• 한국산학기술학회논문지
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• 제22권2호
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• pp.632-637
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• 2021

현재 미래의 건설 산업 기술을 발전시키고자 최근 미래 산업으로 각광받고있는 3D 프린팅을 이용한 콘크리트의 시공기술을 활용하여 구조물을 건설하는 연구가 국내외 건설업계 및 학계에서 활발히 진행되고 있다. 하지만 현재 개발되고 있는 3D 프린팅 기술은 적합한 시공기술, 콘크리트 재료 자체의 물성이 사용기준에 미치지 못하고 실제 현장에서 적용하기가 어려운 상황이다. 또한 시공된 구조물에 대한 내구성 관리 및 유지관리를 위한 연구가 필요한 실정이다. 본 연구에서는 Material extrusion 방식으로 출력한 3D 프린팅 콘크리트를 각각의 적층 방향 X, Y, Z축으로 나누어 측정한 압축강도와 휨강도를 기존의 몰드에 제작한 시험체와 비교 분석하였다. Test direction II Z축의 시험체의 압축강도가 나머지 Test direction I, III Y축, X축의 시험체에 비하여 8~10%의 높은 강도를 발현하였고 몰드 제작 시험체와 비교하였을 경우 4%가량 낮은 강도를 발현하였다. 휨강도 측정결과 재령 28일 기준으로 Test direction II Z축 방향의 시험체의 휨강도가 Test direction I, III Y축, X축의 시험체에 비하여 5~7%의 높은 강도를 발현하였고 몰드 제작 시험체와 비교하였을 경우 2%가량 낮은 강도를 나타내었다.

• 대한영양사협회학술지
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• 제4권1호
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• pp.76-87
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• 1998

The purpose of this study was to examine the nutrition knowledge and attitude of the elderly for developing nutrition education program. The nutrition knowledge test was consisted of nutrition, nutrients, weight control, food safety, and shopping tips by developing the table of specifications. The nutrition attitude test was comprised of seventeen questions for invention, self-efficacy, control, and outcome expectation. A total of 140 elderly living at home responded to both nutrition knowledge and attitude test. According to the results of nutrition knowledge test, the mean was 13.3 at the maximum 18 points and 51.4% respondents got more than 14 points. Significant differences were found with age (p<0.05, $x^2$=21.46), charge of income (p<0.05, $x^2$=8.86) and monthly expenses(p<0.05, $x^2$=22.95). The results of nutrition attitude test showed that the mean value of 40.89 points at the maximum 51 points and 58.6% of respondents rated more than 40.89 points. In exploring the relationship between the demographic variables(sex, age, educational level, and monthly expenses) and for attitude concepts, a significant correlation was found. Correlation among the knowledge for nutrition, nutrients, and the attitudes for nutrition was significant(p<0.05).

• Transactions on Electrical and Electronic Materials
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• 제18권1호
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• pp.46-50
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• 2017

The Zn1-xMnxO ($0.00{\leq}x{\leq}0.06$) samples have been synthesized in the form of powder by the coprecipitation method at low temperature using $Zn(CH_3COO)_2$. $2H_2O$ and $Mn(CH_3COO)_2$. $4H_2O$ powders, as well as HCl and $NH_4OH$ solutions as starting materials. Characterization was conducted using XRD, TEM, XRF, FTIR and VSM. The result shows that the $Zn_{(1-x)}Mn_xO$ ($0.00{\leq}x{\leq}0.06$) nanoparticles have the wurtzite phase with a hexagonal structure and particle sizes ranging from 17.48 to 118.83 nm. In a qualitative analysis of XRF, the peaks that confirm the existence of the manganese element in Mn-doped ZnO samples were observed. Meanwhile, FTIR test result shows that there are peaks at around $500cm^{-1}$ and $400cm^{-1}$ in the FTIR spectra for Mn doped ZnO samples which clearly reveal the existence of the (Zn, Mn)-O strain mode. The (Zn, Mn)-O absorption peak positions have shifted to a lower wave number with increasing Mn doping content. The peak intensity is also lower if compared to that of the ZnO sample without doping. From the VSM test, it is shown that $Zn_{(1-x)}Mn_xO$ ($0.00{\leq}x{\leq}0.06$) nanoparticles are all paramagnetic having monotonically increased susceptibility as increasing Mn content.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.228-231
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• 1996

We prepared $LiCo_{1-x}Ni_{x}O_2$ by reacting stoichiometric mixture of LiOH.$H_2O$, $CoCO_3$.$xH_2O$ and $Ni(OH)_2$ (mole ratio respectively) and heating at $850^{\circ}C$ for 5h. We awared through XRD that from 0 to 0.5 at x in $LiCo_{1-x}Ni_{x}O_2$ is well formed for hexagonal structure, but the more $LiCo_{1-x}Ni_{x}O_2$ involve NI, the more hexagonal structure is not well formed. In the result of charge/discharge test, charge/discharge characteristic of $LiCo_{1-x}Ni_{x}O_2$ is similar to that of $LiCoO_2$. Therefore, $LiCo_{1-x}Ni_{x}O_2$ is superior to $LiCoO_2$ for Li secondary battery

• 한국농공학회지
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• 제30권2호
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• pp.82-94
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• 1988

The purpose of this study is to introduce the Double Punch test method which is an indirect testing method of tensile strength of concrete, and to compare with the tensile strength of concrete as determined by the split-cylinder test, a practical method for performing the Double Punch test to obtain the tensile strength of concrete is proposed and recommended for general use. In this study, the dimensions of cylindrical specimens used in the Double-Punch test were 15X30cm, 15X15cm, 10${\times}$(20cm, and 5${\times}$l0cm, and in the split-cylinder test were 15${\times}$(30cm, 15${\times}$(15cm, and 10${\times}$(20cm. And the diameters of loading punches used in the Double-Punch test were 1.5cm, 2.5cm, and 3.5 cm. The results obtained from tests are summarized as follows ; 1. In the split-cylinder test, the tensile strength of concrete by the linear elasticity theory is similar to that of plasticity theory. 2. Both split-cylinder test and Double-Punch test, tensile strength of concrete is increased with decreasing specimen size. This tendency is identical when the ratio of specimen diameter to height is 1: 2, but that tendency is quite different when the ratio is 1: 3. In the Double-Punch test, if specimen size is constant, by increasing the punch size, tensile strength of concrete is increased, too. 4. Using a 15 ${\times}$( 15 cm cylinder specimen and 3.5 cm diameter punch in the Double Punch test would give the most uniform and consistent result in tensile strength, and the result showed a gQod correlation with splitting tensile strength from 15 x 30cm specimen. 5. In order to obtain satisfactory results and to nuninuze variability, it is proposed that specimens of 15 cm in diameter and 15 cm in height with two 3.5 cm diameter punches should be used. It seems, therefore, reasonable tt) take f't=0.0024 P(kg / cm$^2$) as a working formula for computing the tensile strength in the Double Punch test for concrete.

• 한국세라믹학회지
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• 제34권9호
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• pp.921-926
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• 1997

Two NbCx-C1-x/Y2O3/Ti sputter-coated Al2O3 substrates (L 5.5 cm$\times$W 0.5 cm) were diffusion bonded together using hot press method at 95$0^{\circ}C$ for 3 hours under 1 MPa of applied pressure. 4 points bending tests were used to evaluate the mechanical performance of these precracked laminate beams. Two types of mechanical responses were observed: crack penetration through the interface for x=0.75, 1 and crack deflection into an interface for x=0.25, 0.5. The Al2O3/NbCx-C1-x/Y2O3/Ti system suggested here has been proves to be effective for the thermokinetical stability and tailorability of the interfaces of Al2O3/Ti composites at 95$0^{\circ}C$.

• 항공우주기술
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• 제4권1호
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• pp.103-107
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• 2005

아리랑위성 2호는 수집된 위성 영상의 지상 전송을 위해서 X-대역의 통신 시스템을 갖추고 있으며, 지향 조절이 가능한 고이득의 X-대역 안테나를 가지고 있다. 지상 시험 시에는 위성 안테나의 성능을 시험하여야 하기 때문에 비행 구성 그대로의 시험이 필요한데, 현재 X-대역 구성에 의하면 RF 출력이 너무 강하기 때문에 안전성에 문제가 있을 가능성이 있다. 또한, 발사장에서는 비행모드 구성을 유지하기 위해서 안테나 방사를 반드시 이루어야 하는데, 발사장 시험 시설에서는 RF의 방사를 제한하고 있기 때문에 어려움이 따른다. 따라서 안테나의 RF 방사를 제한하는 안테나 햇의 제작이 필요하며, 제작된 햇은 위성의 안정성을 위해 철저하게 검증이 되어야 한다.

• 한국방사선학회논문지
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• 제14권1호
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• pp.39-44
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• 2020

본 연구에서는 CNN과 빅데이터 기술을 이용한 Deep Learning을 통해 흉부 X-ray 영상 분류 및 정확성 연구에 대하여 알아보고자 한다. 총 5,873장의 흉부 X-ray 영상에서 Normal 1,583장, Pneumonia 4,289장을 사용하였다. 데이터 분류는 train(88.8%), validation(0.2%), test(11%)로 분류하였다. Convolution Layer, Max pooling layer pool size 2×2, Flatten layer, Image Data Generator로 구성하였다. Convolution layer가 3일 때와 4일 때 각각 filter 수, filter size, drop out, epoch, batch size, 손실함수 값을 설정하였다. test 데이터로 Convolution layer가 4일 때, filter 수 64-128-128-128, filter size 3×3, drop out 0.25, epoch 5, batch size 15, 손실함수 RMSprop으로 설정 시 정확도가 94.67%였다. 본 연구를 통해 높은 정확성으로 분류가 가능하였으며, 흉부 X-ray 영상뿐만 아니라 다른 의료영상에서도 많은 도움이 될 것으로 사료된다.

• 한국표면공학회지
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• 제34권2호
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• pp.125-134
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• 2001

($Ti_{1-x}$ $Cr_{x}$ )N coatings were deposited by an ion-plating method in a reactor with two separate metal sources, Ti and Cr. Ti was evaporated using an electron beam, while Cr evaporation was carried out by resistant heating. The Ti and Cr concentrations in the coatings were controlled by the Ti and Cr evaporation ratio. The coating hardness increased with increasing the Cr content(x) and showed a maximum value of 6,000 HK at around x=0.8. The critical load of the coatings, measured by the scratch test, was around 30 N. The wear resistance properties of the ($Ti_{1-x}$$Cr_{ x}$)N coatings were evaluated using a CSEM pin-on-disk type tribometer. A Cr-steel ball as well as a SiC ball, which had hardness values of 590 HK and 2,600 HK respectively, were used as the pin. After the wear test, the surface morphology, roughness and the concentration of the coatings were investigated, with the main focus being on the effect of wear debris and the transferred layer on the wear behavior.

• Journal of Radiation Protection and Research
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• 제41권2호
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• pp.111-115
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• 2016

Background: The scattered photons cause reduction of the contrast of radiographic image and it results in the degradation of the quality of the image. In order to acquire better quality image, an anti-scattering x-ray gird should be equipped in radiography system. Materials and Methods: The X-ray anti-scattering grid of the inclined type based on the hybrid concept for that of parallel and focused type was tested by MCNP code. The MCNPX 2.7.0 was used for the simulation based test. The geometry for the test was based on the IEC 60627 which was an international standard for diagnostic X-ray imaging equipment-Characteristics of general purpose and mammographic anti-scatter grids. Results and Discussion: The performance of grids with four inclined shielding material types was compared with that of the parallel type. The grid with completely tapered type the best performance where there were little performance difference according to the degree of inclination. Conclusion: It was shown that the grid of inclined type had better performance than that of parallel one.