Isothermal phase change model for freezing and thawing soils II: Model

A FORTRAN computer program is available which accomodates two-dimensional heat and soil-water flow models as coupled by an isothermal phase change model. The program can be used to analyze two-dimensional freezing/thawing problems which have sufficient known information to supply the necessary modeling parameters, boundary conditions, and initial conditions. Because of the sophistication of the two-dimensional phase change model and the data requirements needed to properly represent inhomogeneity of the system, boundary conditions, and other complexities, a special data input program is developed in order to aid the model user. This general purpose data preparation program, PROTOØ, develops the data input file to be used directly by the two-dimensional phase change program.     

A heat equation for freezing processes with phase change: stability analysis and applications

In this work, the stability properties as well as possible applications of a partial differential equation (PDE) with state-dependent parameters are investigated. Among other things, the PDE describes freezing of foodstuff, and is closely related to the (potential) Burgers’ equation. We show that for certain forms of coefficient functions, the PDE converges to a stationary solution given by (fixed) boundary conditions that make physical sense. These boundary conditions are either symmetric or asymmetric of Dirichlet type. Furthermore, we present an observer design based on the PDE model for estimation of inner-domain temperatures in block-frozen fish and for monitoring freezing time. We illustrate the results with numerical simulations.     

Microwave emission of soil freezing and thawing observed by a truck-mounted microwave radiometer

This article presents a study of the interference effect of the microwave emission of soil during freezing and thawing processes. The microwave brightness temperature (T _B) was measured at the C (6.925 GHz), X (10.65 GHz), K (18.7 GHz) and K_a (36.5 GHz) bands using a truck-mounted dual-polarized microwave radiometer. Obvious T _B oscillation behaviour was shown in the results, which were compared with both coherent and non-coherent emission models. The characteristics of the measured and modelled results were similar, except for the oscillation frequency and amplitude. This was attributed to the error in estimation of the dielectric constant of frozen soil and some other factors. This effect was important in analysing the experimental data.     

Hybrid automata for linearizing the model of high-pressure thawing

The heat transfer phenomena concerned during thawing usually lead to non-linear distributed parameter systems, due to the existence of water phase change. When pressure changes, the thermodynamic effects make this model more complex. Hybrid automata allow continuous and discrete dynamics to be combined in the same method. Applied to our process, they allow a linear model to be obtained, and conserve its linearity when pressure changes are taken into account. The discrete events considered here are ice/water transitions and pressure changes. The continuous part of the model is heat transfer, either in solid, liquid or melting state of water.     

Entransy dissipation minimization for liquid-solid phase change processes

The liquid-solid phase change process of a simple one-dimensional slab is studied in this paper.By taking entransy dissipation minimization as optimization objective,the optimal external reservoir temperature profiles are derived by using optimal control theory under the condition of a fixed freezing or melting time.The entransy dissipation corresponding to the optimal heat exchange strategies of minimum entransy dissipation is 8/9 of that corresponding to constant reservoir temperature operations,which is ...     

相变存储器写寿命延长关键技术研究进展

随着大数据分析应用时效性提升和“存储墙”问题日益突出,存储系统已成为当前计算机系统整体性能的瓶颈。以相变存储器（PCM）为代表的新型非易失性存储器（NVM）具有集成度高、功耗低、读写访问速度高、非易失、体积小和抗震等优良特性,已成为最具潜力的下一代存储设备。然而,写寿命有限是PCM实用化的一道障碍,如何通过减少写操作和磨损均衡以提升PCM使用寿命是当前的研究热点。 从减少PCM写操作、均匀写操作分布以及在混合内存中的页面迁移等三个方面介绍了当前PCM写寿命延长技术的研究现状以及优缺点,最后探讨未来进一步改进PCM寿命可能的研究方向。     

Explaining information systems change: a punctuated socio-technical change model

We outline a Punctuated Socio-Technical Information System Change model. The model recognizes both incremental and punctuated socio-technical change in the context of information systems at multiple levels – the work system level, the building system level, and the organizational environment. It uses socio-technical event sequences and their properties to explain how a change outcome emerged. The critical events in these sequences correspond to gaps in socio-technical systems. By conceiving information system (IS) change as a multi-level and punctuated sequence of socio-technical events, IS researchers can conceive plausible and accurate process explanations of IS change outcomes, including IS failures. Such explanations are located in the middle range and thus avoid the highly abstract and stylized closed-boxed factor models of change, but go beyond the idiographic open box histories of singular change processes.     

相变存储器单元阵列的自动化演示系统

计算机通过GPIB卡和串口分别控制脉冲信号发生器和单片机实现对C-RAM（Chalcogenide-Random Access Memory）储阵列芯片的数据存储、数据读取和简单的数据运算的直观演示.本文重点介绍了其硬件构成、软件实现.     

A pair-wise interaction model of the sigma phase I—thermodynamic properties

The composition dependence of the thermodynamic properties of binary sigma phases is examined on the basis of a simple pair-wise interaction model. The structure is considered in terms of its five sublattices, characterised by sites identified with Kasper-Frank surrounding co-ordinated polyhedra of 12, 12, 14, 14 and 15 respectively. It is assumed that the smallest (CN12) and the largest (CN15) sites are each preferentially occupied by different single alloy components while the intermediate size (CN14) sites are subject to random occupation. The numbers of substitutional defects on the ordered sub-lattices are defined by two independent disorder parameters and the variation of defect concentration and thermodynamic properties with composition is computed. Application of the model is illustrated by reference to thermodynamic and structural data for sigma phases in the V-Fe, V-Co, Cr-Fe, Cr-Co and Mo-Co alloy systems.     

A new segmentation method for phase change thermography sequence

A new segmentation method for image sequence is proposed in order to get the isotherm from phase change thermography sequence (PCTS). Firstly, the PCTS is transformed into a series of synthesized images by compression and conversion, so the isotherm extraction can be transformed into the segmentation of a series of synthesized images. Secondly, a virtual illumination model is constructed to eliminate the glisten of the aerocraft model. In order to get the parameters of virtual illumination model, a coordination-optimization method is employed and all parameters are obtained according to the similarity constraint. Finally, the proving isotherms are gained after the threshold coefficients are compensated. The eventual results demonstrate the efficiency of the proposed segmentation method.     

From octahedral structure motif to sub-nanosecond phase transitions in phase change materials for data storage

Phase change random access memory (PCRAM) has been successfully applied in the computer storage architecture, as storage class memory, to bridge the performance gap between DRAM and Flashbased solid-state drive due to its good scalability, 3D-integration ability, fast operation speed and compatible with CMOS technology. Focusing on phase change materials and PCRAM for decades, we have successfully developed 128 Mb embedded PCRAM chips, which can meet the requirements of most embedded systems. 3D Xpoint (3D PCRAM), invented by Intel and Micron, has been regarded as a new breakthrough in the last 25 years since the application of NAND in 1989, which represents state-of-the-art memory technology. This technology has some remarkable features, such as the confined device structure with 20 nm size, the metal crossbar electrodes to reduce the resistance variations in PCRAM arrays, and the ovonic threshold switching selector that can provide a high drive current and a low leakage current. A good understanding of phase change mechanism is of great help to design new phase change materials with fast operation speed, low power consumption and long-lifetime. In this paper, we firstly review the development of PCRAM and different understandings on phase change mechanisms in recent years, and then propose a new view on the mechanism, which is based on the octahedral structure motifs and vacancies. Octahedral structure motifs are generally found in both amorphous and crystalline phase change materials. They are considered to be the basic units during phase transition, which are severely defective in the amorphous phase. These configurations turn into more ordered ones after minor local rearrangements, the growth of which results in the crystallization of rocksalt (RS) phase with a large amount of vacancies in the cation sites. Further driven by thermodynamic driving force, these vacancies move and layer along certain directions; consequently, the metastable RS structure transforms into the stable hexagonal (HEX) structure. Based on our results, we find that reversible phase transition between amorphous phase and RS phase, without further changing into HEX phase, would greatly decrease the required power consumption. Robust octahedra and plenty of vacancies in both amorphous and RS phase, respectively avoiding large atomic rearrangement and providing necessary space, are crucial to achieve the nanosecond or even sub-nanosecond operation of PCRAM.     

A general numerical model for grounding analysis in layered soils

Safety of persons, protection of equipment and continuity of power supply are the main objectives of the grounding system of a large electrical installation. For its accurate design, it is essential to determine the potential distribution on the earth surface and the equivalent resistance of the system. In this paper, we present a numerical approach based on the boundary element method for grounding analysis in layered soils. The feasibility of this formulation is discussed by means of its application to a real grounding system with different kinds of layered soil models.     

A multi-agent model system for land-use change simulation

This paper presents a multi-agent model system to characterize land-use change dynamics. The replicable parameterization process should be useful to the development of simulation frameworks, important to environmental policy makers to analyze different scenarios during decision making process. The methodological two-fold approach intends to form a solid backbone based on: (i) the systematic and structured empirical characterization of the model; and (ii) the conceptual structure definition according to the agent-based model documentation protocol – Overview, Design concepts and Details. A multi-agent system for land-use change simulation was developed to validate the model, which is illustrated with a case study of the Brazilian Cerrado using LANDSAT ETM images. The simulation results prove the model importance with a figure of merit greater than 50%, what means the amount of correctly predicted change is larger than the sum of any type of error. The results are very good compared with nine popular peer-reviewed land change models.     

A model for characterizing the motion of the solid-liquid interface in freezing solutions

This paper describes a model for computing the velocities at a set of points which describe the solid-liquid interface in freezing solutions. The model is based on decomposing the motion of a two dimensional boundary, which may change shape with time, into translational and radial components. The major categories of geometry that may typify the morphology of the interface under varying thermal and compositional constraints are planar, cellular and dendritic. The specific objective of this paper is to characterize distinctively the motion of each of the three morphological structures. Several illustrative examples are given to show the performance of the model as applied to the experimentally generated interfaces.     

Development of a wet lime/limestone flue gas desulfurization process model. Phase I: Species distribution model

A new computer code is described which calculates the concentrations (or activities) of chemical species which are at chemical equilibrium. The species distribution model (SDM) is structured so that the user has essentially full control to define a wide variety of problems. Some of the capabilities allow the user (at run-time) to set up a virtually unlimited number and type of solutions and select the activity coefficient technique for each, omit species from consideration, limit the reactivity of species, and edit species and corresponding data (e.g., activity coefficient or equilibrium constant data). The code is highly modular and the routines are short with well-defined purposes and clean interfaces. The code and data structures are set up for ease of model enhancement.     

A communication model for structural design objects. I: Channels and medium

Design objects of integrated engineering systems frequently communicate data and information among each other. The data to be communicated is usually characterized by considerable variability in format and structure. This warrants the development of a uniform mechanism for communicating data and information among design objects. Recent advances in the object-oriented paradigm and the emerging agent-oriented paradigm gave promise to the development of such mechanism for inter-object communication that was difficult to achieve previously. This paper and its companion paper address this issue and propose an object communication model. Specifically, this paper identifies the communication channels among structural engineering design objects and proposes a communication medium based on messenger object for conveying message arguments and responses. The unified modeling language (UML) is used to present the model and its ingredients. A note on implementation of the messenger object, using C++ STL, is shown. Examples to demonstrate the capability of the communication model are presented. The proposed communication model will impose a uniform and consistent mechanism for communicating data and information among design objects. Other ingredients of the communication model such as performatives and protocols are addressed in the companion paper.     

Another stabilized generator model for three phase sinewaves

A new three dimensional oscillator for generating three phases of sinewaves is derived. The model is similar to the previous ones (Ref. 1 and 2) in enabling an undistorted stabilized generation of sinewaves. It possesses certain advantages in comparison to the previous models. The oscillator appears as a viable model for representing synchronous generators in a simplified manner in the simulation of power systems.     

TINYCD: a (not so) deep learning model for change detection

Neural Computing and Applications - In this paper, we present a lightweight and effective change detection model, called TinyCD. This model has been designed to be faster and smaller than current...