A Highly-Sensitive Ba(Ti1—xSnx)O3 Thin Film Dielectric Bolometer for Uncooled IR Sensor

Ba(Ti_1—xSn_x)O₃ (BTS) ferroelectric thin films have been prepared by metal-organic decomposition method whose final annealing temperature was optimized to 700°C for dielectric bolometer. High temperature coefficient of dielectric constant (TCD) of 1–3%/K and low dielectric loss of 0.04 have been obtained in x = 0.15 and 0.17. Field-induced pyroelectricity of the BTS film was calculated to be an excellent value as high as 750 nC/cm²K. A series of dependence of DB output level were examined on important operation factors. The DB output level was increased when the period of supply voltage waveform is longer than both the electrical and thermal time constant of the DB detector. Finally, a stable infrared detection at temperature lower than 30°C was confirmed.     

SOL-GEL PREPARATION AND CHARACTERIZATION OF MULTIFERROIC BiFeO3 THIN FILMS WITH VARIOUS BI/FE RATIO

ABSTRACT

BiFeO₃ thin films have been prepared on Pt/TiO₂/SiO₂/Si substrates by sol-gel method using precursor solutions of various elemental ratio (Bi:Fe = 1.1:1.0, 1.0:1.0, and 1.0:1.1). The θ < eqid2 > 2θ scan XRD patterns show all the films consist mainly of polycrystalline perovskite and the crystallinity of Bi:Fe = 1.1:1.0 is better than the others. SEM and AFM images show all BiFeO₃ film have rosette structures, which consist of perovskite phase and matrix phase. The leakage current density measured at the temperature of 80 K is lower than 10^?4 A/cm² in all the films when the electric field reaches 1.6 MV/cm. The leakage mechanism of BiFeO₃ thin film is dominated by Schottky conduction at 80 K. At 80 K, the remanent polarizations at maximum applied voltage of 2.8 MV/cm are 100, 49, and 44 μC/cm² for the ratio of Bi:Fe = 1.1:1.0, 1.0:1.0, and 1.0:1.1, respectively. The saturated magnetization of BiFeO₃ thin films at 80 K were found to be 14, 22.5, 15 emu/cm³ for the ratio of Bi:Fe = 1.1:1.0, 1.0:1.0, and 1.0:1.1, respectively. Among these ratio, BiFeO₃ thin film deposited from precursor of Bi:Fe = 1. 1:1.0 gives the best ferroelectric property.     

NBG焊接质量控制在不锈钢管道上的探索与应用

为了保证焊接质量及生产效率,采用无背部保护气（NBG）工艺将STT半自动封底焊技术应用于316L奥氏体不锈钢管道的对接,实现了管道对接单面焊双面成形。同时,从STT焊接工艺试验以及焊接全过程出发,针对NBG焊口的固定焊,进行了焊接过程控制,并提出了常见焊接缺陷的规避措施。NBG焊接技术的应用,既实现了奥氏体不锈钢管的背部免充氩气保护焊接,同时避免了由于充气导致的潜在不安全因素的产生。研究结果为STT在不锈钢管道焊接质量控制以及推广提供参考。     

MONTE CARLO SIMULATION OF FAR INFRARED RADIATION HEAT TRANSFER: THEORETICAL APPROACH

We developed radiation heat transfer models with the combination of the Monte Carlo (MC) method and computational fluid dynamic approach and two‐dimensional heat transfer models based on the fundamental quantum physics of radiation and fluid dynamics. We investigated far infrared radiation (FIR) heating in laminar and buoyancy airflow. A simple prediction model in laminar airflow was tested with an analytical solution and commercial software (CFX 4). The adequate number of photon tracks for MC simulation was established. As for the complex designs model, the predicted results agreed well with the experimental data with root mean square error of 3.8 K. Because food safety public concerns are increasing, we applied this model to the prediction of the thermal inactivation level by coupling with the microbial kinetics model. Under buoyancy airflow condition, uniformity of FIR heating was improved by selecting adequate wall temperature and emissivity.     

Fatigue properties of rolled AZ31B magnesium alloy plate

Fatigue strength, crack initiation and propagation behavior of rolled AZ31B magnesium alloy plate were investigated. Axial tension-compression fatigue tests were carried out with cylindrical smooth specimens. Two types of specimens were machined with the loading axis parallel (L-specimen) and perpendicular (T-specimen) to rolling direction. Monotonic compressive 0.2% proof stress, tensile strength and tensile elongation were similar for both specimens. On the other hand, monotonic tensile 0.2% proof stress of the L-specimen was slightly higher than that of the T-specimen. Moreover, monotonic compressive 0.2% proof stresses were lower than tensile ones for both specimens. The fatigue strengths of 107 cycles of the L- and T-specimens were 95 and 85 MPa, respectively. Compared with the monotonic compressive 0.2% proof stresses, the fatigue strengths were higher for both specimens. In other words, the fatigue crack did not initiate and propagate even though deformation twins were formed in compressive stress under the cyclic tension-compression loading. The fatigue crack initiated at early stage of the fatigue life in low cycle regime regardless of specimen direction. The crack growth rate of the L-specimen was slightly lower than of the T-specimen. Consequently, the fatigue lives of the L-specimen were longer than those of the T-specimen in low cycle regime.     

Line identification of extreme ultraviolet(EUV) spectra from low-Z impurity ions in EAST tokamak plasmas

Extreme ultraviolet(EUV) spectra emitted from low-Z impurity ions in the wavelength range of10–500 ? were observed in Experimental Advanced Superconducting Tokamak(EAST)discharges. Several spectral lines from K-and L-shell partially ionized ions were successfully observed with sufficient spectral intensities and resolutions for helium, lithium, boron, carbon,oxygen, neon, silicon and argon using two fast-time-response EUV spectrometers of which the spectral intensities are absolutely calibrated based on the intensity comparison method between visible and EUV bremsstrahlung continua. The wavelength is carefully calibrated using wellknown spectra. The lithium, boron and silicon are individually introduced for the wall coating of the EAST vacuum vessel to suppress mainly the hydrogen and oxygen influxes from the vacuum wall, while the carbon and oxygen intrinsically exist in the plasma. The helium is frequently used as the working gas as well as the deuterium. The neon and argon are also often used for the radiation cooling of edge plasma to reduce the heat flux onto the divertor plate. The measured spectra were analyzed mainly based on the database of National Institute of Standards and Technology. As a result, spectral lines of He Ⅱ, Li Ⅱ–Ⅲ, B Ⅳ–Ⅴ, C Ⅲ–Ⅵ, O Ⅲ–Ⅷ, Ne Ⅱ–Ⅹ,Si Ⅴ–Ⅻ, and Ar Ⅹ–XVI are identified in EAST plasmas of which the central electron temperature and chord-averaged electron density range in T_(e0)=0.6–2.8 keV and n_e=(0.5–6.0)×10~(19) m~(-3), respectively. The wavelengths and transitions of EUV lines identified here are summarized and listed in a table for each impurity species as the database for EUV spectroscopy using fusion plasmas.     

Study on Radial Position of Impurity Ions in Core and Edge Plasma of LHD Using Space-Resolved EUV Spectrometer

Radial profiles of impurity ions of carbon, neon and iron were measured for high-temperature plasmas in large helical device (LHD) using a space-resolved extreme ultraviolet (EUV) spectrometer in the wavelength range of 60 to 400?. The radial positions of the impurity ions obtained are compared with the local ionization energies, Ei of these impurity ions and the electron temperatures TeZ there. The impurity ions with 0.3?Ei?1.0 keV are always located in outer region of plasma, i.e., 0.7?ρ?1.0, and those with Ei?0.3keV are located in the ergodic layer, i.e., 1.0?ρ?1.1, with a sharp peak edge., where ρ is the normalized radial position. It is newly found that TeZ is approximately equal to Ei for the impurity ions with Ei?0.3keV, whereas roughly half the value of Ei for the impurity ions with 0.3?Ei?1.0keV. It is known that TeZ is considerably lower than Ei in the plasma edge and approaches to Ei in the plasma core. Therefore, this result seems to originate from the difference in the transverse transport between the plasma edge at ρ?1.0 and the ergodic layer at ρ?1.0. The transverse transport is studied with an impurity transport simulation code. The result revealed that the difference appearing in the impurity radial positions can be qualitatively explained by the different values of diffusion coefficient, e.g., D=0.2 and 1.0m2/s, which can be taken as a typical index of the transverse transport.     

慢走丝电火花线切割粗加工仿真系统的开发

为对电火花线切割加工机理有更深刻的认识,了解加工参数对加工精度的影响规律,介绍了一个电火花线切割加工粗加工的仿真系统。仿真系统通过对放电点的探索、工件的去除以及对线电极丝振动的分析,将实际的加工现象形象地再现于计算机上。为证实仿真系统的正确性,将仿真结果与试验结果进行了比较。在试验结果的获取中,为能够得到很难测量的线电极周围的放电间隙和工件形状数据,提出一种新的三维形状测量方法。通过对仿真结果和试验结果的比较,定性地证明了仿真方法的正确性。研究结果表明:改变线电极张力及伺服电压值时,从仿真过程得到的加工形状结果与试验得到的加工形状结果其倾向基本一致;加工缝端部的形状呈凸形还是呈凹形,取决于加工过程中放电爆发力和静电引力的相对大小。     

FLOW PATTERNS THROUGH TUBE BUNDLES AND PARTICULATE FOULING ONTO CYLINDERS

ABSTRACT

The shear-stress distributions around cylinders in tube bundles were measured by means of the limiting current method and the flow inside the bundle was also visualized. In the case of the staggered bundle, the shear-stress distributions had two peaks by the effect of the jet streams generated at the front row spacing and the adjacent cylinder. While in the bundle with in-line arrangement, the front stagnant point was shifted about 30° downward and the traverse streams among the rows were observed. This traverse streams caused asymmetry of the shear-stress distributions with respect to the main flow axis.

These results were discussed in connection with the fouling experiments investigated in dusty air. Particle deposition around cylinders could be qualitatively predicted from the shear-stress distributions, namely particles tend to deposit at positions where are less shear-stress in both tube arrangements. The size of particle deposited on the wake zone was coarser than that near the stagnant point behind the third row in both arrangements.