中肋骨条藻和东海原甲藻的散射特性

浮游藻类是海水中的重要组成成分,对其固有光学特性的研究有助于深入了解水体光学的辐射传输。在过去的30年中,大量的研究都集中在藻类吸收特性上,缺少对其散射特性的认识。本文利用分光光度计设计了在实验室中测量含颗粒水体散射和后向散射特性的方法,并利用标准球形颗粒对该方法的可行性进行验证,结果表明,在400～700nm范围内,散射测量结果与理论值的一致性较好,最大误差小于3%,而后向散射测量结果在蓝紫光处的一致性较好,在近红外波段处有一定误差。运用这两种测量方法对东中国海常见的赤潮藻种中肋骨条藻Skeletonema costatum和东海原甲藻Prorocentrum donghaiense进行测量,结果显示:中肋骨条藻与东海原甲藻的散射系数幅值相近但谱形差异较大,前者随波长增加散射强度递减,后者则相反;在色素吸收较强的波段,两者散射强度均出现与其它波长位置变化趋势相反的情况,这主要是受细胞物质物理性质的影响。两者的后向散射差异较小,但可以看出其谱形受色素吸收的影响很大,在幅值上,东海原甲藻略高于中肋骨条藻,在550nm处分别为0.001 74,0.001 43m2/mg(以藻类叶绿素a浓度归一化),后向散射概率分别为1.104%和0.723%。

硬盘盘片表面疵病检测装置的光学系统设计

为了检测硬盘盘片表面疵病的大小是否符合标准,设计了一种检测装置。采用光的散射理论,结合硬盘盘片表面疵病的粗糙度等级和实验结果,利用光照射到粗糙表面时发生的散射现象、散射光的特性以及散射模型建立的理论基础,对4种散射模型进行了分析和比较。并以混合型散射模型为基础,利用光学设计软件完成了该检测装置的光学系统设计。结果表明,混合型散射模型的散射角最大、散射能量密度最大,最适合用于反映硬盘盘片表面疵病造成的散射现象。

Relationships Between Average Molecular Mass and Intrinsic viscosity of Three Typical Polyanhydrides

Aim To study the relationships between average molecular mass and intrinsic viscosity of polyanhydrides. Methods With chloroform as solvent and petroleum ether as the precipitating agent polyanhydride was separated into a series of grades with different average molecular mass. The absolute average molecular mass (M) and intrinsic viscosity ([]) of every grade were measured. Results and Conclusion The relationships between [] and M of three typical polyanhydrides were obtained from bi-logarithm coordinate plotting of [] versus M.

Controllable Absorption and Dispersion Properties of an RF-driven Five-Level Atom in a Double-Band Photonic-Band-Gap Material

The probe absorption-dispersion spectra of a radio-frequency （RF）-driven five-level atom embedded in a photonic crystal are investigated by considering the isotropic double-band photonic-bandogap （PBG） reservoir. In the model used, the two transitions are, respectively, coupled by leading to some curious phenomena. Numerical simulations the upper and lower bands in such a PBG material, thus are performed for the optical spectra. It is found that when one transition frequency is inside the band gap and the other is outside the gap, there emerge three peaks in the absorption spectra. However, for the case that two transition frequencies lie inside or outside the band gap, the spectra display four absorption profiles. Especially, there appear two sharp peaks in the spectra when both transition frequencies exist inside the band gap. The influences of the intensity and frequency of the RF-driven field on the absorptive and dispersive response are analyzed under different band-edge positions. It is found that a transparency window appears in the absorption spectra and is accompanied by a very steep variation of the dispersion profile by adjusting system parameters. These results show that the absorption-dispersion properties of the system depend strongly on the RF-induced quantum interference and the density of states （DOS） of the PBG reservoir.

Significant broadband extinction abilities of bioaerosols

Bioaerosol, an important constituent of the atmosphere, can directly affect light radiation characteristics due to absorption and scattering effects. Current research lacks a reasonable explanation for the extinction abilities of bioaerosols in a broadband. Herein, we measured the reflectance spectra of 12 com m on biomaterials and calculated their complex refractive indexes. The peaks of the imaginary part of the complex refractive indexes are located at wavelengths of approximately 0.7, 2.7, 6.1 and 9.5μm. Based on photographs of the floating structures of bioaerosols, we constructed a model for calculating the extinction abilities of bioaerosols in the wavelength range of 240 nm to 14 (im. Taking AN02 spores as an example, absorption was found to account for more than 90% of the total extinction. In addition, the theoretical calculations and experimental data of transmittance corresponding to the smoke box show that bioaerosol exhibits significant broadband extinction ability from UV to IR bands, which provides new directions for the development of broadband light attenuation materials.

Coagulation behaviors and in-situ flocs characteristics of composite coagulants in cyanide-containing wastewater:Role of cationic polyelectrolyte

In this paper, composite coagulants （PFS, PFSC05, PFSC1 and PFSC5）, prepared by mixing polyferric sulfate （PFS） and cationic polyelectrolyte （CP） coagulants with different weight percent （Wv） of CP （Wp = 0%, 0.5%, 1% and 5%, respectively）, were adopted to treat cyanide-containing wastewater. PFSC5 exhibited superior coagulation performances at optimal conditions： the removal of total cyanide （TCN） and chemical oxygen demand （COD） was 95%-97% and 50%-55%, respectively. The effects of CP on the properties and structure of flocs were investigated by laser diffraction instrument and small-angle laser light scattering （SALLS）, respectively. The results show that the flocs of PFSC5 have higher growth rate, higher strength factor and lower recovery factor than other flocs. They are also much denser and more uniform owing to the higher fractal dimension （DO and less microflocs （10-100μm）. Furthermore, the dense structure of the PFSC5 flocs can be restored after shear and is more resistant to hydraulic conditions. Particularly, detailed morphology evolution of the flocs was in-situ detected by on-line particle imaging. Due to strong ionic strength in wastewater, the CP in PFSC5 plays a significant role of adsorption, while the main mechanism of CP is electrostatic patch aggregation during the PFSC05 systems.

Comparison study of several underwater light scattering phase functions

Scattering phase function is assumed to be one of the most significant factors in the inherent optical properties （lOPs） of natural water. According to three criteria proposed for assessment, several commonly used empirical phase functions are compared with their related practical or theoretical scattering distributions in terms of fitting errors under the circumstances of typical seawater and single-component polydisperse systems. The optimal factors corresponding to the minimum fitting errors are also calculated. It is found that both the one-term Henyey-Greenstein （OTHG） and two-term Henyey-Greenstein （TTHG） phase functions agree well with the theoretical ones for small particles, while the Fouriner-Forand （FF） phase function can be used in the case of suspensions with large suspended particles. The fitting accuracy of OTHG is the worst, FF is better and TTHG is the best.

Single Photon Scattering Properties in Coupled-Resonator Waveguide Coupling with a Nanocavity Interacting with an External Mirror

We investigate theoretically single photon transport properties in coupled-resonator waveguide coupling with a nanocavity interacting with an external mirror. By using the discrete coordinates approach, transmission and reflection amplitudes of the propagating single photon in the waveguide are obtained. The influence of the coupling strength between the nanocavity and the external mirror on the single photon scattering spectra is discussed. We also extend the results to the waveguide with linear and quadratic form dispersion relations.

Feature analysis of LIDAR waveforms from forest canopies

Airborne light detection and ranging (LIDAR) can detect the three-dimensional structure of forest canopies by transmitting laser pulses and receiving returned waveforms which contain backscatter from branches and leaves at different heights.We established a solid scatterer model to explain the widened durations found in analyzing the relationship between laser pulses and forest canopies,and obtained the corresponding rule between laser pulse duration and scatterer depth.Based on returned waveform characteristics,scatterers were classified into three types:simple,solid and complex.We developed single-peak derivative and multiple-peak derivative analysis methods to retrieve waveform features and discriminate between scatterer types.Solid scatterer simulations showed that the returned waveforms were widened as scatterer depth increased,and as space between sub-scatterers increased the returned waveforms developed two peaks which subsequently developed into two separate sub-waveforms.There were slight differences between the durations of simulated and measured waveforms.LIDAR waveform data are able to describe the backscatter characteristics of forest canopies,and have potential to improve the estimation accuracy of forest parameters.