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•A bimodal composite foam with CNT-GNP hybrids was prepared.•CNT and GNP show limited effect in improving electrical properties of composites.•CNT and GNP synergistically enhance ...electrical properties of composite foams.•The synergistic mechanism of CNT and GNP in composite foams is clarified.•The bimodal composite foams can be used in EMI shielding.
Novel PMMA composites were fabricated using two different dimensional nanofillers of MWCNTs and GNPs as bifillers to explore their synergistic effect on the final mechanical and electrical properties. MWCNTs and GNPs display limited effect on the final electrical properties while they show obvious synergistic effect in influencing the mechanical performance. The well-dispersed MWCNTs-GNPs in polymer matrix provide plenty of 1D-2D interconnections for efficient stress transferring when exposed to stress tensile, but the critical distance between nanofiller is not enough for effective electron movements and the significant Schottky barrier between nanofiller contacts has restricted the synergistic effect for electrical properties. Afterwards, PMMA composite foams with microcellular structure were prepared by supercritical fluid assisted processing. The ternary bimodal composite foams present better tensile, electrical and EMI shielding properties than the unimodal composite foams. MWCNTs and GNPs reveal prominent synergistic effect in influencing the tensile and electrical properties of ternary composite foam systems. The obvious enhancement of electrical conductivity results from the in situ exfoliation of GNPs, high-level orientation and redistribution of nanofillers, moderate physical foaming with bimodal microcellular structure as well as attenuated Schottky barriers at few-layer graphene/MWCNTs junctions. The dramatic improvement of EMI shielding performance is attributed to the elevated electrical conductivity, unique foam microstructures and special 1D-2D (MWCNTs-GNPs) hybrid structure. This study paves a feasible road to prepare lightweight and novel composites with superior electrical properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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The functional multi-walled carbon nanotubes (fMWCNTs) and liquid carboxy-terminated butadiene-acrylonitrile copolymer (CTBN) were incorporated into epoxy (EP) resin to fabricate ...thermosetting composites, which were foamed using supercritical carbon dioxide (SCCO2). The foamability, electrical conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) of foams were discussed. Owing to the heterogeneous nucleation caused by carbon nanotube, the average cell size of ∼400nm and cell density of ∼1012 cells/cm−3 were obtained, resulting in the excellent foamability of EP-CTBN-fMWCNTs systems. The biaxial stretching during cell growing facilitates fMWCNTs to align, forming 2D conductive networks, and resulting in the improvement of electrical property. The composite foam with fMWCNTs content of 5.0 wt% possesses EMI SE of 22.90 dB and specific EMI SE of 37.54 dB/(g cm3), which attributes to its high electrical conductivity of 0.43 S/m and cellular morphologies that made electromagnetic microwaves multi-reflect from one cell to another and then be attenuated by conductive filler.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Similarity query processing has been an active research topic for several decades. It is an essential procedure in a wide range of applications. Recently, embedding and auto-encoding methods as well ...as pre-trained models have gained popularity. They basically deal with high-dimensional data, and this trend brings new opportunities and challenges to similarity query processing for high-dimensional data. Meanwhile, new techniques have emerged to tackle this long-standing problem theoretically and empirically. In this tutorial, we summarize existing solutions, especially recent advancements from both database (DB) and machine learning (ML) communities, and analyze their strengths and weaknesses. We review exact and approximate methods such as cover tree, locality sensitive hashing, product quantization, and proximity graphs. We also discuss the selectivity estimation problem and show how researchers are bringing in state-of-the-art ML techniques to address the problem. By highlighting the strong connections between DB and ML, we hope that this tutorial provides an impetus towards new ML for DB solutions and vice versa.
A distance search in Hamming space finds binary vectors whose Hamming distances are no more than a threshold from a query vector. It is a fundamental problem in many applications, such as image ...retrieval, near-duplicate Web page detection, and scientific databases. State-of-the-art approaches to Hamming distance search are mainly based on the pigeonhole principle to generate a set of candidates and then verify them. We observe that the constraint by the pigeonhole principle is not always tight and may bring about unnecessary candidates. We also observe that the distribution in real data is often skewed, but most existing solutions adopt a simple equi-width partitioning and allocate the same threshold to all the parts, hence failing to exploit the data skewness to optimize query processing. In this paper, we propose a new form of the pigeonhole principle which allows variable partitioning and threshold allocation. Based on the new principle, we develop a tight constraint of candidates and devise cost-aware methods for partitioning and threshold allocation to optimize query processing. In addition, we extend our methods to answer Hamming distance join queries. We also discuss the application of the pigeonhole principle in set similarity search, a problem that can be converted to Hamming distance search equivalently. Our evaluation on datasets with various data distributions shows the robustness of our solution and its superior query processing performance to the state-of-the-art methods.
Aim:
The effect of sacubitril-valsartan (ARNI) in heart failure (HF) patients with mid-range ejection fractions (HFmrEF) remains unclear. This study aimed to investigate the effects of ARNI in HFmrEF ...patients.
Methods:
From inception to 15 February 2022, articles were searched
via
PubMed, Embase, Cochrane Library, Web of Science, China National Knowledge Infrastructure, Whip, and Wanfang databases. Left ventricular functions, indicators related to HF, quality of life score, 6-Minute Walk Test, total effective rate, mortality, readmission rate, and adverse events were the outcomes. Relative risk (RR), weighted mean difference (WMD), and 95% confidence interval (CI) were used to evaluate the outcomes. The heterogeneity test was conducted for each indicator and measured by I
2
statistics. Subgroup analysis was performed regarding the type of study and duration of treatment.
Results:
Sixteen studies involving 1,937 patients were included in this study. Our results showed ARNI was likely to improve left ventricular function by increasing the left ventricular ejection fraction (LVEF) (WMD: 2.36, 95%CI: 1.09–3.62), stroke volume (WMD: 16.800, 95%CI: 11.385–22.215), and left ventricular short-axis shortening rate (WMD: 2.05, 95%CI: 0.25–3.86), decreasing left ventricular end-diastolic dimension (WMD: −2.48, 95%CI: −3.83 to −1.13), left atrial diameter (WMD: −2.23, 95%CI: −2.83 to −1.63), C-reactive protein level (WMD: −1.40, 95%CI: −2.62 to −0.18), and N-terminal-pro B-type natriuretic peptide level (WMD: −494.92, 95%CI: −641.34 to −348.50). ARNI has a higher total effective rate (RR: 1.15, 95%CI: 1.08–1.21), Kansas City cardiomyopathy questionnaire (WMD: 4.13, 95%CI: 3.46–4.81), and 6-Minute Walk Test (WMD: 51.35, 95%CI: 26.99–75.71) compared with angiotensin-converting enzyme inhibitors (ACEI) and angiotensin receptor blockers (ARB). In addition, ARNI decreased the readmission rate (RR: 0.54, 95%CI: 0.43–0.68) (all
p
< 0.05). Nevertheless, there were no significant differences in the adverse outcomes.
Conclusion:
This meta-analysis suggests ARNI may be an effective strategy with which to improve the left ventricular function, and quality of life, and reduce the readmission rate in HFmrEF patients. However, long-term clinical studies with large samples are still needed to further explore the efficacy and safety of ARNI compared with ACEI or ARB in the HFmrEF population.
Polyimide foam (PIF) is a rising star in high-end applications such as aerospace thermal insulation and military sound absorption. However, the basic rule on molecular backbone design and uniform ...pore formation of PIF still need to be explored. In this work, polyester ammonium salt (PEAS) precursor powders are synthesized between alcoholysis ester of 3, 3', 4, 4'-benzophenone tetracarboxylic dianhydride (BTDE) and aromatic diamines with different chain flexibility and conformation symmetry. Then, a standard "stepwise heating" thermo-foaming approach is used to prepare PIF with comprehensive properties. A rational thermo-foaming program is designed based on in situ observation of pore formation during heating. The fabricated PIFs have uniform pore structure, and PIF
shows the smallest size (147 μm) and narrow distribution. Interestingly, PIF
also presents a balanced strain recovery rate (SR = 91%) and mechanical robustness (0.051 MPa at 25% strain) and its pore structure maintains regularity after 10 compression-recovery cycles, mainly due to high rigidity of the chains. Furthermore, all the PIFs possess lightweight feature (15-20 kg∙m
), good heat resistance (
at 270-340 °C), thermal stability (
at 480-530 °C), thermal insulation properties (λ = 0.046-0.053 W∙m
K
at 20 °C, λ = 0.078-0.089 W∙m
K
at 200 °C), and excellent flame retardancy (LOI > 40%). The reported monomer-mediated pore-structure control strategy can provide guidelines for the preparation of high-performance PIF and its industrial applications.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Shear thickening fluids (STFs) are energy dissipative materials and affected significantly by the properties of the dispersing media. Most of the dispersing media are polymeric or oligomeric fluids, ...and few studies have made ionic liquids (ILs) as the dispersing media. Since the properties of ILs are strongly dependent on its' ionic structures, the shear thickening behavior of STFs composed of ILs must be influenced by the ionic structures. The rheology and viscoelasticity of STFs of hydrophilic silica nanoparticles in ILs with different ionic structures were investigated systematically. The experimental results demonstrated that the dispersions in hydrophilic ILs displayed shear thickening behavior, while dispersions prepared by hydrophobic ones appeared as a colloidal gel and displayed shear thinning. With changing the length of the alkyl chain substituent on the organic cation, the shear thickening behavior was transformed. Shear thickening behavior was enhanced for the introduction of hydroxyl on the organic cation. Ionic structures influence the interactions between silica nanoparticles and ILs through the hydrogen bonds, and the shear thickening behavior may be induced by the formation of nanoparticle aggregation. The dynamic stabbing resistance, quasi-static tensile strength and conductivity of Kevlar fabric composites treated by STFs composed of ILs were enhanced observably, and the electromagnetic shielding property was improved to a certain degree.
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IJS, KILJ, NUK, UL, UM, UPUK
Similarity joins play an important role in many application areas, such as data integration and cleaning, record linkage, and pattern recognition. In this paper, we study efficient algorithms for ...similarity joins with an edit distance constraint. Currently, the most prevalent approach is based on extracting overlapping grams from strings and considering only strings that share a certain number of grams as candidates. Unlike these existing approaches, we propose a novel approach to edit similarity join based on extracting nonoverlapping substrings, or chunks, from strings. We propose a class of chunking schemes based on the notion of tail-restricted chunk boundary dictionary. A new algorithm, VChunkJoin, is designed by integrating existing filtering methods and several new filters unique to our chunk-based method. We also design a greedy algorithm to automatically select a good chunking scheme for a given data set. We demonstrate experimentally that the new algorithm is faster than alternative methods yet occupies less space.
Query autocompletion is an important feature saving users many keystrokes from typing the entire query. In this paper, we study the problem of query autocompletion that tolerates errors in users’ ...input using edit distance constraints. Previous approaches index data strings in a trie, and continuously maintain all the prefixes of data strings whose edit distances from the query string are within the given threshold. The major inherent drawback of these approaches is that the number of such prefixes is huge for the first few characters of the query string and is exponential in the alphabet size. This results in slow query response even if the entire query approximately matches only few prefixes. We propose a novel neighborhood generation-based method to process error-tolerant query autocompletion. Our proposed method only maintains a small set of active nodes, thus saving both space and time to process the query. We also study efficient duplicate removal, a core problem in fetching query answers, and extend our method to support top-
k
queries. Optimization techniques are proposed to reduce the index size. The efficiency of our method is demonstrated through extensive experiments on real datasets.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
With the development of highly integrated electronic equipment, electromagnetic pollution and heat congregation have become serious problems. Electromagnetic interference (EMI) shielding materials ...with high thermal conductivity and mechanical properties are highly desirable. Herein, the reduced graphene oxide/Ni nanowire aerogels (GNiA) were firstly prepared via hydrothermal reducing process and freeze-drying. Subsequently, using epoxy (EP) as a polymer matrix, the GNiA/EP composites with high compression strength of 147 MPa were fabricated by vacuum filtration and curing. The GNiA endows the composites with great electromagnetic wave loss, as well as improved phonon propagation efficiency, resulting in the super high EMI SE. With the GNiA content of 12.14 wt%, the EMI SE and thermal conductivity of GNiA/EP composites can reach as high as 85 dB and 1.69 W/(m·K) respectively. The obtained GNiA/EP composites provide a strategy to meet the demand for electronic equipment for new-generation EMI shielding materials.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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