본 연구에서는 MnSO4이 B. thuringiensis의 곤충독소 형 성에 미치는 영향을 분석하여 신속 검출배지 개발의 기초 자료를 제안하고자 하였다. 본 실험에 사용한 균주는 순 천대학교 식품위생안전실험실에 보관되어 있던 B. thuringiensis reference 1주(KCTC 1511)와 식품에서 분리 된 wild type strain 9주를 사용하였다. B. thuriengiensis의 곤충독소 생성 확인은 식품의약품안전처의 곤충독소 확인 시험법에 따라 실험하였다. 0.005%-MnSO4이 첨가된 Nutrient agar는 배양 48시간에 3개 평판 중 2개 평판 (66.6%)에서 곤충독소가 관찰되었고, 120시간에 3개 평판 (100%) 모두에서 곤충독소가 관찰되었다. AK agar는 48 시간 배양 후 3개 평판 중 1개 평판(33.3%)에서 곤충독소 가 관찰되었으며, 배양 120시간에 3개 평판(100%) 모두에 서 곤충독소가 관찰되었다. 이러한 결과는 포자형성에 사 용되는 AK agar보다 식품공전에서 제시하고 있는 포자형 성 배지인 0.005%-MnSO4 Nutrient agar가 B. thuringiensis 의 곤충독소를 신속하게 생성시키는 것으로 나타났다. B. thuringiensis 10개 균주를 24시간 배양하여 관찰한 결과, 0.000%-MnSO4 배지에서 10개 평판 중 1개 평판(10%), 0.001%-MnSO4이 첨가된 배지의 10개 평판 중 2개 평판 (20%)에서 곤충독소가 관찰되었다. 0.002%-MnSO4이 첨가 된 배지는 10개 평판 중 3개 평판(30%)에서 곤충독소가 관찰되었다. 0.003%-0.009%-MnSO4이 첨가된 배지에서는 곤충독소가 관찰되지 않았다. 이러한 결과로 보아 24시간 배양 시까지는 0.002%-MnSO4이 첨가된 Nutrient agar가 B. thuringiensis의 곤충독소를 가장 신속하게 생성시키는 것으로 나타났다. B. thuringiensis의 곤충독소는 포자형성 과 동시에 생성된다는 보고와 MnSO4이 포자형성에 기여 한다는 보고를 종합하여 보면, MnSO4이 B. thuringiensis 의 포자형성을 가속화하고 이로 인해 곤충독소도 신속하 게 생성된 것으로 판단된다. 따라서 B. thuringiensis의 곤 충독소를 신속하게 생성하기 위해 기존 식품공전에서 제 시하고 있는 Nutrient agar보다 0.002%-MnSO4이 첨가된 Nutrient agar를 사용하는 것이 효율적일 것으로 판단된다. 그러나 Nutrient agar와 0.002%-MnSO4 Nutrient agar의 24 시간 배양 후 곤충독소 생성율의 차이는 작게 나타나 다 수의 wild type B. thuringiensis를 대상으로 추가적인 연구 가 필요할 것으로 판단된다.

This study was performed to investigate the effects of water molecules on ozone oxidation of acetaldehyde using a manganese oxide catalyst at room temperature. The catalytic ozone oxidation was conducted at different relative humidity (RH) conditions of 0%, 50%, and 80%. As the RH increased, both ozone and acetaldehyde removal efficiencies dropped due to competitive adsorption on the surface of the catalyst. At the highest RH of 80%, the oxidation reaction was severely retarded, and oxidation by-products such as acetic acid were formed and adsorbed on the surface. After the ozone oxidation of acetaldehyde, the regeneration of the catalyst using ozone alone was tested, and the further oxidation of accumulated organic compounds was investigated under the RH conditions of 0%, 50%, and 80%. When the highest relative humidity was introduced in the regeneration step, the ozonation reaction with the by-products adsorbed on the catalyst surface decreased due to the competitive reaction with water molecules. These findings revealed that, only when relative humidity was low to minimize the formation of by-products, the ozone oxidation of acetaldehyde using the manganese oxide catalyst at room temperature can be feasible as an effective control method.

Environmental regulations of the International Maritime Organization (IMO) are getting stricter, and the demand for replacing the fuel of ships with eco-friendly fuels instead of heavy oil in the shipbuilding and marine industries is increasing. Among eco-friendly fuels, LNG (liquefied natural gas) is currently the most popular fuel. This is because it is an alternative that can avoid the IMO's environmental regulations by replacing fuel. In PART 1, as a basic study of laser welding of high manganese steel materials, a fiber laser bead-on-plate experiment was conducted using nitrogen protective gas, and the effect of each factor on the penetration shape was analyzed through cross-sectional observation. In PART II, argon and helium shielding gases, not the nitrogen shielding gas used in PART I, were tested under the same experimental conditions and the effect of the shielding gas on penetration during laser welding was conducted.

Environmental regulations of the IMO (International Maritime Organization) are becoming more and more conservative. In order to respond to IMO, the demand for replacing the fuel of ships with eco-friendly fuels instead of conventional heavy oil is increasing in the shipbuilding and offshore industries. Among eco-friendly fuels, LNG (Liquefied Natural Gas) is currently the most popular fuel. LNG is characteristically liquefied at -163 degrees, and at this time, its volume is reduced to 1/600, so it is transported in a cryogenic liquefied state for transport efficiency. A tank for storing this should have sufficient mechanical/thermal performance at cryogenic temperatures, and among them, high manganese steel is known as a material with high price competitiveness and satisfying these performance. However, high manganese steel has a limitation in that the mechanical performance of the filler metal is lower than that of the base metal called ‘under matching’. In this study, to overcome this limitation, a basic study was conducted to apply the fiber laser welding method without filler metal to high manganese steel. To obtain efficient welding conditions, in this study, bead-on-plate welding was performed by changing the fiber laser welding speed and output using helium shielding gas, and the effect of each factor on the penetration shape was analyzed through cross-sectional observation.

리그닌 분해효소의 생산은 나선형 리본이 있는 새로운 형태의 회전식 통풍관 생물 반응기(RTB)를 사용하여 느타리(Pleurotus ostreatus) No.42에 의해 실시하였다. 락게 이즈(laccase)의 최대 생산량은 배양 3일 후 약 8,200 U/ bioreactor 수준에 도달한 후 감소하였다. 반면에, 망간퍼 옥시데이즈(MnP)의 최대 생산은 6일 배양 후 약 8,400 U/bioreactor의 수준에 도달하였다. 그러나 이 발효조에서 리그닌퍼옥시데이즈(LiP)는 검출되지 않았다. 그 결과 회전식 통풍관 생물 반응기(RTB)가 리그닌 분해효소를 대규모 생산을 위해 성공적으로 생산할 수 있음을 보여주었다. 이 발효기에서 망간퍼옥시데이즈의 정제 과정은 Sepharose CL-6B, Superdex 75 prep grade 및 Mono-Q에 대한 크로마토그래피를 포함하여 정제하였다. 이 주요 효소는 sodium dodecyl sulfate-polyacrylamide 겔 전기영동(SDS-PAGE)에서 분자량 36,400, pI 3.95의 등전점(IEF)으로 각각 확인되었다. 이 발효기의 주요 효소 N-말단 서열은 정치 및 진탕배양과 같은 다른 배양조건에서 보고된 MnP3 효소와 동일하였다.

In this study, chemically enhanced steam cleaning(CESC) was applied as a novel and efficient method for the control of organic and inorganic fouling in ceramic membrane filtration. The constant filtration regression model and the resistance in series model(RISM) were used to investigate the membrane fouling mechanisms. For total filtration, the coefficient of determination(R2) with an approximate value of 1 was obtained in the intermediate blocking model which is considered as the dominant contamination mechanism. In addition, most of the coefficient values showed similar values and this means that the complex fouling was formed during the filtration period. In the RISM, Rc/Rf increased about 4.37 times in chemically enhanced steam cleaning compared to physical backwashing, which implies that the internal fouling resistance was converted to cake layer resistance, so that the membrane fouling hardly to be removed by physical backwashing could be efficiently removed by chemically enhanced steam cleaning. The results of flux recovery rate showed that high-temperature steam may loosen the structure of the membrane cake layer due to the increase in diffusivity and solubility of chemicals and finally enhance the cleaning effect. As a consequence, it is expected that chemically enhanced steam cleaning can drastically improve the efficiency of membrane filtration process when the characteristics of the foulant are identified.

This study investigated the reaction between clay and Mn. Mn was coated using a manganese sulfate on porcelain plate and sintered from 1,100 oC to 1,250 oC. The body begin to shrink around 950 oC with the increase in temperature and rapidly progressed after 1,100 oC. Shrinkage of celadon body was performed at a lower temperature than for other substrates. Quartz, kaolin, and feldspar were the main crystalline phases of the starting materials, but they became mullite and crystobalite during the firing process, and some formed amorphous glass. When manganese sulfate was applied and fired, manganese oxide was fused, and some manganese oxide reacted with the substrate to show a dense microstructure different from that of the substrate; the substrate had pores. The manganese coated porcelain fired at 1,200 oC had L* values of 55.25, 36.87, and 37.13 for the white ware, celadon body, and white mixed ware, respectively; with a* values of 4.63, 3.07, and 2.15, and b* values of 7.93 and 3.98, it was found to be 3.42. This result indicated that the color of the surface was affected during firing by the chemical reaction between the substrate and manganese.

In this study, a manganese catalyst on the surface of a ceramic support was developed for the removal of odor emitted from barbecuing restaurants. Its ozone oxidation at room temperature was tested using acetaldehyde (CH3CHO), the most dominant compound in the barbecuing odor, and the ozonation efficiency under wet conditions was also studied. The manganese catalyst was made with the honeycomb-type ceramic support, and an acid pretreatment was applied to increase its specific surface area, resulting in an increase of the degree of dispersion of manganese oxide. The acetaldehyde removal efficiency using the manganese catalyst on the acidpretreated support (Mn/APS) increased by 49%, and the ozone decomposition rate and the CO2 conversion rate also increased by 41% and 27%, respectively. The catalyst without surface pretreatment (Mn/S) showed a low efficiency for the acetaldehyde ozonation, and other organic compounds such as acetic acid (CH3COOH) and nonanal (CH3(CH3)7CHO) were found as oxidation by-products. In comparison, CO2 was the most dominant product by the ozonation of acetaldehyde using the Mn/APS. When the relative humidity was increased to 50% in the influent gas stream, the acetaldehyde removal efficiency using the Mn/APS decreased, but only the production rates of CO2 and acetic acid were changed. As a result, the manganese oxide catalyst on the surface of the acid-pretreated honeycomb support manifested high acetaldehyde ozonation even at humid and room temperature conditions.

Zinc-ion Batteris (ZIBs) are recently being considered as energy storage devices due to their high specific capacity and high safety, and the abundance of zinc sources. Especially, ZIBs can overcome the drawbacks of conventional lithium ion batteris (LIBs), such as cost and safety issues. However, in spite of their advantages, the cathode materials under development are required to improve performance of ZIBs, because the capacity and cycling stability of ZIBs are mainly influenced by the cathode materials. To design optimized cathode materials for high performance ZIBs, a novel manganese oxide (MnO2) coated graphite sheet is suggested herein with improved zinc-ion diffusion capability thanks to the uniformly decorated MnO2 on the graphite sheet surface. Especially, to optimize MnO2 on the graphite sheet surface, amounts of percursors are regulated. The optimized MnO2 coated graphite sheet shows a superior zinc-ion diffusion ability and good electrochemical performance, including high specific capacity of 330.8 mAh g−1 at current density of 0.1 A g−1, high-rate performance with 109.4 mAh g−1 at a current density of 2.0 A g−1, and remarkable cycling stability (82.2 % after 200 cycles at a current density of 1.0 A g−1). The excellent electrochemical performance is due to the uniformly decorated MnO2 on the graphite sheet surface, which leads to excellent zinc-ion diffusion ability. Thus, our study can provide a promising strategy for high performance next-generation ZIBs in the near future.

As the International Maritime Organization (IMO)'s environmental regulations on ship emissions become strict, the demand for ships powered by Liquefied Natural Gas (LNG) is rapidly increasing worldwide. Compared to other materials, high manganese steel has the advantages of superior impact toughness at cryogenic temperatures, a small coefficient of thermal expansion, and low cost of base materials and welding rods. However, there is a limitation in that the mechanical properties of the filler material are lower than the base material having excellent mechanical properties. In this study, after performing a high manganese steel laser butt welding experiment, the welding performance was evaluated through mechanical property (yield strength, tensile strength, hardness, cryogenic impact strength) tests of the weld. As a result, it was observed that the yield strength and tensile strength of the high manganese steel laser welding part was 97.5% and 93.5% of the base metal respectively. Also the hardness of welding part was 84.2% of the base metal. The cryogenic impact strength of the welding part and the base metal were over the 27J, the level of welding part is 76.1% of the base metal.

As demand for eco-friendly energy increases, demand for natural gas and Liquefied natural gas (LNG) storage technologies continues to increase. LNG is a cryogenic environment with a temperature of -163°C, so ordinary metals cannot be used due to brittleness. Accordingly, IGC Code designates the cryogenic materials such as Invar, STS304L, Al5083-0, and High Manganese Steel. For fabricating those materials, research on welding possibility is the most important. Thus this study focused on the possibility of laser welding of the cryogenic materials. The weldability of High Manganese Steel was researched in this paper, the shape and the dimensions of the beads after bead on plate (BOP) welding were observed. The experiment was conducted on a total of 25 cases with laser power and welding speed of 5 cases each, and the width, height, and penetration of the beads were confirmed. It was confirmed that the paramenter of bead increased linearly with the laser power, and the paramenters of bead increased linearly with decreasing welding speed. Based on this study, high manganese steel can be applied in various industries by applying it to butt welding.

The effect of intercritical annealing temperature on the microstructure and mechanical properties of Fe-9Mn-0.2C- 3Al-0.5Si medium manganese steels containing Cu and Ni is investigated in this study. Six kinds of medium manganese steels are fabricated by varying the chemical composition and intercritical annealing temperature. Hardness and tensile tests are performed to examine the correlation of microstructure and mechanical properties for the intercritical annealed medium manganese steels containing Cu and Ni. The microstructures of all the steels are composed mostly of lath ferrite, reverted austenite and cementite, regardless of annealing temperature. The room-temperature tensile test results show that the yield and tensile strengths decrease with increasing intercritical annealing temperature due to higher volume fraction and larger thickness of reverted austenite. On the other hand, total and uniform elongations, and strain hardening exponent increase due to higher dislocation density because transformation-induced plasticity is promoted with increasing annealing temperature by reduction in reverted austenite stability.

Effect of heat treatment on microstructure and mechanical properties of an Fe-6.5Mn-0.08C medium-manganese steel is investigated in this study. Three kinds of medium-manganese steel specimens are fabricated by varying heat treatments of intermediate quenching (IQ), step quenching (SQ), and intercritical annealing (IA). Hardness and tensile tests are performed to examine the correlation of microstructure and mechanical properties for the Fe-6.5Mn-0.08C medium-manganese steel specimens. The IQ and SQ specimens have microstructures of martensite matrix with ferrite, whereas IA specimen exhibits microstructure of acicular ferrite matrix with martensite. The tensile test results show that the SQ specimen with martensite matrix has the highest yield strength and the lowest elongation. On the other hand, the SQ specimen has the highest hardness due to the relatively lower reduction of carbon content in martensite during intercritical annealing. According to the fractography of tensile tested specimens, the SQ specimen exhibits a dimple and quasi-cleavage fracture appearance while the IQ and IA specimens have fully ductile fracture appearance with fine-sized dimples caused by microvoid coalescence at ferrite and martensite interface.

리그닌 분해 담자균류로 알려져 있는 느타리버섯균 No.42는 망간퍼옥시데이즈(MnP) 및 락게이즈(Lac)를 생산하였으나 글루코오스-펩톤-이스트-밀기울(GPYW)배지를 이용한 정치배양조건하에서 리그닌퍼옥시데이즈(LiP)활성은 검출 되지 않았다. 한편, 동일배지에서 망간퍼옥시데이즈 활성은 11일째 80(3.6) U/flask(ml)의 최대 생산되었다. 망간퍼옥시 데이즈 분리정제는 Sepha-ros CL-6B 및 Mono-Q 컬럼순으로 수행하였으며 주요 망간퍼옥시데이즈 isozyme은 단일밴 드로 분자량은 36.4KDa이였다. N-말단으로부터 19개의 아 미노산 배열은 단백질 자동 분석 장치로 분석한 결과 ATCADGRTTANAACCVLFP를 나타내었다. 느타리버섯균 No.42의 정치배양조건 하에서 세포외로 생산되는 중요한 망간퍼옥시데이즈 isozyme의 N-말단 아미노산 배열은 이전에 보고된 MnP3의 아미노산 배열과 동일하였다.

암모니아성 질소(NH4-N)는 산업 폐수, 농업 및 축산 폐수에 포함되어 있으며 인과 함께 수질의 부영양화를 일으 키는 물질로 잘 알려져 있다. 또한 망간(Mn)과 비소(As)는 광산 처리수 등에 포함되어 있으며, 수질 오염의 원인 물질로 알려져 있다. 천연 제올라이트는 수중에서 암모니아성 질소를 제거하는데 사용되고 있지만 낮은 흡착능력을 가진다. 이러한 천연 제올라이트의 낮은 흡착능력을 개선하기 위해 Na+, Ca2+, K+, Mg2+로 이온 치환을 진행하였다. 암모니아성 질소(NH4-N)의 흡착량과 제거율은 Na+로 이온 치환된 제올라이트에서 0.66 mg/g과 89.8%로 가장 높은 값을 보였다. 이온 치환된 제올라이트 를 이용하여 Mn과 As의 흡착실험을 진행하였다. Mg2+로 이온 치환된 제올라이트에서 Mn과 As의 높은 흡착량과 제거율을 보였다.

In this work, a PAM(Plasma Assisted Machining) technology was applied to milling of high manganese steel, a typical hard-to-machine materials. For this purpose, a transferred type of arc plasma torch was coupled with a 3-axis milling machine, then, used to heat and soften the surface of a high manganese steel plate in front of a 16 mm end mill with 2 blades and hard coatings. From the test results, it was concluded that the cutting load can be significantly reduced down to 57 % by plasma heating with the power level of 3.9 kW, ensuring the improvement of tool life and surface roughness in milling of high manganese work pieces.

The effect of C, Mn, and Al additions on the tensile and Charpy impact properties of austenitic high-manganese steels for cryogenic applications is investigated in terms of the deformation mechanism dependent on stacking fault energy and austenite stability. The addition of the alloying elements usually increases the stacking fault energy, which is calculated using a modified thermodynamic model. Although the yield strength of austenitic high-manganese steels is increased by the addition of the alloying elements, the tensile strength is significantly affected by the deformation mechanism associated with stacking fault energy because of grain size refinement caused by deformation twinning and mobile dislocations generated during deformation-induced martensite transformation. None of the austenitic high-manganese steels exhibit clear ductile-brittle transition behavior, but their absorbed energy gradually decreases with lowering test temperature, regardless of the alloying elements. However, the combined addition of Mn and Al to the austenitic high-manganese steels suppresses the decrease in absorbed energy with a decreasing temperature by enhancing austenite stability.

This study examined the influence of operating parameters on the electrosorptive recovery system of lithium ions from aqueous solutions using a spinel-type lithium manganese oxide adsorbent electrode and investigated the electrosorption kinetics and isotherms. The results revealed that the electrosorption data of lithium ions from the lithium containing aqueous solution were well-fitted to the Langmuir isotherm at electrical potentials lower than –0.4 V and to the Freundlich isotherm at electrical potentials higher than –0.4 V. This result may due to the formation of a thicker electrical double layer on the surface of the electrode at higher electrical potentials. The results showed that the electrosorption reached equilibrium within 200 min under an electrical potential of –1.0 V, and the pseudo-second-order kinetic model was correlated with the experimental data. Moreover, the adsorption of lithium ions was dependent on pH and temperature, and the results indicate that higher pH values and lower temperatures are more suitable for the electrosorptive adsorption of lithium ions from aqueous solutions. Thermodynamic results showed that the calculated activation energy of 22.61 kJ mol–1 during the electrosorption of lithium ions onto the adsorbent electrode was primarily controlled by a physical adsorption process. The recovery of adsorbed lithium ions from the adsorbent electrode reached the desorption equilibrium within 200 min under reverse electrical potential of 3.5 V.