Kyung-Sup Lee

Transport and optical properties of CeTe2

Abstract The electrical resistivity, magnetic susceptibility, specific heat and reflectivity of single crystal CeTe 2 were measured. A weak anisotropy appears in these measurements. Its carrier concentration is extremely low and the valence of Ce is evaluated as trivalence. Its resistivity is abnormal, which seems to be due to the p-f mixing or/and dense Kondo effects. Owing to these effects its magnetic structure phase is complex such as Ce-monopnictides.

Single nucleotide polymorphism (SNP) detection using microelectrode biochip array

In this paper, a microelectrode array DNA chip was fabricated on a glass slide using photolithography technology. Several probe DNAs with mercaptohexyl moiety at their 5 end were immobilized on the gold electrodes by a DNA arrayer utilizing the affinity between gold and sulfur. Then target DNAs were hybridized and reacted with Hoechst 33258, which is a DNA minor groove binder and electrochemically active dye. Cyclic voltammetry in a 5 mM ferricyanide/ferrocyanide solution at 100 mV s–1 confirmed the immobilization of probe DNA on the gold electrodes. Linear sweep voltammetry or cyclic voltammetry showed a difference between target DNA and control DNA in the anodic peak current values. This was derived from Hoechst 33258 concentrated at the electrode surface through association with formed hybrids. It is suggested that this DNA chip could recognize sequence specific genes. It is also suggested that a multichannel electrochemical DNA microarray is useful to develop a portable device for a clinical gene diagnostic system.

Notice of Violation of IEEE Publication Principles New distribution class arrester ground lead disconnector design

This paper examines performance characteristics of existing distribution class arrester ground lead disconnecting devices. The paper also introduces a new Distribution Class ground lead disconnector design that not only extends the claimable detonation range well below the 20 amps specified in industry standards, but is very durable when exposed to severe arrester durability tests. Finally, this paper shows how this next generation disconnector interacts with the connected arrester to improve the overvoltage withstand capability of the arrester assembly.

Notice of Violation of IEEE Publication Principles Practical implications of multi-agent transformer condition monitoring

This paper describes the transition of the transformer condition monitoring multi-agent system (COMMAS) from an off-line partial discharge defect diagnosis system to an online one. The practical difficulties encountered along the way have been highlighted, and solutions outlined. The main issues were related to identifying fragility in the existing system, and making changes to the architecture to produce a more robust system. Additionally, considerations about the processing resources available on site and the communications links to the site influenced the decision to distribute individual agents across multiple computers. Adding a Substation Manager agent to COMMAS satisfies various requirements for data storage and accessibility, and serves as a gateway between the diagnosis side of COMMAS and the user interface. The systempsilas stability was improved by moving to a newer agent platform, which brought additional benefits such as agent relocation abilities. By these means, COMMAS is now ready to be deployed on site, to perform on-line transformer monitoring.

Notice of Violation of IEEE Publication Principles On-line insulation diagnostic system and off-line PD monitoring with HVAC testing

The paper considers the relation between on-line monitoring and diagnostics on the one hand and high-voltage (HV) withstand and partial discharge (PD) on-site testing on the other. HV testing supplies the basic data (fingerprints) for diagnostics. In case of warnings by on-line diagnostic systems, off-line withstand and PD testing delivers the best possible information about defects and enables the classification of the risk. Because alternating voltage (AC) is the most important test voltage, the AC generation on site is considered. Frequency tuned resonant (ACRF) test systems are best adapted to on-site conditions. They can be simply combined with PD measuring equipment. The available ACRF test systems and their application to electric power equipment -from cable systems to power transformers - is described.

Notice of Violation of IEEE Publication Principles Charge transport and electroluminescence in insulating polymers

Polymers submitted to thermo/electrical stress suffer from ageing that can drastically affect their functional behaviour. Understanding the physico/chemical processes at play during ageing and defining transport regimes in which these mechanisms start to be critical is therefore a prime goal to prevent degradation and to develop new formulation or new materials with improved properties. It is thought that a way to define these critical regimes is to investigate under which conditions (in terms of stress parameters) light is generated in the material by electroluminescence (EL). This can happen through impact excitation/ionization involving hot carriers or upon bipolar charge recombination (a definition that excludes light from partial discharges, which would sign an advanced stage in the degradation process). After a brief review of the EL phenomenology under DC, we introduce a numerical model of charge transport postulating a recombinationcontrolled electroluminescence. The model output is critically evaluated with special emphasize on the comparison between simulated and experimental light emission. Finally, we comment some open questions and perspectives.

Notice of Violation of IEEE Publication Principles Wireless sensor for managing electrical distribution networks

In this paper, methods and analysis of a simple wireless sensor concept for detecting and locating faults as well as for load monitoring are presented. The concept is based on distributed wireless sensors that are attached to the incoming and outgoing power lines of secondary substations. A sensor measures only phase current characteristics of the wire it is attached to, is not synchronized to other sensors and does not need configuration of triggering levels. The main novelty of the concept is in detecting and locating faults by combining power distribution network characteristics on system level with low power sampling methods for individual sensors. This concept enables the sensor design to be simple, energy efficient and thus applicable in new installations and for retrofit purposes in both overhead and underground electrical distribution systems.

Notice of Violation of IEEE Publication Principles On-line condition monitoring and diagnostics of power distribution equipment

Continuous on-line temperature monitoring provides the means to evaluate current condition of equipment and detect abnormality. It allows corrective measures to be taken to prevent upcoming failure. Continuous temperature monitoring and event recording provides information on the energized equipmentpsilas respond to normal and emergency conditions. On-line temperature monitoring helps to coordinate equipment specifications and ratings, determine the real limits of the monitored equipment and optimize facility operations. Using wireless technique eliminates any need for special cables and wires with lower installation costs if compared to other types of online condition monitoring equipment. In addition, wireless temperature monitoring works well under difficult conditions in strategically important locations. Wireless technology for on-line condition monitoring of energized equipment is applicable both as standalone system and with an interface with power quality monitoring system. The paper presents the results of wireless temperature monitoring of switchgear at a power plant over a two-year period.

Notice of Violation of IEEE Publication Principles Automatic vacuum capacitor switch with modified digital filter

A high-speed microprocessor based automatic vacuum capacitor switch with a modified digital filter design using distributed arithmetic has been designed in this paper. The automation trends particularly the automatic vacuum capacitor switch has helped ameliorate the power factor essentials and automatically triggered to close when the line current exceeds rated value. Microprocessor relays use digital filters to extract only the fundamental and attenuate harmonics. To provide optimum speed characteristics a distributed arithmetic based filter design in the microprocessor controller which not only enhances filtering speed but additionally enables lower power consumption at the cost of area has been introduced. The result is a unified description that describes a digital filter structure down to bit level.

Electrochemical DNA detecton using indicator-free target DNA on a DNA chip

This research aims to develop an indicator-free DNA chip. We fabricated a DNA microarray by lithography technology. Several probe DNAs consisting of thiol group at their 5-ends were immobilized on the gold electrodes. Then indicator-free target DNA was hybridized by an electrical force and measured electrochemically in potassium ferricyanide solution. Redox peak of cyclic-voltammogram showed a difference between target DNA and mismatched DNA in an anodic peak current. This indicator-free DNA chip microarray resulted in the sequence-specific detection of the target DNA quantitatively ranging from 10-18M to 10-5M in the buffer solution. Therefore, it is able to detect various genes electrochemically after immobilization of various probe DNAs and hybridization of indicator-free DNA on the electrodes simultaneously. It suggested that this DNA chip could recognize the sequence specific genes.