• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.36.3-37
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• 2015

4C39.25 (0923+392) is a distant radio loud AGN placed at redshift 0.695. The motivation of our work is peculiar properties 4C39.25. Firstly, it has a conspicuous distinction of jet direction between kilo-parsec scale observation made by VLA (Kollgaard et al. 1990) and the parsec scale observation by VLBA (Kellermann et al. 1998). This might indicate episodic-jet activity which recently turned on. This object currently shows two stationary compact parsec-scale components which are bright jet component on east and less luminous core on west. Also, it is known that there have been superluminal jet components which are flowing from the core toward east, and then merging with the bright jet component (Marscher et al. 1991, Alberdi et al. 2000, Lister et al. 2013). Although 4C39.25 seems to be a blazar-like source having broad emission lines (SDSS) and superluminal motion, its property that jet component is brighter than the core is different from ordinary blazars. Furthermore, it has young radio galaxy-like properties such as non-variation in total flux (Alberdi et al. 1997, 2000, MOJAVE database) and high frequency peak at spectral energy distribution (Orienti et al 2007). Such complex properties led us to make recent observations to reveal precise properties and new changes of the source. We used Korean VLBI Network (KVN) and VLBI Exploration of Radio Astronomy (VERA) Array (KaVA) which provide high-frequency (23GHz and 43GHz) and high spatial resolution (1.2mas and 0.6mas). Therefore, this system is suitable for morphological and physical research on parsec scale structure. We present results for several epochs observed during 2013 to 2014, mainly focusing on morphological changes of 4C39.25 using KaVA images.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.35.1-35.1
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• 2015

We present the results of extinction measurements toward the main ejecta shell of the Cassiopeia A supernova (SN) remnant using the flux ratios between the two near-infrared (NIR) [Fe II] lines at 1.26 and $1.64{\mu}m$. We find a clear correlation between the NIR extinction (E(J-H)) and the radial velocity of ejecta knots, showing that redshifted knots are systematically more obscured than blueshifted ones. This internal "self-extinction" strongly indicates that a large amount of SN dust resides inside and around the main ejecta shell. At one location in the southern part of the shell, we measure E(J-H) by the SN dust of $0.23{\pm}0.05mag$. By analyzing the spectral energy distribution of thermal dust emission at that location, we show that there are warm (~100K) and cool (~40K) SN dust components and that the latter is responsible for the observed E(J-H). We investigate the possible grain species and size of each component and find that the warm SN dust needs to be silicate grains such as $MgSiO_3$, $Mg_2SiO_4$, and $SiO_2$, whereas the cool dust could be either small (${\leq}0.01{\mu}m$) Fe or large (${\geq}0.01{\mu}m$) Si grains. We suggest that the warm and cool dust components in Cassiopeia A represent grain species produced in diffuse SN ejecta and in dense ejecta clumps, respectively.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.42.2-43
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• 2015

Massive stars play a major role in the interstellar energy budget and the shaping of the galactic environment. The water molecule is thought to be a sensitive tracer of physical conditions and dynamics in star-forming regions because of its large abundance variations between hot and cold regions. Herschel/HIFI allows us to observe the multiple rotational transitions of H2O including the ground-state levels, and its isotopologues toward high-mass star-forming regions in different evolutionary stages. Photodissociation regions (PDRs) are also targeted to investigate the distribution of water and its chemistry. We present line profiles and maps of H2O using data from two guaranteed-time key programs "Water In Star-forming regions with Herschel" and "Herschel observations of EXtra-Ordinary Sources". We analyze the temperature and density structures using LTE and non-LTE methods. We also estimate turbulent and expansion velocities, and abundance of water in the inner and outer envelopes using the 1D radiative transfer code. Around high-mass protostars we find H2O abundances of ~10-8-10-9 for the outer envelope and ~10-4-10-5 for the inner envelope, and expansion and turbulent velocities range from 1.0 km s-1 to 2.0 km s-1. The abundances and kinematic parameters of the sources do not show clear trends with evolutionary indicators. The Herschel/HIFI mapping observations of H2O toward the Orion Bar PDR show that H2O emission peaks between the shielded dense gas and the radicals position, in agreement with the theoretical and the observational PDR structure. The derived H2O abundance is ~10-7 and peaks at the depth of AV ~8 mag from the ionization front. Together with the low ortho-to-para ratio of H2O (~1) presented by Choi et al. (2014), our results show that the chemistry of water in the Orion Bar is dominated by photodesorption and photodissociation.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.121-127
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• 2013

Memory devices including SRAM and DRAM are very susceptible to high energy radiation particles in the space. Abnormal operation of the devices is caused by SEE or TID. This paper presents a method to estimate proton SEU cross section representing the susceptibility of the latch circuit that the unit cell of the SRAM and proposes a new latch circuit to mitigate the SEU. 50b shift register was fabricated by using the conventional latch and the proposed latch in $0.35{\mu}m$ process. Irradiation experiment was conducted at KIRAMS by using 43MeV proton beam. It was found that the proposed latch-shift register is not affected by the radiation environment compared to the conventional latch-shift register.

• Journal of computational fluids engineering
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• v.21 no.2
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• pp.112-119
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• 2016

NEXTSat-1 is the next-generation small-size artificial satellite system planed by the Satellite Technology Research Center(SatTReC) in Korea Advanced Institute of Science and Technology(KAIST). For the control of attitude and transition of the orbit, the system has adopted a RHM(Resisto-jet Head Module), which has a very simple geometry with a reasonable efficiency. An axisymmetric model is devised with two coil-resistance heaters using xenon(Xe) gas, and the minimum required specific impulse is 60 seconds under the thrust more than 30 milli-Newton. To design the module, seven basic parameters should be decided: the nozzle shape, the power distribution of heater, the pressure drop of filter, the diameter of nozzle throat, the slant length and the angle of nozzle, and the size of reservoir, etc. After quasi one-dimensional analysis, a theoretical value of specific impulse is calculated, and the optima of parameters are found out from the baseline with a series of multi-physical numerical simulations based on the compressible Navier-Stokes equations for gas and the heat conduction energy equation for solid. A commercial code, COMSOL Multiphysics is used for the computation with a FEM (finite element method) based numerical scheme. The final values of design parameters indicate 5.8% better performance than those of baseline design after the verification with all the tuned parameters. The present method should be effective to reduce the time cost of trial and error in the development of RHM, the thruster of NEXTSat-1.

• Journal of the Korea Furniture Society
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• v.26 no.1
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• pp.77-91
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• 2015

The appeal of sauna is caused by the fact that through that, one can feel Korea's unique temperament and culture; however, because of its being a public facility and flooding of businesses due to excessive supplies of various additional features such as washing, playing, eating, sleeping and health care functions, issues of social resources and environment come to the fore, so it has reached a situation of red ocean that it is difficult to enter the market anymore. Taking these into account, this study focused on developing a thermal technology and design of the housing of an environment-friendly mobile home sauna, making the most use of the sauna's fundamental purpose and settling it as a tourist product, analyzing the marketing research on the existing sauna and considering the recent housing trends and lifestyles for a new concept sauna. Thus, regarding its characteristics and utilization, it was designed smaller than $10m^2$ (3 pyeong) so that it would be easy to install in any space and convenient to move. It can be installed in separate buildings and rest spaces such as country houses, resorts, pensions, camping grounds as well as outdoor houses, custom produced for a measure of pyeong that customers want so as to match up with the Enforcement Ordinance of the Agricultural Land Act in a concept of the farmer's hut and kitchen, bathroom and bathroom can be installed inside according to an option. In addition, regarding its efficacy, in order to give environment-friendly healing effects, materials such as Hinoki Cypress, red clay and hardwood charcoal were used, a fixed indoor temperature of $70{\sim}100^{\circ}C$ was maintained by heating methods such as electromagnetic wave free, energy saving and low-power boiler, and it was made to have excellent effects on fatigue recovery, relieving stress, skin care and diet through far-infrared emission.

• Journal of Korea Spatial Information System Society
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• v.11 no.2
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• pp.99-110
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• 2009

Currently, there are many applications being developed based on sensor network technology. A tracking method for moving objects in sensor network is one of the main issue of this field. There is a little research on this issue, but most of the existing work has two problems. The first problem is a communication overhead for visiting sensor nodes many times to track a moving object. The second problem is an disability for dealing with many moving objects at a time. To resolve the problems, we, in this paper, propose a signature-based tracking method using efficient data aggregation for moving objects, called SigMO-TRK. For this, we first design a local routing hierarchy tree to aggregate moving objects' trajectories efficiently by using a space filtering technique. Secondly, we do the tracking of all trajectories of moving objects by using signature in a efficient way, our approach generates signatures to method. In addition, by extending the SigMO-TRK, we can retrieve the similar trajectories of moving objects for given a query. Finally, by using the TOSSIM simulator, we show that our signature-based tracking method outperforms the existing tracking method in terms of energy efficiency.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.06a
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• pp.166-168
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• 2014

Coarse-grained reconfigurable architectures (CGRAs) present a potential of high compute throughput with energy efficiency. A CGRA consists of an array of functional units (FU), which communicate with each other through an interconnect network containing transmission nodes and register files. To achieve high performance from the software solutions mapped onto CGRAs, modulo scheduling of loops is generally employed. One of the key challenges in modulo scheduling for CGRAs is to explicitly handle routings of operands from a source to a destination operations through various routing resources. Existing modulo schedulers for CGRAs are slow because finding a valid routing is generally a searching problem over a large space, even with the guidance of well-defined cost metrics. Applications in traditional embedded multimedia domains are regarded relatively tolerant to a slow compile time in exchange of a high quality solution. However, many rapidly growing domains of applications, such as 3D graphics, require a fast compilation. Entrances of CGRAs to these domains have been blocked mainly due to its long compile time. We attack this problem by utilizing patternized routes, for which resources and time slots for a success can be estimated in advance when a source operation is placed. By conservatively reserving predefined resources at predefined time slots, future routings originated from the source operation are guaranteed. Experiments on a real-world 3D graphics benchmark suite show that our scheduler improves the compile time up to 6000 times while achieving average 70% throughputs of the state-of-art CGRA modulo scheduler, edge-centric modulo scheduler (EMS).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.9
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• pp.820-827
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• 2011

Recently, noise has been regarded as one of the most notorious and frequent environmental pollutions which can be often encountered not only in the living space but also in the industrial site. Studies on physiological and psychological effects of long-term noise exposure to human being have commanded the public interest on noise issues. Since environmental noises such as traffic noise and construction noise is mainly flowed through the open window, it is necessary to develop the active noise control system to reduce it inside the building. Although control speakers and microphones for the noise signal measurement in the control region are essential for the conventional active noise control methods, it is impossible to implement them in the control region in the building environment because the control region is the living quarter and they may hinder activities of the residents. Therefore, we proposed the active window system to reduce the exterior noise flowed through the open window with microphones installed outside the window and control speakers installed at the frame of the window. To confirm the performance of the proposed active window, we carried out the simulation and experiment using active window system with 8 control speakers. Simulation results showed the noticeable noise reduction effect inside the control region within the frequency range without the spatial aliasing. Experimental result showed that the total acoustic potential energy inside the room of the scale model is reduced to about 10dB within the interest of frequency range.

• Tunnel and Underground Space
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• v.26 no.2
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• pp.120-130
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• 2016

Considering the applicability of Kuz-Ram model, which has been used extensively for predicting rock fragmentation size distribution by blasting, to domestic open-pit limestone mine, a total of 21 blasting tests have been executed at an open-pit limestone mine in eastern Gangwon of South Korea. A comparative analysis of field measured value and Kuz-Ram predicted value showed that there are a considerable amount of error in the predicted values regardless of application of various correction parameters for rock factor and uniformity factor; up to 56.45% in mean fragmentation size and 37.52% in uniformity index. Also the problem of applying different correction parameters has been derived even though a similar blasting pattern has been adopted for a same blasting bench. The authors therefore suggest that Kuz-Ram model needs to be modified for a proper application to domestic open-pit limestone mine.