Fully computable bounds for a staggered discontinuous Galerkin method for the Stokes equations

Zhao, Lina,Park, Eun-Jae Elsevier 2018 COMPUTERS & MATHEMATICS WITH APPLICATIONS - Vol.75 No.11

<P><B>Abstract</B></P> <P>We first propose a guaranteed upper bound for an arbitrary order staggered discontinuous Galerkin (staggered DG) method for the Stokes equations with the use of the global inf–sup constant. Equilibrated stress reconstruction and velocity reconstruction are the main ingredients in the construction of the error estimator. Next, to improve the error estimation and to overcome the difficulties caused by the calculation of the global inf–sup constant, a refined error control relying on local inf–sup constants is also developed. Some minimization techniques and an explicit method are then established to facilitate the construction of the refined error control. Finally, some benchmark examples are tested to compare the performances of the proposed error estimators.</P>

A priori and a posteriori error analysis of a staggered discontinuous Galerkin method for convection dominant diffusion equations

Zhao, Lina,Park, Eun-Jae Elsevier 2019 Journal of computational and applied mathematics Vol.346 No.-

<P><B>Abstract</B></P> <P>An upwind staggered discontinuous Galerkin (upwind-SDG) method for convection dominant diffusion problems is developed. Optimal a priori error estimates can be achieved for both the scalar and vector functions approximated by the method. To efficiently capture the layer problems, we propose a robust a posteriori error estimator for upwind-SDG method measured in a natural norm and a semi-norm associated with the convective derivative. The semi-norm can be neglected when the mesh Péclet number is sufficiently small. The key is to bound the conforming contribution by the dual norm of the residual, and the robustness arises from the incorporation of the semi-norm associated with the convective derivative. Finally, various numerical examples are tested to illustrate the performance of the robust a posteriori error estimator. The results indicate that optimal convergence rates can be achieved and the singularity can be well-captured by the proposed error estimator.</P>

A staggered DG method of minimal dimension for the Stokes equations on general meshes

Zhao, Lina,Park, Eun-Jae,Shin, Dong-wook Elsevier 2019 Computer methods in applied mechanics and engineer Vol.345 No.-

<P><B>Abstract</B></P> <P>In this paper, a locally conservative, lowest order staggered discontinuous Galerkin method is developed for the Stokes equations. The proposed method allows rough grids and is based on the partition of the domain into arbitrary shapes of quadrilaterals or polygons, which makes the method highly desirable for practical applications. A priori error analysis covering low regularity is demonstrated. A new postprocessing scheme for the velocity earning faster convergence is constructed. Next, adaptive mesh refinement is highly appreciated on quadrilateral and polygonal meshes since hanging nodes are allowed. Therefore, we propose two guaranteed-type error estimators in <SUP> L 2 </SUP> error of stress and energy error of the postprocessed velocity, respectively. Numerical experiments confirm our theoretical findings and illustrate the flexibility of the proposed method and accuracy of the guaranteed upper bounds.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Piecewise constant approximations of the Stokes problem on general meshes are developed. </LI> <LI> The method can be flexibly applied to rough grids and the implementation is simple. </LI> <LI> A new postprocessing scheme is developed based on the superconvergence of the velocity. </LI> <LI> Two guaranteed-type error estimators are proposed for the stress and the velocity. </LI> <LI> Numerical results are given to illustrate the performance of the method. </LI> </UL> </P>

Expression and Detection of Retinol-Binding Protein-4 Gene of Pig in E. coli

LiNa Sun,WanHong Li,ShuXiong Chen,Chao Chen,XiaoFeng Hou,Yun Zhao,Lu Chen,ChunJin Li,Xu Zhou 한국동물생명공학회(구 한국동물번식학회) 2014 한국동물번식학회 한중일 심포지엄 Vol.2014 No.1

Retinol-Binding Protein-4 (RBP-4) is a low molecular weight lipocalin, which mainly functions as a carrier for vitamin A. Though liver is the main machinery for synthesis of this protein, it is also detectable in other extrahepatic tissues, for example, ovary, uterus, and placenta. Recent evidences have shown that RBP-4 plays important roles in animal reproduction, for example, promoting the development of uterus and embryo. To the best of our knowledge, our laboratory firstly reported that high level of RBP-4 existed in follicular fluid from follicular cysts in sows. Moreover, we have also found that RBP-4 could be secreted by granulosa cells, and RBP-4 receptor was detected in granulosa cells. However, there is no any evidence on the role of RBP-4 in regulating the follicular development. Therefore, cloning and expression of RBP-4 and preparation of polyclonal antibody could help us to explore the role of RBP-4 in follicular development. The aim of this work was to construct prokaryotic expression system of swine RBP-4 gene. The total RNA was extracted from swine’s normal ovarian tissue. The sequence including the whole length of RBP-4 was amplified by RT-PCR and inserted into pEASY-E1.Then transformed into E. coli BL21(DE3)pLysS after gene sequencing. Three hours later, adding IPTG with the final concentration of 1mmol/L and inducing five hours. After centrifugation, the supernatant was discarded. By adding Glucose to Luria-Bertani broth, the expressions of protein were increased. SDS-PAGE showed that the RBP-4 gene expressed in the form of inclusion body with a molecular weight of 21KD. Western-Blot results showed that the target protein could be specifically recognized by mouse anti-human monoclonal antibody. Prokaryotic expression vector of RBP-4 gene was successfully established, and the gene was successfully expressed n E. coli, which is ready for purification and RBP-4 polyclone antibody. Meanwhile, these results were beneficial to investigate the function of RBP-4 in follicular development.

Osmanthus fragrans Flower Extract and Acteoside Protect Against d-Galactose-Induced Aging in an ICR Mouse Model

Lina Xiong,Shuqin Mao,Baiyi Lu,Jiajia Yang,Fei Zhou,Yinzhou Hu,Yirong Jiang,Canxi Shen,Yajing Zhao 한국식품영양과학회 2016 Journal of medicinal food Vol.19 No.1

Osmanthus fragrans flower extract (OFE) is an organic extract from O. fragrans flower, which exhibits neuroprotective, free radical scavenging, and antioxidant effects. Therefore, the protective effect of OFE and acteoside against aging was studied. An aging ICR mouse model was established by chronically administering d-galactose (250 mg/kg) for 8 weeks. d-galactose induced spatial learning and memory impairments that were successfully inhibited by OFE and acteoside, which could shorten escape latency, improve platform crossing times, and increase zone time. The antioxidant potential of OFE and acteoside in vivo was evaluated by estimating the following: activities of antioxidant enzymes, such as glutathione peroxidase and aging-related enzyme, particularly monoamine oxidase; contents of lipid peroxidation methane dicarboxylic aldehyde, advanced glycation end products, and 8-hydroxy-2'-deoxyguanosine (a DNA damage product); and levels of nuclear factor-erythroid 2-related factor 2. OFE and acteoside also inhibited d-galactose-induced neurological aging by suppressing the increase in glial fibrillary acidic protein and neurotrophin-3. Considering the dose-dependent protective effects of OFE and acteoside, we concluded that OFE, rich in acteoside, was a good source of natural antiaging compounds.

Mechanistic Insight into Phenolic Compounds Toxicity and State-of-the-art Strategies for Enhancing the Tolerance of Escherichia coli to Phenolic Compounds

Lina Liu,Xiaolong Ma,Muhammad Bilal,Linlin Wei,Shijie Tang,Hong-zhen Luo,Yuping Zhao,Xuguo Duan 한국생물공학회 2022 Biotechnology and Bioprocess Engineering Vol.27 No.4

Efficient use of lignocellulosic biomass is a prerequisite for sustainable biofuel production while simultaneously contributing to environmental protection. However, phenolic compounds produced during the chemical treatment of lignocellulose inhibit the growth and metabolism of microorganisms, such as Escherichia coli, which is one of the ideal strains for producing target products by microbial fermentation. To provide new ideas for studying microbial tolerance to environmental stress and providing technical support for constructing the engineering strains with high yields of phenolic compounds, this review elucidates the inhibition mechanism of phenols to E. coli. Secondly, a comprehensive and systematic review of current approaches for improving the phenolic-tolerance of E. coli is provided, including strain domestication, random mutagenesis, regulating the expression of outer membrane proteins, changing the composition of membrane fatty acids, accelerating the efflux of phenolic compounds, engineered bacterial biofloc formation, and transcriptome analysis. Finally, this review ends with some questions that still exist today, and prospective strategies are outlined for further improving the phenols-tolerance of E. coli. This review provided a theoretical basis for research into microbial tolerance to environmental stress and the development of engineered strains with high yield of phenolic compounds.

Prescribed performance model-free adaptive terminal sliding mode control for the pneumatic artificial muscles elbow exoskeleton

Zhirui Zhao,Lina Hao,Mingfang Liu,Haoze Gao,Xing Li 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.7

This paper focuses on the trajectory tracking issue of the pneumatic artificial muscle (PAM) exoskeleton system. First of all, a new type of the PAM elbow exoskeleton was introduced to assist wearers in elbow flexion/extension movement. Moreover, a model-free adaptive control approach was combined with the prescribed performance control to ensure the tracking errors to be converged to the predefined requirements. Meanwhile, to suffer the influence of the unknown external disturbance on the exoskeleton, a terminal sliding mode control was adopted to reduce the tracking errors. From a theoretical perspective, the stability of the proposed controller can be proved by Lyapunov synthesis. After two sets of experiments, the proposed control method can further improve the tracking accuracy in the PAM elbow exoskeleton, compared with the other three model-free adaptive control methods. Simultaneously, the maximum absolute value of the tracking errors never exceeded the designed boundary.

Spatial spectrum approach for pilot spoofing attack detection in MIMO systems

Ning, Lina,Li, Bin,Wang, Xiang,Liu, Xiaoming,Zhao, Chenglin Electronics and Telecommunications Research Instit 2021 ETRI Journal Vol.43 No.5

In this study, a spatial spectrum method is proposed to cope with the pilot spoofing attack (PSA) problem by exploiting the of uplink-downlink channel reciprocity in time-division-duplex multiple-input multiple-output systems. First, the spoofing attack in the uplink stage is detected by a threshold derived from the predefined false alarm based on the estimated spatial spectrum. When the PSA occurs, the transmitter (That is Alice) can detect either one or two spatial spectrum peaks. Then, the legitimate user (That is Bob) and Eve are recognized in the downlink stage via the channel reciprocity property based on the difference between the spatial spectra if PSA occurs. This way, the presence of Eve and the direction of arrival of Eve and Bob can be identified at the transmitter end. Because noise is suppressed by a spatial spectrum, the detection performance is reliable even for low signal-noise ratios and a short training length. Consequently, Bob can use beamforming to transmit secure information during the data transmission stage. Theoretical analysis and numerical simulations are performed to evaluate the performance of the proposed scheme compared with conventional methods.

Synergistic Effect of Copper and Cobalt in Cu-Co-O Composite Nanocatalyst for Catalytic Ozonation

Yuming Dong,Lina Wu,Guangli Wang,Hui Zhao,Pingping Jiang,Cuiyun Feng 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.11

A novel Cu-Co-O composite nanocatalyst was designed and prepared for the ozonation of phenol. A synergistic effect of copper and cobalt was observed over the Cu-Co-O composite nanocatalyst, which showed higher activity than either copper or cobalt oxide alone. In addition, the Cu-Co-O composite revealed good activity in a wide initial pH range (4.11-8.05) of water. The fine dispersion of cobalt on the surface of copper oxide boosted the interaction between catalyst and ozone, and the surface Lewis acid sites on the Cu-Co-O composite were determined as the active sites. The Raman spectroscopy also proved that the Cu-Co-O composite was quite sensitive to the ozone. The trivalent cobalt in the Cu-Co-O composite was proposed as the valid state.

REVIEW AND IMPLEMENTATION OF STAGGERED DG METHODS ON POLYGONAL MESHES

DOHYUN KIM,LINA ZHAO,EUN-JAE PARK 한국산업응용수학회 2021 Journal of the Korean Society for Industrial and A Vol.25 No.3

In this paper, we review the lowest order staggered discontinuous Galerkin methods on polygonal meshes in 2D. The proposed method offers many desirable features including easy implementation, geometrical flexibility, robustness with respect to mesh distortion and low degrees of freedom. Discrete function spaces for locally H¹ and H(div) spaces are considered. We introduce special properties of a sub-mesh from a given star-shaped polygonal mesh which can be utilized in the construction of discrete spaces and implementation of the staggered discontinuous Galerkin method. For demonstration purposes, we consider the lowest case for the Poisson equation. We emphasize its efficient computational implementation using only geometrical properties of the underlying mesh.