Dissertations / Theses on the topic 'LED heat management'

The efficacy, reliability and versatility of the light emitting diode (LED) can outcompete most established light source technologies. However, they are particularly sensitive to high temperatures, which compromises their efficacy and reliability, undermining some of the technology s key benefits. Consequently, effective thermal management is essential to exploit the technology to its full potential. Thermal management is a well-established subject but its application in the relatively new LED lighting industry, with its specific constraints, is currently poorly defined. The question this thesis aims to answer is how can LED thermal management be achieved most effectively? This thesis starts with a review of the current state of the art, relevant thermal management technologies and market trends. This establishes current and future thermal management constraints in a commercial context. Methods to test and evaluate the thermal management performance of a luminaire system follow. The defined test methods, simulation benchmarks and operational constraints provide the foundation to develop effective thermal management strategies. Finally this work explores how the findings can be implemented in the development and comparison of multiple thermal management designs. These are optimised to assess the potential performance enhancement available when applied to a typical commercial system. The outcomes of this research showed that thermal management of LEDs can be expected to remain a key requirement but there are hints it is becoming less critical. The impacts of some common operating environments were studied, but appeared to have no significant effect on the thermal behaviour of a typical system. There are some active thermal management devices that warrant further attention, but passive systems are inherently well suited to LED luminaires and are readily adopted so were selected as the focus of this research. Using the techniques discussed in this thesis the performance of a commercially available component was evaluated. By optimising its geometry, a 5 % decrease in absolute thermal resistance or a 20 % increase in average heat transfer coefficient and 10 % reduction in heatsink mass can potentially be achieved . While greater lifecycle energy consumption savings were offered by minimising heatsink thermal resistance the most effective design was considered to be one optimised for maximum average heat transfer coefficient. Some more radical concepts were also considered. While these demonstrate the feasibility of passively manipulating fluid flow they had a detrimental impact on performance. Further analysis would be needed to conclusively dismiss these concepts but this work indicates there is very little potential in pursuing them further.

Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Samuel Graham; Committee Member: J. Rhett Mayor; Committee Member: Yogendra Joshi. Part of the SMARTech Electronic Thesis and Dissertation Collection.

The diploma thesis deals with the simulation of heat dissipation for LED Seoul SZ5-P. The heat transfer is discussed first. Further, the issue of thermal management and its design is analyzed. The dependence of LED junction temperature on area of single and double layer printed circuit board is simulated with Ansys Icepak. Additionally, influences of the number and placement of vias on the printed circuit board and aluminum substrate printed circuit board are simulated. Last but not least, the equations describing the dependence of printed circuit board area on desired LED junction temperature are derived. Finally, the values of heat transfer coefficient including convection and radiation are determined for various heat losses and junction temperatures.

Due to the rapid evolution of technology, IT software has become incredibly complex. However the human factor still has a very important role on the application of it, since people are responsible to create software. Consequently, software vulnerabilities represent inevitable drawbacks, found to cost extremely large amounts of money to the companies. “Heartbleed” is a recently discovered vulnerability with no prior investigation that answers questions about the impact it has to the companies affected. This paper focuses on the impact of it on the market value of the companies who participated in the vulnerability disclosure process with the help of an event study methodology. Furthermore our analysis investigates if there is a different affection to the value of the company based on the roles those companies had in the process. Our results suggest that the market did not punish the companies about the existence of vulnerability. However the general negative reaction of the market to the incident reflects the importance of a strategic vulnerability disclosure plan for such cases.

La littérature décrit l'organisation hospitalière comme complexe et cloisonnée. Elle identifie le cadre de santé (CdS) comme un pivot pour traduire et articuler les différentes logiques professionnelles. Sa fonction est habituellement décrite par son travail quotidien de coordination opérationnel au détriment d'un travail destiné à structurer et améliorer l'organisation.En s'intéressant à la gestion de projet, l'objectif de la thèse est d'identifier le travail de coordination organisationnelle porté par les CdS.Elle s'appuie sur un dispositif pédagogique qui met des étudiants cadres en position de tiers pour explorer un problème organisationnel délégué par un CdS. Suite à la restitution au CdS du travail produit par le tiers, la recherche intervention a suivi la mise en œuvre de 17 projets sur une année.La thèse est organisée autour de quatre articles publiés. Le premier qualifie les bénéfices et limites de l'intervention du tiers. Le second présente les deux manières d'utiliser la production du tiers, révélatrices de la relation entre le projet, le CdS et l'équipe. Le troisième article explore les conditions de la conduite du projet porté par le CdS dans trois dimensions relationnelles : en proximité avec l'équipe soignante, en transversal avec d'autres unités de soins et au niveau institutionnel avec les acteurs administratifs et hiérarchiques. Le quatrième définit, parmi 12 variables, les facteurs qui influencent le résultat du plan d'action mis en œuvre.Les résultats montrent que l'acteur-tiers a permis de reconfigurer les relations collectives dans l'unité de soins et a relancé le CdS dans son pouvoir d'agir. Le succès du projet a été plus fréquent quand il a été présenté à l'équipe et discuté en réunion, c'est-à-dire quand le CdS a été un régulateur des débats et un arbitre. A l'inverse, lorsque le CdS a attendu un soutien institutionnel, ou que la conduite de projet a été prescriptive, sans communication formelle avec les soignants, l'échec a été plus fréquent. Au final 71% des actions ont produit une amélioration opérationnelle.La recherche montre que les attributs de méthodes et sociaux, ne sont pas tous identifiés dans la conduite de projet portée par les CdS. Les résultats permettent de qualifier le travail de coordination produit par le CdS de « Projet ordinaire ».Des préconisations sont formulées. Au niveau institutionnel, il est proposé d'identifier une unité de soutien managérial. Il est souligné l'importance de donner de la visibilité au projet ordinaire et de développer des espaces de discussions. Des activités de formation initiale et continue sont identifiées pour accompagner les futurs CdS et les CdS dans leurs pratiques managériales
Literature describes hospital organisation as complex and compartmentalised. It identifies the head nurse (HN) as a pivot to translate and articulate various professional logics. Her function is usually described by their daily operational work of coordination to the detriment of a job destined to structure and improve organisation.By focusing on project management, the aim of this thesis is to identify the work of organisational coordination carried by the HN.It leans on an educational device which puts student executives in the position of a third party to explore an organisational problem delegated by a HN. After the restitution to the HN produced by a third party, research intervention has followed the implantation of 17 projects over one year.The thesis is organised around four published articles: the first one prones the benefits and limits of the third party intervention. The second presents two methods to use the third party production, revealing the link between the project, the HN and the team. The third article explores the conditions of project management carried by the HN in three relational dimensions: in relation to the medical team, in cross section with other units of care, and at institutional level with the administrative and hierarchical actors. The fourth defines, among 12 variables, the factors which influence the result of the implemented action plan.The results show that the third party allowed to re-configure the collective relations in the unit of care and relaunched the HN in his power to act. The success of the project was more frequent when it was presented to the team and discussed in meetings, that is, when the HN helped regulate debates and be referee. On the contrary, when the HN waited for institutional support, or when the project management was prescriptive, without formal communication with the nursing staff, failure was more frequent. In summary, 71 % of the actions encountered resulted in an operational improvement.The research shows that the attributes of methods and social are not all identified in the project management carried by the HN. The results permit to consider the work of coordination produced by the HN as « ordinary Project ».Recommendations are formulated. At an institutional level, it is suggested to identify a unit managerial support. The proposals underline the importance of giving visibility to the ordinary project and necessity to develop spaces of discussion. Activities of initial and continuous training are identified to accompany the future HN and the HN in their managerial practices

This research investigated the efficacy of a post-discharge nurse-led clinic, for patients who underwent a cardiovascular interventional procedure in Australia. A randomised controlled clinical trial measured the effects of the clinic on patient confidence to self-manage and minimise psychological distress given the strong link between anxiety, depression and coronary heart disease. Hospitalisation for the procedure is short and stressful, and patients may wait up to 7-64 days for post-discharge review. This study provides preliminary quantitative and qualitative evidence that nurse-led clinics undertaken within the first week post-percutaneous coronary intervention may fill a much-needed gap for patients during a potentially vulnerable period.

Denna studie syftar till att bidra med kunskap om hur chefer upplever ledarskap i krissituationer. Studien närmar sig syftet genom att ta utgångspunkt i följande tre frågeställningar: Hur upplever chefer att deras ledarskap förändras i kris? Vilka utmaningar och problem uppstår i krissituationer? Vilka typer av strategier använder chefer för att möta de utmaningar och problem som uppstår i kris? Vi har utgått från krisen som orsakas av Covid-19 pandemin under 2020, men vår ambition är att resultatet ska kunna appliceras även på andra typer av kriser. Studien bedrivs med en kvalitativ ansats där semistrukturerade intervjuer används som datainsamlingsmetod. Materialet har analyserats genom en tematisk analys med grund i studiens teoretiska ramverk; Situationsanpassat ledarskap II.  Historiskt är ledarskap ett välbeforskat område med stor variation i både infallsvinklar och fenomen som har undersökts. Vår studie ämnar undersöka ledarskap i kris och hur detta upplevs av dem som utövar det, vilket är en del i fältet som tycks vara tämligen outforskat. Det är sedan tidigare fastställt att ledarskap och ledare har en avgörande roll i kris. Resultatet i vår studie visar att cheferna tvingats ändra sitt ledarskap som en konsekvens av krisen och de använder sig främst av en styrande ledarskapsstil. Upplevelsen av den förändringen skiljer sig mellan cheferna, där några upplever att krisen utmanat dem på ett roligt sätt och andra menar att ledarskapet nu är helt skilt från hur de vill leda. Hos de chefer som menar att krisen varit delvis rolig kan vi identifiera en konflikt mellan vilken ledare de uttrycker att de vill vara och vilken ledare de känner tillfredsställelse av att vara. Cheferna använder olika strategier för att möta de utmaningar som uppstår, men kommunikation tycks vara den främsta. Studien fastställer också att många pedagogiska processer har blivit lidande under krisen, som en konsekvens av att cheferna inte hinner individanpassa sitt ledarskap.
The aim of this study is to contribute with knowledge about how managers experience leadership in crisis. The study approaches the purpose by asking the following questions: How do managers experience  that their leadership changes in crisis? What challenges and problems arise in crisis? What type of strategies do managers use to meet the challenges and problems that arise in crisis? The study is referring to the crisis caused by the Covid-19 pandemic in 2020, however our ambition is that the result should also be applicable to other types of crises. The study is conducted with a qualitative approach where semi-structured interviews are used as a method for data collection. The material has been analyzed through a thematic analysis based on the theoretical framework of the study; Situational leadership II. Historically, leadership has been a well-researched area with considerable variation in both approaches and phenomena. Our study aims to explore leadership in crisis and how this is experienced by those who practice it, which is part of the field that seems to be fairly unexplored. What has been established in earlier studies is that leadership play a crucial role in crisis. Our result shows that the managers were forced to change their leadership as a consequence of the crisis, and they mainly use a directing leadership style. The experience of this change differs among the managers, where some feel that the crisis has challenged them in a fun way and others feel that the leadership is now completely different from how they want to lead. Among the leaders who think the crisis has been partially fun we can identify a conflict when it comes to which leader they express they want to be and which leader they feel satisfaction of being. The leaders tend to use different types of strategies to face the challenges as a consequence of the crisis, the most common one seems to be communication. The study also states that many educational processes have suffered during the crisis, as a consequence of the leaders not being able to adapt their leadership to meet the individual needs of their followers.

On assiste aujourd’hui au développement massif des technologies nomades. L’utilisation de boîtiers compacts est ainsi en plein croissance, non seulement à cause des téléphones portables et tablettes, mais aussi à cause de l’introduction massive de l’électronique dans les appareils portables de la vie quotidienne. La microélectronique embarquée dans ces appareils représente le principal outil d’information et de communication des personnes avec le monde extérieur. Le rythme de développement de ces technologies dans les dernières années est tel que les possibilités d’utilisation des appareils portables d’aujourd’hui étaient de la science-fiction il y a seulement 10 ans.Les fonctionnalités qui verront le jour dans les années à venir ne peuvent donc pas toutes être encore imaginées. Ces fonctionnalités vont toutefois très certainement impliquer une augmentation des performances de calcul des dispositifs, et par conséquent de la chaleur qu’ils dissipent.Aujourd’hui, on envisage des puces complexes comprenant plusieurs niveaux logiques et basées sur technologies hétérogènes. On demande également que ces technologies soient intégrées dans les appareils utilisés dans la vie quotidienne, qu’ils soient connectés entre eux et qu’ils réagissent de façon intelligente. Les stratégies de dissipation de la chaleur doivent donc être en adéquation avec la réduction des dimensions des dispositifs de la microélectronique.L’objectif de la thèse présentée dans ce manuscrit est ainsi d’étudier les stratégies de dissipation thermique des boîtiers compacts avec l’aide de répartiteurs de chaleur intégrés. Ce travail porte sur la caractérisation des performances et contraintes des répartiteurs thermiques avec matériaux carbonés. Les répartiteurs sont capables de dissiper sur sa surface la chaleur produite dans un point chaud.Afin d’étudier le phénomène de la dissipation avec un répartiteur, on a mis en place une méthodologie qui prend en compte le caractère multiniveau de la dissipation thermique. L’objectif est de pouvoir se concentrer sur l’interaction entre le répartiteur thermique et chacun des éléments de l’ensemble. On a réutilisé deux véhicules de test et on a désigné un véhicule de test spécifique pour l’étude de la thermique des puces imageurs.Les travaux sont basés sur deux axes : Les études d’intégration et les études thermiques. Les études d’intégration prennent en compte les contraintes dérivées de l’implémentation des couches répartiteurs dans des boitiers compactes. On se concentre d’abord sur les procès d’implémentation des couches répartiteurs au sein de l’ensemble dans un procès industriel. Ensuite on étudie les effets thermomécaniques et les effets sur l’intégrité des signaux à haute fréquence.Les études thermiques caractérisent le gain en performances dérivé de cette intégration. On analyse ces phénomènes thermiques avec des mesures et des simulations. Premièrement au niveau silicium et répartiteur, deuxièmement au niveau boitier et finalement on se concentre sur les effets dans une puce et boitier imageur.A la lumière des résultats on peut dire que les matériaux carbonés se présentent comme l’alternative plus intéressante pour l’implémentation à grande échelle de répartiteurs dans des boitiers compacts. Cette implémentation sera poussée par la recherche des prestations dans des boitiers de plus en plus complexes et hétérogènes, ou l’empreinte du répartiteur doit être minimale. La combination des couches de carbone a tous les niveaux du boitier, avec des TIMs des épaisseurs réduites sera la tendance dans les années à venir pour ce type de dispositifs.Cette thèse s’inscrit dans le cadre d’une collaboration tripartie entre le CEA-LETI de Grenoble, le laboratoire G2Elab de l’INP Grenoble et STMicroelectronics à Crolles
We witness today an explosion of nomadic technologies. Portable devices have become the main tool that people use to connect with the rest of the world. The microelectronics embedded in these devices is the technology that drives this process. The pace of development of these technologies is such that the versatility of portable devices today were science fiction only 10 years ago.The functionalities that will be integrated in the coming years cannot be imagined yet. These features will imply an increase of the computing demands, and consequently, of the heat dissipated inside them. The trend leads to complex stacks with heterogeneous modules of heat dissipating layers.These technologies will be integrated in everyday life. Internet of Things, as we call it, will demand an increasing amount of independent low footprint devices that will be connected. Heat dissipation strategies must therefore be compatible with increasingly smaller dimensions. Compact packages demand is growing rapidly, not only because of telephones and tablets, but also because of the massive introduction of electronics into in everyday life devices.The objective of the thesis is to study the integration of heat-spreaders in compact packages to enhance its thermal performance. This work goes deeply in the characterization of the thermal performance of carbon-base heat spreaders. Heat-spreaders are able to extract the heat produced in hot spots and transport it along its surface.In order to study the heat spreading phenomenon, a methodology that takes into account the multi-level nature of heat dissipation has been implemented. The objective is to be able to focus on the interaction between the heat-spreader and each one of the elements of the package stack. Two test vehicles have been re-used from previous works. A specific test vehicle was also design in order to emulate the thermal behavior of imaging sensors.The thesis is based on two main axes: Integration studies and thermal studies. The integration studies take into account the constraints derived from the implementation of heat spreaders in compact packages. Firstly, we focus on the implementation processes within an industrial process. Latelly, we study the thermomechanical effects of heat spreaders and the impact on the integrity of high frequency signals.Thermal studies are aimed to characterize the performance gain derived from this heat spreader integration. The thermal phenomena are analyzed with measurements and simulations. First at silicon and interface level, then at package level, finally we focus on the effects in image sensor die and package.In the light of the results it can be said that carbon based materials are the most interesting alternative for large-scale implementation of heat spreaders in compact packages. This implementation will be driven by the research of new functionalities and performances in compact packages. The heat spreader will have to perform while maintaining a minimal footprint. The combination of carbon layers at all package levels, along with reduced thermal interface thickness will be the trend in the coming years for this type of device.This thesis is part of a tripartite collaboration between the CEA-LETI of Grenoble, the G2Elab laboratory of the INP Grenoble and STMicroelectronics in Crolles

La thèse répond à deux problématiques, d'une part la quantification des effacements de consommation d'électricité par technologies gaz dans l'habitat et d'autre part de l'intégration de leurs valorisations dans une perspective de planification des infrastructures. Ces travaux se justifient dans un contexte d'augmentation de la pointe électrique, à l'origine d'une hausse du risque de défaillance du système, et de la baisse des consommations de gaz naturel conduisant à une sous utilisation du réseau de distribution. Pourtant, alors que la demande en gaz naturel croît du fait de l'installation de centrales à cycle combiné sur le réseau de transport, l'interaction des réseaux de distribution gaz/électricité n'est pas exploitée.Ce manuscrit envisage l'intégration des technologies gaz comme moyen de Maîtrise de la Demande en Électricité dans le processus de planification des réseaux. Ainsi les effacements de consommations d'électricité lors des périodes dimensionnantes par des micro-cogénérateurs ou des chaudières hybrides sont des solutions alternatives aux solutions de renforcement de réseaux.Pour quantifier le gisement d'effacement, nous nous intéressons à l'impact marginal des systèmes sur la demande en termes de modification de la quantité d'Énergie Non Distribuée potentielle. Les estimations des impacts de systèmes de chauffage sur la demande sont donc des prérequis à cette approche. Nous modélisons les courbes de charge régionales par une approche Bottom-Up permettant de déterminer les profils de demande marginale de chauffage en fonction des systèmes. La mise en application de cette méthode est à fiabiliser par des études socio-technico-économiques permettant de réduire les incertitudes sur les déterminants des besoins de chauffage. Une calibration en puissance des profils générés a été proposée mais n'a pu être réalisée. En revanche, nous apportons une contribution à l'analyse des courbes de charge agrégées en montrant que le modèle d'estimation actuellement utilisé par le gestionnaire de réseau s'apparente à un modèle simplifié de bâtiment
This PhD thesis addresses two issues: Firstly, the assessment of Demand Side Management (DSM) opportunity of gas and electricity technologies in dwellings, and secondly, the integration of their valuations in infrastructure planning schemes.This work originaites from a context of the growth of electricity peaks (which increased risk of system failure) and the natural gas consumption decrease which leads to an under-utilization of the gas distribution network.This manuscript focuses on the integration of gas technologies as DSM solution to contribute to the planning of electricity grid. Indeed, relieving the electricity consumption during constrained periods by diffusing micro-cogeneration or hybrid boiler, is an actual alternative to network reinforcement solutions. To quantify the load shedding capacity, we are interested in the marginal impact of demand systems on the amount of Energy Not Supplied potential. Estimating systems' impacts on heating demand is a prerequisite to this approach. So we model the regional heating load curves by a Bottom-Up approach to simulate marginal demand profiles depending on heating systems. The implementation of this method requires socio-technico-economic studies to reduce uncertainty of the determinants of heating needs. A load calibration methodology has been proposed but has not been performed. However, we make a contribution to the analysis of aggregated load curves emphasizing that the load model currently used by network operator similar to a simplified building model

Les travaux présentés dans cette thèse concernent l'étude thermique des batteries Li-ion en vue d'une application de gestion thermique pour l'automobile. La compréhension des phénomènes thermiques à l'échelle accumulateur est indispensable avant de réaliser une approche de type module ou pack batterie. Ces phénomènes thermiques sont mis en évidence à partir d'une modélisation thermique globale de deux accumulateurs de différentes chimies, en décharge à courant constant. La complexité du caractère résistif de l'accumulateur Li-ion a mené au développement d'un modèle prenant en compte l'interaction entre les phénomènes électrochimiques et thermiques, permettant une approche prédictive de son comportement. Enfin la réalisation de deux boucles expérimentales, de simulation de systèmes de gestion thermique d'un module de batterie, montre les limites d'un refroidissement classique par air à respecter les critères de management thermique. En comparaison, le second système basé sur l'intégration innovante d'un matériau à changement de phase (MCP) se montre performant lors de situations usuelles, de défauts ou encore lors du besoin d'une charge rapide de la batterie.

An importantmatter in the field of building physics is the questioning of how wellbuildings sustain ageing, and how their overall efficiency evolves over their lifetime.Many causes for degradation are carried by moisture transfer through these porousmaterials. Indeed, infiltratedwatermay transport chemicals, altermechanical properties,and cause freeze thaw damage or mould development. It may also affect thermalproperties and energetic efficiency, as well as the health and comfort of the occupants.The understanding of how moisture transfer properties evolve during the lifespan ofbuildingmaterials is however far fromcomplete. The pore structure of amaterial itselfmay change over time, or be altered by cracks and defects caused bymechanical loadingand aggravated bymoisture-induced degradation. All sizes of fracturesmay have astrong impact on heat and moisture flow in the building envelope, and their influenceis to be accounted for in any long-termperformance assessment, not only of buildingand building components,but of any built structure in general. A considerable amountof work has already been performed in order to allow predicting the hygrothermal behaviourof buildings over longer periods of time. However, an accurate prediction of allranges of damage in a building component, from microscopic to macroscopic cracks,supposes an extensive knowledge of all damage-inducing, time-varying boundary conditionsof the problem during the simulation time. This also implies high computationalcosts, as well as important needs formaterial characterisation.As a complement to these predictive methods, a new approach was undertaken,combining experimental characterisation of crack patterns and numerical simulationsof coupled heat and moisture transfer. First, a preliminary study was conducted, consistingof measurements of the water vapour permeability of diffusely damaged constructionmaterials.This allowed identifying the experimental and numerical requirementsof the remainder of the work, which aimed at providing measurements of fracturenetwork geometries for their explicitmodelling in heat andmoisture transfer simulations.Digital image correlation and acoustic emission monitoring were then performedduring the degradation of cementitiousmaterials, in order to obtain quantitativedata on crack pattern geometries, and to assess the possibilities for damagemonitoringat the building scale. The optical technique, along with an appropriate imageprocessing procedure, was found suitable for providing precisemeasurements of fracturenetworks. Amethodwas also proposed for the interpretation of acoustic emissionrecordings in terms of damage quantification, localisation and identification.Then, a newmodel for coupled heat andmoisturemodelling in cracked porousmediawas developed, that allows including such measurements of fracture patterns intoa finite element mesh, and simulating flow accordingly. This model was validated onthe basis of experimentalmeasurements: digital image correlationwas performed duringthe fracturing of concrete samples, in which moisture uptake was then monitoredusing X-ray radiography. A good accordance was found between experimental and numericalresults in terms of 2-dimensional moisture concentration distributions. The validated code was then used for the simulation of test cases, in order to assess the hygrothermalperformance of damagedmulti-layered building components subjected toreal climatic conditions. The consequences of fractures on themoisture accumulationin walls, on the amplitude of sorption/desorption cycles and on the thermal performance,were observed.

碩士
中原大學
機械工程研究所
100
Abstract High LED operational temperature should be considered. High power LED could generate more heat. Approximately 70-85% LED power is converted into heat. This high operating temperature of LED should be lowered, since high operating temperature will lead to reductions of the luminosity and the lifespan of LED. Many cooling system is used to dissipate heat from LED lamp. Most of the heat dissipation methods is using natural convection; by adding more areas to contact with the lower environment temperature. One effective way to increase the contact areas are by attached a heat sink to the heat source. Heat sink is easy to manufacture, relatively low in cost, light in weight, and can become an adequate cooling means with good reliability In this study, 10 Watt of LED lamp was used as a heat source for studying the effectiveness of extruded fin heat sink. The effectiveness was measured by the thermal resistance value between the LED and the heat sink. Lower thermal resistance value is needed for higher heat dissipation capability. Through the experiments, the effects of heat sink material, thermal interface material and heat sink mounting pressure on the thermal resistance value of the LED lamp system were investigated. Using statistical software Minitab 15, the significance of each factor can be determined. From this study it was shown that the thermal resistance was dominantly influenced by the heat sink mounting pressure, followed by the thermal interface materials and heat sink materials. Moreover, the effect of heat spreader to the heat sink resistance value was also investigated. Three types of heat spreader used in this study were: vapor chamber, copper block and aluminum block. Each of these heat spreaders was attached between the LED and extruded fin heat sink. The results show that vapor chamber is proven to be the most efficient heat spreader. Adding vapor chamber was increasing the heat sink heat dissipation performance, measured by having the lowest resistance value compared with using other types of heat spreader. Numerical simulations of ANSYS ICEPAK 12.1 were built to analyze the thermo-fluidic behavior of the LED lamp system and to visualize the temperature distribution of the system. It was found that the results obtained from numerical simulations were in good agreement with those obtained from the experimental data, with a percentage difference of equal or less than 10%. ANSYS ICEPAK 12.1 is also proven to be a suitable software for electronic cooling simulations.

Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2021
As úlceras venosas são uma patologia com impacto significativo na qualidade de vida dos doentes e nos custos inerentes aos sistemas de saúde. Apesar da evidência científica apontar um claro benefício no tratamento destes doentes com terapia compressiva e em centros especializados a nível nacional, estes doentes são atualmente dispersos por várias especialidades. Com este estudo, pretendeu-se avaliar o impacto da abordagem destes doentes em consulta especializada em feridas crónicas no custo de tratamento, tempo necessário para encerramento da úlcera e impacto na qualidade de vida. Neste sentido, realizou-se um estudo retrospetivo descritivo com base na população de doentes seguidos numa consulta de feridas complexas num período de 2 anos, avaliando-se impacto da úlcera na qualidade de vida, gasto com os cuidados de penso, tempo até encerramento da ferida e tipos de tratamentos realizados. A análise dos dados dos 89 doentes identificou uma diferença significativa relativamente ao custo de tratamento, duração da ferida e qualidade de vida dos doentes quando o tratamento é feito por uma equipa especializada, corroborando as vantagens deste tipo de seguimento e tratamento descritos na evidência cientifica já existente.
Venous leg ulcers are a pathology with significant impact on patients’ quality of life as well as having high costs to the national health systems. Regardless of the evidence stating the benefits of this patients being treated on specialised centres with compressive therapy, this patients are currently spread out throughout many different specialties with lack of evidence-based care. With this study we aimed to evaluate the impact of a specialised consult, directed to chronic wound care, in hospital setting, on the time to heal, the cost of treatment and the impact on quality of life on patients with venous leg ulcer. A retrospective descriptive study was designed with a patient data base from a specialised chronic wound consult in a 2-year period, evaluating ulcer impact on quality of life, costs with management and treatment, time to heal and types of compressive therapy used. After analysing the data regarding 89 patients’ VLUs, we concluded that specialised chronic wound consult and compressive therapy have a significant impact on the management and treatment of the venous leg ulcer, with significantly lower times needed to heal, costs to heal and with ta significant improvement on patients’ quality of life.

Introduction : Il existe beaucoup d’hétérogénéité dans la prise en charge des patients se présentant au département d’urgence avec un traumatisme crâniocérébral léger (TCCL) et des lésions à la tomodensitométrie (TDM) cérébrale. L’objectif principal de cette étude est de valider des critères de gravité du saignement intracrânien afin de prédire le besoin d’intervention neurochirurgicale puis, en deuxième lieu, valider si ces mêmes critères peuvent également prédire le besoin d’admission en centre de neurotraumatologie. Méthodes : Cette étude est une analyse rétrospective d’une cohorte de patients adultes avec TCCL se présentant au département d’urgence d’un centre de neurotraumatologie, de 2008 à 2012. Le besoin d’intervention neurochirurgicale et d’admission était laissé à la discrétion du médecin traitant. La sensibilité et la spécificité des critères de gravité ont été calculées avec des intervalles de confiance à 95% (IC95%). Résultats : En tout, 678 patients (homme = 65.9%, âge moyen = 62.5 ans) ont été inclus. Parmi eux, 114 (16.8%) ont subi une intervention neurochirurgicale. Tous les patients ayant nécessité une intervention neurochirurgicale remplissaient des critères de lésions significatives à leur TDM initiale (sensibilité 100% [IC95% 96.8-100]). Par contre, la spécificité était faible, soit 34.8% (IC95% 30.8-38.8) : 196 (28.9%) patients n’ayant pas nécessité d’intervention neurochirurgicale n’avaient pas de critères de lésions significatives. Ces critères ont une sensibilité de 78.3% (IC95% 74.6-81.7) et une spécificité de 55.9% (IC95% 47.4-64.2) afin de prédire l’admission en centre de neurotraumatologie. Conclusion : Les critères de gravité du saignement intracrânien ont identifié tous les patients ayant requis une intervention neurochirurgicale, sans toutefois démontrer une forte spécificité. Ils étaient moins sensibles, mais plus spécifiques, pour prédire l’admission en centre de neurotraumatologie.
Background: There is variability in the management of patients presenting to the emergency department (ED) with mild traumatic brain injury (MTBI) and abnormal findings on their initial head computed tomography (CT). The main objective of this study was to validate the value of the Important Brain Injury (IBI) criteria, introduced by the Canadian CT-Head Rule, in predicting the need for surgical intervention. The secondary objective was to evaluate the usefulness of IBI criteria to predict admission to a tertiary care hospital. Methods: This is a post hoc analysis of a prospective cohort of adult patients presenting to the ED of one tertiary care, academic center, between 2008 and 2012, with MTBI and an abnormal initial head CT. Neurosurgical intervention and tertiary center admission were at the discretion of the treating physician. The sensitivity and specificity of the IBI criteria were calculated with their 95% confidence intervals (95%CI). Results: A total of 678 patients (male = 65.9%, mean age = 62.5 years) were included, of whom 114 (16.8%) required neurosurgical intervention. All patients requiring neurosurgical intervention met IBI criteria on their initial head CT (sensitivity of 100% [95%CI 96.8-100]). However, only 196 (28.9%) patients who did not require neurosurgical intervention were correctly identified using these criteria (specificity of 34.8% [95%CI 30.8-38.8]). The IBI criteria had sensitivity of 78.3% (CI 74.6-81.7) and specificity of 55.9% (CI 47.4-64.2) to predict admission to a tertiary care center. Conclusion: The IBI criteria for MTBI identified all patients who required neurosurgical intervention, but did not show a high specificity. They were less sensitive, but more specific, in predicting admission to a tertiary care center.