• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.4
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• pp.290-295
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• 2001

Subsets pipelines are exposed to several potential risks of damage due to corrosion, soil instability, anchor impact and other hazards. One of the main risk factors for the safety of a subsea pipeline is its free spanning. This paper examines the safety of subsea pipelines with free span under axial compressive load. The variation of allowable lengths of dynamic free span is examined for generalized boundary conditions. The free span is modelled as a beam with an elastic foundations and the boundary condition is replaced by linear and rotational springs at each end. A dynamic free span curve is obtained with a function of non-dimensional parameters and can be used usefully for the design of subsea pipelines with a free span. A case study is carried out to introduce the application method of the curve.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.2
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• pp.54-62
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• 2003

The free span of a subsea pipeline due to seabed scouring can result in structural failure by severe ocean environmental loads and vortex induced vibrations. This Paper examines the safety of subsea pipelines with free spans under axial compressive load. The variation of allowable lengths of static and dynamic free spans is examined for generalized boundary conditions. The free span is modelled as a beam with an elastic foundations and the boundary condition is replaced by linear and rotational springs at each end. The static and dynamic free span curves are obtained with a function of non-dimensional parameters. A case study is carried out to introduce the application method of the curve. The results of this study can be usefully applied for the design of subsea pipelines with a free span.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.1
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• pp.81-86
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• 1996

Subsea pipelines have an important role in the overall tasks of offshore oil and gas production but arc exposed to various hazards with high potential risks of damage resulting in serious economic loss and impact on ocean environment. In this paper, the dynamic free span is analysed, which is one of main risk factors against the safety of subsea pipelines and the allowable length of dynamic free span which is important for the design of subsea pipelines is determined. The allowable free span length is examined by considering the relationship between vortex shedding frequency and natural frequency of pipeline free span, and the variation of the allowable length is analysed for different boundary conditions of pipe ends. The free span is regarded as a beam on elastic foundations and the boundary condition of the beam is generalized by modelling as restrained by linear and rotational spring at each end. A non-dimensionalized curve is obtained to facilitate the determination of exact allowable length of dynamic free span for subsea pipelines and is applied to the pipelines which is to be installed in the gas fields of the south of East Sea of Korea.

• Journal of the Korean Magnetics Society
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• v.13 no.2
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• pp.76-81
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• 2003

Non-linear anisotropic materials were used to simulate the effects of tensile stress in 3D finite element analysis (FEA). FEA was used to calculate the effects of far and near-side pit depth and tensile stress on magnetic flux leakage (MFL) signals. The axial and radial MFL signals were depended on far and near-side double circular pit depth and on the stress, but the circumferential MFL signal was not depended on them. The axial and radial MFL signals increased with greater pit depth and applied stress, but the circumferential MFL signal was scarcely changed.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.228-234
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• 2001

NTMS(Non-contact Tilted-angle Measuring System) is developed by using the principle that the magnetic field of an anisotropic magnet's inner space is uniform and it's possible to measure the strength of the magnetic field using a linear hall effect sensor. In order to implement the caliper system of the geometry PIG(Pipeline Inspection Gauge) which has high accuracy and proper output voltage of the hall sensor without additional driving module or a signal amplifier, it is necessary to consider the size of the magnet, the inner space and back-yoke and the position of pin-hole in the magnet. So the optimal design method of the caliper system is proposed through analysis of NTMS's magnetic field adopting a FEM(Finite Element Method). The experimental results show that the developed caliper system can be used for the geometry pig with good performances.

• Journal of the Korean Magnetics Society
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• v.13 no.2
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• pp.70-75
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• 2003

Non-linear anisotropic materials were used to simulate the effects of bulk tensile stress in 3D finite element analysis (FEA). FEA was used to calculate the effects of near and far-side racetrack pit depth and simulated bulk tensile stress on magnetic flux leakage (MFL) signals. The axial and radial MFL signals were depended on near and far-side racetrack pit depth and on the bulk stress, but the circumferential MFL signal was not depended on them. The axial and radial MFL signals increased with greater pit depth and applied bulk stress, but the circumferential MFL signal was scarcely changed.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.11
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• pp.73-82
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• 2014

The LM algorithm is used in solving the least square problem in a non linear system, and is used in various fields. However, in cases the applied field's target functionis complicated and high-dimensional, it takes a lot of time solving the inner matrix and vector operations. In such cases, the LM algorithm is unsuitable in embedded environment and requires a hardware accelerator. In this paper, we implemented the LM algorithm in hardware. In the implementation, we used pipeline stages to divide the target function operation, and reduced the period of data input of the matrix and vector operations in order to accelerate the speed. To measure the performance of the implemented hardware, we applied the refining fundamental matrix(RFM), which is a part of 3D reconstruction application. As a result, the implemented system showed similar performance compared to software, and the execution speed increased in a product of 74.3.