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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.
151

The significance of embrasure design on the fracture load of fixed denture prosthesis: an in vitro study

Albar, Nasreen Hassan 09 January 2019 (has links)
OBJECTIVE: This study evaluated two embrasure designs by measuring their differential effect on load at failure of provisional fixed partial dentures (FPDs) fabricated of five commercially available polymer-based restorative materials. METHODS: Five provisional C&B materials were selected to fabricate FPDs with two different embrasure designs: sharp vs. rounded embrasures (n=12 for each material). The test materials included: Telio CAD (Ivoclar-Vivadent), Coldpac (Motloid), Protemp Plus (3M), VersaTemp (Sultan), and Turbo Temp (Danville). The embrasures were formed using prefabricated cutters with measured Radii (0.002r and 0.03r) and a fixture to hold each provisional FPD in place for the uniform standardized cuts. Molds for the CAD/CAM provisional FPDs were used to fabricate the syringeable temporary materials and form bridges with the same geometric design. All provisional bridges were cemented using Temp-Bond (Kerr) to the corresponding standardized abutments and tested to failure in a universal Instron testing machine by loading each specimen compressively in the mid pontic region. The load at break was recorded in Newton. A one-way analysis of variance (ANOVA) was used to compare the difference in each group’s mean. RESULTS: A significant difference in fracture load was found between the two groups of designs, in which the round embrasure was significantly stronger than was the sharp. A significant difference also was found between the type of temporary material used to fabricate the bridge in the two groups, and except for Coldpac, no significant difference between the embrasure anatomies was found. Fatigue loading did not appear to influence the two bridges’ fracture load, but it did show a significant difference with respect to the modulus of elasticity, in that the bridges that underwent fatigue loading showed a higher elastic modulus by comparison to the control group. Another variable that influenced the modulus of elasticity was the type of temporary material used to fabricate the bridge, in which TelioCAD was found to be the stiffest. However, the embrasure design did not seem to affect the bridges’ rigidity. CONCLUSION: A significant difference was found in fracture strength between the rounded and sharp embrasure design. Except for Coldpac, the rounded embrasure showed higher fracture toughness than did the sharp. No significant correlation was found between the two embrasure designs and the modulus of elasticity. Interestingly, the fatigued bridges that underwent cyclic loading showed a higher modulus of elasticity. The sharp embrasure design showed no fracture in the pontic region, while the rounded design did in 5.47% of the sample. This may be explained by the photoelastic bridges, in which the stress diffuses in the rounded design to include the pontic region, while in the sharp design, the stress is concentrated on the connector area. Stress analysis, both by means of photoelastic and finite element analysis, demonstrated that the bridge with the sharp embrasure design’s stress was high in the connector area compared to the round embrasure design.
152

Fed fund target model in presence of unspanned stochastic volatility.

January 2008 (has links)
Lai, Kwok Tung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 64-66). / Abstracts in English and Chinese. / Abstract --- p.i / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Literature Review --- p.9 / Chapter 3 --- Preliminary Analysis of Data --- p.17 / Chapter 3.1 --- Data --- p.17 / Chapter 3.2 --- Preliminary Analysis of Unspanned Stochastic Volatility --- p.20 / Chapter 4 --- A Jump-Diffusion Model for Federal Funds Target Rate --- p.23 / Chapter 4.1 --- Model Specification --- p.23 / Chapter 4.2 --- Estimation Result --- p.31 / Chapter 5 --- Pricing and Hedging Performance of Interest Rate Derivatives --- p.34 / Chapter 5.1 --- Pricing Performance of Interest Rate Cap --- p.34 / Chapter 5.2 --- Hedging Performance of Interest Rate Caplet --- p.38 / Chapter 5.3 --- Hedging Performance of Interest Rate Straddle --- p.42 / Chapter 6 --- Conclusion --- p.49 / Figures --- p.51 / Tables --- p.55 / Bibliography --- p.64
153

Impacto dos radares fixos na velocidade e na acidentalidade em trecho da rodovia Washington Luís / Impact of thefFixed radars in thesSpeed and the analysis of accidents in segment of the Washington Luis highway

Yamada, Mario Guissu 15 December 2005 (has links)
Neste trabalho é avaliado o impacto do emprego de radares fixos na velocidade e na acidentalidade no trecho compreendido entre o Km 153,350 e o Km 227,800 da Rodovia Washington Luís - SP-310 (extensão de 74,450 km), localizado no interior do estado de São Paulo e cuja concessão pertence à empresa Centrovias. A avaliação do impacto na velocidade e na acidentalidade foi realizada em segmentos curtos situados no entorno dos radares e em toda a extensão do trecho. As medições de velocidade foram realizadas nos pontos onde se localizam os radares fixos, em pontos próximos (cerca de 2km antes e 2km depois) e em pontos distantes. Os resultados mostram que o limite legal de velocidade é mais respeitado no local onde se localizam os radares e um pouco antes dos mesmos. Logo depois dos radares e em pontos distantes, o limite máximo de velocidade é muito menos respeitado. É muito alta a porcentagem de veículos que passam pelos radares com velocidade acima do limite legal mais a tolerância de 7km/h (8,4%), e que, portanto, cometem infração e deveriam ser multados. Claramente, a abrangência espacial dos radares fixos no sentido de reduzir as velocidades é limitada a um pequeno segmento localizado, na sua maior parte, imediatamente antes dos mesmos. A evolução dos índices de acidentes mostra que não houve melhoria na segurança com a colocação dos radares nos segmentos localizados no entorno dos mesmos. Praticamente todos os índices apresentaram crescimento. Isso também acontece quando se analisa a evolução dos índices de acidentes ao longo de toda a extensão do trecho de rodovia estudado, pois todos os índices experimentaram crescimento / In this work the impact of the use of fixed radars in the speed and in the analysis of accidents in the segment between the Km 153,350 and the km 227,800 of the Washington Luís Highway is evaluated - SP-310 (extension of 74,450 km), located in the interior of the state of São Paulo and whose concession belongs to the Centrovias company. The evaluation of the impact in the speed and in the analysis of accidents was carried out in short segments situated around of the radars and in all the extension of the segment. The measurements of speed had been done in the points where the fixed radars were located, in points near (about of 2km before and 2km after) and in distant points. The results show that the legal limit of speed is more respected in the place where the radars are located and just before them. Soon after the radars and in distant points, the maximum limit of speed is much less respected. The percentage of vehicles that pass by the radars with speed above of the legal limit plus the tolerance of 7km/h (8,4%), is very high, resulting in infraction that should be fined. Clearly, the use of the fixed radars intending to reduce the speeds is limited to a small segment located, normally immediately before them. The evolution of the indices of accidents shows that did not have improvement in the security using radars in the segments located near them. Practically all the indices had presented growth. This also happens when it is analyzed the evolution of the indices of accidents in all the extension of the studied segment of highway, because all the indices had growth
154

Combinatorial Proofs of Generalizations of Sperner's Lemma

Peterson, Elisha 01 May 2000 (has links)
In this thesis, we provide constructive proofs of serveral generalizations of Sperner's Lemma, a combinatorial result which is equivalent to the Brouwer Fixed Point Theorem. This lemma makes a statement about the number of a certain type of simplices in the triangulation of a simplex with a special labeling. We prove generalizations for polytopes with simplicial facets, for arbitrary 3-polytopes, and for polygons. We introduce a labeled graph which we call a nerve graph to prove these results. We also suggest a possible non-constructive proof for a polytopal generalization.
155

Minimax v úlohách rozvrhování za nejistoty / Minimax in scheduling problems under uncertainty

Jeliga, Jan January 2019 (has links)
In this work, we deal with fixed interval scheduling problems with the possibility of random delay of the end of the tasks (FIS). First, we pre- sent the basic deterministic FIS problems and ways to solve them. Next, we introduce the concept of minimax and present two well-known and one new FIS problem under uncertainty, when random task delays are conside- red to belong to a certain uncertainty set. Next, we deal with the solution of previously presented FIS problems for five chosen uncertainty sets. We present both previously achieved and original results. The work concludes with a summary of a numerical study of two problems. First, we explore the possibility of Lagrange relaxation application to the first presented problem. Next we explore the quality of approximation allowing to solve the later of problems as LP. 1
156

Flexural strength of interim fixed prosthesis materials after simulated function

Heying, Jamie John 01 December 2009 (has links)
Statement of Problem There are limited studies evaluating the effect of a cyclic load on interim fixed prosthetic materials and its effect on flexural strength. Purpose of Study 1) To verify the flexural strength of previously studied interim fixed prosthetic materials. 2) To establish the flexural strength of new, advanced generation and untested interim fixed prosthetic materials. 3) To determine the effect of cyclic load on the flexural strength of interim fixed prosthetic materials. Materials and Methods Bar-type specimens of Caulk Temporary Bridge Resin, VitaVM CC, Protemp 3 Garant and Radica were fabricated according to International Standards Organization 4049 and American National Standards Institute/American Dental Association specification 27. After being stored in distilled water for 10 days, specimens were divided into Noncycled and Cycled Groups. The Noncycled Group specimens were fractured under a 3-point loading in a Bose Electroforce 3300 testing instrument at a crosshead speed of 0.75 mm/min. Cycled Groups specimens underwent a 6-12 Newton 3 Hertz cyclic load for 20,000 cycles in a Bose Electroforce 3300 testing instrument. Immediately following completion of the cycles, the specimens were fractured under a 3-point loading. Maximal loads to fracture in Newtons were recorded and mean flexural strengths were calculated (n = 20 per group). Comparisons were made with analysis of variance and Tukey's Multiple Comparison Test. Results Noncycled (NC) and Cycled (C) groups order of mean flexural strengths (MPa) from lowest to highest mean were as follows: Caulk (Noncycled - 53.83; C - 60.02), Vita VM CC (NC - 65.96; C - 66.83), Protemp 3 Garant (NC - 75.85; C - 77.18), and Radica (NC - 106.1; C - 115.96). In the Noncycled and Cycled groups, Radica was statistically superior when compared to all materials and Protemp 3 Garant was statistically superior to Caulk Temporary Bridge Resin. There was no statistically significant difference between the material's flexural strengths before and after cycles. Conclusion Within the limitations of this study, 20,000 cyclic loads of 6-12 Newtons at 3 Hertz did not have a significant effect on the flexural strength of interim fixed prosthetic materials. Radica demonstrated significantly superior flexural strength over other materials tested.
157

Priming and the Post-Prime Pause in Mixed Fixed-Ratio Schedules

Alferink, Larry Allen 01 May 1975 (has links)
The present study was designed to investigate the effects of a stimulus change inserted in the large component of a mixed fixed-ratio 10 fixed-ratio 100 schedule. In mixed fixed-ratio schedules, a run of responses which approximates the response requirement of the smaller fixed ratio occurs at the beginning of the larger fixed ratio. This run of responses and the pause it precedes is called a prime. In Experiment I, priming acquisition was compared in a mixed schedule in which a change in key-color followed completion of the first 10 responses of the fixed-ratio 100 component and a mixed schedule with no stimulus change. Primes were acquired more rapidly in the mixed schedule with the stimulus change and the number of responses in a priming run was less variable than occurred without the stimulus change. In Experiment II, the effect of the stimulus change on primes was further investigated by removal of the smaller fixed-ratio component or by varying the location of the stimulus change. Primes occurred only when the smaller fixed-ratio component was present. Varying the location of the stimulus change resulted in the transfer of control from the external stimulus to response-produced stimuli. Future investigation of this point of transfer should prove useful in the study of the proprioceptive stimulus control of homogeneous behavior sequences. In Experiments Ill through VI, the variables controlling the length of the post-prime and the post-reinforcement pauses were investigated using the mixed FR x chained FR x FR y schedule. In this series of experiments, FR x was varied with FR y held constant at both high and low values. In addition, FR y was varied with FR x held constant at both high and low values. The results indicate that the post-prime pause is primarily a function of FR y, the number of responses required after the priming run. On the other hand, both post-reinforcement pauses were shown to be a function of FR x, the size of the small fixed ratio. An interaction between FR x and FR y and both the post-reinforcement and the post-prime pauses suggested that pausing in mixed schedules is a closed system. Taken as a whole, these results indicate the importance of mixed chained schedules in the investigation of the priming phenomenon.
158

Effects of intermittent reinforcement upon fixed-ratio discrimination

Lydersen, Tore 01 May 1982 (has links)
Four pigeons had discrimination training that required the choice of a left side-key following completion of a fixed-ratio 10 an the center key, and a right side-key response after fixed-ratio 20. Correct choices were reinforced on various fixed-interval, fixed-ratio, random-interval, and random-ratio schedules. When accuracy was examined across quarters of intervals (fixed-interval schedules) or quarters of median interreinforcerrent intervals (fixed-ratio schedules), accuracy was usually laver in the second quarter than in the first, third, or fourth quarters. When accuracy was examined across quarters of ratios (fixed-ratio schedules) or quarters of median number of correct interreinforcement trials (fixed-interval schedules), accuracy increased across quarters. These accuracy patterns did not occur m random-interval or random-ratio schedules. The results indicate that, when choice patterns differed on fixed-interval and fixed-ratio schedules, these differences were due to the methods of data analyses.
159

Evolución de las terminaciones en las preparaciones dentarias en Rehabilitación Oral

Kawashima Matamoros, Luciana Sachie 14 December 2018 (has links)
El objetivo de esta revisión es reportar las técnicas paso a paso para realizar terminaciones dentarias correctas según el material para la confección de las prótesis fijas. / The aim of this review is to report on the techniques to perform corrected dental terminations according to the preparation material of fixed prostheses. / Tesis
160

中國大陸固定資產投資活動研究

賴文乾, Lai, Wen-Chian Unknown Date (has links)
由於中國大陸的經濟發展屬於投資主導型,固定資產投資的變動在中國大陸的國民經濟發展中扮演著舉足輕重的角色,歷次固定資產投資的過度膨脹,也引發了國民經濟體系嚴重的問題。因此,本論文針對固定資產投資規模、結構以及經濟效益的變動趨勢及特徵做研究分析,並探討其形成的機制及原因。 固定資產是指能長期發揮生產或服務社會的功能且保持其實物形態不變的設備,固定資產投資的規模、結構和經濟效益直接影響著未來的經濟成長、國民收入以及就業狀況,所以研究固定資產投資活動,對於了解經濟發展的模式有其重要性。 中國大陸的固定資產投資規模具有波動頻繁和波動幅度劇烈的特徵,但1981年之後,投資增長率和波動頻率都有下降的趨勢。至於各種經濟類型投資比重的變化趨勢上,從80年代開始,非全民所有制單位的投資比重即大幅上升,而且國家預算內資金佔固定資產投資資金來源的比重也逐漸在下降,自籌資金和其它投資成為固定資產投資的主要資金來源。 關於固定資產投資與通貨膨脹的關係,本論文中對1980-1998年統計資料進行迴歸分析的結果,並不能得出兩者有顯著相關的結論,所以投資膨脹未必是通貨膨脹的充份條件,僅能說是其中一項重要影響因素。 在固定資產投資結構方面,呈現出明顯的非均衡發展趨勢,不但物質生產部門與非物質部門間表現出不均衡的特徵,物質生產部門內各產業的投資結構同樣具有非均衡的特性。而且自從經濟改革以來,固定資產投資的地區結構不均衡現象有持續惡化的趨勢,從投資總量和增長速度來看,東部沿海地區都超過中西部地區,而且投資比重仍持續上升。 除了產業結構和地區結構分佈不均的問題外,固定資產投資尚面臨了外延化趨勢明顯、更新改造投資嚴重不足,以及結構中技術成份低落和大量重複建設、盲目投資等嚴重問題。 最後關於固定資產投資的經濟效益問題,表現固定資產建設效益的指標:建設週期以及固定資產交付使率,在1980年之前都呈現出較大的波動,1980年之後由於投資體制的改革以及提升效益成為經濟工作的重點,固定資產投資效益狀況有所改善,整體表現也逐漸趨於穩定。固定資產投資的整體經濟效益則大致呈現出與建設效益相同的變化趨勢。 儘管在經濟改革之後,固定資產投資效益已有所改善,但依然存在若干問題,其中主要的問題有下列三點:(1)投資效益分佈不均;(2)投資資金分散,未能形成規模經濟,重複建設嚴重,影響了資源的利用效率;(3)現有固定資產設備並未獲得充分利用。 中國大陸整個固定資產投資的演變發展,在改革之前呈現出高增長、差結構與低效益的狀況,改革之後由於政治經濟環境的穩定性有所提升,並且來自非經濟面的干擾因素減少,使得投資的增長速度和結構合理許多,投資效益也因而獲得提升,但不可忽視,中國大陸的固定資產投資依然維持著強大的膨脹動能,需要持續探化投資改革促使經濟結構更加成熟。

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