J. Baek

Yonsei University Hospital, Sŏul, Seoul, South Korea

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Publications (34)60.32 Total impact

  • S Kim, J Park, J Baek
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    ABSTRACT: The blade angle distribution from the inlet to outlet of an impeller in a centrifugal compressor is known to have significant influence on its flow characteristics. With the aim of understanding the effect of the blade angle distribution, particularly on performance, loss generation, and operating range, four different blade angle distributions were defined with fixed inlet and outlet blade angles, and numerical calculations were conducted over their whole operating ranges, as defined by their stall points and choke conditions. The impeller blade Blade80, which has the smallest variation of blade angle and is relatively radial, was found to exhibit the smallest wall skin friction loss due to its small surface area but the highest blade loading loss. Further, the flow separation near the hub at the suction side and the tip and resulting energy loss give rise to the smallest stall margin of the blades. In contrast, Blade110, which has the largest variation of blade angle, exhibits the largest wall skin friction and hub-to-shroud loading losses but the lowest blade loading loss because the flow from the inlet to the outlet is well guided. As the flow coefficient increases, the performance of Blade110 steeply decreases. The poor performance of Blade110 at high mass flowrates can be explained in terms of flow blockage at the narrow throat. An attempt is made to explain the relationships between the blade angle distributions and the flow characteristics, loss generation, and performance of these impellers.
    Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy 03/2012; 226(2):208-217. · 0.64 Impact Factor
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    ABSTRACT: From both spectral analysis and least square fitting on the Earth's polar motion, it has been found that 500-day period component exists with average amplitude of 20 milliarcseconds. Its existence is readily recognized in the residual polar motion time series subtracted of the Chandler and annual components. Prediction of polar motion is enhanced with assuming the existence of this component (r.m.s. error reduction by 50 percent).
    AGU Fall Meeting Abstracts. 12/2011;
  • J. Baek, S. Na, P. Park, B. Choi, S. Cho
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    ABSTRACT: We investigated the effects of different ocean tide models on the prediction of the ocean tide loading in Korean peninsula. The western part of Korean peninsula has large tidal range of water level and complicated rias coasts, so that accurate ocean tidal loading models are necessary for high-precise geodetic applications. The information of coastlines and the accuracy of the ocean tide model are key factors for high accurate ocean tide loading models. Recently, the global ocean tide models based on extensive observations and local tide models for the local area have been released. In this study, we analyzed the accuracy of ocean tide loadings with various ocean tide models. We developed a program for the convolutions of the mass of ocean tide and the load Green's functions. Comparing the computations with GOTIC2, the differences of vertical deformations due to M2 constituent were less than 0.4 mm in the case of the same ocean tide model. The five global ocean tide models, NAO99b, FES2004, DTU10, EOT11a and HAMTIDE, one regional tide model, NAO99Jb, and two local tide models were tested. The tests were performed in two ways. One was to use only global ocean tide models and the other one combined each global tide model and local tide model. Finally, we compared the computations with the GPS observations.
    AGU Fall Meeting Abstracts. 12/2011;
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    ABSTRACT: Background: All-trans-retinoic acid (RA) and all-trans-retinol (ROL) are not widely used as anti-wrinkle agents due to their irritancy and photo-stability, respectively. Therefore, the safety and photo-stability in the development of RA or ROL derivatives have been an important issue. Aim: To identify the efficacy of retinyl retinoate as an anti-aging agent of cosmetics in treating females over 30 years old with periorbital wrinkles. Methods: The clinical study was a prospective, double-blind, randomized, and controlled study with a total of 11 Korean women. At every 4 weeks, the effectiveness was assessed with a global photodamage score, photographs, and image analysis using replicas and visiometers. The dermal distance and intensity was also evaluated using Dermascan C. Results: A statistically significant improvement in facial wrinkles (P<0.05) in eleven volunteers was observed in a clinical trial. The successive application of 0.06% retinyl retinoate cream for 3 months showed decreased depth and area of wrinkles in comparison with 0.075% retinol cream. The visual wrinkle improvement and the maximum roughness improvement rate (R2) for retinyl retinoate cream were 22% higher than that of retinol cream after 12 weeks. A statistically significant increase was observed after 8 and 4 weeks for dermal distance and dermal intensity, respectively (P<0.05). Conclusions: Retinyl retinoate had characteristic features of new anti-aging agents, and effectively improved facial wrinkle conditions.
    Skin Research and Technology 03/2011; · 1.41 Impact Factor
  • J. Baek, Y. Lee, H. Jee, K. Kim, M. Sohn
    Journal of Allergy and Clinical Immunology - J ALLERG CLIN IMMUNOL. 01/2011; 127(2).
  • European Journal of Cancer - EUR J CANCER. 01/2011; 47.
  • European Journal of Cancer - EUR J CANCER. 01/2011; 47.
  • S Kim, J Park, K Ahn, J Baek
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    ABSTRACT: In this article, an effective optimization performed by the authors, at the design mass flowrate, of a vaned centrifugal compressor using the response surface method is presented. The optimization process was carried out consecutively for the impeller and the diffuser. As a result of the optimization process, the efficiency and pressure ratio of the optimized model were found to be better than those of the original model because of some improvements in flow characteristics. Compared with the original model, dramatic changes in the pressure and entropy contours could be obtained in the optimized model. In order to determine the performance in the off-design operating conditions, an off-design analysis was carried out. Also, the numerical calculations in this optimization process are validated by the experimental results and show good agreement with the experimental results except under choking conditions.
    Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy 03/2010; 224(2):251-259. · 0.64 Impact Factor
  • Journal of Allergy and Clinical Immunology - J ALLERG CLIN IMMUNOL. 01/2010; 125(2).
  • Journal of Allergy and Clinical Immunology - J ALLERG CLIN IMMUNOL. 01/2010; 125(2).
  • Journal of Allergy and Clinical Immunology - J ALLERG CLIN IMMUNOL. 01/2010; 125(2).
  • Fuel and Energy Abstracts 01/2010; 78(3).
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    ABSTRACT: With expanding commercial interests from various application areas, the production of carbon nanotubes (CNTs) in large scale is expected to grow rapidly. The inevitable release of CNTs into the environment and identification of the cytotoxicity of dispersed CNTs prompt the necessity of understanding their transport behavior in porous media. In this study, one-dimensional column experiments were conducted to assess the transport and retention of multi-wall nanotubes (MWNTs) in water-saturated 40-50 mesh Ottawa sand as a function of of tube length. In order to avoid damages to nanotube length by ultrasonication or superacids (e.g., HNO3), a chemical modification method involving a mild acid treatment was adopted to prepare suspensions of MWNTs with three different manufacture-reported (MR) lengths (0.5-2, 10-20, and 50 mum). For each experiment, a pulse (e.g., 5 pore volumes) of MWNT suspension was introduced into the column, followed by 3 pore volumes of MWNT-free solution elution. Measured concentrations of MWNTs in effluent and dissected solid samples were used to construct effluent breakthrough curves and retention profiles, respectively. For an input concentration of ca. 90 mg/L, MWNTs breakthrough concentrations decreased with the increasing MR length. Even with an MR length of 50 mum, MWNTs were readily transported through the packed bed, where ca. 80% of total injected nanotubes passed through the column. While the retention of MWNTs increased with MR length, concentrations of retained nanotubes decreased hyper-exponentially with distance from the column inlet. Further analysis of these findings suggests that clean-bed filtration theory alone is not sufficient to describe MWNT transport and retention behavior in a water-saturated quartz sand.
    AGU Fall Meeting Abstracts. 12/2009;
  • S. Na, J. Cho, J. Baek, Y. Kwak, S. Yoo
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    ABSTRACT: New parts of KASI research are the followings - (1) polar motion prediction, (2) data analysis for Chandler period and Q value and other characters of polar motion, (3) theoretical calculation of Chandler period, (4) relation between earthquake occurrence and earth rotation. Currently KASI estimates the pole position with accuracy comparable to IERS bulletin.
    AGU Fall Meeting Abstracts. 12/2009;
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    ABSTRACT: We present a new hierarchical electromagnetic (EM) land surface classification scheme by the integration of high-resolution multi-spectral optical and polarimetric SAR images. In addition to spectral characteristics of the reflected surface conventionally extracted from multispectral images, backscattered amplitude of radar image is used to classify land surface in terms of EM parameters such as permittivity, conductivity, permeability, surface roughness, correlation length, and specific attenuation parameters. A hybrid classification algorithm is developed, in which direct field and lab EM measurements data as well as data from literatures are used. The new classification scheme gives us new insight on the wave propagation modeling for a mobile communication and electrical hazard estimation.
    AGU Spring Meeting Abstracts. 05/2009;
  • Ejc Supplements - EJC SUPPL. 01/2009; 7(2):193-194.
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    ABSTRACT: This randomised multicentre phase II study was conducted to investigate the activity and safety of two oral fluoropyrimidines, capecitabine or S-1, in elderly patients with advanced gastric cancer (AGC). Elderly (>or=65 years) chemo-naive patients with AGC were randomly assigned to receive capecitabine 1250 mg m(-2) two times daily on days 1-14 every 3 weeks or S-1 40-60 mg two times daily according to body surface area on days 1-28 every 6 weeks. Ninety-six patients were enrolled and 91 patients were randomised to capecitabine (N=46) or S-1 (N=45). Overall response rate, the primary end point, was 27.2% (95% CI, 14.1-40.4, 12 of 44 assessable patients) with capecitabine and 28.9% (95% CI, 15.6-42.1, 13 of 45) with S-1. Median times to progression and overall survival in the capecitabine arm (4.7 and 9.5 months, respectively) were similar to those in the S-1 arm (4.2 and 8.2 months, respectively). The incidence of grade 3-4 granulocytopenia was 6.8% with capecitabine and 4.8% with S-1. Grade 3-4 nonhaematologic toxicities were: asthenia (9.1% with capecitabine vs 7.1% with S-1), anorexia (6.8 vs 9.5%), diarrhoea (2.3 vs 0%), and hand-foot syndrome (6.8 vs 0%). Both capecitabine and S-1 monotherapies were active and tolerable as first-line treatment for elderly patients with AGC.
    British Journal of Cancer 09/2008; 99(4):584-90. · 5.08 Impact Factor
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    ABSTRACT: The present study was conducted to evaluate the efficacy and safety of a combination regimen of docetaxel plus oxaliplatin in patients with advanced gastric cancer. Patients with previously untreated metastatic or recurrent, measurable gastric cancer received intravenous docetaxel 65 mg m(-2) plus oxaliplatin 120 mg m(-2) on day 1 based on a 3-week cycle. Forty-two patients were enrolled in the current study, among whom 39 were assessable for efficacy and all assessable for toxicity. One complete response and 18 partial responses were confirmed, giving an overall response rate of 45.2% (95% confidence interval (CI); 31.7-59.7%). At a median follow-up of 7.7 months, the median time to progression and median overall survival was 5.7 (95% CI; 4.3-7.2) months and 9.9 (95% CI; 7.8-12.0) months, respectively. Grade 3/4 neutropenia occurred in 11 patients (26.1%) and febrile neutropenia was observed in four patients (9.5%). The common non-haematologic toxicity was fatigue (grade 1/2, 61.9%) and nausea (grade 1/2, 47.7%). The combination of docetaxel and oxaliplatin was found to be well tolerated and effective in patients with advanced gastric cancer.
    British Journal of Cancer 03/2008; 98(3):542-6. · 5.08 Impact Factor
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    Leukemia 11/2007; 21(10):2227-30. · 10.16 Impact Factor
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    ABSTRACT: GVHD-specific survival (GSS) has been investigated as a potential study end point to describe the clinical course and outcome of chronic GVHD (cGVHD). However, reaching this end point requires a long observation time. We hypothesized that the time to the first flare-up (FFU) of cGVHD (TTF) can be an alternative statistical end point to GSS. This retrospective study included 96 patients with a diagnosis of cGVHD from a cohort of 119 patients with a prior history of acute GVHD. The median TTF was 73 days after the diagnosis of cGVHD. The 2-year cumulative incidences of first, second and third episodes of flare-up (FU) during courses of cGVHD were estimated as 69.5, 46.4 and 22.1%. Those patients who did not have an episode of FU of cGVHD had 96.0% of 2-years GSS rate, while those with 1 and > or =2 episodes had 50.8 and 46.8%, respectively (P=0.001). Shorter TTF was associated with poor GSS and decreased overall survival. The shorter TTF during the course of cGVHD was significantly associated with extensive cGVHD (P=0.002), Hopkins' risk category (P=0.022) and progressive-type cGVHD (P<0.001) in multivariate analysis. We propose that TTF can be an alternative end point to GSS in cGVHD trials.
    Bone Marrow Transplantation 10/2007; 40(8):779-84. · 3.54 Impact Factor

Publication Stats

267 Citations
60.32 Total Impact Points

Institutions

  • 2010–2011
    • Yonsei University Hospital
      • Department of Internal Medicine
      Sŏul, Seoul, South Korea
    • Pohang University of Science and Technology
      • Department of Mechanical Engineering
      Antō, North Gyeongsang, South Korea
  • 2000–2007
    • Kyungpook National University Hospital
      • Department of Hemato-Oncology
      Sŏul, Seoul, South Korea