Hole Exit Research Articles

New evidence on the spread in Catalonia of the invasive longhorn beetle, Xylotrechus chinensis, and the efficacy of abamectin control.

The invasive wasp-mimicking Tiger Longicorn Beetle, Xylotrechus chinensis, a potentially lethal pest of mulberry trees (Moraceae: Morus spp.), was first reported in Europe in 2018. In Catalonia its spread has been impressive: one district, four towns, 44km2 in February 2018; four districts, 12 towns, 378km2 in July 2020; seven districts, 65 towns, 1134km2 in December 2023. It is likely the infestation will spread further in the future, in particular along the Mediterranean coast from Spain to Greece. The flight period of this beetle in Mediterranean countries is expanding on both ends (from the end of April to mid-October), probably due to increasing temperatures because of climate change, although this should be further proved. The adult beetle life span is 18-23 days in insectaria, likely somewhat shorter in the wild since they do not feed and spend more energy flying outside. The single treatment with abamectin carried out in a Catalonian town in June 2022 on a sample of 24 trees (12 treated, 12 untreated) has been effective in reducing the infestation of this beetle in relation to untreated trees. But the reduction was not complete since new exit holes appeared during the summer of the following year. Therefore, an additional treatment carried out during the first ten days of October should be tested to achieve a better control of this pest. It would also be worthwhile trying a single treatment of abamectin in mid-July since it should be able to kill larvae hatching before the treatment and still have sufficient residual activity for larvae hatching after the treatment, and thus cover the entire activity period. Also, to get satisfactory mulberry tree protection, it is likely that treatments might have to be repeated for a few consecutive years. Yearly re-infestations from untreated public and/or private mulberry trees are also a concern and make short-term control of this pest difficult, no doubt accounting for the rapid spread of this beetle.

Facilitators or predators? The role of seed-feeding beetles in the germination of an ornamental and invasive plant in an urban environment

Leucaena leucocephala is a forage legume that provides cellulose, firewood, and shade in cities, although it presents a dangerous allelopathic and invasive potential. Its main natural enemy is the endophytic beetle Acanthoscelides macrophthalmus (Chrysomelidae: Bruchinae), whose larvae penetrate seeds and can consume the entire endosperm and embryos. However, there is much to explore on how the abundance of larvae inside the seed affects the plant germination, resulting in an antagonistic (predation) or mutualistic (facilitation) interaction. Our goal was to test how these beetles affect the germination of L. leucocephala seeds from an urban environment in Uberlândia, MG. We hypothesized that a single larva inside the seed facilitates germination since the exit holes left break the physical dormancy and enable water imbibition. On the other hand, two or more larvae inside the same seed result in predation, as the amount of endosperm is not enough for beetle satiation before they attack the seed embryo. We collected 100 pods, dissected them, and quantified and qualified the seeds. In the germination experiment, we used healthy seeds (control), scarified healthy seeds (physical treatment), and attacked seeds (one, two, or more larvae). We found that beetles infested 74% of the sampled seeds. Independently of the abundance of larvae inside the seed, attacked seeds did not germinate. The scarified seeds germinate faster and in greater quantity. Therefore, our hypothesis was rejected for the studied plant population. Acanthoscelides macrophthalmus acts only as a predator in an antagonistic interaction that decreases the germination rate of L. leucocephala.

Impact of liquid crossflow on the discharge coefficient of a gas jet hole on a flat plate

This study combines the experimental and numerical simulation methods to deeply analyze the impact of liquid crossflow on the discharge coefficient of a gas jet hole on a flat plate. Experiments were conducted to examine the influence of momentum flux ratio and theoretical momentum flux ratio on the discharge coefficient under various crossflow Reynolds numbers. It was found that the variation of the discharge coefficient with the theoretical momentum flux ratio clearly reflects the impact of the crossflow boundary layer velocity profile on the discharge coefficient. The rapid growth of velocity in the boundary layer near the wall in the direction normal to the wall surface, or the decrease in the thickness of the boundary layer, both enhance the shearing effect of the crossflow, leading to a decrease in the discharge coefficient. Analysis of the cavity morphology at the hole exit captured by high-speed camera revealed that the averaged profile of the gas–liquid boundary on the symmetrical plane of the jet below the hole can be approximated as a straight line within the scale of the hole diameter, and the sine of the angle between this line and the upper wall surface is roughly equivalent to the normalized discharge coefficient. This relationship was physically interpreted through the analysis of effective and equivalent flow cross-sectional shapes derived from numerical simulation at different crossflow Reynolds numbers and theoretical momentum flux ratios. Additionally, this paper introduces an innovative method for predicting jet flow rate based on image processing technology. A notable feature of this method is that it does not require the measurement of the pressure inside the gas chamber.

A comprehensive investigation of the effect of hole diameter and number on film cooling performance of rotating blade leading edge

The combined effect of film hole number and diameter on the film cooling were investigated on the rotating blade leading edge by using experimental and numerical methods. The film cooling performance was obtained by pressure sensitive paint technique under rotational condition. To better understand the experimental results, the flow fields obtained from numerical simulation were also analyzed. The effects of hole length-to-diameter ratio (L/d = 2.5/5/7.5), hole number (N = 7/9/10/11/13), hole diameter(d = 0.64∼1.26 mm), Hole to hole pitch, (P/d = 6.3∼9.2) and hole exit area (Ahole/ALE=4 %-14 %) on the film cooling performance are investigated. Five blowing ratios are also employed (M = 0.5 to 2.0). The results indicate that the hole length-to-diameter ratios (L/d = 2.5∼7.5) have a negligible influence on the film cooling effectiveness. Both the film hole number (N = 10/13) and the hole diameter (d = 0.64/0.75 mm) monotonically affect the film cooling performance under each blowing ratios. However, a comprehensive study indicates that there is a significant quadratic correlation between the area-averaged cooling effectiveness and the total film hole exit area for different combinations of hole number and diameter. Meanwhile, there is an optimal film hole exit area on the leading edge and it increases as the blowing ratio or mass flow rate increases.

Large eddy simulation of in-hole blockage effects on cooling performance of fan-shaped holes

Film-cooling and thermal barrier coating approaches are commonly used in gas turbines to protect the turbine parts from the high-temperature flow of gases. However, one drawback of this method is that the coatings can partially obstruct the cooling hole exit on the turbine blade surfaces, resulting in reduced cooling performance. Therefore, this study aimed to investigate the effects of in-hole blockage thickness on cooling effectiveness and flow characteristics of fan-shaped holes using large eddy simulations (LES). A laidback fan-shaped hole located on a flat plate was the reference cooling hole. Numerical simulations were conducted for two different blocked cooling hole configurations with various blockage thicknesses (t/D = 0.5 and 0.9) at three different blowing ratios (0.5, 1.0, and 2.0). The cooling effectiveness computed by the LES method was validated for both unblocked and blocked cooling holes, and the results were compared to the experiments at various blowing ratios. It was revealed that an increase in blockage thickness had a significant impact on the area-averaged cooling effectiveness, particularly at high blowing ratios. The overall area-averaged cooling effectiveness for the t/D = 0.9 case was approximately 75 % lower than that of the unblocked cooling hole. Moreover, assessment of the instantaneous velocity field inside the hole over time revealed that larger blockage thicknesses resulted in greater velocity fluctuations and a more unsteady flow.

Investigation of the effect of symmetrical hybrid stacking on drilling machinability of unidirectional CFRP, GFRP and hybrid composites: Drilling tests and damage analysis

Fiber-reinforced plastics are undoubtedly superior to metals in many sectors due to their advantageous properties. Especially carbon fiber reinforced plastics (CFRP) and glass fiber reinforced plastics (GFRP) are widely used in industry. Although CFRP offers higher strength, its use is limited due to its high cost. However, with hybridisation, it is possible to produce composites that will provide sufficient strength at lower cost. The mechanical behaviour of hybrid composites may be different compared to glass or carbon composites, as well as the damage behaviour during machining. In this study, the influence of hybrid stacking in drilling hybrid composites was investigated. The results showed the hybrid stacking, especially the position of the carbon plate, has a significant impact on the force generation and damage formation in the drilling. Although stacking the carbon layer at bottom caused an increase in thrust forces, it reduced the damage formation at the hole exit.

Flow of water out of a funnel

The unsteady Bernoulli equation is used to numerically determine the surface height and velocity distribution of water flowing out of a conical tube as a function of time. The speed is found to interpolate between freefall for a cylindrical pipe of constant radius and Torricelli’s law for a funnel having a small exit hole. In addition, the applied force needed to hold the conical vessel in place is calculated using Newton’s second law including the rocket thrust due to the water flowing out of the funnel. A comparison is made with the analogous expressions for the flow through and holding force on a right cylindrical tank having a hole in its bottom face. The level of presentation is appropriate for an undergraduate calculus-based physics course in mechanics that includes a module on fluid dynamics.

Design and performance analysis of low damage anti-skid crescent drills for bone drilling

BackgroundWith orthopedic surgery increasing year on year, the main challenges in bone drilling are thermal damage, mechanical damage, and drill skid. The need for new orthopedic drills that improve the quality of surgery is becoming more and more urgent.MethodsHere, we report the skidding mechanism of drills at a wide range of inclination angle and propose two crescent drills (CDTI and CDTII). The anti-skid performance and drilling damage of the crescent drills were analyzed for the first time. Inclined bone drilling experiments were carried out with crescent drills and twist drills and real-time drilling forces and temperatures were collected.ResultsThe crescent drills are significantly better than the twist drill in terms of anti-skid, reducing skidding forces, thrust forces and temperature. The highest temperature is generated close to the upper surface of the workpiece rather than at the hole exit. Finally, the longer crescent edge with a small and negative polar angle increases the rake angle of the cutting edge and reduces thrust forces but increases skidding force and temperature. This study can promote the development of high-quality orthopedic surgery and the development of new bone drilling tools.ConclusionThe crescent drills did not skid and caused little drilling damage. In comparison, the CDTI performs better in reducing the skidding force, while the CDTII performs better in reducing the thrust force.

Comparison of iron aluminide Fe3Al with armour steel in ballistic behaviour

Intermetallic aluminide compounds possess several potential advantages compared to alloyed steels, like enhanced oxidation resistance, lower density and the omittance of critical raw materials. Iron aluminides, compared to other transition metal–aluminides of TM3-Al type, although having a higher density compared to titan-aluminides, have a lower density compared to nickel-aluminides, but also a higher ductility than both alternatives, making this material potentially effective in ballistic protection application. Density–wise, this material may be a worthy alternative to armour steels, which was the aim of this study. Two materials, Fe3Al intermetallic compound (F3A-C) and Armox 500 armour steel were ballistically tested against tungsten-carbide (WC) armour-piercing ammunition, in accordance with STANAG 4569. After ballistic testing, microhardness and metallographic testing were performed, revealing differences in strain hardening, crack propagation mode and exit hole morphology. F3A-C ballistic resistance is similar to that of armour steel, in spite of the lower tensile and impact mechanical properties, relying on a considerably higher strain hardening rate, thermal properties and a lower density.

DETERMINATION OF THE POSSIBILITY OF A LETHAL BULLET INJURY TO THE HEAD DUE TO A PROJECTILE RICOCHET TAKING INTO ACCOUNT THE ANALYSIS OF MORPHOLOGICAL CHARACTERISTICS OF EXPERIMENTALLY FIRED BULLETS

Gunshot wounds always occupy one of the leading places in the structure of violent mortality, however, there is not enough information in the specialised literature that highlights the distinct individual characteristics of projectiles (bullets) that were removed from a biological object and became the instrument of death, and when they ricochet (collide with an obstacle) after a series of experimental shots. Aim: To determine the possibility of causing a fatal bullet injury to the head after the ricochet of a projectile from the road surface, taking into account the analysis of the morphological characteristics of experimentally fired bullets. Material and methods. The archival material of the SSI "Main Bureau of Forensic Medical Examination of the Ministry of Health of Ukraine" ("Expert conclusion") was used. The objects of the study were: bones of the skull of the victim gr. K, gunshot wounds on the head (entrance, exit hole, wound channel), as well as bullets up to 9 mm cartridges of the "Makarov" pistol, namely 1) one bullet removed from the cranial cavity after an autopsy and 2) 6 bullets removed after an experimental series of shots into the road surface. Their characteristics were studied using standard methods generally accepted in forensic medicine and standard methods of variational statistics. Results. During arrest by a law enforcement officer, the man received a fatal gunshot wound to the head with a 9 mm bullet. There was an entrance hole in the occipital bone, a wound channel in the cranial cavity at an angle of approximately 130° to the midline of the body, and a depressed fracture of the frontal bone. A series of experimental shots with 9mm bullets revealed the remains (fragments) of the asphalt coating and their marked deformation, which was not the case with the bullet that caused the fatal wound. Ballistic analysis showed that the angle of movement of the bullet in the cranial cavity was 30°. Conclusion. According to the circumstances contained in the criminal case materials and established during the forensic examination, the bullet wound could not have been caused by the ricochet of the bullet from the asphalt pavement, since no remains (fragments) of the obstacle with which the bullet collided were found, and its deformation does not correspond to the results of the forensic shooting and ballistic examination.

Investigate the optimum design of atomizing nozzles for coal dust suppression by using multifactor level response surface methodology

Mechanized coal extraction generates substantial dust, adversely affecting the physical and mental wellbeing of underground workers and degrading the operational environment. To address the limitations of traditional spray systems, which often suffer from poor atomization effects and limited ability to withstand wind interference, the innovative vortex atomizing nozzle has been developed specifically for dust suppression. This advanced solution was rigorously tested through detailed numerical simulations and comprehensive experimental investigations. These studies focused on examining the impact of critical parameters, including the velocity at the airflow director's exit, the angle of the exit hole, and its radius, on the efficacy of dust suppression. Findings highlighted the paramount importance of the airflow director's exit velocity in enhancing dust removal, with the exit hole's radius having the least impact. Optimal conditions for dust suppression were identified as an airflow director exit velocity of 20 m/s, an angle of 60°, and a radius of 0.6 mm. Field validations under these optimum parameters demonstrated unparalleled dust control efficiency, achieving a reduction in coal dust concentration exceeding 90 %. This apparatus offers a highly effective, user-friendly solution for comprehensive coal dust management across various mine locations.

First Record of Infestation of Amphitrichia flachi (Brenske, 1892) (Coleoptera: Scarabaeidae: Melolonthinae: Rhizotrogini) on Cacao (Theobroma cacao L.) in the Philippines

Amphitricia flachi (Brenske, 1892) (Coleoptera: Scarabaeidae: Melolonthinae: Rhizotrogini) is an emerging insect pest of cacao (Theobroma cacao L.) in the Philippines. The larva of this pest feeds on the roots of cacao, and the adult emerges from the root, as evidenced by an exit hole near the base of the tree, thereby causing significant damage and eventually death to the tree. The pest was monitored from different cacao plantations in Bongabon, Nueva Ecija; Bani, Pangasinan; Sariaya, Quezon; and Tuy, Batangas. The feeding damage of the beetle is characterized, and some integrated pest management considerations were reviewed.

The Evolution of Grain Microstructure in Friction Stir Welding of Dissimilar Al/Mg Alloys with Ultrasonic Assistance.

The process of grain refinement during welding significantly influences both the final microstructure and performance of the weld joint. In the present work, merits of acoustic addition in the conventional Frictions Stir Welding (FSW) process were evaluated for joining dissimilar Al/Mg alloys. To capture the near "in situ" structure around the exit hole, an "emergency stop" followed by rapid cooling using liquid nitrogen was employed. Electron Backscatter Diffraction analysis was utilized to characterize and examine the evolution of grain microstructure within the aluminum matrix as the material flowed around the exit hole. The findings reveal that two mechanisms, continuous dynamic recrystallization (CDRX) and geometric dynamic recrystallization (GDRX), jointly or alternatively influence the grain evolution process. In conventional FSW, CDRX initially governs grain evolution, transitioning to GDRX as material deformation strain and temperature increase. Subsequently, as material deposition commences, CDRX reasserts dominance. Conversely, in acoustic addition, ultrasonic vibration accelerates GDRX, promoting its predominance by enhancing material flow and dislocation movements. Even during the material deposition, GDRX remains the dominant mechanism.

Experimental and numerical investigations on film cooling performance of converging slot holes in plate and turbine conditions

Based on the heat-mass transfer analogy, the Pressure Sensitive Paint (PSP) technique was used to explore the film cooling characteristics of converging slot holes on the plate model and the actual turbine endwall model conditions. Meanwhile, the numerical calculation was also adopted to pursue the flow field details. The width of the converging slot hole exit is a key geometry affecting cooling performance. On the plate model condition, three widths of exit slot Lw (1.7d, 2.3d, 2.9d) were chosen to obtain the optimal exit width. The case with Lw = 2.3d obtained the highest level of adiabatic effectiveness from spanwise and streamwise views. This case operated as a two-dimensional slot and produced a more uniform cooling jet film relative to other cases. Nevertheless, the cooling performance decreased significantly as the converging slot hole width increased to Lw = 2.9d. Then the cooling performance of three patterns of film holes was further investigated in the turbine endwall. Laid-back fan-shaped holes and converging slot holes could improve the film cooling performance effectively compared to the cylindrical holes. Converging slot holes with Lw = 2.3d improved the uniformity of the cooling jet outflow through rows of upstream film holes, and also effectively avoided the phenomenon of coolant blowing away or high-temperature gas entering the film hole, resulting in high film cooling effectiveness performance. Compared to cylindrical holes, the area-averaged adiabatic effectiveness was increased by 216.5 % for the endwall with cylindrical holes with the momentum ratio I = 0.25. Overall, converging slot holes improved cooling performance among all studied film hole configurations.

Experimental analysis and multi-criteria optimization of process parameters in microwave drilling of kenaf-reinforced polypropylene composites

The present work utilizes the CNC-controlled microwave drilling technique to produce the holes in kenaf-reinforced polypropylene composites. The influence of microwave power and feed rate on the hole characteristics, namely, circularity, overcut, taper angle, and surface roughness was investigated. Stereo microscopic images of the hole entrance and exit were used to evaluate the circularity, overcut and taper angle. Optical profilometer was used to acquire the surface roughness of drilled holes. The TOPSIS, GRA, and MOORA multi-criteria decision making techniques were implemented to optimize the microwave drilling process parameters. The 180 W of microwave power and 145 mm/min of the feed rate were the optimum process parameters to yield the best quality holes in kenaf-reinforced polypropylene composites.

Investigation of Delamination in The Drilling of PLA Specimens With Different Lattice Structures

In this study, it was aimed to investigate the effects of processing parameters and different lattice structures on delamination in the drilling of lattice structures. In this context, cylinder PLA (Polylactic acid) parts designed in four different (gyroid, I-WP, nevoius and diamond) lattice structures were produced on a 3D printer and drilled from the centre point with a 5 mm HSS drill. After drilling, entrance and exit hole images were taken with a digital microscope and delamination, burr and circularity around the hole were analysed. According to the results obtained, the lowest delamination at the entrance of the hole was measured in the Gyroid and I-WP lattice structure at the exit. There was no burr at the hole entrance of the specimens. It is seen that the specimen with the lowest value in terms of burr at the hole exit, entrance and exit circularity deviation is Nevoius lattice structure.

Bullet lung injury in adolescent: a case report

Gunshot injuries to adolescents involve a proportionate minority of the overall injury population. Especially thorax bullet injuries are even less common. This report aimed to express our experience by sharing the clinical process of our patient with this injury. A fourteen-year-old female patient was injured by a gunshot from a distance of approximately 10 meters while she was in the garden. It was understood that the bullet entry hole was from the scapular supraspinatus region towards the clavicle and the apex of the left lung. It was determined that the exit hole was in the hemithorax region below the left clavicle. The patient was admitted for follow-up and treatment. Since the patient's general condition was stable, after clinical follow-up, a thoracotomy was performed under elective conditions, intraparenchymal bone fragments were cleaned, and the left apical lobe was excised. Clinical follow-up is problem-free, and post-discharge follow-up is also problem-free.

Cryogenic and ultrasonic-assisted micro-drilling of printed circuit boards using high-frequency-amplitude spindle

Printed circuit boards (PCBs) are key components in computers, 5G, 6G, and other wireless communication devices. On the other hand, the manufacture of micro-holes in PCBs faces severe challenges. Conventional micro-drilling methods often encounter challenges such as poor surface quality and limited tool life. To overcome these issues, a novel micro-drilling method called cryogenic and ultrasonic-assisted micro-drilling (CUAMD) has been developed. This study compared four drilling methods to investigate the benefits of cryogenic and ultrasonic-assisted drilling in hybrid machining processes: conventional micro-drilling (CMD), cryogenic-assisted micro-drilling (CAMD), ultrasonic-assisted micro-drilling (UAMD), and cryogenic and ultrasonic-assisted micro-drilling (CUAMD). The experimental results unequivocally indicate that the utilization of cryogenic-assisted drilling leads to a significant reduction in cutting heat during the machining process. This not only contributes to an improvement in machining accuracy but also exerts a positive influence on tool life and surface morphology. Ultrasonic-assisted drilling separates chips into smaller volumes through high-frequency-vibration, effectively reducing the cutting forces. The high frequency of 38.25 kHz and high amplitude vibration of 5.16 μm of the ultrasonic spindle induced vibrations on the drill bit. Liquid nitrogen with a pressure and temperature of 28 kPa and − 196 °C, respectively, was used in the cryogenic-assisted method. The superior machining performance of the CUAMD approach was evaluated by comparing it to various methods, including cutting forces, tool flank wear, entrance/exit hole morphology, and chip formation. The CUAMD method avoids chip entanglement, suppresses burrs, and reduces the maximum cutting force, maximum torque, and exit hole damage factor Fd by 47.7 %, 56.1 %, and 42.5 %, respectively, compared with CMD.

Numerical study on the heat effect on the drilling damage of Ti/CFRP stacks

AbstractCarbon fiber reinforced plastics (CFRP) has strong sensitivity to temperature, as the stacking sequence is titanium alloy (Ti) to CFRP, the damage of CFRP is more severe due to the accumulation of cutting heat. In this study, a stress‐strain constitutive model of CFRP with the effect of thermal stress is proposed. On the basis, a simulation model of drilling Ti/CFRP stacks is established to explore the heat effect on the drilling damage. Based on the results, it can be concluded that the burr of Ti at hole exit is generally low due to the support of CFRP, and the burr height increases by 56.61% as the temperature rises from 182.02 to 355.69 °C. Besides, the intralaminar damage of CFRP is mainly caused by the fiber tensile failure and matrix tensile failure, and the matrix tensile failure is more affected by temperature. Moreover, delamination of CFRP decreases slightly with the reduce of drilling temperature. In addition, serious damage of CFRP on the hole wall usually occurs within the cutting angle of 90° to 135°, and pit defects can be reduced in a lower drilling temperature.Highlights A thermal effect stress‐strain constitutive model of CFRP is proposed. Ti/CFRP drilling model is developed based on the proposed constitutive model. Fiber and matrix tensile failure are main form of intralaminar damage of CFRP. Matrix tensile failure is more sensitive to temperature.

Ecological Insights and First Confirmed Record of Ooencyrtus nezarae (Hymenoptera: Encyrtidae) on Eggs of Megacopta cribraria (Hemiptera: Plataspidae) in Tennessee and Georgia1

Abstract The kudzu bug, Megacopta cribraria (F.) (Heteroptera: Plataspidae), is native to Asia, was first detected in Georgia, USA, in 2009, and has since been recognized as a damaging pest of soybean (Glycine max (L.) Merrill; Fabales: Fabaceae) in several southeastern states. Megacopta cribraria dispersed rapidly from 2009 to 2013, after which its spread rate declined sharply. Despite this decline, established populations have remained stable. This decline may be partially attributed to natural enemies of kudzu bug. For example, the exotic egg parasitoids Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) and Paratelenomus saccharalis (Dodd) (Hymenoptera: Platygastridae) have been occasionally detected in the United States since 2016 and 2013, respectively. We recovered O. nezarae from M. cribraria eggs collected from wild patches of kudzu (Pueraria montana Lour. (Merrill) var. lobata (Willd.)) throughout summer 2017. Although the occurrence of O. nezarae in southern Georgia has been suggested based on exit holes from kudzu bug eggs, to our knowledge, this report is the first to document and confirm recovery of O. nezarae from kudzu bug eggs in both Tennessee and Georgia. In addition, at the time of collection in 2017, this recovery was the first confirmation of this species from kudzu in North America. This early-season natural enemy combined with the later-occurring entomopathogen Beauveria bassiana (Balsamo-Crivelli) Vuillemin may reduce and maintain kudzu bug densities, which could lessen economic impacts on soybean producers.