The government declared ‘2050 carbon neutrality’ as a national vision in October 2020 and subsequently pursued the establishment of a ‘2050 carbon neutrality scenario’ as a follow-up response. Hydrogen is considered as one of the most promising future energy carriers due to its noteworthy advantages of renewable, environmentally friendly and high calorific value. Liquid hydrogen is thus more advantageous for large-scale storage and transportation. However, due to the large difference between the liquid hydrogen temperature and the environment temperature, an inevitable heat leak into the storage tanks of liquid hydrogen occurs, causing boil-off losses and vent of hydrogen gas. Researches on insulation materials for liquid hydrogen are actively being conducted, but research on support design for minimal heat transfer and enhanced rigidity remains insufficient. In this study, to design support structures for liquid hydrogen storage tanks, a thermal-structural coupled analysis technique was developed using Ansys Workbench. Analytical models were created based on the number and arrangement of supports to propose structurally safe support designs.

본 연구는 폴리케톤(PK) 지지체를 이용한 유기용매 역삼투(OSRO) 분리막 제조를 목적으로 하였다. 비용매 유도 상분리 방법(NIPS)을 통해 PK 지지체를 제작하였고, PK 지지체 위에 polyamide layer를 계면 중합하여 thin-film composite (TFC) 형태로 OSRO 분리막을 완성하였다. 이후 OSRO 분리막의 표면과 단면 구조 및 표면의 화학적 구조를 분석하였고 수 투과도와 염 제거율은 각각 약 1.28 LMH/bar와 99.0%의 결과를 얻었다. 또한 OSRO 분리막의 polyamide layer는 유기용매 침지 1일 동안 매우 안정적이었고, 단일 유기용매 투과도 경향성은 유기용매 나노여과(OSN) 분리막의 투과도 모델과 일치하 였다. OSRO 분리막의 MWCO는 MeOH 상에서 240 g/mol이었다. OSRO 분리막의 MeOH-toluene 혼합용액에 대한 투과도 와 separation factor는 상용 OSN 분리막보다 각각 200%와 60%의 높은 결과를 얻었다.

Hydrogen is considered as one of the most promising future energy carriers due to its noteworthy advantages of renewable, environmentally friendly and high calorific value. However, the low density of hydrogen makes its storage an urgent technical problem for hydrogen energy development. Compared with the density of gas hydrogen, the density of liquid hydrogen is more than 1.5 times higher. Liquid hydrogen is thus more advantageous for large-scale storage and transportation. However, due to the large difference between the liquid hydrogen temperature and the environment temperature, an inevitable heat leak into the storage tanks of liquid hydrogen occurs, causing boil-off losses and vent of hydrogen gas. Researches on insulation materials for liquid hydrogen are actively being conducted, but research on support design for minimal heat transfer and enhanced rigidity remains insufficient. In this study, to design support for liquid hydrogen storage tank, technique of thermal-structural coupled analysis including geometry, mesh, and boundary condition were developed using Ansys workbench, and equivalent stress and deformation distributions were analyzed.

수소는 연소 과정에서 산소와 반응하여 물과 열만을 생성하며 공해 물질이 배출하지 않아 깨끗한 에너지원으로 간주된다. 이러한 특징으로 산업 활동으로 비롯된 대기 오염, 이상 기후 문제 등을 해결 하기 위한 대책안으로써 수소를 활용한 신재생에너지가 세계적으로 주목받고 있다. 이에 따라 선행 연 구에서는 수직형 탱크 구조의 취약부로 평가되는 지지부 단면 변화에 따른 영향성을 평가하기 위해 수소 생산 인프라 현장 조사를 수행한 바 있으며, 현장 조사 중에 현장 설치된 수소 탱크 강재 지지부 의 부식 문제를 확인하였다. 지지부의 부식은 구조물의 전체 강성을 감소시키며, 재난(지진)에 취약해 져 수소 저장 용기가 손상으로 인한 2차 피해로 이어질 수 있다. 이에 따라 본 연구는 선행 연구의 후속 연구로써 강재 지지부의 부식 문제를 개선하고자 고강도-저중량 재료인 CFRP(Carbon Fiber Reinforced Polymer)를 사용한 지지부를 개발하여 수치해석을 통해 CFRP 지지부의 내진 성능평가를 목적으로 한다. 해석에 사용된 수소 탱크는 크게 몸체, 지지부, 기초부, 앵커 볼트로 구성되어 있으며, 지지부는 높이 965mm, 75×75×9.5mm의 L형강 4개로 확인되었다. 지진 하중에 대한 동적 성능을 평가하기 위해 시간이력해석법이 사용되었으며, 적용 동적하중의 경우, ASCE의 ICC-ES에서 제시한 평가 기준에 따라 AC 156 Amplitude 100%의 인공 지진을 적용하였다. 해석 결과, CFRP 지지부와 강재 지지부 상단의 최대 변위가 각각 35.48, 32.54mm로 매우 유사한 것으로 나타났으며, Hashin Damage Criteria를 사용하여 CFRP 지지부의 최대 손상 지수를 측정한 결과 수지의 인장측에서 0.065로 확인되었다. 이는 기준 손상 지수 1 대비 매우 낮은 수준이며, 해석 결과를 종합했을 때 CFRP 지지부는 충분한 안전성을 보이는 것으로 판단된다.

In general, a large mirror without weight reduction in large optical or space telescope systems can increase the system’s weight or lead to significant deformation of the mirror surface. Thus, it is imperative to pursue lightweight design strategies. In this paper, the structure design of a spherical mirror, a diameter of 600mm and a mirror radius of 2,000mm, was investigated to reduce weight and minimize deformation. To establish load paths for internal and external loads, stiffeners were added across the lateral supports. This approach effectively reduced both weight and deformation caused by gravity. Weight reduction and reduction percentages were quantified, and the mirror deformation was evaluated by using finite element analysis (FEA). The proposed structures were compared with honeycomb structures for weight reduction. This evaluation allowed to assess the deformation characteristics and the potential advantages of the proposed structures for lightweight mirrors.

Platinum (Pt) catalysts dispersed on carbon-based support materials are generally used in the polymer electrolyte membrane (PEM) fuel cells. In this study, commercial graphene nanoplatelets (GNPs), with different surface areas (320, 530, 800 m2 g− 1), were used as catalyst supports in PEM fuel cells. These GNPs were also pyrolyzed under the inert atmosphere, with and without melamine, as the nitrogen (N) source. Various characterizations (Elemental analysis, FTIR, Raman spectroscopy, BET, TEM, HRTEM, SAED, XRD, TGA, ICP-MS, contact angle measurement, CV, ORR, chronoamperometry, EIS, PEM fuel cell performance test) were performed for the detailed analysis of Pt/GNPs. Based on the three-electrode cell system, the lowest electrochemical surface area (ECSA) loss (29.9%), Pt mass activity loss (20.3%) and overall (charge and mass) resistance (42.2 Ω) were obtained with the Pt/M-530 catalyst. According to the in-situ PEM fuel cell performance results, the specific peak power density was recorded as (450 mW mg Pt− 1) for the Pt/R-530 catalyst, which has also the second most hydrophobic catalyst layer surface with the 146.5° ± 1.28° contact angle value. On the heels of Pt/R-530, the two best performances also belong to the Pt/M-530 (391 mW mg Pt− 1) and Pt/P-530 (378 mW mg Pt− 1) catalysts of the same group.

Carbon supports for dispersed platinum (Pt) electrocatalysts in direct methanol fuel cells (DMFCs) are being continuously developed to improve electrochemical performance and catalyst stability. However, carbon supports still require solutions to reduce costs and improve catalyst efficiency. In this study, we prepare well-dispersed Pt electrocatalysts by introducing titanium dioxide (TiO2) into biomass based nitrogen-doped carbon supports. In order to obtain optimized electrochemical performance, different amounts of TiO2 component are controlled by three types (Pt/TNC-2 wt%, Pt/TNC-4 wt%, and Pt/TNC-6 wt%). Especially, the anodic current density of Pt/TNC-4 wt% is 707.0 mA g−1 pt, which is about 1.65 times higher than that of commercial Pt/C (429.1 mA g−1 pt); Pt/TNC-4wt% also exhibits excellent catalytic stability, with a retention rate of 91 %. This novel support provides electrochemical performance improvement including several advantages of improved anodic current density and catalyst stability due to the well-dispersed Pt nanoparticles on the support by the introduction of TiO2 component and nitrogen doping in carbon. Therefore, Pt/TNC-4 wt% may be electrocatalyst a promising catalyst as an anode for high-performance DMFCs.

A highly performing and durable forward osmosis (FO) membrane was prepared using a polydopamine-modified polyolefin (DPO) support via an aromatic solvent (toluene)-based interfacial polymerization (IP). The hydrophobic polyolefin support was uniformly hydrophilized by polydopamine coating, which provided long term operation stability. In addition, a highly permselective selective layer was prepared on the hydrophilic DPO support by the toluene-based IP, which promoted amine diffusion and the subsequent IP reaction. As a result, the prepared DPO-supported TFC membrane exhibited significantly high FO performance, which was ~4.9 times higher FO water flux and ~62% lower specific salt flux than those of a commercial FO (HTI-CTA) membrane in FO mode. Furthermore, its excellent mechanical and chemical stability enabled stable operation.

Laminated graphene oxide (GO) membrane has great attention for ultrafast flux membrane with well-defined pore structure. However, laminated structure is sensitive to various factors such as functionalization, fabrication method and especially support morphology due to ultrathin thickness. Herein, we investigated surface roughness effect by controlling systematically wrinkled structure of support with ion beam treatment. Wrinkled surface of support generates free volume at interface, facilitating fast water transport, which confirmed 6.4 times enhancement on permeation of water while maintaining high rejection of all dye molecules. The tunability of nanostructure through support control can provide development for ultrathin GO membrane in water purification.

Nitrogen (N)-doped protein-based carbon as platinum (Pt) catalyst supports from tofu for oxygen reduction reactions are synthesized using a carbonization and reduction method. We successfully prepare 5 wt% Pt@N-doped protein-based carbon, 10 wt% Pt@N-doped protein-based carbon, and 20 wt% Pt@N-doped protein-based carbon. The morphology and structure of the samples are characterized by field emission scanning electron microscopy and transmission electron micro scopy, and crystllinities and chemical bonding are identified using X-ray diffraction and X-ray photoelectron spectroscopy. The oxygen reduction reaction are measured using a linear sweep voltammogram and cyclic voltammetry. Among the samples, 10 wt% Pt@N-doped protein-based carbon exhibits exellent electrochemical performance with a high onset potential of 0.62 V, a high E1/2 of 0.55 V, and a low ΔE1/2= 0.32 mV. Specifically, as compared to the commercial Pt/C, the 10 wt% Pt@N-doped proteinbased carbon had a similar oxygen reduction reaction perfomance and improved electrochemical stability.

The highly performing polyamide (PA) thin film composite (TFC) reverse osmosis (RO) membrane was prepared using the commercialized porous polyolefin (PO) membrane as a support. The PO-supported TFC (PO-TFC) membrane was fabricated via a conventional interfacial polymerization process. The highly permselective PA layer was formed by optimizing membrane fabrication parameters such as monomer/additive composition and post-treatment. The uniform pore structure and high surface porosity of the PO support are beneficial for improving the membrane permselectivity. As a result, the prepared PO-TFC membrane showed ~30% higher water flux and ~0.4% higher NaCl rejection compared to a commercial RO membrane. In addition, the PO-TFC membrane exhibited excellent mechanical properties and organic solvent resistance.

Well-dispersed platinum catalysts on ruthenium oxide nanofiber supports are fabricated using electrospinning, post-calcination, and reduction methods. To obtain the well-dispersed platinum catalysts, the surface of the nanofiber supports is modified using post-calcination. The structures, morphologies, crystal structures, chemical bonding energies, and electrochemical performance of the catalysts are investigated. The optimized catalysts show well-dispersed platinum nanoparticles (1-2 nm) on the nanofiber supports as well as a uniform network structure. In particular, the well-dispersed platinum catalysts on the ruthenium oxide nanofiber supports display excellent catalytic activity for oxygen reduction reactions with a half-wave potential (E1/2) of 0.57 V and outstanding long-term stability after 2000 cycles, resulting in a lower E1/2 potential degradation of 19 mV. The enhanced electrochemical performance for oxygen reduction reactions results from the well-dispersed platinum catalysts and unique nanofiber supports.

A porous polyolefin (e.g. polypropylene and polyethylene) membrane has been commercialized as a lithium ion battery separator. The highly performing thin film composite (TFC) forward osmosis (FO) membrane was fabricated using the porous polyolefin membrane as a support via typical interfacial polymerization process. A very thin thickness (~8 μm) and highly interconnected pore structure of the polyolefin support can greatly reduce the internal concentration polarization, leading to high water flux, as evidenced by its low structural parameter (~168 μm). The prepared polyolefin-supported TFC membrane showed ~3.7 times higher water flux and ~33% lower specific salt flux compared to HTI-CTA commercial FO membrane with 1.0 M NaCl draw solution and DI water feed solution in FO mode. In addition, its excellent mechanical strength enables stable membrane operation.

The purpose of this study was to determine the association between school administrator support as perceived by nutrition teachers (dietitians) and job satisfaction in order to provide data concerning efficient job performance of nutrition teachers, to determine effects of school administrator support on job satisfaction in nutrition teachers, and to provide basic data that could help improve school meals. Major supporters of nutrition teachers (dietitians) were chief administrators (55.3%), principals (27.2%), assistant principals (15.0%), and managers in charge (2.4%). Nutrition teachers (dietitians) scored 3.38 for perception of school administrator support, 3.66 for emotional support, 3.27 for informational support, 3.22 for instrumental support, and 3.11 for evaluation support. Support of nutrition teachers (dietitians) by school managers included emotional support (3.66)>informational support (3.27)>instrumental support (3.22)>evaluative support (3.11). Nutrition teachers (dietitians) scored 3.37 for job satisfaction, as follows: work performance (4.19)>interpersonal relationships (3.39)>job satisfaction in general (3.37)>job itself (3.29)>job environment (3.07)>performance rating and benefits system (2.70). Statistically significant correlation was observed between perception of school administrator support and job satisfaction (r= .771, p< .01). Therefore, school administrators are necessary to provide evaluative supports to nutrition teachers (dietitians), performance assessment, employee benefit packages, and improvement of school meal plans and quality.

Thin-film composite membranes (TFCs) have dominated desalination markets for recent decades, but a higher water permeance is still necessary to reduce the energy consumption. Although most researches have focused on the ultrathin active layer of TFCs, the supports should also be considered to further enhance the membrane performances. In this study, TFCs were fabricated on PSf supports containing carbon nanotubes (CNT) by interfacial polymerization. CNT/PSf supports show rougher and more porous surface morphologies than those of bare PSf supports. Because of such surface characteristics, CNT/PSf supports were favorable to increase the roughness and surface area of TFCs. Consequently, TFCs prepared on CNT/PSf nanocomposite supports showed a 41% enhanced water permeance without losing its salt rejection compared to the bare TFCs.

대인관계의 어려움은 이차적으로 우울과 같은 정신적인 문제 를 유발한다. 이에 이 연구에서는 청소년을 대상으로 대인관계 와 우울 사이에 매개변인을 규명하고자 하였다. 연구대상은 일반 고등학생 291명을 대상으로 대인관계와 우 울사이의 매개변인에 대한 경로모형 분석을 시행하였다. 그 결 과, 대인관계가 자아존중감을 거쳐 우울에 영향을 미치는 것으 로 밝혀졌으며, 자아존중감의 매개효과는 유의미한 것으로 나 타났다(p<0.05). 그러나 대인관계와 우울감에서 사회적 지지의 매개효과는 유의미하지 않았다. 이 연구를 통하여 '자아존중감'과 '사회적 지지'가 대인관계 와 우울 사이의 매개변인으로 작용하는 경로 모형을 검증하였 으며, 이러한 결과가 향후 청소년에 대한 연구의 기초자료로 사용되길 기대한다.

To improve the methanol electro-oxidation in direct methanol fuel cells(DMFCs), Pt electrocatalysts embedded on porous carbon nanofibers(CNFs) were synthesized by electrospinning followed by a reduction method. To fabricate the porous CNFs, we prepared three types of porous CNFs using three different amount of a styrene-co acrylonitrile(SAN) polymer: 0.2 wt%, 0.5 wt%, and 1 wt%, respectively. A SAN polymer, which provides vacant spaces in porous CNFs, was decomposed and burn out during the carbonization. The structure and morphology of the samples were examined using field emission scanning electron microscopy and transmission electron microscopy and their surface area were measured using the Brunauer- Emmett-Teller(BET). The crystallinities and chemical compositions of the samples were examined using X-ray diffraction and X-ray photoelectron spectroscopy. The electrochemical properties on the methanol electro oxidation were characterized using cyclic voltammetry and chronoamperometry. Pt electrocatalysts embedded on porous CNFs containing 0.5 wt% SAN polymer exhibited the improved methanol oxidation and electrocatalytic stability compared to Pt/conventional CNFs and commercial Pt/ C(40 wt% Pt on Vulcan carbon, E-TEK).