• 청정기술
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• 제16권4호
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• pp.284-291
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• 2010

온실가스로 알려진 $N_2O$의 촉매 분해는 최소한 670 K 이상의 온도가 요구되는 난해한 공정으로 알려져 있다. 본 연구는 CO 환원제와 더불어 473 K의 저온에서도 $N_2O$를 전량 분해될 정도로 높은 활성을 나타내는 혼합금속산화물(mixed metal oxide: MMO) 촉매에 Ce을 첨가함으로서 나타나는 $N_2O$ 분해활성에의 영향을 검토하기 위하여 수행되었다. MMO 촉매는 Co 및 Al 외에 Rh과 Pd을 사용하고, 여기에 Ce을 미량 첨가하여 공침전법으로 제조하였으며, 결과적으로 Ce 함량이 증가함에 따라 촉매 표면적은 감소하고 $N_2O$의 직접분해 활성이 감소하는 현상이 나타났다. 그러나 CO 환원제의 분위기 하에서는 이러한 활성 감소를 상쇄하고도 남을 정도의 높은 $N_2O$ 분해활성을 나타냈으며 Ce 첨가비율에 따른 활성저하도 줄일 수 있어서 MMO 촉매의 물리적 안정성 증대를 위해 Ce을 첨가할 경우 CO 환원제에 의한 $N_2O$ 환원 반응계의 활성 안정성도 유지될 수 있는 것으로 확인되었다.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2022년도 추계학술대회
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• pp.50-50
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• 2022

Recently, the use of mulching film has increased in soybean cultivation. Polyethylene (PE) films and biodegradable films (BF) have the advantages of improving soil moisture retention, geothermal maintenance, and CO2 maintenance as well providing weed control. Furthermore, BFs are a material that can compensate for the shortcomings of PE because it has the ability to decompose naturally by soil microorganisms, sunlight, and geothermal heat. Many researches have been carrying out studies regarding the development of BFs for these very reasons. This study was conducted better understand which films are optimal for soybean cultivation after evaluations of soybean growth and film characteristics of various BFs. BFs Farmsbio (Farm Hannong), Heulgro Film (Sejin Bio), Vonto Film (Eco-Hansung), two unnamed biodegradable films (Seojin Bio and Taesung), and a PE film were used in this study. For the control plots, no mulching was used. Experimental fields were fertilized according to conventional cultivation methods, tilled, and then covered with either BFs or PE films. After 1 week, soybean (cv. Daechan) seeds were seeded. Germination rate and plant height were measured at weekly intervals after seeding. In addition, pH, EC, and decomposition and light transmittance levels of films were measured during the experimental period. Daily average temperatures and relative humidity in soils was measured during the experimental period. There was no significant difference in germination rates and plant height in both crops grown with BFs and PE films, but crops grown in the control plot had significantly lower germination rates and growth. Soil pH was not significantly different regardless of treatments (BF, PE, and non-mulching) at 14, 28, and 42 days after seeding. In general, the EC contents in the control plots was lower than in crops grown using BFs and PE films. With the exception of some BFs, light transmittance and decomposition levels of films did not, in general, increase up to 70 days after soybean seeding. Since this study is ongoing, we are continually investigating these parameters. The average daily moisture in soil was higher in crops grown with BFs and PE films than in the control plot. However, the daily average soil temperature was not consistent regardless of treatments. Therefore, the BFs used in this study can be used without negative impacts on soybean growth.

• 한국의학물리학회지:의학물리
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• 제20권3호
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• pp.145-151
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• 2009

본 연구는 관전압(kVp), 관전류량(mAs)과 같은 물리적 인자의 변화에 따른 다양한 구성 물질의 하운스필드 단위(HU, Hounsfield Unit) 평가를 통해 전산화단층촬영(Computed Tomography) 장치에 대한 성능을 평가하고 이들의 응용가능성을 연구하고자 하였다. MDCT (Siemens SOMATOM Sensation 4, Germany)를 이용하여 밀도가 다른 다양한 물질의 물리적 인자의 변화에 따른 HU 값을 측정하였다. 실험결과 관전압이 증가함에 따라 물질의 HU 값은 대체적으로 감소하고, 특히 뼈와 조영제의 구성물질인 요오드(iodine)의 경우 관전압이 80 kVp에서 140 kVp로 증가했을 때 HU 값은 각각 32%, 42% 감소하였다. 반면, 50 mAs에서 400 mAs로 관전류량이 증가함에 따라 HU 값에는 큰 변화가 없었다. 그리고 물질의 밀도가 0.00 $g/cm^3$에서 1.82 $g/cm^3$로 증가함에 따라 HU 값은 선형적으로 증가하였다. 조영제의 구성물질인 요오드의 경우에는 농도가 증가함에 따라 HU 값은 선형적으로 증가하였고 관전압이 증가함에 따라 HU 값이 감소하였다. 관전압 증가에 따른 감소정도는 요오드의 농도에 따라 차이가 있으며 3%의 농도에서 가장 큰 차이를 보였다. 이러한 결과를 이용하여 single source CT 장치에서 혼합물의 물질분리 효과를 얻을 수 있었다. 본 연구를 통해 다양한 물질에 대한 물리적 인자와 HU의 상관관계를 확인하였고, single source CT 장치를 이용하여 물질분리 효과를 구현함으로써 CT 장치의 효율성을 증가시키고, 응용분야를 확장할 수 있을 것으로 기대한다.

• 폴리머
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• 제32권4호
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• pp.390-396
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• 2008

조직공학용 생체재료로 사용하고자 가교제 1,3-butadiene diepoxide(BD)를 사용하여 락타이드(LA)와 가교시킨 히아루론산(HA) 고분자를 제조하였다. 가교된 고분자의 락타이드 및 BD 반응도는 핵자기 공명 분광법으로 결정하였다. 반응도와 팽윤도는 LA/HA 몰비 혹은 가교제 농도를 증가시킴에 따라 증가하였다. 탄성률은 가교제 농도가 증가하거나 HA/LA 몰비가 감소함에 따라 감소하였다. 생분해는 2단계로 진행되었으며 BD 농도가 증가할수록 서서히 진행되었다. 첫 단계 분해는 주로 가교구조에 존재하는 에스테르기의 분해에 기인한 것으로 나타났다. 세포 성장 저해는 BD 농도가 증가함에 따라 증가하였다. 세포 독성은 BD 농도가 클 경우 약간 나타났으나 그 값은 6% 미만으로 세포 성장에 큰 문제는 없는 것으로 나타났다.

• 청정기술
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• 제8권4호
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• pp.173-180
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• 2002

본 연구에서는 MLCC의 원료인 $BaTiO_3$ 분말에 첨가제를 코팅한 core-shell 구조의 복합분말을 제조하였다. 이러한 복합분말은 MLCC 제조공정에서 VOC의 배출을 억제할 뿐만 아니라, MLCC의 초고용량화 및 신뢰성 향상을 목적으로 한다. 첨가제의 성분 및 함량은 국내 MLCC 제조기업으로부터 조사하였으며, 본 연구에서는 $Y_2O_3$와 $MnCO_3$ 두 성분에 대하여 연구하였다. 두 성분의 염은 $70^{\circ}C$이상의 반응온도에서 요소분해반응을 통해서 $BaTiO_3$분말의 표면에 동시에 그리고 균일하게 코팅될 수 있음이 확인되었다. 원소분석 결과, 코팅성분의 함량은 초기에 설정한 값과 근접하게 유지됨을 알 수 있었다. 본 연구실험 결과, 첨가제의 균일코팅을 위해서는 PVP 등의 분산제 역할이 크지 않은 반면, 반응온도 및 반응시간의 최적상태 유지가 매우 중요함이 확인되었다.

• 한국환경과학회지
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• 제10권5호
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• pp.365-371
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• 2001

The optimum dosage of quicklime in producing organic fertilizer using livestock wastes vith a greater than 80% water content was analysed. After one day had elapsed to allow for the organic fentilizer to dry, the quicklime dosage and the composition of the organic fertilizer were analysed. Any from done to the organic fertilizer was also assessed. The amount of the quicklime required to stabilize livestock wastes was determined by water content of livestock wastes. For J farm(slurry style) of which livestock wastes have 94.6% of water concentration, less than 3% of total amount of livestock wastes, for H farm (scraper style) of which livestock wastes have 85% of water concentration, less then 4% of total livestock wastes and Y farm(traditional style) of which livestock wastes have 80% of water concentration, less then 5% of total livestock wastes. Generally, in order to pack the organic fertilizer, water containing quicklime0stabilized livestock wastes should be less than 35%. It takes 9 days to keep this water content for the wastes from H and Y farms(less than 85% in water content), and 12 days for the wastes from J (94.6% in water content). According to the classification standard for compost constitution by Higgins, the crude fertilizers from all 3 farms had high grade $K_2O$ and CaO, the middle grade T-N and middle or low grade $P_2O_5$. Stabilization by quicklime is known to inhibit bacterial decomposition of organic matter and the activity of pathogenic organisms. In this study, more then 99.99% of coliform group, fecal group and viable cell count were reduced. Our results indicate that livestock wastes of greater 80% water content could be used to produce organic fertilizer without the addition of a material for moisture control.

• Journal of Microbiology and Biotechnology
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• 제30권7호
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• pp.1051-1059
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• 2020

Overproduction and accumulation of melanin in the skin will darken the skin and cause skin disorders. So far, components that can inhibit tyrosinase, a melanin synthase of melanocytes, have been developed and used as ingredients of cosmetics or pharmaceutical products. However, most of existing substances can only inhibit the biosynthesis of melanin while melanin that is already synthesized and deposited is not directly decomposed. Thus, their effects in decreasing melanin concentration in the skin are weak. To overcome the limitation of existing therapeutic agents, we started to develop a substance that could directly biodegrade melanin. We screened traditional fermented food microorganisms for their abilities to direct biodegrade melanin. As a result, we found that a kimchi-derived Pediococcus acidilactici PMC48 had a direct melanin-degrading effect. This PMC48 strain is a new strain, different from P. acidilactici strains reported so far. It not only directly degrades melanin, but also has tyrosinase-inhibiting effect. It has a direct melanin-decomposition effect. It exceeds existing melanin synthesis-inhibiting technology. It is expected to be of high value as a raw material for melanin degradation drugs and cosmetics.

• 한국재료학회지
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• 제26권9호
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• pp.504-511
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• 2016

To prepare $Mn^{4+}$-activated $K_2TiF_6$ phosphor, a precipitation method without using hydrofluoric acid (HF) was designed. In the synthetic reaction, to prevent the decomposition of $K_2MnF_6$, which is used as a source of $Mn^{4+}$ activator, $NH_5F_2$ solution was adopted in place of the HF solution. Single phase $K_2TiF_6$:$Mn^{4+}$ phosphors were successfully synthesized through the designed reaction at room temperature. To acquire high luminance of the phosphor, the reaction conditions such as the type and concentration of the reactants were optimized. Also, the optimum content of $Mn^{4+}$ activator was evaluator based on the emission intensity. Photoluminescence properties such as excitation and emission spectrum, decay curve, and temperature dependence of PL intensity were investigated. In order to examine the applicability of this material to a white LED, the electroluminescence property of a pc-WLED fabricated by combining the $K_2TiF_6$:$Mn^{4+}$ phosphor with a 450 nm blue-LED chip was measured.

• 한국동물위생학회지
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• 제40권1호
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• pp.53-59
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• 2017

Foot and mouth disease (FMD) is highly infectious disease of cloven-hoofed animals, particularly problematic in cattle, sheep, pigs and goats for economic reasons. Last FMD outbreak in February, 2017 caused tremendous social and economical impacts. The Korean FMD policy aims to vaccinate intact animals and euthanize and bury infected animals to prevent the disease spread. However, there was a problem that the buried livestock did not decompose after several years. Therefore, the study was purposed to investigate the effect of Corynebacterium glutamicum and Bacillus licheniformis on the degradation of buried cow carcasses and on the soil condition; such as temperature, decomposition course of carcasses, composition of amino acids in the soil around carcasses, and plant root elongation to measure soil conditions. As a result, the composition of amino acids in the soil treated with C. glutamicum and B. licheniformis was generally higher than those in the untreated soil. Plant roots in soil treated with C. glutamicum and B. licheniformis grew longer than in non-treated soil. The results suggested that the toxic effect on a grave land buried with FMD infected livestock is reduced when treated with C. glutamicum and B. licheniformis in regard of odor reduction, promoted decaying process, and soil fertilization.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3290-3294
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• 2011

The properties of monomeric and dimeric salen-aluminum complexes, [salen(3,5-$^tBu)_2$Al(OR)], R = $OC_6H_4-p-C_6H_6$ (H1) and R = [salen(3,5-$^tBu$)AlOPh]C$(CH_3)_2$ (H2) (salen = N,N'-bis-(salicylidene)-ethylenediamine) as host layer materials in red phosphorescent organic light-emitting diodes (PhOLEDs) were investigated. H1 and H2 exhibit high thermal stability with decomposition temperature of 330 and $370^{\circ}C$. DSC analyses showed that the complexes form amorphous glasses upon cooling of melt samples with glass transition temperatures of 112 and $172^{\circ}C$. The HOMO (ca. -5.2~-5.3 eV) and LUMO (ca. -2.3~-2.4 eV) levels with a triplet energy of ca. 1.92 eV suggest that H1 and H2 are suitable for a host material for red emitters. The PhOLED devices based on H1 and H2 doped with a red emitter, $Ir(btp)_2$(acac) (btp = bis(2-(2'-benzothienyl)-pyridinato-N,$C^3$; acac = acetylacetonate) were fabricated by vacuum-deposition and solution process, respectively. The device based on vacuum-deposited H1 host displays high device performances in terms of brightness, luminous and quantum efficiencies comparable to those of the device based on a CBP (4,4'-bis(Ncarbazolyl) biphenyl) host while the solution-processed device with H2 host shows poor performance.