Revealing the key role of non-solvating diluents for fast-charging and low temperature Li-ion batteries

Fast-charging and low temperature operation are of vital importance for the further development of lithium-ion batteries(LIBs),which is hindered by the utilization of conventional carbonate-based electrolytes due to their slow kinetics,narrow operating temperature and voltage range.Herein,an acetonitrile(AN)-based localized high-concentration electrolyte(LHCE)is proposed to retain liquid state and high ionic conductivity at ultra-low temperatures while possessing high oxidation stability.We originally reveal the excellent thermal shielding effect of non-solvating diluent to prevent the aggregation of Li^(+) solvates as temperature drops,maintaining the merits of fast Li transport and facile desolvation as at room temperature,which bestows the graphite electrode with remarkable low temperature performance(264 mA h g^(-1) at-20 C).Remarkably,an extremely high capacity retention of 97%is achieved for high-voltage high-energy graphite||NCM batteries after 250 cycles at-20 C,and a high capacity of 110 mA h g^(-1)(71%of its room-temperature capacity)is retained at-30°C.The study unveils the key role of the non-solvating diluents and provides instructive guidance in designing electrolytes towards fast-charging and low temperature LIBs.

Study on Electromagnetic Shielding Effectiveness of Ni-P-La Alloy Coatings

Ni-P and Ni-P-La alloy coatings were prepared by electroplating. Electromagnetic shielding effectiveness under the different components of rare earth or the different operating conditions was tested by the network analyzer. The results show that electromagnetic shielding effectiveness of Ni-P-La alloy coating varies from 45 dB to 70 dB with the variety of the frequency from 10 MHz to 350 MHz. Corrosion of the salt fog impacts on the electromagnetic shielding effectiveness a little. A small amount of rare earth added to plating bath can not only enhance corrosion resistance of coating, but make electromagnetic shielding effectiveness increase by 1 ~ 5 dB.

Shielding effect and emission criterion of a screw dislocation near an interfacial blunt crack

Shielding effect and emission criterion of a screw dislocation near an interracial blunt crack are dealt with in this paper. Utilizing the conformal mapping technique, the closed-form solutions are derived for complex potentials and stress fields due to a screw dislocation located near the interracial blunt crack. The stress intensity factor on the crack tips and the critical stress intensity factor for dislocation emission are also calculated. The influence of the orientation of the dislocation and the morphology of the blunt crack as well as the material elastic dissimilarity on the shielding effect and the emission criterion is discussed in detail. The results show that positive screw dislocations can reduce the stress intensity factor of the interfacial blunt crack tip （shielding effect）. The shielding effect increases with the increase of the shear modulus of the lower half-plane, but it decreases with the increase of the dislocation azimuth angle. The critical loads at infinity for dislocation emission increases with the increase of emission angle and curvature radius of blunt crack tip, and the most probable angle for screw dislocation emission is zero. The present solutions contain previous results as special cases.

The Shielding Effect of Multi-Pile Structures on Ice Force

The shielding effect of the front pile-row on the ice force acting on the back pile-row is studied by ice force model tests. In the tests, the front pile-row is designed to model jacket legs and the back pile-row to model the water resisting pipe-phalanx within the jacket. The shielding factor for ice force corresponding to different conditions are given in this paper. The research indicates that there are many factors, including the longitudinal and lateral spacing between the front and back pile-row, ice attacking angle and the ratio of pile diameter to ice thickness, that influence the shielding effect on ice force.

Shielding effect of a nano-circular inclusion acting on semi-infinite wedge cracks

The model of a screw dislocation near a semi-infinite wedge crack tip inside a nano-circular inclusion is proposed to investigate the shielding effect of nano inclusions acting on cracks. Utilizing the complex function method, the closed-form solutions of the stress fields in the matrix and the inclusion region are derived. The stress intensity factor, the image force, as well as the critical loads for dislocation emission are discussed in detail. The results show that the nano inclusion not only enhances the shielding effect exerted by the dislocation, but also provides a shielding effect itself. Moreover, dislocations may be trapped in the nano inclusion even if the matrix is softer than the inclusion. This helps the dislocation shield crack, and reduces the dislocation density within the matrix.

Performance study of aluminum shielded room for ultra-low-field magnetic resonance imaging based on SQUID： Simulations and experiments

The aluminum shielded room has been an important part of ultra-low-field magnetic resonance imaging （ULF MRI） based on the superconducting quantum interference device （SQUID）. The shielded room is effective to attenuate the external radio-frequency field and keep the extremely sensitive detector, SQUID, working properly. A high-performance shielded room can increase the signal-to-noise ratio （SNR） and improve image quality. In this study, a circular coil with a diameter of 50 cm and a square coil with a side length of 2.0 m was used to simulate the magnetic fields from the nearby electric apparatuses and the distant environmental noise sources. The shielding effectivenesses （SE） of the shielded room with different thicknesses of aluminum sheets were calculated and simulated. A room using 6-mm-thick aluminum plates with a dimension of 1.5 m x 1.5 m x 2.0 m was then constructed. The SE was experimentally measured by using three-axis SQUID magnetometers, with tranisent magnetic field induced in the aluminum plates by the strong pre-polarization pulses. The results of the measured SE agreed with that from the simulation. In addition, the introduction of a 0.5-mm gap caused the obvious reduction of SE indicating the importance of door design. The nuclear magnetic resonance （NMR） signals of water at 5.9 kHz were measured in free space and in a shielded room, and the SNR was improved from 3 to 15. The simulation and experimental results will help us design an aluminum shielded room which satisfies the requirements for future ULF human brain imaging. Finally, the cancellation technique of the transient eddy current was tried, the simulation of the cancellation technique will lead us to finding an appropriate way to suppress the eddy current fields.

Synthesis of two derivatives of tigogenyl disaccharides containing N-acetylglucosamine and the long range shielding effect of benzoyl groups

Two tigogenyl glycosides containing N-acetylglucosamine were synthesized. Their structures were confirmed by ^1H and ^13C NMR spectra. The shielding effect caused by benzoyl groups was elucidated by ^1H NMR, COSY, HSQC, HMBC spectroscopy.

Analysis on the Magnetic Shielding Effectiveness of DC Current Comparator

There are magnetic interference problems in the applications of DC current comparator. Analysis on the magnetic effectiveness which is applied by the external magnetic field is introduced in this paper. The effectiveness is proved by the actual results which are compared with the magnetic- circuit method and the finite element method. In addition, the reference comment is given which can be used in the practical work of DC current comparator shield design.

Correlation between Electrical Conductivity and Microwave Shielding Effectiveness of Natural Rubber Based Composites, Containing Different Hybrid Fillers Obtained by Impregnation Technology

The paper presents the synthesis and characterization of carbon black/silicone dioxide hybrid fillers obtained by an impregnation technology. The electromagnetic interference shielding effectiveness of the composites filled with carbon black/silicone dioxide hybrid fillers was measured in wide frequency range of 1 - 12 GHz. The dc and ac electrical conductivity of composites also have been investigated. The relationship between electrical (dc and ac) conductivity and shielding effectiveness was analyzed. A positive correlation was found between the absorptive shielding effectiveness and ac conductivity for composites comprising conductive carbon black/silica filler, when the filler loading is above the percolation threshold.

Trace Amounts of Triple-Functional Additives Enable Reversible Aqueous Zinc-Ion Batteries from a Comprehensive Perspective

Although their cost-effectiveness and intrinsic safety,aqueous zinc-ion batteries suffer from notorious side reactions including hydrogen evolution reaction,Zn corrosion and passivation,and Zn dendrite formation on the anode.Despite numerous strategies to alleviate these side reactions have been demonstrated,they can only provide limited performance improvement from a single aspect.Herein,a triple-functional additive with trace amounts,ammonium hydroxide,was demonstrated to comprehensively protect zinc anodes.The results show that the shift of electrolyte pH from 4.1 to 5.2 lowers the HER potential and encourages the in situ formation of a uniform ZHS-based solid electrolyte interphase on Zn anodes.Moreover,cationic NH^(4+)can preferentially adsorb on the Zn anode surface to shield the“tip effect”and homogenize the electric field.Benefitting from this comprehensive protection,dendrite-free Zn deposition and highly reversible Zn plating/stripping behaviors were realized.Besides,improved electrochemical performances can also be achieved in Zn//MnO_(2)full cells by taking the advantages of this triple-functional additive.This work provides a new strategy for stabilizing Zn anodes from a comprehensive perspective.

Direct conversion of CO_(2)to graphene via vapor–liquid reaction for magnesium matrix composites with structural and functional properties

Converting CO_(2)to valuable materials is attractive in environmental protection and resource utilization.In this study,a vapor-liquid interface reaction system for mass production of high-quality graphene is reported.The graphene obtained has high crystallinity and few defects during the reaction of CO_(2)and Mg melt.The growth mechanism of graphene is demonstrated in vapor-liquid interface area by combining the CO_(2)bubbles as a soft template to guide growth with the confinement effect of dense MgO nanoparticles.The quality of the graphene is verified by epoxy composites with high electromagnetic shielding effectiveness.Additionally,the V-L reaction method ingeniously solves the dispersion of graphene in metal,providing a preparation strategy of Mg matrix composites with structure and function integration.

Electromagnetic Shielding and Absorption Properties of Fiber Reinforced Cementitious Composites

In order to investigate the electromagnetic shielding effectiveness （SE） and absorbing properties of fiber reinforced concrete, steel fiber, carbon fiber and synthetic polyvinyl alcohol （PVA） fiber reinforced concrete were researched. The results show that with the increase of fiber Volume fraction, the SE and trend of frequency change of corresponding fiber reinforced concrete are enhanced. When the volume content of steel fiber is 3%, the SE of concrete is above 50 dB and its frequency is above 1.8 GHz. Moreover, in the range of 8-18 GHz, steel fiber, carbon fiber and PVA fiber all can improve the microwave absorption properties of concrete. The concrete with 0.5% carbon fiber can achieve the best absorbing property, the minimum reflectivity is about -7 dB; while steel fiber optimal volume fraction is 2%. The reflectivity curve of PVA fiber reinforced concrete fluctuates with the frequency, and the minimum value of the reflectivity is below -10 dB. The results show that fiber reinforced concrete could be used as EMI（electromagnetic interference） prevention buildings by attenuating and reflecting electromagnetic wave energy.

Aerodynamic characteristics of a high-speed train crossing the wake of a bridge tower from moving model experiments

In a strong crosswind,the wake of a bridge tower will lead to an abrupt change of the aerodynamic forces acting on a vehicle passing through it,which may result in problems related to the transportation safety.This study investigates the transient aerodynamic characteristics of a high-speed train moving in a truss girder bridge and passing by a bridge tower in a wind tunnel.The scaled ratio of the train,bridge,and tower are 1:30.Effects of various parameters such as the incoming wind speed,train speed,and yaw angle on the aerodynamic performance of the train were considered.Then the sudden change mechanism of aerodynamic loads on the train when it crosses over the tower was further discussed.The results show that the bridge tower has an apparent shielding effect on the train passing through it,with the influencing width being larger than the width of the tower.The train speed is the main factor affecting the influencing width of aerodynamic coefficients,and the mutation amplitude is mainly related to the yaw angle obtained by changing the incoming wind speed or train speed.The vehicle movement introduces an asymmetry of loading on the train in the process of approaching and leaving the wake of the bridge tower,which should not be neglected.

Performance of Polyaniline-coated Short Carbon Fibers in Electromagnetic Shielding Coating

Combined nitric acid oxidation method and polyaniline （PANI）-coated method were applied to modify the surface properties of short carbon fibers （SCF）. The electrical and mechanical properties of acrylic coatings with 50 wt pct PANI-coated carbon fiber were investigated by using scanning electron microscope （SEM）, UV-Vis spectrophotometer, four-probe method and the coaxial cable method. The results of the pH measurement and XPS （X-ray photoelectron spectroscopy） patterns showed that the oxygen functional groups, such as -OH and -COOH, were attached on the carbon fiber surfaces after oxidation treatment. The XPS analysis of PANl-coated oxidized SCF （PAOSCF） revealed that PANI may bond on the surface of oxidized SCF with chemical bonds. SEM images and surface roughness analyses showed that PANl-coated layer changed the surface morphology. Compared with SCF/acrylic coating, the surface resistivity of PAOSCF/acrylic coating decreased from17.1 to 5.3 Ω/sq and the shielding efficiency （SE） value increased from 1.54 to 23.3 dB.

A transparent electromagnetic-shielding film based on one-dimensional metal–dielectric periodic structures

In this study, we designed and fabricated optical materials consisting of alternating ITO and Ag layers. This approach is considered to be a promising way to obtain a light-weight, ultrathin and transparent shielding medium, which not only transmits visible light but also inhibits the transmission of microwaves, despite the fact that the total thickness of the Ag film is much larger than the skin depth in the visible range and less than that in the microwave region. Theoretical results suggest that a high dielectric/metal thickness ratio can enhance the broadband and improve the transmittance in the optical range. Accordingly, the central wavelength was found to be red-shifted with increasing dielectric/metal thickness ratio. A physical mechanism behind the controlling transmission of visible light is also proposed. Meanwhile, the electromagnetic shielding effectiveness of the prepared structures was found to exceed 40 dB in the range from 0.1 GHz to 18 GHz, even reaching up to 70 dB at 0.1 GHz, which is far higher than that of a single ITO film of the same thickness.

Elastic behaviour of an edge dislocation near a sharp crack emanating from a semi-elliptical blunt crack

The interaction between an edge dislocation and a crack emanating from a senti-elliptic hole is dealt with. Utilizing the complex variable method, closed form solutions are derived for complex potentials and stress fields. The stress intensity factor at the tip of the crack and the image force acting on the edge dislocation are also calculated. The influence of the morphology of the blunt crack and the position of the edge dislocation on the shielding effect to the crack and the image force is examined in detail. The results indicate that the shielding or anti-shielding effect to the stress intensity factor increases acutely when the dislocation approaches the tip of the crack. The effect of the morphology of the blunt crack on the stress intensity factor of the crack and the image force is very significant.

Measurements of Wind Loads on Side-by-Side Semi-Submersibles in A Wind Tunnel

The multi-body system has been a popular form for offshore operations in terms of high efficiency.The wind effects are crucial which directly affect the relative positions of floating bodies and operating security.In this study,the aerodynamic characteristics for two coupled semi-submersibles were analyzed in a wind tunnel to fill the gaps in literature related to the wind sheltering on offshore platforms.The influences of separation distance were also investigated.According to the results,substantial shielding effects were observed and wind forces on the shielded vessel decreased dramatically:a reduction in the transverse force could be up to 74%.Moreover,the longitudinal wind load was amplified by the platform abreast in a side-by-side configuration.As expected,the interference level became more pronounced with a decreasing separation distance.For cases in which wind interaction decayed rapidly with distance,logarithmic functions were preferable for describing the relationship between them.Whereas linear fitting was reasonable for the transverse wind force when there was still evident sheltering at a quite large distance.The length of shielding area was another important factor that there was approximately a linear relationship between it and the shielding level for two platforms in close proximity at various wind attack angles.Based on the two parameters,a preliminary wind loads estimation method considering shielding effects was proposed.This approach can aid the industry to have a qualitative assessment of wind sheltering especially at early stages.

Interaction of an unwetted liquid Li-based capillary porous system with high-density plasma

This study examined the effects of plasma irradiation on an unwetted liquid lithium-based capillary porous system(Li-CPS). The Li-CPS was irradiated with high-density Ar plasma using a linear plasma device at Sichuan University for Plasma Surface Interaction. The high-speed camera, Langmuir probe, and multi-channel spectrometer were used to characterize the effects of plasma irradiation. Upon Ar plasma irradiation, liquid Li drops were formed on the surface of the unwetted Li-CPS. Immediately after this irradiation, the drops fractured and were ejected into the plasma within ~20 ms scale, which is not observed before to the best of our knowledge. Related results showed that the ejection behavior of Li could effectively cool electron temperature and reduce incident heat flux by ~30% and correspondingly matrix temperature ~150 ℃, revealing an enhanced vapor shielding effect. The involved internal mechanism and physical processes deserve further investigations.

Basic solutions of multiple parallel symmetric mode-III cracks in functionally graded piezoelectric/piezomagnetic material plane

The Schmidt method is adopted to investigate the fracture problem of multiple parallel symmetric and permeable finite length mode-III cracks in a functionally graded piezoelectric/piezomagnetic material plane. This problem is formulated into dual integral equations, in which the unknown variables are the displacement jumps across the crack surfaces. In order to obtain the dual integral equations, the displacement jumps across the crack surfaces are directly expanded as a series of Jacobi polynomials. The results show that the stress, the electric displacement, and the magnetic flux intensity factors of cracks depend on the crack length, the functionally graded parameter, and the distance among the multiple parallel cracks. The crack shielding effect is also obviously presented in a functionally graded piezoelectric/piezomagnetic material plane with mul- tiple parallel symmetric mode-III cracks.

Elastic behaviour of a wedge disclination dipole near a sharp crack emanating from a semi-elliptical blunt crack

The interaction between a wedge disclination dipole and a crack emanating from a semi-elliptic hole is investigated. Utilising the complex variable method, the closed form solutions are derived for complex potentials and stress fields. The stress intensity factor at the tip of the crack and the image force acting on the disclination dipole center are also calculated. The influence of the morphology of the blunt crack and the position of the disclination dipole on the shielding effect to the crack and the image force is examined in detail. The results indicate that the shielding or anti-shielding effect to the stress intensity factor increases when the wedge disclination dipole approaches the tip of the crack. The effects of the morphology of the blunt crack on the stress intensity factor of the crack and the image force are very significant.