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Lisää oa-julkaisu, kun saatavilla. Megahertz-range wireless power transfer has become a promising approach for increasing spatial freedom of charging. This paper proposes a cylindrical-shaped coil, which can produce the homogeneous magnetic field in a plane. The coil consists of two helical windings, which are wound to guide the current in opposite directions. A single power source is used to excite the transmitter without any current amplitude or phase control circuits. Furthermore, since the parasitic capacitance of the coil is not negligible due to the complexity of the coil shape, we develop a general equivalent model with parasitic capacitance for the analysis of complex coils. The system efficiency of the proposed omnidirectional wireless power transfer device is validated by a practical experiment. The measured DC-to-DC efficiency of approximately 72.4% and the load power of 13 W are demonstrated for the proposed wireless charging system at 6.78 MHz operating frequency. Finally, we verify that the electromagnetic exposure satisfies the safety regulations.

Midfield wireless power transfer has proved its advantages in power delivery to miniature implantable medical devices located deeply in the human body; however, the delivered power level is still low. Besides, design proposals for a compact source structure concentrating the transmitter field on a miniature implant remain challenges. This letter presents a novel compact transmitting structure (TX) at the midfield band and shows the capability of focusing the magnetic field inside the human tissue. Source performance has been verified by implantable planar inverted-F antenna (PIFA) with a total size of 9 × 13 mm ${^2}$ (RX) that positioned in the heart tissue layer at a 55 mm separated distance of TX and RX. In addition, the power transfer efficiency has been demonstrated by a measurement setup using pork muscle, which obtained a good match of the transmission coefficient between the simulation and experiment results. Consequently, for 1 W of output power from the midfield transmitter, the received energy could be achieved more than 5.6 mW via the implantable antenna at a subwavelength distance.

This letter presents a novel multiband rectenna for the ambient wireless energy harvesting of an autonomous internet of thing (IoT) sensor. A bow-tie antenna with slits is proposed to obtain four frequency bands at 840 MHz, 1.86, 2.1, and 2.45 GHz, respectively. Furthermore, a multiband rectifying circuit combined of four single ring-loop rectifiers is designed with high conversion efficiency. Finally, a power management circuit with storing and converting the harvested voltage is proposed for smoothing dc output voltage. The energy harvester can be used in practical wireless sensor applications.

The free-positioning wireless power transfer (WPT) system has drawn attention in recent years. Traditionally, a WPT system can transfer energy in one or two directions on the same plane, but it leads the restrictions of angle and axis misalignment between a transmitter and a receiver coil. In this paper, we propose a free-positioning WPT system using a three-dimensional cubic-shaped transmitting coil for portable device charging. A small receiving coil is placed inside the transmitter to achieve the transferred energy through the magnetic resonant coupling. In addition, the equivalent circuit and the mutual inductance between the Tx and Rx coils are analyzed. Finally, a practical experiment is implemented to verify the transfer performance, which can reach up to about 50% power transfer efficiency. The proposed system can charge in spatial freedom.

Reversible H2 gas sensing at room temperature has been highly desirable given the booming of the Internet of Things (IoT), zero-emission vehicles, and fuel cell technologies. Conventional metal oxide-based semiconducting gas sensors have been considered as suitable candidates given their low-cost, high sensitivity, and long stability. However, the dominant sensing mechanism is based on the chemisorption of gas molecules which requires elevated temperatures to activate the catalytic reaction of target gas molecules with chemisorbed O, leaving the drawbacks of high-power consumption and poor selectivity. In this work, we introduce an alternative candidate of cobalt oxysulfide derived from the calcination of self-assembled cobalt sulfide micro-cages. It is found that the majority of S atoms are replaced by O in cobalt oxysulfide, transforming the crystal structure to tetragonal coordination and slightly expanding the optical bandgap energy. The H2 gas sensing performances of cobalt oxysulfide are fully reversible at room temperature, demonstrating peculiar p-type gas responses with a magnitude of 15% for 1% H2 and a high degree of selectivity over CH4, NO2, and CO2. Such excellent performances are possibly ascribed to the physisorption dominating the gas–matter interaction. This work demonstrates the great potentials of transition metal oxysulfide compounds for room-temperature fully reversible gas sensing.

In recent years, wireless power technology has been promoted for recharging systems for portable devices that are used in everyday life. The conventional technology used for this purpose, which is based on magnetically coupled resonators, has provided promising results but is limited in range and direction at the receiving terminal. In this paper, we propose an omnidirectional wireless power transfer (WPT) system with a novel cubic transmitter to achieve relatively high efficiency. Specifically, a single power source is utilized to drive the current of the transmitter without phase and current control methodology. Energy delivery is transmitted to the receiver through magnetic resonant coupling in the medium-range WPT mode. In addition, an equivalent circuit model of a coupling two-coil system is derived and mathematically analyzed. The efficiency of the proposed omnidirectional WPT system depending on the various distances between the transmitter and the receiver, as well as the transmitter structure, is evaluated via analysis and implementation. Finally, practical experimental results from the resonant coupling system confirm the theoretical analysis of the cubic transmitter and the omnidirectional power transfer capability, which demonstrate approximately 60% power transfer efficiency.

Ingestible sensors are potentially a powerful tool for monitoring human health. Sensors have been developed that can, for example, provide pH and pressure readings or monitor medication, but capsules that can provide key information about the chemical composition of the gut are still not available. Here we report a human pilot trial of an ingestible electronic capsule that can sense oxygen, hydrogen, and carbon dioxide. The capsule uses a combination of thermal conductivity and semiconducting sensors, and their selectivity and sensitivity to different gases is controlled by adjusting the heating elements of the sensors. Gas profiles of the subjects were obtained while modulating gut microbial fermentative activities by altering their intake of dietary fibre. Ultrasound imaging confirmed that the oxygen-equivalent concentration profile could be used as an accurate marker for the location of the capsule. In a crossover study, variations of fibre intake were found to be associated with differing small intestinal and colonic transit times, and gut fermentation. Regional fermentation patterns could be defined via hydrogen gas profiles. Our gas capsule offers an accurate and safe tool for monitoring the effects of diet of individuals, and has the potential to be used as a diagnostic tool for the gut. In a human pilot trial, ingestible electronic capsules, which can sense oxygen, hydrogen, and carbon dioxide gas in the gut, have been shown to be capable of monitoring changes in a person’s diet.

There is an increasing recognition that the gas constituents of the colon, which are mainly the metabolic by-products of the colonic microbiota, are associated with the pathogenesis of colonic diseases and can be modulated by drugs or diet. Therefore, a real-time faecal gas profiler can generate invaluable information in the study of colonic disorders and their modulation. Unfortunately, most of the currently available intestinal gas profiling methods are either unreliable, cost-ineffective, rely on off-line measurement equipment which are bulky and expensive. Here, we developed a portable and low-cost in-vitro fecal fermentation system with array of gas and pressure sensors. The system is kept at a constant pressure using a commercial release valve unit. We are able to measure the in-vitro fecal gas production levels in real time and assess the kinetics in the presence of a highly-fermentable fiber as the feeding substrate while the headspace gas mixture was altered to mimic the colon environment. Through the representative measurements, intestinal gas production and bacterial metabolic activities can be assessed in a simulated colon gas environment with/without added substrates. This suggests that the system has potential as a practical research and diagnostic instrument for colonic disorders.

Five smart grid projects was started with large scale at Jeju Island in South Korea from 2009, and smart-grid test-bed was started in Nov. 2010. The five projects are Smart Power Grid (SPG), Smart Renewable (SR), Smart Transportation (ST), Smart Place (SP) and Smart Electric Service (SES). Korea government constructed the smart grid public relations center at Nov. 2010 in Jeju Island and there will be continued the field operation and interface testing among five smart gird projects until May. 2013.

A Distribution Automation System (DAS) is operated by monitoring and control of the field statesusing Feeder Remote Terminal Units (FRTUs) installed together withautomatic switches.An optimal placement of automatic switchescan enhance efficiencyof the operation and restoration, and improve the power supply reliability ofa DAS.This paper proposes an algorithm to decide the optimal placement of automatic switches ina DAS.The proposed algorithm was developed ona DAS witha six sections and three links configuration. The proposed algorithm was provided inaneight-feeder power distribution system.

Quantities of data in the DMS (Distribution management system) or SCADA (Supervisory control and data acquisition) system is enormously large as illustrated by the usage of term flooding of data. This enormous quantity of data is transmitted to the status data or event data of the on-site apparatus in real-time. In addition, if GIS (Geographic information system) and AMR (Automatic meter reading), etc are integrated, the quantity of data to be processed in real-time increases unimaginably. Increase in the quantity of data due to addition of system or increase in the on-site facilities cannot be handled through the currently used Single Thread format of data processing technology. However, if Multi Thread technology that utilizes LF-POOL (Leader Follower -POOL) is applied in processing large quantity of data, large quantity of data can be processed in short period of time and the load on the server can be minimized. In this Study, the actual materialization and functions of LF POOL technology are examined.

This paper focuses on performance evaluation of wireless networked control system (NCS) via IEEE 802.15.4 with time-triggered contention-based carrier sensing multiple access with collision (CSMA/CA) algorithm to satisfy the industrial quality-of-service (QoS). Although the IEEE 802.15.4 is considered to a promising protocol for wireless NCS, its performance is not stable and its delay is not bounded under heavy traffic because its medium access control (MAC) is based on the contention-based CSMA/CA scheme. As an alternative approach to avoid these limitations, this paper presents a time-triggered CSMA/CA algorithm for IEEE 802.15.4 non-beacon mode that relies on a time division multiplexing access (TDMA) method. The time-triggered CSMA/CA algorithm for IEEE 802.15.4 non-beacon mode was implemented an experimental wireless NCS, and its control performance was compared with conventional CSMA/CA algorithm. Based on the experimental results, the time-triggered CSMA/CA algorithm is a feasible alternative for wireless NCS.

The superconductor-triggered type fault current limiter (STFCL), which was developed by Korea Electric Power Corporation (KEPCO) and LS Industrial Systems (LSIS), is under operation for the verification test at KEPCO's power testing center. The STFCL is composed of superconductor, fast switch and current limiting resistor. The fault current is suppressed after a half cycle by the method of a line commutation. In this paper, we investigated the empirical modeling of STFCL using principal components and auto-associative support vector regression (PCSVR) for the prediction and fault detection of the STFCL. Signals for the model are currents and voltages acquired from high-temperature superconductor (HTS), driving coil (DC) and current limiting resistor (CLR). After developing the empirical model we analyse the accuracy of the model. The results were compared with that of auto-associative neural networks (AANN). PCSVR showed much better performance in accuracy aspect. Moreover, this model can be used for the prognosis of STFCL system.

Intelligent home service systems consist of ubiquitous sensors, a home network, and a context-aware computing system that together collect residential environment information and provide intelligent services such as controlling the environment or lighting. Determining a resident's location in the smart home or smart office is a key to such a system. This correspondence presents an enhanced location-recognition algorithm using a Bayesian classifier for the pyroelectric infrared sensor-based indoor location-aware system that is a nonterminal-based location-aware system proposed in a previous paper. This correspondence compares the conventional and enhanced location-recognition algorithms and their performance. The feasibility of the system is evaluated experimentally on a test bed.

Electric load components have different characteristics according to the variation of voltage and frequency. This paper presents the load modeling of an electric locomotive by the parameter identification method. The proposed method for load modeling is very simple and easy for application. The proposed load model of the electric locomotive is represented by the combination of the loads that have static and dynamic characteristics. This load modeling is applied to the KTX in Korea to verify the effectiveness of the proposed method. The results of proposed load modeling by the parameter identification follow the field measurements very exactly.

Current KEPCO's distribution automation system (DAS) provides a very effective restoration solution for the single fault case but cannot handle multiple faults. This paper proposes a two-step restoration scheme-sequential and simultaneous restoration-for multiple fault cases. Efficiency has been achieved by introduction of restoration performance index (RPI) and load-balancing algorithm. Test results to show effectiveness of the proposed scheme are presented, and field experience of DAS in Korea is described as well