POWER REFLECTION AND TRANSMISSION IN BEAM STRUCTURES CONTAINING A SEMI-INFINITE CRACK

Wave reflection and transmission in a beam containing a semi-infinite crack are studied analytically based on Timoshenko beam theory., Two kinds of crack surface conditions： non-contact （open） and fully contact （closed） cracks, are considered respectively for an isotropic beam. The analytical solution of reflection and transmission coefficients for a semi-infinite crack is obtained. The power reflection and transmission ratios depend on both the frequency and the position of the crack. Numerical results show the conservation of power transport. The transmitted energy among various wave modes is also investigated. A finite element method is used to verify the validity of the analytical results.

Layered-stacking of titania films for solar energy conversion:Toward tailored optical,electronic and photovoltaic performance

Nanostructured TiO2 with differentiate morphologies has attracted tremendous attention due to its wide band-gap nature as well as outstanding optical and electric properties for solar-driven light-toelectricity conversion application. Layered-stacking TiO2 film such as double-layer, tri-layer, quadrupleor quintuplicate-layer, is highly desirable to the design of high-performance semiconductor material photoanodes and the development of advanced photovoltaic devices. In this minireview, we will summarize the recent progress and achievements on proof-of-concept of layered-stacking TiO2 films（LTFs） for solar cells with emphasis on the tailored properties and synergistic functionalization of LTFs, such as optimized sensitizer adsorption, broadened light confinement as well as facilitated electron transport characteristics.Various demonstrations of LTFs photovoltaic systems provide lots of possibilities and flexibilities for more efficient solar energy utilization that a wide variety of TiO2 with distinguished morphologies can be integrated into differently structured photoanodes with synergistic and complementary advantages. This key structure engineering technology will also pave the way for the development of next generation state-ofthe-art electronics and optoelectronics. Finally, from our point of view, we conclude the future research interest and efforts for constructing more efficient LTFs as photoelectrode, which will be highly warranted to advance the solar energy conversion process.

Titanylphthalocyanine as hole transporting material for perovskite solar cells

Titanylphthalocyanine （TiOPc） as hole transporting material （HTM） was successfully synthesized by a simple process with low cost. Perovskite solar cells using the TiOPc as HTM were fabricated and characterized. TiOPc as HTM plays an important role in increasing the power conversion efficiency （PCE） by minimizing recombi- nation losses at the perovskite/Au interface because TiOPc as HTM can extract photogenerated holes from the perovskite and then transport quickly these charges to the back metal electrode. In the research, the β-TiOPc gives a higher PCE than α-TiOPc for the devices due to sufficient transfer dynamics, The β-TiOPc was applied in perovskite solar cells without clopping to afford an impressive PCE of 5.05% under AM 1.5G illumination at the thickness of 40 nm which is competitive with spiro-OMeTAD at the same condition. The present work suggests a guideline for optimizing the photovoltaic properties ofperovskite solar cells using the TiOPc as the HTM.

Optimal Coordination of Transportable Power Sources and Repair Crews for Service Restoration of Distribution Networks Considering Uncertainty of Traffic Congestion

This paper proposes a new method for service restoration of distribution network with the support of transportable power sources(TPSs)and repair crews(RCs).Firstly,a coupling model of distribution networks and vehicle routing of TPSs and RCs is proposed,where the TPSs serve as emergency power supply sources,and the RCs are used to repair the faulted lines.Considering the uncertainty of traffic congestion,the probability distribution of the travel time spent on each road is derived based on the Nesterov user equilibrium model,and a two-stage stochastic program is formulated to determine the optimal routings of TPSs and RCs.To efficiently solve the proposed stochastic mixed-integer linear program(MILP),a two-phase scenario reduction method is then developed to scale down the problem size,and an adaptive progressive hedging algorithm is used for an efficient solution.The effectiveness of the proposed methods and algorithms has been illustrated in a modified IEEE 33-bus system.

Proactive Resilience Enhancement of Power Systems with Link Transmission Model-based Dynamic Traffic Assignment Among Electric Vehicles

The rapid development of electric vehicles(EVs)is strengthening the bi-directional interactions between electric power networks(EPNs)and transportation networks(TNs)while providing opportunities to enhance the resilience of power systems towards extreme events.To quantify the temporal and spatial flexibility of EVs for charging and discharging,a novel dynamic traffic assignment(DTA)problem is proposed.The DTA problem is based on a link transmission model(LTM)with extended charging links,depicting the interaction between EVs and power systems.It models the charging rates as continuous variables by an energy boundary model.To consider the evacuation requirements of TNs and the uncertainties of traffic conditions,the DTA problem is extended to a two-stage distributionally robust version.It is further incorporated into a two-stage distributionally robust unit commitment problem to balance the enhancement of EPNs and the performance of TNs.The problem is reformulated into a mixed-integer linear programming problem and solved by off-the-shelf commercial solvers.Case studies are performed on two test networks.The effectiveness is verified by the numerical results,e.g.,reducing the load shedding amount without increasing the unmet traffic demand.

Research on the Innovative Development of China’s Comprehensive Transportation System

The comprehensive transportation system is the intensive development stage of the transportation industry,which has gradually become the mainstream transportation mode in the world by giving full play to the advantages of different modes of transportation,promoting the effective use of resources,saving energy and reducing environmental pollution.Since the beginning of reform and opening up,China has achieved a steady improvement in the quality of transportation and a rapid growth in quantity,and has made remarkable achievements in stimulating economic growth and improving people’s well-being.During the14th Five-Year Plan period,China’s comprehensive transportation development will continue to take into account the basic needs and diversified needs,promote the diversified and high-quality development of transportation services,gradually realize the enjoyment of people’s travels and the smooth flow of goods,and continuously meet the growing needs of the people for a better life.We must follow the general idea of“forcing market entities to take the initiative to compete,guiding the development of emerging industries,cultivating the core carrier that drives the integrated development of transportation services,improving regional transportation coordination capabilities,and comprehensively using cutting-edge technologies”,constantly innovating and making breakthroughs in infrastructure,technological innovation,institutional mechanisms,investment and financing policies,and promoting the innovative development and overall leap of China’s comprehensive transportation.

Organic functional materials based buffer layers for efficient perovskite solar cells

In this review, we highlight the recent development of organic π-functional materials as buffer layers in constructing efficient perovskite solar cells（PVSCs）. By following a brief introduction on the PVSC development, device architecture and material design features, we exemplified the exciting progresses made in field by exploiting organic π-functional materials based hole and electron transport layers（HTLs and ETLs） to enable high-performance PVSCs.

Inverted polymer solar cells with Zn_2SnO_4 nanoparticles as the electron extraction layer

In this study, we report narrow-size distribution Zn_2SnO_4（ZSO） nanoparticles, which are produced by low-temperature solution-processed used as the electron extraction layer（EEL） in the inverted polymer solar cells（i-PSCs）. Moreover, poly[（9,9-bis（30-（N,N-dimethylamino）propyl）-2,7-fluorene）-alt-2,7-（9,9-dioctylfluorene）]（PFN） is used to modify the surface properties of ZSO thin film. By using the ZSO NPs/PFN as the EEL, the i-PSCs fabricated by poly[4,8-bis（2-ethylhexyloxyl）benzo[1,2-b：4,5-b0] dithio-phene-2,6-diyl-altethylhexyl-3-fluorothithieno [3,4-b]thiophene-2-carboxylate-4,6-diyl]（PTB7） blended with（6,6）-phenyl-C_（71）-butyric acid methylester（PC_（71）BM） bulk heterojunction（BHJ） composite, exhibits a power conversion efficiency（PCE） of 8.44%, which is nearly 10% enhancement as compared with that of7.75% observed from the i-PSCs by PTB7：PC_（71）BM BHJ composite using the ZnO/PFN EEL. The enhanced PCE is originated from improved interfacial contact between the EEL with BHJ active layer and good energy level alignment between BHJ active layer and the EEL. Our results indicate that we provide a simple way to boost efficiency of i-PSCs.