A series elastic actuator using air and water and its force control

Iksu Choi,Chanyong Park,양기훈,Hyoukryeol Choi,Hugo Rodrigue,문형필 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9

This study proposes a new type of series elastic actuator (SEA) utilizing a mixture of air and water. Instead of simply mixing air and water, a control method for its output force based on piston position control is suggested using the stiffness model of the mixture. The actuator is driven by the pressure generated when a stiff linear actuator compresses or decompresses the mixture in the syringe. The pneumatic medium makes the actuator compliant but slow, whereas the hydraulic one has a high bulk modulus, allowing for a fast but stiff response from the actuator. These characteristics can be adjusted by changing the air-to-water mixing ratio in the preparation stage before operation. After applying this actuator to the parallel jaw gripper system, grasping force control was performed without a load cell by utilizing the stiffness model of the mixture and the output force model. In an additional experiment, a very flexible object (a rose flower) and a very hard object (a glass vase) were successfully grasped by the gripper, which confirms the effectiveness of the actuator in controlling the grasping force.

Universal renormalization group flow toward perfect Fermi-surface nesting driven by enhanced electron-electron correlations in monolayer vanadium diselenide

Jang, Iksu,Duvjir, Ganbat,Choi, Byoung Ki,Kim, Jungdae,Chang, Young Jun,Kim, Ki-Seok American Physical Society 2019 Physical Review B Vol.99 No.1

악성 프로세스 제어 시스템의 성능 향상을 위한 보안 프레임워크

김익수 ( Iksu Kim ),최종명 ( Jongmyung Choi ) 한국인터넷정보학회 2013 인터넷정보학회논문지 Vol.14 No.2

지금까지 인터넷 웜에 대응하기 위한 다양한 연구가 진행되어 왔다. 대부분의 인터넷 웜 탐지 및 차단 시스템은 탐지룰을 이용하여 인터넷 웜 공격에 대응하지만 새로운 인터넷 웜에 대응할 수 없는 문제가 있다. 이에 인터넷 웜의 멀티캐스트 특징을 이용한 악성프로세스 제어 시스템이 제안되었다. 하지만 이 시스템은 서비스를 제공해야 할 서버의 수가 많을수록 시스템 구축비용이 증가하고 부분적 공격 유형의 인터넷 웜 공격 탐지 확률이 낮다. 본 논문에서는 악성 프로세스 제어 시스템의 구축비용을 절감하고, 부분적 공격 유형의 인터넷 웜 공격 탐지 확률을 높일 수 있는 보안 프레임워크를 제안한다. 제안된 보안 프레임워크에서는 가상머신을 이용하여 제어서버 구축비용을 줄이며, 사용되지 않는 여분의 IP 주소를 동적으로 인터넷 웜 공격 탐지에 이용함으로써 부분적 공격유형의 인터넷 웜 공격 탐지 확률을 증가시킬 수 있다. 결국 제안된 보안 프레임워크는 비교적 낮은 비용으로 새로운 유형의 다양한 인터넷 웜에 효과적으로 대응할 수 있다. Until now, there have been various studies against Internet worms. Most of intrusion detection and prevention systems against Internet worms use detection rules, but these systems cannot respond to new Internet worms. For this reason, a malicious process control system which uses the fact that Internet worms multicast malicious packets was proposed. However, the greater the number of servers to be protected increases the cost of the malicious process control system, and the probability of detecting Internet worms attacking only some predetermined IP addresses is low. This paper presents a security framework that can reduce the cost of the malicious process control system and increase the probability of detecting Internet worms attacking only some predetermined IP addresses. In the proposed security framework, virtual machines are used to reduce the cost of control servers and unused IP addresses are used to increase the probability of detecting Internet worms attacking only some predetermined IP addresses. Therefore the proposed security framework can effectively respond to a variety of new Internet worms at lower cost.

셀룰라 CDMA 시스템에서 음성 통화시 얼랑 용량 계산

한익수(IkSu Han),최승덕(SeungDuk Choi) 한국정보기술학회 2005 한국정보기술학회논문지 Vol.3 No.4

In FDMA and TDMA(IS-54) cellular systems, a requested call will be blocked when all frequency or time slots have been assigned to other users. In a CDMA cellular system, blocking will occur when the reverse link multiple access interference power reaches a predetermined level which is set to maintain acceptable signal quality. The number of users for which the CDMA blocking probability equals a certain value (usually 1% or 2%) is defined to be the Erlang capacity of the system and is related to an equivalent number of channels in an FDMA or TDMA cellular system. In this paper, the calculation of the CDMA blocking probability is based on a new analysis of the total squared power of other-cell interference. The calculation of CDMA Erlang capacity based on this result gives a result that is a equal that given in previous analyses.

E-Textbook with Lecturer-Created Quiz Capabilities

Jongmyung Choi,Iksu Kim 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.5

The e-book industry has been growing very fast for the last several years, and the e-book sales at Amazon.com already surpassed the printed books at the end of 2010. In the near future, the printed textbooks in K-12 and in higher education will be replaced by the e-textbooks that support multimedia and user interaction. Furthermore, the future e-textbooks will support user interactive quizzes and instant feedbacks on the quizzes for students’ better learning and lecturers’ better teaching. Quizzes and feedback in classes are very common and helpful to check students’ understanding and to correct their misunderstanding. However, the current e-textbooks support only limited capabilities for quizzes and feedback. For example, they do not support interactive quizzes, instant feedbacks, statistics for students’ understanding, or methods for lecturers to make their quizzes in the e-textbooks. In this paper, we propose an e-textbook system that supports interactive quizzes, instant feedback, and quiz-maker, which allows lecturers to make their own quizzes at schools after deploying e-textbooks. Using this e-textbook system, lecturers can make quizzes at any pages in the e-textbooks, and students are able to check their understanding efficiently with instant feedback while reading the books. We also introduce our prototype system, which is implemented utilizing HTML5. The prototype system has advantages such as device independence, ease to implement and low cost.

Emergence of a Metal-Insulator Transition and High-Temperature Charge-Density Waves in VSe₂ at the Monolayer Limit

Duvjir, Ganbat,Choi, Byoung Ki,Jang, Iksu,Ulstrup, Søren,Kang, Soonmin,Thi Ly, Trinh,Kim, Sanghwa,Choi, Young Hwan,Jozwiak, Chris,Bostwick, Aaron,Rotenberg, Eli,Park, Je-Geun,Sankar, Raman,Kim, Ki-Seo American Chemical Society 2018 NANO LETTERS Vol.18 No.9

<P>Emergent phenomena driven by electronic reconstructions in oxide heterostructures have been intensively discussed. However, the role of these phenomena in shaping the electronic properties in van der Waals heterointerfaces has hitherto not been established. By reducing the material thickness and forming a heterointerface, we find two types of charge-ordering transitions in monolayer VSe<SUB>2</SUB> on graphene substrates. Angle-resolved photoemission spectroscopy (ARPES) uncovers that Fermi-surface nesting becomes perfect in ML VSe<SUB>2</SUB>. Renormalization-group analysis confirms that imperfect nesting in three dimensions universally flows into perfect nesting in two dimensions. As a result, the charge-density wave-transition temperature is dramatically enhanced to a value of 350 K compared to the 105 K in bulk VSe<SUB>2</SUB>. More interestingly, ARPES and scanning tunneling microscopy measurements confirm an unexpected metal-insulator transition at 135 K that is driven by lattice distortions. The heterointerface plays an important role in driving this novel metal-insulator transition in the family of monolayer transition-metal dichalcogenides.</P> [FIG OMISSION]</BR>

PAL-EUV 가속기 터널 공조 환경 정밀제어

이동영(Dong-Young Lee),최영호(Young-Ho Choi),목익수(Iksu Mok),양정무(Jeong-Mu Yang),김영선(Yeong-Seon Kim),최민철(Min-Cheol Choi) 한국유체기계학회 2023 한국유체기계학회 학술대회 논문집 Vol.2023 No.12

진디혹파리에 대한 오이에 등록된 47종 살충제의 저독성 농약 선발

최용석,남윤규,황인수,한익수,박덕기,Choi, YongSeok,Nam, YunGyu,Hwang, InSoo,Han, IkSu,Park, DeokGi 한국응용곤충학회 2013 한국응용곤충학회지 Vol.52 No.3

본 실험은 오이재배시 사용되는 살충제 47종이 진딧물 포식성 천적인 진디혹파리(Aphidoletes aphidimyza Rondani)의 모든 발육단계에 얼마나 영향을 주는가를 평가하였다. 진디혹파리 알에 대한 살충제의 독성평가 결과 emamectin benzoate 등 22종의 살충제가 낮은 독성을 보였다. 알에 독성이 낮은 22종 살충제 중 flonicamid를 포함하는 12종 살충제가 진디혹파리 유충에 대하여 0~27%로 낮은 독성을 보였으나, indoxacarb + teflubenzuron와 chlorantraniliprole의 독성은 각각 35.4%와 64.6%였다. 진디혹파리 유충에 보통독성 이하의 독성을 보인 indoxacarb + teflubenzuron와 chlorantraniliprole을 포함한 14종 살충제는 진디혹파리의 번데기와 성충에도 낮은 독성을 보였다. From the results achieved by the evaluation of toxicities to an aphid predator, Aphidoletes aphidimyza Rondani eggs with 47 pesticides used for cucumber farming, 22 pesticides including emamectin benzoate showed low toxicity. 12 pesticides with flonicamid among 22 pesticides tested on eggs showed low toxicity (mortality, 0~2.7%) to A. aphidimyza lavae and indoxacarb + teflubenzuron and chlorantraniliprole showed toxicity of 35.4% and 64.6%, respectively. 14 pesticides including indoxacarb + teflubenzuron and chlorantraniliprole demontrating low toxicity against A. aphidimyza lavae showed low toxicity to A. aphidimyza pupae and adults as well.

모션 센서를 이용한 군대 수신호 전송 시스템

신건 ( Geon Shin ),전재철 ( Jaechol Jeon ),전민호 ( Minho Jeon ),최석원 ( Sukwon Choi ),김익수 ( Iksu Kim ) 한국정보처리학회 2016 정보처리학회논문지. 컴퓨터 및 통신시스템 Vol.5 No.10

본 논문에서는 모션 센서를 이용한 군대 수신호 전송 시스템을 제안한다. 제안 시스템은 분대장 디바이스와 분대원 디바이스, 서버로 구성된다. 분대장 디바이스와 분대원 디바이스는 마이크로 아두이노와 가속도 센서, 자이로스코프 센서로 구현되었으며, 서버는 라즈베리파이3을 사용하여 구현되었다. 분대장 디바이스와 분대원 디바이스는 밴드 형태로 제작되었기 때문에 가볍고 휴대성이 좋다. 또한, 제안 시스템은 시야가 확보되지 않는 상황에서 진동을 통해 수신호를 전송할 수 있다. 제안 시스템에서 구현된 디바이스는 4가지의 수신호를 인식할 수 있으며, 실험을 통해 88.82%의 인식 성공률을 보였다. 본 연구의 결과물을 통해 군 작전의 효율성과 병사의 생존율을 높일 것을 기대한다. In this paper, we propose a system for transmitting army hand signals using motion sensors. The proposed system consists of a squad commander device, squad member devices, and a server. The squad command device and squad member device have been implemented using a micro arduino, an accelerometer sensor, and a gyroscope sensor, and the server has been implemented using a Rasberry Pi 3. Because the devices are made in the form of band, they are lightweight and portable. The proposed system can transmit the hand signals through vibration in conditions of poor visibility. We have designed and implemented the squad member device to be able to recognize four military hand signals. Through experiments, the proposed system have shown 88.82% of correct recognition. In conclusion, we expect to increase effectiveness of army operations and survival rate of soldiers.

Genome analysis of <i>Hibiscus syriacus</i> provides insights of polyploidization and indeterminate flowering in woody plants

Kim, Yong-Min,Kim, Seungill,Koo, Namjin,Shin, Ah-Young,Yeom, Seon-In,Seo, Eunyoung,Park, Seong-Jin,Kang, Won-Hee,Kim, Myung-Shin,Park, Jieun,Jang, Insu,Kim, Pan-Gyu,Byeon, Iksu,Kim, Min-Seo,Choi, JinH Oxford University Press 2017 DNA research Vol.24 No.1

<P><B>Abstract</B></P><P><I>Hibiscus syriacus</I> (L.) (rose of Sharon) is one of the most widespread garden shrubs in the world. We report a draft of the <I>H. syriacus</I> genome comprised of a 1.75 Gb assembly that covers 92% of the genome with only 1.7% (33 Mb) gap sequences. Predicted gene modeling detected 87,603 genes, mostly supported by deep RNA sequencing data. To define gene family distribution among relatives of <I>H. syriacus</I>, orthologous gene sets containing 164,660 genes in 21,472 clusters were identified by OrthoMCL analysis of five plant species, including <I>H. syriacus</I>, <I>Arabidopsis thaliana, Gossypium raimondii, Theobroma cacao</I> and <I>Amborella trichopoda.</I> We inferred their evolutionary relationships based on divergence times among Malvaceae plant genes and found that gene families involved in flowering regulation and disease resistance were more highly divergent and expanded in <I>H. syriacus</I> than in its close relatives, <I>G. raimondii</I> (DD) and <I>T. cacao</I>. Clustered gene families and gene collinearity analysis revealed that two recent rounds of whole-genome duplication were followed by diploidization of the <I>H. syriacus</I> genome after speciation. Copy number variation and phylogenetic divergence indicates that WGDs and subsequent diploidization led to unequal duplication and deletion of flowering-related genes in <I>H. syriacus</I> and may affect its unique floral morphology.</P>