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Feedback Control of an Achiral Robotic Microswimmer

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Journal of Bionic Engineering 2017年第2期14卷 245-259页

作者： U Kei Cheang Hoyeon kim Dejan Milutinovic Jongeun Choi min Jun kim Department of Mechanical Engineering and Mechanics Drexel University Philadelphia PA 19104 USA Department of Mechanical Engineering Southern Methodist University Dallas TX75275 USA Department of Computer Engineering University of California Santa Cruz Santa Cruz California 95064 USA School of Mechanical Engineering Yonsei University Seoul South Korea

Magnetic microswimmers are useful for navigating and performing tasks at small scales. To demonstrate effective control over such microswimmers, we implemented feedback control of the three-bead achiral microswimmers in both simulation and experiment. The achiral microswimmers with the ability to swim in bulk fluid are controlled wirelessly using magnetic fields generated from electromagnetic coils. The achirality of the microswimmers introduces unknown handedness resulting in uncertainty in swimming direction. We use a combination of rotating and static magnetic fields generated from an approximate Helmholtz coil system to overcome such uncertainty. There are also movement uncertainties due to environmental factors such as unsteady flow conditions. A kinematic model based feedback controller was created based on data fitting of experimental data. However, the controller was unable to yield satisfactory performance due to uncertainties from environmental factors; i.e., the time to reach target pose under adverse flow condition is too long. Following the implementation of an integral controller to control the microswimmers＇ swimming velocity, the mieroswimmers were able to reach the target in roughly half the time. Through simulation and experiments, we show that the feedback control law can move an achiral microswimmer from any initial conditions to a target pose.

关键词： microrobotics magnetic control low Reynold number chirality feedback control

Improvement of hydrogen embrittlement and stress corrosion cracking by annealing for Al-4.4Mg-0.6Mn alloy

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Transactions of Nonferrous Metals Society of China 2011年第A01期21卷 17-22页

作者： Seong-Jong kim min-Su HAN Seong-Kweon kim Seok-Ki JANG Division of Marine Engineering Mokpo National Maritime University Media Engineering Seoul National University of Technology

With no annealing treatment, cathodic polarization trends in 5083F A1 alloy revealed concentration polarization and activation polarization. However, the annealed specimens have lower current densities at corrosion protection potential compared to the non-annealed specimen. The results of SSRTs conducted in seawater at the applied potential range of-l.8 V to -0.5 V indicated that the maximum tensile strength, elongation, and time-to-fracture had high values at applied potentials of -0.7 to -1.4 V. The maximum tensile strength, elongation, and time-to-f？acture decreased when the potential values were beyond this range in either anodic or cathodic direction. In general, the increased shear lip caused by annealing treatment indicates elongation. Time-to-fracture would likely increase with elongation. Potentials between -0.5 V to -0.6 V were found to be in the region of stress corrosion cracking. The corrosion protection zone was determined to be -0.7 V to -J,4 V because these potential ranges produced good mechanical properties. Potential less than -1.4 V produced a fractured surface with a mixture of dimples （ductile fractures） and a quasi-cleavage pattern resulting from the effects of hydrogen gas.

关键词： annealing 5083F A1-Mg alloy corrosion seawater slow strain rate tests

Histogram equalization using a reduced feature set of background speakers' utterances for speaker recognition

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Frontiers of Information Technology & Electronic Engineering 2017年第5期18卷 738-750页

作者： Myung-jae kim Il-ho YANG min-seok kim Ha-jin YU School of Computer Science University of Seoul

We propose a method for histogram equalization using supplement sets to improve the performance of speaker recognition when the training and test utterances are very short. The supplement sets are derived using outputs of selection or clustering algorithms from the background speakers' utterances. The proposed approach is used as a feature normalization method for building histograms when there are insufficient input utterance *** addition, the proposed method is used as an i-vector normalization method in an i-vector-based probabilistic linear discriminant analysis(PLDA) system, which is the current state-of-the-art for speaker verification. The ranks of sample values for histogram equalization are estimated in ascending order from both the input utterances and the supplement set. New ranks are obtained by computing the sum of different kinds of ranks. Subsequently, the proposed method determines the cumulative distribution function of the test utterance using the newly defined ranks. The proposed method is compared with conventional feature normalization methods, such as cepstral mean normalization(CMN), cepstral mean and variance normalization(MVN), histogram equalization(HEQ), and the European Telecommunications Standards Institute(ETSI) advanced front-end methods. In addition, performance is compared for a case in which the greedy selection algorithm is used with fuzzy C-means and K-means *** YOHO and Electronics and Telecommunications Research Institute(ETRI) databases are used in an evaluation in the feature space. The test sets are simulated by the Opus Vo IP codec. We also use the 2008 National Institute of Standards and Technology(NIST) speaker recognition evaluation(SRE) corpus for the i-vector system. The results of the experimental evaluation demonstrate that the average system performance is improved when the proposed method is used, compared to the conventional feature normalization methods.

关键词： Speaker recognition Histogram equalization i-vector

Effect of friction on the contact stress of a coated polymer gear

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Friction 2020年第6期8卷 1169-1177页

作者： Su-min BAE Kuk-Jin SEO Dae-Eun kim Department of Mechanical Engineering Yonsei UniversitySeoul 03722Republic of Korea

Polymer gears are used extensively in various ***,durability issues have been emerging because of friction at gear tooth contact *** extend the lifetime of polymer gears,a low-frictional coating has been considered as a possible *** this study,a finite element simulation method was performed to investigate the contact stress between a pair of coated polymer *** simulation included various friction coefficients(COFs)for studying the effects of friction during the *** results revealed that the friction causes the contact stress to shift over the roll angle,which is attributed to the direction of the sliding friction based on a free-body *** also investigated the effects of coating and found that a thin coating has little effect on the bulk deformation behavior of the ***,the stress distribution in the coating at the pitch point was investigated as the COF *** zero friction,three notable stress regions were observed:1)the center of the surface,2)the end of the contact,and 3)the overall contact *** COF was increased in the micro-slip region of the contact interface,both tensile and compressive stresses in the coating *** study provides significant aid to engineers for understanding the stress response of the coating applied to polymer gears to achieve an optimal design.

关键词： coating contact stress finite element method(FEM) friction polymer gear

Management of symptomatic cervical facet cyst with cervical interlaminar epidural block: A case report

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World Journal of Clinical Cases 2022年第32期10卷 11936-11941页

作者： Seong min Hwang min Kyu Lee Saeyoung kim Department of Anesthesiology and Pain Medicine School of MedicineKyungpook National UniversityDaegu 41944South Korea

BACKGROUND Symptomatic cervical facet cysts are relatively rare compared to those in the lumbar *** cysts are usually located in the 7th cervical and 1st thoracic vertebral(C7/T1)area,and surgical excision is performed in most ***,facet cysts are associated with degenerative conditions,and elderly patients are often ineligible for surgical *** interlaminar epidural block has been used in patients with cervical radiating symptoms and achieved good ***,cervical interlaminar epidural block may be the first-choice treatment for symptomatic cervical facet *** SUMMARY A 70-year-old man complained of a tingling sensation in the left hand,focused on the 4th and 5th fingers,for 1 year,and posterior neck pain for over 5 *** patient’s numeric rating scale(NRS)score was 5/*** patient was diagnosed with symptomatic cervical facet cyst at the left C7/T1 facet *** cervical interlaminar epidural block at the C7/T1 level with 20 mg triamcinolone and 5 mL of 0.5%lidocaine was *** patient's symptoms improved immediately after the block,with an NRS score of 3 *** 3 mo,his left posterior neck pain and tingling along the left 8th cervical dermatome were relieved,with an NRS score of *** A cervical interlaminar epidural block is a good alternative for managing symptomatic cervical facet cysts.

关键词： Cervical vertebrae Cysts Epidural Injections Neck pain Therapeutics Zygapophyseal joint Case report

Multi-Stream CNN-Based Personal Recognition Method Using Surface Electromyogram for 5G Security

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Computers, Materials & Continua 2022年第8期72卷 2997-3007页

作者： Jin Su kim min-Gu kim Jae Myung kim Sung Bum Pan IT Research Institute Chosun UniversityGwangju61452Korea Interdisciplinary Program in IT-Bio Convergence System Chosun UniversityGwangju61452Korea

As fifth generation technology standard(5G)technology develops,the possibility of being exposed to the risk of cyber-attacks that exploits vulnerabilities in the 5G environment is *** existing personal recognitionmethod used for granting permission is a password-basedmethod,which causes security ***,personal recognition studies using bio-signals are being conducted as a method to access control to *** bio-signal,surface electromyogram(sEMG)can solve the existing personal recognition problem that was unable to the modification of registered information owing to the characteristic changes in its signal according to the performed ***,as an advantage,sEMG can be conveniently measured from arms and *** paper proposes a personal recognition method using sEMG,based on a multi-stream convolutional neural network(CNN).The proposed method decomposes sEMG signals into intrinsic mode functions(IMF)using empirical mode decomposition(EMD)and transforms each IMF into a *** recognition is performed by analyzing time–frequency features from the spectrogram transformed *** database(DB)adopted in this paper is the Ninapro DB,which is a benchmark EMG *** experimental results indicate that the personal recognition performance of the multi-stream CNN using the IMF spectrogram improved by 1.91%,compared with the singlestream CNN using the spectrogram of raw sEMG.

关键词： Personal recognition electromyogram signal multi-stream network empirical mode decomposition

Computing the User Experience via Big Data Analysis:A Case of Uber Services

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Computers, Materials & Continua 2021年第6期67卷 2819-2829页

作者： Jang Hyun kim Dongyan Nan Yerin kim Hyung Park min Department of Interaction Science/Department of Human-Artificial Intelligence Interaction Sungkyunkwan UniversitySeoul03063Korea Department of Applied Artificial Intelligence/Department of Human-Artificial Intelligence Interaction Sungkyunkwan UniversitySeoul03063Korea

As of 2020,the issue of user satisfaction has generated a significant amount of ***,we employ a big data approach for exploring user satisfaction among Uber *** develop a research model of user satisfaction by expanding the list of user experience(UX)elements(i.e.,pragmatic,expectation confirmation,hedonic,and burden)by including more elements,namely:risk,cost,promotion,anxiety,sadness,and ***,we collect 125,768 comments from online reviews of Uber services and perform a sentiment analysis to extract the UX *** results of a regression analysis reveal the following:hedonic,promotion,and pragmatic significantly and positively affect user satisfaction,while burden,cost,and risk have a substantial negative ***,the influence of expectation confirmation on user satisfaction is not ***,sadness,anxiety,and anger are positively related to the perceived risk of *** with sadness and anxiety,anger has a more important role in increasing the perceived burden of *** on these findings,we also provide some theoretical implications for future UX literature and some core suggestions related to establishing strategies for Uber and similar *** proposed big data approach may be utilized in other UX studies in the future.

关键词： User satisfaction user experience big data sentiment analysis Uber

A Rapid Adaptation Approach for Dynamic Air‑Writing Recognition Using Wearable Wristbands with Self‑Supervised Contrastive Learning

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Nano-Micro Letters 2025年第2期17卷 417-431页

作者： Yunjian Guo Kunpeng Li Wei Yue Nam‑Young kim Yang Li Guozhen Shen Jong‑Chul Lee Department of Electronic Convergence Engineering Kwangwoon UniversitySeoul 01897South Korea Radio Frequency Integrated Circuit(RFIC)Bio Centre Kwangwoon UniversitySeoul 01897South Korea Department of Electronic Engineering Kwangwoon UniversitySeoul 01897South Korea School of Microelectronics Shandong UniversityJinan 250101People’s Republic of China State Key Laboratory of Integrated Chips and Systems Fudan UniversityShanghai 200433People’s Republic of China School of Integrated Circuits and Electronics Beijing Institute of TechnologyBeijing 100081People’s Republic of China

Wearable wristband systems leverage deep learning to revolutionize hand gesture recognition in daily *** existing approaches that often focus on static gestures and require extensive labeled data,the proposed wearable wristband with selfsupervised contrastive learning excels at dynamic motion tracking and adapts rapidly across multiple *** features a four-channel sensing array composed of an ionic hydrogel with hierarchical microcone structures and ultrathin flexible electrodes,resulting in high-sensitivity capacitance *** wireless transmission from a Wi-Fi module,the proposed algorithm learns latent features from the unlabeled signals of random wrist ***,only few-shot labeled data are sufficient for fine-tuning the model,enabling rapid adaptation to various *** system achieves a high accuracy of 94.9%in different scenarios,including the prediction of eight-direction commands,and air-writing of all numbers and *** proposed method facilitates smooth transitions between multiple tasks without the need for modifying the structure or undergoing extensive task-specific *** utility has been further extended to enhance human–machine interaction over digital platforms,such as game controls,calculators,and three-language login systems,offering users a natural and intuitive way of communication.

关键词： Wearable wristband Self-supervised contrastive learning Dynamic gesture Air-writing Human-machine interaction

Micro Manipulation Using Magnetic Microrobots

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Journal of Bionic Engineering 2016年第4期13卷 515-524页

作者： Hoyeon kim Jamel Ali U Kei Cheang Jinwoo Jeong din Seok kim min dun kim Department of Mechanical Engineering Southern Methodist University Dallas TX75272 USA Department of MechanicaI Engineering and Mechanics Drexel University Philadelphia PA 19104 USA Center for Bionics Korea Institute of Science and Technology 5 Hwarang-ro 14-gil Seongbuk-gu Seou102792 Republic of Korea

When developing microscale robotic systems it is desired that they are capable of performing microscale tasks such as small scale manipulation and transport. In this paper, we demonstrate the transport of microscale objects using single or multiple microrobots in low Reynolds number fluidic environment. The microrobot is composed of a ‘U＇ shaped SU-8 body, coated on one side with nickel. Once the nickel coating is magnetized, the motion of the microrobots can be driven by external magnetic fields. To invoke different responses from two microrobots under a global magnetic field, two batches of microrobots were fabricated with different thicknesses of nickel coating as a way to promote heterogeneity within the microrobot population. The heterogeneity in magnetic content induces different spatial and temporal responses under the same control input, resulting in differences in movement speed. The nickel coated microstructure is manually controlled through a user interface developed using C＋＋. This paper presents a control strategy to navigate the microrobots by controlling the direction and strength of ex- ternally applied magnetic field, as well as orientation of the microrobots based on their polarity. In addition, multiple micro- robots are used to perform transport tasks.

关键词： microrobot magnetic control microtransport magnetic polarity micromanipulation