Hydrodynamic Characteristics of Undular Tidal Bores in the Qiantang River Based on Field Observations

Understanding the undular tidal bores in the Qiantang River is essential for effective river management and maintenance.While breaking tidal bores have been studied extensively, reports on undular tidal bores in the Qiantang Riverremain limited. Furthermore, observed data on undular tidal bores fulfilling the requirements of short measurementtime intervals, and spring, medium, and neap tide coverage, and providing detailed data for the global vertical stratificationof flow velocity are quite limited. Based on field observations at Qige in the Qiantang estuary, we analyzedthe characteristics of undular tidal bores. The results showed that the flooding amplitude (a) of the first wave isalways larger than its ebbing amplitude (b). Moreover, the vertical distribution of the maximum flood velocity exhibitesthree shapes, influenced by the tidal range, while that of the maximum ebb velocity exhibites a single shape. Duringthe initial phase of the flood tide in the spring and medium tides, the upper water body experiences multiple oscillatingchanges along the flow direction, corresponding to the alternating process of the crest and trough of the tide levelupon the arrival of the tidal bore. The tidal range is a crucial parameter in tidal bore hydrodynamics. By establishingthe relationship between hydrodynamic parameters and tidal range, other hydrodynamic parameters, such as the tidalbore height, maximum flood depth–averaged velocity, maximum flood stratified velocity at the measurement points,and duration of the flood tide current, can be effectively predicted, thereby providing an important reference for rivermanagement and maintenance.

The Impact of Jams on the Vending Robot

This study aims to identify the causes of sensor jams and its impact on the operation of vending machines. The vending machine is a machine that automatically dispenses products such as drinks, tickets, sandwiches and biscuits, by inserting change or credit card into the machine. This technological feat is due to the advent of sensors. A sensor is a part of the measurement chain, it receives the quantity to be measured and provides information directly linked to this quantity. However, these vending robots are faced with malfunctions linked to sensor jams. The identification of the jam phenomenon was possible thanks to the inspection and monitoring of the various sensors installed on the vending robot. And Cadence software was used to model, control and locate the jammed sensor(s). The various tests were carried out by setting the robot in motion to better understand the causes of the phenomenon. The jam is therefore the phenomenon which triggers the sensors permanently, which causes the automatic vending robot to stop functioning. And this jam was due to the presence of water droplets on the sensor or dirt. This presence of water droplets on the sensor is linked to an increase in temperature. Controlling the temperature and locating the jammed sensor has made it possible to considerably reduce jamming and its harmful effects on the vending machine robot.

Intelligent Detection and Identification of Attacks in IoT Networks Based on the Combination of DNN and LSTM Methods with a Set of Classifiers

Internet of Things (IoT) networks present unique cybersecurity challenges due to their distributed and heterogeneous nature. Our study explores the effectiveness of two types of deep learning models, long-term memory neural networks (LSTMs) and deep neural networks (DNNs), for detecting attacks in IoT networks. We evaluated the performance of six hybrid models combining LSTM or DNN feature extractors with classifiers such as Random Forest, k-Nearest Neighbors and XGBoost. The LSTM-RF and LSTM-XGBoost models showed lower accuracy variability in the face of different types of attack, indicating greater robustness. The LSTM-RF and LSTM-XGBoost models show variability in results, with accuracies between 58% and 99% for attack types, while LSTM-KNN has higher but more variable accuracies, between 72% and 99%. The DNN-RF and DNN-XGBoost models show lower variability in their results, with accuracies between 59% and 99%, while DNN-KNN has higher but more variable accuracies, between 71% and 99%. LSTM-based models are proving to be more effective for detecting attacks in IoT networks, particularly for sophisticated attacks. However, the final choice of model depends on the constraints of the application, taking into account a trade-off between accuracy and complexity.

The Effect of Retrofit Technologies on Formaldehyde Emissions from a Large Bore Natural Gas Engine

Formaldehyde is an air toxic that is typically emitted from natural gas-fired internal combustion engines as a product of incomplete combustion. The United States Environmental Protection Agency (EPA) regulates air toxic emissions, including formaldehyde, from stationary reciprocating internal combustion engines. National air toxic standards are required under the 1990 Clean Air Act Amendments. This work investigates the effect that hardware modifications, or retrofit technologies, have on formaldehyde emissions from a large bore natural gas engine. The test engine is a Cooper-Bessemer GMV-4TF two stroke cycle engine with a 14” (35.6 cm) bore and a 14” (35.6 cm) stroke. The impact of modifications to the fuel injection and ignition systems are investigated. Data analysis and discussion is performed with reference to possible formaldehyde formation mechanisms and in-cylinder phenomena. The results show that high pressure fuel injection (HPFI) and precombustion chamber (PCC) ignition significantly reduce formaldehyde

Contribution of Electrical Resistivity Tomography and Boring Technique in the Realization of Ten (10) Large Boreholes in a Crystalline Basement Rocks in the Centre-West of Benin

In order to ensure access to drinking water for Benin populations by 2021, the Emergency Measure program for the reinforcement of the drinking water supply system of Savalou city was initiated in 2018. This program focuses on densification and extension of hydraulic infrastructures. Therefore, it is prominent to use rigorous approach for implementation and execution of drilling activities. The present work has the advantage of combining the use of electrical resistivity tomography and borehole technique to locate ten high flow drilling in Savalou city. The electrical resistivity tomography (ERT) panels were made based on the dipole-dipole arrays with 48 electrodes with 5 m inter-electrode spacing. The drilling was carried out over ten selected points and in two stages: confirmation test using piezometer and borehole diameter enlargement. Moreover, only piezometers with flow rate greater than 10 m3/h were enlarged. The tomography processing has identified 10 fractured zones that are defined by 250 - 1000 ohm.m resistivity values and a width between 15 - 55 m. The confirmation test carried out over ten piezometers exhibits high flow rates ranging from 9 to 35 m3/h with depths of 30 to 68 m. Nine over the ten boreholes with a flow rate equal or greater than 10 m3/h, have improved their flow rates by 50% to 100% after the boring technique. Thus, the cumulative flow rate has reached 252. 7 m3/h for Savalou city and his surrounding areas.

Assessment of Organ Dose by Direct and Indirect Measurements for a Wide Bore X-Ray Computed Tomography Unit That Used in Radiotherapy

The aim of this study was to investigate the organ doses of patients undergoing computed tomography (CT) examination using the wide bore General Electric (GE) “Light Speed RT” unit. The head, chest and pelvic regions of the Rando-phantom were scanned with 120 kV, 200 mA, and 2.5 mm slice thickness for helical and axial modes. Thermoluminescent Dosimeter (TLD) pairs were used for the dosimetry of 10 organs. TL-counts were converted to dose by using CTDIcenter dose on CT-phantom. For the calculation of the organ doses, the ImPACT software was utilized by entering CTDIair (100 mAs) in small and large field of view (26.43 and 21.17 mGy respectively). The in-field dose ranges in helical and axial modes were 64.3 - 38 mGy and 47.6 - 19.7 mGy in head, 48.3 - 14.1 mGy and 34.1 - 10 mGy in chest, 28.4 - 10.2 mGy and 21 - 8.5 mGy in pelvic, respectively. The organ doses from software and TLD were compared and tailored as the in-field and the out-field radiation. First results showed that the organ dose was relatively higher in the helical mode on both direct and indirect measurement. The in-field organ dose differences between TLD and software were seen. In helical and axial modes, the dose differences ranged from +1 to +13.3 and -8.3 to +9.6 mGy for head exam, +1.1 to +15.3 and +0.3 to +9.1 mGy for chest, and -21.7 to +1.9 and -15.5 to +1.8 mGy for pelvic. The availability of this program for organ dose calculations by measuring CTDIair value for CT device used in the radiotherapy would be considered valuable.

On the critical conditions of traffic jams

Traffic wave theory is used to study the critical conditions for traffic jams according to their features. First, the characteristics of traffic wave propagation is analyzed for the simple signal-controlled lane and the critical conditions for oversaturation is established. Then, the basic road is decomposed into a series of one-way links according to its topological characteristics. Based on the decomposition, traffic wave propagation under complex conditions is studied. Three complicated factors are considered to establish the corresponding critical conditions of jam formation, namely, dynamic and insufficient split, channelized section spillover and endogenous traffic flow. The results show that road geometric features, traffic demand structures and signal settings influence the formation and propagation of traffic congestion. These findings can serve as a theoretical basis for future network jam control.

Research on the Dynamic Model of Spindle Rotation Induced Error Compensation System of Boring and its Simulation

In this paper we address the dynamics of compensation cutting process from both Laplace s frequency domain and the time domain of the first time, using the two computer aided analyzing softwares: MATLAB and SIMULINK. Theoretical analysis and simulation experiments firstly show that not only the systematical stiffness of workpiece, spindle and tools, but also the regenerated coefficient affects the compensation displacement effect. The results show that the SREC is practicable in reality to decease the spindle induced errors in many engineering applications such as hard boring through simulation and the preliminary experiment results.

Modulated-ISRJ rejection using online dictionary learning for synthetic aperture radar imagery

In electromagnetic countermeasures circumstances,synthetic aperture radar(SAR)imagery usually suffers from severe quality degradation from modulated interrupt sampling repeater jamming(MISRJ),which usually owes considerable coherence with the SAR transmission waveform together with periodical modulation patterns.This paper develops an MISRJ suppression algorithm for SAR imagery with online dictionary learning.In the algorithm,the jamming modulation temporal properties are exploited with extracting and sorting MISRJ slices using fast-time autocorrelation.Online dictionary learning is followed to separate real signals from jamming slices.Under the learned representation,time-varying MISRJs are suppressed effectively.Both simulated and real-measured SAR data are also used to confirm advantages in suppressing time-varying MISRJs over traditional methods.

Examining the effect of adverse geological conditions on jamming of a single shielded TBM in Uluabat tunnel using numerical modeling

Severe shield jamming events have been reported during excavation of Uluabat tunnel through adverse geological conditions, which resulted in several stoppages at advancing a single shielded tunnel boring machine(TBM). To study the jamming mechanism, three-dimensional(3D) simulation of the machine and surrounding ground was implemented using the finite difference code FLAC3D. Numerical analyses were performed for three sections along the tunnel with a higher risk for entrapment due to the combination of overburden and geological conditions. The computational results including longitudinal displacement contours and ground pressure profiles around the shield allow a better understanding of ground behavior within the excavation. Furthermore, they allow realistically assessing the impact of adverse geological conditions on shield jamming. The calculated thrust forces, which are required to move the machine forward, are in good agreement with field observations and measurements. It also proves that the numerical analysis can effectively be used for evaluating the effect of adverse geological environment on TBM entrapments and can be applied to prediction of loads on the shield and preestimating of the required thrust force during excavation through adverse ground conditions.

The influence of microwave irradiation on rocks for microwaveassisted underground excavation

Demand is growing for explosive-free rock breakage systems for civil and mining engineering, and space industry applications. This paper highlights the work being undertaken in the Geomechanics Laboratory of Mc Gill University to make a real application of microwave-assisted mechanical rock breakage to fullface tunneling machines and drilling. Comprehensive laboratory tests investigated the effect of microwave radiation on temperature profiles and strength reduction in hard rocks(norite, granite, and basalt)for a range of exposure times and microwave power levels. The heating rate on the surface of the rock specimens linearly decreased with distance between the sample and the microwave antenna, regardless of microwave power level and exposure time. Tensile and uniaxial compressive strengths were reduced with increasing exposure time and power level. Scanning electron micrographs(SEMs) highlighted fracture development in treated basalt. It was concluded that the microwave power level has a strong positive influence on the amount of heat damage induced to the rock surface. Numerical simulations of electric field intensity and wave propagation conducted with COMSOL Multiphysics~ software generated temperature profiles that were in close agreement with experimental results.

Design Theory of Full Face Rock Tunnel Boring Machine Transition Cutter Edge Angle and Its Application

At present, the inner cutters of a full face rock tunnel boring machine (TBM) and transition cutter edge angles are designed on the basis of indentation test or linear grooving test. The inner and outer edge angles of disc cutters are characterized as symmetric to each other with respect to the cutter edge plane. This design has some practical defects, such as severe eccentric wear and tipping, etc. In this paper, the current design theory of disc cutter edge angle is analyzed, and the characteristics of the rock-breaking movement of disc cutters are studied. The researching results show that the rotational motion of disc cutters with the cutterhead gives rise to the difference between the interactions of inner rock and outer rock with the contact area of disc cutters, with shearing and extrusion on the inner rock and attrition on the outer rock. The wear of disc cutters at the contact area is unbalanced, among which the wear in the largest normal stress area is most apparent. Therefore, a three-dimensional model theory of rock breaking and an edge angle design theory of transition disc cutter are proposed to overcome the flaws of the currently used TBM cutter heads, such as short life span, camber wearing, tipping. And a corresponding equation is established. With reference to a specific construction case, the edge angle of the transition disc cutter has been designed based on the theory. The application of TBM in some practical project proves that the theory has obvious advantages in enhancing disc cutter life, decreasing replacement frequency, and making economic benefits. The proposed research provides a theoretical basis for the design of TBM three-dimensional disc cutters whose rock-breaking operation time can be effectively increased.

Mathematic principle of active jamming against wideband LFM radar

The inherent mathematic principle of active jamming against the wideband linear frequency modulated（LFM） radar is investigated. According to different generation strategies, the active jamming methods are reclassified into three groups, i.e.,non-coherent jamming（NCJ）, convolution jamming（CJ） and multiplying jamming（MJ）. Based on the classification, the mathematic principles of different active jamming groups are put forward, which describe the relationships between the modulated signals and the jamming results. The advantages and disadvantages of different groups are further analyzed, which provides a new perspective for the study of jamming/anti-jamming methods and a potential for engineers to integrate similar jamming methods into one jammer platform. The analyses and simulation results of some typical active jamming methods prove the validity of the proposed mathematics principle.

Laboratory tests to study the influence of rock stress confinement on the performances of TBM discs in tunnels

To clarify some aspects of rock destruction with a disc acting on a high confined tunnel face, a series of tests were carried out to examine fracture mechanisms under an indenter that simulates the tunnel boring machine （TBM） tool action, in the presence of an adjacent groove, when a state of stress （lateral confinement） is imposed on a rock sample. These tests proved the importance of carefully establishing the optimal distance of grooves produced by discs acting on a confined surface, and the value （as a mere order of magnitude） of the increase of the thrust to produce the initiation of chip formation, as long as the confinement pressure becomes greater.

Theoretical prediction of wear of disc cutters in tunnel boring machine and its application

Predicting the cutter consumption and the exact time to replace the worn-out cutters in tunneling projects constructed with tunnel boring machine(TBM) is always a challenging issue. In this paper, we focus on the analyses of cutter motion in the rock breaking process and trajectory of rock breaking point on the cutter edge in rocks. The analytical expressions of the length of face along which the breaking point moves and the length of spiral trajectory of the maximum penetration point are derived. Through observation of rock breaking process of disc cutters as well as analysis of disc rock interaction, the following concepts are proposed: the arc length theory of predicting wear extent of inner and center cutters, and the spiral theory of predicting wear extent of gage and transition cutters. Data obtained from5621 m-long Qinling tunnel reveal that among 39 disc cutters, the relative errors between cumulatively predicted and measured wear values for nine cutters are larger than 20%, while approximately 76.9% of total cutters have the relative errors less than 20%. The proposed method could offer a new attempt to predict the disc cutter's wear extent and changing time.

Modeling and simulation of bullet-barrel interaction process for the damaged gun barrel

In this paper,the influences of bore damage on the bullet-barrel interaction process and the mechanism of how bore damage results in the end of a machine gun barrel’s service life were studied,which had seldom been paid attention to in the past several decades.A novel finite element mesh generation method for the damaged barrel and a new transient coupled thermo-mechanical finite element(FE)model,which were based on the damage data obtained through barrel life tests,were developed to simulate the interior ballistics process of a coupled bullet-barrel system.Additionally,user subroutine VUAMP was developed in the FE model in order to take the bullet base pressure brought by propellant gas into account.Good consistency between the simulation results and the experimental results verified the preciseness of the proposed mesh generation method and the FE model.The simulation results show that the increase of bullet’s initial disturbance at the muzzle and the variation of its surface morphology caused by bore damage are primarily responsible for the life end of this 12.7 mm machine gun barrel.

Feedback control scheme of traffic jams based on the coupled map car-following model

Based on the pioneering work of Konishi et al. [Phys. Rev. E （1999） 60 4000], a new feedback control scheme is presented to suppress traffic jams based on the coupled map car-following model under the open boundary condition. The effect of the safe headway on the traffic system is considered. According to the control theory, the condition under which traffic jams can be suppressed is analyzed. The results are compared with the previous results concerning congestion control. The simulations show that the suppression performance of our scheme on traffic jams is better than those of the previous schemes, although all the schemes can suppress traffic jams. The simulation results are consistent with theoretical analyses.

Influence of friction on buckling of a drill string in the circular channel of a bore hole

Enhancement of technology and techniques for drilling deep directed oil and gas bore hole is one of the most important problems of the current petroleum industry.Not infrequently, the drilling of these bore holes is attended by occurrence of extraordinary situations associated with technical accidents. Among these is the Eulerian loss of stability of a drill string in the channel of a curvilinear bore hole. Methods of computer simulation should play a dominant role in prediction of these states. In this paper, a new statement of the problem of critical buckling of the drill strings in 3D curvilinear bore holes is proposed. It is based on combined use of the theory of curvilinear elastic rods, Eulerian theory of stability, theory of channel surfaces, and methods of classical mechanics of systems with nonlinear constraints. It is noted that the stated problem is singularly perturbed and its solutions have the shapes of localized harmonic wavelets. The calculation results showed that the friction effects lead to essential redistribution of internal axial forces, as well as changing the eigenmode shapes and sites of their localization. These features make the buckling phenomena less predictable and raise the role of computer simulation of these effects.

The Effect of the Relative Velocity on Traffic Flow

The optimal velocity model of traffc is extended to take the relative velocity into account. The traffcbehavior is investigated numerically and analytically with this model. It is shown that the car interaction with therelative velocity can effect the stability of the traffic flow and raise critical density. The jamming transition between thefreely moving and jamming phases is investigated with the linear stability analysis and nonlinear perturbation methods.The traffic jam is described by the kink solution of the modified Korteweg-de Vries equation. The theoretical result isin good agreement with the simulation.

A case study of the stability of a non-typical bleeder entry system at a U.S.longwall mine

Longwall abutment loads are influenced by several factors,including depth of cover,pillar sizes,panel dimensions,geological setting,mining height,proximity to gob,intersection type,and size of the gob.How does proximity to the gob affect pillar loading and entry condition?Does the gob influence depend on whether the abutment load is a forward,side,or rear loading?Do non-typical bleeder entry systems follow the traditional front and side abutment loading and extent concepts?If not,will an improved understanding of the combined abutment extent warrant a change in pillar design or standing support in bleeder entries?This paper details observations made in the non-typical bleeder entries of a moderate depth longwall panel—specifically,data collected from borehole pressure cells and roof extensometers,observations of the conditions of the entries,and numerical modeling of the bleeder entries during longwall extraction.The primary focus was on the extent and magnitude of the abutment loading experienced due to the extraction of the longwall panels.Due to the layout of the longwall panels and bleeder entries,the borehole pressure cells(BPCs)and roof extensometers did not show much change due to the advancing of the first longwall.However,they did show a noticeable increase due to the second longwall advancement,with a maximum of about 4 MPa of pressure increase and 5mmof roof deformation.The observations of the conditions showed little to no change from before the first longwall panel extraction began to when the second longwall panel had been advanced more than 915 m.Localized pillar spalling was observed on the corners of the pillars closest to the longwall gob as well as an increase in water in the entries.In addition to the observations and instrumentation,numerical modeling was performed to validate modeling procedures against the monitoring results and evaluate the bleeder design.ITASCA Consulting Group’s FLAC3D numerical modeling software was used to evaluate the bleeder entries.The results of the models indicated only a minor increase in load during the extraction of the longwall panels.These models showed a much greater increase in stress due to the development of the gateroad and bleeder entries--about 80%development and 20%longwall extraction.The FLAC3D model showed very good correlation between modeled and expected gateroad loading during panel extraction.The front and side abutment extent modeled was very similar to observations from this and previous panels.