Application of improved support vector machine regression analysis for medium- and long-term vibration trend prediction

Aircraft engine fault diagnosis plays a crucial role in cost-effective operations of aircraft engines. However, successful detection of signals due to vibrations in multiple transmission channels is not always easy to accomplish, and traditional tests for nonlinearity are not always capable of capturing the dynamics. Here we applied a new method of smooth support vector machine regression (SSVMR) to better fit complicated dynamic systems. Since quadratic loss functions are less sensitive, the constrained quadratic optimization could be transferred to the unconstrained optimization so that the number of constraint conditions could be reduced. Meanwhile, the problem of slow operation speed and large memory space requirement associated with quadratic programming could be solved. Based on observed input and output data, the equivalent dynamic model of aircraft engineers was established, and model verification was done using historical vibration data. The results showed that SSVMR had fast operation speed and high predictive precision, and thus could be applied to provide early warning if engine vibration exceeds the required standard

Effect of Nanoparticle Surface Modification and Filling Concentration on Space Charge Characteristics in TiO 2

This paper focuses on the space charge characteristics in TiO2/cross-linked polyethylene (XLPE) nanocomposites; the unmodified and modified by dimethyloctylsilane (MDOS) TiO2 nanoparticles were added to XLPE matrix with different mass concentrations (1 wt%, 3 wt%, and 5 wt%). The scanning electron microscope (SEM) showed that the MDOS coupling agent could improve the compatibility between TiO2 nanoparticles and XLPE matrix to some extent and reduce the agglomeration of TiO2 nanoparticles compared with unmodified TiO2 nanoparticles; the volume resistivity testing indicated that the volume resistivity of TiO2/XLPE nanocomposites was higher than Pure-XLPE and increased with the increase of filling concentrations. According to the pulsed electroacoustic (PEA) measurements, it was concluded that the space charge accumulation was suppressed by filling TiO2 nanoparticles and the distribution of electric field in samples was improved greatly. In addition, it was found that the injection of homocharge was more obvious in MDOS-TiO2/XLPE than that in UN-TiO2/XLPE and the homocharge injection decreased with the increase of filling concentration

Distinct fingerprints of charge density waves and electronic standing waves in ZrTe3_3

Experimental signatures of charge density waves (CDW) in high-temperature superconductors have evoked much recent interest, yet an alternative interpretation has been theoretically raised based on electronic standing waves resulting from quasiparticles scattering off impurities or defects, also known as Friedel oscillations (FO). Indeed the two phenomena are similar and related, posing a challenge to their experimental differentiation. Here we report a resonant X-ray diffraction study of ZrTe$_3$, a model CDW material. Near the CDW transition, we observe two independent diffraction signatures that arise concomitantly, only to become clearly separated in momentum while developing very different correlation lengths in the well-ordered state. Anomalously slow dynamics of mesoscopic ordered nanoregions are further found near the transition temperature, in spite of the expected strong thermal fluctuations. These observations reveal that a spatially-modulated CDW phase emerges out of a uniform electronic fluid via a process that is promoted by self-amplifying FO, and identify a viable experimental route to distinguish CDW and FO.Comment: 6 pages, 4 figures; supplementary information available upon reques

The fast light of CsI(Na) crystals

The responds of different common alkali halide crystals to alpha-rays and gamma-rays are tested in our research. It is found that only CsI(Na) crystals have significantly different waveforms between alpha and gamma scintillations, while others have not this phenomena. It is suggested that the fast light of CsI(Na) crystals arises from the recombination of free electrons with self-trapped holes of the host crystal CsI. Self-absorption limits the emission of fast light of CsI(Tl) and NaI(Tl) crystals.Comment: 5 pages, 11 figures Submit to Chinese Physics

Picoeukaryotic Diversity And Activity in the Northwestern Pacific Ocean Based on rDNA and rRNA High-Throughput Sequencing

Picoeukaryotes play an important role in the biogenic element cycle and energy flow in oligotrophic ecosystems. However, their biodiversity and activity are poorly studied in open ocean systems, such as the northwestern Pacific Ocean, which is characterized by a complex hydrological setting. Here, we investigated the diversity and activity of picoeukaryotes in the northwestern Pacific Ocean using high-throughput sequencing targeting the V9 region of 18S rDNA and rRNA. Our results showed that the DNA picoeukaryotic communities were mainly represented by Mamiellophyceae, MAST, MALV-II, Spirotrichea, Prymnesiophyceae, and MALV-I (69.33% of the total DNA reads), and the RNA communities were dominated by Spirotrichea, Mamiellophyceae, MAST, Pelagophyceae, and MALV-II (67.46% of the total RNA reads). The number of operational taxonomic units (OTUs) was significantly affected by temperature and salinity, and was decreased with the increasing nutrient concentration both in the DNA and RNA surveys. Significant differences were observed in the community composition between DNA-based and RNA-based molecular approaches, and these differences were mainly attributed to Mamiellophyceae, Spirotrichea, and Pelagophyceae. The RNA: DNA ratio was used as a proxy for relative metabolic activity of the individual OTUs. We found that the relative metabolic activities of Mamiellophyceae, Spirotrichea, and Pelagophyceae species in the northwestern Pacific Ocean were highly affected by the nutrient concentration, i.e., the NO3 + NO2 and SiO3 concentration. Overall, our study shed light on picoeukaryotic diversity and distribution in the northwestern Pacific Ocean and revealed the correlation between the diversity, relative metabolic activities of marine picoeukaryotes, and the environmental factors

Influence of Monodisperse Fe 3

Insulating oil modified by nanoparticles (often called nanofluids) has recently drawn considerable attention, especially concerning the improvement of electrical breakdown and thermal conductivity of the nanofluids. In this paper, three sized monodisperse Fe3O4 nanoparticles were prepared and subsequently dispersed into insulating vegetable oil to achieve nanofluids. The dispersion stability of nanoparticles in nanofluids was examined by natural sedimentation and zeta potential measurement. The electrical breakdown strength, space charge distribution, and several dielectric characteristics, for example, permittivity, dielectric loss, and volume resistivity of these nanofluids, were comparatively investigated. Experimental results show that the monodisperse Fe3O4 nanoparticles not only enhance the dielectric strength but also uniform the electric field of the nanofluids. The depth of electrical potential well of insulating vegetable oils and nanofluids were analyzed to clarify the influence of nanoparticles on electron trapping and on insulation improvement of the vegetable oil

Posterior hemivertebra resection without internal fixation in the treatment of congenital scoliosis in very young children

ObjectiveTo retrospectively analyze the feasibility and efficacy of posterior hemivertebra resection without internal fixation in the treatment of congenital scoliosis in very young children.MethodsSixteen cases of very young children with congenital scoliosis treated at our hospital from April 2000 to July 2019 were collected, including 8 cases of each sex, all of whom had type I/III congenital scoliosis and were operated on at a median (interquartile range) of 9.00 (7.75) months (range, 0.5–48 months) of age. All cases underwent posterior hemivertebra resection without internal fixation and wore orthopedic braces or plaster undershirts for more than six months after surgery, with a mean follow-up of 94.31 ± 65.63 months (range, 36–222 months).ResultsCoronal plane: the preoperative Cobb angle for the segmental curve was 39.50 ± 9.70° compared to postoperative (19.19 ± 8.56°) and last follow-up (14.94 ± 12.11°) (both P < 0.01); the preoperative Cobb angle for the main curve was 34.19 ± 14.34° compared to postoperative (17.00 ± 11.70°) and last follow-up (17.56 ± 16.31°) (both P < 0.01); the preoperative Cobb angle of the proximal compensated curve was 14.88 ± 9.62° compared to postoperative (7.88 ± 4.66°) and last follow-up (8.38 ± 8.36°) (both P < 0.05); and the preoperative Cobb angle of the distal compensated curve was 13.50° (10.50°) (range, 4°–30°) compared with postoperative 4.50° (9.25°) (range, −3° to 25°) and final follow-up 5.50° (9.50°) (range, −3° to 33°) (both P < 0.01). Sagittal plane: the difference in the preoperative Cobb angle was 10.00° (14.00°) (range, −31° to 41°) for segmental kyphosis compared to postoperative 14.00° (24.50°) (range, −6° to 46°) and last follow-up 17.00° (22.55°) (range, −40° to 56°), and these were not statistically significant (both P > 0.05). There was a tendency for the thoracolumbar kyphosis to worsen and the lumbosacral kyphosis to improve during the follow-up period.ConclusionPosterior hemivertebra resection without internal fixation is a feasible treatment for type I/III congenital scoliosis in very young children, but the correction of the sagittal deformity of the thoracolumbar spine is not satisfactory, and postoperative external fixation may require further improvement

Increasing Cytosine Base Editing Scope and Efficiency With Engineered Cas9-PmCDA1 Fusions and the Modified sgRNA in Rice

Base editors that do not require double-stranded DNA cleavage or homology-directed repair enable higher efficiency and cleaner substitution of targeted single nucleotides in genomic DNA than conventional approaches. However, their broad applications are limited within the editing window of several base pairs from the canonical NGG protospacer adjacent motif (PAM) sequence. In this study, we fused the D10A nickase of several Streptococcus pyogenes Cas9 (SpCas9) variants with Petromyzon marinus cytidine deaminase 1 (PmCDA1) and uracil DNA glycosylase inhibitor (UGI) and developed two new effective PmCDA1-based cytosine base editors (pBEs), SpCas9 nickase (SpCas9n)-pBE and VQR nickase (VQRn)-pBE, which expanded the scope of genome targeting for cytosine-to-thymine (C-to-T) substitutions in rice. Four of six and 12 of 18 target sites selected randomly in SpCas9n-pBE and VQRn-pBE, respectively were base edited with frequencies of 4–90% in T0 plants. The effective deaminase window typically spanned positions 1–7 within the protospacer and the single target C showed the maximum C-to-T frequency at or near position 3, counting the end distal to PAM as position 1. In addition, the modified single guide RNA (sgRNA) improved the base editing efficiencies of VQRn-pBE with 1.3- to 7.6-fold increases compared with the native sgRNA, and targets that could not be mutated using the native sgRNA were edited successfully using the modified sgRNA. These newly developed base editors can be used to realize C-to-T substitutions and may become powerful tools for both basic scientific research and crop breeding in rice

Ising Superconductivity and Quantum Phase Transition in Macro-Size Monolayer NbSe2

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have a range of unique physics properties and could be used in the development of electronics, photonics, spintronics and quantum computing devices. The mechanical exfoliation technique of micro-size TMD flakes has attracted particular interest due to its simplicity and cost effectiveness. However, for most applications, large area and high quality films are preferred. Furthermore, when the thickness of crystalline films is down to the 2D limit (monolayer), exotic properties can be expected due to the quantum confinement and symmetry breaking. In this paper, we have successfully prepared macro-size atomically flat monolayer NbSe2 films on bilayer graphene terminated surface of 6H-SiC(0001) substrates by molecular beam epitaxy (MBE) method. The films exhibit an onset superconducting critical transition temperature above 6 K, 2 times higher than that of mechanical exfoliated NbSe2 flakes. Simultaneously, the transport measurements at high magnetic fields reveal that the parallel characteristic field Bc// is at least 4.5 times higher than the paramagnetic limiting field, consistent with Zeeman-protected Ising superconductivity mechanism. Besides, by ultralow temperature electrical transport measurements, the monolayer NbSe2 film shows the signature of quantum Griffiths singularity when approaching the zero-temperature quantum critical point

Participação no grupo cooperativo do movimento da escola moderna: contributos para o desenvolvimento profissional docente

Dissertação apresentada à Escola Superior de Educação de Lisboa para obtenção do grau de Mestre em Ciências da Educação, especialidade Supervisão em EducaçãoO trabalho cooperativo entre os professores tem merecido destaque nos últimos anos, relacionando-se com ajuda mútua (Carneiro, Geller & Nitzke, 2008), onde todos trabalham com o intuito de alcançar objetivos pré definidos entre si (Dillenbourg, 1999) e de obter competências profissionais. Muito embora as práticas de trabalho individual ainda sejam uma tentação para os professores na atualidade há uma maior tendência para trabalharem colaborativamente nas escolas ou em grupos de formação organizados pelas associações de professores. Neste contexto, o estudo que apresentamos tem como finalidade compreender os processos de autoformação cooperada no contexto dos grupos cooperativos do Movimento da Escola Moderna (MEM) e o seu impacto no desenvolvimento profissional docente. Tendo em conta o objeto de estudo, identificaram-se as seguintes questões: i) Que motivações levam os professores a integrar os grupos cooperativos do MEM? ii) Como se organiza e desenvolve a autoformação cooperada nos grupos cooperativos do MEM? iii) Quais os aspetos positivos e constrangimentos identificados pelos professores no trabalho desenvolvido nos grupos cooperativos? iv) Quais as razões que levam os professores a permanecer e a abandonar a sua participação nos grupos cooperativos do MEM? v) Qual o impacto das experiências realizadas no contexto dos grupos cooperativos no desenvolvimento profissional docente? Para o efeito, contámos com a participação de seis professores pertencentes a um grupo cooperativo do MEM. Tendo como referência o objeto de estudo recorremos a uma metodologia de natureza qualitativa e privilegiámos como técnica de recolha de dados a entrevista semiestruturada. Para o tratamento dos dados sustentámo-nos na análise de conteúdo seguindo os passos recomendados para a análise de conteúdo por Bardin (2009). Os resultados do estudo permitiram constatar que o trabalho realizado no seio do grupo cooperativo promove o desenvolvimento profissional docente dado que fomenta a competência reflexiva sobre a prática pedagógica, bem como o desenvolvimento de outras competências da praxis, nomeadamente, a identificação de estratégias mais adequadas à resolução de problemas emergentes do quotidiano profissional do professor.Abstract The cooperative work between teachers has been receiving more attention over the last years, in relation with the mutual assistance (Carneiro, Geller & Nitzke, 2008), where everybody works with an aim to achieve predefined goals, which were created in relation to one another (Dillenbourg, 1999) and to obtain professional skills. Although individual work practices are still tempting to teachers, there is currently a greater trend to work as a group in schools or in training groups organized by teachers’ associations. In this context, this study aims to understand the cooperative self-training processes within the context of MEM’s cooperative groups and their impact in the professional teacher development. Considering the subject of study, the following questions were identified: i) What motivations lead the teachers to integrate MEM’s cooperative groups? ii) How is the cooperative self-training organized and how is it developed within in MEM’s cooperative groups? iii) What are the positive aspects and constraints identified by the teachers within the work developed in the cooperative groups? iv) What are the reasons that lead the teachers to stay or abandon its participation in MEM’s cooperative groups? v) What is the impact of experiences carried in the context of cooperative groups in the professional teacher development? For this purpose, we had the participation of six teachers belonging to one of MEM’s cooperative groups. Keeping the subject of study as a reference, we use a qualitative methodology and gave preference to the semi structured interview as the data collection technique. We based the data processing in the content analysis, following the recommended steps for content analysis by Bardin (2009). The study’s results allowed determining that the executed work promotes the teachers professional development, given that it increases the reflexive competence about the pedagogic practice, as well as the development of other competences of praxis, namely, the identification of the most adequate strategies for the resolution of emerging issues in the teacher’s professional everyday life.N/