바이오물질을 포함하는 나노발전기는 무공해 에너지원이며 생분해성 전자폐기물이라는 점에서 친환경적인 전자소자이다. 특히 바이오 물질이 바이오폐기물로부터 추출될 수 있다면 바이오폐기물의 양도 줄어들 것이다. 본 연구에서는 포유동물의 피부에 존재하는 동물성 콜라겐을 이용하여 마찰전기 나노발전 기를 제작하였고 그 특성평가를 진행하였다. 마찰전기 나노발전기의 전기적 양극층은 회전 도포방법을 이 용하여 콜라겐 막을 형성하여 구성하였으며, 주사전자현미경으로 막이 다공성임을 확인하였다. 제작한 마 찰전기 나노발전기는 주기적인 기계적 운동에 의해 3 Hz에서 7 V부터 5 Hz에서 15 V의 개방전압과 5 Hz에서 3.8 μA의 단락전류를 보였다. 결론적으로, 콜라겐 함유 마찰전기 나노발전기는 센서와 같은 저전 력 구동 장치의 전원이 될 수 있으며 전자 폐기물 감소에도 유용할 것으로 기대된다.

This study analyzed the duct characteristics of hubless rim-driven propeller (RDP) used in underwater robots. In the previous study, flow visualization experiments were performed with an advancing ratio of 0.2 to 1. The vortex at the front of the duct increased in strength while maintaining its size as the advancing ratio decreased. Therefore, it is necessary to study the optimization of the duct shape. Conventional propeller thrusters use acceleration/deceleration ducts to increase their efficiency. However, unlike conventional propellers, it is impossible to apply to airfoil acceleration/deceleration ducts due to the RDP structure. In this study, duct wake flow characteristics, thrust force, and efficiency according to the duct shape of RDP were analyzed using numerical analysis techniques. Duct design is limited and six duct shapes were designed. As a result, an optimized duct shape was designed considering duct wake flow characteristics, thrust force, and efficiency. The shape that the outlet width of the RDP was kept constant until the end of the duct showed higher thrust force and efficiency.

In this study, a graphite block is fabricated using artificial graphite processing byproduct and phenolic resin as raw materials. Mechanical and electrical property changes are confirmed due to the preforming method. After fabricating preforms at 50, 100, and 150 MPa, CIP molding at 150 MPa is followed by heat treatment to prepare a graphite block. 150UP-CIP shows a 12.9% reduction in porosity compared with the 150 MPa preform. As the porosity is decreased, the bulk density, flexural strength, and shore hardness are increased by 14.9%, 102.4%, and 13.7%, respectively; and the deviation of density and electrical resistivity are decreased by 51.9% and 34.1%, respectively. Therefore, as the preforming pressure increases, the porosity decreases, and the electrical and mechanical properties improve.

In order to apply to high-nickel cathodes for high-capacity and stability enhancement of lithium-ion batteries, the characteristics of the coating film were reviewed using the conventional nickel plating method. The surface morphology of the plating layer and the measurement of the surface roughness were analyzed according to scan size and rate using the contact mode of Atomic Force Microscopy. The hydrogen ion concentration (pH) of the electrolyte played an important role in shaping the metal ion plating. As the overpotential of the surface increased during plating, the crystals grew in a direction other than the main crystal growth direction. The increase in on-time during pulse plating appears to result in coarse particles as much of the applied current is consumed by the reduction of hydrogen ions, resulting in lower current efficiency. From the AFM image, it was confirmed that the blackening of the plated film was due to a partial overvoltage phenomenon during electrolytic degreasing. In order to be used as a high-nickel cathode, it seems that the current must be uniformly distributed on the surface of the substrate during plating.

리튬 금속 기반 전극의 높은 용량에도 불구하고, 제어가 어려운 덴드라이트 성장은 낮은 쿨롱 효율, 안전 문제를 야기해, 리튬금속 배터리의 상용화를 제한한다. 본 연구에서는 압전 복합체인 BaTiO3/PVDF (BTO@PVDF) 기반 보호층을 리튬금속에 코팅, 덴드라이트에 의한 부피팽창으로 발생한 변형을 분극을 이용하여, 리튬 금속 전극의 안정성 및 성능을 향상 하고자 한다. 이를 통해, 균일한 리튬이온의 증착이 가능해졌으며, BTO@PVDF 전극은 100 사이클 동안 약 98.1% 이상의 쿨 롱 효율을 나타내었다. 또한, CV를 통해 향상된 리튬이온의 확산계수(DLi+) 증가를 보였으며, 본 연구에서 제시된 전략은 리 튬 금속 전극의 성능 향상에 새로운 길을 나타내준다.

전기 설비는 원자력 발전소와 같은 발전소에서 발전 시스템을 운영하고 시설물 전체의 안전을 유지하는데 중요한 역 할을 한다. 이러한 전기 설비들은 캐비닛 내부에 설치되어 외부의 위험으로부터 보호된다. 캐비닛 자체 구조와 내부의 전기 장 치들의 내진검증은 발전소의 안전한 운영을 위해 필수적이다. 부분 전기 캐비닛의 내진검증 연구들은 진동대 시험에 의존하여 진행되고 있다. 그러나 시험을 기반으로 한 내진검증의 경우 다양한 종류의 전기 캐비닛의 특성을 포함하기에는 한계가 있다. 이러한 문제는 상세 3D 유한요소 모델을 통한 내진 검증평가는 진동대 시험으로 인한 비용 및 시간을 절약할 수 있고 다양한 형태 및 위치의 전기설비 설치에 따른 내부의 응답 민감성을 확인해 볼 수 있다. 본 연구에서는 단문형 전기 캐비닛의 내진응 답에 대한 연구를 실시하였다. 먼저 진동대 시험으로 얻은 모달해석 결과를 바탕으로 ABAQUS software를 통해 구축된 3D 상세 유한요소 모델을 검증하였다. 그리고 캐비닛 내부의 다양한 기기 설치를 모사하기 위해 캐비닛 하부 및 상부 위치에 캐비닛 총 무게의 2%, 4%, 6%의 질량을 유한요소 모델에 추가하였다. 또한 2개의 고주파 지진과 2개의 저주파 지진을 입력 지진으로 선 정하여 캐비닛 내부 기기의 질량 변화에 따른 캐비닛 내부와 외부의 가속도 응답 변화를 분석하였다.

This research studied the electrical characteristics, IR transmission characteristics, stealth functions, and thermal characteristics of infrared thermal-imaging cameras of copper-sputtered samples. Nylon samples were prepared for each density as a base material for copper-sputtering treatment. Copper-sputtered NFi, NM1, NM2, NM3, NM4, and NM5, showed electrical resistance of 0.8, 445.7, 80.7, 29.7, 0.3, and 2.2 Ω, respectively, all of which are very low values; for the mesh sample, the lower the density, the lower the electrical resistance. Measuring the IR transmittance showed that the infrared transmittance of the copper-sputtered samples was significantly reduced compared to the untreated sample. Compared to the untreated samples, the transmittance went from 92.0–64.1%. When copper sputtered surface was directed to the IR irradiator, the IR transmittance went from 73.5 to 43.8%. As the density of the sample increased, the transmittance tended to decreased. After the infrared thermal imaging, the absolute values of △R, △G, and △B of the copper phase increased from 2 to 167, 98 to 192, and 7 to 118, respectively, and the closer the density of the sample (NM5→NFi), the larger the absolute value. This proves that the dense copper phase-up sample has a stealth effect on the infrared thermal imaging camera. It is believed that the copper-sputtered nylon samples produced in this study have applications in multifunctional uniforms, bio-signal detection sensors, stage costumes, etc.

The electromembrane process, which has advantages such as scalability, sustainability, and eco-friendliness, is used in renewable energy fields such as fuel cells and reverse electrodialysis power generation. Most of the research to visualize the internal flow in the electromembrane process has mainly been conducted on heterogeneous ion exchange membranes, because of the non-uniform swelling characteristics of the homogeneous membrane. In this study, we successfully visualize the electroconvective vortices near the Nafion homogeneous membrane in PDMS-based microfluidic devices. To reinforce the mechanical rigidity and minimize the non-uniform swelling characteristics of the homogeneous membrane, a newly developed swelling supporter was additionally adapted to the Nafion membrane. Thus, a clear image of electroconvective vortices near the Nafion membrane could be obtained and visualized. As a result, we observed that the heterogeneous membrane has relatively stronger electroconvective vortices compared to the Nafion homogeneous membranes. Regarding electrical response, the Nafion membrane has a higher limiting current and less overlimiting current compared to the heterogeneous membrane. Based on our visualization, it is assumed that the heterogeneous membrane has more activated electroconvective vortices, which lower electrical resistance in the overlimiting current regime. We anticipate that this work can contribute to the fundamental understanding of the ion transport characteristics depending on the homogeneity of ion exchange membranes.

Tin-antimony sulfide nanocomposites were prepared via hydrothermal synthesis and a N2 reduction process for use as a negative electrode in a sodium ion battery. The electrochemical energy storage performance of the battery was analyzed according to the tin-antimony composition. The optimized sulfides exhibited superior charge/discharge capacity (770 mAh g-1 at a current density of 100 mA g-1) and stable lifespan characteristics (71.2 % after 200 cycles at a current density of 500 mA g-1). It exhibited a reversible characteristic, continuously participating in the charge-discharge process. The improved electrochemical energy storage performance and cycle stability was attributed to the small particle size, by controlling the composition of the tin-antimony sulfide. By optimizing the tin-antimony ratio during the synthesis process, it did not deviate from the solubility limit. Graphene oxide also acts to suppress volume expansion during reversible electrochemical reaction. Based on these results, tin-antimony sulfide is considered a promising anode material for a sodium ion battery used as a medium-to-large energy storage source.

Flexible zinc-air batteries have many merits, including low cost, high safety, environmentally friendliness applicability, etc. One of the key factors to improve the performance of flexible zinc-air batteries is to use a gel electrolyte. In this study, gel electrolytes were synthesized from potato, sweet potato, and corn starch. In a comparison of each starch, the corn starch-based gel electrolyte showed the highest discharge capacity of 12.41 mAh/cm2 in 20 mA and 6.47 mAh/cm2 in 30 mA. It also delivered a higher specific discharge capacity of 7.06 mAh/cm2 than the other materials after 100° bending. In addition, the electrochemical impedance spectroscopy (EIS) was analyzed to calculate the ionic conductivity. The potato, sweet potato, and corn starch-based gel electrolytes showed electrolyte resistances (Re) of 0.306, 0.298, and 0.207 Ω, respectively. In addition, the corn starch-based gel electrolyte delivered the highest ionic conductivity of 0.121 S cm-1 among the other gel electrolytes. Thus, the corn starch-based gel electrolyte was verified to improve the performance of flexible zinc-air batteries

본 연구는 전기투석과 용매추출을 융합한 희유금속 회수 공정에서 분리막과 음이온교환막의 개질을 통해 유기상 과 수상에 대한 분리막의 낮은 젖음성 및 AEM을 통한 수소이온 투과로 인한 금속이온의 회수 효율 감소를 개선하였다. 구체 적으로, 분리막 표면 중 한면은 polydopamine (PDA) 통한 친수성 개질, 다른 면은 SiO2 또는 graphene oxide를 통한 친유성 개질을 함으로써 분리막의 젖음성을 개선하였다. 또한, 음이온교환막의 표면을 polyethyleneimine, PDA, poly(vinylidene fluoride) 등을 이용, 개질해 수분 흡수(Water uptake) 감소 및 기공구조 변화를 통해 수소이온 수송을 억제해 수소이온 투과를 억 제할 수 있다. 개질된 막 표면 형상과 화학적 특성 및 조성은 주사전자현미경과 푸리에변환 적외선 분광법을 통해 확인되었 고, 이를 구리 이온 회수 시스템에 적용해 향상된 추출 및 탈거 효율과 수소이온 수송 억제능을 확인하였다.

목적 : 본 연구에서는 2019년 생활시간조사 자료를 분석 대상으로 작업치료 분야에서 최초로 작업연결망 (occupational network)을 구성하여 전기고령자와 후기고령자의 24시간 작업(occupation)들 간의 관계 를 분석하여 특성을 분석하고 파악하는데 목적이 있다. 연구방법 : 분석 대상은 통계청의 2019년 생활시간조사 자료의 전기고령자 331명과 후기고령자 331명의 24시 간 행동 항목들을 키워드 네트워크 분석 방법으로 분석하여 작업연결망(occupational network)을 구성하고 네트워크 분포의 지표로서 고립 정도, 밀도, 포괄성과 연결 중심성, 근접 중심성을 NetMiner 4.0으로 분석하였 다. 일반적 특성은 SPSS ver.25.0으로 독립표본 t 검정(two-sample t-test), 기술통계를 실시하였다. 결과 : 네트워크 분포 분석결과 전기고령자와 후기고령자의 밀도는 0.793, 0.649, 포괄성은 100%로 나타 났으며, 평균 거리는 1.207, 1.351이며, 고립된 노드는 나타나지 않았다. 중심성 지표 분석 결과 연결 중심성과 근접 중심성이 높은 작업으로는 전기고령자는 교제활동, 스포츠 및 레포츠, 미디어를 이용한 여가활동, 음식준비, 개인위생 및 외모 관리, 후기고령자 미디어를 이용한 여가활동, 개인위생 및 외모관 리, 식사 및 간식 섭취, 수면, 청소 및 정리 순으로 나타났다. 결론 : 본 연구는 2019년 생활시간 조사 자료를 키워드 네트워크 분석 방법을 적용하여 최초로 작업연결 망을 구성하여 전기고령자와 후기고령자 집단 간의 작업 수행의 차이를 분석하고 시각적으로 파악하여 제시 및 분석하였다는 점에 학문적인 의의를 가지며, 이를 통해 작업치료 분야에서 사회연결망 분석 방 법을 사용할 수 있도록 기초자료로 활용할 수 있을 것이다.

Due to the issue of the sustainability in transportation area, the number of electric vehicles has significantly increased. Most automakers have decided or planned to manufacture the electric vehicles rather than carbon fueled vehicles. However, there are still some problems to figure out for the electric vehicles such as long charging time, driving ranges, supply of charging stations. Since the speed of growing the number of electric vehicles is faster than that of the number of charging stations, there are lack of supplies of charging stations for electric vehicles and imbalances of the location of the charging stations. Thus, the location problem of charging stations is one of important issues for the electric vehicles. Studies have conducted to find the optimal locations for the charging stations. Most studies have formulated the problem with deterministic or hierarchical models. In this paper, we have investigated the fluctuations of locations and the capacity of charging stations. We proposed a mathematical model for the location problem of charging stations with the vehicle routing problem. Numerical examples provide the strategy for the location routing problems of the electric vehicles.

This research investigated how adding Sb (0.75, 1.0, 2.0 and 5.0 wt%) to as-extruded aluminum alloys affected their microstructure, mechanical properties, electric and thermal conductivity. The addition of Sb resulted in the formation of AlSb intermetallic compounds. It was observed that intermetallic compounds in the alloys were distributed homogenously in the Al matrix. As the content of Sb increased, the area fraction of intermetallic compounds increased. It can be clearly seen that the intermetallic compounds were crushed into fine particles and homogenously arrayed during the extrusion process. As the Sb content increased, the average grain size decreased remarkably from 282.6 μm (0.75 wt%) to 109.2 μm (5.0 wt%) due to dynamic recrystallization by the dispersed intermetallic compounds in the aluminum matrix during the hot extrusion. As the Sb content increased from 0.75 to 2.0 wt%, the electrical conductivity decreased from 61.0 to 59.8 % of the International Annealed Copper Standard. Also, as the Sb content increased from 0.75 to 2.0 wt%, the ultimate tensile strength did not significantly change, from 67.3 to 67.8 MPa.