西安市主城区夜间光污染现状调查研究

为了探寻西安市区在夜景照明及其他因素影响下的光污染现状，笔者随机对西安市区的夜天空进行了多地点、多方位的现场观测，主要对大气光污染，眩光和光侵入三种主要光污染形式进行了调查，并分析了大气光污染形成的主要原因。期望此次研究能为西安市相关部门今后制定夜间照明规划和相关法律法规立项等提供一定的参考和借鉴。

Ecological adaptation of Eupatorium adenophorum populations to light intensity

Eupatorium adenophorum is one of main invasive plants in China and has caused great economic losses. A study was conducted to determine the biomass allocation, leaf morphology and growth response of E. adenophorum seedlings that grew under five different intensities （relative irradiances RI 10%, 20 %, 30%, 55%, 100%） for 14 months. Results reveal that the species shows typical leaf morphological adaptation to different light conditions. The total biomass of seedlings increased with the increase of light intensity from 10% to 55% RI but decreased at RI 100% （full sunlight）. Height growth increased with the increase of light intensity from 10% to 30% RI but decreased when light intensity was over 30% RI. At low light levels, plants enhanced light availability by means of increasing biomass allocation to leaves and formation of larger, thinner leaves with high specific leaf area （SLA）, leading to a high leaf area ratio （LAR） and high stem strips length （SSL）. The mean relative growth rate （RGR） of the plant increased with the light intensity increase and attained the maximum at 55% RI. The growth of seedlings at 30%-55% RI was much better than that at full light condition. This might be an adaptive strategy that supports the vigorous invasiveness of this species, because a high-shaded canopy could prevent other plant species from surviving and growing. This study indicates that E. adenophorum could adapt to different light conditions, especially to low light habit. This can explain its greater invasiveness.

Photosynthetic Carbon Gain, Allocation and Resources-Use Efficiency in Invasive Eupatorium Adenophorum and Its Native Congener E. Japonicum under Different Light and Nutrient Conditions

Invasion is often facilitated by high resources availabilities and suppressed under low resources habitats. However, a number of invasive plants can successfully establish and dominate in resource-poor and （or） the understory of closed forests, indicating the plant＇s performances are habitats-dependent and species-specific. It is therefore necessary to explore the ecophysiological characteristics associated invasiveness for one invasive species across multiple resources availabilities whilst taking the relatedness into these comparative studies. In this study, invasive Eupitorium adenophorum and its native congener E. japonicum grew under different resource gradients in terms of light levels and soil nitrogen additions to identify the functional significance morphological and physiological traits associated closely with invasion and to examine their comparative responses. Photosynthetic carbon gain, biomass allocation and resource-use efficiency are evaluated in this pot experiment. Across treatments, E. adenophorum exhibited consistently higher values for most of the morphological variables including plant stature, relative growth rate （RGR）, leaf root ratio （LRR）, leaf area ratio （LAR）, total leaf area, and lower root： shoot ratio （RSR）. Significantly higher Pmax corresponded with higher photosynthetic nitrogen use efficiency （PNUE） and photosynthetic energy use efficiency （PEUE） especially in low light and （or） unfertile condition. Higher Gs and Pmax but lower photosynthetic water use efficiency （WUE） indicated the trade-off relationship between WUE and PNUE for E. adenophorum. Final biomasses were higher for E. adenophorum in nutrient and（or） light limited conditions, in which higher leaf construction cost（CC） compared with E. japonicum could be over-compensated by its significantly higher assimilation rates. The effects of light levels on these plant attributes were stronger than soil nutrient contents. The responses of these two congeneric species to light and nitrogen availabilities were similar, but the differences were magnified in resources limited conditions, indicating the better performancer at acquiring and at using limited resources of E. adenophorum over its co-occurring native flora. Our study presented the distinctive advantages of E. adenophorum in resources-poor environments, indicating conventional strategy of managing resources levels to control the invasion and expending of exotic species may not be as effective as expected.

Investigation of non-premixed flame combustion characters in GO_2/GH_2 shear coaxial injectors using non-intrusive optical diagnostics

Single-element combustor experiments are conducted for three shear coaxial geometry configuration injectors by using gaseous oxygen and gaseous hydrogen(GO2/GH2) as propellants. During the combustion process, several spatially and time- resolved non-intrusive optical techniques, such as OH planar laser induced fluorescence(PLIF), high speed imaging, and infrared imaging, are simultaneously employed to observe the OH radical concentration distribution, flame fluctuations, and temperature fields. The results demonstrate that the turbulent flow phenomenon of non-premixed flame exhibits a remarkable periodicity, and the mixing ratio becomes a crucial factor to influence the combustion flame length. The high speed and infrared images have a consistent temperature field trend. As for the OH-PLIF images, an intuitionistic local flame structure is revealed by single-shot instantaneous images. Furthermore, the means and standard deviations of OH radical intensity are acquired to provide statistical information regarding the flame, which may be helpful for validation of numerical simulations in future. Parameters of structure configurations, such as impinging angle and oxygen post thickness, play an important role in the reaction zone distribution. Based on a successful flame contour extraction method assembled with non-linear anisotropic diffusive filtering and variational level-set, it is possible to implement a fractal analysis to describe the fractal characteristics of the non-premixed flame contour. As a result, the flame front cannot be regarded as a fractal object. However, this turbulent process presents a self-similarity characteristic.

Research on Optical Fiber Flow Test Method With Non-Intrusion

In the field of oil well logging, real-time monitoring of the fluid flow parameter provides a scientific basis for oil and gas optimization exploration and increase in reservoir recovery, so a non-intrusive flow test method based on turbulent vibration was proposed. The specific length of the sensor fiber wound tightly around the outer wall of the pipe was connected with the optical fiber gratings at both ends, and the sensor fiber and the optical fiber gratings composed the flow sensing unit. The dynamic pressure was generated by the turbulence when fluid flows through the pipe, and the dynamic pressure resulted in the light phase shift of the sensor fiber. The phase information was demodulated by the fiber optic interferometer technology, time division multiplexing technology, and phase generated carrier modulation and demodulation techniques. The quadratic curve relationship between the phase change and flow rate was found by experimental data analysis, and the experiment confirmed the feasibility of the optical fiber flow test method with non-intrusion and achieved the real-time monitoring of the fluid flow.

Non-invasive human extremely weak pulse wave measurement based on a high-precision laser self-mixing interferometer

In this paper, a technique based on laser self-mixing effect for acquiring pulse wave profile is proposed and demonstrated. For the characteristics of extremely weak vibration in human pulse waves, a method of multiple reflections with external cavity is designed to improve the measurement accuracy to λ/4. Based on the fringe counting algorithm, one period of pulse wave is successfully reconstructed. The measurement results show that the root mean square error(RMSE) of the reconstructed pulse wave is 0.912 μm at sampling rate of 8 k Hz. Besides, the correlation coefficients and heart beats of this method and the traditional photoplethysmography(PPG) measurement are analyzed.