Effect of Nanoclay along with Other Effective Parameters on Gelation Time of Hydro Polymer Gels

In this work, a hydrogel was prepared by crosslinking of aqueous solutions of sulfonated polyacrylamide/chromium triacetate for the purpose of water shut-off treatment in oil fields. In order to screen the factors that affect the gelation time and investigate their interactions, a 32 run fractional factorial design was used in experimentation with eight factors (pH, CaCl₂ concentration, crosslinker/copolymer ratio, NaCl concentration, copolymer concentration and presence or absence of sodium lactate, nanoclay, and thiouria) and one response (gelation time). Furthermore, the analysis of variance (ANOVA) was implemented as a significant tool to evaluate the quality of the quadratic model. The ANOVA results of the developed model showed it was significant with a 99% confidence limit. Among the eight factors, presence of sodium lactate, copolymer concentration, presence of nanoclay, presence of thiouria, and crosslinker/copolymer ratio had, in order, the main effects, and the interactions between sodium lactate and crosslinker/copolymer ratio and between pH and crosslinker/copolymer ratio were highly significant.     

APS图像传感器及其在星敏感器中的应用

星敏感器是当前广泛应用于航天器姿态测量的高精度光学敏感器。小型化、低功耗、高精度、高更新率是现阶段星敏感器发展的共同特点。介绍了APS图像传感器的特点,并将其与CCD进行了详细的比较。对APS图像传感器的重要特性参数进行了分析,并介绍了一种由北京控制工程研究所研制的小型化高精度APS星敏感器及其设计方法。介绍了适用于GEO轨道的APS星敏感器图像在轨校正方法和APS图像传感器的发展方向。     

Swelling and Gelation Time Behavior of Sulfonated Polyacrylamide/Chromium Triacetate Hydrogels

A hydrogel was prepared by crosslinking of aqueous solutions of sulfonated polyacrylamide/chromium triacetate for use in water shut-off operations in oil reservoirs. The effects of pH, salinity, retarder and temperature, as well as co-polymer and crosslinker concentration, on the gelation time were investigated. The results indicated that as temperature increased, gelation occurred more rapidly. The activation energy was measured as about 86 kJ/mol. The effects of initial pH and retarder on the gelation time were also examined. The results showed that addition of retarder and increasing of pH increased and decreased the gelation time, respectively. The increase of co-polymer concentration in solution increased the gel swelling. However, the increase of crosslinker concentration decreased the gel swelling. In the presence of electrolytes, the gel swelling decreased by about 80%. Finally, some usable practical recommendations are offered for the gelling systems in reservoirs.     

连续变焦大气相干长度测量系统设计

望远镜在大气光学参数测量中起到至关重要的作用,测量方法是通过跟踪恒星或者信标实时测量数据。基于不同速度信标的移动特点,需要设计3 m~6 m变焦大气相干长度测量系统用于大气相干长度的测量,设计波段为可见光486 nm~656 nm,探测元全视场11 mm,入瞳直径300 mm。利用光学设计软件设计出一款折返式变焦望远系统,光学结构由卡式望远系统和三组元机械补偿式连续变焦系统组成,系统结构简单,成本低,凸轮曲线平滑,压力升角均小于45。系统可对变焦焦距数据实时输出,适合于快速和慢速不同场合下实时进行大气参数测量。     

大型Schmidt望远镜光学系统调整方法

安装于紫金山天文台盱眙观测站用以观测近地天体的大型Schmidt望远镜,采用了平场Schmidt光学系统,改正镜通光口径为1m,球面反射镜口径为1.2m,焦距为1.8m,接收器用了4K×4K的高灵敏度CCD。本文叙述了该仪器光轴调整的方法及调整后观测获得的初步结果。叙述了望远镜光轴校正方法、校正结果、CCD靶面的调整及望远镜极轴高度、方位的调整及相应的照片。经实际观测的结果是:露光1s可拍到18等星;露光4s可拍到19.3等星;露光20s可拍摄到21.2等星。     

CCD星图模拟器的设计及验证

为了方便星图识别算法和星敏感器性能的测试,设计了一种CCD星图模拟器,开发了星图模拟软件。采用高分辨率显示设备及平行光管模拟无穷远处平行光,实现了高质量星图的模拟。通过高精度QUEST算法求解姿态,对模拟的星图进行了验证。计算了3颗以上恒星的偏航角、俯仰角和滚动角,对100幅模拟星图进行了统计分析,结果显示其定位精度已达98．1％。目前,该星图模拟器已成功用于实际项目,为后续的测试星图识别算法提供了良好的依据,并缩短了开发周期。     

Autonomous satellite constellation orbit determination using the star sensor and inter-satellite links data

A method of autonomous orbit determination for a satellite constellation using a star sensor combined with inter satellite links(ISLs) is studied.Two types of simulated observation data,Three-Satellite Constellation ISLs and background stellar observations by a CCD star sensor,are first produced.Based on these data,an observation equation is built for the constellation joint autonomous orbit determination,in which the simulations are run.The accuracy of this method with different orbital determination model...     

自适应光学系统时域特性分析

分析了激光导星发出的波前通过湍流大气所造成的波前相位畸变的时间功率谱 ;根据湍流相位时间功率谱和自适应光学系统的传递函数 ,比较了使用自然导星和激光导星时自适应光学系统的时间响应误差 ;讨论了使用自然导星时自适应光学系统的时域优化问题。     

Critical Behavior of the Generalized Srnoluchovski's Coagulation Equation

The critical behavior of the gelation of polymers is studied by means of the generalized Srnoluchovski's coagulation equation. The exact solution of the kinetic equation with a factorial coagulation rate R(i₁, i₂, . . . i_n) = s_i1 × s_i2 × . . . × s_in and s_k = A × k + B is derived for the monodisperse initial condition c_m(O) = δ_{m, 1}. It is shown that a gelation transition takes place within a finite time t_c and the gelation time t_c ii characterized by the parameters A and B.     

A fast onboard star-extraction algorithm optimized for the SVOM Visible Telescope

The Space multi-band Variable Object Monitor (SVOM) is a proposed Chinese astronomical satellite, dedicated to the detection, localization and measurement of gamma-ray bursts (GRBs) on a cosmological scale. An efficient algorithm is developed for the purpose of onboard star extraction from the CCD images obtained with the Visible Telescope (VT) onboard the SVOM. The CCD pixel coordinates of the reference stars will be used to refine the astronomical position of the satellite, which will facilitate triggering rapid ground-based follow-up observations of the GRBs. In this algorithm, the image is divided into a number of grid cells and the “global” pixel-value maximum within each cell is taken as the first-guess position of a “bright” star. The correct center position of a star is then computed using a simple iterative method. Applying two additional strategies, i.e., scanning the image only by even (or odd) lines or in a black-white chess board mode, we propose to further reduce the time to extract the stars. To examine the efficiency of the above algorithms, we applied them to the experimental images obtained with a ground-based telescope. We find that the accuracy of the astronomical positioning achieved by our method is comparable to that derived by using the conventional star-extraction method, while the former needs about 25 times less CPU time than the latter. This will significantly improve the performance of the SVOM VT mission.     

Hybrid stars and quark hadron phase transition in chiral colour dielectric model

We investigate the properties of hybrid stars consisting of quark matter in the core and hadron matter in outer region. The hadronic equation of state (EOS) is calculated by using nonlinear Walecka model. Strange baryons are included in the hadronic EOS calculation. The chiral colour dielectric (CCD) model, in which quarks are confined dynamically, is used to calculate quark matter EOS. We find that the phase transition from hadron to quark matter is possible in a narrow range of the parameters of nonlinear Walecka and CCD models. The transition is strong or weak first order depending on the parameters used. The EOS thus obtained, is used to study the properties of hybrid stars. We find that the calculated hybrid star properties are similar to those of pure neutron stars.     

一种高速CCD视频实时存储方案的速度分析

为了满足高帧频、大面阵CCD数字视频实时存储要求,在分析数字视频的信号特点和SCSI系统数据传输过程的基础上,建立了缓冲并行预处理和SCSI直接存储阵列数据传输的理论模型。从理论和实验两个方面分析了SC SI总线速度和SCSI硬盘持续存储速率两个决定存储速率的主要因素,并且分析了数据分块大小,LBA(逻辑块地址)范围以及系统调度策略对SCSI硬盘阵列数据存储速度的影响。实验表明,通过选择合适的应用背景来减少总线冲突,可以满足100MB/s视频数据的存储要求。     

空间扫描型光纤法布里珀罗传感解调系统中CCD的光照度数学模型研究

针对空间扫描型光纤法布里珀罗（F-P）传感解调系统中CCD的光照度分布建立了数学模型,研究了不同帧扫描频率下CCD输出信号和信噪比。利用已设计的解调模块进行了CCD光照度分布的实验,实验结果表明,当帧扫描频率不同时,CCD各个像素输出信号电压的实验值与计算值的相对误差均小于2.5%,同一像素输出信号电压的实验值与计算值的相对误差变化数值均小于0.005,随实验所用CCD帧扫描频率变化,信噪比以184 Hz为分界点以两种变化斜率改变,验证了数学分析模型的有效性。     

一种改进全天自主栅格星图识别算法

栅格算法是一种较优秀的星图识别算法 ,但它要求视场中有较多的恒星 ,从而要求星跟踪器有大的视场或高的星等灵敏度。为了克服这一缺点 ,引入主星的概念 ,并在星图识别过程中加入星等信息。仿真结果表明改进后的算法只需较少的恒星就能保证算法的鲁棒性 ,且实时性得到显著改善。     

基于线阵CCD的光学测角嵌入式系统设计

CCD作为一种光电转换器件,具有成本低、结构简单、扫描速度快、频率响应高等优点,越来越广泛地运用到测量领域。提出采用单色线阵CCD,以非接触的光学方式对角度信息进行编码调试,通过采集该信号利用数据处理模块,完成对图像信号的解调,实现角度值的测量。系统选用TSL1401和LPC2138为核心构成嵌入式测量系统,利用TSL1401采集信号,通过A/D传输到LPC2138中进行数据处理,最终得到角度值。系统通过光学的方式对角度进行测量,实现了非接触式测量。     

Gelation of Milk Protein Concentrates Induced by Moderate Hydrostatic Pressures

Gelation of aqueous milk protein concentrates made up of spray dried milk was monitored both at atmospheric pressure and at moderate pressures (up to 1000 bar) using rheological methods. A Paar Physica UDS 200 rheometer was used to measure the gelation time at atmospheric pressure as a function of the temperature for a protein concentration of 16% [w/w]. The temperature dependence of the gelation time is well approximated by the Ross-Murphy model, which was originally developed to describe the concentration dependence of the gelation time. Using a purpose built Haake High Pressure High Temperature Rheometer, the effects of moderate pressures upon the gelation of milk protein concentrates (13% [w/w] protein content) were investigated. It was found that the gelation time reduces significantly (by up to almost an order of magnitude), when pressures of up to 1000 bar were applied. These findings, combined with the work of others indicate that these pressures bring about two effects: (1) casein micelle dissociation and as a result facilitate reassociation of those smaller micelle fragments, and (2) denaturation of beta-lactoglobulin. However, the main contribution to enhanced gelation was attributed to the caseins. It is not clear if association of whey proteins with caseins occur at moderate pressures around 50 °C. We have modelled the dependence of the rate of gelation on pressure by an Eyring reaction rate process type equation. The major contribution to enhanced gelation upon pressurisation was attributed to a disruption of hydrophobic groups and ionisation of charged groups caused by an increase in electrostriction - however, disruption of hydrogen bonds was suggested to contribute to a lesser but still important extent.     

Effect of electrostatics on aggregation of prion protein Sup35 peptide

Self-assembly of misfolded proteins into ordered fibrillar structures is a fundamental property of a wide range of proteins and peptides. This property is also linked with the development of various neurodegenerative diseases such as Alzheimer's and Parkinson's. Environmental conditions modulate the misfolding and aggregation processes. We used a peptide, CGNNQQNY, from yeast prion protein Sup35, as a model system to address effects of environmental conditions on aggregate formation. The GNNQQNY peptide self-assembles in fibrils with structural features that are similar to amyloidogenic proteins. Atomic force microscopy (AFM) and thioflavin T (ThT) fluorescence assay were employed to follow the aggregation process at various pHs and ionic strengths. We also used single molecule AFM force spectroscopy to probe interactions between the peptides under various conditions. The ThT fluorescence data showed that the peptide aggregates fast at pH values approaching the peptide isoelectric point (pI = 5.3) and the kinetics is 10 times slower at acidic pH (pH 2.0), suggesting that electrostatic interactions contribute to the peptide self-assembly into aggregates. This hypothesis was tested by experiments performed at low (11 mM) and high (150 mM) ionic strengths. Indeed, the aggregation lag time measured at pH 2 at low ionic strength (11 mM) is 195 h, whereas the lag time decreases ~5 times when the ionic strength is increased to 150 mM. At conditions close to the pI value, pH 5.6, the aggregation lag time is 12 ± 6 h under low ionic strength, and there is minimal change to the lag time at 150 mM NaCl. The ionic strength also influences the morphology of aggregates visualized with AFM. In pH 2.0 and at high ionic strength, the aggregates are twofold taller than those formed at low ionic strength. In parallel, AFM force spectroscopy studies revealed minimal contribution of electrostatics to dissociation of transient peptide dimers.     

WinCE多线程在微型光谱仪中的应用

Windows CE是一个多任务操作系统,具有占用资源少、实时性特点.CCD作为较高灵敏度的光电传感器被广泛应用在非接触位移领域和光信息测量中.提出通过WinCE多线程编程设计应用软件设计完成嵌入式系统和FPGA配合下的CCD驱动和数据采集;成功的应用在便携式光谱仪的设计中,给出了使用该软件所测得的光谱响应曲线.该软件...     

一种新的提高CCD成像分辨率的方法

提高数字图像的分辨率一直是一个热门话题,在现代高技术战争中发挥着重要的作用。从CCD成像原理出发,分析了1／2像素错位的低分辨率图像与高分辨率图像各像素灰度值之间的对应关系,提出了一种新的提高CCD成像分辨率的方法。通过多次移动CCD获得多幅低分辨率图像,按照介绍的算法合成一幅高分辨率图像,达到了CCD分辨率提高多倍的目的,算法的本质是使一超定解多元方程组变成有唯一解的方程组。通过仿真实验和分析表明：所建立的提高分辨率的方法是正确的,分辨率可以提高2倍、3倍甚至更高在理论上是可行的,而计算时间的复杂度远远小于其它方法。     

TG-2/MAI CCD像元响应特性不一致性的在轨分析及校正

CCD像元响应特性的差异是制约MAI成像质量及其数据定量化应用的主要因素之一。为了提高MAI数据质量,本文基于全量程多段分析与校正法,利用2016年9月至2018年3月期间共104403帧观测数据,分别对MAI偏振通道和非偏振通道的像元响应特性的不一致性开展了在轨分析与校正,并利用GOME-2和MODIS数据产品对校正结果进行了验证。首先,假定观测样本足够多,即每个CCD像元观测的样本具有相同的遍历性,则各CCD像元对应的所有样本的平均DN值可以代表CCD各像元的响应特性;其次,利用104 403帧观测数据构建各个通道的参考图像,并利用MAI中心5×5像元给出各参考图像对应的标准DN值;在此基础上分别对MAI偏振通道和非偏振通道开展了像元响应特性的分析,结果表明,MAI各通道均存在CCD像元响应特性不一致的问题,各通道的不一致性大约在4%～10%之间,对偏振通道而言,同一偏振波段的三个偏振通道之间像元响应特性的不一致性有一定的相似性,像元响应特性不一致性的差异基本在1%以内。然后,将MAI近两年的观测数据分为前后两个时间段进行对比分析。结果表明：前后两个时间段偏振通道和非偏振通道的图像均具有很好的一致性,即CCD像元响应特性未随时间发生显著变化,这也进一步验证了前面MAI数据量充足的假定。因此,可以利用全量程多段校正法逐通道逐像元开展CCD像元响应特性不一致性的校正。基于该方法校正后,MAI图像质量得到显著改善,图像四周响应偏低的区域明显改善,基本和周围像元的响应达到了同一水平;图像更加平滑,颗粒感基本消除;部分区域的场景发生了变化,特别是碎云等反射率介于中低反射率之间的目标。基于GOME-2的交叉对比结果表明,MAI 565,670和763 nm波段反射率与GOME-2的参考反射率之间的平均绝对偏差分别由校正前的1.6%,4.2%和2.2%减小至校正后的0.5%,2.6%和0.4%;此外,基于多通道云识别方法开展的云检测表明,校正后的MAI云检测结果与MODIS云检测产品一致性更好。因此,全量程多段校正方法可以有效解决MAI CCD像元响应特性的不一致性,显著提高MAI在轨观测的质量,且该方法也可以应用于其他CCD仪器的在轨校正。