Flat Head Research Articles

A framework for three-dimensional statistical shape modeling of the proximal femur in Legg-Calvé-Perthes disease.

The pathomorphology of Legg-Calvé-Perthes disease (LCPD) is a key contributor to poor long-term outcomes such as hip pain, femoroacetabular impingement, and early-onset osteoarthritis. Plain radiographs, commonly used for research and in the clinic, cannot accurately represent the full extent of LCPD deformity. The purpose of this study was to develop and evaluate a methodological framework for three-dimensional (3D) statistical shape modeling (SSM) of the proximal femur in LCPD. We developed a framework consisting of three core steps: segmentation, surface mesh preparation, and particle-based correspondence. The framework aims to address challenges in modeling this rare condition, characterized by highly heterogeneous deformities across a wide age range and small sample sizes. We evaluated this framework by producing a SSM from clinical magnetic resonance images of 13 proximal femurs with LCPD deformity from 11 patients between the ages of six and 12 years. After removing differences in scale and pose, the dominant shape modes described morphological features characteristic of LCPD, including a broad and flat femoral head, high-riding greater trochanter, and reduced neck-shaft angle. The first four shape modes were chosen for the evaluation of the model's performance, together describing 87.5% of the overall cohort variance. The SSM was generalizable to unfamiliar examples with an average point-to-point reconstruction error below 1mm. We observed strong Spearman rank correlations (up to 0.79) between some shape modes, 3D measurements of femoral head asphericity, and clinical radiographic metrics. In this study, we present a framework, based on SSM, for the objective description of LCPD deformity in three dimensions. Our methods can accurately describe overall shape variation using a small number of parameters, and are a step toward a widely accepted, objective 3D quantification of LCPD deformity.

Mitogenome-Based Phylogeny with Divergence Time Estimates Revealed the Presence of Cryptic Species within Heptageniidae (Insecta, Ephemeroptera).

Heptageniidae are known for their flat heads and bodies and are divided into three subfamilies. Despite the extensive diversity within this group and considerable efforts made to understand their evolutionary history, the internal classifications and origin time of Heptageniidae remains controversial. In this study, we newly sequenced 17 complete mitogenomes of Heptageniidae to reconstruct their phylogenetic positions within this family. Because of the ambiguous time of origin, our study also estimated the divergence time within Heptageniidae based on five fossil calibration points. The results of BI and ML trees all highly supported the monophyly of Heptageniidae and three subfamilies. The phylogenetic relationship of Rhithrogeninae + (Ecdyonurinae + Heptageniinae) was also recovered. The divergence time showed that Heptageniidae originated from 164.38 Mya (95% HPD, 150.23-181.53 Mya) in the mid-Jurassic, and Rhithrogeninae originated from 95.54 Mya (95% HPD, 73.86-120.19 Mya) in the mid-Cretaceous. Ecdyonurinae and Heptageniinae began to diverge at 90.08 Mya (95% HPD, 68.81-113.16 Mya) in the middle Cretaceous. After morphological identification, analysis of the mitogenome's composition, genetic distance calculation, phylogenetic analysis, and divergence time calculation, we suggest that two different populations of Epeorus montanus collected from Aksu, Xinjiang Uygur Autonomous Region (40°16' N, 80°26' E) and Xinyuan, Xinjiang Uygur Autonomous Region (43°20' N, 83°43' E) in China are cryptic species of E. montanus, but further detailed information on their morphological characteristics is needed to fully identify them.

End Connectors Stress Analysis for Horizontal Pressure Vessel

The gas and oil industry extensively utilizes horizontal pressure vessels to store its primary sources. These vessels are designed to withstand high levels of pressure and to release contents in a controlled manner. Although the sphere-shaped storage container is widely regarded as a better-engineered structure, the ease of manufacturing makes horizontal pressure vessels the preferred choice. This paper presents an in-depth analysis of stress distribution in horizontal pressure vessels with various end connections, including hemispherical, ellipsoidal, flat head, and tori-spherical configurations. The study involves analytical and finite element analysis (FEA) to compare the stress distribution across these above-mentioned end connections. Key vessel dimensions, such as internal diameter, vessel thickness, and end connections, have been determined through analytical design. A detailed structural analysis aided in determining which among the different end connectors is best suitable for industry usage.

Bioecology of African Catfish and Poisonous Marine Fish (Actinopterygii: Teleostei)

Clarias gariepinus (Burchell, 1822) (Siluriformes: Clariidae) the African catfish is a large, eel-like fish, usually dark gray or black on the back and white on the ventral part, a smoother flat bony head compared to other catfish, and a wide, terminal mouth with four pairs of barbels. It has an accessory respiratory organ that allows it to breathe atmospheric air and survive in environments with low oxygen levels. They remain in the muddy substrates of lakes and occasionally swallow air through their mouths. It can leave the water at night and walk on dry land using its strong fins and spines, in search of food or migrating to other bodies of water to reproduce. During aggressive intraspecies interactions, this species was observed to generate single-phase discharges through electrical organs in its head that lasted from 5 to 260 ms. The manuscript aimed to investigate the bioecology of African catfish and venomous marine fish (Actinopterygii: Teleostei). To develop the study, the methodology used an integrative literature review, which is a synthesis process with the objective of expanding the understanding of knowledge and achieving the expected results. In this way, the researcher can prepare an integrative review with different purposes, which can be aimed at defining concepts, reviewing theories, or methodological analysis of studies included on a given topic. In its construction process, it is necessary to go through six distinct stages, which are: identification of the theme and selection of the hypothesis or research question; establishment of inclusion and exclusion criteria for studies/sample or literature search; definition of information to be extracted from selected studies/categorization of studies; evaluation of included studies; interpretation of results; and presentation of knowledge review/synthesis. To carry out the study, a search for scientific articles was carried out through the Virtual Health Library, in the SCIELO, LILACS, and Pubmed databases.

DESIGN AND ANALYSIS OF PRESSURE VESSEL USING DIFFERENT MATERIALS

This project explores the field of Finite Element Analysis (FEA) in relation to pressure vessels that have different head configurations, while ensuring that the cylindrical volume and thickness remain uniform. The project adheres to ASME standards, specifically Section VIII, Division I, and focuses on designing a pressure vessel that can withstand a pressure of 8 bar within a volume of 24 liters. The main objective of using FEA is to identify areas of stress concentration in each head design. In industrial settings, pressure vessels play a crucial role in containing fluids or gases under varying pressures. The choice of head configuration significantly impacts the distribution of stress and the overall structural strength. This project specifically utilizes ANSYS software for static and thermal analyses to compare stress distribution in pressure vessels with flat heads, elliptical heads, and other common head designs. The goal is to identify configurations that exhibit lower stress levels, with a particular emphasis on practical scenarios that favor elliptical heads. Additionally, the project explores finite element modeling techniques to evaluate pressure vessels made from different materials such as Nimonic 80A and SA516 Gr70 under high-stress conditions

Metacarpophalangeal hyperextension in trapeziometacarpal osteoarthritis: Relationship to first metacarpal head shape, and clinical impact

PurposeThe aim of this study was to determine whether the shape of the first metacarpal head influences metacarpophalangeal hyperextension, and to evaluate the influence of metacarpophalangeal hyperextension on hand pain and function in patients with trapeziometacarpal osteoarthritis. Methods362 patients with painful basal thumb osteoarthritis were evaluated over a 2-year period. Pain rating on a visual analog scale, trapeziometacarpal and metacarpophalangeal motion, and grip and pinch strength were evaluated. The shape of the metacarpal head was assessed on strict lateral radiographs using the “A/r” ratio. ResultsRound metacarpal heads had significantly greater and more frequent metacarpophalangeal hyperextension than flat heads (28° vs. 8°, and 78% vs. 29%). Metacarpophalangeal hyperextension adversely impacted trapeziometacarpal motion in antepulsion (27° vs. 32°), abduction (25° vs. 30°) and pinch strength (3.6 vs. 4.6 KgF). ConclusionOur findings indicate that the shape of the metacarpal head influences metacarpophalangeal hyperextension in trapeziometacarpal osteoarthritis. Metacarpophalangeal hyperextension adversely impacted pinch strength and trapeziometacarpal motion. Level of EvidenceLevel IV, Retrospective case series.

Direct spot joining of thin gauge aluminum alloy to stainless steel and joint performance in a corrosion environment

Direct joining of aluminum alloy and steel sheets offers a great potential for achieving effective structural lightweighting for transportation systems. The major challenge is how to avoid the formation of brittle intermetallic compounds (IMCs), which can be detrimental to joint load capacity and corrosion resistance. This paper presents a friction-based direct solid-state joining method for welding thin aluminum alloy (AA6061-T6) to stainless steel (316). Using a flat head friction heating tool, high quality interfacial bonding was achieved under a spot time of 20s and 1000 rpm without detrimental IMCs. The effects of an automotive-relevant corrosion environment condition on joint strengths were then examined through mechanical testing. The test results show that aluminum and stainless-steel spot joints produced by the proposed method exhibit no corrosion-induced damage or cracking nor any noticeable reduction in strengths, resulting in dominantly ductile failure mode.

Drag reduction of locomotive and practical scene

As an important tool for peoples long-distance travel and transportation, the design accuracy of the high-speed railway must be strictly controlled. In addition, the train design needs to conform to aerodynamics, such as improving the linearity of the train flow to ensure that the gas flows smoothly through every part of the train, or reducing the front pressure to reduce the wind resistance, so as to reduce the problems of train instability, high noise and high energy consumption. This paper will analyse the design concept, flow linearity and how to reduce the resistance of locomotives under high-speed motion of Shinkansen trains in Japan. Because the Shinkansen trains developed in the early and later generations are mainly flat-headed, the study of Shinkansen can understand the significance of flat-headed trains. The practicability and manoeuvrability of ' flat head and 'bullet head' locomotives and the application of locomotives in real life are analysed in detail. Finally, it is concluded that the bullet train has a large turning angle and needs to open up a special road to run smoothly, but the bullet train is faster than the flat head. The flat-head train is highly practical and suitable for driving in the city, and another advantage of the flat-head train is that it can still maintain high stability and safety when carrying many passengers.

Research of Slamming Load Characteristics during Trans-Media Aircraft Entry into Water

The trans-media aircraft water entry process generates strong slamming loads that will seriously affect the stability and safety of the aircraft. To address this problem, we design a fixed-wing aircraft configuration and employ numerical simulations with the volume of fluid (VOF) multiphase flow model, standard k-epsilon turbulence model, and dynamic mesh technique. We explore the characteristics of aircraft subjected to bang loads under different conditions. The results show the following: the pressure load on the aircraft surface increases with higher water entry velocity; larger entry angles lead to more drastic changes in the aircraft’s drag coefficient, demonstrating strong nonlinear characteristics; the greater the angle of attack into the water, the greater the pressure load on the root underneath the wing, with little effect on the pressure load on the head; and the water entry drag coefficient and average pressure load follow an increasing order of conical head, hemispherical head, and flat head. These findings provide theoretical references for studying the load characteristics during trans-media water entry of various flying bodies and optimizing fuselage structural strength.

Characterisation of Paratylenchus cacao n. sp. from Ghana, and P. enigmaticus (Nematoda: Paratylenchinae) from Belgium

Summary Paratylenchus cacao n. sp., a pin nematode associated with cocoa (Theobroma cacao L.) from Ghana, is described herein based on morphology, morphometrics and phylogenetic relationships with other species. Morphologically, P. cacao n. sp. is characterised by a female body length of 174-265 μm, body assuming a ‘C’ or ‘J’ shape after heat relaxation, a flat head, slightly set off lip region, a truncated anterior end, a rigid stylet of 24-31 μm, four lateral lines, vulval region with distinct vulval flaps, and a finely rounded tail with a mucron-like terminus. The findings of the phylogenetic analyses utilising the D2-D3 expansion segments of 28S, ITS of rDNA, and COI of mitochondrial DNA sequences indicate that P. cacao n. sp. is a species closely related to P. leptos. Additionally, based on butterhead lettuce and leek populations from Belgium, the first description of a male, SEM pictures and COI sequences of P. enigmaticus are presented. Both studies exemplify how even potentially important plant-parasitic nematode species can remain unnoticed for a long time. This suggests the need to conduct more nematode diversity studies and underscores the significance of correct nematode identification through the utilisation of tools such as integrative taxonomy.

An evaluation of cutting head design of current tunnel Boring machines and suggestions to improve machine Performance

ABSTRACT This paper evaluates cutterhead design of current tunnel boring machines (TBMs) in considerations with the actual cutting action of discs observed on the most common cutter heads. The discs on the current TBM cutter heads were found to predominantly perform asymmetrical cutting action, which generates excessive sideway forces impairing steering action of the machine. The effective s/p ratios related to actual cutting action of discs emerge to be significantly higher than those of the laboratory-determined values, and this consequently leads to adverse cyclic deepening effect. The gross lateral loads arising from excessive side forces were stated to be minimised if the adjacent discs are arranged to cut in symmetrical position by adopting appropriate cutterhead design methods suggested in this paper. Furthermore, a dynamic analysis was carried out in terms of reaction forces on cutter heads of different geometries, and it was indicated that flat face cutter heads have better steering abilities than conical or domed types, in mixed face conditions. Similar analysis on disc angular spacing also inferred that scattered type disc arrangements with equal angular spacing are preferable to cutterheads with spoke or star type lacing, in terms of cutterhead balance.

Evaluation of the Effect of Gluteus Maximus Contraction by Electrical Stimulation on Interfacial Pressure in Supine Bed Positions.

This study investigated the impact of neuromuscular electrical stimulation (NMES) to the gluteus maximus in the bed flat position (F position) and 30-degree head elevation position (30 HE position) on sacral pressure. Twenty volunteers consented to participate in this study. Sacral pressure was measured in the F position and at the 30 HE position with and without NMES in the supine positions. NMES was applied to the gluteus maximus (frequency, 50 Hz; pulse width, 300 μs) with sufficient stimulus intensity to induce muscle contraction. Sacral maximum pressure was determined as peak pressure index (PPI) by averaging the values from the central nine sensors of the maximum pressure zone. The effect of NMES on pressure gradient and the influence of sex difference were also explored. Sacral PPI was significantly lower after NMES implementation in both the F position and the 30 HE position when compared with conditions without NMES (P <0.001). The pressure gradient was also significantly decreased with NMES (P <0.001). Analysis of sex difference in subjects treated with NMES revealed a significantly greater effect on maximum sacral pressure in males than in females. Application of NMES to the gluteus maximus helps to disperse sacral pressure in supine positions. NMES on the gluteus maximus can be a clinical means to manage interfacial pressure in supine positions.

Anatomic Characteristics of Ultrasound Imaging of the Temporomandibular Joint at Rest and in Various Jaw Positions in Healthy Individuals: A Descriptive Study

This study examined the temporomandibular joint (TMJ) anatomy and biomechanics using Ultrasound (US) imaging to examine the TMJ anatomy at rest and in various positions of normal jaw movement in healthy individuals. A secondary aim was to describe US imaging parameters used to visually observed the TMJ. The study included 11 participants (8 M and 3 F; 22.9 ± 3.4 yrs) University with no history of TMJ problems. All 11 participants had some atypical anatomy (flat mandibular head, altered articular disc shape, displacement or deformation of the disc during movement) while using US imagining. No participants had current pain or dysfunction and none met the Diagnostic Criteria for Temporomandibular Dysfunction (DC-TMD) classifications for the condition. Most participants denied symptoms during testing, although one participant did have pain with retrusion and another had popping without pain. This study in part has added to the growing interest of using US imaging as modality to investigate the anatomy and biomechanics of the TMJ and the relationship to TMD. Future studies are warranted to examine TMJ anatomy and biomechanics via US imaging in order to provide further recommendations on the techniques and settings for the modality for the end-user.

DESIGN AND STATIC THERMAL ANALYSIS OF PRESSURE VESSELS WITH VARIOUS MATERIALS USING FEM

Stress assessments are required for a great deal of plant components, including the pressure vessel. A pressure vessel is a container designed to store liquids or gases at pressures much higher than the surrounding air. The finite element analysis of pressure vessels with various types of heads that maintain the same cylindrical volume and thickness is the focus of this project. The intended pressure vessel is made for 8 bar of pressure and 24 lit of volume in accordance with ASME standard section VIII, division I. In order to identify the source of the stress concentration zone in each kind of pressure vessel head at the same volume and reasonable pressure, certain end connections are evaluated under FEA. The project's goal is to use Ansys software to analyse various designs and static and thermal data. It finds that elliptical and flat head pressure vessels have lower distributed stresses than other types of heads, making them the preferred choice for most applications. It displays the fundamental construction and uses finite element modelling to analyse pressure vessels made of various materials, such as Nimonic 80A and SA516 Gr70, and with several types of heads under high stress conditions. In this project, we use the Finite Element tool to compute the estimated stresses that occur in cylindrical pressure vessels supported by two saddles under various end connection types. In order to determine the appropriate design and material, static structural analysis and thermal analysis are performed to compute the stresses in the vessel.

A Group of Urartu Pins from the Ahlat, Erzurum, and Van Archeology Museums

The data on ornaments and jewelry in the Kingdom of Urartu has been obtained from archaeological excavations rather than written documents. This study covers the data on the pins obtained from the Urartu centers in the Eastern Anatolia Region and mostly from their necropoleis. From this point of view, we analyzed the pins in Van, Ahlat, and Erzurum Archeology Museums in this study. Pins, one of the types of jewelry used for decoration, are generally thin, flat, cylindrical and mostly made of metal, and used for sewing clothes and attaching the ends of the clothes and the hair. The pin consists of a head, body and tip shaped in various ways. Some archaeological finds include a crown decorated with plant or animal figures on the head and elements called torus and bracelets on which it is placed. On the other hand, the body consists of a hole and a pin that tapers toward the tip. We analyzed the chronology, meanings, usage methods, and construction techniques of Urartian pins, which consist of animal heads, animal figures, fruit and plant heads, bud and knot heads, and flat heads. We obtained results by dating the settlement finds within the Urartu State’s borders and the contemporary neighboring region by conducting analogies between them. We also tried to identify the symbolic meanings Urartian pins can have as protection from evil, magic, decoration, status indicators, and the belief that the person will be protected forever after death.

Defensive phragmosis and cathaptosis in Trichoptera larvae

Phragmosis, or the use of specially modified body parts and associated behaviors to block an opening as defense against predators, is a commonly observed phenomenon in certain ants and termites that block entrances of their subterranean nests with large, flat heads. It has been reported in some beetles and other insects and even in some frogs. Common features of phragmosis in caddisfly larvae include a hard and usually flat body surface, with or without stout spines, and the behavior of fitting that body surface tightly in the opening of its case. A different defensive strategy occurs in snails and case-making larvae of camptosomate leaf beetles (Chrysomelidae: Cryptocephalinae and Lamprosomatinae) that protect themselves from predators by securing the openings of their shells or cases firmly against the substrate, a behavior we call “cathaptosis.” Common features of cathaptosis in caddisfly larvae include a case with its vulnerable opening oriented parallel with the substrate and accompanied by behavior that grips the substrate, fixing the case opening firmly against it when threatened. We suggest that these defensive strategies have evolved multiple times in Trichoptera, especially in case-making larvae. We demonstrate some examples and provide tentative lists of caddisflies whose larvae may have evolved these defensive strategies.

Research on Lifting Characteristics of Flat-Head Jib Tower Crane Based on Hydraulic Luffing Force

This paper investigates a design and computational method for its lifting characteristics using the flathead jib tower crane as a research object. We use a mechanical model based on classical mechanical theory and derive the expression for the characteristic lifting equation. The influence of different hinge points of the hydraulic cylinder on the boom and other hinge points of the hydraulic cylinder on the slewing frame on the lifting characteristics is discussed by using MATLAB with examples, providing a theoretical benchmark for calculating the bearing characteristics of the flat head jib tower crane.

Comparative evaluation of open tray impression technique: investigating the precision of four splinting materials in multiple implants

BackgroundThis study aimed to determine the relative positioning accuracy of multiple implants utilizing four distinct types of splinting materials.MethodsThe purpose of this in-vitro study was to compare the precision of four splinting materials in an open tray impression technique in multiple implant situations. Based on the material used for splinting, four groups were made (n = 40)- Group A: Conventional Method, Group B: Prefabricated Pattern Resin Framework, Group C: Prefabricated Metal Framework, Group D: Light Cured Pattern Resin, these groups were compared with the master model. A heat-cured clear acrylic resin and a master model were constructed. A pilot milling machine drill was used to drill four parallel holes in the anterior and premolar regions, which were later labeled as A, B, C, and D positions from right to left. Then, sequential drilling was carried out, and four 3.75‑mm diameter and 13-mm long ADIN implant analogs with internal hex were placed in the acrylic model using a surveyor for proper orientation. The impression posts were then manually screwed to the implant analogs using an open tray, and they were secured to the implants using 10 mm flat head guide pins with a 15 N.cm torque. 10 Open tray polyether impressions were made, and casts were poured. Each splinting method’s distortion values were measured using a coordinate measuring machine capable of recordings in the X-, Y-, and Z-axes. Comparison of mean distances for X1, X2, and X3 was made using the Kruskal-Wallis test, and Pairwise comparison was done using Post Hoc Tukey’s Test.ResultsThe differences between the groups were significant when assessing the distances X1, X2, and X3 (p < 0.05). The comparison of deviations between the groups revealed a statistically significant difference (p < 0.05) for the deviation distance X3 but not for the deviation distances X1 and X2. For distance Y1, the difference between the groups was statistically significant (p0.05), but it was not significant for distances Y2 and Y3. A statistically significant difference was seen in the comparison between the groups (p < 0.05) for the deviation distances Y1, Y2, and Y3. The results were statistically significant for the distance Z1 comparisons, namely, control vs. Group A (p = 0.012), control vs. Group B (p = 0.049), control vs. Group C (p = 0.048), and control vs. Group D (p = 0.021), and for distance Z3 comparison for control vs. Group A (p = 0.033). The results were statistically insignificant for the distance Z2 comparisons (p > 0.05).ConclusionsAll splinting materials produced master casts with measurements in close proximity to the reference model. However, prefabricated pattern resin bars splinting showed the highest accuracy among the studied techniques. The most recent splinting techniques using prefabricated metal framework and light-cure pattern resin showed similar accuracy.

Screw preload loss under occlusal load as a predictor of loosening risk in varying dental implant designs

PurposeScrew loosening is a critical aspect of an implant design, as it can lead to implant failure. This study proposes a methodology and qualitatively assesses the potential of screw loosening risk for various types of screw heads and implant fixture-abutment connections. It is assumed that the risk of screw loosening is related to the drop in loosening moment under occlusal loads. The methodology and an assumption is verified by confronting the results with laboratory tests. MethodsNumerical simulations supplemented with semi-empirical equations were employed to estimate a loosening moment change under occlusal loads. The loosening risk was estimated by comparing the value before and after application of a compressive occlusal load of 150N. The procedure was carried out for 289 implant designs with smooth transition between flat to tapered shape of a screw head and an fixture-abutment connection. All analyses were conducted using Abaqus software. Pearson and Spearman correlation coefficients for normalised change in a screw loosening moment drop has been computed for numerical and laboratory tests. ResultsThe statistical analysis (Pearson, ρ = 0.8, Spearman, rs = 0.85) indicates very high correlation and confirms that the general tendencies observed in laboratory tests are reflected in the proposed procedure. The procedure was used for various geometries and the following results are presented: a screw loosening drop, implant stiffness and a tightening moment. The loosening moment drop achieves the extreme values of 6% and 24%. The biggest drop is an effect of a conical implant-abutment connection and a flat screw head while the lowest was recorded for a flat implant-abutment interface regardless of a screw head type. A low drop is also observed for a strongly conical screw head. ConclusionsThe proposed methodology exhibited very good correlation when confronted with laboratory tests, supporting a screw preload reduction under occlusal load as a key factor in screw loosening. Analysis across a wide spectrum of implant designs revealed geometry significantly impacts loosening potential under occlusal loads. Two key features were identified as favourable - an abutment-fixture butt joint and a tapered screw. The results also enable prediction of qualitative geometry effects on loosening risk.

Ballistic Characteristics of High-Speed Projectiles Entering Water Vertically

The formation of supercavitation after a high-speed projectile enters water has a decisive impact on the underwater ballistic and penetration of the projectile. In this study, Ansysfluent19.0 simulation software is used to study water entry of a chosen projectile at velocities of 300, 400, 500, and 600 m/s. The underwater cavitation characteristics, trajectories, and flow-field characteristics are analyzed for a 5.8-mm caliber conical flat head projectile, as well as for t wo other projectiles of the same caliber and different head shapes — conical cone head and elliptical flat head — entering water vertically at the same velocities. The attenuation rate of water entry velocity increases with the increase of velocity. Within first 3ms, the velocity attenuation rate of the conical flat-head projectile with a water entry velocity of 600m / s is 55.6 %, while the velocity attenuation rate of the projectile with a water entry velocity of 300m / s is only 16.3 % within 3ms. Among the head shapes considered, the conical flat head projectile is the most stable for vertical water entry. The stability of an elliptical flat head projectile is worse, and the trajectory stability of a conical cone head projectile is still worse