合成空干性不饱和聚酯树脂的评述

本文评述了空干性不饱和聚酯树脂的合成方法与机理。

高速铁路轨道不平顺与车辆动力响应的空频相干分析

轨道几何不平顺是轮轨系统产生振动及动力响应的主要原因,但轨道不平顺与车辆动力响应并非直接对应。为探究对车辆动力响应有显著影响的几何不平顺参数及其对应的波长和里程位置,利用运营线路实测的轨道检测数据,基于小波变换的时频多分辨特性,提出从空-频联合平面内分析轨道不平顺参数之间的关系,以及与车辆动力学指标的相干性。研究表明,影响车体垂向加速度的主要因素是波长16.0~64.0 m范围的高低,其次是波长64.0~189.6 m波段的水平、三角坑,而轨向、轨距等横向几何不平顺参数对其几乎没有影响。影响车体横向加速度的主要因素是波长96.0~155.0 m范围的轨向及波长128.0 m附近的水平、三角坑,轨距与车体横向加速度相关性较弱,对其影响较小。研究结果表明,通过小波时频相干函数可以同时确定对车辆动力响应有较大影响的几何不平顺波长分布和空间位置,为科学、合理地评价轨道几何状态奠定基础。

空场诱导相干性对倒转Y-型四能级原子系统中单光子和双光子吸收性质的影响

当倒转Y-型四能级原子的两基态能级邻近简并时,连接基态的两个跃迁路径与同一个真空辐射场相互作用便导致了空场诱导相干性.空场诱导相干性能使该原子在探测光共振点处的单光子和双光子电磁诱导透明现象减弱,而在其它失谐量处会导致单光子增益现象.同时,外加相干光场的相对相位对原子的吸收性质也有重要影响.

在三能级Λ系统中空场诱导相干性对介质吸收和色散性质的影响

由于两基态能级邻近简并的三能级Λ型原子系统与空场的相互作用,该原子的两个跃迁之间会产生空场诱导相干性.该相干项对原子系统的吸收和色散性质有重要影响.另外,由于空场诱导相干性的存在,原子的光学性质还与外加相干场的相位有关.

空场诱导相干性对K-型五能级原子系统单光子和双光子吸收性质的影响

当K-型五能级原子的两基态能级邻近简并时,连接基态的两个跃迁路径与同一个真空场辐射场相互作用导致的量子干涉效应便产生了空场诱导相干性。空场诱导相干性对K-型五能级原子系统的单光子和双光子电磁诱导透明有重要的影响。

双环戊二烯改性对苯型不饱和聚酯树脂的研制

探讨了双环戊二烯 (DCPD)改性对苯型不饱和聚酯树脂的合成方法 :对苯二甲酸用二元醇酯化后 ,加入装有顺丁烯二酸酐和DCPD的反应器中 ,在 80 -12 0℃下滴加与DCPD等摩尔的水 ,反应 2 5h ;加入其它成分 ,升温酯化直至反应完全。DCPD的含量影响对苯型不饱和聚酯与苯乙烯的互容性和固化过程。与标准树脂相比 ,DCPD改性对苯型不饱和聚酯树脂力学强度高 ,耐热性和耐腐蚀性强 。

烯丙基醚改性不饱和聚酯的合成

用对苯二甲酸二甲酯、丙二醇、马来酸酐以及三羟甲基丙烷二烯丙基醚合成了空干性不饱和聚酯 ,探讨了合成反应的条件 ,并与邻苯型、间苯型树脂作比较。

Optical Properties of Neutral and Charged Low Band Gap Alternating Copolyfluorenes： TD-DFT Investigation

Electronic structure and optical properties of neutral and charged low band gap alternating copolyfluorenes （Green 1, which is based on alternating repeating units consisting of alkyl-substituted fluorene and a thiophene-[1,2,5]thiadiazolo-[3,4]quinoxaline-thiophene （T-TDQ-T） unit were investigated theoretically with time-dependent density functional theory （TD-DFT） method, and their excited state properties were further analyzed with 2D site and 3D cube representations. For neutral Green 1, the band gap, binding energy, exciton binding energy, and nuclear relaxation energy were obtained. The transition dipole moments of neutral and charged Green 1 are compared using 3D transition density, which reveals the orientation and strength of transition dipole moments. The charge redistribution of neutral and charged Green 1 upon excitation are displayed and compared with 3D charge difference density. The electron-hole coherences of neutral and charged Green 1 upon excitation are investigated with 2D site representation （transition density matrix）. The excited state properties of neutral Green 1 calculated with TD-DFT method are compared with that calculated with ZINDO method, which reveals the importance of electron-electron interaction （in TD-DFT） in the excited state properties.

Analyses of Dry Intrusion and Instability during a Heavy Rainfall Event that Occurred in Northern China

The 1°×1° National Center for Environmental Prediction/National Center for Atmospheric Research （NCEP/NCAR） data and mesoscale numerical simulation data are analyzed to reveal a mechanism for the formation of heavy rainfall in Northern China; this mechanism is the non-uniformly saturated instability induced by a dry intrusion. The dry intrusion and the accompanying downward transport of air with a high value of potential vorticity （PV） are maintained during the precipitation event. As the dry air intrudes down into the warm and moist sector in the lower troposphere, the cold, dry air and the warm, moist air mix with each other, and, as a result, the atmosphere becomes non-uniformly saturated. On the basis of this non-uniform saturation, a new Brunt-Vaisaila frequency （BVF） formula is derived and applied to the precipitation event. It is shown that, compared to the conditions of either a dry or a saturated atmosphere, the BVF in a non-uniformly saturated, moist atmosphere （BVF） may be more appropriate for depicting the atmospheric instability in rainy regions.

A Nonparametric Approach to Foreground Detection in Dynamic Backgrounds

Foreground detection is a fundamental step in visual surveillance.However,accurate foreground detection is still a challenging task especially in dynamic backgrounds.In this paper,we present a nonparametric approach to foreground detection in dynamic backgrounds.It uses a history of recently pixel values to estimate background model.Besides,the adaptive threshold and spatial coherence are introduced to enhance robustness against false detections.Experimental results indicate that our approach achieves better performance in dynamic backgrounds compared with several approaches.

Volatile Organic Compound Emissions when Drying Wood Particles at High Dewpoints

Emission of volatile organic compounds (VOCs) during drying of wood particles for particleboard manufacture, or for production of refined biofuels, is a potential environmental problem. The aim of this work is to study the emissions of VOCs during drying, and the influence on the emissions by different drying parameters.The experiments have mainly been done in a batch fluidized bed dryer, but measurements have also been done in a, pilot scale, continuous fluidized bed dryer. The parameters studied are air flow rate through the bed, air temperature, air dewpoint, and bed height. Since the present trend in biofuels and particle drying is towards very high dewpoints during drying, some measurements have been made at dewpoints up to 95℃, corresponding to a water content of 3.2 kg water per kilogram dry air. The emissions have been measured in two different ways,online during drying with a flame ionization detector and through wood analyses of the terpene content in the wood particles before and after drying. Substantial work has been made in developing the latter method as well as developing the drying equipment to be able to produce a wide range of conditions of the drying medium. It was shown that the VOCs emitted, during wood particle drying, mainly consist of terpenes. The behavior of the emissions was typical, at first contact with the drying gas a sharp peak in the release rate was detected. After that,the release rate stabilizes and declines slowly to a point where the material temperature increases and results in a second small peak in the release rate. Typically 80%-90% of the initial terpene content in the material was emitted during drying to low moisture content and it is not possible to significantly influence this release by changing the drying conditions. Up to 50% of the emitted terpenes are released during a very short period after contact with the drying medium. This fact could be utilized by employing a 2-step drying process. The fact that the VOC concentration in the inert gas gets much higher when drying at higher dewpoints could be taken into consideration when dealing with closed loop applications where the inert gas after the dryer is burnt.

相干光场的相对相位对K-型五能级原子的单光子和双光子吸收性质的影响

当K-型五能级原子的两基态能级邻近简并时,连接基态的两个跃迁路径与同一个真空场辐射场相互作用导致的量子干涉效应便产生了空场诱导相干性。K-型五能级原子系统的单光子和双光子电磁诱导透明受空场诱导相干性的作用效果十分明显,单光子吸收性质与外加相干光场的相对相位也有直接联系。

The Structure of a Typical Mei-Yu Front Identified by the Equivalent Temperature

In China's Mainland, the summer monsoon rainy band is referred to as the mei-yu precipitation front, which extends northward from South China to the Yangtze River, Huaihe River, and Yellow River, depending on the season. This paper describes the structure of the mei-yu front associated with a persistent heavy rainfall event that occurred in the summer of 2007. The mei-yu front occurs when the subtropical oceanic warm, moist air mass and the extra tropical continental dry, cold air mass converge on the lee side of the Tibetan Plateau. The authors defined the equivalent temperature using two terms of dry-air temperature and the specific humidity and calculated its horizontal gradient to indicate the mei-yu front. The vertical structure of the mei-yu front and the moist thermal winds surrounding it were examined based on the equivalent temperature.

Effects of Vacuum-Induced Coherence on One- and Two-Photon Absorption Spectra of Transient Process in a Y-Type System

We investigate the influence of the vacuum-induced coherence on one- and two-photon absorption of the transient process in a four-level Y-type atomic system. We find that the one- and two-photon t, ransient absorption and amplification properties are quite sensitive to the vacuum-induced coherence. It is also shown that the one- and two-photon absorption spectra of the transient process can be dramatically affected by modulating the relative phase of the applied fields. By apprdpriately choosing the relative phase, the amplification of the probe field can be achieved.

Charge and Energy Transfer in the Metal-free Indoline Dyes for Dye-sensitized Solar Cells

Metal-free indoline dyes for dye-sensitized solar cells were studied by employing quantum chemistry methods. Comparative study of the properties of both ground and excited states of metal-free indoline dyes for dye-sensitized solar cells revealed： （i） as the number of rhodanine rings increases, the energy difference between HOMO and LUMO decreases and there is a red shift in the absorption spectrum with the binding energy increased, and the transition dipole moment decreased; （ii） Based on an analysis of charge differential density, we observed that the charge and energy are transfered from the phenylethenyl to the indoline and rhodanine rings; （iii） The electron-hole coherences are mainly on the indoline and rhodanine rings, and the exciton sizes are 30 and 40 atoms for indoline dyes with one and two rhodanline rings, respectively. These results serve as a good example of computer-aided design in metal-free indoline dyes for dye-sensitized solar cells.

Spectrum spatial structure characteristic analysis of remote sensing alteration information and interference factors

Based on the statistical characteristics of remote sensing data, the spatial geometric structure characteristics of spectral data and distribution of background, interference and alteration information in characteristic space were researched through the analysis of two-dimensional and three-dimensional scatter diagrams. The results indicate that the hyper-space of remote sensing multi-data aggregation belongs to low-dimensional geometric structure, i.e. hyperplane form, and anomalous point groups including alteration information usually dissociate out of hyperplane. Scatter diagrams of remote sensing data band are mainly presented as two distribution forms of single-ellipse and dual-ellipse. Clarifying the relations of three objects of background, disturbance and alteration information in remote sensing images provides an important technical thought and guidance for accurately detecting and extracting remote sensing alteration information.

Performance and Economic Analysis of Mulberry Paper Handmade Dryer by Using Downdraft Gasifier

The mulberry paper handmade dryer uses downdraft gasifier, which is a continuous hot air dryer. The downdraft gasifier uses charcoal or wood chip as fuel to produce the producer gas for a dryer heat source. Two steps operation of a dryer as follows： The frst was to reduce mulberry paper pulp moisture by an air vacuum pump; the second was a continuous hot air drying process. The optimum condition drying, the capacity of dryer, the fuel consumption, the drying constant （k） and economics analysis were investigated. It was found that the first step could be to reduce mulberry paper pulp moisture content about 25% and the suitable condition drying was 80 ~C drying temperature, 0.04 kg/s air mass flow rate and 0.29 m/min chain conveyor speed, respectively. The capacity of this dryer was 20 sheets per hour. The quality of mulberry paper product was very good （based on the standard of mulberry paper community 41/2546） and the fuel consumption rate was 5 kg/h （charcoal）. The drying constant was about 0.532933-0.541367 min~ and the drying constant was a function of drying temperature （T）, air mass flow rate （F） and conveyor speed （10 as equation of k（T, F, V） = 0.567494 ＋ 0.000422T- 1.40588F- 0.000205 V （R2 = 0.9254） and the breakeven point of dryer was 0.79 years.

Mathematical Models for Vacuum Drying Characteristics of Pomegranate Aril

The aim of this study was to investigate and determine the best mathematical models in describing vacuum drying characteristic of pomegranate arils in the range of 55-75 ℃. The vacuum batch dryer used in the evaluation was successful in drying a thin layer of pomegranate arils from the initial moisture content of 464.02% （d.b.） to 6.18% （d.b.） within 6.5 to 13.5 hr of continuous drying at the above mentioned temperature range. The drying rates increased with an increase in temperature and drying time. Five of the well known semi-theoretical and empirical models were fitted to the vacuum drying of pomegranate arils. The semi-empirical Midilli model has shown an excellent fit to predict drying behavior of the pomegranate arils because this model gave the highest coefficient of determination （RE）, the least chi-square （X2）, and the lowest root mean square error （RMSE）. The total drying occurs during falling period, signifying the influence of moisture diffusion during the drying. The effective diffusivity varied from 1.25× 10^10 to 2.91 × 10^10 m^2/s over the temperature range. Temperature dependence of the diffusivity was well documented by Arrhenius models. The activation energy of moisture diffusion during drying was found to be 40.46 kJ/mol.

Automatic Carrier Landing System with Gust-rejection Capability

A new direct-lift control carrier landing mode is advanced, and it is proved to be very effective to keep the attitude angle and path angle constant when the aircraft is in the blind area of tracking radar and the guidance system is shut off. The direct-lift control mode is achieved with the symmetric deflection of the flaps and dynamic decoupling for minor disturbance of the angle of attack. This mode changes an aircraft' s model from a short-period oscillation model to a non-oscillation one, which could evidently increase the gust-rejection capability of the aircraft.

What is going up in smoke?——A study of emissions in the wood industry

The requirements that a business needs to consider when building a wood panels manufacturing plant are much the same as they have been for decades, but today there is also the need for multiple environmental studies and permits. These are costly and time consuming additional expenses that often are the longest lead-time items on any project. Most industrialized countries have legislation in place to limit and control the negative impact that emission of pollutants may have on the environment. This paper discusses what is actually happening inside wood drying plants, and the prerequisite conditions for genesis of pyrolytic products relative to the operational parameters, such as choice of input raw materials, driers design and operational regime, choice of fuels for the heat generation and how these factors influence production of stack emission. The characterization of emission condensate by analytical methods is described, and survey of emission control system in use worldwide is described, and means of investigating what may be the optimum design for the control of emission is discussed. Alternate uses of utilizing the condensate, other than burning, are presented for consideration.