Seung Ho Choi

Korea University, Sŏul, Seoul, South Korea

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Publications (96)226.89 Total impact

  • Seung Ho Choi, Yun Chan Kang
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    ABSTRACT: The electrochemical properties of binary transition metal sulfide-reduced graphene oxide (RGO) composite powders, relevant for their performance as anode materials in sodium ion batteries, are firstly studied. (Ni,Co)O-RGO composite powders prepared by spray pyrolysis are transformed into Ni3Co6S8-RGO composite powders by a simple sulfidation process. Plate-shape nanocrystals of nickel-cobalt sulfide (Ni3Co6S8) are uniformly distributed over the crumpled RGO structure. The discharge capacities of the Ni3Co6S8-RGO composite powders for 2nd and 100th cycles at a current density of 0.5 A g-1 are 504 and 498 mA h g-1, respectively. However, the discharge capacities of the bare Ni3Co6S8 powders for 2nd and 100th cycles are 522 and 125 mA h g-1, respectively. The NiO-Co3O4 and (Ni,Co)O-RGO composite powders prepared by spray pyrolysis also show low discharge capacities of 122 and 119 mA h g-1, respectively, after 100 cycles. The high structural stability of the Ni3Co6S8-RGO composite powders during repeated sodium ion intercalation/deintercalation processes results in excellent cycling and rate performances for Na+ storage.
    Nanoscale 03/2015; DOI:10.1039/C5NR00012B · 6.74 Impact Factor
  • Seung Ho Choi, Yun Chan Kang
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    ABSTRACT: Layered WS2 nanosheet-decorated three-dimensional reduced graphene oxide (3D-RGO) microspheres are prepared as anode materials for sodium ion batteries. WO3 nanocluster-decorated 3D RGO microspheres are transformed into multi-layered WS2-3D RGO microspheres by a simple sulfidation process. The WS2-3D RGO microspheres show Na(+) storage properties superior to those of the WO3-3D RGO microspheres.
    Nanoscale 02/2015; 7(9). DOI:10.1039/c4nr06880g · 6.74 Impact Factor
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    ABSTRACT: Background To investigate the role of lymph node density (LND) as an independent prognostic factor in high-grade salivary gland cancers.Methods All 87 patients with high-grade salivary gland cancers underwent curative surgery combined with neck dissection and most of them received postoperative radiotherapy or chemoradiotherapy. LND was calculated as the ratio of positive lymph nodes to total lymph nodes harvested. Clinicopathologic variables associated with cancer-specific survival (CSS) and overall survival (OS) were identified by univariate and multivariate analyses using the Cox-proportional hazards model.ResultsSalivary duct carcinoma was the most common tumor (54%), followed by carcinoma ex pleomorphic adenoma (22%), and others. The 5-year CSS and OS were 50.9% and 49.6%, respectively, during a median follow-up of 61 months. In univariate analysis, tumor site, pathologic nodal stage, overall tumor-node-metastasis (TNM) stage, primary tumor size >3 cm, lymphovascular invasion, perineural invasion, extranodal extension, number of metastatic lymph nodes, and LND >4.0 were significant prognostic factors for CSS and OS (P < 0.05 each). Tumor site, perineural invasion, and LND were independent prognostic factors for both CSS and OS in multivariate analysis (P < 0.01).Conclusion Our findings support the prognostic value of LND for high-grade salivary gland cancers. J. Surg. Oncol. © 2015 Wiley Periodicals, Inc.
    Journal of Surgical Oncology 01/2015; DOI:10.1002/jso.23874 · 2.84 Impact Factor
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    ABSTRACT: BACKGROUND The prognostic role of swallowing-related, pretreatment subjective and objective findings has not been investigated in detail. The authors evaluated the association between pretreatment MD Anderson Dysphagia Inventory (MDADI) or videofluorographic swallowing study (VFSS) results and standard outcomes, including early recurrence and survival, in patients with treatment-naïve head and neck squamous cell carcinoma (HNSCC).METHODS Patients with HNSCC (n = 191) who received treatment at the authors' institution and were examined by self-administered MDADI questionnaires and VFSS were prospectively enrolled. MDADI and VFSS findings were analyzed in correlation with clinicopathologic variables, and factors that predicted 2-year disease-free survival (DFS) and overall survival (OS) were identified using a Cox proportional-hazards regression model.RESULTSThe 2-year OS and DFS rates were 80.1% and 77.5%, respectively. Clinical tumor (T) and lymph node (N) classifications, overall TNM stage, sex, tumor site, and educational level were significantly associated with specific MDADI subdomains, whereas Karnofsky performance score was significantly associated with all MDADI subdomains. After controlling for clinical factors, total scores, global assessment scores, and emotional and physical MDADI subscores were significantly predictive of 2-year OS and DFS (P < .05 for each). VFSS findings were not significantly associated with survival (P > .05).CONCLUSIONS The current results provide evidence of the prognostic role of the MDADI in predicting early survival outcomes in patients with HNSCC. The MDADI may be a practical and noninvasive method for the identification of patients at risk who would benefit from close follow-up. Cancer 2015. © 2015 American Cancer Society.
    Cancer 01/2015; DOI:10.1002/cncr.29245 · 4.90 Impact Factor
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    ABSTRACT: Maintenance of a remifentanil infusion during anesthetic emergence has been reported to decrease the incidence of coughing and thereby help to ensure a smooth emergence. It may, however, cause respiratory depression and possibly delay emergence. The purpose of this study was to investigate the effect of a single dose of dexmedetomidine combined with a low-dose remifentanil infusion on cough suppression during emergence from general anesthesia. American Society of Anesthesiologists physical status I-II adults undergoing elective thyroidectomy under sevoflurane anesthesia were recruited and randomly allocated to receive either dexmedetomidine 0.5 μg·kg(-1) iv (Group D, n = 70) or saline (Group S, n = 71), each combined with a low-dose remifentanil infusion ten minutes before the end of surgery. Coughing was assessed using a four-point scale. The respiratory rate (RR), heart rate (HR), and mean arterial pressure were also recorded. The incidence of coughing was lower in Group D than in Group S (64% vs 91%, respectively; mean difference 27%; 95% confidence interval [CI] 13 to 41; P < 0.001). The median cough grade at extubation was also lower in Group D. Mean arterial pressure and HR were elevated in Group S during tracheal extubation but were similar to baseline values in Group D. There was no difference in RR between the two groups throughout the study. A small delay in extubation was observed in Group D (3 minutes longer than Group S; 95% CI 2 to 4; P < 0.001). Compared with an infusion of low-dose remifentanil alone, the addition of a single dose (0.5 μg·kg(-1)) of dexmedetomidine during emergence from sevoflurane-remifentanil anesthesia was effective in attenuating coughing and hemodynamic changes and did not exacerbate respiratory depression after thyroid surgery. This trial was registered at Clinicaltrial.gov, identifier: NCT01774305.
    Canadian Journal of Anaesthesia 12/2014; 62(4). DOI:10.1007/s12630-014-0295-6 · 2.50 Impact Factor
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    ABSTRACT: It is difficult to precisely detect the lateral margin during endoscopic submucosal dissection (ESD) for signet ring cell carcinoma (SRC) because SRC often expands to lateral direction through the lamina propria. Thus, the aim of this study was to classify the intramucosal spreading patterns of SRC and to analyze the patients' clinicopathological findings according to the spreading patterns. The intramucosal spreading patterns of SRC were classified as expansive or infiltrative types. A total of 100 surgical and 42 ESD specimens were reviewed. In the surgical specimens, the proportions of expansive and infiltrative types were 44% and 56%, respectively. The infiltrative type was more commonly associated with old age, atrophy, and intestinal metaplasia in surrounding mucosa and the absence of Helicobacter pylori compared with the expansive type. In ESD specimens, the proportions of expansive and infiltrative types were each 50%. When lateral margin-positive lesions were compared with -negative lesions, larger size, residual lesion, and the lack of a neutrophil infiltration were more significantly associated with lateral margin-positive lesions. All cases with residual tumors in lateral margin-positive lesions were classified as the infiltrative type. SRC surrounded with atrophy and/or intestinal metaplasia often spreads subepithelially in the margin. This finding may suggest that a larger safety margin is necessary in this type during ESD. (Gut Liver, Published online December 5, 2014).
    Gut and liver 12/2014; DOI:10.5009/gnl14203 · 1.49 Impact Factor
  • Min-Soo Kim, Seung Ho Choi
    Journal of endourology / Endourological Society 12/2014; 29(1). DOI:10.1089/end.2015.0156 · 2.10 Impact Factor
  • Minsu Kwon, Seung‐Ho Choi
    The Laryngoscope 12/2014; DOI:10.1002/lary.25096 · 2.03 Impact Factor
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    ABSTRACT: Background To evaluate the usefulness of metabolic tumor volume (MTV) and total lesion glycolysis (TLG) measured by pretreatment fluorine 18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) as predictors of clinical outcome in hypopharyngeal squamous cell carcinoma (HPSCC).Methods Seventy-eight patients with HPSCC treated with definitive radiotherapy with or without chemotherapy underwent 18F-FDG PET/CT. Maximum standardized uptake value (SUVmax), MTV, and TLG were measured. For calculation of MTV, 3-D regions of interest were drawn and a SUV threshold of 2.5 was used for defining region. Univariate and multivariate analyses identified variables associated with disease-free survival (DFS) and overall survival (OS).ResultsMedian SUVmax, MTV, and TLG were 9.0 (range, 1.7–24.5), 20.5 (0.3–339.9) ml, and 98.9 (0.8–1877.1) g, respectively. The four-year DFS and OS were 56.1% and 52.6%, respectively. On univariate and multivariate analyses, MTV (P = 0.014) and TLG (P = 0.029) were independent prognostic factors for DFS, and MTV (P = 0.002) and TLG (P = 0.002) were independent prognostic factors for OS.ConclusionMTV and TLG measured by pretreatment 18F-FDG PET/CT may be useful in predicting the clinical outcomes of HPSCC patients undergoing radiotherapy. J. Surg. Oncol. © 2014 Wiley Periodicals, Inc.
    Journal of Surgical Oncology 12/2014; 110(7). DOI:10.1002/jso.23729 · 2.84 Impact Factor
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    ABSTRACT: BACKGROUND This study was aimed at investigating the change in the prevalence of human papillomavirus (HPV) genotypes in tonsillar squamous cell carcinoma (TSCC) and the association of the HPV genotype with the prognosis.METHODS This multicenter study included 175 patients with TSCC from 3 general hospitals between 1991 and 2009. HPV DNA was detected in paraffin-embedded tissues with genotyping chips. A survival analysis that considered clinicopathological factors, the HPV genotype, and the expression of p53, retinoblastoma protein, p16, and epidermal growth factor receptor (assessed with immunohistochemistry) was performed with Cox regression analysis.RESULTSHigh-risk HPV types were found in 23.4% of the cases. The prevalence of HPV-18 (10.3%) was as high as that of HPV-16 (10.3%). The proportion of high-risk HPV-positive tumors increased from 5.9% in 1991 to 31.6% in 2009. HPV-16 positivity was associated with an advanced stage and lymph node metastasis, whereas HPV-18 positivity was associated with old age and an advanced T stage. The survival analysis showed that old age and T classification were poor prognostic factors, whereas the expressions of various biomarkers were not associated with prognosis. HPV-18–positive cases had a poorer prognosis than HPV-16–positive cases and non–HPV-related TSCC cases. A multivariate analysis revealed that HPV-18 positivity, old age, and an advanced T stage were independent prognostic factors for predicting poor outcomes for patients with TSCC.CONCLUSIONS The proportion of HPV-positive tonsillar cancer cases has increased during the last 20 years in the Republic of Korea. The presence of HPV-18 may serve as a biomarker for a poor prognosis. Cancer 2014. © 2014 American Cancer Society.
    Cancer 10/2014; 121(4). DOI:10.1002/cncr.29086 · 4.90 Impact Factor
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    Woo Shik Jeong, Jong Woo Choi, Seung Ho Choi
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    ABSTRACT: In the present study, a fibular osteotomy guide based on a computer simulation was applied to a patient who had undergone mandibular segmental ostectomy due to oncological complications. This patient was a 68-year-old woman who presented to our department with a biopsy-proven squamous cell carcinoma on her left gingival area. This lesion had destroyed the cortical bony structure, and the patient showed attenuation of her soft tissue along the inferior alveolar nerve, indicating perineural spread of the tumor. Prior to surgery, a three-dimensional computed tomography scan of the facial and fibular bones was performed. We then created a virtual computer simulation of the mandibular segmental defect through which we segmented the fibular to reconstruct the proper angulation in the original mandible. Approximately 2-cm segments were created on the basis of this simulation and applied to the virtually simulated mandibular segmental defect. Thus, we obtained a virtual model of the ideal mandibular reconstruction for this patient with a fibular free flap. We could then use this computer simulation for the subsequent surgery and minimize the bony gaps between the multiple fibular bony segments.
    09/2014; 41(5):584-587. DOI:10.5999/aps.2014.41.5.584
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    ABSTRACT: Background Aspiration cytologic findings of mammary analogue secretory carcinoma (MASC), a newly established salivary gland neoplasm defined by a t(12;15)(p13;q25) ETV6-NTRK3 translocation, are not fully characterized to date. We report cytologic descriptions of nine cases of molecularly confirmed MASC, including two with unusual findings.Methods Aspiration smears from nine MASCs of the salivary glands were retrospectively reviewed and analyzed according to the cellular and structural features of the corresponding surgical specimens.ResultsAspiration smears of MASC generally reflected the histologic diversity of the tumors. Among usual histologic findings, a micropapillary pattern was associated with a predominance of vacuolated individual cells on aspiration smears, a papillary-cystic pattern with a predominance of thin branching papillary structures, and a microcystic pattern with a predominance of irregular sheets of eosinophilic cells. There were two unusual cases, one with three-dimensional groups of high-grade atypical cells, and one with epithelial clusters floating in a notably mucinous background. These cases represented MASC with high-grade transformation and MASC with cystadenocarcinoma-like features, respectively. The secretory activity of MASC was not prominent in the aspiration specimens.Conclusions Although unusual cases were present, most MASC cases showed characteristic cytologic findings, which could aid the cytologic diagnosis of MASC. And knowledge of the histologic spectrum of MASC, including high-grade transformation, could be valuable for cytological differential diagnoses of salivary gland tumors, and the management of patients with MASC. Diagn. Cytopathol. 2014. © 2014 Wiley Periodicals, Inc.
    Diagnostic Cytopathology 08/2014; 43(4). DOI:10.1002/dc.23208 · 1.52 Impact Factor
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    ABSTRACT: PurposeEpidural analgesia has been the preferred analgesic technique after major abdominal surgery. On the other hand, the combined use of intrathecal morphine (ITM) and intravenous patient controlled analgesia (IVPCA) has been shown to be a viable alternative approach for analgesia. We hypothesized that ITM combined with IVPCA is as effective as patient controlled thoracic epidural analgesia (PCTEA) with respect to postoperative pain control after conventional open gastrectomy.Materials and MethodsSixty-four patients undergoing conventional open gastrectomy due to gastric cancer were randomly allocated into the intrathecal morphine combined with intravenous patient-controlled analgesia (IT) group or patient-controlled thoracic epidural analgesia (EP) group. The IT group received preoperative 0.3 mg of ITM, followed by postoperative IVPCA. The EP group preoperatively underwent epidural catheterization, followed by postoperative PCTEA. Visual analog scale (VAS) scores were assessed until 48 hrs after surgery. Adverse effects related to analgesia, profiles associated with recovery from surgery, and postoperative complications within 30 days after surgery were also evaluated.ResultsThis study failed to demonstrate the non-inferiority of ITM-IVPCA (n=29) to PCTEA (n=30) with respect to VAS 24 hrs after surgery. Furthermore, the IT group consumed more fentanyl than the EP group did (1247.2±263.7 µg vs. 1048.9±71.7 µg, p<0.001). The IT group took a longer time to ambulate than the EP group (p=0.021) and had higher incidences of postoperative ileus (p=0.012) and pulmonary complications (p=0.05) compared with the EP group.ConclusionITM-IVPCA is not as effective as PCTEA in patients undergoing gastrectomy, with respect to pain control, ambulation, postoperative ileus and pulmonary complications.
    Yonsei Medical Journal 07/2014; 55(4):1106-14. DOI:10.3349/ymj.2014.55.4.1106 · 1.26 Impact Factor
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    Kwang Myung Jeon, Seung Ho Choi
    05/2014; 9(5):107-120. DOI:10.14257/ijmue.2014.9.5.10
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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 05/2014; 124(5). DOI:10.1002/lary.24470 · 2.03 Impact Factor
  • Ji Hun Park, Seung Ho Choi
    04/2014; 9(4):43-50. DOI:10.14257/ijmue.2014.9.4.05
  • Seung Ho Choi, Young L. Kim
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    ABSTRACT: Although irregular open nanostructures are typically inadequate for achieving strong light-matter interactions, incorporating irregularity can be advantageous as an alternative strategy, which is not affected by unavoidable structural variations and imperfections. In our recent study,1 we have demonstrated a framework to capitalize on natural disordered nanostructures as highly efficient optical resonators for light confinement and amplification. As one of the wondrous nanocomposite found in nature, the colors of mother-of-pearl (as also known as nacre) have been studied conventionally in terms of diffraction and interference. Surprisingly, we reveal that their color origin is highly attributed to the irregular and disordered nanostructures of nacre, in which disorder-driven resonances can be self-formed by multiple scattering without relying on well-configured closed cavities. We further demonstrate that the highly multilayered nanostructures of nacre can serve as a new class of disordered resonators to realize low lasing threshold and high energy conversion efficiency. Multiple resonances in such nanostructures, which are formed closely in frequency and space, can easily be overlapped to form hybridized states. This ensemble acting of multiple resonances drastically increases the effective cavity size, boosting light-matter interactions. For example, lasing action can be achieved using an edible food dye with a low quantum yield. Indeed, while ordered and closed resonators are commonly thought to be crucial, this biogenic approach can offer a novel strategy for designing and fabricating photonic nanostructures. The simplicity and efficiency of the natural resonators will open the new possibility of studying light propagation in complex media, measuring photoluminescence properties, and developing cost-effective photonic devices.
    03/2014
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    ABSTRACT: Objectives Postoperative surgical site infection (SSI) is a frequent postoperative complication in oral cancer patients and significantly effects patient recovery and medical expenses. The aim of study is to examine the predictors of surgical site infection (SSI) in patients undergoing major surgery for oral or oropharyngeal squamous cell carcinoma (OSCC) and to determine the relationship between perioperative albumin and the development of SSI. Subjects and methodsIn 337 consecutive patients who underwent clean-contaminated surgery for OSCC, serum albumin, glucose, and hemoglobin were perioperatively measured. Differences between groups were examined using Fisher's exact test, Mann-Whitney U test, and multiple logistic regression analysis. ResultsSSI was detected in 88 (26.1%) patients with median time to development of 10 (2–25) days. Multiple logistic regression analysis showed that only postoperative serum albumin < 2.5 g/dL were independent variables predictive of SSI (P = 0.003). The duration of hospital stay was negatively correlated with postoperative albumin (R2 = –0.302, P < 0.001). Conclusion Early postoperative hypoalbuminemia <2.5 g/dL is an independent risk factor for the development of SSI in patients undergoing oral cancer surgery. Clinicians should be aware of the implications of postoperative hypoalbuminemia and consider more intensive postoperative care in these patients.This article is protected by copyright. All rights reserved.
    Oral Diseases 03/2014; 21(2). DOI:10.1111/odi.12232 · 2.40 Impact Factor
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    ABSTRACT: Purpose: The purpose of this study was to assess the extent of the increased intracranial pressure (ICP) resulting from carbon dioxide (CO2) pneumoperitoneum and steep Trendelenburg positioning using ultrasonographic measurement of optic nerve sheath diameter (ONSD) in patients undergoing robot-assisted laparoscopic radical prostatectomy (RALRP). Methods: Twenty patients who underwent elective RALRP were enrolled in this study. ONSD and regional cerebral oxygen saturation (rSO2) were investigated noninvasively using ocular ultrasound and near-infrared spectroscopy before anesthesia (T0), 10 minutes after anesthesia induction in the supine position (T1), 10 and 30 minutes after CO2 pneumoperitoneum with 30° Trendelenburg positioning (T2 and T3), and after returning to supine position without CO2 pneumoperitoneum at the conclusion of the RALRP (T4). Results: The mean values of ONSD at all time points (T1, T2, T3, and T4) after general anesthesia significantly increased compared to that before general anesthesia (T0). During CO2 pneumoperitoneum with 30° Trendelenburg positioning (T2, T3), a significant increase of 12.5% in ONSD was observed in comparison to ONSD after anesthesia induction in the supine position without CO2 pneumoperitoneum (T1). Three patients had an ONSD value equivalent to an ICP above 20 mmHg and these patients did not experience a decrease of rSO2 or any neurologic complications. Conclusions: In patients undergoing RALRP, the increase of 12.5% in ONSD during CO2 pneumoperitoneum with steep Trendelenburg positioning was observed and thus the increase of ICP corresponding to this change of ONSD could be predicted. In 15% of the enrolled patients, ONSD increased by values equivalent to an ICP above 20 mmHg without a deterioration of rSO2 or any neurologic complications.
    Journal of endourology / Endourological Society 02/2014; DOI:10.1089/end.2014.0019 · 2.10 Impact Factor
  • 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.
    International Journal of Engineering Systems Modelling and Simulation 01/2014; 6(1/2):31 - 36. DOI:10.1504/IJESMS.2014.058421

Publication Stats

1k Citations
226.89 Total Impact Points

Institutions

  • 2015
    • Korea University
      • Department of Materials Science and Engineering
      Sŏul, Seoul, South Korea
  • 2014–2015
    • University of Ulsan
      Urusan, Ulsan, South Korea
    • Yonsei University
      Sŏul, Seoul, South Korea
    • Asan Medical Center
      Sŏul, Seoul, South Korea
  • 2013–2014
    • Ulsan University Hospital
      Urusan, Ulsan, South Korea
    • Konkuk University
      • Department of Chemical Engineering
      Sŏul, Seoul, South Korea
  • 2009–2013
    • Seoul National University
      • Department of Internal Medicine
      Sŏul, Seoul, 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
  • 2011
    • Sungkyunkwan University
      • Department of Surgery
      Sŏul, Seoul, South Korea
    • Catholic University of Korea
      Sŏul, Seoul, South Korea
  • 2010–2011
    • Purdue University
      • Weldon School of Biomedical Engineering
      ウェストラファイエット, Indiana, United States
  • 2007–2010
    • Seoul National University Hospital
      • • Department of Neurology
      • • Department of Internal Medicine
      Sŏul, Seoul, South Korea
    • Seoul National University Bundang Hospital
      Sŏul, Seoul, South Korea
    • University of Canterbury
      • Department of Electrical and Computer Engineering
      Christchurch, Canterbury, New Zealand
    • Gwangju Institute of Science and Technology
      Gwangju, Gwangju, South Korea
  • 2002–2010
    • Dongshin University
      South Korea
  • 2008
    • Yonsei University Hospital
      • Department of Internal Medicine
      Sŏul, Seoul, South Korea
  • 1998–2008
    • Korea Advanced Institute of Science and Technology
      • • Department of Biological Sciences
      • • Department of Electrical Engineering
      Sŏul, Seoul, South Korea
  • 2000
    • AT&T Labs
      Austin, Texas, United States
  • 1999–2000
    • Samsung Advanced Institute of Technology
      Usan-ri, Gyeonggi Province, South Korea
    • SK Telecom
      Sŏul, Seoul, South Korea