• Korean Journal of Applied Biomechanics
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• v.34 no.2
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• pp.81-92
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• 2024

Objective: The purpose of this study was to analyze the impact acceleration, shock attenuation and biomechanical variables at various running speed. Method: 20 subjects (height: 176.15 ± 0.63 cm, weight: 70.95 ± 9.77 kg, age: 27.00 ± 4.65 yrs.) participated in this study. The subjects ran at four different speeds (2.5 m/s, 3.0 m/s, 3.5 m/s, 4.0 m/s). Three-dimensional accelerometers were attached to the distal tibia, sternum and head. Gait parameters, biomechanical variables (lower extremity joint angle, moment, power and ground reaction force) and acceleration variables (impact acceleration, shock attenuation) were calculated during the stance phase of the running. Repeated measures ANOVA was used with an alpha level of .05. Results: In gait parameters, decreased stance time, increasing stride length and stride frequency with increasing running speed. And at swing time 2.5 m/s and 4.0 m/s was decreased compared to 3.0 m/s and 3.5 m/s. Biomechanical variables statistically increased with increasing running speed except knee joint ROM, maximum ankle dorsiflexion moment, and maximum hip flexion moment. In acceleration variables as the running speed increased (2.5 m/s to 4.0 m/s), the impact acceleration on the distal tibia increased by more than twice, while the sternum and head increased by approximately 1.1 and 1.2 times, respectively. And shock attenuation (tibia to head) increased as the running speed increased. Conclusion: When running speed increases, the magnitude and increasing rate of sternum and head acceleration are lower compared to the proximal tibia, while shock attenuation increases. This suggests that limiting trunk movement and increasing lower limb movement effectively reduce impact from increased shock. However, to fully understand the body's mechanism for reducing shock, further studies are needed with accelerometers attached to more segments to examine their relationship with kinematic variables.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.6
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• pp.202-214
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• 1997

In automotive industries, one of major issues is the shifting shock, which is brought out when two clutches are engaged in an automatic transmission. The engagement and disengagement if two clutches means the variation of the D.O.F(degree of freedom) of system. Therefore to analyze the shifting performance, the variation of D.O.F should be considered in detail. Generally, the programs for analyzing the shifting transients have been developed as the problem-dependent codes because the artificial maris were usually used to indicate the change of shifting phase. To develop a software applicable to a general mechanism of transmissions, a self-determining algorithm of D.O.F must be applied. Through the experiences for the last several years, a generalized analysis software of shifting mechanism(so called by POTAS-MSM Version 2.0) has been developed. In this study, some major ideas of the software and the concept for the analysis of shifting characteristics are presented. In addition to that, this paper shows how to self -determine D.O.F of he multi-slipping systems using the stick-slip criterion on a single slipping mechanism. By using this software, the shifting characteristics of a vehicle are analyzed and compared with the experimental results.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.293-296
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• 2008

Most of the guided weapons have been kept and transferred at the launching tube and fired in case of necessity in these day. Launching tube is a kind of case to protect the guided weapons from external environments and conducted as a guide when they are fired. When we attached the guided weapons to launching tube we usually has used explosive bolt. Explosive bolts have been used explosives when they had to be separated. But when they are separated there are some bad effects; a flame, fragments and pyro-shock. Because of these bad effects there are many restriction to use bolt as joining devices to precision guided weapons. To solve these problems, it has been invented ball type bolt. The present work was represented quantitively the margin of separation safty and separation mechanism in ball type bolt to analyse the dynamic separation test. Unlike explosive bolt, ball type bolt is separated without a flame, fragments and pyro-shock. And it also has a good mechanical properties as much as those of explosive bolt.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.2
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• pp.67-74
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• 2016

Explosive bolt is one of separation device that uses high explosive charge, and is separated by pressure formed by an explosion and the resulting shock waves. Explosive bolt having such a mechanism would have to be designed to minimize shock and debris formation generated during separation. In this study, separation tests were carried out with distance as variable for restraining the explosive bolt (Air Gap). Bolt release and its separating shape with variation of air gap is observed, and we used accelerometer to measure the shock wave transmitted through a bound object. In addition, separation behavior of explosive bolt is analyzed using ANSYS AUOTODYN program. By comparing the results of previously performed experiments and analysis, we could confirm the effects of air gap to the release behavior of explosive bolt, and decide optimum constraining environment for specific separation bolts.

• Journal of Trauma and Injury
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• v.21 no.1
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• pp.22-27
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• 2008

Purpose: Treatment and prognosis in patients with pelvic bone fracture depend on the characteristics of the fracture and the stability of the pelvic ring. The purpose of this study is to analyze the characteristics of and the relationships between fracture patterns, injury mechanisms, clinical courses, and prognoses according to the hemodynamic pattern. Methods: Between January 2004 and September 2006, 89 patients under diagnosis of pelvic bone fracture were retrospectively analyzed on the basis of medical records and radiologic examinations. Patients with confirmed hemorragic shock with a systolic pressure of less than 90 mmHg were defined as the shock group. Young's classification was used to characterize fracture patterns. Factors relating to the clinical manifestation and to treatments such as transfusion and surgery were analytically compared. Results: The mean age of the patients was $48.8{\pm}18.7$, among which 49 (55.1%) were male. The numbers of shock and non-shock patients were 35 (39.3%) and 54 (60.7%) respectively. Eighteen (51.4%) of the shock patient had injuries resulting from pedestrian accidents (p=0.008). According to Young's classification, lateral impact fractures amounted to 20 and 33, front-rear impact fractures to 9 and 20, and multiple fractures to 6 and 1 among the shock and non-shock patients, respectively (p=0.027). Thirty-nine (39) cases in non-shock injuries were conservatively managed while 18 cases in shock injuries were surgically treated. In the shock group, the liver and the kidney were often damaged, as well. Among the shock patients, the average admission period was $7.5{\pm}8.7days$ in intensive care and $55.1{\pm}47.9days$ in total, which were longer than the corresponding numbers of days for the non-shock patients (p<0.05). No deaths occurred in the non-shock group while 5 deaths (14.2%) occurred in the shock group (p=0.007). Conclusion: The factors affecting hemodynamic instability in patients with pelvic bone fracture are injury mechanism, classification of fracture, and associated injuries.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1995.11a
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• pp.69-83
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• 1995

A great number of experimental data indicating shock-induced separation(SIS) in internal or external supersonic flows were reviewed to make clear the mechanism of SIS and to present the criterion of turbulent boundary layer separation. The interesting conclusions were obtained for the considerably wide range of flow geometries that the incipient separation is almost independent of the flow geometries, and that it is relatively unaffected by changes in gas specific heat, and boundary layer Reynolds number, Furthermore, the pressure rise necessary to separate boundary layer in external flows was found to be applicable to SIS in overexpanded propulsion nozzles. This is due to the fact that the SIS phenomenon caused by the interaction between shock waves and turbulent boundary layers is processed through a supersonic deceleration. This is, the SIS in almost all of interacting flow fields is governed by the concept of free interaction, and criterion of SIS is only a Function of upstream Mach number.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.93-99
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• 2003

In this study, new shock absorbing system is proposed by using nano-technology based on the theoretical analysis. The new shock absorbing system is complementary to the hydraulic damper, having a cylinder-piston-orifice construction. Particularly for new shock absorbing system, the hydraulic oil is replaced by a colloidal suspension, which is composed of a porous matrix and a lyophobic fluid. The matrix of the suspension is consisted of porous micro-grains with a special architecture: they present nano-pores serially connected to micro-cavities. Until now, only experimentally qualitative studies of new shock absorbing system have been performed, but the mechanism of energy dissipation has not been clarified. This paper presents a modeling and theoretical analysis of the new shock absorbing system thermodynamics, nono-flows and energy dissipation. Compared with hydraulic system, the new shock absorbing system behaves more efficiently, which absorb a large amount of mechanical energy, without heating. The theoretical computations agree reasonably well with the experimental results. As a result. the proposed new shock absorbing system was proved to be an effective one, which can replace with the conventional one.

• YAKHAK HOEJI
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• v.51 no.1
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• pp.44-50
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• 2007

Acute septic shock is one of inflammatory diseases mediated by pro-inflammatory cytokines such as tumor necrosis factor (TNF)-${\alpha}$. In this study, we examined the pathological difference and mechanism of lipopolysaccharides isolated from E. coli (E-LPS) or S. abortus (S-LPS) on inducing acute septic shock in ICR mouse. All mice were died by intraperitoneal treatment of S-LPS with 0.75 mg/kg, whereas E-LPS treated with even 3 mg/kg only showed 30% of mice lethal, indicating that S-LPS may be more feasible in triggering a strong septic shock condition. The secretion pattern of TNF-${\alpha}$, a critical pro-inflammatory cytokine in septic shock condition, was also distinct between E-LPS- and S-LPS-treated groups. Thus, S-LPS strikingly increased serum level of TNF-${\alpha}$ (6 ng/ml) at 1 h, while E-LPS just displayed at 2 ng/ml level. However the interaction of S-LPS with LPS receptor toll like receptor (TLR)-4, was not stronger than that of E-LPS, according to experiments with macrophage cell line RAW264.7 cells. Thus, E-LPS rather than S-LPS strongly enhanced the production of TNF-${\alpha}$. Interestingly, S-LPS more strongly up-regulated splenocyte proliferation, compared to E-LPS group, whereas there was no difference between S- or E-LPS treated groups in proliferation of Balb/c- or C57BL/6-originated splenic lymphocytes. Therefore, our data suggest that S-LPS is a more active endotoxin and that the strong septic shock-inducing effect of S-LPS seems due to the enhancement of early TNF-${\alpha}$ production and S-LPS-sensitive lymphocyte proliferation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.7
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• pp.32-40
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• 2003

An experimental research has been carried out for flow visualizations of the shock wave/turbulent boundary-layer interaction control utilizing the aeroelastic flaps, Spark shadowgraphs, kerosene-lampblack tracings for the surface streakline pattern, and interference fringe patterns over a thin oil-film applied at the downstream of the shock interactions have been obtained , Effects of variation of the shapes and thicknesses of the flaps are tested, and all the results are compared to the solid-wall reference case without flow-control mechanism , From the qualitative observation of the variation of skin friction utilizing the interference fringe patterns over the silicone oil-film, a strong spanwise variation of the skin friction with a narrow and long region of separation has been noticed near the centerline behind the shock structure, which phenomenon demonstrate a strong three-dimensionality of the shock interaction flows, Influence of the shape of the cavity under the flaps to the shock interaction is also tested, and it is observed that the shape of the cavity is not negligible.

• Journal of Trauma and Injury
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• v.33 no.3
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• pp.162-169
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• 2020

Purpose: There is increasing evidence in the literature regarding resuscitative endovascular balloon occlusion of the aorta (REBOA) globally, but few cases have been reported in Korea. We aimed to describe our experience of successful Zone III REBOA and to discuss its algorithm, techniques, and related complications. Methods: We reviewed consecutive cases who survived from hypovolemic shock after Zone III REBOA placement for 4 years. We reviewed patients' baseline characteristics, physiological status, procedural data, and outcomes. Results: REBOA was performed in 44 patients during the study period, including 10 patients (22.7%) who underwent Zone III REBOA, of whom seven (70%) survived. Only one patient was injured by a penetrating mechanism and survived after cardiopulmonary resuscitation. All patients underwent interventions to stop bleeding immediately after REBOA placement. Conclusions: This case series suggests that Zone III REBOA is a safe and feasible procedure that could be applied to traumatic shock patients with normal FAST findings who receive a chest X-ray examination at the initial resuscitation.