952 resultados para Multivariate statistical method


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Biomass-To-Liquid (BTL) is one of the most promising low carbon processes available to support the expanding transportation sector. This multi-step process produces hydrocarbon fuels from biomass, the so-called “second generation biofuels” that, unlike first generation biofuels, have the ability to make use of a wider range of biomass feedstock than just plant oils and sugar/starch components. A BTL process based on gasification has yet to be commercialized. This work focuses on the techno-economic feasibility of nine BTL plants. The scope was limited to hydrocarbon products as these can be readily incorporated and integrated into conventional markets and supply chains. The evaluated BTL systems were based on pressurised oxygen gasification of wood biomass or bio-oil and they were characterised by different fuel synthesis processes including: Fischer-Tropsch synthesis, the Methanol to Gasoline (MTG) process and the Topsoe Integrated Gasoline (TIGAS) synthesis. This was the first time that these three fuel synthesis technologies were compared in a single, consistent evaluation. The selected process concepts were modelled using the process simulation software IPSEpro to determine mass balances, energy balances and product distributions. For each BTL concept, a cost model was developed in MS Excel to estimate capital, operating and production costs. An uncertainty analysis based on the Monte Carlo statistical method, was also carried out to examine how the uncertainty in the input parameters of the cost model could affect the output (i.e. production cost) of the model. This was the first time that an uncertainty analysis was included in a published techno-economic assessment study of BTL systems. It was found that bio-oil gasification cannot currently compete with solid biomass gasification due to the lower efficiencies and higher costs associated with the additional thermal conversion step of fast pyrolysis. Fischer-Tropsch synthesis was the most promising fuel synthesis technology for commercial production of liquid hydrocarbon fuels since it achieved higher efficiencies and lower costs than TIGAS and MTG. None of the BTL systems were competitive with conventional fossil fuel plants. However, if government tax take was reduced by approximately 33% or a subsidy of £55/t dry biomass was available, transport biofuels could be competitive with conventional fuels. Large scale biofuel production may be possible in the long term through subsidies, fuels price rises and legislation.

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The purpose of this study is to investigate the impact of human resource (HR) practices on organizational performance through the mediating role of psychological contract (expressed by the influence of employer on employee promises fulfillment through employee attitudes). The study is based on a national sample of 78 organizations from the public and private services sector in Greece, including education, health, and banking, and on data obtained from 348 employees. The statistical method employed is structural equation modeling, via LISREL and bootstrapping estimation. The findings of the study suggest that employee incentives, performance appraisal, and employee promotion are three major HR practices that must be extensively employed. Furthermore, the study suggests that the organization must primarily keep its promises about a pleasant and safe working environment, respectful treatment, and feedback for performance, in order for employees to largely keep their own promises about showing loyalty to the organization, maintaining high levels of attendance, and upholding company reputation. Additionally, the study argues that the employee attitudes of motivation, satisfaction, and commitment constitute the nested epicenter mediating construct in both the HR practices–performance and employer–employee promise fulfillment relationships, resulting in superior organizational performance. © 2012 Wiley Periodicals, Inc.

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Accurate T-cell epitope prediction is a principal objective of computational vaccinology. As a service to the immunology and vaccinology communities at large, we have implemented, as a server on the World Wide Web, a partial least squares-base multivariate statistical approach to the quantitative prediction of peptide binding to major histocom-patibility complexes (MHC), the key checkpoint on the antigen presentation pathway within adaptive,cellular immunity. MHCPred implements robust statistical models for both Class I alleles (HLA-A*0101, HLA-A*0201, HLA-A*0202, HLA-A*0203,HLA-A*0206, HLA-A*0301, HLA-A*1101, HLA-A*3301, HLA-A*6801, HLA-A*6802 and HLA-B*3501) and Class II alleles (HLA-DRB*0401, HLA-DRB*0401and HLA-DRB* 0701).

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Word Sense Disambiguation, the process of identifying the meaning of a word in a sentence when the word has multiple meanings, is a critical problem of machine translation. It is generally very difficult to select the correct meaning of a word in a sentence, especially when the syntactical difference between the source and target language is big, e.g., English-Korean machine translation. To achieve a high level of accuracy of noun sense selection in machine translation, we introduced a statistical method based on co-occurrence relation of words in sentences and applied it to the English-Korean machine translator RyongNamSan. ACM Computing Classification System (1998): I.2.7.

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2000 Mathematics Subject Classification: 62H30, 62M10, 62M20, 62P20, 94A13.

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The paper is a new element in a series of studies analyzing macroeconomic inventory behavior by use of multi-country data. In this paper, seven hypotheses are tested with positive result. These hypotheses include subjects like relations of inventories with growth and with some other macroeconomic indicators of the use of GDP and the long-term tendencies of global inventory formations. Multivariate statistical analysis is used for evaluation.

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A kockázat statisztikai értelemben közvetlenül nem mérhető, azaz látens fogalom éppen úgy, mint a gazdasági fejlettség, a szervezettség vagy az intelligencia. Mi bennünk a közös? A kockázat is komplex fogalom, több mérhető tényezőt foglal magában, és bár sok tényezőjét mérjük, fel sem tételezzük, hogy pontos eredményt kapunk. Ebben a megközelítésben az elemző kezdettől fogva tudja, hogy hiányos az ismerete. Ezt Bélyácz [2011[ nyomán úgy is megfogalmazhatjuk: „A statisztikusok tudják, hogy valamit éppen nem tudnak.” / === / From statistical point of view risk, like economic development is a latent concept. Typically there is no one number which can explicitly estimate or project risk. Variance is used as a proxy in finance to measure risk. Other professions are using other concepts for risk. Underwriting is the most important step in insurance business to analyse exposure. Actuaries evaluate average claim size and the probability of claim to calculate risk. Bayesian credibility can be used to calculate insurance premium combining frequencies and empirical knowledge, as a prior. Different types of risks can be classified into a risk matrix to separate insurable risk. Only this category can be analysed by multivariate statistical methods, which are based on statistical data. Sample size and frequency of events are relevant not only in insurance, but in pension and investment decisions as well.

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Tanulmányunkban a European Values Study adatai alapján megvizsgáljuk, miben tér el Európában a vállalkozók értékrendje más társadalmi csoportokétól, különös tekintettel az egyéni és a kormányzati felelősségvállalás megítélésére. Kísérletet teszünk a vállalkozói értékrend különböző szintjei – személyes, társadalmi és kormányzattal kapcsolatos értékrend – közötti összefüggések feltárására. Összehasonlítjuk, mennyire jellemzi a vállalkozói értékrend az egyes európai országok lakosságát, kiemelt figyelmet fordítva Magyarországra. Egy hazai vállalkozói adatbázis alapján megvizsgáljuk, hogy a magyar vállalkozók értékrendje eltér-e az európai átlagtól, továbbá milyen törésvonalak húzódnak a vállalkozói populáción belül az értékrend szempontjából. _____ Data from the European Values Study are used to examine what sets apart the normative views of entrepreneurs from those of other social groups in Europe about individual and state responsibility. Different levels of an individual’s value system are distinguished: personal, social and state-related values are differentiated. The interrelationships among these levels are explored. Using multivariate statistical analysis, we examine the prevalence of ‘entrepreneurial’ views in European countries, especially in Hungary. Relying on data from a survey of 300 Hungarian small entrepreneurs, we explore if their value system differs from the average value system of European entrepreneurs. Finally, we examine the factors social and economic factors that influence entrepreneurs’ views on personal and state responsibility.

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The impact of climate change on the potential distribution of four Mediterranean pine species – Pinus brutia Ten., Pinus halepensis Mill., Pinus pinaster Aiton, and Pinus pinea L. – was studied by the Climate Envelope Model (CEM) to examine whether these species are suitable for the use as ornamental plants without frost protection in the Carpathian Basin. The model was supported by EUFORGEN digital area database (distribution maps), ESRI ArcGIS 10 software’s Spatial Analyst module (modeling environment), PAST (calibration of the model with statistical method), and REMO regional climate model (climatic data). The climate data were available in a 25 km resolution grid for the reference period (1961–1990) and two future periods (2011–2040, 2041–2070). The regional climate model was based on the IPCC SRES A1B scenario. While the potential distribution of P. brutia was not predicted to expand remarkably, an explicit shift of the distribution of the other three species was shown. Northwestern African distribution segments seem to become abandoned in the future. Current distribution of P. brutia may be highly endangered by the climate change. P. halepensis in the southern part and P. pinaster in the western part of the Carpathian Basin may find suitable climatic conditions in the period of 2041–2070.

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The future northward expansion of the arthropod vectors of leishmaniasis caused by climate change seems to be essential veterinary and medical problem. Our aim was to build and evaluate a Climate Envelope Model (CEM) to assess the potential effects of climate change on five European sandfly species. The studied species – Phlebotomus ariasi Tonn., P. neglectus Tonn., P. papatasi Scop., P. perfiliewi Parrot, P. perniciosus Newst., P. sergenti Parrot, P. similis Perfiliev, P. tobbi Adler, Theodor et Lourie – are important vectors of the parasite Leishmania infantum or other Leishmania species. The projections were based on REMO regional climate model with European domain. The climate data were available in a 25 km resolution grid for the reference period (1961-90) and two future periods (2011-40, 2041-70). The regional climate model was based on the IPCC SRES A1B scenario. Three types of climatic parameters were used for every month (averaged in the 30-years periods). The model was supported by VBORNET digital area database (distribution maps), ESRI ArcGIS 10 software’s Spatial Analyst module (modeling environment), PAST (calibration of the model with statistical method). Iterative model evaluation was done by summarizing two types of model errors based on an aggregated distribution. The results show that the best model results can be achieved by leaving 5-5 percentiles from the two extrema of the mean temperature, 2-2 percentiles from the two extrema of the minimum temperature, 0 percentile from the minimum of and 8 percentiles from the maximum of the precipitation.

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The potential future distribution of four Mediterranean pines was aimed to be modeled supported by EUFORGEN digital area database (distribution maps), ESRI ArcGIS 10 software’s Spatial Analyst module (modeling environment), PAST (calibration of the model with statistical method), and REMO regional climate model (climatic data). The studied species were Pinus brutia, Pinus halepensis, Pinus pinaster, and Pinus pinea. The climate data were available in a 25 km resolution grid for the reference period (1961-90) and two future periods (2011-40, 2041-70). The climate model was based on the IPCC SRES A1B scenario. The model results show explicit shift of the distributions to the north in case of three of the four studied species. The future (2041-70) climate of Western Hungary seems to be suitable for Pinus pinaster.

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This study explored Taiwanese technological higher education administrators' perceptions about the motivation and capability of their institutions to form intercollegiate alliance, their preferred areas of collaboration, and their preferred partner attributes. Possible differences in perceptions of administrators from public and private institutions were also explored. ^ The study targeted six chief administrators in each of 88 technological and vocational higher education institutions in Taiwan. A mix of quantitative and qualitative research designs was used to collect and analyze data. Quantitative data were collected from 328 administrators through a questionnaire and analyzed using univariate and multivariate statistical techniques. In addition, to obtain a deeper understanding of the process of alliance formation, qualitative data were collected through interviews with 13 administrators and content analyzed using emergent themes analysis. ^ Findings revealed that Taiwanese technological education administrators were not strongly confident in the competitive positions of their institutions. They perceived themselves as non-competitive in faculty research performance, in getting financial support, and having easy-access locations. Administrators believed that forming an alliance would help them obtain more external resources, achieve academic enhancement, provide better services, have a stronger voice, and obtain promotion to a higher institutional level. Cost cutting was not believed to be an attainable goal. ^ Strong interest was expressed for an alliance in the sharing of technology, information networks, and library resources; cross-registration; admissions and recruitment practices; school-industry endeavors; and international academic exchanges. Sharing of administrators and staff, joint bidding and purchasing, and cooperative fundraising were considered of less interest. ^ Administrators favored partners who have excellent academic programs, who have complementary skills, who are willing to share resources, and who are enthusiastic leaders. They also wanted partners to match their institutions in performance and prestige and to be geographically close to them. ^ Multivariate analysis of variance did not reveal significant differences between the perceptions of the administrators from public and private institutions. It was concluded that despite governmental encouragement and the institutions' eagerness for forming an alliance, the administrators had little confidence that a sustainable alliance could be arranged. ^

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Why do Argentines continue to support democracy despite distrusting political institutions and politicians? Support for democracy is high even though performance of the regime is poor. One would suspect that poor economic and political performance would open the door for military intervention given the history of Argentina. What changed? What explains variance across the multiple dimensions of political trust, such as trust in the regime, trust in political institutions, and trust in politicians? This dissertation is a case study of political culture through public opinion exploring the multiple dimensions of political trust in Argentina during the 1990s. ^ Variance across the different dimensions of political trust may be an indicator of the rise of a new type of citizens called "critical citizens." Critical citizens are citizens who criticize the regime to obtain democratic reforms but support the ideals of democracy. In established democracies, the rise of critical citizens is explained by a shift in individuals' value priorities towards postmaterialism. Postmaterialism is a cultural change in the direction of values that emphasize self-realization and individual well-being. Postmaterialism influences various social and political attitudes. ^ Because Argentina is experiencing a cultural change and a rise of critical citizens similar to more advanced societies, the theory of postmaterialism generated the main hypothesis to explain the multiple dimensions of political trust. This dissertation also tested an alternative explanation: the multiple dimensions of political trust responded instead to citizens' evaluations of performance. Ultimately, postmaterialism explained trust in the political regime and trust in the political institutions. Contrary to expectations, postmaterialism did not explain trust in the political elites or politicians. Trust in politicians was better explained by the alternative hypothesis, performance. ^ The main method of research was the statistical method supplemented with the comparative method when data were available. Two main databases were used: the World Values Surveys and the Latinobarometer. ^

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A multivariate statistical analysis was applied to a 10 year, multiparameter data set in an effort to describe the spatial dependence and inherent variation of water quality patterns in the mangrove estuaries of Ten Thousand Islands – Whitewater Bay area. Principal component analysis (PCA) of 16 water quality parameters collected monthly resulted in five groupings, which explained 72.5% of the variance of the original variables. The “Organic” component (PCI) was composed of alkaline phosphatase activity, total organic nitrogen, and total organic carbon; the “Dissolved Inorganic N” component (PCII) contained NO 3 − , NO 2 − , and NH 4 + ; the “Phytoplankton” component (PCIII) was made up of total phosphorus, chlorophyll a, and turbidity; dissolved oxygen and temperature were inversely related (PCIV); and salinity and soluble reactive phosphorus made up PCV. A cluster analysis of the mean and SD of PC scores resulted in the spatial aggregation of the 47 fixed stations into six classes having similar water quality, which we defined as: Mangrove Rivers, Whitewater Bay, Gulf Islands, Coot Bay, Blackwater River, and Inland Waterway. Marked differences in physical, chemical, and biological characteristics among classes were illustrated by this technique. Comparison of medians and variability of parameters among classes allowed large scale generalizations as to underlying differences in water quality in these regions. A strong south to north gradient in estuaries from high N - low P to low N - high P was ascribed to marked differences in landuse, freshwater input, geomorphology, and sedimentary geology along this tract. The ecological significance of this gradient discussed along with potential effects of future restoration plans.

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In the 1980s, government agencies sought to utilize research on drug use prevention to design media campaigns. Enlisting the assistance of the national media, several campaigns were designed and initiated to bring anti-drug use messages to adolescents in the form of public service advertising. This research explores the sources of information selected by adolescents in grades 7 through 12 and how the selection of media and other sources of information relate to drug use behavior and attitudes and perceptions related to risk/harm and disapproval of friends' drug-using activities.^ Data collected from 1989 to 1992 in the Miami Coalition School Survey provided a random selection of secondary school studies. The responses of these students were analyzed using multivariate statistical techniques.^ Although many of the students selected media as the source for most of their information on the effects of drugs on the people who use them, the selection of media was found to be positively related to alcohol use and negatively related to marijuana use. The selection of friends, brothers, or sisters was a statistically significant source for adolescents who smoke cigarettes, use alcohol or marijuana.^ The results indicate that the anti-drug use messages received by students may be canceled out by media messages perceived to advocate substance use and that a more persuasive source of information for adolescents may be friends and siblings. As federal reports suggest that the economic costs of drug abuse will reach an estimated $150 billion by 1997 if current trends continue, prevention policy that addresses the glamorization of substance use remains a national priority. Additionally, programs that advocate prevention within the peer cluster must be supported, as peers are an influential source for both inspiring and possibly preventing drug use behavior. ^