20位单片音频数模转换器PCM63P

PCM63P是美国BB公司生产的具有超低失真性能(满量程输出最大为-93dB)的精密20位数模转换器，可应用于低失真频率合成、高级消费品和特殊的数字音频应用等方面。文中介绍了PCM63P的工作原理及应用电路。     

基于TC8830AF的智能语音卡结构与设计

本文描述一种基于８０３１单片机和ＴＣ８８３０ＡＦ语音处理器的ＰＣ机智能语音卡，通过软硬件设计解决了ＰＣ－８０３１－ＴＣ８８３０ＡＦ结构中的通讯问题。该语音卡在进行语音的合成、编辑和播放时，仅占用极少的ＰＣ机ＣＰＵ处理时间，能满足计算机系统进行实时语音合成的要求。     

心电图信号的频域分析

提出了一种简便有效的、由心电图（ECG）曲线提取QRS-T复合波的新方法，从而获得P波（当房颤未发生时）或f波（当房颤时）；利用功率谱、自相关、互相关等信号处理技术，对它进行了处理和分析，特别是，比较了未房颤时和发生房颤时的相关信息的显著差别。     

Resveratrol Butyrate Esters Inhibit BPA-Induced Liver Damage in Male Offspring Rats by Modulating Antioxidant Capacity and Gut Microbiota

Resveratrol can affect the physiology or biochemistry of offspring in the maternal–fetal animal model. However, it exhibits low bioavailability in humans and animals. Fifteen-week SD pregnant female rats were orally administered bisphenol A (BPA) and/or resveratrol butyrate ester (RBE), and the male offspring rats (n = 4–8 per group) were evaluated. The results show that RBE treatment (BPA + R30) compared with the BPA group can reduce the damage caused by BPA (p < 0.05). RBE enhanced the expression of selected genes and induced extramedullary hematopoiesis and mononuclear cell infiltration. RBE increased the abundance of S24-7 and Adlercreutzia in the intestines of the male offspring rats, as well as the concentrations of short-chain fatty acids (SCFAs) in the feces. RBE also increased the antioxidant capacity of the liver by inducing Nrf2, promoting the expression of HO-1, SOD, and CAT. It also increased the concentration of intestinal SCFAs, enhancing the barrier formed by intestinal cells, thereby preventing BPA-induced metabolic disruption in the male offspring rats, and reduced liver inflammation. This study identified a potential mechanism underlying the protective effects of RBE against the liver damage caused by BPA exposure during the peri-pregnancy period, and the influence of the gut microbiota on the gut–liver axis in the offspring.     

Preparation and characterization of TiO2 and polymer nanocomposite films with high refractive index

Novel nanocomposite films of TiO₂ nanoparticles and hydrophobic polymers having polar groups, poly (bisphenol‐A and epichlorohydrin) or copolymer of styrene and maleic anhydride, with high refractive indices, high transparency, no color, solvent‐resistance, good thermal stability, and mechanical properties were prepared by incorporating surface‐modified TiO₂ nanoparticles into polymer matrices. In the process of preparing colloidal solution of TiO₂ nanoparticles, severe aggregation of particles can be reduced by surface modification using carboxylic acids and long‐chain alkyl amines. These TiO₂ nanoparticles dispersed in solvents were found not to aggregate after mixing with polymer solutions. Transparent colorless free‐standing films were obtained by drying a mixture of TiO₂ nanoparticles colloidal solution and polymer solutions in vacuum. Transmission electronic microscopic studies of the films suggest that the TiO₂ nanoparticles of 3–6 nm in diameter were dispersed in polymer matrices while maintaining their original size. Thermogravimetric analysis results indicate that the nanocomposite film has good thermal stability and the weight fraction of observed TiO₂ nanoparticles in the film is in good accordance with that of theoretical calculations. The refractive index of nanocomposite films of TiO₂ and poly(bisphenol‐A and epichlorohydrin) was in the range of 1.58–1.81 at 589 nm, which linearly increased with the content of TiO₂ nanoparticles from 0 to 80 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Viscoelastic, Thermal and Mechanical Properties of Dicyclopentadiene Bisphenol Diyanate Ester / Epoxy Co-polymers

Summary Dicyanate ester containing dicyclopentadiene cycles and epoxy co-polymers were prepared by copolymerization between epoxy and dicyclopentadiene bisphenol cyanate esters (DCPDCE). Viscoelastic properties of the co-polymers were characterized by the technique of dynamic mechanical analysis (DMA), which indicated that the introduction of E51 in the co-polymers would effectively improve the toughness of DCPDCE, while the thermal dimensional stability would be weakened. Results from thermogravimetric analysis (TGA) are in good accordance with the T_g values from DMA curves. Mechanical testing of the cured co-polymers shows that E51 can improve the mechanical properties of the co-polymers while its usage is controlled among 5% to 15%.     

Synthesis and characterization of aromatic copolyesters containing siloxane linkages in the polymer backbone

A new series of aromatic copolyesters containing siloxane linkages were prepared by the melt polymerization of bisphenol A (BPA) with eugenol end‐capped siloxane (EuSi), diphenyl terephthalate (DPT), and diphenyl isophthalate (DPI) in varying ratio in the temperature range 220–290°C under reduced pressure in the presence of dibutyl tin dilaurate (DBTL) catalyst. The siloxane copolyesters prepared were characterized by FTIR, ¹H‐NMR spectroscopy, solution viscosity, thermogravimetric analysis, differential scanning calorimetry, and X‐ray diffraction. The effect of incorporation of eugenol end‐capped siloxane was studied on the properties of BPA/DPI/DPT copolyesters. The glass‐transition temperature of copolyester was decreased from 184 to 70°C by incorporation of 20% of eugenol end‐capped siloxane. All copolyesters were found to be soluble in commonly used aprotic polar solvents and had film‐forming properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3222–3228, 2006     

水杨酸双酚A酯的合成与表征

研究了以水杨酸乙酯、双酚A为原料，二丁基氧化锡为催化剂合成水杨酸双酚A醇，考查了催化剂及用量、反应温度、反应时间及物料配比等因素的影响。结果表明：催化剂用量为0．6g，反应温度为120-130℃，反应时间为4h，物料配比为2．10：1，在此条件下，产率在94%以上。产物结构经元素分析、红外光谱、核磁氢谱进行了表征。     

双酚A苯并恶嗪一环氧树脂基印制电路基板的研究

采用双酚A苯并恶嗪与环氧树脂共混改性制得胶液,经浸渍玻璃布、烘焙、压制得到了一系列玻璃布覆铜板基板其中含溴型基板的玻璃化转变温度为145.2℃,加强耐热性在300s以上,常温下表面电阻率和体积电阻率分别为1.51×1014Ω、5 75×1014Ω@m,无溴型基板玻璃化转变温度为160.3 ℃,加强耐热性在300 s以上.常温下表面电阻率和体积电阻率分别为1.91×1013Ω、5.01×1013Ω@m,覆铜板的耐浸焊性能优异,达到60s以上     

苯酚产需现状及市场分析

2000年世界苯酚总生产能力约为740万t/a,总消费量为636万t/a,主要用于生产双酚A和酚醛树脂。预计世界苯酚需求将以每年4％-5％的速度增长。美国、西欧和日本是世界上3个最主要的苯酚生产国家和地区,北美地区的总生产能力为300万t/a,占世界总产能的40.6％,而德国酚化学公司是世界最大的苯酚生产厂家,其产能为145万t/a,占世界总产能的19.6％。2000年,我国有30家苯酚生产企业,总生产能力为28.9万t/a,总产量为24.94万t/a,主要用于酚醛树脂和水杨酸的生产。在1996-2000年间,中国大陆苯酚的净进口量分别为9.79万t、6.22万t、3.72万t、7.38万t和9.69万t,从2000年9月开始,从中国台湾的苯酚进口量增长很快。为增强市场竞争力,中国大陆苯酚生产企业应提高单套装置的生产能力,采用一体化生产模式。