Linear Cuts Research Articles

An experimental study of ultrasonic-knife cutting for a woven carbon fiber preform by an industrial robot

This study investigates the effect of the cutting process parameters on the cutting forces and the quality parameters of a woven carbon fiber preform during robotic ultrasonic-knife cutting. An ultrasonic cutting device, with a power of 1200 W, a frequency of 24 kHz, and an amplitude of 60 µm, mounted on the end effector of a six-axis degree of freedom industrial robot to make linear cuts. A three-level factorial experimental design was used to examine the effect of the feed rate (1 m/min to 5 m/min) and the knife’s attack angle (45° to 75°) on the cutting forces, the dimensional accuracy of the machined preform coupons, and the damage on the machined preform edges. The cutting force analysis results show that the increasing feed rate resulted in increasing feed force and thrust force. However, the increase of the attack angle increases the feed force but decreases the thrust force. The average width and damage of the ultrasonic knife cut preform coupons are highly related to the process conditions. The combination of the low feed rate, 1 m/min, and the low attack angle, 45°, resulted in dimensional errors ranging from 253 μm to 365 μm oversized from the programmed 15.0 mm width with no damage. When the feed became 3 m/min and 5 m/min at the attack angle of 75°, the preform coupons’ dimensional accuracy and damage formation worsened. In these conditions, the ultrasonic knife attached to the industrial robot arm could not cut the preform plate effectively, so the tows on the preform were unevenly cut or dislodged.

Repair of concrete-filled FRP tube columns with damaged tubes

The effectiveness of repairing damaged Concrete-Filled Fiber Reinforced Polymer (FRP) Tube (CFFT) axial members is studied. The damage was introduced in the form of linear cuts through the full tube thickness. The effectiveness of adhesively-bonded FRP patches that may or may not include mechanical fasteners is investigated. The study varied the cut angle, the bond length of the patch, the fiber type being glass or carbon, the number and pattern of mechanical fasteners, the patch extension beyond cut tips, and compared wet layup glass-FRP (GFRP) patches to prefabricated GFRP shells cut from a similar tube. It was shown that the vertical cut reduced axial compressive strength significantly. As the bond length of the GFRP repair patch increased the axial strength recovery increased, but not fully. When the ends of the GFRP patch were overlapped, a full strength recovery was achieved. The prefabricated GFRP shell patch (cut from similar tube) provided the highest strength recovery, compared to FRP wet layup. Adding mechanical fasteners enhanced strength recovery further, to a certain point. A simple empirical design model is proposed and a design example is presented.

The cylindrical surface characteristics of AA7075 aluminum alloy machined by abrasive waterjet with circular cuts

Abrasive waterjet (AWJ) is an untraditional machining tool that has been used in numerous applications. This study aims at clarifying the cylindrical surface characteristics machined by AWJ under different radii (Rc) of circular cuts. AA7075 aluminum alloy was used as the specimen, and the morphologies and roughness of the cut surfaces were used to evaluate the cutting quality. The main processing parameters include the working pressure, the tangential velocity, and the standoff distance. Additionally, a linear cut under the same parameters was conducted for comparison. Results show that linear and circular cuts share the same material removal mechanism, but the quality of cylindrical surface is worse than that of the plane one. Roughness in all the three regions gradually increases with the decrease of Rc and varies the most in the rough zone. The roughness at the bottom of the workpiece with Rc = 2.5 mm is more than twice that of a linear cut. The micro-morphologies of the surfaces are distinctly different under various Rc, and the jet lag effect is more obvious at smaller Rc. The analysis result of variance (ANOVA) showed that the ranking of prominent parameters affecting the cylindrical surface quality are the tangential velocity, the circular cut radius, the working pressure, and the standoff distance. To achieve a high cutting quality when using AWJ for circular cuts, it is recommended to prioritize optimizing the tangential velocity. Furthermore, the regression model of input parameters and roughness was developed, whose mean error and correlation coefficient R2 were 5.51% and 0.9489, respectively.

Linear cuts in Boolean networks

Boolean networks are popular tools for the exploration of qualitative dynamical properties of biological systems. Several dynamical interpretations have been proposed based on the same logical structure that captures the interactions between Boolean components. They reproduce, in different degrees, the behaviours emerging in more quantitative models. In particular, regulatory conflicts can prevent the standard asynchronous dynamics from reproducing some trajectories that might be expected upon inspection of more detailed models. We introduce and study the class of networks with linear cuts, where linear components—intermediates with a single regulator and a single target—eliminate the aforementioned regulatory conflicts. The interaction graph of a Boolean network admits a linear cut when a linear component occurs in each cycle and in each path from components with multiple targets to components with multiple regulators. Under this structural condition the attractors are in one-to-one correspondence with the minimal trap spaces, and the reachability of attractors can also be easily characterized. Linear cuts provide the base for a new interpretation of the Boolean semantics that captures all behaviours of multi-valued refinements with regulatory thresholds that are uniquely defined for each interaction, and contribute a new approach for the investigation of behaviour of logical models.

Corneal Stromal Fragmentation Instead of Cataract Fragmentation During Femtosecond Laser–Assisted Cataract Surgery (FLACS): Case Report

Purpose: To report a case of a misdirected laser beam delivery on the cornea instead of cataract fragmentation during femtosecond laser–assisted cataract surgery (FLACS). Methods: An 88-year-old man underwent FLACS. Intraoperatively, inadvertent movement led to loss of suction wherein the supposed laser beam cataract fragmentation was shifted on the corneal side. One day postoperatively, there was a formed chamber and clear central cornea with no signs of edema in the fragmented part. Anterior segment optical coherence tomography showed various cuts in the endothelium extending to the anterior one-third of the cornea. Slit-lamp photographs documented the extent of circular and linear cuts in the paracentral and limbal 3-o'clock position location in the cornea. Conclusions: It is important that cataract surgeons be aware of this potential for corneal injury so that proper intraoperative management can be instituted suitably. [ Journal of Refractive Surgery Case Reports . 2023;3(2):e19–e23.]

Most common movements preceding goal scoring situations in female professional soccer

ABSTRACT This study aimed to assess movements occurring during goal scoring situations in a female professional league. Data from all the goals on the Women’s Super League 2018/2019 were collected through time-motion analysis using a modified version of the Bloomfield Movement Classification with differences analysed through chi-square. Analysis was performed on players (assistant, scorer [attackers], defender of assistant and defender of scorer [defenders]), movements, intensities and directions. Linear advancing motion (walking, jogging, running or sprint) (total percentage [95% CI] 37% attackers and 32.7% defenders) was the most common action preceding a goal, followed by deceleration (21.5% attackers; 18.4% defenders) and turn (19.2% attackers; 17.6% defenders). Other movements involved but with lower percentages were change in angle run (cut and arc run), ball blocking, lateral advancing motion (crossover and shuffle) and jumps. Players displayed similar tendencies but presented variations based on the role, with attackers performing more linear actions, subtle turns and cuts and defenders more ball blocking actions, lateral movements and high intensity linear actions and decelerations. Assistant performed the less percentage of involvements with at least 1 high intensity action (67.4%), scorer and defender of assistant showed similar values (86.3% and 87.1%), while defender of scorer had the highest percentage (97.3%). This study shows the importance of linear actions with other movements also being of high significance but with differentiated characteristics based on the role. This study could help practitioners design drills for the enhancement of physical capabilities related to movements occurring in goal scoring situations.

An Enhanced Second-Order Cone Programming-Based Evaluation Method on Maximum Hosting Capacity of Solar Energy in Distribution Systems with Integrated Energy

In order to adjust to the change of the large-scale deployment of photovoltaic (PV) power generation and fully exploit the potentialities of an integrated energy distribution system (IEDS) in solar energy accommodation, an evaluation method on maximum hosting capacity of solar energy in IEDS based on convex relaxation optimization algorithm is proposed in this paper. Firstly, an evaluation model of maximum hosting capacity of solar energy for IEDS considering the electrical-thermal comprehensive utilization of solar energy is proposed, in which the maximization of PV capacity and solar collector (SC) capacity are fully considered. Secondly, IEDS’s potential in electricity, heat, and gas energy coordinated optimization is fully exploited to enhance the hosting capacity of solar energy in which the electric distribution network, heating network, and natural gas network constraints are fully modeled. Then, an enhanced second-order cone programming (SOCP)-based method is employed to solve the proposed maximum hosting capacity model. Through SOCP relaxation and linearization, the original nonconvex nonlinear programming model is converted into the mixed-integer second-order cone programming model. Meanwhile, to ensure the exactness of SOCP relaxation and improve the computation efficiency, increasingly tight linear cuts of distribution system and natural gas system are added to the SOCP relaxation. Finally, an example is given to verify the effectiveness of the proposed method. The analysis results show that the maximum hosting capacity of solar energy can be improved significantly by realizing the coordination of an integrated multi-energy system and the optimal utilization of electricity, heat, and gas energy. By applying SOCP relaxation, linearization, and adding increasingly tight linear cuts of distribution system and natural gas system to the SOCP relaxation, the proposed model can be solved accurately and efficiently.

Value function gradient learning for large-scale multistage stochastic programming problems

A stagewise decomposition algorithm called “value function gradient learning” (VFGL) is proposed for large-scale multistage stochastic convex programs. VFGL finds the parameter values that best fit the gradient of the value function within a given parametric family. Widely used decomposition algorithms for multistage stochastic programming, such as stochastic dual dynamic programming (SDDP), approximate the value function by adding linear subgradient cuts at each iteration. Although this approach has been successful for linear problems, nonlinear problems may suffer from the increasing size of each subproblem as the iteration proceeds. On the other hand, VFGL has a fixed number of parameters; thus, the size of the subproblems remains constant throughout the iteration. Furthermore, VFGL can learn the parameters by means of stochastic gradient descent, which means that it can be easil0y parallelized and does not require a scenario tree approximation of the underlying uncertainties. VFGL was compared with a deterministic equivalent formulation of the multistage stochastic programming problem and SDDP approaches for three illustrative examples: production planning, hydrothermal generation, and the lifetime financial planning problem. Numerical examples show that VFGL generates high-quality solutions and is computationally efficient.

Experimental investigation of axial strength of damaged concrete-filled FRP tubes

Axial compressive strength of circular concrete-filled fiber-reinforced polymer (FRP) tubes (CFFTs) benefits greatly from a significant concrete confinement by the tube. Accidentally or deliberately induced damage to the tube would undermine the CFFT strength. In this study 33 CFFT short columns of 144–168 mm (5.67–6.61 in.) outer diameter (D) and 420–460 mm (16.53–18.11 in) height (H) (i.e. H/D = 2.74–2.92) were tested under concentric loading to failure. Tube damage was artificially induced in the form of through-thickness linear cuts at mid-height. The cut length (x) and orientation (θ) with respect to the longitudinal axis were varied. Two types of GFRP tubes were studied, namely a nominal [±55o] angle-ply tube with diameter-to-thickness ratio (D/t) = 35 and a [86°/−12°] near cross-ply with D/t = 48, to investigate two commonly available but distinctly different tubes. The effect of cuts in the two tubes studied was very similar. A nonlinear descending trend can be seen in axial strength ratio (Pn/Pno), relative to the intact CFFT strength (Pno), with x/H ratio. Initially, a rapid decent from 1.0 to 0.6 occurs in (Pn/Pno) (i.e. reduction in confinement effectiveness fcc’/fc’ from 2.0 to 1.2), as x/H ratio increases from zero to 20 % (i.e.x/D = zero to 60 %) followed by a lower rate decline to 0.52 (fcc’/fc’=1.0) at x/H = 60 % (x/D = 175 %). Vertical and diagonal cuts significantly affected strength, whereas horizontal cuts had insignificant effect on strength. Strain measurements revealed stress concentrations at the tip of the cut, where crack propagations occurred in the tube. A design-oriented simple model is presented to capture the strength reduction of the damaged CFFT column.

Erysipelas in a stranded common bottlenose dolphin: first report in a South American odontocete.

Erysipelas is a zoonotic disease caused by Erysipelothrix rhusiopathiae. In cetaceans, this disease has two main clinical forms: a cutaneous one, grossly characterized by rhomboid lesions, and a septicemic and often fatal form. Erysipelas is considered an important cause of morbidity and mortality in captive cetaceans; however, information in free-ranging cetaceans is limited. An adult common bottlenose dolphin (Tursiops truncatus) was found dead and in advanced autolysis in Paraíba state, northeastern Brazil, on July 19th, 2020. Upon gross examination, 80% of the body surface presented disseminated rhomboid cutaneous lesions ranging from 4 to 6cm-width, characterized by well-defined edges and occasional ulceration, consistent with erysipelas. Additionally, anthropic-made postmortem linear cuts and partial mechanical removal of the flank musculature were noted. Skin samples were collected for histopathologic and molecular analyses. Microscopically, it was possible to observe multifocal dermatitis with vasculitis. Erysipelothrix sp. was detected by PCR. Despite previous reports of human consumption of cetacean meat in northeastern Brazil, the observed marks and advanced carcass autolysis suggested that the animal was most likely used as bait for fishing instead of human intake. This case highlights the value of postmortem examination and PCR even in poorly preserved cadavers and contributes to the understanding of the epidemiology of cutaneous erysipelas in free-ranging cetaceans (first report in an odontocete from the Southern Hemisphere). Due to the zoonotic potential of certain Erysipelothrix species (i.e., E. rhusiopathiae), active public health policies are required to inform field professionals and the general public about the health threats associated with marine mammal manipulation and consumption.

Tight Neural Network Verification via Semidefinite Relaxations and Linear Reformulations

We present a novel semidefinite programming (SDP) relaxation that enables tight and efficient verification of neural networks. The tightness is achieved by combining SDP relaxations with valid linear cuts, constructed by using the reformulation-linearisation technique (RLT). The computational efficiency results from a layerwise SDP formulation and an iterative algorithm for incrementally adding RLT-generated linear cuts to the verification formulation. The layer RLT-SDP relaxation here presented is shown to produce the tightest SDP relaxation for ReLU neural networks available in the literature. We report experimental results based on MNIST neural networks showing that the method outperforms the state-of-the-art methods while maintaining acceptable computational overheads. For networks of approximately 10k nodes (1k, respectively), the proposed method achieved an improvement in the ratio of certified robustness cases from 0% to 82% (from 35% to 70%, respectively).

Fiber-laser platform for precision brain surgery.

Minimally invasive neurological surgeries are increasingly being sought after for treatment in neurological pathologies and oncology. A critical limitation in these minimally invasive procedures is lack of specialized tools that allow for space-time controlled delivery of sufficient energy for coagulation and cutting of tissue. Advent of fiber-lasers provide high average power with improved beam quality (lower M2), biocompatible silica fiber delivery, reduced cost of manufacturing, and radiant output stability over long operating periods. Despite these advancements, no fiber-laser based surgical tools are currently available for tissue resection in vivo. Here we demonstrate a first to our knowledge, fiber-laser platform for performing precise brain surgery in a murine brain model. In this study, our primary aims were to first demonstrate efficacy of fiber-lasers in performing precise blood-less surgery in a murine brain with limited non-specific thermal damage. Second, fiber-lasers' ability to deliver radiant energy through biocompatible silica fibers was explored in a murine brain model for blood less resection. A bench-top optical coherence tomography (OCT) guided fiber-laser platform was constructed with a stereotactic stage for performing precision brain surgery. A pulsed quasi-continuous wave ytterbium (Yb) fiber-laser (1.07 µm) was used to perform vascular specific coagulation while a pulsed nanosecond thulium fiber-laser (1.94 µm) was used to conduct bloodless cutting, all under the guidance of a swept-source OCT system centered at 1310 +/- 70 nm. Specialty linear and circular cuts were made in an in vivo murine brain for bloodless brain tissue resection. The two fiber-lasers were combined into a single biocompatible silica fiber to conduct brain surgery resection under the bench-top OCT system's imaging microscope. Vascular specific coagulation was demonstrated in all five mice studied. Bloodless linear cuts and point cuts were demonstrated in vivo. Histologically, thermal injury was measured to be less than 100 µm while a removal rate of close to 5 mm3/s was achieved with an average Tm fiber-laser power of 15 W. To the authors' knowledge, this is the first demonstration of a fiber-laser platform for conducting in vivo bloodless brain tissue resection with a pulsed thulium (Tm) fiber-laser and a quasi-continuous wave (QCW) Yb fiber-laser. The demonstrated fiber-laser platform, if successfully configured for use in the operating room (OR), can provide surgeons a tool for rapid removal of tissue while making surgical resections of brain regions more precise, and can be basis for a flexible cutting tool capable of reaching hard-to-operate regions.

Linear advancing actions followed by deceleration and turn are the most common movements preceding goals in male professional soccer

ABSTRACT Data were collected through time-motion analysis from soccer players participating in the English Premier League using a modified version of the Bloomfield Movement Classification with differences analysed through chi-square. The most common individual movement preceding a goal was a linear advancing motion (32.4 ± 1%), followed by deceleration (20.2 ± 0.9%) and turn (19.8 ± 0.9%). Actions also involved were change in angle run (cut and arc run), ball blocking, lateral advancing motion (crossover and shuffle) and jumps. Although players followed similar trends, there were dissimilarities based on the role, with attackers (assistant and scorer) performing more linear actions, subtle turns and cuts and defenders (defender of assistant and defender of scorer) more ball blockings, lateral movements and arc runs. In 82.9 ± 1.5% of player involvements, there was at least one high intensity (HI) movement with assistant showing the lowest percentage and defender of scorer the highest. This study shows the multidirectional nature and context specificity of soccer during goal scoring situations, with linear actions such as sprints being the most common movements, followed by decelerations and turns. Moreover, it highlights the recurrent application of these at HI, and so, training strategies should prioritize the development of player’s explosiveness.

A cutting plane method and a parallel algorithm for packing rectangles in a circular container

We study a two-dimensional packing problem where rectangular items are placed into a circular container to maximize either the number or the total area of items packed. We adapt a mixed-integer linear programming model from the case with a rectangular container and design a cutting plane method to solve this problem by adding linear cuts to forbid items from being placed outside the circle. We show that this linear model allows us to prove optimality for instances larger than those solved using the state-of-the-art non-linear model for the same problem. We also propose a simple parallel algorithm that efficiently enumerates all non-dominated subsets of items and verifies whether pertinent subsets fit into the container using an adapted version of our linear model. Computational experiments using large benchmark instances attest that this enumerative algorithm generally provides better solutions than the best heuristics from the literature when maximizing the number of items packed. Instances with up to 30 items are now solved to optimality, against the eight-item instance previously solved.

A journey from the octonionic ℙ² to a fake ℙ²

We discover a family of surfaces of general type with K 2 = 3 K^2=3 and p g = q = 0 p_g=q=0 as free C 13 C_{13} quotients of special linear cuts of the octonionic projective plane O P 2 \mathbb O \mathbb P^2 . A special member of the family has 3 3 singularities of type A 2 A_2 , and is a quotient of a fake projective plane. We use the techniques of earlier work of Borisov and Fatighenti to define this fake projective plane by explicit equations in its bicanonical embedding.

Resilient Microgrid Scheduling With Secure Frequency and Voltage Transient Response

The resilient operation of microgrids (MGs) relies strongly on their ability to operate in islanded mode, autonomously from the bulk grid, whilst adhering to secure operation requirements. Catastrophic events in the transmission grid can lead to abrupt MG islanding accommodated by large frequency and voltage excursions due to power imbalances within the MG. It is vital that MG scheduling algorithms incorporate both static and transient security metrics to ensure a secure transition during islanding, immunised against the transient phenomena. In this paper, we incorporate both frequency- and voltage-related security constraints in a MG operational planning problem to ensure robust operation against abrupt islanding events. We employ an iterative dynamic optimization approach, based on the sensitivities of active and reactive power injections to the system security metrics, to incorporate the transient and static security constraints in the planning problem. Due to their non-linear and intractable nature, the transient security constraints are reformulated as linear sequential resilience cuts resulting in a computationally efficient problem. The performance of the algorithm is shown on a 30-bus, 20 kV, distribution network, subject to a 24-hour variation in load and renewable generation.

Generalized Benders Decomposition Method to Solve Big Mixed-Integer Nonlinear Optimization Problems with Convex Objective and Constraints Functions

The paper presents the Generalized Benders Decomposition (GBD) method, which is now one of the basic approaches to solve big mixed-integer nonlinear optimization problems. It concentrates on the basic formulation with convex objectives and constraints functions. Apart from the classical projection and representation theorems, a unified formulation of the master problem with nonlinear and linear cuts will be given. For the latter case the most effective and, at the same time, easy to implement computational algorithms will be pointed out.

Cutting force analysis of oak for the development of a cutting force model

ABSTRACT The cutting process of oak (Quercus robur) was investigated by means of a novel testing approach. A unique testing device, enabling nearly linear stand-alone cuts, was used. The specimens climatized to 6 different moisture content levels were machined within cutting velocities ranging from 5 to 80 m·s−1, at 5 cutting fibre angles from along to across the grain, and at different uncut chip thicknesses of up to 0.5 mm. The precise quartz sensor utilized for observing cutting forces enabled insights into the cutting mechanism involved while wood disintegration. Cutting velocity evolved as a key process parameter strongly influencing cutting force. Evaluation of uncut chip thickness showed a regression that was strongly influenced by particular force components. The friction force generated by “ploughing” the surface was relevant when cutting thin chips. In contrast, the part of force introduced by chip formation affected the process weightily in the case of cutting a thick chip. When cutting parallel to the grain lower forces were observed than cutting perpendicular to grain orientation. Obtained data supported the mathematical force prediction model establishment involving several parameters (e.g. cutting velocity, cutting fibre angle, uncut chip thickness, and moisture content).

Short-Term Voltage Stability-Constrained Unit Commitment for Receiving-End Grid With Multi-Infeed HVDCs

With the increasing development of AC/DC hybrid power systems, local synchronous generators in receiving-end grids are being replaced by high-voltage direct current (HVDC) power. The risk of short-term voltage instability exists because of the decline in dynamic reactive power resources from generators, the presence of high-proportioned induction motors and the demand for vast reactive power of HVDC under AC faults. In this situation, unit commitment (UC) should take short-term voltage stability into account. Hence, crucial generators can be retained to provide sufficient dynamic reactive power. This paper proposes a UC model incorporating short-term voltage stability constraints (SVSCUC). Furthermore, a decomposition-based solution approach is presented, which involves an alternate iterative solving of UC and differential-algebraic equations (DAEs). Time-domain simulation (TDS) is utilized to quantify the stability with an indicator. Linear stable cuts are formulated through trajectory sensitivity analysis and added into the UC. The UC is decomposed into a master problem based on mixed-integer linear programming (MILP) and subproblems. The SVSCUC is illustrated using benchmark systems and a real system in eastern China. The results show the effectiveness and efficiency of the proposed methods. Violations of short-term voltage stability for credible contingencies are eliminated under the commitment of SVSCUC.

Prediction of laser drilled hole geometries from linear cutting operation by way of artificial neural networks

This paper deals on artificial intelligence (AI) application for the estimation of kerf geometry and hole diameters for laser micro-cutting and laser micro-drilling operations. To this aim laser cutting and laser drilling operation were performed on NIMONIC 263 superalloy sheet, 0.38 mm in nominal thickness, by way of a 100 W fibre laser in modulated wave regime. Linear cuts and holes (by trepanning) were performed fixing the average power at 80 W and changing the pulse duration, the cutting speed, the focus depth and the laser path (the latter only for the drilling operations). Kerf width and the holed diameter, at the upper and downsides, were measured by digital microscopy. Different artificial neural networks (ANNs) were developed and tested to predict the kerf widths and the diameters (at the upper and downside). Two ANNs were addressed to the linear cutting process modelling; also, two further ANNs were developed for micro-drilling on the base of the linear cutting process features. The networks were trained with a subset of data containing the process conditions and the kerf/hole geometry. The ANN test was performed with the remaining data. The results show that ANNs can model the cut and hole geometry as a function of the process parameters. Moreover, the ANN trained with kerf geometry is more efficient. Therefore, a functional correlation between the kerf geometries achievable in the linear cutting process and micro-drilling was assessed.