• Journal of the Korean Geotechnical Society
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• v.21 no.3
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• pp.43-54
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• 2005

The ground movements during three. full-scale trial diaphragm wall (DW) panel constructions were monitored and analysed. The DW panels were constructed in reclaimed fill where sedimentary marine deposit and residual weathered soils are being consolidated. The monitoring data showed exceptionally large lateral ground movements of up to 293 mm near a trench due to the DW panel constructions, which is about 0.8$\%$ D, where D is the maximum excavation depth. It was observed that deliberate holding period of the trench resulted in a significant increase in the lateral ground movements of about 50-225$\%$. A pre-treatment of the marine deposit by installing a single line of jet grout columns around the trench prior to the excavation was found to be a very effective way of reducing the ground movements. The measured ground settlements were compared with some relevant case histories. DW panel constructions in sedimentary marine deposit are likely to cause maximum ground surface settlement up to 0.225$\%$ D.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.8
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• pp.748-755
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• 2012

Friction causes self-excited vibration, stick-slip vibration and any other friction-induced phenomena. That kinds of vibrations cause chatter and squeal. In order to predict such vibrations accurately, employing an accurate friction model is very important because a dynamic behavior of a system with friction is dominantly governed by a friction model. A Coulomb friction model is the most widely known model. Coulomb friction model is useful model to obtain analytical solutions of the system with friction and the model gives relatively good simulation result. However, defining a friction force at a stick state in simulation is hard because of the characteristic itself and a Coulomb friction model is discontinuous function between a static and a dynamic friction coefficient. Therefore, applying the Coulomb friction model to a simulation is not appropriate. In order to resolve these problems, an approximated Coulomb friction model was developed using simple and continuous function. However, an approximated Coulomb friction model cannot realize stick. Therefore, an approximated Coulomb friction model cannot describe friction phenomena accurately. In order to analyze a friction phenomenon accurately, a friction model for a simulation was proposed in this paper. A proposed friction model realizes stick and gives reasonably good results compared to results obtained by the simulation employing an approximated Coulomb friction model. Accuracy of a proposed friction model was verified by comparing experimental results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.297-304
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• 2019

In this research, crack propagation in a silicon anode during two-phase lithiation was evaluated using a cohesive zone model. The phase transition from crystalline silicon to lithiated silicon causes compressive yielding due to the high volume expansion rate. Li-ion diffuses from the surface of the silicon to its core, and the complex deformation mechanisms during lithiation cause tensile hoop stress along the surface. The Park-Paulino-Roesler (PPR) potential-based cohesive zone model that guarantees consistent energy dissipation in mixed-mode fracture was adopted to simulate edge crack propagation. It was confirmed that the edge crack propagation characteristics during lithiation from the FEM simulation results coincided with the real experimental results. Crack turning observed from real experiments could also be predicted by evaluating the angles of maximum tensile stress directions.

• Physical Therapy Korea
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• v.28 no.1
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• pp.72-76
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• 2021

Background: A pressure ulcer is common in soft tissue over the greater trochanter (GT) in side-lying position, and sustained tissue deformation induced by the prolonged external force is a primary cause, which can be discussed with soft tissues' viscoelastic properties (i.e., stress relaxation, creep response). Objects: Using an automated hand-held indentation device, we measured the viscoelastic properties of soft tissue over the hip area, in order to examine how the properties are affected by site with respect to the GT. Methods: Twenty participants (15 males and 5 females) who aged from 21 to 32 were participated. An automated hand-held indentation device was used to measure the stress relaxation time and creep response. Trials were acquired for three different locations with respect to the GT (i.e., right over the GT, 6 cm anterior or posterior to the GT). For each location, five trials were acquired and averaged for data analyses. Results: Soft tissues' stress relaxation time and creep response were associated with site (F = 23.98, p < 0.005; F = 24.09, p < 0.005; respectively). The stress relaxation time was greatest at posterior gluteal region (19.22 ± 2.49 ms), and followed by anterior region (15.39 ± 2.47 ms) and right over the GT (14.40 ± 3.18 ms). Similarly, creep response was greatest at posterior gluteal region (1.16 ± 0.14), and followed by anterior region (0.95 ± 0.14) and right over the GT (0.89 ± 0.18). Conclusion: Our results showed that the stress relaxation and creep were greatest at the posterior gluteal region and least at right over the GT, indicating that the gluteal soft tissue is more protective to the prolonged external force, when compared to the trochanteric soft tissue. The results suggest that a risk of pressure ulcer over the GT may decrease with slightly posteriorly rotated side-lying position.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.106-112
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• 2021

In this study, we performed a design and structural analysis of a blade-shaped antenna installation on the rear fuselage of a rotary wing aircraft operated by the military. When the structure is damaged while the aircraft is in operation, it is separated from the aircraft main structure and may collide with the rotor or blades to cause the aircraft to crash. Therefore, structural safety for the modified structure must be secured. The design requirement for the newly installed modified part were established, and the load condition was constructed by applying the load that may occur in the aircraft after the modification. Structure safety for the modified structure was secured by performing structure analysis. To analysis stress and deformation of aircraft structure, we developed finite element model and verified it by using hand calculation method. We confirmed the safety of the modified structure through the final structural integrity analysis.

• The Journal of Korean Medical History
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• v.24 no.1
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• pp.43-56
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• 2011

Everyone once in a life experience headaches as symptoms are very common. According to a study in a country of more than a week and as many as those who have experienced a headache amounts to 69.4%. In addition, the high reported prevalence of migraine in 30s for 80% of all migraine sufferers daily life interfere with work or was affected. In Western medicine, the cause of headaches is traction or deformation of pain induced tissue like scalp, subcutaneous tissue, muscle, fascia, extracranial arteriovenous, nerves, periosteum. But it turns out there are not cause why pain induced tissue is being tracted or deformated. Therefore, most of the western-therapy is mainly conducted with regimen for a temporary symptom reduction. Therefore, I examined how it has been developed in Chinese Ming Dynasty, the perception of headache, change in disease stage and an etiological cause. Oriental medicine in the treatment of headache is a more fundamental way to have an excellent treatment. The recognition of head in "素問($s{\grave{u}}$ $w{\grave{e}}n$)" and "靈樞($l{\acute{i}}ng$ $sh{\bar{u}}$)" began to appear in 'Soul-神($sh{\acute{e}}n$) dwelling place' and 'where to gather all the Yang-'諸陽之會($zh{\bar{u}}$ $y{\acute{a}}ng$ $zh{\bar{i}}$ $hu{\grave{i}}$)'. Also, head was recognized as '六腑($li{\grave{u}}f{\check{u}}$) 淸陽之氣($q{\bar{i}}ng$ $y{\acute{a}}ng$ $zh{\bar{i}}$ $q{\grave{i}}$) and 五臟($w{\check{u}}$ $z{\grave{a}}ng$) 精血($j{\bar{i}}ng$ $xu{\grave{e}}$) gathering place'. More specific structures such as the brain is considered a sea of marrow(髓海-$su{\check{i}}$ $h{\check{a}}i$) in "內經($n{\grave{e}}i$ $j{\bar{i}}ng$)" and came to recognized place where a stroke occurs. Accompanying development of the recognition about head, there had been changed about the perception of headache and the recognition of the cause and mechanism of headache. And the recognition of headache began to be completed in Ming Dynasty through Jin, Yuan Dynasty. Chinese Ming Dynasty, specially 樓英($l{\acute{o}}u$ $y{\bar{i}}ng$), in "醫學綱目($y{\bar{i}}xu{\acute{e}}$ $g{\bar{a}}ngm{\grave{u}}$)", first enumerated prescription in detail by separating postpartum headache. and proposed treatment of headache especially due to postpartum sepsis(敗血-$b{\grave{a}}i$ $xu{\grave{e}}$). 許浚($x{\check{u}}$ $j{\grave{u}}n$) accepted a variety of views without impartial opinion in explaining one kind of headache in "東醫寶鑑($d{\bar{o}}ng-y{\bar{i}}$ $b{\check{a}}oji{\grave{a}}n)$" 張景岳($zh{\bar{a}}ng$ $j{\check{i}}ng$ $yu{\grave{e}}$), in "景岳全書($j{\check{i}}ng$ $yu{\grave{e}}$ $qu{\acute{a}}nsh{\bar{u}}$)", established his own unique classification system-新舊表裏($x{\bar{i}}nji{\grave{u}}$ $bi{\check{a}}ol{\check{i}}$)-, and offered a clear way even in treatment. Acupuncture treatment of headache in the choice of meridian has been developed as a single acupuncture point. Using the classification of headache to come for future generation as a way of locating acupoints were developed. Chinese Ming Dynasty, there are special treatments like 導引按蹻法($d{\check{a}}o$ y ${\check{i}}n$ ${\grave{a}}n$ $ji{\check{a}}o$ $f{\check{a}}$), 搐鼻法($ch{\grave{u}}$ $b{\acute{i}}$ $f{\check{a}})$, 吐法($t{\check{u}}$ $f{\check{a}}$), 外貼法($w{\grave{a}}i$ $ti{\bar{e}}$ $f{\check{a}}$), 熨法($y{\grave{u}}n$ $f{\check{a}}$), 點眼法($di{\check{a}}n$ $y{\check{a}}n$ $f{\check{a}}$), 熏蒸法($x{\bar{u}}nzh{\bar{e}}ng$ $f{\check{a}}$), 香氣療法($xi{\bar{a}}ngq{\grave{i}}$ $li{\acute{a}}of{\check{a}}$). Most of this therapy in the treatment of headache, it is not used here, but if you use a good fit for today's environment can make a difference.

• The Korean Journal of Petroleum Geology
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• v.13 no.1
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• pp.1-16
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• 2007

The southeastern Korean Peninsula has experienced crustal multi-deformations according to changes of global tectonic setting during the Cenozoic. Characteristic features of the crustal deformations in relation to major Cenozoic tectonic events are summarized as follows. (1) Collision of Indian and Eurasian continents and abrupt change of movement direction of the Pacific plate (50${\sim}$43 Ma): The collision of Indian and Eurasian continents caused the eastward extrusion of East Asia block as a trench-rollback, and then the movement direction of the Pacific plate was abruptly changed from NNW to WNW. As a result, the strong suction-force along the plate boundary produced a tensional stress field trending EW or WNW-ESE in southeastern Korea, which resultantly induced the passive intrusion of NS or NNE trending mafic dike swarm. (2) Opening of the East Sea (25${\sim}$16 Ma): The NS or NNW-SSE trending opening of the East Sea generated a dextral shear stress regime trending NNW-SSE along the eastern coast line of the Korean Peninsula. As a result, pull-apart basins were developed in right bending and overstepping parts along major dextral strike slip faults trending NNW-SSE in southeastern Korea. The basins can be divided into two types on the basis of geometry and kinematics: Parallelogram-shaped basin (rhombochasm) and wedged-shaped basin (sphenochasm), respectively. In those times, the basins and adjacent basement blocks experienced clockwise rotation and northwestward tilting contemporaneously, and the basins often experienced a kind of propagating rifting from NE toward SE. At about 17Ma, the Yonil Tectonic Line, which is the westernmost border fault of the Miocene crustal deformation in southeastern Korea, began to move as a major dextral strike slip fault. (3) Clockwise rotation of southeastern Japan Island (about 15 Ma): The collision of the Izu-Bonin Arc and southeastern Japan Island, as a result of northward movement of the Philippine sea-plate, induced the clockwise rotation of southeastern Japan Island. The event caused the NW-SE compression in the Korea Strait as a tectonic inversion, which resultantly tenninated the basin extension and caused local counterclockwise rotation of blocks in southeastern Korea. (4) E-W compression in the East Asia (after about 5 Ma): Decreasing subduction angle of the Pacific plate and eastward movement of the Amurian plate have constructed the-top-to-west thrusts and become a major cause for earthquakes in southeastern Korea until the present time.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.583-594
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• 2000

Dislodgement of a crown or extension bridge and the loosening of a retainer of a bridge is a serious clinical problem in fixed restoration. Generally these problems are considered to be associated with deformation of the restoration. During biting, the restoration is subjected to complex forces and deforms considerably within the limit of its elasticity. Deformation of the restoration under the occlusal force induces excessive stress in the cement film, which then leads to the cement fracture. Such a fracture may eventually cause loss of the restoration. Because most of the past retention tests for full veneer crown were done without fatigue loading, they were not exactly simulating intraoral environment. And the purpose of this study was to evaluate the effect of cyclic cantilever loading on the retentive strength of full veneer crowns depending on different type of cements and taper of prepared abutment. Steel dies with $8^{\circ}\;or\;16^{\circ}$ convergence angle were fabricated through milling and crowns with the same method. These dies and crowns were divided into 8 groups. Group 1 : $16^{\circ}$ taper die, cementation with zinc phosphate cement, without loading Group 2 : $16^{\circ}$ taper die, cementation with zinc phosphate cement, with loading Group 3 : $8^{\circ}$ taper die, cementation with zinc phosphate cement, without loading Group 4 : $8^{\circ}$ taper die, cementation with zinc phosphate cement, with loading Group 5 : $16^{\circ}$ taper die, cementation with Panavia 21, without loading Group 6 : $16^{\circ}$ taper die, cementation with Panavia 21, with loading Group 7 : $8^{\circ}$ taper die, cementation with Panavia 21 without loading Group 8 : $8^{\circ}$ taper die, cementation with Panavia 21, with loading After checking the fit of die and crown, the luting surface of dies and inner surface of crowns were air-abraded for 10 seconds. The crowns were cemented to the dies, with cements mixed according to the manufacturer's recommendations. A static load of 5kg was then applied for 10 minutes with static loading device. Twenty-four hours later, group 1, 3, 5, 7 were only thermocycled, group 2, 4, 6, 8 were subjected to cyclic loading after thermocycling. Retentive tests were performed on the Instron machine. From the finding of this study, the following conclusions were obtained 1. Panavia 21 showed significantly higher retentive strength than zinc phosphate cement for all groups (p<0.05). 2. There was a significant difference in the retentive strength between $8^{\circ}\;and\;16^{\circ}$ taper for zinc phosphate cement(p<0.05), but no significant difference for Panavia 21 (p>0.05). 3. Cyclic loading significantly decreased the retentive strength for all groups(p<0.05). 4. For zinc phosphate cement, there was 35% reduction of the retentive strength after loading in the $16^{\circ}$ taper die, 25% in the $8^{\circ}$ taper die, and for Panavia 21, 21% in the $16^{\circ}$ taper die, 18% in the $8^{\circ}$ taper die.

• Economic and Environmental Geology
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• v.6 no.4
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• pp.201-216
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• 1973

Being believed thus far to be distributed in the wide areas in the vicinity of Seoul, the capital city of Korea, the Yonchon System in its type locality in Yonchon-gun from which the name derived was never previously traced down or correlated to the Precambrian metamorphic complex in Seoul area where the present study was carried out. Due to in accessibility to Yonchon area, the writer also could not trace the system down to the area studied so as to correlate them. The present study endeavored to differentiate general stratigraphy and interprete the structure of the metamorphic complex in the area. In spite of the complexity of structure and rapid changes in lithofacies of the complex, it was succeeded to find out the key bed by which the stratigraphy and structure of the area could be straightened out. The keybeds were the Buchon limestone bed in the western parts of the area; Daisongri quartzite bed cropped out in the southeastern area; Jangrak quartzite bed scattered in the several localities in the northwest, southwest, and eastern parts of the area; and Earn quartzite bed isolated in the eastern part of the area. These keybeds together with the broad regional structure made it possible to differentiated the Precambrian rocks in ascending order into the Kyonggi metamorphic complex, Jangrak group and Chunsung group which are in clinounconformable relation, and the first complex were again separated in ascending order into Buchon, Sihung, and Yangpyong metermorphic groups. Althcugh it has being vaguely called as the Yonchon system thus far, the Kyonggi metamorphic complex have never been studied before. The complex might, however, belong to early to early-middle Precambrian age. The Jangrak and Chunsung group were correlated to the Sangwon system in North Korea by the writer (1972), but it became apparent that the rocks of the groups have different lithology and highly metamorphosd than those of the Sangwon system which has thick sequence of limestone and slightly metamorphosed. Being deposited in the margin of the basin, it is natural that the groups poccess terrestrial sediments rather than limestone, yet no explanation is at hand as to what was the cause of bringing such difference in grade of metamorphism. Thus the writer attempted to correlate the both groups to those of pre-Sangwon and post-Yonchon which might be middle to early-late Precambrian time. Judging from difference in grade of deformation and unconformity between the Kyonggi metamorphic complex, Jangrak group, and Chunsung group, three stages of orogeny were established: the Kyonggi, Jangrak orogenies, and Chunsung disturbance toward younger age. It is rather astonishing to point out that the structure of these Precambrian formations. was not effected by Daebo orogeny of Jurassic age. The post-tectonic block faulting was accompanied by these orogenies, and in consequence NNE and N-S trending faults were originated. These faulting were intermittented and repeated until Daebo orogeny at which granites intruded along these faults. The manifestation of alignment of these faults is indicated by the parallel and straight linear development of valleys and streams in the Kyonggi Massifland.

• Earthquakes and Structures
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• v.23 no.4
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• pp.373-384
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• 2022

To improve the seismic performance of suspended ceiling structures, various vibration-damping devices have been developed. However, the devices made of metals have a limit in that they cause large deformation and seriously damages the exterior of the suspended ceiling structure from the wall. As a results, their strengthening effect of the suspended ceiling structure was minimal. Thus, this study employed a spring and vibration-proof rubber effectively controlled vibrations without increasing horizontal seismic loads on the ceiling to enhance the seismic resistance of suspended ceiling structures. The objective of the study is to examine the dynamic properties of a seismic damping-isolation unit (SDI) with various details developed. The developed SDI was composed of a spring, embossed rubbers, and prestressed bolts, which were the main factors enhancing the damping effect. The shaking table tests were performed on eight SDI specimens produced with the number of layers of embossed rubber (n_s), presence or absence of a spring, prestressed force magnitude introduced in bolts (f_ps), and mass weight (W_m) as the main parameters. To identify the enhancement effect of the SDI, the dynamic properties of the control specimen with a conventional hanger bolt were compared to those of the SDI specimens. The SDI specimens were effective in reducing the maximum acceleration (A_{c max}), acceleration amplification factor (α_p), relative displacement (δ_R), and increasing the damping ratio (ξ) when compared to the control specimen. The A_{c max}, α_p, and δ_R of the SDI specimens with two rubbers, spring, and f_ps of 0.1f_by, where f_by is the yielding strength of the screw bolt were 57.8%, 58.0%, and 61.9% lower than those of the conventional hanger bolt specimens, respectively, resulting in the highest ξ (=0.127). In addition, the α_p of the SDI specimens was 50.8% lower than those specified in ASCE 7 and FEMA 356. Consequently, to accurately estimate the α_p of the SDI specimens, a simple model was proposed based on the functions of f_ps, stiffness constant of the spring (K), W_m, and n_s.