岸坡角度对塌岸宽度的影响较小,且主要影响首次塌岸宽度,对后续塌岸宽度的影响不大。随着岸坡坡度的增大,塌岸宽度呈波动上升趋势。同时,塌岸参数敏感性分析结果显示,参数敏感性排序由大到小依次为岸坡高度、水下岸坡内摩擦角、水下岸坡黏聚力、水上岸坡重度、水深与岸高比、水上岸坡黏聚力、岸坡坡度、水上岸坡内摩擦角、水下岸坡重度,这与岸坡稳定性的参数敏感性分析结果基本一致。研究结果对黄土岸坡塌岸宽度预测具有重要意义。

降低社保缴费基数下限对城镇职工基本养老保险基金可持续性的影响研究

近年来,我国面临社会保险缴费负担较重和基金收支失衡的双重压力。以重庆发布的《关于调整城镇职工社会保险缴费基数下限的通知》中“将社保缴费基数下限从社会平均工资的60%下调至40%”的规定为切入点,基于31个省份2010—2014年的面板数据,采用合成控制法评估降低社保缴费基数下限对城镇职工基本养老保险征缴率的影响,并借助精算模型分析这一政策对该保险基金可持续性的影响发现:降低社保缴费基数下限可使城镇职工基本养老保险征缴率提高8个百分点;与未降低社保缴费基数下限的情况相比,降低社保缴费基数下限扩大了城镇职工基本养老保险基金的收入规模,基金累计赤字的时点向后推迟4年;降低社保缴费基数下限使2055年累计赤字规模减少6.53%,基金支付压力得以缓解。建议建立科学、公平、合理的缴费基数动态调整机制与弹性缴费机制,为提升税务机关和社保经办机构在扩面、征缴、监管过程中的效率和能力提供更多支持,进一步健全社保基金保值增值和安全监管体系。

新疆难解吸煤可溶有机质对瓦斯吸附解吸特征的影响研究

新疆焦煤公司煤层瓦斯难解吸,导致抽采难度增大。而煤中可溶有机质对瓦斯的吸附解吸有重要影响。为了研究其影响,使用四氢呋喃对煤中的可溶有机质进行抽提,采用低温氮吸附测试抽提前后煤的孔隙结构,利用煤岩高压瓦斯吸附装置进行抽提前后煤样的吸附解吸实验。研究结果表明:经过四氢呋喃抽提后,发现所有煤样的平均孔径、孔体积和比表面积均有不同程度的增大,认为煤中的可溶有机质被溶解,形成了新的微孔,同时原孔隙被扩大;4^(#)煤、5^(#)煤和6^(#)煤的吸附常数a分别减小了2.73%、16.09%、14.57%,4^(#)煤和5^(#)煤吸附常数b分别增大了12.18%、2.58%,6^(#)煤的吸附常数b减小了8.59%,煤的吸附能力降低,解吸速度增大,可溶有机质促进了煤对瓦斯的吸附。

菌剂添加条件下通风量对食品废弃物好氧发酵过程的影响

通风量是影响食品废弃物好氧发酵产物质量且关系过程成败的重要制约因素。本文通过调整发酵过程中的通风量,控制食品废弃物中油脂的降解与有机酸的产生和累积,实现发酵过程的有限酸化,不仅可减少NH_(3)挥发与流失,还可提高发酵产物的质量。研究结果表明,随着通风量增大,发酵物料的峰温度升高,但高温期缩短,有机质降解率和腐熟度先升高后降低,当通风量为0.2L/(L·min)时,发酵效果较佳。通风量越大,NH_(3)累积挥发量越低。通风量为0.1L/(L·min)时,高温期较长,不利于硝化微生物的生长繁殖,NH_(3)排放量最大。通风量为0.3L/(L·min)时,高温期最短,同时水分散失严重,有机物降解不彻底,NH_(3)挥发量也最低。与未添加自制除油微生物菌剂(ORMI)相比,接种ORMI可以有效促进食品废弃物好氧发酵的效果,发酵结束时,油脂降解率、种子发芽指数和总养分含量分别提高了23.08%、29.48%和7.36%。通风量通过影响相关微生物活性及脂肪酶酶活促进油脂降解,减少氨的累积挥发量,最终有效提升发酵产物的腐熟度和总养分含量。

统计过程控制方法在放疗患者计划质控中的应用

目的运用统计过程控制(SPC)方法建立基于电子射野影像设备(Electronic Portal Imaging Device,EPID)在不同部位、不同放疗技术下使用3%/2mm和3%/3mm基准进行伽马分析的容差限值与干预限值。方法分别选取头颈部、胸部、腹部及其他部位的129例IMRT计划和89例VMAT计划使用EPID进行剂量验证,根据每个部位前20例患者计划的伽马通过率结果计算对应的容差限值与干预限值,绘制相应的单值控制图,实时监测各部位所有计划在不同测量基准下的伽马通过率。结果两种放疗技术在3%/3mm基准下,各部位的容差下限均大于97%,干预下限均接近于97%。3%/2mm基准下,各部位的容差下限均大于94%,干预下限均大于92%。结论SPC方法能够实时、有效的监测改进放疗患者计划质控流程,制定不同部位、不同放疗技术在不同测量基准下的个体化容差干预限值,降低失误风险,减少临床事故的发生。