bluuebunny/crossref_metadata_2025 huggingface dataset:
Corrigendum to: Survey of paediatric telehealth benefits from the caregiver perspective
Authors: Hiscock Harriet , Pelly Rachel , Hua Xinjang , West Sue , Tucker Dianne , Raymundo Chin-Mae , Dalziel Kim
Published: April 2022

ObjectiveThis study determined caregivers’ evaluations of telehealth consultations for their child, preference over in-person consultations and potential cost savings by child condition, family socioeconomic status and location. MethodsA survey was conducted of 2436 caregivers attending a telehealth consultation with their child for a broad group of conditions between 3 June and 25 August 2020 at a tertiary paediatric hospital in Melbourne, Australia. ResultsMost caregivers found telehealth consultations convenient, acceptable, safe and private, and capable of answering their questions and concerns. However, caregivers who spoke a language other than English and patients attending for behavioural and mental health, developmental or other (e.g. allied health) concerns were more likely to prefer in-person consultations over telehealth. Mean (±s.d.) reported cost savings on caregiver time were A$144.98 ± 99.04 per family per consultation, whereas mean (±s.d.) transport cost savings were A$84.90 ± 100.74 per family per consultation. Cost savings were greatest for families living in low and middle socioeconomic areas and regional or rural areas. ConclusionsPaediatric telehealth video consultations were largely viewed favourably by caregivers, except for those attending for behavioural and mental health or developmental concerns. What is known about the topic?Adult consumers of telehealth consultations view them as useful, convenient and cost saving, but less is known about caregivers’ evaluations of telehealth consultations and potential cost savings for paediatric patients, and whether these differ by family location, socioeconomic status or child condition. What does this paper add?This is the first Australian paper to report on caregivers’ evaluations across a range of paediatric conditions and locations. Most caregivers found telehealth consultations convenient, safe, acceptable, able to answer their questions and concerns about their child’s health and cost saving. What are the implications for practitioners?Caregivers of children with behavioural, mental health or developmental problems were less likely to prefer telehealth over in-person consultations, so practitioners should consider providing such consultations in person.
Testing gravity with black hole shadow subrings
Authors: Ayzenberg Dimitry
Published: April 2022

The black hole shadow, first observed by the Event Horizon Telescope in 2017, is the newest method for studying black holes and understanding gravity. Much work has gone into understanding the shadow of a Kerr black hole, including all of the complex astrophysics of the accretion disk, and there are numerous studies of the ideal shadow in non-Kerr black holes and exotic compact objects. This paper presents one of the first studies of the black hole shadow of non-Kerr black holes when the illumination source is an accretion disk. In particular, the ability of current and future very long baseline interferometers to estimate the physical parameters of the black hole spacetime and accretion disk is investigated using two different parametrized black hole metrics that encode a number of possible deviations from Kerr. Both the full shadow image and the individual subrings of the shadow are analyzed as the higher order subrings are weakly dependent on the disk physics and may be a more viable observable for studying the spacetime. The results suggest that with current telescope capabilities and any future earth-based telescopes it will be quite difficult to place strong constraints on departures from the Kerr spacetime, primarily due to the low resolution and strong degeneracies between the spacetime parameters. More optimistically, space-based interferometers may be capable of testing the Kerr nature of black holes and general relativity to comparable or better precision than is currently possible with other observations.
The accidental flatness constraint does not mean a wrong classical limit
Authors: Engle Jonathan , Rovelli Carlo
Published: April 2022

We shed some light on the reason why the accidental flatness constraint appears in certain limits of the amplitudes of covariant loop quantum gravity. We show why this constraint is harmless, by displaying how analogous accidental constraints appear in transition amplitudes of simple systems, when certain limits are considered.
Minimizing L
1 over L
2 norms on the gradient
Authors: Wang Chao , Tao Min , Chuah Chen-Nee , Nagy James , Lou Yifei
Published: April 2022

In this paper, we study the L
1/L
2 minimization on the gradient for imaging applications. Several recent works have demonstrated that L
1/L
2 is better than the L
1 norm when approximating the L
0 norm to promote sparsity. Consequently, we postulate that applying L
1/L
2 on the gradient is better than the classic total variation (the L
1 norm on the gradient) to enforce the sparsity of the image gradient. Numerically, we design a specific splitting scheme, under which we can prove subsequential and global convergence for the alternating direction method of multipliers (ADMM) under certain conditions. Experimentally, we demonstrate visible improvements of L
1/L
2 over L
1 and other nonconvex regularizations for image recovery from low-frequency measurements and two medical applications of magnetic resonance imaging and computed tomography reconstruction. Finally, we reveal some empirical evidence on the superiority of L
1/L
2 over L
1 when recovering piecewise constant signals from low-frequency measurements to shed light on future works.
Burr removal from high-aspect-ratio micro-pillars using ultrasonic-assisted abrasive micro-deburring
Authors: Kumar A Sravan , Deb Sankha , Paul S
Published: April 2022

The demand for high-aspect-ratio microstructures is ever increasing in the fields of microelectromechanical systems, biomedicine, aerospace, telecommunication, and heat transfer. Mechanical micromachining processes have a distinct advantage over lithography-based processes for machining complex three-dimensional microstructures on a variety of materials with high accuracy and surface finish. But the tool-based micromachining operations face inherent issues in the form of excessive burr formation, which needs to be addressed by post-machining burr removal operations. In this study, an ultrasonic-assisted abrasive micro-deburring process employing a probe sonotrode and abrasive particles has been investigated for deburring high-aspect-ratio micro-pillars machined on aluminium 6061 and copper. Deburring of micromilled pillars of aspect ratio 5:1 has been achieved while maintaining pillar integrity. The mechanism of deburring has been observed to be mainly by the impact of the abrasive particles with a minor role played by liquid cavitation. Burr reduction as high as 88.75% for Al 6061 and 90.1% for copper has been achieved in a short processing time of 10 s. This is a significantly faster process than other ultrasonic cavitation-based deburring processes described in literature (deburring time ranging from 60 min to a few hours). With proper control of the process parameters like stand-off distance and power, burr removal has been achieved while maintaining the integrity of the micro-pillars. Pure water cavitation has also been studied for comparison, which has resulted in a burr removal by 51.5% and 53.1% for Al 6061 and copper, respectively. Upon proper selection of the process parameters, this process can be a viable alternative to existing deburring methods in terms of minimal processing time and structure damage.
Characteristics of the molecular above-threshold ionization by a bichromatic elliptically polarized field with co-rotating components
Authors: Habibović D , Gazibegović-Busuladžić A , Busuladžić M , Milošević D B
Published: April 2022

We address ionization of a diatomic molecule by a bichromatic elliptically polarized field with co-rotating components. Using the strong-field approximation we investigate symmetry properties of the photoelectron momentum distribution and explore the minima which appear in the photoelectron spectra. We distinguish two types of minima: (i) two-center interference minima which appear due to the destructive interference of the contributions of two electron wave packets emitted from the two centers of the diatomic molecule and (ii) the one-center minima which are caused by the interference of the parts of the wave packet emitted from the same atomic center at different times. The position of the two-center interference minima depends on the molecular orientation. When a molecular orbital is modelled using the atomic orbitals of a specific parity, the position of the two-center interference minima does not depend on the ellipticity of our driving field. However, when a molecular orbital consists of both odd and even atomic orbitals the interference of their contributions and the position of the minima depend on the ellipticity. The position of the interference minima in the photoelectron momentum plane is confirmed using the saddle-point method. The position and the number of the one-center minima do not depend on the molecular orientation, but they strongly depend on the ellipticity of the field components. Finally, comparing the photoelectron spectra of the CO molecule with the spectra of homonuclear molecules and the NO molecule we show that the electron probability density distribution plays a significant role for the high-energy rescattered electrons.
Spatio-temporal evolution of ion current extracted from pulsed dielectric barrier discharge
Authors: Khomich Vladislav Yu , Rebrov Igor E , Voevodin Vadim V , Yamshchikov Vladimir A , Zharkov Yaroslav E
Published: April 2022

In the present study, the influence of various factors on the shape of the ion cloud extracted from the specific discharge setup was investigated. The overall installment presented a surface dielectric barrier discharge plasma in the air fed by impulse high voltage. The effect of the amplitude, polarity, and duration for single and repetitive voltage pulses were examined. The patterns of ion current distribution depending on the gas gap length and the average field strength were obtained, and the effect of pulse duration and frequency on the amount of the extracted charge were examined. It was shown that the extracted charge was non-uniformly distributed in the gap volume during single and periodic voltage pulses. The effect of volume charge accumulation in the gap at high pulse repetition rate was shown. Computer simulations demonstrated that the main role in the ion cloud shape distortion was caused by the surface charge deposited on the dielectric barrier.
Exceptional points in an optically pumped magnetometer
Authors: Qin Haoye , Ding Ming
Published: April 2022

The exceptional points (EPs) in a system are the eigenvalue degeneracy that has been demonstrated in a wide range of optical arrangements. In this paper, EP is analyzed schematically in an optically pumped magnetometer, which is governed by the Bloch equation with a

3
×
3

matrix. We numerically illustrate EP enhanced sensing for magnetic field and EP encircling induced 2π phase shift by employing the sensing field along with transverse modulation field. These findings may contribute to the realization of EP magnetometers and atomic gyroscopes for improved field and rotation sensitivity.
Theoretical design of ultracompact three-dimensional isotropic two-photon 4Pi STED microscopy based on multifunctional metalenses focusing system
Authors: Li Yang , Zhao Shihu , Ju Dandan , Luo Mingyan , Xiu Dongming , Liu Shujing , Shen Hui
Published: April 2022

4Pi stimulated emission depletion (STED) microscopy shows outstanding three-dimensional (3D) isotropic super-resolution imaging performance. However, this technology is still difficult for achieving long-term studying of the synapses that are deeply embedded inside brain tissue. Metalens, which can realize arbitrary nanoscale amplitude, phase, and polarization modulations, is a very useful tool to solve this limitation. In this paper, an ultracompact two-photon 4Pi STED microscopy involved two multifunctional metalenses patterned on the two fiber facets respectively for focusing the excitation and depletion laser beams to the same position was proposed to realize the 3D isotropic super-resolution imaging. The designed complementary structure of two metalenses and the optimized pupil ratio β assured the symmetry of the STED spot. Furthermore, the isotropic super-resolution of 27 nm was theoretically implemented based on the two-photon STED theoretical model. Our approach will greatly increase the viability of the 3D super-resolution morphological imaging in the deep brain.
The development of new oral vaccines using porous silica
Authors: Oliveira C L P , Lopes J L S , Sant’Anna O A , Botosso V F , Bordallo H N , Fantini M C A
Published: April 2022

Ordered mesoporous silica (OMS) was proved to be an efficient oral adjuvant capable to deliver a wide in size variety of different antigens, promoting efficient immunogenicity. This material can be used in single or polivalent vaccines, which have been developed by a group of Brazilian scientists. The experiments performed with the model protein Bovine Serum Albumin (BSA) gave the first promissing results, that were also achieved by testing the virus like particle surface antigen of hepatitis B (HBsAg) and diphtheria anatoxin (dANA). Nanostructured OMS, SBA-15 type, with bi-dimensional hexagonal porous symmetry was used to encapsulate the antigens either in the mesoporous (pore diameter ∼ 10 nm) or macroporous (pore diameter > 50 nm) regions. This silica vehicle proved to be capable to create an inflammatory response, did not exhibit toxicity, being effective to induce immunity in high and low responder mice towards antibody production. The silica particles are in the range of micrometer size, leaving no trace in mice organs due to its easy expulsion by faeces. The methods of physics, usually employed to characterize the structure, composition and morphology of materials are of fundamental importance to develop proper oral vaccines in order to state the ideal antigen load to avoid clustering and to determine the rate of antigen release in different media mimicking body fluids.
Experimental and computational approaches to study the high temperature thermoelectric properties of novel topological semimetal CoSi
Authors: Sk Shamim , Shahi Nisha , Pandey Sudhir K
Published: April 2022

Here, we study the thermoelectric properties of topological semimetal CoSi in the temperature range 300–800 K by using combined experimental and density functional theory (DFT) based methods. CoSi is synthesized using arc melting technique and the Rietveld refinement gives the lattice parameters of a = b = c = 4.445 Å. The measured values of Seebeck coefficient (S) shows the non-monotonic behaviour in the studied temperature range with the value of ∼−81 μV K−1 at room temperature. The |S| first increases till 560 K (∼−93 μV K−1) and then decreases up to 800 K (∼−84 μV K−1) indicating the dominating n-type behaviour in the full temperature range. The electrical conductivity, σ (thermal conductivity, κ) shows the monotonic decreasing (increasing) behaviour with the values of

∼
5.2
×
1

0

5

(12.1 W m−1 K−1) and

∼
3.6
×
1

0

5

(14.2 W m−1 K−1) Ω−1 m−1 at 300 K and 800 K, respectively. The κ exhibits the temperature dependency as, κ ∝ T
0.16. The DFT based Boltzmann transport theory is used to understand these behaviour. The multi-band electron and hole pockets appear to be mainly responsible for deciding the temperature dependent transport behaviour. Specifically, the decrease in the |S| above 560 K and change in the slope of σ around 450 K are due to the contribution of thermally generated charge carriers from the hole pockets. The temperature dependent relaxation time (τ) is computed by comparing the experimental σ with calculated σ/τ and it shows temperature dependency of 1/T
0.35. Further this value of τ is used to calculate the temperature dependent electronic part of thermal conductivity (κ
e) and it gives a fairly good match with the experiment. Present study suggests that electronic band-structure obtained from DFT provides a reasonably good estimate of the transport coefficients of CoSi in the high temperature region of 300–800 K.
High precision measurement of blade profile curve using iterative normal vector approximation
Authors: Liu Junfeng , He Xiaomei , Zhang Li , Huang Xiang , Wang Yizhang
Published: April 2022

The precision measurement of blades has always been a complex problem in free-form surface inspection. For contact inspection of blades by coordinate measuring machine (CMM), the probe radius compensation has a critical influence on the measurement accuracy. In this study, an iterative approach based on the normal vector approximation is proposed to measure the blade profile curve, which aims to reduce the measurement error caused by the conventional method relying on a computer aided design model for compensation. The proposed method combines the local reconstruction of blade surface and CMM measurement software. It first takes the measured results of conventional method as a base, then the resulting corrected points of several sectional profiles are fitted to a B-spline surface to provide an alternative nominal model for CMM software, leading to the next same measurement task. Thus, the measurement-fitting process iterates, in which the current nominal model in CMM software is updated by the reconstructed model of foregoing iteration, until a preset condition is reached. Consequently, the proposed method is implemented on a four-axis CMM, and two blade samples are designed to verify the approach’s effectiveness. Experiments show that our approach is superior to the conventional one in blade profile measurement accuracy.
Measurement of laser powder bed fusion surfaces with light scattering and unsupervised machine learning
Authors: Liu Mingyu , Senin Nicola , Su Rong , Leach Richard
Published: April 2022

Quality monitoring for laser powder bed fusion (L-PBF), particularly in-process and real-time monitoring, is of importance for part quality assurance and manufacturing cost reduction. Measurement of layer surface topography is critical for quality monitoring, as any anomaly on layer surfaces can result in defects in the final part. In this paper, we propose a surface measurement method, based on the use of scattered light patterns and a convolutional autoencoder-based unsupervised machine learning method, designed and trained using a large set of scattering patterns simulated from reference surfaces using a scattering model. The advantage of using an autoencoder is that the monitoring model can be trained using solely data from acceptable surfaces, without the need to ensure the presence of representative observations for all the types of possible surface defects. The advantage of using simulated data for training is that we can obtain an effective monitoring solution without the need for a large collection of experimental observations. Here we report the results of a preliminary investigation on the performance of the proposed solution, where the trained autoencoder is tested on experimental data obtained off-process, using a dedicated experimental apparatus for generating and collecting light scattering patterns from manufactured L-PBF surfaces. Our results indicate that the proposed monitoring solution is capable of detecting both acceptable and anomalous surfaces. Although further validation is required to fully assess performance within an on-machine and in-process setup, our preliminary results are encouraging and provide a glimpse of the potential benefits of using our surface measurement solution for L-PBF in-process monitoring.
A new laser-based monitoring method for the cryomodule components alignment
Authors: He Zhenqiang , Wang Tong , Wang Xiaolong , Lu Shang , Liu Huachang , Li Xiao , Men Lingling , Ma Na , Ke Zhiyong , Liang Jing , Dong Lan , Li Bo
Published: April 2022

Alignment of superconducting cavities is one of the important issues for the China Spallation Neutron Source Phase II (CSNS II) linac. In order to obtain the cavity displacement in the process of cooling down to the liquid helium temperature, a laser-based Poisson Spot Monitor (PSM) system was newly proposed and a verification system in the laboratory was built. The PSM system uses the diffraction spot formed on the CMOS camera after a beam of parallel laser passes through a spherical target to monitor the position of the measured object, where the spherical target is fixed on the monitored object. The displacement during the cooling process of the cryomodule is replaced by the movement of the high-precision two-axis motorized translation stage. A spherical target is fixed on the translation stage as the monitoring object. A beam of parallel laser passes through the spherical monitoring target to form a Poisson spot image on a CMOS camera. The coordinates of the Poisson spot center are obtained through image processing. Through experiments, the PSM system obtained a high accuracy within 5 μm, which meets the displacement monitoring requirement of the CSNS II cryomodule components. The system is fairly simple and able to be constructed without highly specialized parts and can also be used in other high-precision alignment and monitoring fields.
Synthesis of silver nanoparticles by atmospheric pressure plasma jet
Authors: Habib Tatiana , Caiut José Mauricio A , Caillier Bruno
Published: April 2022

Silver nanoparticles are one of the most extensively used metallic nanomaterials due to their unusual physical and chemical properties as well as their promising applications in a wide range of different fields. In this study, a non-thermal atmospheric pressure helium plasma jet was used to successfully synthesize silver nanoparticles with silver nitrate as a precursor and trisodium citrate as a capping agent. The browning of the solution after only 5 min of plasma irradiation is a result of the surface plasmon resonance (SPR) from the obtained silver nanoparticles. The SPR was confirmed by the presence of an absorption band in the visible range between 400 and 450 nm demonstrated in the UV–vis spectra. The effect of different chemical parameters such as the concentration of silver nitrate and the concentration of citrate on the silver nanoparticles have been studied. These nanoparticles were further characterized using transmission electron microscopy and dynamic light scattering. Therefore, the plasma jet was advantageous to fast produce silver nanoparticles in friendly conditions. In addition, the used experimental setup allows further studies in different solvents conditions and with different capping agents. So, this methodology could be useful for the preparation of silver nanoparticles required for numerous applications such as bioactivity, catalysis, surface enhanced Raman scattering, and photonic.
Electronic properties and behavior of carbon network based on graphene and single-walled carbon nanotubes in strong electrical fields: quantum molecular dynamics study
Authors: Slepchenkov Michael M , Glukhova Olga E
Published: April 2022

Using the self-consistent-charge density-functional tight-binding method (SCC-DFTB) and extended lagrangian DFTB-based molecular dynamics, we performed in silico studies of the behavior of graphene–nanotube hybrid structures that are part of a branched 3D carbon network in strong electrical fields. It has been established that strong fields with strength ranging from 5 to 10 V nm−1 cause oscillating deformations of the atomic framework with a frequency in the range from 1.22 to 1.38 THz. It has been revealed that the oscillation frequency is determined primarily by the topology of the atomic framework of graphene–nanotube hybrid, while the electric field strength has an effect within 1%–2%. A further increase in electric field strength reduces the oscillation frequency to 0.7 THz, which accompanies the partial destruction of the atomic framework. The critical value of the electric field strength when the graphene is detached from the nanotube is ∼20 V nm−1.
Fabrication of high-performance carbon nanotube/copper composite fibers by interface thiol-modification
Authors: Guo Lei , Li Huifang , Liu Dandan , Zhou Yurong , Dong Lizhong , Zhu Siqi , Wu Yulong , Yong Zhenzhong , Kang Lixing , Jin Hehua , Li Qingwen
Published: April 2022

Carbon nanotube (CNT)/copper (Cu) composite fibers are placed great expectations as the next generation of light-weight, conductive wires. However, the electrical and mechanical performances still need to be enhanced. Herein, we demonstrate a strategy that is electrodeposition Cu on thiolated CNT fibers to solve the grand challenge which is enhancing the performance of CNT/Cu composite fibers. Thiol groups are introduced to the surface of the CNT fibers through a controllable O2 plasma carboxylation process and amide reaction. Compared with CNT/Cu composite fibers, there are 82.7% and 29.6% improvements in electrical conductivity and tensile strength of interface thiol-modification composite fibers. The enhancement mechanism is also explored that thiolated CNT fibers could make strong interactions between Cu and CNT, enhancing the electrical and mechanical performance of CNT/Cu composites. This work proposes a convenient, heat-treatment-free strategy for high-performance CNT/Cu composite fibers, which can be manufactured for large-scale production and applied to next-generation conductive wires.
End-to-end deep learning for interior tomography with low-dose x-ray CT
Authors: Han Yoseob , Wu Dufan , Kim Kyungsang , Li Quanzheng
Published: April 2022

Objective. There are several x-ray computed tomography (CT) scanning strategies used to reduce radiation dose, such as (1) sparse-view CT, (2) low-dose CT and (3) region-of-interest (ROI) CT (called interior tomography). To further reduce the dose, sparse-view and/or low-dose CT settings can be applied together with interior tomography. Interior tomography has various advantages in terms of reducing the number of detectors and decreasing the x-ray radiation dose. However, a large patient or a small field-of-view (FOV) detector can cause truncated projections, and then the reconstructed images suffer from severe cupping artifacts. In addition, although low-dose CT can reduce the radiation exposure dose, analytic reconstruction algorithms produce image noise. Recently, many researchers have utilized image-domain deep learning (DL) approaches to remove each artifact and demonstrated impressive performances, and the theory of deep convolutional framelets supports the reason for the performance improvement. Approach. In this paper, we found that it is difficult to solve coupled artifacts using an image-domain convolutional neural network (CNN) based on deep convolutional framelets. Significance. To address the coupled problem, we decouple it into two sub-problems: (i) image-domain noise reduction inside the truncated projection to solve low-dose CT problem and (ii) extrapolation of the projection outside the truncated projection to solve the ROI CT problem. The decoupled sub-problems are solved directly with a novel proposed end-to-end learning method using dual-domain CNNs. Main results. We demonstrate that the proposed method outperforms the conventional image-domain DL methods, and a projection-domain CNN shows better performance than the image-domain CNNs commonly used by many researchers.
Photoinduced transient states of antiferromagnetic orderings in La1/3Sr2/3FeO3 and SrFeO3−δ
thin films observed through time-resolved resonant soft x-ray scattering
Authors: Yamamoto Kohei , Tsuyama Tomoyuki , Ito Suguru , Takubo Kou , Matsuda Iwao , Pontius Niko , Schüßler-Langeheine Christian , Minohara Makoto , Kumigashira Hiroshi , Yamasaki Yuichi , Nakao Hironori , Murakami Youichi , Katase Takayoshi , Kamiya Toshio , Wadati Hiroki
Published: April 2022

The relationship between the magnetic interaction and photoinduced dynamics in antiferromagnetic perovskites is investigated in this study. In La1/3Sr2/3FeO3 thin films, commensurate spin ordering is accompanied by charge disproportionation, whereas SrFeO3−δ
thin films show incommensurate helical antiferromagnetic spin ordering due to increased ferromagnetic coupling compared to La1/3Sr2/3FeO3. To understand the photoinduced spin dynamics in these materials, we investigate the spin ordering through time-resolved resonant soft x-ray scattering. In La1/3Sr2/3FeO3, ultrafast quenching of the magnetic ordering within 130 fs through a nonthermal process is observed, triggered by charge transfer between the Fe atoms. We compare this to the photoinduced dynamics of the helical magnetic ordering of SrFeO3−δ
. We find that the change in the magnetic coupling through optically induced charge transfer can offer an even more efficient channel for spin-order manipulation.
Evolution of surface morphology and helium bubble in tungsten under 40 keV helium ions implantation followed by deuterium plasma exposure
Authors: Xia Tongjun , Wang Zizhao , Jiang Zhenyu , Shi Yongzhi , Wu Jianwei , Ren Xinyu , Zhu Kaigui
Published: April 2022

Surface morphology and internal microstructure of tungsten (W) pre-implanted by 40 keV mass-separated helium (He) ions with different fluences at room temperature were investigated in this work. The morphology changes of the samples were analyzed almost in situ, by repetitively examined the specified irradiation area which is marked by focused ion beam technology. As the samples were implanted by He ion with a fluence of 6 × 1020 He m−2, no He blisters or other microstructures could be found on the surface. When the fluence reaches 6 × 1021 He m−2, a large number of He blisters with the size of ∼1 μm were observed on the W specimens. For the results of the subsequent deuterium plasma exposure, instead of deuterium-induced blistering, no changes on the W surface which pre-irradiated by He ion irradiation at low fluence (6 × 1020 He m−2). Surprisingly, for He ions pre-implanted W with high fluence (6 × 1021 He m−2), almost all the He blisters were cracked and their lids even peeled off. It could be attributed to the lateral stress caused by subsequent D exposure. Moreover, the size of He bubbles was also increased under subsequent deuterium exposure, suggesting that He atoms can attract D atoms. No deuterium blisters were found on these samples which were pre-implanted with high and low fluences, suggesting that He ion pre implantation can effectively inhibit the surface blistering caused by deuterium exposure.
Image lossless encoding and encryption method of SPECK based on 1D chaotic map
Authors: Xiao Yantong , Tong Xiaojun , Zhang Miao , Wang Zhu
Published: April 2022

In order to satisfy the requirements of high quality and security during image transmission and storage, this paper proposes an image lossless compression encryption algorithm based on 1D chaotic map and Set Partitioned Embedded block encoder (SPECK). Initially, this paper proposes a new 1D chaotic map, and applies the chaotic sequences generated by it to each stage of the compression encryption algorithm. In addition, according to the feature that the degree of energy concentration in the wavelet coefficient matrix gradually decreases from low frequency to high frequency, this paper proposes a wavelet coefficient encryption algorithm, which can balance security and compression performance. Furthermore, multiple encryption points are introduced in the SPECK encoding process, and a secure SPECK encoding algorithm is proposed. Finally, theoretical analysis and simulation results show that the proposed algorithm is close to the theoretical value in terms of information entropy, correlation coefficient, mean square error of reconstructed image and other related indicators. Therefore, the algorithm has high security and lossless compression performance.
Pt/SeO2 optical receivers designed for terahertz and 5G/6G technologies
Authors: Alfhaid Latifah Hamad Khalid , Qasrawi A F
Published: April 2022

Selenium oxide thin films are highly transparent optical layers proper for optoelectronic technology. However, SeO2 films are rarely studied and observed suffering from clustery surface morphology, low light absorbability and low dielectric constant. For this reason herein, in an attempt to enhance its properties, platinum nanosheets (10–50 nm) are used as plasmonic substrates to grow transparent selenium oxide thin films. The films are deposited onto glass and Pt substrates using thermal evaporation technique under a vacuum pressure of 10−5 mbar. Both films of the glass/SeO2 and Pt/SeO2 are characterized by the techniques of x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, optical spectrophotometry and impedance spectroscopy. While no significant effect of Pt nanosheets on the amorphous nature of structure of SeO2 is observed, remarkable enhancements in the light absorbability by 50 times and in dielectric constant by three times are achieved. In addition, Pt nanosheets form plasmonic interfaces resulting in improving the plasmon frequency, drift mobility and free carrier density of the films. Pt/SeO2 films showed plasmon frequency larger than 6.0 GHz and free carrier density of 1018 cm−3. Moreover, analysis of the terahertz cutoff frequency and impedance spectra have shown that the Pt/SeO2 interfaces can also be employed as terahertz receivers and as low pass filters suitable for 5G/6G technologies.
Homodyne detection in quantum optics: deterministic extractors and quantum random number generators on ‘vacuum fluctuations’
Authors: Molotkov S N
Published: April 2022

Quantum random number generators with a continuous variable are considered based on a primary randomness of the outcomes of homodyne measurements of a coherent state. A deterministic method of extraction of truly random 0 and 1 from the primary sequence of measurements of the quadrature of the field in homodyne detection is considered. The method, in the case of independence of successive measurement outcomes, in the asymptotic limit of long sequences, allows us to extract with a polynomial complexity all the true randomness contained in the primary sequence. The method does not require knowledge of the probability distribution function of the primary random sequence, and also does not require additional randomness in the extraction of random 0 and 1. The approach with deterministic randomness extractors, unlike other methods, contains fewer assumptions and conditions that need to be satisfied in the experimental implementation of such generators, and is significantly more effective and simple in experimental implementation. The fundamental limitations dictated by nature for achieving statistical independence of successive measurement outcomes are also considered. The statistical independence of the measurement outcomes is the equivalent of true randomness, in the sense that is possible in the case of the independence of the measurement outcomes, provably, with deterministic extractor, to extract a ‘truly random sequence of 0 and 1’. It is shown that in the asymptotic limit it is possible to extract all the true randomness contained in the outcomes of physical measurements.
Variable viscosity effects on the flow of MHD hybrid nanofluid containing dust particles over a needle with Hall current—a Xue model exploration
Authors: Ramzan Muhammad , Alotaibi Hammad
Published: April 2022

This study scrutinizes the flow of engine oil-based suspended carbon nanotubes magneto-hydrodynamics (MHD) hybrid nanofluid with dust particles over a thin moving needle following the Xue model. The analysis also incorporates the effects of variable viscosity with Hall current. For heat transfer analysis, the effects of the Cattaneo–Christov theory and heat generation/absorption with thermal slip are integrated into the temperature equation. The Tiwari–Das nanofluid model is used to develop the envisioned mathematical model. Using similarity transformation, the governing equations for the flow are translated into ordinary differential equations. The bvp4c method based on Runge–Kutta is used, along with a shooting approach. Graphs are used to examine and depict the consequences of significant parameters on involved profiles. The results revealed that the temperature of the fluid and boundary layer thickness is diminished as the solid volume fraction is raised. Also, with an enhancement in the variable viscosity parameter, the velocity distribution becomes more pronounced. The results are substantiated by assessing them with an available study.
Coherent control of spin tunneling in a driven spin–orbit coupled bosonic triple well
Authors: Luo Yuxin , Yi Jia , Li Wenjuan , Xie Xin , Luo Yunrong , Hai Wenhua
Published: April 2022

We investigate the coherent control of spin tunneling for a spin–orbit (SO) coupled boson trapped in a driven triple well. In the high-frequency limit, the quasienergies of the system are obtained analytically and the fine energy band structures are shown. By regulating the driving parameters, we reveal that the directed spin-flipping or spin-conserving tunneling of an SO-coupled boson occurs along different pathways and in different directions. The analytical results are demonstrated by numerical simulations and good agreements are found. Further, an interesting scheme of quantum spin tunneling switch with or without spin-flipping is presented. The results may have potential applications in the design of spintronic devices.
Optical bistability in a negative refractive index media using the electron tunneling effect
Authors: Sahandi Rima , Darkhosh Ahad
Published: April 2022

In this letter, we proposed a brand-new version for investigating the optical bistability (OB) and optical multistability (OM) through electron tunneling impact in a defect one-dimensional photonic crystal (1DPC). The defect layer of 1DPC is doped with double quantum dot (DQD) nanostructure which interacts with an indirect incoherent pump and a susceptible probe incident light, respectively. By the usage of the quantum mechanical density matrix method, we first examine the refractive index properties of the defect layer through electron tunneling and indirect incoherent pumping effects. Then, through the usage of the transfer matrix methods, we acquire the reflection and transmission coefficients of the defect 1DPC. At the end, we discuss the OB and OM properties of the reflected and transmitted lighting in negative refractive index situation of the DQD. We determine that during a few parametric conditions the switching from OB to OM or vice versa is feasible for reflected and transmitted light beams.
Generation of entangled states of light using discrete solitons in waveguide arrays
Authors: Martynov V O , Munyaev V O , Smirnov L A
Published: April 2022

We study the quantum properties of light propagating through an array of coupled nonlinear waveguides and forming a discrete soliton. We demonstrate that it is possible to use certain types of quasi-solitons to form continuous variables entanglement between the certain pair of waveguides. Moreover, there is a possibility to entangle several pairs of waveguides independently. We show that the entanglement is generated for arbitrary high intensity of the input laser field, so it does not require a special material with an extremely high nonlinearity coefficient. Also, absorption in the waveguide media does not influence the discussed process too much.
Spatial transfer of entangled states in the correlated quantum dots system
Authors: Maslova N S , Mantsevich V N , Arseyev P I , Sokolov I M
Published: April 2022

We propose a protocol for spatial ‘stretching’ of an initially prepared entangled state along chains of quantum dots (QDs) or quantum wires arranged in perpendicular directions. We theoretically analyze such stretching for a triplet superposition of symmetric and antisymmetric single-electron states with opposite spins formed in a diamond-like arrangement of four QDs. Under specific choice of parameters of the system, the probability amplitude to find the system in an entangled state localized at the end dots of the chains can reach unity at particular instants of time.
The myokinetic stimulation interface: activation of proprioceptive neural responses with remotely actuated magnets implanted in rodent forelimb muscle
Authors: Montero J , Thumser Z C , Masiero F , Beckler D T , Clemente F , Marasco P D , Cipriani C
Published: April 2022

Objective. Proprioception is the sense of one’s position, orientation, and movement in space, and it is of fundamental importance for motor control. When proprioception is impaired or absent, motor execution becomes error-prone, leading to poorly coordinated movements. The kinaesthetic illusion, which creates perceptions of limb movement in humans through non-invasively applying vibrations to muscles or tendons, provides an avenue for studying and restoring the sense of joint movement (kinaesthesia). This technique, however, leaves ambiguity between proprioceptive percepts that arise from muscles versus those that arise from skin receptors. Here we propose the concept of a stimulation system to activate kinaesthesia through the untethered application of localized vibration through implanted magnets. Approach. In this proof-of-concept study, we use two simplified one-DoF systems to show the feasibility of eliciting muscle-sensory responses in an animal model across multiple frequencies, including those that activate the kinaesthetic illusion (70–115 Hz). Furthermore, we generalized the concept by developing a five-DoF prototype system capable of generating directional, frequency-selective vibrations with desired displacement profiles. Main results. In-vivo tests with the one-DoF systems demonstrated the feasibility to elicit muscle sensory neural responses in the median nerve of an animal model. Instead, in-vitro tests with the five-DoF prototype demonstrated high accuracy in producing directional and frequency selective vibrations along different magnet axes. Significance. These results provide evidence for a new technique that interacts with the native neuro-muscular anatomy to study proprioception and eventually pave the way towards the development of advanced limb prostheses or assistive devices for the sensory impaired.
Study on the growth and redistribution of deuterium–deuterium layer driven by temperature gradient
Authors: Tao Chaoyou , Wu Kewei , Dai Fei , He Zhibing , Yang Hong , Lin Wei , Wang Kai , Zhang Hui
Published: April 2022

We report results of crystal growth, layering of the deuterium–deuterium (D2) layers in cylindrical cryogenic targets. For the first time, we realized the global coverage of the D2 layer on the inner surface of the capsule through the crystal growth of D2 ice, and the control of the temperature field without the infrared radiation, foam lining, and magnetic field. Analysis of the image of x-ray phase contrast imaging shows that the thickness of the D2 layer is about 36.53 μm, and the inner surface roughness is 3.23 μm. The finite element method is applied to simulate the temperature field of the target, and the phase transition process of D2, revealing the mechanism of D2 covering the inner surface of the capsule. These initial experiments provide a new vision and method for exploring and achieving the pure crystal growth as well as layering of D2 without operation of radioactive tritium.
Stress analysis of key components of finger rehabilitation exoskeleton robot based on finite element method
Authors: Zhang Qiuyue , Lu Guangda , Chen Ying , Guo Tinghang , Han Yu , Qie Tongtong
Published: April 2022

This paper analyzes the flexion and extension of three joints of a single exoskeleton mechanical finger. According to the motion characteristics of the finger, a finger rehabilitation exoskeleton robot is designed to assist patients with hand function for rehabilitation training. The three-dimensional model was established by SolidWorks, and the initial state of the robot was set under the action of gravity. The finite element analysis method was used to analyze the stress of the key components, including calculate and analyze its stress and strain. The simulation showed that the maximum stress of key components in rehabilitation training was 2140 (Pa), which is far less than the yield strength of the material 60 (MPa), and the maximum deformation was 0.092 (mm). The simulation result revealed that our design did not lead to failure of mechanical structure, which would provide a certain reference basis for its structural optimization design.
An IPSO-SA algorithm based on feedback mechanism for smooth path planning of UAV
Authors: Xu Haiqin , Yu Xujian , Dong Jie , Li Ranfei
Published: April 2022

The traditional PSO algorithm has been widely used in the path planning of unmanned equipment, but its algorithm is faced with the problem of premature convergence, which is easy to fall into the local optimal solution. When the initial position is not suitable, it can’t even plan the path in complex environment. At the same time, its line trajectory does not meet the requirements of the path curvature of realistic unmanned equipment. To solve the above problems, this paper proposes a new path planning strategy for unmanned equipment, and designs a new path planning algorithm for unmanned aircraft by combining the improved particle swarm optimization (IPSO) algorithm with simulated annealing algorithm (SA). At the same time, it solves the two problems that PSO algorithm is easy to fall into local optimal solution and abandoning all possible feasible solution regions in the early stage because of an illegal path. The path planned by IPSO-SA algorithm is processed by cubic spline interpolation to solve the curvature problem of its motion path. In addition, in view of the problem that the initial point is not suitable in complex environment, this algorithm designs a feedback mechanism to correct the initial point in time. The effectiveness of the algorithm is verified by theoretical derivation and simulation experiments, that is, the algorithm only needs a small number of point sequences to plan the path of UAV in simple and complex environment, and has less search amount and space-time overhead.
Wireless communication system throughput maximization based on UAV path planning
Authors: Guo Jing , Yang Shuai , Lu Dongkun , Zhang Caixia
Published: April 2022

This paper studies the path planning of unmanned aerial vehicle (UAV) in wireless information and energy transmission system of wireless sensor network. UAV transmits radio frequency energy to enable ground sensors, and the ground sensors transmit information to the UAV. In order to solve the non-convex optimization problem in path planning, a new alternate optimization framework is proposed to optimize the fly trajectory of the UAV and maximize the throughput of the entire system. The proposed framework firstly utlizes the lagrangian method to obtain relaxation solution without maximum speed constraint, then implements genetic algorithm and continuous convex optimization algorithm to obtain optimal trajectory and energy allocation strategy. Numerical simulations results show that the UAV-assisted wireless information and energy transmission system can realize self-powered sensor network and data collection in special environments, and improve the throughput of the sensor network system.
An Improved Unscented Kalman Filter for Maneuvering Target Tracking*
Authors: He Xiaoyou , Su Yu , Qiu Yuhe
Published: April 2022

The photoelectric pod provides angular information and distance information for the UAV (Unmanned Aerial Vehicle), and the UAV uses it to estimate the status information of the moving target. Since the measurement information of the photoelectric pod is the angle of sight and relative distance, the measurement equation contains some nonlinear functions in the Cartesian coordinate system, and the output frequency of the photoelectric pod is low. The improved unscented Kalman filter combines the function of prediction and correction, introduces the prior information of the target acceleration constraint, and uses the offline data to obtain steady gain, and then estimates the target state online. The simulation result show that the algorithm can track the target and need less time compared with the traditional unscented Kalman filter.