硬质泡沫塑料耐热性测试方法研究

在分析泡沫塑料受热行为的基础上,对硬质聚甲基丙烯酰亚胺(PMI)、聚氨酯(PUR)、酚醛(PF)及交联硬质聚氯乙烯(PVC)泡沫塑料进行了差示扫描量热(DSC)、热失重(TG)、静态热机械分析(TMA)、马丁耐热温度、热变形温度(HDT)、尺寸稳定性、高温压缩蠕变、均匀受压时高温体积收缩率等热性能测试。研究表明,DSC,TG,TMA等热分析仅反映了硬质泡沫塑料中聚合物部分的耐热性,不能反映硬质泡沫塑料的整体耐热性,也不能反映密度对耐热性的影响;依照GB/T 1699–2003测试马丁耐热温度的方法和依照GB/T 1634–2004测试HDT的方法不适用于硬质泡沫塑料耐热性的测试;依照GB/T 8811–2008测试的尺寸稳定性和依照DIN 53424–1978测试的HDT可以初步作为硬质泡沫塑料耐热性的表征方法;依照GB/T 15048–1994测试高温压缩蠕变的方法以及依据固化工艺条件测试均匀受压时的体积收缩率的方法能够更加准确地表征硬质泡沫塑料的实际耐热性。     

Photodependent release from poly(vinyl alcohol)/epoxypropoxy coumarin hydrogels

To obtain a photoresponsive hydrogel, poly(vinyl alcohol) (PVA) having coumarin residue as a pending group was crosslinked by photodimerizing the coumarin pendants. PVA having coumarin pendants was prepared by reacting the polymer with epoxypropoxy coumarin (EPC) in a strong alkali condition with EPC/PVA molar ratio of 200/1. According to the 1H NMR spectrum of PVA‐EPC conjugate, the molar ratio of EPC residue to PVA was about 4.3/1, indicating that EPC was attached to PVA every 444 repeating units of vinyl alcohol. An aqueous solution of PVA‐EPC (5%, w/v) became a semi‐solid hydrogel by the irradiation of a light (λ = 365 nm; 400 W) for 1 hr. The dimerization degree of EPC residues of the hydrogel decreased and increased in a periodical manner under the cyclic irradiation between two UV lights (λ = 365 nm and λ = 254 nm). The release of 5(6)‐carboxyfluorescein (CF) from PVA‐EPC hydrogel was significantly enhanced by the 5 min‐irradiation of λ = 254 nm (6 W), possibly due to the photodedimerization of EPC residues of the hydrogel. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

熔断电阻器瞬态特性仿真分析

为了简单有效地改进熔断电阻器的性能,采用有限元分析软件ANSYS建立了熔断电阻器的模型,对其在过电流状态下的瞬态温度场变化过程进行了数值模拟,并进行了实验验证。通过对熔断电阻器的热电耦合模拟,得到了不同电流下的熔断时间和温度分布云图。熔断时间的实验结果和模拟结果误差率为5%左右,这为熔断电阻器的设计和生产提供了方法和理论依据。     

一种超低功耗、容错的静态随机存储器设计

为了减轻辐射环境中静态随机存储器（SRAM）受单粒子翻转（SEU）的影响以及解决低功耗和稳定性的问题,采用TSMC 90nm工艺,设计了一款可应用于辐射环境中的超低功耗容错静态随机存储器。该SRAM基于双互锁存储单元（DICE）结构,以同步逻辑实现并具有1KB（1K×8b）的容量,每根位线上有128个标准存储单元,同时具有抗SEU特性,提高并保持了SRAM在亚阈值状态下的低功耗以及工作的稳定性。介绍了这种SRAM存储单元的电路设计及其功能仿真,当电源电压VDD为0.3V时,该SRAM工作频率最大可达到2.7MHz,此时功耗仅为0.35μW;而当VDD为1V时,最大工作频率为58.2MHz,功耗为83.22μW。     

16‐QAM‐Based Highly Spectral‐Efficient E‐band Communication System with Bit Rate up to 10 Gbps

This paper presents a novel 16‐quadrature‐amplitude‐modulation (QAM) E‐band communication system. The system can deliver 10 Gbps through eight channels with a bandwidth of 5 GHz (71‐76 GHz/81‐86 GHz). Each channel occupies 390 MHz and delivers 1.25 Gbps using a 16‐QAM. Thus, this system can achieve a bandwidth efficiency of 3.2 bit/s/Hz. To implement the system, a driver amplifier and an RF up‐/down‐conversion mixer are implemented using a 0.1 µm gallium arsenide pseudomorphic high‐electron‐mobility transistor (GaAs pHEMT) process. A single‐IF architecture is chosen for the RF receiver. In the digital modem, 24 square root raised cosine filters and four (255, 239) Reed‐Solomon forward error correction codecs are used in parallel. The modem can compensate for a carrier‐frequency offset of up to 50 ppm and a symbol rate offset of up to 1 ppm. Experiment results show that the system can achieve a bit error rate of 10^?5 at a signal‐to‐noise ratio of about 21.5 dB.     

Relationship between HOMO energy level and open circuit voltage of polymer solar cells

A series of π-conjugated polymers (PDHF-BT and PDHF-TBT) with 4-(3,4-ethylenedioxythienyl)-2,1,3-benzothiadiazole (BT), 4,7-bis(3,4-ethylenedioxythienyl)-2,1,3-benzothiadiazole (TBT), and 9,9′-dihexylfluorene were synthesized by the Suzuki coupling reaction. The HOMO energy level of PDHF-BT was −5.47 eV, which was lower than that of PDHF-TBT (−5.22 eV), while the LUMO energy level of PDHF-BT (−3.45 eV) was very similar to that of PDHF-TBT (−3.42 eV). These energy levels of PDHF-BT and PDHF-TBT were also supported by a DFT calculation. The power conversion efficiency (PCE) of the polymer solar cell (PSC) with a structure of ITO/PEDOT:PSS/PDHF-BT:PCBM (1:1)/Al was determined as 0.34% and it was larger than that of the device based on PDHF-TBT (0.22%). Correspondingly, the V_oc of the PSC based on PDHF-BT (0.71 V) was much larger than that of the device based on PDHF-TBT (0.40 V). The results support that the V_oc of polymer based PSCs is strongly related to the HOMO energy level of the active polymers.     

Octupolar Films with Large Second Harmonic Generation and Electro‐Optical Effects

Thin films that benefit from efficient octupolar molecular packing are prepared for second harmonic generation (SHG) and electro‐optic (EO) applications. The films are composed of 1,3,5‐tricyano‐2, 4,6‐tris(p‐diethylaminostyryl)benzene (TTB) in a ploymethylmetacrylate (PMMA) matrix on aluminum/BK7 glass (Al/BK7) and polyimide/indium tin oxide (PI/ITO) substrates. Octupolar films prepared on both substrates display polycrystalline and cylindrical domains. The molecular orientation, SHG efficiencies, and EO coefficients of the crystalline domains are measured. In the cylinders, the molecular crystal planes are oriented perpendicularly to the major cylinder axis, whereas in the polycrystals, the planes are randomly oriented. While both structures exhibit high and stable SHG and EO efficiencies, the cylinders, in particular, exhibited a very large SHG, a large EO coefficient, and high thermal stability; these characteristics will be useful in second order nonlinear optical applications.     

走滑断层错动下山岭隧道关键断面变形及损伤演化

山岭隧道受选线制约大多要穿越活动断裂带,而活动断裂带的运动会对与之相交的隧道结构的安全产生影响。为此,对穿越走滑断层的隧道在地震中所遭受的破坏展开调研具有现实意义。以滇中引水工程香炉山隧洞为背景,建立隧道-断层三维有限元分析模型,研究走滑断层错动下隧道关键断面的变形特征。基于所建立的有限元模型,采用相对位移法对断层错动量、断层破碎带宽度和穿越角度的影响进行参数分析。研究结果表明：穿越角度为45°时,截面的变形模式为水平椭圆,而穿越角度为135°时,截面的变形模式为直立椭圆;随着断层破碎带宽度的增加,位于断层中间位置处的隧道截面的变形程度减小;走滑断层错动下,隧道截面变形最为严重的区域出现在拱顶和拱底,在进行山岭隧道的设计时需要重点关注。