• Journal of Advanced Marine Engineering and Technology
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• 제34권4호
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• pp.508-514
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• 2010

본 논문은 커먼레일 디젤엔진의 정속운전시 배출되는 나노크기의 입자상 물질을 분석하는데 초점을 두었다. 디젤산화촉매 후단에서 나노입자상 물질의 개수농도 저감수준은 크지 않았으나 매연여과장치 후단에서 분석한 결과 1,000배 정도 저감되는 결과를 확인하였다. 고속 고부하 조건에서는 매연여과장치의 자연재생 효과로 인해 입자상 물질은 증가하였다. 연료분사시기를 BTDC $6^{\circ}CA$ 에서 ATDC $4^{\circ}CA$까지 지각시킨 결과 입자상 물질의 개수농도는 감소하였지만 최지각 조건인 ATDC $9^{\circ}CA$에서는 증가하는 결과를 확인하였다. EGR 적용시 핵화모드 입자상 물질은 저감되는 경향을 보였으며 축적모든 입자는 증가하였다.

• Journal of Forest and Environmental Science
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• 제30권1호
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• pp.1-14
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• 2014

Timber harvest in natural forests and its implications on carbon sequestration were investigated in the Southwestern Nigeria. Data on timber harvest from forest estates for a 3-year period were collected from the official record of States' Forestry Department. The data registered the species, volume and number of timbers exploited during the study period. The data were analyzed accordingly for rate of timber harvest and carbon value of the exploited timbers using existing biomass functions. Values were compared for significant differences among states using one way analysis of variance. The results showed that the most exploited logs, in terms of volume and number of trees, have the highest amount of carbon removal. There was a variation in type of timber species being exploited from each state. The total number of harvested trees from Oyo, Ondo, Ogun, Ekiti and Osun were estimated at 100,205; 111,789; 753; 15,884 and 18,153 respectively. Total quantity of carbon removed for the 3-year period stood at 2.3 million metric tons, and this translated to 8.4 million metric tons of $CO_2$. The annual carbon and $CO_2$ removal therefore were estimated at 760,120.73 tons and 2.8 million tons/ year respectively. There were significant differences (p<0.05) in the amount of $CO_2$ removed from the five states. Based on our result, we inferred that there is increasing pressure on economic tree species and it is plausible that they are becoming scarce from the forests in Southwestern Nigeria.. If the present rate of log removal is not controlled, forests could become carbon source rather than carbon sink and the on biological conservation, wood availability and climate change may turn out grave. For the forest to perform its environmental role as carbon sink, urgent conservation measures and logging policies are needed to be put in place.

• Bulletin of the Korean Chemical Society
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• 제26권3호
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• pp.440-446
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• 2005

A method is described for the determination of dibutyltin (DBT) in sediment by isotope dilution using liquid chromatography inductively-coupled plasma/mass spectrometry (LC-ICP/MS). To achieve the highest accuracy and precision, special attentions are paid in optimization and evaluation of overall processes of the analysis including extraction of analytes, characterization of the standards used for calibration and LC-ICP/MS conditions. An approach for characterization of natural abundance DBT standard has been developed by combining inductively-coupled plasma/optical emission spectrometry (ICP/OES) and LC-ICP/MS for the total Sn assay and the analysis of Sn species present as impurities, respectively. An excellent LC condition for separation of organotin species was found, which is suitable for simultaneous DBT and tributyltin (TBT) analysis as well as impurity analysis of DBT standards. Microwave extraction condition was also optimized for high efficiency while preventing species transformation. The present method determines the amount contents of DBT in sediments with expanded uncertainty of less than 5% and its result shows high degree of equivalence with reference values of an international inter-comparison and a certified reference material (CRM) within stated uncertainties.

• International Journal of Concrete Structures and Materials
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• 제8권3호
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• pp.213-228
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• 2014

Alkali-activated binder (AAB) is recently being considered as a sustainable alternative to portland cement (PC) due to its low carbon dioxide emission and diversion of industrial wastes and by-products such as fly ash and slag from landfills. In order to comprehend the behavior of AAB, detailed knowledge on relations between microstructure and mechanical properties are important. To address the issue, a new approach to characterize hardened pastes of AAB containing fly ash as well as those containing fly ash and slag was adopted using scanning electron microscopy (SEM) and energy dispersive X-ray spectra microanalyses. The volume stoichiometries of the alkali activation reactions were used to estimate the quantities of the sodium aluminosilicate (N-A-S-H) and calcium silicate hydrate (CSH) produced by these reactions. The 3D plots of Si/Al, Na/Al and Ca/Si atom ratios given by the microanalyses were compared with the estimated quantities of CSH(S) to successfully determine the unique chemical compositions of the N-A-S-H and CSH(S) for ten different AAB at three different curing temperatures using a constrained nonlinear least squares optimization formulation by general algebraic modeling system. The results show that the theoretical and experimental quantities of N-A-S-H and CSH(S) were in close agreement with each other. The $R^2$ values were 0.99 for both alkali-activated fly ash and alkali-activated slag binders.

• 한국수소및신에너지학회논문집
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• 제20권1호
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• pp.22-30
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• 2009

Energy environment has been changing rapidly such as the fluctuation of oil prices and the effect on UNFCCC. Oil price change affects Korea's economy heavily due to her poor natural resources and large dependence of consumed energy resources. Korea takes the 4th place of importing the crude oil and 9th place in $CO_2$ emissions with the 1st place of $CO_2$ emissions increasing rate. Considering the current statue of Korea including oil price change and UNFCCC, Korea will be expected to be the Annex I nation due to Korean energy environments and the quantity of $CO_2$ emission. Energy technology development is a crucial key to cope with Korea's national energy security and environments. In this study, we establish the framework, which allocates the relative weights of assessment criteria and sub-criteria, for assessing and selecting R&D programs of energy technologies strategically. We integrated fuzzy theory and analytic hierarchy process (AHP) approach since the fuzzy AHP approach reflects the vagueness of human thoughts and perception effectively as making pairwise comparisons of criteria and alternatives. The fundamental data of this research results will support R&D planning phase for policy-makers and the production of well focused R&D outcomes.

• 한국수산과학회지
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• 제49권4호
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• pp.436-444
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• 2016

Clamshells, which comprise more than 50% of a clam’s weight, are a major byproduct of the clam industry and are mainly composed of insoluble calcium carbonate. This study investigates the use of clamshells as a natural calcium resource. Highly soluble powdered calcium lactate (LCCL) was prepared from the calcined powdered shells of littleneck clams (LCCP) using response surface methodology (RSM) to predict optimum conditions. These conditions, as derived from pH, solubility, and yield of 11 LCCLs manufactured according to the RSM model, were 1.80 M lactic acid and 1.13 M LCCP. The actual values of pH (6.98), solubility (93.99%), and yield (351.23%) under the optimized conditions were as predicted. The derived LCCL exhibited a strong buffering capacity in the range of pH 2.78-3.90 when combined with less than 2 mL of 1 N HCl. The ranges of calcium content and solubility of LCCL were 7.7-17.5 g/100 g and 96.6-98.9%, respectively. Fourier transform infrared spectroscopy (FT-IR) of the LCCL identified it as calcium lactate pentahydrate, and field emission scanning electron microscopy (FESEM) revealed an irregular and rod-like microstructure. These results confirm the potential use of clamshells, converted to highly soluble organic acid calcium, as an additive to enhance calcium content in food ingredients.

• 셀메드
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• 제10권1호
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• pp.7.1-7.6
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• 2020

Plants produce a wide range of active principles, making them a rich source of different types of medicines. Without any knowledge of the phytoconstituents or active principles the medicinal plants itself or in the form of polyherbal formulations, were used by all society of human being from ancient times for prevention and cure of disease, but most of the traditional formulations including the formulation of Ayurveda and Unani have not been scientifically validated in order to establish the pharmacopoeial standards to improve the efficacy. Globally, the people become conscious that uses of synthetic drugs for a long period is not safe; the trend of medical society at large is looking at alternatives from natural, safe sources to combat diseases. Due to this comprehension, it has been increased the demand for plant-derived medicine, and on the other side, it is extremely important to standardize the polyherbal formulations and validate them scientifically to improve their safety and efficacy. The polyherbal Unani formulation Safuf-e-Muallif is widely used and recommended in Unani system of medicine (USM) as a spermatogenic agent, semen thickening agent, etc. to treat sexual disorders viz. premature ejaculation, nocturnal emission, etc. The study mainly deals with phytochemical screening for the detection of nature of phytoconstituents and analytical technique like High-performance thin-layer chromatography (HPTLC) for developing fingerprint of Safuf-e-Muallif revealing specific identities of the drug. The phytochemical screening and HPTLC fingerprint profile for SM reported here may be used as a reference standard for quality control purpose in future.

• 전기전자학회논문지
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• 제24권3호
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• pp.821-827
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• 2020

자동차에서 배출되는 배기가스가 대도시의 대기 오염원 중 큰 비중을 차지하고 있다. 특히 디젤이나 CNG버스 등 대중교통의 내연기관 차량은 매일 총 주행거리와 운행시간이 길고 차량 수량이 많기 때문에 배출가스 저감 대책이 시급하다. 본 논문에서는 실제로 전기버스의 도로 주행시험을 통한 연료소모율(km/kWh)을 측정하였다. 측정값을 근거로 버스 한 대당 내연기관과 전기버스에서 발생되는 CO₂배출량을 계산하였다. 전기버스를 시내버스로 대체할 경우 CNG버스 대비 예상되는 이산화탄소 저감 등 환경개선 효과와 더불어 전기버스로 대체가 확대될 경우 부가적인 효과를 분석하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2017년도 춘계학술대회 논문집
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• pp.153-153
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• 2017

The application of the coating supports the mechanical characteristics of the implant, and various materials and coatings are currently being used in the implant in a way to accelerate adhesion. Especially, plasma electrolytic oxidation (PEO) coating has been proposed continually with good surface treatment of titanium alloys. Also, the PEO process can incorporate Ca and P ions on the titanium surface through variables varied factor. PEO process for bioactive surface has carried out in electrolytes containing Ca and P ions. Natural bone is composed of mineral elements such as Mg, Si, Zn, Sr, and Mn, etc. Especially, Mg and Si of these elements play role in bone formation and growth after clinical implantation of bio-implants. In this study, corrosion charateristics of PEO-treated Ti-6Al-4V alloy in solution containing Si and Mg ions has been investigated using several experimental techniques. The PEO-treated surfaces were identified by X-ray diffraction, using a diffractometer (XRD, Philips X' pert PRO, Netherlands) with Cu $K{\alpha}$ radiation. The morphology was observed by field-emission scanning electron microscopy (FE-SEM, Hitachi 4800, Japan) and energy-dispersive X-ray spectroscopy (EDX, Oxford ISIS 310, England). The potentiodynamic polarization and AC impedance tests for electrochemical degradations were carried out in 0.9% NaCl solution at similar body temperature using a potentiostat with a scan rate of 1.67mV/s and potential range from -1500mV to + 2000mV.

• 한국지역지리학회지
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• 제23권2호
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• pp.366-375
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• 2017

본 연구는 자연적 풍화, 인위적 파괴 및 반출, 환경오염으로 인한 원형 손상의 위기에 처한 지형자원인 스트로마톨라이트의 보존과 활용 방안에 관한 것이다. 우선 스트로마톨라이트의 보존을 위해서는 교육을 통한 인식의 전환이 절실하고, 스트로마톨라이트를 건물로 덮어 화석의 훼손이나 멸실에 대한 위험요인들을 모두 차단하는 방안이 가장 적합하다. 경산 스트로마톨라이트는 중생대 백악기 호수에서 형성된 것으로 추정된다. 따라서 중생대 지층 및 지표 상황의 교육 자료와 관찰 및 체험프로그램의 자원으로 활용할 수 있다. 특히, 중생대 백악기를 모티브로 하여 스트로마톨라이트와 지역 대학 박물관을 연계하여 교육장소로 활용하고자 하며, 지역 사회를 기반으로 하는 4H(Healing, Hiking, Hand, History) 체험프로그램을 제시하는데 의미가 있다. 최근 역동적인 프로그램과 관람객의 편의를 도모할 수 있는 증강현실을 이용한 소프트웨어 프로그램 제안하며 추후 관련 분야와의 논의가 있어야 될 것으로 사료된다.