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Rust is a young systems programming language, but it has gained tremendous popularity thanks to its assurance of memory safety. However, the performance of Rust has been less systematically understood, although many people are claiming that Rust is comparable to C/C++ regarding efficiency. In this paper, we aim to understand the performance of Rust, using C as the baseline. First, we collect a set of micro benchmarks where each program is implemented with both Rust and C. To ensure fairness, we manually validate that the Rust version and the C version implement the identical functionality using the same algorithm. Our measurement based on the micro benchmarks shows that Rust is in general slower than C, but the extent of the slowdown varies across different programs. On average, Rust brings a 1.77x “performance overhead” compared to C. Second, we dissect the root causes of the overhead and unveil that it is primarily incurred by run-time checks inserted by the compiler and restrictions enforced by the language design. With the run-time checks disabled and the restrictions loosened, Rust presents a performance indistinguishable from C. 

All‐inorganic lead halide perovskite nanocrystals (NCs) have great optoelectronic properties with promising applications in light‐emitting diodes (LEDs), lasers, photodetectors, solar cells, and photocatalysis. However, the intrinsic toxicity of Pb and instability of the NCs impede their broad applications. Shell‐coating is an effective method for enhanced environmental stability while reducing toxicity by choosing non‐toxic shell materials such as metal oxides, polymers, silica, etc. However, multiple perovskite NCs can be encapsulated within the shell material and a uniform epitaxial‐type shell growth of well‐isolated NCs is still challenging. In this work, lead‐free vacancy‐ordered double perovskite Cs₂SnX₆(X = Cl, Br, and I) shells are epitaxially grown on the surface of CsPbX₃NCs by a hot‐injection method. The effectiveness of the non‐toxic double perovskite shell protection is demonstrated by the enhanced environmental and phase stability against UV illumination and water. In addition, the photoluminescence quantum yields (PL QYs) increase for the CsPbCl₃and CsPbBr₃NCs after shelling because of the type I band alignment of the core/shell materials, while enhanced charge transport properties obtained from CsPbI₃/Cs₂SnI₆core/shell NCs are due to the efficient charge separation in the type II core/shell band alignment.

 

Fuzz testing, or fuzzing, has become one of the de facto standard techniques for bug finding in the software industry. In general, fuzzing provides various inputs to the target program with the goal of discovering unhandled exceptions and crashes. In business sectors where the time budget is limited, software vendors often launch many fuzzing instances in parallel as a common means of increasing code coverage. However, most of the popular fuzzing tools — in their parallel mode — naively run multiple instances concurrently, without elaborate distribution of workload. This can lead different instances to explore overlapped code regions, eventually reducing the benefits of concurrency. In this paper, we propose a general model to describe parallel fuzzing. This model distributes mutually-exclusive but similarly-weighted tasks to different instances, facilitating concurrency and also fairness across instances. Following this model, we develop a solution, called AFL-EDGE, to improve the parallel mode of AFL, considering a round of mutations to a unique seed as a task and adopting edge coverage to define the uniqueness of a seed. We have implemented AFL-EDGE on top of AFL and evaluated the implementation with AFL on 9 widely used benchmark programs. It shows that AFL-EDGE can benefit the edge coverage of AFL. In a 24-hour test, the increase of edge coverage brought by AFL-EDGE to AFL ranges from 9.5% to 10.2%, depending on the number of instances. As a side benefit, we discovered 14 previously unknown bugs. 

In this paper, we present a new computational pipeline for designing and fabricating 4D garments as knitwear that considers comfort during body movement. This is achieved by careful control of elasticity distribution to reduce uncomfortable pressure and unwanted sliding caused by body motion. We exploit the ability to knit patterns in different elastic levels by single-jersey jacquard (SJJ) with two yarns. We design the distribution of elasticity for a garment by physics-based computation, the optimized elasticity on the garment is then converted into instructions for a digital knitting machine by two algorithms proposed in this paper. Specifically, a graph-based algorithm is proposed to generate knittable stitch meshes that can accurately capture the 3D shape of a garment, and a tiling algorithm is employed to assign SJJ patterns on the stitch mesh to realize the designed distribution of elasticity. The effectiveness of our approach is verified on simulation results and on specimens physically fabricated by knitting machines. 

ABSTRACT X-ray observations provide a unique probe of the accretion disc corona of supermassive black holes (SMBHs). In this paper, we present a uniform Chandra X-ray data analysis of a sample of 152 z ≥ 4.5 quasars. We firmly detect 46 quasars of this sample in 0.5–2 keV above 3σ and calculate the upper limits of the X-ray flux of the remaining. We also estimate the power-law photon index of the X-ray spectrum of 31 quasars. 24 of our sample quasars are detected in the FIRST or NVSS radio surveys; all of them are radio-loud. We statistically compare the X-ray properties of our z ≥ 4.5 quasars to other X-ray samples of active galactic nuclei (AGNs) at different redshifts. The relation between the rest-frame X-ray luminosity and other quasar parameters, such as the bolometric luminosity, UV luminosity, or SMBH mass, shows large scatters. These large scatters can be attributed to the narrow luminosity range at the highest redshift, the large measurement error based on relatively poor X-ray data, and the inclusion of radio-loud quasars in the sample. The LX–LUV relationship is significantly sublinear. We do not find a significant redshift evolution of the LX–LUV relation, expressed either in the slope of this relation, or the departure of individual AGNs from the best-fitting αOX–LUV relation (ΔαOX). The median value of the X-ray photon index is Γ ≈ 1.79, which does not show redshift evolution from z = 0 to z ∼ 7. The X-ray and UV properties of the most distant quasars could potentially be used as a standard candle to constrain cosmological models. The large scatter of our sample on the Hubble diagram highlights the importance of future large unbiased deep X-ray and radio surveys in using quasars in cosmological studies. 

The optical momentum alignment effect is demonstrated in WSe₂phototransistors . When the photon energy is above the A exciton energy, the maximum photocurrent response occurs for the light polarization direction parallel to the metal electrode edge, suggesting that electrons in the valence band of WSe₂prefer to absorb photons with the polarization direction perpendicular to their momentum direction. Further studies indicate that the anisotropic distribution of photo‐excited carriers is likely due to the pseudospin‐induced optical transition selection rules. If the photon energy is below the A exciton energy, the photocurrent signals are maximized when the incident light is polarized in the direction perpendicular to the electrode edge, which is mainly attributed to the polarized absorption of the plasmonic gold electrodes. Moreover, the photocurrent peak can be controlled by an electric field via the quantum confined Stark effect. This resonance peak can also be shifted by adjusting environmental temperatures due to the temperature‐dependent nature of the WSe₂band gap. These experimental studies shed light on the knowledge of photocurrent generation mechanisms, opening the door for engineering future anisotropic optoelectronics.