• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.396-408
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• 2019

The tubes which are applied in jacket platforms as the supporting structure might be collided by supply vessels. Such kind of impact will lead to plastic deformation on tube members. As a result, the ultimate strength of tubes will decrease compared to that of intact ones. In order to make a decision on whether to repair or replace the members, it is crucial to know the residual strength of the tubes. After being damaged by lateral impact, the simply supported tubes will definitely loss a certain extent of load carrying capacity under uniform axial compression. Therefore, in this paper, the relationship between the residual ultimate strength of the damaged circular tube by collision and the energy dissipation due to lateral impact is investigated. The influences of several parameters, such as the length, diameter and thickness of the tube and the impact energy, on the reduction of ultimate strength are investigated. A series of numerical simulations are performed using nonlinear FEA software LS-DYNA. Based on simulation results, a non-dimensional parameter is introduced to represent the degree of damage of various size of tubes after collision impact. By applying this non-dimensional parameter, a simplified formula has been derived to describe the relationship between axial compressive residual ultimate and lateral impact energy and tube parameters. Finally, by comparing with the allowable compressive stress proposed in API rules (RP2A-WSD A P I, 2000), the critical damage of tube due to collision impact to be repaired is proposed.

• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.78-91
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• 2024

Double steel plate concrete composite shear wall (SCSW) has been widely utilized in nuclear power plants and high-rise structures, and its shear connectors have a substantial impact on the seismic performance of SCSW. Therefore, in this study, the mechanical properties of SCSW with angle stiffening ribs as shear connections were parametrically examined for the reactor containment structure of nuclear power plants. The axial compression ratio of the SCSW, the spacing of the angle stiffening rib arrangement and the thickness of the angle stiffening rib steel plate were selected as the study parameters. Four finite element models were constructed by using the finite element program named ABAQUS to verify the experimental results of our team, and 13 finite element models were established to investigate the selected three parameters. Thus, the shear capacity, deformation capacity, ductility and energy dissipation capacity of SCSW were determined. The research results show that: compared with studs, using stiffened ribs as shear connectors can significantly enhance the mechanical properties of SCSW; When the axial compression ratio is 0.3-0.4, the seismic performance of SCSW can be maximized; with the lowering of stiffener gap, the shear bearing capacity is greatly enhanced, and when the gap is lowered to a specific distance, the shear bearing capacity has no major affect; in addition, increasing the thickness of stiffeners can significantly increase the shear capacity, ductility and energy dissipation capacity of SCSW. With the rise in the thickness of angle stiffening ribs, the improvement rate of each mechanical property index slows down. Finally, the shear bearing capacity calculation formula of SCSW with angle stiffening ribs as shear connectors is derived. The average error between the theoretical calculation formula and the finite element calculation results is 8% demonstrating that the theoretical formula is reliable. This study can provide reference for the design of SCSW.

• Transactions of Materials Processing
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• v.33 no.5
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• pp.348-353
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• 2024

The S355NL steel has garnered attention as a structural material for applications in extremely challenging environments owing to its excellent mechanical properties. This study investigated the hot deformation behavior of S355NL steel through compression tests conducted in a temperature range of 900-1200℃ and a strain rate range of 10^-3-1 s^-1 to explore the optimal processing parameters. The flow behaviors consisted of an initial rapid increase and subsequent plateau with a marginal decrease in stress. This phenomenon was interpreted in terms of microstructural evolution, such as dislocation density and dynamic recrystallization. The efficiency of power dissipation and instability domains were derived using the dynamic material model based on the compression test dataset, providing a series of processing maps. In contrast to conventional processing maps plotted for a single strain value, this study has established ten maps at a strain interval of 0.1. This approach allowed for the consideration of continuously variable strain parameters, which is inherent to an actual metal-forming process. The efficiency of power dissipation was strongly governed by the high temperatures (≥ 1100℃). The strain rates barely affected the efficiency, but it primarily contributed to the instability domains. The application of high strain rates (≥ 10^-1s^-1) generated a region of negative instability due to the absence of dynamic recrystallization and the presence of cracks at grain boundaries.

• Journal of the Korean Geotechnical Society
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• v.40 no.4
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• pp.127-135
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• 2024

The purpose of this paper is to establish the relationship between compression wave velocity and porosity in unsaturated soil using a deep neural network (DNN) algorithm. Input parameters were examined using the error norm method to assess their impact on porosity. Compression wave velocity was conclusively found to have the most significant influence on porosity estimation. These parameters were derived through both field and laboratory experiments using a total of 266 numerical data points. The application of the DNN was evaluated by calculating the mean squared error loss for each iteration, which converged to nearly zero in the initial stages. The predicted porosity was analyzed by splitting the data into training and validation sets. Compared with actual data, the coefficients of determination were exceptionally high at 0.97 and 0.98, respectively. This study introduces a methodology for predicting dependent variables through error norm analysis by disregarding fewer sensitive factors and focusing on those with greater influence.

• Geotechnical Engineering
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• v.3 no.1
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• pp.65-76
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• 1987

This study has been carried out as a basic course for the analysis of foundation deformations based on the Cap model using the finite element methods. Material parameters should firstly be determined in order to use the Cap model for numerical solution. Associated with the fact described above, a method determining the soil parameters is suggested using algorithm for numerical ana])isis from raw truly triaxial compression laboratory test data of Pueblo.Colorado sand by Zaman, et at. (1982) More specifically, the change of soil parameters Is thoroughly examined by weighting the data obtained from CTC and RTE tests, respectively. The main results obtained are as follows; 1. The obtained values of parameters (E, V and 2) are same irrespective of data obtained from various kind of tests. 2. The values of the other parameters are dependent on data used. 3. The determination of parameters is little affected by the weighting factor.

• Structural Engineering and Mechanics
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• v.24 no.5
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• pp.621-639
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• 2006

Stability of a cylindrical shell subject to a uniform axial compression, which is a power function of time, is examined within the framework of small strain elasto-plasticity. The material of the shell is incompressible and the effect of the elastic unloading is considered. Initially, employing the infinitesimal elastic-plastic deformation theory, the fundamental relations and Donnell type stability equations for a cylindrical shell have been obtained. Then, employing Galerkin's method, those equations have been reduced to a time dependent differential equation with variable coefficient. Finally, for two initial conditions applying a Ritz type variational method, the critical static and dynamic axial loads, the corresponding wave numbers and dynamic factor have been found. Using those results, the effects of the variations of loading parameters and the variations of power of time in the axial load expression as well as the variations of the radius to thickness ratio on the critical parameters of the shells for two initial conditions are also elucidated. Comparing results with those in the literature validates the present analysis.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.1
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• pp.28-36
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• 1993

Present-day there are two of theories which have considerable scientific support to explain the knock phenomenon in S.I. engine, the detonation theory and the autoignition theory. But they still have some problems to explain effects of knock parameters, i.e.. compression ratio, spark timing, mixture quality, engine speed, ect, on knocking process in S.I. engine. Accordingly, it is essential to find out whish is more adequate theory of two and to develop the method of analyzing knock phenomenon, that is the aim of this paper. The Authors develop the method of predicting transient temperature and pressure at the end-gas zone during the combustion period and analyze knocking process by this method based on the knock theories. The caluculated values based on the autoignition theory show reasonablly correct relations between knock parameters and knock process but there is no evidence of knock occurred by detonation theory through the calculation according to the all parameters. The authors find out that the autoignition theory is more adequate than detonation theory to analyze knocking process in S.I. engine.

• Transactions of Materials Processing
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• v.30 no.6
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• pp.275-283
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• 2021

A parametric study was conducted on the effects of five fundamental design parameters on springback, including die clearance, step height, step width, punch radius, and taper relief in an L-bending process, controlled by the compression force. The experiment was also conducted to verify the usefulness of the parametric study procedure for process design, as well as the finite element predictions. The elastoplastic finite element method was utilized. The L-bending process of the york product, which is a key part of the breaker mechanism, was employed. The deformation of the material was assumed to be due to plane strain. Five samples of each design parameter were selected based on experiences in terms of process design. The finite element predictions were analyzed in detail to show a shortcut towards the process design improvement which can replace the traditional process design procedure relying on trial-and-errors. The improved process design was verified to meet all the requirements and the predictions and experiments were in good agreement.

• Journal of Korea Multimedia Society
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• v.22 no.7
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• pp.790-803
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• 2019

The effects of different heat treatments on the sensory characteristics of abalones are studied in this study. In this paper, the sensory evaluation of abalone samples under different heat treatment conditions is carried out, and the evaluation results are analyzed. The three-dimensional (3D) scanning and reverse engineering are used in tooth modeling of the sensory evaluation of abalone samples under different heat treatment conditions. Besides, the chewing movement models are simplified into three modes, including the cutting mode, compressing mode and grinding mode, which are simulated using finite element simulation. The elastic modulus of the abalone samples is obtained through the compression testing using a texture analyzer to distinguish their material properties under different heat treatments and to obtain simulated mechanical parameters. Finally, taking the mechanical parameters of the finite element simulation of abalone chewing as input and sensory evaluation parameters as the output, BP neural network is established in which the sensory texture evaluation model of abalone samples is obtained. Through verification, the neural network prediction model can meet the requirements of food texture evaluation, with an average error of 9.12%.

• Computers and Concrete
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• v.24 no.2
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• pp.95-102
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• 2019

Current article proposes a cheap prototype of an embedded wireless sensor to monitor concrete structures. The prototype can measure temperature and relative humidity concurrently at a controlled through smartphone time interval. It implements a maturity method to estimate in-place concrete strength, which is considered as an alternative for traditional shock impulse method and compression tests used in Kazakhstan. The prototype was tested and adequately performed in the laboratory and field conditions. Tests aimed to study the effect of internal and ambient temperature and relative humidity on the concrete strength gain. According to test results revealed that all parameters influence the strength gain to some extent. For a better understanding of how strongly parameters influence the strength as well as each other, proposed a multicolored cross-correlation matrix technique. The technique is based on the determination coefficients. It is able to show the value of significance of correlation, its positivity or negativity, as well as the degree of inter-influence of parameters. The prototype testing also recognized the inconvenience of Bluetooth control due to weakness of signal and inability to access several prototypes simultaneously. Therefore, further improvement of the prototype presume to include the replacement of Bluetooth by Narrow Band IoT standard.