• Korean Journal of Materials Research
• /
• v.2 no.2
• /
• pp.126-132
• /
• 1992

Experiment has been performed to investigate the thermal and magnetic properties of Mn-ferrite by electrolysis. Using the 0.2%C mild steel as soluble anode and SUS 304 stainless steel as cathode, Mn-ferrite could be made from the sulfuric acid leaching of the wasted manganese dry cell and $MnSO_4$reagent by electrolysis. As the result of X-ray diffraction, thermal analysis and magnetic measurement, Mn-ferrite was the spinel type in $Mn_{x}Fe_{3-x}O_4$ (X=1), the weight loss rate of $Mn_{x}Fe_{3-x}O_4$ were linearly increased up to the $200^{\circ}C$. Ms, Mr and Hc values were decreased with increasing Mn content and heating temperature. When Mn-ferrite was formed by $MnCl_2$reagent electrolysis, Ms values were higher than those formed from the sulfuric acid leaching of the wasted manganese dry cell and $MnSO_4$reagent by electrolysis. In Mn-ferrite, which was formed from the sulfuric acid leaching of the wasted manganese dry cell by electrolysis, Ms and Mr values were higher, Hc values were lower than which was formed by $MnSO_4$ reagent electrolysis at $200^{\circ}C\;and\;300^{\circ}C, while the same values at $100^{\circ}C$. The shape of particles was spherical type, the sizes of them were about $0.1{\mu}m$ sub-micron in $MnSO_4$reagent electrolysis, $0.5{\mu}m$ in the sulfuric acid leaching of the wasted manganese dry cell by electrolysis.

• Journal of Food Hygiene and Safety
• /
• v.38 no.4
• /
• pp.228-235
• /
• 2023

Peanut is a well-known food allergen that causes adverse reactions ranging from mild urticaria to life-threatening anaphylaxis. Consumers suffering from peanut allergies should thus avoid consuming undeclared peanuts in processed foods. Therefore, effective cleaning methods are needed to remove food allergens from manufacturing facilities. To address this, wet cleaning methods with washing water at different temperatures, abstergents (peracetic acid, sodium bicarbonate, dilute sodium hypochlorite, detergent), and cleaning tools (brush, sponge, paper towel, and cotton) were investigated to remove peanuts from materials used in food manufacture, including plastics, wood, glass, and stainless steel. Peanut butter was coated on the surface of the glass, wood, stainless steel, and plastic for 30 min and cleaned using wet cleaning. The peanut residue on the cleaned surfaces was swabbed and determined using an optimized enzyme-linked immunosorbent assay (ELISA). Cleaning using a brush and hot water above 50℃ showed an effective reduction of peanut residue from the surface. However, removing peanuts from wooden surfaces was complicated. These results provide information for selecting appropriate materials in food manufacturing facilities and cleaning methods to remove food allergens. Additionally, the cleaning methods developed in this study can be applied to further research on removing other food allergens.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.1
• /
• pp.545-551
• /
• 2011

Recently, demands for generating high quality tap waters are increasing with high concern of water pollution and corrosion of water pipelines. For the reasons, developing water quality stabilization technique in water purification system is sought rather than replacing to a new pipelines. In this study, high-purity liquid lime($Ca(OH)_2$) was introduced for a water quality stabilization technique in water purification process and simulated water distribution system of pilot-scale size was applied to evaluate anti-corrosion control effect. The effect of anti-corrosion control was calculated in terms of LSI(Langelier Saturation Index) In conclusion, the result of pilot plant showed improvement of corrosiveness by liquid lime($Ca(OH)_2$) with reduction of released iron(Fe). Application of anti-corrosion control technique to the mild steel coupon and the copper coupon were effective by indicating 35.4, 44.5% of improvements. Besides, sample pipes which were treated with liquid lime had formated more thicker layer of corrosion product inside of pipes. As a result, the process of injecting water stabilizer can greatly contribute to the high quality of tap water.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.24 no.1
• /
• pp.126-132
• /
• 2018

This paper discusses about results of advanced buckling strength design for several kinds of perforated plated in the twin-hull car-ferry. For medium / small sized high speed vessels with a length of more than 50 meters and a length / width ratio of more than 12, such as car-ferries, it is highly possible that the buckling strength becomes weak due to the relatively thin thickness and the use of low strength capacity such as mild steel. Especially, it becomes big problem about weak buckling rigidity around the opening to access purpose in the perforated. As regarding safety design point of view for perforated plate, it is necessary to clarify buckling strength and ultimate strength by the distribution of in-plane load distribution around the opening. In this study, nonlinear series analysis using ANSYS was performed to clarify the influence of parameters such as aspect ratio, opening ratio and opening shape affecting the buckling and ultimate strength characteristics of the perforated plate under axial compression and we are derived the optimum design as buckling strength point of view. Based on these results, the governing factor determining the buckling strength of the perforated plate was the opening ratio, and the aspect ratio and the shape of the hole were not influenced.

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.46-46
• /
• 2009

과거 고강도강 용접부에서 발생하는 저온균열은 주로 용접열영향부에서 발생하였는데, 이러한 문제점을 해결하기 위하여 강재 메이커들은 고강도강의 용접성을 향상시키고자 노력하였다. 이러한 노력의 결과로 TMCP, HSLA 강 등이 개발되었고 이들 강재는 예열온도를 저하시킬 수 있다는 장점 때문에 보편화되어 사용되었다. 이러한 강재는 모재 예열온도를 기준으로 적용하게 되면 용착금속에서 저온균열이 발생하는 경우가 있다. 따라서 이제는 용접재료의 용접성, 즉 용접재료의 저온균열 저항성을 평가 할 수 있는 기법이 요구된다. 본 연구의 목적은 용착금속의 저온균열 저항성을 평가하는 것인데, 저온균열 저항성은 용착금속의 미세조직에 따라 다르게 나타날 수 있다. 용착금속의 합금조성은 기본적으로 용착금속에 요구되는 최저 강도와 충격인성을 만족할 수 있도록 설계한다. 하지만 유사한 강도의 유사한 합금조성이더라도 일부 합금 성분에 의해 용착금속의 미세조직들은 상이하게 나타날 수 있는데, 미세조직 특성에 의하여 용착금속의 강도와 저온인성이 결정된다. 용착금속의 저온균열 저항성을 평가하기위하여 Gapped Bead-on-Groove(G-BOG) 시험에 사용된 모재는 50mm 두께의 mild steel을 사용하였으며, 모재의 희석을 방지하기위해 15mm 깊이로 V-groove 가공 후 buttering 용접 하였다. 용접된 시편은 다시 5mm 깊이로 V-groove로 2차 가공 후 Ar + 20% $Co_2$ gas를 사용하여 용접하였다. 용접재료는 ER-100S-G grade로 비슷한 합금조성을 갖는 2 종류를 사용하였다. A용접재료는 Ti 이 0.1% 함유 되었으며, B용접재료는 Ti 함유되지 않은 것을 사용하였다. 또한 예열 온도에 따라 저온균열 감수성을 평가하기위하여 모재의 예열온도를 각각 상온, $50^{\circ}C,\;75^{\circ}C,\;100^{\circ}C$로 하여 실험을 진행하였다. 용착금속의 미세조직을 확인해본 결과 Ti 함유된 A 용착금속 미세조직은 대부분 침상형페라이트로 나타났으며, Ti 함유되지 않은 B 용착금속 미세조직은 대부분 베이나이트로 나타났다. G-BOG 시험 결과 Ti 함유된 A 시편이 Ti 함유되지 않은 B 시편보다 저온균열 발생량이 적었다. 이는 용착금속의 미세조직분포 및 특성에 따라 저온균열감수성이 다르다는 것을 나타낸다.

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.97-97
• /
• 2009

The use of thin plate increases due to the need for light weight in large ship. Thin plate is easily distorted and has residual stress by welding heat. Therefore, the thin plate should be carefully joined to minimize the welding deformation which costs time and money for repair. For one effort to reduce welding deformation, it is very useful to predict welding deformation before welding execution. There are two methods to analyze welding deformation. One is simple linear analysis. The other is nonlinear analysis. The simple linear analysis is elastic analysis using the equivalent load method or inherent strain method from welding experiments. The nonlinear analysis is thermo-elastic analysis which gives consideration to the nonlinearity of material dependent on temperature and time, welding current, voltage, speed, sequence and constraint. In this study, the welding deformation is analyzed by using thermo-elastic method for PCTC(Pure Car and Truck Carrier) which carries cars and trucks. PCTC uses thin plates of 6mm thickness which is susceptible to welding heat. The analysis dimension is 19,200mm(length) * 13,825mm(width) * 376mm(height). MARC and MENTAT are used as pre and post processor and solver. The boundary conditions are based on the real situation in shipyard. The simulations contain convection and gravity. The material of the thin block is mild steel with $235N/mm^2$ yield strength. Its nonlinearity of conductivity, specific heat, Young's modulus and yield strength is applied in simulations. Welding is done in two pass. First pass lasts 2,100 second, then it rests for 900 second, then second pass lasts 2,100 second and then it rests for 20,000 second. The displacement at 0 sec is caused by its own weight. It is maximum 19mm at the free side. The welding line expands, shrinks during welding and finally experiences shrinkage. It results in angular distortion of thin block. Final maximum displacement, 17mm occurs around welding line. The maximum residual stress happens at the welding line, where the stress is above the yield strength. Also, the maximum equivalent plastic strain occurs at the welding line. The plastic strain of first pass is more than that of second pass. The flatness of plate in longitudinal direction is calculated in parallel with the direction of girder and compared with deformation standard of ${\pm}15mm$. Calculated value is within the standard range. The flatness of plate in transverse direction is calculated in perpendicular to the direction of girder and compared with deformation standard of ${\pm}6mm$. It satisfies the standard. Buckle of plate is calculated between each longitudinal and compared with the deformation standard. All buckle value is within the standard range of ${\pm}6mm$.

• The Journal of Korea Assosiation for Disability and Oral Health
• /
• v.12 no.2
• /
• pp.87-91
• /
• 2016

Pierre Robin syndrome (PRS) is characterized by the triad of congenital mandibular hypoplasia, glossoptosis and cleft palate. Infant PRS patients are frequently suffering from upper airway obstruction, gastroesophageal reflux and growth retardation caused by above mentioned problems. We report a dental caries treatment of 3-year old girl with Pierre Robin syndrome with multiple caries. The cause of multiple caries was mainly presumed as patient's eating habit caused by her general condition. She had some feeding problems and had history of gastric tube. She was still using milk bottle and took more than an hour to finish a meal. The treatment was performed under general anesthesia considering patient's condition; mild autism, poor cooperation and respiratory problem due to micrognathia. Severely affected upper incisors were treated with pulp treatment and restored with zirconia crown for esthetic purpose. Lower incisors were treated with pulp treatment and restored with composite resin. Upper right first primary molar was restored with stainless steel crown and other primary molars were treated with composite resin. There were no postoperative complications. According to her parents, the patient's compliance to oral hygiene management was greatly improved after the treatment since she was very pleased with the esthetic result and highly motivated by her looks. The treatment without sedation or general anesthesia would be possible once the airway is improved as the mandible grows.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.13 no.3
• /
• pp.404-410
• /
• 1989

Friction and wear tests were conducted with several different ceramics sliding against ceramic and metal couples with and without lubricant in a two disk type sliding machine. The purpose was to know the tribological properties of ceramics. With very different physical and chemical properties of ceramics compared to metal, the tribological properties of ceramics should be defined in detail. Among them, the wear and friction with same or different couple is very important. Also the lubrication of ceramic is one of the major area to be studied. From this research, SiC, SI$_{3}$N$_{4}$ and ZrO$_{2}$ were slid against SiC, AISI 4340 and bronze under various sliding condition. It was found that the friction and wear of ceramics are strongly dependent on the sliding condition. For unlubricated sliding against SiC, ZrO$_{2}$ shows low wear and friction coefficient over wide lange of load, but with lubricated sliding, SiC shows better performance whatever lubricants were used. Also the effect of lubricant depended upon the material properties of sliding pairs. The general tribological properties of ceramics were not correlated with chattering and noise at low load but it could be reduced or avoided effectively by using lubricants. SiC and Si$_{3}$N$_{4}$ slid against SiC have transition from mild to severe wear at high load but ZrO$_{2}$-SiC and SiC-steel have not. Wear debris formed on the contact area of SiC couples was main cause of the initiation of transition. At high speed, only ZrO$_{2}$ sliding against SiC has transition of wear by low thermal conductivity.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.20 no.6
• /
• pp.752-757
• /
• 2017

Analysis has been performed for the penetration of a long-rod into MMC/Ceramic layered armour system with several shot test and a series of simulations. Two types of MMC plate have been fabricated by a liquid pressing method; A356/45%vol.%SiCp with a uniform distribution of SiC particle and Al7075/45%vol.B4Cp with B4C particle. The mechanical properties were measured with the high-speed split Hopkins bar test, hardness test and compression test. The popular Simplified Johnson-Cook model was adopted to represent the material characteristics for FEM simulations. The performance of the MMC applied armour system has been made by comparing with the semi-infinite mild steel target using the depth of penetration(DOP). The results show that placing ceramic front layer provides a certain gain in protection, and that placing another ductile front layer provides a further gain. The application of MMC is found to be attractive.

• Journal of Surface Science and Engineering
• /
• v.13 no.3
• /
• pp.146-154
• /
• 1980

The effects of various electrodeposition conditions (deposition temperature and cathode current density) on preferred orientation and microhardness of electrodeposited Ni-Sn and Sn-Zn alloys were studied. At deposition temperatures from 25$^{\circ}$ to 95$^{\circ}C$ and constant cathode current density of 270 and 530 A/$m^2$ Ni-Sn and Sn-Zn were codeposited in chloride-fluoride acid and stannate-cyanide alkaline electrolyte bath respectively. Ni-Sn alloy deposited at temperatures from 25$^{\circ}$ to 35$^{\circ}C$ was composed of single phase of $Ni_3Sn_4$ with 73 wt.% Sn and the one deposited at temperatures from 45$^{\circ}$ to 95$^{\circ}C$ was made of multiphase mixture of NiSn, $Ni_3Sn_2$ and $Ni_3Sn_4$ with nearly equiatomic composition (65.5 wt.% Sn). The random orientation of thermody-namically metastable NiSn phase (hexagonal structure) predominated at deposition temperature range 25$^{\circ}$-45$^{\circ}C$, and the strong (110) preferred orientation was found at 65$^{\circ}$-85$^{\circ}C$ and then disappeared again at 95$^{\circ}C$. The microhardness of Ni-Sn deposits increased with deposition temperature up to 85$^{\circ}C$, and then decreased at constant cathode current density. The preferred orientation and the maximum microhardness were discussed in terms of lattice contractile stress which result from desorption of hydrogen atom absorbed in deposit lattice. The Sn content of Sn-Zn alloy deposits increased with deposition temperature up to 75$^{\circ}C$, and then decreased at constant cathode current density of 530 A/$m^2$. It also decreased with cathode current density up to 530 A/$m^2$, and then increased at constant deposition temperature of 25$^{\circ}C$. Sn-Zn alloy deposits were composed of two-phase mixture of ${beta}$-Sn and Zn. The preferred orientations of ${beta}$-Sn (tetragonal structure) changed with deposition temperature. The microhardness of Sn-Zn deposits decreased with deposition temperature. It also increased with cathode density up to 530 A/$m^2$, and then decreased at constant deposition temperature of 25$^{\circ}C$. The microhardness of Sn-Zn deposits was observed to be determinded more by the Sn content than by the preferred orientation.