Electrical properties of Ln2Mo2O7 pyrochlores (Ln=SmYb,Y)

Cubic oxide pyrochlores, Ln₂Mo₂O₇, Ln=SmYb,Y, (Nd_1?xA_x), A=Er and Yb; 0 < x < 1.0, have been synthesized and electrical properties were examined in the range 77-600K. Semiconductor behavior is observed for Ln=EuYb, Y but the resistivity and E_a are low. Sm₂Mo₂O₇ and Nd_1?xYb_xMo₂O₇ (0.05 ≤ x ≤ 0.1) exhibit semimetallic or metallic behavior. The mechanism of conduction in these compounds is explained on the basis of band model proposed by Sleight et al.     

Deformation twinning during impact – numerical calculations using a constitutive theory based on multiple natural configurations

When materials such as Armco iron, titanium etc., are subject to impact it can be observed that two basic inelastic processes take place – slip and deformation twinning. Of these processes, inelasticity associated with the slip mechanism has received considerable attention. For example, Zerilli and Armstrong (1988) modeled the Taylor impact test for a variety of materials using traditional plasticity theories. They found that there was a significant discrepancy between the theoretical and experimental results for some materials. They attributed this to the fact that they had neglected deformation twinning in their models. Subsequent metallurgical studies have indicated that twinning had indeed taken place in these materials. In this study, we focus on the inelastic processes solely due to deformation twinning (i.e., neglecting slip). We model these processes using the approach of Rajagopal and Srinivasa (1995, 1997) and Srinivasa et al., (1997), the results of which are briefly summarized in section 2.1. In order to better understand the twinning process, we study the Taylor impact test for a 2-D slab under the assumption that only deformation twinning takes place and solve the governing dynamical equations by using the finite element method. The results show that the twinned zone is concentrated near the point of impact and indeed it contributes significantly to the overall permanent shape change due to the impact.     

Wärmeübertragung bei pulsierender Strömung

Ohne Zusammenfassung     

Stresses around an axial crack in a pressurized cylindrical shell

Perturbation solutions are obtained for stresses around the tip of an axial crack in a pressurized circular cylindrical shell. The analysis, using a differential equation approach, involves perturbation in a curvature parameter relating crack length to shell diameter and thickness. The results are valid for cracks of small length and agree completely with those obtained earlier by Folias by the method of integral equations.     

Preparation,dosimetric characterisation and investigation of related TSL defect centres in Li3Po4:Mg,Cu phosphor

L3PO4:Mg,Cu, a low effective atomic number and high sensitivity TSL phosphor, has been prepared. Its TSL glow curve shows a major peak around 360 degrees C with minor peaks around 110 degrees C and 230 degrees C. The optimum concentrations of the dopants are found to be 200 ppm each. Its gamma sensitivity is 1.2 times as compared to CaSO4:Dy (0.1 mol%). The optimum preirradiation annealing treatment is found to be 650 degrees C, 15 min. Its PL emission shows a band at 370 nm with excitation band at 250 nm. Dose to TSL response shows that its response is linear up to the gamma dose of 100 Gy for irradiations carried out at RT. An irradiated sample shows a distinct new ESR signal, which is tentatively assigned to an electron/hole localised on one of the oxygen(s) of the phosphate group. Step annealing experiments show decay of the defect centre around 340 degrees C. This correlates well with the TSL peak around 360 degrees C.     

管棚注浆支护隧道开挖引起地表变形特征分析

隧道开挖引起的地表变形是工程安全的重要指标,基于管棚注浆隧道开挖引起的地层受力分析,将地表变形影响因素分为注浆压力、附加荷载和地层损失,并引入Mindlin解和Peck公式,获得了隧道引起的地表变形计算公式.通过对地表变形特征进行分析,结果表明:岩土力学参数对地表变形最大值有显著影响,但对沉降影响宽度影响甚微;沉降槽宽...     

Construction and field measurement of high-speed railway test embankment built on Indian expansive soil “Black Cotton Soil”

The railway embankment applied to high-speed railways is required to have high performance in terms of strength and deformation characteristics. Especially in the case of railway embankments that support slab tracks, the allowable settlement is very small. There are two technical challenges in constructing high-speed rail embankments to support slab tracks in India. The first challenge is dealing with problematic black cotton soil (BCS), which is widely distributed in India but very unusual soil in Japan. The second challenge is posed by the strict deformation requirement in the construction of the embankments. In this study, a 6 m-high test embankment was constructed on BCS in India. The deformation of the embankment and changes in water content were measured over a period of 18 months. In the construction of the test embankment, two different BCS countermeasures were applied. The results of the tests on this embankment were compared with those from an embankment without countermeasures. Complicated deformation behaviors, including settlement and the uplift of embankment, were observed in the section without countermeasure. However, in the embankment with cement-mixed gravelly soil (CGS) slab improvement with geosynthetics, the much lower amplitude of embankment deformation is evidence of the effectiveness of this countermeasure. The cohesive non-swelling soil (CNS) layer applied immediately below the embankment to reduce the water content fluctuation of BCS was not effective enough for use for high-speed railway embankment. Besides determining the technical challenges for the BCS countermeasures, the results of this study confirmed that a high-performance embankment can be constructed with Indian embankment material by performing sufficient compaction management.     

铝蜂窝板在济康住院大楼幕墙工程中的应用

十堰市太和医院济康住院大楼平面造型为梭形,幕墙板设计为弧形,结合大楼对幕墙板的要求和铝蜂窝板的性能特点,经对比分析,最后选择铝蜂窝板作为幕墙板。深入介绍了铝蜂窝板材质、表面处理、外观质量以及其装配和生产、技术装备要求,详细介绍了铝蜂窝板幕墙的安装工艺,总结了主要质量控制措施。实践表明,铝蜂窝板幕墙满足了大楼整体外墙大分块光滑平整、抗风和大尺寸内外对缝的要求,整体效果良好。     

Changes in bimodal oxygen uptake of an obligate air breather Anabas testudineus (Bloch) exposed to lindane

Bimodal [aquatic (V_O2) and aerial (V_O2)] oxygen consumption of the air-breathing fish, Anabas testudineus (Bloch) exposed to 0.075 and 0.59 mg 1⁻¹ lindane was measured for 120 and 6 h respectively. In the controls 67.9% of O₂ was obtained from air (V_O2) whereas only 32.1% was obtained from water (v_O2) indicating that A. testudineus predominantly relies on aerial gas exchange. The fish held in both the concentrations of lindane showed a consistent increase in v_O2, V_O2 and (v + V)_O2 (total O₂ consumption) in most of the periods of exposure; but the increases observed in mean O₂ consumption at higher concentration were relatively lower than those in lower concentration. In 0.075 mg 1⁻¹ lindane, the stimulation seen in aerial respiration was more than that in aquatic respiration up to 24 h. The oxygen consumption returned to normal at 96 h in the lower concentration of lindane.