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Study of Advance Tungsten Nano-crystal for Non-Volatile Memory Device ApplicationXi, Peng-bo 23 July 2007 (has links)
Recently, memory-cells employing discrete traps as the charge storage media have been attracting a lot of attention as a promising candidate to replace conventional DRAM or Flash memories. Conventional floating gate (FG) non-volatile memories (NVMs) present critical issues on device scalability beyond the sub-50nm node. In achieving non-volatility in conventional FG memories, thicker control and tunnel oxide (~8nm) are required to guarantee longer retention time. Relatively, nano-dots memories causes more resistant leakage charges by localized storage sites, thus improving the device retention characteristics. Hence, nano-dots memories allow more aggressive scaling of the tunnel oxide and exhibit superior characteristics compared to Flash memories in term of operation voltage, write / erase speed, retention time and endurance.
The advantages of metal nano-dots compared with other material counterparts include higher density of states , stronger coupling with the channel, better size scalability, and the design freedom of engineering the work function to optimize device characteristics. However, tungsten nano-dots are the most interested in all of metal dots is that tungsten metal has more extra attractive advantages, such as ultra high melting point make high process temperature caused superior thermal stability of device and wide application in VLSI technology nowadays caused real possibility of tungsten nano-dots NVMs fabricated in industry in practice.
This dissertation is divided into four sections: (1) discussion of basic properties for tungsten nano-dots memory devices; (2) Tunneling Oxide Engineering,; (3) Improvement by novel processes; and (4) The influence with supercritical CO2 (SCCO2) and vapor treatment. Initially, formative mechanism of tungsten nano-dots and electrical characteristics of devices was investigated in the first section. Tungsten nano-dots were formed by oxidizing tungsten silicide / amorphous silicon double stack film at high temperature condition. From electrical measurement, the better characteristics have been achieved for oxidation condition at 1050¢XC / 120 sec. Secondly, the rapid thermal anneal (RTA) oxidation is used to grow tunnel oxide by two different forming gas (O2/N2O). Comparison of electrical characteristics, program characteristics of the device using tunnel oxide with N2O process is inferior than the common device. However, endurance is a important electrical characteristics in the semiconductor device especially apply on the non-volatile memory. Thirdly, novel processes were employed into fabrication of tungsten nano-dots memory devices, include the N2O oxidation and NH3 plasma treatment. The purpose of novel processes is production additional trapping states in nonvolatile memories, which is considerably as combination nano-dots with SONOS structure. In the final section, the application of supercritical CO2 with vapor on tungsten nano-dots memoery devices have been studying. It is found that the device treated by SCCO2 which electrical characteristics is improved obviously. Furthermore, this technology also can fabricate the nano-dots memory which is like the device used high temperature oxidation process. It suggests that the SCCO2 with vapor treatment could oxidize silicide film under a low temperature environment. This novel oxidation process has some advantages and could be noticed in the semiconductor industry.
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Volatile cycling and the thermal evolution of planetary mantleJanuary 2011 (has links)
The thermal histories of terrestrial planets are investigated using two parameterized mantle convection models for either Earth like planets and planets with no active plate tectonics. Using parameterized models of mantle convection, we performed computer simulations of planetary cooling and volatile cycling. The models estimate the amount of volatile in mantle reservoir, and calculate the outgassing and regassing rates. A linear model of volatile concentration-dependent is assumed for the activation energy of the solid-state creep in the mantle. The kinematic viscosity of the mantle is thus dynamically affected by the activation energy through a variable concentration in volatile. Mantle temperature and heat flux is calculated using a model derived from classic thermal boundary layer theory of a single layered mantle with temperature dependent viscosity. The rate of volatile exchanged between mantle and surface is calculated by balancing the amount of volatiles degassed in the atmosphere by volcanic and spreading related processes and the amount of volatiles recycled back in the mantle by the subduction process. In the cases that lack plate tectonics, the degassing efficiency is dramatically reduced and the regassing process is absent. The degassing effect is dependent on average spreading rate of tectonic plates and on the amount of volatile in the melt extract in the transition zone between mantle and upper boundary laver. The regassing effect is dependent on the subduction rate and on the amount of volatile present on a hydrated layer on top of the subducting slab. The degassing and regassing parameters are all related to the intensity of the convection in the mantle and to the surface temperature of the planet, and they are regulated by the amount of volatiles in reservoir. Comparative study with the previous models display significant differences and improve the versatility of the model. The optimum efficiency factors found are in the range of 0.01-0.06 for degassing/regassing processes, in agreement with more recent estimates. An important effect of the volatile cycling process is a general negative feedback effect that results in a general trend to adjust the mantle volatile content in time to a value set by the energy balance in the system. As a result, the initial amount of volatile in the mantle is rendered irrelevant for late stage of thermal evolution. In the case of no plate tectonics, the opposite effect takes place: initial volatilization plays an important role through entire evolution. The implications of mantle convection on the stability of the lithosphere were investigated further using the thermal history calculations and numeric simulations. They point to the conclusion that mantle convection induced stress levels increase from the past to the present fact that leads to a greater potential of craton deformation. The main consequence of this trend is that sections of continental lithosphere that have remained stable since the Archean and Proterozoic are becoming progressively more prone to instability in the geologically modem era. After the volatiles are degassed from the mantle, they are cycled through the atmosphere. The interact with the climate influencing the surface temperature, and further controlling the mantle convection. Using a grey radiative-convective model for the atmosphere, we analyzed the feedback relationships between volatiles, especially water, and surface temperature. We showed that large amount of water degassed during a hot, possible melt ocean phase after the planet formation could conserve large amount of water in atmosphere and maintain the surface temperature at moderate level.
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System Level Exploration of RRAM for SRAM ReplacementDogan, Rabia January 2013 (has links)
Recently an effective usage of the chip area plays an essential role for System-on-Chip (SOC) designs. Nowadays on-chip memories take up more than 50%of the total die-area and are responsible for more than 40% of the total energy consumption. Cache memory alone occupies 30% of the on-chip area in the latest microprocessors. This thesis project “System Level Exploration of RRAM for SRAM Replacement” describes a Resistive Random Access Memory (RRAM) based memory organizationfor the Coarse Grained Reconfigurable Array (CGRA) processors. Thebenefit of the RRAM based memory organization, compared to the conventional Static-Random Access Memory (SRAM) based memory organization, is higher interms of energy and area requirement. Due to the ever-growing problems faced by conventional memories with Dynamic Voltage Scaling (DVS), emerging memory technologies gained more importance. RRAM is typically seen as a possible candidate to replace Non-volatilememory (NVM) as Flash approaches its scaling limits. The replacement of SRAMin the lowest layers of the memory hierarchies in embedded systems with RRAMis very attractive research topic; RRAM technology offers reduced energy and arearequirements, but it has limitations with regards to endurance and write latency. By reason of the technological limitations and restrictions to solve RRAM write related issues, it becomes beneficial to explore memory access schemes that tolerate the longer write times. Therefore, since RRAM write time cannot be reduced realistically speaking we have to derive instruction memory and data memory access schemes that tolerate the longer write times. We present an instruction memory access scheme to compromise with these problems. In addition to modified instruction memory architecture, we investigate the effect of the longer write times to the data memory. Experimental results provided show that the proposed architectural modifications can reduce read energy consumption by a significant frame without any performance penalty.
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Effects of dietary inclusion levels of a low lignin hull, high-oil groat oat on the performance, carcass characteristics and rumen fermentation characteristics of feedlot cattleArya, Sushama 17 March 2010
Two experiments were conducted to evaluate the effects of dietary inclusion level of a low lignin hull, high-oil groat (CDC SO-I) oat on the performance, carcass characteristics and rumen degradation characteristics of feedlot cattle. In the first trial, 200 crossbred steers (average weight of 427.3 ± 22.4 kg) were allocated to 20 pens. Five treatments, formulated by replacing barley with increasing levels of CDC SO-I oat (Barley grain:CDC SO-I oat ratios of 100:0; 75:25; 50:50; 25:75 and 0:100 ; DM basis) were used. Four pens were randomly allocated to each treatment diet. Over the entire study there was a linear decrease (P< 0.01) in DMI and ADG with increasing inclusion level of CDC SO-I oat, whereas feed efficiency (gain:feed) decreased (P= 0.03) quadratically. Days on feed also increased (P= 0.03) quadratically for the steers fed the higher levels of CDC SO-I oat. Increasing the inclusion level of CDC SO-I oat in the diet also decreased (P< 0.01) carcass weight, dressing percentage and grade fat linearly. However, there was no effect of treatment on rib eye area and lean yield percentage. There was no significant effect of treatment on marbling score. While the results of this trial point to a negative effect of CDC SO-I oat on finishing performance, there were minimal differences between cattle fed 100% barley as the concentrate versus those fed 75% barley: 25% oat blend.<p>
Trial 2 involved a metabolism trial to determine the effect of CDC SO-I oat inclusion level on rumen fermentation parameters of 5 fistulated heifers fed the same diets used in Trial 1. A 5 × 5 Latin square experiment design was used. Rumen degradation parameters (rumen pH, VFA, osmolality and ammonia nitrogen levels) and feeding behavior (time spent eating, ruminating, chewing and drinking) were measured. Mean rumen pH for the barley-based diet was 5.88 which was not different (P> 0.05) than the mean pH of 5.5 for the oat-fed cattle. Treatment did not affect (P> 0.05) time spent below pH cutoff values of 5.8, 5.5 and 5.2. No effect of oat inclusion level (P> 0.05) was observed on total VFA levels, molar proportion of individual fatty acids and osmolality while isobutyrate (P= 0.05) and ruminal ammonia nitrogen concentrations decreased linearly (P= 0.02) with the higher inclusion of CDC SO-I oat. Time spent eating was linearly (P< 0.01) increased with higher inclusion level of CDC SO-I oat.<p>
Over all, the results of this study indicate that the replacement of barley by CDC SO-I oat in finishing diets decreases dry matter intake and as a result leads to reduced ADG, increased days on feed and lower slaughter and carcass weights. The reduced performance might be the result of higher fat content, high hull and/or faster degradation rate of oat starch leading to subacute ruminal acidosis in cattle fed higher levels of oat. However, replacing barley with CDC SO-I oat does not significantly change the rumen environment. The results of this study indicate that CDC SO-I oat can be successfully included up to a maximum level of 25% without any adverse effect on performance and carcass characteristics in the diets of finishing cattle.
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A Spin-torque Transfer MRAM in 90nm CMOSSong, Hui William 25 August 2011 (has links)
This thesis presents the design and implementation of a high-speed read-access STT MRAM. The proposed design includes a 2T1MTJ cell topology, along with two different read schemes: current-based and voltage-based. Compared to the conventional read scheme with 1T1MTJ cells, the proposed design is capable of reducing the loading on the read circuit to minimize the read access time. A complete STT MRAM test chip including the proposed and the conventional schemes was fabricated in 90nm CMOS technology. The 16kb test chip's measurement results confirm a read access time of 6ns and a write access time of 10ns. The read time is 25% faster than other works of similar array size published thus far, while the write time is able to match the fastest result.
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A Spin-torque Transfer MRAM in 90nm CMOSSong, Hui William 25 August 2011 (has links)
This thesis presents the design and implementation of a high-speed read-access STT MRAM. The proposed design includes a 2T1MTJ cell topology, along with two different read schemes: current-based and voltage-based. Compared to the conventional read scheme with 1T1MTJ cells, the proposed design is capable of reducing the loading on the read circuit to minimize the read access time. A complete STT MRAM test chip including the proposed and the conventional schemes was fabricated in 90nm CMOS technology. The 16kb test chip's measurement results confirm a read access time of 6ns and a write access time of 10ns. The read time is 25% faster than other works of similar array size published thus far, while the write time is able to match the fastest result.
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Design and Performance of a VOC Abatement System Using a Solid Oxide Fuel CellBorwankar, Dhananjai January 2009 (has links)
There has always been a desire to develop industrial processes that minimize the resources they use, and the wastes they generate. The problem is when new guidelines are forced upon long established processes, such as solvent based coating operations. This means instead of integrating an emission reduction technology into the original design of the process, it is added on after the fact. This significantly increases the costs associated with treating emissions.
In this work the ultimate goal is the design of an “add-on” abatement system to treat emissions from solvent based coating processes with high destruction efficiency, and lower costs than systems in current use. Since emissions from processes that utilize solvent based coatings are primarily comprised of volatile organic compounds (VOCs), the treatment of these compounds will be the focus.
VOCs themselves contain a significant amount of energy. If these compounds could be destroyed by simultaneously extracting the energy they release, operational costs could be substantially reduced. This thesis examines the use of model-based design to develop and optimize a VOC abatement technology that uses a Solid Oxide Fuel Cell (SOFC) for energy recovery. The model was built using existing HYSYS unit operation models, and was able to provide a detailed thermodynamic and parametric analysis of this technology.
The model was validated by comparison to published literature results and through the use of several Design of Experiment factorial analyses. The model itself illustrated that this type of system could achieve 95% destruction efficiency with performance that was superior to that of Thermal Oxidation, Biological Oxidation, or Adsorption VOC abatement technologies. This was based upon design criteria that included ten year lifecycle costs and operational flexibility, as well as the constraint of meeting (or exceeding) current regulatory thresholds.
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Hydrolys av primärslam för förbättrande av biologisk fosforreduktion vid behandling av hushållsavloppsvatten [Hydrolysis of primary sludge for enhancement of biological phosphorus removal in household wastewater]Elfving, Erik January 2005 (has links)
Hammarby Sjöstad is a new district of southern Stockholm built with focus on reduced environmental impact by recirculation of materials and sustainability. The environmental goals aim to cut the water consumption by half and a separate storm water treatment. Thus, the wastewater will be more concentrated and will originate from the households only. The Sjöstad project includes the idea of a local treatment plant for the household wastewater. To evaluate this possibility, Sjöstadsverket, an experimental treatment plant was constructed. New wastewater treatment processes are tested and evaluated and compared to conventional methods including both aerobic and anaerobic treatment processes. One of the aerobic treatment processes includes enhanced biological phosphorus removal (EBPR or Bio-P) as the method for the removal of phosphorus. In biological phosphorus removal the wastewater is alternately being exposed to anaerobic and aerobic conditions, which favours a certain bacteria, which can accumulate more phosphorus than is required for their growth. For this phosphorus accumulation the bacteria need volatile fatty acids (VFA) to cover their energy demand, but normally there is a shortage in VFA in the incoming wastewater. The main purpose of this master thesis work has been to create the best possible conditions in order to produce VFA by hydrolysis and fermentation of primary sludge. In this way the organic material in the incoming wastewater can be used in biological phosphorus removal. The sludge temperature, total solids (TS) and retention time are regarded as important parameters for a successful biological phosphorus removal and a laboratory study was set up to investigate these conditions for the wastewater at the Hammarby Sjöstad experimental plant. These laboratory-scale hydrolysis experiments showed that high temperature and high TS favours VFA-production. The results have also shown that four to five days retention time is suitable at a process temperature higher than 23°C, but also that the retention time likely should be extended at lower temperatures. In a full-scale process experiment, primary sludge was pumped from a primary clarifier to a hydrolysis tank and then back to the primary clarifier. The hydrolysis gave rise to increased VFA-production when TS was increased. A temperature difference between the primary sludge and the hydrolysis sludge of 3°C was observed. The reason behind the difference has not been determined, but is considered important, since the temperature affects the VFA-production. Further on, analyses with gas chromatograph (GC) have shown that acetate has been the most frequently occurring VFA, although significant levels of other VFA, such as propionate, has also been detected. Phosphorus release tests in laboratory-scale, where phosphorus was released during an anaerobic phase and taken up during an aerobic phase, proved that biological phosphorus removal occurred at the full-scale experimental train. The full-scale hydrolysis experiment has shown that the VFA contribution by the hydrolysis tank to the biological phosphorus removal was low. The main reason is that the sludge-flow through the hydrolysis tank has been insignificant compared to the incoming wastewater flow. The problem is most likely connected to the incoming wastewater characteristics, since the low share of suspended solids (SS) entailed that not enough organic material in the primary clarifier settled. / I figur 57 på sidan 76 stämmer inte trendlinjernas ekvationer i den tryckta versionen. Dessa är nu korrigerade i den elektroniska versionen, så att rätt ekvationer finns i den aktuella figuren.
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Design and Performance of a VOC Abatement System Using a Solid Oxide Fuel CellBorwankar, Dhananjai January 2009 (has links)
There has always been a desire to develop industrial processes that minimize the resources they use, and the wastes they generate. The problem is when new guidelines are forced upon long established processes, such as solvent based coating operations. This means instead of integrating an emission reduction technology into the original design of the process, it is added on after the fact. This significantly increases the costs associated with treating emissions.
In this work the ultimate goal is the design of an “add-on” abatement system to treat emissions from solvent based coating processes with high destruction efficiency, and lower costs than systems in current use. Since emissions from processes that utilize solvent based coatings are primarily comprised of volatile organic compounds (VOCs), the treatment of these compounds will be the focus.
VOCs themselves contain a significant amount of energy. If these compounds could be destroyed by simultaneously extracting the energy they release, operational costs could be substantially reduced. This thesis examines the use of model-based design to develop and optimize a VOC abatement technology that uses a Solid Oxide Fuel Cell (SOFC) for energy recovery. The model was built using existing HYSYS unit operation models, and was able to provide a detailed thermodynamic and parametric analysis of this technology.
The model was validated by comparison to published literature results and through the use of several Design of Experiment factorial analyses. The model itself illustrated that this type of system could achieve 95% destruction efficiency with performance that was superior to that of Thermal Oxidation, Biological Oxidation, or Adsorption VOC abatement technologies. This was based upon design criteria that included ten year lifecycle costs and operational flexibility, as well as the constraint of meeting (or exceeding) current regulatory thresholds.
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Effects of dietary inclusion levels of a low lignin hull, high-oil groat oat on the performance, carcass characteristics and rumen fermentation characteristics of feedlot cattleArya, Sushama 17 March 2010 (has links)
Two experiments were conducted to evaluate the effects of dietary inclusion level of a low lignin hull, high-oil groat (CDC SO-I) oat on the performance, carcass characteristics and rumen degradation characteristics of feedlot cattle. In the first trial, 200 crossbred steers (average weight of 427.3 ± 22.4 kg) were allocated to 20 pens. Five treatments, formulated by replacing barley with increasing levels of CDC SO-I oat (Barley grain:CDC SO-I oat ratios of 100:0; 75:25; 50:50; 25:75 and 0:100 ; DM basis) were used. Four pens were randomly allocated to each treatment diet. Over the entire study there was a linear decrease (P< 0.01) in DMI and ADG with increasing inclusion level of CDC SO-I oat, whereas feed efficiency (gain:feed) decreased (P= 0.03) quadratically. Days on feed also increased (P= 0.03) quadratically for the steers fed the higher levels of CDC SO-I oat. Increasing the inclusion level of CDC SO-I oat in the diet also decreased (P< 0.01) carcass weight, dressing percentage and grade fat linearly. However, there was no effect of treatment on rib eye area and lean yield percentage. There was no significant effect of treatment on marbling score. While the results of this trial point to a negative effect of CDC SO-I oat on finishing performance, there were minimal differences between cattle fed 100% barley as the concentrate versus those fed 75% barley: 25% oat blend.<p>
Trial 2 involved a metabolism trial to determine the effect of CDC SO-I oat inclusion level on rumen fermentation parameters of 5 fistulated heifers fed the same diets used in Trial 1. A 5 × 5 Latin square experiment design was used. Rumen degradation parameters (rumen pH, VFA, osmolality and ammonia nitrogen levels) and feeding behavior (time spent eating, ruminating, chewing and drinking) were measured. Mean rumen pH for the barley-based diet was 5.88 which was not different (P> 0.05) than the mean pH of 5.5 for the oat-fed cattle. Treatment did not affect (P> 0.05) time spent below pH cutoff values of 5.8, 5.5 and 5.2. No effect of oat inclusion level (P> 0.05) was observed on total VFA levels, molar proportion of individual fatty acids and osmolality while isobutyrate (P= 0.05) and ruminal ammonia nitrogen concentrations decreased linearly (P= 0.02) with the higher inclusion of CDC SO-I oat. Time spent eating was linearly (P< 0.01) increased with higher inclusion level of CDC SO-I oat.<p>
Over all, the results of this study indicate that the replacement of barley by CDC SO-I oat in finishing diets decreases dry matter intake and as a result leads to reduced ADG, increased days on feed and lower slaughter and carcass weights. The reduced performance might be the result of higher fat content, high hull and/or faster degradation rate of oat starch leading to subacute ruminal acidosis in cattle fed higher levels of oat. However, replacing barley with CDC SO-I oat does not significantly change the rumen environment. The results of this study indicate that CDC SO-I oat can be successfully included up to a maximum level of 25% without any adverse effect on performance and carcass characteristics in the diets of finishing cattle.
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