bluuebunny/crossref_metadata_2025 huggingface dataset:
A High-resolution Imaging Survey of Massive Young Stellar Objects in the Magellanic Clouds
Authors: Kalari Venu M. , Salinas Ricardo , Zinnecker Hans , Rubio Monica , Herczeg Gregory , Andersen Morten
Published: August 2024

Constraints on the binary fraction of massive young stellar objects (mYSOs) are important for binary and massive star formation theory. Here, we present speckle imaging of 34 mYSOs located in the Large Magellanic Cloud (1/2 Z
⊙) and Small Magellanic Cloud (∼1/5 Z
⊙), probing projected separations in the 2000 to 20,000 au (at angular scales of 0.″02–0.″2) range, for stars above 8 M
⊙. We find two wide binaries in the Large Magellanic Cloud (from a sample of 23 targets), but none in a sample of 11 in the Small Magellanic Cloud, leading us to adopt a wide binary fraction of 9% ± 5% and <5%, respectively. We rule out a wide binary fraction greater than 35% in the Large Magellanic Cloud and 38% in the Small Magellanic Cloud at the 99% confidence level. This is in contrast to the wide binary fraction of mYSOs in the Milky Way (presumed to be 1 Z
⊙), which within the physical parameter space probed by this study is ∼15%–60% from the literature. We argue that while selection effects could be responsible for the lower binary fraction observed, it is more likely that there are underlying physical mechanisms responsible for the observed properties. This indicates that metallicity and environmental effects may influence the formation of wide binaries among massive stars. Future larger, more statistically significant samples of high-mass systems in low-metallicity environments for comparison to the Milky Way, are essential to confirm or repudiate our claim.
Time Profile Study of Type III Solar Radio Bursts Using Parker Solar Probe
Authors: Thapa Tulsi , Yan Yihua
Published: August 2024

Solar type III radio bursts are crucial indicators of energetic electron activity in the solar corona and interplanetary space. Our assessment of 43 interplanetary type III bursts, recorded by the FIELDS instrument on board the Parker Solar Probe during Encounters 05 to 11, has led to significant and complex findings. We have analyzed time profile features across a frequency range of 19–0.5 MHz, revealing dependencies on frequency and providing insights into duration, burst speeds, bandwidths, and drift rates. This novel analysis has unveiled a spectral index of −0.63 ± 0.04 for rise, −0.69 ± 0.03 for decay time, and −0.68 ± 0.03 for the total duration. We have determined the average electron beam velocities for front, middle, and back as 0.15c, 0.13c, and 0.08c, respectively. Our findings show that faster electron beams generate emissions with shorter duration. The average ratio of the front-to-back velocity is 1.87, and the ratio of front-to-middle velocity is 1.23. We have also discovered a strong relationship between burst duration with rise, peak, and decay times, particularly pronounced with decay time (correlation coefficient = 0.95). This indicates that the entire temporal profile, including rise, peak, and decay phases, collectively contributes to event duration and is not solely influenced by external factors like plasma conditions or electron beam dynamics but also by internal burst processes. These complex findings shed light on the physical mechanisms governing burst dynamics, revealing intricate interactions between electron beam characteristics and observed temporal and spectral traits of type III solar radio bursts.
Magnetization Factors of Gamma-Ray Burst Jets Revealed by a Systematic Analysis of the Fermi Sample
Authors: Li An , Gao He , Lan Lin , Zhang Bing
Published: August 2024

The composition of gamma-ray burst (GRB) jets remained a mystery until recently. In practice, we usually characterize the magnetization of the GRB jets (σ
0) through the ratio between the Poynting flux and matter (baryonic) flux. With the increasing value of σ
0, magnetic energy gradually takes on a dominant role in the acceleration and energy dissipation of the jet, causing the proportion of thermal component in the prompt-emission spectrum of GRBs to gradually decrease or even be completely suppressed. In this work, we conducted an extensive analysis of the time-resolved spectrum for all Fermi GRBs with known redshift, and we diagnose σ
0 for each time bin by contrasting the thermal and nonthermal radiation components. Our results suggest that most GRB jets should contain a significant magnetic energy component, likely with magnetization factors σ
0 ≥ 10. The value of σ
0 seems to vary significantly within the same GRB. Future studies with more samples, especially those with lower-energy spectral information coverage, will further verify our results.
STELLA Lightcurves of Energetic Pair-instability Supernovae in the Context of SN2018ibb
Authors: Nagele Chris , Umeda Hideyuki , Maeda Keiichi
Published: August 2024

SN2018ibb is a recently observed hydrogen-poor superluminous supernova that appears to be powered by the decay of 30 M
⊙ of radioactive nickel. This supernova has been suggested to show hybrid signatures of a pair-instability supernova and an interacting supernova. In a previous paper, we found that rotating, metal-enriched pair-instability supernova progenitors appeared to check both of these boxes. In this paper, we model the lightcurves of the pair-instability supernovae using STELLA. We find that the STELLA models can explain the overall shape of the bolometric lightcurve of SN2018ibb, though not specific morphological features such as the luminosity peak or the bump at roughly 300 days after the peak. We also estimate the contribution from interaction and find that with relatively low wind velocities, the circumstellar medium originating from the stellar winds is consistent with the evidence for interaction in the spectra. The observed values of the photosphere velocity in the 100 days after peak luminosity are similar to the STELLA models, but the deceleration is lower. This leads to the biggest inconsistency, which is the blackbody temperature of SN2018ibb being much hotter than any of the STELLA models. We note that this high temperature (and the flat velocity) may be difficult to reconcile with the long rise time of SN2018ibb, but nevertheless conclude that if it is accurate, this discrepancy represents a challenge for SN2018ibb being a robust PISN candidate. This result is noteworthy given the lack of other scenarios for this supernova.
Local Transition of Electron Pitch Angle Distribution within Flux Pileup Region behind Dipolarization Front
Authors: Xing X. N. , Liu C. M. , Cao J. B. , Liu Y. Y. , Zhao B. N.
Published: August 2024

Dipolarization fronts (DFs), earthward-propagating magnetic transients with a strong magnetic field, are important regions favorable for energetic electron acceleration in the magnetotail. The DF-driven electron acceleration usually generates coherent pitch angle distributions (PADs) inside flux pileup regions (FPRs), i.e., strong magnetic field regions behind the DFs, such as pancake, butterfly, and cigar distributions, which dominate at different tail regions and often occur separately. Here we present unique observations of electron PAD evolution inside the FPR, showing that electron PAD underwent local transition from cigar distribution, to butterfly distribution, then toward pancake distribution, forming a U-shaped distribution. During the local transition, electron perpendicular flux (relative to the local magnetic field) is anticorrelated with magnetic field strength, contrary to traditional expectation. The unexpected feature of the electron U-shaped distribution is associated with multiple physical processes at different scales, including local expansion of flux tubes and pitch angle variation near the neutral sheet. These atypical observations can advance our current understanding of electron acceleration and transport in the magnetosphere.
Identification of Carbon Stars in LAMOST DR9 Based on Deep Learning
Authors: He YiMing , Cao Zhong , Deng Hui , Wang Feng , Mei Ying , Tan Lei
Published: August 2024

Carbon stars play a crucial role in astronomical research and are significant for understanding stellar evolution, measuring cosmic distances, and studying galaxy kinematics. In recent years, identifying carbon stars using machine learning methods and traditional line-index methods has become a research hotspot, but there are still limitations regarding accuracy and automation. In this study, we propose to build a five-class model to identify carbon stars using spectral data from LAMOST DR9. The model achieved 99.45% precision and 91.21% recall on the carbon star testing set. We conducted independent tests using a sample of 1333 known carbon stars that were not used in the training and testing phases, and our model ultimately identified 1199 carbon stars. On this basis, we used this model to screen 11,226,252 spectra of LAMOST DR9 and identified 4383 carbon stars, including 1197 newly discovered carbon stars. To gain a more comprehensive understanding of the characteristics of the 4383 carbon stars obtained, further visual inspection of these spectra was performed to provide more detailed carbon star subtypes.
Altimella gen. nov., a new genus of Cicurinidae (Arachnida, Araneae) from Xizang, China, with description of two new species
Authors: Wang Lu-Yu , Mu Yan-Nan , Xu Yong-Qiang , Zhang Feng , Zhang Zhi-Sheng
Published: August 2024

Altimella Wang & Zhang, gen. nov., a new genus belonging to Cicurinidae, is established, and two new species are described, Altimella nedong Wang & Zhang, sp. nov. (♂♀, type species) and A. ngamring Wang & Zhang, sp. nov. (♂♀), from Xizang, China. Detailed descriptions of somatic features and genital characteristics, photos of the habitus, photos and drawings of the copulatory organs, and a distribution map are provided.
Clinical Outcomes and Re-Tear Rates for Partial Arthroscopic Rotator Cuff Repair With or Without Biceps Augmentation for Large-to-Massive Tears: A Systematic Review and Meta-analysis
Authors: Baumann Anthony N. , Fiorentino Andrew , Sidloski Katelyn , Lee Hannah A. , Anastasio Albert T. , Walley Kempland C. , Kelly John D.
Published: August 2024

Background:

The recent addition of biceps tendon augmentation to partial arthroscopic rotator cuff repair (ARCR) for the treatment of large-to-massive rotator cuff tears is proposed to improve clinical outcomes and reduce re-tears.

Materials and Methods:

The purpose of this systematic review and meta-analysis (5 studies) was to compare outcomes between partial ARCR with (142 patients) and without (149 patients) biceps augmentation.

Results:

Partial ARCR with and without biceps augmentation were comparable in pain, function, and range of motion. However, biceps augmentation vs no augmentation at all during ARCR may lower re-tear rates for irreparable large-to-massive rotator cuff tears (42.9% vs 72.5%,
P
=.007).

Conclusion:

More research is needed to investigate this technique and guide surgical decision-making. [
Orthopedics
. 2024;47(5):e217–e224.]
Nondiabetic Vitreous Hemorrhage: A Review of Management Strategy and Outcomes
Authors: Strand Eric , Meshkin Ryan S. , Hoyek Sandra , Miller John B. , Patel Nimesh A.
Published: August 2024

Vitreous hemorrhage involves blood leakage into or around the vitreous cavity, which presents complex management decisions. Treatment options for nondiabetic vitreous hemorrhage (NDVH) traditionally include observation or early vitrectomy. Traditional guidelines have long emphasized an initial period of cautious observation. This systematic review shows that a significant portion (∼62% to 75%) of NDVH patients present a retinal tear and/or detachment upon initial presentation. B-scan ultrasonography, the primary diagnostic tool, exhibits variable sensitivities and may miss approximately half (46.4%) of underlying tears or detachments. Only 25% of observed NDVH cases clear spontaneously, while the remaining will ultimately require vitrectomy due to nonclearance (45%) or sight-threatening complications (30%). Patients under observation experience visual deficits as hemorrhage clears slowly, challenging the efficacy of traditional guidelines favoring observation. While there is no clear guideline concerning the management of NDVH, our findings suggest that early vitrectomy for severe NDVH may be the safest and most appropriate approach, provided the patient accepts procedural risks like cataract development.

[
Ophthalmic Surg Lasers Imaging Retina
2024;55:660–667.]
Retinal Detachment Following Cataract Surgery: A Systematic Review and Meta-analysis of Incidence, Preoperative Risk Factors, and Postoperative Complications
Authors: Alshammari Abdulmohsen Jameel , Alqam Rakan Abu , Aldeej Maram Abdulaziz , Al-Omair Abdullah Mohammed , Wazira Lamar Abed , Shafei Jumana Abdullah , Kaki Abdulrahman Abdulaziz , Raffa Lina Hassan
Published: August 2024

Cataract surgery is the most common surgical operation in the developed world, for treating cataracts, currently the leading cause of blindness worldwide. Retinal detachment (RD) is a potentially sight-threatening adverse effect of cataract surgery. The overall RD case numbers are high due to the common practice of cataract surgery. The Medline, Scopus, and Directory of Open Access Journals databases were searched for relevant articles using the keywords (phacoemulsification OR cataract surgery) AND (retinal detachment, detached retina). The included studies involved 5,480,448 patients, where 36,886 had RD (pooled incidence: 0.66 events per 100 patients, 95% CI 0.43 to 1.00). Male patients had significantly higher odds of developing RD than female patients (odds ratio = 1.73, 95% CI 1.68 to 1.78,
P
< 0.001). The RD incidence rate across locations was not significantly different. RD is one of the most significant complications following cataract surgery.

[
Ophthalmic Surg Lasers Imaging Retina
2024;55:668–674.]
A Novel CEP78 Variant Presenting as Cone Dystrophy and Hearing Loss
Authors: Faruque Promie R. , Hou Baichun , Oh Jin Kyun , Tsang Stephen H.
Published: August 2024

Mutations in CEP78 lead to abnormal production of cilia and have previously been identified to cause cone-rod dystrophy (CRD) with progressive sensorineural hearing loss. The authors describe a case of cone dystrophy (CD) with sensorineural hearing loss in a variant that had previously been reported to be of unknown significance and associated with CRD only. This report corroborates the pathogenicity of this variant and highlights that different phenotypes may be associated with one genotype.

[
Ophthalmic Surg Lasers Imaging Retina
2024;55:742–746.]
Assessing mental resilience with individual and lifestyle determinants among nursing students: An observational study from Greece
Authors: Antoniou Maria , Fradelos Evangelos C. , Roumeliotaki Theano , Malli Foteini , Symvoulakis Emmanouil, K. , Papagiannis Dimitrios
Published: August 2024

The educational environment is important for the development of life skills of nursing students in late- and post-adolescence. Strengthening their mental resilience, enhancing their individual confidence, and controlling stress are necessary conditions in this direction, which will help them cope with the future challenges of their chosen profession. We aimed to study the resilience profiles of nursing students by investigating their mental resilience and its association with their individual characteristics and lifestyle factors. The Connor-Davidson Resilience Scale (CD–RISC–25) scale for resilience, the Perceived Stress Scale (PSS–14) scale for perceived stress, and the Personal Trust and Connection (PerTC) scale for trust and connections were used. The lifestyle determinants were also assessed. An e-survey that targeted 250 nursing students was conducted from November 22 to April 23. Descriptive and advanced statistical analyses were performed. 146 students participated in the study via an on-line questionnaire; the students were predominantly female (82.2%) with mean age of 22 years (SD = 6.8). Two out of ten students smoked (20.5%), 66.4% consumed at least one drink during a usual week, and 48.0% participated in sports during the last year. The mean hours spent on the Internet daily was 4.2 (SD = 1.8) and on social media was 2.7 (SD = 1.6) hours/day. The students scored highly on the 1-to-10 life-satisfaction item (Mean = 6.3, SD = 1.9), where the perceived stress was assessed as moderate/high with a mean of 33 (SD = 4.4) and trust and connections had a mean of 6.2 (SD = 1.1). In the multivariate analysis, the factors found to significantly associate with resilience (CD–RISC–25; Mean = 64.2, SD = 11.8) were age (β = 0.4; 95% CI: 0.1, 0.7), sports participation (β = 5.7; 95% CI: 2.3, 9.1), hours per day spent on social media (β = -1.3; 95% CI: -2.3, -0.3), and the number of friends (β = 0.3; 95% CI: 0.05, 0.5). Finally, resilience was positively associated with life satisfaction and the trust and connections scale (β = 1.8; 95% CI: 0.9, 2.7 and β = 1.8; 95% CI: 0.2, 3.4, respectively).
Societal Transformation Projects and the Role and Influence of Human Factors on Natural Resources (RIHFNR)
Authors: Trad Antoine Toni
Published: August 2024

Societal transformation projects (simply a Project) take very long-time and are complex to achieve. Such Projects depend on many domains, and especially on the Human Factor (HF). The Role and Influence of HF on Natural Resources (RIHFNR) is determinant. A Project has many cycles and depends on the Speed of Change (SoC); and other related societal fundaments and factors. Actually, the RIHFNR has inflicted much damage to the environment and the exponential use of Natural Resources (NR) have created a historical global societal crisis. A Project has an archaic societal composition, many dependencies, and other related factors that have to be correlated. In this chapter the influence of major societal, environment/resources, geopolitical changes, management technics, and events are analyzed. Projects' (like all other types of transformations) related research activities, depend on the selected Critical Success Areas (CSA), which are the following: 1) Rate, cycles, and speed of changes and the effects on NR; 2) HF and societal values that are relevant; 3) Levels and types of NRs; 4) The roles of Demography, cultures, religions, and historical backgrounds; 5) The role of technologies; 6) Ethical, governance, and legal system; 7) HF's managements' profile and capabilities; 8) The roles of financial and resources management; 9) Mitigating NR risks; 10) The roles of conflicts, and ecology; 11) Societal policies; 12) Globally defined objectives; 13) Role of geopolitical changes events; 14) Weapons of mass destruction; 15) The role of democracy and civilized behavior; 16) The role and effects of extreme crisis; and 17) Applied research method. This chapter uses the author's Applied Holistic Mathematical Model (AHMM) to support Societal/Geopolitical Analysis (SA) for eXtreme Crisis (XC) (Trad, & Kalpić, 2019a). SA needs a cross-functional/domain and Polymathic concept that is abstracted with the SA Concept (SAC) for XC (SAC4XC), like in many XC related cases that result from the RIHFNR like, massive immigrations, Pandemics/COVID-19, global reginal wars, and major financial crisis/crashes (Trad, 2022a).
Demystifying the World of Blockchain Startups
Authors: Kumar Narendra , Sharma Swati
Published: August 2024

This chapter conducts a thorough examination of the landscape surrounding blockchain startups in India, aiming to unravel the intricacies, challenges, and transformative potential within this dynamic ecosystem. Leveraging secondary data from reputable sources such as industry reports, government publications, and academic literature, the study delves into critical aspects including investment trends, sector-wise distribution, and the pivotal role of government support. The research also addresses challenges unique to the Indian context, such as regulatory uncertainties, skill gaps, and the imperative for public awareness. By synthesizing existing knowledge, the chapter contributes a nuanced understanding of the trajectory and contributions of blockchain startups in India.
Efeitos de um programa multicomponente para promoção da atividade física nos indicadores de saúde mental de adolescentes: um estudo randomizado controlado piloto
Authors: Silva Jadson Marcio da , Dias Pedro Henrique Garcia , Silva Thais Maria de Souza , Francisquini Maria Carolina Juvêncio , Correa Renan Camargo , Barbosa Rodrigo de Oliveira , Santos Géssika Castilho dos , Stabelini Neto Antonio
Published: August 2024

O objetivo do presente estudo foi verificar os efeitos de 12 semanas de um programa para promoção da atividade física nos indicadores de saúde mental de adolescentes. A amostra foi composta por adolescentes de ambos os sexos com idades entre 12 e 15 anos, os quais foram alocados em grupo intervenção ou grupo controle. O programa de intervenção incluía os seguintes componentes: sessões de atividade física na escola; incentivo a prática de atividade física fora do ambiente escolar; orientações sobre estilo de vida saudável. Os indicadores de saúde mental analisados ​​foram: sintomas de ansiedade e depressão, qualidade do sono e bem-estar psicológico. Os efeitos da intervenção nas variáveis ​​de resultados foram analisados ​​mediante ANOVA para medidas repetidas. A comparação intergrupos foi realizada pela análise de covariância. Foi adotado um nível de significância de p<0,05. Após 12 semanas, a intervenção em grupo apresentou diminuição significativa da pontuação média do sono (diferença média: -0,96, IC 95%: -1,8; -0,09), sintomas de ansiedade (diferença média: -1,7, IC 95%: -2,9; -0,64) e depressão (diferença média:-1,5, IC 95%: -2,5; -0,56) em comparação aolinha de base. Nas comparações intergrupos, foi observado um efeito significativo favorável à intervenção em grupo para os sintomas de depressão (-2,39; IC 95%: -4,68; -0,11). Para o controle do grupo, não foram identificados diferenças nos indicadores de saúde mental entre os momentos. Conclui-se que 12 semanas de intervenção de um programa para a promoção da atividade física promoveu uma melhora significativa nos indicadores de saúde mental nos adolescentes do grupo de intervenção.
250 μm Thick Detectors for Neutron Detection: Design, Electrical Characteristics, and Detector Performances
Authors: Trovato Gabriele , Meli Alessandro , Muoio Annamaria , Reitano Riccardo , Calcagno Lucia , Kushoro Matteo Hakeem , Rebai Marica , Tardocchi Marco , Trotta Antonio , Parisi Miriam , Meda Laura , La Via Francesco
Published: August 2024

Solid State Detectors (SSD) are crucial for fast neutron detection and spectroscopy in tokamaks due to their solid structure, neutron-gamma discrimination, and magnetic field resistance. They provide high energy resolutions without external conversion stages, enabling compact array installations in the harsh environment of a tokamak. Research comparing diamond and 4H-SiC detectors highlights thickness as a key efficiency factor. A 250 μm SiC epilayer with low doping, grown using a high-growth-rate process, exhibits sharp interfaces and minimal defects, essential for neutron detectors. The study evaluates detector designs, and performance using a 4H-SiC substrate. Various detector designs, such as Schottky diodes and p/n diodes, are assessed via I-V and C-V measurements, addressing high depletion voltage challenges. Preliminary neutron irradiation tests validate detector functionality, energy resolution and confirming detector reliability.
Metal Contact Processing Experiments towards Realizing 500 °C Durable RF 4H-SiC BJTs
Authors: Rajgopal Srihari , Spry David J. , Lukco Dorothy , Neudeck Philip G.
Published: August 2024

This paper presents results from metal contact processing experiments towards the implementation of durable 500 °C high-frequency 4H-SiC bipolar junction transistors (BJTs). Specifically, p-type ohmic contacts have been demonstrated on a 0.25 μm-thick p-type homoepitaxial layer of doping 8 × 1018 ± 4 × 1018 cm-3. Finally, preliminary current-voltage characteristics of fabricated BJTs are presented.
Spin-Orbit Coupling of Color Centers for Quantum Applications
Authors: Neubauer Mirjam , Schober Maximilian , Dobersberger Witold , Bockstedte Michel
Published: August 2024

Color centers in 4H-SiC and diamond are candidates for single photon sources and qubits for the implementation of quantum applications. The CI-cRPA method is able to correctly reproduce the structure of the underlying highly correlated wave functions for low and high spin multiplets. Aiming for a more complete understanding of spin-orbit mediated intersystem crossing between such states, we have extended CI-cRPA by a first order treatment of the spin-orbit interactions. We present preliminary results for intercrossing matrix elements and contributions of spin-orbit coupling to the zero field splitting of the silicon vacancy and di-vacancy in 4H-SiC, as well as the NV center in diamond using this approach.
High Mobility 4H-SiC P-MOSFET via Ultrathin ALD B2O3 Interlayer between SiC and SiO2
Authors: Ashik Emran K. , Misra Veena , Lee Bong Mook
Published: August 2024

This article presents an innovative approach to achieve a high channel mobility for 4H-SiCp-MOSFET via dielectric-semiconductor interface engineering involving atomic layer deposition(ALD) of ultrathin B2O3 and SiO2 stacks. The application of ultrathin boron oxide via ALD introducesa highly manufacturable solution for the passivation of SiC interface. The interface states near valenceband reduces the channel mobility for SiC p-MOSFETs and increases the threshold voltage. Theintroduction of ultrathin B2O3 interlayer reduces the threshold voltage and improves the field effectmobility to 12.60 cm2/Vs while the p-MOSFET without the interlayer provides the mobility of 8.91cm2/Vs. This work also includes the optimization of the post-deposition annealing (PDA) conditionsspecific to ultrathin B2O3 and bulk SiO2 dielectric stack to obtain high field effect channel mobilityfor SiO2/SiC p-MOSFETs.
Buffer Layer Dependence of Defectivity in 200mm 4H-SiC Homoepitaxy
Authors: Raciti Domenica , Anzalone Ruggero , Isacson Mathias , Piluso Nicolo , Severino Andrea
Published: August 2024

The effect of increasing Buffer Layer (BL) thickness on crystal defectivity has been investigated in 4° off-axis 4H-SiC homoepitaxy on 200mm substrates coming from different suppliers. The results, based on optical microscopy and scatter light methods, show a slight increase in morphological defects in the case of a thicker BL with respect to the standard thickness for both suppliers.
Study on Quantification of Correlation between Current Density and UV Irradiation Intensity, Leading to Bar Shaped 1SSF Expansion
Authors: Igarashi Yasuyuki , Takano Kazumi , Matsushita Yohsuke , Morita Takuya
Published: August 2024

In 4H-SiC devices, the reliability issue of the bipolar degradation, which is caused by the nucleation and expansion of 1SSF (single Shockley stacking fault) defects originating from basal plane dislocations (BPDs), has not been completely eliminated. To avoid the reliability issue, in some device manufacturers is currently introduced so-called "burn-in" (accelerated current stress) screening operation, which is very time-consuming process which raises a total cost of production. While, the bipolar degradation is explained by the REDG (recombination-enhanced dislocation glide) mechanism, and the same degradation can be induced by UV (ultraviolet) irradiation. Using this property, we have been proposing a new screening method to detect latent defects with expanding to 1SSFs at an early stage of manufacturing. In order to bring this screening method to a practical level, it is essential to correlate the accelerated current stress with the UV irradiation quantitatively in terms of the effect of 1SSF expansion. We have attained some progress in an attempt to quantify this correlation and describe it in this paper.
Analysis of Defect Structures during the Early-Stages of PVT Growth of 4H-SiC Crystals
Authors: Hu Shanshan , Liu Yafei , Chen Ze Yu , Cheng Qian Yu , Raghothamachar Balaji , Dudley Michael , Dukes Douglas , Torres Victor , Young Liam , Griswold Samantha , Bricetti Hunter , Liu Chu Hang , Zhu Yi Mei
Published: August 2024

To better understand the effects of various growth parameters during the early-stages of PVT growth of 4H-SiC on resulting defect structures, multiple short duration growths have been carried out under varying conditions of seed quality, nucleation rate, thermal gradients, and N incorporation. Besides the replication of TSDs/TMDs and TEDs as well as the deflection of TSDs/TMDs into Frank dislocations, synchrotron monochromatic beam x-ray topography (SMBXT) studies also reveal the formation of stacking faults bounded by Frank dislocations. Using ray tracing simulations to characterize the Frank dislocations, three types of stacking faults are revealed: Type 1 stacking fault resulting from 2D nucleation of 6H polytype on terraces; Type 2 stacking fault resulting from macrostep overgrowth of the surface growth spiral steps of TSDs/TMDs which separate into c/2 or c/4 increments; Type 3 stacking fault resulting from vicinal step overgrowth of surface growth spiral steps of TSDs/TMDs which separate into c/4 and 3c/4 increments. Analysis of atomic resolution scanning transmission electron microscopy (STEM) images reveals the mechanism of the Type 3 fault.
Early Detection of Bar-Shaped 1SSF before Expansion by PL Imaging
Authors: Morita Takuya , Matsushita Yohsuke , Igarashi Yasuyuki , Takano Kazumi
Published: August 2024

In this study, we investigated how bar-shaped 1SSF (Single Shockley-type stacking fault) in a chip of a SiC (Silicon Carbide) epitaxial wafer expanded with UV (ultraviolet) irradiation and observed it with PL (Photoluminescence) imaging and demonstrated early detection of bar-shaped 1SSF with an algorithm for automatic detection for the initial shape of bar-shaped 1SSF. Furthermore, we estimated that it was 83% how much UV irradiation time could be reduced.
Development of 3-Channel Inspection Analysis Technique for Defects of SiC Epitaxial Wafers Using Optical Inspection, Photoluminescence and X-Ray Topography
Authors: Senzaki Junji , Nishino Junichi , Osanai Tsutom
Published: August 2024

3-channel analysis technique consisting of optical inspection, photoluminescence and X-ray topography methods for defect inspection of SiC epitaxial wafers has been investigated. The effectiveness of SiC wafer inspection image correction to enable automatic defect analysis is verified. Next, it is shown that the 3-channel analysis technique improves SiC defect inspection accuracy compared to conventional 2-channel analysis one.
Investigation of BPD Faulting under Extreme Carrier Injection in Room vs High Temperature Implanted 3.3kV SiC MOSFETs
Authors: Mahadik Nadeemullah A. , Liao Michael E. , Mastro Michael E. , Kallon Elias M. , Stahlbush Robert E. , Soto Jake , Odekirk Bruce
Published: August 2024

Implantation process for high Al dose p+ contact layers in SiC MOSFETs can generate new basal plane dislocations (BPDs). Such BPD faulting under high carrier injection was investigated in SiC MOSFET layers designed for 3.3kV operation with either room temperature (RT) or high temperature (HT) implantations performed for their high dose p+ contact layer. For excess carrier injection levels of ~1x1018 cm-3 implant induced BPDs faulted from the termination regions of the MOSFETs in the case of RT samples, while the HT samples show no BPD faulting because there were no implant-induced BPDs. However, in the active region of the device no BPDs faulted for both the RT as well as HT samples even at a higher carrier injection of ~1x1019 cm-3. Technology computer-aided design (TCAD) simulations show that the lower doped p-well region below the p+ contact in the active area of the device prevents the minority electron density in the p+ contact layer to below 10x the hole density, which limits BPD faulting even when they are present in that layer as in the case of RT implanted samples.
Accuracy of EVC Method for the PiN Diode Pattern on SiC Epi-Wafer
Authors: Takano Kazumi , Morita Takuya , Matsushita Yohsuke , Igarashi Yasuyuki
Published: August 2024

In the previous report, we proposed the EVC (Expansion-Visualization-Contraction) method (Fig. 1) that effectively screens for malignant BPDs (basal plane dislocations) in the epi layer and near substrate interface, which expand to SSFs (Shockley-type stacking faults), leading to forward voltage degradation. The method intentionally utilizes the REDG (recombination enhanced dislocation glide) mechanism by UV (ultraviolet) irradiation in wafer sorting to replace the so-called burn-in (accelerated current stress) process, which is time-consuming during mass production. In this report, to verify the effectiveness of this method, we compared the SSFs expanded by forward biasing the PiN diode (Fig.3) on a wafer with the SSFs expanded by UV irradiating at the same PiN diode area where the metal electrode was removed by etching. The accuracy of the EVC method requires that SSFs expanded by forward biasing should be detected in the same positions as those of SSFs expanded by UV irradiation. Not all BPDs expand at the same time, but the number of expanded SSFs increases over time under constant forward current conditions. In this experiment, the current density was 400 A/cm2 for 8 minutes, and the excessive UV irradiation conditions was 143 W/cm2 for 20 minutes to avoid missing. Missing means the inability to check the SSFs expanded by forward biasing against the SSFs expanded by UV irradiation (Fig.2). For each diode electrode window, the presence or absence of SSFs were determined, and as shown in Table 2, 2 out of 49 window areas were missing, with the EVC method accuracy rate of 96 %.
Improving HfO2 Thick Films for SiC Power Devices by Si, Y and La Doping
Authors: Krause Sandra , Mikolajick Thomas , Schroeder Uwe
Published: August 2024

We investigated the electrical and structural effects of silicon (Si), yttrium (Y) and lanthanum (La) doping in 10-45 nm thick hafnium dioxide (HfO2) films on silicon carbide (SiC) and Si substrates. We show that the introduction of Si dopants leads to a significant enhancement of the electric breakdown field and a reduction of the leakage current density by elevating the crystallization temperature. This effect becomes stronger with higher Si content. In contrast, Y and La doping does not raise TC but increases the tetragonal and orthorhombic phase portion within the crystalline films and therefore enhances the dielectric constant k. Furthermore, we show that larger grains in crystalline films are associated with a higher leakage current density.
Aeromechanical Loads on a Mars Coaxial Rotor
Authors:   University of Maryland, Escobar Daniel , Chopra Inderjit , Datta Anubhav
Published: August 2024

A detailed aeromechanical understanding of a coaxial rotor flying on Mars is presented using a combination of vacuum chamber tests and free-wake based comprehensive analysis. The objectives are to understand the limits of performance, structural loads, control loads (pitch link), wake interaction, and blade strike for hingeless and articulated coaxial rotors. Because of the uniqueness of Martian conditions and the impossibility of testing a rotor at such conditions on Earth on ground a variety of unit tests and a progressively refined set of analysis are used to build up the problem. The unit tests include: construction of composite blades, structural testing, development of a vacuum chamber rotor rig, inclusion of full swashplate controls and hover testing of an isolated rotor. The analysis suite include: 3D FEA, 2D CFD, and a coaxial comprehensive analysis with flexible blades and free-wake. The key conclusions of the research are: (1) the hingeless rotor has high blade root loads and hub loads as expected but the articulated rotor experiences much greater pitch link loads across all the rotor cases explored due to C.G. offsets dictated by an ideal low Re sharp leading edge airfoil (2) the hingeless and articulated rotors both have similar blade tip separation for rotor spacing of 20% R or lower (3) the blade tip separation in fact increases with advance ratio–not decreases–because of the cyclic phasing of the blade passing locations, and (4) tip separation is determined not by blade dynamics but cyclic inputs on relatively wide chord blades.
A Time Parallel Approach to Computational Analysis of Rotors in Trimmed Flight
Authors:   Continuum Dynamics Inc., Silbaugh Benjamin ,   University of Maryland, Baeder James
Published: August 2024

A new method is proposed for computing periodic solutions to asymptotically stable dynamical systems, along with a strategy for adapting the proposed method to the helicopter trim problem. The method may be characterised as a Periodic Multiple Shooting method. The utility of the proposed method is that it enables parallel computation along a temporal direction. The method may be succesfully applied to small systems of equations. However, unlike traditional multiple shooting methods, the proposed method does not strictly require solving a (large) system of algebraic equations. Thus, the proposed method has potential to be scaled to larger systems (e.g. CFD/CSD models). The proposed method is formally shown to be locally convergent. Numerical tests using model problems demonstrate the success of the method.
Maneuver Generation for Regime Recognition Design and Validation
Authors:   Spire Innovations LLC, Monaco Jeffrey ,   Sikorsky a Lockheed Martin Co., Davis Mark ,   Naval Air Systems Command, Semidey Roberto , Hull Jason , Beale Raymond , Glucksman-Glaser Mark
Published: August 2024

Accurate characterization of fleet and individual aircraft usage spectrums would allow component retirement times to be based on actual aircraft usage rather than on an assumed worst case usage spectrum used in a traditional time-based maintenance approach. A key enabling technology for such a Usage or Condition Based Maintenance (UBM/CBM) program is Regime Recognition (RR). The development and validation of such algorithms commonly employs flight loads survey data, which captures critical regimes and the corner points of the operational envelope. Such maneuver examples are flown precisely and don’t necessarily capture how fleet aircraft are flown. The maneuver generation approach presented herein presents the foundational elements of a methodology to augment existing flight loads survey data with statistically independent maneuvers that address the desire to capture the variation that would be observed in the fleet as a result of different pilots, vehicle load-out, and environmental conditions via a simulation based autopilot. Such a capability allows developers to cost-effectively conduct comprehensive sensitivity analyses and verification of RR algorithms and the end-to-end process, while reserving high-cost flight test data for true blind validation.
Canadian Rotors: Evolution of the Canadian Helicopter Industry
Authors:   Aeromedia Communications, Swartz Kenneth
Published: August 2024

This paper tracks the development of the Canadian helicopter industry from its birth to present day highlighting the role that helicopter manufacturers played in the industry's development. Canada has been the home for the world's second largest civil helicopter market for almost seven decades, but the creation of a domestic helicopter manufacturing capability took much longer to achieve. In 2018, there are more than 5,000 Canadian-assembled helicopters flying throughout the world and thousands more helicopters take off every day powered by Canadian made gas turbine engines.
Full-Envelope Stitched Simulation Model of a Quadcopter Using STITCH
Authors:   U.S. Army Aviation Development Directorate (AMRDEC), Tobias Eric , Sanders Frank , Tischler Mark
Published: August 2024

Accurate real-time simulation models of small-scale multi-rotor vehicles are desirable for full-mission simulation and flight control evaluations within hardware-in-the-loop simulation. This paper presents the development and verification of a continuous, full-envelope stitched simulation model of a quadcopter using flight-identified models of the 3D Robotics IRIS+ and the newly-developed model stitching simulation software STITCH. Two flight-identified point models (one at hover and one at forward flight), plus some additional trim data, are shown herein to adequately and accurately capture the bare-airframe dynamics of the IRIS+ over its nominal flight envelope. The stitched simulation model is verified in the frequency domain for multiple airspeeds. Additionally, the off-nominal mass-, CG-, and inertia-extrapolation capabilities of STITCH are investigated and the results are verified against flight data for a heavy loading configuration. The overall findings are considered to provide flight-test guidance for the development of stitched simulation models of small-scale multi-rotor vehicles.
Application of a Heterogeneous CFD Framework Towards Simulating Complete Rotorcraft Configurations
Authors:   University of Maryland, Jude Dylan , Lee Bumseok , Jung Yong , Petermann Jannik , Govindarajan Bharath , Baeder James
Published: August 2024

In the present work, a heterogeneous CPU-GPU framework, Mercury, is presented for simulations of complete helicopter configurations. Mercury incorporates three RANS flow solvers, 1) OverTURNS, a structured solver on CPUs, 2) HAMSTR, a line based unstructured solver on CPUs, and 3) GARFIELD, a structured solver on GPUs. The three solvers use the same mesh deformation module and communicate with the overset grid assembler (TIOGA) through a light-weight Python infrastructure. The framework allows seperate connectivity groups for reconnecting and stationary meshes to avoid unnecessary communication and accelerate simulations. The first of three cases presented is a transonic Caradonna-Tung rotor over a sphere, a simple case used for initial validation and load-balancing analysis. The second case presents a ROBIN fuselage with main rotor for comparison against unsteady pressure distributions measured in wind tunnel tests. The final case adds a notional tail rotor and hub to the ROBIN fuselage and rotor for interactional aerodynamic analysis of a full configuration.
Joint Multi-Role Technology Demonstrator Fuselage Proof Test
Authors:   The Boeing Company, McCarthy Dennis ,   Sikorsky A Lockheed Martin Company, Toni Darryl ,   US Army AMRDEC, Spies Matt , Solari Dan , Maack Jasmina
Published: August 2024

Sikorsky, Boeing, and the U.S. Army Aviation and Missile Research Development and Engineering Center are developing the most technically advanced Joint Multi-Role (JMR) rotorcraft designed to meet aggressive Future Vertical Lift requirements. The Sikorsky-Boeing team has designed and is currently fabricating the SB>1 DEFIANTTM Technology Demonstrator (TD) Aircraft to integrate and mature advanced technologies to demonstrate speed, maneuverability, and weight efficiency on a full-scale vertical lift platform. The JMR TD is currently being assembled to support upcoming flight testing. The JMR TD fuselage and empennage are light-weight, hybrid carbon/epoxy designs which were fabricated and successfully ground tested in the past year clearly demonstrating an ample safe envelope for flight test. Contained herein is a discussion of test load derivation, test details, load calibration for flight test, and test data correlation validating the JMR TD analysis and design.
A Nondestructive Evaluation and Structural Health Monitoring Framework for X-COR Sandwich Composites
Authors:   Arizona State University, Li Guoyi ,   The Boeing Company, Huff Daniel , Neerukatti Rajesh , Rajadas Abhishek , Chattopadhyay Aditi
Published: August 2024

A combination of nondestructive evaluation (NDE) and structural health monitoring technique has been used to detect and localize in situ damage in X-COR sandwich composites. The NDE techniques, flash thermography and ultrasonic C-Scan, were used, and the inspection results showed promising capabilities as well as their inherent limitations. Subsequently, a guided wave based active interrogation technique was used to enable real-time damage detection and localization capabilities. Macro fiber composite and piezoelectric wafers were used for actuation and sensing, and the interaction of guided waves with the primary damage modes, delaminations and foam core separations, were studied. The results showed that delaminations lead to the guided wave mode conversion phenomenon within the material discontinuity area. A multidimensional signal processing technique, which was developed with a real-time and reference-free perspective, was used to analyze the converted wave modes in the time-space domain for damage localization. The results indicate that the converted wave mode is an effective indicator of in situ damage, especially when the received signal contains wave modes transmitted from multiple source locations.
Development and Initial Testing of the Tiltrotor Test Rig
Authors:   NASA Ames Research Center, Jr. C.W. , Sheikman A.L.
Published: August 2024

The NASA Tiltrotor Test Rig (TTR) is a new, large-scale proprotor test system, developed jointly with the U.S. Army and Air Force, to develop a new, large-scale proprotor test system for the National Full-Scale Aerodynamics Complex (NFAC). The TTR is designed to test advanced proprotors up to 26 feet in diameter at speeds up to 300 knots, and even larger rotors at lower airspeeds. This combination of size and speed is unprecedented and is necessary for research into 21st-century tiltrotors and other advanced rotorcraft concepts. The TTR will provide critical data for validation of state-of-the-art design and analysis tools.
Geochemical Characterization and Presence of Rare Earth Elements in the Recent Depositions at the Islands of the Eastern Bay of Bengal, Bangladesh
Authors: Deeba Farah , Rahman Syed Hafizur , Kabir Mohammad Zafrul , Rajib Mohammad
Published: August 2024

This study presents geochemical characterization, as well as, quantification of rare earth elements in the recent beach deposition at the two major islands of the eastern Bay of Bengal-Kutubdia and Moheshkhali. Placer sand samples from near surface depositions were analyzed by heavy mineral separation, mineralogical identification, chemical composition and elemental mapping. X-ray diffraction (XRD), X-ray fluorescence (XRF), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) were used to obtain these results. The heavy mineral concentration in different raw sand samples resulted by heavy liquid separation technique revealed that the average abundance of heavy minerals is 69.67% in Kutubdia island and 9.32% in Moheshkhali island, respectively. The X-ray patterns of Kutubdia and Moheshkhali sand samples show the presence of zircon, quartz, hematite, magnetite, ilmenite, chromite, kyanite, anatase, rutile and garnet. Chemical composition of heavy mineral sands from Kutubdia and Moheshkhali islands were analyzed using X-ray fluorescence method (XRF) for major oxides and trace elements. The concentration is of Na2O, MgO, Al2O3, SiO2, P, K2O, CaO, TiO2, V2O5, Cr2O3, MnO, Fe2O3, CoO, ZnO, SrO, Y2O3 ZrO2, Nb2O5, MoO3, HfO2, WO3, ThO2, U3O8, CeO2, Nd2O and Er2O3 were determined. A significant amount of various rare earth elements (REEs) in the elemental composition of few samples was also identified. The study is expected to be useful in the baseline and environmental aspects of both the islands.