• Proceedings of the KIEE Conference
• /
• 2003.10a
• /
• pp.89-91
• /
• 2003

The determination of DNA hybridization reaction can apply the molecular biology research, clinic diagnostics, bioengineering, environment monitoring, food science and other application area. So, the improvement of DNA detection system is very important for the determination of this hybridization reaction. In this study, we report the characterization of the probe and target oligonucleotide hybridization reaction using the evanescent field microscopy. First, we have fabricated DNA chip microarray. The particles which were immobilized oligonucleotides were arranged by the random fluidic self-assembly on the pattern chips, using hydrophobic interaction. Second, we have detected DNA hybridization reaction using evanescent field microscopy. The 5'-biotinylated probe oligonucleotides were immobilized on the surface of DNA chip microarray and the hybridization reaction with the Rhodamine conjugated target oligonucleotide was excited fluorescence generated on the evanescent field microscopy. In the foundation of this result, we could be employed as the basis of a probe olidonucleotide, capable of detecting the target oligonucleotide and monitoring it in a large analyte concentration range and various mismatching condition.

• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.7
• /
• pp.796-804
• /
• 2011

Railway vehicles are capable of indicating several types of instability. This phenomenon, which is called hunting motion, is a self excited lateral oscillation that is caused by the running velocity of the vehicle and wheel frail interactive forces. The interactive forces act to change effectively the damping characteristics of railway vehicle systems. This paper will show the impact of instability on the transfer function behavior using damping characteristics of secondary suspension. The vehicle dynamics are modeled using a 17 degree of freedom considering linear wheel/rail contact. The paper deals with certain condition of the damper characteristics that one is about various damping coefficient and another is equipped damper direction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11b
• /
• pp.1022-1027
• /
• 2002

This paper describes the fluttering characteristics of the upper pad in a tilting pad journal bearing(6-pad, LOP type) using a steam turbine. In order to investigate the phenomena of the upper pad fluttering experimentally, the absolute vibration of the upper pads the relative vibration between bearing and shaft and the circumferential distribution of the film thickness are measured under the different values of supply oil flow rate, shaft speed and bearing load. It can be known that the fluttering mechanism of the upper pads has a tendency of the self-excited vibration from the study of fluttering frequencies and amplitudes with the change of shaft speed. furthermore, it is observed that the incipient upper pad fluttering velocity is increased by the increase of oil supply flow rate and fluttering amplitude of the upper pads is increased by the decrease of the oil flow rate and by the increase of the bearing load.

• Wind and Structures
• /
• v.7 no.4
• /
• pp.251-264
• /
• 2004

The effects of a class of nonlinear Tuned Mass Dampers on the aeroelastic behavior of SDOF systems are investigated. Unlike classical linear TMDs, nonlinear constitutive laws of the internal damping acting between the primary oscillator and the TMD are considered, while the elastic properties are keept linear. The perturbative Multiple Scale Method is applied to derive a set of bifurcation equations in the amplitude and phase and a parametric analysis is performed to describe the postcritical scenario of the system. Both cubic- and van der Pol-type dampings are considered and the dependence of the limit-cycle amplitudes on the system parameters is studied. These new results, compared with the previously obtained bifurcation scenario of a SDOF aeroelastic oscillator equipped with a linear TMD, show a detrimental effect on the maximum limit-cycle amplitude reduction of the nonlinear TMD. However, the analyses evidence that in the parameter region away from the perfect tuning condition the nonlinear connection can be used to tune the system with an enhancement of the limit-cycle amplitude reduction.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.22 no.3
• /
• pp.156-164
• /
• 2010

Combustion instability is a major issue in design of gas turbine combustors for efficient operation with low emissions. Combustion instability is induced by the interaction of the unsteady heat release of the combustion process and the change in the acoustic pressure in the combustion chamber. In an effort to develop a technique to predict self-excited combustion instability of gas turbine combustors, a new stability analysis method based on the transfer matrix method is developed. The method views the combustion system as a one-dimensional acoustic system with a side branch and describes the heat source as the input to the system. This approach makes it possible to use not only the advantages of the transfer matrix method but also well established classic control theories. The approach is applied to a gas turbine combustion system, which shows the validity and effectiveness of the approach.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.24 no.6
• /
• pp.274-278
• /
• 2014

Machining performance is often limited by chatter vibration at the tool-workpiece interface. Chatter vibration is a type of machining self-excited vibration which originated from the variation in cutting forces and the flexibility of the machine tool structure. Cutting tooling method is one of major factor to chatter vibration in turning process. Even though lots of cutting tooling methods are developed and used in machining process, precise analysis of cutting tooling effect in view of chatter vibration behavior. This study presents numerical and experimental approaches to verify and effects of various cutting tooling geometry and clamping method on the onset of chatter vibration. Acquired knowledge from this study will apply the optimal geometry design of cutting tooling and adjusting of machining process.

• Journal of Ocean Engineering and Technology
• /
• v.24 no.1
• /
• pp.10-19
• /
• 2010

ANSYS multi-physics software was applied to solve the coupled dynamic problem related to a full-scale TLP foundation for floating wind turbines. In this coupled dynamics simulation, the forced oscillation imposed on the tethers' top resulting from the sway of the wind turbine platform and the self-excited vortex-induced vibration (VIV) along the tether span have been taken into account. The stability of this tensioned tether system has been validated in the form of separate static and dynamic analyses. The dynamic characteristics of the tensioned tether linked to the floating wind turbine were analyzed by the resultant modal form and its corresponding vortex shedding pattern. The calculated result shows that even a slight forced oscillation imposed on the tethers' top leads to the VIV amplification and enhances the risk of instability in the case of low pretension. It is also found that the "synchronization" would be aggravated when the top tension decreases and the "2P" vortex shedding mode takes place. The increased top tension imposed on the tethers contributes to the stability of the tensioned legs by diminishing the oscillation amplitude markedly.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.5 no.5
• /
• pp.501-507
• /
• 2000

A nobel low-cost, simple and unity-power-factor electronic ballast is presented. The proposed electronic ballast employs a bypassing capacitor- and load networks composed of ballast capacitors and small charge pump capacitors as power factor correction circuit combined with the secondary winding of the transformer in the self-excited current-fed push-pull resonant inverter(CF-PPRI), resulting in cost-effectiveness and higher efficiency. By analyzing the princip1es of power factor correction mathematically, optimum design guidelines are presented. Since the lamps are used in power factor correction stage, the input power is automatically adjusted according to the number of the lamps.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2010.05a
• /
• pp.11-12
• /
• 2010

PSC girder with holed web have several benefits. Most of all placing tendon anchorage in the holes can make prestressing forces be loaded stepwise. In addition it can reduce the self-weight of the beams and increase the span length of beams. And holed web might minimize the interference of view. In this study, a 50-meter long full scale multilevel post-tensioned PSC girder was fabricated and modal test was carried out. In order to obtain precise frequency response, vibration exciter was placed at the middle of the girder and excited with several frequencies. Natural frequency and damping ratio were evaluated from FFT and PSD using the obtained frequency response and compared with numerical analysis result.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.2
• /
• pp.495-508
• /
• 1995

The self-excited vibrations of airfoil is related to the classical flutter problems, and it has been studied as a system with linear stiffness and small damping. However, since the actual aircraft wing and the many mechanical elements of airfoil type have various design variables and parameters, some of these could have strong nonlinearities, and the nonlinearities could be unexpectedly strong as the parameters vary. This abrupt chaotic behavior undergoes ordered routes, and the behaviors after these routes are uncontrollable and unexpectable since it is extremely sensitive to initial conditions. In order to study the chaotic behavior of the system, three parameters are considered, i.e., free-stream velocity, elastic distance and zero-lift angle. If the chaotic parameter region can be identified from the mathematically modeled nonlinear differential equation system, the designs which avoid chaotic regions could be suggested. In this study, by using recently developed dynamically system methods, and chaotic regions on the parameter plane will be found and the safe design variables will be suggested.