bluuebunny/crossref_metadata_2025 huggingface dataset:
An application of artificial neural networks to maintenance scheduling covering of thermal units over several consecutive years
Authors: Sasaki Hiroshi , Takiuchi Yoshiyuki , Kukobawa Junji
Published: July 2007

Thermal units must be maintained periodically as prescribed by the electric utility industry law. As time to execute maintenance works increases with thermal unit capacity, maintenance scheduling has a great influence on the reliability and economy of a power system. In the recent amendment in the law, three inspection rankings have been introduced and scheduling over several consecutive years becomes mandatory, thus making maintenance scheduling extremely difficult. Reflecting a recent stringent supply capability, the emphasis is laid on security rather than a minimum operating cost, having been the primary objective in determining the schedules. Therefore, this study aims to level the spinning reserve at each period under study in the maintenance scheduling while taking into consideration all the amendments in the law. Although rigorous methods such as integer programming and branch and bound method can solve small scale problems, large size problems are beyond these techniques due to an exponential explosion in the number of possible combinations.

The prime objective of this paper is to investigate the capability of the Hopfield neural network (HNN) in solving the newly formulated maintenance scheduling problem. The scheduling problem has been mapped on the HNN with slight problem relaxations to facilitate the implementation. A small scheduling problem that determines the maintenance schedules of 3 generators over 3 years (divided to 78 periods) has been solved by the neural network simulator. It has been made clear from simulation results that the proposed approach is very promising in handling a complicated combinatorial optimization problem.
Method of detecting the index position of a spindle motor for slim flexible disk drive
Authors: Imai Yasuaki
Published: July 2007

A slim flexible disk drive, which could be mounted on a hand‐held personal computer, is now under intensive study in Japan. The spindle motor for the flexible disk drive has an index‐position detecting means, an index magnet attached to the outer wall of the periphery of the rotor yoke, and a magnetic sensor which detects the magnetic flux from the index magnet. As a result, spaces for providing the index magnet and the magnetic sensor prevent the motor from being made smaller in size and reduced in thickness.

This paper describes the method for detecting the index position of a spindle motor without both the index magnet and the magnetic sensor. This method detects an index position per rotation from two different kinds of frequency generating signals (main FG and sub FG) through an index‐detecting circuit. The thin spindle motor to which this index‐detecting method is applied, performed a smaller degree of rotational speed variation compared with another well‐known one without both the index magnet and the magnetic sensor. This index‐detecting method is most suitable for a less‐inertia‐thin spindle motor, and is easy to assemble.
Trajectory control of controlled‐PM linear synchronous motor magnetic levitation vehicle—FEM dynamics simulations and experiments in mass‐reduced‐control mode
Authors: Yoshida Kinjiro , Takami Hiroshi , Yokota Dai , Nishitani Mitsumasa , Sonoda Akihiro
Published: July 2007

A novel magnetic levitation train system can be constructed by using a long‐stator controlled‐PM linear synchronous motor having propulsion and attractive‐mode levitation functions and minimum loss. Realizing this system requires simplifying manufacture of the long‐stator guideway. In the long‐stator on the ground, semiclosed large slots are adapted and designed for one‐turn coils of a waveform to be easily installed. The large slots cause the PM LSM detent forces to give strong influences on dynamic operations of the running vehicle. A two‐dimensional FEM used for the dynamics simulations is capable of precisely analyzing the detent forces produced between the stator teeth and the PMs.

This paper presents FEM dynamics simulations and experiments in mass‐reduced‐control mode of a 1/2 scale model magnetic levitation vehicle supported by small rubber rollers. The simulation model developed here includes the vehicle speed performance, position sensors and drag force due to friction between rubber roller and rail. The detent force problem in propulsion motion is successfully solved by adapting the feedback control of the vehicle propulsion based on the I10‐controlled method. The trajectory control is thus accomplished for the vehicle to follow speed and position patterns. The dynamics simulations are verified from the experiments. The simulation program proposed here enables us to investigate the magnetic levitation train system, including LSM design and vehicle dynamic operations.
Magnetic characteristics of oxide superconductors for the application of running systems with magnetic levitation
Authors: Suzuki Haruhiko , Yogiashi Kozo , Kusano Koichi , Takashige Masaaki
Published: July 2007

A model vehicle is constructed which runs without contact to its magnetic rail using oxide superconductors. This paper describes the forces acting between the superconductor and the rail for such a purpose. The attractive and repulsive forces were measured at 77 K as a function of distance between the superconducting pellet and the magnetic rail. As suprconducting pellets, three kinds of materials, i.e., MPMG‐Y123, BiPb2223, and Hg1223, were investigated for three kinds of permanent magnets, i.e., Nd‐Fe‐B, Sm‐Co and ferrite.
Quantitative analysis of swarming pulsive microdischarges by using very low frequency voltage application
Authors: Ishida Takahiro , Nagao Masayuki , Kosaki Masamitsu
Published: July 2007

Partial discharge (PD) degradation phenomena is one of the most important factors to decide the performance and the lifetime of the high voltage apparatus. During PD degradation tests of an epoxy specimen with an internal void, PD often change to a large number of very small PD known as swarming pulsive microdischarges (SPMD). Because the appearance of SPMD is concerned with the degradation of the insulating materials, the insulation diagnosis with the detection of SPMD becomes possible. However, SPMD cannot be detected with the conventional PD Detector because the PD magnitude of SPMD is too small. The computer‐aided partial discharge analyzing system (CAPDAS) has been developed to detect and analyze the SPMD. Furthermore, a new PD parameter, the SPMD ratio has been introduced for quantitative analysis of SPMD. In this paper, the time variation of SPMD characteristics of a CIGRE Method‐II specimen are investigated by using the CAPDAS. Further, the effect of the frequency of the applied voltage on SPMD is also investigated at 60 Hz and a very low frequency of 0.1 Hz. As a result, the comparison of PD magnitudes measured at 60 Hz with those at 0.1 Hz enables a quantitative analysis of SPMD characteristics to be possible by using only the conventional PD detector.
Fast calculation using parallel processing and pipeline processing in power system analysis
Authors: Oda Yoshifumi , Oyama Tsutomu
Published: July 2007

This paper presents an application of parallel processing and pipeline processing to power system analysis. The system matrix is transformed to a bordered block diagonal form (BBDF) matrix for effective utilization of the processors. After LU factorization, subnetworks organize sparse matrices and the boundary network organizes a full matrix. First, a parallel processing technique is used to calculate subnetworks. Then, as pipeline processing is applied, inverse matrix of the boundary network is multiplied. The proposed method is made operational on a parallel computing system including a pipeline processor. A consideration on the transient stability analysis using the proposed method also is presented at the end of this paper.
Commercialization of an extra high‐voltage nonflammable transformer
Authors: Mizuno Kazuhiro , Sakamoto Takeshi , Endo Kaoru , Fujita Hiroyuki , Hiraishi Kiyoto
Published: July 2007

A perfluorocarbon (PFC)‐immersed 275‐kV transformer with compressed SF6, gas has been developed. This paper describes the basic cooling and insulation characteristics of PFC, the ac partial discharge voltage, and the aging of PFC‐immersed insulation. The results demonstrate that a prototype 275‐kV 100‐MVA three‐phase transformer can be operated without any difficulties for an extended period of overvoltage. This prototype has an ac partial discharge initiation strength which is 1.5 times that of the ac test voltage and a lightning impulse breakdown strength which is 1.5 times that of the test voltage. A 275‐kV 250‐MVA three‐phase transformer was built and is being operated at the Abe substation of Chubu Electric Power Co., Inc. The transformer has been operating satisfactorily.
Control system design for an ideal transient control performance—proposal of simulator‐based foresight control
Authors: Uchida Motomiki , Nakano Kazushi
Published: July 2007

A new concept to achieve an ideal transient control performance is described. It is also possible to examine control performance on the frequency domain. Generally speaking, better control performance will be realized by using more exact information on the plant. A simulator should be built that has both correct initial values of state variables and parameters on dominant parts of the plant. The internal states of the simulator are used to represent the internal states of the plant, and control input is synthesized with the internal states of the simulator and the plant output. Using information on the simulator allows an ideal control performance at a dominant frequency area to be obtained in spite of the existence of unmodeled dynamics at a higher frequency domain. This control system is called simulator‐based foresight control (SFC), and is available for both nonlinear and timevarying plants.
Basic characteristics of five‐phase cylindrical linear pulse motors
Authors: Dohmeki Hideo , Satomi Hirofumi , Iwasa Takao
Published: July 2007

A cylindrical linear pulse motor (CLPM) of a new construction is proposed in this paper. The conventional CLPM, which has a permanent magnet between A‐phase and B‐phase stators, has a problem: thrust unbalance occurs because the magnetic flux of the outer poles is longer than that of the inner poles. This paper proposes a CLPM of completely new construction, in which the field magnetic flux and the armature magnetic flux perpendicularly intersect each other as a result of a restructured magnetic circuit. This new CLPM has the same magnetic field as the stepping motor, and has the distinctive characteristic of being available in a multiphase design, as well as the conventional two‐phase design. A five‐phase 10‐pole CLPM was experimentally manufactured and the static thrust was measured to identify its basic characteristics. The experiment confirmed the theory that the torque did not differ from phase to phase and that controllability equal to that of the stepping motor was obtainable. The CLPM proposed here is effective as an alternate linear electromagnetic actuator for electrical servos of air actuators (such as air cylinders).
Space charge behavior in an antistatic polymer including polymer solid electrolyte
Authors: Fukunaga Kaori , Maeno Takashi
Published: July 2007

A polymer dielectric material tends to be easily charged and may cause an electrostatic discharge, due to the serious problems that result when consequent electromagnetic noise damages the electronic circuits in various kinds of apparatus. The antistatic polymers that have been developed to prevent electrostatic discharge contain polymer solid electrolytes so that space charge originally exists inside them. The mechanism of the antistatic discharge effect of the polymer has been investigated by measuring the space charge distribution using the high‐resolution pulsed‐electroacoustic method. The experimental results suggest that the internal space charge of the polymer accumulates at the surface and forms heterocharge distribution at the interface between the electrodes and the specimen. Thus, internal space charge compensates the applied electric field, resulting in preventing the increase of the surface potential. In addition, internal space charge behavior relates to the dispersion condition of the polymer solid electrolyte that depends on the quantity of the electrolytes and the specimen procedures.
Development of a distribution line state monitoring system
Authors: Fudou Hiroyuki , Kawasaki Yukio , Egawa Susumu , Shinozaki Kouichi , Abe Norio , Toda Kazuro
Published: July 2007

To improve the electricity service reliability, a distribution line state monitoring system has been developed. It is composed of a central control unit, remote control switches, the slave unit and monitoring sensors. The first system employed fiber‐optic voltage and a current sensor. The latest system employs a unique form of cost reduction, with no voltage sensors incorporated. This system can detect the grounding direction by the information of the phase difference between the line‐to‐line voltage and I0 provided by the monitoring sensor, and grounded line information (64ϕ) from the substation. Installation of the system has been underway since 1992.
Suppression of lightning‐induced overvoltages by distribution line surge arresters
Authors: Fujiwara Nobuyuki , Yoneyama Tsukasa , Hamada Yoshiyuki , Yokota Tsutomu , Asakawa Akira , Shimomura Tetsuro , Yamaoka Koichi , Ishibe Shinji
Published: July 2007

The primary aim of surge arresters in power distribution lines is to protect lines and equipment from the voltage induced by nearby lightning strokes. To further improve power systems, methods to protect distribution lines against direct lightning strokes are still needed. An effective measure against direct lightning strokes is to increase the number of arresters. However, if the surge current is too large, some surge arresters absorb energy in excess of their capability and may break; this leads to a line fault. To evaluate the protective effect of the surge arresters against direct lightning strokes to overhead ground wire, the authors measured both the voltage across the surge arresters and the energy absorbed by them using a full‐scale model line and a 12 MV impulse generator. The results were compared with simulation results by EMTP. There have been no previous studies making a comparison of this kind.
Development of negotiation expert system for subtransmission system planning
Authors: Aihara Yasuhiko , Hayashi Yasuhiro , Terashima Takayuki , Takemoto Ikuko , Iwamoto Shin'Ichi
Published: July 2007

Recently, the task of planning in power systems is becoming a very complicated process for utility planners. This kind of planning has many objectives to accomplish. This paper employs the negotiation algorithm, which was proposed by the Chen‐Ching Liu group for subtransmission power system planning to create a plan having many objectives. First, the goal‐decision network (GDN) is constructed to model this planning problem, and the negotiation algorithm is applied to utilize both subtransmission system planning GDN, which attempts to capture its knowledge, and negotiation operators, which search for the most feasible and promising decisions in this planning GDN. Finally, the negotiation expert system is demonstrated for the subtransmission system planning using a real system.
Characteristics and classification of high‐current fault arcs on distribution systems
Authors: Goda Yutaka , Okazaki Masayuki , Inaba Tsuginori
Published: July 2007

When a fault occurs on transmission or distribution systems due to lightning or overvoltage, often an arc discharge occurs at the fault point. The arc discharge, which is caused by a fault current, has a high current, high temperature, strong light emission, etc., thus it sometimes causes heavy damages to electric power equipment.

The arc discharge is influenced by the conditions around the arcs, i.e., gas, insulation materials, gap length, weather, etc. Also, the arc voltage along the arc column indicates the characteristics of the arc. If the voltage waveforms of the arcs caused by the fault on transmission or distribution systems are classified, it is possible to find the location and the equipment where the fault occurred.

In this paper, the arc voltage data in 6‐kV class XLPE cables and 6‐kV class overhead lines are analyzed and an artificial neural network method is applied to classify the arc voltage waveforms. The results obtained from the six artificial neural networks developed show that the artificial neural network method is effective for classification of arc voltage waveforms if adequate input parameters are selected.
Fast power flow for radial power systems using parallel processing
Authors: Fukuyama Yoshikazu , Nakanishi Yosuke
Published: July 2007

Power flow calculation is a basic tool for power system planning and control which includes power flow analysis, voltage control, service restoration, network reconfiguration, and other operation functions for control centers. In these applications, it is very important to solve the power flow problem as efficiently as possible.

This paper presents a fast power flow using parallel processing for radial power systems. This method can be applied to secondary systems and distribution systems. Since it uses as state variables only active and reactive power injection to main lines and laterals, reduction of the number of state variables can be realized. Radical networks are mapped to the tree structure of parallel processor systems in the proposed method. The forward/backward sweep approach is realized by communication from a root processor to leaf processors and vice versa. Using the mapping scheme of the proposed method, each processor has to communicate with only neighboring processors. The proposed method is evaluated on various radial systems with promising results.
Suppression effects of active power filter on harmonics of distribution system including capacitors
Authors: Oku Kiyoshi , Nakamura Osamu , Inoue Jun‐Ichi , Kohata Masakasu
Published: July 2007

Voltage distortion of 6.6‐kV distribution systems has been increasing recently especially in commercial areas. Harmonic currents of certain orders are amplified and voltage distortions are generated by the resonance between system impedance and static capacitor under the leading power factor condition.

This paper describes the results of a test on suppression effects on model systems and an actual system. The effect of the use of an active power filter on the resonant harmonics of the system including capacitor was verified.
Medium‐size distribution transformer diagnostics
Authors: Susaki Yoshiki , Nakamura Osamu , Kawachi Fumio , Yamaoka Masayoshi , Nishimura Takeshi , Kuriyama Tadashi
Published: July 2007

An improved method of degradation diagnosis for medium‐size distribution transformers is described. The proposed method uses refined criteria of degradation for specific application for 200‐ to 1000‐kVA range transformer diagnostics. The new criteria were established with a 95 percent confidence limit of data after extensive case studies focusing on the relationship between the amounts of CO and CO2 generated in transformer oil and the length of operating time of the transformer. Another feature of this diagnostic technique is the provision of a capability to estimate the thermal history of the insulation material by examining the amounts of certain trace products of decomposition present in the transformer oil. For this purpose, a thermal history discriminant chart was devised by application of a canonical discriminant analysis method.
Transmission line tower models in frequency domain
Authors: Kato Shohei , Mochizuki Azuma , Zaima Eiichi
Published: July 2007

This paper proposes a transmission line tower model in frequency domain for back‐flashover analysis, which has a uniform characteristic impedance and a uniform propagation constant. Most conventional tower models are constructed as a constant and uniform parameter transmission line that is independent of frequency. However, the authors' models have the frequency dependency of the characteristic impedance and the propagation constant to express the frequency characteristic of the transmission line tower.

Two models, a cylinder model and a four‐frames model, were investigated to simulate the tower. Their surge responses were computed by numerical electromagnetic field analysis based on the moment method. From the results, the two‐port circuit constants were calculated in the frequency domain, and the characteristic impedance and the propagation constant are derived from them. The complex artificial oscillations appeared in frequency dependency of the parameters because the parameters were calculated numerically. The equations with analytical form were obtained by approximating with a smooth curve to the oscillations. It is possible for the equations to represent the transmission line constants as a function of geometrical parameters such as the tower height and the radius. Close agreement was found between the surge response computed by the numerical electromagnetic field analysis and the result calculated by inverse Laplace transformation of the analytical equations. To prove the model, the experimental results were compared with the computed ones of the cylinder model that has arms, and it was shown that the new model agrees closer with the experiment than conventional transmission line models.
Transient analysis of an advanced static var compensator using quad‐series voltage‐source PAM inverters
Authors: Tominaga Shinji , Fujita Hideaki , Akagi Hirofumi
Published: July 2007

This paper deals with an advanced static Var compensator (ASVC) using quad‐series voltage‐source PAM inverters. The ASVC consists of four three‐phase voltage‐source inverters with a common dc capacitor and four three‐phase transformers, each primary winding of which is connected in series with each other. Each inverter outputs a square‐wave voltage, while the synthesized output voltage of the ASVC has a 24‐step wave shape. This results not only in a great reduction of harmonic currents and dc voltage ripples but also in fewer switching and snubbing losses.

In this paper, transient analysis is performed with the focus on the response of reactive power and the resonance between the dc capacitor and ac reactors. Experimental results obtained from a small‐rated laboratory model of 10 kVA are also shown to verify analytical results based on thep‐qtransformation. The analytical results help in the design of system parameters such as the capacity of the dc capacitor and feedback gains.
A static voltage fluctuation compensator for AC electric railway using self‐commutated inverters
Authors: Uzuka Tetsuo , Hase Shin‐Ichi , Mochinaga Yoshifumi , Takeda Masatoshi , Miyashita Takeshi , Ueda Tsuyoshi
Published: July 2007

In this paper, the authors describe the basic configuration of an RPC (Railway Static Power Conditioner), its compensation principles and successful test results (using a small model of RPC).

An ac electric railway is placed under a rapidly changing single‐phase load. To avoid a voltage fluctuation under single‐phase loads, electric power is received from a large source. At a feeding substation, three‐phase electric power is transformed into two kinds of directional single‐phase feeding electric power.

The authors have already proposed a static voltage compensator for the ac electric railway, called “RPC.” The RPC links a pair of feeding circuits, using two self‐commutated inverters.

At the substation, the RPC accommodates an active power in the directional pair of feeding circuits to balance three‐phase power, and possess a reactive power to regulate a three‐phase voltage fluctuation. At a sectioning post, it can compensate for voltage drop using reactive power. It can also act as an active filter to compensate for harmonics.

The authors have made a small model (220 V, 20 kVA) of the RPC, and report on the test results obtained using this small model under various conditions. The results indicate that the RPC can accommodate single phase loads, such as transformers and thyristors, can handle an exciter rush current from a transformer, can compensate for harmonics, and so on.
Self‐excited synchronous induction motor
Authors: Fukami Tadashi , Ishizaka Takashi , Miyamoto Toshio
Published: July 2007

A synchronous‐induction motor, with the features of both a synchronous motor and a wound‐rotor induction motor, far excels other synchronous motors in starting characteristics. However, a major drawback of the synchronous‐induction motor is the need for an excitation power supply with low‐voltage, large‐current power rating. For this reason, its driving equipment becomes large, and increases overall cost.

This paper proposes a new synchronous‐induction motor, absent the problems involved in making the motor a self‐excited type. It employs the second‐space harmonic component of armature reaction field to obtain the self‐excitation of the field system, and installs a harmonic winding, which is used for extraction of an excitation power, in the rotor. This new self‐excited motor has the following advantages: (1) the driving equipment is small, since no excitation power supply is involved; and (2) due to the effect of the series characteristic by which the field current varies in proportion to the load current automatically, the motor can be operated with a good power factor.

In the present paper the structure and operating principle of the new motor are explained and the basic characteristics are also investigated by means of a simple analysis and experimental results with a 1.5‐kV trial machine.
Damping enhancement of multimachine power system using adaptive generator control system with neural networks
Authors: Kobayashi Takenori , Morioka Yasuo , Yokoyama Akihiko
Published: July 2007

The authors proposed a nonlinear adaptive generator control system with neutral networks for improving damping of power systems, and showed its effectiveness in a one‐machine infinite bus test power system in a previous paper. The proposed neurocontrol system adaptively generates appropriate supplementary control signals to the conventional controllers such as the automatic voltage regulator and speed governor so as to enhance transient stability and damping of the power system.

In this paper, the applicability of the proposed neurocontrol system to multimachine power systems is discussed. Digital time simulations are carried out for a 4‐machine test power system, where one or several synchronous generators is equipped with the neurocontrol system. As a result, also in the multimachine power system, the proposed adaptive neurocontrol systems improve the system damping effectively and they work adaptively against the wide changes of the operating conditions and the network configuration.
Development of transient stability controller system (TSC) based on on‐line stability calculation
Authors: Ota Hiroji , Inoue Toshihiro , Ito Hisanori , Fukushima Nobuo , Omata Kazuya , Morita Ken‐Ichi , Kokai Yutaka
Published: July 2007

A new transient stability controller system (TSC) based on on‐line transient stability calculation has been developed. The TSC system prevents the power system from wide‐area blackout by shedding generators optimally when a serious fault occurs. This system consists of a central processing unit (TSC‐P), and four local units for fault detection (TSC‐C), and seventeen units for generator shedding (TSC‐T). The TSC‐P selects optimal generators to be shed for stabilization based on on‐line transient stability calculation for contingencies at 500 kV lines and buses every five minutes. The results are transmitted to the TSC‐Cs periodically. Should any fault occur, only one TSC‐C will detect the fault occurrence and send control signals to the TSC‐Ts which actually generate shedding signals. To realize the TSC system, essential are fast stability evaluation methods for a large number of contingencies and effective selection methods of optimal generators to be shed for stabilization.

This paper presents total algorithms applied in the TSC‐P, the results of algorithm verification tests using a prototype system combined with a large‐scale analog simulator, and the characteristics of the actual system.
Forecasting of cloud‐to‐ground discharge by SAFIR
Authors: Matsui Toshiaki , Adachi Mikio , Onuki Jun , Kawasaki Zen‐Ichiro , Wada Masakazu , Matsuura Kenji
Published: July 2007

The possibility of forecasting cloud‐to‐ground discharges is investigated. It is empirically well known that the cloud‐to‐ground discharges occasionally follow the cloud discharges, and the objective of this paper is to determine if it is true or false, using the SAFIR data for a few years. Since the development of thunderclouds is determined by the movement of its active area, the coordinate fixed to the moving thunderclouds is applied for analysis.

The analyzed results suggest that forecasting cloud‐to‐ground discharges with 10‐min advance notice for both summer and winter thunderstorms is a possibility.
Development of weatherproof mobile impulse voltage generator and its application to experiments on nonlinearity of grounding resistance
Authors: Morimoto Atsuo , Hayashida Hiroshi , Sekioka Shozo , Isokawa Masahiko , Hiyama Tatsuya , Mori Hitoshi
Published: July 2007

This paper describes a newly developed impulse voltage generator (IG). It has the following features: (1) The IG consists of three components (a 1.6 MV unit, a 1.4‐MV unit and a base box); this facilitates mounting on 10‐ton trucks, therefore making it easier to move to a test field. (2) Capacitors, discharge gaps and a control unit are enclosed in fiber‐reinforced plastics, making it possible to use the IG in all weather. (3) The IG can generate several ten kA when a load is a few ten Ω. (4) Composition of the circuits for lightning/switching impulse voltage/current tests can be easily done by changing the damping and discharge resistance cassettes. Control and data acquisition are made by personal computer.

For IG application during an outdoor test, this paper presents the characteristics of resistances of a 77‐kV substation grounding and a concrete pole when applying a high impulse current. The resistances are dependent on the crest value of the applied current.
Three‐phase current‐fed type converter with direct control of instantaneous current vector
Authors: Ohnishi Tokuo , Minamoto Yoshikazu
Published: July 2007

A new PWM technique for the current‐fed PWM converter is proposed. As the control variables, the instantaneous active and reactive powers are used instead of the line current. They are proportional to the instantaneous active and reactive current vector. The switching state of the PWM converter is given by the selection method of the appropriate current vector among the seven kinds of the current vectors with the zero current vector. The active current is controlled by the zero current vector and the reactive current depends on the kind of selected current vector. These variables basically are controlled by PWM switching from two kinds of hysteresis comparator. In addition to this, the compensation of the filter circuit can be obtained automatically by the PWM control based on the active and reactive current detected from the source current.

In this paper, the principle of the PWM technique for the current‐source PWM converter is proposed. Then, some simulation results are shown. After that, the feasibility of the system is verified by experimental results.
Application of SiC‐Si functionally gradient material to thermoelectric energy conversion device
Authors: Okano Kazuo , Takagi Yoshimitsu
Published: July 2007

Because of its high–temperature chemical stability, SiC ceramic is a promising material for high‐temperature device applications such as thermoelectric energy converters. However, the electrical conductivity of SiC ceramic is too low for it to be used as a thermoelectric energy converter at the cold junction. Therefore, we propose a SiC‐Si functionally gradient material (FGM) in order to improve the electrical conductivity of the SiC ceramic at the cold junction.

An SiC rod was fired in a temperature gradient furnace. One end of the SiC rod was maintained at 2473 K and the other end was maintained at 1973 K for 30 min. After firing, the porous SiC edge fired at 1973 K was dipped into molten Si in order to infiltrate molten Si into the porous SiC.

The microstructure of the FGM is classified into three regions: the SiC‐Si composite material; the porous SiC ceramic; and the densified SiC ceramic. The electrical conductivity, the Seebeck coefficient and the thermal conductivity for each region of SiC‐Si FGM was measured at 300 K; a figure of merit was calculated. The figure of merit of the SiC‐Si FGM at the cold junction, at room temperature, was 108 times higher than that of a nongradient SiC ceramic.
Synthesis of Phosphorylated, Conjugation‐Ready Di‐, Tri‐ and Tetrasaccharide Fragments of the O‐Specific Polysaccharide of V. cholerae O139
Authors: Ruttens Bart , Saksena Rina , Kováč Pavol
Published: July 2007

The fragments described contain a galactose residue with cyclic 4,6‐phosphate and are equipped with an amino‐functionalized spacer, allowing further derivatization or directconjugation to suitable carriers. The core Gal‐(1→3)‐GlcNAc disaccharide was obtained by condensation of 8‐azido‐3,6‐dioxaoctyl 2‐acetamido‐4,6‐O‐benzylidene‐2‐deoxy‐β‐D‐glucopyranoside with 2,3,4,6‐tetra‐O‐acetyl‐α‐D‐galactopyranosyl bromide under Helferich conditions. Reductive opening of the benzylidene acetal, followed by deacetylation and selective benzylation gave 8‐azido‐3,6‐dioxaoctyl 2‐acetamido‐6‐O‐benzyl‐3‐O‐(3‐O‐benzyl‐β‐D‐galactopyranosyl)‐2‐deoxy‐β‐D‐glucopyranoside, which was regioselectively phosphorylated to give two isomeric 4,6‐cyclic 2,2,2‐trichloroethyl phosphates. The (R)‐phosphate was subjected to catalytic hydrogenation/hydrogenolysis to give the fully deprotected title disaccharide fragment. Glycosylation of the (S)‐phosphate diol with 2,4‐di‐O‐benzyl‐3,6‐dideoxy‐α‐L‐xylo‐hexopyranosyl bromide under halide‐assisted conditions yielded a mixture of the tetrasaccharide and a trisaccharide, which were readily separable by chromatography. Their hydrogenation/hydrogenolysis effected global deprotection as well as reduction of the azide, to furnish the deprotected title tri‐ and tetrasaccharide.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Practice and theory of high temperature liquid chromatography
Authors: McNeff Clayton V. , Yan Bingwen , Stoll Dwight R. , Henry Richard A.
Published: July 2007

High temperature liquid chromatography (HTLC) exists in a temperature region beyond ambient (ca. 40°C) and below super critical temperatures. The promises of HTLC, such as increased analysis speed, enhanced separation productivity, “green” LC with pure water mobile phases coupled to universal FID detection, and fast analysis of complex samples by combination with fast 2‐D techniques, have become an option for routine practice. The focus of this paper is to review the key developments that have made the application of HTLC a practical technique and draw attention to new developments in 2‐D techniques that incorporate HTLC that offer an opportunity to vastly increase the usefulness of HPLC for the analysis of complex samples.
Erratum: A quantitative approach to benefit‐risk assessment of medicines — part 2: the practical application of a new model
Authors: Mussen Filip , Salek Sam , Walker Stuart
Published: July 2007

Pharmacoepidemiology and Drug Safety 2007; 16: S16—S41; DOI: 10.1002/pds.1434

It has come to the attention of the authors that this published article contained an error.

The author Lawrence Phillips was mistakenly omitted from the original article. The full list of authors and affiliations can be seen below.

Filip Mussen1,2, Sam Salek2, Stuart Walker3 and Lawrence Phillips4

1Regulatory Affairs Europe, Merck Sharp & Dohme (Europe), Inc., 5 Lynx Binnenhof, Brussels, B‐1200, Belgium

2Centre for Socioeconomic Research, Welsh School of Pharmacy, Redwood Building, King Edward VII Avenue, Cardiff CF10 3XF, UK

3CMR International, Novellus Court, 61 South Street, Epsom, Surrey, KT18 7PX, UK

4Visiting Professor of Decision Sciences, Department of Management, Operational Research Group, London School of Economics, UK

The authors wish to apologise for any inconvenience caused.
Novel polymer monolith prepared from a water‐soluble crosslinking agent
Authors: Kubo Takuya , Kimura Naomi , Hosoya Ken , Kaya Kunimitsu
Published: July 2007

In this study, we described the fundamental properties of novel polymer monoliths that were prepared from a water‐soluble crosslinking agent. Each monolith was evaluated by scanning electron microscope (SEM) and scanning probe microscope (SPM) to observe the monolithic structure, and the polymer films that were prepared from several monomers were evaluated by the contact angle of water. As results of evaluations, the polymer prepared from a water‐soluble crosslinking agent had high hydrophilicity. Furthermore, SEM evaluations suggested that polymer porogenic solvent (PEG) was contributed to the construction of monolithic structure, and the polymerization degree of PEG was also taken effect of the structural changing by the variation of phase separation. Additionally, the results of SPM evaluations and the differences of monolithic structure were also reflected under water condition although the swelling of polymer was observed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3811–3817, 2007
The breast cancer experience of rural women: a literature review
Authors: Ann Bettencourt B. , Schlegel Rebecca J. , Talley Amelia E. , Molix Lisa A.
Published: July 2007

This report is a review of studies that focus on rural breast cancer survivorship. It includes a total of 14 studies using large databases and 27 other studies using qualitative and quantitative methods. In our review of this literature, we identified four broad themes, including access to treatment and treatment type, medical providers and health information, psychosocial adjustment and coping, and social support and psychological support services. We review the findings of the rural breast cancer survivorship studies within each of these broad themes. A few of the findings of the review include that rural and urban women receive different primary treatments for breast cancer, that rural women may have greater difficulty negotiating their traditional gender roles during and after treatment, that rural women desire greater health‐related information about their breast cancer, and that rural women have less access to mental health therapy. The review discusses the implications of these findings as well as the weakness in the literature. Copyright © 2007 John Wiley & Sons, Ltd.
Quality of life before and one year following stem cell transplantation using an individualized and a standardized instrument
Authors: Wettergren L. , Sprangers M. , Björkholm M. , Langius‐Eklöf A.
Published: July 2007

Objective: The aim was to prospectively measure quality of life in patients with malignant blood disorders following stem cell transplantation (SCT) using an individualized and a standardized measure.

Methods: Twenty‐two consecutive patients were assessed before and one year following SCT, using a generic and disease‐related version of the Schedule for the Evaluation of Individual Quality of Life‐Direct Weighting (SEIQoL‐DW) and the EORTC QLQ‐C30. Results of the QLQ‐C30 were compared with Swedish norm values.

Results: A majority of the patients reported concerns related to health before as well as one year after SCT, recorded by both instruments. Mean scores produced by the SEIQoL‐DW, and four scales of the EORTC QLQ‐C30, showed a change over time, indicating improved quality of life one year after SCT. In comparison with Swedish norm values for the EORTC QLQ‐C30, SCT recipients reported a worse functioning.

Conclusions: In addition to well‐known disease and treatment‐related problems, areas not typically included in standardized instruments were nominated in the disease‐related SEIQoL‐DW. Such areas included positive aspects, e.g. a changed view of life and oneself. The results support the use of the generic and disease‐related SEIQoL‐DW to achieve a comprehensive picture of patient's clinical situation under treatment or when recovering from illness. Copyright © 2007 John Wiley & Sons, Ltd.
Nanostructured cobalt on porous silicon substrate: Structure and magnetic behaviour
Authors: Belkacem W. , Mliki N. , Belhi R. , Saikaly W. , Yangui B.
Published: July 2007

During an anodization process, porous silicon (PS) consisting of pores with a diameter of about 40 nm and a depth from 5 µm to 40 µm has been produced. To achieve oriented channels in this mesoporous range, a p+‐type Si wafer was electrochemically etched in an aqueous electrolyte of HF. We report the formation, after the anodization step, of a cobalt nanostructure in a porous silicon matrix. Co nanocrystals on and in a porous silicon layer have been prepared by the UHV evaporation technique and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). This technique was performed to show the chemical element distribution within the channels. It is found that the deposition condition is an important factor for obtaining nano‐structures. Initial deposition leads to Co particle penetration in silicon pores whereas subsequent deposition results only in an increase of the thickness at the surface with no further penetration. Additional experiments were carried out by using the magneto‐optical Kerr effect to obtain information about the magnetic properties. The first results show that the magnetic response for layers <5 nm presents an important perpendicular component of magnetization whereas for thicker deposited layers (8 nm < t < 20 nm) the magnetic response seems to act as that of a thin film in which the squareness of the hysteresis loop decreases with increasing film thickness. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Insignificant mixed‐alkali effect in Li2O–Na2O–Fe2O3–P2O5 glasses
Authors: Tashtoush N. M. , El‐Desoky M. M.
Published: July 2007

Conductivity spectra of mixed‐alkali ions in iron phosphate glasses have been studied in the frequency range from 400 Hz to 200 kHz, and over a temperature range from 333 K to 493 K. The ac conductivity as a function of temperature was divided into two domains; one where the absolute of ac conductivity is close to the dc conductivity, and one where the absolute magnitude of the ac conductivity is larger than the dc conductivity. The concentration of charge carriers was found to be almost independent of temperature, but was weakly dependent on composition. It seems that the conductivity was essentially determined by the hopping frequency. The activation energy for the hopping frequency is close to that of the dc conductivity and the glasses behave as strong electrolytes. The frequency exponent appears to be independent of temperature, but depends very weakly on composition. The glasses show weak pronounced mixed‐alkali effect in the mixed lithium and sodium iron phosphate glasses. The small minimum and maximum in dc conductivity and activation energy, respectively, are further evidence of the low mobility of the lithium and sodium ions in these iron phosphate glasses. We have also presented a scaling of the conductivity spectra, which implies that the relaxation dynamics of charge carriers in the present glasses is weakly dependent on temperature and composition. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of nano‐ and microstructured GaN in bulk powder and on substrate
Authors: Ghosh R. , Basak D.
Published: July 2007

A detailed investigation has been carried out to study the effects of growth temperature, NH3 flow rate, grinding‐mediated annealing of the as‐synthesized GaN powder, different substrates and Au catalyst on the products grown by a direct reaction of Ga with NH3. Nanowires of diameter in the range 15–40 nm are grown around a narrow temperature zone, 1000 °C < t < 1100 °C, with a 150 sccm NH3 gas flow rate. Beyond this temperature zone, GaN platelets are formed in a large scale. Annealing of the as‐synthesized GaN powder at 800 °C after a grinding process results in the growth of dendrite‐like GaN nanostructures and above 800 °C, only hillocks of GaN platelets are grown. The layers formed on sapphire and ZnO/quartz substrates consist of GaN nano‐ and microrods of diameter 40–100 nm and 1–1.5 μm respectively that show ultraviolet (UV) emission peaks below 400 nm. Large‐scale synthesis of GaN nanorods of diameter 60–100 nm has been achieved on Au/quartz substrate at 1050 °C with a 150 sccm of NH3 gas flow rate. The nanorods exhibit a strong UV emission peak indicating a better optical quality. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hydride electronics
Authors: Karazhanov Smagul Zh. , Ravindran P. , Vajeeston P. , Ulyashin Alexander G.
Published: July 2007

With the help of first‐principles density functional calculations, using AlH3 as a model system, we have shown that some of the hydrides possess the features of transparent conducting oxides (TCO). Based on this observation we discuss here the possible novel applications of hydrides in electronic device technology as electrical conducting materials, which can have both n‐ and p‐type conductivity and at the same time transparent in the infrared (IR), near IR, or visible regions. Moreover, some advantages concerning properties of interfaces in case of using hydrides in modern multilayer based device structures are discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoemission from the potassium halides in the photon energy range 7 to 30 eV
Authors: Blechschmidt D. , Skibowski M. , Steinmann W.
Published: July 2007

The spectral distribution of the photocurrent at different retarding potentials as well as the energy distribution of the photoelectrons at a fixed photon energy have been measured for all potassium halides. The synchrotron radiation of DESY was used as a light source. The samples were thin films evaporated under ultra‐high vacuum. The threshold energy, the distance between the valence band and the K+3p core level, and the position of the Fermi level have been determined. The onset of electron–electron scattering and the appearence of inelastically scattered electrons in the photoemission has been demonstrated. The decay of the core excitons has been investigated. The core exciton structure in the spectra of the photoyield is due to direct recombination. There is some evidence that an Auger process occurs as additional decay mechanism.
Transport Phenomena in Thin Films of Semi‐Metals with Non‐Spherical Energy Surfaces at Low Temperatures
Authors: Kamal J. , Tewari D. P.
Published: July 2007

The size dependence of the transport coefficients of semi‐metals has been studied assuming nonspherical energy surfaces and taking into account the energy dependence of the relaxation time. Detailed calculations have been performed for thin bismuth films at low temperatures considering the anisotropy in the mass tensor. Cartesian tensor expansion technique has been used to solve the Boltzmann transfer equation in the presence of a static electric field applied along the surface of the film and a magnetic field in the transverse direction. Results obtained are in good qualitative agreement with the experimental results of Colombani and Huet.
Identification of Three Trapping Centers in Calcium Tungstate
Authors: Koehler H. A. , Kikuchi C.
Published: July 2007

Partial thermal annealing of nominally pure calcium tungstate, after gamma irradiation at 78 °K, provided evidence for identifying three major 4900 Å thermoluminescence peaks at 0.36, 0.55, and 0.72 eV with three groups of electron spin resonance lines of paramagnetic tungsten at g001 = 2.009 and 1.843 and niobium at g001 = 2.021, respectively. The impurity center identified with the paramagnetic Nb+4 ion is assigned to a tungsten site and a NbO complex. Arguments are presented for the assignment of two lattice defect models, a WO complex with nearby WO3 and NbO complexes, and a WO complex with a nearby calcium deficiency, to the paramagnetic (W+5)A and (W+5)B ions, respectively.