Front Angle Research Articles

Horizontal/vertical motion and wedge geometry of the Sinú Fold Belt, South-Caribbean accretionary prism, NW Colombia: Implications for a morphostructural zoning

The Sinú Fold Belt, located in the southwestern part of the South Caribbean Deformed Belt, northwest Colombia, has been interpreted as the outer portion of an accretionary wedge resulting from the subduction of the Caribbean Plate under the South American Plate. Several geological sections, across and along the offshore portion of the Sinú Fold Belt, have been constructed through geological interpretation of 2D seismic sections constrained by a few exploration wells. Their analysis has allowed us to quantify the amount of horizontal motion (shortening responsible for the structures and basal detachment displacement) and vertical motion (tectonic subsidence/uplift and wedge vertical thickening) undergone by the belt over time; unravel its recent evolution consisting of almost no active structures in the south edge and a large amount of active structures northwards; quantify its pore pressure, coefficient of friction and strength using its wedge geometry consisting of high taper angles in the lower continental slope near the deformation front and lower taper angles in the upper continental slope away from it; and understand the aseismic and trench-lacking character of the belt. These observations have been crucial to identify the main features of the morphostructural zones across the belt (Colombian Basin, lower continental slope, upper continental slope and continental shelf) and establish a new along-strike zoning (north region influenced by the Magdalena Fan/Canoas Oblique Ramp, Sinú Fold Belt s.s., and south salient influenced by the Uramita Fault).

Development of an Android Grocery Checklist Application

Purpose – Grocery shopping is a regular affair in most people’s lives. With a variety of necessities such as food, toiletries, and the like being purchased whenever people go grocery shopping, shopping lists are usually made to help buyers remember and organize what they need to purchase. This research introduces a mobile application that allows users to create and manage shopping lists for grocery shopping, as well as allowing them to mark what they’ve purchased by scanning the barcode of the purchased product. It also allows users to track their stocks of purchased items as well as view their expenditures and what kinds of products take up most of their expenses. 4 Method – The barcode data used is a selection of 100 unique products taken by the researchers, and the application uses SQLite to store both checklist data and the barcodes. Result – Based on the results, all the test cases were able to pass the expected result which means that the main features of the application were able to run smoothly. There are times that the barcode scanner was not able to read the barcode properly. This scenario is seen especially when the camera is at the right angle when scanning the product’s barcode. The front angle the scanner's success rate was 99%, but from the right, left, top, and bottom, the success rate was 84%, 93%, 97%, and 94%, respectively. Although the success rate is still high, it is still preferable to scan barcodes from the front. Overall, it has an average success rate of 93.8% on all the angles. The stocks screen was able to change the number of stocks it recorded when adding and removing items from each category of item. The system was also able to display if an item was running out of stock and if it already is out of stock. It was found that the stock system's functions were working properly. The maps function was tested via changing the current area and testing if it can pin locations based on the set condition. All in all, 5 locations were tested, with each location successfully having pins on multiple locations. The charts were able to display different expenditures for different weeks and months. Conclusion – The research has resulted in the creation of an app that can help users in managing their grocery shopping. It can create and edit checklists, access, and manage checklists from the local storage, as well as add and remove items from the created checklists. The system can scan barcodes of items that are in the internal database and automatically record them in both item stocks and expenditure statistics. These can help the user in managing their shopping, as well as showing them what they need to buy and how much they are spending on certain kinds of items. The app was built at a minimum Android SDK of 16. This left the researchers with difficulties in implementing some functions due to much simpler ways of implementation added in later SDKs being unavailable, but this also meant that the app was compatible with a lot more devices. Recommendation – Organize the list of products into categories to make searching for items faster. Add an option for statistics to break down expenditures even further to individual items instead of just categories. It is also recommended to integrate the product database with different grocery stores to be more accurate in terms of getting the total price of a checklist. Practical Implication – Developing of an Android grocery checklist application for the beneficiaries is useful because it can be use and can able to track the grocery or stock the user has. Also, the application as the capability to pin the location of the available grocery store with in the area.

A Novel 3D Light Assisted Drawing (3D-LAD) Method to Aid Intraoperative Reproduction of Osteotomy Lines Surrounding a Bone Tumor During Wide Resection: An Experimental Study.

IntroductionComputer navigation and customized 3D-printed jigs improve accuracy during bone tumor resection, but such technologies can be bulky, costly, and require intraoperative radiation, or long lead time to be ready in OR.MethodsWe developed a method utilizing a compact, inexpensive, non-X-ray based 3D surface light scanner to provide a visual aid that helps surgeons accurately draw osteotomy lines on the surface of exposed bone to reproduce a well-defined preoperative bone resection plan. We tested the accuracy of the method on 18 sawbones using a distal femur hemimetaphyseal resection model and compared it with a traditional, freehand method.ResultsThe method significantly reduces the positional error from 2.53 (±1.13) mm to 1.04 (±0.43) mm (p<0.001), and angular error of the front angle from 2.10° (±0.83°) to 0.80° (±0.66°) (p=0.001). The method also reduces the mean maximum deviation of the bone resection, with respect to the preoperative path, from 3.75mm to 2.69mm (p=0.003). However, no increased accuracy was observed at the back side of the bone surface where this method would not be expected to provide information.DiscussionIn summary, we developed a novel 3D-LAD navigation technology. From the experimental study, we demonstrated that the method can improve the ability of surgeons to accurately draw the preoperative osteotomy lines and perform resection of a primary bone sarcoma, with comparison to traditional methods, using 18 sawbones.

A novel method of light projection and modular jigs to improve accuracy in bone sarcoma resection.

We developed a novel method using a combined light-registration/light-projection system along with an off-the-shelf, instant-assembly modular jig construct that could help surgeons improve bone resection accuracy during sarcoma surgery without many of the associated drawbacks of 3D printed custom jigs or computer navigation. In the novel method, the surgeon uses a light projection system to precisely align the assembled modular jig construct on the bone. In a distal femur resection model, 36 sawbones were evenly divided into 3 groups: manual-resection (MR), conventional 3D-printed custom jig resection (3DCJ), and the novel projector/modular jig (PMJ) resection. In addition to sawbones, a single cadaver experiment was also conducted to confirm feasibility of the PMJ method in a realistic operative setting. The PMJ method improved resection accuracy when compared to MR and 3DCJ, respectively: 0.98 mm versus 7.48 mm (p < 0.001) and 3.72 mm (p < 0.001) in mean corner position error; 1.66 mm versus 9.70 mm (p < 0.001) and 4.32 mm (p = 0.060) in mean maximum deviation error; 0.79°-4.78° (p < 0.001) and 1.26° (p > 0.999) in mean depth angle error. The PMJ method reduced the mean front angle error from 1.72° to 1.07° (p = 0.507) when compared to MR but was slightly worse compared to 0.61° (p = 0.013) in 3DCJ. The PMJ method never showed an error greater than 3 mm, while the maximum error of other two control groups were almost 14 mm. Similar accuracy was found with the PMJ method on the cadaver. A novel method using a light projector with modular jigs can achieve high levels of bone resection accuracy, but without many of the associated drawbacks of 3D printed jigs or computer navigation technology.

A model predictive control approach for highly automated vehicles in urban environments

AbstractIn this paper, a model predictive control (MPC) approach for the lateral and longitudinal control of a highly automated electric vehicle with all-wheel drive and dual-axis steering is presented. For the prediction of state trajectories a two-track vehicle model is used. The MPC problem for trajectory tracking is formulated by controlling the front and rear steering angle as well as the individual drive torques with respect to actuator and design constraints. Beside the steering angles, the MPC controller computes the individual drive torques to not only match the reference velocity but also to support the lateral dynamics of the vehicle using torque vectoring. The MPC problem is solved using ACADOS, a software package for efficiently solving optimal control problems. The effectiveness of the proposed MPC scheme is demonstrated via simulation.

Optimal Control Method of Path Tracking for Four-Wheel Steering Vehicles

Path tracking is a key technique for intelligent electric vehicles, while four-wheel steering (4WS) technology is of great significance to improve its accuracy and flexibility. However, the control methods commonly used in path tracking for a 4WS vehicle cannot take full advantage of the additional steering freedom of the 4WS vehicle, because of restricting the relationship between the front and rear wheels steering angle. To address this issue, we derive a kinematic model without the restriction based on the small-angle assumption. Then, the objective function and constraints of system control quantity optimization are designed based on the tracking error model. After the optimization problem is solved in the form of quadratic programming with constraints, the control sequence with the smallest performance index is obtained through rolling optimization. The proposed method is tested on a high-fidelity Carsim/Simulink co-simulation platform and an experimental vehicle. The results show that the standard deviation of the lateral error and the yaw angle error of the algorithm is less than 0.1 m and 3.0°, respectively. Compared with the other two algorithms, the control of the front and rear wheels angle of this method is more flexible and the tracking accuracy is higher.

Research of the Influence of Cutting Conditions on the Temperature Field during Turning

Numerical simulation of the temperature field and parameters of the turning process of workpieces made of 45 and 12Kh18N10T steels is performed. The front angle of the cutter, as well as the coefficients of chip friction on the front surface of the tool μ1, the flank surface on the workpiece μ2, and the coefficient of friction on the yield stress μ were selected as variable parameters. The degree of influence of the variable parameters on the tangential component of the cutting force, the friction force on the front and flank surfaces of the cutting tool, the power of heat sources, contact temperatures and the average temperature of the workpiece is estimated.

Manipulating geometric and optical properties of laser-inscribed nanogratings with a conical phase front.

The formation of volumetric nanogratings in fused silica by femtosecond laser pulses are shown to afford new opportunities for manipulating the physical shape and tailoring the optical properties of the modification zone by harnessing unconventional beam shapes. The nanograting assembly was observed to rigorously follow the beam elongation effects induced with conical-shaped phase fronts, permitting a scaling up of the writing volume. Detailed optical characterization of birefringence, dichroism, and scattering loss pointed to flexible new ways to tune the macroscopic optical properties, with advantages in decoupling the induced phase retardation from the modification thickness by controlling the conical phase front angle. Further insights into an unexpected asymmetric response from Gaussian beams modified with concave and convex phase fronts have been provided by nonlinear propagation simulations of the shaped-laser light.

The influence of the value of the front angle and the angle of inclination of the cutting edge on the radial force when threading with taps

The purpose and normalization of the accuracy of the geometric parameters of the cutting part of the tool is directly related to the indicators of functional and parametric reliability of taps. The comparison of the taps test results showed that reducing the range of scatter of geometric parameters of the tool of the cutting part of taps makes the threading process more stable (leads to a significant reduction in the resistance dispersion, to a decrease in the number of breakdowns, and a decrease in the coefficients of variation of resistance and wear) and reduces the breakdown of the flank of the thread being cut. In this paper, the dependences of the change in the magnitude of the radial force on the elementary cutting profiles of the tap on the error of the spacing angle between the cutting teeth due to angular displacements of the main cutting blade owing to the presence of the front angle and the angle of inclination of the cutting edge are obtained. The obtained patterns of changes in the radial force on the cutting teeth of the tap can be used when considering alternative options for assigning the angle λ based on the criterion of minimum (limitation) of cutting forces during processing. A change in the front angle in the range of known recommended values does not significantly affect the nature of the change and the amount of radial force on the cutting teeth of the tap, as well as does not affect the one-sided direction of the radial force vector, characteristic of taps with a uniform spacing angle. The error of the spacing angle between the cutting teeth of the tap, due to the presence of the angle of inclination of the cutting edge λ, leads to an increase in the radial force and a change in the nature of the load on the cutting teeth of the tool. The obtained patterns of changes in the radial force on the cutting teeth of the tap can be used when considering alternative options for assigning the angle λ based on the criterion of minimum (limitation) of cutting forces during processing.

Analysis of solar radiation changes in Chinese solar greenhouses with different roof structures based on a solar radiation model

Chinese solar greenhouses (CSGs) are important agricultural production facilities. Under non-artificial heating conditions, solar radiation is the only CSGs energy source. It is highly important to optimally obtain solar energy in greenhouse construction and production. In this study, a solar radiation model for solar greenhouses was adopted to explore the quantities of solar radiation in greenhouses considering different front roof forms and angles. Herein, the solar radiation amounts corresponding to five roof forms, namely, double-section arc, parabolic, oval, arc, and linear roofs, are compared and analyzed during the four solar periods (beginning of spring, vernal equinox, beginning of winter, and winter solstice). It was found that the solar radiation of oval roof greenhouses on the ground was the largest and was 4.44%-23.68% higher than that of parabolic roofs. In addition, the cumulative sum of light on the linear roof greenhouse wall is also the largest and was 6.02% to 12.08% higher than the parabolic roof greenhouse in the four solar terms. Moreover, the solar radiation in CSGs was compared with front roof angles of 25°, 30°, and 35°. It was observed that the solar radiation amount gradually increases with increasing angles. Notably, the variation at an angle of 35° influences the solar radiation of the paraboloidal CSGs ground and elliptical CSGs north wall to the greatest extent, which increased by 8.23% and 12.74%, respectively. This study confirms the role of front roof form and inclination angle in enhancing the greenhouse solar radiation level. Keywords: Chinese solar greenhouse, roof structure, roof angle, solar radiation model DOI: 10.25165/j.ijabe.20221502.6763 Citation: Liu K, Xu H J, Li H, Wu X, Sang S Y, Gao J. Analysis of Solar radiation changes in Chinese solar greenhouses with different roof structures based on a solar radiation model. Int J Agric & Biol Eng, 2022; 15(2): 221–229.

Milling performance of stone‐plastic composite with diamond cutters

AbstractIn order to meet the requirements of cutting efficiency and economy in the processing of stone plastic composite, milling tests of the stone plastic composite were conducted using straight tooth diamond tools. Cutting forces and temperature were measured under different cutting parameters. Response surface methodology was used to analyze the variation of cutting forces and temperature and to determine the significant contribution of each variable and its two‐level interaction. The correlation between actual and predicted results was found by building mathematical models of cutting forces and temperatures, which can be used to make accurate predictions. At last, the optimal cutting parameters for stone plastic composite straight‐tooth milling with low cutting forces and cutting temperatures were found to be 10° front angle, 37.9 m/s cutting speed, 0.32 mm feed per tooth, and 0.5 mm milling depth. It is possible to improve processing efficiency and reduce production costs by using these parameters in industrial processing.

Исследование сил при съеме тонких слоев строганием и фрезерованием

The problem of machining structural elements with removal of metal layers with thickness less than 0.01 mm by carbide tools, when the conditional radius of the blade rounding is less than or equal to the thickness of the cut layer, is considered. These cutting conditions can be considered constricted which requires research into cutting forces and chip shape. The problem of recording and measuring small cutting forces arising during blade machining of small grooves that serve for gas drainage in the manufacture of rubber products is solved. To measure forces, a lever fixed in a universal dynamometer, which has a supporting support with small friction, is used. Value of force moment measured with dynamometer can be used for optimization of cutting conditions, selection of tool geometry when processing small relief elements. Dependences of lever system cutting forces and displacements on the use of lubricant-cooling liquids, values of front angles during planing and milling with small-size tools are investigated. Experimental discrepancies between theoretical calculations of cutting forces according to classical and modern reference data and fixed results with the use of cutting liquids during cutting with small values of feed for carbide tools are found

The Crack Angle of 60° Is the Most Vulnerable Crack Front in Graphene According to MD Simulations

Graphene is a type of 2D material with unique properties and promising applications. Fracture toughness and the tensile strength of a material with cracks are the most important parameters, as micro-cracks are inevitable in the real world. In this paper, we investigated the mechanical properties of triangular-cracked single-layer graphene via molecular dynamics (MD) simulations. The effect of the crack angle, size, temperature, and strain rate on the Young’s modulus, tensile strength, fracture toughness, and fracture strain were examined. We demonstrated that the most vulnerable triangle crack front angle is about 60°. A monitored increase in the crack angle under constant simulation conditions resulted in an enhancement of the mechanical properties. Minor effects on the mechanical properties were obtained under a constant crack shape, constant crack size, and various system sizes. Moreover, the linear elastic characteristics, including fracture toughness, were found to be remarkably influenced by the strain rate variations.

Application of infrared thermography for irrigation scheduling of horticulture plants

Infrared thermal imaging has acquired remarkable acceptance in the agricultural field for numerous applications ranging from irrigation scheduling, crop yield estimation, plant disease detection, fruit maturity evaluation, bruise detection to nursery monitoring. This paper presents a practical application of thermal imaging for irrigation scheduling of horticulture plants under different irrigation treatments. Four similar hibiscus potted plants were considered under different water conditions (slight, mild, moderate, and severe water stress). The thermal images were obtained from different canopy zones (front view, top view, left side view, right side view, and front angle view) using a ground-based hand-held thermal camera. The main objectives of the present study include (i) finding the effect of different irrigation treatments on potted plants and a corresponding change in their thermal signature, (ii) finding a relation between plant-based variables and soil-based variables, and to further develop a threshold value for irrigation scheduling (iii) to compare and simplify the calculation of the temperature of the canopy (Tc) and water stress indices namely crop water stress index (CWSI) and stomatal conductance index (Ig) using various reference and non-reference thresholding techniques and to improve their diagnostic accuracy. We can establish quantitative relationships between plant and soil-based parameters. The relationship between temperature of canopy (Tc) and temperature of soil (Ts) pair is best suited to find the plant under water stress. The threshold value pair (Tc and Ts) for the plants under study are 29.5°C (Tc) and 28°C (Ts) for plant A, 29.5°C (Tc) and 27.5°C (Ts) for plant B, 29.5°C (Tc) and 27°C (Ts) for plant C, and 29.5°C (Tc) and 26.5°C (Ts) for plant D. The most suitable method in terms of applicability and scalability, is histogram gradient thresholding (HG) method to determine Tc accurately. The critical m (for standard deviation envelope thresholding SDE method) and ratio of pixel change (RPC) (for HG method) value estimated can be considered an important indicator of water stress in the plants. Among different approaches to compute water stress indices, simplified and HG methods have minimum root mean square error (RMSE) for plants A, B, C, and D compared to statistical and SDE methods.

Analysis of the Upper and Lower Limbs Movement in Elite Fencing Attack Skills

PURPOSE This study aims to help improve performance by comparing and analyzing the kinematic variables for each upper and lower extremities segment when two groups of players attack the national women’s fencing players in a match situation.METHODS This study divided the movement time, movement time ratio, Fente step length change, angle factor at each event, and velocity factor of the fencing point of a sword at each event into the Olympic medalists’ group (Group A) and the international competition winners group (Group B) during the fencing Marche Fente. An independent t-test was performed for each factor, and the results were compared.RESULTS As a result, the difference between the two groups in movement time was statistically significant in the front of the foot in the velocity factor. However, no statistical significance was found between the two groups in the front angle of the trunk, the elbow angle, and the knee angle.CONCLUSIONS This indicates that group A and group B are both outstanding players with the best performance, so they are similar in the details of the movements except for the very slight difference in time and velocity. Therefore, the average of the result values of the joint angle will be a feedback index for fencing beginners or education subjects who are now starting to fencing.

A Monte Carlo Parametric Sensitivity Analysis of Automobile Handling, Comfort, and Stability

This paper investigates the bandwidth sensitivity of automobile handling, comfort, and stability based on Monte Carlo sensitivity simulations. Performed bandwidth sensitivity simulations include the effects of vehicle geometry and suspension parameters on lateral acceleration, roll angle, front/rear sideslip angles, and yaw rate angle, including both time- and frequency-domain sensitivity analyses. To replicate actual automobile responses, a full-vehicle roll-oriented suspension seven-degree-of-freedom (7-DOF) model was developed and implemented considering a 2-DOF planar two-track model with a nonlinear Pacejka tire model. During the Monte Carlo simulations, 10 mm and 20 mm amplitude sine-wave excitations were used for the left and right sides, respectively, and the frequency was uniformly sampled over the range of 0–30 Hz. Simultaneously, each investigated vehicle parameter varied by ±25% relative to the reference model parameters. These simulations illustrate the sensitivity of the lateral acceleration, roll angle, yaw angle, and sideslip angles to their parameter variations. The results confirm that the road excitation frequency, tire properties, vehicle geometry, and suspension parameters significantly influence the vehicular lateral and roll stabilities when considering the lower and higher peaks and the frequency bandwidths of the lateral and roll stabilities. Interestingly, the longitudinal location of the center of gravity and the tire properties can achieve more significant peak lateral stability responses, as represented by the front and rear sideslip angles and the frequency bandwidth, compared to the other vehicle parameters at high frequencies. Choosing the correct tire properties and vehicle geometry, as well as suspension characteristics, plays an essential role in increasing the vehicular lateral stability and the rollover threshold. Variations in the studied parameters allow for higher vehicular stability when a vehicle is driven on random road surfaces.

Effects of tip clearance, number of teeth, and tooth front angle on the sealing performance of straight and stepped labyrinth seals

In the gas turbine, gaps inevitably exist between the stationary and rotating parts. To improve the performance of gas turbines, tip leakage flow through the gaps must be minimized. The labyrinth seal increases the flow resistance by placing a number of teeth to minimize leakage flow. The labyrinth seal is still adopted in many fields because of its relatively high thermal resistance, simple structure, and wide pressure range. In this paper, the effects of geometric parameters (straight and stepped with solid land, tip clearance, number of teeth, and tooth front angle) on leakage flow were experimentally studied and the seal performance was described using the flow function. Also, flow visualization within the labyrinth seal was conducted using the Schlieren method. The dimensionless tip clearance (C/a) was adjusted from 0.8 to 3.3 (where a is tooth tip width) and the pressure ratio was adjusted from 1.1 to 3.0. The tooth front angle of the stepped seal was 90° and 60°. Results show that the flow function increased as the pressure ratio increased, however it tended to remain constant if the pressure ratio was higher than 2.0. At the same test condition, the flow function of the stepped labyrinth seal was smaller than that of the straight seal for all tested pressure ratios. Also, the seal performance was better for larger number of teeth, smaller tip clearance, and smaller tooth front angle cases. Based on the measured results, a new correlation for the labyrinth seals was suggested.

User capabilities in eyes-free spatial target acquisition in immersive virtual reality environments

In immersive virtual reality (VR) environments, users rely on the vision channel to search for objects. Such eyes-engaged interactive techniques may significantly degrade the interaction efficiency and user experience, particularly when users have to turn their head frequently to search for a target object in the limited field of view (FOV) of a head-mounted display (HMD). In this study, we systematically investigated user capabilities in eyes-free spatial target acquisition considering different horizontal angles, vertical angles, distances from the user's body, and body sides. Our results show that high acquisition accuracy and low task load are achieved for target locations at front and middle horizontal angles as well as those at middle vertical angles. Meanwhile, a trade-off cannot be achieved between the acquisition accuracy and the task load for target locations at long distances from the user's body. In addition, the acquisition accuracy and task load for the target locations vary with the body side. Our research findings can provide a deeper understanding of user capability in eyes-free target acquisition and offer concrete design guidelines for appropriate target arrangement for eyes-free target acquisition in immersive VR environments.

Raw materials and functional designs of Fishtail projectile points from southern Brazil

This study analyses the lithic landscape and the selection of rocks used to manufacture Fishtail points (FP) in southern Brazil, their designs, and some functional aspects. In order to identify the offer of lithic resources, we carried out several surveys throughout 15 months in 47 counties in the Southern Brazil covered by the Botucatú - Serra Geral Vulcano Sedimentary Complex. The lithic composition of numerous hill slopes, fallen rocks, and accumulations of pebbles and boulders in the riversides was evaluated. The results show that basalts (including a small proportion of andesites and rhyodacites-rhyolites), and silicified sandstones, are ubiquitous in the landscape. Conversely, non-translucent cherts are scarce, so their acquisition would have been time-consuming. However, these local cherts were the rocks mostly used to manufacture these points, being another example of the selectivity for high quality rocks by Paleoamerican hunter-gatherers. The same cherts selected in southern Brazil to produce the FP were used to manufacture other point-types by local hunter-gatherers of the early and middle Holocene grouped in the so-called “Umbú Tradition”. Not a single FP of the entire collection analyzed here was made from silicified limestones, which is one of the most common raw materials among the Uruguayan FPs, nor were they made from quartzites as were most of the FPs of the Pampean plains.&#x0D; Regarding to the designs of these projectiles, some morphotypes appear to have been designed to produce multiple injuries through successive thrusts and withdrawals in the bodies of the prey, while in others, the design seems to have favoured penetration and fixation on the prey, suggesting in this case, a single shot technique for each projectile. As the maintenance process unfolded, especially for points below ~ 80 mm in length, they show features that negatively impacted their efficiency, including distinct asymmetries, somewhat open front angles, a decrease in the cutting perimeter and cross-sectional area, an increase in the bevel angle of the blade edges, and a tendency to a conical cross-section. Behaviours intended to counteract these problems were maximizing the length of the leading edge, maintaining the symmetry and the triangular blade resting on straight shoulders, and maintaining the aerodynamic properties as much as it were possible, in order to improve their lethality and the fixation capacity.&#x0D; Beyond these rejuvenation processes, three different morphotypes of points appear to be included within the sample. The first includes points over 120 mm and ~ 80 g in weight, with triangular or slightly lanceolate limbs, which mostly present straight shoulders, but there are also examples of rounded shoulders. The second design corresponds to projectiles between 110 and 87 mm and ~30 g in weight, with triangular or slightly lanceolate blades and straight shoulders. The third design presents the classic shape of these projectiles, with a fish silhouette, with maximum lengths below 90 mm, with a more robust and conceptually different design, where the angles of the edges of the blades and of the shoulders are equal, perhaps with the intention to facilitate the spear withdrawal to produce multiple injuries.

Comprehensive study of the process of cutting screw grooves on the inner surface of a cylindrical steel sleeve with rotary cutting mandrels

The paper presents the results of a comprehensive study of the process of cutting helical internal grooves on the basis of computer simulation in order to establish the influence of technological parameters of cutting on the forming force. Researches of cutting of screw grooves on thinwalled steel sleeves by a cutting mandrel with various cutting speeds have been carried out. The method of processing internal screw grooves on machines with simple kinematics is presented. The dependences of the influence of cutting rates on implementation of the hidden kinematical connection are established. Graphs reflecting the dependence of the cutting rate on the angle of inclination of the cut helical groove are constructed, and a regression equation is obtained describing the dependence of the studied factors on the axial force. Ranges of cutting rates are established, allowing to provide the maximum productivity at various angles of the spiral inclination. The results of processing the experimental data of the study of the influence of tool geometrical parameters on the forming force when cutting helical grooves on the inner surface of the cylindrical shell are shown. Levels of change of factors, variance of experiment results on each of experiments are defined. The regression coefficients are calculated, the regression equation is compiled, the variance of model adequacy is estimated and adequacy of the regression equation is checked, the nature of infl uence of interaction of cutting rate parameters, front angle and the allowable allowance on the forming force is determined. Based on the results of modeling using the Maple program, a regression equation was obtained that reflects dependence of influence of factors on the axial force per tool tooth, dependence of the influence of the studied factors on the change in temperature in a cutting zone, and also constructed a temperature field reflecting the heat distribution in the processing zone on the example of one experiment. The study was performed with the financial support of the Russian Foundation for Basic Research within the research project No. 19-38-90057.