수처리 및 의약바이오 분야에서 유효물질 분리에 활용되고 있는 알루미나 중공사 분리막은 얇은 두께로 인해 취 급 및 적용시 쉽게 파괴되는 단점이 있기 때문에 분리막의 강도를 100 MPa 이상으로 향상시키기 위한 연구가 필요하다. 본 연구에서는 나노입자의 함량을 0, 1, 3, 5 wt%로 증가시켰을 때 제조된 중공사 분리막의 특성을 평가하였다. 그 결과, 나노입 자의 함량이 증가함에 따라 중공사 분리막의 강도는 79 MPa에서 115 MPa로 증가하였으며, 밀도는 1.76 g/m3에서 1.88 g/m3 으로 증가하였고 기공률과 평균기공크기는 각각 51%에서 48%로, 416 nm에서 352 nm로 감소한 것을 확인하였다. 스폰지구 조가 발달하고 스폰지구조의 기공크기가 향상된 알루미나 중공사 분리막은 100 MPa 이상으로 기계적 강도가 향상되었으며, 약 100000 GPU의 높은 질소 투과도 및 약 3000 L/m2h의 높은 물 투과도를 나타내었다. 따라서, γ-알루미나 나노입자를 소 결조제로 첨가하는 것은 α-알루미나 중공사 분리막의 기계적 강도를 효과적으로 증진시키고 높은 투과성능을 유지할 수 있 는 매우 유효한 방법임을 확인하였다.

Conversion to modern hydrogen energy is required, and research on liquefied hydrogen cargo containment systems is needed for large-capacity transport and storage. In this study, changes in the mechanical properties of the adhesive required for storage and transport in liquid hydrogen were confirmed. The lap shear test was performed by realizing cryogenic conditions in a small chamber using liquid nitrogen and liquid helium. There was an increase of 11.0% in the -180℃ condition compared to room temperature, and an increase of 1.8% in the -230℃ condition compared to the -180℃ condition was confirmed. In the case of shear strain, it is known that it decreases as the temperature goes down. As a result of the experiment, it was confirmed that the value at room temperature and the value at -180℃ reduced the shear strain by 5.0%, and -230˚ compared to the -180℃ condition. An increase of 1.5% was confirmed in the C condition. In the case of the specimen tested at -230℃, the deformation in the gripper part was larger than in other tests, and it is judged that the maximum shear strength and shear strain were affected. In addition, in this study, there is a limitation in the experiment at -230°C rather than 253°C, which is the boiling point of hydrogen

증기운 폭발의 폭압을 예측하거나 위험성 분석을 위하여 다양한 폭압 산정법이 존재하지만 대표적으로 경험적 방법인 TNT 등가량 환산법과 멀티에너지법을 주로 사용한다. 멀티에너지법은 환경적 요인을 고려한 폭발강도계수를 사용한다. 본 연구에서는 문헌 분석 을 통하여 점화원 강도를 세분하고 강도분류를 확장하여 개선한 폭발강도계수 가이드라인을 제안하였다. 개선한 폭발강도계수 가이 드라인의 합리성 검증과 기존 Kinsella 가이드라인과의 비교를 위하여 실제 추정 폭압과 대조가 가능한 4가지의 증기운 폭발 사례를 적용하였다. 결과적으로 기존 Kinsella 가이드라인은 실제 추정 폭압에 비하여 광범위하거나 부정확한 폭압 산정 결과를 나타내는 것 으로 확인하였다. 반면, 개선한 폭발강도계수 가이드라인은 명확한 점화원의 강도 선정이 가능하고 분류의 확장을 통하여 더욱 세분 화된 계수 값의 선정이 가능함에 따라 실제 사례와 비교적 유사한 폭압 산정이 가능하다.

In the current steel structures of high-rise buildings, high heat input welding techniques are used to improve productivity in the construction industry. Under the high heat input welding, however, the microstructures of the weld metal (WM) and heat-affected zone (HAZ) coarsen, resulting in the deterioration of impact toughness. This study focuses mainly on the effects of fine TiN precipitates dispersed in steel plates and B addition in welding materials on grain refinement of the HAZ microstructure under submerged arc welding (SAW) with a high heat input of 200 kJ/cm. The study reveals that, different from that in conventional steel, the γ grain coarsening is notably retarded in the coarse grain HAZ (CGHAZ) of a newly developed steel with TiN precipitates below 70 nm in size even under the high heat input welding, and the refinement of HAZ microstructure is confirmed to have improved impact toughness. Furthermore, energy dispersive spectroscopy (EDS) and secondary-ion mass spectrometry (SIMS) analyses demonstrate that B is was identified at the interface of TiN in CGHAZ. It is likely that B atoms in the WM are diffused to CGHAZ and are segregated at the outer part of undissolved TiN, which contributes partly to a further grain refinement, and consequently, improved mechanical properties are achieved.

Lead free (Ba0.7Ca0.3) TiO3 thick films with nano-sized grains are prepared using an aerosol deposition (AD) method at room temperature. The crystallinity of the AD thick films is enhanced by a post annealing process. Contrary to the sharp phase transition of bulk ceramics that has been reported, AD films show broad phase transition behaviors due to the nanosized grains. The polarization-electric hysteresis loop of annealed AD film shows ferroelectric behaviors. With an increase in annealing temperature, the saturation polarization increases because of an increase in crystallinity. However, the remnant polarization and cohesive field are not affected by the annealing temperature. BCT AD thick films annealed at 700 ℃/2h have an energy density of 1.84 J/cm3 and a charge-discharge efficiency of 69.9%, which is much higher than those of bulk ceramic with the same composition. The higher energy storage properties are likely due to the increase in the breakdown field from a large number of grain boundaries of nano-sized grains.

The demand for environmental consideration is on the increase in civil engineering. This study focuses on the development of technology to reduce the use of carbonate cement and improve its performance by using a silicate mineral and hardening agents, and presents the test results for the demonstrative evaluation of the properties of the raw material. Highly active feldspar was used as a binder to augment the bonding of the carbonate cement, and their change in strength was observed after test piece construction with the addition of soluble hardening agent. The uniaxial compression strength of the test piece of the general Portland cement with the addition of 0.5% soluble hardening agent, showed an increase by 33% and that of the test piece of cement with the addition of 70% substituted with feldspar increased by 28%. The strength of viscous soil; classified as soft ground, showed an increase of a maximum of 1.7 times when it was mixed with cement and solidifier depending on the curing period. These tests confirmed that a soluble solidifier is effective for improving the strength of a cement binder and that the highly active feldspar can be used as a binder.

High temperature plasma coating technology has been applied to recover damaged aluminum dies from wear by spraying pure aluminum and alumina powder. However, the coated mixed powder layer composed of aluminum and alumina often undergoes a detachment from the substrate, making the coated substrate die unable to maintain its expected life span. In this study, in order to increase the bonding strength between the substrate and the coating layer, a pure aluminum layer was applied as an intermediate bond layer. In order to prepare the specimen with variable bond coating conditions, the bond coat layers with a various gun speed from 10 cm/sec to 30 cm/sec were prepared with coating cycle variations ranging from three to nine cycles. The specimen with a bond coat layer coated with a gun speed of 20 cm/sec and three coating cycles exhibited ~13MPa of adhesion strength, while the specimen without a bond coat layer showed ~6 MPa of adhesion strength. The adhesion strength with a variation of bond coat layer thickness is discussed in terms of coating parameters.

The purpose of this study lies in figuring out the factors of how soldiers' digital games experiences make influence on combat power improvement of the military.. For this study, based on the technology acceptance model, we have analyzed how causation is formed between self-efficacy and the collective-efficacy, perceived usefulness, perceived ease of use and the behavior intention. As a result of validating structure equation modeling targeting the sample of 101 soldiers, self-efficacy on digital game has a significant impact on perceived usefulness, perceived ease of use and the behavior intention. This result implies that soldiers’ digital game experiences have compelling relations on improving combat power of individual, which is a component of the military combat power, and the members of the organization. This study’s result offers an insight for implementing and utilizing small unit war game cyber combat system, which is based on digital games related to improving the military combat power in the future

This study was performed with an aim to improve the early-age strength of concrete containing fly ash, which is known to increase the long-age strength of concrete, reduce drying shrinkage, and enhance water tightness. The composition was partially substituted with calcium sulfoaluminate (CSA), from which ettringite is actively produced, in the early stages of hydration to verify its effect on improving the early-age strength and to determine the optimal mixing ratio. For this purpose, up to 30 % of the cement weight was substituted with fly ash, and the amount of CSA substitution was 8% of the fly ash weight. The mixtures were then fabricated into concrete specimens for compressive strength measurement and analysis of the correlation between the hydration products and the compressive strength.

CSA, a cement mineral compound that is mainly composed of 3CaO·3Al2O3·CaSO4, generates ettringite as a hydration product after a reaction with glass (lime), gypsum and water to speed up the hardening process and enhance the strength and degree of expansion. When used as a cement admixture, there is increased production of ettringite, which can improve the initial strength in the first three days and ameliorate the reduction in the initial strength caused by the use of fly ash in particular. In this study, a hydrate analysis was performed using XRD and SEM after substitution with fly ash (30%) and CSA (8%) with the goal of observing the effect of CSA on the initial strength of a cement mixture containing fly ash. The results of the analysis showed that an addition of CSA promoted the production of ettringite and improved the initial strength, resulting in the generation of hydrates, which can effectively enhance the long-term strength of these materials.

목 적: 본 연구는 3-VPBA(3-vinylphenylboronic acid)를 기존의 콘택트렌즈 재료에 첨가하여 공중합하였으며, 제조된 콘택트렌즈의 물리적 특성을 비교하여 내구성을 갖는 안의료용 고분자로서의 활용을 알아보았다. 방 법: 실험에 사용한 콘택트렌즈를 제조하기 위해 ca캐스트 몰드법을 사용하였으며, 배합한 재료들을 몰드에 주입시키고, 진공 오븐(vacuum oven)을 사용하여 70℃에서 40분, 80℃에서 40분, 100℃에서 40분간 가열하여 중합 및 제조하였다. 개시제로는 0.10%(wt) AIBN(azobisisobutyronitrile)을 사용하였다. 결 과: 3-VPBA를 첨가한 콘택트렌즈 재료의 경우, 3-VPBA의 첨가량이 증가할수록 인장강도와 굴절률이 각각 1.437~1.461과 0.295~0.789 kgf으로 점차적으로 증가하는 경향을 나타냈다. 결 론: 본 실험결과를 토대로 했을 때 생성된 공중합체는 높은 내구성과 고 굴절률을 갖는 안 의료용 재료로 사용되기에 적합할 것으로 판단된다.

The present case study highlights the effects of a novel Comprehensive Hand Repetitive Intensive Strengthening Training (CHRIST) on morphological changes and associated upper extremity (UE) muscle strength and motor performance in a child with spastic quadriplegic cerebral palsy (CP). The Child, a 10-year-old girl with spastic quadriplegic CP, was treated with CHRIST for 60 minutes a day, five times a week, for 5 weeks. The CHRIST was designed to improve motor function and strength. Clinical tests including the modified Wolf Test, Jebsen-Taylor Hand Function Test, and Pediatric Motor Activity Log questionnaire were used to determine motor function. Ultrasound imaging was performed to determine the changes in the cross-section area (CSA) of the extensor carpi radialis (ECR) and triceps brachii (TRI). Muscle strength was measured with a dynamometer at pretest, and post-test, and 3-month follow-up. Ultrasound imaging data showed that the CSAs of both ECR and TRI muscles were enhanced as a function of the intervention. These changes were associated with muscle strength and motor performance and their effects remained even at a 3-month follow-up test. Our results suggest that the CHRIST was effective at treating muscle atrophy, weakness and motor dysfunction in a child with spastic quadriplegic CP.

본 연구는 건설 디지털 제조를 위한 3D 프린팅 기술 개발을 위하여, 플라이애시 및 고로슬래그 미분말 등의 알칼리 활성화 결합재를 Binder Jetting 3D 프린팅 방식으로 출력하고, 후처리 방법을 통해 출력물의 압축강도를 증진하는 것이다. 진공 펌프 및 규산나트륨-수산화나트륨 복합 수용액을 적용하여 후처리 방법을 검토하였으며, 후처리 용액에 침지한 후 -0.1 MPa 진공 압력으로 처리한 공시체의 압축강도는 11.04 MPa 로써 강도 증진을 확인하였다.

최근 선진국을 중심으로 MWCNT(Multi-walled carbon nanotube)의 우수한 기계적 성질을 이용한 시멘트 모르타르의 압축강도 향상 연구가 활발하다. 그러나 국내에서 MWCNT 모르타르와 관련된 연구는 국외에 비해 상당히 미미한 실정이다. 따라서 본 연구에서는 MWCNT 수용액을 시멘트 모르타르에 적용하여 MWCNT 모르타르의 압축강도 증진 효과를 분석하고자 한다. 실험 매개변수는 최적의 MWCNT 모르타르 제작법 도출을 목적으로 강도시험에 큰 영향을 미칠 것으로 예상되는 물시멘트비, 재령일, MWCNT의 농도로 선정하였다. 물시멘트비는 0.4, 0.5, 0.6으로 변화시켰고 재령일은 7일, 14일 28일로 구분하였으며 MWCNT수용액의 농도는 2.0wt%로 선정하였다. MWCNT 모르타르에 혼입한 MWCNT 수용액의 분산은 계면활성제와 초음파로 처리하였으며, 증류수를 기반으로 제작 하였다. 실험결과 물시멘트비 0.4, 0.5, 0.6일 때 일반 시멘트 모르타르의 압축강도보다 MWCNT 모르타르의 압축강도가 각각 최대 35%, 20%, 25% 높게 측정되었다. MWCNT 모르타르의 압축강도가 일반 시멘트 모르타르의 압축강도보다 높은 이유는 모르타르의 수화 과정에서 MWCNT의 우수한 기계적 성질이 모르타르 내부의 결합력을 증진시켜 주는 것으로 분석되었다.