• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.11
• /
• pp.138-145
• /
• 2009

A suspended membrane micro fluidic heat flux sensor that is able to measure the heat flow rate was designed and fabricated by a complementary-metal-oxide-semiconductor-compatible process. The combination of a thirty-junction gold and nickel thermoelectric sensor with an ultralow noise preamplifier, low pass filter, and lock-in amp has enabled the resolution of 50 nW power and provides the sensitivity of $11.4\;mV/{\mu}W$. The heater modulation method was used to eliminate low frequency noises from sensor output. It is measured with various heat flux fluid of DI-water to test as micro fluidic application. In order to estimate the heat generation of samples from the output measurement of a micro fluidic heat-flux sensor, a methodology for modeling and simulating electro-thermal behavior in the micro fluidic heat-flux sensor with integrated electronic circuit is presented and validated. The electro-thermal model was constructed by using system dynamics, particularly the bond graph. The electro-thermal system model in which the thermal and the electrical domain are coupled expresses the heat generation of samples converts thermal input to electrical output. The proposed electro-thermal system model shows good agreement with measured output voltage response in transient state and steady-state.

• Journal of the Korean Society for Precision Engineering
• /
• v.30 no.7
• /
• pp.702-708
• /
• 2013

The white-light scanning interferometer (WSI) is an effective optical measurement system for high-precision industries (e.g., flat-panel display and electronics packaging manufacturers) and semiconductor manufacturing industries. Its major disadvantages include a slow image-capturing speed for interferogram acquisition and a high computational cost for peak-detection on the acquired interferogram. Here, a WSI system is proposed for the semiconductor inspection process. The new imaging acquisition technique uses an 'on-the-fly' imaging system. During the vertical scanning motion of the WSI, interference fringe images are sequentially acquired at a series of pre-defined lens positions, without conventional stepwise motions. To reduce the calculation time, a parallel computing method is used to link multiple personal computers (PCs). Experiments were performed to evaluate the proposed high-speed WSI system.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.16 no.5
• /
• pp.108-114
• /
• 2007

A new cutting force estimating approach and machining state monitoring examples are presented which uses a cylindrical displacement sensor built into the spindle. To identify the tool-spindle system dynamics with frequency up to 2 kHz, a home-built electro-magnetic exciter is used. The result is used to build an algorithm to extract the dynamic cutting force signal from the spindle error motion; because the built-in spindle sensor signal contains both spindle-tool dynamics and tool-workpiece interactions. This sensor is very sensitive and can measure broadband signal without affecting the system dynamics. The main characteristic is that it is designed so that the measurement is irrelevant to the geometric errors by covering the entire circumferential area between the target and sensor. It is also very simple to be installed. Usually the spindle front cover part is copied and replaced with a new one with this sensor added. It gives valuable information about the operating condition of the spindle at any time. It can be used to monitor cutting force and chatter vibration, to predict roughness and to compensate the form error by overriding spindle speed or feed rate. This approach is particularly useful in monitoring a high speed machining process.

• Structural Engineering and Mechanics
• /
• v.58 no.1
• /
• pp.163-179
• /
• 2016

The Cuckoo search (CS) algorithm is a simple and efficient global optimization algorithm and it has been applied to figure out large range of real-world optimization problem. In this paper, a new formula is introduced to the discovering probability process to improve the convergence rate and the Tournament Selection Strategy is adopted to enhance global search ability of the certain algorithm. Then an approach for structural damage identification based on modified Cuckoo search (MCS) is presented. Meanwhile, we take frequency residual error and the modal assurance criterion (MAC) as indexes of damage detection in view of the crack damage, and the MCS algorithm is utilized to identifying the structural damage. A simply supported beam and a 31-bar truss are studied as numerical example to illustrate the correctness and efficiency of the propose method. Besides, a laboratory work is also conducted to further verification. Studies show that, the proposed method can judge the damage location and degree of structures more accurately than its counterpart even under measurement noise, which demonstrates the MCS algorithm has a higher damage diagnosis precision.

• Structural Monitoring and Maintenance
• /
• v.4 no.1
• /
• pp.33-52
• /
• 2017

A cantilever beam with a breathing crack is studied to improve the breathing crack identification sensitivity by the parametric optimization of sample entropy and wavelet transformation. Crack breathing is a special bi-linear phenomenon experienced by fatigue cracks which are under dynamic loadings. Entropy is a measure, which can quantify the complexity or irregularity in system dynamics, and hence employed to quantify the bi-linearity/irregularity of the vibration response, which is induced by the breathing phenomenon of a fatigue crack. To improve the sensitivity of entropy measurement for crack identification, wavelet transformation is merged with entropy. The crack identification is studied under different sinusoidal excitation frequencies of the cantilever beam. It is found that, for the excitation frequencies close to the first modal frequency of the beam structure, the method is capable of detecting only 22% of the crack depth percentage ratio with respect to the thickness of the beam. Using parametric optimization of sample entropy and wavelet transformation, this crack identification sensitivity is improved up to 8%. The experimental studies are carried out, and experimental results successfully validate the numerical parametric optimization process.

• Computers and Concrete
• /
• v.21 no.1
• /
• pp.1-9
• /
• 2018

Electrical resistivity is a property associated with both the physical and chemical characteristics of concrete. It allows the evaluation of the greater or lesser difficulty with which aggressive substances penetrate the concrete's core before the dissolution of the passive film process and the consequent reinforcement's corrosion begin. This work addresses the steel fiber addition to concrete with two types and various contents from 0% to 1.3%, correlating it with its electrical resistivity. To that effect, 9 different mixes of steel fiber reinforced concrete (SFRC) were produced. The electrical resistivity was evaluated on the on six years aged SFRC by direct measurement at different frequency from 0.1 kHz to 100 kHz. The results indicate that steel fiber content is strongly conditioned by the type and quantity of the additions used. It was also found that long type of fibers has more effect on decreasing the electrical resistivity of concrete than short fibers. Therefore, they increase the corrosion risk of concrete depending on fiber volume fraction and moisture percentage.

• Journal of ILASS-Korea
• /
• v.16 no.2
• /
• pp.104-109
• /
• 2011

The present study investigated experimentally the spreading characteristics of a single liquid impinging on the inclined micro-textured aluminum (Al 6061) surfaces manufactured by using a micro computerized numerical control (${\mu}$-CNC) milling machine. The textured surfaces were composed of patterned micro-holes (diameter of $125\;{\mu}m$ and depth of $125\;{\mu}m$). In our experiment, the de-ionized (DI) water droplet of $4.3\;{\mu}l$ was impinged normally on the non-textured and textured surfaces at two different Weber numbers, and the droplet impinged on the inclined surfaces with different angles. A high speed camera was used to capture sequential digital images for measurement of the maximum spreading distance. It was found that for the textured surface, the measured apparent equilibrium contact angle (ECA) increased up to $105.8^{\circ}$, higher than the measured ECA of $87.6^{\circ}$ for the non-textured (bare) surface. In addition, it is conjectured that the spreading distance decreased because of a liquid penetration during droplet spreading through the holes, the increase in hydrophobicity, and viscous dissipation during impact process.

• Journal of the Microelectronics and Packaging Society
• /
• v.21 no.2
• /
• pp.31-35
• /
• 2014

The thickness dependent electrical, structural, and optical properties of ZnO films grown by atomic layer deposition (ALD) at various growth temperatures were investigated. In order to deposit ZnO films, diethylzinc and deionized water were used as metal precursor and reactant, respectively. ALD process window was found at the growth temperature range from $150^{\circ}C$ to $250^{\circ}C$ with a growth rate of about $1.7{\AA}/cycle$. The electrical properties were studied by using van der Pauw method with Hall effect measurement. The structural and optical properties of ZnO films were analyzed by using X-ray diffraction, field emission scanning electron microscopy, and UV-visible spectrometry as a function of thickness values of ZnO films, which were selected by the lowest electrical resistivity. Finally, the figure of merit of ZnO films could be estimated as a function of the film thickness. As a result, this investigation of thickness dependent electrical, structural, and optical properties of ZnO films can provide proper information when applying to optoelectronic devices, such as organic light-emitting diodes and solar cells.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.5
• /
• pp.36-43
• /
• 1999

A new design of a Direct Digital Frequency Synthesizer(DDFS) is presented, where a pipelined Coordinate Rotate Digital Computer(CORDIC) circuit is employed to calculate amplitude values of all the phase angles of sinusoidal waveforms produced. a near-optimal number of pipeline stages is determined based on an error analysis of calculated amplitude values in terms of the number of bits. The DDFS was implemented using a field programmable gate array, yielding a stable operating frequency of 11.75MHz. The measurement results show higher resolution, faster operating speed and simpler fabrication process, compared to ROM-based counterparts. The CORDIC-based DDFS yields 5 times higher resolution than conventional ROM-based versions.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.44 no.2
• /
• pp.25-33
• /
• 2007

In this paper, a fourth-order single-bit delta-sigma modulator is presented and implemented. The loop-filter is composed of both feedback and feedforward paths. Measurement results show that maximum 99dB dynamic range is achievable at a clock rate of 3.2MHz for 20kHz baseband. The proposed modulator has been fabricated in a $0.18{\mu}m$ standard CMOS process.