• 한국산학기술학회논문지
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• 제20권7호
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• pp.347-352
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• 2019

본 연구는 소형 유도전동기 회전자를 생산공장에서 금형주조(die casting)로 제작 시 발생하는 cast 부 품질문제를 개선하기 위하여 수행되었다. 1차 연구결과와 현장 적용성을 고려한 수많은 parametric study를 통하여 새로운 rotor core cast model을 제안하였으며, 그 제안된 model에 대한 유효성을 평가, 검증하기 위하여 주조해석 전용프로그램을 사용한 수치해석과 실제품에 대한 현장실험을 통하여 다음과 같은 결론을 얻었다. 첫째, 유도전동기 회전자의 새로운 cast model에 대한 충진해석을 수행한 결과 용탕은 하부 end ring 부를 먼저 충진하고 이동하여 상부 end ring, core slot 부분을 충진하고 최종적으로 core slot 부분에서 충진이 완료된다. 둘째, 새롭게 제안된 rotor core cast model에 대한 용탕의 유동 양상을 보면 하부 end ring 부에 용탕의 유동에 의한 와류가 적게 발생하였으며, 현장실험 결과 하부 end ring 부 단면에서 소량의 작은 결함만이 발견되었다. 셋째, 유도전동기 회전자 제작 시 rotor core cast 형상 변경을 통하여 end ring 부 결함 발생 면적이 약 70 % 감소한 양호한 품질의 회전자를 생산할 수 있다.

• 조명전기설비학회논문지
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• 제26권10호
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• pp.52-59
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• 2012

In this paper, The cast resin transformer's vibration is measured using noncontact raser vibrometer(LV110D). The vibration characteristics of transformer windings and core are analyzed for relation between vibration magnitude and cause. Using the analysis results, the technique is presented to diagnose cast resin transformer. which is able to diagnose transformer' deformation in winding and core geometry. The magnetostriction and electromagnetic force act on the core and windings, causing them to vibrate. The vibration from windings and core penetrates into transformer cast resin and reaches the outside walls. The fundamental frequency of the core and windings vibration signal is twice that of the power frequency(120Hz). The results show that the magnitude of core vibration is linear to driving voltage amplitude and magnitude of windings vibration is increased to loading current under the some level and then stabilized.

• 한국산학기술학회논문지
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• 제19권10호
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• pp.115-120
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• 2018

본 연구에서는 산업현장에서 널리 사용되고 있는 소형 유도전동기의 회전자를 생산공장에서 금형주조(die casting)로 제작 시 rotor core cast의 품질을 평가하기 위하여 주조해석 전용 프로그램을 사용하여 수치해석을 수행하였으며, 그 결과를 실험결과와 비교하여 다음과 같은 결론을 얻을 수 있었다. 첫째, 유도전동기 회전자의 고압 금형주조 시 고속으로 사출된 알루미늄 용탕의 충진 양상을 시간 경과에 따라 평가한 결과, 용탕은 하부 end ring 부를 먼저 충진하고 수평으로 이동하여 상부 end ring, core slot 부분을 충진하여 최종적으로 core slot 부분에서 충진이 완료된다. 둘째, mould 내부에서의 용탕의 충진 양상을 보면 상부 end ring, core slot 부분보다 하부 end ring 부분에서 용탕의 유동에 의한 와류가 발생하여 결함 발생이 예측되었으며, 현장 실험결과 하부 end ring 부 단면에서 작고 큰 다수의 결함이 발견되었다. 셋째, 금형주조 작업으로 양호한 품질의 회전자를 제작하기 위해서는 cast 형상 변경이나 작업조건 등 추가적인 연구가 필요하며 이에 대해서는 추후에 보고할 예정이다.

• 대한치과보철학회지
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• 제46권3호
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• pp.269-279
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• 2008

STATEMENT OF PROBLEM: Recently, various all-ceramic crowns fabricated with CAD/CAM systems have come into wide use in dental clinic. However, there are only few domestic studies on CAD/CAM restorations. PURPOSE: Purpose of this study was to compare the fidelity (absolute marginal discrepancy and internal gap) between various cores fabricated with different CAD/CAM systems (Procera system, Lava system, Cerec inLab system) and conventional metal cast core. MATERIALS AND METHODS: 10 cores per each system were fabricated. The absolute marginal discrepancies were measured using measuring microscope and digital counter. The internal gaps were calculated using a silicone paste. The results were statistically analyzed using the one-way ANOVA test and Tukey's HSD test. RESULTS: Within the limits of this study the results were as follows. 1. The absolute marginal discrepancies were $32.5{\pm}3.7\;{\mu}m$ for metal cast core, $72.2{\pm}7.0\;{\mu}m$ for Procera core, $40.8{\pm}5.4\;{\mu}m$ for Lava core, and $55.3{\pm}8.7\;{\mu}m$ for Cerec inLab core. The internal gaps were $38.4{\pm}5.7\;{\mu}m$ for metal cast core, $71.4{\pm}5.3\;{\mu}m$ for Procera core, $45.9{\pm}7.3\;{\mu}m$ for Lava core, and $51.8{\pm}6.2\;{\mu}m$ for Cerec inLab core. 2. The fidelity of metal cast core showed the smallest gaps, followed by Lava core, Cerec inLab core, and Procera core. CONCLUSION: The fidelities of 4 core groups were all within the clinically acceptable range ($120\;{\mu}m$).

• 대한치과보철학회지
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• 제38권2호
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• pp.169-177
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• 2000

The purpose of this study was to compare the retention of complete cast crown over amalgam ores, composite resin cores, and cast gold cores when cemented with three different luting agents. Eighteen core specimens each of amalgam(Bestaloy, Dong Myung, Seoul, Korea), composite resin (Z100, 3M Dental product, st. Paul, Minn) and type IV gold alloy (Ba-4, Heesung Engelhard Corp., Korea) were made in a customized milling stainless steel die. A wax pattern with a loop attached to occlusal surface was made for each core and a type II gold alloy casting was fabricated. The castings which had clinically acceptable marginal fit were used as test samples. The following luting cements were used to cement cast crowns on each core material : (1) zinc phosphate cement (Confi-dental Products Co., USA) (2) glass-ionomer cement (Fuji Plus, GC Industrial Corp., Tokyo, Japan) (3) resin cement (Panavia 21, Kuraray Co., USA). All cements were mixed according to manufacturers' instructions. A static load of 5kg was then applied for 10 minutes on the crowns. All specimens were stored in saline solution for 24 hours at $37^{\circ}C$ and thermocycled for 500 cycles. After storage and cycling, the tensile bond strengths were measured by using a universal testing machine (Instron Corp., Canton, Mass.) at a crosshead speed of 0.5mm/min. The results were as follows 1. The retentive strength of resin cement was the highest of alt three types of cement for resin core (p<0.05). 2. There was no statistical difference among the retentive strengths of three cements for amalgam core (p>0.05). 3. The retentive strength of resin cement was higher than that of zinc phosphate for cast core, but there was no difference between the retentive strength of glass ionomer cement and those of rein and zinc phosphate cement. 4. The retentive strength of the zinc phosphate cement for amalgam core was the highest of all type of cores.

• 대한치과보철학회지
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• 제24권1호
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• pp.55-65
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• 1986

An in vitro study was performed to evaluate adaptation of custom direct, custom indirect, and prefabricated post system on 15 extracted upper central incisors. 15 specimens were prepared and equally devided into 3 groups under random sampling. Each group of 5 cast posts was made with custom direct, custom indirect, and prefabricated post core method. Gap between inner wall of the dentin and outer wall of the cast post was measured on electron microphotographic prints at x500 magnification. The result were as follows ; 1. No significant difference of adaptation at cervical portion was found between each method. 2. Prefabricated post core method had poor adaptation compared with other methods. 3. Even distribution of adaptation was found in custom direct method between each portion. 4. Prefabricated post core method showed remarkable difference in adaptation between each portion.

• 전기학회논문지P
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• 제64권4호
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• pp.256-260
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• 2015

In this paper, achieved rise temperature distribution about degradation phenomenon of 24 MVA distribution cast resin transformer using CFD(Computational Fluid Dynamics). Usually, life of transformer is depended on temperature distribution of specification region than thermal special quality of transformer interior. Specially, life of transformer by decline of dielectric strength decreases rapidly in case rise by strangeness transformer interior hot spot temperature value permits. Because calculating high-voltage(HV) winding and low-voltage(LV) winding of cast resin transformer and Joule's loss of core for improvement these life, forecasted heat source, and HV winding and LV winding of cast transformer rise temperature distribution of core for supply of electric power and temperature distribution of highest point on the basis of the results. Also, calculated temperature rise limit of cast resin transformer and permission maximum temperature using analysis by electromagnetic heat source. Calculated and forecasted rise temperature distribution by heat source of thermal analysis with calculated result.

• 한국기계가공학회지
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• 제12권6호
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• pp.60-68
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• 2013

The present research aims to develop aluminum disc brakes to replace existing cast iron disc brakes in automobiles. The foundation for developing an aluminum disc is laid by investigating the performance characteristics of existing cast iron disc brakes and comparing those characteristics with those of aluminum disc brakes. This study involves FEM thermal/structural analysis of disc materials and experimental tests using a brake dynamometer. The results of this study show that, aluminum discs have not only better thermal/mechanical properties than existing cast iron discs, including better heat, wear, and crack resistance, but also that aluminum discs. Weigh less than existing cast iron discs, which results in improved maneuverability. Aluminum discs will become a more essential part of automobiles as electric cars become the major means of transportation.

• 대한치과보철학회지
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• 제32권2호
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• pp.225-233
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• 1994

The restorations of the severely damaged teeth by post core have been increased with the developement of endodontic procedures. But high failure rates of these procedures being reported, various restorative modifications were induced for successful treatments. Cast post-core and prefabricated post with core buildups are choice of treatment. The main causes of failure of the restorations are the fracture of post and core, root fracture, and recurrent caries due to microleakage. Recently, the acid etching technique and the use of dentin bonding agent at tooth surface to reduce the possible microleakage at the tooth-restoration interfaces were introduced. The object of this study was to measure and compare the microleakage by the types and cementation methods of post-core. For this study, forty extracted human anterior teeth were selected for specimen. After cleansing and routine endodontic procedures, anatomic crowns of each specimen were removed at the level of 2mm above the cementoenamel junction. Canals were preparated for post insertion and specimens were divided into four groups randomly. Post-cores were fabricated according to method for each group. Microleakage was measured by length of dye penetration at the tooth-restoration interfaces with measuring microscope at 50 magnification. Oneway ANOVA and t-test were performed for statistical analysis of resulting data. The following results were obtained from this study. 1. There wert significant statistical differences in degree of microleakage between each group (p<0.01). 2. Cast post-core cemented with ZPC (Group I) showed the most severe microleakage pattern$(1.5547{\pm}0.0872mm)$, and cast post-core cemented with adhesive resin cement after tooth surface treatment with dentin bonding agent (Group II) showed the least microleakage $(0.1497{\pm}0.0872mm)$. 3. Group IV revealed less dye penetrations than group III, but no statistical significance was seen between two groups.

• The Journal of Advanced Prosthodontics
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• 제9권3호
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• pp.170-175
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• 2017

PURPOSE. The aim of the present study was to evaluate the fracture resistances of zirconia, cast nickel-chromium alloy (Ni-Cr), and fiber-composite post systems under all-ceramic crowns in endodontically treated mandibular first premolars. MATERIALS AND METHODS. A total of 36 extracted human mandibular premolars were selected, subjected to standard endodontic treatment, and divided into three groups (n=12) as follows: cast Ni-Cr post-and-core, one-piece custom-milled zirconia post-and-core, and prefabricated fiber-glass post with composite resin core. Each specimen had an all-ceramic crown with zirconia coping and was then loaded to failure using a universal testing machine at a cross-head speed of 0.5 mm/min, at an angle of 45 degrees to the long axis of the roots. Fracture resistance and modes of failure were analyzed. The significance of the results was assessed using analysis of variance (ANOVA) and Tukey honest significance difference (HSD) tests (${\alpha}=.05$). RESULTS. Fiber-glass posts with composite cores showed the highest fracture resistance values ($915.70{\pm}323N$), and the zirconia post system showed the lowest resistance ($435.34{\pm}220N$). The corresponding mean value for the Ni-Cr casting post and cores was reported as $780.59{\pm}270N$. The differences among the groups were statistically significant (P<.05) for the zirconia group, as tested by ANOVA and Tukey HSD tests. CONCLUSION. The fracture resistance of zirconia post-and-core systems was found to be significantly lower than those of fiber-glass and cast Ni-Cr post systems. Moreover, catastrophic and non-restorable fractures were more prevalent in teeth restored by zirconia posts.