闭孔泡沫铝吸声板复合软质吸声布吸声性能

研究了覆盖软质吸声布的打孔闭孔泡沫铝板的吸声效果,将闭孔泡沫铝与软质吸声布组成组合结构,对组合结构不同背后空腔条件下的吸声性能进行测试。结果表明,覆盖软质吸声布后,打孔闭孔泡沫铝的吸声系数得到提高,最高吸声系数达0.98,高频吸声系数增加明显,主吸声频带变宽。随空腔深度的增加,吸声系数峰值向低频迁移,迁移规律与打孔闭孔泡沫铝裸板类似。     

电沉积泡沫镍的中频吸声性能

噪声污染是一个受到社会广泛关注的重要问题,因此噪声控制得到国内外的大量研究。多孔结构的吸声材料可以有效地消音降噪,探讨三维网状孔隙结构的泡沫镍的吸声性能。这种结构的泡沫镍在很多国家都已有大规模的生产,质量稳定,孔隙尺寸规格丰富。以常用作多孔电极的泡沫镍片材为研究对象,采用驻波管法测定其吸声系数。结果发现,泡沫镍片材总厚为8 mm左右的叠层试样对频率4000 Hz的入射声波显示出优良的吸声效果,吸声系数接近0.8。设置厚度为18.5 mm左右的空腔还可以大大提高叠层试样在2500和3150 Hz等较低声频下的吸声效果,吸声系数增加到0.5以上。研究还表明,通过空腔与试样两者的交替叠加,可以在2000 Hz的低频下获得良好的吸声效果,吸声系数接近0.5。因此,三维网状泡沫镍可以用作人耳敏感频段的优质吸声体。     

闭孔泡沫铝材料吸声性能分析

为更全面地反映闭孔泡沫铝材料的吸声降噪能力,从密度、厚度、背后空腔深度、打孔率几个方面,对闭孔泡沫铝材料的吸声性能进行研究.改变以往单纯用吸声系数的峰值表征的方法,而是用吸声系数的峰值、降噪系数、半峰宽3个指标来评价闭孔泡沫铝材料的吸声性能.通过驻波管法测试吸声系数,用Origin软件进行吸声曲线的分析,建立一次函数.结果表明:在以往研究中个别吸声系数的峰值较高的样品,整体吸声效果不佳;而一些吸声系数的峰值处于中等水平的却具有较好的整体吸声效果,因此更适合于在实际应用中用于吸声结构的设计.     

添加氮化硅对莫来石碳化硅材料性能的影响

以莫来石、红柱石为主要原料,加入不同含量的氮化硅、碳化硅细粉,探讨了添加氮化硅对莫来石碳化硅材料性能的影响。结果表明:在1 450℃下制备的材料的显气孔率基本维持在15%左右,体积密度在2.45 g/cm~3左右,烧后线变化率相差不大,高温抗折强度和荷重软化温度也分别能够达到29.8 MPa和1 560℃,都表现出了较高的水准,且基本不受氮化硅加入量的影响;添加氮化硅能够提高材料的抗热震性能,但材料的常温耐压强度随着氮化硅含量的增加呈降低趋势;材料在烧结过程中,氮化硅和碳化硅均发生了氧化并在材料表面形成一层黄褐色氧化产物,其主要为玻璃相;在材料的截面出现致密层,且致密层的厚度随着氮化硅含量的增加而减小。     

多孔电气石滤球的制备与性能研究

以电气石粉为主要原料,采用高温烧结法制备了粒径30 mm左右的轻质通孔电气石滤球.采用阿基米德称重法测试了滤球的气孔率和密度,通过微控电子万能实验机测试了滤球的抗压强度,采用热重分析、X射线衍射分析、扫描电镜等方法对滤球中电气石材料的化学结构、热稳定性及表观形貌进行表征.结果表明:掺杂量不大于50 %,烧结温度在700~750 ℃范围内,电气石滤球的结构和性能稳定,密度在1.0~1.5 g/cm3之间,随烧结温度的升高滤球的气孔率增大,抗压强度增加.      

打孔提高闭孔泡沫铝吸声性能的机理分析

采用驻波管吸声系数测试仪分别测定闭孔泡沫铝板、打孔闭孔泡沫铝板、打孔铝板的吸声系数,结合共振结构吸声特性曲线,分析闭孔泡沫铝打孔后的结构特征,对吸声机理进行探讨。结果表明,打孔后闭孔泡沫铝吸声系数峰值可达0.68,高于未打孔时的0.42,也高于打孔铝板的0.45,降噪系数同样有所升高。打孔闭孔泡沫铝吸声机理主要是由于表面漫反射的干涉消声、内部微孔和裂纹造成声波的能量耗散、打孔后与背板间形成共振结构及打孔对内部孔洞的结构改变增大了吸声。     

凝胶注模工艺制备闭孔多孔Al_2O_3基陶瓷

以亚微米Al_2O_3粉末为原料,Mg O为掺杂剂,Si C为高温发泡剂,利用Al_2O_3基陶瓷在高温下具有超塑性变形能力的特点,采用凝胶注模工艺制备了闭孔多孔Al_2O_3基陶瓷.研究了不同Si C含量对Al_2O_3基陶瓷烧结密度、开口气孔率、闭口气孔率及微观结构的影响,考察了Al_2O_3基陶瓷的物相组成及气孔孔径的分布和大小,并且与传统的球磨混合工艺进行了对比.研究结果表明,坯体中Mg O与Al_2O_3反应完全,多孔陶瓷的物相组成为Al_2O_3和Mg Al2O4,并伴有少量的SiO_2晶相存在.随着Si C含量的增加,其烧结密度和开口气孔率逐渐降低,闭口气孔率逐渐增加.与球磨混合工艺相比,凝胶注模工艺制备的Al_2O_3基陶瓷中闭口气孔的孔径大小和分布更加均匀.     

铌对钴基和铁基金属玻璃磁致伸缩及其它性能影响的研究

本工作叙述了铁磁金属玻璃磁致伸缩的主要特性及目前的研究概况,对含铌铁磁金属玻璃的研究情况也做了简单回顾。建立了用应变电阻法测量铁磁材料饱和磁致伸缩的设备,灵敏度达到2×10~(-7)。制备了Co-Nb-B和Fe-Nb-SiB两个系列的金属玻璃样品,对它们的晶化过程、饱和磁化强度、居里温度以及饱和磁致伸缩系数进行了研究。在所研究的范围内,发现Nb能有效地提高Co-B和Fe-Si-B金属玻璃的温度稳定性、降低其磁致伸缩系数、提高性能。用虚束缚态的概念和裂带模型对两个系列金属玻璃的饱和磁化强度、饱和磁致伸缩系数随其成分的变化进行了讨论。本文提出金属玻璃的λ_S/σ_S~2值与其成分有关。     

汽轮机汽封系统优化的研究与实践

通过在现有有效空腔内,增加密封齿数;在不影响安全的情况下,减小密封间隙;在不影响密封寿命的前提下,减小齿的厚度;改善密封结构,使用新型蜂窝式汽封的方式对汽封改造来实现提高机组发电效率。     

焦炭气孔结构对热性能指标的影响

通过40kg试验焦炉炼焦试验,研究了焦炭气孔结构对热性能指标的影响。结果表明,随着气孔率及焦炭平均气孔直径的增加,焦炭反应性增加,反应后强度下降,热性质恶化;随着焦炭平均气孔壁厚度的增加,焦炭反应性降低,反应后强度提高,热性质改善。配煤结构、炼焦条件、熄焦方式等是影响焦炭气孔结构的主要因素。     

Flow through Side Sluice Gate

The hydraulic characteristics of a side sluice gate were studied experimentally. It was found that the specific energy remains constant along the side sluice gate. The coefficient of discharge for the side sluice gate is related to the main channel Froude number and the ratio of upstream depth of flow to sluice gate opening for free flow. It also depends on an additional parameter: the ratio of tailwater depth to the gate opening for submerged flow. Suitable equations for discharge coefficient are obtained.     

Complex Permittivity and Microwave Absorption Properties of Zinc Oxide Leach Residues

Cylindrical cavity perturbation method was used to measure complex permittivity of zinc oxide leach residues (ZOLR) at frequency of 2.45 GHz. The results indicate that both dielectric constant and Loss factor of ZOLR increased with increased of temperature and moisture content. The research of ZOLR’s microwave absorption properties were performed based on reflection loss (RL) theory. Microwave absorption peak of ZOLR moves towards higher material thickness with decreasing of moisture content. However, microwave absorption peak of ZOLR moves towards smaller material thickness with increasing of temperature. RL of ZOLR sensitively depends on material thickness of itself. If want to keeping microwave absorption properties of ZOLR greater than 90% in the process of microwave drying, 10 mm, 40 mm, and 50 mm should be selected as the optimum material thickness.     

Effect of geometric structure parameters on the sound absorbing properties of a metal fiber material

Conclusions The sound absorbing properties of the PFM(C) depend on such parameters of the material as porosity, fiber diameter, type of wire interlocking in the starting bonded semifinished product, and number of fibers in the yarn of the semifinished product. By suitable choice of fiber diameter, type of interlocking, and number of wires in a yarn, it is possible to attain an optimum porosity, which ensures a value of coefficient of sound absorption close to unity. Decreasing the fiber diameter shifts the optimum porosity toward higher values. Use of bonded semifinished products with a looser type of fiber interlocking leads to the maximum of sound absorption being observed at slightly higher porosities. When the active impedance component is greater than the wave resistance of air, the coefficient of sound absorption can be increased by increasing the number of fibers in the yarn of the gauze semifinished product.Translated from Poroshkovaya Metallurgiya, No. 11(215), pp. 43–47, November, 1980.     

多孔结构对材料吸波性能的影响

总结了当前多孔材料吸波性能的研究现状，指出多孔结构可改善材料的吸波性能，而孔径、相对密度及厚度是影响多孔材料吸波性能的重要因素，对多孔陶瓷材料而言，适当降低孔径、增加相对密度与厚度有利于提高材料的吸波性能．在此基础上对多孔金属材料泡沫铝的吸波性能进行了初步研究，分析了相对密度与微波频率对材料吸波性能的影响，研究表明，降低多孔金属的相对密度可以显著提高材料的吸波性能；随着微波频率的增加，材料的吸波性能也随之增加．     

高碳钢矩形坯凝固末端永磁搅拌试验

 为了改善高碳钢82A断面180 mm×240 mm矩形坯内部质量,首次在凝固末端进行了永磁搅拌工业试验。根据射钉结果,确定了搅拌器安装位置为距弯月面7 m。搅拌器磁体采用液压系统驱动,通过增加永磁搅拌器入口油压来提高搅拌频率。随着搅拌频率从0增加到5 Hz,矩形坯凝固中心平均碳偏析值从1.18降到1.09。此外,永磁搅拌改善连铸坯中心疏松和缩孔效果显著,铸坯中心疏松0.5级的比例增加了40%,中心缩孔0级比例从0增加到20%。     

Homogenization Approach of Advection and Diffusion in Cracked Porous Material

The present paper aims at studying the effect of microcracks opening on the diffusion and advection processes in a saturated porous medium. It is based on a micromechanical homogenization approach. The effects of porosity and microcracks are addressed in microscopic and mesoscopic levels to yield estimates of the effective diffusion and permeability tensors. Closed-form expressions and numerical results are obtained. For instance, the effect of the crack density parameter ε on the overall properties is discussed: (1) for a given value of ε, the maximum overall diffusion coefficient decreases for increasing values of crack radius; and (2) for large crack opening, the overall permeability is mainly controlled by ε and almost independent of the applied stress and the crack radius.     

Discharge Characteristics of Skew Sluice Gates

Discharge characteristics for a skew sluice gate, ranging between the two extreme cases of a side sluice gate and a normal sluice gate, have been explored. The concept of an elementary discharge coefficient was utilized for obtaining the discharge through a skew sluice gate. Based on experimental investigation, equations for elementary discharge coefficients for skew sluice gates in free- and submerged-flow conditions were obtained. These equations describe the behavior of the elementary discharge coefficients for large ranges of the upstream water depth to gate opening ratio, tailwater depth to gate opening ratio, and skew angle. Using these equations, it is possible to obtain the discharge passing through a bifold skew sluice gate and it is expected that these equations will be useful to obtain the discharge through sluice gates having any plan shape.     

Acoustic characteristics of high-porosity permeable cellular materials

Conclusions High-porosity permeable cellular materials are comparable in their acoustic properties to the conventional materials (glass fiber and foam polyurethane). The key role in sound absorption by these materials is played by their structure (pore size and porosity). At a porosity of 0.85–0.9 the optimum pore size lies in the range 0.5–0.7 mm. The values of wave parameters determined in the frequency range 200–6000 Hz can be employed in calculations of HPCM sound-absorbing constructions and silencers.Translated from Poroshkovaya Metallurgiya, No. 11(287), pp. 33–36, November, 1986.     

榆神府矿区采煤地表裂缝发育规律及特征

榆神府矿区是陕北一个重要的原煤产地，煤炭开发利用规模大、强度高，但区内生态环境脆弱，采煤诱发的矿山地质环境问题尤为显著。为全面掌握榆神府矿区采煤地表裂缝“静”、“动”态发育规律、揭示其形成机理，以榆神府矿区的安山煤矿、柠条塔煤矿和小保当一号井的典型工作面为对象开展研究。研究结果表明:① 地表裂缝分为台阶型、挤压隆起型、滑动型和拉张型4种类型以及“塌陷槽”、“平行并列”2种组合方式；② 榆神府矿区地表裂缝平面展布规律具有相对统一性，而地表裂缝表现特征具有差异性，且与采深采厚比呈负相关关系；③ 极浅埋煤层开采、浅埋煤层开采以及中深埋煤层开采地表裂缝分别具有滞后回采位置1.0 m、超前回采位置8.5 m和滞后回采位置30.14 m的动态展布规律，且地表裂缝滞后距与采深采厚比之间存在多项式的函数关系；④ 边界裂缝和面内正向坡裂缝具有“只开不合”的活动特征，面内逆向坡裂缝具有“先开后合”的活动特征，面内平坦区裂缝则具有“先开后合再开”和“先开后合”两种裂缝活动特征，平均活动时间3.7～7.0 d；裂缝“先开后合再开”的活动受覆岩运移控制，“只开不合”和“先开后合”的裂缝活动受地表移动变形控制，而斜坡裂缝活动机理则与坡体滑移密切相关。研究成果可为榆神府矿区地表裂缝治理和生态修复提供指导。