基于单轴压缩的岩体破坏机制细观试验研究

 岩石在荷载作用下产生宏观破坏,其断裂面的细观形态变化,可以间接地反映岩石内部损伤演化进程,并与其宏观力学状态和结构破坏特性之间存在必然联系。主要对巴西劈裂试验和剪切试验试样的断裂面进行电镜扫描,总结典型力学特征下试样断裂面的细观形貌特征,建立裂纹断裂面细观形貌与宏观力学特性匹配的判断标准。进而对含不同倾角预制单裂纹试样单轴压缩试样的破坏全断面进行细观扫描分析,采用判断标准对其细观形貌判别,得到断裂面的拉剪应力分布权重,探究断裂面拉、剪应力分布随裂纹扩展过程的变化规律。试验结果表明：全断面拉剪应力权重与预制裂纹倾角有密切关系。预制裂纹倾角小于45°时,断裂面以拉应力为主,且随着裂纹扩展拉应力权重逐渐减小,剪应力权重逐渐增大;当裂纹倾角大于45°时,其结论与前述结论相反;预制裂纹倾角为45°时,拉、剪应力共同作用产生翼裂纹及次生裂纹2种扩展方式,翼裂纹扩展由拉应力主导向剪切应力主导过渡,次生裂纹扩展过程中主导应力变化规律与之相反。     

Line identification of boron and nitrogen emissions in extreme-and vacuumultraviolet wavelength ranges in the impurity powder dropping experiments of the Large Helical Device and its application to spectroscopic diagnostics

An impurity powder dropper was installed in the 21 st campaign of the Large Helical Device experiment(Oct. 2019–Feb. 2020) under a collaboration between the National Institute for Fusion Science and the Princeton Plasma Physics Laboratory for the purposes of real-time wall conditioning and edge plasma control. In order to assess the effective injection of the impurity powders,spectroscopic diagnostics were applied to observe line emission from the injected impurity. Thus,extreme-ultraviolet(EUV) and vacuum-ultraviolet(VUV) emission spectra were analyzed to summarize observable impurity lines with B and BN powder injection. Emission lines released from B and N ions were identified in the EUV wavelength range of 5–300 ? measured using two grazing incidence flat-field EUV spectrometers and in the VUV wavelength range of 300–2400 ? measured using three normal incidence 20 cm VUV spectrometers. BI–BV and NIII–NVII emission lines were identified in the discharges with the B and BN powder injection, respectively. Useful B and N emission lines which have large intensities and are isolated from other lines were successfully identified as follows: BI(1825.89, 1826.40) ?(blended), BII 1362.46 ?, BIII(677.00, 677.14,677.16) ?(blended), BIV 60.31 ?, BV 48.59 ?, NIII(989.79, 991.51, 991.58) ?(blended), NIV765.15 ?, NV(209.27, 209.31) ?(blended), NVI 1896.80 ?, and NVII 24.78 ?. Applications of the line identifications to the advanced spectroscopic diagnostics were demonstrated, such as the vertical profile measurements for the BV and NVII lines using a space-resolved EUV spectrometer and the ion temperature measurement for the BII line using a normal incidence 3 m VUV spectrometer.     

PURIFICATION AND PROPERTIES OF DESMUTAGENIC FACTOR FROM BROCCOLI (BRASSICA OLERANCEA VAR. ITALICA PLENCK) FOR MUTAGENIC PRINCIPLE OF TRYPTOPHAN PYROLYSATE

A desmutagenic factor which inhibited the mutagenicity of the mutagens, Trp-P-1 (3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole), Trp-P-2 (3-amino-1-methyl)-5H-pyrido[4,3-b]indole), ethidiumbromide and 2-aminoanthracene, was purified from broccoli (Brassica olerancea var. italica plenck). The factor was not sedimented by ultra-centrifugation at 200,000 xg for 2 h. It adsorbed to a DEAE-cellulose column and was eluted with low concentration of potassium chloride. The purified factor exhibited a heme-like protein absorption spectrum with a Soret band at 403 nm and α and β bands at 640 and 504 nm, respectively. The molecualr weight was estimated to be approximately 53,000 by SDS-gel electrophoresis.     

PP/LCP复合材料的物性及力学特性

通过对容易再生的PP/LCP复合材料的微观结构、动态粘弹性特性、热膨胀特性以及力学特性进行讨论,明确了PP/LCP虽为不相溶的两相复合材料,但由于PP和LCP相的热膨胀系数不同,使两相具有比较好的界面结合强度。当LCP加入量低于40 ％时,形成以PP为基LCP为纤维状的强化相并沿流动方向分布。LCP的含量高于60 ％后,PP相的存在对复合材料的延性及强度均带来不利影响。      

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.     

Optimization of Switching Phase of a Single‐Phase PWM dc–ac Inverter

The purpose of this paper is to improve the efficiency of the single‐phase pulse width modulation (PWM) dc–ac inverter based on optimization of the switching phase of the PWM. Improvement of the efficiency means improvement of the quality of the output waveform and the conversion efficiency, and reduction of the switching loss. We propose an evaluation method involving minimization of the evaluation function by using the particle swarm optimization algorithm. We improve efficiency by setting a criterion for each index. As a result, the proposed algorithm can reduce high harmonic components in switching times shorter than the conventional triangle wave comparison method. Also, we confirm that the algorithm can improve the quality of the output waveform and the efficiency of conversion.     

Enterotoxin C2 Production by S. aureus in Entree Salads

Staphylococcus aureus strain 361 was inoculated into salads containing chicken, macaroni, potato, or artificially flavored soy product. Egg was added to some. The pH averaged 6.2 in the control made with water dressing rather than vinegar, 4.7 with home-style cooked salad dressing, and 4.9 with commercial salad dressing. Following incubation at 37°C for 8 or 24 hr, pH, total counts, and enterotoxin C₂ were determined. Enterotoxin was detected at 8 hr in all macaroni and potato dressing types. At 8 hr, enterotoxin was not detected in most soy product or chicken salads. By 24 hr the lowest levels were in the soy product salads but all products contained toxin. When the inoculum level was reduced below the 10⁵ CFU per g used in the main study, enterotoxin production was delayed but occurred at 8 hr if the inoculum level was 10³.     

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.