基于用户特征属性和云模型的协同过滤推荐算法

随着数据的极端稀疏性,仅仅依赖于传统的协同过滤相似性的度量方法已无法取得精确的推荐结果。针对这一问题,提出基于用户特征属性和云模型的协同过滤算法。首先,算法利用云模型计算用户评分云相似性,结合用户打分偏好对原矩阵进行填充,在此基础上得到用户的评分云相似性;其次,再结合用户特征属性相似性通过加权因子计算用户的最终相似性,得到一种新的相似性度量方法;最后,得到算法的评分预测。实验结果表明,该方法能够提高推荐质量。     

Single‐pack,self‐curable,aqueous‐based polyurethane dispersion containing a disperse dye

An organic‐solvent‐soluble disperse dye was introduced into an aqueous phase by a reaction with a self‐emulsified, aqueous‐based polyurethane (PU), and this resulted in the formation of a homogeneous, aqueous polymeric dye dispersion. This aqueous polymeric dye was stable in a water phase with excellent color extension upon application. It was formulated with a latent curing agent, polyaziridine (e.g., TMPTA‐AZ), as a single‐component, self‐curable, aqueous polymeric dye. The curing reaction took place between PU carboxylic acid and the latent curing agent upon drying. A self‐cured polymeric dye was obtained with excellent color extension and fastness and resistance to organic solvents and water after drying. This single‐component, self‐curable, aqueous‐based PU system containing a dye has potential for printing, writing, and dyeing applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 2006 © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3741–3747, 2006     

Mechanical characterization and chemical resistances of cured unsaturated polyester resins modified with vinyl ester resins based on recycled poly(ethylene terephthalate)

Unsaturated polyester resin (UP) was prepared from glycolyzed oligomer of poly(ethylene terephthalate) (PET) waste based on diethylene glycol (DEG). New diacrylate and dimethacrylate vinyl ester resins prepared from glycolysis of PET with tetraethylene glycol were blended with UP to study the mechanical characteristics of the cured UP. The vinyl ester resins were used as crosslinking agents for unsaturated polyester resin diluted with styrene, using free‐radical initiator and accelerator. The mechanical properties of the cured UP resins were evaluated. The compressive properties of the cured UP/styrene resins in the presence of different vinyl ester concentrations were evaluated. Increasing the vinyl ester content led to a pronounced improvement in the compression strength. The chemical resistances of the cured resins were evaluated through hot water, solvents, acid, and alkali resistance measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3175–3182, 2007     

Blends of poly(propylene) and polyacetal compatibilized by ethylene vinyl alcohol copolymers

Polymer blends of poly(propylene) (PP) and polyacetal (polyoxymethylene, POM) with ethylene vinyl alcohol (EVOH) copolymers were investigated by differential scanning calorimetry (DSC), rheological, tensile, and impact measurements, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The PP–POM–EVOH blends were extruded with a co‐rotating twin‐screw extruder. The ethylene group in the EVOH is partially miscible with PP, whereas the hydroxyl group in the EVOH can form hydrogen bonding with POM. The EVOH tends to reside along the interface, acting as a surfactant to reduce the interfacial tension and to increase the interfacial adhesion between the blends. Results from SEM and mechanical tests indicate that a small quantity of the EVOH copolymer or a smaller vinyl alcohol content in the EVOH copolymer results in a better compatibilized blend in terms of finer phase domains and better mechanical properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1471–1477, 2003     

Effect of montmorillonite on the swelling behavior and drug‐release behavior of nanocomposite hydrogels

A series of nanocomposite hydrogels were prepared from various ratios of N‐isopropylacrylamide (NIPAAm) and organic montmorillonite (MMT). The influence of the extent of MMT in the NIPAAm/MMT nanocomposite hydrogels on the physical properties and drug‐release behavior was the main purpose of this study. The microstructure and morphology were identified by X‐ray diffraction (XRD) and scanning electronic microscopy (SEM). The results showed that the swelling ratios for these nanocomposite hydrogels decreased with increase in the content of MMT. The gel strength and Young's modulus of the gels also increased with increase in the content of MMT. XRD results indicated that the exfoliation of MMT was achieved in the swollen state. Finally, the drug‐release behavior for the gels was also assessed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3652–3660, 2003     

Biomorphic Silicon Nitride Ceramics with Fibrous Morphology Prepared by Sol Infiltration and Reduction–Nitridation

Biomorphic silicon nitride (Si₃N₄) ceramics with fibrous morphology were fabricated by combining sol–gel infiltration with carbothermal reduction nitridation from wood precursor. Y₂O₃-incorporated silica sol was used as the infiltrated solution to promote the formation of fibrous Si₃N₄ grain at 1600°C under high nitrogen pressure (0.6 MPa). The influence of sintering conditions (additive and temperature) on the phase composition and microstructure of sintering bodies was analyzed, and the reaction mechanism is discussed.     

混炼胶门尼粘度的预测与控制

使用ＭＧＫＪ型密炼机混炼微机监控系统，在ＢＢ２７０型密炼机上预测混炼胶的门尼粘度值，实现了胎面胶门尼粘度值的预测。预测值与实测值的差平均为０８（相对误差１％）。借助预测门尼粘度的数学模型，对排胶点进行控制，使混炼胶门尼粘度的波动范围为－３～＋３。     

改进教与学优化算法的LQR控制器优化设计

为了快速有效地确定线性二次最优控制(linear quadratic regulator,LQR)问题中的加权矩阵Q和R,针对主动悬架LQR控制器权系数设计问题,提出一种改进的教与学优化算法进行LQR优化设计。算法对基本教与学优化算法中的"教"与"学"阶段进行了进一步的改进,同时提出一种"自我学习"策略。通过仿真实验表明,和基本教与学算法、粒子群算法、遗传算法相比,本文算法在对主动悬架LQR控制器优化时,具有收敛速度快,求解精度高和稳定性强等优势。     

一种实时低成本压缩算法的VLSI实现

针对传统视频图像压缩算法时延长和成本高的问题,提出一种新的无损/近无损视频压缩算法。该算法由码率控制器和熵编码器组成,其中码率控制器通过对已有信息进行分析（上下文）来确定当前宏块的可用比特数,然后根据大量实验得出的高效Huffman码表,并结合位平面编码器对残差进行编码。实验结果表明,文中提出的视频图像压缩算法能够工作在300 MHz,吞吐量最差为1.3 pixel/cycle,同时仅用一块120＊720的SRAM来存储上一行像素值,因此很好地解决了时延和成本问题。     

新型丙烯-乙烯共聚物增韧聚丙烯的研究

丙烯-乙烯共聚物Vistamaxx（VM）是一种丙烯摩尔含量占70％以上的新型弹性体。用VM增韧聚丙烯（PP），考察了PP／VM共混物的力学性能、微观形态结构以及结晶性能，并与乙烯-辛烯共聚物（POE）与PP的共混体系进行了对比。结果表明，常温下VM增韧效果优于POE，PP／VM体系拉伸性能优于PP／POE体系；VM在PP中表现出比POE更好的分散性；VM具有与PP相同的晶型，VM的加入细化了PP的晶粒。