bluuebunny/crossref_metadata_2025 huggingface dataset:
Augmentative and Alternative Communication in an Elementary School Setting: A Case Study
Authors: Walker Virginia L. , Chung Yun-Ching
Published: December 2021

Purpose:

Although there is a strong evidence base supporting the use of augmentative and alternative communication (AAC) in school settings, the research-to-practice gap in this area remains a concern. Few studies have examined how AAC systems are implemented in school settings and whether these systems adequately promote communicative competence for students with complex communication needs. The aim of this case study was to better understand the ways in which elementary-age students with complex communication needs used AAC throughout daily routines.

Method:

Observations of five students, four receiving services under the category of autism and one under intellectual disability, in school settings were conducted to document the communication function, type of AAC systems used, and the times and activities during which AAC systems were accessible. In addition, supplemental interviews were conducted to understand the rationale for AAC implementation from the perspective of the special education teacher and speech-language pathologist.

Results:

Overall, findings from the observations and interviews indicated that a variety of AAC modes were utilized. Interactions represented a range of communicative functions, with the exception of social closeness, and were primarily observed during academic activities. However, there were some discrepancies between observations and interview data.

Conclusions:

Although these findings provide insight into how students with complex communication needs may use AAC in elementary school settings, more research is needed to explore AAC use across a range of students, classrooms, and schools. We present specific future research directions, along with implications and recommendations for AAC teams and researchers.
3‐D low numerical dispersion WLP‐FDTD method with artificial anisotropy parameters
Authors: Liu Gui‐Ying , Ma Ping , Tian Jing , Quan Jun , Chen Wei‐Jun
Published: December 2021

Based on the weighted Laguerre polynomials (WLPs) and artificial anisotropic (AA) parameters, a 3‐D unconditionally stable finite‐difference time‐domain (FDTD) electromagnetic simulation approach is proposed. The implementation of WLPs in time domain effectively eliminates the time step and AA parameters in spatial difference, resulting in suppressed numerical dispersion error. The monochromatic wave is employed as an example to obtain the numerical dispersion relationship of 3‐D AA‐WLP‐FDTD under AA parameter, in which reduced numerical dispersion error is observed. Compared with the conventional WLP‐FDTD technique, this approach demonstrates smaller numerical dispersion error under similar calculation cost.
Accurate fault location method for distribution network in presence of DG using distributed time‐domain line model
Authors: Mohajer Faeze , Sadeh Javad
Published: December 2021

In this paper a novel technique is presented for fault location in distribution networks in the presence of distributed generators (DGs). The proposed approach uses recorded voltage and current at the beginning of feeder and DG terminals. This method is based on transient state data, and due to presence of high frequencies in this state, to achieve high accuracy it utilizes the distributed time‐domain (DTD) line model. The fault location problem is formulated as an optimization problem and is solved using Genetic Algorithm (GA). Through modal transformation, in addition to locate the symmetrical three‐phase to ground (3LG) faults, the location of asymmetrical faults including single line to ground (SLG) and double line (LL) faults can also be determined. The effects of fault distance, fault resistance and fault inception angle on the accuracy of the proposed algorithm have also been investigated. A solution is also proposed to overcome the multi‐response problem. The simulations are conducted and the results are obtained via PSCAD and MATLAB softwares, respectively. The effectiveness of the proposed approach has been verified using the modified IEEE 34‐node test feeder under different fault conditions. The simulation results demonstrate the high efficiency and accuracy of the proposed method.
A feed‐forward framework integrating saliency and geometry discrimination for shadow detection in SAR images
Authors: Li Haixiang , Yu Xuelian , Zou Lin , Zhou Yun , Wang Xuegang
Published: December 2021

Shadow has been increasingly a kind of significant aid information for object extraction and scene interpretation in synthetic aperture radar images, which makes SAR shadow detection an important issue. In this paper, we propose a feed‐forward framework integrating saliency and geometry discrimination for shadow detection in SAR images. We firstly develop a global contrast based shadow saliency model to extract suspected shadows. Considering that such suspected regions mostly contain some non‐shadow areas, a discrimination strategy based on geometric relationships between objects and shadows is designed to remove falsely detected areas. Then the remaining regions become the final shadow detection results. Several experiments are carried out on images from two real datasets, Moving and Stationary Target Acquisition Recognition and MiniSAR, to evaluate the performance of our method. From the perspectives of three commonly used metrics, the proposed algorithm comprehensively outperforms two other classic methods, presenting reliable shadow detection ability. Moreover, the detection results of the two classic methods are significantly enhanced in controlling false alarms after the discrimination module is introduced. The results demonstrate that our algorithm is practically applicable to shadow detection in SAR images, and the discrimination strategy can be flexibly extended for related tasks.
The BINGO project
Authors: Costa Andre A. , Landim Ricardo G. , Novaes Camila P. , Xiao Linfeng , Ferreira Elisa G. M. , Abdalla Filipe B. , Wang Bin , Abdalla Elcio , Battye Richard A. , Marins Alessandro , Wuensche Carlos A. , Barosi Luciano , Brito Francisco A. , Queiroz Amilcar R. , Villela Thyrso , Fornazier Karin S. F. , Liccardo Vincenzo , Santos Larissa , dos Santos Marcelo V. , Zhang Jiajun
Published: December 2021

Context. The 21 cm line of neutral hydrogen (H I) opens a new avenue in our exploration of the structure and evolution of the Universe. It provides complementary data to the current large-scale structure (LSS) observations with different systematics, and thus it will be used to improve our understanding of the Λ cold dark matter (ΛCDM) model. This will ultimately constrain our cosmological models, attack unresolved tensions, and test our cosmological paradigm. Among several radio cosmological surveys designed to measure this line, BINGO is a single-dish telescope mainly designed to detect baryon acoustic oscillations (BAOs) at low redshifts (0.127 < z < 0.449).

Aims. Our goal is to assess the fiducial BINGO setup and its capabilities of constraining the cosmological parameters, and to analyze the effect of different instrument configurations.

Methods. We used the 21 cm angular power spectra to extract cosmological information about the H I signal and the Fisher matrix formalism to study BINGO’s projected constraining power.

Results. We used the Phase 1 fiducial configuration of the BINGO telescope to perform our cosmological forecasts. In addition, we investigated the impact of several instrumental setups, taking into account some instrumental systematics, and different cosmological models. Combining BINGO with Planck temperature and polarization data, the projected constraint improves from a 13% and 25% precision measurement at the 68% confidence level with Planck only to 1% and 3% for the Hubble constant and the dark energy (DE) equation of state (EoS), respectively, within the wCDM model. Assuming a Chevallier–Polarski–Linder (CPL) parameterization, the EoS parameters have standard deviations given by σw0 = 0.30 and σwa = 1.2, which are improvements on the order of 30% with respect to Planck alone. We also compared BINGO’s fiducial forecast with future SKA measurements and found that, although it will not provide competitive constraints on the DE EoS, significant information about H I distribution can be acquired. We can access information about the H I density and bias, obtaining ∼8.5% and ∼6% precision, respectively, assuming they vary with redshift at three independent bins. BINGO can also help constrain alternative models, such as interacting dark energy and modified gravity models, improving the cosmological constraints significantly.

Conclusions. The fiducial BINGO configuration will be able to extract significant cosmological information from the H I distribution and provide constraints competitive with current and future cosmological surveys. It will also help in understanding the H I physics and systematic effects.
Study on spacecraft formation capture control method based on disturbance observer
Authors: WANG Xiaolong , SUN Chong , FANG Qun , LI Qi , SONG Shuo
Published: December 2021

In the presence of compound disturbances, a multi-spacecraft cooperative collision avoidance capture control method based on disturbance observer was proposed, which can solve the problem of low speed rolling non-cooperative target close-range capture in space. Firstly, a relative motion model of attitude and orbit coupling is established. Secondly, the disturbance observer is used to estimate and cancel the compound disturbance in the capture process. At the same time, the hyperquadric surfaces are used to describe the shape of space non-cooperative targets and capture spacecraft to establish a composite artificial potential field, and a robust control law with collision avoidance function is also designed. Finally, the stability of the controlled system is proved by using Lyapunov function, and the collision avoidance performance of the system is analyzed. Numerical simulations are carried out to evaluate the effectiveness of the proposed control scheme.
Intelligent recommendation algorithm of mobile application crowdsourcing test based on deep learning
Authors: CHENG Jing , WANG Wei , SHUAI Zhengyi
Published: December 2021

As the functions of mobile applications become more and more complex, the crowdsourcing testing puts higher demands on the professional skills of testers. Therefore, it is an important factor to ensure test quality how to effectively match test task requirements with test personnel's skill level and achieve accurate crowdsourcing test task recommendation. This paper proposes a crowdsourcing test task recommendation algorithm for mobile applications based on deep learning. Firstly, feature analysis is carried out for testing tasks and testers, and feature systems are designed respectively. Second, the resulting characteristic data is used as input data for the Stacked Marginalized Denoising Autoencoder (SMDA). The deep feature data learned from SMDA are combined as the input of Deep Neural Networks (DNN). Finally, the learning ability of DNN is used for prediction. Experimental results show that the proposed algorithm has obvious advantages in both performance and training time compared with CDL and AUTOSVD ++, which verifies the effectiveness of the proposed algorithm. The proposed algorithm can recommend testing tasks to appropriate testers and improve the precision of the algorithm.
Estudo antropométrico tomográfico do quadril em uma população regional brasileira
Authors: Busato Thiago Sampaio , Milan Taiuã Verdasca , Matioski Filho Gladyston Roberto , Godoi Lucas Dias , Morozovski Marcelo Gavazzoni , Capriotti Juan Rodolfo Vilela
Published: December 2021

Objetivo Determinar a antropometria média do quadril de uma população regional brasileira através de medidas obtidas pela tomografia axial computadorizada (TAC).

Método Análise analítico-descritiva, retrospectiva, de medidas coxofemorais de 200 TACs do abdômen de pacientes atendidos em um centro médico. Foram selecionados aleatoriamente exames que permitissem a aferição de 30 medidas antropométricas previamente definidas. Os dados foram estatisticamente analisados e comparados quanto a sexo e idade.

Resultados A prevalência de displasia do quadril foi de 6%. Sinais sugestivos de impacto fêmoro-acetabular foram vistos em 26% dos casos. A análise dos resultados no grupo acima de 50 anos demonstrou medidas significativamente maiores dos: setores horizontais do acetábulo, do ângulo centro-borda e do arco acetabular, acompanhados de menor índice de extrusão, ângulo cérvico-diafisário e offset vertical. Algumas medidas foram significativamente diferentes em função do sexo: o ângulo centro-borda lateral (µ = 35.5°) e o arco acetabular (µ = 68.7°) se mostraram maiores no sexo feminino. No grupo masculino, foram maiores o índice de extrusão (µ = 16%), o offset lateral (µ = 38,3mm), a profundidade (µ = 19,5 mm) e o diâmetro do colo (µ = 26,4 mm).

Conclusão O presente estudo caracterizou a antropometria do quadril de uma população brasileira. Demonstrou ainda diferenças morfológicas significativas do quadril entre diferentes faixas etárias e sexos.
Artificial Intelligence: A New Tool in Oncologist's Armamentarium
Authors: Talwar Vineet , Chufal Kundan Singh , Joga Srujana
Published: December 2021

Artificial intelligence (AI) has become an essential tool in human life because of its pivotal role in communications, transportation, media, and social networking. Inspired by the complex neuronal network and its functions in human beings, AI, using computer-based algorithms and training, had been explored since the 1950s. To tackle the enormous amount of patients' clinical data, imaging, histopathological data, and the increasing pace of research on new treatments and clinical trials, and ever-changing guidelines for treatment with the advent of novel drugs and evidence, AI is the need of the hour. There are numerous publications and active work on AI's role in the field of oncology. In this review, we discuss the fundamental terminology of AI, its applications in oncology on the whole, and its limitations. There is an inter-relationship between AI, machine learning and, deep learning. The virtual branch of AI deals with machine learning. While the physical branch of AI deals with the delivery of different forms of treatment—surgery, targeted drug delivery, and elderly care. The applications of AI in oncology include cancer screening, diagnosis (clinical, imaging, and histopathological), radiation therapy (image acquisition, tumor and organs at risk segmentation, image registration, planning, and delivery), prediction of treatment outcomes and toxicities, prediction of cancer cell sensitivity to therapeutics and clinical decision-making. A specific area of interest is in the development of effective drug combinations tailored to every patient and tumor with the help of AI. Radiomics, the new kid on the block, deals with the planning and administration of radiotherapy. As with any new invention, AI has its fallacies. The limitations include lack of external validation and proof of generalizability, difficulty in data access for rare diseases, ethical and legal issues, no precise logic behind the prediction, and last but not the least, lack of education and expertise among medical professionals. A collaboration between departments of clinical oncology, bioinformatics, and data sciences can help overcome these problems in the near future.
A Case of İntrapancreatic Accessory Spleen Mimicking a Pancreatic Metastasis on the 18F-FDG PET/CT Scan: A Case with Breast Cancer
Authors: Yıldırım Mustafa , Artas Hakan
Published: December 2021

The accessory spleen is a focus of splenic tissue which is separated from the main of the spleen. Although accessory spleens are generally recognized on computed tomography (CT), intrapancreatic accessory spleen (IPAS) may be mistaken for other pancreatic tail lesions. We report a case of IPAS mimicking a pancreatic metastasis on the 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT). A 41-year-old with diagnosed breast cancer (invasive ductal carcinoma) woman patient underwent an 18F-FDG PET/CT for metastasis screening and staging. 18F-FDG PET/CT showed a focal uptake in the pancreatic tail. The patient underwent a contrast-enhanced CT and magnetic resonance imaging (MRI) for lesion characterization. The density and intensity of lesion were similar to spleen on all phases and all sequences. The lesion was evaluated as IPAS. The diagnosis was confirmed by endoscopic ultrasound (EUS) biopsy. A case of IPAS positive at 18F-FDG PET/CT could not found in the literature. We present a case of IPAS mimicking a pancreatic metastasis positive at 18F-FDG PET/CT.
Trauma-Associated Tension Pneumocephalus with Characteristic Mount Fuji Sign—Case Report
Authors: Khandelwal Utkarsh , Ajayababu Anuj , Sinha Tej Prakash , Bhoi Sanjeev
Published: December 2021

Tension pneumocephalus is a rare and life-threatening neurosurgical emergency in the setting of blunt or penetrating head trauma, especially in those with craniofacial fractures, which emergency physicians should be aware about. Early identification and appropriate treatment measures including supine positioning, 100% oxygen via mask, early neurosurgery consultation and, if required, operative intervention are paramount to optimal neurological and survival outcome. Definitive diagnosis requires imaging usually in the form of computed tomography (CT) head and serial monitoring of neurological status, optic nerve sheath diameter measurement and repeat imaging, essential to identify patients who might have features of increased pressure on brain matter, which could lead to adverse neurological and clinical outcomes. We present two cases of tension pneumocephalus with the characteristic Mount Fuji sign on CT head, who were managed nonoperatively with optimal neurological outcome. In patients with severe head or maxillofacial trauma presenting to emergency department, CT should be evaluated for signs of tension pneumocephalus, and such patients need to be closely observed for complications of pressure effect on brain matter to ensure optimal neurological and survival outcomes.
Bilateral Submandibular Gland Aplasia: An Unusual Cause of Sublingual Swelling—The Role of Imaging in Patient Management
Authors: Thimmappa Srividya B , Suman Abhishek , Dixit Rashmi , Garg Anju
Published: December 2021

There are very limited reports of aplasia of bilateral submandibular glands. We report the case of a 55-year-old male who presented with nontender palpable sublingual masses. On computed tomography and magnetic resonance imaging, bilateral submandibular gland aplasia and compensatory hypertrophy of bilateral parotid and sublingual glands were seen with herniation of hypertrophied sublingual glands through the bilateral mylohyoid muscles presenting as palpable sublingual region masses. Additional finding of bilateral accessory parotid glands was also noted. Prolapsed hypertrophied sublingual glands should be considered in patients presenting with bilateral sublingual masses to avoid unnecessary invasive procedures. We suggest radiological evaluation of such cases prior to any intervention.
Neuroendoscopic Navigated One-Step Removal of Crossed Ventricular Catheter Fragments: Technical Note
Authors: Calì Alessandro , Scalia Gianluca , Marrone Salvatore , Riolo Carmelo , Vasta Giuseppe , Umana Giuseppe Emmanuele , Cicero Salvatore , Iacopino Domenico Gerardo , Nicoletti Giovanni Federico
Published: December 2021

Introduction Neuroendoscopy plays an important role in minimally invasive neurosurgery. The authors reported an interesting case of a pediatric patient with multiple ventriculoperitoneal shunt (VPS) revision surgeries, presenting with VPS infection and with two crossed intraventricular floating catheter fragments, successfully removed through a neuroendoscopic navigated one-step procedure. A literature review regarding this exceedingly rare condition has also been discussed.

Case Description An 11-year-old female patient with a history of congenital hydrocephalus was admitted to the emergency department with symptoms of intracranial hypertension, psychomotor agitation, and tetraparesis. She had a history of previous multiple VPS revisions. She had an urgent brain computed tomography scan that documented hydrocephalus; the VPS's intraventricular catheter tip was sited at the level of the right frontal horn. Two small floating catheter fragments, not connected to the VPS, were identified: the first close to the right lateral ventricle at the level of the right occipital horn, the second one between the right occipital horn and the third ventricle. First, she underwent an exteriorization of the distal catheter for VPS. Cerebrospinal fluid examination documented hyperproteinorrachia and a positive culture for Staphylococcus
aureus. Then a navigated right transfrontal endoscopic approach to the right lateral ventricle was performed extending to the previous burr hole and achieving a wide range of working angle with a rigid 0-degree lens endoscope. Intermittent irrigation generating convective flow was performed such as to mobilize the catheters tip gently upward, to remove them by grasping. Finally, a whole VPS replacement has been performed.

Conclusion Persistence of intraventricular floating catheter fragments can lead to subacute or chronic infections. Neuroendoscopic retrieval represents a safe and effective alternative to a more extensive and invasive surgical approach. However, the exact catheter tip identification, grasping, and removal can be difficult to achieve, due to the technical instrumentation characteristics and altered intraventricular anatomy in chronic congenital hydrocephalus. In our experience, endoscopic convective flow induction through saline irrigation can determine floating intraventricular catheter fragments movement aiming to their identification and subsequent successful endoscopic retrieval.
Imaging of Noncontact Anterior Cruciate Ligament Injuries and Associated Bone Marrow Contusion Patterns
Authors: Pringle Lauren , Wissman Robert D.
Published: December 2021

Anterior cruciate ligament (ACL) tears are commonly associated with bone contusions. Bone contusions can lend important insight into increased risk for more subtle concurrent injuries based on common injury mechanisms and patterns, as higher energy trauma has been tied to patterns of specific bone contusions and concomitant injuries. Lateral compartment contusions are most common and occur in pivot shift injuries. Medial compartment contusions may represent a contrecoup mechanism after the initial lateral injuries. Patellotibial contusions require axial loading but are also typically seen in conjunction with lateral and medial compartment contusions. The differences in ACL injury mechanics and physiology as shown by imaging contusion patterns can help clinicians better identify and treat the concurrent associated injuries.
Blau Syndrome Complicated by Atypical Type IIa Takayasu Arteritis
Authors: Bikouli Efstathia Danai C. , Vazeou Andriani , Xatzipsalti Maria , Servos Georgios , Delis Dimitrios , Maritsi Despoina N.
Published: December 2021

Blau syndrome (BS) is a rare, autosomal dominant monogenic autoinflammatory disease, usually presenting as a triad of symptoms (granulomatous dermatitis, uveitis, and nonerosive arthritis) and caused by gain-of-function mutations in the nucleotide oligomerization domain 2 (NOD2) gene. However, very few reports in children of copresence of BS with large vessel vasculitis exist. We hereby describe a case of BS associated with clinical features of Takayasu arteritis. An 8.5-year-old boy presented with hypertension, cardiac insufficiency, arthritis, and ocular disease. Among other investigations, he underwent cervical and chest computed tomography and computed tomography angiography scans that revealed the presence of type IIa Takayasu arteritis lesions. Genetic analysis revealed a heterozygous mutation of NOD2 gene leading to the amino acid exchange Arg-587-Cys in the NACHT domain of the NOD2 protein (R587C) as pathogenic cause of BS. He received treatment with prednisolone, methotrexate, and infliximab (antitumor necrosis factor-α) in addition to antihypertensive medication with a favorable clinical response. Cases of BS should be investigated for the coexistence of Takayasu arteritis. However, further research is required to delineate a possible common pathogenic mechanism between the two clinical entities.
A Case of Postoperative SMART Syndrome in a Medulloblastoma Survivor
Authors: Cirjan Cristian , Jamal Ali , Mercier Philippe , Berkovich Rachel , Navalkele Pournima
Published: December 2021

Stroke-like migraine attacks after radiation therapy (SMART) syndrome is a rare neurological phenomenon characterized by reversible symptoms of headache, seizure, hemiparesis, and visual changes associated with a remote history of cranial irradiation. We describe a case of a medulloblastoma survivor, presenting with postoperative neurological deficits, along with neuroimaging findings and subsequent resolution of symptoms, highly suggestive of SMART syndrome. We have also reviewed the common epidemiological and diagnostic factors associated with this rare disease, as well as discussed pathophysiological mechanisms.
Simulations of ion heating due to ion-acoustic instabilities in presheaths
Authors: Beving Lucas P. , Hopkins Matthew M. , Baalrud Scott D.
Published: December 2021

Particle-in-cell, direct simulation Monte Carlo simulations reveal that ion-acoustic instabilities excited in presheaths can cause significant ion heating. Ion-acoustic instabilities are excited by the ion flow toward a sheath when the neutral gas pressure is small enough and the electron temperature is large enough. A series of 1D simulations were conducted in which neutral plasma (electrons and ions) was uniformly sourced with an ion temperature of 0.026 eV and different electron temperatures (0.1 eV–50 eV). Ion heating was observed when the electron-to-ion temperature ratio exceeded the minimum value predicted by linear response theory to excite ion-acoustic instabilities at the sheath edge (Te/Ti≈28). When this threshold was exceeded, the temperature equilibration rate between ions and electrons rapidly increased near the sheath so that the local temperature ratio did not significantly exceed the threshold for instability. This resulted in significant ion heating near the sheath edge, which also extended back into the bulk plasma; presumably due to wave reflection from the sheath. This ion-acoustic wave heating mechanism was found to decrease for higher neutral pressures, where ion-neutral collisions damp the ion-acoustic waves and ion heating is instead dominated by inelastic collisions in the presheath.
Predicting the onset of consequent stenotic regions in carotid arteries using computational fluid dynamics
Authors: Albadawi Muhamed , Abuouf Yasser , Elsagheer Samir , Ookawara Shinichi , Ahmed Mahmoud
Published: December 2021

Carotid arteries are the major blood vessels that carry oxygenated blood to the brain and face. Carotid artery disease is characterized by the narrowing of the carotid arteries due to plaque buildup at the arterial walls, leading to major consequences such as brain stroke and death. Hemodynamics such as wall shear stress (WSS) and velocity distribution can be employed to investigate the severity and location of stenosis in the carotid arteries. Furthermore, the potential of stenosis in other regions along the carotid arteries is affected by local variations in hemodynamics. To investigate other potential high-risk regions, a comprehensive blood flow model was utilized through a reconstructed three-dimensional patient-specific geometry with realistic boundary conditions. The developed model was numerically simulated and validated. The results indicated that hemodynamics can be successfully used to investigate the degree of stenosis severity and location. Two different locations along the carotid artery were examined. At location 1 (near the artery bifurcation) of the common carotid artery, the WSS increased from 11 Pa in the case of 42% stenosis to 27 Pa in the case of 61% stenosis and 263 Pa for 84% stenosis. Such values significantly decreased at location 2 (far from the artery bifurcation) because of the increasing distance from the artery bifurcation. In addition, the maximum value of the oscillatory shear index (OSI) downstream of the stenosis throat reached 0.5, and the outlet mass flow rate changed significantly with varying stenosis location. Carotid artery stenosis affects the artery bifurcation, which appears to be at high risk because of thrombus and arterial wall rupture, which are clearly indicated by the WSS and OSI values in this region. The current findings support the efficient use of a computational fluid dynamics approach for the diagnosis and prediction of carotid artery stenosis.
Ultra-broadband THz/IR upconversion and photovoltaic response in semiconductor ratchet-based upconverter
Authors: Bai Peng , Yang Ning , Chu Weidong , Zhang Yueheng , Shen Wenzhong , Fu Zhanglong , Shao Dixiang , Zhou Kang , Tan Zhiyong , Li Hua , Cao Juncheng , Li Lianhe , Linfield Edmund Harold , Xie Yan , Zhao Ziran
Published: December 2021

An ultra-broadband upconversion device is demonstrated by direct tandem integration of a p-type GaAs/AlxGa1-xAs ratchet photodetector (RP) with a GaAs double heterojunction light emitting diode (DH-LED) using the molecular beam epitaxy. An ultra-broadband photoresponse from the terahertz (THz) to near-infrared (NIR) region (4–200 THz) was realized, which covered a much wider frequency range compared with existing upconversion devices. Broadband IR/THz radiation from a 1000 K blackbody was upconverted into NIR light that could be detected via a commercial Si-based device. The normal incidence absorption of the RP simplified the structure of the RP-LED device and made it more compact than the intersubband transition-based upconverters. In addition to upconversion, the proposed upconverter was investigated as a photovoltaic detector in the infrared region (detection range from 18 to 150 THz) based on the ratchet effect without an applied bias voltage.
Study on energy extraction of Kármán gait hydrofoils from passing vortices
Authors: Tong Ying , Xia Jian , Chen Long
Published: December 2021

How swimming fish extract energy from environmental vortices is still an open question. In this work, fish swimming in unsteady flow is numerically investigated by using the immersed boundary lattice Boltzmann method. The swimming fish is modeled as a forced Kármán gait hydrofoil, and the vortical flow is generated by a stationary circular cylinder. We calculate the Fourier spectra of hydrodynamic forces on the hydrofoil surface and found that there is a coupling between lateral force and drag, which results from a nonlinear wave interaction. The Kármán gait hydrofoil adjusts the lateral force by applying lateral excitation to the vortical flow and improves the drag/thrust through nonlinear wave interaction. We find that suppressing the harmonic energy of the viscous mode is the key ingredient to extract energy from the passing vortex. In turn, the downstream distance LN and foil-vortex phase φ determine whether the viscous harmonic energy can be suppressed. If the viscous mode harmonic is strong, the interaction between the vortex shedding mode and the viscous mode leads to a series of combined modes, which extract energy from the fundamental mode. These combined modes that appear in the fluid force spectra reduce the efficiency of energy extraction.
Modeling combined global, beam, and diffuse clear-sky indices with Markov-chain mixture distribution models
Authors: Munkhammar J. , Widén J.
Published: December 2021

This study uses the N-state Markov-chain mixture distribution model and the multiple-component N-state Markov-chain mixture distribution model to simulate global, beam, and diffuse horizontal clear-sky index. The models are data-driven such that when trained on single or multiple clear-sky index time-series, the models generate arbitrarily long synthetic clear-sky index time-series for the same components. The models were tested on solar irradiance datasets from two different climatic regions: Norrköping, Sweden, and Oahu, Hawaii, USA. The results show high probability distribution and temporal autocorrelation goodness-of-fit for all models and high cross correlation goodness-of-fit as well as accurate correlation between the component datasets for the multiple component model simulations. When combined with, e.g., the Hay and Davies model, the output from this model could, for example, be used to generate realistic time-series of incident solar irradiance on tilted planes.
Vapor deposition rate modifies anisotropic glassy structure of an anthracene-based organic semiconductor
Authors: Bishop Camille , Bagchi Kushal , Toney Michael F. , Ediger M. D.
Published: December 2021

We control the anisotropic molecular packing of vapor-deposited glasses of ABH113, a deuterated anthracene derivative with promise for future organic light emitting diode materials, by changing the deposition rate and substrate temperature at which they are prepared. We find that at substrate temperatures from 0.65 Tg to 0.92 Tg, the deposition rate significantly modifies the orientational order in the vapor-deposited glasses as characterized by x-ray scattering and birefringence. Both measures of anisotropic order can be described by a single deposition rate–substrate temperature superposition (RTS). This supports the applicability of the surface equilibration mechanism and generalizes the RTS principle from previous model systems with liquid crystalline order to non-mesogenic organic semiconductors. We find that vapor-deposited glasses of ABH113 have significantly enhanced density and thermal stability compared to their counterparts prepared by liquid-cooling. For organic semiconductors, the results of this study provide an efficient guide for using the deposition rate to prepare stable glasses with controlled molecular packing.
Turbulence modulations and drag reduction by inertialess spheroids in turbulent channel flow
Authors: Wang Ze , Xu Chun-Xiao , Zhao Lihao
Published: December 2021

Previous studies on nonspherical particle-fluid interaction were mostly confined to tiny fiber-like particles, which were observed to induce turbulence drag reduction. Nevertheless, with the presence of disk-like particles how wall turbulence is modulated and whether drag reduction occurs are still unknown. Motivated by those open questions, we perform two-way coupled direct numerical simulations of inertialess spheroids in a turbulent channel flow with additional particle stresses to account for the feedback from spheroids on the fluid phase. The results demonstrate that tiny disk-like particles can also lead to significant turbulence modulations and drag reduction in wall turbulence. Moreover, the attenuation of turbulent activities and the alteration of turbulence anisotropy are observed in the laden flows. To explain the different performances of drag reduction by fibers and disks in the channel flow, we propose a mechanism by analyzing the modulated near-wall turbulence structures and particle shear stress. We find that the spheroidal particles weaken the quasistreamwise vortices through negative work and, therefore, attenuate the Reynolds shear stress. However, the mean shear stress generated by particles, which is particle shape-dependent, partly compensates for the reduction of Reynolds shear stress and thus affects the efficiency of drag reduction. The present study implies that tiny disk-like particles can be an alternative drag reduction agent applied in wall turbulence.
Analysis of assumption about the possibility of the highly effective scenario of in-flight muon catalyzed fusion
Authors: Shmatov Mikhail L.
Published: December 2021

It is shown that an average number of in-flight fusion reactions catalyzed by one negative muon in the reactor proposed by Iiyoshi et al. [AIP Conf. Proc. 2179, 020010 (2019)] will be less than 120 rather than about 1000, and therefore, the efficiency of the use of this reactor for practical purposes will be much less than expected earlier.
Room temperature large photoresponse in p-n heterojunction composed of WSe2 and 2D electron gas at LaAlO3/KTaO3 interface
Authors: Li Ju , Zhou Xiaowei , Jiang Yucheng , Zhao Run , Gao Ju , Xing Jie , Liu Guozhen , Qiu Jie
Published: December 2021

The heterostructures combining 2D layered material and two-dimensional electron gas (2DEG) at the surface or interfaces of complex oxides may exhibit abundant and interesting physical properties. In this paper, we report the development and photoelectrical properties of a p-n heterojunction composed of a p-type 2D layered material WSe2 and n-type 2DEG at the LaAlO3/KTaO3 interface. The WSe2 flake was first fabricated by mechanical exfoliation and then integrated with 2DEG at the LaAlO3/KTaO3 interface obtained using pulsed laser deposition. The WSe2/2DEG heterostructure shows good rectifying behavior with a low leakage current at room temperature. Additionally, compared with oxide 2DEG, the WSe2/2DEG heterostructure exhibits greatly enhanced visible-light photoresponse. The results imply that the 2D heterostructures based on disparate material systems can be realized and demonstrate potential applications in nanoscale electronics and optoelectronics, which are of great scientific and technological significances.
Visually Directed Walking to Briefly Glimpsed Targets is not Biased toward Fixation Location
Authors: Philbeck John W
Published: December 2021

When observers indicate the magnitude of a previously viewed spatial extent by walking without vision to each endpoint, there is little evidence of the perceptual collapse in depth associated with some other methods (eg visual matching). One explanation is that both walking and matching are perceptually mediated, but that the perceived layout is task-dependent. In this view, perceived depth beyond 2–3 m is typically distorted by an equidistance effect, whereby the egocentric distances of nonfixated portions of the depth interval are perceptually pulled toward the fixated point. Action-based responses, however, recruit processes that enhance perceptual accuracy as the stimulus configuration is inspected. This predicts that walked indications of egocentric distance performed without vision should exhibit equidistance effects at short exposure durations, but become more accurate at longer exposures. In this paper, two experiments demonstrate that in a well-lit environment there is substantial perceptual anisotropy at near distances (3–5 m), but that walked indications of egocentric distance are quite accurate after brief glimpses (150 ms), even when the walking target is not directly fixated. Longer exposures do not increase accuracy. The results are clearly inconsistent with the task-dependent information processing explanation, but do not rule out others in which perception mediates both walking and visual matches.
Bifurcations changing the homotopy type of the closure of an invariant saddle manifold of a surface diffeomorphism
Authors: Nozdrinova E. V. , Pochinka O. V.
Published: December 2021

It is well known from the homotopy theory of surfaces that an ambient isotopy does not change the homotopy type of a closed curve. Using the language of dynamical systems, this means that an arc in the space of diffeomorphisms that joins two isotopic diffeomorphisms with invariant closed curves in distinct homotopy classes must go through bifurcations. A scenario is described which changes the homotopy type of the closure of the invariant manifold of a saddle point of a polar diffeomorphism of a 2-torus to any prescribed homotopically nontrivial type. The arc constructed in the process is stable and does not change the topological conjugacy class of the original diffeomorphism. The ideas that are proposed here for constructing such an arc for a 2-torus can naturally be generalized to surfaces of greater genus.

Bibliography: 32 titles.
Indigenous peoples’ attitudes and social acceptability of invasive species control in New Zealand
Authors: Black Amanda , Garner Gary , Mark-Shadbolt Melanie , Balanovic Jovana , MacDonald Edith , Mercier Ocean , Wright Janine
Published: December 2021

Context In Aotearoa New Zealand, a significant threat to biodiversity, conservation efforts and Indigenous cultural identity is the unwanted introduction of invasive pests, plants and pathogens. Currently methods to control invasive species in Aotearoa New Zealand, in particular mammalian pests (i.e. possums (Trichosurus vulpecula)) have had decreasing public support. This has likely come about for a number of reasons, including lack of social engagement and concerns over impacts combined with an increasing distrust of top-down initiatives. Aims and methods We analysed opinions towards existing and emerging technologies to manage invasive species. Data were obtained from 1015 respondents who identified as Indigenous Māori from a national survey of 8199 respondents. Utilising psychological frameworks to investigate underlying beliefs of social acceptance, we analysed the responses using exploratory and latent class analysis methods to summarise the main perspectives. Key results Our results revealed four distinct clusters of viewpoints amongwithin Māori respondents that were explained by known (objective) and subjective scientific knowledge around pest control methods, and Indigenous community wellbeing. We also observed a general neutrality in trust towards science, but more trust in scientists than science institutions. Conclusions and implications Understanding the underlying values and viewpoints associated with pest control and including these in developing engagement plans will ensure a responsible process that empowers Māori. This way forward is key to sustain pathways of engagement and positive participation in decision-making.
Disguised electromagnetic connections in classical electron theory
Authors: Boyer Timothy H
Published: December 2021

In the first quarter of the 20th century, physicists were not aware of the existence of classical electromagnetic zero-point radiation nor of the importance of special relativity. Inclusion of these aspects allows classical electron theory to be extended beyond its 19th century successes. Here we review spherical electromagnetic radiation modes in a conducting-walled spherical cavity and connect these modes to classical electromagnetic zero-point radiation and to electromagnetic scale invariance. Then we turn to the scattering of radiation in classical electron theory within a simple approximation. We emphasize that, in steady-state, the interaction between matter and radiation is disguised so that the mechanical motion appears to occur without the emission of radiation, even though the particle motion is actually driven by classical electromagnetic radiation. It is pointed out that, for nonrelativistic particles, only the harmonic oscillator potential taken in the low-velocity limit allows a consistent equilibrium with classical electromagnetic zero-point radiation. For relativistic particles, only the Coulomb potential is consistent with electrodynamics. The classical analysis places restrictions on the value of e
2/ℏc.
Study of notched MEMS specimen: elasto-plastic modeling and experimental testing
Authors: Somà Aurelio , Pistorio Francesca , Mubasher Saleem Muhammad
Published: December 2021

This paper investigates the effect of stress and strains concentration, due to the notch presence, on the elasto-plastic behavior of gold microstructures subjected to tensile loading under electrostatic actuation. A kinematic model for the test microstructure which relates the experimentally measured deflection to the induced stress in the central specimen with applied electrostatic load is developed. The local maximum stress and strains at the notch root are analytically estimated using the Neuber’s rule and verified through a detailed non-linear coupled-field electric-structural finite element method (FEM)-based analysis. Several experimental tests are carried out to analyze the accumulation of plastic strain and the consequent development of plastic hinges induced in the central notched specimen due to repeated cyclic tensile loading by measuring the corresponding deflection with each loading cycle. The comparison between the failure condition observed experimentally in the test notched specimens and the FEM-based simulation results shows that the notch acts as stress and strains raiser fostering the initiation and expansion of plastic hinges in the thin film gold specimen which can lead to the specimen breakdown.
Soft x-ray spectra of cerium laser-produced plasmas
Authors: White Elgiva , O’Sullivan Gerry , Dunne Padraig
Published: December 2021

Spectra of laser-produced plasmas of cerium have been recorded in the 1.5 to 15.5 nm spectral region. The plasmas were formed using the frequency doubled pulsed output of a neodymium-doped yttrium aluminium garnet (Nd:YAG) laser at 532 nm. At the power densities incident on-target, ranging from 8.6 × 109–2.1 × 1013 W cm−2, Ce4+ to Ce27+ ions gave rise to emission from Δn = 0, 1 transitions to final states where n = 4. The spectra are dominated by an intense unresolved transition array (UTA) in the 8–10 nm region arising from n = 4 to n = 4 transitions. Two distinct components of this UTA are observed whose appearance is strongly dependent on laser power density, corresponding to transitions involving ions with open 4d and open 4f subshells, the latter at longer wavelengths. Multiple other transition arrays are identified and UTA statistics are given. The analysis was aided by atomic structure calculations and the use of a steady state collisional-radiative model.
Calculated electron impact ionisation fragmentation patterns
Authors: Graves Vincent , Cooper Bridgette , Tennyson Jonathan
Published: December 2021

There are many measurements and calculations of total electron impact ionisation cross sections. However, many applications, particularly in plasma physics, also require fragmentation patterns. Approximate methods of deducing partial cross sections are tested based on the use of total cross section computed within the well-used binary encounter Bethe approximation. Partial ionisation cross sections for three series of molecules including CH4, CF4 and CCl4; SiH4 and SiCl4; NH3 and PH3, were estimated using two methods. Method one is semi-empirical and uses mass spectroscopy data to fix the partial cross sections at a single electron energy. The second is a fully computational method proposed by Huber et al (2019 J. Chem. Phys.
150 024306). Comparisons with experimental results suggest that the mass spectroscopy method is more accurate. However, as Huber’s method requires no experimental input, this method could be used as a first approximation when no experimental data is available. As mass spectroscopy sometimes provides incomplete datasets, a hybrid method based on the use of both methods is also explored.