板钉连接CFST柱-RC梁节点梁端塑性铰区受力性能数值模拟

建立竖板-栓钉连接钢管混凝土（CFST）柱-钢筋混凝土（RC）梁节点试件（SSJD）拟静力加载试验有限元模型,并在节点损伤情况、梁端荷载-位移曲线等数值模拟结果与试验结果吻合较好的基础上,进一步开展了RC梁混凝土强度、配筋率ρs和连接竖板长度Lb及界面连接情况等对CFST柱-RC梁节点梁端塑性铰区域力学性能的影响。研究结果表明,RC梁混凝土强度对试件SSJD塑性铰区域受力性能的影响较小;适筋范围内RC梁配筋率增加可适当提高试件SSJD承载力和延性;随着连接竖板长度的增加,梁端塑性铰区域外移,梁破坏荷载增大;本研究给出的RC梁与CFST柱之间的界面抗剪承载力模拟值与计算值吻合较好,可用于界面抗剪设计。     

机器基础动力相互作用的研究

本文分别对单台、双台、联合基础与地基土相互作用体系在扰力作用下的振动特性进行了研究。在计算中考虑了外围土体的影响。通过算例,得到了单台、双台、联合基础的一些振动规律。     

Initial Characterisation of SK01 Sanidine: A Candidate 40Ar/39Ar Reference Material

The precision and accuracy of ⁴⁰Ar/³⁹Ar dates are ultimately linked to co-irradiated reference materials of known age. Here we provide new data from the SK01 sanidine, which was analysed in three different laboratories to evaluate it as a ⁴⁰Ar/³⁹Ar reference material. Aliquots of 5 mg, incrementally heated in two laboratories, yielded indistinguishable results with a weighted mean age of 27.58 ± 0.06 Ma (95% confidence level). Single-crystal step heating and single-crystal total fusion analyses of SK01 sanidine were undertaken in the third laboratory to further test the intracrystalline homogeneity. For the seven step-heating analyses, six crystals yielded nearly concordant age spectra with ⁴⁰Ar/³⁹Ar ages ranging from 26.853 ± 0.094 Ma to 26.963 ± 0.067 Ma, whereas one crystal gave an older age of 27.774 ± 0.071 Ma with a slightly discordant age spectrum. Twenty-three single-crystal total fusion analyses yielded ⁴⁰Ar/³⁹Ar ages ranging from 27.070 ± 0.108 Ma to 27.736 ± 0.062 Ma with a dispersion of ~ 3.8%. The older ages from single-crystal total fusion dates are interpreted to reflect an inherited or excess argon component in some crystals. This is an initial characterisation of the SK01 sanidine, and additional work needs to be conducted to further evaluate the age dispersion so that it can be utilised as a ⁴⁰Ar/³⁹Ar reference material.     

Theoretical analysis and engineering solution of parasitical spectrum in the CINRAD transmitter

To deal with the universal problem of parasitical frequency spectrum in China New Generation Weather Radar transmitter, this paper establishes mathematical models for parasitical signals existing in radar transmitters and analyzes their effects on weather radar performance. Based on an engineering analysis of their possible sources, a step-by-step method to eliminate parasitical spectrum is presented, which is applied to troubleshooting experimental weather radar. Eventually, parasitical spectrum is basically eliminated. As a result, improved spectrum purity and reduced phase noise is achieved. Moreover, accuracy for velocity estimate as well as ground clutter suppression ability of the radar system is enhanced.     

Distinguishing volcanic debris avalanche deposits from their reworked products: the Perrier sequence (French Massif Central)

Debris avalanches associated with volcanic sector collapse are usually high-volume high-mobility phenomena. Debris avalanche deposit remobilisation by cohesive debris flows and landslides is common, so they can share textural characteristics such as hummocks and jigsaw cracks. Distinguishing original deposits from reworked products is critical for geological understanding and hazard assessment because of their different origin, frequency and environmental impact. We present a methodology based on field evidence to differentiate such epiclastic breccias. Basal contact mapping constrained by accurate altitude and location data allows the reconstruction of deposit stratigraphy and geometry. Lithological analysis helps to distinguish the different units. Incorporation structures, kinematic indicators and component mingling textures are used to characterise erosion and transport mechanisms. We apply this method to the enigmatic sequence at Perrier (French Massif Central), where four units (U1–U4) have been interpreted either as debris flow or debris avalanche deposits. The sequence results from activity on the Monts Dore Volcano about 2 Ma ago. The epiclastic units are matrix supported with an almost flat top. U2 and U3 have clear debris flow deposit affinities such as rounded clasts and intact blocks (no jigsaw cracks). U1 and U4 have jigsaw cracked blocks with matrix injection and stretched sediment blocks. U1 lacks large blocks (>10 m wide) and has a homogenous matrix with an upward increase of trapped air vesicle content and size. This unit is interpreted as a cohesive debris flow deposit spawned from a debris avalanche upstream. In contrast, U4 has large mega-blocks (up to 40 m wide), sharp contacts between mixed facies zones with different colours and numerous jigsaw fit blocks (open jigsaw cracks filled by monogenic intra-clast matrix). Mega-blocks are concentrated near the deposit base and are spatially associated with major substratum erosion. This deposit has a debris avalanche distal facies with local debris flow affinities due to partial water saturation. We also identify two landslide deposits (L1 and L2) resulting from recent reworking that has produced a similar facies to U1 and U4. These are distinguishable from the original deposits, as they contain blocks of mixed U1/U4 facies, a distinctly less consolidated and more porous matrix and a fresh hummocky topography. This work shows how to differentiate epiclastic deposits with similar characteristics, but different origins. In doing so, we improve understanding of present and past instability of the Monts Dore and identify present landslide hazards at Perrier.     

Evapotranspiration from citrus trees growing in sandy soil under drip irrigation with saline water

An experiment on evapotranspiration from citrus trees under irrigation with saline water was carried out for 4 months. Two lysimeters planted with a citrus tree in the green house were used. One lysimeter was irrigated with saline water (NaCl and CaCl₂ of 2000 mg/L equivalence,EC = 3.8 dS/m, SAR = 5.9) and the other was irrigated with freshwater using drip irrigation. The applied irrigation water was 1.2 times that of the evapotranspiration on the previous day. Evapotranspiration was calculated as the change in lysimeter weight recorded every 30 minutes. The lysimeters were filled with soil with 95.8% sand. The results of the experiment were as follows. (i) The evapotranspiration from citrus tree was reduced after irrigation with saline water. The evapotranspiration returns to normal after leaching. However it takes months to exhaust the salt from the tree. (ii) To estimate the impact of irrigation with saline water on the evapotranspiration from citrus trees, the reduction coefficient due to salt stress (K_s) was used in this experiment. Evapotranspiration under irrigation with saline water (ET _s ) can be calculated from evapotranspiration under irrigation with freshwater (ET) by the equationET _s =K _s × ET. K_s can be expressed as a function ofEC _sw . (iii) The critical soil-water electrical conductivity (EC _sw ) is 9.5 dS/m, beyond which adverse effects on evapotranspiration begin to appear. IfEC _sw can be controlled at below 9.5 dS/m, saline water can be safely used for irrigation.     

Bed-load transport rate based on the entrainment probabilities of sediment grains by rolling and lifting

A function for the bed-load sediment transport rate is derived. This function is obtained by using the entrainment probabilities of the rolling and lifted sediment grains, and by introducing two travel lengths, respectively. The predictions from the new bed-load function agree well with experimental results over the entire experimental range and show significant improvement over the commonly used formula for the bed-load transport rate. The new function shows that, in terms of contributing to the bed-load transport rate, the total entrainment probability of the sediment grains is a weighted summation of those for the lifted and rolling grains, rather than a simple addition of the two. The function is also used to predict the total entrainment probability, saltation length, and the bed layer thickness at a high bed-load transport rate. These predictions all agree well with the experimental results. It is found that, on average, the travel length for the rolling sand grains is about an order of magnitude less than that of the lifted grains.     

A first arrival detection method for low SNR microseismic signal

Most of the microseismic signals have low signal-to-noise ratio (SNR) due to the strong background noise, which makes it difficult to locate the first arrival time. Both accuracy and stability of conventional methods are poor in this situation. To overcome this problem, here we proposed a new method based on the adaptive Morlet wavelet and principal component analysis process in wavelet coefficients matrix. The three components of microseismic signal make it possible to extract the features in wavelet coefficients domain. Then the reconstructed signal from weighted features presents an obvious first arrival. Tests on synthetic signals and real data provide a solid evidence for its feasibility in low SNR microseismic signal.     

Tomographic inversion of near-surface <Emphasis Type="Italic">Q</Emphasis> factor by combining surface and cross-hole seismic surveys

The estimation of the quality factor Q plays a fundamental role in enhancing seismic resolution via absorption compensation in the near-surface layer. We present a new geometry that can be used to acquire field data by combining surface and cross-hole surveys to decrease the effect of geophone coupling on Q estimation. In this study, we drilled number of receiver holes around the source hole, each hole has different depth and each geophone is placed geophones into the bottom of each receiver hole to avoid the effect of geophone coupling with the borehole wall on Q estimation in conventional cross-hole seismic surveys. We also propose a novel tomographic inversion of the Q factor without the effect of the source signature, and examine its stability and reliability using synthetic data. We estimate the Q factors of the near-surface layer in two different frequency bands using field data acquired in the Dagang Oilfield. The results show that seismic absorption in the near-surface layer is much greater than that in the subsurface strata. Thus, it is of critical practical importance to enhance the seismic solution by compensating for near-surface absorption. In addition, we derive different Q factors from two frequency bands, which can be treated, to some extent, as evidence of a frequency-dependent Q.