科创中国

地下水数值模拟是目前定量研究地下水的重要手段.分析了数值法求解地下水流数学模型的基本步骤,对于采用试估一校正法进行模型识别率定和验证过程中,在遵循模型的识别率定和验证的基本要求和四个基本原则基础上,对于如何评价模型率定和验证的效果、定量分析模型精度、以及达到模型可实际应用的要求,总结众多地下水数值模型调试的经验,提出了地下水数值模型识别率定和验证的定量评价标准.

等级医院评审标准为医院管理带来了新的理念.为适应评审标准的要求,达到评审的目的,护理部通过解读标准、强化培训、反复自查整改等措施,逐步使各级人员落实标准的意识不断增强,各项工作的落实更加规范,持续质量改进的理念不断强化,逐步形成了按照标准良性运行的有效机制.

Several typical flexible pneumatic actuators(FPA) and different mechanical models describing their behaviors have been proposed, however, it is difficult to balance compliance and load capacity in conventional designs, and these models still have limitations in predicting behavior of FPAs. A new flexible pneumatic bending joint(FPBJ) with special anisotropic rigidity structure is proposed. The FPBJ is developed as an improvement with regard to existing types of FPA, and its principal characteristic is derived from the special anisotropic rigidity structure. With this structure, the load capacity in the direction perpendicular to bending plane is strengthened. The structure of the new FPBJ is explained and a mathematical model is derived based on Euler-Bernoulli beam model and Hook's law. To obtain optimum design and usage, some key structure parameters and input-output characteristics are simulated. The simulation results reveal that the relationship between the structure parameters and FPBJ's bending angle is nonlinear. At last, according to the simulation results, the FPBJ is manufactured with optional parameters and tested. The experimental results show that the joint's statics characteristics are reflected by the mathematical model accurately when the FPBJ is deflated. The maximum relative error between simulation and experimental results is less than 6%. However, the model still has limitations. When the joint is inflated, the maximum relative error reaches 20%. This paper proposes a new flexible pneumatic bending joint which has sufficient load capacity and compliance, and the mathematical model provides theoretical guidance for the FPBJ's structure design.

报告1例变形综合征.患者男,42岁,具有偏侧肥大、巨趾、脊柱侧凸、线状表皮痣、淋巴管瘤等变形综合征的表现.文中对该病进行文献回顾性总结及对最新诊断标准进行讨论.

Most researches on transient fuel control of port fuel injection S.I. engine are carried out from the perspective of advanced mathematical theories. When it comes to practical control, there exist many limitations although they are more intelligent. In order to overcome the fuel wetting effect of PFI engine, the application-oriented transient fuel control is studied by analyzing the key parameters which are closely related with the engine transient characteristics. Both validity and simplicity are taken into consideration. Based on the fuel wall-wetting theory and popular fuel compensation strategy, short-term transient fuel(STF) and long-term transient fuel(LTF), as well as their individual decay approaches, are introduced. STF is to compensate the drastic fuel film loss caused by sudden throttle change, while the function of LTF is to compensate the fuel film loss by manifold air pressure(p) fluctuation. Each of them has their respective pros and cons. The engine fuel mass and air mass are also calculated for air-fuel ratio(AFR) according to ideal gas state equation and empirical equations. The vehicle acceleration test is designed for model validation. The engine experiences several mild and heavy accelerations corresponding to the gear change during vehicle acceleration. STF and LTF control are triggered reliably. The engine transient fuel control simulation adopts the same inputs as the test to ensure consistency. The logged test data are used to check the model output. The results show that the maximum fuel pulse width(FPW) error reaches 2 ms, and it only occurs under engine heavy acceleration condition. The average FPW error is 0.57 ms. The results of simulation and test are close overall, which indicates the accuracy of steady and transient fuel. The proposed research provides an efficient approach not only suitable for practical engineering application, but also for AFR prediction, fuel consumption calculation, and further studies on emission control.

水平衡测试是加强用水科学管理,最大限度地节约用水与合理用水的一项基础工作.解释了水平衡测试的定义及开展测试工作的依据,分析了水平衡测试参数之间关系,介绍了水平衡测试的方法,结合承德市中心医院水平衡测试实例,分析其用水现状,为制定用水定额和计划用水量指标,提供了较准确的基础数据,为今后节约用水提出了合理化的建议.

指出了快递企业在内件验视、快件代收、收件人验收等问题上的矛盾,分析了执行国家标准与考虑经济效率之间的博弈问题,认为两者之间是长远统一的,提出了快递公司兼顾经济效率与法律效力的解决方案.

标准普尔首开先河下调美国的主权信用评级,是美国经济持续衰退、国会债务上限讨论、恢复公司声誉、同行激烈竞争、监管政策变化等主客观因素综合作用的结果.标准普尔采取借话说事、预先警告、事先沟通、利用矛盾、瞅准时机等策略避免监管部门的制裁,以最少的代价取得了较好的效果,对维护公司声誉、敦促美国解决财政赤字和债务问题产生了重大的影响和作用.

Parallel kinematic machines have drawn considerable attention and have been widely used in some special fields.However,high precision is still one of the challenges when they are used for advanced machine tools.One of the main reasons is that the kinematic chains of parallel kinematic machines are composed of elongated links that can easily suffer deformations,especially at high speeds and under heavy loads.A 3-RRR parallel kinematic machine is taken as a study object for investigating its accuracy with the consideration of the deformations of its links during the motion process.Based on the dynamic model constructed by the Newton-Euler method,all the inertia loads and constraint forces of the links are computed and their deformations are derived.Then the kinematic errors of the machine are derived with the consideration of the deformations of the links.Through further derivation,the accuracy of the machine is given in a simple explicit expression,which will be helpful to increase the calculating speed.The accuracy of this machine when following a selected circle path is simulated.The influences of magnitude of the maximum acceleration and external loads on the running accuracy of the machine are investigated.The results show that the external loads will deteriorate the accuracy of the machine tremendously when their direction coincides with the direction of the worst stiffness of the machine.The proposed method provides a solution for predicting the running accuracy of the parallel kinematic machines and can also be used in their design optimization as well as selection of suitable running parameters.

医用直线加速器是实现放疗的重要医疗设备,其机架、治疗头及治疗床等部件由于日常运行、老化和磨损而导致故障出现.分析探讨直线加速器设备常见故障产生的原因及处理的方法,合理的运用故障处理方法,对于排除设备故障具有积极的指导意义.