帘线钢表面氧化优化工艺及控制机理研究

采用OM和SEM分析方法研究了帘线钢空气气氛下连续氧化行为以及高线精轧、吐丝温度对热轧盘条表面氧化铁皮厚度和相组成的影响,同时采用热模拟方法分析了FeO层发生先共析、共析转变生成Fe3O4的条件.实验结果表明,945℃是帘线钢快速氧化起点温度,随着温度升高,氧化速率急剧增加;而当温度降低到700℃时,氧化过程极其缓慢.控制700~945℃范围内的冷速是控制氧化铁皮厚度及相组成的关键工艺.高线生产控制精轧和吐丝温度在900~940℃,氧化铁皮厚度7~20μm,FeO质量分数为65%~80%,具有最佳除鳞性能.热模拟分析表明,400~500℃是FeO层发生共析转变的"鼻尖"温度,孕育期最短.提高400~500℃区间冷速可抑制FeO层发生共析转变,使机械除鳞率提高3%左右.     

950 keV, 3.95 MeV and 6 MeV X-band linacs for nondestructive evaluation and medicine

We are developing compact X-band linac X-ray sources for nondestructive evaluation and medicine. First, we develop a portable X-ray system by a 950 keV 9.4 GHz X-band linac to realize on-site inspection. We use a low power (250 kW) magnetron as an RF source for compactness of the whole system. Since the RF power source is quite small and the stored energy in the structure is also small, we faced the problem of beam loading and current/RF-power oscillation. We are analyzing the problem by the circuit model. We plan to use this system for erosion inspection of metal pipes of petrochemical complex. By adopting a side-coupling cavity design to avoid the oscillation, we have developed 6 MeV X-band (9.3 GHz) linac for pinpoint dynamic tracking cancer therapy. Furthermore, we are manufacturing 3.95 MeV X-band (9.3 GHz) linac X-ray source with flexible waveguides for on-site bridge inspection. Updated results and situations are presented.     

Negative faradaic resistance in extracellular electron transfer by anode-respiring Geobacter sulfurreducens cells

Geobacter sulfurreducens is a gram-negative δ-proteobacterium that is capable of transferring respiratory electrons to solid-state extracellular acceptors, including anodes, via abundant c-type cytochromes expressed in the outer membrane. As extracellular electron transfer (EET) to solid-state acceptors can proceed without the addition of exogenous mediators, this microbe has attracted significant attention with respect to energy conversion between electrical and chemical energy. Here, we revealed that clear redox peaks were present in the whole-cell cyclic voltammogram of G. sulfurreducens at around -0.15 V vs Ag|AgCl when tin-doped In(2)O(3) (ITO) glass was used as an anode. Interestingly, the EET current decreased in the potential region more positive than the midpoint potential (E(m)) of the redox peak. Thus, EET of anode-respiring G. sulfurreducens cells exhibited a negative Faradaic resistance (NFR) characteristic at the E(m) of the redox peak, in contrast to general electrochemical systems where the Faradaic current typically increases with increasing overpotential.     

Bubble behavior in vertical tube banks installed in a fluidized bed

Fluidized bed combustion is one of the advantageous technologies for coal and/or incineration firing especially with respect to the environmental protection of emissions, such as NO_x/SO_x. Bed material movement in such a fluidized bed has a prime importance in the heat transfer process. Thus, quantitative measurement of the bed material movement and the void fraction are indispensable for better understanding of the fluidized bed. In this investigation, neutron radiography is applied to visualize the bed material movement in a simulated fluidized bed heat exchanger installed with vertical tubes. Bubble behavior and void fraction profile are obtained by the image processing technique. Bubble movement is highly restrained by these vertical tubes, so that the bubbles rise up along the tube. The bubble diameter is well correlated by the modified Mori and Wen's correlation taking into account the pitch of the tube arrangement. The bubble rise velocity and void fraction are well correlated by applying the drift‐flux model. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(8): 727–739, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10127     

Feasibility study on 1.6 μm continuous-wave modulation laser absorption spectrometer system for measurement of global CO2 concentration from a satellite

A feasibility study is carried out on a 1.6 μm continuous-wave modulation laser absorption spectrometer system for measurement of global CO(2)concentration from a satellite. The studies are performed for wavelength selection and both systematic and random error analyses. The systematic error in the differential absorption optical depth (DAOD) is mainly caused by the temperature estimation error, surface pressure estimation error, altitude estimation error, and ON wavelength instability. The systematic errors caused by unwanted backscattering from background aerosols and dust aerosols can be reduced to less than 0.26% by using a modulation frequency of around 200 kHz, when backscatter coefficients of these unwanted backscattering have a simple profile on altitude. The influence of backscattering from cirrus clouds is much larger than that of dust aerosols. The transmission power required to reduce the random error in the DAOD to 0.26% is determined by the signal-to-noise ratio and the carrier-to-noise ratio calculations. For a satellite altitude of 400 km and receiving aperture diameter of 1 m, the required transmission power is approximately 18 W and 70 W when albedo is 0.31 and 0.08, respectively; the total measurement time in this case is 4 s, which corresponds to a horizontal resolution of 28 km.     

Oxidation behavior of copper nanoparticles at low temperature

A mass gain for copper nanoparticles with a mean diameter of 20 nm in a 20% oxygen-nitrogen atmosphere was measured at 150-300 °C using thermogravimetry (TG). The mass gain equilibrium of the copper particles differed at each temperature, and a threshold temperature was recorded. Oxide products, consisting mainly of Cu₂O, formed on the copper nanoparticles below the threshold temperature. Above the threshold temperature, there was an initial, and drastic, formation of Cu₂O, which then changed to CuO. The activation energy for the oxidation of the copper nanoparticles that could be calculated from the rate of the mass gain was an indication of the nano-effect of the copper nanoparticles.     

ITU-R P.434计算F2层基本最高可用频率与实测值的比较

利用我国2011年1月和7月10条斜测电路的F₂层基本最高可用频率(MUF)月中值数据,与ITU-R P.434方法计算的F₂层基本MUF进行了比较,分析了该方法在中国地区的适用性。结果表明:ITU-R P.434方法在中国地区具有较好的适用性,但在某些电路的个别时段偏差较大。其中,1月份在中纬地区日出时段,该方法给出的基本MUF与月中值相比偏低20%~30%,在日落时段则偏高20%~30%;低纬地区夜间时段两者的相对偏差较大,最大值达到40%.7月份,该方法的结果与各条电路的实测结果基本一致,相对偏差在-10%~20%之间。上述结果对短波通信的选频等具有一定的指导意义。     

扩展F全球分布特点的理论分析

考虑到我国区域电离层扩展F发生的物理机制和相关因素以及观测数据的可获取性,利用适宜于时间序列预测的长短期记忆网络建立了我国不同区域电离层扩展F事件的预测模型,对未来3 h是否会发生扩展F事件进行预测。以处于我国典型纬度地区的满洲里、北京、海口站为例,利用2015和2016年测试数据集对模型预测精度进行了检验,满洲里、北京、海口站平均准确率分别为92.4%、95.3%、96.0%,平均精确率分别为75.0%、61.2%、62.6%,平均召回率分别为73.0%、50.6%、31.5%。由此可见：在某些情况下,比如在低纬度地区的海口站,模型的召回率较低;除此之外,所建立的扩展F模型在多数情况下具有较高的预测能力。     

等离子体散射分析的改进型交替隐式时域方法

提出了一种改进的交替隐式时域有限差分(FDTD)方法,运用该方法分析了等离子体涂覆导体圆柱的散射特性,为等离子体隐身技术的运用提供了一定的理论指导.该方法在整个问题空间采用完整场形式的场量进行迭代计算,并运用中心差分格式离散极化电流密度辅助方程.仿真实验表明,提出的算法具有无条件稳定特性,其计算效率明显优于以往文献提出的交替隐式FDTD方法,在精度和效率上也稍高于普通的显式FDTD方法.     

Long-term follow-up (8 to 17 years) after thromboexclusion operation for thoracic aortic aneurysms

Forty-eight Russell's viper bite patients (40 males, 8 females), age ranging from 16-76 years were studied. Out of 48 patients, 14 were found to have a prolonged whole blood clotting time test (WBCT) (i.e. incoagulable blood) (Group 1); 23 had a normal WBCT (i.e. clotted blood) (Group II); and 11 patients had a normal WBCT on admission which changed to non-clotting during the clinical course (Group III). Four patients from group I developed hypotension and 2 expired. The serum cortisol concentration (mean +/- SEM) on admission among groups I and II were 639 +/- 45.6 and 424 +/- 33.2 nmol/l respectively. The blood cortisol level in 35 subjects (controls) were 370.7 +/- 17.7 nmol/l (mean +/- SEM). There was a significant rise of blood cortisol in patients with incoagulable blood when compared to controls at the time of admission to the hospital (p < 0.05); but there was no significant difference among those patients with clotted blood. A much higher mean serum cortisol level was observed in 4 patients with hypotension as compared to 10 patients without shock. These patients with hypotension according to our study shown to have a favorable response to steroid therapy and eventually recovered. Whether higher doses of steroid in addition to antiserum confer extra benefit in suppressing nonspecific venom effects on the pituitary and/or adrenal is not known.