This study tried to survey air quality inside and outside the schools where are located in about 5km of industrial complex targeting aldehyde, PM10, PM2.5. Also, the aim was also to examine both a change in indoor air after 3 years and within 3 years of addition and improvement, and a change according to season. It collected specimens at totally 20 places. Aldehyde was analyzed through HPLC. PM10 and PM2.5 were measured by using Met One 831. Formaldehyde and Acetaldehyde were detected with 42.1 μg/m3 and 5.7 μg/m3 at the school where is located inside 5km of the industrial complex, and were detected with 55.0 μg/m3 and 6.8 μg/m3 at the school where is located outside 5 km. This could be confirmed to have been detected more highly in the indoor air than the outdoor air regardless of the distance from the industrial complex. Most substances were indicated to be higher by about 150% in the indoor air within 3 years than the indoor air following 3 years of addition and improvement. However, PM10 and PM2.5 were measured with 32.6 μg/m3 and 14.9 μg/m3 after 3 years and were gauged with 22.4 μg/m3 and 14.2 μg/m3 within 3 years. Seeing a seasonal change, Formaldehyde and Propionaldehyde were detected with 5.5 μg/m3 and 1.0 μg/m3 in spring, 7.7 μg/m3 and 1.6 μg/m3 in summer, and 8.3 μg/m3 and 1.9 μg/m3 in autumn. This could be confirmed the tendency of growing according to season.

A spherical Sr4Al14O25:Eu2+ phosphor for use in white-light-emitting diodes was synthesized using a liquid-state reaction with two precipitation stages. For the formation of phosphor from a precursor, the calcination temperature was 1,100˚C. The particle morphology of the phosphor was changed by controlling the processing conditions. The synthesized phosphor particles were spherical with a narrow size-distribution and had mono-dispersity. Upon excitation at 395 nm, the phosphor exhibited an emission band centered at 497 nm, corresponding to the 4f65d→4f7 electronic transitions of Eu2+. The critical quenching-concentration of Eu2+ in the synthesized Sr4Al14O25:Eu2+ phosphor was 5 mol%. A phosphor-converted LED was fabricated by the combination of the optimized spherical phosphor and a near-UV 390 nm LED chip. When this pc-LED was operated under various forward-bias currents at room temperature, the pc-LED exhibited a bright blue-green emission band, and high color-stability against changes in input power. Accordingly, the prepared spherical phosphor appears to be an excellent candidate for white LED applications.

Numerical analysis has been carried out to investigate particles behavior characteristics during the grinding process in the air. Grinding particles behavior is largely affected by many parameters such as operating conditions and process room geometry. Transient particle motion in the air is predicted, and the effects of particle diameter and device rotational speed on the behavior characteristics were compared. When particle size is not large enough, they shortly moves in a tangential direction of the device rotation, and then are mostly influenced by the air flow in the room. These results could be applicable to the optimal design of the grinding process room.

In this article, to predict the wear amount of nano particles in a worn nano composite, computational analysis pre/post-processor were developed using ABAQUS and visual basic programs. The abrasion, which is one of nano particles release scenarios, was applied in the computational analysis. Moreover, reciprocation, which is the abrasion type, was selected and incarnated in abrasion computational analysis. Also, to predict wear amount of nano composite in computational analysis, archard equation was applied and the predicted wear amount was evaluated compare with experimental value. The predicted wear amount of nano composite was increased in accordance with increasing force and was similar to result of experimental value.

혼탁매질에서 형광, 산란과 응집의 영향은 파장과 산란된 형광세기로 나타내는데, laser induced fluorescence(LIF) 분광학에 의한 분자특성으로 나타난다. 산란매질에서 광학적 효과는 광학적 파라미터들(μs, μa, μt)에 의해 표현되고 응집은 고-액상 분리공정과 Photodynamic therapy에서 중요하게 활용되고 있다. 따라서 입자가 서로 접근될 때 콜로이드 입자들의 상호작용을 LIF와 응집효과로 분석하였다. 우리는 레이저 광원에서 검출기까지 농도의 함수에 의해 in vitro 시료의 산란과 형광 스펙트라를 측정하였다. 산란계수 μs는 산란체의 입자가 증가함에 크게 나타났다. 그리하여 Phorphyrin A 는 Phorphyrin C보다 산란세기는 증가하였으나, 침투깊이 δ는 감소하였다.

Polyfluorene (PFO) 발광 층과 두 개의 전극으로 이루어진 단순한 구조의 PFO polymer base OLED를 기본으로 강유전성의 BaTiO₃나노입자를 PFO 발광 층 내에 분산시킨 OLED 소자를 제작하여 분산된 강유전체 나노입자의 영향과 동작에 미치는 역할을 알아보았다. 140 nm 두께의 발광 층 내부에 대비 80 nm의 크기를 가지는 강유전성 BaTiO₃입자들은 OLED 동작 중에 인가전압에 의해 대전되어 전기쌍극자를 형성하고, PFO의 발광 층 내로 주입된 전자 및 정공들과 각각 coulomb force에 기인하는 상호작용을 하여 OLED 소자의 전류밀도가 증가하는 결과를 나타내었다. PFO의 질량대비 10 wt% 에 해당하는 소량을 첨가하였을 때에 OLED소자의 문턱전압이 약 2 V 감소하는 개선된 결과를 나타내었다. 또한 유전체가 첨가되지 않은 소자에 비하여 휘도가 약 2 배 증가한 결과를 나타내었다.

In this study, a novel method was proposed to test the integrity of water treatment system specifically equipped with membrane filtration process. We applied the silica particles coated with a fluorescent agent (rhodamine B isothiocyanate) as a surrogate to detect a membrane process integrity and evaluate the reliability of effluent quality in the system. Additionally, a series of experiments was conducted to evaluate the sensitivity of the method through the laboratory scale experiment. The laboratory scale experiments showed that the feasibility of application of proposed method to detect a breach or damaged part on the membrane surface. However, the sensitivity on predicting the area of a breach was significantly influenced by the testing conditions such as a concentration of surrogate, filtration flux, and detection time. The lowest error of predicting the area of breach was 3.5 % at the testing condition of surrogate concentration of 80 mg/L injected with flux of 20 L/m2/hr for 10 minutes of detection time for the breach having the actual area of 7.069 mm2. However, the error of estimation was increased at the small breach with area less than 0.785 mm2. A future study will be conducted to estimate a damaged area with more accuracy and precision.

The current interest in atmospheric particulate matter (PM) is mainly due to its effect on human health.Exposure to outdoor PM is associated with a wide range of adverse health effects. Indoor air contains a complexmixture of bioaerosols such as bacteria, fungi and allergens. Children are known to be more susceptible tothe exposures of PM and bioaerosols which are represented by airborne bacteria, fungi, and allergens. Thisstudy is to assess concentrations of the atmospheric PM and bioaerosols indoors and outdoors at 15 daycarecenters for children located in Seoul. Particles were measured indoors and outdoors with automatic particlemonitoring using beta radiation absorption. Airborne bacteria and fungi were sampled by Anderson sampler.Analysis shows that average indoor PM10 was 95.7µg/m³ (SD 26.6µg/m³) and average level of airbornebacteria and fungi were 575.0CFU/m³ (SD 431.6CFU/m³) and 77.9CFU/m³ (SD 45.6CFU/m³), respectively.Finally, efficient ventilation and effective air cleaning strategies are necessary to reduce indoor concentrationsof particles and bioaerosols.

In this study, we fabricated Nd2Fe14B hard magnetic powders with various sizes via spray drying combined with reduction-diffusion process. Spray drying is widely used to produce nearly spherical particles that are relatively homogeneous. Thus, the precursor particles were prepared by spray drying using the aqueous solution containing Nd salts, Fe salts and boric acid with the target stoichiometric composition of Nd2Fe14B. The mean particle sizes of the spray-dried powders are in the range from one to seven micrometer, which are adjusted by controlling the concentra- tions of precursor solutions. After debinding the as-prepared precursor particles, ball milling was also conducted to con- trol the particle sizes of Nd-Fe-B oxide powders. The resulting particles with different sizes were subjected to subsequent treatments including hydrogen reduction, Ca reduction and washing for CaO removal. The size effect of Nd-Fe-B oxide particles on the formation of Nd2Fe14B phase and magnetic properties was investigated.

The crystallization of polypropylene (PP) particles in PP/decalin solution was conducted using the thermally induced phase separation(TIPS). During the control of particles sizes followed by the cooling of PP/decalin solution, particles were formed controllably, the concentrated PP resulted in an increase in the average diameter of PP particles. The effects of surfactants changes on particles sizes were investigated by using a field emission scanning electron microscope (FE-SEM). The PP crystals showed spherical shapes with a diameter 5∼18 μm. Additionally, as an effect of concentration of PP, the size distribution of the PP particles became broad with higher concentration of PP in the solution.

We study and describe-from the point of view of the interactions of the adsorbed particles-three types of the adsorption isotherms, namely, Langmuir type adsorption isotherms, phase transition type adsorption isotherms, and adsorption limited type adsorption isotherms, which are observed by experiments. By introducing and using a one dimensional statistical occupancy model, we derived analytical adsorption isotherms for the no force, the attractive force, and the repulsive force exerted on the other adsorbed particles. Our derived adsorption isotherms qualitatively pretty well agree with the experimental results of the adsorption isotherms. To specify each adsorption type, Langmuir type adsorption is a phenomenon that occurs with no forces between the adsorbed particles, phase transition type adsorption is a phenomenon that occurs with the strong attractive forces between the adsorbed particles, and adsorption limited type adsorption is a phenomenon that occurs with the repulsive forces between the adsorbed particles. The theoretical analysis-only using fundamental thermodynamics and occupancy statistics though-qualitatively quite well explains the experimental results.

Fe-based oxide dispersion strengthened (ODS) powders were produced by high energy ball milling, fol- lowed by spark plasma sintering (SPS) for consolidation. The mixed powders of 84Fe-14Cr-2Y2O3 (wt%) were mechanically milled for 10 and 90 mins, and then consolidated at different temperatures (900~1100o C). Mechani- cally-Alloyed (MAed) particles were examined by means of cross-sectional images using scanning electron micros- copy (SEM). Both mechanical alloying and sintering behavior was investigated by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM). To confirm the thermal behavior of Y2O3, a replica method was applied after the SPS process. From the SEM observation, MAed powders milled for 10 min showed a lamella structure consisting of rich regions of Fe and Cr, while both regions were fully alloyed after 90 min. The results of sintering behavior clearly indicate that as the SPS temperature increased, micro-sized defects decreased and the den- sity of consolidated ODS alloys increased. TEM images revealed that precipitates smaller than 50 nm consisted of YCrO3.

The present work investigated the dispersion behavior of Y2O3 particles into AISI 316L SS manufactured using laser cladding technology. The starting particles were produced by high energy ball milling in 10 min for pre- alloying, which has a trapping effect and homogeneous dispersion of Y2O3 particles, followed by laser cladding using CO2 laser source. The phase and crystal structures of the cladded alloys were examined by XRD, and the cross section was characterized using SEM. The detailed microstructure was also studied through FE-TEM. The results clearly indi- cated that as the amount of Y2O3 increased, micro-sized defects consisted of coarse Y2O3 were increased. It was also revealed that homogeneously distributed spherical precipitates were amorphous silicon oxides containing yttrium. This study represents much to a new technology for the manufacture and maintenance of ODS alloys.

Magnetic and dielectric properties of rubber composites are controlled by using two kinds of high-permeability metal particles with different electrical conductivity (Sendust, Permalloy), and their effect on microwave absorbance has been investigated, focusing on the quasi-microwave frequency band (0.8-2 GHz). Noise absorbing sheets are composite materials of magnetic flake particles of high aspect ratio dispersed in polymer matrix with various filler amount of 80-90 wt.%. The frequency dispersion and magnitude of complex permeability is almost the same for Sendust and Permalloy composite specimens. However, the complex permittivity of the Permalloy composite (, ) is much greater than that of Sendust composite (, ). Due to the large dielectric permittivity of Permalloy composite, the absorbing band is shifted to lower frequency region. However, the investigation of impedance matching reveals that the magnetic permeability is still small to satisfy the zero-reflected condition at the quasi-microwave frequency band, resulting in a small microwave absorbance lower than 10 dB.

The mechanical properties and microstructures of aluminum-matrix composites fabricated by the dispersion of fine alumina particles less than 20μm in size into 6061 aluminum alloys are investigated in this study. In the as-quenched state, the yield stress of the composite is 40~85 MPa higher than that of the 6061 alloy. This difference is attributed to the high density of dislocations within the matrix introduced due to the difference in the thermal expansion coefficients between the matrix and the reinforcement. The difference in the yield stress between the composite and the 6061 alloy decreases with the aging time and the age-hardening curves of both materials show a similar trend. At room temperature, the strain-hardening rate of the composite is higher than that of the 6061 alloy, most likely because the distribution of reinforcements enhances the dislocation density during deformation. Both the yield stress and the strain-hardening rate of the T6-treated composite decrease as the testing temperature increases, and the rate of decrease is faster in the composite than in the 6061 alloy. Under creep conditions, the stress exponents of the T6-treated composite vary from 8.3 at 473 K to 4.8 at 623 K. These exponents are larger than those of the 6061 matrix alloy.

전도성 고분자 PFO(Polyfluorene)에 양전극 ITO와 음전극으로 AI 를 추가한 단순한 양극성 구조의 ITO/PFO/Al 소자를 제작하였다. PFO에 BaTIO₃나노세라믹스 분말을 중량비로 0wt%, 10wt%, 20wt% 와 30wt% 로 달리한 4종류의 시편에 만들고, Keithley 사의 2400 Sourcemeter를 이용하여 0V에서 21V까지 DC전압을 인가하면서 소자에 흐르는 전류량을 관찰하였다. 수 나노 크기의 BaTIO₃분말의 첨가는 PFO/AI 계면에서의 전위장벽을 감소시켜 Fowler-Nordheim Tunneling이 시작되는 전압이 BaTIO₃가 첨가되지 않은 시편의 경우에 비하여 7V에서 최대 10V가 낮아진 결과를 얻었다. 소자에 흐르는 최대 전류값은 인가 전압 DC21V일 때 BaTIO₃첨가량에 비례하여 4배에서 5.5배까지 증가하였다. BaTIO₃의 첨가효과는 20wt% 이상 첨가된 경우 효과가 포화되기 시작하여, 30wt%의 BaTIO₃를 첨가한 시편의 전류량은 오히려 감소하였고 전류주입도 어려워지는 상반된 결과를 얻었다. 이것은 첨가한 나노 분말의 표면전하가 만드는 미세전계의 영향이 인접한 거리에서 서로 중첩되어 전류의 흐름이 오히려 감소하는 결과를 보인 것을 판단된다. 이로서 강유전체가 첨가된 전도성 고분자/금속 계면의 I-V 특성은 나노 세라믹스 분말의 표면전하가 만드는 국소미세전계의 영향을 받아 Trap Charge Limited Current 모델에 부합하는 결과를 가짐을 알 수 있었다.

Hollow silica spheres were prepared by spray drying of precursor solution of colloidal silica. The precursor solution is composed of 10-20 nm colloidal silica dispersed in a water or ethanol-water mixture solvent with additives of tris hydroxymethyl aminomethane. The effect of pH and concentrations of the precursor and additives on the formation of hollow sphere particles was studied. The spray drying process parameters of the precursor feeding rate, inlet temperature, and gas flow rate are controlled to produce the hollow spherical silica. The mixed solvent of ethanol and water was preferred because it improved the hollowness of the spheres better than plain water did. It was possible to obtain hollow silica from high concentration of 14.3 wt% silica precursor with pH 3. The thermal conductivity and total solar reflectivity of the hollow silica sample was measured and compared with those values of other commercial insulating fillers of glass beads and TiO2 for applications of insulating paint, in which the glass beads are representative of the low thermal conductive fillers and the TiO2 is representative of infrared reflective fillers. The thermal conductivity of hollow silica was comparable to that of the glass beads and the total solar reflectivity was higher than that of TiO2.

수중 이 취미를 유발시키는 대표적인 미량오염물질인 2-methylisoborneal (MIB)과 geosmin(지오스민)의 배제율을 소수성 polyethersulfone (PES) 나노분리막(분획분자량 : 400 Da)을 적용하여 다양한 용액조성에서 관찰하였다. 실험결과 적용된 모든 조건에서 지오스민이 2-MIB보다 다소 높은 배제율을 나타내었다. 용액의 pH 효과를 관찰한 결과 pH가 증가할수록 2-MIB와 지오스민 양쪽 모두 배제율이 증가하는 경향을 나타내었다. 한편, 수중 자연유기물질의 존재는 두 미량유기물질의 배제율을 크게 증가시켰으며 이와 같은 현상은 높은 pH일수록 더욱 뚜렷하게 나타났다. 소수성 분리막을 친수성 TiO2 입자로 표면코팅 시킨 후 배제율을 관찰한 결과 분리막의 표면을 친수화한 후 소수성인 2-MIB와 지오스민의 배제율은 증가하는 경향을 나타내었다. 따라서 소수성 상호작용은 미량유기물질 나노여과 배제율의 중요한 기작 중 하나임을 확인할 수 있었다.