• 유기물자원화
• /
• 제22권2호
• /
• pp.50-56
• /
• 2014

일반적으로 도금 폐수를 비롯한 산업 폐수 내 중금속 처리에 적용되는 응집-침전은 응집제의 비용과 침전 효율의 불안정성이라는 한계가 존재한다. 본 연구에서는 수산화물 생성-분리막 공정을 전제로 하여, pH와 교반조건에 따른 수용액 상의 중금속 제거 효율과 생성된 수산화물의 입도 분포를 고찰하였다. pH별 실험 결과, pH 9-10에서 최적의 중금속 제거 효율이 확인되었으며, 무기응집제인 $FeCl_3$의 투입은 오히려 제거 효율을 저하시켰다. 완속교반 시간 및 강도는 70 rpm, 20 min 조건이 최대 효율을 보였으며 Cu, Ni, Zn 모두 청정 지역 기준 폐수 배출 기준을 만족하였다. 나타났다. 생성된 중금속 수산화물의 입도 분석을 수행한 결과, 입자의 99.9 %가 $2{\mu}m$ 이상이었다.

• Bulletin of the Korean Chemical Society
• /
• 제35권4호
• /
• pp.1182-1190
• /
• 2014

$Cd_{1-x}Zn_xS$-sensitized $K_4Nb_6O_{17}$ composite photocatalysts (designated $Cd_{1-x}Zn_xS/K_4Nb_6O_{17}$) were prepared via a simple deposition-precipitation method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), $N_2$ sorption, ultraviolet-visible light diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence measurements (PL), and X-ray photoelectron spectroscopy (XPS). The $Cd_{0.8}Zn_{0.2}S$ particles were scattered on the surface of $K_4Nb_6O_{17}$, and had a relatively uniform size distribution around 50 nm. The absorption edge of $K_4Nb_6O_{17}$ was shifted to the visible light region and the recombination of photo-generated electrons and holes suppressed after $Cd_{0.8}Zn_{0.2}S$ loading. The $Cd_{0.8}Zn_{0.2}S$(25 wt %)/$K_4Nb_6O_{17}$ composite possessed the highest photocatalytic activity for hydrogen production under visible light irradiation, evolving 8.278 mmol/g in 3 h. Recyclability tests were performed, and the composite photocatalysts were found to be fairly stable. The mechanism of charge separation between the photogenerated electrons and holes at the $Cd_{0.8}Zn_{0.2}S/K_4Nb_6O_{17}$ composite was discussed.

• 대한기관식도과학회:학술대회논문집
• /
• 대한기관식도과학회 1977년도 제11차 학술대회연제 순서 및 초록
• /
• pp.8.5-9
• /
• 1977

기도 및 식도이물은 이비후과영역에서 적지않게 경험하게 된다. 그중 특히 유소아에서 발생하는 기도이물은 응급을 요하게 되며 진단 및 치료를 지체함으로써 예기치 않은 불행한 사태를 초래하기도 한다. 유소아에서 주로 보이는 기도이물의 증상은 기침, 기침음, 호흡곤란 등이며 천식, 폐염, 후두염 등으로 혼동되기도 한다. 이물의 종류파 빈도를 환자의 연령, 생활방식, 환경, 문과수준에 따라 그 양상을 달리한다. 저자들은 1975년부터 1977년 4월까지 본원에 내원하여 기도이물의 진단하에 ventilating bronchoscopy, thoracotomy (이중 1례는 사망)을 시행하여 치유된 35례를 분석하였다. 1. 연령층은 1세부터 5세까지가 48%로 가장많고 다음이 0세에서 1세까지 였다. 또한 남과여의 비는 2.1 : 1로 남자가 많았다. 2. 주증상은 호흡곤란, 기침, 기침음의 순서였다. 3. Foreign body의 종류는 peanut, metal, vegetable의 순이였다. 4. 이물의 소재는 주로 우측 주기관지 였으며 우측과 좌측의 비는 2 : 1이었다. 5. 내원까지의 기간은 24시간 이내가 65%로 가장 많았다. 6. 치료는 ventilating bronchoscopy가 27례로 가장 많았으며, 4례는 자연적으로 치유되었다. 이에 과거의 여러 보고들과 비교하여 문헌적 고찰과 함께 보고하는 바이다.

• 천문학회보
• /
• 제37권2호
• /
• pp.122-122
• /
• 2012

Geosynchronous electron flux dropouts are most likely due to fast drift loss of the particles to the magnetopause (or equivalently, the "magnetopause shadowing effect"). A possible effect related to the drift loss is the radial diffusion of PSD due to gradient of PSD set by the drift loss effect at an outer L region. This possibly implies that the drift loss can affect the flux levels even inside the trapping boundary. We recently investigated the details of such diffusion process by solving the diffusion equation with a set of initial and boundary conditions set by the drift loss. Motivated by the simulation work, we have examined observationally the energy spectrum and pitch angle distribution near trapping boundary during the geosynchronous flux dropouts. For this work, we have first identified a list of geosynchronous flux dropout events for 2007-2010 from GOES satellite electron measurements and solar wind pressures observed by ACE satellite. We have then used the electron data from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft measurements to investigate the particle fluxes. The five THEMIS spacecraft sufficiently cover the inner magnetospheric regions near the equatorial plane and thus provide us with data of much higher spatial resolution. In this paper, we report some case studies showing energy dependence during magnetopause shadowing effect.

• 공업화학
• /
• 제23권6호
• /
• pp.561-566
• /
• 2012

PtRuW/C 촉매를 Pt : Ru : W 비를 5 : 4 : 1, 2 : 1 : 1, 1 : 1 : 1, 1 : 2 : 2로 각각 합성하였다. 촉매의 조성은 EDX분석을 통해 이론값과 비슷하다는 것을 확인하였다. TEM분석과 XRD분석으로부터 3.5~5.5 nm의 균일한 입자 크기 및 결정질 분포를 가지고 있음을 확인하였다. 유효표면적, 전류밀도, 고유 활성 및 피독률과 같은 전기화학적 특성은 CO 스트리핑, 선형쓸음 전기량 측정법, 대시간 전류법 등과 같은 방법으로 분석하였다. 이러한 분석으로부터, $PtRu_2W_2/C$를 제외한 촉매는 상업촉매보다 우수한 반응성과 안정성을 가지고 있음을 확인하였다. 이 중 가장 우수한 촉매는 $Pt_5Ru_4W/C$였으며, $121.05mA{\cdot}m^{-2}$의 specific activity와 $0.01%{\cdot}s^{-1}$의 피독률을 보였다.

• 대한안전경영과학회지
• /
• 제25권1호
• /
• pp.7-14
• /
• 2023

We attempted to provide an overview of the laws and current state of the 3D printing industry in South Korea and around the world, using the annual industry surveys and the Wohler report. Additionally, we reviewed articles relating to the potential exposure to hazards associated with 3D printing using metal materials. In South Korea, there were 406 3D printing-related businesses, employing 2,365 workers, and the market size was estimated at 455.9 billion won in 2021. Globally, the average growth rate of the 3D printing industry market over the past 10 years was 27.4%, and the market size was estimated at $11.8 billion in 2019. The United States had the highest cumulative installation ratio of industrial 3D printers, followed by China, Japan, Germany, and South Korea. A total of 6,168 patents related to 3D printing were registered in the US between 2010 and 2019. Harmful factors during metal 3D printing was mainly evaluated in the powder bed fusion and direct energy deposition printing types, and there is a case of material extrusion type with metal additive filaments. The number, mass, size distribution, and chemical composition of particles were mainly evaluated. Particle concentration increases during the opening of the chamber or post-processing. However, operating the 3D printer in a ventilated chamber can reduce particle concentration to the background level. In order to have a safe and healthy environment for 3D printing, it is necessary to accumulate and apply knowledge through various studies.

• Journal of Electrochemical Science and Technology
• /
• 제14권1호
• /
• pp.85-95
• /
• 2023

In recent years, solid-state Li metal batteries (SSLBs) have attracted significant attention as the next-generation batteries with high energy and power densities. However, uncontrolled dendrite growth and the resulting pulverization of Li during repeated plating/stripping processes must be addressed for practical applications. Herein, we report a plastic-crystal-based polymer/ceramic composite solid electrolyte (PCCE) to resolve these issues. To fabricate the one-side ceramic-incorporated PCCE (CI-PCCE) film, a mixed precursor solution comprising plastic-crystal-based polymer (succinonitrile, SN) with garnet-structured ceramic (Li₇La₃Zr₂O₁₂, LLZO) particles was infused into a thin cellulose membrane, which was used as a mechanical framework, and subsequently solidified by using UV-irradiation. The CI-PCCE exhibited good flexibility and a high room-temperature ionic conductivity of over 10^-3 S cm^-1. The Li symmetric cell assembled with CI-PCCE provided enhanced durability against Li dendrite penetration through the solid electrolyte (SE) layer than those with LLZO-free PCCEs and exhibited long-term cycling stability (over 200 h) for Li plating/stripping. The enhanced Li⁺ transference number and lower interfacial resistance of CI-PCCE indicate that the ceramic-polymer composite layer in contact with the Li anode enabled the uniform distribution of Li⁺ flux at the interface between the Li metal and CI-PCCE, thereby promoting uniform Li plating/stripping. Consequently, the Li//LiFePO₄ (LFP) full cell constructed with CI-PCCE demonstrated superior rate capability (~120 mAh g^-1 at 2 C) and stable cycle performance (80% after 100 cycles) than those with ceramic-free PCCE.

• 한국입자에어로졸학회지
• /
• 제10권2호
• /
• pp.83-91
• /
• 2014

Since airborne bacteria have been known to aggravate indoor air quality, studies on reducing bacteria particles increase recently. In this study, a chamber(0.8m x 0.8m x 1.56m) system was built in order to simulate real conditions for reducing airborne bacteria, and evaluated by a simple aerosol reduction test. A method utilizing CFD(Computational Fluid Dynamics) simulation was used to detect the horizontal cross-sectional area which represents particle distribution in the chamber. Then an air-cleaner with HEPA filter and Carbon Fiber Ionizer was located on that area for aerosol reduction test. The CFD result found the area was located at 0.2m height from the bottom of the chamber, and the test showed aerosol reduction efficiencies using measurements of number concentration and CFU(colony forming unit) per each case. At the measurement of number concentration, the reduction efficiency of air-cleaner with filter and ionizer(Case 3) was about 90% after 4 minutes from the stop of the bacteria injection, and that with only filter(Case 2) was about 90% after 8 minutes from the beginning. Lastly, that without filter and ionizer(Case 1) was about 30% after 10 minutes. At the measurement of CFU, it shows similar results but it is related to viability of bio-aerosol.

• 한국산학기술학회논문지
• /
• 제16권3호
• /
• pp.2314-2320
• /
• 2015

MBR (Membrane Bio-Reactor) 공정은 막 오염을 해결하기 위해 막대한 에너지 소비를 하는 공정으로 알려져 있다. 이를 해결하기 위한 일환으로 전기응집 기술을 MBR에 적용하는 시도가 보고되고 있다. 본 연구에서는 전류밀도를 변화시켜가며 활성슬러지의 막 여과를 수행하여 전기응집이 막 오염 저감에 미치는 영향과 메커니즘을 파악하고자 하였다. 활성슬러지 혼합액을 전기응집한 후 회분식교반셀로 분리 막의 여과성능을 평가하였다. 전류밀도(A/m2)를 10에서 40으로 증가시켰을 때 총 오염 저항 (Rc+Rf) 값이 18%에서 79%까지 감소하여 전기응집으로 인해 분리 막의 여과성능이 향상됨을 확인할 수 있었다. 전기응집 전후로 유기물 농도와 활성슬러지 입도분포 변화는 거의 일어나지 않았다. 여과 성능의 향상은 수산화알루미늄, Al(OH)3이 생성되어 막 표면에 부착되면서 오염물질이 쌓이게 됨을 방지하는 역할, 즉 dynamic membrane 으로 작용하였기 때문인 것으로 판단되었다.

• 한국대기환경학회지
• /
• 제34권5호
• /
• pp.677-686
• /
• 2018

An intensive measurement was conducted to study the mass and number concentrations of atmospheric aerosols in Anheung ($36.679^{\circ}N$, $126.186^{\circ}E$), the west coastal measurement site of Korea during December 2017~April 2018. To evaluate relationships between the aerosols and meteorological parameters, comparisons of Optical Particle Counter (OPC) measured data and Auto Weather System (AWS) data were performed. Measured PM mass concentrations are $PM_{10}=42.814{\pm}30.103{\mu}g/m^3$, $PM_{2.5}=29.674{\pm}25.063{\mu}g/m^3$, $PM_1=28.958{\pm}24.658{\mu}g/m^3$, respectively. The PM ratios showed that the $PM_{10}$ concentrations contained about 67.8% of $PM_{2.5}$, while most part of $PM_{2.5}$ was $PM_1$ (about 97.1%). Timely collocation with AWS data were performed, exploring relations with the PM concentrations. PM concentrations can be explained by wind direction and relative humidity conditions. The significant reductions of fine particles in mass and number concentrations may attribute to actions on particle growth and wet removal. In these results, we suppose that the aerosol concentrations and size distributions are affected by inflow direction and air mass sources from the origin.