• Ocean Systems Engineering
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• 제1권1호
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• pp.59-72
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• 2011

The objective of this work is to investigate the possibility of using the longitudinal strain on the surface of a pipe to determine the inception of dangerous free spanning. The long term objective is to develop an online monitoring technique to detect the development of dangerous free spanning in subsea pipelines. This work involves experimental study as well as finite element modeling. In the experiments, the strains at four points on a cross section of a pipeline inside the free span zone are measured. Pipes with different boundary conditions and different diameter to length ratios were tested. The pipe is treated as a simple beam with fixed-fixed or simply supported boundary conditions. The variation of the strains as a function of the diameter to length ratio gives a pointer to the inception of dangerous free spanning. The finite element results agree qualitatively with the experiments. The quantitative discrepancy is a result of the difficulty to replicate the exact boundary conditions that is used by the finite element program.

• 대한기계학회논문집
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• 제17권10호
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• pp.2518-2534
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• 1993

Fracture behavior of carbon/epoxy laminates under pin loading is studied experimentally and analytically. Effects of ratios of specimen width to hole diameter and edge distance to hole diameter on bearing strength are investigated. Characteristic length of the laminates obtained using HK model has good agreement with the experimental data. The larger hole size induced, the lower bearing strength is measured under pin loading . The bearing strength and failure mode could be predicted using HK model and Zhangs analytical solution of stress distribution around a pin loaded hole. Chamis' prediction method of bearing strength is also considered to predict failure mode and bearing strength. A modification of Chamis' method is made using the factor of rupturc. The predicted bearing strength by the modified method is reasonably close to the experimental data.

• 대한기계학회논문집B
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• 제38권4호
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• pp.321-328
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• 2014

고고도 모사를 위한 축소형 디퓨저의 비연소장 조건에서의 성능특성을 수치적으로 파악하였다. 디퓨저 입구길이를 노즐 출구직경과 비교해 0, 50, 100%로 변화 시켰고, 디퓨저 목의 길이는 2차목의 직경과 비교해 3, 5, 6, 7, 8, 12로 다양화하여 해석하고 실제 모사실험 값과 비교하였다. 그 결과 디퓨저의 입구길이가 짧아질수록 plume의 형상은 수축되었다. 또한, 디퓨저의 2차목 길이가 디퓨저 지름의 최소 8배보다 짧으면 내부에 마하디스크가 형성되어 압력의 급격한 상승을 일으킨다. 아음속 디퓨저의 길이는 설계치의 0, 50, 75, 100%로 변화시켜 유동의 변화를 관찰하였고, 길이가 짧아질수록 2차목 내부에 갑작스런 압력 상승을 야기함을 확인하였다.

• Journal of the Korean Wood Science and Technology
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• 제23권4호
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• pp.91-97
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• 1995

Cyclic tests were performed with dowel joints which are being widely used for furniture manufacturing in Korea. In this study, effects of various factors-such as species of joint members, diameter and length of dowels, and space between dowels-on stiffness, strength and damping ratio of joints were evaluated and concluded as follows: 1. Under cyclic loads, failure of dowel joints were caused by bending failure of dowels. 2. Dowel joints were evaluated to be stiff but general load carrying capacities were relatively low. 3. Joint moduli and damping ratios of dowel joints decreased as diameter and length of dowels, and space between dowels increased. 4. In dowel joints, properties of dowel itself have greater effects on stiffness and strength of joints than properties of joint members.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.746-752
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• 2000

A study on discharge characteristics of a rotating discharge hole is very important to enhance the performance of an induction motor which have external forced cooling system. The discharge characteristics of rotating discharge holes are influenced by rotating speed, length-to-diameter ratio, inlet shape of rotor holes, etc. An experimental study on the effect of chamfered inlet edge of rotor inlet part with various depth-to-diameter and inlet chamfered edge angle is conducted. Depth-to-diameter ratios range from 0 to 0.5 and inlet chamfered edge angle range from 0 to 60. As a result, there is an optimal design point of inlet chamfered edge depth. And the inlet edge angle far maximum discharge coefficient is influenced mainly by the rotating speed of discharge holes.

• Steel and Composite Structures
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• 제49권4호
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• pp.457-471
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• 2023

To make up for the performance weaknesses of recycled aggregate concrete (RAC), expand the application range of RAC, and alleviate the environmental problems caused by excessive exploitation of natural coarse aggregates (NCA), this study proposes a basalt fiber-reinforced recycled aggregate concrete (BFRRAC)-filled square steel tubular columns that combines two modification methods of steel tube and fiber, which may greatly enhance the mechanical properties of RAC. The axial compression performance for BFRRAC-filled square steel tubular columns was reported during this study. Seven specimens with different replacement ratios of recycled coarse aggregate (RCA), length-diameter ratios, along with basalt fiber (BF) contents were designed as well as fabricated for performing axial compression test. For each specimen, the whole failure process as well as mode of specimen were discovered, subsequently the load-axial displacement curve has obtained, after which the mechanical properties was explained. A finite element analysis model for specimens under axial compression was then established. Subsequently, based on this model, the factors affecting axial compression performance for BFRRAC-filled square steel tubes were extended and analyzed, after which the corresponding design suggestion was proposed. The results show that in the columns with length-diameter ratios of 5 and 8, bulging failure was presented, and the RAC was severely crushed at the bulging area of the specimen. The replacement ratio of RCA as well as BF content little affected specimen's peak load (less than 5%). As the content of BF enhanced from 0 kg/m³ to 4 kg/m³, the dissipation factor and ductility coefficients increased by 10.2% and 5.6%, respectively, with a wide range.

• Journal of Biosystems Engineering
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• 제19권1호
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• pp.9-16
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• 1994

135 and 136 pine cones were sampled from age class of II to VI Korean pine trees for the study of their physical properties in 1991 and 1992, respectively. The length, width, weight, volume, and the largest projected area of cones were measured, and the specific gravity, apparent volume ratio sphericity, and roundness were calculated. Regression analysis were performed for the weight, volume, and projected area to the cone length and width. The length, and major and minor diameters of the cone stalks were measured and analyzed. 1. The range of the length of cone stalks was 0 to 47.3mm. The average length of stalks were 9mm ('91) and 10mm('92), respectively. Cross section of the stalks was ellipse with average major and minor diameters of 9.1mm and 10.1mm, and 8.6 and 8.7mm in 91 and 92, respectively. 2. The length of pine cones distributed from 8cm to 17cm and the average length were about 13cm('91, '92). The width varied from 5cm to 9.5cm and the average width were 6.7cm('91) and 6.9cm('92). The ratios of the length to the width were 0.56('91) and 0.65('91) and the shape of the cones were found to be ellipse with minor diameter of 1/2 to 2/3 of the major diameter. 3. The roundnesses and sphericity of cones were 0.74 and 0.75('91), 0.63 and 0.67('92), respectively. The average of the largest projected area of cones were $85.3cm^2$('91) and $93.1cm^2$('92) and the criterion areas were $71.0cm^2$ and $74.5cm^2$, respectively. 4. Cone weights were from 83g to 467g('91 and '92) and averages were 186g('91) and 220g('92). The average specific gravities were 0.89 and 0.96('91 and '92). The true volumes were $212cm^2$('91) and $230cm^2$('92), and the average bulk volume was $321cm^2$('91, '92). The average apparent volume ratios of cones were 35% ('91) and 28% ('92), respectively. 5. The weight and the volume were proportional to the length of the cone multiplied by the width squred and the largest projected area was proportional to the length multiplied by the width of cones.

• Steel and Composite Structures
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• 제17권6호
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• pp.929-949
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• 2014

Thirty one push-out tests were carried out in order to investigate the bond behavior between shape steel, steel tube (named steels) and recycled aggregate concrete (RAC), including 11 steel reinforced recycled aggregate concrete (SRRAC) columns, 10 recycled aggregate concrete-filled circular steel tube (RACFCST) columns and 10 recycled aggregate concrete-filled square steel tube (RACFSST) columns. Eleven recycled coarse aggregate (RCA) replacement ratios (i.e., 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100%) were considered for SRRAC specimens, while five RCA replacement ratios (i.e., 0%, 25%, 50%, 75% and 100%), concrete type and length-diameter ratio for recycled aggregate concrete-filled steel tube (RACFST) specimens were designed in this paper. Based on the test results, the influences of all variable parameters on the bond strength between steels and RAC were investigated. It was found that the load-slip curves at the loading end appeared the initial slip earlier than the curves at the free end. In addition, eight practical bond strength models were applied to make checking computations for all the specimens. The theoretical analytical model for interfacial bond shear transmission length in each type of steel-RAC composite columns was established through the mechanical derivation, which can be used to design and evaluate the performance of anchorage zones in steel-RAC composite structures.

• 한국어류학회지
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• 제5권1호
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• pp.96-112
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• 1993

한국산 연어속에 속하는 연어, 산천어 및 무지개송어 3종의 형태학적 비교 연구를 하였다. 연어속 어류인 연어, 산천어, 무지개송어의 계측, 계수형질을 비교한 결과 체형에선 암컷이 두장을 비롯한 13개, 수컷이 11개 형질에서 차이가 있었고, 계수 형질에선 유문수와 새파수에서 가장 뚜렷한 차이를 나타내었다. 이들 세 종은 암, 수컷 모두에서 표준체장에 대한 체고, 미병고, 등지느러미 길이, 뒷지느러미의 길이와 두장에 대한 주둥이 길이, 안경, 위턱, 뺨의 비에서 차이를 보였다. 이중 두장에 대한 안경은 암수 모두에서 산천어 무지개송어, 연어 순으로 크게 나타나 3종을 분류할 수 있는 새로운 형질로 나타났다. 유문수 수는 연어가 103~236개(평균 151개)로 무지개송어 37~84개(평균 56개), 산천어 23~63개(평균 41개)로 종간에 좋은 분류 형질로 나타났다. 본 연구에 나타난 체형 및 계수 형질 분석 결과 산천어는 연어와 무지개송어의 중간 형질을 가지고 있는 종으로 나타나, Smith and Stealy(1989)의 계통수와 잘 일치하였다.

• 한국환경보건학회지
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• 제26권4호
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• pp.21-28
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• 2000

Various man-made mineral fibers(MMMF) including refractory ceramic fiber(RCF) have been used widely in industries as insulation materials. The effect of fibrous dust on human health depends on fiber size, concentration (exposure level), and durability in biological system. Therefore, these parameters should be determined to evaluate accurately the potential risk of fibers on human health. The purpose of this study was to characterize the size of airborne fiber and the workers＇ exposure to airborne fibers in refractory ceramic fiber manufacturing and processing factories. Airborne fibers were collected on 25-mm mixed cellulose ester membrane filters at personal breathing zones, and analyzed by A and B counting rules of the National Institute for Occupational Safety and Health(NIOSH) Method # 7400. The average ratios of the fiber density by B rule to the fiber density by A rule was 0.84. This result indicates that the proportion of respirable fibers (<3 ${\mu}{\textrm}{m}$ diameter) in air samples was high. The average diameter and length of airborne fibers were 1.05${\mu}{\textrm}{m}$ and 35${\mu}{\textrm}{m}$, respectively. The average fiber concentrations (GM) of all personal samples was 0.26f/cc, and the average concentration was highest at blanket cutting and packing processes. The fifty seven percent of personal air samples was exceeded the proposed American Conference of Governmental Industrial Hygienists(ACGIH) Threshold Limit Value(TLV), i.e. 0.2 f/cc. It was concluded that the RCF industrial workers had the higher potential health risk due to small fiber diameter, long fiber length, and high exposure level to the airborne fibers.