Topology Control in Heterogeneous Wireless Networks: Problems and Solutions

Previous work on topology control usually assumes homogeneous wireless nodes with uniform transmission ranges. In this paper, we propose two localized topology control algorithms for heterogeneous wireless multi-hop networks with nonuniform transmission ranges: Directed Relative Neighborhood Graph (DRNG) and Directed Local Spanning Subgraph (DLSS). In both algorithms, each node selects a set of neighbors based on the locally collected information. We prove that (1) the topologies derived under DRNG and DLSS preserve the network connectivity; (2) the out degree of any node in the resulting topology by DLSS is bounded, while the out degree cannot be bounded in DRNG; and (3) the topologies generated by DRNG and DLSS preserve the network bi-directionality

Empowering women : the effect of women's decision-making power on reproductive health services uptake -- evidence from Pakistan

A large body of research has attempted to explore the links between women's autonomy and their uptake of reproductive health services in the South Asia region, but the evidence so far is inconclusive. This study uses the Pakistan Social and Living Standards Measurement Survey to examine the influence of household decision making on women's uptake of reproductive health services. The analysis finds that women's decision-making power has a significant positive correlation with reproductive health services uptake and that influential males'decision-making power has the opposite effect, after controlling for socio-economic indicators and supply-side conditions. The findings suggest that empowering women and increasing their ability to make decisions may increase their uptake of reproductive health services. They also suggest that policies directed toward improving women's utilization of maternity services must target men as well as women in Pakistan.Health Monitoring&Evaluation,Population Policies,Adolescent Health,Gender and Health,Health Systems Development&Reform

Eutectic growth and microstructure selection in electronic solder alloys

This thesis develops the understanding of eutectic growth and microstructure selection in electronic solder alloys, including the Sn-Ni, Sn-Cu and Sn-Ag binary systems, and alloys from the ternary Sn-Ag-Cu system. These systems are relevant to Pb-free soldering and the development of optimised Pb-free solder compositions. Past research has reported the presence of both stable Sn-Ni3Sn4 eutectic and metastable Sn-NiSn4 eutectic in Sn-Ni alloys and Sn-3.5wt%Ag/Ni solder joints. The present work follows up on these initial findings with a detailed investigation into competitive growth between these stable and metastable eutectics. As no information was available for the metastable Sn-NiSn4 eutectic phase diagram, the eutectic points of the two eutectics and the Ni3Sn4 liquidus line were measured in this thesis. Controlled Bridgman solidification experiments were then used to explore eutectic growth mechanisms of the stable and metastable eutectics and investigate the origins of metastable eutectic formation in this system. The dynamics of eutectic growth and the transition between the two eutectics were investigated by synchrotron radiography, and the crystallography of eutectic growth was measured by EBSD. The competition between Sn dendrite growth and metastable Sn-NiSn4 eutectic growth was then measured and compiled into a microstructure selection map in the range of C0 = 0.05 wt%Ni – 0.26 wt%Ni and V = 0.5 µm/s – 1000 µm/s. Sn-Cu, Sn-Ag and Sn-Ag-Cu (SAC) alloys are commonly used as soldering materials and past researchers have focussed on microstructure selection maps in these systems. However, there has been limited research on the eutectic crystallography and growth mechanisms. In the present work, laboratory and synchrotron Bridgman solidification is used to observe the eutectic growth front and its response to changes in pulling rate, and to analyse the eutectic crystallography and growth mechanisms in Sn-Ag, Sn-Cu and Sn-Ag-Cu alloys. First, the binary Sn-Ag3Sn and Sn-Cu6Sn5 eutectics are investigated. The growth of the ternary Sn-Ag3Sn-Cu6Sn5 eutectic is then compared with the two binary eutectics. Next, research explores the more complex case of Sn-1Ag-0.9Cu (wt%) which lies on the Sn-Cu6Sn5 univariant eutectic groove where there is competition between Sn dendrite growth, univariant SnCu6Sn5 growth, and invariant ternary Sn-Ag3Sn-Cu6Sn5 growth. Orientation relationships between Sn and the intermetallic compounds (IMCs) and the IMC growth directions are determined in all systems. The experimental observations of the growth microstructure as a function of velocity and composition in the Sn-Ni, Sn-Ag and Sn-Cu systems were combined with literature data to construct experimental eutectic coupled zones for the three binary systems and for the Sn-Pb system. The transition between fully eutectic growth and Sn dendrite growth ahead of a eutectic front was considered using the criterion that the microstructure whose tips can grow at highest temperature is selected (i.e. wins). Since eutectic growth often did not occur at the extremum for these nonfaceted-faceted eutectics, the eutectic growth temperature versus growth velocity was measured for the Sn-NiSn4 and Sn-Ag3Sn eutectics in this thesis, and literature data for this relationship in the Sn-Pb system was used. To calculate the fully eutectic / Sn dendrite transition, a combination of the measured eutectic growth temperature response function (TE* vs. V) and Lipton, Glicksman and Kurz (LGK) calculated dendrite tip growth temperature response function (Td* vs. V) were used to calculate eutectic coupled zones. With this approach, reasonable agreement between the calculated and measured coupled zones was obtained.Open Acces

Long-term Stabilization of Fiber Laser Using Phase-locking Technique with Ultra-low Phase Noise and Phase Drift

We review the conventional phase-locking technique in the long-term stabilization of the mode-locked fiber laser and investigate the phase noise limitation of the conventional technique. To break the limitation, we propose an improved phase-locking technique with an optic-microwave phase detector in achieving the ultra-low phase noise and phase drift. The mechanism and the theoretical model of the novel phase-locking technique are also discussed. The long-term stabilization experiments demonstrate that the improved technique can achieve the long-term stabilization for the MLFL with ultra-low phase noise and phase drift. The excellent locking performance of the improved phase-locking technique implies that this technique can be used to stabilize the mode-locked fiber laser with the highly stable H-master or optical clock without stability loss

Agent-Based Overlapping Generations Modeling for Educational Policy Analysis

Educational systems are complex adaptive systems (CAS). The macroeffects of an educational policy emerge from and depend on individual students\u27 reactions to the policy. However, educational policymakers traditionally rely on equation-based models, which are deficient in reflecting the work of microbehaviors. Using inappropriate tools to make policies may be a reason why there were many unintended educational consequences in history. A proper methodology to design and analyze policies for complex educational systems is agent-based modeling (ABM). Grounded in the theories of CAS and computational irreducibility, ABM is capable of connecting microbehaviors with macropatterns. The purpose of this study was to contribute to the application of ABM in educational policy analysis by constructing an agent-based overlapping generations model with hypothesized inputs to qualitatively represent the environment of the Taipei School District. Four research questions explored the effects of Taipei\u27s 2016 student-assignment mechanism and its free tuition policy on educational opportunity and school quality under different assumptions of students\u27 school-choice strategies. The simulated outputs were analyzed using descriptive statistics and paired samples t tests. The findings, which could hardly be revealed by traditional models, showed that the effects were complex and depended on students\u27 strategies along with the number of choices students were allowed to make; the assignment outcomes for elite students were robust to the mechanism, and the free tuition policy worsened school quality. Although exploratory, these findings can serve as hypotheses and a guide for Taipei\u27s policymakers to collect empirical data in evaluating their 2016 mechanism and tuition policy