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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.
91

The Formation and Run-off of Condensate on a Vertical Glass Surface: An Experimental Study

Kansal, Vivek January 2006 (has links)
An experimental study of condensate was performed by exposing a sheet of glass, cooled at its bottom edge, to an enclosure with a controlled environment. The air in the enclosure was maintained at a constant relative humidity (RH) and a constant dry bulb temperature (Tdb). Experiments were conducted at Tdb = 22.1°C and RH of 30%, 35%, 40%, 45%, and 50%. It was found that the time until initial condensation run-off was sensitive to low RH (RH = 30%, 35%, 40%) and insensitive to high RH (RH = 45%, 50%). Time until run-off decreased with increasing RH. It was found that, at first, condensation run-off occurred near the bottom of the glass and left one to believe that the remaining condensate was in steady state with the enclosure. Over a 16 hour period however, it was found that the condensation run-off front, in every case, progressed upward to include the entire condensate area. Similar to time of initial run-off, speed of condensation front movement increased with RH and was also insensitive at high RH. A summary plot showing run-off front position is presented. This chart can be used to predict initial run-off and front progression at the bottom edge of any window if the surface temperature profile is known.
92

Determination of Geosmin and 2-Methylisoborneol in Fish using In-vivo Solid Phase Microextraction

Bai, Ziwei January 2012 (has links)
The presence of off-flavor compounds in fish represents one of the significant economic problems encountered in aquaculture. These off-flavor compounds are due to the absorption of substances produced by microorganisms. Currently, a number of strategies have been employed to prevent or limit the growth of these microorganisms in recirculating aquaculture system. Therefore, it is important to evaluate the effectiveness of these strategies by monitoring the concentrations of off-flavor compounds in fish. In-vivo solid phase microextraction (SPME), a rapid and simple sample preparation method, allows the monitoring of concentrations of off-flavor compounds in live fish. In this research, geosmin and 2-methylisoborneol (2-MIB), which are produced by cyanobacteria and actinomycetes being the major sources for “earthy” and “muddy” flavors in fish, were selected as representatives. In order to accurately quantify these compounds in fish muscle, two kinetic calibration methods, on-fibre standardization and measurement using pre-determined extraction rate, were used. Results obtained were validated by traditional methods. The detection limit of in-vivo SPME in fish muscle was 0.12 ng/g for geosmin and 0.21 ng/g for 2-MIB, both below the human sensory threshold. Additionally, the binding effect of geosmin and 2-MIB in fish muscle was investigated in details. Facilitated by the agarose gel model, it was proven that binding did not impact the extraction rate under the pre-determined sampling time. Furthermore, an optional sampling position was undertaken by inserting the fibre into the fat tissue found under the fish belly, the results indicating that this method could decrease extraction time by up to two-thirds of its usual time.
93

Nest characteristics, breeding dispersal, and nest defence behaviour of Northern Flickers in relation to nest predation

Fisher, Ryan Jeffrey 28 April 2005 (has links)
I studied nest characteristics, breeding dispersal, and nest defence behaviour of Northern Flickers (<i>Colaptes auratus</i>, hereafter flickers) in central interior British Columbia with respect to nest predation. My research focused on three questions: (1) Are there nest characteristics associated with the risk of nest predation and nest loss to European Starlings (<i>Sturnus vulgaris</i>)? (2) Does nest predation influence breeding dispersal? (3) Do parental attributes influence nest defence behaviour? <p> An examination of flicker nest-site characteristics at five spatial scales revealed that nests were safer from mammalian predators (N=81) when they were higher, concealed by vegetation, farther from continuous coniferous forest blocks, and contained fewer conifers within the nesting clump. Proximity to conifers increased predation risk, but nests safe from competitors (N=18) were closer to coniferous forest blocks and contained a higher percentage of conifers in the nesting clump. Flickers face a trade-off between being safe from predators and safe from competitors. <p> Nesting success did not influence between-year breeding dispersal by 159 male or 76 female flickers. Because nests and forest clumps were not predictably safe from predators, benefits of dispersing likely outweigh costs. Other factors such as mate-switching, nest ectoparasites, and a fluctuating food source may play larger roles in dispersal than nest predation. Within years, 73% of pairs switched nest sites after their first attempt failed due to predation (N=37); however, there was no reproductive advantage for these pairs compared to pairs that remained at their original nest. Stressful encounters with predators involving nest defence may trigger dispersal, although it seems to offer no greater nest success. Of 24 flicker pairs presented with a control model before egg-laying, 3 pairs abandoned their nest, whereas 4 out of 24 pairs presented with a squirrel model abandoned their nest. This suggests that a one-time encounter with a nest predator is not a sufficient deterrent against continued nesting. Rather, costs of finding and excavating or renovating a new cavity may cause individuals to tolerate some risk in nesting at a location with an active predator. <p> In experimental trials (N=94), intensity of nest defence behaviour against a model predator was not related to the sex, age, body size, and body condition of the defending adult(s). The sexes may have behaved similarly because they are similar in size and have similar survival patterns. Costs and benefits of nest defence for flickers of different ages may also be equal because flickers are relatively short-lived and their survival rate is not linked with age. Brood size of the defending adult was also unrelated to the intensity of nest defence. If flickers have adjusted their clutch size in relation to the number of young for which they can optimally provide care, then no effects of brood size on nest defence behaviour should be recorded, as was the case here.</p>
94

Conditional regulation of Hoxa2 gene expression in CG4 cells

Wang, Juan (Monica) 02 August 2007 (has links)
Oligodendrocytes (OLs) are the glial cells responsible for the synthesis and maintenance of myelin in the central nervous system. Recently, Hoxa2 was found by our laboratory to be expressed by OLs and down-regulated at the terminal differentiation stage during oligodendrogenesis in mice (Nicolay et al., 2004b). To further investigate the role of Hoxa2 in oligodendroglial development, a tetracycline regulated controllable expression system was utilized to establish two stable cell lines where the expression level of Hoxa2 gene could be up-regulated (CG4-SHoxa2 [sense Hoxa2]) or down-regulated (CG4-ASHoxa2 [Antisense Hoxa2]) in CG4 glial cells. Morphologically, no obvious differences were observed between CG4-SHoxa2 and CG4 wild-type cells, whereas CG4-ASHoxa2 cells exhibited much shorter processes compared with those of CG4 wild-type cells. Data from BrdU uptake assays indicated that an up-regulation of Hoxa2 gene promoted the proliferation of CG4-SHoxa2 cells. PDGF&alphaR (Platelet-derived growth factor [PDGF] receptor alpha), a receptor for the mitogen PDGF that enhances the survival and proliferation of OLs, was assessed at the mRNA level in both CG4 and CG4-SHoxa2 cells, but no significant differences were observed between Hoxa2 up-regulated cells and wild-type CG4 cells with respect to the mRNA level of PDGF&alphaR. In addition, specific investigations of the differentiation of CG4-SHoxa2 cells were carried out by characterizing the composition of stage specific oligodendroglial subpopulations in culture. Our immunocytochemical study did not indicate the differentiation course of the genetically engineered cells was significantly altered compared to CG4 wild-type cells, although results from semi-quantitative RT-PCR of oligodendrocyte-specific ceramide galactosyltransferase (CGT) and myelin basic protein (MBP) indicate that the differentiation of CG4-SHoxa2 cells was delayed when Hoxa2 gene was up-regulated.
95

THE OPERATING PERFORMANCE FOR SPIN-OFF- A CASE STUDY ON AN INTERNATIONAL HOTEL

Wang, Ming-Feng 25 August 2005 (has links)
Summary This research is to discuss the change of the operating performance after the company experiences the spin-off. An international tourism hotel is chosen as the research case. There are 10 items, relating the operating performance objective of the international tourism hotel, as the metric of the company before and after experiencing the company¡¦s spin-off. The purpose of this research is to discuss how the company¡¦s spin-off impacts the operating performance of the international tourism hotel and the example research is a real spin-off case. The findings of this research are as followings: 1. The operation performance is improved after this international tourism hotel spits the Room Division and the Food & Beverage Division off. 2. Focusing operations can improve the operating performance. 3. Through the spin-off process, the reduction of the organization dimension can decrease the management cost. 4. The company¡¦s spin-off can improve the management information quality, and also enhance the resource allocation to increase the corporation value. 5. After the spin-off, the company provides the superior reward strategy which also improves the operating performance. 6. The performance of internal control system and the cost control cannot have the improvement through the company¡¦s spin-off. 7. The performance is more explicitly measured after the company¡¦s spin-off. Key words: International Tourism Hotel, Spin-off, Operating Performance
96

Surface Acoustic Wave Properties of AlN Films on LiNbO3 Substrate

Chen, Chien-Hsing 04 July 2001 (has links)
Aluminum nitride (AlN) thin films were deposited on Z-cut LiNbO3 substrates using the reactive RF magnetron sputtering in this thesis. By means of the analyses of XRD, SEM and AFM, the optimal deposition conditions of highly C-axis oriented AlN films were sputtering pressure of 3.5 mTorr, nitrogen concentration (N2/N2+Ar) of 60%, RF power of 165W and substrate temperature of 400¢J. The piezoelectric bi-layers structure of SAW devices was then fabricated. The interdigital transducers (IDTs) were fabricated on bi-layers structure. The AlN thin film thickness of piezoelectric bi-layers structure was varied in order to discuss its effects on SAW devices. From the experimental results, it reveals that the center frequency of SAW filters increases with the increased AlN thin films thickness. It means that the SAW velocity increases as the AlN thin films thickness increases. The effects of bi-layers structure on SAW devices can be discussed in detail by measuring the parameters of SAW devices like insertion loss (IL), electromechanical coupling coefficient (K2) and the temperature coefficient of delay (TCD).
97

The effects of temperature, photoperiod and density on sexual and asexual reproductions of the sea anemone Aiptasia pulchella Carlgren 1943.

Chang, Herng-Yuan 20 July 2003 (has links)
Abstract In order to explore the mechanisms causing trade-offs between sexual and asexual reproductions, the sea anemones Aiptasia pulchella were taken as objects since they can reproduce by both modes simultaneously. Specimens were reared under different temperatures, photoperiods, and densities. Total weights of lacerates were used as an index of investment in asexual reproduction, whereas gonad weights as an index of investment in sexual reproduction. Sea anemones reared under low temperature (22¢J) reached larger pedal disks and produced larger, heavier lacerates, they also produced heavier gonads than those under high temperature (29¢J). Those reared under long light hours (15¡G9) reached smaller sizes and produced heavier gonads than those under short light hours (9¡G15). But the effect of photoperiod on lacerate size, number and weight are not significant. Interaction effect was not significant between these two factors. Correlation between sexual and asexual investments was not significant, either. In addition, A. pulchella reared under low density (1 sea anemone/beaker) produced more, heavier lacerates and heavier gonads than those under crowding conditions (4 sea anemones/beaker). There was a significantly positive correlationship between sexual and asexual reproduction investments. It seems there was no trade-offs between sexual and asexual investiments of the sea anemone A. pulchella.
98

Characterization of infield vehicle activity data and exhaust emissions from diesel powered off-road vehicles

Barnett, Ryan A. January 2001 (has links)
Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xv, 164 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 154-156).
99

Initial studies of structure coupling effects for a trolley/RRDF interface /

Teh, Chong-Ann. January 2003 (has links) (PDF)
Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, March 2003. / Thesis advisor(s): Fotis A. Papoulias. Includes bibliographical references (p. 61). Also available online.
100

OFFSHORE WIND FARM DECOMMISSIONING: INTRODUCING A MULTI-CRITERIA DECISION AID APPROACH

Kerkvliet, Hans January 2015 (has links)
The objective of this Thesis is to develop a methodological framework to guide the decision maker in selecting a decommissioning method for offshore wind farms which is supported by the majority of relevant stakeholders. Initially, a literature review has been conducted to find out which methods are available to decommission an off-shore wind farm and which criteria can influence the outcome.Two methods have been found in literature, namely partial and total removal of the foundation. Furthermore, twenty one (21) criteria have been found which could influence the results. These criteria can be divided in four categories which are economical, environmental, social and technical.Subsequently, a methodological framework was developed that included four steps. First, the possible decommissioning methods should be identified. Following on that, information should be collected and stakeholders should be selected. Subsequently, criteria should be selected and as last a multi criteria decision aid method should be used. It is expected that this procedure would lead to a decommissioning method which is supported by most of the stakeholders.To validate the methodological framework, a case study in the Netherlands has been selected. For this case study, four (4) stakeholders were identified and eleven (11) criteria were assessed. The outranking multi-criteria decision aid method PROMETHEE II was selected and results were obtained. Analyzing the results, it was possible to conclude that only one stakeholder preferred the total removal method while the other three stakeholders preferred the partial removal method.

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