灯泡贯流式水轮机增减负荷动态特性分析

水轮机频繁经历变负荷工况转换过程,使得机组在较短时间内工作参数急剧变化,严重影响电站稳定运行。该研究以某贯流式水轮机为研究对象,在考虑自由液面和水体重力的情况下,采用动网格技术对贯流式水轮机相同出力范围下的减、增负荷过渡过程的动态特性进行分析。研究结果表明：由于增负荷和减负荷过渡过程的起始工况导致起始流动状态不同,因此在相同出力时,机组内的流动分布不同,减负荷过程尾水管内的涡流面积及强度明显小于增负荷工况,且尾水管涡带尺度也明显小于增负荷过程;相比于增负荷过程,减负荷过程中转轮叶片大范围的低压区极易引发空化;机组内的水压力脉动主要以尾水管涡带引起的0.1fn(fn为转频)低频压力脉动和转轮的旋转引起3fn的高频压力脉动为主,增负荷过程的压力脉动幅值明显大于减负荷过程,两种压力脉动共同作用,使得贯流式水轮机主要振动区域集中于转轮。研究结果对贯流式水轮机的设计与运行具有一定的指导意义。     

有限元法钢丝滚道轴承接触问题研究

对钢丝滚道球轴承滚动体与钢丝滚道的点接触问题进行研究,由Hertz接触理论给出接触区的主要几何参数,应力极值以及接触体弹性趋近量的计算公式,并根据实际应用进行简化,计算出所研究轴承接触区的主要参数。在对钢丝滚道球轴承点接触理论分析的基础上,利用有限元法对钢丝滚道球轴承的接触问题进行仿真。对仿真的结果进行分析,并且与理论计算的结果和实际工作过程中的结果相比较,对其不同之处进行分析。     

Tagging effects on three non-native fish species in England (Lepomis gibbosus, Pseudorasbora parva, Sander lucioperca) and of native Salmo trutta

Abstract –  To address the dearth of information on tagging effects and long-term survivorship of tagged fish in native and introduced species, laboratory and field investigations were undertaken on three non-native fish species (pumpkinseed Lepomis gibbosus ; topmouth gudgeon Pseudorasbora parva ; pikeperch Sander lucioperca ) tagged with coded-wire (CW), passive integrated transponder (PIT), radio (RT) telemetry and/or acoustic tags (AT), with survivorship of native brown trout ( Salmo trutta ) examined in the field. Laboratory results revealed high survivorship following tag attachment/insertion and resumption of feeding within 24–48 h of tagging (all mortalities could be attributed to an unrelated outbreak of fungal infection), with retention rates being high in both pumpkinseed and pikeperch but low in topmouth gudgeon (excluded from field studies). In the field, short-term post-operation survival was high in pikeperch, pumpkinseed and brown trout. In pumpkinseed and trout, 100% of RT fish survived a 24–30 day tracking study, with 60% and 80%, respectively, recaptured alive at least 3 months post-tagging. Of PIT tagged pumpkinseed, 44% were recaptured (after 6–18 months), with small-sized, CW-tagged fish (0.38 g weight) captured up to 1 year after tagging. In pikeperch, all AT fish except one (the smallest specimen) survived their full expected tracking period (i.e. tag life) – the single lost specimen survived at least half of its expected tracking period (i.e. 6 month battery life). Overall, the tagging methods used were highly effective in pumpkinseed and pikeperch, showing good retention and survival, but PIT tagging of topmouth gudgeon was plagued by low survivorship and tag rejection.     

短叶片连接为整圈叶片的结构

通过对短叶片常用结构的探讨，介绍了几种叶冠连接方法及拉筋连接方式，给出了各种连接方式的作用及对叶片安全可靠性的影响。     

线切割与镂铣图形的CNC自动编程及虚拟加工技术研究

以AutoCAD R14为开发平台，综合运用ObjectARX SDK、Visual C^ 6.0及CNC技术，在研究了AutoCAD R14的数据结构、平面图形CNC自动编程及加工过程仿真和虚拟现实算法基础上，开发出一种适用于CNC木工镂铣、CNC线切割和CNC激光平面轨迹加工的、集CAD／CNC APT／虚拟加工功能于一体的集成技术。该技术可直接将二维AutoCAD图形快速自动转换成二维CNC加工程序，并可对所编程序进行虚拟加工实验，以检验加工的正确性和可靠性；解决了实际二维平面图形加工CAD／CAM集成及其一体化的瓶颈问题。     

关于漏电保护器误动作的原因分析

本文以单相漏电保护器为例,阐明其几种错误接线的原因,并针对其不同的错误安装接线方法,提出了具体的改进措施。     

牛鼻绳牵出10600年前苑和囿

苑和囿是业界认定属早期园林类型之一,囿的出现不早于殷商。野牛须先驯为畜,方可进囿。牛鼻绳是嫩竹篾扭成的绳,穿进牛鼻两孔间壁肉的穿孔,大犍牛就可被驾驭。这是迄今发现最早的大家畜驯化工具,是人类从原始社会跨进农牧社会门槛的"门栓"。这是人类1万年前首次改造和利用自然、发现自我价值的时代,也是苑和囿同时涌现的时代。     

一例金毛犬胫骨斜骨折的髓内针逆向插入法联合钢丝内固定术治疗

通过对一例金毛犬胫骨斜骨折进行内固定术,详细介绍了髓内针逆向插法联合钢丝进行内固定术的手术要点,为同行进行犬胫骨斜骨折内固定术治疗提供参考。     

Genetic covariation in production traits of sub-adult black bream Acanthopagrus butcheri after grow-out

Predicting the suitability and reliability of traits associated with juvenile growth as indirect selection criteria for choosing future broodstock requires accurate and repeatable estimates of genetic (co)variation for growth traits at different ages. We compared juvenile wet weight of black bream Acanthopagrus butcheri (Munro) at 6 months of age with wet weight, dressed weight, fillet yield and gonad weight in tagged individuals at 18 months of age, following 12 months of farm grow‐out. Fish survival and tag retention was high, and there was significant among‐family variation for all traits. The phenotypic correlations among wet weight, dressed weight and fillet yield at 18 months of age were very high (0.93–0.97) and similar to their genetic correlations (0.96). Importantly, the phenotypic correlations between wet weight at 6 months and wet weight, dressed weight and fillet yield at 18 months were high (0.63–0.65), and so too were their genetic correlations (0.66–0.73), indicating the potential for using wet weight in the hatchery as a selection criterion for improved weight and meat yield of fish at harvest. Gonad weight shared little or no phenotypic or genetic correlation with these other traits, suggesting that selection for faster growing fish will not affect fecundity or sexual maturation rate. It appears, however, that cultured black bream do become sexually mature more rapidly than wild fish, as 78% of all fish harvested in this study had developing or mature gonads, whereas less than 50% of fish in wild populations are reproductively mature by the same age. Precocious sexual development may lead to uncontrolled spawning in grow‐out ponds and a potential loss of selection gains.     

大型屋面板制作主肋钢筋的改进

本文通过分析、计算、现场实践.采用高强钢丝Φ_5~k,取代原Ⅰ、Ⅱ级钢筋制作大型屋面板,结果表明.提高了强度等级.工期、观感、降低了工程造价.