• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.306-309
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• 2005

One of the most critical issues in sol id oxide fuel cell (SOFC)running on hydrocarbon fuels is the risk of carbon formation from the fuel gas. The simple method to reduce the risk of carbon formation from the reactions is to add steam to the fuel stream, leading to the carbon gasification react ion. However, the addition of steam to fuel is not appropriate for the auxiliary power unit (APU) and potable power generation (PPG) systems due to an increase of complexity and bulkiness. In this regard, many researchers have focused on so-called 'direct methane' operation of SOFC, which works with dry methane without coking. However, coking can be suppressed only by the operation with a high current density, which may be a drawback especially for the APU and PPG systems. The single chamber fuel cell (SC-SOFC) is a novel simplification of the conventional SOFC into which a premixed fuel/air mixture is introduced. It relies on the selectivity of the anode and cathode catalysts to generate a chemical potential gradient across the cell. Moreover it allows compact and seal-free stack design. In this study, we fabricated honeycomb type mixed-gas fuel cell (MGFC) which has advantages of stacking to the axial direction and increasing volume power density. Honeycomb-structured SOFC with four channels was prepared by dry pressing method. Two alternative channels were coated with electrolyte and cathode slurry in order to make cathodic reaction sites. We will discuss that the anode supported honeycomb type cell running on mixed gas condition.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.11
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• pp.2535-2540
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• 2010

In traditional Publish/Subscribe system, the first procedure to deliver event from publisher to subscriber is that publisher publishes publisher's event to broker. Next step is that broker checks simple binary notion of matching : an event either matches a subscription or it does not. Lastly, broker delivers the event matched with subscriptions to the corresponding subscribers. In this system, information delivery has been accomplished in one way only. However, current some applications require two way delivery between subscriber and publisher. Therefore, we initiate an extended Publish/Subscribe system that supports two way delivery. Extended Publish/Subscribe system requires additional functions of delivering subscription to publisher and especially deciding top-n subscriptions using priority because broker might has a number of subscriptions. In this paper, we propose two priority retrieval techniques based on SIF using IS-List with deciding priority among subscriptions and defining SIF(Specific Interval First). The performance measurements show that RSO(resulting set sorting) technique results in better performance in index creation time and ITS&IS(insertion time sorting and inverse search using stack) technique results in better performance in search time.

• The KIPS Transactions:PartC
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• v.14C no.4
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• pp.371-382
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• 2007

In this paper, we propose a real-time sensor node platform that efficiently manages periodic and aperiodic tasks. Since existing sensor node platforms available in literature focus on minimizing the usage of memory and power consumptions, they are not capable of supporting the management of tasks that need their real-time execution and fast average response time. We first analyze how to structure periodic or aperiodic task decomposition in the TinyOS-based sensor node platform as regard to guaranteeing the deadlines of ail the periodic tasks and aiming to providing aperiodic tasks with average good response time. Then we present the application and efficiency of the proposed real-time sensor node platform in the sensor node equipped with a low-power 8-bit microcontroller, an IEEE802.15.4 compliant 2.4GHz RF transceiver, and several sensors. Extensive experiments show that our sensor node platform yields efficient performance in terms of three significant, objective goals: deadline miss ratio of periodic tasks, average response time of aperiodic tasks, and processor utilization of periodic and aperiodic tasks.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.85-91
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• 2018

Recently, there have been a lot of casualties due to fires in high-rise buildings. The toxic gases and smokes generated by fires in high-rise buildings spread rapidly through the elevator shaft and stairwell, due to the stack effect, and can cause critical casualties. To reduce the number of casualties, smoke control systems have been introduced. Smoke control systems play an essential role in preventing the spread of smoke in high-rise buildings and securing the evacuation route. Also, in high-rise buildings, evacuation by an elevator is considered to be indispensable. However, the pressure field in the shaft is strongly disturbed when the elevator is moving and this can affect the performance of the smoke control system. Therefore, in this study, we experimentally and numerically analyzed the effect of elevator movement on the pressure difference between the vestibule and living room by building a model using the sandwich pressurization method based on the performance based design. To consider the leakage areas in high-rise buildings, e.g. the windows, fire door and elevator, the National Fire Safety Codes and area ratio were used. The elevator speed in the model building was varied between 20 m/s and 100 m/s corresponding to a real elevator speed of 7 m/s~17 m/s. As a result, the relationship between the pressure difference and elevator speed was found to be ${\Delta}P=40{\cdot}{\exp}$(-Ves /-104.7)-23.735. This result can be used to take into consideration the effect of elevator movement when designing smoke control systems.

• Journal of Magnetics
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• v.11 no.4
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• pp.195-207
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• 2006

The recently published and new results on design and fabrication of magnetophotonic crystals of different dimensionality are surveyed. Coupling of polarized light to 3D photonic crystals based on synthetic opals was studied in the case of low dielectric contrast. Transmissivity of opals was demonstrated to strongly depend on the propagation direction of light and its polarization. It was shown that in a vicinity of the frequency of a single Bragg resonance in a 3D photonic crystal the incident linearly polarized light excites inside the crystal the TE- and TM-eigen modes which passing through the crystal is influenced by Brags diffraction of electromagnetic field from different (hkl) sets of crystallographic planes. We also measured the faraday effect of opals immersed in a magneto-optically active liquid. It was shown that the behavior of the faraday rotation spectrum of the system of the opal sample and magneto-optically active liquid directly interrelates with transmittance anisotropy of the opal sample. The photonic band structure, transmittance and Faraday rotation of the light in three-dimensional magnetophotonic crystals of simple cubic and face centered cubic lattices formed from magneto-optically active spheres where studied by the layer Korringa-Kohn-Rostoker method. We found that a photonic band structure is most significantly altered by the magneto-optical activity of spheres for the high-symmetry directions where the degeneracies between TE and TM polarized modes for the corresponding non-magnetic photonic crystals exist. The significant enhancement of the Faraday rotation appears for these directions in the proximity of the band edges, because of the slowing down of the light. New approaches for one-dimensional magnetophotonic crystals fabrication optimized for the magneto-optical Faraday effect enhancement are proposed and realized. One-dimensional magnetophotonic crystals utilizing the second and the third photonic band gaps optimized for the Faraday effect enhancement have been successfully fabricated. Additionally, magnetophotonic crystals consist of a stack of ferrimagnetic Bi-substituted yttrium-iron garnet layers alternated with dielectric silicon oxide layers of the same optical thickness. High refractive index difference provides the strong spatial localization of the electromagnetic field with the wavelength corresponding to the long-wavelength edge of the photonic band gap.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.20 no.1
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• pp.1-9
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• 2010

Objectives : The purposes of this study were to evaluate exhaust ventilation systems(EVSs) and to suggest problems and improvements. Methods : For 50 small and medium-sized enterprises, we carried out evaluation of EVSs. We evaluated hoods with smoke tester and measurement of capture velocity. In addition, we used several indicators for performance evaluation designed in this study. Results : 1. Based on the smoke flow pattern and the criteria of occupational health and safety act, 67.8% of hoods were rated 'good' level at smoke test whereas 26.3% were rated 'good' level at measurement of capture velocity. 2. 29.3% of hoods, of which ratio of measured actual air flow at hood(Qah) to required ideal exhaust air flow at hood(Qih) was 1 or more, were rated 'good' level. 3. The % of EVS, of which ratio of measured actual air flow at stack(Qast) to total required ideal exhaust air flow at hood(Qith) was 1 or more, was 29.0%. 4. For the ratio of measured Qast to existing air flow at fan(Qfan), only 5% of EVSs were 1 or more and 26.0% were 0.8 or more but less than 1.0. 5. For the ratio of measured Qast to total measured actual exhaust air flow at hood(Qath), 74.0% were 0.8 or more but less than 1.0. 6. The percentage of EVS, of which ratio of total measured Qath to existing Qfan was 0.8 or more, was 19.0%. 7. The percentage of EVS, of which ratio of total measured Qath to total required ideal exhaust Qith was 1 or more, was 26.0%. 8. For the comprehensive evaluation indicators designed in this study, 29.0% were 0.8 or more. Conclusions : We found that few exhaust local ventilations at small and medium-sized enterprises were rated 'good' level and that most exhaust local ventilations had 'poor' design and installation. Therefore, relevant professional manpower and enterprises have to construct exhaust local ventilation where it is needed, and technical guidance and economic support are needed to improve 'poor' exhaust local ventilation after self-evaluation.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.44-52
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• 2002

Low temperature thermal desorption (LTTD) has become one of the cornerstone technologies used for the treatment of contaminated soils and sediments in the United States. LTTD technology was first used in the mid-1980s for soil treatment on sites managed under the Comprehensive Environmental Respones, Compensation and Liability Act (CERCLA) or Superfund. Implementation was facilitated by CERCLA regulations that require only that spplicable regulations shall be met thus avoiding the need for protracted and expensive permit applications for thermal treatment equipment. The initial equipment designs used typically came from technology transfer sources. Asphalt manufacturing plants were converted to direct-fired LTTD systems, and conventional calciners were adapted for use as indirect-fired LTTD systems. Other innovative designs included hot sand recycle technology (initially developed for synfuels production from tar sand and oil shale), recycle sweep gas, travelling belts and batch-charged vacuum chambers, among others. These systems were used to treat soil contaminated with total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAHs), pesticides, polychlorinated biphenyls (PCBs) and dioxin with varying degrees of success. Ultimately, performance and cost considerations established the suite of systems that are used for LTTD soil treatment applications today. This paper briefly reviews the develpoment of LTTD systems and summarizes the design, performance and cost characteristics of the equipment in use today. Designs reviewed include continuous feed direct-fired and indirect-fired equipment, batch feed systems and in-situ equipment. Performance is compared in terms of before-and-after contaminant levels in the soil and permissible emissions levels in the stack gas vented to the atmosphere. The review of air emissions standards includes a review of regulations in the U.S. and the European Union (EU). Key cost centers for the mobilization and operation of LTTD equipment are identified and compared for the different types of LTTD systems in use today. A work chart is provided for the selection of the optmum LTTD system for site-specific applications. LTTD technology continues to be a cornerstone technology for soil treatment in the U.S. and elsewhere. Examples of leading-edge LTTD technologies developed in the U.S. that are now being delivered locally in global projects are described.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.3
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• pp.3-12
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• 2015

Recently, various studies have been attempted to provide a biological information monitoring service through integrating with the web service. The medical information transmission standard ISO/IEEE 11073 PHD defines the optimized exchange protocol ISO/IEEE 11073-20601 based on the No-IP to exchange the biometric information between the ISO/IEEE 11073 agent and the manager. It's system structure based on the No-IP using ISO/IEEE 11073-20601 is not suitable for providing a remote biological information monitoring services. That is because it is difficult to provide to control and manage the biological information measurement devices, which have installed IP protocol stack at the remote. Furthermore, ACSE and CMDISE in ISO/IEEE 11073-20601 are not suitable to provide U-healthcare services based on IoT because they are complicated and difficult to implement it caused by the structural complexity. In order to solve the problems, in this paper, we propose the biological information monitoring architecture based on ISO/IEEE 11073 DIM/REST of IoT environment to provide the biological information monitoring service based on IoT. To do this, we designed biological information monitoring system architecture based on IoT and the message exchange protocol of ISO/IEEE 11073 DIM/REST between the ISO/IEEE 11073 agent and the ISO/IEEE 11073 manager. In order to verify the realistic possibility of the proposed system architecture, we developed the service prototype.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.6
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• pp.584-597
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• 2011

In this paper, low-loss and high-power RF SP6T switch chips are designed, fabricated and measured for GSM/EGSM/DCS/PCS applications using WIN Semiconductors 0.5 ${\mu}m$ pHEMT process. We utilized a combined configuration of series and series-shunt structures for optimized switch performance, and a common transistor structure on a receiver path for reducing chip area. The gate width and the number of stacked transistors are determined using ON/OFF input power level of the transceiver system. To improve the switch performance, feed-forward capacitors, shunt capacitors and parasitic FET inductance elimination due to resonance are actively used. The fabricated chip size is $1.2{\times}1.5\;mm^2$. S-parameter measurement shows an insertion loss of 0.5~1.2 dB and isolation of 28~36 dB. The fabricated SP6T switch chips can handle 4 W input power and suppress second and third harmonics by more than 75 dBc.

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.278-284
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• 2006

We have fabricated and measured electrooptic modulator using coupled stack InAs/InGaAs quantum dots. The height of the quantum dot is 16 nm and quantum dots are stacked including an InGaAs capping layer. The peak wavelength of photoluminescence is 1260 nm at room temperature and 1158 nm at 12 K. The operation characteristics of the quantum dots show high modulation efficiency of electrooptic modulator at 1550 nm compared to that of existing III-V bulk and MQW type semiconductor. The measured switching voltage ($V\pi$) is 540 and 600 mV, for TE mode and TM mode, respectively. From the results, the modulation efficiency can be determined as 333.3 and $300^{\circ}/V{\cdot}mm$ for TE and TM modes. The results reported here may lead to the design and fabrication of a novel electrooptic modulator with low switching voltage and high efficiency.