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The external insulation strength of the power equipment sleeve in the substation and converter station will be reduced with the increase in altitude and atmosphere pollution. The weakness of external insulation seriously threatens the safe operation of electrical equipment. At present, there are few studies and conclusions that focus on the flashover characteristics of power equipment bushing in high-altitude polluted areas. Therefore, this paper takes the 220 kV voltage level bushing as the research object and studies the Alternating Current (AC) pollution flashover characteristics and lightning and switching impulse flashover characteristics at low pressure. The insulation configuration at high-altitude polluted areas is analyzed. Finally, the insulation configuration scheme, which is suitable for high-altitude polluted areas, is proposed. The results show that the AC pollution flashover voltages of the bushing decrease with the decrease in the atmospheric pressure and the increase in the salt density as a power exponent function. The impulse flashover voltages also decrease with the decrease in the atmospheric pressure as a power exponent function. The atmospheric pressure/pollution impact characteristic index is related to the type of voltage, the value of the atmospheric pressure, and the value of the salt density. The test bushing does not meet the insulation configuration requirements in some high-altitude polluted areas. Through the analysis and calculation of the test results, the bushing insulation configuration scheme in high-altitude polluted areas is proposed. The research results can provide a reference for the external insulation design of bushings in substations and converter stations in high-altitude polluted areas. [ABSTRACT FROM AUTHOR]

Oxygen stoichiometry (OS) and stack temperature (ST) significantly affect the output performance and durability of proton exchange membrane fuel cells. This paper investigates the prescribed performance tracking control strategy of OS and ST under external disturbances, modeling errors, actuators faults and limited communication resources. The total disturbances are compensated by a variable-bandwidth extended state observer to simplify the control design and enhance the system robustness. To tolerate excessive disturbances and relax the strict requirement on the initial conditions, a new event-triggered adaptive sliding mode controller that integrates modified dynamic performance constraints and nonsingular error transformation is developed to ensure the user-designed transient and steady-state performance constraints, while saving the communication costs and avoiding the chattering and jump in control signals. The numerical validation results under combined working scenarios indicate that the proposed controller always ensures the preset error constraints and possesses superior performance in tracking the optimal OS value 2 and the optimal ST value 353.15K than other three representative controllers, with the integral absolute errors of 0.732 for OS tracking and 12.94 for ST tracking; besides, it achieves satisfactory robustness to uncertain model parameters and relatively large initial tracking errors. [Display omitted] • A robust event-triggered prescribed performance controller for PEM fuel cell systems. • Oxygen stoichiometry (OS) and stack temperature (ST) are simultaneously controlled. • Integral absolute errors when tracking OS and ST are 0.732 and 12.94 respectively. • A better compromise between control performance and communication cost. • The chattering and jump phenomena in control signals are suppressed. [ABSTRACT FROM AUTHOR]

Silicone rubber insulators are widely used in power grids because of their excellent performance, but aging has been an inevitable problem of silicone rubber, especially in extreme conditions, such as acidic conditions. In order to clarify the performance changes in silicone rubber in an acidic environment, this paper uses the developed acid-resistant silicone rubber sheet and common silicone rubber samples as the research objects, and conducts an aging comparison test on them in a natural acidic environment. The electrical properties, physical properties, and chemical properties of the two types of silicone rubber specimens with different aging times are analyzed to obtain the performance characteristics of silicone rubber under a natural acidic environment. The research results show that the dry flash voltage and pollution flashover voltage of the acid-resistant silicone rubber after one year of aging are greater than those of the common type; the water repellency of both types of silicone rubber remains in good condition. The silicone rubber produced by our team according to the self-developed acid-resistant silicone rubber formula has indeed played a role in delaying aging in an acidic environment compared with the common-type silicone rubber. [ABSTRACT FROM AUTHOR]

Railway system insulators are affected by pollution, altitude, and other environmental situations during operation, which causes reduced electrical performance or even flashover accidents. These factors threaten the safety of railway operations in high-altitude areas. However, the natural contamination characteristics of a railroad in a plateau area is still unclear. In this study, a natural pollution accumulation test for railway insulators in a high-altitude area was carried out, and the distribution rules of nonsoluble deposit density (NSDD), equivalent salt deposit density (ESDD), NSDD/ESDD ratio, and nonuniformity (T/B) of the pollution distribution of the tested insulators were calculated. Meanwhile, the chemical compositions of the pollution from different test sites were analyzed. The differences of pollution accumulation between railway insulators and suspended insulators of a power system and the influencing factors were compared and analyzed by combining with a numerical simulation. The results show that the pollution level of railroad insulators is mainly distributed in level b and above. A pollution sample is mainly composed of sodium chloride, while the NSDD/ESDD ratio of pollution is mostly distributed from 0 to 5, with T/B value ranges from 1/0.62 to 1/1.76. The amount of insulator contamination is influenced by the location inside and outside the tunnel. Additionally, the pollution amount is influenced by the structure and type of insulators. Finally, this paper studies the creepage distance and structural height required by railway insulators in a plateau area according to the natural pollution accumulation characteristics of railway insulators, which can provide a reference for a railway electrical external insulation configuration in a high-altitude area. [ABSTRACT FROM AUTHOR]

Background: N6-methyladenosine (m6A) is associated with mammalian mRNA biogenesis, decay, translation and metabolism, and also contributes greatly to gastrointestinal tumor formation and development. Therefore, the specific mechanisms and signaling pathways mediated by methyltransferase-like 3 (METTL3), which catalyzes the formation of m6A chemical labeling in stomach adenocarcinoma (STAD), are still worth exploring. Methods: Quantitative real-time PCR (qRT-PCR) was constructed to detect the expression of METTL3 in gastric cancer cell lines and patient tissues. The biological function of METTL3 was investigated in vitro/in vivo by Cell Counting Kit-8, colony formation assay, Transwell assay and nude mouse tumorigenesis assay. Based on the LinkedOmics database, the genes co-expressed with METTL3 in the TCGA STAD cohort were analyzed to clarify the downstream targets of METTL3. Methylated RNA immunoprecipitation-qPCR (MeRIP-qPCR) and RNA stability analysis were employed to explore the mechanism of METTL3 in gastric cancer progression. Results: We analyzed TCGA data and found that METTL3 was frequently elevated in STAD, and demonstrated that METTL3 was present at high levels in clinical STAD tissues and cells. High METTL3 expression was more likely to have advanced TNM tumors and distant metastasis. On the other hand, METTL3 silencing effectively impeded the higher oncogenic capacity of AGS and HGC27 cells in vivo and in vitro, as reflected by slowed cell growth and diminished migration and invasion capacities. Continued mining of the TCGA dataset identified the co-expression of angiopoietin-like 3 (ANGPTL3) and METTL3 in STAD. Lower level of ANGPTL3 was related to increased level of METTL3 in STAD samples and shorter survival times in STAD patients. ANGPTL3 enrichment limited the growth and metastasis of STAD cells. Besides, ANGPTL3 mRNA levels could be decreased by METTL3-dominated m6A modifications, a result derived from a combination of MeRIP-qPCR and RNA half-life experiments. Importantly, the inhibitory effect of METTL3 silencing on cancer could be reversed to some extent by ANGPTL3 inhibition. Conclusions: Overall, our findings suggested that METTL3 functioned an oncogenic role in STAD by reducing ANGPTL3 expression in an m6A-dependent manner. The discovery of the METTL3-ANGPTL3 axis and its effect on STAD tumor growth will contribute to further studies on the mechanisms of gastric adenocarcinoma development. [ABSTRACT FROM AUTHOR]

This paper reviews the application of various advanced anti-icing and de-icing technologies in transmission lines. Introduces the influence of snowing and icing disasters on transmission lines, including a mechanical overload of steel towers, uneven icing or de-icing at different times, Ice-covered conductors galloping and icing flashover of insulators, as well as the icing disasters of transmission lines around the world in recent years. The formation of various icing categories on transmission lines, as well as the effect of meteorological factors, topography, altitude, line direction, suspension height, shape, and electric field on ice-covered transmission lines, are all discussed in this study. The application of various advanced anti/de-icing technologies and their advantages and disadvantages in power transmission lines are summarized. The anti/de-icing of traditional mechanical force, AC/DC short-circuit ice melting, and corona effect is introduced. Torque pendulum and diameter-expanded conductor (DEC) have remarkable anti-icing effects, and the early investment resources are less, the cost is low, and the later maintenance is not needed. In view of some deficiencies of AC and DC ice melting, the current transfer intelligent ice melting device (CTIIMD) can solve the problem well. The gadget has a good effect and high reliability for de-icing conductors in addition to being compact and inexpensive. The application of hydrophobic materials and heating coatings on insulators has a certain anti-icing effect, but the service life needs further research. Optimizing the shed's construction and arranging several string kinds on the insulators is advisable to prevent icing and the anti-icing flashover effect. In building an insulator, only a different shed layout uses non-consumption energy. [ABSTRACT FROM AUTHOR]

Polymer insulators using silicone rubber materials as sheds and sheaths are widely used in power systems to replace traditional porcelain and glass insulators which are heavy, inconvenient to install, and prone to pollution flashover. However, in recent years, polymer insulators that have been operating in harsh outdoor environments for many years have experienced different degrees of aging. The aging degree and aging products of silicone rubber are the focus of research. Fourier transform infrared spectroscopy (FTIR) is a technical method to analyze the internal molecular bonds and functional groups of materials, and it is often used to study the aging degree and aging products of silicone rubber. In this paper, the aging characteristics of silicone rubber samples in a high altitude area, salt fog environment, and acid environment were studied by FTIR. The results showed that the silicone rubber in a harsh environment, such as strong radiation, salt fog, and acid fog was degraded to some extent, and its main chain was cut off, the degree of polymerization was reduced, and the content of hydrophobic functional groups was reduced. Infrared spectroscopy can be used to analyze the aging phenomenon of polymers. [ABSTRACT FROM AUTHOR]

Composite insulators operate in harsh field environments all year round. Their various properties and states of aging require attention. It is important to study the performance changes of composite insulator sheds after aging to evaluate the life of insulators operating on grids. For this reason, 22 composite insulator sheds from different factories, with different voltage levels and different ages years were selected to conduct mechanical properties testing. The mechanical properties include hardness, tensile strength, and elongation at break, and were investigated by thermogravimetric (TGA) testing, surface morphology, and nuclear magnetic resonance (NMR) characterization. The changes in mechanical properties of high temperature vulcanization (HTV) composite insulator silicone rubber aged in the natural environment were analyzed, including the reasons for these changes. The results showed that the transverse relaxation time T2 of the sample was closely related to its aging state. The more serious the silicone rubber's aging, the smaller was the T2. The state of the composite insulator can be evaluated by using T2 and aging years simultaneously. With the actual degree of aging in the silicone rubber intensified, its tensile strength and elongation at break generally showed a downward trend. [ABSTRACT FROM AUTHOR]

This paper proposes a reconstruction algorithm for the geometric shapes of static overhead transmission lines that is based on the spatial coordinate data (obtained by field mapping) and the corresponding inclination data (obtained by attitude sensors). The algorithm takes the piecewise cubic Hermite interpolation function as the basic framework and corrects the aforementioned two types of data based on the “minimum energy principle” of the transmission line system. The introduction of a new energy function in modified energy method (MEM) overcame the shortcomings of conventional energy method (CEM) in fairing strategy, and the new Fairing Criterion made result curves more consistent with the mechanical properties of transmission lines. In the numerical simulation tests, the two energy methods were compared in terms of load type, horizontal span, elevation difference, and anti-disturbance ability, which showed that MEM has a higher reconstruction accuracy (average Euclidean distance is less than 1 cm) and better robustness than CEM. Meanwhile, the key parameters involved in the algorithm were discussed to guide the application in practical engineering. In addition, measurement tests under non-uniform icing were carried out in the field test station, and the results showed that the maximum relative error is less than 0.1%. [ABSTRACT FROM AUTHOR]

The production of biodiesel catalyzed by lipase has the advantages of simple process, low energy consumption, and low wastewater treatment requirements. However, low activity, poor stability, and difficulty in recycling still limit the application of lipase in production of biodiesel. Herein, a novel lipase hybrid biocatalyst with superior catalytic activity and stability (lipase from Aspergillus oryzae CJLU-3, AOCL@CaP in DES) was developed by dual activation of Ca2+ and interfacial effect of deep-eutectic solvents (DES)/water two-phase system. AOCL@CaP in DES exhibited significantly enhanced enzymatic activity with a K cat /K m value of 692 s−1 mM−1 and excellent thermostability, tolerance to chemical denaturants, substrate selectivity, and reusability compared with free lipase. Recovery activity of the prepared hybrid biocatalyst in pure water system (AOCL@CaP) and AOCL@CaP in DES was 195% and 250% using p-NPL as substrate, respectively. AOCL@CaP in DES exhibited about 253% of the original activity after 100 days of storage, while free AOCL, AOCL@CaP almost completely lost activity. The FAME content in product biodiesel catalyzed from soybean oil by AOCL@CaP was only 60%, However, the FAME content catalyzed by AOCL@CaP in DES reached 87%, and could be maintained at 50% even after 10 cycles. [Display omitted] [ABSTRACT FROM AUTHOR]

The safety and stability of power systems are seriously threatened by the decay-like fracture of composite insulators. This paper analyzes the aging characteristics (physical properties, NMR, and FTIR) of the silicone rubber sheds of the decay-like fractured insulator. The same V-string insulator and a new insulator are used for comparison. The study shows that the sheds' degradation is concentrated on the side with heavy pollution. The physical properties (appearance, pollution, hardness, and hydrophobicity) of the high voltage end decrease significantly compared to other positions, but there is no direct connection between the physical properties of sheds and the decay-like fracture of the core rod. The severity of aging increases with a decrease in the equivalent transverse relaxation time T2. The main chain of the PDMS material was severely damaged at the location of the insulator fracture. NMR and FTIR can well judge the aging degree of silicone rubber housings. However, no definite characteristic quantity can characterize the decay-like fracture. It is challenging to evaluate the decay-like fracture of the silicone rubber shed only by its aging degree. [ABSTRACT FROM AUTHOR]

The leakage current and current density of the wet insulators were higher than those of the dry insulators, and the surface resistance was lower than that of the dry insulators. Although a lot of research has been conducted by domestic and foreign institutions, the problem has not been fundamentally solved, and insulator flashover accidents still occasionally occur, so further research on insulators is needed. By measuring the phase difference between the applied voltage and leakage current of the insulator, it was found that the dry insulator was almost capacitive, and the wet insulator was resistive and capacitive. [Extracted from the article]

Introduction: With the levodopa threshold effect for dyskinesia observed, threshold dosage of levodopa was identified in the general Parkinson's disease (PD) population. While early-onset PD (EOPD) and late-onset PD (LOPD) differ in the pathogenesis and clinical manifestations, threshold dosage of levodopa for individualized treatment remains unestablished. The objective of this study was to propose threshold dosage of levodopa in EOPD and LOPD patients, respectively. Methods: Data on demographic and clinical and treatment measures were collected in 539 PD patients. Patients were divided into different onset groups using 50 as the cut-off age. We used univariable and multivariable analysis to screen for risk factors for dyskinesia. Receiver operating characteristic curve was used to determine the levodopa threshold dosages for dyskinesia. Results: The prevalence of dyskinesia was 47.7% (53/111) in the EOPD group and 24.1% (103/428) in the LOPD group. Risk factors identified for dyskinesia include high levodopa daily dose and levodopa responsiveness for EOPD patients and high levodopa daily dose, long levodopa treatment duration, low body weight, use of entacapone, and high Hoehn–Yahr stage in off state for LOPD patients. The daily levodopa threshold dosages were 400 mg or 5.9 mg/kg for EOPD and 450 mg or 7.2 mg/kg for LOPD. Conclusion: EOPD patients had lower levodopa threshold dosage comparing with LOPD patients. Treatment of EOPD requires stricter levodopa dose control to delay the onset of dyskinesia. [ABSTRACT FROM AUTHOR]

For the benefit of knowing the method of insulator deicing using hot water, this paper investigated the physical aspects of propagation and the spatial temperature distribution of a hot water jet in the air. The numerical calculation model for the water jet flow field was established and validated, and the temperature spatial variation rule and influencing factors of the water jet were analyzed. The results indicate that the water column breaks as the distance increases. The numerical calculation results and the experimental results of the water jet flow field were approximated. As the distance increases, the mass entrainment rate of the water jet gradually increases, and the normalized axis velocity decreases approximately linearly. The jet temperature rises with the rise in the initial temperature of the hot water, and the rising rate decreases with the increase in distance. The temperature of the water jet falls as the jet distance increases. With the rise in the outlet pressure, the temperature of the water jet drops slightly. The influence of environmental wind speed on the water jet temperature is more significant than ambient temperature—the water jet temperature increases as the nozzle diameter increases. The thorough deicing efficiency is most outstanding when the hot water output temperature is around 86 °C and the jet pressure is ~3.5 MPa. [ABSTRACT FROM AUTHOR]

Lightning strikes and pollution could cause short circuits and tripping of the overhead distribution lines. To alleviate this, a 10-kV post insulator with concentric externally gapped line arrester (EGLA) has been proposed and its performance is studied in service. However, its pollution performance has to be established. This paper studies the AC pollution breakdown characteristics of the EGLA and broaden current knowledge of pollution flashover. Compared with the flashover of the normal insulator, three kinds of specificity of the EGLA were found. Firstly, the pollution flashover process can be divided into three categories. Secondly, the wet flashover voltage, Uf_wet, of the novel insulator is higher than the dry flashover voltage, Uf_dry. Thirdly, the piecewise fitting methods with a × ESDD^−b + d and a × ESDD^−b + c × ESDD^−d are more suitable for fitting the empirical formula of flashover voltage. Furthermore, to explain specificity, the electric potential and electric field distribution are calculated based on the finite element method. Calculated results indicate that when the EGLA is covered with a 0.5mm water film, the maximum electric field intensity decreased from 2.17 kV/cm to 1.99 kV/cm. Also, U_arrester (the withstand voltage of the insulation section) was obtained from the tests and it presents a discontinuous and random increasing trend until flashover occurs, which is considered to be one of the important reasons for the specificity. Besides, based on the Obenaus’ model and Hampton's criterion, we further analyzed the arc development process by a simplified plate model. [ABSTRACT FROM AUTHOR]

• The experiment observed, recorded and analyzed the natural icing process of insulators, but most of the previous studies were simulated in the laboratory. • This paper analyzed the icing process of different types of insulators (shed structure, Shed diameter) under natural icing environment. • The influence of wind speed, humidity, precipitation and temperature on the natural icing process were analyzed. • Based on the final icing morphology under natural condition, this paper took the of icicle number, icicle length, icicle diameter, icing thickness of shed surface and icing mass as characteristics, analyzed the differences in icing results of different structures insulators, and got the conclusion (4), which provides reference for insulator selection of transmission lines in icing areas. Icing flashover of insulator strings has always been a serious factor threatening the safety and stability of the power grid. Researchers have simulated icing based on an artificial climate chamber, but it cannot fully simulate the growth process of insulator strings during the icing period in the natural environment. The icing growth characteristics of insulator strings in the natural environment are not clear. In this paper, three kinds of porcelain insulators were tested in the Xuefeng Mountain natural icing test base of Chongqing University. The results show that the freezing rain, alternating icing of freezing rain and freezing fog can cause the insulator stings to form glaze and mixed rime, and the icing degree on the windward side is more serious than leeward side. The higher the test environment's precipitation, humidity and wind speed, the faster the insulator strings' icing speed. And there are also some influences of the ambient temperature on the icing morphology in this test. The icing thickness on the windward side of the insulator shed will gradually increase. The number of icicles of insulators is positively correlated with the diameter of insulator sheds. The icing mass of insulator strings is seriously affected by their shed structure. [ABSTRACT FROM AUTHOR]

To improve feature learning ability and accurately diagnose the faults of rolling bearings under a strong background noise environment, we present a new shrinkage function named leaky thresholding to replace the soft thresholding in the deep residual shrinkage networks (DRSNs). In this work, we discover that such improved deep residual shrinkage networks (IDRSNs) can be realized by using a group searching method to optimize the slope value of leaky thresholding, and leaky thresholding in the IDRSNs can more effectively eliminate the noise of signal features. We highlight that our techniques can significantly improve the performance on various fundamental tasks. Experimental results show that IDRSNs achieve better fault diagnosis results on noised vibration signals compared with DRSNs. Moreover, we also provide a normalized processing to further improve the fault diagnosing accuracy of rolling bearing under a strong background noise environment. [ABSTRACT FROM AUTHOR]

• Switching impulse discharge experiments of rod-plane air gaps with different front times and absolute humidity are carried out. • Corrected U 50% of different front times when considering atmospheric parameters and absolute humidity. • Analyzed the main influencing factors of air gap discharge time under different conditions. In long-distance transmission lines, the switching overvoltage waveform differs from that of ordinary lines. The wave front time is primarily distributed above 1000 μs. And the switching overvoltage waveform has an important influence on the design of external insulation. This paper aims to deeply study the effect of various factors on the discharge of air gaps under the long front switching impulse voltage. This paper selects three kinds of rod-plane air gaps, and the switching impulse discharge experiments with different front lengths and absolute humidity under positive polarity are carried out. The effects of front time T f , absolute humidity h , and gap distance d on the discharge characteristics of the air gap are analyzed. The results show that the U 50% of an air gap is positively correlated with absolute humidity, front time, and gap distance. When considering the additional influence of humidity, the humidity additional influence factor c and the atmospheric parameter influence index n at different front times are almost unchanged. With the increase in gap distance, the influence of front time on U 50% is more obvious. With the growth of the operating wave front time, the rising rate of U 50% tends to slow down. The discharge time of the air gap under different conditions is mainly determined by the front time. The research results can provide a theoretical and experimental reference for the influence of front time T f and atmospheric parameters on the discharge characteristics of air gaps under long front switching impulse. [ABSTRACT FROM AUTHOR]

• Pollution flashover experiments were carried out on railway insulators under lightning impulse and AC, and the flashover characteristics were analyzed. • Insulation configuration of railway insulators at high altitude and polluted areas was analyzed. • Altitude correction for existing transmission line insulators does not apply to railway insulators, and the altitude correction method for railway insulators is given. • Recommended values of insulation height and creepage distance are proposed for railway insulators intended to work at various altitudes and under various pollution conditions. The reduction of electrical performance of railway insulators at high altitude and polluted areas affects the safe operation of the railway. A lot of studies have been carried out on transmission line insulators at home and abroad, but whether the results can guide the design of railway insulators has not yet been determined. This paper takes the railway insulator QBG-25/16 as the research object, experimentally studied the lightning impulse and AC pollution flashover characteristics of the railway insulator under low air pressure, analyzed its insulation configuration under high altitude and pollution environment, and finally proposed its altitude correction method. The results show that the flashover voltages of the insulator decrease in a power function as the air pressure decreases, and decrease in a power function as the salt deposit density increases, and the air pressure influence characteristic index and pollution influence characteristic index are related to voltage type, air pressure and salt deposit density. The tested insulators do not satisfy the requirements for insulation strength at certain high altitude and polluted areas. Finally, the altitude correction method for railway insulators is given. The results of the study provide guidance for the selection of external insulation for electrified railway systems at high altitude. [ABSTRACT FROM AUTHOR]

Background: Circular RNAs (circRNAs) have been documented as key regulators during progression of malignant human cancer, including colorectal cancer (CRC). However, the underlying molecular mechanisms of circNOL10 in CRC remain unclear. Methods: The real-time quantitative polymerase chain reaction was used to quantify the expression of circNOL10, miR-135a-5p, miR-135b-5p, and Krüppel-like factor 9 (KLF9). Kaplan–Meier curve was employed to assess the relationship between survival time of CRC patients and expression level of circNOL10. Cell ability of proliferation was measured by Cell Counting Kit8 and colony formation assays. Cell-cycle analysis was performed using flow cytometry assay. In addition, migration and invasion of CRC cell were examined with transwell analysis. The protein expression level was measured with Western blot assay. The interaction relationship of different molecules was analyzed by bioinformatics database and confirmed by dual-luciferase reporter, RNA immunoprecipitation, and RNA pulldown assay. The functional role of circNOL10 in vivo was determined by xenograft experiment. Results: CircNOL10 was decreased in CRC tissues and cells and was associated with poor outcomes. Gain-of-functional experiment revealed that overexpression of circNOL10 constrained proliferation, cell-cycle progression, migration, and invasion of CRC cells, which was abolished by overexpression of miR-135a-5p or miR-135b-5p. Additionally, miR-135a-5p and miR-135b-5p, targets of circNOL10, regulated KLF9 expression in a negative feedback. Consistently, the results of xenograft experiment suggested that overexpression of circNOL10 inhibited tumor growth in vivo. Conclusion: In summary, our results showed that circNOL10 impeded CRC development by mediating proliferation, cell cycle, migration, and invasion by sponging miR-135a-5p and miR-135b-5p, which provided new understanding for CRC treatment. [ABSTRACT FROM AUTHOR]

Development of cisplatin resistance in colorectal cancer is largely caused by dysregulation of signaling pathways, including the Wnt/β-catenin signaling pathway, in cancer cells. Further investigation into the molecular mechanism of chemoresistance could improve outcomes for patients with colorectal cancer. The present study determined that fibroblast growth factor 9 (FGF9) was overexpressed in tumor tissues compared with normal tissues from patients with colorectal cancer. Using the colorectal cancer cell line LoVo, transfection of recombinant FGF9 decreased cisplatin-induced cell apoptosis whilst FGF9 silencing increased cisplatin-induced apoptosis. Western blot analysis and reverse transcription-quantitative polymerase chain reaction demonstrated that FGF9 decreased adenomatous polyposis coli (APC) mRNA and protein expression and contributed to activation of the Wnt/β-catenin signaling pathway. Notably, an increase in FGF9 and β-catenin protein expression and a decrease in APC protein expression was observed in the established LoVo cisplatin resistant cell line (LoVo/cisplatin). Silencing of FGF9 reversed cisplatin resistance of LoVo/cisplatin cells. In conclusion, the present findings suggested that FGF9 activated the Wnt signaling pathway and was a mediator of cisplatin resistance in colorectal cancer. [ABSTRACT FROM AUTHOR]

• This paper develops variational mode reconstruction to augment faulty samples. • Variational mode reconstruction can preserve intrinsic components in original samples. • Variational mode reconstruction can balance faulty and healthy classes. • The usefulness and superiority of the developed method have been validated in few-shot diagnosis of rolling bearings. Currently, the popular fault diagnosis methods based on deep learning encounter a common limitation in that their accuracy heavily relies on an adequate number of training samples. However, collecting fault samples in real-world scenarios is often challenging. To overcome this challenge, this paper develops a novel data augmentation method named variational mode reconstruction (VMR) to generate augmented samples with similar features to the original samples. The first key point is the random weighting of a certain randomly chosen intrinsic mode function (IMF). Another key point is that the mean values and standard deviations of the augmented samples remain consistent with the original samples. Next, the augmented balanced dataset is utilized to train a deep residual shrinkage network (DRSN), which is then employed for the classification of test samples. Finally, the effectiveness and superiority of the developed VMR in few-shot fault diagnosis are verified through a series of experiments. [ABSTRACT FROM AUTHOR]

Effects of vertical magnetic field on the breakdown process of the nanosecond pulse discharge in atmospheric air are studied via two-dimensional particle-in-cell/Monte Carlo collision simulations. The numerical model is chosen and defined reasonably, with reference to experimental situations and literature reports. It is shown that when the applied magnetic field is strong enough, the evolutionary characteristics of the ionization channel are greatly affected due to the Lorentz force on charged particles. The impact is manifested macroscopically by the slowing down of the ionization channel evolution speed, the ionization channel shift, and the improvement of the discharge uniformity. At the microscopic level, the impact is mainly reflected in the regulation of the highest-energy electrons and the regulation of the overall electron energy distribution. That is, the adoption of a strong vertical magnetic field is capable of suppressing the generation of energetic electrons. The authors' results explicitly demonstrate the regulation of vertical magnetic field on the breakdown process of the nanosecond pulse discharge, which provides more comprehensive knowledge for the atmospheric air gap nanosecond pulse discharge physics and the theoretical basis for application design. [ABSTRACT FROM AUTHOR]

The usage of medium‐voltage switchgear is more and more common in high altitude areas. Few relative standards about the selection of switchgear air gap in low air pressure conditions are currently available for referring. In this study, four different types of switchgear air gaps, as well as a typical rod‐plane gap, are taken as the samples, and their positive and negative lightning strike discharge characteristics under low air pressure are tested in the artificial climate chamber. The effects of the electrode structure, polarity, air pressure, humidity, and gap distance on the discharge performances are analysed as well. Research results indicate that the four switchgear air gaps and typical rod‐plane gap differs greatly in lightning impulse discharge performances and polarity effects. In low air pressure conditions, the lightning impulse breakdown voltage of either positive or negative polarity can be corrected by U50 = U50,0 × (P/P0)n. The discharge voltage under positive lightning impulse is more easily affected by air pressure than that under negative lightning impulse. Atmosphere humidity will cause dispersiveness of air‐gap lightning impulse discharge voltage, which performs to be non‐linear with a gap distance lower under 400 mm. Research results are referable for the design, selection and installation of medium‐voltage switchgear in high altitude areas. [ABSTRACT FROM AUTHOR]

Energized insulator's surface contamination is greatly affected by its electric field properties. However, few reports about the electric field influencing mechanism on the pollution deposition have been presented. In this paper, the coupling-physics model of a three-unit XP-160 insulator string was established, and the particles' deposition process was simulated by using the finite element method. The effects of the electric field on the pollution particles' motion were analyzed. Research results indicate that the closer to the insulator string, the larger the intersection angle q between the electric force and its horizontal component. The main function of the electric field on insulator contamination is that it changes the pollution particles' vertical moving speed, thus accelerating the particles' deposition process. The particle capture coefficient ratio ck can be used to reflect the pollution degree discrepancy between DC-energized and non-energized insulators. In this paper the ratio ck of the DC-energized to non-energized condition is in the range of 1.04 to 1.98, very close to the field measurement results of the DC pollution ratio k. [ABSTRACT FROM AUTHOR]

The inner area close to cap and pin of insulator is sometimes heavier polluted than the outer area, causing the contamination pattern on insulator surface look like ring-shape. This kind of non-uniform pollution may affect insulator flashover voltage. In this paper, artificial pollution tests of 4 types of porcelain and glass insulators with ring-shaped non-uniform pollution were carried out. Experimental results indicate that the SDD (salt deposit density), the non-uniform pollution degree K (the SDD ratio of inner part to outer part), the heavily polluted area with radius r, and the insulator profile all have significant effects on insulator flashover performance. The effects of K and r on flashover performance can be reflected by the change of pollution layer conductivity during flashover. Under ring-shaped non-uniform pollution, the relationship between Uso and SDD can still be expressed by negative power function, while coefficient a varies obviously with pollution non-uniformity, but exponent n does not. Finally the correction coefficients of flashover voltage considering non-uniform pollution degree K were also calculated for outdoor insulation design. [ABSTRACT FROM AUTHOR]

The bare conductor in switchgear constitutes complicated air gaps, and their AC withstand characteristic will obviously affect switchgear insulation performance. In this paper, AC withstand tests of various types of air gap were carried out. The air gap samples were rod-plane air gap and 4 typical types of air gap from the bus chamber of 40.5 kV metal-enclosed switchgear. The samples were tested in climate chamber where high altitude environment was simulated. And correction of withstand voltage for switchgear air gaps at low air pressure were conducted. Test results indicate that, the withstand characteristic of 4 typical types of air gap in switchgear are different from that of rod-plane air gap. The relationship between withstand voltage Uw and air gap distance d is nonlinear. The influencing characteristic exponent n of air pressure on Uw is related with air gap type. Linearity value m and air pressure index n are independent to some degree. An equation was proposed to express the relationship of Uw with air gap distance d and altitude H, and this equation can be used to calculate the safety distance of air gaps in switchgear under low air pressure situations. The results are significant for the design and selection of switch devices. [ABSTRACT FROM AUTHOR]

Rice is an important monocotyledonous crop worldwide; it differs from the dicotyledonous plant Arabidopsis in many aspects. In Arabidopsis, ethylene and auxin act synergistically to regulate root growth and development. However, their interaction in rice is still unclear. Here, we report that the transcriptional activation of OsEIL1 on the expression of YUC8/REIN7 and indole-3-pyruvic acid (IPA)-dependent auxin biosynthesis is required for ethylene-inhibited root elongation. Using an inhibitor of YUC activity, which regulates auxin biosynthesis via the conversion of IPA to indole-3-acetic acid (IAA), we showed that ethylene-inhibited primary root elongation is dependent on YUC-based auxin biosynthesis. By screening phenotypes of seedling primary root from mutagenesis libraries following ethylene treatment, we identified a rice ethylene-insensitive mutant, rein7-1, in which YUC8/REIN7 is truncated at its C-terminus. Mutation in YUC8/REIN7 reduced auxin biosynthesis in rice, while YUC8/REIN7 overexpression enhanced ethylene sensitivity in the roots. Moreover, YUC8/REIN7 catalyzed the conversion of IPA to IAA, truncated version at C-terminal end of the YUC8/REIN7 resulted in significant reduction of enzymatic activity, indicating that YUC8/REIN7 is required for IPA-dependent auxin biosynthesis and ethylene-inhibited root elongation in rice early seedlings. Further investigations indicated that ethylene induced YUC8/REIN7 expression and promoted auxin accumulation in roots. Addition of low concentrations of IAA rescued the ethylene response in the rein7-1, strongly demonstrating that ethylene-inhibited root elongation depends on IPA-dependent auxin biosynthesis. Genetic studies revealed that YUC8/REIN7-mediated auxin biosynthesis functioned downstream of OsEIL1, which directly activated the expression of YUC8/REIN7. Thus, our findings reveal a model of interaction between ethylene and auxin in rice seedling primary root elongation, enhancing our understanding of ethylene signaling in rice. [ABSTRACT FROM AUTHOR]

• Electrical aging test of silicone rubber in a corrosive environment is firstly carried out. • Illustrate the flashover gradient of silicone rubber has a negative power function relationship with the charging duration. • Proposes the area ratio k of the hydrophobic loss area on the surface of silicone rubber to evaluate its insulating state. • Illustrate k = 0.35 can be used as the critical condition to characterize the failure of silicone rubber composite insulation. The performance of high temperature vulcanized (HTV) silicone rubber used in composite insulator will be worse in harsh environment. Acid and alkali pollutants in the atmospheric environment will affect the performance of silicone rubber. In this paper, the electrical aging test of silicone rubber in a corrosive environment is firstly carried out. It is found that the AC flashover voltage decreases with the increase of applied voltage and fog water conductivity, and the flashover gradient of silicone rubber has a negative power function relationship with the charging duration. In addition, this paper also pays attention to the change of hydrophobicity of the sample, and proposes the area ratio k of the hydrophobic loss area on the surface of silicone rubber to evaluate its insulating state. By calculating the value of k when the sample fails in a corrosive environment, it is found that k = 0.35 can be used as the critical condition to characterize the failure of silicone rubber composite insulation. [ABSTRACT FROM AUTHOR]

Due to electric field, meteorological conditions and insulator structure, the natural contamination of insulators is complex and so it is difficult to discuss the relationship between various factors and contamination. In this study, contamination characteristics of insulator in a circulating wind tunnel were studied. The results show that speed of the wind and its direction has an obvious influence on the pollution distribution on the insulator and under crosswind, contamination degree of top surface is greater than that of bottom surface and leeward side greater than the windward side. What is more, the contamination characteristics of insulator are affected by wind speed, wind direction, relative humidity (RH) and other factors. Wind speed increment will make its non‐soluble deposit density (NSDD) raise and the higher wind speed is, the more obvious non‐uniform pollution distribution of windward and leeward side becomes. When RH is up to 90%, the growth of NSDD becomes more rapid. The decrease of particle size and the rise of its concentration, NSDD will increase; the NSDD under uniform wind will increase. The results have certain reference significance for insulator design and selection. [ABSTRACT FROM AUTHOR]

Pollution materials affect insulator flashover performance, and there is long-term significance in researching it. In this paper, common kinds of nitrates were used as the soluble pollution, and the ac flashover performance of four types of insulators under different nitrates were investigated. Basing on a large amount of primary data, the calculation of flashover gradient in specific to different pollution materials was discussed, and the effects of nitrates on it were analyzed. Research results indicate that, flashover gradient of insulator under nitrates is commonly higher than that under NaCl; among the nitrates, KNO3 corresponds to lower insulator flashover gradient while Ca(NO3)2 corresponds to a higher one; the exponent b, which characterizing the influence of ESDD on flashover gradient, is lower under nitrites than that under NaCl; for the four insulator samples polluted by nitrates, the flashover gradient of the porcelain type can be expressed by A?ESDD?0.21?NSDD?0.16, the flashover gradient EL of the glass type can be expressed by A?ESDD?0.22?NSDD?0.14, while that of the composite samples can be expressed by A?ESDD?0.19?NSDD?0.13. Research data may provide references for the better prediction of flashover voltage as well as for the better design of external insulation. [ABSTRACT FROM AUTHOR]

Polluted insulators frequently face flashover accident and it threatens the safety and stability of power system. In order to help to reduce the occurrence of flashover, it is necessary to study the contamination characteristics of insulators and its influence factors. In this study, the contamination of insulator is simulated by the Eulerian multiphase model in computational fluid dynamics. The flow field around insulators is calculated and the volume fraction of the particle phase is used to characterise the pollution degree on insulator surface. Results show that the pollution is mainly distributed on windward side and leeward side of insulator. The crosswind side of insulator is slightly contaminated. The four influence factors, wind velocity, particle concentration, particle diameter and flow angle have different effects on insulator contamination. Among these factors the particle concentration contributes most to the whole contamination degree of insulators. A wind tunnel contamination test on insulator is carried out to verify the feasibility of the numerical simulation. It can be found that simulated contamination distribution and variation of contamination degree with wind velocity well coincide with the results of wind tunnel test. The numerical simulation in this study is practical in studying the insulator contamination. [ABSTRACT FROM AUTHOR]

Affected by long‐term crosswind, insulator surface will get coated with fan‐shaped non‐uniform pollution, which lowers insulator flashover voltage as previous study revealed. In this study, a further research in specific to HVDC line insulation is presented. Taking typical dc insulator as the sample, its dc flashover performance under fan‐shaped non‐uniform pollution was tested. Then the influence of that kind non‐uniformity was investigated through analysing the pollution layer residual resistance, the flashover process and critical flashover voltage. Finally the relevant HVDC insulation selection was made. Research results indicate that: under fan‐shaped non‐uniform pollution, insulator flashover voltage (U50) gets impaired, and is more obviously impaired by ratio J of windward to leeward side salt deposit density (SDD) than leeward side area proportion T; under various T and J, there is still an exponential relationship between U50 and SDD; under fan‐shaped non‐uniform pollution the pollution layer residual resistance decreases, which theoretically promotes the arc propagation and flashover process, and thus finally lowers flashover voltage; for the transmission line in area with fan‐shaped non‐uniform pollution, adding insulator units to strengthen the withstand property are needed. [ABSTRACT FROM AUTHOR]

• A sensitivity analysis of stepped-lip chamber geometry parameters was carried out. • The lip radius has the greatest influence on power due to fuel splitting at lip. • A methodology is established with MIGA for combustion chamber design at high load. • The optimized chamber shows a good performance on combustion and emission. An optimization of spray angle and combustion chamber geometry was conducted to improve the in-cylinder fuel/air mixing process and optimize the combustion process of a heavy-duty diesel engine at full load. The chamber is based on the stepped-lip piston bowl, and the lip radius, lip depth, bowl radius and bowl distance are optimized. A sensitivity analysis of fuel/air mixing and combustion process to stepped-lip chamber geometry parameters was carried out. The simulated results show that the lip radius affects the fuel splitting at the lip, and has the greatest influence on the stepped-lip combustion chamber. The bowl radius is the second most important optimization parameter, followed by the bowl distance and finally the lip depth. To obtain the optimal combination of the combustion chamber geometry in a wide searching space, a total of 100,000 different combustion chambers were solved with multi-island genetic algorithm. Compared to the baseline, the optimized chamber has higher enhanced air utilization, more homogeneous fuel/air mixture, rapider combustion process, higher indicted power delivery and lower emissions. The results of this study are important to guide the stepped-lip combustion chamber design of heavy-duty diesel engines for better fuel/air mixture and combustion performance. [ABSTRACT FROM AUTHOR]

Previous simulation and observations showed that, the air flow field at windward and leeward side of insulator string will probably be different if the wind velocity is over a certain value, and thus causing the imparity of contamination degree at the two sides. In this paper, fan-shaped non-uniform polluting method was used to artificially simulate the different pollution severity at windward and leeward side of insulator string. Then, the effects of fan-shaped non-uniform pollution on ac flashover performance of 5 types of insulators were discussed. Test results indicate that, SDD, the ratio SDD of windward to leeward side (W/L), the occupation ratio of leeward side (k), will affect the ac flashover performance of insulator string. U50 and SDD still can be expressed by the negative power function. A reduction in W/L from 1/1 to 1/15 would give a decrease about 23% in a value, which causes U50 reducing about 25%, but n value changes little. The correction method proposed by EPRI is also applicable for fan-shaped non-uniform pollution, but has difference. A larger creepage distance of insulator does not mean that the creepage distance utilization rate is higher. Due to the influence of fan-shaped non-uniform pollution, the existing insulation configuration of transmission lines in heavily polluted areas may not satisfy the required insulation margin. The results have certain reference significance for the design and selection of transmission line external insulation. [ABSTRACT FROM AUTHOR]

UV imager has promising application prospect in the detection of corona discharge because of its advantages, such as high sensitivity, intuitive and non-contact discharge detection. In order to make better use of ultraviolet imager to detect corona of the high voltage electrical equipment, experiments are carried out to observe insulator corona discharge using the DayCor® Superb UV imager in this paper. During the experiments, voltages are applied on a FXBW-35/70 insulator, and corona discharge was detected through the ultraviolet imager. The relationship between the detected photon number, the instrument gain and the distance are studied. Then through extracting the discharge facular area from UV image using Matlab package, the differences of photon number and facular area in quantifying the corona discharge intensity are compared and analyzed. Research shows that the photon number increases first and then decrease with the rise of UV gain. Differently, the facular area increases monotonically with the rise of gain. There will be no multi-valued problem when the facular area is used to quantify the discharge. Both the photon number and facular area decrease with the increase of detecting distance, but the fluctuation of the facular area-distance curve is smaller than the photon number — distance curve. Using the facular area to quantify the corona discharge can be more accurate. The study results of this paper provide references for better assessing the electric equipment corona discharge intensity by ultraviolet imager. [ABSTRACT FROM AUTHOR]

Observations of contamination tests showed that, the contamination distribution of insulators is usually uneven. In this study, the solid layer method was used to imitate different non‐uniform pollution conditions and the AC pollution flashover tests of 7‐unit insulators were carried out. The results indicate that the increase of uneven pollution degree J from 1 to 15 will give a 39% raise of U50 under non‐uniform pollution on top and bottom surfaces, a 23% decrease for fan‐shaped non‐uniform pollution and a 21% higher U50 with ring‐shaped non‐uniform pollution. A higher occupation ratio (k) of leeward side will reduce U50 under fan‐shaped non‐uniform pollution and a bigger radius R of heavy polluted area has certain effect on U50 for ring‐shaped non‐uniform pollution. The U50 and salt deposit density still can be expressed by the negative power function, and non‐uniform pollution conditions and J have great effect on a, but less impact on n. The correction equations of different non‐uniform pollution conditions are obtained and the relative errors are acceptable. The research has certain reference significance for the design and selection of AC transmission line external insulation. [ABSTRACT FROM AUTHOR]

Air pressure affects the electrical performance of polluted insulator. The dc pollution flashover process of 7-unit XP-160 insulator string under low air pressure was presented by laboratory tests in this paper. During the tests, the flashover voltage and the critical flashover current were measured. Also, based on the insight of insulator flashover process, the length of discharge path, the arc propagation velocity and arc radius under different air pressure were investigated and measured. The research results indicate that, the position of arcing point is stochastic and multipoint arcing phenomenon exists. Surface arc will levitate and develop into air-gap arc under low air pressure. The length of discharge path is related to air pressure and pollution degree, and it is always shorter than the total creepage of insulator string. The leakage current, the arc shape and arc propagation velocity, are also related to air pressure. In this study, it was measured that the arc radius (ra) varied from 1.5 to 3.5 mm, and the characteristic exponent describing the influence of air pressure on arc radius (m) varied from -0.35 to -0.65. The research results are of some significance for revealing the mechanism of flashover and discharge performance of arcs. [ABSTRACT FROM AUTHOR]

In areas with heavy dust or continuous wind in a single direction, fan-shaped nonuniform contamination at the windward and leeward side of the insulator string may affect flashover performance. In this paper, dc pollution flashover tests of insulators under fan-shaped nonuniform pollution were presented, and a comparison of flashover performance among 7-unit suspension insulator strings with four different disk profiles was made. Then, the influence of fan-shaped nonuniform pollution on flashover voltage, arc propagation, and critical leakage distance were investigated. Research results indicate that the insulators with different types were influenced variously on their flashover stress, utilization rate of creepage distance, and critical leakage distance by fan-shaped nonuniform pollution. A reduction in the ratio W/L of windward to leeward side salt deposit density (SDD) from 1/1 to 1/15 gave a median 35% \pm 4% decrease in flashover strength. The extrapolation of results for the seven-unit strings suggests that some increment in shed space or structure height of the insulator can be preferable in dc transmission lines where there is fan-shaped nonuniform pollution accumulating at the windward and leeward side of the insulator string. [ABSTRACT FROM AUTHOR]

• A novel fault diagnosis method called GMA-DRSNs is proposed. • The method can achieve better performance for noised vibration signals. • The method uses attention mechanism to dynamically infer self-adaptive parameters. • We firstly give a geometry explanation about DRSNs' structure. The large environmental noise interference has a negative impact on the fault diagnosis of vibration signals. To solve the problems, we present novel global multi-attention deep residual shrinkage networks (GMA-DRSNs), by using attention mechanism. In this paper, the self-adaptive Leaky Thresholding shrinkage function is firstly proposed to substitute the original soft thresholding function in the deep residual shrinkage networks (DRSNs), where all the inner parameters of the approach are automatically inferred based on the attention sub-networks. Secondly, a novel activation function is further presented based on the above improvement, in order to realize the corresponding adaptive nonlinear transformation of each signal. Various experimental results show that our work can achieve better performance compared with the previous works. Finally, we systematically analyze the threshold's tendency, and surprisingly find the same consistency with the receptive field of convolutional neural networks, which is the first geometry explanation work about DRSNs' structure. [ABSTRACT FROM AUTHOR]

The type of pollution materials may influence the flashover performance of an insulator. In this paper the pollution flashover performance of a 7-unit insulator string, consisting of typical discs, is determined by laboratory tests while varying the weight percentage of soluble (NaCl and CaSO4) or non-soluble (SiO2, Al2O3 and Fe2O3) materials. When studying the effect of pollution materials on flashover performance, the influence of volume conductivity and equivalent salt deposit density (ESDD) under different weight percentages of soluble materials is firstly investigated, and then the underlying factor, the thermal ionization of pollution materials, is considered. Finally, the measurement results of leakage current under different pollution materials are presented. The research results indicate that the effect by weight of CaSO4 is not as severe as that of NaCl, and the reason is not just its effect on the layer conductivity and ESDD, but its effect on the thermal ionization during the arc propagation process may also be one of the key factors. The fact that a small amount of Al2O3 and Fe2O3 causes the flashover voltage to decrease by 20%, may result from the lower ionization potentials and the higher leakage currents caused by non-soluble materials containing Al2O3 and Fe2O3. [ABSTRACT FROM AUTHOR]

Under continuous wind of single direction, the leeward area of insulator string may be polluted more seriously than windward area, making the pollution layer distributes like a fan-shape. In this paper, dc pollution flashover tests of 7-unit XP-70 insulator string with fan-shaped non-uniform pollution were carried out. Then the influence of fan-shaped non-uniform pollution on flashover voltage, flashover process, leeward side surface layer conductivity and surface pollution layer resistance were discussed. Research results indicate that, the ratio W/L of windward to leeward side salt deposit density (SDD) affects the dc flashover performance of insulator string. A reduction in W/L from 1/1 to 1/15 would give a decrease of 28% in flashover strength. Flashover voltage may also decrease when the occupation ratio (T) of leeward side increases from 10% to 30%. Under fan-shaped non-uniform pollution, U50 can still be expressed by a negative exponential function of SDD, and the effect of fan-shaped non-uniform pollution on U50-SDD relationship may mainly lie in changing the proportionality coefficient a rather than the exponent n; discharge path was restricted along the leeward side, which may make the air-gap arc easily formed and benefit the flashover process. [ABSTRACT FROM AUTHOR]

Highlights: [•] The addition of ethanol or n-butanol improves the combustion stability. [•] Ethanol/gasoline blends show stronger anti-knock ability than gasoline and n-butanol/gasoline blends. [•] The employment of EGR overcomes the negative effect of n-butanol on knock. [•] Both EGR and alcohol addition are beneficial for the reduction of PN emissions. [ABSTRACT FROM AUTHOR]

As natural contamination of insulators may lead to flashover, its determining factors should be studied to prevent the occurrence of pollution flashover. In this paper, the fluid mechanics models of insulators with typical shed types were established to simulate their flow field distribution and particle collision coefficient (P). At the same time, a natural contamination test lasting for 8 months was carried out in order to contrast the experimental data and simulation results. The research results have shown that: wind velocity and shed type affect the flow field near the insulators; P is affected by particle diameter and wind velocity; under certain particle diameter and wind velocity, P reaches the maximum value; rainfall has different effects on contamination of insulators with different shed types; wind causes non-uniformly distribution of pollution on the surfaces; the simulation test and the experimental test are comparable. The research method and results can provide not only reference to establishing natural contaminating model but also significant meaning for the external insulation design and selection. [ABSTRACT FROM AUTHOR]

Abstract: The effects of tumble combined with EGR (exhaust gas recirculation) on the combustion and emissions were experimentally investigated in a spark ignition engine in this study. A low pressure loop EGR system and a variable tumble valve in intake ports were employed, by which wide range of EGR ratio and tumble ratio could be achieved. All the tests were performed at part loads, and the equivalence ratio was kept constant at 1.0. The results show that the combination of EGR and enhanced tumble motion produces a significant improvement in fuel economy (13.1–19.5%) and a reduction in the coefficient of variations of indicated mean effective pressure (CoVIMEP) due to the significantly shortened combustion duration. By optimizing the combustion process with EGR and enhanced tumble, NO x (nitrogen oxides) emissions drastically decrease, while HC (hydrocarbons) emissions slightly rise. For CO (carbon monoxide) emissions, the enhanced tumble takes a positive effect. [Copyright &y& Elsevier]

The ratio T/B of top to bottom surface salt deposit density (SDD) affects the ac pollution flashover performance of disk insulator strings. The ac pollution flashover stress was established for fifteen different combinations of SDD and T/B in a systematic study, making use of seven-unit suspension strings with six different disk profiles in this paper. Then a comparison was made of pollution performance for glass and porcelain disks with the same profile. The observed relation of ac flashover stress EL to SDD and T/B followed an equation of the form EL=c\cdotSDD^{-b}\cdot(1-A\cdot\log(T/B)). The values of c, b and A were fitted to test results for glass and porcelain disks of identical bottom-rib profile, and to four other bottom-rib and external-rib profiles. A reduction in the ratio T/B from 1/1 to 1/15 gave a median 26% \pm 8% increase in flashover strength, corresponding to the calculated increase in overall pollution layer resistance. Extrapolation of results for the seven-unit strings to UHV dimensions suggests that some reduction in leakage distance can be accepted in areas where there is frequent natural washing of the top surfaces of disk insulators. [ABSTRACT FROM AUTHOR]

Pollution-induced flashover has a serious threat on the safe and reliable operation of power systems. It is known that the pollution flashover voltage is directly related to the wetting degree of the pollution layer. But the wetting performance characteristics and control method of pollution layer on insulators have not been properly specified in the existing pollution test standards. In this paper, the wetting processes of the pollution layer on different types of insulators have been studied in an artificial fog chamber. In our test studies, the leakage current on the surface of polluted insulators under a different test environment is measured and then the curves of leakage current varying with time are plotted. Furthermore, the main influencing factors of the wetting process of the pollution layer have been analyzed in this paper. Test results show that the wetting process of the pollution layer can be characterized well through the change of leakage current, and when the leakage current reaches the maximum value, the pollution layer is saturated with fog. Specifically, during the wetting process, the leakage current gradually increases until the maximum value and then decreases; the time for the pollution layer to become saturated is dependent on the salt-deposited density (SDD), the steam fog input rate, the temperature in the artificial fog chamber, and the type of insulators. It is found that with the increase of SDD and the decrease of the steam fog input rate and the temperature in the climate chamber, the necessary wetting time will increase, and the more complex the insulator structure is, the longer the wetting time will be. [ABSTRACT FROM AUTHOR]

This paper presents the relationship between ac flashover voltage and the varying positioning of iced insulator strings under different icing condition. The results were obtained through laboratory test in multifunction artificial climate chamber located at Chongqing University, China. Also difference of the ac icing flashover performance of single insulator string, double insulator strings, inverted v-type insulator strings and insulators connected with alternately large and small diameter sheds (CALSDS) were analyzed in this paper. According to test results, it is found that the distorted electric field distribution on iced insulator string is the main reason that results in the decrease of flashover voltage. With the same icing degree, the icing flashover voltage of either double insulator strings or as an inverted v-type is lower than that of single insulator string. If insulators are arranged with the type of CALSDS, the speed of icicles to bridge the insulators will decrease. To ensure the height of conductor from the earth remaining unchanged, the ac icing flashover voltage of insulator string can be increased by arranging the insulator strings as an inverted v-type or arranging the insulators with the types of CALSDS with the pattern of "3+1" or "4+1". [ABSTRACT FROM AUTHOR]

Ascorbic acid (AsA) is an important antioxidant in plants, and its biosynthesis is finely regulated through developmental and environmental cues; however, the regulatory mechanism remains unclear. In this report, the knockout and knockdown mutants of Arabidopsis AtERF98 decreased the AsA level, whereas the overexpression of AtERF98 increased it, which suggests that AtERF98 plays an important role in regulating AsA biosynthesis. AtERF98-overexpressing plants showed enhanced expression of AsA synthesis genes in the d-mannose/ l-galactose ( d-Man/ l-Gal) pathway and the myo-inositol pathway gene MIOX4, as well as of AsA turnover genes. In contrast, AtERF98 mutants showed decreased expression of AsA synthesis genes in the d-Man/ l-Gal pathway but not of the myo-inositol pathway gene or AsA turnover genes. In addition, the role of AtERF98 in regulating AsA production was significantly impaired in the d-Man/ l-Gal pathway mutant vtc1-1, but the expression of the myo-inositol pathway gene or AsA turnover genes was not affected, which indicates that the regulation of AtERF98 in AsA synthesis is primarily mediated by the d-Man/ l-Gal pathway. Transient expression and chromatin immunoprecipitation assays further showed that AtERF98 binds to the promoter of VTC1, which indicates that AtERF98 modulates AsA biosynthesis by directly regulating the expression of the AsA synthesis genes. Moreover, the knockout mutant aterf98-1 displayed decreased salt-induced AsA synthesis and reduced tolerance to salt. The supplementation of exogenous AsA increased the salt tolerance of aterf98-1; coincidently, the enhanced salt tolerance of AtERF98-overexpressing plants was impaired in vtc1-1. Thus, our data provide evidence that the regulation of AtERF98 in AsA biosynthesis contributes to enhanced salt tolerance in Arabidopsis. [ABSTRACT FROM AUTHOR]

In this paper, the dc pollution flashover performance of various types of porcelain, glass, and composite insulators is investigated. It also presents analysis of the dc flashover process of polluted insulator string at high altitude using insight from high-speed photography. The research results indicate that the relationship between the dc pollution flashover voltage and the string length of insulators is basically linear, the characteristic exponents describing the influence degree of air pressure on pollution flashover voltage vary between 0.35 and 0.77 and are related to the insulator types and pollution degree, etc., the characteristic exponents describing the influence degree of pollution on flashover voltage vary between 0.24 and 0.36 and are related to the insulator types and air pressure, etc. Based on the flashover phenomena using the insight from high-speed photography, a new physical model explaining the flashover mechanism for a polluted insulator string at high altitude is introduced, which can be expressed as an electrical circuit consisting of a surface arc of length x1 and air-gap arc of length x2 in series with a resistance representing the wet pollution layer. In addition, the exponent n describing the influence degree of air pressure on flashover voltage for the polluted insulator is discussed. [ABSTRACT FROM PUBLISHER]