폴리술폰 고분자는 비대칭 정밀여과 멤브레인 제조에 가장 널리 사용되는 고분자 소재이다. 폴리술폰 멤브레인은 소수성 특성으로 인하여 공정상에서 빠른 막오염이 일어난다. 고분자 블렌딩은 폴리술폰 멤브레인의 수명을 향상시키는데 있어 가장 간단하고 효과적인 방법이다. sPES는 폴리술폰 블렌딩 방법을 통하여 소수성을 해결할 수 있는 유용한 친수성 고분자이다. 본 연구에서는 PSF/sPES/DMF/PVP/BE 고분자 용액을 물에 침지시켜 정밀여과 멤브레인을 제조하였다. 캐스팅 용액에 소량의 sPES 첨가함으로써 정밀여과 멤브레인 구조 변화를 볼 수 있었다. sPES의 첨가는 높은 비대칭성과 활성층의 성장, 그리고 평균 기공 크기의 감소를 가져왔다. 하지만 수투과량은 PSF/sPES/DMF/PVP/BE로 만든 멤브레인이 PSF/DMF/PVP/BE로 만든 멤브레인에 비해 더 큰 값을 보였다.

백색을 띄고 물리적·화학적으로 안정한 지르코니아는 열전도도가 낮고 강도와 인성, 내식성이 우수하여 단열재, 내화물과 같은 고온 재료와 각종 산업용 구조세라믹스에 사용되고 있다. 이러한 지르 코니아를 낮은 경도 및 굴절률 등과 같은 단점을 가진 고분자 코팅제에 도입하게 되면 화학적, 전기적, 광학적인 특성이 향상된다. 이와 같이 유기 소재에 무기 소재를 혼합하여 사용하는 유-무기 하이브리드 코팅을 목적으로 본 연구에서는 지르코니아 표면에 trimethylchlorosilane(TMCS)과 hexamethyldisilazane(HMDZ)을 사용하여 실릴화반응을 통한 -CH3기를 도입하여 소수성을 나노지르코 니아 표면에 도입하였다. 소수화된 지르코니아 표면에서의 TMCS와 HMDZ에 의해 도입된 Si-CH3의 존재는 FT-IR ATR spectroscopy를 통해 확인하였고, silicon 원소의 존재를 FE-SEM/EDS와 ICP-AES 를 통해 확인하였다. 또한, 개질 전후의 지르코니아를 아크릴레이트 단량체에 분산하여 침강속도를 확인 하여 분산성이 향상되는 것을 확인하였다. 지르코니아 입자의 크기 및 분포는 입도 분석기를 통해 확인 하였으며, BET 분석을 통해 개질 반응 전후의 비표면적은 18 m2/g 정도로 큰 변화가 없었다.

본 연구에서는 graphene oxide (GO)를 polyacrylonitrile (PAN)에 첨가하여 전기방사법을 이용해 나노섬유 복합막 을 제조한 뒤 물리적 특성을 관찰하였다. GO의 제조는 개선된 Hummer’s 방법을 이용하였으며, 표면처리가 되지 않은 GO의 경우 0.5 wt% 이상에서 전기방사가 이루어지지 않았다. GO의 안정성 및 분산도 증가를 개선하기 위해 계면활성제를 이용하 여 GO의 표면처리를 하였다. 표면처리가 된 GO를 사용하여 나노섬유 복합막의 GO의 함량을 0.5 wt% 이상 첨가할 수 있었 다. 특히, 표면처리가 된 GO가 첨가된 나노섬유 복합막은 향상된 물리적 특성을 가지며, 이는 나노섬유 분리막 내의 GO의 분산도와 상관관계가 있는 것으로 보인다.

This study attempted to establish the optimal conditions for storage of spring kimchi cabbage to stably control supply and demand. To this end, this study stored kimchi cabbages in various manners for different periods and compared the quality characteristics of kimchi using these cabbages. According to the results, pre-drying with photocatalytic and pre-cooling treatments showed average selectivity loss rates of 18.83 and 21.37%, respectively, which were lower than those of other treatments. Spring kimchi cabbages were stored for 15 weeks under various conditions, and the kimchi was stored for 4 weeks at 4°C. After ripening, each kimchi was analyzed for their soluble solid content, pH, acidity, and salinity. The average pH of kimchi was 4.60 and tended to rise, whereas average acidity was 0.38% and fell by 0.24 to 0.31% as the storage period was extended. Extension of the storage period caused decreases in soluble solid content and salinity, and the number of lactic acid bacteria decreased due to increased pH and reduced acidity (p<0.05). Sensory evaluation showed that all experts and non-professionals preferred kimchi treated by precooling compared to any other treatment.

Spherical-type zirconia granules are successfully fabricated by a spray-drying process using a water solvent slurry, and the change in the green density of the granule powder compacts is examined according to the organic polymers used. Two organic binders, polyvinyl alcohol (PVA) and 2-hydroxyethyl methacrylate (HEMA), which are dissolved in a water solvent and have different degrees of polymerization, are applied to the slurry with a plasticizer (polyethylene glycol). The granules employing a binder with a higher degree of polymerization (PVA) are not broken under a uniaxial press; consequently, they exhibit a poor green density of 2.4 g/cm3. In contrast, the granule powder compacts employing a binder with a lower degree of polymerization (HEMA) show a higher density of 2.6 g/cm3 with an increase in plasticizer content. The packing behavior of the granule powders for each organic polymer system is studied by examining the microstructure of the fracture surface at different applied pressures.

One of the challenges facing precision manufacturers is the increasing feature complexity of tight tolerance parts. All engineering drawings must account for the size, form, orientation, and location of all features to ensure manufacturability, measurability, and design intent. Geometric controls per ASME Y14.5 are typically applied to specify dimensional tolerances on engineering drawings and define size, form, orientation, and location of features. Many engineering drawings lack the necessary geometric dimensioning and tolerancing to allow for timely and accurate inspection and verification. Plus-minus tolerancing is typically ambiguous and requires extra time by engineering, programming, machining, and inspection functions to debate and agree on a single conclusion. Complex geometry can result in long inspection and verification times and put even the most sophisticated measurement equipment and processes to the test. In addition, design, manufacturing and quality engineers are often frustrated by communication errors over these features. However, an approach called profile tolerancing offers optimal definition of design intent by explicitly defining uniform boundaries around the physical geometry. It is an efficient and effective method for measurement and quality control. There are several advantages for product designers who use position and profile tolerancing instead of linear dimensioning. When design intent is conveyed unambiguously, manufacturers don’t have to field multiple question from suppliers as they design and build a process for manufacturing and inspection. Profile tolerancing, when it is applied correctly, provides manufacturing and inspection functions with unambiguously defined tolerancing. Those data are manufacturable and measurable. Customers can see cost and lead time reductions with parts that consistently meet the design intent. Components can function properly-eliminating costly rework, redesign, and missed market opportunities. However a supplier that is poised to embrace profile tolerancing will no doubt run into resistance from those who would prefer the way things have always been done. It is not just internal naysayers, but also suppliers that might fight the change. In addition, the investment for suppliers can be steep in terms of training, equipment, and software.

This study investigates the oxidation properties of Fe-14Cr ferritic oxide-dispersion-strengthened (ODS) steel at various high temperatures (900, 1000, and 1100°C for 24 h). The initial microstructure shows that no clear structural change occurs even under high-temperature heat treatment, and the average measured grain size is 0.4 and 1.1 μm for the as-fabricated and heat-treated specimens, respectively. Y–Ti–O nanoclusters 10–50 nm in size are observed. High-temperature oxidation results show that the weight increases by 0.27 and 0.29 mg/cm2 for the asfabricated and heat-treated (900°C) specimens, and by 0.47 and 0.50 mg/cm2 for the as-fabricated and heat-treated (1000°C) specimens, respectively. Further, after 24 h oxidation tests, the weight increases by 56.50 and 100.60 mg/cm2 for the as-fabricated and heat-treated (1100°C) specimens, respectively; the latter increase is approximately 100 times higher than that at 1000°C. Observation of the surface after the oxidation test shows that Cr2O3 is the main oxide on a specimen tested at 1000°C, whereas Fe2O3 and Fe3O4 phases also form on a specimen tested at 1100°C, where the weight increases rapidly. The high-temperature oxidation behavior of Fe-14Cr ODS steel is confirmed to be dominated by changes in the Cr2O3 layer and generation of Fe-based oxides through evaporation.

Harmonic structure materials are materials with a core–shell structure having a shell with a small grain size and a core with a relatively large grain size. They are in the spotlight because their mechanical properties reportedly feature strength similar to that of a sintered powder with a fine grain size and elongation similar to that of a sintered powder with a coarse grain size at the same time. In this study, the tensile properties, microstructure, and stretchflangeability of harmonic structure SUS304L made using powder metallurgy are investigated to check its suitability for automotive applications. The harmonic powders are made by mechanical milling and sintered using a spark plasma sintering method at 1173 K and a pressure of 50 MPa in a cylindrical die. The sintered powders of SUS304L having harmonic structure (harmonic SUS304L) exhibit excellent tensile properties compared with sintered powders of SUS304L having homogeneous microstructure. In addition, the harmonic SUS304L has excellent stretch-flangeability compared with commercial advanced high-strength steels (AHSSs) at a similar strength grade. Thus, the harmonic SUS304L is more suitable for automotive applications than conventional AHSSs because it exhibits both excellent tensile properties and stretch-flangeability.

Porous polytetrafluoroethylene (PTFE) thin films are fabricated by spin-coating using a dispersion solution containing PTFE powders, and their crystalline properties are investigated after thermal annealing at various temperatures ranging from 300 to 500°C. Before thermal annealing, the film is densely packed and consists of many granular particles 200-300 nm in diameter. However, after thermal annealing, the film contains many voids and fibrous grains on the surface. In addition, the film thickness decreases after thermal annealing owing to evaporation of the surfactant, binder, and solvent composing the PTFE dispersion solution. The film thickness is systematically controlled from 2 to 6.5 μm by decreasing the spin speed from 1,500 to 500 rpm. A triboelectric nanogenerator is fabricated by spin-coating PTFE thin films onto polished Cu foils, where they act as an active layer to convert mechanical energy to electrical energy. A triboelectric nanogenerator consisting of a PTFE layer and Al metal foil pair shows typical output characteristics, exhibiting positive and negative peaks during applied strain and relief cycles due to charging and discharging of electrical charge carriers. Further, the voltage and current outputs increase with increasing strain cycle owing to accumulation of electrical charge carriers during charge-discharge.

Abstract Y2Ti2O7 nanoparticles (0.3 mol%) have been successfully synthesized by the co-precipitation process. The samples, adjusted to pH7 with ammonia solution as catalyst and calcined at 700~900 ℃, exhibit very fine particles with close to spherical shape and average size of 10-30 nm. It was possible to control the size of the synthesized Y2Ti2O7 particles by manipulating the conditions. The Y2Ti2O7 nanoparticles were coated on a glass substrate by a dipping coating process with inorganic binder. The Y2Ti2O7 solution coated on the glass substrate had excellent adhesion of 5B; pencil hardness test results indicated an excellent hardness of 6H. The thickness of the thick film was about 30 μm. Decomposition of MB on the Y2Ti2O7 thin film shows that the photocatalytic properties were excellent.

Abstract In this study, Fe-Ni slag, converter slag and dephosphorization slag generated from the steel industry, and fly ash or bottom ash from a power plant, were mixed at an appropriate mixing ratio and melted in a melting furnace in a massproduction process for glass ceramics. Then, glass-ceramic products, having a basalt composition with SiO₂, Al₂O₃, CaO, MgO, and Fe₂O₃ components, were fabricated through casting and heat treatment process. Comparison was made of the samples before and after the modification of the process conditions. Glass-ceramic samples before and after the process modification were similar in chemical composition, but Al₂O₃ and Na₂O contents were slightly higher in the samples before the modification. Before and after the process modification, it was confirmed that the sample had a melting temperature below 1250 ℃, and that pyroxene and diopside are the primary phases of the product. The crystallization temperature in the sample after modification was found to be higher than that in the sample before modification. The activation energy for crystallization was evaluated and found to be 467 kJ/mol for the sample before the process modification, and 337 kJ/mol for the sample after the process modification. The degree of crystallinity was evaluated and found to be 82% before the process change and 87% after the process change. Mechanical properties such as compressive strength and bending strength were evaluated and found to be excellent for the sample after process modification. In conclusion, the samples after the process modification were evaluated and found to have superior characteristics compared to those before the modification.

Fe-Si-Cr ferroalloy is predominantly produced by carbothermic reduction. In this study, silicothermic and carbothermic mixed reduction of chromite ore to produce Fe-Si-Cr alloy is suggested. As reductants, silicon and silicon carbide are evaluated by thermochemical calculations, which prove that silicon carbide can be applied as a raw material. Considering the critical temperature of the change from the carbide to the metallic form of chromium, thereduction experiments were carried out. In these high temperature reactions, silicon and silicon carbide act as effective reductants to produce Fe-Si-Cr ferroalloy. However, at temperatures lower than the critical temperature, silicon carbide shows a slow reaction rate for reducing chromite ore. For the proper implementation of a commercial process that uses silicon carbide reductants, the operation temperature should be kept above the critical temperature. Using equilibrium calculations for chromite ore reduction with silicon and silicon carbide, the compositions of reacted metal and slag were successfully predicted. Therefore, the mass balance of the silicothermic and carbothermic mixed reduction of chromite ore can be proposed based on the calculations and the experimental results.

Today, the management environment of the manufacturing industry is faced with drastic changes. The manufacturing industry is planning to innovate for itself via upgrading manufacturing technology and securing manufacturing competitiveness through 'Industry 4.0' and 'Manufacturing 3.0' strategies combined with ICT (information and communications technologies) for smart factory construction. In addition, as the era of the fourth industrial revolution began, the smart factory is emerging as a new paradigm that can lead to new changes in the manufacturing industry and achieve sustainable development. However, most of SMEs (small and medium-sized manufacturing enterprises) in Korea have very low technology, investment capital and expertise for smartization, and the level of informatization is so low that they cannot build basic systems such as a management module of production records. Therefore, this study proposes a framework that integrates cloud-based production data management and production scheduling with intuitive rules for smart production site management of SMEs. The main features of the proposed framework for SMEs are as follows: 1) the collection and management of production data using the cloud system; 2) operation management using intuitive heuristic algorithm; 3) production scheduling through timing constraints-based simulation.

분리막을 이용한 산업은 석유에너지 자원의 고갈과 동시에 친환경 에너지자원의 필요성이 대두되어 최근 들어 많은 연구가 이루어지고 있다. 이온기 그룹을 포함하는 고분자 분리막의 경우 해수담수, 전지 시스템 등 친환경 에너지 자원의 개발과 더불어 많은 연구가 이루어지고 있다. 본 연구에서는 이미다졸륨 그룹의 도입을 통해서 이온교환 관능기를 포함하는 폴리에테르에테르케톤계열고분자를 합성하여 음이온교환막 제조를 하였으며 이에 따른 연료전지 적용을 위한 다양한 특성평가를 진행하였다. 이온교환능 및 이온전도도를 분석하였다. 도입된 이미다졸륨기의 함량이 증가함에 따라 이온교환능 및 이온전도도가 향상이 되었음을 확인 할 수 있었다.

본 연구에서는 높은 이산화탄소 분리성능을 가지는 폴리이미드 제조를 위해 3가지 모노머를 이용하여 합성하였다. 합성된 고분자를 비용매 상전이법으로 비대칭 분리막을 제조하기 위하여 고분자의 용해도 지수 추정 값과 비용매 상전이 계수 측정을 통해 용매를 선정하였고, 고분자 용액 점도 측정을 통해 분리막제조를 위한 도프용액 중의 고분자의 함량을 결정하여 질산리튬을 첨가제로 사용하여 최종적으로 분리막을 제조하였다. 제조된 비대칭 분리막은 전자주사현미경(SEM)을 통해 질산리튬과 휘발성 용매 함량에 변화에 따른 모폴로지의 변화를 확인하였으며, 이의 변화에 따른 기체 투과도 변화를 확인하였다. 휘발성 용매 함량이 작을수록 선택도는 유지되면서 이산화탄소 투과도가 증가하는 것을 확인하였다.

Recently, a few-layered graphene oxide (GO), which high CO2/N2 selective characters in the humidified feed, has been extensively investigated as a membrane material for gas and liquid separation. Although GO membrane is considered as one of promising membranes, it has a limitation to apply for practical application because of low CO2 permeance and low stability under dry condition. As such, in this study, we fabricated CO2-philic polymers and GO composite membranes by using GO as a filler for high CO2/N2 selectivity. We used two kinds of PEO-containing polymers to increase CO2 permeability by controlling the ratio of free volume in polymer networks. High CO2 permeability (~850barrer) and high CO2/N2 selectivity (~55) were achieved in CO2-philic composite membranes.