Scheduling with subcontracting options

Department of Logistics2008-2009 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Mechanism of optical degradation in microstructured InGaN light-emitting diodes

While the enhancement of light extraction efficiency from microstructured InGaN light-emitting diodes (μLED) has been firmly established, there is concern over the effect of microstructuring on the device lifetimes. A study on the electrical characteristics and reliability of μLED arrays has been carried out. Despite improved optical performance, expanded device sidewalls served to accelerate the rate of optical degradation, adversely affect the lifetimes of devices. Through current-voltage plots and noise spectrum measurements, vertical current conduction along the plasma-damaged sidewalls was identified as the key degradation mechanism. © 2010 American Institute of Physics.published_or_final_versio

A reliability study on green InGaN-GaN light-emitting diodes

In this letter, the reliability of green InGaN-GaN light-emitting diodes (LEDs) has been analyzed by correlating the defect density of wafers with various device parameters, including leakage current, 1/f noise, and degradation rate. It was found that as the wavelength of green LEDs increases from 520 to 550 nm by increasing the indium content in the quantum wells, the defect density also increases, thus leading to larger leakage current, enhanced noise magnitude, and shortened device lifetime. © 2009 IEEE.published_or_final_versio

论合作

2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

空间数据的关注问题 : 从质量到可用性

2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

地理空间数据处理的尺度理论

Author name used in this publication: LI Zhi-lin2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Effect of indium content on performance and reliability of InGaN/GaN light-emitting diodes

While longer wavelength emission from InGaN/GaN light-emitting diodes (LEDs) can be achieved by increasing the indium (In) content in the quantum wells, the increased In content gives rise to side effects to the material and device performance and reliability. It was found that the induced strain in the wafer and the density of threading dislocations increase with increasing In content. From current-voltage and 1/f noise measurements, it was observed that the leakage currents, static resistance, and noise magnitudes rise monotonically with increasing emission wavelength (In composition), which can be attributed to higher defect concentrations. After undergoing a 1000 h reliability test, it was discovered that the optical degradation rates for the longer wavelength green LEDs were significantly higher than those of shorter wavelength. © 2009 American Institute of Physics.published_or_final_versio

Isolation and antigenicity evaluation of &#946-lactoglobulin from buffalo milk

Buffalo &#946-lactoglobulin in phosphate buffer (0.02 M, pH6.8) was adsorbed on DEAE-Sepharose Fast Flow gel, and eluted with a linear gradient of NaCl (0-0.5 M) in 0.02 M phosphate buffer, pH 6.8. A furtherpurification was performed on Sephadex G-75 gel by loading a concentrated and dialyzed fraction of samples containing buffalo &#946-lactoglobulin from ion-exchange chromatography, and seperating at a flow rate of 0.15 ml/min in 0.02 M phosphate buffer, pH 6.8. The purity of the isolated buffalo &#946-lactoglobulin was above 90% in comparison to the standard bovine &#946-lactoglobulin by SDS-PAGE and IEF-PAGE. The antigencity of the buffalo &#946-lactoglobulin was evualuted by indirect ELISA, Westernblotting and inhibition ELISA with anti-buffalo and anti-bovine &#946-lactoglobulin rabbit serum. The results showed that buffalo &#946-lactoglobulin could be seperated and purified by anion-exchange chromatography combined with gel filtration chromatography, and with a well-preserved antigenicity

Efficient key integrity verification for quantum cryptography using combinatorial group testing

Quantum Information and Computation VIII 77020F (April 23, 2010)In quantum cryptography, the key can be directly distributed to the communicating parties through the communication channel. The security is guaranteed by the quantum properties of the channel. However, the transmitted key may contain errors due to the noise of the channel. Key integrity verification is an indispensable step in quantum cryptography and becomes an important problem in higher speed systems. Computing only one hash value for the key string does not provide an effective solution as it may lead to dropping all the bits once the hash values on both sides do not agree. In this paper, we introduce a new idea of using the technique of combinatorial group testing, which seems to be an unrelated topic, to design a scheme to identify the error bits to avoid dropping all the bits. Our scheme can precisely locate the error bits if the number of error bits is within the maximum set by the scheme while the overhead is insignificant based on our experiments (additional bits: 0.1% of the key; time for computing the hash values: 16ms; verification time: 22 ms). Also, even if the number of error bits is higher than the maximum set by the scheme, only some correct bits may be misclassified as error bits but not the vice versa. The results show that we can still keep the majority of the correct bits (e.g. the bits discarded due to misclassification is only 5% of the whole string even if the number of error bits is 10 times of the maximum). © 2010 SPIE.published_or_final_versionThe 2010 SPIE Conference on Defense, Security, and Sensing, Orlando, FL., 5 April 2010. In Proceedings of SPIE - The International Society for Optical Engineering, v. 7702, p. 77020F-1 - 77020F-

Design of vertically-stacked polychromatic light-emitting diodes

A new design for a polychromatic light-emitting diode (LED) is proposed and demonstrated, LED chips of the primary colors are physically stacked on top of each other. Light emitted from each layer of the stack passes through each other, and thus is mixed naturally without additional optics. As a color-tunable device, a wide range of colors can be generated, making it suitable for display purposes. As a phosphor-free white light LED, luminous efficacy of 30 lm/watt was achieved. © 2009 Optical Society of America.published_or_final_versio