This paper presents the theoretical analysis for the flow driven by surface tension and gravity force in an inclined circular tube. The previously developing equation for Power-Law model is a simple ordinary differential type. A governing equation is developed for describing the displacement of a non-Newtonian fluid(Casson model) that continuously flows into a circular tube by surface tension, which represents a second-order, nonlinear, non-homogeneous, and ordinary differential form. It was found that the theoretical predictions of the governing equation were in good agreement with the results for considering the Newtonian model.
We evaluate the properties of friction welded STK400 steel tube in terms of the relationship between microstructures and mechanical properties. Friction welding is conducted at a rotation speed of 1,600 rpm and upset time of 3-7 sec for different thicknesses of STK 400 tubes. To analyse the grain boundary characteristic distributions(GBCDs) in the welded zone, electron backscattering diffraction(EBSD) method is introduced. The results show that a decrease in welding time (3 sec.) creates a notable increase grain refinement so that the average grain size decreases from 15.1 μm in the base material to 4.5 μm in the welded zone. These refined grains achieve significantly enhanced microhardness and a slightly higher yield and higher tensile strengths than those of the base material. In particular, all the tensile tested specimens experience a fracture aspect at the base material zone but not at the welded zone, which means a soundly welded state for all conditions
갭색법(gap & sag method)은 선박 건조과정에서 축을 조립하기 전 최종적으로 축이 축계정렬 설계치와 동일한 위치에 거치되었는지의 여부를 확인하기 위해 사용되고 있는 방법이며, 조립 전 프로펠러축을 기준축으로 하여 양 축의 플랜지에서 축 자중에 의해 발생하는 갭색값을 통해 나머지 축계의 위치를 순차적으로 확정해 나간다. 만일 설계치와 다르게 기준축이 거치되는 경우 연쇄적으로 나머지 축의 거치에 영향을 주게 된다. 또한, 축 조립 후 검증과정에서 측정된 베어링 반력이 설령 설계치를 만족하더라도 선미관 후부측에서의 프로펠러축과 베어링간 상대적경사각을 추정할 수 없게 됨으로써 결과적으로 축계의 안정성에 부정적인 영향을 미칠 수 있다. 이러한 문제를 해결하기 위하여 본 연구에서는 실제 선미관 베어링 발열 및 개방검사 사례를 통해 선미관 베어링 유효지지점에 관한 이론계산 및 실측치분석 연구를 수행하고 이를 바탕으로 축계 정렬오차를 최소화하기 위한 축계 시공방법을 제안하였다.
Vortex tubes are simple tubes that can separate hot and cold air from compressed air without any internal device configuration and are used in many industries. If the vortex tube with these advantages is applied to an air conditioning system, it will be free from the use of refrigerant. In this study, basic study on discharge flow rate and temperature separation characteristics was carried out by varying the number of generator nozzle hole in various shapes of the vortex tube according to the inlet pressure of the vortex tube. Experimental results show that as the number of nozzles increases, the discharge flow rate tends to decrease and the temperature separation characteristics were excellent in the number of nozzles 6~7.
We evaluated three previously known repellents of Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), i.e., carvacrol, cis-jasmone, and methyl jasmonate for the attraction of commercialized predators, Orius laevigatus (Fieber) (Hemiptera: Anthocoridae), and native predator, O. minutus (L.), in Y-tube olfactometer. Higher proportion of O. laevigatus (mated unfed adult females) moved to the arm of methyl jasmonate or cis-jasmone than the arm of clean air. However, O. minutus did not show any significant preference to the chemicals tested. These results suggest that, among the tested chemicals, methyl jasmonate or cis-jasmone would be a good attractant for O. laevigatus.
목적: 셀룰로오스 필터를 삽입하여 개발 제작된 튜브형눈물검사키트(cellulose tube-type tear test kit, Kit-CEL)의 임상적 유용성을 평가하고자 하였다.
방법: 안질환이 없고 건강한 20대 성인 62명(124안)이 참여하였다. Kit-CEL의 신뢰도 분석을 위해서 단 일 검사자가 하루 간격을 두고 총 3회 동일한 방법으로 검사를 실시하였고, 타당도는 현재 사용되고 있는 SMTube를 이용하여 평가하였다. 건성안에 대한 Kit-CEL의 민감도와 특이도 평가는 ROC curve를 활용하였고, 건성안의 판별 기준은 TBUT 검사를 활용하였다. 정확도의 지표는 ROC curve의 곡선아래면적을 정확도의 지표로 활용하였으며, 유의수준은 p<0.05로 하였다.
결과: Kit-CEL의 신뢰도는 0.77로 SMTube의 신뢰도 0.43보다 높았으며, Kit-CEL의 건성안에 대한 민 감도와 특이도는 각각 74.63%, 50.88%로 SMTube 32.84%, 82.46%보다 민감도는 높았고 특이도는 낮았다. 제작된 Kit-CEL 측정값은 시판되고 있는 SMTube 측정값과 중등도의 상관성을 보였다(r=0.56, p<0.00).
결론: Kit-CEL의 측정값은 기존 SMTube와 유의한 상관성을 보였고, 신뢰도와 민감도가 높게 나타나 임 상에서 활용할 수 있는 눈물검사키트로 판단된다.
본 연구는 소와 돼지 식육부산물의 위생처리를 위한 볼텍스 튜브를 이용한 오존수 제조 장치를 개발 하기 위해 수행되었다. 오존가스발생에 있어서 가장 중요한 인자는 원료공기의 온도이며, 위생처리를 위한 오존수 내 오존농도에 크게 영향을 미친다. 이러한 이유 때문에 오존발생기로 유입되는 원료공기의 온도를 낮추기 위해 볼텍스 튜브가 이용되었다. 성능평가의 결과에 의하면, 공기압축기의 배출공기 압력 3~5bar, 볼텍스 튜브의 냉기비율 40~80%와 냉각공기의 압력 0.0~0.4bar가 28.2℃의 주변 공기 온도 하에서 볼텍스 튜브의 냉각공기의 온도에 교호적으로 작용하는 것으로 나타났으며(p<0.05), 최적 조건은 공기압축기의 배출공기 압력 4bar, 볼텍스 튜브의 냉기비율 40%, 냉각공기의 압력 0.3bar이었다. 최적조건과 주변 공기온도 35℃ 하에서 볼텍스 튜브를 이용한 오존수 제조 장치의 성능을 평가한 결과에 의하면, 오존수 내 오존농도가 0.43ppm 이상이었다. 따라서 볼텍스 튜브를 이용한 오존수 제조 장치의 성능이 우수하여 여름철 악조건 하에서도 이용이 가능한 것으로 판단된다.
In this study, the CFD analysis was performed by changing the geometry of coil-tube diameter ratio, coil winding number, coil pitch, and cross section of the tube to investigate the heat flow characteristics of forced convection in a helical coil-tube heat exchanger using RSM (Reynolds Stress Model). As a result, the secondary flow was developed in the tube caused by the influence of centrifugal force. It improved the heat transfer on the outer side of the tube, but on the inner side was not performed well. And the temperature rose locally in the tube region. Also the pressure drop in the tube was proportional to the diameter ratio of the coil-tube and the inlet velocity, and it was found that pressure drop and friction factor were inversely proportional. When the coil winding number and coil pitch were increased, it affected heat transfer in the low speed range of 0.1 ~ 0.2 m/s, but did not affect the flow condition after this range.
Concrete using recycled aggregate instead of natural aggregate reduces environmental waste and is a future oriented material. However, use of the structure is limited to negative recognition of recycled aggregate quality. In this study, 50 MPa concrete was developed using recycled aggregate. In order to verify the possibility of using as a column member, we aimed to confirm the compressive behavior of RCFT (Recycled Concrete Filled Tube) columns filled with concrete using recycled aggregate. Circular type steel pipe was used, and concrete strength (30, 40, 50MPa) and mixing ratio were the experimental parameters. Through 72 specimen compression tests, 50MPa strength of recycled aggregate concrete was confirmed and stable behavior of 9 RCFT columns was confirmed.
In this study, a drainage-regulated type geotextile tube structure was proposed. The structure is composed of high permeability polypropylene(PP) and low permeability (PET) fabric in which the lengths of the fabric depend on the circumference ratio of the cross section. The purpose is to reduce the pressure inside the geotextile tube structure during filling as much as possible. Experimental study on the characteristics of the geotextile tube structure according to the permeability of the geotextile was also carried out. Experimental results of 4 small scaled geotextile tube structures showed that the bottom section formed as drainage type can reduce the filling pressure as well as increase the sedimentation height which confirms as the optimum cross section of the tube.
The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is an important pest of horticultural and agricultural crops worldwide. The repeated use of chemical insecticides resulted in the development of insecticide resistance. We evaluated response of F. occidentalis to three synthetic herbivore-induced plant volatiles (HIPVs), methyl salicylate, methyl anthranilate, and nonanal known as attractants of thrips’ natural enemy, in Y-tube olfactometer. Mated fed adult females of F. occidentalis showed lowest response rate to methyl salicylate than methyl anthranilate, and nonanal. These results show that methyl salicylate may act as repellent to F. occidentalis, and can be used as a component of push-pull strategies for the management of F. occidentalis.
Artificial light is frequently used for plant growth and pest attraction traps in greenhouses. In addition, natural enemies may utilize this artificial light for colonization in greenhouses. Orius laevigatus is a biological control agent of whiteflies and thrips. The Y-tube selection test was conducted against O. laevigatus for 11 wavelengths (365, 385, 395, 405, 410-420, 420-430, 440-450, 490-500, 520-530, 590-595 and 620-630 nm) of LED and white light (5000k) for a control . One pipe of the Y-tube was allocated for insect entrance and other two pipes of the Y-tube were installed transparent sticky trap along with white LED and test wavelength, respectively. At least, three replications were conducted for each wavelength and 40 to 60 individuals of O. laevigatus were used for each replication. Attraction rate of 365 to 405 nm wavelength was above 50 % and highest at 385 nm (83.7 %). Attraction rate of 490 to 630 nm was below 20 % and lowest at 620-630 nm (1.4 %). The results indicate that O. laevigatus attracted most to 385 nm wavelength and this light may be useful for using O. laevigatus in green houses. Further research is needed using selected LED wavelength.