318 research outputs found
Spatially-Coupled QDLPC Codes
Spatially-coupled (SC) codes is a class of convolutional LDPC codes that has
been well investigated in classical coding theory thanks to their high
performance and compatibility with low-latency decoders. We describe toric
codes as quantum counterparts of classical two-dimensional spatially-coupled
(2D-SC) codes, and introduce spatially-coupled quantum LDPC (SC-QLDPC) codes as
a generalization. We use the convolutional structure to represent the parity
check matrix of a 2D-SC code as a polynomial in two indeterminates, and derive
an algebraic condition that is both necessary and sufficient for a 2D-SC code
to be a stabilizer code. This algebraic framework facilitates the construction
of new code families. While not the focus of this paper, we note that small
memory facilitates physical connectivity of qubits, and it enables local
encoding and low-latency windowed decoding. In this paper, we use the algebraic
framework to optimize short cycles in the Tanner graph of 2D-SC HGP codes that
arise from short cycles in either component code. While prior work focuses on
QLDPC codes with rate less than 1/10, we construct 2D-SC HGP codes with small
memory, higher rates (about 1/3), and superior thresholds.Comment: 25 pages, 7 figure
Texture Segmentation using LBP embedded Region Competition
In this paper, we modify the region competition method to segment textures. First, local Binary pattern (LBP) histogram is adopted to capture the texture information. Then, considering the specific goal of texture segmentation, we propose new assumption about region competition and rewrite the energy function based on LBP histograms. We also develop the two-stage iterative algorithm to make our energy converge to a local minimum. Because of the fast LBP operator and nonparametric histogram model, we can simplify the step of parameter estimating, which is always the most time-consuming. Besides, LBP' s high performance for texture characterization helps to make our method more suitable for texture segmentation problem. Experiments show that the performance of our proposed method is promising, and a robust and fast segmentation of texture images is obtained
Government R&D subsidies and the manipulative innovation strategy of Chinese renewable energy firms
Renewable energy technology innovation is the key to alleviating
environmental issues. The Chinese government promotes corporate
innovation in the renewable energy industry by providing
R&D subsidies. This paper investigates the impact of R&D subsidies
on innovation strategies in Chinese renewable energy listed
firms from 2008 to 2017. The results show that R&D subsidies
induce firms to adopt a manipulative innovation strategy that
increases innovation quantity but reduces innovation quality,
especially in regions with low marketization or unfair competition.
We further find that the choice of manipulative innovation strategy
is caused by the flawed subsidy distribution system and
examination procedures of subsidy use. This paper deepens the
understanding of the relationship between government subsidies
and corporate innovation strategy and provides new enlightenments
for emerging economies to enhance the effectiveness of
subsidy policies
Smartphone data usage : downlink and uplink asymmetry
Mobile phone usage has changed significantly over the past few years
and smartphone data usage is still not well understood on a statistically
significant scale. This Letter analyses 2.1 million smartphone usage
data values and explore the current wireless downlink–uplink
demand asymmetry for different time periods and across different
radio access networks. The current data demand over 2G networks
remains largely symmetric with strong temporal variations, whereas
the demand over 3G networks is asymmetric with surprisingly weak
temporal variations is shown here
Multiply robust estimators in longitudinal studies with missing data under control-based imputation
Longitudinal studies are often subject to missing data. The ICH E9(R1)
addendum addresses the importance of defining a treatment effect estimand with
the consideration of intercurrent events. Jump-to-reference (J2R) is one
classically envisioned control-based scenario for the treatment effect
evaluation using the hypothetical strategy, where the participants in the
treatment group after intercurrent events are assumed to have the same disease
progress as those with identical covariates in the control group. We establish
new estimators to assess the average treatment effect based on a proposed
potential outcomes framework under J2R. Various identification formulas are
constructed under the assumptions addressed by J2R, motivating estimators that
rely on different parts of the observed data distribution. Moreover, we obtain
a novel estimator inspired by the efficient influence function, with multiple
robustness in the sense that it achieves -consistency if any pairs of
multiple nuisance functions are correctly specified, or if the nuisance
functions converge at a rate not slower than when using flexible
modeling approaches. The finite-sample performance of the proposed estimators
is validated in simulation studies and an antidepressant clinical trial
Yield improvement of exopolysaccharides by screening of the Lactobacillus acidophilus ATCC and optimization of the fermentation and extraction conditions
Exopolysacharides (EPS) produced by Lactobacillus acidophilus play an important role in food processing with its well-recognized antioxidant activity. In this study, a L. acidophilus mutant strain with high-yielding EPS (2.92±0.05 g/L) was screened by chemical mutation (0.2 % diethyl sulfate). Plackett-Burman (PB) design and response surface methodology (RSM) were applied to optimize the EPS fermentation parameters and central composite design (CCD) was used to optimize the EPS extraction parameters. A strain with high-yielding EPS was screened. It was revealed that three parameters (Tween 80, dipotassium hydrogen phosphate and trisodium citrate) had significant influence (P < 0.05) on the EPS yield. The optimal culture conditions for EPS production were: Tween 80 0.6 mL, dipotassium hydrogen phosphate 3.6 g and trisodium citrate 4.1 g (with culture volume of 1 L). In these conditions, the maximum EPS yield was 3.96±0.08 g/L. The optimal extraction conditions analyzed by CCD were: alcohol concentration 70 %, the ratio of material to liquid (M/L ratio) 1:3.6 and the extraction time 31 h. In these conditions, the maximum EPS extraction yield was 1.48±0.23 g/L. It was confirmed by the verification experiments that the EPS yield from L. acidophilus mutant strains reached 5.12±0.73 g/L under the optimized fermentation and extraction conditions, which was 3.8 times higher than that of the control (1.05±0.06 g/L). The results indicated that the strain screening with high-yielding EPS was successful and the optimized fermentation and extraction conditions significantly enhanced EPS yield. It was efficient and industrially promising
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