• Journal of Powder Materials
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• v.25 no.5
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• pp.415-419
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• 2018

Porous metals demonstrate not only excessively low densities, but also novel physical, thermal, mechanical, electrical, and acoustic properties. Thus, porous metals exhibit exceptional performance, which are useful for diesel particulate filters, heat exchangers, and noise absorbers. In this study, SUS316L foam with 90% porosity and $3,000{\mu}m$ pore size is successfully manufactured using the electrostatic powder coating (ESPC) process. The mean size of SUS316L powders is approximately $12.33{\mu}m$. The pore properties are evaluated using SEM and Archimedes. As the quantity of powder coating increases, pore size decreases from 2,881 to $1,356{\mu}m$. Moreover, the strut thickness and apparent density increase from 423.7 to $898.3{\mu}m$ and from 0.278 to $0.840g/cm^3$, respectively. It demonstrates that pore properties of SUS316L powder porous metal are controllable by template type and quantity of powder coating.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.32-32
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• 2008

X-ray detector는 의료용, 산업용 등 다양한 분야에서 사용되어지고 있으며 기존의 Analog X-ray 방식의 환경오염, 저장공간 부족, 실시간 분석의 어려움 등의 문제점들을 해결하기 위하여 Digital X-ray로의 전환과 연구가 활발하며 이에 따른 관심도 높아지고 있는 살점이다. Digital X-ray detector는 p-영역과 n-영역 사이에 아무런 불순물을 도핑하지 않은 진성반도체(intrinsic semiconductor) 층을 접합시킨 이종접합 PIN 구조의 photodiode 이다. 이 소자는 역바이어스를 가해주면 p영역과 n영역 사이에서 캐리어 (carrier)가 존재하지 않는 공핍 영역이 발생하게 된다. 이런 공핍 영역에서 광흡수가 일어나면, 전자-정공 쌍이 발생한다. 그리고, 발생한 전자-정공 쌍에 전압이 역방향으로 인가되는 경우, 전자는 양의 전극으로 이동하고, 정공은 음의 전극으로 이동한다. 이와 같이, 발생한 캐리어들을 검출하여 전기적인 신호로 변환 시킨다. 고해상도의 Digital X-ray detector를 만들기 위해서는 누설전류에 의한 noise 감소와 소자의 높은 안정성과 내구성을 위한 높은 breakdown voltage를 가져야 한다. 본 연구에서는 Digital X-ray detector의 leakage current 감소와 breakdown voltage를 높이기 위하여 guradring과 gettering technology를 사용하여 전기적 특성을 분석하였다. 기판으로는 $10k\Omega{\cdot}cm$ resistivity를 갖으며, n-type <111>인 1mm 두께의 4인치 Si wafer를 사용하였다. 그리고 pixel pitch는 $100{\mu}m$이며 active area는 $80{\mu}m{\times}80{\mu}m$인 $32\times32$ array를 형성하여 X-ray를 조사하여 소자의 특성을 평가 하였다.

• The Research Journal of the Costume Culture
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• v.4 no.2
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• pp.277-302
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• 1996

The purpose of this study is to suggest fundamental information about wearing method and production of brassiere, which is suitable for physiological hygiene and efficient action for elderly women. The subject is 418 elderly women aged 50∼69 years old. Data is processed by a computer(SAS) and is analyzed by using frequency, percentage, x²-test. The main results of this study are as follows. 1. Elderly women'weight and breast size are higher thant their younger counterparts'in their 20's, but the older and poorer women with more children have smaller weight and breast. Most of the elderly women feel that their breasts are drooped or falling apart. I fact, those elderly women who gave birth to more children have more drooped and wider breasts. The major type of elderly women'breast is the 'drooped breast' featured more by those elderly women who have more children. 2. Most of the elderly women began to wear the brassiere for the first time in their 20's the older women with more children began to wear the brassiere earlier, while those less educated and poorer began to protect their breasts with brassiere later. Many elderly women wear the brassiere to be protected from dirt, noise or look more neat, but day tend to wear the brassiere not all day around but at certain times, older, less educated and proper women with more children tend to use the brassiere for etiquette and less often. This group of elderly women feel tedious, stage or uncomfortable for the brassiere. 3. Most of the elderly women know about their brassiere size. Such variables as age, education and income are correlated positively with the interest in and consciousness of the brassiere size. All in all, the statistical distribution of elderly women's brassiere size is very wide, while most of them use 90A, 85A and 95A sizes. On the other hand, the most popular size of the under bust circumference is 85∼90cm, while their primary cup size is A.

• Journal of Sensor Science and Technology
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• v.6 no.4
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• pp.258-264
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• 1997

$YBa_{2}Cu_{3}O_{7}$ single layer dc SQUID magnetometers, prepared on $1\;cm^{2}\;SrTiO_{3}$ substrates, have been fabricated and characterized. Based on the analytical description, a SQUID magnetometer design having a 8.5 mm pickup coil with 2.6 mm linewidth, and a SQUID inductance Ls = 50 pH with $3\;{\mu}m$ Josephson junctions is presented. The devices showed a maximum modulation voltage depth of $65\;{\mu}V$ and a magnetic field noise of 0.6 pT /$\sqrt{Hz}$ at 1 Hz. Clear traces of human magnetocardiogram could be obtained with the SQUID magnetometer operating at 77 K.

• Journal of Coastal Disaster Prevention
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• v.4 no.4
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• pp.189-196
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• 2017

Ocean Research Stations (ORSs) is the ocean platform type observation towers and measured oceanic, atmospheric and environmental data. These station located on the offshore area far from the coast, so they can produce the data without land effect. This study focused to improve the wave data quality of ORS station. The wave observations at ORSs are used by the C-band (5.8 GHz, 5.17 cm) MIROS Wave and Current Radar (MWR). MWR is convenient to maintenance and produce reliability wave data under bad weather conditions. MWR measured significant wave height, peak wave period, peak wave direction and 2D wave spectrum, so it's can provide wave information for researchers and engineers. In order to improve the reliability of MWR wave data, Datawell Waverider Buoy was installed near the one ORS (Socheoncho station) during 7 months and validate the wave data of MWR. This study found that the wave radar tend to be overestimate the low wave height under wind condition. Firstly, this study carried out the wave Quality Control (QC) using wind data, however the quality of wave data was limited. So, this study applied the four filters (Correlation Check, Direction Filter, Reduce White Noise and Phillips Check) of MWR operating software and find that the filters effectively improve the wave data quality. After applying 3 effective filters in combination, the RMSE of significant wave height decreased from 0.81m to 0.23m, by 0.58m and Correlation increased from 0.66 to 0.96, by 0.32, so the reliability of MWR significant wave height was significantly improved.

• Advances in nano research
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• v.10 no.1
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• pp.59-69
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• 2021

Electrospinning is a cost-effective and versatile method for producing submicron fibers. Although this method is relatively simple, at the theoretical level the interactions between process parameters and their influence on the fiber morphology are not yet fully understood. In this paper, the aim was finding optimal electrospinning parameters in order to obtain the smallest fiber diameter by using Taguchi's methodology. The nanofibers produced by electrospinning a solution of Thermoplastic Polyurethane (TPU) in Dimethylformamide (DMF). Polymer concentration and process parameters were considered as the effective factors. Taguchi's L9 orthogonal design (4 parameters, 3 levels) was applied to the experiential design. Optimal electrospinning conditions were determined using the signal-to-noise (S/N) ratio with Minitab 17 software. The morphology of the nanofibers was studied by a Scanning Electron Microscope (SEM). Thereafter, a tensile tester machine was used to assess mechanical properties of nanofibrous scaffolds. The analysis of DoE experiments showed that TPU concentration was the most significant parameter. An optimum combination to reach smallest diameters was yielded at 12 wt% polymer concentration, 16 kV of the supply voltage, 0.1 ml/h feed rate and 15 cm tip-to-distance. An empirical model was extracted and verified using confirmation test. The average diameter of nanofibers at the optimum conditions was in the range of 242.10 to 257.92 nm at a confidence level 95% which was in close agreement with the predicted value by the Taguchi technique. Also, the mechanical properties increased with decreasing fibers diameter. This study demonstrated Taguchi method was successfully applied to the optimization of electrospinning conditions for TPU nanofibers and the presented scaffold can mimic the structure of Extracellular Matrix (ECM).

• Journal of the Society of Naval Architects of Korea
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• v.59 no.1
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• pp.46-54
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• 2022

A magnetohydrodynamic (MHD) seawater propulsion thruster has been proposed to reduce propeller noise, propeller pitting, and vessel vibration originated from the propeller cavitation. The MHD thruster was also focused to overcome the limitation of propulsion velocity for the special purpose of marine ships. The research trends and key technologies in the worldwide leading countries are reviewed for the development of MHD propulsion thrusters in Korea. A small performance test device was developed firstly with a conventional solenoid magnet of ≤0.6 Tesla and a helical-type cylindrical duct(inner diameter of 5 cm) of thruster. The artificial seawater was fabricated by a salt solution including a conductivity of 5~6 S/m. The measured flow velocity of artificial seawater in the test device was 0.03~0.42 m/s (0.06~0.84 Knot) with a magnetic field strength of 0.6 Tesla and the applied currents of 10~80 A including the change of anode materials. It was found that the flow direction of seawater was reversed by the directional change of applied current in the solenoid magnet.

• Journal of Biomedical Engineering Research
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• v.44 no.2
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• pp.139-146
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• 2023

Osteoporosis is a disease in which the risk of bone fractures increases due to a decrease in bone density caused by aging. Osteoporosis is diagnosed by measuring bone density in the total hip, femoral neck, and lumbar spine. To accurately measure bone density in the lumbar spine, the vertebral region must be segmented from the lumbar X-ray image. Deep learning-based automatic spinal segmentation methods can provide fast and precise information about the vertebral region. In this study, we used 695 lumbar spine images as training and test datasets for a deep learning segmentation model. We proposed a lumbar automatic segmentation model, CM-Net, which combines the center point of the spine and the modified U-Net network. As a result, the average Dice Similarity Coefficient(DSC) was 0.974, precision was 0.916, recall was 0.906, accuracy was 0.998, and Area under the Precision-Recall Curve (AUPRC) was 0.912. This study demonstrates a high-performance automatic segmentation model for lumbar X-ray images, which overcomes noise such as spinal fractures and implants. Furthermore, we can perform accurate measurement of bone density on lumbar X-ray images using an automatic segmentation methodology for the spine, which can prevent the risk of compression fractures at an early stage and improve the accuracy and efficiency of osteoporosis diagnosis.

• Journal of Biomedical Engineering Research
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• v.44 no.6
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• pp.384-391
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• 2023

Among the elderly, fatal injuries and deaths are significantly attributed to falls. Therefore, a pre-impact fall detection system is necessary for injury prevention. In this study, a robust threshold-based algorithm was proposed for pre-impact fall detection, reducing false positives in highly dynamic daily-living movements. The algorithm was validated using public datasets (KFall and FARSEEING) that include the real-world elderly fall. A 6-axis IMU sensor (Movella Dot, Movella, Netherlands) was attached to S2 of 20 healthy adults (aged 22.0±1.9years, height 164.9±5.9cm, weight 61.4±17.1kg) to measure 14 activities of daily living and 11 fall movements at a sampling frequency of 60Hz. A 5Hz low-pass filter was applied to the IMU data to remove high-frequency noise. Sum vector magnitude of acceleration and angular velocity, roll, pitch, and vertical velocity were extracted as feature vector. The proposed algorithm showed an accuracy 98.3%, a sensitivity 100%, a specificity 97.0%, and an average lead-time 311±99ms with our experimental data. When evaluated using the KFall public dataset, an accuracy in adult data improved to 99.5% compared to recent studies, and for the elderly data, a specificity of 100% was achieved. When evaluated using FARSEEING real-world elderly fall data without separate segmentation, it showed a sensitivity of 71.4% (5/7).

• Journal of the Korean Society of Radiology
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• v.12 no.5
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• pp.669-675
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• 2018

This study aimed to investigate the difference of X-ray exposure by comparing and analyzing entrance surface dose and absorbed dose according to the frame change in coronary angiography using an X-ray machine. Moreover, appropriate frame selection measures for examination, including the effect of frame change on the image quality, were sought by measuring and analyzing the SNR and CNR of the image through image J. The study was conducted on 30 patients (19 males and 11 females) who underwent CAG at this hospital from June 2017 to October 2017. In regard to the patients, their age range was 49-82 years (mean of $65{\pm}9$ years), body weight was 45-91 kg (mean of $67{\pm}8.9kg$), height was 150-179cm (mean of $165.1{\pm}8.9kg$), and BMI was 19.5-30.5(mean of $24.5{\pm}2.9$). For the entrance surface dose and absorbed dose, air kerma value and DAP were obtained and analyzed retrospectively. The SNR and CNR were measured and analyzed through imageJ, and the result values were derived by applying the values to the formula. As for the statistical analyses, the correlations between the entrance surface dose and absorbed dose, and between the SNR and CNR were analyzed by using the SPSS statistical program. The relationship between the entrance surface dose and absorbed dose was not statistically significant for both 10 f/s and 15 f/s (p>0.05). In terms of the relationship between the SNR and CNR, the SNR ($3.374{\pm}2.1297$) and CNR ($0.234{\pm}0.2249$) in 10 f/s were $1.43{\pm}0.4861$ and $0.132{\pm}0.0555$ lower, respectively, than the SNR ($4.929{\pm}2.8532$) and CNR ($0.391{\pm}0.3025$) in 15 f/s, which were not statistically significant (p>0.05). In the correlation analysis, statistically significant results were obtained among the BMI, air kerma, and DAP; between air kerma and DAP; and between SNR and CNR (p<0.001, p<0.001). In conclusion, there was no significant difference between the entrance surface dose and absorbed dose even when the images were taken by changing the frame from 10 f/s to 15 f/s at the time of the coronary angiography. SNR and CNR increased at 15 f/s than at 10 f/s, but they were not statistically significant. Therefore, this study suggests that the concern of the patient and practitioner regarding image quality degradation, as well as the problem of X-ray exposure caused by imaging at 10 f/s and 15 f/s, may be reduced.