关于基坑规程中围护结构变形计算的探讨

《建筑基坑支护技术规程》(JGJ120)中弹性支点法首先计算围护结构的变形,然后再根据围护结构的变形计算锚杆轴力和围护结构的内力.然而在计算围护结构变形时存在3个方面的不足:首先,如何合理的考虑预应力锚杆刚度及其随开挖深度的变化规律;其次,施加预应力工况下的变形计算模型合理性;最后,土方开挖前后的变形均为独立受力体系的总变形而非变形增量之和等.通过分析这些不足之处及其相应的解决方案,可使基坑围护结构变形计算更合理、更符合实际变形,使变形计算过程和原理更清晰,有助于基坑支护设计人员对围护结构变形计算结果的理解和合理应用.     

Interannual and interdecadal variations in the North Atlantic Oscillation spatial shift

The spatial shift of the North Atlantic Oscillation (NAO) is analyzed by using the Twentieth Century Reanalysis version 2 dataset and identifying NAO action centers directly on winter mean sealevel pressure (SLP) anomaly maps. The spatial shift of the NAO is characterized by four NAO spatial shift indices: the zonal and meridional shifts of the NAO southern and northern action centers. It is found that the zonal and meridional shift trends of the NAO action centers move along a path of southwest-northwest direction. Spectral analysis shows that the four NAO spatial shift indices have periodicity of 2-6 years and the NAO index has periodicity of 2-3 years in terms of high-frequency variations. On a decadal time scale, the NAO spatial shift indices are closely (positively) related to the NAO index, which is in agreement with previous studies of the relationship between the NAO index and the spatial shift of the NAO pattern. However, there is no relationship between the NAO index and the meridional shift of the northern action center on an interannual time scale. The significant relationship between the NAO index and the interannual variability of NAO spatial shift indices is very likely to be associated with synopticscale Rossby wave breaking, which generates surface pressure anomalies and thus affects the phase and pattern of the NAO. The correlations of winter westerly winds over 90°W-0° and the NAO index and the NAO spatial shift indices have a ’+ - + -’ structure from the Equator to the North Pole. Although there is close correlation between the NAO spatial shift indices and the strength of the zonal winds in the North Atlantic region, the effect of the zonal winds on the NAO spatial shift differs at different latitudes. Hence, the role of the zonal winds is probably a result of the NAO spatial shifts.     

Asymmetric energy flow in coupled nonlinear LC transmission line

We constructed a coupled LC transmission line and studied the propagation of waves in it. We found asymmetric energy flow when we changed the driving conditions at the boundary. We analyzed this change and believe that it occurs because of the bandpass characteristics of the LC transmission line and high-order harmonic waves induced by nonlinearities. The LC transmission line could be used to simulate a microscopic crystal lattice. Therefore, we hope to observe thermal rectification in the system. We investigated the dependence of the system on different parameters, and then discussed the multi-frequency condition to aid in experimental verification.     

Diagnosis of prostate cancer by quantitative analysis of 3DMRSI data: A new model

Prostatecancer (PC)hasthehighestmorbidityrateinmaleurinarysystemdisordersinEuropeandAmerica ,anditisoneoftheprimaryreasonsofmaledeath[1] .InChina ,althoughtheattackofPCisrela tivelylow ,ithasa growingtrendinrecent 10years[2— 4 ] .Inclinicalpractice ,magneticresonanceimaging (MRI)could providehighresolutionmor phologicalstructureandhasthecapabilityofmulti parameterimaging ,butitcannotreliablydifferentiatePCfrombenignprostatehyperplasia (BPH)andnor maltissues ,particularlyforthepatientswi…     

Density-functional formula for strongly correlated systems

Up to now, computation method dealing withthe many electron systems has been based on single particle approximation. That is to say, the wavefunctions of a system are composed of single particlewave functions (SPWF’s), and all the physical prop erties are determined by the SPWF’s. There havebeen two sophisticate techniques to solve the SPWF’s.One is the well known Hartree Fock self consistent e quations (HFSCE). The other is the Kohn Sham e quations of density funct…     

毛乌素沙地沙柳人工林最优平茬周期的确定

摘要 针对毛乌素沙地沙柳人工林衰退问题,从防风固沙角度探讨沙柳林最佳平茬周期,为今后平茬作业提供理论依据。以毛乌素沙地丘间低地沙柳人工林为研究对象,测定平茬后不同林龄沙柳林林内粗糙度和风速廓线与林后沙丘迎风坡粗糙度,分析确定出兼顾沙柳特殊平茬生态学特性和防风固沙效益的最佳平茬周期。试验结果表明：沙柳在平茬后第4a,林内粗糙度呈现最大值,地表比较稳定,之后开始出现下降趋势;沙柳林林后沙丘迎风坡的粗糙度在平茬后初期,地表粗糙度低于起沙时粗糙度,易发生风蚀现象,之后随着沙柳的生长,平茬后第3a开始,林后7H（H为沙柳平均高度）内地表粗糙度均大于起沙时粗糙度,沙柳林对林后迎风坡防护效果较好,而4a后,沙柳林防风能力下降,地表粗糙度下降,地表抗风蚀能力减弱。研究得出沙柳林最优的平茬周期为4年。     

A new design method for asymmetrical head gradient coils used for superconducting MRI scanner

Highstrength,highslewrategradientsproducedoverthehumanheadaredesiredinmodernMRI(magneticresonanceimaging)formanyimportantimagingapplications.Forinstance,ahighbvalueindiffusionweightedimagingofhumanbrainforidentifyingstrokerequiresahighgradientstrength[1],andthehighgradientslewrateisimportantforthebrainspecificapplicationoffMRI(functionalMRI)inwhichhighspatialresolutionisthemaingoal[2].Therefore,itisdesiredthatoptimizationmethodsofheadcoilswillachievethesehighcoilperformances.Additionally,t…     

Gastric vagal afferent inputs reach the glycemia-sensitive neurons of lateral hypothalamic area in the rat

The lateral hypothalamic area (LHA) is one of the most important central areas in the regulation of feeding behavior[1]. The glycemia-sensitive neurons within the LHA sense the blood glucose level and subsequently trig-ger various visceral and somatic responses for maintaining the homeostasis of blood glucose concentration. Some electrophysiological studies have demonstrated that the gastric vagal afferent inputs could reach the LHA in the cat[2,3], but the studies did not reveal whether th…     

Re-Os isotopes and PGE geochemistry of black shales and intercalated Ni-Mo polymetallic sulfide bed from the Lower Cambrian Niutitang Formation, South China

The paleo oceanenvironmentalchangeduringthePrecambrian Cambriantransitionisakeyissuere latedtothecausesforanexplosiveradiationofdiffer entmetazoanphyladuringtheEarlyCambrianera .Thechemicalandisotopiccompositionsofmarinesed iments (carbonates ,phosphorites ,siliceousrocks ,andblackshales)recordthechangingcompositionandphysicalconditionsoftheseawaterinwhichtheserocksaccumulated .Organiccarbon richblackshalesfrommarineenvironmentsarecommonlyenrichedinanumberoftraceelementssuchasNi,Mo ,V ,Co ,…     

建立铜陵淡水豚自然保护区考察研究

报道了铜陵江段白鱀豚 (Lipotesvexillifer )和长江江豚 (Neophocaenaphocaenoidesasiaeorientalis)资源现状及影响豚类生存制约因子 ,提出建立铜陵淡水豚自然保护区 ,加强栖息地保护 ,具有良好的生态效益和社会效益。