Imbalanced multiclass datasets pose challenges for machine learning algorithms.They often contain minority classes that are important for accurate predictions.However,when the data is sparsely distributed and overlaps...Imbalanced multiclass datasets pose challenges for machine learning algorithms.They often contain minority classes that are important for accurate predictions.However,when the data is sparsely distributed and overlaps with data points fromother classes,it introduces noise.As a result,existing resamplingmethods may fail to preserve the original data patterns,further disrupting data quality and reducingmodel performance.This paper introduces Neighbor Displacement-based Enhanced Synthetic Oversampling(NDESO),a hybridmethod that integrates a data displacement strategy with a resampling technique to achieve data balance.It begins by computing the average distance of noisy data points to their neighbors and adjusting their positions toward the center before applying random oversampling.Extensive evaluations compare 14 alternatives on nine classifiers across synthetic and 20 real-world datasetswith varying imbalance ratios.This evaluation was structured into two distinct test groups.First,the effects of k-neighbor variations and distance metrics are evaluated,followed by a comparison of resampled data distributions against alternatives,and finally,determining the most suitable oversampling technique for data balancing.Second,the overall performance of the NDESO algorithm was assessed,focusing on G-mean and statistical significance.The results demonstrate that our method is robust to a wide range of variations in these parameters and the overall performance achieves an average G-mean score of 0.90,which is among the highest.Additionally,it attains the lowest mean rank of 2.88,indicating statistically significant improvements over existing approaches.This advantage underscores its potential for effectively handling data imbalance in practical scenarios.展开更多
Early and accurate detection of Heart Disease(HD)is critical for improving patient outcomes,as HD remains a leading cause of mortality worldwide.Timely and precise prediction can aid in preventive interventions,reduci...Early and accurate detection of Heart Disease(HD)is critical for improving patient outcomes,as HD remains a leading cause of mortality worldwide.Timely and precise prediction can aid in preventive interventions,reducing fatal risks associated with misdiagnosis.Machine learning(ML)models have gained significant attention in healthcare for their ability to assist professionals in diagnosing diseases with high accuracy.This study utilizes 918 instances from publicly available UCI and Kaggle datasets to develop and compare the performance of various ML models,including Adaptive Boosting(AB),Naïve Bayes(NB),Extreme Gradient Boosting(XGB),Bagging,and Logistic Regression(LR).Before model training,data preprocessing techniques such as handling missing values,outlier detection using Isolation Forest,and feature scaling were applied to improve model performance.The evaluation was conducted using performance metrics,including accuracy,precision,recall,and F1-score.Among the tested models,XGB demonstrated the highest predictive performance,achieving an accuracy of 94.34%and an F1-score of 95.19%,surpassing other models and previous studies in HD prediction.LR closely followed with an accuracy of 93.08%and an F1-score of 93.99%,indicating competitive performance.In contrast,NB exhibited the lowest performance,with an accuracy of 88.05%and an F1-score of 89.02%,highlighting its limitations in handling complex patterns within the dataset.Although ML models show superior performance as compared to previous studies,some limitations exist,including the use of publicly available datasets,which may not fully capture real-world clinical variations,and the lack of feature selection techniques,which could impact model interpretability and robustness.Despite these limitations,the findings highlight the potential of ML-based frameworks for accurate and efficient HD detection,demonstrating their value as decision-support tools in clinical settings.展开更多
In this paper, considering both cluster heads and sensor nodes, we propose a novel evolving a network model based on a random walk to study the fault tolerance decrease of wireless sensor networks （WSNs） due to node...In this paper, considering both cluster heads and sensor nodes, we propose a novel evolving a network model based on a random walk to study the fault tolerance decrease of wireless sensor networks （WSNs） due to node failure, and discuss the spreading dynamic behavior of viruses in the evolution model. A theoretical analysis shows that the WSN generated by such an evolution model not only has a strong fault tolerance, but also can dynamically balance the energy loss of the entire network. It is also found that although the increase of the density of cluster heads in the network reduces the network efficiency, it can effectively inhibit the spread of viruses. In addition, the heterogeneity of the network improves the network efficiency and enhances the virus prevalence. We confirm all the theoretical results with sufficient numerical simulations.展开更多
We investigated erosion-corrosion(E-C) and its mitigation on the internal surface of the expansion segment of N80 steel tube in a loop system using array electrode technique, weight-loss measurement, computational-flu...We investigated erosion-corrosion(E-C) and its mitigation on the internal surface of the expansion segment of N80 steel tube in a loop system using array electrode technique, weight-loss measurement, computational-fluid-dynamics simulation, and surface characterization techniques.The results show that high E-C rates can occur at locations where there is a high flow velocity and/or a strong impact from sand particles, which results in different E-C rates at various locations.Consequently, it can be expected that localized corrosion often occurs in such segments.The E-C rate at each location in the expansion segment can be significantly mitigated with an imidazoline derivative inhibitor, as the resulting inhibitor layer significantly impedes the electrochemical reaction rate.However, we found that this inhibitor layer could not effectively reduce the difference in the erosion rates at different locations on the internal surface of the expansion segment.This means that localized corrosion can still occur at the expansion segment despite the presence of the inhibitor.展开更多
To restrain the formation of AuSnx intermetallic components (IMCs) in solder joints, Zn was added into Sn-rich solders. The solder joints were fabricated by a laser reflow soldering method, and then they were aged at ...To restrain the formation of AuSnx intermetallic components (IMCs) in solder joints, Zn was added into Sn-rich solders. The solder joints were fabricated by a laser reflow soldering method, and then they were aged at 125 ℃. The results show that the total thickness of AuSnx IMCs at the interface of pure Sn solder and Au foils reaches about 54 μm under the condition of 600 h aging. In Sn-1.5Zn solder joints, however, formation of AuSn4 IMCs is restrained greatly. As the content of Zn in the solder is increased to 3.5%(mass fraction), no AuSn4 IMC is observed at the interface. Au-Zn phases form beside AuSn2 and AuSn IMCs layers. As for Sn-9.0Zn solder joints, Au-Zn and Au-Zn-Sn phases and few AuSnx IMCs form at the interface. Moreover, total thickness of the phases and IMCs is far less than that of AuSnx IMCs in the pure Sn solder joints.展开更多
This paper designs the thermal crystals composed of alloy materials with air holes and analyzes their properties of band structures,heat transmission,and flux spectra.Thermal crystals composed of Si-A(A=Ge,Sn,Pb)alloy...This paper designs the thermal crystals composed of alloy materials with air holes and analyzes their properties of band structures,heat transmission,and flux spectra.Thermal crystals composed of Si-A(A=Ge,Sn,Pb)alloys as background materials and air holes with square array are used to construct an elastic-constant periodic structure and their high-frequency phononic band is calculated by deploying finite element methods.Moreover,this paper investigates heat transmission through a finite array of thermally excited phonons and presents the thermal crystal with maximum heat transport.The results show that a wider bandgap could be achieved by increasing the air hole radius and decreasing the lattice constant.In the alloy materials,with increasing atomic radius and thus atomic mass(Ge,Sn,Pb),the frequency range(contributed to thermal conductivity)shifts towards lower frequency.Hence,the bandgap frequencies also shift toward low frequency,but this decreasing rate is not constant or in order,so former may have a faster or slower decreasing rate than the later.Thus,the frequency range for the contribution of heat transportation overlaps with the bandgap frequency range.The development of thermal crystals is promising for managing heat and controlling the propagation of the thermal wave.展开更多
Formation of AuSnx intermetallic compounds （IMCs） in laser reflowed solder joints was investigated. The results showed that few IMCs formed at the solder/0. 1μm Au interface. Needlelike AuSn4 IMCs were observed at ...Formation of AuSnx intermetallic compounds （IMCs） in laser reflowed solder joints was investigated. The results showed that few IMCs formed at the solder/0. 1μm Au interface. Needlelike AuSn4 IMCs were observed at the solder/0.5μm Au interface. In Sn-2.0Ag-O,75Cu-3,0Bi and Sn-3.5Ag-O.75Cu solder joints, when the laser input energy was increased, AuSn4 IMCs changed .from a layer to needlelike or dendritic distribution at the solder/0.9μm Au interface. As for the solder joints with 4.0 μm thickness of Au surface finish on pads, AuSn4 , AuSnx, AuSn IMCs, and Au2Sn phases formed at the interface. Moreover, the content of AuSnx IMCs, such as, AuSn4 and AuSn2, which contained high Sn concentration, would become larger as the laser input energy increased. In the Sn-37Pb solder joints with 0.9 μm or 4.0 μm thickness of the Au surface finish on pads, AuSn4 IMCs were in netlike distribution. The interspaces between them were filled with Pb-rich phases.展开更多
The Dielectric Spectroscopy technique is a tool that can be used to provide information regarding the physical and chemical properties of materials. In this work Dielectric Spectroscopy (DS) measurements were conducte...The Dielectric Spectroscopy technique is a tool that can be used to provide information regarding the physical and chemical properties of materials. In this work Dielectric Spectroscopy (DS) measurements were conducted on marble specimens that were previously subjected to uniaxial compressive stress up to fracture in order to investigate the influence of the mechanical stress on the dielectric properties of the specimens. Specifically, the ac conductivity (σac) was measured when an ac electric field in the frequency range 1 kHz - 1 MHz was applied upon dry and saturated specimens which were subjected successively to higher levels of mechanical stress. The experimental results indicate that there are systematic variations in the values of the ac conductivity after each stress application at a higher stress level. Such variations become more intense at higher stress values and can be used to indicate the upcoming fracture since significant increase of conductivity is recorded when microcracks formations appear and propagate in the sample bulk.展开更多
In this paper, to study rumor spreading, we propose a novel susceptible-infected-removed （SIR） model by introducing the trust mechanism. We derive mean-field equations that describe the dynamics of the SIR model on ...In this paper, to study rumor spreading, we propose a novel susceptible-infected-removed （SIR） model by introducing the trust mechanism. We derive mean-field equations that describe the dynamics of the SIR model on homogeneous networks and inhomogeneous networks. Then a steady-state analysis is conducted to investigate the critical threshold and the finaJ size of the rumor spreading. We show that the introduction of trust mechanism reduces the final rumor size and the velocity of rumor spreading, but increases the critical thresholds on both networks. Moreover, the trust mechanism not only greatly reduces the maximum rumor influence, but also postpones the rumor terminal time, which provides us with more time to take measures to control the rumor spreading. The theoretical results are confirmed by sufficient numerical simulations.展开更多
A novel scheme‘user assisted cooperative relaying in beamspace massive multiple input multiple output(M-MIMO)non-orthogonal multiple access(NOMA)system’has been proposed to improve coverage area,spectrum and energy ...A novel scheme‘user assisted cooperative relaying in beamspace massive multiple input multiple output(M-MIMO)non-orthogonal multiple access(NOMA)system’has been proposed to improve coverage area,spectrum and energy efficiency for millimeter wave(mmWave)communications.A downlink system for M users,where base station(BS)is equipped with beamforming lens antenna structure having NRF radio frequency(RF)chains,has been considered.A dynamic cluster of users is formed within a beam and the intermediate users(in that cluster)between beam source and destination(user)act as relaying stations.By the use of successive interference cancellation(SIC)technique of NOMA within a cluster,the relaying stations relay the symbols with improved power to the destination.For maximizing achievable sum rate,transmit precoding and dynamic power allocation for both intra and inter beam power optimization are implemented.Simulations for performance evaluation are carried out to validate that the proposed system outperforms the conventional beamspace M-MIMO NOMA system for mmWave communications in terms of spectrum and energy efficiency.展开更多
In this paper, an extended version of standard susceptible-infected （SI） model is proposed to consider the influence of a medium access control mechanism on virus spreading in wireless sensor networks. Theoretical a...In this paper, an extended version of standard susceptible-infected （SI） model is proposed to consider the influence of a medium access control mechanism on virus spreading in wireless sensor networks. Theoretical analysis shows that the medium access control mechanism obviously reduces the density of infected nodes in the networks, which has been ignored in previous studies. It is also found that by increasing the network node density or node communication radius greatly increases the number of infected nodes. The theoretical results are confirmed by numerical simulations.展开更多
In order to prevent and control the spread of rumors, the implementation of immunization strategies for ignorant individuals is very necessary, where the immunization usually means letting them learn the truth of rumo...In order to prevent and control the spread of rumors, the implementation of immunization strategies for ignorant individuals is very necessary, where the immunization usually means letting them learn the truth of rumors.Considering the facts that there is always a delay time between rumor spreading and implementing immunization, and that the truth of rumors can also be spread out, this paper constructs a novel susceptible-infected-removed(SIR) model.The propagation dynamical behaviors of the SIR model on homogeneous networks are investigated by using the meanfield theory and the Monte Carlo method. Research shows that the greater the delay time, the worse the immune effect of the immunization strategy. It is also found that the spread of the truth can inhibit to some extent the propagation of rumors, and the trend will become more obvious with the increase of reliability of the truth. Moreover, under the influence of delay time, the existence of nodes' identification force still slightly reduces the propagation degree of rumors.展开更多
In this work,a novel compact wideband reconfigurable circularly polarised(CP)dielectric resonator antenna(DRA)is presented.The L-shaped Dielectric resonator antenna is excited by an inverted question mark shaped feed....In this work,a novel compact wideband reconfigurable circularly polarised(CP)dielectric resonator antenna(DRA)is presented.The L-shaped Dielectric resonator antenna is excited by an inverted question mark shaped feed.This arrangement of feed-line helps to generate two orthogonal modes inside the DR,which makes the design circularly polarised.A thin micro-strip line placed on the defected ground plane not only helps to generate a wideband response but also assist in the positioning of the two diode switches.These switches located at the left and right of the micro-strip line helps in performing two switching operations.The novel compact design offers the reconfigurability between 2.9–3.8 GHz which can be used for different important wireless applications.For the switching operation I,the achieved impedance bandwidth is 24%while axial ratio bandwidth(ARBW)is 42%.For this switching state,the design has 100%CP performance.Similarly,the switching operation II achieves 60%impedance bandwidth and 58.88%ARBW with 76.36%CP performance.The proposed design has a maximum measured gain of 3.4 dBi and 93%radiation efficiency.The proposed design is novel in terms of compactness and performance parameters.The prototype is fabricated for the performance analysis which shows that the simulated and measured results are in close agreement.展开更多
Fuzzy sets theory cannot describe the neutrality degreeof data, which has largely limited the objectivity of fuzzy time seriesin uncertain data forecasting. With this regard, a multi-factor highorderintuitionistic fuz...Fuzzy sets theory cannot describe the neutrality degreeof data, which has largely limited the objectivity of fuzzy time seriesin uncertain data forecasting. With this regard, a multi-factor highorderintuitionistic fuzzy time series forecasting model is built. Inthe new model, a fuzzy clustering algorithm is used to get unequalintervals, and a more objective technique for ascertaining membershipand non-membership functions of the intuitionistic fuzzy setis proposed. On these bases, forecast rules based on multidimensionalintuitionistic fuzzy modus ponens inference are established.Finally, contrast experiments on the daily mean temperature ofBeijing are carried out, which show that the novel model has aclear advantage of improving the forecast accuracy.展开更多
Audio communications and computer networking play essential roles in our daily lives,including many domains with different scopes.Developments in these technologies are quick.In consequence,there is a dire need to sec...Audio communications and computer networking play essential roles in our daily lives,including many domains with different scopes.Developments in these technologies are quick.In consequence,there is a dire need to secure these technologies up to date.This paper presents an efficient model for secure audio signal transmission over the wireless noisy uncorrelated Rayleigh fading channel.Also,the performance of the utilized multiple secret keys-based audio cryptosystem is analyzed in different transformation domains.The discrete cosine transform(DCT),the discrete sine transform(DST),and the discrete wavelet transform(DWT)are investigated in the utilizedmultiple secret key-based audio cryptosystem.Simulation results show consistent results with the wireless noisy channel.The performance of the proposed multiple secret keys-based audio cryptosystem can be ranked concerning the employed domain as DWT,DCT,and DST transform techniques.The simulation experiments proved that the presented multiple secret keysbased audio cryptosystemfor audio signals transmitted over the wireless noisy uncorrelatedRayleigh fading channel achieves reliable and secure wireless link utilizing combined multi security layers.展开更多
Wireless Local Area Network(WLAN) with high data bit rates can be used with cellular network to achieve higher level of Quality of Service(QoS) by sharing their total resources efficiently.The integration between cell...Wireless Local Area Network(WLAN) with high data bit rates can be used with cellular network to achieve higher level of Quality of Service(QoS) by sharing their total resources efficiently.The integration between cellular and WLAN networks should be ensured considering different channel-allocation strategies of both networks and efficient resource management techniques should be developed.In this paper,we propose a new call admission scheme to use the coupled resource effectively.The proposed scheme,by taking the different resource sharing strategies for two access networks,limits the new,horizontal and vertical handoff voice and data call arrivals with respect to their call-level QoS requirements.Numerical results show that the proposed integrated cellular/WLAN network model uses the resources more effectively and achieves all upper bound QoS requirements for voice and data users as compared with the non-integrated network model.展开更多
Recent reports from World Health Organization(WHO)show the impact of human negligence as a serious concern for road accidents and casualties worldwide.There are number of reasons which led to this negligence;hence,nee...Recent reports from World Health Organization(WHO)show the impact of human negligence as a serious concern for road accidents and casualties worldwide.There are number of reasons which led to this negligence;hence,need of intelligent transportation system(ITS)gains more attention from researchers worldwide.For achieving such autonomy different sensors are involved in autonomous vehicles which can sense road conditions and warn the control system about possible hazards.This work is focused on designing one such sensor system which can detect and range multiple targets under the impact of adverse atmospheric conditions.A high-speed Linear Frequency Modulated Continuous Wave(LFMCW)based Photonic Radar is proposed to detect multiple targets by integrating Mode division multiplexing(MDM).Reported results in terms of range frequency,Doppler frequency and range resolution are demonstrated using numerical simulations with the bandwidths of 1 and 4 GHz and under adverse atmospheric conditions carrying 75 dB/km of attenuation.To prove the effectiveness of the proposed photonic radar,moving targets are also demonstrated with different speed.System reported substantial range resolution of 15 cm using 1 GHz of bandwidth and 3 cm using 4 GHz of bandwidth.展开更多
This article presents a novel modified chuck wagon dinner bell shaped millimeter wave(mm-wave)antenna at 28 GHz.The proposed design has ultra-thin Rogers 5880 substrate with relative permittivity of 2.2.The design con...This article presents a novel modified chuck wagon dinner bell shaped millimeter wave(mm-wave)antenna at 28 GHz.The proposed design has ultra-thin Rogers 5880 substrate with relative permittivity of 2.2.The design consists of T shaped resonating elements and two open ended side stubs.The desired 28 GHz frequency response is achieved by careful parametric modeling of the proposed structure.The maximum achieved single element gain at the desired resonance frequency is 3.45 dBi.The efficiency of the proposed design over the operating band is more than 88%.The impedance bandwidth achieved for−10 dB reference value is nearly 2.9 GHz.The proposed antenna is transformed into four element linear array which increases the gain up to 10.5 dBi.The fabricated prototype is tested for the measured results.It is observed that measured results closely match the simulated results.By considering its simple structure and focused radiation patterns,the proposed design is well suited for IoT(Internet of Things),mmWave microwave sensing,5G and future RF(Radio Frequency)frontends.展开更多
Emotion Recognition in Conversations(ERC)is fundamental in creating emotionally intelligentmachines.Graph-BasedNetwork(GBN)models have gained popularity in detecting conversational contexts for ERC tasks.However,their...Emotion Recognition in Conversations(ERC)is fundamental in creating emotionally intelligentmachines.Graph-BasedNetwork(GBN)models have gained popularity in detecting conversational contexts for ERC tasks.However,their limited ability to collect and acquire contextual information hinders their effectiveness.We propose a Text Augmentation-based computational model for recognizing emotions using transformers(TA-MERT)to address this.The proposed model uses the Multimodal Emotion Lines Dataset(MELD),which ensures a balanced representation for recognizing human emotions.Themodel used text augmentation techniques to producemore training data,improving the proposed model’s accuracy.Transformer encoders train the deep neural network(DNN)model,especially Bidirectional Encoder(BE)representations that capture both forward and backward contextual information.This integration improves the accuracy and robustness of the proposed model.Furthermore,we present a method for balancing the training dataset by creating enhanced samples from the original dataset.By balancing the dataset across all emotion categories,we can lessen the adverse effects of data imbalance on the accuracy of the proposed model.Experimental results on the MELD dataset show that TA-MERT outperforms earlier methods,achieving a weighted F1 score of 62.60%and an accuracy of 64.36%.Overall,the proposed TA-MERT model solves the GBN models’weaknesses in obtaining contextual data for ERC.TA-MERT model recognizes human emotions more accurately by employing text augmentation and transformer-based encoding.The balanced dataset and the additional training samples also enhance its resilience.These findings highlight the significance of transformer-based approaches for special emotion recognition in conversations.展开更多
文摘Imbalanced multiclass datasets pose challenges for machine learning algorithms.They often contain minority classes that are important for accurate predictions.However,when the data is sparsely distributed and overlaps with data points fromother classes,it introduces noise.As a result,existing resamplingmethods may fail to preserve the original data patterns,further disrupting data quality and reducingmodel performance.This paper introduces Neighbor Displacement-based Enhanced Synthetic Oversampling(NDESO),a hybridmethod that integrates a data displacement strategy with a resampling technique to achieve data balance.It begins by computing the average distance of noisy data points to their neighbors and adjusting their positions toward the center before applying random oversampling.Extensive evaluations compare 14 alternatives on nine classifiers across synthetic and 20 real-world datasetswith varying imbalance ratios.This evaluation was structured into two distinct test groups.First,the effects of k-neighbor variations and distance metrics are evaluated,followed by a comparison of resampled data distributions against alternatives,and finally,determining the most suitable oversampling technique for data balancing.Second,the overall performance of the NDESO algorithm was assessed,focusing on G-mean and statistical significance.The results demonstrate that our method is robust to a wide range of variations in these parameters and the overall performance achieves an average G-mean score of 0.90,which is among the highest.Additionally,it attains the lowest mean rank of 2.88,indicating statistically significant improvements over existing approaches.This advantage underscores its potential for effectively handling data imbalance in practical scenarios.
基金funded by Princess Nourah bint Abdulrahman University Researchers Supporting Project number(PNURSP2025R235),Princess Nourah bint Abdulrahman University,Riyadh,Saudi Arabia.
文摘Early and accurate detection of Heart Disease(HD)is critical for improving patient outcomes,as HD remains a leading cause of mortality worldwide.Timely and precise prediction can aid in preventive interventions,reducing fatal risks associated with misdiagnosis.Machine learning(ML)models have gained significant attention in healthcare for their ability to assist professionals in diagnosing diseases with high accuracy.This study utilizes 918 instances from publicly available UCI and Kaggle datasets to develop and compare the performance of various ML models,including Adaptive Boosting(AB),Naïve Bayes(NB),Extreme Gradient Boosting(XGB),Bagging,and Logistic Regression(LR).Before model training,data preprocessing techniques such as handling missing values,outlier detection using Isolation Forest,and feature scaling were applied to improve model performance.The evaluation was conducted using performance metrics,including accuracy,precision,recall,and F1-score.Among the tested models,XGB demonstrated the highest predictive performance,achieving an accuracy of 94.34%and an F1-score of 95.19%,surpassing other models and previous studies in HD prediction.LR closely followed with an accuracy of 93.08%and an F1-score of 93.99%,indicating competitive performance.In contrast,NB exhibited the lowest performance,with an accuracy of 88.05%and an F1-score of 89.02%,highlighting its limitations in handling complex patterns within the dataset.Although ML models show superior performance as compared to previous studies,some limitations exist,including the use of publicly available datasets,which may not fully capture real-world clinical variations,and the lack of feature selection techniques,which could impact model interpretability and robustness.Despite these limitations,the findings highlight the potential of ML-based frameworks for accurate and efficient HD detection,demonstrating their value as decision-support tools in clinical settings.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61103231 and 61103230)the Innovation Program of Graduate Scientific Research in Institution of Higher Education of Jiangsu Province, China (Grant No. CXZZ11 0401)
文摘In this paper, considering both cluster heads and sensor nodes, we propose a novel evolving a network model based on a random walk to study the fault tolerance decrease of wireless sensor networks （WSNs） due to node failure, and discuss the spreading dynamic behavior of viruses in the evolution model. A theoretical analysis shows that the WSN generated by such an evolution model not only has a strong fault tolerance, but also can dynamically balance the energy loss of the entire network. It is also found that although the increase of the density of cluster heads in the network reduces the network efficiency, it can effectively inhibit the spread of viruses. In addition, the heterogeneity of the network improves the network efficiency and enhances the virus prevalence. We confirm all the theoretical results with sufficient numerical simulations.
基金financially supported by the 111 Project (No.D18016)the Application and Fundamental Research of Sichuan Province, China (No.2017JY0171)the Scientific and Technological Innovation Team for the Safety of Petroleum Tubular Goods in Southwest Petroleum University (No.2018CXTD01)。
文摘We investigated erosion-corrosion(E-C) and its mitigation on the internal surface of the expansion segment of N80 steel tube in a loop system using array electrode technique, weight-loss measurement, computational-fluid-dynamics simulation, and surface characterization techniques.The results show that high E-C rates can occur at locations where there is a high flow velocity and/or a strong impact from sand particles, which results in different E-C rates at various locations.Consequently, it can be expected that localized corrosion often occurs in such segments.The E-C rate at each location in the expansion segment can be significantly mitigated with an imidazoline derivative inhibitor, as the resulting inhibitor layer significantly impedes the electrochemical reaction rate.However, we found that this inhibitor layer could not effectively reduce the difference in the erosion rates at different locations on the internal surface of the expansion segment.This means that localized corrosion can still occur at the expansion segment despite the presence of the inhibitor.
基金Project(50675047) supported by the National Natural Science Foundation of China
文摘To restrain the formation of AuSnx intermetallic components (IMCs) in solder joints, Zn was added into Sn-rich solders. The solder joints were fabricated by a laser reflow soldering method, and then they were aged at 125 ℃. The results show that the total thickness of AuSnx IMCs at the interface of pure Sn solder and Au foils reaches about 54 μm under the condition of 600 h aging. In Sn-1.5Zn solder joints, however, formation of AuSn4 IMCs is restrained greatly. As the content of Zn in the solder is increased to 3.5%(mass fraction), no AuSn4 IMC is observed at the interface. Au-Zn phases form beside AuSn2 and AuSn IMCs layers. As for Sn-9.0Zn solder joints, Au-Zn and Au-Zn-Sn phases and few AuSnx IMCs form at the interface. Moreover, total thickness of the phases and IMCs is far less than that of AuSnx IMCs in the pure Sn solder joints.
基金National Natural Science Foundation of China(No.61975119)。
文摘This paper designs the thermal crystals composed of alloy materials with air holes and analyzes their properties of band structures,heat transmission,and flux spectra.Thermal crystals composed of Si-A(A=Ge,Sn,Pb)alloys as background materials and air holes with square array are used to construct an elastic-constant periodic structure and their high-frequency phononic band is calculated by deploying finite element methods.Moreover,this paper investigates heat transmission through a finite array of thermally excited phonons and presents the thermal crystal with maximum heat transport.The results show that a wider bandgap could be achieved by increasing the air hole radius and decreasing the lattice constant.In the alloy materials,with increasing atomic radius and thus atomic mass(Ge,Sn,Pb),the frequency range(contributed to thermal conductivity)shifts towards lower frequency.Hence,the bandgap frequencies also shift toward low frequency,but this decreasing rate is not constant or in order,so former may have a faster or slower decreasing rate than the later.Thus,the frequency range for the contribution of heat transportation overlaps with the bandgap frequency range.The development of thermal crystals is promising for managing heat and controlling the propagation of the thermal wave.
基金This study was financially supported by National Natural Science Foundation of China （No.50675047）.
文摘Formation of AuSnx intermetallic compounds （IMCs） in laser reflowed solder joints was investigated. The results showed that few IMCs formed at the solder/0. 1μm Au interface. Needlelike AuSn4 IMCs were observed at the solder/0.5μm Au interface. In Sn-2.0Ag-O,75Cu-3,0Bi and Sn-3.5Ag-O.75Cu solder joints, when the laser input energy was increased, AuSn4 IMCs changed .from a layer to needlelike or dendritic distribution at the solder/0.9μm Au interface. As for the solder joints with 4.0 μm thickness of Au surface finish on pads, AuSn4 , AuSnx, AuSn IMCs, and Au2Sn phases formed at the interface. Moreover, the content of AuSnx IMCs, such as, AuSn4 and AuSn2, which contained high Sn concentration, would become larger as the laser input energy increased. In the Sn-37Pb solder joints with 0.9 μm or 4.0 μm thickness of the Au surface finish on pads, AuSn4 IMCs were in netlike distribution. The interspaces between them were filled with Pb-rich phases.
文摘The Dielectric Spectroscopy technique is a tool that can be used to provide information regarding the physical and chemical properties of materials. In this work Dielectric Spectroscopy (DS) measurements were conducted on marble specimens that were previously subjected to uniaxial compressive stress up to fracture in order to investigate the influence of the mechanical stress on the dielectric properties of the specimens. Specifically, the ac conductivity (σac) was measured when an ac electric field in the frequency range 1 kHz - 1 MHz was applied upon dry and saturated specimens which were subjected successively to higher levels of mechanical stress. The experimental results indicate that there are systematic variations in the values of the ac conductivity after each stress application at a higher stress level. Such variations become more intense at higher stress values and can be used to indicate the upcoming fracture since significant increase of conductivity is recorded when microcracks formations appear and propagate in the sample bulk.
基金Supported by the National Natural Science Foundation of China under Grant Nos.61103231,61103230the Innovation Program of Graduate Scientific Research in Institution of Higher Education of Jiangsu Province of China under Grant No.CXZZ110401+1 种基金the Basic Research Foundation of Engineering University of the Chinese People's Armed Police Force under Grant No.WJY201218 the Natural Science Basic Research Plan in Shaanxi Province of China under Grant No.2011JM8012
文摘In this paper, to study rumor spreading, we propose a novel susceptible-infected-removed （SIR） model by introducing the trust mechanism. We derive mean-field equations that describe the dynamics of the SIR model on homogeneous networks and inhomogeneous networks. Then a steady-state analysis is conducted to investigate the critical threshold and the finaJ size of the rumor spreading. We show that the introduction of trust mechanism reduces the final rumor size and the velocity of rumor spreading, but increases the critical thresholds on both networks. Moreover, the trust mechanism not only greatly reduces the maximum rumor influence, but also postpones the rumor terminal time, which provides us with more time to take measures to control the rumor spreading. The theoretical results are confirmed by sufficient numerical simulations.
文摘A novel scheme‘user assisted cooperative relaying in beamspace massive multiple input multiple output(M-MIMO)non-orthogonal multiple access(NOMA)system’has been proposed to improve coverage area,spectrum and energy efficiency for millimeter wave(mmWave)communications.A downlink system for M users,where base station(BS)is equipped with beamforming lens antenna structure having NRF radio frequency(RF)chains,has been considered.A dynamic cluster of users is formed within a beam and the intermediate users(in that cluster)between beam source and destination(user)act as relaying stations.By the use of successive interference cancellation(SIC)technique of NOMA within a cluster,the relaying stations relay the symbols with improved power to the destination.For maximizing achievable sum rate,transmit precoding and dynamic power allocation for both intra and inter beam power optimization are implemented.Simulations for performance evaluation are carried out to validate that the proposed system outperforms the conventional beamspace M-MIMO NOMA system for mmWave communications in terms of spectrum and energy efficiency.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61103231 and 61103230)the Natural Science Foundation of Jiangsu Province, China (Grant No. BK2012082)+2 种基金the Innovation Program of Graduate Scientific Research in Institution of Higher Education of Jiangsu Province,China (Grant No. CXZZ11 0401)the Natural Science Basic Research Plan in Shaanxi Province of China (Grant No. 2011JM8012)the Basic Research Foundation of Engineering University of the Chinese People’s Armed Police Force (Grant No. WJY201218)
文摘In this paper, an extended version of standard susceptible-infected （SI） model is proposed to consider the influence of a medium access control mechanism on virus spreading in wireless sensor networks. Theoretical analysis shows that the medium access control mechanism obviously reduces the density of infected nodes in the networks, which has been ignored in previous studies. It is also found that by increasing the network node density or node communication radius greatly increases the number of infected nodes. The theoretical results are confirmed by numerical simulations.
基金Supported by the National Natural Science Foundation of China under Grant No.61402531the Natural Science Basic Research Plan in Shaanxi Province of China under Grant Nos.2014JQ8358,2015JQ6231,and 2014JQ8307+1 种基金the China Postdoctoral Science Foundation under Grant No.2015M582910the Basic Research Foundation of Engineering University of the Chinese People’s Armed Police Force under Grant Nos.WJY201419,WJY201605 and JLX201686
文摘In order to prevent and control the spread of rumors, the implementation of immunization strategies for ignorant individuals is very necessary, where the immunization usually means letting them learn the truth of rumors.Considering the facts that there is always a delay time between rumor spreading and implementing immunization, and that the truth of rumors can also be spread out, this paper constructs a novel susceptible-infected-removed(SIR) model.The propagation dynamical behaviors of the SIR model on homogeneous networks are investigated by using the meanfield theory and the Monte Carlo method. Research shows that the greater the delay time, the worse the immune effect of the immunization strategy. It is also found that the spread of the truth can inhibit to some extent the propagation of rumors, and the trend will become more obvious with the increase of reliability of the truth. Moreover, under the influence of delay time, the existence of nodes' identification force still slightly reduces the propagation degree of rumors.
基金supported by the National Science Foundation of China Grant funded by the Chinese Government(No.61861043).
文摘In this work,a novel compact wideband reconfigurable circularly polarised(CP)dielectric resonator antenna(DRA)is presented.The L-shaped Dielectric resonator antenna is excited by an inverted question mark shaped feed.This arrangement of feed-line helps to generate two orthogonal modes inside the DR,which makes the design circularly polarised.A thin micro-strip line placed on the defected ground plane not only helps to generate a wideband response but also assist in the positioning of the two diode switches.These switches located at the left and right of the micro-strip line helps in performing two switching operations.The novel compact design offers the reconfigurability between 2.9–3.8 GHz which can be used for different important wireless applications.For the switching operation I,the achieved impedance bandwidth is 24%while axial ratio bandwidth(ARBW)is 42%.For this switching state,the design has 100%CP performance.Similarly,the switching operation II achieves 60%impedance bandwidth and 58.88%ARBW with 76.36%CP performance.The proposed design has a maximum measured gain of 3.4 dBi and 93%radiation efficiency.The proposed design is novel in terms of compactness and performance parameters.The prototype is fabricated for the performance analysis which shows that the simulated and measured results are in close agreement.
基金supported by the National Natural Science Foundation of China(61309022)
文摘Fuzzy sets theory cannot describe the neutrality degreeof data, which has largely limited the objectivity of fuzzy time seriesin uncertain data forecasting. With this regard, a multi-factor highorderintuitionistic fuzzy time series forecasting model is built. Inthe new model, a fuzzy clustering algorithm is used to get unequalintervals, and a more objective technique for ascertaining membershipand non-membership functions of the intuitionistic fuzzy setis proposed. On these bases, forecast rules based on multidimensionalintuitionistic fuzzy modus ponens inference are established.Finally, contrast experiments on the daily mean temperature ofBeijing are carried out, which show that the novel model has aclear advantage of improving the forecast accuracy.
基金This study was funded by the Deanship of Scientific Research,Taif University Researchers Supporting Project number(TURSP-2020/08),Taif University,Taif,Saudi Arabia.
文摘Audio communications and computer networking play essential roles in our daily lives,including many domains with different scopes.Developments in these technologies are quick.In consequence,there is a dire need to secure these technologies up to date.This paper presents an efficient model for secure audio signal transmission over the wireless noisy uncorrelated Rayleigh fading channel.Also,the performance of the utilized multiple secret keys-based audio cryptosystem is analyzed in different transformation domains.The discrete cosine transform(DCT),the discrete sine transform(DST),and the discrete wavelet transform(DWT)are investigated in the utilizedmultiple secret key-based audio cryptosystem.Simulation results show consistent results with the wireless noisy channel.The performance of the proposed multiple secret keys-based audio cryptosystem can be ranked concerning the employed domain as DWT,DCT,and DST transform techniques.The simulation experiments proved that the presented multiple secret keysbased audio cryptosystemfor audio signals transmitted over the wireless noisy uncorrelatedRayleigh fading channel achieves reliable and secure wireless link utilizing combined multi security layers.
文摘Wireless Local Area Network(WLAN) with high data bit rates can be used with cellular network to achieve higher level of Quality of Service(QoS) by sharing their total resources efficiently.The integration between cellular and WLAN networks should be ensured considering different channel-allocation strategies of both networks and efficient resource management techniques should be developed.In this paper,we propose a new call admission scheme to use the coupled resource effectively.The proposed scheme,by taking the different resource sharing strategies for two access networks,limits the new,horizontal and vertical handoff voice and data call arrivals with respect to their call-level QoS requirements.Numerical results show that the proposed integrated cellular/WLAN network model uses the resources more effectively and achieves all upper bound QoS requirements for voice and data users as compared with the non-integrated network model.
基金This research project is supported by the Second Century Fund(C2F)Chulalongkorn University,Thailand.This research work is also funded by TSRI Fund(CU_FRB640001_01_21_8)+1 种基金The authors also would like to thank Taif University Researchers supporting project number(TURSP-2020/228)Taif University,Taif,Saudi Arabia.
文摘Recent reports from World Health Organization(WHO)show the impact of human negligence as a serious concern for road accidents and casualties worldwide.There are number of reasons which led to this negligence;hence,need of intelligent transportation system(ITS)gains more attention from researchers worldwide.For achieving such autonomy different sensors are involved in autonomous vehicles which can sense road conditions and warn the control system about possible hazards.This work is focused on designing one such sensor system which can detect and range multiple targets under the impact of adverse atmospheric conditions.A high-speed Linear Frequency Modulated Continuous Wave(LFMCW)based Photonic Radar is proposed to detect multiple targets by integrating Mode division multiplexing(MDM).Reported results in terms of range frequency,Doppler frequency and range resolution are demonstrated using numerical simulations with the bandwidths of 1 and 4 GHz and under adverse atmospheric conditions carrying 75 dB/km of attenuation.To prove the effectiveness of the proposed photonic radar,moving targets are also demonstrated with different speed.System reported substantial range resolution of 15 cm using 1 GHz of bandwidth and 3 cm using 4 GHz of bandwidth.
文摘This article presents a novel modified chuck wagon dinner bell shaped millimeter wave(mm-wave)antenna at 28 GHz.The proposed design has ultra-thin Rogers 5880 substrate with relative permittivity of 2.2.The design consists of T shaped resonating elements and two open ended side stubs.The desired 28 GHz frequency response is achieved by careful parametric modeling of the proposed structure.The maximum achieved single element gain at the desired resonance frequency is 3.45 dBi.The efficiency of the proposed design over the operating band is more than 88%.The impedance bandwidth achieved for−10 dB reference value is nearly 2.9 GHz.The proposed antenna is transformed into four element linear array which increases the gain up to 10.5 dBi.The fabricated prototype is tested for the measured results.It is observed that measured results closely match the simulated results.By considering its simple structure and focused radiation patterns,the proposed design is well suited for IoT(Internet of Things),mmWave microwave sensing,5G and future RF(Radio Frequency)frontends.
文摘Emotion Recognition in Conversations(ERC)is fundamental in creating emotionally intelligentmachines.Graph-BasedNetwork(GBN)models have gained popularity in detecting conversational contexts for ERC tasks.However,their limited ability to collect and acquire contextual information hinders their effectiveness.We propose a Text Augmentation-based computational model for recognizing emotions using transformers(TA-MERT)to address this.The proposed model uses the Multimodal Emotion Lines Dataset(MELD),which ensures a balanced representation for recognizing human emotions.Themodel used text augmentation techniques to producemore training data,improving the proposed model’s accuracy.Transformer encoders train the deep neural network(DNN)model,especially Bidirectional Encoder(BE)representations that capture both forward and backward contextual information.This integration improves the accuracy and robustness of the proposed model.Furthermore,we present a method for balancing the training dataset by creating enhanced samples from the original dataset.By balancing the dataset across all emotion categories,we can lessen the adverse effects of data imbalance on the accuracy of the proposed model.Experimental results on the MELD dataset show that TA-MERT outperforms earlier methods,achieving a weighted F1 score of 62.60%and an accuracy of 64.36%.Overall,the proposed TA-MERT model solves the GBN models’weaknesses in obtaining contextual data for ERC.TA-MERT model recognizes human emotions more accurately by employing text augmentation and transformer-based encoding.The balanced dataset and the additional training samples also enhance its resilience.These findings highlight the significance of transformer-based approaches for special emotion recognition in conversations.
