A Divide-and-Conquer Approach to Syntax-Guided Synthesis

Program synthesis aims to generate programs automatically from user-provided specifications. One critical research thrust is called Syntax-Guideds Synthesis. In addition to semantic specifications, the user should also provide a syntactic template of the desired program, which helps the synthesizer reduce the search space. The traditional symbolic approaches, such as CounterExample-Guided Inductive Synthesis (CEGIS) framework, does not scale to large search spaces. The goal of this project is to explore a compositional, divide-n-conquer approach that heuristically divides the synthesis task into subtasks and solves them separately. The idea is to decompose the function to be synthesized by creating a set of auxiliary functions. In this way, the whole synthesis task can be reduced to synthesizing the auxiliary functions. The auxiliary functions are of bounded size and hence can be encoded into a logic constraint in linear-integer arithmetic and solved by modern Satisfiability-Modulo-Theories (SMT) solvers. In each iteration of the synthesis algorithm, an auxiliary function is synthesized and added into the syntax for synthesizing other auxiliary functions. The algorithms repeats until a syntax-correct implementation equivalent to the reference implementation is found. Preliminary experimental results show that this approach is promising

Ions-induced Epitaxial Growth of Perovskite Nanocomposites for Highly Efficient Light-Emitting Diodes with EQE Exceeding 30%

Cesium lead bromide (CsPbBr3) is a widely used emitter for perovskite light-emitting diodes (PeLEDs), benefiting from its large carrier mobility, high color purity and good thermal stability. However, the three-dimensional CsPbBr3 films encounter challenges due to their massive intrinsic defects and weak exciton binding effect, which limited their electroluminescence efficiency. To address this issue, the prevailing approach is to confine carriers by reducing dimensionality or size. Nonetheless, this method results in an increase in surface trap states due to the larger surface-to-volume ratio and presents difficulties in carrier injection and transport after reducing lattice splitting to smaller sizes. Here, we successfully achieved proper control over film crystallization by introducing sodium ions, which facilitate the epitaxial growth of zero-dimensional Cs4PbBr6 on the surface of CsPbBr3, forming large grain matrixes where CsPbBr3 is encapsulated by Cs4PbBr6. Notably, the ions-induced epitaxial growth enables the CsPbBr3 emitter with significantly reduced trap states, and generates coarsened nanocomposites of CsPbBr3&Cs4PbBr6 with grain size that surpass the average thickness of the thin perovskite film, resulting in a wavy surface conducive to light out-coupling. Additionally, another additive of formamidinium chloride was incorporated to assist the growth of nanocomposites with larger size and lower defects as well as better carrier injection and transportation. As a result, our demonstrated PeLEDs based on the coarsened nanocomposites exhibit low nonradiative recombination, enhanced light extraction and well-balanced carrier transportation, leading to high-performance devices. The champion device achieved an external quantum efficiency of 31.0% at the emission peak of 521 nm with a narrow full width at half-maximum (FWHM) of 18 nm

Mitigating Autogenous Shrinkage of Alkali-Activated Slag Mortar by Using Porous Fine Aggregates as Internal Curing Agents

Alkali-activated slag (AAS) is beneficial for resource conservation in that it consumes little primary industrial energy, and it also performs well in terms of its mechanical properties and durability. However, its higher autogenous shrinkage compared to OPC mortars is a serious issue impeding AAS-based binder development for practical applications. This study investigated the feasibility and performance of active recycled aggregates when applied as man-made internal curing agents (MAs) for AAS mortars. They were applied as aggregate replacements for sand in this study to investigate the effects on the autogenous shrinkage, internal relative humidity (IRH), compressive strength, hydration properties and pore structure of AAS mortars. Three MAs with the sizes of 0.63–1.25 mm (MA 0.63), 1.25–2.5 mm (MA 1.25) and 2.5–4.75 mm (MA 2.5) were used. The results showed that MAs have potential as internal curing agents to mitigate the autogenous shrinkage of AAS mortars. When using saturated MAs, the autogenous shrinkage of AAS mortars was reduced by 87.68%. The addition of MAs also significantly prolonged the critical time taken for the IRH to start decreasing from 100%

Mitigating Autogenous Shrinkage of Alkali-Activated Slag Mortar by Using Porous Fine Aggregates as Internal Curing Agents

Alkali-activated slag (AAS) is beneficial for resource conservation in that it consumes little primary industrial energy, and it also performs well in terms of its mechanical properties and durability. However, its higher autogenous shrinkage compared to OPC mortars is a serious issue impeding AAS-based binder development for practical applications. This study investigated the feasibility and performance of active recycled aggregates when applied as man-made internal curing agents (MAs) for AAS mortars. They were applied as aggregate replacements for sand in this study to investigate the effects on the autogenous shrinkage, internal relative humidity (IRH), compressive strength, hydration properties and pore structure of AAS mortars. Three MAs with the sizes of 0.63–1.25 mm (MA 0.63), 1.25–2.5 mm (MA 1.25) and 2.5–4.75 mm (MA 2.5) were used. The results showed that MAs have potential as internal curing agents to mitigate the autogenous shrinkage of AAS mortars. When using saturated MAs, the autogenous shrinkage of AAS mortars was reduced by 87.68%. The addition of MAs also significantly prolonged the critical time taken for the IRH to start decreasing from 100%

Organocatalytic regio- and enantioselective formal [4 + 2]-annulation of chiral nitrogen-containing dipoles

Quinidine-catalyzed regio- and enantioselective formal [4 + 2]-cycloadditions of 2-(4H-benzo[d][1,3]oxazin-4-yl)acrylates with N-tosyl-2-methylenebut-3-enoates and 2-methylene-3-oxoalkanoates have been developed for the first time. The reaction features the in situ formation of chiral nitrogen-containing dipolar intermediates, a ring-opening/Michael addition/annulation cascade reaction, and works well over a broad substrate scope to furnish the tetrahydroquinolines in high yields with high asymmetric induction under mild conditions

An optimization method for reducing the voltage fluctuation of the floating‐capacitor in ANPC five‐level inverter

Abstract The excessive fluctuation of the floating capacitance's (FCs) voltage affects the output performance and output power of the 3P‐5L‐ANPC converter. In order to minimize the fluctuation of the FCs voltage, an optimization control method based on zero‐sequence voltage (ZSV) injection is proposed. The method takes reducing the maximum amplitude of the voltage fluctuation of the three‐phase floating capacitor as the control target. Firstly, the mathematical equation between the modulation voltage and the voltage fluctuation of the FCs are established, and then the maximum fluctuation amplitude of the FCs voltage is obtained by using the established mathematical equations. Secondly, the range of ZSV injection is determined according to the conditions such as the control of neutral point voltage and the limitation of high‐phase voltage leaps. Finally, the equations of the maximum amplitude in the voltage fluctuation of the three‐phase FCs are established, and the ZSV with the minimum voltage amplitude fluctuation of the FCs is obtained within the effective range of the ZSV injection. Compared with the traditional shifted pulse width modulation (SPWM)/space vector pulse width modulation (SVPWM) method, the proposed method can effectively reduce the fluctuation of the FC voltage by 50%. Simulation and experimental results are presented to verify the effectiveness of the proposed method