J.H. Ku

Hanyang University, Ansan, Gyeonggi, South Korea

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Publications (26)16.6 Total impact

  • [Show abstract] [Hide abstract]
    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
    12/2009: pages 722-724;
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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
    Neural Engineering, 2007. CNE '07. 3rd International IEEE/EMBS Conference on; 06/2007
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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.
    Control, Automation and Systems, 2007. ICCAS '07. International Conference on; 01/2007
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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.
    Applied Physics Letters 02/2004; 84(7):1171-1173. · 3.79 Impact Factor
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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.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 01/2004; 22(3). · 1.27 Impact Factor
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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.
    VLSI Technology, 2003. Digest of Technical Papers. 2003 Symposium on; 07/2003
  • Schizophrenia Research - SCHIZOPHR RES. 01/2003; 60(1):173-173.
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    ABSTRACT: Virtual reality therapy (VRT), based on this sophisticated technology, has been recently used in the treatment of subjects diagnosed with acrophobia, a disorder that is characterized by marked anxiety upon exposure to heights and avoidance of heights. Conventional VR systems for the treatment of acrophobia have limitations, over-costly devices or somewhat unrealistic graphic scenes. The goal of this study was to develop an inexpensive and more realistic virtual environment (VE) in which to perform exposure therapy for acrophobia. It is based on a personal computer, and a virtual scene of a bunge-jump tower in the middle of a large city. The virtual scenario includes an open lift surrounded by props beside a tower, which allows the patient to feel a sense of heights. The effectiveness of the VE was evaluated through the clinical treatment of a subject who was suffering from the fear of heights. As a result, it was proved that this VR environment was effective and realistic at overcoming acrophobia according not only to the comparison results of a variety of questionnaires before and after treatment but also to the subject's comments that the VE seemed to evoke more fearful feelings than the real situation.
    IEEE Transactions on Information Technology in Biomedicine 10/2002; 6(3):213-7. · 1.98 Impact Factor
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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 enabled us to use virtual reality (VR) for the treatment of the fear of public speaking. There have been two techniques used to construct a virtual environment for the treatment of the fear of public speaking: model-based and movie-based. Virtual audiences and virtual environments made by model-based technique are unrealistic and unnatural. The movie-based technique has a disadvantage in that each virtual audience cannot be controlled respectively, because all virtual audiences are included in one moving picture file. To address this disadvantage, this paper presents a virtual environment made by using image-based rendering (IBR) and chroma keying simultaneously. IBR enables us to make the virtual environment realistic because the images are stitched panoramically with the photos taken from a digital camera. And the use of chroma keying allows a virtual audience to be controlled individually. In addition, a real-time capture technique was applied in constructing the virtual environment to give the subjects more interaction, in that they can talk with a therapist or another subject.
    CyberPsychology & Behavior 07/2002; 5(3):191-5. · 2.71 Impact Factor
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    ABSTRACT: We developed a virtual reality (VR) driving simulator in order to safely evaluate and improve the driving ability of spinal injury patients. The simulator is composed of an actual car, a beam projector, and a large screen. For the interface of our driving simulator, an actual car was adapted and then connected to a computer. We equipped the car with hand control driving devices especially adapted for spinal injury patients. A beam projector was used so that the subjects could see the virtual scene on a large screen set up in front of them. The virtual environment (VE) consisted of 18 sections (e.g., a speed-limited road, a straight road, a curved road, a left turn) and each section was linked naturally to the next. The subjects selected for this trial were 10 normal drivers with valid driving licenses and 15 patients with thoracic or lumbar cord injuries who had prior driving experience. For evaluation, five driving skills were measured, including average speed, steering stability, centerline violations, traffic signal violations, and driving time in various road conditions such as straight and curved roads. The normal subjects manipulated the gas pedal and the brake with their feet, while the patients manipulated a hand control with their hands. After they finished driving the whole course, the participants answered the questions such as "How realistic did the virtual reality driving simulator seem to you?" and "How much was your fear reduced?" In this study, we found that the difference in manipulation method (i.e., the patient group's hand control versus the normal driver's foot controls) does not seem to influence relative performance in the VR driving simulator, though training to improve the use of hand controls in the VR driving simulator would be useful to reduce the fear that the patients feel while driving.
    CyberPsychology & Behavior 05/2002; 5(2):151-6. · 2.71 Impact Factor
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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.
    Studies in health technology and informatics 02/2002; 85:258-60.
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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.
    VLSI Technology, 2002. Digest of Technical Papers. 2002 Symposium on; 02/2002
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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.
    Electron Devices Meeting, 2002. IEDM '02. International; 02/2002
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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.
    Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 01/2002; 20(3):865-872. · 1.43 Impact Factor
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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.
    Virtual Reality Conference, IEEE. 01/2002;
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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.
    Electron Devices Meeting, 2002. IEDM '02. International; 01/2002
  • CyberPsychology & Behavior 07/2001; 4(3):349-54. · 2.71 Impact Factor
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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.
    Engineering in Medicine and Biology Society, 2001. Proceedings of the 23rd Annual International Conference of the IEEE; 02/2001
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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.
    Engineering in Medicine and Biology Society, 2001. Proceedings of the 23rd Annual International Conference of the IEEE; 02/2001
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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.
    Engineering in Medicine and Biology Society, 2001. Proceedings of the 23rd Annual International Conference of the IEEE; 02/2001