In the present work, we address the new route for the green synthesis of manganese dioxide (MnO2) by an innovative method named the solution plasma process (SPP). The reaction mechanism of both colloidal and nanostructured MnO2 was investigated. Firstly, colloidal MnO2 was synthesized by plasma discharging in KMnO4 aqueous solution without any additives such as reducing agents, acids, or base chemicals. As a function of the discharge time, the purple color solution of MnO4 - (oxidation state +7) was changed to the brown color of MnO2 (oxidation state +4) and then light yellow of Mn2+ (oxidation state +2). Based on the UV-vis analysis we found the optimal discharging time for the synthesis of stable colloidal MnO2 and also reaction mechanism was verified by optical emission spectroscopy (OES) analysis. Secondly, MnO2 nanoparticles were synthesized by SPP with a small amount of reducing sugar. The precipitation of brown color was observed after 8 min of plasma discharge and then completely separated into colorless solution and precipitation. It was confirmed layered type of nanoporous birnessite- MnO2 by X-ray powder diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), and electron microscopes. The most important merits of this approach are environmentally friendly process within a short time compared to the conventional method. Moreover, the morphology and the microstructure could be controllable by discharge conditions for the appropriate potential applications, such as secondary batteries, supercapacitors, adsorbents, and catalysts.

참외는 동북아시아 지역에서 대부분 재배되고 있고, 한국에 서 주로 생산되는 과일로서 단위면적당 수확량은 지속적으로 향상되고 있지만 재배방식은 토경재배에 국한되어 있기 때문 에 규모화, 생력화를 위한 수경재배 기술 개발이 필요하다. 본 연구에서는 보온부직포를 이용한 수경재배로 참외를 재배할 때 영양생장기 배양액 내 질산태질소 비율에 따른 참외 생육 의 변화를 확인했다. 배양액에서 질산태질소 비율이 증가할 수록 초장은 길어지고, 엽장, 엽폭, 절간장도 함께 증가하였다. 생육 30일차의 SPAD값은 질산태질소 비율이 증가할수록 감 소하였다. 질산태질소 비율에 낮을수록 암꽃 개화가 빨리 되 었고, 과실 성숙에서는 처리 간 차이가 없었다. 질산태질소 비 율에 따른 과실의 형태는 차이가 없었고, 경도는 질산태질소 의 비율이 낮을수록 높아 과실이 단단하였다. 3월에서 7월까 지 총 수확량은 KM3 5,650kg/10a, KM1 4,439kg/10a로 KM3가 27% 높았고 특히, 참외 가격이 높은 3월에서 5월까지 수량은 KM3가 KM1보다 36% 높았다. 따라서 12월 정식되 어 봄철부터 생산되는 참외의 수경재배에 적합한 질산태질소는 6.5－10me·L-1 수준으로 공급하는 것이 적당할 것으로 판 단되었다.

Mesophase pitch is a unique graphitizable material that has been used as an important precursor for highly graphitic carbon materials. In the current study, we propose to consider a spinnable mesophase pitch as a lyotropic liquid crystalline solution composed of solvent components and liquid crystalline components, so-called mesogen or mesogenic components. Among mesophase pitches, the supermesophase pitch is defined as a mesohpase pitch with 100% anisotropy, and can only be observed in pitches with a proportion of mesogenic components exceeding the threshold concentration (TC). We also examined the critical limit of AR synthetic pitch and 5 experimental spinnable mesophase pitches (SMPs). Then, we examined the effect of the solvent component on the minimum required amount of mesogenic component using a selected solvent component instead of their own solvent components. AR pitch showed 100% anisotropy with the least amount of its mesogenic component, THF insoluble components, of 60 wt.%. The solvent component, THF soluble components, extracted from AR-pitch, which has a molecular weight pattern similar to that of the original material but more amount of naphthenic alkyl chains, showed better solvent functionality than those of other THF solubles (THFSs) from other as-prepared spinnable mesophase pitches. This is why a lower amount of AR THFS can produce a supermesophase pitch when combined with the THFI (mesogenic components) of other experimental mesophase pitches. As a result of the current analysis, we define the mesogens as molecules that not only readily stack, but also maintain stacking structures in a fused state in the solution. The solvent component, on the other hand, is defined as molecules with a structure that readily decomposes in a fused state in the solution.

KAERI has been developing a new decontamination process that does not contain any organic chemicals in the decontamination solution and minimizes the use of ion exchange resin in the solution as a purifying step. The process is hydrazine based reductive metal ion decontamination for decommissioning (HyBRID) and consists of N2H4, H2SO4 and Cu+ ions. The primary system of the LWR is composed of materials with high corrosion resistance, such as stainless steel and Inconel, but among the materials, the feeder and header of the primary system of the PHWR are composed of carbon steel (SA106Gr.B) with low corrosion resistance. Therefore, when decontamination of PHWRs, attention should be paid to corrosion of carbon steel. Since Fe3O4, a contaminating oxide film formed on the surface of carbon steel dissolves faster than ferrite or chromite formed on the surface of Inconel or stainless steel, the base material is exposed to the solution and is corroded during decontamination. When a large amount of iron ions is eluted into the decontamination agent due to corrosion of carbon steel, not only the soundness of the base metal is adversely affected, but also the amount of decontamination waste increases. The purpose of this study is to develop inhibitors that can minimize corrosion of carbon steel when decontamination of PHWRs using the HyBRID decontamination process. CG, 570S and PP3 were selected as corrosion inhibitors. In addition, corrosion tests of carbon steel were conducted in the HyBRID solution with corrosion inhibitors. The best corrosion inhibitors and optimal operating conditions were selected, and HyBRID decontamination agents with corrosion inhibitors were much better in corrosion resistance than existing commercial decontamination agents.

It has been investigated on the management of the nuclides in KAERI. Strontium-90 is a high heatgenerating nuclide in spent nuclear fuel. It is needed to separate the salt from the salt solution for the recovery of strontium after the chlorination of the strontium oxide in molten salt. A vacuum distillation technology was used for the separation of strontium from the molten salt. It was investigated on operating conditions of reactive distillation process for the recovery of the strontium from the salt solution. At a reduced pressure, considerable amount of the carbonation agents such as K2CO3 and Li2CO3 were reduced during heating in the distiller due to the thermal decomposition. Therefore, the two step process was proposed, which is composed of a reaction step at an atmospheric pressure and a salt distillation step at a reduced pressure. In the reaction step, the condition of low temperature and high pressure is suitable to suppress the decomposition of the carbonation agent. In the salt distillation step, reduced pressure is preferable at a suitable temperature depending on the evaporation rate of the salt.

Concentration of nitrogen, one of the major elements, and ratio of two nitrogen forms (NH4 + and NO3 –) in the nutrient solution affect the quality and food safety of fresh vegetable produce. This study was conducted to find an appropriate strength and NH4 +:NO3 – ratio of a nutrient solution for growth and development of a Romaine lettuce (Lactuca sativa L. var. longiflora) ‘Caesar Green’, a representative leafy vegetable, grown in a home hydroponic system. In the first experiment, plants were grown using three types of nutrient solution: A commercial nutrient solution (Peters) and two strengths (GNU1 and GNU2) of a multipurpose nutrient solution (GNU solution) developed in a Gyeongsang National University lab. Plants grown with the GNU1 and GNU2 had greater shoot length, leaf length and width, and biomass yield than Peters. On the other hand, the root hairs of plants grown with Peters were short and dark in color. Tissue NH4 + content in the Peters was higher than that of the GNU1 and GNU2. The higher contents of NH4 + in this solution may have caused ammonium toxicity. In the second experiment, eight treatment solutions, combining GNU1 and GNU2 solutions with four ratios of NO3 –:NH4 + named as 1, 2, 3 and 4 were used. Both experiments showed more growth in the GNU2 group, which had a relatively low ionic strength of the nutrient solution. The growth of Romaine lettuce showed the greatest fresh weight along with low tissue NO3 – content in the GNU2-2. This was more advantageous in terms of food safety in that it suppressed the accumulation of surplus NO3 – in tissues due to the low ionic strength of the GNU2 subgroup. In addition, this is preferable in that it can reduce the absolute amount of the input of inorganic nutrients to the nutrient solution.

Sucrose (suc) is a disaccharide that consists of glucose (glu) and fructose (fru). It is a carbohydrate source that acts as a nutrient molecule and a molecular signal that regulates gene expression and alters metabolites. This study aimed to evaluate whether suc-specific signaling induces an increase in bioactive compounds by exogenous suc absorption via roots or whether other factors, such as osmotic stress or biotic stress, are involved. To compare the osmotic stress induced by suc treatment, 4-week-old cultured mugwort plants were subjected to Hoagland nutrient solution with 10 mM, 30 mM, and 50 mM of suc or mannitol (man) for 3 days. Shoot fresh weight in suc and man treatments was not significantly different from the control. Both man and suc treatments increased the content of bioactive compounds in mugwort, but they displayed different enhancement patterns compared to the suc treatments. Mugwort extract treated with suc 50 mM effectively protected HepG2 liver cells damaged by ethanol and t-BHP. To compare the biotic stress induced by suc treatment, 3-week-old mugwort plants were subjected to microorganism and/or suc 30 mM with Hoagland nutrient solution. Microorganisms and/or suc 30 mM treatments showed no difference about the shoot fresh weight. However, sugar content in mugwort treated with suc 30 mM and microorganism with suc 30 mM treatment was significantly higher than that of the control. Suc 30 mM and microorganism with suc 30 mM were effective in enhancing bioactive compounds than microorganism treatment. These results suggest that mugwort plants can absorb exogenous suc via roots and the enhancement of bioactive compounds by suc treatment may result not from osmotic stress or biotic stress because of microorganism, but by suc-specific signaling.

The nonlinear simple pendulum is investigated to find the exact closed-form analytical solution, satisfying initial conditions of angular position and angular velocity. While previous numerous studies have been conducted on the nonlinear simple pendulum, the exact closed-form analytical solution still remains not available in public domain for the most general initial condition including initial angular velocity as well as initial angular displacement. In this paper, the exact closed-form analytical solution for the general initial conditions is derived using Jacobi’s elliptic function and elliptic integral. The result was verified by comparing it with previous studies and the numerical solution of the equation of motion through the Runge-Kutta integration method.

This paper introduces a container loading problem and proposes a theoretical approach that efficiently solves it. The problem is to determine a proper weight of products loaded on a container that is delivered by third party logistics (3PL) providers. When the company pre-loads products into a container, typically one or two days in advance of its delivery date, various truck weights of 3PL providers and unpredictability of the randomness make it difficult for the company to meet the total weight regulation. Such a randomness is mainly due to physical difference of trucks, fuel level, and personalized equipment/belongings, etc. This paper provides a theoretical methodology that uses historical shipping data to deal with the randomness. The problem is formulated as a stochastic optimization where the truck randomness is reflected by a theoretical distribution. The data analytics solution of the problem is derived, which can be easily applied in practice. Experiments using practical data reveal that the suggested approach results in a significant cost reduction, compared to a simple average heuristic method. This study provides new aspects of the container loading problem and the efficient solving approach, which can be widely applied in diverse industries using 3PL providers.

PURPOSES : The effects of strontium cations on the strength of hydrated cement composites as well as the morphology and chemical composition changes of cement hydrates due to strontium treatment are investigated in this study. Subsequently, the potential of a strontiumbased aqueous solution as a near-surface treatment method for hydrated cement composites is evaluated. METHODS : To supply strontium cations to a hydrated cement composite, a 30% strontium nitrate aqueous solution was used. Cement paste (w/c = 0.4) specimens were prepared and cured in the 30% strontium nitrate aqueous solution, which allows the strontium ions to penetrate into the specimen and treat the near-surface region. Compressive and flexural strength tests were performed on both specimens treated by the strontium ions and untreated specimens cured in deionized water, and the test results were compared. To investigate the changes in the morphology and chemical compositions of the cement hydrates due to the treatment, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) analyses were performed. RESULTS : The results of the strength tests indicate that both the compressive and flexural strengths of the specimens cured in the 30% strontium nitrate aqueous solution improved significantly compared with the specimens cured in deionized water for the same duration. In particular, the strontium nitrate aqueous solution shows greater improvement in terms of the flexural strength compared with the compressive strength. The maximum penetration depth of strontium into the hydrated cement composite is 5 mm during the first 7 d of immersion and increases to 6.5 mm during the subsequent 14 d. The SEM results show that the microstructure of the hydrated cement composite is densified by the strontium nitrate aqueous solution treatment. The EDS results show that morphology and chemical compositions of the cement hydrates are altered. This implies that the strontium cations can be combined with C–S–H and C–S–A–H phases to form new types of hydrates. CONCLUSIONS : The experimentally results show that the strength of hydrated cement composites can be improved by modifying their near-surface regions via the strontium cation penetration technique. This implies that the strontium-based aqueous solution exhibits high potential for the maintenance and rehabilitation of concrete structures.

The home hydroponic system used in this experiment supplied the nutrient solution using the ebb and flow-type system, and the supply time, interval, and water levels of the nutrient solutions were fixed. This experiment was conducted to find a more favorable growth medium for plant growth in the hydroponic system. The medium used in the experiment was of two types, phenolic foam and rockwool, and the heights were 28 and 38 mm, respectively. As for the the multipurpose nutrient solutions (GNU1 and GNU2) were prepared in the lab. The composition of the GNU1 and GNU2 was the same, and there was a difference between 100 and 70% in ion concentrations. The plants used were Ssamchoo (Brassica lee ssp. namai) and Romaine lettuce (Lactuca sativa L. var. longiflora). First, in the physicochemical measurements of the empty medium, change in the pH and EC of the distilled water passing through the medium was less in the rockwool than in the phenolic foam. This indicates that there is less change in the chemical properties of the nutrient solution due to the medium when rockwool is used. After hydroponic culture of Ssamchoo and Romaine lettuce, the medium showed more residual salts in Romaine lettuce. Both Ssamchoo and Romaine lettuce showed less salt accumulation in rockwool. The emergence rate was significantly higher in rockwool for both species. The lower height of the medium, the faster the emergence was. Ssamchoo displayed significantly higher fresh weight (124.7%), shoot length (107.6%), and leaf width (107.9%) when grown in GNU1, but there were no significant differences as affected by the medium. However, in Romaine lettuce, the type and height of the medium resulted in significant differences. The fresh weight of Romaine lettuce was significantly higher in rockwool (119.6%) than in phenolic foam, and significantly higher at 38 (114.6%) than 28 mm. Although there is a difference depending on the species, rockwool is more suitable for the ebb and flow-type system than phenolic foam, and the height of 38 is more advantageous than 28 mm.

본 연구에서는 양액재배 시 발생되는 폐양액의 적절한 농업 적 이용방안을 강구하기 위해 폐양액의 비료 효과시험, 토양 컬럼 시험, 그리고 작물 재배시험을 수행하였다. 폐양액의 비 료 효과시험은 무기질소를 기준으로 질소비료와 폐양액의 토 양 처리에 따른 열무의 생육특성과 토양의 화학적 특성을 조 사하였다. 폐양액 비료 효과시험과 작물 재배시험을 위한 토양에 대한 폐양액의 처리는 무처리; A, 질소비료 100%; B, 질 소비료 70%+폐양액 30%; C, 질소비료 50%+폐양액 50%; D, 질소비료 30%+폐양액 70%; E 총 5개 처리구로 하였다. 토양컬럼 시험을 위한 토양에 대한 폐양액의 처리는 무처리, 질 소비료 100%, 폐양액 50%+질소비료 50% 3개 처리구로 하 였다. 폐양액의 화학성은 pH 6.0, EC 2.4dS·m-1, 총인(T-P) 28mg·L-1, 암모늄태 질소(NH4-N) 5.0mg·L-1, 질산태 질소 (NO3-N) 301mg·L-1로 나타났다. 토양의 화학성은 pH 5.51, EC 0.31dS·m-1, 유기물 2.08g·kg-1, 질산태 질소 9.64mg·kg-1, 암모늄태 질소 3.20mg·kg-1으로 나타났다. 질소비료 50% 이 하와 폐양액 50% 이상의 비율이 열무 생육에 효과가 높은 것 으로 나타났다. 폐양액을 질소비료와 함께 혼합하여 적용한 C-E 처리구에서 토양의 이화학성은 질소비료만을 적용한 B 처 리구와 통계적으로 유의한 차이가 없었다. 토양컬럼 시험 결과 질소비료 100%와 폐양액 50%+질산비료 50% 처리구의 NO3 와 NH4의 농도는 큰 차이가 없는 것으로 나타났다. 폐양액을 화 학비료의 표준시비량을 기준으로 이용하여 토양에 처리하면 토양 내 질소 성분의 이동과 주변의 영향은 일반 화학비료와 유 사하게 나타나는 것으로 판단된다. 열무 토경재배에 폐양액과 질소비료를 혼합하여 사용하면 폐양액의 재이용으로 환경적 부담도 줄일 수 있고, 질소비료의 사용량도 줄일 수 있어 농가에 경제적 부담 감소와 열무 생산량 증대 효과도 기대할 수 있다.

본 연구는 ‘암기조생’ 감귤 과실의 표면온도와 일사량 간의 상관관계를 분석하여 일소가 유발되는 과실 표면온도를 예측 하고 일소 발생을 경감시키고자 수행하였다. 이를 위해 기온 이 31℃일 때 30분 간격으로 5분 미세살수와 1% 탄산칼슘, 4% 카올린 용액을 10일 간격으로 3회 엽면살포하여 일소과 발생과 과실 품질을 조사하였다. 과실 표면온도는 일사량과 R = 0.788(p < 0.01)로 유의한 정의 상관관계를 나타냈으며 한 낮에는 기온보다 최고 16℃가 높았다. 과실 표면온도를 추정 하는 회귀식 y = 0.099 × (대기온도) + 0.018 × (일사량) + 20.779(R = 0.687, p < 0.01)을 도출하였다. 30분 간격으로 5 분 미세살수시 수관 내부 온도가 무처리보다 5.1℃ 낮았다. 일 소과 발생률은 미세살수구가 2.1%로 무처리구보다 2배 이상 낮았고 통계적으로 유의성을 나타냈으나, 과실 품질은 처리 간에 비슷하였다. 햇빛을 반사하거나 미세살수를 실시하여 과실 표면온도를 낮추면 일소 발생을 줄일 수 있을 것으로 보 인다.

본 논문은 직접해법 기반 FETI 알고리즘의 개선 방안을 제시하였다. 개선 대상은 FETI-local로, 해당 알고리즘은 국부 Lagrange 승 수를 통해 부영역 간 경계 문제를 정의한다. 부영역 경계 강성 및 하중 계산 단계의 경우, 전체 역행렬 계산 등 과도한 비용을 요구했던 기존 알고리즘을 Boolean 행렬 특성을 활용한 선택적 역행렬 성분 계산으로 개선하였다. 전역 경계 행렬식 계산 단계의 경우, 기존 단 일 프로세서 연산을 다중 프론탈 기법 기반 병렬 연산으로 대체하였다. 제시된 FETI-local 알고리즘의 성능 개선은 64만 자유도 수치 예제를 통해 검증되었으며, 기존 대비 최대 97.8%의 계산 시간 감소가 달성되었다. 또한, 기존 대비 안정적이고 개선된 확장성이 가속 지표를 통해 확인되었다. 추가로, 432만 자유도의 대용량 계산 성능 비교가 제시된 알고리즘과 상용 프로그램인 ANSYS 간에 수행되 었다. 그 결과, 계산 시간 측면에선 ANSYS가 우수하였으나, 프로세서 수에 따른 가속 성능 증가율 측면에선 제시된 알고리즘이 우수 한 것이 확인되었다.