http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Chandrasekar, R.,Manohar, Suganthi L.,Krishnan, M. Korean Society of Applied Entomology 2007 Journal of Asia-Pacific Entomology Vol.10 No.3
In insects, the source of storage protein-1 (SP1) in ovaries has been the subject of controversy for several decades, and both extraovarian and intraovarian synthesized proteins have been implicated. Ovarian SP1 is presumed to contribute towards the chorion formation. The amino acid analysis of SP-1 of A. albistriga revealed that it consists of relatively high methionine content (10.9%) and is female-specific. The paper deals with the intraovarian synthesis and tissue distribution of SP1 in the pupal ovaries of A. albistriga. Northern hybridization analysis clearly demonstrates that the SP1 gene was expressed in the developing follicles, the maximum accumulation of its transcript at vitellogenic stage (day 4-8) during the mid pupal periods. Further, the result of EM studies regarding the localization of this protein in follicular epithelial cells is confirmed by immunogold labeling tracer techniques. A possible role for ovarian SP1 in A. albistriga and its relationship with SP1 synthesis by the fat body is discussed.
Computational Analysis of Apolipophorin-III in Hyphantria cunea
Chandrasekar R.,Dhanalakshmi R.,Krishnan M.,Kim H. J.,Jeong H. C.,Seo S. J. Korean Society of Sericultural Science 2005 International Journal of Industrial Entomology Vol.10 No.1
Recently a cDNA clone of apoLp-III from Hyphantria cunea was isolated and subjected to computational analysis to compare with other available sequences. Multiple sequence alignments were carried out using the amino acid sequences of apoLp-III from six insects. It was found that the H. cunea apoLp-III has relatively high sequence identities to Spodoptera litura ($69.5\%$), Manduca sexta ($66.8\%$), Galleria mellonella ($65.1\%$), Bombyx mori N4 ($54.3\%$) but less identity to Locusta migratoria ($18.3\%$). The amino acid composition was compared with other insects using EXPASY tools; it shows that alanine (Ala), glutamine (Gln), leucine (Leu) and lysine (Lys) are the major amino acid components of apoLp-III in H. cunea as well as other lepidopterans. Homology modeling performed using PSI-BLAST (PDB template M. sexta) reveals that the apoLp-III molecules consist of five, long amphipathic alpha helical bundles with short loops connecting the helices and shows homology with other insects. Phylogenetic analysis shows that the orthopteran apoLp-III represented by locust was most distantly related to the lepidopteran insects.
R. Yuvaraj,S. Chandrasekar 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.1
Breakdown of gas insulated switchgears due to partial discharges (PD) is a major threat for the safe and reliable operation of power system network. In recent times, PD based diagnostics has been widely adopted by electrical utilities in order to evaluate the health of high voltage insulation system. However, very few reports are only available on the PD characteristics of gas insulated medium voltage (MV) circuit breaker prototypes, in particular with mixture of gases, over a wide range of pressure and voltage stress. Deep analysis of nature of PD signals in mixture of gas insulation and its time–frequency characteristics is important in order to develop effi cient online condition monitoring systems for circuit breakers. This paper is aimed at the analysis of PD characteristics of a 22 kV MV circuit breaker prototype fi lled with SF 6 /N 2 gas mixtures using time–frequency (T-F) mapping and clustering technique. PD tests are carried out at diff erent gas pressures (1–5 bar) and at diff erent gas mixture ratios. Important PD parameters such as PD inception voltage, phase resolved PD (PRPD) pattern and PD repetition rate are evaluated. Clustering analysis of PD signals from the time–frequency mapping is carried out and formation of three diff erent clusters consisting of short, long and repetitive PD pulses is identifi ed. Online real time monitoring of individual cluster density will be helpful to understand the degradation of gas insulation of circuit breakers. Keeping in mind the minimal usage of SF 6 gas, from the results, it is noted that 10% SF 6 gas can be mixed with 90% N 2 at 3 bar pressure to get satisfactory PD performance of a 22 kV medium voltage circuit breaker.
R. Gandhi,S. Chandrasekar,C. Nagarajan 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.4
In recent times, gas insulated medium voltage (MV) circuit breakers (CB) form a vital component in power system network, considering its advantages such as reduced size and safety margins. Gas insulation characteristics of circuit breakers are generally measured by lightning impulse (LI) test according to IEC standard 60060-1 as a factory routine test. Considering the environmental issues of SF6 gas, many research works are being carried out towards the mixture of SF6 gases for high voltage insulation applications. However, few reports are only available regarding the LI withstand and streamer propagation characteristics (at both positive and negative polarity of waveform) of SF6/N₂ gas mixture insulated medium voltage circuit breakers. In this paper, positive and negative polarity LI tests are carried out on 22 kV medium voltage circuit breaker filled with SF6/N₂ gas mixture at different gas pressures (1-5 bar) and at different gas mixture ratios. Important LI parameters such as breakdown voltage, streamer velocity, time to breakdown and acceleration voltage are evaluated with IEC standard LI (1.2/50 μs) waveform. Weibull distribution analysis of LI breakdown voltage data is carried out and 50% probability breakdown voltage, scale parameter and shape parameter are evaluated. Results illustrate that the 25% SF6+75%N₂ gas filled insulation considerably enhances the LI withstand and breakdown strength of MV circuit breakers. LI breakdown voltage of circuit breaker under negative polarity shows higher value when compared with positive polarity. Results show that maintaining the gas pressure at 0.3 MPa (3 bar) with 10% SF₆ gas mixed with 90% N₂ will give optimum lighting impulse withstand performance of 22 kV MV circuit breaker.
R. Gandhi,S. Chandrasekar,C. Nagarajan 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.4
In recent times, gas insulated medium voltage (MV) circuit breakers (CB) form a vital component in power system network, considering its advantages such as reduced size and safety margins. Gas insulation characteristics of circuit breakers are generally measured by lightning impulse (LI) test according to IEC standard 60060-1 as a factory routine test. Considering the environmental issues of SF6 gas, many research works are being carried out towards the mixture of SF6 gases for high voltage insulation applications. However, few reports are only available regarding the LI withstand and streamer propagation characteristics (at both positive and negative polarity of waveform) of SF6/N2 gas mixture insulated medium voltage circuit breakers. In this paper, positive and negative polarity LI tests are carried out on 22 kV medium voltage circuit breaker filled with SF6/N2 gas mixture at different gas pressures (1-5 bar) and at different gas mixture ratios. Important LI parameters such as breakdown voltage, streamer velocity, time to breakdown and acceleration voltage are evaluated with IEC standard LI (1.2/50 µs) waveform. Weibull distribution analysis of LI breakdown voltage data is carried out and 50% probability breakdown voltage, scale parameter and shape parameter are evaluated. Results illustrate that the 25% SF6+75%N2 gas filled insulation considerably enhances the LI withstand and breakdown strength of MV circuit breakers. LI breakdown voltage of circuit breaker under negative polarity shows higher value when compared with positive polarity. Results show that maintaining the gas pressure at 0.3 MPa (3 bar) with 10% SF6 gas mixed with 90% N2 will give optimum lighting impulse withstand performance of 22 kV MV circuit breaker.
R. Rajeswari,S. Chandrasekar,B. Karthik 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.2
Recent concern towards environmental and fi re safety of transformer operation has led to the development of natural ester based liquid insulation for power transformers. Recent advancements in nano technology confi rm that the nano modifi ed liquid insulation provides superior dielectric and thermal properties. Statistical analysis of the dielectric properties of nano modifi ed liquid dielectrics is very important to qualify them for high voltage insulation applications. In this work, experimental works are carried out to understand the partial discharge (PD), lightning impulse (LI) and breakdown voltage (BDV) characteristics of corn oil fi lled with SiO 2 nano fi llers at diff erent wt% concentration such as 0.01%, 0.05% and 0.1%. Needle/ plane and rod/plane electrode geometry was used for creation of PD source. PD inception voltage, time domain and frequency domain characteristics of PD signals are evaluated. Weibull parameters of Phase Resolved PD pattern are evaluated. LI tests are performed at needle/plane and needle/sphere electrode geometry with standard 1.2/50 μs waveform at both positive and negative polarity. Weibull distribution analysis of LI breakdown voltage values are evaluated at diff erent experimental conditions. BDV tests are carried out at diff erent electrode gap distances such as 1, 2.5, 4 and 5 mm. Scale parameter and shape parameter of Weibull distribution of BDV values are computed. It is mostly observed that addition of nano SiO 2 fi ller at lower wt% concentration in the range of 0.01–0.05% has substantial eff ect in enhancing the PD, LI and BDV characteristics of corn oil. Improvement in PD, LI and BDV characteristics gives confi dent that nano modifi ed corn oil may be considered for outdoor transformer applications.