• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.442-447
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• 2007

A very abnormal vibration was occurred at the LP(low pressure) turbine continuously during the pre-operation for a 550MW class USC(ultra super critical) steam turbine. This vibration was initiated at the rotating speed of about 3,450rpm and then the vibration amplitude was highly increased the number by $2{\sim}3$ times with the increase of the rotating speed to the rated speed(3,600rpm). In this paper, this abnormal vibration named spike vibration. This spike vibration was caused by the rubbing between the rotating bucket tip seal and the Lower Half of spill strip. Also, this paper presents the mechanism of the spike vibration and the proper method to eliminate this abnormal vibration problem. This result would be good practice to find the solution of similar high vibration in the USC steam turbines for power plant as well as industrial rotating machineries.

• 한국소음진동공학회논문집
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• 제17권12호
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• pp.1238-1245
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• 2007

A very abnormal vibration was occurred at the LP(low pressure) turbine continuously during the pre-operation for a 550MW class USC(ultra super critical) steam turbine. This vibration was initiated at the rotating speed of about 3,450 rpm and then the vibration amplitude was highly increased the number by $2{\sim}3$ times with the increase of the rotating speed to the rated speed (3,600 rpm). In this paper, this abnormal vibration named spike vibration. This spike vibration was caused by the rubbing between the rotating bucket tip seal and the lower half of spill strip. Also, this paper presents the mechanism of the spike vibration and the proper method to eliminate this abnormal vibration problem. This result would be good practice to find the solution of similar high vibration in the USC steam turbines for power plant as well as industrial rotating machineries.

• Tribology and Lubricants
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• 제31권4호
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• pp.177-182
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• 2015

Tapered roller bearings are widely used in equipment where high combined thrust and radial loads are experienced. A certain amount of tilting between the tapered rollers and the races always occurs because of bending moment load conditions and shaft deflection. It is now well understood that a coherent elastohydrodynamic lubrication (EHL) film separates the rollers and races. In spite of extensive study on EHL problems for over half a century, relatively few studies have focused on the finite line contacts problem. This study presents a complete numerical analysis of the effects of roller tilting on the EHL characteristics in a tapered roller bearing. We systematically analyze this highly nonlinear problem using finite differences with fully non-uniform grids and the Newton-Raphson method. Detailed EHL pressure distributions and film shapes are presented under moderate loads and material parameters. A very small roller tilting significantly affects the pressure distributions and film shapes near both ends of the roller. Moreover, the effect of tilting on the EHL characteristics at the small end is much greater than that at the large end. Therefore, in designing optimum profiles for tapered roller bearings, the profile radius should be larger at the small end.

• 설비공학논문집
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• 제17권4호
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• pp.325-332
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• 2005

This paper addresses the development of a scroll expander for power generation from relatively low temperature steam source. It has a double-sided orbiting scroll member so that no thrust bearing is needed to support the base plate of the orbiting scroll. Three power transmission shafts are placed at the periphery of the orbiting scroll base plate, and these shafts can also function as anti-rotation devices. Final output is obtained from the main central shaft engaged with the three power transmission shafts through gear assembly. The clearance between the fixed and orbiting scroll elements was estimated by comparing measurement of the mass flow rate with calculation results of a computer simulation. Due to large clearance, the expander total and volumetric efficiencies were measured to be $34\%\;and\;43\%$, respectively. It has been shown through the computer simulation that the total and volumetric efficiencies could be improved to $65\%\;and\;83\%$, respectively, if the current clearance is reduced by half.

• 건축역사연구
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• 제7권2호
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• pp.29-48
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• 1998

The first Pagoda of Korea was introduced from China, and adapted from the wooden multi-storied pavilion. Also in Bronze one, multi-storied type of wooden pagoda was adapted. Bronze pagoda was used to buddhist ossuary and a kind of metalwork. Metalworks were made of gold, silver, copper, or iron by one of the methods of production-casting or hammering and decorated design of incision, raise, openwork, gold- plating or inlaying with gold and silver. Sometimes it was used as the easy carriage of Buddha image by guess. In most cases, the plan of Bronze pagoda was square and podium was one story. but in the advance of podium two-storied platform appeared. Column appeared in a symbol, so it didn't appear in a square and circular form. It means that the column was vertical member which only divided the wall. In koryo period, Gabled roof and Half-hipped roof was spreaded in public but Bronze pagoda was used to square Hipped roof. Vertical shaft over roof(上輪部), apart from body of pagoda(塔身部), was inserted on the hole above the Bokbal(覆鉢) for the balance of pagoda. And a thick iron bar put in the roof to the platform. It was sustained the balance of pagoda. The stories of pagoda were various from 3rd stories to 9, the lower stories was larger scale and the higher was smaller one.

• Archives of Plastic Surgery
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• 제37권2호
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• pp.187-190
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• 2010

Purpose: Pediatric trigger thumb is a condition of flexion deformity of the interphalangeal (IP) joint. The known surgical treatment is the release of the flexor pollicis longus by transection of the A1 pulley. We report two cases of pediatric trigger thumb that were resolved by releasing of additional pulley as well as A1 pulley. Methods: From March 2006 to April 2008, a total of 10 children with trigger thumb were operated. In two cases, transection of only the A1 pulley was insufficient to relieve the triggering. When more distally dissection, we found an additional pulley. After release of the additional pulley, the full extension of IP joint is obtained. Results: There were no significant complications. In 8 cases, the trigger thumbs were resolved by transecting only the A1 pulley, does not extend beyond the base of the proximal phalanx. In one case, the additional pulley was found to be more distal to the A1 pulley. It was necessary to extend the release up to the half in the proximal phalangeal shaft. In other case, the additional pulley was immediately adjacent to the A1 pulley. Conclusion: In most cases of trigger thumb, division of just A1 pulley is sufficient to relieve the triggering. However, dividing the A1 pulley in two patients proved to be insufficient to relieve the flexed deformity. In these cases, we found that the additional pulley, different from previous known A1 pulley, had existed, which must be transected to allow full excursion of flexor pollicis longus.

• Smart Structures and Systems
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• 제4권2호
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• pp.221-232
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• 2008

This paper represents the final results of a research program sponsored by the European Commission through project WIND-CHIME ($\underline{W}$ide Range Non-$\underline{IN}$trusive $\underline{D}$evices toward $\underline{C}$onservation of $\underline{HI}$storical Monuments in the $\underline{ME}$diterranean Area), in which the possibility of using advanced seismic protection technologies to preserve historical monuments in the Mediterranean area is investigated. In the current research, the dynamic characteristics of two outstanding Mamluk-Style minarets, which similar minarets were reported to experience extensive damage during Dahshur 1992 earthquake, are investigated. The first minaret is the Qusun minaret (1337 A.D, 736 Hijri Date (H.D)) located in El-Suyuti cemetery on the southern side of the Salah El-Din citadel. The minaret is currently separated from the surrounding building and is directly resting on the ground (no vaults underneath). The total height of the minaret is 40.28 meters with a base rectangular shaft of about 5.42 ${\times}$ 5.20 m. The second minaret is the southern minaret of Al-Sultaniya (1340 A.D, 739 H.D). It is located about 30.0 meters from Qusun minaret, and it is now standing alone but it seems that it used to be attached to a huge unidentified structure. The style of the minaret and its size attribute it to the first half of the fourteenth century. The minaret total height is 36.69 meters and has a 4.48 ${\times}$ 4.48 m rectangular base. Field investigations were conducted to obtain: (a) geometrical description of the minarets, (b) material properties of the minarets' stones, and (c) soil conditions at the minarets' location. Ambient vibration tests were performed to determine the modal parameters of the minarets such as natural frequencies and mode shapes. A $1/16^{th}$ scale model of Qusun minaret was constructed at Cairo University Concrete Research Laboratory and tested under free vibration with and without SMA wire dampers. The contribution of SMA wire dampers to the structural damping coefficient was evaluated under different vertical loads and vibration amplitudes. Experimental results were used along with the field investigation data to develop a realistic 3-D finite element model that can be used for seismic risk evaluation of the minarets. Examining the updated finite element models under different seismic excitations indicated the vulnerability of such structures to earthquakes with medium to high a/v ratio. The use of SMA wire dampers was found feasible for reducing the seismic risk for this type of structures.

• 터널과지하공간
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• 제24권4호
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• pp.297-307
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• 2014

암반공동을 이용한 열에너지 저장은 대용량 저장이 가능하며 열저장매체를 선택할 수 있는 장점이 있다. 본 연구에서는 사일로 형태의 열저장공동이 지반 내 두 개 이상 배치될 때 공동 사이에 형성되는 암반 필라의 안정성에 대해 3차원 유한차분해석 프로그램인 $FLAC^{3D}$를 이용하여 분석하였으며, 저장된 열에너지로 인해 암반에 발생하는 열응력을 반영할 수 있도록 열-역학적 연계모델을 사용하였다. 해석 결과, 열에너지 장기 저장으로 인해 암반 필라에 작용하는 최대주응력이 상당량 증가하였으며, 필라 폭이 좁아질수록 근접한 열원 때문에 열응력 증가량도 커짐을 확인하였다. 필라 안정성에 영향을 미치는 주요인자로서 저장공동 간격, 측압계수, 심도를 선정하고 민감도 분석을 실시한 결과, 측압계수, 저장공동 간격, 심도 순서로 영향력이 크게 평가되었다. 저장공동 간격의 경우 동일한 크기의 공동 건설 시 필라 폭을 최소 저장공동 직경 이상 확보해야 할 것으로 판단되었다. 큰 규모의 저장공동 주변에 소규모 수직갱이 설치될 때는 최소한 저장공동 직경의 0.5배 이상 이격함으로써 크기 차이로 인해 수직갱에 응력이 집중되는 현상을 해소할 수 있었다. 또한 최대수평주응력 작용방향과 공동 중심을 잇는 축이 평행하도록 배치하여 저장공동에 의한 방패효과가 발휘될 수 있게 함으로써 현지응력이 공동 사이 암반 필라에 미치는 영향을 최소화할 수 있었다.

• 헤리티지:역사와 과학
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• 제47권2호
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• pp.4-19
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• 2014

조선시대 공신교서는 국가의 특정한 사건에 공을 세운 공신을 포상하기 위하여 발급하였다. 공신으로 녹훈(錄勳)된 가문에서는 이 공신교서를 가보(家寶)로서 후대에 전승하였다. 그러나 이 과정에서 전란 등의 피치 못할 상황 속에서 소실되는 경우가 발생하기도 하였는데, 이러한 경우 국가에서 다시 교서를 발급해 준 사례가 남아있다. 현전하는 공신교서 중에서 확인되는 재발급 교서는 박동량 호성공신교서, 구굉 정사공신교서, 박정 정사공신교서 3점이다. 본 연구에서는 이상 3점에 대한 문서양식과 장황에 대해 검토하였다. 재발급 공신교서는 원본 공신교서와 동일한 양식, 곧 평출(平出)과 대두(擡頭) 등을 준수하여 작성하는 것으로 나타났다. 단, 원본 공신교서와는 달리 재발급된 시점에서 공신의 신분에 변화가 있을 때는 이를 반영하는 것으로 나타났다. 정사공신교서의 경우는 원본 공신교서는 '정원군 부(定遠君 ?)'가 재발급된 시점에는 인조의 아버지가 되었기 때문에 '원종대왕휘(元宗大王諱)'로 나타났다. 또 재발급 정사공신교서의 경우 '김자점(金自點), 김련(金鍊), 심기원(沈器遠), 심기성(沈器成)'과 같이 역모에 의해 삭훈된 경우는 원본 문서대로 작성을 하고 먹으로 검게 삭거(削去)한다는 사실을 확인할 수 있었다. 서사자의 경우도 원본 공신교서는 국가에서 지정한 선서자가 작성하는 반면에, 재발급의 경우는 그 공신 가문의 선서자가 문서를 필사한다는 새로운 사실을 확인할 수 있었다. 공신교서의 장황(粧?)은 물자를 조달해야 하는 조정의 경제적 상황, 배접장 등 실제 제작에 관여한 장인의 기호와 기술 등에 따라 시대적으로 변모한다고 할 수 있는데, 이 3점의 경우 모두 병자호란으로 그 원형이 소실된 상황이었으므로, 재발급본과 최초 발급본의 장황이 달랐을 가능성이 크다. 이와 관련해서 교서 제작과정에 대한 의궤의 기록, 최초 발급본과 같은 시기에 제작된 공신교서와 비교해 본 결과, 재발급본은 최초 발급본에 비하여 장황의 형태나 비율이 커진 것으로 보인다. 우선 변아(邊兒)의 폭은 2배 정도 넓어지고, 중앙좌우회장(中央左右回粧) 역시 평균 2cm이상 커진 형태이고, 하회장(下回粧)의 경우도 평균 10cm 넓어졌다. 상회장(上回粧)과 하회장(下回粧)의 비율은 최초 발급본의 경우 상회장이 하회장에 비해 1.5배 정도 넓고, 재발급본의 경우 거의 1:1의 비율을 갖추고 있었다. 상축(上軸)의 단면은 박동량 호성공신교서의 경우 현재의 반달형태가 아닌 부등변삼각형의 형태였을 것으로 추정되며, 구굉과 박정 정사공신교서 축(軸)은 단면의 모양은 같지만 크기가 작아진 형태일 것이다. 축수(軸首)는 크기에 큰 변화가 없고, 오색다회(五色多繪)는 최초 발급본이 재발급본에 비해 그 폭이 훨씬 좁았을 것으로 추정된다. 재발급본 3점은 제작시기가 같은 보사공신교서(保社功臣敎書)의 장황 형태를 고증할 수 있는 실마리를 제공한다. 현전하는 보사공신교서 중에 제작당시의 장황을 갖추고 있는 것이 확인되지 않은 상황에서 중요한 자료라고 할 수 있겠다.