• The Journal of Engineering Geology
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• v.26 no.3
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• pp.383-392
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• 2016

This study is to evaluate the physical and mechanical properties on the Ipseok-dae columnar joints of Mt. Mudeung National Park. For these purposes, physical and mechanical properties as well as discontinuity property on the Mudeungsan tuff, measurement of vibration and local meteorology around columnar joints, and ground deformation by self-weight of columnar joints were examined. For the physical and mechanical properties, average values were respectively 0.65% for porosity, 2.69 for specific gravity, 2.68 g/cm³ for density, and 2411 m/s for primary velocity, 323 MPa for uniaxial compressive strength, 81 GPa Young's modulus, and 0.25 for Poisson's ratio. For the joint shear test, average values were respectively 3.15 GPa/m for normal stiffness, 0.38 GPa/m for shear stiffness, 0.50 MPa for cohesion, and 35° for internal friction angle. The JRC standard and JRC chart was in the range of 4~6, and 1~1.5, respectively. The rebound value Q of silver schmidt hammer was 57 (≒ 90 MPa). It corresponds 20% of the uniaxial compressive strength of intact rock. The maximum vibration value around the Ipseok=dae columnar joints was in the range of 0.57 PPV (mm/s)~2.35 PPV (mm/s). The local meteorology of surface temperature, air temperature, humidity, and wind on and around columnar joints appeared to have been greatly influenced the weather on the day of measurement. For the numerical analysis of ground deformation due to its self-weight of the Ipseok-dae columnar joints, the maximum displacement of the right ground shows when the ground distance is approximately 2 m, while drastically decreased by 2~4 m, thereafter was insignificant. The maximum displacement of the middle ground shows when the ground distance is approximately 0~2 m, while drastically decreased by 3~10 m, thereafter was insignificant. The maximum displacement of the left ground shows when the ground distance is approximately 5~6 m, while drastically decreased by 6~10 m, thereafter was insignificant.

• Journal of the Korean Arthroscopy Society
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• v.8 no.2
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• pp.82-88
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• 2004

Purpose: In this study, we intended to ascertain the benefit of KT-2000 Knee arthrometer(KT-2000) in the diagnosis of ACL(Anterior cruciate ligament) injury by comparing the anterior displacement of normal knee with that of ACL deficient knee. Materials and Methods: We designated two examiners to measure the anterior displacement of the knee joint of 30 healthy individuals, using KT-2000, at 30$^{\circ}$ flexion setting of muscle full relaxation, contraction, 25$^{\circ}$ internal rotation and 25$^{\circ}$ external rotation and analyzed these results according to the variables and measured the preoperative anterior displacement of the ACL injured knee in the 30 patients who have gone through an arthroscopic ACL reconstruction later. Results: The results of examiner 1 are 6.5${\pm}$1.5 mm, 2.5${\pm}$0.9 mm, 4.8${\pm}$1.2 mm, 6.4${\pm}$1.3 mm in right knee and 5.6${\pm}$1.3 mm, 2.1${\pm}$0.8 mm, 4.5${\pm}$1.2 mm, 5.2${\pm}$1.3 mm in left knee, in order of muscle full relaxation, contraction, 25$^{\circ}$ internal rotation and 25$^{\circ}$ external rotation. The results of examiner 2 are 6.9${\pm}$1.2mm, 2.9${\pm}$1.1mm, 5.6${\pm}$1.6mm, 6.9${\pm}$1.5mm in right, 5.5${\pm}$1.7 mm,1.9${\pm}$0.9 mm, 5.1${\pm}$1.9 mm, 5.7${\pm}$1.6 mm in left knee, The side to side difference of examiner 1 in the setting of muscle relaxation is 0.9${\pm}$1.0 mm. The anterior displaement of ACL injured knee is average 11${\pm}$2.93 mm and difference of average 6.5${\pm}$2.31 mm form that of normal. In comparison between the right and left knees of healthy individuals, the both results of two examiners showed the statistical difference in the setting of muscle full relaxation but, the results showed the side to side difference below 2 mm in 25case(83%), 21case(70%) respectively and above 3 mm in just 1 case. In the comparison between the normal and ACL injured knees, the results show the statistical difference of the side to side difference in the setting of muscle relaxation(p<0.05). Conclusion: The KT-2000 result is affected by relaxation of muscles around knee, flexion angle of knee joint, rotation of tibia, the strength of displacing force, time of the test and physical factors as height and weight. However, the Accuracy of diagnosis of ACL injury by KT-2000 will increase if the examiner is skillful and the tests are made on the exact position of knee joint.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.20 no.3
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• pp.191-200
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• 1998

This study was intended to perform the influence of condyle positional change after surgical correction of skeletal Class III malocclusion after orthognathic surgery in 37 patients(male 13, female 24) using computed tomogram that were taken in centric occlusion before, immediate after, and long term after surgery and lateral cephalogram that were taken in centric occlusion before, 7 days within the period of intermaxillary fixation, at the 24 hours later removing intermaxillary fixation and long term after surgery. 1. Mean intercondylar distance was $84.42{\pm}5.30mm$ and horizontal long axis of condylar angle was $12.79{\pm}4.92^{\circ}$ on the right, $13.53{\pm}5.56^{\circ}$ on the left side. Condylar lateral poles were located about 12mm and medial poles about 7mm away from the reference line(AA') on the axial tomogram. Mean intercondylar distance was $83.15{\pm}4.62mm$ and vertical axis angle of condylar angle was $76.28{\pm}428^{\circ}$ on the right, $78.30{\pm}3.79^{\circ}$ on the left. 2. In amount of set back, We found the condylar change(T2C-T1C) which had increasing tendency in group III (amount of setback : 10-15mm). but there was no statistical significance(p>0.05). 3. There was some correlation between condylar change(T2C-T1C) and TMJ dysfunction. It seemed that postoperative condylar change had influenced postoperative TMJ dysfunction, through there was no statistical significance (p>0.05). As we have observed the change of condylar axis in the group that complained of TMJ dysfunction in cases of large amount of mandibular setback. So we consider that the more trying to conserve condylar position will decrease occurrence rate of post operational TMJ dysfunction.

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.769-780
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• 2004

This paper's objective is to evaluate the experimental behavior of gap N-joints made of cold-formed, square, hollow steel sections, with a connection plate as a tension member. The principal parameters for testing included the ratio of chord width to thickness, the ratio of brace width to chord width, eccentric ratio, the shape of the compression member, the branch angle, and the stiffening plate of the chord flange. The strength and failure mode were examined through the test for the gap N-joint, consisting of several parameters. Based on the results of the test, the gap N-joints were determined according to the capacity preceding the displacement of the tension, regardless of the width ratio, and the split failure mode-connected surface for a chord in joints. The strength of the gap N-joints increased proportionally as the $2\gamma$(B/T) ratio decreased, and as the width ratio(${\beta}$) of branch to chord increased. Particularly, $2\gamma$(B/T) decreased as the capacity of gap N-joint increased. The results of the test were summarized for the capacity, initial stiffness, ductility, and change of the failure mode of each gap N-joint.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.2
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• pp.1-8
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• 2012

This paper presents the accelerometer which is a key component of TPMS(Tire Pressure Monitoring System). Generally a piezoresistive accelerometer has characteristics of lower cost, better linearity and better immunity about the environmnet noise than a capacitive one. Three types of piezoresistive accelerometers are degined and simulated using ANSYS program. The best one is a piezoresistive sensor which is supported by four beams located at the center of the edge of the mass after comparing the characteristics of resonant frequency of the three types. Considering the sensor size and a simulated maximum stress and maximum displacement, the length of beams is set as $200{\mu}m$. The size of a piezoresistive accelerometer is $3.0mm{\times}3.0mm{\times}0.4mm$. The sensor output is characterized by measuring the output characteristic depending on angle. As a result the offset voltage of the accelerometer is 43.2 mV and its sensitivity is $42.5{\mu}V/V/g$. The temperature bias drift is measured. The shock durability of the sensor is 1500g and the measuring range is 0 ~ 60 g.

• Journal of Korean Society of Steel Construction
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• v.30 no.1
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• pp.1-12
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• 2018

A curved member should resist bending and torsional moments simultaneously even though the primary load is usually supposed to be gravitational load. The torsional moment causes complicate stress state and also can result in early yielding of material to reduce member strength. According to analysis results, the strength of a curved member that has 45 degrees of subtended angle could decrease more than 50% compare to straight girder. Nevertheless, there have been very few of researches related with ultimate strength of curved girders. In this study, various kinds of stiffness about bending, pure torsion and warping were considered with a number of models in order to verify the main factor that affects ultimate behavior of curved girder. Lateral and rotational displacement of curved member were introduced as lateral-torsional-vertical behavior and bending-torsional moment interaction curve was derived. Finally, a strength equation for ultimate moment of horizontally curved steel I-girders subjected to equal end moments based on the interaction curves. The equation could take account of the effect of curvature, unbraced length and sectional properties.

• Korean Journal of Applied Biomechanics
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• v.25 no.2
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• pp.157-165
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• 2015

Object : The goals of this research were to make Performance Enhanced Model(PE) taken the largest performance index (PI) through artificial variation of principle components calculated by principle component analysis for trial data, and to verify the effect through comparing kinematic factors between trial data (Raw) and PE. Method : Ten subjects (5 men, 5 women) were recruited and 80% of their maximal record was considered. The PI is a regression equation. In order to develop PE, we extracted Principle components from trial position data (by Principle Components Analysis (PCA)). Before PCA, we made 17 position data to 3 row matrix according to components. We calculated 3 eigen value (principle components) through PCA. And except Y (medial-lateral direction) component (because motion of Y component is small), principle components of X (anterior-posterior direction) and Z (vertical direction) components were changed as following. Changed principle components = principle components + principle components ${\times}$ k. After changing the each principle component, we reconstructed position data using the changed principle components and calculated performance index (PI). A Paired t-test was used to compare Raw data and Performance Enhanced Model data. The level of statistical significance was set at $p{\leq}0.05$. Result : The PI was significantly increased about 12.9kg at PE ($101.92{\pm}6.25$) when compared to the Raw data ($91.29{\pm}7.10$). It means that performance can be increased by optimizing 3D positions. The difference of kinematic factors as follows : the movement distance of the bar from start to lock out was significantly larger (about 1cm) for PE, the width of anterior-posterior bar position in full phase was significantly wider (about 1.3cm) for PE and the horizontal displacement toward the weightlifter after beginning of descent from maximal height was significantly greater (about 0.4cm) for PE. Additionally, the minimum knee angle in the 2-pull phase was significantly smaller (approximately 2.7cm) for the PE compared to that of the Raw. PE was decided at proximal position from the Raw (origin point (0,0)) of PC variation). Conclusion : PI was decided at proximal position from the Raw (origin point (0,0)) of PC variation). This means that Performance Enhanced Model was decided by similar motion to the Raw without a great change. Therefore, weightlifters could be accept Performance Enhanced Model easily, comfortably and without large stress. The Performance Enhance Model can provide training direction for athletes to improve their weightlifting records.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1309-1315
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• 2014

The switch for a maglev vehicle should be designed such that the vehicle safely changes its track without touching the guiderail. In particular, a medium-to-low-speed EMS -type maglev train relies heavily on a U-type electromagnet where it generates levitation force and guidance force simultaneously. Therefore, it is necessary to evaluate the safety of the vehicle whenever it passes the switch, as it lacks active control of the guidance force. Furthermore, when the vehicle passes a segmented switch, which is a group of curves made up of connected lines with a small radius of curvature, it may come into mechanical contact with the guiderail owing to the excessive lateral displacement of the electromagnet. The goal of this study is to analyze the influence of a segmented switch on the safety of major design-related variables for achieving improved running safety. We propose a three-dimensional multibody dynamics model composed of two cars with one body. Using the proposed model, we perform a simulation of the lateral air gap, which is one of the measurements of the running safety of the vehicle when it passes the switch. The analyzed design variables are the length between short span girder, the articulation angle, the length between two centers of a fixed girder at its ends, and the number of girders. On the basis of the effects of the considered design variables, we establish an optimized design of a switch with improved safety.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.8
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• pp.3729-3744
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• 2011

As the size of structures become larger by civil and architectural structures becoming large, deeply underground, and high-rise, the conditions of underground foundation vary according to the location that the lack of bearing capacity locally because of ununiform of foundation in some parts is frequent. Generally, when the foundation is not homogeneous, the acquisition of safety through applying the most conservative foundation method possible becomes the focus to secure the stability of the superstructures. It is considered as because of inability to verify the application and stability and application of construction of different foundations through an outlined review because of lack of study in case of different foundation of mixed use of direct foundation and pile foundation. Therefore, through measurement interpretation of the different foundation in which the direct foundation and pile foundation are mixed in use, the grounds in which the hypothetical bearing capacity changes dramatically was modeled to evaluate the applicability of different foundations. Also, based on the results of measurement interpretation, various foundations are created by using plaster, Joomunjin standard soil, and rubble to conduct an indoor model test to compare and analyze the movement of pile foundation and different foundations. Based on such research results, the stability and applicability of the different foundations which is more efficient and economical than the existing foundations in case of grounds in which the bearing capacity changes dramatically by comparing and analyzing the different foundations (direct foundation + pile foundation) with the conservative pile foundation and mat foundation. As a result, when the different foundation is applied, the overall settlement amount increased than the conservative pile foundation. However, the difference was very minute and it has been confirmed to be no issue as a result of assessment of stability of the differential settlement of structures through critical angle displacement.

• The Journal of Engineering Geology
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• v.20 no.3
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• pp.243-255
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• 2010

The slope design of an open-pit mine must consider economical efficiency and stability. Thus, the overall slope angle is the principal factor because of limited support or reinforcement options available in such a setting. In this study, slope displacement, as monitored by a GPS system, was analyzed for a coal mine at Pasir, Indonesia. Predictions of failure time by inverse velocity analysis showed good agreement with field observations. Therefore, the failure time of an unstable slope can be roughly estimated prior to failure. A GIS model that combines fuzzy theory and the analytical hierarchy process (AHP) was developed to assess slope instability in open-pit coal mines. This model simultaneously considers seven factors that influence the instability of open-pit slopes (i.e., overall slope gradient, slope height, surface flows, excavation plan, tension cracks, faults, and water body). Application of the proposed method to an open-pit coal mine revealed an enhanced prediction accuracy of failure time and failure site compared with existing methods.