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Search Results: 1 - 10 of 127222 matches for " Pengcheng Li "
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Optimization of Spatial Dose Distribution for Controlling Sidewall Shape in Electron-beam Lithography
Pengcheng Li
Physics , 2015,
Abstract: Electron-beam (e-beam) lithography is widely employed in fabrication of 2-D patterns and 3-D structures. A certain type or shape of the sidewall in the remaining resist profile may be desired in an application, e.g., an undercut for lift-off and a vertical sidewall for etching, or required for a device. Also, as the feature size is decreased well below a micron, a small variation of the sidewall slope can lead to a significant (relative) CD error in certain layers of resist. Therefore, it is important to understand effects of spatial dose distribution on sidewall shape and be able to achieve the desired shape. In this study, via simulation, the relationship among the total dose, spatial distribution of dose, developing time and sidewall shape, and performance of the method developed to optimize the dose distribution for a target sidewall shape have been analyzed. The simulation results have been verified through experiments.
A Review of Proximity Effect Correction in Electron-beam Lithography
Pengcheng Li
Physics , 2015,
Abstract: I review the work of proximity effect correction (PEC) in electron-beam (e-beam) lithography with emphasis on dose modification and shape modification PEC techniques.
A rapid and efficient synthetic route to terminal arylacetylenes by tetrabutylammonium hydroxide- and methanol-catalyzed cleavage of 4-aryl-2-methyl-3-butyn-2-ols
Jie Li,Pengcheng Huang
Beilstein Journal of Organic Chemistry , 2011, DOI: 10.3762/bjoc.7.55
Abstract: Tetrabutylammonium hydroxide with methanol as an additive was found to be a highly active catalyst for the cleavage of 4-aryl-2-methyl-3-butyn-2-ols. The reaction was performed at 55–75 °C and gave terminal arylacetylenes in good to excellent yields within several minutes. Compared with the usual reaction conditions (normally >110 °C, several hours), this novel catalyst system can dramatically decrease the reaction time under much milder conditions.
Local Feature Extraction and Information Bottleneck-Based Segmentation of Brain Magnetic Resonance (MR) Images
Pengcheng Shen,Chunguang Li
Entropy , 2013, DOI: 10.3390/e15083295
Abstract: Automated tissue segmentation of brain magnetic resonance (MR) images has attracted extensive research attention. Many segmentation algorithms have been proposed for this issue. However, due to the existence of noise and intensity inhomogeneity in brain MR images, the accuracy of the segmentation results is usually unsatisfactory. In this paper, a high-accuracy brain MR image segmentation algorithm based on the information bottleneck (IB) method is presented. In this approach, the MR image is first mapped into a “local-feature space”, then the IB method segments the brain MR image through an information theoretic formulation in this local-feature space. It automatically segments the image into several clusters of voxels, by taking the intensity information and spatial information of voxels into account. Then, after the IB-based clustering, each cluster of voxels is classified into one type of brain tissue by threshold methods. The performance of the algorithm is studied based on both simulated and real T1-weighted 3D brain MR images. Our results show that, compared with other well-known brain image segmentation algorithms, the proposed algorithm can improve the accuracy of the segmentation results substantially.
A Hybrid De-Noising Method on LASCA Images of Blood Vessels  [PDF]
Cong Wu, Nengyun Feng, Koichi Harada, Pengcheng Li
Journal of Signal and Information Processing (JSIP) , 2012, DOI: 10.4236/jsip.2012.31012
Abstract: A de-noising approach is proposed that based on the combination of wiener filtering, nonlinear filtering and wavelet fusion, which de-noise the LASCA (LAser Speckle Contrast Analysis) image of blood vessels in Small Animals. The approach first performs laser spectral contrast analysis on brain blood flow in rats, get their spatial and temporal contrast images. Then, a de-noising filtering method is proposed to deal with noise in LASCA. The image restoration is achieved by applying the proposed admixture filtering, and the subjective estimation and objective estimation are given to the de-noising images. As our experimental results shown, the proposed method provides clearer subjective sense and improved to over 25 db for PSNR.
Spatial perturbation with synthetic protein scaffold reveals robustness of asymmetric cell division  [PDF]
Jiahe Li, Pengcheng Bu, Kai-Yuan Chen, Xiling Shen
Journal of Biomedical Science and Engineering (JBiSE) , 2013, DOI: 10.4236/jbise.2013.62017
Abstract:

Asymmetric cell division is an important mechanism for creating diversity in a cellular population. Stem cells commonly perform asymmetric division to generate both a daughter stem cell for self-renewal and a more differentiated daughter cell to populate the tissue. During asymmetric cell division, protein cell fate determinants asymmetrically localize to the opposite poles of a dividing cell to cause distinct cell fate. However, it remains unclear whether cell fate determination is robust to fluctuations and noise during this spatial allocation process. To answer this question, we engineered Caulobacter, a bacterial model for asymmetric division, to express synthetic scaffolds with modular protein interaction domains. These scaffolds perturbed the spatial distribution of the PleC-DivJ- DivK phospho-signaling network without changing their endogenous expression levels. Surprisingly, enforcing symmetrical distribution of these cell fate de terminants did not result in symmetric daughter fate or any morphological defects. Further computational analysis suggested that PleC and DivJ form a robust phospho-switch that can tolerate high amount of spatial variation. This insight may shed light on the presence of similar phospho-switches in stem cell asymmetric division regulation. Overall, our study demonstrates that synthetic protein scaffolds can provide a useful tool to probe biological systems for better understanding of their operating principles.

 

Optimization Design of Fracturing Parameters for Coalbed Methane Wells in Dafosi Mine Field  [PDF]
Chuantao Wang, Dongmin Ma, Qian He, Qian Li, Pengcheng Liu
Journal of Power and Energy Engineering (JPEE) , 2017, DOI: 10.4236/jpee.2017.59010
Abstract: Being controlled by the gas content of the reservoir, the productivity of CBM well is also mainly determined by its engineering quality and the physical property of the reservoir. In Dafosi mine field, 22 vertical wells from the “26 + 1” CBM wells project that was implemented since 2014 showed great difference in productivity after fracturing construction. With the consistent geological condition of coal reservoirs, fracturing construction parameters are suggested as the priority factor that controlling the well productivity. In this study, being combined with historical production and geological data, an optimized designation of fracturing construction parameters was established based on systematically comparative analysis of construction parameters such as discharge, the total volume of fracturing fluid, the quality of sand, sand ratio, which provides engineering basis for further fracturing construction of CBM wells.
Normal State Nernst Effect in Electron-doped Pr2-xCexCuO4: Superconducting Fluctuations and Two-band Transport
Pengcheng Li,R. L. Greene
Physics , 2007, DOI: 10.1103/PhysRevB.76.174512
Abstract: We report a systematic study of normal state Nernst effect in the electron-doped cuprates Pr$_{2-x}$Ce$_x$CuO$_{4-\delta}$ over a wide range of doping (0.05$\leq x \leq$0.21) and temperature. At low temperatures, we observed a notable vortex Nernst signal above T$_c$ in the underdoped films, but no such normal state vortex Nernst signal is found in the overdoped region. The superconducting fluctuations in the underdoped region are most likely incoherent phase fluctuations as found in hole-doped cuprates. At high temperatures, a large normal state Nernst signal is found at dopings from slightly underdoped to highly overdoped. Combined with normal state thermoelectric power, Hall effect and magnetoresistance measurements, the large Nernst effect is compatible with two-band model. For the highly overdoped films, the large Nernst effect is anomalous and not explainable with a simple hole-like Fermi surface seen in photoemission experiments.
GUCY2D Gene Mutation in a Family with Leber Congenital Amaurosis
Wu Li,Li Pengcheng,Xing Yiqiao
Journal of Animal and Veterinary Advances , 2012, DOI: 10.3923/javaa.2012.2953.2956
Abstract: To detect and analyze GUCY2D gene mutations in a family with Leber Congenital Amaurosis (LCA) in China. Researchers collected peripheral blood samples from affected family members in three generations. Genomic DNA was extracted and all 20 exons of the GUCY2D gene were amplified using the DNA of the proband as the template. The ABI 3100 automated sequencer was used for sequencing. The sequencing results revealed one Single Nucleotide Polymorphism (SNP): c.154G.T (p.A52S) on exon 2 of the GUCY2D gene. The encoded amino acid changed from alanine to serine. All affected family members carried this SNP.
On the Generalized Ertel--Rossby Invariant

GAO Shouting,XU Pengcheng,LI Na,

大气科学进展 , 2012,
Abstract: A new invariant called the generalized Ertel--Rossby invariant (GER) was developed in this study. The new invariant is given by the dot product of the generalized vorticity and the generalized velocity. The generalized vorticity is the absolute vorticity minus the cross--product of the gradient of Lagrangian--time integrated temperature and the gradient of entropy. The generalized velocity is the absolute velocity minus the sum of the gradient of Lagrangian--time integrated kinetic potential and the Lagrangian--time integrated temperature multiplied by the gradient of entropy. In addition to the traditional potential vorticity, the GER invariant may provide another useful tool to study the atmospheric dynamic processes for weather phenomena ranging from large scales to small scales.
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