• Earthquakes and Structures
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• v.9 no.1
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• pp.127-143
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• 2015

In conventional seismic design, structures are assumed to be fixed at the base. To reduce the impact of earthquake loading, while at the same time providing an economically feasible structure, minor damage is tolerated in the form of controlled plastic hinging at predefined locations in the structure. Uplift is traditionally not permitted because of concerns that it would lead to collapse. However, observations of damage to structures that have been through major earthquakes reveal that partial and temporary uplift of structures can be beneficial in many cases. Allowing a structure to move as a rigid body is in fact one way to limit activated seismic forces that could lead to severe inelastic deformations. To further reduce the induced seismic energy, slip-friction connectors could be installed to act both as hold-downs resisting overturning and as contributors to structural damping. This paper reviews recent research on the concept, with a focus on timber shear walls. A novel approach used to achieve the desired sliding threshold in the slip-friction connectors is described. The wall uplifts when this threshold is reached, thereby imparting ductility to the structure. To resist base shear an innovative shear key was developed. Recent research confirms that the proposed system of timber wall, shear key, and slip-friction connectors, are feasible as a ductile and low-damage structural solution. Additional numerical studies explore the interaction between vertical load and slip-friction connector strength, and how this influences both the energy dissipation and self-centring capabilities of the rocking structure.

• Smart Structures and Systems
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• v.4 no.1
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• pp.1-17
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• 2008

This study proposes a conceptual framework of in-situ vibration tests and analyses for quality appraisal of non-slender, cast-in-place piles with irregular cross-section configuration. It evaluates a frequency index from vibration recordings to a series of impulse loadings that is related to total soil-resistance forces around a pile, so as to assess if the pile achieves the design requirement in terms of bearing capacity. In particular, in-situ pile-vibration tests in sequential are carried out, in which dropping a weight from different heights generates series impulse loadings with low-to-high amplitudes. The high-amplitude impulse is designed in way that the load will generate equivalent static load that is equal to or larger than the designed bearing capacity of the pile. This study then uses empirical mode decomposition and Hilbert spectral analysis for processing the nonstationary, short-period recordings, so as to single out with accuracy the frequency index. Comparison of the frequency indices identified from the recordings to the series loadings with the design-based one would tell if the total soil resistance force remains linear or nonlinear and subsequently for the quality appraisal of the pile. As an example, this study investigates six data sets collected from the in-situ tests of two piles in Taipu water pump project, Jiangshu Province of China. It concludes that the two piles have the actual axial load capacity higher than the designed bearing capacity. The true bearing capacity of the piles under investigation can be estimated with accuracy if the amplitude of impact loadings is further increased and the analyses are calibrated with the static testing results.

• Journal of Korean Society of Steel Construction
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• v.13 no.2
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• pp.211-221
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• 2001

The dynamic force estimation and strength design of KALES(Korea Accelerated Loading and Environmental Simulator) are studied. The KALES is continuously rotating the test track and subjected to the dynamic or impact forces during operation since the track is composed of straight and curved line. To estimate the dynamic equation for the model car which was already made is derived with analytical and experimental techniques. Using similarity relationships between the model car and KALES, the dynamic force and stability properties for KALES can be predicted. The stress analysis and fatigue life estimation of KALES is also estimated with the calculated dynamic load. From the stress analysis and fatigue life estimation results, it was found that the design of KALES is safe.

• Structural Engineering and Mechanics
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• v.59 no.6
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• pp.1139-1153
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• 2016

Elastic constraints are usually simplified as "spring forces" exerted on beam ends without considering the "spring deformation". The partial differential equation governing the free vibrations of a cantilever Bernoulli-Euler beam considering the deformation of elastic constraints is firstly established, and is nondimensionalized to obtain two dimensionless factors, $k_v$ and $k_r$, describing the effects of elastically vertical and rotational end constraints, respectively. Then the frequency equation for the above Bernoulli-Euler beam model is derived using the method of separation of variables. A numerical analysis method is proposed to solve the transcendental frequency equation for the continuous change of the frequency with $k_v$ and $k_r$. Then the mode shape functions are given. Finally, effects of $k_v$ and $k_r$ on free vibration characteristics of the beam with different slenderness ratios are calculated and analyzed. The results indicate that the effects of $k_v$ are larger on higher-order free vibration characteristics than on lower-order ones, and the impact strength decreases with slenderness ratio. Under a relatively larger slenderness ratio, the effects of $k_v$ can be neglected for the fundamental frequency characteristics, while cannot for higher-order ones. However, the effects of $k_r$ are large on both higher- and lower-order free vibration characteristics, and cannot be neglected no matter the slenderness ratio is large or small.

• The Journal of Advanced Prosthodontics
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• v.5 no.4
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• pp.409-415
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• 2013

PURPOSE. The midline fracture of maxillary complete dentures is a frequently encountered complication. The purpose of this study was to assess the effect of frenulum height on midline strains of maxillary complete dentures. MATERIALS AND METHODS. A removable maxillary complete denture was fabricated and duplicated seven times. Four different labial frenulum heights were tested for stresses occurring on the palatal cameo surface. The strains were measured with strain gauges placed on 5 different locations and the stresses were calculated. To mimic occlusal forces bilaterally 100 N of load was applied from the premolar and molar region. RESULTS. A statistically significant association between the height of the labial frenulum and the calculated stresses and strains was shown (P<.05) predominantly on the midline and especially on the incisive papilla. The results showed that stress on the anterior midline of the maxillary complete denture increases with a higher labial frenulum. CONCLUSION. Within the limitations of this in vitro study, it can be concluded that the stress on the anterior midline of the maxillary complete denture increases with a higher labial frenulum. Surgical or mechanical precautions should be taken to prevent short-term failure of maxillary complete dentures due to stress concentration and low cycle fatigue tendency at the labial frenulum region.

• Journal of the Korean Institute of Landscape Architecture
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• v.14 no.3
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• pp.21-31
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• 1987

The overuse in the outdoor recreation lands has been deteriorating the natural resources and landscapes. So this study was executed to measure the users'impacts on vegetation and soil at Hwaum Temple District Campsite in the Mt. Jiri National Park, the southern part of Korea. Five sites were sampled in the study area according to the extent of impact observed. Then the users'densities and impacts on vegetation and soil were measured at each site. According to the result of this study, the numbers of species and individuals and the coverage of lower-layer vegetation showed outstanding changes by only light use. The numbers of species and individuals of middle-layer vegetation, species diversity indices, change rate in species composition of lower and middle-layer vegetation, damage rate of forces, contents of clay, soil moisture and organic matters, exchangeable base ions, soil hardness, organic matter depth and bare area of the campsite showed conspicuous changes from the site 4(19.6men / 1,000㎡). Especially, the self-repair of vegetation was impossible as the result of analysis of soil hardness and the formation of natural vegetation was expected to be difficult as the result of vegetation sturcture analysis over the users'average density of 19.6men /1,000㎡. The campsite management of this area shall be proposed as follows to prevent serious deterioration of natrual environment. A limitation of the present use and a conservation on soil and vegetation should be required at the site 4 and 5. Specially, prevention of camping recreation and artificial rehabilitation are necessary at the site 5(24. 3 men/1000㎡)

• Journal of the Korean Geographical Society
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• v.49 no.1
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• pp.57-76
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• 2014

Conventional treatments of war diffusion focus extensively on dyadic relationships, whose impact is thought to be immutable over the course of the conf lict. This study indicates that such conceptions are at best incomplete, and more likely misleading to explain the spatial diffusion of wars. Using social network analysis, we examine war joining behavior during World War I. By employing social network analysis, we attempted to overcome the dichotomous understanding of geography as space and network in the discipline of conflict studies. Empirically, networked structural elements of state relationships (e.g., rivalry, alliances) have explanatory and predictive value that must be included alongside dyadic considerations in analyzing war joining behavior. In addition, our analysis demonstrates that the diffusion of conflict involves different driving forces over time.

• The Journal of Advanced Prosthodontics
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• v.6 no.5
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• pp.346-350
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• 2014

PURPOSE. Impact forces in implant supported FDP (fixed dental prosthesis) are higher than that of tooth supported FDPs and the compositions used in frameworks also has a paramount role for biomechanical reasons. The aim of this study was to evaluate the flexural strength of two different zirconia frameworks. MATERIALS AND METHODS. Two implant abutments with 3.8 mm and 4.5 mm platform were used as premolar and molar. They were mounted vertically in an acrylic resin block. A model with steel retainers and removable abutments was fabricated by milling machine; and 10 FDP frameworks were fabricated for each Biodenta and Cercon systems. All samples were thermo-cycled for 2000 times in $5-55^{\circ}C$ temperature and embedded in $37^{\circ}C$ artificial saliva for one week. The flexural test was done by a rod with 2 mm ending diameter which was applied to the multi-electromechanical machine. The force was inserted until observing fracture. The collected data were analyzed with SPSS software ver.15, using Weibull modulus and independent t-test with the level of significance at ${\alpha}=.05$. RESULTS. The mean load bearing capacity values were higher in Biodenta but with no significant differences (P>.05). The Biodenta frameworks showed higher load bearing capacity ($F_0=1700$) than Cercon frameworks ($F_0=1520$) but the reliability (m) was higher in Cercon (m=7.5). CONCLUSION. There was no significant difference between flexural strengths of both zirconia based framework systems; and both Biodenta and Cercon systems are capable to withstand biting force (even parafunctions) in posterior implant-supported bridges with no significant differences.

• Archives of Plastic Surgery
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• v.41 no.1
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• pp.57-62
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• 2014

Background Achieving symmetry is a key goal in breast reconstruction. Anatomically shaped tabbed expanders are a new tool in the armamentarium of the breast reconstruction surgeon. Suture tabs allow for full control over the expander position and thus inframammary fold position, and, in theory, tabbed expanders mitigate many factors responsible for poor symmetry. The impact of a tabbed expander on breast symmetry, however, has not been formally reported. This study aims to evaluate breast symmetry following expander-implant reconstruction using tabbed and non-tabbed tissue expanders. Methods A chart review was performed of 188 consecutive expander-implant reconstructions that met the inclusion criteria of adequate follow-up data and postoperative photographs. Demographic, oncologic, postoperative complication, and photographic data was obtained for each patient. The photographic data was scored using a 4-point scale assessing breast symmetry by three blinded, independent reviewers. Results Of the 188 patients, 74 underwent reconstruction with tabbed expanders and 114 with non-tabbed expanders. The tabbed cohort had significantly higher symmetry scores than the non-tabbed cohort ($2.82/4{\pm}0.86$ vs. $2.55/4{\pm}0.92$, P=0.034). Conclusions The use of tabbed tissue expanders improves breast symmetry in tissue expander-implant-based breast reconstruction. Fixation of the expander to the chest wall allows for more precise control over its location and counteracts the day-to-day translational forces that may influence the shape and location of the expander pocket, mitigating many factors responsible for breast asymmetry.

• Journal of National Security and Military Science
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• s.7
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• pp.55-89
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• 2009

This article aims to critically review recent U. S. RMA-centered theories of warfare having prevailed after the 1991-92 Gulf War upon which the current ROKA military transformation project, the Vision 2020, largely based. In order to evaluate validity as a universal warfighing theory of NCW (Network Centric Warfare) and EBO (Effects-Based Operations), this article reviews the intrinsic strength and weakness of the theories as well as results of several recent wars that the U. S. Army conducted based on doctrines derived form such theories, In addition, this article examines the impact of certain military technology or weapon system in some well-known historical wars to draw lessons regarding the relationship between technology(weapon system) and military victory. Historical examples has shown that victories in war were not achieved by new technologies alone in most cases. Rather military victories tended to owe to combination of new technology, original doctrine and well conceived organization. Although the U. S. Armed Forces showed brilliant records of operational successes anchored on the system of PGMs and NCW concepts in Iraq (1991-92; 2003) and Afghanistan (2001-02), it must be pointed out that the operational successes did not bring about political ones in cases of Iraq and Afghanistan. It reminds us of perils of too technologically tilted approach to the conduct of war. In sum, one ought to recognize that superior technology nowadays became a necessary condition of success but is not yet a sufficient condition, the ROKA needs to be abreast with development trends of military technologies and related theoretical concepts, it need not too be in a hurry in adopting cutting edged war-making technologies at the expense of large amount of budget. The essay recommends for the ROKA several basic requirements for coping with conduct of future wars as well as establishing a 'Korean style military thought'; (1) Recognition of importance of technology in conduct of war; (2) Imposition of officer self-study hours in working days; (3) Establishing a lifestyle of military professionalism in the Korean officer corps; (4) Setting up small or large groups of think-tanks that are specialized in army doctrinal formulation.