基于小波阈值降噪 EEMD分解的潮汐河网地区纳潮引水调度周期研究

鉴于在分析纳潮引水方案时,基于潮位周期变化规律的典型潮位过程选取难度较大,将小波阈值降噪与EEMD信号处理方法引入潮位特征分析中,结合径流量变化影响分析、端点效应消除及周期合理性检验等,提出基于小波阈值降噪 EEMD分解的潮汐河网地区纳潮引水调度周期识别方法。对福州市南台岛纳潮引水调度周期的分析结果表明,南台岛纳潮引水调度周期为14 d,利用小波阈值降噪 EEMD分解法提取潮汐河网地区纳潮引水调度周期合理可行。     

复凝聚法制备鱼油微胶囊工艺研究

以鱼油作为芯材,壳聚糖(Ch)和大豆分离蛋白(SPI)作为壁材,采用复凝聚法制备鱼油微胶囊。采用单因素实验考察均质速度、pH、芯壁比、壁材总质量分数、SPI溶液与Ch溶液体积比及固化时间对鱼油微胶囊包埋效果的影响,在此基础上,采用正交实验对工艺条件进行优化。结果表明:最佳工艺条件为均质速度8 000 r/min、pH 7. 0、壁材总质量分数2. 5%、SPI溶液与Ch溶液体积比7∶3、芯壁比1∶3、固化时间4 h;在最佳工艺条件下,鱼油微胶囊包埋率为90. 21%,包埋效率为99. 04%,表面油含量为4. 87%。通过不同温度下过氧化值变化和气味分析,表明微胶囊化能显著延缓鱼油氧化,同时有效地弱化鱼油的气味。     

基于模糊算法的岩心图像层理特征提取

在岩心图像的分析中,提取图像的层理特征,对于识别岩石的层理类型,完成对获取的岩心图像进行自动识别十分重要。本文介绍了Pal.King算法,并且针对岩心图像的多数像素点处在低灰度级的特点,使用最大类间方差法(Otsu)得到Tr变换中的最佳隶属度的阈值,根据阈值建立自己的隶属函数G和G~(-1);同时对Tr变换增强后的空间域图像进行平滑处理,减少噪声对层理边缘提取的影响。实验结果表明,该算法提取岩心图像层理特征效果较好。     

相似系数阈值滤波的数据驱动控制束偏移

高斯束偏移不仅具有接近波动方程偏移的精度,而且具有Kirchhoff偏移灵活、高效的特点。然而当实际地震采集数据中含有较强噪声时,易产生偏移假象而影响成像质量。为此,在传统高斯束偏移的基础上,根据有效信号和干扰信号在τ-p域中的相干性差异,发展了一种基于相似系数阈值滤波的数据驱动控制束偏移方法。采用数据驱动策略,在高斯束偏移成像过程中,先计算τ-p道集的相似系数,再通过设定相似系数阈值控制干扰信号,从而降低偏移剖面中的随机噪声;控制束偏移可以直接提取角度域共成像点道集,无需复杂的角度映射变换且具有更高信噪比。模型测试及实际资料处理结果表明：对于低信噪比数据,控制束偏移剖面的信噪比明显高于常规高斯束偏移,但会损失相对振幅的可靠性;尽管控制束偏移在τ-p道集的滤波过程增加了一定的计算量,但总体与常规高斯束偏移方法的计算效率相当;相似系数阈值参数选取十分关键,阈值较小时偏移噪声较强,但过大阈值也可能压制部分有效信息或产生偏移假象,选取合适的阈值参数才能得到较理想的偏移剖面。     

基于Shearlet变换的自适应地震资料随机噪声压制

传统的阈值选取方法是对所有变换域系数使用统一阈值,但对Shearlet变换而言,各尺度、各方向的有效信号和噪声均存在差异,因此全局硬阈值存在一定局限性;局部阈值可根据一定范围内的系数分布情况确定。针对地震数据去噪过程中传统阈值选取方法的局限性,通过改进自适应阈值函数压制随机噪声,在局部阈值的基础上改进贝叶斯阈值,形成一种适用于Shearlet变换的自适应阈值函数。具体做法为：将信噪比与阈值函数有机关联,并将信噪比作为阈值设定的因素,即不同的信噪比的权值系数不同,可以自适应求取不同尺度阈值,从而最大限度地改善去噪效果,避免有效信号损失,实现自适应去噪。模型试算与实际资料去噪效果表明,在保证有效信号不受损失的情况下,所提方法可恢复被噪声掩盖的弱信号,有效改善去噪效果。     

Synergistic effects of conductive carbon nanofillers based on the ultrahigh-molecular-weight polyethylene with uniform and segregated structures

To discuss the synergistic effects of mixed conductive filler on nanocomposites, different structural carbon nanofiller/ultrahigh-molecular-weight polyethylene (UHMWPE) hybrid nanocomposites with uniform and segregated structure were prepared by using ethanol-assisted dispersion, hydrazine reduction, and hot-pressing methods. Scanning electron microscopy and polarized optical microscopy images of the nanocomposites fracture showed that the complete conductive channels could be formed in segregated nanocomposites prepared by powder mixing method. By contrast, the discontinuous electric path could be observed in the homogeneous nanocomposites prepared by the solution method. The test of conductivity performance demonstrated that the percolation threshold of carbon black (CB)/UHMWPE and multiwalled carbon nanotubes (MWCNTs)-CB/UHMWPE nanocomposites with segregated structure were 0.42 and 0.18 vol %, which were lower than those of the nanocomposites with uniform structure (4.91 and 2.62%). The electrical conductivity of MWCNTs-CB/UHMWPE nanocomposites with segregated structure reached to 3.0 × 10⁻² S m⁻¹ with the filler content of 1.5 vol %. In addition, the results of differential scanning calorimetry indicated that the crystallinity of UHMWPE decreased slightly with the addition of mixed filler. All of the study showed that the conductivity of MWCNTs-CB/UHMWPE nanocomposites with segregated structure has better electrical conductivity than the uniform. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47317.     

Evaluation of quality properties and water mobility in vacuum microwave-dried carrot slices using pulse-spouted bed with hot air

Fried carrot slices feature high fat content to impair people healthy. To resolve this issue, microwave hot air-assisted pulse-spouted vacuum drying (MHAPSVD) has been designed using microwave vacuum dry on pulse-spouted bed with hot-air steam. Dying characteristics, moisture mobility and qualities of carrot slices had been confirmed after dying using 915?MHz microwave generator. Experiment was carried out at 3 W/g, 90?°C air stream, 0.08?MPa vacuum pressure and 2?s pulse interval for drying time of 10–80?min. The quality properties of color, odor, rehydration ratios, shrinkage ratios as well as tastes in 70?min drying are found to be suitable for a snack food. High moisture stability of carrot slices was achieved after 50?min. Free water decreased dramatically from start to 20?min and bound water declined sharply from 20 to 50?min. MHAPSVD could be a high efficient and quality drying technology for crisp product.     

Sensitivity and wound healing after hot-iron disbudding in goat kids

Hot-iron disbudding in goat kids causes acute pain and tissue damage. However, the duration of healing and wound sensitivity is unknown. We assessed wound healing and pain sensitivity in 18 female dairy goat kids disbudded with a heated iron at 10 d of age (range: 5–15 d). Pressure algometry was carried out twice a week from d 1 after disbudding to determine the mechanical nociceptive threshold (MNT) in 4 locations on each bud (front, lateral, caudal, and middle). At the same time, digital and infrared images of the wounds were used to visually and thermally describe the healing process. Wounds were visually scored daily for the presence of 7 tissue types: attached necrotic tissue, detached necrotic tissue, burns outside the necrotic ring, exudate, granulation, crust, and epithelium. All data were taken until epithelium was present for 4 consecutive days. Necrotic tissue detached completely from the scalp 26 ± 5 d after the procedure (mean ± SD; range: 17–43 d), and wounds took 50 ± 8 d (35–63 d) to re-epithelialize. Wounds were more sensitive at all stages of the healing process compared with re-epithelialized tissue. The caudal and middle locations were the most- and least-sensitive test sites (1.24 ± 0.10 and 1.90 ± 0.10 N, respectively; mean ± SE). Goats became less responsive to stimulation as their wounds decreased in size. Sensitivity did not differ between left and right sides of the head. Maximum surface temperature of necrotic tissue, when present, tended to be higher than that of epithelium (38.8 ± 0.2 vs. 38.1 ± 0.2°C); temperature did not differ among other tissue types. Our results indicate that hot-iron disbudding wounds in goats take, on average 7, wk to re-epithelialize (35–63 d) and are painful throughout this time, raising additional welfare concerns about this procedure.     

不同制作工艺欧李果酒品质比较

采用浸泡法、鲜汁发酵和熟汁发酵3种工艺制作欧李果酒,通过顶空固相微萃取-气相色谱-质谱联用技术（HS-SPME-GC-MS）,结合相对气味活度值（ROAV）,比较了3种制作工艺欧李果酒的色泽、挥发性风味物质以及涩味,并进行了感官品评,为欧李果酒的制作方法提供了理论依据。结果表明,浸泡酒呈宝石红色,香气特征主要表现为果实的香气,涩味最淡,在色泽和澄清度上较好但酒体单薄且偏酸。两种发酵型酒呈桃红色,增加了以己酸乙酯为主的代谢香气,鲜汁发酵酒挥发性香气种类多,熟汁发酵酒相对含量最高。鲜汁发酵酒口感持久但涩味偏重;熟汁发酵酒在香气浓郁度、香气质量、口感质量和整体平衡性方面均为最佳,口感细腻柔顺、涩味适口,综合品质最佳。