We have constructed a single molecule detection system with the capability to simultaneously measure many parameters, including transient fluorescence intensity, fluorescence lifetime, and photon anti-bunching behavior via the Hanbury Brown-Twiss photon-correlation technique. In addition, we apply the system to study the single DiI (1, 1 '- dioctadecyl- 3, 3 , 3 ', 3 ' - tetramethylindocarbocyanine perchlorate) molecule, to characterize the photo-physical behaviors. Cyanine dyes are the molecules that constitute of two nitrogen centers, one of which is positive charged, and is linked by a conjugated chain with odd number of carbon atoms to the other nitrogen center. Cyanine dyes are interested in the photo sensitization, optical recording media, nonlinear optics, laser dyes, and many interesting photophysical and photochemical behaviors. Among them, DiI plays an important role in single molecule fluorescence investigations. The high photo-stability, good QE, and low inter-system crossing rates, make it a pioneer for the widely investigations in single molecule studies. Our experimental goal is to understand the characteristic of the monitored single molecule by the measuring photo-physical parameters. Our results include the typical behaviors in DiI molecules: clear on-off blinking, fluorescence anti-bunching, one-step photo-bleaching, and consistent fluorescence polarization orientation. In addition, we also observed some change during measurement, which indicates the corresponding change of structure. Few molecules also exhibit non-zero probability around the zero delay time, which indicates the simultaneous existence of more than one quantum emitters in the detected region. These results demonstrate that the parameters are essential for understanding and characterizing the observed molecules in single molecule level.

The efficiency of the fuel cell depends on both the kinetics of the electrochemical process and performance of the components. The main aim of this research is to analysis the reliability of the cracked Ag-SU8 interface on the channel wall in a micro-PEMFC. An existed surface crack on the channel wall subjected to the flow induced compressive stresses and shear stresses will propagate and lead to the spall formation. The results show that as the crack length increases, the value of KI will increase, but the value of KII decreases slightly. The reliability analysis of the interfacial crack between Ag and SU8 on the Micro-channel wall in PEMFC is discussed in this thesis.

The main aim of this study is to develop three dimensional models for micro flow-field plate of PEMFC and use numerical simulations to discuss the reliability of micro flow-field plate which works in real. A crack exists in the plate is loaded by the shear force, which is produced by the fuel H2 enter from inlet, and will propagate. The Ag, which is used to collect the electrons, will peel off and the efficiency of fuel cell will decrease. The commercial package software ANSYS was used to simulate the stress state around crack tip. Three modes of stress intensity factors K£L, K£L£L and K£L£L£L, were calculated in order to describe the stressed behavior of crack. Finally, the inlet pressure, geometry of crack and channel size is changed and Taguchi method with ANOVA is used to find the factors which influence the stressed behavior of crack most. The simulation results show that K£L and K£L£L are influenced most by geometry of crack and K£L£L£L is influenced more by geometry of crack and channel size

Spiking representing a periodic melting and solidification in the depth of fusion zone during high-intensity beam welding is experimentally and theorectically investigated in this work . A spike is a sudden increase in penetration beyond what might be called the average penetration line. Many spikes have voids in their lower portions because molten metal does not fuse to the sides of the hole, producing a condition similar to a cold shut in a casting. These defects seriously reduce the strength of the joint. Due to the significant role of specular reflection on absorption, an investigation of the beam characteristics, especially the focal location, on spiking is important. Furthermore, as the cavity base oscillates upward and downward relatively from the focal location, a central region subject to direct irradiation changes instantaneously from maximum to zero and vice versa. This leads to several hundred time difference in energy absorption and strongly periodic melting at the cavity base. Physical phenomenon of spiking is obtained by comparing between the measured and predicted data based on scale anlaysis of transport process near the cavity base and energy absorption as a function of focal location.

Jellyfish blooms create problems worldwide, which may increase with global warming, water pollution, and over-fishing. Benthic polyps (scyphistomae) asexually produce buds and small jellyfish (ephyrae), and this process may determine the population size of the large, swimming scyphomedusae. Environmental factors that affect the asexual reproduction rates include food, temperature, salinity, and light. In the present study, polyps of Aurelia aurita (L.), originated from Tapong Bay, southwest Taiwan, were studied in different combinations of temperatures (T), light intensities (L), and salinities (S). In the T (20, 25, 30¢XC) ¡Ñ L (372, 56, and 0 lux) experiment which was with a 12 h light-12 h dark photoperiod, production of new buds decreased with warmer temperatures and stronger light intensity. Warm temperatures accelerated strobilation and increased the daily production of ephyrae. The proportion of ephyrae to total asexual reproduction (new buds + ephyrae) increased dramatically in warmer temperatures and stronger light. Survival period was reduced at the highest temperature. Strobilation did not occur at the lowest temperature in darkness. All measures of total asexual reproduction indicated that medium to high temperatures would lead to faster production of more jellyfish; however, continuous high temperatures might result in high polyp mortality. Light intensity affected asexual reproduction less than did temperature, only significantly accelerating the strobilation rate. Because the interactive effects of light and temperature were significant for polyp survival time and the production of jellyfish per polyp, combined light and temperature effects are likely important for strobilation in situ. In the T (27, 31, 35¢XC) ¡Ñ S (25, 30, and 35) experiment which was in dark environment, production of new buds decreased with higher temperatures and salinity. The proportion of ephyrae to total asexual reproduction (new buds + ephyrae) increased with warmer temperatures, but survival period was reduced at the highest salinity, and strobilation was substantially reduced, even though the temperature was warmer compared to the T ¡Ñ L experiment. Salinity affected asexual reproduction less than did temperature, only significantly affecting production of new buds, and slightly affecting survival period and the proportion of ephyrae to total asexual reproduction. According to these two experiments, warmer temperature may accelerate strobilation in light condition and lead to better yield of swimming jellyfish, however continuously warm temperature would reduce the yield by decreasing budding and higher mortality. Complete dark led to much less strobilation, especially at low temperatures, suggesting that the existence of light might be more important than light intensity. The effects of salinity on asexual reproduction were not as conspicuous as that of temperature and light.

Thesis (M.S. in Operations Research)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Thomas Lucas. Includes bibliographical references (p. 82). Also available online.

Thesis (M.S. in C.E.)--School of Civil and Environmental Engineering, Georgia Institute of Technology, 2004. Directed by Glenn J. Rix. / Includes bibliographical references (leaves 94-97).

Traffic signs, which transportation agencies must inventory and manage, are one of the most important roadway assets because they are used to ensure roadway safety and provide important travel guidance/information. Traffic sign inventory and condition assessment are two important components that are essential for establishing a cost-effective and sustainable traffic sign management system. Traditionally, state departments of transportation (DOTs) have conducted traffic sign inventory and condition assessment manually, a process that is labor-intensive, time-consuming, and sometimes hazardous to field engineers in the roadway environment. Methods have been developed to automate sign inventory and condition assessment using video log images in previous studies. However, the performance of these methods still needs to be improved. Based on the need to inventory signs and manage them more effectively, this study has two focuses. The first focus is to develop an enhanced traffic sign detection methodology to improve the productivity of an image-based sign inventory for state DOTs. The proposed methodology includes two enhanced algorithms: a) a lighting dependent statistical color model (LD-SCM)-based color segmentation algorithm that is robust to different image lighting conditions, especially adverse lighting and b) an ordinary/partial differential equation (ODE/PDE)-based shape detection algorithm that is immune to discontinuous sign boundaries in a cluttered background. The second focus of the study is to explore a new traffic sign retroreflectivity condition assessment methodology to develop a mobile method that uses emerging computer vision and mobile light detection and ranging (LiDAR) technologies to assess traffic sign retroreflectivity conditions. The proposed methodology includes a) an image-LiDAR registration method employing camera calibration and point co-planarity to register the 3D LiDAR point cloud with 2D video log images, b) a theoretical-empirical normalization scheme to adjust the magnitude of the LiDAR retro-intensity values with respect to LiDAR beam distance and incidence angle based on the radiometric responses, and c) a population-based retroreflectivity condition assessment method to evaluate the adequacy of a traffic sign retroreflectivity condition based on the correlation between the normalized LiDAR retro-intensity and the retroreflectivity values. For the proposed traffic sign detection methodology, comprehensive tests using representative datasets (e.g. with different road functions, data collection sources, and data qualities) were conducted to validate the performance of the two enhanced algorithms and the complete methodology. For the proposed retroreflectivity condition assessment methodology, the fundamental behavior of LiDAR retro-intensity was comprehensively tested and simulated under a controlled lab and roadway environment to quantify the impact of beam distance and incidence angle. A preliminary test on Type 1 engineer grade stop signs was conducted in the field to validate the performance of the proposed sign retroreflectivity condition assessment method. The results from both of the proposed methodologies are promising.

応用力学論文集v.15

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