bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photovoltage generation and fluorescence of charged tetraphenylporphyrins with dopa melanin
Authors: Hanyz I. , Wróbel D. 
Published: April 2003

AbstractPositively charged tetra(4‐N,N,N,N‐ trimethylanilinium) porphyrin (TAP) and negatively charged tetrakis(4‐sulphonatophenyl) porphyrin (TPPS4) and their mixtures with dopa melanin in polyvinyl alcohol have been investigated. On the basis of the absorption and fluorescence spectra it has been established the formation of TAP–dopa melanin complex which fluorescence is quenched whereas TPPS4fluorescence behaviour is only slightly changed in the presence of dopa melanin. Photovoltaic effects and photocurrent generation in a photoelectrochemical cell consisting of a layer dye solutions sandwiched between the semiconducting and gold electrodes have been investigated. The dependence of photovoltage signal on excitation wavelength (photovoltage action spectrum), kinetics of photocurrent rise and decay in the second time scale have been presented. Electric parameters of the photoelectrochemical cell (conductivity and capacitance) with porphyrin dyes, dopa melanin and their mixtures in the dark and upon illumination have been estimated. It was shown that all investigated dyes are able to generate photosignal but the values of photocurrent generated depend on the dye used in the experiment and the presence or absence of dopa melanin.
Effect of melt composition on the electrical conductivity and IR absorption of CsLiB6O10 crystals
Authors: Hartmann E. , Péter Á. , Lengyel K. , Kovács L. 
Published: April 2003

AbstractThe dc conductivity of cesium lithium borate crystals grown from different melt composition has been studied in the 50 – 750 °C range. The temperature dependence of the electrical conductivity followed the Arrhenius law in most cases. The anisotropy of the electrical conductivity of crystals was rather small. The vibrational modes of water molecules present in the crystals were detected by infrared absorption technique. It was found that the intensity of the two OH stretching vibrational bands depends on the thermal history of the crystals, and, beside the two main water bands, some additional weak lines appear at –185 °C in the crystals with low Cs/B ratio.
Electrical properties of hydrogen‐implanted Si annealed under high hydrostatic pressure
Authors: Kaniewska M. , Misiuk A. 
Published: April 2003

AbstractCzochralski p‐type Si: B was implanted with H2‐ions at energy of 130 keV and a dose of 4 × 1016 cm‐3. The specimens were annealed at 720 K/10 h in argon ambient under a hydrostatic pressure of 1.2 GPa. Reference specimens were annealed under atmospheric pressure. Schottky‐barrier diodes were fabricated and then capacitance‐voltage (C‐V) measurements and C‐V profiling in the temperature range 80‐370 K were performed to characterise the samples. It has been found that the implantation followed by high temperature annealing is effective in producing deep as well as shallow acceptor levels in the Si energy gap. The deep acceptor is a dominant defect that acts as a strong compensating centre in the n‐type material. The latter was formed as a result of a conversion of the initially p‐type material due to creating thermal donors (TDs) during heat treatment. Unusual properties in C‐V curves and complex carrier profiles were attributed to the presence of the deep‐level defect. Moreover, it has been found that the generation and thermal activation energy of TDs showed a substantial dependence on the hydrostatic pressure. It is interpreted that high‐pressure gives rise to thermal donors that are distinctly different from those that form during annealing under normal pressure.
Hydrogen implantation effect on optical properties of GaAs doping superlattices
Authors: Kunert H. W. , Dale D. , Hayes M. , Malherbe J. , Kononenko V. K. , Barnas J. 
Published: April 2003

AbstractExperimental results on the response of GaAs doping superlattices to 1 MeV hydrogen implantation at the doses of 5×1016, 1×1017, and 5×1017 cm‐2 are presented. The samples were studied by means of photoluminescence and inelastic light scattering spectroscopy. Several new optically stable transitions above the effective energy band were observed. Structural changes were monitored by Raman spectroscopy. Possible origin of the new transitions is discussed. An attempt is also made to determine character of the tunable behavior of the parameters in as‐grown and treated superlattices.
Deep‐level defects induced by Ar‐ion beam etching in n‐type AlxGa1‐xAs grown by MBE
Authors: Kaniewska M. , Bożek J. 
Published: April 2003

AbstractResults of the electrical study of the damage caused by Ar‐ion beam etching in MBE grown AlxGa1‐xAs : Si laser diode material are reported. This study has involved measurements of capacitance as a function of voltage and temperature as well as deep level transient spectroscopy measurements on Schottky‐barriers diodes. The Schottky contacts were fabricated conventionally by depositing Au in a vacuum onto the etched AlGaAs surface. For a reference the Schottky diodes of the best quality were produced in‐situ by evaporation of Al on the top of the epi‐layer at the end of the MBE growth run. On the basis of the results of a comparative study deep‐level defects related to the subsurface damaged layer have been recognised. Emission signatures as well as depth profiles of the defect concentration have been studied and analysed. Moreover, DLTS spectra revealed the presence of a well‐known DX(Si) centre and M‐type defect related level attributed to a vacancy and impurity complex. The presence of an additional deep‐level defect located in the lower half of the energy gap that was induced by dry etching is also suggested. An extra defect considered has the high enough concentration to disturb carrier spatial profiles and DX centre characteristics. It is suggested that it may be responsible for degradation effects in GaAs/AlGaAs heterostructure lasers, which fabricating involves dry etching.
Raman scattering study of ZnBeSe semiconducting mixed crystals
Authors: Szybowicz M. , Kozielski M. , Firszt F. , Łęgowski S. , Męczyńska H. 
Published: April 2003

AbstractThe results of a study of Raman scattering of Zn1‐xBexSe mixed crystals are reported. Raman measurements were performed for crystals with x = 0.12 and x = 0.25 Be at room temperature and liquid nitrogen temperature. From the Raman spectra the longitudinal optical and transverse optical modes which correspond to ZnSe‐like and BeSe‐like were distinguished. Theoretical calculations of frequencies of BeSe modes and force constants for Zn1‐xBexSe were also performed using modified random element isodisplacement model. It has been shown that the dependence of the phonon energy on temperature may be described by the modified Klemens model.
Raman selection rules in C46v hexagonal crystals: allowed combinations and overtones of vibrational modes in wurtzite GaN
Authors: Kunert H. W. 
Published: April 2003

AbstractA discrete set of oscillators belongs to the critical points in the lattice vibration spectrum. The vibrational states of crystals are classified according to appropriate irreducible representations of the relevant wave vector space groups. Suitable space‐group selection rules are used to determine the active one and two phonon combinations and overtone processes in hexagonal structures. Experimental Raman spectra of the hexagonal C46v GaN are discussed in terms of the derived selection rules.
Elastic and nonlinear optical properties of lithium tetraborate
Authors: Kasprowicz D. , Kroupa J. , Majchrowski A. , Michalski E. , Drozdowski M. , Żmija J. 
Published: April 2003

AbstractThe elastic properties of lithium tetraborate Li2B4O7single crystals have been studied by Brillouin scattering method. Using this method the propagation of the acoustic waves in the [100], [001], [110] and [011] directions has been estimated. The nonlinear optical coefficientsd31andd33were measured using the Maker fringe technique. The temperature dependence of the nonlinear optical coefficientd31does not confirm an earlier report on the existence of a phase transition in the temperature range from room temperature to 600°C.
Growth and properties of LiGaX2 (X = S, Se, Te) single crystals for nonlinear optical applications in the mid‐IR
Authors: Isaenko L. , Yelisseyev A. , Lobanov S. , Titov A. , Petrov V. , Zondy J.‐J. , Krinitsin P. , Merkulov A. , Vedenyapin V. , Smirnova J. 
Published: April 2003

AbstractSingle crystals LiGaX2 (X = S, Se, Te) of optical quality were grown, with transparency ranges at 5 cm‐1 absorption level of 0.32‐11.6 μm, 0.37‐13.2 μm and 0.54‐14.2 μm, respectively. The first two, LiGaS2 and LiGaSe2, have a wurtzite‐type structure whereas LiGaTe2 is tetragonal (chalcopyrite lattice). The three refractive indices were measured in the whole transparency ranges of LiGaS2 and LiGaSe2 and na and nc were found to be very close (quasi‐uniaxial optical anisotropy) with a crosspoint at 6.5 μm (LiGaS2) and 8 μm (LiGaSe2). Sellmeier equations were fitted and phase‐matching conditions for second harmonic generation (SHG) were calculated: the 1.467‐11.72 μm spectral range for the fundamental is covered by LiGaS2 and LiGaSe2.
Transient and stable color centers in pure and Cu‐doped LiNbO3
Authors: Matkovskii A. , Potera P. , Sugak D. , Zhydachevskii Ya. , Pankratov V. , Millers D. , Grigorjeva L. , Pracka I. , Lukasiewicz T. 
Published: April 2003

AbstractThe present work is devoted to investigation of stable and transient color centers that are induced by radiation and temperature in pure and Cu‐doped LiNbO3 single crystals. The transient changes of absorption of the crystals induced by pulsed electron beam (E=0.25 MeV) are studied in 0‐5000 ns time range, as well as stable changes of absorption induced by reducing annealing and irradiation with γ‐quanta, high energy electrons or fast reactor neutrons.
Oxygen agglomeration and formation of oxygen‐related thermal donors in heat‐treated silicon
Authors: Emtsev V. V. , Ammerlaan C. A. J. , Emtsev V. V. , Oganesyan G. A. , Misiuk A. , Surma B. , Bukowski A. , Londos C. A. , Potsidi M. S. 
Published: April 2003

AbstractThe characteristic features of production processes of thermal donors in Czochralski grown silicon heat treated at T=450°C under hydrostatic pressures of about 1 GPa are studied. Two families of oxygen‐related donors are formed under compressive stress. The first one is the well‐known thermal double donors whose production rate is increased by a factor of five as compared with that observed at atmospheric pressure. Along with them, new thermal donors with similar energy states are also produced. This family was found to be a dominant contributor to the thermal donors formed under compressive stress. The features of formation processes of both kinds of thermal donors are briefly discussed.
Optical properties of an In0.22Ga0.78Sb/GaSb single quantum well
Authors: Kudrawiec R. , Bryja L. , Sęk G. , Ryczko K. , Misiewicz J. , Forchel A. 
Published: April 2003

AbstractOptical properties of an In0.22Ga0.78Sb/GaSb single quantum well (SQW) have been investigated by photoluminescence (PL) and photoreflectance (PR). Two electron and heavy hole confined states, which had been expected from envelope function calculations, have been detected experimentally. Besides two allowed transitions (1HH‐1C and 2HH‐2C) also forbidden one (1HH‐2C) has been observed in PR. In PL experiment, which had been performed in broad excitation power (EP) range at different temperatures, the state filling effect has been investigated. At 10 K with the increase of EP density to 2 W/cm2 a linear dependence of integrated PL intensity has been observed. The character of the PL emission is excitonic and does not change with the increase of EP in that excitation range. Above the excitation density of 2 W/cm2 the in‐plane heating of the quantum well carriers occurs. With the increase of temperature the nature of recombination process changes from excitonic to free‐carrier recombination type. Above 60 K only the free‐carrier recombination take place and for high excitation power an emission from the excited state (2HH‐2C) emerges.
Magneto‐transport in single InGaAs quantum wells of different shapes
Authors: Tomaka G. , Sheregii E. M. , Kąkol T. , Strupiński W. , Jakieła R. , Kolek A. , Stadler A. , Mleczko K. 
Published: April 2003

AbstractThe magneto‐transport measurements in InGaAs/InAlAs quantum wells (QW) obtained by MOCVD technology on InP substrates, and known as High Electron Mobility Transistors, were performed at low temperatures of 0.4 ‐ 15 K and high magnetic fields up to 10 T (with the magnetic field induction B perpendicular to the plane of the well). Three kinds of structures were studied. The Shubnikov‐de Haas oscillations demonstrating the occupancy of two subbands were observed. In order to determine the energies of Landau levels in the QW subbands, we have used the Zawadzki‐Pfeffer quazi‐two‐band model. Good agreement between calculated Landau levels and Fermi level from one hand, and positions of the Shubnikovde Haas oscillations peaks from the other, enable us to determine the parameters of 2D electron gas in QW: effective mass and carrier density.
An exact performance model for the reserve channels CAC strategy at a bufferless network node
Authors: Deniz Dervis Z. , Mohamed Nagla O. 
Published: April 2003

AbstractThe reserve channels call admission control (CAC) strategy in which the total number of channels available at the node is divided into active and reserve channels is analysed. Two types of customers are assumed to exist: the narrowband type requiring bandwidth bn=1 channel and wideband type requiring bw⩾1 channels. The active channels are shared by all customer types while the reserve channels are allocated by a predefined rule. An exact matrix algorithmic solution technique is proposed that extends the previous results to the case of calls requiring bw⩾1 channels. Using the developed solution technique, the number of equations to be solved is decreased which reduces the solution time by more than half. The technique is applied to a sample case and performance results in terms of blocking probabilities for both types of calls as well as the mean server utilization are obtained. Copyright © 2003 John Wiley & Sons, Ltd.
Effect of load distribution in path protection of MPLS
Authors: Kim Sook‐Yeon 
Published: April 2003

AbstractWe analyse and compare a protection mechanism based on load distribution with a typical protection mechanism in an multiprotocol label switching (MPLS) network. The protection mechanism based on load distribution is modelled as a fully shared mechanism (FSM) and the typical protection mechanism is a partially shared mechanism (PSM). By comparing the FSM and the PSM, we numerically analyse the effect of load distribution in path protection of MPLS. The comparison is based on numerical equations representing the relationship between service reliability and resource utilization. From the equations, we show that both the FSM and the PSM have a tradeoff between service reliability and resource utilization. In addition, we provide solutions for the FSM and the PSM to determine the amount of bandwidth occupied according to the requested service reliability. The comparison of the FSM and the PSM shows that the PSM cannot provide greater service reliability than the FSM under the same utilization. In addition, the PSM is not capable of accommodating greater resource utilization than the FSM for the same level of service reliability. However, an appropriate choice of the number of protection paths allows the PSM to provide the same level of service reliability as the FSM. The choice is the maximum among the possible numbers of protection paths of the PSM. In short, the typical protection mechanism is as good as the FSM in terms of service reliability and resource utilization even though the FSM is an attractive alternative to the typical protection mechanism. Copyright © 2003 John Wiley & Sons, Ltd.
Explicit TCP window adaptation in a shared memory architecture
Authors: Aweya James , Ouellette Michel , Montuno Delfin Y. 
Published: April 2003

AbstractA multiple (priority) queueing system allows a network node to manage the queueing of packets in such a way that higher priority packets will always be served first, low priority packets will be discarded when the queue is full, and for same‐priority packets any interference between them will be prevented. This paper describes a TCP window control scheme for a shared memory device that has buffer memory logically organized into multiple queues. To handle changing queue traffic loads, the shared memory device uses a dynamic buffer threshold mechanism to allocate buffer space to the queues. The TCP window control scheme allows the receiver's advertised window size in ACK packets to be modified at the network queue in order to maintain the queue size at a computed dynamic threshold. Copyright © 2003 John Wiley & Sons, Ltd.
kW‐value of a photovoltaic power generation system evaluated from actual data on electricity demand and insolation
Authors: Kato Takeyoshi , Nagae Nobuhisa , Tabata Akimori , Yokomizu Yasunobu , Okamoto Tatsuki , Suzuoki Yasuo 
Published: April 2003

AbstractThis paper proposes a new method of evaluating the kW‐value of photovoltaic power generation systems (PV systems). This evaluation is based on actual insolation data, collected by the Japan Meteorological Agency at four locations in the Chubu area in Japan, and the actual electrical load data of the Chubu area in the 1990s. We selected specific days on which the daily peak load was relatively high. For the selected days, we estimated the average output of PV systems using the IEA's method for considering the temperature dependency of cell efficiency. Then, we calculated the reduction of the peak load ΔLp(d). The resultant ΔLp(d) was distributed in the range from 0.4 to 0.5 kW/kWp.We evaluated the average value of the smallest ΔLp(d) as the kW‐value of PV systems. When the kW‐value was evaluated for the two or three days with the smallest ΔLp(d) among the selected 10 days for 1 year, the kW‐value of the PV systems was calculated to be about 30%. This was close to the value obtained by the conventional loss of load probability (LOLP) method. Our study evaluates the relationship between the kW‐value of PV systems and the number of days on which the insolation was low but the daily peak demand was relatively high. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(1): 42–49, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10089
Design of a robust PWM power amplifier using approximate two‐degree‐of‐freedom integral‐type control
Authors: Higuchi Kohji , Nakano Kazushi , Araki Kuniya , Chino Fumiho 
Published: April 2003

AbstractA method is proposed for designing a robust controller for PWM power amplifiers, which are widely used as amplifiers and power supplies. The main technical requirements imposed on PWM power amplifiers are linearity in a wide frequency range and a well‐damped fast dynamic response in the presence of extensive load and DC power supply variations. Therefore, in order to satisfy the design specifications, namely, linearity in a wide frequency range and no overshoots during transients, an approximate two‐degree‐of‐freedom integral control structure is proposed and a design procedure for the robust controller is discussed. It is shown by some simulations and experiments that the designed controller shows especially good dynamic performance and effective disturbance rejection in the presence of external disturbances, that is, load and power‐supply variations. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(1): 68–77, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10102
A design of self‐tuning pole‐assignment control systems based on minimizing quadratic cost functions
Authors: Ohnishi Yoshihiro , Yamamoto Toru , Kaneda Masahiro 
Published: April 2003

AbstractThere are numerous studies of the design of self‐tuning control (STC) systems for linear nonminimum‐phase systems. A wide variety of existing methods on designing STC systems are conceptually classified into two groups. One is based on minimization of an error criterion, and the other on pole assignment of the closed‐loop system. On the other hand, in order to guarantee the tracking property for the reference signals, an internal model which corresponds to the reference signals must be inserted into the control system based on the internal model principle. However, the variance of the control error signal may become large on inserting the internal model, because stochastic noise may be amplified. In this paper, a design method for self‐tuning pole‐assignment control systems with internal models is proposed based on minimizing the linear quadratic cost function. The newly proposed control scheme has the feature that the variance of the stochastic noise in the control system is reduced owing to the minimum variance control scheme, and also the tracking property with respect to the reference signal is assured owing to the internal model. The proposed control scheme is numerically evaluated in some simulation examples. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(1): 50–57, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10120
Fundamental study on location of a partial discharge source with a VHF‐UHF radio interferometer system
Authors: Kawada Masatake 
Published: April 2003

AbstractThe electromagnetic waves emitted from partial discharges (PD) due to material defects in high‐voltage electric power apparatus and facilities are broadband signals including VHF, UHF (Very High Frequency, Ultra High Frequency). A new VHF‐UHF radio interferometer system (VURIS) for locating PD source has been designed, constructed, and tested. The system is based on the idea of using the Fourier transform to extract the phase differences of different frequency components between a pair of received signals and computing the direction of the electromagnetic waves emitted from the PD source. It can be small in size, because UHF half‐wavelength dipole antennas are used to receive the electromagnetic waves and the baseline between the antennas is short. It requires fewer antennas to achieve equivalent angular resolution than a narrow‐band interferometer system, which requires multiple baselines corresponding to a few times the half‐wavelength of the observation frequency. Therefore, its use reduces operating time at the measurement site because it is not necessary to arrange many antennas at many positions. The indoor test results indicate that the system is able to estimate the arrival angle of electromagnetic waves emitted from PD sources. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(1): 32–41, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10145
Changes in capacitance and dielectric dissipation factor of water‐treed XLPE with applied voltage
Authors: Ozaki Tamon , Ito Noriyuki , Nakamura Shuhei , Kawai Jiro 
Published: April 2003

AbstractThe capacitance C and dielectric dissipation factor tan δ of a water‐treed XLPE sheet sample have been measured under the application of 100 V or 1 kV at 60 Hz. The values of C and tan δ at 1 kV are much larger than those at 100 V. The value of tan δ gradually decreases with the length of exposure to a voltage of 1 kV. On the other hand, C is almost constant versus the exposure time. The results have been discussed on the basis of a model in which filling of channels interconnecting voids by water is taken into account. It has been found that the increase of C and tan δ is caused by the growth of the water‐filled channel region on the application of voltage. The gradual decrease in tan δ with the exposure time is explained by the change in the conductivity of the water‐filled channel region, as a result of which the relaxation time shifts to higher frequencies. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(1): 12–20, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10160