Maximum Power Level Research Articles

Pronostic des dysautonomies idiopathiques avec hypotension orthostatique

Radio frequency (RF) and microwave power amplifiers using divider–combiner architecture are important blocks of rapidly developing middle and high power RF and microwave systems used in radars, communication, directed energy, electronic warfare, air traffic control, and scientific facilities such as particle accelerators. Many of these amplifiers need to operate in a wide dynamic range of output power levels. For conventional amplifiers that significantly reduces actual efficiency compared to the maximum efficiency attainable at maximum output power levels. Efficiency of a high power amplifier system can be made close to efficiency of a single amplifying module at compression if graceful degradation performance is dramatically improved. The approach is based on dynamic switching on and off some of the amplifying modules, and switchable termination of the corresponding ports of a reactive combiner with externally controlled phasing. The power-scalable method is validated with simulations demonstrating capability of power dynamic range exceeding 13 dB at nearly saturated efficiency of the active power modules and low insertion loss imposed by the passive RF components.

Materials selection and shield design to improve ignitor operational safety

Neutron transport calculations in the zone of the diagnostic ports and of the cryostat of Ignitor show that streaming of neutrons through the port makes the neutron flux on the cryostat behind the diagnostic ports much higher than in those parts of the cryostat shielded by the magnets and c-clamp structures. Neutron-induced activation of cryostat materials (AISI316) in that zone turns out to be so high to prevent their direct handling soon after the beginning of DT operation at maximum power level. Scope of this study is to determine whether an additional shield for the cryostat put in the port zone could reduce activation of this component, down to permit direct handling of it. Different materials for the shield are examined, and its thickness according to the reduced activation goal is determined. It is recommended the adoption of a Borated Polythene additional shield for cryostat behind diagnostic ports, with a 32 cm thickness. This shield would permit to reduce the activation of the AISI316 steel in the cryostat behind diagnostic ports to about 100 μSv/h, with 3 days of cooling, after 1 year of operation at maximum DT power level.

Power levels and packet lengths in random multiple access

Multiple-power-level ALOHA has been proposed to take advantage of the capture phenomenon in order to improve the throughput of a multiple random access system. We study the effect of the use of multiple transmission power levels and of the corresponding packet lengths on the system throughput and energy efficiency. We prove that the single-power-level system in which all transmit at the maximum allowable power level achieves both optimal throughput and energy usage efficiency under a condition on the decodability threshold value.

Maximum Power Control for a Photovoltaic Power Generation System by Adaptive Hill-climbing Method

A modified hill-climbing method for a photovoltaic generation system (PV system), using an adaptive algorithm, is proposed for the maintenance of its output at maximum power levels. The switch duty ratio of the DC-DC converter of the PV system and its output power are selected as the input and output value, respectively, and its characteristics are described by the characteristic curves (the switch duty ratio vs. output power). The characteristics of the PV system are changed due to the changes of external environmental conditions such as atmosphere, loads and so on. The changes of its characteristic curves are detected as the changes of its gradients, which are estimated as parameters of linear functions by adaptive theory. The change of the switch duty ratio is determined based on the detected characteristic changes. That is, the non-linearity of the PV system and its changing characteristics due to the changes of its external environmental conditions are regarded as deviations of the parameters of the linear functions. It is applied in some experiments under various external environmental conditions and its effectiveness confirmed. Therefore, the proposed method is considered to be generally applicable method as a maximum power controller, for which detailed information of the characteristics of the PV system, including its external environmental conditions, is not required.

The Effects of an In-Season of Concurrent Training on the Maintenance of Maximal Strength and Power in Professional and College-Aged Rugby League Football Players

Fourteen professional (NRL) and 15 college-aged (SRL) rugby league players were observed during a lengthy in-season period to monitor the possible interfering effects of concurrent resistance and energy-system conditioning on maximum strength and power levels. All subjects performed concurrent training aimed at increasing strength, power, speed, and energy-system fitness, as well as skill and team practice sessions, before and during the in-season period. The SRL group significantly improved 1 repetition maximum bench press (1RM BP) strength, but not bench throw (BT Pmax) or jump squat maximum power (JS Pmax) over their 19-week in-season. The results for the NRL group remained unchanged in all tests across their 29-week in-season. The fact that no reductions in any tests for either group occurred may be due to the prioritization, sequencing, and timing of training sessions, as well as the overall periodization of the total training volume. Having athletes better conditioned to perform concurrent training may also aid in reducing the possible interfering effects of concurrent training. Correlations between changes in 1RM BP and BT Pmax suggest differences in the mechanisms to increase power between stronger, more experienced and less strong and experienced athletes.

A 3-V monolithic SiGe HBT power amplifier for dual-mode (CDMA/AMPS) cellular handset applications

A dual-mode (CDMA/AMPS) power amplifier has been successfully implemented by using a monolithic SiGe/Si heterojunction bipolar transistor (HBT) foundry process for cellular handset (824-849 MHz) applications. The designed two-stage power amplifier satisfies both CDMA and AMPS requirements in output power, linearity, and efficiency. At V/sub cc/=3 V,the power amplifier shows an excellent linearity (first ACPR<-44.1 dBc and second ACPR<-57.1 dBc) up to 28 dBm of output power for CDMA applications. Under the same bias condition, the power amplifier also meets AMPS handset requirements in output power (up to 31 dBm) and linearity (with second and third harmonic to fundamental ratios lower than -37 dBc and -55 dBc, respectively). At the maximum output power level, the worst power-added efficiencies (PAEs) are measured to be 36% for CDMA and 49% for AMPS operations. The power amplifier also tolerates severe output mismatch (VSWR>12:1) up to V/sub cc/=4 V, with spurs measured to be <-22 dBc in CDMA outputs at two specific tuning angles, but with no spur in AMPS outputs at any tuning angle.

An electronic dimming ballast with bifrequency and fuzzy logic control

This paper presents the analysis and design of a series-resonant parallel-loaded inverter applied to electronic dimming ballasts with bifrequency and fuzzy logic control. The analysis of the ballast is carried out in conjunction with the fluorescent lamp represented in a plasma model. The component values of the power stage, as well as two switching frequencies, according to the desired maximum and minimum power levels are, therefore, determined. The power levels in between are controlled by varying the ratio between two time intervals for which the two frequencies last, respectively. This mechanism is achieved by using a fuzzy logic controller (FLC). A ballast prototype with the FLC which is implemented on an 8-bit microprocessor with a reduced instruction set computer architecture has been built. Experimental measurements have shown the feasibility of the ballast with the proposed control strategy.

Suggested method for evaluating measurement uncertainty to determine the maximum gas turbine exhaust sound power level determined according to ISO Standard 10494

Suggested method for evaluating measurement uncertainty to determine the maximum gas turbine exhaust sound power level determined according to ISO Standard 10494

Thermo-Mechanical Analysis of Single-Disc Edge-Cooled Silicon Nitride Millimeter Wave Window for 200 kW CW Gyrotrons

This paper investigates the possibility of using Silicon Nitride Composite (Kyocera SN-287) as single-disc, edge-cooled window for gyrotrons operating below 200 kW CW in the frequency range 28-42 GHz. Rotationally symmetric TE0n, and TEM00 Gaussian modes of rf transmission through the window have been considered. Analysis performed using a one dimensional (1D) finite difference (FD) code reveals that thermal stresses developed due to non-uniform temperature distribution on the disc surface are well within manageable limits for a 200 kW 42 GHz gyrotron proposed for some ECRH applications. For industrial gyrotrons, for microwave material processing and operating at a maximum power level of 100 kW CW, Si3N4 windows may be a cost effective replacement for sapphire windows. It is found that a TE02 profile results in lower peak temperature at the window disc in comparison to a Gaussian beam profile and allows the use of smaller discs.

YBaCuO disk resonator filters operating at high power

We have developed and successfully operated a compact tunable one-pole filter at 2 GHz for transmitter combiners in mobile radio base stations. The concept is based on edge-current free modes in circular symmetric resonators. Unloaded quality factors Q/sub 0/>5.10/sup 5/ were achieved with double-sided 2''-diameter YBaCuO films on Czochralski-grown LaAlO/sub 3/. The dielectric loss tangent limited Q/sub 0/ around 60 K to values below 10/sup 5/. A circulating (transmitted) power of 800 kW (130 W), 700 kW (115 W) and 90 kW (15 W) could be handled in pulsed operation (pulse duration 10 ms, duty cycle 3%) at 23, 45 and 76 K, respectively, without measurable Q-degradation. These results approach the best microwave field performance measured so far with unpatterned films at 19 GHz. The power handling of the filter degraded in proportion to the duty cycle, indicating heating as the dominant limitation. The filter could be tuned by 3% by moving a plunger film by 36 /spl mu/m above the ring-shaped groundplane of the resonator. The CW power handling was not affected by the tuning, but the radiation losses and the maximum achievable power levels were degraded compared to the fixed-frequency filter.

First high power experiments with the Dutch free electron maser

A free electron maser (FEM) has been built as a mm-wave source for applications on future fusion research devices such as ITER, the international tokamak experimental reactor [M. A. Makowski, F. Elio, and D. Loeser, April 97, Proc. 10th Workshop on ECE and ECRH, EC10, 549-559. World Scientific (1998)]. A unique feature of the Dutch fusion-FEM is the possibility to tune the frequency over the entire range from 130 to 260 GHz at an output power exceeding 1 MW. In the first phase of the project, a so-called inverse setup is used. The electron gun is mounted inside the high-voltage terminal. The entire beam line was tested successfully with extremely low loss current, lower than 0.05%. This included the accelerating structure up to 2 MV level and the transport through the undulator. First generation of mm-waves was achieved in October 1997. With an electron beam current around 8 A and an accelerator voltage of 1.76 MV the mm-wave pulse starts after 3 μs and lasts for 3 μs, reaching a maximum saturated peak power level of more than 500 kW at a frequency of 200 GHz. Output power, start-up time, and frequency correspond well with simulation results.

Optical modeling of the Jefferson laboratory IR demo FEL

The Thomas Jefferson National Accelerator Facility (Jefferson Lab) is in the process of a building a 1 kW free-electron laser operating 3 μ m. The details of the accelerator driver are given in other papers in these proceedings. The optical cavity consists of a near-concentric resonator with transmissive outcoupling. Though several free-electron lasers have used similar designs, they have not had to confront the high average-power loading present in this laser. It is useful to know the limits of this type of optical cavity design. The optical system of the laser has been modeled using the commercial code GLAD ® by using a Beer’s-law region to mimic the FEL interaction. The effects of mirror heating have been calculated and compared with analytical treatments. The magnitude of the distortion for several materials and wave lengths has been estimated. The model developed here allows one to quickly determine whether the mirror substrates and coatings are adequate for operation at a given optical power level once the absorption of the coatings, substrate, and transmission are known. Results of calculations of the maximum power level expected using several different sets of mirrors will be presented. Measurements of the distortion in calcium fluoride from absorption of carbon dioxide laser light are planned to benchmark the simulations. Multimode simulations using the code ELIXER have been carried out to characterize the saturated optical mode quality. The results will be presented.

Repetition-rate dependence of the saturation power of gain-clamped semiconductor optical amplifiers

We show theoretically that, when using gain-clamped semiconductor optical amplifiers (GCSOAs) for the amplification of a train of pulses, the saturation power of the GCSOAs strongly depends on the repetition rate of the pulse train. This saturation power is 3 dB higher at very high repetition rates than at low repetition rates. It reaches a minimum for intermediate repetition rates, where it can even be 6 or more decibels smaller than the maximum saturation power level.

Vibration Analysis of Primary Inlet Pipeline of Pakistan Research Reactor-1 during Steady State and Transient Conditions

Pakistan Research Reactor-1 (PARR-1) has been converted to low enriched uranium (LEU) fuel and upgraded to a maximum power level of 9MW. During conversion and upgradation most of the reactor systems were modified and several additional facilities were provided. Major changes were carried out in the cooling system. These include installation of new primary pumps, set of heat exchanger assemblies, a cooling tower and piping system. Vibration tests on these systems were performed to check the integrity and detect any abnormality in normal operation. Results of the tests performed on the primary pumps and core support structure comply with the requirements for pre-operational and initial startup vibration testing of nuclear power plant (NPP) system. Attempt is now being made to analyze vibrations of primary piping.The Primary Water Inlet Pipeline (PW-IPL) is of stainless steel conveying demineralized water from holdup tank to the reactor pool. The section of the pipeline from heat exchangers to the valve pit is hanger supported, and the rest from valve pit to the reactor pool is embedded. Vibration of the PW-IPL may be categorized into steady state and transient. The reactor pumps mainly contribute the steady state vibrations, while transient vibrations arise due to instant closure of check valves (water hammer). The ASME Boiler and Pressure Vessel code provides data only about the limits of acceptable vibrations and stresses related to the primary static stress due to steady state vibrations. However, due to complexity and diversity in the pipe structure, stresses related to the transient vibrations are neglected in the code.In this paper steady state and transient vibration behavior of PW-IPL of PARR-1 has been analyzed. In the analysis vibration data was used for comparison with the allowable limits, estimations of pressure wave velocity, deflection, natural frequency, tensile and shear load on hanger support, and to obtain the ratio of maximum combine stress to the allowable.

Generation of ultrashort pulse based ом the superradiance of isolated electron bunch

The radiation of spatially—localised electron ensembles with the infinite lifetime of particles is considered as the classical analogy of superradiation effect. The results of theoretical and experimental investigation are presented for different kinds of superradiance: cyclotron, cherenkov, undulator. First the microwave superradiation effect pulses of indicated types were registrated. The electromagnetic pulse duration were between 300-800 ps. The maximum power level about several megawatts was achieved under cherenkov radiation in dielectric waveguide, while the maximum stability and reproducibility of radiated pulses were observed when the electron bunch passed through the corrugated waveguide.

Vibration Analysis of Primary Inlet Pipeline of Pakistan Research Reactor-l during Steady State and Transient Conditions.

Pakistan Research Reactor-1 (PARR-1) has been converted to low enriched uranium (LEU) fuel and upgraded to a maximum power level of 9MW. During conversion and upgradation most of the reactor systems were modified and several additional facilities were provided. Major changes were carried out in the cooling system. These include installation of new primary pumps, set of heat exchanger assemblies, a cooling tower and piping system. Vibration tests on these systems were performed to check the integrity and detect any abnormality in normal operation. Results of the tests performed on the primary pumps and core support structure comply with the requirements for pre-operational and initial startup vibration testing of nuclear power plant (NPP) system. Attempt is now being made to analyze vibrations of primary piping. The Primary Water Inlet Pipeline (PW-IPL) is of stainless steel conveying demineralized water from holdup tank to the reactor pool. The section of the pipeline from heat exchangers to the valve pit...

Broadly tunable mid-infrared femtosecond optical parametric oscillator using all-solid-state-pumped periodically poled lithium niobate

We describe a high-repetition-rate femtosecond optical parametric oscillator (OPO) that was broadly tunable in the mid infrared. The all-solid-state-pumped OPO was based on quasi-phase matching in periodically poled lithium niobate. The idler was tunable from approximately 1.7 mum to beyond 5.4 mum, with maximum average power levels greater than 200 mW and more than 20 mW of average power at 5.4 mum. We used interferometric autocorrelation to characterize the mid-infrared idler pulses, which typically had durations of 125 fs. This OPO had a pumping threshold as low as 65 mW of average pump power, a maximum conversion efficiency of >35% into the near-infrared signal, a slope efficiency for the signal of approximately 60%, and a maximum pump depletion of more than 85%.

Reduction of InGaAs/GaAs laser facet temperatures by band gap shifted extended cavities

Reflectance modulation measurements have been used to determine facet temperatures of InGaAs/GaAs double quantum well (QW) graded-index separate-confinement heterostructure ridge-waveguide lasers possessing band gap tuned passive cavity sections. We find that the incorporation of transparent extended cavities, produced by ion-implantation enhanced QW intermixing, significantly decreases the laser facet temperatures. The reduced photoabsorption occurring at the facets, achieved by the QW intermixing process, should lead to increases in both the maximum optical power levels and device longevity prior to the onset of catastrophic failure.

Sound amplifying apparatus with automatic howl-suppressing function

A sound signal picked-up by a microphone is processed in a howl suppresser including a digital filter. A frequency analyzer performs frequency analysis of the picked-up sound signal. A howl detector detects a howl contained in the sound signal from a result of frequency analysis by the frequency analyzer. A coefficient calculator calculates coefficients to be input to the digital filter to suppress the howl according to a detection result by the howl detector, and a controller inputs the calculated coefficients to the digital filter. The howl detector judges that a maximum peak power level among power levels of the sound signal in a frequency region analyzed by the frequency analyzer is a howl component when a ratio of the maximum peak power level to a mean power level of the sound signal is larger than a predetermined threshold level, preferably for a predetermined threshold time. Also, a threshold controller is provided for controlling the threshold level and/or the threshold time so as to enhance the accuracy of the howl detection.

Neutron scattering facility at 3 MW TRIGA mark II reactor in Bangladesh

Abstract A 3 MW TRIGA Mark II research reactor became operational in Bangladesh in 1987. It is an inherently safe, light-water-cooled and graphite reflected pool-type reactor. Its maximum steady state power level is 3 MW. For short time operation up to 500 KW, natural convection cooling is good enough. Forced flow cooling is required for higher power and long time operation. It has 100 cylindrical 19.7 percent enriched U235 fuel rods. The reactor has four beam ports, two of which are radial, one is tangential and one is radial piercing.