温家溪大桥预应力混凝土全连续特长箱梁张拉施工质量控制

温家溪大桥为预应力混凝土全连续箱梁,单联整体长度达233m。针对本桥预应力施工的特点、难点,采取一定的措施进行施工技术分析,使预应力张拉施工质量得到有效控制。     

锡渣的形成特点和减少措施

随着无铅钎料的广泛使用,波峰焊过程将产生更多的锡渣,造成生产成本增加。通过对其分布特点的研究,将锡炉熔融钎料表面氧化物分为A~E5个氧化物区,并分析了各区域氧化物的特点,列举了几种减少氧化渣的办法,分析了他们的实用性。     

离散多音调制可见光信道非线性失真及参数优化

为了改善离散多音调制(DMT)点对点可见光通 信(VLC)性能,首先给出了 DMT技术原理并建立了实验装置,进而研究了16-相位键控(16-PSK)DMT信号直 流偏压和探测器偏置电阻对VLC信道非线性失真的影响。为了使VLC信道工作于良好的线 性区,优化得到了不同通信距离下系统的最佳直流偏压和探测器偏置电阻。在VLC信道响 应存在非线性失真和调节系统参数使其工作于线性区两种情况下,在0.2Mbit/s数据传输速 率下分别开展了通信实验,并测试了系统在不同通信距离处的误码率(BER )。结果显示,BER可 由未做参数优化时的10－1量级降至10－3量级;且在20~90cm通信距离范围内 BER几乎恒 定,表明系统稳定性也得到了明显改善。本文的实验测试和分析结果为进一步优化系统参数 及改进通信性能提供了数据依据。     

2μm波段Tm,Ho:YAlO_3激光器研究进展及展望

2μm波段激光在医疗、环境监测、激光雷达、遥感探测、测距领域具有十分广阔的应用,近年来成为中红外光源研究的热点。Tm,Ho:YAlO3晶体具有较好的机械和热性能,能实现多种2μm波段激光连续及脉冲输出。对国内外2μm波段Tm,Ho:YAlO3激光器的研究进展进行了归纳与总结,包括Tm/Ho单掺YAlO3激光连续及脉冲振荡技术手段,Tm,Ho:YAlO3激光连续及脉冲振荡技术手段,高功率Tm,Ho:YAlO3激光器研究的最新进展等。技术手段涉及主动调Q、被动调Q、Tm激光抽运Ho激光等,并对Tm,Ho:YAlO3激光器的进一步发展及应用给予了展望。     

谈某大型深基坑支护设计

以某大型基坑支护设计为例,根据本工程开挖的地质条件和开挖深度的特点,选取了桩锚支护为主要的形式,并对桩锚支护体系设计及计算过程进行了详细的分析,以供其他工程参考。     

多粒度机械加工设计意图建模方法研究

针对抽象的机械加工设计意图难以直接用于检索工艺知识,以及在应用中难以描述的特性,在论述加工意图的组成要素的基础上,提出了加工意图多粒度结构化描述方法。通过对加工意图属性域的描述以及结合二维流形的结构化加工拓扑描述,建立了多粒度加工意图在加工过程演变中的描述模型。最后以实例验证,表明多粒度加工意图建模方法的有效性与实用性。     

Analysis of oil content of groundnuts by nuclear magnetic resonance spectrometry

One hundred groundnut germplasm accessions were analysed for their oil content by the standard Soxhlet extraction procedure using petroleum ether: the results were compared using functional analysis with those obtained with a commercial nuclear magnetic resonance (n.m.r.) spectrometer. On another 78 experimental samples, oil content was first obtained using the n.m.r. method and the Soxhlet values were predicted using the above functional relationship. On the 78 samples the predicted values were highly correlated (r=0.972) with those obtained by Soxhlet extraction. The n.m.r. method is rapid, easy, acurate and non-destructive.     

分光光度计测定无卤低烟电缆氟含量方法的改进

目前无卤低烟电缆氟含量的测试一般按lEG60684-2标准执行,可选用离子选择电极法或分光光度计法。该标准中规定的分光光度计法,仅依靠茜素氟兰试剂与氟元素形成一种不稳定的二元体系来显色,且未对稳定显色所需的时间和溶液pH值进行规定,导致试验结果的准确度和精密度较差。对此方法做出了改进,采用茜素氟兰-硝酸亚铈-氟三元络合体系,并严格控制显色时间和体系pH值,确保体系稳定显色,提高了试验结果的准确度和精密度。     

高效液相色谱法测定亚油酸甲酯含量

建立一种高效液相色谱测定亚油酸甲酯含量的方法。采用IntertsilO D S-SP柱,紫外检测器,检测波长为243 nm ,流动相为甲醇－水（体积比为95∶5）混合液,流速为0.8 m L/m in,进样体积为20μL,柱温为30℃。结果可知,亚油酸甲酯质量浓度和峰面积的线性回归方程是y=（2E＋06）x-43628,R 2=0.9999,线性范围是0～4.16 g/L,平均加样回收率为99.92%。     

Cryoprotective additives and cryostabilisation effects on muscle fillets of the freshwater teleost fish Rohu carp (Labeo rohita) during prolonged frozen storage

The effects of various cryoprotective additives separately and in combination were studied on the myofibrillar protein integrity, biochemical enzyme activity levels and muscle ultrastructure in the freshwater teleost fish Rohu carp (Labeo rohita). Fish muscle samples were divided into eight groups and immersed in different mixtures of cryoprotective additives (S1–S8), then frozen at ? 20 or ? 30 °C for 24 months. Electrophoretic studies revealed early (within 6 months) alteration of the myofibrillar proteins myosin light chain, α‐actinin and tropomyosin. Reduction of the storage temperature from ? 20 to ? 30 °C slowed down the degradative processes. Sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated that fish muscle treated with cryoprotective mixture S8 (40 g L^?1 sorbitol/3 g L^?1 sodium tripolyphosphate/4 g L^?1 sodium alginate) showed minimal post mortem changes in myofibrillar proteins. Ultrastructural results also revealed post mortem damage to the muscle, seen earliest (within 6 months) in the sample frozen‐stored without additives (S2), as compared with the normal, unfrozen muscle (S1). The influence of cryoprotectants alone and in combination on fish muscle structural proteins, myosin and actin filaments (A and I bands), during prolonged frozen storage was investigated. After 12 months, samples frozen‐stored with various cryoprotective additives (S2‐S7), except S8, showed signs of myofibrillar disintegration. Beyond that time the degradative processes started showing up in all samples, with minimal muscle ultrastructural damage in sample S8. Again, reducing the storage temperature from ? 20 to ? 30 °C slowed down the degradative processes. Ultrastructural results correlated well with levels of biochemical enzymes (Ca²⁺ myofibrillar ATPase and succinic dehydrogenase) during frozen storage. This is the first report of the cryoprotective effects of these additives on this popular edible fish species. Of the various combinations of additives tested, cryoprotective mixture S8 was found to preserve the muscle structure longest under frozen storage conditions. However, even this mixture was only effective for 18 months at ? 30 °C. Beyond that time the myofibrillar degradative processes were apparent with correlative electrophoretic, biochemical and ultrastructural studies. Copyright © 2006 Society of Chemical Industry