• Title/Summary/Keyword: Micro-mixing

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Cellulose based Electro-Active Paper Actuator: Materials and Applications (셀룰로오스 기반 Electro-Active Paper 작동기: 재료 및 응용)

  • Jang, Sang-Dong;Yang, Sang-Yeol;Ko, Hyun-U;Kim, Dong-Gu;Mun, Sung-Chul;Kang, Jin-Ho;Jung, Hye-Jun;Kim, Jae-Hwan
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.11
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    • pp.1227-1233
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    • 2011
  • Cellulose Electro-Active Paper (EAPap) has been known as a new smart material that is attractive for a bio-mimetic actuator due to its merits in terms of lightweight, dry condition, large displacement output, low actuation voltage and low power consumption. Cellulose EAPap is made by regenerating cellulose and aligning its micro-fibrils. This paper introduces several EAPap materials, which are based on natural cellulose and its hybrid nanocomposites mixed/blended with inorganic functional materials. By chemically bonding and mixing with carbon nanotubes and inorganic nanoparticles, the cellulose EAPap can be a hybrid nanocomposite that has versatile properties and can meet material requirements for many applications. Recent research trend of the cellulose EAPap is introduced in terms of material preparations as well as application devices including actuators, temperature and humidity sensors, biosensors, chemical sensors, and so on. This paper also explains wirelessly driving technology for the cellulose EAPap, which is attractive for bio-mimetic robotics, surveillance and micro-aerial vehicles.

Chemical Properties of Indoor Individual Particles Collected at the Daily Behavior Spaces of a Factory Worker

  • Ma, Chang-Jin;Kang, Gong-Unn;Sakai, Takuro
    • Asian Journal of Atmospheric Environment
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    • v.11 no.2
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    • pp.122-130
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    • 2017
  • The main purpose of the study was to clarify the properties of individual particles collected at each behavior space of a factory worker. The samplings of size-segregated ($PM_{2.1-1.1}$ and $PM_{4.7-3.3}$) indoor particles were conducted at three different behavior spaces of a factory worker who is engaged in an auto parts manufacturing plant (i.e., his home, his work place in factory, and his favorite restaurant). Elemental specification (i.e., relative elemental content and distribution in and/or on individual particles) was performed by a micro-PIXE system. Every element detected from the coarse particulate matters of home was classified into three groups, i.e., a group of high net-counts (Na, Al, and Si), a group of intermediate net-counts (Mg, S, Cl, K, and Ca), and a group of minor trace elements (P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pb). The results of EF for $PM_{4.7-3.3}$ in home indicated that several heavy metals were generated from the sources within the house itself. An exceptional feature shown in the individual particles in workplace is that Cr, Mn, and Co were clearly detected in both fine and coarse particles. Cluster analysis suggested that the individual coarse particles ($PM_{4.7-3.3}$) collected at the indoor of factory were chemically heterogeneous and they modified with sea-salt, mineral, and artificially derived elements. The principal components in individual coarse particles collected at restaurant were sea-salt and mineral without mixing with harmful trace elements like chromium and manganese. Compared to the indoor fine particles of home and restaurant, many elements, especially, Cl, Na, Cr, Mn, Pb, and Zn showed overwhelmingly high net-counts in those of factory.

Food-Web Structures in the Lower Trophic Levels of the Korean Seas (East Sea, West Sea, South Sea, and East China Sea) during the Summer Season: Using Carbon and Nitrogen Stable Isotopes (하계 한반도 해역(동해, 서해, 남해 및 동중국해)의 하위영양단계 먹이망 구조 : 탄소 및 질소 안정동위원소 활용)

  • Min, Jun-Oh;Lee, Chang-Hwa;Youn, Seok-Hyun
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.26 no.5
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    • pp.493-505
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    • 2020
  • Food web structures in the lower trophic levels of the seas around the Korean peninsula were investigated in August 2019 using stable isotopes. There were variable ratios of the carbon (-26.18 ~ -20.61 ‰) and nitrogen stable (5.36 ~ 15.20 ‰) isotopes in the particulate organic matter (POM). Most of the organisms ingested micro-POM as a major food source, but this varied spatially. The chaetognaths (3.40 ± 0.61) occupied the highest trophic level. The isotope mixing model showed that the proportions (13 ~ 51 %) of some organisms (i.e., copepods and euphausiids) reflected the relative contributions as major food sources for chaetognaths at each site.

Study on optimum structure of air-lift bio-reactor using numerical analysis of two-phase flow (이상 유동 수치해석을 이용한 기포 구동 생물 반응기 내부 최적 구조에 관한 연구)

  • Kim, San;Chung, Ji Hong;Lee, Jae Won;Sohn, Dong Kee;Ko, Han Seo
    • Journal of the Korean Society of Visualization
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    • v.17 no.3
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    • pp.24-31
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    • 2019
  • Recently, an air-lift bio-reactor operated by micro bubbles has been utilized to product hydrogen fuel. To enhance the performance, characteristics of hydrodynamics inside the bio-reactor were analyzed using a numerical simulation for two-phase flow. An Eulerian model was employed for both of liquid and gas phases. The standard k-ε model was used for turbulence induced by micro bubbles. A Population Balance Model was employed to consider size distribution of bubbles. A hollow cylinder was introduced at the center of the reactor to reduce a dead area which disturbs circulation of CO bubbles. An appropriate diameter of the draft tube and hollow cylinder were optimized for better performance of the bio-reactor. The optimum model could be obtained when the cross-sectional area ratio of the hollow cylinder to the reactor, and the width ratio of the riser to the downcomer approached 0.4 and 3.5, respectively. Consequently, it is expected that the optimum model could enhance the performance of the bio-reactor with the homogeneous distribution and higher density of CO, and more effective mixing.

Influence of Micro-Structural Characteristics of Concrete on Electrical Resistivity (콘크리트의 미세구조 특성이 전기저항에 미치는 영향)

  • Yoon, In-Seok
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.17 no.6
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    • pp.122-129
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    • 2013
  • Since electrical resistivity of concrete can be measured in a more rapid and simple way than chloride diffusivity, it should be primarily regular quality control of the electrical resistivity of concrete which provides the basis for indirect of quality control of chloride diffusivity during concrete construction. If this is realized, the electrical resistivity of concrete can be a crucial parameter to establish maintenance strategy for marine concrete structures. The purpose of this study is to develop, design and test a surface electrical resistivity measurement protocol. Microstructural affecting factors such as capillary water, porosity, tourtousity, and so on, on the electrical resistivity of concrete were examined taking into account for mixing proportion properties, and hydration stage. This study can provide a non-destructive approach for durability design of marine concrete. From the relationship between electrical resistivity and chloride diffusivity, it is expected that the result is subsequently used as a calibration curve for an indirect control of the chloride diffusivity based on regular measurements of the electrical resistivity during concrete construction.

Development of Hybrid/Dual Swirl Jet Combustor for a MGT (Part II: Numerical Study on Isothermal Flow) (마이크로 가스터빈용 하이브리드/이중 선회제트 연소기 개발 (Part II: 비반응 유동에 관한 수치해석))

  • Mun, Sun-Yeo;Hwang, Cheol-Hong;Lee, Kee-Man
    • Journal of the Korean Society of Propulsion Engineers
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    • v.17 no.5
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    • pp.70-79
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    • 2013
  • The isothermal flow structure and mixing characteristics of a hybrid/dual swirl jet combustor for micro-gas turbine (MGT) were numerically investigated. Location of pilot burner, swirl angle and direction were varied as main parameters with the identical thermal load. As a result, the variations in location of pilot nozzle, swirl angle and direction resulted in the significant change in turbulent flow field near burner exit, in particular, center toroidal recirculation zone (CTRZ) as well as turbulent intensity, and thus the flame stability and emission performance might be significantly changed. With the comparison of experimental results, the case of swirl angle $45^{\circ}$ and co-swirl flow including optimum location of pilot burner were chosen in terms of the flame stability and emissions for the development of hybrid/dual swirl jet combustor.

Numerical Study of Turbulent Flow and Combustion in a Micro Combustor with a Baffle Plate (배플이 부착된 마이크로 연소기의 난류유동 및 연소에 대한 수치해석 연구)

  • Kim, Won Hyun;Park, Tae Seon
    • Journal of the Korean Society of Propulsion Engineers
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    • v.17 no.6
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    • pp.20-29
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    • 2013
  • Turbulent flow and combustion characteristics in a micro can combustor with a baffle plate are investigated by a Reynolds Stress Model. In order to examine the geometric effects on the turbulent combusting flow, several baffle configurations are selected. The interrelation between the flow structure and the thermal field are investigated by examing the variation of recirculation region, flame length and heat loss. For the flow mixing, the decreasing air hole is more efficient than the decrease of the fuel hole. As the fuel or air hole diameter decreases, combustion efficiency is enhanced and flame length is decreased. Additionally, as the diameter of air hole decreases, the heat loss and combustion temperature are increased, while they are reduced with decreasing the diameter of fuel hole.

Equipment Development for Inorganic-Compound Concentration Measurement in a Hydroponic Culture Solution (수경배양액 무기성분농도 측정장치 개발)

  • Heo, Jeong-Wook;Park, Kyeong-Hun;Hong, Seung-Gil;Lee, Jae-Su;Baek, Jeong-Hyun;Park, Jong-Taek;Lee, Seung-Kee
    • Korean Journal of Environmental Agriculture
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    • v.39 no.4
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    • pp.319-326
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    • 2020
  • BACKGROUND: Measurement equipment was developed for inorganic nutrient concentration inside the hydroponic culture medium with several macro- and micro compositions, and applied for measuring the compositions of conventional medium. METHODS AND RESULTS: Before the equipment development, sonicator and heater were utilized to control temperature around of the module mixing with color reagents and target samples among the inorganic compositions. The measurement module and multi-sampler were also manufactured based on the COMS (Complementary Metal-Oxide Semiconductor) and installed inside the measurement equipment. Concentration of standard solution, value measured by the equipment, standard deviation or measured average value were used for estimating the accuracy and average recall of the equipment. Yamazaki solutions with EC of 0.5, 1.5, and 2.5 dS/m were offered to confirm the equipment accuracy and standard error. CONCLUSION: It was suggested that the developed equipment could be automatically applied for measurement with accuracy of over 96% and standard errors of less than 5% on 12 macro- and micro compositions such as a NO3-N, PO43- or Fe.

Preparation of Emulsion from Biodegradable Polymer (I) - Preparation of PLA and PBS Emulsions - (생분해성 고분자를 이용한 발수 에멀션의 제조 (I) - PLA 및 PBS 에멀션의 제조 -)

  • Lee, Min-Hyung;Kim, Kang-Jae;Eom, Tae-Jin
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.44 no.6
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    • pp.28-35
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    • 2012
  • Water-in-oil emulsion (W/O) and oil-in-water emulsion (O/W) types biodegradable polymer emulsions prepared to PLA and PBS. The optimal mixing ratio of polymer : solvent : OA : TEA : water was found be 10 : 40 : 4 : 6 : 30(g) when preparing emulsions. Biodegradability was most retained after preparation of polymer emulsions. Particle size of PLA and PBS emulsions were 2-3 ${\mu}m$ and 3-4 ${\mu}m$, respectively. Molecular weight of PLA and PBS emulsions were 108,000 and 92,000, respectively. And molecular weight of PLA and PBS emulsions became slightly lower than those of pellets.

Noise Reduction of an Underexpanded Supersonic Jet via Steady Blowing with Microjets (마이크로 제트를 이용한 과소팽창 음속 제트에서의 소음저감)

  • Kim, Jin-Hwa;Kim, Jung-Hoon;Yoo, Jung-Yul
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.27 no.10
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    • pp.1472-1479
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    • 2003
  • An attempt to reduce supersonic jet noise is carried out by using two steady microjets in a round jet. The jet is issued from a round sonic nozzle with an exit diameter of 10 mm. Two micro-nozzles with an inside diameter of 1 mm each are installed on the exit plane at an angle of 45 relative to the main jet axis. Far-field noise was measured at 40 diameters off the jet axis. The angle between a microphone and the jet axis is 30 or 90$^{\circ}$. For an injection rate of 4-6% of the main jet, screech tones were completely suppressed by the microjets. The reduction in the overall sound pressure levels were 2.4 and 2.7 dB for 90 and 30 measuring directions, respectively. However, the enhancement of mixing/spreading of the jet by the microjet was negligible. The reduction of noise is probably due to distorted shock cell structures and/or deformed large scale vortical structures by the microjets.