• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.11
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• pp.26-35
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• 2007

We characterized the properties of the fabricated filter with the total internal reflection mirror (TIR) in the rectangular ring resonator and very small multimode interference (MMI) couplers on an InP material platform for photonic integrated circuits. Coupling power in and out of a resonator is increased by using an optimum MMI length of 110 ${\mu}m$ and a width of 9 ${\mu}m$, respectively. The semiconductor optical amplifier with the length of 120 ${\mu}m$ is integrated in the resonator to compensate the loss of the internal waveguide and the TIR mirror. A free spectral range of approximately 2 nm (244 GHz) is observed with an on-off ratio of 13 dB. The curve fitting also yields the power coupled per pass as 42%. To reach critical coupling at this coupling level would require a round trip loss of about 2.4 dB.

• ALGAE
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• v.20 no.2
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• pp.121-125
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• 2005

The modern integrated fish-seaweed mariculture has been tested to reduce the environmental impacts of an intensive fed culture. To obtain the best seaweed bioremediation performance, the effects of therapeutants used for fish disease control on the selected seaweed species should be considered. As a selected seaweed, Porphyra yezoensis was tested with six commercial antibiotics including erythromycin thiocyanate_A, erythromycin thiocyanate_B, oxytetracycline, doxycycline, pefloxacin, and amoxicillin trihydrate under the batch incubation at a photon flux density of 10 $\mu$mol ${\cdot}m^{-2}\;{\cdot}\;s^{-1}$ at 15$^{\circ}C$. Among the tested commercial antibiotics, erythromycin thiocyanate_A, erythromycin thiocyanate_B, oxytetracycline, and doxycycline showed decreases in Fv/Fm, the photochemical efficiency of photosystem II, with a dose-dependant and time-dependant manner. From the quenching analysis of chlorophyll fluorescence, three differential patterns were observed in the antibiotics-treated Porphyra: (1) high nonphotochemical quenching (NPQ) and low photochemical quenching (qP) in the cases of Erythromycin thiocyanate_B and amoxicillin trihydrate, (2) high NPQ and high qP in the case of pefloxacin and (3) low NPQ and low qP in the case of oxytetracycline. These results indicated that antibiotics affected in various ways on the photosynthetic apparatus, reflecting differential lesion sites of antibiotics. In addition, the rates of ammonium uptake also decreased with a decrease of Fv/Fm in P. yezoensis thalli treated with erythromycin thiocyanate_B and oxytetracycline. Therefore, the four antibiotics mentioned could affect the bioremediation capacity of the selected seaweed species in the integrated fish-seaweed mariculture system due to the decrease of photosynthetic activity and the simultaneous decrease of ammonium uptake.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.1
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• pp.62-69
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• 2020

This study intended to evaluate noise level of dental handpieces and the effects of noise cancelling devices. An ear model was designed to measure the level of the noise delivered to the inner ear during dental handpiece operation. The level of noise was measured in various conditions using the ear model and the portable noise meter. Noise level was measured again after applying of 4 different noise cancelling devices to the model ear. The noise level of dental handpieces was 82.5 - 84.4 dB. When 4 types of noise canceling devices were applied, the noise level reduced to 67.4 - 73.8 dB. All 4 devices had statistically significant effect in reducing the noise of the handpiece. Considering the intensity and exposure time, noise in dental clinics can cause hearing damage to dentists. For protection from the risk of occupational hearing damages, noise canceling devices can be recommended.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.12 s.103
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• pp.1206-1212
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• 2005

In this paper, we propose a novel antenna structure which uses the electric and magnetic currents so as to eliminate nulls on their radiation pattern. The tag antenna was matched to the conjugate impedance of the commercial tag chip using the modified double T matching network. The radiation efficiency is about $90\%$, and the bandwidth($S_{11}< -10 dB$) is 848${\~}$926 MHz. Also it shows the gain deviation between the maximum and minimum gains about 4 dB at any direction of the tag antenna at the operating frequency. The readable range of the tag is 1.7${\~}$2.4 m for an arbitrary rotation angle of the tag with a commercial tag chip.

• Bulletin of the Korean Chemical Society
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• v.35 no.8
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• pp.2438-2442
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• 2014

A kinetic study is reported for $S_NAr$ reaction of 1-fluoro-2,4-dinitrobenzene (5a) and 1-chloro-2,4-dinitrobenzene (5b) with alkali-metal ethoxides (EtOM, M = Li, Na, K and 18-crown-6-ether complexed K) in anhydrous ethanol. The second-order rate constant increases in the order $k_{EtOLi}$ < $k_{EtO^-}$ < $k_{EtONa}$ < $k_{EtOK}$ < $k_{EtOK/18C6}$ for the reaction of 5a and $k_{EtOLi}$ < $k_{EtONa}$ < $k_{EtO^-$ < $k_{EtOK}$ < $k_{EtOK/18C6}$ for that of 5b. This indicates that $M^+$ ion behaves as a catalyst or an inhibitor depending on the size of $M^+$ ion and the nature of the leaving group ($F^-$ vs. $Cl^-$). Substrate 5a is more reactive than 5b, although the $F^-$ in 5a is ca. $10pK_a$ units more basic than the $Cl^-$ in 5b, indicating that the reaction proceeds through a Meisenheimer complex in which expulsion of the leaving group occurs after the rate-determining step (RDS). $M^+$ ion would catalyze the reaction by increasing either the nucleofugality of the leaving group through a four-membered cyclic transition state or the electrophilicity of the reaction center through a ${\pi}$-complex. However, the enhanced nucleofugality would be ineffective for the current reaction, since expulsion of the leaving group occurs after the RDS. Thus, it has been concluded that $M^+$ ion catalyzes the reaction by increasing the electrophilicity of the reaction center through a ${\pi}$-complex between $M^+$ ion and the ${\pi}$-electrons in the benzene ring.

• Research in Plant Disease
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• v.12 no.3
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• pp.249-253
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• 2006

Several fungicides such as polyoxine B, fludioxonil, tebuconazole, tebuconazole+dichlofluanid, and fenbuconazole were sprayed once a week on roses in greenhouse. Botrytis infection on stalks was reduced by 71-89% after regular fungicide spray. The reduction of conidial inoculum by these treatments is also observed. The rose petal infections were controlled significantly by these fungicides only 2 days after the application. The development of gray mold on rose flowers harvested just after spray of fludioxonil, tebuconazole and tebuconazole+dichlofluanid were reduced compared to untreated control. This beneficial effect was also shown in flowers artificially inoculated with B. cinerea conidia after harvest. Post-harvest treatments by spraying cut flowers with the fungicides such as iprodine plus thiram, tebuconazole+dichlofluanid and polyoxin D reduced disease incidence by 50-55%.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.11
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• pp.1142-1155
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• 2014

The classical PCM/PSK/PM scheme has been commonly used for TC & R applications between satellites and ground stations in the S-band. We analyzed TC & R link performance between ground station and the geostationary satellite which employs PCM/PSK/PM, when the satellite are particularly on the Super Synchronous Transfer Orbit(SSTO). The satellite parameters on SSTO are assumed to be those operating on the geostationary orbit, considering heritage aspect. In the uplink, the results shown indicate that sufficient margins over 3 dB are obtained when the EIRP of ground station is greater than 65 dBW. The down link performance is of great interest. By adjusting the telemetry modulation index and ranging modulation index, we could obtain the required margin of 3.0 dB in the down link, and find out the minimum G/T of ground station. In conclusion, the previously operated ground stations during LEOP at COMS launch, can be operational when GEO injection is made using SSTO(65,000 km and 70,000 km).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.5
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• pp.568-575
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• 2011

In this paper, we propose a small broadband antenna for mobile device. The proposed antenna consists of a printed rectangular monopole antenna and a parastic element connected to ground using narrow meander line and it is designed on a FR-4 substrate that has a thickness of 0.8 mm and a dielectric constant of 4.4. The FR-4 substrate's size is 50 mm${\times}$90 mm comparable to the real mobile device. The fabricated antenna's size is 12.5 mm${\times}$10.5 mm${\times}$0.8 mm and the measurement shows -10 dB return loss bandwidth of 2,200~6,000 MHz and gains of 2.86~4.01 dBi. Accordingly, the proposed antenna can support mobile device for WiBro(2,300~2,380 MHz), WLAN(IEEE 802.11b/g/n: 2,400~2,480 MHz, IEEE 802.11a: 5,150~5,825 MHz), and mobile WiMAX(IEEE 802.16e : 2,500~2,690 MHz, 3,400~3,600 MHz) service bands.

• Progress in Superconductivity
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• v.8 no.2
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• pp.127-131
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• 2007

We have measured the Hall conductivity (${\sigma}_{xy}$) of c-axis-oriented $MgB_2$ thin films as functions of temperatures and magnetic fields. We found that the Hall conductivity (${\sigma}_{xy}$) is expressed by the sum of two terms, ${\sigma}_{xy}=C_l/H+C_3H$, where the coefficient $C_1\;and\;C_3$ are independent of the magnetic fields and have positive values. The coefficient $C_1$ is strongly dependent on the temperature, while the $C_3$ is weakly dependent on the temperature. We have obtained that the $C_1$ is proportional to $(1- T/T_c)^n$ with n = 4.2, which is consistent with the data observed in $La_{2-x}Sr_xCuO_4$ superconductors with low anisotropy ratio.

• Journal of Korea Foundry Society
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• v.15 no.3
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• pp.252-261
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• 1995

The purposes of this study were to investigate the microstructural changes in alloy ribbons of Al-Fe-Mo-Si quarternary system at $450{\sim}500^{\circ}C$, and to study the coarsening mechanism of fine precipitates. Using the hot stage in TEM, in situ microstructural changes in Al-4Fe-0.5Mo-1.5Si alloy ribbon and Al-8Fe-2Mo-1.5Si alloy ribbon have been examined successively up to 60 hours at $450^{\circ}C$ and $500^{\circ}C$. Cell structure in zone B of Al-4Fe-0.5Mo-1.5Si alloy ribbon was observed to collapse even in 10 minutes by in-situ heating at $450^{\circ}C$ and the size of precipitates in zone B increased twice in 60 hours. The precipitates in zone A of Al-4Fe-0.5Mo-1.5Si alloy ribbon showed slower coarsening rate than those in zone B by in-situ heating at $450^{\circ}C$. The precipitates in zone A of Al-8Fe-2Mo-1.5Si alloy ribbon increased 50% by in-situ heating at $500^{\circ}C$ in 50 hours compared to the initial precipitates while any microstructual change in zone B was not observed by in-situ heating at $500^{\circ}C$ up to 50 hours. Only the precipitates in zone A of Al-4Fe-0.5Mo-1.5Si alloy ribbon satisfied $r^3{\propto}t$ relationship of coarsening mechanism.