bluuebunny/crossref_metadata_2025_split huggingface dataset:
Achievement of a reversible giant magnetocaloric effect via exerting external hydrostatic pressure on a Ni45Co5Mn35In15 metamagnetic Heusler alloy
Authors: He Xijia , Zhang Yuanlei , Wei Shengxian , Cao Yiming , Xu Kun , Li Zhe 
Published: January 2021

Abstract
Magnetocaloric materials with first-order phase transition are potential refrigerant media for solid state refrigeration. In this work, the Ni45Co5Mn35In15 alloy possesses a representative first-order martensitic transition (MT), which is found to be sensitive to both magnetic field and isostatic pressure with rates of ∼−6.4 K T−1 and ∼4.24 K kbar−1. Such an active response to multi-stimuli derives from the strong coupling of the spin and the lattice. A low magnetic field of 1 T can drive nearly 100% of the total entropy change corresponding to the whole transformation in this alloy. However, the prominent magnetocaloric effect (MCE) is almost irreversible owing to the intrinsic hysteresis of the first-order phase transition. By virtue of the strong magnetostructural coupling during the MT, a hydrostatic pressure assisted magnetic field loading loop has been constructed for eliminating the hysteresis and to a large extent improve the reversibility of the MCE.
An ultra-broadband and optically transparent metamaterial absorber based on multilayer indium-tin-oxide structure
Authors: Deng Guangsheng , Lv Kun , Sun Hanxiao , Yang Jun , Yin Zhiping , Chi Baihong , Li Xiangxiang 
Published: January 2021

Abstract
In this work, an ultra-broadband and polarization-insensitive metamaterial absorber (MA) with high optical transparency is presented. Indium-tin-oxide (ITO) films are used as frequency selective surfaces in multiple conductive layers and also as the reflective backplane. Numerical simulation analysis demonstrates that the absorptivity of the proposed absorber exceeds 90% in the frequency range from 10 to 75.5 GHz, corresponding to a relative absorption bandwidth of 153%. The proposed structure has a total thickness of 2.9 mm, which is approximately 1/10 of the free space wavelength of its lowest operating frequency. The absorber also has good polarization insensitivity due to its symmetric geometry. Moreover, for TE-polarized waves, the proposed absorber can maintain an absorptivity greater than 70% for frequencies ranging from 10 to 80 GHz as the incident angle is increased to 45°. For TM-polarized waves, it provides absorptivity of more than 80% at incident angles up to 60°. Surface current distribution on each conductive ITO layer was simulated to analyze the absorption mechanism of the MA. A prototype composed of 16 × 16 unit cells was fabricated and the experimental results show a good agreement with the numerical simulations. Due to its ultra-wideband absorption and wide-incident-angle stability, the proposed MA has potential value in electromagnetic applications such as optically transparent EM shielding and microwave radiation protection.
Controlled high temperature stability of microwave plasma synthesized graphene nanosheets
Authors: Jašek Ondřej , Toman Jozef , Všianský Dalibor , Jurmanová Jana , Šnírer Miroslav , Hemzal Dušan , Bannov Alexander G , Hajzler Jan , St’ahel Pavel , Kudrle Vit 
Published: January 2021

Abstract
High temperature stability of nanomaterials plays an important role for their application in the field of nanocomposites, batteries, and sensors. Few-layer graphene nanosheets prepared by microwave plasma based decomposition of ethanol exhibited high thermal stability in the oxidation atmosphere in dependence on controlled formation of structural disorder. Analysis of differential thermogravimetry (DTG) curve profile showed three temperature regions, around 345 °C, 570 °C and above 700 °C, related to amorphous phase with a carbon–oxygen functional groups, small defective nanostructures and highly crystalline structure of graphene nanosheets, respectively. Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) analysis of the nanosheets showed an increase of D/G Raman band ratio as well as increasing of sp3 phase content, from 6.1 at% to 15.2 at%, for highly crystalline and highly disordered structure of the nanosheets. Thermal annealing under synthetic air was used to investigate the variation in D/G and 2D/G Raman band ratio of the samples and to estimate activation energy of oxidation and disintegration process of graphene nanosheets. The highest oxidation resistance exhibited sample with high 2D/G band ratio (1.54) and lowest oxygen content of 1.7 at%. The synthesis process led to stabilization of nanosheet structure by formation of curved edges and elimination of free dangling bonds. The nanosheets prepared in microwave plasma exhibited high surface area, over 350 m2 g−1, and superior thermal stability with defect activation energy in an oxidation atmosphere higher than 2 eV. Heat release rate during the oxidation process was in correlation with the amount of disorder in the samples. Fast and easy to use technique based on high power Raman spectroscopy was developed for assessment of nanomaterial oxidation resistance.
Radiative B to axial-vector meson decays at NLO in soft-collinear effective theory
Authors: Sikandar Arslan , Aslam M Jamil , Ahmed Ishtiaq , Shafaq Saba 
Published: January 2021

Abstract
The rare decay B → Aγ, with A representing axial-vector mesons such as K
1(1270), K
1(1400), b
1(1300), a
1(1260), is studied at next-to-leading order (NLO) in soft collinear effective theory (SCET). The large outgoing meson energy encourages the study of the decay with an appropriate factorization scheme that separates the factorizable and non-factorizable parts systematically. We have analyzed the leading-power and

O

(

α

s

)

diagrams that contribute to matching to SCETI. The new intermediate theory is matched onto SCETII and the running of SCETI operators is performed to sum large perturbative logarithms. The values of soft-overlap function ζ
⊥ for K
1(1270, 1400), a
1 and b
1 mesons are estimated from the light cone-sum-rules, and later using it the corresponding branching fractions for

B
→

K

1

(

1270
,

1400

)

,

a

1

,

b

1

γ

decays are calculated. We find that in case of B → K
1(1270, 1400)γ decays the results are in good agreement with their experimental measurements. Also the estimated values of the branching ratios of the B → (b
1, a
1)γ decays are potentially large to be measured at the LHCb and future B-factories.
Investigating the effects of U
1 vector leptoquark on

b→uτν̄

mediated B decays
Authors: Kumbhakar Suman , Mohanta Rukmani 
Published: January 2021

Abstract
The recent measurements of lepton flavor universality (LFU) violating observables in semileptonic

b
→
c
ℓ

ν

̄

and b → sℓ
+
ℓ
− transitions by various experiments hint towards the possible role of new physics (NP) in

b
→
c
τ

ν

̄

and b → sμ
+
μ
− decay channels. This in turn suggests that the same class of NP as appeared in

b
→
c
τ

ν

̄

, might also show up in other tree level processes involving

b
→
u
τ

ν

̄

transition. In this paper, we study the implications of the vector leptoquark (LQ) U
1(3, 1, 2/3), which is one of the few scenarios that can simultaneously explain all the observed LFU violating signals, on the semileptonic decays

B
→

(

π
,
ρ
,
ω

)

τ

ν

̄

and

B

s

→

(

K
,

K

*

)

τ

ν

̄

. In particular, we pay our attention to the branching fractions, lepton flavor non-universality (LNU) observables, forward–backward asymmetry and the polarization asymmetry parameters of these decay modes. We find that substantial deviations in the branching fractions as well as LNU observables could be possible due to the additional contributions from U
1 LQ, which can be probed by the currently running experiments LHCb and Belle-II.
Soft mode theory of ferroelectric phase transitions in the low-temperature phase
Authors: Casella Luigi , Zaccone Alessio 
Published: January 2021

Abstract
Historically, the soft mode theory of ferroelectric phase transitions has been developed for the high-temperature (paraelectric) phase, where the phonon mode softens upon decreasing the temperature. In the low-temperature ferroelectric phase, a similar phonon softening occurs, also leading to a bosonic condensation of the frozen-in mode at the transition, but in this case the phonon softening occurs upon increasing the temperature. Here we present a soft mode theory of ferroelectric and displacive phase transitions by describing what happens in the low-temperature phase in terms of phonon softening and instability. A new derivation of the generalized Lyddane–Sachs–Teller (LST) relation for materials with strong anharmonic phonon damping is also presented which leads to the expression ɛ
0/ɛ
∞ = |ω
LO|2/|ω
TO|2. The theory provides a microscopic expression for T
c as a function of physical parameters, including the mode specific Grüneisen parameter. The theory also shows that

ω

T
O

∼

(

T

c

−
T

)

1
/
2

, and again specifies the prefactors in terms of Grüneisen parameter and fundamental physical constants. Using the generalized LST relation, the softening of the TO mode leads to the divergence of ϵ
0 and to a polarization catastrophe at T
c. A quantitative microscopic form of the Curie–Weiss law is derived with prefactors that depend on microscopic physical parameters.
One- and two-dimensional electrical contacts and transport properties in monolayer black phosphorene–Ni interface
Authors: Zhong Kehua , Xu Guigui , Yang Yanmin , Zhang Jian-Min , Huang Zhigao 
Published: January 2021

Abstract
Contacts between black phosphorene (BP) and metal electrodes are critical components of BP-based devices and can dramatically affect device performance. In this paper, we adopted first-principles calculations to explore binding energies, electronic structures, spatial potential distribution of monolayer BP–Ni interfaces in surface contact and edge contact types, and used density functional theoretical coupled with nonequilibrium Green’s function method to investigate the electrical transport properties for transport systems of monolayer BP with Ni electrodes. Our calculated results indicate that contact type between monolayer BP and metal Ni electrodes may much affect the transport properties of monolayer BP–Ni devices. Interfacial interaction between Ni and monolayer BP in edge contact type is stronger than that in surface contact type. The potential distributions indicate that edge contact type is more beneficial for reducing contact resistance of monolayer BP–Ni contacts and conducive to improve the performance of BP–Ni electrode device.
A novel 3D laser scanning defect detection and measurement approach for automated fibre placement
Authors: Tang Yipeng , Wang Qing , Wang Han , Li Jiangxiong , Ke Yinglin 
Published: January 2021

Abstract
Automated fibre placement (AFP) machine in-process layup inspection is essential for composite structure fabrication efficiency and quantity improvement. The laser profilometer scanning technique is one of the automated in-process inspection techniques. Laser profilometers can capture a large number of intensive high-resolution point clouds during the layup. To date, few studies have been published about processing point clouds at high speed for in-process layup defect detection and layup feature measurement. In this study, an algorithm called the cross-sectional line-processing algorithm was proposed, and a testbed was constructed to validate the algorithm. The algorithm processes each laser line captured by the laser profilometer and clusters the processed results together. Finally, the defect features and layup features can be segmented and recognized from the collected point cloud. Layup defect types can be recognized, and the dimensions of the layup features can be measured. The experimental results show that this approach can process at most 200 laser lines (about 160 000 points) per second, and the overall defect type recognition accuracy rate reaches about 78%, which meets basic AFP in-process inspection requirements.
Performance evaluation of terrestrial laser scanners—a review
Authors: Muralikrishnan Bala 
Published: January 2021

Abstract
Terrestrial laser scanners (TLSs) are increasingly used in several applications such as reverse engineering, digital reconstruction of historical monuments, geodesy and surveying, deformation monitoring of structures, forensic crime scene preservation, manufacturing and assembly of engineering components, and architectural, engineering, and construction applications. The tolerances required in these tasks range from few tens of millimeters (for example, in historical monument digitization) to few tens of micrometers (for example, in high precision manufacturing and assembly). With numerous TLS instrument manufacturers, each offering multiple models of TLSs with idiosyncratic specifications, it is a considerable challenge for users to compare instruments or evaluate their performance to determine if they meet specifications. As a result, considerable efforts have been made by research groups across the world to model TLS error sources and to develop specialized performance evaluation test procedures. In this paper, we review these efforts including recent work to develop documentary standards for TLS performance evaluation and discuss the role of these test procedures in establishing metrological traceability of TLS measurements.
Multi-GNSS inter-system model for complex environments based on optimal state estimation
Authors: Shang Rui , Gao Chengfa , Gao Wang , Zhang Ruicheng , Peng Zihan , Liu Qi 
Published: January 2021

Abstract
When calibrating inter-system biases (ISB), especially the fractional part of inter-system phase biases (F-ISPB), a multi-GNSS inter-system model can effectively improve positioning performance under a complex environment. Usually, the F-ISPB is estimated after fixing the intra-system ambiguities. However, this approach seems inapplicable when it is difficult to obtain intra-system ambiguities under a complex environment. A multi-dimensional particle filter (PF)-based F-ISPB estimate method has been proposed to overcome the problem. Nevertheless, the multi-dimensional PF involves a great quantity of computations. In this contribution, four state optimal estimate-based F-ISPB handling schemes are proposed: step-by-step PF, step-by-step particle swarm optimization (PSO), multi-dimensional PF, and multi-dimensional PSO-based F-ISPB estimate methods. Two baselines were selected to investigate the F-ISPB estimate performance in both open and complex environments. The results show that due to the potential of the wrong F-ISPB to bring about the maximum ratio for a long time during the initial stage, the step-by-step PF method can achieve better performance than step-by-step PSO. Besides, the two-dimensional results show that all of the F-ISPB still cannot be extracted under complex environments by multi-dimensional PSO. Furthermore, compared with step-by-step PF, the multi-dimensional PF method costs too much to obtain the right value. For example, in the two-dimensional case, the step-by-step PF searches 200 times for each epoch, while the two-dimensional PF requires 40 000 times for each epoch, so it is difficult for receivers to provide hardware support for this method. In addition, the step-by-step PF can obtain the right F-ISPB with about 100 epochs no matter what scenario. Thus, under challenging observation scenarios, a step-by-step PF method is recommended to extract the F-ISPB.
Synthesis of sea urchin-shaped Au nanocrystals by double-strand diblock oligonucleotides for surface-enhanced Raman scattering and catalytic application
Authors: Gao Jiamin , Huang Lu , Zhang Zhuomin , Li Gongke 
Published: January 2021

Abstract
It is of great significance to construct specially designed gold nanocrystals (AuNCs) with precisely controllable size and morphology to achieve an excellent physicochemical performance. In this work, sea urchin-shaped AuNCs with tunable plasmonic property were successfully synthesized by the hybridized double-strand poly adenine (dsPolyA) DNA-directed self-assembly technique. Hybridized dsPolyA as the directing template had suitable rigidity and upright conformation, which benefited the controllable formation of these anisotropic multi-branched AuNCs with the assistance of surfactant. The effects of essential conditions influencing the synthesis and precise morphology control were investigated in detail. COMSOL simulation was used to evaluate their electromagnetic field distribution according to their morphologies, and the result suggested that sea urchin-shaped AuNCs had abundant ‘hot spots’ for surface-enhanced Raman scattering (SERS) detection due to their regular nanoprotuberance structure. Finally, sea urchin-shaped AuNCs with excellent SERS and catalytic performance were applied for the quantitative analysis of food colorant and catalytic degradation of potential pollutants. The SERS enhancement factor of sea urchin-shaped AuNCs was up to 5.27 × 106, and the catalytic degradation rate for 4-NP by these AuNCs was up to −0.13min−1.
Selective multi-wavelength infrared emission by stacked gap-plasmon thermal emitters
Authors: Hsiao Hui-Hsin , Xu Bo-Ting 
Published: January 2021

AbstractSelective multi-wavelength infrared light sources are important elements to achieve precise molecular detection by the usage of their intrinsic vibrational spectra. In this work, we proposed a double-stacked cross-shaped metal-dielectric-metal (MDM) resonator to achieve penta-wavelength mid-infrared thermal emission. Through the optimization of un-symmetric cross-shaped tri-layers incorporated with two sandwiched dielectric materials, four distinct emission bands associated with the magnetic resonances in stacked MDM resonators were realized, which shows nondispersive and polarization-dependent property due to the localized plasmon oscillations of the magnetic resonances. In addition, the phonon emission in the silicon dioxide layer also contributes one radiation peak atλ = 10μm. Via a simple polarization rotator, the emission wavelengths can be tuned from 4.5 and 7.5μm to 5.5 and 8.5μm. This paves the way for simultaneous detection of multi-band molecular absorption fingerprint, and the polarization-tunable emission wavelengths also facilitate the possibility to achieve multi-compound sensing via one compact system.
About the possible source of seed electrons initiating the very first breakdown in a DBD operating with the air at atmospheric pressure
Authors: Akishev Yuri , Karalnik Vladimir , Medvedev Mikhail , Petryakov Alexander , Shao Tao , Zhang Cheng , Huang Bangdou 
Published: January 2021

Abstract
The conditions of the very first breakdown happening in a periodical dielectric barrier discharge (DBD) are not the same as those in the discharge established regime. The main intriguing problem in the very first breakdown is the source of the initial seed electrons. In this work, the role of atmospheric small negative ions in the appearance of seed electrons is investigated. The very first breakdown was studied by using a pin-to-plane barrier corona and plane-to-plane DBD operated with ambient air. These discharges were driven by fast- and slow-growing applied voltage. The experimental data related to the very first breakdown are presented. A short summary sounds as follows. In the case of a barrier corona initiated by a fast-growing voltage, seed electrons can appear due to their detachment from background negative ions in the bulk. Under a slow-increasing voltage, background ions have the time to be fully adsorbed on the cathode and the anode long before breakdown occurs. In such a case, seed electrons can appear from negative ions desorbed from the cathode. This desorption is induced by a strong electric field in the gap. The latter mechanism can work in a plane-to-plane DBD driven by both fast- and slow-growing applied voltage. Based on numerical calculations, a qualitative explanation of the obtained results is given. The influence of UV irradiation on the very first breakdown was also studied.
Electrically isolated propagating streamer heads formed by strong electron attachment
Authors: Francisco Hani , Bagheri Behnaz , Ebert Ute 
Published: January 2021

Abstract
Streamer discharges occur in the early stages of electric breakdown of gases in lightning, as well as in plasma and high voltage technology. They are growing filaments characterized by a curved charge layer at their tip that enhances the electric field ahead of them. In this study, we analyze the effect of strong electron attachment on the propagation of positive streamers. Strong attachment occurs in insulating gases like sulphur hexafluoride (SF6) or in air at increased density. We use the classical fluid approximation with photo-ionization for streamers in ambient air, and we artificially increase the electron attachment rate where the field is below the breakdown value. This modification approximates air pressures above 1 bar at room temperature. We find that the streamer head can keep propagating even though the ionized channel loses its conductivity closely behind the head; hence, even if it is electrically isolated. We describe how, depending on the attachment rate, the streamer propagation in a constant electric field can be accelerating, uniformly translating, or stagnating.
Current–voltage characteristics and deep-level study of GaN nanorod Schottky-diode-based photodetector
Authors: Reddeppa Maddaka , Park Byung-Guon , Pasupuleti Kedhareswara Sairam , Nam Dong-Jin , Kim Song-Gang , Oh Jae-Eung , Kim Moon-Deock 
Published: January 2021

Abstract
Understanding the metal/semiconductor interface is very significant for real-time optoelectronic device applications. In particular, the presence of interface states and other defects is detrimental to photodetector applications. In this study, the electrical transport properties of a pristine gallium nitride (GaN) nanorod (NR)-based Schottky diode are demonstrated at different temperatures by current–voltage characteristics in the range of 200–360 K. An enhancement in the Schottky barrier height (0.65 eV for hydrogen-passivated GaN NRs compared to 0.56 eV for pristine ones) is noticed. The effect of deep traps residing within the forbidden gap of GaN NRs is investigated using deep-level transient spectroscopy. Two deep defects are found at E
C − 0.19 eV and E
C − 0.31 eV in pristine GaN NRs; the E
C − 0.31 eV defect peak is attributed to V
Ga or nitrogen interstitials. After hydrogenation the peak at E
C − 0.31 eV is suppressed and that at E
C − 0.19 eV remains unchanged. The hydrogenated GaN NRs show a high photoresponse, which is nearly 2.83 times higher than that of pristine GaN NRs. The hydrogenated GaN NRs exhibit a photoresponsivity of 4.7

×

10−3 A W−1 and detectivity of 1.24

×

1010 Jones under UV illumination of λ = 382 nm. The enhanced performance is attributed to the deep defect passivation by hydrogenation along with the surface-state-free interface between the GaN NRs and metal contacts. The experimental results demonstrate the significance of hydrogen treatment use in the fabrication of GaN-based optoelectronic devices.
The effect of stress-induced martensite aging in tension and compression on B2–B19′ martensitic transformation in Ni50.3Ti32.2Hf17.5 high-temperature shape memory alloy
Authors: Tagiltsev A I , Panchenko E Yu , Timofeeva E E , Chumlyakov Yu I , Fatkullin I D , Marchenko E S , Karaman I 
Published: January 2021

Abstract
The present study investigates the high-temperature shape memory effect (SME) in heterophase Ni50.3Ti32.2Hf17.5 polycrystals with nanosized H-phase particles after stress-induced martensite (SIM) aging in tension and compression. SIM aging created the conditions for fully reversible two-way SME with a strain of up to 50% of the one-way shape memory strain. SIM aging altered the viscoelastic properties of material, in particular, the elastic moduli of austenite and martensite increased, as did internal friction. Increased interface mobility is suggested as the reason for internal friction growth.