• Geomechanics and Engineering
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• v.8 no.2
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• pp.237-255
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• 2015

From the related engineering principles, analytical solutions for horizontal crack initiation and propagation on a coal panel floor-underlying strata interface due to coal panel excavation are derived in this paper. Two important concepts, namely the critical panel width of horizontal crack initiation on the panel floor-underlying strata interface and the critical panel width of vertical fracture (crack) initiation in the panel floor, have been presented. The resulting analytical solution indicates that: (1) the first criterion can be used to express the condition under which horizontal plane cracks (on the panel floor-underlying strata interface or in the panel floor because of delamination) due to the mining induced vertical stress will initiate and propagate; (2) the second criterion can be used to express the condition under which vertical plane cracks (in the panel floor) due to the mining induced horizontal stress will initiate and propagate; (3) this orthogonal set of horizontal and vertical plane cracks, once formed, will provide the necessary weak network for the flow of gas to inrush into the panel. Two characteristic equations are given to quantitatively estimate both the critical panel width of vertical fracture initiation in the panel floor and the critical panel width of horizontal crack initiation on the interface between the panel floor and its underlying strata. The significance of this study is to provide not only some theoretical bases for understanding the fundamental mechanism of a longwall floor gas inrush problem but also a benchmark solution for verifying any numerical methods that are used to deal with this kind of gas inrush problem.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.04a
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• pp.26-28
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• 1991

In the recent years, a rigid pavement composed of a flat concrete slab has ken constructed due to the desirable structural strength of concrete, durability and economy. However, despite of precise design and construction of concrete highway pavement, some sections of the 88 Olympic express highway, Jung-bu express highway, and Kyung-bu express highway, which have shown premature cracking, faulting, and pumping before the end of their intended service life, have already been viewed with great concerns by highway officials and engineers. Since environmental variations and traffic loads might be considered as major factors to cause pavement failure problems, the thermal load due to temperature variations between top and bottom surface of the concrete slab was highlighted to verify analytical behavior of concrete slab using the finite element method.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.3
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• pp.25-32
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• 2004

An advanced algorithm for measurement of phase angle between two sinusoidal signals is proposed in this paper. This algorithm uses discrete sample data of two input signals for calculation of phase angle and amplitude. And the key parameters of the measurement algorithm are described by analytical express, so the calculation of phase angle is simplified. In this paper it is proved that harmonic distortion of the input sinusoidal signals does not affect the measurement value of phase angle by using the proposed algorithm when a whole cycle is sampled. And measurement error by the white Gaussian noise is very small compared by other algorithms.

• Ocean Systems Engineering
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• v.4 no.4
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• pp.293-308
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• 2014

Unlike the traditional displacement type vessels, the high speed planing crafts are supported by the lift forces which are highly non-linear. This non-linear phenomenon causes their motions in an irregular seaway to be non-Gaussian. In general, it may not be possible to express the probability distribution of such processes by an analytical formula. Also the process might not be stationary or ergodic in which case the statistical behavior of the motion to be constantly changing with time. Therefore the extreme values of such a process can no longer be calculated using the analytical formulae applicable to Gaussian processes. Since closed form analytical solutions do not exist, recourse is taken to fitting a distribution to the data and estimating the statistical properties of the process from this fitted probability distribution. The peaks over threshold analysis and fitting of the Generalized Pareto Distribution are explored in this paper as an alternative to Weibull, Generalized Gamma and Rayleigh distributions in predicting the short term extreme value of a random process.

• Structural Engineering and Mechanics
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• v.39 no.3
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• pp.411-425
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• 2011

This paper illustrates the results of a seismic vulnerability study aimed to derive the fragility curves for typical Algerian reinforced concrete bridge piers using an analytical approach. Fragility curves express the probability of exceeding a certain damage state for a given ground motion intensity (e.g., PGA). In this respect, a set of 41 worldwide accelerometer records from which, 21 Algerian strong motion records are included, have been used in a non-linear dynamic response analyses to assess the damage indices expressed in terms of the bridge displacement ductility, the ultimate ductility, the cyclic loading factor and the cumulative energy ductility. Combining the damage indices defined for 5 damage rank with the ground motion indices, the fragility curves for the bridge piers were derived assuming a lognormal distribution.

• Journal of Power Electronics
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• v.19 no.3
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• pp.794-802
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• 2019

Magnetic geared motors are driven using the same operating principle as conventional synchronous motors in which a magnetic gear is embedded. The magnetic geared motor is structurally similar to a magnetic gear. However, by applying currents to the stator coil, the high-speed rotor is rotated by a magnetic field and the low-speed rotor is rotated according to the gear ratio. In this paper, the operational principle of a magnetic geared motor and the magnetic flux density in its inner and outer air gaps are described. Then the magnetic flux density in the two air gaps is used to express a method for calculating the electrical and mechanical output. Results obtained with the analytical calculation method are compared with those of the finite element analysis. Finally, a prototype is used to verify the results of the analytical calculation and FEA.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.12-15
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• 1994

To establish the sea surface temperature estimation scheme for the upcoming advanced remote sensor, the quasi-analytical solution of the approximated radiative transfer equation which express the radiative transfer process of the radiant energy radiated from the sea surface to the satellite is approximated into the non-linear equation. To solve the simultaneous approximated radiative transfer equation which express the radiative transfer process of the radiant energy radiated from the sea surface to the satellite is approximated into the nonlinear equation. To solve the simultaneous approximated radiative transfer equation at each channel, the constrained non-linear optimization technique is adopted. To define the coefficients of the approximated radiative transfer equation and the constraints, the satellite detected radiance and the total transmittance are computed from the 1350 kinds of simulated atmosphere / surface models via radiative transfer code. The verification from the simulated data show the sufficient result.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.322-327
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• 2006

Banwol bridge with steel plate girder and Pyongtaek bridge with PSC bos girder have been operated maintenance measuring system by the Seoul-Chonan of Kyongbu express railway. By analyzing the theoretical and experimental values of design load for these two bridge, the establishment of reference maintenance for measuring items was deduced from research. Two materials, steel and concrete plates, were considered as the upper structure. Actual measurement data for the behavior under speed, structural analysis results, and the presented references were analyzed and used to set up the reference establishment. The measuring items are stress(strain), displacement, dynamic acceleration, expansion movement, and dynamic frequency. The maintenance reference was established by comparing analytical and measuring values of the five items with respect to structural state class.

• Architectural research
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• v.13 no.1
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• pp.17-24
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• 2011

Isogeometric solution of Poisson equation is provided. NURBS (NonUniform B-spline Surface) is introduced to express both geometry of structure and unknown field of governing equation. The terms of stiffness matrix and load vector are consistently derived with very accurate geometric definition. The validity of the isogeometric formulation is demonstrated by using two numerical examples such as square plate and L-shape plate. From numerical results, the present solutions have a good agreement with analytical and finite element (FE) solutions with the use of a few cells in isogeometric analysis.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.296-303
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• 2000

The purpose of this study is to find inelastic behavior and ductility capacity of reinforced concrete bridge columns under earthquake. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. In boundary plane at which each member with different thickness is connected, due to the abrupt change in their stiffness local discontinuous deformation can be taken into account by introducing interface element. Also an analytical model is developed to express the confining effects of lateral tie which depend on the existence or nonexistence and the amounts of transverse confinement, etc. The proposed numerical method for inelastic behavior and ductility capacity of reinforced concrete bridge columns will be verified by comparison with reliable experimental results.