基于离散单元法的群楼拆除爆破仿真模拟

基于青岛开发区一商场爆破工程,利用颗粒离散元法建立离散元网格实体模型,用多面体离散元法模拟分析拆除爆破中建筑物的倒塌过程。研发的网格实体模型详细模拟了建筑物从结构局部失稳到整体完全倒塌的整个过程,确定了爆堆轮廓线和爆堆尺寸,直观给出了爆破设计的效果。触地振动、冲击力变化分析结果表明:所给出的爆破方案可达到预期拆除爆破的效果,触地振动符合《爆破安全规程》要求;该模型可优化爆破设计,指导爆破施工,为建筑物拆除爆破的灾害预测与安全评估提供理论依据。     

A review on distributed generation impacts on electric power system

In 2021, the world's total installed capacity of generation units based on renewable energy sources (not including hydropower) amounted to about 1674 GW: over 825 GW and 849 GW of wind and solar power plants were installed respectively. The growing of the installed capacity of these distributed generators is a response to the increasing the power consumption, global environmental issues and has also become possible due to the development of technology in field of power semiconductor devices. However, on the way of large-scale implementation of distributed generators based on renewable energy sources, traditional electric power system meets new challenges to ensure the reliability and sustainability of new electric power systems with renewable energy sources. In particular, distributed generators change processes in the electric power system, impact to the parameters and power balance, change the magnitude and direction of power flow and short-circuit current, which determines the need to update the settings of the relay protection and automation systems of traditional electric power system and to coordinate their operation with automatic control systems of installed distributed generators. The above-mentioned tasks form a number of scientific research directions, one of which is a task of determining optimal size and location of distributed generators. The main purpose of this optimization task is to reduce power losses, operating and total electricity cost, improve the voltage profile, etc. In addition, the correct and reasonable placement of distributed generators defines an effective planning of the operating modes of electric power system and power plants (especially based on renewable energy sources, the operating modes of which depend on weather conditions and can be sharply variable).The paper highlighted the impacts of distributed generators on power losses, the voltage level, maintaining the power balance and the possibility of participating in the frequency regulation, and short-circuit current in power system. The optimization criteria, the main limiting conditions, as well as methods for solving this optimization problem are considered. This review will help the System operators and investing companies, especially in Russia, to form the main aim, objective function and constraints that will aid to meet their load demand at minimum cost and to choose from the options available for optimization of location and capacity of distributed generators.     

Numerical study of microscopic particle arrangement of suspension flow in a narrow channel for the estimation of macroscopic rheological properties

In a narrow channel, the apparent relative viscosity of a suspension with finite-size particles is strongly dependent on its microscopic particle arrangement. Relative viscosity increases when suspended particles flow near the channel wall; thus, a suspension in a narrow channel does not always exhibit the same rheological properties even if the concentration is the same. In this study, we focus on the inertia and concentration of particles in a narrow channel and consider their effects on the microscopic particle arrangement and macroscopic suspension rheology. Two-dimensional pressure-driven suspension flow simulations were performed using a two-way coupling scheme, and normalized particle density distribution (PDD) were implemented to consider their particle arrangements. The results demonstrated that the velocity profiles for the particle suspension were changed by the Reynolds number and particle concentration because of the interactions between particles according to the power-law index. These changes affected the particle equilibrium positions in the channel, and the subsequent changes in solvent layer thickness caused changes in the macroscopic apparent viscosity. The behavior of microscopic particles played important roles in determining macroscopic rheology. Thus, we have confirmed that a normalized PDD can be used to estimate and assess the macroscopic rheology of a suspension.     

Techno-economic assessment of hydrogen refueling station: A case study in Croatia

Hydrogen refueling station (HRS) capacity and location depend on the users, which makes it difficult to select the most favorable option before potential users are actually identified. As in Croatia, at least for now, there are no hydrogen users, this study considers a wide range of HRS capacities and their different configurations. These include hydrogen production and charging station within one existing wind farm in Croatia or both nearby the users, the hydrogen production within the wind farm and the charging station nearby the users, while hydrogen is delivered to the station with a tube trailer, and configuration of hydrogen production within the wind farm with a mobile charging station in case of several users in different locations. Each HRS configuration is evaluated by the obtained levelized cost of hydrogen depending on the capital, and operation and maintenance costs within the HRS techno-economic analysis provided.     

嵌套式复合型材构件制造技术及其专用机床

嵌套式冷轧复合型材构件制造技术包括平整、加强筋成型、第一辊压模具组成型、冲孔、主截面成型、第二辊压模具组的横截面成型、嵌套合抱、第一构件与第二构件嵌套抱合后成为复合型材构件与第三辊压模具组紧贴等工序组成,在冲孔工序之前先完成加强筋成型工序,保证冲孔加工后的孔距尺寸精度,显著提高产品质量;上述所有工序都是设置在同一条生产线上的专用机床连续自动完成,实现了嵌套式冷轧复合型材构件的自动化生产,节约工时,降低产品成本。     

三角平衡轮廓轮胎滚动阻力的仿真研究

三角平衡轮廓轮胎是一种新型的轮胎结构,以低扁平率的传统轮廓轮胎255/30R22为基础,在其胎肩处和胎侧处增加高强度的支撑块来提高轮胎的性能。支撑块起到支撑胎面的作用,提高了胎侧的刚度。本文以滚动阻力计算公式和材料内耗机理为基础,用ABAQUS软件分别模拟2种轮胎的滚动阻力来验证三角平衡轮廓轮胎是否具有较低的滚动阻力。首先建立三角平衡轮廓轮胎和255/30R22轮胎的三维模型,施加相同载荷,对其进行以60km/h滚动工况的力学分析,算出单元积分点的生热率,提取每个单元的体积,最后计算每一种胶料的滚动阻力及轮胎总滚动阻力。通过两者的对比,三角平衡轮廓轮胎的滚动阻力仅18.7N,低于255/30R22轮胎滚动阻力的二分之一。     

Physicochemical Property and Fatty Acid Profile of Cephalotaxus fortunei Nut Oils

This paper focused on the main composition of Cephalotaxus fortunei nuts, the physicochemical property of its oils, the fatty acid profiles and the content of alkaloids and tocopherol in the nuts oils. And these elements were compared among three kinds of C. fortunei nuts and their oil. The results showed the C. fortunei nuts contained about 65 % crude oil. Meanwhile, the content of crude protein, crude fiber, moisture, ash and reduced sugar were presented, respectively. The important physicochemical indicators of the crude C. fortunei nuts oils were presented, including specific gravity, refractive index, viscosity, acid value and saponification value, etc. The contents of alkaloids were 0.41 % in NUT1, 0.24 % in NUT2 and 0.31 % in NUT3. The contents of tocopherol were low. The analysis of the fatty acid composition showed that the three kinds of oils were all rich in unsaturated fatty acids, oleic acid and linoleic acid, and the main triacylglycerols were dioleoyl-monolinoleoyl (OLO) and triolein (OOO). This work might help with the exploration of the applications of C. fortunei nuts and its oil.     

塔里木盆地大坂塔格—一间房奥陶系剖面层序划分及特征

大坂塔格—一间房奥陶系剖面自下而上可划分为蓬莱坝组、鹰山组、一间房组、吐木休克组和良里塔格组。该剖面可以识别出6个三级层序,层序中体系域发育不全,由TST和HST构成。海侵体系域岩石类型以暗色泥晶灰岩、泥质灰岩、泥晶藻灰岩为主,发育水平层理及微波状层理,岩层厚度从中厚层状逐渐减至薄-纹层状。高水位体系域由一系列前积型的准层序组所组成。     

曙一区古潜山油藏气体压锥化学堵水技术研究与应用

曙光油田曙一区古潜山油藏,构造上位于辽河断陷西部凹陷西斜坡中段。属于边底水和裂缝发育的块状稠油潜山油藏,具有油稠、底水能量充足、纵横向裂缝均发育等特点。底水锥进已成为制约该区块开发的主要矛盾。随着油井吞吐轮次的增加,现有技术的局限性日渐凸。气体压锥化学堵水技术,通过气体筛选,配方堵剂及现场施工参数的优化设计,可大幅度增加堵剂的作用半径,提高油井的采收率,改善区块整体开发效果。