某矿井下浅孔毫秒延时爆破地表震动的数值模拟研究

某地下矿山上方地表分布有土坯房,一层、二层砖混结构民房以及水稻田。该矿山生产过程中产生的爆破震动易影响周边民房的稳定。为研究该矿山井下生产爆破时地表的震动强度,确保民房震动强度安全,利用LS-DYNA有限元方法对某次具有代表性的生产爆破下的地表震动强度进行了分析研究。通过对该次具有代表性的生产爆破数值计算与爆破震动现场测试结果对比分析表明,采用ANSYS/LS- DYNA的数值计算结果与实际测试值偏差不大,数值模拟分析方法对爆破震动强度的预测具有一定的指导价值。     

Self-supporting nanoporous Ni/metallic glass composites with hierarchically porous structure for efficient hydrogen evolution reaction

Searching for free-standing and cost-efficient hydrogen evolution reaction (HER) electrocatalysts with high efficiency and excellent durability remains a great challenge for the hydrogen-based energy industry.Here,we report fabrication of a unique hierarchically porous structure,i.e.,nanoporous Ni (NPN)/metallic glass (MG) composite,through surface dealloying of the specially designed Ni40Zr40Ti20 MG wire.This porous composite is composed of micrometer slits staggered with nanometer pores,which not only enlarges effective surface areas for the catalytic reaction,but also facilitates the release of H2 gas.As a result,the NPN/MG hybrid electrode exhibited the prominent HER performance with a low overpotential of 78 mV at 10 mAcm-2 and Tafel slope of 42.4 mV dec-1,along with outstanding stability in alkaline solutions.Outstanding catalytic properties,combining with their free-standing capability and cost efficiency,make the current composite electrode viable for HER applications.     

Reliability sensitivity-based correlation coefficient calculation in structural reliability analysis

The correlation coefficients of random variables of mechanical structures are generally chosen with experience or even ignored,which cannot actually reflect the effects of parameter uncertainties on reliability.To discuss the selection problem of the correlation coefficients from the reliability-based sensitivity point of view,the theory principle of the problem is established based on the results of the reliability sensitivity,and the criterion of correlation among random variables is shown.The values of the correlation coefficients are obtained according to the proposed principle and the reliability sensitivity problem is discussed.Numerical studies have shown the following results:(1) If the sensitivity value of correlation coefficient ρ is less than(at what magnitude 0.000 01),then the correlation could be ignored,which could simplify the procedure without introducing additional error.(2) However,as the difference between ρs,that is the most sensitive to the reliability,and ρR,that is with the smallest reliability,is less than 0.001,ρs is suggested to model the dependency of random variables.This could ensure the robust quality of system without the loss of safety requirement.(3) In the case of |Eabs|ρ0.001 and also |Erel|ρ0.001,ρR should be employed to quantify the correlation among random variables in order to ensure the accuracy of reliability analysis.Application of the proposed approach could provide a practical routine for mechanical design and manufactory to study the reliability and reliability-based sensitivity of basic design variables in mechanical reliability analysis and design.     

Guest-Stimulated Nonplanar Porphyrins in Flexible Metal−Organic Frameworks

Nonplanar porphyrins with out-of-plane distortions play crucial roles in many biological functions and chemical applications. The artificial construction of nonplanar porphyrins usually involves organic synthesis and modification, which is a highly comprehensive approach. However, incorporating porphyrins into guest-stimulated flexible systems allows to manipulate the porphyrin distortion through simple ad/desorption of guest molecules. Here, a series of porphyrinic zirconium metal−organic frameworks (MOFs) is reported that exhibit guest-stimulated breathing behavior. X-Ray diffraction analysis and skeleton deviation plots confirm that the material suffers from porphyrin distortion to form a ruffled geometry under the desorption of guest molecules. Further investigation reveals that not only the degree of nonplanarity can be precisely manipulated but also the partial distortion of porphyrin in a single crystal grain can be readily achieved. As Lewis acidic catalyst, the MOF with nonplanar Co-porphyrin exhibits active properties in catalyzing CO₂/propylene oxide coupling reactions. This porphyrin distortion system provides a powerful tool for manipulating nonplanar porphyrins in MOFs with individual distortion profiles for various advanced applications.     

水盐体系汽液平衡的热力学模型研究

水盐体系的相平衡性质是化工单元操作的基础,在化学化工、海洋、地质等领域有着重要的研究价值。国内外许多学者对水盐体系汽液平衡进行了实验和理论的研究,构筑了各具特色的经验和半经验的模型。针对水盐体系,在NRTL理论的基础上,基于水化作用和混合盐假设建立了能够预测混合体系汽液平衡的活度系数扩展模型。通过对21组二元水盐体系和14组混合体系的关联计算,验证了该模型的可行性;同时,该模型可以采用二元体系参数直接预测计算混合水盐体系汽液平衡。     

Structural reliability updating using experimental data

Journal of Mechanical Science and Technology - Conventional reliability analysis requires the information from an existing structure, such as a mechanical model and random distributed inputs. In...     

同阴离子双盐体系分离过程图解法综合

氯化钾是我国化肥生产的重要原料,包含氯化钾的无机盐体系的分离过程综合研究具有重要理论意义和应用价值。以NaCl-KCl-H₂O体系为例,提出了一种同阴离子双盐体系分离过程的综合方法。该方法是通过分析同阴离子双盐体系的固液平衡关系,在温度的影响和同离子效应的基础上建立的。其利用图解法直接从相图中寻找可行的分离工艺流程,设计过程简便易行。分别给出NaCl-KCl-H₂O体系的两个和MgCl₂-KCl-H₂O体系的一个过程综合案例,并给出了相应的工艺流程。     

模糊聚类算法在银行客户分类管理中的应用

本文以银行业务数据为研究对象,结合聚类分析和模糊数学中模糊相似矩阵的思想,将模糊数学理论应用于聚类分析中,提出了基于模糊聚类分析的综合排序方法,即模糊聚类法。本文采用该算法对现有银行客户的存、贷款、信用卡、转账结算等业务的总体情况进行综合排序,以便于银行客户经理根据排序结果,对不同客户采取支持、维护或淘汰等不同的分类管理策略,最大限度降低银行的客户管理成本。