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232 results on '"Yan, Weijie"'

17. Further study on tensor absolute value equations

Author

Ling, Chen, Yan, Weijie, He, Hongjin, and Qi, Liqun

Subjects
Mathematics - Optimization and Control
Abstract

In this paper, we consider the {\it tensor absolute value equations} (TAVEs), which is a newly introduced problem in the context of multilinear systems. Although the system of TAVEs is an interesting generalization of matrix {\it absolute value equations} (AVEs), the well-developed theory and algorithms for AVEs are not directly applicable to TAVEs due to the nonlinearity (or multilinearity) of the problem under consideration. Therefore, we first study the solutions existence of some classes of TAVEs with the help of degree theory, in addition to showing, by fixed point theory, that the system of TAVEs has at least one solution under some checkable conditions. Then, we give a bound of solutions of TAVEs for some special cases. To find a solution to TAVEs, we employ the generalized Newton method and report some preliminary results., Comment: 26 pages and 4 tables

Published
2018

18. Generalized tensor equations with leading structured tensors

Author

Yan, Weijie, Ling, Chen, Ling, Liyun, and He, Hongjin

Subjects
Mathematics - Optimization and Control
Abstract

The system of tensor equations (TEs) has received much considerable attention in the recent literature. In this paper, we consider a class of generalized tensor equations (GTEs). An important difference between GTEs and TEs is that GTEs can be regarded as a system of non-homogenous polynomial equations, whereas TEs is a homogenous one. Such a difference usually makes the theoretical and algorithmic results tailored for TEs not necessarily applicable to GTEs. To study properties of the solution set of GTEs, we first introduce a new class of so-named ${\rm Z}^+$-tensor, which includes the set of all P-tensors as its proper subset. With the help of degree theory, we prove that the system of GTEs with a leading coefficient ${\rm Z}^+$-tensor has at least one solution for any right-hand side vector. Moreover, we study the local error bounds under some appropriate conditions. Finally, we employ a Levenberg-Marquardt algorithm to find a solution to GTEs and report some preliminary numerical results., Comment: 23 pages, 1 figure and 5 tables

Published
2018

22. Essays on entry and market profitability in the UK pharmaceuticals

Author

Yan, Weijie

Subjects
338.4
Abstract

This thesis applies economic methods developed in industrial organization to assess entry barriers and profitability of the pharmaceutical market in the UK. The thesis has two parts. The first part investigates whether incumbent firms strategically proliferate product varieties to delay and deter entry of competitors, and whether such strategy is effective to be a barrier. Three sets of regressions are employed: a non-monotonicity test between number of products and market size, as proposed by Ellison and Ellison (2011); a hazard rate model of entry probability, with focus on whether entry can be influenced by product varieties; and a regression of incumbent's market share post entry to test whether their share is positively correlated with product varieties built prior to entry. The results suggest that product proliferation can be a barrier to entry in the UK, however, evidence on incumbents' strategic incentive is inconclusive. The second part of the thesis focuses on antibiotic market. With the use of antibiotics, bacteria start to develop resistance, which has became a global crisis in healthcare. Despite the need for new entries because old molecules are losing effectiveness, research firms are leaving this market. We use nested logit and random coefficients logit model to estimate the price elasticity of demand between drugs in order to assess the profitability of the market and to evaluate policy interventions of shifting consumption away from molecules that cause higher resistance. We find that price-cost margin of this market is 35.2% on average but varies by molecules and drug types (branded/generics). We also find that some interventions can be effective to shift demand but with prices to pay.

Published
2019

29. Facile synthesis of O/N co-doped hierarchical porous carbon: for high performance supercapacitors and electromagnetic interference shielding.

Author

Dong, Kaiming, Sun, Zhenjie, Jing, Ge, Wang, Jiajun, Tang, Biao, Zhao, Nanjin, Kong, Lingwei, Yan, Weijie, and Guo, Feiqiang

Subjects
ELECTROMAGNETIC interference, ELECTROMAGNETIC shielding, DOPING agents (Chemistry), CARBON-based materials, ENERGY density, SUPERCAPACITORS
Abstract

Biomass-derived carbon materials are being increasingly utilized in various fields. This paper reports a facile synthesis method for O/N co-doped hierarchical porous carbon, utilizing the inherent pore structure and high heteroatom content of sesame meal. The O/N co-doped hierarchical porous carbon (SC-120) exhibits a hierarchical pore structure and abundant surface functional groups, the specific surface area reached 1743 m2 g−1, and the O and N element contents were measured at 10.87% and 1.95% respectively. In the three-electrode system, the specific capacitance of SC-120 reached 358.6 F g−1 at a current density of 0.5 A g−1, and a specific capacitance of 262.5 F g−1 is maintained even at a high current density of 30 A g−1. Constructed using SC-120 as the electrode, the symmetrical supercapacitor exhibits a high energy density of 9.23 W h kg−1 at a power density of 100 W kg−1 and excellent cyclic stability of 93.58% capacitance retention rate after 7500 charge–discharge testing. Additionally, SC-120 demonstrates potential for electromagnetic interference shielding, attaining an efficiency of 33.18 dB and a shielding effectiveness of 99.59% within the X-band frequency range of 8.2–12.4 GHz. [ABSTRACT FROM AUTHOR]

Published
2024
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30. Application of Diffusion Kurtosis Imaging and Blood Oxygen Level-Dependent Magnetic Resonance Imaging in Kidney Injury Associated with ANCA-Associated Vasculitis.

Author

Yu, Wenhui, Yan, Weijie, Yi, Jing, Cheng, Lu, Luo, Peiyi, Sun, Jiayu, Gou, Shenju, and Fu, Ping

Subjects
DIFFUSION magnetic resonance imaging, FUNCTIONAL magnetic resonance imaging, MAGNETIC resonance imaging, ANTINEUTROPHIL cytoplasmic antibodies, OXYGEN in the blood, KIDNEYS
Abstract

Objective: Functional magnetic resonance imaging (fMRI) has been applied to assess the microstructure of the kidney. However, it is not clear whether fMRI could be used in the field of kidney injury in patients with Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Methods: This study included 20 patients with AAV. Diffusion kurtosis imaging (DKI) and blood oxygen level-dependent (BOLD) scanning of the kidneys were performed in AAV patients and healthy controls. The mean kurtosis (MK), mean diffusivity (MD), and fractional anisotropy (FA) parameters of DKI, the R2* parameter of BOLD, and clinical data were further analyzed. Results: In AAV patients, the cortex exhibited lower MD but higher R2* values compared to the healthy controls. Medullary MK values were elevated in AAV patients. Renal medullary MK values showed a positive correlation with serum creatinine levels and negative correlations with hemoglobin levels and estimated glomerular filtration rate. To assess renal injury in AAV patients, AUC values for MK, MD, FA, and R2* in the cortex were 0.66, 0.67, 0.57, and 0.55, respectively, and those in the medulla were 0.81, 0.77, 0.61, and 0.53, respectively. Conclusions: Significant differences in DKI and BOLD MRI parameters were observed between AAV patients with kidney injuries and the healthy controls. The medullary MK value in DKI may be a noninvasive marker for assessing the severity of kidney injury in AAV patients. [ABSTRACT FROM AUTHOR]

Published
2024
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45. Further study on tensor absolute value equations

Author

Ling, Chen, Yan, Weijie, He, Hongjin, and Qi, Liqun

Abstract

In this paper, we consider the tensor absolute value equations (TAVEs), which is a newly introduced problem in the context of multilinear systems. Although the system of the TAVEs is an interesting generalization of matrix absolute value equations (AVEs), the well-developed theory and algorithms for the AVEs are not directly applicable to the TAVEs due to the nonlinearity (or multilinearity) of the problem under consideration. Therefore, we first study the solutions existence of some classes of the TAVEs with the help of degree theory, in addition to showing, by fixed point theory, that the system of the TAVEs has at least one solution under some checkable conditions. Then, we give a bound of solutions of the TAVEs for some special cases. To find a solution to the TAVEs, we employ the generalized Newton method and report some preliminary results.

Published
2024
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48. Regulating charge distribution of Cu3PdN nanocrystals for nitrate electroreduction to ammonia.

Author

Yao, Kai, Fang, Zhaobin, Wang, Jieyue, Wang, Wenhai, Wang, Mingyue, Yan, Weijie, Ye, Mingfu, Jiang, Binbin, Wu, Konglin, and Wei, Xianwen

Subjects
NANOCRYSTALS, ELECTROLYTIC reduction, ACTIVATION energy, ELECTRONIC modulation, COPPER, DENITRIFICATION
Abstract

As-synthesized Cu3PdN nanocrystals displayed high faradaic efficiency and selectivity for nitrate-to-ammonia conversion. The excellent performances can be attributed to the charge redistribution in Cu3PdN as a result of modulations of the electronic structures of Pd and Cu atoms, which altered the adsorption activation energy of the intermediates during the nitrate reduction reaction process. [ABSTRACT FROM AUTHOR]

Published
2023
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