• 대한기계학회논문집A
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• 제21권10호
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• pp.1694-1701
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• 1997

The residual safety assessment of steel structures, an important subject in practice, is given to much attention. Life prediction in the planning course of steel structures under fatigue loading is mainly based on fatigue design criteria resulting from S-N curves. But for any reason cracks have to be assumed due to fabrication failures or fatigue loading in service which can lead total fracture of structures. The life prediction can be carried out by means of fracture mechanics using Paris-Erdogan equation($da/dN=C {\cdot}{\Delta}K^m$). The paper presents results from charpy test to interpret transition behaviour of charpy energy($A_V$) in a wide temperature range and from constant-load-amplitude test to measure fatigue crack growth of various steels widely used in steel bridges since beginning of 20 centuries in Europe. In the normal service temperature range of steel bridges, the steel S355M shows higher maximum charpy energy($A_{Vmax}$) and lower transition temperature($T_{AVmax/2}$) than other steels considered. The C and m of Paris-Erdogan equation on the steels appear to be correlated, and to be affected by the R-ratios due to crack closure, especially at a low fatigue crack growth rate. Scanning electron microscopy analysis was carried out to interpret an influence of the crack closure effects on the correlation of C and m.

• 한국인터넷방송통신학회논문지
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• 제15권2호
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• pp.273-278
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• 2015

증가하는 전력 수요량을 충족시키기 위하여 송전 설비의 전기적인 용량이 커져야 한다. 고전력의 전기를 생산하고 전달하는 설비들은 대규모화될 뿐만이 아니라 높은 신뢰성으로써 동작하여야 한다. 따라서 전기설비가 안정상태에서 동작해야 한다는 것은 매우 중요한 과제이다. 고전력을 전달하기 위한 유일한 수단으로 체택되고 있는 케이블에서 전류에 의하여 줄 열이 발생하며, 열에 의하여 케이블 시스템의 열화가 발생한다. XLPE 케이블의 경우 $90^{\circ}$에서 30년 수명을 보장한다는 조건으로 제작, 설치 및 운영 되고 있으나, 실제 30 년 사용한 시점에서 수명이 종료될 것이라는 보장이 현재로서는 없는 상태이다. 이 논문에서 기존의 수명 이론을 바탕으로 활선 상태의 6.6 kV 케이블 9회선의 온도를 측정하고, 케이블의 온도와 수명의 상관관계를 파악하기 위하여 우리가 제작하여 (주)서부발전에 설치하여 운영하고 있는 장치를 소개한다.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2361-2366
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• 2014

A new aliphatic acid amide, ZP-amide F (1), and eight known compounds, including bungeanumamide A (2), tumuramide C (3), ZP-amide A (4), ZP-amide B (5), ZP-amide D (6), hyperin (7), quercitrin (8), and (-)-sesamin (9), were isolated from pericarps of Zanthoxylum piperitum. The effects of these compounds on $TNF{\alpha}$-induced NF-${\kappa}B$ activation and transactivational activity of PPARs, including $PPAR{\alpha}$, $PPAR{\beta}({\delta})$ and $PPAR{\gamma}$ subtypes, were evaluated. Compounds 7 and 9 exhibited potent inhibitory effects on $TNF{\alpha}$-induced NF-${\kappa}B$ activation with $IC_{50}$ values of 5.50 and $8.10{\mu}M$, respectively. Aliphatic acid amide compounds 3, 4 and 6 displayed enhanced effects on PPAR transactivational activity with $EC_{50}$ values of 47.12, 19.13 and $12.02{\mu}M$, respectively. Among them, compound 4 demonstrated an increase in $PPAR{\alpha}$ transactivational activity, compound 3 showed a moderate increase on all PPAR subtypes, whereas compound 6 displayed weak PPAR transactivational activity.

• 한국축산식품학회지
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• 제34권2호
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• pp.178-184
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• 2014

The application of ganghwa mugwort (GM), ascorbic acid (AC), and their combinations for reduction of residual nitrite contents was analyzed in pork sausages during storage of 28 d. Six treatments of pork sausages contained the following: Control (no antioxidant added), AC (0.05% AC), GM 0.1 (0.1% GM), GM 0.2 (0.2% GM), AC+GM 0.1 (0.05% AC + 0.1% GM) and AC+GM 0.2 (0.05% AC + 0.2% GM). Results showed that the mixture of 0.05% AC and 0.2% GM was most effective for reducing thiobarbituric acid reactive substances (TBARS) and residual nitrite contents than the control and GM added sausages alone (p<0.05). The color values of all treatments were significantly affected by adding GM (either alone or with AC). Additionally, the total color difference (${\Delta}E$) and hue angle ($H^{\circ}$) values of treatments added with GM were higher than those of the control as the amount of GM increased (p<0.05). However, there were no significant differences in the pH values between the control and all treatments during the storage period (p>0.05). Our results showed possible applications of antioxidant combination, for preventing the lipid oxidation and decreasing the residual nitrite levels of meat products.

• 한국컴퓨터그래픽스학회논문지
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• 제24권1호
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• pp.27-33
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• 2018

본 논문은 컬러 이미지대상 고용량 데이터 은닉을 위한 새로운 적응형 least-significant-bit(LSB) 스테가노그라피 알고리즘을 제시한다. 은닉할 데이터 비트와 교체하기 위한 컬러 이미지 픽셀의 빨강, 초록, 파랑 (RGB) 컴포넌트의 LSB 비트 수는 peak signal noise ratio (PSNR) 최저값 분석을 통해 결정하였다. 은닉 데이터의 70%는 픽셀의 두 색상 컴포넌트 LSB 3비트를, 나머지 컴포넌트 LSB 2 비트를 교체하고, 30%는 모든 RGB 컴포넌트 LSB 4비트를 교체하는 조합을 제안한다. 또한, 데이터를 은닉할 에지영역 픽셀 선택을 위하여 지역적인 정렬방법도 제안한다. 본 방법은 픽셀 당 9.2 비트(9.2bpp)의 고용량 은닉이 가능하다. 30K - 60K바이트 데이터 은닉 실험결과 512x512 컬러 이미지의 평균 PSNR값은 43.9db이고 자연스러운 히스토그램도 도출되었다.

• 한국해양공학회지
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• 제4권2호
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• pp.250-250
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• 1990

In this paper, fatigue tests were carried out at stress test levels of 461 MPa, 441 MPa, and 431 MPa by using smooth specimen of$2_{1/4}$ Cr-1 Mo steel with the stress ratio(R) of 0.05. The initiation, growth and coalescense process of the major cracks and sub-cracks among the fatigue cracks on the smooth specimen are investigated and measured under each stress level at a constant cycle ratio by the replica technique with optical microscope. Some of the important results are as follows: In spite of the difference of stress levels, the major crack data gather into a small band in the curve of surface crack length and crack depth against cycle ratio N/Nf. The sub-crack data, however, deviate from the band of the major crack. The growth rates, da/dN, of major and sub-crack plotted against the stress intensity factor range, ${\Delta}K$, have the tendency to be compressed on a relatively small band. But it is more effective to predict fatigue life through major cracks. The propagation behavior of surface microcracks on the smooth specimens coincides with that of the specimen having an artificial small surface defect or through crack.

• 한국세라믹학회지
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• 제51권3호
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• pp.170-176
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• 2014

Effective glass frit compositions enabled to absorb laser energy, and to seal a commercial dye-sensitized solar-cell-panel substrate were developed by using $V_2O_5$-based glasses with various amounts of $TeO_2$ substitution. The latter was intended to increase the lifetime of the solar cells. Substitution of $V_2O_5$ by $TeO_2$ provided a strong network structure for the glasses via the formation of tetrahedral pyramids in the glass, and changed the various glass properties, such as glass transition temperature ($T_g$), dilatometric softening point ($T_d$), crystallization temperature, coefficient of thermal expansion (CTE), and glass flowage without any detrimental effect on the laser absorption property of the glasses. The thermal expansion mismatch (${\Delta}{\alpha}$) between the glass frit and the substrate could be controlled within less than ${\pm}5%$ by addition of 10 wt% of ${\beta}$-eucryptite. An 810 nm diode laser was used for the sealing test. The laser sealing test revealed that the VZBT20 glass frit with 10 wt% ${\beta}$-eucryptite was successfully sealed the substrates without interfacial cracks and pores. The optimum sealing conditions were provided by a beam size of 3 mm, laser power of 40 watt, scan speed of 300 mm/s, and 200 irradiation cycles.

• Journal of Nutrition and Health
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• 제24권6호
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• pp.547-559
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• 1991

The purposes of this study were to : a)determine the percentage of labor activities expen-ded in various work functionsof hospital foodservice b)estimate the labor time utilized in each work functions c)investigate the overall work patterns of hospital foodservice and d)provide the basic data for effective labor control This study was conducted in two hospitals with 1300 and 1200 ed capacities and every employees of the dietary department were included in 10days work measurement. Work sampling methodology developed by Donaldson and Ostenso was modified and used for observing overall activities of hospital dietary department. Consistency of data and observa-tion period were verified by 3$\delta$ control chart and control chart. Observed data were satisfied with confidence level of 95% and confidence interval of $\pm$0.05, The results of this study were as follows: 1) The direct work function indirect work function and delay were 74.8%, 9.2%, 16.0% respectively with A hospital and 82.2% 7.2%, 10.6% respectively with B hospital 2) The productivity indices of direct work indirect work and delay were 9.05 min/meal 1.12 min/meal 1.94 min/meal respectively and total 12.11 minutes were utilized per meal served in A hospital and 10.72 min/meal 0.94 min/meal 1.38 min/meal respectively and total 13.04 minutes were utilized per meal served in B hospital 3) Full time equivalent(FTE) utilized in daily work of irect work indirect work and delay were 62.24 men 7.69 men 13.35 men respectively in A hospital and 64.09 men 5.63 men 8.22 men respectively in B hospital. 4) The contents of work activities of each employee group showed that delay time of the service personnel group was more than any other employee groups in both A hospital and B hospital 5) Examination of daily work schedule by time intervals showed that transportation work function was carried out all day so it is necessary to improve this work.

• 대한토목학회논문집
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• 제8권2호
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• pp.167-175
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• 1988

본 연구의 목적은 변동하중을 받는 구조부재의 피로거동을 해석하는 것이다. 이 연구의 해석과정은 다음과 같다. (1) 도로교의 실동응력파측정 및 통계적해석 (2) 등가의 일정진폭하중과, 통계적해석에 의해 모형화된 변동하중하(下)의 피로시험 (3) 등가응력개념의 RMC 모델에 의한 변동하중하(下)의 피로해석 등가응력개념에 의한 변동하중하(下)의 피로해석은 대부분의 구조용강재의 균열성장속도회귀지수가 $m{\fallingdotseq}3$이므로 이론적으로 RMC 모델이 합당하다. 변동하중하(下)의 피로시험해석결과 RMC 모델이 기존의 RMC 모델보다 변동하중에 의한 피로거동치(da/dN-${\Delta}K$, $N_f$)에 더 가까웠다. 또 변동하중하(下)에서 응력범위의 변화로 인한 interaction효과나 응력범위적용순서(sequence)효과 등은 피로수명에 거의 영향을 미치지 않으며, 응력범위변화속도가 클수록 피로균열성장속도가 빨라짐을 알 수 있었다.

• Journal of Biosystems Engineering
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• 제40권1호
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• pp.61-66
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• 2015

Purpose: The purpose of this study was to establish conditions to dry a radish by examining the drying and quality characteristics depending on the air temperature and velocity of a far infrared conveyor dryer. Methods: A sample of weighing 6 kg was dried until the moisture content reached $15{\pm}0.5%$ (w.b.). Four temperatures (50, 60, 70, and $80^{\circ}C$) and three air velocity levels (0.4, 0.6, and 0.8 m/s) were employed as the drying factors. Results: The drying rate increased with the increase in the temperature and air velocity but decreased with time. However, the drying rate was influenced by temperature rather than velocity. At a temperature $50^{\circ}C$ with a air velocity of 0.4 m/s, it took 350 min for the radish to dry which was the longest drying time; $80^{\circ}C$ with a air velocity of 0.8m/s, it took 180 min for the radish to dry, which was the shortest drying time. ${\Delta}E$ (the color difference value) increased with the increase in temperature and air velocity. The browning and rehydration ratio increased as the temperature rose. Energy consumption decreased with the increased temperature and air velocity. Conclusions: Based on the results of this study, the best drying conditions for the radish were determined to be a temperature of $70^{\circ}C$ with an air velocity of 0.8 m/s.