有机硅改性聚氨酯海绵的吸声性能分析

为了改善聚氨酯海绵的吸声特性,采用有机硅改性的方法对其进行了研究。在制备的过程中,通过添加有机硅对聚氨酯海绵进行改性,对比了改性后与非改性材料的吸声性能,探究了其随频率变化的关系,测量并分析材料和空气层不同厚度时的吸声系数。通过实验深入探究了该材料对不同频段噪声吸声能力的差异以及材料和空气层不同厚度对材料吸声系数的影响,为该材料在汽车中的应用提供了指导。     

新型橡胶铜复合多孔材料的制造方法及其吸声特性

对200目橡胶粉和500目高纯无氧铜在高能行星式球磨机内进行20 min混料,混料后在模具中,在50℃温度下,在20 MPa压力下,压制成Φ 100 mm×5 mm的圆片,再通过选择性腐蚀方法,把其中的铜腐蚀掉,得到多孔橡胶材料.发现,多孔橡胶中存在大量20 μm以下的小孔以及少量尺寸大于100 μm的大孔.吸声系数试验表明,多孔橡胶对于不同频率的声波均有较好的吸收效果.     

经编间隔织物增强聚氨酯复合材料的制备及其吸声性能

将具有不同结构参数的经编间隔织物与聚氨酯泡沫材料复合,制备了7种经编间隔织物增强聚氨酯复合材料试样.利用驻波管对复合材料进行了吸声性能测试,探讨间隔丝垫纱方式、织物厚度和表面组织结构对复合材料声波吸收性能的影响.测试结果表明,复合材料具有优异的吸声特性,其吸声性能可以通过改变织物结构参数进行调整.     

附加弹性层法抑制夹芯隐身结构中的声波谐振

建立了两种典型夹芯复合隐身结构的声学模型,并推导了斜入射下不同背衬条件的吸声系数及波型转化系数表达式;通过消声水池和脉冲声管试验验证了附加弹性层法抑制夹芯复合隐身结构中声波谐振的效果;保持夹芯结构总厚度一定时,对附加弹性层的材料参数和几何参数进行了声学设计.研究结果表明,附加弹性层阻抗对波型转化系数及抑制夹芯复合隐身结构中声波谐振效果影响显著,通过附加弹性层匹配设计,有效地抑制了夹芯复合隐身结构中的声波谐振,5 kHz以上频段吸声系数达到0.9.     

硅藻泥-草梗复合吸声材料的测试研究

以硅藻泥、草梗、氧化镁为主要原料,加入一定的辅助材料,研制出一种新型复合多孔吸声材料.分析材料的吸声原理及基本特性,采用驻波管法在200~2 000Hz频段范围内测试材料的吸声性能.结果表明,材料的吸声性能受草梗掺量、尺寸、材料的密度和厚度以及背部空腔尺寸的影响,与一般常用吸声材料的吸声系数进行比较,综合吸声性能优良.     

新型多孔水泥基陶粒吸声材料的性能分析

以黏土质陶粒和42.5级普通硅酸盐水泥作为主要原料,添加一定的辅助材料,研制出一种新型多孔水泥基陶粒吸声材料。经过研究发现:颗粒级配、压缩比、空腔、表面形态、不同安装方法等对该材料吸声性能都有一定的影响。0.5~2.5 mm粒径范围的陶粒,对100~1 800 Hz的降噪效果较好;材料压缩比为1.3时,对100~1 800 Hz的吸声效果较好,其降噪系数为0.55;该材料后面预留50 mm背腔,低频吸声性能得到有效提高;表面处理过的材料,其暴露于声场中的面积增大,对声波具有更充分的吸收。     

基于三维声强法的吸声系数测量研究

传统的测量吸声系数的方法主要有混响室法和驻波管法,这类方法易受实验条件限制,在实际工程中的应用有一定的局限性。本文中使用四传声器,基于所测量的三维声强的矢量特性,通过前后两次分别测量被测试件和全反射板反射的声强幅值来计算相应的吸声系数大小,提出了一种新的测量斜入射吸声系数的方法;该方法在测量材料吸声系数的同时,还可以测出声波的入射角和反射角。首先进行了三维声强法测量吸声系数的原理分析;然后利用软件对该系统进行数值仿真,探讨了不同频段、不同吸声系数和不同入射角下吸声系数的测量误差;最后,利用该方法对3种材料进行实验测量,将结果与驻波管法测量得到的结果进行对比,并检验其方向性误差。结果表明:该方法在630～4 000 Hz频段内测得的吸声系数与驻波管法测得的吸声系数的误差在±0.02～±0.10间,方向性误差在1°～6°之间;从0°到80°的不同入射角下方向性误差在1°～3.5°之间。     

高温环境下梯度多孔金属纤维的吸声性能及优化设计

为了研究高温环境下具有梯度结构的多孔金属纤维吸声性能,应用物性参数与温度之间的关系式,将Johnson-Allard吸声理论模型拓展到高温条件下,建立了多孔金属纤维材料高温吸声理论模型。采用高温阻抗管设备,测量了多孔材料试件,实验测试数据与理论计算结果符合很好,验证了理论模型的有效性。应用声阻抗转移公式,进一步将该理论模型拓展为梯度多孔金属纤维的高温吸声理论模型,并结合优化算法对多层梯度材料结构进行了优化设计。研究结果表明:高温条件下,材料吸声效果相比常温条件下稍差;多孔材料孔隙率和纤维丝径对材料吸声性能影响显著,随着孔隙率或纤维丝直径增大,材料吸声系数在低频段减小,在中频段增大;经过结构优化设计后,在同等条件下,多层梯度金属纤维材料吸声性能明显优于单层结构,具有良好的吸声效果。研究工作对多孔金属纤维材料的高温吸声应用及梯度优化设计具有一定的指导意义。     

水声吸声材料与吸声结构研究进展

低频探测技术的发展对水下航行器的隐身性能提出了新的挑战。为了提高水下航行器的生存能力,通常会在其表面敷设水声吸声材料以吸收声纳发出的探测声波。本文综述了水声吸声材料及吸声结构的研究进展,介绍了基体材料改性、不同吸声结构对吸声性能的影响以及声学超材料在水声吸声领域中的应用,并总结了吸声材料和吸声结构中存在的问题与不足。     

烧结金属纤维材料的吸声模型研究

根据金属骨架多孔材料的特点,在Biot-Allard刚性骨架多孔材料内流吸声模型的基础上,考虑金属的热导特性,推导出一种新的、形式较简单的有效体积模量表达式,从而得到了一种扩展的吸声模型.利用该扩展吸声模型对单层烧结不锈钢金属纤维板、2层及3层梯度组合金属纤维板的吸声特性进行了理论计算,并进行了相应的实验测试.研究结果表明,金属骨架对材料低频段的声吸收具有一定的强化作用,烧结作用使得纤维小幅振动对材料声吸收的贡献减小,与Biot-Allard模型相比,采用扩展模型计算出的烧结金属纤维材料的吸声特性理论结果与实验测试值在总体上更为一致,尤其是对高频段表面声阻抗率的计算.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.