On Dependable Wireless Communications through Multi-Connectivity

The realization of wireless ultra-reliable low-latency communications (URLLC) is one of the key challenges of the fifth generation (5G) of mobile communications systems and beyond. Ensuring ultra-high reliability together with a latency in the (sub-)millisecond range is expected to enable self-driving cars, wireless factory automation, and the Tactile Internet. In wireless communications, reliability is usually only considered as percentage of successful packet delivery, aiming for 1 − 10⁻⁵ up to 1 − 10⁻⁹ in URLLC

Markov and Semi-markov Chains, Processes, Systems and Emerging Related Fields

This book covers a broad range of research results in the field of Markov and Semi-Markov chains, processes, systems and related emerging fields. The authors of the included research papers are well-known researchers in their field. The book presents the state-of-the-art and ideas for further research for theorists in the fields. Nonetheless, it also provides straightforwardly applicable results for diverse areas of practitioners

The latent state hazard model, with application to wind turbine reliability

We present a new model for reliability analysis that is able to distinguish the latent internal vulnerability state of the equipment from the vulnerability caused by temporary external sources. Consider a wind farm where each turbine is running under the external effects of temperature, wind speed and direction, etc. The turbine might fail because of the external effects of a spike in temperature. If it does not fail during the temperature spike, it could still fail due to internal degradation, and the spike could cause (or be an indication of) this degradation. The ability to identify the underlying latent state can help better understand the effects of external sources and thus lead to more robust decision-making. We present an experimental study using SCADA sensor measurements from wind turbines in Italy.Comment: Published at http://dx.doi.org/10.1214/15-AOAS859 in the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Reliability Abstracts and Technical Reviews January-December 1967

No abstract availabl

Tehopuolijohteiden lämmönhallintamateriaalien luotettavuus

The purpose of this thesis is to study the reliability and the life time of preselected thermal interface materials and to develop an accelerated life time test system for this task. Thermal interface materials are used between power semiconductor devices and thermal solution to enhance the heat transfer between the two objects. Being one of the critical components in the path of heat flow, any weakening can cause severe damage to the component itself or to the whole application. The theoretical background in this study presents the basics of power semiconductor devices, thermal management and reliability related issues. In addition, as secondary objectives, different thermal interface materials are compared and heat transfer between two solid surfaces is examined. The aim of this thesis is to develop a test system that can be used to analyze the life time behaviour of different thermal interface materials. To achieve this, a mechanical test frame, a control circuit and a printed circuit board will be designed and implemented. The aging of different materials is done by switching power transistors on and off causing heat gradients in the thermal path. Two thermal interface materials, an elastomer film and a phase change material, are tested and a regression analysis will be done to predict the thermal performance further. Furthermore, a general degradation model is established based on the measurement data. In addition, the thermal performance with different interface pressures is compared and the uncertainty of measurements is discussed. Finally, the developed empirical model for thermal interface materials is presented. To fully benefit from the degradation models, additional research must be done. Based solely on the thermal performance analysis, the phase change material should be used instead of elastomer film on similar applications. Futhermore, based on the uncertainty analysis, without the calibration of the temperature measurement device, the results of this study could have been useless.Tämän työn tarkoituksena on tutkia ennalta määriteltyjen lämmönhallintamateriaalien elinikää ja luotettavuutta ja kehittää tätä tarkoitusta varten testausjärjestelmä. Lämmönhallintamateriaaleja käytetään tehopuolijohteiden ja jäähdytyselementin välissä parantamaan lämmönsiirtymistä. Koska lämmönhallintamateriaali sijaitsee jäähdyttämisen kannalta kriittisessä paikassa, voi sen heikkeneminen aiheuttaa komponentin tai koko laitteen tuhoutumisen. Tutkimuksen teoreettinen tausta esittelee tehopuolijohteita sekä lämmönhallintaan ja luotettavuuteen liittyviä aiheita. Lisäksi työssä verrataan eri lämmönhallintamateriaaleja ja tutkitaan kahden kiinteän pinnan välistä lämmönsiirtoa. Työn tavoitteena oli kehittää testausjärjestelmä, jolla voidaan analysoida eri lämmönhallintamateriaalien käyttäytymistä niiden eliniän aikana. Tätä varten työssä suunnitellaan testirunko, ohjauspiiri transistoreille sekä piirikortti. Eri materiaalien vanhentaminen toteutetaan tehosyklauksen avulla. Työssä on tarkoitus tutkia kahta erilaista lämmönhallintamateriaalia, elastomeeria sekä faasimuunnosmateriaalia. Elinikää arvioidaan mittaustuloksiin perustuen regressioanalyysin avulla pidemmälle. Lisäksi mittausdatan avulla materiaaleille kehitetään yleiset hajoamismallit, joita voidaan käyttää apuna suunnittelussa. Tämän lisäksi työssä mitataan lämmönsiirtymistä eri liitospaineilla sekä arvioidaan mittausten luotettavuutta. Työn tuloksena esitellään materiaaleille kehitetyt hajoamismallit. Lisäksi esitellään tarvittava lisätutkimustyö, joka vaaditaan eliniän estimoimiseen. Perustuen pelkästään lämmönsiirto-ominaisuuksiin, faasimuunnosmateriaalia pitäisi käyttää elastomeerin sijasta samanlaisissa käyttökohteissa. Mittausten luotettavuusanalyysin perusteella ilman lämpöantureiden kalibrointeja, mittaustulokset olisivat voineet olla käyttökelvottomia

Mathematical Modeling and Simulation in Mechanics and Dynamic Systems

The present book contains the 16 papers accepted and published in the Special Issue “Mathematical Modeling and Simulation in Mechanics and Dynamic Systems” of the MDPI “Mathematics” journal, which cover a wide range of topics connected to the theory and applications of Modeling and Simulation of Dynamic Systems in different field. These topics include, among others, methods to model and simulate mechanical system in real engineering. It is hopped that the book will find interest and be useful for those working in the area of Modeling and Simulation of the Dynamic Systems, as well as for those with the proper mathematical background and willing to become familiar with recent advances in Dynamic Systems, which has nowadays entered almost all sectors of human life and activity

How does development lead time affect performance over the ramp-up lifecycle? : evidence from the consumer electronics industry

In the fast-paced world of consumer electronics, short development lead times and efficient product ramp-ups are invaluable. The sooner and faster a firm can ramp-up production of a new product, the faster it can start to earn revenues, profit from early market opportunities, establish technology standards and release scarce development resources to support new product development projects. Yet, many companies fail to meet their time-to-market and time-to-volume targets and the complex interrelationships between product characteristics, development lead time and ramp-up performance are largely unexplored. In response to these limitations our study focuses on three research questions: (1) To what extent is ramp-up performance determined by development lead time and product complexity? (2) How do these relationships change in the course of the ramp-up lifecycle? and (3) How can the results be explained? Our results contribute to the field of operations management in three ways. First, we offer a more comprehensive and enriched analysis of the drivers for development lead time and ramp-up performance in the cell phone industry. Second, we demonstrate that late schedule slips – although disastrous for customer relations in which due dates are crucial – provide the opportunity to build up (semi-finished) product buffers which in turn increase the initial ramp-up performance. Third, we show that it is important to take these effects into account in a jointly and lifecycle-dependent manner. Thus, our insights support management efforts to anticipate the consequences of product design decisions, predict development schedule risk levels, and make informed decisions about production volume commitments

Discrete Event Simulations

Considered by many authors as a technique for modelling stochastic, dynamic and discretely evolving systems, this technique has gained widespread acceptance among the practitioners who want to represent and improve complex systems. Since DES is a technique applied in incredibly different areas, this book reflects many different points of view about DES, thus, all authors describe how it is understood and applied within their context of work, providing an extensive understanding of what DES is. It can be said that the name of the book itself reflects the plurality that these points of view represent. The book embraces a number of topics covering theory, methods and applications to a wide range of sectors and problem areas that have been categorised into five groups. As well as the previously explained variety of points of view concerning DES, there is one additional thing to remark about this book: its richness when talking about actual data or actual data based analysis. When most academic areas are lacking application cases, roughly the half part of the chapters included in this book deal with actual problems or at least are based on actual data. Thus, the editor firmly believes that this book will be interesting for both beginners and practitioners in the area of DES