空调水系统变流量节能控制及实验研究

本文研究了阀位控制，设计了可实现变流量控制的实验平台。通过对阀位控制实验数据及其他控制理论结果的对比分析，认为该控制法具有节能性强的特点，易于推广。     

Strain-softening behavior of an Fe-6.5 wt%Si alloy during warm deformation and its applications

An Fe-6.5 wt%Si alloy with columnar grains was compressed at a temperature below its recrystallization temperature. The Vickers hardness and structure of the alloy before and after deformation were investigated. The results showed that with an increase in the degree of deformation, Vickers hardness of the alloy initially increased rapidly and then decreased slowly, indicating that the alloy had a strain-softening behavior after a large deformation. Meanwhile, the work-hardening exponent of the alloy decreased significantly. Transmission electron microscopy confirmed that the decrease of the order degree was responsible for the strain-softening behavior of the deformed alloy. Applying its softening behavior, the Fe-6.5 wt%Si alloy with columnar grains was rolled at 400 °C and then at room temperature. An Fe-6.5 wt%Si thin strip with thickness of 0.20 mm was fabricated. The surface of the strip was bright and had no obvious edge cracks.     

The dimensional nature of same–different discrimination behavior in pigeons.

We studied the dimensional nature of same–different discrimination behavior in pigeons. Birds first learned to discriminate between simultaneously presented displays of 16 identical items (Same arrays) and 16 nonidentical items (Different arrays), conditional on the color of the background. After discrimination mastery, we tested the birds with Mixture arrays comprising both identical and nonidentical items. Accuracy increased and reaction time decreased as the disparity in entropy (a measure of variability) between the arrays increased. As well, within each entropy disparity level, lower entropy values were more discriminable than higher entropy values. These results accord with a logarithmic relation between entropy and discriminative behavior and, thus, with the idea that the discrimination of Same from Different arrays follows Weber's Law. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Performance of degree distribution based HARQ scheme for LDPC-coded OFDM system

This article studies the degree distribution property of low density parity check (LDPC) codes by Gaussian approximation (GA) and presents an efficient hybrid automatic repeat quest (HARQ) scheme for LDPC-coded orthogonal frequency division multiplexing (OFDM) system. In the scheme, the important bits with large degrees have high retransmission priorities and are mapped to the sub-carriers with better channel quality indicator (CQI) levels in the OFDM system. The new scheme provides more protection to the bits with large degrees and thus contributes more to the decoding process by offering more transmission power. In this way the system performance would be improved. The statistics and simulation results also prove the new scheme.     

地质条件对煤成气赋存的影响

煤成气的形成和保存,运移,富集均受地质条件的控制,本文试图从理论的角度阐述沉积环境、变质程度、区域构造和其它地质条件对煤成气赋存的影响,为煤成气的开发利用和矿山灾害的防冶提供参考。     

Starch derivatives with high degree of functionalization. III. Influence of reaction conditions and starting materials on molecular structure of carboxymethyl starch

Carboxymethyl starch (CMS) was prepared in a completely heterogeneous procedure in a methanol/water slurry activated with aqueous sodium hydroxide (45%, w/v) using monochloroacetic acid as the etherifying agent. The influence of the reaction conditions and the type of starting starch (amylose content and preactivation) was evaluated in regard to the formation of the main repeating units (i.e., unfunctionalized and mono‐, di‐, tri‐, and tetra‐O‐carboxymethylated) and the pattern of functionalization within the anhydroglucose units (AGU). The reproducible synthesis gave products with a maximal degree of substitution of CM groups (DS_CM) of 0.66, which was reached in a one‐step synthesis. Repeated carboxymethylation led to products with a DS_CM of 0.88. As revealed by means of HPLC analysis after complete acidic depolymerization, in any sample the mono‐O‐carboxymethylated glucose (mono‐O‐CMglc) was preferably present while the di‐O‐CMglc was formed to a very low extent only. The tri‐O‐CMglc was found in some samples while tetra‐O‐CMglc was not detected. The mole fractions determined did not follow the simple Spurlin statistic as shown for CM cellulose synthesized under comparable conditions. Within the carboxymethylated AGUs a preferred functionalization at position 2 was analyzed by means of ¹H‐NMR spectroscopy after hydrolytic chain degradation. Consequently, the CMS samples synthesized contained mainly 2‐mono‐O‐CM‐AGU. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2036–2044, 2001     

The influence of delayed light curing on the degree of conversion and polymerization contraction stress in dual-cured resin luting agents

The aim of the study was to assess the effect of delayed photo-initiation on the polymerization contraction stress (PCS) and degree of conversion (DC) of a dual-cure resin-luting agent. Thirty-five disk (6 mm × 1 mm) samples (n = 10 each group) of dual cure resin luting agent for PCS assessment were fabricated and polymerized using two illuminated quartz rods. Based on the delay in photo-initiation, 30 disks were divided among six groups [group A-0 min (min) delay, group B-2 min, group C-4 min, group D-6 min, group E-8 min and group F-10 min]. A non-photoinitiated group (group G – chemical cure – n = 5) was included as control. The PCS for all specimens was assessed using a Tensometer. For DC evaluation thirty-five specimens were divided into seven groups with delays in photo-initiation (group H-0 min, group I-2 min, group J-4 min, group K-6 min, group L-8 min and group M-10 min, group N-chemical cure). DC was assessed using attenuated total reflectance spectroscopic technique. Statistical comparison among groups was performed using analysis of variance (α = 0.05). The maximum and minimum PCS and DC values with delayed photo-initiation was observed in group-C (3.34 MPa) & group-F (2.44 MPa); and group-M (0.78 MPa) and group-H (0.55 MPa) respectively. Chemically cured samples showed the least PCS (group-G, 1.94) and DC (group-N, 0.53) values in their respective categories. PCS significantly decreased with delayed photo-initiation. A significant increase in DC was noticed when photo-initiation was delayed in the dual cure resin luting agent.     

Thermal Stability and Crystallization Behavior of TER Blends of Isotactic Polypropylene (iPP)/Ethylene-Propylene Diene Rubber (EPDM)/Nitrile Rubber (NBR)

The blends of isotatic polypropylene (iPP), ethylene-propylene diene rubber (EPDM), and nitrite rubber (NBR) were prepared using dimethylol phenolic resin as a crosslinking system. The dynamically crosslinked blends of iPP/EPDM/NBR showed superior thermal stability to that of virgin isotactic polypropylene (iPP). Dynamic crosslinking rendered the vulcanizate thermally more stable as compared to uncrosslinked blends, which can be attributed due to the variations in degree of crosslinking and degree of crystallinity.

Crystallization of iPP in the blends of iPP/EPDM/NBR was also studied through Temperature Modulated Differential Scanning Calorimetry (TMDSC). Other detailed analysis of endotherm peaks obtained after first and second melts in terms of heat of enthalpy, degree of undercooling, and degree of crystallinity were also evaluated. Various kinetic parameters were also determined. Degree of crosslinking increases the interfacial adhesion between the iPP and EPDM/NBR phases. Dimethylol phenolic resin used as a compatibilizer also enhanced the thermal stability of the iPP/EPDM/NBR blends.     

基于二分图的宝鸡公交线路-站点网络建模及分析

复杂网络理论已成为研究交通系统的有效工具。以陕西省宝鸡市的43个公交线路及344个公交站点数据为基础,基于二分图理论,构建了站点-线路公交网络模型,并对该网络的统计性质进行了分析。研究结果表明,网络中的线路节点度分布呈现泊松分布,大部分线路度值集中在平均值附近;而站点节点度分布呈现幂律分布,其中的少数节点高度连接,为网络中的关键枢纽节点。这些高度连接的线路和站点可被筛选为宝鸡市交通网络研究中的重点规划对象。     

基于关系契约的水利工程代建制激励机制研究

分析了关系契约的特征,构建了水利工程中政府与代建单位间的关系激励契约,讨论了政府与代建单位间基于关系契约的奖金机制及其影响因素,并探讨了关系激励契约的管理。研究表明关系契约中最优奖金决定于政府对双方关系未来价值的评价和代建市场行情等因素;政府可根据代建市场行情来管理与代建单位间的关系激励契约,代建市场行情好时政府更应该提高对双方合作关系的评价、注重建立良好的声誉,以赢得更好的代建服务。