• Nuclear Engineering and Technology
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• v.27 no.6
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• pp.811-824
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• 1995

The CANDU element bowing is attributed to actions of both the thermally induced bending moments and the bending moment due to hydraulic drag and mechanical loads, where the bowing is defined as the lateral deflection of an element from the axial centerline. This paper consider only the thermally-induced bending moments which are generated both within the sheath and the fuel and sheath by an asymmetric temperature distribution with respect to the axis of an element The generalized and explicit analytical formula for the thermally-induced bending is presented in con-sideration of 1) bending of an empty tube treated by neglecting the fuel/sheath mechanical interaction and 2) fuel/sheath interaction due to the pellet and sheath temperature variations, where in each case the temperature asymmetries in sheath are modelled to be caused by the combined effects of (i) non-uniform coolant temperature due to imperfect coolant mixing, (ii) variable sheath/coolant heat transfer coefficient, (iii) asymmetric heat generation due to neutron flux gradients across an element and so as to inclusively cover the uniform temperature distributions within the fuel and sheath with respect to the axial centerline. As the results of the sensitivity calculations of the element bowing with the variations of the parameters in the formula, it is found that the element bowing is greatly affected relatively with the variations or changes of element length, sheath inside diameter, average coolant temperature and its variation factor, pellet/sheath mechanical interaction factor, neutron flux depression factor, pellet thermal expansion coefficient, pellet/sheath heat transfer coefficient in comparison with those of other parameters such as sheath thickness, film heat transfer coefficient, sheath thermal expansion coefficient and sheath and pellet thermal conductivities.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.04a
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• pp.96-99
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• 2003

본 논문에서는 수치 해석 방법을 이용하여 $In_{x}Ga_{1-x}N/GaN$ (x=0.06~0.1) 양자우물 구조의 에너지 준위를 계산하였다. InGaN 벌크 샘플(bulk sample)의 PL(photoluminescence) 데이터로부터 bowing factor를 결정한 후 InGaN의 유효 에너지 밴드갭을 계산하였고, InGaN/GaN 양자우물 구조의 전도대와 가전자대의 오프셋(offset)을 0.67/0.33으로 정하였다. 다음으로, 양자화 효과에 의한 에너지 변위와 압전장(piezoelectric field)을 제외한 양축 압축 변형(biaxial compressive strain)에 의한 에너지 변위를 고려하여 기저준위 전자와 heavy hole(le-1hh)간의 천이 에너지를 계산하였다. 계산된 천이 에너지는 PL로 측정한 천이 에너지에 비해 약 9~15 meV 크게 관찰되었는데, 이것은 InGaN/GaN 양자우물 계면에 발생하는 압전장 때문인 것으로 생각된다.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.3 s.36
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• pp.187-196
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• 2005

MEMS devices such as a vibratory gyroscope often suffer from a lower yield rate due to fabrication errors and the external stress. In the decoupled vibratory gyroscope, the main factor that determines the yield rate is the frequency difference between the sensing and driving modes. The gyroscope, fabricated with SOI (Silicon-On-Insulator) wafer and packaged using the anodic bonding, has a large wafer bowing caused by thermal expansion mismatch as well as non-uniform surfaces of the structures caused by the notching effect. These effects result in large distribution in the frequency difference, and thereby a lower yield rate. To improve the yield rate we propose a packaged SiOG (Silicon On Glass) technology. It uses a silicon wafer and two glass wafers to minimize the wafer bowing and a metallic membrane to avoid the notching. In the packaged SiOG gyroscope, the notching effect is eliminated and the warpage of the wafer is greatly reduced. Consequently the frequency difference is more uniformly distributed and its variation is greatly improved. Therefore we can achieve a more robust vibratory MEMS gyroscope with a higher yield rate.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.165-172
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• 2005

In MEMS (Micro-Electro-Mechanical System), packaging induced stress or stress induced structure deformation becomes increasing concerns since it directly affects the performance of the device. In the decoupled vibratory MEMS gyroscope, the main factor that determines the yield rate is the frequency difference between the sensing and driving modes. The gyroscope, packaged using the anodic bonding at the wafer level and EMC (epoxy molding compound) molding, has a deformation of MEMS structure caused by thermal expansion mismatch. This effect results in large distribution in the frequency difference, and thereby a lower yield rate. To improve the yield rate we propose a packaged SiOG (Silicon On Glass) process technology. It uses a silicon wafer and two glass wafers to minimize the wafer warpage. Thus the warpage of the wafer is greatly reduced and the frequency difference is more uniformly distributed. In addition. in order to increase robustness of the structure against deformation caused by EMC molding, a 'crab-leg' type spring is replaced with a semi-folded spring. The results show that the frequency shift is greatly reduced after applying the semi-folded spring. Therefore we can achieve a more robust vibratory MEMS gyroscope with a higher yield rate.

• Journal of the Korean Orthopaedic Association
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• v.54 no.6
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• pp.519-527
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• 2019

Purpose: To evaluate the treatment result in polyostotic fibrous dysplasia classified according to the involvement of the femoral head. Materials and Methods: Twenty-three patients from March 1987 to March 2014 were reviewed retrospectively. Patients with no involvement of the physeal scar in the femoral head were classified as Type I, and those with involvement of the physeal scar were classified as Type II. A plain radiograph was used to measure the femoral neck shaft angle, articulo-trochanteric distance (ATD), and anterior bowing through the lateral view. A teleoroentgenogram of the lower limb was used to measure the leg length discrepancy and lower extremity mechanical axis. The pre- and postoperative femoral neck-shaft angle and ATD were compared to assess the degree of correction of the deformity. Results: Among a total of 46 cases (23 patients), 28 cases (23 patients) had lesions in the proximal femur. Type I were 16/28 cases (15/23 patients) and Type II were 12/28 cases (9/23 patients). The preoperative proximal femoral neck-shaft angle was 116.8° in Type I and 95.3° in Type II. The ATD was 12.08 mm in Type I and -5.54 mm in Type II. The deformity correction showed significant improvement immediately after surgery, the deformity correction was lost in Type II (neck shaft angle Type I: 133.8°-130.8°, Type II: 128.6°-116.9°, and ATD Type I: 17.66-15.72 mm, Type II: 7.44-4.16 mm). The extent of anterior bowing was 12.74° in Type I and 20.19° in Type II. The mean differences of 12 mm between the 9 patients who showed a leg length discrepancy and the lower extremity mechanical axis showed 4 cases of lateral deviation and 7 cases of medial deviation. Conclusion: In polyostotic fibrous dysplasia, when the femur head is involved, the femur neck shaft angle, ATD, and anterior bowing of the femur had more deformity, and the postoperative correction of deformity was lost, suggesting that the involvement of the femoral head was an important factor in the prognosis of the disease.