A SIMPLE TECHNIQUE FOR ESTIMATING ABSORPTION AND SCATTERING COEFFICIENTS1

ABSTRACT: Results from five different test systems, which include a wide range of optical conditions, indicate credible estimates of the values of the absorption and scattering coefficients can be calculated from paired measurements of Secchi disc transparency and the diffuse attenuation coefficient. The diagnostic utility of the estimates in identifying components and processes that regulate light penetration is demonstrated for three different cases. The simple estimation technique is valuable in the analysis of existing data bases that lack comprehensive optical information to develop and evaluate alternate models for light penetration and to establish the experimental needs of future field programs to support lake management efforts.     

板材激光弯曲成形数值模拟的研究现状及展望

板材的激光弯曲成形是一种利用高能激光束扫描金属板材表面产生非均匀分布的热应力 ,从而使板材发生塑性变形的金属板材柔性成形新工艺。数值模拟已逐渐成为板材激光弯曲成形研究中的热点内容。综述了近年来国内外对激光弯曲成形过程的温度场及变形场进行数值模拟的研究现状 ,并对其应用范围和发展前景作了展望     

B级钢侧架圆角细节耐久性力学模型研究

根据Paris公式推导出适用于B级钢圆角细节耐久性分析的 ,在一定裂纹尺寸范围内的裂纹扩展速率公式及其检验方法 ,笔者模拟货车B级钢转 8A侧架的导框弯角内侧 (A区 )的圆角细部进行耐久性实验 ;以试验数据的检验证明 ,在 0 .4～ 4mm的尺寸范围内 ,选用的断裂力学模型是合理的 ;同时为建立合理的检修周期和寿命体系提供理论模型和安全评价基础。     

激光传输在环境监控中的应用设计

对将激光通信技术在环境监控中的应用进行了研究,探讨了大气环境下数据传输的信号调制方式以及提高通信距离和减少系统噪声的方法,设计了可用于环境监控数据传输的激光传输系统实用电路.经安装、调试、运行,结果表明,该妹系统在视距通信条件下应用,具有电路制作简单、设备架设灵活方便、数据传输性能稳定和传输系统成本低廉等优点.     

水相中羟基自由基诱导二甲基硫氧化的研究

用激光闪光光解技术研究了水相中二甲基硫(DMS)与羟基自由基(·OH)的反应机理,并讨论了溶液pH值和O2对该反应的影响,进而比较了气液相DMS与·OH反应的不同,初步评估了由·OH氧化引起的海洋和大气液相中DMS的寿命.结果表明:在pH 6-9时, ·OH会与DMS反应生成·DMSOH, ·DMSOH在水相中继续与DMS反应生成(DMS) 2, (DMS) 2与氧气的反应速度很慢,其衰减受pH影响较大.     

A remote sensing system of vehicle emissions based on tunable diode laser technology

As being an effective real-time method of monitoring vehicle emissions on-road, a remote sensing system based on the tunable diode laser （TDL） technology was presented, and the key technologies were discussed. A field test in Guangzhou（Guangdong, China） was performed and was found that the factors, such as slope, instantaneous speed and acceleration, had significant influence on the detectable rate of the system. Based on the results, the proposal choice of testing site was presented.     

Airborne Dust Particle Counting Techniques

The paper briefly describes an electro-optical system for counting of dust particles, which is based on the scattering phenomena.Utilizing the scattering of light by various size particles present in the environment, various particle counting techniques have been developed in order to measure the scattered intensity of light. Light scatters in all directions but much more in the so-called near forward direction 17^∘ off axis, at 163^∘ from the light source in the visible range.On the basis of two techniques, the right angle and forward angle scattering, opto-mechanical systems have been developed which measure scattered intensity and particulate matter. The forward scattering Nephelometer is more sensitive and therefore is more suitable for pollution monitoring than the right angle scattering Nephelometer. Whereas the right angle scattering Nephelometer has the utility in extremely low concentration in ppb level owing to the excellent light trap efficiency in comparison to forward scattering Nephelometer. In this paper measurement techniques and measurement results associated with design and development of a real time particle analyser are also discussed.     

起重机主梁变形三维激光扫描检测技术研究

在役起重机主梁变形是导致起重机事故发生的重要因素之一.国内现阶段对于起重机主梁变形检测还停留在传统的检测方法.其检测低效率、实施高风险、结果多误差等因素使传统检测方法暴露出诸多弊端.文章通过对比验证,引入三维激光扫描检测方法,对起重机主梁腹板进行扫描并建模分析得出主梁腹板整体变形的结果,此方法可以提高腹板变形检测数据精...     

Decadal and Episodic Changes in Morphology and Migration of the Confluence Bar of Two Alluvial Rivers in Louisiana,USA

Past research on fluvial dynamics at the confluence of two alluvial rivers has mainly focused on downstream flow structure and bed scoring, often using laboratory experiments and numerical modeling. Little is investigated about yearly and episodic dynamics of confluence mouth bars that can affect downstream morphology using field measurements. In this study, we analyzed the migration of a confluence mouth bar of two free meandering alluvial rivers, the Amite and Comite Rivers in coastal Louisiana, USA from 2002 to 2017. Remote sensing images were utilized to investigate the decade‐long morphologic changes. To assess episodic dynamics, we employed terrestrial laser scanning measurements to acquire high‐accuracy digital elevation models at the confluence before and after three floods in 2017. Our study found that the Amite‐Comite confluence mouth bar migrated downstream 55 m in the past 15 years, and its angle reduced by 55° from 100° to 45°. The fast migration was a result of sediment deposition and channel deformation around the confluence mainly during the years when the tributary‐to‐main channel discharge was lower (<0.25). The study further reveals that a single moderate flood could strongly affect the mouth bar, as shown by an increase of the projected surface area by 114% and an increase of volume of the confluence mouth bar by 68%.     

Multi-group approximation, scattering and calibration coefficients, uncertainty estimates and detection limits of a NaI(Tl)-based gamma spectrometry set-up for low-level activity analysis

This paper describes a quantitative radioactivity analysis method especially suitable for environmental samples with low-level activity. The method, consisting of a multi-group approximation based on total absorption and Compton spectra of gamma rays, is coherently formalized and a computer algorithm thereof designed to analyze low-level activity NaI(Tl) gamma ray spectra of environmental samples. Milk powder from 1988 was used as the example case. Included is a special analysis on the uncertainty estimation. Gamma sensitiveness is defined and numerically evaluated. The results reproduced the calibration data well, attesting to the reliability of the method. The special analysis shows that the uncertainty of the assessed activity is tied to that of the calibration activity data. More than 77% of measured 1461-keV photons of ⁴⁰K were counted in the range of clearly lower energies. Pile-up of single line photons (¹³⁷Cs) looks negligible compared to that of a two-line cascade (¹³⁴Cs). The detection limit varies with radionuclide and spectrum region and is related to the gamma sensitiveness of the detection system. The best detection limit always lies in a spectrum region holding a line of the radionuclide and the highest sensitiveness. The most radioactive milk powder sample showed a activity concentration of 21 ± 1 Bq g⁻¹for ¹³⁷Cs, 323 ± 13 Bq g⁻¹ for ⁴⁰K and no ¹³⁴Cs.