• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.234-237
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• 2003

The absorption and the interference shielding of the electromagnetic wave problem have been a very important issue for commercial and military purposes. This study dealt with the simulation reflection loss for electromagnetic absorbing sandwich type structures in X-band(8.2Ghz~12.4GHz). Glass/epoxy composites containing conductive carbon blacks were used for the face sheets and styrofoams were used for the core. Their permittivities in X-band were measured using the transmission line technique. Simulation results of 3-1ayered sandwich type structures showed the reflection loss using the theory about transmission and reflection in a multi-layered medium.

• Journal of the Korean Society of Clothing and Textiles
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• v.21 no.7
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• pp.1153-1161
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• 1997

The insulation provided by clothing system is usually expressed in terms of a coo units and its distribution of the body, directly affect convective, conductive, and radiant heat loss from the skin to the environment Evaporated heat loss is dependent upon fabric permeability, the amount of body surface area covered by clothing, and the pumping of air between the body and garment layers. Persons at low to medium activity levels, dressed in conventional apparel in door environments, usually do not lose a large amount of heat through evaporation. Thermal manikin technology is used to measure the resistance to heat transfer provided by clothing systems. The reciprocal of this value, 6.45 W/m2.$^{\circ}C$ is often used in calculations for convenience. The purpose of this study was to implement a research program for calculation the insulation value (clo), body surface area and basal metabolic rate of selected clothing system. The project provided for the building of an insulation data base for use in evaluating and comparing new and improved garments.

• Proceedings of the Korean Society of Computer Information Conference
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• 2012.07a
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• pp.411-412
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• 2012

본 논문에서는 인간의 가장 기본적이며 기초적인 운동인 걸음걸이로부터 검출할 수 있는 걸음 수 및 보행분석을 위해 전도성 섬유를 이용한 전기용량성압력 센서를 깔창형태로 개발하였다. 개발된 깔창 형태의 센서는 보행시의 압력을 측정하여 보행신호를 검출하고, 검출된 신호를 이용하여 걸음 수 및 보행 분석을 실시하였다. 개발된 센서의 성능 검증을 위하여 상용 만보계 및 관찰자의 수계로 도출된 보수를 비교하였으며, 자세에 따른 압력차이를 측정하였다. 기존의 상용 만보계는 저속(1 Km/h)으로 걸었을 때 보수가 잘 측정되지 않은 반면 개발된 센서는 저속에서도 관찰자 수계대비 정확한 보수를 도출 할 수 있었다. 또한 자세에 따라 압력 값을 토대로 사용자의 자세를 모니터링 할 수 있음을 보였다. 본 연구는 향후 스마트폰과 무선 연동하는 스마트 보행관리 시스템을 개발하기 위한 기초연구이다.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.8
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• pp.119-126
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• 2016

In this paper, we proposed the planar textile resonator for constructing wearable MR-WPT system and analyzed the characteristic of textile substrates used in resonators. The planar textile resonators were designed to resonate at 1-10 MHz. The loop and coil were fabricated planar structure on textile substrate using conductive materials. Polyester fiber and cotton widely used in real life were chosen as textile resonators for wearable applications and copper tape and silver paste were used for fabricating planar loop and coil on textile substrate. For comparison analysis on transfer efficiency according to the types of textile, transmitter and receiver parts were symmetric. According to the result, for the highest transfer efficiency of wearable WPT system, the planar resonators have specifications of relative thick textile substrate with low permittivity and low surface resistance of conductive pattern. The performed experiments show that the planar textile resonator is possible to be used for resonator in wearable MR-WPT system.

• Fashion & Textile Research Journal
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• v.21 no.6
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• pp.697-707
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• 2019

This review paper deals with materials, classification, and a current article investigation on smart textile sensors for wearable vital signs monitoring (WVSM). Smart textile sensors can lose electrical conductivity during vital signs monitoring when applying them to clothing. Because they should have to endure severe conditions (bending, folding, and distortion) when wearing. Imparting electrical conductivity for application is a critical consideration when manufacturing smart textile sensors. Smart textile sensors fabricate by utilizing electro-conductive materials such as metals, allotrope of carbon, and intrinsically conductive polymers (ICPs). It classifies as performance level, fabric structure, intrinsic/extrinsic modification, and sensing mechanism. The classification of smart textile sensors by sensing mechanism includes pressure/force sensors, strain sensors, electrodes, optical sensors, biosensors, and temperature/humidity sensors. In the previous study, pressure/force sensors perform well despite the small capacitance changes of 1-2 pF. Strain sensors work reliably at 1 ㏀/cm or lower. Electrodes require an electrical resistance of less than 10 Ω/cm. Optical sensors using plastic optical fibers (POF) coupled with light sources need light in-coupling efficiency values that are over 40%. Biosensors can quantify by wicking rate and/or colorimetry as the reactivity between the bioreceptor and transducer. Temperature/humidity sensors require actuating triggers that show the flap opening of shape memory polymer or with a color-changing time of thermochromic pigment lower than 17 seconds.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.1-10
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• 2020

This paper reviews the recent development of electronic textile technology, mainly focusing on chip-textile bonding. Before the chip-textile bonding, a circuit on the textile should be prepared to supply the electrical power and signal to the chip mounted on the fabrics. Either embroidery with conductive yarn or screen-printing with the conductive paste can be applied to implement the circuit on the fabrics depending on the circuit density and resolution. Next, chip-textile bonding can be performed. There are two choices for chip-textile bonding: fixed connection methods such as soldering, ACF/NCA, embroidery, crimping, and secondly removable connection methods like a hook, magnet, zipper. Following the chip-textile bonding process, the chip on the textile is generally encapsulated using PDMS to ensure reliability like water-proof.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.64-71
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• 2004

The object of this study is to design the Radar Absorbing Structures (RAS) having sandwich structures in the X-band ($8.2{\sim}12.4GHz$) frequencies. Glass fabric/epoxy composites containing conductive carbon blacks and carbon fabric/epoxy composites were used for the face sheets. Polyurethane(PU) foams containing multi-walled carbon nanotube (MWNT) were used for the core. Their permittivities in the X-band were measured using the transmission line technique. The reflection loss characteristics for multi-layered sandwich structures were calculated using the theory of transmission and reflection in a multi-layered medium. Three kinds of specimens were fabricated and their reflection losses in the X-band were measured using the free space technique. Experimental results were in good agreements with simulated ones in 10dB absorbing bandwidth.

• Journal of Sensor Science and Technology
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• v.27 no.6
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• pp.397-402
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• 2018

Proper seat design is critical to the safety, comfort, and ergonomics of automotive driver's seats. To ensure effective seat design, quantitative methods should be used to evaluate the characteristics of automotive seats. This paper presents a system that is capable of simultaneously monitoring body pressure distribution and surface deformation in a textile material. In this study, a textile-based capacitive sensor was used to detect the body pressure distribution in an automotive seat. In addition, a strain gauge sensor was used to detect the degree of curvature deformation due to high-pressure points. The textile-based capacitive sensor was fabricated from the conductive fabric and a polyurethane insulator with a high signal-to-noise ratio. The strain gauge sensor was attached on the guiding film to maximize the effect of its deformation due to bending. Ten pressure sensors were placed symmetrically in the hip area and six strain gauge sensors were distributed on both sides of the seat cushion. A readout circuit monitored the absolute and relative values from the sensors in realtime, and the results were displayed as a color map. Moreover, we verified the proposed system for quantifying the body pressure and fabric deformation by studying 18 participants who performed three predefined postures. The proposed system showed desirable results and is expected to improve seat safety and comfort when applied to the design of various seat types. Moreover, the proposed system will provide analytical criteria in the design and durability testing of automotive seats.

• Composites Research
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• v.19 no.5
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• pp.28-33
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• 2006

In this paper, we have studied the complex permittivities and their influence on the design of microwave absorbers of E-glass fabric/epoxy composite laminates containing three different types of carbon-based nano conductive fillers such as carbon black (CB), carbon nano fiber (CNF) and multi-wall nano tube (MWNT). The measurements were performed fur permittivities at the frequency band of 0.5 GHz$\sim$18.0 GHz using a vector network analyzer with a 7 mm coaxial air line. The experimental results show that the complex permittivities of the composites depend strongly on the natures and concentrations of the conductive fillers. The real and imaginary parts of the complex permittivities of the composites were proportional to the filler concentrations. But, depending on the types of fillers and frequency band, the increasing rates of the real and imaginary parts with respect to the filler concentrations were all different. These different rates can have an effect on the thickness in designing the single layer microwave absorbers. The effect of the different rates at 10 GHz was examined by using Cole-Cole plot; the plot is composed of a single layer absorber solution line and measured permittivities from these three types of composites. Single layer absorbers of 3 different thicknesses using carbon nano materials were fabricated and the -10 dB band of absorbing performances were all about 3 GHz.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.215-221
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• 2017

An electromagnetic (EM) wave absorber reduces the possibility of radar detection by minimizing the radar cross section (RCS) of structures. In this study, a radar absorbing structure (RAS) was applied to the leading edge of a blended wing body aircraft to reduce RCS in X-band (8.2~12.4GHz) radar. The RAS was composed of a periodic pattern resistive sheet with conductive lossy material and glass-fiber/epoxy composite as a spacer. The applied RAS is a multifunctional composite structure which has both electromagnetic (EM) wave absorbing ability and load-bearing ability. A two dimensional unit absorber was designed first in a flat-plate shape, and then the fabricated leading edge structure incorporating the above RAS was investigated, using simulated and free-space measured reflection loss data from the flat-plate absorber. The leading edge was implemented on the aircraft, and its RCS was measured with respect to various azimuth angles in both polarizations (VV and HH). The RCS reduction effect of the RAS was evaluated in comparison with a leading edge of carbon fabric reinforced plastics (CFRP). The designed leading edge structure was examined through static structural analysis for various aircraft load cases to check structural integrity in terms of margin of safety. The mechanical and structural characteristics of CFRP, RAS and CFRP with RAM structures were also discussed in terms of their weight.