• Steel and Composite Structures
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• v.16 no.6
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• pp.611-637
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• 2014

A single plate shear connection, or shear tab, is a very popular shear connection due to its merit in ease of construction and material economy. However, problems in understanding the connection behavior, both in terms of strength and ductility, have been well-documented. Suggestions or design model for single plate connections in AISC Design Manual have been altered several times, with the latest edition settling down to giving designers pre-calculated design strength tables if the connection details agree with given configurations. Results from many full-scale tests and finite element models in the past suggest that shear strength of a bolt group in single plate shear connections might be affected by yield strength of plate material; therefore, this research was aimed to investigate and clarify effects of plate yield strength and thickness on shear strength of the bolt group in the connections, including the validity of using a plate thickness/bolt diameter ratio ($t_p/d_b$) in design, by using finite element models. More than 20 models have been created by using ABAQUS program with 19.0- and 22.2-mm A325N bolts and A36 and Gr.50 plates with various thicknesses. Results demonstrated that increase of plate thickness or plate yield strength, with the $t_p/d_b$ ratio remained intact, could significantly reduce shear strength of the bolt group in the connection as much as 15 percent. Results also confirmed that the $t_p/d_b$ ratio is a valid indicator to be used for guaranteeing strength sufficiency. Because the actual ratio recommended by AISC Design Manual is $t_p/d_b$ + 1.6 (mm) for connections with a number of bolts less than six and plate yield strength in construction is normally higher than the nominal value used in design, it is proposed that shear strength of a bolt group in single plate connections with a number of bolts equal or greater than seven be reduced by 15 percent and the $t_p/d_b$ ratio be limited to 0.500.

• Communications of the Korean Mathematical Society
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• v.11 no.3
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• pp.825-829
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• 1996

We prove that if G is the fundamental group of a closed surface or a Seifert fibered space and K is a finitely generated subgroup of G, and if for any element g in G there exists an integer $n_g$ such that $g^{n_g}$ belongs to K, then K is of finite index in G.

• Journal of the Chungcheong Mathematical Society
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• v.20 no.3
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• pp.223-230
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• 2007

We study free actions of finite groups on the 3-dimensional nilmanifold and classify all such group actions, up to topological conjugacy. This work generalize Theorem 3.10 of [1].

• Journal of the Chungcheong Mathematical Society
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• v.23 no.3
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• pp.555-561
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• 2010

For the pure braid groups, this paper gives a positive finite presentation whose generators are the standard Artin generators, and determines whether the submonoid generated by the Artin generators is a Garside monoid or not.

• Computers and Concrete
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• v.3 no.6
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• pp.423-437
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• 2006

Stress wave propagation through concrete is simulated by finite element analysis. The concrete medium is modeled as a homogeneous material with smeared properties to investigate and establish the suitable finite element analysis method (explicit versus implicit) and analysis parameters (element size, and solution time increment) also suitable for rigorous investigation. In the next step, finite element analysis model of the medium is developed using a digital image processing technique, which distinguishes the mortar and aggregate phases of concrete. The mortar and aggregate phase topologies are, then, directly mapped to the finite element mesh to form a heterogeneous concrete model. The heterogeneous concrete model is then used to simulate wave propagation. The veracity of the model is demonstrated by evaluating the intrinsic parameters of nondestructive ultrasonic pulse velocity testing of concrete. Quantitative relationships between aggregate size and testing frequency for nondestructive testing are presented.

• Journal of the Chungcheong Mathematical Society
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• v.10 no.1
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• pp.161-175
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• 1997

We classify free actions of finite abelian groups on the 3-dimensional nilmanifold, up to topological conjugacy. By the works of Bieberbach and Waldhausen, this classification problem is reduced to classifying all normal subgroups of almost Bieberbach groups of finite index, up to affine conjugacy.

• Journal of the Korean Mathematical Society
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• v.32 no.3
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• pp.563-571
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• 1995

The recent work of Hopkins, Kuhn and Ravenel [H-K-R] indicates the Morava K-theory, $K(n)^*(-)$, occupy an important and fundamental place in homology theory. In particular $K(n)^*(BG)$ for classifying spaces of finite groups are studied by many authors [H-K-R], [R], [T-Y 1, 2] and [Hu].

• Kyungpook Mathematical Journal
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• v.56 no.1
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• pp.121-123
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• 2016

In this paper, we compute the number of distinct centralizers and commutativity degree of a class of finite groups. These computations produce a further class of examples of groups answering one question raised by Belcastro and Sherman and another one raised by Lescot.

• Korean Journal of Mathematics
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• v.29 no.3
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• pp.603-612
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• 2021

We generalize 3-manifolds supporting non-positively curved metric to construct manifolds which have the following properties : (1) They are not locally CAT(0). (2) Their fundamental groups are residually finite. (3) They have subgroup separability for some abelian subgroups.

• Design & Manufacturing
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• v.6 no.1
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• pp.84-89
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• 2012

Silicone is recently used for LED chip encapsulment due to its good thermal stability and optical transmittance. In order to predict residual stress which causes optical briefringence and mechanical warpage of silicone, finite element analysis was conducted for both curing and cooling process during silicone molding. For analysis of curing process, a cure kinetics model was derived based on the differential scanning calorimetry(DSC) test and applied to the material properties for finite element analysis. Finite element simulation result showed that the curing as well as the cooling process should be designed carefully so as to reduce the residual stress although the cooling process plays the bigger role than curing process in determining the final residual stress state. In addition, birefringence experiment was carried out in order to observe residual stress distribution. Experimental results showed that cooling-induced birefringence was larger than curing-induced birefringence.