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      • KCI등재

        Mathematical extraction of mechanical characteristics from electrical signals from an electrically driven quartz tuning fork in vacuum, air, and liquid environments

        Kwon Dohyun,Kim Dongwon,Bae Yunbi,Choi Hyoju,Kim Bongsu,Choi MyoungChoul,An Sangmin,Lee Manhee 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.5

        A quartz tuning fork is an electromechanical resonator with self-actuating and self-sensing capabilities and is widely used as a force sensor in atomic force microscopy and spectroscopy. While the electrical response of a tuning fork is affected by the two prongs’ mechanical motion and stray capacitive current, a purely mechanical motion signal of the tuning fork is required for a quantitative analysis. Here, we demonstrate the extraction of a mechanical motion signal from the electrical signal of an electrically driven quartz tuning fork in various environments, including vacuum, air, and liquid. We show that the extraction formalism is well implemented in vacuum and air, but it does not work in liquid due to the largely enhanced damping and ions present in liquids. Furthermore, using the mechanical signal extracted from the electrical signal, we determine the interaction force exerted on the tip of the tuning fork in ambient air. The present extraction method enables versatile use of electrically driven tuning forks for force, mass, and environmental sensing, in which true mechanical motion signals should be used for accurate and quantitative analysis.

      • KCI등재

        연구개에서 발생한 골수외성 형질세포종: 증례보고

        Dohyun Kwon,Hoon Myoung 대한구강악안면병리학회 2016 대한구강악안면병리학회지 Vol.40 No.3

        Extramedullary plasmacytomas (EMPs) are rare soft tissue malignant neoplasms composed of plasma cells. They are sometimes found in soft tissues. The majority of primary EMPs occur in the head and neck region, especially in the upper respiratory tract and oral cavity. We present a case of a 52-year-old female with an EMP. The patient’s initial chief complaint was swelling of the soft palate. An excisional biopsy was performed under general anesthesia. Final pathologic diagnosis was EMP of the soft palate with partial involvement of the resection margin. In order to exclude the possibility of multiple myeloma, a bone marrow exam with chromosomal study was completed. The patient was also referred to the Department of Radiation Oncology for postoperative radiation therapy (PORT); however, the patient refused to undergo PORT. The patient is currently under close observation for signs and symptoms of recurrence or metastases through regular follow-up visits and imaging studies.

      • KCI등재

        Self-Adaptive Power Control with Deep Reinforcement Learning for Millimeter-Wave Internet-of-Vehicles Video Caching

        Dohyun Kwon,Joongheon Kim,David A. Mohaisen,Wonjun Lee 한국통신학회 2020 Journal of communications and networks Vol.22 No.4

        Video delivery and caching over the millimeter-wave(mmWave) spectrum is a promising technology for high data rateand efficient frequency utilization in many applications, includingdistributed vehicular networks. However, due to the short handoffduration, calibrating both optimal power allocation of each basestation toward its associated vehicles and cache allocation are challenging for their computational complexity. Heretofore, most videodelivery applications were based on on-line or off-line algorithms,and they were limited to compute and optimize high dimensionalobjectives within low-delay in large scale vehicular networks. Onthe other hand, deep reinforcement learning is shown for learningsuch scale of a problem with an optimized policy learning phase. In this paper, we propose deep deterministic policy gradient-basedpower control of mmWave base station (mBS) and proactive cacheallocation toward mBSs in distributed mmWave Internet-of-vehicle(IoV) networks. Simulation results validate the performance of theproposed caching scheme in terms of quality of the provisionedvideo and playback stall in various scales of IoV networks.

      • SCOPUSKCI등재

        Clinical validation of the 3-dimensional double-echo steady-state with water excitation sequence of MR neurography for preoperative facial and lingual nerve identification

        Kwon, Dohyun,Lee, Chena,Chae, YeonSu,Kwon, Ik Jae,Kim, Soung Min,Lee, Jong-Ho Korean Academy of Oral and Maxillofacial Radiology 2022 Imaging Science in Dentistry Vol.52 No.-

        Purpose: This study aimed to evaluate the clinical usefulness of magnetic resonance (MR) neurography using the 3-dimensional double-echo steady-state with water excitation (3D-DESS-WE) sequence for the preoperative delineation of the facial and lingual nerves. Materials and Methods: Patients underwent MR neurography for a tumor in the parotid gland area or lingual neuropathy from January 2020 to December 2021 were reviewed. Preoperative MR neurography using the 3D-DESS-WE sequence was evaluated. The visibility of the facial nerve and lingual nerve was scored on a 5-point scale, with poor visibility as 1 point and excellent as 5 points. The facial nerve course relative to the tumor was identified as superficial, deep, or encased. This was compared to the actual nerve course identified during surgery. The operative findings in lingual nerve surgery were also described. Results: Ten patients with parotid tumors and 3 patients with lingual neuropathy were included. Among 10 parotid tumor patients, 8 were diagnosed with benign tumors and 2 with malignant tumors. The median facial nerve visibility score was 4.5 points. The distribution of scores was as follows: 5 points in 5 cases, 4 points in 1 case, 3 points in 2 cases, and 2 points in 2 cases. The lingual nerve continuity score in the affected area was lower than in the unaffected area in all 3 patients. The average visibility score of the lingual nerve was 2.67 on the affected side and 4 on the unaffected side. Conclusion: This study confirmed that the preoperative localization of the facial and lingual nerves using MR neurography with the 3D-DESS-WE sequence was feasible and contributed to surgical planning for the parotid area and lingual nerve.

      • KCI등재

        확률론적 조율 전략 기반의 DASH 시스템

        권도현(Dohyun Kwon),김중헌(Joongheon Kim) 한국통신학회 2018 韓國通信學會論文誌 Vol.43 No.10

        본 논문에서는 최근 미디어 스트리밍 플랫폼들이 채택하고 있는 MPEG-DASH (DASH) 기반의 미디어 스트리밍 방법을 Markov Decision Process (MDP) 형태로 재해석하고, 이에 확률론적 조율 전략을 추가한 미디어 스트리밍 알고리즘을 제안한다. 제안하는 알고리즘에서는 이를 위해 MDP의 구성요소인 상태, 행동, 보상, 감쇠 상수, 마지막으로 전이 확률을 정의 및 결정하고, 비디오 재생의 가장 핵심적이며 실질적 데이터인 비디오 청크를 요청하는 세션들을 진행하면서 큐의 안정성과 품질 변화 빈도, 재생 정지현상과 같은 다양한 문제를 고려하고 클라이언트가 최적의 품질을 서비스 받을 수 있도록 설계한다. 이어지는 소단원들에서는 DASH의 개요를 소개하고, 및 제안하는 DASH 알고리즘에 대한 전반적 설계 사항을 소개한다. 마지막으로 이전 연구로 제안된 DASH 알고리즘들과 제안하는 알고리즘의 성능을 평균 수신 품질 관점에서 비교하는 실험을 통해 제안하는 알고리즘의 우수성을 검증한다. In this article, we reinterpret MPEG-DASH (MPEG Dynamic Adaptive Streaming over HTTP, or DASH) media streaming strategy, which is widely adopted by recent media streaming platforms, and transform sequential media requesting episodes utilizing Markov Decision Process (MDP) and propose a media streaming algorithm with stochastic tuning strategy. Firstly, the algorithm designs and decides elements of MDP, which consists of state, action, reward, discount factor, and transition probability. Plus, along with multiple scenarios of video chunk requesting sessions, which are the most essential and realistic data transmission procedure of entire media streaming, we carefully consider many issues such as queue stability, frequency of quality variation, and freezing phenomenon. Also, we design algorithm for client to experience optimal service under possibly drastically varying network bandwidth. In following subsections, we introduce an overview of DASH and elaborate design features of our proposed DASH algorithm. Lastly, we conduct experiments with proposed algorithm and previous MDP-based DASH system related researches by investigating experiments in terms of average quality of video chunk which impacts quality of experience of users.

      • First principles study of the thermodynamic and kinetic properties of U in an electrorefining system using molybdenum cathode and LiCl-KCl eutectic molten salt

        Kwon, Choah,Kang, Joonhee,Kang, Woojong,Kwak, Dohyun,Han, Byungchan Elsevier 2016 ELECTROCHIMICA ACTA Vol.195 No.-

        <P><B>Abstract</B></P> <P>Using first principles density functional theory (DFT) calculations we obtain thermodynamic and kinetic properties of U in an electrorefining process for spent nuclear fuels using a LiCl-KCl eutectic molten salt and Mo as a cathode. The thermodynamic stability of electrodeposited U from the molten salt onto the Mo(110) surface electrode is evaluated by activity coefficients as function of surface coverages of U and Cl. Additionally, ab-initio molecular dynamic simulations combined with the Stokes-Einstein-Sutherland relation enables us to calculate the viscosity of the LiCl-KCl eutectic molten salt. Our results well agree with previously reported experimental data endorsing the credibility. Based on our atomic-level mechanical understanding we propose that an accurate computational model system incorporating the electrochemical conditions of the electrorefining process essential for the purpose of establishing thermodynamic and kinetic database of U, otherwise critical deviations are inevitable. More interestingly, the effect of coadsorption of Cl with U on the Mo(110) surface plays a key role in stabilizing electrodeposited U on the cathode. Our approach can be useful for validating published experimental database and for identifying key factors guiding a rational design of highly efficient electrorefining system for spent nuclear fuels, and thus reducing high-level radioactive nuclear wastes.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

      • KCI등재SCISCIESCOPUS

        Suppression of T24 human bladder cancer cells by ROS from locally delivered hematoporphyrin-containing polyurethane films

        Kim, Dohyun,Lee, Mi Hee,Koo, Min-Ah,Kwon, Byeong-Ju,Kim, Min Sung,Seon, Gyeung Mi,Hong, Seung Hee,Park, Jong-Chul The Royal Society of Chemistry 2018 PHOTOCHEMICAL AND PHOTOBIOLOGICAL SCIENCES Vol.17 No.6

        <P>Systemic injection of a photosensitizer is a general method in photodynamic therapy, but it has complications due to the unintended systemic distribution and remnants of photosensitizers. This study focused on the possibility of suppressing luminal proliferative cells by excessive reactive oxygen species from locally delivered photosensitizer with biocompatible polyurethane, instead of the systemic injection method. We used human bladder cancer cells, hematoporphyrin as the photosensitizer, and polyurethane film as the photosensitizer-delivering container. The light source was a self-made LED (510 nm, 5 mW cm<SUP>−2</SUP>) system. The cancer cells were cultured on different doses of hematoporphyrin-containing polyurethane film and irradiated with LED for 15 minutes and 30 minutes each. After irradiating with LED and incubating for 24 hours, cell viability analysis, cell cycle analysis, apoptosis assay, intracellular and extracellular ROS generation study and western blot were performed. The cancer cell suppression effects of different concentrations of the locally delivered hematoporphyrin with PDT were compared. Apoptosis dominant cancer cell suppressions were shown to be hematoporphyrin dose-dependent. However, after irradiation, intracellular ROS amounts were similar in all the groups having different doses of hematoporphyrin, but these values were definitely higher than those in the control group. Excessive extracellular ROS from the intended, locally delivered photosensitizer for photodynamic treatment application had an inhibitory effect on luminal proliferative cancer cells. This method can be another possibility for PDT application on contactable or attachable lesions.</P>

      • The Effects of Actual Human Size Display and Stereoscopic Presentation on Users' Sense of Being Together with and of Psychological Immersion in a Virtual Character

        Ahn, Dohyun,Seo, Youngnam,Kim, Minkyung,Kwon, Joung Huem,Jung, Younbo,Ahn, Jungsun,Lee, Doohwang Mary Ann Liebert 2014 CYBERPSYCHOLOGY BEHAVIOR AND SOCIAL NETWORKING Vol.17 No.7

        <P>This study examined the role of display size and mode in increasing users' sense of being together with and of their psychological immersion in a virtual character. Using a high-resolution three-dimensional virtual character, this study employed a 22 (stereoscopic mode vs. monoscopic modeactual human size vs. small size display) factorial design in an experiment with 144 participants randomly assigned to each condition. Findings showed that stereoscopic mode had a significant effect on both users' sense of being together and psychological immersion. However, display size affected only the sense of being together. Furthermore, display size was not found to moderate the effect of stereoscopic mode.</P>

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