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Delay Time (delay + time)
Kinds of Delay Time Selected AbstractsDegradation of TCE with Iron: The Role of Competing Chromate and Nitrate ReductionGROUND WATER, Issue 3 2000Oliver Schlicker This study evaluates the potential of using granular iron metal for the abiotic removal of the organic ground water pollutant trichloroethene (TCE) in the presence of the common inorganic co-contaminants chromate and nitrate, respectively. Our long-term column experiments indicate a competitive process between TCE dechlorination and reductive transformation of chromate and nitrate, which is reflected in a significantly delayed onset of TCE dechlorination. Delay times and therefore the ranges of the nonreactive flowpaths increased with increasing experimental duration, resulting in a migration of the contaminants through the iron metal treatment zone. The present investigation also indicates that the calculated migration rates of TCE and the added cocontaminants chromate and nitrate are linearly related to the initial content of the cocontaminants. With an average pore water velocity of 0.6 m/d and a surface area concentration of 0.55 m2/mL in the column, the calculated migration rates varled between 0.10 cm/d and 5.86 cm/d. The particular similarity between the values of TCE migration and the migration of the strong oxidants chromate and nitrate and the long-term steady state of the TCE dechlorination in the absence of the chromate and nitrate indicates that these competitive transformations are the driving force for the gradual passivation of the granular iron due to the buildup of an electrically insulating Fe(III)-oxyhydroxide. Based on these passivation processes, general formulae were developed that allow a simplified approximation of breakthrough times for the contaminants TCE, chromate, and nitrate. [source] Application of a constant blood withdrawal method in equine exercise physiology studiesEQUINE VETERINARY JOURNAL, Issue 6 2001P. BARAGLI Summary The aim of the present study was to test a constant blood withdrawal method (CBWM) to collect blood samples from horses during treadmill exercise. CBWM was performed in 4 Standardbreds and 5 Haflinger horses. A peristaltic pump was used to control blood aspiration from an i.v. catheter via an extension line. Blood was collected using an automatic fractions collector, with a constant delay time between the drawing of blood and sample collection. Blood withdrawal using CBWM was made during a treadmill standardised exercise test (SET). A blood flow of 12 ml/min was used and samples collected every 60 s during the entire period of exercise. The volume of blood collected in each sample tube was 12.1 ± 0.2 ml, with a delay time of mean ± s.d. 25.3 ± 0.8 s. Plasma lactate kinetics based on measurement of lactate in each fraction showed an exponential increase during the first 13 min of exercise (10.5 min of SET and 2.5 min recovery). The peak plasma lactate concentration was observed between 2.5 and 5.5 min after the end of SET. CBWM permits the kinetics of lactate and other blood-borne variables to be studied over time. This method could be a valuable aid for use in studying equine exercise physiology. [source] Laser-induced breakdown spectroscopy for soil diagnosticsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2001J. Bublitz Summary Laser-optical measurements and fibre optics are potentially attractive tools for applications in soil science because of their great sensitivity and selectivity and their capabilities for on-line and in situ analysis. We have investigated laser-induced breakdown spectroscopy (LIBS) for the quantitative detection of metal ions on the surface of natural soil samples from two sites (Hohenschulen and Oderbruch, Germany). The LIBS technique allows the spatially resolved investigation of adsorption and desorption effects of ions in soil. A frequency doubled (532 nm) and Q-switched Nd:YAG laser with a pulse duration of 8 ns is focused on the soil surface and induces a plasma. Typical power densities are 150 mJ mm,2. The plasma emission is recorded in time and spectrally resolved by a gateable optical multichannel analyser (OMA). A delay time of about 500 ns between laser pulse and OMA gate was used to resolve single atomic and ionic spectral lines from the intense and spectrally broad light that is emitted by the plasma itself. The dependency of the LIBS signal of a single spectral line on the amount of water in the sample is investigated in detail. The results indicate that quenching of water in the plasma plume reduces the line intensities, while the interaction with aquatic colloids increases the intensity. The two processes compete with each other, and a non-linear correlation between measured line intensities and the amount of water in the sample is obtained. This is verified by a simple computer simulation and has to be taken into account for the quantitative interpretation of LIBS signals, e.g. when absolute concentrations are estimated. In the present investigation natural calcium concentrations <,2 ,g kg,1 were measured with the LIBS technique in the samples for the two test sites. In addition, measurements were made with dry and water-saturated BaCl2 mixed soil samples, and no significant difference in the detection limit for barium was obtained. [source] Contractile Properties, Fatigue and Recovery are not Influenced by Short-Term Creatine Supplementation in Human MuscleEXPERIMENTAL PHYSIOLOGY, Issue 4 2000J. M. Jakobi There have been several studies on the effect of short-term creatine (Cr) supplementation on exercise performance, but none have investigated both voluntary and stimulated muscle contractions in the same experiment. Fourteen moderately active young men (19-28 years) were randomly assigned, in a double blind manner, to either a creatine (Cr) or placebo (P) group. The subjects supplemented their regular diet 4 times a day for 5 days with either 5 g Cr + 5 g maltodextrin (Cr group), or 5 g maltodextrin (P group). Isometric maximal voluntary contraction (MVC), muscle activation, as assessed using the modified twitch interpolation technique, electrically stimulated contractile properties, electromyography (EMG), endurance time and recovery from fatigue were measured in the elbow flexors. The fatigue protocol involved both voluntary and stimulated contractions. Following supplementation there was a significant weight gain in the Cr group (1.0 kg), whereas the P group did not change. For each group, pre-supplementation measures were not significantly different from post-supplementation for MVC, twitch and tetanic tensions at rest, time to peak tension, half-relaxation time and contraction duration. Prior to Cr supplementation time to fatigue was 10 ± 4 min (mean ± S.E.M.) for both groups, and following supplementation there was a non-significant increase of 1 min in each group. MVC force, muscle activation, EMG, stimulated tensions and durations were similar for the Cr and P groups over the course of the fatigue protocol and did not change after supplementation. Furthermore, recovery of MVC, stimulated tensions and contractile speeds did not differ as a result of Cr supplementation. These results indicate that short-term Cr supplementation does not influence isometric elbow flexion force, muscle activation, stimulated contractile properties, or delay time to fatigue or improve recovery. [source] A new molecular tool for transgenic diatomsFEBS JOURNAL, Issue 13 2005Control of mRNA, protein biosynthesis by an inducible promoter, terminator cassette Research in diatom biology has entered the postgenomic era since the recent completion of the Thalassiosira pseudonana genome project. However, the molecular tools available for genetic manipulation of diatoms are still sparse, impeding the functional analysis of diatom genes in vivo. Here we describe the first method for inducible gene expression in transgenic diatoms. This method uses a DNA cassette containing both promoter (Pnr) and terminator (Tnr) elements derived from the nitrate reductase gene of the diatom Cylindrotheca fusiformis. By using green fluorescent protein (gfp) cDNA as a reporter gene, it is demonstrated that gene expression under the control of the Pnr/Tnr cassette is switched off when cells are grown in the presence of ammonium ions and becomes switched on within 4 h when cells are transferred to medium containing nitrate. Incubating cells in nitrogen-free medium switches on transcription of the gfp gene, yet gfp mRNA does not become translated into protein. This block on translation is released by the addition of nitrate, resulting in rapid onset of GFP production with a drastically reduced delay time of only 1 h. Altogether we have demonstrated that the Pnr/Tnr cassette enables inducible gene expression and control of both the level and timing of mRNA and protein expression in transgenic diatoms. [source] A Waveguide-Like Effect Observed in Multiwalled Carbon Nanotube BundlesADVANCED FUNCTIONAL MATERIALS, Issue 14 2010Shengyong Xu Abstract The delay time of nanosecond electromagnetic pulses is measured in multiwalled carbon nanotube (MWCNT) bundles and copper wires, with a length of up to 3,cm, as compared with that in standard coaxial cables of the same lengths. Under certain configurations, when the Cu core of a coaxial cable is replaced with a MWCNT bundle of the same length, the measured delay time of a pulsed signal is shortened. The difference between the delay time measured for a device with a Cu core and that of a device with a MWCNT bundle of the same length increases with the length of the samples. The results imply that, compared with Cu wires, MWCNT bundles may be more efficient in guiding the transmission of high-frequency signals along their longitudinal axis, showing a waveguide-like effect. [source] Flashing characteristics in a pipe downstream from a depressurizing tank and temperature fluctuation characteristics at a mixing tee junction with cold water injectionHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2003Koji Shiina Abstract The flashing characteristics in a pipe downstream from a depressurizing tank were experimentally and analytically investigated on the basis of the transient test and two-phase flow analysis. The following conclusions were obtained. (1) When the pressure margin of the pump inlet side and the distance to obtain an isothermal condition were sufficient, flashing phenomena did not occur in spite of the decreasing pressure. (2) When the ratio of the cold water injection flow rate to the hot water flow rate Mc/Mh increased, the peak distance of the water temperature fluctuation moved from L/D = 1 to 0, and the maximum water temperature fluctuation ratio was about 40% of the temperature difference between hot and cold water near the mixing tee junction. Because no problem occurred regarding the pipe material thermal fatigue, reliability of the mixing tee junction was assured. (3) Due to suppression of flashing phenomena of the mixing pipe system, the decision diagram on the flashing occurrence was obtained from the test and the analytical results, taking into consideration three factors: the depressurizing ratio in the tank; the cold water injection flow rate due to remaining subcooling; and the delay time of thermal mixing. The simplified analytical equation was used to decrease the cold water injection flow rate by the optimized pipe length between the mixing tee junction and the drain pump. The cold water injection flow rate was minimized when the pipe length was about 15 to 20 times the pipe inner diameter. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(5): 411,429, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10096 [source] Adaptive backstepping control for a class of time delay systems with nonlinear perturbationsINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 3 2008Chang-Chun Hua Abstract The sliding mode control method has been extensively employed to stabilize time delay systems with nonlinear perturbations. Although the resulting closed-loop systems have good transient and steady-state performances, the designed controllers are dependent on the time delays. But one knows that it is difficult to obtain the precise delay time in practical systems, especially when it is time varying. In this paper, we revisit the problem and use the backstepping method to construct the state feedback controller. First, a coordinate transformation is used to obtain a cascade time delay system. Then, a linear virtual control law is designed for the first subsystem. The memoryless controller is further constructed based on adaptive method for the second subsystem with the uncertainties bounded by linear function. By choosing new Lyapunov,Krasovskii functional, we show that the system state converges to zero asymptotically. Via the proposed approach, we also discuss the case that the uncertainties are bounded by nonlinear functions. Finally, simulations are done to verify the effectiveness of the main results obtained. Copyright © 2007 John Wiley & Sons, Ltd. [source] Automatic characterization of ignition processes with machine learning clustering techniquesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 10 2006Edward S. Blurock Machine learning clustering techniques are used to characterize and, after the training phase, to identify phases within an ignition process. For the ethanol mechanism used in this paper, four physically identifiable phases were found and characterized: the initiation phase, preignition phase, ignition phase, and the postignition phase. The clustering is done with respect to fuzzy logic predicates identifying the maxima, minima, and inflection points of the species profiles. The cluster descriptions characterize the phases found and are in human interpretable form. In addition, these descriptions are powerful enough to be used to predict the phase structure under new conditions. Cluster phases were calculated for the ethanol mechanism at an equivalence ratio of 0.5, a pressure of 3.3 bar, and the temperatures 1200, 1300, 1400, and 1500 K. The resulting cluster phase descriptions were then successfully used to predict the phase structure and ignition delay times for other temperatures in the range from 1200 to 1500 K. The effect of different fuzzy logic predicate profile descriptions is studied to emphasize that the boundaries of some phases, specifically that between the preignition and the ignition phase, are a matter of what the modeler considers important. The end of the ignition phase corresponds to the ignition delay time and was relatively independent of the predicate descriptions used to determine the phases. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 621,633, 2006 [source] Performance evaluation for asynchronous MC-CDMA systems with a symbol timing offsetINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 4 2009Myonghee Park Abstract This paper models a symbol timing offset (STO) with respect to the guard period and the maximum access delay time for asynchronous multicarrier-code division multiple access systems over frequency-selective multipath fading channels. Analytical derivation shows that STO causes desired signal power degradation and generates self-interferences. This effect of the STO on the average bit error rate (BER) and the effective signal-to-noise ratio (SNR) is evaluated using the semi-analytical method, and the approximated BER and the SNR loss caused by STO are then obtained as closed-form expressions. The tightness between the semi-analytical result and the approximated one is verified for the different STOs and SNRs. Furthermore, the derived analytical results are verified via Monte Carlo simulations. Copyright © 2008 John Wiley & Sons, Ltd. [source] Dynamic bandwidth recycle algorithm for OVSF,CDMA systemsINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2006Peng-Jung Wu Abstract This paper presents a dynamic bandwidth recycle algorithm in the downlink of a WCDMA system using orthogonal variable spreading factor codes (OVSF). It consists of a bandwidth recycle algorithm and a bandwidth reservation algorithm. The bandwidth recycle algorithm is used to recycle bandwidth from current serviced connections when the system does not have enough available bandwidth to support a bandwidth request. The bandwidth reservation algorithm is used to reduce transmission delay caused by suddenly increasing bandwidth requests. Four traffic classes, conversational, streaming, interactive, and background classes, defined by universal mobile telecommunication system (UMTS) are considered. Simulation results show that the bandwidth utilization and block rate are improved, the bandwidth guaranteed to conversational and streaming classes are protected, and the delay time of interactive and background classes are kept under an acceptable value even when the traffic load is heavy. Copyright © 2005 John Wiley & Sons, Ltd. [source] Factors affecting the formation of fingering in water-assisted injection-molded thermoplasticsADVANCES IN POLYMER TECHNOLOGY, Issue 2 2006Shih-Jung Liu Abstract Water-assisted injection-molding technology has received extensive attention in recent years, due to the lightweight of plastic parts, relatively low-resin cost per part, faster cycle time, and flexibility in the design and manufacture. However, there are still some unsolved problems that confound the overall success of this technology. One of these is the water "fingering" phenomenon, in which the water bubbles penetrate outside designed water channels and form finger-shape branches. This study has investigated the effects of various processing parameters on the formation of fingering in water-assisted injection-molded thermoplastic parts. Both amorphous and semicrystalline polymers were used to mold the parts. The influence of water channel geometry, including aspect ratio and fillet geometry, on the fingering was also investigated. It was found that water-assisted injection-molded amorphous materials gave less fingering, while molded semicrystalline parts gave more fingering when compared to those molded by gas-assisted injection molding. For the water channels used in this study, the channels with a rib on the top produced parts with the least water fingering. Water fingering in molded parts decreases with the height-to-thickness ratio of the channels. The water pressure, water injection delay time and short-shot size were found to be the principal parameters affecting the formation of water fingering. In addition, a numerical simulation based on the transient heat conduction model was also carried out to help better explain the mechanism for the formation of fingering in water-assisted injection-molded thermoplastics. © 2006 Wiley Periodicals, Inc. Adv Polym Techn 25: 98,108, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20062 [source] Influence of processing conditions and part design on the gas-assisted injection molding processADVANCES IN POLYMER TECHNOLOGY, Issue 4 2001Nan-Shing Ong Gas-assisted injection molding has been developed to solve the problems that the conventional injection molding process is not able to. It is believed that the new process is able to produce final parts with higher quality at a more effective cost. Warpage and sink marks are reduced and there is material-savings to be reaped. This research aims to investigate some of the processing parameters that come with this new process. They include shot size, gas delay time, gas pressure, and melt temperature. The influence of part design is also looked into. Five designs were used in the research and compared. The responses evaluated include gas bubble length, residual wall thickness, bending strength, warpage, and fingering. © 2001 John Wiley & Sons, Inc. Adv Polym Techn 20: 270,280, 2001 [source] Visualization study and analysis on preform growth in polyethylene terephthalate stretch blow moldingJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Han-Xiong Huang Abstract In stretch blow molding (SBM) process, the preform growth during the stretching and blowing is critical to the thickness distribution and properties of the final bottle. Whereas the thickness distribution is one of the most important criteria in the production of bottles. So this work focused on the polyethylene terephthalate (PET) preform growth using a transparent mold, through which the instantaneous images of the preform in the stretching and blowing stage were captured. By changing the delay time of the preblow, the three preform growth types, referred to as dolphin, sandpile, and two-bubble, were observed. The longitudinal and hoop stresses acting on the preform segment during the stretching and blowing were analyzed. Two parameters, on which the longitudinal and hoop stresses depend, respectively, were defined. Then combining the geometry and sizes of the preform, the stresses and temperature distribution on it, and the stress,strain curves of the PET material used, the cause for different preform growth types was systematically analyzed. On the basis of preform growth types, the thickness distributions of the bottles obtained under different delay times of the preblow were explained. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 564,573, 2007 [source] WATER ACTIVITY AND THE INACTIVATION OF ENTEROBACTER CLOACAE INOCULATED IN CHOCOLATE LIQUOR AND A MODEL SYSTEM BY PULSED ELECTRIC FIELD TREATMENTJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5 2002S. MI Effects of water activity (aw) on the inactivation of Enterobacter cloacae inoculated in chocolate liquor and in a model system of 0.1% (w/v) peptone water and glycerol by pulsed electric field (PEF) treatment were investigated. An electric field strength of 24.5 kV/cm, a total treatment time of 320 ,s, a pulse duration time of 4 ,s, a pulse delay time of 15 ,s, and a pulse cycle time of 15 s were selected for PEF treatment. The inactivation ofE. cloacae by PEF increased significantly as aw increased (P < 0. 05). As aw of chocolate liquor increased from 0.48 to 0.89, the log reduction of E. cloacae increased from 0.1 to 1.3. The measured temperature change inside the PEF treatment chamber was 0.4C when the log reduction was 1. 3. Similarly, as aw increased from 0. 51 to 0.91 in the model system, the log reduction increased from 0.4 to 1.3. E. cloacae surviving a low aw environment had high resistance to PEF. PEF inactivated E. cloacae in the chocolate liquor with aw of 0.85 by 1 log at O h incubation. However, the log reduction was only 0.1 when PEF treatment was applied to E. cloacae which was incubated for 2 h in the chocolate liquor with aw of 0.85 before PEF treatment. E. cloacae surviving the low aw environment might have resistance not only to the low aw but also to PEF. The resistance to low aw environment may need to be considered when the inactivation of microorganisms by PEF is evaluated. [source] Ultrasonic processing of suspensions of hematite nanopowder stabilized with sodium polyacrylate,AICHE JOURNAL, Issue 11 2009P. Ding Abstract The effect of power input, solid content, surfactant concentration, and pH on the kinetics of wet deagglomeration of hematite nanopowder in ultrasonic comminution device and on the rheology of resulting suspensions has been investigated and compared with the kinetics of deagglomeration and rheology of the suspensions of goethite nanopowder. It has been found that the main mechanisms are fragmentation and erosion, which leads to bimodal transient size distributions of aggregates. Fragmentation of large aggregates starts after certain delay time but erosion of nanoparticles starts from very beginning of processing. Deaggregation of hematite nanopowder is only possible in the presence of surfactant, but increase of concentration of surfactant above certain critical value does not affect kinetics of deagglomeration. The increase of solid concentration up to 20 w/w% reduces the amount of energy necessary for deagglomeration of unit mass of the powder. Effect of pH on the kinetics of deagglomeration and the morphology/rheology of the resulting suspensions is discussed. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Laser desorption/ionization techniques in the characterization of high molecular weight oil fractions.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 9 2006Part 1: asphaltenes Abstract The molecular weight distribution of the asphaltene fractions of two types of crude oils from two different Italian fields (samples 1 and 2) was investigated. The analytical tools used to perform these analyses were matrix assisted laser desorption ionization (MALDI) and laser desorption ionization (LDI) mass spectrometry. After observing that the use of the matrix (as well as the addition of Ag+) did not improve the quality of the data compared to that obtained in LDI conditions, all further measurements were performed with the latter technique. Operating under usual conditions of laser power and delay time, a very low resolution was observed, showing only macroscopic differences between the two samples in the molecular weight distribution of the different components. An accurate study on the possible reasons of this undesirable behavior indicates that it can originate from space charge phenomena occurring either in the ion source region or during the flight. A valid parameterization of the delay time and the laser power allowed higher quality spectra to be obtained. Surface-enhanced laser desorption ionization (SELDI) measurements were also performed using normal phase (silica) as the sample holder surface. Under these conditions, better results are obtained, proving that the sample,surface interaction is important to achieve, by means of laser irradiation, a homogeneous set of product ions. Both asphaltene samples were fractionated in five subfractions by gel-permeation chromatography (GPC) to obtain a better separation of the molecular weight distributions; the related spectra confirmed these findings. By using different approaches, relevant and reproducible differences between the asphaltene fractions of the two oil samples were observed. Copyright © 2006 John Wiley & Sons, Ltd. [source] How do waiting times affect radiation dose fractionation schedules?JOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 4 2000Conrade Iv Franklin SUMMARY The purpose of the present paper was to evaluate the changing patterns of dose prescription at the Queensland Radium Institute from 1995 to 1998 inclusive. Data were analysed from the treatment files collected on each patient and these were compared with data on delay time. There has been an increased use of shorter fractionation schedules in the period studied. Paradoxically, radical treatments have become longer. The average number of fractions for all patients was 17.4 and for palliative treatments it was 7.4. The monthly delay varied from 0 to 22 working days and the average was 7 working days. When fraction number was compared to treatment delay, there was a negative linear correlation (R = ,0.25). The correlation was stronger (R = ,0.467) when palliative treatments were compared, indicating that clinicians were more prepared to alter palliative treatments in the presence of a treatment delay than curative ones. [source] A study of thunderstorm-induced delays at Frankfurt Airport, GermanyMETEOROLOGICAL APPLICATIONS, Issue 1 2003M Sasse It is a well-known fact that adverse weather significantly influences the safety and operating efficiency of air traffic, particularly in the terminal area. The unavoidable consequences of reduced operating efficiency are delays, diversions and cancellations of flights. In this paper the impact of thunderstorms on landing aircraft at Frankfurt Airport (Germany) during 1997 and 1998 is analysed. Thunderstorms are among the major weather phenomena affecting airport operations. Weather and operating conditions permitting, Frankfurt Airport is operated at more than 100% of its nominal capacity, which in turn lowers the actual capacity during periods of adverse weather. To the authors' knowledge this is the first quantitative study of weather impact on aviation in Germany. To identify thunderstorms as the unambiguous cause of delays, days without thunderstorms were used for reference and the difference in delay time was determined. The study shows that in 1997 thunderstorms increased the accumulated regular delay time by a factor of 6.3 and in 1998 by a factor of 1.1. On average, a thunderstorm typically caused about 740 delay minutes in addition to the 280 regular delay minutes for a sum of 100 arriving aircraft within four hours of average impact time. Copyright © 2003 Royal Meteorological Society [source] Over 55 A, 800 V high power AlGaN/GaN HFETs for power switching applicationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2007Nariaki Ikeda Abstract We developed new ohmic electrodes combined with an Al-silicide and a molybdenum for AlGaN/GaN HFETs to realize a high power switching application. As a result, the maximum drain current of the HFET was over 55 A and the breakdown voltage was about 800 V. The specific on-state resistance of the HFET was smaller than that of a Si Cool MOSFET. Furthermore, we examined the dynamic characteristics. The turn-off and turn-on delay time were 14.8 nsec. and 8.4 nsec. at the condition of 100 V, respectively. These values were considerbly smaller compared with those of Si Cool MOSFETs. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The evolution of the electric field in an optically excited semiconductor superlatticePHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2005Alvydas Lisauskas Abstract We report on time-resolved photocurrent spectroscopy of an intrinsic GaAs/Al0.3Ga0.7As superlattice subsequent to femtosecond optical excitation. Information on the spatio-temporal evolution of the densities of electrons and holes and on the internal electric field is obtained by tracing Wannier-Stark photocurrent spectra as a function of delay time for various bias fields and pump excitation intensities. The experimental results are supplemented by simulations. We employ the combined information to define the conditions to be met for succesful pump-probe Bloch gain experiments. In particular, we find that field screening sets on upper limit for the carrier density of 1016 cm,3, and that the time window during which gain should be found is defined by the duration of the sweep-out of the optically injected electrons from the superlattice which occurs within about 10 ps after excitation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Polymer,nanofiller prepared by high-energy ball milling and high velocity cold compactionPOLYMER COMPOSITES, Issue 3 2008Bruska Azhdar High-energy ball milling using comilling in a solid state by low-temperature mechanical alloying to prepare nickel-ferrite (NiFe2O4) nanopowders and ultrafine poly(methyl methacrylate) (PMMA), dispersing nanoparticles in a polymer matrix, and a uniaxial high-velocity cold compaction process using a cylindrical, hardened steel die and a new technique with relaxation assists have been studied. The focus has been on the particle size distributions of the nanocomposite powder during the milling and on the surface morphology of the nanocomposite-compacted materials after compaction with and without relaxation assists. Experimental results for different milling systems are presented showing the effects of milling time and material ratio. It was found that a longer mixing time give a higher degree of dispersion of the nanopowder on the PMMA particle surfaces. Furthermore, with increasing content of NiFe2O4 nanopowder, the reduction of the particle size was more effective. Different postcompacting profiles, i.e. different energy distributions between the upper and lower parts of the compacted powder bed, lead to different movements of the various particles and particle layers. Uniformity, homogeneity, and densification on the surfaces in the compacted powder are influenced by the postcompacting magnitude and direction. It was found that the relaxation assist device leads to an improvement in the polymer powder compaction process by reducing the expansion of the compacted volume and by reducing the different opposite velocities, giving the compacted composite bed a more homogeneous opposite velocity during the decompacting stage and reducing the delay time between the successive pressure waves. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers [source] The occurrence of surface roughness in gas assist injection molded nylon compositesPOLYMER COMPOSITES, Issue 2 2000Shih-Jung Liu Gas assist injection molding has increasingly become an important industrial process because of its tremendous flexibility in the design and manufacture of plastic parts. However, there are some unsolved problems that limit the overall success of this technique. The purpose of this report was to study the surface roughness phenomenon occurring in gas assist injection molded thermoplastic composities. The materials used were 15 % and 35% glass-fiber filled nylon-6 composites. Experiments were carried out on an 80-ton injection molding machine equipped with a high-pressure nitrogen-gas injection unit. Two "float-shape" axisymmetric cavities were used. After molding, the surface quality of molded parts was measured by a roughness meter. Various processing variables were studied in terms of their influence on formation of surface roughness: melt temperature, mold temperature, melt filling speed, short-shot size, gas pressure, and gas injection delay time. Scanning electronic microscopy was also employed to characterize the composites. It was found that the surface roughness results mainly from the exposure of glass fiber in the matrix. The jetting and irregular flows of the polymer melt during the filling process might be factors causing the fiber exposure. [source] Water-protein interactions in the molten-globule state of carbonic anhydrase b: An NMR spin-diffusion studyPROTEIN SCIENCE, Issue 8 2000Victor P. Kutyshenko Abstract We have used the homonuclear Overhauser effect (NOE) to characterize a model protein: carbonic anhydrase B. We have obtained NOE difference spectra for this protein, centering the on-resonance signals either at the methyl-proton or at the water-proton signals. The spin-diffusion spectra obtained as a function of protein concentration and temperature provide direct evidence of much greater protein,water interaction in the molten-globule state than in the native and denatured states. Furthermore, although the protein loses its gross tertiary structure in both the molten-globule and denatured states, it remains almost as compact in its molten-globule state as it is in the native state. The spin-diffusion spectra, obtained as a function of a variable delay time after the saturation pulse, allowed us to measure the relaxation times of several types of proton in the solution. These spectra contain enough information to distinguish between those water molecules solvating the protein and the free ones present as bulk water. [source] Production of Phytophthora infestans oospores in planta and inoculum potential of in vitro produced oospores under temperate highlands and subtropical plains of IndiaANNALS OF APPLIED BIOLOGY, Issue 3 2004B P SINGH Summary High moisture content of the host tissue ( 88%) and low ambient r.h. (50-54%) favoured oospore formation under controlled environments. It took 14,16 days for oospores to develop; thereafter the number of oospores increased with time and decreased with moisture content of host tissue. High ambient r.h. (> 80%) did not favour oospore formation under field or controlled conditions. Oospore formation was detected in inoculated plants grown in the field when the ambient r.h. declined to 74% and moisture content of host tissue decreased to 83.7,85.6%. It took 8 days (cv. Kufri Chandramukhi) to 13 days (cv. Kufri Jyoti and Kufri Badshah) for oospores to develop. Cultivars also differed in their response to oospore production, cv. Kufri Chandramukhi being more responsive (4800 oospores g,1 f wt) than cv. Kufri Jyoti and Kufri Badshah (1320 and 390 oospores g,1 f wt respectively). Oospores produced in vitro remained viable when buried in soil in the temperate highlands of Himachal Pradesh and sub-tropical plains of Uttar Pradesh, India for more than 150 days, i.e. beginning of the next crop season. The oospores germinated and initiated late blight infection at the base of the stems after 21,30 days of incubation of the potato plants raised in oospore-infested soil. It took 2 days for newly formed oospores to germinate and this delay time increased to 75,77 days after 180-days burial. It took 15 days for their germination (47%) in soil extract as compared to 50 days in sterilised distilled water. [source] The Influence of Operational Protocol on the Fluid Dynamics in the 12 cc Penn State Pulsatile Pediatric Ventricular Assist Device: The Effect of End-Diastolic DelayARTIFICIAL ORGANS, Issue 4 2010Benjamin T. Cooper Abstract The success of adult ventricular assist devices (VADs), coupled with the high transplant waiting list mortality of infants (40%) has prompted Penn State to develop a pediatric version of the clinically successful adult device. Although the primary use of this device will be bridge-to-transplant, there has been sufficient clinical data to demonstrate the efficacy of VADs in a bridge-to-recovery setting. However, removing the patient from the device, a process known as weaning, demands operation of the device at a lower beat rate and concomitant increased risk for thromboembolism. Previous studies have shown that the interrelated flow characteristics necessary for the prevention of thrombosis in a pulsatile VAD are a strong inlet jet, a late diastolic recirculating flow, and a wall shear rate greater than 500/s. In an effort to develop a strong inlet jet and rotational flow pattern at a lower beat and flow rate, we have compressed diastole by altering the end-diastolic delay time (EDD). Particle image velocimetry was used to compare the flow fields and wall shear rates in the chamber of the 12 cc Penn State pulsatile pediatric VAD operated at 50 beats per minute using EDDs of 10, 50, and 100 ms. Although we expected the 100 ms EDD to have the best wall shear profiles, we found that the 50 ms EDD condition was superior to both the 10 and 100 EDD conditions, due to a longer sustained inlet jet. [source] Baroreflex Sensitivity of an Arterial Wall During Rotary Blood Pump AssistanceARTIFICIAL ORGANS, Issue 9 2009Tomoyuki Yambe Abstract It is well known that the baroreflex system is one of the most important indicators of the pathophysiology in hypertensive patients. We can check the sensitivity of the baroreflex by observing heart rate (HR) responses; however, there is no simple diagnostic method to measure the arterial behavior in the baroreflex system. Presently, we report the development of a method and associated hardware that enables the diagnosis of baroreflex sensitivity by measuring the responses of both the heart and the artery. In this system, the measurements are obtained by monitoring an electrocardiogram and a pulse wave recorded from the radial artery or fingertip. The arterial responses were measured in terms of the pulse wave velocity (PWV) calculated from the pulse wave transmission time (PTT) from the heart to the artery. In this system, the HR change corresponding to the blood pressure change in time series sequence was observed. Slope of the changes in blood pressure and HR indicated the sensitivity of the baroreflex system of the heart. This system could also measure the sensitivity of the baroreflex system of an artery. Changes in the PWV in response to the blood pressure changes were observed. Significant correlation was observed in the time sequence between blood pressure change and PWV change after calculating the delay time by cross-correlation. The slope of these parameter changes was easily obtained and it demonstrated the sensitivity of the baroreflex system of an artery. We evaluated this method in animal experiments using rotary blood pump (RBP) with undulation pump ventricular assist device, and PTT elongation was observed in response to increased blood pressure with RBP assistance. Furthermore, when tested clinically, decreased sensitivity of the baroreflex system in hypertensive patients was observed. This system may be useful when we consider the ideal treatment and follow-up of patients with hypertension. [source] A deadlock prevention approach for a class of timed Petri nets using elementary siphons,ASIAN JOURNAL OF CONTROL, Issue 3 2010Jinwei Guo Abstract To solve the problem of deadlock prevention for timed Petri nets, an effective deadlock prevention policy based on elementary siphons is proposed in this paper. Without enumerating reachable markings, deadlock prevention is achieved by adding monitors for elementary siphons, increasing control depth variables when necessary, and removing implicit, liveness-restricted and redundant control places. The final supervisor is live. First, a timed Petri net is stretched into a stretched Petri net (SPN). Unchanging the system performance, each transition in the SPN has a unit delay time. Then the siphon-control-based approach is applied. Monitors computed according to the marking constraints are added to the SPN model to ensure all strict minimal siphons in the net invariant-controlled. A liveness-enforcing supervisor with simple structure can be obtained by reverting the SPN into a TdPN. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] Load control of ball mill by a high precision sampling fuzzy logic controller with self-optimizingASIAN JOURNAL OF CONTROL, Issue 6 2008Hui Cao Abstract A self-optimizing, high precision sampling fuzzy logic controller for keeping a ball mill circuit working stably and efficiently is proposed in this paper. The controller is based on fuzzy logic control strategy, and a fuzzy interpolation algorithm is presented to improve the control precision. The final output of the controller is calculated through the interpolation calculation of the observation and its neighboring antecedents, and the interpolation weight coefficients are obtained according to a fuzzy inference algorithm. In the proposed controller, the sampling control strategy is used to deal with a large delay time and a controller set value which can be adjusted by a self-optimizing algorithm, which can overcome the time-varying characteristic. Simulation results verify that the controller can control the ball mill circuit effectively and have higher control quality. Field service results also verify that the controller can successfully optimize the control of ball mill circuit. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source] Idiopathic generalized epilepsies: a follow-up study in a single-centerACTA NEUROLOGICA SCANDINAVICA, Issue 3 2010E. Kharazmi Kharazmi E, Peltola M, Fallah M, Keränen T, Peltola J. Idiopathic generalized epilepsies: a follow-up study in a single-center. Acta Neurol Scand: 122: 196,201. © 2009 The Authors Journal compilation © 2009 Blackwell Munksgaard. Objective,,, To characterize adult patients with idiopathic generalized epilepsies (IGEs) with precise evaluation and to assess factors related to refractoriness. Materials and methods,,, Hospital records of all our patients with IGEs (n = 128) were evaluated in 2005 and followed-up until 2008. Results,,, In 2005, 76% of patients were 1-year seizure-free. Seizure freedom increased to 82% during the 3-year follow-up. Seizure freedom was not significantly associated with age, age at diagnosis, epilepsy duration, exposure to inappropriate initial antiepileptic drug (AED), or delay time between starting initial AED and appropriate AED. Women constituted 78% of patients with merely provoked seizures. In 58% of women with recent seizure, one to two avoidable precipitating factors, such as lack of sleep, alcohol, and forgetting to take AED, were observed. In 2008, all patients with no medication, 91% of monotherapy patients, 60% of patients on two AED, and 14% of patients on three AED were seizure-free. Conclusions,,, Most of patients with IGEs can be successfully treated with monotherapy. Refractory seizures in some patients may be because of avoidable factors, especially in young women. [source] | ||||||||||||||||||||||||||||