The last decade saw myriad new donor polymers, among which benzodithiophene-co-thienothiophene polymers are attractive due to their relatively high power conversion efficiency in bulk heterojunction solar cells. We examine the effect of UV-light on the stability of these polymers. The relationship between the polymer chemical structure and the UV-stability of the cells is explored on the one hand, and on the other hand, the effect of additives on their UV-stability: 1,8-diiodooctane against 1-chloronaphthalene in the cells and 1,8-octanedithiol in solution. For example, PBDTTT-E with 18% efficiency loss is more stable than PBDTTT-ET with 36% loss throughout the exposure. While 1,8-diiodooctane acts as photo-acid and leads to accelerated degradation of the solar cells, 1-chloronaphthalene does not. Acidity is known to be detrimental to the efficiency and stability of organic solar cells. The degradation is initiated upon UV-irradiation by the cleavage of the side chains, resulting in more electron traps and by the formation of iodine, dissolved HI and carbon-centered radicals from 1,8-diiodooctane as revealed by 1H NMR spectrum. The 1,8-octanedithiol spectra do not show such species. Finally, the mechanisms behind the effect of 1,8-diiodooctane are explained, paving the way for the design of new, efficient as well as stable materials and additives.
In order to deal with the heat dissipation of the integrated permanent magnet motor for a certain shaftless propeller, this paper designs an automatic water-circulation cooling system. The cooling system involves two annular grooves on the inner wall of the duct before and after the blades, the two grooves are connected with the air-gap between the motor stator and rotor to form a cooling passage in which cooling water flows from the rear of the propeller to the front. The performance analysis of the cooling system is a multi-physics problem involving electromagnetic field, flow field, and temperature field. This study combines the finite element method and the finite volume method to simulate and analyze the multi-field coupling problem of the cooling system. Tests of the shaftless propeller prototype are used to prove that the coupling simulation model is accurate and the cooling system is practical. Additionally, the verified simulation model is applied to analyzing the influence of several key factors, such as air-gap flow rate, pouring sealant thermal conductivity, and stator sheath material, on the heat dissipation of the integrated motor. The study made in this paper can provide a reference for developing the same kind of devices. INDEX TERMS Coupling simulation model, integrated motor, shaftless propeller, temperature field.
Using multiple sensors to track targets, due to communication delays and variable signal pre-processing time, will lead to out-of-sequence measurement problems. In this paper, based on sequential Bayesian formula and Gaussian particle filter, a novel out of sequence measurement processing algorithm is developed. In essence, this algorithm uses importance sampling to update the posterior means and their covariances, and also approximates the posterior distributes by single Gaussians. The algorithm has low complexity and its performance is consistent with standard sequential processing algorithm and it is asymptotically optimal as numbers of particles tends to infinity. This paper is the extended version of [15].
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