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Background The treatment of completely displaced midshaft clavicle fractures is still controversial, especially Robinson 2B fractures. Titanium elastic nail (TEN) fixation is a good option for simple fractures, but there are no reports on its use in complex fractures. The aim of this study was to present a surgical method using the Nice knot-assisted TEN fixation to treat Robinson 2B midshaft clavicular fractures.Methods A retrospective analysis of 29 patients who underwent fixation with TEN and had a 1-year postoperative follow-up between 2016 and 2020 was performed. The fractures were classified as Robinson type 2B1 in 17 cases and type 2B2 in 12 cases. Length of the incision, postoperative shoulder function, Disability of Arm Shoulder and Hand (DASH) score, complications, and second surgical incision length were recorded.Results The length of the incision was 2–6 cm (mean, 3.7 cm). All incisions healed by first intention, and no infection or nerve injury occurred. The Constant score was 92–100 (mean, 96) and the DASH score was 0-6.2 (mean, 2.64). ESIN bending and hypertrophic nonunion occurred in one case (3.4%) and implant irritation occurred in four (13.8%) after operation. Internal fixators were removed at 12–26 months (mean, 14.6 months) after operation, and the length of the second incision was 1-2.5 cm (mean, 1.3 cm).Conclusions Intramedullary clavicle fixation with TEN is an ideal surgical technique. Nice knot-assisted fixation effectively stabilizes multifragmentary fractures, thereby achieving fracture healing. Surgeons should consider this technique in cases of Robinson 2B midshaft clavicular fractures.Trial registration: Retrospectively registered. This study was approved by the Ethics Committee of Wuxi Ninth People's Hospital (LW20220021).

Electrochemical water oxidation enables the conversion of H2O to H2O2. It holds distinct advantages to the O2 reduction reaction, which is restricted by the inefficient mass transfer and limited solubility of O2 in aqueous media. Nonetheless, most reported anodes suffer from high overpotentials (usually >1000 mV) and low selectivity. Electrolysis at high overpotentials often causes serious decomposition of peroxides and leads to declined selectivity. Herein, we report a ZnGa2O4 anode with dual active sites to improve the selectivity and resist the decomposition of peroxides. Its faradaic efficiency reaches 82% at 2.3 V versus RHE for H2O2 generation through both direct (via OH−) and indirect (via HCO3−) pathways. The percarbonate is the critical species generated through the conversion of bicarbonate at Ga-Ga dual sites. The peroxy bond is stable on the surface of the ZnGa2O4 anode, significantly improving faradaic efficiency.

Due to the complex and harsh climate environment in Northwest China, the external insulation of power lines and high-speed train are exposed to strong wind-sand environment all year round, which brings severe challenges to the external insulation design and protection of the electric systems. Based on the theories of streamer discharge, the plate-plate electrode was taken as the analysis object, and a theoretical physical model of the strong wind-sand dielectric discharge is established. In this model, the analytical expressions of electron ionization coefficient and positive ion generation coefficient in a wind-sand environment are deduced considering the combined effects of the airflow velocity, the distortion of the electric field caused by sand particles, and the electrons captured by sand particles in the discharge process; furthermore, the streamer breakdown criterion in wind-sand environment is proposed. Research results can provide an important theoretical basis for the quantitative calculation of the breakdown voltage and the external insulation protection in a strong wind-sand environment.

Recently, a Na+-binding aptamer was reported to be embedded in a few RNA-cleaving DNAzymes, including NaA43, Ce13d, and NaH1. The Na+ aptamer consists of multiple GG stretches, which is a prerequisite for the formation of G-quadruplex (G4) structures. These DNAzymes require Na+ for activity but show no activity in the presence of K+ or other metal ions. Given that DNA can selectively bind K+ by forming a G4 structure, this work aims to answer whether this Na+ aptamer also uses a G4 to bind Na+. Through comparative ThT fluorescence spectrometry studies, while a control G4 DNA exhibited notable fluorescence enhancement up to 5 mM K+ with a Kd of 0.28 ± 0.06 mM, the Ce13d DNAzyme fluorescence was negligibly perturbed with similar concentrations of K+. Opposed to this, Ce13d displayed specific remarkable fluorescence decrease with low millimolar concentrations of Na+. NMR experiments at two different pH values suggest that Ce13d adopts a significantly different conformation or equilibrium of conformations in the presence of Na+ versus K+ and has a more stable structure in the presence of Na+. Additionally, absence of characteristic G4 peaks in one-dimensional 1H NMR suggest that G4 is not responsible for the Na+ binding. This hypothesis is confirmed by the absence of characteristic peaks in the CD spectra of this sequence. Therefore, we concluded that the aptamer must be selective for Na+ and that it binds Na+ using a structural element that does not contain G4.

We proposed a dual-band polarization-insensitive metamaterial absorber consisting of merely the square metallic patch and a continuous metallic ground separated by a middle dielectric layer. Two resonance peaks derived from `the fundamental resonance (with 97% absorbance) and the surface lattice resonance (with 99% absorbance) are realized. It is different from previous work that the dual-band response is obtained by combining two resonances of different sizes. Moreover, a first-order diffraction mode of grating predicts the resonance wavelength of the proposed absorber. The surface electromagnetic field distributions of the unit-cell structure reveal the physical origin of the dual-band absorption. Importantly, the first absorption peak results from surface lattice resonance with narrow line-width has large sensitivity perform and high-quality factor, which has significant potential in the application of the biosensors and monitoring.

With the rapid development of large-scale distributed renewable energy in China, the load factor of distribution transformer increases year by year, this directly become a new challenge to the load capacity of the transformer. Once subjected to this condition for a long time will have an impact on the hotspot temperature and consequently, the useful life of the transformer. In this regard, load capacity assessment of the distribution transformer becomes an essential work for unit upgrading or even replacement. This article systematically summarized the evaluation methods of transformer load capacity, as well as the load capacity prediction and dynamic capacity enhancement strategies of transformer. Discussions for the future work regarding this topic are also carried out.

The interactions between two or more particles and the calculation of the local electric field are widely applied in many fields, such as those of insulation, biology, medicine, and microfluidics. The dipole approximation model, which is a classical electric field calculation method, has been widely used in many fields to solve for the local electric field in a multi-particle system, but it does not consider the interactions between particles; as a result, it is easily limited by the calculation situation, and it generates a large calculation error when the distance between particles is small. Based on the physical essence of an interaction between two particles, a concept of the mutual-coupling dipole moment caused by the interactions between particles is defined for the first time. Moreover, by combining the calculation process of the dipole moment and the electric field of polarization, a novel mutual-coupling dipole model considering the interactions between particles is proposed in this paper, and analytical expressions of the local electric field that consider the interaction between two particles are obtained, thus compensating for the large error in the electric field calculation caused by the dipole approximation model when the distance between particles is small. In this paper, a mutual-coupling dipole model considering particle interactions is proposed. This model can effectively reflect the interactions between particles when the distance between particles D/R is less than 0.6 and accurately calculate the local electric fields of the particles. These results can be effectively used to investigate the interactions between particles and the control of particles in electric fields in many fields, such as in the calculation of the insulation of mixed dielectrics, the microscopic transport of medicines, the control of bio-cells and micro-fluids in electric fields, and environmental governance.

In nature, the properties of matter are ultimately governed by the electronic structures. Quantum chemistry (QC) at electronic level matches well with a few simple physical assumptions in solving simple problems. To date, machine learning (ML) algorithm has been migrated to this field to simplify calculations and improve fidelity. This review introduces the basic information on universal electron structures of emerging energy materials and ML algorithms involved in the prediction of material properties. Then, the structure-property relationships based on ML algorithm and QC theory are reviewed. Especially, the summary of recently reported applications on classifying crystal structure, modeling electronic structure, optimizing experimental method, and predicting performance is provided. Last, an outlook on ML assisted QC calculation towards identifying emerging energy materials is also presented.

Moisture damp has been identified as one of the most harmful agents of multilayer composited insulation, which can seriously accelerate its degradation, cause unexpected failure, and even lead to catastrophic accidents. This article proposes a nonintrusive method for moisture inspection of multilayer insulation structure based on terahertz (THz) technology with a focus on the cable terminal of the electric multiple units (EMUs). First, a three-layer scattering model is established based on the actual structure of the composite cable terminal, and theoretical analysis is performed to reveal the potential application mechanism. Based on that, an artificial model of a three-layer structure is then built on which the insulation damp test is carried out. Finally, the THz spectrum and THz imaging tests are performed. Results show that the frequency-domain signal can effectively identify the moisture inside the multilayer composited insulation. The imaging results in the frequency domain of the sample can accurately determine the geometric parameters of the damp area. By further analyzing the time-domain spectroscopy, the thickness of insulation affected by moisture can be identified quantitatively. This article verifies the feasibility of THz technology in inspecting the moisture dampness of multilayer composite insulation and its potential application in the damp condition assessment of EMU cable terminals.

The low absorptivity of quantum dot nano-structures cannot meet the requirements for high-performance next-generation Thz detectors which can be used for environmental pollution detection. In this study, a novel metal-semiconductor-metal (MSM) cavity structure with a square hole array instead of a traditional planar metal electrode was developed to improve and enhance the absorptivity of a quantum dot Thz detector. The possible modes and loss problems in the metal resonant cavity were analyzed using the finite-element transmission matrix, the eigenvector method, and Kirchhoff diffraction theory. The results demonstrate that the MSM cavity structure introduced in the detector can enhance absorption up to 8.666 times higher than that of the conventional counterpart.

Background Grade III open fractures of the lower extremity are serious injuries and are difficult to reconstruct. The optimal treatment for such injuries is unclear. We aimed to determine the safety and efficacy of orthoplastic reconstruction, using a primary free anterolateral thigh flap combined with the Masquelet technique and internal fixation for Gustilo grade IIIB/C open tibial fractures. Methods From April 2018 to April 2019, 15 patients, ranging from 19 to 72 years old, with Gustilo grade IIIB/C open fractures were treated using a primary free anterolateral thigh flap combined with the Masquelet technique and internal fixation. This involved wound debridement and removal of free bone fragments, followed by bone cement packing of the defect, external fixation, and vacuum sealing drainage treatment. The final stage involved switching from external to internal fixation and wound repair using a free anterolateral thigh flap. Repair time ranged from 2 to 7 days. Flap size ranged from 25 × 15 cm2 to 13 × 7cm2. Hospital stay ranged from 11 to 50 days (mean, approximately 33.3 days). Bone cement was removed after 6–19 weeks and replaced with autogenic cancellous bone. Results All flaps survived without incident. One patient experienced a wound infection, but there were no deep infections. For all patients, bone union was achieved after 4 to 7 months. Conclusion The use of a primary free anterolateral thigh flap combined with the Masquelet technique and internal fixation is a safe and effective procedure for reconstruction of Gustilo grade IIIB/C open fractures.

Electrically controlled lateral shift by an electro-optic crystal prism is studied theoretically. The resonance point of excitation of guided-wave surface plasmon resonance (GWSPR) can be controlled by altering the refractive index of the prism. That is to say, the positions corresponding to the least reflectivity and the largest lateral shift could be conveniently modulated while the lithium niobate prism is operated in an external electric field. The maximal lateral shift is obtained at the excitation of GWSPR when the thickness of the silver film is optimized. The results of numerical simulations confirm theoretical calculation.

Background Despite advances in microsurgical techniques of flap transfer, complex upper extremity trauma reconstruction remains a challenge for surgeons. This study aimed to present the outcomes in using flaps in the subacute reconstruction of complex upper extremity injuries. Methods From July 2013 to December 2016, 35 patients ranging in age from 23 to 69 years with complicated upper extremity traumatic injuries were treated using flap reconstruction in subacute period. The number and causes of injury were 12 machine crush injuries, 18 machine strangulation injuries, two chainsaw accidents, two traffic accidents, and one incident of heavy bruising. Thirty-five patients underwent flap procedures, including 24 anterolateral thigh flaps (68.57%), five latissimus dorsi flaps (14.29%), and six lateral arm flaps (17.14%). Flap sizes ranged from 3 × 4 to 42 × 16 cm2. The mean time of flap reconstruction was 14 days (range 5–29). During postoperative follow-up, flap appearance, sensory recovery, scarring and satisfaction were assessed. Results The overall flap survival rate was 94.3%.Two flaps developed partial necrosis, both of which were later treated with skin grafting. Traumatic wound infections occurred in three patients. All upper limb injuries were completely covered. The follow-up periods ranged from 18 to 62 months with an average of 2.9 months. All skin flap textures were soft with varying degrees of pigmentation. Flap sensory recovery was S1 in three cases, S2 in eight cases, S3 in 15 cases, and S4 in nine cases. There were no donor site complications other than three cases with scar hyperplasia. Conclusions The severe upper limb soft tissue defects still achieved satisfactory function and appearance with negligible complications and low amputation rates during the subacute period.

Deposition of platinum (Pt) monolayers (PtML) on Au substrate represents a robust strategy to maximally utilize the Pt atoms and meanwhile achieve high catalytic activity towards methanol oxidation reaction for direct methanol fuel cells owing to a substrate-induced tensile strain effect. However, recent studies showed that PtML on Au substrate are far from perfect smooth monoatomic layer, but actually exhibited three-dimensional nanoclusters. Moreover, the PtML suffered from severe structural instability and thus activity degradation during long-term electrocatalysis. To regulate the growth of PtML on Au surface and also to improve its structural stability, we exploit dealloyed AuCu core-shell nanoparticles as a new substrate for depositing PtML. By using high-resolution scanning transmission electron microscopy and energy dispersive X-ray elemental mapping combined with electrochemical characterizations, we reveal that the dealloyed AuCu core-shell nanoparticles can effectively promote the deposition of PtML closer to a smooth monolayer structure, thus leading to a higher utilization efficiency of Pt and higher intrinsic activity towards methanol oxidation compared to those on pure Au nanoparticles. Moreover, the PtML deposited on the AuCu core-shell NPs showed substantially enhanced stability compared to those on pure Au NPs during long-term electrocatalysis over several hours, during which segregation of Cu to the Au/Pt interface was revealed and suggested to play an important role in stabilizing the PtML catalysts.

In recent years, studies on the organic small molecule fluorescent probes targeting G-quadruplexes have attracted a wide attention, because G-quadruplexes play an important role in various biological functions. Herein, we reported three crescent-shaped carbazole derivatives (4a-4c) and studied their interactions with the single-stranded, duplex, G-quadruplex and i-motif DNA. Both 4b and 4c have an above 100 nm Stokes shift and low fluorescence intensity, moreover, they exhibit the stronger affinity to G-quadruplex than to the other DNA structures. 4b with a cyanovinyl pyridine salt group displays a specific light-up fluorescence response to G-quadruplexes. FRET and CD results suggest that both 4b and 4c are able to improve the stability of G-quadruplexes and maintain their topology, moreover, they induce G-rich sequences (bcl-2, HTG, and KSS) to fold into G-quadruplexes in Na

As a high-standard verdant method of transportation, electric-powered-vehicles have become the development hotspot of the automotive business in recent years. Large scale access to electric-powered vehicles can form a distributed energy storage system, which can improve the operational performance of power grid peak shaving and frequency modulation, and improve the comprehensive utilization efficiency of system energy. But at the same time, large-scale electric-powered vehicles connected to the DC distribution network will have a certain impact on its topology. Therefore, this paper studies the impact of the access location and number of electric-powered vehicles on the network topology and establishes a multi-dimensional evaluation system of the DC distribution network topology. The application of this result can play an evaluation and guidance role in the operation stability of the DC distribution network in the case of large-scale access to electric-powered vehicles.

To evaluate the feasibility and clinical effect of Krackow suturing combined with the suture bridge technique for the treatment of acute inferior pole patella fracture.In this study, 18 patients with acute inferior pole patella fracture who received treatment using Krackow suturing combined with the suture bridge technique between January 2019 and March 2020 were retrospectively reviewed. There were 10 men and 8 women, with an average age of 50.1 years (range 24-69 years). X-ray examinations were performed to assess fracture healing and the Insall-Salvati index. The clinical effect was measured by the range of motion of the knee joint and the Böstman scale.Patients were followed up for 13-26 months, with an average follow-up period of 19.6 months. X-ray indicated that fracture union had occurred in all patients by 10.1 weeks after surgery on average (range 8-14 weeks). The mean Insall-Salvati index immediately after surgery and at the final follow-up was 0.98 ± 0.07 and 0.90 ± 0.22, respectively (P 0.05). At the last follow-up, the mean flexion and extension ranges for the knee joint were 135.8° ± 8.8° and - 2.8° ± 3.9°, respectively, and the mean Böstman scale was 28.9 ± 1.1 points. Functional recovery was excellent in 17 patients and good in one patient, resulting in an overall good/excellent recovery rate of 100%.Our results indicated that Krackow suturing combined with the suture bridge technique can achieve stable fracture fixation, provides good clinical outcomes in the treatment of acute inferior pole patella fracture, and is worthy of clinical application.

In order to reduce the resource and energy consumption of traditional biological nitrogen removal (BNR) process, heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria was in situ enriched in membrane aerated biofilm reactor (MABR) by inoculating conventional activated sludge. Contaminants removal performance, EPS composition and microbial community were explored. The results indicated that the average removal efficiency of COD and TN under optimal condition reached 84.13% and 91.54%, respectively, which demonstrated that the reactor possessed excellent contaminants removal capacity. EPS analysis suggested that abundant protein especially tryptophan protein-like substance played a vital role in maintaining the microbial stability of biofilms. Multiple HN-AD genera, mainly Paracoccus, were detected with the highest relative abundance of 54.70%, which confirmed the successful enrichment of the HN-AD bacteria. Conventional nitrifiers and denitrifiers also thrived in biofilm, which demonstrated the synergistic nitrogen removal of multiple microorganisms. This study provided important insights into application of HN-AD bacteria and synergistic nitrogen removal in BNR system.

A theoretical physical model of gas–solid two-phase flow mixed dielectric discharge in a uniform field based on Townsend's discharge theory is presented. This model extends the classical Townsend's theory to be applicable to the quantitative analysis of dielectric discharge questions related to gas–solid two-phase flow environments, reveals the influence mechanism of flowing gases and solid-phase particles on discharge, and provides a theoretical basis for expanding the application of discharge plasma technology in various fields. In the model, based on the basic physical process of gas discharge and our previous studies, the effects of the attraction and obstructive factors of solid-phase particles on the number density of electrons or ions and the local space electric field in the inception and development of gas discharge were taken into account. On this basis, the analytical expression of the breakdown voltage in a gas–solid two-phase flow mixed dielectric is obtained, Paschen's law of gas breakdown is modified, and Townsend's breakdown criterion for gas–solid two-phase flow situation is proposed. It is shown that the breakdown voltage of the gas–solid two-phase flow mixed dielectric decreases with increasing gas flow velocity. The gas flow velocity is the main factor affecting the variation trend of the breakdown voltage. The concentration and size of solid-phase particles determine the values of breakdown voltage. The breakdown voltage of the smaller size and higher concentration of solid-phase particles is greater, which has a stronger suppression effect on the discharge.

G-quadruplex DNA has attracted the widespread attention as a novel target of anticancer strategy. Herein, two novel stilbene derivatives 2a and 2b were designed and synthesized under mild reaction conditions, and their interactions with G-quadruplex DNA, cytotoxicity, and distribution in living cells were investigated in detail. Both compounds display a low cytotoxicity and the higher affinity to G-quadruplex DNA than to the other secondary structures, including duplex, single-stranded and i-motif DNA, moreover, the affinity of 2b with m-allyl pyridine salt group to G-quadruplex DNA is about 10-fold stronger than that of 2a with p-allyl pyridine salt group. The interactions of the compounds with the promoter G-quadruplexes are enthalpy-driven by an ITC assay. 2a and 2b not only stabilize the G-quadruplex structure but also induce the G-rich sequences (bcl-2, HRCC and KSS) to fold into the mixed-type G-quadruplex in Na

In order to make the absorptivity of the quantum dot infrared detector better meet the application requirements, the metal grating with the cross strip and the holes is introduced in the conventional quantum dot infrared photodetector to construct the enhanced photodetector. The enhanced photodetector shows the high absorptivity due to the local coupling enhanced effect and this absorptivity can reach 99.38%, which is 2.74 times of that of conventional photodetector.

The severe degradation of Fe-N-C electrocatalysts during a long-term oxygen reduction reaction (ORR) has become a major obstacle for application in proton-exchange membrane fuel cells. Understanding the degradation mechanism and regeneration of aged Fe-N-C catalysts would be of particular interest for extending their service life. Herein, we show that the by-product hydrogen peroxide during the ORR not only results in the oxidation of the carbon surface but also causes the demetallation of Fe active sites. Quantitative analysis reveals that the Fe demetallation constitutes the main reason for catalyst degradation, while previously reported carbon surface oxidation plays a minor role. We further reveal that post thermal annealing of the aged catalysts can transform the oxygen functional groups on the carbon surface into micropores. These newly formed micropores not only help to increase the active-site density but also the intrinsic ORR activity of the neighbouring Fe-N

According to the technical requirements of the tempo-spatially mixed modulated polarization imaging interference spectrometer (TSMMPIIS), we designed and verified the maximum optical path difference (OPD) through two different schemes, and analyzed the influences of the field of view and calcite dispersion on the OPD. When the angles between the incident plane and the principal section of the Savart left plate were 0 ° , 45 ° and 90 ° , we simulated the variations of the OPDs changing with different parameters. We found that the variations were proportional to the thickness t and the incident angle i . In order to reduce the influences of the Savart polariscope dispersion and field of view on the OPD, the corrected models were established, and the correctness was validated by the experiment. This work would provide theoretical and practical guidance for the design and engineering of the TSMMPIIS.

Large tunable lateral shift from guided wave surface plasmon resonance (GWSPR) is theoretically predicted. The dip of reflectivity and magnitude of the lateral shift can be controlled by the thickness of silver layer. The position of minimum reflection and maximum Goos-Hanchen (GH) shift can be conveniently adjusted by guided layer. The largest GH shifts at the optimal thickness of silver film can be hundreds of wavelengths when GWSPR is excited. The numerical calculation results from the Gaussian beam are in accordance with theoretical results.

This paper analyzes the effect of sliding speed on the electrical conductivity and friction properties of the contact pair of an on-load tap changer (OLTC). Reciprocating current-carrying tribological tests were carried out on a rod–plate–copper–tin–copper contact galvanic couple at different sliding speeds in air and insulating oil media. The results show that as the sliding speed increases from 24 mm/s to 119 mm/s, the average contact resistance in air increases from 0.2 Ω to 0.276 Ω, and the average contact resistance in insulating oil also increases from 0.2 Ω to 0.267 Ω. At 119 mm/s, the maximum contact resistance in insulating oil reaches 0.3 Ω. The micro-topography images obtained by scanning electron microscopy show that with the increase in sliding speed, the wear mechanisms in the air are mainly abrasive wear and adhesive wear, and the wear mechanisms in oil are mainly layered wear and erosion craters; high sliding speed and arcing promote contact surface fatigue and crack generation. X-ray photoelectron spectroscopy was used to analyze the surface. The copper oxide in the air and the cuprous sulfide in the insulating oil cause the surface film resistance, and the total contact resistance increases accordingly. In addition, the test shows that 119 mm/s in air and 95 mm/s in insulating oil are the speed thresholds. Below these speed thresholds, the increase in contact resistance is mainly caused by mechanical wear. Above these thresholds, the increase in contact resistance is mainly caused by arc erosion and chemical oxidation processes. Non-mechanical factors exacerbate the deterioration of the contact surface and become the main factor for the increase in contact resistance.

As aerospace, electrified railway, weapon equipment manufacturing, and other fields have leapt forward, the operating environment of current-carrying friction pairs is becoming increasingly severe, and research on the current-carrying friction and wear theory and its vital technologies are progressively in demand. This study summarizes the relevant research on the current-carrying friction and wear. In this study, the essential characteristics and classification of current-carrying friction and wear are summarized, the effect of working parameters on current-carrying friction and wear performance is clarified, and the generation mechanism, failure mechanism, and factors of current-carrying friction and wear are emphatically investigated. Moreover, the mechanism of arc generation and the effect of environmental conditions and surface facial masks on the friction and wear process are summarized. This paper also introduces the preparation technology of a conductive wear-resistant self-lubricating material, the main factors affecting the conductive wear-resistant property of the coating, and the action mechanism. The simulation and prediction results of the current-carrying friction and wear temperature field and the wear amount are presented. Finally, the problems in the current-carrying friction and wear research are classified, and future research directions in this field are proposed. The future’s critical development and improvement directions are also proposed from the aspects of developing coating quality evaluation equipment, optimizing the coating quality, and studying the coating self-lubricating mechanisms.

Because the traditional insulation paper state detection method has some shortcomings, this paper proposes a non-destructive detection method, which uses the texture feature value of insulation paper image to establish a relationship with the degree of polymerization (DP) of insulation paper state, and then indirectly estimates the aging state of insulation paper. Firstly, the insulation paper images in different aging states are collected, and the texture feature values of the images are extracted by gray histogram, gray level co-occurrence matrix and gray level run-length matrix; then, the texture feature values are selected by correlation; then, the validity of the selected texture feature values to represent the insulation paper state is verified by support vector machine (SVM); finally, the multiple linear regression method is used. The relationship between the degree of polymerization and the texture feature value is established and verified by the actual results. The results show that the texture feature value has a good fitting relationship with the degree of polymerization, which verifies the effectiveness of this method in evaluating the state of insulating paper.

The three-phase composite structure is widely used in the power industry, especially for insulation systems of power equipment. As delamination defects always take place on such equipment, i.e. defects occur inside the three-phase composite structure. Therefore, this paper proposes to used the terahertz time-domain spectroscopy (THz-TDS) to detect the inner defects of the three-phase composite structure. Firstly, a three-layer reflection model of the terahertz wave is established, and a corresponding theoretical analysis of three-phase composite with insulation delamination defect is carried out. After then, an artificial sample with a delamination defect is prepared according to the actual structure of the three-phase composite. Besides, the THz-TDS analysis of the samples is carried out after tested by the THz-TDS system with the reflective mode. The experimental results show that the insulation delamination of the three-phase composite can be effectively identified by collecting the signals of the THz-TDS system. This paper theoretically and experimentally proves the feasibility of the new method based on the THz-TDS system for three-phase composite delamination nondestructive testing, which provides a new idea for inner defects detection within the three-phase composite and its condition assessment.

Background The application of free skin flaps to repair severe peri-knee soft tissue defects is a common clinical approach. This article aims to investigate clinical efficacy and precautions of using a free anterolateral thigh flap with the descending genicular vessels as a recipient pedicle for repairing Gustilo IIIB and IIIC soft tissue defects around the knee. Methods We retrospectively analyzed the data of the patients with severe peri-knee Gustilo IIIB or IIIC soft tissue defects operated on from January 2015 to December 2019. All patients underwent repair of the severe soft tissue defect using anterolateral thigh flap transplantation with the descending genicular vessels as the recipient pedicle. Results All patients completed effective follow-up for an average of 14.1 [6-30] months. For two patients with larger flaps, necrosis occurred in the distal tip of the flaps, 6 cm and 4 cm in size. The necrotic flaps were removed, and the wound healed after skin grafting. In the other 12 patients, the skin flaps fully survived. Conclusions Using a free anterolateral thigh flap with descending genicular vessels as the recipient pedicle to repair Gustilo IIIB and IIIC soft tissue defects around the knee is a convenient and preferred technique that can achieve satisfactory efficacy.