谐波小波包方法及其对转子亚频轴心轨迹的提取

转子轴心轨迹,特别是亚频轴心轨迹的提取,在转子故障识别中是十分重要的。分析了谐波小波的优势,在研究了谐波小波的频段分解基础上,提出了谐波小波包变换的频段分析表达式,并给出了实现方法,实现了谐波小波的任意频段“任意细化”能力。对转子振动信号进行了频域细化分析,并用谐波小波包变换对实际的高速转子振动信号进行了分析,在得到细化频谱的同时,直接实现了常规方法难以实现的转子亚频信号的轴心轨迹提取,得到了满意结果,为转子故障信号的分析创造了条件。

东山岛外海表层水温的亚潮频波动初步研究

本研究通过对东山岛外海浮标观测的表层水温(SST)数据进行分析,发现2016、2017年夏季东山岛外海表层水温均存在周期为5~8 d的亚潮频波动信号,最大振幅分别为3.1℃和2.1℃。结合卫星遥感SST数据以及风场数据,采用小波分析、交叉小波分析等方法对该现象进行研究分析,结果表明:2016年夏季表层水温中出现的亚潮频波动信号源自短波辐射,表层水温变化滞后短波辐射1天左右;2017年夏季的亚潮频波动源自沿岸风应力,表层水温变化滞后沿岸风应力2天左右。2016年和2017年表层水温出现的亚潮频波动均与台风有关,但信号的来源出现差异是因为2017年台风过境引起了较强的沿岸风松弛现象,在沿岸风中出现了亚潮频波动信号,沿岸风影响上升流变化,进而引起表层水温的变化;2016年由于台风过境引起的沿岸风松弛现象较弱,沿岸风中并未出现亚潮频波动信号,而表层水温中的亚潮频波动信号源自短波辐射,这可能与台风引起局地天气系统的变化有关。

第3届亚洲物理奥林匹克竞赛力学实验试题解答与分析

介绍第 3届亚洲物理奥林匹克竞赛力学实验试题及解答 ,并分析了该实验的设计思想、特点与要求 .

试析变频调速技术在矿山机电中的应用

矿井所用设备以大型设备为主要特点,要求优良的电气传动系统,以保证这些大型设备的高效率运行。在矿井应用变频调速技术对于提高矿井生产设备的效率,节约电能都是至关重要的。

转子轴心轨迹的谐波小波提纯

分析了常用二进小波变换对转子故障信号分析的优势与缺陷 ,介绍了谐波小波分析的基本概念 ,提出了用谐波小波变换对转子振动信号进行频域细化分析并进行轴心轨迹提取的方法 ,并用谐波小波变换对实际的高速压缩机转子振动信号进行了分析 ,在得到细化频谱的同时 ,成功地直接得到了转子的提纯轴心轨迹 ,特别是亚频信号的提纯轴心轨迹 。

基于非线性理论的海底管跨涡激共振可靠性研究

管跨的涡激振动是引发管跨发生共振失效和疲劳失效的主要因素之一 ,也是对管跨进行可靠性设计、可靠性评估工作所要解决的主要问题。针对由涡激振动引发的海底管跨共振失效和疲劳失效两种主要失效形式 ,基于非线性动力学理论、随机过程理论和可靠性分析理论 ,建立了更为符合海底管线实际工况的共振失效和疲劳失效的可靠性分析方法。

The Assessment of Heavy Rains in the Region of Annaba （NE Algeria） to Improve Extreme Flood Forecasting ,, Use of Depth-Duration-Frequency Curves

The knowledge of space and time distribution of short duration rainfall depths is of primary interest in hydrotechnical studies and in extreme floods modelling. This work is carried out to establish a ＂DDF （Depth-Duration-Frequency）＂ relationship for the region of Annaba （Northeast of Algeria） through the examples of Pont Bouchet （El Hadjar）, Ain Berda and Chafia-Dam rainfall gauges. The results of the frequency study of stochastically generated annual series （Pearson＇s distribution type III model） and the regression analysis （least square method） permitted to develop a master curve that well describes heavy rainfalls distribution in the Annaba region. This 2-parameter model is used to predict, with sufficient accuracy, the amount of rain that could be recorded over a shorter duration from daily rainfall data in basins that lack recording rain gauges.

Risk modification of colorectal cancer susceptibility by interleukin-8-251T>A polymorphism in Malaysians

AIM: To investigate the allele and genotype frequencies and associated risk of interleukin (IL)-8-251T>A polymorphism on colorectal cancer (CRC) susceptibility risk. METHODS: Peripheral blood samples of 255 normal controls and 255 clinically and histopathologically confirmed CRC patients were genotyped for IL-8-251T>A polymorphism employing allele-specific polymerase chain reaction. The relative association of variant allele and genotypes with CRC susceptibility risk was determined by calculating the odds ratios (ORs). Corresponding χ 2 tests on the CRC patients and controls were carried out and 95% confidence intervals (CIs) were determined using Fisher's exact test. The allele frequencies and its risk association were calculated using FAMHAP, haplotype association analysis software. RESULTS: On comparing the frequencies of genotypesof patients and controls, the homozygous variant AA was significantly higher in CRC patients (P = 0.002) compared to controls. Investigation on the association of the polymorphic genotypes with CRC susceptibility risk, showed that the homozygous variant IL-8 -251AA had a significantly increased risk with OR 3.600 (95% CI: 1.550-8.481, P = 0.001). In the case of allele frequencies, variant allele A of IL-8 -251 showed a significantly increased risk of CRC predisposition with OR 1.32 (95% CI: 1.03-1.69,P = 0.003). CONCLUSION: Variant allele and genotype of IL-8 (-251 T>A) was significantly associated with CRC susceptibility risk and could be considered as a high-risk variant for CRC predisposition.

Diurnal variation of phytoplankton community in a high frequency area of HABs: Daya Bay, China

Phytoplankton community was investigated in the cage culture area of Daya Bay during a diurnal cycle. Two rainfalls occurred during the course of the experiment and decreased the surface seawater salinity in the aquaculture area. A total of 38 species were identified, of which the dominant species included Pseudo-nitzschia spp. and Skeletonema costatum. Water stratification obstructed the vertical migration of dinoflagellates. Statistical analysis indicated that Synechococcus showed negative relationship with silicate and ammonia, which indicated that Synechococcus adapted to grow at oligotrophic environment. Phytoplankton community structure implied the risk of Pseudo-nitzschia spp. blooms in the aquaculture area of Daya Bay.

Preparation of Fe_3O_4/Mn OOH core–shell nanoparticles by a high-frequency impinging stream reactor

Well-defined Fe3O4/Mn OOH nanoparticles with 61.1 emu·g-1in magnetization intensity and 90.53 m2·g-1in surface area have been synthesized by a new-style of high-frequency impinging stream(HFIS)reactor.In this reactor,two streams first collided together to form nano Fe3O4suspension,which subsequently flew through an S-shaped main channel to generate high-frequency reversing high-gravity fields.At the same time,24 thin liquid sheets impinged into the main channel at the frequencies higher than 100 Hz to create nano Fe3O4/Mn OOH colloids.The obtained powders were characterized by transmission electron microscopy/energy dispersive spectrometer(TEM/EDS),X-ray diffraction(XRD),Brunner–Emmet–Teller(BET)and vibrating sample magnetometer(VSM).Experimental results indicated that low coating ratio prolonged the induction period of heterogeneous nucleation.The high-frequency impingements of 24 thin liquid sheets greatly accelerated the macro-mixing and the initial dispersion.The high-frequency reversing high-gravity fields promoted the mesoand micro-mixing.As a result,nano Fe3O4cores were fleetly and uniformly covered by Mn OOH precursor.As a continuously operated and static high-gravity reactor,the high-frequency impinging stream(HFIS)reactor is being developed to the large-scaled and low-cost production of various nanocomposites.

Infrared-to-green upconversion properties of Er^(3+)/Yb^(3+) co-doped TeO_2-TiO_2-K_2O glasses upon excitation with 976 nm lasers diode

The energy transfer and upconversion of Er 3+ /Yb 3+ co-doped TeO2-TiO2-K2O glasses upon excitation with 976nm lasers diode were studied. The tellurite glasses were prepared by conventional melting methods. Their optical properties and sensitization upconversion spectra were performed. The dependence of green upconversion luminescence intensity on the mole ratio of Yb 3+ to Er 3+ and Er 3+ concentration were discussed in detail. When the mole ratio of Yb 3+ to Er 3+ is 25/1 and Er 3+ concentration is 0.1% （mole fraction）, or when the mole ratio of Yb 3+ to Er 3+ is 10/1 and Er 3+ concentration is 0.15%, the optimal upconversion luminescence intensity is obtained. The obtained glasses can be one of the potential candidates for lasers-diode pumping microchip solid-state lasers.

The Simulation and Optimization Design of Adams-based Engine Suspension System

In this study, the engine suspension system was optimized for making the vibration between engine and car body minimized, and also the optimization was simulated using software Adams. The purpose of this study was to research the vibration isolation of the engine mounting system and implement multi-objective optimization for the intrinsic frequency. In this paper, the optimization was implemented in two ways： （1） the intrinsic frequency was optimized by reasonably allocating it： （2） the intrinsic frequency was optimized using energy decoupling. The optimized intrinsic frequencies were simulated using software Adams and then the simulation results were compared. The simulation results showed that the optimized energy distribution was almost up to 90% and the decoupling degree was greatly improved by comparing the initial data, proving the optimized data played a geater effect on engine vibration isolation and further verifying the feasibility of optimization design method.

感应手持电台控制电路的实现

本文介绍了采用可编程逻辑器件ＧＡＬ１６Ｖ８在车长感应电台控制电路中的应用，文章通过ＧＡＵ６Ｖ８产生振荡器，分频器以及逻辑门控制电路的具体实例较为详细地论述了ＧＡＬ１６Ｖ８硬件电路和软件设计的原理和设计方法。

Simulation and Optimization Design Based on Adams Engine Mounting System

The content of this subject research is to conduct optimization for engine mounting system, and through optimization, it can make the vibration between engine and vehicle body achieve a minimum, using Adams software for simulation. It studies the isolation vibration of the engine mounting system and conducts goal optimization for fixed frequency. This paper uses two methods for optimization. One is to use the rational allocation of fixed frequency to optimize the fixed frequency, and the other is to use energy decoupling method to optimize the fixed frequency. It uses Adams software for simulation of the optimized fixed frequency and conducts comparison of simulated results. The simulated results show that the optimized energy distribution situation almost achieves 90%. Compared with original data, decoupling degree also has a very great improvement, illustrating that the optimized data has greater effect for the isolated vibration of engine, in order to further verify the feasibility of optimization design method.

GIS-based Frequency Ratio and Logistic Regression Modelling for Landslide Susceptibility Mapping of Debre Sina Area in Central Ethiopia

Ethiopia has a mountainous landscape which can be divided into the Northwestern and Southeastern plateaus by the Main Ethiopian Rift and Afar Depression. Debre Sina area is located in Central Ethiopia along the escarpment where landslide problem is frequent due to steep slope, complex geology, rift tectonics, heavy rainfall and seismicity. In order to tackle this problem, preparing a landslide susceptibility map is very important. For this, GISbased frequency ratio(FR) and logistic regression(LR) models have been applied using landslide inventory and the nine landslide factors(i.e. lithology, land use, distance from river & fault, slope, aspect, elevation, curvature and annual rainfall). Database construction, weighting each factor classes or factors, preparing susceptibility map and validation were the major steps to be undertaken. Both models require a rasterized landslide inventory and landslide factor maps. The former was classified into training and validation landslides. Using FR model, weights for each factor classes were calculated and assigned so that all the weighted factor maps can be added to produce a landslide susceptibility map. In the case of LR model, the entire study area is firstly divided into landslide and non-landslide areas using the training landslides. Then, these areas are changed into landslide and non-landslide points so as to extract the FR maps of the nine landslide factors. Then a linear relationship is established between training landslides and landslide factors in SPSS. Based on this relationship, the final landslide susceptibility map is prepared using LR equation. The success-rate and prediction-rate of FR model were 74.8% and 73.5%, while in case of LR model these were 75.7% and 74.5% respectively. A close similarity in the prediction and validation rates showed that the model is acceptable. Accuracy of LR model is slightly better in predicting the landslide susceptibility of the area compared to FR model.

Images of Women in Nigerian Home Videos： An Impact Assessment

This research is about the relationship between Nigerian home videos production, women and cultural ideologies. It is general agreed that there is a sexist problem which has dominated the entire mass media. The study researches that an impact assessment of the images of women in Nigerian home videos is designed to examine the sway Nigerian home videos portrayal of women have on women＇s position and status in the society. The study also investigates the influence of home videos on women＇s and girl＇s perception of themselves and its effect on their development potentials. With 300 respondents drawn from a select range of home videos viewers, a survey research was designed using Awka-urban, Capital of Anambra State, Nigeria as the research area and finds a negative perception of women as regards their image portrayal in the home videos by the viewers. However, this image portrayal has a negative effect on the development potentials of women and that of girl child and as well reflects on how women are seen and treated in Nigerian society.

The Reality of Nigerian Image From the Perspective of The Home Videos

The home video through its offering plays pivotal roles of information, education and entertainment. It has provided knowledge to the viewing audience and directs their attention to issues to think about and/or learn. Popularly called Nollywood, the home video industry has brought scholars, reporters, reviewer, journalists, investors, and different kinds of people to the country; to investigate, invest, and observe the industry or network with people. Through the portrayals and representations of Nigeria and its people, a lot of people, especially foreigners and Nigerians in the Diaspora have come to understand the socio-economic and political terrain of the nation based on the home videos offerings; thus the need to x-ray the depictions in the Nigerian home video films to ascertain the reality of their Nigerian image from the perspectives. The study was undertaken through content analysis of 50 video films which were televised as programmes on television stations in Lagos and Africa Magic （a cable network station）, within the framework of agenda-setting and cultivation theories. The results reveal that while the home video producers have effectively revealed Nigerians as religious and traditional people, very little has been done to portray the economic and investment potentials of the nation; the nation＇s symbols like flags, coat of arm, currencies amongst others are barely revealed; negative attitudes of get-rich-quick, get-rich-at-all-cost, witchcraft, and fetish practices as well as violence, hooliganism, and ritualism amongst other things are often exaggerated in the films. Following the home video portrayals and representations, it could be imagined that the Nigerian urban environment is as beautiful and rich with predominantly affluent and flamboyant people as are depicted in the home videos. The misrepresentations, overrepresentations, and under-presentations of the nation＇s image in the home video can be very detrimental to the nation＇s socio-economic development especially as the nation＇s destiny is indirectly related to its image. They can further pose challenges to the attitudes and responses of people from other nations to the Nigerian citizens within and outside the country. Furthermore, some Nigerian citizens, especially the youths could aspire to and learn certain lifestyles and attitudes projected in the home videos as acceptable.

The Frequency of Y Alu Polymorphism （YAP） Indel in the Minangkabau Malays in Peninsular Malaysia

Background： Minangkabau Malays （Melayu Minangkabau） is one of the Malay sub ethnic groups in Peninsular Malaysia. During the late 17th and early 18th centuries, migration of the Minangs from West Sumatra to the state of Negeri Sembilan Darul Khusus in Peninsular Malaysia took place and their descendants now form the main sub ethnic group in this state. The genetic polymorphisms of Y chromosome at DYS 287 locus were analyzed in Minangkahau Malays. Methods： A total of 41 buccal cells from healthy unrelated individual＇s males from Minangkabau Malays were typed for the DYS 287. The PCR products were separated on 2% （w/v） agarose gel followed by visualization under UV light. Results： Three out of 41 samples （7.32%） showed insertion （YAP＋） polymorphism, while the rest of the samples （92.68%） showed deletion （YAP-） polymorphism. This is the first report concerning the YAP in Malay population at Peninsular Malysia. Conclusion： The vAluable data obtained in this study will contribute to fill in the gap in the knowledge of YAP distribution in Malaysian population and will allow continuous interpretation of the evolution of YAP.

Flood Frequency Analysis at Oshun River in Asejire Dam Site, Nigeria

Flood frequency analysis procedure was performed on annual maximum discharge data of River Oshun at Iwo in Osun State, Nigeria for the period 1985 to 2002 utilizing three probability distribution models namely： Extreme EVI （value Type-l）, LN （Log normal） and LPIII （Log Pearson Type III）. The models were used to predict and compare corresponding flood discharge estimates at 2, 5, 10, 25, 50, 100 and 200 years return periods. The results indicated that Extreme Value Type 1 distribution predicted discharge values ranging from 26.6 m3/s for two years to 431.8 m3/s for 200 years return periods; the Log Pearson Type III distribution predicted discharge values ranging from 127.2 m3/s for two years to 399.54 m3/s for 200 years return periods and the Log normal distribution predicted discharge values ranging from 116.2 m3/s for two years to 643.9 m3/s for 200 years return periods. From the results~ it was concluded that for lower return periods （T_〈 50 yrs） Extreme Value Type 1 and Log Pearson Type III could be used to estimate flood quantile values at the station while for higher return periods （T 〉 50 yrs） Log Normal probability distribution model which gives higher estimates could be utilized for safe design in view of the short length of discharge records used for the analysis.

Contribution of Forest Management Credits in Kyoto Protocol Compliance and Future Perspectives

Article 3 paragraph 3 and paragraph 4 of the Kyoto Protocol （KP） allow parties to use credits from land-based activities for offsetting their emission reduction/limitation target committed in the KP. Forest management （FM） is the dominant activity accounted by Annex I parties of the United Nation Framework Convention on Climate Change in the first commitment period of KP （2008-2012）. Data reported for 2008 and 2009 indicate that over half of the emission reduction target of 24 Annex I parties that expect to use FM removals can be offset by FM credits in the first commitment period. EspeciMly the majority of the emission reduction target of Slovenia, Sweden, Latvia, Finland, Japan, and Croatia may be achieved through FM credits. The total FM CAP as contained in decision 16/CMP.1 in the first commitment period was over-estimated significantly by 50% for all KP parties and 36% for parties that elected FM. Some parties such as Russia, Japan, Italy, Germany, and Switzerland that elected FM activity may benefit largely from the over-estimated CAP. Presuming a significant increase of the harvest rate, the FM reference level （FMRL） for 2013-2020 is only 1/5 of the historical mean value of FM removals even though most parties show an increasing or a steady trend of net removals from 1990 to 2009. As a result Annex I parties would be able to use FM credits in the future that are over 4 times of FM CAP in the first commitment period. This potentiM FM credit would account for 7.7% of total emissions by sources without land use, land-use change and forestry activities （LULUCF） in the base year or 1990, and more Annex I parties would share the ＂benefit＂ from the FMRL accounting approach.