Fabrication and characterization of rugate structures composed of SiO_2 and Nb_2O_5

1Introduction Opticalcoatingdesignsbasedonlayers,whichareinhomogeneousalongthestackaxis,haveopticalandmechanicalpropertiesthatdiffer fromthoseofconventionalhigh low index stacks.Particularly,thewideaccessibleangular rangeandthelowopticalscatterlevelmake themsuperiortotraditionalstackswithrespect toselectedpurposessuchasomni directionalde vicesornotchfilters[14].Manufacturingsuch systemsinpracticerequiresthecalculation,dep osition,monitoringandcharacterizationofopti calcoatingswithawelldefinedc…     

Journal of Measurement Science and Instrumentation

Journal of Measurement Science and Instrumentation(CN14-1357/TH,ISSN 1674-8042)is published by North University of China.It is a comprehensive academic journal,aiming to present scientific research papers in the fields of measurement science and instrumentation,including general principles,technologies and instrumentation of measurement and control applied to such academic and industrial fields as mechanics,electric and electronic engineering,magnetics,optics,chemistry,biology,and so on.     

Journal of Measurement Science and Instrumentation

Journal of Measurement Science and Instrumentation(CN14-1357/TH,ISSN 1674-8042)is published by North University of China.It is a comprehensive academic journal,aiming to present scientific research papers in the fields of measurement science and instrumentation,including general principles,technologies and instrumentation of measurement and control applied to such academic and industrial fields as mechanics,electric and electronic engineering,magnetics,optics,chemistry,biology,and so on.     

Fretting Wear Behavior of UHMWPE—Influence of Load and Stroke

In this study, the tribological behavior of ultra-high-molecular-weight polyethylene (UHMWPE) against a GCr 15 steel ball during fretting wear conditions was investigated using an oscillating reciprocating tribometer. The aim of this study was to characterize the critical value of normal load and stroke corresponding to this transition in UHMWPE worn surface at room temperature. Results showed that there existed a critical value of load or stroke at fixed condition. The friction coefficient and wear volume loss of UHMWPE at or near the critical values of load and stroke exhibited extreme changes. Based on observation of the worn surface by scanning electron microscopy (SEM) and 3D surface profiler measurements, it can be found that damage to the worn surface can be linked to the contact load and stroke. In addition, results showed that during the process of fretting wear under different load or stroke conditions, the gross slip regime dominated throughout the whole test period.     

Parameter optimization and mechanism of laser–arc hybrid welding of dissimilar Al alloy and stainless steel

Laser–cold metal transfer arc hybrid welding of 6061 Al alloy and AISI304 stainless steel (304SS) was carried out. Bead morphologies and intermetallic compound (IMC) layer characterizations of the joints were studied in detail. The optimal parameter range for accepted bead appearances (OPRBA) without surface and interface defects was obtained, and the growth mechanism of the IMC layer was summarized. The results showed that the nonuniformity in the thickness and shape along the fusion zone/304SS interface from the top surface to the bottom increases with increasing heat input and is more sensitive to laser power because the interface temperature is dominated by a high-temperature laser keyhole throughout the molten pool. As the welding parameters are within the OPRBA and the heat input is within the range of 80–110 J/mm, the joints are stronger than 130 MPa and the corresponding IMC layer thickness is at the range of 3–6.5 μm. The kinetic analysis showed that a controlling interface temperature no more than 1,120 °C may limit the growth of the IMC layer.     

Role of Third Bodies in Friction and Wear of Cold-Sprayed Ti and Ti–TiC Composite Coatings

Titanium (Ti) and Ti-based alloy wear performance is often poor unless coating or lubricants are used. An alternative is to use hard phase reinforcement. Cold spray is a relatively new method to deposit composite coatings, where here we report the deposition of a Ti–TiC coating and its sliding wear behavior. Mixtures of mechanically blended Ti–TiC with various TiC content were injected into a de Laval nozzle and sprayed onto substrates. Two composite coatings and a pure Ti coating are reported here, where the as-sprayed compositions of the composites were 13.8 and 33.4 vol% TiC. Reciprocating dry sliding wear was performed using a custom-built in situ tribometer. All tests were conducted with a sliding speed of 3 mm/s and at a normal load of 0.5 N. Using a transparent sapphire hemisphere of 6.25 mm as counterface, dynamic behavior of third bodies was directly observed. It was found that adhesive transfer of Ti was the primary wear mechanism for the Ti coating, with oxidative and abrasive wear also occurring for longer sliding cycles. The superior wear resistance of the composite coatings compared to Ti was related to dual function of TiC particles, where they reinforced the Ti matrix and facilitated the formation of a stable and protective tribofilms. The tribofilms contained carbonaceous material that provided easier shear and lower friction. The formation of these tribofilms was highly dependent on the TiC particles, which contained excess carbon compared to the equilibrium composition. Higher TiC content was more effective in quickly developing and sustaining the tribofilms.     

Experimental research and analysis of three-finger micro-tweezers

1Introduction Withthedevelopmentofmicro electro me chanicalstructure(MEMS),grasping,manipu latingandassemblingofmicroobjectsarequite fascinating.Newtoolsforthesepurposeshave beendevelopedrapidly.However,mostofthese researchesarefocusedontwo fingermicro tweezers[1～3].Thestabilityandapplicationof two fingermicro tweezersinmanipulationand assemblyareverylimitedingraspingsphere,co lumnarorcomplicatedmicroobjects[4].Inorder tograspparticlesmoresteadily,carbonfibers areusedtocreatethethreefingers…     

Three-point method of differential correction of coordinates and pseudo-range in GPS

本文提出了对坐标和伪距进行差分修正的内插值法。它使用三个参考点的系统提高了所生成的修正的质量和稳定性。实验证明,与标准差分校正法相比,内插值法在修正质量和稳定性方面具有优越性。     

Fabrication,characterization and evaluation of the effect of PLGA and PLGA–PEG biomaterials on the proliferation and neurogenesis potential of human neural SH-SY5Y cells

In recent years with regard to the development of nanotechnology and neural stem cell discovery, the combinatorial therapeutic strategies of neural progenitor cells and appropriate biomaterials have raised the hope for brain regeneration following neurological disorders. This study aimed to explore the proliferation and neurogenic effect of PLGA and PLGA–PEG nanofibers on human SH-SY5Y cells in in vitro condition. Nanofibers of PLGA and PLGA–PEG biomaterials were synthesized and fabricated using electrospinning method. Physicochemical features were examined using HNMR, FT-IR, and water contact angle assays. Ultrastructural morphology, the orientation of nanofibers, cell distribution and attachment were visualized by SEM imaging. Cell survival and proliferation rate were measured. Differentiation capacity was monitored by immunofluorescence staining of Map-2. HNMR, FT-IR assays confirmed the integration of PEG to PLGA backbone. Water contact angel assay showed increasing surface hydrophilicity in PLGA–PEG biomaterial compared to the PLGA substrate. SEM analysis revealed the reduction of PLGA–PEG nanofibers' diameter compared to the PLGA group. Cell attachment was observed in both groups while PLGA–PEG had a superior effect in the promotion of survival rate compared to other groups (p < .05). Compared to the PLGA group, PLGA–PEG increased the number of Ki67⁺ cells (p < .01). PLGA–PEG biomaterial induced neural maturation by increasing protein Map-2 compared to the PLGA scaffold in a three-dimensional culture system. According to our data, structural modification of PLGA with PEG could enhance orientated differentiation and the dynamic growth of neural cells.     

Effects of cold working and heat treatment on microstructure and wear behaviour of Cu–Be alloy C17200

The effects of cold work process between aging and solution heat treatment on the microstructure, hardness and the tribologic behaviour of a copper–beryllium (Cu–Be) alloy C17200 were investigated. The wear behaviour of the alloys was studied using ‘pin on disc’ method under dry conditions. The results show that the formation of fine grained structure and γ phase particles enhances the mechanical properties of the alloy; nonetheless, they do not reduce the wear rate. This is attributed to the capability of the softer specimens to maintain oxygen rich compounds during the dry sliding test.     

Design and Optimization of Wheel-legged Robot：Rolling-Wolf

Though the studies of wheel-legged robots have achieved great success, the existing ones still have defects in load distribution, structure stability and carrying capacity. For overcoming these shortcomings, a new kind of wheel-legged robot（Rolling-Wolf） is designed. It is actuated by means of ball screws and sliders, and each leg forms two stable triangle structures at any moment, which is simple but has high structure stability. The positional posture model and statics model are built and used to analyze the kinematic and mechanical properties of Rolling-Wolf. Based on these two models, important indexes for evaluating its motion performance are analyzed. According to the models and indexes, all of the structure parameters which influence the motion performance of Rolling-Wolf are optimized by the method of Archive-based Micro Genetic Algorithm（AMGA） by using Isight and Matlab software. Compared to the initial values, the maximum rotation angle of the thigh is improved by 4.17%, the maximum lifting height of the wheel is improved by 65.53%, and the maximum driving forces of the thigh and calf are decreased by 25.5% and 12.58%, respectively. The conspicuous optimization results indicate that Rolling-Wolf is much more excellent. The novel wheel-leg structure of Rolling-Wolf is efficient in promoting the load distribution, structure stability and carrying capacity of wheel-legged robot and the proposed optimization method provides a new approach for structure optimization.     

Design and implementation of 30„ geometry PIG

This paper introduces the developed geometry PIG (Pipeline Inspection Gauge), one of several ILI (In-Line Inspection) tools, which provide a full picture of the pipeline from only single pass, and has compact size of the electronic device with not only low power consumption but also rapid response of sensors such as calipers, IMU and odometer. This tool is equipped with the several sensor systems. Caliper sensors measure the pipeline internal diameter, ovality and dent size and shape with high accuracy. The IMU (Inertial Measurement Unit) measures the precise trajectory of the PIG during its traverse of the pipeline. The IMU also provide three-dimensional coordination in space from measurement of inertial acceleration and angular rate. Three odometers mounted on the PIG body provide the distance moved along the line and instantaneous velocity during the PIG run. The datum measured by the sensor systems are stored in on-board solid state memory and magnetic tape devices. There is an electromagnetic transmitter at the back end of the tool, the transmitter enables the inspection operators to keep tracking the tool while it travels through the pipeline. An experiment was fulfilled in pull-rig facility and was adopted from Incheon LT (LNG Terminal) to Namdong GS (Governor Station) line, 13 km length.     

2007年Ten News of Rubber and Plastic

中国石油和化工勘察设计协会橡胶塑料设计专业委员会和全国橡塑机械信息中心于2008年初组织信息中心部分资深顾问、高级顾问和技术中心技术委员,并特邀橡塑机械行业有关专家推荐、汇总,评选出2007年度中国橡塑机械行业十大新闻如下：     

Role of thermal,mechanical and oxidising treatment on structure and chemistry of carbon black and its impact on wear and friction: Part 2 – Boundary lubrication condition

Mineral oil formulations with zinc dialkyl dithiophosphate (ZDDP) and dispersant (poly isobutylene succinimide ashless dispersant or ‘PIBSA’) and fully formulated oils with and without carbon black were subjected to thermal and mechanical treatment and tribologically tested on TE 77 (high frequency reciprocating rig or ‘HFRR’) machine to examine the frictional performance during the test. These results were compared to oils without carbon black and oils with diesel soot. Results indicate that oils with just ZDDP and dispersant had the highest friction that remains constant for the duration of the test while oils with carbon black in the milled and oxidised condition had the lowest coefficient of friction and the smallest surface roughness in the tribofilm. The mechanism of wear with treated carbon black and diesel soot was found to be polishing wear as evidenced by the scanning probe microscopy images of the tribofilms. Tribofilms were analysed with X-ray absorption near edge structure (XANES) and it was seen that oils without carbon black or even with untreated carbon black had sulphates at the surface, while the oils with carbon black that were treated had a higher proportion of sulphides. A combination of both FeS and ZnS was found in the tribofilms along with short chain phosphates of Zn.     

Development of a Setup for the Discrimination of β+ and γ Rays

Abstract

A β⁺–γ discrimination set‐up was developed and applied to the ²²Na radioisotope. The radioisotope emits positrons (β⁺) and these positrons create γ rays by annihilating with electrons. These annihilation γ rays were used here, and the discrimination between these positrons and γ rays was investigated by the coincidence measurement between time signals and the energy signals. The detection system presented here uses a 3 inch (diameter) by 3 inch (length) NaI(Tl) inorganic scintillation detector for γ detection and 3 inch (diameter) by 3 inch (length) plastic scintillation detector for β⁺ detection.     

Experimental and theoretical analysis of friction stir welding of Al–Cu joints

This paper presents a study of friction stir welding of aluminium and copper using experimental work and theoretical modelling. The 5083-H116 aluminium alloy and pure copper were successfully friction-stir-welded by offsetting the pin to the aluminium side and controlling the FSW parameters. A theoretical analysis is presented along with key findings. The process temperatures are predicted analytically using the inverse heat transfer method and correlated with experimental measurements. The temperature distribution in the immediate surroundings of the weld zone is investigated together with the microstructures and mechanical properties of the joint. This was supported by a finite element analysis using COMSOL Multiphysics. In this study, two rotational speeds were used and a range of offsets was applied to the pin. The microstructure analysis of the joints was undertaken. This revealed some particles of Cu inclusion in the nugget zone. The energy dispersive spectroscopy showed a higher diffusion rate of aluminium towards the interface while copper maintained a straight base line.     

Effects of electromagnetic stirring and rare earth compounds on the microstructure and mechanical properties of hypereutectic Al–Si alloys

In this paper, the effects of rare earth addition and electromagnetic stirring on the microstructure and the mechanical properties of hypereutectic Al–Si alloys have been reported. Hypereutectic Al–Si alloy was prepared using liquid metallurgy route and modified with the addition of cerium oxide. To control the structure, slurry of hypereutectic Al–Si alloy was subjected to electromagnetic stirring before pouring into the mould. It was observed that the addition of cerium oxide (0.2 wt.%) refined the primary silicon particles and modified the eutectic silicon particles. Further, the electromagnetic stirring of the hypereutectic Al–Si alloy reduced the average size of primary silicon particles, from 152?±?9 to 120?±?6 μm, and the length of β-intermetallic compounds decreased from 314?±?12 to 234?±?10 μm. Similarly, the application of electromagnetic stirring on cerium oxide-modified hypereutectic Al–Si alloy also reduced the average size of primary silicon particles from 98?±?5 to 76?±?4 μm and the average length of β-intermetallic compounds from 225?±?7 to 203?±?5 μm. Mechanical properties namely tensile strength, ductility and hardness of the alloys were improved with electromagnetic stirring and addition of cerium oxide appreciably.