Browsing by Author "Li, Wei"

Now showing 1 - 12 of 12
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    Activity of bacteria isolated from bats against Pseudogymnoascus destructans in China
    Li, Zhongle; Li, Aoqiang; Hoyt, Joseph R.; Dai, Wentao; Leng, Haixia; Li, Yanfei; Li, Wei; Liu, Sen; Jin, Longru; Sun, Keping; Feng, Jiang (2021-02)
    White-nose syndrome, a disease that is caused by the psychrophilic fungus Pseudogymnoascus destructans, has threatened several North America bat species with extinction. Recent studies have shown that East Asian bats are infected with P. destructans but show greatly reduced infections. While several factors have been found to contribute to these reduced infections, the role of specific microbes in limiting P. destructans growth remains unexplored. We isolated three bacterial strains with the ability to inhibit P. destructans, namely, Pseudomonas yamanorum GZD14026, Pseudomonas brenneri XRD11711 and Pseudomonas fragi GZD14479, from bats in China. Pseudomonas yamanorum, with the highest inhibition score, was selected to extract antifungal active substance. Combining mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy analyses, we identified the active compound inhibiting P. destructans as phenazine-1-carboxylic acid (PCA), and the minimal inhibitory concentration (MIC) was 50.12 mu g ml(-1). Whole genome sequencing also revealed the existence of PCA biosynthesis gene clusters. Gas chromatography-mass spectrometry (GC-MS) analysis identified volatile organic compounds. The results indicated that 10 ppm octanoic acid, 100 ppm 3-tert-butyl-4-hydroxyanisole (isoprenol) and 100 ppm 3-methyl-3-buten-1-ol (BHA) inhibited the growth of P. destructans. These results support that bacteria may play a role in limiting the growth of P. destructans on bats.
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    Applying software maintenance metrics in the object oriented software development life cylce
    Li, Wei (Virginia Tech, 1992-09-05)
    Software complexity metrics have been studied in the procedural paradigm as a quantitative means of assessing the software development process as well as the quality of software products. Several studies have validated that various metrics are useful indicators of maintenance effort in the procedural paradigm. However, software complexity metrics have rarely been studied in the object oriented paradigm. Very few complexity metrics have been proposed to measure object oriented systems, and the proposed ones have not been validated. This research concentrates on several object oriented software complexity metrics and the validation of these metrics with maintenance effort in two commercial systems. The results of an empirical study of the maintenance activities in the two commercial systems are also described. A metric instrumentation in an object oriented software development framework is presented.
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    Asymmetric cryptosystem based on optical scanning cryptography and elliptic curve algorithm
    Chang, Xiangyu; Li, Wei; Yan, Aimin; Tsang, Peter Wai Ming; Poon, Ting-Chung (Nature Portfolio, 2022-05-11)
    We propose an asymmetric cryptosystem based on optical scanning cryptography (OSC) and elliptic curve cryptography (ECC) algorithm. In the encryption stage of OSC, an object is encrypted to cosine and sine holograms by two pupil functions calculated via ECC algorithm from sender's biometric image, which is sender's private key. With the ECC algorithm, these holograms are encrypted to ciphertext, which is sent to the receiver. In the stage of decryption, the encrypted holograms can be decrypted by receiver's biometric private key which is different from the sender's private key. The approach is an asymmetric cryptosystem which solves the problem of the management and dispatch of keys in OSC and has more security strength than the conventional OSC. The feasibility of the proposed method has been convincingly verified by numerical and experiment results.
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    Autonomous Vehicles for Small Towns: Exploring Perception, Accessibility, and Safety
    Li, Wei; Ye, Xinyue; Li, Xiao; Dadashova, Bahar; Ory, Marcia G.; Lee, Chanam; Rathinam, Sivakumar; Usman, Muhammad; Chen, Andong; Bian, Jiahe; Li, Shuojia; Du, Jiaxin (Safe-D University Transportation Center, 2023-09)
    As of 2021, there were 18,696 small towns in the US with a population of less than 50,000. These communities typically have a low population density, few public transport services, and limited accessibility to daily services. This can pose significant challenges for residents trying to fulfill essential travel needs and access healthcare. Autonomous vehicles (AVs) have the potential to provide a convenient and safe way to get around without requiring human drivers, making them a promising transportation solution for these small towns. AV technology can become a first-line mobility option for people who are unable to drive, such as older adults and those with disabilities, while also reducing the cost of transportation for both individuals with special needs and municipalities. The report includes our research findings on 1) how residents in small towns perceive AV, including both positive and negative aspects; 2) the impacts of ENDEAVRide—a novel “Transport + Telemedicine 2-in-1” microtransit service delivered on a self-driving van in central Texas—on older adults’ travel and quality of life; and 3) the potential safety implications of AVs in small towns. This report will help municipal leaders, transportation professionals, and researchers gain a better understanding of how AV deployment can serve small towns.
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    Developing A Framework for Guiding Interaction Design in Distance Learning
    Li, Wei (Virginia Tech, 2015-12-07)
    As one of the most critical elements in distance learning, interaction has been identified empirically as increasing learner motivation, satisfaction, participation, communication, and achievement. Fostering pedagogically effective interaction is a major challenge for educators in distance learning. In response to this challenge, the goal of this research was to develop a theoretically- and empirically- grounded framework for guiding interaction design in distance learning. It is anticipated that this framework can assist educators and instructional designers in designing quality interaction in distance learning. This study employed a design and developmental research methodology with three phases: analysis, development and evaluation, and revision. Findings from a systematic literature review of peer-reviewed interaction theory and research in distance learning as well as expert review informed the building of a three-phase framework for guiding interaction instructional design in distance learning.
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    An Empirical Study of Maintenance Activities in an Object OrientedSystem
    Li, Wei; Henry, Sallie M. (Department of Computer Science, Virginia Polytechnic Institute & State University, 1993)
    Decades of research on maintenance activities in the procedural paradigm has produced several conclusions. Among these conclusions are recommendations that a reduction in maintenance cost could be achieved by a more controlled design process, by more rigorous testing of potential problem areas earlier in the life cycle. With the increasing emphasis on the object oriented paradigm, the authors performed an empirical study of the maintenance patterns in a commercial object oriented system. Although this is a preliminary study, intuition is presented as insight into the object oriented maintenance activities.
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    An Empirical Study of Maintenance Activities in Two Object Oriented Systems
    Li, Wei; Henry, Sallie M. (Department of Computer Science, Virginia Polytechnic Institute & State University, 1993)
    Decades of research on maintenance activities in the procedural paradigm has produced several conclusions. Among these conclusions are recommendations that a reduction in maintenance cost could be achieved by a more controlled design process, by more rigorous testing of potential problem areas earlier in the life cycle. With the increasing emphasis on the object oriented paradigm, the authors performed an empirical study of the maintenance patterns in two commercial object oriented systems. Although this is a preliminary study, intuition is presented as insight into the object oriented maintenance activities.
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    Kinetics and Mechanism of Ozone Decomposition and Oxidation of Ethanol on Manganese Oxide Catalysts
    Li, Wei (Virginia Tech, 1998-05-28)
    Understanding and establishing reaction mechanisms is an important area in heterogeneous catalysis. This dissertation describes the use of in situ laser Raman spectroscopy combined with kinetic measurements and dynamic experiments to determine the mechanism of catalytic reactions. Two cases involving ozone reactions on manganese oxide catalysts were treated. Manganese oxide was chosen because it is the most active of the transition metal oxides for ozone decomposition and because it is a well-known catalyst for complete oxidation reactions. The first case studied was that of the ozone decomposition reaction on a supported manganese oxide catalyst. An adsorbed species with a Raman signal at 884 cm-1 was observed and assigned to a peroxide species based on results of in situ Raman spectroscopy, 18O isotopic substitution measurements, and ab initio MO calculations. The reaction pathway of ozone decomposition was elucidated with carefully designed isotopic experiments. The reaction sequence was found to involve two irreversible, kinetically significant steps: 1) dissociative adsorption of ozone to form a peroxide species and an atomic oxygen species, and 2) desorption of the peroxide intermediate. The kinetic behavior of the peroxide species and the overall decomposition reaction were investigated to test the validity of the proposed sequence. The transient kinetics were found to be consistent with the steady state kinetics, and both were well represented by the two-step sequence, indicating that the proposed reaction sequence accurately described the mechanism of decomposition. The surface was found to be non-uniform, with activation energies that varied linearly with coverage. At zero surface coverage the activation energy for ozone adsorption was found to be 6.2 kJ mol-1, while that for desorption of the peroxide species was found to be 69.0 kJ mol-1. The second case investigated was that of ethanol oxidation using ozone on alumina and silica supported manganese oxide catalysts. Ethanol was found to react with ozone at lower temperatures than with oxygen, and also with a lower activation energy. The reaction kinetics was found to be well described by a power law equation with the reaction orders on ozone and ethanol being 0.89 and 0.81 respectively. The oxidation reactivity was found to be closely related to that of ozone decomposition, suggesting an important role of ozone decomposition in the reaction mechanism. In situ laser Raman spectroscopic studies showed the existence of adsorbed ethoxide species on the catalyst surface under reaction conditions, however, at a much lower concentration than when oxygen alone was used as the oxidant. Transient experiments provided direct evidence that surface peroxide (an adsorbed species due to ozone) and surface ethoxide (an adsorbed species due to ethanol) reacted with each other on the catalyst surface.
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    A Lifecycle Which Incorporates Software Metrics
    Li, Wei; Henry, Sallie M. (Department of Computer Science, Virginia Polytechnic Institute & State University, 1990)
    The traditional waterfall life cycle model of software development provides a systematic method to separate the development process into different stages with explicit communication boundaries between each subsequent stage. But the waterfall model does not provide quantitative measurements for the products of each phase in the software life cycle. The model provides a base to develop methodologies which emphasize the completeness of the documents, the use of certain disciplines, and the consistency among documents. On the other hand, it is very hard to use the model to develop methodologies which provide 1) the quantitative evaluation of the quality of the documents (products) from each phase, 2) feedback information to help the manager make management decisions, and 3) criteria for redesigning or recoding a system. To ensure the quality of software products, a common basis for more meaningful evaluation leading to better understanding of software quality must be provided.
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    Object-Oriented Metrics Which Predict Maintainability
    Li, Wei; Henry, Sallie M. (Department of Computer Science, Virginia Polytechnic Institute & State University, 1993)
    Software metrics have been studied in the procedural paradigm as a quantitative means of assessing the software development process as well as the quality of software products. Several studies have validated that various metrics are useful indicators of maintenance effort in the procedural paradigm. However, software metrics have rarely been studied in the object oriented paradigm. Very few metrics have been proposed to measure object oriented systems, and the proposed ones have not been validated. This research concentrates on several object oriented software metrics and the validation of these metrics with maintenance effort in two commercial systems. Statistical analyses of a prediction model incorporating ten metrics are performed. In addition, a more compact model with fewer metrics was sought, analyses performed, and also presented.
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    Software Metrics and the Object-Oriented Paradigm
    Li, Wei; Cooley, Charles; Lewis, John A.; Henry, Sallie M. (Department of Computer Science, Virginia Polytechnic Institute & State University, 1990)
    Software metrics are in use to guide current software development practices. As commercial organizations make use of the benefits of the object-oriented paradigm, the desire to apply metrics to that paradigm has logically followed. However, standard procedural metrics are limited in their ability to describe true object-oriented designs and code, and in some aspects fail outright. This paper describes the difficulties in applying standard metrics to object-oriented code and defines a set of metrics which are specifically geared toward the features which make the object-oriented approach unique.
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    The Use of Complexity Metrics Throughout the Software Lifecycle
    Henry, Sallie M.; Wake, Steven A.; Li, Wei (Department of Computer Science, Virginia Polytechnic Institute & State University, 1992-05-01)
    Software metrics attempt to uncover difficult or complex components of a software system. The hypothesis is that complex components are more difficult to understand, hence they are hard to maintain and more prone to error. Discovery of these complex components can aid the software developer in selecting which components to redesign, direct the testing effort, and indicate the maintenance effort required. Previous studies have demonstrated two main concepts: (1) there exists a high correlation between design complexity and source code complexity, and (2) metrics applied to source code have a high correlation to the maintenance activity needed. This previous research motivates us to develop a methodology which uses complexity metrics throughout the software life cycle. Programmer productivity may be increased and software development cost may be reduced if error prone software is discovered early in the life cycle.