Impact resistant behaviour of RC slab strengthened with FRP sheet

To investigate the impact resistance of RC slabs strengthened with Fibre Reinforced Plastic (FRP) sheet to the back of the slab, falling-weight impact tests were conducted. Two loading types were applied: iterative loading and single loading. The impact load was applied to the centre of the RC slab with a free falling 300 kg steel striker with a diameter of 60 mm. A total of 12 RC slabs that were 1,650 (L) × 1,650 (W) × 150 (h) mm were used for these experiments. In this study, the strengthening method and material properties of the FRP sheet and the number of FRP sheet layers were varied. The results obtained from this study are as follows: (1) the impact resistance of the RC slabs can be improved by attaching a strengthened FRP sheet to the back surfaces; (2) the load bearing mechanism of RC slabs depends on the loading type and strengthening volume of the FRP sheet; and (3) the dynamic amplification factor is about two, which is independent of the load bearing mechanism of the RC slab and the strengthening volume and tensile rigidity of the FRP sheet.     

Chemical potentials of oxygen for three-phase assemblages of CaSiO3(s) + Ca3Si2O7(s) + {CaO + SiO2 + FexO} melt and Ca3Si2O7(s) + Ca2SiO4(s) + {CaO + SiO2 + FexO} melt

By employing an electrochemical technique involving stabilized zirconia as solid electrolyte and Mo + MoO₂ mixture as reference electrode, the equilibrium oxygen partial pressures for three-phase assemblages of CaSiO₃(s) + Ca₃Si₂O₇(s) + {CaO + SiO₂ + Fe_xO} melt and Ca₃Si₂O₇(s) + Ca₂SiO₄(s) + {CaO + SiO₂ + Fe_xO} melt were determined as: - log {P_O2 (CS + C₃S₂ + L)/bar} = - 3.22 13000/(T/K) ± 0.05 - log {P_O2 (C₃S₂ + C₂S + L)/bar} = - 0.92 16400/ (T/K) ± 0.04. respectively, where CS, C₃S₂ and C₂S indicate CaSiO₃(s), Ca₃Si₂O₇(s). and Ca₂SiO₄(s), respectively.     

粉末冶金结构零件材料的泊松比

研究了粉末冶金机械零件使用的烧结材料的杨氏模量、切变模量及泊松比与孔隙度的关系.制备了三种钢粉,在不同条件下进行了压制、烧结与热处理.孔隙度对杨氏模量、切变模量及泊松比的影响最大.特别是泊松比还受孔隙形状的影响,而孔隙形状随粉末类型、烧结温度与烧结气氛及热处理条件而变化.对于大部分实际应用的粉末组成来说,烧结气氛对经烧结和热处理后材料的泊松比影响不大.对于部分预合金化粉末(Fe4%Ni1.5%Cu0.5%Mo)+0.8%石墨,只有在孔隙度低于20%时,烧结温度对泊松比与孔隙度的关系才有影响.在这种情况下.提出了烧结与热处理试样泊松比与孔隙度关系的较简单近似方程:在烧结温度1 423K下,v=0.300-0.266P+0.579P2;在烧结温度1 523K下,v=0.304-0.264P+0.548P2.     

Numerical Cracking and Debonding Analysis of RC Beams Reinforced with FRP Sheet

Bonding a fiber reinforced polymer (FRP) sheet to the tension-side surface of reinforced concrete (RC) structures is often performed to upgrade the flexural capacity and stiffness. Except for upper concrete crushing, FRP sheet reinforcing RC structure may fail in sheet rupture, sheet peeloff failure due to opening of a critical diagonal crack, or concrete cover delamination failure from the sheet end. Accompanying the occurrence of these failure modes, reinforcing effects of the FRP sheet will be lost and load-carrying capacity of the RC structures will be decreased suddenly. This study is devoted to developing a numerical analysis method by using a three-dimensional elasto-plastic finite element method to simulate the load-carrying capacity of RC beams failed in the FRP sheet peeloff mode. Here, the discrete crack approach was employed to consider geometrical discontinuities such as opening of cracks, slipping of rebar, and debonding of the FRP sheet. Comparisons between analytical and experimental results confirm that the proposed numerical analysis method is appropriate for estimating the load-carrying capacity and failure behavior of RC beams flexurally reinforced with a FRP sheet.     

Solar to chemical conversion using metal nanoparticle modified microcrystalline silicon thin film photoelectrode

Microcrystalline silicon (μc-Si:H) thin films, which are prospective low-cost semiconductor materials, are used as photoelectrodes for the direct conversion of solar energy to chemical energy. An n-type microcrystalline cubic silicon carbide layer and an intrinsic μc-Si:H layer are deposited on glassy carbon substrates using the hot-wire cat-CVD method. The μc-Si:H electrodes are modified with platinum nanoparticles through electroless displacement deposition. The electrodes produce hydrogen gas and iodine via photoelectrochemical decomposition of hydrogen iodide with no external bias under solar illumination. Surface modification with platinum nanoparticles and surface termination with iodine improve the conversion efficiency.     

Dendrites creating in silver metaphosphate glass treated by direct current of high density

Applying high voltage to an ion-conducting glass at high temperature is equivalent to electrolyse a glass. We observed several morphologies of electro-deposited silver and other conducting ions on dc biasing of silver metaphosphate glass. One of the findings is that electro-deposited silver underneath the gold cathode pushed up the cathode.     

High-temperature electro-ceramics and their application to SiC power modules

This paper presents the research achievement in Japan to develop highly-refractive electro-ceramics for application to silicon carbide (SiC) power modules such as heat-resistive passive components (snubber capacitors and resistors), metalised substrates, ceramic circuit boards, and high-temperature packaging technologies. To enable the operation of SiC devices at high temperatures, the ability to withstand 250 °C and temperature cycle between ?40 and 250 °C must be ensured for all the ceramic components and packaging technologies. For the passive components, the following properties were achieved, which would enable the operation of SiC devices at high switching speeds and high temperatures: low-resistance resistors which exhibit a resistance variation of less than 2% over a temperature range of ?40 to 250 ℃ and with almost no variation at frequencies of less than 10 MHz; multi-layered ceramic capacitors (MLCCs) with a capacitance variation of less than ± 10% within the above-mentioned temperature range and with high self-resonant frequencies of about 10 MHz. In addition, Cu-metalised ceramic substrates using high thermal conductive Si₃N₄ (180 W /(m·K)) and ceramic circuit boards produced using a co-firing process were developed. It was shown that prototype SiC power modules (2-in-1 structure) fabricated using the developed ceramic components could be operated at 225 °C, while exhibiting a high switching speed, 10–20 times faster than that of conventional Si IGBT (150 °C operation).     

Development of Resistive Oxygen Sensors Based on Cerium Oxide Thick Film

It is important to shorten the response time of resistive oxygen sensor in order to reduce harmful emission of automobiles. The diffusion and surface reaction theory tells us that reducing particle size leads to shortening the response time. The fine ceria powder was prepared a by new precipitation method and the oxygen sensors having ceria thick film with the particle size of 120 nm were fabricated using fine ceria (cerium oxide) powder. The thick film exhibited good adhesion to alumina substrate. The value of n in R P(O₂)^1/n at 1073 and 1173 K were 6.2 and 6.4 in the oxygen partial pressures range from 10^{– 13} to 10⁵ Pa, respectively. The response time for the sensor was 22 and 12 ms at 1073 and 1173 K, respectively. The sensor fabricated in this study showed fast response.     

Thermoresponsive Emission Switching via Lower Critical Solution Temperature Behavior of Organic–Inorganic Perovskite Nanoparticles

Lead halide perovskites have shown much promise for high‐performing solar cells due to their inherent electronic nature, and though the color of bright‐light emitters based on perovskite nanoparticles can be tuned by halide mixing and/or size control, dynamic switching using external stimuli remains a challenge. This article reports an unprecedented lower critical solution temperature (LCST) for toluene solutions containing methylammonium lead bromide (MAPbBr₃), oleic acid, alkylamines, and dimethylformamide. The delicate interplay of these molecules and ions allows for the reversible formation and decomposition of MAPbBr₃ nanoparticles upon heating and cooling, which is accompanied by green and blue photoemissions at each state. An intermediate 1D crystal with PbBr₂‐amine coordination is found to play pivotal role in this, and a mechanistic insight is provided based on a three‐state model. In addition to a high quantum yield (up to 85%), this system allows for control over the cloud point (30?80 °C) through compositional engineering and the luminescent color (blue to red) via halogen exchange, thus making it a versatile solution for developing functional molecular organic–inorganic LCST quantum dots.     

Human nails analysis as biomarker of exposure to perfluoroalkyl compounds

Extensive human exposure to perfluoroalkyl compounds (PFAA) together with their persistence and various toxicities have arisen increasing concern. A noninvasive method would improve exposure assessment for large population, especially the children susceptible to contaminants. The aim of the study was to assess the use of PFAA measurements in human nails as a biomarker of exposure to PFAAs. Fingernail, toenail, and blood samples were collected from 28 volunteers. The PFAA concentrations were determined by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Six PFAA were detected in nails, with perfluorooctane sulfonate (PFOS) being the compound with the highest median concentration (33.5 and 26.1 ng/g in fingernail and toenail, respectively). Followed was perfluorononanoate (PFNA), with the median concentrations of 20.4 and 16.8 ng/g, respectively, in fingernail and toenail. Other PFAA detected were perfluorooctanoate (PFOA), perfluorodecanoate (PFDA), perfluorododecanoate (PFDoA), and perfluorotetradecanoate (PFTA), with median levels ranging between 0.19 and 8.94 ng/g. PFOS and PFNA concentrations in fingernail significantly correlated with those in serum. Fingernail PFOS and PFNA levels were 2.8 and 24.4 times, respectively, higher than the serum levels. The accumulation of PFAA in nails, together with its advantages in noninvasive sampling and ability of reflecting long-term exposure, made nails PFAA an attractive biomarker of exposure.