bluuebunny/crossref_metadata_2025 huggingface dataset:
High voltage power transformer condition assessment considering the health index value and its decreasing rate
Authors: Tamma Winanda Riga , Prasojo Rahman Azis , Suwarno
Published: March 2021

A health index method is a useful tool for the transformer assessment condition. This method has been used in several previous studies. However, most of them have not observed the health index decreasing rate as an aspect to improve the transformer condition assessment. A health index method with different approaches is proposed, considering the values and decreasing rate to assess the transformer condition. Inspection data from in‐service and out‐of‐service 150 kV power transformers provided by the Indonesian electric company are included. The correlation between operating age and Health Index value and Health Index decreasing rate was also observed. With increasing operation age, the Health Index value tends to decrease with a correlation coefficient R
2 of 0.631. Further analysis was conducted to power transformers with historical data of 3 years or more, which showed that the tendency of the Health Index value decreasing rate is higher with older transformers. This paper also illustrates the Health Index analysis of 35 out‐of‐service transformers, resulting in a more suitable Health Index value compared to the previous approach. This study proposes the transformer risk assessment based on its health index value and the decreasing rate.
Propagation and localisation of partial discharge in transformer bushing based on ultra‐high frequency technique
Authors: Jiang Jun , Chen Judong , Li Jiansheng , Yang Xiaoping , Albarracín‐Sánchez Ricardo , Ranjan Prem , Zhang Chaohai
Published: March 2021

As an essential component of power transformers, the detection and diagnosis of incipient partial discharge (PD) activities of bushings are of great significance. A 35‐kV oil‐impregnated paper (OIP) bushing is investigated. The bushing is modelled by coaxial theory and electromagnetic (EM) simulation. As the paths of PD‐induced ultra‐high frequency (UHF) signal propagating in the bushing are OIPs and oil gap, small attenuation during signal propagation is seen. Since OIP is composed of heterogeneous media compared with pure oil, there will be relatively less UHF signal leakage from OIPs, whereas more leakage from the oil gap. This leakage provides the possibility of non‐contact detection outside the bushing by UHF method. PD measurements with UHF method are carried out on the bushing. Then, the minimum energy method is used to extract time‐difference‐of‐arrival (TDOA), and Chan algorithm is adopted to locate points of UHF signal radiation. High accuracy locating with a small error of 15 cm has been achieved. The contactless UHF method‐based tests have demonstrated the effectiveness of online monitoring and locating of bushing PD.
Affine linear parameter‐varying embedding of non‐linear models with improved accuracy and minimal overbounding
Authors: Sadeghzadeh Arash , Sharif Bardia , Tóth Roland
Published: March 2021

In this study, automated generation of linear parameter‐varying (LPV) state‐space models to embed the dynamical behaviour of non‐linear systems is considered, focusing on the trade‐off between scheduling complexity and model accuracy and the minimisation of the conservativeness of the resulting embedding. The LPV state‐space model is synthesised with affine scheduling dependency, while the scheduling variables themselves are non‐linear functions of the state and input variables of the original system. The method allows to generate complete or approximative embedding of the non‐linear system model and also it can be used to minimise the complexity of existing LPV embeddings. The capabilities of the method are demonstrated on simulation examples and also in an empirical case study where the first‐principle motion model of a three degrees of freedom (3DOF) control moment gyroscope is converted by the proposed method to an LPV model with low scheduling complexity. Using the resulting model, a gain‐scheduled controller is designed and applied on the gyroscope, demonstrating the efficiency of the developed approach.
Finite‐time H2/H∞ control for linear Itô stochastic Markovian jump systems: mode‐dependent approach
Authors: Yan Zhiguo , Song Yunxia , Park Ju H.
Published: March 2021

This study focuses on the finite‐time (FT) control problem for linear Itô‐type stochastic Markovian jump systems (SMJS). According to the characteristics of SMJS, a mode‐dependent approach (MDA) is provided. Through MDA, state feedback and observer‐based FT controllers are designed. Compared with the mode‐independent approach, the advantages of MDA are clearly shown. In the sequel, two new optimisation algorithms for deriving the optimal FT controller are proposed. Finally, a numerical example is utilised to show the merits of the obtained results.
Impacts on Quality of Life with Escitalopram Monotherapy and Aripiprazole Augmentation in Patients with Major Depressive Disorder: A CAN-BIND Report
Authors: Morton Emma , Bhat Venkat , Giacobbe Peter , Lou Wendy , Michalak Erin E. , Chakrabarty Trisha , Frey Benicio N. , Milev Roumen V. , Müller Daniel J. , Parikh Sagar V. , Rotzinger Susan , Kennedy Sidney H. , Lam Raymond W. ,   on behalf of the CAN-BIND Investigator Team
Published: March 2021

Introduction Many individuals with major depressive disorder (MDD) do not respond to initial antidepressant monotherapy. Adjunctive aripiprazole is recommended for treatment non-response; however, the impacts on quality of life (QoL) for individuals who receive this second-line treatment strategy have not been described.

Methods We evaluated secondary QoL outcomes in patients with MDD (n=179). After 8 weeks of escitalopram, non-responders (<50% decrease in clinician-rated depression) were treated with adjunctive aripiprazole for 8 weeks (n=97); responders continued escitalopram (n=82). A repeated-measures ANOVA evaluated change in Quality of Life Enjoyment and Satisfaction Short Form scores. QoL was described relative to normative benchmarks.

Results Escitalopram responders experienced the most QoL improvements in the first treatment phase. For non-responders, QoL improved with a large effect during adjunctive aripiprazole treatment. At the endpoint, 47% of patients achieving symptomatic remission still had impaired QoL.

Discussion Individuals who were treated with adjunctive aripiprazole after non-response to escitalopram experienced improved QoL, but a substantial degree of QoL impairment persisted. Since QoL deficits may predict MDD recurrence, attention to ways to support this outcome is required.
Total Synthesis of Mycocyclosin and the Herqulines
Authors: Schindler Corinna S. , Ryan Jonathon S.
Published: March 2021

Since the first reports of their isolation, mycocyclosin and the herquline family of natural products have attracted interest from the synthetic community for their uniquely strained macrocyclic architectures. This review describes the attempted and successful total syntheses of these natural products and provides a summary of the strategies developed in the years since their isolation.

1 Introduction

2 Biosynthesis

3 Early Studies

4 Total Synthesis of Mycocyclosin

5 Overview

6 Wood’s Total Syntheses of Herqulines B and C

7 Baran’s Total Syntheses of Herqulines B and C

8 Schindler’s Total Syntheses of Herqulines B and C

9 Conclusions
Unlocking the Synthetic Potential of Light-Excited Aryl Ketones: Applications in Direct Photochemistry and Photoredox Catalysis
Authors: Dell’Amico Luca , Mateos Javier , Cuadros Sara , Vega-Peñaloza Alberto
Published: March 2021

In this Account, we summarize the contributions of our group to the field of photochemistry and photocatalysis. Our work deals with the development of novel synthetic methods based on the exploitation of photoexcited aryl ketones. The application of new technologies, such as microfluidic photoreactors (MFPs), has enhanced the synthetic performance and scalability of several photochemical methods, e.g., Paternò–Büchi and photoenolization/Diels–Alder processes, while opening the way to unprecedented reactivity. In addition, careful mechanistic analysis of the developed methods has been instrumental in disclosing a new family of powerful organic photocatalysts that can mediate several thermodynamically extreme photoredox processes.

1 Introduction

1.1 Shining Light on Aryl Ketones: From the Historical Background to Recent Synthetic Applications

1.2 Preliminary Mechanistic Considerations

2 Synthetic Transformations Driven by Triplet State Benzophenones

3 Synthetic Transformations Driven by Triplet State o-Alkyl-Substituted Benzophenones

4 The Evolution of Aryl-Ketone-Derived Products: Applications in Organophotoredox Catalysis

5 Conclusions and Future Directions
The Multiple Rhomboid Vector Suture—Our Experience of Two Years with a Modified Suspension Approach for SMAS Plication Facelifts
Authors: Kaye Kai , Paprottka Felix , Kaestner Sonja , Gonser Phillipp
Published: March 2021

Purse string sutures in superficial musculoaponeurotic system (SMAS) plication facelifts may cause technique-related problems, such as soft tissue deformities, dimpling, and bulkiness inside and between the independent sutures. Therefore, the authors have developed a new approach named the multiple rhomboid vector (MRV) suture. A total of 103 patients (89 female, 14 male patients; median age: 57 years) received a primary rhytidectomy with the MRV SMAS plication suture in our clinic (2015–2017). Intraoperative time to perform the suture per side was recorded. Postoperative complications and dimpling and bulkiness of subcutaneous tissues were judged by three independent surgeons from 1 (= none) to 4 (= extreme) after 1 week, 1, 3, 6, and 12 months. A standardized survey, the FACE-Q questionnaire, was performed to evaluate postoperative patient satisfaction. Mean time to perform the suture was 5:14 minutes per side (minimum: 3:20 minutes, maximum: 5:53 minutes; standard deviation: 0:51 minutes). During the follow-up period, four complications were detected (two cases of temporary neurapraxia of the marginal branch of the mandibular nerve {n = 2 [1.9%]} and two cases of retroauricular hematoma {n = 2 [1.9%]}). Postoperative dimpling or bulkiness of subcutaneous tissues was judged as absent. Overall patient satisfaction rate, after the surgery was performed, was measured as “very high.” The MRV suture offers a combined horizontal and vertical suspension approach, which effectively addresses the different vectors of age-related facial soft tissue descent with complication rates equal to other surgical lifting techniques. Apart from that, it may help reduce the possibility of contour irregularities, whereby it must be noted that a thorough preoperative assessment together with the patient and surgical planning is crucial to ensure realistic expectations of the surgical outcome.
Vitamin B12 Deficiency and West Syndrome: An Uncommon but Preventable Cause of Neurological Disorder. Report on Three Cases, One of Them with Late Onset during Vitamin B12 Treatment
Authors: Pavone Piero , Sullo Federica , Falsaperla Raffaele , Greco Filippo , Crespo Agustina , Calvo Agustin , Caraballo Roberto
Published: March 2021

Vitamin B12 is a water-soluble vitamin that plays a fundamental role as an essential cofactor for two enzymes responsible for the production of succinyl-CoA and methionine. Vitamin B12 deficiency can occur in infants and may be related to the breastfeeding mother's adherence to a vegan diet or somatic diseases in the mother. It should be differentiated from inborn errors of vitamin B12 metabolism. Herein, we report the cases of three infants with West syndrome; all three were breastfed by mothers who followed a strict vegan diet. In one of the three infants, West syndrome developed during treatment with vitamin B12 and normalization of the vitamin B12 level. Early treatment and replacement therapy are worthwhile to prevent serious neurological problems and to improve the patient's clinical course.
Complication Rates after Endoscopic Transsphenoidal Surgery for ACTH-Secreting Pituitary Adenomas: A Comparative Analysis with GH and Nonfunctioning Adenomas
Authors: Aibar-Durán Juan Á. , Oladotun-Anka Michael , Asencio-Cortés Carlos , Valassi Elena , Webb Susan , Gras-Cabrerizo Juan R. , Monserrat-Gili Joan , Ribó Pere Tresserras , Muñoz-Hernández Fernando
Published: March 2021

Objectives Some complications have been more frequently reported after surgery for adrenocorticotropin hormone (ACTH)-secreting pituitary adenomas. We compared complication rates in patients with ACTH-secreting pituitary adenomas with those in patients with growth hormone secreting pituitary adenomas (growth hormone [GH] group) and nonfunctioning adenomas (nonfunctioning group).

Design A comparative three-group analysis was performed for all patients who had endoscopic transsphenoidal surgery for pituitary adenomas at our center between January 2011 and May 2019. Variables included demographics, preoperative clinical and radiological characteristics, and postoperative radiological and endocrinological outcomes. Complications were divided into four categories: endocrinological, neurosurgical, medical, and ENT (ear–nose–throat)-related complications. Univariate and multivariate statistical analysis were performed.

Results A total of 111 patients with pituitary adenomas and a mean age of 53.7 years were included (25 ACTH, 35 GH, and 51 nonfunctioning adenomas). Overall, 28 patients had microadenomas (25.2%) and 83 had macroadenomas (74.8%). Univariate statistical analysis for complications between groups showed no differences in neurosurgical and medical complications. Transient diabetes insipidus and postsurgical bacterial sinusitis were the only variables more frequently seen in the ACTH group (p = 0.01 and 0.04, respectively). Multivariate analysis for transient diabetes insipidus showed no differences between groups (p = 0.58).

Conclusion Complication rates were similar in all three adenoma groups, particularly concerning major infections, thrombotic events, postoperative cerebrospinal fluid (CSF) leak, and transient diabetes insipidus. Transient diabetes insipidus was related with adenoma size and intraoperative CSF leak. Despite postoperative bacterial sinusitis was statistically higher in the ACTH group, this data should be interpreted with caution given the low number of patients with this complication.
Contemporary Surgical Management of Juvenile Nasopharyngeal Angiofibroma
Authors: Cohen-Cohen Salomon , Scheitler Kristen M. , Choby Garret , Janus Jeffrey , Moore Eric J. , Kasperbauer Jan L. , Cloft Harry J. , Link Michael , Gompel Jamie J. Van
Published: March 2021

Objectives Juvenile nasopharyngeal angiofibromas (JNAs) are uncommon tumors with an evolving treatment paradigm. The objective of this study was to compare our prior experience reported in 2005 with our most contemporary series to compare practice improvements and the impact of expanded endonasal procedures.

Design Retrospective review comparing a contemporary 22 patients with JNA who underwent surgical management between 2005 and 2019, compared with a historical cohort of 65 patients from the same center.

Results The most common presenting symptom was epistaxis (68%). The median maximum tumor diameter was 4.4 cm. All patients underwent preoperative embolization. An endoscopic endonasal approach (EEA) was used in 18 patients (82%), compared with 9% in the series prior to 2005. Gross total resection was achieved in all patients. The median estimated blood loss was 175 and 350 mL for EEA and open (transfacial) cases, respectively. Only two patients (9%) required a blood transfusion compared with 52% on the previous series. The median follow-up was 19 months. The overall recurrence rate was 9% in this series and 24% in the previous series. No patient required radiation therapy in follow-up compared with 3% in our historical cohort.

Conclusion There have been significant changes regarding the management of patients with JNA compared with the previous Mayo Clinic experience. The EEA has become the preferred route over the transfacial approaches to treat JNA in selected patients who do not have intracranial extension. Preoperative embolization has aided in reducing the postoperative transfusion rates.
The Selection of Facelift Approach on the Basis of Midfacial Ptosis
Authors: Quatela Vito C. , Ahmedli Nigar N.
Published: March 2021

Facial aging in the midface has been described to encompass both soft tissue descent and volumetric change. Currently, there is no established and widely accepted grading system for midfacial ptosis. We propose a simplified grading system for midfacial ptosis ranging from mild to severe in terms of Grades I through III. Using this classification system, we describe an algorithm to help select the facelift approach most appropriate for each patient. The sub-superficial musculoaponeurotic system rhytidectomy, deep plane rhytidectomy, and subperiosteal midface lift techniques are described in detail. The nuances of the selection process also include a discussion on the various approaches to the orbital fat, namely a transconjunctival lower lid blepharoplasty with skin pinch versus a lower lid blepharoplasty with fat transposition, as well as the aging neck. Furthermore, we integrate the addition of postoperative adjunctive procedures which include injectables, chemical peels, and dermabrasion to address facial rejuvenation from not only a gravitational aspect but also the volumetric and textural components.
Respiratory Syncytial Virus Immunoprophylaxis with Palivizumab: 12-Year Observational Study of Usage and Outcomes in Canada
Authors: Mitchell Ian , Li Abby , Bjornson Candice L. , Lanctot Krista L. , Paes Bosco A. ,   the CARESS investigators
Published: March 2021

Objective This study aimed to evaluate palivizumab (PVZ) use, trends in indications, and outcomes of respiratory illness hospitalizations (RIH) and respiratory syncytial virus hospitalizations (RSVH).

Study Design It involves a large, Canadian prospective (2005–2017) observational multicenter study of children at high risk for RSV infection.

Results A total of 25,003 infants (56.3% male) were enrolled at 32 sites; 109,579 PVZ injections were administered. Indications included: prematurity (63.3%); “miscellaneous” (17.8%); hemodynamically significant congenital heart disease (10.5%); bronchopulmonary dysplasia/chronic lung disease (8.4%). The “miscellaneous” group increased over time (4.4% in 2005–2006 to 22.5% in 2016–2017) and included: trisomy 21, airway anomalies, pulmonary disorders, cystic fibrosis, neurological impairments, immunocompromised, cardiac aged >2 years, multiple conditions, and a residual “unclassified” group. Adherence measured by expected versus actual doses plus correct interdose interval was 64.7%. A total of 2,054 RIH occurred (6.9%); 198 (9.6%) required intubation. Three hundred thirty-seven hospitalized children were RSV-positive (overall RSVH 1.6%). Risk factors for RSVH included having siblings, attending daycare, family history of atopy, smoking exposure, and crowded household. Infants with 5 risk factors were 9.0 times (95% CI or confidence interval 4.4–18.2; p < 0.0005) more likely to have RSVH than infants without risk factors. Three adverse events occurred; none were fatal.

Conclusion Results are relevant to both clinicians and decision-makers. We confirmed the safety of PVZ. Use of PVZ increased steadily for children with miscellaneous conditions and medical complexity. Medical and social factors pose a risk for severe RIH and RSVH with accompanying burden of illness. A vaccine that protects against RSV is urgently required.

Key Points
Electroencephalogram Background Predicts Time to Full Oral Feedings in Hypoxic–Ischemic Encephalopathy
Authors: Takle Mrinmayee , Conaway Mark , Burnsed Jennifer
Published: March 2021

Objective Infants with a history of neonatal hypoxic-ischemic encephalopathy (HIE) are at risk for oral motor dysfunction. Previous studies have associated the need for gastrostomy tube at neonatal intensive care unit discharge with brainstem injury on magnetic resonance imaging (MRI). However, the factors associated with time to full oral feeds in this population have not been previously described. This study aimed to study factors associated with time to full oral feeds in this population.

Study Design This is a single-center, retrospective study that examined these factors using Cox regression.

Results A total of 150 infants who received therapeutic hypothermia from 2011 to 2017 were included in this study. The single clinical factor significantly associated with time to full oral feeds was the severity of background abnormality on electroencephalogram in the first 24 hours of age (severe vs. mild 95% confidence interval [CI]: 0.34–0.74; moderate vs. mild 95% CI: 0.19–0.45). Brainstem injury on MRI was the factor most highly associated with need for gastrostomy tube placement (p = 0.028), though the overall incidence of need for gastrostomy tube feeds in this population was low (5%).

Conclusion These findings may help clinicians counsel families on what to expect in neonates with HIE and make decisions on the need for and timing to pursue gastrostomy tube in this population.

Key Points
Two-community noisy Kuramoto model with general interaction strengths. I
Authors: Achterhof S. , Meylahn J. M.
Published: March 2021

We generalize the study of the noisy Kuramoto model, considered on a network of two interacting communities, to the case where the interaction strengths within and across communities are taken to be different in general. By developing a geometric interpretation of the self-consistency equations, we are able to separate the parameter space into ten regions in which we identify the maximum number of solutions in the steady state. Furthermore, we prove that in the steady state, only the angles 0 and π are possible between the average phases of the two communities and derive the solution boundary for the unsynchronized solution. Last, we identify the equivalence class relation in the parameter space corresponding to the symmetrically synchronized solution.
Normalized ground state solutions for Kirchhoff type systems
Authors: Yang Zuo
Published: March 2021

We consider the existence of ground state solutions for nonlinear Kirchhoff type systems in the whole space RN (2 ≤ N ≤ 4) with prescribed normalization. Two cases are studied: one is L2-supercritical and the other is mixed. In the first case, assuming that the coupling coefficient is big enough, we prove the existence of a ground state solution via minimax methods. In the second case, assuming that the coupling coefficient is sufficiently small, we show the existence of a local minimizer, which is, of course, also a ground state solution.
Characterization of micrometer-size laser beam using a vibrating wire as a miniature scanner
Authors: Arutunian S. G. , Margaryan A. V. , Harutyunyan G. S. , Lazareva E. G. , Darpasyan A. T. , Gyulamiryan D. S. , Chung M. , Kwak D.
Published: March 2021

A new method for profile measurements of small transverse size beams by means of a vibrating wire is presented. A vibrating wire resonator with a new magnetic system was developed and manufactured to ensure that the wire oscillated in a single plane. Presented evidence gives us confidence that the autogenerator creates vibrations at the natural frequency of the wire in a plane of the magnetic system, and these vibrations are sinusoidal. The system for measuring the laser beam reflected from the vibrating wire by means of a fast photodiode was upgraded. The experiments allowed the reconstruction of a fine structure of the focused beam of the semiconductor laser using only a few vibrating wire oscillations. The system presented here would eventually enable the implementation of tomographic measurements of the thin beam profile.
Compressed cylindrical shell with a rigid core and a gap
Authors: Fan Chiang Hung-Chieh , Li Hsin-Huei , Hong Tzay-Ming
Published: March 2021

Compressed cylindrical shells are common in our daily life, such as rolled-up sleeves and a retreated package of drinking straws. The deformations on these cylindrical shells with a rigid core are often random and unpredictable. In contrast, compressed beer can exhibit uniform arrays of diamonds, called the Yoshimura pattern. To elucidate the difference between these systems, we combine molecular dynamics simulations and experiments to study the deformation on a compressed cylindrical shell with a rigid core. By thoroughly exploring different material parameters, we are able to pin down the mode diagram.
Taylor–Couette flows undergoing orthogonal rotation subject to thermal stratification
Authors: Khawar Obaidullah , Baig M. F. , Sanghi Sanjeev
Published: March 2021

The present study involves direct numerical simulation of turbulent Taylor–Couette flow undergoing orthogonal rotation (gravity and rotation axis are perpendicular) subject to thermal stratification in the radial direction. The simulations were performed based on the finite-difference approach for a radius ratio (η) = 0.5 and an aspect ratio (Γ) = 2π, with Reynolds number (Re=UθDν) ranging from 1000 to 5000. For this wide gap, the role of spatially varying buoyancy forces (Ri ranging from 0 to 0.3) in flow physics has been explored using flow statistics, flow dynamics, near-wall coherent structures, and quadrant analysis. It is observed that near-wall streaks are concentrated at the outflow boundaries of Taylor vortex cells with uniform axial spacing, which decreases with the increasing Reynolds number. Heating of the outer cylinder results in more intense streaks and coherent structures in the half-circumferential domain due to unstable stratification aiding turbulence, while in the other half-domain, stable stratification mitigates turbulence. Quadrant contribution of ur′ and uθ′ reveals that on heating the outer cylinder, there is an increase in turbulence near both the walls due to the enhanced generation of Reynolds shear stresses (sweep and ejection events).
Effect of visco-plastic and shear-thickening/thinning characteristics on non-Newtonian flow through a pipe bend
Authors: Li Yue , Mu Jinlei , Xiong Chengwang , Sun Zizheng , Jin Caiyun
Published: March 2021

This study investigates the influence of the rheological parameters on the unyielded zone, pressure drop, and secondary flow pattern of non-Newtonian fluid like fresh cement mortar through a pipe bend with different curvatures. The regularized Herschel–Bulkley model is employed in the framework of lattice Boltzmann method to model the effects of the visco-plastic and shear-thickening/thinning characteristics with variations on the yielding stress σ0 and the power-law index n. The sharper curvature, higher power-law index contributes to a smaller and more asymmetric unyielded zone and even vanishes for curvature radius Rc=1D and n = 1.4, as the width and distribution of plug region are governed by the comparison between yielding stress and shear stress. The increased yielding stress and power-law index lead to an increase in the total pressure drop and additional pressure loss; however, their variations with respect to the curvature radius display an opposite trend. The intensity of the helical secondary flow in the elbow, primarily governed by the competition between the centrifugal and viscous force, is reduced to about one quarter when σ0 and n increase from 0 Pa and 0.6 to 50 Pa and 1.4.
Control of a sedimenting elliptical particle by electromagnetic forces
Authors: Qin Jianhua , Dong Guodan , Zhang Hui
Published: March 2021

In this paper, the effectiveness of electromagnetic forces on controlling the motion of a sedimenting elliptical particle is investigated using the immersed interface-lattice Boltzmann method (II-LBM) in which a signed distance function is adopted to apply the jump conditions for the II-LBM and to add external electromagnetic forces. First, mechanisms of electromagnetic control on suppressing vorticity generation based on the vorticity equation and vortex shedding based on the streamwise momentum equation are discussed. Then, systematic investigations are performed to quantify and qualify the effects of the electromagnetic control by changing the electromagnetic strength, the initial orientation angle of the elliptical particle, and the density ratio of the particle to the fluid. To demonstrate the control effect of different cases, comparisons of vorticity fields, particle trajectories, orientation angles, and energy transfers of the particles are presented. The results show that the rotational motion of the particle can be well controlled by appropriate magnitudes of electromagnetic forces. In a relatively high solid to fluid density ratio case where vortex shedding appears, the sedimentation speed can increase nearly 40% and the motion of the particle turns into a steady descending motion once an appropriate magnitude of the electromagnetic force is applied. When the magnitude of the electromagnetic force is excessive, the particle will deviate from the center of the side walls. In addition, the controlling approach is shown to be robust for various initial orientation angles and solid to fluid density ratios.
Chirped ordered pulses for ultra-broadband ESR spectroscopy
Authors: Verstraete Jean-Baptiste , Myers William K. , Foroozandeh Mohammadali
Published: March 2021

Recently, applications of swept-frequency pulses proved to be a useful approach to circumvent the problem of limited excitation bandwidth in pulsed ESR posed by conventional pulses. Here, we present a chirped excitation sequence, CHirped ORdered pulses for Ultra-broadband Spectroscopy (CHORUS), for ultra-broadband ESR spectroscopy. It will be demonstrated that the application of this sequence can address the problems of excitation non-uniformity and sensitivity to instrumental instabilities to a greater extent compared to the current state of the art. This sequence is highly promising for finding applications beyond single excitation in many ESR experiments. Theoretical and experimental results for the proposed method are presented along with calibration strategies for experimental implementation.
Challenges for machine learning force fields in reproducing potential energy surfaces of flexible molecules
Authors: Vassilev-Galindo Valentin , Fonseca Gregory , Poltavsky Igor , Tkatchenko Alexandre
Published: March 2021

Dynamics of flexible molecules are often determined by an interplay between local chemical bond fluctuations and conformational changes driven by long-range electrostatics and van der Waals interactions. This interplay between interactions yields complex potential-energy surfaces (PESs) with multiple minima and transition paths between them. In this work, we assess the performance of the state-of-the-art Machine Learning (ML) models, namely, sGDML, SchNet, Gaussian Approximation Potentials/Smooth Overlap of Atomic Positions (GAPs/SOAPs), and Behler–Parrinello neural networks, for reproducing such PESs, while using limited amounts of reference data. As a benchmark, we use the cis to trans thermal relaxation in an azobenzene molecule, where at least three different transition mechanisms should be considered. Although GAP/SOAP, SchNet, and sGDML models can globally achieve a chemical accuracy of 1 kcal mol−1 with fewer than 1000 training points, predictions greatly depend on the ML method used and on the local region of the PES being sampled. Within a given ML method, large differences can be found between predictions of close-to-equilibrium and transition regions, as well as for different transition mechanisms. We identify key challenges that the ML models face mainly due to the intrinsic limitations of commonly used atom-based descriptors. All in all, our results suggest switching from learning the entire PES within a single model to using multiple local models with optimized descriptors, training sets, and architectures for different parts of the complex PES.
A field programmable gate array based synchronization mechanism of analog and digital local oscillators in bandwidth-interleaved data acquisition systems
Authors: Zhao Yu , Ye Peng , Yang Kuojun , Meng Jie , Lei Maolin
Published: March 2021

This paper studies the synchronization between the analog and digital local oscillators (LOs) in bandwidth-interleaved (BI) data acquisition systems (DAQS). It gives a detailed analysis of the random synchronization phase difference between the analog and digital LOs in the BI-DAQS among different acquisition frames. Exploiting the synchrony relation between the analog LO and sampling clock of the BI-DAQS, the synchronization between analog and digital LOs, where the digital LO is generated in the sampling clock domain, in each acquisition frame is realized in the Field Programmable Gate Array (FPGA). A BI-DAQS platform with a 5.5 GHz bandwidth and 20 Gs/s sampling rate is built to validate the proposed synchronization mechanism. Experimental results in the platform show the efficacy of the proposed synchronization mechanism, which consumes only a small amount of the flip-flops and look-up tables in the FPGA without any additional hardware assistance.
Combined multiplet theory and experiment for the Fe 2p and 3p XPS of FeO and Fe2O3
Authors: Bagus Paul S. , Nelin Connie J. , Brundle C. R. , Crist B. Vincent , Lahiri N. , Rosso Kevin M.
Published: March 2021

The Al K alpha, 1486.6 eV, based x-ray photoelectron spectroscopy (XPS) of Fe 2p and Fe 3p for Fe(III) in Fe2O3 and Fe(II) in FeO is compared with theoretical predictions based on ab initio wavefunctions that accurately treat the final, core-hole, multiplets. The principal objectives of this comparison are to understand the multiplet structure and to evaluate the use of both the 2p and 3p spectra in determining oxidation states. In order to properly interpret the features of these spectra and to use the XPS to provide atomistic insights as well as atomic composition, it is necessary to understand the origin of the multiplet energies and intensities. The theoretical treatment takes into account the ligand field and spin–orbit splittings, the covalent mixing of ligand and Fe 3d orbitals, and the angular momentum coupling of the open shell electrons. These effects lead to the distribution of XPS intensity into a large number of final, ionic, states that are only partly resolved with energies spread over a wide range of binding energies. For this reason, it is necessary to record the Fe 2p and 3p XPS spectra over a wide energy range, which includes all the multiplets in the theoretical treatment as well as additional shake satellites. We also evaluate the effects of differing assumptions concerning the extrinsic background subtraction, to make sure our experimental spectrum may be fairly compared to the theory. We conclude that the Fe 3p XPS provides an additional means for distinguishing Fe(III) and Fe(II) oxidation states beyond just using the Fe 2p spectrum. In particular, with the use of the Fe 3p XPS, the depth of the material probed is about 1.5 times greater than for the Fe 2p XPS. In addition, a new type of atomic many-body effect that involves excitations into orbitals that have Fe f,ℓ = 3, symmetry has been shown to be important for the Fe 3p XPS.
A beyond Born–Oppenheimer treatment of C6H6+ radical cation for diabatic surfaces: Photoelectron spectra of its neutral analog using time-dependent discrete variable representation
Authors: Mukherjee Soumya , Ravi Satyam , Naskar Koushik , Sardar Subhankar , Adhikari Satrajit
Published: March 2021

We employ theoretically “exact” and numerically “accurate” Beyond Born–Oppenheimer (BBO) treatment to construct diabatic potential energy surfaces (PESs) of the benzene radical cation (C6H6+) for the first time and explore the workability of the time-dependent discrete variable representation (TDDVR) method for carrying out dynamical calculations to evaluate the photoelectron (PE) spectra of its neutral analog. Ab initio adiabatic PESs and nonadiabatic coupling terms are computed over a series of pairwise normal modes, which exhibit rich nonadiabatic interactions starting from Jahn–Teller interactions and accidental conical intersections/seams to pseudo Jahn–Teller couplings. Once the electronic structure calculation is completed on the low-lying five doublet electronic states (X̃2E1g, B̃2E2g, and C̃2A2u) of the cationic species, diabatization is carried out employing the adiabatic-to-diabatic transformation (ADT) equations for the five-state sub-Hilbert space to compute highly accurate ADT angles, and thereby, single-valued, smooth, symmetric, and continuous diabatic PESs and couplings are constructed. Subsequently, such surface matrices are used to perform multi-state multi-mode nuclear dynamics for simulating PE spectra of benzene. Our theoretical findings clearly depict that the spectra for X̃2E1g and B̃2E2g−C̃2A2u states obtained from BBO treatment and TDDVR dynamics exhibit reasonably good agreement with the experimental results as well as with the findings of other theoretical approaches.
High frame rate emission spectroscopy for ablation tests in plasma wind tunnel
Authors: Ravichandran Ranjith , Leiser David , Zander Fabian , Löhle Stefan , Matlovič Pavol , Tóth Juraj , Ferrière Ludovic
Published: March 2021

This article describes a novel high frame rate emission spectroscopy setup developed for measurements in high enthalpy flow fields. The optical setup and the associated hardware arrangements are described in detail followed by test case data to demonstrate the capability of recording spectral images at 1 kHz frame rate. The new system is based on a classical Czerny–Turner spectrograph but with a particular setup for high frame rate detection using a Generation II intensifier coupled with a high-speed camera. The high frame rate spectral images acquired enable, for the first time, investigation of the spatial distribution and temporal tracking and evolution of molten droplets of an ablating sample. In this paper, an example is shown from ablating meteorite samples tested in a high enthalpy plasma flow field corresponding to a flight scenario at an altitude of 80 km. This new instrumental configuration allows emission spectroscopic analysis of transient phenomena simulated in the high enthalpy ground test facilities with kHz resolution. The particular feature of this system is the ability to measure very faint spectral lines at high temporal and spatial resolution.
Enhanced performance of antimony selenide thin film solar cell using PbI2 as a dopant
Authors: Li Wen-Hui , Li Meng , Hu Yu-Jie , Cheng Chuan-Hui , Kan Ze-Ming , Yu Dongqi , Leng Jing , Jin Shengye , Cong Shulin
Published: March 2021

Antimony selenide (Sb2Se3) is an emerging photovoltaic material. We demonstrate that PbI2 is an effective p-type dopant for Sb2Se3. The Sb2Se3 film was doped by PbI2 by thermal diffusion. Both the hole concentration and conductivity are dramatically increased by doping. We fabricated the Sb2Se3 solar cell using C60 as an electron transport layer by vacuum thermal evaporation. By PbI2 doping, the open-circuit voltage (Voc) is increased from 0.32 to 0.38 V, and the power conversion efficiency is improved from 2.87% to 4.43%. This work provides an effective p-type dopant for Sb2Se3.
Diameter and charge of the first droplet emitted in electrospray
Authors: Rubio M. , Sadek S. H. , Gañán-Calvo A. M. , Montanero J. M.
Published: March 2021

The first droplet produced by a low-conductivity pendant/sessile droplet subject to a strong electric field is particularly important at the fundamental level because, in contrast to steady electrospray phenomena, its ejection entails complex charge relaxation and electrokinetic processes. Besides, it is technologically relevant because of its very small diameter and large electric charge per unit volume. In this work, we present an experimental technique to measure with unprecedented accuracy the diameter of the droplet and to determine for the first time its electric charge. We discuss both the advantages of our technique over possible alternatives and the limitations of the method. The proposed method is applied to two alcohols with electrical conductivities of the order of a few μS/m. The high sensitivity of our experimental technique allows us to determine the influence of both the magnitude and the polarity of the applied voltage on the size and charge of the ejected droplet. The electric charge of the first-emitted droplet lies in the interval 0.51≲q/qR≲0.66 (qR is the Rayleigh limit of charge) for the two liquids analyzed. These experimental values are slightly larger than those obtained from theoretical predictions. The value of q/qR for the first droplet is very relevant because it can be regarded as an upper bound of those of the droplets subsequently emitted in the cone-jet mode of electrospray.
A convenient method for the strength evaluation of cracked functionally graded material plates under different loadings
Authors: Li R. , Yang M. , Bai S. , Liang B.
Published: March 2021

As functionally graded material (FGM) plates are widely used in engineering and industrial fields, the fracture strength evaluation of the cracked FGM plate becomes increasingly important. However, due to the gradation of the mechanical properties of FGM, few analytical methods are simple and available. In this paper, a convenient strength evaluation method for the cracked FGM plates under different loadings is proposed in terms of the stress intensity factor (SIF) appearing at a crack tip. This method uses the stable relationship of singular stress fields between FGM and homogeneous material to greatly simplify the complex SIF calculation process of the cracked FGM plate. The results show that the SIFs of FGM plates under tension, bending, and three-point bending (experiment) can be obtained conveniently and accurately by using two simple formulas, and the trends of critical SIF can also be investigated directly even if the SIF solution of the homogeneous plate (reference problem) is unknown. Comparisons with the published theoretical and experimental results indicated that the present method is reliable, precise, and practical to determine SIF and perform strength prediction.
An adaptive binary friction model for multicomponent gas transport in tight porous media
Authors: Ren Wenxi , Duan Youjing , Guo Jianchun , Wang Tianyu
Published: March 2021

A new multicomponent gas transport model called the adaptive binary friction model (ABFM) was developed. The merit of the ABFM lies in the rigorous treatment of viscous slip and diffusion slip. The ABFM uses the general slip boundary condition to characterize viscous slip and thus is applicable in multiple flow regimes. The ABFM uses the Kramers and Kistemaker model to describe diffusion slip and thus satisfies Graham's law in a natural way. The ABFM also eliminates the restrictive assumptions made in previous models, such as uniform flow. Published experimental data on multicomponent gas transport were used to test the ABFM. The agreement of the ABFM results with the experimental data is good. Moreover, the ABFM can predict the transport of different gas mixtures under various conditions based on the determined pore structure parameters. Considering its versatility, the ABFM is anticipated to be useful in heterogeneous catalysis, membrane transport, etc.
Fast modulating electron cyclotron emission (FMECE) diagnostic for tokamaks
Authors: Houshmandyar Saeid , Xie Ruifeng , Austin Max E. , Rowan William L. , Zhao Hailin
Published: March 2021

Utilizing variable-frequency channels, e.g., yttrium iron garnet (YIG) bandpass filters, in the intermediate frequency (IF) section of an electron cyclotron emission (ECE) radiometer facilitates flexibility in the volume viewed by the ECE channels as well as high resolution electron temperature and temperature fluctuation measurements in tokamaks. Fast modulating electron cyclotron emission (FMECE), a stand-alone IF section with eight channels, is a novel application of YIG filters for real-time electron temperature gradient and gradient scale length measurements. Key to FMECE is a simultaneous input/output data acquisition unit, as well as a modified type of YIG filters, which is capable of fast switching of their center (set) frequencies with a frequency slew rate of 600 µs/GHz. A new FMECE has been implemented and tested on the DIII-D tokamak, demonstrating its capability in real-time gradient measurements. The data presented here shows that FMECE can identify flattening in the electron temperature profile; the latter can be used as a sensor for real time monitoring and control of plasma instabilities. Implementation and application are planned for the EAST tokamak.
Fast production of microwave component prototypes by additive manufacturing and copper coating
Authors: Korsholm S. B. , Leipold F. , Madsen R. B. , Gutierrez H. , Jensen T. , Jessen M. , Larsen A. W. , Rasmussen J. , Salewski M.
Published: March 2021

We present a novel method for efficient production of prototypes of microwave components by fused depositing modeling, also known as 3D plastic printing, and vapor deposition coating of a 1 μm copper layer. We demonstrate that the properties of the components follow the predicted performance for low power microwave propagation. The production method offers new opportunities for cheap and efficient production of mock-ups and prototypes of advanced-geometry components for tests with low-power microwaves.
Enhanced field electron emission properties of graphite nanoplatelet paste emitters using graphite binder and graphite nanoparticle filler
Authors: Lee Sang Heon , Han Jun Soo , Go Hanbin , Lee Cheol Jin
Published: March 2021

Graphite nanoplatelet (GNP) paste field emitters fabricated using all-carbon-based materials, such as GNPs, graphite nanoparticles, graphite binders, and a graphite rod substrate have been demonstrated. The GNP field emitters on the graphite rod substrate showed an emission current density of 84.3 mA/cm2 and good emission stability with a degradation rate of less than 10%, indicating higher emission performance than other GNP field emitters. The enhanced field emission performance of the GNP field emitter is attributed to a low work function barrier between carbon materials, low contact resistance between GNPs and the graphite rod substrate, and good GNP paste bulk electrical conductivity. The new approach to fabricate GNP field emitters using all-carbon-based materials can be useful for various field emission devices.
Evidence for a thermally driven charge-density-wave transition in 1T-TaS2 thin-film devices: Prospects for GHz switching speed
Authors: Mohammadzadeh Amirmahdi , Baraghani Saba , Yin Shenchu , Kargar Fariborz , Bird Jonathan P. , Balandin Alexander A.
Published: March 2021

We report on the room-temperature switching of 1T-TaS2 thin-film charge-density-wave devices, using nanosecond-duration electrical pulsing to construct their time-resolved current–voltage characteristics. The switching action is based upon the nearly commensurate to incommensurate charge-density-wave phase transition in this material, which has a characteristic temperature of 350 K at thermal equilibrium. For sufficiently short pulses, with rise times in the nanosecond range, self-heating of the devices is suppressed, and their current–voltage characteristics are weakly nonlinear and free of hysteresis. This changes as the pulse duration is increased to ∼200 ns, where the current develops pronounced hysteresis that evolves nonmonotonically with the pulse duration. By combining the results of our experiments with a numerical analysis of transient heat diffusion in these devices, we clearly reveal the thermal origins of their switching. In spite of this thermal character, our modeling suggests that suitable reduction of the size of these devices should allow their operation at GHz frequencies.