• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.16-22
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• 2013

A two-dimensional photonic crystal structure was investigated using a roll-to-roll nanoreplication and physical vapor deposition processes for the inexpensive enhanced fluorescence substrate which is not sensitive to the polarization directions of excitation light source. An 8 inch silicon master having nano dot array with a diameter of 200 nm, a height of 100 nm and a pitch of 400 nm was prepared by KrF laser scanning lithography and reactive ion etching processes. A flexible polymer mold was fabricated by flat type UV replication process and a deposition of 10 nm nickel layer as an anti-adhesion layer. A roll mold was prepared by warping the flexible polymer mold on an aluminum roll base and a roll-to-roll UV replication process was carried out using the roll mold. After the deposition of ~ 100 nm $TiO_2$ layer on the replicated nano dot array, a 2 dimensional photonic crystal structure was realized with a resonance wavelength of 635 nm for both p- and s-polarized light sources.

• Journal of Power System Engineering
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• v.3 no.2
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• pp.26-33
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• 1999

Pressure pulsation Inside the discharge and suction cavity of rotary and scroll compressor are often a major source of objectionable noise and vibration. The key factor of these noise and vibration is due to the cavity resonance. It is not only necessary to understanding the characteristics of pulsation in order to reduce the excitation force of gas to the cavity but also to verifying the phenomena of cavity resonance. For the purpose of these understandings, measurement and simulation of cavity resonance can lead to a better understandings how they occur and be very important to identify the ways to reduce the noise efficiently. In this paper, modeling of the cavity(internal acoustics inside the shell) is discussed and simulated using FEM. Results from the simulation are compared with those measurement in experiments. In describing of cavity mode by experiments, it is very important to specify the exact conditions under which they are measured. Finally, this paper shows the one example of reduced cavity resonance in the compressor.

• Journal of KSNVE
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• v.6 no.6
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• pp.701-708
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• 1996

Diesel power plants are frequently used as a power supplier on the island and the isolated places where electric power is required. The heat efficiency of the low speed 2 stroke diesel engines is higher than those of 4 stroke diesel engines or other heat engines and further its mobility and durability is also better than other engines. They can be also easily repaired and maintained. With these advantages, demand for the use of the low speed 2 stroke diesel engine as a power source is increasing. However, there are some disadvantages with these diesel engines such as the bigger vibrating excitation forces generated by higher combustion pressure in cylinder and by the inertia force of the reciprocating parts. Further, engine vibrations are transfered into their adjacent buildings and manufacturing factories and eventually produces local vibrations. In order to reduce X-mode vibration of engine body, several methods have been introduced in the recent researches. In this paper, accordingly, a new vibrationcontrol method applying a synchrophaser and a top bracing between two diesel engines is adopted in order to reduce these structural vibrations of diesel power plant. It was experimentally verified that the structural vibrations were greatly reduced by the phase adjustment for the 6th order X-mode vibration with the synchrophaser and the top bracing.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.4
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• pp.5-12
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• 2001

This paper presents the simulation methodology of the interior noise of vehicle using the frequency response function based hybrid modeling of the system which consists of multi-subsystem models obtained by the test or analysis. The complex systems such as a trimmed body of high modal density and a powertrain were modeled by using experimental data, and a sub-frame of a vehicle of low modal density was modeled by finite element data. Modeling of the whole system was executed and validated in the two stages. The first stave is combining the trimmed body and the sub-frame, and the second stage is attaching the powertrain, which is a exciting source, to the combined model of the first stage. The input force to the system was modeled as an equivalent force in the virtual space, which was obtained from impedance method using the FRFs of the powertrain and the responses. The interior noise predicted by the proposed method was very close to the direct measurement, which showed feasibility of the proposed modeling procedure. Since the methodology is easily applied to both the transfer path analysis of structure-borne noise and the analysis of noise contribution of a sub-system, it is expected to be a strong tool for design change of a vehicle in the earlier stare.

• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.9-16
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• 2001

This paper deals with the inverse reconstruction of sectional area in nonuniform ducts by using the acoustical measurement. There have been many theoretical and experimental studies on the duct area reconstruction. In this research, the method using the impulse response function and area reconstruction algorithm was employed because of its mathematical and experimental simplicity. Based on the study results on the drawback of conventional impulse excitation method, a new measurement method is proposed, that uses the random noise source and the discrete inverse Fourier transform. It is found that the reconstruction errors of the present method is smaller than the conventional method. A random error analysis is performed in order to investigate the causes of reconstruction error and to clarify the applicable data range for area reconstruction.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1890-1892
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• 2002

The technology of sulfur lamps that has physical and electrical characteristics comparable to current HID source has been reported. The fundamental principles of the operation of microwave discharges that are used to convert microwave energy to broad spectrum visual light are known. In this paper, emission dependance of microwave discharges in mixture content of sulfur with noble gases was studied. It is shown that the excitation of this gaseous mixture is carried out in two phases: (l) ionization of noble gas atoms by a microwave field and (2) the consequent maintenance of slightly ionized nonequilibrium plasma by the field. These two processes have essentially various thresholds for the microwave pump. The purpose of this work is to investigate spectral properties of the high frequency discharges in a mixture sulfur vapors with noble gases.

• International Journal of Automotive Technology
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• v.8 no.1
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• pp.67-73
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• 2007

This study analyzes the interior noise that is generated during acceleration of a passenger car in terms of car body structure and panel contribution. According to the transfer method, interior noise is classified into structure-borne noise and air-borne noise. Structure-borne noise is generated when the engine's vibration energy, an excitation source, is transferred to the car body through the engine mount and the driving system and the panel of the car body vibrates. When structure-borne noise resonates in the acoustic cavity of the car interior, acute booming noise is generated. This study describes plans for improving the car body structure and the panel form through a cause analysis of frequency ranges where the sound pressure level of the rear seat relative to the front seat is high. To this end, an analysis of the correlation between body attachment stiffness and acoustic sensitivity as well as a panel sensitive component analysis were conducted through a structural sound field coupled analysis. Through this study, via research on improving the car body structure in terms of reducing rear seat noise, stable performance improvement and light weight design before the proto-car stage can be realized. Reduction of the development period and test car stage is also anticipated.

• Journal of Biosystems Engineering
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• v.35 no.2
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• pp.124-131
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• 2010

Chlorophyll fluorescence has been researched for assessing fruit post-harvest quality and condition. The objective of this preliminary research was to investigate the potential of fluorescence spectroscopy for measuring apple fruit quality. Ultraviolet (UV) and blue light was used as an excitation source for inducing fluorescence in apples. Fluorescence spectra were measured from 'Golden Delicious' (GD) and 'Red Delicious' (RD) apples using a visible/near-infrared spectrometer after one, three, and five minutes of continuous UV/blue light illumination. Standard destructive tests were performed to measure fruit firmness, skin and flesh color, soluble solids and acid content from the apples. Calibration models for each of the three illumination time periods were developed to predict fruit quality indexes. The results showed that fluorescence emission decreased steadily during the first three minutes of UV/blue light illumination and was stable within five minutes. The differences were minimal in the model prediction results based on fluorescence data at one, three or five minutes of illumination. Overall, better predictions were obtained for apple skin chroma and hue and flesh hue with values for the correlation coefficient of validation between 0.80 and 0.90 for both GD and RD. Relatively poor predictions were obtained for fruit firmness, soluble solids content, titrational acid, and flesh chroma. This research has demonstrated that fluorescence spectroscopy is potentially useful for assessing selected quality attributes of apple fruit and further research is needed to improve fluorescence measurements so that better predictions of fruit quality can be achieved.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.306-306
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• 2010

A high density (> $10^{11}\;cm^{-3}$) and low electron temperature (< 2 eV) plasma is produced by using a conventional HF (13.56 MHz) plasma enhanced chemical vapor deposition (PECVD) with an additional ultra high frequency (UHF, 314 MHz) plasma source utilizing two parallel antenna assembly. It is applied for the high rate synthesis of high quality nanocrystalline silicon (nc-Si) films. A high deposition rate of 1.8 nm/s is achieved with a high crystallinity (< 70%), a low spin density (< $3{\times}10^{16}\;cm^{-3}$) and a high light soaking stability (< 1.5). Optical emission spectroscopy measurements reveal emission intensity of $Si^*$ and $SiH^*$, intensity ratio of $H{\alpha}/Si^*$ and $H{\alpha}/SiH^*$ which are closely related to film deposition rate and film crystallinity, respectively. A high flux of precursor and atomic hydrogen which are produced by an additional high excitation frequency is effective for the fast deposition of highly crystallized nc-Si films without additional defects.

• Journal of the Korean Society of Visualization
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• v.11 no.2
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• pp.41-45
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• 2013

Two-photon microscopy (TPM) is minimally-invasive 3D fluorescence microscopy based on nonlinear excitation, and TPM can visualize cellular structures based on auto-fluorescence. Line-scanning TPM is one of high-speed TPM methods without sacrificing the image resolution by using spatial and temporal focusing. In this paper, we developed line-scanning TPM based on spatial and temporal focusing for auto-fluorescence imaging by exciting the tryptophan. Laser source for this system was an optical parametric oscillator (OPO) and it made near 570 nm femtosecond pulse laser. It had 200fs pulse width and 1.72 nm bandwidth, so that the achievable depth resolution was 2.41um and field of view (FOV) is 10.8um. From the characterization, our system has 3.0 um depth resolution and 12.3 um FOV. We visualized fixed leukocyte cell sample and compared with point scanning system.