• Smart Structures and Systems
• /
• v.6 no.5_6
• /
• pp.675-687
• /
• 2010

Structural Health Monitoring (SHM) is the science and technology of monitoring and assessing the condition of aerospace, civil and mechanical infrastructures using a sensing system integrated into the structure. Impedance-based SHM measures impedance of a structure using a PZT (Lead Zirconate Titanate) patch. This paper presents a low-power wireless autonomous and active SHM node called Autonomous SHM Sensor 2 (ASN-2), which is based on the impedance method. In this study, we incorporated three methods to save power. First, entire data processing is performed on-board, which minimizes radio transmission time. Considering that the radio of a wireless sensor node consumes the highest power among all modules, reduction of the transmission time saves substantial power. Second, a rectangular pulse train is used to excite a PZT patch instead of a sinusoidal wave. This eliminates a digital-to-analog converter and reduces the memory space. Third, ASN-2 senses the phase of the response signal instead of the magnitude. Sensing the phase of the signal eliminates an analog-to-digital converter and Fast Fourier Transform operation, which not only saves power, but also enables us to use a low-end low-power processor. Our SHM sensor node ASN-2 is implemented using a TI MSP430 microcontroller evaluation board. A cluster of ASN-2 nodes forms a wireless network. Each node wakes up at a predetermined interval, such as once in four hours, performs an SHM operation, reports the result to the central node wirelessly, and returns to sleep. The power consumption of our ASN-2 is 0.15 mW during the inactive mode and 18 mW during the active mode. Each SHM operation takes about 13 seconds to consume 236 mJ. When our ASN-2 operates once in every four hours, it is estimated to run for about 2.5 years with two AAA-size batteries ignoring the internal battery leakage.

• Journal of Power Electronics
• /
• v.19 no.5
• /
• pp.1303-1314
• /
• 2019

This paper studies the harmonic characteristics of ship electric propulsion systems and their treatment methods. It also adopts effective measures to suppress and prevent ship power systems from affecting ship operation due to the serious damage caused by harmonics. Firstly, the harmonic characteristics of a ship electric propulsion system are reviewed and discussed. Secondly, aiming at problems such as resonant frequency and filter characteristics variations, resonance point migration, and unstable filtering performances in conventional passive filters, a method for fully tuning of a passive dynamic tunable filter (PDTF) is proposed to realize harmonic suppression. Thirdly, to address the problems of the uncontrollable inductance L of traditional air gap iron core reactors and the harmonics of power electronic impedance converters (PEICs), this paper proposes an electromagnetic coupling reactor with impedance transformation and harmonic suppression characteristics (ECRITHS), with the internal filter (IF) designed to suppress the harmonics generated by PEICs. The ECRITHS is characterized by both harmonic suppression and impedance change. Fourthly, the ECRITHS is investigated. This investigation includes the harmonic suppression characteristics and impedance transformation characteristics of the ECRITHS at the fundamental frequency, which shows the good performance of the ECRITHS. Simulation and experimental evaluations of the PDTF are carried out. Multiple PDTFs can be configured to realize multi-order simultaneous dynamic filtering, and can effectively eliminate the current harmonics of ship electric propulsion systems. This is done to reduce the total harmonic distortion (THD) of the supply currents to well below the 5% limit imposed by the IEEE-519 standard. The PDTF also can eliminate harmonic currents in different geographic places by using a low voltage distribution system. Finally, a detailed discussion is presented, with challenges and future implications discussed. The research results are intended to effectively eliminate the harmonics of ship electric power propulsion systems and to improve the power quality of ship power systems. This is of theoretical and practical significance for improving the power quality and power savings of ship power systems.

• The Journal of Korean Institute of Information Technology
• /
• v.16 no.11
• /
• pp.35-41
• /
• 2018

Electrical impedance tomography (EIT) is a kind of nondestructive testing technique that obtains the internal resistivity distribution from the voltages measured at the electrodes located outside the area of interest. However, an image reconstruction problem in EIT has innate non-linearity and ill-posedness, so that it is difficult to obtain satisfactory reconstructed results. In general, a neural network can efficiently model the input and output relationships of a non-linear system. This paper proposes a method for estimating the position and size of a circular target using a multi-layer neural network. To verify the performance of the proposed method, neural network was trained and various computer simulations were performed and satisfactory performance was verified.

• The Journal of Internal Korean Medicine
• /
• v.42 no.2
• /
• pp.207-214
• /
• 2021

Objectives: This study aimed to identify whether herbal medicine improves the clinical symptoms and abnormal blood tests of a patient with fatty liver accompanied by hypertriglyceridemia. Methods: A 44-year-old man with fatty liver and hypertriglyceridemia was prescribed Saenggangunbi-tang from July 20, 2020, to November 11, 2020, to reduce fatigue and to improve laboratory findings, such as liver enzymes and the lipid profile. We observed changes in symptoms, serum levels of liver enzymes, and the lipid profile during about 4-month treatment. We also recorded changes in the bioelectrical impedance analyzer findings during that time. Results: In this case study, an approximately 4-month treatment with Saenggangunbi-tang led to considerable improvement in laboratory findings and visceral fat area. In particular, the patient experienced a noticeable decrease in triglyceride levels compared with the baseline parameters of the first visit. In addition, no side effects-including weight gain and liver enzyme increases-were observed during treatment. Conclusion: This study suggests that appropriately prescribed herbal medicine is a therapeutic option to manage fatty liver combined with hypertriglyceridemia.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.6 no.2
• /
• pp.113-118
• /
• 2007

KPCS internal antenna in this paper, is designed and fabricated using the theory based on the folded monopole antenna. I propose folded monopole internal antenna which has high gain low profile structure with easy installation into the handset of mobile phone. Design frequency is 1.8 GHz that is a center frequency of Korea PCS frequency band, and the impedance variances due to change of antenna structure as a length and width are simulated. Measurements show that input VSWR range under 2:1 is 1.72 - 1.88 GHz, and radiated H-plane pattern is omnidirectional under passive state. Active sensitivities and output power of phone applied antenna are $-105\;{\sim}\;-108\;dBm$ and $22.5\;{\sim}\;23.6\;dBm$ max., respectively.

• The Journal of Internal Korean Medicine
• /
• v.43 no.2
• /
• pp.184-190
• /
• 2022

Objectives: This study aims to report the clinical efficacy of Korean medical treatment of a patient with nonalcoholic fatty liver disease accompanied by obesity and dyslipidemia. Methods: A 52-year-old man with nonalcoholic fatty liver disease, obesity, and dyslipidemia was treated with Saenggangunbi-tang extract from November 3, 2021 to January 8, 2022. During the treatment period, the patient also undertook exercise and maintained a hypocaloric diet to reduce body weight. Changes were observed in the patient's symptoms, laboratory findings, such as liver enzymes and lipid profiles, and bioelectrical impedance analyzer results. Results: After taking Saenggangunbi-tang extract for approximately two months, with concomitant adjustments to exercise and diet, the serum levels of liver enzymes and triglyceride were decreased and the patient's body weight, body mass index, hepatic steatosis index, and visceral fat area were also reduced. In addition, symptoms including fatigue and dyspepsia improved. Conclusion: This study suggests that Saenggangunbi-tang extract with exercise and a regulated diet could be a helpful treatment strategy for managing nonalcoholic fatty liver disease with metabolic disorders.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.2060-2060
• /
• 2011

This paper was investigated the frequency property for optimal operating conditions of mono-crystalline Si solar cell. An internal impedance of mono-crystalline Si solar cell was influenced frequency. An optimal operating conditions of solar cell was under about 10[kHz].

• Proceedings of the IEEK Conference
• /
• 2002.06e
• /
• pp.303-306
• /
• 2002

The EMI filter used in switching apparatus is designed on the basis of personal designer experience. A try and error approach leads to a considerables waste of time without assurance to come out to a good solution. The difficulty in the right choice of the component values resides on the dominant role played by their parasitic components at high frequencies and is aggravated by the poor knowledge of the internal impedance of the noise generators. In this paper, we proposed the design technique for the EMI filter effectively using the LISN and the EMI analyzer in the industrial field.

• Journal of Industrial Technology
• /
• v.9
• /
• pp.101-107
• /
• 1989

The magnetic forming system must be able to store very important electric energy, several tens kilojoules, and flow this energy through the forming coil within some hundreds microseconds. So several hundreds kiloamperes of current can flow through the branch conductor. For the good performance of this type of machine, internal impedance must be minimized. By the computation of distribution of current inside the conductors using integral equation method, we can obtain the inductance and resistance of some dispositions of branch conductors and by comparison obtain some principles for the design of branch conductors in the high power magnetic pulse generator.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.131-134
• /
• 1999

Microstructure modification and electrochemical properties are investigate to estimate the effects of internal chlorides on the steel corrosion in the blended cement systems. According to the test results, slag cement system showed high chloride binding capacity and low corrosion rate. The impedance data showed three distince arcs from lowest(mHz) frequency to highest (MHz) frequency due to product layer, interfacial reaction and bulk matrix. Through the microstructural investigation, fine steel-matrix interface of slag cement system was observed but rough steel-matrix interface of OPC system was observed. Friedel's salt was thought that the substantial material contributed to the chloride binding of slag cement system.