Low bandgap carbazole copolymers containing an electron-withdrawing side chain for solar cell applications

A new series of low bandgap carbazole copolymers containing an electron-withdrawing moiety as a side chain, via Suzuki, Yamamoto, and Stille polymerization reactions has been synthesized. Their bandgaps and molecular energy levels can be tuned by copolymerizing with different conjugated electron-donating units. The resulting copolymers have low optical and electrochemical bandgaps. The optical bandgaps of the copolymers range from 1.79 to 1.24 eV. In order to investigate their photovoltaic properties, polymer solar cell devices based on low bandgap copolymers were fabricated with a structure of ITO/PEDOT:PSS/copolymers:PCBM/Al, under the illumination of AM 1.5 G, 100 mW/cm². The power conversion efficiencies (PCE) of the polymer solar cells based on these low bandgap copolymers were measured. The best performance was obtained by using PC-CARB as the electron donor and 6,6-phenyl C₇₁-butyric acid methyl ester (PC₇₁BM) as the electron acceptor. The PCE of the solar cell based on PC-CARB/P₇₁CBM (1:4) was 1.27% with an open-circuit voltage (V_oc) of 0.65 V, and a short-circuit current (J_sc) of 6.69 mA/cm².     

Distorted symptom perception in patients with medically unexplained symptoms.

The present study investigated differences in symptom perception between a clinical sample with medically unexplained symptoms (MUS) and a matched healthy control group. Participants (N = 58, 29 patients) were told that they would inhale different gas mixtures that might induce symptoms. Next, they went through 2 subsequent rebreathing trials consisting of a baseline (60 s room air breathing), a rebreathing phase (150 s, which gradually increased ventilation, PCO2 in the blood, and perceived dyspnea), and a recovery phase (150 s, returning to room air breathing). Breathing behavior was continuously monitored, and dyspnea was rated every 10 s. The within-subject correlations between dyspnea on the one hand and end-tidal CO2 and minute ventilation on the other were used to index the degree to which perceived dyspnea was related to specific relevant respiratory changes. The results showed that perceived symptoms were less strongly related to relevant physiological parameters in MUS patients than in healthy persons, specifically when afferent physiological input was relatively weak. This suggests a stronger role for top-down psychological processes in the symptom perception of patients with MUS. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Norms and screening utility of the Dutch version of the Children's Depression Inventory in clinical and nonclinical youths.

This study aimed to (a) assess relationships between the Children's Depression Inventory (CDI) and DSM-oriented depression and anxiety scales of the Youth Self Report, (b) develop reliable norms for the CDI, and (c) determine CDI cutoff scores for selecting youngsters at risk for depression and anxiety. A total of 3,073 nonclinical and 511 clinically referred children and adolescents from The Netherlands and Belgium were included. Results showed that CDI scores were significantly related to DSM-oriented symptoms of both depression and anxiety. CDI scores correlated highly with depression symptoms and moderately with anxiety symptoms. Norms for the CDI were determined by means of multiple regression analysis and depended on sex, age, and country. CDI cutoff scores for selecting individuals at risk for depression and anxiety as measured by the DSM-oriented depression and anxiety scales of the Youth Self Report were determined by means of multiple regression analysis and receiver operating characteristic analysis. A CDI score of 16 was found to have the most optimal balance between sensitivity and specificity for depression, whereas a score of 21 provided the best sensitivity and specificity for anxiety in a subsample of children. We conclude that the CDI is an effective instrument for screening depression and to a lesser extent anxiety in primary and secondary care centers, before applying further assessment of high-risk individuals. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Implementing Fourier algorithm by linear modulation method for distance relaying application

Abstract

The Fourier algorithm, due to its good frequency response characteristics, is frequently used in calculating the peak value of a distorted wave for real time measuring applications. A new method, using the linear modulation method, is proposed to implement the algorithm. It improves the defect of a large number of arithmatic operations during implementation of the algorithm. This paper describes the structure and theory of the proposed linear modulated Fourier algorithm. Test results, including the required arithmatic operations and the numerical accuracy, are reported. Moreover, application to the digital impedance relay was simulated, and the simulation results show that the proposed algorithm is suitable for relaying applications.     

Delay‐dependent H∞ observer‐based control for uncertain neutral systems via LMI optimization approach

Abstract

In this paper, the delay‐dependent H∞ observer‐based control for a class of uncertain neutral systems with time‐varying delays is considered. The linear matrix inequality (LMI) optimization approach is used to design the H∞ robust control with disturbance attenuation. The control and observer gains are given from the LMI feasible solutions. Some numerical examples are given to illustrate the use of the main result.     

Stability criteria for neutral systems with time‐varying delays and nonlinear uncertainties

Abstract

The asymptotic stability problem for a class of neutral systems with time‐varying delays and nonlinear uncertainties is investigated in this paper. LMI‐based delay‐dependent criteria are proposed to guarantee the asymptotic stability of the considered systems. New Lyapunov‐Krasovskii functional and Leibniz‐Newton formulae are used to find the delay‐dependent stability results. Finally, some numerical examples are illustrated to show the improved results from using this method.     

An approach to the implementation and verification of abstract data

Abstract

The concept of abstraction can be used to simplify and formalize the design of software. However, most of the existing techniques based on abstraction only consider the control structure but not the data structures in the software. The transformation of a data abstraction, i.e., an abstract data type, to a physical data structure is a complicated process. It is composed of three major parts: a specification technique for describing a data abstraction; a deriving process for deriving the representation of the abstraction based on the specification; and a verification method for verifying the correctness of the specification and the representation of the abstraction. In this paper, we will concentrate on the last two problems, and it is assumed that the algebraic specification technique is used for describing abstract data types. Also, we will use examples to illustrate the use of the proposed approach.     

Fabrication and characteristics of n-Si/c-Si/p-Si heterojunction solar cells using hot-wire CVD

A double-side (bifacial) heterojunction (HJ) Si solar cell was fabricated using hot-wire chemical vapor deposition. The properties of n-type, intrinsic and p-type Si films were investigated. In these devices, the doped microcrystalline Si layers (n-type Si for emitter and p-type Si for back contact) are combined with and without a thin intrinsic amorphous Si buffer layer. The maximum temperature during the whole fabrication process was kept below 150 °C. The influence of hydrogen pre-treatment and n-Si emitter thickness on performance of solar cells have been studied. The best bifacial Si HJ solar cell (1 cm² sample) with an intrinsic layer yielded an active area conversion efficiency of 16.4% with an open circuit voltage of 0.645 V, short circuit current of 34.8 mA/cm² and fill factor of 0.73.