平台经济生态下制造业企业的生存之道——规模扩张抑或技术创新

在平台经济生态背景下,制造业企业的生产和经营方式呈现出向数字化、网络化、智能化转型发展。本文采用121家A股制造业上市公司2015−2019年的面板数据,实证考察了制造业企业电商平台应用对企业绩效的影响及作用机理。研究发现,电商平台应用显著提升了制造业企业绩效。机制分析发现,电商平台应用有利于促进制造业企业产销规模扩大,在规模经济带动下,企业绩效水平得到了显著提升,但是,其技术创新的影响机制却缺乏显著性。究其原因可能在于:平台经济增强了制造业全行业的竞争效应和匹配效应,为此,制造业企业开始寻求低成本的规模扩张之路,但是却忽视了或无暇顾及具有远期战略意义的技术创新。在使用替换变量法和工具变量法后,上述实证结果仍然是稳健的。本研究对于平台经济生态下如何激励制造业企业转型发展具有启发意义。

Improving the Performance of Motor Drive Servo Systems via Composite Nonlinear Control

This paper presents a discrete-time design of robust compositenonlinear controller to achieve fast and accurate set-pointtracking for motor servo systems subject to actuator saturationand disturbances.The basic idea here is to use a combination oflinear and nonlinear control,together with a disturbancerejection mechanism based on extended state observer.The linearcontrol part is designed to yield a fast response,and thenonlinear part serves to reduce the overshoot,while the extendedstate observer estimates simultaneously the state vector and theunknown disturbance for control and compensation.The closed-loopstability is analyzed using the Lyapunov theory.Practicalapplication in a permanent magnet synchronous motor position servosystem is given to demonstrate the effectiveness of the proposedcontrol scheme.

Tunable and highly sensitive temperature sensor based on graphene photonic crystal fiber

Optical fiber temperature sensors have been widely employed in enormous areas ranging from electric power industry,medical treatment,ocean dynamics to aerospace.Recently,graphene optical fiber temperature sensors attract tremendous attention for their merits of simple structure and direct power detecting ability.However,these sensors based on transfer techniques still have limitations in the relatively low sensitivity or distortion of the transmission characteristics,due to the unsuitable Fermi level of graphene and the destruction of fiber structure,respectively.Here,we propose a tunable and highly sensitive temperature sensor based on graphene photonic crystal fiber(Gr-PCF)with the non-destructive integration of graphene into the holes of PCF.This hybrid structure promises the intact fiber structure and transmission mode,which efficiently enhances the temperature detection ability of graphene.From our simulation,we find that the temperature sensitivity can be electrically tuned over four orders of magnitude and achieve up to~3.34×10^(-3) dB/(cm·℃)when the graphene Fermi level is~35 meV higher than half the incident photon energy.Additionally,this sensitivity can be further improved by~10 times through optimizing the PCF structure(such as the fiber hole diameter)to enhance the light–matter interaction.Our results provide a new way for the design of the highly sensitive temperature sensors and broaden applications in all-fiber optoelectronic devices.

Modulation of carrier lifetime in MoS2 monolayer by uniaxial strain

Carrier lifetime is one of the most fundamental physical parameters that characterizes the average time of carrier recombination in any material.The control of carrier lifetime is the key to optimizing the device function by tuning the electro-optical conversion quantum yield,carrier diffusion length,carrier collection process,etc.Till now,the prevailing modulation methods are mainly by defect engineering and temperature control,which have limitations in the modulation direction and amplitude of the carrier lifetime.Here,we report an effective modulation on the ultrafast dynamics of photoexcited carriers in two-dimensional(2D)MoS2 monolayer by uniaxial tensile strain.The combination of optical ultrafast pump-probe technique and time-resolved photoluminescence(PL)spectroscopy reveals that the carrier dynamics through Auger scattering,carrier-phonon scattering,and radiative recombination keep immune to the strain.But strikingly,the uniaxial tensile strain weakens the trapping of photoexcited carriers by defects and therefore prolongs the corresponding carrier lifetime up to 440%per percent applied strain.Our results open a new avenue to enlarge the carrier lifetime of 2D MoS2,which will facilitate its applications in high-efficient optoelectronic and photovoltaic devices.

Protective Effect of Buyang Huanwu Decoction on Cerebral Ischemia/Reperfusion Injury by Inhibiting Autophagy Based on AMPK/UIK1Signaling Pathway

The aim of the paper is to explore whether AMPK/U1K1 signaling pathway is involved in regulating autophagy and alleviating cerebral ischemia/reperfusion(I/R)injury.On this basis,study the regulatory effect of Buyang Huanwu Decoction(BHD)on AMPK/U1K1 signaling pathway,aiming to clarify the molecular mechanism of BHD in alleviating cerebral I/R injury and the protective effect of BHD containing serum(BHDS)on OGD/R neurons.The research group adopted the following methods:Neurons cultured for 7 days in vitro were randomly divided into normal control group,model group(OGD/R),AMPK activator(AICAR)group(3 mmol/L),Buyang Huanwu Decoction medicated serum(BHDS)group(3%),Buyang Huanwu Decoction medicated serum+AMPK activator(BHDS+AICAR)group.The protein expressions of p-AMPK,AMPK,p-UlKl,U1K1,Beclin-1 and LC3B in neurons were detected by Western blot,the fluorescence intensity and apoptosis rate of neuron autophagosome CYTO-ID staining were detected by flow cytometry,the fluorescence intensity and morphological changes of neuron LC3B were detected by immunofluorescence double labeling method,the morphological changes of neurons were observed by inverted microscope,and the survival rate of neurons was detected by CCK-8 method.Neuron OGD/R model and the optimal concentration of BHDS.The neurons in the model group were subjected to hypoxia and glucose deprivation for 1 h,2 h,3 h,4 h and reoxygenation and glucose deprivation for 24 h.The survival rate of neurons and the release rate of 1DH to determine whether the model was successfully established.And the results show that BHDS group,the survival rate of OGD/R neurons was significantly increased,and the apoptosis rate was significantly decreased.Among them,3%BHDS intervention at the same time of hypoxia glucose deprivation for 3 h and reoxygenation glucose for 24 h was the best condition.In BHDS group,the levels of p-AMPK/AMPK,p-UlKl/UlKl,beclin-1,CYTO-ID and LC3B fluorescence intensity,and the transformation from LC3B-I to LC3B-II of OGD/R neurons were significantly decreased.So we can draw a conclusion that BHD can inhibit autophagy and alleviate cerebral I/R injury through AMPK/U1K1 signaling pathway.

Emerging Geography of Creativity and Labor Productivity Effects in China

The paper presents an alternative approach to explain why regional productivity is different across regions by utilizing the creative class approach in China. First, we analyze the extent of spatial agglomeration of the creative class across regions in China. Second, we develop a model with spatial externalities to investigate how the concentration of the creative class can promote regional productivity. Our analysis confirms the importance of spatial agglomeration of the creative class in stimulating regional productivity. The results also imply that regional productivity is greater in markets with higher levels of innovation, capital stock, manufacturing and urbanization. In light of the results of our analysis, we discuss a number of policy implications.

Application of biochar-based materials in environmental remediation:from multi-level structures to specific devices

The development of biochar has triggered a hot-spot in various research fields including agriculture,energy,environment,and materials.Biochar-based materials provide a novel approach against environmental challenging issues.Considering the rapid development of biochar materials,this review serves as a valuable platform to summarize the recent progress on the theoretical investigation and engineering applications of biochar materials in environmental remediation.For a better understanding of the structure-application relationships,the structural properties of biochar from macroscopic and microscopic aspects are summarized.The multilevel structures including elements,phases,surface chemistry,and molecular are highlighted to elucidate the multi-functional properties of biochars.Sorption,catalysis,redox reaction,and biological activity of biochar are briefly illustrated,which influence the transport,transformation,and removal of organic and inorganic pollutants in the environments.According to the multi-level structures and structure-application relationships of biochar,specific biochar-based materials and devices have been designed for practical environmental application.The important progress on the functionalization and device of biochar-based materials,including magnetic biochars,2D and 3D biochar-based macrostructures,immobilized microorganism on biochar,and biochar-amended biofilters are highlighted.The environmental friendliness and sustainability of biochar-based materials,considering the whole cycle from synthesis to application,are evaluated.

Copper-Catalyzed Benzylic C—H Functionalization, Oxidation and Cyclization of Methylarenes: Direct Access to z-Arylbenzothiazoles

Background and Originality Content As an inexpensive,fundamental and important feedstock for the petrochemical industry,methylarenes have long been regarded as one of the most widely used raw materials for a great variety of organic transformations.Therefore,the selective benzylic C(sp3)—H functionalization is particularly important,which provides a strategic means to utilize this resource.

Giant pattern evolution in third-harmonic generation of strained monolayer WS2 at two-photon excitonic resonance

Strong geometrical confinement and reduced dielectric screening of two-dimensional(2D)materials leads to strong Coulomb interaction and eventually give rise to extraordinary excitonic effects,which dominates the optical and optoelectronic properties.For nonlinear 2D photonic or optoelectronic applications,excitonic effects have been proved effective to tune the light-matter interaction strength.However,the modulation of excitonic effects on the other aspect of nonlinear response,i.e.,polarization dependence,has not been fully explored yet.Here we report the first systemic study on the modulation of excitonic effects on the polarization dependence of second and third harmonic generation(SHG and THG)in strained monolayer WS2 by varying excitation wavelength.We demonstrated that polarization-dependent THG patterns undergo a giant evolution near two-photon excitonic resonance,where the long-axis of the parallel component(originally parallel to the strain direction)has a 90°flip when the excitation wavelength increases.In striking contrast,no apparent variation of polarization-dependent SHG patterns occurs at either two-or three-photon excitonic resonance conditions.Our results open a new avenue to modulate the anisotropic nonlinear optical response of 2D materials through effective control of excitonic resonance states,and thus open opportunity for new designs and applications in nonlinear optoelectronic 2D devices.

Research progress on three different types of noncoding RNAs related to ionizing radiation

Non-coding RNAs(ncRNAs)have attracted wide attention in the field of ionizing radiation(IR).They have been found to be involved in cell development,proliferation,differentiation,and apoptosis in both clinical radiotherapy and radiation protection studies.Despite the production of an increasing number of relevant reports in recent years,the molecular mechanisms involved are yet to be clearly understood.In the last few years,ncRNAs have received a lot of research attention,especially microRNAs,long noncoding RNAs,and circular RNAs,which have a well-known association with the development of human disease and are closely related to the biological phenotypic changes caused by IR.With recent developments of research methods,these ncRNAs might play a significant regulatory role in future radiation protection and radiotherapy.This review will summarize the research progress of various types of ncRNAs as biomarkers of IR and potential new targets for radiotherapy,aiming to provide references for future research and the formulation of new strategies.