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복합하중을 받는 원통형 적층복합재 구조의 파괴에 대한 열응력의 영향
조희근 한국생산제조학회 2023 한국생산제조학회지 Vol.32 No.6
As the mechanical behavior of cylindrical structures subjected to complex loads is very complex, predicting phenomena such as displacement, stress, and failure is very difficult. In this study, the effect of thermal stress due to temperature on the failure of a laminated composite cylindrical structure, in which tension, bending, and torsion are applied simultaneously, was evaluated through FEA numerical analysis. Five types of models: Tsai-Wu, Tsai-Hill, Puck, Hoffman, and Hashin, were used to predict the failure of a cylindrical laminated composite shell structure having eight layers. The type of composite failures appeared very different owing to the influence of thermal stress. Contrary to general predictions, we confirmed that thermal stress has a positive effect on failure in certain combinations of layer stacking angles in the case of cylinders.
추나요법과 근막이완요법의 연소성 특발성 측만증 환자 3례에 대한 증례 보고
조희근,이상영,한세혁,신준혁,박수곤,김민성,황춘호,박진우,성인형,정필선,설재욱,김대훈,최은실,Jo, Hee-Guen,Lee, Sang-Young,Han, Sae-Hyuk,Shin, Jun Hyuk,Park, Su-Gon,Kim, Min-Sung,Hwang, Choon-Ho,Park, Jin-Woo,Sung, In-Hyung,Jung, Pil-Sun,Sul, 척추신경추나의학회 2013 척추신경추나의학회지 Vol.8 No.2
Objectives: This report of three cases illustrates the potential effect of chuna therapy and myofascial release technique on back pain and curve regression in the at-risk, skeletally immature patient with adolescent idiopathic scoliosis. Methods: The correction program for scoliosis takes 3 month per case. Chuna Therapy and MRT were given once a week and other oriental medicine care was given twice a week to care the complications of scoliosis. The Cobb's angle(by X-ray, Full spine view) and Visual analogue scale(VAS) were evaluated before and after the treatments. Results: After the program, both of Cobb's angle and VAS decreased. Conclusion: Though it is a case report, we found Chuna Therapy and MRT might have valid effect on adolescent idiopathic scoliosis patients. Further rigorous case series and controlled trials are warranted.
Characteristics and applications of sugar transporter mutated Escherichia coli
조희근,정휘민,임대균,정규열,오민규 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-
Most bacteria have evolved to maximize growth rate, with rapid consumption of carbon sources. However, fast growth feature secretion of organic acid or ethanol and reduce biomass yield in aerobic conditions. Several glucose uptake pathways exist in Escherichia coli, and when these transporters or their subunits were knocked out, the growth and glucose uptake rates decreased but acetate overflow was relieved and biomass yield was improved. Alteration of metabolism caused by the mutations was investigated with transcriptome analysis and <sup>13</sup>C metabolic flux analysis. As a result, various perturbations were identified in the sugar transporter mutants. Based on these findings, robust production hosts were constructed. When pathway genes for producing value-added compounds were introduced, the specific yields of the compounds were improved significantly in the sugar transporter mutants, suggesting that controlling the sugar uptake rate is a good strategy for improving metabolite production.
조희근,진도훈,윤문철,Cho, Hee-Geun,Chin, Do-Hun,Yoon, Moon-Chul 한국생산제조학회 2009 한국생산제조학회지 Vol.26 No.3
The end-milling force behaviour is very complex and it is related to a de-noising phenomenon, so it is very difficult to detect and diagnose this static cutting force phenomenon. This paper presents a new method of filtering of end-milling force in end-milling operation using filter bank technique, based on the wavelet transform. In this paper by comparing the history of end-milling force using wavelet filtering the fundamental end-milling property of the wavelet transform is well reviewed and analyzed. This result of wavelet transform using filter bank shows the possible static prediction of end-milling force with severe dynamic properties such as chatter in end-milling operation.
조희근,박영원 한국군사과학기술학회 2000 한국군사과학기술학회지 Vol.3 No.2
Multi-disciplinary optimization design concept can provide a solution to many engineering problems. In the field of structural analysis, much development of size or topology optimization has been achieved in the application of research. This paper demonstrates an optimum design of a multi-layer cylindrical tube which behaves thermoelastically. A multi-layer cylindrical tube that has several different material properties at each layer is optimized within allowable stress and temperature range when mechanical and thermal loads are applied simultaneously. When thermal loads are applied to a multi-layer tube, stress phenomena become complicated due to each layer's thermal expansion and the layer thicknesses. Factors like temperature; stress; and material thermal thicknesses of each tube layer are very difficult undertaking. To analyze these problems using an efficient and precise method, the optimization theories are adopted to perform thermoelastic finite element analysis.
조희근,안진효 한국복합신소재구조학회 2018 복합신소재구조학회 학술발표회 Vol.2018 No.04
Optimization was performed on the static dynamic behavior of a simply supported laminated composite plate. Thickness optimization was performed with respect to Gr/E laminated composites with simultaneous mechanical load, thermal load and hygro-load. Displacement, fundamental frequency and composite damping were imposed as constraints for optimization. The results of the optimization were much better than those of the conventional methods.
조희근,조은경,최준영,박원규 한국복합신소재구조학회 2016 복합신소재구조학회 학술발표회 Vol.2016 No.04
Grate bar is a metal part being used in the sintering process in a steel company. It is exposed to severe operating conditions such as high temperature, corrosion, wear and chemical reaction and etc. In this paper, the surface of the grate bar is coated with high performance materials. They are Al2O3, Cr2O3, WC. These materials have enhanced grate bar’s performances of life time, corrosion, thermal resistance, abrasion, chemical resistance and etc. These high quality characteristics are verified through experimental tests. The results are presented and discussed.
조희근 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.1
The most frequently encountered structure in design is the cylindrical shell. This study analyzed, methods to optimize the design of a composite cylindrical shell against buckling and failure. Buckling and failure characteristics were investigated when an axial load, a torsional load or both loads were applied simultaneously. Optimization of the composite cylindrical shell was performed with respect to a loading boundary condition using a genetic algorithm. All analyses were performed numerically using finite element analysis. By optimizing the layer angle of the laminate composite, the buckling load of the cylindrical shell was maximized. The thinwalled shell with the strongest resistance to failure was achieved by optimizing the angle of the composite layer based on the Tsai- Wu composite failure theory. The optimized composite cylindrical shell exhibited significantly improved mechanical properties compared to the conventional design.