Due to advancements made in 3D weaving process, 3D woven composites have evolved as an attractive structural material for multi-directional load bearing and impact applications, due to their unique ...transverse properties such as stiffness, strength, fracture toughness and damage resistance. Substantial progress has been made in recent years for the development of new modeling techniques in design and analysis to understand the unique mechanical behavior of 3D woven composites. This paper systematically reviews the modeling techniques along with their capabilities and limitations for characterization of the micro-geometry, mechanical/thermo-mechanical behavior and impact behavior of 3D woven composites. Advantages, disadvantages and applications of 3D woven composites have also been delineated. In addition, this reference list provides a good database for future research on 3D woven composites.
Over the last two decades, with the fast development of micro/nanomaterials, including micro/nanoscale and micro/nanostructured materials, significant attention has been attracted to study the energy ...transport in them ....
•Critically review the mechanisms of Raman spectrum response to temperatures and the conjugation of various physical and optical factors•Cover the steady-state Raman spectroscopy for temperature and ...thermal properties measurement and discuss the large error sources and ways to reducing them•Provide detailed discussion and review of the spatial resolution of Raman-based temperature measurement•Cover the frontier research on conjugated phonon and hot carrier transfer and how to use Raman spectroscopy to distinguish and characterize them•Critically review the time-domain, frequency domain, and energy transport domain Raman spectroscopies for thermal response and thermal properties characterization•Provide invaluable comments for future Raman development to further improve the accuracy, spatial resolution, and time resolution. Abstract
Raman-based thermal characterization is regarded as an invaluable tool in micro/nanoscale heat transfer research, offering exceptional contrast in conjunction with high specificity of noncontact and material specific temperature measurement compared with competing thermometry techniques at the micro/nanoscale. It has been extensively used to determine the thermophysical properties of micro/nanoscale materials. However, for commonly used steady state Raman methods, as two concluded main factors, the temperature coefficients of Raman properties and heating level (or optical absorption) will affect the accuracy of resulting temperature and thermal properties. In this review, we critically discuss the mechanism of Raman spectrum response to temperature and possible error factors in calibration and measurement. In addition, the influence of measurement setup is discussed, and possible technical solutions for improving the measurement accuracy are reviewed. Among noble developments in Raman-based thermal characterizations, the transient heat transfer analysis has been coupled to advances in noncontact Raman-based thermal measurement. By enhancing the temporal and spatial resolution in existing technical conditions, more efficient and accurate transient thermal properties measurement can be realized. Particular attention is paid to the so-called resolved Raman techniques for simultaneous measurement of multiple thermal properties at the micro/nanoscale. In particular, we critically review how these tools can reveal new insights into the complex energy transport processes in 2D semiconductors, which have been impossible to tackle using traditional tools. Considering its precision and sensitivity, there is still a large room for development of Raman techniques for the investigation of complex and coupled heat transfer process in low dimensions and new materials.
We developed a facile technique to produce ethylene glycol based nanofluids containing graphene nanosheets. The thermal conductivity of the base fluid was increased significantly by the dispersed ...graphene: up to 86% increase for 5.0 vol % graphene dispersion. The 2D structure and stiffness of graphene and graphene oxide help to increase the thermal conductivity of the nanofluid. The thermal conductivity of graphene oxide and graphene in the fluid were estimated to be ∼4.9 and 6.8 W/m K, respectively.
Atomic layer deposition (ALD) of cobalt sulfide (Co9S8) is reported. The deposition process uses bis(N,N′-diisopropylacetamidinato)cobalt(II) and H2S as the reactants and is able to produce ...high-quality Co9S8 films with an ideal layer-by-layer ALD growth behavior. The Co9S8 films can also be conformally deposited into deep narrow trenches with aspect ratio of 10:1, which demonstrates the high promise of this ALD process for conformally coating Co9S8 on high-aspect-ratio 3D nanostructures. As Co9S8 is a highly promising electrochemical active material for energy devices, we further explore its electrochemical performance by depositing Co9S8 on porous nickel foams for supercapacitor electrodes. Benefited from the merits of ALD for making high-quality uniform thin films, the ALD-prepared electrodes exhibit remarkable electrochemical performance, with high specific capacitance, great rate performance, and long-term cyclibility, which highlights the broad and promising applications of this ALD process for energy-related electrochemical devices, as well as for fabricating complex 3D nanodevices in general.
Developing low‐cost, high‐performance electro‐catalysts is essential for large‐scale application of electrochemical energy devices. In this article, reported are the findings in understanding and ...controlling oxygen defects in PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) for significantly enhancing the rate of oxygen evolution reaction (OER) are reported. Utilizing surface‐sensitive characterization techniques and first‐principle calculations, it is found that excessive oxygen vacancies promote OH− affiliation and lower the theoretical energy for the formation of O* on the surface, thus greatly facilitating the OER kinetics. On the other hand, however, oxygen vacancies also increase the energy band gap and lower the O 2p band center of PBSCF, which may hinder OER kinetics. Still, careful tuning of these competing effects has resulted in enhanced OER activity for PBSCF with oxygen defects. This work also demonstrates that oxygen defects generated by different techniques have very different characteristics, resulting in different impacts on the activity of electrodes. In particular, PBSCF nanotubes after electrochemical reduction exhibit outstanding OER activity compared with the recently reported perovskite‐based catalysts.
Oxygen vacancies in PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) are found to promote OH‐ affiliation and lower the theoretical energy for the formation of O* on the surface. However, oxygen vacancies also increase the energy band gap and lower the O 2p band center of PBSCF. Careful tuning of these competing effects has resulted in enhanced oxygen evolution reaction activity for PBSCF with oxygen defects.
Vapor-phase atomic layer deposition (ALD) of nickel sulfide (NiS x ) is comprehensively reported for the first time. The deposition process employs bis(N,N′-di-tert-butylacetamidinato)nickel(II) ...and H2S as the reactants and is able to produce fairly smooth, pure, godlevskite-structured NiS x thin films following an ideal layer-by-layer ALD growth fashion for a relatively wide process temperature range from 90–200 °C. Excellent conformal coating is demonstrated for this ALD process, as the deposited NiS x films are able to uniformly and conformally cover deep narrow trenches with aspect ratio as high as 10:1, which highlights the general and broad applicability of this ALD process for fabricating complex 3D-structured nanodevices. Further, we demonstrate the applications of this ALD NiS x for oxygen-evolution reaction (OER) electrocatalysis. The ALD NiS x is found to convert to nickel (oxy)hydrate after electrochemical aging, and the aged product shows a remarkable electrocatalytic activity and long-term stability, which is among the best electrocatalytic performance reported for nonprecious OER catalysts. Considering that ALD can be easily scaled up and integrated with 3D nanostructures, we believe that this ALD NiS x process will be highly promising for a variety of applications in future energy devices.
The pentatricopeptide repeat (PPR) proteins constitute one of the largest nuclear-encoded protein families in higher plants, with over 400 members in most sequenced plant species. The molecular ...functions of these proteins and their physiological roles during plant growth and development have been widely studied. Generally, there is mounting evidence that PPR proteins are involved in the post-transcriptional regulation of chloroplast and/or mitochondrial genes, including RNA maturation, editing, intron splicing, transcripts' stabilization, and translation initiation. The cooperative action of RNA metabolism has profound effects on the biogenesis and functioning of both chloroplasts and mitochondria and, consequently, on the photosynthesis, respiration, and development of plants and their environmental responses. In this review, we summarize the latest research on PPR proteins, specifically how they might function in the chloroplast, by documenting their mechanism of molecular function, their corresponding RNA targets, and their specific effects upon chloroplast biogenesis and host organisms.
The adhesion of as‐formed gas bubbles on the electrode surface usually impedes mass‐transfer kinetics and subsequently decreases electrolysis efficiency. Here it is demonstrated that nanostructured ...MoS2 films on conductive substrates show a faster hydrogen evolution reaction (HER), current increase, and a more‐stable working state than their flat counterpart by significantly alleviating the adhesion of as‐formed gas bubbles on the electrode. This study clearly reveals the importance of a nano‐porous structure for HER, which should be general and beneficial for constructing other gas‐evolution electrodes.
The parameter uncertainty has an important effect on the motion planning of overhead cranes, especially in relation to its industrial safety of production activities. Thus, a novel uncertain ...estimation-and-optimization strategy is proposed for motion planning of overhead cranes with uncertainty in this paper. The main work of this paper includes the following aspects. First, the overhead crane is simplified as a double pendulum model and the corresponding motion planning is described as an optimal control problem with uncertainty. Second, uncertainties are expressed as interval parameters where only the upper and lower bounds are required without probability information and a bounds estimation problem for optimal control with uncertainty is established; the solution contains all possible values. Third, the bounds estimation problem is solved by a surrogate model-based method, the motion trajectory intervals of overhead cranes are obtained. Fourth, in order to reduce the influence of uncertainty on the motion planning of overhead cranes, an optimization method is introduced to reduce the sensitivity to uncertainty. Finally, the numerical examples show that high accurate interval estimation results are obtained with a reasonable computational cost, and the sensitivity of motion trajectory to uncertainty is reduced obviously with the help of optimization. The proposed strategy provides a guidance for uncertain analysis and online controller design of overhead cranes.
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