在特定情况下电流表并联使用更合理

通常电流表是串联在电路中使用的,但是,在设计性实验的特定情况下,电流表也可以并联在电路中使用.而且,有时并联在电路中使用才更符合实验的合理性、便利性、精确性和安全性的基本原则.     

多增益段串接的液体激光系统特性研究

液体激光系统在抑制热畸变方面具有突出优势,能实现长时间稳定的高能激光输出.在液体激光系统中,常规双侧抽运的激光增益分布呈现边缘很强、中间较弱的特点,难以获得单横模激光输出,限制了光束质量.介绍了一种多增益段串接的液体激光系统,其抽运方式介于侧面抽运和端面抽运之间,然后对其增益分布和激光能量传输效率进行了数值模拟.数值模拟表明多增益段串接的液体激光系统能产生近似于高斯型增益分布,激光光束质量很高;同时该多增益段串接的液体激光系统的腔内传输损耗较小,激光能量转换效率可达30%以上.     

Persistent Currents in the Double Aharonov-Bohm Ring Connected to Electron Reservoirs

We study persistent currents in the double Aharonov-Bohm ring connected to two electron reservoirs by quantum waveguide theory. It is found that the persistent currents in the double Aharonov-Bohm ring depend on the direction of the current flow from one reservoir to another. When the direction of the current flow reverses, the persistent current in each ring of the double Aharonov-Bohm ring changes. If the two rings are of the same size, the persistent currents in the left and the right rings exchange at the reversal of the current flow direction.     

测望远镜光瞳计算其放大率

提出了测量望远镜光瞳来求望远镜放大率的新方法,该方法原理易懂,人为因素影响小,操作简单,且能对成品、不易拆分的望远镜进行测量．     

A Multi-Method Survey on the Use of Sentiment Analysis in Multivariate Financial Time Series Forecasting

In practice, time series forecasting involves the creation of models that generalize data from past values and produce future predictions. Moreover, regarding financial time series forecasting, it can be assumed that the procedure involves phenomena partly shaped by the social environment. Thus, the present work is concerned with the study of the use of sentiment analysis methods in data extracted from social networks and their utilization in multivariate prediction architectures that involve financial data. Through an extensive experimental process, 22 different input setups using such extracted information were tested, over a total of 16 different datasets, under the schemes of 27 different algorithms. The comparisons were structured under two case studies. The first concerns possible improvements in the performance of the forecasts in light of the use of sentiment analysis systems in time series forecasting. The second, having as a framework all the possible versions of the above configuration, concerns the selection of the methods that perform best. The results, as presented by various illustrations, indicate, on the one hand, the conditional improvement of predictability after the use of specific sentiment setups in long-term forecasts and, on the other, a universal predominance of long short-term memory architectures.     

Series solution to the laser-ion interaction in a Raman-type configuration

The Raman interaction of a ultracold ion trapped with two travelling wave lasers is studied analytically with series solutions, in the absence of the rotating wave approximation (RWA) and without restrictions of both the Lamb-Dicke limit and the weak excitation regime. The comparison is made between our solutions and those obtained under the RWA in order to demonstrate the validity region of the RWA. As a practical example, the preparation of Schr?dinger-cat states is proposed beyond the weak excitation regime, using our calculations. Received 12 March 2001 and Received in final form 16 October 2001     

A Novel Series Solution to the Renormalization-Group Equation in QCD

Recently, the QCD renormalization-group (RG) equation at higher orders in MS-like renormalization schemes has been solved for the running coupling as a series expansion in powers of the exact two-loop-order coupling. In this work, we prove that the power series converge to all orders in perturbation theory. Solving the RG equation at higher orders, we determine the running coupling as an implicit function of the two-loop-order running coupling. Then we analyze the singularity structure of the higher-order coupling in the complex two-loop coupling plane. This enables us to calculate the radii of convergence of the series solutions at the three- and four-loop orders as a function of the number of quark flavours n _f . In parallel, we discuss in some detail the singularity structure of the coupling at the three- and four-loops in the complex-momentum squared plane for 0 ≤ n _f ≤ 16. The correspondence between the singularity structure of the running coupling in the complex-momentum squared plane and the convergence radius of the series solution is established. For sufficiently large n _f values, we find that the series converges for all values of the momentum-squared variable Q ² = −q ² > 0. For lower values of n _f , in the scheme, we determine the minimal value of the momentum-squared Q _min ² above which the series converges. We study properties of the non-power series corresponding to the presented power-series solution in the QCD analytic perturbation-theory approach of Shirkov and Solovtsov. The Euclidean and Minkowskian versions of the non-power series are found to be uniformly convergent over the whole ranges of the corresponding momentum-squared variables.     

Efficiency of Mode Excitation in an Open Resonator Connected to a Waveguide

Based on an analysis of the equivalent circuit of a reflection open resonator (OR), we derive an expression for the efficiency of mode excitation in such a resonance system and compare the efficiency of excitation of the lowest OR mode by aperture and slot couplers. It is shown that the excitation efficiency of the same mode by each of the considered couplers is high for small diffraction losses and amounts to no less than 95%. To excite an OR with a large distance between the mirrors, it is expedient to use an aperture coupler ensuring a higher efficiency of excitation of the studied mode.