• Journal of electromagnetic engineering and science
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• v.9 no.3
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• pp.118-123
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• 2009

This paper discusses the design and fabrication of a reference signal generator for a naval radar system, including the vibration environment test. The transmit signals of the S-band radar system are synthesized by the reference signal and the phase noise must lower than - 130 dBc/Hz at a 10 kHz offset frequency. To achieve this specification, the phase noise of the reference signal needs to be less than -165 dBc/Hz at a 10 kHz offset. For achieving very low phase noise performance by the reference signal generator, the phase locked loop technique is applied with a 10 Hz loop bandwidth. Also, this reference signal generator has ${\pm}0.35\;ppb$ short-term stability to minimize instant phase errors and high vibration sensitivity against a ship's shaking, unbalanced rotating of antennas and so on.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1996.04a
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• pp.194-202
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• 1996

An approach to increase the seismic resistance of large structures is to reduce the seismic forces, to which structures are subjected by base isolation systems. The anti-seismic performance of base-isolated beatings has been verified experimentally by shaking table tests. However, it may be difficult to perform the tests for the full-scale beatings of base-isolated structures. Therefore, the test program was designed to evaluate the reliability and properties of the beatings under a range of loading conditions including axial stress, loading frequency and direction, and temperature. The effects of scale were also evaluated by comparing the results of the 1/4-scale beatings with those from the full-scale bearings, and the ultimate behavior of both types of bearings with evaluated through a series of roll-out tests. This report draws comparisons among the different tests and bearings to determine the importance of various factors including load history, axial stress, and frequency. Comparisons between the 1/4-scale bearings were difficult because of the scaling effects in manufacturing and thermal radiation, but qualitative results from the 1/4-scale bearings can certainly be extrapolated the full-scale bearings.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.465-470
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• 2007

In this paper, a two-way tuned liquid mass damper(TLMD) using a tuned liquid column damper(TLCD) and a rubber-bearing-type tuned mass damper(TMD) was manufactured for controlling two-way direction acceleration responses of a high-rise building structure. The proposed controlling device behaves as a tuned liquid column damper in one direction and as a tuned mass damper in the other direction. In this study, Performance evaluation of the downscaled model is conducted. The results show that the two-way controllability is behaved independently each other and realscale TLMD applicable to the high-rise building can be designed.

• Journal of the Korean Geotechnical Society
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• v.16 no.3
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• pp.15-21
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• 2000

액상화되기 쉬운 모래지반 위에 축조된 제방의 지진시 거동을 조사하고 액상화 경감을 위한 대책공법의 효과를 비교하기 위하여 12가지 경우에 대해 진돈대 시험을 수행하였다. 본 시험에는 널말뚝, 자갈배수재, 모래다짐 말뚝과 강관말뚝 등의 대책공법이 적용되었다. 진동대 시험에 사용된 투명토조의 길이는 194cm이고 폭은 44cm 그리고 높이는 60cm이다. 기초지반은 포화된 모래이며 수중침강법을 적용하여 상대밀도 약 30%로 조성되었다. 이 포화된 느슨한 모래지만 위에 15cm 높이의 제방이 경사 1:1.5로 축조되었다. 진동대 시험시 제방과 기초지반의 거동을 측정하기 위해서 간극수압계 12개, 가속도계 4개 및 LVDT 2개가 시험모델에 설치되었다. 진동대의 크기는 2m$\times$2m이며, 진동시의 입력가속도는 0.1g에서 시작하여 최고 0.4g까지 증가시켰다. 본 모델에 적용된 공법 모두가 일반적인 진동법위에서 액상화 발생을 억제시키는데 유용한 것으로 증명이 되었으며, 그 중에서 모래다짐말뚝이 액상화로 인한 피해를 감소시키는데 가장 효과적인 것으로 나타났다. 또한 각각의 대책공법에 대한 최적 배치안의 본 연구에서 제시되었다.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.201-204
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• 2010

Earthquake load to design a structure has been calculated from a fixed base SDOF model using amplified surface accelerations along soft soil layers. But the method dose not consider a soil-structure interaction. Centrifugal experiments that were consisted of soil, a shallow foundation and a structure were performed to find the effects of soil-structure interaction. The experiments showed that mass and stiffness of the foundation affected a response of the structure and nonlinear behavior of soil near the foundation. And a rocking displacement caused by overturning moment affected the response and increases a damping effect. In this study, the centrifugal experiment was simulated as a two dimensional finite element model. The finite element model was used for nonlinear time domain analysis of the OpenSees program. The numerical model accurately evaluated the behaviors of soil and the foundation, but the rocking effect and the behavior of structure were not described.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3805-3810
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• 2013

The surface modification of silica particles (SPs) was systemically conducted by the treatment of 0.1-10 wt % phenylsilanetriol (PST) on the basis of SPs used through two step processes: 1) the PST coating of SPs via evaporation under reduced pressure and 2) their thermal condensation leading to Si-O-Si bond formation via heating at $130^{\circ}C$. The evaluation of the modified SPs was conducted by the simple floating test on water and the measurement of the contact angle (CA) of water droplet on the 2-dimensional layer of modified SPs on slide glass. When PST was used about 2 wt % or above on the basis of SPs (about average size: 50 nm) used, the modified SPs were fully floated on the water and all dispersed into upper organic solvent layer after a shaking with the mixture of the water and benzene, indicating that the modified SPs have hydrophobic properties. The modified SPs were characterized by $^{29}Si$ MAS NMR and physicochemical properties including SEM, TEM, BET, adsorption/desorption isotherms, etc. were measured and compared each other in details. This research demonstrates that the organosilanetriol is a good modifier applicable for the surface modification of inorganic oxide particles using a low amount of modifier on the basis of oxide particles used.

• Smart Structures and Systems
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• v.15 no.6
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• pp.1481-1501
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• 2015

MR-TLCD (Magneto-Rheological Tuned Liquid Column Damper) is a new developed vibration control device, which combines the traditional passive control property with active controllability advantage. Based on traditional TLCD governing equation, this study further considers MR-fluid viscosity in the equation and by transforming the non-linear damping term into an equivalent linear damping, a solution can be obtained. In order to find a countable set of parameters for the design of the MR-TLCD system and also to realize its applicability to structures, a series of experimental test were designed and carried out. The testing programs include the basic material properties of the MR-fluid, the damping ratio of a MR-TLCD and the dynamic responses for a frame structure equipped with the MR-TLCD system subjected to strong ground excitations. In both the analytical and experimental results of this study, it is found that the accurately tuned MR-TLCD system could effectively reduce the dynamic response of a structural system.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.129-139
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• 2000

The liquefaction of reclaimed land generally caused the harbor facilities to hazards. In Korea, the major harbor quay walls are gravity type and the gravity quay wall is not a good earthquake resistant structure. Recently, various earthquake resistant quay walls have been suggested, but the study on the efficiency of reinforced quay wall was not much performed. In this study, numerical analysis is carried out for performance evaluation of easily adoptable earthquake resistant quay walls. The results of numerical analysis are compared with shaking table test that is performed at the same cross-section.

• Journal of Environmental Health Sciences
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• v.37 no.2
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• pp.133-140
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• 2011

Antimicrobial activity and bactericidal activity of Caesalpinia sappan L. extracts were investigated against five food-borne pathogens, E. coli, S. aureus, S. typhimurium, B. cereus and L. monocytogenes. Methanol extract of Caesalpinia sappan L. revealed antimicrobial activities against five pathogens. In particular, by paper disc diffusion the highest activity was shown against L. monocytogenes. Antimicrobial activities of methanol extracts showed the most potent activities, but hexane fraction had no activity. Fractions of ethyl acetate and butanol turned out to have higher antimicrobial activities against Gram(+) bacteria than Gram(-) bacteria. The minimum inhibitory concentration against five food-borne pathogens was 1.563 mg/ml on Gram(+) bacteria and 3.125 mg/ml on Gram(-) bacteria. The result of antimicrobial activity in a shaking flask method showed that bacterial growth rate fell by more than 99.999% at 3.125 mg/ml of methanol extract. The highest rate of viable reduction (99.998%) was shown at 0.781 mg/ml of methanol extract against L. monocytogenes. After five minutes of reaction between test strains and methanol extracts, the growth rates of five kinds of bacteria were reduced by more than 99.999% at a concentration of 100 mg/ml. Therefore, it is suggested that methanol extracts of Caesalpinia sappan L. can be developed as a natural sanitizer or disinfectant.

• Structural Engineering and Mechanics
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• v.58 no.1
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• pp.121-142
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• 2016

The national standard being used in Turkey for suspended ceiling systems (SCS) regulates material and dimensional properties but does not contain regulations regarding installation instructions which cause substandard applications of SCSs in practice. The lack of installation instructions would potentially affect the dynamic performance of these systems. Also, the vast majority of these systems are manufactured using substandard low-quality materials, and this will inevitably increase SCS related damages during earthquakes. The experimental work presented here focuses on the issue of dynamic performance of SCSs with different types of carrier systems (lay-on and clip-in systems), different weight conditions, and material-workmanship qualities. Moreover, the effects of auxiliary fastening elements, so called seismic perimeter clips, in improving the dynamic performance of SCSs were experimentally investigated. Results show that clip-in ceiling system performs better than lay-on system regardless of material and workmanship qualities. On the other hand, the quality aspect becomes the most important parameter in affecting the dynamic performance of lay-on type systems as opposed to tile weights and usage of perimeter clips. When high quality system is used, tile weight does not change the performance of lay-on system, however in poor quality system, tile weight becomes an important factor where heavier tiles considerably decrease the performance level. Perimeter clips marginally increase the dynamic performance of lay-on ceiling system, but it has no effect on the clip-in ceiling system under the shaking levels considered.