• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.81-85
• /
• 2006

The motion of a system composed of a plate, constant springs and varying dampers is considered when the system is subject to harmonic force. Letting the frequencies of harmonic force and damper variation ${\Large f}_1\;and\;{\Large f}_2$, respectively, the displacement at the center of the plate has the strongest component at frequency ${\Large f}_1$. The angular displacement of the plate has strong components at ${\Large f}_1-{\Large f}_2$, and the natural frequency of the rotational mode of the system. If these two frequencies coincide, the plate oscillates with almost single frequency and a large amplitude. These results can be applied to development of a moment shatter with low frequencies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1997.04a
• /
• pp.81-85
• /
• 1997

It is a well known fact that the exciter used in the vibration test interacts with the test structure and thus influences the test results. A two degree of freedom model of exciter is suggested and the vibration parameters of this model is experimentally extracted. According to this experimental results, the vibration parameters of the exciter can vary with respect to the test structure as well as the stinger used in the connecting mechanism. It is also found that the vibration parameters provided by the manufacturer can not be accurate and these parameter values should be revaluated based on the test environments.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.15 no.3
• /
• pp.24-32
• /
• 2007

In this research, using Terfenol-D actuator composed of magnetostrictive material as shaker and controller, active vibration control theory was applied and verified by experiments. PPF(positive Position Feedback) algorithm which is effective for the control of low frequency vibration was used for the control of a structure. Responses of inputs due to various design variable used for the PPF filter were observed. To investigate the characteristics of magnetostrictive materials, actuator responses were measured for known inputs and satisfactory results were obtained to reduce the vibration level after applying the control input for the actuator.

• Fibers and Polymers
• /
• v.7 no.2
• /
• pp.158-163
• /
• 2006

Standard extraction procedure for examining chromophoric substances of turmeric was investigated. Acetone and methanol were used as extracting solvents with different extraction procedures and pH levels. GC-MS analysis identified curcumene 2 (6.7 min), feruloylmethane 3 (8.3 min), coumaran 4 (6.09 min), vanillin 5 (6.2 min), and zingiberene 6 (10.5 min) as the major products. Curcumin 1 which has been known as the major chromophoric substance of turmeric was not detected in any samples. The maximum amount of curcumene 2, which was used as the fingerprint product for turmeric dye, was obtained by utilizing presoaking and decanting step with methanol prior to actual extraction step using a waterbath shaker (WMM). The highest relative abundance of curcumene 2 was detected in pH 6 sample followed by pH 5 indicating that the most appropriate pH level was in the range of pH 6-5.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2002.10a
• /
• pp.489-496
• /
• 2002

Monitoring frequency change is a tool to indicate the change ill structural parameters. However, even critical reduction of stiffness is predicted in the range of indication errors due to the effect of temperature on the frequency change. In this study, an experimental work to examine the effect of various temperatures on modal characteristics of steel plate-girders is presented. A model plate-girder used for the experiment is described. Natural frequencies are monitored by using two different excitation sources-impact and shaker. The relation between measurement temperatures and natural frequencies are analyzed.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.1
• /
• pp.284-291
• /
• 1995

This paper proposes a method for determination of optimal reference spectrum in random vibration control. The least square method is used to minimize the spectrum deviation between the specified reference spectrum and spectra at the specimen-mounted points. This method needs only the measured FRF's at the control point and specimen-mounted points in pre-vibration test. Using the proposed method as reference spectrum, it is possible to easily predict spectra at the specimen-mounted points, and also to reduce overtest resulting from dynamic characteristics of shaker and fixture. This method is shown through theoretical and experimental results to be an effective method.

• ETRI Journal
• /
• v.28 no.2
• /
• pp.175-181
• /
• 2006

A new CMOS voltage-controlled fully-differential transconductor is presented. The basic structure of the proposed transconductor is based on a four-MOS transistor cell operating in the triode or saturation region. It achieves a high linearity range of ${\pm}\;1\;V$ at a 1.5 V supply voltage. The proposed transconductor is used to realize a new fully-differential Gm-C low-pass filter with a minimum number of transconductors and grounded capacitors. PSpice simulation results for the transconductor circuit and its filter application indicating the linearity range and verifying the analytical results using $0.35\;{\mu}m$ technology are also given.

• Bulletin of the Korean Chemical Society
• /
• v.24 no.10
• /
• pp.1429-1432
• /
• 2003

A novel fused thiouracil containing a heterocyclic ring system, dipyrimidinopyridine (3), has been prepared through the cyclization of compound 2. Compound 2 was formed by the formylation of 6-amino-2-thiouracil 1, pyrazolopyrimidines 8-10 via the heating of 6-arylhydrazono-2-thiouracils 5-7, compound 11, using Vilsmeier reagent with compound 4, pyrazolylpyrimidine 12, indolodiazinopyrimidine 14 and pyridazinopyrimidine 15. Pyridazino-pyrimidine 15 was formed by the condensation of compound 4 with acetylacetone, isatin and benzyl, respectively.

• Proceedings of the KSME Conference
• /
• 2001.06b
• /
• pp.398-403
• /
• 2001

A simplified modeling approach of forced vibration for occupied car seats was demonstrated by using a mathematical model presented in previous paper. Nonlinear and linear equations of motions were rederived for forced vibration, and the transfer function was used to calculate the frequency response function. The experimental apparatus were set up and hydraulic shaker was used to obtain the system responses. Through the tests, mannequin's head had a lot of problems, and the responses with a head and without a head were measured. To explore the effects of linear dampings and friction moments at the joints, linear analyses were performed. New sets of linear spring and damping coefficients, and torsional dampings at the joints were calculated through parameter study to match up with experimental results. Good agreement between experimental and simulation frequency response estimates were obtained both in terms of locations of resonances and system deflection shapes at resonance, indicating that this is a feasible method of modeling seated occupants.

• Journal of the Korean Chemical Society
• /
• v.57 no.5
• /
• pp.560-567
• /
• 2013

A series of new Iron(II) Schiff base amino acid complexes derived from the condensation of amino acid and sodium 2-hydroxybenzaldehyde-5-sulfonate have been synthesized. The complexes were characterized by elemental, electronic, IR spectral analyses and conductance measurements. The stability and solubility of the prepared complexes were determined. Two spectral methods used to determine the stoichiometry of the prepared complexes which exhibited divalent tridentate coordination and formed chelates of octahedral structures. The antibacterial activity of the prepared complexes has been tested against Bacillus cereus, Pseudomonas aeruginosa and Micrococcus bacteria. The effect of HCl on investigated complexes studied spectrophotometrically.