Browsing by Author "Ma, Jing"

Now showing 1 - 7 of 7
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    Fox Hunting in Wild Apples: Searching for Novel Genes in Malus Sieversii
    Wisniewski, Michael; Artlip, Timothy; Liu, Jia; Ma, Jing; Burchard, Erik; Norelli, John; Dardick, Christopher (MDPI, 2020-12-14)
    Malus sieversii is considered the progenitor of modern apple (Malus pumila) cultivars and to represent a valuable source of genetic diversity. Despite the importance of M. sieversii as a source of disease resistance, stress tolerance, and novel fruit traits, little is known about gene function and diversity in M. sieversii. Notably, a publicly annotated genome sequence for this species is not available. In the current study, the FOX (Full-length cDNA OvereXpressing) gene hunting system was used to construct a library of transgenic lines of Arabidopsis in which each transgenic line overexpresses a full-length gene obtained from a cDNA library of the PI619283 accession of M. sieversii. The cDNA library was constructed from mRNA obtained from bark tissues collected in late fall–early winter, a time at which many abiotic stress-adaptative genes are expressed. Over 4000 apple FOX Arabidopsis lines have been established from the pool of transgenic seeds and cDNA inserts corresponding to various Gene Ontology (GO) categories have been identified. A total of 160 inserts appear to be novel, with no or limited homology to M. pumila, Arabidopsis, or poplar. Over 1300 lines have also been screened for freezing resistance. The constructed library of transgenic lines provides a valuable genetic resource for exploring gene function and diversity in Malus sieversii. Notably, no such library of t-DNA lines currently exists for any Malus species.
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    Identification and Functional Analysis of NLP-Encoding Genes from the Postharvest Pathogen Penicillium expansum
    Levin, Elena; Raphael, Ginat; Ma, Jing; Ballester, Ana-Rosa; Feygenberg, Oleg; Norelli, John; Aly, Radi; Gonzalez-Candelas, Luis; Wisniewski, Michael; Droby, Samir (MDPI, 2019-06-15)
    Penicillium expansum is a major postharvest pathogen that infects different fruits, mainly through injuries inflicted during harvest or subsequent handling after harvest. Several effectors were suggested to mediate pathogenicity of P. expansum in fruit tissue. Among these effectors Nep1-like proteins (NLPs), produced by various microorganisms with different lifestyles, are known for their ability to induce necrosis in dicot plants and were shown to be involved in virulence of several plant-related pathogens. This study was aimed at the identification and functional characterization of two NLP genes found in the genome of P. expansum. The genes were designated Penlp1 and Penlp2 and were found to code type1 and type3 NLP respectively. Necrosis-inducing activity of the two proteins was demonstrated by transient expression in Nicotiana benthamiana leaves. While Penlp1 expression was induced during apple infection and in liquid culture, the highest level of Penlp2 expression was found in ungerminated spores. Deletion of Penlp1, but not Penlp2, resulted in reduced virulence on apples manifested by reduced rate of lesion development (disease severity).
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    Incremental Design Techniques with Non-Preemptive Refinement for Million-Gate FPGAs
    Ma, Jing (Virginia Tech, 2003-01-13)
    This dissertation presents a Field Programmable Gate Array (FPGA) design methodology that can be used to shorten the FPGA design-and-debug cycle, especially as gate counts increase to many millions. Core-based incremental placement algorithms, in conjunction with fast interactive routing, are investigated to reduce the design processing time by distinguishing the changes between design iterations and reprocessing only the changed blocks without affecting the remaining part of the design. Different from other incremental placement algorithms, this tool provides the function not only to handle small modifications; it can also incrementally place a large design from scratch at a rapid rate. Incremental approaches are inherently greedy techniques, but when combined with a background refinement thread, the incremental approach offers the instant gratification that designers expect, while preserving the fidelity attained through batch-oriented programs. An incremental FPGA design tool has been developed, based on the incremental placement algorithm and its background refiner. Design applications with logical gate sizes varying from tens of thousands to approximately one million are built to evaluate the execution of the algorithms and the design tool. The results show that this incremental design tool is two orders of magnitude faster than the competing approaches such as the Xilinx M3 tools without sacrificing much quality. The tool presented places designs at the speed of 700,000 system gates per second. The fast processing speed and user-interactive property make the incremental design tool potentially useful for prototype developing, system debugging and modular testing in million-gate FPGA designs.
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    A new pilot directional protection method for HVDC line based on the polarity of inductive energy
    Ma, Jing; Kang, Jingya; Zhou, Yiqing; Wu, Yuchong; Cheng, Peng (2021-11)
    Concerning the poor immunity of DC line protection to fault resistance in the case of internal fault and its mal-operation proneness in the case of external fault, a new pilot directional protection scheme for HVDC line in AC/DC hybrid system based on the polarity of inductive energy is proposed. First, by analysing the conducting state of converter at different time sections, the impedance characteristic equations of converter in different commutation failure scenes are derived. On this basis, by combining the impedance characteristics of other components in DC system, the fault component network of an AC/DC hybrid system consisting of inductive impedances is established. Then, according to the difference in the flowing direction of the inductive energy in the fault component networks of internal and external faults, a protection criterion for identifying internal and external faults is constructed. Finally, simulation tests in RT-LAB verify that, the proposed method can accurately identify internal and external faults in different fault cases, unaffected by commutation failure and lightning interference and highly immune to the fault resistance. Besides, the proposed method does not involve real-time interaction of synchronous information, thus it is simple and reliable.
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    A novel AC line distance protection scheme for AC/DC hybrid system based on fault likeness factor
    Ma, Jing; Wu, Yuchong; Phadke, Arun G. (2020-12)
    Concerning the mal-operation of distance protection in AC/DC hybrid system due to commutation failure in DC system caused by AC-side fault, a novel AC line distance protection scheme based on fault likeness factor is proposed. First, by analysing the conducting state of converter in different time intervals, the expression of feed-in current from DC system to AC system is derived. On this basis, combining AC-side fault component network, the fault location equation considering the impact of feed-in current from DC system is established. Thus, by solving the equation consisting of information at multiple time sections, the fault location is calculated. And then, according to the consistency between the calculated fault location and actual fault location, the fault likeness factor is constructed to distinguish between in-zone and out-of-zone faults. Finally, simulation tests in RT-LAB verify that, the proposed scheme can identify in-zone and out-of-zone faults fast and accurately in the case of commutation failure caused by different types of fault, strongly immune to fault resistance.
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    Research on sub/super-synchronous oscillation suppression method for direct-drive wind turbine based on energy compensation
    Ma, Jing; Zhang, Min; Phadke, Arun G. (2021-08-17)
    A method to suppress sub/super-synchronous oscillation of direct-drive wind turbines based on energy compensation is proposed. First, the transient energy model of direct-drive wind turbine is built, and the negative damping energy terms that lead the oscillation of direct-drive wind turbine are extracted. On this basis, the expressions of voltage compensation terms corresponding to negative damping energy terms are derived by backward deduction, thus supplementary energy branches are constructed, and their impact on fundamental frequency characteristics of wind turbine is analyzed. And then, with the compensation energy of supplementary branches reaching the maximum and the increment of fundamental-frequency voltage being the minimum as the objective, and with the frequency-domain characteristic and fundamental-frequency voltage characteristic of control links being satisfied as constraints, a scheme to optimize the compensation coefficients of multiple branches is established. Finally, the model of direct-drive wind turbine is built in RT-LAB for hardware-in-the-loop tests. Simulation results verify that, the method can realize fast frequency-dependent suppression of sub/super-synchronous oscillation in different frequency bands concerning different grid strengths.
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    Stability analysis of sub-synchronous oscillation in power system connected with virtual synchronous DFIGs
    Ma, Jing; Xu, Honglu; Li, Pengchong; Cheng, Peng (2021-10-29)
    Concerning sub-synchronous oscillation in power system connected with virtual synchronous DFIGs, an oscillatory stability analysis method based on the dissipation rate of dynamic energy is proposed. First, the dynamic energy function that reflects the sub-synchronous oscillation characteristics of virtual synchronous DFIG is built, and the expression of dynamic energy considering virtual synchronous control parameters is analysed. Then, according to Lyapunov's stability law, the variation rate of dynamic energy function is defined as the energy dissipation rate. The energy dissipation rate reflects the variation trend of system dynamic energy during oscillation, thus it is used as the stability criterion of sub-synchronous oscillation. On this basis, the effects of different virtual synchronous control parameters on sub-synchronous oscillation are analysed for a comprehensive consideration of system stability. Finally, simulation tests are conducted on RT-LAB platform. The results verify that, when the energy dissipation rate is positive, system oscillation diverges; when the energy dissipation rate is negative, system oscillation converges. Meanwhile, the larger the virtual resistance is, the worse the stability of system is; the larger PI control parameters of reactive power control loop are, the worse the stability of system is.