A Study on the Role of UIG Triple Helix Intensity in the Level of Regional Entrepreneurship

UIG triple helix is a relatively stable relationship among universities, industries, and governments formed in the relationship due to long-term formal and informal cooperation and communication. According to previous studies, in accordance with whether to achieve the tripartite cooperation among universities, industries and government, UIG triple helix can be divided into positive overlap and negative overlap, positive overlap refers to the three parties to achieve effective cooperation, and negative overlap refers to other forms of cooperation except the cooperation of positive overlap. The present study argues that the positive overlap is more conducive to the optimization of the regional entrepreneurial environment and the improvement of the regional entrepreneurial level than the negative overlap. In addition, this study argues that while positive overlap is more conducive to the promotion of the level regional entrepreneurship, it is undeniable that positive overlap also has some limitations, which have the disadvantages of high cost of coordination, poor flexibility and low efficiency. Therefore, trust governance can reduce the coordination costs brought by positive overlap, improve the efficiency of cooperation, and mediate the relationship between UIG triple helix intensity and regional entrepreneurial level. Through the collection of public data, the author test the model. Keywords: UIG triple helix intensity, positive overlap, negative overlap, trust governance, the level of regional entrepreneurshi

Endogenous BDNF augments NMDA receptor phosphorylation in the spinal cord via PLCγ, PKC, and PI3K/Akt pathways during colitis

Background Spinal central sensitization is an important process in the generation and maintenance of visceral hypersensitivity. The release of brain-derived neurotrophic factor (BDNF) from the primary afferent neurons to the spinal cord contributes to spinal neuronal plasticity and increases neuronal activity and synaptic efficacy. The N-Methyl-D-aspartic acid (NMDA) receptor possesses ion channel properties, and its activity is modulated by phosphorylation of its subunits including the NMDA receptor 1 (NR1). Methods Colonic inflammation was induced by a single dose of intracolonic instillation of tri-nitrobenzene sulfonic acid (TNBS). NR1 phosphorylation by BDNF in vivo and in culture was examined by western blot and immunohistochemistry. Signal transduction was studied by direct examination and use of specific inhibitors. Results During colitis, the level of NR1 phospho-Ser896 was increased in the dorsal horn region of the L1 and S1 spinal cord; this increase was attenuated by injection of BDNF neutralizing antibody to colitic animals (36 μg/kg, intravenous (i.v.)) and was also reduced in BDNF+/− rat treated with TNBS. Signal transduction examination showed that the extracellular signal-regulated kinase (ERK) activation was not involved in BDNF-induced NR1 phosphorylation. In contrast, the phosphatidylinositol 3-kinase (PI3K)/Akt pathway mediated BDNF-induced NR1 phosphorylation in vivo and in culture; this is an additional pathway to the phospholipase C-gamma (PLCγ) and the protein kinase C (PKC) that was widely considered to phosphorylate NR1 at Ser896. In spinal cord culture, the inhibitors to PLC (U73122), PKC (bisindolylmaleimide I), and PI3K (LY294002), but not MEK (PD98059) blocked BDNF-induced NR1 phosphorylation. In animals with colitis, treatment with LY294002 (50 μg/kg, i.v.) blocked the Akt activity as well as NR1 phosphorylation at Ser896 in the spinal cord. Conclusion BDNF participates in colitis-induced spinal central sensitization by up-regulating NR1 phosphorylation at Ser896. The PI3K/Akt pathway, in addition to PLCγ and PKC, mediates BDNF action in the spinal cord during colitis

Development of a hydrodynamic model and the corresponding virtual software for dual-loop circulating fluidized beds

Dual-loop circulating fluidized bed (CFB) reactors have been widely applied in industry because of their good heat and mass transfer characteristics and continuous handling ability. However, the design of such reactors is notoriously difficult owing to the poor understanding of the underlying mechanisms, meaning it has been heavily based on empiricism and stepwise experiments. Modeling the gas-solid CFB system requires a quantitative description of the multiscale heterogeneity in the sub-reactors and the strong coupling between them. This article proposed a general method for modeling multiloop CFB systems by utilizing the energy minimization multiscale (EMMS) principle. A full-loop modeling scheme was implemented by using the EMMS model and/or its extension models to compute the hydrodynamic parameters of the sub-reactors, to achieve the mass conservation and pressure balance in each circulation loop. Based on the modularization strategy, corresponding interactive simulation software was further developed to facilitate the flexible creation and fast modeling of a customized multi-loop CFB reactor. This research can be expected to provide quantitative references for the design and scale-up of gas-solid CFB reactors and lay a solid foundation for the realization of virtual process engineering

A general EMMS drag model applicable for gas-solid turbulent beds and cocurrent downers

Eulerian-Eulerian models incorporated with the kinetic theory of granular flow were widely used in the simulation of gas-solid two-phase flow, while the effects of mesoscale structures such as particle clusters and gas bubbles could not be considered adequately if traditional homogeneous drag models were adopted in the coarse grid simulations. The energy minimization multiscale (EMMS) model has been proved to facilitate calculating a structure-dependent drag coefficient by considering particle clustering phenomena, which can be coupled with the two-fluid model (TFM) to improve the accuracy of coarse-grid simulation of gas-solid circulating fluidized beds. However, the original EMMS drag model cannot be further applied to the simulation of gas-solid fluidized beds with solids flow rate smaller than zero, e.g., turbulent fluidized beds and cocurrent downward flow, because the original cluster diameter correlation gives rise to a value smaller than single particle diameter or even negative value at extremely low solids fluxes or downward gas-solid flow. In this study, a new proposed cluster evolution equation is proposed by quantifying local clustering dynamics to replace the original cluster diameter correlation. The newly formulated EMMS drag model can be used to avoid a negative cluster diameter to be involved in calculating interphase drag force in the overall fluidization regime. The improved EMMS drag law is incorporated into the Eulerian-Eulerian model to simulate gas-solid turbulent fluidized beds and cocurrent downer reactors, since they both were widely used in many industrial processes. By analyzing local hydrodynamics as well as the axial and radial heterogeneous distributions in the two kinds of fluidized beds, it is clarified that the simulation using the improved EMMS drag model shows a better agreement with the experimental data than the computation using the homogeneous drag law. (C) 2019 Elsevier Ltd. All rights reserved

A CFD-PBM-EMMS integrated model applicable for heterogeneous gas-solid flow

Accurate prediction of the structure-dependent interphase drag coefficient in a computational cell is of importance for the simulation of heterogeneous gas-solid flow. However, the cluster diameter in the cell was usually correlated with macroscopic hydrodynamic parameters or simply approximated as a constant value, though there is a cluster size distribution (CSD) at the sub-grid scale. Based on the energy minimization multiscale (EMMS) model and the population balance model (PBM), a CFD-PBM-EMMS integrated model was proposed to account for the effect of CSD on the interphase drag within the computational grid in this article, in which the PBM was used to describe the spatio-temporal evolution of CSD by introducing an EMMS-based cluster growth rate model. The CFD-PBM-EMMS model was validated by the experiments in a pilot-scale circulating fluidized bed riser of Geldart A and/or B particles. Comparing with the two-fluid model using the EMMS drag or homogeneous drag law, the CFD-PBM-EMMS integrated model shows the best agreement with the experiments under various operating conditions. Much effort is being devoted to incorporating the coalescence and breakage kinetics of clusters to the PBM further to improve the simulation accuracy of the CFD-PBM-EMMS integrated model, especially for dense gas-solid flow

CFD-PBM simulation of gas?solid bubbling flow with structure-dependent drag coefficients

Bubble size distribution resulted from bubble coalescence and breakup has significant effects on the effective interphase drag in gas?solid bubbling fluidized beds, which was however not taken into account in previous coarse-grid simulations. In this study, the population balance model (PBM) was used to describe the dynamic evolution of gas bubbles in gas?solid bubbling fluidization, wherein the coalescence and breakup kernels were derived by considering the effects of bubble velocity difference, wake capture and bubble instability. An improved energy-minimization multi-scale (EMMS) bubbling model was developed to calculate the effective interphase drag in sub-grid scale. By incorporating both the PBM and the EMMS drag into an Eulerian continuum model, a CFD-PBM-EMMS coupled scheme was further proposed to predict the hydrodynamics of bubbling fluidized beds. The scheme was validated through comparison of simulated results with experimental data. The bed expansion characteristics and the lateral profiles of solids velocities were reasonably predicted at acceptable computational cost. Satisfactory agreement was also achieved between the measured and simulated bubble size distributions. The proposed sub-grid drag model and coupled simulation scheme can facilitate capturing the salient features of the hydrodynamics of gas?solid bubbling fluidized beds

Steady-state modeling of axial heterogeneity in CFB risers based on one-dimensional EMMS model

Axial heterogeneity in circulating fluidized bed (CFB) risers is very important to the design of fluidized bed reactors, which is, however, still unable to be described in theory. Based on a successful description of local hydrodynamics in gas solid flow, the Energy-Minimization Multi-Scale (EMMS) theory further relates axial hydrodynamics with local and global stability conditions in the system, providing a theoretical way to account for the axial heterogeneity in CFB risers. This research reveals that the interaction between particle clusters and the dilute phase as well as the surrounding dense phase has a significant effect on their dynamical evolution. Similar to cluster diameter in the EMMS theory, number density of particle clusters serving as a comprehensive indicator to the heterogeneity in gas solid flow is constrained by both local and global stability conditions in the system. With the above cognition, a one-dimensional EMMS model is developed to perform steady-state modeling of the axial heterogeneity in CFB risers. The model successfully reproduces a complete transition zone and the parametric effects on it at the choking condition. The S-shaped axial voidage profile calculated by the one-dimensional EMMS model is in good agreement with the experimental results in gas solid fast fluidization. This research is not only the first step toward implementing the three-scale computation in virtual process engineering (VPE), but also of referential significance to industrial chemical process development. (C) 2013 Elsevier Ltd. All rights reserved

Kinetic modelling and experimental validation of single large particle combustion of coal char

Understanding apparent kinetics of single large fuel particle combustion is of significance to the design and optimization of grate-firing and circulating fluidized bed boilers. Based on the concept of finite reaction zone approximation, a simple heterogeneous single particle model was formulated to consider the effects of external gas film, ash layer and chemical reaction simultaneously. To validate the proposed model and gain insight into the prevailing rate-controlling mechanism during the single particle combustion process at different combustion temperatures and particle sizes, the experiments on the combustion of coal char powder and single large char particles were carried out in a thermal gravimetric analyzer and a bench scale fixed-bed reactor, respectively. The intrinsic and apparent kinetics as well as the effective reacting zone thickness of single large particle combustion were quantified by combining theoretical analyses and experimental data. Both the bulk flow temperature and particle size have a remarkable influence on the global reactivity. The rate-controlling process was found to shift from the intrinsic chemical reaction to ash layer diffusion and return again to the intrinsic kinetics at the burnout stage. Particularly, an external effectiveness factor was defined as a function of conversion degree to better describe the ash diffusion effect on the apparent reactivity of large particles. The proposed model is physically general but simple enough to be incorporated into the computational fluid dynamic simulation of large-scale grate-firing and fluidized bed boilers

A method of accurate location for island away from mainland by remote sensing

The accuracy of geographic location is important for island investigations by remote sensing. However, many islands are far away from land, and it is impossible to obtain accurate ground control points (GCPs) that could be used for geometric correction. We propose a geometric correction method without using GCP to orientate islands accurately. The test data are four SPOT-5 images that were obtained from the same orbit and at the same time; one of these images does not include islands but allows one or more GCPs to be acquired. Firstly, we initially correct the image with GCPs by using a physical model, metadata, and a digital elevation model derived from SRTM data, but the accuracy is slightly better than 50 m. We calculate the offset between the corrected image and its GCPs and use this offset to correct the digital elevation model to make its coordinates to agree with that from the metadata. Then, we further correct the image by using a physical model, metadata and the corrected digital elevation model to suppress the hypsographical distortion. Finally, We use an affine transformation model to calculate the distortion parameters from the corrected image by using its GCPs, and further used these parameters to correct the other three images without GCPs. Our experiment is quite encouraging as when some islands are 159 km away from land we still achieve a location accuracy better than 5 m