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Flexible DC technology has revolutionary significance in flexibly solving the problem of high proportion of new energy consumption. Due to the vulnerability of high-ratio power electronic equipment and the difficulty in extracting fault information, traditional line protection schemes can no longer be reliably adapted to the flexible DC transmission system. A rapid protection scheme for flexible DC transmission lines based on voltage traveling wave steepness is proposed in this paper. By analyzing the transient characteristics of DC line faults, and utilizing the differences in the steepness and polarity of fault voltage traveling waves on both sides of the current-limiting reactor, the range of effective transient information extraction is increased, and the fault identification inside or outside the region is realized. The faults are classificated by utilizing the significant difference in the degree of voltage traveling wave variation between the faulty and sound poles. Lightning interference is considered and a rapid identification method is proposed by using its initial change characteristics. Finally, the performance of the protection scheme under various influencing factors is verified by simulation, which can identify faults quickly and reliably and has good sensitivity and anti-interference ability.

The build-up and occurrence of earthquakes are due to the accumulation and release of stress in fault zones. When subjected to tectonic extrusion stress, the crystal structure of the minerals within a fault zone will change. In this study, Raman spectroscopy analysis was conducted on the concurrently deposited quartz veins from Shenxigou, along the Yingxiu-Beichuan fault, and from Niyang River mouth, in the southern section of the Milin fault. The test results reveal a 3.29 cm−1 shift in the characteristic 464 cm−1 peak of the quartz in the veins along the fault plane of the Yingxiu-Beichuan fault, which was significantly lower than the shifts in the quartz peaks of the quartz on both sides of the vein. The 464 cm−1 peak shifts of the samples collected 10 m to the NW and 21 m to the SE of the fault plane were approximately 4.40 and 4.62 cm−1. In the veins from the Milin fault, considerable shifts of the 464 cm−1 quartz peaks occurred at the fault plane and to both sides within 5.5 m of the fault plane. No significant change in the 464 cm−1 Raman peak of quartz was observed for the samples 5–28 m to the SE of the fault plane. These results indicate that the tectonic extrusion stress accumulated more easily in proximity to the fault plane, resulting in significant changes in the crystals near the fault plane. We conclude that there is a correlation between the degree of change in the crystal structures of the minerals in thrust fault zones and fault activity, and such a correlation can provide a new method for studying the activity of thrust faults in areas with bedrock.

The amplitude of AC line current at the inverter side is affected by DC commutation failure and fluctuates for a short time after single-phase trip.The fluctuation range increases with the increase of the number of DC commutation failures,resulting in the misjudgment of the traditional single-phase fault nature criterion based on the amplitude of the recovery voltage. To solve this problem,a transmission line fault equivalence model is built firstly to evaluate the impact of DC commutation failure on the sound phase voltage. Then the time domain expressions are derived for the disconnected phase voltage during the recovery voltage stage for different fault nature. After that,a single-phase fault nature identification criterion based on time domain voltage integration is proposed,and its effectiveness is verified by PSCAD/EMTDC simulation. The results show that the proposed method has good resistance to transition resistance and DC interference,and the fault nature identification criterion is suitable for DC commutation failure.

In the present study, nonlinear dynamic process data are mapped into the kernel state space by kernel gauge variable analysis method to obtain decorrelated state data. The time-lapse covariance matrix of the state data is weighted and summed to obtain the time-lapse structure matrix of the state data, and then supervised kernel independent component analysis (SKICA) is established, the independent component feature data is extracted from the status data and the monitoring statistics are constructed to detect the process faults. The data show that kernel independent component analysis (ICA) method (KICA) method can detect slow fault faster than the ICA method, except that the statistical detection ability of F3 and FS is reduced, and the KICA method can significantly improve the detection performance of other faults and statistics. By analyzing the detection results of SKICA method, it is obvious that in the detection process of all five kinds of slow faults, the fault detection capability of SKICA is better than that of ICA and KICA. The results of continuous stirred reactor simulation system show that, compared with the basic linear process, the slow fault detection has a good monitoring performance, it can detect the small deviation in the process sensitively and give alarm information to the slow fault in time, to improve the fault detection rate.

If commutation failure does not occur when single-phase high resistance grounded in single-circuit AC line of inverter,then single-phase circuit breaker tripping may lead to commutation failure. Firstly,the expression of converter bus voltage after single-phase circuit breaker trip is derived by using symmetrical component method. Based on the expression,the main factors affecting the converter bus voltage are analyzed,and it is found that it is related to the equivalent parameters of the system. Then,the influence mechanism of voltage deviation angle of commutator bus on extinction angle is studied. It is found that the zero-crossing forward angle of commutation bus voltage after the single-phase breaker trips is the main factor leading to the decrease of the extinction angle,and commutation failure will be induced in serious cases. Finally,the AC/DC simulation model was built on the PSCAD/EMTDC electromagnetic transient simulation software platform. The simulation verifies the effect of the tripping of single-phase breaker in single-circuit AC line on the commutation process of inverter. The simulation results are consistent with the theoretical analysis.

Abstract Quorum sensing (QS) can function to shape the microbial community interactions, composition, and function. In wastewater treatment systems, acylated homoserine lactone (AHL)-based QS has been correlated with the conversion of floccular biomass into microbial granules, as well as EPS production and the nitrogen removal process. However, the role of QS in such complex communities is still not fully understood, including the QS-proficient taxa and the functional QS genes involved. To address these questions, we performed a metagenomic screen for AHL genes in an activated sludge microbial community from the Ulu Pandan wastewater treatment plant (WWTP) in Singapore followed by functional validation of luxI activity using AHL biosensors and LC–MSMS profiling. We identified 13 luxI and 30 luxR homologs from the activated sludge metagenome. Of those genes, two represented a cognate pair of luxIR genes belonging to a Nitrospira spp. and those genes were demonstrated to be functionally active. The LuxI homolog synthesized AHLs that were consistent with the dominant AHLs in the activated sludge system. Furthermore, the LuxR homolog was shown to bind to and induce expression of the luxI promoter, suggesting this represents an autoinduction feedback system, characteristic of QS circuits. Additionally, a second, active promoter was upstream of a gene encoding a protein with a GGDEF/EAL domain, commonly associated with modulating the intracellular concentration of the secondary messenger, c-di-GMP. Thus, the metagenomic approach used here was demonstrated to effectively identify functional QS genes and suggests that Nitrospira spp. maybe QS is active in the activated sludge community.

Along the lower reaches of the Yarlung Zangbo River, scattered alluvium sections appear on T1 and T2 terraces. The alluvial deposits on the T1 terrace in Linduo and Ximogou and the T2 terrace in Guoguotang are composed principally of coarse-grained sand particles and rock fragments, with no observable fine-grained components. The T1 terrace alluvium section is dominated by clay and silt and occurs near the town of Dexing, and optically stimulated luminescence dating of sample from this site revealed an age of 18.2 kyear, which indicates that the incision rate of the Yarlung Zangbo River has been 4.7 mm/year since the formation of this section. On the basis of the component characteristics of terraces in Motuo County, the provenance for the terraces is probably related to the breaking of the palaeo-dammed lakes in the middle reaches of the Yarlung Zangbo River. A 430 m elevation difference still exists between the study area and the local base level downstream of the Yalung Zangbo River (Assam Plain), although this river has a strong incision capability (4.7 mm/year), which suggests that tectonic uplift remains very intense east of the Namche Barwa syntaxis.

Recycling is the most effective way to dispose of waste polymer materials. It can not only reduce the harm of polymer materials to the natural environment, but also achieve the purpose of saving cost and turning waste into treasure. A self-made melt differential electrospinning device was used to recover the degraded polypropylene (PP) non-woven fabric as a raw material, and the special powder for recycling and degrading PP non-woven fabric after acid treatment and adding different plasticizers with a mass fraction of 10%. A blend of materials of sodium stearate, acetyl tributyl citrate (ATBC), and dioctyl adipate (DOA) was spun, and a nanofiber membrane was prepared at 300 ℃. The optimum degradation time of PP nonwoven fabric spinning and the effect of adding different plasticizers on the morphology, oil absorption performance and reusability of PP-degraded non-woven fabric nanofibers were investigated. Studies have shown that the addition of plasticizer ATBC works best. When the spinning voltage is 40 kV, the spinning distance is 70 mm, the spinning temperature is 300 ℃, and the ATBC mass fraction is 10%, the fiber diameter is as fine as 1.13 μm. The fiber membrane oil absorption ratio is 115.4 g/g, and the oil retention ratio is 70.3 g/g, which are 4 times and 3 times that of the initially commercially available PP nonwoven fabric, and has good reusability.

By the theory of equivalent substitution,the FT455 model with high precision FT pin-cycloid is used as the carrier,and based on the way of eccentricity modification,the equivalent substitution of stress balanced tooth profile is carried out. To ensure that the tooth profile error is the smallest as target function,the VB programming and MATLAB optimization is carried out,to optimize the design of eccentricity modification tooth profile to replace the stress balanced tooth profile. So that make the meshing tooth number and transmission error of the equivalent substitution tooth profile are within the allowable range,and the transmission accuracy of equivalent stress balanced tooth profile and the stress distribution of the tooth surface are calculated.Through ANSYS finite element analysis of the theoretical programming results to verify the analysis. It is determined that this equivalent stress equalization tooth profile can replace the stress equalization tooth profile.

The FT pin-cycloid reducer and RV reducer are new type of pin-cycloid transmission reducer with closed two stage transmission. The both type of reducer has the advantages of more compact structure,high rigidity,low vibration,high efficiency of low speed operation zone and so on. The structure of the two is similar in transmission mode,and the transmission performance is greatly improved compared with the previous generations of reducer and the transmission efficiency is also greatly higher. The FT455-81 prototype and RV-160 E-81-B-B prototype are taken as examples to compare the performance,price and other aspects.The 3D model of the FT and RV reducers is built. Its transmission principle,transmission characteristics and structure are analyzed and compared. The advantages and disadvantages of RV reducer and FT reducer are expounded. The suitable for application of the two reducer is found.

To study the stress of plastic helical gears in the new type car door lock under the working condition,establish the finite element model of helical gear mesh through ABAQUS,the contact process of plastic helical gears is simulated and analyzed based on nonlinear contact algorithm,and obtain the contact stress and bending stress of plastic helical gears. According to Lewis equation and gear Hertz stress theory to calculate the stress of the plastic helical gear meshing process,and compare with the finite element simulation results. The results verify the strength of plastic gears meet actual requirements,and point out the maximum contact stress in the normal engagement process appears in the double teeth meshing zone,the maximum bending stress appears in the three teeth meshing zone,gear prone to fatigue failure in those positions,propose advice to improve the strength of the gear teeth. The study prodives theory basis for the strength analysis of plastic gears.

The FT Pin-cycloid drive is a new double-stage driving structure. In order to design and develop the reducer in the future,a relatively convenient parametric modeling and assembly scheme is provided,taking Creo3. 0 as platform,the 3 D parametric model of parts and components is established,the feature parameters in the model are related to each other,the assembly around benchmark is reasonable selection,a virtual prototype is established. When the characteristic parameters of the model are changed,the assembly relation is invariable,and the correctness of assembly is determined through the model verification. It is convenient for the designer to operate.

Brachial artery aneurysms are rare disease that can be encountered. It is divided into true and false. The frequency of true aneurysm of the brachial artery is so much unusual. So, we present a case of a 59 year old male who presented to us with complaint of mass in left upper limb since many years ago. Now, there was sudden onset of progressive pain with coldness, numbness, tingling sensationand blackish discolouration of skin from 8 hours. The left upper limb was pulseless and color Doppler ultrasound showed a non-pulsatile aneurysm at the mid level of left brachial artery associated with arterial occlusion in its distal branch by thrombus. The patient was successfully revascularised by interposing a saphenous vein graft.Thus,this case suggest that the prompt diagnosis of true brachial artery aneurysm by ultrasound or color Doppler ultrasound and the proper treatment by surgical repair can save limb from dangerous sequel Keywords: brachial artery aneurysm; color doppler ultrasound; true aneurysm; ultrasound.