Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: PULSE CHARACTERISTICS.
Дисертації з теми "PULSE CHARACTERISTICS"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "PULSE CHARACTERISTICS".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Turner, Kevin E. "Stiffness Characteristics of Airfoils Under Pulse Loading." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259113516.
Повний текст джерела
2
Liewkongsataporn, Wichit. "Characteristics of Pulsating Flows in a Pulse Combustor." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11542.
Повний текст джерелаАнотація:
Pulsating flows in a Helmholtz pulse combustor tailpipe were numerically simulated by a commercial CFD software package, FLUENT. The effects of ambient temperature on the characteristics of the pulsating tailpipe flows were studied. Two study cases, with high and low levels of ambient temperature, were simulated with compressible flow equations. An additional case, with high ambient temperature, was simulated with incompressible (temperature-dependent density) flow equations. Results showed that the effect of ambient temperature on the mean temperature profile in the tailpipe was limited to the distance where the ambient fluid traveled into the tailpipe during the period of flow reversal. In this region, the amplitude of mass flow rate oscillation significantly increased, due to higher density associated with low ambient temperature. The overall effects of cooler ambient temperature included an increase in mean pressure at the entrance of the tailpipe and a decrease in the magnitude of velocity amplitude profile along the tailpipe. Interestingly, the mean velocities along the tailpipe, even at the tailpipe exit, were not affected by the cooler ambient air. The mean velocity at the exit corresponded to the higher temperature of fresh fluid from upstream, which was not affected by the ambient temperature, driven out of the tailpipe in each oscillation cycle. The linear acoustic theory with appropriate assumptions could be used to calculate the magnitude of the profiles of velocity amplitude along the tailpipe as a fair approximation, at least for the study cases in this thesis.
3
Chang, Wing Chien Christopher. "Operational characteristics of an SCR-based pulse generating circuit." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/44535.
Повний текст джерелаАнотація:
Approved for public release; distribution is unlimitedA commercial off-the-shelf silicon controlled rectifier (SCR) was connected in series with a parallel RC load under DC bias to produce self-terminating voltage pulses. The physics underlying the switching mechanism of the SCR in such a circuit was investigated and the values of load resistance and capacitance varied to ascertain their role on the pulse-generating capability of the circuit. When pulsing was successfully achieved, a reverse recovery current was always present to return the SCR from its on state to its off state. In addition, the regenerative process responsible for turning the SCR is through the avalanche multiplication of charge carriers within the device. This appeared to be independent of the mode of triggering, either by increasing the DC bias or using a current at the gate. Significantly, pulsing was discovered to be sustainable for a specific range of RC values that depends on the SCR’s intrinsic turn-off time. Specifically, it was found that without making modifications to the SCR itself, the minimum dead time achievable between pulses was essentially the turn-off time of the SCR. The findings of the research will help to design optimum SCR-based circuits for pulse mode detection of light and ionizing radiation without external amplification circuitry.
4
Melia, Thomas. "Heat transfer characteristics of pulse combustors for gas turbine engines." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/10278.
Повний текст джерелаАнотація:
Conventional gas turbine combustors operate with a designed drop in pressure over the length of the device. This is desired in order to encourage mixing within the combustor. Compared to this, pulse pressure gain combustors are an alternative to the conventional combustor that produces an increase in static pressure between the inlet and exhaust of the device. The removal of the combustor pressure loss increases the efficiency of the combustion process by increasing the amount of work produced. Many types of pulsed pressure gain combustors exist. Of these, the valveless pulse combustor is the simplest featuring no moving parts. Whilst some research has been conducted into investigating the performance and workings of a pulse combustor, little has been conducted with the view of cooling the combustor. This has been the focus for the research contained herein. The research has focussed on establishing an understanding of the heat transfer characteristics within a pulse combustor tailpipe. This has involved experimental, analytical and computational research on a pulse combustor as well as on a cold-flow model of a pulse combustor tailpipe. This has enabled a study into the feasibility of cooling a pulse combustor to be conducted. The research has found that for conditions where the unsteady velocity amplitude within the cold-flow model of the pulse combustor tailpipe exceeds the mean velocity, an enhancement to the heat transfer coefficient is measured compared to the value expected in a similar non-oscillating flow. When there is no enhancement to the heat transfer coefficient, the cyclic variation of the unsteady heat flux follows the variation of the unsteady pressure within the device. However, at times of enhancement, the instantaneous heat flux structure shows a large deviation from the structure of the pressure field driving the oscillations. This change is shown to be caused by the reversal in the near-wall velocity and may indicate a mechanism for the enhancement in the mean heat flux. The cooling feasibility study showed that with further investigation, it may be possible to cool a pulse combustor within a gas turbine engine.
5
Mutsuura, Keita, Hirotaka Shimizu, Yasunobu Yokomizu, and Toshiro Matsumura. "Flux flow resistance in Bi2223 generated by pulse currents." IEEE, 2005. http://hdl.handle.net/2237/6789.
Повний текст джерела
6
Belshe, Elizabeth F. "Evaluating pulse-amplitude modulated fluorometry for landscape scale assessment of photosynthetic characteristics /." Electronic version (PDF), 2005. http://dl.uncw.edu/etd/2005/belshee/elizabethbelshe.pdf.
Повний текст джерела
7
Wolters, G. "Characteristics of wave impact induced pressure pulse propagation into cracks of coastal structures." Thesis, Queen's University Belfast, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419521.
Повний текст джерела
8
DeSantis, Dylan David. "CH3NH3PbBr3-xClx Device Characteristics for Gamma Spectroscopy with Simulations of Real Time Pulse Height Analysis." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1501878848404021.
Повний текст джерела
9
Clark, Jeffrey. "Double Negative Metamaterials in Dielectric Waveguide Configurations." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/28708.
Повний текст джерелаАнотація:
With the recent resurgence of interest in double negative (DNG) materials and the reported construction of a metamaterial with DNG characteristics, applications of these materials become feasible and examination of the behavior of systems and devices a potentially fruitful topic. The most promising area of research, upon inquiry into past work related to DNG materials, proves to be dielectric waveguides. The present investigation, then, focuses on the inclusion of DNG materials in various planar dielectric waveguide configurations. These waveguides involve a core region surrounded by various numbers of symmetrically-placed cladding layers.
The present investigation involves the review of the electromagnetic properties of DNG materials by a thorough analysis based on Maxwell's equations. The use of a negative index of refraction for these materials is justified. These results are then used to perform a frequency domain analysis of an N-layer formulation for dielectric waveguides which is general for any combination of DNG and double positive (DPS) materials. This N-layer formulation allows for the derivation of the characteristic equation, which relates the operating frequency and the propagation constant solutions, along with the cutoff conditions and field distributions. A causal material model which obeys the Kramers-Kronig relations and which is based on measurements of a realized metamaterial is studied and used in the investigation in order to produce realistic results.
The N-layer formulation is then applied to the three-layer (slab) waveguide and known results are reviewed. A new interpretation of intramodal degeneracy is given, whereby degenerate modes are split into two separate modes, one with positive phase velocity and one with negative phase velocity but both with a causal positive group (energy) velocity. Next, the formulation is applied to the five-layer waveguide. New behaviors are observed in this case which are not seen for the three-layer waveguide, including the return of the fundamental mode in some cases, whereas it is never present for the three-layer guide, the absence of certain higher-order modes in some situations and the appearance of new modes. Additionally, for some configurations the order of the even and odd modes in the DNG frequency range is found to be reversed from that of conventional waveguides.
The photonic crystal waveguide, which involves an infinite number of periodically placed cladding layers, is next studied using ray analysis, and a slight variation of the N-layer formulation is used to compare these results with those of the pseudo-photonic crystal waveguide. The pseudo-photonic crystal waveguide is identical to the photonic crystal waveguide with the exception that it has only large but finite number of layers. It is seen that the results of these two cases are similar for conventional modes, but the photonic crystal waveguide allows for new modes called photonic crystal modes which are inaccessible through conventional waveguides. Interesting phenomena such as mode crossings among the photonic crystal modes are observed and discussed.
Using the results from the frequency domain analysis of the five-layer waveguide, a Fourier transform technique is used to study pulse propagation in a waveguide containing DNG materials. A Gaussian pulse is launched in the waveguide over the frequency range covering a portion of the positive- and negative-phase-velocity fundamental transverse electric (TE) modes. Splitting of the input pulse into two separate pulses is observed, where both of these new pulses have a causal, positive energy velocity. The interpretation of intramodal degeneracy given in previous discussions is buttressed with evidence from this portion of the investigation, thus completing the analysis and bringing the present study to its conclusion.Ph. D.
10
Kalinichenko, A. I., V. E. Strel'nitskij, and V. V. Vasyliev. "Characteristics of DLC Coating Prepared by Pulse Biasing: Analysis in Model of Thermoelastic Peak of Ion." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35398.
Повний текст джерелаАнотація:
A mode of pulse biasing of DLC coating deposition is theoretically investigated. In this mode a deposited
ion flow of plasma with energy of E0 (20 200) eV is modified by superimposing of pulse potential
~ 1000 V. It was shown that intrinsic stress in a DLC coating can be decreased in several times without of
essential decrease of sp3-bonded carbon concentration compared with DLC made in stationary mode deposition
at E0 ion energy. A method of optimization of pulse mode parameters is proposed which is based on
analysis of location of thermoelastic peaks of ions on phase P, T-diagram of carbon.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35398
11
Poole, W. D. B. "Deriving planetary surface characteristics from orbiting laser altimeter pulse-widths on Mars, the Moon, and Earth." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1469361/.
Повний текст джерелаАнотація:
A set of equations linking the time-spread of a laser altimeter echo-profile, commonly known as the pulse-width, to the variance of topography within the pulse-footprint are tested by comparing pulse-width data to surface characteristics measured from high-resolution Digital Terrain Models. The research is motivated by the advent of high-resolution Digital Terrain Models over Mars, which enables the calibration of Mars Orbiter Laser Altimeter pulse-widths, and evolves to include lunar and terrestrial data in an attempt to validate the theory and develop new methods. Analysis of Mars Orbiter Laser Altimeter pulse-width data reveals mixed results. Over homo- geneously rough terrain, at kilometre-scales, these pulse-widths show some correlation to surface characteristics, once poor pulse data has been removed. However, where roughness is highly vari- able over short baselines, little correlation is observed, which is attributed to a mix of georeferencing errors and instrument methods. In a similar study, Lunar Orbiter Laser Altimeter pulse-widths are shown to produce only poor correlations with surface characteristics over local study sites. Instead, the observed correlations differ from orbit to orbit, with the majority of those used appearing to contain poor quality pulse- width data - attributed to the instrument methods - and only 14 % revealing correlations similar, or better, than observed over Mars. Finally, an examination of the relationship between footprint-scale surface characteristics and pulse-width estimates derived from smoothed Ice, Cloud, and land Elevation Satellite echo-profiles enables different pulse-width thresholds to be tested. Here, pulse-widths measured using a 10 % Peak Energy threshold are shown to produce greater correlations than those observed using the Mars Orbiter Laser Altimeter and the Lunar Orbiter Laser Altimeter data, which use a Full Width Half Maximum threshold. To conclude, pulse-widths can show strong correlations to surface roughness and slope within the pulse-footprint. However the assumption that detrended surface roughness can be derived by applying a slope contribution effect is shown to be unfounded. The principal recommendation is for future instruments to use a full echo-profile in estimating pulse-width values at a 10 % Peak Energy threshold, providing both efficient noise removal and a better correlated dataset.
12
Bandaru, Sreekanth. "Effect of high frequency pulse voltages and high temperature on the lifetime characteristics of magnet wires." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-05132004-135217.
Повний текст джерела
13
Esa, Mona Riza Mohd. "Temporal and Wavelet Characteristics of Initial Breakdown and Narrow Bipolar Pulses of Lightning Flashes." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-233671.
Повний текст джерелаАнотація:
Temporal and wavelet characteristics of initial breakdown pulses are meticulously studied especially during the earliest moment of lightning events. Any possible features during the earliest moment that may exist which lead to either negative cloud-to-ground (CG), positive cloud-to-ground, cloud or isolated breakdown flashes in Sweden are investigated. Moreover, the occurrence of narrow bipolar pulses (NBPs) as part of a CG event that has been recorded from tropical thunderstorms are also included in the investigation. Electric field signatures selected from a collection of waveforms recorded using fast electric field broadband antenna system installed in Uppsala, Sweden and Skudai, South Malaysia are then carefully analyzed in order to observe any similarities or/and differences of their features. Temporal analysis reveals that there are significant distinctions within the first 1 ms among different types of lightning flashes. It is found that a negative CG flash tends to radiate pulses more frequently than other flashes and a cloud flash tends to radiate shorter pulses than other flashes but less frequently when compared to negative CG and isolated breakdown flashes. Perhaps, the ionization process during the earliest moment of negative CG flashes is more rapid than other discharges. Using a wavelet transformation, it can be suggested that the first electric field pulse of both negative CG and cloud flashes experiences a more rapid and extensive ionization process compared to positive CG and isolated breakdown flashes. Further temporal analysis on NBPs found to occur as part of CG flashes show the disparity of the normalized electric field amplitude between the NBPs prior to and after the first return stroke. This indicates that the NBPs intensities were influenced by the return stroke events and they occurred in the same thundercloud. The similarity between the temporal characteristics of NBPs as part of CG flashes and isolated NBPs suggests that their breakdown mechanisms might be similar.
14
Hackard, Charles N. "Ignition characteristics for transient plasma ignition of ethylene/air and JP-10/air mixtures in a Pulse Detonation Engine." Thesis, Monterey California. Naval Postgraduate School, 2007. http://hdl.handle.net/10945/3169.
Повний текст джерелаАнотація:
The inlet mass flow, fuel injection profile, igniter characteristics, ignition delay, and operational frequency all dictate the success of a Pulse Detonation Engine (PDE). An optical sensor was developed and utilized for the observation of ignition zone characteristics over varying refresh conditions that showed decreasing ignition delay times when approaching marginally fuelrich reactant mixtures. A wide range of equivalence ratios for ethylene/air mixtures were explored and a limited number of JP-10/air mixtures. The JP-10/air fuel mixtures were nearly impossible to ignite at characteristic velocities greater than 35 m/s until a porous ignition shield was installed. The porous shield, surrounding the Transient Plasma Ignition (TPI) electrode, demonstrated the successful ignition at characteristic velocities up to 100 m/s for C2H4/air and 55 m/s for JP-10/air mixtures. The ignition shield slowed down a portion of the fuel-air mixture to increase the local residence time, allowing for more reliable ignition. The resulting combustion products proceeded to ignite the remaining fuel-air mixture. The ignition shield design appears to locally prevent a complete purge of the previous cycle's products, and a transient plasma discharge was still required for subsequent ignition to occur. This effect further reduced the observed ignition delay time in ethylene/air and JP-10/air fuel mixtures.
15
Inclan, Eric. "The Development of a Hybrid Optimization Algorithm for the Evaluation and Optimization of the Asynchronous Pulse Unit." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1582.
Повний текст джерелаАнотація:
The effectiveness of an optimization algorithm can be reduced to its ability to navigate an objective function’s topology. Hybrid optimization algorithms combine various optimization algorithms using a single meta-heuristic so that the hybrid algorithm is more robust, computationally efficient, and/or accurate than the individual algorithms it is made of. This thesis proposes a novel meta-heuristic that uses search vectors to select the constituent algorithm that is appropriate for a given objective function. The hybrid is shown to perform competitively against several existing hybrid and non-hybrid optimization algorithms over a set of three hundred test cases. This thesis also proposes a general framework for evaluating the effectiveness of hybrid optimization algorithms. Finally, this thesis presents an improved Method of Characteristics Code with novel boundary conditions, which better characterizes pipelines than previous codes. This code is coupled with the hybrid optimization algorithm in order to optimize the operation of real-world piston pumps.
16
Sygeryč, Daniel. "Optimalizace pulzního nabíjecího režimu olověného akumulátoru." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-221018.
Повний текст джерелаАнотація:
This thesis deals with pulse charging lead acid batteries. The theoretical part provides the basic electrochemical reactions that take place in the lead pack, then this section discusses important parameters of lead-acid battery, its structure and distribution of the various types depending on the application. The next section describes the theory of charging lead-acid battery. The practical part deals with constructing experimental cells, which are then tested. The subject of the experimental execution and optimization of pulse charging modes in order to find a suitable pulse mode, which reduces the duration of charging, while significantly shorten the life of lead-acid battery.
17
Weerasinghe, Hasitha C. "Electrical characterization of metal-to-insulator transition in iron silicide thin films on sillicone substrates." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001677.
Повний текст джерела
18
Schmidt, Peter H. (Peter Harrison). "The transfer characteristic of neurons in a pulse-code neural network." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14594.
Повний текст джерела
19
Garza, Ezra. "Pulsed Laser Deposition of Thin Film Heterostructures." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/459.
Повний текст джерелаАнотація:
Thin films of Strontium Ruthenate have been grown on Strontium Titanate and Lanthanum Aluminate (100) substrates by pulsed laser deposition. X-ray diffraction results show that the films grown on the Strontium Titanate are amorphous and polycrystalline on the Lanthanum Aluminate. Resistances versus temperature measurements show that the films exhibit semiconducting characteristics. In addition to the growth of Strontium Ruthenate thin films, multilayer heterostructures of Terfenol-D thin films on polycrystalline Lead Titanate thin films were grown by pulsed laser deposition. By using a novel experimental technique called magnetic field assisted piezoelectric force microscopy it is possible to investigate the magnetoelectric coupling between the electrostrictive Lead Titanate and magnetostrictive Terfenol-D thin film. Upon examination of the produced thin films the phase and amplitude components of the piezoelectric signal experience changes in response to an applied in-plane magnetic field. These changes provide experimental evidence of a magnetoelectric coupling between the Terfenol-D and Lead Titanate layers.
20
Hangya, Josef. "Účinky elektrického namáhání na vlastnosti elektroizolačních materiálů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-220958.
Повний текст джерелаАнотація:
Diploma thesis treat of effect of direct, alternate and pulse electrical stress on the properties surveyed electrical insulating material. Object of this experiment is crystalline high-density polystyrene QUINN PS. To monitor the stress is used the method of dielectric relaxation spectroscopy. Under examinations are the resultant dielectric spectra, which constitute the frequency dependencies of components of complex permitivity. Samples of the selected material are exposed to effects of alternate and pulse electrical stress on the different intensities of the electric field. In the direct field are then monitored absorption characteristics and specific volume resistance of the samples.
21
Corrêa, Fábio Ricardo Torrano. "Efeito dos parâmetros de pulso sobre as características geométricas e desempenho da soldagem com arame tubular autoprotegido e corrente pulsada /." Bauru : [s.n.], 2006. http://hdl.handle.net/11449/96497.
Повний текст джерелаАнотація:
Orientador: Yukio KobayashiBanca: Paulo César Rioli Duarte de Souza
Banca: Gilberto de Magalhães Bento Gonçalves
Resumo: No presente trabalho buscou-se determinar o comportamento das características geométricas do cordão da solda e o desempenho da soldagem, através do processo de soldagem com arame tubular autoprotegido e corrente pulsada. As características geométricas estudadas foram largura do cordão, penetração da solda e altura do reforço. Para definir o desempenho da soldagem analisou-se o rendimento de deposição e a taxa de deposição. Como metal de base utilizou-se o aço ABNT 1010 de espessura 6,35mm. O arame utilizado foi o AWS E71T-11 com diâmetro 1,1mm. A soldas foram realizadas por simples deposição, utilizando-se uma fonte de solda microprocessada, mantendo-se a velocidade de soldagem e a distancia tocha/peça constante. Durante o processo de soldagem os parâmetros de pulso analisados foram a corrente de pico (Ap), corrente de base (Ab), freqüência de pulso (F) e tempo de pico (Tp). Para coleta dos dados foi utilizada uma placa de aquisição de dados com interface a um microcomputador. De posse dos dados, foi aplicada a técnica de ANOVA, com o objetivo de identificar, quantificar e localizar a significância das dispersões. Verificou-se que a tensão média tem grande influência nas características geométricas do cordão de solda e de desempenho da soldagem. Para cada incremento de F provocou uma redução da largura do cordão de solda e aumento da penetração, altura do reforço, taxa de deposição e rendimento de deposição. O incremento Tp acarretou a formação de cordões mais largos, como também a redução na altura do reforço, penetração, taxa de deposição e rendimento de deposição. A variação de Ap não teve influência sobre largura do cordão, a altura do reforço, taxa de deposição e rendimento de deposição.
Abstract: In the present work one searched to determine the behavior of the geometric characteristics of the bead weld and the performance of the welding, through the process self-shielded flux cored arc welding and pulsed current. The studied geometric characteristics had been width of bead, penetration of the weld, height of the reinforcement. To define the performance of the welding one analyzed the deposition efficiency and the deposition rate. As metal base was used steel ABNT 1010 with thickness 6, 35 mm. The used wire was the AWS E71T-11 with diameter 1,1 mm. The welds had been carried through by simple deposition, using themselves a microprocessed weld power source, remaining constant it welding speed and the stick-out. During the welding process the analyzed parameters of pulse had been the peak current (Ap), base current (Ab), pulse frequency (F) and peak duration (Tp). For collection of the data a plate of acquisition of data with interface to a microcomputer was used. Of ownership of the data, the ANOVA technique was applied, with the objective to identify, to quantify and to locate the significance of the dispersions. It was verified that the mean voltage has great influence in the geometric characteristics of the bead weld and the performance of the welding. For each increment of F it provoked a reduction of the width of the bead weld and increase of the penetration, height of the reinforcement, deposition rate and deposition efficiency. The Tp increment caused the wider bead weld formation, as also the reduction in the height of the reinforcement, penetration, deposition rate and deposition efficiency. The variation of Ap did not have influence on width of the bead weld, the height of the reinforcement, deposition rate and deposition efficiency.
Mestre
22
Ipakchi, Hassan. "Development and performance characteristics of a family of gas-fired pulsed combustors." Thesis, Middlesex University, 2000. http://eprints.mdx.ac.uk/13374/.
Повний текст джерелаАнотація:
Two nominally 15, and 30 kW Helmholtz-type pulsed combustors were designed and constructed. These were bench mounted with the heat exchangers (i.e. combustion chamber and tailpipe) immersed in the water bath. Their design was based upon the design of a nominally 7.5 kW pulsed unit previously developed at Middlesex University. The design enabled the lengths of the combustion chambers to be varied so that various combustion chamber volumes could be achieved. This provided a new dimension to the study of pulsed combustors which is lacking in many reported works. It was found that the required input rates could be achieved by scaling up or down each combustion chamber dimensions linearly by a factor of 1.5, while maintaining the geometry identical. Tests showed that the present design of pulsed combustors can operate successfully at various input rates of mains natural gas (93 % methane) with a maximum turn-down ratio of 1.8:1. Results indicated that the three developed combustors would generally operate in the fuel-lean condition. Interestingly, these tests revealed that the amount of excess air reduced as the combustion chamber volume (CCV) was increased. Systematic investigation on the three developed combustors showed that the temperature within the combustor was principally controlled by the air-to-fuel ratio (A/F). Analysis of the average measured NOx concentrations at various operating conditions indicated that NOx emission in this type of pulsed combustor is principally controlled by combustion temperature with no significant influence of combustion chamber volume, tailpipe length or scale of the combustors except in so far as these influenced the A/F and hence the temperature within the combustor. The dominant role of temperature on NOx production from these combustors become more evident when nitrogen or argon was injected into the system resulting in reduced NOx emissions at a given A/F. Systematic analysis of data indicated that as the amount of diluent increased, the temperature within the combustor decreased. Almost all the NOx values recorded were in the form of NO which is believed to be as a result of the high flame temperature (typically above 1850K). The minimum recorded NOx value was 5 ppm at the upper limiting value of excess air ratio, λ ; importantly it was round that at these high A/F values there was no significant reduction in overall efficiency of the pulsed units, showing calculated values above 90%. Analysis of data indicated that combustion temperature is also a primary factor controlling CO emissions from the present design of pulsed combustors. CO concentrations exhibited U-shaped characteristics when plotted vs λ, showing maximum values at the lowest and highest λ values. By changing water bath temperature (WBT) and hence modifying heat losses to the combustion chamber wall, it was shown that the quenching of the combustion reactions and incomplete mixing of air and gas prior to combustion are contributing factors to CO formation in this type of pulsed combustor. The developed pulsed combustors were operated successfully with standard test gases. The composition and flame stability of these test gases were similar to the standard test gases G21 (incomplete combustion gas), G222 (light back gas) and G23 (flame lift gas). Analysis of the exhaust gas composition showed similar trends to those obtained when burning mains natural gas; as the heat input was increased, O2 levels decreased while CO2 and NOx emission levels increased. Similarly, CO concentrations showed U-shaped characteristics when plotted against firing rate. Measurements of peak pulsing pressure and frequency were used as a guide to operation and stability performance of the pulsed units. It was found that the operating frequency was a function of configuration of the combustors and temperature of the internal gases. Frequency of operation showed a reciprocal correlation with volume of combustion chamber and tailpipe length and increased as the heat input was increased. Pulsing pressure amplitude also was influenced by change of configuration of the combustors, increasing as the CCV and tailpipe length were decreased. Analysis of experimental data obtained at fixed configuration of the combustors showed that the peak pulsing pressure was a strong function of the heat release per cycle in the present design of pulsed combustors. A major drawback of the use of pulsating combustors is the high noise level which is associated with their operation. It was found that it is possible to reduce overall noise levels of the pulsed burners to acceptable values by configuring the system appropriately. This included the use of expansion chambers at the inlet and the exhaust outlet which reduced the overall noise levels to a minimum value of 65 dBA.
23
Péroumal, Armelle. "Caractérisation des fruits et de la pulpe de six accessions de Mammea americana : Aptitude à la transformation des fruits et caractérisation des composés phénoliques de la pulpe." Thesis, Antilles-Guyane, 2014. http://www.theses.fr/2014AGUY0702/document.
Повний текст джерелаАнотація:
Dans cette étude, nous nous sommes intéressés aux propriétés physiques et chimiques de six accessions de Mammea americana afin de pouvoir identifier les accessions les plus prometteuses pour la vente en frais ou la transformation. Nous avons également cherché à évaluer l’activité antioxydante de la pulpe, identifier et quantifier ses composés phénoliques et optimiser leur extraction à l’aide de la technique assistée par ultrasons.Nos résultats montrent que les accessions étudiées présentent des caractéristiques physiques, physico-chimiques et fonctionnelles significativement différentes. Pavé 11, Lézarde et Ti Jacques sont intéressants pour la vente en frais, en raison de leurs fruits sucrés avec une teneur élevée en caroténoïdes et composés phénoliques totaux. Sonson, Pavé 11 et Lézarde présentent une adaptabilité à la transformation. La composition polyphénolique de la pulpe déterminée par HPLC-DAD et UPLC-MS, a mis en évidence la présence d’acides phénoliques, de tanins condensés, de flavonols et flavanols dans nos échantillons. D’autre part, les tests d’activité antioxydante (DPPH et ORAC) révèlent que Ti jacques est l’extrait le plus actif. Un plan d’expérimentation a été mis en œuvre afin d’optimiser l’extraction des polyphénols à l’aide d’une technique d’extraction assistée par ultrasons. Les résultats montrent que l’extrait obtenu est riche en polyphénols et contient les mêmes teneurs en acides phénoliques et flavonols comparé à celui obtenu par la méthode conventionnelle. De plus, l’extrait obtenu à l’aide d’un solvant « vert » possède de bonnes propriétés organoleptiquesOur work focuses on the physical and chemical properties of six mamey apple cultivars in order to select elite cultivars suitable for food processing or as table fruit. The antioxidant activity of the fruit pulp, the identification and quantification of the polyphenols responsible for it, and ultrasound assisted extraction method were also investigated.According to our results, the postharvest routes for every cultivar could be different. Pavé 11, Lézarde and Ti Jacques were found to be good for consumption, giving sweeter fruits with high total phenolic and carotenoid contents. Sonson, pavé 11 and Lézarde had suitable characteristics for the manufacturing of mamey products. The polyphenolic composition of the pulp determined by HPLC-DAD and UPLC-MS showed the presence of phenolic acids, condensed tannins, flavonols and flavanols. The results of the antioxidant test (DPPH and ORAC) point out that the most antioxidant cultivar was Ti Jacques. The design and optimization of the ultrasound assisted extraction method has done for polyphenols extraction. The results showed that the polyphenols rich extract contains the same content of phenolic acids and flavonols in comparison to the conventional method. Additionally, the dry extract obtained with a “green” solvent, had good organoleptic properties
24
Höft, Hans [Verfasser]. "Characteristics of pulsed operated dielectric barrier discharges in molecular gas mixtures / Hans Höft." Greifswald : Universitätsbibliothek Greifswald, 2015. http://d-nb.info/1072434830/34.
Повний текст джерела
25
Lado, Beatrice H. "Characteristics of Listeria monocytogenes Important for Pulsed Electric Field Process Optimization." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1070169899.
Повний текст джерела
26
McGhee, Jason R. "Investigation of the acoustic source characteristics of high energy laser pulses models and experiment." Thesis, Monterey, Calif. : Naval Postgraduate School, 2008. http://bosun.nps.edu/uhtbin/hyperion-image.exe/08Jun%5FMcGhee.pdf.
Повний текст джерелаАнотація:
Thesis (M.S. in Engineering Acoustics)--Naval Postgraduate School, June 2008.Thesis Advisor(s): Kapolka, Daphne. "June 2008." Description based on title screen as viewed on August 26, 2008.. Includes bibliographical references (p. 71-72). Also available in print.
27
Jiang, Ge. "Preparation and Characteristics of Bi0.5Na0.5TiO3 based Lead-Free thin films by Pulsed Laser Deposition." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-247872.
Повний текст джерелаАнотація:
Lead-based piezoelectric materials, such as PbZrxTi1-xO3 (PZT), have attracted considerable attention and have been widely used in actuators, sensors and transducers due to their excellent electric properties. However, considering the toxicity of lead and its oxides, environmentally friendly lead-free piezoelectric materials are attracting more attention as potential replacements for PZT. Among them, Bi0.5Na0.5TiO3 (BNT)-based materials exhibit good electrical properties and electromechanical coupling response. In this work, the 0.97Bi0.5Na0.5TiO3-0.03BiAlO3 (BNTBA) thin films (~120 nm thickness) were successfully prepared using the pulsed laser deposition (PLD) method on Pt/TiO2/SiO2/Si substrates. The effects of substrate temperature, oxygen pressure, laser repetition rate, and post-annealing treatment were investigated. X-ray diffraction (XRD) and scanning electron microscope (SEM) are used to study the structure of the films and the ferroelectric and dielectric properties are measured. The results show that it is necessary to introduce excess sodium and bismuth to compensate for their evaporation in further thermal treatment. The values of remnant polarization increase from 8.7 μC/cm2 to 12.3 μC/cm2 with the introduction BiAlO3. The dielectric constant increases from 600-550 to 710-600 and the dielectric loss increases from 4.2% to 6.7% at higher frequency when the oxygen pressure increases from 20 Pa to 30 Pa.Blybaserade piezoelektriska material, såsom PbZrxTi1-xO3 (PZT), har väckt stor uppmärksamhet och har använts i stor utsträckning på grund av deras utmärkta elektriska egenskaper. Men med tanke på toxiciteten hos bly och dess oxider lockar miljövänliga blyfria piezoelektriska material mer uppmärksamhet från forskare som potentiella utbyten för PZT. Bland dem uppvisar Bi0.5Na0.5TiO3 (BNT) -baserade material bra elektriska egenskaper och elektromekanisk kopplingssvar. I detta arbete framställdes 0,97Bi0.5Na0.5TiO3-0.03BiAlO3 (BNTBA) tunna filmer (~ 120 nm tjocklek) med användning av pulserad laseravsättningsmetod på Pt / TiO2 / SiO2 / Si-substrat. Effekterna av substrattemperatur, syretryck, laserrepetitionshastighet och efterglödande behandling undersöktes. Röntgendiffraktions (XRD) och skanningelektronmikroskop (SEM) används för att studera filmens struktur och de ferroelektriska och dielektriska egenskaperna mäts. Resultaten visar att det är nödvändigt att införa överskott av natrium och vismut för att kompensera för deras avdunstning vid vidare termisk behandling. Värdena för återstående polarisation ökar från 8,7 μC / cm2 till 12,3 μC / cm2 med introduktionen BiAlO3. Den dielektriska konstanten ökar från 600-550 till 710-600 och den dielektriska förlusten ökar från 4,2% till 6,7% vid högre frekvens när syretrycket ökar från 20 Pa till 30 Pa.
28
Corrêa, Fábio Ricardo Torrano [UNESP]. "Efeito dos parâmetros de pulso sobre as características geométricas e desempenho da soldagem com arame tubular autoprotegido e corrente pulsada." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/96497.
Повний текст джерелаАнотація:
Made available in DSpace on 2014-06-11T19:28:21Z (GMT). No. of bitstreams: 0
Previous issue date: 2006-01-20Bitstream added on 2014-06-13T20:17:59Z : No. of bitstreams: 1
correa_frt_me_bauru.pdf: 1326371 bytes, checksum: a4dd5287d93dc0ae01a81f1278a10ffd (MD5)No presente trabalho buscou-se determinar o comportamento das características geométricas do cordão da solda e o desempenho da soldagem, através do processo de soldagem com arame tubular autoprotegido e corrente pulsada. As características geométricas estudadas foram largura do cordão, penetração da solda e altura do reforço. Para definir o desempenho da soldagem analisou-se o rendimento de deposição e a taxa de deposição. Como metal de base utilizou-se o aço ABNT 1010 de espessura 6,35mm. O arame utilizado foi o AWS E71T-11 com diâmetro 1,1mm. A soldas foram realizadas por simples deposição, utilizando-se uma fonte de solda microprocessada, mantendo-se a velocidade de soldagem e a distancia tocha/peça constante. Durante o processo de soldagem os parâmetros de pulso analisados foram a corrente de pico (Ap), corrente de base (Ab), freqüência de pulso (F) e tempo de pico (Tp). Para coleta dos dados foi utilizada uma placa de aquisição de dados com interface a um microcomputador. De posse dos dados, foi aplicada a técnica de ANOVA, com o objetivo de identificar, quantificar e localizar a significância das dispersões. Verificou-se que a tensão média tem grande influência nas características geométricas do cordão de solda e de desempenho da soldagem. Para cada incremento de F provocou uma redução da largura do cordão de solda e aumento da penetração, altura do reforço, taxa de deposição e rendimento de deposição. O incremento Tp acarretou a formação de cordões mais largos, como também a redução na altura do reforço, penetração, taxa de deposição e rendimento de deposição. A variação de Ap não teve influência sobre largura do cordão, a altura do reforço, taxa de deposição e rendimento de deposição.
In the present work one searched to determine the behavior of the geometric characteristics of the bead weld and the performance of the welding, through the process self-shielded flux cored arc welding and pulsed current. The studied geometric characteristics had been width of bead, penetration of the weld, height of the reinforcement. To define the performance of the welding one analyzed the deposition efficiency and the deposition rate. As metal base was used steel ABNT 1010 with thickness 6, 35 mm. The used wire was the AWS E71T-11 with diameter 1,1 mm. The welds had been carried through by simple deposition, using themselves a microprocessed weld power source, remaining constant it welding speed and the stick-out. During the welding process the analyzed parameters of pulse had been the peak current (Ap), base current (Ab), pulse frequency (F) and peak duration (Tp). For collection of the data a plate of acquisition of data with interface to a microcomputer was used. Of ownership of the data, the ANOVA technique was applied, with the objective to identify, to quantify and to locate the significance of the dispersions. It was verified that the mean voltage has great influence in the geometric characteristics of the bead weld and the performance of the welding. For each increment of F it provoked a reduction of the width of the bead weld and increase of the penetration, height of the reinforcement, deposition rate and deposition efficiency. The Tp increment caused the wider bead weld formation, as also the reduction in the height of the reinforcement, penetration, deposition rate and deposition efficiency. The variation of Ap did not have influence on width of the bead weld, the height of the reinforcement, deposition rate and deposition efficiency.
29
Hou, Jianbo. "Transport and Anisotropy inside Ionic Polymer Membranes." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/39540.
Повний текст джерелаАнотація:
Water and ion transport critically determine the performance of many functional materials and devices, from fuel cells to lithium ion batteries to soft mechanical actuators. This dissertation aims to address some fundamental issues regarding transport and anisotropy, structural heterogeneity and molecular interactions inside ionic polymers.
I first discuss a main deficiency of a standard protocol for calibrating high pulsed-field-gradient NMR. I show that high gradient calibration using low γ nuclei is not amenable to measurements on slow diffusing high γ nuclei. Then I employ NMR diffusometry to investigate transport and anisotropy for a series of ionic polymers, from poly(arylene ether sulfone) hydrophilic-hydrophobic multi-block copolymers to polymer blends to perfluorosulfonate random copolymers.
For the multi-block copolymers, NMR diffusion measurements yield diffusion anisotropy as a function of water uptake and block lengths. 2H NMR spectroscopy on absorbed D2O probes membrane alignment modes. These measurements also provide insights into average defect distributions.
For the blend membranes, we examine the impact of compatibilizer on their transport properties. An increase in compatibilizer significantly improves the membrane phase homogeneity confirmed by SEM and transport studies. Theories of diffusion in porous media yield changes in domain size and tortuosity that correspond to drastic changes in local restrictions to water diffusion among different blend membranes. NMR
relaxometry studies yield multi-component T1 values, which further probe structural heterogeneities on smaller scales than diffusion experiments.
For the random copolymer, the exploration of ion transport reveals inter-ionic associations of ionic liquids (ILs) modulated by hydration level and ionic medium. When ILs diffuse inside ionic polymers, isolated anions diffuse faster (â ¥ 4X) than cations at high hydration whereas ion associations result in substantially faster cation diffusion (â ¤ 3X) at low hydration inside membranes, revealing prevalent anionic aggregates.
Finally, I present the strategy and analytical protocol for studying ionomer membranes using ILs. The normal cation diffusion contrasts to the anomalous anion diffusion caused by local confinement structures inside the membranes, which vary drastically with temperature and hydration level. These structures correspond to a density variation of SO_3^- groups, which define a distribution of local electrical potentials that fluctuate with temperature and nature of ionic media.Ph. D.
30
Lopes, Monica Maria de Almeida. "Effects of pulsed light on metabolism and physico-chemical characteristics of "Tommy Atkins" mangoes during storage." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15180.
Повний текст джерелаАнотація:
CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel SuperiorThe pulsed light (PL) is a technology emergent used as abiotic stressor to increase the content of phytochemicals of fruits and vegetables. However, their effects vary depending on the cultivar, the dose hormetic, the mode of application of dose and the maturation stage of fruits. In this work, we start from the main hypothesis that changes in the metabolism of the fruits of mangoes treated with low doses of pulsed light would trigger responses that result in a positive impact on the content of phytochemicals, without any negative effect on the fruit quality parameters. This work was divided into three chapters. Chapter I is a literature review and state of the art of the main topics covered throughout the study. In the second chapter (experiment I), mangoes mature physiologically (maturation stage 3) were subjected to a hormetic dose of pulsed light 0.6 J cm-2 and analyzed after 7 days storage at 20 ÂC, for the physicochemical characteristics [soluble solid (SS), titratable acidity (TA), SS/TA ratio, overall appearance, color and firmness], enzymatic antioxidant metabolism [superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX)] and non-enzymatic [ascorbate, total carotenoids, total anthocyanins, yellow flavonoids, total phenolic, mangiferin content and total antioxidant activity], membrane integrity [lipid peroxidation (MDA), hydrogen peroxide content and electrolyte leakage], phenylalanine ammonia lyase activity (PAL), enzymes of enzymatic browning [polyphenoloxidase (PPO), peroxidase of guaiacol (GPOD) and activity of enzymes wall cell [pectinmethylesterase (PME) and polygalacturonase (PG)] and the influence of treatment on tissue histology. The activity of antioxidant enzymes such as catalase and superoxide dismutase was found to be substantially enhanced in both the epicarp and the mesocarp of fruits exposed to PL after 7 days at 20 ÂC. There were no differences in indicators of cell wall and membrane integrity such as MDA content suggesting that the PL-associated oxidative stress was effectively prevented by the enhanced activity of antioxidant enzymes after 7 days. Activities of cell wall enzymes were reduced after 7 days in the PL-treated fruits. Microscopic as well as macroscopic observations confirmed that PL-treated fruits were not damaged. We observed that contents in total carotenoids, in total phenolic, and, to a lesser extent, in vitamin C, were dramatically increased after 7 days, generally in both the epicarp and the mesocarp PL-treated resulting in fruits with high antioxidant capacity. Carotenoids increased 350% in treated-pulp at J7. The higher levels in phenolics in treated-peel (+97%) were associated with enhanced activity of PAL (+98%) and enhanced content in mangiferin (+42%). Although G-POD in the mesocarp and PPO in the epicarp increased 1268% and 22% respectively, after 7 days in the PL-treated fruits, we did not observe increases in browning. Was observed at the end of the experiment I an increase of phytochemicals in mangoes subjected to hormetic dose of 0.6 J cm-2 without negative changes in fruit quality. In the third chapter (experiment II), mangoes minimally processed (maturation stage 4) were subjected to four different treatments: control (not flashed), 1 pulse, 4 pulses, and 1 pulse (4 days) prior to storage at 6 ÂC in order to assess whether the mode of application of the different doses used could interfere on physiochemical variables [firmness, color, SS, loss weight and rate respiration] the bioactive compounds [ascorbate (AsA) and carotenoids] and total antioxidant activity by a storage period of 7 days at 6 ÂC. Samples flashed with 1 pulse during 4 alternated days (4 x 0.6 J cm-2 = 2.80 J cm-2) increased the total ascorbate (AsA) (~40% more than the control) at time 7 days but the cubes of mangoes are darker than treatment that received the same dose of 4 successive pulses (2.80 J cm-2). At end of storage fresh cut mangoes received 4 successive pulses exhibited a better quality in comparison to the other treatments that was associated a higher content carotenoid (0.894 mg g-1) and antioxidant activity (~145 μmol trolox 100 g-1). In conclusion, our data suggest that a hormetic dose of pulsed light can be used to increase concentrations of phytochemical compounds without negative effects on the quality criteria.
A luz pulsada (LP) à uma tecnologia emergente usada como estressor abiÃtico para aumentar o teor de fitoquÃmicos em frutos e vegetais. No entanto, seus efeitos variam dependendo da cultivar, da dose hormÃtica, do modo de aplicaÃÃo da dose e do estÃdio de maturaÃÃo do fruto. Neste trabalho, partimos da hipÃtese de que alteraÃÃes no metabolismo dos frutos de mangas tratadas por baixas doses de luz pulsada desencadeariam respostas que resultariam em um impacto positivo sobre o conteÃdo de fitoquÃmicos, sem qualquer efeito negativo sobre os parÃmetros de qualidade dos frutos. Este trabalho foi dividido em trÃs capÃtulos. O capÃtulo I trata de uma revisÃo de literatura e estado da arte dos principais tÃpicos abordados ao longo do estudo. No segundo capÃtulo (experimento I), mangas fisiologicamente maduras (estÃgio de maturaÃÃo 3) foram submetidas a uma dose de luz pulsada de 0,6 J cm-2 e analisadas decorridos 7 dias de armazenamento a 20 ÂC, quanto Ãs caracterÃsticas fisico-quÃmicas [sÃlidos solÃveis (SS), acidez titulÃvel (AT), relaÃÃo SS/AT, aparÃncia geral cor, firmeza], metabolismo antioxidante enzimÃtico [dismutase do superÃxido (SOD), catalase (CAT) e peroxidase do ascorbato (APX)] e nÃo-enzimÃtico [vitamina C, carotenÃides totais, antocianinas totais, flavonÃides amarelos, polifenÃis totais, conteÃdo de mangiferina e atividade antioxidante total], integridade de membrana [peroxidaÃÃo lipÃdica (MDA), perÃxido de hidrogÃnio e extravasamento de eletrÃlitos], atividade da fenilalanina amÃnia liase (PAL), atividade das enzimas de escurecimento [polifenoloxidase (PPO) e peroxidase do guaiacol (G-POD)], atividade das enzimas de parede celular [pectinametilesterase (PME) e poligalacturonase (PG)] e a influÃncia do tratamento na histologia dos tecidos. A atividade das enzimas antioxidantes como a dismutase superÃxido e a catalase encontraram-se elevadas tanto na polpa quanto na casca dos frutos expostos à LP apÃs 7 dias a 20 ÂC. NÃo foram encontradas diferenÃas significativas nos indicadores de parede celular e integridade de membrana como o MDA, sugerindo que o estresse oxidativo associado à LP foi efetivamente prevenido atravÃs do aumento da atividade das enzimas antioxidantes apÃs 7 dias. Atividades das enzimas de parede celular foram reduzidas apÃs 7 dias nos frutos tratados. ObservaÃÃes macroscÃpicas e microscÃpicas confirmaram que os frutos nÃo foram danificados pela LP. O conteÃdo de carotenÃides totais, fenÃlicos, e em menor extensÃo, a vitamina C, foram dramaticamente aumentados apÃs 7 dias, tanto no epicarpo como mesocarpo tratados pela LP, resultando em frutos com alta capacidade antioxidante. CarotenÃides aumentaram 350% na polpa tratada pela LP apÃs 7 dias. Os nÃveis mais elevados de compostos fenÃlicos (+97%) na casca tratada foram associados a uma atividade aumentada da PAL (+98%) e conteÃdo de mangiferina (+42%). As atividades da G-POD no mesocarpo e da PPO no epicarpo aumentaram 1268% e 22% respectivamente, apÃs 7 dias nos frutos tratados, no entanto, nÃo foi observado escurecimento dos frutos. Observou-se, ao final do primeiro experimento, um aumento dos fitoquÃmicos em mangas submetidas a dose hormÃtica de 0,6 J cm-2 sem alteraÃÃes negativas na qualidade dos frutos. No terceiro capÃtulo (experimento II), mangas minimamente processadas (estÃgio de maturaÃÃo 4), foram submetidas a quatro diferentes tratamentos: controle, 1 pulso, 4 pulsos e 1 pulso por dia durante 4 dias, com o objetivo de avaliar se o modo de aplicaÃÃo da LP poderia interferir nas variÃveis fisico-quÃmicas [firmeza, SS, cor, perda de matÃria fresca e taxa de respiraÃÃo], compostos bioativos [carotenÃides e vitamina C] e atividade antioxidante total quando armazenamentos durante 7 dias a 6 ÂC. Amostras que receberam 4 pulsos alternados (4 x 0,7 J cm-2 = 2,80 J cm-2), aumentaram o conteÃdo de ascorbato total (~40%) apÃs 7 dias, no entanto, os cubos apresentaram-se mais escuros do que o tratamento que recebeu a mesma dose de 4 pulsos sucessivos. No final do perÃodo de armazenamento, as mangas minimamente processadas que receberam 4 pulsos sucessivos exibiram uma melhor qualidade em comparaÃÃo com os demais tratamentos, que foi associado ao elevado teor de carotenÃides (0,894 mg g-1 MF) e atividade antioxidante (~145 μmol trolox 100 g-1). Como conclusÃo, nossos dados sugerem que uma dose hormÃtica de luz pulsada pode ser utilizada para aumentar as concentraÃÃes de compostos fitoquÃmicos sem efeitos negativos na qualidade de frutos de mangas âTommy Atkinsâ.
31
Al-Jimaz, A. S. "The hydrodynamic behaviour and mass transfer characteristics of single droplets in a pulsed sieve plate column." Thesis, Aston University, 1992. http://publications.aston.ac.uk/9791/.
Повний текст джерелаАнотація:
The literature relating to the performance of pulsed sieve plate liquid-liquid extraction columns and the relevant hydrodynamic phenomenon have been surveyed. Hydrodynamic behaviour and mass transfer characteristics of droplets in turbulent and non-turbulent conditions have also been reviewed. Hydrodynamic behaviour, i.e. terminal and characteristic velocity of droplets, droplet size and droplet breakup process, and mass transfer characteristics of single droplets (de0.6 cm) were investigated under pulsed (mixer-settler & transitional regimes) and non-pulsed conditions in a 5.0 cm diameter, 100 cm high, pulsed sieve plate column with three different sieve plate types and variable plate spacing. The system used was toluene (displaced) - acetone - distilled water. Existing photographic techniques for following and recording the droplet behaviour, and for observing the parameters of the pulse and the pulse shape were further developed and improved. A unique illumination technique was developed by which a moving droplet could be photographed using cine or video photography with good contrast without using any dye. Droplet size from a given nozzle and droplet velocity for a given droplet diameter are reduced under pulsing condition, and it was noted that this effect is enhanced in the presence of sieve plate. The droplet breakup processes are well explained by reference to an impact-breakup mechanism. New correlations to predict droplet diameter based on this mechanism are given below. vskip 1.0cm or in dimensionless groups as follows:- (We)_crit= 3.12 - 1.79 (Eo)_crit A correlation based on the isotropic turbulence theory was developed to calculate droplet diameter in the emulsion regime. vskip 1.0cm Experimental results show that in the mixer-settler and transitional regimes, pulsing parameters had little effect on the overall dispersed phase mass transfer coefficient during the droplet formation and unhindered travel periods.
32
Zhang, Yin. "Performance Characteristics of Lithium Coin Cells for Use in Wireless Sensing Systems." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3588.
Повний текст джерелаАнотація:
Understanding the pulsed discharge behavior of low-rate lithium coin cells in wireless sensing systems is critical to prolong the operating life and/or reduce the size of battery-powered WSs. This dissertation presents the battery transient analysis for a sensor duty cycle, experimental studies for sustained pulse discharge cycling, and investigation on recharge strategies for a battery/power harvesting hybrid system for WSs. The transient behavior of the lithium coin cells during pulse discharge and subsequent relaxation was investigated with single-pulse experiments and theoretical analysis. The voltage response for a pulsed discharge had two parts: a region of rapid voltage change and a region of slower change. The magnitude of the rapid voltage losses was associated with ohmic and interfacial resistances. Solid phase diffusion in the cathode was found to be the major contributor to the "slow" transient voltage change that occurred during and after a pulse. An analytical model was developed to describe the time-dependent voltage and the corresponding non-uniform concentration distribution for the thick porous electrode. A fit of the analytical model to experimental data permitted an estimate of the solid phase diffusivity. Independent fitting of the pulse data and relaxation data both yielded a diffusivity of D ~ 4×10-11 cm2/s, which agreed well with measured values reported in literature. The interactive effect of battery characteristics and WS operating conditions was investigated during sustained pulsed-discharge cycling. At low standby currents (≤50 μA), the influence of the standby current on the operating voltage and battery capacity was negligible. The pulse current had a significant impact on the lower voltage and determined the maximum capacity that could be extracted from a battery regardless of the duty cycle factor. For each pulse length studied, the battery capacity increased as the standby time increased, until a maximum capacity was reached, which could not be increased by further increase in the standby time. The minimum standby time for full (or near full) relaxation for duty cycles with different pulse length was found to correlate well with ratio ts/tp2. Battery pulse discharge-recharge cycling as would occur in a hybrid power system was investigated, and the recharge strategies were evaluated in terms of capacity loss over cycling and energy efficiency. Results from the cycling tests suggested the importance of a rest period between the discharge and charge step of a cycle. PRCR cycling with a 2 s rest period could lower the capacity loss to 25% or less of that of PC cycling with no rest period over 10,000 cycles. Cycling the battery at 80% SOC rather than at 100% SOC (3.1 V) significantly reduced the capacity loss during cycling.
33
Pratt, Phillip Roger. "Analysis of thermo-mechanical characteristics of the LENS[TM] process for steels using the finite element method." Master's thesis, Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-12082008-183521.
Повний текст джерела
34
Sobol, О. V., V. A. Stolbovoy, S. V. Aleshin, A. A. Andreev, S. N. Grigorev, V. F. Gorban, and M. A. Volosova. "Stucture and mechanical characteristics of vacuum arc TiN coatings deposited with high-voltage high frequency pulses on the substrate." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20579.
Повний текст джерела
35
Vasyliev, V. V., A. A. Luchaninov, E. N. Reshetnyak, and V. E. Strelnitskij. "Comparative Characteristics of Stress and Structure of TiN and Ti0.5-xAl0.5YxN Coatings Prepared by Filtered Vacuum-Arc PIIID Method." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34913.
Повний текст джерелаАнотація:
A comparative study of the structure and stress state of Ti0.5-xAl0.5YxN and TiN coatings deposited under
identical conditions from the filtered vacuum-arc plasma under high voltage pulsed bias potential on
the substrate was carried out. It was found that for Ti0.5Al0.5N coatings the dependence of the residual
stress on the amplitude of the pulsed voltage potential is non-monotonic with a minimum when the amplitude
is of 1 kV. As for TiN films, a monotonic decrease in the level of residual stresses takes place when the
amplitude of the potential is increased in the range 0-2.5 kV. Non-monotonic dependence for multicomponent
coatings Ti-Al-Y-N may occur due to the possibility of phase transition associated with the decay
of the supersaturated solid solution (Ti,Al)N stimulated by high energy ion bombardment.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34913
36
JAIN, MANISHA. "DESIGN OF SPIKE PULSER FOR ULTRASONIC APPLICATIONS." Thesis, 2023. http://dspace.dtu.ac.in:8080/jspui/handle/repository/20134.
Повний текст джерелаАнотація:
The spike pulser serves the purpose of generating high-energy pulses with precise
characteristics necessary to excite ultrasonic transducers effectively. It consists of essential
elements including an amplifier stage, timing/control circuitry, and power supply components.
By receiving an input signal, typically in the form of pulses or square waves, the spike pulser
triggers the production of high-energy pulses with specific timing and amplitude properties.
In the realm of ultrasonic imaging, the spike pulser plays a vital role in exciting the transducer,
which converts electrical energy into ultrasonic waves that propagate through the target
medium. The resulting echoes from the medium are subsequently received and processed to
produce detailed images of internal structures or potential defects. The pulse characteristics of
the spike pulser, including amplitude, duration, and repetition rate, significantly impact the
quality and resolution of the resulting ultrasound images.
Non-destructive testing and industrial applications also heavily rely on the spike pulser to
assess the integrity of materials. By transmitting ultrasonic waves and detecting their
reflections, the spike pulser facilitates flaw detection, identification of cracks, and evaluation
of material properties. Its ability to generate high-energy pulses enables the detection of subtle
flaws and the accurate characterization of materials.
This thesis discusses the design and simulation of a high-voltage spike pulser that can deliver
voltage up to 650V . The pulse width of the input signal given to the spike pulser is in range
from 20ns to 100000ns. Also discussed were power consumed, the amplitude of the spike at
the output of spike pulser, and current at load for different pulse widths of input signal given
to spike pulser.
37
Huang, Chin-Ming, and 黃進明. "The Characteristics of Radial Pressure Pulse at the Right/Left Three Pulse Diagnosis Positions." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/57394785530816870399.
Повний текст джерелаАнотація:
博士中國醫藥大學
中醫學系博士班
99
The factors influencing the radial Pressure Pulse (RPP) were studied to investigate the characteristics of RPP at the right/left three diagnosis positions by four series of experiments. For the first series, each subject had immersed his/her left hand into 45℃ and 7℃ water for two minutes separately, and the RPP of Right Guan was detected to investigate the influences of heat and cold stress. The second series of experiments was for investigating the differences between the RPP in the normotensives and the hypertensives. The influences of Ginger Tea on RPP and the dynamic influences of exercise were investigated in the third and the fourth series of experiments, respectively. The results showed that the heat stress significantly reduced radial augmentation index (AIr) (p < 0.05) and enhanced the spectral energy of 10-50 Hz (SE10-50Hz) (p < 0.05), but the effects of cold stress were contrary (p < 0.05) and the spectral energy of 0-10 Hz (SE0-10Hz) had no statistical difference. The results of the second series showed a significant difference in the energy proportion, 10-50 Hz% (EP10-50Hz), between the six positions within each group, and a significant reduction at only Left Chun in both hypertensive groups. But the AIr showed no significant difference. The results of the third series of experiments showed that early systolic pressure (p1), later systolic pressure (p2) and SE0-10Hz were significantly reduced (p < 0.05) after the intake. Relatively, EP10-50Hz was significantly increased (p < 0.05). These significant changes occurred only at Right Guan. The results of the fourth showed that AIr and p2 significantly decreased after the exercise (p < 0.05). And SE10-50Hz and EP10-50Hz significantly increased after the exercise and then recovered to the preexercise level after a 10-minute rest (p < 0.05). In conclusion, our study demonstrates the following results: 1) SE10-50Hz presented more physiological characteristics than SE0-10Hz did under thermal stresses. 2) EP10-50Hz significantly varied at the six positions, revealing the specific characteristics of RPP. And the Left Chun is qualified to discriminate the differences of RPP between the normotensives and hypertensives. 3) The influences of Ginger Tea on RPP revealed only at the Right Guan. 4) SE10-50Hz and EP10-50Hz presented more dynamic characteristic than AIr did in the preexercise, immediately after the exercise and after a 10-minute rest. And EP10-50Hz better revealed the physiological variations than SE10-50Hz did.
38
WANG, YI-FENG, and 王一峰. "The mosfet device characteristics under ac pulse operations." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/64526252663910052861.
Повний текст джерела
39
Jiang, Lianghuei, and 蔣良慧. "Characteristics of electrodepositiontrivalent chromium-carbon alloys using pulse." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/me67be.
Повний текст джерелаАнотація:
碩士國防大學理工學院
化學工程碩士班
100
Purpose of this study the chromium carbon coating of high conductivity and corrosion resistance between chromium.Duty Cycle experiment with the frequency of the operating parameters, corrosion resistance and composition of the detection analysis on the coating of different frequencies and Duty Cycle.Coating microstructure and composition of the chromium carbide coating surface morphology observed by SEM; use of XRD and XPS observation chrome carbon coating structure and composition; EPMA measurements chromium carbon coating amount of ingredients.Bipolar plate performance testing: the potentiostat to detect the corrosion resistance by potentiodynamic polarization in 0.5 M H2SO4(aq); contact angle measurements of chromium carbon coating hydrophobic; contact with the electrical conductivity of the chromium carbon coatings for impedance measurement. The experimental results show that at low current density of 10A∙dm-2, operating temperature 10℃with the main salt 0.1 M, the pulse parameters frequency 10 Hz and Duty Cycle 90% of the coating surface cracks and dense, corrosion current of up to 9.8E-8 A∙cm-2; different frequency Duty Cycle of coating thickness variation results show that the precipitation rate performance of the pulse plating are compared with DC plating outstanding, of which 50% of the thickness of the coating frequency of 1000 Hz and Duty Cycle up to 40 um ; In addition, the different frequencies and under the Duty Cycle of pulse plating coating carbon atom content in this range of operating conditions are up to 20%; DC plating coating metal bipolar plate performance test contact angle of 74.9∘, pulse parameters frequency of 10 Hz and Duty Cycle 90% coating contact angle of 83.8∘; DC plating and pulse parameters, frequency of 10 Hz with Duty Cycle 90% of the coating in contact resistance values were 22 mΩ∙cm and 14 mΩ∙cm in 140N∙cm-2; DC plating and pulse parameters of frequency 10 Hz andDuty Cycle90% average corrosion current of 2.7E-2 A∙cm-2 and iv 8.9E-6 A∙cm-2.
40
Cheng, Jung-Chieh, and 鄭戎傑. "Investigation on Pulse Charging Characteristics of Lead-Acid Batteries." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/39596760381127823759.
Повний текст джерелаАнотація:
碩士國立中山大學
電機工程學系研究所
91
This thesis investigates the performance of pulse charging, which is believed to be superior to constant current charging in some respects, such as charging efficiency and charging speed. The investigation is focused upon the extensively used secondary batteries, lead-acid batteries. The consecutive orthogonal arrays method is applied to search for the optimum operating variables of pulse charging, including pulse amplitude, duty ratio and frequency of the charging current. Unfortunately, the experimental results of consecutive orthogonal arrays reveal that charging efficiency is not obviously affected by pulse amplitude, duty ratio or frequency. Instead, charging rate is dominantly influenced by average charging current. These results indicate that pulse charging scheme is not superior to constant current charging. To compare these two charging schemes further, a series of experiments are carried out to discuss the effects of each operating variables. Unfortunately, no evidence from the experimental results can prove the superiority of pulse charging to constant current charging as formerly documented.
41
Chu, Yu-Lin, and 朱又麟. "The characteristics of PMOSFET devices under AC pulse operations." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/62438819863564359807.
Повний текст джерелаАнотація:
碩士國立交通大學
電子研究所
81
In this thesis, the substrate geometric component current of the PMOSFET devices under AC pulse operations is investigated and analyzed. This current is due to holes in the inversion layer injecting into the bulk during turn-off transient and recombining in the bulk with elections. It is found that the geometric component currents of the long channel devices is larger than that of the short channel devices with grounded source and drain. However, the geometric component currents of the short channel devices with the drain biased at a fixed voltage increase significantly due to both the parasitic bipolar effect and the gate pulse-induced source and drain bias fluctuation effect. The current is larger than that of the long channel devices with the same bias. The gate pulse-induced source and drain bias fluctuation is mainly due to the wiring inductances which induce some voltage changes during the turn- on or turn-off transient of the gate pulse. In this thesis, an equivalent circuit is proposed to simulate the gate pulse- induced source and drain bias fluctuation in SPICE. The simulation results consistent with the measured results in the experiments. This proves the correctness of the proposed mechanism and the equivalent circuit.
42
FAN, ZHI-XIANG, and 范智翔. "Physiological Signal Analysis of Peripheral Arteries by Pulse Wave Characteristics." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/70970454543295251842.
Повний текст джерелаАнотація:
碩士中原大學
電機工程研究所
103
Heart rate variability (HRV) can be applied to observe the autonomic nervous system activity of human beings. With the development of wearable device technology, the PPG signal is often applied to measure pulse rate and furthermore to analyze the pulse rate variability (PRV), considered to be equivalent to HRV. However, the heart rate is affected by depth and speed of breath that causes different results when HRV and PRV are measured on different locations. Based on the characteristics of the respiratory sinus arrthymia (RSA), the beat rate and tide volume of breath were controlled and the variability of PPG and ECG signals were discussed; furthermore, the characteristics of peripheral arteries were evaluated. Several PSG applied were respiration rate measured with sitting position, and ECG signals and PPG variability of four limbs to analyze the SDNN of normal to normal beat. It was found that obvious difference ( p <0.05) shown between HRV and PRV when normal young groups were controlling different beat rate and tide volume; however, no obvious ones shown on the PRV of four limbs. To analyze based on age, obvious difference between upper limbs and lower ones was shown on the PTT of young group instead of the elderly. Therefore, the result showed there are difference between PRV and HRV during breath.
43
Chen, Hsun-Chieh, and 陳勳傑. "Characteristics of Higher-Mode Structural Responses under Pulse-Like Ground Motions." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/16057250459869097452.
Повний текст джерелаАнотація:
碩士國立臺灣科技大學
營建工程系
89
The main objective of this study is to investigate the characteristics of structural seismic demands under pulse-like ground motions in the near field. Considerations of analytical structural models are given to shear- beam and frame systems. The corresponding seismic base shear demands are evaluated for a set of artificial ground velocity pulse models. The study is separated into two parts. The first part is to evaluate the contribution of higher-mode responses under the pulse-like ground motions for the shear-beam and frame systems. For both systems, the study results indicate that higher-mode responses are significant for long-period structures. The second part is to investigate the applicability of the response spectral method for the near-field ground motions. The investigation is based on three modal summation approaches: the absolute sum(ABS), the square root of sum of the square(SRSS), and the complete quadratic combination(CQC). The resulting base shear demands are compared to the numerically exact solutions to determine the accuracy for each approximation approach. The study results reveal that the ground pulse shape is a major factor that dominates the accuracy of the response spectral method.
44
Jhu, Jia-Liang, and 朱家亮. "Pulse characteristics of Low Repetition Rate Mode-Locked Yb-doped Fiber Laser." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/k8qw2b.
Повний текст джерелаАнотація:
碩士國立臺北科技大學
光電工程系研究所
100
Through nonlinear polarization rotation mechanism, we generate 365 kHz low repetition rate and high energy pulses without pulse breaking from Yb-doped fiber ring laser by adding 520 m long single mode fiber inside laser cavity. With 90% output coupler, the highest pulse energy above 83 nJ can be experimentally obtained using 258.7 mW pump power and the shortest pulsewidth about 616 ps was measured from the high speed oscilloscope. Besides, we reshape the spectrum of the ML pulses through the tunable spectrum filter outside laser cavity by using the knife and the grating pairs. The measured pulsewidth will decrease as the spectrum bandwidth shrinkage and the shortest pulsewidth was 322 ps at 2 nm spectrum bandwidth. Besides, we investigate the relationship between the central wavelength and pulsewidth by changing the center wavelength of selective spectrum band and maintaining the spectrum bandwidth about 3 nm. With central wavelength at 1031.4 nm, we measured the shortest pulsewitth about 332 ps. It demonstrates existence of nonlinear chirp in our mode-locked pulses. After amplification by the Yb-doped fiber amplifier, the highest pulse energy of mode-locked pulse was 385 nJ. In addition, multiple-pulses can be observed in our laser system by rotating the PC. When I reduced the output coupling ratio to 40%, ten pulses can be seen at higher pump power. From the relationship between pump powers and pulse numbers, we can observe the hysteresis phenomenon for multiple-pulses generation as pumping power increase or decrease.
45
Kuo, Kai-Chen, and 郭開誠. "Effect of Pulse-Width Modulation on the Electromagnetic Characteristics of Electrical Steels." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/00560000681383946973.
Повний текст джерелаАнотація:
博士國立臺灣大學
機械工程學研究所
99
This thesis reveals that a new “standardized ring type tester” has been successfully developed. Comparing to the traditional Epstein method, the test pieces can be significantly minimized without special requirements of direction and don’t need to be piled up with the new tester. Besides, it also helps to standardize the process of winding toroid with magnetic wire. For the electric circuit on test mechanism, a Pulse-Width Modulation (PWM) digital signal was designed in addition to the traditional analogy sine wave signal so as to evaluate the electrical steel being applied to high efficient and easily-controlled motor circuit. In this study, 8 test specimen with two thicknesses, various flux densities and different makers were selected for both the traditional Epstein method and new toroid test, respectively. During the tests, both the traditional analogy sine wave and PWM digital signal were input to obtain various data of electro-magnetic properties for comparative analysis. The test result shows that this mechanism has a high identification. It can also prove the variation of the metallurgical properties of materials, like textures, and the relationship of the electro-magnetic properties of PWM signal input. By means of a precise evaluation of electro-magnetic properties, this study found that the electrical steel can cause motors more efficient, and also meet the requirements of environmental protection by saving energy and reducing carbon emission.
46
Liu, Te-Chin, and 劉德欽. "Apply Gaussian Pulse Train to Analyze the Electromagnetic Characteristics of 3D Microwave Circuits." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/44279413418039679705.
Повний текст джерелаАнотація:
碩士國防大學中正理工學院
電子工程研究所
89
Recently, the wireless communication become widely used in high frequency bands. Due to the demand of small size, light-weight, low-power and low-cost, microwave integration circuits(MICs) developes progressively. In the design of MICs , besides the characteristics of circuits, electro- magnetic characteristics of the 3D structure also effect the whole response of the circuits. So, we must practice the electromagnetic analysis of MICs in the design procedure of microwave circuits. TLM method is a kind of simple numerical analysis. In this thesis, using the structure of Yee-based expanded node with gaussian pulse train excition, we can apply transient analysis of 3D microwave circuits. These transient analysis include the rise time, ripple, damping, capacitive/inductive and dispersion, which can provide the important considerations of designing 3D microwave circuit in MICs.
47
Hsieh, Kuo-Chiang, and 謝國強. "Analysis of the characteristics of human arterial pulse waves using ultrasound image processing." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/56585033157216493395.
Повний текст джерелаАнотація:
碩士國立臺灣大學
應用力學研究所
86
Abstract An image processing system is developed for the analysis of medica l images from various sources , the traces of curves in the image are digitize d and processed to provide the dynamic of Bio-motion . Our image processin g system are validated with a few clinical examples . (1) CCA (Common Carotid Artery ) impedance measurements : The normal side of CCA occlusion patients an d normal subjects have the same results .The first harmonic of illed side is l arger than the normal side ,and the impedance increase at frequencies before t heir fifth harmonic .For one side CCA hemorrhagic infarction patients ,the res ults show low frequency impedance increases for both sides. (2) PWV (Pulse Wav e Velocity) measurement of Popliteal a. to Dorsal Pedis a. : We find PWV incre ases when normal subjects change their position from supine to stand ,but the DM patients show different results ,and both legs associated with may have lar ge difference . The changes of PWV may be autonomic and muscle contraction abi lity .(3) Pressure and blood vessel variation measurements : The curviliner sh ap of pressure/diameter curve was observed which reveals the characteristics of pressure/diameter curve was observed which reveals the characteristics of the viscoelasticity of the blood vessel .During the change of blood pressure ,the contribution from the elastin fiber and collagen fiber varies which agree we ll with the literature. Keyword : edge detection ,CCA ,CCA occlusion ,ultrasound doppler ,blood vesse impedance
48
Hou, Kung-Hsu, and 侯光煦. "Study on Tribological Characteristics of Ni-P Based CoatingsProduced by Pulse Current Electroforming." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/97226644429046926838.
Повний текст джерелаАнотація:
博士國立中央大學
機械工程研究所
95
In this study, attempt has been made to investigate the wear resistance of Ni-P alloy coatings and Ni-P-SiC composite coatings that manufactured by pulse current (PC) electroforming technology. The tribological tests of such plated coatings were carried out at ambient temperature, evaluated temperature(100~300℃) and without lubricants conditions. The results of this investigation showed that the internal stress of the PC-deposited Ni-P coating is much lower than that of direct current (DC) deposited Ni-P coatings. The analytical results of the high phosphorous contents (P > 8 wt.%) coatings indicate that increasing the phosphorus content in the layer reduces the hardness of the Ni-P electroformed coatings, and the gradually leading to the coatings structure from micro-crystalline transform to X-ray amorphous. Wear test results of as-plated Ni-P coatings under normal temperature show that the wear resistance of Ni-P alloy layers increases with the hardness of the coatings. The hardness primarily affects the wear resistance of the Ni-P as plated coatings; and the optimum wear resistance of Ni-P coatings can reach 11 times that of Ni coatings. After heat-treatment that would be enhancing the strength of the Ni-P coatings and leads to a lower wear rate for heat-treated coating. The wear resistance of heat-treated coating can be as high as 2.5 times that of as-plated coating. In addition, the wear resistance and hardness increases with the increasing of grain size for both as-plated and heat-treated coatings. It suggests that the strength and grain size of the Ni-P coating with high phosphorus content obeys the inverse Hall-Petch relationship. Under evaluated temperature saturation, the wear tests show that the wear resistance of the as-plated Ni-P (P: 8.7wt.% ~13.9wt.%) coatings was increased with temperature increased. In the Ni-P-SiC composite coatings, the study attempted to incorporate 0.3μm SiC particles into a Ni-P alloy matrix by pulse current (PC) and direct current (DC) plating. Both plating methods showed that the phosphorus content in the deposit falls with increasing SiC content in the bath, and that the SiC content in the composite coating rises with rising SiC content in the bath. The pulse plating deposit with SiC particles 0.2 - 1.5 wt.% was higher than direct current plating with SiC particles 0.2 - 0.5 wt. % in deposits. The wear-proof shows that the tribological behavior of Ni-P-SiC of the PC plating is better than that of the DC plating deposit. At normal temperature, experimental results show that the wear resistance of Ni-P-SiC composite coatings is superior to Ni-P composite coatings if under the same level of hardness. The wear weight loss of Ni-P-SiC composite coatings is even about 62% less than that of Ni-P composite coatings, in which is based on the same produced condition. Further more, both the hardness and wear resistance of Ni-P-SiC composite coatings are superior to pure Ni coating, wherein its wear resistance is even up to 10 times better than the pure that of Ni coating.
49
Murali, Pandarinath. "Dynamic modeling of six-pulse rectifier for short-circuit current characterization." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-12-4401.
Повний текст джерелаАнотація:
Existing models describing the dynamic behavior of a six-pulse rectifier during a short-circuit fault condition are derived from switch models using time-domain average value parametric functions. Unlike these models, novel non-parametric dynamic models have been developed using analytical average-value modeling approach in this work. In this modeling approach, depending upon the number of switches conducting during a switching cycle, the operating point of the rectifier is brought into one of three modes of operation of a six-pulse rectifier. The model for each mode is represented by a differential equation. During output current calculation for the rectifier the operating model is selected based on firing angle and overlap angle functions derived in this paper. They completely characterize the dynamic behavior of current flowing through the dc inductor for a wide range of operating conditions with the exception of harmonics and asymmetrical currents which are dominant for faults occurring at the terminals of the rectifier upstream of the smoothing inductor. The results from the average value model and few other simple models have been applied for Thevenin ac source and synchronous generator supplied rectifier models to determine the characteristics of short circuit current from the rectifier.text
50
Jin, Jiang-Sheng, and 金強生. "A Feasibility Study for Identifying the Characteristics of Flexible Tubes using Pulse Wave Signals." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/68pacb.
Повний текст джерелаАнотація:
碩士國立臺北科技大學
自動化科技研究所
99
In the research of Department of Health, the larger proportion of the ten leading casues of death in Taiwan is cardiovascular disease. Keeping this in mind, we mainly measure input and output siginals to examine cardiovascular disease in this research. First we do research on the model of radial resonance theory to consider elasticity, viscosity, and the radial blood-pressure of wave equation, which is derived from tension of blood vesse. And the function of cardiac output is applied to this external force of perturbation to lead to the formula solution of the radial blood pressure wave. The amplitude of blood pressure, which is simulated by Matlab, will tend to attenuate as the elastic constant increases. This is one of the causes of hypertension. On the model of blood pressure in this research, Matlab helps us simulate the power consumption on the separate multiple frequencies and the total power consumption of blood vessel system by means of theory of single input modulation. The result of the simulation shows that blood vessel system’s power consumption is the highest on the triple frequency. In this condition, the total power consumption rises as the increase of thickness-to-radius ratio, length-to-radius ratio, and heartbeating rate, but it has a tendency toward inversely proportional attenuation as the increase of area compliance and elastic constant. Therefore, the result of this research shows that area compliance and elastic constant can respectively be the norm of judging the elasticity and sclerosis of blood vessel. In the experimental aspect, by using a transparent pipe, we have tensile test and water pressure distention test to reapectively find out physical properties of elastic constants and area compliance. This method can be also applied to other soft pipes. We use the oil pressure experiment to measure input and outpu signals, so we can find out power consumption by means of theory of single input modulation. Moreover, this method can applied to other fields to do research on signals. Consequently, the method, which we use in this research, can help people effectively and instantaneous examine heart and cardiovascular disease and reduce and prevent the casues of cardiovascular disease. And because the experiment in this research belongs to in vitro, it is suggested to do further experiment which is closer to entity.