• 대한기계학회논문집B
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• 제28권2호
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• pp.146-153
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• 2004

A Promising new approach to achieve low pollutant emissions and improvement of flame stability is tested experimentally using a cyclone jet hybrid combustor employing both premixed and diffusion combustion mode. Three kinds of nozzle are tested for mixing enhancement of fuel and air. The LNG (Liquified Natural Gas) is used as a fuel. The combustor is operated by two methods. One is DC (Diffusion Combustion) mode generated swirl flow by air as general swirl combustor, and the other is HC (Hybrid Combustion) mode. The HC mode consists of diffusion jet flame of axial direction and premixed cyclone flame of tangential direction in order to stabilized the diffusion jet flame. The results showed that the flame stability of HC mode is significantly enhanced than that of DC mode through the change of mixing characteristics by modifications of fuel nozzle. In addition, the reductions of CO and NOx emission in HC mode, as compared with that for the DC mode, is large than about 50% in stable region. Also, even using the low calorific fuel as $CO_2$-blended gas, it is identified that the cyclone jet hybrid combustor has the high performance of flame stability.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.508-513
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• 2003

Experiments are performed to investigate the detailed structure of underexpanded twin jet impinging on a perpendicular flat plate. The major parameters, such as nozzle operating pressure and nozzle spacing, are varied to create different jet flow fields resulted from the complicated interactions of the twin jets. From the surface pressure measurements and shadowgraphs taken by schlieren optical system, the jet structure is strongly dependent on the nozzle operation pressure and the spacing. The results obtained show that the closer nozzle spacing may induce to decrease the diameter of the Mach disk within the first shock cell in the underexpanded twin jet. With the increasing nozzle operating pressure and decreasing the nozzle spacing, a new shock wave appears at the entrainment region between the two jets, due to the enhancement of mixing effect of the both jets. The closer nozzle spacing makes the overall impinging pressure level higher, while severe pressure oscillation along the axis of symmetry. Furthermore it is recommended the wider spacing to obtain higher thrust under the present experimental conditions.

• 공업화학
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• 제17권1호
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• pp.62-66
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• 2006

본 연구에서는 폐 알루미늄을 이용하여 제조한 환경친화형인 발포 알루미늄 기능성 판넬의 특성을 조사하였고, 증점 공정, 교반 혼합 공정, 발포 공정, 냉각 공정을 거쳐 첨색 공정에 의한 제품 품질의 고급화를 추구하였다. 시험은 크게 세 가지로 구분하여 음향투과 손실 시험, 흡음율 측정 시험, 그리고 발포작업조건 및 스크랩 혼합시험을 시행하였다. 그 결과 폐 알루미늄을 이용해 만든 기능성 판넬은 초경량성이며 방음과 차음, 유해전자파 차폐에 탁월하고 약 $2.2kcal/mh^{\circ}C$ 정도로 낮은 열전도율 및 뛰어난 단열효과를 보이는 것으로 나타났다.

• 한국융합학회논문지
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• 제9권11호
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• pp.75-81
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• 2018

블록체인 내의 모든 트랜잭션이 공개되기 때문에 익명성과 프라이버시 문제는 중요해지고 있다. 공개 블록체인은 사용자 대신 공개키 주소를 사용하여 익명성을 보장하는 것처럼 보이지만 트랜잭션 그래프를 기반으로 다양한 기법을 통해 추적함으로써 익명성을 약화시킬 수 있다. 본 논문에서는 블록체인 환경에서 익명성과 프라이버스를 보호하기 위하여 다양한 보안 기법을 융합하여 사용자의 추적을 어렵게 하는 기법을 제안한다. 제안 기법은 k-anonymity 기술, 믹싱 기술, 은닉서명, 다단계 기법, 램덤 선택기법, 영지식 증명 기법 등을 융합하여 인센티브 및 기여자의 참여를 통해 익명성과 프라이버시를 보호한다. 성능 분석을 통해 제안기법은 기여자의 수가 공모자의 수보다 많은 환경에서는 공모를 통한 프라이버시 및 익명성 훼손이 어렵다는 것을 보였다.

• 공업화학
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• 제31권5호
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• pp.552-559
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• 2020

Activated carbon-nickel (II) oxide (AC-NiO) electrodes were studied as materials for the capacitive deionization (CDI) of aqueous sodium chloride solution. AC-NiO electrodes were fabricated through physical mixing and low-temperature heating of precursor materials. The amount of NiO in the electrodes was varied and its effect on the deionization performance was investigated using a single-pass mode CDI setup. The pure activated carbon electrode showed the highest specific surface area among the electrodes. However, the AC-NiO electrode with approximately 10 and 20% of NiO displayed better deionization performance. The addition of a dielectric material like NiO to the carbon material resulted in the enhancement of the electric field, which eventually led to an improved deionization performance. Among all as-prepared electrodes, the AC-NiO electrode with approximately 10% of NiO gave the highest salt adsorption capacity and charge efficiency, which are equal to 7.46 mg/g and 90.1%, respectively. This finding can be attributed to the optimum enhancement of the physical and chemical characteristics of the electrode brought by the addition of the appropriate amount of NiO.

• Applied Science and Convergence Technology
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• 제25권6호
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• pp.162-165
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• 2016

APhotocatalysis process uses ambient oxygen from air and irradiation, fundamentally UV light, to generate oxidation and reduction which can degrade almost all harmful organic and inorganic compounds to nontoxic substances. This study was focused on enhancement of photocatalytic activity which improves the photocatlytic efficiency with $TiO_2$ particle by mixing of certain amounts of Zn particles. We analyzed degradation of organic pollutant materials such as toluene and phenol with the mixed photocatalysis by using UV-visible spectrophotometer and obtained a result that photocatalytic activity is increased with increasing amount of Zn particle. Especially, in the case of $TiO_2$ (1 mmol) and Zn (0.1 mmol) mixture photocatalyst, we obtained at least 2 times higher photocatalytic activity compared with the commercially available $TiO_2$ photocatalyst (Degussa P-25), indicating that our mixed photocatalyts (Zn-doped $TiO_2$) is very effective of removing both organic dye and pollutants and the conversion rate of toluene is much faster than that of phenol.

• 대한금속재료학회지
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• 제49권12호
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• pp.930-936
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• 2011

In the present study, we show that the addition of Ag, an element having a positive enthalpy of mixing with Cu in the liquid state, enables the simultaneous enhancement of the glass forming ability and the plasticity in Cu-Zr-Ag bulk metallic glasses (BMGs). Rods of 4 mm diameter could be prepared with a fully amorphous structure and values of plastic strain up to 18% were measured under a compression mode for compositions around $Cu_{42.5}Zr_{47.5}Ag_{10}$. The possible role of Ag in the change of the atomic structure and the enhancement of the plastic strain in the ternary Cu-Zr-Ag BMGs is discussed based on analyses from transmission electron microscopy and EXAFS (extended X-ray absorption fine structure).

• 한국지진공학회논문집
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• 제25권1호
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• pp.21-32
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• 2021

Concrete masonry prisms are strengthened with steel fiber-reinforced mortar (SFRM) overlay and tested for compressive and diagonal tension strength. Masonry prisms are produced in poor condition considering standard workmanship for masonry buildings in Korea. Amorphous steel fibers are adopted for SFRM, and appropriate mixing ratios of SFRM are derived considering constructability and strength. Masonry prisms are strengthened with different fiber volume ratios, while numerous strengthened faces and additional reinforcing meshes are produced for compression and diagonal tension tests. Compression and diagonal tension strength are increased by up to 122% and 856%, respectively, and the enhancement effect for diagonal tension strength was superior compared to compression strength. Finally, the test results and strength prediction equations based on existing literature and regression analysis are compared.

• 한국광학회지
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• 제35권1호
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• pp.30-34
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• 2024

실크 단백질과 녹색 형광 단백질을 결합한 순수 단백질 기반 녹색 형광체의 구현과, 산화티타늄 나노 입자에 의한 형광 증폭 현상을 보고한다. 실크 단백질은 인간에게 다양한 이점을 제공하는 소재로서, 다양한 마이크로/나노 구조 형성 가능성과 투명한 성질을 가지고 있어 광학소재로서의 활용 가능성 또한 높다. 본 연구에서 제작한 소재는 강한 녹색 형광을 띠고 있으며, 산화티타늄 나노 입자에 의해 녹색 형광이 7.5배 증폭되는 것을 확인하였다.

• 한국환경과학회지
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• 제11권5호
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• pp.419-436
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• 2002

The current paper reports on the enhancement of O$_3$, CO, NO$_2$, and aerosols during the Asian dust event that occurred over Korea on 1 May 1999. To confirm the origin and net flux of the O$_3$, CO, NO$_2$, and aerosols, the meteorological parameters of the weather conditions were investigated using Mesoscale Meteorological Model 5(MM5) and the TOMS total ozone and aerosol index, the back trajectory was identified using the Hybrid Single-Particle Lagrangian Integrated Trajectory Model(HYSPLIT), and the ozone and ozone precursor concentrations were determined using the Urban Ashed Model(UAM). In the presence of sufficiently large concentrations of NO$\sub$x/, the oxidation of CO led to O$_3$ formation with OH, HO$_2$, NO, and NO$_2$ acting as catalysts. The sudden enhancement of O$_3$, CO, NO$_2$ and aerosols was also found to be associated with a deepening cut-off low connected with a surface cyclone and surface anticyclone located to the south of Korea during the Asian dust event. The wave pattern of the upper trough/cut-off low and total ozone level remained stationary when they came into contact with a surface cyclone during the Asian dust event. A typical example of a stratosphere-troposphere exchange(STE) of ozone was demonstrated by tropopause folding due to the jet stream. As such, the secondary maxima of ozone above 80 ppbv that occurred at night in Busan, Korea on 1 May 2001 were considered to result from vertical mixing and advection from a free troposphere-boundary layer exchange in connection with an STE in the upper troposphere. Whereas the sudden enhancement of ozone above 100 ppbv during the day was explained by the catalytic reaction of ozone precursors and transport of ozone from a slow-moving anticyclone area that included a high level of ozone and its precursors coming from China to the south of Korea. The aerosols identified in the free troposphere over Busan, Korea on 1 May 1999 originated from the Taklamakan and Gobi deserts across the Yellow River. In particular, the 1000m profile indicated that the source of the air parcels was from an anticyclone located to the south of Korea. The net flux due to the first invasion of ozone between 0000 LST and 0600 LST on 1 May 1999 agreed with the observed ground-based background concentration of ozone. From 0600 LST to 1200 LST, the net flux of the second invasion of ozone was twice as much as the day before. In this case, a change in the horizontal wind direction may have been responsible for the ozone increase.