abstract: 本文采用2010年1月1日至2017年12月31日在香港主板IPO上市的共574家公司作为研究样本，系统采集包括与发行人、承销商、投资人、发行热度、市场每日交易数据等相关的数据近100项，对超额配售选择权在香港IPO中的实际效用进行实证研究，研究发现：1）超额配售选择的确可以起到提高发行价格，降低IPO抑价率的作用，但是同时也是破发的主要原因。2）由超额配售选择权赋予承销商稳价行为中，市场买入量越大，最大回撤越大，市场下跌风险越大同时超额配售选择权还导致了最大回撤日的推后，增大了稳价结束后的市场风险，而这很有可能是由于承销商追求更高利益造成的。3）没有证据显示，超额配售选择权会降低承销商的佣金比例，但是，超额配售选择权却为承销商带来非常高的额外收益，而这个收益与市场下跌幅度和承销商从市场购买股份的比例直接相关。 其中，本文首次对最大回撤率、最大回撤日与承销商市场买入量之间的关系进行实证研究，揭示了承销商市场买入量与承销商收益正相关，与最大回撤率负相关，与最大回撤日正相关的关系，可能是增加市场下跌风险的因素。这与现有理论中及监管机构的预期中，“超额配售选择权具有向上稳定价格的作用”是有一定偏差的。 根据研究结果，本文首先建议发行人要客观对待超额配售选择权提升发行价格的作用，以免引起破发。其次建议市场投资人要客观认识超额配售选择权的作用，不要由于超额配售选择权的存在给与发行过高的认同价格。再次建议发行人要能够认识到超额配售选择权是承销商零成本获得的一个有固定收益保障的看空期权，是承销商在承销IPO时的收益之一，而股价下跌幅度与承销商的收益正相关。因此要对承销商的稳价行为进行一定管控，同时可以因为超额配售选择权的存在而要求更低的承销佣金比例。最后建议承销商要维护市场公平，爱护自己的声誉，尽可能避免因超额配售选择权的使用对市场造成不应有的干扰。 / Dissertation/Thesis / Doctoral Dissertation Business Administration 2019

Today's distributed systems exist on a scale that was unimaginable only a few decades ago. Distributed systems now can consist of thousands or even millions of computers spread across the entire world. These large systems are often organized into overlay networks - networks composed of virtual links, with each virtual link realized by one or more physical links. Self-stabilizing overlay networks promise that, starting from any weakly-connected configuration, the correct network topology is always built. This area of research is young, and prior examples of self-stabilizing overlay networks have either been for simple topologies, or involved complex algorithms that were difficult to verify and extend. We address these limitations in this thesis. First, we present the Transitive Closure Framework, a generic framework to transform any locally-checkable overlay network into a self-stabilizing network. This simple framework has a running time which is at most a logarithmic number of rounds more than optimal, and in fact is optimal for a particular class of overlay networks. We also prove the only known non-trivial lower bound on the convergence time of any self-stabilizing overlay network. To allow fast and efficient repairs for local faults, we extend the Transitive Closure Framework to the Local Repair Framework. We demonstrate this framework by implementing an efficient algorithm for node joins in the Skip+ graph. Next, we present the Avatar network, which is a generic locally checkable overlay network capable of simulating many other overlay networks. We design a self-stabilizing algorithm for a binary search tree embedded onto the Avatar network, and prove this algorithm requires only a polylogarithmic number of rounds to converge and limits degree increases to within a polylogarithmic factor of optimal. This algorithm is the first to achieve such efficiency, and its modular design makes it easy to extend. Finally, we introduce a technique called network scaffolding, which builds other overlay network topologies using the Avatar network.

Ubiquitous computing has become a widespread phenomenon in today's modern world, with the computing technology integrating with our daily life in an invisible manner. Embedded systems and wireless sensor networks are popular choices to achieve this. Programming embedded and sensor network systems has always been a challenge for the programmers due to the lack of sufficient high-level programming support. To deal with this serious limitation, we have developed DESAL (Dynamic Embedded Sensing and Actuation Language) which is a user-friendly high-level programming language for wireless sensor networks with an integrated middleware, which hides the low-level detail from the programmers. In this thesis we present the design and development of DESAL. We have made DESAL programs rule based. Programs are written in guard-action format defined in terms of the program states. There are established formal correctness proving methods that can work on guard-action formats to mathematically check a program for errors. Also, there is no hidden control context like events or interrupts. Time synchronization has been developed as part of the middleware that lets DESAL programs to coordinate through synchronized actions throughout the network. This facilitates classic coordination algorithms like clock synchronization, spanning tree construction and consensus. Also, synchronized wake up saves energy. Neighborhood management, including node discovery and monitoring, is also provided by the middleware. DESAL programs communicate via state sharing. There is no network programming required. The middleware provides that automatically. Combining all these features DESAL provides major network management services, and yet presents the users with a simple high-level programming interface. We implemented the DESAL compiler to convert DESAL programs to NesC on TinyOS and to Java. Another novel feature we have introduced in DESAL is a variable of type 'token'. The concept of token is commonly used in mutual exclusion algorithms. One of the case studies we have done uses the token variable to achieve increased lifetime of sensors in a ring topology. The working of token is hidden from the user. The token mechanism developed achieves self-stabilization in the system. Another case study with tokens involves selective activation of RFID tags in a scenario where among the three RFID tags present only one can work at a time. Struct is a new data structure introduced in DESAL. Sometimes we need to group together two or more variables. It is important to receive them at the same time. Hence, it is important to send these grouped data over the radio together. Struct does that. Function is another newly added feature to DESAL. Function is added to group together repeated statements in a program. The unique feature of function is that, it uses only global variables. No new local variable is declared. This can significantly reduce the stack overhead of the program, thus saving memory and running time. Case studies have been done to illustrate the features of DESAL and to find scope for improvement.

Breathing Stabilization System is a new idea and method. The purpose of this system is to produce a device to control a patient's breathing for gated radiotherapy. This thesis focuses on building a simple Breathing Stabilization System that includes five solenoids, a power supply and five force sensors to build up the whole system. Significantly, this thesis will introduce the modeling of solenoids in detail that include how to build a mathematical model of the solenoids. The simulation of the electromagnetic in professional multi-physics software COMSOL will also be explained. To drive the solenoid system, a voltage-to-current converter is used. This part will be introduced as well as the operational amplifier circuit used by the force sensors.

Modern building procedures and requirements demand that the selection and stabilisation of soils for the purposes of rammed earth construction be better quantified. This study examines the relationships between soil properties, stabiliser treatments, and stabilised strength and density for 111 soil samples taken from sites in New South Wales (Australia), and develops new quantitative criteria for soil assessment, selection, and stabilisation. Laboratory measurements of soil particle size distribution, plasticity, and shrinkage were made for each soil. Various quantities from 0-6 % of lime, cement, and asphalt were added to the soil samples, and the resulting 230 specimens were compacted, and cured for 28 days. Determinations were made of the optimum moisture content, maximum dry density, and compressive strength of the stabilised material. The samples showed stabilised strengths ranging from 1.0-5.4 MPa, with a mean of 2.62 MPa, and densities from 1.44-2.21 t/m3, with a mean of 1.86 t/m3. The results show that over 90 % of the variation in stabilised strength and density of the samples is due to variation in soil properties, with differences in stabiliser type or stabiliser quantity being relatively minor. The most important soil properties explaining stabilised strength are linear shrinkage and plasticity index. These properties have been used to categorise the soils into three groups on the basis of their suitability for stabilisation as measured against a compressive strength criterion of 2 MPa. Favourable soils have shrinkages of &lt 7.1 % and plasticities of &lt 16 %, and 90 % of these samples passed the 2 MPa criterion. Satisfactory soils have shrinkages of 7.1-13.0 % and plasticities of 16-30 %, and 65 % of these samples had strengths in excess of 2 MPa. Unfavourable soils have shrinkages of &gt 13 % and plasticities of &gt 30 %, and only 10 % of these samples exceeded the 2 MPa value. Soils in the favourable and satisfactory categories can be further discriminated using textural information. On that basis, all soils classified as favourable, and those classified as satisfactory and which also have sand contents &lt 60 %, are recommended as being suitable for stabilisation. Soils not fulfilling these criteria are unlikely to be successfully stabilised and should be rejected. These results stress the importance of selecting a soil favourably predisposed to stabilisation. Field techniques to search for such soils could be refined on the basis of the new soil criteria presented. Use of the criteria should also minimise unnecessary laboratory testing of the density and strength of soils that subsequently prove unsuitable for stabilisation. A flow chart is presented to guide practitioners through the different stages of soil testing, assessment, and rammed earth stabilisation.

<p>A colloid of magnesium hydroxide is used to stabilize droplets of monomers before suspension polymerisation. The characteristics of precipitated magnesium hydroxide changes significantly during the first hours. The viscosity is high and flucctuating at first but decreases and becomes low and stable after a few hours. When the colloid ages the primary particles agglomerate into larger particles which increases in size by time due to, among other things, Oswald ripening and aggregation. This can cause problems with poor reproducibility in the production. Therefore, the purpose of this study was finding a way to age the colloid without an increase in particle size and without changing any other features. Several experiments were made to optimize the precipitation procedure and to find out what parameters that are most important. The results showed that the stirring rate and colloidal concentration have big influence.</p><p>Small amounts of chemicals that modifies the surface of the colloid was added. This made the particle size near constant over time and the colloid was aged for two months without increasing in size or changing other properties. This was confirmed by making microspheres that had the same characteristics as microspheres made with a fresh colloid.</p>

This thesis presents different control design approaches for stabilizing networks of quasi-linear hyperbolic partial differential equations. These equations are usually conservative which gives them interesting properties to design stabilizing control laws. Two main design approaches are developed: a methodology based on entropies and Lyapunov functions and a methodology based on the Riemann invariants. The stability theorems are illustrated using numerical simulations. Two practical applications of these methodologies are presented. Netword of navigation channels are modelled using Saint-Venant equations (also known as the Shallow Water Equations). The stabilization problem of such system has an industrial importance in order to satisfy the navigation constraints and to optimize the production of electricity in hydroelectric plants, usually located at each hydraulic gates. A second application deals with the regulation of water waves in moving tanks. This problem is also modelled by a modified version of the shallow water equations and appears in a number of industrial fields which deal with liquid moving parts.

We introduce a new method for computing a posteriori bounds on engineering outputs from finite element discretizations of the incompressible Stokes equations. The method results from recasting the output problem as a minimization statement without resorting to an error formulation. The minimization statement engenders a duality relationship which we solve approximately by Lagrangian relaxation. We demonstrate the method for a stabilized equal-order approximation of Stokes flow, a problem to which previous output bounding methods do not apply. The conceptual framework for the method is quite general and shows promise for application to stabilized nonlinear problems, such as Burger's equation and the incompressible Navier-Stokes equations, as well as potential for compressible flow problems. / Singapore-MIT Alliance (SMA)

There are many variants of leader election algorithm in distributed networks. In this research, an agent based approach to leader election in distributed networks is investigated. Agents have shown to be useful in several ways. In the theoretical perspective, agents sometime help in reducing the message complexity of the system and sometimes help in lowering time complexity. In a more practical sense, agents perform operations independent of the processors, thereby lending a more flexible algorithm supporting different types of networks.

Current municipal solid waste (MSW) practices have encouraged rapid waste degradation (stabilization) as an alternative to past methods of isolating the waste from the surrounding environment. There are challenges to rapid-stabilization technology, in particular, the management of the in-situ MSW moisture content.<p> The primary objective of this study was to evaluate the use of capacitance moisture probes for the purpose of measuring the moisture content within MSW. Capacitance moisture probes have not previously been used in MSW, however their use in agriculture is extensive and knowledge of their potential for monitoring MSW is limited.<p> The specific objectives of this research were to: i) establish a laboratory based correlation between sensor data and volumetric moisture content in MSW, ii) establish a correlation between field-installed capacitance sensors and moisture content derived from continuous-depth in-situ sampling of MSW, and iii) demonstrate the ability of capturing advancing/receding moisture fronts with the field-installed capacitance sensors.<p> Laboratory trials were conducted using hand-compacted MSW at volumetric moisture contents ranging from 15%-55% and a manual type of capacitance sensor. This series of laboratory trials successfully produced a correlation between sensor output and volumetric moisture content.<p> To evaluate the sensors in a real-world application, two configurations of capacitance moisture probes were installed in the field: i) an in-place, continuous-time capacitance probe, and ii) a portable, continuous-depth at discrete time, capacitance probe.<p> Field results indicated that capacitance moisture probes were able to capture the passing of both an artificially and naturally induced moisture front, though quantitative correlation between the in-situ moisture content of the sampled MSW and the readings of the sensors could not be achieved.<p> The reasons for this were a combination of three factors:<p> 1. The introduction of void-space during sensor installation significantly reduced sensor output;<p> 2. Poor MSW sampling technique resulted in 57% recovery (causing the exact origin of samples to be unknown); and<p> 3. The sampling technique disturbed the MSW samples, resulting in incorrect volumetric moisture contents in the samples.