泥质粉砂岩点荷强度与单轴抗压强度对比研究

对抚州泥质粉砂岩的点荷载强度与岩石单轴抗压强度进行对比研究,结果表明,两者之间存在良好的线性相关性,并建立了显著线性相关的关系式。同时分析表明,现有的经验公式在推广应用时存在局限性,宜慎用。     

竖向荷载下考虑桩土接触的桩基沉降分析

运用有限元软件ANSYS建立群桩-土体-承台三维有限元非线性模型,考虑桩土间接触,在其接触面引入接触单元,模拟桩土间复杂的相互作用,对群桩沉降性状进行了分析。     

地质条件误判导致山岭隧道二衬开裂及对策

介绍在地质及水文条件复杂的山岭隧道,因人为误判地质及水文条件使设计与实际不符而带来的二次衬砌开裂现象,并提出了相应的对策措施。     

厂区道路路面养护方案选择方法研究

以宝钢厂区道路养护管理为背景,针对厂区道路在路面养护方案选择中存在的问题,对厂区道路路面养护工程进行分类和定义,并结合路面管理系统提出养护方案选择的流程与方法,以实现科学制定养护方案和合理分配有限资源的目的.     

高烈度地震区公路隧道洞口段地震响应分析

根据隧道地震安全性评价报告和地勘资料,建立了三维数值计算模型并采用一致粘弹性人工边界模拟动力边界,对高烈度地震区公路隧道洞口段进行了瞬态动力计算。计算结果表明:在三向地震荷载激励下,洞口段衬砌的地震响应具有明显滞后性,衬砌以水平横向振动为主、轴向振动次之、竖向振动最弱;洞口段衬砌的拱腰部位将承受极大拉应力和剪应力,可设减震层吸收地震能量。通过对衬砌相对位移的分析得出,衬砌横向和轴向变形都很小,衬砌稳定性尚好。     

降雨入渗对浅埋偏压隧道及其支护系统的影响

利用渗流-应力耦合方法对浅埋偏压隧道在降雨入渗情况下的稳定性做了三维数值分析.模拟了隧道的开挖、锚杆支护和衬砌支护过程,以及完工后长期降雨对隧道及其支护系统的影响.锚杆使用杆单元模拟,采用杆单元埋入实体单元技术,简化了有限元建模过程.计算模型对隧道有无排水系统的情况作了仔细分析,结果表明,在不排水条件下,降雨入渗将使隧道衬砌的最大弯矩增加近1倍,锚杆上的最大轴力增加近20%;而在排水条件下,衬砌和锚杆上的力学行为和降雨前相比,并无明显变化.因此,隧道排水系统的合理设置,对于降雨期间的隧道稳定性和支护系统的力学行为有重要影响.     

Improvement of the second order approximation of the smoothed particle hydrodynamics

The smoothed particle hydrodynamics (SPH), as a fully Lagrangian particle method, has been successfully applied to astrophysical problems and extended to elastic dynamics and computational fluid dynamics.High order derivatives have to be approximated when elastic dynamics problems are modeled. However, the approximation errors in SPH could lead to computational failure in the case that the order of derivative is high.A novel method was proposed in order to improve the accuracy of SPH method, which shows the relationship between the selected functions and their SPH approximations. The entire involved system was represented by a finite number of particles that carry individual mass and occupy individual space, and the integral interpolation was approximated by a summation interpolation. In addition, error comparison was made between SPH method with and without the present improvement.     

Control method of three-level neutral-point-clamped inverter based on voltage vector diagram partition

A new modulation approach was presented for the control of neutral-point (NP) voltage variation in the three-level NP-clamped voltage source inverter, and the average NP current model was established based on vector diagram partition. Thus, theory base was built for balancing control of NP potential. Theoretical analysis and experimental results indicate that the proposed method for NP balancing control vector synthesizing concept based can make the average NP current zero, and do not influence NP potential within every sample period. The effectiveness of proposed research approach was verified by simulative and experimental results.     

A bintree energy approach for colour image segmentation using adaptive channel selection

A new hierarchical approach called bintree energy segmentation was presented for color image segmentation. The image features are extracted by adaptive clustering on multi-channel data at each level and used as the criteria to dynamically select the best chromatic channel, where the segmentation is carried out. In this approach, an extended direct energy computation method based on the Chan-Vese model was proposed to segment the selected channel, and the segmentation outputs are then fused with other channels into new images, from which a new channel with better features is selected for the second round segmentation. This procedure is repeated until the preset condition is met. Finally, a binary segmentation tree is formed, in which each leaf represents a class of objects with a distinctive color. To facilitate the data organization, image background is employed in segmentation and channels fusion. The bintree energy segmentation exploits color information involved in all channels data and tries to optimize the global segmentation result by choosing the ＂best＂ channel for segmentation at each level. The experiments show that the method is effective in speed, accuracy and flexibility.     

A new channel allocation scheme for hierarchical wireless networks

A channel allocation scheme for hierarchical wireless networks was proposed in terms of the connection-level quality of service. The channel allocation scheme was analyzed using both horizontal channel borrowing and vertical traffic overflowing. Pre-emptive priority strategies are used to classify real-time services and non-real-time services, real-time service is given higher priority for it is allowed to pre-empt channels used by non-real-time service. Some channel borrowing thresholds and acceptance ratios are used to avoid channel locking or dynamic power control, which can also be dynamically adjusted according to network load. Simula-tion results show that the proposed schemes can improve the system performance.