A study of two-phase flow in annular channels with annular gaps of less than 1 mm is useful for the design and safety analysis of high power density systems such as accelerator targets and nuclear reactor cores. Though much work has been done on pressure drop in two-phase flow, designers rely mostly on empirical models and correlations; hence, it is valuable to study their applicability for different channel sizes, geometries, and gas qualities. The pressure drop along a concentric annular test section was measured for cases of either constant quality or variable quality along its length (such as in sub-cooled and flow boiling). A porous tube was used to inject gas along the inner surface of the annular channel, thereby simulating the case of flow boiling along the inner surface. The data were compared to predictions of various models and correlations. Additionally, the effect of wall vibrations on the pressure drop was examined. Experiments were conducted by imposing vibrations of known amplitudes and frequencies on the outer tube of the annulus. Wall vibrations were thought to be important for flow in microchannels where the vibration amplitudes may be significant compared to the channel hydraulic diameter. The results obtained in this investigation indicate that the pressure drop correlation given by Beattie and Whalley provides the best agreement with the data for both porous tube gas injection (i.e. variable quality) and constant quality two-phase flow within the narrow annulus. Furthermore, the results show that there is a minimal effect of vibrations on two-phase pressure drop over the range of frequencies and amplitudes studied.

The Wafer Level Chip Scale Package (WLCSP) is gaining popularity for its performance and ability to meet the miniaturization requirements of portable consumer electronics, such as cell phones. For the industry of electronic package, the package life of electronic products is deemed as the essential consideration in the operation period. In practice, electronic products are usually damaged due to a harsh mechanical impact, such as drop and bending. The solder interconnections provide not only the electronic path between electric components and printing circuit board, but also the mechanical support of components on the printing circuit board, so that the reliability of solder interconnection becomes an essential consideration for a package. In the thesis several parameters, including redistribution layer (RDL) material and thickness, passivation material and thickness, under-bump metallization (UBM) structure factors are discussed. A variety of WLCSP structures are investigated for solder joint reliability performance. In addition to the fatigue lives of the test vehicle, locations and modes of fractured solder joints were observed. It was found that wafer level packaging structure under drop clearly related with the characteristic life. The weakest point of solder ball was intermetallic compound (IMC), and wafer level packaging structure was the crack into the second passivation layer and UBM interface of the corner. WLCSP under temperature cycling test was done and observed the fracture only occurred at the solder ball near the package.

Applicability of the Hartree-Fock (HF) based random phase approximation (RPA) with several Skyrme effective interactions to the description of the isoscalar giant monopole (ISGMR) and the isoscalar giant dipole resonance (ISGDR) in 90Zr, 116Sn, 144Sm and 208Pb nuclei has been investigated. The existing Skyrme interactions SL1, SkM*, SGII, Sly4 and Sk255 were used. Hartree-Fock description of the ground state properties of all nuclei of interest was obtained using these Skyrme interactions. Transition strength distributions for the ISGMR and the ISGDR in nuclei of interest were calculated using coordinate space representation for the RPA in the Green’s function formalism with discretized continuum. A method of projecting out the spurious state contribution from the transition strength distribution and the transition density of the ISGDR was employed to eliminate spurious state mixing, due to a not fully selfconsistent description of the particle-hole interaction within the RPA. Differential cross sections of 240 MeV alpha-particles inelastic scattering on all nuclei of interest were calculated using the folding model within the distorted wave Born approximation (DWBA). Optical potentials were obtained by folding HF ground state densities with a alpha-nucleon density dependent Gaussian interaction. Parameters of the interaction were obtained by fitting experimental angular distribution of alpha-nucleus elastic scattering. The inelastic differential cross sections were calculated using both collective and microscopic transition densities. Possible underestimations of the energy weighted sum rule for the case of the ISGDR are reported. An alternative description for the ISGDR in nuclei based on the Fermi liquid drop model (FLDM) with the collisional Fermi surface distortion was investigated. The FLDM dispersion relation was obtained from the linearized Landau-Vlasov equation. Centroid energies, E0 and E1, and widths, gamma-0 and gamma-1, of the ISGMR and ISGDR, respectively, were calculated as functions of the damping parameter using appropriate boundary conditions. Comparison of the theoretical ratios of the ISGDR and ISGMR centroid energies, E1/E0, to the experimental values resulted in a damping parameter equal to 0.5, however, systematic overestimation of energy of the ISGMR and ISGDR by 2.0-2.5 MeV was observed. The applicability of the HF-RPA to the description for the ISGDR in nuclei is confirmed.

Two-phase liquid-gas flow has a wide variety of applications in space, including active thermal control systems, high-power communications satellites, heat pumps and space nuclear reactors. Two-phase systems have many potential advantages over current single-phase systems due to reductions in system size, weight and power consumption. The mechanisms of pressure drop, heat transfer coefficients, void fractions, and flow regimes must be well understood under microgravity conditions in order to design reliable two-phase systems. The main objective of this present research is to develop a new mathematical model that can accurately predict the annular two-phase friction pressure drop to optimize the design of two-phase systems. The two-phase flow tests were conducted aboard the NASA KC-135 aircraft by the Interphase Transport Phenomena (ITP) group from Texas A&M University. The two-phase flow pressure drops were measured across a single transparent test section 12.7 mm ID and 1.63 m long in annular regimes under microgravity conditions during two flight campaigns. Different from previous work, this was the first time both the void fraction and the film thickness were measured under microgravity conditions. The empirical correlations for the interfacial friction factor and void fraction were developed from 57 experimental data using a linear least squares regression technique. The annular two-phase friction pressure drop can be predicted by the new mathematical model requiring only knowledge of the length and diameter of the tube, liquid and vapor mass flow rates, and properties of the working fluid. In addition, the new mathematical model was validated using Foster-Miller & ITP data collected over twelve flights aboard the KC-135 with working fluid R-12 (77 data points), Sundstrand data collected aboard the KC-135 with working fluid R-114 (43 data points) and Zhao and Rezkallah data aboard the KC-135 with working fluid water and air (43 data points). Compared with the LockhartMartinelli model, Wheeler model, Chen model and homogeneous model, the new mathematical model is the optimal model for predicting the two-phase friction pressure drop in annular regimes. The majority of the data falls within +-20% of the proposed correlation and the average error is 12%.

We propose an object-based multimedia model for specifying the QoS (quality of service) requirements, such as the maximum data-dropping rate or the maximum data-delay rate. We also present a resource allocation model, called the net-profit model, in which the satisfaction of user¡¦s QoS requirements is measured by the benefit earned by the system. Based on the net-profit model, the system is rewarded if it can allocate enough resources to a multimedia delivery request and fulfill the QoS requirements specified by the user. At the same time, the system is penalized if it cannot allocate enough resources to a multimedia delivery request. In this dissertation, we present our research in developing optimal solutions for multimedia stream delivery in bandwidth limited networks. To fulfill the QoS requirements, the resource, such as bandwidth, should be reserved in advance. Hence, we first investigate how to allocate a resource such that the QoS satisfaction is maximized, assuming that the QoS requirements are given a priori. The proposed optimal solution has significant improvement over the based line algorithm, EDF (Earliest Deadline First). Among all the optimal solutions found from the above problem, the net-profit may be distributed unevenly among the multimedia delivery requests. Furthermore, we tackle the fairness problem -- how to allocate a resource efficiently so that the difference of the net-profit between two requests is minimized over all the possible optimal solutions of the maximum total net-profit. A dynamic programming based algorithm is proposed to find all the possible optimal solutions and, in addition, three filters are conducted to improve the efficiency of the proposed algorithm. The experimental results show that the filters prune out unnecessary searches and improve the performance significantly, especially when the number of tasks increases. For some multimedia objects, they might need to be delivered in whole, indivisible, so we extend the proposed multimedia object-based model to indivisible objects. A dynamic programming based algorithm is presented to find an optimal solution of the delivery problem, where the total net-profit is maximized.

Abstract This research studied the dropouts who later attended the Cih-Huei class of Yong Ren Junior High School in Tainan County, by using methods such as document analysis, participant observation and deep interview. The goal was to assess the impact of the Cih-Huei class upon dropouts regarding their learning, daily living, family perspective and technical ability. It also examined the general courses, technical courses and living improvement activities provided by the Cih-Huei class in order to make suggestions that would improve the effectiveness of the Cih-Huei class. The growing track and family background of the dropouts were obtained through their personal information; their performance in the Cih-Huei class were assessed by the researchers who participated in the dropouts¡¦ living and teaching activities; and a semi-structured interview with the dropouts was employed to understand their true feeling about the Cih-Huei class. Finally, several suggestions were made on the course arrangement, living improvement activities and other related tasks for the Cih-Huei class. Hopefully these suggestions could serve as useful references for the future planning of general courses, technical courses, living management and improvement activities for the Cih-Huei class.

The communication system using Wavelength-division multiplexing (WDM) allows for better utilization of the spectral bandwidth. Photonic crystals (PhCs) exhibit photonic bandgap (PBG) due to the periodic variation of the dielectric constant and photons with a range of frequencies within the PBG cannot travel through the crystal. By introducing defects into PhCs, it is possible to control the light propagation along certain paths. In this thesis, the characteristics of coupled cavity waveguides (CCWs) and drop filter are discussed. Then we propose a multi-channel WDM system based on CCWs. It can be applied in FTTH to filter the wavelengths of 1310, 1490 and 1550 nm in different CCWs and also can make the bandwidth of output wavelength become narrow to filter more wavelengths. In addition, by modulating the size of the resonator on the PhCs, it can drop the particular wavelength into the waveguide. Finally, we proposed a multi-channel drop filter with FHWM 0.8 nm. This device design is leading the way to achieve CWDM specification with 100% drop efficiency, high quality factor and almost no crosstalk. The operations of such an ultra-compact demultiplexer and drop filter based on PhCs are suitable to be used in WDM optical communication systems.

The aim of this study is to answer to questions of how the null subject parameter properties in Turkish are reorganized by Turkish learners of English and whether there is a relationship between the null subject parameter properties in acquiring them. Firstly, a pilot study was conducted to detect the possible inadequacy in data collecting methods. Following the pilot study, a main study was conducted in order to answer the research questions.Thirty-four intermediate and thirty-four upper-intermediate students from METU English Preparation Department participated in the study. Along with these two proficiency groups, a control group of native speakers also contributed to the study whose answers were taken as criteria in evaluating students answers. Two types of tests were used: a 30item grammaticality judgment test and a 17item dialogue task. the test results were analyzed using a statistical program. In the end, it was found that students acquire the properties independently and as their proficiency levels increase, the acquisition of those properties also increases. However, it was also seen that students were not able to acquire these properties which was thought to be a result of parametric difference between Turkish and English. In order to overcome these acquisition problems, some teaching techniques were suggested in the conclusion part.

The main objective in this study is to compare breakage parameters of narrow size fractions of cement clinker taken from the product end and feed end of industrial-scale high pressure grinding rolls (HPGR) in order to assess whether the breakage parameters of clinker broken in HPGR are improved or not. For this purpose, drop weight tests were applied to six narrow size fractions above 3.35 mm, and batch grinding tests were applied to three narrow size fractions below 3.35 mm. It was found that the breakage probabilities of coarse sizes and breakage rates in fine sizes were higher in the HPGR product. This indicated that clinker broken by HPGR contained weaker particles due to cracks and damage imparted. However, no significant weakening was observed for the -19.0+12.7 mm HPGR product. Although HPGR product was found to be weaker than HPGR feed, fragment size distribution of HPGR product did not seem to be finer than that of the HPGR feed at a given loading condition in either the drop weight test or batch grinding test. Also, drop weight tests on HPGR product and HPGR feed showed that the breakage distribution functions of coarse sizes depended on particle size and impact energy (J). Batch grinding tests showed that the specific breakage rates of HPGR product and HPGR feed were non-linear which could be represented with a fast initial breakage rate and a subsequent slow breakage rate. The fast breakage rates of each size fraction of HPGR product were higher than HPGR feed due to cracks induced in clinker by HPGR. However, subsequent slow breakage rates of HPGR product were close to those of HPGR feed due to elimination of cracks and disappearance of weaker particles. Besides, the variation in breakage rates of HPGR product and HPGR feed with ball size and particle size also showed an abnormal breakage zone where ball sizes were insufficient to effectively fracture the coarse particles. Breakage distribution functions of fine sizes of HPGR product and HPGR feed were non-normalizable and depended on particle size to be ground. However, batch grinding of -2.36+1.7 mm and -1.7+1.18 mm HPGR feed yielded the same breakage pattern.

With increasing level of distributed generation¡]DG¡^on radial feeders in electric distribution systems, it could cause over-voltages as well as under-voltages depending on several factors including DG capacity, locations, and the strategy of voltage regulation. This thesis describes the typical and proposed voltage control strategies that could allow the increase of DG interconnection capacity. By using probabilistic load flow technique, voltage regulation performance for cases with different levels of DG outputs, demands and voltage control strategies are presented. They are compared by using a voltage profile improvement index and a risk assessment technique.