• 전자공학회논문지A
• /
• 제31A권3호
• /
• pp.28-39
• /
• 1994

We experimented on memory multichip modules to increase the packing density of memory devices and to improve their electrical characteristics. A 128K$\times$8bit SRAM module was made of four 32K$\times$8bit SRAM memory chips. The memory multichip module was constructed on a low-cost double sided PCB(printed circuit boared) substrate. In the process of fabricating a multichip module. we focused on the improvement of its electrical characteristics. volume, and weight by employing bare memory chips. The characteristics of the bare chip module was compared with that of the module with four packaged chips. We conducted circuit routing with a PCAD program, and found the followings: the routed area for the module with bare memory chips reduced to a quarter of that area for module with packaged memory chips. 1/8 in volume, 1/5 in weight. Signal transmission delay times calculated by using transmission line model was reduced from 0.8 nsec to 0.4 nsec only on the module board, but the coupling coefficinet was not changed. Thus, we realized that the electrical characteristics of multichip packages on PCB board be improved greatly when using bare memory chips.

• 한국해양공학회지
• /
• 제21권4호
• /
• pp.1-7
• /
• 2007

Based on the eigenfunction expansion method, the wave-absorbing performance of a square or circular pile breakwater was investigated. Flow separation resulting from sudden contraction and expansion is generated and is the main cause of significant energy loss. Therefore, evaluation of an exact energy loss coefficient is critical to enhancing the reliability of the mathematical model. To obtain the energy loss coefficient, 2-dimensional turbulent flow is analyzed using the FLUENT commercial code, and the energy loss coefficient can be obtained from the pressure difference between upstream and downstream. It was found that energy loss coefficient of circular pile is 20% that of a square pile. To validate the fitting equation for the energy loss coefficient, comparison between the analytical results and the experimental results (Kakuno and Liu, 1993) was made for square and circular piles with good agreement. The array of square piles also provides better wave-absorbing efficiency than the circular piles, and the optimal porosity value is near P=0.1.