Impact of Technology Scaling on Leakage Reduction Techniques

CMOS technology is scaling down to meet the performance, production cost, and power requirements of the microelectronics industry. The increase in the transistor leakage current is one of the most important negative side effects of technology scaling. Leakage affects not only the standby and active power consumption, but also the circuit reliability, since it is strongly correlated to the process variations. Leakage current influences circuit performance differently depending on: operating conditions (e.g., standby, active, burn in test), circuit family (e.g., logic or memory), and environmental conditions (e.g., temperature, supply voltage). Until the introduction of high-K gate dielectrics in the lower nanometer technology nodes, gate leakage will remain the dominant leakage component after subthreshold leakage. Since the way designers control subthreshold and gate leakage can change from one technology to another, it is crucial for them to be aware of the impact of the total leakage on the operation of circuits and the techniques that mitigate it. Consequently, techniques that reduce total leakage in circuits operating in the active mode at different temperature conditions are examined. Also, the implications of technology scaling on the choice of techniques to mitigate total leakage are investigated. This work resulted in guidelines for the design of low-leakage circuits in nanometer technologies. Logic gates in the 65nm, 45nm, and 32nm nodes are simulated and analyzed. The techniques that are adopted for comparison in this work affect both gate and subthreshold leakage, namely, stack forcing, pin reordering, reverse body biasing, and high threshold voltage transistors. Aside from leakage, our analysis also highlights the impact of these techniques on the circuit's performance and noise margins. The reverse body biasing scheme tends to be less effective as the technology scales since this scheme increases the band to band tunneling current. Employing high threshold voltage transistors seems to be one of the most effective techniques for reducing leakage with minor performance degradation. Pin reordering and natural stacks are techniques that do not affect the performance of the device, yet they reduce leakage. However, it is demonstrated that they are not as effective in all types of logic since the input values might switch only between the highly leaky states. Therefore, depending on the design requirements of the circuit, a combination, or hybrid of techniques which can result in better performance and leakage savings, is chosen. Power sensitive technology mapping tools can use the guidelines found as a result of the research in the low power design flow to meet the required maximum leakage current in a circuit. These guidelines are presented in general terms so that they can be adopted for any application and process technology

Comparison of diagnostic indices of MRI and EMG in diagnosis of lumbar radiculopathy

BACKGROUND: lumbosacral radiculopathy is one of the most common disorders that can be examined by neurologists. Electromyography (EMG) and magnetic resonance imaging (MRI) are used to inspect this disease; however, the application of MRI and EMG in patients with back pain is still under study. This study was designed and implemented to compare the diagnostic values of MRI and EMG in the diagnosis of lumbar radiculopathy. METHODS: This was cross-sectional study which included 62 patients with suspected lumbosacral radiculopathy in a referral neurology clinic in Sanandaj, Iran, in 2009-2010. EMG was considered as the gold standard test. Inclusion criteria were being older than 20 years of age, and suffering from back pain or radicular pain in the lower limbs for more than four weeks. Data were entered into SPSS software and the diagnostic indices and agreement were calculated. RESULTS: The percentage of agreement between MRI and EMG results were calculated as 80.6%. The sensitivity of MRI compared with EMG at different levels was calculated between 44.4% and 79.6% and its specificity was calculated between 46.1% and 94.3%. In total, sensitivity and specificity of MRI were 68.9% and 86.3%, respectively. The Lasègue's sign, used for detection of disc herniation, had the sensitivity, specificity, and positive and negative predictive value of 28.8%, 50%, 75%, and 11.9%, respectively. CONCLUSION: MRI and EMG tests have no superiority over one another for the evaluation of lumbar radiculopathy and it is necessary to do both. The Lasègue's sign is also not an appropriate test for detection of lumbar spine disc herniation, and it is not helpful in diagnosing or ruling out the disease

Oil palm shell as an agricultural solid waste in artificial lightweight aggregate concrete

The aim of this study was to produce a sustainable construction material by incorporating an agricultural solid waste, namely oil palm shell (OPS), in an artificial lightweight aggregate concrete. For this purpose, in a structural lightweight aggregate concrete made of expanded clay, the lightweight aggregate was substituted with OPS in 0, 25 and 50% by volume. Properties such as compressive strength under different curing conditions, as well as density, splitting tensile and flexural strengths, modulus of elasticity and drying shrinkage of expanded clay–OPS concretes were measured and discussed. The test results showed that partial substitution of expanded clay by OPS increased the density, compressive strength, specific strength (compressive strength to weight ratio), as well as splitting tensile and flexural strengths of lightweight concrete. However, it was observed that the modulus of elasticity decreased by about 4 and 13% in the 25 and 50% substitution levels, respectively. The expanded clay–OPS concretes showed greater drying shrinkage strain compared to expanded clay lightweight concrete. In addition, it was found that the sensitivity of compressive strength of concretes containing OPS to the lack of curing is due to high drying shrinkage and consequently micro-cracks formation in the interfacial transaction zone of the concretes