Yongjun Kim

18.1 A 20nm 9Gb/s/pin 8Gb GDDR5 DRAM with an NBTI monitor, jitter reduction techniques and improved power distribution

A 9Gb/s/pin 8Gb GDDR5 DRAM is implemented using a 20nm CMOS process. To cover operation up to 9Gb/s, which is the highest data-rate among implemented GDDR5 DRAMs [1], this work includes an NBTI monitor, a WCK clock receiver with equalizing and duty-cycle correction modes, CML-to-CMOS converters with wide range operation, active resonant loads at the end of WCK lane, and an on-chip de-emphasis circuit at a 4-to-1 multiplexer output as shown in Fig. 18.1.1. In addition, extra power pads improve the power distribution and release the frequency limitation at the memory core.

Theoretical background discussion on variable polarity arc welding of aluminum

Cleaning effect is well known mechanism of oxide layer removal in DCEP polarity. It is also known that DCEN has higher heat input efficiency than DCEP in GTAW process. Based on these two renowned arc theories, conventional variable polarity arc for aluminum welding was set up to have minimum DCEP and maximum DCEN duty ratio to achieve the highest heat input efficiency and weldability increase. However, recent several variable polarity GTA research papers reported unexpected result of proportional relationship between DCEP duty ratio and heat input. The authors also observed the same result then suggested combination of tunneling effect and random walk of cathode spot to fill up the gap between experiment and conventional arc theory. In this research, suggested combinational work of tunneling effect and rapid cathode spot changing is applied to another unexpected phenomena of variable polarity aluminum arc welding. From previous research, it is reported that wider oxide removal range, narrower bead width and shallower penetration depth are observed in thin oxide layered aluminum compared to the case of thick oxide. This result was reported for the first time and it was hard to explain the reason at that time therefore the inference by the authors was hardly acceptable. However, the suggested combinational theory successfully explains the result of the previous report in logical way.

Enhancing Solar Cell Properties of Heterojunction Solar Cell in Amorphous Silicon Carbide

In this paper, the efficiency improvement of the heterojunction with intrinsic thin layer (HIT) solar cells is obtained by optimization process of p-type a-SiC:H as emitter. The optoelectronic of p-type a-SiC:H layers including the optical band-gap and conductivity under the methane gas content variation is conducted in detail. A significant increase in the Jsc by and Voc by 30 mV are attributed to enhanced photon-absorption due to broader band-gap of p-a-SiC:H and reduced band-offsets at p-side interface, respectively of HIT solar cells.

Evaluation and solution of noise making weldment in automotive body

The importance of emotional quality of car is getting higher in these days. Noise takes great portion in emotional quality because it is detectable problem with just a few rides. The sources of car noise during operation are various and the related technical issues are vast. Sometimes weldments of auto body are referred as the source of noise and the suspicious weldment shows unsatisfactory welding quality in most cases. In this research, cases of noise making weldments are investigated to figure out the solution for welding quality improvement. They are categorized into several groups in according to the inferred types of the error source then appropriate solutions are suggested. Auto body has weldments of resistance spot welding and gas metal arc welding in general. Therefore the solutions are suggested as adjustment of welding process variables and related machineries. Inevitable error source is also referred which is originated from thermal expansion rate difference between ultra high strength steel and mild steel. This new approach is validated through simple calculation then more concrete investigation with numerical analysis is remained as further works to be done.