This paper is predicated on determining the effectiveness of angles-only initial orbit determination (IOD) methods when limited observational data is available for low-Earth orbit (LEO) rocket body debris. The analysis will be conducted with data obtained from Lockheed Martin Space’s Space Object Tracking (SpOT) facility, focusing on their observational data from 2018 that contains tracking of rocket body debris for less than one minute per overhead pass. After the IOD accuracies are better understood, a feasibility study will follow that investigates the possibility of cataloguing LEO orbital debris from a single optical observation facility with similar observational capabilities as that of the SpOT facility. The IOD accuracy analysis will investigate nine different rocket bodies, with a total of 50 orbital passes of data included in the research. Three main IOD approaches will be tested for each data set to determine the best method in achieving high levels of IOD accuracy: a traditional three-point method, an iterative method, and an assumed-circular orbit method. Application of the iterative approach results in increased accuracy for the resultant initial orbit determination as compared to the three-point IOD method, and an assumed-circular orbit assumption allows for a further increase in accuracy, especially for observed objects in near-circular orbits. The feasibility of cataloguing debris from a singular optical facility shows promise, as subsequent target acquisition after an object’s initial observation is determined to be achievable under the correct circumstances. By choosing a correct telescope pointing angle based on the IOD results from one pass of data, an observed rocket body debris object would pass through the field of view of SpOT’s spotter scope (0.7-degrees) during its next overhead pass for two different test cases. An increase field of view would increase both the likelihood of acquiring the target object and the amount of time the object is visible by the telescope.

The purpose of this investigation was to integrate the knowledge and techniques of marine geotechnical engineering, underwater acoustic and optical observation into studying the engineering problems of artificial reefs off south-western coast of Taiwan (Fang-Liau ,Lin-Yang, Yung-An artificial reefs etc.) and the destruction of mooring system on farming cages caused by the interaction of wave-current system. The ultimate goal of this investigation was to understand the scouring activities of loosely and closely spaced artificial reefs; as well as, to evaluate the feasibility of using artificial reefs as deadweight anchoring devices for farming cages at Fang-Liau reef site. The results of this research were as follows: Fang-Liau artificial reef site: The maximum scouring depth can reach as deep as 2.2m around closely distributed reefs at this site. Only a few loosely deployed reefs were buried there, and the scouring depressions around these buried reefs had been filled up completely. To sum up, the behavior of scouring produced by the action of wave, current and typhoon around this site, merely limited to loosely distributed reefs, and the rim of closely distributed reefs. With the scouring time increasing, there were no obvious evidences for the burial of artificial reefs at this site. Lin-Yang artificial reef site: The scouring depressions around part of loosely deployed reefs expand as typhoons attacking at this site. The horizontal range of the scouring depressions can reach 92.3m in length, and parts of the reefs were buried during the process of scouring. Besides, as time went on, part of closely distributed reefs illustrated periodic variations of being buried by sediments with ripple marks, then shown up with evident height, and then buried again. To sum up, the behavior of scouring produced by the action of wave, current and typhoon around this site could cause the complete burial of the reefs. The possible procedures for the burial of reefs in the scouring depression were the actions of backfill of sandy sediments at this site. Yung-An artificial reef site: During summer time, especially with typhoons passed by, surficial sediments at this site were evident with mega ripple marks. The effects of scouring at this site were prominent than those at Fang-Liau reef site. The textures of surficial sediments were the major factor which induced this difference. Based on the considerations of safety of sliding, bearing capacity and overturning, the usage of artificial reefs as anchoring devices for farming cages could not satisfy the basic engineering requirements under the action of extreme wave and current. This research suggested the usage of cubical concrete block with shear keys for anchoring devices on farming cages. The minimum buoyant weight of this block should reach 28.8 to 38.7ton. The problem regarding construction and deployment techniques of this block need further considerations.

Polymer powder bed fusion (PBF/P) is one of many additive manufacturing (AM) processes utilized for producing polymer parts from digital 3D models. AM is preferred over traditional manufacturing methods in many applications due to advantages including tool-less manufacturing, high geometric complexity, short lead times, and reduced material waste. However, many industries that stand to benefit the most from AM are limited in their ability to use AM parts in large part due to low confidence in AM part quality. Among the polymer AM processes, PBF/P processes show significant promise for these applications due to their comparatively high isotropy and mechanical properties. Due to the many process variables present in PBF/P, printing conditions can vary from print to print resulting in poor repeatability of physical properties in printed parts. Many approaches have been studied for addressing this issue such as modeling of print dynamics, print parameter optimization, and process control. However, PBF/P remains largely unutilized in applications where quality control and assurance are high priorities. This work presents a novel approach for in-situ process monitoring and control in PBF/P and is demonstrated for the large area projection sintering (LAPS) process. The method proposed in this study monitors the powder bed surface via visible light cameras and identifies critical steps in the melting process defined as optical melting states (OMSs). The relationship between print parameters, process signatures, and resulting physical properties are studied. This thesis shows that during melting, the changing surface geometry and optical properties of the powder bed can be effectively monitored with optical cameras and are strongly correlated with the final density and ultimate tensile strength (UTS) of the printed part. By implementing closed-loop OMS control, consistent physical properties can be obtained despite different processing conditions. While established methods of identifying the property plateau for other PBF/P processes are not effective for the LAPS process, such as energy density methods, OMS control has been shown to effectively achieve full density and UTS in LAPS parts while optimizing print time. However, OMS methods are limited in their ability to evaluate ductility and percent crystallinity.

Presented diploma thesis deals with experimental study of fluid induced instabilities which occur in rotating machinery with journal bearings. The first part describes the oil whirl and oil whip instabilities. It also gives an example of optical methods used for observation of journal bearings. Next part is dedicated to modifications of an existing test rig that were necessary for carrying out experiments. Finally, there are presented results of experiments that define the effect of initial conditions on appearance of instabilities.