Analog/RF Circuit Design Techniques for Nanometerscale IC Technologies

CMOS evolution introduces several problems in analog design. Gate-leakage mismatch exceeds conventional matching tolerances requiring active cancellation techniques or alternative architectures. One strategy to deal with the use of lower supply voltages is to operate critical parts at higher supply voltages, by exploiting combinations of thin- and thick-oxide transistors. Alternatively, low voltage circuit techniques are successfully developed. In order to benefit from nanometer scale CMOS technology, more functionality is shifted to the digital domain, including parts of the RF circuits. At the same time, analog control for digital and digital control for analog emerges to deal with current and upcoming imperfections

Analog Circuits in Ultra-Deep-Submicron CMOS

Modern and future ultra-deep-submicron (UDSM) technologies introduce several new problems in analog design. Nonlinear output conductance in combination with reduced voltage gain pose limits in linearity of (feedback) circuits. Gate-leakage mismatch exceeds conventional matching tolerances. Increasing area does not improve matching any more, except if higher power consumption is accepted or if active cancellation techniques are used. Another issue is the drop in supply voltages. Operating critical parts at higher supply voltages by exploiting combinations of thin- and thick-oxide transistors can solve this problem. Composite transistors are presented to solve this problem in a practical way. Practical rules of thumb based on measurements are derived for the above phenomena

TAMTAMS: a flexible and open tool for UDSM process-to-system design space exploration

Ultra Deep Sub-Micron (UDSM) processes, as well as beyond CMOS technology choices, influence circuits performance with a chain of consequences through devices, circuits and systems that are difficult to predict. Nonetheless effective design-space exploration enables process optimization and early design organization. We introduce TAMTAMS, a tool based on an open, flexible and simple structure, which allows to predict system level features starting from technology variables. It is modular and based on a clear dependency tree of modules, each related to a model of specific quantities (e.g. device currents, circuit delay, interconnects noise, ....) presented in literature. Models can be compared and sensitivity to parameters observed. We believe our contribution gives a fresh point of view on process-to-system predictors. Though still in development, it already shows flexibility and allows a traceable path of a technology parameter on its way to the system level

COVID-19’s Impact on Climate Change Research and Institutional Resilience in Higher Education in Vermont and Tanzania

The COVID-19 pandemic impacts all sectors of society. It is necessary to understand how higher education institutions (HEIs) react to, adapt to, and build resilience in the face of such a crisis. HEIs around the world shifted how they deliver education to their students and struggled to adapt to a changing economy. Yet, there is little information on how HEIs bolster their resilience to exogenous shocks, like the coronavirus. This study assesses how the COVID-19 crisis impacted institutional resilience and climate change research at four HEIs: the University of Vermont (UVM) and Vermont Law School (VLS) in Vermont, United States of America, and the University of Dar es Salaam (UDSM) and the Nelson Mandela African Institution of Science and Technology (NM-AIST) in Tanzania, East Africa. Resilience in HEIs during COVID-19 provides insight into how such institutions may fare when faced with other crises, like climate change. Furthermore, the current crisis provides evidence of how these institutions can mitigate the effects of crises in the future. In this project, the focus of assessment is resilience related to community and funding in HEIs. Twenty interviews conducted with faculty, staff, and administrators at four institutions indicate that climate change research will continue at HEIs; however, there is concern, especially at institutions in Tanzania, about external funding. While each university differed in its decisions for the continued education of students, the two HEIs in Vermont independently turned to hybrid and online education, while the two institutions in Tanzania continued in-person classes based on a government order. The school most resilient to the COVID-19 shock was VLS. The other three HEIs made incremental changes to ensure educational services and research going forward. The project recommends four strategies to bolster institutional resilience at HEIs: institutions should act as independent communities and universities should strive to diversify their funding sources, guarantee faculty and staff members a voice in decision-making, and create flexible emergency plans disseminated across their institution. If acted on, the lessons learned by HEIs during the COVID-19 crisis can strengthen institutional resilience to other exogenous shocks, like climate change

A Comparative Study of Antioxidant Activities between Fresh and Dry Mushrooms in the Genera Cantharellus and Afrocantharellus from Tanzania

Cantharellus and Afrocantharellus mushrooms are widely consumed in both fresh and dry forms. However, their antioxidant and whether their values changing with drying processes are not known. This study establishes their values and the effect of sun drying on their quality and quantity. Methanolic extracts of five Cantharellus and two Afrocantharellus species were investigated. The investigation used (1,1-diphenyl-2-picrylhydrazyl radical) DPPH as a substrate to determine radical scavenging abilities. Further quantitative analyses for carotenoids, flavonoid, total phenolic compounds and vitamin C content were done using spectrophotometric assay at 515 nm. Comparatively, fresh mushroom had higher vitamin C and Lycopene contents than their dry counterparts with β-carotene. Flavonoid and phenolic compounds were higher in dry forms than those in their fresh counterparts. Radical scavenging ability also varied with fresh forms depicting higher activity compared to dry forms. The variation was low in Afrocantharellus species (0.8% and 0.99%) while it was higher in Cantharellus species (24.12% and 7.52%). The highest ability was observed in fresh forms of Cantharellus pseudocibarius (EC50 < 0.14 mg/ml) while the least ability (EC50 = 0.4 mg/ml) was from dry form of Cantharellus rufopunctatus. This shows that studied mushrooms are rich in antioxidants and their quality and quantities are affected differently in both forms. Both dry and fresh mushrooms are potential sources of natural antioxidants. The portrayed high scav- enging ability by these mushrooms envisages promoting them into potential nutraceutics

An Electromigration and Thermal Model of Power Wires for a Priori High-Level Reliability Prediction

In this paper, a simple power-distribution electrothermal model including the interconnect self-heating is used together with a statistical model of average and rms currents of functional blocks and a high-level model of fanout distribution and interconnect wirelength. Following the 2001 SIA roadmap projections, we are able to predict a priori that the minimum width that satisfies the electromigration constraints does not scale like the minimum metal pitch in future technology nodes. As a consequence, the percentage of chip area covered by power lines is expected to increase at the expense of wiring resources unless proper countermeasures are taken. Some possible solutions are proposed in the paper

X-Ray Peak Broadening Analysis and Optical Studies of ZnO Nanoparticles Derived by Surfactant Assisted Combustion Synthesis

In this paper, synthesis of ZnO nanoparticles is done by a simple and facile surfactant assisted combustion synthesis. The synthesis of ZnO nanoparticles has been prepared using Zinc nitrate as a precursor material, glycine as a fuel with the support of non-ionic surfactant TWEEN 80. The obtained ZnO nanoparticles have been studied using characterization techniques like X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and UV-Vis Spectroscopy. XRD results reveal that the sample is crystalline with a hexagonal wurtzite phase. X-ray peak broadening analysis was used to evaluate the crystallite sizes and lattice strain by the Williamson-Hall (W-H) analysis. Further appropriate physical parameters such as strain, stress, and energy density values were also calculated using W-H analysis with different models, viz, uniform deformation model, uniform deformation stress model and uniform deformation energy density model. Transmission electron microscopy (TEM) result reveals that the ZnO nanoparticles sample is spherical in shape showing particle sizes less than 40 nm. The optical properties of ZnO nanoparticles were studied by UV-Vis spectroscopy. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3102

Rain-Fed Farming System at a Crossroads in Semi-Arid Areas of Tanzania: What Roles do Climate Variability and Change Play?

Positive changes, like adopting drought resistant crop varieties, in the rain-fed farming system (RFFS) in response to climate variability and change enhance system’s ability to support people’s living as opposed to negative changes, like lack of pastures, which put the system at risk of failure in supporting the living. Using participatory rural appraisal (PRA) and household survey, this paper examined the roles of climate variability and change in triggering changes in RFFS. Specifically, the paper: (i) assessed dominant crop and livestock farming system; (ii) assessed the change element of crop and livestock production systems; and (iii) examined factors for the changes in RFFS. A random sample of 388 households was used. Qualitative data analysis was done through content analysis. Binary logistic regression was used to assess factors that explain changes on RFFS. The results showed that dominant crops were different in each village. Secondly, some changes in crop varieties and in livestock grazing arrangements were noted in response to climate variability and change. Unlike the hypothesis (P&gt;0.05), the results demonstrated that warming (ß = -10.61, Wald = 36.26, P ? 0.001) showed highest significant impact on likelihood of adopting new crop varieties relative to other factors. Similarly, drought (ß = 2.16, Wald = 6.82, P ? 0.009) showed highest impact on the likelihood of changing a grazing place. Yet, the changes were constrained by factors like natural resources protective policies, failure of crop varieties to withstand warming and drought, and poor land use management. Therefore, the RFFS was at a crossroads with implications on system sustainability and livelihoods. The government and private interventions should support farmers and agro-pastoralists to manage risks related to the changes in RFFS in response to climate variability and change. Keywords: Climate change, agro-pastoralism, livelihoods, semi-arid, Tanzani