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A Study of the Relationship between Structure and Properties of Cadmium Phosphate Glasses
Wongyu Choi,Taehee Kim,Donggun Gwoo,Kyungbum Kee,Jong-Hwan Kim,Kyung-Suk Han,류봉기 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.1
It analysed the structure and chemical durability which it follows in CdO content in Cadmium phosphate glasses. We prepared glasses with the composition, xCdO-(100-x)P2O5 (x = 10 mol. % to 50 mol. %), and analyzed their density (ρ), molar volume (VM), glass transition/softening temperature (Tg/Td), thermal expansion coefficient (α), fourier transform infrared spectroscopy, and dissolution rate. All of these of the values were found to vary with the CdO content of the glasses. It is observed that the dissolution rate increase with with CdO contents. This suggests that Cadmium ion breaks the p-o-p bonds.
Q-DRAM: Quick-Access DRAM with Decoupled Restoring from Row-Activation
Wongyu Shin,Jungwhan Choi,Jaemin Jang,Jinwoong Suh,Yongkee Kwon,Youngsuk Moon,Hongsik Kim,Lee-Sup Kim IEEE 2016 IEEE Transactions on Computers Vol. No.
<P>The relatively high latency of DRAM is mostly caused by the long row-activation time which in fact consists of sensing and restoring time. Memory controllers cannot distinguish between them since they are performed consecutively by a single row-activation command. If these two steps are separated, the restoring can be delayed until DRAM access is uncongested. Hence, we propose Quick-Access DRAM (Q-DRAM) which discriminates between sensing and restoring. Our approach is to allow destructive access (i.e., only sensing is performed without restoring by a row-activation command) using per-bank multiple row-buffers. We call the destructive access and per-bank multiple row-buffers quick-access and quick-buffers (q-buffers) respectively. In addition, we propose Quick-access Trigger (Q-TRIGGER) and RESTORER to utilize Q-DRAM. Q-TRIGGER makes a decision whether quick-access is required or not, and RESTORER decides when to restore the data at the destructed cell. Specifically, RESTORER detects the proper timing to hide restoring time by predicting data bus occupation and by exploiting bank-level locality. Evaluations show that Q-DRAM significantly improved performance for both single-and multi-core systems.</P>
DRAM-Latency Optimization Inspired by Relationship between Row-Access Time and Refresh Timing
Wongyu Shin,Jungwhan Choi,Jaemin Jang,Jinwoong Suh,Youngsuk Moon,Yongkee Kwon,Lee-Sup Kim IEEE 2016 IEEE Transactions on Computers Vol. No.
<P>It is widely known that relatively long DRAM latency forms a bottleneck in computing systems. However, DRAM vendors are strongly reluctant to decrease DRAM latency due to the additional manufacturing cost. Therefore, we set our goal to reduce DRAM latency without any modification in the existing DRAM structure. To accomplish our goal, we focus on an intrinsic phenomenon in DRAM: electric charge variation in DRAM cell capacitors. Then, we draw two key insights: i) DRAM row-access latency of a row is a function of the elapsed time from when the row was last refreshed, and ii) DRAM row-access latency of a row is also a function of the remaining time until the row is next refreshed. Based on these two insights, we propose two mechanisms to reduce DRAM latency: NUAT-1 and NUAT-2. NUAT-1 exploits the first key insight and NUAT-2 exploits the second key insight. For evaluation, circuit-and system-level simulations are performed, which show the performance improvement for various environments.</P>
Wongyu Jang,Baekil Nam,Minji Gu,Shanigaram Mallesh,Ki Hyeon Kim 한국물리학회 2021 New Physics: Sae Mulli Vol.71 No.5
We have designed a jig that employed the flanged, coaxial transmission line through a 3D finite-element-method (FEM) simulation to measure the broadband electromagnetic (EM) shielding effectiveness (SE) in the frequency range from 0.5 GHz to 18 GHz. The flanged, coaxial transmission line comprises the ground (outer diameter: 7.00 mm) and the signal line (inner diameter: 3.04 mm). Representative specimens were prepared with metallic materials (Al, Ni, Cu sheets, & Ni mesh) and non-metallic materials (graphene oxide and magnetic polymer composite) to evaluate the SE. We analyzed the EM properties, the reflection, absorption, and total EM SE, of the fabricated specimens. Further, the SE results acquired from the flanged, coaxial transmission line which compared with those of a rectangular waveguide by measuring the S parameters. The SE measured using the flanged, coaxial transmission line correlates well with those of the rectangular waveguides (WR-90, WR-62).