27 research outputs found
Error control coding for semiconductor memories
All modern computers have memories built from VLSI RAM chips.
Individually, these devices are highly reliable and any single chip
may perform for decades before failing. However, when many of the
chips are combined in a single memory, the time that at least one
of them fails could decrease to mere few hours. The presence of
the failed chips causes errors when binary data are stored in and
read out from the memory. As a consequence the reliability of the
computer memories degrade. These errors are classified into hard
errors and soft errors. These can also be termed as permanent and
temporary errors respectively.
In some situations errors may show up as random errors, in
which both 1-to-O errors and 0-to-l errors occur randomly in a
memory word. In other situations the most likely errors are
unidirectional errors in which 1-to-O errors or 0-to-l errors may
occur but not both of them in one particular memory word.
To achieve a high speed and highly reliable computer, we need
large capacity memory. Unfortunately, with high density of
semiconductor cells in memory, the error rate increases
dramatically. Especially, the VLSI RAMs suffer from soft errors
caused by alpha-particle radiation. Thus the reliability of
computer could become unacceptable without error reducing schemes.
In practice several schemes to reduce the effects of the memory
errors were commonly used. But most of them are valid only for hard errors. As an efficient and economical method, error control
coding can be used to overcome both hard and soft errors.
Therefore it is becoming a widely used scheme in computer industry
today.
In this thesis, we discuss error control coding for
semiconductor memories. The thesis consists of six chapters.
Chapter one is an introduction to error detecting and correcting
coding for computer memories. Firstly, semiconductor memories and
their problems are discussed. Then some schemes for error reduction
in computer memories are given and the advantages of using error
control coding over other schemes are presented.
In chapter two, after a brief review of memory organizations,
memory cells and their physical constructions and principle of
storing data are described. Then we analyze mechanisms of various
errors occurring in semiconductor memories so that, for different
errors different coding schemes could be selected.
Chapter three is devoted to the fundamental coding theory. In
this chapter background on encoding and decoding algorithms are
presented.
In chapter four, random error control codes are discussed.
Among them error detecting codes, single* error correcting/double
error detecting codes and multiple error correcting codes are
analyzed. By using examples, the decoding implementations for
parity codes, Hamming codes, modified Hamming codes and majority
logic codes are demonstrated. Also in this chapter it was shown
that by combining error control coding and other schemes, the reliability of the memory can be improved by many orders.
For unidirectional errors, we introduced unordered codes in
chapter five. Two types of the unordered codes are discussed. They
are systematic and nonsystematic unordered codes. Both of them are
very powerful for unidirectional error detection. As an example of
optimal nonsystematic unordered code, an efficient balanced code
are analyzed. Then as an example of systematic unordered codes
Berger codes are analyzed. Considering the fact that in practice
random errors still may occur in unidirectional error memories,
some recently developed t-random error correcting/all
unidirectional error detecting codes are introduced. Illustrative
examples are also included to facilitate the explanation.
Chapter six is the conclusions of the thesis.
The whole thesis is oriented to the applications of error
control coding for semiconductor memories. Most of the codes
discussed in the thesis are widely used in practice. Through the
thesis we attempt to provide a review of coding in computer
memories and emphasize the advantage of coding. It is obvious that
with the requirement of higher speed and higher capacity
semiconductor memories, error control coding will play even more
important role in the future
Unimodal productivity-biodiversity relationship along the gradient of multidimensional resources across Chinese grasslands
Resources can affect plant productivity and biodiversity simultaneously and thus are key drivers of their relationships in addition to plant-plant interactions. However, most previous studies only focused on a single resource while neglecting the nature of resource multidimensionality. Here we integrated four essential resources for plant growth into a single metric of resource diversity (RD) to investigate its effects on the productivity-biodiversity relationship (PBR) across Chinese grasslands. Results showed that habitats differing in RD have different PBRs â positive in low-resource habitats, but neutral in medium- and high-resource onesâwhile collectively, a weak positive PBR was observed. However, when excluding direct effects of RD on productivity and biodiversity, PBR in high-resource habitats became negative, which leads to a unimodal instead of a positive PBR along the RD gradient. By integrating resource effects and changing plant-plant interactions into a unified framework with the RD gradient, our work contributes to uncovering underlying mechanisms for inconsistent PBRs at large scales
Spatiotemporal transcriptomic atlas of mouse organogenesis using DNA nanoball-patterned arrays.
Spatially resolved transcriptomic technologies are promising tools to study complex biological processes such as mammalian embryogenesis. However, the imbalance between resolution, gene capture, and field of view of current methodologies precludes their systematic application to analyze relatively large and three-dimensional mid- and late-gestation embryos. Here, we combined DNA nanoball (DNB)-patterned arrays and in situ RNA capture to create spatial enhanced resolution omics-sequencing (Stereo-seq). We applied Stereo-seq to generate the mouse organogenesis spatiotemporal transcriptomic atlas (MOSTA), which maps with single-cell resolution and high sensitivity the kinetics and directionality of transcriptional variation during mouse organogenesis. We used this information to gain insight into the molecular basis of spatial cell heterogeneity and cell fate specification in developing tissues such as the dorsal midbrain. Our panoramic atlas will facilitate in-depth investigation of longstanding questions concerning normal and abnormal mammalian development.This work is part of the ââSpatioTemporal Omics Consortiumââ (STOC) paper package. A list of STOC members is available at: http://sto-consortium.org. We would
like to thank the MOTIC China Group, Rongqin Ke (Huaqiao University, Xiamen,
China), Jiazuan Ni (Shenzhen University, Shenzhen, China), Wei Huang (Center
for Excellence in Brain Science and Intelligence Technology, Chinese Academy
of Sciences, Shanghai, China), and Jonathan S. Weissman (Whitehead Institute,
Boston, USA) for their help. This work was supported by the grant of Top Ten
Foundamental Research Institutes of Shenzhen, the Shenzhen Key Laboratory
of Single-Cell Omics (ZDSYS20190902093613831), and the Guangdong Provincial Key Laboratory of Genome Read and Write (2017B030301011); Longqi Liu
was supported by the National Natural Science Foundation of China
(31900466) and Miguel A. Estebanâs laboratory at the Guangzhou Institutes of
Biomedicine and Health by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA16030502), National Natural Science Foundation of China (92068106), and the Guangdong Basic and Applied Basic Research
Foundation (2021B1515120075).S
Cell transcriptomic atlas of the non-human primate Macaca fascicularis.
Studying tissue composition and function in non-human primates (NHPs) is crucial to understand the nature of our own species. Here we present a large-scale cell transcriptomic atlas that encompasses over 1 million cells from 45 tissues of the adult NHP Macaca fascicularis. This dataset provides a vast annotated resource to study a species phylogenetically close to humans. To demonstrate the utility of the atlas, we have reconstructed the cell-cell interaction networks that drive Wnt signalling across the body, mapped the distribution of receptors and co-receptors for viruses causing human infectious diseases, and intersected our data with human genetic disease orthologues to establish potential clinical associations. Our M.âfascicularis cell atlas constitutes an essential reference for future studies in humans and NHPs.We thank W. Liu and L. Xu from the Huazhen Laboratory Animal Breeding
Centre for helping in the collection of monkey tissues, D. Zhu and H. Li from the Bioland
Laboratory (Guangzhou Regenerative Medicine and Health Guangdong Laboratory) for
technical help, G. Guo and H. Sun from Zhejiang University for providing HCL and MCA gene
expression data matrices, G. Dong and C. Liu from BGI Research, and X. Zhang, P. Li and C. Qi
from the Guangzhou Institutes of Biomedicine and Health for experimental advice or providing
reagents. This work was supported by the Shenzhen Basic Research Project for Excellent
Young Scholars (RCYX20200714114644191), Shenzhen Key Laboratory of Single-Cell Omics
(ZDSYS20190902093613831), Shenzhen Bay Laboratory (SZBL2019062801012) and Guangdong Provincial Key Laboratory of Genome Read and Write (2017B030301011). In
addition, L.L. was supported by the National Natural Science Foundation of China (31900466),
Y. Hou was supported by the Natural Science Foundation of Guangdong Province
(2018A030313379) and M.A.E. was supported by a Changbai Mountain Scholar award
(419020201252), the Strategic Priority Research Program of the Chinese Academy of Sciences
(XDA16030502), a Chinese Academy of SciencesâJapan Society for the Promotion of Science
joint research project (GJHZ2093), the National Natural Science Foundation of China
(92068106, U20A2015) and the Guangdong Basic and Applied Basic Research Foundation
(2021B1515120075). M.L. was supported by the National Key Research and Development
Program of China (2021YFC2600200).S
Design of intelligent wireless monitoring platform
Taking STC89C52 single chip microcomputer as the controller, the communication carrier adopts low-power Bluetooth 4.0, LCD12864 display screen as the human-computer interaction interface, open-loop stepping motor and closed-loop steering gear as the action actuator, reflective infrared sensor and reflective photoelectric sensor as the detection sensing system, integrating electronics, machinery This set of intelligent wireless monitoring platform developed by *software and other aspects realizes three functions: wireless remote control monitoring, automatic panoramic detection and automatic intrusion alarm. The design has strong practicability. The whole system has the characteristics of low cost and low power consumption. It can play an important role in the field of security
Effects of Curing Methods on the Permeability and Mechanism of Cover Concrete
 Curing methods are one of the most important factors in determining the quality and compactness of cover concrete. The effect of curing methods on the water absorption and sorptivity coefficient of cover concrete with the substitution ratio of fly ash (FA) and ground granulated blast slag (GGBS) for cement between 30 and 40 wt % was studied by capillary water absorption test. The vacuum saturation test and mercury intrusion test were employed to characterize these differences in the pore structure of cover concrete under different curing methods. With further analysis of the compactness of microstructure by SEM, the mechanism of the impact of curing methods on the permeability of cover concrete was revealed. The results obtained indicate that the effect of curing methods on the water absorption, sorptivity coefficient and porosity of cover concrete shows the trend of natural curing > cover curing > water curing > standard curing. It is also shown that reasonable curing is advantageous to reduce the porosity and permeability of cover concrete. In natural curing conditions, the appearance of porosity increasing and pore structure coarsening is more critical for cover concrete with mineral admixtures than for pure cement concrete. Therefore, the permeability of cover concrete with mineral admixtures is more sensitive to the early-age curing methods
Fluidic aligned, dense SWNTs arrays as potential die adhesive and thermal interface material
National Natural Science Foundation of China [61071010]Purpose - The purpose of this paper is to report a simple, room temperature approach to assemble dense, vertically aligned single-walled carbon nanotubes (SWNTs) between a chip and its substrate acting as a kind of thermal interface material by virtue of better mechanical and thermal properties. Design/methodology/approach - Two silicon chips, with shallow trenches about 2 mu m deep on the surface, were pressed together face to face with the trench direction perpendicular to each other. SWNT aqueous solution was driven into the gap between the two chips by capillary force. Later, the sample was baked to remove the moisture completely. Findings - SWNTs beams were found to be assembled in the gap and have their two ends bonding with the interface of the two chips, respectively. The shear strength of the two chips was measured, and the thermal conductivity of the stacked chip-SWNTs-chip was tested using a laser flash method. In result, shear strength up to about 100 kPa, and an average thermal conductivity of 19.3 W.m(-1).K-1 were demonstrated. Originality/value - The paper proposes an approach to grown dense SWNT array bridging a chip and its substrate, and these SWNTs have potential capability to provide mechanical strength and higher thermal conductance instead of commercial thermal interface materials