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발사체 후방동체형상에 따른 기저항력에 대한 수치적 연구
박남은(Nam-Eun Park),김재수(Jae-Soo Kim) 한국전산유체공학회 2001 한국전산유체공학회 학술대회논문집 Vol.2001 No.-
The projectile afterbodies for zero-lift drag reduction has been analyzed using the Navier-Stokes equations with the k-ε turbulence model. The numerical method of a second order upwind scheme has been used on unstructured adaptive meshes. Base drag reduction methods that have been found effective on axisymmetric bodies include boattailing, base bleed, base comustion, locked vortex afterbodies and multistep afterbodies. In this paper, the charateristics of turbulence flow have been studied for geomeries of multistep afterbodies, The important geometrical and flow parameters relevant to the design of such afterbodies have been identified by number, length and height of step. The flow over multistep afterbodies has been analyzed including expansion waves I recompression waves, recirculating flow, shear flow and wake flow, The numerical results have been compared and analyzed with the experimental datum.
박남은(Nam-Eun Park),박동일(Dong-Il Park),임성균(Sung-Kyun Lim),곽윤근(Yoon-Keun Kwak) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.6
Rescue robot’s performance of climbing stairs depends on some factors. For example, maximum friction force, motor torque, dimensions of system, climbing moment, and so on. We analyzed the grip force between the track and the ground, because motor torque and dimensions of system were already determined by optimal design. The shape of the rubber-band track is important for improving the performance of climbing stairs. Considering the grouser shape effect in climbing stairs, we found that grouser shape determined the number of the contact point, the width of the contact surface and direction of force. Consequently, we found the efficient grouser shape by maximizing the climbing moment and grip force in the mathematical model. We have confirmed the performance improvement of climbing stairs and the importance of optimal rubber-band track shape by experiments.
초음속 난류 유동장내의 발사체 후방 동체형상에 따른 기저유동의 수치적 계산
박남은(Nam-Eun Park),노형운(Hyung-Hun Roh),김재수(Jae-Soo Kim) 한국전산유체공학회 2002 한국전산유체공학회지 Vol.7 No.4
The projectile afterbodies for zero-lift drag reduction has been analyzed using the Navier-Stokes equations with the k-ε turbulence model. The numerical method of a second order upwind scheme has been used on an unstructured adaptive grid system. Base drag reduction methods that have been found effective on axisymmetric bodies are boattailing, base bleed, base combustion. locked vortex afterbodies and multistep afterbodies. In this paper, turbulence flow and pressure characteristics have been studied for geometries of multistep afterbodies. The important geometrical and flow parameters relevant to the design of such afterbodies have been identified by step number, length and height. The flow over multistep aftoerbodies or base have many kinds of compressible flow characteristics including expansion waves at the trailing edge, recompression waves, separation and recirculating flow in the base region, shear flow and wake flow. The numerical results have been compared and analyzed with the experimental data. The flow characteristics have been clearly shown.
박남은(Park Nam-Eun),박동일(Park Dong-Il),곽윤근(Kwak Yoon-Keun) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
In this paper, we studied the rubber-band track shape of the rescue robot for improving the performance when going up the stairs. Previous researches showed that grousers are modeled into the track for increasing the traction force under severe ground condition. Considering the grouser effect in climbing the stairs, we found that grouser shape is most important because of determining the number of contact point and the width of contact surface. There are 3 cases of contact shape according to grouser shape, attack angle and size of stair. Consequently we found the efficient shape of the grouser by maximizing the traction moment of a rescue robot in the mathematical model.
Effect of Dietary Fiber on the In Vitro Digestibility of Fish Protein
류홍수(Hong-Soo Ryu),박남은(Nam-Eun Park),이강호(Kang-Ho Lee) 한국식품영양과학회 1992 한국식품영양과학회지 Vol.21 No.3
단백소화율에 미치는 식이 섬유소의 영향에 대하여 알아보기 위해, 채소류 (상치, 깻잎, 고추, 다시마)로 부터 추출한 식이 섬유소와 시판용 정제 식이 섬유소 (cellulose, pectin, sodium alginate, gum karaya)를 어류 단백질인 말쥐치 단백질(냉동건조육 및 myofibrils)에 첨가 반응시켜, 단백질의 소화율에 어느 정도 영향을 미치는가에 대해 알아보았다. 각 시료의 중성세제 추출섬유소 (neutral detergent fiber) 함량은 24.21%(고추) 9.75%(다시마)의 범위였고, 산성세제 추출섬유소 (acid detergent fiber) 함량은 20.85%(고추) 11.97%(깻잎)의 범위였으며, 수용성 섬유소 함량은 13.79%(다시마) 4.41%(상치)의 범위였다. 말쥐치 단백질에 대한 식이 섬유소의 반응 비율을 1 : 1 (wt/wt)로 하고, 37℃에서 2시간 동안 반응시켰을 때, 말쥐치 단백소화율은 정제 식이 섬유소 첨가의 경우, 1.52%(cellulose) 9.97%(pectin)가 감소되었고, 추출한 식이 섬유소 첨가의 경우, 5.15%(고추) 12.36%(다시마)가 감소되었다. 섬유소의 trypsin 활성저해능은 단백소화율이 감소함에 따라 증가하여, ANRC casein에 대한 soybean trypsin inhibitor 22㎎/g (cellulose) 61.82㎎/g (gum karaya), 49.75㎎/g(고추) 171.52㎎/g(상치)에 상응하는 것으로 나타났다. 정제 식이 섬유소에 의한 단백분해효소의 활성 변화는 sodium alginate를 제외하고는 거의 없어, 어류 단백소화율의 저하는 식이 섬유소가 단백질에 직접 결합하여 비소화성 물질을 형성한 결과가 주도 하리라 생각되었다. 말쥐치 단백질과 섬유소를 반응시킨 것을 효소 가수분해시킨 후에 측정한 유리 필수 아미노산의 함량은 sodium alginate와 다시마 섬유소의 경우 현저하게 저하하였으며 (75% 이상), isoleucine과 valine이 크게 영향을 받았다. In vitro digestibility of filefish, protein was substantially decreased by fiber constituents in the following order : pectin (9.97%), gum karaya (7.03%), sodium alginate (6.12%),and cellulose (1.52%). The order of reduction by fibrous residues from vegetables ranked as follows: sea tangle (12.36%), Romaine lettuce (11.12%), perillar leaf (8.96%), and green pepper (5.15%). The inhibitory effect of the dietary fibers towards filefish protein digestion, expressed as soybean trypsin inhibitor equivalents, increased with added levels, but the inhibition differed with the sources of dietary fibers. Sea tangle and sodium alginate were most active in decreasing the concentration of essential amino acid from filefish protein hydrolysis. Sodium alginate exerted an inhibitory effect on the activity of trypsin, but the other fiber constituents did not have an inhibitory potency on trypsin and bacterial protease (Streptomyces griceus). Results supported that dietary fiber components may reduce protein digestibility through the interaction of dietary fiber components with filefish protein.