Solar-driven carbon dioxide (CO 2 ) conversion to fuels and high-value chemicals can contribute to the better utilization of renewable energy sources. Photosynthetic (PS), photocatalytic (PC), photoelectrochemical (PEC), and photovoltaic plus electrochemical (PV+EC) approaches are intensively studied strategies. We aimed to compare the performance of these approaches using unified metrics and to highlight representative studies with outstanding performance in a given aspect. Most importantly, a statistical analysis was carried out to compare the differences in activity, selectivity, and durability of the various approaches, and the underlying causes are discussed in detail. Several interesting trends were found: (i) Only the minority of the studies present comprehensive metrics. (ii) The CO 2 reduction products and their relative amount vary across the different approaches. (iii) Only the PV+EC approach is likely to lead to industrial technologies in the midterm future. Last, a brief perspective on new directions is given to stimulate discussion and future research activity.

Extension flow induced crystallization of isotatic polypropylene (iPP) has been studied with a combination of extension rheological and in situ small-angle X-ray scattering (SAXS) measurements at 140 °C. Rheological data of step extension on iPP melt are divided into before and beyond fracture strain zones in strain–strain rate space, where intermediate strains between them lead to fracture of samples. Coincidently, weak and strong accelerations of nucleation are observed in the before and beyond fracture strain zones respectively, where distinctly different features of crystallization kinetics and nucleation form occur in these two zones. The microrheological model explains the acceleration of nucleation in the “before fracture strain zone” well, while a “ghost nucleation” mechanism is proposed to interpret the strong acceleration of nucleation in the “beyond fracture strain zone”. The “ghost nucleation” is due to the displacement of initial parent point nuclei, where daughter nuclei are induced along the trails. This new mechanism explains well the acceleration of nucleation in orders of magnitude and the formation of shish in iPP melt.

We perform a detailed vertical analysis of application performance atop a range of modern file systems and SSD FTLs. We formalize the "unwritten contract" that clients of SSDs should follow to obtain high performance, and conduct our analysis to uncover application and file system designs that violate the contract. Our analysis, which utilizes a highly detailed SSD simulation underneath traces taken from real workloads and file systems, provides insight into how to better construct applications, file systems, and FTLs to realize robust and sustainable performance.

Abstract-The performance gap between computing power and the I/O system is ever increasing, and in the meantime more and more High Performance Computing (HPC) applications are becoming data intensive. This study describes an I/O data replication scheme, named Pattern-Direct and Layout-Aware (PDLA) data replication scheme, to alleviate this performance gap. The basic idea of PDLA is replicating identified data access pattern, and saving these reorganized replications with optimized data layouts based on access cost analysis. A runtime system is designed and developed to integrate the PDLA replication scheme and existing parallel I/O system; a prototype of PDLA is implemented under the MPICH2 and PVFS2 environments. Experimental results show that PDLA is effective in improving data access performance of parallel I/O systems.

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Mutation-based fault localization (MBFL) is a recently proposed technique with the advantage of high fault localization accuracy. However, such a mutation analysis based technique is difficult to be accepted by industry due to its huge computational cost on mutation analysis. There are three ways to improve MBFL's efficiency, which are reducing the number of mutants, optimizing the mutants' execution process, and reducing the number of test cases. The former two ways have been mainly studied and shown promising results, but for the latter way, the related studies are limited since this kind of method will reduce the precision of MBFL. In this paper, we mainly focus on the latter way and propose an information entropy based test case reduction (IETCR) strategy for MBFL. In particular, we first calculate the entropy change of test cases and select a proportion of them according to their value. Then we use a reduced test suite to execute mutants. To show the effectiveness of the IETCR strategy, we choose six real-world programs with faulty versions. In terms of mutation reduction rate, we find MBFL with the IETCR strategy can reduce 56.3%∼88.3% cost while keeping almost the same fault localization accuracy when compared to the original MBFL without test case reduction. Moreover, we use Wilcoxon signed-rank test for statistical analysis, which shows that there is no statistically significant difference between MBFL with IETCR strategy and the original MBFL. INDEX TERMS Software fault localization, Mutation based fault localization, Information entropy, Test case reduction Recent studies [11], [12] have shown that mutation-based fault localization (MBFL) techniques outperform state-ofthe-art SBFL techniques in terms of the fault localization

The I/O bottleneck in high-performance computing is becoming worse as application data continues to grow. In this work, we explore how patterns of I/O within these applications can significantly affect the effectiveness of the underlying storage systems and how these same patterns can be utilized to improve many aspects of the I/O stack and mitigate the I/O bottleneck. We offer three main contributions in this paper. First, we develop and evaluate algorithms by which I/O patterns can be efficiently discovered and described. Second, we implement one such algorithm to reduce the metadata quantity in a virtual parallel file system by up to several orders of magnitude, thereby increasing the performance of writes and reads by up to 40 and 480 percent respectively. Third, we build a prototype file system with pattern-aware prefetching and evaluate it to show a 46 percent reduction in I/O latency. Finally, we believe that efficient pattern discovery and description, coupled with the observed predictability of complex patterns within many high-performance applications, offers significant potential to enable many additional I/O optimizations.