The main raw material utilized in wood adhesives comes from petrochemical extractives.However,due to the excessive dependence on petrochemical resources and the adverse impact on the ecosystem and human wellbeing,ther...The main raw material utilized in wood adhesives comes from petrochemical extractives.However,due to the excessive dependence on petrochemical resources and the adverse impact on the ecosystem and human wellbeing,there is an increasing trend to develop byproduct protein-based adhesives in the current global food safety context.In this research,flaxseed meal was subjected to pretreatment,and trimethylolpropane triglycidyl ether(TTE)and ethylenediamine(EN)were utilized as crosslinkers to establish a more compact adhesive layer and to prevent water intrusion.The pretreatment decreased the FM/UB viscosity by 60%compared to FM.The combination of CD analysis indicated that the Urea-NaOH pretreatment effectively stretched the flaxseed meal protein.According to Fourier transform infrared(FTIR)spectroscopy,X-ray diffraction(XRD),and differential scanning calorimetry(DSC)were used to analyze the resulting adhesive’s reaction mechanism and thermal response.Furthermore,the physical properties of the adhesive were characterized using wet shear strength testing and SEM observation.Remarkably,the dry bond strength increased from 0.72 to 2.12 MPa,representing a 194.4%increase.The wet bonding strength of the adhesive was improved from 0.22 to 1.21 MPa,representing a 550%increase compared to the original flaxseed protein-based adhesive,which far exceeded the minimum requirement for plywood of Type II(≥0.7 MPa,by GB/T 9846-2015).This study demonstrated an eco-friendly and sustainable method for the development of protein adhesives as viable substitutes for petrochemical resins.展开更多
高超声速转捩研究飞行器(Hypersonic Transition Research Vehicle,HyTRV)是为研究高超声速复杂三维边界层转捩而设计的升力体标模,其外形更接近真实飞行器。为深入认识HyTRV边界层稳定性特征及转捩机制,验证数值模拟和理论分析结果,本...高超声速转捩研究飞行器(Hypersonic Transition Research Vehicle,HyTRV)是为研究高超声速复杂三维边界层转捩而设计的升力体标模,其外形更接近真实飞行器。为深入认识HyTRV边界层稳定性特征及转捩机制,验证数值模拟和理论分析结果,本文在马赫数6常规风洞中,采用红外热成像技术和高频压力传感器,获得了0°和2°攻角时HyTRV标模下表面(迎风面)的边界层转捩阵面及不稳定波的演化特征,并与一维稳定性分析结果进行了对比。研究结果表明:攻角为2°时,标模下表面的横流失稳区较0°攻角时范围缩小且位置后移,标模中心线处转捩早于两侧横流区。另外,横流区存在宽频的高频信号,信号幅值在转捩完成前达到饱和。该信号包含多频段扰动,多种扰动之间相互作用导致频谱变宽,最终促使边界层转捩变为湍流。展开更多
The catalytic performance of a series of cobalt(Ⅱ) hydroxamates (CoL2) and the synergistic catalytic action of the cobalt complexes combined with N-hydroxyphthalimide (NHPI) in the aerobic oxidation of p-xylene to p-...The catalytic performance of a series of cobalt(Ⅱ) hydroxamates (CoL2) and the synergistic catalytic action of the cobalt complexes combined with N-hydroxyphthalimide (NHPI) in the aerobic oxidation of p-xylene to p-toluic acid (PTA) were investigated. The results showed that the existing synergistic action in the catalytic oxidation can shorten the induction period of the radical reaction and improve the yield of PTA.展开更多
对比分析现行国家标准GB/T 31248—2014《电缆或光缆在受火条件下火焰蔓延热释放和产烟特性的试验方法》与欧盟标准EN 50399:2022 Common test methods for cables under fire conditions—Heat release and smoke production measureme...对比分析现行国家标准GB/T 31248—2014《电缆或光缆在受火条件下火焰蔓延热释放和产烟特性的试验方法》与欧盟标准EN 50399:2022 Common test methods for cables under fire conditions—Heat release and smoke production measurement on cables during flame spread test—Test apparatus,procedures,results主要技术差异,相比于国标,欧标关于试验装置的规定更加详细,同时增加了标准电缆试样校准、火焰形状校准、非圆形电缆数量及安装规定等技术内容。针对外径小于或等于5 mm的电缆,分析国标和欧标试样安装方式异同,并给出GB/T 31248—2014修订建议。展开更多
We present a computer-modeling framework for photovoltaic(PV)source emulation that preserves the exact single-diode physics while enabling iteration-free,real-time evaluation.We derive two closed-form explicit solvers...We present a computer-modeling framework for photovoltaic(PV)source emulation that preserves the exact single-diode physics while enabling iteration-free,real-time evaluation.We derive two closed-form explicit solvers based on the Lambert W function:a voltage-driven V-Lambert solver for high-fidelity I–V computation and a resistance-driven R-Lambert solver designed for seamless integration in a closed-loop PV emulator.Unlike Taylor-linearized explicit models,our proposed formulation retains the exponential nonlinearity of the PV equations.It employs a numerically stable analytical evaluation that eliminates the need for lookup tables and root-finding,all while maintaining limited computational costs and a small memory footprint.The R-Lambert model is integrated into a buck-converter emulator equipped with a discrete PI regulator,which generates current references directly from sensed operating points,thus supporting hardware-constrained implementation.Comprehensive numerical experiments conducted on six commercial modules from various technologies(mono,poly,and multicrystalline)demonstrate significant accuracy improvements under the IEC EN 50530 near-MPP criterion:the V-Lambert solver reduces the±10%Vmpp band error by up to 61 times compared to an explicit-model baseline.Dynamic simulations under varying irradiance,temperature,and load conditions achieve millisecond-scale settling with accurate trajectory tracking.Additionally,processor-in-the-loop experimental validation on an embedded microcontroller supports the simulation results.By unifying exact analytical modeling with embedded realization,this work advances computer modeling for PV emulation,MPPT benchmarking,and controller verification in integrated renewable energy systems.展开更多
In order to extend the eN method to general three-dimensional boundary layers, the conservation law of the imaginary parts for the wave parameters with a fixed wave vector is deduced. The compatibility relationship ...In order to extend the eN method to general three-dimensional boundary layers, the conservation law of the imaginary parts for the wave parameters with a fixed wave vector is deduced. The compatibility relationship （CR） and the general theory of ray tracing （RT）, which have been extensively used in conservative systems, are applied to a general three-dimensional boundary layer belonging to non-conservative systems. Two kinds of eN methods, i.e., the eN-CR method and the eN-RT method, are established. Both the two kinds of methods can wavenumber and the amplitude of the be used to predict the evolutions of the spanwise disturbances in general three-dimensional boundary layers. The reliability of the proposed methods is verified and validated by performing a direct numerical simulation （DNS） in a hypersonic general three-dimensional boundary layer over an aircraft model. The results are also compared with those obtained by other eN methods, indicating that the proposed methods have great potential applications in improving the transition prediction accuracy in general three-dimensional boundary layers.展开更多
Among six major types of tea(white,green,oolong,yellow,black,and dark teas)from Camellia sinensis,oolong tea,a semi-fermented tea,with its own unique aroma and taste,has become a popular consumption as indicated by th...Among six major types of tea(white,green,oolong,yellow,black,and dark teas)from Camellia sinensis,oolong tea,a semi-fermented tea,with its own unique aroma and taste,has become a popular consumption as indicated by the increasing production.Representing the characteristic flavonoids of oolong tea,theasinensins are dimeric flavan-3-ols.Many recent studies have indicated that oolong tea and theasinensins possess several health benefit properties.We consider it significant and necessary to have a comprehensive review in the recent advances of oolong tea.Therefore,the aim of the present review is to provide a new perspective on oolong tea and its characteristic phytochemicals,theasinensins associated with health benefits,molecular action pathway,and chemical mechanism of theasinensin formation from scientific evidences available on the literature.Furthermore,the chemical characterization of the oxidation products and the model oxidation system to the chemical changes of theasinensins are also discussed.展开更多
The development of electrical engineering and electronic, communications, smart power grid, and ultra-high voltage transmission technologies have driven the energy system revolution to the next generation: the energy ...The development of electrical engineering and electronic, communications, smart power grid, and ultra-high voltage transmission technologies have driven the energy system revolution to the next generation: the energy internet. Progressive penetration of intermittent renewable energy sources into the energy system has led to unprecedented challenges to the currently wide use of coal-fired power generation technologies. Here, the applications and prospects of advanced coal-fired power generation technologies are analyzed. These technologies can be summarized into three categories:(1) large-scale and higher parameters coal-fired power generation technologies, including 620/650/700 oC ultra-supercritical thermal power and double reheat ultra-supercritical coal-fired power generation technologies;(2) system innovation and specific, highefficiency thermal cycles, which consist of renewable energy-aided coal-fired power generation technologies, a supercritical CO_2 Brayton cycle for coal-fired power plants, large-scale air-cooling coal-fired power plant technologies, and innovative layouts for waste heat utilization and enhanced energy cascade utilization;(3) coal-fired power generation combined with poly-generation technologies, which are represented by integrated gasification combined cycle(IGCC) and integrated gasification fuel cell(IGFC) technologies. Concerning the existing coal-fired power units, which are responsible for peak shaving, possible strategies for enhancing flexibility and operational stability are discussed. Furthermore, future trends for coal-fired power plants coupled with cyber-physical system(CPS) technologies are introduced. The development of advanced, coal-fired power generation technologies demonstrates the progress of science and is suitable for the sustainable development of human society.展开更多
To analyze the effects of width and thickness of each composition element of mixed steel U-rib-stiffened plates on the welding residual stress distribution, the distribution of the U-rib and the plate residual stress ...To analyze the effects of width and thickness of each composition element of mixed steel U-rib-stiffened plates on the welding residual stress distribution, the distribution of the U-rib and the plate residual stress was calculated using a simplified calculation method. The method involved welding the mixed steel U-rib-stiffened plates for a structure with different sizes and different strength ratios of U-rib to plate. Based on a welding residual stress numerical simulation method validated by the blind hole method test, the distribution law of the mixed steel U-rib stiffened plate was studied. The results showed that the change of plate width has little impact on the welding residual stress and that the ratio of the thicknesses of the plate to U-rib stiffeners, the thickness of the plate, and the thickness of the U-rib has a great influence on the distribution of the welding residual stress. The thickness of plate and steel strength also greatly influenced the distribution width of the residual tensile stress. While analyzing the compression capacity of U-rib-stiffened plates, the simplified distribution of welding residual stress was used.展开更多
AIM: To evaluate the efficacy of circumferential endoscopic mucosal resection (EMR) with a tissue-anchoring device in comparison to forceps precut EMR and conventional endoscopic submucosal dissection (ESD). METHODS: ...AIM: To evaluate the efficacy of circumferential endoscopic mucosal resection (EMR) with a tissue-anchoring device in comparison to forceps precut EMR and conventional endoscopic submucosal dissection (ESD). METHODS: The study was designed as a prospective, randomized, ex vivo study. Fresh ex vivo specimens were harvested from adult white Yorkshire pigs weighing 30-50 kg. Seventy-five standardized, artificial lesions measuring 3 cm × 3 cm were created by methy- lene blue tattoo at the greater curvature in fresh ex vivo stomachs using the EASIE-R simulator platform (Endosim LLC, Berlin, MA, United States). The three advanced endoscopists performed the three resection techniques such as circumferential EMR using the tissue-anchoring device (TA-EMR), forceps precut EMR (FP-EMR), and endoscopic submucosal dissection. The endoscopists and the type of cutting methods were determined randomly by grouped randomized selection.The resection bed was grossly inspected to determine whether the lesion was resected "en-bloc " (defined as no remaining mucosal tattoo remaining on specimen). The resection bed was also probed for evidence of perforation. The procedural time of circumferential resection, submucosal dissection, and injection frequency were recorded by an independent observer.RESULTS: All 75 created lesions were successfully resected by three advanced endoscopists using the three techniques. The mean ± SD size of resected specimens (long axis) were 39.5 ± 5.6 mm, 36.5 ± 7.3 mm, and 44.6 ± 5.6 mm for TA-EMR, FP-EMR, and ESD respectively. The overall mean dissection time of both the TA- EMR and FP-EMR was significant shorter than ESD (TA- EMR: 5.1 ± 3.3 min, FP-EMR: 3.5 ± 2.0 min vs ESD: 15.8 ± 9.5 min, P < 0.001, P < 0.001). The overall mean total procedure time of both the tissue-anchoring and forceps circumferential EMR was significantly shorter than ESD (TA-EMR: 17.5 ± 6.0 min, FP-EMR: 16.6 ± 6.6 min vs ESD: 28.6 ± 13.9 min, P < 0.001, P < 0.001). The en-bloc resection rate of ESD was 100% (25/25) and the en-bloc resection rate of the TA-EMR (84.0%, 21/25) was higher than for the FP-EMR (60.0%, 15/25), yet not statistically significant (P = 0.18). The perforation rate of each technique was 8.0% (2/25). CONCLUSION: TA-EMR appears to be quicker than ESD, and there was a trend towards improved en bloc resection rate with the TA-EMR when compared to the FP-EMR.展开更多
文摘The main raw material utilized in wood adhesives comes from petrochemical extractives.However,due to the excessive dependence on petrochemical resources and the adverse impact on the ecosystem and human wellbeing,there is an increasing trend to develop byproduct protein-based adhesives in the current global food safety context.In this research,flaxseed meal was subjected to pretreatment,and trimethylolpropane triglycidyl ether(TTE)and ethylenediamine(EN)were utilized as crosslinkers to establish a more compact adhesive layer and to prevent water intrusion.The pretreatment decreased the FM/UB viscosity by 60%compared to FM.The combination of CD analysis indicated that the Urea-NaOH pretreatment effectively stretched the flaxseed meal protein.According to Fourier transform infrared(FTIR)spectroscopy,X-ray diffraction(XRD),and differential scanning calorimetry(DSC)were used to analyze the resulting adhesive’s reaction mechanism and thermal response.Furthermore,the physical properties of the adhesive were characterized using wet shear strength testing and SEM observation.Remarkably,the dry bond strength increased from 0.72 to 2.12 MPa,representing a 194.4%increase.The wet bonding strength of the adhesive was improved from 0.22 to 1.21 MPa,representing a 550%increase compared to the original flaxseed protein-based adhesive,which far exceeded the minimum requirement for plywood of Type II(≥0.7 MPa,by GB/T 9846-2015).This study demonstrated an eco-friendly and sustainable method for the development of protein adhesives as viable substitutes for petrochemical resins.
文摘高超声速转捩研究飞行器(Hypersonic Transition Research Vehicle,HyTRV)是为研究高超声速复杂三维边界层转捩而设计的升力体标模,其外形更接近真实飞行器。为深入认识HyTRV边界层稳定性特征及转捩机制,验证数值模拟和理论分析结果,本文在马赫数6常规风洞中,采用红外热成像技术和高频压力传感器,获得了0°和2°攻角时HyTRV标模下表面(迎风面)的边界层转捩阵面及不稳定波的演化特征,并与一维稳定性分析结果进行了对比。研究结果表明:攻角为2°时,标模下表面的横流失稳区较0°攻角时范围缩小且位置后移,标模中心线处转捩早于两侧横流区。另外,横流区存在宽频的高频信号,信号幅值在转捩完成前达到饱和。该信号包含多频段扰动,多种扰动之间相互作用导致频谱变宽,最终促使边界层转捩变为湍流。
基金supported by the National Natural Science Foundation of China(Grant No.20072025).
文摘The catalytic performance of a series of cobalt(Ⅱ) hydroxamates (CoL2) and the synergistic catalytic action of the cobalt complexes combined with N-hydroxyphthalimide (NHPI) in the aerobic oxidation of p-xylene to p-toluic acid (PTA) were investigated. The results showed that the existing synergistic action in the catalytic oxidation can shorten the induction period of the radical reaction and improve the yield of PTA.
文摘对比分析现行国家标准GB/T 31248—2014《电缆或光缆在受火条件下火焰蔓延热释放和产烟特性的试验方法》与欧盟标准EN 50399:2022 Common test methods for cables under fire conditions—Heat release and smoke production measurement on cables during flame spread test—Test apparatus,procedures,results主要技术差异,相比于国标,欧标关于试验装置的规定更加详细,同时增加了标准电缆试样校准、火焰形状校准、非圆形电缆数量及安装规定等技术内容。针对外径小于或等于5 mm的电缆,分析国标和欧标试样安装方式异同,并给出GB/T 31248—2014修订建议。
基金funded by Scientific Research Deanship at University of Ha’il-Saudi Arabia through project number(RG-24014).
文摘We present a computer-modeling framework for photovoltaic(PV)source emulation that preserves the exact single-diode physics while enabling iteration-free,real-time evaluation.We derive two closed-form explicit solvers based on the Lambert W function:a voltage-driven V-Lambert solver for high-fidelity I–V computation and a resistance-driven R-Lambert solver designed for seamless integration in a closed-loop PV emulator.Unlike Taylor-linearized explicit models,our proposed formulation retains the exponential nonlinearity of the PV equations.It employs a numerically stable analytical evaluation that eliminates the need for lookup tables and root-finding,all while maintaining limited computational costs and a small memory footprint.The R-Lambert model is integrated into a buck-converter emulator equipped with a discrete PI regulator,which generates current references directly from sensed operating points,thus supporting hardware-constrained implementation.Comprehensive numerical experiments conducted on six commercial modules from various technologies(mono,poly,and multicrystalline)demonstrate significant accuracy improvements under the IEC EN 50530 near-MPP criterion:the V-Lambert solver reduces the±10%Vmpp band error by up to 61 times compared to an explicit-model baseline.Dynamic simulations under varying irradiance,temperature,and load conditions achieve millisecond-scale settling with accurate trajectory tracking.Additionally,processor-in-the-loop experimental validation on an embedded microcontroller supports the simulation results.By unifying exact analytical modeling with embedded realization,this work advances computer modeling for PV emulation,MPPT benchmarking,and controller verification in integrated renewable energy systems.
基金supported by the National Natural Science Foundation of China(No.11332007)the Natural Science Foundation of Tianjin(No.15JCYBJC19500)
文摘In order to extend the eN method to general three-dimensional boundary layers, the conservation law of the imaginary parts for the wave parameters with a fixed wave vector is deduced. The compatibility relationship （CR） and the general theory of ray tracing （RT）, which have been extensively used in conservative systems, are applied to a general three-dimensional boundary layer belonging to non-conservative systems. Two kinds of eN methods, i.e., the eN-CR method and the eN-RT method, are established. Both the two kinds of methods can wavenumber and the amplitude of the be used to predict the evolutions of the spanwise disturbances in general three-dimensional boundary layers. The reliability of the proposed methods is verified and validated by performing a direct numerical simulation （DNS） in a hypersonic general three-dimensional boundary layer over an aircraft model. The results are also compared with those obtained by other eN methods, indicating that the proposed methods have great potential applications in improving the transition prediction accuracy in general three-dimensional boundary layers.
基金This study was made possible by Naresuan University,Phisanulok,Thailand under the International Research University(IRU)program and Anhui Major Demonstration Project for Leading Talent Team on Tea Chemistry and Health,Anhui Department of Education,Hefei,China.
文摘Among six major types of tea(white,green,oolong,yellow,black,and dark teas)from Camellia sinensis,oolong tea,a semi-fermented tea,with its own unique aroma and taste,has become a popular consumption as indicated by the increasing production.Representing the characteristic flavonoids of oolong tea,theasinensins are dimeric flavan-3-ols.Many recent studies have indicated that oolong tea and theasinensins possess several health benefit properties.We consider it significant and necessary to have a comprehensive review in the recent advances of oolong tea.Therefore,the aim of the present review is to provide a new perspective on oolong tea and its characteristic phytochemicals,theasinensins associated with health benefits,molecular action pathway,and chemical mechanism of theasinensin formation from scientific evidences available on the literature.Furthermore,the chemical characterization of the oxidation products and the model oxidation system to the chemical changes of theasinensins are also discussed.
基金supported by the National Nature Science Foundation of China(Grant No.51821004)supported by National Soft Science Projects:"Frontier tracking research on science and technology in the field of energy" program
文摘The development of electrical engineering and electronic, communications, smart power grid, and ultra-high voltage transmission technologies have driven the energy system revolution to the next generation: the energy internet. Progressive penetration of intermittent renewable energy sources into the energy system has led to unprecedented challenges to the currently wide use of coal-fired power generation technologies. Here, the applications and prospects of advanced coal-fired power generation technologies are analyzed. These technologies can be summarized into three categories:(1) large-scale and higher parameters coal-fired power generation technologies, including 620/650/700 oC ultra-supercritical thermal power and double reheat ultra-supercritical coal-fired power generation technologies;(2) system innovation and specific, highefficiency thermal cycles, which consist of renewable energy-aided coal-fired power generation technologies, a supercritical CO_2 Brayton cycle for coal-fired power plants, large-scale air-cooling coal-fired power plant technologies, and innovative layouts for waste heat utilization and enhanced energy cascade utilization;(3) coal-fired power generation combined with poly-generation technologies, which are represented by integrated gasification combined cycle(IGCC) and integrated gasification fuel cell(IGFC) technologies. Concerning the existing coal-fired power units, which are responsible for peak shaving, possible strategies for enhancing flexibility and operational stability are discussed. Furthermore, future trends for coal-fired power plants coupled with cyber-physical system(CPS) technologies are introduced. The development of advanced, coal-fired power generation technologies demonstrates the progress of science and is suitable for the sustainable development of human society.
文摘To analyze the effects of width and thickness of each composition element of mixed steel U-rib-stiffened plates on the welding residual stress distribution, the distribution of the U-rib and the plate residual stress was calculated using a simplified calculation method. The method involved welding the mixed steel U-rib-stiffened plates for a structure with different sizes and different strength ratios of U-rib to plate. Based on a welding residual stress numerical simulation method validated by the blind hole method test, the distribution law of the mixed steel U-rib stiffened plate was studied. The results showed that the change of plate width has little impact on the welding residual stress and that the ratio of the thicknesses of the plate to U-rib stiffeners, the thickness of the plate, and the thickness of the U-rib has a great influence on the distribution of the welding residual stress. The thickness of plate and steel strength also greatly influenced the distribution width of the residual tensile stress. While analyzing the compression capacity of U-rib-stiffened plates, the simplified distribution of welding residual stress was used.
文摘AIM: To evaluate the efficacy of circumferential endoscopic mucosal resection (EMR) with a tissue-anchoring device in comparison to forceps precut EMR and conventional endoscopic submucosal dissection (ESD). METHODS: The study was designed as a prospective, randomized, ex vivo study. Fresh ex vivo specimens were harvested from adult white Yorkshire pigs weighing 30-50 kg. Seventy-five standardized, artificial lesions measuring 3 cm × 3 cm were created by methy- lene blue tattoo at the greater curvature in fresh ex vivo stomachs using the EASIE-R simulator platform (Endosim LLC, Berlin, MA, United States). The three advanced endoscopists performed the three resection techniques such as circumferential EMR using the tissue-anchoring device (TA-EMR), forceps precut EMR (FP-EMR), and endoscopic submucosal dissection. The endoscopists and the type of cutting methods were determined randomly by grouped randomized selection.The resection bed was grossly inspected to determine whether the lesion was resected "en-bloc " (defined as no remaining mucosal tattoo remaining on specimen). The resection bed was also probed for evidence of perforation. The procedural time of circumferential resection, submucosal dissection, and injection frequency were recorded by an independent observer.RESULTS: All 75 created lesions were successfully resected by three advanced endoscopists using the three techniques. The mean ± SD size of resected specimens (long axis) were 39.5 ± 5.6 mm, 36.5 ± 7.3 mm, and 44.6 ± 5.6 mm for TA-EMR, FP-EMR, and ESD respectively. The overall mean dissection time of both the TA- EMR and FP-EMR was significant shorter than ESD (TA- EMR: 5.1 ± 3.3 min, FP-EMR: 3.5 ± 2.0 min vs ESD: 15.8 ± 9.5 min, P < 0.001, P < 0.001). The overall mean total procedure time of both the tissue-anchoring and forceps circumferential EMR was significantly shorter than ESD (TA-EMR: 17.5 ± 6.0 min, FP-EMR: 16.6 ± 6.6 min vs ESD: 28.6 ± 13.9 min, P < 0.001, P < 0.001). The en-bloc resection rate of ESD was 100% (25/25) and the en-bloc resection rate of the TA-EMR (84.0%, 21/25) was higher than for the FP-EMR (60.0%, 15/25), yet not statistically significant (P = 0.18). The perforation rate of each technique was 8.0% (2/25). CONCLUSION: TA-EMR appears to be quicker than ESD, and there was a trend towards improved en bloc resection rate with the TA-EMR when compared to the FP-EMR.
