본 연구의 목적은 무릎 푸시업 플러스 동작 시 슬링과 진동기 적용이 체간 근육의 근활성도 변화에 미치는 영향에 대해 알아보는 것이었다. 본 연구의 대상자는 신체 건강한 20대 남성 10명을 대상으로 실시하였고(연령, 23.00±0.45 세; 신장, 176.60±1.64 cm; 체중, 67.50±1.22 kg; 신체질량지수, 21.65±0.34 kg/m2), 3가지의 기본 무릎 푸시업 플러스 동작, 슬링을 적용한 무릎 푸시업 플러스 동작, 및 진동기를 적용한 무릎 푸시업 플러스 동작을 수행하였으며, 표면전극 부착 부위는 체간 근육의 오른쪽 상부 승모근, 대흉근, 전거근, 복직근, 및 외복사근으로 설정하였다. 본 연구의 결과는 다음과 같다. 승모근, 대흉근, 전거근, 복직근, 및 외복사근의 근활성도는 진동기를 적용한 무릎 푸시업 플러스 동작 시 통계적으 로 가장 높게 나타났다(p<.001). 따라서 본 연구의 결과는 향후 무릎 푸시업 플러스 동작 적용 시 효과적인 체간 근육을 강화시키기 위한 트레이닝 프로그램의 기초자료가 될 것으로 기대된다.

For use in ultrasonic actuators, we investigated the structural and piezoelectric properties of (1 - x)Pb(Zr0.515Ti0.485)O3 - xPb(Sb1/2Nb1/2)O3 + 0.5 wt% MnO2 [(1 - x)PZT - xPSN + MnO2] ceramics with a variation of x (x = 0.02, 0.04, 0.06, 0.08). All the ceramics, which were sintered at 1250˚C for 2 h, showed a typical perovskite structure, implying that they were well synthesized. A homogeneous micro structure was also developed for the specimens, and their average grain size was slightly decreased to 1.3μm by increasing x to 0.8. Moreover, a second phase with a pyrochlore structure appeared when x was above 0.06, which resulted in the deterioration of their piezoelectric properties. However, the 0.96PZT-0.04PSN+MnO2 ceramics, which corresponds with a morphotropic phase boundary (MPB) composition in the (1 - x)PZT - xPSN + MnO2 system, exhibited good piezoelectric properties: a piezoelectric constant (d33) of 325 pC/N, an electromechanical coupling factor (kp) of 70.8%, and a mechanical quality factor (Qm) of 1779. The specimens with a relatively high curie temperature (Tc) of 305˚C also showed a significantly high dielectric constant (εr) value of 1109. Therefore, the 0.96PZT - 0.04PSN + MnO2 ceramics are suitable for use in ultrasonic vibrators.

Ultrasonic vibrator is an equipment which atomizes and homogenizes the oils by breaking the oil particles with ultrasonic vibration cavity, and possibly improves the properties. There are various parameters on the effect of ultrasonic irradiation. Especially, this study intended to investigate the matrix structure of sludge oils and the erosion damages for horn disc SS41 according to the variation of the oil temperature and the immersing depth of horn disc. Sludge oils were irradiated with ultrasonic vibration and then observed the aspects of the change of oil particles. From these, the recycling feasibility of sludge oil for useable oil to be burnt was determined. The erosion damages for horn disc SS41 were examined with weight loss, weight loss rate and the irradiation time to max. erosion rate. These data will be useful to the development of ultrasonic breaking systems to recycle sludge oil and to consider a countermeasure for the prevention of erosion damages.

Many investments and works being continued to preserve green ocean in each countries of the world. Especial1y, the researches on the prevention of marine oil pollution being strengthened. It is not easy to disclose sludge oils that were produced necessarily in the ships operation, so that they are transferred to shore treating facility after collected inside the ship＇s sludge tank mostly. However, this shore transferring method is not only costly and time consuming but also entails risk of oil pollution. In this regard, it will be the best way to manage the sludge oils inside ship itself. The purpose of this study is to device an ultrasonic breaking systems which recycle the sludge oil from ships into usable oil to be burnt. In this paper, the first place, matrix structures of sludge fuel oil(SFO) and sludge lubricating oil(SLO) with the irradiation time for ultrasonic vibrator were interpreted. And, erosion damage for vibrator horn tip which is one of important part of ultrasonic breaking systems was examined under such an environment of the sludge oils. The material for horn tip is being made of SS41 steel and its erosion phase was investigated with variation of the vibration amplitude of 50μm and 24μm as well as the change of temperature in the oil environments. It is suggested that the experimental results can be helpful to the development of sludge oil disposing systems for the vessel.