Hierarchical Interface Research Articles

Simple Hierarchical Interface Design Strategy for Accelerating Solar Evaporation

AbstractInterface design is an efficient way to improve the steam generation performance of solar evaporators. Accompanied with the formation of cellulose nanofiber/polylactic acid/polyaniline (PANI) hybrid aerogel (HA) by Pickering emulsion and in situ polymerization, this paper proposes a new perspective of hierarchical interface design strategy to accelerate the water evaporation driven by solar energy. By changing the concentration and type of doped acid, the distribution gap of different PANI forms in HA can be microscopically designed. PANI nanoclusters with smaller gaps facilitate HA to achieve an improved light absorption, photothermal conversion capability and steam generation rate. Moreover, macro interface design introduces hemispherical depression structures to the HA surface through a simple mold. These recessed surfaces not only increase the light absorption by increasing the multiple reflections and refractions of light on the recesses, but also recover part of the heat radiation loss to the environment. A higher evaporation rate of 1.65 kg m−2 h−1 with a steam generation efficiency of 94.6% is achieved under the irradiation of 1 Sun (100 mw cm−2). Finally, HAs have strong purification ability for various raw water, and are promising in terms of their application potential in the field of energy conversion.

A new route to fabricate multilayer steel with multiscale hierarchical structure

SUS304/A283-C multilayer steels are processed via vacuum hot rolling, which possesses homogeneous layer thickness, straight interface and strong interfacial bonding. The austenite in SUS304 stainless steel layers can transform into α’-martensite in the process of cold rolling deformation, causing the hard SUS304 layer and the soft A283-C layer deformation inconsistency, as a result of the decrease of fracture elongation and the formation of laminated/network hierarchical interface. Annealing could availably regulate the grain characteristics, and the diffusion behavior of alloying element, and could also eliminate dislocation plugging. The hard layer and soft layer present a dual-scale distribution, besides, the grains of every layer change from the nanoscale structure to ultrafine structure. Thus, the multiscale hierarchical structure can be obtained by cold rolling and succedent annealing. Superior tensile properties can be obtained at 650 °C with the ultimate strength of 748 MPa and fracture elongation of 25%. Besides, the excellent bending deformation capacity can be also obtained at 650 °C. Therefore, the multilayer steel with multiscale hierarchical structure containing laminated/network structure in micro scale, hierarchical grain structure in submicron scale is conducive to strengthening and toughening multilayer steels.

Bioinspired hierarchical interface design for improved mechanical and safety properties in energetic polymer composites

Weak interfacial interaction and poor surface wettability always restrict and weaken the performances of energetic composites. Conventional surface modifications can hardly achieve a desired result, due to the inadequacy for solving the interfacial incompatibility. We here demonstrated bioinspired hierarchical-structured 2,6-diamino-3,5-dinitropyrazine-1-oxide particles through in situ “grafting from” polymerization of hyperbranched polyurethane (HBPU) on polydopamine surface. Benefiting from the enhanced interfacial interaction and surface wettability which facilitated mechanical performance, the final results revealed that a remarkable mechanical enhancement was successfully achieved through this way. Meanwhile, improved safety performance was gained, and the impact sensitivity was reduced to a large extent which was ascribed to the cushioning and protective effects of HBPU shells with soft segments. We believe this approach of constructing bioinspired hierarchical interface aiming at solving low surface wettability and weak interface will shed light on the design and preparation of high-performance composites through a novel and effective way.

Enhanced out of Plane Electrical Conductivity in Polymer Composites Induced by CO2 Laser Irradiation of Carbon Fibers

The creation of a hierarchical interface between the carbon fiber (CF) and the epoxy resin matrix of fiber-reinforced polymer (CFRP) composites has become an effective strategy for introducing multifunctional properties. Although the efficacy of many hierarchical interfaces has been established in lab-scale, their production is not amenable to high-volume, continuous, cost effective fiber production, which is required for the large-scale commercialization of composites. This work investigates the use of commercially available CO2 laser as a means of nano-structuring the surface of carbon fiber (CF) tows in an incessant throughput procedure. Even though the single carbon fiber tensile strength measurements showed a decrease up to 68% for the exposed CFs, the electrical conductivity exhibited an increment up to 18.4%. Furthermore, results on laminates comprised of irradiated unidirectional CF cloth, demonstrated an enhancement in out of plane electrical conductivity up to 43%, while preserved the Mode-I interlaminar fracture toughness of the composite, showing the potential for multifunctionality. This work indicates that the laser-induced graphitization of the CF surface can act as an interface for fast and cost-effective manufacturing of multifunctional CFRP composite materials.

How does the non-conscious become conscious?

In this My Word, Joseph LeDoux describes how his work as a graduate student got him interested in human consciousness. Although he has not studied this topic since 1970s, he never stopped thinking and writing about it during his four-decade career exploring how non-conscious processes involving the amygdala detect and respond to danger. Here, he tells us what is on his mind about consciousness these days.

Electrophysiological evidence of phonemotopic representations of vowels in the primary and secondary auditory cortex

How the brain encodes the speech acoustic signal into phonological representations is a fundamental question for the neurobiology of language. Determining whether this process is characterized by tonotopic maps in primary or secondary auditory areas, with bilateral or leftward activity, remains a long-standing challenge. Magnetoencephalographic studies failed to show hierarchical and asymmetric hints for speech processing. We employed high-density electroencephalography to map the Salento Italian vowel system onto cortical sources using the N1 auditory evoked component. We found evidence that the N1 is characterized by hierarchical and asymmetrical indexes in primary and secondary auditory areas structuring vowel representations. Importantly, the N1 was characterized by early and late phases. The early N1 peaked at 125–135 msec and was localized in the primary auditory cortex; the late N1 peaked at 145–155 msec and was localized in the left superior temporal gyrus. We showed that early in the primary auditory cortex, the cortical spatial arrangements—along the lateral-medial and anterior-posterior gradients—are broadly warped by phonemotopic patterns according to the distinctive feature principle. These phonemotopic patterns are carefully refined in the superior temporal gyrus along the inferior-superior and anterior-posterior gradients. The dynamical and hierarchical interface between primary and secondary auditory areas and the interaction effects between Height and Place features generate the categorical representation of the Salento Italian vowels.

Improvement of Stiffness and Energy Absorption by Harnessing Hierarchical Interlocking in Brittle Polymer Blocks

The objective of the present work is to investigate the possibility of improving both stiffness and energy absorption in interlocking, architectured, brittle polymer blocks through hierarchical design. The interlocking mechanism allows load transfer between two different material blocks by means of contact at the mating surfaces. The contacting surfaces further act as weak interfaces that allow the polymer blocks to fail gradually under different loading conditions. Such controlled failure enhances the energy absorption of the polymer blocks but with a penalty in stiffness. Incorporating hierarchy in the form of another degree of interlocking at the weak interfaces improves stress transfer between contacting material blocks; thereby, improvement in terms of stiffness and energy absorption can be achieved. In the present work, the effects of hierarchy on the mechanical responses of a single interlocking geometry have been investigated systematically using finite element analysis (FEA) and results are validated with experiments. From finite element (FE) predictions and experiments, presence of two competing failure mechanisms have been observed in the interlock: the pullout of the interlock and brittle fracture of the polymer blocks. It is observed that the hierarchical interface improves the stiffness by restricting sliding between the contacting surfaces. However, such restriction can lead to premature fracture of the polymer blocks that eventually reduces energy absorption of the interlocking mechanism during pullout deformation. It is concluded that the combination of stiffness and energy absorption is optimal when fracture of the polymer blocks is delayed by allowing sufficient sliding at the interfaces.

Ferroelectric nanocomposite networks with high energy storage capacitance and low ferroelectric loss by designing a hierarchical interface architecture.

Nanoscale design of nanofillers and interfacial architecture are vital to achieve high-capacity and high-energy-conversion efficiency poly(vinylidene fluoride) [(PVDF)-based] nanocomposite materials for vast potential applications in modern electronic devices and electric power systems. Using traditional methods, the addition of ceramic nanoparticles can only produce one type of interface between the nanoparticles and this matrix, achieving an enhanced dielectric constant and energy density at the expense of the charge-discharge efficiency. Herein, we demonstrate a novel class of cross-linking nanofiller system, poly(vinylidene fluoride-chlorotrifluoroethylene)/γ-methacryloylpropyl trimethoxysilane@BaTiO3 [P(VDF-CTFE)/MPS@BT]. This novel approach can not only provide the interfaces between the nanoparticle and the matrix, but also scale down the size of crystalline domains, which results in producing more additional interfaces between the crystalline and amorphous phases to achieve an improved discharged energy density. Remarkably, the smaller crystalline domains, which were characterized by XRD and FTIR spectroscopy, could be beneficial for improving the dipole switchability from the polar phases to non-polar phases during the charge-discharge cycles, leading to unprecedented charge-discharge efficiency. Furthermore, the addition of MPS@BT NPs can regulate two stages of the discharge rate. The early discharge process can be accelerated, while the following stage is obviously delayed. The simplicity of the hierarchical interfacial engineering method provides a promising path to design ferroelectric polymer nanocomposites for dielectric capacitor applications.

Tribochemistry of adaptive integrated interfaces at boundary lubricated contacts

Understanding how an adaptive integrated interface between lubricant additives and solid contacts works will enable improving the wear and friction of moving engine components. This work represents the comprehensive characterization of compositional and structural orientation at the sliding interface from the perspective of surface/interface tribochemistry. The integrated interface of a lubricant additive-solid resulting from the friction testing of Graphite-like carbon (GLC) and PVD-CrN coated rings sliding against cast iron under boundary lubrication was studied. The results indicate that in the case of the CrN/cast iron pair the antiwear and friction behavior were very strongly dependent upon lubricant. In contrast, the tribology of the GLC surface showed a much lower dependence on lubrication. In order to identify the compounds and their distribution across the interface, x-ray microanalysis phase mapping was innovatively applied and the principle of hard and soft acids and bases (HSAB) to understand the behaviour. Phase mapping clearly showed the hierarchical interface of the zinc-iron polyphosphate tribofilm for various sliding pairs and different sliding durations. This interface structure formed between lubricant additives and the sliding surfaces adapts to the sliding conditions – the term adaptive interface. The current results help explain the tribology of these sliding components in engine.

To Thread or Not to Thread: The Impact of Conversation Threading on Online Discussion

Online discussion is essential for the communication and collaboration of online communities. The reciprocal exchange of messages between users that characterizes online discussion can be represented in many different ways. While some platforms display messages chronologically using a simple linear interface, others use a hierarchical (threaded) interface to represent more explicitly the structure of the discussion. Although the type of representation has been shown to affect communication, to the best of our knowledge, the impact of using either one or the other has not yet been investigated in a large and mature online community. In this work we analyze Meneame, a popular Spanish social news platform which recently transitioned from a linear to a hierarchical interface, becoming an ideal research opportunity for this purpose. Using interrupted time series analysis and regression discontinuity design, we observe an abrupt and significant increase in social reciprocity after the adoption of a threaded interface. We furthermore extend state-of-the-art generative models of discussion threads by including reciprocity, a fundamental feature to explain better the structure of the discussions, both before and after the change in the interface.

Protective molecular passivation of black phosphorus

Black phosphorus is a fascinating layered material, with extraordinary anisotropic mechanical, optical and electronic properties. However, the sensitivity of black phosphorus to oxygen and moisture poses significant challenges for technological applications of this unique material. Here, we report a viable solution that overcomes degradation of few-layer black phosphorus by passivating the surface with self-assembled monolayers of octadecyltrichlorosilane that provide long-term stability in ambient conditions. Importantly, we show that this treatment does not cause any undesired carrier doping of the bulk channel material, thanks to the emergent hierarchical interface structure. Our approach is compatible with conventional electronic materials processing technologies thus providing an immediate route toward practical applications in black phosphorus devices.

Mapping metadata to DDC classification structures for searching and browsing

In this paper, we introduce a metadata visual interface based on metadata aggregation and automatic classification mapping. We demonstrate that it is possible to aggregate metadata records from multiple unrelated repositories, enhance them through automatic classification, and present them in a unified visual interface. The main features of the interface include dynamic querying using DDC classes as filters, interactive visual views of search results and related DDC classes, and drill-down options for searching and browsing in different levels of details. The interface was tested in a user study of 30 subjects. A comparison was done on three modules of the interface, namely `search interface', `hierarchical interface', and `visual interface.' The results indicate that subjects performed well with all the three interfaces, and they had more positive experience with the hierarchical interface than with the search interface and the visual interface.

Parallel Iterative Solvers for Ill-conditioned Problems with Heterogeneous Material Properties

The efficiency and robustness of preconditioned parallel iterative solvers, based on domain decomposition for ill-conditioned problems with heterogeneous material properties, are evaluated in the present work. The preconditioning method is based on the BILUT(p,d,t) method proposed by the author in a previous study, and two types of domain decomposition procedures, LBJ (Localized Block Jacobi) and HID (Hierarchical Interface Decomposition), are considered. The proposed methods are implemented using the Hetero3D code, which is a parallel finite-element benchmark program for solid mechanics problems, and the code provides excellent scalability and robustness on up to 240 nodes (3,840 cores) of the Fujitsu PRIMEHPC FX10 (Oakleaf-FX) at the Information Technology Center, the University of Tokyo. Generally, HID provides better efficiency and robustness than LBJ for a wide range of values of parameters.

Biomimetic Nanostructured Interfaces for Hierarchical Composites

Creating a hierarchical interface between the reinforcement and matrix phases of fiber reinforced polymer composites has become an effective strategy toward development of bioinspired structural composites. The resulting materials display exceptional characteristics such as having both high stiffness and high toughness simultaneously, which is rare in homogeneous materials. Although the efficacy of nanostructured interfaces has been established, the mechanisms associated with their performance have not been explored yet. Here, strain transfer across a nanowire interphase is visualized in order to understand the working principles of physical interface modifications. This is accomplished by using a functionally graded piezoelectric interface composed of nanowires, as their piezoelectric properties can be utilized to control the strain on one side of the interface. It is demonstrated that the nanowire “whiskers” cause an even strain transfer from the reinforcement phase into the matrix phase, eliminating stress concentration between the phases.

Pickering Emulsion Gels Prepared by Hydrogen-Bonded Zein/Tannic Acid Complex Colloidal Particles.

Food-grade colloidal particles and complexes, which are formed via modulation of the noncovalent interactions between macromolecules and natural small molecules, can be developed as novel functional ingredients in a safe and sustainable way. For this study was prepared a novel zein/tannic acid (TA) complex colloidal particle (ZTP) based on the hydrogen-bonding interaction between zein and TA in aqueous ethanol solution by using a simple antisolvent approach. Pickering emulsion gels with high oil volume fraction (φ(oil) > 50%) were successfully fabricated via one-step homogenization. Circular dichroism (CD) and small-angle X-ray scattering (SAXS) measurements, which were used to characterize the structure of zein/TA complexes in ethanol solution, clearly showed that TA binding generated a conformational change of zein without altering their supramolecular structure at pH 5.0 and intermediate TA concentrations. Consequently, the resultant ZTP had tuned near neutral wettability (θ(ow) ∼ 86°) and enhanced interfacial reactivity, but without significantly decreased surface charge. These allowed the ZTP to stabilize the oil droplets and further triggered cross-linking to form a continuous network among and around the oil droplets and protein particles, leading to the formation of stable Pickering emulsion gels. Layer-by-layer (LbL) interfacial architecture on the oil-water surface of the droplets was observed, which implied a possibility to fabricate hierarchical interface microstructure via modulation of the noncovalent interaction between hydrophobic protein and natural polyphenol.

Constructing Hierarchical Interfaces: TiO2-Supported PtFe-FeO(x) Nanowires for Room Temperature CO Oxidation.

In this communication, we report a facile approach to constructing catalytic active hierarchical interfaces in one-dimensional (1D) nanostructure, exemplified by the synthesis of TiO2-supported PtFe-FeO(x) nanowires (NWs). The hierarchical interface, constituting atomic level interactions between PtFe and FeO(x) within each NW and the interactions between NWs and support (TiO2), enables CO oxidation with 100% conversion at room temperature. We identify the role of the two interfaces by probing the CO oxidation reaction with isotopic labeling experiments. Both the oxygen atoms (Os) in FeO(x) and TiO2 participate in the initial CO oxidation, facilitating the reaction through a redox pathway. Moreover, the intact 1D structure leads to the high stability of the catalyst. After 30 h in the reaction stream, the PtFe-FeO(x)/TiO2 catalyst exhibits no activity decay. Our results provide a general approach and new insights into the construction of hierarchical interfaces for advanced catalysis.

Influence of thermo-oxidative aging on vibration damping characteristics of conventional and graphene-based carbon fiber fabric composites

The effect of thermo-oxidative aging on the vibration damping characteristics of the conventional fabric composites reinforced by three-dimensional (3D) and four-directional (4Dir) braided preform and laminated plain woven fabric and the 3D-4Dir braided graphene-based carbon fiber composites was investigated. Specimens were isothermally aged at 140 °C for various periods of time up to 1,200 h. The results indicated that the thermo-oxidative aging resulted in deterioration of the matrix and interface performance, in the form of chain scissions, weight loss, microcracks and interfacial debonding, which should be responsible for the decrease of nature frequency and the increase of damping coefficient of the composites. After aging for 1,200 h, the first nature frequency and first damping coefficient retention rates of 3D-4Dir braided graphene-coated carbon fiber/epoxy composite were 5.5% and 6.4% higher than those of laminated composite, respectively. One of the reasons was the integrated structure of 3D-4Dir braided composite exposed lower fiber end area to air than that of laminated composite, leading to less interface oxidation. Another reason was that the graphene reinforced gradient interphase provided an effective shield against interface oxidation and restricted the movement of the different phase of the materials at the composites interface. This synergetic reinforcing effect of 3D-4Dir braided structure and graphene reinforced hierarchical interface provides an easy and effective way to design and improve the thermo-oxidative stability of carbon fiber reinforced polymer composites. POLYM. COMPOS., 37:2871–2883, 2016. © 2015 Society of Plastics Engineers

Experimental study and numerical simulation of spread law for fire on tunnel

In order to research spread law and distribution law of temperature nearby fire sources on roadway in mine, according to combustion theory and other basic, the theory model of temperature attenuation was determined under unsteady heat-exchange between wind and roadway wall. The full-size roadway fire simulation experiments were carried out in Chongqing Research Institute of China Coal Technology & Engineering Group Corporation. The development processes of mine fire and flow pattern of high temperature gas were analyzed. Experimental roadway is seen as physical model, and through using CFD software, the processes of mine fire have been simulated on computer. The results show that, after fire occurs, if the wind speed is less than the minimum speed which can prevent smoke from rolling back, then the smaller wind speed can cause smoke to roll back easily. Hot plume will lead to secondary disasters in upwind side. Because of roadway wall, hot plume released from roadway fire zone has caused the occurrence of the ceiling jet, and the hot plume has been forced down. Whereas, owing to the higher temperature, buoyancy effect is more obvious. Therefore, smoke rises gradually along the roadway in the flow process, and the hierarchical interface appears wavy. Oxygen-enriched combustion and fuel-enriched combustion are the two kinds of combustion states of fire. The oxygen content of downwind side of fire is maintained at around 15% for oxygen-enriched combustion, and the oxygen content of downwind side of fire is maintained at around 2% for fuel-enriched combustion. Furthermore, fuel-enriched combustion can lead to secondary disasters easily.

Influence of thermo-oxidative aging on the impact property of conventional and graphene-based carbon fabric composites

The effects of reinforced structure (three-dimensional braided preform and laminated plain woven fabric) and graphene nanoplatelet-reinforced hierarchical interface on the impact properties of carbon fabric composites after thermo-oxidative aging were investigated. The results indicated that the impact properties decreased with increasing aging time due to the degradation of the matrix and fiber–matrix interface. After exposure to 140℃ for 1200 h, the peak impact force and impact strength retention rates of 3D-braided graphene nanoplatelet-coated carbon fiber-reinforced composite were 13% and 8% higher than those of the laminated composite, respectively. One of the reasons was the graphene nanoplatelet-reinforced gradient interphase may provide an effective shield against interface oxidation, transfer the localized thermal stress, and restrict the movement of the different phase of the materials at the composites interface. Another reason was the integrated structure of the 3D-braided composite can make the fiber bear impact force together although the resin was damaged and the adhesive force between fiber bundles and resin decreased after thermo-oxidative aging. This synergetic reinforcing effect of 3D-braided structure and graphene nanoplatelet-reinforced hierarchical interface provides an easy and effective way to design and improve the thermo-oxidative stability of carbon fiber-reinforced composites.

Development and Usability Testing of Dr. Liver™

The present study developed a user-centered 3D virtual liver surgery planning system called Dr. Liver™ to assist surgeons in preoperative planning of liver surgeries such as living donor liver transplantation and tumor resection. Use scenarios of Dr. Liver were developed through literature review, benchmarking, and interviews with surgeons. The major functions of Dr. Liver include (1) 3D reconstruction of the liver, vessels, and tumors from abdominal CT images, (2) virtual resection simulation for liver surgery planning, and (3) volumetric measurement of the liver, vessels, tumors, remnant, and/or graft. Novel image processing algorithms were developed and implemented into Dr. Liver for accurate and efficient liver surgery planning. Various user-friendly features such as a hierarchical interface were integrated into Dr. Liver for better usability. The usability of Dr. Liver was systematically evaluated with eight medical doctors from three different medical centers using various performance and preference measures. Dr. Liver received a high score of user satisfaction (6.1 ± 0.2) as measured using a 7-point Likert scale. Dr. Liver will be used in preoperative liver surgery planning for safe and rational liver surgery.