• Journal of the Korea Concrete Institute
• /
• v.17 no.5 s.89
• /
• pp.709-716
• /
• 2005

The objective of this study is to develop a high ductile fiber reinforced mortar, ECC(Engineered Cementitious Composite) with using raw material commercially available in Korea. A single fiber pullout test and a wedge splitting test were employed to measure the bond properties in a matrix and the fracture toughness of mortar matrix respectively, which are used for designing mix proportion suitable for achieving strain-hardening behavior at a composite level. Test results showed that the properties tended to increase with decreasing water-cement ratio. A high ductile fiber reinforced mortar has been developed by employing micromechanics-based design procedure. Micromechanical analysis was initially peformed to properly select water-cement ratio, and then basic mixture proportion range was determined based on workability considerations, including desirable fiber dispersion without segregation. Subsequent direct tensile tests were performed on the composites with W/C's of 47.5% and 60% at 28 days that the fiber reinforced mortar exhibited high ductile uniaxial tension property, represented by a maximum strain capacity of 2.2%, which is around 100 times the strain capacity of normal concrete. Also, compressive tests were performed to examine high ductile fiber reinforced mortar under the compression. The test results showed that the measured value of compressive strength was from 26MPa to 34 MPa which comes under the strength of normal concrete at 28 days.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.28 no.1
• /
• pp.42-48
• /
• 2006

Open reduction and rigid internal fixation is the most popular treatment method for maxillofacial fracture patients, and it is unevitable that postoperative pain can be developed. Many surgeons including oral & maxillofacial surgeons have made constant efforts to decrease postoperative pain. This study is a comparison of postoperative analgesia and intramuscular analgesia in patients with mandibular fractures. In this study, twenty-one patients (Experimental group) were randomly selected and they were injected with IV patient-controlled analgesia (PCA; Walkmed$^{(R)}$, USA). For control group another twenty-one patients were injected with intramusclar non-steroid anti-inflammatory drugs (Rheoma$^{(R)}$, Samsung Pharm. Co.). And then, we measured visual analogue scale (VAS) scores from first postoperative day to second day at regular time interval. The following results were uptained; 1. In patient group who with open reduction and rigid internal fixation, there was significant difference of postoperative analgesic effect during the first postoperative day(p<0.05). 2. In patient group with over 90 minutes surgery time, there was significant difference of postoperative analgesic effect during the first and second postoperative day when compared between experimental group and control group(p<0.05). 3. In patient group with less than 90 minutes surgery time, there was no significant difference of postoperative analgesic effect during the first and second postoperative day when compared between experimental group and control group(p>0.05). 4. In patient group with surgery of open reduction using rigid internal fixation at single fractured site, there was no significant difference of postoperative analgesic effect during the first and second postoperative day when compared between experimental group and control group(p>0.05). 5. In patient group with surgery at two fractured sites, there was significant difference of postoperative analgesic effect during the first postoperative day when compared between experimental group and control group(p<0.05). As mentioned above, it suggest that patient-controlled analgesia is more effective for postoperative pain relief than intramuscular injection in patients with rigid internal fixation by open reduction after mandibular fracture occurred. Especially, it is considered that in patient with more than 90 minutes surgery time or in cases with multiple fractured sites had more effective results with PCA therapy than conventional intramuscular analgesics.

• Journal of Trauma and Injury
• /
• v.26 no.3
• /
• pp.170-174
• /
• 2013

Purpose: A flail chest is one of most challenging problems for trauma surgeons. It is usually accompanied by significant underlying pulmonary parenchymal injuries and mayled to a life-threatening thoracic injury. In this study, we evaluated the treatment result for a flail chest to determine the effect of trauma localization on morbidity and mortality. Methods: Between 2004 and 2011, 46 patients(29 males/17 females) were treated for a flail chest. The patients were divided into two group based on the location of the trauma in the chest wall; Group I contained patients with an anterior flail chest due to a bilateral costochondral separation (n=27) and Group II contained patients with a single-side posterolateral flail chest due to a segmental rib fracture (n=19). The location of the trauma in the chest wall, other injuries, mechanical ventilation support, prognosis and ISS (injury severity score) were retrospectively examined in the two groups. Results: Mechanical ventilation support was given in 38 patients(82.6%), and 7 of these 38 patients required a subsequent tracheostomy. The mean ISS for all 46 patients was $19.08{\pm}10.57$. Between the two groups, there was a significant difference in mean ventilator time (p<0.048), but no significant difference in either trauma-related morbidity (p=0.369) or mortality (p=0.189). Conclusion: An anterior flail chest frequently affects the two underlying lung parenchyma and can cause a bilateral lung contusion, a hemopneumothorax and lung hemorrhage. Thus, it needs longer ventilator care than a lateral flail chest does and is more frequently associated with pulmonary complications with poor outcome than a lateral flail chest is. In a severe trauma patient with a flail chest, especially an anterior flail chest, we must pay more attention to the pulmonary care strategy and the bronchial toilet.

• Korean Journal of Radiology
• /
• v.23 no.2
• /
• pp.264-270
• /
• 2022

Objective: This study aimed to investigate the usefulness of bone single-positron emission tomography/computed tomography (SPECT/CT) of the hip in predicting the later occurrence of avascular necrosis (AVN) after slipped capital femoral epiphysis (SCFE) or femoral neck fracture in pediatric patients. The quantitative parameters of SPECT/CT useful in predicting AVN were identified. Materials and Methods: Twenty-one (male:female, 10:11) consecutive patients aged < 18 years (mean age ± standard deviation [SD], 11.0 ± 2.7 years) who underwent surgery for SCFE or femoral neck fracture and postoperative bone SPECT/CT were included. The maximum standardized uptake value (SUV), mean SUV, and minimum SUV of the femoral head were measured. The ratios of the maximum SUV, mean SUV, and minimum SUV of the affected femoral head to the contralateral side were determined. Patients were followed up for > 1 year after the surgery. The SPECT/CT parameters were compared between patients who developed AVN and those who did not. The accuracy of SPECT/CT parameters for predicting AVN was assessed. Results: Six patients developed AVN. There was a significant difference in the ratio of the mean SUV among patients who developed AVN (mean ± SD, 0.8 ± 0.3) and those who did not (1.1 ± 0.2, p = 0.018). However, there were no significant differences in the ratios of the maximum and minimum SUV between the groups (all p = 0.205). For the maximum, mean, and minimum SUVs, no significant differences were observed between the groups (p = 0.519, 0.733, and 0.470, respectively). The cutoff mean SUV ratio of 0.87 yielded a 66.7% sensitivity and 93.2% specificity for predicting AVN. Conclusion: Quantitative bone SPECT/CT is useful for evaluating femoral head viability in pediatric patients with SCFE or femoral neck fractures. Clinicians should consider the high possibility of later AVN development in patients with a decreased mean SUV ratio.

• The Journal of Korean Orthopaedic Ultrasound Society
• /
• v.6 no.1
• /
• pp.1-9
• /
• 2013

Purpose: The purpose is to perform objective evaluation for rotator cuff using ultrasonography and validate factors influencing cuff integrity as well as efficacy of follow-up ultrasonography after unreamed antegrade intramedullary nailing for humerus fracture. Materials and Methods: Seventeen patients with an average age of $55.7{\pm}18.6$ years underwent antegrade intramedullary nailing for humerus fracture and follow-up ultrasonography of shoulder joint. Mean follow-up period was $43.5{\pm}32.2$ months. Intraoperative evaluation for preoperative cuff tear was performed, of which four cuffs were repaired by single row repair technique. Clinical evaluation included visual analogue scale (VAS), range of motion, Korean Shoulder Scoring System (KSS) and American Shoulder and Elbow Society (ASES) score. Ultrasonographic evaluation was performed on cuff integrity and protrusion of proximal nail tip as well. Radiographic evaluation included time to union, protrusion of proximal nail tip and migration of proximal interlocking screw which could affect shoulder joint function. Results: Mean VAS at last follow-up was $1.65{\pm}1.84$ points. Range of motion showed forward flexion of $137.0{\pm}33.5^{\circ}$, external rotation of $43.5{\pm}12.7^{\circ}$ and internal rotation of $16.4{\pm}2.0^{\circ}$ while KSS score and ASES score were $79.6{\pm}20.7$ and $83.7{\pm}17.0$ points, respectively. Bone union was demonstrated in all cases and average time to union was $3.4{\pm}1.3$ months. Migration of proximal interlocking screw was shown in 6 cases (35%). On ultrasonographic evaluation, there were normal in 8 (47%), weaving in 4 (24%), partial tear in 5 cases (29%), but no complete tear. Protrusion of proximal nail tip was demonstrated in 8 cases (47%) on plain radiographs whereas in 11 cases (65%) on ultrasonography and was associated with increasing age (p=0.038). Ultrasonographic weaving and partial tear was associated with protrusion of proximal nail tip (p=006), but not with repair of preoperative tear (p>0.05). Conclusion: Because weaving and partial tear on ultrasonography originated from protrusion of proximal nail tip, careful insertion of nail and meticulous repair of cuff during operation lead to stable fixation with satisfactory recovery of shoulder function follow-up ultrasonography can be a useful tool for evaluating protrusion of nail tip and rotator cuff tear, of which diagnosis is difficult on plain X-ray after antegrade intramedullary nailing for humerus fracture.

• Journal of the Korean Orthopaedic Association
• /
• v.54 no.4
• /
• pp.336-342
• /
• 2019

Purpose: To examine the relationship between the progression of a kyphotic deformity and the magnetic resonance imaging (MRI) findings in conservatively treated osteoporotic thoracolumbar compression fracture patients. Materials and Methods: This study categorized the patients who underwent conservative treatment among those patients who underwent treatment under the suspicion of a thoracolumbar compression fracture from January 2007 to March 2016. Among them, this retrospective study included eighty-nine patients with osteoporosis and osteopenia with a bone density of less than -2.0 and single vertebral body fracture. This study examined the MRI of anterior longitudinal ligament or posterior longitudinal ligament injury, superior or inferior endplate disruption, superior of inferior intravertebral disc injury, the presence of low signal intensity on T2-weighted images, and bone edema of intravertebral bodies in fractured intravertebral bodies. Results: In cases where the superior endplate was disrupted or the level of bone edema of the intravertebral bodies was high, the kyphotic angle, wedge angle, and anterior vertebral compression showed remarkably progression. In the case of damage to the anterior longitudinal ligament or the superior disc, only the kyphotic angle was markedly prominent. On the T2-weighted images, low signal intensity lesions showed a high wedge angle and high anterior vertebral compression. On the other hand, there were no significant correlations among the posterior longitudinal ligament injury, inferior endplate disruption, inferior disc injury, and the progression of kyphotic deformity and vertebral compression. The risk factors that increase the kyphotic angle by more than 5° include the presence of injuries to the anterior longitudinal ligament, superior endplate disruption, and superior disc injury, and the risk factors were 21.3, 5.1, and 8.5 times higher than those of the uninjured case, and the risk differed according to the level of bone edema. Conclusion: An osteoporotic thoracolumbar compression fracture in osteoporotic or osteopenic patients, anterior longitudinal ligament injury, superior endplate and intravertebral disc injury, and high level of edema in the MRI were critical factors that increases the risk of kyphotic deformity.

• Applied Chemistry for Engineering
• /
• v.10 no.5
• /
• pp.711-717
• /
• 1999

A multilayer-structure material containing ductile and brittle layer simultaneously was examined and compared with a single layer material using fracture mechanical properties. We found that impact strength of multilayer structure material was considerably higher than single layer's and toughness was enhanced by about two times or higher in similar glass transition temperature($T_g$) region and the same dimension. The superposition principle of impact pulse was used for interpretation of kinetic stress wave as a high-velocity crack proceeds in the plastic. It was understood that the optimum condition of ductile/brittle thickness ratio could be designed in the final toughness enhancement of multilayer.

• Clinics in Shoulder and Elbow
• /
• v.20 no.4
• /
• pp.208-216
• /
• 2017

Background: This study compared the clinical and radiological outcomes of the single calcar screw plate and Polarus nail techniques for the treatment of the proximal humerus fractures. Methods: Seventy-two patients diagnosed with displaced proximal humerus fracture were enrolled for the study. Of these, 50 patients underwent the locking plate surgery with a single calcar screw (plate group), whereas 22 patients underwent the Polarus nail surgery (nail group). The plate group was further divided into plate 1 group (with medial support), and plate 2 group (without medial support). The radiological and functional results of both groups were compared to the nail group. Results: The ${\alpha}$ angle 1 year after surgery was significantly different between plate 1 and plate 2, and plate 2 and nail groups (p=0.041, p=0.043, respectively). The ratio that does not satisfy the reference value of ${\gamma}$ angle was 2.8% in plate 1, 7.1% in plate 2 and 22.7% in nail group (p=0.007); there was a significant difference between plate 1 and nail group, and plate 2 and nail group (p=0.014, p=0.033, respectively). Conclusions: No significant differences were observed in the clinical results between locking plate and Polarus nail. However, in the plate 2 group and nail group, the rate of failure to maintain reduction during the 1-year period after surgery was statistically and significantly higher than the plate 1 group (level of evidence: level IV, case series, treatment study).

• Transactions of Materials Processing
• /
• v.20 no.3
• /
• pp.257-264
• /
• 2011

Multilayer(clad) sheets, composed of two or more materials with different properties, are fabricated using the roll-bonding process. A good formability is an essential property for a multilayered sheet in order to manufacture parts by plastic deformation. In this study, the influences of temperature and strain rate on the plastic properties of stainless steel-aluminum-magnesium multilayered(STS-Al-Mg) sheets were investigated. Tensile tests were performed at various temperatures and strain rates on the multilayered sheet and on each separate layer. Fracture of the multilayered sheet was observed to be temperature-dependent. At the base temperature of $200^{\circ}C$, all materials fractured simultaneously. At lower temperatures, the Mg alloy sheet fractured earlier than the other materials. Conversely, the other materials fractured earlier than the Mg alloy sheet at higher temperatures. The uniform and total elongations of the multilayered sheet were observed to be higher than that of each material at a temperature of $250^{\circ}C$. Larger uniform elongations were obtained for higher strain rates at constant temperature. The same trend was observed for the Mg alloy sheet, which exhibited the lowest elongation among the three materials. The tensile strengths and elongations of the single layer sheets were compared to those of the multilayer material. The strength of the multilayered sheet was successfully calculated by the rule of mixture from the values of each single layer. However, no simple correlation between the elongation of each layer and that of the multilayer was obtained.

• Journal of Ocean Engineering and Technology
• /
• v.6 no.2
• /
• pp.21-34
• /
• 1992

The behavior of fatigue crack growth in the single spot welded joint of zinc galvanized steel sheets was studied experimentally and analytically based on fracture mechanics. Axial tension fatigue tests were carried out with the BSxGAB specimen that the bare plane(GAB) of monogalvanized steel sheet was spot welded to the double thickness bare steel sheet(BS), and with the GAxGAB specimen that the galvanized plane (GA) was spot welded to the equal thickness bare plane (GAB) 1. The relation between maximum stress intensity factor, K sub(max) and the number of cycles to failure, N sub(f) has shown a linear relation on log-log plot in the spot weld of the zinc galvanized steel sheet. 2. The fatigue strength of BSxGAB specimens is about 23% higher than that of GAxGAB specimens at the fatigue strength of $1\times10^6$ cycles. And the fatigue life of BSxGAB specimens at the same load range increases 6~9 times higher than that of GAxGAB specimens. 3. The general tendency at the angle of bending($\theta$) in an applied load has changed rapidly at the initial 20% of its life. After then, it has changed slowly. The change at the angle of bending has increased linearly as the load range increases. 4. It has shown a linear relation between the location ratio of initiation ${\gamma}$ and fatigue life $N_f$ on the semi-log graph paper. Here $\gamma$ means that the crack distance between main crack and sub-crack, 2L is divided by the nugget diameter, 2r. $\gamma=a{\cdot}log N_f+n$ (where a and n are material constant.)