Joo Hyun Moon

Gyeongju University, Gyeongju, Gyeongsangbuk-do, South Korea

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Publications (36)37.29 Total impact

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    ABSTRACT: This study numerically investigated the influence of spanwise pressure gradient on heat transfer of a 3D turbulent boundary layer with longitudinal vortices. A 30° bend in the passage provided the spanwise pressure gradient. The longitudinal pair vortices were generated using a pair of delta winglets. The Reynolds-averaged Navier-Stokes and energy equations based on the conventional Reynolds stress model were used. The predictions agreed well with the experimental data for the straight plate. The turbulent boundary layer was significantly perturbed with the longitudinal vortices. The spanwise pressure gradient contributed to faster degradation of the longitudinal vortices and widened the perturbed flow region. The local Stanton number distributions were asymmetric because of the difference in the evolution of the longitudinal vortices in the curved region. Moreover, comparison showed that the local Stanton number in the downstream of the straight channel increased near the surface because of the secondary re-circulating vortex. The thickness of the thermal boundary layers increased in the streamwise direction because of the significant flow mixing and heat transfer.
    Journal of Mechanical Science and Technology 02/2015; 29(2):867-875. DOI:10.1007/s12206-015-0150-x · 0.70 Impact Factor
  • Journal- Korean Physical Society 01/2015; 66(1):46-50. DOI:10.3938/jkps.66.46 · 0.43 Impact Factor
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    ABSTRACT: A fiber-optic sensor system using a multiplexed array of sensing probes based on an aqueous solution of sodium chloride (NaCl solution) and an optical time-domain reflectometer (OTDR) for simultaneous measurement of temperature and water level is proposed. By changing the temperature, the refractive index of the NaCl solution is varied and Fresnel reflection arising at the interface between the distal end of optical fiber and the NaCl solution is then also changed. We measured the modified optical power of the light reflected from the sensing probe using a portable OTDR device and also obtained the relationship between the temperature of water and the optical power. In this study, the water level was simply determined by measuring the signal difference of the optical power due to the temperature difference of individual sensing probes placed inside and outside of the water. In conclusion, we demonstrate that the temperature and water level can be obtained simultaneously by measuring optical powers of light reflected from sensing probes based on the NaCl solution. It is anticipated that the proposed fiber-optic sensor system makes it possible to remotely monitor the real-time change of temperature and water level of the spent fuel pool during a loss of power accident.
    Sensors 10/2014; 14(10):18823-18836. · 2.05 Impact Factor
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    ABSTRACT: A fiber-optic sensor system using a multiplexed array of sensing probes based on an aqueous solution of sodium chloride (NaCl solution) and an optical time-domain reflectometer (OTDR) for simultaneous measurement of temperature and water level is proposed. By changing the temperature, the refractive index of the NaCl solution is varied and Fresnel reflection arising at the interface between the distal end of optical fiber and the NaCl solution is then also changed. We measured the modified optical power of the light reflected from the sensing probe using a portable OTDR device and also obtained the relationship between the temperature of water and the optical power. In this study, the water level was simply determined by measuring the signal difference of the optical power due to the temperature difference of individual sensing probes placed inside and outside of the water. In conclusion, we demonstrate that the temperature and water level can be obtained simultaneously by measuring optical powers of light reflected from sensing probes based on the NaCl solution. It is anticipated that the proposed fiber-optic sensor system makes it possible to remotely monitor the real-time change of temperature and water level of the spent fuel pool during a loss of power accident.
    Sensors 10/2014; 14(10):18823-18836. DOI:10.3390/s141018823 · 2.05 Impact Factor
  • Joo Hyun Moon, Dae Yun Kim, Seong Hyuk Lee
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    ABSTRACT: The present study aims to investigate the influence of the Weber number and surface temperature on the spreading and receding characteristics of Newtonian (DI-water) and non-Newtonian (xanthan gum solution) droplets impinging on heated surfaces. The surface temperature was in the range from 25°C to 85 °C, which is below the Leidenfrost temperature (∼ 300 °C). Using high-speed camera images, this study measured the dynamic contact angle as well as spreading and receding diameters. It also used a modified model to predict the maximum spreading diameter by using the effective viscosity. From the results, the modified model using the effective viscosity was in good agreement with the experimental data in predicting the maximum spreading diameter. In addition, the maximum spreading diameter for a DI-water droplet was larger than that of a non-Newtonian droplet because of the difference in liquid viscosity. In particular, for the Newtonian and non-Newtonian droplets, the dynamic contact angle was almost similar in the spreading regime, but in the receding regime, it substantially changes with temperature owing to the variation of viscosity with temperature. Moreover, the spreading diameter rapidly decreased with the increase in surface temperature in the receding regime in which the change in viscous dissipation energy would be important for the receding motion. Finally, the retraction rates of the Newtonian droplet remained constant with temperature, whereas those of the non-Newtonian droplet increased with temperature, thereby supporting the assertion that the viscosity effect is dominant in the receding characteristics after impact.
    Experimental Thermal and Fluid Science 09/2014; 57. DOI:10.1016/j.expthermflusci.2014.04.003 · 2.08 Impact Factor
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    ABSTRACT: Aluminum-hydroxide-covered multi-walled carbon nanotubes (A-MWCNT) were fabricated as a thermally conductive material. The thermal conductivity of A-MWCNT was estimated based on Casimir theory. The effective thermal conductivity of A-MWCNT was estimated at about similar to 26 W/mK. The thermal conductivity of A-MWCNT/epoxy-terminated polydimethylsiloxane (ETDS) composite was examined as a function of A-MWCNT loading, and the results showed the maximum value at 1.5 wt% of A-MWCNT loading, above which it decreased slightly. The effective medium approximation (EMA) developed by Maxwell-Garnett (M-G) was used to analyze the thermal conducting behavior of the composite. The experimental results showed negative deviation from the expected thermal conductivity, k(e), beyond 1.5 wt% of A-MWCNT loading, because the composites containing A-MWCNT were strongly affected by interfacial resistance. The interfacial resistance value calculated from M-G approximation increased when filler loading was higher than 1.5 wt% because of the folded and partially agglomerated A-MWCNT along with insufficient interfacial interactions.
    Composites Part A Applied Science and Manufacturing 11/2013; 54:159-165. DOI:10.1016/j.compositesa.2013.07.020 · 3.01 Impact Factor
  • Chan Hee Park, Joo Hyun Moon, Bum Kyoung Seo
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    ABSTRACT: In this study, we developed and characterized an integrated fiber-optic sensor for the remote detection of alpha radiation emitted from radioactive contamination in areas relatively inaccessible by radiation workers. The fiber-optic sensor consisted of an epoxy-resin supporter and a sensing probe attached to it. The epoxy-resin supporter to hold the optical fiber tightly was fabricated by using epoxy-resin and a small amount of hardener. The sensing probe was fabricated by mixing epoxy-resin with inorganic scintillator ZnS(Ag) powder and solidifying the mixture. Then, the sensing probe was attached to the epoxy-resin supporter. As a light guide, an optical fiber, which was also compatible with the epoxy-resin, was used. The optical fiber was submerged in the epoxyresin supporter before solidification to make it in an integral form to minimize the loss of scintillation light due to incomplete connections between them. The four assembled fiber-optic sensors with sensing probes whose density thicknesses of ZnS(Ag) were 10, 15, 20 and 25 mg/cm2, respectively, were evaluated in terms of the total counts of alpha radiation to determine the optimum density thickness of ZnS(Ag). From the evaluation, a density thickness of 15 mg/cm2 was found to be the best for detecting alpha radiation.
    Journal- Korean Physical Society 11/2013; 63(9):1720-1723. DOI:10.3938/jkps.63.1720 · 0.43 Impact Factor
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    ABSTRACT: The aim of this study was to survey the radon concentrations at 21 elementary schools in Gyeongju, Republic of Korea, to identify those schools with high radon concentrations. Considering their geological characteristics and the preliminary survey results, three schools were finally placed under close scrutiny. For these three schools, continuous measurements over 48h were taken at the principal's and administration office. The radon concentrations at one school, Naenam, exceeded the action level (148Bq/m(3)) established by the U.S. EPA, while those at the other two schools were below that level.
    Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 04/2013; 81. DOI:10.1016/j.apradiso.2013.03.020 · 1.06 Impact Factor
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    ABSTRACT: A fiber-optic radiation sensor (FORS), which is composed of an inorganic scintillator, a plastic optical fiber (POF), a photomultiplier tube (PMT), and a multichannel analyzer (MCA), was developed for gamma-ray energy spectroscopy. In this study, we selected a cerium-doped lutetium yttrium orthosilicate (LYSO:Ce) as the sensitive element of the FORS and found that LYSO:Ce with dimensions of 3 × 3 × 15mm3 gives the best performance in obtaining a gammaray energy spectrum. The FORS allows us to measure the energy spectra of Co-60, Na-22, and Cs-137.
    Optical Review 03/2013; 20(2):205-208. DOI:10.1007/s10043-013-0036-z · 0.55 Impact Factor
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    ABSTRACT: This study investigated the impact dynamics of single Newtonian and non-Newtonian droplets impinging on a textured aluminum (Al 6061) surface fabricated by using a u-computer numerical control (u-CNC) machine. DI-water was chosen as a Newtonian fluid, while 0.5 wt.% Xanthan Gum (Sigma-Aldrich) solution was selected for a non-Newtonian fluid. The non-Newtonian droplets show a shear-thinning characteristics, higher zero shear viscosity than DI-water. The textured surfaces are composed of micro-holes (diameter: 250 um, depth: 500 um) with equivalent pitches, without showing very similar apparent equilibrium contact angles of both Newtonian and non-Newtonian droplets. We measured spreading and receding diameters from images captured by a high-speed camera of 10,000 fps (HG-LE, Redlake). 6.4 ul droplets impinged on the textured surfaces (s=0.28) with an impact velocity of 1.213 m/s. The normalized maximum spreading diameter (D*) of a non-Newtonian impinging droplet is the smaller, and the corresponding lamella thickness is the larger because of the increase in viscosity dissipation. For a non-Newtonian fluid, the receding is also slower than that of Newtonian fluid at the relaxation phase because of the viscosity effect.
    Journal of Heat Transfer 08/2012; 134:080905-1. DOI:10.1115/1.4006719 · 2.06 Impact Factor
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    MATERIALS TRANSACTIONS 01/2012; 53(11):2043-2048. DOI:10.2320/matertrans.M2012217 · 0.61 Impact Factor
  • Chan Hee Park, Joo Hyun Moon, Bum Kyong Seo
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    ABSTRACT: Measuring the level of radioactive contamination in a high-radiation area with a complex geometry requires a new measuring system that can be operated remotely and free of electronic noise by radiation. In this study, a measuring system suitable for measuring high-level radioactive contamination in the narrow gap of a nuclear facility was developed. The measuring system was a fiber-optic remote system using an organic scintillator, epoxy resin and an optical fiber. The measuring system was tested for Cs-137 and Sr/Y-90 radiation sources, and could measure radioactive contamination remotely in a narrow area.
    Radiation Measurements 08/2011; 46(8):687-693. DOI:10.1016/j.radmeas.2011.06.003 · 1.14 Impact Factor
  • Kyoung Won Jang, Bong Soo Lee, Joo Hyun Moon
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    ABSTRACT: Sometimes, detection of thermal neutrons in the presence of gamma rays is required. This study developed and characterized an integrated fiber-optic radiation sensor for the simultaneous detection of thermal neutrons and gamma rays in a mixed radiation field. The performance of the integrated sensor was verified by measuring the distributions of thermal neutrons and gamma rays released from a nuclear fuel rod at the Kyoto University Critical Assembly. The experimental results show that the integrated sensor produced similar distribution patterns to those of thermal neutrons and gamma rays released from a fuel rod.
    Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 04/2011; 69(4):711-5. DOI:10.1016/j.apradiso.2011.01.009 · 1.06 Impact Factor
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    ABSTRACT: A Novel Planar Small Electrode Sensor (NPSES) using the semi-conductor process was developed in this study to find out Acupuncture Points (APs) or Biological Active Points (BAP) on the human being's skin. The NPSES with eight (8) electrodes tracks generates the electrical properties of the BAPs on the skin. These eight tracks are located in a circle of 2 mm diameter. The BAP locations generated by the NPSES are characterized by high electric potential, high electric capacity, and low electric resistance, compared to non-Acupuncture Points (non-APs). The traditional unit applied for the BAP is the cun, the Chinese anatomical inch. The BAPs are distinguished by the difference in voltage between the measurement electrode and the reference one, i.e., the difference in the resistance and reactance of BAPs. The BAP size might be in the range of 1 to 2 mm2. Five (5) healthy human subjects of between 27 and 42 years were examined to investigate the effectiveness of the NPSES for finding out the BAPs. The current and frequency applied to this experiment were in the range of 7.5 A and 0.1 Hz to 1.5 kHz, respectively. We believe that the NPSES system developed in this study is highly reliable for and scientifically applicable to locating the BAPs on the human being's skin.
    Sensor Letters 02/2011; 9(1):218-222. DOI:10.1166/sl.2011.1453 · 0.56 Impact Factor
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    ABSTRACT: In this study, we have fabricated a fiber-optic radiation sensor using an organic scintillator for brachytherapy dosimetry. Organic scintillators are made from a polystyrene base with wavelength-shifting fluors, and they do not disturb the radiation field due to their tissue or water-equivalent characteristics in a wide range of energies. The fiber-optic radiation sensor developed for this study provides a fast real-time response and convenient usage for brachytherapy dosimetry. For more accurate measurement, we have measured Cerenkov light using a dummy fiber and avoided dose measurement errors arising from high dose gradients in brachytherapy dosimetry. The Cerenkov light has been eliminated using a modified subtraction method. Also, the relative depth dose without the dose generated from Cerenkov lights is measured and compared with the results obtained using conventional EBT dosimetry films.
    IEEE Transactions on Nuclear Science 07/2010; DOI:10.1109/TNS.2010.2043263 · 1.46 Impact Factor
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    ABSTRACT: In this study, we developed scintillation-fiber sensors that could measure net closes in mixed neutron-gamma. fields. The scintillation-fiber sensors were tested with (252)Cf and (60)Co sources to demonstrate, the capability to discriminate the gamma-ray dose contained in the mixed neutron-gamma field. Furthermore, we tested the scintillation-fiber sensors to measure the distributions of them ad neutrons as a function of the distance from the center of the reactor core at the Kyoto University Critical Assembly (KUCA), and the results were compared with the distribution of thermal neutrons obtained using an Au-wire activation method.
    Journal- Korean Physical Society 06/2010; 56(6). DOI:10.3938/jkps.56.1777 · 0.43 Impact Factor
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    Journal- Korean Physical Society 03/2010; 56(3):765-769. · 0.43 Impact Factor
  • Byeong Soo Kim, Joo Hyun Moon
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    ABSTRACT: An optimization method based on genetic algorithm (GA), which is referred as MACroscopic Near-Optimal Shielding design (MACNOS), is proposed for the search for an optimal radiation shield configuration subject to a given set of constraints. In MACNOS, a GA is used to search for the optimal shielding design and the penalty strategy is employed to deal with the constraints. In order to confirm its capability to search for the optimal shielding design, MACNOS is applied for solving a simple problem with regard to radiation shielding optimization of a hypothetical spaceship reactor. The application shows that, keeping the constraints satisfied, MACNOS is able to seek for the shielding design that minimizes the total weight by changing the thickness and the material of the shield. Therefore, it is expected that MACNOS is potentially useful in the search for the optimal design configuration in the conceptual design phase, where the selection of the shielding material and the estimate of the thickness are necessary.
    Annals of Nuclear Energy 02/2010; 37(2):120-129. DOI:10.1016/j.anucene.2009.11.014 · 1.02 Impact Factor
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    ABSTRACT: In this study, we have fabricated non-contact temperature sensor using an infrared optical fiber for measuring temperature distributions during radiofrequency ablation. We have measured an infrared radiation, which is transferred by a silver halide optical fiber from the multi-points on the water around inserted electrode, using a thermopile sensor and the output voltages of a thermopile sensor are compared with those of the thermocouple recorder. Also, the relationship between the temperatures and the output voltages of a thermopile sensor at the measuring points is determined to obtain the temperature distribution. The measurable temperature range of a fiber-optic non-contact temperature sensor is from 37 to 80 °C. Keywordsfiber-optic sensor-infrared radiation-noncontact temperature sensor-radiofrequency ablation-silver halide optical fiber
    Optical Review 05/2009; 16(3):387-391. DOI:10.1007/s10043-009-0073-9 · 0.55 Impact Factor

Publication Stats

124 Citations
37.29 Total Impact Points

Institutions

  • 2013–2014
    • Gyeongju University
      Gyeongju, Gyeongsangbuk-do, South Korea
  • 2012–2014
    • Chung-Ang University
      • School of Mechanical Engineering
      Sŏul, Seoul, South Korea
  • 2007–2013
    • Dongguk University
      • • Department of Civil and Environmental System Engineering
      • • College of Science and Technology
      Sŏul, Seoul, South Korea
  • 2010
    • Konkuk University
      • Department of Biological Engineering
      Seoul, Seoul, South Korea
  • 2001–2006
    • Seoul National University
      • Department of Nuclear Engineering
      Sŏul, Seoul, South Korea
  • 2004–2005
    • Korea Institute of Nuclear Safety
      Sŏul, Seoul, South Korea
  • 1999
    • Korea Hydro and Nuclear Power - Central Research Institute
      Sŏul, Seoul, South Korea