基于改进PSO-BP神经网络的冰蓄冷空调冷负荷动态预测模型

当前多数冰蓄冷空调冷负荷动态预测方法中,由于模型输入变量与输出结果相关性差、信息冗余度高等原因,导致多数预测模型在预测精度和收敛速度方面都未达到理想的预测效果,因此,提出一种改进的PSO-BP神经网络算法预测大型公共建筑的冷负荷。对于输入变量与输出结果采用灰色关联度分析,消除样本输入变量对数的耦合性,确定影响冰蓄冷空调系统冷负荷的关键性因素,将其作为输入变量,预测冰蓄冷空调系统动态冷负荷。结果表明：T时刻室外空气温度、T-1 h时刻室外空气温度、T时刻室外空气湿度、T时刻太阳辐射强度、T-1 h时刻太阳辐射强度、T-1 h时刻空调冷负荷是影响T时刻冰蓄冷空调系统冷负荷的关键因素,并以此作为预测模型的输入变量。相对于传统PSO-BP神经网络全输入变量预测算法,该模型预测结果精确度更高、收敛速度更快。     

冷冲高硬度材料模具的失效分析与选材

用WC-Co型硬质合金和高合金钢以不同的匹配方式制作冷冲模具,对高硬度材料2Cr13不锈钢进行冲裁,发现以高合金钢制作的模具寿命远高于硬质合金制作的模具。其失效方式及所占比例表明,硬质合金主要以掉渣和崩刃为主,而高合金钢以正常磨损为主。分析可知,由于剧烈磨损而引起WC-Co型硬质合金Co的缺失,破坏了WC骨架,最终导致模具局部韧性不足而掉渣;而高合金钢韧性相对较好,延长了使用寿命,但同时由于热加工工艺的不适当导致碳化物不均或硬度不稳定而未充分发挥材料的潜能,对提高高合金钢的使用寿命给出了改进方案。     

溶胶-凝胶法制备LED用Ca10(Si2O7)3Cl2∶Ce3+荧光粉

以硝酸钙、氯化钙、正硅酸乙酯为原料,采用溶胶凝胶法制备LED用Ca1(0Si2O7)3Cl2:Ce3+荧光粉。探讨了烧结温度,CaCl2的量对基质纯度的影响及Ce3+在此基质中的光谱性质。结果表明,溶胶-凝胶法可以得到纯相氯硅酸钙基质,在该基质中掺适量铈可以合成LED用的Ca1(0Si2O7)3Cl2:xCe3+荧光粉,该荧光粉在434 nm处有强发射峰,且最佳掺杂浓度x=0.02。     

超音速等离子喷涂Cr2O3陶瓷涂层的微观组织及其耐磨性能

采用超音速等离子喷涂技术在纯铜基体上制备Cr2O3-Ni-5%A(l质量分数)陶瓷涂层。利用XRD、SEM、激光共聚焦显微镜(LSCM)、显微硬度仪对涂层进行表征与分析,通过Image-pro Plus图形软件计算涂层的孔隙率,并通过摩擦磨损试验评价涂层的耐磨性能。结果表明:除了喷涂过程中出现了少量铬的氧化外,起始粉末和涂层的物相没有发生变化;陶瓷涂层表面呈双态组织,其表面粗糙度(Ra)为4.763μm;涂层断口形貌为典型的片层状组织,在涂层的抛光截面上可见紧密的富铬带均匀分布;Cr2O3涂层的孔隙率为1.2%,显微硬度为1 640HV0.3;涂层在室温下的摩擦因数约为0.4,其磨损机制为磨粒磨损。     

含氟连铸保护渣黏度检测与预测模型

采用旋转柱体法对不同类型的含氟连铸保护渣黏度进行检测,并基于Arrhenius方程通过非线性回归分析建立了新的黏度预测模型,分析了组分变化对黏度的影响。结合模型计算和实验检测,建立了CaF₂?Na₂O?Al₂O₃?CaO?SiO₂?MgO渣系的等黏度图。结果表明,与传统的含氟连铸保护渣黏度预测模型相比,该模型计算的偏差在10%以内,当渣中w（CaF₂）超过20%时,偏差逐渐增大,主要由于氟化物挥发造成炉渣成分变化,最终黏度实测值与炉渣初始成分不符,造成模型无法对黏度有效预测。此外,研究发现,CaF₂的增加能显著降低炉渣黏度,而Al₂O₃和Na₂O对黏度的影响受CaF₂含量的限制。当w(CaF₂)>17%,炉渣黏度随Al₂O₃含量增加而减小,当w(CaF₂)<17%,Al₂O₃的增加使炉渣黏度显著增大;当w(CaF₂)>11.5%,炉渣黏度随Na₂O含量增加显著下降,当w(CaF₂)<11.5%,Na₂O含量变化对黏度的影响并不明显。此外,该等黏度图表明低黏度区w(CaF₂)接近14%。通过调整等黏度图中各组分比例,可以改善保护渣的黏度和流动性,供钢铁工业应用。      

Enhanced thermoelectric effect of carbon fiber reinforced cement composites by metallic oxide/cement interface

Thermoelectric power of carbon fiber reinforced cement composites was firstly enhanced efficiently by metallic oxide microparticles in the cement matrix. The absolute Seebeck coefficient of these composites increased steadily with increasing metallic oxide content and achieved 4–5 folds of the original one. The largest absolute thermoelectric power of +100.28 µV/°C was obtained for the composite with 5.0 wt% Bi₂O₃ microparticles. The carrier scattering of the interface between oxide microparticles and cement matrix is probably attributed to the Seebeck effect enhancement.     

Multiwalled carbon nanotubes–BaTiO3/silica composites with high complex permittivity and improved electromagnetic interference shielding at elevated temperature

Composites with silica matrix and mixed filler of multiwalled carbon nanotubes (MWCNTs) and BaTiO₃ powder were fabricated. Excellent uniform dispersion of MWCNTs can be obtained using a two-step mixing method. Both of the real and imaginary parts of complex permittivity increased with increasing MWCNT content and measured temperature. The electromagnetic interference (EMI) shielding results showed that the absorption mechanism is the main contribution to the total EMI shielding effectiveness (SE). Compared with the EMI SE resulting from reflection, the absorption showed more dependence on the MWCNT content, measured temperature and frequency. The total EMI SE is greater than 20 dB at 25 °C and 50 dB at 600 °C in the whole frequency range of 12.4–18 GHz with a 1.5 mm composite thickness, which suggests that the MWCNT–BaTiO₃/silica composites could be good candidates for the EMI shielding materials in the measured frequency and temperature region.     

改性钛酸钾晶须增强聚氨酯跑道面层材料力学及耐久性能研究

采用偶联剂对钛酸钾晶须进行表面改性,再与甲苯二异氰酸酯、聚醚多元醇等原料制备了改性钛酸钾晶须增强聚氨酯跑道面层复合材料。考察了偶联剂种类、改性钛酸钾晶须含量对改性钛酸钾晶须增强聚氨酯复合材料力学性能和耐久性能的影响。结果表明,该材料拉伸强度达到2.9 MPa、扯断伸长率达到340%,经加速老化试验后满足田径场地规定的技术要求。     

Benefit-based cost allocation for residentially distributed photovoltaic systems in China: A cooperative game theory approach

Distributed photovoltaic (PV) systems have constantly been the key to achieve a low-carbon economy in China. However, the development of Chinese distributed PV systems has failed to meet expectations because of their irrational profit and cost allocations. In this study, the methodology for calculating the levelized cost of energy (LCOE) for PV is thoroughly discussed to address this issue. A mixed-integer linear programming model is built to determine the optimal system operation strategy with a benefit analysis. An externality-corrected mathematical model based on Shapley value is established to allocate the cost of distributed PV systems in 15 Chinese cities between the government, utility grid and residents. Results show that (i) an inverse relationship exists between the LCOEs and solar radiation levels; (ii) the government and residents gain extra benefits from the utility grid through net metering policies, and the utility grid should be the highly subsidized participant; (iii) the percentage of cost assigned to the utility grid and government should increase with the expansion of battery bank to weaken the impact of demand response on increasing theoretical subsidies; and (iv) apart from the LCOE, the local residential electricity prices remarkably impact the subsidy calculation results.     

烧结矿低温还原粉化影响因素研究进展

烧结矿入炉后,会在高炉上部发生低温还原粉化现象,严重时会影响高炉料柱透气性,破坏高炉顺行.为了改善烧结矿的这一性能,揭示烧结矿粉化机制,归纳了化学成分、添加物、微观结构、外部还原气氛和烧结工艺等对烧结矿低温还原粉化的影响,分析了改善烧结矿低温还原粉化性能的方法,为粉化机制研究、烧结配矿提供参考.