Biomechanical Comparison of Spinal Fusion Methods Using Interspinous Process Compressor and Pedicle Screw Fixation System Based on Finite Element Method

Choi, Jisoo,Kim, Sohee,Shin, Dong-Ah The Korean Neurosurgical Society 2016 Journal of Korean neurosurgical society Vol.59 No.2

Objective : To investigate the biomechanical effects of a newly proposed Interspinous Process Compressor (IPC) and compare with pedicle screw fixation at surgical and adjacent levels of lumbar spine. Methods : A three dimensional finite element model of intact lumbar spine was constructed and two spinal fusion models using pedicle screw fixation system and a new type of interspinous devices, IPC, were developed. The biomechanical effects such as range of motion (ROM) and facet contact force were analyzed at surgical level (L3/4) and adjacent levels (L2/3, L4/5). In addition, the stress in adjacent intervertebral discs (D2, D4) was investigated. Results : The entire results show biomechanical parameters such as ROM, facet contact force, and stress in adjacent intervertebral discs were similar between PLIF and IPC models in all motions based on the assumption that the implants were perfectly fused with the spine. Conclusion : The newly proposed fusion device, IPC, had similar fusion effect at surgical level, and biomechanical effects at adjacent levels were also similar with those of pedicle screw fixation system. However, for clinical applications, real fusion effect between spinous process and hooks, duration of fusion, and influence on spinous process need to be investigated through clinical study.

Direction Vector-Based Algorithm for the Nash Bargaining Solution in Dynamic Networks

Choi, Jisoo,Park, Hyunggon IEEE 2018 IEEE communications letters Vol.22 No.7

<P>It is essential for multiuser networks to determine how to efficiently and fairly allocate shared and limited resources. Moreover, it is critical to optimally allocate these resources while ensuring quality of service requirements for users who require tolerable levels of quality. In this letter, we adopt a game-theoretic approach, referred to as the Nash bargaining solution (NBS), for resource allocation across multiple users. While the NBS can provide a fair and optimal resource allocation, finding the NBS is generally a computationally-intensive task, which becomes even more difficult in dynamic networks. We propose a direction vector-based approach that finds accurate solutions to a bargaining problem with relatively low and consistent complexity requirements. The proposed approach exploits the relationship between the direction vectors of utility functions of each user and is used to reduce the search space of the feasible utility set. The simulation results confirm that the proposed approach can efficiently compute the NBS even for a considerable number of users and resources with better accuracy.</P>

Biomechanical Effects of the Geometry of Ball-and-Socket Artificial Disc on Lumbar Spine: A Finite Element Study

Choi, Jisoo,Shin, Dong-Ah,Kim, Sohee Wolters Kluwer Health, Inc. All rights reserved. 2017 1528-1159) Vol.42 No.6

<P>Study Design. A three-dimensional finite element model of intact lumbar spine was constructed and four surgical finite element models implanted with ball-and-socket artificial discs with four different radii of curvature were compared. Objective. To investigate biomechanical effects of the curvature of ball-and-socket artificial disc using finite element analysis. Summary of Background Data. Total disc replacement (TDR) has been accepted as an alternative treatment because of its advantages over spinal fusion methods in degenerative disc disease. However, the influence of the curvature of artificial ball-and-socket discs has not been fully understood. Methods. Four surgical finite element models with different radii of curvature of ball-and-socket artificial discs were constructed. Results. The range of motion (ROM) increased with decreasing radius of curvature in extension, flexion, and lateral bending, whereas it increased with increasing radius of curvature in axial torsion. The facet contact force was minimum with the largest radius of curvature in extension, flexion, and lateral bending, whereas it was maximum with the largest radius in axial torsion. It was also affected by the disc placement, more with posterior placement than anterior placement. The stress in L4 cancellous bone increased when the radius of curvature was too large or small. Conclusion. The geometry of ball-and-socket artificial disc significantly affects the ROM, facet contact force, and stress in the cancellous bone at the surgical level. The implication is that in performing TDR, the ball-and-socket design may not be ideal, as ROM and facet contact force are sensitive to the disc design, which may be exaggerated by the individual difference of anatomical geometry.</P>

Domestic and foreign disinfection industry trends in response to COVID-19

Jisoo kim(김지수),Jungsook Choi(최정숙),Jihoon Seo(서지훈),Inwoo Choi(최인우),Philjoon Kim(김필준),Jongryul Sohn(손종렬) 환경독성보건학회 2021 한국독성학회 심포지움 및 학술발표회 Vol.2021 No.5

Since the COVID-19, there has been a growing interest in disinfection in the space where many people stay for a long time, with the spread of new infections caused by Cluster Infection in multi-use facilities in Korea soaring. Since COVID-19, natural ventilation and mechanical ventilation alone have difficulty in controlling bio-aerosols in multi-use facilities, and considering water-borne infections as an infection path of COVID-19, a diverse disinfection process is required. Since the declaration of COVID-19 pandemic, attempts to replace human resources with robots or drones have been increasing due to the spread of non-face-to-face culture that minimizes interpersonal contact. Domestic disinfection is carried out through disinfectants approved by the Ministry of Environment for coronavirus, such as cleaning, spraying disinfection through dispensing drugs, and direct disinfection. Disinfecting spray is also avoided by the Central Disaster and Safety Countermeasures Headquarters in Korea and the WHO. This is because the effect of disinfection is low except in the space where the disinfectant is directly contacted, and the disinfectant stimulates the skin, eyes, and respiratory system, which is not recommended due to the high risk of exposure to the human body. Although most of the domestic and international development and commercialized disinfection technologies have UV lamp and spray disinfection methods, they have clear limitations such as weak spray disinfection effects or ozone from ultraviolet lamps. the disinfection technology needs to be considered for the harmful effects of human exposure of chemicals in disinfectants that are made for the purpose of removing microorganisms, so continuous interest and verification of the technology is needed.

Nash 협상 해법 기반 전력 최소화를 위한 다중 청소로봇 간 영역분배 알고리즘

최지수(Jisoo Choi),박형곤(Hyunggon Park) 한국통신학회 2014 韓國通信學會論文誌 Vol.39 No.4(융합기술)

본 논문에서는 주어진 영역 안에서 다중 청소로봇을 동시에 운용하여 전력 소비량을 최소화하는 방법을 제안한다. 협력 게임 이론 중 Nash 협상 해법을 이용하여 다중 청소로봇 사이의 가용 자원 및 대상 영역의 특성을 고려하여 대상 영역을 공평하고 효율적으로 관리하여 자원 효용을 극대화하였으며 궁극적으로 이를 통하여 총 소비전력량을 최소화 할 수 있다. 본 논문에서는 가용 자원 및 대상 영역의 특성을 포괄할 수 있는 효용 함수를 정의하고 이를 통한 다중 로봇 간 협상 게임을 통하여 공평하고 효용이 파레토 최적인 지점에서 각 청소로봇의 해당 영역이 결정된다. 시뮬레이션을 통하여 제안한 해결 방법이 임의 공간 할당 방법 대비 소비전력량 면에서 15-30% 이상의 효율이 개선되는 것을 확인할 수 있었다. In this paper, we propose an approach to minimizing total power consumption by deploying multiple clean-up robots simultaneously in a given area. For this, we propose to use the cooperative game theoretic approaches (i.e., Nash bargaining solution (NBS)) such that the robots can optimally and fairly negotiate the area division based on available resources and characteristics of the area, thereby leading to the minimum total power consumption. We define a utility function that includes power consumptions for characteristics of areas and the robots can agree on a utility pair based on the NBS. Simulation results show that the proposed approach can reduce the total average power consumption by 15-30% compared to a random area division approach.

Improving collection efficiency in two-photon endoscopy with reflective waveguiding

Han, Jisoo,Lee, Sungho,Choi, Pyonggang,Wu, Jiamin,Lee, Keunhyung,Dai, Qionghai,Park, Jinhyung,Lee, Kyung-Bok,Choi, Myunghwan The Optical Society 2018 Optics express Vol.26 No.25

양자점을 이용한 플래시 메모리 기반 뉴로모픽 소자 연구‘

최지수(Jisoo Choi),양정목(Jeongmok Yang),김예은(Yeeun Kim),강다현(Dahyun Kang),박찬규(Changyu Park),정소연(Soyeon Jung),김석규(Seokgyu Kim),김용덕(Yongduk Kim),손병희(Byunghee Son),장문규(Moongyu Jang) 한국물리학회 2022 새물리 Vol.72 No.10

뇌에서는 외부 자극에 의해 뉴런들의 연관성이 높아지면 시냅스를 통하여 연결 강도가 달라지게 된다. 본 연구에서는 양자점을 사용하여 이러한 시냅스를 구현하는 소자를 제작하고 평탄대 전압을 변화시키며 메모리 효과를 확인하였다. Pt/Cr/Al₂O₃/Quantum Dots/SiO₂/Si 기판의 수직 구조를 가진 소자를 제작하였고, 소자의 동작을 위해 게이트 전극에 전압을 가하였다. 이때, 절연막 손상이 발생하지 않는 적절한 프로그래밍/이레이징 전압 범위 설정이 필요하므로 전류-전압을 측정하여 절연막의 항복 전압을 도출하였다. 이후, 적절한 프로그래밍 전압을 인가하며 정전용량-전압 측정을 진행하였고 이를 통해 양자점의 메모리 효과를 확인하였다. 우리는 소자에 인가하는 전압의 크기와 시간을 변경하며 양자점에 포획되는 전자의 수를 조절하였고, 양자점에 포획된 전자의 수에 따라 평탄화 전압을 변화시켜 여러 단계의 상태를 표현할 수 있었다. 이를 통해 상태가 다양한 강도의 아날로그 형태로 변화하는 시냅스 특성을 표현할 수 있는 가능성을 확인하였다. In the human brain, when the neuron association is increased by an external stimulation, the strength of the connection changes through the synapses. The semiconductor devices emulating these synapses are called neuromorphic devices. In this research, a device acting as a synapse was manufactured using quantum dots (QDs), and the memory effect was confirmed by changing the flatband voltage (VFB) through the injection and depletion of electrons into the QDs. The fabricated device contained a vertical gate stack Pt/Cr/QDs/Al₂O₃/SiO₂/Si substrate, and a current-voltage characteristic was used to determine the breakdown voltage and the select programming voltage within a range that did not affect the oxide. Subsequently, the capacitance-voltage was measured by applying the programming voltage, and the memory effect of QDs was confirmed. The number of electrons stored in QDs were adjusted by changing the voltage and time to the device, and the state of several steps was implemented by varying the VFB depending on the number of electrons stored in QDs. Through the manufactured device, we confirmed that the implementation of a synaptic device was possible with multiple connection strengths.

선형 제약 조건화를 통한 내쉬 협상 해법 기반 효율적 자원 할당 방법

최지수(Jisoo Choi),정승현(Seunghyun Jung),박형곤(Hyunggon Park) 대한전기학회 2016 전기학회논문지 Vol.65 No.3

The overall performance of multiuser systems significantly depends on how effectively and fairly manage resources shared by them. The efficient resource management strategies are even more important for multimedia users since multimedia data is delay-sensitive and massive. In this paper, we focus on resource allocation based on a game-theoretic approach, referred to as Nash bargaining solution (NBS), to provide a quality of service (QoS) guarantee for each user. While the NBS has been known as a fair and optimal resource management strategy, it is challenging to find the NBS efficiently due to the computationally-intensive task. In order to reduce the computation requirements for NBS, we propose an approach that requires significantly low complexity even when networks consist of a large number of users and a large amount of resources. The proposed approach linearizes utility functions of each user and formulates the problem of finding NBS as a convex optimization, leading to nearly-optimal solution with significantly reduced computation complexity. Simulation results confirm the effectiveness of the proposed approach.

WebRTC를 활용한 온라인 감독 서비스 개발

최지수(Jisoo Choi),문현수(Hyunsu Mun),이영석(Youngseok Lee) 한국정보과학회 2021 한국정보과학회 학술발표논문집 Vol.2021 No.12

정상파 영상화 기반 3차원 형상정보를 이용한 3차원 구조물 결함 탐지

최지수(Jisoo Choi),전준영(Junyoung Jeon),남현우(Hyeonwoo Nam),공예슬(Yeseul Kong),박규해(Gyuhae Park),박찬익(Chan Yik Park) 한국비파괴검사학회 2022 한국비파괴검사학회 춘계학술대회 초록집 Vol.2022 No.5