气泡帷幕衰减水中冲击波频谱特性实验研究

在小型爆炸实验水池中测量冲击波通过气泡帷幕后的压力,对结果进行FFT变换并进行频谱分析。得到了气流量、帷幕层数、孔径等帷幕参数改变时对水下冲击波频谱特性的影响,为气泡帷幕在工程中的实际应用提供依据。

模拟输配水系统中化合氯衰减模型研究

通过模拟输配水系统和主体水烧杯试验模拟化合氯的衰减过程,考察了水温、pH、初始氯浓度以及水力流速等因素对化合氯衰减的影响。结果表明:管壁对化合氯衰减影响的速率常数kt远大于主体水化合氯自身的衰减速率常数kb。流速、水温与衰减系数成正比,pH、初始氯浓度与衰减系数成反比,同时建立了化合氯衰减速率常数与上述各因素的数学模型。同时发现,管道细菌繁殖和生物膜增长对化合氯衰减有重要影响,为提高管网水质,管道应定期清洗、消毒。

一种水衰减长度测量装置的机械结构设计

针对在水面以上测量水衰减长度的不准确性和实时性不好的缺点,设计了一种在水中测量水衰减长度的测量装置。首先,由于测量装置在水中使用,所有材料优先选用防水材料;然后利用同步齿形带作为主要的传动机构设计了一种升降装置,对测量装置的各部分结构进行了设计,包括导轨和准直光筒的结构设计、电机的型号选择等,同时配合步进电机和导轨使升降机构的重复定位精度可以达到0.5 mm,使测量装置满足使用要求,为水中测量装置的设计提供了新思路。

氯胺在水中衰减模型的研究

通过烧杯实验，以南方某水厂炭滤后出水为原水，采用氯胺为消毒剂，研究氯胺在水中衰减的影响因素。结果表明：有机物浓度、NO2^-、水温、pH值对水中氯胺衰减影响显著，初始氯浓度对衰减速率影响不大。可用一级动力学模型模拟氯胺在水中的衰减情况，其相关系数〉0．96。在综合分析各个因素对水中氯胺衰减影响的基础上，建立了水中氯胺衰减模型，并进行了验证，该预测模型具有较好的预测效果。

环状管网余氯衰减和THMs动力学模型优化

为研究大型环状管网中余氯衰减和三卤甲烷(THMs)的生成模型,在占地570 m2的大型中试环状管网中进行。研究温度、初始余氯浓度和总有机碳(TOC)变化条件下对余氯衰减和三卤甲烷生成的影响。根据接近实际管网的中试实验数据,发现温度对余氯衰减的影响最为明显,其次是水中的总有机碳,影响最小的是初始余氯浓度。比较主体水余氯衰减和管壁余氯衰减在不同温度影响下的变化。研究结果表明:随着温度升高,管壁余氯衰减系数基本不变,而主体水中的余氯衰减系数逐渐增加。此外,确定三卤甲烷生成潜能(THMs formation potential,THMFP)与较易检测指标总有机碳(TOC)浓度之间的关系,并在此基础上结合优化的余氯衰减模型,建立能较好拟合实验数据的三卤甲烷生成模型。由于模型是基于大型环状管网的实验数据并考虑实际温度、TOC浓度和初始余氯浓度变化的影响,使优化的余氯衰减模型和三卤模型具有更好的适用性。

一种用于水下图像的光谱重构方法:理论及应用（英文）

多光谱成像是一项非常有前景的图像高保真获取与再现技术,近年来在水下物体颜色还原的应用中也受到的极大的需求和关注。然而,不同于空气中的物体的成像过程,在水下成像过程中,当光通过水而进行传播,光被水体严重吸收和散射,导致图像变暗,在其光谱和颜色方面发生模糊和扭曲。文中讨论的是基于水下图像的水衰减系数的校准和其多光谱图像的光谱重构。首先在不同的距离处获取物体的图像,提出了基于不同距离的图像进行水体衰减系数的校准并恢复原始图像的技术;在此基础上,分析并导出满足系数校准和图像复原所需的在不同距离获取到的最少的原始图像个数。最后,通过比较复原的水下图像与空气中获取的彩色图像,实验结果证明:文中提出的技术能够对水下光谱图像的进行精确颜色复原,所有测试图像的平均相对残留误差仅为5.87%。

基于WCDA水质监测分析

水切伦科夫探测器阵列(Water Cherenkov Detector Array,WCDA)是高海拔宇宙线观测站(Large High Altitude Air Shower Observatory,LHAASO)的主体探测器之一,水作为探测器的唯一探测介质,水的洁净度直接影响探测器对切伦科夫光的探测效率.为保证水切伦科夫探测器阵列物理目标的实现,水衰减长度的实时测量和监测至关重要,是探测器正常运行和标定的关键工作之一.分别介绍了水衰减长度测量装置和紫外可见分光光度计的工作原理,并通过不同波长的发光二极管(Light Emitting Diode,LED)对各种样品水进行测量,将两种方法的数据结果进行对比分析,得出两种装置的测量误差分别为0.22 m和0.18 m,以及工业指标吸光度与科研指标水衰减长度之间的对应关系,并为几何和跟踪(GEometry AND Tracking,GEANT4)模拟确定了一种Querry水质模型,进一步推进了模拟的真实化.通过对水切伦科夫探测器阵列1号水池水衰减测量装置的验证及从注水到稳定运行期间的水质监测的数据研究,总结了一套稳定可靠的水质监测方案,为2、3号水池的监测工作奠定了良好的基础.

LHAASO水切伦科夫探测器阵列工艺水系统设计

高海拔宇宙线观测站是国家重大科技基础设施建设项目。水切伦科夫探测器阵列是主要的探测器阵列,水是探测器的介质。采用预处理+膜过滤+后级精处理水处理工艺,调试运行结果表明该工艺出水能满足探测器进水水质高要求。工艺出水浊度、TOC、颗粒数(> 1μm)都达到了设计预期要求,能为水切伦科夫探测器阵列提供合格的探测器介质。

EXPERIMENTAL STUDY ON DARCY′S LAW IN HELE-SHAW CELLS

The basic physics of unsteady Hele-Shaw flow at high Reynolds numbers is mainly studied by an experimental measurement. In order to confirm the Darcy′s law in Hele-Shaw cell, since there is an analogy between flow in cells and that in porous media, progressive water waves are utilized to build an unsteady flow in a Hele-Shaw cell, and which complex wave number is measured by a wave height gauge. Meanwhile, theoretical analyses are used to compare with experimental data. Result shows Darcy′s Law is not exactly correct for unsteady Hele-Shaw flows, and it is expected to conduct a modified Darcy′s Law.

Wave attenuation mechanism of cross-plates applied in landslide-induced tsunami in river course

Since the impounding of the Three Gorges Reservoir, the channel of the Yangtze River has become a busy watercourse and the probability of landslide-induced tsunamis has increased. In the case of landslide-induced tsunamis in the Three Gorges Reservoir, even after shipping closures in advance, there are still facilities and objects in urgent need of protection within the risk zone of the watercourse, such as wharfs, marine fueling stations, berthed ships. The emergency protection against and decay of landslide-induced tsunamis in inland watercourses is a new challenge. In this study, 37 sets of wave decay experiments were conducted with the hydromechanics numerical method. The wave decay efficiencies of common simple structures including submerged horizontal plate, horizontal plate on the water surface, inclined thin plate and cross-plates in coastal areas were compared and analyzed. Cross-plates structure showed better wave decay capacity than other simple plates. The wave decay performance of cross-plates was related to five modes of energy dissipation and transformation, namely run-up/run-down, overtopping, reflecting, return flow and disturbed wave orbital path. The type of wave had little relation with the decay performance of cross-plates, but a strong correlation with cross-plates structure, especially the height of the vertical emerged plate. The best decay performance was observed when the ratio of wave amplitude to emerged vertical plate height was between 1 and 1.5, which can reduce up to about 8o% of the incoming wave amplitude. Finally, the emergency way of cross-plates applied to the decay of landslide-induced tsunami in river course is discussed. This study provides a conceptual reference for related studies to practice the attenuation of landslide-induced tsunami in reservoirs.

用土力学的新概念解读和修正经典饱和土力学

论述了应该用有效应力的新概念代替经典有效应力原理。总应力压缩模量与渗流水等效压缩模量的曲线相似;有效应力压缩模量起加劲作用,而不是起决定性作用。土的压缩变形计算中应用有效应力原理是错误的。对于起始水力坡降,引入饱和粘性土的自由水压力衰减概念。在饱和粘性土中,自由水通道率折减不大,相对自由水压力通过一定厚度后衰减为零。所以,新概念土力学的算法接近我国规范:"对粘性土宜按水土合算计算"。还解读了地下室浮力折减、流沙陷阱等等。

Directivity Effect on PGV Attenuation Relationships in Silakhor Earthquake （2006, Mw6.1）

Rupture directivity effect causes spatial variation in strong ground motion parameters. It causes difference between the strike- normal （V.） and strike-parallel （Vp） components of horizontal ground motion amplitudes. These variations become significant for strong ground motion velocity and the authors have developed a modification to define directivity effect factor to account for the effect of rupture directivity in empirical velocity attenuation relations which are based on modeling Silakhor earthquake, using finite element method by ANSYS. The ground motion parameters that are modified include ratio of Vn/Vp component of horizontal velocity and Vn component to average horizontal velocity （V）. The ratio of Vn to Vp is large in both the forward directivity direction, where velocity is larger, and in the backward directivity direction, where velocity is smaller. Therefore the authors expected that the Vn/Vp was mainly controlled by directivity angle. Also the variation of fault normal velocity to average horizontal velocity ratio by directivity angle （0） is defined from earthquake modeling. It shows Vn/V is controlled by directivity angle, distance between the site, epicenter and rupture length. This ratio has the same trend in Silakhor earthquake strong ground velocity data. In this paper the equation for Vn/Vp variations by directivity angle is recommended. The authors used Somervill et al. （1997） directivity model parameters as （R/L） cos2 ~ to define directivity effect on Vn/V ratio and therefore directivity factor is determined to account in near field empirical strong ground velocity attenuation relationships.

The Formation of Precipitation Anomaly Patterns during the Developing and Decaying Phases of ENSO

This study proposes a new explanation for the formation of precipitation anomaly patterns in the boreal summer during the E1 Nifio-Southem Oscillation （ENSO） developing and decaying phases. During the boreal sum- mer June-July-August （JJA） （0） of the E1 Nino （La Nina） developing phase, the upper level （300-100 hPa） positive potential temperature anomalies resemble a Ma- tsuno-Gill-type response to central Pacific heating （cool- ing）, and the lower level （1000-850 hPa） potential tem- perature anomalies are consistent with local SST anoma- lies. During the boreal summer JJA（1） of the E1 Nifio （La Nifia） decaying phase, the upper level potential tempera- ture warms over the entire tropical zone and resembles a Matsuno-Gill-type response to Indian Ocean heating （cooling）, and the lower level potential temperature anomalies follow local SST anomalies. The vertical heterogeneity of potential temperature anomalies influences the atmospheric stability, which in turn influences the precipitation anomaly pattern. The results of numerical experiments confirm our observations.

Characteristics of K_d (490) around Nansha Islands in the South China Sea

The diffusion attenuation coefficient for downwelling irradiance, Kd (490), is an important optical parameter of seawater. The optical property, Kd (490), around Nansha Islands in the South China Sea was analyzed based on optical data profiles measured with SPMR ( SeaWiFS Profiling Multichannel Radiometer ) and SMSR ( SeaWiFS Multichannel Surface Reference ) instrument in April and May, 1999. The results show that Kd (490) is closely correlated with chlorophyll-a concentration, Cchl.a, and that the vertical distribution of Kd (490) shows the strong stratification of the water column in this area. Kd (490) has a similar vertical co-variation as KL (490), the diffusive attenuation coefficient for upwelling radiance. Both coefficients increase with depth in the upper layer, where KL (490) is greater than Kd (490); and after a depth, approximatively at the chlorophyll maximum, they decrease with depth, with the former being smaller than the latter.

颅脑MRI压脂成像:Dixon-FLAIR和FS-FLAIR的对比研究

目的对比水脂分离液体衰减反转恢复(Dixon-FLAIR)序列和频率选择脂肪抑制液体衰减反转恢复(FS-FLAIR)序列进行颅脑MRI脂肪抑制成像的效果及可靠性。方法前瞻性收集46例怀疑颅脑病变的患者并运用1.5 T MRI对其进行包括Dixon-FLAIR与FS-FLAIR序列在内的头颅MRI扫描。两个观察者以5分法分别对Dixon-FLAIR和FS-FLAIR的整体脂肪抑制图像质量及皮下脂肪抑制效果(包括上颌窦、眼眶、额窦和中央沟四个层面)进行评估,并对两组图像中间层面的同一区域白质的信噪比(SNR)进行测量。结果整体图像质量及上颌窦层面、眼眶层面、额窦层面和中央沟层面的脂肪抑制效果在Dixon-FLAIR序列上的评分分别为4(3,5)、3(1,5)、4(1,5)、4(3,5)和4(3,5),两个观察者的一致性评估的Kappa系数为0.823、0.89、0.886、0.803和0.826。在FS-FLAIR序列的评分分别为1.5(1,3)、1(1,2)、2(1,3)、1(1,3)和3(1,4),两个观察者的一致性评估的Kappa系数为0.926、1.000、0.823、0.819和0.924。Dixon-FLAIR序列所有的脂肪抑制效果评分都高于FS-FLAIR序列,差异具有统计学意义(P<0.05)。两个观察者对图像质量及不同层面脂肪抑制效果的评分具有极好的一致性(Kappa系数均>0.8);Dixon-FLAIR图像SNR优于FS-FLAIR序列(195.44±37.96比165.88±35.31),差异具有统计学意义(P<0.05)。结论Dixon-FLAIR比FS-FLAIR具有更好的脂肪抑制效果及更高的图像信噪比,推荐其代替常规FS-FLAIR序列获得更佳的MRI脂肪抑制效果。

Effects of Postharvest Hot Water and Hot Air Treatments on Storage Decay and Quality Traits of Kumquat （Fortunella japonica Lour. Swingle, cv. Ovale） Fruit

Heat treatments such as hot-water dipping （HWD）, hot water rinsing and brushing （HWRB）, and hot air treatment （HAT） have been applied on a wide range of horticultural crops to control postharvest decay and to maintain quality characteristics. In this study we compared the influence of hot-water dipping （HWD） for 2 rain at 50℃and hot air treatment （HAT） at 37 ℃ for 30 hours, on postharvest performance of kumquat （Fortunellajaponica Lour. Swingle, cv. Ovale） fruit. Decay development, transpiration rate （fruit weight loss）, external appearance, and nutritive （sugars and organic acids） and functional properties （ascorbic acid, total phenolic compounds, and total antioxidant activity） were evaluated over 21 days＇ simulated shelf-life at 17 ℃. Untreated fruits were used as control. There was no visible damage to the fruit following HWD or HAT and after storage. However, while HWD and control fruit maintained their fresh appearance during the first 14 days of storage and were rated as fairly fresh after the 21 days, HAT fruits had lost their gloss and no longer appeared fresh. HWD did not affect fruit weight loss while HAT induced significant weight loss with respect to control. HAT did not significantly affect decay incidence after 14 days＇ storage but effectively reduced decay after 21 days＇. HWD notably reduced decay development after 14 and 21 days of storage and proved significantly more effective than HAT. Neither HWD nor HAT significantly affected the nutritive and functional properties of fruit. Thus, present results indicate that while HWD can be applied on kumquats to control postharvest decay without impairing the quality traits, HAT conditions （treatment time and temperature） should be optimized, due to adverse effects to fruit quality.

Underwater Image Enhancement Based on the Dark Channel Prior and Attenuation Compensation

Aimed at the two problems of underwater imaging, fog effect and color cast, an Improved Segmentation Dark Channel Prior(ISDCP) defogging method is proposed to solve the fog effects caused by physical properties of water. Due to mass refraction of light in the process of underwater imaging, fog effects would lead to image blurring. And color cast is closely related to different degree of attenuation while light with different wavelengths is traveling in water. The proposed method here integrates the ISDCP and quantitative histogram stretching techniques into the image enhancement procedure. Firstly, the threshold value is set during the refinement process of the transmission maps to identify the original mismatching, and to conduct the differentiated defogging process further. Secondly, a method of judging the propagating distance of light is adopted to get the attenuation degree of energy during the propagation underwater. Finally, the image histogram is stretched quantitatively in Red-Green-Blue channel respectively according to the degree of attenuation in each color channel. The proposed method ISDCP can reduce the computational complexity and improve the efficiency in terms of defogging effect to meet the real-time requirements. Qualitative and quantitative comparison for several different underwater scenes reveals that the proposed method can significantly improve the visibility compared with previous methods.

饱和土的大气张力郎肯土压力

该文总结了饱和土的大气张力郎肯土压力算法。其计算要点有:饱和度系数、自由水通道率、膜的抗剪强度贡献、大气张力郎肯土压力。算例分析表明,按大气张力郎肯土压力,饱和粘土的自由水通道率折减不大,相对自由水压力通过一定厚度后衰减为零,其结果与水土合算的接近。饱和土的大气张力郎肯土压力算法,接近我国规范,对砂性土宜按水土分算计算,对粘性土宜按水土合算计算。表层为较硬的饱和粘土的基坑,按经典郎肯土压力,基坑上部主动土压力为负值,表示土体拉住支护,处理为零,这是错误的;而按大气张力郎肯土压力,表示坑内支护上的大气压强能抵抗主动土压力,扶住支护。

Study on the Water Surge Height Line of Landslide Surge of Linear River course Reservoir Based on FLOW-3D

The occurrence and transmission attenuation of surge is always a problem that researchers pay much attention to. The influence of the first wave height of landslide surge and the following transmission attenuation of surge are involved with many factors, which are mainly： landslide water entry angle, river course depth, river course geometrical properties and landslide mass and material, etc.. This thesis is mainly a research on the properties and transmission attenuation rules of landslide surge which is caused by linear narrow river course. Numerical value simulation will be applied in this thesis to discuss about the features and rules of the occurrence and transmission of surge in different landslide water entry angles and under different influences.

Electrochemical Performance and Capacity Fading Mechanism of LiFePO4 at Different pH Aqueous Electrolyte Solutions

The electrochemical stability of LiFePO4 in a Li＋-containing aqueous electrolyte solution is critically dependent on the pH value of the aqueous solution. It shows a considerable decay in capacity of LiFePO4 upon cycling when the pH value is increased to 11. The mechanism responsible for the capacity fading is extensively investigated by means of cyclic voltammogram, ac impedance, charge/discharge, ex situ X-ray diffraction, and chemical analysis. LiFePO4 is relatively electrochemically stable in LiNO3 aqueous solution with pH=7. But the electrochemical performance of LiFePO4 in aqueous electrolyte is inferior to that in organic electrolyte. It is attributed to the loss of Li and the Fe, P dissolution during prolonged charge-discharge in aqueous medium. A precipitate is formed on the surface of LiFePO4 electrodes. It results in the change of crystalline structure, a large electrode polarization, and capacity fading.