作物残体去向与利用及对土壤氮素转化的影响

近年来,作物残体还田受到了很大的关注,一方面它可以改进土壤氮素的动态变化,减少硝态氮淋失;另一方面可作为提高耕地土壤作为潜在氮储库的一种手段。作物残体是碳、氮的重要源和库,因此还田后会影响土壤中的氮素循环。本文综述了作物残体还田后对土壤氮素转化的影响及残体氮素的利用与去向问题。具体阐述了以下几个方面内容:作物残体的降解过程及影响因素,残体氮素的利用率及去向问题,以及作物残体对土壤无机氮库、有机氮库、微生物特征的影响。     

Parallel Cloth Simulation Using OpenGL Shading Language

The primary goal of cloth simulation is to express object behavior in a realistic manner and achieve real-time performance by following the fundamental concept of physic. In general, the mass–spring system is applied to real-time cloth simulation with three types of springs. However, hard spring cloth simulation using the mass–spring system requires a small integration time-step in order to use a large stiffness coefficient. Furthermore, to obtain stable behavior, constraint enforcement is used instead of maintenance of the force of each spring. Constraint force computation involves a large sparse linear solving operation. Due to the large computation, we implement a cloth simulation using adaptive constraint activation and deactivation techniques that involve the mass–spring system and constraint enforcement method to prevent excessive elongation of cloth. At the same time, when the length of the spring is stretched or compressed over a defined threshold, adaptive constraint activation and deactivation method deactivates the spring and generate the implicit constraint. Traditional method that uses a serial process of the Central Processing Unit (CPU) to solve the system in every frame cannot handle the complex structure of clothmodel in real-time. Our simulation utilizes the Graphic Processing Unit (GPU) parallel processing with compute shader in OpenGL Shading Language (GLSL) to solve the system effectively. In this paper, we design and implement parallel method for cloth simulation, and experiment on the performance and behavior comparison of the mass–spring system, constraint enforcement, and adaptive constraint activation and deactivation techniques the using GPU-based parallel method.     

Polymer solutions confined in slit-like pores with attractive walls: An off-lattice Monte Carlo study of static properties and chain dynamics

Summary Using a bead spring model of flexible polymer chains, the density profiles and chain configurational properties of polymer solutions confined between parallel plates were studied. A wide range of density , chain length N, and strength of a short-range attractive wall potential was investigated. Both a temperature T in the good solvent regime (T > , being the Theta temperature where a chain in unconfined bulk three-dimensional solution would behave ideally) and a temperature in the bad solvent regime (T < ) were considered. It is shown that phase separation in a polymer-rich and polymer-poor solution in the slit competes with polymer adsorption at the walls. A qualitative connection to the wetting behavior of semi-infinite polymer solutions is drawn. The acceptance rate for monomer motions was studied for various conditions, and profiles of monomer mobility across the slit were recorded. Also, average chain relaxation times were extracted from the time dependence of mean-square displacements. Although with increasing density the chain radii (at T > ) show a crossover from two-dimensional excluded volume behavior (R_g N² with = 3/4) to ideal random walk behavior ( = 1/2), the relaxation times show effective exponents Z_eff ( N^{Z eff}) that clearly deviate from the Rouse prediction in concentrated confined solutions.     

某型制氧制氮车仿真系统设计

随着某型制氧制氮车在航空领域的使用量逐渐增大,相关单位对能熟练操作该型制氧制氮车的人才的需求也将随着增大。而相关院校和培训机构由于没有实际装备,教学效果不理想,另外制氧制氮车在实际运行时,存在能耗高、运行周期长、不安全因素多等问题。针对以上问题,本文提出了该型制氧制氮车仿真系统设计和开发的总体方案,介绍了该仿真系统实现的主要功能,为开发该仿真培训系统提供了一条明确而清晰的思路。     

Polypyrrole functionalized with FePcTSA for NO2 sensor application

The nitrogen dioxide (NO₂) sensing capability of polypyrrole (PPy) was enhanced dramatically after functionalized with iron(III)phthalocyanine-4,4′,4″,4-tetrasulfonic acid monosodium salt (FePcTSA). The incorporated phthalocyanine was confirmed by different characterization techniques such as UV–vis spectroscopy, FTIR, GFAAS, EDAX, etc. The resistance of the functionalized PPy decreased spontaneously during exposure to NO₂ gas at room temperature. This material exhibited excellent stability, reversibility, and reproducibility. The lowest response time (t₅₀) thus obtained is 47 s with a highest response factor (ΔR/R₀ × 100) of 50.25.     

基于Flex的RIA与J2EE应用的整合

为了将基于Flex的RIA应用于J2EE,以现有的J2EE框架Struts,Spring,Hibernate为基础,分析了Flex和J2EE框架中各层整合的有效性和实用性,并以Flex与J2EE业务层的整合模犏发了Flex与J2EE整合的实例,验证了Flex与J2EE整合的可行性,提出了Flex与J2EE整合的合理方案。     

应用于Template框架的SVG Tiny创作工具的设计与实现

通过对Template框架的研究,对在该框架中引入SVG Tiny技术进行了研究,并为该框架设计和实现了SVG Tiny创作工具。     

The application of a proportional difference type iterative learning control in active vibration control

Active vibration control is used to instead passive solutions in order to increase the performance at low frequencies, in a variety of different engineering systems. This method has improved the performance specifically. The paper will propose a proportional difference type iterative learning control algorithm to deal with the periodic sources and to investigate the active solution as the three degrees of freedom ＂mass spring damping＂ mount. Simulation shows that this method could get a better tracking performance, also the displacement could converge to zero with a fast speed.     

Modeling and experimentation of a passive low frequency nanoforce sensor based on diamagnetic levitation

This paper is focused on the study of a new low frequency micro and nanoforce sensor based on diamagnetic levitation. The force sensitive part is a 10-cm long macroscopic capillary tube used as a levitating seismic mass. This tube presents a naturally stable equilibrium state with six degrees of freedom thanks to the combination of diamagnetic repulsive and magnetic attractive forces. It is only used as a one-direction force sensing device along its longitudinal axis. This force sensor is passive. The force measurement is based on the displacement of the capillary tube and in steady-state this displacement is proportional to the force. This sensor is characterized by an under-damped second-order linear force-displacement dynamic which remains linear on several hundred micrometers and can thus measure a wide range of microforces. Because of the magnetic springs configuration used, the capillary tube presents a horizontal mechanical stiffness that can be adjusted between 0.01 and 0.03 N/m (similar to the stiffness of a thin AFM cantilever). The measurement range typically varies between ±50 μN. Bandwidth is 4 Hz. The resolution depends on the sensor used to measure the capillary tube displacement and on noises induced by environmental conditions (ground and air vibrations). The resolution typically reached with a STIL confocal chromatic sensor is 5 nN inside a test chamber located on a anti-vibration table. This study is illustrated by a pull-off force measurement.     

Light composite elliptic springs for vehicle suspension

For composites to compete in vehicle suspension applications, it is essential to control their failure by utilising their strength in principal direction instead of shear. This can be achieved efficiently by employing a new configuration instead of existing one. This study marries between an elliptical configuration and the woven roving composites.

In this paper, the influence of ellipticity ratio on performance of woven roving wrapped composite elliptical springs has been investigated both experimentally and numerically. A series of experiments was conducted for composite elliptical springs with ellipticity ratios (a/b) ranging from one to two. Typical failure histories of their failure mechanism are presented and discussed. In general, this study demonstrated that composites elliptical spring can be used for light and heavy trucks and meet the requirements, together with substantial weight saving. The results showed that the ellipticity ratio significantly influenced the spring rate and failure loads. Composite elliptic spring with ellipticity ratios of a/b 2.0 displayed the highest spring rate.