矿区资源承载力预测研究——以马钢南山矿区为例

要实现矿区的持续发展,需定量地知道矿区资源承载力未来将发生怎样的变化,以保证其资源消耗在承载力允许范围内。矿区是一个开放复杂巨系统,且常缺乏资源情况的历史数据。系统动力学不需要历史数据就能揭示开放复杂巨系统的运行规律;情景分析法通过定量地设定未来多种可能的发展情景,能解决使用系统动力学模型进行预测时,控制变量难以定量的问题。以马钢南山矿区为例,证实系统动力学与情景分析法的结合定量预测矿区资源承载力的可行性,并阐述如何利用该方法进行资源承载力的预测。     

Mechanical properties of calcium silicate hydrate (C–S–H) at nano-scale: A molecular dynamics study

Calcium silicate hydrate (C–S–H) is the most important binding phase of cement paste and can determine the mechanical properties of cementitious material. The multi-scale nature of C–S–H gel brings about challenges in interpreting the mechanical properties of C–S–H. C–S–H models at the nano scales are commonly formulated by the aggregation of colloids that consist of layered molecular structures. In this study, the mechanical properties of C–S–H were investigated at the molecular level (∼5 nm). Uniaxial tension testing in the x, y, z directions was applied to the layered structure of C–S–H. The structural difference in the layer leads to heterogeneous mechanical properties in three directions. Particularly in the z direction, the C–S–H layer connected by H-bonds and Ca²⁺, has the weakest tensile strength. Resulting from the investigation, it can be concluded that the simulation can provide molecular insights into the linkage between molecular and larger scale structures.     

Computer-Aided Targeting of the PI3K/Akt/mTOR Pathway: Toxicity Reduction and Therapeutic Opportunities

The PI3K/Akt/mTOR pathway plays an essential role in a wide range of biological functions, including metabolism, macromolecular synthesis, cell growth, proliferation and survival. Its versatility, however, makes it a conspicuous target of many pathogens; and the consequential deregulations of this pathway often lead to complications, such as tumorigenesis, type 2 diabetes and cardiovascular diseases. Molecular targeted therapy, aimed at modulating the deregulated pathway, holds great promise for controlling these diseases, though side effects may be inevitable, given the ubiquity of the pathway in cell functions. Here, we review a variety of factors found to modulate the PI3K/Akt/mTOR pathway, including gene mutations, certain metabolites, inflammatory factors, chemical toxicants, drugs found to rectify the pathway, as well as viruses that hijack the pathway for their own synthetic purposes. Furthermore, this evidence of PI3K/Akt/mTOR pathway alteration and related pathogenesis has inspired the exploration of computer-aided targeting of this pathway to optimize therapeutic strategies. Herein, we discuss several possible options, using computer-aided targeting, to reduce the toxicity of molecularly-targeted therapy, including mathematical modeling, to reveal system-level control mechanisms and to confer a low-dosage combination therapy, the potential of PP2A as a therapeutic target, the formulation of parameters to identify patients who would most benefit from specific targeted therapies and molecular dynamics simulations and docking studies to discover drugs that are isoform specific or mutation selective so as to avoid undesired broad inhibitions. We hope this review will stimulate novel ideas for pharmaceutical discovery and deepen our understanding of curability and toxicity by targeting the PI3K/Akt/mTOR pathway.     

Stable imposition of stiff constraints in explicit dynamics for embedded finite element methods

We investigate various strategies to enforce the kinematics at an embedded interface for transient problems within the extended finite element method. In particular, we focus on explicit time integration of the semi‐discrete equations of motion and extend both dual and primal variational frameworks for constraint enforcement to a transient regime. We reiterate the incompatibility of the dual formulation with purely explicit time integration and the severe restrictions placed by the Courant–Friedrichs–Levy condition on primal formulations. We propose an alternate, consistent formulation for the primal method and derive an estimate for the stabilization parameter, which is more amenable in an explicit dynamics framework. Importantly, the use of the new estimate circumvents the need for any tolerances as an interface approaches an element boundary. We also show that with interfacial constraints, existing mass lumping schemes can lead to prohibitively small critical time steps. Accordingly, we propose a mass lumping procedure, which provides a more favorable estimate. These techniques are then demonstrated on several benchmark numerical examples, where we compare and contrast the accuracy of the primal methods against the dual methods in enforcing the constraints. Copyright © 2012 John Wiley & Sons, Ltd.     

Simulation of membrane chemical degradation in a proton exchange membrane fuel cell by computational fluid dynamics

Membrane chemical degradation is a major contributor to the still limited lifetime of proton exchange membrane (PEM) fuel cells. In the present work, this phenomenon is simulated by computational fluid dynamics (CFD). The main advantage of the CFD model is that it can provide the degradation profile across the cell active area. Results reveal that degradation accelerates when voltage, temperature and pressure are increased and when reactants humidity and membrane thickness are decreased. Moreover, membrane deterioration is found to be more severe where oxygen pressure is higher, and more heterogeneous when oxygen distribution is less uniform. Generally, conditions that increase current production and thus oxygen depletion along the cell increase degradation heterogeneity. The flow field design is also found to influence the membrane degradation spatial profile. The modeling strategy here applied, the incorporation of a degradation sub-model into a general-purpose CFD code, can be used to include other degradation mechanisms.     

颗粒微切削表面创成的分子动力学仿真研究

颗粒微切削的性能和行为直接影响工件的表面质量,从材料去除规律和能量变化规律的角度对颗粒微切削作用的表面创成机理进行研究,分别采用EAM势、Morse势、Tersoff势描述单晶铜原子间、工件与颗粒、颗粒刀具原子间的作用力。分析纳米尺度下颗粒切削方向、颗粒切削速度、系综温度对颗粒微切削作用,通过探讨体系动能、体系势能、体系总能对工件原子运动规律的影响及颗粒微切削加工前后键角的变化形态,为阐述颗粒微切削作用的表面创成机理提供理论依据。研究结果表明正交切削比斜切削能获得更好的表面质量,颗粒速度与能量不存在线性关系,颗粒温度对体系能量有直接影响。通过分子动力学数值模拟得到体系的结构信息及相关热力学性质并对分子动力学的微观统计量进行分析计算,寻找合适的加工参数,为颗粒微切削加工工艺的发展提供技术支持。     

OPM3要素对项目组合管理能力影响的SD建模与仿真

根据组织项目管理成熟度模型（OPM3），确定影响项目组合管理能力的OPM3要素，分析OPM3要素与项目组合管理能力的因果关系，构建系统动力学模型，仿真模拟OPM3要素对项目组合管理能力的影响。仿真结果表明：OPM3要素与项目组合管理能力正相关；OPM3要素对项目组合管理能力的影响在短期内并不显著；在OPM3要素中，对项目组合管理能力影响较为显著的是战略执行与规划、组织领导能力和信息分析。     

Experimental investigation on no-vent fill process using tetrafluoromethane (CF4)

This paper investigates the transfer of liquid cryogens using a no-vent fill (NVF) process experimentally to identify the dominant NVF parameters. The experimental apparatus has been fabricated with extensive instrumentations to precisely study the effects of each NVF parameter. Liquid tetrafluoromethane (CF₄) is selected as the working fluid due to its similar molecular structures and similar normal boiling point and triple point with liquid methane which has been considered as an attractive future cryogenic propellant. The experimental results show that the initial receiver tank wall temperature and the incoming liquid temperature are the primary factors that characterize the (non-equilibrium) thermodynamic state at the start of a NVF transfer. The supply pressure is also critical as it indicates the ability to condense vapor in the receiver tank. A non-dimensional map based on energy balance is proposed to find acceptable initial conditions of the filling volume at the desired final tank pressure. The non-dimensional map shows good agreement with the NVF data not only in this paper but also in the previous research.     

Auslegung von Blasensäulen mithilfe von Compartmentmodellen

In bubble columns, the phenomena of mass and heat transfer as well as the reaction are closely linked to the complex fluid dynamics. Compartment modeling offers the opportunity to integrate these phenomena while enabling an axial and radial distribution with acceptable computing effort. This article includes methods for generating the compartment geometry and fluid dynamic parameters of this modeling approach, facilitating the opportunity to optimize an industrial bubble column.     

Predicting dust emissions – Experimental study compared to coupled DEM/CFD simulations using a reference test bulk material

The awareness of dust emissions is crucial regarding safe industrial processes, environmental protection and health care. For this purpose, closely linked experimental and numerical investigations are performed. This work presents the results of an experimental study which is used for the calibration of a modelling framework based on the Discrete Element Method (DEM) coupled with Computational Fluid Dynamics (CFD) and applied for the calculation of dust emissions for predictive purposes. The key objective of the approach is to come up with a dust source term which enables to describe and to quantify the release of particle emissions. For the presented experimental study, a wind tunnel and a rotating drum setup, which cover various handling types of bulk materials, are used in order to gain data about parameters having an impact on the dust release. The special feature of the investigations is the use of a reference test bulk material which represents a bulk material in its generally main fractions, the fine and the coarse material, keeping the discrepancy between experiments and simulations low. With the help of the experimental results the calibration of the simulation model was carried out and followed by a comparison.