A Variation-aware Hold Time Fixing Methodology for Single Flux Quantum Logic Circuits

Single flux quantum (SFQ) logic is a promising technology to replace complementary metal-oxide-semiconductor logic for future exa-scale supercomputing but requires the development of reliable EDA tools that are tailored to the unique characteristics of SFQ circuits, including the need for active splitters to support fanout and clocked logic gates. This article is the first work to present a physical design methodology for inserting hold buffers in SFQ circuits. Our approach is variation-aware, uses common path pessimism removal and incremental placement to minimize the overhead of timing fixes, and can trade off layout area and timing yield. Compared to a previously proposed approach using fixed hold time margins, Monte Carlo simulations show that, averaging across 10 ISCAS’85 benchmark circuits, our proposed method can reduce the number of inserted hold buffers by 8.4% with a 6.2% improvement in timing yield and by 21.9% with a 1.7% improvement in timing yield.

Evaluation of marginal microleakage in composite restorations with different placement techniques

Aim: The purpose of this in vitro study was to evaluate the effect of different layering techniques (bulk, oblique, centripetal, split horizontal) on the marginal microleakage of Class II adhesive restorations. Methodology: Forty-eight standardised Class II cavities were prepared on both mesial and distal sides of extracted non-carious human molar teeth. Following preparation, all specimens were randomly divided into four groups (n=12). Group 1: bulk technique; Group 2: oblique incremental technique; Group 3: centripetal incremental technique; Group 4: split horizontal incremental technique. The teeth were restored with a total-etch adhesive system and a microhybrid composite resin. After thermocycling and immersion in a 0.2% methylene blue solution for 24 hours, the restorations were sectioned, and dye penetration was evaluated under a stereomicroscope. The microleakage scores (0 to 4) obtained from the occlusal and gingival margins were analysed with Kruskal-Wallis and Mann-Whitney U tests (p<0,05). Results: Incremental placement techniques showed lower microleakage compared with bulk and lower microleakage was seen at occlusal margin compared with gingival margin. However, there were no statistically significant differences among four placement techniques and the margins (p>0,05). Conclusion: Based on the results of the present study, none of the four placement techniques were found to be effective in eliminating marginal microleakage entirely in Class II restorations. All of the placement techniques showed similar results when the cavity margins were located on the enamel.

Comparative Evaluation of Microleakage in Class 2 Cavities Restored with A Nanohybrid Composite Using Three Different Increment Techniques- An in vitro Stereomicroscopic Study

ABSTRACT Context Purpose of the study was to compare the microleakage in class II cavities using Horizontal oblique increment (G1), Centripetal oblique increment (G2) and Oblique increment (G3), techniques Aims To determine ideal incremental placement technique in restoring class II cavity. Methods and Material Class II cavities were prepared in 45 extracted permanent molars. The teeth were restored with nanohybrid composite (Ceram X) and bonding with adhesive systems (Xeno V). Microleakage evaluated after thermocycling of the specimens. Statistical analysis used ANOVA test at the 0.05 level of significance. Results Mean microleakage score of group G1, G2 and G3 was 2.86 ± 1.43, 1.86 ± 1.65 and 2.46 ± 1.50 respectively. Conclusions None of the insertion techniques used in this study was able to prevent microleakage, though the lowest microleakage values were obtained when the centripetal oblique technique was used.