Mean residual life and its association with failure rate

The life time distributions having decreasing, increasing, or upside-down bathtub shaped MRL (mean residual life) are used as models in many applications. Mi (1995) has shown that if a component has a bathtub shape failure rate function, then the MRL is unimodal but the converse does not hold. This paper develops sufficient conditions for the unimodal MRL to imply that the failure rate function has a bathtub shape     

A variability tolerant system-on-chip ready nano-CMOS analogue-to-digital converter

As integrated circuit technologies progress to nanoscale, process variations become relatively large and significantly impact circuit performance. The proactive management of process variation during the design process is critical to ensure effective device yield and to keep manufacturing costs down. In the present scenario, designers are searching for analogue-to-digital converter (ADC) architectures which are nanoscale CMOS processes tolerant. Expectations of the performance of ADCs are continuously increasing along with the progress of digital systems. A process and supply variation tolerant, System-on-Chip (SoC) ready, 1 GS/s, 6-bit flash ADC suitable for integration into nanoscale digital CMOS technologies is presented. The physical design of the ADC has been done using a generic 90 nm Salicide 1.2 V/2.5 V 1 Poly 9 Metal process design kit. Baseline post layout simulation results at nominal supply and threshold voltages are presented. The parasitic-extracted physical design of the ADC is then subjected to a corner-based methodology of process variation. The results show that process variation causes a maximum variation of 10.5% in the integral non-linearity (INL) and 5.7% in the differential non-linearity (DNL), with both INL and DNL being less than 0.5 LSB. The 90 nm ADC consumes a peak power of 5.794 mW and an average power of 3.875 mW. The comparators for the ADC have been designed using the threshold inverting technique. To show technology scalability of the design, the ADC has also been presented using a 45 nm Predictive Technology Models (PTM). At 45 nm, INL = 0.46 LSB, DNL = 0.7 LSB and a sampling rate of 100 MS/s were obtained. The 45 nm ADC consumes a peak power of 45.42 μW, and average power of 8.8 μW.     

Catalytic effect of carbon nanostructures on the hydrogen storage properties of MgH2–NaAlH4 composite

The present investigation describes the hydrogen storage properties of 2:1 molar ratio of MgH₂–NaAlH₄ composite. De/rehydrogenation study reveals that MgH₂–NaAlH₄ composite offers beneficial hydrogen storage characteristics as compared to pristine NaAlH₄ and MgH₂. To investigate the effect of carbon nanostructures (CNS) on the de/rehydrogenation behavior of MgH₂–NaAlH₄ composite, we have employed 2 wt.% CNS namely, single wall carbon nanotubes (SWCNT) and graphene nano sheets (GNS). It is found that the hydrogen storage behavior of composite gets improved by the addition of 2 wt.% CNS. In particular, catalytic effect of GNS + SWCNT improves the hydrogen storage behavior and cyclability of the composite. De/rehydrogenation experiments performed up to six cycles show loss of 1.50 wt.% and 0.84 wt.% hydrogen capacity in MgH₂–NaAlH₄ catalyzed with 2 wt.% SWCNT and 2 wt.% GNS respectively. On the other hand, the loss of hydrogen capacity after six rehydrogenation cycles in GNS + SWCNT (1.5 + 0.5) wt.% catalyzed MgH₂–NaAlH₄ is diminished to 0.45 wt.%.     

Carbon Nanotubes Grown by RF Heating and Their Morphological and Structural Properties

Multiwall and single-wall carbon nanotubes were synthesized on Fe-Co/CaCO₃ and a Fe-Co/MgO catalyst system, respectively, by using two different catalytic chemical vapor deposition methods, external furnace (EF) heating and radio frequency (RF) excitation. The carbon nanotubes synthesized with radio frequency excitation have a smaller outer diameter, fewer layers (smaller outer/inner diameter ratio), and better crystalline properties than the nanotubes grown with external furnace heating. The radio frequency process was found to be responsible for a faster growth rate of the carbon nanotubes over longer periods of time due to a higher localized heating. These findings can be explained by the skin currents induced in the metallic catalytic clusters, which keep the catalysts active for longer periods of time and diminish the amount of noncrystalline carbon formed in the synthesis process.     

Adaptive helical mirror for generation of optical phase singularity

We report a specially designed adaptive mirror that can be bent into a helical shape for generation of an optical phase singularity. The adaptive helical mirror (AHM) reported here is a reflective device that can provide a continuous phase variation of the optical field in the azimuthal direction. The construction details and evaluation of the AHM are presented. A Michelson interferometer is used for the detection of the phase singularity. The AHM can be used for generation of a singular beam having multiple topological charges, positive or negative, just by controlling the excitation voltage of the AHM.     

Budgetary and personnel support levels of psychology departments offering graduate programs.

The present survey of psychology departments was started in August 1968 to provide comparative data relating to such items as average number of students per staff member, average number of secretaries per staff member, and average dollar support per student. A cover letter and questionnaire were sent to the 226 psychology departments in the US offering graduate programs. Timely and complete responses were received from 104 departments. The most important feature of the present survey was the wide variability in support levels of psychology departments. While there was considerable variance on most items, it was of interest that there were no differences as a function of geographic region. Cursory examination with regard to breakdown by athletic conferences, for example, Big Ten, Big Eight, etc., also indicates no large discrepancies with regard to critical items involving number of students per staff member, support per student, etc. The present survey, in addition to providing a comparative base for department heads, may prove helpful to students examining graduate programs and to candidates interviewing for academic positions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of response force and intertrial interval on extinction in children.

Gave 64 4-yr-old boys acquisition and extinction training on a lever-pressing task. The 2 * 2 * 2 * 2 design employed 2 force requirements (4 and 80 oz.) and 2 ITIs (5 and 20 sec.) in both acquisition and extinction. The ITI values had no effect on extinction performance, but number of responses to extinction was an inverse function of the force requirements of both acquisition and extinction. Results are discussed in terms of several theories which are pertinent to the effect of force and ITI on extinction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experimenting with experience: A psychotherapeutic case study.

Applied personal construct theory to a 24-yr-old Australian female who was anxiety-ridden to demonstrate some of its advantages as a therapeutic tool. The limited choices available to the client (because of her oversimplified and confused ways of viewing her world) are described, together with her related anxiety, shame, fear, and depression. Implications for the selection and training of therapists are explored. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)