• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1254-1259
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• 2009

과거 관측된 수문자료는 분석을 통해 다양한 수문모형의 평가 및 예측과 수자원 정책결정에서 활용된다. 하지만 관측장비의 오작동 및 관측범위의 한계에 의해 수집된 자료에는 결측이 존재한다. 단순히 결측이 존재하는 벡터를 제외하거나, 결측이 존재하는 자료 구간에 선형성이 존재한다는 가정 하에 평균을 활용하기도 했으나, 이로 인하여 자료의 통계특성에 왜곡이 야기될 수 있다. 본 연구는 결측의 보정으로 자료가 보유하는 정보의 손실 및 왜곡을 최소화 할 수 있는 방안을 연구하고자 한다. 자료의 결측은 크게 완벽한 무작위 결측(missing completely at random, MCAR), 무작위 결측(missing at random, MAR), 무작위성이 없는 결측(nonrandom missingness)으로 분류되며, 수문자료는 결측을 포함한 기간이 그 외 기간의 자료와 통계적으로 동일하지는 않지만 결측자료의 추정이 가능한 MAR에 속하는 것이 일반적이므로 이를 가정으로 결측을 보정하였다. Local Lest Squares Imputation(LLSimput)을 결측의 추정을 위해 사용하였으며, 기존에 쉽게 사용되던 선형보간법과 비교하였다. 적용성 평가를 위해 소양강댐 일 유입량 자료에 1 - 5 %의 결측자료를 임의로 생성하였다. 동일한 양의 결측자료에 대해 100개의 셋을 사용하여 보정의 불확실성 범위를 적용된 방법에 대해 비교..평가하였으며, 결측 증가에 따른 보정효과의 변화를 검토하였다. Normalized Root Mean Squared Error(NRMSE)를 사용하여 적용된 두 방법을 평가한 결과, (1) 결측자료의 비가 낮을수록 간단한 선형보간법을 사용한 보정이 효과적이었다. (2) 하지만 결측의 비가 증가할수록 선형보간법의 보정효과는 점차 큰 불확실성과 낮은 보정효과를 보인 반면, (3) LLSimpute는 결측의 증가에 관계없이 일정한 보정효과 및 불확실성 범위를 나타내는 것으로 드러났다.

• Restorative Dentistry and Endodontics
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• v.13 no.1
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• pp.151-158
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• 1988

The purpose of this study was to evaluate the effect of canal filling methods and post-space preparation time on the apical seal of endodontically treated teeth. Seventy-six single-rooted human teeth were divided into 6 groups and each tooth was obturated and prepared post-space according to the purpose of this study. After all specimens were immersed in Indian ink, decalcified and cleared, the degree of dye penetration into the root canals observed by magnifying glass (X20) and measured by caliper. The results were as follows: 1. In the thermatic condensation, no significant difference in ink penetration occured when the post-spaces were created immediately after obturation or when they were made a week later. 2. In the lateral condensation, no significant difference in ink penetration existed between teeth whose post-space were prepared immediately or delayed. 3. In comparison of experimental groups and control groups, no significant difference showed when the groups were obturated with McSpadden compactor but when the teeth were laterally condensed, the experimental groups showed less ink penetration than controls. 4. Thermatic condensed teeth with McSpadden compactor were less ink penetration thn laterally condensed teeth.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.4
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• pp.717-730
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• 1998

The Finite Element Analysis has been used for stress analysis of prosthesis, orthodontic or orthopedic appliances and filling materials. The primary purpose of the present studying was to evaluate the effectiveness of needle post in promoting the retention and integrity of composite crown restored on the pulpotomized primary central incisor. Three finite element models-natural tooth (Sample I), composite crown with (Sample II) and without (Sample III) needle post-were constructed and the stress distribution within each model were analyzed and compared one another. The results can be summarized as follows: 1. In sample I, the stress was shown to have distributed uniformly throughout the whole tooth even to the alveolar bone. 2. In sample II, the transmission of stress from the crown to the root area was shown to be very poor and irregular. 3. In sample III, the needle post was proved to be very effective in distributing the stress well to the aveolar bone which might help in maintaining the stability of crown restoration.

• The Journal of the Korean dental association
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• v.10 no.1
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• pp.35-40
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• 1972

저자는 임상에서 널리 사용되는 근관충전재료인 산화아연유지놀, N2, MN2 및 Triozinc Paste의 살균효과를 비교하기 위하여 한천배양기 및 혈액가한천배양기상에서 백색포도상구균 및 α-용혈성연질상구균의 두균주를 사용, 실험하여 다음과 같은 결과를 얻었다. 1) 백색포도상구균을 심은 한천배양기상에서 비건조도판을 사용한 실험군에서의 균성장억제대는 MN2, 6. 83; Triozinc paste, 5. 77; N 2, 5. 61; 산화아연유지놀, 3.49mm였다. 2) 백색포도상구균을 심은 한천배양기상에서 건조도판을 사용한 실험군에서의 균성장억제대는 MN2, 4.40; Triozinc paste, 1.46; 산화아연유지놀, 0.99; ㅜ2, 0.84mm였다. 3) 백색포도상구균을 심은 혈액가한천배양기상에서 건조도판을 사용한 실험군에서의 균성장억제대는 MN 2, 1.15; Triozinc paste, 0.55; 산화아연유지놀, 0.54; N2, 0.43mm였다. 4) α-용혈성연질상구균을 심은 용혈가한천배양기상에서 건조도판을 사용한 실험군에서의 균성장억제대는 MN 2, 2.14; Triozinc paste, 1.00; 산화아연유지놀, 0.75; N 2, 0.43mm였다.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.4
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• pp.474-481
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• 2011

The purpose of this study was to investigate the effect of rigidity of post core systems on stress distribution by the finite element stress analysis method. Three-dimensional finite element models simulating an endodontically treated maxillary central incisor restored with a zirconia crown were prepared. Each model contained cortical bone, trabecular bone, periodontal ligament, 4mm apical root canal filling, and post-and-core. A 50N static occlusal load was applied to the palatal surface of the crown with a $60^{\circ}$ angle to the long axis of the tooth. And three parallel type post (zirconia, glass fiber and stainless steel) and two core (Paracore and Tetric ceram) materials were evaluated, respectively. The differences in stress transfer characteristics of the models were analyzed. von Mises stresses were chosen for presentation of results and maximum displacement and hydrostatic pressure were also calculated. For the Result of the research, the model applied glass fiber to post material has lowest von Mises stress and it is suitable for material of post core systems.

• Transactions of Materials Processing
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• v.26 no.3
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• pp.156-161
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• 2017

In this study, the reason of die fracture occurring in hot forging of an aluminum fixed scroll was studied, based on experiments and finite element predictions. The material is assumed to be rigid-viscoplastic, and the die is rigid for the finite element predictions. The stress in the tension at the wrap root is known to cause brittle fracture, and the increase in the tensile stress is owing to the unbalanced filling of material into the die cavities between both sides of the warp. Based on the empirical and numerical achievements, the effects of geometrical parameters of the material on the die fracture were examined to find practical measures for elongated die life. It has been shown from the parametric study that the material with the optimized trapezoidal cross-section, which can be easily made during cutting or the optimized cylindrical billet with its eccentric placement in the die cavity, can considerably reduce the magnitude of the tensile stress around the die corner fractured, indicating that economical manufacturing with reduced number of stages and elongated die life can be realized at once using the optimized practical initial material.

• Restorative Dentistry and Endodontics
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• v.41 no.1
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• pp.63-67
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• 2016

During clinical endodontic treatment, we often find radiopaque filling material beyond the root apex. Accidental extrusion of calcium hydroxide could cause the injury of inferior alveolar nerve, such as paresthesia or continuous inflammatory response. This case report presents the extrusion of calcium hydroxide and treatment procedures including surgical intervention. A 48 yr old female patient experienced Calcipex II extrusion in to the inferior alveolar canal on left mandibular area during endodontic treatment. After completion of endodontic treatment on left mandibular first molar, surgical intervention was planned under general anesthesia. After cortical bone osteotomy and debridement, neuroma resection and neurorrhaphy was performed, and prognosis was observed. But no improvement in sensory nerve was seen following surgical intervention after 20 mon. A clinician should be aware of extrusion of intracanal medicaments and the possibility of damage on inferior alveolar canal. Injectable type of calcium hydroxide should be applied with care for preventing nerve injury. The alternative delivery method such as lentulo spiral was suggested on the posterior mandibular molar.

• Restorative Dentistry and Endodontics
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• v.6 no.1
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• pp.123-132
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• 1980

The author conducted a dental survey of a college girl students and compared with that of E college students 10 years ago which based on the same criteria. The items of this survey included the prevalence of dental caries, DMFT and the kinds of restored material. All college students 1,414 were examined in May 1978, with the recommended criteria and method of W.H.O.. Among them, the data of 1,393 were analyzed for this study. The following results were obtained: 1. The average number of present teeth were 28.97${\pm}$1.64. 2. The prevalence of dental caries was 84.92% and D.M.F. index was 15.51. Average D.M.F. teeth were 4.49${\pm}$3.69. 3. The average number of decayed (D) teeth were 2.09${\pm}$2.16. 4.30% of the present decayed teeth was secondary decay, and 2.44% of the decayed teeth was indicated for extraction. 4. The average number of missing(M) teeth were 0.32${\pm}$0.79. It included 8.56% of root fragements. 5. Average number of filled(F) teeth were 2.09${\pm}$3.17. F-ratio of this group was 46.45%. The analysis revealed 50.88% of amalgam alloy, 31.41% of gold inlays, and 1.20%, the least among the filling materials, silicate cement or composite resin. 6. While the prosthodontic treatment, such as crown and bridge has reduced than that of 10 years ago, the fillings and inlays as the conservative means has increased.

• Restorative Dentistry and Endodontics
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• v.38 no.3
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• pp.113-118
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• 2013

Nowadays, oral anticoagulants are commonly prescribed to numerous patients for preventing cardiovascular accident such as thromboembolism. An important side effect of anticoagulant is anti-hemostasis. In a major surgery, the oral anticoagulant therapy (OAT) regimen must be changed before the surgery for proper post-operative bleeding control. However, in a minor dental surgery and endodontic surgery, the necessity for changing or discontinuing the OAT is open to debate. In this study, risks of the consequences were weighed and analyzed. In patients who stop the OAT, the occurrence of thromboembolic complication is rare but the result is fatal. In patients who continuing the OAT, post-operative bleeding can be controlled well with the local hemostatic measures. In the endodontic surgery, there are almost no studies about this issue. The intra-operative bleeding control is particularly important in the endodontic surgery because of its delicate and sensitive procedures such as inspection of resected root surface using dental microscope and retrograde filling. Further studies are necessary about this issue in the viewpoint of endodontic surgery.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.8
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• pp.63-72
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• 1995

Closed-die forging of spur gears with hollow cylindrical billet has been analysed by using the upper-bound method. A kinematically admissible velocity field has been developed, wherein, an involute curve has been introduced to represent the forging die profile. In the analysis, the deformation region has been divided into nine zones. A constant frictional stress has been assumed on the contacting surfaces. Utilizing the formulated velocity field, numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth and friction factor, on the forging of spur gears. Hardness and accuracy of forged gears are measured. The following results have been obtained: (1) It is verified that an axisymmetric deformation zone exists between root circle and center of gear through forged gears. (2) The average relative forging pressure is predominantly dependent on the number of teeth and increases near the final filling stage as the addendum modification coefficient increases. (3) Close agreement was found between the predicted values of forging load and those obtained from experimental results.