In recent years, many investigators have predicted that with a semiactive suspension it is possible to attain performance gains comparable to those possible with a fully active suspension. In achieving this, the method by which the damper is controlled is one of the crucial factors that ultimately determines the success or failure of a particular semiactive suspension. This study is an investigation into the effectiveness of a number of basic control strategies at controlling vehicle dynamics, particularly vehicle roll. The test vehicle is a Sport Utility Vehicle (SUV), a class of vehicle that regularly sees widely varying vehicle weight (as a result of passengers and load) and can exhibit undesirable levels of vehicle roll. This study includes a suspension system comprised of four controllable magneto-rheological dampers, associated sensors, and controller. There are three distinct phases in this investigation, the first of which is a numerical investigation performed on a four-degree-of-freedom vehicle roll-plane model. The model is subjected to a variety of road and driver induced inputs, and the vehicle response is characterized, with each semiactive control policy. The second phase of this study consists of laboratory testing performed on a Ford Expedition, with the front axle of the vehicle placed on a two-post dynamic rig (tire coupled), and a variety of road inputs applied. The third phase of this testing involves road testing the test vehicle to further evaluate the effectiveness of each of the semiactive control policies at controlling both vehicle comfort (vibration) and stability (roll). In each phase, the semiactive control policies that are investigated are tuned and modified such that the best possible performance is attained. The performance of each of these optimal semiactive systems is then compared. In the first phase of this investigation, two basic skyhook control strategies are investigated and two modified strategies are proposed. Upon numerically investigating the effectiveness of the four control strategies, it is found that the performance achievable with each of the control strategies is heavily dependent on the properties of the controllable damper. The properties of the controllable damper that were particularly important were the upper and lower levels of force that the controllable damper was able to apply. Based on numerical results, the controllable dampers were tuned for each control system. The results indicate that a velocity-based skyhook control policy, in conjunction with force control, is most effective at controlling both road-induced vibration and driver-induced roll. In the second phase of this investigation, the effects of the two skyhook control strategies were again examined. Multiple system inputs including step inputs, chirp inputs, and multi-sine inputs were used, and the results indicate that significant performance gains using the basic skyhook policies are unlikely. The third phase involved road testing the vehicle through specific maneuvers modeling a wide variety of common driving situations. In addition to the two basic skyhook policies, two additional policies augmented with steering wheel position feedback were also examined. It was found that the velocity based skyhook control policy augmented with steering wheel position feedback achieved performance superior to both the stock passive dampers and other control policies tested here. / Ph. D.

Photocatalytic treatment has the potential to become a cost effective method of organic contaminant removal from water. Photocatalytic materials are semiconductors that enhance chemical reactions such as the breakdown of organic molecules in the presence of light. One of the most studied photocatalysts for water purification is titanium dioxide (TiO2). Variations in the composition of photocatalysts can affect the outcome of the experiments, the detection of the change in behaviour of the photocatalyst is of significant scientific interest. It requires minimisation of the impact of all other factors affecting the photocatalytic process, such as temperature, light intensity, wavelength and uniformity. Repeatability of the experiments is also affected by these factors. If their impact is not considered and addressed the outcome of multiple seemingly identical experiments with a single sample of the photocatalyst will produce different results. Light is one of the most important factors in a photocatalytic process. The undoped TiO2 has a sharp drop in its light absorbtion characteristics between UV and visible spectral regions. It is theregion of the spectrum where most efficient UV LEDs radiate. As the characteristics of the light produced by LEDs are temperature dependent, heat management is important in achieving light with stable characteristics and prolonged lifetime of the LEDs. One of the contributions of this thesis is a novel method of not only stabilisation of the LED radiation parameters, namely optical output power and wavelength, but also the independent control of these parameters. The importance of LED calibration is also a significant contribution as commercial LEDs have dierent radiation parameters between devices. Possibility of independent control of optical power and wavelength of the LEDs has allowed to demonstrate the importance of radiant flux (total spectral power) over the peak spectral flux (power of a single wavelength component) for TiO2 activation, which is another significant contribution of this work. Uniformity of the produced light is another factor that needs to be addressed when a light source for the photocatalytic experimentation is designed. Non-uniform light distribution in a photocatalytic reactor will result in bright spot formation that will affect the overall performance of the photocatalytic sample. This together with the temperature control of the photocatalyst and the water sample are key issues that need to be addressed for achieving ecient and repeatable experimentation outcomes. Photocatalytic reactors developed from simulation to the working prototypes and tested during the work described in this thesis address the problem of light distribution uniformity. They have been designed to remove as many sources of uncertainty usually present in photocatalytic reactors as possible, such as for example temperature stability of the liquid sample, dierent sizes or of the photocatalytic samples and same volume of the liquid sample. As such, these novel reactors together with LED light sources provide a contribution of having a potential of becoming a photocatalytic experimentation standard for achieving the repeatable and comparable results.

The aim of this thesis is to design a controllable DC-link output voltage for isolated slotless tubular linear generators (STLG), which is capable of directly harnessing wave and solar thermal energies. For supplying stable DC-link voltage to load, a suitable voltage regulation circuit is designed based on the integrate system performance assessment. Electrical and mechanical parameters in this refined STLG design are involved to analyze the operational behaviors through magnetic equivalent circuit analysis at different operating modes. From the theoretical modeling and experimental results, both the AC-side and DC-side properties of generator outputs can then be thoroughly investigated. Finally, based on the performance of controllable rectifier model, a three-phase PWM rectifier has been established, and then the regulated DC-link voltage can be implemented using a DSP-based controller combined with required peripheral circuits.

Research Doctorate - Doctor of Philosophy (PhD) / This dissertation presents some new approaches to addressing the main issues encountered by practitioners in the implementation of linear model predictive control(MPC), namely, stability, feasibility, complexity and the size of the region of attraction. When stability guaranteeing techniques are applied nominal feasibility is also guaranteed. The most common technique for guaranteeing stability is to apply a special weighting to the terminal state of the MPC formulation and to constrain the state to a terminal region where certain properties hold. However, the combination of terminal state constraints and the complexity of the MPC algorithm result in regions of attraction that are relatively small. Small regions of attraction are a major problem for practitioners. The main approaches used to address this issue are either via the reduction of complexity or the enlargement of the terminal region. Although the ultimate goal is to enlarge the region of attraction, none of these techniques explicitly consider the upper bound of this region. Ideally the goal is to achieve the largest possible region of attraction which for constrained systems is the null controllable set. For the case of systems with a single unstable pole or a single non-minimum phase zero their null controllable sets are defined by simple bounds which can be thought of as implicit constraints. We show in this thesis that adding implicit constraints to MPC can produce maximally controllable systems, that is, systems whose region of attraction is the null controllable set. For higher dimensional open-loop unstable systems with more than one real unstable mode, the null controllable sets belong to a class of polytopes called zonotopes. In this thesis, the properties of these highly structured polytopes are used to implement a new variant of MPC, which we term reduced parameterisation MPC (RP MPC). The proposed new strategy dynamically determines a set of contractive positively invariant sets that require only a small number of parameters for the optimisation problem posed by MPC. The worst case complexity of the RP MPC strategy is polylogarithmic with respect to the prediction horizon. This outperforms the most efficient on-line implementations of MPC which have a worst case complexity that is linear in the horizon. Hence, the reduced complexity allows the resulting closed-loop system to have a region of attraction approaching the null controllable set and thus the goal of maximal controllability.

abstract: 摘要 在复杂多变的商业环境中，企业传统的人力资源管理已经难以应对日益频发的员工职业倦怠、人际间矛盾冲突、频繁跳槽等局面与问题。企业员工工作的价值与意义早已不再是传统的雇佣模式下，通过出卖劳动力或智力从而获得工资以实现“养家糊口”的目的那么单纯与简单，员工也希望通过辛勤的工作，以获得个体的幸福感、荣誉感与认同感等。对于现代企业的管理者而言，员工追求事业的提升、个人价值的实现，不仅体现在薪酬、福利待遇的提升，更重要的是员工个人的成长以及潜能和竞争力的提升。 随着组织行为学和心理学的不断发展与演变，与员工幸福感相关的研究备受关注。对现代企业而言，管理者借助制度设计对员工幸福积极管理，可以最大限度地发挥员工的积极性、主动性与创造性，实现员工与企业之间的利益相趋同，从而更为高效地实现组织的目标。基于此，本文以民营企业员工工作幸福感作为研究的切入点，借助理论分析、问卷调查和实证分析相结合的研究方法，系统深入地研究我国民营企业员工工作幸福感的构成、可控前因和绩效后果等问题。 本文研究发现： 第一，员工薪酬的提高有助于员工工作幸福感的提升，薪资对基层员工幸福感的影响显著高于其对高层员工幸福感的影响； 第二，完善的晋升机制对于中层员工而言更能提升其幸福感，完善的晋升机制更有利于中层员工； 第三，公平性的提高有助于提高员工工作幸福感，而且这种正效应更多体现在基层员工群体之中； 第四，高层员工更注重自我价值的实现，高层员工的工作挑战性越高，其自我实现需求获得的满足感则约高，但是对于基层员工和中层员工而言，其效果则恰恰相反，基础员工和高层员工更多地将工作挑战性和压力看作是一种负面的因素； 第五，员工幸福感的确会给企业带来正向的绩效。 本文的研究框架和实证结论不仅可以丰富学术界有关员工工作幸福感的研究，而且为企业管理者进行绩效管理以及员工工作质量的提升提供理论和实证借鉴。 / Dissertation/Thesis / Doctoral Dissertation Business Administration 2019

This thesis investigates several different aspects of the physics of few state quantum systems and their use in information processing applications. The main focus is performing high precision computations or experiments using imperfect quantum systems. Specifically looking at methods to calibrate a quantum system once it has been manufactured or performing useful tasks, using a quantum system with only limited spatial or temporal coherence. / A novel method for characterising an unknown two-state Hamiltonian is presented which is based on the measurement of coherent oscillations. The method is subsequently extended to include the effects of decoherence and enable the estimation of uncertainties. Using the uncertainty estimates, the achievable precision for a given number of measurements is computed. This method is tested experimentally using the nitrogen-vacancy defect in diamond as an example of a two-state quantum system of interest for quantum information processing. The method of characterisation is extended to higher dimensional systems and this is illustrated using the Heisenberg interaction between spins as an example. / The use of buried donors in silicon is investigated as an architecture for realising quantum-dot cellular automata as an example of quantum systems used for classical information processing. The interaction strengths and time scales are calculated and both coherent and incoherent evolution are assessed as possible switching mechanisms. The effects of decoherence on the operation of a single cell and the scaling behaviour of a line of cells is investigated. / The use of type-II quantum computers for simulating classical systems is studied as an application of small scale quantum computing. An algorithm is developed for simulating the classical Ising model using Metropolis Monte-Carlo where random number generation is incorporated using quantum superposition. This suggests that several new algorithms could be developed for a type-II quantum computer based on probabilistic cellular automata.

Smart skins are integrating an increasing number of functionalities in order to improve the interaction between the systems they equip and their ambient environment. Here we have developed an electromechanical soft actuator with controlled surface texture due to applied thermal gradient via electrical voltage. The device was fabricated and integrated with optimized process parameters for a prepared heater element [doped PEDOT: PSS (poly-(3, 4 ethylenedioxythiophene): poly (styrene sulfonic acid))], a soft actuator (Ecoflex 00-50/ethanol) and overall packaging case [PDMS (polydimethylsiloxane)]. To study a potential application of the proposed smart skin, we analyze the fluid drag reduction in a texture controlled water flow unit. As a result, we obtained a reduction of approximately 14% in the skin drag friction coefficient during the actuation. We conclude that the proposed soft actuator device is a preferred option for a texture-controlled skin that reduces the skin drag friction coefficient.

Thesis (MTech (Business Administration))--Cape Peninsula University of Technology, 2019 / The outsourcing of facility management services has become increasingly competitive and success now depends on companies’ ability to assess and manage risks of low employee morale, intellectual property right, legal, increased costs, unrealistic savings projections and reputational damage successfully. This paper examined outsourcing risks at selected facility management companies in Cape Town. Previous study identifies loss of control, cost and life cycle impact and time inefficiency as anecdotal evidence of outsourcing risks. In the facility management sector, the identification and management of risks have begun to shift progressively from external to internal – like resource and capability management and the strengthening of internal control mechanism. This quantitative study utilised self-administered questionnaire to collect data from 142 randomly selected respondents; employees of participating facility management companies in Cape Town. The paper found that top 6 risks ranked from the highest are information security, legal, ethics/compliance, contractual, financial and economic. The higher end of the mean scoring indicates a greater emphasis on controllable (internal) risks, with 4 out of the top 6 ranked items identified within the internal risks’ category. This research provides insight to understand outsourcing, risks of outsourcing and risk assessment techniques with emphasis on internal risk management. The examination of outsourcing risks enables companies to understand risk assessment, evaluation and mitigation requirements and categorisation for successful management of risks associated with the outsourcing of facility management services.

Electrically controllable solid propellants are an area of interest as a viable solution to the lack of throttle-ability in solid propellant rocket motors. Existing studies have focused on propellants compositions using hydroxyl-ammonium nitrate, ammonium nitrate, or lithium perchlorate as oxidizers. Additionally, the thermochemical and electrochemical reaction mechanisms have not yet been fully defined. The research in this thesis explores the nitrate and perchlorate oxidizer families to compare their cation-anion relationships. Using these oxidizers, pseudo electrically controllable solid propellant compositions were created with the addition of multi-wall carbon nanotubes to enhance ohmic heating capabilities. These additives were selected based on theory that with a non-complexing polymer, an oxidizer melt layer is required for ions to dissociate and electrically controlled ignition to occur. Using an applied voltage, ignition delay and current draw experiments were performed to expand on prior findings that ignition delay follows oxidizer melt temperature while mobility is associated with the size of the ionic radii. Additionally, neat oxidizer pellets were electrically decomposed to determine their linear regression rate. These results help to characterize the mechanism of reaction. This advances the knowledge of oxidizers in electrically controllable applications. / Master of Science / Solid propellant rocket motors have been extensively studied and used in both space and military applications because they do not use air as the source of oxygen. Their main limitation is the lack of throttle-ability, or inability to control propellant burning. This is because solid propellants, which are generally composed of an ionic oxidizer salt, a polymer fuel, and additives, are pre-combined and stored within the rocket motor. An emerging viable solution to this limitation is electrically controllable solid propellants. With an applied voltage, the oxidizer is heated and melts, allowing ions to dissociate and current to flow between electrodes. This reaction can then be controlled by turning the power supply on and off. Cations, or ions which have a net positive charge, move to the negatively charged cathode while anions, which have a net negative charge, move to the negatively charged anode. The research in this thesis explores different cation-anion oxidizer pairings using both a propellant composition and as a pure oxidizer under an applied voltage. The results help to characterize the mechanism of reaction of each oxidizer in an electrically controllable context and determine their effectiveness in these propellant applications.

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