29 resultados para Reliability in refrigeration systems


Relevância:

100.00% 100.00%

Publicador:

Resumo:

Internationalization and the following rapid growth have created the need to concentrate the IT systems of many small-to-medium-sized production companies. Enterprise Resource Planning systems are a common solution for such companies. Deployment of these ERP systems consists of many steps, one of which is the implementation of the same shared system at all international subsidiaries. This is also one of the most important steps in the internationalization strategy of the company from the IT point of view. The mechanical process of creating the required connections for the off-shore sites is the easiest and most well-documented step along the way, but the actual value of the system, once operational, is perceived in its operational reliability. The operational reliability of an ERP system is a combination of many factors. These factors vary from hardware- and connectivity-related issues to administrative tasks and communication between decentralized administrative units and sites. To accurately analyze the operational reliability of such system, one must take into consideration the full functionality of the system. This includes not only the mechanical and systematic processes but also the users and their administration. All operational reliability in an international environment relies heavily on hardware and telecommunication adequacy so it is imperative to have resources dimensioned with regard to planned usage. Still with poorly maintained communication/administration schemes no amount of bandwidth or memory will be enough to maintain a productive level of reliability. This thesis work analyzes the implementation of a shared ERP system to an international subsidiary of a Finnish production company. The system is Microsoft Dynamics Ax, currently being introduced to a Slovakian facility, a subsidiary of Peikko Finland Oy. The primary task is to create a feasible base of analysis against which the operational reliability of the system can be evaluated precisely. With a solid analysis the aim is to give recommendations on how future implementations are to be managed.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Finnish food producers' trade with Russia has experienced profound changes since the collapse of the Soviet Union. Simultaneously, the distribution systems of foodstuffs have changed remarkably. This study sheds some light into these changes and analyses the current situation in distribution systems of foodstuffs in Russia. In addition, the study discusses the possibilities of Finnish food producers to get more of their products to the shelves of Russian food retail stores. Before the 1998 financial crisis, the import of foreign foodstuffs was booming in Russia due to the overvalued rouble. As a result of the financial crisis, food import collapsed. The export of Finnish foodstuffs to Russia has been slowly recovering during the past few years, but in the most important product categories the pre-crisis levels have so far not been reached and maybe will not be reached. In certain product categories the growth has been only marginal. It seems that starting localproduction will become increasingly important in the future. This is further encouraged by the fact that Russian consumers favour domestic food products. Russian consumers are very price conscious and demand quality in food products. The perceived price-quality ratio is an important criterion in the purchase decision.The majority of foodstuff retail is still conducted via unorganised forms of trade (e.g. kiosks and marketplaces) but modern retail chains are developing at a fast pace in Russia. They are also expected to dominate the retail trade in foodstuffs over the unorganised forms of trade in the future. This will change the distribution systems as well. The retail chains are trying to shorten the distribution chain, similarly to what has been seen in the Western countries. This together with the strengthening of retail chains is likely to shrink the role of wholesalers, as the chains increasingly want to work directly with the producers. Many large retail chains are acquiring or have already acquired a distribution centre or centres in order to boost efficiency and control the flow of products. The strengthening of the retail chains also gives them power in negotiations, which the producers and distributors have to adjust to. For example store entry fees and retail chains' own private label products pose challenges to the food producers. In the food production sector the competition is fierce, as large Russianand foreign producers want to ensure their piece of the market. The largest producers utilise their size: they invest in big marketing campaigns and are willing to pay high entry fees to retail chains in order to secure a place on the store shelves and to build a strong brand in Russia. This complicates the situation from the viewpoint of small producers. Currently, the most popular type of distribution system among the interviewed Finnish food producers is based on a network of local distributors. There is, however, a strong consensus on the importanceof starting local production in order to be a serious actor in Russia in the future. Factors that hinder the starting of local production include the lack of local infrastructure and qualified staff, and the low risk tolerance of Finnish firms. Major barriers for entry in Russia are the actions of authorities, fierce competition, fragmented market and Finnish producers' heavy production costs. The suggested strategies for increasing the market share include focusing geographically or segment-wise, introducing new products, starting local production, andcooperation between Finnish producers. Smallness was one reason why Finnish producers had to cut down their operations in Russia due to the 1998 crisis. Smaller producers had fewer resources to tolerate losses during the period of crisis. Smallness is reflected also on trade negotiations with retail chains and distributors. It makes it harder to cope with the store entry fees and to differentiatefrom the mass of products propped up by expensive advertising. Finally, it makes it harder for Finnish producers to start or expand local production, as it is more difficult for a small producer to get financing and to tolerate the increased risks. Compensating for the smallness might become the crucial factor determining the future success of Finnish food producers in the Russian market.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Reaaliaikaisten käyttöjärjestelmien käyttö sulautetuissa järjestelmissä on kasvamassa koko ajan. Sulautettuja tietokoneita käytetään yhä useammassa kohteessa kuten sähkökäyttöjen ohjauksessa. Sähkökäyttöjen ohjaus hoidetaan nykyisin yleensä nopealla digitaalisella signaaliprosessorilla (DSP), jolloin ohjelmointi ja päivittäminen on hidasta ja vaikeaa johtuen käytettävästä matalan tason Assembler-kielestä. Ratkaisuna yleiskäyttöisten prosessorien ja reaaliaikakäyttöjärjestelmien käyttö. Kaupalliset reaaliaikakäyttöjärjestelmät ovat kalliita ja lähdekoodin saaminen omaan käyttöön jopa mahdotonta. Linux on ei-kaupallinen avoimen lähdekoodin käyttöjärjestelmä, joten sen käyttö on ilmaista ja sitä voi muokata vapaasti. Linux:iin on saatavana useita laajennuksia, jotka tekevät siitä reaaliaikaisen käyttöjärjestelmän. Vaihtoehtoina joko kova (hard) tai pehmeä (soft) reaaliaikaisuus. Linux:iin on olemassa valmiita kehitysympäristöjä mutta ne kaipaavat parannusta ennen kuin niitä voidaan käyttää suuressa mittakaavassa teollisuudessa. Reaaliaika Linux ei sovellus nopeisiin ohjauslooppeihin (<100 ms) koska nopeus ei riitä vielä mutta nopeus kasvaa samalla kun prosessorit kehittyvät. Linux soveltuu hyvin rajapinnaksi nopean ohjauksen ja käyttäjän välille ja hitaampaan ohjaukseen.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The present work is a part of the large project with purpose to qualify the Flash memory for automotive application using a standardized test and measurement flow. High memory reliability and data retention are the most critical parameters in this application. The current work covers the functional tests and data retention test. The purpose of the data retention test is to obtain the data retention parameters of the designed memory, i.e. the maximum time of information storage at specified conditions without critical charge leakage. For this purpose the charge leakage from the cells, which results in decrease of cells threshold voltage, was measured after a long-time hightemperature treatment at several temperatures. The amount of lost charge for each temperature was used to calculate the Arrhenius constant and activation energy for the discharge process. With this data, the discharge of the cells at different temperatures during long time can be predicted and the probability of data loss after years can be calculated. The memory chips, investigated in this work, were 0.035 μm CMOS Flash memory testchips, designed for further use in the Systems-on-Chips for automotive electronics.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Energy consumption and energy efficiency have become an issue. Energy consumption is rising all over the world and because of that, and the climate change, energy is becoming more and more expensive. Buildings are major consumers of energy, and inside the buildings the major consumers are heating, ventilation and air-conditioning systems. They usually run at constant speed without efficient control. In most cases HVAC equipment is also oversized. Traditionally heating, ventilation and air-conditioning systems have been sized to meet conditions that rarely occur. The theory part in this thesis represents the basics of life cycle costs and calculations for the whole life cycle of a system. It also represents HVAC systems, equipment, systems controls and ways to save energy in these systems. The empirical part of this thesis represents life cycle cost calculations for HVAC systems. With these calculations it is possible to compute costs for the whole life cycle for the wanted variables. Life cycle costs make it possible to compare which variable causes most of the costs from the whole life point of view. Life cycle costs were studied through two real life cases which were focused on two different kinds of HVAC systems. In both of these cases the renovations were already made, so that the comparison between the old and the new, now existing system would be easier. The study indicates that energy can be saved in HVAC systems by using variable speed drive as a control method.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Broadcasting systems are networks where the transmission is received by several terminals. Generally broadcast receivers are passive devices in the network, meaning that they do not interact with the transmitter. Providing a certain Quality of Service (QoS) for the receivers in heterogeneous reception environment with no feedback is not an easy task. Forward error control coding can be used for protection against transmission errors to enhance the QoS for broadcast services. For good performance in terrestrial wireless networks, diversity should be utilized. The diversity is utilized by application of interleaving together with the forward error correction codes. In this dissertation the design and analysis of forward error control and control signalling for providing QoS in wireless broadcasting systems are studied. Control signaling is used in broadcasting networks to give the receiver necessary information on how to connect to the network itself and how to receive the services that are being transmitted. Usually control signalling is considered to be transmitted through a dedicated path in the systems. Therefore, the relationship of the signaling and service data paths should be considered early in the design phase. Modeling and simulations are used in the case studies of this dissertation to study this relationship. This dissertation begins with a survey on the broadcasting environment and mechanisms for providing QoS therein. Then case studies present analysis and design of such mechanisms in real systems. The mechanisms for providing QoS considering signaling and service data paths and their relationship at the DVB-H link layer are analyzed as the first case study. In particular the performance of different service data decoding mechanisms and optimal signaling transmission parameter selection are presented. The second case study investigates the design of signaling and service data paths for the more modern DVB-T2 physical layer. Furthermore, by comparing the performances of the signaling and service data paths by simulations, configuration guidelines for the DVB-T2 physical layer signaling are given. The presented guidelines can prove useful when configuring DVB-T2 transmission networks. Finally, recommendations for the design of data and signalling paths are given based on findings from the case studies. The requirements for the signaling design should be derived from the requirements for the main services. Generally, these requirements for signaling should be more demanding as the signaling is the enabler for service reception.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

The present manuscript represents the completion of a research path carried forward during my doctoral studies in the University of Turku. It contains information regarding my scientific contribution to the field of open quantum systems, accomplished in collaboration with other scientists. The main subject investigated in the thesis is the non-Markovian dynamics of open quantum systems with focus on continuous variable quantum channels, e.g. quantum Brownian motion models. Non-Markovianity is here interpreted as a manifestation of the existence of a flow of information exchanged by the system and environment during the dynamical evolution. While in Markovian systems the flow is unidirectional, i.e. from the system to the environment, in non-Markovian systems there are time windows in which the flow is reversed and the quantum state of the system may regain coherence and correlations previously lost. Signatures of a non-Markovian behavior have been studied in connection with the dynamics of quantum correlations like entanglement or quantum discord. Moreover, in the attempt to recognisee non-Markovianity as a resource for quantum technologies, it is proposed, for the first time, to consider its effects in practical quantum key distribution protocols. It has been proven that security of coherent state protocols can be enhanced using non-Markovian properties of the transmission channels. The thesis is divided in two parts: in the first part I introduce the reader to the world of continuous variable open quantum systems and non-Markovian dynamics. The second part instead consists of a collection of five publications inherent to the topic.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Energy efficiency is one of the major objectives which should be achieved in order to implement the limited energy resources of the world in a sustainable way. Since radiative heat transfer is the dominant heat transfer mechanism in most of fossil fuel combustion systems, more accurate insight and models may cause improvement in the energy efficiency of the new designed combustion systems. The radiative properties of combustion gases are highly wavelength dependent. Better models for calculating the radiative properties of combustion gases are highly required in the modeling of large scale industrial combustion systems. With detailed knowledge of spectral radiative properties of gases, the modeling of combustion processes in the different applications can be more accurate. In order to propose a new method for effective non gray modeling of radiative heat transfer in combustion systems, different models for the spectral properties of gases including SNBM, EWBM, and WSGGM have been studied in this research. Using this detailed analysis of different approaches, the thesis presents new methods for gray and non gray radiative heat transfer modeling in homogeneous and inhomogeneous H2O–CO2 mixtures at atmospheric pressure. The proposed method is able to support the modeling of a wide range of combustion systems including the oxy-fired combustion scenario. The new methods are based on implementing some pre-obtained correlations for the total emissivity and band absorption coefficient of H2O–CO2 mixtures in different temperatures, gas compositions, and optical path lengths. They can be easily used within any commercial CFD software for radiative heat transfer modeling resulting in more accurate, simple, and fast calculations. The new methods were successfully used in CFD modeling by applying them to industrial scale backpass channel under oxy-fired conditions. The developed approaches are more accurate compared with other methods; moreover, they can provide complete explanation and detailed analysis of the radiation heat transfer in different systems under different combustion conditions. The methods were verified by applying them to some benchmarks, and they showed a good level of accuracy and computational speed compared to other methods. Furthermore, the implementation of the suggested banded approach in CFD software is very easy and straightforward.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Agile methods have become increasingly popular in the field of software engineering. While agile methods are now generally considered applicable to software projects of many different kinds, they have not been widely adopted in embedded systems development. This is partly due to the natural constraints that are present in embedded systems development (e.g. hardware–software interdependencies) that challenge the utilization of agile values, principles and practices. The research in agile embedded systems development has been very limited, and this thesis tackles an even less researched theme related to it: the suitability of different project management tools in agile embedded systems development. The thesis covers the basic aspects of many different agile tool types from physical tools, such as task boards and cards, to web-based agile tools that offer all-round solutions for application lifecycle management. In addition to these two extremities, there is also a wide range of lighter agile tools that focus on the core agile practices, such as backlog management. Also other non-agile tools, such as bug trackers, can be used to support agile development, for instance, with plug-ins. To investigate the special tool requirements in agile embedded development, the author observed tool related issues and solutions in a case study involving three different companies operating in the field of embedded systems development. All three companies had a distinct situation in the beginning of the case and thus the tool solutions varied from a backlog spreadsheet built from scratch to plug-in development for an already existing agile software tool. Detailed reports are presented of all three tool cases. Based on the knowledge gathered from agile tools and the case study experiences, it is concluded that there are tool related issues in the pilot phase, such as backlog management and user motivation. These can be overcome in various ways epending on the type of a team in question. Finally, five principles are formed to give guidelines for tool selection and usage in agile embedded systems development.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Environmental threats are growing nowadays, they became global issues. People around the world try to face these issues by two means: solving the current affected environs and preventing non-affected environs. This thesis describes the design, implementation, and evaluation of online water quality monitoring system in Lake Saimaa, Finland. The water quality in Lake Saimaa needs to be monitored in order to provide responsible bodies with valuable information which allows them to act fast in order to prevent any negative impact on the lake's environment. The objectives were to design a suitable system, implement the system in Lake Saimaa, and then to evaluate the applicability and reliability of such systems for this environment. The needs for the system were first isolated, and then the design, needed modifications, and the construction of the system took place. After that was the testing of the system in Lake Saimaa in two locations nearby Mikkeli city. The last step was to evaluate the whole system. The main results were that the application of online water quality monitoring systems in Lake Saimaa can benefit of many advantages such as reducing the required manpower, time and running costs. However, the point of unreliability of the exact measured values of some parameters is still the drawback of such systems which can be developed by using more advanced equipments with more sophisticated features specifically for the purpose of monitoring in the predefined location.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Efficient production and consumption of energy has become the top priority of national and international policies around the world. Manufacturing industries have to address the requirements of the government in relation to energy saving and ecologically sustainable products. These industries are also concerned with energy and material usage due to their rising costs. Therefore industries have to find solutions that can support environmental preservation yet maintain competitiveness in the market. Welding, a major manufacturing process, consumes a great deal of material and energy. It is a crucial process in improving a product’s life-cycle cost, strength, quality and reliability. Factors which lead to weld related inefficiencies have to be effectively managed, if industries are to meet their quality requirements and fulfil a high-volume production demand. Therefore it is important to consider some practical strategies in welding process for optimization of energy and material consumption. The main objective of this thesis is to explore the methods of minimizing the ecological footprint of the welding process and methods to effectively manage its material and energy usage in the welding process. The author has performed a critical review of the factors including improved weld power source efficiency, efficient weld techniques, newly developed weld materials, intelligent welding systems, weld safety measures and personnel training. The study lends strong support to the fact that the use of eco-friendly welding units and the quality weld joints obtained with minimum possible consumption of energy and materials should be the main directions of improvement in welding systems. The study concludes that, gradually implementing the practical strategies mentioned in this thesis would help the manufacturing industries to achieve on the following - reduced power consumption, enhanced power control and manipulation, increased deposition rate, reduced cycle time, reduced joint preparation time, reduced heat affected zones, reduced repair rates, improved joint properties, reduced post-weld operations, improved automation, improved sensing and control, avoiding hazardous conditions and reduced exposure of welder to potential hazards. These improvement can help in promotion of welding as a green manufacturing process.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Product assurance is an essential part of product development process if developers want to ensure that final product is safe and reliable. Product assurance can be supported withrisk management and with different failure analysis methods. Product assurance is emphasized in system development process of mission critical systems. The product assurance process in systems of this kind requires extra attention. Inthis thesis, mission critical systems are space systems and the product assurance processof these systems is presented with help of space standards. The product assurance process can be supported with agile development because agile emphasizes transparency of the process and fast response to changes. Even if the development process of space systems is highly standardized and reminds waterfall model, it is still possible to adapt agile development in space systems development. This thesisaims to support the product assurance process of space systems with agile developmentso that the final product would be as safe and reliable as possible. The main purpose of this thesis is to examine how well product assurance is performed in Finnish space organizations and how product assurance tasks and activities can besupported with agile development. The research part of this thesis is performed in survey form.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Product assurance is an essential part of product development process if developers want to ensure that final product is safe and reliable. Product assurance can be supported with risk management and with different failure analysis methods. Product assurance is emphasized in system development process of mission critical systems. The product assurance process in systems of this kind requires extra attention. In this thesis, mission critical systems are space systems and the product assurance process of these systems is presented with help of space standards. The product assurance process can be supported with agile development because agile emphasizes transparency of the process and fast response to changes. Even if the development process of space systems is highly standardized and reminds waterfall model, it is still possible to adapt agile development in space systems development. This thesis aims to support the product assurance process of space systems with agile development so that the final product would be as safe and reliable as possible. The main purpose of this thesis is to examine how well product assurance is performed in Finnish space organizations and how product assurance tasks and activities can be supported with agile development. The research part of this thesis is performed in survey form.

Relevância:

100.00% 100.00%

Publicador:

Resumo:

Fluid handling systems account for a significant share of the global consumption of electrical energy. They also suffer from problems, which reduce their energy efficiency and increase life-cycle costs. Detecting or predicting these problems in time can make fluid handling systems more environmentally and economically sustainable to operate. In this Master’s Thesis, significant problems in fluid systems were studied and possibilities to develop variable-speed-drive-based detection methods for them was discussed. A literature review was conducted to find significant problems occurring in fluid handling systems containing pumps, fans and compressors. To find case examples for evaluating the feasibility of variable-speed-drive-based methods, queries were sent to industrial companies. As a result of this, the possibility to detect heat exchanger fouling with a variable-speed drive was analysed with data from three industrial cases. It was found that a mass flow rate estimate, which can be generated with a variable speed drive, can be used together with temperature measurements to monitor a heat exchanger’s thermal performance. Secondly, it was found that the fouling-related increase in the pressure drop of a heat exchanger can be monitored with a variable speed drive. Lastly, for systems where the flow device is speed controlled with by a pressure measurement, it was concluded that increasing rotational speed can be interpreted as progressing fouling in the heat exchanger.