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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.
451

Frictional studies and high strain rate testing of wood under refining conditions

Svensson, Birgitta January 2007 (has links)
When producing thermomechanical pulps (TMP), wood chips and fiber material are loaded mechanically in a disc-refiner to separate the fibers and to make them flexible. In the process, much of the energy supplied is transferred to the fiber material through cyclic compression, shear and friction processes. Therefore, compression and friction characteristics are needed in order to gain a better grasp of the forces acting during refining. To this end, in this thesis, the compressive and frictional behaviors of wood were investigated under simulated chip refining conditions (i.e., hot saturated steam, high strain rate compression, and high sliding speed). Two new, custom-designed, experimental setups were developed and used. The equipment used for compression testing was based on the split Hopkinson pressure bar (SHPB) technique and the friction tester was a pin-on-disc type of tribotester (wear rig). Both pieces of equipment allow a testing environment of hot saturated steam.   In the wood–steel friction investigation, the influence of the steam temperature (100-170°C) was of primary interest. The wood species chosen for the friction tests were spruce (Picea abies), pine (Pinus sylvestris, Pinus radiata), and birch (Betula verrucosa). When performing measurements in the lower-temperature region (100-130°C), the friction coefficients registered for the softwoods were generally low and surface properties such as lubrica­tion were suggested to have a great influence on the results; however, in the higher-tempera­ture region (~130 -170°C), the friction coefficients of all investigated wood species were probably determined by bulk properties to a much greater extent. When most of the wood extractives had been removed from the specimens, testing results revealed distinct peaks in friction at similar temperatures, as the internal friction of the different wood species are known to have their maxima at ~110–130°C. One suggested explanation of these friction peaks is that reduced lubrication enabled energy to dissipate into the bulk material, causing particularly high friction at the temperature at which internal damping of the material was greatest. During the friction measurements in the higher-temperature region, the specimens of the different wood species also started to lose fibers (i.e., produce wear debris) at different characteristic temperatures, as indicated by peaks in the coefficient of friction. In refining, the generally lower shives content of pine TMP than of spruce TMP could partly be explained by a lower wear initiation temperature in the pine species.   Wood stiffness is known to decrease with temperature, when measured at low strain rates. The results presented in this thesis can confirm a similar behavior for high strain rate compression. The compressive strain registered during impulsive loading (using a modified split Hopkinson equipment) increased with temperature; because strain rate also increased with temperature. Accordingly, the strain rates should determine the strain magnitudes also in a refiner, since the impulsive loads in a refiner are of similar type. Larger strains would thus be achieved when refining at high temperatures. The results achieved in the compression tests were also considered in relation to refining parameters such as plate clearance and refining intensity, parameters that could be discussed in light of the stress–strain relations derived from the high strain rate measurements. Trials recorded using high-speed photography demonstrated that the wood relaxation was very small in the investigated time frame ~6 ms. As well, in TMP refining the wood material has little time to relax, i.e., ~0.04–0.5 ms in a large single disc refiner. The results presented here are therefore more suitable for comparison with the impulsive loads arising in a refiner than are the results of any earlier study. It can therefore be concluded that the modified SHPB testing technique combined with high-speed photography is well suited for studying the dynamic behavior of wood under conditions like those prevalent in a TMP system.
452

Behavioral change for energy conservation : case study of post-Fukushima experience in Japan

Kano, Chizu January 2013 (has links)
Environmental, social, and economic pressure on energy issues has been a serious and urgent concern in countries like Japan, which is heavily reliant on imported energy. After the Fukushima incident in March 2011, energy issues, notably nuclear energy maters, have drawn a special attention in Japan. For long-term and promising solutions for the issue, demand side of the energy consumption at individual level should be focused. This study hence was carried out to find out possibility of sustainable energy consumption in Japan at individual level and key barriers and drivers to change behavior for energy conservation. 7 in-depth interviews were conducted to examine public reception on energy issues, and barriers and drivers to trigger energy conservation behavior among Japanese people. Also, perspective on energy issues from Japanese government and Japan Business Federation were comparably analyzed. The results identified that the Fukushima incident has little impact on people’s behavior, while there has been increasing anxiety on energy systems among them. The Fukushima incident itself therefore does not seem to affect energy conservation behavior among the Japanese. Rather, it can be assumed that energy conservation can be triggered by personal aspects or situational aspects such as perception on preferable outcome, perceived easiness of achieving the behavior, moral norm (sense of “mottainai”), past habit, and community level of social mood on energy conservation. On the other hand, family support and discomfort were found to prevent from making the behavior to occur. Moreover, since there was an evident distrust of the public towards the government, it was difficult to share the same energy issues between the two sectors, hence, restoration of the distrust is a crucial challenge for the government.
453

Study on optimal train movement for minimum energy consumption

Gkortzas, Panagiotis January 2013 (has links)
The presented thesis project is a study on train energy consumption calculation and optimal train driving strategies for minimum energy consumption. This study is divided into three parts; the first part is a proposed model for energy consumption calculation for trains based on driving resistances. The second part is a presentation of a method based on dynamic programming and the Hamilton-Jacobi-Bellman equation (Bellman’s backward approach) for obtaining optimal speed and control profiles leading to minimum energy consumption. The third part is a case study for a Bombardier Transportation case. It includes the presentation of a preliminary algorithm developed within this thesis project; an algorithm based on the HJB equation that can be further improved in order to be used online in real-time as an advisory system for train drivers.
454

Measurements and Models Related to Solar Optics in Windows with Shading Devices

Kotey, Nathan Amon 06 April 2009 (has links)
Shading devices have the potential to reduce peak cooling load and annual energy consumption because they can be used to control solar gain. Thus, the need to model shading devices in a glazing system analysis is important. This thesis deals with various measurement techniques and model development related to solar optics in windows with shading devices. It also considers longwave radiative properties of shading devices via model development and experimentation. The different shading devices examined were roller blinds, insect screens, pleated drapes and venetian blinds. The energy performance of windows with shading devices was modeled using a two step procedure. Solar radiation was considered in the first step by developing a multi-layer solar optical model for glazing/shading systems. This newly developed model is an extension of an existing model for systems of specular glazing layers and includes the effect of layers that create scattered, specifically diffuse, radiation in reflection and/or transmission. Spatially-averaged (effective) optical properties were used to characterise shading layers, including their beam-diffuse split. The multi-layer solar optical model estimates the system solar transmission and absorbed solar components. The absorbed solar components appear as energy source terms in the second step – the heat transfer analysis. The heat transfer analysis involves the formulation of energy balance equations and requires both effective longwave properties and convective heat transfer coefficients as input. The simultaneous solution of the energy balance equations yields the temperature as well as the convective and radiative fluxes. The effective solar optical properties of flat materials like drapery fabrics, roller blinds and insect screens were obtained by developing a new measurement technique. Special sample holders were designed and fabricated to facilitate measurements using an integrating sphere installed in a commercially available spectrophotometer. Semi-empirical models were then developed to quantify the variation of solar optical properties with respect to incidence angle. In turn, effective layer properties of venetian blinds and pleated drapes were modeled using a more fundamental net radiation scheme. The effective longwave properties of flat materials were obtained by taking measurements with an infrared reflectometer using two backing surfaces. The results enabled simple models to be developed relating emittance and longwave transmittance to openness, emittance and longwave transmittance of the structure. In turn, effective longwave properties of venetian blinds and pleated drapes were modeled using a net radiation scheme. Convective heat transfer correlations were readily available. Finally, the newly developed models were validated by measuring the solar gain through various shading devices attached to a double glazed window using the National Solar Test Facility (NSTF) solar simulator and solar calorimeter. Solar gain results were also obtained from simulation software that incorporated the models. There was good agreement between the measured and the simulated results thus strengthening confidence in the newly developed models.
455

Energy consumption of manufacturing line with special emphasis on lighting system

Saršon, Bruno January 2011 (has links)
The main focus of this project is to investigate the energy consumption of the manufacturing lines in the car industry and look for the potential methods regarding energy saving. Special emphasis is put on the lighting technologies that can be used in the manufacturing processes. Two lighting technologies are tested in order to see which one has better performance and lower energy consumption. Fluorescent tube and LED tube are compared concerning illuminance, UV irradiance and power consumption. Economic evaluation is also conducted to exam the feasibilities replacing fluorescent tubes with LED tubes. Results of the study show that the LED tubes have much lower energy consumption than fluorescent tubes, produce more direct and „colder“ light, and have much lower UV irradiance. However, the payback period of LED is relatively long at current price situation. Since it is expected that the price of LED tubes will decrease in future, it is reasonable to predict that the LED technology will change the fluorescent one in many applications. The energy consumption has been estimated for two manufacturing lines which use different technologies to produce car underbodies. In order to identify the differences from the energy consumption point of view, some measurements are conducted, such as the consumption of electricity, compressed air, air for ventilation and cooling water. The measured results show a disproportion in the power consumption when the lines are in stand-by mode. This affects the energy consumption per produced unit significantly. The line that has a higher capacity and a lower power consumption in the stand-by mode has a lower energy consumption per produced unit when it is operating with lower production loading. So, in order to improve the energy efficiency, it is necessary that it works at as high volume as possible and to have the stand-by power consumption as low as possible.
456

Beräkning av värmeenergiförluster i flerbostadshus genom analys av den totala fjärrvärmeenergianvändningen : / Calculation of the thermal energy losses in apartment buildings through analyze of the total district thermal energy consumption :

Fredhav, Dennis, Briggert Sjöstrand, Carl Andreas January 2012 (has links)
This thesis has been carried out on behalf of IV Produkt AB and intends to set an average ratio of thermal energy losses in apartment buildings that were built during the 1960-1990. This shall be derived by analyzing the total district energy consumption that has been divided into three parts: heat energy losses (the actual heating requirements), the heating of domestic hot water and heating energy consumption for the controlled ventilation. Three different residential areas that were built during the years 1962-1966 and one that was built in 1993 has been analyzed. All residential areas are located in Växjö urban and contains between four and six apartment buildings. The analyzed objects have a mechanical exhaust ventilation systems and district heating as the heating method. No own laboratory work or experiments have been done in this thesis, the calculations have been done on the basis of parameters from VEAB, interviews with property managers, and literature studies. By calculations, we have got a result that is reported in Chapter 6. The result is given as a thermal energy loss as a percentage of the total heat consumption. In this thesis there has also been a review of the rules on requirements for the specific energy consumptions in buildings, indoor environment and indoor temperature from the National Board of Housing and the National Board of Health and Welfare.
457

Energy Consumption in Location Sharing Protocols for Android Applications

Prihodko, Mihails January 2012 (has links)
This thesis studies the Message Queue Telemetry Transport protocol (MQTT) as an application layer protocol in geographical location sharing applications using third generation cellular communication (3G). The MQTT protocol is compared in terms of energy efficiency and amount of data generated with the Hypertext Transfer Protocol (HTTP), which is currently used in typical location sharing applications. In order to compare the communication energy efficiency of both protocols a location sharing application prototype was developed for the Android platform. The application allows the use of HTTP and MQTT and was used to perform a number of experiments. The evaluation experiments show that MQTT is a good candidate as a protocol for location sharing. At comparable bandwidth and energy expenses MQTT offers better quality of user experience, since the subscribers are notified at once when the location of clients of interest has changed. The MQTT protocol is more energy-efficient than the HTTP protocol when the number of other uses with whom the client shares location is low and the location updates are frequent. The experiments also indicate that MQTT protocol is more energy-efficient than HTTP protocol in idle state, when there are no location information updates due to inactivity of all the clients, for example, if they are stationary. This is because MQTT client does not spend energy to poll the server for information updates.
458

Measurements and Models Related to Solar Optics in Windows with Shading Devices

Kotey, Nathan Amon 06 April 2009 (has links)
Shading devices have the potential to reduce peak cooling load and annual energy consumption because they can be used to control solar gain. Thus, the need to model shading devices in a glazing system analysis is important. This thesis deals with various measurement techniques and model development related to solar optics in windows with shading devices. It also considers longwave radiative properties of shading devices via model development and experimentation. The different shading devices examined were roller blinds, insect screens, pleated drapes and venetian blinds. The energy performance of windows with shading devices was modeled using a two step procedure. Solar radiation was considered in the first step by developing a multi-layer solar optical model for glazing/shading systems. This newly developed model is an extension of an existing model for systems of specular glazing layers and includes the effect of layers that create scattered, specifically diffuse, radiation in reflection and/or transmission. Spatially-averaged (effective) optical properties were used to characterise shading layers, including their beam-diffuse split. The multi-layer solar optical model estimates the system solar transmission and absorbed solar components. The absorbed solar components appear as energy source terms in the second step – the heat transfer analysis. The heat transfer analysis involves the formulation of energy balance equations and requires both effective longwave properties and convective heat transfer coefficients as input. The simultaneous solution of the energy balance equations yields the temperature as well as the convective and radiative fluxes. The effective solar optical properties of flat materials like drapery fabrics, roller blinds and insect screens were obtained by developing a new measurement technique. Special sample holders were designed and fabricated to facilitate measurements using an integrating sphere installed in a commercially available spectrophotometer. Semi-empirical models were then developed to quantify the variation of solar optical properties with respect to incidence angle. In turn, effective layer properties of venetian blinds and pleated drapes were modeled using a more fundamental net radiation scheme. The effective longwave properties of flat materials were obtained by taking measurements with an infrared reflectometer using two backing surfaces. The results enabled simple models to be developed relating emittance and longwave transmittance to openness, emittance and longwave transmittance of the structure. In turn, effective longwave properties of venetian blinds and pleated drapes were modeled using a net radiation scheme. Convective heat transfer correlations were readily available. Finally, the newly developed models were validated by measuring the solar gain through various shading devices attached to a double glazed window using the National Solar Test Facility (NSTF) solar simulator and solar calorimeter. Solar gain results were also obtained from simulation software that incorporated the models. There was good agreement between the measured and the simulated results thus strengthening confidence in the newly developed models.
459

Analysis of Relationship between Energy Consumption and Economic Growth Before and After Asian Financial Crisis in Taiwan and South Korea

Chuang, Wen-Chi 22 June 2012 (has links)
Before a government makes economic policies, it must first fully understand the causality between energy consumption and economic growth. This study uses Chow Test, Unit Root Test, Co-integration Test, Vector Autoregressive Model, Vector Error Correction Model, Granger Causality Test, Impulse Response Function and Variance Decomposition to examine whether the relationships between energy consumption and economic growth for Taiwan and Korea had changed after the Asian Financial Crisis of 1997, in order to understand whether their economic policies have changed in response. Taiwan¡¦s energy consumption and GDP had one-way effect ¡V that is, her energy consumption affected GDP but not vice versa ¡V while that of South Korea exhibited a two-way relationship. However, after the Crisis, such relationship for Taiwan had changed to that of two-way. The relationship between energy consumption and GDP for South Korea remained two-way after the Crisis.
460

Glass as a Building Element – A Sustainable Approach: A Study of an Existing Academic Building

Jori, Swapnil Shriram 2010 December 1900 (has links)
In the aspects of global sustainability, buildings are known to be one of the largest energy consumers. Though sustainable building construction through technological advances is helping in achieving environment friendly buildings, a considerable amount of energy is also being consumed by existing buildings. While many factors at all different stages of building life are responsible for this, the building material is one of the most important considerations. Glass being the most sensitive building material can lead to high energy consumption in the building if used in an improper way. This study takes this factor into account, and tries to investigate the potential of energy savings in buildings through the simple and basic considerations in design. An energy analysis model of an existing academic building in College Station, Texas was developed using Design Builder computer simulation software. This model was then analyzed for the total amount of energy consumption in the base case. The existing building model was then modified by replacing the glass used for external fenestrations. Latest building codes and standards for the site location, glass properties, and parametric simulation results were taken into consideration. Again the model was simulated for annual energy consumption and the results are noted. This formed the first option for the retrofitting scenario. A hypothetical redesign scenario was also established in which the revision of building orientation was taken into consideration. The building was re-oriented to suit the weather conditions and recommendations by Advanced Energy Design Guidelines (30 percent energy savings over ASHRAE Standard 90.1-1999). The building was then simulated for annual energy consumption. A comparative analysis was performed between the three cases and the study concluded by showing 23 percent savings in the annual fuel consumption, 23.35 percent reduction in CO2 emission of the building and 25 percent reduction in annual solar heat gain under Modified case 1. Modified case 2, however, did not show any further savings due to the form of the building (almost square). However, modified case 1 settings emitted 31.8 percent more CO2 over the Energy Star office building in Texas. This methodology sets up a set of guidelines which can be followed while investigating a building for minimum annual energy consumption.

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