Ki Hong Park

Chung-Ang University Hospital, Sŏul, Seoul, South Korea

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Publications (31)68.34 Total impact

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    ABSTRACT: Prolonged use of bisphosphonates in patients with osteoporosis reportedly induces femoral insufficiency fractures. However, the natural course of these fractures and how to treat them remain unknown. We determined the rates of fracture displacement and subsequent operations of undisplaced insufficiency fractures of the femur in patients treated with prolonged bisphosphonate therapy. We retrospectively collected and reviewed the clinical course of 11 patients (14 fractures) who had been diagnosed as having an insufficiency fracture of the femur after prolonged use (mean, 4.5 years; range, 3-10 years) of bisphosphonate. All patients were women with a mean age of 68 years (range, 57-82 years). The fracture site was subtrochanteric in six and femoral shaft in eight. The minimum followup was 12 months (mean, 27 months; range, 12-60 months). During the followup period, secondary displacement of the fracture occurred in five of the 14 fractures after a mean of 10 months (range, 1-19 months). Three fractures were treated with internal fixation using a compression hip screw and two with intramedullary nailing. Because five additional fractures were treated surgically owing to intractable pain, surgery was performed in 10 of 14 insufficiency fractures during the followup period. All 10 fractures healed during followup. The remaining four patients (four fractures) not undergoing any surgery had persistent pain. Femoral insufficiency fractures after prolonged bisphosphonate therapy seldom healed spontaneously and most patients had surgery either for fracture displacement or persistent pain.
    Clinical Orthopaedics and Related Research 12/2010; 468(12):3393-8. DOI:10.1007/s11999-010-1583-2 · 2.88 Impact Factor
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    ABSTRACT: Nanocomposite materials composed of poly (ethylene terephthalate) (PET) and montmorillonite (MMT) clays were prepared by in situ polymerization. Samples consisted of PET blended with various quantities of either pristine (Na+-MMT) or organically modified MMT (A10-MMT). The morphology and thermal and mechanical properties were evaluated for each sample. TEM micrographs, acquired at a 20 nm resolution, provide direct evidence of exfoliation of the clay particles into the PET matrix and show the effect of the alkyl-modifier on clay dispersibility. The dispersion of PET/A10-MMT was greater than that observed for the PET/Na+-MMT nanocomposites. The greatest degree of exfoliation occurred for PET/A10-MMT 0.5 wt %. However, PET/Na+-MMT exhibited higher crystallization temperatures and rates suggesting that Na+-MMT is a more efficient nucleating agent. Both mechanically and thermally, PET/A10-MMT nanocomposites exhibited superior properties over pure PET. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1022–1035, 2008
    Journal of Polymer Science Part B Polymer Physics 06/2008; 46(11):1022 - 1035. DOI:10.1002/polb.21435 · 2.55 Impact Factor
  • Jong Chan Lee · Dong Li · Ki Hong Park · Hong-Jin Kim
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    ABSTRACT: It is widely accepted that the coverage with high user densities can only be achieved with small cell such as Micro / Pico-cell. The smaller cell size causes frequent handoffs between cells and a decrease in the permissible handoff processing delay. This may result in the handoff failure, in addition to the loss of some packets during the handoff. In this paper we propose new handoff control scheme in the next generation mobile communications, in which the handoff setup process is done in advance before a handoff request by predicting the handoff cell based on mobile terminal’s current position and moving direction.
    08/2006: pages 1006-1011;
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    ABSTRACT: Poly(vinyl alcohol) (PVA)/poly(vinyl acetate) (PVAc) microspheres with a skin/core structure were prepared through the heterogeneous surface saponification of PVAc microspheres suspension-polymerized. The PVA skin formed through the heterogeneous saponification was hydrogel swellable in water. In addition, to obtain monodisperse PVA/PVAc microspheres having various skin/core ratios and morphologies, the ion-specificities to the heterogeneous saponification were investigated using SO, Cl−, NO, Br−, and I− for anions and Li+, Na+, and K+ for cations, respectively. The ions were not specific significantly to the rate of the heterogeneous saponification, while were related to the degree of saponification (DS). DSs had different values between by weight loss (DSw) and by proton nuclear magnetic resonance spectroscopy (DSNMR) measurements. The order of DSws was SO < Cl− < NO < Br− < I− for anions and K+ < Na+ < Li+ for cations, and that of DSNMRs, I− < Br− < NO < Cl− < SO for anions and Li+ < Na+ < K+ for cations. The differences in values between DSws and DSNMRs were caused by the dissolution of PVA skin and were significantly decreased for SO. The peaks at melting temperature of PVA were sharp and their areas were large for ions deswelling PVA skins.
    Journal of Polymer Science Part A Polymer Chemistry 06/2006; 44(11):3567 - 3576. DOI:10.1002/pola.21406 · 3.54 Impact Factor
  • Jongchan Lee · Dong Li · Ki Hong Park · Hong-Jin Kim
    Emerging Directions in Embedded and Ubiquitous Computing, EUC 2006 Workshops: NCUS, SecUbiq, USN, TRUST, ESO, and MSA, Seoul, Korea, August 1-4, 2006, Proceedings; 01/2006
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    ABSTRACT: A simple organic glass with a connection of two nonlinear optical (NLO) moieties was synthesized by condensation reaction of alkyl-substituted dibenzaldehyde with barbituric acid. This organic glass with T g of 81 °C was formed to be optically transparent films without any phase separation even at the highest chromophore content (100 wt% loading without host matrix). The sec-ond-order NLO properties with various organic glass/PMMA composition systems were systematically studied by Maker fringe method at a wavelength of 1064 nm. We demonstrate that second-order optical nonlinearity of this organic glass/PMMA system can be progressively enlarged with increasing chromophore loading from 0 to 100 wt%.
    Chemical Physics Letters 08/2005; 411(s 4–6). DOI:10.1016/j.cplett.2005.06.074 · 1.99 Impact Factor
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    ABSTRACT: N-Vinylcarbazole (VCZ) was solution-polymerized in tetrahydrofuran (THF) at 25, 35, and 45 °C using a room temperature initiator, 2,2′-azobis(2,4-dimethylvaleronitrile) (ADMVN); the effects of amount of solvent, polymerization temperature, and initiator concentration were investigated. On the whole, the experimental results corresponded to predicted ones. Room polymerization temperature using ADMVN proved to be successful in obtaining poly(N-vinylcarbazole) (PVCZ) of high molecular weight with small temperature rise during polymerization, nevertheless of free radical polymerization by azoinitiator. The polymerization rate of VCZ in THF was proportional to the 0.47 power of ADMVN concentration. The molecular weight was higher and the molecular weight distribution was narrower with PVCZ polymerized at lower temperatures. For PVCZ prepared in THF at 25 °C using ADMVN concentration of 0.00005 mol/mol of VCZ, weight-average molecular weight of 221,000 was obtained, with polydispersity index of 2.05, and degree of lightness converged to about 99 %.
    Fibers and Polymers 06/2004; 5(2):89-94. DOI:10.1007/BF02902920 · 1.11 Impact Factor
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    ABSTRACT: A series of amorphous molecules that possess both photoconductive and electro-optic properties was synthesized in order to investigate photorefractive properties of bifunctional organic-glasses. Diethylaminobenzaldehyde-diphenylhydrazone was covalently attached to 5-(4-diethylamino-benzylidene)-1,3-dimethylpyrimidine-2,4,6-trione through a flexible alkyl chain (3, 4, 5, 6 and 10 carbons) containing two ether linkages. The longer linkage not only lowered the glass transition temperature () of the molecules, but also allowed faster orientation of the chromophore. To examine the photorefractive properties, a 50 m-thick film was prepared from the mixture of a bifunctional molecule, butyl benzyl phthalate, and . The photoconductivity of this composite was as high as S/cm at 60 V/ m, and the maximum diffraction efficiency ( ) of 50 m-thick film was about 5% at 80 V/ m.
    ChemInform 05/2004; 35(19). DOI:10.1002/chin.200419217
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    Ho Sang · Woong Lee · Jahng Sang · Ki Hong Park · Nakjoong Kim · Won-Jae Joo · Hoon Dong · Choi
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    ABSTRACT: A new photoconducting polymer, diphenyl hydrazone-substituted polysiloxane, was successfully syn-thesized by the hydrosilylation method and characterized by FT-IR, 1 H-NMR, and 29 Si-NMR spectroscopy. The glass transition temperature (T g) of the polysiloxane having pendant diphenyl hydrazone was ca. 62 ο C, which enabled a component of a low-T g photorefractive material to be prepared without the addition of any plasticizers. This polysiloxane, with 1 wt% of C 60 dopant, showed a high photoconductivity (2.8 Ý 10 -12 S/cm at 70 V/µm) at 633 nm, which is necessary for fast build-up of the space-charge field. A photorefractive composite was prepared by adding a nonlinear optical chromophore, 2-{3-[2-(dibutylamino)-1-ethenyl]-5,5-dimethyl-2-cyclohexenylidene} malononitrile, into the photoconducting polysiloxane together with C 60. This composite shows a large orientation birefringence (∆n = 2.6 Ý 10 -3 at 50 V/µm) and a high diffraction efficiency of 81% at an electric field of 40 V/µm.
    Macromolecular Research 12/2003; 11(6):431-436. DOI:10.1007/BF03218972 · 1.68 Impact Factor
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    ABSTRACT: Acrylate- and styrene-derived polymers having pendant phenoxyquinones for photochromism were prepared by 2,2′-azoisobutyronitrile (AIBN)-initiated radical polymerization. Synthesis of the monomers were straightforward and the polymers were obtained in high yields in spite of the quinone moieties presented in the monomers, which usually can function as radical scavengers and/or catalysts poison. Photo-induced rearrangement from the “trans”-quinone forms to the “ana”-quinone forms readily occurred when the polymer films were irradiated with UV light.
    Journal of Photochemistry and Photobiology A Chemistry 08/2003; 160(3):151-157. DOI:10.1016/S1010-6030(03)00211-9 · 2.50 Impact Factor
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    Min Ho · Jung-Il Jin · Chul Joo Lee · Nakjoong Kim · Ki Hong Park
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    ABSTRACT: We synthesized three kinds of chromophores incorporating aromatic quinoline unit as a π-conjugated bridge in order to prepare more thermally stable nonlinear optical (NLO) chromophores than general stilbene unit. The NLO poly(methylmethacrylate) copolymer, polyimides, and polyester were successfully synthesized by these corresponding quinoline-based monomers. Their physical and optical properties were investigated by thermogravimetry, gel permeation chromatography, ultraviolet-visible spectroscopy, second harmonic generation (SHG) and electro-optic (EO) measurement. All the polymers exhibited better thermal stability, however their NLO activity was a little lower than that of general stilbene-based NLO polymers. Among three kinds of polymers, the PMMA copolymer with quinoline chromophores had the largest SHG coefficient d 33 value of 27 pm/V (at 1.064 µm) and EO coefficient r 33 value of 6.8 pm/V (at 1.3 µm).
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    ABSTRACT: Triphenylamine(TPA) substituted polysiloxane was synthesized as the hole-transporting material. Field dependence of the hole mobility and photoconductivity were measured using the time-of flight and simple DC photocurrent measurement, respectively. We demonstrated that the film of polysiloxane with pendant TPA units higher hole mobility (3.2×10 −5 cm 2 /Vsec at E=6×10 5 ) than that of the conventional poly( N -vinylcarbazole) and carbazole substituted polysiloxane. Further experiments are required to test these new materials as hole transporting layers in photorefractive and electroluminescent devices.
    Molecular Crystals and Liquid Crystals 01/2002; 377(1):329-332. DOI:10.1080/10587250211647 · 0.49 Impact Factor
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    ABSTRACT: New styryl dyes for the recording layer of digital versatile disc-recordable (DVD-R) were synthesized and analyzed by UV-vis spectroscopy and thermal analyzer. Using these dyes, we prepared two-type DVD-R discs, with/without metallic thin film between substrate and organic buffer layer. The metal-polymer deformation 4.7 GB DVD-R discs were recorded by high-power 658nm-wavelength laser diode and their recording characteristics were evaluated at 650nm wavelength. The optimum writing power and jitter value was in the range of 10 mW and 12∽13 %, respectively.
    Molecular Crystals and Liquid Crystals 10/2001; 370(1):165-168. DOI:10.1080/10587250108030062 · 0.58 Impact Factor
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    ABSTRACT: The Norbornene-derived polymers having pendant phenoxyquinones for photochromism were synthesized. The polymerizations were initiated by adding the organo-palladium catalyst to the monomer solution under nitrogen atmosphere at room temperature. The feasibility and degree of photo-induced rearrangement of the chromophores was investigated by irradiating solutions containing polymer 8 or 9 in toluene with 360 nm UV light.
    Macromolecules 05/2001; 34(13). DOI:10.1021/ma002061n · 5.93 Impact Factor
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    ABSTRACT: N-Vinylcarbazole (VCZ) was solution polymerized in 1,1,2,2,-tetrachloroethane (TCE) at 30, 40, and 50°C using a low-temperature initiator, 2,2'-azobis(2,4-dimethylvaleronitrile) (ADMVN); the effects of polymerization temperature and concentrations of initiator and solvent were investigated. On the whole, the experimental results corresponded to predicted ones. Low-polymerization temperature using ADMVN proved to be successful in obtaining poly(N-vinylcarbazole) (PVCZ) of high molecular weight with smaller temperature rise during polymerization, nevertheless of free radical polymerization by azoinitiator. The polymerization rate of VCZ in TCE was proportional to the 0.46 power of ADMVN concentration. The molecular weight was higher and the molecular weight distribution was narrower with PVCZ polymerized at lower temperatures. For PVCZ produced in TCE at 30°C using ADMVN concentration of 0.00005 mol/mol of VCZ, weight-average molecular weight of 271 000 was obtained, with polydispersity index of 1.66. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1558–1563, 2000
    Journal of Applied Polymer Science 06/2000; 76(10):1558-1563. DOI:10.1002/(SICI)1097-4628(20000606)76:103.0.CO;2-I · 1.64 Impact Factor
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    ABSTRACT: Vinyl acetate (VAc) was bulk-polymerized at 30, 40 and 50°C using a low temperature initiator, 2,2′-azobis(2,4-dimethylvaleronitrile) (ADMVN), and effects of polymerization temperature and initiator concentration were investigated in terms of polymerization behavior and molecular structures of poly(vinyl acetate) (PVAc) and corresponding poly(vinyl alcohol) (PVA) obtained by saponifying it with sodium hydroxide. Low polymerization temperature and low conversion by adopting ADMVN proved to be successful in obtaining PVA of high molecular weight. PVAc having number-average degree of polymerization (Pn) of 6,800–10,100 was obtained, whose degree of branching for acetyl group of 0.6–0.7 at 30°C, 0.8–1.1 at 40°C, and 1.0–1.9 at 50°C at conversion of below 40%. Saponifying so prepared PVAc yielded PVA having Pn of 3,100–6,200, and syndiotactic diad (S-diad) content of 51–53%. The whiteness, S-diad content, and crystal melting temperature were higher with PVA prepared from PVAc polymerized at lower temperatures.
    International Journal of Polymeric Materials 06/2000; 46(1-2):181-194. DOI:10.1080/00914030008054852 · 2.78 Impact Factor
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    ABSTRACT: Fluorescent images can be photochemically generated in thin films of the copolymer 1. This fluorescent copolymer has been designed in such a way that interaction with a photochemically formed acid HA, leading to the protonated species, quenches the fluorescence. When this quenching occurs in selected areas patterned images are obtained.
    Angewandte Chemie International Edition 05/2000; 39(10):1780-1782. DOI:10.1002/(SICI)1521-3757(20000515)112:10<1850::AID-ANGE1850>3.0.CO;2-J · 11.26 Impact Factor
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    ABSTRACT: A polymer having fluorescent pyridylbenzoxazole groups has been prepared for the purpose of detecting of metal ions. Metal ions such as Co2+, Ni2+, Cu2+ and Fe2+ were found to coordinate with the bipyridyl-like fluorescent benzoxazole chromophores. Among the metal ions investigated, the Fe2+ ion was shown to be the most effective in terms of its fluorescence quenching ability. The addition of a metal scavenger 2,2'-dipyridyl to the metal ion-quenched polymer solution resulted in the recovery of the fluorescence.
    Polymer Bulletin 02/2000; 44(1). DOI:10.1007/s002890050576 · 1.49 Impact Factor
  • Chemistry Letters 01/2000; 13(3):493-496. DOI:10.2494/photopolymer.13.493 · 1.30 Impact Factor
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    ABSTRACT: Novel methyl metacrylate (MMA) and maleimide copolymers P1 and P2 containing 5-[5'-(p-diethylaminostyryl)furfurylidene]-N,N'-diethylthiobarbituric acid in the side chain have been synthesized and their electro-optic properties were determined. Copolymers P1 and P2 exhibited the maximum r(33) values of 45.1 and 23.3 pm/V at 1.3 mu m with poling fields of 0.6 and 0.4 MV/cm, respectively. The r(33) values of the copolymers P1 and P2 retained 80% and 90% of the original values, respectively, after heating at 80 degrees C for 50 h.
    Chemistry of Materials 06/1999; 11(6):1406-1408. DOI:10.1021/cm9901313 · 8.54 Impact Factor

Publication Stats

177 Citations
68.34 Total Impact Points

Institutions

  • 2010
    • Chung-Ang University Hospital
      Sŏul, Seoul, South Korea
  • 2008
    • Korea Testing & Research Institute
      Sŏul, Seoul, South Korea
  • 2006
    • Kunsan National University
      Gunzan, North Jeolla, South Korea
  • 1996–2006
    • Korea Institute of Science and Technology
      • Electronic Materials Research Center
      Sŏul, Seoul, South Korea
  • 2004
    • Yeungnam University
      • School of Chemical Engineering
      Onyang, South Chungcheong, South Korea
  • 2001–2002
    • Hanyang University
      • • Department of Chemistry
      • • Division of Chemical Engineering and Bioengineering
      Sŏul, Seoul, South Korea