J.H. Ku

Hanyang University, Sŏul, Seoul, South Korea

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Publications (22)11.01 Total impact

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    ABSTRACT: The shoulder can control the range of motion of upper-limb. However, proprioception declines of shoulder of patients with stroke have affected the control of upper-limb motion. The motor learning regulates body movement posture by integrating the proprioception feedback (muscle force, joint position, etc.) as well as exteroceptive feedback (vision, audition). Proprioception feedback plays important role in the motor learning. Virtual reality (VR) is able to provide an environment which manipulates visual feedback of movement of stroke patients. In this study, we developed a system that can provide the continuous matching angle task with manipulating visual feedback using virtual reality for shoulder proprioception training of patients with stroke. Nineteen patients with stroke (age: 58.16 ± 12.27 years, onset: 40.16 ± 49.76 months, males: 17, females: 2) were recruited for this experiment. Participants performed the angle matching task and continuous matching angle task. In the results, error angle of angle matching task were not different between the first half of angle matching task and the second half of angle matching task (p = 0.202). Accumulated error angle of continuous matching angle task were more reduced in the second half of continuous matching angle task than in the first half of continuous matching angle task (p = 0.002). These results are similar to the result from a study assessing balance training using vision cue deprivation. It can be explained that manipulated visual feedback using virtual reality affects the proprioception of shoulder of patients with stroke. As conclusion, we found that visual feedback manipulation using virtual reality could provide an effective proprioception feedback for proprioception training of shoulder of patients with stroke. KeywordsVirtual reality-Shoulder-proprioception-Visual feedback
    No preview · Chapter · Dec 2009
  • W. H. Lee · J. H. Ku Ph. D · H. R. Lee · K. W. Han · J. S. Park · J. J. Kim · I. Y. Kim · S. I. Kim
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    ABSTRACT: The sense of one’s own body as part of the self is a fundamental aspect of self-awareness. The recent distinction between sense of agency and sense of body-ownership has attracted considerable empirical and theoretical interest. In this study, we compared the strength of virtual hand illusion induced by agency controlled movement, to investigate the contributions of visual-motor stimulation and ownership to body using fMRI and behavioral study. In the synchronous conditions, virtual hand angle scaled by a scale factor of real hand angle, while the asynchronous condition showed virtual hand angle didn’t correspond to real hand angle. Left precentral gyrus, left SMA, left anterior cingulate cortex and right parahippocampal were significant differences between synchronous condition and asynchronous condition with visual feedback. Left SMA was correlated positively with ownership score. The SMA function is integrated various sensory inputs and optimized action selected and compare body forward model with proprioception, then estimate body image.
    No preview · Article · Jan 2009 · IFMBE proceedings
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    ABSTRACT: The aim of this study is to investigate the possibility that human sleep EEGs can be characterized by a multifractal spectrum using wavelet transform modulus maxima (WTMM). We used sleep EEGs taken from healthy subjects during the four stages of sleep and REM sleep. Our findings showed that the dynamics in human sleep EEGs could be adequately described by a set of scales and characterized by multifractals. We performed multivariate discriminate analysis to evaluate the use of multifractal features for classification. The multivariate discriminate analysis using within-groups covariance matrices for all sleep stages yielded a total error rate of 41.8%. In conclusion, multifractal formalism, based on the WTMM, appears to be a good tool for characterizing dynamics in sleep EEGs
    No preview · Conference Paper · Jun 2007
  • K.J. Kim · J.H. Ku · I.Y. Kim · S.I. Kim · S.W. Nam
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    ABSTRACT: A new design approach is proposed for sharp notch FIR filters, whereby a modified alpha- scaled sampling kernel is utilized. In particular, the proposed approach provides closed-form formulae for filter coefficients, leading to an effective design procedure for sharp notch filters with given specifications. Simulation results demonstrate that the proposed design method yields high performance in removing the power line interference from ECG signals.
    No preview · Conference Paper · Jan 2007
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    ABSTRACT: Tungsten oxide whiskers were prepared on a tungsten thin film by oxidation with H 2 O and a subsequent annealing treatment at a temperature of over 900 °C in a vacuum. The tungsten oxide formed by oxidation was transformed into smooth, straight whiskers with a monoclinic-crystalline structure after the vacuum annealing treatment. The whiskers showed an oxygen-deficient stoichiometry and a crystalline structure consistent with W 18 O 49 , which was dependent on the annealing temperature and vacuum used. The competition between the whisker growth and the dissociation of W oxide has a significant effect on the crystal shape, as well as the size of the whiskers. A change in the binding state during whisker formation indicates that some of the dissociated W oxide contributes to whisker formation and that crystalline whiskers are grown at nucleation sites through this process. © 2004 American Vacuum Society.
    Full-text · Article · May 2004 · Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society
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    ABSTRACT: The interfacial characteristics of gate stack structure of HfO2 dielectrics on strained Si0.7Ge0.3 deposited by atomic-layer deposition were investigated. An interfacial layer including GeOx layers was grown on a SiGe substrate, and the thickness of the GeOx layer at the interfacial layer was decreased after the annealing treatment, while SiO2 layer was increased. The ∼50-Å-thick HfO2 film with an amorphous structure was converted into a polycrystalline structure after rapid annealing at temperature of over 700 °C for 5 min. The interfacial silicate layer was effectively suppressed by GeOx formation, while the silicate layer was formed after the annealing treatment. GeOx formation in an as-grown film resulted in a decrease in the accumulation capacitance and an increase in the oxide trap charge. © 2004 American Institute of Physics.
    No preview · Article · Feb 2004 · Applied Physics Letters
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    ABSTRACT: For sub-50 nm device application, Self-Aligned siLICIDE (SALICIDE) process by NiTa alloy has been developed for the first time. Use of NiTa-alloy makes nickel silicide on 50 nm gate thermally-robust up to 600°C during device fabrication. NiTa SALICIDE process can also achieve excellent value and distribution of sheet resistance on 30 nm gate as well as low junction leakage current compared to Co SALICIDE. Furthermore, the drive current of PMOS is greatly increased. As a result, high-performance 90 nm MOSFETs is successfully integrated with NiTa SALICIDE process.
    No preview · Conference Paper · Jul 2003

  • No preview · Article · Mar 2003 · Schizophrenia Research
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    M.-H Cho · YS Rho · H.-J Choi · S W Nam · H Ko · J H Ku · H C Kang · D Y Noh · C N Whang · K Jeong
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    ABSTRACT: The annealing effects of the thin aluminum silicate films grown on Si100 by sputtering method were investigated using various physical and electrical measurements. All the films grown at the temperature of 300 °C using sputtering Al 2 O 3 target show an amorphous structure as examined by x-ray diffraction and transmission electron microscopy. The amorphous structure is maintained up to 700 °C and then transformed to crystalline Al 1.7 SiO 0.15 O 2.85 or mullite phase above the annealing temperature of 800 °C. The conduction process, charge trapping and detrapping characteristics, and trap charge density in metal–oxide–semiconductor structure are influenced by the annealing temperature. The depth profiling data using x-ray photoelectron spectroscopy show that the properties are closely related to the change of the interfacial layer and chemical state under the high temperature annealing. The breakdown characteristics are degraded after the annealing temperature of 900 °C due to the rapid change of the interfacial layer thickness and chemical state of the silicate layer. © 2002 American Vacuum Society.
    Full-text · Article · May 2002 · Journal of Vacuum Science & Technology A Vacuum Surfaces and Films
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    ABSTRACT: Sub-100 nm DRAM is successfully fabricated for the first time with several key technologies, including W/W<sub>x</sub>N-poly gate, bitline structure having low parasitic capacitance, Ru/Ta<sub>2</sub>O<sub>5</sub>/poly-Si capacitor and advanced CVD-Al contact processes. A fully functional working device is obtained with promising cell performance. Each technology also shows its extendibility as a manufacturable module process for further scaled DRAM.
    No preview · Conference Paper · Feb 2002
  • J M Lee · H Kim · M J Oh · J H Ku · D P Jang · I Y Kim · S I Kim
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    ABSTRACT: The fear of speaking is often cited as the world's most common social phobia. The rapid growth of computer technology has enabled the use of virtual reality (VR) for the treatment of the fear of public speaking. There are two techniques for building virtual environments for the treatment of this fear: a model-based and a movie-based method. Both methods have the weakness that they are unrealistic and not controllable individually. To understand these disadvantages, this paper presents a virtual environment produced with Image Based Rendering (IBR) and a chroma-key simultaneously. IBR enables the creation of realistic virtual environments where the images are stitched panoramically with the photos taken from a digital camera. And the use of chroma-keys puts virtual audience members under individual control in the environment. In addition, real time capture technique is used in constructing the virtual environments enabling spoken interaction between the subject and a therapist or another subject.
    No preview · Article · Feb 2002 · Studies in health technology and informatics
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    ABSTRACT: For the first time, a novel robust (square-shape cylinder type) TiN/AHO (Al<sub>2</sub>O<sub>3</sub>-HfO<sub>2</sub>)/TiN capacitor with Co-silicide on landing cell pad suitable for both stand-alone and embedded DRAMs are successfully developed with 88nm (pitch 176nm) feature size, which is the smallest feature size ever reported in DRAM technology, using ArF lithography for aiming 70nm stand-alone and embedded DRAM technology. The capacitor with Toxeq of 1.5nm and leakage current of less than 1 fA/cell is achieved. The cell contact resistance is greatly improved by using Co-silicidation on landing cell pad and metal storage node contact plug, which results in high performance.
    No preview · Conference Paper · Feb 2002
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    ABSTRACT: For the first time, a novel robust (square-shape cylinder type) TiN/AHO (Al/sub 2/O/sub 3/-HfO/sub 2/)/TiN capacitor with Co-silicide on landing cell pad suitable for both stand-alone and embedded DRAMs are successfully developed with 88nm (pitch 176nm) feature size, which is the smallest feature size ever reported in DRAM technology, using ArF lithography for aiming 70nm stand-alone and embedded DRAM technology. The capacitor with Toxeq of 1.5nm and leakage current of less than 1 fA/cell is achieved. The cell contact resistance is greatly improved by using Co-silicidation on landing cell pad and metal storage node contact plug, which results in high performance.
    No preview · Conference Paper · Jan 2002
  • JH Lee · YS Kim · HS Jung · NI Lee · HK Kang · JH Ku · HS Kang · YK Kim · KH Cho · KP Sub
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    ABSTRACT: For the first time, we have integratcd poly-Si gate CMOSFETs with HfO2-Al2O3 laminate gate dielectric (EOT-14.6Angstrom) grown by Atomic Layer Deposition (ALD). The gate leakage currents are 3.7muA/cm(2) (Vg=+1.0V) for nMOSFET and 0.2 muA/cm(2) (Vg=-1.0V) for pMOSFET. These extremely low leakage currents sufficiently satisfy the specification (EOT=12similar to20Angstrom, Jg=2.2mA/cm(2)) estimated by ITRS. The fixed charge is decreased using HfO2-Al2O3 laminate gate dielectric, arid consequently flatband voltage (Vfb) shift is within 0.20V compared with the Vfb of nitrided SiO2 control. In addition, the low gate induced drain leakage (GIDL) is obtained using HfO2-Al2O3 laminate gate dielectric. Ion vs. loff plots of the planar CMOS transistor with high-k is shown for the first time in this paper. The measured saturation currents at 1.2V Vdd are 430muA/mum (I-off=10nA/mum) for nMOSFET and 160muA/mum (I-off=10nA/mum) for pMOSFET. These are the highest currents compared with previous reports for the planar poly-Si gate CMOSFETs with high-k gate dielectric.
    No preview · Conference Paper · Jan 2002
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    ABSTRACT: Attention Deficit Hyperactivity Disorder (ADHD) is a childhood syndrome characterized by short attention span, impulsiveness, and hyperactivity, which often lead ? to learning disabilities and various behavioral problems. For the treatment of ADHD, medication and cognitive-behavior therapy is applied in recent years. Although psychostimulant medication has been widely used for many years, current findings suggest that, as the sole treatment for ADHD, it is an inadequate form of intervention in that parents don't want their child to use drug and the effects are limited to the period in which the drugs are physiologically active. On the other hand, EEG biofeedback treatment studies for ADHD have reported promising results not only in significant reductions in hyperactive, inattentive, and disruptive behaviors, but also improvements in academic performance and IQ scores. However it is too boring for children to finish the whole treatment. The recent increase in computer usage in medicine and rehabilitation has changed the way health care is delivered. Virtual Reality technology provides specific stimuli that can be used in removing distractions and providing environments that get the subjects' attention and increasing their ability to concentrate. And Virtual Reality technology can hold a patient's attention for a longer period of time than other methods can, because VR is immersive, interactive and imaginal. Based on these aspects, we developed Attention Enhancement System (AES) using Virtual Reality technology and EEG biofeedback for assessing and treating ADHD children as well as increasing the attention span of children who have attention difficulty.
    Full-text · Article · Jan 2002
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    ABSTRACT: The fear of public speaking is a kind of social phobia. The patients having the fear of public-speaking show some symptoms like shame and timidity in the daily personal relationship. They are afraid that the other person would be puzzled, feel insulted, and they also fear that they should be underestimated for their mistakes. For the treatment of the fear of public speaking, the cognitive-behavioral therapy is generally used. The cognitive-behavioral therapy is the method that makes the patients gradually experience some situations inducing the fears and overcome those at last. But if the real situations inducing fears cause dangerous symptoms or the patients have difficulty in imagining the situations, the effect of this method is notably reduced. And making the situations inducing the fears to patients requires a vast amount of effort and time. In this study, we developed the public-speaking simulator and the virtual environment for the treatment of the fear of public speaking. The head-mounted display, the head-tracker and the 3-dimensional sound system were used for immersing in the virtual environment. The virtual environment of this system is suggested in a seminar room where 6 virtual audiences are seated. The virtual audiences were made with real movies and inserted into the virtual environment. The patient speaks in front of these virtual audiences and the therapist can make virtual audience members respond with some motions. Moreover, clinical tests have been made to verify the effectiveness of the treatment.
    Full-text · Conference Paper · Feb 2001
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    J.M. Lee · B.H. Cho · J.H. Ku · J.S. Kim · J.H. Lee · I.Y. Kim · S.I. Kim
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    ABSTRACT: Attention Deficit Hyperactivity Disorder (ADHD) is a disorder characterized by a persistent pattern of inattention and/or hyperactivity/impulsivity that occurs in academic, occupational, or social settings. Though the number of men having this disorder increases gradually all over the world, the treatment for ADHD is limited to stimulant medications or a cognitive behavioral treatment. This fact caused us to develop the newly system for treatment of ADHD using Virtual Reality technology. Psychotherapy using VR has some advantages that it is safer and more effective than conventional therapeutic methods. We divided subjects into control group and VR group depending on whether they will have VR therapy with HMD & Tracking system. And we compared the results of CPT (Continuous Performance Test) between before and after the experiments. So we will show the effect of this VR system and the possibility VR technology can contribute greatly to the treatment of ADHD in this paper.
    Full-text · Conference Paper · Feb 2001
  • H.B. Ahn · J.H. Ku · B.H. Cho · H. Kim · H.J. Jo · J.M. Lee · I.Y. Kim · S.I. Kim
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    ABSTRACT: As the number of automobiles is increasing, a automobile is a general means of transportation. Therefore the driving ability became an important part in normal life. But accidents or diseases cause a reduction of some people's driving ability. When they try to acquire a driver's licence, "on-road test" may be very dangerous and difficult. So therapists have tried to assess and enhance handicapped peoples driving ability in the virtual environment safely. The goal of this study is to make a virtual reality driving simulator in order to check and enhance the subjects' driving ability. The driving simulator includes a real car that we remodelled for handicapped and connecter with a personal computer (PC) for more immersion. Also it includes a module to analyze the subject's driving ability variable.
    No preview · Conference Paper · Feb 2001
  • H J Jo · J H Ku · D P Jang · M B Shin · H B Ahn · J M Lee · B H Cho · S I Kim
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    ABSTRACT: The fear of public speaking is a kind of social phobias. The patients having the fear of public speaking show some symptoms like shame and timidity in the daily personal relationship. They are afraid that the other person would be puzzled, feel insulted, and they also fear that they should be underestimated for their mistakes. For the treatment of the fear of public speaking, the cognitive-behavioral therapy has been generally used. The cognitive-behavioral therapy is the method that makes the patients gradually experience some situations inducing the fears and overcome those at last. Recently, the virtual reality technology has been introduced as an alternative method for providing phobic situations. In this study, we developed the public speaking simulator and the virtual environments for the treatment of the fear of public speaking. The head-mounted display, the head-tracker and the 3 dimensional sound system were used for the immersive virtual environment. The imagery of the virtual environment consists of a seminar room and 8 virtual audiences. The patient will speak in front of these virtual audiences and the therapist can control motions, facial expressions, sounds, and voices of each virtual audience.
    No preview · Article · Feb 2001 · Studies in health technology and informatics
  • J.H. Ku · D.P. Jang · H.J. Jo · I Y Kim · S I Kim
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    ABSTRACT: Augmented reality is a technology in which a computer-generated image is superimposed onto the user's vision of the real world. This gives the user additional information generated from the computer generated model. Especially, in the medical field, this technique can be used for understanding the spatial position of a patient's organ during an operation. We applied this technique to an image guided surgery (IGS) system and tested it with a skull phantom
    No preview · Conference Paper · Feb 2000