• Transactions of Materials Processing
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• v.10 no.1
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• pp.75-79
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• 2001

The study has been performed for the relation between die and product during forward extrusion by the experiment. Stains of the die have been given by the simple experiment using the strain gauge located at the outer surface of the die. The history of the deformation of the die and the product has been given by the experiment and Lame's formula. The inner pressure of the die causes the deformation of die that affects the accuracy of dimension as well as shape of the product. The product with accurate dimension and shape can be obtained by analysing elastic deformation of the die during the process. The deformation of the die during metal forming process has been usually predicted by the experience of industrial engineer or finite element analysis. But it is difficult to predict the dimension of the product at unloading and ejected states. In the present study, useful results for the deformation history of the die and the product were obtained through the experiment and Lame's formula in forward extrusion which can be applied to the die design for the product with accurate dimension.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.347-351
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• 2007

The influence of compaction pressure and sintering temperature on the hydraulic cylinder block fabricated by powder metallurgy is investigated in this study. The cylinder block is powder compacted under various compaction pressures and sintered under various sintering temperatures, and its density and dimensions are measured to reveal the relation of the process condition with the product quality. Moreover, finite element analyses of the density distributions are conducted under the same conditions with the experiments and the predicted results are compared with the measured ones.

• Transactions of Materials Processing
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• v.4 no.1
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• pp.17-27
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• 1995

The tact switch is widely used in electric and electronic products. The dome type tact spring is produced by stamping. Stamping of the tact spring and operation of the tact switch have been simulated by the elasto-plastic finite element method. The operating characteristics of the switch may be given by the relation between the operating force and stroke. For a given material, this is affected by two main factors. One is the geometry of dome spring which is determined by the geometry of stamping dies and the stamping pressure, and another one is the dimension of switch. From the calculation, it was possible to obtain the stamping conditions and switch dimension for a predetermined force-stroki relation And, the hoop stresses and effective strains distributions due to the stamping and during the operation of the switch indicate a possibility of cracking in the center and rim of dome spring.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.95-98
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• 2000

Film bulk acoustic resonator used in microwave region can be analyzed by one-dimension Mason's model and one-dimensional numerical method, but it had several constraints to analyze effects of area variation, electrode-area variation, electrode-shape variation and spurious characteristics. To overcome these constraints film bulk acoustic resonator must be analysed by three dimensional numerical method. So, in this paper three dimensional finite element method was used to analyze several moles of resonance and was compared with the one dimension Mason's model analysis and analytic solution.

• Transactions of Materials Processing
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• v.17 no.3
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• pp.155-160
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• 2008

We analyzed a sequence of multi-stage automatic cold forging processes composed of four axisymmetric processes followed by a non-axisymmetric process using rigid-plastic finite element based forging simulators. The forging sequence selected for an example involves a piercing process and a heading process accompanying folding or overlapping, which all make it difficult to simulate the processes. To reduce computational time and to enhance the solution reliability, only the non-symmetric process was analyzed by the three-dimensional approach after the axisymmetric processes were analyzed by the two-dimensional approach. It has been emphsized that this capability is very helpful in simulating the multi-stage automatic forging processes which are next to axisymmetric or involve several axisymmetric processes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.879-882
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• 2002

To control the vibration and sound of structure, it is important to analyze the dynamic action of structure. And through those analysis, the vibration source and the flow path is understood. To grasp that, when the two-dimension plate structure is shaken by a harmonic point excitation with the natural frequency using the finite element method, this paper presents the relation between vibration power flow and mode shape. As those results present to vector flow, the vibration power flow is visualized.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.244-249
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• 2007

The influence of powder compaction pressure on the hydraulic cylinder block fabricated by powder metallurgy is investigated in this study. The cylinder block is compacted with powder under various compaction pressures and then sintered, and its density and dimensions are measured to reveal the relationship of the powder compaction pressure with the product quality. Moreover, finite element analyses of the density distributions are carried out under the same conditions with the experiments and the predicted results are compared with the measured ones.

• Journal of the Korean Data Analysis Society
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• v.20 no.6
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• pp.2733-2746
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• 2018

The two inverse regression estimation methods, SIR and SAVE to estimate the central space are computationally easy and are widely used. However, SIR and SAVE may have poor performance in finite samples and need strong assumptions (linearity and/or constant covariance conditions) on predictors. The two non-parametric estimation methods, MAVE and dMAVE have much better performance for finite samples than SIR and SAVE. MAVE and dMAVE need no strong requirements on predictors or on the response variable. MAVE is focused on estimating the central mean subspace, but dMAVE is to estimate the central space. This paper explores and compares four methods to explain the dimension reduction. Each algorithm of these four methods is reviewed. Empirical study for simulated data shows that MAVE and dMAVE has relatively better performance than SIR and SAVE, regardless of not only different models but also different distributional assumptions of predictors. However, real data example with the binary response demonstrates that SAVE is better than other methods.

• Bulletin of the Korean Mathematical Society
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• v.58 no.6
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• pp.1483-1494
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• 2021

Let A and B be rings and U be a (B, A)-bimodule. If _BU has finite flat dimension, U_A has finite flat dimension and U ⊗_A C is a cotorsion left B-module for any cotorsion left A-module C, then the Gorenstein flat-cotorsion modules over the formal triangular matrix ring $T=\(\array{A&0\\U&B}\)$ are explicitly described. As an application, it is proven that each Gorenstein flat-cotorsion left T-module is flat-cotorsion if and only if every Gorenstein flat-cotorsion left A-module and B-module is flat-cotorsion. In addition, Gorenstein flat-cotorsion dimensions over the formal triangular matrix ring T are studied.

• Bulletin of the Korean Mathematical Society
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• v.42 no.3
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• pp.433-441
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• 2005

The concepts linearly independent elements and u-linearly independent elements in an N-group G where N is a near-ring, were introduced and studied. A few important results in the theory of vector spaces were generalized to N-groups.