• 한국재료학회지
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• 제9권8호
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• pp.810-816
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• 1999

유성밀로써 사문석과 활석을 분쇄시 X-ray 회절분석, FT-IR, DSC-TG, 입도분석 그리고 SEM관찰 등을 이용하여 결정조직과 물리적 특성변화를 조사하였다. 분쇄기간이 증가함에 따라 사문석과 활석 원시료의 결정피크가 점처 감소하여 120분 이상 분쇄시 비정질상으로 변하였으며 이와 같은 변화는 마그네슘 결정 조직의 무질서에 기인한다. 분쇄된 시료에서 나타나는 흡열반응의 피크는 원시료보다 낮은 온도에서 관찰되었다. 또한 불규칙한 모양의 원시료는 분쇄처리를 실시함에 따라 구형의 응집체로 변하였다.

• Geomechanics and Engineering
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• 제17권5호
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• pp.439-444
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• 2019

It is generally known that high strength soil is indicative of well-graded particle size distribution. However, there are some special cases of firm ground despite poor grade distribution, especially a specific gap-graded soil. Based on these discoveries, this study investigated the development of an additive of gap-graded soils designed to increase soil strength. This theoretical concept was used to calculate the mixed ratio required for optimal soil strength of the ground sample. The gap-graded aggregate was added according to Plato's polyhedral theory and subsequently calculated ratio and soil strength characteristics were then compared to characteristics of the original soil sample through various test results. In addition, the underground stress transfer rate was measured according to the test conditions. The test results showed that the ground settlement and stress limit thickness were reduced with the incorporation of gap-graded soil. Further field tests would confirm the reproducibility and reliability of the technology by using gap-graded soil to reinforce soft ground of a new construction site. Gap-graded soil has the potential to reduce the construction cost and time of construction compared to other reinforcing methods.

• Korean Chemical Engineering Research
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• 제51권6호
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• pp.685-691
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• 2013

이부프로펜은 비스테로이드성 소염진통제(Non-Steroidal Anti-Inflammatory Drugs; NSAIDs)의 대표적인 성분이다. 이부프로펜은 결정성이 크기 때문에 난용성이며, 따라서 생체이용률(bioavailability)도 낮다. 이와 같은 난용성을 개선하기 위해서는 이부프로펜의 입도를 감소시킬 필요가 있다. 본 연구의 목적은 이부프로펜의 분쇄조건을 최적화하는데 있다. 이부프로펜을 분쇄하기 위하여 유성밀을 사용하였으며, Box-Behnken 방법을 이용하여 분쇄변수들의 최적조건을 구하였다. 이부프로펜 분쇄생성물의 물성을 조사하기 위하여 입도, 결정크기 및 인장강도 측정에는 각각 입도분석기, XRD, tensile/compression tester를 사용하였다. 분쇄 최적조건은 밀회전수는 290 rpm, 시료장입량은 24.6 g, 분쇄시간은 10분이었으며, 이 조건에서 이부프로펜 분쇄생성물의 입도는 $13.5{\mu}m$이었다. 이부프로펜은 분쇄 후 결정크기가 감소하였다. 이부프로펜 분쇄생성물의 정제의 상대밀도가 0.85~0.90인 범위에서 그 정제의 인장강도는 $12{\sim}14Kg_f/cm^2$ 이었다.

• 한국산학기술학회논문지
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• 제7권4호
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• pp.625-634
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• 2006

이 논문에서는 FIR(Finite Impulse Response) 필터의 연산의 양을 줄이는 효율적인 직접방식의 고속 알고리즘을 제안하였다. 제안된 알고리즘은 임의의 다운샘플링 크기로 병렬화가 가능하며, 다운샘플링의 크기가 결정되면 쉽게 구조를 유도할 수 있다. 특히 제안된 알고리즘은 이론적인 샘플당 곱셈연산의 수를 감소시킴과 동시에 실제 구현에 있어서도 효과가 있음을 실험을 통하여 입증하였다. 이론적으로 연산의 양이 감소함을 보이기 위하여 부필터의 수와 샘플당 곱셈연산의 수를 기존의 고속 알고리즘과 비교하였으며, 실제적으로 구현의 효과를 입증하기 위하여 하드웨어 구현소자의 수와 Verilog-HDL (Hardware Description Language) 구현으로 기존의 방식들과 비교하여 제안된 구조가 효과적임을 보였다.

• 설비공학논문집
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• 제2권3호
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• pp.243-255
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• 1990

The objective of this study is to present an efficient measurement method of the effective thermal diffusivity for the fibrous insulation material. The non-linear parameter estimation (NPE) method is adapted for this analysis because of its accuracy and its results are compared with those by other direct methods such as CTP, CHP and STD method. A experimental system is constructed with bell-jar vaccum chamber, diffusion pump, tube type furnace, control unit and data acquisition system included with A/D converter and IBM XT/AT personal computer. The typical results obtained from this study are as follows; 1) NPE method can be recommended as an useful and accurate method to measure the effective thermal diffusivity of insuation material because it is shown that the measurement error compared with those by other direct methods is reduced for standard material, NBS-1450b. 2) NPE method can minimize the effects of ill-measured temperature due to external disturbance, because the final value is found by point to point estimating. 3) NPE method dose not depend on the kinds of heat flux, since the surfac temperature are used to estimate the thermal diffusivity. 4) With NPE method, compared with the steady state method, a measuring time and a sample size could be reduced.

• E2M - 전기 전자와 첨단 소재
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• 제9권6호
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• pp.605-615
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• 1996

In this paper, the effect of alkaline oxide addition such as Li$_{2}$O and Na$_{2}$O on the microstructure and humidity sensitivity of V$_{2}$O$_{5}$(2 mol%)-doped TiO$_{2}$(98 mol%) was investigated as a function of amount (0, 1, 2, 5, 10 mol%) of Li$_{2}$O and Na$_{2}$O additives. The pores in the alkaline free sample were distributed mostly in the range between 0.16 and 1.0.mu.m in diameter and its porosity was 23.29%. Li$_{2}$O caused grain overgrowth and reduced the porosity with a narrow distribution of the pore size, leading to poor humidity sensitivity. Na$_{2}$O helped to enlarge the distribution of the pore size through the formation of small soluble phases. The pore sizes of the sample containing Na$_{2}$O 2mol% were distributed mostly in the range between 1.0 and 2.5.mu.m in diameter and its porosity and intrusion volume of mercury were 31.13 % and 0.1155 mL/g respectively, which consequently improved the humidity sensing characteristics such as the sensitivity and temperature-stability. Especially, the addition of 2mol% of Na$_{2}$O improved the humidity-sensing characteristics such as sensitivity and linearity in the whole range between 30 and 90 %RH (Percentage Relative Humidity)y)

• 문화경제연구
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• 제20권2호
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• pp.3-18
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• 2017

본 연구에서는 콘텐츠산업 인력의 업무 자율성 변화를 분석했다. 한국근로환경조사(2011, 2014) 자료에서 콘텐츠산업 인력과 업무 자율성 변수를 추출하고 이중차감추정법을 활용하여 분석한 결과 전체 표본에서는 콘텐츠산업 인력의 업무 자율성(업무 순서, 업무 방법, 업무속도)에 유의미한 변화가 나타나지 않았다. 반면 최근 콘텐츠업계의 자율성 감소는 논의는 대규모 인력과 자본이 투입되는 경우라는 것을 고려하여 30인 이상 사업체 표본을 대상으로 분석하면 콘텐츠산업 인력의 자율성이 유의미하게 감소한 것으로 나타난다. 업무의 자율성은 직위와 역량과는 정(+)의 관계가, 사업체 규모와는 부(-)의 관계가 나타난다. 본 연구는 그동안 사례 중심으로 논의되어 왔던 콘텐츠산업 인력의 업무 자율성 변화를 실증분석했다는 의의를 가진다. 또한, 인력들의 부여되는 자율성이 콘텐츠 제작 유통 과정에서 긍정적인 효과를 창출하기 위해서는 인력에 대한 보상 및 관리 체계 개선이 수반되어야 함을 제시하였다.

• 간호행정학회지
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• 제19권1호
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• pp.108-117
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• 2013

Purpose: To analyze trends in salaries for registered nurses when compared with salaries for elementary school teachers from 2002 to 2009 and identify salary gaps of nurses according to workplace size and geographic location. Methods: Data were obtained from the Occupational Employment Statistics collected by the Korea Employment Information Services each year from 2002 to 2009. The study sample consisted of 2,281 registered nurses and 2,578 elementary school teachers. Linear multiple regression analyses were conducted to analyze salary trends and differences. Results: Elementary school teachers had higher monthly salaries than nurses with a baccalaureate degree after adjusting for years of work. Salary differences increased significantly by 40,000 won every year (p<.001). Nurses working in large facilities in Seoul had the highest salaries, whereas those in small/medium, non-Seoul facilities had the lowest salaries consistently over time. Salary differences between the two groups increased by 47,000 won every year (p=.001); salary differences between nurses in large, non-Seoul facilities and those in small/medium, non-Seoul facilities also increased by 40,000 won annually (p=.001). Conclusion: Geographical imbalances in the nurse workforce and nurse shortages in small/medium, non-capital facilities could be reduced by increasing the salary of nurses working in those facilities.

• 한국분말재료학회지
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• 제25권2호
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• pp.126-131
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• 2018

In the present study, we investigate the effects of milling time and the addition of a process control agent (PCA) on the austenite stability of a nanocrystalline Fe-7%Mn alloy by XRD analysis and micrograph observation. Nanocrystalline Fe-7%Mn alloys samples are successfully fabricated by spark plasma sintering. The crystallite size of ball-milled powder and the volume fraction of austenite in the sintered sample are calculated using XRD analysis. Changes in the shape and structure of alloyed powder according to milling conditions are observed through FE-SEM. It is found that the crystallite size is reduced with increasing milling time and amount of PCA addition due to the variation in the balance between the cold-welding and fracturing processes. As a result, the austenite stability increased, resulting in an exceptionally high volume fraction of austenite retained at room temperature.

• Journal of Computational Design and Engineering
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• 제1권4호
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• pp.223-232
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• 2014

This paper describes a variant of the extended Gaussian image based registration algorithm for point clouds with surface color information. The method correlates the distributions of surface normals for rotational alignment and grid occupancy for translational alignment with hue filters applied during the construction of surface normal histograms and occupancy grids. In this method, the size of the point cloud is reduced with a hue-based down sampling that is independent of the point sample density or local geometry. Experimental results show that use of the hue filters increases the registration speed and improves the registration accuracy. Coarse rigid transformations determined in this step enable fine alignment with dense, unfiltered point clouds or using Iterative Common Point (ICP) alignment techniques.