Seung Ho Choi

Konkuk University, Seoul, Seoul, South Korea

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Publications (72)165.08 Total impact

  • Jin Ah Kang, Seung Ho Choi
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    ABSTRACT: In this paper, we describe the influence of speaking rate on speech recognition. Speaking rate of input speech is controlled by applying a time-scale modification (TSM) algorithm and speaking rate normalisation is achieved by selecting a scale factor of TSM. The scale factor selection for training and testing of a speech recognition system is performed based on a maximum likelihood criterion during HMM decoding. From the experimental results, we showed that optimal selection of a TSM scale factor in speaking rate normalisation can reduce WER by 47.6% compared to the baseline.
    Int. J. of Engineering Systems Modelling and Simulation. 01/2014; 6(1/2):31 - 36.
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    ABSTRACT: Objectives: This study evaluated the efficacy of commonly used treatment modalities and determined predictors of treatment outcome for contact granuloma Study Design: Retrospective study Methods: Twenty otolaryngologists from 18 university hospitals reviewed the medical records of their own contact granuloma patients for the most recent 4 years. To be enrolled as a valid case, each treatment had to continue for at least 3 months. After excluding intubation granuloma, 590 cases of contact granuloma were analyzed. Treatment outcomes were assessed as complete response (CR), marked response (MR), partial response (PR) and no response. The chi-square test was used to compare the efficacy of each treatment modality and logistic regression to determine the predictors of treatment outcome Results: The long-term outcomes of good response (GR) (sum of CR and MR) rates after each treatment were 20.5% for observation, 31.6% for steroid inhaler, 44.0% for PPI, 44.3% for voice therapy, 60.0% for surgical removal, and 74.2% for botulinum toxin injection. Voice therapy, PPI, and botulinum toxin had more good responses than simple observation for the long term outcome (P < 0.05). Surgical removal had a significantly higher recurrence rate (37.1%) than simple observation (10.3%) (P < 0.05) Conclusions: Voice therapy or PPI are recommended as first-line treatments. Surgical removal should be reserved for selected patients because of the high chance of recurrence. Botulinum toxin injection can be used not only for primary cases but also for refractory cases with an expected high response rate.
    The Laryngoscope 10/2013; · 1.98 Impact Factor
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    ABSTRACT: Inverse correlations of high serum bilirubin with metabolic and cardiovascular disease have been suggested. However, anti-atherogenic effects of bilirubin have not been well-established in terms of the presence of plaques and stenosis identified in coronary computed tomography (CT). A cross-sectional study was conducted on 2862 men who were free of cardiovascular disease and underwent coronary CT as part of a routine medical screening examination. Coronary stenotic lesions were considered to be incidences of coronary atherosclerosis, and stenosis was classified as stenosis <50% or ≥50%, according to degree of stenosis. The prevalences of coronary atherosclerosis and stenosis ≥50% in subjects with elevated bilirubin levels (>1.2 mg/dL) were lower than those in subjects with normal bilirubin levels (≤1.2 mg/dL) (19.9% vs. 27.9%, p < 0.001, 8.5% vs. 10.3%, p = 0.044). Bilirubin was inversely associated with total plaques (odds ratio [OR] 0.59, 95% confidence interval [CI] 0.48-0.73 in the 4th quartile vs. 1st quartile) and calcified plaques (OR 0.60, 95% CI 0.49-0.75) in univariate analysis. After adjusting for traditional risk factors, it was found that coronary atherosclerosis (OR 0.73, 95% CI 0.56-0.94 in the 4th quartile vs. 1st quartile) and calcified plaque (OR 0.66, 95% CI 0.53-0.84) were inversely associated with the bilirubin grade in a dose-dependent manner. The serum bilirubin level was inversely associated with coronary atherosclerosis and calcified plaques in a dose-dependent manner. These results suggested that serum bilirubin could be used as a protective biomarker of coronary artery disease.
    Atherosclerosis 10/2013; 230(2):242-8. · 3.71 Impact Factor
  • Young Han Lee, Seung Ho Choi
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    ABSTRACT: A bandwidth extension (BWE) algorithm from wideband to superwideband (SWB) is proposed for a scalable speech/audio codec that uses modified discrete cosine transform (MDCT) coefficients as spectral parameters. The superwideband is first split into several subbands that are represented as gain parameters and normalized MDCT coefficients in the proposed BWE algorithm. We then estimate normalized MDCT coefficients of the wideband to be fetched for the superwideband and quantize the fetch indices. After that, we quantize gain parameters by using relative ratios between adjacent subbands. The proposed BWE algorithm is embedded into a standard superwideband codec, the SWB extension of G.729.1 Annex E, and its bitrate and quality are compared with those of the BWE algorithm already employed in the standard superwideband codec. It is shown from the comparison that the proposed BWE algorithm relatively reduces the bitrate by around 19% with better quality, compared to the BWE algorithm in the SWB extension of G.729.1 Annex E.
    Advances in Multimedia 07/2013; 2013.
  • Chul Min Sim, Seung Ho Choi, Yun Chan Kang
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    ABSTRACT: LiMn2O4 yolk-shell powders with a distinctive filled-core@void@shell configuration are prepared by a spray pyrolysis process. The yolk-shell powders have discharge capacities of 127, 120, and 115 mA h g(-1) after 200 cycles, even at high current densities of 3 C (360 mA g(-1)), 5 C, and 10 C, respectively.
    Chemical Communications 05/2013; · 6.38 Impact Factor
  • Seung Ho Choi, Yun Chan Kang
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    ABSTRACT: SnO2-CuO composite nanorods with a Janus structure were prepared by one-step flame spray pyrolysis. High-aspect-ratio SnO2 nanorods were positioned on one side of the spherical CuO powder. The mean length of the rod-shaped crystals decreased from 200 to 20 nm when the SnO2 content in the composite powders decreased from 70 to 10 wt%. Initially, SnO2-CuO composite nanopowders formed from the vapors in the high-temperature diffusion flame by surface growth and coagulation. Phase separation of the composite nanopowders occurred and rod-like Janus structures evolved during the growth of SnO2 and CuO crystals in the quenching process. The maximum charge capacities of pure SnO2 and the composite powders with SnO2/CuO of 90/10, 70/30, and 50/50 were 547, 499, 493, and 316 mA h g(-1), respectively, at a high current density of 3000 mA g(-1). The corresponding capacity retentions after 50 cycles were found to be 39, 47, 80, and 85%, respectively. The decrease in the charge capacity with increasing current density was slower in SnO2-CuO (70/30) composite powders than in pure SnO2. The Janus-structured SnO2-CuO (70/30) composite powders showed a high charge capacity and excellent cycling performance at high current densities.
    Nanoscale 04/2013; · 6.73 Impact Factor
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    ABSTRACT: An ultrasonic sensor-based personalized multichannel audio rendering method is proposed for multiview broadcasting services. Multiview broadcasting, a representative next-generation broadcasting technique, renders video image sequences captured by several stereoscopic cameras from different viewpoints. To achieve realistic multiview broadcasting, multichannel audio that is synchronized with a user’s viewpoint should be rendered in real time. For this reason, both a real-time person-tracking technique for estimating the user’s position and a multichannel audio rendering technique for virtual sound localization are necessary in order to provide realistic audio. Therefore, the proposed method is composed of two parts: a person-tracking method using ultrasonic sensors and a multichannel audio rendering method using MPEG Surround parameters. In order to evaluate the perceptual quality and localization performance of the proposed method, a MUSHRA listening test is conducted, and the directivity patterns are investigated. It is shown from these experiments that the proposed method provides better perceptual quality and localization performance than a conventional multichannel audio rendering method that also uses MPEG Surround parameters.
    International Journal of Distributed Sensor Networks 04/2013; 2013. · 0.92 Impact Factor
  • Eun Key Kim, Sung Jun Yang, Seung Ho Choi
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    ABSTRACT: BACKGROUND: When the required dimension of skin paddle of a pectoralis major musculocutaneous (PMMC) flap is very small, its survival often becomes questionable. We introduce a simple technique which enlarges the practical dimension of a very small skin paddle, leading to ensure the survival of a PMMC flap. METHOD AND RESULT: A PMMC flap size of 1.5 × 4 cm was required for repair of leakage which developed 2 weeks after the primary ablative surgery for hypopharyngeal cancer. The skin paddle was designed in the size of 4.5 × 7 cm and was deepithelized except the original dimension. After the skin edge was sutured to the defect margin, the deepithelized dermal portion covered the repair site to enhance the suture. CONCLUSION: The effective dimension of a very small skin paddle can be quite enlarged thus increasing the possibility of capturing perforators. This could decrease the risk of avulsion during flap transfer and provide backing of the repair site. © 2012 Wiley Periodicals, Inc. Head Neck, 2012.
    Head & Neck 03/2013; · 2.83 Impact Factor
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    ABSTRACT: Amorphous V2O5 powders with zirconia (ZrO2) dopant are prepared by one-pot spray pyrolysis at temperatures above the melting temperature of V2O5. The powders with 7 wt% ZrO2 are completely spherical and dense with a clean surface, on which crystals of pure V2O5 powders are scarcely observed. The V2O5 powders with 7 wt% ZrO2 have uniformly distributed V and Zr components. The uniformly distributed Zr component disturbs the crystallization of V2O¬5 during the quenching of the melted powders. These powders also give smooth initial discharge curves with a single slope, which is typical to amorphous materials. The discharge capacities of the V2O5 powders with 7 wt% ZrO2 are 309, 269, and 222 mAh g-1 after the 1st, 2nd, and 50th cycles, respectively, even at a high current density of 294 mA g-1. The capacity retention measured after the first cycle is 83% after 50 cycles.
    ACS Applied Materials & Interfaces 03/2013; · 5.90 Impact Factor
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    Archives of plastic surgery. 07/2012; 39(4):439-41.
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    ABSTRACT: We review our recent studies on random lasers for spectroscopic and biosensing approaches, using the unique combination of its intriguing physical principle, its simplicity of realization, and its sensitivity to nanoscale perturbations.
    Biomedical Optics; 04/2012
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    ABSTRACT: In many cases of trapdoor-type orbital blowout fracture, the bony segment has a stable hinge consisting of a greenstick fracture and the sinus mucoperiosteum that is attached to the intact orbital wall. If the displaced bony segment opposite the hinge will be reduced into its original position and will be fixed onto the unaffected bone, the orbital fracture may be reconstructed via the internal fixation of the bony segment itself rather than requiring substitution with an alloplastic implant or a bone graft. A retrospective study was conducted from January 2008 to February 2010 in 34 patients with blowout fracture, via retrospective chart review, including detailed preoperative and postoperative evaluations, age, sex, symptoms, and signs, and based on the postoperative complications. The subciliary, transconjunctival, and transcaruncular approaches were used to expose the orbital floor under general anesthesia. The herniated orbital soft tissue was carefully reduced. The displaced bony segment was carefully pulled up and placed in its original anatomic position with a skin hook. A small absorbable mesh plate was inserted between the normal orbital wall and the bony segment, tangential to the edge of the bony defect at the dependent portion. Postoperative examinations such as the traction and forced duction tests showed no eye movement limitation and surgical complications. During the follow-up period, no complications occurred, and the orbital wall was accurately reconstructed in its original anatomic position, as confirmed by postoperative computed tomography scans. The advantages of internal fixation include anatomic reconstruction of the orbital wall, preservation of the original orbital bone and the mucoperiosteum of the sinus resulting in rapid wound healing and normal mucus drainage function of the sinus, simplicity of the procedure, and the absence of surgery-related complications. This technique is presented as one of the preferred treatments for trapdoor-type orbital blowout fracture.
    The Journal of craniofacial surgery 11/2011; 22(6):2263-7. · 0.81 Impact Factor
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    ABSTRACT: Helicobacter pylori causes numerous extragastric manifestations, including coronary heart disease. The coronary artery calcification (CAC) score, measured using computed tomography (CT) has been used as a screening test for coronary atherosclerosis. This study investigated the association between H. pylori seropositivity and CAC scores in a screening population. Patients who underwent a health checkup between October 2003 and July 2007 and who did not have a history of ischemic heart disease were enrolled in the study. Subjects were screened with a multidetector CT scan to determine the CAC score and for anti-H. pylori antibody immunoglobulin G; traditional risks for coronary heart disease were evaluated using a structured questionnaire, anthropometric measurements, and laboratory tests. Of the 2,029 subjects enrolled (1,295 males), 1,214 (59.8%) subjects were H. pylori positive and 815 were H. pylori negative. There were no significant differences in the baseline characteristics of the seropositive and seronegative patients. When the CAC presence or absence scores were considered, multivariate analysis revealed that H. pylori seropositivity was statistically associated with the presence of CAC and that this association was stronger in the mild CAC score category. H. pylori seropositive patients are at a higher risk for coronary atherosclerosis regardless of traditional cardiovascular risk factors. This association is particularly applicable for early coronary atherosclerosis.
    Gut and liver 09/2011; 5(3):321-7. · 1.31 Impact Factor
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    ABSTRACT: In this study, we investigated the enhanced sensing performance of a localized surface plasmon resonance (LSPR) biosensor by employing metal-dielectric double-layered subwavelength grating structures. The numerical results showed that the LSPR substrate with a dielectric spacer can provide not only a better sensitivity but also a significantly improved reflectance characteristic. While the presence of metallic gratings leads to a broad and shallow reflectance curve inevitably, the dielectric spacer can prevent the propagating surface plasmons from being interfered by the locally enhanced fields excited at the gold gratings, finally resulting in a strong and deep absorption band at resonance. Therefore, the proposed structure could potentially open a new possibility of the enhanced LSPR detection for monitoring biomolecular interactions of low molecular weights.
    Applied Optics 06/2011; 50(18):2846-54. · 1.69 Impact Factor
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    ABSTRACT: Although an inverse relationship between abdominal adiposity and pulmonary function has been suggested, direct measurement of abdominal adipose tissue has rarely been attempted. Our object is to determine the impact of abdominal adiposity on pulmonary function by directly measuring abdominal adipose tissue with abdominal computed tomography (CT). In this cross-sectional study, we included never-smokers between the ages of 18 and 85 yr, who had undergone spirometry and abdominal adipose tissue analysis with CT scans during November 1, 2005 to October 31, 2009 as part of the comprehensive health examination. Among a total of 3,469 participants, 890 (25.7%) were male. The mean body mass index and waist circumference among males and females were 24.6 kg/m(2) and 87.8 cm and 23.0 kg/m(2) and 83.0 cm, respectively. Although total adipose tissue (TAT) of the abdomen in males (269.1 cm(2)) was similar to that in females (273.6 cm(2)), the ratio of visceral adipose tissue (VAT)/subcutaneous adipose tissue (SAT) was different; 0.99 in males and 0.50 in females. In males, TAT, SAT, and VAT were inversely associated with the absolute value of forced vital capacity (FVC), and TAT and VAT were inversely associated with forced expiratory volume in one second (FEV(1)). However, in females, TAT and VAT, but not SAT, were inversely associated with absolute FVC and FEV(1) values. In conclusion, the amount of abdominal adipose tissue directly measured using CT is inversely associated with lung function.
    Journal of Korean medical science 06/2011; 26(6):771-7. · 0.84 Impact Factor
  • Jae-Won Lee, Seung Ho Choi
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    ABSTRACT: Indoor audio feedback is a common problem in many audio amplification systems. The audio feedback can be out of control in some indoor conditions, which results in howling. Also, the howling frequency is subject to variation by the changes of indoor environments. Most conventional methods attempt to eliminate the howling, but they do not provide a way to predict the occurrence of howling. This paper presents a novel method to predict the howling frequency using temporal variations in power spectrum. KeywordsHowling–acoustic feedback circuit–moving average–power spectrum
    04/2011: pages 46-51;
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    ABSTRACT: An anorectal melanoma (AM) is a very rare tumor. However, sufficient data supporting effective surgical options for the disease do not exist. This retrospective review aimed to analyze treatment outcomes for an AM. From June 1999 to December 2008, we retrospectively reviewed a prospectively collected consecutive series of 19 patients who had undergone a surgical resection for an AM at a single institute. Surgical method and clinicopathological factors were analyzed. The median age was 61.4 years (range, 46 to79 years). Main symptoms were an anal mass, hematochezia, perianal pain, tenesmus, fecal incontinence, and bowel habit change. The average duration of symptoms before diagnosis was 7.8 months (range, 1 to 36 months). S-100 and HMB-45 were positive in all patients, even in non-melanin pigmentation. There were 12 abdominoperineal resections (APRs) and 7 wide local excisions (WEs). The APR showed longer overall survival when compared with the WE (64.1 months vs. 10.9 months, P < 0.001). No patients who underwent a WE survived more than 13 months. A high index of suspicion is necessary to establish the diagnosis for an AM in patients with anal symptoms, and S-100 and HMB-45 can be useful markers for an AM. Even with the small number of cases and the short follow-up, our data suggest that an APR for an AM may provide longer survival than a WE.
    Journal of the Korean Society of Coloproctology 02/2011; 27(1):27-30.
  • Jae-Won Lee, Seung Ho Choi
    Communication and Networking - International Conference, FGCN 2011, Held as Part of the Future Generation Information Technology Conference, FGIT 2011, in Conjunction with GDC 2011, Jeju Island, Korea, December 8-10, 2011. Proceedings, Part II; 01/2011
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    ABSTRACT: In this paper, a virtual elevation method of a sound source is proposed for a stereo loudspeaker reproduction. To achieve this goal, the proposed method first applies a head-related transfer function (HRTF) to the sound source to vertically localize it. Then, spectral notch filtering followed by directional band boosting is used for the further elevation of the sound source. In particular, a filter having three notches is designed by analyzing the spectral characteristics estimated from the measured HRTF database and by investigating the effect of spectral boosting on the perception of sound elevation. To evaluate the elevation performance of the proposed method, subjective listening tests are subsequently conducted using several sound sources, including male and female speech, as well as guitar, violin, and pop music. It is shown from the tests that the sound sources processed by the proposed method are most likely to be perceived as if they are played from stereo loudspeakers located at around 20°, even though the stereo loudspeakers are actually located on a horizontal plane, i.e., 0º.1
    IEEE Transactions on Consumer Electronics 01/2011; 57(4):1915-1920. · 1.09 Impact Factor
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    ABSTRACT: In this paper, a packet loss concealment (PLC) algorithm for CELP-type speech coders is proposed in order to improve the quality of decoded speech under burst packet loss conditions in a wireless sensor network. Conventional receiver-based PLC algorithms in the G.729 speech codec are usually based on speech correlation to reconstruct the decoded speech of lost frames by using parameter information obtained from the previous correctly received frames. However, this approach has difficulty in reconstructing voice onset signals since the parameters such as pitch, linear predictive coding coefficient, and adaptive/fixed codebooks of the previous frames are mostly related to silence frames. Thus, in order to reconstruct speech signals in the voice onset intervals, we propose a multiple codebook-based approach that includes a traditional adaptive codebook and a new random codebook composed of comfort noise. The proposed PLC algorithm is designed as a PLC algorithm for G.729 and its performance is then compared with that of the PLC algorithm currently employed in G.729 via a perceptual evaluation of speech quality, a waveform comparison, and a preference test under different random and burst packet loss conditions. It is shown from the experiments that the proposed PLC algorithm provides significantly better speech quality than the PLC algorithm employed in G.729 under all the test conditions.
    Sensors 01/2011; 11(5):5323-36. · 2.05 Impact Factor

Publication Stats

700 Citations
165.08 Total Impact Points

Institutions

  • 2013
    • Konkuk University
      • Department of Chemical Engineering
      Seoul, Seoul, South Korea
    • University of Ulsan
      Urusan, Ulsan, South Korea
    • Ulsan University Hospital
      Urusan, Ulsan, South Korea
  • 2003–2013
    • Seoul National University of Technology
      • • Department of Electronic IT Media Engineering
      • • Department of Electric Information System Engineering
      Sŏul, Seoul, South Korea
  • 2012
    • Catholic University of Korea
      • Department of Plastic Surgery
      Sŏul, Seoul, South Korea
  • 2011
    • Gwangju Institute of Science and Technology
      • School of Information and Communications
      Kwangju, Gwangju, South Korea
    • Sogang University
      • Department of Mechanical Engineering
      Sŏul, Seoul, South Korea
  • 2010–2011
    • Purdue University
      • Weldon School of Biomedical Engineering
      West Lafayette, IN, United States
  • 2009–2010
    • Seoul National University
      • School of Computer Science and Engineering
      Seoul, Seoul, South Korea
  • 2002–2010
    • Dongshin University
      South Korea
  • 2007–2009
    • Seoul National University Hospital
      • Department of Internal Medicine
      Seoul, Seoul, South Korea
    • Seoul National University Bundang Hospital
      Sŏul, Seoul, South Korea
    • University of Canterbury
      Christchurch, Canterbury Region, New Zealand
  • 1998–2008
    • Korea Advanced Institute of Science and Technology
      • • Department of Biological Sciences
      • • Department of Electrical Engineering
      Seoul, Seoul, South Korea
  • 2000
    • AT&T Labs
      Austin, Texas, United States