High Power Range Research Articles

A Saturated Synchronous Machine Study for the Converter-Machine-Command Set Simulation

The electromagnetic study presented models a saturated synchronous machine for the Converter-Machine-Command (CMC) set simulation. The proposed method is based on a modified Park model (Garrido and De Jaeger Model: GDJ model [1,2]) when calculating the GDJ model laws and the GDJ model parameters using a field computation based on the Finite Element Method (FEM). The first model (GDJ model) is modified in accordance to the field results and a 4.8% improvement has been estimated. The model validity is obtained when comparing the computed and measured reactances. The improved model is elaborated in order to be introduced into the saturated machine algorithm to simulate the CMC set. In comparison with the model based on experiments, the proposed one avoids complex tests on high power range synchronous machines. On the other hand, this study reveals Potier parameter variations with the saturation state whereas the conventional methods consider it as a constant value. Finally we develop the saturated synchronous machine model associated with the converter.

Stability of NdBa 2Cu 3O 7− x based resonators in humid conditions

The surface stability of NdBa 2Cu 3O 7− x thin film is utudied using the conditions referred to as standard accelerated humidity testing. NdBa 2Cu 3O 7− x thin film is compared with well studied YBa 2Cu 3O 7− x thin film by evaluating the surface resistance ( R s) obtained from their film-based microstrip line resonators. The R s of the NdBa 2Cu 3O 7− x thin film indicates better stability than that of YBa 2Cu 3O 7− x in the low and relatively high microwave power range.

Mechanisms of recombination in GaN photodetectors

Steady-state and transient responses of a nonintentionally doped GaN photodetector are investigated. The kinetics of the photoresponse demonstrate the existence of deep levels in the gap, acting as recombination centers with an acceptor character. The photoresponse displays two competing processes: a bimolecular recombination, dominating at high optical power range, and a monomolecular recombination involving long response times. The observed persistent photoconductivity and the huge photoconductive gain are due to the small electron capture cross section and a much faster hole capture rate.

Low-loss quasi-parallel resonant DC link inverter with advanced PWM capability

A low-loss quasi-parallel resonant DC link (L2QPRDCL) circuit with advanced PWM capability is proposed for soft switching a three-phase PWM inverter. This L2QPRDCL has minimum voltage stress for the devices, and an advanced PWM capability due to the variable zero voltage duration of the DC-link over a wide range. Owing to there being scarcely any freewheeling current in the L2QPRDCL during the zero voltage period, low-loss operation in the resonant circuit can be obtained. As a result, the proposed L2QPRDCL inverter is applicable to the highpower range. Operational principles and detailed analyses are presented. By adopting the non-nearest four vectors (N2FV) selection law in the space vector PWM technique, the narrow pulse problem originating from the link operation, which should be considered in those inverters having resonant DC-links, can be eliminated. Experimental results are also presented to verify the link operation and the performance of the selected space vector PWM method.

Direct torque control for brushless doubly-fed machines

Work has illustrated the potential benefits of brushless doubly-fed machines in adjustable speed drive applications. While it has been shown that the drive is open-loop stable over a wide speed range, the resultant steady-state and dynamic performance characteristics are far from optimum. Thus, a closed-loop controller is desirable to achieve competitive drive performance. The controller proposed here is applicable for general purpose industrial drives in the medium to high power range. The nature of the doubly-fed machine, with two separate sources of excitation, only one of which is controllable, rules out field-oriented control strategies applied to conventional induction machines. However, the concept of direct torque control based on instantaneous error shows promise for this machine geometry. The present paper extends the concept of predictive torque control for induction machines to the doubly-fed machine. The controller calculates the value of converter voltage which leads to desired changes of flux and torque. Once the voltage is determined, conventional algorithms, such as space vector pulsewidth modulation (PWM), can be used to generate the inverter switching function.

Start up performance of load-commutated inverter fed synchronous machine drives

Load-commutated inverter (LCI) synchronous machine drives are common in the high power range. However, the starting performance of these systems is a concern since load-commutation cannot occur at arbitrarily low speeds. This paper compares three different starting strategies including one apparently neglected method-normal load commutation. In particular, it is shown that, depending on system parameters, it may be possible to start the system with no special provision for start up. A method to determine whether a given system can be started using load commutation is presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Broadband superfluorescent emission of the ^3H_4 → ^3H_6 transition in a Tm-doped multicomponent silicate fiber

We report the observation of amplified spontaneous emission in the (3)H(4) ? (3)H(6) transition of Tm(+3) in a Ta(2)O(5)-doped multicomponent silicate fiber. The evolutions of the spectral shape, output power, and center wavelength were measured as a function of fiber length and pump power in the previously unstudied high-power range, where saturation effects dominate. An output power of 1 mW has been achieved at 1.91 microm with a bandwidth of 77 nm.

600 mW CW single-mode GaAlAs triple-quantum-well laser with a new index guided structure

A very-high-power, single-mode GaAlAs triple-quantum-well (TQW) laser with a novel real refractive index guided structure has been developed. The maximum output power of 720 mW CW and single transverse- and longitudinal-mode operation up to 600 mW CW have been achieved in a single-element device. This excellent mode operation is attained by using the real refractive index guided structure with a GaAlAs current-blocking layer which gives a low effective refractive index step, suppressing the spatial hole-burning effect in the high-power range.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optical nonlinear responses of a quantum well photodiode with a non-ohmic contact

The dependence of photocurrent properties on incident optical power in a quantum well p-i-n photodiode with a nonohmic contact was investigated. The experimental results showed that a significant absorption peak shift, in an extremely low optical power range, as well as a notable modification in the spectral shape at a higher power range was observed, without any external feedback element. The mechanism for the optical nonlinear responses can be explained in terms of the built-in field screening at the p-i-n junction or by taking into account the load characteristics of the Schottky-like contact.

Analog-to-digital conversion using custom CMOS analog memory for the EOS time projection chamber

A multiplexing scheme for custom CMOS analog memory integrated circuits having 16 channels *256 cells and acting as analog-to-digital converters (ADCs) to handle the 15360 signal channels of the Equation-Of-State Time Projection Chamber (EOS TPC) is described. The primary requirements of this system are high density, low power, and large dynamic range. The analog memory device multiplexing scheme was designed to digitize the information stored in the memory cells. The digitization time of the ADCs and the settling times for the memory unit were carefully interleaved to optimize the performance and timing during the multiplexing operation. This kept the total number of ADCs, a costly and power-consuming component, to an acceptable minimum. >

老人斑, Alzheimer神経原線維変化, Pick嗜銀球の超高倍率走査電顕的観察

Senile plaques, neurofibrillary tangles, and Pick bodies were examined by modified scanning electron microscopy from a low-power to an ultra high-power range. The amyloid core of the typical plaques was found to be composed of radially arranged rod-shaped components, which were made up of dense aggregation of meandering moniliform amyloid filaments about 15 nm in diameter. Bands with a mesh-like structure were observed outside the crown around the core. The compact plaques were nearly identical to the core alone of the typical plaques. The primitive plaques as a whole were analogous to the mesh-like structure around the typical plaques, and they both contained aggregates of filaments closely resembling amyloid fibers. In neurofibrillary tangles, the flamed shape stretched straight to the peripheries, the globosed shaped formed vortices, and only bundles of parallel filaments were observed. PHFs that constituted these structures were 25-30 nm in diameter, and many appeared constricted to a diameter of about 15 nm by rotating 180° to the left at a cycle of 70-80 nm. In Pick bodies, filaments were interwoven and formed a mesh-like structure, numerous granules were attached the filaments. Some filaments were large, being 20-30 nm in diameter, others were thin, being about 15 nm in diameter.

A versatile force balance for ultrasound power measurement

The passing decades have witnessed many designs of instrument for measuring the radiated power output from ultrasound equipment, both in the low power, diagnostic range and in the higher power range as used in therapy, for example. Criteria to be considered during design, encompass the following: high sensitivity/resolution- to microwatts; power handling to tens of watts; simplicity of use and calibration; quick response time; stability of readings and zero; the need for a frequency-independent linear response; ability to accept all current sizes of transducer; portability and ruggedness. The criteria must be accommodated in a single instrument. This paper starts with a brief review of but some of the previous designs, and identifies a fundamental problem with many. The instrument here described hopefully eliminates this problem and essentially meets the above criteria. Using the force-balance principle, the instrument has a 70 mm diameter reflecting target, plus a concentric absorber, in a water-filled chamber. The maximum sensitivity is 1 mW FSD, resolution better than 50 mu W and a maximum power capability of 10 W. The instrument is very portable, weighing only 3 kg.

Aspheric high positive power lenses and third order theory.

To correct third order (primary) oblique astigmatism of thin spectacle lenses outside an approximate lens power range of -22 D to +7 D, one surface must be aspherized. Aspherizing is of particular importance in the high positive power range used for the correction of aphakia. Graphs are presented showing the required front surface asphericities and power drops required to correct oblique astigmatism in this range. The results are a guide to the required asphericities in thick lenses.

Argon laser treatment of bleeding canine gastric ulcers: Limitations and guidelines for endoscopic use

We systematically evaluated an endoscopically deliverable argon laser with coaxial CO2. The purposes were to determine limitations and guidelines for effective and safe use. In a series of studies, important variables (power, treatment distance, spot size, power density, and/or coaxial CO2 pressure) for treatment of experimental bleeding gastric ulcers in dogs were controlled, and their influence upon treatment efficacy and histologic damage were quantitated. Separate studies via laparotomy and endoscopy were done. Our conclusions were: 1.Much greater power was required to efficiently treat bleeding lesions via the endoscope than at laparotomy.2.The ideal effective treatment range was 1.0–2.0 cm with an argon delivery system of this design. Long treatment distance was restricted by the necessity to maintain adequate CO2 pressure at the target. Short treatment distance and high-power density were dangerous because of an erosive effect producing arterial bleeding, deep tissue injury, and actual vaporization of the gastric wall.3.Argon laser treatment in the presence of gastric overdistension increased histologic damage compared with normal gastric distension.4.High total treatment energy and low animal weights were major determinants of deep tissue damage with the argon laser in the ideal treatment range.5.Using the treatment guidelines of 1–2 cm treatment distance, adequate CO2 at the target, high-power range, and normal gastric distension, argon laser was effective and relatively safe both endoscopically and at laparotomy.

低バイパス比ターボファンエンジンの騒音低減化のための野外試験について

Noise measuring tests of a low-bypass-ratio turbofan engine were conducted, using the hybrid bulk-resonator type acoustic treatment in the fan section and the lobe type internal mixer in the exhaust section.The bulk-resonator type acoustic treatment is composed with a thin layer of polyamid fiber felt protected by the perforated sheet metal on its surface and backed by an air cavity behind the felt layer. Test results revealed that this kind of acoustic treatment was effective for reduction of fan noise thru broad frequency rang from approach to take-off power, and the mixing nozzle was effective for jet noise reduction in high power range with a slight thrust loss which was not considered to be caused only by installation of the mixing nozzle.

Study of the Crystalline to Amorphous Silicon Boundary Following Laser Induced Solid Phase Epitaxy.

ABSTRACTEBIC and voltage contrast SEM microscopy, combined with optical microscopy. chemical etching and Talystep profiling have been used to investigate cw laser annealing of a-Si in the slip-free SPE regime. Special attention is devoted to the edges and extremities of the line scans, i.e. to the c-to a-Si boundary. At very low power, evidence is given for an initial reordering and thus electrical activation stage of the a-Si. For the higher power range regrowth occurs through two different processes. The EBIC yield is interpreted in terms of a balance between annealing of the ion implantation damage and defect generation in the si substrate during the laser annealing. These results are extended to the case of a scanned electron beam annealing.

Experiments on plasma interactions with powerful R.F. discharges

Linear discharges in a steady axial magnetic field are produced in hydrogen plasmas by means of unconventional line generators. Non-decaying current pulses ranging from 1 to 50 kA at a frequency of 3 MHz. The penetration of the azimuthal oscillating field is observed, and the influence of limiters is investigated. A critical current is found, and this result is compared with the previous theory. Anomalous skin depth results from analysis of the complex wave vector, which shows energy exchanges with the plasma, in addition to the normal Joule heating. Decreasing conductivity at low densities indicates possible turbulent behaviour. An interesting feature of the discharges in the highest power range is the excitation of magnetoacoustic compressional waves at the second harmonic of the axial current with typical resonance effect. This quadratic interaction is explained with a simple model considering the pressure gradient at the plasma boundary.

Multi-Detector Integrated Fission Counter Array

A multi-chamber fission array has been designed, fabricated, and tested with integrated and condensed electronic circuitry. The intention was to develop an array of over 100 channels of detectors able to cover the high power range of TREAT transients in conjunction with the fast neutron hodoscope. The array has been developed through a prototype stage consisting of 31 possible channels. A wide variety of operating conditions have been tested, including choice of fissile isotope, coating thickness, gas filling, plate spacing, high voltage, and electronic circuitry. The configuration tested at TREAT consisted of ten active channels incorporated in a doubly contained system. Miniaturized electronic circuits are appended almost directly to the parallel plates of the fission counters. Cost and space limitations were major factors in the design.

Accurate Determination of Organic Oxygen in Coal

Determination of organic oxygen in coal is specially important for advanced utilization of coal. However, the direct and indirect analyses conventionally used are not always reliable presumablly because of the thermal decompofition of ash in coal in the processes of the analyses. The present investigation has been carried out to establish an accurate determination of organic oxygen in coal by using a low temperature asher which has recently been developed.A IPC model 1101 plasma asher was used for this pwrpose and the fast neutron activation analysis and the thermal decomposition method were used for the determination of oxygen content. First, several clay minerals and their mixtures with pure carbon wese treated in a stream of oxygen plasma in a total high frequency power range between 200 and 900 watt for six sample chambers. The reaction temperatures were deduced by checking melting point of pure substances in amples under the similai reaction conditions.From these results and also results on the differential themal and the products, it was conclusively found that the oxygen flow rate of 600 ml/min and the high frequency power of 600 watt were most snitable for complete oxidation of organic matter without prodneing the thermal decomposition of ash in coal and organic oxygen content of coal was accurately determined as the difference beween the total oxygen content of coal and the oxygen content of ash in the coal.