Multidisciplinary Optimization Approach for Design and Operation of Constrained and Complex-shaped Space Systems.

The design of a small satellite is challenging since they are constrained by mass, volume, and power. To mitigate these constraint effects, designers adopt deployable configurations on the spacecraft that result in an interesting and difficult optimization problem. The resulting optimization problem is challenging due to the computational complexity caused by the large number of design variables and the model complexity created by the deployables. Adding to these complexities, there is a lack of integration of the design optimization systems into operational optimization, and the utility maximization of spacecraft in orbit. The developed methodology enables satellite Multidisciplinary Design Optimization (MDO) that is extendable to on-orbit operation. Optimization of on-orbit operations is possible with MDO since the model predictive controller developed in this dissertation guarantees the achievement of the on-ground design behavior in orbit. To enable the design optimization of highly constrained and complex-shaped space systems, the spherical coordinate analysis technique, called the ``Attitude Sphere'', is extended and merged with an additional engineering tools like OpenGL. OpenGL's graphic acceleration facilitates the accurate estimation of the shadow-degraded photovoltaic cell area. This technique is applied to the design optimization of the satellite Electric Power System (EPS) and the design result shows that the amount of photovoltaic power generation can be increased more than 9%. Based on this initial methodology, the goal of this effort is extended from Single Discipline Optimization to Multidisciplinary Optimization, which includes the design and also operation of the EPS, Attitude Determination and Control System (ADCS), and communication system. The geometry optimization satisfies the conditions of the ground development phase; however, the operation optimization may not be as successful as expected in orbit due to disturbances. To address this issue, for the ADCS operations, controllers based on Model Predictive Control that are effective for constraint handling were developed and implemented. All the suggested design and operation methodologies are applied to a mission “CADRE”, which is space weather mission scheduled for operation in 2016. This application demonstrates the usefulness and capability of the methodology to enhance CADRE's capabilities, and its ability to be applied to a variety of missions.PhDAerospace EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120694/1/daylee_1.pd

Screening Effects on Nonrelativistic Bremsstrahlung in the Scattering of Electrons by Neutral Atoms

Atomic screening effects on nonrelativistic electron-atom bremsstrahlung radiation are investigated using a simple analytic solution of the Thomas-Fermi model for many-electron atoms. The Born approximation is assumed for the initial and final states of the projectile electron. The results show that the screening effect is important in the soft radiation region and is decreasing with increasing radiation. These results help provide correct information about the behavior of bound electrons in the target atom in bremsstrahlung processes

Wireless Testing of Integrated Circuits.

Integrated circuits (ICs) are usually tested during manufacture by means of automatic testing equipment (ATE) employing probe cards and needles that make repeated physical contact with the ICs under test. Such direct-contact probing is very costly and imposes limitations on the use of ATE. For example, the probe needles must be frequently cleaned or replaced, and some emerging technologies such as three-dimensional ICs cannot be probed at all. As an alternative to conventional probe-card testing, wireless testing has been proposed. It mitigates many of the foregoing problems by replacing probe needles and contact points with wireless communication circuits. However, wireless testing also raises new problems which are poorly understood such as: What is the most suitable wireless communication technique to employ, and how well does it work in practice? This dissertation addresses the design and implementation of circuits to support wireless testing of ICs. Various wireless testing methods are investigated and evaluated with respect to their practicality. The research focuses on near-field capacitive communication because of its efficiency over the very short ranges needed during IC manufacture. A new capacitive channel model including chip separation, cross-talk, and misalignment effects is proposed and validated using electro-magnetic simulation studies to provide the intuitions for efficient antenna and circuit design. We propose a compact clock and data recovery architecture to avoid a dedicated clock channel. An analytical model which predicts the DC-level fluctuation due to the capacitive channel is presented. Based on this model, feed-forward clock selection is designed to enhance performance. A method to select proper channel termination is discussed to maximize the channel efficiency for return-to-zero signaling. Two prototype ICs incorporating wireless testing systems were fabricated and tested with the proposed methods of testing digital circuits. Both successfully demonstrated gigahertz communication speeds with a bit-error rate less than 10^−11. A third prototype IC containing analog voltage measurement circuits was implemented to determine the feasibility of wirelessly testing analog circuits. The fabricated prototype achieved satisfactory voltage measurement with 1 mV resolution. Our work demonstrates the validity of the proposed models and the feasibility of near-field capacitive communication for wireless testing of ICs.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/93993/1/duelee_1.pd

Great Expectations: The Past, Present & Future of Product Liability Laws in Korea

The Product Liability Act (hereinafter, the "PL" Act) was entered into force in Korea on July 1, 2002. The purpose of the PL Act is to protect consumers against damages caused by defective products, and to contribute to the safety of citizens and the sound development of the national economy by regulating the liability of manufacturers for damages caused by the defective products. This paper reviews past relevant tort case decisions in order to predict the future development of product liability theory by the Korean courts. In reviewing decisions made before the enactment of the PL Act, it was found that the courts had applied the negligence principle instead of the concept of defects, which means the plaintiff had the 'burden of proof,' the obligation to prove the manufacturer's negligence. Another tendency held by the court was to deny liability for damages if no causation existed. As the cases show, negligence is difficult to prove, as most laypeople do not have the necessary expertise regarding the intricacies of the products, making it disadvantageous for the plaintiff. The courts, even before the enactment of the PL Act, recognized the need to improve laws related to torts by setting case precedents that gave remedy to the victims. Analysis of these milestone cases can be divided into three categories. First, the plaintiff would no longer bear the burden of proof while the defendant would be required to rebut presumed negligence, thereby strengthening consumer protection. Second, information representation could now be a cause for negligence, thus broadening the basis for the plaintiff's claim of negligence. Third, through reasoning by torts, the concept of defect was introduced by the Korean Supreme Court. The PL Act grants the following benefits to society. First, consumers are given the right to claim against manufacturers for losses caused by defective products. Second, comparing the economic efficiency of negligence rule with strict liability rule, the PL Act has proven to be more efficient because the manufacturer is imposed with a higher standard of due care, giving the manufacturer a voluntary incentive to reduce risks. Third, the legal scheme of product liability is to shift the risk or harm incurred to the unfortunate consumer to the manufacturer. The precedents set by the legal structure of other countries should also be considered, in which death and personal injury are covered by product liability while damages to property or economic loss are covered under warranties. Therefore, we should take into account the fact that the product liability cannot be expanded to include property losses when basing suits on product liability laws