干支流不同典型洪水组成的梯级水库防洪极限风险分析

不同的典型洪水组成对梯级水库的联合防洪调度风险有重要影响,为研究其对极限风险的具体影响以提高梯级水库洪水资源利用率,以黄河上游龙羊峡和刘家峡梯级水库为例,选取干流和支流实测洪水流量资料的年最大洪量过程,按洪峰在洪水过程中出现的位置划分为4场典型洪水,并从中各筛选出4场典型洪水过程线组合成16种情景,采用同倍比放大法推出梯级水库入库设计洪水,以下游水库设计洪水位作为极限风险控制指标,通过调洪演算得到防洪极限风险率。经分析干流洪峰靠后支流洪峰靠前的典型洪水组合对刘家峡水库的极限风险起决定作用。不同起调水位的联合防洪补偿调度计算结果表明,视不同来水情况可将刘家峡水库起调水位抬升至1 728~1 730m,以充分利用黄河流域的洪水资源。     

Fisher最优分割法在李仙江流域汛期分期中的应用

针对目前常用的汛期分期方法存在的主观性强、考虑因素单一和分期结果不确定等问题,提出利用Fisher最优分割法进行汛期分期。基于Fisher最优分割法的基本原理和应用步骤,以李仙江流域为例,选择反映汛期暴雨洪水特性的5个指标,将该流域的汛期划分成了4个分期,即前汛期为6月1日~6月30日,主汛期为7月1日~9月10日,过渡期为9月11日~10月31日,后汛期为11月1日~11月30日,并将Fisher最优分割法的汛期分期结果与数理统计法以及模糊集合分析法两种常用的汛期分期方法的分期结果进行比较。结果表明,Fisher最优分割法的分期结果不仅合理可信,而且相对于常用的汛期分期方法具有一定的优越性。     

Compound machining of titanium alloy by super high speed EDM milling and arc machining

A novel compound machining of titanium alloy (Ti6Al4V) by super high speed electrical discharge machining (EDM) milling and arc machining was proposed in this paper. The power supply consisted of a pulse generator and a DC power source which were isolated from each other. A rotating pipe graphite electrode was connected to the negative pole of the power supply. The plasma channel was able to deionize, and maximum material removal rate (MRR) reached 21,494 mm³/min with a relative electrode wear ratio (REWR) of 1.7% because of high current and efficient flushing. Compared with traditional EDM, the compound machining achieved a significantly higher MRR but a similar REWR. To investigate the characteristics of the compound machining, the effects of electrode polarity, peak voltage, peak current, and flushing pressure on the performance of the process, including its MRR, REWR, and radius of overcut (ROC), were determined. In addition, scanning electron microscopy, X-ray diffraction, and microhardness analysis were conducted. Result shows that the proposed method can machine difficult-to-machine materials efficiently.     

对马斯理论中K_1值的实验研究

针对光伏供电系统的特点,结合马斯理论可显著缩短充电时间、减少气化、提高充电效率的优点,提出了在光伏供电系统中应用马斯理论进行快速充电的思想,并通过测试对马斯理论的参数K1值进行了深入的实验研究,以探索马斯定律在光伏供电系统中应用的实现方法。结果发现:K1值在任何条件下都并非定值。     

Invited review: Systematic review of diagnostic tests for reproductive-tract infection and inflammation in dairy cows

The objective of this study was to conduct a systematic and critical appraisal of the quality of previous publications and describe diagnostic methods, diagnostic criteria and definitions, repeatability, and agreement among methods for diagnosis of vaginitis, cervicitis, endometritis, salpingitis, and oophoritis in dairy cows. Publications (n = 1,600) that included the words “dairy,” “cows,” and at least one disease of interest were located with online search engines. In total, 51 papers were selected for comprehensive review by pairs of the authors. Only 61% (n = 31) of the 51 reviewed papers provided a definition or citation for the disease or diagnostic methods studied, and only 49% (n = 25) of the papers provided the data or a citation to support the test cut point used for diagnosing disease. Furthermore, a large proportion of the papers did not provide sufficient detail to allow critical assessment of the quality of design or reporting. Of 11 described diagnostic methods, only one complete methodology, i.e., vaginoscopy, was assessed for both within- and between-operator repeatability (κ = 0.55–0.60 and 0.44, respectively). In the absence of a gold standard, comparisons between different tests have been undertaken. Agreement between the various diagnostic methods is at a low level. These discrepancies may indicate that these diagnostic methods assess different aspects of reproductive health and underline the importance of tying diagnostic criteria to objective measures of reproductive performance. Those studies that used a reproductive outcome to select cut points and tests have the greatest clinical utility. This approach has demonstrated, for example, that presence of (muco)purulent discharge in the vagina and an increased proportion of leukocytes in cytological preparations following uterine lavage or cytobrush sampling are associated with poorer reproductive outcomes. The lack of validated, consistent definitions and outcome variables makes comparisons of the different tests difficult. The quality of design and reporting in future publications could be improved by using checklists as a guideline. Further high-quality research based on published standards to improve study design and reporting should improve cow-side diagnostic tests. Specifically, more data on intra- and interobserver agreement are needed to evaluate test variability. Also, more studies are necessary to determine optimal cut points and time postpartum of examination.     

基于用户利益与出行意愿的电动汽车充放电调度策略

如今,随着越来越多智能充电桩的建立,人们对电动汽车的需求量日益加大,电动汽车不仅可以提高能源利用率、减少污染,而且还可以反向对电网进行供电,达到削峰填谷的目的。但是随着越来越多的电动汽车接入到电网,越来越多的用户参与到电动汽车调度中,电动汽车的充放电调度也变得越为复杂,在以往的一些调控中总是优先考虑电网的峰值负荷如何降低,却很少考虑用户的需求与利益。事实上,在保证电网负荷曲线的同时更应该考虑到用户的利益与需求,因为用户的利益与需求才是保证调度计划顺利实施的基础。文中基于用户的利益与出行意愿,利用粒子群算法对电动汽车的充放电进行调度,保证了用户的利益与满意度,同时有效削减了电网峰值时刻的负荷。     

微小孔加工质量和效率的控制系统稳定性分析

根据对电火花加工原理以及进给系统的分析,可知放电间隙是影响微小孔加工质量的重要因素,可靠地控制放电间隙是提高微小孔加工质量和效率的关键。为了更好地控制放电间隙,分析放电间隙的控制规律,应用模糊理论,设计了电火花加工控制系统的模糊控制器。并运用李雅普诺夫稳定性理论,对控制系统的稳定性进行了分析,并进行了验证。结果表明：该系统是稳定性且可行的。     

制浆造纸清洁生产与废水处理 写于制浆造纸废水动态平衡短流程循环零排放清洁生产技术推广应用十周年

研究并推广应用了制浆造纸废水动态平衡短流程循环零排放清洁生产技术,打破了＂以废水处理来适应制浆造纸生产系统＂的思维定式,提出了对制浆造纸系统进行调整改造以适应生产用水不经净化处理的分段短流程封闭循环回用的清洁生产方式。     

Enhancing the ammonia to hydrogen (ATH) energy efficiency of alternating current arc discharge

In order to enhance the ammonia to hydrogen (ATH) energy efficiency, systematic study was carried out with atmospheric pressure alternating current arc discharge reactor (using a pair of stainless steel (SS) tube electrodes). Results showed that, using small-diameter SS tube electrodes with small discharge gaps forced more ammonia molecules to go through the effective plasma volume and obtained high electrodes temperature. Adopting low discharge frequency increased the discharge time, the effective plasma volume and the electrode temperature. These changes can enhance both the gas-phase plasma decomposition and the electrode-surface catalytic decomposition of ammonia. Insulating the reactor significantly increased the electrode temperature in small-diameter reactor, so as to enhance the electrode-surface catalytic decomposition of ammonia. In large-diameter reactors, however, the electrodes temperature increased less rapidly and more ammonia bypass of the effective plasma volume occurred. A 12.5 mol/kW h ATH energy efficiency was reached when ammonia was completely converted under the conditions of electrode diameter 3 mm, electrode gap 4 mm, discharge frequency 5 kHz, reactor diameter 8 mm, NH₃ flow rate 150 ml/min and input power 48 W. The ATH energy efficiency was further enhanced under similar conditions when incomplete ammonia conversion was allowed.