• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.1
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• pp.9-16
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• 2014

This paper presents the theoretical analysis of a flow driven by surface tension and gravity in an inclined circular tube. A governing equation is developed for describing the displacement of a non-Newtonian fluid(Power-law model) that continuously flows into a circular tube owing to surface tension, which represents a second-order, nonlinear, non-homogeneous, and ordinary differential form. It was found that quantitatively, the theoretical predictions of the governing equation were in excellent agreement with the solutions of the equation for horizontal tubes and the past experimental data. In addition, the predictions compared very well with the results of the force balance equation for steady.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5A
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• pp.255-266
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• 2012

Main cable of a suspension bridge is the important member which shows the overall structure integrity at bridge completion. Configuration of main cable is a free hanging state at cable erection completion and is different from that at bridge completion supporting the dead loads such as hanger, girder, and so on. Accordingly, the configuration control under cable erection is considerably significant because the configuration at cable erection completion has direct influence on that at bridge completion. That is performed by sag adjustments at center, side span and tension adjustments at anchor span. The former needs the sag sensitivity which represents the control quantity of strand length corresponding to that of sag. The latter requires the tension sensitivity which shows the change of strand tension according to that of strand temperature. In this study, the fundamental equations of cable were derived with the assumption of either catenary or parabola shape, the differential-related equations using chain rule on horizontal tension were drawn from those and finally the estimation methods of the sag / tension sensitivity were proposed from both those. The nonlinear numerical analysis flow charts of sag sensitivity based on the catenary equations were proposed and the sag sensitivities grounded on the differential-related equations were compared with the results using them for various parameters of sag change. Also, considering the combinations of sag change parameters, the calculation method of the final variation for the cable sag was suggested. For the real suspension bridge under construction with PPWS method, the sag/tension sensitivity were estimated considering the construction conditions like the change of PPWS length, PPWS temperature, bridge span, etc.. We hope that this study will be a systematic guideline for the configuration control under main cable erection and improved highly by field verification in the real bridge site.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.2
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• pp.99-111
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• 2003

The fundamental studies on the productivity improvement of the purse seine fishery are presented in this paper. The experiment on net shooting and hauling was carried out in the near sea of Jeju Island (33$^{\circ}$37.8' N, 126$^{\circ}$31.1' E) by using the Cheju national university training ship (A-Ra, 990tons) which was constructed for the one boat system operation of purse seine. The corkline and leadline of the purse seine used for the experiment were 829.1m and 995.7m in length, respectively. Micro data recorder system, net sonde, and tensiometer were used to measure the depth of leadline and the tension of purse seine. Based on the measurement data, the motion and tension of purse seine at the time of shooting, hauling, and pursing were characterized. The experimental results are summarized as follows ; 1. The shooting and hauling of net were found to be possible in the one boat system experimental operation. 2. At the time of purse seine shooting, the relationship between the depth (Dp) of leadline and elapsed time (Et) was found to be Dp=7.58Et-6.48. 3. At the time of pursing, the relationship between the depth (Dp) of leadline and elapsed time (Et) was found to be Dp=-0.8Et$^2$＋7.42Et＋92.04. 4. At the time of pursing, the tension (metric tons) of purse seine attained its maximum value (14.7tons) when the elapsed time is 8 minutes. The relationship with the elapsed time was found to be T=-0.13Et$^2$＋3.23Et-5.72.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.181-188
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• 2009

Measuring the tensile strength of steel cables used to support bridges is a critical inspection item in terms of the safety of a bridge. Today, cable tension is measured with the vibration method and loadcell. Recently, some advanced countries have conducted studies on measuring tension with magnetic method and are suggesting prospective results. Since there were no such studies ongoing in Korea, we began a study on measuring tension with magnetic method as we are undergoing researches to improve the precision of measurements. It is necessary to consider the influence for the magnetic field and the temperature of steel cables in tension measurement of magnetic method. In this paper, we tested an output characteristic of tension sensor according to temperature and deduced temperature compensation coefficient in the given magnetic field and applied the compensation coefficient to the tension measurement system in the lab. We analyzed and evaluated testing results for the output voltages of the tension sensor according to cable tensions.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.103-106
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• 2003

원형의 물체에 접해 있는 섬유 또는 실의 장력에 관하여 기존의 capstan equation의 잘못된 점을 보완하는 일반적인 capstan Equation을 유도하였다. 해석은 주로 섬유-물체의 접촉부위에 초점을 맞추었다. 그 결과 유도된 지배방정식은 2차 상미분 방정식의 형태를 갖는다. 지배방정식의 해를 구한 뒤, 접촉영역 전체에 작용하는 힘의 평형조건을 이용하여 입력 장력(incoming tension)과 출력 장력(outgoing tension)간의 관계식을 얻을 수 있었으며 우리는 이것을 True capstan equation이라 명하였다. (중략)

• Journal of the Korean Chemical Society
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• v.12 no.1
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• pp.18-25
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• 1968

액체 분자는 고체, 천이상태 및 기체와 같은 자유도를 갖는다는 액체구조에 관한 천이상태이론을 적용하여 액체의 표면장력과 점도를 계산하여 측정 치와 좋은 일치를 얻었다. 표면장력을 계산함에 있어서 표면 각층의 밀도는 이웃 층 사이의 밀도를 주는 관계식으로부터 쉽게 얻었다. 그리고 액체가 점성 흐름을 할때 활성화된 분자는 흐르는 방향으로는 기체와 같은 자유도를 가지나, 이에 직교한 평면상에서는 천이상태 및 기체와 같은 자유도를 갖는다고 가정하였다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.562-563
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• 2011

초고압케이블을 관로식으로 포설할 경우 케이블 포설장력이 증가함에 따라 측압은 커지게 된다. 측압은 지중관로 내 케이블 포설시 도르래 및 굴곡부에서 발생하는 관로 내면과 케이블 사이의 압력을 의미하며, 단심배열의 경우 곡률반경과 장력에 의존한다. 케이블의 측압을 정확하게 알고 안전성에 기초하여 장경간 포설을 한다면, 케이블 포설 시 긴 케이블 조장에 따라 접속함과 굴착개소의 감소로 이어지기 때문에 원가절감 뿐 아니라 공기 단축 차원에서도 큰 역할을 할 수 있다. 그러나 현재 케이블 측압은 포설 장력을 이용하여 계산되기 때문에 실제 측압과 오차가 발생할 수 있으며, 정확한 장력을 케이블에 인가하는것 또한 어려운 일이다. 따라서 본 논문에서는 케이블 포설시 발생하는 측압을 작용시키며, 장력을 케이블에 정확히 인가할 수 있는 측정기기 개발에 관한 내용을 정리하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.325-325
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• 2018

파랑 중 4점 계류식 해상부유체의 운동 특성은 4점 계류의 상태에 따라 운동해석이 달라질 수 있다. 본 연구에서는 부상체의 부력과 파랑의 파고 및 풍압으로 인한 계류색에 미치는 장력에 대하여 검토하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.837-846
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• 1989

Belt tension distribution for an abrasive blet grinding was investigated analytically and experimentally for (1) slack side and (2) tight side blet grinding. Classical Eytelwein equation was used to predict the belt tension distribution with dividing contact angles into (1) inactive and (2) active angles. General friction theory was modified based on the friction force between the belt and the support in the grinding contact area that was obtained by experiments. It was found that analytical results were in good agreement with the experimental results. Also, the tight side belt grinding was recommended since it could carry out more grinding load than that of slack side belt grinding.

• Current Research on Agriculture and Life Sciences
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• v.27
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• pp.7-11
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• 2009

Persimmon occupied the second largest cultivation area next to apple among the fruits in Korea. Since 70 % of its cultivating field is located at slope, the efficiency of its harvesting operation is very low. Also, the traditional high-ground trimmer show very low efficiency due to its structure problem.. In this paper, a high-ground trimmer which is a persimmon cultivator was developed by solving the problem of a traditional high ground trimmer. The results of the research are summarized as follows : 1. In case of the developed hydraulic type high ground trimmer, the required average lever tension is 2.9 N. 2. However, the required average tension force of the existing spring type is 25.5 N, which was 8.7 times greater than developed hydraulic lever type trimmer in this study.