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.     

Gel chromism and anomalous luminescence in poly(3-alkylthiophene)

The absorption spectrum of poly(3-alkylthiophene) gel changes drastically in association with a volume instability upon changing the solvent composition and also the temperature. In the expanded state in chloroform and at high temperature, the photoluminescence is much enhanced compared with the shrunken state in ethanol and at low temperature. This gel chromism and anomalous luminescence are discussed in terms of the change of effective conjugation length induced by the steric hindrance and the dynamics of the photoexcited species.     

Measurement of human red blood cell deformability using a single micropore on a thin Si3N4 film

The filtration method for the evaluation of the RBC deformability has been further refined to simulate the deformations encountered in the recticuloendothelial system (in particular the spleen), a recognized site of aged and sickled cells removal. The core of the developed measuring system is a very thin (0.4 micron thick) filter that consists of single micropore (diameters down to 1 micron) on a Si3N4 film which has been constructed using silicon microfabrication techniques. Individual RBC's deformability is quantified measuring the cell pore passage time. From one blood sample 200 passage times are analyzed by a computer, displaying mean and median values as deformability indexes, and class and cumulative histograms for studying the passage times distribution. In this paper the effectiveness of the developed system as a routine clinical evaluation tool is demonstrated by studying several factors that are known to affect the RBC deformability, such as temperature, addition of diamide and glutaraldehyde, and blood storage conditions. In addition, it is experimentally demonstrated that the human RBC can traverse a pore with a diameter as small as 1 micron when the pore length is very short, thus broadening the experimental conditions under which the RBC deformability (fluidity) can be studied.     

Interconnected power systems with superconducting magnetic energy storage

The objective of this work is to discuss the concept of back‐to‐back interconnection systems with energy storage, especially with a Superconducting Magnetic Energy Storage (SMES) incorporated into a back‐to‐back DC link. In this case, each converter of the back‐to‐back system is used as a power conditioning system for the SMES coils. Since the AC–DC converter can be designed independently of the frequency of the power system, a two‐way switch is connected to the AC side of each converter. This two‐way switch can select the interconnected power systems. By using the two‐way switches, this system can provide the stored energy in the SMES system to each interconnected power system through two AC–DC converters. For instance, lower‐cost power of each power network can be stored through two converters during the off‐peak hours and made available for dispatch to each power network during periods of demand peak. Then this system increases the reliability of electric power networks and enables the economical operations depending on the power demand. This paper describes the unique operations of the back‐to‐back interconnection with SMES and discuses the optimal SMES configuration for a 300‐MW‐class back‐to‐back interconnection. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 37–43, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20482     

Helium gas permeability of montmorillonite/epoxy nanocomposites

Helium gas permeability of silicate clay (montmorillonite) particles/epoxy nanocomposites was examined. The incorporation of increasing amounts of montmorillonite particles reduced the helium gas permeability. Based on Fick’s law, gas permeation behavior of the nanocomposite was evaluated. With the increase of montmorillonite loading, gas diffusivity decreased, while gas solubility increased. Helium diffusion behavior is in agreement to the numerical results based on the Hatta–Taya–Eshelby theory. It has been revealed that dispersion of nanoscale platelets in polymer is effective in improving gas barrier property.     

Highly sensitive InGaAs/InAlAs quantum wire photo-FET

An InGaAs/InAlAs quantum wire photo-FET has been fabricated on a V-grooved (311) InP substrate by atomic hydrogen assisted molecular beam epitaxy. The room-temperature photosensitivity of the quantum wire photo-FET reached 350 kA/W near a wavelength of 700 nm at a drain-source voltage of 1 V.     

Relationship between dipole parameter estimation errors andmeasurement conditions in magnetoencephalography

In this study, a model in a computer simulation uses a single current dipole in a spherical homogeneous medium. Dipole parameters are estimated using a moving dipole procedure. Signal-to-noise ratio (SNR) is defined as the square-root of the ratio of the average signal power to the average noise power over all measurement points. At SNR>20, accurate estimation can be carried out independently of dipole depth and coil size. At SNR<20, dipole depth influences estimation error. When the dipole is located near the center of the sphere, the measurement region should include both extrema of the magnetic field to minimize estimation error. However, when the dipole is not so deep, the position of the measurement region does not influence estimation error. When SNR<4, estimation error increases as coil size increases. Coil size minimizing estimation error is determined by the ratio of environmental magnetic field noise to electrical noise. For a constant size of measurement region, increasing the number of measurement points decreases estimation error to a certain level. This error level depends on SNR     

Small-signal analysis of semiconductor lasers modulated atfrequencies on the order of the beat frequency

A small-signal analysis of direct modulation of laser diodes is presented. The analysis is valid over a wide frequency range, up to the frequency corresponding to the round trip time of the active region. This theory is best for laser diodes with small active regions but with large and complicated optical cavities. Optical resonances may occur in this range, resulting in a large response to direct modulation as a result of interaction of the lasing mode with the optical resonance. This theory can predict the linear response of the laser to direct modulation throughout this frequency range. It also predicts the lower frequency relaxation oscillation effect, thus unifying these different effects with a single treatment. The form of the modulation response is found to be the same as the standard relaxation oscillation formula, modified by a factor the form of which depends on the optics of the laser cavity alone     

Determination of power reflectivity of quasi-graded distributedBragg reflectors using stopband width

The authors examine the reflectivity of the quasi-graded distributed Bragg reflector using the stopband width. The stopband width of about 1000 Å for a reflectivity of about 99% is able to be measured with an accuracy of ± 1 Å. Thus, the reflectivity is determined with high accuracy from the stopband width. It is found that the quasi-graded distributed Bragg reflector is a high-quality reflector with high reflectivity and low resistance     

Optimizing the design of large-scale ground-coupled heat pump systems using groundwater and heat transport modeling

In order to predict the long-term performance of large-scale ground-coupled heat pump (GCHP) systems, it is necessary to take into consideration well-to-well interference, especially in the presence of groundwater flow. A mass and heat transport model was developed to simulate the behavior of this type of system in the Akita Plain, northern Japan. The model was used to investigate different operational schemes and to maximize the heat extraction rate from the GCHP system.