板式换热器中蒸汽凝结换热特性

在板式换热器的蒸汽凝结换热试验台上进行了实验研究,获取蒸汽完全凝结和部分凝结两种典型工况下的换热和压降特性．且就板式换热器中蒸汽凝结过程的换热进行分析和处理,得到了一个在板片槽道中蒸汽凝结换热系数关联式．并推荐用于板式换热器的蒸汽凝结换热系数的计算．     

目标定位的分布式MIMO雷达资源分配算法

为了提高分布式多输入多输出(multiple input multiple output,MIMO)雷达的目标定位精度,分析了阵元、发射功率和信号带宽对定位精度的影响,进而提出一种将三者联合优化的资源分配算法。首先,以最小化目标的平方位置误差下限(squared position error bound,SPEB)为目标函数,建立了包含阵元、功率和带宽3个变量的优化模型;然后,通过推导最优功率分配矢量和带宽分配矢量的关系简化模型;最后利用凸松弛和循环最小化算法将优化问题转化成二阶锥形式,求解得到最优的资源分配策略。仿真结果表明,利用所提出的算法进行资源分配能明显提高目标的定位精度;信号有效带宽对目标定位精度的影响大于发射功率。     

基于反演滑模和扩张观测器的带角度约束制导律设计

针对水下动能武器末制导段攻击机动目标,为获得最佳的毁伤效果,结合反演滑模控制方法与线性扩张状态观测器理论,设计了一种带角度约束的非线性制导律。通过对攻击角度的分析,设计了非线性滑模面,并根据滑模面可达条件,将制导律分为两部分设计,既满足了系统能够到达滑模面,又保持了系统状态在滑模面上运动。通过反演变结构获得的制导律,既保证了系统稳定,又具有了滑模控制理论所具有的鲁棒性。考虑到目标机动,将目标机动作为未知扰动,并对该扰动采用线性扩张状态观测器进行估计。该制导律作用下,视线角变化率收敛到零,攻击角度收敛到期望值,实现攻击角度约束。理论证实了制导系统的稳定性,仿真验证了本文所设计制导律的有效性。     

黄大铁路黄河特大桥顶推施工分析与监控技术

针对黄大铁路黄河特大桥连续钢桁梁多点同步顶推施工,利用倒拆法建模计算顶推施工全过程,找出主桁杆件在支点处的最大应力值以及导梁悬臂端变形规律和最大变形值,确定出全过程施工中的最不利工况为M2工况;设置变形监测点,监控导梁前段竖向位移变形,实测值基本与理论值吻合,施工线形可控;在M2工况中,将主桁和导梁自重荷载乘以1.35的放大系数,计算主梁在导梁悬臂140m,悬臂160m和导梁上墩20m后的主桁杆件的应力值,并在主桁上设置24个监测点监测杆件应力值,对比发现实测值均略小于理论值,施工过程中材料强度储备是安全可靠的。作为国内最大跨度的平行弦桁架桥顶推成功,对其他同类大跨度桥梁顶推施工具有较高的参考价值。     

NaOH改性花生壳去除水中亚甲基蓝的吸附特性研究

利用亚甲基蓝水溶液进行实验,测定了NaOH改性处理的花生壳对其的吸附能力.运用单因素实验方法,探讨了改性花生壳的物理化学特性、吸附时间、吸附剂添加量、pH值、温度和离子强度等因素对吸附性能的影响以及等温吸附过程.结果表明,改性能够提高吸附剂的吸附效果.在低温碱性条件下,改性花生壳粉投加量为0.6 g·L~(-1),吸附时间为1 h时,亚甲基蓝的去除率可达94.43%,饱和吸附容量为294.12 mg·g~(-1),等温吸附过程遵循Langmuir方程.     

Melatonin and mitochondrial function during ischemia/reperfusion injury

Ischemia/reperfusion (IR) injury occurs in many organs and tissues, and contributes to morbidity and mortality worldwide. Melatonin, an endogenously produced indolamine, provides a strong defense against IR injury. Mitochondrion, an organelle for ATP production and a decider for cell fate, has been validated to be a crucial target for melatonin to exert its protection against IR injury. In this review, we first clarify the mechanisms underlying mitochondrial dysfunction during IR and melatonin’s protection of mitochondria under this condition. Thereafter, special focus is placed on the protective actions of melatonin against IR injury in brain, heart, liver, and others. Finally, we explore several potential future directions of research in this area. Collectively, the information compiled here will serve as a comprehensive reference for the actions of melatonin in IR injury identified to date and will hopefully aid in the design of future research and increase the potential of melatonin as a therapeutic agent.     

<Emphasis Type="Italic">Yersinia pseudotuberculosis</Emphasis> supports Th17 differentiation and limits de novo regulatory T cell induction by directly interfering with T cell receptor signaling

Adaptive immunity critically contributes to control acute infection with enteropathogenic Yersinia pseudotuberculosis; however, the role of CD4⁺ T cell subsets in establishing infection and allowing pathogen persistence remains elusive. Here, we assessed the modulatory capacity of Y. pseudotuberculosis on CD4⁺ T cell differentiation. Using in vivo assays, we report that infection with Y. pseudotuberculosis resulted in enhanced priming of IL-17-producing T cells (Th17 cells), whereas induction of Foxp3⁺ regulatory T cells (Tregs) was severely disrupted in gut-draining mesenteric lymph nodes (mLNs), in line with altered frequencies of tolerogenic and proinflammatory dendritic cell (DC) subsets within mLNs. Additionally, by using a DC-free in vitro system, we could demonstrate that Y. pseudotuberculosis can directly modulate T cell receptor (TCR) downstream signaling within naïve CD4⁺ T cells and Tregs via injection of effector molecules through the type III secretion system, thereby affecting their functional properties. Importantly, modulation of naïve CD4⁺ T cells by Y. pseudotuberculosis resulted in an enhanced Th17 differentiation and decreased induction of Foxp3⁺ Tregs in vitro. These findings shed light to the adjustment of the Th17-Treg axis in response to acute Y. pseudotuberculosis infection and highlight the direct modulation of CD4⁺ T cell subsets by altering their TCR downstream signaling.     

基于园林卓越人才培养的观赏植物组织培养课程实践改革

以园林专业卓越人才培养为目标,提出教学过程以应用与创新为导向,更新教学内容体系,探索引入项目式教学形式,调整考核方法.改革后的课程体系侧重学生实践动手能力与创新能力的培养,学生的学习主动性显著提高,在学生中反馈效果好,教学效果显著.     

基于条件蒙特卡罗方法的信用违约互换合约定价

多标的资产违约相关性结构的度量及其联合违约时间的模拟是信用违约互换合约定价的关键.Copula函数和蒙特卡罗模拟是解决此关键问题的有力工具,被广泛应用于信用衍生品定价.本文基于因子t-copula模型,结合条件蒙特卡罗模拟,构建了计算第7n次信用违约互换合约的条件蒙特卡罗算法.该算法能够捕捉多标的资产违约的尾部相关性,更准确地度量标的资产组合的违约风险及提高违约事件的模拟效率.数值结果表明,在考虑尾部相关性的情形下,采用重要抽样技术的JK算法和改进的JK算法是不稳定的,不能达到减方差的目的;而本文新构建的定价算法更稳定,在高斯copula和t-copula模型下,都能够有效减小估计量的方差,提高信用违约互换合约的定价精度和可靠性.     

灰色关联度在甜高粱材料筛选中的应用

对甘肃省兰州市榆中县中试基地种植的11种甜高粱材料进行试验,以筛选出适合在兰州榆中地区种植的甜高粱材料。采用灰色关联度对材料的茎干鲜重、生物产量、茎杆平均含糖量进行分析,同时参考株高、穗长、穗颈长、物候期等指标,选定适合榆中地区不同用途的甜高粱材料。灰色关联度分析结果:茎秆鲜重、生物产量、茎秆平均含糖量三个指标中,茎秆平均含糖量灰色关联度最大,对结果影响最大;灰色综合评判排序显示08-2、2043、09-1、雅津43号分别排列前4位。08-2、2043、09-1、雅津43号综合表现最好,适合兰州榆中地区种植,可用于饲料生产和生物质能源储备种植。