The curvature of spacetime represented by Einstein field equation has many physical implications, including gravity. As light is deflected by the curvature of spacetime, a magnetic field will also be influenced by the curved spacetime. A permanent magnet is generally known to maintain its persistent magnetic field on the ground as long as there is no external magnetic interference. However, a series of experiments find that there are noticeable changes in the magnetic fields distribution while the permanent magnet rotates. The magnetic field lines of the permanent magnet are deflected towards Earth’s centre, implying a possibility that we can use magnetic field, a more efficient tool than a satellite, to measure the curvature of spacetime. However, comparing the experimental results of this study with theoretically obtained values of the curvature of spacetime remains a vast area of research for future studies.

Magnetostrictive actuator is fabricated with powder nano bonding method instead of sputtering method. Fabrication process and experimental measurement method for magneto-mechanical characteristics is proposed. For the design of highly flexible magnetostrictive actuator, TbDyFe nano powder bonding with Teflon substrate is adopted. The fabrication process for Teflon substrate and nano powder bonding is suggested and magnetostrictive behaviors are investigated. Variable magnetic field is applied to measure the magnetostrictive characteristics and magnetostriction is measured with different waves and different magnitude of magnetic field.

In this study, TbDyFe thin films with the thickness of 1000 Å are fabricated by DC magnetron sputtering. TbDyFe thin films are prepared by DC magnetron sputtering method. The pressure of Ar gas below 1.33 kPa and DC input power of 200 W are used for the sputtering conditions. During sputtering process the substrate holder is heated up to 150 ℃. The thin films are deposited to a thickness of 1000 Å on polyimide substrate with a thickness of 2 μm. The fabricated microstructures are observed by X-ray diffraction (XRD) and the film thickness is measured. Magnetostrictions are determined from the curvature of the thin films which are measured by the optical cantilever method. The experimental results are discussed with numerical data.

Magnetostrictive actuator is fabricated with epoxy bonding method instead of sputtering method in this study. Fabrication process and experimental measurement method for magneto-mechanical characteristics is proposed. For the design of highly flexible magnetostrictive actuator, TbDyFe epoxy bonding with SU-8 substrate is adopted. The fabrication process for SU-8 substrate and the epoxy bonding is suggested and magnetostrictive behavior is investigated. Variable magnetic field is applied to measure the various magnetostrictive characteristics and magnetostriction is measured with different waves and different magnitude of magnetic field.

비정질 Tb45.7 Fe54.3-x /Cox 및 Tb50.2 /Fe 49.8-x/Cox (0≤x≤9.6) 합금박막의 자기적 특성 및 자기변형특성에 대하여 체계적으로 조사하였다. 박막제조는 Fe 타게트에 Tb, Co 소편으로 구성된 복합타겟 방식의 rf 마그네트론 스퍼터링법에 의해 제조하였다. XRD 조사에의 한 박막의 미세구조는 잘 발달된 비정질 구조를 나타내었다. Tb45.7 Fe54.3-x Cox (x=2~4)에서 우수한 고유자기변형특성 및 저자기장자기변형특성을 얻었다. 즉, 100 Oe의 저자장에서 130ppm의 자기변형을 나타내었으며 고유자기변형 (인가 자기장, 5 kOe)은 330ppm에서 400ppm으로 증가하였다.

최근 건설분야에서도 스마트(Smart)라는 개념을 도입한 재료 및 구조방식의 개발에 관한 관심이 고조되고 있다. 특히 기존 콘크리트와 같은 시멘트 복합체에 다양한 전도물질을 혼입하여 외력의 작용시 유발되는 변형을 시멘트 복합체의 저항변화로 평가하는 자기 감지형 건설재료 개발 연구가 활발히 진행되고 있다. 통상적으로 시멘트 복합체는 인장변형에 대한 저항능력이 낮기 때문에 주로 압축변형과 전기적인 저항특성의 상관성을 평가하는 연구 즉, 압축변형 감지능력을 갖는 시멘트 복합체 개발에 관한 연구가 대부분이었다. 본 연구에서는 직접인장하에서 0.5% 인장변형시까지 자기 감지능력을 갖는 변형 경화형 시멘트 복합체(SHCC)를 개발하고 또한 철근의 보강이 SHCC의 자기 감지능력에 끼치는 영향을 평가한다.

This study was conducted to evaluate the effect of self-sensing performance on strain-hardening cement composite containing CNT by curing age. The mixing amount of CNT was set at 1.0%, and SHCC fibers were mixed with PE 1.0% and steel fiber 0.5%. The electrical resistance measurement for the tensile strain sensing performance was based on AC method and 4 probe methods. Test results indicated that electrical sensitivity of SHCC decreased with an increase in curing age.

The effect of steel fiber types on the self-sensing capacity of strain-hardening fiber-reinforced cementitious composites (SH-SFRCs) was investigated. Three types of fiber, including twisted, smooth and hooked fibers, were used with a volume content of 1.5% in a mortar matrix. Although all the SH-SFRCs exhibited self damage-sensing capacity, the gauge factor, representing for damage-sensing ability, was different according to the types of fiber as follows: twisted (138.09) > smooth (99.85) > hooked (88.50). The SH-SFRC with twisted fiber produced the highest gauge factor which is very favorable for development of self damage-sensor.