J H Park

Korea Advanced Institute of Science and Technology, Sŏul, Seoul, South Korea

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Publications (94)101.21 Total impact

  • W J Choi, J S Lee, M Lee, J H Park, J W Lee
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    ABSTRACT: We compared the clinical and radiographic results of total ankle replacement (TAR) performed in non-diabetic and diabetic patients. We identified 173 patients who underwent unilateral TAR between 2004 and 2011 with a minimum of two years' follow-up. There were 88 male (50.9%) and 85 female (49.1%) patients with a mean age of 66 years (sd 7.9, 43 to 84). There were 43 diabetic patients, including 25 with controlled diabetes and 18 with uncontrolled diabetes, and 130 non-diabetic patients. The clinical data which were analysed included the Ankle Osteoarthritis Scale (AOS) and the American Orthopaedic Foot and Ankle Society (AOFAS) scores, as well the incidence of peri-operative complications. The mean AOS and AOFAS scores were significantly better in the non-diabetic group (p = 0.018 and p = 0.038, respectively). In all, nine TARs (21%) in the diabetic group had clinical failure at a mean follow-up of five years (24 to 109), which was significantly higher than the rate of failure of 15 (11.6%) in the non-diabetic group (p = 0.004). The uncontrolled diabetic subgroup had a significantly poorer outcome than the non-diabetic group (p = 0.02), and a higher rate of delayed wound healing. The incidence of early-onset osteolysis was higher in the diabetic group than in the non-diabetic group (p = 0.02). These results suggest that diabetes mellitus, especially with poor glycaemic control, negatively affects the short- to mid-term outcome after TAR. Cite this article: Bone Joint J 2014;96-B:1674-80. ©2014 The British Editorial Society of Bone & Joint Surgery.
    The bone & joint journal. 12/2014; 96-B(12):1674-80.
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    ABSTRACT: InGaAs-capped InAs quantum dots (QDs) and InAs QDs were adopted for the study of the effects through growth temperature and the band structure of InAs QDs on the performance of GaAs-based QD solar cell. It has been shown that the defects due to low temperature growth resulted in the decrease of Voc, Jsc and external quantum efficiency for GaAs bulk solar cell and QD embedded solar cells. It has been also found that InAs QDs act as defects by trapping photo-generated carries which affect the carrier transport in QD solar cell. The QD solar cell with InGaAs-capped InAs QDs showed higher performance than the QD solar cell with only InAs QDs. Such result has been explained by photo-generated carrier trapping and tunneling through InGaAs QW state in InGaAs-capped InAs QDs.
    Journal of Nanoscience and Nanotechnology 04/2014; 14(4):2955-9. · 1.34 Impact Factor
  • J. H. Park, S. K. Lee
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    ABSTRACT: The intake system in an automotive engine has a short duct compared with that of the exhaust system. The filtered-x LMS (FX-LMS) algorithm has been applied to the active noise control (ANC) system in a short acoustic duct. This algorithm design is based on the FIR (finite impulse response) filter; however, it has a slow convergence issue due to a large number of zero coefficients. To improve the convergence performance, the step size of the LMS algorithm was modified from fixed to variable. However, this algorithm is still not suitable for the ANC system of a short acoustic duct because the reference signal is affected by the backward acoustic wave propagated from a secondary source. Therefore, the recursive filtered-u LMS algorithm (FU-LMS) based on the infinite impulse response (IIR) is developed to consider backward acoustic propagation. Generally, this algorithm has a stability problem. The stability issue was improved using an error-smoothing filter. In this paper, the recursive LMS algorithm with a variable step size and smoothing error filter is designed. This recursive LMS algorithm, the FU-VSSLMS algorithm, uses an IIR filter. With fast convergence and good stability, this algorithm is suitable for the ANC system in a short acoustic duct, such as the intake system of an automotive engine. This algorithm is applied to the ANC system of a short acoustic duct. The disturbance signals used as primary noise source are a sinusoidal signal embedded in white noise and the chirp signal, which has a variable instantaneous frequency. The test results demonstrate that the FU-VSSLMS algorithm has a superior convergence performance when compared with the FX-LMS and FX-LMS algorithms. The algorithm can be successfully applied to the ANC system in a short duct, such as the intake duct.
    International Journal of Automotive Technology 02/2012; 13(2). · 0.82 Impact Factor
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    ABSTRACT: A high-speed phase rotator (PR) using simple resistive interpolation is proposed for high-speed serial I/O. It operates from 1.875 to 3.45GHz and generates eight phases, spread over a full 360°, which are divided into 136 equal parts to give a resolution of 2.65°. To demonstrate the effectiveness of the proposed PR, a prototype half-rate 3.75°6.9Gbit/s serial-link receiver is designed and fabricated.
    Electronics Letters 01/2012; 48(8):429-430. · 1.07 Impact Factor
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    ABSTRACT: Presented is an ambient light sensor (ALS) for portable electronic devices. The proposed ALS employs illuminance-dependent resolution adjustment and dark current compensation auxiliary circuits to consume low power, occupy small area, as well as achieve temperature-independent linearity. The ALS can convert illuminance of up to 16Klx to digital data without temperature-dependent dark current disturbance, while consuming a maximum 75 μA current and occupying only 640 × 420 m area, including a 120 × 120 m photodiode.
    Electronics Letters 01/2011; 47(17):981-983. · 1.07 Impact Factor
  • S. KIM, J. H. PARK
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 05/2010; 26(21).
  • Transplantation 01/2010; 90. · 3.78 Impact Factor
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    ABSTRACT: A CANDU core is composed of lots of fuel channels of a pressure tube type which creates an independent flow passage different from that of a LWR. Hence, most of the aging effects for a CANDU’s operating performance originate from a crept pressure tube as its operating years proceed. Since the early 1990’s, Korea Atomic Energy Research Institute (KAERI) and Atomic Energy of Canada Limited (AECL) have cooperated to develop, verify, and demonstrate an advanced CANDU fuel, called a CANFLEX-NU (CANdu FLEXible-Natural Uranium) fuel, which has been specially designed so as to compensate for a deterioration of the heat transfer rate in a crept pressure tube and also to enhance the safety margin of it by a reduction of the maximum linear element power of a fuel bundle. Now, a CANFLEX-NU fuel is ready to be commercialized in a CANDU-6 because its design and demonstration irradiation have been completed in both of Korea and Canada. Recently, some CANDU plants are being refurbished as they are approaching their life time. One of the refurbished CANDU’s is Wolsong Unit 1 in Korea. It has been operated for 25 years and the operating power at the present time is less than 90% of a full power because of a reduction of the margin for the ROP trip set point. The most appropriate way, up-to now, to overcome such a power de-rating due to a crept pressure tube is the introduction of a CANFLEX-NU fuel into a CANDU. Before commercializing a CANFLEX-NU fuel in the Wolsong Units, it was required to estimate the economic benefit analysis for a CANFLEX-NU fuel in the Wolsong Units because the Uranium price at present is very different from that during the development phase of the CANFLEX-NU fuel. The present paper proposes an economic evaluation model for a CANFLEX-NU fuel in the Wolsong Units and its result for a CANFLEX-NU fuel are compared with that for a 37-element fuel. It was found that the introduction of a CANFLEX-NU fuel into the Wolsong units would have economical benefits due to a better operating performance even where it is assumed that the fuel fabrication cost of a CANFLEX-NU fuel is 1.4 times that of a 37-element fuel. Once the final results are obtained, they will be used as one of important parameters to determine the introduction of a CANFLEX-NU fuel in the Wolsong Units, or not.
    17th International Conference on Nuclear Engineering; 01/2009
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    ABSTRACT: As many people are westernizing their life style and food consumption habits, a number of patients who have malignant tumors which grow very rapidly and hazardously destroy the human body are increasing. Ultrasonic hyperthermia is not only one of the tumor treatment methods which employs the non-radioactive ultrasonic waves to increase the temperature at the tumor region up to to destroy and suppress tumor cells but also has been proved by many studies. Due to the rapid development of High Intensity Focused Ultrasound(HIFU), the ultrasound hyperthemia extensively boosts its applications in clinical field. For those reasons, Computed simulation factor should be needed before inspection to patients. To prove efficiency of ultrasonic hyperthermia, precise acoustic field measurement considering tissue characteristics and a heating experiment with tissue mimicking material phantom were conducted for effectiveness of simulation program. Finally, in this study, the computer simulation program verified the anticipated temperature effects induced by ultrasound hyperthermia. In the near future, it is hoped that this simulation program could be utilized to improve the efficiency of ultrasound hyperthermia.
    Journal of Biomedical Engineering Research. 01/2009; 30(5).
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    ABSTRACT: The foot-pressure while walking represents the status of the geometrical balance of the human’s musculoskeletal system. The foot-pressure in unbalanced anatomical position causes physiological disorders to the human body and accumulates stress to the musculoskeletal system. Repetitious abnormal impacts become the direct cause of vertebrae disease. The purpose of this study is to evaluate the correlation between the degree of scoliosis and the foot-pressure distribution in twenty males who have no clinical history of vertebral disease. The F-scan system(Tekscan Inc., USA, 850Hz sampling frequency) was used to measure the foot-pressure. The sole was divided into 7 regions of interest(ROI), and an analysis was performed for these ROIs. The degree of scoliosis was expressed as the angle, calculated with X-ray image, which showed lumbar vertebra number 5 to thoracic vertebra number 7. This angle was used to evaluate the correlations with the result of the foot-pressure analysis. Measurement of footpressure on the subjects was executed using the same protocol. The correlation between the measured foot-pressure and the degree of scoliosis was evaluated under a 0.05 level of significance. The results of the evaluation revealed the tendency that, as the degree of scoliosis increases, a difference in footpressure also increases. The variables used for analysis showed high correlations. The obtained results will be used to determine the occurrence of vertebra and lower limb disease and to present a qualitative evaluation basis for the rehabilitation of patients with lower limb disease.
    01/2009;
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    ABSTRACT: The quality of ultrasonic images is crucially affected by the applied ultrasonic probe; thus, it is necessary to evaluate the ultrasonic probe to achieve optimal performance. In this paper, the 3D acoustic field analysis method using a hydrophone, one of the probe evaluation methods, was performed, and the efficacy of this evaluation method for quantitative evaluation was evaluated. To acquire the acoustic field distribution of ultrasound at 7.5 MHz, a 128-multi-element medical ultrasonic array probe, that is considered to be inferior, was attached to a shaft. The shaft could be controlled in the x, y, and z directions. The hydrophone was attached in a water bath. The acoustic field distribution of each channel was displayed, and some parameters such as maximum acoustic pressure, the volume of -3dB field, and the symmetry of acoustic field were calculated. Using these parameters, the acoustic fields of normal, abnormal and simulated channels were compared. Comparing acoustic field characteristics of each channel proves that the proposed 3D acoustic field parameters are reliable and efficient to assess the performance of the ultrasonic probe.
    01/2009;
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    ABSTRACT: We have compared the performances of 980-nm InGaAs quantum-dot and quantum-well laser diode grown by molecular beam epitaxy. The quantum-dot laser diodes show superior performance to the quantum-well laser diodes in their lower threshold current density and temperature sensitivity.
    Lasers and Electro-Optics - Pacific Rim, 2007. CLEO/Pacific Rim 2007. Conference on; 09/2007
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    ABSTRACT: Programming with larger current than optimized one is often preferable to ensure a good resistance distribution of high-resistive reset state in high-density phase-change random access memories because it is very effective to increase the resistance of cells to a target value. In this paper, we firstly report that this larger current writing may conversely degrade the reset distribution by reducing the resistance of normal cells via the partial crystallization of amorphous Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub> and this degradation can be suppressed by designing a novel cell structure with a heat dissipating layer.
    VLSI Technology, 2007 IEEE Symposium on; 07/2007
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    ABSTRACT: We have successfully demonstrated a world smallest 0.25 μm<sup>2</sup> cell ITIC 64 Mb FRAM at a 130 nm technology node. This small cell size was achieved by scaling down a capacitor stack, using the following technologies: a robust glue layer onto the bottom electrode of a cell capacitor; 2-D MOCVD PZT technology, novel capacitor-etching technology; and a top-electrode-contact-free (TEC-free) scheme. The new FRAM cell is suitable for a mobile SoC (System-on-a-Chip) application. This is due to realization of four metal technology required for high-speed logic devices. As a result, the remanent polarization value of 32 μC/Cm<sup>2</sup> was achieved after full integration and the sensing window was evaluated to 370 mV at 85degC, 1.3 V.
    VLSI Technology, 2007 IEEE Symposium on; 07/2007
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    ABSTRACT: We discuss key technologies of 180 nm-node ferroelectric memories, whose process integration is becoming extremely complex when device dimension shrinks into a nano-scale. This is because process technology in ferroelectric integration does not extend to conventional shrink technology due to many difficulties of coping with MIM (metal-insulator-metal) capacitors. The key integration technologies in ferroelectric random access memory (FRAM) comprise (1) etching technology to have less plasma damage; (2) stack technology for the preparation of robust ferroelectrics; (3) capping technology to encapsulate cell capacitors; and (4) vertical conjunction technology to connect cell capacitors to the plate-line. What has been achieved from these novel approaches is not only to have a peak-to-peak value of 675 mV in bit-line potential but to ensure sensing margin of 300 mV in opposite-state retention even after 1000 hours at 150degC.
    Applications of Ferroelectrics, 2007. ISAF 2007. Sixteenth IEEE International Symposium on; 06/2007
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    ABSTRACT: In order to realize a cost-effective high density FRAM product over 64-Mb, it is inevitable to develop technologies for a small cell and large wafer size without degradation during full integration. We have successfully demonstrated a fully functional 0.16 mum<sup>2</sup> capacitor size, 64-Mb, 1T1C FRAM on an 8-inch wafer by introducing new integration technologies at 150 nm technology node. One of the key technologies is the use of novel capping layer, i.e. Al<sub>2</sub>O<sub>3</sub>, which prevents the capacitor from the degradation caused by following integration process. It was found that novel capping Al<sub>2</sub>O<sub>3</sub> layer was very effective to block chronic hydrogen diffusion, and depending on the wafer size, the effective capping layer condition is changed. By introducing a novel capping layer of Al<sub>2</sub>O<sub>3</sub> and optimizing its process conditions, the fully integrated ferroelectric capacitor for the 150 nm, 64-Mb, 1T1C FRAM on the 8-inch Si-substrate shows good ferroelectric properties such as a polarization value of 33 muC/cm<sup>2</sup> with an uniform distribution of sigma = 1.27, and the sensing window of 300 mV at 85degC.
    Applications of Ferroelectrics, 2007. ISAF 2007. Sixteenth IEEE International Symposium on; 06/2007
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    ABSTRACT: 64 Mb FRAM with 1T1C (one-transistor and one-capacitor) cell architecture has progressed greatly for a robust level of reliability. Random-single-bits appeared from package-level tests are attributed mostly to extrinsic origins (e.g. interconnection failures) rather than intrinsic ones. The extrinsic failures can be linked to two activation energies: while one is 0.27 eV originated from oxygen-vacancy movements at the top interface and grain boundary in the ferroelectric films, the other is 0.86 eV caused by imperfection in either the top-electrode contact (TEC), or the bottom-electrode contact (BEC), or both, of the cell capacitor. As a result of applying novel schemes to remove the analyzed defectives, we have the FRAM with no bit failure up to 1000 hours over both high-temperature-operating-life (HTOL) and high-temperature-storage (HTS) tests
    Reliability physics symposium, 2007. proceedings. 45th annual. ieee international; 05/2007
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    ABSTRACT: We have developed new BEOL technologies for mass-productive FRAM embedded smart card from which better device productivity was obtained. We have changed previous Al-2 plate line to new Al-1 plate line to improve bad step coverage of Al-2 plate line arising from deep via contact. Additional integration related damage on PZT capacitor by using Al-1 plate line scheme has been prevented by introducing new inter metallic dielectric (IMD) layer and new anneal process. As a result, a mass productive 1.6 V operational FRAM embedded smart card has been successfully demonstrated by the new Al-1 plate line BEOL technology.
    Integrated Ferroelectrics 04/2007; 89(1):123-130. · 0.37 Impact Factor
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    ABSTRACT: We successfully developed 256Mb Phase Change Random Access Memory (PRAM) based on 0.10μ m-CMOS technologies using ring type contact. The writing current with uniform CD process variation of Bottom Electrode Contact (BEC) was achieved by improving CMP process and developing core dielectric material. Also, the ring type contact scheme provided strong reliability such as the cycling endurance and data retention time for 256 Mb high density PRAM.
    Integrated Ferroelectrics 03/2007; 90(1):88-94. · 0.37 Impact Factor
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    ABSTRACT: Fully functional 512Mb PRAM with 0.047mum<sup>2</sup> (5.8F<sup>2</sup>) cell size was successfully fabricated using 90nm diode technology in which the authors developed novel process schemes such as vertical diode as cell switch, self-aligned bottom electrode contact scheme, and line-type Ge<sub>2</sub>Sb<sub>2</sub>Te<sub>5</sub>. The 512Mb PRAM showed excellent electrical properties of sufficiently large on-current and stable phase transition behavior. The reliability of the 512Mb chip was also evaluated as a write-endurance over 1E5 cycles and a data retention time over 10 years at 85degC
    Electron Devices Meeting, 2006. IEDM '06. International; 01/2007

Publication Stats

891 Citations
101.21 Total Impact Points

Institutions

  • 2010
    • Korea Advanced Institute of Science and Technology
      • Department of Chemistry
      Sŏul, Seoul, South Korea
  • 2009
    • Korea Atomic Energy Research Institute (KAERI)
      Daiden, Daejeon, South Korea
  • 1996–2007
    • Korea Institute of Science and Technology
      • Center for Opto-Electronic Convergence Systems
      Sŏul, Seoul, South Korea
  • 2000–2005
    • Sungkyunkwan University
      • • Samsung Medical Center
      • • Department of Surgery
      Seoul, Seoul, South Korea
  • 2000–2003
    • Korea University
      • • Department of Electrical Engineering
      • • College of Medicine
      Sŏul, Seoul, South Korea
  • 2002
    • Pohang University of Science and Technology
      • Department of Physics
      Andong, North Gyeongsang, South Korea
  • 1999–2002
    • Wonkwang University
      • • Department of Medicine
      • • College of Pharmacy
      • • Department of Oriental Pharmacy
      Riri, North Jeolla, South Korea
    • Chonbuk National University
      • College of Veterinary Medicine
      Seoul, Seoul, South Korea
  • 1994–2001
    • Seoul National University
      • • Department of Laboratory Animal Medicine
      • • College of Pharmacy
      • • College of Medicine
      Sŏul, Seoul, South Korea
  • 1994–1999
    • Seoul National University Hospital
      • Department of Radiology
      Sŏul, Seoul, South Korea
  • 1998
    • University of California, San Francisco
      San Francisco, California, United States
    • Pukyong National University
      Tsau-liang-hai, Busan, South Korea