This research aims at evaluating a new ventilation concept: personal displacement ventilation (PDV) for improving indoor air quality. The new ventilation method combines room displacement ventilation with task ventilation, the latter being directed at controlling air quality and comfort in the microenvironment where the building occupant is working, with the premise that such directed ventilation will maintain air quality where it matters. This approach could lead to improved ventilation system design that could even provide individual control of indoor microclimate. The effectiveness of PDV was studied by using computational fluid dynamics (CFD) modeling and rigorous validation experiments. First, a small office setup was built in a controlled environmental chamber. Three PDV cases with different locations of contaminant source and one general displacement ventilation (DV) case were investigated. Spatial distributions of airflow, temperature, and hypothetical pollutant distributions were measured. The measured data were then used to evaluate the performance of PDV against defined indoor air quality and thermal comfort criteria, and to validate the CFD model. The validated CFD program was further used to study PDV under various conditions. This study found that basic equipped PDV acts no different from DV from airflow pattern?s point of view. Due to the lack of heat generation around occupant?s legs, local buoyancy effect is not strong enough to attract supply air, which is generated from diffuser nearby, to join in the plume around occupant. However, auxiliary activities adjusting the direction of supply air and adding high panels around person can improve the fraction of supply air to join the plume around person or decrease the average contaminant concentration in breathing zone.

No description available.

Carbonate reservoirs are usually diffcult to map and identify in seismic sections due to their complex structure, lithology and diagenetic frabrics. The Midland Basin, located in the Permian Basin of West Texas, is an excellent example of these complex carbonate structures. In order to obtain a better characterization and imaging of the carbonate buildups, an acoustic impedance inversion is proposed here. The resolution of the acoustic impedance is the same as the input seismic data, which is greatly improved with the addition of the low frequency content extracted from well data. From the broadband volume, high resolution maps of acoustic impedance distributions were obtained, and therefore the locations of carbonate buildups were easily determined. A correlation between acoustic impedance and porosity extracted from well data shows that areas with high acoustic impedance were correlated with low porosity values, whereas high porosities were located in areas of low acoustic impedance. Theoretical analyses were performed using the time-average equation and the Gassmann equation. These theoretical models helped to understand how porosity distributions affect acoustic impedance. Both equations predicted a decrease in acoustic impedance as porosity increases. Inversion results showed that average porosity values are 5% [plus or minus] 5%, typical for densely cemented rocks. Previous studies done in the study area indicate that grains are moderately to well-sorted. This suggests that time-average approximation will overestimate porosity values and the Gassmann approach better predicts the measured data. A comparison between measured data and the Gassmann equation suggests that rocks with low porosities (less than 5%) tend to have high acoustic impedance values. On the other hand, rocks with higher porosities (5% to 10%) have lower acoustic impedance values. The inversion performed on well data also shows that the fluid bulk modulus for currently producing wells is lower than in non-productive wells, (wells with low production rates for brine and hydrocarbons), which is consistent with pore fluids containing a larger concentration of oil. The acoustic impedance inversion was demonstrated to be a robust technique for mapping complex structures and estimating porosities as well. However, it is not capable of differentiating different types of carbonate buildups and their origin.

In this thesis, we survey some popular pricing methods of average options. They can be classified into three cateogries include approximation, Monte Carlo, and binomial tree approaches. We examine the accuracy of these methods by two cases, exchange rate and stock price. Numerical testing results show the accuracy of approximation and binomial tree are not stable. For the big-size feature of average option, their outputs are doubtful and damaging in pactice. Despite this, they are still valuable. This is because they own the other advantages. For example, the approximation approach can give us a quick formlas to calculate the Greek, and the binomial tree approach can price the American style options.

This thesis aims at investigating the technologies of the active power-factor correction (PFC) circuit. The system originally in the article is based on a boost converter circuit as the structure, the control method is to adopt the average current mode. We doesn¡¦t only narrate the circuit principle of the systematic circuit in the article but also use the OrCAD PSpice A/D software to simulation. Finally, we implemented make a prototype circuit and verified the proposed method. The experimental result shows that it can reach the goal for the power-factor correction.

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Several cruises of current measurements along various cross-Taiwan Strait transects were conducted by using shipboard Acoustic Doppler Current Profiler (ADCP) during 2001-2003. The main purpose of these experiments is to obtain seasonal variations of flow structures and volume transport in the central and southern regions of the Taiwan Strait. In each cruise the semidiurnal tidal currents were eliminated from the ADCP currents by two different methods, i.e., the phase averaging method and the TSNOW calculation. The subtidal current in the Taiwan Strait generally flows in the parallel-strait direction. In summer when the southwest monsoon prevails, the water in the strait originates from the South China Sea (SCS) or the Kuroshio. This northward-flowing water is divided into two parts by the archipelago of Penghu; the majority keeps flowing northward along the Penghu Channel (PHC), the minority flows northwestward around the Penghu Island. The flows in the surface layer of the PHC reach a maximum speed of 60 cm/s or greater. In winter, strong NE winds push the fresh and cold China Coastal water southward, along the western part of the Taiwan Strait. The SCS or Kuroshio water still flows northward on the eastern part of the strait. The maximum northward current still occurs in the PHC and is around 20 cm/s or less in the winter. Our results from the phase averaging method of all six cruises indicate that the net transports along the Taiwan Strait are all flowing northward, with a maximum value of about 2.5 Sv in summer (August 2001) and a minimum value of about 0.5 Sv in winter (March 2003). The standard deviation of the volume transport is 0.3 Sv. Due to its greater depths and strong currents, the volume transport in the PHC amounts to approximately 75% of the total transport of the Taiwan Strait. Based on the phase averaging results, the transport is related to the along-strait wind by a simple regression: , the sign convention is positive for southwesterly wind and transport.

Carbonate reservoirs are usually diffcult to map and identify in seismic sections due to their complex structure, lithology and diagenetic frabrics. The Midland Basin, located in the Permian Basin of West Texas, is an excellent example of these complex carbonate structures. In order to obtain a better characterization and imaging of the carbonate buildups, an acoustic impedance inversion is proposed here. The resolution of the acoustic impedance is the same as the input seismic data, which is greatly improved with the addition of the low frequency content extracted from well data. From the broadband volume, high resolution maps of acoustic impedance distributions were obtained, and therefore the locations of carbonate buildups were easily determined. A correlation between acoustic impedance and porosity extracted from well data shows that areas with high acoustic impedance were correlated with low porosity values, whereas high porosities were located in areas of low acoustic impedance. Theoretical analyses were performed using the time-average equation and the Gassmann equation. These theoretical models helped to understand how porosity distributions affect acoustic impedance. Both equations predicted a decrease in acoustic impedance as porosity increases. Inversion results showed that average porosity values are 5% [plus or minus] 5%, typical for densely cemented rocks. Previous studies done in the study area indicate that grains are moderately to well-sorted. This suggests that time-average approximation will overestimate porosity values and the Gassmann approach better predicts the measured data. A comparison between measured data and the Gassmann equation suggests that rocks with low porosities (less than 5%) tend to have high acoustic impedance values. On the other hand, rocks with higher porosities (5% to 10%) have lower acoustic impedance values. The inversion performed on well data also shows that the fluid bulk modulus for currently producing wells is lower than in non-productive wells, (wells with low production rates for brine and hydrocarbons), which is consistent with pore fluids containing a larger concentration of oil. The acoustic impedance inversion was demonstrated to be a robust technique for mapping complex structures and estimating porosities as well. However, it is not capable of differentiating different types of carbonate buildups and their origin.

Syftet med denna studie var att undersöka om vistelse på hög höjd påverkar den anaeroba arbetsförmågan. Sex aktiva universitetsstudenter, fyra män och två kvinnor, deltog frivilligt i studien. Expeditionen till Nepal varade i 40 dagar och under den perioden sov och vandrade försökspersonerna mellan 1400 och 5100 meter över havet. Före och efter expeditionen genomförde försökspersonerna ett anaerobt wingatetest där peak power, average power, minimum power and power drop uppmättes. Resultatet visade en signifikant sänkning av average power efter den genomförda expeditionen på hög höjd, med ett medelvärde på 8.44 ± 0,84 w/kg före expeditionen och 7.81 ± 0,87 w/kg efter expeditionen. Inga signifikanta förändringar sågs hos övriga uppmätta parametrar. Konklusionen är att average power försämras efter 40 dagars vistelse på hög höjd.

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: Jay F. Coughenour, Dept. of Finance. Includes bibliographical references.