587 research outputs found
Analysis of Bounds on Hybrid Vector Clocks
No full textHybrid vector clocks (HVC) implement vector clocks (VC) in a space-efficient manner by exploiting the availability of loosely-synchronized physical clocks at each node. In this paper, we develop a model for determining the bounds on the size of HVC. Our model uses four parameters, epsilon: uncertainty window, delta: minimum message delay, alpha: communication frequency and n: number of nodes in the system. We derive the size of HVC in terms of a differential equation, and show that the size predicted by our model is almost identical to the results obtained by simulation. We also identify closed form solutions that provide tight lower and upper bounds for useful special cases.
Our model and simulations show the HVC size is a sigmoid function with respect to increasing epsilon; it has a slow start but it grows exponentially after a phase transition. We present equations to identify the phase transition point and show that for many practical applications and deployment environments, the size of HVC remains only as a couple entries and substantially less than n. We also find that, in a model with random unicast message transmissions, increasing n actually helps for reducing HVC size
Microstructure-property relaltionship in silicon carbide armor ceramics
No full textDefects are one of the factors that show a negative effect on the ballistic performance. Uniform microstructures with a low percentage of well distributed porosity could possibly demonstrate high ballistic strength; therefore, it is of interest to estimate the parameters that define the spatial arrangement of defects. This aspect of microstructures was investigated in a variety of silicon carbide ceramics ranging from off-density sintered samples to high density hot-pressed armor grade samples.
The spatial distribution of defects was examined by various techniques including nearest neighbor distance distributions, tessellation analysis, and pair correlation functions. Random distributions were observed for most of the samples with some degree of clustering. Hardness was selected as a mechanical property to correlate with microstructural findings. Hardness contour maps were constructed by indenting samples with a statistically significant number of indents per load to see the variation in terms of location. The large number of indents allowed for Weibull analysis to be used to examine the spread in the data and to test spatial variability. A high degree of correlation was obtained between microstructural parameters and hardness/Weibull modulus values. Smaller defect sizes and homogenous distribution of defects were shown to provide higher hardness values.
A sintered SiC tile was examined using ultrasound to determine high and low amplitude regions in C-scan image maps. Serial sectioning was performed on diced samples from these two regions. Although no significant difference was observed in terms of density and average defect size, statistical tests showed that the difference in the largest defect size detected in low amplitude and high amplitude regions was significant. Clusters of defects were also identified in the samples from the low amplitude regions. The signal loss that was observed in C-scans maps could partially be attributed to these results.
A particularly high degree of correlation was shown between average defect size, spatial distribution parameters and hardness data. These findings exhibit the strong effect of microstructure on the quasi-static properties and may affect ballistic performance.Ph.D.Includes bibliographical references (p. 210-219)
Transport and energy in India. Energy used by Indian transport systems and consequent emissions: the need for quantitative analyses (Well-to-Wheel, Lifecycle)
No full textThe purpose of this work is, at first, a general overview on the state-of-art of the transportation system in India outlining the related energy consumption, for the different transport modes, with consequent estimated emissions. These elements are essential for the preparation of a high-level strategic transport planning on the whole energy issue, to help India in the choices of most suitable transportation systems, according to the well-to-wheel analysis (WTW). Pursuing a WTW global index for India that takes into account both the energy and environmental aspects on a uniform basis is an important aim: it allows the best choices to be made as well as enabling the comparison between some of the most important powertrain and fuel options on the Indian market, the results are discussed from three different points of view: energy, environmental and economic impac
Turkey's renewable energy policy
No full textThis article expresses both Turkey's present and future renewable energy policy. Air pollution is becoming a great environmental concern in Turkey. Air pollution from energy utilization in the country is due to the combustion of coal, lignite, petroleum, natural gas, wood, and agricultural and animal wastes. In 1992, Turkish Ministry of Environment issued a regulation providing for emissions testing for cars, trucks, and vans. Achieving a solution to environmental problems requires long-term policies for sustainable development. In this aspect, renewable energy resources appear to be the one of the most efficient and effective solutions. Turkey has substantial reserves of renewable energy resources. However, actual utilization of these resources is quite low
Turkish Version Study of Parkinson's Disease Quality of Life Questionnaire (PDQL)
No full textIntroduction: This study aimed to evaluate Turkish transcultural adaptation, reliability, and validity of Parkinson's Disease Quality of Life Questionnaire (PDQL), which has been developed to assess the quality of life of patients with Parkinson's disease. Methods: Eighty-nine patients who were included in the study were diagnosed with Parkinson's disease. They were presented to the outpatient clinic of the Istanbul Faculty of Medicine, Physical Medicine and Rehabilitation department between July 2005 and April 2008. The Turkish translated version of PDQL (PDQL-TR), Unified Parkinson's Disease Rating Scale (UPDRS), and Hoehn & Yahr (HY) were used as the main outcome measures. Results: The calculated Pearson correlation coefficient for PDQL, H&Y, and UPDRS ranged between -0.36 and -0.80. Cronbach's alpha coefficients of the PDQL-TR complete questionnaire and subdomains were higher than 0.80. The absolute value of item-total score correlation coefficients by Pearson fluctuated between 0.40 (question 4-total score) and 0.88 (question 26-total score), whereas the subdomain-total score correlation coefficients ranged between 0.81 and 0.96. PDQL-TR showed high stability according to the ICC results, ranging between 0.75 (Emotional Function) and 0.88 (Parkinsonian Symptoms). Conclusion: The psychometric features of PDQL-TR are satisfactory, and our results are consistent with the previous literature findings. PDQLTR is a valid and reliable tool to measure health-related quality of life in patients with Parkinson's disease
Produção de biodiesel supercrítico a partir de semente de soja via processo não catalítico
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2012Para o mercado de motores a Diesel, a possibilidade de utilizar o biodiesel, um combustível renovável, tem motivado a realização de estudos relacionados à reações químicas com óleos vegetais. A transesterificação não catalítica de óleo vegetal utilizando um álcool em condições supercríticas vem se destacando como um método alternativo para produção de biodiesel. Quando comparado com os tradicionais métodos de catalise ácida e catálise básica usuais na indústria, o método supercrítico não catalítico tem o tempo de reação bruscamente reduzido, não há necessidade de padronização da matéria prima, a pureza do produto gerado é elevada e a geração de água residual é reduzida. Com um reator de 150 mL, capaz de suportar temperaturas de 300 °C e pressões de 250 bar, um sistema de aquecimento elétrico, válvulas e linhas para trabalho com alta pressão, busca-se o desenvolvimento do processo supercrítico para produção de biodiesel a partir da semente de soja in natura. Foi utilizada semente em três granulometrias, diferentes razões molares (etanol:óleo), percentuais de água no leito e temperaturas. Para análise estatística utilizou-se um planejamento experimental fatorial fracionário . As análises dos ésteres formados foram realizadas em cromatógrafo gasoso. Foi construída uma curva para estimativas do rendimento de ésteres em função do tempo experimental onde foram obtidos rendimentos máximos de 94,07 %. Verificou-se a presença dos ésteres palmitato, estearato, oleato, linoleato e linolenato. O biodiesel apresentou baixa susceptibilidade a oxidação tendo maiores concentrações de éster oleato. Como subproduto do processo realizado obteve-se grão de soja carbonizado com potencial calorífico de 2203,17 kcal/kg próximo da lenha (40% p/p água), madeira verde e cavacos de pinho. O modelo de balanço das espécies químicas desenvolvido foi capaz de representar a curva de rendimento para o processo de produção de biodiesel proposto, demonstrando respostas adequadas. O balanço energético realizado indicou uma relação de 1,19:1. O balanço econômico indicou que, dependendo do custo da matéria prima, etanol e semente, é possível obter viabilidade econômica.Abstract : In the diesel engine market, the possibility of using biodiesel, a renewable fuel, has motivated studies related to the transformation of vegetable oils. The non-catalytic transesterification of vegetable oil using alcohol in supercritical conditions has emerged as an alternative method for biodiesel production, since this, when compared with traditional methods of acidic and basic catalysis in industry usual, the reaction time is sharply reduced, there is no need for standardization of the raw material, the purity of the product generated is high and generation of residual water is reduced. By using a 150 ml reactor with a temperature of 300 °C and pressures of up to 250 bar, equipped with an electric heating system with valves and lines to work for high pressure, it was sought to develop the supercritical process for biodiesel production from soybean seed. The seed was used in three particle sizes, different molar ratios (ethanol:oil) 10:1, 20:1 and 30:1, three different water concentrations and temperatures of 245 °C, 255 ºC and 265 ºC. The experimental design chosen was the type factorial design . The analyses of the esters formed were carried out in a gas chromatograph. A curve was constructed to estimate the conversion efficiency. It was obtained an efficiency of 94.07%. It was possible to verify the presence of the esters: palmitate, sterate, oleate, linoleate and linolenate. Biodiesel had low susceptibility to oxidation because higher concentrations of oleate ester. As a by-product of the process carried out carbonized soybean was obtained as by-product of the process, with calorific potential of 2.203, 17 kcal/Kg same to the wood (40% water), raw wood and pine chips. The development chemical species balance model was capable of representing the yield curve for the production process, demonstrating adequate answers. The energy balance indicated a relationship of 1,19:1. The economic balance indicated that depending on the cost of raw materials, ethanol e seed, it is possible to obtain a favorable yield
Detection of volatile organic compounds in aqueous solutions by phthalocyanine coated quartz crystal microbalance
No full textThe surface of the quartz crystal microbalance was coated with using soluble three phthalocyanine coating materials for detection of a variety of volatile organic compounds such as ethanol, 2-propanol, etc. in aqueous solutions. The changes of the physico-chemical properties of phthalocyanine thin films were observed by the variation of sensitivity of the coated quartz crystal microbalance with detection media. The fundamental determination mechanism was based on the shifts in resonance frequency of the quartz crystal due to adsorption of volatile organic compounds on the coated surface of the sensor. The pi-pi or hydrogen bonding interaction were proposed as interaction mechanism to explain the sensor response during the adsorption. A two-step adsorption model for non-linear response curves and Henry's Law for linear response curves were used to describe for the adsorption mechanism. The free adsorption energies of the specific interactions from the adsorption isotherm model were also evaluated
Pyrolysis of ground beech wood in irregular heating rate conditions
No full textIn this study, pyrolysis process of beech wood was carried out a horizontal cylindrical reactor of stainless-steel, 127.0 mm height, 17.0 mm inner diameter and 25.0 mm outer diameter inserted vertically into an electrically heated tubular furnace in the absence of oxygen in irregular heating rate conditions. The increases of the pyrolysis temperatures with time of pyrolysis are considerably irregular in the reaction conditions. From 60 s to 90 s period, the average heating rate is higher than 6 K/s for the samples with -0.063 mm, +0.060 mm and +0.150 mm. The average increase of temperature is slow from 170 s to 350 s period. The increase of temperature is highly regular in 450600 s periods. The completion time of pyrolysis decreases from -0.063 turn to +0.150 mm and then it increases with increasing size of particle. The lowest completion time and completion temperature for a +0.150 mm particle size is 445 s and 670 K, respectively, in the reaction conditions. The increases of liquid yields are considerably sharply for all of the samples in 90-170 s periods. (c) 2004 Elsevier B.V. All rights reserved
Determination of heavy metal ions in aqueous solutions by phthalocyanine coated quartz crystal microbalance
No full textIn this study, thin films of phthalocyanines coated on a quartz crystal microbalance were used to investigate amount of heavy metal ions (Pb2+ and Zn2+) present in aqueous solutions. The coated materials on quartz crystal microbalance were exposed to various concentrations of Pb2+ (129510360 ppm) and Zn2+ (409-3274 ppm) ions in aqueous solutions, respectively. Determination was based on the shifts in resonance frequency of a quartz crystal microbalance responds to small changes in mass due to the adsorption of heavy metal ions on its coated surface. The adsorption mechanism in between phthalocyanine films and heavy metal ions were analysed with using two adsorption isotherm models including two-step adsorption model and Henry's Law based on the experimental data in which two-step adsorption model is for non-linear response curves and the other is for linear response curves, respectively. The effect of changes in viscosity and density of aqueous heavy metal ion solutions on changes in the resonance frequency of the quartz crystal microbalance was explored. The free adsorption energies were also calculated which indicated that the adsorption process was spontaneous
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