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Design for the Lift Platform Humanoid Climb Assisting Unit of the Space Launch Site
Get PDFHumanoid climb assisting unit (HCAU) is a key mechanism for the lift platform to adjust its height-level of the space launch site. It is widely used for lift platforms of launch towers, service towers, vertical assembly test building for launch vehicles and that of silos for missiles. In this paper, its working principal is illustrated. The design requirements and terms, design steps and effecting factors are discussed. Three types of HCAU design methods and their calculating formulae are derived. Design examples are presented
Hydroxyapatite from Natural Resources
Get PDFThe improve of well-being and longevity of the population in Europe results in an increasing demand for the development of biocompatible materials with new properties which can be applied as implants for several decades. The one of most used biomaterial worldwide is a hydroxyapatite (HAP). This chemically similar material to the mineral component of bone and hard tissues is one of the bioactive materials, which can react with the tissue and generates good chemical bonding. The different preparation routes of HAP are known. In this study, the environmental friendly and cheap process from natural resources is shown. The examination of biogenic HAP confirmed the submicron sized structure with ~ 100 – 150 nm globular grains. The measurements confirmed the high structural stability of HAP grains
The SPH-EL Method for the Simulation of the Interaction between Water Drops and Solid Wall
Get PDFIn raining days, the water drops can enter the compressor and cause security problems. However, there is still no appropriate numerical method for simulating the interaction between water drops and solid wall. The Euler-Lagrange (EL) method is usually regarded as the best solution for this problem, but it considers each water drop as a fluid particle and cannot allow the simulation of deformation. We propose to combine the Smoothed Particle Hydrodynamics (SPH) method with the EL method, which is named as SPH-EL method. In this contribution we introduce the idea of SPH-EL method as well as two key techniques: tracking the particle deformation and regrouping the distorted particles. Finally we present a 2D simulation with SPH method and will apply the SPH-EL method to improve the simulation in the future
Photocatalytic Properties of BiOCl/Bi2WO6 Composite
Get PDFBiOCl/Bi2WO6 composite was prepared by a hydrothermal synthesis method. The photocatalytic activity of the product was investigated by degrading Methyl Orange (MO) under visible light irradiation. The as-synthesized sample showed more efficient photocatalytic activity than that of single BiOCl or Bi2WO6
Effect of Tropospheric Nitrogen Dioxide on Incoming Solar Radiation
Get PDFIncoming solar radiation is known to undergo an interaction with the constituents of the Earth’s atmosphere. This interaction is expressed by means of the mechanisms of absorption, scattering and reflection. The occurrence of each such mechanism depends on the size of the molecules in relation with the wavelength of the incoming radiation. The study of the interaction of solar radiation with atmospheric constituents, including aerosols, has long attracted scientific interest; such an interaction is related to climate-change issues. Among the atmospheric constituents, interest has been given to the anthropogenically-derived nitrogen dioxide (NO2) in the troposphere, since there has been found that anthropogenic aerosols have been playing an important role in their interaction with the incoming solar radiation. That is the reason for the recent discovery of the global dimming phenomenon. Mean daily solar radiation values from the Actinometric Station of the National Observatory of Athens (ASNOA) are compared with simultaneous ones of NO2 measured by the network of the Greek Ministry of Environment within the Athens basin. The period considered in this study covers the years 1990 – 2004. The study examines clear-sky conditions in order to show the influence of NO2 alone on solar radiation. The results show that increasing levels of NO2 cause smaller/greater scattering of solar radiation (global/diffuse components) at different rates, thus resulting in an attenuation of solar radiation; this attenuation rate is greater in the global component than in the diffuse one, in absolute terms
Moisture Flow as Driving Force behind Drying Shrinkage and Microcracking in Interfacial Transition Zone in Concrete
Get PDFIn order to determine drying shrinkage in early age cementitious paste and ITZ, prior to a calculation of shrinkage coefficient and further complex coupling, experimental methods at micro-level and numerical methods at meso-level are separately performed as the initial steps. Digital images of a small-size 1-mm thick cement paste specimen with an embedded obstacle as a concrete model are captured at different magnifications and analyzed in drying experiments with Environmental Scanning Electron Microscope (ESEM) and Vic-2D. The drying shrinkage shows the dependence on image magnification, chosen Area of Interest (AOI) and RH variations. Numerical moisture flow/ drying simulations by Lattice Gas Automata (LGA) show the difference in a moisture gradient depending on the heterogeneity of the LGA domain (population with smaller and/ or larger solids). Expected higher moisture gradient around larger solids is confirmed in the LGA simulations, which could be an initial sign of gaps/microcracks in real ITZ
Shock-Induced C-N-S Tridoped TiO2 with Improved Photocatalytic Activity Under Visible Light
Get PDFUsing metatitanic acid (H2TiO3) and thiourea (CN2H4S) as titanium precursor and dopant sourcerespectively, a visible-light responsiblenon-metalC-N-S tridoped TiO2 photocatalyst is prepared by shock loading. X-ray powderdiffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and UV-visiblediffusereflectancespectroscopy (UV-Vis DRS)are employed to characterize thecrystalline structure,morphology,chemical composition and optical property of recovered samples.The results indicate the metatitanic acid transformsto pure anatase phase by shock wave and that theaverage size of particles is3-5 nm.The as-synthesized TiO2 nano-particles are well dispersedand possess large surface area (309.02m2/g), and the edge adsorptionwavelength of the samples exhibitsslight red shifts with corresponding energy gap reduced to 3.16 eV.Carbon forms carbonate on the surface of TiO2,N may coexist inthe forms of substituted N (N-O-Ti) and interstitial N (O-Ti-N) in TiO2, and S6+is incorporated into the lattice of TiO2through substituting titanium atoms.The photocatalyticactivities of the as-synthesized samples are evaluated for the degradation of Rhodamine B under simulatedsunlight irradiation.Results revealthat these C-N-StridopedTiO2exhibit higherphotocatalyticdegradation activities than that of undoped TiO2samples and achieve an 83% removal rate for RB dye under the visible light irradiation for 70min with the thiourea-to-metatitanic acid mass of 2:1 and flyervelocity 2.52 km·s-1,whichis mainly attributed to the synergistic effects of well-formed anatase phase, high specific surface area and band gap narrowing resulting from C-N-S tridoping
Carrier Transport Mechanism of Copper Phthalocyanine Based Photodiode for Solar Cell Applications
Get PDFCopper phthalocyanine (CuPc)/n-silicon junction was fabricated using thermal evaporator method. X-ray analysis of the CuPc film confirms the b-phase with preferred orientation along (100) direction. The crystallite size of the CuPc film was estimated using XRD data and observed to be about 12.6 nm. The current-voltage characteristics of Au/CuPc/n-Si/Au device was studied in dark and under illumination. The device showed diode characteristics. The diode parameters such as ideality factor, barrier height and series resistance were determined using different techniques such as conventional forward bias I-V characteristics, Cheung method and Norde’s function. A good agreement between the diode parameters calculated form these methods was observed. The analysis of the diode characteristics confirmed that the transport mechanism of the Au/CuPc/n-Si/Au diode at the higher electric fields was governed by the space-charge-limited currents. The photoconducting behavior of the diode suggests that it can be used as a photosensor in optoelectronic applications
In vitro and In vivo Degradation Evaluation of Mg-Based Alloys for Biomedical Applications
Get PDFBiodegradable metals have attracted interest for implant applications because of the potential to eliminate secondary surgeries. Magnesium-based (Mg-based) alloys are potential candidates. The purpose of this study was to evaluate the in vitro and in vivo degradation performances of two custom-made magnesium-based alloys and to determine whether they are sustainable for further investigation. The performances of Magnesium-Zinc-Manganese (Mg-Zn-Mn) alloys at 5% and 1% zinc levels were compared using a mechanical test, hydrogen evolution test, cell viability (MTT) test, and a short term mice subcutaneous implantation. The results showed that the corrosion resistance of the Mg was improved by alloying. While Mg-5Zn-1Mn was more corrodible compared with Mg-1Zn-1Mn, neither of the alloys presented any adverse effects preliminarily and both were suitable for long-term testing for biomedical applications
Investigation of Displacements Fields Due to Normal and Tangential Loads on Bars of Finite Thickness
Get PDFThe challenging topic of a cylinder in line contact with bars of finite thickness, reproducing typical fretting fatigue experiments, is studied by means of the super moiré interferometry technique. The authors consider a normal load on a model producing a contact area of about 4 mm, and subsequently on a tangential load at nearly the sliding limit. The displacement fields, due to the normal load, show that the maximum principal stresses at the edge of the contact area are significantly different from those predicted for the half plane, as well as for bars with a significant thickness, so that the dimension of the contact area and the pressure distribution are nearly the same as those of the half plane. This is confirmed by numerical results obtained by Fellows et al. [7].
Moreover, the experimental results show that the surface stresses induced are not as dependent on the thickness of the bar as those induced by the normal load