• 한국가시화정보학회:학술대회논문집
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• 2006.12a
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• pp.17-20
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• 2006

Passenger safety is fundamental factor in automobile. Among much equipment for passenger safety, the air bag system is the most fundamental and effective device. Beside of the front air bag system which installed on most of all automobiles, a curtain-type air bag is increasingly adapted in deluxe cars fur protecting passengers from the danger of side clash. Curtain type airbag system consists of inflator housing, fill hose, curtain airbag. Inflator housing is a main part of the curtain-type air bag system for supplying high-pressure gases to deploy the air bag-curtain. Fill hose is a passageway to carry the gases from inflator housing to each part of curtain airbag. Therefore, it is very important to design the vent holes of fill hose for good performance of airbag deployment. But, the flow information from vent holes of fill hose is very limited. In this study, we measured instantaneous velocity fields of a high-speed flow ejecting from the vent holes of fill hose using a dynamic PIV system. From the velocity Held data measured at a high frame-rate, we evaluated the variation of the mass flow rate with time. From the instantaneous velocity fields of flow ejecting from the vent holes in the initial stage, we can see a flow pattern of wavy motion and fluctuation. The flow ejecting from the vent holes was found to have very high velocity fluctuations and the maximum velocity was about 480m/s at 4-vent hole region. From the mass flow rate with time, the accumulated flow of 4-vent hole has occupied about 70% of total flow rate.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.3
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• pp.479-485
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• 2007

In this paper, a hierarchical simulation with an approximate implicit method is proposed in order to efficiently and plausibly animate mass-spring based cloth models. The proposed hierarchical simulation method can generate realistic motion of extremely fine mesh in interactive rate. The proposed technique employs a fast and stable simulation method which approximates the implicit integration. Although the approximate method is efficient, it is extremely inaccurate and shows excessively damped behavior. The hierarchical simulation technique proposed in this paper constructs multi-level mesh structure in order to represent the realistic appearance of cloth model and performs simulation on each level of the mesh with constraints that enforce some of the mass-points of current level to follow the movement of the previous level. This hierarchical method efficiently generates a plausible movement of a cloth model composed of large number of mass points. Moreover, this hierarchical method enables us to generate realistic wrinkles on the cloth, and the wrinkle pattern on the cloth model can be easily controlled because we can specify different contraction resistance force of springs according to their hierarchical level.

• Nuclear Engineering and Technology
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• v.43 no.2
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• pp.133-140
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• 2011

In this paper, a deformation measurement technology for nuclear fuel rods is proposed. The deformation measurement system includes a high-definition CMOS image sensor, a lens, a semiconductor laser line beam marker, and optical and mechanical accessories. The basic idea of the proposed deformation measurement system is to illuminate the outer surface of a fuel rod with a collimated laser line beam at an angle of 45 degrees or higher. For this method, it is assumed that a nuclear fuel rod and the optical axis of the image sensor for observing the rod are vertically composed. The relative motion of the fuel rod in the horizontal direction causes the illuminated laser line beam to move vertically along the surface of the fuel rod. The resulting change of the laser line beam position on the surface of the fuel rod is imaged as a parabolic beam in the high-definition CMOS image sensor. An ellipse model is then extracted from the parabolic beam pattern. The center coordinates of the ellipse model are taken as the feature of the deformed fuel rod. The vertical offset of the feature point of the nuclear fuel rod is derived based on the displacement of the offset in the horizontal direction. Based on the experimental results for a nuclear fuel rod sample with a formation of surface crud, an inspection resolution of 50 ${\mu}m$ is achieved using the proposed method. In terms of the degree of precision, this inspection resolution is an improvement of more than 300% from a 150 ${\mu}m$ resolution, which is the conventional measurement criteria required for the deformation of neutron irradiated fuel rods.

• Journal of Korean Society of Disaster and Security
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• v.12 no.2
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• pp.57-63
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• 2019

The road sinks in the sewer line or subway section are affected by the ground characteristics. Therefore, it is necessary to accurately identify the relationship between the soil properties and the ground motion in the area where cavities occurred in order to establish a countermeasure against the road sink. In this paper, simulation was performed by using EDEM program, which is one of the Discrete Element Method programs, for sandy soil and clayey soil, which are most common in alluvial deposits, with different locations and sizes of cavities in the underground. As a result, it was found that the sink size occurred more in the sandy soil than in the cohesive soil. Deeper and larger cavity is more likely to occur the road sink In the sand soil model while road sink in the clay model is easy to occur when the cavity is more shallower.

• Korean Journal of Applied Biomechanics
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• v.29 no.2
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• pp.79-88
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• 2019

Objective: The aim of this study was to determine the peak torques of the knee and ankle joint and local stability of the lower extremity's joints, and muscle activation patterns of the lower extremity's muscles between fallers and non-fallers in the elderly women during walking. Method: Four elderly women (age: $74.5{\pm}5.2yrs.$; height: $152.1{\pm}5.6cm$; mass: $55.3{\pm}5.4kg$; preference walking speed: $1.19{\pm}0.06m/s$) who experienced falls within six months since experiment had been conducted (falls group) and thirty-six subjects ($74.2{\pm}3.09yrs.$; height: $153.6{\pm}4.9cm$; mass: $56.7{\pm}6.4kg$; preference walking speed: $1.24{\pm}0.10m/s$) who had no experience in falls (non-falls group) within this periods participated in this study. They were measured torque peaks of the knee and ankle joint using a Human Norm and while they were walking on a treadmill at their natural pace, kinematic variables and EMG signals were collected with using a 3-D motion capture system and a wireless EMG system, respectively. Lyapunov Exponent (LyE) was determined to observe the dynamic local stability of the lower extremity's joints, and muscles activation and their co-contraction index were also analysed from EMG signals. Hypotheses between falls and non-falls group were tested using paired t-test and Mann-Whitey. Level of significance was set at p<.05. Results: Local dynamic stability in the adduction-abduction movement of the knee joint was significantly lower in falling group than non-falling group (p<.05). Conclusion: In conclusion, muscles which act on the abduction-adduction movement of the knee joint need to be strengthened to prevent from potential falls during walking. However, a small number of samples for fallers make it difficult to generalize the results of this study.

• Structural Engineering and Mechanics
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• v.78 no.1
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• pp.53-66
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• 2021

The determination of the damage index to reveal the performance level of a structure can constitute the seismic risk generalization approach based on the parametric analysis. This study implemented this concept to one kind of civil engineering structure that is the concrete gravity dam. Different cases of the structure exhibit their individual responses, which constitute different considerations. Therefore, this approach allows the parametric study of concrete as well as soil for evaluating the seismic nature in the generalized case. To ensure that the target algorithm applicable to most of the concrete gravity dams, a very simple procedure has been considered. In order to develop a correlated algorithm (by response surface methodology; RSM) between the ground motion and the structural property, randomized sampling was adopted through a stochastic method called half-fractional central composite design. The responses in the case of fluid-foundation-dam interaction (FFDI) make it more reliable by introducing the foundation as being bounded by infinite elements. To evaluate the seismic generalization of FFDI models, incremental dynamic analysis (IDA) was carried out under the impacts of various earthquake records, which have been selected from the Pacific Earthquake Engineering Research Center data. Here, the displacement-based damage indexed fragility curves have been generated to show the variation in the seismic pattern of the dam. The responses to the sensitivity analysis of the various parameters presented here are the most effective controlling factors for the concrete gravity dam. Finally, to establish the accuracy of the proposed approach, reliable verification was adopted in this study.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.257-267
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• 2021

Constraints on the structure and composition of the active layer are important for understanding permafrost evolution. Soil convection owing to repeated moisture-induced freeze-thaw cycles within the active layer promotes the formation of self-organized patterned ground. Here we present the results of ground penetrating radar (GPR) surveys across a selected sorted circle near King Sejong Station, Antarctica, to better delineate the active layer and its relation to the observed patterned ground structure. We acquire GPR data in both bistatic mode (common mid-points) for precise velocity constraints and monostatic mode (common-offset) for subsurface imaging. Reflections are derived from the active layer-permafrost boundary, organic layer-weathered soil boundary within the active layer, and frozen rock-fracture-filled ice boundary within the permafrost. The base of the imaged sorted circle possesses a convex-down shape in the central silty zone, which is typical for the pattern associated with convection-like soil motion within the active layer. The boundary between the central fine-silty domain and coarse-grained stone border is effectively identified in a radar amplitude contour at the assumed active layer depth, and is further examined in the frequency spectra of the near- and far-offset traces. The far-offset traces and the traces from the lower frequency components dominant on the far-offset traces would be associated with rapid absorption of higher frequency radiowave due to the voids in gravel-rich zone. The presented correlation strategies for analyzing very shallow, thin-layered GPR reflection data can potentially be applied to the various types of patterned ground, particularly for acquiring time-lapse imaging, when electric resistivity tomography is incorporated into the analysis.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.27 no.1
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• pp.21-30
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• 2021

Background: This study aimed to investigate the effects of muscle energy technique (MET) and instrument assisted soft tissue mobilization (IASTM) on knee extension ROM, knee extensor/flexor strength and muscle thickness immediately and after 24 hours. Methods: A total of 30 subjects participated in this study. The participants were assigned to either MET (n=15) or IASTM (n=15). 90-90 straight leg raise, knee extensor/flexor muscle strength, muscle thickness test were measured before, immediately after and 24 hours after the intervention. Results: Both groups significantly improved knee extension ROM on immediate (MET 10.7°, IASTM 10.21° increased) and after 24 hours assessment (MET 5.61°, IASTM 5.47° increased)(p<.05). In the MET group, knee extension and flexion muscle strength increased immediately after intervention (p<.05). In the IASTM group, knee extension muscle strength increased and knee flexor muscle strength decreased immediately after intervention (p<.05). Furthermore, both groups showed a pattern of returning to the initial strength after 24 hours. In both groups, no significant difference in muscle thickness immediately and after 24 hours was observed (p>.05). Conclusion: According to the results of the present study, MET and IASTM technique showed lasting effectiveness in flexibility of shortened hamstring immediately after and in 24 hours after the intervention. In both groups, MET increased muscle strength and increased ROM, while IASTM decreased muscle strength and increased ROM, with no change in muscle thickness.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.1
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• pp.37-47
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• 2023

A new clamped mechanical splice system was proposed to develop structural performance and constructability for precast concrete connections. The proposed mechanical splice resists external loading immediately after the engagement. The mechanical splices applicable for both large-scale rebars for plants and small-scale rebars for buildings were developed with the same design concept. Quasi-static lateral cyclic loading tests were conducted with reinforced and precast concrete members to verify the seismic performance. Also, shaking table tests with three types of seismic wave excitation, 1) random wave with white noise, 2) the 2016 Gyeongju earthquake, and 3) the 1999 Chi-Chi earthquake, were conducted to confirm the dynamic performance. All tests were performed with real-scale concrete specimens. Sensors measured the lateral load, acceleration, displacement, crack pattern, and secant system stiffness, and energy dissipation was determined by lateral load-displacement relation. As a result, the precast specimen provided the emulative performance with RC. In the shaking table tests, PC frames' maximum acceleration and displacement response were amplified 1.57 - 2.85 and 2.20 - 2.92 times compared to the ground motions. The precast specimens utilizing clamped mechanical splice showed ductile behavior with energy dissipation capacity against strong motion earthquakes.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.29 no.3
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• pp.43-53
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• 2023

Background: Patients with neck pain develop instability due to muscle imbalance, decreased proprioception, and balance disorders. Studies have examined various exercise methods as treatment methods, but few studies have compared the effects of cervical stabilization exercise and dynamic balance exercise. The purpose of this study was to investigate the effects of dynamic balance exercise on pain, functional level, and psychosocial level in patients with non-specific chronic neck pain. Methods: Thirty-four non-specific chronic neck pain patients were randomly assigned to the experimental group (EG, n=17) and control group (CG, n=17); the cervical stabilization exercise and dynamic balance exercise program were applied to the EG; and only the cervical stabilization exercise program was applied to the CG. The intervention was conducted twice a week, for six weeks. Assessment items evaluated pain, dysfunction (Korean version neck disability index), range of motion, craniocervical flexion test, cervical deep flexor endurance test, and psychosocial level. Data analysis was performed using intention-to-treat analysis as assigned. To analyze differences in the items assessed in the two groups, we used a repeated measures analysis of variance with an interaction between group (EG, CG) and time point (baseline, 6 weeks, 12 weeks). Results: The endurance of the cervical flexor muscles between the group and the measurement point after intervention (p<.05). Both groups showed significantly improved endurance between time points after the intervention (p<.05), with the EG showing a greater change than the CG. None of the other measurement items differed in the pattern of change between measurement points. Conclusion: In conclusion, the EG applying a cervical stabilization exercise and a dynamic balance exercise experienced a significant difference in muscle endurance improvement compared to the CG. We propose an exercise intervention program that includes stabilization exercises and dynamic balance exercises for patients with chronic cervical pain who lack muscle endurance.