Analysis and simulation of incident photon to current efficiency in dye sensitized solar cells

Conversion of solar energy into electricity is a challenging issue of today’s renewable energy. Electrochemical dye solar cells (DSC), based on nanostructured TiO₂ particles are a very promising class of photovoltaic devices [6]. The mechanism beyond the conversion of the light is quite different from any other solid state solar cell, resulting from the interplay of a fine tuning of the energy levels of the cell components and a delicate fabrication process. This complexity needs a reliable transport model, able to catch the device as a whole and applicable to experimental set up. We developed an extension of TiberCAD [7] code to simulate such kind of devices and compared the calculation with incident photon to current efficiency (IPCE) measurements.     

Hölder estimates for fractional parabolic equations with critical divergence free drifts

This work focuses on drift-diffusion equations with fractional dissipation ${(?\mathrm{\Delta })}^{\alpha }$ in the regime $\alpha \in (1/2,1)$. Our main result is an a priori Hölder estimate on smooth solutions to the Cauchy problem, starting from initial data with finite energy. We prove that for some $\beta \in (0,1)$, the $C^{\beta }$ norm of the solution depends only on the size of the drift in critical spaces of the form $L_t^q({\mathrm{BMO}}_x^{?\gamma })$ with $q>2$ and $\gamma \in (0,2\alpha ?1]$, along with the $L_x^2$ norm of the initial datum. The proof uses the Caffarelli/Vasseur variant of De Giorgi's method for non-local equations.     

On finite long run costs and rewards in infinite Markov chains

Conditions for the finiteness of long run costs and rewards associated with infinite recurrent Markov chains that may be discrete or continuous in time are considered. Without resorting to results from the theory of Markov processes on general state spaces we provide instructive proofs in the course of which we derive auxiliary results that are of interest in themselves. Potential applications of the finiteness conditions are outlined in order to elucidate their high practical relevance.     

Target detection for low cost uncooled MWIR cameras based on empirical mode decomposition

In this work, a novel method for detecting low intensity fast moving objects with low cost Medium Wavelength Infrared (MWIR) cameras is proposed. The method is based on background subtraction in a video sequence obtained with a low density Focal Plane Array (FPA) of the newly available uncooled lead selenide (PbSe) detectors. Thermal instability along with the lack of specific electronics and mechanical devices for canceling the effect of distortion make background image identification very difficult. As a result, the identification of targets is performed in low signal to noise ratio (SNR) conditions, which may considerably restrict the sensitivity of the detection algorithm. These problems are addressed in this work by means of a new technique based on the empirical mode decomposition, which accomplishes drift estimation and target detection. Given that background estimation is the most important stage for detecting, a previous denoising step enabling a better drift estimation is designed. Comparisons are conducted against a denoising technique based on the wavelet transform and also with traditional drift estimation methods such as Kalman filtering and running average. The results reported by the simulations show that the proposed scheme has superior performance.     

非晶硒合金膜载流子特性研究

在X射线医学成象和无损检测方面,非晶硒现在被认为是最有前途的探测材料之一,其我流子特性对应用至关重要。本文描述了非晶硒(掺砷)合金材料的制备和合金膜的真空蒸镀制备方法,并用滚越时间方法测量了载流于的漂移迁移率和寿命。讨论了一些对非晶硒合金膜性能有重要影响的因素。实验表明,制备方法对非晶硒合金膜的性能有显着影响。可以看到,在低电场下被陷讲捕获的我流子形成的空间电荷对测量我流永寿命和对光的敏感度有很大影响.实验得到了良好的结果,在10v/μm场强下,空穴迁移长度约1500μm,电子迁移长度约1200μm.该结果表明,可以用几百微米厚的非晶硒合金膜作为X射线探测或成象的光电导接受器。     

Experiment and modeling of exit-selecting behaviors during a building evacuation

The evacuation process in a teaching building with two neighboring exits is investigated by means of experiment and modeling. The basic parameters such as flow, density and velocity of pedestrians in the exit area are measured. The exit-selecting phenomenon in the experiment is analyzed, and it is found that pedestrians prefer selecting the closer exit even though the other exit is only a little far. In order to understand the phenomenon, we reproduce the experiment process with a modified biased random walk model, in which the preference of closer exit is achieved using the drift direction and the drift force. Our simulation results afford a calibrated value of the drift force, especially when it is 0.56, there is good agreement between the simulation results and the experimental results on the number of pedestrians selecting the closer exit, the average velocity through the exits, the cumulative distribution of the instantaneous velocity and the fundamental diagram of the flow through exits. According to the further simulation results, it is found that pedestrians tend to select the exit with shorter distance to them, especially when the people density is small or medium. But if the density is large enough, the flow rates of the two exits will become comparable because of the detour behaviors. It reflects the fact that a crowd of people may not be rational to optimize the usage of multi-exits, especially in an emergency.     

激光多面体旋转扫描测试系统入瞳漂移的研究

在近代激光测试技术中多面体旋转反射扫描测试系统存在入瞳漂移的问题,带来测试误差,然而经典资料中均未作讨论.本文在理论上推导了激光扫描测试系统中的入瞳漂移,详尽讨论了八面体旋转反射扫描测试系统的入瞳漂移问题,并且分析了旋转半径及入射角与入瞳漂移的关系,得出精确的结论.实际应用中如何根据精度要求设计旋转反射镜、如何选择入射角、f-θ物镜设计中如何考虑入瞳漂移的影响均可利用这一结论.     

漂移管道中再电离损失实验

本文给出了无杂散磁场时,高能中性束经漂移管道传输途中再电离损失率的实验结果与理论值,并对有杂散磁场时的再电离率作了相应的计算。在本底气压为1.33×10~(-2)Pa情况下,能量在10—25keV范围内,测得损失率为3.3％～5.2％。     

托卡马克装置磁轴附近的低频漂移波稳定性计算

一、基本方程和定解条件 为了研究低频漂移波不稳定性,文[1]给出了无量纲化的本征摸方程     

Working principles,behavior, and performance of MOEAs on MNK-landscapes

This work studies the working principles, behavior, and performance of multiobjective evolutionary algorithms (MOEAs) on multiobjective epistatic fitness functions with discrete binary search spaces by using MNK-landscapes. First, we analyze the structure and some of the properties of MNK-landscapes under a multiobjective perspective by using enumeration on small landscapes. Then, we focus on the performance and behavior of MOEAs on large landscapes. We organize our study around selection, drift, mutation, and recombination, the four major and intertwined processes that drive adaptive evolution over fitness landscapes. This work clearly shows pros and cons of the main features of MOEAs, gives a valuable guide for the practitioner on how to set up his/her algorithm, enhance MOEAs, and presents useful insights on how to design more robust and efficient MOEAs.