• Journal of the Korean Magnetics Society
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• v.7 no.3
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• pp.140-145
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• 1997

The amorphous state of $NdFe_{10.7}TiB_{0.3}$ and its nanocrystallization have been studied by X-ray diffraction, 모스바우어 spectroscopy, and a vibrating sample magnetometer (VSM), $NdFe_{10.7}TiB_{0.3}$ amorphous ribbons were fabricated by a sigle-roll melt-spinning method. The average hyperfine field $H_{hf}$(T) of the amorphous state shows a temperature dependence of $[H_{hf}(T)-H_{hf}(0)]/H_{hf}(0)=-0.46(T/T_c)^{3/2}-0.34(T/T_c)^{5/2}$ for $T/T_c<0.7$ indicative of spin wave excitation. The quadrupole splitting just above the Curie temperature $T_c$ is 0.46 mm/s, whereas the average quadrupole shift below $T_c$ is zero. The Curie and crystallization temperatures are determined to be $T_c$=380K and $T_x=490K$, respectively, for a heating rate of 5 K/min. The occupied area of nanocrystalline phase at around 770K is about 65%. Above the Curie temperature, VSM data show magnetic moments increases again. The formation of $\alpha$-Fe is the main reason for the increasing moment as conformed with the 모스바우어 measurements.

• Progress in Medical Physics
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• v.19 no.1
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• pp.42-48
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• 2008

Bio-implantable devices such as heart pacers, gastric pacers and drug-delivery systems require power for carrying out their intended functions. These devices are usually powered through a battery implanted with the system or are wired to an external power source. This paper describes an inductive power transmission link, which was developed for an implantable stimulator for direct stimulation of denervated muscles. The carrier frequency is around 1MHz, the transmitter coil has a diameter of 46mm, and the implant coil is 46mm. Data transmission to the implant with amplitude shift keying (ASK) and back to the transmitter with passive telemetry can be added without major design changes. We chose the range of coil spacing (2 to 30mm) to care for lateral misalignment, as it occurs in practical use. If the transmitter coil has a well defined and reliable position in respect to the implant, a smaller working range might be sufficient. Under these conditions the link can be operated in fixed frequency mode, and reaches even higher efficiencies of up to 37%. The link transmits a current of 50 mA over a distance range of 2-15 mm with an efficiency of more than 20% in tracking frequency. The efficiency of the link was optimized with different approaches. A class E transmitter was used to minimize losses of the power stage. The geometry and material of the transmitter coil was optimized for maximum coupling. Phase lock techniques were used to achieve frequency tracking, keeping the transmitter optimally tuned at different coupling conditions caused by coil distance variations.

• Atmosphere
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• v.26 no.3
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• pp.387-400
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• 2016

In this study, the atmospheric $CO_2$ concentrations estimated by CT2013B, a recent version of CarbonTracker, are compared with $CO_2$ measurements from the Comprehensive Observation Network for Trace gases by Airliner (CONTRAIL) project during 2010-2011. CarbonTracker is an inversion system that estimates surface $CO_2$ fluxes using atmospheric $CO_2$ concentrations. Overall, the model results represented the atmospheric $CO_2$ concentrations well with a slight overestimation compared to observations. In the case of horizontal distribution, variations in the model and observation difference were large in northern Eurasia because most of the model and data mismatch were located in the stratosphere where the model could not represent $CO_2$ variations well enough due to low model resolution at high altitude and existing phase shift from the troposphere. In addition, the model and observation difference became larger in boreal summer. Despite relatively large differences at high latitudes and in boreal summer, overall, the modeled $CO_2$ concentrations fitted well to observations. Vertical profiles of modeled and observed $CO_2$ concentrations showed that the model overestimates the observations at all altitudes, showing nearly constant differences, which implies that the surface $CO_2$ concentration is transported well vertically in the transport model. At Narita, overall differences were small, although the correlation between modeled and observed $CO_2$ concentrations decreased at higher altitude, showing relatively large differences above 225 hPa. The vertical profiles at Moscow and Delhi located on land and at Hawaii on the ocean showed that the model is less accurate on land than on the ocean due to various effects (e.g., biospheric effect) on land compared to the homogeneous ocean surface.

• Journal of the Korean Ceramic Society
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• v.40 no.12
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• pp.1202-1207
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• 2003

Using a recently developed Hybric Plasma-Particle Accelerating Impact Deposition (HP-PAID) process, synthesis of nanostructured silicon coatings has been investigated by injecting vapor-phase TEOS (tetraethosysilane, (C$_2$H$\_$5/O)$_4$Si) into an Ar hybrid plasma. The plasma jet with reactants was expanded through nozzle into a deposition chamber, with the pressure dropping from 700 to 10 torr. Ultrafine particles accelerated in the free jet downstream of the nozzle, deposited by an inertial impaction onto a temperature controlled substrate. By using this process, nanostructured amorphous silicon coatings with grain size smaller than 10 nm could be synthesized. These samples were annealed in an Ar and crystallized at 900$^{\circ}C$ for 30 min. TEM analysis showed that the annealed coatings were also composed of nanoparticles smaller than 10 nm, which showed a good consistency that the average grain size of 7 nm was also estimated from a peak shift of 2.39 cm$\^$-1/ and Full Width at Half Maximum (FWHM) 5.92 cm$\^$-1/ of Raman analysis. The noteworthy is that a strong PL peak at 398 nm was also obtained for this sample, which indicates that the deposited coatings also contained 3∼4 nm nanostructured grains.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.693-697
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• 2007

The SSB modem performs the modulation process which converts the digital voltage level to the audible frequency band signal and the demodulation process which converts reversely the audible frequency signal to the digital voltage level. The modulator and the demodulator are implemented with a single DSP chip. Because of the SSB specific character, the distortion occurs when the frequency is changed. This distortion has no effect on voice communication, but it has an significant effect on data communication. In other words, it is impossible to send data stream with adjacent 2 periods. Therefore, in case of using 2-tone FSK, it is needed to send at least 3 periods to transmit 1 bit. Therefore we implemented the modem using modified phase-delay shift keying to transmit 1 tone signal for high speed transmission. In the 1200[bps] mode, it generates 0, $187{\mu}s$ delay time at 1.3kHz symbol frequency, and in the 2400[bps] mode, 0, $70{\mu}s$, $130{\mu}s$, $200{\mu}s$ delay time at 1.5kHz symbol frequency. Finally, in the maximum 3600[bps] mode, it generates 0, $100{\mu}s$, $160{\mu}s$, $250{\mu}s$ delay time at 2.0kHz symbol frequency. The measured results of the implemented SSB modem shows a good transfer functional characteristic by spectrum analyzer, almost same bandwidth in pass band and 20dB higher SNR comparing the German PACTOR and American CLOVER and in the experimental transmitting test, we verified the transmitted data is received correctly in platform.

• Korean Journal of Materials Research
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• v.11 no.1
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• pp.3-7
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• 2001

$M\"{o}ssbauer$ spectra of the $Ni_{1+x}Ti_xFe_{2-2x}O_4$ systems ($0{\leqq}x{\leqq}0.7$), which appear as single phase spinel structure, were examined at RT. The $M\"{o}ssbauer$ spectra reveal two sextet for $0{\leqq}x{\leqq}0.3$, two sextet and a doublet for $0.4{\leqq}x{\leqq}0.6$, and a doublet for x=0.7 As x increases, the area ratio of B-site and A-site($A_B/A_A$) of the sextet decreases, and the area ratio of the doublet and the total areas($A_{doublet}/A_{tot.}$) increases. The isomer shift(I.S.) of A-site slightly increases and magnetic hyperfine fields($H_{hf}$) of two sites decrease as the increasing x. From these results, we have obtained the cation distributions of the samples and concluded that the increasing x leads to the decrease of covalency of $Fe^{3+}-O^{2-}$ bond in A-sites and A-B superexchange interactions.eractions.

• Journal of the Korean Magnetics Society
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• v.17 no.1
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• pp.47-50
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• 2007

[ $ZnCr_2O_4$ ] shows geometrically frustrated magnet. Recently, $CoCr_2O_4$ has been investigated for multiferroic property and dielectric anomalies by spin-current model. Polycrystalline $CoCr_2O_4$ and $CoCrFeO_4$ compounds was prepared by wet-chemical process. Crystallographic and magnetic properties of $CoCr_2O_4$ and $CoCrFeO_4$ were investigate by using the x-ray diffractometer(XRD), vibrating sample magnetometer(VSM), superconducting quantum interference device magnetometer(SQUID), and $M\"{o}ssbauer$ spectroscopy. The crystal structure was found to be single-phase cubic spinel with space group of Fd3m. The lattice constants of $CoCr_2O_4$ and $CoCrFeO_4$ $a_0$ were determined to be 8.340 and 8.377 ${\AA}$, respectively. The ferrimagnetic transition temperature for the both samples were observed at 97 K and 320 K. The $M\"{o}ssbauer$ absorption spectra at 4.2 K show that the well developed two sextets are superposed with small difference of hyperfine field($H_{hf1}=507\;and\;H_{hf2}=492\;kOe$). Isomer shift values($\delta$) of the two sextets are found to be 0.33 and 0.34 mm/s relative to the Fe metal, respectively, which are consistent with the high spin $Fe^{3+}$ charge state.

• Journal of Korean Society of Archives and Records Management
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• v.18 no.1
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• pp.129-154
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• 2018

It is time to prepare for the imminent development from the field of records management through decentralization to the records management of the new age in accordance with the flow of decentralization. To overcome a centralized record management system, more archives should be established to realize autonomous and decentralized records management. In accordance with the shift to a full-scale electronic record management environment, the appropriateness and effectiveness of the three-phase system of processing-archival-permanent record management based on physical transfer should be reviewed in terms of transfer cost and work efficiency. The archives should function as institutional archives to carry out the continuous volume record management and the autonomous record management at the institution level. This study examined the possibilities and implications of the archives to expand their functions as archives of institutions for the decentralization of record management and information governance orientation. In addition, the study diversified the types of records management institutions as a way to accomplish this and determined a way to design the functions of archives that integrate the current-end-end-end records management. At each level, institutions should set up archives based on their circumstances and aim at information governance at the level of each archive. Moreover, each archive level should establish a horizontal network to govern record information management.

• Environmental and Resource Economics Review
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• v.26 no.4
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• pp.577-612
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• 2017

In response to climate change, Korea is attempting to shift the paradigm of energy and climate change policies by introducing carbon pricing based on market mechanisms. While policy adoption is proceeding at a rapid pace, the introduction of carbon pricing has been faced with great opposition from industry. This study measures to what extent Korean companies understand and accept carbon pricing, using data from a questionnaire survey covering energy consuming companies in 2012, when discussions between the government and such companies about the introduction of a domestic emission trading system were active. It further identifies how preparations and practices for carbon and energy management of companies correlate with their policy understanding and acceptance. The analysis results show that the surveyed companies indicate moderate understanding of, as well as resistance to carbon pricing policies, while appreciating the economic incentives and accepting the mandatory regulations in this phase. Companies' understanding is more related to characteristics, i.e., sector, size, etc. than external pressures. This study found that the extent to which companies understand policy is the essential factor in their policy acceptance and related practices. In particular, understanding of carbon policy significantly influences their managerial practices and voluntary activities for carbon and energy practices. This study substantiates the correlation between the level of policy understanding of a company and its carbon and energy practices - something that all countries seeking to introduce carbon pricing in response to climate change should consider prior to policy actually being implemented; in other words, enhancing the understanding of major policy subjects of the new instrument is a key policy strategy that should be elaborated as it will lead to better performance of companies and smoother policy implementation.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.3
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• pp.110-119
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• 2017

This study develops a passive traffic signal priority control algorithm for emergency vehicles. The passive priority control estimates and applies signal times for each signalized intersection on the emergency vehicle's route when an emergency call is received. As signals are controlled before the emergency vehicle leaves for its destination, it is possible to clear the queues at each intersection more effectively. Most of the previous studies applied preemption, which ends green time of cross streets when the emergency vehicle arrives at each intersection. This study applies green extension and early green in order not to shift the order of phases, and guarantees minimum green time for each phase. Simulation results show that the delay of emergency vehicles decreases when the signals are controlled. It is expected that delays can be decreased further by integrating the active priority control with the passive priority control algorithm presented in this study.