Efficient organic solar cells enabled by simple non-fused electron donors with low synthetic complexity

Abstract Fused‐ring electron donors boost the efficiency of organic solar cells (OSCs), but they suffer from high cost and low yield for their large synthetic complexity (SC > 30%). Herein, the authors develop a series of simple non‐fused‐ring electron donors, PF1 and PF2, which alternately consist of furan‐3‐carboxylate and 2,2′‐bithiophene. Note that PF1 and PF2 present very small SC of 9.7% for their inexpensive raw materials, facile synthesis, and high synthetic yield. Compared to their all‐thiophene‐backbone counterpart PT‐E, two new polymers feature larger conjugated plane, resulting in higher hole mobility for them, especially a value up to ≈10 −4 cm 2 V −1 ·s for PF2 with longer alkyl side chain. Meanwhile, PF1 and PF2 exhibit larger dielectric constant and deeper electronic energy level versus PT‐E. Benefiting from the better physicochemical properties, the efficiencies of PF1‐ and PF2‐based devices are improved by ≈16.7% and ≈71.3% relative to that PT‐E‐based devices, respectively. Furthermore, the optimized PF2‐based devices with introducing PC 71 BM as the third component deliver a higher efficiency of 12.40%. The work not only indicates that furan‐3‐carboxylate is a simple yet efficient building block for constructing non‐fused‐ring polymers but also provides a promising electron donor PF2 for the low‐cost production of OSCs.A simple structure non‐fused‐ring electron donor PF2 alternately consisting of furan‐3‐carboxylate and 2,2′‐bithiophene presents very small synthetic complexity of 9.7% as well as low material cost of ≈19.0 $ g −1 . More importantly, PF2 delivers a high efficiency of 12.4% coupled with strong operational stability. imag

A Novel Engineering Education Innovation Pattern with Design Ideas and Robot Maker Practice

Traditional engineering education of innovative thinking mainly focused on knowledge imparting, thinking and learning, but it weakens the cultivation of students' practical ability. In this paper, a new pattern of innovative thinking engineering education is proposed, which combines abstract design innovation with specific robot maker practice. By offering general course for all professional students, it teaches the theory, methods and tools of systematic innovative thinking, and cultivates students' system design methods and innovative thinking. Taking the design and production process of robots as the object and content of practical teaching, the traditional teaching pattern centered on teachers, classrooms and textbooks is changed, teachers' reflection on teaching is promoted, so that it can be truly changedfrom a lecturer to an inspirator of learning, at the same time, teaching flexibility is increased, and students' highlevel thinking and practical abilities are improved. Classroom statistics show that 92.14% of the students think that their innovative thinking ability has been improved, and 90.71% of the students consider that their practical ability has been enhanced. It shows that the engineering education innovation pattern with design ideas and robot maker practice can inspire students' innovative thinking, while improving students' robotic practical ability

Efficient processing of Top-k queries on spatial and temporal data

Spatial and temporal databases play a vital role in many applications in different areas such as Geographic Information Systems (GIS), stock market, wireless sensor network, traffic monitoring and internet applications, etc. Due to their importance, a huge amount of work has focused on efficiently computing various spatial and temporal queries. Among the applications, end-users are more interested in the most important query answers in the potentially enormous answer space. Therefore, different types of information systems use various techniques to rank query answers and return the most important query results to users. Observed in real world scenario, top-k results are more interesting to users and a top-k query is a natural way to be asked to reflect a users preference in terms of a user-defined scoring function. In this thesis, we provide efficient solutions for the top-k queries under various settings and different criteria for users preferences. Specifically, we tackle three types of top-k queries in a systematic way. Below is a brief description of our contributions. We are the first to study the efficient monitoring of top-k pairs queries over data streams. We present the first approach to answer a broad class of top-k pairs and top-k objects queries over sliding windows. Our framework handles multiple top-k queries and each query is allowed to use a different scoring function, a different value of k and a different size of the sliding window. Furthermore, the framework allows the users to define arbitrarily complex scoring functions and supports out-of-order data streams.We are the first to study the top-k loyalty queries. We propose a measure named loyalty that reflects how persistently an object satisfies the criteria. Formally, the loyalty of an object is the total time (in past T time units) it satisfied the query criteria. We propose an optimal approach to monitor the loyalty queries over sliding windows that continuously report k objects with the highest loyalties. We also experimentally verify the effectiveness of the proposed approach by comparing it with a classic sweep line algorithm. We are the first to study the I/O efficient solution for depth-related problems which can be used for retrieving the top-k objects with linear scoring functions. Half-plane depth of a plane is the number of objects lying in the plane. Location depth of a point p is the minimum half-plane depth of any plane that is bounded by any line passing through p. We propose disk-based algorithms for a few important depth-related problems namely k-depth contour, k-snippet and k-upper envelope. We show that one of our proposed algorithms is I/O optimal for k-snippet and k-upper envelope problems

An Adaptive Sliding Mode Variable Admittance Control Method for Lower Limb Rehabilitation Exoskeleton Robot

As passive rehabilitation training with fixed trajectory ignores the active participation of patients, in order to increase the active participation of patients and improve the effect of rehabilitation training, this paper proposes an innovative adaptive sliding mode variable admittance (ASMVA) controller for the Lower Limb Rehabilitation Exoskeleton Robot. The ASMVA controller consists of an outer loop with variable admittance controller and an inner loop with an adaptive sliding mode controller. It estimates the wearer’s active muscle strength and movement intention by judging the deviation between the actual and standard interaction force of the wearer’s leg and the exoskeleton, thereby adaptively changing admittance controller parameters to alter training intensity. Three healthy volunteers engaged in further experimental studies, including trajectory tracking experiments with no admittance, fixed admittance, and variable admittance adjustment. The experimental results show that the proposed ASMVA control scheme has high control accuracy. Besides, the ASMVA can not only increase training intensity according to the active muscle strength of the patient during positive movement intention (so as to increase active participation of the patient), but also increase the amount of trajectory adjustment during negative movement intention to ensure the safety of the patient

Mechanical Properties, Crystallization Behaviors and Phase Morphologies of PLA/GTR Blends by Reactive Compatibilization

Different ratios of Polylactic acid/Ground tire rubber (PLA/GTR) were prepared by melt blending and adding dicumyl peroxide (DCP) as a reactive compatibilizer. The compatibilizer could initiate a reaction between PLA and GTR to increase the compatibility and interfacial adhesion of the two phases, as indicated by Fourier transform infrared (FTIR) spectrometry and scanning electron microscopy (SEM). Adding the compatibilizer significantly improved the impact strength of the PLA/GTR blends without compromising the tensile strength. The elongation at the break and notched Izod impact strength of the blend increased by 61.8% and 150%, respectively, but there was only a 4.1% decline in tensile strength compared with the neat PLA. The plastic deformation on the impact fractured surface showed that the improvement of toughness could be attributed to the compatibilization initiated by DCP. Therefore, the improvement of the interfacial adhesion and compatibility of the two phases induced a brittle–ductile transition that occurred in the failure of blends. Moreover, the crystallinity of blends reached 40.5% without a further annealing treatment, which was nearly 24 times of the neat PLA, and the crystallization rate was enhanced simultaneously. These exciting findings suggest that compatibilization can provide a promising avenue for fabricating GTR-toughened PLA blends with balanced stiffness–toughness

Ternary amide-hydride system: A study on LiAl(NH2)(4)-LiAlH4 interaction

LiAl(NH2)(4) is a ternary amide that readily decomposes to release ammonia at temperatures as low as similar to 90 degrees C. Owing to such instability as compared to binary amides, we hypothesize that the dehydrogenation mechanism involving ternary amide-hydride interaction would be significantly different from those of binary metal amide-hydride interaction. Therefore, in this study, interaction of LiAl(NH2)(4) and LiAlH4 has been investigated by means of mechanical milling and thermal method. It was found that dehydrogenation occurred spontaneously during the milling process and the rate of dehydrogenation increased with increasing amount of LiAlH4, suggesting an ion migration mediated dehydrogenation. As reaction progressed, the formation of Li3AlH6 as an intermediate was detected and a total of 8 equiv. of H-2 (7.5 wt%) can be released, forming LiH and AlN as the final product. In contrast, heating the homogenously ground LiAl(NH2)(4) and LiAlH4 sample resulted in the release of NH3 at low temperatures, indicating that NH3 mediation would take place in case of dehydrogenation. Further increase in temperature resulted in a rapid release of hydrogen from the interaction of the LiAl(NH)(2) and LiAlH4. It was also found that hydride with higher basicity is required to trigger amide-hydride interaction for dehydrogenation at low temperatures. (C) 2019 Elsevier B.V. All rights reserved

Investigations on the solid state interaction between LiAlH4 and NaNH2

10.1016/j.jssc.2010.07.014Journal of Solid State Chemistry18392040-2044JSSC