• Strategy21
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• s.41
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• pp.174-207
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• 2017

Human history shows diverse strategies for survival and prosperity. This study introduces the concept of the expansion of wealth as a key to explain choice and behavior of political entities. American scholar, -Bruce Bueno de Mesquita-, offers theoretical grounds for this concept in that the cores of selectorate theory is settled. The political entity consists of two groups, -the winning coalition that has power to replace leader and non-winning coalition that has not. Leaders implement policies serving for the welfare of winning coalition in return for their loyalty. Both internal problems caused by demographic changes and external ones of climate changes, epidemic disease, or invasion compel leader and winning coalition to adopt policies of expansion that they believe may lead to the acquisition of wealth needed to counter those problems. The process starts by occupying one spot where other entities reside and then connecting it to its own. The line between spots functions as a foothold to form a new line to other spots. By repeating this process, a space is created in which new laws and orders are instated. In the early stage of expansion, war is hardly avoidable. Once finished successfully, the political circumstance tilts to encourage economic activities in order to generate national revenues to strengthen political power of winning coalition. However, as scale of economic activities grows, so does political power of civic classes in production and trade. To gain financial support required to run the political entity, delegation of power or bestowing autonomy to non-winning coalition is inevitable. Thus, expansion is not the ultimate solution, only to prolong the political survival if succeed. Maritime power came to attractive option when overland expansion had become obstructed. It offered much greater advantages in terms of political risks and financial burdens in exploring new regions of precious commodities than overland expansion. Each political entity around world have been, for the first time in human history, connected by maritime means since 15th century. It is worthy of noting that land conditions propelled people out to sea. Political and economic situations created opportunities to exploit geographical position in pursuit of wealth. In the 21st century, we witness the operation of international winning coalition that presides over the rules of expansion. Competing for market is synonymous to the expansion in this era, the cause and aim of it has not been changed though. Energy and dollars are key factors of expansion since the end of the 2nd world war. No matter what the forms and conditions change, naval power is still the most relevant means for expansion as it retains unique characters of maneuver, flexibility, continuity, display and projection of power. The strategy for using naval power should be in line with two different approaches for expansion: Approaches to the international winning coalition by making contribution to world order, and approaches to the non-international winning coalition by enhancing military diplomatic activities. The former will serve our share of winning coalition while the latter will open chances to acquire further prosperity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.1 no.1
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• pp.75-87
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• 1997

To study the behavior a deck when it was collide with the ship approaching to the deck to berth, it was analyzed the effect zone by the ship collision which consists of deck slab and PC piles of the quay. The numerical technique is used to simulate the behavior of the deck when the ship hit the expansion joint of deck between the deck slabs. The failure behavior and zone of the deck are determinated by the comprehensive numerical study. The impact energy by the ship is also evaluated. It is concluded that these numerical analysis gave a reasonable estimation of the remedial area of the deck damaged by ship collision.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.17-18
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• 2003

Swelling behaviors of Lyocell and Polynosic fibers are investigated by measuring fiber sizes in ferric sodium tartrate complex (FeTNa) and NaOH solution. They showed an anisotropic swelling behavior, i.e., a large expansion in a radius and small shrinking in a longitudinal direction. Birefringent structure was maintained in Lyocell fibers in the swollen state but not in Polynosic fibers for both solvent systems.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.182-182
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• 2010

The behavior of properties of ion exchanged substrate glasses was investigated in this study. In order to study the effects of ion exchange, ion exchange behavior with ion penetration depth, amount of ion exchange, density and thermal expansion was measured according to the time and temperature. The mechanical properties were evaluated by the three point bending test and curvature change, and then fracture patterns were investigated by optical microscope.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.10a
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• pp.15-18
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• 1989

The planar effects on the concrete pavements Is mainly due to the concrete shrinkage, subgrade friction, and thermal expansion or contraction. A complete understanding of analytical behavior of concrete pavement requires the development of computer model, stiffness matrix and equivalent nodal load matrices due to the effects mentioned above. A computer program, INPLANE II, has been written to evaluate the planar effects on concrete pavements. The planar effects determine to what degree the joint open and also help In determining factors which affect the joint stiffnesses and structural behavior of concrete Pavements.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.5
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• pp.135-141
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• 2009

The bearing clearance is influenced by shrink fit and thermal expansion during operation. The designer must take into account the reduction of clearance after installation to the interference fits, and thermal expansion must be considered. The purpose of this study is to grasp the internal clearance variation and behavior of a bearing which is a deep connected with fatigue life of bearing and performance of spindle through FEM(Finite Element Method). Finite element analysis is performed by using commercial code ANSYS according to variation of thermal condition and rotational speeds. This paper presents correct negative internal clearance according to temperature during operation. Furthermore, interrelation between thermal expansion and contraction are presented to maintain adequate contact force for three type of spindle system (HSK-A60, HSK-40E, HSK-32E). The influence of the centrifugal force and Internal clearance variation of bearing is studied to operating rotational speed.

• Korean Journal of Materials Research
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• v.25 no.7
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• pp.330-335
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• 2015

A low thermal expansion ceramic, cordierite ($2MgO{\cdot}2Al_2O_3{\cdot}5SiO_2$), was synthesized using pyrophyllite. Pyrophyllite usually consists of $SiO_2$ and $Al_2O_3$, which are the main components of cordierite. $MgCO_3$ and $Al(OH)_3$ were added in various amounts to pyrophyllite and fired for synthesis and sintering. ${\alpha}$-cordierite crystallized from $1000^{\circ}C$ with mixing of 20 wt% $MgCO_3$ and 1.7 wt% $Al(OH)_3$, and un-reacted cristobalite was also detected with the cordierite. As the temperature was increased to $1400^{\circ}C$, the cordierite yield was gradually increased. Powder compacts of the synthesized cordierite were sintered between $1250^{\circ}C{\sim}1400^{\circ}C$; the sintered samples showed a low thermal expansion coefficient of $2.1{\times}10^{-6}/^{\circ}C$ and typical sintering behavior. It is anticipated that it will be possible to synthesize cordierite ceramics on a mass production scale using the mineral pyrophyllite.

• Journal of the Korean Society for Railway
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• v.7 no.3
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• pp.283-289
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• 2004

According to continuos welded rails on a bridge, temperature changes bring about the expansion of the bridge deck adding axil forces on the track. Moreover, the ballast on the bridge deck expansion joint is moved due to the bridge deck. If bridge decks are longer, the influence is greater, loosening ballast, causing track irregularities, and deteriorating passengers' comfort. Considering structure of bridge itself and tolerance of track irregularities caused by the loosened ballast on bridges, the maximum length of a deck should be less than 80m, which is the same as the standard of the French railway. In this study, an interaction between the expansion related to the bridge length and irregularity in longitudinal level referring to measurements and maintenance works performed in the high-speed railways was analyzed. This research shows that installation of sliding plate or vertical ballast stopper is not a good option since it is difficult to install. On the other hand, installation of movable fastener or gluing is easy but its influence is insignificant. To conclude, switch tie tamping or manual tamping is more effective than others.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.5
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• pp.226-232
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• 2021

The relationship between precipitation and coefficient of thermal expansion of Al-6%Si-0.4%Mg-0.9%Cu-(Ti) alloy (in wt.%) after various heat treatments were studied by the thermodynamic analyzer (TMA) and differential scanning calorimetry (DSC). Solution heat treatment of the alloy was carried out at 535℃ for 6 h followed by water quenching, and the samples were artificially aged in the air at 180℃ and 220℃ for 5 h. The coefficient of thermal expansion (CTE) curve showed some residual strain and decreased with increasing aging temperature. The CTE curves changed sharply in the temperature range of 200℃ to 400℃, and the corresponding peak shifted for the aged samples due to the change in the precipitation behavior of the secondary phase. These transformation peaks in the aged sample are related to the volume of the precipitation of the Si phase as determined by DSC analysis. The change in CTE is mainly caused by the precipitation of the Si phase in the Al-Si alloy, and the size of the change occurs simultaneously with the size of the precipitate.

• Korean Journal of Materials Research
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• v.33 no.10
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• pp.422-429
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• 2023

High-strength low-alloy steel is one of the widely used materials in onshore and offshore plant engineering. We investigated the alloying effect of solute atoms in α-Fe based alloy using ab initio calculations. Empirical equations were used to establish the effect of alloying on the Vicker's hardness, screw energy coefficient, and edge dislocation energy coefficient of the steel. Screw and edge energy coefficients were improved by the addition of V and Cr solute atoms. In addition, the addition of trace quantities of V, Cr, and Mn enhanced abrasion resistance. Solute atoms and contents with excellent mechanical properties were selected and their thermal conductivity and thermal expansion behavior were investigated. The addition of Cr atom is expected to form alloys with low thermal conductivity and thermal expansion coefficient. This study provides a better understanding of the state-of-the-art research in low-alloy steel and can be used to guide researchers to explore and develop α-Fe based alloys with improved properties, that can be fabricated in smart and cost-effective manners.