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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
221

Destination After Entering Foster Care: Road Toward Stability

Yang, Dong 11 December 2012 (has links)
The duration of children stay in a temporary foster care system needs to be minimal in order to ensure a stable and successful life. However, a time-consuming procedure of investigations is usually taken to decide whether they can reunite with their birth parents. Moreover, if the child fails to reunite with their family, another discharge decision needs to be assessed, leading to even longer time without a normal life. Based on the data from Adoption and Foster Care Analysis and Reporting System (AFCARS), this thesis derives a prediction model to discriminate the children with a tendency of unsuccessful reunification from the rest. An alternative discharge option can therefore be prepared concurrently for the foster youth with high non-reunification probability. The model is obtained by logistic regression and evaluated with receiver operating characteristic (ROC) curve.
222

China Strategy for ESP Wire : A study of the Chinese market from Sandvik's perspective

Eriksson Enquist, Joel January 2008 (has links)
Aim: SMT Wire has noticed that their sales of ESP wire are very low in China compared to India. SMT Wire now wonders how they can increase their market share in China. Method: Personal interviews, telephone interviews and interactive conversations. Result & Conclusions: SMT Wire should work each tier in the supply chain to gain more orders and increase their market share. It is important to have local representation and work close to the customers so that the customers can feel trust for Sandvik and Sandvik’s employees. The market for spiral discharge electrode material is good in China (the annual consumption is about cccc tonnes) and the market will probably be more and more mature for Sandvik’s high quality materials in a couple of years. Suggestions for future research: Is it possible to have a more long-term price on the products on the Asia market? How can Sandvik keep its Chinese personnel? How can the Chinese personnel be trained to make contacting new companies easier for them? How can a foreign company create a guanxi-based selling with a high personnel turnover? Contribution of the thesis: A strategy that can be adapted for stainless steel wire companies that want to increase their market share in China.
223

Patienters upplevelse av utskrivning till hemmet från en dagkirurgisk enhet : En intervjustudie

Afra, Elnas January 2011 (has links)
Syfte: Att beskriva dagkirurgiska patienters upplevelse av att bli utskrivna hem samma dag efter operation utförd i generell anestesi. Metod: Kvalitativ intervjustudie med induktiv ansats. Elva patienter som har opererats via en handkirurgisk mottagning i mellersta Sverige har intervjuats utifrån en semistrukturerad intervjuguide. Sju kvinnor och fyra män i åldrarna mellan 28-71 år har deltagit i studien. Innehållsanalys användes för analys av materialet. Resultat: Patienterna upplevde hemgången som väldigt positiv. De faktorer som bidrog till en lyckad hemgång var framförallt; Patientens goda grundhälsa, en trygg hemmiljö att återvända till och återhämta sig i, samt att patienterna får sina frågor och funderingar besvarade inför hemgången, och stöd från anhöriga. Vårdpersonalens bemötande och professionella förhållningssätt bidrog till att patienterna upplevde en känsla av trygghet som skapade en förutsättning för delaktighet.  Resultatet visar även att patienter önskar mer information om det postoperativa förloppet. Slutsats: Att skrivas ut och komma hem efter ett dagkirurgiskt ingrepp är en positiv upplevelse för patienterna, dock behöver informationen inför hemgången samt möjligheten till stöd från den dagkirurgiska enheten efter hemgången förbättras. / Aim: To describe the day-surgery patients´ experience to be discharge the same day after surgery in general anesthesia. Methods: Qualitative interview study with inductive approach. Eleven patients, operated by a hand surgical receptions in central Sweden were interviewed, using a semi- structured interview guide. Seven women and four men between 28-71 years participated in the study. Content analysis was used for analysis of the material. Result: Patients experienced the discharge as very positive. The factors which contributed to a successful discharge was above all, patient good basic health, a safe home to return to and recover in, and that the patients have their questions and concerns answered before discharge, and the support from relatives. Health professionals' reception and professional approach helped the patients to feel a sense of security that created a condition for participation. The results also show that patients want more information about the postoperative recovery. Conclusions: To be discharged, and come home, after day surgery procedures is a positive experience for patients, however, the information at discharge and the possibility of support from the day surgery unit after discharge needs to improve.
224

The Effect of Electrohydraulic Discharge on Flotation Deinking Efficiency

Carleton, James Richard 12 January 2005 (has links)
Firing an underwater spark discharge generates an expanding plasma which causes a spherical shockwave to propagate through the surrounding water. The shockwave can have many effects, including resonance effects on bubbles, mechanical destructive effects on solid surfaces and living organisms, and sonochemical oxidative effects on particles and chemical species present in the water. This phenomenon has been shown to improve the efficiency of ink removal in a laboratory flotation deinking cell, while simultaneously decreasing fiber loss. These process improvements are attributed to the sonochemical oxidation of ink particle surfaces, caused by shockwave-induced cavitation. This finding is supported by zeta potential measurements. Sparking was found to reduce the zeta potential of ink particles by up to 20 mV. When sparking was performed during deinking, no effect was found on either ink removal or solids loss. However, when the pulp was pretreated with sparking before flotation, a significant improvement was seen in the brightness gain. Further, fiber loss was decreased by up to 25% in a single flotation stage. The economics of this process are attractive; payback is on the order of three months based on fiber savings alone. Also, at about 1.5 kJ per spark, the power requirements are minimal with respect to the benefit derived.
225

Synthesis of Endohedral Metallofullerenes and Phosphino-fullerene Metal Complexes

Chen, Chia-Hsiang 23 July 2012 (has links)
none
226

Microplasma Discharges in High Pressure Gases Scaling Towards the Sub-micron Regime

Chitre, Aditya Rajeev 2010 December 1900 (has links)
Atmospheric pressure microplasmas are uniquely characterized by their very high energy densities and also by their small discharge sizes. These properties allow for unique applications in plasma processing technologies. We have investigated the operational characteristics of microplasmas at higher energy densities and smaller sizes by operating microplasma configurations at high pressure conditions. We studied the discharge and analyzed its variation with changes in current and pressure. The discharge was analyzed by microscopic visualization and data from the images and was processed to measure the current density and estimate charged particle density. By increasing the pressure beyond 200 psi and by minimizing the discharge current required for sustaining the plasma, we have been able to achieve discharge sizes of 7 mu m in nitrogen and as small as 20 μm in helium. Optical emission spectroscopic studies were carried out to measure gas temperature and vibrational temperature using the nitrogen 2nd positive system. With increase in pressure, the transition from non-equilibrium plasma to equilibrium plasma was also studied using the OES temperature measurements. iv Temperature measurements are also used to estimate normalized current densities. Normalized current density results obtained after introducing the corrected effective pressure based on the increased gas temperature are close to the value of 400 mu A /cm^2*Torr^2 obtained for low pressure normal glow discharges in nitrogen. This research presents further validation of the general operational characteristics of microplasmas being pressure scaled versions of normal glow discharges. Attained energy densities are ten to twenty times higher than in atmospheric pressure microplasmas. Discharge sizes are also significantly smaller, decreasing with increasing pressure, but the scaling is with density ‘nd’ rather than pressure ‘Pd’ due to the increase in gas temperature with pressure, indicating a dependence on collisional processes. We can infer that at higher pressures, the operational characteristics of more complex plasma discharges like dielectric barrier discharges, RF plasmas, etc. follow scaling patterns, transitions and limits similar to the microplasma discharge studied in this thesis.
227

Structural Modifications and Capacity Fading of LiMn2O4 Cathode during Charge-Discharge of Secondary Lithium Ion Batteries

Huang, Ming-Ren 04 October 2003 (has links)
Abstract A vast majority of the studies devoted to Lithium manganese oxide deals with their electrochemical characteristics in lithium batteries. The main project of this study is to realize the structure evolution upon electrochemical cycling. The phase transformations under the charge and discharge testing are an interesting project. Nitrate or oxide precursor calcined at 800¢XC can produce single phase stoichiometric LiMn2O4. The hypo-stoichiometric compositions (xLi2O¡Ñ4MnO, x < 1) synthesized by Li-poor situation contain LiMn2O4 and Mn2O3. The hyper- stoichiometric compositions (xLi2O¡Ñ4MnO, x > 1) synthesized by Li-rich situation contain non-stoichiometric spinel LixMn2O4 (such as Li4Mn5O12 or Li2Mn4O9) and Li2MnO3. The lattice parameter of LiMn2O4 increases slightly with increase of the lithium content at x < 1 (0.823 ~ 0.824 nm), but decreases sharply for x = 1.0 ~ 1.8 (0.824 to 0.817 nm). Differential thermal analysis showed at temperature higher than 935&#x00BA;C, rocksalt phase (with tetragonal symmetry), Mn3O4 will be produced. Above 1045&#x00BA;C, the crystallite phases contain cubic LiMn2O3 spinel, tetragonal Mn3O4 and orthorhombic symmetry LiMnO2. After high temperature annealing (> 935&#x00BA;C), the residual phase is lithium-deficient structure, Mn3O4. Apparent facets with {111}, {011}, and {001} (and {113}) planes are usually observed. The LiMn2O4 crystallite appears to be a truncated cubo-octahedron. The lowest surface energy gsv for LiMn2O4 spinel is located at the {111} planes. Lamellae domain and twinned structure are usually observed in LiMn2O4 particles. The occurrence of domain boundary and twin plane are {111} mostly. Forbidden reflections {200}, {420} in the initial powder and 1/2{311} and 1/3{422} superlattice reflections occurred after charging and discharging test reveal LiMn2O4 structure is a violation of space group. [311]/[111] peak ratio in the XRD traces is increase after electrochemical cycling. Fraction of inverse phase increased upon electrochemical cycling. The results for structure evolution under charging and discharging test can be divided into two parts for reversible and irreversible. First, unit cell of cubic spinel contracted upon charging and returned to original after discharging. The lattice constant varies back and forth between 0.824 nm to 0.814 nm for cycle between 3.3 and 4.3 V. LiMn2O4 transits to Li4Mn5O12 and l-MnO2 after fully charging to 4.3 V, which then recovers to cubic spinel LixMnyO4 after discharging to 3.3 V. The structure variations in the cycle of changing and discharging are LiMn2O4 ¡V (Li4Mn5O12 + l-MnO2) ¡V LixMnyO4. And metastable circular or rectangle LiMn2O4 particles observed in the surface can be extracted and inserted Li+ ion upon charging and discharging test. This process is reversible. Second, (1) tetragonal, rhombohedral and triclinic distorted within cubic spinel particles; (2) nanoscale regions of highly disordered lattices observed; (3) amorphous film observed in the powder particle surface; (4) crystalline phase Mn2O3 increased; (5) structure collapse inside the particle and the domain boundary; (6) inverse spinel structure. The structure of LixMn2O4 had distorted upon electrochemical cycling. These results are irreversible.
228

Balance Discharging for Series Connected Batteries

Chou, Su-Ping 15 June 2004 (has links)
Charge imbalance may happen to series-connected batteries during charging or discharging due to the discrepancies among batteries. The charge imbalance will cause some batteries being over-charged or over-discharged and is harmful to the battery cycle-life. Moreover, the storage capacity of the battery bank will not be effectively utilized. This thesis brings forth first the concept of charge equalization on discharging for battery banks. Various control strategies are implemented on a flyback converter with a multi-input transformer to provide the balance discharging function as well as output voltage regulation. Each battery of the battery bank is connected to a primary winding of the transformer via an active power switch. The batteries transfer their energy to load according to the residual energy in each battery. Meanwhile, by continually monitoring battery voltages, exhausted batteries can be disconnected to avoid being over-discharged. A battery bank with four series-connected lead-acid batteries is used as an example to illustrate the operation of the balance discharging circuit. The complicated calculations and precise control are accomplished by a digital signal processor (DSP). The experimental results advocate the applicability of the discharging circuit and control strategies.
229

Electronic Ballasts for Fluorescent Lamps with Programmed Rapid-Start

Chen, Wei-Ming 05 July 2004 (has links)
Three programmed rapid-start control schemes for the electronic ballasts with a half-bridge series-resonant inverter are proposed to improve the starting performance of the rapid-start fluorescent lamps. Included are: (1) programmed rapid-start control scheme with an ac switch, (2) programmed rapid-start control scheme with inductively coupled filament-heating circuit, and (3) programmed frequency control scheme with a series-resonant energy-tank. The first control scheme is simply to add a solid-state ac switch onto the series-resonant electronic ballast to provide programmed rapid-start for the rapid-start fluorescent lamp. The ac switch is turned on to have a zero voltage across the lamp to eliminate the glow current during the preheating interval. By adjusting the operation frequency and the duty-ratio, the electronic ballast produces first an adequate resonant current for preheating the cathode filaments, then a sufficiently high lamp voltage for ignition, and finally a stable lamp arc of the required lamp power. The second control scheme is accomplished by adding two auxiliary windings on the inductor of the power-factor-correction (PFC) circuit for the filament-heating circuits. During the preheating period, the PFC circuit is activated to provide the filament heating while the inverter remains idle to keep the lamp voltage at zero and hence to eliminate the glow current. After the filaments have been heated to the appropriate temperature, the inverter is initiated to ignite the lamp and then operate it at the required power. The third control scheme is realized by programming the operation frequency of the electronic ballast with an additional series-resonant energy-tank on the load resonant network. During the preheating interval, the electronic ballast is programmed to operate at the resonance frequency of the series-resonant energy-tank to reduce the lamp voltage and hence to eliminate the glow discharge. With carefully designed circuit parameters, the electronic ballast is able to provide an adequate current for preheating. After the emission temperature has been reached, the operation frequency is adjusted to generate a high lamp voltage for ignition, and then is located at the steady-state frequency driving the lamp with the desired power and filament current. In this dissertation, the mode operations of the proposed ballast circuits are analyzed in accordance with the conducting conditions of the power switches. The equivalent resistance model of fluorescent lamp is implemented to calculate the performances of the ballast-lamp circuit at steady-state. The design equations are derived and the computer analyses are performed with the fundamental approximation on the equivalent circuit models of fluorescent lamps. In addition, in order to accurately predict the operating characteristic of the preheating circuit, a mathematical model is developed to interpret the variations of the filament resistance during preheating. Finally, the laboratory electronic ballasts with the proposed control schemes are built and tested. Satisfactory performances are obtained from the experimental results.
230

Erosion Characteristics of the Composite Electroplated Layer of Nickel-Diamond Powder under Static Single-Arc Discharge

Gao, Jian-ming 02 August 2004 (has links)
Diamond has superior characteristics, such as high hardness, high isolation, and high breakdown voltage, but it is also difficult to manufacture for industrial application. Because diamond is a nonconductor, the usual electrical discharge machining (EDM) method cannot be used. Hence, this study uses the plating nickel to keep the diamond powder as the composite electroplated layer of nickel-diamond powder. The variation of the composite layer and the diamond particle erosion characteristic after arc discharge can be realized by single-arc discharge. By the result of experiment, it can be known that the erosion area will be enlarged when the diamond particle is near to central erosion area, because the diamond that has good heat stability makes plasma to spread. The erosion area will be decreased when the diamond particle is near to edge of erosion area, because it stops the melted nickel to spread. The surface of diamond particle is broken slightly that the particle become more spherical and has some nickel remain on it when pulse voltage is less than 300 volt or the diamond particle is near to edge of erosion area. The surface of diamond particle is broken seriously that the particle is cracked to pieces when pulse voltage is more than 300 volt or the diamond particle is near to central erosion area.

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