Practical method for generation expansion planning based on dynamic programming

This paper presents an efficient method which provides the optimal generation mix and the optimal generation construction process. The approximation method in which the dynamic programming technique and gradient method are combined is applied to determine the optimal generation mix with hydropower generation technologies. The successive approximations dynamic programming (SADP) technique, which is very suitable for high-dimensional multistage decision process problems, is used for obtaining the optimal generation construction process. The effectiveness and feasibility of the developed technique are demonstrated on a practical power system model which has five types of generation technologies including a hydropower generation technology.     

Basic concept and decentralized autonomous control of super‐distributed energy systems

New small‐scale dispersed generation systems, such as fuel cells and micro gas turbines, have made remarkable advances lately and they will be applied practically in the near future. Although a large number of researches on the introduction of small‐scale dispersed generation systems have been carried out, only a small number of small‐scale dispersed generation systems are considered in these researches. Therefore, little is known about problems to be solved when a large number of small‐scale dispersed generation systems are introduced into electric power systems. This paper deals with a super‐distributed energy system that consists of a great number of dispersed generation systems such as fuel cells, micro gas turbines, and so on. The behavior of a customer with a dispersed generation system is simulated as the Ising model in statistical mechanics. The necessity of a distribution network in super‐distributed energy systems is discussed based on the Ising model. The feasibility of decentralized autonomous control using vicinity information is also investigated on the basis of stability analysis of the Hopfield neural network model. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(1): 43–55, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10368     

Processing,deformation, and failure in superplastic aluminum alloys: Applications of orientation-imaging microscopy

The importance of grain size refinement in enabling superplasticity is reviewed, and the current understanding of grain boundary characteristics is summarized. The application of orientation-imaging microscopy (OIM) methods to the processing response and the deformation and failure modes in superplastic aluminum alloys are illustrated through microtexture analysis and determination of grain boundary characteristics in selected commercial materials. Continuous and discontinuous recrystallization reactions exhibit distinct microtextures and grain boundary characteristics. The application of OIM and microtexture analysis to the evaluation of both deformation and failure mechanisms during superplastic forming is illustrated. This paper was presented at the International Symposium on Superplasticity and Superplastic Forming, sponsored by the Manufacturing Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium was organized by Daniel G. Sanders, The Boeing Company.     

Statistical analyses and prediction of coking properties of coal

Using regression analyses between the properties of coals and the strengths of their cokes several significant correlations are derived, which are useful to evaluate coals in the making of metallurgical coke. Slight but significant modification was necessary for their application to coal blends. For example, plasticities of the coal blends required a different equation from that derived for the single coals. The region of high coke-strength in the diagram of volatile matter vs. total dilatation was expanded considerably towards coals of lower caking properties by blending of coals, suggesting that the blending may serve to increase the coking properties of component coals. The coke strength, especially after the gasification was found to increase with the increasing inert maceral content in the parent coals up to 30 wt %. The high level of strength was maintained even above 35 wt % of inert content.     

Monte Carlo simulation of stress corrosion cracking on a smooth surface of sensitized stainless steel type 304

Stress corrosion cracking (SCC) on a smooth surface of structural metal materials occurs by initiation and coalescence of micro cracks, subcritical crack propagation and multiple large crack formation or final failure under combination of material, stress and corrosive environment. In this paper, a Monte Carlo simulation of the SCC process is proposed based on stochastic properties for micro crack initiation and concepts in fracture mechanics for crack coalescence and propagation. The procedure is as follows: The possible number of grain-sized micro cracks which can be initiated is set for a given space and initiation times for all cracks are assigned by random numbers based on exponential distribution. Sites and sizes of cracks are assigned by uniform random numbers and normal random numbers, respectively. Coalescence and propagation of cracks are determined based on fracture mechanics. The emphasis in the model is put on the influence of semi-elliptical surface cracks. Numerical simulations are carried out based on the results of creviced-bent-beam tests for sensitized stainless steel type 304 under high-temperature and high-purity water containing dissolved oxygen and the influence of micro crack initiation rate and coalescence condition on the simulation results is discussed.     

Adaptive dynamic range shift (ADRIFT) quantitative phase imaging

Quantitative phase imaging(QPI)with its high-contrast images of optical phase delay(OPD)maps is often used for label-free single-cell analysis.Contrary to other imaging methods,sensitivity improvement has not been intensively explored because conventional QPI is sensitive enough to observe the surface roughness of a substrate that restricts the minimum measurable OPD.However,emerging QPI techniques that utilize,for example,differential image analysis of consecutive temporal frames,such as mid-infrared photothermal QPI,mitigate the minimum OPD limit by decoupling the static OPD contribution and allow measurement of much smaller OPDs.Here,we propose and demonstrate supersensitive QPI with an expanded dynamic range.It is enabled by adaptive dynamic range shift through a combination of wavefront shaping and dark-field QPI techniques.As a proof-of-concept demonstration,we show dynamic range expansion(sensitivity improvement)of QPI by a factor of 6.6 and its utility in improving the sensitivity of mid-infrared photothermal QPI.This technique can also be applied for wide-field scattering imaging of dynamically changing nanoscale objects inside and outside a biological cell without losing global cellular morphological image information.     

Experimental analysis of 2D-unsteady temperature field by using Mach-Zehnder interferogram images

A measurement method for an unsteady temperature field by using a Mach-Zehnder interferometer and image processing technique is presented. In this study, the results measured by this method were compared with the calculated results under Reynolds numbers (Re = UL/v) ranging to less than 350 in the steady-state. The unsteady characteristics of the local Nusselt numbers (Nu_x = α_xL/λ) around an elastically vibrating plate were investigated under the conditions that the reduced frequency (N = 1/Ro) ranged from 4.8 to 8.6 and the amplitude of vibration was kept small relative to the plate length. In this study it was clarified that the distributions of the Local Nusselt numbers were observed flutteringly, and that the phase of the time-averaged Nusselt number is delayed compared to the phase of the velocity at the trailing edge. These results indicate that the enhancement of the time-averaged heat transfer coefficient around the vibrating plate depended on the Rossby number. © 1997 Scripta Technica. Inc. Heat Trans Jpn Res. 25 (2): 88–102, 1996     

Fatigue crack initiation and growth under mixed mode loading in aluminum alloys 2017-T3 and 7075-T6

Fatigue crack initiation and growth characteristics under mixed mode loading have been investigated on aluminum alloys 2017-T3 and 7075-T6, using a newly developed apparatus for mixed mode loading tests. In 2017-T3, the fatigue crack initiation and growth characteristics from a precrack under mixed mode loading are divided into three regions—shear mode growth, tensile mode growth and no growth—on the ΔK_I-ΔK_II plane. The shear mode growth is observed in the region expressed approximately by ΔK_II > 3MPa√m and ΔK_II/ΔK_I > 1.6. In 7075-T6, the condition of shear mode crack initiation is expressed by ΔK_II > 8 MPa√m and ΔK_II/ΔK_I > 1.6, and continuous crack growth in shear mode is observed only in the case of ΔK_I/ΔK_II, 0. The threshold condition of fatigue crack growth in tensile mode is described by the maximum tensile stress criterion, which is given by Δσ_θmax √2πr 1.6MPa√m, in both aluminum alloys. The direction of shear mode crack growth approaches the plane in which K_I decreases and K_II increases towards the maximum with crack growth. da/dN-ΔK_II relations of the curved cracks growing in shear mode under mixed mode loading agree well with the da/dN-ΔK_II relation of a straight crack under pure mode II loading.     

An incremental damage theory for micropolar composites taking account of progressive debonding and particle size effect

The paper presents an incremental damage model for determining the overall mechanical behaviors of particulate-reinforced micropolar composites. The particle size effect and progressive-debonding damage are fully accounted for within the present framework, which makes use of the micropolar Eshelby’s tensor for characterizing the size-dependent constraint of the matrix microstructure on the particles, a critical stress criterion for the interfacial debonding, and Qiu-Weng’s energy approach, together with Hu’s variation method for the equivalent stress of the matrix. Finally, the present model was applied for the predictions of the overall stress–strain relations of the composites that reinforced by either particles or voids, and are subjected to the uniaxial tension. It is shown that all the predictions are in good agreement with the experiments and finite element computations.