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Experimental and numerical study on the dynamic behavior of a semi-active impact damper
Jiawei Zhang,Zheng Lu,Mengyao Zhou,Zhikuang Huang,Sami F. Masri 국제구조공학회 2023 Smart Structures and Systems, An International Jou Vol.31 No.5
Impact damper is a passive damping system that controls undesirable vibration with mass block impacting with stops fixed to the excited structure, introducing momentum exchange and energy dissipation. However, harmful momentum exchange may occur in the random excitation increasing structural response. Based on the mechanism of impact damping system, a semi-active impact damper (SAID) with controllable impact timing as well as a semi-active control strategy is proposed to enhance the seismic performance of engineering structures in this paper. Comparative experimental studies were conducted to investigate the damping performances of the passive impact damper and SAID. The extreme working conditions for SAID were also discussed and approaches to enhance the damping effect under high-intensity excitations were proposed. A numerical simulation model of SAID attached to a frame structure was established to further explore the damping mechanism. The experimental and numerical results show that the SAID has better control effect than the traditional passive impact damper and can effectively broaden the damping frequency band. The parametric studies illustrate the mass ratio and impact damping ratio of SAID can significantly influence the vibration control effect by affecting the impact force.
클로로필 색이 안정화된 새싹보리분말을 첨가한 전통 발효 기정떡의 색소 안정성
노준희(Junhee No),Mengyao Huang,이주리(Jooree Lee),신말식(Malshick Shin) 한국식품조리과학회 2017 한국식품조리과학회지 Vol.33 No.5
Purpose: To promote young barley leaf (BL) powder as a functional and natural green pigment, traditional fermented rice cakes, Gijeongtteok with BL and stabilized BL (BLAZ) powders were evaluated in terms of color stability and antioxidant activity. Methods: To make BLAZ powder, BL was autoclaved twice in 0.01% zinc citrate solution (pH 5) at 110°C for 30 min, washed, dried in a low pressure/temperature oven, ground, and passed through a 100 mesh sieve. Gijeongtteok samples were prepared with addition of BLAZ (1, 2, and 3%) or BL (1%) power. The doughs were fermented in two stages (1<SUP>st</SUP> stage at 35°C for 3 h, and 2<SUP>nd</SUP> stage at 35°C for 1 hr), and then steamed for 30 min. After fermentation, dough was divided into 15 g samples. The chlorophyll was extracted from Gijeongtteok with 80% EtOH for 4 hr. Results: After steaming, the green color of Gijeongtteok-added BL changed to olive green, whereas Gijeongtteok-added BLAZ remained a green color. Gijeongtteok-added BL 1% and BLAZ 1% showed similar values of adhesiveness and springiness. During storage of Gijeongtteok at 4°C and 25°C, BLAZ-added samples showed lower hardness than the control (not contained barley leaf), which demonstrated anti-staling effect of barley leaf. Absorbance spectra of extracts from BL- and BLAZ-added Gijeongtteok ranged from 400-700 nm. The antioxidant activity of extract from BL-added Gijeongtteok was higher than that of BLAZ-added Gijeongtteok extract. Conclusion: From these results, BLAZ powder could be applied as a natural green pigment by improving the visual quality of fermented rice cake.