北疆地区混凝土衬砌渠道损坏原因及治理措施

通过对混凝土渠道损坏的具体原因进行分析,并提出一些相应的治理措施,以期能够对类似情况的混凝土渠道设计提供一定的借鉴。     

太阳辐射作用下冻结期衬砌渠道温度场分析

【目的】对季节性冻土区衬砌渠道在太阳辐射作用下的温度场进行数值模拟,分析太阳辐射对渠道温度分布的影响。【方法】利用Hottel太阳辐射模型,结合热传导理论和有限元分析方法,考虑渠道自身的遮蔽作用,对太阳辐射作用下的梯形衬砌渠道的温度场进行计算。【结果】提出了梯形渠道太阳辐射的计算方法;衬砌渠道表面太阳辐射的日变化表现为早晚最小、中午最大;渠道阴、阳坡接受到的太阳辐射差异明显,阴坡太阳总辐射约为阳坡的20%;渠道表面温度的日变化趋势与大气温度相同,近似为正弦分布,其温度变幅小于大气温度变幅,变化滞后于太阳辐射约2.5h,阴、阳坡温度最大相差4℃左右,阳坡温度值与日间温度增加速率均大于阴坡。【结论】渠道温度变化与太阳辐射有密切关系,阴、阳坡接受到的太阳辐射量不同是渠道温度存在较大差异的原因,太阳辐射是渠道冻融循环的动力,在渠道冻胀研究中必须考虑太阳辐射的影响。     

Note on the Taxonomy of Genetta

The recruitment patterns of six teleosts were studied at King’s Beach, Algoa Bay. February to May marked the major recruitment period for Diplodus sargus, Lithognathus mormyrus, Rhabdosargus globiceps and Trachurus capensis. The major recruitment of Sarpa salpa fry took place between August and September. Pomadasys olivaceum fry of < 5 cm total length were caught throughout the year indicating an extended breeding period. The estimated growth rates of new recruits between February and May (autumn/winter) was 0,60 cm month ^-1 for L. mormyrus, 0,75 cm month^-1 for ft globiceps and 0,40 cm month^-1 for T. capensis. The empirical growth curve derived for S. salpa indicated a growth rate of 0,75 cm month^-1. No growth estimates could be made for P. olivaceum or D. sargus.     

Atrioventricular septal defects: Natural history,echocardiographic, electrocardiographic,and radiographic findings in 26 cats

ObjectivesTo evaluate signalment, echocardiographic, electrocardiographic, and radiographic findings as well as natural history in a group of cats with atrioventricular septal defects (AVSD).Animals26 client owned cats.MethodsMedical records were reviewed retrospectively for signalment, morphologic type of AVSD, presence of concurrent congenital heart disease (ConcCHD), diagnostic findings, and natural history.ResultsSeventeen cats had an isolated AVSD; 13/17 had a partial and 4/17 had a complete AVSD. Double outlet right atrium (DORA) was diagnosed in 4/17 cats. Of those with a partial AVSD, 7/13 had an atrial communication while 6/13 had a ventricular communication. Congestive heart failure (CHF) developed in 5/17 cats; all 3 cats diagnosed with a DORA not lost to follow-up developed pulmonary edema. Sudden death was documented in 4/17 (23.5%). The 5 year survival was 53.0% (9/17). Concurrent congenital heart disease was identified in 9/26 cats with 7/9 having a conotruncal abnormality. Electrocardiography was performed in 14 cats with 11/14 diagnosed with a conduction disturbance.ConclusionsOverall the echocardiographic and electrocardiographic findings with AVSD are similar to that seen in humans. Cats may have a higher prevalence than humans of partial AVSD with ventricular communication only as well as a higher prevalence of DORA. Cats with an AVSD have an overall guarded prognosis although some can live for a protracted time.     

Using urea dilution to standardise components of pleural and bronchoalveolar lavage fluids in the dog

AIM: To develop a technique to estimate the volume of epithelial lining fluid (ELF) obtained during bronchoalveolar lavage (BAL) and pleural lavage (PL) in the dog, using the urea dilution method.

METHODS: BAL and PL fluids were obtained by saline lavage of pulmonary and pleural cavities of nine clinically healthy mixed-breed dogs immediately after euthanasia. Cell counts in the BAL and PL fluids were measured using standard techniques. The concentration of ELF in each lavage fluid was calculated from the relative concentration of urea in plasma and in each type of lavage fluid. Cell counts in ELF were then calculated.

RESULTS: There were substantially higher cell counts in ELF compared to BAL or PF fluid. However, nucleated cell counts in ELF could not be predicted from cell counts in BAL or PL fluid.

CONCLUSIONS AND CLINICAL RELEVANCE: These results suggest that accurate assessment of cellular or non-cellular components in lavage fluids should include a calculation of the proportion of ELF recovered, using a method such as urea dilution.     

Heritable characters of the red blood cells of sheep

Extract

From the start I want to make it clear that the research work described here is the work of one of us (J.V.E.), and the reason why I am presenting his work is that Evans comes from New Zealand and presented a paper on this subject to the annual meeting of the British Association for the Advancement of Science last September in Sheffield, so that it seemed appropriate that his work should also be presented to this Society.     

沙土地区渠道防渗衬砌技术

近几年来,渠道衬砌技术发展较快,类型较多,是节约用地,节省用水,方便管理,提高灌溉效益的有效途径。该文就沙土地区常用的几种渠道衬砌技术的设计,施工,质量控制以及配套建筑物等方面进行了总结,并提出了渠道防渗衬砌施工过程中的注意事项,对沙土地区应用和推广渠道衬砌技术具有直接的指导作用和一定的参考价值。     

Strategies to improve manual operation of irrigation systems in Sri Lanka

Improvements to normal operational procedures are investigated for the main types of irrigation system identified in Sri Lanka. Scheduled and unscheduled changes of flow regime the systems are likely to experience and the opportunities for improved operations related to the physical characteristics of each type are analyzed.Performance of several alternative manual operational procedures are evaluated and compared using a hydraulic model (Simulation of Irrigation Canal, SIC) for three different irrigation subsystem types (Single Bank canal; Double Bank canal; Canals with intermediate Storage). Results of these simulations show that current practice, based on a fixed frequency of operation of 12 hrs and a target water depth set to the spill level of the cross-regulator, is not far from the optimal for systems without on-line storage. A slight improvement can be expected if the frequency of operation is increased to 6 hrs. For systems with on-line storage it is recommended to split operational procedures into two parts, one related to the canal and one to the storage. Among different options investigated, discharge control at the downstream regulator of the storage appears to be the most reliable as it performs well whatever operation procedures are selected for the canal.Irrigation systems in Sri Lanka are subject to frequent positive flow changes (Supply fluctuations, Runoff, Return-flow changes). As far as water management is concerned, improvements to be expected from normal operation procedures appear to be somewhat limited because management of flow changes is not an objective. For instance little effort is made to harvest runoff under the current practices. One conclusion of the study is that new strategies for the harvest, storage and release of positive flow changes should be tested and, where appropriate, implemented to improve the overall efficiency of operation in irrigation systems in Sri Lanka.     

渠道衬砌抗渗型粉煤灰-稻壳混凝土抗渗性能试验

为了满足渠道衬砌的需要,提高稻壳混凝土的抗渗性能,在稻壳混凝土中加入了粉煤灰。该文通过试验对渠道衬砌抗渗型粉煤灰-稻壳混凝土的抗渗性能进行了研究,得到粉煤灰质量分数、稻壳质量分数和水灰比对粉煤灰稻壳混凝土抗渗性能的影响规律,同时得到了粉煤灰-稻壳混凝土相对渗透系数小于0.783×10-8 cm/s的混凝土配合比。通过对混凝土抗渗性能主效应分析得到混凝土抗渗性能的影响因素顺序：水灰比>稻壳质量分数>粉煤灰质量分数;粉煤灰-稻壳混凝土的相对渗透系数随着粉煤灰质量分数和稻壳质量分数的增大呈现出先减小后增大的抛物线的变化趋势,随着水灰比的增大呈现出一直增大的线性变化的规律。试验结果表明在不降低混凝土导热系数的前提下,在稻壳混凝土中掺入粉煤灰后确实能提高稻壳混凝土的抗渗性能。     

膨润土防渗毯用于渠道衬砌及其老化因素对力学性能的影响

膨润土防水毯(GCL)在渠道衬砌工程有较大的应用价值.为了测试膨润土防渗毯用于渠道衬砌其老化因素对力学性能的影响,以内蒙古河套灌区为研究区域,采用室内模拟及工程现场试验相结合,对5种老化因素的3种GCL力学性能影响进行了测试.结果表明:温度、湿度、紫外线照射都会对GCL的力学性能造成影响.高温对GCL力学性能影响大于低...