Graphene oxide (GO) has been utilized to strengthen composite materials. In this study, the effects of GO on hydration degrees, macro-mechanical strength and calcium-silicate-hydrate (C-S-H) ...structure of cement based composites were investigated through comprehensive experimental tests. In addition, the aggregation mechanism of GO was verified by alkaline solution simulations, using Ca(OH)2 and NH3·H2O. Based on the experimental results, it was found that the 3-day and 7-day compressive strengths of cement based composites with 0.2wt% of GO were increased by 35.7% and 42.3%, respectively as compared to the control. Moreover, the C-S-H structure of cement paste with GO was not observed to have undergone any change via qualitative and quantitative analyses combined with FT-IR, XRD and 29Si-NMR. Besides, the test results of TGA, DTG and 29Si-NMR showed that the hydrated degree of cement paste increased to 10.4% at 28days when incorporating with 0.1% of GO.
Does familiarity with alliance partners promote breakthrough innovations? This study draws on the literature of interorganizational routines to examine the impact of repeated R&D collaborations ...within a firm's alliance portfolio on its breakthrough innovations. Specifically, we contend that the benefits and liabilities of interorganizational routines, arising from alliance partner repeatedness at a firm's alliance portfolio level, lead to an inverted U‐shaped relationship between alliance partner repeatedness and breakthrough innovations. Further, we build on the recent theoretical development of interorganizational routines to propose that technological dynamism will make the inverted U‐shaped relationship steeper. Analyses of approximately 230 firms in the US biopharmaceutical industry from 1983 to 2002 support our hypotheses. Our findings provide important implications for research on alliance portfolio and management of firm innovation.
Attacking your partners Cui, Victor; Yang, Haibin; Vertinsky, Ilan
Strategic management journal,
December 2018, Volume:
39, Issue:
12
Journal Article
Peer reviewed
Research Summary: This study contributes to the literature on strategic alliances by examining the impact of collaboration on competition between partners in product markets. We integrate the ...alliance learning and social network perspectives to examine how different combinations of exploratory and exploitative alliances between a firm and its partner influence the firm’s competition against its partner in product markets. Using a longitudinal dataset collected in the U.S. pharmaceutical industry (1984–2003), we find an inverted U‐shaped relationship between relative exploration (i.e., the proportion of exploratory alliances in the collaborative portfolio between a firm and its partner) and the firm’s competition against its partner. This relationship is negatively moderated by firms’ relational and structural embeddedness, but positively moderated by their positional embeddedness.
Managerial Summary: This study examines how different combinations of exploratory and exploitative alliances between two firms affect their competition in the product market. Using a 20‐year dataset collected in the U.S. pharmaceutical industry, we find that the proportion of exploratory alliances (i.e., joint development of critical innovations) in the alliance portfolio between a firm and its partner increases the firm’s competition against its partner, up to a tipping point at which such competition starts to decline. Given a certain combination of the two types of alliances, such competition is stronger if the firm has more alternative allies than its partner but weaker if the firm and its partner have previously collaborated or share common allies in their networks.
Cement based composite materials (CBCM) with superior mechanical strength and excellent durability are always desirable in practical applications. Although considerable research has been reported in ...the past decades about the use of Nano materials (NMs) for strength and durability enhancement of cement matrix, there is little information available on the use of graphene nano-sheets and their derivatives (GND) in cement-based materials. Particularly the role of GND in hydration processes and their mechanisms of strengthening in cement matrix are unclear. In this paper, a critical review on recent research findings about GND modified cement-based materials was conducted. The review mainly discussed the influence of GND on properties of cement matrix including microstructure, hydration, mechanical properties, etc. The information revealed in this paper would not only provide a comprehensive understanding of the effect of GND on cement composites, but also provide valuable ideas and guidance for similar studies in the future.
Abstract
Visco‐elastic‐plastic modeling approaches for long‐term tectonic deformation assume that co‐seismic fault displacement can be integrated over 1000s–10,000s years (tens of earthquake cycles) ...with the appropriate failure law, and that short‐timescale fluctuations in the stress field due to individual earthquakes have no effect on long‐term behavior. Models of the earthquake rupture process generally assume that the tectonic (long‐range) stress field or kinematic boundary conditions are steady over the course of multiple earthquake cycles. This study is aimed to fill the gap between long‐term and short‐term deformations by modeling earthquake cycles with the rate‐and‐state frictional (RSF) relationship in Navier‐Stokes equations. We reproduce benchmarks at the earthquake timescale to demonstrate the effectiveness of our approach. We then discuss how these high‐resolution models degrade if the time‐step cannot capture the rupture process accurately and, from this, infer when it is important to consider coupling of the two timescales and the level of accuracy required. To build upon these benchmarks, we undertake a generic study of a thrust fault in the crust with a prescribed geometry. It is found that lower crustal rheology affects the periodic time of characteristic earthquake cycles and the inter‐seismic, free‐surface deformation rate. In particular, the relaxation of the surface of a cratonic region (with a relatively strong lower crust) has a characteristic double‐peaked uplift profile that persists for thousands of years after a major slip event. This pattern might be diagnostic of active faults in cratonic regions.
Plain Language Summary
The numerical modeling method for long‐term tectonic deformations averages out the co‐seismic fault displacement into thousands to tens of thousands of years, and neglects near‐fault damages of earthquakes; therefore, it may not be able to decipher fault activities in detail. Software simulating earthquake rupture dynamics may not have a good estimation of background stress due to long‐term tectonic deformations. In this study, we develop a numerical framework that embeds earthquake rupture dynamics into a long‐term tectonic deformation model by adding inertial terms and using highly adaptive time‐stepping that can capture deformation at plate‐motion rates as well as individual earthquakes. The inertia term, which is neglected in long‐term large‐scale modeling methods, is considered to simulate the dynamic rupture processes. The rate‐and‐state frictional relationship for co‐seismic fault slip is implemented in viscoelastic‐plastic earth. Benchmarks of viscous flow, viscoelastic wave propagation and earthquake cycle simulations are tested. Based on these benchmarks, we undertake a generic study of a thrust fault in crust. We find that lower crustal rheology affects the periodic time of characteristic large earthquake cycles and the inter‐seismic free surface movement. Cratons with a relatively strong lower crust due to lower temperature remain two peaks in surface uplift profiles around the fault zone for thousands of years after one characteristic earthquake, which help identify active faults in cratons.
Key Points
We build code modeling earthquake cycles based on the long‐term tectonic modeling software Underworld
Benchmarks at the earthquake timescale are used to demonstrate the effectiveness of our approach
Cratons may remain two peaks in surface uplift profiles near the active fault for >1000 years after one characteristic earthquake
•The influence of NS on fresh properties and hydration characteristic of CBM has been reviewed.•Incorporation of NS can significantly enhance the mechanical strengths and durability of CBM.•There are ...three main reasons for the performance improvement of CBM with NS.•The addition of NS modified the microstructure and micromechanical strength of C-S-H.
Nowadays, many nanomaterials such as graphene oxide (GO), carbon nanotubes (CNTs), nano silica (NS) etc. have been introduced to improve the microstructures and performances of cement-based materials (CBM). Compared with other nanomaterials, NS has attracted much attention because of its pozzolanic reaction with calcium hydroxide (CH) to form calcium-silicate-hydrate (C-S-H) gel. Although several review papers have been published, the breadth and depth of literature coverage on NS and its effects on CBM is insufficient. This paper is aimed to keep researchers abreast of the latest research in the field. In particular, the influence of NS on CBM properties including workability, setting time, hydration characteristic, calcium leaching, porosity, mechanical strengths, and durability is critically reviewed. It is believed that this review paper will not only arouse new ideas to promote practical application of NS in construction materials but also provide some constructive guidance for similar research in the future.
The global concern regarding the monitoring of construction workers' activities necessitates an efficient means of continuous monitoring for timely action recognition at construction sites. This ...paper introduces a novel approach-the multi-scale graph strategy-to enhance feature extraction in complex networks. At the core of this strategy lies the multi-feature fusion network (MF-Net), which employs multiple scale graphs in distinct network streams to capture both local and global features of crucial joints. This approach extends beyond local relationships to encompass broader connections, including those between the head and foot, as well as interactions like those involving the head and neck. By integrating diverse scale graphs into distinct network streams, we effectively incorporate physically unrelated information, aiding in the extraction of vital local joint contour features. Furthermore, we introduce velocity and acceleration as temporal features, fusing them with spatial features to enhance informational efficacy and the model's performance. Finally, efficiency-enhancing measures, such as a bottleneck structure and a branch-wise attention block, are implemented to optimize computational resources while enhancing feature discriminability. The significance of this paper lies in improving the management model of the construction industry, ultimately aiming to enhance the health and work efficiency of workers.
•Sika-PCE is capable of keeping dispersed GO separated even in alkaline environment.•The dispersing process has a significant impact on the dispersion of GO.•GO can remarkably improve the flexural ...and compressive strength of cement mortar.•SEM and BSE images reveal GO leads to denser matrix and ITZ of cement mortar.
The effects of both the alkaline environment and calcium ions present in cementitious materials leads to the re-agglomeration of previously dispersed GO, and as a result decreases the dispersion of GO in cement matrix. To solve the aforementioned issues, this study compared 6 different kinds of superplasticizers (SP) to optimize the dispersion of GO in saturated Ca(OH)2 solution which can simulate the strong alkaline environment in the microstructure of cement matrix. And the mechanical properties and microstructures of the resulting cement mortar were investigated systematically. The experimental results present that, among the 6 SPs, Sika-PCE exhibits the best dispersibility with the optimal parameters found to be 30% ultrasonication energy and a SP-to-GO ratio of 1:1. Additionally, the dispersing process was found to have a significant impact on the dispersion of GO. The mechanical properties tests indicate that GO can remarkably improve the flexural and compressive strength of cement mortar in early age. The maximum improvement after 3d curing time was 15.48% for flexural strength with the addition of 0.02 wt% and 14.39% for compressive strength with the addition of 0.04 wt%. Scanning electron microscopy (SEM) and Back scattering images reveal that the incorporation of GO in the cement mortar leads to a denser matrix and stronger interfacial transition zone (ITZ) as compared to plain cement mortar. It can be also found that low GO dosage (0.02 wt%) contributes more to the hydration degree enhancement of the matrix of the cement mortar sample, while higher GO dosage (0.04 wt%) results in a denser ITZ in the cement mortar system. With the GO dosage increasing, energy dispersive X-Ray spectrum (EDS) results demonstrate a strong increasing trend in the Ca/Si ratio in both the interface and matrix regions.
Three-dimensional (3D) printed concrete has recently received considerable research attention. In buildings, phase change materials (PCMs) with excellent thermoregulatory properties and thermal ...storage capacity can improve the insulation capacity of external walls and reduce energy consumption. In this study, microencapsulated paraffin was added to a 3D printable material and a 3D printed phase-change concrete was developed, resulting in good printability and buildability. The compressive and flexural strengths were declined maximally by 44.6% and 37.5%, respectively, with 20 wt% PCM mixed. Results from 3D printed room models proved the thermo-regulated performance by regulating the room temperature when mixed with 20 wt% PCM. With the addition of PCM, 3D printed facilities can have sufficient thermal comfort.
Kindlins and talins are integrin-binding proteins that are critically involved in integrin activation, an essential process for many fundamental cellular activities including cell-matrix adhesion, ...migration, and proliferation. As FERM-domain–containing proteins, talins and kindlins, respectively, bind different regions of β-integrin cytoplasmic tails. However, compared with the extensively studied talin, little is known about how kindlins specifically interact with integrins and synergistically enhance their activation by talins. Here, we determined crystal structures of kindlin2 in the apo-form and the β1- and β3-integrin bound forms. The apo-structure shows an overall architecture distinct from talins. The complex structures reveal a unique integrin recognition mode of kindlins, which combines two binding motifs to provide specificity that is essential for integrin activation and signaling. Strikingly, our structures uncover an unexpected dimer formation of kindlins. Interrupting dimer formation impairs kindlin-mediated integrin activation. Collectively, the structural, biochemical, and cellular results provide mechanistic explanations that account for the effects of kindlins on integrin activation as well as for how kindlin mutations found in patients with Kindler syndrome and leukocyte-adhesion deficiency may impact integrin-mediated processes.
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