bluuebunny/crossref_metadata_2025 huggingface dataset:
Noise modelling of perfusion CT images for robust hemodynamic parameter estimations
Authors: Li Sui , Zeng Dong , Bian Zhaoying , Ma Jianhua
Published: May 2022

Objective. The radiation dose of cerebral perfusion computed tomography (CPCT) imaging can be reduced by lowering the milliampere-second or kilovoltage peak. However, dose reduction can decrease image quality due to excessive x-ray quanta fluctuation and reduced detector signal relative to system electronic noise, thereby influencing the accuracy of hemodynamic parameters for patients with acute stroke. Existing low-dose CPCT denoising methods, which mainly focus on specific temporal and spatial prior knowledge in low-dose CPCT images, not take the noise distribution characteristics of low-dose CPCT images into consideration. In practice, the noise of low-dose CPCT images can be much more complicated. This study first investigates the noise properties in low-dose CPCT images and proposes a perfusion deconvolution model based on the noise properties. Approach. To characterize the noise distribution in CPCT images properly, we analyze noise properties in low-dose CPCT images and find that the intra-frame noise distribution may vary in the different areas and the inter-frame noise also may vary in low-dose CPCT images. Thus, we attempt the first-ever effort to model CPCT noise with a non-independent and identical distribution (i.i.d.) mixture-of-Gaussians (MoG) model for noise assumption. Furthermore, we integrate the noise modeling strategy into a perfusion deconvolution model and present a novel perfusion deconvolution method by using self-relative structural similarity information and MoG model (named as SR-MoG) to estimate the hemodynamic parameters accurately. In the presented SR-MoG method, the self-relative structural similarity information is obtained from preprocessed low-dose CPCT images. Main results. The results show that the presented SR-MoG method can achieve promising gains over the existing deconvolution approaches. In particular, the average root-mean-square error (RMSE) of cerebral blood flow (CBF), cerebral blood volume, and mean transit time was improved by 40.3%, 69.1%, and 40.8% in the digital phantom study, and the average RMSE of CBF can be improved by 81.0% in the clinical data study, compared with tensor total variation regularization deconvolution method. Significance. The presented SR-MoG method can estimate high-accuracy hemodynamic parameters andachieve promising gains over the existing deconvolution approaches.
Beyond automatic medical image segmentation—the spectrum between fully manual and fully automatic delineation
Authors: Trimpl Michael J , Primakov Sergey , Lambin Philippe , Stride Eleanor P J , Vallis Katherine A , Gooding Mark J
Published: May 2022

Semi-automatic and fully automatic contouring tools have emerged as an alternative to fully manual segmentation to reduce time spent contouring and to increase contour quality and consistency. Particularly, fully automatic segmentation has seen exceptional improvements through the use of deep learning in recent years. These fully automatic methods may not require user interactions, but the resulting contours are often not suitable to be used in clinical practice without a review by the clinician. Furthermore, they need large amounts of labelled data to be available for training. This review presents alternatives to manual or fully automatic segmentation methods along the spectrum of variable user interactivity and data availability. The challenge lies to determine how much user interaction is necessary and how this user interaction can be used most effectively. While deep learning is already widely used for fully automatic tools, interactive methods are just at the starting point to be transformed by it. Interaction between clinician and machine, via artificial intelligence, can go both ways and this review will present the avenues that are being pursued to improve medical image segmentation.
Laser ablation as a method for microsampling of paint layers
Authors: Balakhnina I A , Brandt N N , Dedova A E , Zagladin A A , Chikishev A Yu
Published: May 2022

It is proposed to use nanosecond laser pulses to obtain microsamples of paint layers with subsequent identification of the substance using Raman microspectroscopy. It is shown that the ablation of the paint layer on the primed canvas is a two-threshold process. The proposed technique can be used to study paintings.
Development of the microbubble pump having ‘S-shape’ impeller using experimental and numerical analysis
Authors: Lee S-M , Jang C-M
Published: May 2022

Microbubble pumps for water treatment can be used in a variety of fields, including wastewater treatment of semiconductor factories, sewage treatment, and aquaculture. In this study, a microbubble pump, with the ‘S-shape’ impeller, for sewage treatment has been developed in two steps. In the first step, a numerical design optimization was performed to develop a small-scaled microbubble pump. In the second step, a microbubble pump with a capacity that can be used in an actual water treatment facility has been developed through the scale-up process of a small-scaled optimum design of microbubble pump. The experimental test rig of the microbubble pump has been developed to investigate the performances of the microbubble pump, such as air and water flow rate, pressure differences and torque. To analyse three-dimensional flow field in the micro-bubble pump, general analysis code, CFX, has been employed. SST turbulence model has been employed to estimate the eddy viscosity and compared the pump performance to k-ε model. Unstructured grids have been used to represent a hybrid grid system including blade, casing and inlet casing. The results in the first step, a small-scaled optimum design shows the efficiency about 30.4%, which corresponds to a 0.4 percentage points increase compared to the conventional one. The results in the second step, the final design of microbubble pump shows an efficiency of 32.5% at the flow rate of 200 lpm.
LES investigation of different shedding cloud behaviors around the typical NACA66 hydrofoil
Authors: Wang Ziyang , Cheng Huaiyu , Ji Bin
Published: May 2022

The unsteady cavity dynamics induced by the reverse flow and shock wave is a crucial issue in studies of cloud cavitation. In the current meeting paper, numerical simulation of cavitating flow around the NACA66 hydrofoil is performed based on the self-developed program. LES method is introduced to adequately account for the transient turbulence effects in compressible cavitating flow. The simulation agrees favorably with the previous experiment for the cavity shedding behaviors. The results showed that the unsteady cavity dynamics is induced by both the reverse flow and shock wave mechanism. Besides, the different cavity shedding behaviors of the reverse flow and shock wave are compared in details.
Effects of dissolved gas on surface pressure of a hydrofoil under cavitation condition
Authors: Matsuura Y , Tsuji D , Watanabe S , Tsuda S
Published: May 2022

Dissolved gas in water is known as one of the factors which affect cavitation. The present study focuses on the effect of dissolved gas on cavitation around a hydrofoil, more specifically on the hysteresis of cavitation and surface pressure of the hydrofoil. The pressure measurement on a hydrofoil of Clark Y-11.7% was carried out under various dissolved gas conditions. Pressure in the test section was reduced stepwise from an atmospheric pressure to that in a super-cavitation condition, then was increased stepwise to the atmospheric pressure condition. Amount of dissolved oxygen (DO) was used as a parameter representing the degree of air content, and three DO conditions were set at low DO: under 30%, middle DO: around 50%, and high DO: over 70% of saturation under atmospheric pressure. Also, two angles of attack, 8 and 20 degrees were selected. Although there is no significant difference of the surface pressure and its hysteresis at the angle of attack of 8 degrees, dissolved gas seems to affect the behavior of cavitation. At the angle of attack of 20 degrees, it was found that the appearance of cavity was changed by DO conditions, and it would affect surface pressure of the foil. Under high DO condition, when the cavity oscillated with large amplitude, dissolved gas seemed to enhance the growth of the cavity, and the cavity tended to grow as covering the suction surface of the foil; it would make the time-averaged surface pressure of high DO condition lower than that of the other DO condition.
Reduction of flow-induce noise of a high-speed centrifugal pump by applying blade leaning on guide vane
Authors: Wei Z C , Li N , Xiao R F , Tao R , Yang W , Hu H L
Published: May 2022

The generation of noise is harmful to worker’s health and the stable operation of the system. Due to the high speed and high head of the high-speed centrifugal pump, the noise performance needs improvement. Therefore, a high-speed centrifugal pump was studied both in experiment and numerical way. The noise performance of the high-speed pump is improved by optimizing the design of the impeller and the guide vane. The blade leaning is also applied as an improvement with forming the X-shape stagger between rotor and stator. Base on the numerical simulation, the characteristic curves and unsteady characteristics of different optimized cases are predicted. The optimal case is selected as the final experimental object to verify the effectiveness. Numerical result indicated that the pressure fluctuation at blade pass frequency (BPF) and the fluctuated radial force is the main component of the original pump. The noise spectrum distribution of the original pump is concentrated near the BPF in the experiment, which means that the rotation effect of the impeller is the main reason for the noise of the pump. By improving the hydraulic design, the pressure fluctuation and the radial force in the pump can be effectively suppressed. But many factors affect the pump noise, the improvement of hydraulic design is limited.
Computational fluid dynamic simulation of hull reservoir wave energy device
Authors: De Alwis V A U , De Silva A P K , Gunawardane S D G S P , Lee Young-Ho
Published: May 2022

This paper presents a Computational Fluid Dynamics (CFD) analysis of a wave energy device called the Hull Reservoir Wave Energy Converter (HRWEC). The device consists of a floating hull and a flap connected to the shaft of power take-off system (PTO), which is integral to the hull structure. It is unique due to its ability to convert wave energy by utilizing the pitch motion of the hull and rotating flap due to the internal water movement in the hull. Due to the complexity of the internal fluid dynamics, a CFD-based analysis was considered most appropriate. The CFD investigation of the dynamics of the device was done under regular wave conditions by using the ANSYS-AQWA and ANSYS FLUENT. Relative pitch angle variation, the hydrodynamic coefficients, which determine the degree of power extraction, were obtained from simulated results. A simulation was designed exhibiting complete system dynamics for different configurations varying on internal water height. Excellent convergence was observed, and an optimum configuration was identified. It is expected to validate the simulation results through experiments in the foreseeable future.
Influence of distance from water surface of a horizontally installed Savonius turbine in a rectangular open channel on turbine performance
Authors: Katayama Y , Watanabe S , Tsuda S
Published: May 2022

The aim of this investigation is to develop a nano-hydro turbine that can effectively utilize the wasted hydraulic energy in infrastructure such as agricultural and industrial canals and irrigation waterways. Up to this time, the utilization of such a small hydropower has not progressed owing to economic reasons. Therefore, we focus on the Savonius type, which has the advantages of low manufacturing cost and excellent maintainability because of its simple structure. Conventionally, the Savonius type has been developed and researched as a vertical axis wind turbine. In order to effectively utilize the water surface flow, which is particular to open channels, we place the turbine runner perpendicular to the water flow and horizontally on the channel bottom. In the present study, we experimentally investigated the effect of the parameters for the turbine installation and its operation, namely distance between a runner and the water surface and the rotation direction of the runner, on the performance at each water level. As a result, it was found that the suitable installation depth differs depending on the rotation direction of the turbine.
Optimization design and unsteady flow analysis of stall characteristics in a vertical centrifugal pump
Authors: Yang Gang , Zhao Xutao , Zhang Desheng , Yang Xueqi , Geng Linlin , Gao Xiongfa
Published: May 2022

In this paper, an optimization design of the vertical centrifugal pump with vaned diffuser was accomplished, and analyzed the internal flow pattern of the model before and after optimization under stall conditions to explore the relationship between design parameters and the stall characteristics. The reasons for the improvement of efficiency and hump characteristics curve after optimization were revealed combined with streamline distributions, entropy production theory and pressure fluctuation. The results show that the error between the external characteristic result calculated by Computational Fluid Dynamics (CFD) and the experimental value is less than 5%, which proves the reliability of the numerical simulation method adopted in this paper. The hydraulic efficiency under multiple operating conditions and stall characteristics of the optimized model have been significantly improved. After optimization, the entropy production rate in the vaned diffuser is greatly reduced, and the improvement of the internal flow pattern in the vaned diffuser is the main reason for slowing down the hump characteristic curve. The hydraulic performance and the stall characteristics of the vertical centrifugal pump can be significantly improved by properly increasing the radial distance of the vaneless region. The matching relationship between the vaned diffuser and the impeller is one of the important factors that affect the stall characteristics. The large-scale vortices in the vaned diffuser is the main reason for the low-frequency pressure fluctuation signal when operating in the hump region. The low-frequency signal in the vaned diffuser of the optimized model is obviously weakened.
Numerical simulation of unsteady flow characteristics in a centrifugal pump during runaway process caused by power failure
Authors: Zhang Chenying , Wang Wen Jie , Pei Ji , Yuan Shouqi
Published: May 2022

Centrifugal pump is widely used in agricultural irrigation, petrochemical, mining, metallurgy and other industries. A special centrifugal pump with elbow pipe is researched in this paper. The flow rate and rotating speed change rapidly, especially in elbow pipe, causing serious pressure fluctuation and complex vorticity in the centrifugal pump. A user-defined function to solve the angular momentum equation was calculated the pump rotational speed. Unsteady numerical simulation with SST turbulence model is carried out and Short time Fourier transform (STFT) and vorticity strength are used to analyse the pressure fluctuation and vortexes respectively. The results indicate that the rotational speed first decreases to zero and then reversely increases to runaway speed. Large area vorticity appeared at the elbow pipe when the high amplitude frequency of pressure fluctuation increased. The change law of main frequency of pressure fluctuation at the elbow pipe is consistent with the rotational speed change ruler, which is equal to blade passing frequency (BPF). The main source of pressure fluctuation was rotor stator interaction. This study’s results provide a meaningful reference about pump runaway process caused by power failure, leading to the prevention of dangerous situations, for safe operations of the pumping unit.
Effect of the number of blades on diffuser unsteady loss of centrifugal pump
Authors: Ueda Akihito , Takeda Tomoki , Sugiyama Daisuke , Miyagawa Kazuyoshi
Published: May 2022

In recent years, an unshrouded impeller is being developed for rocket turbopumps to reduce production costs and disk friction losses. However, the internal flow structure in a diffuser influenced by an impeller has not been clarified yet. In this study, we focused on the investigation of unsteady flow in turbopumps with unshrouded impellers and vaned diffusers by experiments and CFD. Furthermore, we investigated the effect of changing the number of blades of the impeller and diffuser on the unsteady losses in the diffuser. First, we measured the static pressure at the shroud side in the impeller and the velocity at the diffuser inlet and outlet. Second, we confirmed the accuracy of the CFD by comparing CFD results with experimental results. Third, we investigated unsteady losses in diffusers by CFD. We could confirm increased entropy at the suction surface and shroud side because of the tip leakage and the vortex. Finally, we changed the number of impeller blades or diffuser blades. In conclusion, the loss region at the suction surface and the high-pressure region at pressure surface in the unshrouded impeller were mixed and caused unsteady losses through the diffuser. And diffuser efficiency decreased because channel width in diffuser became narrower by the number of diffuser blades increasing.
Performance characteristics of propeller turbine using an outer ring runner
Authors: Morii R , Iio S
Published: May 2022

The authors focus on a small propeller turbine utilizing the extremely low head and relatively much flow rate sites. The proposed propeller turbine by the authors previously had fixed pitch vanes, and the vane was made of a constant thickness metal plate to reduce manufacturing cost and required technology. The turbine was in a step in the casing and had an outer ring on the runner vane periphery. The structure effectively suppressed the tip leakage flow but had no significant effect on turbine efficiency improvement. This is the limit of the constant thickness blade rotor. So, this study focuses on making the runner by additive manufacturing by the 3D printer because it is faster and cheaper than conventional production methods and is expected to improve turbine efficiency and physical strength. This study aims to compare the performance of the new ring runner model designed to further improve the efficiency of the turbine by CFD analysis and experiment. As a result, the turbine efficiency improved, tip leakage flow was suppressed by attached to the outer ring compared with the previous model
Flow characteristics around a guide vane in cross-flow turbine
Authors: Tanaka T , Otsuka K , Goto M , Iio S
Published: May 2022

A swing-type guide vane is the most popular in a cross-flow turbine, which controls the water flow rate into the turbine. The flow under the guide vane may turn away from the optimum direction in partial load operation by the flow separation from the guide vane leading edge. Maintaining the ideal velocity triangle at the runner inlet is essential to improve the turbine efficiency and to avoid noise and vibration for partial load operation. It is essential to reveal how the angle and shape of those guide vanes affect the flow behavior at the runner inlet and turbine performance. Therefore, this study focuses on the flow characteristics around the guide vane and at the cross-flow runner inlet. The authors verify the evaluation by CFD simulation and compare turbine performance and internal flow between different operating conditions with two guide vanes, the swing-type, and circular segment type. As a result, it is revealed that the swing-type guide vane affects the flow direction, and especially the flow angle is far from the optimum at partial operation. The circular segment type shows superior performance at partial load than the swing-type guide vane.
Physical model setup and tests on cooling circulation water pumping intake system
Authors: Lee Fong-Zuo , Lai Jihn-Sung , Katayama Keiichi , Tomimatsu Shigeyuki , Yang Shu-Yuan
Published: May 2022

The thermal power plant built by the Taiwan power company intends to use multiple cooling circulation water intake systems to introduce seawater from adjacent sea areas. The water in the front pool of the water inlet is introduced into the pump chamber through the large pump in the circulating water pump sump. The primary function of the pump chamber is to provide a stable and uniform flow condition before the large pump sucks in the seawater. When the hydro-dynamic conditions outside the pumping station are not ideal, and the inflow is relatively unstable, the pumping chamber can provide a buffer space for rectification. In addition, when the flow field near the suction intake of a large pump can maintain a certain degree of stability in space and time, it can reduce the frequency and intensity of the vortex or other harmful factors caused by the flow field. Moreover, a pump sump flow field can also maintain the pump's working efficiency, reducing vibration and maintenance costs. Although the relevant design standards such as the Hydraulic Institute (H.I.) standard in the United States or the British Hydromechanics Research Association (B.H.R.A.) standard in the United Kingdom can be consulted for different types of pumping room geometric layout planning and design recommendations. However, most design references are obtained from the boundary conditions of general cases. Therefore, these design criteria indicate that when the pump room geometry and flow conditions have special considerations or detail design, physical model tests should be conducted to verify it or correct the layout according to the model test results. Because the fluid mechanisms involved in the relevant research are complex, the current theoretical or numerical models are not enough to fully simulate flow fields. Therefore, it is necessary to conduct a physical model test based on the feasibility model scale. Based on the similarity theory to scale down prototype structures, the flow mechanism of preliminary design is reproduced, and the revised plan is also verified in the physical model to satisfy the project objectives. The qualitative flow field visualization method was used to observe the free surface vortex, subsurface vortices, and the swirl angle in the suction pipe under different layout schemes at each physical test case. The tested results show that the flow pattern and vortex strength are both acceptable with designed anti-vortex devices.
Effect of guide vane on the performance of a sail wing turbine for wave energy conversion
Authors: Iitsuka H , Takao M , Alam M M A , Okuhara S , Taniguchi H , Matsuura S
Published: May 2022

In an Oscillating Water Column (OWC) based wave energy plant, the sea wave motion is used to drive an air column in an air chamber and that results in a bi-directional airflow. An air turbine for bi-directional airflow is used to convert the pneumatic energy into mechanical energy. The sail wing turbine can be used as an air turbine for wave energy conversion because it has a special structure in which the shape of the sail changes in reciprocating airflow and always can rotate in the same direction. In addition, the sail wing turbine does not experience the stalling effect and can acquire energy at a wide range of rotational speed and flow rate. In our previous studies, the performance of the sail wing turbine for bi-directional airflow has been investigated by using a wind tunnel test. In the present study, in order to further improve the performance of the sail wing turbine, guide vanes were installed, and the effect of the guide vane on the performance was investigated by a wind tunnel test and a computational fluid dynamics (CFD) analysis under a steady flow condition.
Impact by double scroll on variable geometry turbine performance
Authors: Kobayashi T , Morita I , Nagao K , Bamba T
Published: May 2022

This paper describes the numerical study for the development of a double scroll(DS) turbine stage combined with a variable geometry system (VGS). Our conventional VGS turbine stage is composed of a mono-scroll housing, variable nozzles and a turbine wheel. A potential to improve engine performance by applying a DS with VGS turbine stage (DS-VGS) was shown by the study. In addition, a DS-VGS has some advantage in the layout for V type engine. Therefore, this study has focused on clarifying the characteristics of aerodynamic performance of a DS-VGS, since the understanding of these fundamental characteristics is important for product development. The differences of performance between a mono-scroll with VGS and a DS with VGS were evaluated as the starting point. In the development for a vaneless DS turbine so far, it has been clarified that the distance from tongue to turbine wheel is one of the important parameters for performance. Therefore, numerical simulations were performed with different tongue-to-nozzle distances. Further, from reliability point of view, the influences of a DS on nozzle moments and aerodynamic forces on nozzle have been examined. The interesting characteristics of a DS-VGS compared to a mono-scroll with VGS are shown.
Modeling and Investigation of the Reduction Zone in A Downdraft Biomass Gasifier
Authors: Zhou Junjie , Han Kui , Tang Songzhen , Tao Wu , Fu Weidong
Published: May 2022

The fixed bed gasifier has simple structure, convenient operation and maintenance, and is suitable for use in rural areas. In this paper, a downdraft fixed bed gasifier was designed for biomass gasification using corn cob as raw material. COMSOL Multiphysics software was used to simulate the reduction zone of biomass gasifier. The temperature field and concentration distribution of the reduction zone were studied. The influence of structural parameters of the reduction zone on the composition of syngas was analyzed. The rates of major chemical reactions in the reduction zone were also compared in detail.
Simulation Research on Phase Locking Technology Based on Modified DSOGI-PLL
Authors: Huang Yubo , Zhang Jundong , Chen Dong , Jia Zhiwei
Published: May 2022

For complex working conditions in power grid, it is easy to produce a large number of harmonics, and the double second-order generalized integrator phase-locked loop (DSOGI-PLL) cannot effectively suppress low-order harmonics, a new DSOGI-PLL based on modified sequential cascaded harmonic cancellation module is proposed in this paper. By designing a harmonic cancellation module that eliminates specific frequency harmonics, different frequency harmonic cancellation modules are cascaded in order from small to large to eliminate low frequency harmonics near the basic frequency. By building the simulation model, the comparison analysis verifies that the modified DSOGI-PLL has higher accuracy in tracking the frequency and phase of the voltage signal, and is more suitable for the power grid.
Modeling of Direct Drive Wind Turbine for Wide-band Oscillation Analysis in Large Power Grid
Authors: Gao Feng , Zhang Weiwei , Shi Hongtao
Published: May 2022

Aiming at the problem of wide-band oscillation caused by power grid with high proportion of direct drive wind turbine (DDWT), a transient model of DDWT for wide-band oscillation analysis is established in this paper. Firstly, the mechanism and key factors of wide-band oscillation occurred in large power grid with high proportion of DDWT was analyzed. Secondly, the model of DDWT was established by simplifying the full electromagnetic transient model of DDWT while the key factors of wide-band oscillation mode were retained and the secondary factors unrelated or weakly related to wide-band oscillation mode were ignored. Finally, the simulation result shows that the model can improve the convergence and computational efficiency of the simulation analysis and ensure the accuracy of the simulation result at the same time, and can be applied to the simulation analysis of wide-band oscillation occurred in large power grid with high proportion of DDWT.
An Improved Model for Predicting the Trapped Annular Pressure in the Deepwater’s Annulus Containing Foam Material
Authors: Chen Xingwang , Gao Baokui , Zhang Yihan , Zhang Yanhuan
Published: May 2022

An improved model for calculating the trapped annular pressure in deepwater was created in order to precisely estimate the trapped annular pressure using foam materials. the model fits the pressure-volume experimental data using the constitutive equation of foam material put forward by Goga V. A temperature influence factor is calculated to explain the effect of temperature. During calculation, the annulus is divided into segments for the calculation, the variable temperature is loaded in increments, and the pressure is calculated using the method of bisection. Through an example, the effect of foam volume on the results of annular pressure is analyzed, and the improved model is compared to the prior model. The results show that the actual annular pressure does not increase monotonically with the wellbore temperature due to the decrease of foam material’s crushing pressure caused by the temperature increase, but there will be a small decrease. And foam material has good applicability and strong effect in the mitigation of trapped annular pressure in deepwater.
Equivalent Modulus and Mass Loss of C/C-SiC Gradient Matrix Composites at High Temperature
Authors: Li Zhaoyi , Liang Wei , Liu Yufeng
Published: May 2022

The oxidation at high temperature of carbon fiber reinforced carbon-silicon carbide (C/C-SiC) gradient matrix composites results in structural damages and performance degradation. Oxidation kinetics model of C/C-SiC gradient matrix composites was built. A representative volume element (RVE) was established according to the microstructure of the composites. The evolution law of the structure characterization of the composites and the mass loss model were derived from the oxidation kinetics model. And equivalent elastic modulus with oxidation time at different temperatures and coefficient of thermal expansion(CTE) at different temperatures were calculated by RVE. The results show that the equivalent elastic modulus decreases with oxidation time and increases rapidly after the crack heals. The higher the temperature, the lower decreasing rate. And the equivalent CTE increases with temperature, while the increasing rate decreases with temperature. The calculated result of mass loss is consistent with the previous research.
Design, Modeling and Motion Simulation of a Setback Arming Mechanism under Weak Acting Forces
Authors: Lv Bing , Wang Dongya , Zhang Zhenze , Sui Li
Published: May 2022

A parallel two-degree-of-freedom (two-DOF) setback arming mechanism was designed in this study according to acceleration signal characteristics of weak launch and service conditions. A model of an inertia switch with a low g-feature was designed to be used in the electromechanical fuze of the proposed mechanism. Simulations were conducted to analyze the motion characteristics of the inertia switch that was based on the parallel two-DOF spring-mass system under the launch overload and the service dropping overload. The reliability and safety of the inertia switch were validated.
Fractal Dimension Calculation Method from NMR Measurement and Its Application
Authors: Song Xiaodong , Tan Maojin , Wang Zhizhan , Xie Guanbao
Published: May 2022

The pore structure of organic shale with nano-scale pores is important for reservoir evaluation. Fractals shows the self-similarity of shale rocks and can reflect the pore structure. The fractal dimension of organic shale from nuclear magnetic resonance (NMR) measurement was studied and some equations were directly derived based on NMR transverse relaxation time (T2) distribution. In a case study, the fractal dimensions were calculated by the proposed method and numerical simulation, and the formation cementation index in Archie equation for saturation evaluation was calculated from the fractal dimension of NMR logging. The comparison of calculated water saturation and the core experiment result prove that the proposed method is more effective than the previous Archie’s equation with default cement index.
Exploiting Reservoir Computing for Optical Secure Communication
Authors: Tang Qianfeng , Xie Yiyuan , Jiang Xiao , Liu Bocheng , Chai Junxiong , Ye Yichen , Song Tingting , Feng Manying
Published: May 2022

A reservoir computing (RC) based on vertical cavity surface emitting laser (VCSEL) subjected to optical feedback is adopted to realize chaos synchronization in optical chaotic communication. Combined with the application of chaos masking (CMS) technology in chaotic secure communication, chaotic signal generated by distribution feedback (DFB) laser after optical feedback and optical injection, that is used as chaotic carrier of hiding original information, and act as target signal of the RC. Then masked information is used for RC training and transmission. Next, utilizing the weights and error offsets trained out by RC at transmitter, carrier can be reconstructed by RC at receiver. Finally, message is acquired by subtracting the reconstructed carrier from received masked signal. Taking image data transmission in 10 km fiber as an example, the chaos synchronization between the carrier signal and the constructed carrier signal is 0.9935, Q-factor is 10 and bit error rate (BER) is 5×10-28 with simulation.
Carrying Capacity Calculation Method Based on Operation Chain and its Application
Authors: Xu Jinchen , Li Xiaohong , Sun Wanhua , Wu Yizhi
Published: May 2022

Railway border reloading station is an important node of the interconnectivity of international railway transport corridor, which overall carrying capacity is critical to keep the corridor unblocked. Compared with general technical stations, the organization of cargo reloading at the station definitely has an impact on transport efficiency and capacity in addition to arriving, departing and conventional technical operations. By analyzing the operation steps and characteristics of railway border reloading station, the concept of overall carrying capacity was defined and its composition was confirmed. Based on this, the operation chain analysis method of the overall carrying capacity of the border reloading station was developed. Then we conduct a case study of Erlian station. Five operation chains were built to calculate the overall carrying capacity and identify the bottleneck. The operation chain analysis method proposed in this paper overcomes the defect of not considering the impact of the reloading operation on station capacity in the existing general technical station transport capacity calculation method. It can comprehensively consider the facilities and equipment of the station and the current traffic flow, so as to accurately find the weak links among them and provide a basis for the improvement of the transportation organization. Therefore, the conclusion is more scientific and reasonable.
Research on LncRNA and Disease Associations Prediction Base on Data Mining
Authors: Jia Fengjiao , Jiang Shaohua , Wu Zaoyang , Liang Yigao
Published: May 2022

The accumulated experiments show that lncRNA has a role in biophysiological and case processes. Prediction of the relationship between diseases and lncRNA will contribute to clarify the etiology of diseases, develop new drugs and treat complex diseases. However, the traditional biological experiment method has long experiment period and high cost. Therefore, based on existing biological data and biological experimental data, data mining techniques have been used to propose many models and methods to predict the lncRNA-disease correlation. This article will provide a specific introduction to lncRNA and disease-related databases, which summarizes some relevant predictions classical models (matrix factorization, heterogeneous networks, machine learning). At the end of the article, the problems of lncRNA and the current prediction of the disease are analyzed, and some ideas and help are provided for later researchers.
A Mathematical Model for the Routing Optimization Problem with Time Window
Authors: Cheng R , Lu X , Yu X
Published: May 2022

This paper establishes a mathematical model for the routing optimization problem. Then, the model is solved by a genetic algorithm. Finally, to verify the proposed method, a case study is carried out. According to the results, the proposed model and algorithm can be used to solve the problem and obtain the optimal vehicle route with minimum time cost and travel distance.
Research on Optimal Allocation of Flight Slots Based on Wake Interval Constraints
Authors: Zou Guoliang , Hou Jia , Geng Xi , Wang Qiang , Luo Yao , Liu Jihong
Published: May 2022

The limited airspace of civil aviation cannot meet the demand for airspace due to the rapid increase in flight volume. This is one of the main reasons for flight delays. This forces us to carry out flight flow management, and the main means of flow management is the resource of flight slots. Optimize the configuration to relieve the moments of “congestion” and the moments of “digging” that are not fully utilized. According to the feature that different types of aircraft need to be equipped with different wake intervals, the article establishes a flight schedule optimization model and develops a flight schedule optimization system. Taking a double runway hub airport as an example, experiments show that the proposed method can effectively alleviate flight delay and reduce flight delay rate.
Complex Scene Segmentation Network Based on Multi-scale Encoding-decoding Architecture
Authors: Ren Shasha , Zhang Xiaodong
Published: May 2022

With the progress of artificial intelligence, the study of scene segmentation for complex scene understanding is of great significance. Due to the large number of activities, there are many target categories, large scale changes, many mutual occlusions, difficult target recognition, and large data labeling costs. In order to achieve accurate understanding of the complex scene, this paper proposes to add a scale adaptive feature module on the basis of Encode-Decode, so that the network can make good use of the features and context information of each level to effectively adapt to changes in target size. At the same time, we use the scale size function to weight encode different levels of features, which improves the prediction accuracy of pixels in the intersection area of each class. Experiments conducted on Cityscapes, Put_campus and PASCAL VOC 2012 datasets show that the method in this article is improved by about 1% compared with the three segmentation algorithms such as FCN, PSPNet, and Deeplabv3 +.
Augmentation Performance Analysis of Beidou-3 SBAS under Single Frequency and Dual Frequency
Authors: Xiao Yamu , Xiao Zhibin , Liu Xiaohui
Published: May 2022

Based on the principle of satellite based augmentation information positioning, this paper uses the standard positioning algorithm of SBAS, IGMAS site data and augmentation information messages to evaluate the single point positioning performance of BDS satellite based augmentation information in China. From the results, the accuracy of single frequency augmentation information for single point positioning is improved by about 30%, which is equivalent to that of EGNOS. The accuracy of dual frequency augmentation information for single point positioning is improved by nearly 40%, which is better than that of single frequency.
Web Service Recommendation Based on QoS Analysis
Authors: Xin Mindong , Xing Xing , Han Qiuyang , Jia Zhichun
Published: May 2022

To correctly recommend the web services and help users choose more appropriate web services, a QoS analysis and recommendation method based on radial basis function (RBF) neural network is proposed (this method is referred to as WSR-RBF). This method constructs an optimized RBF neural network to analyze the correlation between qualities of service attributes and uses a set of irrelevant attributes to accurately predict quality of service. To find the number of hidden layer nodes in our proposed model and determine the center value of the hidden layer in a short time, we propose a clustering algorithm combining Affinity Propagation and K-means. The experimental results show that the proposed method has low error values on three data sets, which verifies its good recommendation effect.
Research on Automatic Control Model of Two-wheeled Differential Robot
Authors: Zhang Xinyu , Wu Ziyang , Xie Wenjie , Zhan Jinpeng
Published: May 2022

Aiming at the problem that the speed control of the traditional two-wheeled differential robot is cumbersome and requires a lot of manpower, the intelligent two-wheeled speed matching and intelligent path finding model of the robot under the known surrounding environment are studied. The extended method is used to process the environment image to solve the volume problem of the robot itself, and the improved PRM algorithm is used to solve the shortest path, and the post-alignment of the shortest path is distinguished. Using the radius of curvature, the speed ratio of the two-wheeled differential robot at each position can be obtained, thus establishing the automatic control of the two-wheeled differential robot. The automatic control model of two-wheeled robot is synthesized. The model can effectively reduce the manpower consumed by the robot in path finding and control, and it has important case reference significance for saving the economic cost of two-wheeled differential robot control.
Ultrabright photoluminescence spikes and step-wise photoluminescence increase from colloidal silver nanoparticles for patch nanoantennas
Authors: Lukishova Svetlana G. , Brone Jerome , Khan Darman , Li Zihao
Published: May 2022

Ultrabright intensity spikes (up to ∼400—900 kcounts/s) appear sporadically in time traces of photoluminescence from 100-nm silver nanocubes used in nanopatch antennas for single-photon source applications. Both 532 and 633 nm laser excitation causes them.
Quality Improvement of Aluminum Alloy Thin-walled Laminations Based on Process Capability Analysis
Authors: Wang Xiaoyuan , Wang Renche , Li Zi’ang
Published: May 2022

The flatness of a certain batch of aluminum alloy thin-walled laminations is the key quality control object. The calculation result of the process performance index Pp
U
in the initial manufacturing stage showed that the process capability was insufficient. In order to solve the above problem, through analysing the structural characteristics of the lamination and combing the production process, an end factors’ analysis model of the out-of-tolerance flatness was established; by means of investigation and experimental verification, the main causes of out-of-tolerance flatness were confirmed. Targeted improvement measures such as optimization of mould inspection strategies and replacement of qualified moulds had been taken. After the improvement, using the MINITAB software, the Xbar-R control chart and process capability chart were drawn, and the calculation and analysis of process performance index Pp
U
were completed. The results showed that the improved production process was in a state of statistical control and the process capability was sufficient. The effectiveness of the improved measures was verified.
Effect of laser quenching process on surface hardness and wear performance of cylindrical slideway on the upper base of combined vibration separation equipment
Authors: Zhang Haoqiang , Juanatas Ronaldo , Niguidula Jasmin , Cai Liu
Published: May 2022

Combined vibration equipment is widely used in the separation and classification of grain, mineral and other granular materials. The cylindrical slideway on the upper part of the base of the combined vibration equipment bears all the weight of the vibrating silo and the particulate matter in the vibrating silo during the vibration process, and supports the combined vibration of the vibrating silo and the particulate matter in the vibrating silo, the cylindrical slideway on the upper part of the base is seriously worn. The vibrating silo can only vibrate horizontally and linearly along the cylindrical slide on the upper part of the base and swing back and forth around the center of the bottom surface of the cylindrical slide on the upper part of the base. It is required that the cylindrical slide on the upper part of the base has good strength and toughness, and the contact surface has a hardness of more than 35HRC to ensure wear resistance. The effect of laser surface quenching process on the surface hardness of the upper cylindrical slide of the base is studied by using the method of three factors and four levels. The experimental results show that after laser surface quenching, the minimum surface hardness and the maximum surface hardness of the upper cylindrical slide of the base are 35.6HRC and 39.6HRC, which meet the hardness requirements of vibration equipment for the slide of the base. When 1450W laser quenching power, 500mm/min laser scanning speed and 2.25mm laser spot diameter are used, the maximum surface hardness will be 39.6HRC, which is about 38.6% higher than that of the pretreated sample. The maximum section hardness of test sample 14 after laser quenching reaches 388HV, which is about 1.25 times higher than that of the matrix in the quenching areas of samples 13, 15 and 16. It is close to the matrix hardness when it is 1.6mm away from the surface. The thickness of the surface hardened layer exceeds 0.6mm, indicating that the greater the laser power, the greater the thickness of the hardened layer. In the wear test, the minimum wear amount of sample 14 is 0.0331g, which is about 25.2% of the matrix wear amount of 0.1312g. The larger the laser power is, the smaller the scanning speed and spot diameter are, which plays a positive role in promoting the reduction of sample wear. We will use the laser surface quenching process parameters of sample 14: laser power 1450W, spot diameter 2.25mm and scanning speed 500mm/min to conduct laser quenching on the upper cylindrical slide surface of the base of the combined vibration equipment in order to obtain a thicker hardened layer and higher hardness, and greatly improve the service life, safety and stability of the combined vibration equipment.
Performance inspection and defect cause analysis of girth weld of high steel grade pipeline
Authors: Xu Yan , Wu Mingchang , Nie Xianghui , Feng Zhenjun , Li Liang , Yang Fengping
Published: May 2022

The suspected circumferential weld defects found in the pipeline inspection process were tested and studied. It was found that there was slag inclusion in the girth weld at 9 o’clock, which had not been found in the early stage or in the laboratory nondestructive testing process. The defects are most likely due to incomplete slag removal between layers and low welding wire energy. There was a root crack at the 6 o’clock position of the weld, and the crack length was 10 mm, which was close to the original film and the detection result of excavation. The misjudgment of the field rebeat and the laboratory test results may be caused by the pits in the weld cover and the bottom weld. The crack is caused by the crystal crack formed along the middle of the columnar crystal during the solidification process of backing welding due to the increase of residual stress caused by the reduction of welding layers and the group stress caused by the steel tube.