改进EMD算法在滚动轴承振动信号分析中的应用

针对传统的经验模态分解处理非平稳、非线性振动信号存在的模态混淆问题,提出了一种改良的经验模态分解处理滚动轴承的振动信号。针对采集振动信号过程中存在多频率信号、噪声和间歇信号的特点,构建了高低频率信号和带有噪声及间歇信号的混合信号,并对仿真信号进行传统的经验模态分解和改进经验模态分解。结果表明,使用改进经验模态分解对实际采集的轴承振动信号进行分析,能够较好地改善模态混淆现象。     

L型螺旋式消声器

一、前言我国的风机消声器虽然已经有不少定型产品,但大多数低频消声效果较差。一般250赫和500赫的插入损失,不到20～25分贝。而这2个频率却正是我国电机通常的运行频率(1450转/分和2900转/分),即风机的基频所在,噪声都比较高,因而大大地影响了消声器的实际使用效果。提高这2个频率的消声量,是改进消声器     

电机防噪声措施中的一些具体问题

电机噪声包括机械噪声和电磁噪声。其中机械噪声频率较高,电磁噪声的频率较低。目前一般的防噪声措施有隔声罩、吸声屏、消声器等及近年来使用机翼型节能风叶也能达到降低电机噪声的目的。一、电机采用隔声罩的利弊1.电机采用隔声罩后对噪声的影响我们公司有一个地下油泵房,装有五台燃油泵。油泵型号为3Y—     

轻型汽车YZ—Ⅰ型消声器研制获得成功

排气噪声是汽车发动机最主要的噪声源,安装排气消声器是降低汽车噪声最有效最常见的措施,对改善交通噪声具有显著的意义。为此重庆大学采矿系和重庆渝州汽车钢圈厂共同研制了 YZ—1型消声器。该消声器是在分析130系列汽车用发动机进行排气噪声的测试分析,获得不同转速的排气噪声频率特性曲线,找出了130系列汽车原配消声器的主要优缺点的基础上,设计了新型消声器基本单元,并经过分析计算,找出基本单元各参数对其消声效果的影响关系,用最优化理论,设计和制作了轻型汽车 YZ—1型消声器。经现场测试结果表明,     

FWZ型系列消声器的研制

消声器是一种允许气流通过而使声能衰减的装置,把它安装在气流通道上,能够有效地降低空气动力性噪声。消声器形式繁多,有阻性消声器,抗性消声器,阻抗复合式消声器,微穿孔板消声器等。阻性消声器主要用于吸收中高频噪声,抗性消声器用于吸收中低频噪声、阻抗复合式消声器吸收宽频带噪声,微穿孔板消声器     

探讨消声器结构对气流再生噪声的影响

设计了 3种具有代表性的抗性消声器 ,并进行了试验。试验结果表明 :消声器结构对气流再生噪声以及消声量有影响。并进行了气流再生噪声的估算     

舱门振动对舱室噪声特性影响研究

目的研究舱门结构振动特性对舱室声场特性的影响与控制方法。方法基于声固耦合分析方法,对典型舱门结构的振动声辐射特性进行仿真分析,研究材料、板厚以及阻尼层对舱门结构声辐射特性的影响规律。建立舱室声学分析模型,分析舱门结构振动对舱室声学环境的影响。结果计算了典型舱门结构的固有频率和声辐射特性,舱门结构在固有频率处容易辐射出较大的噪声能量。通过分析舱室典型位置声压频率响应可知,声压峰值频率以舱室模态频率为主,且响应最大值出现在舱门结构频率和舱室模态频率重合处。仿真分析结果显示,采用在舱门表面增加约束阻尼层的降噪方法,可以有效降低舱室噪声。结论舱门结构振动模态频率与舱室声学模态频率的重合产生较大的共鸣噪声。在舱门上增加约束阻尼层是一种简易且有效的舱室噪声控制措施。     

焙烧炉除尘系统的噪声治理

对某铝业公司焙烧炉除尘系统风机噪声和排气噪声进行治理,研究了风机噪声和排气噪声产生的原因和特点,提出了噪声控制方案,采用了风机出口管道安装消声器、针对排气噪声扩散在烟囱出口安装排气消声器、对排气烟囱管道支撑设置减振垫等措施,通过治理使该炉环境噪声影响得到有效控制。经环保部门监测,达到国家有关噪声标准要求。     

消声器的气流再生噪声

消声器是控制管道噪声的重要手段,在工业用鼓风机、压缩机和公共建筑、民用建筑的通风设备上被广泛应用,消声器可以阻止通风设备的空气动力性噪声沿管道传播至使用房间或环境,达到抑制噪声,保护环境的目的。在消声器的设计和选用上,人们只注意消声器的消声作用,而往往忽视了消声器在使用中要产生气流再生噪声这一事实,致使在消声器的使用上碰到一些问题,如:消声器的计算消声量和实际使用效果不一致;有气流的动态     

阻性消声器在煤矿风井噪声控制中的应用

本文对煤矿风井噪声的产生机理及特性进行了分析。针对煤矿风井噪声高、风量大、频带宽的特性,结合阻性消声器消声频带宽、消声量大等特点,提出了用阻性片式消声器治理风井噪声的方法及该方法在煤矿中的实际应用效果。并阐述了阻性消声器消声量的计算方法。     

Toxic effects of acetochlor, methamidophos and their combination on nifH gene in soil

Toxic effects of two agrochemicals on nifH gene in agricultural black soil were investigated using denaturing gradient gel electrophoresis （DGGE） and sequencing approaches in a microcosm experiment. Changes of soil nifH gene diversity and composition were examined following the application of acetochlor, methamidophos and their combination. Acetochlor reduced the nifH gene diversity （both in gene richness and diversity index values） and caused changes in the nifH gene composition. The effects of acetochlor on nifH gene were strengthened as the concentration of acetochlor increased. Cluster analysis of DGGE banding patterns showed that nifH gene composition which had been affected by low concentration of acetochlor （50 mg/kg） recovered firstly. Methamidophos reduced nifH gene richness that except at 4 weeks. The medium concentration of methamidophos （150 mg/kg） caused the most apparent changes in nifH gene diversity at the first week while the high concentration of methamidophos （250 mg/kg） produced prominent effects on nifH gene diversity in the following weeks. Cluster analysis showed that minimal changes of nifH gene composition were found at 1 week and maximal changes at 4 weeks. Toxic effects of acetochlor and methamidophos combination on nifH gene were also apparent. Different nifH genes （bands） responded differently to the impact of agrochemicals： four individual bands were eliminated by the application of the agrochemicals, five bands became predominant by the stimulation of the agrochemicals, and four bands showed strong resistance to the influence of the agrochemicals. Fifteen prominent bands were partially sequenced, yielding 15 different nifH sequences, which were used for phylogenetic reconstructions. All sequences were affiliated with the alpha- and beta-proteobacteria, showing higher similarity to eight different diazotrophic genera.     

Arsenic uptake by arbuscular mycorrhizal maize （Zea mays L.） grown in an arsenic-contaminated soil with added phosphorus

The effects of arbuscular mycorrhizal (AM) fungus (Glomus mosseae) and phosphorus (P) addition (100 mg/kg soil) on arsenic (As) uptake by maize plants (Zea mays L.) from an As-contaminated soil were examined in a glasshouse experiment.Non-mycorrhizal and zero-P addition controls were included.Plant biomass and concentrations and uptake of As,P,and other nutrients,AM colonization,root lengths,and hyphal length densities were determined.The results indicated that addition of P significantly inhibited root colonization and development of extraradical mycelium.Root length and dry weight both increased markedly with mycorrhizal colonization under the zero-P treatments,but shoot and root biomass of AM plants was depressed by P application.AM fungal inoculation decreased shoot As concentrations when no P was added,and shoot and root As concentrations of AM plants increased 2.6 and 1.4 times with P addition,respectively.Shoot and root uptake of P,Mn,Cu,and Zn increased,but shoot Fe uptake decreased by 44.6%,with inoculation, when P was added.P addition reduced shoot P,Fe,Mn,Cu,and Zn uptake of AM plants,but increased root Fe and Mn uptake of the nonmycorrhizal ones.AM colonization therefore appeared to enhance plant tolerance to As in low P soil,and have some potential for the phytostabilization of As-contaminated soil,however,P application may introduce additional environmental risk by increasing soil As mobility.     

Potential of plant polyphenol oxidases in the decolorization and removal of textile and non-textile dyes

In this study an effort has been made to use plant polyphenol oxidases; potato （Solanum tuberosum） and brinjal （Solanum melongena）, for the treatment of various important dyes used in textile and other industries. The ammonium sulphate fractionated enzyme preparations were used to treat a number of dyes under various experimental conditions. Majority of the treated dyes were maximally decolorized at pH 3.0. Some of the dyes were quickly decolorized whereas others were marginally decolorized. The initial first hour was sufficient for the maximum decolorization of dyes. The rate of decolorization was quite slow on long treatment of dyes. Enhancement in the dye decolorization was noticed on increasing the concentration of enzymes. The complex mixtures of dyes were treated with both preparations of polyphenol oxidases in the buffers of varying pH values. Potato polyphenol oxidase was significantly more effective in decolorizing the dyes to higher extent as compared to the enzyme obtained from brinjal polyphenol oxidase. Decolorization of dyes and their mixtures, followed by the formation of an insoluble precipitate, which could be easily removed simply by centrifugation.     

Removal of heavy metals from sewage sludge by low costing chemical method and recycling in agriculture

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Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.     

Isolation and preliminary characterization of a 3-chlorobenzoate degrading bacteria

A study was conducted to compare the diversity of 2-, 3-, and 4-chlorobenzoate degraders in two pristine soils and one contaminated sewage sludge. These samples contained strikingly different populations of mono-chlorobenzoate degraders. Although fewer cultures were isolated in the uncontaminated soils than contaminated one, the ability of microbial populations to mineralize chlorobenzoate was widespread. The 3- and 4-chlorobenzoate degraders were more diverse than the 2-chlorobenzoate degraders. One of the strains isolated from the sewage sludge was obtained. Based on its phenotype, chemotaxonomic properties and 16S rRNA gene, the organism S-7 was classified as Rhodococcus erythropolis. The strain can grow at temperature from 4 to 37℃. It can utilize several （halo）aromatic compounds. Moreover, strain S-7 can grow and use 3-chlorobenzoate as sole carbon source in a temperatures range of 10-30℃ with stoichiometric release of chloride ions. The psychrotolerant ability was significant for bioremediation in low temperature regions. Catechol and chlorocatechol 1,2-dioxygenase activities were present in cell free extracts of the strain, but no （chloro）catechol 2,3- dioxygenase activities was detected. Spectral conversion assays with extracts from R. erythropolis S-7 showed accumulation of a compound with a similar UV spectrum as chloro-cis,cis-muconate from 3-chlorobenzoate. On the basis of these results, we proposed that S-7 degraded 3-chlorobenzoate through the modified ortho-cleave pathway.     

Organochlorine pesticides in soils under different land usage in the Taihu Lake region, China

A field study was conducted in the Taihu Lake region, China in 2004 to reveal the organochlorine pesticide concentrations in soils after the ban of these substances in the year 1983. Thirteen organochlorine pesticides (OCPs) were analyzed in soils from paddy field, tree land and fallow land. Total organochlorine pesticide residues were higher in agricultural soils than in uncultivated fallow land soils. Among all the pesticides, ΣDDX (DDD, DDE and DDT) had the highest concentration for all the soil samples, ranging from 3.10 ng/g to 166.55 ng/g with a mean value of 57.04 ng/g and followed by ΣHCH, ranging from 0.73 ng/g to 60.97 ng/g with a mean value of 24.06 ng/g. Dieldrin, endrin, HCB and α-endosulfan were also found in soils with less than 15 ng/g. Ratios of p,p'-(DDD DDE)/DDT in soils under three land usages were: paddy field ＞ tree land ＞ fallow land, indicating that land usage inlfuenced the degradation of DDT in soils. Ratios of p,p'-(DDD DDE)/DDT ＞1, showing aged residues of DDTs in soils of the Taihu Lake region. The results were discussed with data from a former study that showed very low actual concentrations of HCH and DDT in soils in the Taihu Lake region, but according to the chemical half-lives and their concentrations in soils in 1980s, the concentration of DDT in soils seemed to be underestimated. In any case our data show that the ban on the use of HCH and DDT resulted in a tremendous reduction of these pesticide residues in soils, but there are still high amounts of pesticide residues in soils, which need more remediation processes.     

Sorption of 1-naphthol by plant cuticular fractions

The contribution of aliphatic-rich plant biopolymer to sorption of hydrophobic organic compounds is significantly important because of their preservation and accumulation in the soil environment,but sorption mechanism is still not fully understood.In this study, sorption of 1-naphthol by plant cuticular fractions was examined to better understand the contributions of respective fraction.Toward this end,cuticular materials were isolated from the fruits of tomato by chemical method.The tomato cuticle sheet consisted of waxes (6.5 wt%),cuticular monomer (69.5 wt%),and polysaccharide (24.0 wt%).Isotherms of l-naphthol to the cuticular fractions were nonlinear (N value (0.82-0.90)) at the whole tested concentration ranges.The KodKow ratios for bulk cuticle (TC1),dewaxed cuticle (TC2),cutin (TC4),and desugared cuticle (TC5) were larger than unity,suggested that tomato bulk cuticle and cutin are much powerful solption medium.Sorption capability of cutin (TC4) was 2.4 times higher than the nonsaponifiable fraction (TC3).The 1-naphthol interactions with tomato cuticular materials were governed by both hydrophobic-type interactions and polar (H-bonding) interactions. Removal of the wax and polysaccharide materials from the bulk tomato cuticle caused a significant increase in the sorption ability of the cuticular material.There was a linear negative trend between K_(oc) values and the amount of polysaccharides or fraction's polarities ((N O)/C);while a linear positive relationship between K_(oc) values and the content of cutin monomer (linear R~2=0.993) was observed for present in the cuticular fractions.Predominant sorbent of the hydrophobic organic compounds (HOCs) in the plant cuticular fraction was the cutin monomer,contributing to 91.7% of the total sorption of tomato bulk cuticle.     

Alterations of organ histopathology and metallolhionein mRNA expression in silver barb, Puntius gonionotus during subchronic cadmium exposure

Common silver barb,Puntius gonionotus,exposed to the nominal concentration of 0.06 mg/L Cd for 60 d,were assessed for histopathological alterations(gills,liver and kidney),metal accumulation,and metallothionein(MT)mRNA expression.Fish exhibited pathological symptoms such as hypertrophy and hyperplasia of primary and secondary gill lamellae,vacuolization in hepatocytes,and prominent tubular and glomerular damage in the kidney.In addition,kidney accumulated the highest content of cadmium,more than gills and liver.Expression of MT mRNA was increased in both liver and kidney of treated fish.Hepatic MT levels remained high after fish were removed to Cd-free water.In contrast,MT expression in kidney was peaked after 28 d of treatment and drastically dropped when fish were removed to Cd-free water.The high concentrations of Cd in hepatic tissues indicated an accumulation site or permanent damage on this tissue.     

Seed selections for crystallization of calcium phosphate for phosphorus recovery

Seed induces and promotes the crystallization of calcium phosphate, and acts as carrier of the recovered phosphorus （P）. In order to select suitable seed for P recovery from wastewater, three seeds including Apatite （AP）, Juraperle （JP） and phosphate-modified Juraperle （M-JP） were tested and compared. Batch and fixed-bed column experiments of seeded crystallization of calcium phosphate were undertaken by using synthetic wastewater with 10 mg/L P phosphate. It shows that AP has bad enduring property in the crystallization process, while JP has better performance for multiple uses, and M-JP is a hopeful seed for P recovery by crystallization of calcium phosphate.