Helium-filled drives and thermally assisted magnetic recording (TAMR) systems are the most promising next-generation magnetic recording technologies. Currently, a fused TAMR system under helium- or air-helium-filled conditions is expected. In the fused system, it is important to accurately predict thermal deformation for a full TAMR head model and change of flying height (FH) at near filed transducer (NFT). In this paper, we first constructed an iterative coupled-field analysis process and a more realistic TAMR head model, including the NFT and even the epoxy components. The heat transfer coefficient was calculated using derived gas mixture properties. And the thermal deformation and protrusion of TAMR head was investigated for various temperature and helium fraction ratios. From the simulation results, the maximum temperature at the laser diode (LD) decreased up to 20% due to changes in the heat transfer coefficient and environmental temperature. The epoxy effect induced by the LD heating was around 40%, which is in no way negligible. A thermal protrusion of 1.0-1.5 nm occurred at the NFT at various conditions. After considering the thermal deformation of the epoxy and the protrusion at the NFT, we found that the total FH was reduced with increasing helium fraction ratio and temperature.
We propose a new load/unload (L/UL) suspension featuring shape memory alloy (SMA) thin film and demonstrate its effectiveness through the L/UL simulation. We estimated the mechanical properties of the SMA with respect to the material phases by experiment and designed the proposed suspension by considering the vibration modes related to the L/UL performance. In order to effectively verify the effectiveness of the proposed suspension, we designed the suspension to have similar L/UL performance to that obtained from the conventional suspension when the SMA film is not activated. After analyzing the L/UL design parameters of the proposed suspension when the SMA is activated, we examine the relative performance of the conventional and proposed suspensions by L/UL simulation by comparing the vibration motions of the slider and the minimum gap size between the disk and slider
Holographic data storage system is one of next generation high density optical memories. Thereby storing multiple data pages using multiplexing method in one spot, we can achieve high store density and fast access time. However, for uniform writing, we must control exposure time properly by the change of writing material characteristics. Many studies have been investigated about exposure time scheduling. However, once it is decided, we cannot change the scheduled time. Therefore, it is hard to obtain uniform data intensity. In this study, we propose exposure time control method using additional red beam as the monitoring signal. Through reconstructed red beam intensity in real time, we can adjust exposure time by the writing condition change. We construct compensation method mathematically and verify the feasibility of proposed method through the experiments.
A control method for the angle servo of reference beam during reading recoded data images of a holographic data storage system is presented. The recording scheme with angle offset is adopted in order to verify the proposed angle servo. Using this recording scheme, the angle error signal is generated and we can implement the angle servo. Experiments have been performed on recording and reading data images to compensate Bragg angle mismatch.
Cover thickness influence to the vibration of multilayer ceramic capacitor was analyzed in this study. The results can be helpfully taken to the capacitor design for vibration reduction. 3-D detailed simulation model based on the finite element method was constructed for parametric study and it was verified through the vibration tests. Parametric study with respect to the cover thickness shows that thickening the L cover and W cover increase the vibration amplitude of top surface and decrease the head and side surface. On the other hand, T cover was not related to the vibration amplitude of MLCC.
We analyzed the characteristic of the electric field in a focal plane consisting of a solid immersion lens (SIL), an air-gap, and a measurement sample for radially polarized illumination in SIL based near-field optics with an annular aperture.
Comparing with other industrial structures, the nuclear reactors needs strengthen safety standard. In this research we focus on the reactor internal which are main components in the nuclear reactor. The reactor internal are classified as seismic category I which requires complete level of the seismic analysis. The seismic analysis of the reactor internal is generally performed with the numerical method such as the FE method. The main purpose of the seismic analysis of the reactor internal is to identify the accurate dynamic behaviors, and it requires thorough inspection of the fluid-structure interaction between internals and inner coolant. Thus, it needs detailed analysis model which can reflect accurate dynamic characteristics of the reactor internal for obtaining the reliable results. However, a numerous number of degrees of freedom in the detailed FE model causes large computation costs, thus, it needs to reduce the size of the FE model for performing the seismic analysis. In this thesis, we suggest to apply the model reduction methods, which reduce the overall degrees of freedom of the total system, in order to perform the seismic analysis efficiently. The final purpose of this thesis is constructing the vibration analysis model of the reactor internal using the model reduction method which satisfies accuracy and efficiency. To develop this, researches are progressed as follows. First we constructed detailed FE model of the reactor internal. In order to verify the FE model, the modal test with the scaled-down model which reflects the geometries and boundary conditions of the original reactor internal is performed. Second, the model reduction methods using this thesis are reviewed and application method for the reactor internal is introduced. The validity of the model reduction method is verified with the simple numerical examples and the detail application method is suggested. Then, it is applied to the reactor internal in the APR (Advanced Power Reactor) 1400 and the system-integrated small modular nuclear reactor (SMART; System-integrated Modular Advanced ReacTor), and the reduced models of the reactor internal are verified in the static and dynamic problems. Finally, the seismic analysis was performed with the suggested reduced model which most satisfies efficiency and accuracy. With the seismic analysis model, the time history analysis is performed to extract important seismic responses at the specified locations. Moreover, the stress analysis is also performed to identify that the reactor internal satisfy the seismic design, and design modification is suggested to reduce the stress intensity at the support locations. As a result, the reduced model shows reliable results compared with the full model, moreover, it shows great efficiency by reducing total computation time. The reduced model is expected for applying other types of vibration analyses such as the flow-induced vibration analysis and loss of the coolant accident analysis, and it can contribute to the improvement of structural integrity assessment of the reactor.
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