Engineering the spectra of photon triplets generated from micro/nanofiber

Quantum light sources are the core resources for photonics-based quantum information processing.We investigate the spectral engineering of photon triplets generated by third-order spontaneous parametric down-conversion in micro/nanofiber.The phase mismatching at one-third pump frequency gives rise to non-degenerate photon triplets,the joint spectral intensity of which has an elliptical locus with a fixed eccentricity of√6/3.Therefore,we propose a frequency-division scheme to separate non-degenerate photon triplets into three channels with high heralding efficiency for the first time.Choosing an appropriate pump wavelength can compensate for the fabrication errors of micro/nanofiber and also generate narrowband,non-degenerate photon triplet sources with a high signal-to-noise ratio.Furthermore,the long-period micro/nanofiber grating introduces a new controllable degree of freedom to tailor phase matching,resulting from the periodic oscillation of dispersion.In this scheme,the wavelength of photon triplets can be flexibly tuned using quasi-phase matching.We study the generation of photon triplets from this novel perspective of spectrum engineering,and we believe that this work will accelerate the practical implementation of photon triplets in quantum information processing.

Performance analysis of a 2-stroke micro free-piston swing engine

The micro free-piston swing engine （MFPSE） is a new structure, free-piston internal combustion engine. The dynamic model integrated MFPSE with a power generator and thermodynamic models in compression, power and scavenge processes based on the open thermodynamic systems were presented. A simulation was executed at given geometric parameters and initial conditions. The results manifest that the working principle of MFPSE is feasible.

CAUSALITY DIAGRAM BASED SAFETY ANALYSIS OF MICRO TURBOJET ENGINE

An improved safety analysis based on the causality diagram for the complex system of micro aero-engines is presented.The study is examined by using the causality diagram in analytical failure cases due to rupture or pentration in the receiver of micro turbojet engine casing,and the comparisons are also made with the results from the traditional fault tree analysis.Experimental results show two main advantages：（1）Quantitative analysis which is more reliable for the failure analysis in jet engines can be produced by the causality diagram analysis;（2）Graphical representation of causality diagram is easier to apply in real test cases and more effective for the safety assessment.

Numerical Simulation of a Spark Ignited Two-Stroke Free-Piston Engine Generator

A numerical program is built to simulate the performance of a spark ignited two-stroke free-piston engine coupled with a linear generator. The computational model combines a series of dynamic and thermodynamic equations that are solved simultaneously to predict the performances of the engines. The dynamic analysis performed consists of an evaluation of the frictional force and load force introduced by the generator. The thermodynamic analysis used a single zone model to describe the engine＇ s working cycle which includes intake, scavenging, compression, combustion and expansion, and to evaluate the effect of heat transfer based on the first law of thermodynamics and the ideal gas state equation. Because there is no crankshaft, a time based Wiebe equation was used to express the fraction of fuel burned in the combustion. The calculated results were validated by using the experimental data from another research group. The results indicate that the free-piston generator has some advantages over conventional engines.

Engineering properties and microstructure of expansive soil treated with nanographite powder

To reduce geological disasters caused by expansive soil,it is crucial to use a new type of modified material to rapidly improve soil strength instead of traditional soil improvement materials such as lime and cement.Nanographite powder(NGP)has excellent properties,such as high adsorption,conductivity,and lubrication,since it has the characteristics of small size,large specific surface area,and high surface energy.However,previous studies on the improvement of expansive soil with NGP are not processed enough.To study the improvement effect of NGP on expansive soil,non-load swelling ratio tests,consolidation tests,unconfined compressive strength tests,mercury injection tests,and micro-CT tests on expansive soil mixed with different NGP contents were performed.The results show that the non-load swelling ratio,mechanical properties,and porosity of expansive soil show some increasement after adding NGP.The strength of expansive soil reaches the maximum when the NGP content is 1.450%.The cumulative mercury volume and compressive strain of expansive soil reach the maximum with the 2.0%NGP content.Finally,the modification mechanism of swelling,compressibility,microstructure,and compressive strength of expansive soil by NGP is revealed.

Effects analysis on catalytic combustion characteristic of hydrogen/air in micro turbine engine by fuzzy grey relation method

In order to enhance catalytic combustion efficiency, a premixed hydrogen /air combustion model of the micro turbine engine is established under different excess air ratio, inlet velocity and heat transfer coefficient. And effects of inlet velocity, excess air coefficient and heat transfer coefficient on the catalytic combustion efficiency of the hydrogen have been analyzed by the FLUENT with CHEMKIN reaction mechanisms and the fuzzy grey relation theory. It is showed that inlet velocity has a more intuitive influence on the catalytic combustion efficiency of the hydrogen. A higher efficiency can be obtained with a lower inlet velocity. The optimum excess air coefficient is in the range of 0.94 to 1.0, the catalytic combustion efficiency of the hydrogen will be declined if the excess air coefficient exceeded 1.0. The effect of heat transfer coefficient on the catalytic combustion efficiency of the hydrogen mainly embodies in the case of the excess air coefficient exceeded 1.0, however, the effect will be declined if the heat transfer coefficient exceeded 4.0. The fuzzy grey relation degrees of the inlet velocity, heat transfer coefficient and excess air coefficient on the catalytic combustion efficiency of the hydrogen are 0.640945, 0.633214 and 0.547892 respectively.

EFFECT OF THE CONTROLLED ROLLING CONTROLLED COOLING ON STRENGTH AND DUCTILITY OF THE BAINITE MICRO ALLOYED ENGINEERING STEEL

The continuous cooling transformation of hot deformation austenite austenite of test steel and the effect of different processing schedules of controlled rolling and controlled cooling on the strength and ductility have been studied. The theory and the experiment base are presented for controlled rolling and controlled cooling of the SBL micro alloyed engineering steel.

Design and fabrication of alumina micro reciprocating engine

Microengines are regarded as the potential replacements for batteries.Aimed at the unsatisfactory thermal property of silicon used in the combustion chambers,ceramics are chosen as the construction material in this paper.The fabrication process where alumina has been chosen as the microengine material is discussed.Vigorous FEA has been carried out,and it is found that the material satisfies the stress and deformation requirements of the design.Then the alumina fabrication process is described.Soft reusable polydimethylsiloxane(PDMS)moulds are produced from SU-8 resist masters,and alumina microengine parts are produced using the PDMS moulds.Images of the ceramic components show that the fabrication satisfies the design requirements.

Angiogenesis in tissue-engineered nerves evaluated objectively using MICROFIL perfusion and micro-CT scanning

Angiogenesis is a key process in regenerative medicine generally, as well as in the specific field of nerve regeneration. However, no convenient and objective method for evaluating the angiogenesis of tissue-engineered nerves has been reported. In this study, tissue-engineered nerves were constructed in vitro using Schwann cells differentiated from rat skin-derived precursors as supporting cells and chitosan nerve conduits combined with silk fibroin fibers as scaffolds to bridge 10-mm sciatic nerve defects in rats. Four weeks after surgery, three-dimensional blood vessel reconstructions were made through MICROFIL perfusion and micro-CT scanning, and parameter analysis of the tissue-engineered nerves was performed. New blood vessels grew into the tissue-engineered nerves from three main directions： the proximal end, the distal end, and the middle. The parameter analysis of the three-dimensional blood vessel images yielded several parameters, including the number, diameter, connection, and spatial distribution of blood vessels. The new blood vessels were mainly capillaries and microvessels, with diameters ranging from 9 to 301 μm. The blood vessels with diameters from 27 to 155 μm accounted for 82.84% of the new vessels. The microvessels in the tissue-engineered nerves implanted in vivo were relatively well-identified using the MICROFIL perfusion and micro-CT scanning method, which allows the evaluation and comparison of differences and changes of angiogenesis in tissue-engineered nerves implanted in vivo.

Experimental study on compression stroke characteristics of free- piston engine generator

The compression stroke characteristics of free-piston engine generator were studied. The numerical model of the compression stroke was established based on thermodynamics and dynamics equation,and the leak loss,heat loss and friction loss were considered. Through solving numerical equations,the in-cylinder pressure of compression stroke under different compression ratios was calculated,energy transfer and conversion process was analyzed,and the calculated results were experimentally verified. The results showed that the actual effective output of electronic energy and the compression energy stored in the com-pressed gas accounted for about 70%. The compression energy gradually increased with the increasing com-pression ratio. When the compression ratio was more than 7. 5,the actual compression energy increased slowly and the energy error between simulation and test decreased.

仿生双相磷酸钙生物陶瓷支架的Micro-CT评价

[目的]体外用MicroCT(Microcomputedtomography)图像对仿生双相磷酸钙生物陶瓷支架的三维结构进行计算机重建和评价。[方法]犬股骨头的松质骨样本行MicroCT扫描,提取图像信息;三维凝胶叠层成型法制备出具有仿骨小梁结构的双相磷酸钙仿生生物陶瓷支架。随后用MicroCT对支架扫描,以三维结构参数对支架和松质骨样本作三维评价和比较。三维参数包括骨体积分数(BoneVolumeFraction,BVF,BV/TV)、骨表面积体积比(Bonesurface/bonevolumeratio,BS/BV)、骨小梁厚度(Trabecularthickness,TbTh)、骨小梁数目(Trabecularnumber,TbN)、骨小梁间隙(Trabecularspacing,TbSp)、结构模型指数(StructureModelIndex,SMl)和各向异性程度(degreeofanisoropy,DA)。[结果]与犬股骨头松质骨样本相比,用本方法制备出的BCP支架具有相似的三维空间结构,二者的BV/TV、TbTh、TbN无显著差别(P>0.05)。小梁结构呈板状模型。[结论]本研究制备的BCP多孔支架的小梁具有一定的取向性,力学强度和良好的适于血管长入的空间结构。

Micro-CT技术结合逆向工程软件建立上颌第一前磨牙的三维有限元模型

目的利用简便有效的方法建立离体上颌第一前磨牙三维有限元模型,为生物力学研究提供数学模型基础。方法使用Micro-CT对离体、完整的左侧上颌第一前磨牙进行牙体扫描,将获得的CT影像转化格式,通过Mimics10.0软件采集釉质、本质及髓腔的点数据,导入Imageware 12.0软件中进行点云处理和曲线反求,通过Ansys 11.0软件完成曲面拟合形成牙体组织的三维实体模型并进行布尔运算,整合釉质、牙本质及髓腔系统;建立牙周膜以及牙槽骨的实体模型,分别进行网格划分,同时对模型进行力学加载。结果建立了包含髓腔、牙周膜、牙槽骨的上颌第一前磨牙的精细三维有限元模型,网格划分后的牙体三维有限元模型:釉质具有26 685个单元,牙本质具有114 082个单元,牙髓腔具有11 843个单元,牙周膜具有22 004个单元,牙槽骨具有66 767个单元,共有241 381个10节点四面体单元。模型具有非常高的精确度,真实反映了釉牙骨质界的形态。从应力分布来看釉质上应力主要集中在面中央窝和釉质与本质交界的边缘;同样牙本质的应力集中部分也在釉牙本质界处。结论通过Micro-CT技术与逆向工程软件相结合的方法建立了左侧上颌第一前磨牙的三维有限元模型,该模型具有良好的几何相似性和力学相似性。

Novel Micro Free-Piston Swing Engine and Its Feasibility Validation

To develop high energy-density micro power generation systems, a novel two-stroke cycle micro free-piston swing engine (MFPSE), inspired by the concept of the micro internal combustion swing engine, is proposed to supply mechanical power for a micro power generation system. The working principle, gas exchange and ignition timing control cycles, and structure and operation advantages of the MFPSE are dis- cussed in detail. A prototype where the timing control and geometric parameters are designed with refer- ence to a traditional two-stroke cycle internal combustion engine is fabricated. The successful ignition ex- periment shows that this new concept engine is feasible and is worthy of further study.

Micro-CT技术结合逆向工程软件和CAD软件在建立模拟根管治疗术后牙体组织三维有限元模型中的应用

目的:通过Micro-CT技术和逆向工程软件及CAD软件建立牙齿根管治疗术后的三维有限元模型。方法:通过Micro-CT对获得的完整人下颌第一磨牙进行扫描,将获得的图片导入Mimics 10.01软件进行初步拟合,之后导入Geomagic 10软件中精修细化获得NUBS曲面。在Pro/Engineer Wildfire 4.0软件中根据根管器械的形态学参数建立模拟根管预备后的根管形态。最后,将精修细化的曲面文件和在Pro/E中建立的根管系统在ANSYS前处理软件Workbench中进行布尔运算和切割,并且进行属性定义和网格划分。结果:建立了根管锥度为0.02、根尖直径为0.35mm的下颌第一磨牙的精细有限元模型。结论:Micro-CT技术结合逆向工程软件和CAD软件可有效建立出牙齿模拟根管治疗后精细三维有限元模型。

Potential application of functional micro-nano structures in petroleum

This paper takes micro-nano motors and metamaterials as examples to introduce the basic concept and development of functional micro nano structures, and analyzes the application potential of the micro-nano structure design and manufacturing technology in the petroleum industry. The functional micro-nano structure is the structure and device with special functions prepared to achieve a specific goal. New functional micro-nano structures are classified into mobile type(e.g. micro-nano motors) and fixed type(e.g. metamaterials), and 3 D printing technology is a developed method of manufacturing. Combining the demand for exploration and development in oil and gas fields and the research status of intelligent micro-nano structures, we believe that there are 3 potential application directions:(1) The intelligent micro-nano structures represented by metamaterials and smart coatings can be applied to the oil recovery engineering technology and equipment to improve the stability and reliability of petroleum equipment.(2) The smart micro-nano robots represented by micro-motors and smart microspheres can be applied to the development of new materials for enhanced oil recovery, effectively improving the development efficiency of heavy oil, shale oil and other resources.(3) The intelligent structure manufacturing technology represented by 3 D printing technology can be applied to the field of microfluidics in reservoir fluids to guide the selection of mine flooding agents and improve the efficiency of mining.

一流专业背景下的微波课程群改革与实践

研究了“双一流”建设背景下河北大学通信工程专业微波课程群建设工作。探讨和研究通信工程专业课程改革措施和实践过程,包括强化知识一体化建设、思政元素与专业知识融合、改革课程评价机制等。通过以上措施,有效提升了学生对相关课程概念的理解,提高了学生学习兴趣和创新及实践能力。

大型工程项目品质工程建设场景中的微创新研究

品质工程建设是工程经济高质量发展的重要内容。作为品质工程建设的抓手,微创新在大型工程项目建设场景中受到越来越多的关注。大广高速南康至龙南段扩容工程采用微创新在品质工程建设方面取得显著成效,以其为案例,通过访谈与调研获得一手数据,在场景驱动创新理论视角下探索大型工程项目品质工程建设场景中的微创新要素、内容和策略。结果发现:①大型工程项目品质工程建设场景要素包括战略、需求愿景、参与主体、市场、技术、资源和环境;②在场景驱动下,围绕品质目标的微创新活动内容包括设计理念微创新、工程技术、方法与信息化微创新以及管理制度微创新;③促进微创新的关键策略为沿着微创新活动作好顶层设计、班组管理与工程品质考核验收。研究结论有助于丰富大型工程项目品质工程建设场景驱动微创新理论研究,并为我国大型工程项目品质提升提供参考借鉴。

城市小微湿地生态修复——以九江市十里河小微湿地为例

利用小微湿地生态恢复技术修复九江市十里河河段历史河流湿地环境。文中通过实施微地形设计、土壤处理、黏土坝和溢洪道设计和植被群落设计等工程措施,增加湿地水量、净化水体,提高河道土壤湿度饱和度,改善野生动物栖息地环境,提高城市的生态环境质量。研究城市小微湿地生态修复技术,旨在为我国其他城市小微湿地建设和水环境治理提供经验和借鉴。

安全帽送风强度对人体呼吸微环境影响研究

为改善作业人员呼吸微环境,对送风式安全帽佩戴者呼吸微环境温度场、速度场和浓度场进行研究。通过假人试验方法测试安全帽在不同送风强度下的人体呼吸微环境温度、速度和粉尘质量浓度,研究人体呼吸微环境温度分布及速度分布规律,阐明安全帽送风强度对人体呼吸微环境中总尘及呼尘降尘效果的影响,进而分析佩戴者对安全帽送风强度的满意程度。结果显示,人体面中部位降温效果优于人体脸颊两侧,其中人体鼻子处降温效果较为明显;安全帽在不同送风强度下对人体呼吸微环境速度场的分布规律一致;当送风强度为Ⅳ级时,人体呼吸微环境内粉尘降尘效率最高,佩戴者满意率最高;人体微环境总尘和呼尘降尘效率分别可达到81.39%和82.89%。研究结果可为改善人体呼吸微环境提供参考。

基于逆向工程法培养小学生微创新能力的实践研究——以“3D打印”为例

逆向工程法是一种“从成品出发”的教学方法,降低了创新门槛,容易实现微创新。文章以微创新能力内涵为导向,遵循“从仿到创”的阶段式教学理念,在项目式教学理论、做中学理论的支持下,提出了基于逆向工程法培养小学生微创新能力的教学活动框架,以“3D打印”为例进行三轮教学实践,并采用三角互证的方法从教师、学生、教学过程三个角度探究实践效果,以此修正与完善活动框架。研究结果表明,基于逆向工程法设计的教学活动从总体上显著提高了小学生微创新能力水平,对创新思维与创新技能要素也有显著促进作用,但对创新人格的影响不显著。研究结果为小学生微创新能力培养及国家创新人才培养提供了理论指导和实践参考。