• Transactions of Materials Processing
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• v.17 no.5
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• pp.364-372
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• 2008

In this study, the circumferential creep behaviors ofpilgered advanced Zirconium alloy tubes such as Zr-Nb-O and Zr-Nb-Sn-Fe were investigated in the temperature range of $400\sim500^{\circ}C$ and in the stress range of 80$\sim$150MPa. The test results indicate that the stress exponent for the steady-state creep rate of the Zr-Nb-Sn-Fe alloy decreases with the increase of stress(from 6$\sim$7 to 4), while that of the Zr-Nb-O alloy is nearly independent of stress(5$\sim$6). The activation energy of creep deformation is found to be nearly the same as the activation energy for Zr self diffusion. This indicates that the creep deformation may be controlled by dislocation climb mechanism in Zr-Nb-O. On the other hand, the transition of stress exponent(from 6-7 to 4) in Zr-Nb Sn-Fe strongly suggests the transition of the rate controlling mechanism at high stresses. The lower stress exponent at high stresses in Zr-Nb-Sn-Fe can be explained by the dynamic deformation aging effect caused by interaction of dislocations with Sn substitutional atoms.

• Journal of Yeungnam Medical Science
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• v.10 no.1
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• pp.114-126
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• 1993

The fractures of the cervical spine are relatively uncommon, but they may cause serious neurologic deficits temporarily or permanently. So, it is very important to treat the patients early by way of exact evaluation for the sites and the mechanisms of the injuries. The authors reviewed retrospectively 188 cervical spinal fractures in 100 patients from Sep. 1984 to Aug. 1990. Commonly involved levels were $C_5$ and $C_6$ in lower cervical level and $C_2$ in upper cervical level and the sites in each spine were body, lamina and odontoid process. The hyperflexion injury was the most common type of the cervical spinal fractures occupying 53% of all cervical fractures and cause more multiple fractures(2.26 fractures/patient) than in hyperextension(1.68 fractures/patient). In hyperflexion injuries, body, transverse and spinous process were commonly involved but lamina fracture was relatively common in hyperextension injury. The dislocations associated with fractures were developed most commonly in hyperflexion injury and 70% of these were anterior dislocation and the most commonly involved levels were $C_{5-6}$ and $C_{6-7}$. In conclusion, hyperflexion injury needs more close examination for the entire spinal levels than injuries of other mechanisms because it results in more severe fractures with or without dislocation and relatively frequent multiple fractures in different levels.

• Journal of agricultural medicine and community health
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• v.33 no.1
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• pp.82-89
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• 2008

Objective:　We compared the prevalence of injury and poisoning in the agricultural and fishery population with that of the general population.Methods: The national health insurance data and agricultufor this study. The age-adjusted standardized morbidity ratio was used to compare the prevalence of all injuries and poisonings of the agricultural and fishery population with that of the general population for the year 2002, as well as the prevalence of certain injuries and poisonings common to the agricultural and fishery population. The age-adjusted standardized morbidity ratio and 95% confidence intervals were attained by using the general population as the standard population group.Results: The age-adjusted standardized morbidity ratio of total injuries and poisonings was significantly high in the agriculture and fishery population. The standardized morbidity ratio was 137.6 in the male agriculture and fishery population and 123.3 in the female agriculture and fishery population. In terms of injuries and poisonings common to the agriculture and fishery population, the age-adjusted standardized morbidity ratio was significantly high regarding the dislocations and strains of lumbar spine/pelvis, shoulder and neck, the fracture of rib/thoracic spine/sternum and pesticide poisoning.Conclusions: The overall prevalence of injury/poisoning was significantly higher in the agriculture and fishery population than in the general population. Various forms of research should be conducted on the injuries of the agriculture and fishery population in the future. In order to compare the differences in the prevalence rates of injuries according to time and region, standard definitions of injuries and occupation related injuries are required.

• Journal of the Korean Society for Heat Treatment
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• v.5 no.1
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• pp.41-49
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• 1992

The effects of alloying elements on the superplastic properties of Al-Li based alloys had been investigated. The intermediate thermo-mechanical treated (ITMT) Al-2.0wt%Li, Al-2.0wt%Li-1.0wt%Mg, Al-2.0wt%Li-0.12wt%Zr and Al-2.0wt%Li-1.2wt%Cu-1.0wt%Mg-0.12wt%Zr alloys were tested in tension at various temperature (400, 450, 500 and $550^{\circ}C$) and strain rate($6.7{\times}10^{-3}$, $1.0{\times}10^{-2}$, $1.6{\times}10^{-2}$ and $5.0{\times}10^{-2}/sec$). The results were as follows : The superplasticity in binary, ternary and pentanary alloys appeared at 500 to $550^{\circ}C$, and good strain rate for superplasticity. $1.6{\times}10^{-2}/sec{\sim}1.0{\times}10^{-2}/sec$ for a binary alloy and $1.0{\times}10^{-2}/sec{\sim}6.7{\times}10^{-3}/sec$ for ternary and pentanary alloys. A Zr-added ternary alloy had best value of elongation (730%) in four alloys at $550^{\circ}C$ of tension temperature and $1.0{\times}10^{-2}/sec$ of strain rate. The strain rate was greatly dependent on tension temperature and true strain rate was more than 1.0 at all test temperature and strain rate. In binary and Mg-added teranry alloys. the necks were slightly formed and their fracture surface had lips shape, but Zr-added ternary and pentanary alloy fractured along the grain boundary without necking. Their dislocations moved to grain boundary during superplasticity deformation and arranged perpendicular to grain boundary. Super plastic deformation was made by grain boundary slip of dislocation slip creep and model of core and mantle.

• Korean Journal of Materials Research
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• v.30 no.6
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• pp.292-300
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• 2020

In this study, the effect of tempering on the stretch-flangeability is investigated in 980 MPa grade dual-phase steel consisting of ferrite and martensite phases. During tempering at 300 ℃, the strength of ferrite increases due to the pinning of dislocations by carbon atoms released from martensite, while martensite is softened as a consequence of a reduction in its carbon super-saturation. This strength variation results in a considerable increase in yield strength of the steel, without loss of tensile strength. The hole expansion test shows that steel tempered for 20 min (T20 steel) exhibits a higher hole expansion ratio than that of steel without tempering (T0 steel). In T0 steel, severe plastic localization in ferrite causes easy pore formation at the ferrite-martensite interface and subsequent brittle crack propagation through the highly deformed ferrite area during hole expansion testing; this propagation is mainly attributed to the large difference in hardness between ferrite and martensite. When the difference in hardness is not so large (T20 steel), on the other hand, tempered martensite can be considerably deformed together with ferrite, thereby delaying pore formation and hindering crack propagation by crack blunting. Eventually, these different deformation and fracture behaviors contribute to the superior stretch-flangeability of T20 steel.

• Journal of Korean Orthopaedic Sports Medicine
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• v.2 no.2
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• pp.77-81
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• 2003

Purpose: The biomechanics and kinematics of knee joint were reviewed in this article. And then the common sports injuries were presented. Anatomy and Kinetics: None of the pairs of bearing surfaces in the knee joint is exactly congruent This allows the knee six degrees of freedom of motion. Tibiofemoral Kinematics: In flexion and extension, the axis of motion is not perpendicular to the medial-lateral plane of the joint, nor is it perpendicular to the axis of longitudinal rotation. This results in coupled varus angulation and internal rotation with flexion and in valgus angulation and external rotation with extension. Patellofemoral Articulation: Loads across the patellofemoral joint are indirectly related to the angle of knee flexion and directly related to the force generated within the quadriceps mechanism. Fractures of the Patella: Nonoperative treatment is indicated if the extensor mechanism is intact and if displacement of fragment is minimal. The specific type of internal fixation depends on the fracture pattern. It is important to repair retinaculum. Acute and Recurrent Patellar Instability: The degree of dysplasia and the extent of the instability play a large part in determining the success of nonoperative treatment. Patients who experience recurrent dislocations and patients with major anatomic variations require surgery to minimize their instability. Sports Injuries in School-age Atheletes: Patellar pain in young athletes groups a number of conditions, including Idiopathic Adolescent Anterior Knee Pain, Osgood- Schlatter Disease, and Sinding-Larsen-Johansson Disease.

• Journal of Korean Neurosurgical Society
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• v.29 no.3
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• pp.379-388
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• 2000

Objective : Although transoral transpharyngeal approach is a very useful method for the lesions of craniovertebral junction, it is not frequently used because of anatomical unfamilarity, risk of cerebrospinal fluid(CSF) leakage, and resultant postoperative meningitis. To evaluate the usefulness of transoral transpharyngeal approach for various lesions of craniovertebral junction, clinical characteristics and the results of this approach are investigated. Methods : Transoral transpharyngeal approaches were performed in eight cases between 1996 and 1999. Among them, there were three basilar invaginations due to congenital anomalies, two odontoid type I fractures, two atlantoaxial dislocations, and one pseudotumor. Surgical methods included five cases of anterior decompression and posterior fusion, two anterior approaches for decompression and one transoral approach for biopsy. Results : This procedure allowed immediate clinical improvement in all cases. In seven patients with preoperative motor deficit showed a progressive neurological improvement. The follow-up plain x-rays demonstrated successful bony fusion in all patients. Only one patient suffered from postoperative wound dehiscence, but she completely recovered after wound revision. There was no complication of postoperative CSF leakages. Conclusions : Transoral transpharyngeal approach for the ventral lesions of craniovertebral junction, can be used as a relatively simple and effective method.