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There are some factors that play a crucial role in deciding the image quality during the optical as well as the micrographic association with the technique of the shadow casting in which contrast of the image has influenced with obliquely depositing of a thin layer of the metal during the process of the microscopic preparations. Further castingadvantages of the using shadow technique are to be observed during the process if shadow casting itself. Shadow casting posses’ number of the advantages over the other casting methods. The most prominent advantage is that if the height and thickness of an object is not completely flat that can be easily notice by the shadow of that object. The lengths of the shadow of the uneven part are so differentiate from other part that can be easily determined. Shadow casting uses the scattering power or even the optical efficiency to bring out the specimens contours and will easily get notice in order to check the flatness of the surfaces.

Recognizing the risk of fluvial bank erosion is an important challenge to ensure the early warning and prevention or control of bank collapse in river catchments, including in the Yangtze River. This study introduces a geomorphons-based algorithm to extract river bank erosion information by adjusting the flatness from multibeam echo-sounding data. The algorithm maps 10 subaqueous morphological elements, including the slope, footslope, flat, ridge, peak, valley, pit, spur, hollow, and shoulder. Twenty-one flatness values were used to build an interpretation strategy for the subaqueous features of riverbank erosion. The results show that the bank scarp, which is the erosion carrier, is covered by slope cells when the flatness is 10°. The scour pits and bank scars are indicated by pit cells near the bank and hollow cells in the bank slope at a flatness of 0°. Fluvial subaqueous dunes are considered an important factor accelerating bank erosion, particularly those near the bank toe; the critical flatness of the dunes was evaluated as 3°. The distribution of subaqueous morphological elements was analyzed and used to map the bank erosion inventory. The analysis results revealed that the near-bank zone, with a relatively large water depth, is prone to form large scour pits and a long bank scarp. Arc collapse tends to occur at the long bank scarp to shorten its length. The varied assignment of flatness values among terrestrial, marine, and fluvial environments is discussed, concluding that diversified flatness values significantly enable fluvial subaqueous morphology recognition. Consequently, this study provides a reference for the flatness-based recognition of fluvial morphological elements and enhances the targeting of subaqueous signs and risks of bank failure with a range of multibeam bathymetric data.

This paper presents a differential flatness-based approach to trajectory planning and tracking for helicopters and demonstrates this strategy for time-optimal autonomous helicopter shipboard landing. For planning and outer-loop tracking control, helicopter dynamics are captured by a simplified nonlinear model that is shown to be differentially flat, which enables the transformation of the original nonlinear system dynamics into an equivalent linear form with endogenous nonlinear constraints. For time-optimal trajectory planning, this equivalent model is used to construct a computationally-efficient optimization problem for free end-time end-state problems, where the decision-space is that of the trajectories of the flat outputs and their derivatives. While the attitude dynamics are stabilized by an inner loop controller, for tracking the planned trajectory a flatness-based outer loop control law is designed to stabilize the unstable zero dynamics. Further, analytical guarantees that relate inner loop tracking error to outer loop robust stability and tracking performance are derived. Simulations are performed on a high-fidelity numerical UH-60 helicopter model under ground effect and ship airwake disturbances, together with ship motion profiles collected from a naval environment to validate the proposed approach for realistic landing scenarios.

The flatness target curve is important in the flatness control theory. The accuracy of flatness target curve is an important factor to determine the load of flatness control means and flatness quality. Aiming at the defect that crown of each pass after rolling cannot be controlled quantitatively in the traditional target curve formulation of cold rolling, a new method considering the target crown was proposed. Specifically, the target crown of each pass can be set by combining the total proportional crown change in hot rolling field to each pass and the instability discrimination model in cold rolling field. the total proportional crown change of incoming material and finished product is allocated to each pass, and the instability discrimination model is applied to ensure the stability of the plate. The purpose of new method is to control of the crown of each pass quantitatively, so that the flatness and thickness of plate can meet the production requirements. Taking SUNDWIG 20-high mill and typical rolling products as an example, the simulation results show that, on the basis of ensuring the flatness and obtaining the minimum available crown after rolling, the model can make the flatness and crown meet the production requirements at the same time and control the crown of each pass after rolling quantitatively by setting the target crown of each pass.

This paper presents the design, implementation, and validation of a novel robust control strategy based on variables transformation, i.e., transforming variables to obtain the triangular flat canonical normal form (TCNF) for nonlinear dynamic systems satisfying the flatness geometric property. A differential flatness, integrated with a geometrical transformation-based method, was developed to control an exoskeleton robot named Smart Robotic Exoskeleton (SREx). The SREx was designed to provide upper limb rehabilitation therapy to the stroke survivors. The proposed flatness control technique ensures continuous enhanced trajectory tracking and the system's high robustness during following a trajectory representing rehabilitation exercises. Furthermore, utilizing the Lyapunov theory, all signals were shown to be bounded in the closed-loop form. Experiments and comparative studies were carried out to validate the effectiveness of the proposed control scheme. Controlled experiments were further conducted using healthy subjects, maneuvering the SERx to provide rehabilitation exercise and to validate the control scheme in real-time.

This article proposes a new design approach of the wideband passive equalizer for improving the gain flatness with multiple peaks which often appears in the modern transmitter systems, and the general design formulas of this passive equalizer under different practical circumstances are obtained through theoretical analysis. The proposed equalizer mainly adopts multi-stage RCL series or parallel resonant circuit structure. According to the actual multi-peak gain flatness, the structure of the single-stage equalizer, the combination mode of each stage, and the required number of stages can be determined. The proposed equalizer can design the equalization frequency, bandwidth and attenuation flexibly according to the actual situation. Finally, the proposed design approach has been well verified by experimental tests of two four-stage broadband passive equalizers with different structures operating in 0.5-2 GHz.

In this letter, a hybrid multi-order wide bandpass FSS with high selectivity and low insertion loss is achieved by combining the 2D FSS structure and 3D vertical structure. The 3D periodic vertical printed circuit board pieces (PVPCB) are used as the dielectric layer in the unit cell to achieve a proper band flatness without introducing great insertion loss. The multi-order response of the proposed FSS is achieved using a series of 3D PVPCB instead of stacking the 2D FSS layers. The proposed FSS unit cell is constructed by combining the full-wave and equivalent circuit simulations, since the physical structures have a good one-to-one correspondence with the circuit elements. The module design method is used to accelerate the design procedure, and the simulation result proves the effectiveness of this design method. Finally, the prototype is fabricated and measured to prove the effectiveness of the proposed FSS. The measured relative bandwidth and rectangle coefficient achieve 130.4% and 0.76, respectively. The measured maximum insertion loss over whole passband is 0.7 dB. Because of its strong capability of out-of-band rejection, the proposed FSS structure is a good candidate to enhance high frequency electromagnetic pulse protection of wideband radar systems.

Rail corrugation (RC) is one of the most important indicator to evaluate the quality of rail, which is used to describe the irregularity of rail surface, also known as rail's vertical flatness. However, the definition of RC is still an empirical description for low-speed measurement devices. In this paper, the process of RC measurement is divided into two steps, sampling and extraction, which helps the users to understand more clearly. Then a new mathematic model is proposed to make the process of RC's extraction be an executable operation for machine calculation. The model adopts a new concept of flexible virtual ruler to perform sliding filtering on an overall rail and extract the instantaneous RC with a successive approximation algorithm according to user's requirements and national standards. The proposed FVR model can not only be fully compatible with the traditional extraction method of RC, but also provide a new idea for evaluating RC's quality. Comparing with the current popular methods, the proposed model gives a meaningful strategy for rail maintenance with a complete mathematic description having more degrees of freedom. Experiment results demonstrate its validity and reliability for both indoor simulation and actual outdoor experiments.

The hyperbolic distributed-parameter system under consideration comprises a second-order partial differential equation that is bidirectionally coupled with a first-order ordinary differential equation. The system models the transmission at a pneumatic test bench with boundary control and collocated measurement, yet stands in place for several other lossy or loss-free transmission problems. In the paper, an observer-based output feedback tracking controller is designed using the concept of flatness. It is a design based on normal forms, as both the state feedback tracking controller and the state observer are derived using canonical coordinates, which in turn rely on special parametrizations of the system’s solutions. Additionally, a new transformation between the coordinates of the so-called hyperbolic controller and observer canonical form is presented that allows for the implementation of the observer-based controller. Overall, the closed-loop system is exponentially stable. Simulation results illustrate the tracking behavior.

In this contribution, tracking control designs using output feedback are presented for a two-phase Stefan problem (SP) arising in the modeling of the vertical gradient freeze process. The two-phase SP, consisting of two coupled free boundary problems, is a vital part of many crystal growth processes due to the temporally varying spatial extent of the solid and liquid domains during growth. After discussing the special needs of the process, collocated and flatness-based state feedback designs are carried out. The quality of the provided approximations and the performance and robustness against parameter uncertainties of the open- and closed-loop control setups are analyzed in several simulations.

A century after the first attempts of Wentworth to characterise the shape of cobbles, our understanding of particle morphology is still expanding. A plethora of shape indices has been proposed in the literature to characterise the morphology of individual particles. This study aims to shed light on the merits and limitations of the indices currently used to characterise particle elongation, flatness and compactness, adopting a unified classification framework. Second, new indices are proposed to address the identified shortcomings. Third, a new particle classification system derived from the proposed indices is illustrated. It is shown the new system overcomes the misclassification of a range of particles that are incorrectly classified as bladed in the Zingg system.

Purpose The main purpose of this work was to generate and validate the dosimetric accuracy of proton beams of dimensions that are appropriate for in vivo small animal and in vitro ultra-high dose rate (FLASH) radiotherapy experiments using a synchrotron-based treatment delivery system. This study was performed to enable future investigations of the relevance of a spread-out Bragg peak (SOBP) under FLASH conditions. Methods The spill characteristics of the small field fixed horizontal beam line were modified to deliver accelerated protons in times as short as 2 ms and to control the dose delivered. A Gaussian-like transverse beam profile was transformed into a square uniform one at FLASH dose rates, while avoiding low-dose regions, a crucial requirement to protect normal tissue during FLASH irradiation. Novel beam-shaping devices were designed using Monte Carlo techniques to produce up to about 6 cm3 of uniform dose in SOBPs while maximizing the dose rate. These included a scattering foil, a conical flattening filter to maximize the flux of protons into the region of interest, energy filters, range compensators, and collimators. The shapes, sizes, and positions of the components were varied to provide the required field sizes and SOBPs. Results The designed and fabricated devices were used to produce 10-, 15-, and 20-mm diameter, circular field sizes and 10-, 15-, and 20-mm SOBP modulation widths at uniform physical dose rates of up to 375 Gy/s at the center of the SOBP and a minimum dose rate of about 255 Gy/s at the entrance, respectively, in cylindrical volumes. The flatness of lateral dose profiles at the center could be adjusted to within ± 1.5% at the center of the SOBP. Assessment of systematic uncertainties, such as impact of misalignments and positioning uncertainties, was performed using simulations, and the results were used to provide appropriate adjustments to ensure high-accuracy FLASH beam delivery for both in vitro and in vivo preclinical experiments. Conclusions It is feasible to use synchrotron-generated proton beams of sufficient dimensions for FLASH radiobiology experiments. We expect to use the system we developed to acquire in vitro and in vivo small animal FLASH radiobiology data as a function of dose, dose rate, oxygen content, and linear energy transfer to help us understand the underlying mechanisms of the FLASH phenomenon. This article is protected by copyright. All rights reserved.

This letter presents the design of five-cell cascode distributed amplifiers (DAs) in the WIN Semiconductor PIH1-10 enhancement-mode GaAs pHEMT process. Single- and two-stage DA monolithic microwave integrated circuits (MMICs) are demonstrated, with die areas not exceeding 2.5 x 1.5 mm² and same-polarity supply and bias voltages. The cascode cells are stabilized using an RC drain-gate feedback network at the common-gate transistor of each cell, and a stability analysis is presented. All transistors have a gate width of 2 μm x 75-μm, with 750-μm total common-source gate periphery per single-stage design. The measured small-signal gain is 11.5 dB with 2.6 dB flatness and 23.2 dB with 3.2 dB flatness for the one- and two-stage amplifiers, respectively, from 10 MHz to 22 GHz. The amplifiers produce over 20-dBm output power at 3-dB gain saturation across the band.

In this paper, a new method for controlling battery emulators in the shape of bidirectional step-down converters driving constant power loads (CPL) is presented. The CPL introduces nonlinear behavior into the system and causes unstable system dynamics. This property and the discontinuity introduced by the switches makes it challenging to develop a suitable control strategy. Usually, switching frequencies are assumed to be fast enough for the controller to neglect the fact that the switches are either on or off. As the desired dynamics of the system approaches the switching frequency of the converter, the discontinuity of the switches can no longer be ignored and the controller has to generate a suitable piecewise constant control input. A novel approach for arriving at a piecewise constant control input is presented and compared to state of the art approaches. The advantages of the new control method are demonstrated with simulations as well as measurements from a hardware-in-the-loop testbed.

In this work, Er3+-doped phosphate glass with good flatness of the emission spectrum of the L+ band was prepared by optimizing the content of BaO. The absorption and emission spectra were measured. Increase of BaO content is conducive to the broadening of the emission spectrum in the L+ band. The dependence of flatness with Raman intensity has been shown by linear fitting. The results show that B31 sample has best flatness of the emission spectrum in the L+ band. It is showed that the largest emission cross-section at 1630 nm is 0.0529 × 10-20 cm2 and higher than other Er3+-doped phosphate glass. Decay curves of the 4I13/2 level were measured and the longest fluorescent lifetime is 10.18 ms and longer than other glass except germinate glass. The broadening of the Er3+-doped phosphate glass spectrum of the L+ band has been achieved successfully, which provides a reference for the material of optical amplifiers.

This study dealt with the rotary draw bending method most used for tube bending and investigates how applied bending such as normal bending, using mandrels or pressing with booster have an effect on machining accuracy, focusing on dimensional defects due to springback and flat deformation to the transverse plane. The study used particle swarm optimization (PSO) algorithms to investigate the optimal machining conditions for improving the accuracy of dimension and shape of a bent part. The following findings were obtained: The springback during applied machining using a mandrel, or using a mandrel and booster together, is almost the same as during normal processing; The flattening near the center of the bend in applied processing using a mandrel, or a mandrel and booster together, decreases more than with normal processing at mandrel protrusion L ≥ 4 mm, and the maximum can be suppressed to approximately 0.15%; When the sum of the springback and the flattening is taken as the objective function and the minimum value is obtained, the optimal solution is around L = 7 mm.

We propose a photonic method for flat spectrum millimeter-wave (mm-wave) noise generation. Specifically, the flat spectrum mm-wave noise is obtained by slicing the broadband ASE optical spectrum into multiple Gaussian-shaped spectra with different central wavelengths, then beating in a wideband photomixer. Our simulation demonstrates that flat spectrum mm-wave noise can be generated in a very large range of frequency of F-band (90-140 GHz) and G-band (140-220 GHz). For the quantitative comparison of the quality of generated mm-wave noise, we define the relative flatness ( $\eta$ ) as the ratio of the generated noise power fluctuation to its average power within a certain frequency range. Our experimental results show that the relative flatness of the generated mm-wave noise is as low as 0.46 (@35 ± 15 GHz).

In this article, we experimentally propose an efficient wide flat gain bandwidth with a parallel hybrid fiber amplifier. The setup includes parallel amplifier branches. In the first branch, serial erbium-doped and Raman fiber amplifiers are used. In the second branch, only a Raman fiber amplifier is used. Three Raman pump power units (i.e., 1410, 1480, and 1495 nm) are used to achieve Raman gain at different optical communication bands. At optimum pump powers and at a small-signal power of -30 dBm, an average gain of 18.5 dB with a maximum gain variation of 3 dB and a gain flatness bandwidth of 83 nm, that is, from 1527 to 1610 nm, is achieved. This gain flatness is expanded to 92 nm (1525-1617 nm) at a large input signal power of -5 dBm with an average gain level of 13 dB. In our proposed amplifier, the Raman amplification peaks (1510 and 1595 nm) are chosen to be far from the erbium amplification peak (1530-1570 nm) in order to avoid the overlapping and the saturation in the first amplifier branch. Therefore, due to such wavelength optimization in addition to the recycling the residual Raman pump power, a wide flatness gain bandwidth is achieved for both of low and large input signal powers.

Wire and Arc Additive Manufacturing (WAAM) aims to be a cost-effective and material-efficient process to produce medium and large-scale metal parts. Nevertheless, post-processing is still required due to the low quality of the as-deposited surface. With the objective to divulge the complex interaction between the welding and machining phenomena, which determines the final surface quality, this paper focuses on the machinability of WAAM parts through a comprehensive investigation on the key parameters of both additive and subtractive processes. The effect of the WAAM parameters on the as-deposited part characteristics (i.e., hardness, flatness deviation, wall thickness, and initial surface waviness) and machining process has been analyzed. Consequently, the first of its kind, a non-linear function that can predict the effect of welding and milling parameters on the final surface roughness, is presented. The complex interaction between the local (e.g., surface irregularities and hardness) and global (e.g., wall thickness) effects of welding heat input and the resulting impact on the machining stability is analyzed. For example, slow welding speed results in a soft and irregular surface that is not easy to machine. Still, at the same time, the slow speed increases the wall width that provides the essential damping to reduce the chatter during machining. The obtained results help understand the interactions between the WAAM and milling processes and further determine the optimal machining allowances and optimal process conditions.

Toward an ultralight antenna structure for a preliminary radar satellite with a 30 m class phased array antenna as a midway target for future solar power satellites, this study examines the feasibility of an antenna structure made of an ultrathin plate mounted with multiple antenna patches and strips. In this structure, the thermal deformation caused by the difference in the coefficients of thermal expansion of each constituent is a critical issue to guarantee the flatness requirement from the aspect of electromagnetic performance. In this study, the thermal deformation of this structure was regarded as a generalized eigenstrain problem and was studied theoretically. In the theoretical model, Eshelby's equivalent inclusion method and Mori–Tanaka's mean-field method were combined in the framework of the classical lamination theory. The effects of the in-plane geometry, alignment, and layered structure of the antenna components on the deformation of the entire antenna structure were investigated to obtain the design guidelines. Based on these results, the optimized layered structure was examined for the suppression of thermal deformation.

Non-collocated feedback control of water waves in a tube with moving boundary described by the one-dimensional Saint-Venant equations is considered. Two control approaches are developed both relying on a measurement of the water level at the non-actuated boundary. Firstly, a flatness based approach for a partially linearized model of the system is introduced. Secondly, a non-linear collocated Lyapunov based feedback law relying on a non-linear collocated observer is considered. Both approaches are studied and compared in simulations and experimental studies.

Numerous studies have shown that the choice of measurement strategy (number and position of measurement points) when measuring form error on a coordinate-measuring machine (CMM) depends on the characteristics of the machining process which was used to machine the examined surface. The accuracy of form error assessment is the primary goal of verification procedures and accuracy is considered perfect only in the case of the ideal verification operator. Since the ideal verification operator in the “point-by-point” measuring mode is almost never used in practice, the aim of this study was to examine a relationship which had not been examined in earlier studies, namely how the machining process, surface roughness and a reduced number of points in the measurement strategy affect the accuracy of flatness error assessment. The research included four most common cutting processes applied to flat surfaces divided into nine different classes of roughness. In order to determine functional dependency between the observed input variables and the output, statistical regression models and neuro-fuzzy logic (artificial intelligence tool) were used. The analyses confirmed the significance of all three input parameters, with surface roughness being the most significant one. Both the statistical regression models and neuro-fuzzy models proved to be adequate, matching the experimental results. The use of these models makes it possible to determine flatness error measured on a CMM if input variables considered in the paper are known.

In this study, the thermomechanical behavior of multifunctional (photovoltaic/ aluminum core/ skin) sandwich structures is investigated numerically using the finite element simulation. Parametric s...

The static deflections of the cutting tool and thin-walled components are key sources contributing to the deviation of a machined surface from the design specifications during the end milling operation. The machined surface deviation is expressed using geometric tolerances such as flatness and cylindricity parameters specified as per the Geometric Dimensioning and Tolerancing (GD&T) standard (ASME Y14.5-2009 or ISO 1101). The present work investigates the effect of component configuration, engagement area, and workpiece curvature by comparing geometric errors during the end milling of zero and constant curvature thin-walled components. An integrated computational framework incorporating the mechanistic force model, finite element (FE)-based workpiece deflection model, cantilever beam formulation-based tool deflection model, and particle swarm optimization (PSO)-based geometric tolerance estimation model has been adopted from the previous work of authors. The effect of component geometry and cutter-workpiece transition are investigated on the geometric tolerance (flatness and cylindricity) by conducting computational studies and machining experiments under identical cutting conditions. The concept of “Equivalent Radial Depth of Cut (RDOC)” is introduced to derive component configurations with the identical cutter-workpiece transition area. The influence of workpiece curvature on the geometric tolerance parameters is also investigated in the paper. The outcomes are substantiated by performing computational studies and machining experiments. It is recognized that the relatively enhanced stiffness of the curved components offers an inherent machining advantage in comparison to straight components to the process planners.

In this paper, we study the problem of constructing flat inputs for multi-output dynamical systems, in particular, we address the issue of the minimal modification of the initial dynamical system (the measure of modification being the number of equations that have to be changed by adding flat inputs). We show that in the observable case, control vector fields that distort m equations only (where m is the number of measurements) can always be constructed (and this is the minimal possible number of equations that have to be modified by adding flat inputs), while in the unobservable case, the best that we can hope for is that m + 1 equations only are modified such that they involve flat inputs. We discuss when the original output is a flat output of minimal possible differential weight for the minimally modified control system (where by differential weight, we mean the minimal number of derivatives of components of a flat output needed to express all states and controls). We propose a solution for constructing flat inputs leading to a minimally modified control system consistent with the minimal differential weight and, moreover, for which the observable part is affected by the minimal possible number of controls (this last property being important in applications). We show that, in that case, at least 2m − 1 equations have to be affected by the flat inputs.

The current work demonstrates a novel multi-criteria decision-making (MCDM) technique to optimize the process parameters during the wire electric discharge machining of Inconel 718. A hybrid GRA-TOPSIS algorithm using entropy weights is developed to optimize wire electric discharge machining processes parameters for maximizing the cutting speed and simultaneously minimizing the surface roughness and flatness error. Experiments were conducted according to Taguchi L18 orthogonal array considering pulse on time, pulse off time, servo voltage, wire feed rate, and wire electrode types as the input parameters. The weights of each responses were calculated by entropy weights method. The different alternatives were ranked using the hybrid technique, and an optimum parameter combination is found that maximizes the process outcome. The analysis of variance (ANOVA) was performed to study the relative significance of process parameters on the performance index. The results were finally validated by performing confirmation tests. The entropy weighted GRA-TOPSIS method was observed to improve the overall process performance compared to conventional TOPSIS. Microstructural analysis, morphological studies, and EDS analysis were conducted to study the surface integrity of the machined surface under optimal parameter settings.

Response surface methodology was adopted to establish the mathematical model between the parameters (overlap ratio, Y-axis lift, and X-axis offset) and responses (non-fusion area, flatness ratio, and width of clad). The results indicated that the non-fusion area reduced at first and increased afterwards as overlap ratio decreased and Y-axis lift increased, while gradually reduced when overlap ratio increased and X-axis offset decreased. The flatness ratio gradually decreased by lowering the overlap ratio and raising the X-axis offset but gradually increased as Y-axis lift and X-axis offset lowered simultaneously. The clad width gradually reduced when overlap ratio or X-axis offset increased. A validation experiment was carried out with the target of minimizing the non-fusion area and maximizing the flatness ratio. The error rate for both responses was 7.7% and 3.6%, respectively. This article provides a theoretical basis for the forming control and prediction of double-layer and multi-track coatings by laser cladding.

Stable operations as resistive switching memory were demonstrated in amorphous TaOx (a-TaOx) thin films with very flat surfaces by conductive atomic force microscopy (c-AFM). The a-TaOx thin films fabricated on glass and Nb-doped SrTiO3 substrates by pulsed laser deposition showed high surface flatness with root-mean-square roughness of less than 0.2 nm. The c-AFM observations on the surfaces revealed that the resistive switching in a-TaOx causes almost no change in the topographic structures, and the significant structural deformation appears after the electrical breakdown by longer-range migration of the constituent ions. The possible mechanisms of the resistive switching phenomena were discussed based on the changes in the topographic structures and conduction states.

During the blasting excavation of deep underground caverns, the effects of the structural surface on crack propagation are usually considered in addition to the clamping effects of high in situ stress. Based on the notched borehole and timing sequence control (TSC) fracture blasting method, this paper studies the effects of different borehole shapes on the degree of damage of the surrounding rock and profile flatness of the rock anchor beams and the effects of different filled joint characteristics on the blasting crack propagation rules. The results show that the damage depth of the surrounding rocks by round hole smooth blasting is approximately twice that by notched hole smooth blasting, by which the profile formed is flatter. The notched primary borehole (PBH) remains a strong guidance for crack propagation in a rock mass with filled joints, while the stress concentration effects of the round target borehole (TBH) cannot fully guide the cracks until they fall within a certain distance between the PBH and TBH. It is favourable for cracks to propagate along the lines between boreholes with larger filled joint strengths and larger angles between boreholes.

A method of generating flat broadband chaos by using a semiconductor laser subject to asymmetric dual-path optical feedback is proposed and demonstrated experimentally. In the asymmetric dual-path optical feedback, one path is connected with an optical band-pass filter (OBPF) to form filtered path, and the other is a traditional optical feedback path named non-filtered path. Through the beating frequency effect between the filtered mode and the non-filtered chaos mode, a chaotic signal with the standard bandwidth of 36.1 GHz and the spectrum flatness of 5.8 dB is generated experimentally. Furthermore, the effects of filter frequency detuning, filter bandwidth and feedback strength on the bandwidth and flatness of chaos are investigated. The results show that the bandwidth enhancement and the flat spectrum can be achieved simultaneously in a wide range of operating parameters.

Electrically assisted (EA) forming is a promising process due to its advantages, such as reducing forming load and increasing formability. In this study, the EA micro-rolling process was used to form surface texture on T2 copper sheets. Compared with the traditional rolling process, the EA one significantly increases the feature height of texture, improves the flatness of the rolled strip, and relieves the surface cracks due to the action of the current. These might be attributed to the electron wind theory and microscale Joule heating effect. The effects of current for different grain sizes were not identical. High voltage was demanded to significantly increase feature height for coarse grains in comparison with that for fine grains. Moreover, the surface quality for fine grains was better than that for coarse grains. The high-quality surface texturing strip was manufactured by EA rolling process using annealed specimen. This study proves that forming quality for the surface texturing strip can be improved by adopting appropriate electrical parameters; EA micro-rolling process seems a prospective forming method with surface texture.

Titanium alloy and its thin-walled structures are widely used in the aerospace field. Aiming at the processing chatter and difficult-to-machine problem of titanium alloy thin-walled workpieces, rotary ultrasonic milling technology (RUM) is employed to restrict machining vibration in this paper. Firstly, the titanium alloy web with low stiffness is equivalent to a mass-spring-damping system with three degrees of freedom for describing its dynamic characteristics. Then, a novel stability analysis method is proposed for RUM thin-walled workpiece (RUM-tww) through defining an ultrasonic function angle. Furthermore, RUM-tww stability lobe diagrams (SLDs) are achieved based on the semi-discrete method (SDM). The simulation results show that the milling stability of titanium alloy webs is improved effectively under the effect of ultrasonic vibration energy. Compared with conventional milling thin-walled workpiece (CM-tww), the stability region of RUM-tww is increased by 80.32% within the spindle speed from 1000r/min to 5000r/min. Finally, milling experiments are carried out to verify the validity and rationality of SLDs via analyzing chatter marks, cutter marks and flatness on the machined surface. The experimental results are in good agreement with the theoretical prediction.

Despite Lawrence’s well-documented interest in ‘Alpine’ landscapes, characters in his Sons and Lovers (1913), The Lost Girl (1920) and Kangaroo (1923) repeatedly find themselves lingering in and on flat spaces. This essay attends to the dynamics of these flat spaces to complicate critical models which have emphasised sympathy, vitality and responsiveness in encounters with the Lawrentian Other. It finds that in Lawrence’s prose, physical flatness (of landscapes, faces and objects) offers a mode of habitation, and an occasion for a literary style, which encode a reserved self-presentation, a failure of mutuality and sympathy, and a refusal to participate in an economy of responsiveness between viewer and land, person and person. The first section examines the stakes of Lawrence’s peculiar insistence that the reader invests in characters and situations which will later vanish from the plot, refusing stable focal points in the novel’s narrative landscape. The second section then investigates the relationship between protagonist and flat landscape in Kangaroo to uncover a fundamental Lawrentian trope: openness which is nevertheless inaccessible, demanding a sustained attention that it cannot justify. The essay ends by arguing for the importance, in Lawrence, of relationship which may be at once intense and unresponsive, with one or more of the entities involved flatly complete in themselves.

This paper proposes a robust finite-time control scheme for the high-precision tracking problem of (FJRs) with various types of unpredictable disturbances. Specifically, based on a flatness dynamic model, a finite-time disturbance observer (FTDO) with only link-side position measurements is firstly developed to estimate the lumped unknown time-varying disturbance and unmeasurable states. Then, through the information of the states and disturbances provided by the FTDO, a robust output feedback controller is constructed, which can accomplish the tasks of disturbance suppression and trajectory tracking in finite time. Moreover, a rigorous stability analysis of the closed-loop system based on a finite-time bounded (FTB) function is conducted. Finally, the simulation results validate the feasibility and superiority of the proposed control scheme against other existing control results.

The advanced SmartCrown technology, one of the Variable Crown by Axial Shifting (VCAS) technologies, can significantly enhance the cross-directional control capability of strip mill, and alleviate or eliminate complex high-order flatness defects. In this paper, the mathematical modeling for SmartCrown system including roll contour design and roll-gap profile comparison based on shape pattern recognition is implemented. The results indicate that the unloaded roll-gap morphology formed by the SmartCrown roll is affected by the contour angle in terms of the spatial frequency distribution. When the contour angle is less than 30 degrees, the SmartCrown roll contour is basically coincident with the continuous variable crown (CVC) roll contour, and its capacity to control the quartic crown is almost zero. Meanwhile, a 3D elastic-plastic finite element analysis (FEA) model of 6-high SmartCrown mill for strip rolling is established. The accuracy and convergence of the numerical model are verified by rolling force data and targeted damping application. The relative errors of roll force between the simulated result and the theoretical value are less than 5.0% even with the limitation that the exit strip thickness should not be less than 1.50 mm. The validated model is applied to investigate the cross-directional characteristics of the SmartCrown-contoured intermediate roll shifting (IMR Shifting) in terms of inter-roll pressure, thickness profile and flatness control of rolled strips with different widths.

Trajectory following of autonomous vehicle is a challenging task because of the multiple constraints imposed on the plant. Therefore, Model Predictive Control (MPC) is becoming prevail in vehicle motion control as it can explicitly handle system constraints. However, MPC, grounded in real-time iterative optimization, entails a considerable computational burden for current electronic control units. To mitigate the MPC execution load, a popular strategy is to linearize the original (nonlinear) system around the current working point and then design a Linear Time-Varying MPC (LTVMPC). Nevertheless, the successive linearization introduces extra modeling errors, which may impair the control performance. Indeed, if the plant model satisfies the ‘differential flatness’ condition, it can be exactly linearized to the Brunovsky’s canonical form. In contrast to the LTV model, this newly appeared linear form reserves all the nonlinear features of the native plant model. Based on this equivalent linear system, a Flatness Model Predictive Controller (FMPC) can be formulated. FMPC on the one hand, improves the control performance over an LTVMPC because it avoids extra modeling errors from the local linearization. On the other hand, it entails a much lighter computational load versus a nonlinear MPC thanks to its linear nature. Real-time simulations conducted on a hardware-in-the-loop system indicate the advantages of the proposed FMPC in autonomous vehicle trajectory following.

In radiotherapy treatment planning process, quality assessment (QA) is indispensable for achieving accuracy and avoidance of treatment errors. In this perspective, present study focused on the Photon and Electron beams characterization of a medical linear accelerator (LINAC) to ascertain dosimetric QA in Absolute and Reference dosimetry. In this connection, the beam outputs were investigated in terms of Dmax and Dw,max (dose at depth dmax) in absolute dosimetry for Photon and Electron beams, respectively. In accordance with the measured Dmax and Dw,max parameters, Photon and Electron beam outputs were standardized to ensure standard output of 1 cGy/MU. In reference dosimetry, the parametric evaluation was performed for dosimetric QA in terms of percent depth dose (PDD), beam profile flatness and symmetry, output factors: Scp, Sc, Sp with varying field size (FS) ranging from 4´4 cm2 to 40´40 cm2 normalized at FS 10´10 cm2 for the 6 MV and 10 MV Photon beams. The measured PDDs at 10 cm depth (D10) were found to be 66.8% and 73.6% for 6 MV and 10 MV Photon beams, respectively, with significantly small deviation of 1% and 0.8% in comparison with an international PDD protocol of British Journal of Radiology-25 (BJR -25). In the case of Electron beams characterization, PDD was verified with 10´10 cm2 cone/applicator, beam profile flatness and symmetry were analyzed at the field sizes ranging from 6´6 cm2 to 25´25 cm2 normalized at 10´10 cm2 cone/applicator, and Electron cone ratios were investigated for a given cone/applicator relative to the 15´15 cm2 one for the 6, 9, 12, 15 MeV Electron energies. The PDDs of all the Electron beams revealed reasonable consistency with manufacturer’s estimations of 90%, 80%, and 50% PDDs at various depths of ionization.

The endless diamond wire is a special application of diamond wire cutting. The loss of wire machining accuracy will cause the fluctuate and unflat surface, which will cause drum shape error with large dimension in the middle of silicon ingot and small dimension on the head and tail of silicon ingot. In this paper, based on the phenomenon of drum shape error processed by a single wire, the factors affecting the machining accuracy, including the stiffness of wire web, tension, and fluctuation of wire were studied. The reason for the influence of machining accuracy during the endless diamond wire sawing process was mainly determined by the position of diamond wire. In view of the wire-lag effect of diamond wire, the definition and evaluation method of the stiffness of the endless diamond wire web were proposed. It was found that the formation of wire bow, especially the lateral wire bow induced by the lateral force, was the main reason causing the machining accuracy. In view of the evaluation of machining accuracy, the flatness evaluation method could be used instead of the current method of extreme deviation analysis, which could provide more comprehensive evaluation of the sawing accuracy.

Improving the production efficiency is the task with the increasing difficulty. Therefore, it is important to constantly expand the set of tools and perfect the methodology for improving the processes. Some of the losses associated with the negative technological events (breaks, drifting, etc.) are difficult to eliminate completely due to the complexity of making changes to the basic technology. But if you know in advance that the event will occur, you can significantly reduce the probability and consequences, thereby significantly improve the efficiency of the production process. Therefore, it is important to develop and introduce the applied approaches to forecasting the negative technological events in the production processes. This paper presents the method of the forecast-event statistical analysis of the cause-and-effect relationships. The technique was tested on the events of strip’s breakage during rolling at the cold rolling mill 1400 and strip’s drifting in the input storage of the continuous etching unit (CEU). Based on the presented methodology, the specialized digital service was developed and introduced in the production processes of the dynamo steels shop.

Microstrip ultra-wide band (UWB) delay lines consisting of a novel periodically loaded transmission line (PLTL) are presented, along with discontinuous structured guard lines (DSGLs). The distinctive advantage of the proposed approach is that the far-end crosstalk (FEXT) between the adjacent lines is effectively suppressed comparing to the conventional circuits. Afterward, the crosstalk of connected adjacent lines is effectively suppressed by modifying the DSGLs, since the current distributions are different from the separated adjacent lines. Subsequently, the strong reflection points are eliminated, which seriously deteriorate the performances in amplitude and group delay. Moreover, the serpentine delay line (SDL) and serpentine meandered delay line (SMDL) are studied, respectively, using the conventional microstrip (CMS) and the proposed PLTL with DSGLs. As a result, the SMDL pattern is also demonstrated useful to suppress the near-end crosstalk (NEXT) between the adjacent second-level curves, which in turn reduce the fluctuations in the group delay. In addition, the PLTL SMDL with DSGLs consequently have the superiority of suppressing the NEXT and FEXT simultaneously. Further simulations and measurements indicate that the performances of the PLTL SMDL with DSGLs lines are superior to the conventional method in a UWB range of dc to 25 GHz, including amplitude and group delay flatness, along with high time delay efficiency due to the slow wave property.

The problems of the strip flatness defects are always severe in the tandem cold rolling process. It is of great significance to predict flatness for flatness control according to the process conditions of products. A prediction model based on convolutional neural network (CNN) was developed in this paper, and it can accurately predict strip flatness under various conditions. According to the distribution characteristics of industrial data collected in the rolling process, the isolated forest algorithm was used to eliminate outliers. Considering the special requirements of CNN on the dimension of input features, the data folding method was used to process the input features. Additionally, since strip flatness data is a vector rather than a scalar, and the length of this vector varies with strip width, which decreases the network's training accuracy. To deal with the problems, the loss function was modified. Taking the Inception module as the basic network structure and inspired by Wide & Deep learning, a strip flatness prediction model with high accuracy was developed. The optimal architecture and parameters of our network were determined through a lot of experimental explorations. The performances of BPNN (Back Propagation Neural Network), DNN (Deep Neural Network), and the proposed model were compared by mean square error (MSE) and coefficient of determination (R2). The result indicates that the proposed model has the highest prediction accuracy and better adaptability. It has the lowest MSE, 0.9891, and the highest R2, 0.9555. Finally, the fitting coefficients of Legendre polynomials were used to further prove the excellent prediction performance of the proposed model for strip flatness. Compared with other prediction models, it can obtain the lowest prediction error for the first quadratic and quartic components of strip flatness and it can be well-applied to tandem cold rolling production.

Purpose Recently, high-precision radiotherapy systems have been developed by integrating computerized tomography or magnetic resonance imaging to enhance the precision of radiotherapy. For integration with additional imaging systems in a limited space, miniaturization and weight reduction of the linear accelerator (linac) system have become important. The aim of this work is to develop a compact medical linac based on 9.3 GHz X-band RF technology instead of the S-band RF technology typically used in the radiotherapy field. Methods The accelerating tube was designed by 3D finite-difference time-domain and particle-in-cell simulations because the frequency variation resulting from the structural parameters and processing errors is relatively sensitive to the operating performance of the X-band linac. Through the 3D simulation of the electric field distribution and beam dynamics process, we designed an accelerating tube to efficiently accelerate the electron beam and used a magnetron as the RF source to miniaturize the entire linac. In addition, a side-coupled structure was adopted to design a compact linac to reduce the RF power loss. To verify the performance of the linac, we developed a beam diagnostic system to analyze the electron beam characteristics and a quality assurance (QA) experimental environment including 3D lateral water phantoms to analyze the primary performance parameters (energy, dose rate, flatness, symmetry, and penumbra) The QA process was based on the standard protocols AAPM TG-51, 106, 142 and IAEA TRS-398. Results The X-band linac has high shunt impedance and electric field strength. Therefore, even though the length of the accelerating tube is 37 cm, the linac could accelerate an electron beam to more than 6 MeV and produce a beam current of more than 90 mA. The transmission ratio is measured to be approximately 30% ~ 40% when the electron gun operates in the constant emission region. The percent depth dose ratio at the measured depths of 10 and 20 cm was approximately 0.572, so we verified that the photon beam energy was matched to approximately 6 MV. The maximum dose rate was measured as 820 cGy/min when the source-to-skin distance was 80 cm. The symmetry was smaller than the QA standard and the flatness had a higher than standard value due to the flattening filter-free beam characteristics. In the case of the penumbra, it was not sufficiently steep compared to commercial equipment, but it could be compensated by improving additional devices such as multileaf collimator and jaw. Conclusions A 9.3 GHz X-band medical linac was developed for high-precision radiotherapy. Since a more precise design and machining process are required for X-band RF technology, this linac was developed by performing a 3D simulation and ultraprecision machining. The X-band linac has a short length and a compact volume, but it can generate a validated therapeutic beam. Therefore, it has more flexibility to be coupled with imaging systems such as CT or MRI and can reduce the bore size of the gantry. In addition, the weight reduction can improve the mechanical stiffness of the unit and reduce the mechanical load.

The flexible transmission system benchmark was proposed to evaluate the robustness of digital controllers. The multi-model uncertainty coupled with the non-minimum phase (NMP) zero is a challenging issue for the controller design. Therefore, a flatness-based discrete active disturbance rejection control (ADRC) scheme is formulated in this work, constituting an extended state observer, a linear feedback law and a set-point filter. The NMP zero issue is overcome by the flatness-based transformation, and the multi-model uncertainty is compensated by the discrete ADRC. The performances of set-point tracking and disturbance rejection are analyzed theoretically. Furthermore, the proposed control scheme is simulated and discussed in the time domain and the frequency domain.

Optimization of a flatness error inspection activity on coordinate measuring machine (CMM) is a very crucial problem which demands minimization of a probe path for productive inspection. In the present work, the approach is explained to minimize the total probe travelling length and hence, the time of flatness inspection. Three sampling methods with eight sample sizes have been considered for this work. The ant colony optimization (ACO) algorithm based on travelling salesman problem (TSP) approach was developed in MATLAB environment to find the shortest probe paths. It was verified that the probe path depends on the sampling method used to measure the flatness. The sampling method giving the shortest probe path was selected as the best-suited method for a particular sample size. The results obtained by analyzing an illustrative example shows that the proposed approach is both effective and optimum.