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Wide-gap semiconductor SiC is generally considered as a superior candidate for high-radiation applications, due to its higher displacement energy for both Si and C lattice atoms. In this work, we find that the current gain ( $\beta $ ) of 4H-SiC bipolar junction transistors (BJTs) can severely deteriorate after neutron irradiation. Deep-level transient spectroscopy (DLTS) reveals that two major carrier-killer centers, Z1/2 and EH6/7, were produced in neutron-irradiated devices. Surprisingly, we find that the shallow Z1/2 center can play a dominant role over the deep EH6/7 defects in carrier recombination under high-injection conditions, which contributes to the unusual smaller hole capture cross section than that of the electron one, as indicated by the first-principles calculations. Finally, technology computer aided design (TCAD) simulation confirms that the enhanced carrier recombination from the Z1/2 centers is responsible for the degraded performance of SiC BJTs after irradiation. Our findings not only provide a deep insight into the underlying physics for displacement damage in SiC BJTs, but also are of interest for technological applications field related to high-energy particle irradiation or implantation.

The loss of metallic area is the most important factor affecting the quality of wire ropes. Therefore, it is very important to detect the loss of metallic area values of wire rope defects quickly and accurately. At present, the main flux detection approach is one of the most effective methods, and the detection signal is related directly to the metal cross-sectional area of the wire rope. However, when the defect width is less than a specific value, the existence of the leakage magnetic field means that the amount of the magnetic flux change is not only related to the loss of metallic area of the defect but also has a complex nonlinear relationship with the defect width. The resulting calculation is highly complex and means that the loss of metallic area cannot be determined quickly and quantitatively. This article presents an in-depth study of the theoretical basis of magnetic flux detection, analyzes the problems of the main magnetic flux detection method and their causes, and proposes a method to improve main magnetic flux detection using the axial magnetic flux density. Simulation analysis and experimental results show that the method presented in this article can be used to calculate the loss of metallic area values of defects quickly and accurately without the need for complex calculation processes.

The magnetostrictive torsional wave sensors are focused on magnetostrictive patch transducer. These transducers use a material with a high magnetostrictive coefficient on the pipe surface to increase the excitation efficiency for detection. However, this approach loses the noncontact characteristic of the magnetostrictive guided waves. To enable noncontact detection in small-diameter pipes using torsional waves, a magnetostrictive torsional wave sensor with a tile-shaped magnet is designed in this article. By optimizing the structure of the static magnetic field, the circumferential magnetic field of the pipe is enhanced. The amplitude and the signal-to-noise ratio of the guided waves are also improved. The tile-shaped magnet with shoving magnetic structure is used to realize a uniform circumferential magnetic field. A solenoid coil is used to provide the axial dynamic magnetic field to generate the torsional waves that are used to detect the pipes. In this article, the principles of torsional wave sensors are studied first. The static magnetic field results for different structures are then analyzed via simulations. Finally, experiments show that the magnetostrictive torsional wave sensors with the tile-shaped magnets can realize the excitation and detection of torsional waves in pipes, which can be used to detect the locations and sizes of defects in these pipes.

Defects are crucial in determining the overall physical properties of semiconductors. Generally, the charge-state transition level (TEL), one of the key physical quantities that determines the dopability of defects in semiconductors, is temperature dependent. However, little is known about the temperature dependence of TEL, and, as a result, almost all existing defect theories in semiconductors are built on a temperature-independent approximation. In this article, by deriving the basic formulas for temperature-dependent TEL, we have established two fundamental rules for the temperature dependence of TEL in semiconductors. Based on these rules, surprisingly, it is found that the temperature dependences of TEL for different defects are rather diverse: it can become shallower, deeper, or stay unchanged. This defect-specific behavior is mainly determined by the synergistic or opposing effects between free energy corrections (determined by the local volume change around the defect during a charge-state transition) and band edge changes (which differ for different semiconductors). These basic formulas and rules, confirmed by a large number of state-of-the-art temperature-dependent defect calculations in GaN, may potentially be widely adopted as guidelines for understanding or optimizing doping behaviors in semiconductors at finite temperatures.

Wire rope is a chain structure, and the strength of the weakest link is the strength of the entire wire rope. The axial resolution of loss of metallic cross-sectional area (LMA) detection using the induction coil is related to the length of the detection probe, which is usually greater than or equal to the length of the probe. Improving the axial resolution is an important technical indicator of the LMA. In this article, through theoretical analysis based on the principle of magnetic aggregation and 3-D transient magnetic field simulation, a particular kind of magnetic aggregation structure used for winding coil is proposed and optimized. Simulation and experimental results show that for wire rope LMA detection adding the proposed magnetic aggregation structure, the defect signals’ signal-to-noise ratio (SNR) is improved and the axial resolution of the LMA is increased to 20 mm. At the same time, the cross-sectional area loss can be quantitatively evaluated by the magnetic flux peak-to-peak value. The difference between the maximum and minimum values of the derivative of the magnetic flux signal can be used to evaluate the defect length.

Magnetostrictive guided waves are widely used in nondestructive testing and structural health monitoring of pipes to ensure their integrity. These guided waves are mechanical waves, and if the natural frequencies of the pipe are used as excitation frequencies, the mechanical vibration amplitude can be enhanced, which will then improve the amplitude of the guided waves. Comparison of the various methods to determine the natural frequencies of pipes shows that the white noise signals remain relatively smooth in both time and frequency domains. White noise has a wide bandwidth and uniform energy distribution. It does not require high energy within a short time period, so it is easy to generate. In this article, white noise is used to determine the natural frequencies of pipes. Comparison of the white noise spectra produced by analog and digital circuits shows that the energy spectrum of white noise produced by the analog circuit is high and uniform, so the analog circuit is used as the white noise source and this noise is loaded onto a magnetostrictive sensor. The detected signal spectrum is then analyzed and the frequencies with high power density spectra are determined to be the natural frequencies. The natural frequencies of the pipeline detected using white noise are compared with the results of modal analysis. Simulation results and experimental results demonstrate that the use of white noise allows the natural frequencies of pipes to be determined quickly and accurately. These natural frequencies can be used in magnetostrictive guided-wave nondestructive testing.

Identifying atomic configurations of impurities in semiconductors is of fundamental interest and practical importance in designing electronic and optoelectronic devices. C impurity acting as one of the most common impurities in GaN, it is believed for a long time that it substitutes at Ga site forming CGa with +1 charge-state in p-type GaN, while it substitutes at N site forming CN with -1 charge-state in n-type GaN. However, by combining x-ray absorption spectroscopy and first-principles simulations, we observed that C is mainly occupying the N site rather than the Ga one in p-GaN. We further reveal that this is due to an H-induced EF-tuning effect. During growth, the existing H can passivate Mg dopants and upshifts the EF to the upper region of bandgap, leading to the CN formation. After the p-type activation by annealing out H, although the EF is pushed back close to the valence band maximum, whereas the extremely large kinetic barrier can prevent the migration of C from the metastable CN site to ground-state CGa site, hence stabilizing the CN configuration. Additionally, the CN with neutral charge-state ([Formula: see text]) in the p-GaN is further observed. Therefore, the real C-related hole-killer in p-type GaN could be CN rather than the commonly expected CGa. Our work not only offers the unambiguous evidence for the C defect formation in p-GaN but also contributes significantly to an in-depth understanding of the C-related hole-killers and their critical role on electrical and optoelectrical properties of p-GaN and even p-AlGaN.

Prunus mume is one of the most important woody perennials for edible and ornamental use. Despite a substantial variation in the flowering phenology among the P. mume germplasm resources, the genetic control for flowering time remains to be elucidated. In this study, we examined five blooming time-related traits of 235 P. mume landraces for 2 years. Based on the phenotypic data, we performed genome-wide association studies, which included a combination of marker- and gene-based association tests, and identified 1,445 candidate genes that are consistently linked with flowering time across multiple years. Furthermore, we assessed the global transcriptome change of floral buds from the two P. mume cultivars exhibiting contrasting bloom dates and detected 617 associated genes that were differentially expressed during the flowering process. By integrating a co-expression network analysis, we screened out 191 gene candidates of conserved transcriptional pattern during blooming across cultivars. Finally, we validated the temporal expression profiles of these candidates and highlighted their putative roles in regulating floral bud break and blooming time in P. mume. Our findings are important to expand the understanding of flowering time control in woody perennials and will boost the molecular breeding of novel varieties in P. mume.

Hierarchical arrays of ZnO/Si nanowires were prepared through very convenient two-step solution method on silicon substrates. The tree-like nanowire structures showed high crystal quality, where well aligned Si nanowires were grown vertical to the substrate surface, whereas uniform assembly of branched ZnO nanowires was grown normal to the Si nanowires (backbones). Raman analysis indicated that among all the specimens having identical chemical compositions and dimensions but different forms (thin films or nanowires), Ag-decorated hierarchical arrays of ZnO/Si nanowires possessed the highest intensity peak in surface enhanced Raman scattering spectra. Such arrays demonstrated exceptional ability of detecting Rhodamine 6 G, limiting to a value as low as 1×10−8 mol/L and an enhancement factor up to 1.5 × 104. Both, experimental designing and band structure analysis indicated that electromagnetic effect of the localized surface plasmon resonance of Ag nanoparticles caused eight times enhancement, whereas chemical effect of hierarchical arrays of ZnO/Si nanowires played a more critical role in the high Raman sensitivity. Our results would be helpful to better understand the enhancement mechanisms and meanwhile, could be extended for further potential applications of hierarchical semiconducting nanowires.

Additional file 6: Fig. S6. Heatmap of average RSCU scores estimated for different codons in five Rosaceae PEBP gene lineages.

Additional file1: Fig. S1. Phylogenetic trees were constructed using three different algorithms.

Additional file 9: Fig. S9. Relative expression of PEBP family genes in floral bud, leaf, stem, and root tissues of P. mume.

Additional file 5: Fig. S5. Distribution and collinearity of PEBP family genes within genomes of nine Rosaceae species.

Additional file4: Fig. S4. Inter-genomic synteny blocks between species.

Additional file 3: Fig. S3. Protein sequence alignment of FT and TFL1-like proteins in Arabidopsis and nine Rosaceae species.

Background Phosphatidylethanolamine-binding proteins (PEBPs) constitute a common gene family found among animals, plants and microbes. Plant PEBP proteins play an important role in regulating flowering time, plant architecture as well as seed dormancy. Though PEBP family genes have been well studied in Arabidopsis and other model species, less is known about these genes in perennial trees. Results To understand the evolution of PEBP genes and their functional roles in flowering control, we identified 56 PEBP members belonging to three gene clades (MFT-like, FT-like, and TFL1-like) and five lineages (FT, BFT, CEN, TFL1, and MFT) across nine Rosaceae perennial species. Structural analysis revealed highly conserved gene structure and protein motifs among Rosaceae PEBP proteins. Codon usage analysis showed slightly biased codon usage across five gene lineages. With selection pressure analysis, we detected strong purifying selection constraining divergence within most lineages, while positive selection driving the divergence of FT-like and TFL1-like genes from the MFT-like gene clade. Spatial and temporal expression analyses revealed the essential role of FT in regulating floral bud breaking and blooming in P. mume. By employing a weighted gene co-expression network approach, we inferred a putative FT regulatory module required for dormancy release and blooming in P. mume. Conclusions We have characterized the PEBP family genes in nine Rosaceae species and examined their phylogeny, genomic syntenic relationship, duplication pattern, and expression profiles during flowering process. These results revealed the evolutionary history of PEBP genes and their functions in regulating floral bud development and blooming among Rosaceae tree species.

The diameter of fine steel wire rope (FSWR) is generally a few millimeters. Its magnetic flux leakage (MFL) signal is weak, and the number of magnetic sensors installed for defect detection is limited because of the small diameter. In FSWR production workshops, different kinds of machinery work together, deteriorating the power quality and making the spatial electromagnetic environment complex; the weak MFL is thus interfered with further. It is difficult to carry out online nondestructive testing (NDT) of FSWR in the process of manufacturing. In this paper we present a novel MFL method for FSWR NDT in a strong electromagnetic interference environment. We use a three-dimensional finite element method (FEM) to analyze the MFL signals. A simplified magnetic circuit is presented to excite the FSWR; the circuit comprises two half-sized radial magnetizing ring NdFeB magnets, and because there is no need for a magnetic yoke, the device is simple and light. A single Hall sensor is used to measure the flux leakage field. A stable performance power system is designed for the NDT power supply, which is not only resistant to voltage sags, but also has very low output noise. To enhance the signal-to-noise ratio (SNR) of the MFL defects signal, a signal conditioning and processing circuit are designed to enhance the detectability of signals in MFL data. The novel and small FSWR NDT system realizes on-line testing in an environment of strong electromagnetic interference, and for the experiment with a 1.5-mm-diameter wire rope twisted by 19 wires, the minimum damage of a pit on half of a wire can be identified.

Inductive coil is used as the nondestructive testing sensor of a wire rope or a pipe, because of its low cost and high durability. However, the winding structure is complex and difficult to design during the field test. Hundreds or even thousands of turns are needed to improve the signal to noise ratio (SNR) and the data processing is cumbersome. In this paper, based on the theoretical analysis and 3D transient magnetic field simulation, a kind of iron core is presented as coil winding skeleton for the wire rope nondestructive testing. Additional iron core plays a role of magnetism concentration, where the magnetic flux leakage (MFL) path is changed and the MFL of the defect is converged to the core. Therefore, the SNR of the coil which is wound on the iron core is improved, and the coil winding skeleton is simplified with the iron core structure optimization. Meanwhile, the influence of the coil cross-section area on the test result analysis is eliminated, and the influence of the lift-off distance between coil and wire rope on the detection result is also reduced. Finally, it is proved by experiment that the SNR of coil with the iron core proposed in this paper is increased almost six times, which makes it easier for defect analysis.

Enhancing the dopability of semiconductors via strain engineering is critical to improving their functionalities, which is, however, largely hindered by the lack of basic rules. In this study, for the first time, we develop a universal theory to understand the total energy changes of point defects (or dopants) with different charge states under strains, which can exhibit either parabolic or superlinear behaviors, determined by the size of defect-induced local volume change (Δ V). In general, Δ V increases (decreases) when an electron is added (removed) to (from) the defect site. Consequently, in terms of this universal theory, three basic rules can be obtained to further understand or predict the diverse strain-dependent doping behaviors, i.e., defect formation energies, charge-state transition levels, and Fermi pinning levels, in semiconductors. These three basic rules could be generally applied to improve the doping performance or overcome the doping bottlenecks in various semiconductors.

Silicon carbide (SiC) has been considered one of the most important wide bandgap semiconductors for both scientific interest and technological applications. The existence of stacking faults induced inclusions, originated from the “wrong” stacking sequences of Si–C bilayers, is a general feature in SiC. Until now, however, a systematical understanding of the role of cubic inclusions (CIs) in the electronic and doping properties of hexagonal SiC is still lacking, which may prevent further improvement of its electronic performance. In this article, using advanced first-principles calculations, we have systematically studied the stability, electronic structures, and doping properties of hexagonal SiC with CIs. First, we find that the CIs in SiC have rather low formation energies but high kinetic stability. Second, we find that the electronic structures of SiC can be dramatically tuned by the ratio of CIs in SiC. Third, we demonstrate that the CI-induced band offset and the dipole-discontinuity-induced dipole field in the system can give rise to different ground-state doping sites for dopants at their different charge-states, which can consequently result in novel doping-site-dependent charge-state transition levels (CTLs). Meanwhile, the intrinsic dipole field can dramatically enhance the structural relaxation effects during the ionization of the dopants, which can push the CTLs deeper inside the bandgap compared to the case without CIs. Our findings suggest that CIs could play unusual roles in determining the overall electronic and doping properties of SiC and other similar semiconductors.

The detection of internal and external defects in steel wire rope is a very important task. Current nondestructive testing methods cannot distinguish between internal and surface defects, and cannot determine the quantitative characteristics of internal defects. This paper first analyzes the advantages and disadvantages of induction coil magnetic flux detection and Hall sensor-based magnetic flux leakage detection. The problem of simultaneous detection using these two methods is then solved, and a new quantitative detection method is proposed for internal and surface defects in wire rope. Finally, a calculation method that uses a two-step training algorithm to establish two sets of neural networks is proposed. Results from simulations and experiments verify that the proposed method can accurately distinguish between internal and surface defects in wire rope, and can also quantitatively detect the width, cross-sectional loss rate, and depth of the defects.

Phosphatidylethanolamine-binding proteins (PEBPs) are a common gene family found among animals, plants and microbes. Plant PEBP proteins play an important role in regulating flowering time, as well as seed and bud dormancy. PEBP proteins can be divided into three major clades: FLOWERING LOCUS T-like (FT-like), TERMINAL FLOWER1-like (TFL1-like), and MOTHER OF FT AND TFL1-like (MFT-like). Though PEBP family genes have been well studied in Arabidopsis and other model species, their functional role in perennial trees is not fully understood. To characterize the evolution of PEBP genes and their role in flowering control among Rosaceae species, we identified a total of 46 PEBP members in seven Rosaceae species. Sequence and gene structure analysis revealed highly conserved intron/exon distributions and featured motifs among Rosaceae PEBP proteins. Analysis of synonymous/nonsysnonymous substitution rates showed purifying selection constraining divergence within most lineages, while positive selection appears to have driven divergence of FT-like and TFL-like genes from the MFT clade. The expression of PEBP genes varied among different tissues indicating their functional divergence during gene family evolution. Furthermore, by employing a weighted gene co-expression network approach, we inferred a putative FT regulatory module essential for dormancy release and floral induction in P. mume. Our study sheds new light on the evolution of PEBP genes and their functional roles in controlling flowering time among Rosaceae tree species.

The traditional electromagnetic nondestructive testing probe structure includes magnets and yokes, and forms an excitation circuit with the wire rope. The wire rope is excited to a near-saturation state. The magnetic sensor is used for qualitative or quantitative detection of leakage flux from defects. The yoke is essential in the traditional excitation circuit. However, the use of a yoke in a detection probe of such an excitation mechanism has a large volume and is heavy. Through simulation, we improved the magnetization direction and installation position of the permanent magnets. Without a yoke, the permanent magnets were placed in the direction of co-extrusion. The wire rope was excited to near saturation in the permanent-magnet part. However, there was no excitation in the center of the two permanent magnets. The magnetic sensor was placed in the center of two permanent magnets to pick up the magnetic-flux-leakage signal for nondestructive testing of the steel wire rope. This method simplifies the permanent-magnet magnetization. The excitation probe with the yoke removed was also reduced in volume and weight. Through experimental testing, it was proven that the proposed shoving-magnetic-field structure and the traditional detection structure have the same detection effect.

The traction technology used for elevators in the current market has gradually changed from wire rope-type to steel strip technology. The traditional nondestructive testing of elevator wire ropes mainly involves manual observation. The steel strip is composed of both rubber and multiple wire ropes. Therefore, manual observation can only detect wear of the rubber surface or wire leakage and cannot detect internal defects in the wire ropes. The wire ropes in the steel strip are thus generally electrified to determine whether or not any of these wire ropes have broken. This approach cannot detect whether the wire ropes contain small defects. In this paper, different modes are designed for magnetostrictive guided wave sensors according to the structural characteristics of elevator steel strips. The different sensor modes are determined by comparing the detection effects of the various sensors. Finally, the magnetostrictive guided wave sensors are used to detect defects in the steel strip. The experiments show that the sensor designed in this paper can detect defects within the steel strip effectively.

As a wide bandgap semiconductor, SiC holds great importance for high temperature and high power devices. It is known that the intrinsic defects play key roles in determining the overall electronic properties of semiconductors; however, a comprehensive understanding of the intrinsic defect properties in the prototype 4H-SiC is still lacking. In this study, we have systematically investigated the electronic properties and kinetic behaviors of intrinsic point defects and defect complexes in 4H-SiC using advanced hybrid functional calculations. Our results show that all the point defects in 4H-SiC have relatively high formation energies, i.e., low defect concentrations even at high growth temperatures. Interestingly, it is found that the migration barriers are very high for vacancies (>3 eV) but relatively low for interstitial defects (∼1 eV) in SiC. Meanwhile, the diffusion energy barriers of defects strongly depend on their charge states due to the charge-state-dependent local environments. Furthermore, we find that VSi in SiC, a key defect for quantum spin manipulation, is unstable compared to the spin-unpolarized VC–CSi complex in terms of the total energy (under p-type conditions). Fortunately, the transformation barrier from VSi to VC–CSi is as high as 4 eV, which indicates that VSi could be stable at room (or not very high) temperature.

Epigenetic changes caused by methylcytosine modification participate in gene regulation and transposable element (TE) repression, resulting in phenotypic variation. Although the effects of DNA methylation and TE repression on flower, fruit, seed coat, and leaf pigmentation have been investigated, little is known about the relationship between methylation and flower color chimerism. In this study, we used a comparative methylomic&ndash, transcriptomic approach to explore the molecular mechanism responsible for chimeric flowers in Prunus mume &ldquo, Danban Tiaozhi&rdquo, High-performance liquid chromatography-electrospray ionization mass spectrometry revealed that the variation in white (WT) and red (RT) petal tissues in this species is directly due to the accumulation of anthocyanins, i.e., cyanidin 3,5-O-diglucoside, cyanidin 3-O-glucoside, and peonidin 3-O-glucoside. We next mapped the first-ever generated methylomes of P. mume, and found that 11.29&ndash, 14.83% of the genomic cytosine sites were methylated. We also determined that gene expression was negatively correlated with methylcytosine level in general, and uncovered significant epigenetic variation between WT and RT. Furthermore, we detected differentially methylated regions (DMRs) and DMR-related genes between WT and RT, and concluded that many of these genes, including differentially expressed genes (DEGs) and transcription factor genes, are critical participants in the anthocyanin regulatory pathway. Importantly, some of the associated DEGs harbored TE insertions that were also modified by methylcytosine. The above evidence suggest that flower color chimerism in P. mume is induced by the DNA methylation of critical genes and TEs.

Devices used for nondestructive testing of wire rope often include a guide wheel, which is connected to an encoder to measure the running distance of the wire rope and to provide information about defect positions. However, in use, problems with the guide wheel such as contact jittering, slipping, idling, and bouncing cause encoder pulse loss, which affects the location measurements and quantitative analysis of the defects. Also, the wire rope running at high speed is a safety problem. However, these issues can be avoided by using the unique winding of the wire rope to provide a strand wave signal. Using wave signal processing, the distance traveled by the wire rope can be measured. Then, a phase-locked loop locks and multiplies the frequency of the strand wave signal. The multiple-frequency signal is used as a trigger signal for equal distance sampling of the wire rope. This method not only replaces the use of guide wheels and encoders when the wire rope is running at uniform velocity, but also improves the precision of the positioning and quantitative analysis of defects.