兰州至关中电线积冰与导线线径及高度关系   总被引：3，自引：1，他引：2       下载免费PDF全文

吴素良  范建勋  姜创业  李卫林  何晓嫒  崔巍 《应用气象学报》2010,21(1):63-69

对2006—2007年、2007—2008年冬季甘肃、陕西、宁夏多个测点不同线径、不同架线高度电线积冰观测资料分析可知,不同线径电线积冰的净直径、净厚度、等效厚度、积冰重量间存在显著线性关系。直径为26 mm导线电线积冰重量约为18 mm导线的1.2倍,是4 mm铁丝的1.3倍。直径为26 mm导线与直径为18 mm导线电线积冰间的各项关系都较26 mm导线与4 mm铁丝的线性关系更为显著;大直径导线电线积冰的净直径、净厚度、等效厚度均小于4 mm铁丝;26 mm导线与18 mm导线电线积冰的净直径、等效厚度基本相等。电线积冰等效厚度是架设高度比的幂函数;忽略水滴下沉速度,在假定捕获系数为常数、假定时间各物理量均衡不变情况下,电线积冰重量与电线导线线径成正比,且随架设高度的增加而增加。  相似文献   

地质勘探金刚石岩心钻探中浅孔主体口径探讨   总被引：1，自引：0，他引：1       下载免费PDF全文

YANG Xiao-qi 《探矿工程》2009,36(11):1-3

针对地质勘探金刚石岩心钻探采用的钻孔口径进行分析,从采心质量满足研究和评价地质矿产的要求、钻探技术经济效益、钻探方法可行性角度,提出在地质勘探金刚石岩心钻探施工中浅孔时主体孔段口径应采用B规格。  相似文献   

Solar Radius Determination from Total Solar Eclipse Observations on 29 March 2006     

A. Kilcik  C. Sigismondi  J. P. Rozelot  K. Guhl 《Solar physics》2009,257(2):237-250

Solar diameter measurements have been made nearly continuously through different techniques for more than three centuries. They were obtained mainly with ground-based instruments except for some recent estimates deduced from space observations. One of the main problems in such space data analysis is that, up to now, it has been difficult to obtain an absolute value owing to the absence of an internally calibrated system. Eclipse observations provide a unique opportunity to give an absolute angular scale to the measurements, leading to an absolute value of the solar diameter. However, the problem is complicated by the Moon limb, which presents asphericity because of the mountains. We present a determination of the solar diameter derived from the total solar eclipse observation in Turkey and Egypt on 29 March 2006. We found that the solar radius carried back to 1 AU was 959.22±0.04 arcsec at the time of the observations. The inspection of the compiled 19 modern eclipses data, with solar activity, shows that the radius changes are nonhomologous, an effect that may explain the discrepancies found in ground-based measurements and implies the role of the shallow subsurface layers (leptocline) of the Sun.  相似文献   

PHYTOPLANKTON,ESPECIALLY DIATOMS,IN THE GUT CONTENTS AND FECES OF TWO PLANTIVOROUS CYPRINIDS-SILVER CARP AND BIGHEAD CARP     

谢平  刘建康 《中国海洋湖沼学报》1994,(4)

In order to clarify whether the planktivorous silver carp and bighead carp can collect phytoplanktonas small as Cyclotella(<20μm)in Donghu Lake,studies on phytoplankton in their gut contents and feceswere made in 1990.The fish were cultured in both net cage in Donghu Lake and aquaria with the lakewater.Past the intestine,the average valve diameter of Cyclotella changed little.The average ratio of emptyfrustule of Cyclotella to total Cyclotella in the foregut contents of the fishes were 1.8—1.9 times higherthan that in the lake water,but changed little from foregut to feces.The aquarium experiment showedthat both carps could collect particles as small as 8-10μm, which was obviously narrower than the dis-tance between their gill rakers.Probably,secretion of mucus plays an important role in collecting suchsmall particles  相似文献   

一元Laplace分布的L1—范估计的无偏性     

王振杰  欧吉坤  曲国庆 《武汉大学学报(信息科学版)》2001,26(4):361-363

根据Laplace分布的概率密度函数公式，推导了了中位数的概率密度，在此基础上证明了L1－范估计的无偏性。  相似文献   

上海软土地区大直径钻孔灌注桩承载力偏低原因浅析     

陆惠泉  金清山 《上海国土资源》1997,(4):15-18

就上海软土地区大直径(设计直径≥800mm)钻孔灌注桩承载力普遍低于按规范计算的极限承载力的原因进行了分析,认为大直径尺寸效应、编制规范时引用的资料存在一定的局限性以及成桩工艺时间长短等对大直径钻孔灌注桩承载力充分发挥都有不同程度的影响。建议在设计取值时,以取f_i和f_p的低限值为宜;同时,施工队伍应加强管理,缩短成桩时间;并应视具体情况适当增大泥浆比重。  相似文献   

沉入式大圆筒结构码头工作机理离心模型试验研究   总被引：6，自引：0，他引：6  

徐光明  章为民等 《海洋工程》2001,19(1):38-44

沉入式大圆筒结构码头，由于筒体下部有一定长度嵌入港地泥面以下的地基土层中，因此，其工作机理不仅不同于其它挡土岸壁式码头，而且也有别于基床式大圆铜结构码头。本文介绍了用土工物理离心试验对这一结构形式码头工作机理所作的研究，就沉入式大圆的深高比、径高比和筒壁摩擦作用对工作性状影响规律进行了初步研究，另外还尝试测定了大圆筒侧壁土压力分布规律，并探讨了码头面沉降发展趋势特征。  相似文献   

High inside corners at ridge-transform intersections   总被引：1，自引：0，他引：1  

Jeff P. Severinghaus  Ken C. Macdonald 《Marine Geophysical Researches》1988,9(4):353-367

A large topographic high commonly occurs near the intersection of a rifted spreading center and a transform fault. The high occurs at the inside of the 90° bend in the plate boundary, and is called the high inside corner, while the area across the spreading center, the outside corner, is often anomalously low. To better understand the origin of this topographic asymmetry, we examine topographic maps of 53 ridge-transform intersections. We conclude the following: (1) High inside corners occur at 41 out of 42 ridge-transform intersections at slow spreading ridges, and thus should be considered characteristic and persistent features of rifted slow spreading ridges. They are conspicuously absent at fast spreading ridges or at spreading centers that lack a rift valley. (2) High inside corners occur wherever an axial rift valley is present, and an approximate 1:1 correlation exists between the relief of the rift valley and the magnitude of the asymmetry. (3) Large high inside corners occur at both long and short transform offsets. (4) High inside corners at long offsets decay off-axis faster than predicted by the square root of age cooling model, precluding a thermalisostatic origin, but consistent with dynamic or flexural uplift models.These observations support the existing hypothesis that the asymmetry is due to the contrast in lithospheric coupling that occurs in the active transform versus the inactive fracture zone. Active faulting in the transform breaks the lithosphere along a high angle fault, permitting vertical movement of the inside corner block, whereas the inactive fracture zone forms a weld that couples the outside corner to the adjacent block, preventing it from rising. Large asymmetry at very short transform offsets appears to be caused by the added effect of a second uplift mechanism. Young lithosphere in the rift valley couples to the older plate, and when it leaves the rift valley it lifts the older plate with it. At very short offsets, this coupled uplift acts upon the high inside corner; at long offsets, it may upwarp the older plate or its expression may be muted.  相似文献   

氯化钠和碱度对罗氏沼虾仔虾的毒性研究     

王桂春  张兆琪  董双林  陈兆波  张美昭 《中国海洋大学学报(自然科学版)》2001,31(4):523-528

实验研究氯化钠、碱度对罗氏沼虾仔虾的急性毒性作用。用概率单位法求出了其氯化钠2 4、4 8、72、96 h的半致死浓度分别为 8.58、 5.32、 3.4 7、 2 .19g/ L;碱度的 2 4、4 8、72、96 h半致死浓度分别为 51.0 2、 37.0 7、 2 7.19、 2 1.54mmol/ L。对氯化钠和碱度混合作用的结果进行的方差分析表明 ,氯化钠和碱度对仔虾的死亡率影响显著 ,而两者的交互作用不显著。碱度 (AL K)与罗氏沼虾仔虾氯化钠 2 4、4 8h L C50 (S)关系式分别为 S=- 0 .12 78AL K+ 9.2 346 ,S=- 0 .0 715AL K +5.530 1。  相似文献   

大连中远浮船坞工程海上基桩施工技术     

李华 卢飞赵振峰  李贵华 《探矿工程》2007,34(4):6-8,11

大连中远30万t浮船坞工程是目前国内最大的浮船坞工程，共设计海上基桩30根，桩径800mm，嵌入中风化岩石4～5m，最深达8m。利用驳船进行海上基桩施工，采用FGC-15D型大直径湿式反循环潜孔锤钻进成孔，满足施工工艺和工期要求。  相似文献