A novel method to enhance oil production during cyclic steam injection has been developed. In the Top-Injection and Bottom-Production (TINBOP) method, the well contains two strings separated by two packers (a dual and a single packer): the short string (SS) is completed in the top quarter of the reservoir, while the long string (LS) is completed in the bottom quarter of the reservoir. The method requires an initial warm-up stage where steam is injected into both strings for 21 days; then the LS is opened to production while the SS continues to inject steam for 14 days. After the initial warm-up, the following schedule is repeated: the LS is closed and steam is injected in the SS for 21 days; then steam injection is stopped and the LS is opened to production for 180 days. There is no soak period. Simulations to compare the performance of the TINBOP method against that of a conventional cyclic steam injector (perforated across the whole reservoir) have been made. Three reservoir types were simulated using 2-D radial, black oil models: Hamaca (9°API), San Ardo (12°API) and the SPE fourth comparative solution project (14°API). For the first two types, a 20x1x20 10-acre model was used that incorporated typical rock and fluid properties for these fields. Simulation results indicate oil recovery after 10 years was 5.7-27% OIIP with TINBOP, that is 57-93% higher than conventional cyclic steam injection (3.3-14% OIIP). Steam-oil ratios were also decreased with TINBOP (0.8-3.1%) compared to conventional (1.2-5.3%), resulting from the improved reservoir heating efficiency.

This paper is to study the scattering problem and radiation problem between incident wave and a moored dual pontoon platform by using both a fully nonlinear numerical wave tank (NWT) and a physical tank. The nonlinear numerical wave tank is developed based on the velocity potential function and the boundary element method (BEM). In addition, a moored dual floating pontoon physical model is tested in an experimental wave tank to validate the numerical model for simulation of wave and structure interaction including mooring tension, structure translation and rotation. The phenomena of wave reflection and transmission due to a floating platform are also considered in the study. The experimential results indicate that the platform surge-RAO decays as the wave frequency increases. Similarly, the platform heave-RAO decays first until at the vicinity of the resonance frequency happening where the vertical amplitude rises up and then decays again. The tension-RAO has two resonance frequencies, the lower resonance is resulted by the surge montion, while the higer resonance is caused by the heave motion. Both wave reflection and transmission coefficients decrease near the heave resonance frequency. This indicates that the platform has the best performance in wave shelter effect at heave resonance to protect costal zone. In general, the comparisons of the numerical simulations and experimental results indicate the numerical horizontal motion have a good agreement, but for the vertical motion, the numerical predictions are larger than experiments especially near the heave resonance frequency. This may be due to the structure vertical velocity increases dramatically causing flow separation occurred below the structure sharp corner, thus the fluid viscous damping effect may play an important role in heave motion.

This thesis studies the subcarrier power allocation for the relayed signal in Orthogonal Frequency-Division Multiplexing (OFDM) based dual-hop system where the relay node operated in amplify-and-forward (AF) scheme. The investigated system assumes that each subcarrier at the source node transmits the signal with uniform power distribution. Considering the separated sum power constraints which the power constraint at source and relay node are uncorrelated, the conventional iterative water-filling algorithm can maximize the system capacity. However, it requires high computational complexity and the performance improvement is limited when the source node transmits the signal with uniform power distribution, subcarrier power allocation at relay node for capacity maximization is impractical. To further enhance the system performance, a novel subcarrier power allocation method is derived into a closed-form for the relayed signal to minimize the summation of equivalent noise power of the destination node. Comparing with the existing schemes, simulation results demonstrate that the proposed power scaling scheme significantly improves system average bit error rate (ABER).

This paper adopts a dual-point measurement technique to predict the resonance frequency and operation modes of a high speed rotor at different operating speed. The effect of balance policy on the operating mode shapes of a rotor has also been investigated. Displacement signals measured at two different points of a rotating shaft are used to estimate the operation mode shapes at the main operating frequency based on the definition of transmissibility function. To verify the feasibility of this technique, the dynamic parameters, i.e. natural frequencies, damping ratio and normal modes of a stationary rotor are measured in advance by applying the traditional frequency response method for comparison. The values of modal assurance criterion (MAC) and mode shape diagrams indicate that both methods are in a good agreement on the normal modes when the system is undamped or lightly damped. However, a significant difference is observed for highly damped modes. The dual-point measurement technique is applicable to investigate the effect of rotating speed on measured operation modes at different speed. Results indicate that the rotating speed may affect the dynamic parameters of a rotating shaft significantly. Furthermore, the dynamic unbalance effect on the response of a rotating shaft has also been studied in this thesis. Results indicate that the position of the unbalance is quite sensitive to the response of a rotating shaft. The sensitivity of unbalance and its position is dependent on the operation mode correspondence to the driving speed. The measured results indicate the dual-point measurement is quite available to study the dynamic responses of a rotating shaft or rotor.

¡@¡@The countershaft transmission is a device connected between engine and driving wheel for transferring power. This device can provide variable gear ratios to maintain engine speed in certain operating range and is well applied for vehicle transmission systems for its high performance. In this thesis, the systematic design methodology for dual-clutch countershaft automatic transmission (DCT) is proposed. This methodology can provide a systematic design procedure for the gear box prototype, number of teeth, computer-aid program and preliminary layout. First, the fundamentals and gear-shifting operations for DCT are illustrated to establish the design requirements. Secondly, 12 kinds and 8 kinds for 7-speed DCT prototype are synthesized for the gear mechanism with FR type and FF type respectively. Then, according to both FR and FF types, calculate the proper number of teeth for ideal gear ratio and build the computer-aided calculating interface. Finally, the preliminary layouts of the above prototypes and number of teeth are built by CAD models. The result of this research will be beneficial for further newly DCT designs.

This dissertation consists of three essays in Housing and Family Economics. In the first chapter, I analyze the interstate migration patterns of families and the effect of labor force attachment of women on joint migration decisions. I show that as the earned income of spouses become similar, the probability of migration falls substantially. This observation is robust in the sense that 1) it holds even after controlling for a rich set of factors that are strongly correlated with relative income, 2) it yields qualitatively similar results when I model the incidence of attrition as another exit, 3) it consistently disappears for the shorter distance moves. I also find that the negative relationship between income similarity of couples and interstate migration is especially strong for supposedly more settled families and couples that have similar labor market characteristics beyond income levels. In the second chapter, I quantify the contribution of women's labor force attachment to the declining trend in interstate migration. I first document that for families in which both spouses have similar incomes, the propensity to migrate is significantly lower than for families with unequal spousal earnings. I then construct a labor search model in which households make location, marriage, and divorce decisions. I calibrate the model to match aggregate U.S. statistics on mobility, marriage and labor flows and use it to quantify the effect of a fall in the gender wage gap on interstate migration. Narrowing the gender wage gap increases women's contribution to total family income; it induces a higher share of families with both spouses working and more couples with similar incomes. The model predicts that the observed change in the gender wage gap accounts for 35% of the drop in family migration since 1981. Finally, in the third chapter, I examine the effects of homeownership on individuals' unemployment durations in the USA. I take into account that an unemployment spell can terminate with a job or with a non-participation transition. The endogeneity of homeownership is addressed through the estimation of a full maximum likelihood function which jointly models the competing hazards and the probability of being a homeowner. Unobserved factors contributing to the probability of being a homeowner are allowed to be correlated with unobservable heterogeneity in the hazard rates. Tentative results suggest that unemployed homeowners are less likely to find a job which is especially stronger for outright owners. I also find that homeowners' nonparticipation hazard does not significantly differ from that of renters' although having a mortgage lowers the chance of exiting the labor force. / text

This ethnographic case study is situated in a suburban elementary school’s third grade Two-Way 50:50 Dual Language immersion model in Central Texas. Interviews, surveys and observations were conducted to examine the students’ use of the two languages targeted in the Dual Language Immersion program, English and Spanish. Drawing on the notion of “investment” (Norton, 2000) and Bourdieu’s theory of “cultural and linguistic capital” (Bourdieu, 1986), this research studies the language use of six students representing the two language groups in the program. In the data analysis, the researcher finds that the notion of investment is consistent in all the participants, although the aspect that they choose to invest in varies and is represented in their culture, language and identity. / text

Posterior pedicle screw and rod fixation has become standard in the treatment of oncological resections requiring stabilization, deformity correction and unstable thoracolumbar fractures. Given the high mechanical stress at the points of highest instability, some clinicians have utilized dual rods on each side to augment the construct. The added advantage of this type of construct has not been previously evaluated in-vitro. The goal of this study is to evaluate the biomechanical advantage of a dual rod construct in the thoracolumbar spine, using a burst fracture cadaveric model. Methods: Seven fresh human cadaveric (T9-L3) spines were tested in normal conditions, after an iatrogenic T12 burst fracture, and successively after laminectomy and standard two rod pedicle screw stabilization (two level above and two below) and two different dual rod overlapping constructs. Pure moment torque was applied quasistatically, while 3D motion was measured optoelectronically. Thoracolumbar range of motion was measured during flexion, extension, left / right lateral bending, and left / right axial rotation. Results: All constructs significantly stabilized the simulated burst fracture in all modes of testing. There was no statistically significant difference, however, in the ability to restrict motion between the 3 different constructs, either from T10-L2, or across the fracture segment of T11-L1. Conclusions: There does not appear to be a biomechanical advantage to using dual rods over standard single rods for immediate fixation in an unstable segment. Whether dual rods protect the construct against long-term failure is not yet known.

The tube hydroforming process has gained increasing attention in recent years. Coordination of the internal pressurization and axial feeding curves is critical in the tube hydroforming process to generate successful parts without fracture or wrinkling failure. The stress state at a given time and location varies with the process history and the design and control of the load paths. A new process parameter, counter-pressure, is introduced to achieve a favorable tri-axial stress state during the deformation process. The new process is referred to as dual hydroforming. The benefits offered by dual hydroforming will be characterized based upon the amount of wall thinning, plastic instability limit and final bulged configuration. An analytical model is developed to analyze the stress and strain state in the part (tube) during the dual hydroforming process. The stress-strain condition analyzed will be used to evaluate and compare thinning for tube hydroforming and dual hydroforming. The effect of applying counter-pressure on the plastic instability of thin-walled tubes with only internal pressure and combination of internal pressure and independent axial loading is considered. Finite element analysis is used to quantify the merits of dual hydroforming in terms of final bulged configuration. A parametric study has been conducted to investigate the effectiveness of dual hydroforming based on the various material properties and process conditions. Dual hydroforming results in different stress and strain states compared to tube hydroforming. The counter-pressure enabled favorable tri-axial stress state during deformation that resulted in different thickness and percentage thinning. Finite element analysis showed that for a particular amount of wall thinning there is an increase of around 8% in bulge height for dual hydroforming. Dual hydroforming delays the onset of plastic instability. This increase in the value of effective strain to failure results in an increase of around 12% in bulge height for dual hydroforming as shown by finite element simulations. Results of this study indicate that dual hydroforming can increase expansion i.e. more difficult parts can be designed and manufactured. Also, for a given part geometry, higher strength and less formable materials can be used.

The purpose of this correlational and descriptive study was to examine the influence of an agricultural dual credit course curriculum on student self-efficacy of college readiness as students matriculate to post-secondary education. To evaluate the personal characteristics, postsecondary plans, program perceptions and college readiness self-efficacy, a quantitative survey and online instrument was used to gather data and analyze information on high school students enrolled in agricultural education in both dual credit and non-dual credit courses primarily in the Middle Tennessee Region. The target population (N = 543) for this study was defined as students at 16 schools where the dual credit course was offered with the Middle Tennessee State University, School of Agribusiness and Agriscience in the 2011-2012 academic year. A total of 245 students from 16 secondary agricultural programs in seven different school districts across Tennessee, primarily in the Middle Tennessee region, participated in the study for a response rate of approximately 45%. This study examined college readiness of student participation in an agricultural dual credit course and sought to determine the relationship between student participation in a dual credit course offering and college readiness self-efficacy as well as student perceptions of the course offering. Course self-efficacy was higher among dual credit participants versus non-dual credit participants. Social self-efficacy was also higher for dual credit participants. Females had higher Course self-efficacy, and there was a positive relationship between GPA and each construct of the college readiness self-efficacy inventory. Participant perceptions of the agricultural dual credit program were also high. This study indicates that dual credit participants can confidently approach post-secondary options, and that they are more likely to be successful in college due to level of self-efficacy as they matriculate into college. Recommendations from the study include: Using the MTSU dual credit model in future dual credit course developments and collaborations; using findings as a basis for training future agricultural education teachers on how to improve CRSE; and additional and longitudinal studies to track dual credit students’ success in college.