Network structures and dynamics of dry and swollen poly(acrylate)s. Characterization of high- and low-frequency motions as revealed by suppressed or recovered intensities (SRI) analysis of C NMR

We recorded temperature-dependent high-resolution ¹³C NMR spectra of dry and swollen poly(acrylate)s [poly(2-methoxyethyl acrylate) (PMEA), poly(2-hydroxyethyl methacrylate) (PHEMA), and poly(tetrahydrofurfuryl acrylate) (PTHFA)] by dipolar decoupled-magic angle spinning (DD-MAS) and cross-polarization-magic angle spinning (CP-MAS) methods, to gain insight into their network structures and dynamics. Suppressed or recovered intensities (SRI) analysis of ¹³C CP-MAS and DD-MAS NMR was successfully utilized, to reveal portions of dry and swollen polymers which undergo fast and slow motions with fluctuation frequencies in the order of 10⁸ Hz and 10⁴-10⁵ Hz, respectively. Fast isotropic motions with frequency higher than 10⁸ Hz at ambient temperature were located to the portions in which ¹³C CP-MAS NMR signals of swollen PMEA were selectively suppressed. In contrast, low-frequency motion was identified to the portions in which ¹³C DD-MAS (and CP-MAS) signals are most suppressed at the characteristic suppression temperature(s) T_s. Network of PMEA gels (containing 7 wt% of water) turns out to be formed by partial association of backbones only, as manifested from their T_s gradient at lowered temperature, whereas networks of PHEMA (containing 40 wt% of water) and PTHFA (9 wt% of water) gels are tightly formed through mutual inter-chain associations of both backbones and side-chains, as viewed from the raised T_s values for both near at ambient temperature. It is also interesting to note that flexibility of gel network (PMEA > PTHFA > PHEMA) characterized by the suppression temperature T_s (PMEA < PTHFA < PHEMA) is well related with a characteristic parameter for biocompatibility such as the production of TAT (thrombin-antithrombin III complex) as a marker of activation of the coagulation system.     

用缓释指数评价化学缓释肥的缓释特性及其生物效应

在实验室条件下,采用简化的工艺制备了对氮、磷、钾三元素均有部分缓释作用的复混肥(化学缓释肥),用特定淋洗装置测定肥料各养分随时间的溶出率,通过双曲线方程Xt=b-a/t对其养分累计溶出率与时间的关系进行拟合,以方程常数b和a计算出的缓释指数(SR I)来定量评价肥料缓释特性,同时进行盆栽试验,探讨了缓释指数与复混肥中相应缓释添加剂百分含量(X)之间、各复混肥处理的油菜产量与复混肥中缓释添加剂总含量(X'')之间的关系。结果表明:各养分的缓释指数(SR I)与相应缓释添加剂含量(X)均有很好的线性正相关;各化学缓释肥处理的油菜产量随缓释添加剂总含量(X'')增加而增加;化学缓释肥以较少的荚数获得更高的产量。这预示着通过肥料的室内淋洗试验得到的缓释指数SR I不仅可以用来评价肥料的缓释性能,且在一定程度上可预测肥料的增产效应。     

双层轻质板结构隔声量的实验研究

本文为了研究轻质板材面密度、空气层厚度、吸声材料层厚度对双层轻质板墙结构隔声量的影响,组成了46种不同组合的轻质板结构试件,并测量了其隔声量.研究结果显示,单层轻质板的隔声量随板材面密度的增加而增加;双层“板—空气层—板”结构的隔声量在低于临界频率的频域随空气层厚度的增加而增加;双层“板—空气层—吸声材料层—板”结构的...     

倏逝波光纤布拉格光栅归一化反射率特性研究

基于光波导理论与光纤布拉格光栅（FBG）的模式耦合理论,对倏逝波FBG传感器的能量衰减特性进行了分析研究。最后得到了FBG的归一化反射率的表达式,它是外部介质折射率（SRI）和FBG纤芯直径的函数。理论仿真显示FBG归一化反射率会随着SRI增大和FBG腐蚀程度的加深而减小,呈非线性关系。实验结果也证明增大SRI（小于包层介质折射率）或者增大FBG的腐蚀程度都会使光纤纤芯中的传输能量减小,增强倏逝波与外部媒介的相互作用,从而增加传感器的灵敏度。     

彩铃业务及其在移动网的实现方式

本文对现阶段移动网中各种实现彩铃业务的技术方案做了较为系统的总结和利弊对比,并结合移动网的特性提出了较好地实现彩铃业务的方案.     

强化栽培条件下不同氮肥运筹对水稻氮素利用及土壤微生物的影响

以高产杂交稻组合两优培九和国稻6号为材料,设置基肥:分蘖肥:穗肥比例分别为50:30:20,60:10:30和40:20:40的不同氮肥管理,研究了强化栽培(SRI)条件下不同氮肥运筹对土壤微生物及植株氮素利用的影响。结果表明,强化栽培下每穗粒数增加,不同处理的结实率差异不明显,不施氮肥千粒重下降。强化栽培下穗肥施入增加,其土壤的铵态氮含量提高。土壤铵态氮以穗分化期最高,在孕穗期、开花灌浆期和成熟期的土壤铵态氮含量较低,基本不足20 mg kg-1;而土壤硝态氮含量穗分化期最低,各处理之间均不到4mg kg-1,而孕穗期达到20mg kg-1以上,开花灌浆期略有下降,成熟期土壤的硝态氮含量高。强化栽培能促进土壤细菌和放线菌数量增加。在穗分化期和孕穗期土壤微生物中放线菌含量最多,细菌次之,真菌量最少;灌浆期和成熟期细菌最多,放线菌次之,真菌量远低于前两者。细菌数以穗分化期较低,孕穗期快速上升,灌浆期略下降,成熟期最高。真菌量开花灌浆期低,成熟期高。土壤放线菌数量在穗分化后基本呈现下降的趋势。后期施氮对放线菌有一定的促进作用。另外,在等量的氮肥水平下,增施穗肥有利于提高籽粒的含氮量,水稻的氮吸收利用率品种间差异较大,强化栽培下两优培九品种氮吸收利用率提高。     

A hybrid inversion method for mapping leaf area index from MODIS data: experiments and application to broadleaf and needleleaf canopies

Leaf area index (LAI) is an important variable needed by various land surface process models. It has been produced operationally from the Moderate Resolution Imaging Spectroradiometer (MODIS) data using a look-up table (LUT) method, but the inversion accuracy still needs significant improvements. We propose an alternative method in this study that integrates both the radiative transfer (RT) simulation and nonparametric regression methods. Two nonparametric regression methods (i.e., the neural network [NN] and the projection pursuit regression [PPR]) were examined. An integrated database was constructed from radiative transfer simulations tuned for two broad biome categories (broadleaf and needleleaf vegetations). A new soil reflectance index (SRI) and analytically simulated leaf optical properties were used in the parameterization process. This algorithm was tested in two sites, one at Maryland, USA, a middle latitude temperate agricultural area, and the other at Canada, a boreal forest site, and LAI was accurately estimated. The derived LAI maps were also compared with those from MODIS science team and ETM+ data. The MODIS standard LAI products were found consistent with our results for broadleaf crops, needleleaf forest, and other cover types, but overestimated broadleaf forest by 2.0-3.0 due to the complex biome types.     

磷缓释复混肥的制备及其氮、磷缓释性评价

在实验室条件下制得不同程度磷缓释的复混肥(磷缓释肥),分别测定以水为淋洗剂和以2%柠檬酸溶液为淋洗剂时在特定淋洗装置下水溶性氮、磷及有效磷随时间的溶出率,采用双曲线方程Xt=b a/t对肥料的累计养分溶出率进行分段拟合,在此基础上引入缓释指数评价各养分缓释特性。结果表明:磷缓释肥对磷的缓释作用强于氮,对有效性磷的缓释作用强于水溶性磷;其水溶性氮、磷缓释指数(SR IWN、SR IW P)和有效磷缓释指数(SR IAP)与肥料中加入的缓释剂硫酸镁相对含量(X)具有很好的正相关,其直线相关系数为0.7414、0.8958和0.9829,后两者分别达到显著和极显著水平;2%柠檬酸溶液几乎能溶出肥料中全部有效磷,从而证明了自制磷缓释肥的有效性。     

基于SWAP和SRI的汉江流域旱涝急转时空特征分析

汉江流域受亚热带季风影响,易旱易涝,旱涝急转事件时有发生,灾害突发、抢险难度大,对社会发展易造成重大威胁。以汉江流域为研究对象,采用SWAP和SRI指数分析和研究汉江流域的旱涝演变及旱涝急转变化规律。结果表明:①SWAP和SRI指数均能对旱涝急转事件作出合理诊断,具有良好的适用性。②干旱及旱涝急转事件频次均呈现从汉江上游的西北地区到下游的东南地区先逐渐减少后增加的趋势;洪涝事件频次呈从北到南逐渐增加的趋势;旱涝急转事件平均强度呈现从上游的西北地区到下游的东南地区逐渐增大的趋势。③干旱事件在任意时间段均可能发生,洪涝事件和旱涝急转事件主要集中在夏季,且旱涝急转事件发生的时间短且急,强度较高,更具威胁性。     

Investigations on the Transient Mould Friction Force in Slab Continuous Casting based on Fast Fourier Transformation

In continuous casting, the friction forces in the mould reflect the lubrication between the mould and slab, moreover, they affect the slab surface quality and caster productivity. In the present research the friction force is calculated by measuring the difference of working forces during HOT and COLD tests, which are carried out on the slab continuous caster equipped with hydraulic oscillators. Through analysing the mould friction using the Fast Fourier Transformation (FFT) method, the effects of mould oscillation mode and casting speed on the mould friction force are evaluated. The characteristics of the friction signal in the frequency domain are also investigated. Especially, the characteristics of friction force fluctuations before breakouts are discussed. The experimental and analytical results may contribute to more clearly understand the transient lubrication behaviour not only in the time domain but also in the frequency domain, which is also useful for the application of FFT in data analysis of mould processes.