•We developed a green accessibility index to study access to urban green space.•The cold and hot spots of green accessibility were identified to offer policy insights.•Shanghai and its urban ...periphery have improved the green accessibility.•The inner and outer suburbs diverged in improvement of green accessibility.•Institutional factors affected urbanization and green accessibility in urban periphery.
We studied the accessibility of public urban green spaces in the context of rapid land transformation within the urban periphery. By using Shanghai, China as a case study, we illustrated how to evaluate the access to public green spaces of an urban periphery and how planning processes can influence the improvement of such access. We constructed a composite index named the “green accessibility index” (GAI), which measures how well residents are treated in terms of access to different types of public urban green spaces. Shanghai and its districts have improved their green accessibility index from 2000 to 2010. However, the GAI in the urban periphery fell behind the city average. Furthermore, while the inner suburbs, especially Pudong and Baoshan, had fared quite well in green accessibility improvement, outer suburbs made moderate progress in comparison to the city average. We identified hot/cold spots and spatial clustering that had a high/low green accessibility index in the urban periphery. The cold spots are in urgent need of substantial improvements to green space accessibility.
•The effect of steel-polypropylene hybrid fiber on the flexural behavior of concrete was investigated.•Favorable improvements in failure modes, flexural loads, toughness and ductility of HFRC were ...observed.•The synergy of hybrid fibers with various fiber parameters was analyzed.
This paper presents an experimental study on the flexural behavior of steel-polypropylene hybrid fiber reinforced concrete (HFRC) using four-point bending tests on 51 samples. Three types of steel fibers, i.e., straight, hooked-end and corrugated fiber, and a type of monofilament polypropylene fiber are considered. The flexural behavior in terms of load-deflection curves, load and deflection characteristics, toughness, cracking properties as well as the synergetic effect of hybrid fibers is studied. The results show that synergetic effect is observed for all the three types of steel fiber with the combination of polypropylene fiber on improving the flexural behavior of HFRC. Specimens with hooked-end fibers show the best flexural performance. However, the combination of straight steel and polypropylene fibers presents the most obvious synergy. Moreover, an increase in volume fractions of both steel and polypropylene fibers leads to an increase in the compressive, splitting tensile and flexural strengths of concrete. The post-peak ductility of concrete is improved and the strength degradation is alleviated with increasing fiber volume fraction and steel fiber aspect ratio. In addition, specimens with corrugated and hooked-end fibers exhibit a better failure behavior than specimens with straight fibers, with multiply micro-cracks induced by mechanical interlocks of deformed steel fibers observed at the main cracks. Finally, based on a comprehensive fiber reinforcing index, analytical equations for flexural loads, deflections, and toughness of HFRC are developed with varying fiber parameters taken into consideration.
•The effect of blending hybrid steel-polypropylene fiber and coarse aggregate on the.•UHPC compressive stress–strain behavior were investigated for the first time.•The evolutions of the key ...mechanical properties in terms of peak stress, peak strain, elastic modulus and toughness index were analyzed.•The mechanism of hybrid fiber and coarse aggregate’s effect on the UHPC compressive behavior was deeply discussed.
This paper investigates for the first time the effect of blending hybrid steel-polypropylene fiber (SF-PF) and coarse aggregate (CA) on the stress–strain behavior of ultra-high performance concrete (UHPC) under uniaxial compression. The uniaxial compression tests of UHPC specimens were carried out for different SF-PF, CA dosages and PF aspect ratios. Results show that the addition of hybrid SF-PF not only helps build stronger interfaces in UHPC, but also alters the failure pattern. The single corporation of SF significantly enhances the toughness, while the compressive strength and elastic modulus are diminished due to the less strong and compact ‘skeleton’ structure composed of the cement unhydrated core and hydrated coating. The toughness can be further improved under larger PF aspect ratio for the higher PF utilization ratio in restraining micro-cracks’ growth. The inclusion of CA leads to an evident increase in both the strength and modulus attributed to the increasing packing density and stronger ‘skeleton’, but simultaneously reduces the deformability and toughness. PF could compensate for the adverse effects of CA on the toughness without sinking too much. Finally, a developed analytical model is presented for predicting the UHPC compressive stress–strain behavior considering the dosage of SF, PF and CA.
•Nanoindentation tests on the ITZs between steel/polypropylene fiber and pure cement paste were performed.•The microstructure mapping and gradient of ITZs were analyzed based on the elastic property ...distributions.•The hydrated products in ITZs with the corresponding volume fractions were determined.•The formation mechanisms of the steel fiber ITZ and polypropylene fiber ITZ were analyzed with experimental supports.
The fiber-matrix interfacial transition zone (ITZ) at nanoscale plays an important role in determining the mechanical performance of hybrid steel-polypropylene fiber reinforced concrete at upper scales. This paper investigates the elastic behavior of the ITZ between steel/polypropylene fiber and pure cement paste through nanoindentation for different water/cement ratios. The microstructure mapping and gradient of ITZ were analyzed based on the elastic modulus (E) and hardness (H) distributions. The morphology of ITZs was observed with the help of Scanning Electron Microscope. In addition, to probe into the formation mechanism of ITZ, distinct phases in ITZ were statistically determined from the frequency density distributions of E and H values through the deconvolution technique. Results show that the thickness of fiber-matrix ITZ mainly depends on the fiber type, where the steel fiber and polypropylene fiber ITZ are about 30μm and 15μm in thickness respectively. It is also found from E distribution that a trough in the steel fiber ITZ exists at lower w/c ratios, whereas a gradual growth of E and H values is demonstrated away from polypropylene fiber surface for all cases shown. The ITZ’s chemical compositions at nanoscale suggest that the volume fractions of HD C-S-H, CH/C-S-H and porosity are noted to be the main determinants for the overall properties of ITZ. In comparison with steel fiber samples, a larger amount of porosity exists in the vicinity of polypropylene fiber surface. Finally, based on the test data, the ITZ formation mechanism was discussed with water/cement ratio effect considered.
•Effects of fiber parameters on the flexural and AE behaviors of SFRC were investigated.•The flexural strength, toughness, fracture process and failure mode of SFRC was studied.•The reinforcing ...mechanism of steel fiber with various fiber parameters was analyzed.
This paper investigates the effects of fiber type, volume fraction and aspect ratio on the flexural and acoustic emission (AE) behaviors of steel fiber reinforced concrete (SFRC) using four-point bending tests. Three types of steel fibers, i.e., straight, hooked-end and corrugated fiber, four volume fractions of 0.5%, 1.0%, 1.5% and 2.0%, three corrugated fiber aspect ratios of 40, 60 and 80, were respectively selected. The flexural behavior of SFRC in terms of load-deflection curve, ultimate flexural load and toughness was studied. The AE parameters with respect to AE events, average frequency, RA value etc. were used to describe the fracture process and fracture mode of SFRC. The results showed that the flexural and AE behaviors of SFRC vary with various fiber types, volume fractions and aspect ratios. Hooked-end SFRC owns the best flexural behavior. Compared to plain concrete, the ultimate flexural strengths of specimens are maximally improved by 74.29%, 165.07% and 112.65% for straight, hooked-end and corrugated fibers, respectively. The peak load, deflection and toughness of concrete increase with increasing fiber volume fraction and aspect ratio. It is noted from AE results that the cumulative AE events, shear cracks and AE source location points mainly induced by fiber pull-out and sliding increase with the increase of fiber volume fraction and aspect ratio. Hooked-end SFRC has the largest AE events, shear cracks and the amount of scatter points for all the four fiber volume fractions owing to the large amount of fibers sustaining the load at cracks and the good bond performance of hook-end steel fiber and concrete matrix. Moreover, the failure of plain concrete is dominated by tensile cracks, and that is changing to shear cracks with increasing fiber volume fraction.
•The effects of hybrid fibers on the local bond performance were investigated.•Improvements in bond strength, slip and energy dissipation capacity were observed.•Empirical laws for monotonic and ...cyclic bond stress–slip relations were developed.
The performance of the bond between reinforcing bars and fiber reinforced concrete (FRC) plays an important role in determining the mechanical behavior of FRC structures when they are subjected to static or dynamic loadings. This paper presents an experimental study on the local bond performance of rebar embedded in steel-polypropylene hybrid fiber reinforced concrete (HFRC). A total of 102 specimens under monotonic and cyclic loading are investigated by means of pull-out tests. The main variables include fiber volume fraction and aspect ratio, concrete strength and stirrup confinement. The results show that the introduction of hybrid fibers had a synergetic effect on improving the bond performance in terms of peak bond strength and corresponding slip, resulting in a more ductile bond behavior. The improvement becomes more pronounced as the fibers content and concrete strength increase. With respect to the energy dissipation capacity, the hybrid fibers also exhibit a great influence. Specimens with higher fibers content always demonstrate a better energy dissipation capacity, while the opposite is true for increasing the aspect ratio of both fibers. Furthermore, two phenomenological models were proposed to predict the monotonic and cyclic bond behavior of well-confined HFRC specimens, in which the benefits of hybrid fibers were taken into account. The models, as well as involved equations, were verified by independent experimental results.
Positive psychology (PP) has received increasing attention in the field of education. Therefore, it would be of utmost importance to analyze the relationship between the constructs falling under the ...category of positive psychology and other constructs to pave the way for both educational authorities and teachers themselves. Reviewing the previous studies, it turned out that there have been no studies to discuss the interplay between teachers’ psychological capital and their job commitment and academic optimism particularly in the context of China. To fill this gap, the current study set out to inspect the function of Chinese English as a Foreign language (EFL) teachers’ psychological capital in promoting their job commitment and academic optimism. To accomplish this, 316 Chinese teachers (i.e., 97 males, 219 females) were asked to complete “Psychological Capital Scale,” “Job Commitment Scale,” and “Academic Optimism Scale.” The results of regression analyses revealed that Chinese EFL teachers’ psychological capital can strongly predict their job commitment and academic optimism. The conclusion and implications of the results are finally discussed and it is mentioned that both educational authorities and teachers can benefit from this study and make the experience of teaching much more productive.
BACKGROUND The aims of this study were to use RNA expression profile bioinformatics data from cases of thyroid cancer from the Cancer Genome Atlas (TCGA), the Kyoto Encyclopedia of Genes and Genomes ...(KEGG), and the Gene Ontology (GO) databases to construct a competing endogenous RNA (ceRNA) network of mRNAs, long noncoding RNAs (lncRNAs), and microRNAs (miRNAs). MATERIAL AND METHODS TCGA provided RNA profiles from 515 thyroid cancer tissues and 56 normal thyroid tissues. The DESeq R package analyzed high-throughput sequencing data on differentially expressed RNAs. GO and KEGG pathway analysis used the DAVID 6.8 and the ClusterProfile R package. Kaplan-Meier survival statistics and Cox regression analysis were performed. The thyroid cancer ceRNA network was constructed based on the miRDB, miRTarBase, and TargetScan databases. RESULTS There were 1,098 mRNAs associated with thyroid cancer; 101 mRNAs were associated with overall survival (OS). Multivariate analysis developed a risk scoring system that identified seven signature mRNAs, with a discriminative value of 0.88, determined by receiver operating characteristic (ROC) curve analysis. A ceRNA network included 13 mRNAs, 31 lncRNAs, and seven miRNAs. Four out of the 31 lncRNAs and all miRNAs were down-regulated, and the remaining RNAs were upregulated. Two lncRNAs (MIR1281A2HG and OPCML-IT1) and one miRNA (miR-184) were significantly associated with OS in patients with thyroid cancer. CONCLUSIONS Differential RNA expression profiling in thyroid cancer was used to construct a ceRNA network of mRNAs, lncRNAs, and miRNAs that showed potential in evaluating prognosis.
Optical metasurfaces have shown unprecedented capabilities in the local manipulation of the light's phase, intensity, and polarization profiles, and represent a new viable technology for applications ...such as high‐density optical storage, holography and display. Here, a novel metasurface platform is demonstrated for simultaneously encoding color and intensity information into the wavelength‐dependent polarization profile of a light beam. Unlike typical metasurface devices in which images are encoded by phase or amplitude modulation, the color image here is multiplexed into several sets of polarization profiles, each corresponding to a distinct color, which further allows polarization modulation‐induced additive color mixing. This unique approach features the combination of wavelength selectivity and arbitrary polarization control down to a single subwavelength pixel level. The encoding approach for polarization and color may open a new avenue for novel, effective color display elements with fine control over both brightness and contrast, and may have significant impact for high‐density data storage, information security, and anticounterfeiting.
A novel metasurface platform is proposed and experimentally demonstrated to simultaneously encode color and intensity information into the wavelength‐dependent polarization profile of a light beam. This unique approach features the combination of wavelength selectivity and arbitrary polarization control down to a single subwavelength pixel level. A linear polarizer is required for the acquisition of the image's color and brightness profiles.
This paper studied an integrated process planning and scheduling problem from a machining workshop for large-size valves in a valve manufacturing plant. Large-size valves usually contain several key ...parts and are generally produced in small-series production. Almost all the parts need to be manufactured in the same workshop at the same time in the plant. Facilities have to handle various items in one order, including different models, sizes, and types. It is a classical NP-hard problem on a large scale. An improved NSGA-II algorithm is suggested to obtain satisfactory solutions for makespan and manufacturing costs, which involve large optimization parameters and interactions. A two-section encoding method and an inserting greedy decoding method are chosen to enable the algorithm. The dynamic population update strategy based on dynamic population update and the adaptive mutation technique depending on the population entropy changing rate are selected for enhancing both the solution quality and population diversity. The methodology was successfully implemented in a real-life case at a major valve machining workshop operated by Yuanda Valve Company in China. By taking into account realistic factors and restrictions that have been identified from a real-world manufacturing setting, this technique aids in bridging the knowledge gap between present IPPS research and practical valve production implementations.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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