A framework for hull form reverse engineering and geometry integration into numerical simulations

The thesis presents a ship hull form specific reverse engineering and CAD integration framework. The reverse engineering part proposes three alternative suitable reconstruction approaches namely curves network, direct surface fitting, and triangulated surface reconstruction. The CAD integration part includes surface healing, region identification, and domain preparation strategies which used to adapt the CAD model to downstream application requirements. In general, the developed framework bridges a point cloud and a CAD model obtained from IGES and STL file into downstream applications

Rational design to control multipotent stromal cell migration for applications in bone tissue engineering and injury repair

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biological Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 151-162).Multipotent stromal cells derived from bone marrow hold great potential for tissue engineering applications because of their ability to home to injury sites and to differentiate along mesodermal lineages to become osteocytes, chondrocytes, and adipocytes to aid in tissue repair and regeneration. One key challenge, however, is the scarcity of MSC numbers isolated from in vivo, suggesting a role for biomimetic scaffolds in the cells' ex vivo expansion before reintegration into target tissue. Toward this end, immobilized epidermal growth factor (tEGF) has recently been found to promote MSC survival and proliferation and is a prime candidate to be incorporated into scaffolds to control MSC behavior. To rationally and effectively design scaffolds to drive MSC responses of survival, proliferation, migration, and differentiation, we must first understand these responses and the underlying protein signaling pathways that mediate them. While our knowledge of MSC behavior is limited as a field, MSC migration is particularly less studied despite being critical for tissue and scaffold infiltration. In this thesis, we quantitatively investigate the effects of tEGF and extracellular matrix (ECM) on MSC migration response and signaling. We take a systems level computational view to show a combined biomaterials and small molecule approach to control MSC migration. Cell migration is a delicately integrated biophysical process involving polarization and protrusions at the cell front, adhesion and translocation of the cell body through contractile forces, followed by disassembly of adhesion complexes at the cell rear to allow detachment and productive motility. This process is mediated by a multitude of crosstalking signaling pathways downstream of integrin and growth factor activation. Using a poly(methyl methacrylate)-grafted-poly(ethylene oxide) (PMMA-g-PEO) copolymer base, we modify the PEO sidechains with immobilized epidermal growth factor (tEGF) as a model system for biomimetic scaffolds. We systematically adsorb fibronectin, vitronectin, and collagen ECM proteins to alter surface adhesiveness and measure MSC migration responses of speed and directional persistence alongside intracellular activities of EGFR, ERK, Akt, and FAK phosphoproteins. While tEGF and ECM proteins differentially affected signaling and migration, univariate correlations between signals and responses were not informative, prompting the need for multivariate modeling to identify key patterns. Using decision tree "signal-response" modeling, we predicted that inhibiting ERK on collagen-adsorbed tEGF polymer surfaces would increase cell mean free path (MFP) by increasing directional persistence. We confirmed this experimentally, successfully demonstrating a two-layer approach-"coarse" biomaterials followed by small molecules "fine-tuning"-to precisely and differentially control MSC migration speed and persistence, setting the stage for combination therapies for bone tissue engineering.by Shan Wu.Ph.D

박막형 태양전지 수치해석을 위한 효율적 알고리즘에 관한 연구

학위논문 (박사)-- 서울대학교 대학원 : 협동과정 계산과학 전공, 2013. 8. 신동우.본 논문에서는 무작위의 복잡한 3차원 표면 형상을 가진 물체를 평균적으로 O(logN) 시간 복잡도를 가지고 교차검사를 수행할 수 있는 새로운 알고리즘을 기반으로 박막형 태양전지 (Thin Film Solar Cell)의 흡수 효율을 효과적으로 시뮬레이션 하기 위한 방법을 논하였다. 3차원 피라미드 형상을 박막형 태양전지 표면에 양각한 경우, 3차원 표면 형상의 크기와 밀도가 흡수 효율에 영향을 미치게 되므로 이들에 대한 최적 설계 값들을 찾고자 시뮬레이션 방법을 이용한다. 본 연구에서는 무수히 많은 3차원 표면 형상들에 대한 최적의 교차검사 알고리즘을 kd-tree 가속화 구조를 변형하여 개발하였고, 이를 광선 추적 법 (Ray tracing)에 적용하여 평균 교차검사 시간을 O((log N)으로 하는 새로운 광선 추적에 의한 시뮬레이션 방법을 고안하였다. 이 방법은 기존 연구들에서 한번도 연구되지 않은 새로운 방법으로, 표면 형상들을 실제 객체로 인지하여 교차검사를 수행하면서도 종래의 O(N)~O(N2) 교차검사 시간을 O(log N)으로 단축시키는 결과를 얻었다. 또한 이전 연구들에서 반사율 시뮬레이션에 의존하여 간접적으로 계산하던 에너지 흡수 효율을 직접적으로 시뮬레이션 함은 물론이고 각 층별 에너지 흡수율을 간섭현상을 반영하여 직접적으로 시뮬레이션 할 수 있는 방법을 고안하였다. 이 알고리즘의 효율성 및 정확성은 다른 알고리즘과의 수행 시간 비교 및 실측 자료와 시뮬레이션 결과와의 오차 분석을 통해 검증 하였다. 박막형 태양전지의 크기가 나노미터 단위로 작아진 경우, 유한차분 시간영역 (FDTD)법을 이용하게 되는데, 현재까지 연구된 방법들로는 적은 전산 자원을 사용하여 빠른 시간 내에 정확한 흡수 에너지를 계산하는데 한계가 있었다. 본 연구에서는 이 문제를 해결하기 위하여 자유로운 형태의 시스템에 대해서 각 물질들의 연속된 경계 면을 효율적으로 추출하여 Poynting 이론의 발산 (Divergence) 부분의 식을 적용하는 방법으로 적은 전산 자원으로 빠른 시간 내에 상당한 정확도를 가지고 흡수 에너지를 계산할 수 있는 방법을 고안하였다. 이 방법의 정확성은 해석 가능한 모델의 Mie 확산 모델의 계산 결과와 시뮬레이션 결과를 비교함으로써 검증하였으며, 곡면 모델에 대해서는 곡률 반경을 변화시켜가며 시뮬레이션 한 결과가 물리적 유의성을 나타냄을 보임으로써 검증 하였다.In this thesis, I proposed a novel intersection algorithm based absorption en-ergy simulation methods for thin film solar cells which use a 3-D randomly textured geometry or plasma effects. For the case of pyramidal textured thin film solar cells, Optimizing the de-sign of the surface texture is an essential aspect of the thin film Si solar cells technology as it can maximize the light trapping efficiency of the cells. Thus, the appropriate simulation tools can provide efficient means of designing and analyzing the effects of the texture patterns on light confinement in an active medium. A ray tracing method is a powerful numerical simulation methodol-ogy for this. However, in past researches, a real object intersection method take an O(N2) time complexity and some height map method take an O(N) time complexity. These are time consuming process and inaccurate process, so I developed a novel intersection algorithm with an O(logN) time com-plexity and with keeping the accuracy. Also, an absorption energy calculation algorithm for each layer with a direct method did not exist in the past. To solve the intersection finding problem, I proposed a novel and an efficient 3-D texture intersection algorithm using a modified kd-tree traversal method in Chapter 2. Also, to solve the absorption efficiency calculation problem with ray tracing method, I proposed a new method in Chapter 3. The correctness and efficiency of the algorithms was validated by a measured data and numer-ical simulations. The thickness of the thin film solar cells reach to the nanometer size. The ray tracing method is useless for the nanometer size systems except for a flat surface type. In this case, the FDTD method can be used to solve this nanome-ter scale problems. However, by the past researches, an auto-discretization problem and an absorption efficiency calculation problem were not solved efficiently. In this research, I proposed a robust and an efficient auto-discretization algorithm and an efficient absorption energy calculation algo-rithm with a continuous boundary extraction algorithm in Chapter 4. The correctness and efficiency of the algorithms was validated by an exact solu-tion and numerical simulations. Through this thesis, I proposed an efficient absorption efficiency calcula-tion algorithms for all system ranges of the thin film solar cells.Abstract Publications Table of Contents List of Figures List of Tables List of Algorithms Symbols Abbreviations 1. Introduction 1.1 Motivation 1.2 Thin Film Solar cells 1.2.1 Reduction of Front Surface Reflectance 1.2.2 Enhancement of Back Surface Reflectance 1.2.3 Efficient Light Trapping 1.3 Ray Tracing 1.3.1 Finding Intersection 1.3.1.1 Primitive Object Case 1.3.1.2 CSG Object Case 1.3.2 Acceleration Scheme 1.4 Finite Difference Time Domain (FDTD) 1.4.1 Discretization of the System Domain 1.4.2 Dispersive Materials 1.4.2.1 Lorentz Model 1.4.2.2 Drude Model 1.4.2.3 Drude-Lorentz Model 1.4.3 Boundary Condition 1.4.3.1 Absorbing Boundary Condition (ABC) 1.4.3.2 Periodic Boundary Condition (PBC) 1.5 Scope and Objectives 1.6 Achievements 2. Slab-Outline Algorithm for Fast Intersection Finding 2.1 Overview 2.2 Algorithm 2.2.1 Non-overlapped texture case 2.2.2 Overlapped pyramidal texture case 2.3 Numerical Results : Validation 2.3.1 Examine of Backward Ray Tracing Results 2.3.2 Comparison of Experimental Results 2.3.3 Error Analysis 2.3.4 Time Complexity 2.4 Numerical Analysis : Applications 2.4.1 Simulation 2.4.2 Results and discussion 2.5 Conclusion 3. Simulation with Ray Tracing Method 3.1 Overview 3.2 Algorithm 3.3 Validation 3.3.1 Case I - coherent system 3.3.2 Case II - incoherent system 3.3.3 Case III - coherent + incoherent complex system 3.4 Numerical Analysis : Applications 3.4.1 High-efficiency Grid-type Si Solar Cell Structure 3.4.1.1 Overview 3.4.1.2 Simulation model 3.4.1.3 Results and Discussion 3.4.2 Effect of oxide thin films in back contact on the optical absorption efficiency of thin crystalline Si solar cells 3.4.2.1 Overview 3.4.2.2 Simulation model 3.4.2.3 Results and Discussion 3.5 Conclusion 4. Simulation with FDTD Method 4.1 Overview 4.2 Auto-Discretization of the System Domain 4.2.1 Algorithm 4.2.2 Results of Auto-Discretization 4.3 Implementation of Lorentz Model with ADE 4.4 EffectiveMaterial Function 4.4.1 Round-Off Algorithm 4.4.2 Dispersive Conformal FDTD (D-CFDTD) Algorithm 4.4.3 Validation 4.4.4 Numerical Analysis 4.5 Simulation of Absorption Energy 4.5.1 Algorithm 4.5.1.1 Extract Object's Continuous Boundary 4.5.1.2 Memory allocation and index mapping for the boundary cells 4.5.1.3 Calculation of the absorption energy 4.5.2 Numerical Analysis 4.5.2.1 Flat system 4.5.2.2 Non-Flat system 4.6 Conclusion 5. Conclusion 5.1 Summary 5.2 Evaluation 5.3 Future Work References Appendix I 국문초록 감사의 글Docto

The application of robotics to the assembly of flexible parts by sewing.

This thesis concerns the development of a robotic cell to perform assembly and handling operations on cloth.- A flexible automation approach was adopted, in which the robot was required to control the cloth panel during both handling and sewing operations, without the aid of hard automation attachments which might limit the flexibility of the system. The cell consisted of an adaptively controlled robot, a hierarchy of controllers, a conventional sewing machine, a two-fingered fabric steering end-effector, and several sensor systems. A technique was developed for producing a seam parallel to an edge of arbitrary contour, in which two cameras, a cloth tension sensor and the sewing machine's shaft encoder provided the sensory input. Two sensory servo control systems were required, one control system generated the robot's trajectory to maintain a small constant cloth tension, and the other directed the robot to manipulate the cloth panel to maintain a constant seam width. The design of the cloth tension control was based on the measured frequency response of the open loop system. The seam width control was designed using simulation studies, which accounted for the control transfer function, and nonlinearities such as camera pixel resolution, time delays and robot motion limitations. Several robotic handling techniques were developed, so that a cloth panel placed arbitrarily on the sewing table could be set up for an edge seaming operation, and the cloth could be rotated about the needle. The system's flexibility was demonstrated in the assembly of an irregularly shaped cloth panel, in which three adjacent sides were sewn up

Bioremediality: Biomedia, imaging and shifting notions of liveliness across art and science

Biomedia and imaging practices have an important role to play in the representation, construction and generation of life and liveliness. Living Viral Tattoos is a research-creation project that reflects on tissue culture engineering practices of imaging cellular life in the laboratory. Various media art works created as part of the research conducted while culturing cells in the laboratory are referred to as "bioremediale images". The concept of bioremediality is proposed to reconsider biomedia and images as biosubjects in an era of global risk culture. The multi-dimensionality and liveliness of bioremediale images is situated as a (bio)remediation of images, materials, human and non-human entities across artistic and scientific processes. This dissertation proposes that an expanded range of literacy across the fields of media arts and life sciences is necessary to perceive and "read" images of life and liveliness

The optimal choice of a generic laser system for the commercial sterilisation of micro-organisms.

This thesis describes the theory and practical application of controlled laser radiation to denature micro-organisms on the surface of a given substrate in a commercial scale system. The described research system has been proven to achieve these aims tested on one specific bacterial example and one substrate. The investigation evaluates the cell physiology of micro-organisms and the required physical and chemical parameters that are capable of denaturing them. A summary of the current state of sterilisation technologies with respect to their relative efficiencies and applications is presented, with specific attention being focused on the use of laser light sources and their associated photo-thermal effects. The optimal choice of laser wavelength is discussed together with its required spatial and temporal profiles to denature a broad range of microorganisms. The investigation centres on the use of continuous wave carbon dioxide lasers (with a wavelength of 10.6 ?m) as the preferred choice to denature a variety of organisms, predominately Salmonella enteritidis, residing on the surface of chicken eggs destined for hatching. The initial trials showed that a kill rate of 99.988 % (3.9 log) could be achieved. The research system has been developed in conjunction with ADAS Consulting Limited (ADAS), which was formerly a government body affiliated to the Ministry of Agriculture, Fisheries and Food

Development of A Versatile Multichannel CWNIRS Instrument for Optical Brain-Computer Interface Applications

This thesis describes the design, development, and implementation of a versatile multichannel continuous-wave near-infrared spectroscopy (CWNIRS) instrument for brain-computer interface (BCI) applications. Specifically, it was of interest to assess what gains could be achieved by using a multichannel device compared to the single channel device implemented by Coyle in 2004. Moreover, the multichannel approach allows for the assessment of localisation of functional tasks in the cerebral cortex, and can identify lateralisation of haemodynamic responses to motor events. The approach taken to extend single channel to multichannel was based on a software-controlled interface. This interface allowed flexibility in the control of individual optodes including their synchronisation and modulation (AM, TDM, CDMA). Furthermore, an LED driver was developed for custom-made triple-wavelength LEDs. The system was commissioned using a series of experiments to verify the performance of individual components in the system. The system was then used to carry out a set of functional studies including motor imagery and cognitive tasks. The experimental protocols based on motor imagery and overt motor tasks were verified by comparison with fMRI. The multichannel approach identified stroke rehabilitation as a new application area for optical BCI. In addition, concentration changes in deoxyhaemoglobin were identified as being a more localised indicator of functional activity, which is important for effective BCI design. An assessment was made on the effect of the duration of the stimulus period on the haemodynamic signals. This demonstrated the possible benefits of using a shorter stimulus period to reduce the adverse affects of low blood pressure oscillations. i