The printed circuit heat exchanger(PCHE) is receiving wide attention as a new kind of compact heat exchanger and is considered as a promising vaporizer in the LNG process. In this paper, a PCHE straight channel in the...The printed circuit heat exchanger(PCHE) is receiving wide attention as a new kind of compact heat exchanger and is considered as a promising vaporizer in the LNG process. In this paper, a PCHE straight channel in the length of 500 mm is established, with a semicircular cross section in a diameter of 1.2 mm.Numerical simulation is employed to investigate the flow and heat transfer performance of supercritical methane in the channel. The pseudo-boiling theory is adopted and the liquid-like, two-phase-like, and vapor-like regimes are divided for supercritical methane to analyze the heat transfer and flow features.The results are presented in micro segment to show the local convective heat transfer coefficient and pressure drop. It shows that the convective heat transfer coefficient in segments along the channel has a significant peak feature near the pseudo-critical point and a heat transfer deterioration when the average fluid temperature in the segment is higher than the pseudo-critical point. The reason is explained with the generation of vapor-like film near the channel wall that the peak feature related to a nucleateboiling-like state and heat transfer deterioration related to a film-boiling-like state. The effects of parameters, including mass flow rate, pressure, and wall heat flux on flow and heat transfer were analyzed.In calculating of the averaged heat transfer coefficient of the whole channel, the traditional method shows significant deviation and the micro segment weighted average method is adopted. The pressure drop can mainly be affected by the mass flux and pressure and little affected by the wall heat flux. The peak of the convective heat transfer coefficient can only form at high mass flux, low wall heat flux, and near critical pressure, in which condition the nucleate-boiling-like state is easier to appear. Moreover,heat transfer deterioration will always appear, since the supercritical flow will finally develop into a filmboiling-like state. So heat transfer deterioration should be taken seriously in the design and safe operation of vaporizer PCHE. The study of this work clarified the local heat transfer and flow feature of supercritical methane in microchannel and contributed to the deep understanding of supercritical methane flow of the vaporization process in PCHE.展开更多
In order to solve the problem of low precision and complication of three-dimensional modeling about micro-segment gear, one method of setting up the accurate 3D model is introduced. At first, the equation of the profi...In order to solve the problem of low precision and complication of three-dimensional modeling about micro-segment gear, one method of setting up the accurate 3D model is introduced. At first, the equation of the profile curve and the dedendum transition curve is set up, and the coordinates of the whole tooth profile are calculated by the program developed by Dephi software. And then the data of coordinates is imported to Catia, three-dimensional modeling can be got through the operations of rotating, mirror, incision and array. The method used in this paper is accurate and simple, which supplies the academic basis of CAE analysis and virtual design for micro-segment gear and relevant products.展开更多
Two series of polyurethanes based on mixed polychloromethyl methyl siloxane and poly-tetramethylene oxide in different weight fractions were synthesized. The phase separation ofsamples was studied using DSC and dynami...Two series of polyurethanes based on mixed polychloromethyl methyl siloxane and poly-tetramethylene oxide in different weight fractions were synthesized. The phase separation ofsamples was studied using DSC and dynamic mechanical property analysis. The results showedthat the introduction of chloromethyl group into polysiloxane increased its polarity and henceimproved the miscibilities with polytetramethylene oxide and polyurethane hard segment.Particularly, in the case of N-methyldiethanolamine extended materials, the surface and tensileproperties of these samples can be adjusted by various ratios of two soft segments.展开更多
Breast cancer is one of the most common cancers in the world,survival rates of breast cancer are rising as screening and treatment improve.Many new technologies applied in the biomedical domain have been born for rapi...Breast cancer is one of the most common cancers in the world,survival rates of breast cancer are rising as screening and treatment improve.Many new technologies applied in the biomedical domain have been born for rapid diagnosis and treatment.In this work,visualization cell microarray chip with threedimensional(3 D)embedded cell scaffold for cell diagnosis and treatment was designed.DNA segment,targeting on breast cancer cells SK-BR-3,were modified with camptothecin and used as model drug.Cell microarray chip system successfully control the diffusion of small molecules and locally introduced the compounds into cells.3 D embedded cell scaffold in the cell array chip afforded an environment with continuous medium supplementary and help controlling the diffusion of small molecules drugs.By cell microarray chip system,SK-BR-3 was targeted screening and killing in one step.Cell microarray chip system can achieve accurate,rapid diagnosis and target treatment of breast cancer cells SK-BR-3 and have a potential to develop to be an effective and accurate drug screen method for evaluating the drug effect of the booming chemicals.展开更多
An automated approach is proposed for a microassembly task, which is to insert a 10 μm diameter glass tube into a 12 μm diameter hole in a silicon substrate, and bond them together with ultraviolet （UV） curable ad...An automated approach is proposed for a microassembly task, which is to insert a 10 μm diameter glass tube into a 12 μm diameter hole in a silicon substrate, and bond them together with ultraviolet （UV） curable adhesive. Two three-degree-of-freedom micromanipulators axe used to move the glass tube and the dispensing needle, respectively. Visual feedback is provided by an optical microscope. The angle of the microscope axis is precisely calibrated using an autofocus strategy. Robust image segmentation method and feature extraction algorithm are developed to obtain the features of the hole, the glass tube and the dispensing needle. Visual servo control is employed to achieve accurate aligning for the tube and the hole. Automated adhesive dispensing is used to bond the glass tube and the silicon substrate together after the insertion. On-line monitoring ensures that the diameter of the adhesive spot is within a desired range. Experimental results demonstrate the effectiveness of the proposed strategy.展开更多
工业物联网(industrial Internet of things,IIoT)正面临着日益严峻的安全威胁,传统边界型安全模型已无法应对复杂多变的需求.零信任作为一种新兴的安全模型,以“绝不信任,始终认证”为核心原则,逐渐受到关注.然而,零信任在IIoT中的研...工业物联网(industrial Internet of things,IIoT)正面临着日益严峻的安全威胁,传统边界型安全模型已无法应对复杂多变的需求.零信任作为一种新兴的安全模型,以“绝不信任,始终认证”为核心原则,逐渐受到关注.然而,零信任在IIoT中的研究与应用仍处于起步阶段,亟需更加全面且系统的探索.系统综述了近年来工业领域零信任的发展与应用,重点分析其核心技术与实践场景,并明确当前研究趋势和未来方向.首先介绍了工业零信任的基本概念和原则,为后续讨论奠定理论基础.随后,系统梳理了工业零信任架构的迁移与评估方法,并总结了身份认证、软件定义边界、微隔离、信道安全及信任评估等关键技术,这些技术构成了工业零信任的核心支撑体系.此外,深入探讨了访问控制在零信任中的关键作用及其在权限管理中的价值.结合IIoT的典型应用场景,进一步分析零信任在复杂环境中的实践优势,最后总结了工业零信任的现存挑战和未来发展.展开更多
基金provided by Science and Technology Development Project of Jilin Province(No.20230101338JC)。
文摘The printed circuit heat exchanger(PCHE) is receiving wide attention as a new kind of compact heat exchanger and is considered as a promising vaporizer in the LNG process. In this paper, a PCHE straight channel in the length of 500 mm is established, with a semicircular cross section in a diameter of 1.2 mm.Numerical simulation is employed to investigate the flow and heat transfer performance of supercritical methane in the channel. The pseudo-boiling theory is adopted and the liquid-like, two-phase-like, and vapor-like regimes are divided for supercritical methane to analyze the heat transfer and flow features.The results are presented in micro segment to show the local convective heat transfer coefficient and pressure drop. It shows that the convective heat transfer coefficient in segments along the channel has a significant peak feature near the pseudo-critical point and a heat transfer deterioration when the average fluid temperature in the segment is higher than the pseudo-critical point. The reason is explained with the generation of vapor-like film near the channel wall that the peak feature related to a nucleateboiling-like state and heat transfer deterioration related to a film-boiling-like state. The effects of parameters, including mass flow rate, pressure, and wall heat flux on flow and heat transfer were analyzed.In calculating of the averaged heat transfer coefficient of the whole channel, the traditional method shows significant deviation and the micro segment weighted average method is adopted. The pressure drop can mainly be affected by the mass flux and pressure and little affected by the wall heat flux. The peak of the convective heat transfer coefficient can only form at high mass flux, low wall heat flux, and near critical pressure, in which condition the nucleate-boiling-like state is easier to appear. Moreover,heat transfer deterioration will always appear, since the supercritical flow will finally develop into a filmboiling-like state. So heat transfer deterioration should be taken seriously in the design and safe operation of vaporizer PCHE. The study of this work clarified the local heat transfer and flow feature of supercritical methane in microchannel and contributed to the deep understanding of supercritical methane flow of the vaporization process in PCHE.
基金Support by Nation Science and Technology (2009BAG12B03)
文摘In order to solve the problem of low precision and complication of three-dimensional modeling about micro-segment gear, one method of setting up the accurate 3D model is introduced. At first, the equation of the profile curve and the dedendum transition curve is set up, and the coordinates of the whole tooth profile are calculated by the program developed by Dephi software. And then the data of coordinates is imported to Catia, three-dimensional modeling can be got through the operations of rotating, mirror, incision and array. The method used in this paper is accurate and simple, which supplies the academic basis of CAE analysis and virtual design for micro-segment gear and relevant products.
文摘Two series of polyurethanes based on mixed polychloromethyl methyl siloxane and poly-tetramethylene oxide in different weight fractions were synthesized. The phase separation ofsamples was studied using DSC and dynamic mechanical property analysis. The results showedthat the introduction of chloromethyl group into polysiloxane increased its polarity and henceimproved the miscibilities with polytetramethylene oxide and polyurethane hard segment.Particularly, in the case of N-methyldiethanolamine extended materials, the surface and tensileproperties of these samples can be adjusted by various ratios of two soft segments.
基金supported by the National Natural Science Foundation of China(Nos.11204033,51773093)the Natural Science Foundation of Jiangsu Province(No.BK20141397)+4 种基金the Research Fund for the Doctoral Program of Higher Education of China(No.20120092120042)the CMA L’OREAL CHINA SKIN GRANT 2015(No.S2015121421)the Open Research Fund of State Key Laboratory of Natural Medicines,China Pharmaceutical University(No.SKLNMKF201803)Southeast University and Nanjing Medical University Cooperation Project(No.2242018K3DN14)Open Research Fund of State Key Laboratory of Bioelectronics,Southeast University
文摘Breast cancer is one of the most common cancers in the world,survival rates of breast cancer are rising as screening and treatment improve.Many new technologies applied in the biomedical domain have been born for rapid diagnosis and treatment.In this work,visualization cell microarray chip with threedimensional(3 D)embedded cell scaffold for cell diagnosis and treatment was designed.DNA segment,targeting on breast cancer cells SK-BR-3,were modified with camptothecin and used as model drug.Cell microarray chip system successfully control the diffusion of small molecules and locally introduced the compounds into cells.3 D embedded cell scaffold in the cell array chip afforded an environment with continuous medium supplementary and help controlling the diffusion of small molecules drugs.By cell microarray chip system,SK-BR-3 was targeted screening and killing in one step.Cell microarray chip system can achieve accurate,rapid diagnosis and target treatment of breast cancer cells SK-BR-3 and have a potential to develop to be an effective and accurate drug screen method for evaluating the drug effect of the booming chemicals.
基金supported by National Natural Science Foundation of China under(Nos.61227804 and 61105036)
文摘An automated approach is proposed for a microassembly task, which is to insert a 10 μm diameter glass tube into a 12 μm diameter hole in a silicon substrate, and bond them together with ultraviolet （UV） curable adhesive. Two three-degree-of-freedom micromanipulators axe used to move the glass tube and the dispensing needle, respectively. Visual feedback is provided by an optical microscope. The angle of the microscope axis is precisely calibrated using an autofocus strategy. Robust image segmentation method and feature extraction algorithm are developed to obtain the features of the hole, the glass tube and the dispensing needle. Visual servo control is employed to achieve accurate aligning for the tube and the hole. Automated adhesive dispensing is used to bond the glass tube and the silicon substrate together after the insertion. On-line monitoring ensures that the diameter of the adhesive spot is within a desired range. Experimental results demonstrate the effectiveness of the proposed strategy.
文摘工业物联网(industrial Internet of things,IIoT)正面临着日益严峻的安全威胁,传统边界型安全模型已无法应对复杂多变的需求.零信任作为一种新兴的安全模型,以“绝不信任,始终认证”为核心原则,逐渐受到关注.然而,零信任在IIoT中的研究与应用仍处于起步阶段,亟需更加全面且系统的探索.系统综述了近年来工业领域零信任的发展与应用,重点分析其核心技术与实践场景,并明确当前研究趋势和未来方向.首先介绍了工业零信任的基本概念和原则,为后续讨论奠定理论基础.随后,系统梳理了工业零信任架构的迁移与评估方法,并总结了身份认证、软件定义边界、微隔离、信道安全及信任评估等关键技术,这些技术构成了工业零信任的核心支撑体系.此外,深入探讨了访问控制在零信任中的关键作用及其在权限管理中的价值.结合IIoT的典型应用场景,进一步分析零信任在复杂环境中的实践优势,最后总结了工业零信任的现存挑战和未来发展.
