Browsing by Author "Wang, Kai"

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A bundled time domain reflectometry-based sensing cable for monitoring of bridge scour
(2019-05-01)
Wang, Kai
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Lin, Chih-Ping
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Chung, Chih-Chung
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土木工程學系
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Department of Civil Engineering
Scour monitoring is crucial for providing early warning of bridge safety and extending the knowledge of scour process. Traditional methods that rely on underwater instruments encounter difficulties in installation and operation in harsh fluvial environment. Time domain reflectometry (TDR)-based scour sensing wire was recently introduced as a promising technique to improve field deployment and durability. This study focused on further improving the concept of TDR sensing wire for better sensor package and performance. An innovative bundled bottom-up sensing cable was proposed to improve sensor durability and avoid the adverse effect of sensor fouling. The sensor durability is enhanced by twisting two sets of steel strands (as two opposing electrodes for the waveguide) around a coaxial cable into a composite sensing cable. The inner coaxial cable is introduced and armored by the sensing steel strands to direct TDR pulse to the bottom end before connecting to the sensing waveguide formed by steel strands for bottom-up sensing. Furthermore, taking advantage of a new data reduction method by using time-lapse differential waveform, robustness of system calibration and scour estimation is further enhanced. Experimental results revealed the optimal design of bundled TDR sensing cable, effectiveness of the bottom-up sensing approach, and better performance of the differential waveform method.
Advances in Quantum-Dot-Based Displays
(2020-07-01)
Huang, Yu-Ming
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Singh, Konthoujam James
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Liu, An-Chen
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Lin, Chien-Chung
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Chen, Zhong
In terms of their use in displays, quantum dots (QDs) exhibit several advantages, including high illumination efficiency and color rendering, low-cost, and capacity for mass production. Furthermore, they are environmentally friendly. Excellent luminescence and charge transport properties of QDs led to their application in QD-based light-emitting diodes (LEDs), which have attracted considerable attention in display and solid-state lighting applications. In this review, we discuss the applications of QDs which are used on color conversion filter that exhibit high efficiency in white LEDs, full-color micro-LED devices, and liquid-type structure devices, among others. Furthermore, we discuss different QD printing processes and coating methods to achieve the full-color micro-LED. With the rise in popularity of wearable and see-through red, green, and blue (RGB) full-color displays, the flexible substrate is considered as a good potential candidate. The anisotropic conductive film method provides a small controllable linewidth of electrically conductive particles. Finally, we discuss the advanced application for flexible full-color and highly efficient QD micro-LEDs. The general conclusion of this study also involves the demand for a more straightforward QD deposition technique, whose breakthrough is expected.
Applicability and limitations of time domain reflectometry bridge scour monitoring system in general field conditions
(1970-01-01)
Wang, Kai
;
Lin, Chih-Ping
;
土木工程學系
;
Department of Civil Engineering
A real-time and durable system for scour process monitoring with sufficient spatial precision is in pressing need for bridge safety management. In light of this, an innovative bundled time domain reflectometry sensing cable was recently proposed to enhance the time domain reflectometry technique for scour monitoring. However, current development only dealt with the construction of bundled sensing cable and the corresponding new data reduction method. Before it can be put into practical use, issues related to the effect of hydrological conditions, long-distance measurement, and actual field implementation are yet to be investigated. This study used both numerical simulations and laboratory experiments to examine the time domain reflectometry signals in response to both scour and deposition in different water-level conditions. As a result, the first guideline of waveform classification and interpretation is newly proposed to validly determine scour depth under various field conditions. Since field measurements often come with significant signal attenuation from resistance loss of long cable and dielectric and conductive loss in the sensing section, numerical simulations and a series of full-scale experiments were also conducted to assess the time domain reflectometry scour measurement range. The maximum measurement range of the latest time domain reflectometry scour sensing cable was found to be about 6 m. Within this range, the maximum error of scour estimation is within 0.2 m. Considering the new findings, a field time domain reflectometry scour monitoring system using the bundled time domain reflectometry sensing cable was designed accordingly and implemented at a bridge for the first time. The monitoring system successfully captured the scour process during a storm event and revealed some practical issues for future improvement as well.
Dependence of operating conditions on lifetime of Phosphor Quantum dots-based white LEDs
(2019-01-01)
Singh, Preetpal
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Tan, Cher Ming
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Kuo, Hao-Chung
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Wang, Kai
;
Yang, Hongchen
Lifetime of packaged Phosphor- Quantum dot (QDs) based white LEDs is studied. Various stress parameters such as blue light luminance, temperature and moisture are considered and their effect on the performance of the Phosphor- QD based LED is investigated. The lumen degradation rate and degradation trend for LEDs is observed to be different under varying stress conditions. Lumen recovery process is also observed under light stress test.
Improved TDR Method for Quality Control of Soil-Nailing Works
(2016-01-01)
Chung, Chih-Chung
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Lin, Chih-Ping
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Wang, Kai
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Lin, Chih-Sheng
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Ngui, Yin Jeh
Time domain reflectometry (TDR) has become an effective nondestructive testing method for soil-nailing inspection. Previous studies utilized a preinstalled, single-core, electric wire alongside the rebar within the soil nail. Measurements may be affected by possible grout defects and excessively overestimate the rebar length if the wire is coiled around the rebar. An improved TDR waveguide and a corresponding decoupled data reduction method (for both soil-nail length determination and grout condition inspection) are proposed herein. The feasibility and advantages of the new approach were experimentally verified with two types of TDR device. The proposed methodology makes it possible to use a portable, low-cost, and low-speed TDR device as a quick and economical tool for quality control of soil nailing.
Meta-analysis of Dense Genecentric Association Studies Reveals Common and Uncommon Variants Associated with Height
(2011-01-07)
Lanktree, Matthew B.
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Guo, Yiran
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Murtaza, Muhammed
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Glessner, Joseph T.
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Bailey, Swneke D.
Height is a classic complex trait with common variants in a growing list of genes known to contribute to the phenotype. Using a genecentric genotyping array targeted toward cardiovascular-related loci, comprising 49,320 SNPs across approximately 2000 loci, we evaluated the association of common and uncommon SNPs with adult height in 114,223 individuals from 47 studies and six ethnicities. A total of 64 loci contained a SNP associated with height at array-wide significance (p < 2.4 x 10(-6)), with 42 loci surpassing the conventional genome-wide significance threshold (p < 5 x 10(-8)). Common variants with minor allele frequencies greater than 5% were observed to be associated with height in 37 previously reported loci. In individuals of European ancestry, uncommon SNPs in IL11 and SMAD3, which would not be genotyped with the use of standard genome-wide genotyping arrays, were strongly associated with height (p < 3 x 10(-11)). Conditional analysis within associated regions revealed five additional variants associated with height independent of lead SNPs within the locus, suggesting allelic heterogeneity. Although underpowered to replicate findings from individuals of European ancestry, the direction of effect of associated variants was largely consistent in African American, South Asian, and Hispanic populations. Overall, we show that dense coverage of genes for uncommon SNPs, coupled with large-scale meta-analysis, can successfully identify additional variants associated with a common complex trait.
New types of time domain reflectometry sensing waveguides for bridge scour monitoring
(2017-07-01)
Lin, Chih-Ping
;
Wang, Kai
;
Chung, Chih-Chung
;
Weng, Yu-Wen
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土木工程學系
Scour is a major threat to bridge safety, especially in harsh fluvial environments. Real-time monitoring of bridge scour is still very limited due to the lack of robust and economic scour monitoring device. Time domain reflectometry (TDR) is an emerging waveguide-based technique holding great promise to develop more durable scour monitoring devices. This study presents new types of TDR sensing waveguides in forms of either sensing rod or sensing wire, taking into account of the measurement range, durability, and ease of field installation. The sensing rod is composed of a hollow grooved steel rod paired up with a metal strip on the insulating groove, while the sensing wire consists of two steel strands with one of them coated with an insulating jacket. The measurement sensitivity is inevitably sacrificed when other properties such as the measurement range, field durability, and installation easiness are enhanced. Factors affecting the measurement sensitivity were identified and experimentally evaluated for better arranging the waveguide conductors. A data reduction method for scour-depth estimation without the need for identifying the sediment/water reflection and a two-step calibration procedure for rating propagation velocities were proposed to work with the new types of TDR sensing waveguides. Both the calibration procedure and the data reduction method were experimentally validated. The test results indicated that the new TDR sensing waveguide provides accurate scour depth measurements regardless of the sacrificed sensitivity. The insulating coating of the new TDR sensing waveguide was also demonstrated to be effective in extending the measurement range up to at least 15 m.