Design and Analysis of Low-power SRAMs

The explosive growth of battery operated devices has made low-power design a priority in recent years. Moreover, embedded SRAM units have become an important block in modern SoCs. The increasing number of transistor count in the SRAM units and the surging leakage current of the MOS transistors in the scaled technologies have made the SRAM unit a power hungry block from both dynamic and static perspectives. Owing to high bitline voltage swing during write operation, the write power consumption is dominated the dynamic power consumption. The static power consumption is mainly due to the leakage current associated with the SRAM cells distributed in the array. Moreover, as supply voltage decreases to tackle the power consumption, the data stability of the SRAM cells have become a major concern in recent years. To reduce the write power consumption, several schemes such as row based sense amplifying cell (SAC) and hierarchical bitline sense amplification (HBLSA) have been proposed. However, these schemes impose architectural limitations on the design in terms of the number of words on a row. Beside, the effectiveness of these methods is limited to the dynamic power consumption. Conventionally, reduction of the cell supply voltage and exploiting the body effect has been suggested to reduce the cell leakage current. However, variation of the supply voltage of the cell associates with a higher dynamic power consumption and reduced cell data stability. Conventionally qualified by Static Noise Margin (SNM), the ability of the cell to retain the data is reduced under a lower supply voltage conditions. In this thesis, we revisit the concept of data stability from the dynamic perspective. A new criteria for the data stability of the SRAM cell is defined. The new criteria suggests that the access time and non-access time (recovery time) of the cell can influence the data stability in a SRAM cell. The speed vs. stability trade-off opens new opportunities for aggressive power reduction for low-power applications. Experimental results of a test chip implemented in a 130 nm CMOS technology confirmed the concept and opened a ground for introduction of a new operational mode for the SRAM cells. We introduced a new architecture; Segmented Virtual Grounding (SVGND) to reduce the dynamic and static power reduction in SRAM units at the same time. Thanks to the new concept for the data stability in SRAM cells, we introduced the new operational mode of Accessed Retention Mode (AR-Mode) to the SRAM cell. In this mode, the accessed SRAM cell can retain the data, however, it does not discharge the bitline. The new architecture outperforms the recently reported low-power schemes in terms of dynamic power consumption, thanks to the exclusive discharge of the bitline and the cell virtual ground. In addition, the architecture reduces the leakage current significantly since it uses the back body biasing in both load and drive transistors. A 40Kb SRAM unit based on SVGND architecture is implemented in a 130 nm CMOS technology. Experimental results exhibit a remarkable static and dynamic power reduction compared to the conventional and previously reported low-power schemes as expect from the simulation results

Effect of TiO2 nanoparticle on wicking phenomenon in PAN nanofiber yarns

In this research, different concentrations of PAN polymeric solutions with various percentages of TiO2 nanoparticles were electrospun to investigate vertical wicking of PAN/TiO2 nanofiber yarns. Results showed by the presence of nanoparticles in the nanofiber structure, the capillary rise increased, although by increasing concentrations of polymeric solutions and nanoparticles, capillary rises were statistically insignificant

Effect of different rates of zinc on root morphological traits among different upland rice landraces in Malaysia

Billions of people globally are estimated to suffer from Zn deficiency due to their low dietary intake, especially those with rice. Global efforts are under way to improve the Zn concentrations in rice to increase Zn in diets. Zinc uptake in relation to morphological root parameters among 7 upland rice varieties were studied by conducting a solution culture experiment using modified Yoshida solution in Agriculture Faculty of University Putra Malaysia. Five Zinc levels were developed by the addition of 0, 5, 10, 20, 30 mg L-1 ZnSO4. Seedlings were harvested in week 4. Zn uptake in roots and shoots of upland rice showed significant differences among all varieties. Root Zn uptake significantly increased at all rates. Other root parameters (length, average diameter, surface area, volume, and number of root tips) did not show any significant differences in 0 to 20 mg Zn L-1, but they decreased significantly in 30 mg Zn L-1 in 4th week of observation. In addition shoot Zn uptake like other root parameters followed this trend and decreased significantly in 30 mg Zn L-1 in 4th week of observation

Effects of application of different sources of Zn and composts on Zn concentration and uptake by upland rice

Global efforts are under way to improve the Zn concentrations in rice to increase Zn in human diets. Therefore, this pot experiment was conducted to examine the effects of Zn sources and different composts on two upland rice varieties. This study was a 3 factors experiment with 3 replications arrange in RCBD. Experimental units include: 2 selected upland rice varieties with highest and lowest Zn uptake, 12 treatments, including 3 types of composts (oil palm compost, vermicompost and poultry compost) and 2 different sources of Zn (ZnS04 and Zn-EDTA). Soil samples were analyzed before and after harvest. The plants were harvested 16-20 weeks after planting and analysed. All types of composts showed positive effects on Zn concentration and uptake in all parts of rice. Vermicompost is the most effective compost among these three composts. Both inorganic Zn sources used showed almost the same Zn concentration and uptake by rice in this experiment. The magnitude of Zn uptake response was magnified when zinc sulphate was applied along with organic compost. Application of Zn-amended organic composts increased the percentage distribution of Zn in grain more than the application of ZnSO4 or Zn-EDTA alone

Upland rice root parameters and their relationship on utilizing different levels of applied zinc

Global efforts are under way to improve the Zn concentrations in rice to increase Zn in diets. Zinc uptake in relation to morphological root parameters among 7 upland rice varieties was studied by conducting a solution culture experiment using modified Yoshida solution in Agriculture Faculty of University Putra Malaysia. Five zinc levels were developed by the addition of 0, 5, 10, 20, 30 mgL-1 ZnSO4. Seedlings were harvested in week 4. Zn uptake in roots of upland rice showed significant differences among all varieties. Zn uptake significantly increased at all rates. Other root parameters (length, average diameter, surface area, volume, and number of root tips) did not show any significant differences in 0 to 20 mg ZnL-1, but they decreased significantly in 30 mg ZnL-1 in 4th week of observation

Elucidating the expression of zinc transporters involved in zinc uptake by upland rice landraces in Malaysia

Zinc (Zn) is an essential nutrient that plays important roles in numerous physiological processes in plants, serving as a cofactor for many enzymes and as the key structural motifs in transcriptional regulatory proteins. A deficiency of Zn, therefore, decreases growth, but excess Zn has significant toxicity to biological systems through metal-based cytotoxic reactions. Zinc uptake in relation to gene expression was studied by conducting a solution culture experiment. Two upland rice landraces were selected from Malaysia. Germinated seedlings were grown in Yoshida standard solution culture for 2 weeks. Plants were transferred into a modified nutrient culture for a further 2 weeks. (The ZnSO4 was omitted from the solution to induce Zn deficiency). Total RNA were extracted from shoots and roots. Quantitative analysis of 7 genes (OsZIP1, OsZIP3, OsZIP4, OsZIP5, OsZIP8, α-tubulin, and 18srRNA) using commercial primers were carried out by Q-PCR. Results of this study in roots showed over expression of OsZIP4, OsZIP1, OsZIP8 and OsZIP5 under Zn deficiency condition, but the expression of OsZIP3 was not shown. OsZIP4, OsZIP8 and OsZIP5 were expressed in the shoots, while OsZIP1 and OsZIP3 were not up regulated by Zn deficiency (OsZIP3 was not expressed in roots and shoots). OsZIPs were expressed more in the Zn-deficient Bertih than in the Zn-deficient Nabawan variety

Design and Analysis of Low-power SRAMs

I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners

In vitro culture of Aloe vera barbadensis mill

Aloe vera is an important medicinal plant species belonging to the family Liliaceae.The gel of Aloe vera makes an excellent treatment for wounds, burns and other skin disorders. Tissue culture technique offers certain advantages over traditional methods of propagation, including making exact copies of the plant;quickly producing mature plants andregeneratingtissue of genetically modified plant. In traditional method of propagation and culture of Aloe verausing adventitious shoots and/or buds the frequency of formation of vegetative shoots is very low. Due to increasing industrial demand for Aloe vera for production of gel, the development of in-vitroregeneration system is necessary to produce unique form and true-to-type plant. The overall goal of this study was to develop a method of in-vitro micropropagation of Aloe vera through shoot regeneration from segment disk explants,follow by rooting and acclimatization. In the experiment on detecting the most suitable explant for in-vitro propagation, leaf tips, ring cross-section discs, adaxial leaf parts, abaxial leaf parts, segment nodal discs and terminal buds of Aloe vera plant were selected for culturing on MS media with and without 6-benzilaminopurine (BAP)and Kinetin (Kin) as plant growth regulator. Among the parts mentioned above, only segment nodal discs regenerated shootson MS medium supplemented with hormones. In determining the most suitable sterilization treatment for reducing explants contamination, without the use of mercuric chloride, explants were treated with different concentrations of sodium hypochlorite(0.525%, 0.787%, 1.050%, 1.312%, and 1.575%).In this method sodium hypochlorite was an alternative to mercuric chloride. The explants were exposed to each concentration for a period of 20 minutes with vigorous and constant shaking. By Kruskal-Walis test (a nonparametric test), 1.050% sodium hypochlorite gave the highest number (91.7%) of alive and sterilized explants with regeneration potential.Based on theseresults, segment nodal discs of Aloe vera were sterilized and cultured on MS media supplemented with different concentrations ofBAP (0, 0.5,1,2,4 and5 mg/l). Data showed that, the number of shoots, increased with the highest mean of shoots per explant on medium supplemented with 4 mg/l BAP and the highest mean percentage of explants producing 100% shootswas obtained on medium with 4 mg/l BAP.The analysis of variance showed significant difference between the treatments. Different concentrations of Kincontrol, 0.5, 1, 2 and 4 mg/l (0, 2.33μM, 4.66μM, 9.30μM and 18.6 μM) were also assessed on shoot multiplication from segment nodal disks.The results reveal that there was no significant difference among different concentrations of Kinetin.Shoot multiplication from segment nodal disks was also studied using different concentrations of Thidiazuron (TDZ) either alone or in combination with Indole-3-butyric acid (IBA). The concentrations of TDZ were 1, 2, 3 and 4 mg/l and five concentrations of IBA were 0, 0.22, 0.57, 1.15 and 2.30 mg/l. Hormone-free MS medium (MSO)was used as control. The highest mean number of shoots proliferated per explant (5.10) was observed on moderate concentration of 2 mg/l TDZ and 1.15 mg/lIBA after eight weeks of culture, which was significantly different with the rest of the treatments. In the study on root induction MS media contain different concentrations of IBA were used. The explants which were previously regenerated using BAP and TDZ - IBA subsequently were cultured on MS media with different concentrations of IBA 0.22, 0.57, 1.15 and 2.30 mg/l. Results showed that the highest mean number of root per explant (5.06) was attained in MS medium supplemented with 1.15 mg/l IBA Highest percentage of root regeneration (100 %) was observed in two concentrations of 1.15 mg/l and 2.30 mg/l IBA followed by 93.33% in 0.57 mg/l IBA. Moreover, highest mean length of roots (14.05 cm) was found in MS medium supplemented with 0.57 mg/l IBA. In the acclimatization study, by applying one-sample Kolmogorove-Smirnove test normality of data was confirmed. On the other hand, the results showed that the plantlets were successfully (96.66 ± 3.33 %) transferred after rooting of microshoots. Using one-sample T-test, no significant difference was revealed between 96.66 % and 100% value of acclimatization of plantlets

Essays in Empirical Asset Pricing

In my dissertation, I study different channels through which shocks in the real economy can affect financial asset returns. The first chapter studies immigration policy shocks as a source of risk in the financial markets. Using a comprehensive set of data on H-1B visa petitions, I construct an occupation-level measure for labor market competition between skilled immigrant and local workers. I find that stocks of firms with a high share of labor for which skilled immigrants are close substitutes outperform their peers with a low share. I show that this premium is explained by firms' differential exposures to priced immigration policy shocks that shift the supply of skilled immigrant labor. These shocks differentially impact wages across occupations, leading to an asymmetric effect on firms' cash flows through labor expenditure. In the second chapter, based on a joint work with Esther Eiling and Raymond Kan, we investigate the asset pricing implications of sectoral labor reallocation shocks that change the optimal allocation of workers across industries. We find that a proxy for this type of labor market shocks has very strong predictive power for future stock market returns. We propose a production-based asset pricing model that links the return predictability to time-varying labor adjustment costs. When human capital is tied to the industry, hiring workers from other industries involves more search and training costs. Hence, sectoral reallocation shocks lead to lower returns to hiring and therefore lower future stock returns. In the third chapter, we identify inter-sectoral trade networks as important conduits of industry shocks and provide the first explanation for an empirical regularity in the term structure of industry returns. Specifically, my co-author Mikhail Simutin and I show that industry shocks propagating along this network can feed back to the originating industry, causing an "echo'' - intermediate-term autocorrelation in returns. Adopting techniques from graph theory, we find that the strength of the trade network feedback is a crucial determinant of the echo effect in industry returns. Consistent with limited-information models, the relation between feedback strength and echo profits is strongest in industries with information diffusion frictions along the feedback loop.Ph.D

TiltedBERT: Resource Adjustable Version of BERT

In this paper, a novel adjustable fine-tuning method is proposed that improves the inference time of BERT model on downstream tasks. The proposed method detects the more important word vectors in each layer by the proposed Attention Context Contribution (ACC) metric and eliminates the less important word vectors by the proposed strategy. In the TiltedBERT method the model learns to work with a considerably lower number of Floating Point Operations (FLOPs) than the original BERTbase model. The proposed method does not need training from scratch, and it can be generalized to other transformer-based models. The extensive experiments show that the word vectors in higher layers have less contribution that can be eliminated and improve the inference time. Experimental results on extensive sentiment analysis, classification and regression datasets, and benchmarks like IMDB and GLUE showed that TiltedBERT is effective in various datasets. TiltedBERT improves the inference time of BERTbase up to 4.8 times with less than 0.75% accuracy drop on average. After the fine-tuning by the offline-tuning property, the inference time of the model can be adjusted for a wide range of Tilt-Rate selections. Also, A mathematical speedup analysis is proposed to estimate TiltedBERT method's speedup accurately. With the help of this analysis, a proper Tilt-Rate value can be selected before fine-tuning and during offline-tuning phases