When Teachers' and Parents' Values Differ: Teachers' Ratings of Academic Competence in Children From Low-Income Families.

The authors examined predictors of teachers' ratings of academic competence of 105 kindergarten children from low-income families. Teachers rated target children's expected competence in literacy and math and completed questions about their perceptions of congruence-dissonance between themselves and the child's parents regarding education-related values. Independent examiners assessed children's literacy and math skills. Teachers' instructional styles were observed and rated along dimensions of curriculum-centered and student-centered practices. Controlling for children's skills and socioeconomic status, teachers rated children as less competent when they perceived value differences with parents. These patterns were stronger for teachers who exhibited curriculum-centered, rather than student-centered, practices. The findings suggest a mechanism by which some children from low-income families enter a path of diminished expectations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

弹力竹节牛仔布织造工艺优化

介绍了弹力竹节牛仔布的生产工艺 ,同时对KT36 8剑杆织机织造该织物的工艺进行了优化研究     

Formation of composites fabricated by exothermic dispersion reaction in A1-TiO2-B2O3 system

The formation of aluminum matrix composites fabricated by exothermic dispersion reaction in A1-TiO2-B2O3 system was investigated. The thermal analysis results show that the reactions are spontaneous and exothermic. The Gibbs free energy of α-Al2O3 is the lowest among all the combustion products, followed by TiB2 and Al3Ti. It is noted that when the B2O3/TiO2 mole ratio is below 1, the reaction products are composed of particle-like α-Al2O3, TiB2 and rod-like Al3Ti. The α-Al2O3 crystallites, resulting from the reaction between A1 and TiO2 or B2O3, are segregated at the grain boundaries due to a lower wettability with the matrix. SEM micrographs show that rod-like Al3Ti phase distributes uniformly in the matrix. When the BEO3/TiO2 mole ratio is around 1, the Al3Ti phase almost disappears in the composites, and the distribution of α-Al2O3 particulates is improved evidently.     

From Long Infrared to Very Long Infrared Wavelength Focal Plane Arrays Made with HgCdTe n + n ?/ p Ion Implantation Technology

This paper aims at studying the feasibility of very long infrared wavelength (VLWIR) (12–18 μm) focal plane arrays using n-on-p planar ion-implanted technology. To explore and analyze the feasibility of such VLWIR detectors, a set of four Cd _x Hg_1−x Te LPE layers with an 18 μ cutoff at 50 K has been processed at Defir (LETI/LIR–Sofradir joint laboratory), using both our “standard” n-on-p process and our improved low dark current process. Several 320 × 256 arrays, 30-μm pitch, have been hybridized on standard Sofradir readout circuits and tested. Small dimension test arrays characterization is also presented. Measured photonic currents with a 20°C black body suggest an internal quantum efficiency above 50%. Typical I(V) curves and thermal evolution of the saturation current are discussed, showing that standard photodiodes remain diffusion limited at low biases for temperatures down to 30 K. Moreover, the dark current gain brought by the improved process is clearly visible for temperatures higher than 40 K. Noise measurements are also discussed showing that a very large majority of detectors appeared background limited under usual illumination and biases. In our opinion, such results demonstrate the feasibility of high-performance complex focal plane arrays in the VLWIR range at medium term.     

新型水泥浆实心减轻材料FXW在固井中的应用研究

低密度水泥浆常用泡沫和漂珠作为减轻材料，但泡沫和漂珠的一个共同缺陷是承压能力有限。在现场使用时，地面密度和井下密度是不一致的，这将打破注水泥压力平衡，给固井施工带来一定的风险。为此，通过大量实验，根据颗粒紧密堆积原则，以粉煤灰、改性橡胶粉、微硅、石灰类矿物等为原料，复配出一种新型实心耐压减轻材料 FXW 。由于FXW为实心减轻材料，能够承受压力，因而能够适应井下高压条件。实验表明，FXW低密度水泥浆强度高，韧性好，可更好地满足油气井后期开发需求。     

小波包变换压缩与地震数据处理

探讨了地震数据经小波包变换压缩后对后续处理过程的影响,以及经过某些处理后的数据会对小波包变换压缩产生什么影响等问题。将小波包变换压缩地震数据的结果与快速傅里叶变换压缩地震数据的结果进行了对比,其结果表明:应用小波包变换压缩地震数据,有效信号的损失非常小,压缩比大于快速傅里叶变换的压缩比。在大批量地震数据处理中可以使用小波包变换压缩地震数据。     

低渗透油田合理注采井距的确定--以纯41块沙4段低渗透油田为例

以纯41块沙4段低渗透油田为例，从低渗透油田渗流机理出发，分析了造成低渗透油田开发效果差的主要原因。在计算注水井最大井底流压、油井最小井底流压、油水井之间可建立的最大注采压差的基础上，结合室内试验确定的最小启动压力梯度公式计算油田技术极限注采井距，并结合经济合理井距计算结果，确定了油田合理注采井距，并提出了下二步调整方案，实施后取得了显著的效果。该方法为低渗透油田合理井距的确定、提高低渗透油田的开发效果提供了理论依据。     

Breakdown of oil films and formation of residual films

The breakdown processes of oil films under quasi-static loading have been investigated by using a newly developed steel-oil-mercury system. The relationship between the thickness and breakdown ratio of a hexadecane film is represented by a single master curve independently of the indentation speed, indentation load, and temperature. The master curve shows that the breakdown process of hexadecane includes two stages; one is the decrement of the thickness without breakdown and the other is the decrement of the thickness with a drastic progress of breakdown. By solving a small amount of fatty acid in hexadecane, the thickness increases and the breakdown ratio decreases noticeably; a multilayer residual film supporting normal load is formed between two metal surfaces. Experiments at different temperatures reveal a negative relationship between the temperature and thickness of residual film, which indicates that the residual film is organized by physical interaction rather than chemical interaction. At least under a lower concentration, the residual film appears to consist of not only fatty acid molecules but also hexadecane molecules.     

粉煤灰降失水水泥浆在天然气井固井中的研究与应用

长庆天然气田属于低压、低渗透气田,存在承压能力较低的地层,固井设计要求全井段封固,并且采用双级双凝施工工艺。但由于用于低密度水泥浆中的漂珠生产量降低,价格上升,研究应用替代产品是固井技术发展的方向。在一级领浆中研究应用了粉煤灰水泥浆体系,其性能和固井质量可完全满足固井要求。粉煤灰水泥浆体系价格低和固井质量优良,使其成为漂珠水泥浆体系的替代配方。     

The Minimum PAPR Code for OFDM Systems

In this letter, a block code that minimizes the peak‐to‐average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals is proposed. It is shown that peak envelope power is invariant to cyclic shift and codeword inversion. The systematic encoding rule for the proposed code is composed of searching for a seed codeword, shifting the register elements, and determining codeword inversion. This eliminates the look‐up table for one‐to‐one correspondence between the source and the coded data. Computer simulation confirms that OFDM systems with the proposed code always have the minimum PAPR.