Abstract: Dynamic stability of axially accelerated beams is investigated in this paper. The equations
of motion of a fixed-free beam undergoing axially accelerated motion are derived. Unstable regions
due to the acceleration are obtained by using the Floquet’s theory. Stability diagrams are presented to
illustrate the influence of the acceleration characteristics. Large unstable regions of flutter type
instability exist around the first, twice the first, and twice the second bending natural frequencies.
Divergence type instability also occurs when the acceleration exceeds a certain value. The validity of
the stability diagram is confirmed by direct numerical integration of the equations of motion.
Abstract: This paper presents experimental and simulation results of discharge in spherically
convergent beam fusion device. The deuterium-deuterium (D-D) fusion reaction in that device will
generate neutron. The experimental device is consists of a vacuum chamber made of stainless steel,
spherical mesh type anode and concentric grid cathode of 5cm diameter. The pressure of chamber
maintained constant by injecting gas and pulsed voltage applied to grid cathode. A star mode
discharge which has possibility of neutron generation was observed.
Abstract: Neutron imaging using a pulsed neutron time-of-flight method can give an energy
dependent transmission image, namely, spectroscopic image. This image includes the structure
information if the sample is coherent scatterer. Here, two examples are introduced. First, we
obtained the transmission image of a welded sample of SS304 and 308. Change of the crystal
structure depending on the position was observed. Furthermore, we measured spatial dependent
transmission of SS samples treated in different ways, surface treatment and whole body treatment.
There were almost no spatial dependent change, but the cross section change was found between
surface and whole body treatment samples. It was suggested that this might be due to the
difference of a grain size. These results demonstrated that the spectroscopic imaging using a
pulsed neutron source is a useful tool for material characterization.
Abstract: The irradiation induced defects of irradiated reactor pressure vessel(RPV) steel were
investigated by a small angle neutron scattering. The degradation of the mechanical properties of RPV
steels during an irradiation in a nuclear power plant is closely related to the irradiation induced
defects. The size of these defects is known to be a few nanometers, and the small angle neutron
scattering technique is regarded as the best non destructive technique to characterize the nano sized
inhomogeneities in bulk samples. The RPV steel was irradiated in the HANARO reactor in KAERI.
The small angle neutron scattering experiments were performed at SANS instrument in the
HANARO reactor. Both unirradiated and irradiated RPV steels were measured and the SANS data of
both steels were compared. The nano sized irradiation induced defects were quantitatively analyzed
by SANS. The type of defects was also analyzed based on the SANS results, and the effect of the
chemical composition of the RPV steel on the irradiation induced defects was discussed.
Abstract: In this paper, we propose a dynamic Electrical Capacitance Tomography (ECT) image
reconstruction algorithm based on the extended Kalman filter (EKF) to estimate the rapidly
time-varying changes in the permittivity within the time taken to acquire a full set of independent
measurement data. The ECT inverse problem is formulated as a state estimation problem in which the
system is modeled with the state equation and the observation equation. Computer simulation with
synthetic data is provided and comparison is done with existing modified Newton Raphson (mNR)
method to illustrate the reconstruction performance of the proposed algorithm.
Abstract: Adhesion of flexible copper clad laminates (FCCL) on two different types of polyimide
(PI), sputtering raw polyimide (SRPI) and casting raw polyimide (CRPI), were studied. Chromium
(Cr), strongly reacts with dangling O bonds, was used as tie-coating layer in order to improve low
adhesion between copper (Cu) and polyimide (PI). Polyimide surfaces were pretreated with gas
plasma that was generated with a mixture of argon and oxygen before sputtering process. Adhesion
measurement was performed on these samples according to IPC specification. The results show that
the peel strength of the FCCL on SRPI was higher than on CRPI. This is considered to be due to the
formation of Cu-Cr-O solid solution at the metal- PI interface.
Abstract: As the TFT-LCDs are getting more attention for the next generation display device,
specifications of the mechanical functionalities of the device is to be more tighter as well as the
electrical user specifications. Due to its brittle characteristics of TFT-LCD panels, maintaining
mechanical integrity under an impact loading situation is the one of the key design concerns.
Furthermore, as the TFT-LCDs are popularly adopted for various mobile equipments such as cellular
phones and digital cameras, shock failure of the display should be prohibitive for the design engineers.
A major incident being monitored during the shock loading is of course the local material failure of
the TFT-LCD panel that might happen at its maximum deformation. The present work delivers a
systematic approach for the shockproof design of mobile TFT-LCD. A specially designed shock test
setup evaluated by a set of rigorous FEM analyses is shown and comments for the shockproof method
is to be also delineated.
Abstract: In this paper, nano-sized Al2O3 powders are synthesized by a thermal MOCVD (Metal
Organic Chemical Vapor Deposition) combined with plasma. The effect of reaction temperature on
the characteristics of the synthesized Al2O3 powders is investigated. The experimental results
demonstrate that while the temperature is increased from 200oC to 1000oC, the mean diameter of
Al2O3 powders reaches from 400nm to 10nm. Hence, the increment of temperature can promote
the synthesis of fine Al2O3 particle. Furthermore, the powder morphologies and crystallite size are
also examined by the transmission electron microscopy (TEM) and XRD. Based on TEM
observation, it is found that the particles are sphere shape. The XRD analysis shows that the
particles are typical γ-Al2O3 crystalline phase over 400oC. Lastly, the effect of plasma on the
characteristic of Al2O3 synthesized by thermal MOCVD is also considered.
Abstract: In the paper, zinc oxide (ZnO) thin films are deposited by plasma enhanced chemical
vapor deposition (PECVD) at different substrate temperatures. The ZnO films are characterized by
X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The analysis results indicate
that highly crystalline films with high orientation can be obtained at a substrate temperature of 300
oC with 50 ml/min flow rate from Diethylzinc (DEZ). Furthermore, the investigation of optical
property shows that ZnO films are transparent, and the peak transmittance in the visible region is as
high as 85%.
Abstract: Optical emission spectra from plasma during deposition of diamond film were investigated
by an optic multi-channel spectrometer using a CCD array sensor. The diamond film was deposited by
DC plasma enhanced (PE) chemical vapor deposition (CVD) using hydrogen and methane gas
mixture, where substrate was located at near the plasma and the discharge was performed by
intermittent discharge. When Pg during the deposition was increased from 50 to 250 Torr, the optical
emissions of hydrogen (Hα and Hβ) and C2 were increased, and corresponding to these increases,
deposition rate of the diamond film was increased and crystalline quality became superior. When Cm
was changed from 1 to 3 %, the emission from C2 was increased, and whereas, the emission from
hydrogen was decreased. Corresponding to these changes of the emission, the deposition rate of the
film was increased and amorphous component in the deposited film was also increased. These results
show that the increase of C2 results in the increase of the deposition rate, and increase of hydrogen is
effective to eliminate amorphous component, and therefore, monitoring of the optical emission from
hydrogen and C2 is useful for the deposition process of the diamond film.