• Journal of The Korean Astronomical Society
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• v.48 no.6
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• pp.343-355
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• 2015

There is much observational evidence that active star formation is taking place in the Hii regions Sh 2-255 – 257. We present a photometric study of this star forming region (SFR) using imaging data obtained in passbands from the optical to the mid-infrared, in order to study the star formation process. A total of 218 members were identified using various selection criteria based on their observational properties. The SFR is reddened by at least E(B −V ) = 0.8 mag, and the reddening law toward the region is normal (R_V = 3.1). From the zero-age main sequence fitting method it is confirmed that the SFR is 2.1 ± 0.3 kpc from the Sun. The median age of the identified members is estimated to be about 1.3 Myr from a comparison of the Hertzsprung-Russell diagram (HRD) with stellar evolutionary models. The initial mass function (IMF) is derived from the HRD and the near-infrared (J, J −H) color-magnitude diagram. The slope of the IMF is about Γ = −1.6 ± 0.1, which is slightly steeper than that of the Salpeter/Kroupa IMF. It implies that low-mass star formation is dominant in the SFR. The sum of the masses of all the identified members provides the lower limit of the cluster mass (169M_⊙). We also analyzed the spectral energy distribution (SED) of pre-main sequence stars using the SED fitting tool of Robitaille et al., and confirm that there is a significant discrepancy between stellar mass and age obtained from two different methods based on the SED fitting tool and the HRD.

• Wind and Structures
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• v.23 no.1
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• pp.1-18
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• 2016

This work experimentally and numerically analyzes the flow configurations and the dynamic wind loads on panels of rectangular L/h 5:1 cross section mounted on a structural frame of rectangular bars of L/h 0.5:1, corresponding to a radar structure. The fluid dynamic interaction between panels and frame wakes imposes dynamic loads on the panels, with particular frequencies and Strouhal numbers, different from those of isolated elements. The numerical scheme is validated by comparison with mean forces and velocity spectra of a panel wake obtained by wind tunnel tests. The flow configuration is analyzed through images of the numerical simulations. For a large number of panels, as in the radar array, their wakes couple in either phase or counter-phase configurations, changing the resultant forces on each panel. Instantaneous normal and tangential force coefficients are reported; their spectra show two distinct peaks, caused by the interaction of the wakes. Finally, a scaled model of a rectangular structure comprised of panels and frame elements is tested in the boundary layer wind tunnel in order to determine the influence of the velocity variation with height and the three-dimensionality of the bulk flow around the structure. Results show that the unsteady aerodynamic loads, being strongly influenced by the vortex shedding of the supporting elements and by the global 3-D geometry of the array, differ considerably on a panel in this array from loads acting on an isolated panel, not only in magnitude, but also in frequency.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.49-53
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• 2013

Second-order rate constants have been measured spectrophotometrically for the reactions of phenyl Y-substituted-phenyl carbonates 7a-g with butane-2,3-dione monoximate ($Ox^-$) in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$. The ${\alpha}$-nucleophile $Ox^-$ is 53-95 times more reactive than the corresponding normal-nucleophile 4-$ClPhO^-$ toward 7a-g, indicating that the ${\alpha}$-effect is operative. The magnitude of the ${\alpha}$-effect (e.g., the $k_{Ox^-}/k_{4-ClPhO^-}$ ratio) is independent of the electronic nature of the substituent Y. The cause of the ${\alpha}$-effect for the reactions of 7a-g has been suggested to be ground-state (GS) effect rather than transition-state (TS) stabilization through a six-membered cyclic TS, in which $Ox^-$ behaves a general acid/base catalyst. This idea is further supported by the result that $OH^-$ exhibits negative deviation from the linear Br${\o}$nsted-type plot composed of a series of aryloxides, while $Ox^-$ deviates positively from the linearity. Differential solvation of the GS of $Ox^-$ and 4-$ClPhO^-$ has been suggested to be responsible for the ${\alpha}$-effect exerted by $Ox^-$.

• The Journal of Korean Academy of Prosthodontics
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• v.44 no.1
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• pp.51-62
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• 2006

Purpose: The purpose of this study was to evaluate the pattern and the magnitude of stress distribution in the supporting tissues surrounding three different types of implants(ITI, 3i. and Bicon implant system) Material and method: Photoelastic models were made with PL-2 resin(Measurements Group, Raleigh, USA) and three implants of each kind were placed in the mandibular posterior edentulous area distal to the canine. For non-splinted restorations, individual crowns were fabricated on three titanium abutments. For splinted restorations, 3-unit axed partial dentures were fabricated. Photoelastic stress analyses were carried out to measure the fringe order around the implant supporting structure under simulated loaded conditions(15 lb. 30 lb). Conclusion: The results were as follows; 1 Regardless of the implant design, stresses were increased in the apex region of loaded implant when non-splinted restorations were loaded. While relatively even stress distribution occurred with splinted restorations. Splinting was effective in the second implant. 2. Strain around Bicon implant were lower than those of other implants, which confirmed the splinting effect. The higher the load, the more the stress occurred in supporting tissue, which was most obvious in the Bicon system. 3. Stress distribution in the supporting tissue was favorable in the ITI system. while the other side of 3i system tended to concentrate the stress in some parts.

• Journal of Digital Convergence
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• v.19 no.5
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• pp.295-305
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• 2021

The purpose of this study is to empirically verify how UI usability of mobile healthcare applications affects the perception of technostress and continuous use of elderly users. Through this, the effect of UI usability of mobile healthcare applications on technostress and continuous use intention was demonstrated for 199 people aged over 60. As a result, all four sub-factors of UI usability had a significant effect on technostress, and the magnitude of the influence was found to be in the order of content, process, design, and system. On the other hand, it was found that technostress had a significant effect on the intention of continued use. Through the above results, a UI design strategy that can lead to continuous use by relieving the technostress experienced by the elderly was suggested. This provides academic and practical implications for the future development and service direction of mobile healthcare applications for the elderly.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1754-1759
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• 2022

The activity of gamma-ray emitting nuclides is calculated assuming that each gamma-ray is detected individually; thus, the magnitude of the coincidence summing signal must be considered during activity calculations. Here, the correction factor for the coincidence summing effect was calculated, and the detection efficiencies of two HPGe detectors were compared. The CANBERRA Inc. GC4018 high-purity Ge detector provided an estimate for the peak-to-total ratio using a point source to determine the coincidence summing correction factor. The ORTEC Inc. GEM60 high-purity Ge detector uses EFFTRAN in LVis to obtain the parameters of the detector and source model and the gamma-gamma and gamma-X match estimates, in order to determine the coincidence summing correction factor. Nuclide analyses, radioactivity comparisons, and analyses of reference material samples were performed utilizing certified reference materials to accurately determine the detection efficiencies. For both Co-60 and Y-88, the detection efficiency for a point source increased by an average of at least 12-13%, whereas the detection efficiency determined using LVis increased by an average of at least 13-15%. The calculated radioactivity values of the certified reference material and reference material samples were accurate to within 3% and 6% of the measured values, respectively.

• Fisheries and Aquatic Sciences
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• v.4 no.4
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• pp.201-207
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• 2001

To study the distribution of organophosphorus pesticides which are extensively used for agriculture in Korea. Sea water samples were taken from 4 coastal areas during May and August of 1997 and sediment samples were collected from two coastal areas in August of 1997. These samples were analyzed using a Gas Chromatography/Nitrogen Phosphorus Detector (GC/NPD). In August the most commonly found organophosphorus pesticides in the surface waters of Kunsan area were IBP < S-Benzyl O,O-di-isopropyl phosphorothioate > $(m=432.5ng\;L^{-1})$ and EDDP < O-ethyl S,S-diphenyl phosphorodithioate > $(m=37.4ng\;L^{-1}) $ which are largely used between June and September to prevent rice blast disease. In Danghang Bay, dry fields located near the mouth of the estuary seemed to affect the concentrations of certain organophosphorus pesticides in the surface waters. Since organophosphorus pesticides applied in the watershed are rapidly decomposed while being transported along freshwater streams, watershed size is not proportional to the concentrations of these pesticides in the coastal waters. Pesticides concentrations measured in August were compared with those in May. IBP concentrations in coastal waters were about an order of magnitude higher in August than in May. Temporal and geographical distribution of individual organophosphorus pesticides is likely to be affected by types of agricultural practices in the watershed. Chloropyrifos was the most important of the organophosphorus pesticides in the sediments of the study area because of its persistent nature and high affinity to particulates.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.6
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• pp.256-263
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• 2007

For $P_B=50Torr,\;P_T=5401Torr,\;T_S=450^{\circ}C,\;{\Delta}T=20K$, Ar=5, Pr=3.34, Le=0.01, Pe=4.16, Cv=1.05, adiabatic and linear thermal profiles at walls, the intensity of solutal convection (solutal Grashof number $Grs=7.86{\times}10^6$) is greater than that of thermal convection (thermal Grashof number $Grt=4.83{\times}10^5$) by one order of magnitude, which is based on the solutally buoyancy-driven convection due to the disparity in the molecular weights of the component A ($Hg_2Cl_2$) and B (He). With increasing the partial pressure of component B from 20 up to 800 Torr, the rate is decreased exponentially. It is also interesting that as the partial pressure of component B is increased by a factor of 2, the rate is approximately reduced by a half. For systems under consideration, the rate increases linearly and directly with the dimensionless Peclet number which reflects the intensity of condensation and sublimation at the crystal and source region. The convective transport decreases with lower g level and is changed to the diffusive mode at $0.1g_0$. In other words, for regions in which the g level is $0.1g_0$ or less, the diffusion-driven convection results in a parabolic velocity profile and a recirculating cell is not likely to occur. Therefore a gravitational acceleration level of less than $0.1g_0$ can be adequate to ensure purely diffusive transport.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.3
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• pp.360-369
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• 2012

The causes of showing different subthreshold slopes (SS) in programmed and erased states for two different charge trap flash (CTF) memory devices, SONOS type flash memory with gate-all-around (GAA) structure and TANOS type NAND flash memory with planar structure were investigated. To analyze the difference in SSs, TCAD simulation and low-frequency noise (LFN) measurement were fulfilled. The device simulation was performed to compare SSs considering the gate electric field effect to the channel and to check the localized trapped charge distribution effect in nitride layer while the comparison of noise power spectrum was carried out to inspect the generation of interface traps ($N_{IT}$). When each cell in the measured two memory devices is erased, the normalized LFN power is increased by one order of magnitude, which is attributed to the generation of $N_{IT}$ originated by the movement of hydrogen species ($h^*$) from the interface. As a result, the SS is degraded for the GAA SONOS memory device when erased where the $N_{IT}$ generation is a prominent factor. However, the TANOS memory cell is relatively immune to the SS degradation effect induced by the generated $N_{IT}$.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.11 no.3
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• pp.165-172
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• 1999

A probability density function of reliability function is derived in this paper, by which the stability of armor units on the rubble-mound breakwater can be studied on the probabilistic approach. To obtain the distribution, each random variable of the reliability function is assumed to follow Gaussian distribution. The distribution function of reliability function is in agreement with the histogram simulated by the Monte-Carlo method. In addition, the failure probability of armor units on the rubble-mound breakwater evaluated by the derived probability density function is shown to have the same order of magnitude as those calculated by FMA and AFDA of moment method. In particular, it is important to note that random variables of the reliability function may be considered to be statistically independent in the reliability analysis of armor units on the rubble-mound breakwater. Therefore, the present approach may be straightforwardly applicable to all of the cases that any random variables in the reliability function are controlled by other distribution functions as well as normal distribution.