Non-metallic catalysts for diamond synthesis under high pressure and high temperature

Recent results on conversion from graphite to diamond by aid of non-metallic catalysts are reviewed. The current status of experimental advances is presented and typical examples from relevant literature are provided for understanding the mechanism of the graphite-diamond conversion by aid of these non-metallic catalysts. Furthermore, a tendency of graphite-diamond transformation assisted by carbonates, sulfates or phosphorus under high pressure and high temperature has been investigated by calculating the activation energy and transformation probability of the carbon atoms over a potential barrier. It was found that the activation energy is highly sensitive to the catalyst chosen. The probability sequence of graphite-diamond transformation with these catalysts was put forward. Project supported by the National Natural Science Foundation of China (Grant No. 19674970).     

Bioeconomic modeling of household waste recovery

The ecological consciousness has driven developed societies to explore alternatives to the growing need for energy and the consequent increase in waste production. The adjustment towards the waste recovery and their transformation into energy, by various processes, is then necessary. However, so far, the domain has not benefited much from a mathematical modeling approach. The main contribution of this work consists of building a bioeconomic model describing the problem of a potential investor who aims to maximize his net profit generated by selling the produced energy from the household waste transformation. We first study the evolution of a waste stock, the energy quantity produced, and the capital dedicated to the transformation process in a giving landfill and recovery center. Then we insert decision variables to this dynamic which are both the investment and the part of waste to be treated. This leads to an optimal control problem which we solve by the deductive method. The resulted solution is then illustrated by some numerical simulations. This investment policy would be to support the decision makers to go towards investment in this activity.     

Nucleation Barriers for the Cubic‐to‐Tetragonal Phase Transformation

We are interested in the phase transformation from austenite to martensite. This transformation is typically accompanied by the generation and growth of small inclusions of martensite. We consider a model from geometrically linear elasticity with sharp energy penalization for phase boundaries. Focusing on a cubic‐to‐tetragonal phase transformation, we show that the minimal energy for an inclusion of martensite scales like $\max \{ V^{2/3}, V^{9/11} \}$ in terms of the volume V. Moreover, our arguments illustrate the importance of self‐accommodation for achieving the minimal scaling of the energy. The analysis is based on Fourier representation of the elastic energy. © 2012 Wiley Periodicals, Inc.     

构造容许位移的转换边界法

本文提出了在复杂边界条件下构造容许位移的转换边界法.所谓转换边界法,就是首先根据叠加原理将实际系统转换为基本系统及附加边界力和附加边界位移,然后应用变分原理于基本系统,最后应用级数转换的办法求得实际系统的容许位移.本文还给出了边界条件变化的混合能量原理.这边界条件变化的混合能量原理和边界条件变化的势能原理和余能原理都是转换边界法的主要理论基础.应用转换边界法我们构造了复杂边界条件平面应力问题和弯曲问题矩形板的容许位移.由于转换边界法构造容许位移是遵循着变分原理和确定的程序进行的,因而克服了Rayleigh-Ritz法猜测、拼凑容许位移的困难.     

Energy cycle of brushless DC motor chaotic system

The vector field of the brushless DC motor (BLDCM) chaotic system is regarded as the force field of a pure mechanical system via the transformation of Kolmogorov system. The BLDCM force field is decomposed into four types of torque: inertial, internal, dissipative, and generalized external torque. The forcing effect of each term in the force field is identified via the analogue of the electrical and mechanical system. The BLDCM energy transformation of four forms of energy—kinetic, potential, dissipative, and generalized external is investigated. The physical interpretation of force decomposition and energy exchange is given. The rate of change of the Casimir energy is equivalent to the power exchanged between the dissipative energy and the energy supplied to the motor, and it governs the different dynamic modes. A simple and optimal supremum bound for the chaotic attractor is proposed using the Casimir function and optimization.     

基于多指标区间逼近的住宅建筑节能改造方案评价

鉴于住宅建筑节能改造的效果的总体评价的复杂性及其影响因素的不确定性,将区间数关联决策方法应用于节能改造效果的评价领域.通过引入区间数序列的范数完成多指标决策矩阵的规范化处理,建立多指标区间数整体逼近关联决策模型,完成住宅建筑节能效果评估得出最终结论.计算实例验证了该模型的有效性和实用性,较好地解决了住宅建筑节能改造效果评价的实际问题,取得较为满意的结果.     

Maximum norm error estimates of the Crank-Nicolson scheme for solving a linear moving boundary problem

The Crank-Nicolson scheme is considered for solving a linear convection-diffusion equation with moving boundaries. The original problem is transformed into an equivalent system defined on a rectangular region by a linear transformation. Using energy techniques we show that the numerical solutions of the Crank-Nicolson scheme are unconditionally stable and convergent in the maximum norm. Numerical experiments are presented to support our theoretical results.     

Modelling of linguistic variables in multicriteria energy policy support

The climate change and the increasing complexity of the energy sector along with the prerequisite for sustainability have broadened the energy policy shaping field by bringing out new challenges. Decision support tools and methods, such as Multicriteria Decision Aid (MCDA), are necessary for energy policy, in the pursuit of appropriate approaches necessary to support the restructuring of the energy sector, concerning patterns of energy extraction, generation, transformation and use, from unsustainable to sustainable forms of development. Papers devoted to the investigation of MCDA models using linguistic variables for energy policy support seem to be not available in the international literature. The scope of this paper is to explore different linguistic representation and computational models in MCDA that are or can be applied to energy policy support and to establish a clear linkage between them. This paper argues that MCDA methodologies with direct computation on linguistic variables can support energy policy frameworks, bridging the gap between energy policy makers thinking, reasoning, representation and computing. Finally, current trends, open questions and prospects in this topic are pointed out.     

Multi-mode model of a piezomagnetoelastic energy harvester under random excitation

Abstract: The transformation of ambient vibrational energy into electric energy through the use of piezoelectric energy harvesting devices has been the subject of numerous investigations [1]. A commonly studied energy harvesting device performing especially well under broadband excitation, is the piezomagnetoelastic energy harvester investigated by Erturk et al. [2], which is usually discretised for the fundamental vibration mode resulting in a single-mode model. This contribution presents the study of a multi-mode model of the piezomagnetoelastic energy harvester under random excitation. The probabilty density function (PDF) is computed to be the solution of the corresponding Fokker-Planck equation using a Galerkin type method [3,4]. Based on the PDF, the resulting voltage variance is computed as a measurement for the expected power output as demonstrated in [5]. The results of the multi-mode model are then compared with the results of the single-mode model. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Analysis of a thermomechanical phase transition model

Subject of this work is a macroscopic thermomechanical model of phase transitions in steel. Effects like transformation strain and transformation plasticity induced by the phase transitions are considered and used to formulate a consistent thermomechanical model. The resulting system of state equations consists of a quasistatic momentum balance coupled with a nonlinear stress-strain relation, a nonlinear energy balance equation and a system of ODEs for the phase volume fractions. We prove the existence of a unique weak solution using fixed-point arguments. A key issue is a regularity analysis for the mechanical subsystem to obtain continuity of the stress tensor. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A new formulation of relativistic quantum field theory

Quantum field theory is reformulated in sucha manner that a complete set of ocillators for modes with both positive and negative energies are introduced. The theory leads to the proper connection between spin and statistics as in the standard formulation, but it implements the time reversal transformation and the TCP transformation as linear unitary transformations. Negative energy particles in the initial states are identified with antiparticles in the final state with reversed motion (andvice versa) as far as scattering amplitudes are concerned. A covariant perturbation theory is developed which yields scattering amplitudes which are essentially the same as in the usual theory.     

Numerical model for vibration damping resulting from the first-order phase transformations

A numerical model is constructed for modelling macroscale damping effects induced by the first-order martensite phase transformations in a shape memory alloy rod. The model is constructed on the basis of the modified Landau–Ginzburg theory that couples nonlinear mechanical and thermal fields. The free energy function for the model is constructed as a double well function at low temperature, such that the external energy can be absorbed during the phase transformation and converted into thermal form. The Chebyshev spectral methods are employed together with backward differentiation for the numerical analysis of the problem. Computational experiments performed for different vibration energies demonstrate the importance of taking into account damping effects induced by phase transformations.     

The construction of the energy space

In this paper, the method of transformation of the phase space to obtain the energy space is presented. This new kind of space allows for a new, geometrical view on energy changes in vibrating systems.     

A Phase Field Model for Martensitic Transformations

The martensitic transformation is described using a phase field model which is in mathematical terms the regularization of a sharp interface approach. In this work, up to two martensitic orientation variants are considered. The evolution of microstructure is assumed to follow a time dependent Ginzburg-Landau equation. The coupled problem of the mechanical balance equation and the evolution equations is solved using finite elements and an implicit time integration scheme. In this work, the global energy evolution during the martensitic transformation and the influence of external loads on the formation of the different martensitic phases are studied in 2d. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The construction of the energy space

In this paper, the method of transformation of the phase space to obtain the energy space is presented. This new kind of space allows for a new, geometrical view on energy changes in vibrating systems.     

Implications of Shield’s inverse deformation theorem for compressible finite elasticity

Some properties of the Shield transformation on elastic strain energy functions are established. It is reflexive, it preserves objectivity and material symmetry for isotropic materials, and it also preserves infinitesimal strain response, ellipticity and Hadamard stability, and the Baker–Ericksen condition. Two new classes of strain energies for compressible isotropic materials are introduced, one of them being the image under the Shield transformation of the class of harmonic strain energies. In view of Shield’s Inverse Deformation Theorem, these new classes of strain energies will allow solution in closed form of a variety of problems in finite elastostatics.     

既有建筑合同能源管理中的政府角色——基于模糊Shapley值的研究

通过合同能源管理模式进行建筑节能改造,节能收益的分配问题比传统模式复杂。而节能改造的外部性导致利益相关者主动参与意愿不强,阻碍合同能源管理模式的发展。研究以合同能源管理模式中的能源费用托管型为例,基于利益相关者的利己性和逐利性,采用模糊区间Shapley值方法,构建核心利益相关者(建筑业主、节能服务公司和金融机构)的节能收益分配模型;分析建筑节能改造的外部性特征,运用系统动力学厘清合同能源管理模式产生的非节能收益(经济、环境、社会),形成全部利益相关者的因果关系正负反馈回路;尝试将政府纳入分配机制中,构建新的合同能源管理收益分配模型,有助于提高核心利益相关者的综合收益;提出政府不应仅仅为了完成节能目标来鼓励节能改造项目,更应优化建筑节能改造的外部环境。     

复合材料单层板非弹性主方向的裂纹尖端应变能释放率

本文研究线弹性正交异性复合材料单层板非弹性主方向的断裂问题.推出了非弹性主方向坐标系和弹性主方向坐标系的特征根和柔度系数的变换公式.将裂纹尖端应力与位移代入应变能释放率的基本公式,得到了在斜对称载荷作用下,用弹性主方向坐标系的工程参量表示的裂纹尖端应变能释放率的计算公式.     

Implications of Shield’s inverse deformation theorem for compressible finite elasticity

Some properties of the Shield transformation on elastic strain energy functions are established. It is reflexive, it preserves objectivity and material symmetry for isotropic materials, and it also preserves infinitesimal strain response, ellipticity and Hadamard stability, and the Baker–Ericksen condition. Two new classes of strain energies for compressible isotropic materials are introduced, one of them being the image under the Shield transformation of the class of harmonic strain energies. In view of Shield’s Inverse Deformation Theorem, these new classes of strain energies will allow solution in closed form of a variety of problems in finite elastostatics. Received: January 30, 2002