bluuebunny/crossref_metadata_2025 huggingface dataset:
A high‐gain IΓ‐source hybrid single‐phase multilevel inverter for photovoltaic application
Authors: Ghasimi Sako , Lahooti Eshkevari Alireza , Mosallanejad Ali
Published: December 2020

Impedance‐based step‐up converters are widely developed for photovoltaic applications due to providing single‐stage conversion, high‐efficiency, low voltage and current stresses, and high boost‐factor. An improved Γ‐source (IΓ‐source) single‐phase hybrid multilevel inverter is proposed. This structure has a better voltage gain characteristic, high‐efficiency, multilevel output voltage, low output current total harmonic distortion (THD), and continuous input current. It is extensible for attaining higher voltage levels. Furthermore, higher non‐shoot‐through modulation indexes are obtainable by this topology in comparison with previous works due to performing higher gains in lower shoot‐through duty cycles. Also, the output harmonics are reduced because of applying lower shoot‐through duty cycles. This article demonstrates the operating principle of this hybrid multilevel inverter in detail. Simulation and experimental results are exhibited to evaluate the performance of this converter. Results confirm the proposed IΓ‐source hybrid multilevel inverter, its operating principle, and the modulation strategy.
Design and control of battery charger for electric vehicles using modular multilevel converters
Authors: Quraan Mahran , Abu‐Khaizaran Muhammad , Sa'ed Jaser , Hashlamoun Wael , Tricoli Pietro
Published: December 2020

Double‐star modular multilevel converters with embedded battery cells are a ground breaking technology for the power converter of electric vehicles. In this topology, the battery cells are connected in series via half bridge DC–DC buck converter and can be independently discharged and recharged. This paper proposes a novel control system for this converter topology that can charge the battery cells from the grid at unity power factor and instantaneously balance them in terms of their state of charges without affecting the grid voltages and currents. The grid current controller is designed and implemented in the stationary reference frame using a proportional‐resonant controller, while the state of charge balancing algorithm is designed using sorting algorithm and circulating current control. The simulation and experimental results have demonstrated that the proposed control strategy can effectively charge the battery cells with a negligible distortion of the grid current and can ensure the balance of cells during the recharge without affecting the grid current.
Design, analysis, and implementation of a new high‐gain P‐type step‐up dc/dc converter with continuous input current and common ground
Authors: Lahooti Eshkevari Alireza , Mosallanejad Ali , Sepasian Mohammad Sadegh
Published: December 2020

Step‐up converters are increasingly developed for renewable energy and storage systems in order to raise the output voltage of those resources to higher voltage levels. Conventional step‐up structures, such as P‐type boost converter, provide low voltage gain, and they must be cascaded with the same modules to produce higher boost factors. This conversion method reduces overall efficiency. Affording higher gains with lower duty cycles and single‐stage conversion increase efficiency. This paper proposes a new step‐up P‐type dc/dc converter with high voltage gain even with lower duty ratios. Additionally, it has continuous input current, high efficiency, and common ground between the input and the output. Detailed analysis is presented, and the performance of this new topology is compared with other high‐gain step‐up converters. Simulations and experiments evaluate the achievements of this topology. Results prove the proposed structure.
Performance of a coupled inductor for interleaved buck converter with improved step‐down conversion ratio
Authors: Biswas Mriganka , Majhi Somanath , Nemade Harshal
Published: December 2020

This paper proposes a dual‐winding coupled inductor (DWCI) based interleaved buck converter (IBC) with improved step‐down conversion ratio to improve the ripple in inductor currents and to achieve lower value of the output filter capacitor. The proposed IBC achieves a high step‐down conversion ratio by using a switch‐capacitor cell. In the continuous conduction mode (CCM), the systematic analysis of ripple current in the windings of DWCI shows the improvement of ripple in inductor current compared to the existing IBCs. Further, the coupling factor of the DWCI reduces the requirement of the minimum value of the output filter capacitor. The operation principle and boundary load condition of the proposed IBC with DWCI are analysed. Furthermore, the small‐signal modelling of the proposed IBC with DWCI is investigated. In the voltage‐mode control framework, a PI‐controller is designed to investigate the sensitivity to the load parameter variation and the performance of the reference output voltage. The proposed converter with DWCI is implemented and experimental results are provided.
A single‐stage AC‐AC solid‐state transformer with ZVS operation
Authors: Wang Hui , Xu Ming , Zhang Yichun , Sun Yao , Zhang Guanguan , Blaabjerg Frede , Liang Xiao , Liu Yonglu , Feng Jianghua
Published: December 2020

Solid‐state transformer (SST) is an attractive concept, which provides galvanic isolation and voltage scaling by means of a medium‐frequency link. In this paper, a single‐stage alternative current (AC)‐AC SST solution without bulky energy storage elements is presented. The front‐end rectifier (FER) and rear‐end inverter (REI) of the SST works at line‐frequency, while the intermediate LLC series resonant converter (SRC) fulfils the tasks of galvanic isolating and regulating the output voltage. To achieve high efficiency and bidirectional power flow capability of the SST, the zero voltage switching (ZVS) condition of the LLC SRC is comprehensively analysed, and the parameters design method of the LLC SRC is developed, where the resonant currents are constructed by applying the same gating signals to the primary‐side and secondary‐side bridges and the dead‐time is properly selected. Consequently, the presented SST has the merits of high conversion efficiency, naturally bidirectional power flow capability, potentially high power density and high reliability. The experimental results on a 1.5 kW SST prototype show that sinusoidal input and output current, ZVS operation over the full load range are achieved, and the peak efficiency is 97.63%. The experimental results verify the functionality and effectiveness of the developed methods.
Improved and accurate low‐frequency average modelling and control of a conventional power factor correction boost converter in continuous conduction mode
Authors: Pereira Dênis de C. , Rosa Bruno T. , Soares Guilherme M. , Almeida Pedro S. , Tofoli Fernando L. , Braga Henrique A. C.
Published: December 2020

When dealing with power factor correction (PFC) rectifiers that require the use of high filter capacitances, conventional small‐signal modelling techniques are not capable of reproducing the converter behaviour accurately owing to the impact of the low‐frequency dynamics on the system. In this context, this work presents an improved modelling technique applied to a conventional PFC boost converter operating in continuous conduction mode (CCM). The proposed approach leads to a more accurate analysis than the traditional modelling developed for dc–dc converters, which is often extended to rectifiers. It consists of a fast and concise solution for the implementation of several PFC techniques from the derived transfer functions. The introduced method is described aiming at the development of a boost‐based PFC stage using the well‐known one‐cycle control technique (OCC). Simulation and experimental results are presented and thoroughly discussed to validate the theoretical assumptions.
Photovoltaic‐battery powered grid connected system using multi‐structural adaptive circular noise estimation control
Authors: Singh Yashi , Singh Bhim , Mishra Sukumar
Published: December 2020

The intermittent nature of renewable energy sources results in an interruptible and inadequate power. The integration of the battery energy storage to renewable energy sources provides reliable and continuous power to the loads. Further, the high penetration of renewable energy sources raises the power quality problems in the grid. This work deals with performance improvement of PV‐battery energy storage based energy conversion system achieved through implementing a multi‐structural adaptive circular noise estimation control for its grid connected mode. The control is developed for the grid side voltage source converter, which provides the power quality improvement and automated transition from grid connected mode to standalone mode or vice‐versa. It provides multi‐functional features such as harmonics extraction, DC offset elimination, and power quality improvement in PV‐battery energy storage based energy conversion system even at nonlinear loading condition in grid connected mode. In standalone mode, the amplitude and waveform of load voltage are controlled sinusoidal by the voltage control. Performance of PV‐battery energy storage based energy conversion system is studied to validate the acceptability of these controls according to the IEEE‐519 standard.
A novel gate driver for Si/SiC hybrid switch for multi‐objective optimization
Authors: Li Zongjian , Dai Xiaoping , Jiang Xi , Qi Fang , Liu Yang , Ke Pan , Wang Yongzhi , Wang Jun
Published: December 2020

A novel gate driver with simple functional and structural integration is proposed here, which splits the input gate signal and outputs two separate signals with a dedicated delay time to drive the two constitutional switches, aiming at the cost‐effectiveness and power loss reduction of the Si/SiC hybrid switch. The dependency of the hybrid switch's thermal and efficiency performance on the parameters of the gate driver are theoretically and experimentally investigated in a 9 kW 20 kHz Si/SiC hybrid switch based boost converter. A novel load current dependent gate control strategy is proposed to be implemented in the proposed gate driver to achieve the high conversion efficiency under light to medium load condition and balanced junction temperature between the two internal devices under heavy load conditions. The experimental results based on a 20 kHz boost converter show that the Si/SiC hybrid switch with the novel gate driver and optimal current dependent control strategy offers a 163% and 10% rise in power handling capability, respectively, compared to that using the all‐IGBT device and all‐SiC MOSFET device, and yet a considerably lower device cost.
A new magnetron driving method using a phase‐shifted active clamp forward converter for sulfur plasma tube applications
Authors: Nasiri Abolfazl , Banaei Mohamad Reza
Published: December 2020

This paper presents a new method for driving the magnetron for a sulfur plasma tube using the two‐switch forward converter structure with a phase‐shifting active clamp (1000±40 W, 285 mA, 4 kV). Depending on the output voltage level required, the magnetron driver circuit is boosted and insulated and also has high gain. The use of the two‐switch forward converter reduces the transistor voltage stress. In addition, applying the clamp structure balances the magnetization current. Besides, by controlling the phase shift of the clamp transistor, while maintaining the magnetic current balance of the power transformer, the duty cycle of the main transistors can be increased. This allows more voltage level transfer to the secondary winding of the transformer. Therefore, with a fixed transformer core, more voltage transmission is possible in comparison with a conventional forward converter.

Moreover, using the PFC converter improves the power factor and stabilizes the DC‐link voltage. The magnetron driver circuit provides a maximum power of 1 kW with an average power of 125–250 W by adjusting the converter's active time under minimum loss conditions. The magnetron driver circuit provided is validated by the simulation and experimental results.
An improved permanent‐magnet synchronous machine sensorless drive based on the fuzzy‐PI phase‐locked loop and the adjustable boundary‐layer FOSMO
Authors: Ye Shuaichen , Yao Xiaoxian
Published: December 2020

This study proposes a variable boundary‐layer full‐order sliding‐mode observer (FOSMO) with a fuzzy proportional plus integral (PI) phase‐locked loop (PLL) for the sensorless control of a permanent‐magnet synchronous machine (PMSM). The sigmoid switching function‐based FOSMO, which includes feedback speed information, is presented and considered as the conventional method. To address the contradiction between the convergence performance and the chatter‐reduction ability of the sliding‐mode control, a fuzzy logic controller (FLC) is introduced to adjust the boundary‐layer thickness according to the estimation error. Furthermore, a real‐time parameter tuning module is integrated into the PI regulator of the conventional PLL to adjust its noise bandwidth. Hence, adverse effects of disturbance and external noise, especially under transient operations, can be eliminated. An overall PMSM sensorless field‐oriented control scheme incorporating the proposed method is designed, and the corresponding experimental platform is constructed. Several groups of comparative experiments reveal that system chatters are largely reduced using the proposed method under both of the high‐ and low‐speed running conditions and the dynamic anti‐interference performance can also be significantly improved under load and speed disturbances. Therefore, the feasibility and effectiveness of the proposed variable boundary‐layer FOSMO + fuzzy‐PI PLL method are validated.
Sliding mode controller for extraction and supply of photovoltaic power using switched series parallel sources reduced switch count multilevel inverter
Authors: Gowd G. Eshwar , Sreenivasarao Dharmavarapu , Vemuganti Hari Priya
Published: December 2020

The reduced switch count multilevel inverter (RSC‐MLI) is the latest trend in power electronic converters due to reduction in the switch count and cost. However, a large number of RSC‐MLIs have not yet reached to the application level because of the absence of modularity, unequal load‐sharing among DC sources and the absence of switching redundancies. On the other hand, multilevel dc‐link (MLDCL) and switched series parallel sources (SSPS) RSC‐MLI topologies are modular structures with adequate switching redundancies and can be an alternative to conventional cascaded H‐bridge (CHB) for grid‐connected photovoltaic (PV) systems. Therefore, in this paper, a comprehensive comparison among CHB, MLDCL and SSPS topologies has been carried out for grid connected PV application. Based on the outcome, an asymmetric 11 kV three‐phase 11‐level SSPS RSC‐MLI is chosen. In this combination, a common non‐linear sliding mode controller (SMC) is developed for generating maximum PV power from asymmetric single‐stage PV sources by linearizing the non‐linear PV system using an effective feedback linearization scheme. The PV power extracted is delivered to the grid by controlling SSPS RSC‐MLI using another SMC. The performance of the system under wide variations of insolation levels is verified in MATLAB and further validated in hardware‐in‐the‐loop OPAL‐RT controller.
Association of Antimicrobial Susceptibility and Treatment Outcome in Acne Vulgaris Patients: A Pilot Study
Authors: Yadav Ashvini K. , Bhooshan Suneel , Johnson Allen , Asati Dinesh P. , Nema Shashwati , Biswas Debasis
Published: December 2020

Purpose Cutibacterium acnes (C. acnes) is an emerging pathogen that is highly resistant to antibiotics and is capable of causing persistent infections that are difficult to treat.

Methods & Materials Acne vulgaris patients visiting dermatology OPD of our tertiary care hospital during the study period of 2 months were recruited. Skin swabs were collected, and the sample was processed on 5% sheep-blood agar for anaerobic culture by the GasPak method. Isolates were identified by the standard biochemical test. Antimicrobial susceptibility testing was performed for clinically relevant antibiotics by the E-strip method. The clinical response was evaluated after 1-month follow-up to the prescribed antibiotics.

Results Minocycline, doxycycline, ceftriaxone, and tetracycline were the most effective antibiotics. Nonsusceptibility to clindamycin and erythromycin were observed in 11.9% and 31% isolates, respectively, with 9.5% isolates being nonsusceptible to both. For none of the antibiotics we found significant difference in the proportion of susceptible and nonsusceptible isolates between mild, moderate, and severe grades of acne vulgaris. For none of the antibiotic regimens, significant difference was observed between nonresponders and responders. Twenty-seven patients received clindamycin and among them 16 of 19 responders and 6 of 8 nonresponders yielded growth of clindamycin-susceptible isolates (p = 0.57).

Conclusion We observed significant prevalence of resistant strains of C. acnes among patients with acne vulgaris. No association was observed between in vitro susceptibility results and treatment outcome.
Challenging Presentations of Seven Cases of Gastrointestinal Basidiobolomycosis in Sudan: Clinical Features, Histology, Imaging, and Recommendations
Authors: Mohammed Sawsan A. , Abdelsatir Azza A. , Abdellatif Mohamed , Suliman Suliman Hussein , Elbasheer Omer Mohammed Ibrahim , Abdalla Awad Rhmattalla , Widattalla Abubakr H. , Tamimeldar Safeya Ahmed M. , Amin Abdelgadir A. , Ahmed Mohamed H. , Abdelsatir Ali Mohammed
Published: December 2020

Abstracts

Basidiobolomycosis is a fungal infection caused by Basidiobolus ranarum which affects the skin and subcutaneous tissue and rarely the gastrointestinal tract. We report seven cases of gastrointestinal basidiobolomycosis with interesting clinical, radiological, and histological presentations. To our knowledge, this is the first case series of abdominal basidiobolomycosis to be reported from Sudan.
Hepatobiliary Scintigraphy to Evaluate Biliary Complications of Pediatric Liver Transplantation: An Account of an Experience
Authors: Gutierrez-Villamil Claudia , Velez-Gutierrez Camila , Arevalo-Leal Sinay , Rivera-Baquero Jairo , Marín-Oyaga Víctor
Published: December 2020

Introduction Hepatobiliary scintigraphy (HS) is a noninvasive imaging technique whose use in the follow-up of liver transplantation has not been duly documented. The main objective of this study is to describe the experience of using this technique to detect biliary complications in pediatric patients following liver transplantation.

Materials and Methods A retrospective, observational, and descriptive study involving 86 pediatric patients who had undergone liver transplantation between 2013 and 2018. Of the 86, 31 had undergone at least one HS during their postoperative period.

Results A total of 45 studies were performed on 31 patients (36% of the patients undergoing transplantation during that time period). Patient ages ranged from 5 to 204 months (mean = 50 months). A total of 22 transplants (71%) were from living donors and 9 (29%) were from cadaveric donors. Of the 45 studies, 22 were positive for biliary complications, and all of them had an impact on clinical decision-making. The remaining 23 studies were negative. Of these 23, 19 continued under medical treatment and the other four underwent an additional intervention with positive surgical outcomes in all cases. All scintigraphy studies revealed hepatocellular dysfunction and cholestasis.

Conclusion The HS is a useful, noninvasive, and diagnostic procedure for the early diagnosis of biliary complications that may impact the evolution of disease in liver transplant patients. It allows the treating physician to make a more informed decision regarding expectant management, surgical management, or a less invasive course of action for transplantation complications.
Benign Ovarian Cysts with Raised CA-125 Levels: Do We Need to Evaluate the Fallopian Tubes?
Authors: Sharma Devesh , Vinocha Anjali
Published: December 2020

Objectives It is not clearly known whether some benign (simple) ovarian cysts can convert into cancerous cysts. Size of cyst and wall abnormalities do predict the potentiality of malignancy. Not many studies have been done to explore the malignant potential of large-sized (> 5 cm) unilocular ovarian cysts without wall abnormalities. This study evaluated the correlation between ultrasonographic size of benign ovarian cysts and carbohydrate antigen 125 (CA-125) levels.

Methodology Sixty (60) premenopausal women were recruited for the study preoperatively, based on transvaginal ultrasound (TVUS) findings present in the case record sheet received along with the CA-125 sample in the biochemistry laboratories. Those cases with elevated CA-125 levels were selected, where patients had unilocular ovarian cysts without wall abnormalities. CA-125 was done using ECLIA methodology (Cobas e411, Germany). Statistical correlation was calculated between the ovarian cyst size and CA-125 levels using Spearman’s Rho coefficient.

Results Mean age group of subjects were 29.7 ± 7.3 years and mean value of CA-125 (normal < 35 IU/mL) was found to be increased: 118.0 ± 147.1 IU/mL so was the mean diameter of cysts (cut off ≤ 5 cm): 48.6 ± 59.8 cm. No correlation was found between CA-125 levels and volume of ovarian cyst (r = 0.005, p = 0.680) for all subjects.

Conclusions The lack of correlation between size of ovarian cysts and CA-125 levels provides a hint that the ovarian cyst epithelium does not directly express CA-125 and it may come from sites like the fallopian tube. Thus, raised level of CA-125 in benign ovarian cyst should be followed-up more closely, demanding assessment of fallopian tubes for early diagnosis of ovarian cancer. Also, algorithms can be explored to include size of ovarian cyst and CA 125 levels to predict ovarian cancer.
Potential Role of Proteasome Accessory Factor-C in Resistance against Second Line Drugs in Mycobacteria
Authors: Narain Apoorva , Dubey Rikesh K. , Verma Ajay Kumar , Srivastava Anand , Kant Surya
Published: December 2020

Objectives Mycobacterium tuberculosis (MTB), the causative agent of tuberculosis (TB), can survive inside the host granuloma courtesy the various extrinsic and intrinsic factors involved. Continuous use or misuse of the anti TB drugs over the years has led to the development of resistance in MTB against antibiotics. Drug-resistant TB in particular has been a menace since treating it requires exposing the patient to drugs for a prolonged period of time. Multidrug-resistant (MDR) and extensively drug resistant TB cases have increased over the years mostly due to the exposure of MTB to suboptimal levels of drug. Proteasomes provide MTB its pathogenicity and hence helps it to survive inside the host even in the presence of drugs.

Materials and Methods The recombinantly expressed proteasome accessory factor-C (PafC) protein was purified via Ni-NTA affinity chromatography and overexpressed in the nonpathogenic strain of mycobacteria (Mycobacterium smegmatis) for the comparative analysis of minimum inhibitory concentrations of antimycobacterial drugs. The bacteria were subjected to various stress conditions. Secretory nature of PafC was analyzed by probing the purified protein against patient sera. Quantitative mRNA analysis of pafC, lexA, and recA was performed to check for their level under fluoroquinolone (FQ) presence. The data were validated in clinical samples of pulmonary TB patients.

Results pafC, that forms one part of paf operon, is involved in providing MTB its resistance against FQs. Through a series of experiments, we established the fact that PafC is upregulated in mycobacteria upon exposure to FQs and it leads to the increased intracellular survival of mycobacteria under the stresses generated by FQs. The study also refers to the correlation of pafC to deoxyribonucleic acid (DNA) damage repair enzymes lexA and recA at transcriptional level. The results obtained in vitro corroborated when the pulmonary TB patients’ samples were subjected to the same molecular analysis.

Statistical Analysis All experiments were conducted at least in triplicate. p-Value of <0.05 was considered to be statistically significant

Conclusion PafC plays a significant role in providing resistance to mycobacteria against FQ class of drugs by increasing its intracellular survival through increased drug efflux and getting involved with DNA damage repair machinery.
Multibranched gold nanoparticles coated with serum proteins fit for photothermal tumor ablation
Authors: Carreón-Álvarez Clara , Sánchez-García José Luis , Sanabria-Ayala Víctor , Ortiz-Frade Luis Antonio , García-Rodríguez Mario E. , Rodríguez-López José Luis , López-Revilla Rubén
Published: December 2020

Photothermal tumor ablation might be carried out with multibranched gold nanoparticles (MBAuNPs) having maximum absorbance (Amax) in the infrared region and functionalized with ligands that would bind them to the target tumor markers. However, in nanomedicine applications, the nanostructures must reach their target tissues to be effective, but the corona of serum proteins they instantaneously acquire when administered by intravenous injection may affect their activity; for this reason, we decided to analyze the effect that exposing MBAuNPs to bovine serum albumin (BSA) and human serum (HS) have on their protein corona and physical properties. The synthesized spherical Au seeds stoichiometrically generate piñata-like MBAuNPs of 8–20 peaks potentially useful for photothermal tumor ablation since they induce hyperthermia of more than 4 °C in phantom gels mimicking the skin irradiated with an 808 nm laser at 0.75 W/cm2. The calculated surface area of MBAuNPs ranges from 24 984 nm2 to 40 669 nm2, depending on the number of peaks we use for modeling the NPs. When MBAuNPs are exposed to BSA, they acquire a protein corona with an internal “hard” portion composed by one or two layers of BSA containing ∼1000–4000 molecules covalently bound to their surface, and an external “soft” portion formed by agglomerated BSA molecules linked by non-covalent bonds. Functionalization with BSA decreases the tendency of MBAuNPs to agglomerate and increases their size dispersion. MBAuNPs and MBAuNPs–BSA exposed to HS bind HS albumin and other HS proteins ranging from 25 kDa to 180 kDa that increase their hydrodynamic diameter and decrease their stability. We conclude that MBAuNPs exposed to serum albumin and HS instantaneously acquire a hard and soft protein corona that may affect prior or subsequent functionalization aiming to direct them to specific cell or tissue targets.
Self-induced ferroelectric 2-nm-thick Ge-doped HfO2 thin film applied to Ge nanowire ferroelectric gate-all-around field-effect transistor
Authors: Lin Yi-Wen , Sun Chong-Jhe , Chang Hao-Hsiang , Huang Yu-Hsien , Yu Tung-Yuan , Wu Yung-Chun , Hou Fu-Ju
Published: December 2020

This paper reports a self-induced ferroelectric 2-nm-thick Ge-doped HfO2 (Ge:HfO2) thin film. Ge thermal desorption, incorporation into HfO2, and further Ge:HfO2 crystallization were all performed through rapid thermal annealing simultaneously. The ferroelectric property of a 2-nm-thick Ge:HfO2/2-nm-thick Al2O3 dielectric stack was confirmed using the polarization-electric field measurement. X-ray photoelectron spectroscopy was used to confirm that Ge bonded to HfO2 as Hf-germanates. Piezoresponse force microscopy was used to demonstrate the piezoelectric property of Ge:HfO2/Al2O3. Furthermore, a dielectric stack of Ge:HfO2/Al2O3 was applied as a gate insulator in a Ge nanowire gate-all-around ferroelectric field-effect transistor (Ge NW Fe-GAAFET). The device exhibited a minimum steep-sub-threshold slope of 47 mV/dec, a high ION/IOFF ratio of >106, and low gate leakage current; moreover, it was free of a drain-induced barrier lowering effect. The proposed self-induced ferroelectric Ge:HfO2 Ge NW Fe-GAAFET is feasible for future ultra-low power integrated circuit applications.
Directional shock diode behavior through the interaction of geometric voids in engineered polymer assemblies
Authors: Branch Brittany A. , Frank Geoff , Abbott Andrew , Lacina David , Dattelbaum Dana M. , Neel Christopher , Spowart Jonathan
Published: December 2020

With the advent of additive manufacturing (AM) techniques, a new class of shockwave mitigation and structural supports has been realized through the hierarchical assembly of polymer materials. To date, there have been a limited number of studies investigating the role of structure on shockwave localization and whether AM offers a means to tailor shockwave behavior. Of particular interest is whether the mesoscopic structure can be tailored to achieve shockwave properties in one direction of impact vs the other. Here, we illustrate directional response in engineered polymer foams. In situ time-resolved x-ray phase contrast imaging at the Advanced Photon Source was used to characterize these diode-like structures. This work offers a breakthrough in materials technology for the development of protective structures that require augmentation of shock in one direction while diminishing transmission in the opposite direction.
The W2020 Database of Validated Rovibrational Experimental Transitions and Empirical Energy Levels of Water Isotopologues. II. H217O and H218O with an Update to H216O
Authors: Furtenbacher Tibor , Tóbiás Roland , Tennyson Jonathan , Polyansky Oleg L. , Kyuberis Aleksandra A. , Ovsyannikov Roman I. , Zobov Nikolay F. , Császár Attila G.
Published: December 2020

The W2020 database of validated experimental transitions and accurate empirical energy levels of water isotopologues, introduced in the work of Furtenbacher et al. [J. Phys. Chem. Ref. Data 49, 033101 (2020)], is updated for H216O and newly populated with data for H217O and H218O. The H217O/H218O spectroscopic data utilized in this study are collected from 65/87 sources, with the sources arranged into 76/99 segments, and the data in these segments yield 27 045/66 166 (mostly measured) rovibrational transitions and 5278/6865 empirical energy levels with appropriate uncertainties. Treatment and validation of the collated transitions of H216O, H217O, and H218O utilized the latest, XML-based version of the MARVEL (Measured Active Rotational-Vibrational Energy Levels) protocol and code, called xMARVEL. The empirical rovibrational energy levels of H217O and H218O form a complete set through 3204 cm−1 and 4031 cm−1, respectively. Vibrational band origins are reported for 37 and 52 states of H217O and H218O, respectively. The spectroscopic data of this study extend and improve the data collated by an International Union of Pure and Applied Chemistry Task Group in 2010 [J. Tennyson et al., J. Quant. Spectrosc. Radiat. Transfer 110, 2160 (2010)] as well as those reported in the HITRAN2016 information system. Following a minor but significant update to the W2020-H216O dataset, the joint analysis of the rovibrational levels for the series H216O, H217O, and H218O facilitated development of a consistent set of labels among these three water isotopologues and the provision of accurate predictions of yet to be observed energy levels for the minor isotopologues using the combination of xMARVEL results and accurate variational nuclear-motion calculations. To this end, 9925/8409 pseudo-experimental levels have been derived for H217O/H218O, significantly improving the coverage of accurate lines for these two minor water isotopologues up to the visible region. The W2020 database now contains almost all of the transitions, apart from those of HD16O, required for a successful spectroscopic modeling of atmospheric water vapor.
Dynamical heterogeneities in non-entangled polystyrene and poly(ethylene oxide) star melts
Authors: Bačová Petra , Gkolfi Eirini , Hawke Laurence G. D. , Harmandaris Vagelis
Published: December 2020

Star polymers can exhibit a heterogeneous dynamical behavior due to their internal structure. In this work, we employ atomistic molecular dynamics simulations to study translational motion in non-entangled polystyrene and poly(ethylene oxide) star-shaped melts. We focus on the local heterogeneous dynamics originating from the multi-arm star-like architecture and quantify the intramolecular dynamical gradient. By examining the translational motion at length scales of the order of the Kuhn length, we aim at finding common features for both studied chemistries and at providing a critical and direct comparison with theoretical models of polymer dynamics. We discuss the observed tendencies with respect to the continuous Rouse model adjusted for the star-like architectures. Two versions of the Rouse model are examined: one assuming uniform friction on every Rouse bead and another one considering larger branch point friction. Apart from chain connectivity between neighboring beads, both versions disregard interactions between the chains. Despite the tolerable description of the simulation data, neither model appears to reflect the mobility gradient accurately. The detailed quantitative atomistic models employed here bridge the gap between the theoretical and general, coarse-grained models of star-like polymers, which lack the indispensable chemical details.
Full color emission of all-bromide inorganic perovskite nanocrystals
Authors: Shi Huafeng , Zhang Qi , Shi Pengyang , Zhang Xinhai
Published: December 2020

Inorganic perovskites have attracted intensive research attention. The perovskites ABX3 (X = Cl, Br, and I) can be used for blue, green, and red emission by adjusting the halogen X. However, it is very hard to avoid halogen exchanging when different halide perovskites are used together for optoelectronic devices. We synthesized the all-bromide inorganic perovskite nanocrystals with full color emission. The blue emission with a center wavelength of 405 nm originates from the exciton recombination through the charge-transfer exciton state in perovskite Cs4PbBr6. The green emission with a center wavelength of 520 nm results from band edge-exciton recombination in perovskite CsPbBr3. The red emission with a center wavelength of 606 nm comes from the trapped- and self-trapped-exciton recombination in perovskite CsPb2Br5. Our experimental results show that all-bromide inorganic perovskite nanocrystals have great potential for full color light emitting devices.
Unveiling the coexistence of cis- and trans-isomers in the hydrolysis of ZrO2: A coupled DFT and high-resolution photoelectron spectroscopy study
Authors: Abou Taka Ali , Babin Mark C. , Sheng Xianghai , DeVine Jessalyn A. , Neumark Daniel M. , Hratchian Hrant P.
Published: December 2020

High-resolution anion photoelectron spectroscopy of the ZrO3H2− and ZrO3D2− anions and complementary electronic structure calculations are used to investigate the reaction between zirconium dioxide and a single water molecule, ZrO20/− + H2O. Experimental spectra of ZrO3H2− and ZrO3D2− were obtained using slow photoelectron velocity-map imaging of cryogenically cooled anions, revealing the presence of two dissociative adduct conformers and yielding insight into the vibronic structure of the corresponding neutral species. Franck–Condon simulations for both the cis- and trans-dihydroxide structures are required to fully reproduce the experimental spectrum. Additionally, it was found that water-splitting is stabilized more by ZrO2 than TiO2, suggesting Zr-based catalysts are more reactive toward hydrolysis.
Optimisation of dual structure recording media for microwave-assisted magnetic recording
Authors: Greaves Simon John , Kanai Yasushi
Published: December 2020

Dual structure recording media with a “notched” anisotropy configuration were optimised for use in a microwave-assisted magnetic recording system. First of all the effective head field gradient was maximised by tuning the anisotropy of the layers in each structure. Next, intergranular and interlayer exchange coupling was adjusted to maximise the signal to noise ratio of written tracks. A grain switching probability model was trained and used to generate written bit sequences for read bit error rate calculations. For two structures with different ferromagnetic resonance frequencies the total amount of user data that could be stored on the two structures was estimated to be 2.98 Tbit/in2.
Synthesis and delivery ofStreptococcus pneumoniaecapsular polysaccharides by recombinant attenuatedSalmonellavaccines
Authors: Su Huali , Liu Qing , Bian Xiaoping , Wang Shifeng , Curtiss Roy , Kong Qingke
Published: December 2020

Significance

Pneumococcal infection-caused diseases are responsible for substantial morbidity and mortality worldwide. Traditional pneumococcal vaccines are developed based on purified capsular polysaccharides (CPS) or CPS conjugated to a protein carrier. Production processes of the traditional vaccines are laborious, and thereby increase the vaccine cost and limit their use in developing nations. A cost-effective pneumococcal vaccine using the recombinant attenuatedSalmonellavaccine (RASV) was developed in this study. We cloned and expressed genes for seven serotypes of CPSs in the RASV strain. The RASV-delivered CPSs induced robust humoral and cell-mediated responses and mediated efficient protection of mice against pneumococcal infection. Our work provides an innovative strategy for mass producing low-cost bioconjugated polysaccharide vaccines for needle-free mucosal delivery against pneumococcal infections.
In-situ studies and simulation of equiaxed solidification in Al–20Cu alloy
Authors: Luo Shifeng , Yang Guangyu , Chen Jieming , Xiao Lei , Huang Wanxia , Yuan Qingxi , Jie Wanqi
Published: December 2020

The equiaxed solidification of Al–20Cu alloy under different cooling rates was investigated using in-situ synchrotron X-ray radiography. The results showed that mean grain size increases rapidly at the early stage of solidification, then reaches the final grain size gradually. And the change of final mean grain size with cooling rate follows d = 4132.3 ×  R−0.86. In addition, the evolution of grain size in Al–20Cu alloy was also simulated by ProCAST software. The experimental and simulation results indicated that, in the range of the cooling rate (5.0–7.5 K min−1), the major factor influencing the final grain size is the maximum nucleation density, while the nucleation undercooling has an insignificant effect on the final grain size.
Auto-adaptive positive airway pressure improves lung function and arterial stiffness parameters in patients with severe obstructive sleep apnea syndrome over a 1 year follow-up
Authors: Milicevic Tanja , Katic Josip , Milovac Stjepanka Nakic , Matetic Andrija , Aljinovic Jure , Dogas Zoran , Gunjaca Grgo
Published: December 2020

Objective: Auto-adaptive positive airway pressure (APAP) is an emerging therapeutic modality for obstructive sleep apnea (OSA) patients. However, their associated physiological effects have not been well-defined. Therefore, we aimed to investigate the impact of a 1 year APAP treatment on lung function and arterial stiffness parameters. Approach: This study enrolled male patients with newly diagnosed severe OSA who have undergone APAP treatment. A total of 35 patients completed a 1 year follow up. Blood pressure, arterial stiffness (PWV, cAIx, pAIx, cSBP), and lung function readings (FEV1, FVC, FEV1/FVC, PEF) were obtained basally and after 1, 3, 6, and 12 months of treatment. Main results: A gradual increase in FEV1 has been observed over the follow-up (2.92 ± 0.88 versus 3.07 ± 0.92 versus 3.18 ± 0.93 versus 3.28 ± 0.93 versus 3.41 ± 0.97 L), while PWV showed a gradual decrease over the follow-up (9.72 ± 1.64 versus 9.32 ± 1.73 versus 8.89 ± 1.65 versus 8.53 ± 1.61 versus 8.46 ± 1.60 m s−1), as measured by absolute values. Linear mixed effects model analysis revealed a statistically significantly higher FEV1 values (coefficient of 0.11, 0.20, and 0.33 for 3rd month, 6th month, and 12th month, respectively, P < 0.001) and lower PWV values (coefficient of −0.69, −0.63, and −0.34 for 3rd month, 6th month, and 12th month, respectively, P < 0.001), after the initiation of APAP treatment. Significance: We conclude that APAP treatment improves main lung function and arterial stiffness parameters in male patients with severe OSA over a 1 year follow-up.
Quench dynamics in 1D model with 3rd-nearest-neighbor hoppings*
Authors: Yue Shuai , Zhou Xiang-Fa , Zhou Zheng-Wei
Published: December 2020

The non-equilibrium dynamics of a one-dimensional (1D) topological system with 3rd-nearest-neighbor hopping has been investigated by analytical and numerical methods. An analytical form of topological defect density under the periodic boundary conditions (PBC) is obtained by using the Landau–Zener formula (LZF), which is consistent with the scaling of defect production provided by the Kibble–Zurek mechanism (KZM). Under the open boundary conditions (OBC), quench dynamics becomes more complicated due to edge states. The behaviors of the system quenching across different phases show that defect production no longer satisfies the KZM paradigm since complicated couplings exist under OBC. Some new dynamical features are revealed.
Review of quantum simulation based on Rydberg many-body system
Authors: Zhang Zheng-Yuan , Ding Dong-Sheng , Shi Bao-Sen
Published: December 2020

Quantum simulation has been developed extensively over the past decades, widely applied to different models to explore dynamics in the quantum regime. Rydberg atoms have strong dipole–dipole interactions and interact with each other over a long distance, which makes it straightforward to build many-body interacting quantum systems to simulate specific models. Additionally, neutral atoms are easily manipulated due to their weak interactions. These advantages make Rydberg many-body system an ideal platform to implement quantum simulations. This paper reviews several quantum simulations for different models based on Rydberg many-body systems, including quantum Ising models in one dimension and two dimensions mainly for quantum magnetism, XY model for excitation transport, SSH model for symmetry-protected topological phases, and critical self-organized behaviors in many-body systems. Besides, some challenges and promising directions of quantum simulations based on Rydberg many-body system are discussed in this paper.
Quantum walk under coherence non-generating channels*
Authors: Chen Zishi , Hu Xueyuan
Published: December 2020

We investigate the probability distribution of the quantum walk under coherence non-generating channels. We define a model called generalized classical walk with memory. Under certain conditions, generalized classical random walk with memory can degrade into classical random walk and classical random walk with memory. Based on its various spreading speed, the model may be a useful tool for building algorithms. Furthermore, the model may be useful for measuring the quantumness of quantum walk. The probability distributions of quantum walks are generalized classical random walks with memory under a class of coherence non-generating channels. Therefore, we can simulate classical random walk and classical random walk with memory by coherence non-generating channels. Also, we find that for another class of coherence non-generating channels, the probability distributions are influenced by the coherence in the initial state of the coin. Nevertheless, the influence degrades as the number of steps increases. Our results could be helpful to explore the relationship between coherence and quantum walk.
Effect of electrical contact on performance of WSe2 field effect transistors*
Authors: Pang Yi-Di , Wu En-Xiu , Xu Zhi-Hao , Hu Xiao-Dong , Wu Sen , Xu Lin-Yan , Liu Jing
Published: December 2020

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) such as tungsten diselenide (WSe2) have spead many interesting physical properties, which may become ideal candidates to develop new generation electronic and optoelectronic devices. In order to reveal essential features of 2D TMDCs, it is necessary to fabricate high-quality devices with reliable electrical contact. We systematically analyze the effect of graphene and metal contacts on performance of multi-layered WSe2 field effect transistors (FETs). The temperature-dependent transport characteristics of both devices are tested. Only graphene-contacted WSe2 FETs are observed with the metal-insulator transition phenomenon which mainly attributes to the ultra-clean contact interface and lowered contact barrier. Further characterization on contact barrier demonstrates that graphene contact enables lower contact barrier with WSe2 than metal contact, since the Fermi level of graphene can be modulated by the gate bias to match the Fermi level of the channel material. We also analyze the carrier mobility of both devices under different temperatures, revealing that graphene contact can reduce the charge scattering of the device caused by ionized impurities and phonon vibrations in low and room temperature regions, respectively. This work is expected to provide reference for fabricating 2D material devices with decent performances.
Aperture-averaged scintillation index and fade statistics in weak oceanic turbulence*
Authors: Wang Hao , Kang Fu-Zeng , Wang Xuan , Zhao Wei , Sun Shu-Wei
Published: December 2020

With the rapid demand for underwater optical communication (UOC), studies of UOC degradation by oceanic turbulence have attached increasing attention worldwide and become a research hot-spot in recent years. Previous studies used a simplified and inaccurate oceanic turbulence spectrum, in which the eddy diffusivity ratio between temperature and salinity is assumed to be unity and the outer scale of turbulence is assumed to be infinite. However, both assumptions are not true in most of the actual marine environments. In this paper, based on the Rytov theory in weak turbulence, we derive analytical expressions of “the aperture-averaged scintillation index” (SI) for both plane and spherical waves, which can clearly demonstrate how SI is influenced by several key factors in UOC. Then, typical fade statistics of the UOC system in weak turbulence is discussed including the probability of fade, the expected number of fades per time, the mean fade time, signal-to-noise ratio and bit error rate. Our results show that spherical wave is preferable in the UOC system in weak turbulence compared to plane wave, and the aperture-averaged effect has a significant impact on UOC system’s performance. Our results can be used to determine those key parameters for designing the UOC system over reasonable ranges.
Review on ionization and quenching mechanisms of Trichel pulse*
Authors: Sun Anbang , Zhang Xing , Guo Yulin , He Yanliang , Zhang Guanjun
Published: December 2020

Trichel pulse is a kind of pulsed mode in negative DC corona discharge, which has attracted significant attention because of its considerable applications in industry. Over eighty years, plenty of effort including simulations and experiments has been spent to reveal the ionization and quenching mechanisms of Trichel pulse. By revisiting and summarizing the basic characteristics and well-accepted ionization and quenching mechanisms, this review provides a basic understanding and the current status of Trichel pulse.