• Restorative Dentistry and Endodontics
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• v.20 no.2
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• pp.758-767
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• 1995

The purpose of this study was to evaluate canal shaping ability after canal preparation by using engine-driven nickel-titanium file and endosonic file in curved canals. 30 mesiobuccal canals of molars extracted within recent 3 months were divided into 3 groups. Group I and group II were prepared by using engine-driven nickel-titanium Gates-Glidden drill type and the engine-driven nickel-titanium file type. Group III prepared by using en do sonic file. The image of preinstrumented canals was taken by X-ray. The image of postinstrumented canal was taken by X-ray in the same condition of preinstrumentation. A magnified X-ray image on magnifier screen was traced and then compared the preinstrumentated canal image with the postinstrumentated canal image by superimposing method. The following results were obtained : 1. In the change of canal curvature, the engine-driven nickel-titanium Gates-Glidden drill type showed the least change and the ultrasonically filing showed the greatest change. 2. In the percentage of canal enlargement, the engine-driven nickel-titanium file type was greatest at all level(p<0.05), the apex of all group was the greatest, the difference of ultrasonically filing group showed greater between apex and cervix. 3. The percentage of canal enlargement on convex side was greater than that of on concave side in apex of each group(p<0.05). In the ultrasonically filing group, both sides of canal enlargement showed sharply difference(p<0.01). 4. The percentage of canal enlargement on convex side was greater than that of on concave side in the third of cervix of the engine-driven nickel-titanium file type and the ultrasonically filling. The percentage of canal enlargement of convex and concave side in the third of middle of the engine-driven nickel-titanium Gates-Glidden drill type show a similar canal enlargement between convex side and concave side. As above result, the engine-driven nickel-titanium file type was greater in canal enlargement than the other instruments. The engine-driven nickel-titanium Gates-Glidden dirll type was efficient endodontic instrument for curved canal preparation because it was least change in canal curvature.

• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.73-79
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• 2000

We measure a beam diameter of scan and sub-scan direction of LSD (Laser Scanning Urnt) which uses $fheta$ lens produced by injecLion molding method as a scanning lens. While the measured beam diameter in scan direction, which is $62muextrm{m}$ to $68\mu\textrm{m}$, shows similar size comparing to the design beam diameter, the sub-scan beam diameter shows sIzable beam diameter deviation as much as 37 11m ranging from $78\mu\textrm{m}$ to $115\mu\textrm{m}$. Injection molding lens has the surface figure error due to the shrinkage III the cooling time and the internal distortion (birefringence) due to the uneven cooling conditIOn so that these bring about wavefront aberration (i.e., the enlargement of beam size), and are eventually expre~sed as the deterioration of the pdnting image. In this paper. we first measure and analyze beam diameter, birefringence (polanzation ratio), and asphedcal figure error of mIens in order to know the principle cause of the beam diameter deviation in sub-scan directIOn. And Lhen. through the analysis of a designed depth of focus and a calculated field curvature (imaging position of the optical axis directIon) using the above figure elTor data, we know Lhat the birefringence IS the main factor of sizable beam diameter deVIation in sub-scan direction. ction.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.304-312
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• 2005

Field performance of several different types of diffractive optical elements(DOEs) has been carried out. Using Zemax model, we have designed five different types of DOEs, such as transmissive flat-DOE, transmissive curved-DOE, reflective flat-DOE, reflective curved-DOE and parabolic mirror, We have applied two different wavelengths, i.e., 13 m(EUV) and 632.8 nm(visible) to above DOEs. Off_axis dominate aberrations and the diffraction limiting (Rayleigh limit) field angles have been investigated and compared at both wavelengths for each DOE. At diffraction limit, field angle of curved-DOEs was much greater than that of flat-DOEs for both transmission and reflective types. We also showed that dominated off_axis aberration of flat-DOEs was coma, but that of curved-DOEs was mixture of astigmatism and curvature of field. The measured field angle and expected OPD aberrations were well coincided with theoretical ones. Increasing the ratio of field angle with wavelength was more effective in curved-DOEs than flat-DOEs.

• Proceedings of the Korea Water Resources Association Conference
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• 2012.05a
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• pp.535-535
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• 2012

하천 환경의 변화는 자연적으로 일어나기도 하지만, 우리나라 경우 대부분 하천 정비, 골재 채취, 수중보와 하구둑 등 하천시설물의 건설, 그리고 댐 및 교량건설 등 인위적인 요인에 의한 변화가 지배적이다 이렇게 환경이 변화하면 하천의 평형 상태는 파괴되며 하천의 평형 상태를 복원하는 과정에서 하천의 침식 또는 퇴적이 일어나며 이러한 과정의 총체적인 결과로서 하상변동이 일어나게 된다. 하상변동은 단기적인 면에서는 하천에서의 취수, 배수, 주운동 하천관리에 직접적인 영향을 주며, 장기적인 면에서는 하천시설물의 안정, 홍수위 및 지하수위 변화, 홍수터와 같은 하천부지의 변화 등 하천 및 유역 관리에 광범위한 영향을 주고 있다 하천의 유황 및 하상재료의 인위적인 변화에 의한 장기적인 하상변동 효과를 예측하고 분석하는 것은 하천계획 및 관리 면에서 매우 중요하다. 또한 하천 정비사업 등에 의한 영향을 제대로 평가하기 위해서는 비교적 단기간의 홍수 또는 호우 사상에 대한 단기적인 하상변동 효과를 정확하게 예측하는 것은 필수적이다. 외국에서는 하상변동 예측의 필요성을 일찍이 인식하여 다수의 하상변동 예측모형이 개발되어 하천 실무에 사용되고 있으며, 국내에서도 하천 흐름의 등수 역학적 해석을 위해 여러 가지 수치 기법들에 대한 연구가 진행되고 발전되어져 왔다. 현재 국내에서는 측량 자료이용과 모형적용의 용이성을 이유로 1차원 점변 부정류 해석프로그램인 HEC-RAS 모형을 많이 사용하고 있으며 대부분의 하천 정비 기본계획 수립에 있어서도 1차원 해석 모형을 적용하고 있는 실정이다. 국내에 서 수행된 하상변동 예측에 관한 연구들은 대부분 1차원 모형이므로 하천의 사행의 진행이나 유사의 횡방향 분포 등은 고려할 수 없다. 또한 하상변동 계산 시 이동상 부분의 전체가 균일하게 상승 또는 하향하는 것으로 가정하기 때문에 흐름이 급변하는 데 적용하는 것은 적합하지 않다. 따라서 본 연구에서는 4대강살리기 사업이 진행중인 낙동강유역 구미보지점을 대상으로 2차원 흐름 및 하상변동 수치모형인 CCHE2D 모형을 적용하여 50년, 100년, 200년 빈도별로 모의를 실시, 보설치 전 후의 하상변동을 비교 분석 하였다. 모의 결과 보설치 후의 경우 보 상류단은 전반적으로 퇴적의 양상을 보였으며, 보 하류단의 만곡부의 경우 홍수량이 증가함에 따라 유속 및 소류력이 비슷한 패턴으로 증가하여 침식이 관찰되었다. 특히 보 직하류의 경우 수문을 기준으로 다량의 침식이 있음을 보였으며, 침식이 계속 진행된다면 보유실과 같은 심각한 결과를 초래할 수 있기 때문에 침식을 방지 할 수 있는 다양한 장치가 마련되어야 할 것으로 판단된다.

• Korean Journal of Soil Science and Fertilizer
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• v.39 no.1
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• pp.46-51
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• 2006

Phosphorus accumulation in fertilized soils becomes serious problem for agriculture and the environment. In this investigation, we conducted a laboratory scale investigation to find the most desirable displacement methods of the adsorbed phosphate onto the soil particle surfaces. Soil samples which contained high amount of phosphate were collected at two different depths (0-10 cm and 10-20 cm) from four locations at the moderate highland located in Nonsan, Chungnam. To observe the mobilization of solid-phase phosphate, soil samples were equilibrated with oxalic acid solutions ranging from $10^{-5}$ to $10^{-1}cmol\;L^{-1}$ with the dilution factors of 1:1, 1:2.5, 1:5, 1:10, and 1:20. The mineralized P sharply increased as the concentration of oxalic acid was greater than $5{\times}10^{-4}cmol\;L^{-1}$ under dilution factors of 1:1, 1:2.5, and 1:5. The breaking concentration of oxalic acid was lowered to $10^{-4}cmol\;L^{-1}$ and $5{\times}10^{-5}cmol\;L^{-1}$ for dilution factors of 1:10 and 1:20, respectively. The curve fit obtained from the graph can be described by exponential growth when the dilution factors were 1:1, 1:2.5, and 1:5 while the sigmoidal shape for 1:10 and 1:20, showing the mineralization of P were significantly dependent on the dilution factor.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.25 no.1
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• pp.6-11
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• 1989

Some distinctive defects in the conventional stow net were examined and presented in the previous report of this series. To find out the more effective gear by correcting the defects, the authors carried out another experiment by using a newly designed gear. 1. Special features of the newly designed gear are: (1) stretched width of front end on top, bottom and side panel are decreased 20%, on the other hand, the frank of the panels are increased 10% compared with the conventional gear. Front end of top and bottom panels are bias cutten up to 20% of the length of panels. (2) Length of the head rope and ground rope are shortened 6% by changing of the shape of the top and bottom panels. (3) Lacing lines are attached to four longitudinal seaming lines with suitable hanging ratio. (4) Stretched height of the shearing device were shortened 17%, and the buoyancy on top of the device were increased 20%. (5) Length of the biforked pendants were arranged to be shorter on top-most and bottom-most ones, and loner on middle ones. 2. The observed result can be expressed as (1) Wrinkles in the front end of top panels are removed and fringe line of panels become smooth. (2) Opening height of mouth is observed 3% higher than that of the conventional gear. (3) Opening width is 1.5 to 1.6 times wider than that of the conventional gear. (4) Hydrodynamic resistance is decreased 10%-17%.

• Journal of fish pathology
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• v.8 no.1
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• pp.57-67
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• 1995

Twenty-four hours, acute toxicity and the histopathological effect of formaline to flounder, Paralichthys olivaceus larvae were examined. The $LC_{50}$ values obtained to farmaline were 2,520 ppm in 1 hour treatment. 1.610 ppm in 2 hours treatment, 868 ppm in 4 hours treatment and 141 ppm in 24 hours treatment. Many pathological features such as hypertrophy of mucous and epithelial cells in secondary gill lamella, hyaline droplet degeneration of tubular epithelial cells in the proximal convoluted segment of renal tubules, focal or massive necrosis in liver cells and pycnotic nucleus in heart cells were recognized. The above results were discussed in relation to the application of formaline as therapeutic agent in flounder disease.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.257-268
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• 1998

During cleaning and shaping of narrow and curved canals, it is very difficult or nearly impossible to maintain the original canal shape. Procedural accidents such as, ledge, zipping, perforation, and instrument breakage are frequently occurred and even may lead to failure of endodontic therapy. To prevent these kinds of accidents, various instrumentation techniques and materials have been introduced. Recently some nickel titanium (NiTi) files are introduced and it is reported that These NiTi files created rounder preparations with less transportation than conventional instruments in curved canals. This study compared the change of the canal curvature and procedural accidents after instrumentation produced by stainless steel K-flexo file, and NiTi rotary files (Profile 29 and Quantec 2000). Thirty narrow and curved canals (25-45 degree) of extracted human molars were randomly divided into three groups. In group 1, canals were instrumented using a step-back and watch-winding/pull motion with K-flexo files. In group 2, canals were prepared with Profile 29. Group 3, canals were prepared with Quantec 2000 files. Before and after preparation of canals, periapical radiographs were taken and scanned. The change of canal curvature were measured using Photoshop 4.0 program and the incidence of procedural accidents were also evaluated. The results were as follows: 1. All group showed some loss of canal curvature after instrumentation. 2. Average loss of canal curvature was $6.70{\pm}5.31$ degree for group 1, $3.80{\pm}2.57$ degree for group 2, and $5.40{\pm}4.83$ degree for group 3. All group There was significant change in curvature between before and after instrumentation (p<0.05). But there was no statistical difference amoung 3 groups. 3. In group I, there were no procedural accidents, such as ledging, perforation, or instrument fracture. In group 2, two cases of ledge and one case of instrument fracture were produced Goup 3, each one case of ledge, perforation and instrument fracture were occurred. Whthin the limits of above results, It seems that NiTi rotary instrumentation is not All Mighty and if we use uncarefully, it is more dangerous to produce some procedural accidents than conventional hand files. But more studies should be taken to evaluate the exact effects of NiTi rotary instrumentations.

• Restorative Dentistry and Endodontics
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• v.32 no.1
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• pp.61-68
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• 2007

The purpose of this study was to compare the centering abilities of four root canal instrument systems and the amounts of dentin removed after root canal shaping using them. The mesial canals of twenty extracted mandibular first molars having $10-20^{\circ}$ curvature were scanned using X-ray micro-computed tomography (XMCT)-scanner before root canals were instrumented. They were divided into four groups (n = 10 per group). In Group 1, root canals were instrumented by the step-back technique with stainless steel K-Flexofile after coronal flaring. The remainders were instrumented by the crown-down technique with Profile (Group 2), ProTaper (Group 3) or K3 system (Group 4). All canals were prepared up to size 25 at the end-point of preparation and scanned again. Scanned images were processed to reconstruct three-dimensional images using three-dimensional image software and the changes of total canal volume were measured. Pre-and post-operative cross-sectional images of 1, 3, 5, and 7 mm from the apical foramen were com pared. For each level, centering ratio were calculated using Adobe Photoshop 6.0 and image software program. ProTaper and K3 systems have a tendency to remove more dentin than the other file systems. In all groups, the lowest value of centering ratio at 3 mm level was observed. And except at 3 mm level, ProTaper system made canals less centered than the other systems (p < 0.05).

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.28 no.2
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• pp.37-44
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• 2010

Our country traditionally employed a defensive system against the aggression by foreign powers by using a town castle and mountain castle. The moat was one of such a defensive system; however, there is few research work on a moat in comparison with its long history. This study was carried out to see the process of the changes of the Wolseong Fortress at Gyuongju, focused on the moat of the scale and nature of the construction methods to analyze such a Wolseong Fortress at Gyuongju as a result of consideration through bibliographical study, on-site investigation, and interviews, etc. This research discovered some facts as follows: the moats of Wolseong fortress at Gyeongju are roughly divided into three types; the first one is a natural moat flowing curved by the south side of Wolseong using the natural stream[Namcheon]as it is; the second one is a pond-type moat made by digging up plane non-rectangular pond along stereobate of castle wall with lakefront built with stream pebbles, and the last one is masonry moat at the east side of Wolseong with chisel-trimmed granites orderly piled in a plane triangular form. Among these, the pond-type moat was identified at the east-north-west side of Wolseong and the pond slopes from east to west as a separate one constructed with the terraces.