27,439 research outputs found
Asynchronous Early Output Dual-Bit Full Adders Based on Homogeneous and Heterogeneous Delay-Insensitive Data Encoding
This paper presents the designs of asynchronous early output dual-bit full
adders without and with redundant logic (implicit) corresponding to homogeneous
and heterogeneous delay-insensitive data encoding. For homogeneous
delay-insensitive data encoding only dual-rail i.e. 1-of-2 code is used, and
for heterogeneous delay-insensitive data encoding 1-of-2 and 1-of-4 codes are
used. The 4-phase return-to-zero protocol is used for handshaking. To
demonstrate the merits of the proposed dual-bit full adder designs, 32-bit
ripple carry adders (RCAs) are constructed comprising dual-bit full adders. The
proposed dual-bit full adders based 32-bit RCAs incorporating redundant logic
feature reduced latency and area compared to their non-redundant counterparts
with no accompanying power penalty. In comparison with the weakly indicating
32-bit RCA constructed using homogeneously encoded dual-bit full adders
containing redundant logic, the early output 32-bit RCA comprising the proposed
homogeneously encoded dual-bit full adders with redundant logic reports
corresponding reductions in latency and area by 22.2% and 15.1% with no
associated power penalty. On the other hand, the early output 32-bit RCA
constructed using the proposed heterogeneously encoded dual-bit full adder
which incorporates redundant logic reports respective decreases in latency and
area than the weakly indicating 32-bit RCA that consists of heterogeneously
encoded dual-bit full adders with redundant logic by 21.5% and 21.3% with nil
power overhead. The simulation results obtained are based on a 32/28nm CMOS
process technology
Latency Optimized Asynchronous Early Output Ripple Carry Adder based on Delay-Insensitive Dual-Rail Data Encoding
Asynchronous circuits employing delay-insensitive codes for data
representation i.e. encoding and following a 4-phase return-to-zero protocol
for handshaking are generally robust. Depending upon whether a single
delay-insensitive code or multiple delay-insensitive code(s) are used for data
encoding, the encoding scheme is called homogeneous or heterogeneous
delay-insensitive data encoding. This article proposes a new latency optimized
early output asynchronous ripple carry adder (RCA) that utilizes single-bit
asynchronous full adders (SAFAs) and dual-bit asynchronous full adders (DAFAs)
which incorporate redundant logic and are based on the delay-insensitive
dual-rail code i.e. homogeneous data encoding, and follow a 4-phase
return-to-zero handshaking. Amongst various RCA, carry lookahead adder (CLA),
and carry select adder (CSLA) designs, which are based on homogeneous or
heterogeneous delay-insensitive data encodings which correspond to the
weak-indication or the early output timing model, the proposed early output
asynchronous RCA that incorporates SAFAs and DAFAs with redundant logic is
found to result in reduced latency for a dual-operand addition operation. In
particular, for a 32-bit asynchronous RCA, utilizing 15 stages of DAFAs and 2
stages of SAFAs leads to reduced latency. The theoretical worst-case latencies
of the different asynchronous adders were calculated by taking into account the
typical gate delays of a 32/28nm CMOS digital cell library, and a comparison is
made with their practical worst-case latencies estimated. The theoretical and
practical worst-case latencies show a close correlation....Comment: arXiv admin note: text overlap with arXiv:1704.0761
Estimation of biomass density and carbon storage in the forests of Andhra Pradesh, India, with emphasis on their deforestation and degradation conditions
The current study evaluates the growing stock, biomass and carbon content of Andhra Pradesh state’s forest (India) along with its current status of forest degradation and loss. For this purpose, the study used the growing stock data collected by state forest department in 2010 for the calculation of biomass and carbon storage using the standard conversion and expansion factors given by IPCC. The analysis shows low biomass and carbon values for the state’s forest in comparison to the mean values recorded in different studies made for Andhra Pradesh. It is also observed to be lower when compared with the average carbon and biomass for Indian forests. Overall, the analysis showed degradation and loss of forest in the state, coupled with reduction in biomass and
carbon sink
Source Regions of Coronal Mass Ejections
Observations of the solar corona with the Large Angle Spectrometric
Coronograph (LASCO) and Extreme ultraviolet Imaging Telescope (EIT) instruments
on the Solar and Heliospheric Observatory (SOHO) provide an unprecedented
opportunity to study coronal mass ejections (CMEs) from their initiation
through their evolution out to 30 \rsun. The objective of this study is to gain
an understanding of the source regions from which the CMEs emanate. To this
end, we have developed a list of 32 CMEs whose source regions are located on
the solar disk and are well observed in EIT 195 {\AA} data during the period
from so lar minimum in January 1996 through the rising part of the cycle in May
1998. We compare the EIT source regions with photospheric magnetograms from the
Michelson Doppler Imager (MDI) instrument on SOHO and the NSO/Kitt Peak
Observatory and also with H data from various sources. The overall
results of our study show that 41% of the CME related transients observed are
associated with active regions and have no prominence eruptions, 44% are
associated with eruptions of prominences embedded in active regions and 15% are
associated with eruptions of prominences outside active regions. Those CMEs
that do not involve prominence eruptions originate in active regions both with
and without prominences. We describe 6 especially well observed events. These
case studies suggest that active region CMEs (without eruptive prominences) are
associated with active regions with lifetimes between 11--80 days. They are
also often associated with small scale emerging or cancelling flux over
timescales of 6--7 hours. CMEs associated with active region prominence
eruptions, on the other hand, are typically associated with old active regions
with lifetimes 6-7 months.Comment: Accepted for publication in ApJ, scheduled for Nov 1, 2001 issu
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