Energy Technology Data Exchange (ETDEWEB)

The compound GdPd{sub 2}Si, which is reported to order antiferromagnetically at 13 K, has been investigated by heat capacity and electrical resistivity measurement in the presence of external magnetic fields. In contrast to an earlier report, the zero-field heat capacity and resistivity data indicate two magnetic transitions at 13 and 17 K. The external magnetic field substantially influences the resistivity and heat capacity of the compound around the magnetic ordering temperature. The magnetocaloric effect, which is calculated from in-field heat capacity data, is quite large around the magnetic transition temperature. The magnetoresistance is also large near the magnetic ordering temperature. The metamagnetic transition is observed for 10 kOe magnetic field both in magnetocaloric and in magnetoresistance data. The metamagnetic transition strongly influences ...

Energy Technology Data Exchange (ETDEWEB)

The magnetoresistance in an FeNi submicron-structure comprising two wires of 80 and 200 nm in width connected in series was measured at 77 K. When the external magnetic field was applied parallel to the wire axis, two switching fields corresponding to the distinct coercive force of the two wires were observed. When the external magnetic field was applied at an angle of {theta}>30 deg. to the wire axis one switching field was observed, indicating simultaneous magnetization reversal in both wires. This indicates that the domain-wall trapping around the joint can be controlled systematically in terms of the direction of the external magnetic field.

Energy Technology Data Exchange (ETDEWEB)

The possibility of switching the heat transfer consists of varying heat transfer surfaces and making the heat transfer temporarily more intensive. Heat tubes prove to be particularly suitable, which must be exposed to a heat carrier fluid or removed from its effect for switching the heat transfer. This report gives a survey of the possibilities of switching heat flows and for making the heat transfer more intensive. Further, the report contains a survey of patents limited to heat transfer in the fields of cooling internal combustion engines and exhaust systems. (orig.) With 17 figs., 183 refs.

KoreaScience (Korea)

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Energy Technology Data Exchange (ETDEWEB)

The authors address the question of the limitations on voltage and current transfer to loads in magnetic storage systems utilizing microsecond conduction time plasma opening switches. They propose that the limitation of performance results from neutral atoms that are not entrained into the ionized material that is driven by the magnetic field of the rising generator current. Evidence in support of this proposition is gathered from experiments performed on the Ace-4 and Hawk generators. They set forth a theory to describe the effect of neutrals on the electrical performance of plasma opening switches. The neutral gas is assumed to be present in the region between the moving plasma mass and the generator, primarily in the region in which the plasma is injected initially. The essential elements of the theory are a weak photoionization source to seed the gas with a low concentration of electrons, and joule heating accompanied ...

International Nuclear Information System (INIS)

... susceptibility magnetization magnetoresistance monocrystals order-disorder

Energy Technology Data Exchange (ETDEWEB)

Airborne pollutants can cause failures in switching and computing equipment. This paper focuses on a subset of such pollutants - airborne fine particles (<2.5 [mu]m diameter). It begins by examining the extent to which different improvements in heating, ventilating and air conditioning (HVAC) systems reduce indoor concentrations of fine particles. For each modification, the consequent reduction in soiling rate is derived. The concomitant increase in operating costs is also calculated. These costs are then compared with the costs of failures in telephone switching offices, leading to estimates of failure rate reductions that would make improvements cost-effective. Finally, the reduction in failures required to offset the costs of the improvements are compared with documented differences in failure rates between unimproved and improved environments. This study suggests that, in many telephone switching ...

Energy Technology Data Exchange (ETDEWEB)

A cooling system was developed which could be used even in such areas where the maximum and minimum temperatures of a day might differ widely. The system features in that a latent heat storage unit is connected to the natural circulation cooling unit consisting of 2 heat exchangers where condensed gas (refrigerant) which performs gas-liquid change has been sealed, enabling to cool objects night and day without the requirement for any power source. Electronic equipment was installed in an insulated shelter. Lauric acid and refrigerant R-22 were used as the latent heat storage medium and the heat transport medium respectively. Natural convection heat transfer performance of the outside surfaces of the condenser and the evaporator and the transient behavior of the system during the melting and solidification periods of the latent heat storage medium were tested. As ...

Science.gov (United States)

... thus can function as switches -6 ... Akkari, "Optical Channel Waveguide Switch and Coupler ... Wide-Band Guided Wave Acousto-Optic Bragg Diffraction ...

Energy Technology Data Exchange (ETDEWEB)

The work in the past year has primarily involved four areas of magnetic thin films: amorphous rare earth-transition metal alloys, epitaxial CoPt{sub 3} and Ni-Pt alloy thin films, amorphous rare earth doped Si (a new class of dilute magnetic semiconductor with large negative magnetoresistance which the authors have discovered), and exchange-coupled antiferromagnetic insulators. In the amorphous alloys, they made a systematic study of the effects of local anisotropy, macroscopic (perpendicular) anisotropy, and exchange constant on the fundamental (and practical) properties of these magnetic alloys, as originally described in the grant proposal. The work on the epitaxial Co-Pt (and more recently Ni-Pt) alloys was originally undertaken as a comparison study to the amorphous alloys. Crystalline Co-Pt alloys have many striking similarities to the amorphous rare earth-transition metal alloys: perpendicular magnetic anisotropy, magneto-optic activity, and a {Tc} (for ...

Science.gov (United States)

... Abstract : The acousto-optic filter (AOF) is ... for large switch networks. ... FOURIER TRANSFORMATION, OPTICAL SWITCHING, SURFACE ACOUSTIC ...

Energy Technology Data Exchange (ETDEWEB)

A geothermal heat pump-assisted heating system is introduced into Changchun City and a survey is conducted to determine if the system may be popularized in this extremely cold region located in the northeastern part of China. In concrete terms, the hot water that circulates through the office building of Changchun Ground Heat Development Co., Ltd., is switched to hot water prepared by a geothermal heat pump. The test continued from December 2000 to March 2001. It is then concluded that heating by geothermal heat pumps will be fully serviceable to Changchun City. Implemented are (1) the shift from the coal fired boiler system to a geothermal heat pump system comprising 16 subterranean heat exchangers for the heating of the office building which is approximately 1000 m{sup 2} ...

Energy Technology Data Exchange (ETDEWEB)

Boiling jet impingement cooling is currently being explored to cool power electronics components. In hybrid vehicles, inverters are used for DC-AC conversion. These inverters involve a number of insulated-gate bipolar transistors (IGBTs), which are used as on/off switches. The heat dissipated in these transistors can result in heat fluxes of up to 200 W/cm{sup 2}, which makes the thermal management problem quite important. In this paper, turbulent jet impingement involving nucleate boiling is explored numerically. The framework for these computations is the CFD code FLUENT. For nucleate boiling, the Eulerian multiphase model is used. The numerical results for boiling water and R113 jets (submerged) are validated against existing experimental data in the literature. Some representative IGBT package simulations that use R134a as the cooling fluid are also presented. (author)

Energy Technology Data Exchange (ETDEWEB)

The authors present design methodology and initial experimental results for a high power microwave switch. The switch is designed for application to the pulse compression system associated with the Next Linear Collider Test Accelerator (NLCTA). The switch is based on the excitation of a plasma layer within a silicon wafer by either a laser or an electron beam. They investigate problems associated with high power operation of such a switch. They explore solutions to the problems of thermal runaway, avalanche breakdown, photo-emission, and secondary emission.

Energy Technology Data Exchange (ETDEWEB)

Recognizing that a high percentage of transmission-line faults are single-phase to earth and temporary in nature, provides the impetus for considering single-pole switching as a means to enhance the reliability of EHV transmission systems. The effectiveness of single-pole switching schemes is largely determined by the speed with which the secondary arcs extinguish, and hence allow system restoration. Simulation techniques that enable better prediction of the faulted-system response are of obvious importance to the design and assessment of the various single-pole switching scheme applications. In this thesis, digital methods are developed to enable the faulted response of EHV systems to be simulated for a variety of different single-pole switching schemes. These include conventional single-pole switching, the hybrid method of autoreclosure, the neutral switched ...

Science.gov (United States)

The performance of a 42/28 V, 175 W, 50 kHz pulse-width modulated buck dc/dc switching power

Energy Technology Data Exchange (ETDEWEB)

We present the recent results of our research on the high power ultra-fast silicon RF switches. This switch is composed of a group of PIN diodes on a high purity silicon wafer. The wafer is inserted into a cylindrical waveguide under TE{sub 01} mode, performing switching by injecting carriers into the bulk silicon. Our current design uses a CMOS compatible process and the device was fabricated at SNF (Stanford Nanofabrication Facility). 300 ns switching time has been observed, while the switching speed can be improved further with 3-D device structure and faster driving circuit. Power handling capacity of the switch is at the level of 10 MW. The switch was designed for active X-band RF pulse compression systems--especially for NLC, but it is also possible to be modified for other applications and other frequencies.

Energy Technology Data Exchange (ETDEWEB)

The present project examined the operating characteristics and application possibilities of a new, compact combined heating and electricity generating unit with a thermal output of 14,5 kW and a generating capacity of 5,5 kW. Such a module was installed in a plant in Arlesheim (Canton of Basel-Country) and subject to performance measurements. The small heating and generating plant is designed for cyclic operation (without heat storage) and is very compact and low in cost. The heating and generating unit conforms to all Swiss regulations relating to electrical installations and air pollution control. The NO{sub x} emissions of the unit (400 mg/m{sup 3} in steady state operation) are above the limits of LRV 92 (80 mg/m{sup 3}), but the regulation does not apply for units in this power range. The electricity generation costs are approximately CHF 0.16/kWh. It therefore makes sense to install the module in ...

Energy Technology Data Exchange (ETDEWEB)

We report the performance of a micro gas turbine on biomass producer gas and mixtures of biomass producer gas with natural gas. The micro gas turbine delivers full power on gas mixtures with a heating value of at least 15 MJ/Nm{sup 3}. For gas of lower heating value, the maximum fuel gas flow limits the attainable power. The lower limit for stable operation is about 8 MJ/Nm{sup 3}. The gross efficiency of the micro gas turbine depends on output power but not on the gas heating value, within our measurement accuracy. Above 70% of full power, emissions of CO and NO are 40 and 10 times lower than those of a gas engine of similar size. At part load below 70% of full power, the micro gas turbine burner switches to a different operating mode which produces higher CO and NO levels, but still significantly below those of a gas engine.

International Nuclear Information System (INIS)

This paper provides a brief overview of the young, but rapidly growing field of spintronics. Its primary objective is to explain how as electrons tunnel through simple insulators such as MgO, wavefunctions of certain symmetries are preferentially transmitted. This symmetry filtering property can be converted into a spin-filtering property if the insulator is joined epitaxially to a ferromagnetic electrode with the same two-dimensional symmetry parallel to the interface. A second requirement of the ferromagnetic electrodes is that a wavefunction with the preferred symmetry exists in one of the two spin channels but not in the other. These requirements are satisfied for electrons traveling perpendicular to the interface for Fe-MgO-Fe tunnel barriers. This leads to a large change in the resistance when the magnetic moment of one of the electrodes is rotated relative to those of the other electrode. This large tunneling magnetoresistance effect is being used as the ...

KoreaScience (Korea)

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Science.gov (United States)

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British Library Electronic Table of Contents (United Kingdom)

This paper introduces a new way of estimating parameters in a Brownian motion regime switching asset model to incorporate volatility clustering. The regime switching model is then applied to pricing of up-and-in barrier call options. We take the probability of crossing the barrier between simulation points into account, and we increase accuracy in simulations by importance sampling. The regime switching model is compared to the Normal Inverse Gaussian model and the traditional Black-Scholes model, and option prices from the regime switching model are compared to the closed form expression of up-and-in barrier calls in a Black-Scholes market.

Energy Technology Data Exchange (ETDEWEB)

The authors present design methodology for high power microwave switches. Among all possible applications for such a switch they emphasize the design parameters for application to the pulse compression system associated with the Next Linear Collider (NLC). The switch is based on the excitation of a plasma layer within a silicon wafer by either a laser or an electron beam. They investigate problems associated with high power operation of such a switch. Mainly, they explore solutions to the problems of thermal runaway, avalanche breakdown, photo-emission, and secondary emission. Different design methodologies are presented.

Energy Technology Data Exchange (ETDEWEB)

Properties of highly correlated electrons, such as heavy fermion compounds, metal-insulator transitions, one-dimensional conductors and systems of restricted dimensionality are studied theoretically. The main focus is on Kondo insulators and impurity bands due to Kondo holes, the low-temperature magnetoresistivity of heavy fermion alloys, the n-channel Kondo problem, mesoscopic systems and one-dimensional conductors.

Energy Technology Data Exchange (ETDEWEB)

New furnaces were built based on fused silica with NiChrome heating elements custom-wound on alumina ceramic to self-compensate for induced magnetic fields during operation. During tests these furnaces failed due to thermal stresses caused by the high temperature cement used to hold the alumina ceramic in place. As a third solution pieces of boron nitride have been procured from which new furnace bodies will be machined during the third quarter. In order to increase the in-house capacity for machining ceramic parts a small lathe was ordered. The implementation of the LabView data acquisition software from National Instruments, Inc. took more time than anticipated and is still not completed. Major difficulties had to be overcome during the integration of the separate positive and negative high voltage supplies ({plus_minus}1000V). It became apparent that a custom-designed switch had to be installed to safeguard the data acquisition modules and ...

UK PubMed Central (United Kingdom)

DEXD/H-box RNA helicases couple ATP hydrolysis to RNA remodeling by an unknown mechanism. We used x-ray crystallography and biochemical analysis of the human DEXD/H-box...Full Text Available

International Nuclear Information System (INIS)

Heavy ion tests of a switching converter using power MOSFETs have allowed us to identify the main parameters which affect the burnout sensitivity of these components. The differences between static and dynamic conditions are clarified in this paper. (author). 7 refs., 16 figs., 3 tabs.

Science.gov (United States)

... Abstract : A COMMERCIALLY AVAILABLE CAMOO4 TUNABLE ACOUSTO- OPTIC FILTER HAS BEEN ... OF THE FILTER CAN BE SWITCHED IN 20 ...

Science.gov (United States)

PMID:21910487

Science.gov (United States)

... In 1982 an acousto-optic spectrum analyzer incorporated ... the OPTIMP is the optically controlled optical ... switch that changes the intensity reflectance ...

Energy Technology Data Exchange (ETDEWEB)

The objective of this study was to analyze the industrial demand for energy in seven Organization for Economic Cooperation and Development (OECD) countries with particular emphasis on fuel substitution between oil, natural gas, coal, and electricity. Changing fuel demand also results from economic growth, changes in industrial structure, and changes in the energy intensity of industrial output. A historical analysis of these factors and fuel substitution is undertaken for industry as an aggregate, and for 12 specific industries. The major results of the historical analysis are: (1) fuel use changes are a result of fuel switching, changing energy intensity, changing industrial structure, and economic growth; (2) fuel substitutability depends upon fuel use. The three fossil fuels are substitutes in the industrial heat market, but there are numerous special industrial processes where a particular fuel is required; (3) large substitutions have ...

CERN Document Server

Aims: The production of saturated organic molecules in hot cores and corinos is not well understood. The standard approach is to assume that, as temperatures heat up during star formation, methanol and other species evaporate from grain surfaces and undergo a warm gas-phase chemistry at 100 K or greater to produce species such as methyl formate, dimethyl ether, and others. But a series of laboratory results shows that protonated ions, typical precursors to final products in ion-molecule schemes, tend to fragment upon dissociative recombination with electrons rather than just ejecting a hydrogen atom. Moreover, the specific proposed reaction to produce protonated methyl formate is now known not to occur at all. Methods: We utilize a gas-grain chemical network to probe the chemistry of the relatively ignored stage of hot core evolution during which the protostar switches on and the temperature of the surrounding gas and dust rises from 10 K to ...

Energy Technology Data Exchange (ETDEWEB)

Full text: Magnetic multilayer materials are becoming technologically important as they provide a more efficient means of magnetic reading and storage through utilisation of their giant magnetoresistance and oscillatory magnetic coupling. This study presents preliminary tight-binding calculations with a view of developing a consistent tight-binding model of `spin valve` Fe-Cu-Fe tri-layer materials. Further work involves using a self-consistent tight-binding approach to obtain a more accurate picture of this system and a better understanding of surface effects at the Fe-Cu interface 1 fig., 4 refs.

International Nuclear Information System (INIS)

Several recent experiments on micro- (or nano-) structured samples of ferromagnetic materials are introduced. Magnetization reversal phenomena are investigated on submicron wire samples of trilayer structure using the giant magnetoresistance effect. Domain wall movements are sensitively monitored by resistivity measurements and the velocity of propagation is determined. The contribution of domain wall to the resistivity is argued from the results on artificially designed samples of a spring-magnet system. In circular dots of permalloy, the existence of vortex magnetization is confirmed and the reversal of the vortex core magnetization is studied from magnetic force microscopy measurements. (author)

Science.gov (United States)

New industrial Non Destructive Testing requires the development of new probes: technologies such as high spatial resolution probes for small breaking flaws detection or flexible probes for complex curved surfaces inspection. The CEA/LIST has designed and integrated 2 probes to answer industrial's constraints. The first one is based on Giant Magneto-Resistance and is able to detect 50 ?m3 flaws. The second one is based on micro-coils etched on kapton and its flexibility is adapted to curved surfaces inspection. Both are multi-elements probes, allowing fast inspection. This paper presents those new probes, their design and their performances.

British Library Electronic Table of Contents (United Kingdom)

Resistive switching memory is a very promising technology for emerging nonvolatile memory applications. Generally, the switching behavior is triggered by a sweep or pulse voltage. In this paper, a charged capacitor is proposed to be used as the external electrical source to program a resistive switching element. From theoretical analyses based on a set behavior model, the capacitor approach can program the device efficiently. Compared with sweep or pulse mode, capacitor driving method can greatly reduce over-programming after the set event, and thus improve the resistance uniformity. The experimental results performed on Cu/ZrO2:Cu/Pt device support this conclusion quite well. The proposed methodology has great value for achieving a reliable resistive switching, which is important for high...

Energy Technology Data Exchange (ETDEWEB)

Cooling of residential California buildings contributes significantly to electrical consumption and peak power demand mainly due to very poor load factors in milder climates. Thermal mass can be utilized to reduce the peak-power demand, downsize the cooling systems, and/or switch to low-energy cooling sources. Large thermal storage devices have been used in the past to overcome the shortcomings of alternative cooling sources, or to avoid high demand charges. The manufacturing of phase change material (PCM) implemented in gypsum board, plaster or other wall-covering material, would permit the thermal storage to become part of the building structure. PCMs have two important advantages as storage media: they can offer an order-of-magnitude increase in thermal storage capacity, and their discharge is almost isothermal. This allows the storage of high amounts of energy without significantly changing the temperature of the room envelope. As heat ...

Energy Technology Data Exchange (ETDEWEB)

The R and D were carried out of a detecting system for measurement of data on the bottom of geothermal well, data transmission and signal processing, and an analysis system for well drilling trajectory control and well assessment while geothermal well drilling based on the data obtained by the detecting system. The paper reported the results of the technology development in fiscal 1996. In the development of the detecting system, improvement/design were conducted on a mud pulse generator constituting sonde, well bottom signal processing equipment, mode switch and inclined information sensor, and the system equivalent to the actual one was manufactured to conduct a running test at high temperature/pressure. Moreover, a test to confirm heat resistance of electronic parts was made for further improvement in heat resistance of the sonde, in order to obtain the data. In the development of an analysis system, conducted were ...

Energy Technology Data Exchange (ETDEWEB)

Phenomena associated with induced currents and voltages on high voltage transmission lines were discussed. Basic principles were reviewed. Action taken by Hydro-Quebec to assess the importance of associated problems on its grid was described. Hydro-Quebec`s findings and recommendations were compared with those of the International Standard, IEC 1129. It was concluded that for most cases, induced currents and voltages were higher than those listed under Class A recommendations of IEC 1129 as rated switching capabilities for ground switches assigned to this duty. For worst case scenarios, it was also found that, values of induced currents and voltages were lower than those of Class B recommendations. Hydro-Quebec and GEC Alsthom T and D collaborated to design and type test a full range of low cost and efficient ground interrupter switches tailored to Hydro-Quebec`s needs. A list of general application criteria of ground ...

Science.gov (United States)

Two experiments examined the role of compatibility of input and output (I-O) modality mappings in task switching. We define I-O modality compatibility in terms of similarity of stimulus modality and modality of response-related sensory consequences. Experiment 1 included switching between 2 compatible tasks (auditory-vocal vs. visual-manual) and between 2 incompatible tasks (auditory-manual vs. visual-vocal). The resulting switch costs were smaller in compatible tasks compared to incompatible tasks. Experiment 2 manipulated the response-stimulus interval (RSI) to examine the time course of the compatibility effect. The effect on switch costs was confirmed with short RSI, but the effect was diminished with long RSI. Together, the data suggest that task sets are modality specific. Reduced switch costs in compatible tasks may be due to special linkages between input and output ...

International Nuclear Information System (INIS)

This paper shows that a stochastic regime-switching model can represent the volatile behavior of wholesale electricity prices associated with price spikes effectively. The structure of the model is very flexible because the mean prices in the two regimes and the two transition probabilities are functions of the load and/or the implicit reserve margin. Using price data from the single settlement market in PJM (May 1999 to May 2000), the results show that the estimated switching probability from the low to the high regime predicts price spikes well if the reserve margin is measured accurately.

International Nuclear Information System (INIS)

Non-linear autoregressive Markov regime-switching models are intuitive. Time-series approaches for the modelling of electricity spot prices are frequently proposed. In this paper, such models are compared with an ordinary linear autoregressive model with regard to their forecast performances. The study is carried out using German daily spot-prices from the European Energy Exchange in Leipzig. Four non-linear models are used for the forecast study. The results of the study suggest that Markov regime-switching models provide better forecasts than linear models. (author)

Science.gov (United States)

... The acousto-optic device have a 30 MHz 1 ... coherent systems including compact non-coherent optical ... a relatively simple phase switching approach. ...

Science.gov (United States)

... electronic feedback system' connected to a Q switch ... The use of acousto-optic (AO) beam steering devices for BMDO (SDI) applications is very ...

British Library Electronic Table of Contents (United Kingdom)

Multi-fiber WDM networks are becoming the major telecommunication platforms for transmitting exponentially increasing data traffic. While today's networks are mainly providing circuit-switched connections, optical packet-switching technologies have been investigated for years, aiming at achieving more efficient utilizations of network resources. In this paper, we have evaluated, for the first time, the packet-loss performance of multi-fiber optical packet switches (MOPS). Our main contributions are threefold. Firstly, we have proposed simple and accurate analytical models for analyzing packet-loss performance of (i) the most fundamental MOPS configuration, (ii) MOPS equipped with fiber delay lines (FDLs) and (iii) shared wavelength converters (SWCs). Secondly, we have shown that the MOPS n...

Science.gov (United States)

... is a standard in the utility industry which is used to study switching transients on power distribution networks and high-voltage transmission lines. ...

British Library Electronic Table of Contents (United Kingdom)

This study looks for the presence of rational speculative bubbles in Real Estate Investment Trusts (REITs) using unit-root, variance ratio, duration dependence and regime switching regression tests. The regime switching method provides weak evidence of speculative bubble behaviour in both the mortgage and hybrid REITs sectors even though traditional econometric bubble tests do not provide evidence of rational speculative bubbles in all REIT markets. Findings suggest that price movement in mortgage and hybrid REITs may be induced by bubble-like behaviour of investors. This behaviour may be traced to the real estate market bubble. Our results provide evidence that the real estate bubble that started in early 2000 was transmitted into securitized real estate markets. A regime switching model ...

Energy Technology Data Exchange (ETDEWEB)

This research deals with in the study of the use of innovating magnetic sensors in eddy current non destructive inspection. The author reports an analysis survey of magnetic sensor performances. This survey enables the selection of magnetic sensor technologies used in non destructive inspection. He presents the state-of-the-art of eddy current probes exploiting the qualities of innovating magnetic sensors, and describes the methods enabling the use of these magnetic sensors in non destructive testing. Two main applications of innovating magnetic sensors are identified: the detection of very small defects by means of magneto-resistive sensors, and the detection of deep defects by means of giant magneto-impedances. Based on the use of modelling, optimization, signal processing tools, probes are manufactured for these both applications.

Energy Technology Data Exchange (ETDEWEB)

We demonstrate a two-dimensional device simulator for MOSFET structures that incorporates models for defect distributions and show predicted effects on device switching performance for various spatial distributions of defects in amorphous and polycrystalline silicon.

Energy Technology Data Exchange (ETDEWEB)

A method for bistable storage of binary optical information includes an antiferroelectric (AFE) lead lanthanum zirconate titanate (PLZT) layer having a stable antiferroelectric first phase and a ferroelectric (FE) second phase obtained by applying a switching electric field across the surface of the device. Optical information is stored by illuminating selected portions of the layer to photoactivate an FE to AFE transition in those portions. Erasure of the stored information is obtained by reapplying the switching field.

Science.gov (United States)

In this communication we propose a method to implement an all-optical astable multivibrator using the non-linear material based switches and logic gates. The scheme can operate in real time. The delay time can achieve ps(pico-second). The pulse duration can be made very low and may cross the THz easily by selecting proper material and laser source.

British Library Electronic Table of Contents (United Kingdom)

Taking both white noise and colored environmental noise into account, a general stochastic logistic model under regime switching is proposed and studied. Sufficient conditions for extinction, nonpersistence in the mean, weak persistence, stochastic permanence and global attractivity are established. The critical number between weak persistence and extinction is obtained. Moreover, some simulation figures are introduced to illustrate the main results.

Energy Technology Data Exchange (ETDEWEB)

The traveling-wave mode in ring lasers is achieved by two methods: by a reversing mirror, and by using an intracavity nonreciprocal device. This paper is devoted to realization of the traveling-wave mode in a mode-locked YAG-Nd ring laser by a method proposed by Tomov et al. This method uses two intracavity Q-switches. In mode-locked operation, pulses are generated that can be considered short compared with the period of modulation T = L/C (where L is the length of the perimeter of the cavity). Analysis shows that if the shift of the switching signals corresponds to the time of travel of a light pulse between Q-switches, the pulse in one direction will pass the Q-switches at instants of zero losses, while losses in the other direction will be maximized for a distance between Q-switches of L/4, and will be zero for a distance L/2. Experimental verification of the proposed method gave ...

Energy Technology Data Exchange (ETDEWEB)

The magnetically controlled plasma opening switch (MCPOS) is an advanced plasma opening switch that utilizes magnetic fields to improve operation. Magnetic fields always dominate terawatt, pulsed power plasma opening switches. For that reason, the MCPOS uses controlled applied magnetic fields with magnitude comparable to the self-magnetic field of the storage inductor. One applied field holds the plasma in place while energy accumulates in the storage inductor, then another applied field pushes the plasma away from the cathode to allow energy to flow downstream. Over a ten month period, an MCPOS was designed, built, and tested on DECADE Module 2 at Physics International. The peak drive current was 1.8 MA in 250 ns. The output parameters were up to 1 MA into an electron beam load. The radiation temporal pulse width averaged 60 nanoseconds full-width at half-maximum. The peak load voltage ranged from one to two megavolts. The ...

KoreaScience (Korea)

Full Text Available

Energy Technology Data Exchange (ETDEWEB)

We report on the software aspects of the development of a switch-based data acquisition system at Fermilab. This paper describes how, with the goal of providing an ``integrated systems engineering`` environment, several powerful software tools were put in place to facilitate extensive exploration of all aspects of the design. These tools include a simulation package, graphics package and an Expert System shell which have been integrated to provide an environment which encourages the close interaction of hardware and software engineers. This paper includes a description of the simulation, user interface, embedded software, remote procedure calls, and diagnostic software which together have enabled us to provide real-time control and monitoring of a working prototype switch-based data acquisition (DAQ) system.

Science.gov (United States)

This is a continuation of our paper [Liu, M., Wang, K., 2010. Persistence and extinction of a stochastic single-species model under regime switching in a polluted environment, J. Theor. Biol. 264, 934-944]. Taking both white noise and colored noise into account, a stochastic single-species model under regime switching in a polluted environment is studied. Sufficient conditions for extinction, stochastic nonpersistence in the mean, stochastic weak persistence and stochastic permanence are established. The threshold between stochastic weak persistence and extinction is obtained. The results show that a different type of noise has a different effect on the survival results. PMID:20816991

Energy Technology Data Exchange (ETDEWEB)

A dielectric-wall linear accelerator is improved by a high-voltage, fast rise-time switch that includes a pair of electrodes between which are laminated alternating layers of isolated conductors and insulators. A high voltage is placed between the electrodes sufficient to stress the voltage breakdown of the insulator on command. A light trigger, such as a laser, is focused along at least one line along the edge surface of the laminated alternating layers of isolated conductors and insulators extending between the electrodes. The laser is energized to initiate a surface breakdown by a fluence of photons, thus causing the electrical switch to close very promptly. Such insulators and lasers are incorporated in a dielectric wall linear accelerator with Blumlein modules, and phasing is controlled by adjusting the length of fiber optic cables that carry the laser light to the insulator surface. 12 figs.

Energy Technology Data Exchange (ETDEWEB)

We have generated approximately 100 watts of frequency doubled light from the output of an electro-optically Q-switched, diode-pumped Nd:YAG slab laser oscillator operating at an average power of 200 watts (2.5 kHz repetition rate, 80 mJ/pulse, 25 ns pulsewidth). The Q-switch was a compensated z-axis propagation LiNbO{sub 3} electro-optic modulator, and the frequency conversion crystal was a thin slab of KTP. In addition, Q-switched operation at an average power of approximately 250 watts with 26 ns pulsewidths has been demonstrated.

UK PubMed Central (United Kingdom)

PurposeTo date there remains no effective therapy for metastatic melanoma and at the molecular level disease progression remains poorly understood. Recent work by...Full Text Available

Science.gov (United States)

In systems of fast decimal counters, there are three problems to be resolved: to study a bistable having a short switching time, to form with the aid of three bistables a circuit divisible by 5, and to normalize the input pulses. The solutions to these problems for the nonsecond scaler are presented. (J.S.R.)

UK PubMed Central (United Kingdom)

Numerical calculations of static, switched, and radiofrequency (RF) electromagnetic (EM) fields considering the geometry and EM properties of the human body are used increasingly in MRI to explain...Full Text Available

Science.gov (United States)

Upon illumination of an optically driven Q-switch 35 over conventional electro- optic, acousto-optic and medium located inside the laser cavity with an ...

CERN Document Server

This paper presents and implements an iterative feedback design algorithm for stabilisation of discrete-time switched systems under arbitrary switching regimes. The algorithm seeks state feedback gains so that the closed-loop switching system admits a common quadratic Lyapunov function (CQLF) and hence is uniformly globally exponentially stable. Although the feedback design problem considered can be solved directly via linear matrix inequalities (LMIs), direct application of LMIs for feedback design does not provide information on closed-loop system structure. In contrast, the feedback matrices computed by the proposed algorithm assign closed-loop structure approximating that required to satisfy Lie-algebraic conditions that guarantee existence of a CQLF. The main contribution of the paper is to provide, for single-input systems, a numerical implementation of the algorithm based on iterative approximate common eigenvector ...

Energy Technology Data Exchange (ETDEWEB)

Two types of switched electrode electronics beam position monitors are in use at Jefferson Lab. Together they provide accurate beam position to the control system for beam intensities between 50 nA and 2 mA. One version, called the linac style, has a switching frequency of 125 kHz. The other, called the transport type, has a switching frequency of 7 kHz. The basic system provides information to the control system at a 1 Hz update rate. The systems are regularly used to measure the AC component of beam position and energy as well as suppress this motion as part of a fast feedback system. Position data produced by the system are also acquired on an event by event basis as part of the nuclear physics program in two of the experimental halls. This paper will focus on the AC characteristics of the system. These characteristics are affected by analog filter frequencies and a time delay between the measurement of the positive ...

Science.gov (United States)

... Steady State 16.0-28.0 5.05 to 5.36 0 Key switch turned on. ... version may have been the better choice since the acousto-optic modulator also ...

UK PubMed Central (United Kingdom)

Escherichia coli infection of the endometrium causes uterine disease after parturition and is associated with prolonged luteal phases of the ovarian cycle in cattle. Termination...Full Text Available

International Nuclear Information System (INIS)

An optical klystron is built in the 800 MeV electron storage ring at University of Science and Technology of China for harmonic super-radiation generation. In single bunch operation mode the repetition rate of the spontaneous radiation pulses is about 4.533 MHz, and the repetition rate of the seed laser pulses is about 3 Hz, while the radiation pulse duration is 300 ps. For measuring harmonic radiation a high on/off ratio ICCD is used as an optical switch to reject spontaneous radiation pulses of high repetition rate

Energy Technology Data Exchange (ETDEWEB)

The reliability of an electrical power system is influenced by the operation of circuit-breaker (CB). A good indicator of circuit-breaker condition is its switching time. Based on it some of the critical circuit-breaker irregularities can be detected and removed before they develop to a failure. In this paper, the evaluation of time measurements (timings) in case of different failures will be carried out for two circuit-breaker solutions, i.e. with spring and hydraulic drive. Moreover, the relationships between switching time and failure type/location will be derived. Thereby, the influence of failure trend will also be taken into account. (author)

Science.gov (United States)

A dc-to-dc converter has been designed which employs the synchronizing phenomenon in the transistor core multivibrator. In the proposed circuit, the voltage feedback is applied from the control transistor and the current feedback is applied from the main transistor. The operation of the converter is analyzed by the averaging method of the state space technique. The converter features small switching loss and is suitable for high frequency operation. An efficiency of more than 95% is obtained for 5 V, 3 A output at a switching frequency of 200 kHz.

Energy Technology Data Exchange (ETDEWEB)

This paper presents the analysis and novel hybrid controller design for an interleaved 2-quadrant switched capacitor (SC) bidirectional DC/DC converter for a hybrid electric vehicle (HEV) dual energy storage system. The designed novel control strategy enables simpler dynamics compared to a standard buck converter with input filter, good regulation capability, low EMI, lower source current ripple, ease of control, and continuous input current waveform in both buck as well as boost modes of operation.

International Nuclear Information System (INIS)

Network reconfiguration is an operation problem, which entails altering the topological structure of the distribution feeders by rearranging the status of switches in order to obtain an optimal configuration in order to minimise the system losses. This paper presents a new reconfiguration algorithm that enhances voltage stability and improves the voltage profile besides minimising losses without incurring any additional cost for installation of capacitors, tap changing transformers and related switching equipment in the distribution system. Test results on a 69 node distribution system reveal the superiority of this algorithm.

Energy Technology Data Exchange (ETDEWEB)

This thesis examines the design of a propulsion system for a series hybrid vehicle and includes the study of an energy storage unit using double-layer capacitors and a lightweight soft-switched converter system, and two new components in series hybrid vehicles. The development of environmentally sustainable vehicles is more urgent now given the fact that pollution levels are ever increasing. No electric vehicle has yet been developed that can compete with a normal vehicle based only on internal combustion engines. The dilemma lies in the difficulty of storing the amount of energy needed and supply it a high power levels. An attractive and viable option to reducing pollution and maintaining good performance may lie in hybrid electric-powered vehicles. The double-layer power capacitors are an interesting option because of their high power density and long lifetime. The devices are new and assembling large energy storage units must be thoroughly examined before using ...

Energy Technology Data Exchange (ETDEWEB)

Recent progress in the metallic conducting Langmuir-Blodgett (LB) films built from TTF derivative and fatty acids is reported. A simple LB method of transferring the mixed Langmuir (L) film of BEDO-TTF (BO) and stearic acid (SA) onto substrates provided metallic conducting LB films. A homogeneous L film formation on the water surface observed by Brewster angle microscope (BAM) is an essential factor for the well-ordered LB films. In the L film, the carboxylate group of fatty acid forms anion layer bringing about a spontaneous formation of mixed valence state (MVS) of BO layer. Similar spontaneous formation was also found in the molecular combination of nonoxygen-substituted donor of EDT-TTF and octadecanesulfonic acid (OS). This type of reaction would be useful for obtaining conducting LB films. For the LB films of BEDO-TTF and stearic acid, we found a negative transverse magnetoresistance at low temperature that was interpreted in the weak localization of a ...

Science.gov (United States)

... turbine blade heat-transfer and study the heat-transfer augmentation in idealized geometry and its ... responsible for heat transfer augmentation. ...

International Nuclear Information System (INIS)

This paper deals with construction types of high temperature heat exchangers, their circulation loops and temperature differences. Most attention is given to gas dynamics, convective heat transfer, convection and radiant heat transfer interaction in high temperature heat exchangers. The ways of heat transfer augmentation and efficient heat exchanger construction are discussed.

Energy Technology Data Exchange (ETDEWEB)

Power quality problems are caused by activities normal to utility operations such as maintenance outages and capacitor switching or events that are abnormal such as lightning strikes and equipment failures. Disconnection and reconnection of transmission lines and transformers can cause switching surges, and are more severe on extra high voltage transmission lines than high voltage lines. Capacitor switching can cause transients and harmonics that may affect sensitive equipment, and are the source of 3rd, 5th, 7th and 9th harmonics in the hundreds of hertz ranges. Overload, sudden loss of generating capacity and transmission line faults are typical problems affecting system stability. Fault interruptions and reclosings can cause surges in the distribution system, and lightning strikes may cause voltage surges or dips due to arrester sparkover. Blackouts, brownouts, voltage fluctuations, travelling wave overvoltages, ...

DEFF Research Database (Denmark)

This paper presents a new method to improve sensorless performance of matrix converter drives using a parameter estimation scheme. To improve low-speed sensorless performance, the non-Iinearities of a matrix converter drive such as commutation delays, turn-on and turn-off times of switching devices, and on-state switching device voltage drop is modelled using PQR transformation and compensated using a reference current control scheme. To eliminate the input current distortion due to the input voltage unbalance, a simple method using PQR transformation is also presented. The proposed compensation method is applied for high performance induction motor drives using a 3 kW matrix converter system without a speed sensor. Experimental results are shown to illustrate the feasibility of the proposed strategy.

Energy Technology Data Exchange (ETDEWEB)

The Advanced Networking Integration Department at Sandia National Laboratories has used the annual Supercomputing conference sponsored by the IEEE and ACM for the past three years as a forum to demonstrate and focus communication and networking developments. For Supercomputing `95, Sandia elected: to demonstrate the functionality and capability of an AT&T Globeview 20Gbps Asynchronous Transfer Mode (ATM) switch, which represents the core of Sandia`s corporate network, to build and utilize a three node 622 megabit per second Paragon network, and to extend the DOD`s ACTS ATM Internet from Sandia, New Mexico to the conference`s show floor in San Diego, California, for video demonstrations. This paper documents those accomplishments, discusses the details of their implementation, and describes how these demonstrations supports Sandia`s overall strategies in ATM networking.

Energy Technology Data Exchange (ETDEWEB)

Ways of reducing energy consumption in plastics processing are examined. Examples are given which illustrate how the awareness of everyone in the company to energy saving is essential with particular reference to switching arrangements to ensure such things as lights, machinery, compressed air systems are switched off when not needed or run at a lower level where appropriate. An understanding of the various elements of the electricity bill can inform a company`s planning of its operations to take advantage of lower tariffs. Machinery selection both with regard to efficiency of processing, quality of engineering and appropriate size can achieve significant savings and attention to maintenance is important. Fundamental to all aspects of energy saving is the monitoring of energy usage to identify where savings can be made and to evaluate the effectiveness of any measures taken. (UK)

Science.gov (United States)

An analysis is made of the basic principles and methods of construction of integrated optical circuits (IOC) for data processing, which are optical waveguide processors in the integrated form. A classification is provided of IOC in accordance with the nature of the input connections to optical components and in accordance with their intended function. An analysis is made of the current status of research and development of analog IOC for handling analog and digital signals, IOC for computing technology, and switching IOC. A detailed analysis is made of IOC with different functions in data processing: spectrum analyzers and correlators, analog-digital converters, circuits for identification of data sets and for encoding of signals, threshold and multistable circuits, logic and arithmetic units, and switching arrays. Descriptions are given of IOC for optically controlled data handling: bistable purely optical logic circuits, multivibrators, ...

Energy Technology Data Exchange (ETDEWEB)

In this effort, the nonlinear responses and stability of a spindle system supported by ball bearings are presented. The dynamics of this system is described by a set of second order differential equations with a nonlinear piecewise smooth force. The Floquet theory is applied to investigate the stability of the periodic solution. Due to the loss of contact between the raceways and balls in the ball bearing, the bending of the frequency response curves switch to the left at the weak resonance region, which is similar to the frequency response curves of a system with a soft spring. With the decrease of the bearing clearance, the bending of the frequency response curves switch to the right, which is similar to the frequency response curves of a system with a hard spring. Increase of the frequency ratio, the bending of frequency response curves transforms from left to right. The route to chaos through a period doubling process is also observed in ...

International Nuclear Information System (INIS)

This Letter reports the first experimental results from the world's first distributed optical-klystron (DOK) free-electron laser (FEL), the DOK-1 FEL, at Duke University. The DOK-1 FEL is a hybrid system, comprised of four wigglers: two horizontal and two helical. With the DOK-1 FEL, we have obtained the highest FEL gain among all storage ring based FELs at 47.8% (#+-#2.7%) per pass. We have also demonstrated that the FEL gain can be enhanced by increasing electron bunching using wigglers with a different polarization. Furthermore, we have realized controlled polarization switches of the FEL beam by a nonoptical means through the manipulation of a buncher magnet.

DEFF Research Database (Denmark)

This paper presents a new method to compensate the nonlinearities for matrix converter drives. The nonlinearities of matrix converter drives such as commutation delay, turn-on and turn-off time of the switching devices, and on-state switching device voltage drop is corrected by a new matrix converter model using the direction of current. The proposed method does not need any additional hardware or complicated software and it is easy to realize by applying the algorithm to the conventional vector control. The proposed compensation method is applied for high-performance induction motor drives using a 3-kW matrix converter system without a speed sensor. Experimental results show the proposed method provides good compensating characteristics.

Energy Technology Data Exchange (ETDEWEB)

This book contains nine selections. Some of the titles are: High Heat-Flux, Forced-Convection Heat Transfer for Tubes with Twisted-Tape Inserts; Heat Transfer Augmentation by Interrupted Surfaces - Experimental Consideration; Turbulent Flow Heat Transfer from Externally Roughened Tubes in Axial Flow in Concentric Pipe Heat Exchangers; and Heat Transfer Enhancement of Turbulent Flow in Pipes with an Internal Circular Rib.

International Nuclear Information System (INIS)

Purpose : To obtain an emergency core cooling device in a FBR type reactor by utilizing heat pipes which are not actuated at usual operation condition but actuated reliably upon emergency. Constitution : A system for injecting heat medium into heat pipes is provided. By injecting the heat medium into the heat pipes upon emergency to actuate the heat pipes, the reactor core is cooled. During normal reactor operation, the inside of the heat pipes is evacuated from a vacuum pump and no heat medium is filled therein, whereby unnecessary heat loss during the normal operation can be prevented. (Ikeda, J.).

International Nuclear Information System (INIS)

In this paper, numerical simulation of a concentric tube heat exchanger is presented to determine the convective heat transfer coefficient and friction factor in a smooth tube. Increasing the convective heat transfer coefficient can increase heat transfer rate in a concentric tube heat exchanger from a given tubular surface area. This can be achieved by using heat transfer augmentation devices. This work constitutes the initial phase of the numerical simulation of heat transfer from tubes employing augmentation devices, such as twisted tapes, wire-coil inserts, for heat transfer enhancement. A computational fluid dynamics (CFD) simulation tool was developed with CFX software and the results obtained from the simulations are validated with the empirical correlations for a smooth tube heat exchanger. ...

Energy Technology Data Exchange (ETDEWEB)

This is the first text and reference book to be devoted completely to the very important and timely subject of heat transfer augmentation. This book is of equal appeal to both researchers and designers of heat transfer equipment.

UK PubMed Central (United Kingdom)

We report a pH-dependent conformational transition in short, defined homopolymeric deoxyadenosines (dA₁₅) from a single helical structure with stacked nucleobases at neutral pH to a double-helical,...Full Text Available

Wastenet

... The dawn of Bio-Mecha and a Biomechanical Revolution May 31 2011: Hi Julian, Yes, but i dont think we would ... The dawn of Bio-Mecha and a Biomechanical Revolution May 31 2011: A BBC Documentary: All Watched Over by Machines of Loving ... The dawn of Bio-Mecha and a Biomechanical Revolution May 17 2011: Ed Boyden: A light switch for neurons is an amazing ... The dawn of Bio-Mecha and a Biomechanical Revolution May 16 2011: Thank you Meher Like Spring Rabbit, its a great contribution....

UK PubMed Central (United Kingdom)

The luminescent characteristics of Ru(bpy)₂dppz²⁺ (dppz = dipyrido[3,2-a:2′,3′-c]phenazine), a DNA light switch, were...Full Text Available

Environmental Research Database

DescriptionThe switch from production-linked to environmental payments has focussed attention on the environmental impacts of farming. There is a growing awareness of the need to reduce the contamination of air with carbon dioxide, methane, ammonia and nitrogen gases (which contribute to the greenhouse effect) and to prevent the contamination of soil and water with excessive amounts of nitrogen, phosphorus and potassium. As beef production moves to become more sustainable and fully integrated with the wide [continued...

Energy Technology Data Exchange (ETDEWEB)

Special Issue on Automotive Bearings and Applicable Products; Reports include Performance of Ceramic Cam Roller Follower for Automotive Engine; Performance of Drawn Cup Needle Roller Bearing for Propellershaft; Plastic Bearing Retainer for High Temperature Oil Lubrication; Bearing Device for Vehicle Axle; and Flush Mounting Type Programmable Cam Switches.

Energy Technology Data Exchange (ETDEWEB)

A gas-diesel dual fuel engine apparatus is described having a diesel engine, a diesel fuel supply system including a diesel fuel injection pump, a gaseous fuel supply system including a gaseous fuel regulating valve, and a governing and controlling device for governing the speed of the engine through the control of fuel supplied to the engine and controlling the switchover of the operation of the engine between a diesel fuel mode and a gaseous fuel mode. The improvement of the governing and controlling device consists of: (a) at least one electronic governor means adapted to compare a speed signal representing the actual operating speed of the diesel engine with a set speed signal representing the set speed thereof; (b) a pair of electric actuator means having respective power amplifier circuits and mechanically connected to the diesel fuel injection pump and the gaseous fuel regulating valve, respectively, for the actuation thereof; (c) mode switching control ...

CERN Document Server

Predictions and measurements of a multimode waveguide interferometer operating in a fibre coupled, ``dual-mode'' regime are reported. With a 1.32 micrometer source, a complete switching cycle of the output beam is produced by a 10.0 nanometer incremental change in the 8.0 micrometer width of the hollow planar mirror waveguide. This equates to a fringe spacing of $\\sim\\lambda /130$. This is an order of magnitude smaller than previously reported results for this form of interferometer.

Energy Technology Data Exchange (ETDEWEB)

The physical layout of the Time-Of-Flight spectrometer at the new spallation source SINQ is presented. The concept shows up a hybrid-TOF combining a Fermi-chopper with a crystal monochromator. The demand of a versatile and flexible instrument for several applications is taken into account by the option of switching from time-focusing to monochromatic focusing mode such that the spectrometer can be optimised for both quasielastic and inelastic scattering applications. (author) 5 figs., 2 tabs., 16 refs.

CERN Document Server

Families of regimes for discrete control systems are studied possessing a special quasi-controllability property that is similar to the Kalman controllability property. A new approach is proposed to estimate the amplitudes of transient regimes in quasi-controllable systems. Its essence is in obtaining of constructive a priori bounds for degree of overshooting in terms of the quasi-controllability measure. The results are applicable for analysis of transients, classical absolute stability problem and, especially, for stability problem for desynchronized (asynchronous, switching) systems.

Energy Technology Data Exchange (ETDEWEB)

Some motor operated valves now have higher torque switch settings due to regulatory requirements to ensure valve operability with appropriate margins at design basis conditions. Verifying operability with these settings imposes higher stem loads during periodic inservice testing. These higher test loads increase stresses in the various valve internal parts which may in turn increase the fatigue usage factors. This increased fatigue is judged to be a concern primarily in the valve disks, seats, yokes, stems, and stem nuts. Although the motor operators may also have significantly increased loading, they are being evaluated by the manufacturers and are beyond the scope of this study. Two gate valves representative of both relatively weak and strong valves commonly used in commercial nuclear applications were selected for fatigue analyses. Detailed dimensional and test data were available for both valves from previous studies at the Idaho National Engineering ...

UK PubMed Central (United Kingdom)

Immature seeds of castor bean (Ricinus communis) removed from the capsule at 25 to 40 days after pollination (25-40 DAP) and placed in an atmosphere of high relative humidity undergo...Full Text Available

Science.gov (United States)

A description is given of an automatic liquid nitrogen pumping system. Pamping of liquid nitrogen iato cooling traps up to a predetermined level is achieved by an automatically controlled compressed air system. An impontant feature of the equipment is the ability to switch automatically from an empty liquid nitrogen reservoir to a full one. This allows for a much more flexible operation than in conventional systems where the reservoir has to be replaced manually when empty. (auth)

UK PubMed Central (United Kingdom)

To understand how DEXD/H-box proteins recognize and interact with their cellular substrates, we have been studying Prp28p, a DEXD/H-box splicing factor required for switching the U1 snRNP with the U6...Full Text Available

KoreaScience (Korea)

Full Text Available

UK PubMed Central (United Kingdom)

Approximately 400 people die from extreme heat each year in the United States, and the risk of heat waves may increase as a result of global climate change. Despite the risk of heat-related morbidity...Full Text Available

International Nuclear Information System (INIS)

This textbook contains the following main topics: Heat conductivity, convection, condensation and evaporation, radiation heat transfer and heat exchangers. It includes the physical foundations for all these aspects and many examples. (orig.)

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

An analytical study of the ice-formation process associated with heat-conducting plates located perpendicularly to isothermally heated and cooled surfaces with some clearance is presented. It is proposed that the onset conditions, which describe whether the ice-volume fraction in a steady state is greater than or less than that without heat-conducting plates, are defined by the dimensionless distances between the heated/cooled walls and the heat-conducting plates. It is shown that the onset conditions are dependent on the pitch and the thickness of the heat-conducting plates and are less dependent on the thermal conductivity of the plates.

Science.gov (United States)

... Accession Number : ADD326926. Title : SPECIAL EDDY CURRENT PROBES FOR HEAT EXCHANGER INSPECTION. Corporate Author : ...

Energy Technology Data Exchange (ETDEWEB)

In the development of a geothermal heat pump a water source heat pump was connected to a 1-1/2'' water line, 2200' long, buried in an endless loop 10' deep. The system is closed, circulating the same water continuously through the heat pump back to the field again. This water line 10' deep is the geothermal heat source. No matter how cold the air temperature gets on a winter day the water temperature to the heat pump will always be above 45/sup 0/F. This system has efficiently heated our house the past year using no supplemental heat.

Energy Technology Data Exchange (ETDEWEB)

The paper reports on the results of a study of the synthesis conditions effects on magnetic and transport properties of nanosized layers of high-T{sub c} diluted magnetic semiconductors (DMS), such as Ge:Mn, Si:Mn and Si:Fe, fabricated by laser-plasma deposition over a wide range of the growth temperature, T{sub g}=(20-550) deg. C on single-crystal GaAs or Al{sub 2}O{sub 3} substrates. Ferromagnetism of the layers was detected by measurement data of the magneto-optical Kerr effect, anomalous Hall effect, negative magnetoresistance and ferromagnetic resonance (FMR) at 5-500 K. The optimum growth temperature, T{sub g}, for Si:Mn/GaAs layers with T{sub c}{approx}400 K is shown to be about 400 deg. C. The Si:Mn/Al{sub 2}O{sub 3} layers with 35% of Mn have the metal-type of conductivity with manifestation of magnetization up to room temperature. Different types of uniformly doped structures and digital alloys have been investigated. In contrast to GaSb:Mn films, ...

International Nuclear Information System (INIS)

Heat transfer augmentation by straight grid spacers in rod bundles is studied for single phase flow and for post critical heat flux dispersed flow. The heat transfer effect of swirling grid spacers in single phase flow is also examined. Governing heat transfer mechanisms are analyzed, and predictive formulations are established. For single phase flow, the local heat transfer at a straight spacer and at its upstream or downstream locations are treated separately. 18 refs.

Energy Technology Data Exchange (ETDEWEB)

The behavior of air flows in complex heat exchanger passages is reviewed with a focus on the heat transfer effects of boundary-layer development, turbulence, spanwise and streamwise vortices, and wake management. Each of these flow features is discussed for the plain, wavy, and interrupted passages found in contemporary compact heat exchanger designs. Results from the literature are used to help explain the role of these mechanisms in heat transfer enhancement strategies.

Energy Technology Data Exchange (ETDEWEB)

A heat transfer (condenser) of a domestic freezer was tested in a vertical channel in order to study the influence of the chimney effect in the optimization of the heat transfer coefficient. The variation of the opening of the channel, position and the heating power of the heat exchanger in the heat transfer coefficient was considered. The influence of the surface emissivity on the heat transfer by thermal radiation was studied with the heat exchanger testes without paint and with black paint. The air velocity entering the channel was measured with a hot wire anemometer. In order to evaluate the chimney effect, the heat exchanger was testes in a open ambient. This situation simulates its operational conditions when installed on the freezer system. The variables collected in the experimental procedures was gathered in the ...

International Nuclear Information System (INIS)

The authors discuss a two-phase two-component experimental system developed to study enhancement of heat transfer from a vertical chip size heater to surrounding liquid (Freon 113 or Ethanol) due to air jet impingement. Heat transfer coefficient was measured as function of jet velocity, heat flux and the distance between exit of jet tube and heated surface. The injector was placed very close to the hot surface. It was found that the heat transfer was notably enhanced with foreign gas impingement, especially in the cases of small temperature differences between wall and coolant. In fact for higher jet velocities the heat transfer coefficients tended to infinite while the temperature differences between wall and coolant were zero. The heat transfer coefficients decreased with the increasing of heat flux. High-speed camera ...

Energy Technology Data Exchange (ETDEWEB)

This report introduces a microprocessor system composed of a Z-80 single-board computer controlling a gas-carburizing process. The system has 7 analogical input and output signals 24 switch signal-input and 12 switch signal-output signals, which are applicable for temperature, carbon potential, and mechanical-movement control of multipurpose sealed furnaces, or for mutiple-zone temperature, carbon potential, and mechanical-movement control of continuous gas carburizing furnaces; or for distributed control of pit-type carburizing furnaces. The setpoints of variables, such as treating time, temperature, carbon potential of carburizing period, carbon potential of diffusion period, depth of carburizing layer, P.I.D. etc., are entered by keyboard and stored into memories, and actual values are displayed by digital tubes. Furthermore, the fault of thermocouple, oxygen probe, or infrared CO/sub 2/ analyzer; carbon potential, or temperature exceeding ...

CERN Document Server

The production of X-ray radiation with a high degree of circular polarization constitutes an important goal at XFEL facilities. A simple scheme to obtain circular polarization control with crossed undulators has been proposed so far. In its simplest configuration the crossed undulators consist of pair of short planar undulators in crossed position separated by an electromagnetic phase shifter. An advantage of this configuration is a fast helicity switching. A drawback is that a high degree of circular polarization (over 90%) can only be achieved for lengths of the insertion devices significantly shorter than the gain length, i.e. at output power significantly lower than the saturation power level. The obvious and technically possible extension considered in this paper, is to use a setup with two or more crossed undulators separated by phase shifters. This cascade crossed undulator scheme is distinguished, in performance, by a fast helicity ...

CERN Document Server

Each of the two LHC injection kicker magnet systems must produce a kick of 1.3 T.m with a flattop duration variable up to 7.86 microseconds, and rise and fall times of less than 900 ns and 3 microseconds, respectively. A kicker magnet system consists of four 5 Ohm transmission line magnets with matching terminating resistors, four 5 Ohm Pulse Forming Networks (PFN) and two Resonant Charging Power Supplies (RCPS). Nine PFNs, together with associated switch tanks, and dump switch terminating resistors have been built at TRIUMF and all have been tested at high voltage (54 kV) to ensure that the performance is within specification. This paper describes the HV measurements, compares these results with low voltage measurements and analyses the pulse performance of the PFNs. The measurements are compared with results from PSpice simulations and small discrepancies between the predictions and measurements are explained.

Energy Technology Data Exchange (ETDEWEB)

A new approach to dynamic security assessment in electric power systems is proposed. A power system is modeled as a dynamical system with random variable structure. Structural variations are caused by primary and secondary events. Primary events are state-independent disturbances representing line and unit faults and load changes and are modeled by random jump processes. Secondary events that represent forced line and unit outages and load sheddings are modeled through an aggregate representation of the protection system as random processes whose change in time corresponds to the crossing of switching surfaces by the state process. These switching surfaces are defined by the setting of the protective relays. Commensurate with this model a three-state decomposition of the operating conditions into normal, emergency, and partial load operating states is suggested. Transitions between these states are described in terms of set-valued mappings in ...

International Nuclear Information System (INIS)

The DOE is conducting a comprehensive technical analysis of a flexible-fuel transportation system in the United States -- that is, a system that could easily switch between petroleum and another fuel, depending on price and availability. The DOE Alternative Fuels Assessment is aimed directly at questions of energy security and fuel availability, but covers a wide range of issues. This report examines environmental, health, and safety concerns associated with a switch to alternative- and flexible-fuel vehicles. Three potential alternatives to oil-based fuels in the transportation sector are considered: methanol, compressed natural gas (CNG), and electricity. The objective is to describe and discuss qualitatively potential environmental, health, and safety issues that would accompany widespread use of these three fuels. This report presents the results of exhaustive literature reviews; discussions with specialists in the vehicular and ...

International Nuclear Information System (INIS)

One of the most profound features of electricity spot prices are the price spikes. Markov regime-switching (MRS) models seem to be a natural candidate for modeling this spiky behavior. However, in the studies published so far, the goodness-of-fit of the proposed models has not been a major focus. While most of the models were elegant, their fit to empirical data has either been not examined thoroughly or the signs of a bad fit ignored. With this paper we want to fill the gap. We calibrate and test a range of MRS models in an attempt to find parsimonious specifications that not only address the main characteristics of electricity prices but are statistically sound as well. We find that the best structure is that of an independent spike 3-regime model with time-varying transition probabilities, heteroscedastic diffusion-type base regime dynamics and shifted spike regime distributions. Not only does it allow for a seasonal spike intensity throughout the year and ...

International Nuclear Information System (INIS)

This paper presents a novel organization of switch capacitor charge pump circuits based on voltage doubler structures. Each voltage doubler takes a DC input and outputs a doubled DC voltage. By cascading voltage doublers the output voltage increases up to 2 times. A two-phase voltage doubler and a multiphase voltage doubler structures are discussed and design considerations are presented. A simulator working in the Q-V realm was used for simplified circuit level simulation. In order to evaluate the power delivered by a charge pump, a resistive load is attached to the output of the charge pump and an equivalent capacitance is evaluated. To avoid the short circuit during switching, a clock pair generator is used to achieve multi-phase non-overlapping clock pairs. This paper also identifies optimum loading conditions for different configurations of the charge pumps. The proposed charge-pump circuit is designed and simulated by SPICE with TSMC ...

Energy Technology Data Exchange (ETDEWEB)

A novel compact CT-guided intensity modulated proton radiotherapy (IMPT) system is described. The system is being designed to deliver fast IMPT so that larger target volumes and motion management can be accomplished. The system will be ideal for large and complex target volumes in young patients. The basis of the design is the dielectric wall accelerator (DWA) system being developed at the Lawrence Livermore National Laboratory (LLNL). The DWA uses fast switched high voltage transmission lines to generate pulsed electric fields on the inside of a high gradient insulating (HGI) acceleration tube. High electric field gradients are achieved by the use of alternating insulators and conductors and short pulse times. The system will produce individual pulses that can be varied in intensity, energy and spot width. The IMPT planning system will optimize delivery characteristics. The system will be capable of being sited in a conventional linac vault and provide intensity ...

Energy Technology Data Exchange (ETDEWEB)

The performance of a commercial heat pipe was investigated both experimentally and theoretically. The effect of the temperature difference, the surface area ratio, and the operational conditions on the performance were studied. The heat flow rate and the vapor temperature were estimated on a ready-made commercial heat pipe. Its performance varied considerably with operational conditions. Theoretical consideration of a mathematical model and several nomographs are also presented. This work is applicable to the design and use of heat pipes in the field.

Energy Technology Data Exchange (ETDEWEB)

This book brings recommendations and information on the choice and the operating of heating systems and domestic hot water production in order to better choose the house, to better use the heating and to preserve the environment. General notions on the different heating systems and their operating on the renewable energies used and the heating emitters offer advices for the purchase of a house. (A.L.B.)

Energy Technology Data Exchange (ETDEWEB)

The development of a gas-operated diffusion absorption heat pump for the heating of living spaces is described. By various improvement an energy efficiency of the prototypes of 1.5 was achieved. Structural alterations led to a lower overall height and lower production costs. The CFCs used in electric heat pumps were replaced by environmentally neutral ammonia. Compared with conventional gas heating systems, the CO2 output could be reduced by more than 30%. figs., tabs.

British Library Electronic Table of Contents (United Kingdom)

Abstract This paper proposes and analyses the autoregressive conditional root (ACR) time-series model. This multivariate dynamic mixture autoregression allows for non-stationary epochs. It proves to be an appealing alternative to existing nonlinear models, e.g. the threshold autoregressive or Markov switching class of models, which are commonly used to describe nonlinear dynamics as implied by arbitrage in presence of transaction costs. Simple conditions on the parameters of the ACR process and its innovations are shown to imply geometric ergodicity, stationarity and existence of moments. Furthermore, consistency and asymptotic normality of the maximum likelihood estimators are established. An application to real exchange rate data illustrates the analysis.

Science.gov (United States)

This paper presents a systematic study on the stability of a two-dimensional vibration isolation floating raft system with a time-delayed feedback control. Based on the generalized Sturm criterion, the critical control gain for the delay-independent stability region and critical time delays for the stability switches are derived. The critical conditions can provide a theoretical guidance of chaotification design for line spectra reduction. Numerical simulations verify the correctness of the approach. Bifurcation analyses reveal that chaotification is more likely to occur in unstable region defined by these critical conditions, and the stiffness of the floating raft and mass ratio are the sensitive parameters to reduce critical control gain.

CERN Document Server

The paper develops a new class of financial market models. These models are based on generalized telegraph processes: Markov random flows with alternating velocities and jumps occurring when the velocities are switching. While such markets may admit an arbitrage opportunity, the model under consideration is arbitrage-free and complete if directions of jumps in stock prices are in a certain correspondence with their velocity and interest rate behaviour. An analog of the Black-Scholes fundamental differential equation is derived, but, in contrast with the Black-Scholes model, this equation is hyperbolic. Explicit formulas for prices of European options are obtained using perfect and quantile hedging.

Energy Technology Data Exchange (ETDEWEB)

The purpose of the course is to present an overview of the power conditioning aspects of energy transfer systems. The objective, then, is to develop an understanding and appreciation of the physical processes that govern the performance of these systems, including the role of such elements as switches, capacitors, inductors, and resistors. Secondly, to discuss where are the sources of information once a problem area has been identified. All the information will be current and state-of-the-art, and directed toward these pulse components, with particular emphasis on the area of high-repetition-rate systems, as these are taking on ever increasing significance.

International Nuclear Information System (INIS)

In this paper extended models for estimating price developments on electricity markets are presented. The models consider deviations from the normality hypothesis of the prices. Based on an ARMA model combination with GARCH, Gaussian-mixture and switching-regime approaches are comparatively discussed. The comparison is based on historic electricity prices of the spot and two reserve markets in Germany. It is shown that the proposed extended models lead to significantly improved representations of the considered stochastic price processes. It is inferred that these models may be preferred for estimating price developments on electricity markets. (author)

International Nuclear Information System (INIS)

In dual-energy projection radiography with double exposures, rapid energy switching is mandatory to eliminate motion artifacts, but it is costly for use in a clinical environment. We developed a system with practical exposure intervals at reasonable cost by modifying a condenser-type X-ray generator. A commercially available system for digital radiography (Fuji Computed Radiography, FCR) was used to subtract images. This report dealt with technical factors to obtain adequate kV and mAs settings in this technique. (author).

Energy Technology Data Exchange (ETDEWEB)

This work describes the development of a synchronous key based on micro controller to the switching of three-phase power transformers, which makes possible the achievement of tests to register the inrush current, and the previous establishment of the instantaneous values of the voltage firstly applied to different phases of the energy process. This key is a value tool to the development electric power system projects and to the teaching and researching activities at the laboratory related to transitory phenomena and electric system protection.

British Library Electronic Table of Contents (United Kingdom)

The computational analysis of the model system consisting of the processes of CO2 assimilation and photorespiration shows the appearance of sustained oscillations in the system which might reflect their presence in photosynthesizing cells. Concentrations of CO2 and O2 oscillate in opposite phases causing Rubisco switching continuously between the carboxylase (CO2 assimilation) and the oxygenase (photorespiration) reactions. The results of modeling are consistent with carbon isotopic and other observed data. They show that the oscillation period varies from about 1 s to 3 s depending on the values of parameters taken. Too high concentrations of O2 suppress the oscillations.

Wastenet

...it only highlights the different feedstocks used in the production of fiber-based packaging materials or fossil-fuel ones; what about the energy required to convert ...feedstock, is unacceptable in trying to quantify the overall burden a specific packaging material has on the environment. As an aside, the point ... Consequentially, it is difficult to speculate on how much packaging material a company diverts from the landfill by switching from one material to another ...without specifying what geographical region said packaging material resides in. In addition, there is a lot of interest in diverting PET thermoforms from ...

Scientific Electronic Library Online (English)

Abstract in english In the last decade it has been experimentally found a periodic domain pattern arising in smectic C* liquid crystals in surface stabilized bookshelf geometry. Such a periodic texture appears after switching-off an external electric field, even in strong anchoring conditions. It has a static character and can be bidimensional, being dependent on both directions normal to the smectic planes and normal to the cell plates. In the present work an explanation to this phenomenon (more) is proposed. According to our model in the antiferroelectric phase the biperiodic texture is a threshold phenomenon, appearing for values of the spontaneous polarization greater than a critical value, whereas in the ferroelectric phase this type of bidimensional instability is hindered.

Energy Technology Data Exchange (ETDEWEB)

Cell voltage monitoring (CVM) systems are essential for the operation of fuel cell stacks and some battery systems, in the field as well as in the laboratory, because they allow the diagnosis and correction of problems that would otherwise go unnoticed and cause impaired performance or even permanent damage. A robust, safe, and low-cost design for a CVM unit is presented, using electromechanical relays as multiplexing switches. Some examples from the application of the unit on the University of Delaware's fuel cell battery hybrid buses are presented, including its use in automatically correcting anode flooding and diagnosing air channel blockage. (author)

Energy Technology Data Exchange (ETDEWEB)

Detecting a camouflaged target in a visually noisy background depends on the ability of the observer to discriminate the target from the surrounding terrain. Visible laser irradiation at less than damage levels can act as a masking source by compromising or reducing the observer's ability to resolve differences in the visual scene. Previous research has examined this concept by investigating laser flash effects on: acuity (size discrimination); tracking (motion discrimination); visual sensitivity (color); and contrast sensitivity functions (luminance contrast). In all cases, flashes from continuous-wave (CW) sources have proven more effective visually than pulsed (Q-switched) sources, when compared on peak-energy criteria (i.e., MPE), even though Q-switched lasers induce damage at lower energy doses. Additionally, the inherent safety of ultra-short laser pulses has been questioned. Past animal research has shown that, on the measures ...

Energy Technology Data Exchange (ETDEWEB)

The dwelling is equipped with solar collectors which heat the air circulating in the cavity walls and the space beneath the floors. The thermal aspects of such a building are described. Heat balance, losses, heating by the sun in different seasons are described. Different measures taken to reduce the energy losses are described.

Science.gov (United States)

The computer program CNHSPM is listed which predicts heat pump seasonal energy consumption (including defrost, cyclic degradation, and supplementary heat) using steady state rating point performance and binned weather data. (LEW)

Science.gov (United States)

The paper investigates the effect of the wall heat flux ratio on the local heat transfer augmentation in a square channel with two opposite in-line ribbed walls for Reynolds numbers from 15,000 to 80,000. The square channel composed of 10 isolated copper sections has a length-to-hydraulic diameter ratio of 20. The rib height-to-hydraulic diameter ratio is 0.0625 and the rib pitch-to-height ratio equals 10. Six ribbed side to smooth side wall heat flux ratios are studied for four rib orientations. The results show that the ribbed side wall heat transfer augmentation increases with increasing ribbed side to smooth side wall heat flux ratios, but the reverse is true for the smooth side wall heat transfer augmentation. The average heat transfer augmentation of the ribbed side and smooth side wall decreases slightly with increasing wall ...

Science.gov (United States)

In this paper, the authors first describe a fourth order accurate finite difference discretization for both the Laplace equation and the heat equation with Dirichlet boundary conditions on irregular domains. In the case of the heat equation, they use an i...

UK PubMed Central (United Kingdom)

In heat-shocked tomato cell cultures, cytoplasmic heat shock granules (HSGs) are tightly associated with a specific subset of mRNAs coding mainly for the untranslated control proteins. This messenger...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

The in-plane resistivity, in-plane absolute thermopower, and upper critical field measurements are reported for single-crystal samples of YNi{sub 2}B{sub 2}C and LuNi{sub 2}B{sub 2}C superconductors. The in-plane resistivity shows metallic behavior and varies approximately linearly with temperature near room temperature (RT) but shows nearly quadratic behavior in temperature at low temperatures. The YNi{sub 2}B{sub 2}C and LuNi{sub 2}B{sub 2}C single-crystal samples exhibit large transverse magnetoresistance ({approx}6{endash}8{percent} at 45 kOe) in the ab plane. The absolute thermopower S(T) is negative from RT to the superconducting transition temperature T{sub c}. Its magnitude at RT is a few times of the value for a typical good metal. S(T) is approximately linear in temperature between {approx}150 K and RT. Extrapolation to T=0 gives large intercepts (few {mu}V/K) for both samples suggesting the presence of a much larger {open_quotes}knee{close_quotes} than ...

International Nuclear Information System (INIS)

We present a high temperature heat oven with merits of conventional heat pipe oven and study ots thermal characteristics. The oven consists of stainless steel body and heating part of three layers of ceramic tubes. We obtained the maximum temperature of about 1350. deg. C at the center which was measured by thermocouple and infrared thermometer. And we compared the heating characteristics in the cases of external heating and no extent heating. It was applied to self diffraction experiment in the samarium gas which was one of the high melting point material.

International Nuclear Information System (INIS)

The effect of heat transfer is described from heat exchange tubes of a horizontal steam generator on the distribution of primary water to the individual tubes of the tube bundle. It is shown that in a broad interval of mass flow rates and lengths of heat exchange tubes, the simplified method of calcualtion, i.e., calculation of the distribution of primary water into heat exchange tubes neqlecting the changes of physical properties of water along the heat exchange tubes, will yield sufficiently accurate results. (author).

Energy Technology Data Exchange (ETDEWEB)

Heat-of-fusion storage materials for low temperature latent heat storage in the temperature range 0-120 C are reviewed. Organic and inorganic heat storage materials classified as paraffins, fatty acids, inorganic salt hydrates and eutectic compounds are considered. The melting and freezing behavior of the various substances is investigated using the techniques of Thermal Analysis and Differential Scanning Calorimetry. The importance of thermal cycling tests for establishing the long-term stability of the storage materials is discussed. Finally, some data pertaining to the corrosion compatibility of heat-of-fusion substances with conventional materials of construction is presented.

Science.gov (United States)

... Accession Number : ADD135317. Title : Workability and Heat Treatment Characteristics of Beta Titanium Alloy, Ti-15V-3Cr-3Sn-3Al,. ...

International Nuclear Information System (INIS)

The problem of fast wave plasma heating in reactor-torsatron at the ICRF range in scenarios, optimal for fusion reactor, is numerically studied.

Energy Technology Data Exchange (ETDEWEB)

The installation and performance of a water source heat pump in Minnesota are discussed. The operating cost was found to be higher than expected. (MHR)

Science.gov (United States)

heat transfer augmentation was found to increase with decreasing length scale but no optimum length scale was found. Heat transfer augmentation due to turbu- ...

Energy Technology Data Exchange (ETDEWEB)

Stochastic models for the simulation of global radiation are discussed. Thermal transients in the ground are analyzed. The performance of buried-pipe storage and a space heating system with long-term storage is described.

Energy Technology Data Exchange (ETDEWEB)

A numerical analysis is made of the unsteady flow and heat transfer characteristics of mixed convection in a vertical block-heated channel with and without installing an inclined plate above an upstream block. Parameter studies including the inclined plate angle, Reynolds number (ranging from 260 to 530), and Grashof number (in the range of 0--3,200,000) on heat transfer performance have been explored in detail. The results show that the installation of an inclined plate in the vertical block-heated channel can effectively augment the blocks` heat transfer performance in the channel. This can be applied to heat exchangers.

Science.gov (United States)

Fundamental study of heat transfer augmentation of tube inside surface by cascade smooth surface-turbulence promoters

Energy Technology Data Exchange (ETDEWEB)

The invention concerns a device for the energy-saving heating of fuel in the supply pipe to an internal combustion engine to regain energy from the fuel itself, particularly but not exclusively for a Diesel engine. A part of the quantity of heat added to the fuel between the tank and the injection nozzles is given up by excess fuel not to the tank, but to the fuel lifted upstream of the injection pump. The device is characterised by the fact that it has a heat exchanger, which absorbs heat from the fuel at the level of the injection pump or upstream of it, and takes this to the fuel above the injection pump. The heat exchanger is preferably mounted upstream of a filter and close to it. A bridging pipe, which may be integrated in the heat exchanger, permits the heat exchanger to be short-circuited depending on the fuel temperature.

Science.gov (United States)

Eninger, J. E.: "Menisci Coalesence as a Mechanism for Venting Noncondensible. Gas From Heat-Pipe Arteries", AIAA Paper No. 74-748. ...

Science.gov (United States)

... roughness. Since T u'v' and q v'"F the heat transfer augmentation is the square root of the skin friction augmentation: - 1/2 (( St - ,Cf 0 ...

International Nuclear Information System (INIS)

A statistical survey is conducted of air pollution in the city of Rome (Italy) due to conventional building space heating systems burning fossil fuels. The survey identifies the annual consumption of the different fuels and the relative amounts of the various pollutants released into the atmosphere by the heating plants, e.g., sulfur and nitrogen oxides, carbon monoxide, etc. Comparisons are then made between the ratios of urban heating plant air pollutants produced per tonne of fuel employed and those for ENEL (Italian National Electricity Board) coal, oil and natural gas fired power plants, in order to demonstrate the better environmental performances of the utility operated energy plants. The building space heating system energy consumption and pollution data are then used in a cost benefit analysis favouring the retrofitting of conventional heating systems with ...

Science.gov (United States)

The authors solve the two-dimensional stefan problem of solidification in a half-space, where the heat flux at the wall is a slightly varying function of positioning along the wall, by means of a large Stefan number approximation (which turns out to be equivalent to a small time solution), and then by means of the Heat Balance Integral Method, which is valid for all time, and which agrees with the large Stefan number solution for small times. A representative solution is given for a particular form of the heat flux perturbation.

International Nuclear Information System (INIS)

Short communication.

KoreaScience (Korea)

Full Text Available

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Science.gov (United States)

The thermal evolution predicted by current models of the superfluid-crust interaction is noted to

Science.gov (United States)

Not Available

UK PubMed Central (United Kingdom)

Long-term heat acclimation (AC, 30d/34°C) is a phenotypic adaptation leading to increased thermotolerance during heat stress (HS, 2 h 41°C). AC also renders protection against...Full Text Available

International Nuclear Information System (INIS)

The heat transfer augmentation is reviewed in view of high temperature heat exchangers illuminating the contribution of radiative heat transfer. A number of means and/or devices are presented as well as the sophisticated concept which will be promoted to the extended applications in matured industries such as iron and steel, oir refinery, petro-chemical. It should be emphasized that the more creative and innovatory technology has to be promoted in order to stimulate and refresh the foregoing industries, recognizing the increasing importance of the energy resources.

UK PubMed Central (United Kingdom)

Chinese hamster lung fibroblasts V79 cells were treated with heat stress for 4 weeks with short duration (15 min) heat shock every alternate day in culture. It was observed that Hsp...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

Apparent molar heat capacities for KI[sub 3](aq) were determined from flow-microcalorimetric measurements of KI(aq) solutions containing dissolved iodine. From these, the conventional partial molar heat capacity C[sub p,2][sup [infinity

Energy Technology Data Exchange (ETDEWEB)

This 2001 edition of the guide to UK renewable energy companies examines the geothermal heat pump sector, and discusses the technology involved, installations of geothermal heat pumps, the activity in the UK market with increased interest in UK geothermal heat pump products from abroad, and developments in the building sector. The UK government's increased support for the industry including its sponsorship of the Affordable Warmth programme, and the future potential of ground source systems are discussed.

Energy Technology Data Exchange (ETDEWEB)

Ground water ranging in temperature from only 38/sup 0/ to 140/sup 0/F can supply a considerable amount of heat energy when couple with a geothermal or ground-water heat pump. The heat pump's method of operation is examined as well as its performance characteristics. (MHR)

Energy Technology Data Exchange (ETDEWEB)

Experimental investigation was carried out for friction factor and heat transfer coefficient in the case of a rotating tube with a twisted-tape insert for heat transfer augmentation. The data obtained were compared with existing data for a stationary tube with a twisted-tape insert. It has been observed that the enhancement in heat transfer offsets the rise in friction factor due to rotation, with respect to a plain tube under stationary conditions. A correlation has been proposed for the data obtained.

KoreaScience (Korea)

Full Text Available

KoreaScience (Korea)

Full Text Available

KoreaScience (Korea)

Full Text Available

KoreaScience (Korea)

Full Text Available

Science.gov (United States)

The present study numerically investigates the enhancement of forced convective heat transfer from a single circular cylinder embedded in a packed bed of spherical particles confined by two impermeable parallel plates. The heat transfer results from the heated cylinder, with and without the presence of a porous medium, are compared. The results show that the presence of the porous particles enhances the heat transfer from the cylinder; however, the significant heat transfer augmentation is produced at high Re due to the effect of thermal dispersion. In addition, the effect of Re on Nut is much greater than that of kr and Bi in the porous channel. It is also found that the %?p is much higher than %HTE producing from packing the empty channel.

CERN Document Server

We study the temporal evolution of coronal loops using data from the Solar X-ray Imager (SXI) on board of GOES-12. This instrument allows us to follow in detail the full lifetime of coronal loops. The observed light curves suggest three somewhat distinct evolutionary phases: rise, main, and decay. The durations and characteristic timescales of these phases are much longer than a cooling time and indicate that the loop-averaged heating rate increases slowly, reaches a maintenance level, and then decreases slowly. This suggests that a single heating mechanism operates for the entire lifetime of the loop. For monolithic loops, the loop-averaged heating rate is the intrinsic energy release rate of the heating mechanism. For loops that are bundles of impulsively heated strands, it is an indication of the frequency of occurrence of individual heating events, or ...

CERN Document Server

In order to describe quantum heat engines, here we systematically study isothermal and isochoric processes for quantum thermodynamic cycles. Based on these results the quantum versions of both the Carnot heat engine and the Otto heat engine are defined without ambiguities. We also study the properties of quantum Carnot and Otto heat engines in comparison with their classical counterparts. Relations and mappings between these two quantum heat engines are also investigated by considering their respective quantum thermodynamic processes. In addition, we discuss the role of Maxwell's demon in quantum thermodynamic cycles. We find that there is no violation of the second law, even in the existence of such a demon, when the demon is included correctly as part of the working substance of the heat engine.

International Nuclear Information System (INIS)

This experiment investigated the effects of free-stream turbulence intensity, length scale, Reynolds number, and leading-edge velocity gradient on stagnation-region heat transfer. Heat transfer was measured in the stagnation region of four models with elliptical leading edges downstream of five turbulence-generating grids. Stagnation-region heat transfer augmentation increased with decreasing length scale but an optimum scale was not found. A correlation was developed that fit heat transfer data for isotropic turbulence to within #+-#4 percent but did not predict data for anisotropic turbulence. Stagnation heat transfer augmentation caused by turbulence was unaffected by the velocity gradient. The data of other researchers compared well with the correlation. A method of predicting heat transfer downstream of the stagnation point was developed. 28 refs., 12 ...

Energy Technology Data Exchange (ETDEWEB)

This study reported on the performance of a passive solar radiant floor heating system designed for standard energy-saving farmhouses in northeast China. Weather data in the region was analyzed in terms of solar radiation, temperature, humidity and light levels. The heating characteristics of the building materials such as windows, doors, walls and roofs were also analyzed along with the indoor thermal environment of the farmhouse. The heating load was then calculated along with the size of the thermal storage element and the area of the collector element. The passive solar radiant floor heating system was designed for heating during the winter and cooling in summer. According to the results, the heating characteristics of the system have the potential to improve farming villages environment and the use of renewable energy.

British Library Electronic Table of Contents (United Kingdom)

Heat pipes, loop heat pipes (LHP), and capillary pumped loops (CPL) have already proven their potential to remove high heat fluxes from a small electronic device and transport the heat to a heat sink that is large enough to transfer it into the ambient air. We introduce a novel two-loop system similar in design to CPLs but with an additional buoyancy-driven fluid loop. Non-degassed methanol is used as a working fluid. Key benefits compared to LHPs and CPLs are easy filling procedure, easy startup, and the tolerance toward noncondensable gases in the fluid. The amount of fluid in the system can be varied over a broad range without affecting the heat transfer performance. Three different inverted-meniscus-type evaporators have been employed in this study. A maximum evaporator heat transfer r...

Energy Technology Data Exchange (ETDEWEB)

(Boiling site densities and heat-transfer coefficients have been measured for ethanol-water and ethanol-benzene mixtures at 1.01 bar for a heated vertical brass disk. A strong effect of composition on the boiling site density was observed, which was attributed to the nature of the activation of the boiling surface and mass diffusion effects. The boiling heat-transfer coefficient was found to decrease with increasin subcooling, but for the mixtures at a given level of subcooling the decrease was less than that for the single components and azeotropic mixtures.) The heat-transfer coefficient at a given heat flux was seen to be quite insensitive to the very large increase in boiling site density in comparing the pure water and the ethanol-water azeotrope results, leading one to question pool boiling models that predict heat-transfer rates on the basis of boiling ...

Energy Technology Data Exchange (ETDEWEB)

A metal matrix is inserted into a phase-change material to enhance the heat transfer during phase-change processes. The metal matrix tends to act like a heat transfer fin from the heated or cooled surface and to increase the effective thermal conductivity of the phase-change fluid. The scope of the study involves numerically modeling the heat transfer to and from constant-temperature cylindrical tubes surrounded by water during the freezing and melting processes. Comparisons of heat transfer with and without the metal matrix are made, with different porosities and densities of the metal matrix being examined. The results of this study are discussed in terms of the effectiveness of the metal matrix as a heat transfer enhancement device.