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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.
241

Proposta de um modelo de planejamento agregado da produção numa usina de açúcar e álcool vinculado à flutuação de preços em mercados à vista e no mercado futuro. / A model of aggregate production planning in a sugar mill and alcohol linked the decisions of prices in future markets and present markets.

Carvalho, Marcelo Dias 09 November 2009 (has links)
O objetivo de estudo desta dissertação é o desenvolvimento de um modelo de planejamento agregado da produção que apóie as decisões de nível gerencial e de diretoria das usinas de açúcar e álcool no que tange às variedades de cana colhidas em cada semana, às compras de cana-de-açúcar de terceiros, ao tipo de transporte (próprio ou terceirizado) a se utilizar em cada semana, ao total de cana moída por semana para atendimento da demanda e aos processos (industrial e comercial) que se devem escolher para produzir e comercializar açúcar e álcool. As decisões devem ocorrer em função de preços nos mercados interno, externo e mercado futuro, do fluxo de caixa da empresa, da capacidade da usina para armazenar açúcar e álcool e da possibilidade de uso de estoque de terceiros. As decisões por compra de cana, escolha de processos e venda de produtos são tomadas semanalmente num horizonte móvel de planejamento de 52 semanas, que inclui o tempo de safra no centro-sul do Brasil (meados de março a meados de dezembro, aproximadamente 36 semanas) mais o período de entressafra (aproximadamente 16 semanas, de meados de dezembro a meados de março). A procura por melhores estratégias de comercialização de tal forma a auxiliar a tomada de decisões é uma necessidade constante dos empresários do setor, que muitas vezes são surpreendidos pelas variações de preços de açúcar e álcool no mercado interno, externo e mercado futuro. Na parte comercial, este trabalho utiliza o método Delphi de previsão de preços de açúcar e álcool que balizam as tomadas de decisão no planejamento e controle da produção das usinas de açúcar e álcool. Define-se Hedge como a operação financeira de proteger determinado ativo de uma empresa contra variações inesperadas de preços. Neste trabalho, utiliza-se um modelo de escolha de mix de produto para Hedge vinculado à lucratividade e minimização de risco denominado Modelo de Semi- Variância com análise de cenários de Markowitz. Nas decisões relacionadas com as partes agrícola, industrial e comercial, faz-se uso de um modelo de programação linear inteira mista e para resolvê-lo utiliza-se o software de programação matemática LINGO e suas interfaces com a planilha eletrônica Excel. Nas decisões vinculadas ao mix ótimo para o Hedge em cada semana, faz-se uso de um modelo de programação quadrática resolvido pelo LINGO e suas interfaces com a planilha eletrônica Excel. Um estudo de caso foi realizado numa usina de açúcar e álcool no município de Junqueirópolis (SP) para validar o modelo proposto. / The objective of study this dissertation is to develop a model of aggregate production planning to support the decisions of management and board level of sugar and alcohol plants in regard to varieties of cane harvested each week, purchasing cane of nonsugar, the type of transport (own or outsourced) to use each week, the total cane processed per week for taking care of the demand and processes (industrial and commercial) and that must be chosen to produce and sell sugar and alcohol. Decisions must occur in terms of domestic, foreign and future market prices, the company\'s cash flow and the capacity to store sugar and alcohol and the possibility of using stock to third parties. Decisions about buying cane, choice of processes and products for sale are made in a weekly mobile planning horizon of 52 weeks, which includes the time of harvest in central-southern Brazil (mid-March to mid-December, approximately 36 weeks) plus the off-season (approximately 16 weeks, from mid-December to mid March). The demand for better marketing strategies to help such decision making is a constant need for entrepreneurs in the sector, which are often surprised by the changes in prices of sugar and alcohol in the internal, external and future market. In the commercial part, this study uses the Delphi method of forecasting the price of sugar and alcohol that guides the decision-making in planning and controlling the production of sugar and alcohol plants. Hedging is defined as a financial transaction to protect certain assets of a business against unexpected changes in prices. In this work, it is used a model of choice of product mix for Hedge linked to profitability and minimizing risk named Model of Semi-Variance analysis with scenarios of Markowitz. In decisions related to the agricultural, industrial and commercial parts it is used a type of mixed integer linear programming and to solve it is used the mathematical programming software LINGO and its interface with Excel spreadsheets. In decisions related to the optimal mix for Hedge in each week, is used a quadratic programming model solved by LINGO and its interface with Excel spreadsheets. A case study was conducted in a sugar mill and alcohol in the city of Junqueirópolis (SP) to validate the proposed model.
242

Applications of Advanced Time Series Models to Analyze the Time-varying Relationship between Macroeconomics, Fundamentals and Pan-European Industry Portfolios / Anwendungen moderner Zeitreihenverfahren zur Analyse zeitvariabler Zusammenhänge zwischen gesamtwirtschaftlichen Entwicklungen, Fundamentaldaten und europäischen Branchenportfolios

Mergner, Sascha 04 March 2008 (has links)
No description available.
243

Curriculum 2005 assessment policy and its implementation in grade 9 in the Limpopo Province

Thomas, Solly 08 1900 (has links)
The study investigates the implementation of the Curriculum 2005 assessment policy guidelines in natural sciences in grade nine in five secondary schools selected by judgement sampling in Limpopo Province. Data were gathered by means of a literature study, examination of learner and educator portfolios and interviews with educators. Findings show that most participants were unable to carryout the continuous assessment (CASS) tasks as required. A discrepancy in the quality and quantity of assessment tasks among the schools emerged. All schools replaced the final common tasks for assessment (CTA) with internal examinations due to the late arrival of materials and the level of difficulty. Contributing factors were lack of a well-planned curriculum, proper resource materials, lack of coordination of efforts due to poor curriculum support and management and inadequate professional competence in the Outcomes-based methods of teaching, learning and assessment. Recommendations to address the above problems are made. / Educational Studies / M.Ed. (Education Management)
244

Educators' experience of the implementation of outcomes-based education in grade nine

Ghanchi Badasie, Razia Banoo 30 November 2005 (has links)
This research focuses on educators' experience of implementing outcomes-based education in grade nine in secondary schools in South Africa. Two schools were chosen as settings for the qualitative research project. Three focus groups with 20 educators, two focus groups with 14 managers and seven personal interviews were conducted. Twelve classrooms were also observed where grade nine learners were being taught. Findings indicated that some educators found the experience of implementing OBE positive in that it improved their repertoire of facilitating and assessing skills. The reasons for citing OBE as a negative experience were given as the following: an increased workload, poor training and lack of follow-up by the Department and the school management team's degree of involvement. Recommendations were made on how to ease the burden on educators implementing OBE in their classrooms and to empower school managers to manage the implementation of OBE within their respective areas of responsibility. / Educational Studies / M. Ed. (Education Management)
245

Proposta de um modelo de planejamento agregado da produção numa usina de açúcar e álcool vinculado à flutuação de preços em mercados à vista e no mercado futuro. / A model of aggregate production planning in a sugar mill and alcohol linked the decisions of prices in future markets and present markets.

Marcelo Dias Carvalho 09 November 2009 (has links)
O objetivo de estudo desta dissertação é o desenvolvimento de um modelo de planejamento agregado da produção que apóie as decisões de nível gerencial e de diretoria das usinas de açúcar e álcool no que tange às variedades de cana colhidas em cada semana, às compras de cana-de-açúcar de terceiros, ao tipo de transporte (próprio ou terceirizado) a se utilizar em cada semana, ao total de cana moída por semana para atendimento da demanda e aos processos (industrial e comercial) que se devem escolher para produzir e comercializar açúcar e álcool. As decisões devem ocorrer em função de preços nos mercados interno, externo e mercado futuro, do fluxo de caixa da empresa, da capacidade da usina para armazenar açúcar e álcool e da possibilidade de uso de estoque de terceiros. As decisões por compra de cana, escolha de processos e venda de produtos são tomadas semanalmente num horizonte móvel de planejamento de 52 semanas, que inclui o tempo de safra no centro-sul do Brasil (meados de março a meados de dezembro, aproximadamente 36 semanas) mais o período de entressafra (aproximadamente 16 semanas, de meados de dezembro a meados de março). A procura por melhores estratégias de comercialização de tal forma a auxiliar a tomada de decisões é uma necessidade constante dos empresários do setor, que muitas vezes são surpreendidos pelas variações de preços de açúcar e álcool no mercado interno, externo e mercado futuro. Na parte comercial, este trabalho utiliza o método Delphi de previsão de preços de açúcar e álcool que balizam as tomadas de decisão no planejamento e controle da produção das usinas de açúcar e álcool. Define-se Hedge como a operação financeira de proteger determinado ativo de uma empresa contra variações inesperadas de preços. Neste trabalho, utiliza-se um modelo de escolha de mix de produto para Hedge vinculado à lucratividade e minimização de risco denominado Modelo de Semi- Variância com análise de cenários de Markowitz. Nas decisões relacionadas com as partes agrícola, industrial e comercial, faz-se uso de um modelo de programação linear inteira mista e para resolvê-lo utiliza-se o software de programação matemática LINGO e suas interfaces com a planilha eletrônica Excel. Nas decisões vinculadas ao mix ótimo para o Hedge em cada semana, faz-se uso de um modelo de programação quadrática resolvido pelo LINGO e suas interfaces com a planilha eletrônica Excel. Um estudo de caso foi realizado numa usina de açúcar e álcool no município de Junqueirópolis (SP) para validar o modelo proposto. / The objective of study this dissertation is to develop a model of aggregate production planning to support the decisions of management and board level of sugar and alcohol plants in regard to varieties of cane harvested each week, purchasing cane of nonsugar, the type of transport (own or outsourced) to use each week, the total cane processed per week for taking care of the demand and processes (industrial and commercial) and that must be chosen to produce and sell sugar and alcohol. Decisions must occur in terms of domestic, foreign and future market prices, the company\'s cash flow and the capacity to store sugar and alcohol and the possibility of using stock to third parties. Decisions about buying cane, choice of processes and products for sale are made in a weekly mobile planning horizon of 52 weeks, which includes the time of harvest in central-southern Brazil (mid-March to mid-December, approximately 36 weeks) plus the off-season (approximately 16 weeks, from mid-December to mid March). The demand for better marketing strategies to help such decision making is a constant need for entrepreneurs in the sector, which are often surprised by the changes in prices of sugar and alcohol in the internal, external and future market. In the commercial part, this study uses the Delphi method of forecasting the price of sugar and alcohol that guides the decision-making in planning and controlling the production of sugar and alcohol plants. Hedging is defined as a financial transaction to protect certain assets of a business against unexpected changes in prices. In this work, it is used a model of choice of product mix for Hedge linked to profitability and minimizing risk named Model of Semi-Variance analysis with scenarios of Markowitz. In decisions related to the agricultural, industrial and commercial parts it is used a type of mixed integer linear programming and to solve it is used the mathematical programming software LINGO and its interface with Excel spreadsheets. In decisions related to the optimal mix for Hedge in each week, is used a quadratic programming model solved by LINGO and its interface with Excel spreadsheets. A case study was conducted in a sugar mill and alcohol in the city of Junqueirópolis (SP) to validate the proposed model.
246

E-portfolio as an alternative assessment approach enhancing self-directed learning in an Open Distance Learning environment

Nkalane, Patience Kelebogile 11 1900 (has links)
Assessment is an integral part of teaching and learning in higher education. The use of technology in higher education, particularly in the ODL environment, has brought some changes on how we teach and assess students. The traditional assessment practices needed to be reviewed and reconfigured to meet the requirements of the 21st century assessment practices. The purpose of this doctoral study was to design a framework to guide the assessment of an E-portfolio as an alternative assessment approach in an ODL context. The integrated theoretical framework of the learning theories (behaviourism, cognitive and constructivist) and the ODL theories (connectivist, online collaborative and self-directed) underpinned the study. This integrated framework explored lecturer and student experiences in the use of Eportfolio, as an alternative assessment to enhance self-directed learning. In striving to get in-depth insight into this study, the pragmatism paradigm, which calls for the mixed methods research design, was employed for the collection and analysis of data. The sample was drawn from a cohort of six participants and fifty-six respondents in the three colleges of the university. This sequential exploratory mixed methods design employed semi-structured interviews, document analysis for qualitative data collection while a Likert scale of an online questionnaire was used to collect quantitative data. The findings of this research indicated that the E-portfolio can be of greater use as an alternative assessment approach and was able to empower students with higher order thinking skills, critical thinking skills and self-directed learning equipping them with the 21st century skills. Several challenges were experienced during the implementation of the E-portfolio, which included lack of digital literacies and technical assistance, nonsynchronisation of the learning management system for hosting E-portfolio (myUnisa), UNISA’s policies which do not include E-portfolio assessment processes and procedures. In conclusion, the literature study, the findings of the empirical research and the recommendation of this study formed the basis for designing the framework to guide the assessment of an E-portfolio as an alternative assessment strategy for an ODL context. / Curriculum and Instructional Studies / Ph. D. (Curriculum Studies)
247

Evaluación del comportamiento de carteras con gestión automatizada comparada con los rendimientos de carteras aleatorias y fondos de inversión

Plá María, Marcos 24 July 2014 (has links)
Este trabajo se plantea la cuestión que millones de inversores se han planteado en algún momento: ¿cuál es la mejor opción para sus ahorros, fondos de inversión, inversión aleatoria o estrategias de análisis técnico? Para este propósito se describen en primer lugar las normas que regulan a las instituciones de inversión colectiva (IIC) en España, distinguiendo entre los diferentes tipos de fondos en cuanto a su forma legal. A continuación se repasan las teorías sobre eficiencia en los mercados financieros. Estas teorías se enlazan con los estilos de gestión; gestión pasiva para aquellos ortodoxos que defienden la eficiencia fuerte y gestión activa para los gestores que no toman la eficiencia como un dogma. Estos últimos creen en las anomalías de mercado y recurren a estrategias basadas en fundamentos contables (estimación de beneficios, ventas, etc.). Esta primera parte concluye con una evaluación del rendimiento de los fondos españoles según su estilo de inversión. Puesto que esta no es del todo favorable para las gestoras se intentan aportar motivos por los cuales los fondos siguen disfrutando de amplia aceptación. La segunda parte del trabajo describe la metodología empleada para estudiar el comportamiento de una cartera de inversión gestionada mediante estrategias de análisis técnico. Con este fin ha sido necesario desarrollar un software capaz de realizar la gestión de carteras y que se alimenta de cotizaciones históricas desde 1/2003 hasta 1/2012. Los datos se separan en dos estudios paralelos, uno para Europa y el otro para EE.UU con el objetivo de analizar diferencias y semejanzas. El programa permite el control completo sobre la cartera, gestión de liquidez, stop-loss, etc.; y nos abastece al mismo tiempo de una gran cantidad de información estadística. La particularidad del software es la capacidad de poder variar los parámetros de las estrategias mediante barrido, obteniendo así no solamente una única simulación sino una población de simulaciones referidas a una estrategia. En la tercera parte se recurre a este conjunto de simulaciones a las que denominaremos estudios y están compuestas por varios millones de operaciones de compra y venta. Estos estudios se aproximan a funciones normales que describen la esperanza de rentabilidades que tendría un inversor que decidiera participar en el mercado siguiendo alguna de las estrategias descritas. Para poder comparar el comportamiento de las estrategias técnicas se utilizan diferentes métodos aleatorios que pretenden simular una operativa al azar. Por último se confrontan los tres métodos de inversión: fondos, análisis técnico y aleatorio; comparados con los índices de referencia correspondientes. / Plá María, M. (2014). Evaluación del comportamiento de carteras con gestión automatizada comparada con los rendimientos de carteras aleatorias y fondos de inversión [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/38987
248

Criteria for sound Christian education, with reference to Christian Education South Africa (CESA) 1984-1993 : a historical-educational investigation and evaluation

Nel, Monika Barbara Elisabeth 11 1900 (has links)
Christian Education South Africa (CESA), formerly known as Accelerated Christian Education (South Africa) or ACE(SA), represents a significant number of evangelical Christian schools in South Africa. Most CESA schools are multiracial· and part of charismatic fellowships. The purpose of this study was to investigate CESA {its roots, philosophy of education and methodology) and to evaluate the quality of Christian education offered at CESA schools. Firstly, 'sound Christian education' was defined. Secondly, a model for assessing Christian education was developed. The SAPPAB model with its six criteria (spiritual, academic, physical, practical, administrative and balance) assess both the biblical and t educational 'soundness' of an education programme . . Information was gathered over six years by way of interviews, surveys, ethnographic and in-depth case studies. Evaluations included individual CESA schools, CESA as an organization and the ACE programme. The major finding was that individual CESA schools do contribute meaningfully to sound Christian education, but that the organization as such lost its vision and its influence. / Educational Studies / M. Ed. (History of Education)
249

Lecturers' perceptions on the value of the experience of completing a teaching portfolio

Grace, Elaine Lydia 01 1900 (has links)
A teaching portfolio allows lecturers to track their own growth and development in teaching and learning, as it helps to document their career’s journey. This study gained insight into this experience from the lecturers’ perspectives. The research paradigm was qualitative and the study used a sample of lecturers from an independent tertiary institution in Johannesburg. Personal interviews provided rich data and themes were developed from the data to answer the research questions concerning the value of doing a teaching portfolio. Lecturers’ perceptions provided clear evidence of the value of doing a teaching portfolio, because it developed their personal competence, knowledge, skills and higher-order thinking. However, the findings showed that the success of a teaching portfolio remained dependent on individual motivation and how the process was implemented. Any challenges experienced tended to negatively affect motivation, thereby decreasing the perceived value of a teaching portfolio. This study recommended that a teaching portfolio might offer a solution to some of the current education issues within the South Africa context, especially with regard to the lack of content knowledge and the disempowerment of teachers. / ʼn Onderrigportefeulje maak dit vir dosente moontlik om hul eie groei en ontwikkeling ten opsigte van onderrig en leer te monitor, omdat dit hulle help om hul loopbaan te dokumenteer. Hierdie studie gee insig in hierdie ervaring vanuit dosente se oogpunt. Die navorsingsparadigma was kwalitatief en die studie het ʼn steekproef van dosente van ʼn onafhanklike tersiêre instelling in Johannesburg behels. Persoonlike onderhoude het ryk data opgelewer en temas is op grond van die data ontwikkel om die navorsingsvrae oor die waarde van ʼn onderrigportefeulje te beantwoord. Dosente se persepsies was ʼn duidelike bewys van die waarde van ʼn onderrigportefeulje, omdat dit hul persoonlike bevoegdheid, kennis, vaardighede en hoërorde-denke ontwikkel. Die bevindinge het egter getoon dat die sukses van ʼn onderrigportefeulje steeds onderhewig is aan individuele motivering en hoe die proses geïmplementeer is. Enige uitdagings was geneig om ʼn negatiewe invloed op motivering te hê en sodoende die vermeende waarde van ʼn onderrigportefeulje te verlaag. Hierdie studie beveel aan dat ʼn onderrigportefeulje ʼn oplossing kan bied vir sommige van die opvoedingskwessies in die Suid-Afrikaanse konteks, veral met betrekking tot die gebrek aan inhoudkennis en die ontneming van onderwysers se mag. / Photefolio ya go ruta e kgontša bafahloši go latišiša kgolo le tšwetšopele tše e lego tša bona ka go goruta le go ithuta, ka ge e thuša go rekhota leeto la mošomo wa bona. Thutelo ye e hweditše tshedimošo maitemogelong a go tšwa tebelelong ya bafahloši. Dikgopolo ka ga nyakišišo e bile tša go hwetša tshedimošo ka go kwešiša le go lemoga mabaka a bothata gomme thutelo ye e dirišitše sampolo ya bafahloši go tšwa institušeneng ye e ikemetšeng ya morago ga marematlou go la Johannesburg. Ditherišano tša motho ka botee di tšweleditše datha ye bohlokwa gomme merero e hlagišitšwe go tšwa datheng go fa karabo ya dipotšišo tša dinyakišišo tše di lebanego bohlokwa bja go dira photefolio ya go ruta. Dikgopolo tša bafahloši di file bohlatse bjo bo kwešišegago bja bohlokwa bja go dira photefolio ya go ruta, ka gobane e godišitše, botsebi, tsebo, mabokgoni tša bona le mokgwa wa go nagana wa maemo a godimo. Le ge go le bjalo, dikhwetšo di bontšhitše gore katlego ya photefolio ya go ruta e dutše e ithekgile go tutuetšo ya motho le ka moo tshepedišo e phethagaditšwego. Ditlhohlo dife goba dife tšeo di itemogetšwego di bile le go huetša tutuetšo, ka gorealo tša fokotša boleng bjo bo lebeletšwego bja photefolio ya go ruta. Thutelo ye e šišintše gore photefolio ya go ruta e ka fa tharollo go tše dingwe tša ditlhagišo tša bjale tša thuto kemong ya Afrika Borwa, gagolo malebana le tlhokego ya dintlhatsebo, dikgopolo le melaotshepetšo tšeo di rutwago le go ithuta ka tšona gammogo le go se be le maatla ga barutiši. / Psychology of Education / M. Ed. (Psychology of Education)
250

Alliance portfolios and value creation: Theory and empirical evidence from the global airline industry

Wassmer, Ulrich Franz 21 May 2007 (has links)
Les carteres d'aliances importen? Com afecten els recursos als quals les empreses accedeixen per diverses aliances estratègiques simultànies amb socis diferents a la creació de valor i a l'apropiació de valor? Les carteres d'aliances expliquen l'heterogeneïtat entre empreses respecte del valor que capten quan entren en noves aliances estratègiques? Aquesta tesi doctoral es basa en la teoria dels recursos i en la bibliografia sobre el comportament estratègic i les dinàmiques competitives, i presenta un model teòric que es refereix a la creació de valor i l'apropiació en empreses que accedeixen a recursos a través de diverses aliances simultànies amb socis diferents. El model mostra que la creació de valor en les carteres d'aliances és una funció del valor creat per combinacions sinergètiques de recursos que impliquen recursos als quals tenen accés diferents socis, com també del valor destruït a causa de la incompatibilitat entre la combinació de recursos d'una empresa focal i els recursos dels seus socis. Sobre la base d'aquest model teòric, s'han desenvolupat diverses hipòtesis en un ambient marginal en què una empresa connectada multilateralment afegeix una nova aliança estratègica a la seva cartera d'aliances. Per comprovar aquestes hipòtesis, s'ha emprat la metodologia de l'event study i s'han utilitzat dades de la indústria de els línies aèries globals sobre acords de code share subscrits entre 1994 i 1998. Els resultats mostren que el mercat recompensa les empreses que formen aliances amb socis que tenen recursos complementaris i poden aportar recursos que no només es poden combinar amb els recursos propis de l'empresa sinó també amb els relacionals i que també són compatibles amb els dels socis que formen l'aliança. D'altra banda, els resultats també mostren que el mercat penalitza les empreses que formen aliances que aporten recursos incompatibles amb les carteres d'aliances, atès que creen un conflicte competitiu amb alguns dels socis existents. Els resultats de la part empírica d'aquesta anàlisi abonen la tesis que les carteres d'aliances afecten els resultats de les empreses que entren en aliances estratègiques. Aquest estudi conclou que els recursos als quals es té accés per mitjà d'aliances entre empreses s'han d'avaluar no tan sols per les seves característiques pròpies y diàdiques sinó també en el context de les carteres d'aliances. / ¿Importan los portafolios de alianzas? ¿Cómo afectan los recursos a los que acceden las empresas por varias alianzas estratégicas simultáneas con socios diferentes a la creación de valor y a la apropiación de valor? Los portafolios de alianzas ¿explican la heterogeneidad entre empresas con respecto al valor que captan cuando entran en nuevas alianzas estratégicas? Esta tesis doctoral se basa en la teoría de los recursos y en la bibliografía sobre el comportamiento estratégico y las dinámicas competitivas, y presenta un modelo teórico que se refiere a la creación de valor y apropiación en empresas que acceden a recursos a través de varias alianzas simultáneas con socios diferentes. El modelo muestra que la creación de valor mediante un portafolio de alianzas es una función del valor creado por combinaciones sinergéticas de recursos que implican recursos a los cuales acceden diferentes socios, así como del valor destruido a causa de la incompatibilidad entre la combinación de recursos de una impresa focal y los recursos de sus socios. Sobre la base de este modelo teórico, se han desarrollado varias hipótesis en un ambiente marginal en el que una empresa conectada multilateralmente añade una nueva alianza estratégica a su cartera de alianzas. Para comprobar estas hipótesis se ha empleado la metodología del event study, y se han utilizado datos de la industria global de las aerolíneas sobre acuerdos de code share suscritos entre 1994 y 1998. Los resultados muestran que el mercado recompensa a las empresas que forman alianzas con socios que tienen recursos complementarios y pueden aportar recursos que no sólo pueden combinarse con los recursos propios de la empresa sino también con los relacionales y que también son compatibles con los de los socios que forman la alianza. Por otra parte, los resultados también muestran que el mercado penaliza a las empresas que forman alianzas que aportan recursos que son incompatibles con los portafolios de alianzas, en el sentido de que crean un conflicto competitivo con algunos de los socios existentes. Los resultados de la parte empírica de este análisis abonan la tesis de que los portafolios de alianzas afectan a los resultados de empresas que entran en alianzas estratégicas. Este estudio concluye que los recursos a los que se accede a través de las alianzas entre empresas han de evaluarse no sólo por sus características propias y diádicas sino también en el contexto de los portafolios de alianzas. / Do alliance portfolios matter? How do resources accessed from multiple simultaneous strategic alliances with different partners affect value creation and value appropriation? Do alliance portfolios explain heterogeneity across firms with respect to the value that they derive from entering into new strategic alliances? This dissertation builds on insights from the resource-based view of the firm and the strategic behaviour and competitive dynamics literature and advances a theoretical model that addresses value creation and appropriation in firms that access resources through multiple simultaneous inter-firm alliances with different partners. The model illustrates that value creation on the alliance portfolio level is a function of the value created from synergistic resource combinations involving resources accessed from different partners as well the value destroyed by incompatibilities between a focal firm's resource combinations and those deployed by its partners. Based on this theoretical model, empirically testable hypotheses are developed in a marginal setting, in which a multilaterally connected firm adds one new strategic alliance to its alliance portfolio. The hypotheses are tested using an event study method approach and data from the global airline industry on code share agreements formed between 1994 and 1998. The results show that the market on one side rewards firms entering into strategic alliances with partners that possess complementary resources and that contribute resources that cannot only be combined with firms' own but also existing relational resources and that are compatible with the firms' alliance portfolios. On the other side, results show that the market penalizes firms entering into alliances that contribute resources that are alliance portfolio incompatible in the sense that they create a competitive conflict with some of the existing alliance partners. The findings of the empirical part of this dissertation support the view that alliance portfolios affect the performance of firms entering into strategic alliances. This study concludes that resources accessed through inter-firm alliances should not only be evaluated on their standalone and dyadic attributes but also in the context of alliance portfolios.

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