• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.462-466
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• 1999

As the spectrum migrates to the higher frequency band around several milimeters wavelength for implementing wideband highspeed communications, it is more important to consider the channel attenuation characteristics of microwave signals. Microwave channels in 27GHz used in B-WLL system must be considered by compensating the power attenuation due to rainfall. So, in the design of one cell, the radiation power enhancement considering rainfall attenuation has an effort on the receiver in other cell as interference. In this paper we consider the main characteristics for B-WLL systems, optimum cell radius, and serviceable limit of heavy rainfall the design of the radiation power control system in case of enhancing the power that prevents from reducing the system capacity by interference.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.550-553
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• 2010

The enhancement of quantum efficiency using a surface modified Ag anode in top-emitting organic light emitting diodes (TEOLEDs) is reported. The operation voltage at the current density of $1\;mA/cm^2$ of TEOLEDs decreased from 9.3 V to 4.3 V as the surface of anode coated with $CuO_x$ layer. The work function of these structures were quantitatively determined using synchrotron radiation photoemission spectroscopy. Secondary electron emission spectra revealed that the work function of the Ag/$CuO_x$ structure is higher by 0.6 eV than that of Ag. Thus, the $CuO_x$ structure acts as a role in reducing the hole injection barrier by about 0.6 eV, resulting in a decrease of the turn-on voltage of top-emitting light emitting diodes.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.1
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• pp.59-66
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• 1998

The combustion instability analysis of solid propellants is generally done by the simplified governing equations for chemically inert condensed phase region with QSHOD assumption. Since the gas phase and surface reaction layer can be more rapidly relaxed to the external perturbations than the condensed phase, these regions are treated as quasi-steady manner in the analysis. In this paper, the classical ZN(Zeldovic-Novozhilov)approach was re-examined with the presence of radiation augmented burning enhancement in the combustion. Also, the surface reaction was assumed to partially absorb the incident radiant heat fluxes and pass the remaining to the chemically inert condensed phase. As a result of the analysis, the burning rate response function was obtained which consists of a pressure response function and a radiation response function. The response function was shown to be able to predict the results of T-burner tests.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.66.1-66.1
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• 2021

Extinction curves observed toward individual Active Galactic Nuclei (AGN) usually show a steep rise toward Far-Ultraviolet (FUV) wavelengths and can be described by the Small Magellanic Cloud (SMC)-like dust model. This feature suggests the dominance of small dust grains of size a < 0.1 ㎛ in the local environment of AGN, but the origin of such small grains is unclear. In this paper, we aim to explain this observed feature by applying the RAdiative Torque Disruption (RATD) to model the extinction of AGN radiation from FUV to Mid-Infrared (MIR) wavelengths. We find that in the intense radiation field of AGN, large composite grains of size a > 0.1 ㎛ are significantly disrupted to smaller sizes by RATD up to dRATD > 100 pc in the polar direction and dRATD ~ 10 pc in the torus region. Consequently, optical-MIR extinction decreases, whereas FUV-near-Ultraviolet extinction increases, producing a steep far-UV rise extinction curve. The resulting total-to selective visual extinction ratio thus significantly drops to RV < 3.1 with decreasing distances to AGN center due to the enhancement of small grains. The dependence of RV with the efficiency of RATD will help us to study the dust properties in the AGN environment via photometric observations. In addition, we suggest that the combination of the strength between RATD and other dust destruction mechanisms that are responsible for destroying very small grains of a <0.05 ㎛ is the key for explaining the dichotomy observed "SMC" and "gray" extinction curve toward many AGN.

• Journal of Sensor Science and Technology
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• v.32 no.6
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• pp.418-424
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• 2023

Natural killer (NK) cells play a crucial role in combating infections and tumors. However, their therapeutic application in solid tumors is hindered by challenges, such as limited lifespan, tumor penetration, and delivery precision. Our research introduces a novel ultrasonic actuation technique to navigate NK cells more effectively in the vascular system, particularly at vessel bifurcations where targeted delivery is most problematic. We use a hemispherical ultrasonic transducer array that generates phase-modulated traveling waves, focusing on an ultrasound beam to steer NK cells using blood-flow dynamics and a focused acoustic field. This method enables the precise obstruction of non-target vessels and efficiently directs NK cells toward the tumor site. The simulation results offer insights into the behavior of NK cells under various conditions of cell size, radiation pressure, and fluid velocity, which inform the optimization of their trajectories and increase targeting efficiency. The experimental results demonstrate the feasibility of this ultrasonic approach for enhancing NK cell targeting, suggesting a potential leap forward in solid tumor immunotherapy. This study represents a significant step in NK cell therapeutic strategies, offering a viable solution to the existing limitations and promising enhancement of the efficacy of cancer treatments.

• Journal of Radiation Industry
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• v.18 no.1
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• pp.63-70
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• 2024

Phlorocyclin (PC) and isophorocyclin (IPC) are rare benzofuran derivaitves obtained from the representive dihydrochalcone glucoside, phloridzin (PZ) and are a type of neolignan backbone with a potential anti-glycative agents. However, research related to the enhancement of biological functionallites to inflammation of the newly converted products is very limited. This research was directed with the purpose of discovery more effective anti-inflammatory agents in macrophages of newly radiolysis products PC and IPC. The anti-inflammatory capacities of the characterized products in RAW 264.7 and DH82 macrophages treated with lipopolysaccharide (LPS) to stimulate an inflammation response were examined. The pro-inflammatory factors such as prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α), nitric oxide (NO), interleukin-6 (IL-6), and IL-10, without cytotoxicity in LPS-stimulated macrophages, were significantly inhibited after treatment with PC and IPC, when compared to PZ. Moreover, PC and IPC decreased the appearance of cyclooxygenase-2 (COX-2) and inducible NO synthase (iNOS) proteins in macrophages. The cyclization products modified by radiolysis showed the greatest anti-inflammatory effects in macrophage cells, indicating PC and IPC are a potential candidate for use in anti-inflammatory agents.

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.80-80
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• 2003

${\beta}$-lapachone(${\beta}$-Lap), a natural o-naphthoquinone, presents in the bark of the Lapacho tree. ${\beta}$-Lap is cytotoxic against a variety of human cancer cells and it potentiates the anti-tumor effect of Taxol. In addition, ${\beta}$-Lap has been reported to radiosensitize cancer cells by inhibiting the repair of radiation-induced DNA damage.In the present study, we investigated the cytotoxicity of ${\beta}$-Lap against RKO human colorectal cancer cells as well as the combined effect of ${\beta}$-LaP and ionizing radiation. An incubation of RKO cells with 5 ${\mu}$M of ${\beta}$-Lap for 4 h killed almost 90％ of the clonogenic cells. An incubation of RKO cells with 5 ${\mu}$M of ${\beta}$-Lap for 4 h or longer also caused massive apoptosis. Unlike other cytotoxic agents, ${\beta}$-Lap did not increase the expression of p53 and p21 and it suppressed the NFkB expression. The expression of Caspase 9 and 3 was minimally altered by ${\beta}$-Lap. Radiation and ${\beta}$-Lap acted synergistically in inducing clonogenic cell death and apoptosis in RKO cells when ${\beta}$-Lap treatment was applied after but not before the radiation exposure of the cells. Interestingly, a 4 h treatment with 5 ${\mu}$M of ${\beta}$-Lap starting 5 h after irradiation was as effective as that starting immediately after irradiation. The mechanisms of ${\beta}$-Lap-induced cell killing is controversial but a recent hypothesis is that ${\beta}$-Lap is activated by NAD(P)H: quinone-onidoreductase (NQO1) in the cells followed by an elevation of cytosolic Ca$\^$2+/ level and activation of proteases leading to apoptosis. It has been reported that NQO1 level in cells is markedly up-regulated for longer than 10 h after irradiation. Indeed, using immunological staining of NQO1, we observed a significant elevation of NQO1 expression in RKO cells 5h after 2-4 Gy irradiation. Such a prolonged elevation of NQO1 level after irradiation may be the reasons why the ${\beta}$-Lap treatment applied S h after irradiation was as effective as that applied immediately after irradiation in killing the cells. In view of the fact that the repair of radiation-induced damage is usually completed within 1-2 h after irradiation, it is highly likely that the ${\beta}$-Lap treahment applied 5 h after irradiation could not inhibit the repair of radiation-induced damage. For in vivo study, RKO cells were injected S.C. into the hind-leg of Nu/Nu mice, and allowed to grow to 130 mm3 tumor. The mice were i.p. injected with ${\beta}$-lapachone or saline 2 h after irradiation of tumors with 10 Gy of X-rays. The radiation induced growth delay was increased by 2.4 $\mu\textrm{g}$/g of ${\beta}$-lapachone. Taken together, we may conclude that the synergistic interaction of radiation and ${\beta}$-Lap in killing cancer cells is not due to radiosensitization by ${\beta}$-Lap but to an enhancement of ${\beta}$-Lap cytotoxicity by radiation through an upregulation of NQO1. The fact that NQO1 is elevated in tumors and that radiation causes prolonged increase of the NQO1 expression may be exploited to preferentially kill tumor cells using ${\beta}$-Lap in combination with radiotherapy.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.10 s.113
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• pp.1000-1006
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• 2006

In this paper, the gain of the square hem antenna is enhanced with $3{\times}3$ latticed aperture. In order to get the uniform field distribution on the aperture, the different thicknesses of dielectric plates for the phase compensation are inserted into the center and the edge of the aperture respectively. The proposed horn antenna is designed at 12.5 GHz band, and then the analysis of the field distribution on the aperture is performed by using FDTD method. The radiation pattern is also calculated from the analysis. Based on the measured data, it is verified that the gain of a horn antenna with latticed aperture is 18 dBi and this is 2 dB gain enhancement compare with a normal horn antenna without latticed aperture.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.257-258
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• 2012

The SERS spectra of 4-aminobenzenethiol (ABT) have served as the "probe" molecule, which have helped spectroscopists to build up the electromagnetic (EM) and chemical (CHEM) enhancement mechanisms. In particular, the b2-peaks (9b, 3, and 19b) of the SERS spectra of ABT have been attributed to arise from the vibronic charge-transfer (CT) between Au or Ag surface and the ABT. Quite recently, however, Tian and co-workers [1] claimed that the b2-peaks are not the CT-enhanced spectra of ABT. Instead, these peaks arise from the 4,4'-dimercaptoazobenzenes (DMABs) that are produced by the oxidative coupling of two ABTs. Their claim is under intense debate currently. Herein, we studied spatially and temporally resolved SERS spectra of ABTs on Ag thin film (thickness of 10 nm), to investigate such claim. Herein, we present a series of additional evidences that strongly support that the b2 intensities of ABTs do not arise from the CT-enhancement: (1) the b2-peaks can be locally "activated" (i. e. turned on) irreversibly with focused laser radiation; (2) the TOF-SIM spectrometry on the activated region show depletion of ABT-Ag+ ions; and finally (3) the spatially resolved FT-IR spectra of the activated region show two pronounced peaks at 1377 cm-1 and 1460 cm-1, both of which can be assigned to the stretching mode of N=N bond. While the result does not disprove the existence of CT or CHEM enhancement in general, the results do show that previous interpretations of the spectra of ABTs should be re-interpreted.

• Journal of Environmental Health Sciences
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• v.40 no.5
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• pp.425-434
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• 2014

Objectives: The purpose of this study is to introduce the establishment process and results of the Seoul Metropolitan Government's road map on environmental health policy. Methods: The process consisted of expert group meetings, civic participation, research, and questionnaire survey for priority environmental health policy agenda items in Seoul. Results: The announced vision for the environmental health policy was "a healthy environment, safety in Seoul". This policy was established in order to define environment health policy initiatives for a period of five years with an aim to protect Seoul citizens' health from hazardous environmental factors. The resulting Seoul environmental health policy consisted of four areas and 16 key agenda items. The four areas were "Protection for children against hazardous materials", "Enhancement of health and safety of all", "Carcinogen-free and endocrine-disrupting chemical-free Seoul (reducing environmental exposure to hazardous materials), and "Establish the foundation of environmental health policy". Sixteen key agenda items include the enhancement of management of spaces for children, certification of environmental health status at schools, establishment of a unit responsible for the environmental health of children, strengthening environmental health management for susceptible populations (children, the aged, and the socioeconomically vulnerable), management of hazardous materials, physical hazardous factors (noise, radiation, etc.), indoor air quality, and the enhancement of monitoring, research, and regulation of environment health. Conclusion: The Seoul Metropolitan Government established an environmental health policy road map for a five-year period (2013-2017). To implement this environmental health policy, budget allocation, and detailed execution plans are required.