Publications by authors named "Woo Young Choi"

87 Publications

Si photonic-electronic monolithically integrated optical receiver with a built-in temperature-controlled wavelength filter.

Opt Express 2021 Mar;29(6):9565-9573

We present a Si photonic-electronic integrated ring-resonator based optical receiver that contains a temperature-controlled ring-resonator filter (RRF), a Ge photodetector, and receiver circuits in a single chip. The temperature controller automatically determines the RRF temperature at which the maximum transmission of the desired WDM signal is achieved and maintains this condition against any temperature or input wavelength fluctuation. This Si photonic-electronic integrated circuit is realized with 0.25-µm photonic BiCMOS technology, and its operation is successfully confirmed with measurement.
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http://dx.doi.org/10.1364/OE.418222DOI Listing
March 2021

Data-Driven Object Vehicle Estimation by Radar Accuracy Modeling with Weighted Interpolation.

Sensors (Basel) 2021 Mar 26;21(7). Epub 2021 Mar 26.

Division of Electrical and Biomedical Engineering, Hanyang University, Seoul 04763, Korea.

For accurate object vehicle estimation using radar, there are two fundamental problems: measurement uncertainties in calculating an object's position with a virtual polygon box and latency due to commercial radar tracking algorithms. We present a data-driven object vehicle estimation scheme to solve measurement uncertainty and latency problems in radar systems. A radar accuracy model and latency coordination are proposed to reduce the tracking error. We first design data-driven radar accuracy models to improve the accuracy of estimation determined by the object vehicle's position. The proposed model solves the measurement uncertainty problem within a feasible set for error covariance. The latency coordination is developed by analyzing the position error according to the relative velocity. The position error by latency is stored in a feasible set for relative velocity, and the solution is calculated from the given relative velocity. Removing the measurement uncertainty and latency of the radar system allows for a weighted interpolation to be applied to estimate the position of the object vehicle. Our method is tested by a scenario-based estimation experiment to validate the usefulness of the proposed data-driven object vehicle estimation scheme. We confirm that the proposed estimation method produces improved performance over the conventional radar estimation and previous methods.
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http://dx.doi.org/10.3390/s21072317DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8037990PMC
March 2021

Leg length discrepancy, overgrowth, and associated risk factors after a pediatric tibial shaft fracture.

J Orthop Traumatol 2021 Mar 15;22(1):12. Epub 2021 Mar 15.

Department of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul National University Bundang Hospital, 82 Gumi-ro 173 Beon-gil, Bundang-Gu, Sungnam, 13620, Gyeonggi, Korea.

Background: This study was performed to investigate leg length discrepancy (LLD), overgrowth, and associated risk factors after pediatric tibial shaft fractures.

Materials And Methods: This study included 103 patients younger than 14 years of age (mean age 7.1 years; 75 boys, 28 girls) with unilateral tibial shaft fracture and a minimum follow-up of 24 months. LLD was calculated as the difference between the lengths of the injured and uninjured limbs. Overgrowth was calculated by adding the fracture site shortening from the LLD. Risk factors were assessed in patients with LLD < 1 cm and ≥ 1 cm and overgrowth < 1 cm and ≥ 1 cm.

Results: Casting and titanium elastic nailing (TEN) were performed on 64 and 39 patients, respectively. The mean LLD and overgrowth were 5.6 and 6.4 mm, respectively. There were significant differences in sex (p = 0.018), age (p = 0.041), fibular involvement (p = 0.005), injury mechanism (p = 0.006), and treatment methods (p < 0.001) between patients with LLDs < 1 cm and ≥ 1 cm. There were significant differences in sex (p = 0.029), fibular involvement (p = 0.002), injury mechanism (p = 0.008), and treatment methods (p < 0.001) between patients with overgrowth < 1 cm and ≥ 1 cm. Sex and treatment methods were risk factors associated with LLD ≥ 1 cm and overgrowth ≥ 1 cm following pediatric tibial shaft fracture. The boys had a 7.4-fold higher risk of LLD ≥ 1 cm and 5.4-fold higher risk of overgrowth ≥ 1 cm than the girls. Patients who underwent TEN had a 4.3-fold higher risk of LLD ≥ 1 cm and 4.8-fold higher risk of overgrowth ≥ 1 cm than those treated by casting.

Conclusions: Patients undergoing TEN showed greater LLD and overgrowth than those undergoing casting, with boys showing greater LLD and overgrowth than girls. Surgeons should consider the possibility of LLD and overgrowth after pediatric tibial shaft fractures, especially when performing TEN for boys.

Level Of Evidence: Level III.
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http://dx.doi.org/10.1186/s10195-021-00575-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7960829PMC
March 2021

Numerical analysis on a viewing angle enhancement of a digital hologram by attaching a pixelated random phase mask.

Appl Opt 2021 Feb;60(4):A54-A61

In a digital hologram, the maximum viewing angle of a computer-generated hologram (CGH) is limited by pixel pitch due to the diffraction grating equation. Since reducing pixel size of display panel is challenging and costly, we propose a method to expand the viewing angle of a digital hologram by attaching an aligned pixelated random phase mask (PRPM) onto the CGH pattern based on analysis of simulation results. By introducing a phase-averaging process to the widely used iterative Fourier transform algorithm, an optimized CGH pattern can be obtained in conjunction with a PRPM. Based on scalar diffraction theory, viewing angle enhancement characteristics were verified by comparing the perspective views of a two-plane hologram using a virtual eye model. In addition, we performed full electromagnetic simulations that included effects due to potential fabrication errors such as misalignment, thickness variation, and internal reflections and diffractions between the CGH and random mask patterns. From the simulation results, by attaching a 1.85 µm-sized pixel pitch PRPM to a 3.7 µm CGH, the viewing angle can be easily expanded almost identical to that of a CGH with 1.85 µm-pixel pitch.
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http://dx.doi.org/10.1364/AO.403534DOI Listing
February 2021

Growth arrest and its risk factors after physeal fracture of the distal tibia in children and adolescents.

Injury 2021 Apr 14;52(4):844-848. Epub 2021 Jan 14.

Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Gyeonggi, South Korea. Electronic address:

Background: . This study performed to investigate the incidence of growth arrest such as leg length discrepancy (LLD) and ankle joint angular deformity and its risk factors after physeal fracture of the distal tibia in children and adolescents.

Materials And Methods: . Consecutive 78 patients (mean age 11.4 ± 2.0 years; mean follow-up period 2.0 ± 1.2 years) treated for the distal tibia physeal fracture were included. All patients underwent preoperative ankle radiographs, three-dimensional computed tomography (CT) scans, and postoperative follow-up teleradiogram. Patients were divided into two groups according to the LLD and the difference of lateral distal tibial angle (LDTA) with the contralateral limb as follows: Group 1 (growth arrest), patients with LLD ≥ 1cm or difference of LDTA ≥ 5°; Group 2 (normal growth), patients with LLD < 1cm and difference of LDTA < 5°.

Results: . The overall incidence of growth arrest was 12.8% (10 of 78). The mean displacement measured using CT scan was 4.4 ± 3.2 mm (range, 0.8-14.9). Of the total 78 fractures, 65 were treated surgically and 13 fractures were treated conservatively. The initial fracture displacement was significantly different between the two groups (p<0.001). However, there were no statistically significant differences between the two groups with respect to other factors. Initial displacement was the only significant risk factor for growth arrest (p<0.003). The cutoff values of initial displacement between the two groups were 5.2mm.

Conclusions: . This study showed that degree of initial displacement was the only significant risk factor for growth arrest after physeal fracture of the distal tibia in children and adolescents. Therefore, physicians should consider the possibility of growth arrest for patients with severely displaced physeal fractures of the distal tibia.
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http://dx.doi.org/10.1016/j.injury.2021.01.014DOI Listing
April 2021

A case of SFTS coinfected with E. coli bacteremia.

BMC Infect Dis 2021 Jan 7;21(1):25. Epub 2021 Jan 7.

Graduate School of Chosun University, Gwangju, Republic of Korea.

Background: Severe fever thrombocytopenia syndrome virus (SFTSV) is the causative agent of severe fever thrombocytopenia syndrome (SFTS). SFTS is an emerging infectious disease, characterized by high fever, gastrointestinal symptoms, leukopenia, thrombocytopenia, and a high mortality rate. Until now, little importance has been given to the association of SFTS with leukocytosis and bacterial co-infection.

Case Presentation: A 51-year old man visited our hospital with fever and low blood pressure. He was a farmer by occupation and often worked outdoors. He had a Foley catheter inserted due to severe BPH. Laboratory tests revealed thrombocytopenia, elevated liver function, and elevated CRP levels. He had marked leukocytosis, proteinuria, hematuria, and conjunctival hemorrhage. Initially, we thought that the patient was suffering from hemorrhagic fever with renal syndrome (HFRS). However, we confirmed SFTS through PCR and increasing antibody titer. However, his blood culture also indicated E. coli infection.

Conclusion: SFTS displays characteristics of fever, thrombocytopenia, elevated liver function, and leukocytopenia. We described a case of SFTS with leukocytosis due to coinfection with E. coli. Since patients with SFTS usually have leukocytopenia, SFTS patients with leukocytosis are necessarily evaluated for other causes of leukocytosis. Here, we report the first case of an SFTS with concurrent E. coli bacteremia.
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http://dx.doi.org/10.1186/s12879-020-05705-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7792358PMC
January 2021

Bioinspired dual-morphing stretchable origami.

Sci Robot 2019 Nov;4(36)

Soft Robotics Research Center, Seoul National University, Seoul, Republic of Korea.

Nature demonstrates adaptive and extreme shape morphing via unique patterns of movement. Many of them have been explained by monolithic shape-changing mechanisms, such as chemical swelling, skin stretching, origami/kirigami morphing, or geometric eversion, that were successfully mimicked in artificial analogs. However, there still remains an unexplored regime of natural morphing that cannot be reproduced in artificial systems by a "single-mode" morphing mechanism. One example is the "dual-mode" morphing of (commonly known as the pelican eel), which first unfolds and then inflates its mouth to maximize the probability of engulfing the prey. Here, we introduce pelican eel-inspired dual-morphing architectures that embody quasi-sequential behaviors of origami unfolding and skin stretching in response to fluid pressure. In the proposed system, fluid paths were enclosed and guided by a set of entirely stretchable origami units that imitate the morphing principle of the pelican eel's stretchable and foldable frames. This geometric and elastomeric design of fluid networks, in which fluid pressure acts in the direction that the whole body deploys first, resulted in a quasi-sequential dual-morphing response. To verify the effectiveness of our design rule, we built an artificial creature mimicking a pelican eel and reproduced biomimetic dual-morphing behavior. By compositing the basic dual-morphing unit cells into conventional origami frames, we demonstrated architectures of soft machines that exhibit deployment-combined adaptive gripping, crawling, and large range of underwater motion. This design principle may provide guidance for designing bioinspired, adaptive, and extreme shape-morphing systems.
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http://dx.doi.org/10.1126/scirobotics.aay3493DOI Listing
November 2019

Progesterone increases blood glucose via hepatic progesterone receptor membrane component 1 under limited or impaired action of insulin.

Sci Rep 2020 10 1;10(1):16316. Epub 2020 Oct 1.

College of Veterinary Medicine, Chungnam National University, 99 Daehak-ro, Suite 401Veterinary medicine Bldg., Yuseong, Daejeon, 34134, Republic of Korea.

Hepatic gluconeogenesis is the main pathway for blood glucose maintenance activated during fasting. Retardation of insulin action, such as in diabetes mellitus, activates gluconeogenesis during the fed state. While the role of progesterone (P4) in diabetes is controversial, the P4 receptor, progesterone receptor membrane component 1 (PGRMC1), is known to stimulate pancreatic insulin secretion. We investigated the role of P4, via hepatic PGRMC1, during gluconeogenesis. The PGRMC1 binding chemical, AG-205, induced PGRMC1 monomer (25 kDa) abundance, and increased PEPCK expression and glucose production in parallel with cyclic AMP (cAMP) induction in Hep3B cells. PGRMC1-mediated cyclic AMP was inhibited by an adenylate cyclase inhibitor (MDL-12,330A). PEPCK suppression in Pgrmc1 KO hepatocyte was not observed after treatment of MDL-12,330A. PGRMC1 knockdown or overexpression systems in Hep3B cells confirmed that PGRMC1 mediates PEPCK expression via phosphorylation of cAMP-response element binding protein (CREB). CREB phosphorylation and PEPCK expression in primary hepatocytes were greater than that in PGRMC1 knock-out hepatocytes. Progesterone increased PGRMC1 expression, which induced cAMP and PEPCK induction and glucose production. In vivo, P4 suppressed gluconeogenesis following plasma insulin induction under normal conditions in a mouse model. However, P4 increased blood glucose via gluconeogenesis in parallel with increases in PGRMC1 and PEPCK expression in mice in both insulin-deficient and insulin-resistant conditions. We conclude that P4 increases hepatic glucose production via PGRMC1, which may exacerbate hyperglycaemia in diabetes where insulin action is limited.
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http://dx.doi.org/10.1038/s41598-020-73330-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7529793PMC
October 2020

Negative Capacitance Vacuum Channel Transistors for Low Operating Voltage.

Authors:
Woo Young Choi

Micromachines (Basel) 2020 May 27;11(6). Epub 2020 May 27.

Department of Electronic Engineering, Sogang University, Seoul 04107, Korea.

This study proposes negative capacitance vacuum channel transistors. The proposed negative capacitance vacuum channel transistors in which a ferroelectric capacitor is connected in series to the gate of the vacuum channel transistors have the following two advantages: first, adding a ferroelectric capacitor in series with a gate capacitor makes the turn-on voltage lower and on-off transition steeper without causing hysteresis effects. Second, the capacitance matching between a ferroelectric capacitor and a vacuum channel transistor becomes simplified because the capacitance of a vacuum channel transistor as seen from a ferroelectric capacitor is constant.
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http://dx.doi.org/10.3390/mi11060543DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7345952PMC
May 2020

The efficacy of dermofat grafts from the groin for correction of acquired facial deformities.

Arch Craniofac Surg 2020 Apr 20;21(2):92-98. Epub 2020 Apr 20.

Department of Plastic and Reconstructive Surgery, Chosun University College of Medicine, Gwangju, Korea.

Background: Posttraumatic acquired facial deformities require surgical treatment, with options including scar revision, fat grafts, implant insertion, and flap coverage. However, each technique has specific advantages and disadvantages.
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Methods: From 2016 to 2018, 13 patients (eight with scar contracture and five with a depressed scar) were treated using dermofat grafts from the groin. The harvested dermofat was then inserted into the undermined dead space after the contracture was released, and a bolster suture was done for fixation considering the patient's contour and asymmetry. A modified version of the Vancouver Scar Scale and satisfaction survey were used to compare deformity improvements before and after surgery.
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Results: In most cases, effective volume correction and an aesthetically satisfactory contour were maintained well after dermofat grafting, without any major complications. In some cases, however, lipolysis proceeded rapidly when inflammation and infection were not completely eliminated. A significant difference was found in the modified Vancouver Scar Scale before and after surgery, with a p-value of 0.001. The average score on the satisfaction survey was 17.07 out of 20 points.
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Conclusion: A dermofat graft with the groin as the donor site can be considered as an effective surgical option that is the simplest and most cost-effective method for the treatment of acquired facial deformities with scar contracture.
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http://dx.doi.org/10.7181/acfs.2020.00038DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7206454PMC
April 2020

Long-term postoperative satisfaction and complications in nasal bone fracture patients according to fracture type, site, and severity.

Arch Craniofac Surg 2020 Feb 20;21(1):7-14. Epub 2020 Feb 20.

Department of Plastic and Reconstructive Surgery, Chosun University College of Medicine, Gwangju, Korea.

Background: It is difficult to completely fix nasal bone fractures with closed reduction, as it is often accompanied by septal cartilage damage, and this often results in postoperative secondary deformities. Thus, patients are often reluctant to undergo closed reduction surgery. The present study aimed to evaluate aesthetic and functional satisfaction, as well as satisfaction with and complications of closed reduction, according to nasal bone fracture type.

Methods: The subjects were patients who underwent closed reduction under general anesthesia from January 2017 to December 2018. Based on the modified Murray classification, patients were classified into five groups according to the fracture site, septal fracture, and deviation. A total of 211 patients were sent a web-based survey on postoperative satisfaction and complications, as well as intention for revision and cosmetic surgery. Sixty-one patients (28.9%) responded.

Results: There were no significant differences in aesthetic and functional satisfaction or satisfaction with closed reduction according to the fracture type, site, or severity. Postoperative functional complications developed in 14 of 61 patients (22.95%). With 10 out of 24 (41.67%) patients (p = 0.044), the bilateral fracture with septal fracture or prominent septal deviation type had a higher incidence of complications than the other types.

Conclusion: The incidence of complications is higher for bilateral fracture with septal fracture or prominent septal deviation compared to the other nasal bone fracture types. Therefore, long-term follow-up after closed reduction surgery for this fracture type can aid in establishing additional postoperative treatment plans and improving patient satisfaction.
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http://dx.doi.org/10.7181/acfs.2019.00626DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7054191PMC
February 2020

Prediction of Lower Eyelid Malpositioning After Surgical Correction of Orbital Fracture Using the Subciliary Approach Through the Canthal Area and Orbital Vector Analysis.

J Craniofac Surg 2020 May/Jun;31(3):e297-e299

Department of Plastic and Reconstructive Surgery, Chosun University Hospital, Gwangju, Republic of Korea.

A subciliary incision has been widely used not only for blepharoplasty but also for facial fracture surgery. However, lower eyelid malpositioning is one of the most common complications after fracture surgery. A limited number of studies have been conducted on the relationships among evaluation of the canthal area, orbital vector analysis, and lower eyelid malpositioning following the subciliary approach for surgical repair of fractures. The primary goal of this study was to identify and analyze the possible risk factors, including incidence of lower eyelid malpositioning and orbital vector after surgical correction of the orbital fracture. A total of 241 cases of orbital fracture surgery was retrospectively reviewed. Data related to the patient and surgery were collected. Orbital vector and angle that reflects the vector, distance between soft tissue and bone in the lateral canthal area were measured for orbital vector analysis. The relationship between the prevalence of the malpositioning of the lower eyelid and each factor was statistically analyzed. The distance between the soft tissue and bone at the lateral canthal area was statistically significant (P = 0.031). The distance between the soft tissue and bone at lateral canthal area illustrates the lateral side or periorbital anatomical morphology. It could be inferred that patients with a negative orbital vector were relatively more vulnerable to scar formation or lower eyelid malpositioning caused by iatrogenic factors. Therefore, it could be analyzed as a risk factor to predict the malpositioning of the lower eyelid postoperatively.
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http://dx.doi.org/10.1097/SCS.0000000000006219DOI Listing
August 2020

Notched Anchor Design for Low Voltage Operation of Nanoelectromechanical (NEM) Memory Switches.

J Nanosci Nanotechnol 2020 07;20(7):4198-4202

Department of Electronic Engineering, Sogang University, Seoul 04107, Korea.

Because nanoelectromechanical (NEM) memory switches generally have higher pull-in voltage () and lower reliability than CMOS devices, reducing and maximum stress () of NEM memory switches have been critical issues for the implementation of monolithic-3D (M3D) CMOS-NEM hybrid reconfigurable logic (RL) circuits. In this paper, a novel notched anchor design is proposed to reduce the and of NEM memory switches. Moreover, the novel design has an advantage in terms of chip density over the conventional design under the same condition. In the case of our proposed NEM memory switches, their anchors are placed in the vias of metal interconnection layers. Thus, even if notched patterns are formed on the anchors, it will be helpful to effectively increase beam length, which eventually lowers and . In this manuscript, the proposed notched anchor design has been confirmed by finite-element-method (FEM) simulation. According to the simulation results, the proposed notched anchor design lowers by ~23% and by ~24%.
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http://dx.doi.org/10.1166/jnn.2020.17789DOI Listing
July 2020

Monolithic-3D (M3D) Complementary Metal-Oxide-Semiconductor-Nanoelectromechanical (CMOS-NEM) Hybrid Reconfigurable Logic (RL) Circuits.

J Nanosci Nanotechnol 2020 07;20(7):4176-4181

Department of Electronic Engineering, Sogang University, Seoul 04107, Republic of Korea.

Monolithic-three-dimensional (M3D) CMOS-nanoelectromechanical (CMOS-NEM) hybrid reconfigurable logic (RL) circuits are compared and analyzed with CMOS-only RL ones in the 130-nm CMOS technology node. M3D CMOS-NEM hybrid RL circuits are superior to CMOS-only ones in terms of power consumption and signal transfer speed thanks to the NEM memory switches. As well as in the routing part, it has many advantages in the logic part following the switch.
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http://dx.doi.org/10.1166/jnn.2020.17790DOI Listing
July 2020

Isolated peritoneal lymphomatosis defined as post-transplant lymphoproliferative disorder after a liver transplant: A case report.

World J Clin Cases 2019 Dec;7(24):4299-4306

Department of Internal Medicine, Hemato-oncology, Chosun University Hospital, Gwangju 501-717, South Korea.

Background: Post-transplant lymphoproliferative disorder (PTLD) is a fatal complication of solid organ transplantation or allogenic hematopoietic stem cell transplantation that is associated with immunosuppressive therapy. Potential manifestations are diverse, ranging from reactive lymphoid hyperplasia to high-grade lymphoma. PTLD is usually of B-cell origin and associated with Epstein-Barr virus (EBV) infection. Herein, we describe a case of PTLD involving the peritoneal omentum. There has been only case of PTLD as a diffuse large B-cell lymphoma (DLBCL) in the peritoneum.

Case Summary: The patient was a 62-year-old man who had been receiving immunosuppressive therapy with tacrolimus since undergoing a liver transplant 15 years prior. He reported that he had experienced abdominal discomfort and anorexia 1 month prior to the current admission. Abdominal pelvic computed tomography (CT) revealed peritoneal and omental mass-like lesions without bowel obstruction. Ultrasonography-guided biopsy was performed, and he was histologically diagnosed with EBV-negative DLBCL. Positron emission tomography (PET)-CT depicted peritoneum and omentum involvement only, without any lymphadenopathy or organ masses, including in the gastrointestinal tract. Six cycles of chemotherapy with a "R-CHOP" regimen (rituximab-cyclophosphamide, doxorubicin, vincristine, prednisolone) were administered, and PET-CT performed thereafter indicated complete remission.

Conclusion: This is the first report of isolated peritoneal lymphomatosis defined as PTLD in a liver transplant recipient.
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http://dx.doi.org/10.12998/wjcc.v7.i24.4299DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6940333PMC
December 2019

Optimal Screw Fixation of Syndesmosis Using a Targeting Drill Guide: A Technical Note.

J Foot Ankle Surg 2020 Jan - Feb;59(1):206-209

Surgeon, Department of Orthopedic Surgery, Myongji Hospital, Hanyang University College of Medicine, Gyeonggi-do, Republic of Korea.

Optimal screw fixation of the syndesmosis is difficult. We introduce a novel technique using a targeting drill guide for centroidal screw fixation of a syndesmosis to ensure a reproducible and optimal screw trajectory for syndesmosis fixation. By using a drill guide for anterior cruciate ligament surgery and intraoperative fluoroscopy, syndesmosis fixation enables reproducible fixation along an individual centroidal axis.
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http://dx.doi.org/10.1053/j.jfas.2019.05.005DOI Listing
June 2020

Vestibular Disorders: Pearls and Pitfalls.

Semin Neurol 2019 12 17;39(6):761-774. Epub 2019 Dec 17.

Departments of Neurology, Ophthalmology, Neurosurgery, Otolaryngology - Head and Neck Surgery, Emergency Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland.

Dizziness and vertigo are symptoms that commonly lead patients to seek neurologic or emergency care. Because symptoms are often vague and imprecise, a systematic approach is essential. By categorizing vestibular disorders based on the timing, triggers, and duration of symptoms, as well as emphasizing focused ocular motor and vestibular examinations, the majority of vestibular diagnoses can be made at the bedside. This paper will discuss the pearls and pitfalls in the history and examination of the most common acute, episodic, and chronic vestibular disorders.
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http://dx.doi.org/10.1055/s-0039-1698752DOI Listing
December 2019

Ocular Motor and Vestibular Disorders in Brainstem Disease.

J Clin Neurophysiol 2019 Nov;36(6):396-404

Neurology, Ophthalmology, Neurosurgery, Otolaryngology-Head and Neck Surgery, Emergency Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, U.S.A.

The brainstem contains ocular motor and vestibular structures that, when damaged, produce specific eye movement disorders. In this review, we will discuss three brainstem syndromes with characteristic ocular motor and vestibular findings that can be highly localizing. First, we will discuss the lateral medullary (Wallenberg) syndrome, focusing on ocular lateropulsion, saccadic dysmetria, and the ocular tilt reaction. Second, we will review the medial longitudinal fasciculus syndrome including the ocular tilt reaction, nystagmus, and the vestibular-ocular reflex. Lastly, we will discuss hypertrophic olivary degeneration and oculopalatal tremor, which may develop weeks to months after a brainstem or cerebellar lesion. In these syndromes, the clinical ocular motor and vestibular examination is instrumental in localizing the lesion.
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http://dx.doi.org/10.1097/WNP.0000000000000593DOI Listing
November 2019

Clinical usefulness of fixation of absorbable implants with cyanoacrylate in comminuted fractures of the maxilla.

Arch Craniofac Surg 2019 Aug 20;20(4):233-238. Epub 2019 Aug 20.

Department of Plastic and Reconstructive Surgery, Chosun University College of Medicine, Gwangju, Korea.

Background: The open reduction of craniofacial bone fractures requires internal fixation using metal plates and screws, which have been considered the gold standard. However, metal implants pose a risk of palpation, protrusion, and foreign body reaction, and they may require an additional operation for removal. Recently, good results have been reported for absorbable implants which complement the disadvantages of metal implants. This study presents the results of using absorbable mesh, plates, and screws with cyanoacrylate for more accurate and firmer fixation of comminuted fractures of the maxilla.

Methods: In total, 235 patients underwent operations for comminuted fractures of the maxilla. From January 2012 to December 2014, absorbable mesh and screws were used in 114 patients, while from January 2015 to December 2017, absorbable mesh, plates, and screws with cyanoacrylate were used in 121 patients. Open reduction of the bone fragments was performed, after which absorbable implants were accurately molded and fixed by screws.

Results: All patients underwent postoperative computed tomography scans, which showed highly accurate reduction and firm fixation in the patients who underwent procedures using absorbable implants, screws, and cyanoacrylate. There were no postoperative complications or cases of abnormal facial contour.

Conclusion: When absorbable implants and screws are used for maxillary fractures, no additional surgery to remove the metal plate is required. In addition, the use of cyanoacrylate enables accurate and firm fixation of the tiny bone fragments that cannot be fixed with screws.
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http://dx.doi.org/10.7181/acfs.2019.00325DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6715555PMC
August 2019

Active Region Formation of Nanoelectromechanical (NEM) Devices for Complementary-Metal-Oxide-Semiconductor-NEM Co-Integration.

J Nanosci Nanotechnol 2019 10;19(10):6123-6127

Department of Electronic Engineering, Sogang University, Seoul, 04107, Republic of Korea.

Considering the isotropic release process for nanoelectromechanical (NEM) devices, defining the specific sacrificial layer of the inter-metal-dielectric (IMD), i.e., , is one of the most important issue for complementary-metal-oxide-semiconductor-NEM (CMOS-NEM) co-integrated circuits. In this paper, novel fabrication method to define the active region of NEM devices is proposed by forming the trenched mesa-shape pattern in the IMD and depositing aluminum oxide (Al₂O₃) protecting layer. By applying the proposed process, the void space for mechanical operation of NEM devices can be formed user-controllably without the damage and collapse of CMOS part located below the NEM part. The feasibility of the proposed process is verified by fabricating and measuring the proof-of-concept prototype consists of the aluminum (Al) interconnects, silicon dioxide (SiO₂) IMD and NEM memory switches.
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http://dx.doi.org/10.1166/jnn.2019.16988DOI Listing
October 2019

A Technology-Computer-Aided-Design-Based Reliability Prediction Model for DRAM Storage Capacitors.

Micromachines (Basel) 2019 Apr 17;10(4). Epub 2019 Apr 17.

Department of DRAM Sensing & Advanced Analysis, SK Hynix, Icheon 17336, Korea.

A full three-dimensional technology-computer-aided-design-based reliability prediction model was proposed for dynamic random-access memory (DRAM) storage capacitors. The model can be used to predict the time-dependent dielectric breakdown as well as leakage current of a state-of-the-art DRAM storage capacitor with a complex three-dimensional structure.
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http://dx.doi.org/10.3390/mi10040256DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6523397PMC
April 2019

Encapsulation of NEM Memory Switches for Monolithic-Three-Dimensional (M3D) CMOS⁻NEM Hybrid Circuits.

Micromachines (Basel) 2018 Jun 23;9(7). Epub 2018 Jun 23.

Department of Electronics Engineering, Sogang University, Seoul 04107, Korea.

Considering the isotropic release process of nanoelectromechanical systems (NEMSs), defining the active region of NEM memory switches is one of the most challenging process technologies for the implementation of monolithic-three-dimensional (M3D) CMOS⁻NEM hybrid circuits. In this paper, we propose a novel encapsulation method of NEM memory switches. It uses alumina (Al₂O₃) passivation layers which are fully compatible with the CMOS baseline process. The Al₂O₃ bottom passivation layer can protect intermetal dielectric (IMD) and metal interconnection layers from the vapor hydrogen fluoride (HF) etching process. Thus, the controllable formation of the cavity for the mechanical movement of NEM devices can be achieved without causing any damage to CMOS baseline circuits as well as metal interconnection lines. As a result, NEM memory switches can be located in any place and metal layer of an M3D CMOS⁻NEM hybrid chip, which makes circuit design easier and more volume efficient. The feasibility of our proposed method is verified based on experimental results.
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http://dx.doi.org/10.3390/mi9070317DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6082272PMC
June 2018

Compact Potential Model for SiGe/Si Heterojunction Double-Gate Tunnel Field-Effect Transistors (TFETs).

J Nanosci Nanotechnol 2018 09;18(9):5953-5958

Department of Electronic Engineering, Sogang University, Seoul 04107, Korea.

In this manuscript, the compact potential model for double-gate (DG) Si1-xGex/Si heterojunction tunnel field-effect transistors (TFETs) is proposed by adopting several strategies to the previous model. Compared with the control model, the enhanced model can describe the effects of additional parameters such as electron permittivity and Si1-xGex affinity, doping dependent bandgap narrowing, temperature, built-in potential change due to degenerately doping condition and energy band off-sets. The model accuracy is examined by benchmarking against to the technology computeraided design (TCAD) device simulations in terms of electrostatic potential profiles, band diagrams and minimum tunneling barrier width (Wt, min). As a result, the enhanced model accurately describes Wt, min in various gate voltages with different Ge mole fractions and gate oxide thicknesses. The DG heterojunction TFETs are regarded as one of the most promising successors to metal-oxide-semiconductor FETs (MOSFETs) as ultra-low-power logic devices, due to their high compatibility with complementary MOS (CMOS)-based integrated circuits (ICs) in terms of structures, materials and fabrication processes. The proposed enhanced model is expected to contribute for examining the TFETs circuit operation as well as understanding device physics, in depth, to extend Moore's Law.
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http://dx.doi.org/10.1166/jnn.2018.15578DOI Listing
September 2018

The efficacy of mobile application use on recall of surgical risks in nasal bone fracture reduction surgery.

Arch Craniofac Surg 2018 Mar 20;19(1):41-47. Epub 2018 Mar 20.

Department of Plastic and Reconstructive Surgery, Chosun University College of Medicine, Gwangju, Korea.

Background: The number of surgical risks recalled by a patient after surgery can be used as a parameter for assessing how well the patient has understood the informed consent process. No study has investigated the usefulness of a self-developed mobile application in the traditional informed consent process in patients with a nasal bone fracture. This study aimed to investigate whether delivery of information, such as surgical risks, through a mobile application is more effective than delivery of information through only verbal means and a paper.

Methods: This prospective, randomized study included 60 patients with a nasal bone fracture. The experimental group (n=30) received preoperative explanation with the traditional informed consent process in addition to a mobile application, while the control group (n=30) received preoperative explanation with only the traditional informed consent process. Four weeks after surgery, the number of recalled surgical risks was compared for analysis. The following six surgical risks were explained: pain, bleeding, nasal deformity, numbness, nasal obstruction, and nasal cartilage necrosis.

Results: The mean number of recalled surgical risks among all patients was 1.58±0.56. The most frequently recalled surgical risk was nasal deformity in both groups. The mean number of recalled surgical risks was 1.72±0.52 in the experimental group and 1.49±0.57 in the control group. There was a significant association between mobile application use and the mean number of recalled surgical risks (=0.047). Age, sex, and the level of education were not significantly associated with the mean number of recalled surgical risks.

Conclusion: This study found that a mobile application could contribute to the efficient delivery of information during the informed consent process. With further improvement, it could be used in other plastic surgeries and other surgeries, and such an application can potentially be used for explaining risks as well as delivering other types of information.
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http://dx.doi.org/10.7181/acfs.2018.19.1.41DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5894552PMC
March 2018

Granulomatous hepatitis in a healthy adult after bacillus Calmette-Guérin injection into a plantar wart.

JAAD Case Rep 2017 11 8;3(6):566-569. Epub 2017 Nov 8.

Department of Internal Medicine, College of Medicine, Chosun University, Gwangju, Republic of Korea.

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http://dx.doi.org/10.1016/j.jdcr.2017.07.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5683750PMC
November 2017

Poly-4-vinylphenol (PVP) and Poly(melamine-co-formaldehyde) (PMF)-Based Atomic Switching Device and Its Application to Logic Gate Circuits with Low Operating Voltage.

ACS Appl Mater Interfaces 2017 Aug 4;9(32):27073-27082. Epub 2017 Aug 4.

Department of Applied Physics, Korea University , Sejong 339-700, Korea.

In this study, we demonstrate a high-performance solid polymer electrolyte (SPE) atomic switching device with low SET/RESET voltages (0.25 and -0.5 V, respectively), high on/off-current ratio (10), excellent cyclic endurance (>10), and long retention time (>10 s), where poly-4-vinylphenol (PVP)/poly(melamine-co-formaldehyde) (PMF) is used as an SPE layer. To accomplish these excellent device performance parameters, we reduce the off-current level of the PVP/PMF atomic switching device by improving the electrical insulating property of the PVP/PMF electrolyte through adjustment of the number of cross-linked chains. We then apply a titanium buffer layer to the PVP/PMF switching device for further improvement of bipolar switching behavior and device stability. In addition, we first implement SPE atomic switch-based logic AND and OR circuits with low operating voltages below 2 V by integrating 5 × 5 arrays of PVP/PMF switching devices on the flexible substrate. In particular, this low operating voltage of our logic circuits was much lower than that (>5 V) of the circuits configured by polymer resistive random access memory. This research successfully presents the feasibility of PVP/PMF atomic switches for flexible integrated circuits for next-generation electronic applications.
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http://dx.doi.org/10.1021/acsami.7b07549DOI Listing
August 2017

Usefulness of the Versajet Hydrosurgery System for the Removal of Foreign Body Granuloma.

Arch Plast Surg 2017 Jul 15;44(4):352-353. Epub 2017 Jul 15.

Department of Plastic and Reconstructive Surgery, Chosun University College of Medicine, Gwangju, Korea.

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http://dx.doi.org/10.5999/aps.2017.44.4.352DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5533069PMC
July 2017

Late-Onset Methicillin-Resistant Infection after Facial Poly-L-Lactic Acid Injection.

Arch Plast Surg 2017 May 22;44(3):248-249. Epub 2017 May 22.

Department of Plastic and Reconstructive Surgery, Chosun University College of Medicine, Gwangju, Korea.

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http://dx.doi.org/10.5999/aps.2017.44.3.248DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5447537PMC
May 2017

Micronized Cross-Linked Human Acellular Dermal Matrices: An Effective Scaffold for Collagen Synthesis and Promising Material for Tissue Augmentation.

Tissue Eng Regen Med 2017 Oct 24;14(5):517-523. Epub 2017 May 24.

4Institute for Human Tissue Restoration, Department of Plastic and Reconstructive Surgery, Yonsei University College of Medicine, 50-1 Yonsei-ro, Seodaemun-gu, Seoul, 03722 Republic of Korea.

Micronized cross-linked human acellular dermal matrices (ADMs) contain the extracellular components necessary for cell integration and tissue remodeling, and have high tensile strength and durability. We hypothesized that such material could serve as a scaffold to enhance the survival of adipocytes in grafted fat. Nude mice (n = 15) were randomly assigned to three groups, each receiving different subcutaneous injections into two dorsal paravertebral areas: fat and saline (control), fat and micronized ADM (E1), and fat and diluted micronized ADM (E2). Digital photographs were taken at 2-week intervals, and the grafted fat volumes and weights were examined after 10 weeks. A histological analysis of the grafted fat was performed, and the expression of vascular endothelial growth factor (VEGF) was examined. The grafted fat volumes decreased over time in all groups; however, at 10 weeks, the grafted fat was better preserved in both experimental groups, with significantly greater weights than in the group C (both,  < 0.001). In the experimental groups, there was more regular arrangement of collagen in the graft tissue, whereas relatively thin, disorderly collagen deposition was observed in the control group. In addition, VEGF expression was significantly greater in the experimental groups than in the control group ( < 0.001). These results are the first to show that micronized cross-linked human ADMs are an excellent scaffold for promoting adipocyte survival and may be an option for maintaining or promoting the survival of grafted fat.
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http://dx.doi.org/10.1007/s13770-017-0054-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6171624PMC
October 2017

Demonstration of hetero-gate-dielectric tunneling field-effect transistors (HG TFETs).

Nano Converg 2016 15;3(1):13. Epub 2016 Jun 15.

Department of Electronic Engineering, Sogang University, Seoul, 04107 Republic of Korea.

The steady scaling-down of semiconductor device for improving performance has been the most important issue among researchers. Recently, as low-power consumption becomes one of the most important requirements, there have been many researches about novel devices for low-power consumption. Though scaling supply voltage is the most effective way for low-power consumption, performance degradation is occurred for metal-oxide-semiconductor field-effect transistors (MOSFETs) when supply voltage is reduced because subthreshold swing (SS) of MOSFETs cannot be lower than 60 mV/dec. Thus, in this thesis, hetero-gate-dielectric tunneling field-effect transistors (HG TFETs) are investigated as one of the most promising alternatives to MOSFETs. By replacing source-side gate insulator with a high- material, HG TFETs show higher on-current, suppressed ambipolar current and lower SS than conventional TFETs. Device design optimization through simulation was performed and fabrication based on simulation demonstrated that performance of HG TFETs were better than that of conventional TFETs. Especially, enlargement of gate insulator thickness while etching gate insulator at the source side was improved by introducing HF vapor etch process. In addition, the proposed HG TFETs showed higher performance than our previous results by changing structure of sidewall spacer by high- etching process.
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http://dx.doi.org/10.1186/s40580-016-0073-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5271161PMC
June 2016
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