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Flow field characteristics and drag reduction performance of high-low velocity stripes on the biomimetic imbricated fish scale surfaces

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Biosurface and Biotribology 2024年第3期10卷 132-141页

作者： dengke chen XianXian Cui Huawei chen College of Transportation Ludong UniversityYantaiShandongChina School of Mechanical Engineering and Automation Beihang UniversityBeijingChina Advanced Innovation Center for Biomedical Engineering Beihang UniversityBeijingChina

Improving energy efficiency and cost reduction is a perennial challenge in *** biological systems have evolved unique functional surfaces or special physiological functions over centuries to adapt to their complex *** these biological wonders,fish,one of the oldest vertebrate groups,has garnered significant attention due to its exceptional fluid dynamics *** are actively exploring the potential of fish skin's distinctive structural and material characteristics in reducing *** this study,models of biomimetic imbricated fish scale are established,and the evolution characteristics of the flow field and drag reduction performance on these bionic surfaces are *** results showed a close relationship between the high-low velocity stripes generated and the fluid motion by the imbricated fish scale *** stripes'prominence increases with the spacing of the adjacent scales and tilt angle of the fish scale,and the velocity amplitude of the stripes decreases as the exposed length of the imbricated fish scale surface ***,the biomimetic imbricated fish scale surface can decrease the velocity gradient and thereby reduce the wall shear *** insights gained from the fish skin-inspired imbricated fish surface provide valuable perspectives for an in-depth analysis of fish hydrodynamics and offer fresh inspiration for drag reduction and antifouling strategies in engineering applications.

关键词： bionic surface drag reduction

Effects of Blending Ratio on Combustion and NO Emission Characteristics during Co-Firing of Semi-Char and Lignite in a 350 kW Pulverized Coal-Fired Furnace

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Journal of Thermal Science 2023年第3期32卷 1292-1305页

作者： YAN Yonghong PENG Zhengkang SUN Liutao chen dengke SUN Rui College of Electrical and Power Engineering Taiyuan University of TechnologyTaiyuan 030024China School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150001China

The influence of the blending ratio of pyrolyzed semi-char(SC)on the ignition,NO emission and burnout characteristics of lignite co-fired with SC was investigated in a 350 kW fuel-rich/lean combustion *** flame temperature and concentrations of gaseous species including O_(2),CO,and NO,were measured in *** results indicated that the ignition characteristics of the blended fuel worsened with increasing SC blending ratio,such as an elongated ignition standoff *** addition of SC to lignite delayed the appearance of a stable flame boundary,and the stable combustion zone moved down,but the final combustion stability was gradually strengthened in the later combustion *** emission concentration at the primary combustion zone(PCZ)outlet was the lowest at 472.6 mg/m^(3)@6%O_(2)when the SC blending ratio was 25%.The combustion zone and reducing zone areas in PCZ were defined to evaluate the NO reduction characteristics,and quantitative analysis using a multiple linear regression model showed that heterogeneous reduction was more important than homogeneous reduction in lowering NO *** Raman spectrum of the char sample indicated that the addition of lignite promoted the formation of small aromatic rings in the early ignition stage,corresponding to a higher char *** burnout ratio of pure lignite was maximal and was decreased by increasing the SC blending ***,considering the ignition standoff distance,NO emission,and burnout ratio,the optimum SC blending ratio was estimated to be 25%.

关键词： co-firing blending ratio ignition characteristics NO emission burnout ratio

Hydrogen embrittlement of grain boundaries in nickel:an atomistic study

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npj Computational Materials 2017年第1期3卷 219-226页

作者： Shan Huang dengke chen Jun Song David LMcDowell Ting Zhu Woodruff School of Mechanical Engineering Georgia Institute of TechnologyAtlantaGA 30332USA Department of Mining and Materials Engineering McGill UniversityMontrealQC H3A OC5Canada

The chemomechanical degradation of metals by hydrogen is widely observed,but not clearly understood at the atomic *** we report an atomistic study of hydrogen embrittlement of grain boundaries in *** the possible interstitial hydrogen sites at a given grain boundary are identified by a powerful geometrical approach of division of grain boundary via polyhedral packing units of *** segregation energies are calculated at these interstitial sites to feed into the Rice-Wang thermodynamic theory of interfacial *** hydrogen embrittlement effects are quantitatively evaluated in terms of the reduction of work of separation for hydrogen-segregated grain *** study both the fast and slow separation limits corresponding to grain boundary fracture at fixed hydrogen concentration and fixed hydrogen chemical potential,*** further analyze the influences of local electron densities on hydrogen adsorption energies,thereby gaining insights into the physical limits of hydrogen embrittlement of grain boundaries.

关键词： grain boundary separation

Bio-inspired drag reduction surface from sharkskin

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Biosurface and Biotribology 2018年第2期4卷 39-45页

作者： dengke chen Yang Liu Huawei chen Deyuan Zhang School of Mechanical Engineering and Automation Beihang UniversityHaidian DistrictBeijingPeople's Republic of China

Nature evolution provides nature surface treasures with special and fascinating surface function to inspiredesign,such as the drag reduction of *** this overview,the morphology and mechanism of the sharkskinexplained from different aspects,and various methods of fabricating surfaces with sharkskin morphology areillustrated in details,and then the applications in different fluid engineering are demonstrated in *** overviewwill improve the comprehension of the morphology and mechanisms of sharkskin,and methods of fabricating thesurface with morphology,and the recent applications in engineering.

关键词： surface details mechanism

Drag reduction capacity of multi-scale and multi-level riblet in turbulent flow

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Biosurface and Biotribology 2024年第1期10卷 7-15页

作者： dengke chen Wenhao Li Yichen Zhao Jinhai Liu Xianxian Cui Zehui Zhao Xiaolin Liu Huawei chen College of Transportation Ludong UniversityYantaiShandongChina School of Mechanical Engineering and Automation Beihang UniversityBeijingChina Advanced Innovation Center for Biomedical Engineering Beihang UniversityBeijingChina

For high-speed moving objects,drag reduction has been a prolonged major *** address this problem,passive and negative strategies have been proposed in the preceding *** integration of creatures and nature has been continuously perfected during biological *** structure characteristics,material properties,and special functions of marine organisms can provide inexhaustible inspirations to solve this intractable problem of drag ***,a simple and low-cost laser ablation method was proposed.A multi-scale and multi-level riblet(MSLR)surface inspired by the denticles of the sharkskin was fabricated by controlling the density of the laser path and ablation *** morphology and topographic features were characterised using an electron microscope and a scanning white-light interfering ***,the drag reduction capacity of the bionic riblet surface was measured in a circulating water ***,the mechanism of drag reduction was analysed by the computational fluid dynamics(CFD)*** results show that the MSLR surface has a stable drag reduction capacity with an increase in Reynold(Re)number which was contributed by high-low velocity stripes formed on the MSLR *** study can provide a reference for fabricating spatial riblets with efficient drag reduction at different values of Re and improving marine antifouling.

关键词： BIOMIMICS BIONIC STRUCTURE DRAG REDUCTION

Design optimization of a silicon-germanium heterojunction negative capacitance gate-all-around tunneling field effect transistor based on a simulation study

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Chinese Physics B 2023年第9期32卷 436-442页

作者：魏伟杰吕伟锋韩颖张彩云谌登科 School of Microelectronics Hangzhou Dianzi UniversityHangzhou 310018China

The steep sub-threshold swing of a tunneling field-effect transistor(TFET)makes it one of the best candidates for lowpower nanometer ***,the low driving capability of TFETs prevents their application in integrated *** this study,an innovative gate-all-around(GAA)TFET,which represents a negative capacitance GAA gate-to-source overlap TFET(NCGAA-SOL-TFET),is proposed to increase the driving *** proposed NCGAA-SOL-TFET is developed based on technology computer-aided design(TCAD)*** proposed structure can solve the problem of the insufficient driving capability of conventional TFETs and is suitable for sub-3-nm *** addition,due to the negative capacitance effect,the surface potential of the channel can be amplified,thus enhancing the driving *** gateto-source overlap(SOL)technique is used for the first time in an NCGAA-TFET to increase the band-to-band tunneling rate and tunneling area at the silicon-germanium *** optimizing the design of the proposed structure via adjusting the SOL length and the ferroelectric layer thickness,a sufficiently large on-state current of 17.20μA can be achieved and the threshold voltage can be reduced to 0.31 V with a sub-threshold swing of 44.98 mV/***,the proposed NCGAA-SOL-TFET can overcome the Boltzmann limit-related problem,achieving a driving current that is comparable to that of the traditional complementary metal-oxide semiconductor devices.

关键词： negative capacitance(NC) gate-all-around(GAA) silicon-germanium heterojunction gate-tosource overlap(SOL)

贸易壁垒下降与环境污染改善——来自中国企业污染数据的新证据

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经济研究 2020年第12期55卷 98-114页

作者：陈登科复旦大学经济学院 200433

贸易与环境是新时期关乎国计民生的重大议题。十九大报告将推进贸易强国建设列为建设现代化经济体系的重要组成部分,将污染防治列为决胜全面建设小康社会的三大攻坚战之一。然而对于贸易与环境污染的关系,现有文献还存在较大争议,且基... 详细信息

贸易与环境是新时期关乎国计民生的重大议题。十九大报告将推进贸易强国建设列为建设现代化经济体系的重要组成部分,将污染防治列为决胜全面建设小康社会的三大攻坚战之一。然而对于贸易与环境污染的关系,现有文献还存在较大争议,且基于微观数据考察二者关系的文献非常之匮乏。鉴于此,本文将中国企业污染这一独特数据库与中国工业企业数据库以及行业关税税率数据合并,借助中国加入WTO准自然实验考察了贸易壁垒下降对中国环境污染的影响及机制。研究发现,贸易壁垒下降显著降低了企业主要污染物SO2排放强度。机制分析表明,企业SO2排放强度下降主要是由于企业污染排放下降而非产出上升;企业污染排放下降主要由企业生产过程更加清洁而非污染排放末端处理;煤炭使用强度下降是贸易壁垒下降导致SO2排放强度下降的重要机制;在贸易壁垒变化影响企业污染排放的技术效应中,有偏技术进步而非中性技术进步占据主导地位。本文研究结论意味着,扩大对外开放不仅可以通过经典文献识别的经济增长机制,还能够通过改善环境增进中国社会福利。这为新时期推进贸易强国建设与打赢污染防治攻坚战提供了有益的政策启示。

关键词：贸易环境污染中国企业污染数据库

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石油冲击对我国宏观经济影响和货币政策调整

中国经济问题 2016年第1期 56-70页

作者：陈晓玲陈登科西南财经大学经济学院复旦大学经济学院社会主义市场经济研究中心

本文建立结构向量自回归(SVAR)模型分析石油价格冲击对我国宏观经济的影响。研究结论表明石油价格上升对我国产出水平带来正面影响,而跨国面板数据回归显示,这可能与石油价格上升对我国主要贸易伙伴一般物价水平影响更大有关,这导致我... 详细信息

本文建立结构向量自回归(SVAR)模型分析石油价格冲击对我国宏观经济的影响。研究结论表明石油价格上升对我国产出水平带来正面影响,而跨国面板数据回归显示,这可能与石油价格上升对我国主要贸易伙伴一般物价水平影响更大有关,这导致我国贸易条件相对改善相关;此外,我国货币政策调整呈现典型的"逆周期"操作特征,且利率"逆周期"特征更加明显;非线性石油价格情形下,主要宏观经济变量对石油冲击反应方向不变,但反应幅度减少,该情况下,货币政策的"不作为"优于微调。

关键词：油价冲击货币政策非线性油价

唑来膦酸联合钙剂治疗老年慢性阻塞性肺疾病患者骨质疏松症的临床疗效

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中国骨质疏松杂志 2018年第2期24卷 222-225页

作者：李沁陈登科贵州省遵义市第一人民医院老年病科贵州遵义563000

目的研究老年慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)合并骨质疏松症患者应用唑来膦酸结合钙尔奇对患者骨密度、生化与骨代谢相关指标的影响。方法 102例COPD合并骨质疏松症患者,按随机数字表法将其分为治疗组(n... 详细信息

目的研究老年慢性阻塞性肺疾病(chronic obstructive pulmonary disease,COPD)合并骨质疏松症患者应用唑来膦酸结合钙尔奇对患者骨密度、生化与骨代谢相关指标的影响。方法 102例COPD合并骨质疏松症患者,按随机数字表法将其分为治疗组(n=51)及对照组(n=51)。对照组给予钙尔奇治疗,治疗组给予唑来膦酸联合钙尔奇治疗,为期12个月。检测治疗后两组患者的腰椎1~4(L1~4)、股骨颈骨密度及血钙(Ca)、血磷(P)、25羟基维生素D[25(OH)D3]、甲状旁腺素(parathyroid hormone,PTH)、骨钙素(osteocalcin,OC)、1型胶原羧基末端肽(type 1 collagen carboxy terminal peptide,β-CTX)、1型前胶原氨基端肽(type 1 procollagen amino terminal peptide,P1NP)、骨源性碱性磷酸酶(bone alkaline phosphatase,BALP)水平的变化情况,记录两组患者药物的不良反应。结果治疗后12个月后,治疗组腰椎1~4(L1~4)、股骨颈骨密度均显著高于同时期对照组(P0.05)。两组药品不良反应发生率比较,差异无统计学意义(P>0.05)。结论唑来膦酸联合钙剂提升COPD患者骨密度,改善骨代谢状态,可以安全有效地防治老年COPD合并骨质疏松症。

关键词：慢性阻塞性肺疾病骨质疏松唑来膦酸钙剂骨密度