• Journal of KIISE:Databases
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• v.36 no.4
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• pp.306-313
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• 2009

Top-k queries are issued to find out the highest (or lowest) readings in many sensor applications. Many top-k query processing algorithms are proposed to reduce energy consumption; FILA installs a filter at each sensor node and suppress unnecessary sensor updates; PRIM allots priorities to sensor nodes and collects the minimal number of sensor reading according to the priorities. However, if many sensor reading converge into the same range of sensor values, it leads to a problem that many false positives are occurred. In this paper, we propose a cluster-based approach to reduce them effectively. Our proposed algorithm operates in two phases: top-k query processing in the cluster level and top-k query processing in the tree level. False positives are effectively filtered out in each level. Performance evaluations show that our proposed algorithm reduces about 70% false positives and achieves about 105% better performance than the existing top-k algorithms in terms of the network lifetime.

• Resources Recycling
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• v.14 no.5 s.67
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• pp.32-39
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• 2005

Leaching behavior of nickel contained in waste Multi-Layer Ceramic Capacitor (MLCC) was investigated using a batch reactor. The effects of acid type, acid concentration, leaching temperature, particle size, and reaction time on the extraction of nickel metal from waste MLCC were examined. As a result, 97% of nickel contained in waste MLCC was leached out in 30 min at the temperature of $90^{\circ}C$ under the condition of $HNO_3$ concentration 1N, solid/liquid ratio 5 g/L and particle size $-300/+180{\mu}m$. It was also found that a Jander equation was useful to fit well the leaching rate data. The rate of nickel leaching is controlled by pore diffusion in $BaTiO_3$ layer and has an activation energy of 37.6 kJ/mol (9.0 kcal/mol).

• Resources Recycling
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• v.4 no.3
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• pp.26-31
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• 1995

The leaching characteristics of manganese nodules were investigated in dilute hydrochloric acid solution using copper malie as a reductant. Thc capper matte has been found to be an effective reductant for exhacting morc than 96% of Mn, 95% of Ni, 91% of Ca, 88% of Cu and 36% of Fe when leached in 2.5 M HCI at 70$^{\circ}$C for 2hr. The dissolutions of Mu, Co, and Ni depend on thc amaunt of added cappcr matte. 7he ratin of liquid and solid is an important [actor on the extraction of metals during leaching The dissolution af Mn, Co, Ni and Cu incrcascd w~th the increase in temperalure of leachant. The leaching rates of Mn, Co, NI and Cu from manganese nodule m the presznce of copper matte is limited by bath thc surface chemical reaction and pare diffusion processes. Thc activation energies far Mn. Co: Ni and Cu were 17. 61, 12.8, 17.2 and 57.88 KcaUmol, rcspcctively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.867-873
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• 2007

Thermal degradation characteristics of polypropylene and polystyrene have been studied in the thermogravimetric(TG) reactor and batch-type microreactor. The dynamic thermogravimetric curve of TG provided a valuable information about pyrolysis temperature. It was found that PS was thermally degraded at lower temperature of $30{\sim}50^{\circ}C$ than PP. It was found that the yield and molecular weight of liquid product in the microreactor were decreased with the increase of reaction temperature and time in the case of PP. The production of styrene monomer was significantly increased by the promotion of depolymerization with the increase of temperature and time. The chain-end scission rate parameters were determined to be 50.0 kcal/mole of PP, 45.2 kcal/mole of PS by the Arrhenius plot.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.59-67
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• 2006

The aim of this study is to evaluate the design table for envelope curve analysis of base isolated buildings, which represent the period of base isolated buildings and the lateral displacement of base isolation devices. For the construction of design table, $V_E$ spectrum, which represents the energy, is developed instead of acceleration of seismic hazard. Based on the seismic coefficient of UBC 97, boundary period $T_G$ and maximum velocity response $V_0$ are proposed considering Korea seismic hazard. Using $T_G$ and $V_0$, finally, $V_E$ spectrum is developed for the four types of soil conditions. Base on the $V_E$ spectrum, design table for envelope curve analysis is also developed for soil types.

• The KIPS Transactions:PartC
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• v.18C no.3
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• pp.179-186
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• 2011

Wireless Mesh Network technology refers to the technology which establishes wireless network whose transmission speed is similar to that of the wire system, and provides more enhanced flexibility in the building of network, compared to the existing wired network. In addition, it has the feature of less mobility and less restriction from the energy effect. However, there follow many considerations such as system overhead in the case of setting or the selection of multi-path. Accordingly, the focus is on the design and optimization of network which can reflect this network feature and the technology to establish path. This paper suggests the methods on the programming of path in Wireless Mesh Network routing by applying the evaluation value of node service, making use of the loss rate of data, the hop count of bandwidth and link and the traffic status of node, considering the performance of link and load in the fitness evaluation function, in order to respond to the programming of multi-path effectively.

• Journal of the Korean Institute of Gas
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• v.17 no.5
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• pp.28-36
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• 2013

The underground coal which is buried in the ground will have a lot of attention to overcome energy crisis as an energy resources standpoint. Many studies of underground coal gasification have been also conducted because of its advantage which does not require mining. In this study, the simulation of underground coal gasification process was carried out with Aspen Plus. This study was executed by Rock Mountain 1 Underground Coal Gasification project in the United States in the late 1980s as a reference. Sensitivity analysis proceeded to investigate synthesis gas characteristics following different injection condition of oxidizing agent. The underground coal gasification model has been implemented. That is divided into drying, pyrolysis, char gasification and the simulation results was confirmed by the production gas flow, yield of synthesis gas and amount of gasified carbon from results of the actual experimental data.

• Journal of the Korean Geographical Society
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• v.38 no.2
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• pp.145-155
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• 2003

In this research, the primary factors affected to the formation of lake current of surface layer and thermal stratification of temperate lake have been analyzed, the daily change of water temperature, relationship with lake current and the research about the elements of meteorological phenomenon have been implemented. As a result, the lake current of surface layer occurring while the period of thermal stratification is showing the proportional difference of water temperature, thermal exchange caused by this has been known as the main energy source, and this is, secondly, considering as the interaction of the wind driven current by the prevailing wind. On the other hand, during the night time when the water surface is cooled, and it is considering as the vertical convection is occurring than horizontal circumfluence. Also, there exists the water mass, which is circumfluent counterclockwise and clockwise direction separately. The prevailing md is rather affected to the moving direction and moving speed of water mass, but it doesn't affect to the whole flowing direction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.342-342
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• 2007

원자층 증착(Atomic Layer Deposition: ALD) 방법은 반응물질들을 펄스형태로 챔버에 공급하여 기판 표면에 반응물질의 표면 포화반응에 의한 화학적 흡착과 탈착을 이용한 박막증착기술이다. ALD법은 박막의 조성 정밀제어가 쉽고, 파티클 발생이 없으며, 대면적의 박막 증착시 균일성이 우수하고, 박막 두께의 정밀 조절이 용이한 장점이 있다. 원자층 증착 공정에서 짧은 시간 안에 소스를 충분히 공급하기 위한 방법으로는 소스 온도를 증가시켜 전구체의 증기압을 높여 반응기로의 유입량을 증가시키는 방법, 전구체의 공급시간을 늘리는 방법 등을 들 수 있다. 그러나 전구체 온도를 상승시키는 경우, 공정 조건의 변화가 요구되며 전구체의 변질에 의하여 형성된 막이 의도하는 막 특성을 만족시키지 못하게 되는 문제점이 발생될 우려가 있다. 그리고 전구체를 충분히 공급하기 위하여 전구체의 공급시간을 늘이는 방법을 사용하면, 원하는 두께의 막을 형성하기 위하여 소요되는 공정시간이 증가된다. 이를 해결하기 위해 수송가스를 이용한 버블러 형태의 전구체 공급 장치를 사용하지만 이 또한 전구체의 수명을 단축시키는 단점을 가지고 있다. 본 논문에서는 위의 문제점을 극복할 수 있는 새로운 개념의 수송가스 도움 전구체 공급 장치를 소개한다. 본 연구에서 사용된 수송가스 도움 전구체 공급 장치를 가지는 ALD 장비는 Lucida-D200 (NCD Technology사)이며 기판으로는 8인치 실리콘 웨이퍼를 사용하였으며 (TEMA)Zr을 사용하여 ZrO2 박막을 성장하였다. 수송가스 도움 전구체 공급 장치를 사용한 경우, 그렇지 않은 경우 보다 $30^{\circ}C$ 이상 전구체 온도를 낮출 수 있으며, 또한 증착 속도를 약 2배정도 증가시킬 수 있었다. 이들 박막들은 XRD, XPS, AFM 등을 이용하여 결정구조, 결합에너지, 표면 거칠기 등의 특성을 관찰하였다. 그리고 C-V, I-V 측정을 이용해 정전용량, 유전율, 누설전류 등의 전기적 특성을 평가하였다.

• Polymer(Korea)
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• v.29 no.1
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• pp.64-68
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• 2005

To recycle collected high-impact polystyrene (HIPS) wastes as liquid fuel, depolymerization characteristics of HIPS by pyrolysis was studied. The effects of temperature and time on the pyrolysis of HIPS were investigated. The depolymerization temperature and activation energy of HIPS pyrolysis increased with increasing heating rate. In general, conversion and liquid yield gradually increased with pyrolysis temperature and pyrolysis time. Each liquid product formed during pyrolysis was classified into gasoline, kerosene, light oil and heavy oil according to the distillation temperature based on the petroleum product quality standard of Korea Petroleum Quality Inspection Institute. As a result, the amount of liquid products produced during HIPS pyrolysis was in the order of gasoline》heavy oil〉kerosene〉light oil. Especially 51${\pm}$6 wt% of HIPS treated was obtained as gasoline.