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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.
1291

Emission Characteristics of Polycyclic Aromatic Hydrocarbons from a Heavy-Duty Diesel Engine mixed with constant H2/O2 and diesel/Biodiesel blends

Wu, Shin-Yi 26 June 2012 (has links)
This study investigated emission characteristics of polycyclic aromatic hydrocarbons (PAHs) and reductions of regulated harmful matters using Premium diesel fuel (PDF), mixed with a 60 L/min flow rate of H2/O2 mixture and blended with biodiesel 5% (B5), 10% (B10), 20% (B20), and 30% (B30). The diesel engine was operated at steady-state condition of 1,600 rpm, with torque and power outputs of 145 Nm and 24.5 kW, respectively. Measured results show that the emission concentrations of total PAHs were 22.42, 20.11, 17.28, 13.45, and 13.13 £gg/m3 for B0, B5, B10, B20, and B30, respectively, with corresponding emission factors of total PAHs being 1334.53, 1198.82, 986.05, 771.93, and 748.82 £gg/bhp-hr, and reductions of total PAHs being 10.3, 22.9, 40.0, and 41.4%. The results indicated that using biodiesel can reduce PAH emissions. However, the emission factors of carbon monoxide (CO) and total hydrocarbons (THC) were decreased by adding biodiesel, but those of carbon dioxides (CO2), nitrogen dioxides (NOx), and particulate matter (PM) were increased. Annual emissions of total PAHs were estimated to be 140.05, 126.92, 105.21, 81.97, and 79.86 ton/year for B0, B5, B10, B20 and B30, respectively, decreasing with increasing biodiesel. Also, the corresponding annual emissions of BaPeq were 5.88, 5.62, 3.50, 3.03, and 2.83 ton/year, respectively.
1292

Case Study for Deep Economy Development

Chen, Yu-Fang 02 August 2012 (has links)
The trend of globalization makes the political, economic, educational, culture and creative develop very fast. It also because of the vitality of the network information pushes the global continuously. So society produces an idea of " think globally, act locally ". Base on this research background, Bill McKibben (2005) brings up an idea of Deep Economy. It means Continues forever the development in local place. The reference shows the relations among country, market and civil society in globalization. The cultural and creative industries development stimulates city competitiveness. Professor Kiyoshi Miyazakithinks that the integrated community construction must include people, cultural, place, production and view. These conditions makes local develop appreciation. How is the real aspects for Deep Economy? In this study, it uses the Delphi expert questionnaire method (Delphi) to investigate this problem. It is invited industry, government and school tripartite expertsto conduct interviews and questionnaires. These factorsare discussed in the two-stage indicators convergence results by score of experts. After aggregating data, it cansanalysis to construct the five principal components by exploratory factor analysis.These data shows that Deep Economy should have five faces which are "Local Empowerment", "Identity Participation","Knowledge Learning","Cultural Connotation" and ¡§Creative Economy". This study has well proposals for the future development for Deep Economy. Keywords¡G Deep Economy¡BGlobalization¡BCulture and Creative¡BDelphi¡BExploratory Factor Analysis
1293

The relationship between hydrological and nutrient conditions in the Dongsha Atoll

Shen, Yi-jie 02 November 2012 (has links)
This study focuses on the relationship between hydrological and nutrient conditions in seawater surrounded by Dongsha Atoll. Dongsha Atoll is located in the northern South China Sea (NSCS), the water properties should be in coherence with the NSCS water masses. However, due to the semi-enclosed topography the water inside Dongsha Atoll is largely affected by local insolation and rainfall. Significant relationships between SiO2 or PO43- and salinity indicate that rainfall could be a major source of these nutrients. Insignificant relationship between N+N and salinity indicates that rainfall and nitrogen fixation both might affect the distribution of N+N. Temporal variations of temperature and chlorophyll a were alike, except for which occurred in July, 2011. It was probably caused by photo inhibition on phytoplankton growth. The inventory of chlorophyll a was positively correlated with both N+N and SiO2 but not with of PO43-, indicating that phytoplankton growth in Dongsha Atoll was mainly affected by N+N and SiO2. Phytoplankton growth maybe limited by N+N but not by SiO2, as the concentration of SiO2 was mostly beyond the limitation concentration for phytoplankton. According to close relationships between chlorophyll a and TSM, POC and PN, the particulate matter maybe mainly derived from biological origins. The inventory of chlorophyll a was positively correlated with both dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), manifesting the importance of biological origins for DOC and DON concentration. The ratios of DOC/DON, DON/DOP and DOC/DOP within the atoll were in ranges of 7.34-303 (mean: 30.4), 3.00-142 (mean: 22.7) and 104-2546 (mean: 421), respectively. The ratios are higher than those values in NSCS and East China Sea, implying the excretion of carbon-enriched DOM by phytoplankton. The concentration of chlorophyll a, DOC and POC were higher in the Small Lagoon than in the Atoll Lagoon, implying a relatively high productivity in the Small Lagoon. The fluxes of carbonate in the atoll was more than 30 times of the flux in the NSCS, due to its unique characteristics in the coral reef habitat. The organic matter of settling particulates was mainly derived from biological sources. The metal of enrichment factor of settling particulates reveals that Fe and Al are mainly derived from crustal sources, while Cu, Zn and Pb are likely influenced by anthropogenic sources.
1294

A science based emission factor for particulate matter emitted from cotton harvesting

Wanjura, John David 15 May 2009 (has links)
Poor regional air quality in some states across the US cotton belt has resulted in increased pressure on agricultural sources of particulate matter (PM) from air pollution regulators. Moreover, inaccurate emission factors used in the calculation of annual emissions inventories led to the identification of cotton harvesting as a significant source of PM10 in California and Arizona. As a result, cotton growers in these states are now required to obtain air quality permits and submit management practice plans detailing the actions taken by the producer to reduce fugitive PM emissions from field operations. The objective of this work was to develop accurate PM emission factors for cotton harvesting in terms of total suspended particulate (TSP), PM10, and PM2.5. Two protocols were developed and used to develop PM emission factors from cotton harvesting operations on three farms in Texas during 2006 and 2007. Protocol one utilized TSP concentrations measured downwind of harvesting operations with meteorological data measured onsite in a dispersion model to back-calculate TSP emission flux values. Flux values, determined with the regulatory dispersion models ISCST3 and AERMOD, were converted to emission factors and corrected with results from particle size distribution (PSD) analyses to report emission factors in terms of PM10 and PM2.5. Emission factors were developed for two-row (John Deere 9910) and sixrow (John Deere 9996) cotton pickers with protocol one. The uncertainty associated with the emission factors developed through protocol one resulted in no significant difference between the emission factors for the two machines. Under the second protocol, emission concentrations were measured onboard the six-row cotton picker as the machine harvested cotton. PM10 and PM2.5 emission factors were developed from TSP emission concentration measurements converted to emission rates using the results of PSD analysis. The total TSP, PM10, and PM2.5 emission factors resulting from the source measurement protocol are 1.64 ± 0.37, 0.55 ± 0.12, and 1.58E- 03 ± 4.5E-04 kg/ha, respectively. These emission factors contain the lowest uncertainty and highest level of precision of any cotton harvesting PM emission factors ever developed. Thus, the emission factors developed through the source sampling protocol are recommended for regulatory use.
1295

Single Inductor Dual Output Buck Converter

Eachempatti, Haritha 2009 May 1900 (has links)
The portable electronics market is rapidly migrating towards more compact devices with multiple functionalities. Form factor, performance, cost and efficiency of these devices constitute the factors of merit of devices like cell phones, MP3 players and PDA's. With advancement in technology and more intelligent processors being used, there is a need for multiple high integrity voltage supplies for empowering the systems in portable electronic devices. Switched mode power supplies (SMPS's) are used to regulate the battery voltage. In an SMPS, maximum area is taken by the passive components such as the inductor and the capacitor. This work demonstrates a single inductor used in a buck converter with two output voltages from an input battery with voltage of value 3V. The main focus areas are low cross regulation between the outputs and supply of completely independent load current levels while maintaining desired values (1.2V,1.5V) within well controlled ripple levels. Dynamic hysteresis control is used for the single inductor dual output buck converter in this work. Results of schematic and post layout simulations performed in CADENCE prove the merits of this control method, such as nil cross regulation and excellent transient response.
1296

Integrated Functions of Transforming Growth Factor Beta, Latency Associated Peptide, and Integrins During Early Porcine Pregnancy

Massuto, Dana A. 2009 December 1900 (has links)
In pigs and other mammals, embryonic losses often occur during implantation when the conceptus (embryo plus its extra-embryonic membranes) attaches to the maternal uterine epithelium. Mechanisms controlling this process are not completely understood. Integrins and growth factors are among many molecules likely involved in controlling implantation. Numerous integrins (ITG), including subunits ITGAV (alpha v), ITGB1 (beta 1), ITGB3 (beta 3), and ITGB5 (beta 5), and transforming growth factor betas (TGFBs), in both latent and active forms, are present at the porcine conceptus-maternal interface. TGFBs are released as latent precursors which cannot interact with TGFBRs prior to their activation. Latency associated peptide (LAP), part of the TGFB latent complex, contains an amino acid sequence Arg-Gly-Asp (RGD) that is found in other extracellular matrix molecules and may interact with and signal through integrins. We hypothesize that LAP will bind to and activate ITGAV-containing heterodimers at the conceptus-maternal interface and that these interactions are a functional component of implantation. We also hypothesize that TGFB acting via TGFBRs has critical roles during peri-implantation, and such roles may include promoting conceptus development, survival, and adhesion. Immunofluorescence was used to colocalize TGFB, LAP, and integrins in porcine peri-implantation uterus and conceptus; immunohistochemistry of phosphorylated SMAD2/3 provided evidence of TGFB activity. Affinity chromatography identified cell surface integrins on porcine trophectoderm that are capable of binding LAP. In vivo, intrauterine infusions of LAP with its native RGD site (LAP-RGD) resulted in inhibition of conceptus elongation; LAP-RGE infusions yielded normal-appearing filamentous conceptuses at d13 of pregnancy. At d24, allantois length and fetal weights were greater in gilts which received LAP-RGE infusions compared to controls which received vehicle only. Results provide evidence for 1) active and latent TGFB in porcine conceptus and uterus; 2) receptor-ligand interactions of integrins and LAP; 3) integrin aggregation and potential focal adhesion formation at the conceptus-maternal interface; and 4) TGFB- and/or integrin-associated mechanisms which regulate conceptus elongation and placental and fetal size. Collectively, results suggest that TGFB and integrins are extensively involved in communication at the porcine conceptus-maternal interface, particularly regulating conceptus development, adhesion, and placental and fetal development.
1297

Prediction of Reflection Cracking in Hot Mix Asphalt Overlays

Tsai, Fang-Ling 2010 December 1900 (has links)
Reflection cracking is one of the main distresses in hot-mix asphalt (HMA) overlays. It has been a serious concern since early in the 20th century. Since then, several models have been developed to predict the extent and severity of reflection cracking in HMA overlays. However, only limited research has been performed to evaluate and calibrate these models. In this dissertation, mechanistic-based models are calibrated to field data of over 400 overlay test sections to produce a design process for predicting reflection cracks. Three cracking mechanisms: bending, shearing traffic stresses, and thermal stress are taken into account to evaluate the rate of growth of the three increasing levels of distress severity: low, medium, and high. The cumulative damage done by all three cracking mechanisms is used to predict the number of days for the reflection crack to reach the surface of the overlay. The result of this calculation is calibrated to the observed field data (severity and extent) which has been fitted with an S-shaped curve. In the mechanistic computations, material properties and fracture-related stress intensity factors are generated using efficient Artificial Neural Network (ANN) algorithms. In the bending and shearing traffic stress models, the traffic was represented by axle load spectra. In the thermal stress model, a recently developed temperature model was used to predict the temperature at the crack tips. This process was developed to analyze various overlay structures. HMA overlays over either asphalt pavement or jointed concrete pavement in all four major climatic zones are discussed in this dissertation. The results of this calculated mechanistic approach showed its ability to efficiently reproduce field observations of the growth, extent, and severity of reflection cracking. The most important contribution to crack growth was found to be thermal stress. The computer running time for a twenty-year prediction of a typical overlay was between one and four minutes.
1298

Friction Factor Measurement, Analysis, and Modeling for Flat-Plates with 12.15 mm Diameter Hole-Pattern, Tested with Air at Different Clearances, Inlet Pressures, and Pressure Ratios

Deva Asirvatham, Thanesh 2010 December 1900 (has links)
Friction factor data are important for better prediction of leakage and rotordynamic coefficients of gas annular seals. A flat-plate test rig is used to determine friction factor of hole-pattern/honeycomb flat-plate surfaces representing annular seals. Three flat-plates, having a hole-pattern with hole diameter of 12.15 mm and hole depths of 0.9 mm, 1.9 mm, and 2.9 mm, are tested with air as the working medium. Air flow is produced between two surfaces, one having the hole-pattern roughness representing the hole-pattern seal and the other smooth, at the following three clearances of 0.254, 0.381, and 0.635 mm and three inlet pressures of 56, 70, and 84 bar with all possible pressure ratios at each configuration. The friction factor data are presented for all tested configurations, with description of the test rig and theory behind the calculations. The effect of hole diameter, hole depth, clearance, Reynolds number, and inlet pressure are analyzed, and friction factor models based on these parameters are calculated. Friction factor upset (an undesirable phenomenon making the test data non repeatable) is also explained. Dynamic pressure data are presented, measured from dynamic pressure probes located at both the hole-pattern plate and the smooth plates at different locations.
1299

Assessing Invariance of Factor Structures and Polytomous Item Response Model Parameter Estimates

Reyes, Jennifer McGee 2010 December 1900 (has links)
The purpose of the present study was to examine the invariance of the factor structure and item response model parameter estimates obtained from a set of 27 items selected from the 2002 and 2003 forms of Your First College Year (YFCY). The first major research question of the present study was: How similar/invariant are the factor structures obtained from two datasets (i.e., identical items, different people)? The first research question was addressed in two parts: (1) Exploring factor structures using the YFCY02 dataset; and (2) Assessing factorial invariance using the YFCY02 and YFCY03 datasets. After using exploratory and confirmatory and factor analysis for ordered data, a four-factor model using 20 items was selected based on acceptable model fit for the YFCY02 and YFCY03 datasets. The four factors (constructs) obtained from the final model were: Overall Satisfaction, Social Agency, Social Self Concept, and Academic Skills. To assess factorial invariance, partial and full factorial invariance were examined. The four-factor model fit both datasets equally well, meeting the criteria for partial and full measurement invariance. The second major research question of the present study was: How similar/invariant are person and item parameter estimates obtained from two different datasets (i.e., identical items, different people) for the homogenous graded response model (Samejima, 1969) and the partial credit model (Masters, 1982)? To evaluate measurement invariance using IRT methods, the item discrimination and item difficulty parameters obtained from the GRM need to be equivalent across datasets. The YFCY02 and YFCY03 GRM item discrimination parameters (slope) correlation was 0.828. The YFCY02 and YFCY03 GRM item difficulty parameters (location) correlation was 0.716. The correlations and scatter plots indicated that the item discrimination parameter estimates were more invariant than the item difficulty parameter estimates across the YFCY02 and YFCY03 datasets.
1300

Decision Making of Mobile Robot in the Presence of Risk on Its Surroundings

Huh, Sung 2011 December 1900 (has links)
Mobile robots are used on many areas and its demand on extreme terrain, hazardous area, or life-threatening place is increasing to reduce the loss of life. A good decision making capability is essential for successful navigation of autonomous robot and it affect finding the shortest or optimal path within given condition. The wavefront algorithm is simple to apply, yet yield an optimal path for a robot to follow in many different configurations. Although the path created using wavefront algorithm is an optimal in the sense that every node has the same cost, the result is not the best result in global perspective because of the algorithm is inconsiderate on the surrounding condition. To solve this issue and create the best result on global perspective, risk factor analysis method was implemented on the wavefront algorithm to improve the performance. In this work, the relationship between the wavefront algorithm and dynamic programming will be explained to show that the wavefront algorithm obeys the principle of optimality. The simulation result displays better performance on safety, while keeping the travelling distance minimum, if the risk factor is used on the wavefront algorithm and the robot on actual test behave accordingly. This work will contribute on decision making of mobile robot using risk factor method to create a most desirable and safe path. In addition to that, it will demonstrate how the risk factor method can be applied to the mobile robot navigation.

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