Adaptive block size for dense QR factorization in hybrid CPU–GPU systems via statistical modeling

QR factorization is a computational kernel of scientific computing. How can the latest computer be used to accelerate this task? We investigate this topic by proposing a dense QR factorization algorithm with adaptive block sizes on a hybrid system that contains a central processing unit (CPU) and a graphic processing unit (GPU). To maximize the use of CPU and GPU, we develop an adaptive scheme that chooses block size at each iteration. The decision is based on statistical surrogate models of performance and an online monitor, which avoids unexpected occasional performance drops. We modify the highly optimized CPU–GPU based QR factorization in MAGMA to implement the proposed schemes. Numerical results suggest that our approaches are efficient and can lead to near-optimal block sizes. The proposed algorithm can be extended to other one-sided factorizations, such as LU and Cholesky factorizations.     

同向双螺杆熔体输送段捏合盘错列角对不相容体系共混物相态结构的影响

对啮合同向双螺杆挤出机,将捏合盘置于熔体输送段,通过改变捏合盘错列角,研究双螺杆挤出过程熔体输送段捏合盘错列角对不相容体系共混物相态结构的影响。应用差示扫描量热仪对两相共混体系HDPE/PS的热性能进行了实验研究,结果表明:螺杆构型对共混物的相容性影响不大。同时采用扫描电子显微镜考察了HDPE/PS共混物在熔体输送段末端位置和机头末端所取试样的相态结构,研究表明:置于熔体输送段捏合盘元件错列角对共混物分散相的相畴尺寸有一定影响。     

Multiple morphologies of self-assembled star aggregates of amphiphilic PEO-b-PNPMA diblock copolymers in solution, synthesis and micellization

Novel amphiphilic block copolymers, poly(ethylene oxide)-b-poly(p-nitrophenyl methacrylate) (PEO-b-PNPMA) with controlled molecular weights and narrow molecular weight distribution were successively synthesized by ATRP of NPMA using PEO-Br as initiator. Self-assembling of the diblock copolymer PEO₁₁₃-b-PNPMA₂₈ in the different solvent mixtures yielded various morphologies of star micelle-like aggregates, such as spheres, vesicles, cauliflower-like aggregates and rod-like aggregates, which are determined by the nature of the common solvents and the selective solvents. Thus the critical selective solvent contents and the solvent contents in PNPMA-rich phase were measured, and they have the following order: ethanol > methanol > water, and THF > CH₃NO₂ > DMSO. The probable self-assembling mechanism is discussed. This method is convenient for preparation of multiple morphological star micelle-like aggregates in solution, especially from the amphiphilic block copolymers with relatively longer block shell.     

西石门铁矿南区崩落卸压采矿法试验及应用效果

在缓倾斜中厚矿体底板岩性不稳固的条件下，采用有底柱崩落法，由于电耙道大多处于空区边部应力集中的部位，致使堑沟及底部结构巷道破坏严重而使回收率极低，采用无底柱崩落卸压则可有效解决上述难题。本文简要介绍该方法的原理、方案结构、安全措施及应用效果，供借鉴。     

BC-8嵌段聚丙烯并非嵌段物

介绍了日本三菱油化公司（现为三菱化学公司）BC-8嵌段聚丙烯的开发经过及实际结构。近年结构分析结果发现BC-8嵌段聚丙烯并非嵌段物，而是由均聚聚丙烯、EPR（乙丙橡胶）以及聚乙烯（链上有少量丙烯单元但并非嵌段物）三者组成的高分子合金。     

Polyamide‐6‐b‐polybutadiene block copolymers: Synthesis and properties

Polyamide‐6 (PA6)/polybutadiene (PB) block copolymers were synthesized with macroactivators (MAs) based on hydroxyl‐terminated polybutadiene functionalized with diisocyanates and having three N‐acyllactam chain‐growing centers per molecule. Two different diisocyanates, hexamethylene diisocyanate and isophorone diisocyanate, were applied as precursors for the MAs. The sodium salt of ε‐caprolactam was chosen as an initiator. The influence of the MA type and concentration on the anionic ring‐opening polymerization of ε‐caprolactam at 180°C was studied. A large percentage of the gel fraction in the copolymers was estimated, indicating crosslinked macromolecules. The structure and phase behavior of the copolymers were investigated with differential scanning calorimetry, wide‐angle X‐ray scattering, thermogravimetric analysis, and dynamic mechanical thermal analysis. In the copolymers, only the PA6 chains crystallized, and the crystallinity depended on the PB content. Different glass‐transition temperatures for the PB blocks and PA6 blocks were observed, indicating microphase separation in the copolymers. The mechanical properties of the copolymers were studied by notched impact testing and hardness measurements. The impact strength increased linearly with the soft component concentration up to 10 wt % and reached values six times higher than those of the PA6 homopolymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 711–717, 2003     

Adsorption of block copolymers at latex surface and their utilization in emulsion polymerization

Amphiphilic block copolymers have been investigated for their utilization in emulsion polymerization of butyl methacrylate. Special attention has been paid to the adsorption mechanism of the block copolymers from systematic measurements of equilibrium adsorption isotherms. A series of well-defined water-soluble amphiphilic block copolymers, composed of poly(butyl methacrylate) and poly(sodium methacrylate) blocks, were synthesized by anionic polymerization of butyl methacrylate and tert-butyl methacrylate followed by the thermal deprotection of the tert-butyl ester groups and final hydrolysis. The number density of emulsion polymer particles N_P varied as [copolymer]^α, α lying between 0.44 and 0.73 according to the hydrophilic content of the copolymers. In contrast with SDS taken as a reference emulsifier, the adsorption of the copolymers was very strong and this provided quite an efficient stabilization of the polymer particles during emulsion polymerization, even at low concentrations (<10⁻⁴ mol L⁻¹) and low coverages (<10% of the interfacial area).     

本体聚合中的预热和过滤

讨论了本体聚合中预热和过滤的顺序，对冷过滤、热过滤的优缺点进行了探讨，提出了建议     

基于前向预测策略的块正交匹配追踪算法研究

在块正交匹配追踪算法中,候选集匹配原子块的选择策略对信号重建具有重要作用,但是该算法在迭代选择原子块的过程中,每次选择当次最优迭代的原子块,并不能保证最终迭代性能是最优的。为此,提出一个基于前向预测的最优匹配原子块选择策略的块正交匹配追踪算法,通过预测原子块在未来迭代过程中的性能选择最优匹配的原子块。实验结果表明,与块正交匹配追踪算法相比,该算法的重建误差随前向预测参数的增大而减小。     

聚(苯乙烯-co-丙烯腈)-b-聚苯乙烯两嵌段共聚物的合成

以CuBr／N，N，N’，N’，N'-五甲基二亚乙基三胺(简称NNN)为催化体系，研究了原子转移自由基聚合法(ATRP)PS-b-P(S-co-AN)两嵌段聚合物的合成。研究了聚合顺序对相对分子质量及其分布和嵌段效率的影响，并且用聚合物末端C—Br键的断裂能对实验结果进行了初步解释。