• Tribology and Lubricants
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• v.39 no.5
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• pp.167-172
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• 2023

Titanium alloys are widely recognized among engineering materials owing to their impressive mechanical properties, including high strength-to-weight ratios, fracture toughness, resistance to fatigue, and corrosion resistance. Consequently, applications involving titanium alloys are more susceptible to damage from unforeseen events, such as scratches. Nevertheless, the impact of microscopic damage remains an area that requires further investigation. This study delves into the microscopic wear behavior of α-titanium crystal structures when subjected to linear scratch-induced damage conditions, utilizing molecular dynamics simulations as the primary methodology. The configuration of crystal lattice structures plays a crucial role in influencing material properties such as slip, which pertains to the movement of dislocations within the crystal structure. The molecular dynamics technique surpasses the constraints of observing microscopic phenomena over brief intervals, such as sub-nano- or pico-second intervals. First, we demonstrate the localized transformation of lattice structures at the end of initialization, indentation, and wear processes. In addition, we obtain the exerted force on a rigid sphere during scratching under linear movement. Furthermore, we investigate the effect of the relaxation period between indentation and scratch deformation. Finally, we conduct a comparison study of nanoindentation between crystal and amorphous Ti substrates. Thus, this study reveals the underlying physics of the microscopic transformation of the α-titanium crystal structure under wear-like accidental events.

• Journal of the Korean Society of Radiology
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• v.82 no.1
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• pp.82-98
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• 2021

Sesamoid bones and accessory ossicles are normal anatomic variants with varying morphological appearances and incidences. They are usually small osseous fragments with well-corticated margins located adjacent to the joint space and bone. Patients with sesamoid bones and accessory ossicles are usually asymptomatic and commonly encountered in clinical practice. These sesamoids and accessory bones are occasionally painful because of fractures, dislocations, degenerative changes, avascular necrosis, accessory bone infections, or abnormalities of the adjacent tissue, such as nerve entrapment, tenosynovitis, or soft tissue impingement. This article aimed to illustrate the imaging features of symptomatic sesamoids bones and accessory ossicles at various anatomic locations and describe their clinical features and radiological differential diagnosis.

• Clinics in Shoulder and Elbow
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• v.26 no.4
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• pp.373-379
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• 2023

Background: The purpose of this study was to determine the association between smoking and clinical outcomes of hook plate fixation for acute acromioclavicular (AC) joint injuries. Methods: This study retrospectively investigated 82 patients who underwent hook plate fixation for acute AC joint dislocation between March 2014 to June 2022. The patients were grouped by smoking status, with 49 in group N (nonsmokers) and 33 in group S (smokers). Functional scores and active range of motion were compared among the groups at the 1-year follow-up. Coracoclavicular distance (CCD) was measured, and difference with the uninjured side was compared at initial injury and 6 months after implant removal. Results: No significant differences were observed between the two groups in demographic factors such as age and sex, as well as parameters related to initial injury status, which included time from injury to surgery, the preoperative CCD difference value, and the Rockwood classification. However, the postoperative CCD difference was significantly higher in group S (3.1±2.6 mm) compared to group N (1.7±2.4 mm). Multivariate regression analysis indicated that smoking and the preoperative CCD difference independently contributed to an increase in the postoperative CCD difference. Despite the radiographic differences, the postoperative clinical outcome scores and active range of motion measurements were comparable between the groups. Conclusions: Smoking had a detrimental impact on ligament healing after hook plate fixation for acute AC joint dislocations. This finding emphasizes the importance of smoking cessation to optimize reduction maintenance after AC joint injury. Level of evidence: III.

• Clinics in Shoulder and Elbow
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• v.13 no.1
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• pp.20-26
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• 2010

Purpose: To evaluate clinical features and surgical results for rotator cuff tear secondary to shoulder dislocation in middle-aged and elderly patients. Materials and Methods: We reviewed 19 patients over 50 years of age who had rotator cuff tears combined with shoulder dislocation between October 2004 and October 2008. There were 7 males and 12 females with a mean age 64.7 years (range, 50 to 78 years). The average follow-up duration was 22 months (range, 8 to 56 months). We investigated the number of dislocations, the size of the cuff tear, the presence of Bankart lesions and the time interval from dislocation to surgery. We also investigated the ASES score, UCLA score, SST score, and shoulder range of motion before and after surgery. We analyzed clinical outcomes and contributing factors. Results: ASES scores improved from 30.2 preoperatively to 72.3 postoperatively; UCLA scores improved from 12.9 to 26.5; SST scores improved from 2.4 to 7.3. Range of motion improved significantly: forward flexion, abduction, external rotation and internal rotation were, respectively, $110.8({\pm}39.3)^{\circ}$, $107.7({\pm}40)^{\circ}$, $22.5({\pm}17.6)^{\circ}$ and L5 level preoperatively; postoperatively they were $153.6({\pm}20.6)^{\circ}$, $152.1({\pm}20.8)^{\circ}$, $36.4({\pm}22.7)^{\circ}$ and L1 level. Age, the presence of Bankart lesions and the number of dislocations were not correlated with clinical outcomes. But the size of the cuff tear was correlated with clinical results. Also, the duration from dislocation to surgery was correlated with postoperative UCLA and SST scores (p=0.039, p=0.038). Conclusion: For shoulder dislocation, it is important to achieve early diagnoses of rotator cuff tears in middle-aged and elderly patients. If these injuries are both present, early rotator cuff repair should be performed for better clinical results.

• Journal of Trauma and Injury
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• v.19 no.2
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• pp.164-172
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• 2006

Background: The authors conducted a retrospective study to evaluate the mechanism of injury, the surgical techniques, the clinical features, the combined injuries, the treatment results, and the surgical complications in patients with atlantoaxial fracture/subluxations. Methods: The authors reviewed 71 cervical fracture/dislocations during a four-year period from September 2002 to August 2006. Among them, there were twenty one C1,2 fracture/subluxations. There were thirteen men (mean age : 43.5 years) and eight women (mean age : 50 years). Their follow-up period was at least 6 months, and the mean follow-up period was 9.6 months. Gardner-Wells tongs traction was used in all patients immediately on presentation. Surgical treatment was performed, depending on the pathologic conditions. Results: Of all 21 cases, 14 cases were injured in motor vehicle accidents, 5 were falls, and 2 were miscellaneous. There were four C1 fracture (5.6%), fourteen C2 fracture (66.7%), one C1 and 2 combined fracture (4.8%), and one C1-2 subluxation (4.8%). The C1 fractures in our series were classified as two Jefferson's fractures and two C1 lateral mass fracture. The C2 fractures were classified as one odontoid type I fracture, two odontoid type II fractures, five odontoid type III fractures, one hangman's fracture, and four C2 body tear-drop fractures. Atlantoaxial fractures were associated with six (28.6%) head injuries, four (19.0%) other spinal injuries, two (9.5%) chest injuries, and three (14.3%) spinal cord injuries. Surgical treatment was performed in nine cases, which included anterior odontoid screw fixation in two cases, transarticular screw fixation with iliac bone graft in one case, posterior fixation by using C2 pedicle screw and C3 lateral mass screw in three cases, lateral mass screw fixation C1-2 with iliac bone graft in one case, O(occipito)-C1-3-4 screw fixation in one case, posterior C2-3 wiring with allograft in one case, and halo vest in six cases. Conservative management was used in the rest of the patients in our trials. Bone fusion was complete in all cases. There were no operation-related complication, except one pin site infection in the case of halo vest. Conclusion: In this study, the choice of appropriate treatment according to the fracture types resulted in safe and effective management of unique atlantoaxial fracture/subluxations.

• Korean Journal of Crystallography
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• v.5 no.2
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• pp.51-66
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• 1994

Y3Al5O2 and Nd: Y3Al5012 single crystals were grown by Czochralskl technique. The effectt of pulling rate rotation rate, and doping level of Nd3+ ion on the crystal quality were studied Various types of defects were analysed by photo-elastic effect and chemical etching method Finally, spectroscopic and laser poputies of grown crystal were measured. Optirmum pulling rate for good quality was dependant on the doping level of Nd3+ ion. It was found that the suitable pulling rates for pure Y3Al5O12 for 3.0∼3.5 a/o Nd3+ ion doped Y3Al5012 and for more than 40 a/o Nd3+ ion doped Y3Al5012 were 2∼4mm/hr, 0.6∼0.5mm/hr, and less than 0.4mm/hr respectively. Solid-liquid interface was convex at the rotation rate of 27∼60rpm, and concave at the rotation rate of 80∼100rpm. Growth axis was confired to <111> direction and lattice parameter was measured to 12.017A. Core (211) facets,striations, inclusions of metal particles, dislocations and optical inhonngeneities were detected. Four level laser transition of Nd3+ion in YIAls012 single crystal were identified by the spectroscopic measurements. Laser rod with tam diameter and 63mm length was fabricated from grown Nd3+ Y3Al5012 sin91e crystals. 1.8lJ of lasing threshould and 0.49% of soope efficiency were measured by the Pulsed laser action.

• Journal of the Korean Arthroscopy Society
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• v.5 no.2
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• pp.104-110
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• 2001

Purpose : To analyze the patterns of osteochondral fracture associated with patellar dislocation and to assess the results of arthroscopic treatment. Materials and Methods : Fourteen patients were treated from March, 1989 to April, 1998 for patellar dislocations with osteochondral fracture. The average follow-up was 32 months. All were treated by arthroscopic procedures. The location and size of the fracture fragments were recorded. To assess the functional results, we used Larsen & Lauridson's score system. Results : Osteochondral fractures were found 8 cases in medial side of patella, 1 case in lateral side of patella, 5 cases in lateral margin of lateral femoral condyle. The range of maximal diameter of osteochondral fragment was from 1cm to 4.2cm. Treatments include fragment excision only in 6 cases, excision and medial retinacular repair in 2 cases, excision and medial retinacular repair and lateral retinacular release in 3 cases, and internal fixation only in 3 cases. The functional results were excellent in 5 cases$(36\%)$. good in 6 cases$(43\%)$, fair in 1 case$(7\%)$ and poor in 2 cases$(14\%)$. Conclusion : In osteochondral fractures associated with patellar dislocation, arthroscopic treatment is useful to diagnose precisely, to determine proper treatment modality, and to minimize the complications.

• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.286-286
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• 2016

Hexagonal boron nitride (hBN) is a dielectric insulator with a two-dimensional (2D) layered structure. It is an appealing substrate dielectric for many applications due to its favorable properties, such as a wide band gap energy, chemical inertness and high thermal conductivity[1]. Furthermore, its remarkable mechanical strength renders few-layered hBN a flexible and transparent substrate, ideal for next-generation electronics and optoelectronics in applications. However, the difficulty of preparing high quality large-area hBN films has hindered their widespread use. Generally, large-area hBN layers prepared by chemical vapor deposition (CVD) usually exhibit polycrystalline structures with a typical average grain size of several microns. It has been reported that grain boundaries or dislocations in hBN can degrade its electronic or mechanical properties. Accordingly, large-area single crystalline hBN layers are desired to fully realize the potential advantages of hBN in device applications. In this presentation, we report the growth and transfer of centimeter-sized, nearly single crystal hexagonal boron nitride (hBN) few-layer films using Ni(111) single crystal substrates. The hBN films were grown on Ni(111) substrates using atmospheric pressure chemical vapor deposition (APCVD). The grown films were transferred to arbitrary substrates via an electrochemical delamination technique, and remaining Ni(111) substrates were repeatedly re-used. The crystallinity of the grown films from the atomic to centimeter scale was confirmed based on transmission electron microscopy (TEM) and reflection high energy electron diffraction (RHEED). Careful study of the growth parameters was also carried out. Moreover, various characterizations confirmed that the grown films exhibited typical characteristics of hexagonal boron nitride layers over the entire area. Our results suggest that hBN can be widely used in various applications where large-area, high quality, and single crystalline 2D insulating layers are required.

• Clinics in Shoulder and Elbow
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• v.1 no.1
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• pp.26-34
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• 1998

The management of acute acromioclavicular dislocations has usually followed the accepted principles of obtaining an anatomical reduction of the joint and maintaining it until soft tissue healing has occurred. So, the preferred treatment for acute acromioclavicular dislocation is controversial. We analysed operatively treated twenty-eight cases for acute acromioclavicular dislocation between February 1994 and January 1997 and reviewed postoperatively to evaluate the results of three different methods. We collected retrospectively the data via clinical history, associated injury, type of injury, radiographic review, Taft score, and final results. Follow up time averaged 14 months. (range, 12 to 21 ) In according to Rockwood's classification, ]7 cases were type Ⅲ, 1 case was type IV, and 10 cases were type V. Ten cases were treated with the modified Phemister method, ten cases with the modified Bosworth method and eight cases with the modified Weaver-Dunn method. ]n patients treated by modified Phemister method, the Taft score was 9.4 points and 8 cases achieved good or excellent results. In patients treated by modified Bosworth method, the Taft score was 9.8 points and 8 cases achieved good or excellent results. In patients treated by modified Weaver-Dunn method, the Taft score was 10.3 points and 7 cases achieved good or excellent results. The overall Taft score was 9.9 points and 23 cases achieved good or excellent results. There were four complications, such as calcification or metallic loosening or breakage of K-wire, but did not influence late results. In conclusions, there was no significant difference of results regarding the different three methods. However, our results indicated that the coracoclavicular ligament reconstruction by transfer of coracoacromial ligament produced better results.