Study on the characteristics of erbium-doped waveguide ring laser

A theoretical model of the erbium-doped waveguide ring laser is established according to the theory of erbium-doped waveguide amplifier and the transmission matrix of waveguide directional coupler. The influence of bend radius, coupling coefficient and doped erbium ion concentration on the characteristics of waveguide ring laser is investigated. It is shown that due to the co-action of waveguide bend loss and other relevant loss there is an optimal bend radius which can provide simultaneously low threshold pumping power and high laser light output power. As one part of the resonator’s loss, the laser light coupling coefficient of directional coupler has an impact on the laser property. The analysis indicates that the laser achieves the high output power when the coupling coefficient is about 0.2. The threshold pumping power is the minimum when the doped erbium ion concentration is 0.85×10²⁶ m⁻³. Increasing the concentration of doped erbium ions will enhance the output power of laser light as long as the concentration doesn’t introduce remarkable up-conversion effect. The results give a good theoretical basis for the design and fabrication of erbium-doped waveguide ring laser devices. Supported by the National Natural Science Foundation of China (Grant No. 60807015), the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 200801411037), the Young Teacher Cultivation Foundation of Dalian University of Technology (Grant No. 893210) and Doctor Start-up Foundation of Dalian University of Technology (Grant No. 893322)     

A fast and adaptive method for complex-valued SAR image denoising based on l_k norm regularization

This paper developed a fast and adaptive method for SAR complex image denoising based on lk norm regularization, as viewed from parameters estimation. We firstly establish the relationship between denoising model and ill-posed inverse problem via convex half-quadratic regularization, and compare the difference between the estimator variance obtained from the iterative formula and biased Cramer-Rao bound, which proves the theoretic flaw of the existent methods of parameter selection. Then, the analytic expre...     

Study on the protection of Er-doped phosphate glass waveguide surface in ion-exchange processing

A novel method, sputtering K9 glass film, is proposed to solve the surface corrosion of Er-doped phosphate glass during ion-exchange processing for optical waveguide fabrication. The corrosion causes are analyzed to be the intrinsically weak stabilization of phosphate glass structure, hydrophile and weakly acidic property of phosphate radical. Experimental results show that the K9 glass film could not only protect the Er-doped phosphate glass surface from being corroded but also give no influence on the waveguide fabrication. The effect of thickness of K9 glass film on the optical property of waveguide is also investigated and the optimal thickness is found to be 60–80 nm. It provides a good base for further fabrication of active phosphate glass optical waveguide devices. Supported by the Optical Science and Technology Foundation of Shanghai Technology Committee (Grant No. 022261009), the Young Teacher Cultivation Foundation of Dalian University of Technology (Grant No. 893210), and the Doctor Startup Foundation of Dalian University of Technology (Grant No. 893322)     

Experimental study of a micro-scale solar organic Rankine cycle system based on compound cylindrical Fresnel lens solar concentrator

In the present study, a micro-scale solar organic Rankine cycle power generation system was developed. The system comprises of a solar collection system based on compound cylindrical Fresnel lens concentrator and an organic Rankine cycle power generation system integrated with a scroll expander. YD320 and R245 fa were used as the heat transfer fluid and the working fluid, respectively. The effects of the evaporation pressure, the degree of superheat, and the mass flow rate of the working fluid were analyzed to evaluate the solar collection efficiency, the electric power output, the thermal efficiency and exergy efficiency of the system. The results illustrate that both the increasing evaporation pressure and decreasing superheat degree have positive impacts on solar collection efficiency. The electric power increases as the evaporation pressure increases, while the thermal efficiency and the exergy efficiency decrease. However, the system overall efficiency decreases slowly due to the increase of solar collection efficiency. The electric power increases with the increment of the working fluid mass flow rate. The increasing mass flow rate has no visible impact on the thermal and exergy efficiencies of organic Rankine cycle subsystem, whereas a slightly increase of the thermal and exergy efficiencies of the integrated system. The electric power decreases with the increase of the superheat degree, whereas the thermal and the exergy efficiencies of the system increase. The system works more suitably with a higher degree of superheat for the small mass flow rate condition.     

轻质焦油洗萘新工艺

莱钢焦化厂采用轻质焦油洗萘新工艺，将从煤气初冷器来的冷凝液，沉淀分离后得到的轻质焦油，用以洗涤煤气中的萘，消除了洗氨塔堵塞问题，保证了化产回收工序的正常运行，萘的净化效率由50％～60％提高到70％。     

Phase noise floor suppression of the output carrier from double sideband-carrier suppressed modulation system

A theoretical model of all the influencing factors on the phase noise floor of the output carrier from the double sideband-carrier suppressed (DSB-CS) modulation system is presented. Based on the established DSB-CS modulation system with different cases, the phase noise of the input carrier and the output doubled frequency carrier is measured and calculated using the theoretical model, respectively. The calculation results basically agree with the measurement results. It is shown that the phase noise floor ...     

A fast and adaptive method for complex-valued SAR image denoising based on <Emphasis Type="Italic">l</Emphasis><Subscript><Emphasis Type="Italic">k</Emphasis></Subscript> norm regularization

This paper developed a fast and adaptive method for SAR complex image denoising based on l _k norm regularization, as viewed from parameters estimation. We firstly establish the relationship between denoising model and ill-posed inverse problem via convex half-quadratic regularization, and compare the difference between the estimator variance obtained from the iterative formula and biased Cramer-Rao bound, which proves the theoretic flaw of the existent methods of parameter selection. Then, the analytic expression of the model solution as the function with respect to the regularization parameter is obtained. On this basis, we study the method for selecting the regularization parameter through minimizing mean-square error of estimators and obtain the final analytic expression, which resulted in the direct calculation, high processing speed, and adaptability. Finally, the effect of regularization parameter selection on the resolution of point targets is analyzed. The experiment results of simulation and real complex-valued SAR images illustrate the validity of the proposed method. Supported by the National Natural Science Foundation of China (Grant No. 60572136), the Fundamental Research Fund of NUDT (Grant No. JC0702005)     

山西河东煤田明珠一号煤层对比的研究方法

山西省河东煤田明珠一号普查区含煤地层主要为山西组和太原组,共含煤14层,主要可采煤层为2煤、9煤和10煤,因此煤层对比非常重要,煤层对比必须在正确地层对比的前提下进行,对比的依据、方法主要为标志层对比、地层组合特征对比、煤层自身特征对比、物性特征对比和综合对比,另外煤层对比的可靠性评价也是对比工作的重要内容。     

Flow characteristics of tangential leakage in a scroll compressor for automobile heat pump with CO2

Tangential leakage loss reduction has great significance on improving the performance of scroll compressors. In this study, the flow field of a scroll compressor working with CO_2 was numerically investigated. The development characteristics of the tangential leakage flow in different working chambers were carried out, which was obtained by analyzing the field quantities distributions. The impacts of the radial clearances and sidewall roughness on the tangential leakage were also taken into consideration, in order to explore the feasible method of the flow control for the tangential leakage in scroll compressors. Results showed that the tangential leakage flow had various characteristics in the suction and compression chambers due to the different interactions between the tangential leakage flow and mainstream. Owing to little reverse pressure gradient, the tangential leakage flow maintained the typical jet form in the suction chambers. By contrast, the mixing of the tangential leakage flow and mainstream induced the passage vortex and secondary flows in the compression chamber. The secondary flow was the primary factor that results in the occurrence of localized high temperature region rather than the tangential leakage. With the increase of the radial clearance, the volumetric efficiency declined and the discharge temperature increased rapidly. In terms of flow control of the tangential leakage, the increase of sidewall roughness by 2 μm could achieve the same effect as the decrease of the radial clearance by 4 μm, while the volumetric efficiency increased by almost 5% and average discharge temperature decreased by 5K.