• 대한기계학회논문집A
• /
• 제24권2호
• /
• pp.378-385
• /
• 2000

Fracture resistance (J-R) curves, which are used for elastic-plastic fracture mechanics analyses, decreased under tension-compression loading condition. This phenomenon was proved by several former researches, but the causes have not been clear yet. The objective of this paper is to investigate the cause of this phenomenon. On the basis of fracture resistance curve test results, strain hardening hypothesis, stress redistribution hypothesis and crack opening hypothesis were built. In this study, hardness tests, Automated Ball Indentation(ABI) tests, theoretical stress field analyses, and crack opening analyses were performed to prove the hypotheses. From this study, strain-hardening of material, generation of tensile residual stress at crack tip, and crack opening effects are proved as the causes of the decrease hypothesis.

• Membrane and Water Treatment
• /
• 제4권2호
• /
• pp.127-142
• /
• 2013

In order to investigate the significance of "salting-out" and "pore swelling" effects on the nanofiltration of neutral solutes, rejection properties of two NF ceramic and polymeric membranes were studied with single polyethyleneglycol (PEG) solution and mixed PEG/inorganic electrolyte solutions. For both membranes, the rejection rate of PEG was found to decrease significantly in the presence of ions. In the case of the ceramic membrane (rigid pores), this phenomenon was imputed to the sole partial dehydration of PEG molecules induced by the surrounding ions. This assumption was confirmed by the lowering of the PEG rejection rates which followed the Hofmeister series. Experimental data were used to compute the resulting decrease in the Stokes radius of PEG molecules in the presence of the various salts. Concerning the polymeric membrane, the decrease in the rejection rate was found to be systematically higher than for the ceramic membrane. The additional decrease was then ascribed to the swelling of the pores. The experimental data of rejection rates were then used to compute the variation in the mean pore radius in the presence of the various salts. The pore swelling phenomenon due to accumulation of counterions inside pores was supported by electrokinetic charge density measurements.

• 한국화재소방학회논문지
• /
• 제20권2호
• /
• pp.80-86
• /
• 2006

본 고찰은 화재시 고강도 콘크리트의 주요 이슈 중의 하나인 폭열 현상에 초점을 맞추어 폭열의 정의, 분류 및 각각의 특징, 발생원인과 그 반응기구에 대하여 선행연구를 중심으로 분석하였다. 폭열은 급격한 온도 상승, 높은 수분 함유량, 낮은 물시멘트비(W/C), 콘크리트 내에 국부적인 높은 응력 발생 등과 같은 요인이 복합적으로 작용하여 발생한다. 이러한 요인을 토대로 폭열을 방지하기 위한 방법으로 크게 콘크리트의 온도 상승을 억제하는 방법, 콘크리트의 비산을 억제하는 방법, 그리고 빠르게 내부 수분을 건조시키는 방법 등을 들 수 있다. 본 고찰에서는 이러한 방법 가운데 가장 효율적인 폭열 방지 방안으로서 콘크리트 내부의 수분을 빠르게 건조시킴으로써 폭열에 이르게 하는 함수율 이하로 낮추어서 콘크리트 자체의 내폭열성을 높이는 방안을 고찰하였다. 실제 강제건조를 통해 함수율을 어떤 임계치(critical value) 이하로 낮추게 되면 폭열을 방지할 수 있으며 이를 위해서는 수동적인 자연건조 외에 강제건조 등으로 함수율을 낮출 필요가 있을 것이다. 이러한 임계치 결정을 위해 추가적인 많은 실험 및 자료가 도출되어야 할 것이다.

• 가족자원경영과 정책
• /
• 제19권3호
• /
• pp.17-40
• /
• 2015

The purpose of this study was to analyze the in-home child care support service experience of twenty child rearing families. In order to conduct this study, grounded theory method was employed. The central phenomenon of the service experience digged out from this study was 'difficulty' (i. e. insecurity and a feeling of helplessness). The causal conditions which brought about the central phenomenon were 'defect of system' and 'service characteristics' The intervening conditions included 'alternative resources' 'working conditions' and 'service institute manager discretion'. The contextual conditions consisted of 'maternal ideology' 'the public nanny's personality awareness'. The action/interaction strategies on the central phenomenon were 'inaction' 'insecurity decrease strategy' and 'dissonance decrease strategy. The final outcome was 'rearing gap fillup "the method of nanny managing" dissatisfaction accumulation' ''system improvement demand'. The families were classified as four types: 'management/subject' 'adaptation/dependent' 'patience/acceptant' 'supplementation/overcoming'. Based on these results, this study provided a few political and practice suggestions to improve this system.

• 전기학회논문지
• /
• 제65권8호
• /
• pp.1392-1399
• /
• 2016

Blackout effect occurs when a driver misadapts to the changed lighting conditions upon entering a tunnel. This could lead to a decrease in visibility especially in the daylight, depending on the difference in the degree of brightness between inside and outside the tunnel. To alleviate such a problem, we decrease windshield transparency before the driver arrives at the tunnel entrance. Controlled amount of light inside the car can allow the drivers to adjust to the dark prior to entering. The windshield transparency coefficient is to be determined by the arrival time at the tunnel and difference in the level of brightness between inside and outside the tunnel. Navigation, road sign detection, and tunnel entrance detection provide the arrival time. We also designed an opto-electronic conversion function to estimate the level of brightness. The black-hole phenomenon alleviation method is verified by field experiments using an automobile camera and a navigation. The result shows that the adjusted windshield transparency is able to provide an environment with a comfortable level of brightness with which the drivers can enter tunnels without the visibility problem.

• 한국환경보건학회지
• /
• 제1권1호
• /
• pp.5-8
• /
• 1974

A survey was carried out in order to figure out of phenomenon of increasing and decreasing rate of WBC during a day in normal and healthy person from Oct. 1, 1972 to Nov. 31, 1972. For this survey, it was classified by two groups 50 male students and 35 female students who are from 18 to 25 years old. The blood sampling was collected by thin smear method 8 times from 7:30 A.M. to 10:30 P.M. by 2 hours intervals and calculated by direct manual method. As the results of this survey, the following conclusions were obtained 1) Number of WBC was the lowest degree during the forenoon, and it was the highest degree around the midnight. It was increase from around the noon up to the midnight and decrease from the midnight up to around the noon. 2) Increasing and decreasing curve of WBC of male and female was keeping same pace with both sex in a day. 3) Increase and decrease of lymphocyte and eosinophil was keeping almost same pace with WBC. 4) Increasing rate of number of monocyte was more speedily increasing during the afternoon than the night.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
• /
• pp.9-11
• /
• 2003

Image sticking, the phenomenon that the previously displayed pattern still remains after the image is changed into different image, is one of the most serious problem in realizing high picture quality. There are various methods decreasing the image sticking phenomenon. In this paper, we have tried to decrease boundary image sticking by reducing the discharge concentration phenomenon in the boundary of pattern using the new driving method that is applied to bias in the address electrode.

• 한국태양에너지학회:학술대회논문집
• /
• 한국태양에너지학회 2008년도 춘계학술발표대회 논문집
• /
• pp.241-246
• /
• 2008

In this paper, we analyze the I-V curve and hot-spot phenomenon caused by solar cells' serial and parallel connected circuit. The mis-match loss of parallel interconnection with low Isc string decrease lower than serially interconnected one and temperature caused by hot-spot does. Also, mis-match loss of parallel interconnection with low Voc string increase more than serially interconnected one. The string having low Voc happened hot-spot phenomenon when open circuit. The bad solar cell in string gives revere bias to good solar cell and make hot-spot phenomenon. If we consider the mis-match loss, when designing PV module and array. the efficiency of PV system might increase.

• 오토저널
• /
• 제11권4호
• /
• pp.35-42
• /
• 1989

The major purpose of this paper is a study on the effect of die profile radius on the formability of spring-type blankholder system in deep drawing process. By drawing the various materials, formability is studied by means of checking the drawing force, blankholding force variation, limiting drawing ratio and wall wrinkling phenomenon. As the die profile radius increases, the maximum drawing force and maximum blankholding force decrease regardless of lubrication condition. Because better lubrication induces blankholding force to rise, spring type blankholder system is better to protect flange wrinkling phenomenon than constant pressure type. And wall wrinkling phenomenon was not detected in experimental die radius range, so the Miyakawa's upper wrinkling limit is understimated in case of material tested.

• The Korean Journal of Physiology
• /
• 제23권2호
• /
• pp.329-337
• /
• 1989

Cardiac muscles show stimulation frequency-dependent tension changes i.e. Bowditch phenomenon and Woodworth phenomenon, the former is an increase of tension with the increase of stimulation frequency, whereas the latter is an increase of tension with a decrease of stimulation frequency. Bowditch phenomenon is seen in the range of frequency 1.0 cps and above, and Woodworth phenomenon below the frequency 1.0 cps in the most of mammalian cardiac atrium. To throw some light on the possible mechanism of both phenomena in rat atrium, influences of drugs affecting $Ca^{2+}$ influx through the plasma membrane $(verapamil,\;La^{3+},\;norepinephrine)$ and $Ca^{2+}$ release from sarcoplasmic reticulum (SR) on frequency-tension curve were studied. The results obtained are summarized as follows: 1) At low temperature $(27.5^{\circ}C)$, both Bowditch and Woodworth phenomenon were demonstrated. But Bowditch phenomenon disappeared at the temperature above $(32.5^{\circ}C)$. 2) At $(27.5^{\circ}C)$, in the presence of verapamil, a $Ca^{2+}$ channel blocker, a time course of change in the frequency-tension was studied. It was found that Bowditch phenomenon was affected before the Woodworth phenomenon, then the former was completely disappeared. At $(32.5^{\circ}C)$, where no Bow-ditch is seen in normal atrial muscle, Bowditch phenomenon was reappeared by an administration of norepinephrine suggesting again that slow inward current of such as $Ca^{2+}$ channel is closely related to Bowditch phenomenon. 3) At $27.5^{\circ}C$, in the presence of $La^{3+}$, although tensions were decreased at all stimulation frequencies, Bowditch and Woodworth phenomenon were still demonstrated. However in the presence of both $La^{3+}$ and verapamil, Bowditch phenomena was disappeared suggesting that $La^{3+}$ is less effective in blocking $Ca^{2+}$ channel than verapamil. 4) At $27.5^{\circ}C$, in the presence of ryanodine, an inhibitor of calcium release from SR, Woodworth phenomenon was disappeared, which was consistent with previous reports of others, suggesting that $Ca^{2+}$ release from SR is closely related to Woodworth phenomenon. From the above findings, it may be concluded that Bowditch phenomenon is dependent on the magnitude of $Ca^{2+}$ influx through slow channel and Woodworth phenomenon is dependent on the amount of $Ca^{2+}$ stored in SR.