Entry Angle Research Articles

Femtosecond laser-assisted cataract surgery: an incision efficacy review

Purpose: This study reviewed the scientific literature on corneal incisions in femtosecond laser-assisted cataract surgeries compared to keratome incisions in conventional phacoemulsification. Conclusion: There are differences in the results of the studies. Automated incisions are more advantageous in the structure of the cut (reproducible tunnel architecture) and healing time of incisions (epithelial and endothelial gap, endothelial misalignment, Descemet membrane detachment and corneal thickening) compared to manual incisions, in addition to astigmatism correction <1.0 diopter with arcuate incisions. The induction of astigmatism and corneal aberrations is similar between the techniques. Incisions with an angle of entry of 110º in the cornea, triplanar shape, and width of <2.65 mm with the femtosecond laser platforms have presented the best results.

A Novel Technique for Obtaining Neutral Entrance Angle During Suprapatellar Nailing of Tibial Shaft Fractures

A Novel Technique for Obtaining Neutral Entrance Angle During Suprapatellar Nailing of Tibial Shaft Fractures

Improvement of housing with knives crushers for non-tillage technology

The paper gives justification of the options of the housing with crumbling knives for non-tillage technology. The dumpless housing with crumbles carries out intensive crumbling of the soil of the lower and middle arable soil layer. The body consists of a ploughshare, a ploughshare expander, knives and a chisel. When determining the parameters of a non-shaft housing based on a ploughshare, adopt a triangular wedge. Analytical dependences for determining the parameters of the components body without shaft are obtained. According conducted theoretical studies, without a tipper is 0. 45 m, entry angle the ploughshare on the soil is 25°, nook of installation relative to the direction of travel is 42°, corner of installation with respect to the bottom egate is 35°, grinder the blade quantity 4, the elevated is 35 mm, the longitude is 120-140 mm, the angle of installation regarding the direction of peregrinate is 10°, the installation related to the skyline is 30°, the height body sans a tipper is 420 mm processing is provided.

An algorithm for cognitive fusion targeted tumor puncture based on 3-D mathematical modelling

BackgroundPercutaneous puncture is an important means of tumor diagnosis and treatment. At present, most puncture operations are still based on imaging location and clinical experience, and quantitative and accurate targeted puncture cannot be achieved. How to improve the accuracy of percutaneous tumor puncture, avoid errors to the greatest extent, reduce the occurrence of complications, and improve the overall clinical diagnosis and treatment quality and curative effect, are scientific problems worthy of further study. MethodIn the present study, mathematical modeling was first used to construct the tumor puncture path, determine the needle entry angle, and define the relevant limited parameters and the substitution formula. Secondly, relevant parameters were extracted from CT and other imaging data and substituted into formulas, the deviation angle and puncture path were determined, and the personalized tumor puncture scheme was carried out. Third, targeted puncture was precisely implemented under the guidance of B-ultrasound. Compared with the traditional empirical puncture, our model improved the accuracy, decreased the puncture time, and reduced the pain of diagnosis and treatment for patients. ResultsA tumor-targeted puncture model was established based on mathematical theory and imaging data. By extracting clinical data, such as tumor radius, projection distance of tumor center and projection distance from puncture point to body surface, the optimal puncture deviation angle was modeled and calculated and a personalized puncture scheme was established. Compared with the conventional method, our model markedly increased the puncture accuracy rate by ∼30%. The puncture number was decreased by ∼50% using our model. Furthermore, our model shortened the operation time by 20% to ease pain of patients and guarantee greater security for patients. Doctor satisfaction and patient discomfort scores were examined. Our model improved doctor satisfaction by ∼20% and reduced subjective discomfort of patients by ∼25%. These data revealed that the model could markedly improve the accuracy and efficiency of puncture, clinical efficacy and accuracy of tumor diagnosis. Additionally, the confidence of doctors in the operation was greatly enhanced and patient discomfort was greatly reduced. ConclusionThe present study analyzed in detail how to find the best puncture path using a mathematical model. Based on the mathematical model of cognitive fusion puncture, combined with clinical personalized data and mathematical calculation analysis, accurate puncture was effectively realized. It not only greatly improved the effectiveness of puncture, but also ensured the safety of clinical patients and reduced injury, which means it may be worthy of clinical application.

A retrospective analysis of mid-infrared observations of the Comet D/Shoemaker-Levy 9 and Wesley impacts on Jupiter

We present a retrospective analysis of Earth-based mid-infrared observations of Jupiter capturing the aftermath of the impacts by Comet D/Shoemaker-Levy 9 (henceforth SL9) in July 1994 and the unknown object previously termed the “Wesley impactor” in July 2009. While the effects of both impacts on Jupiter’s atmosphere have been reported previously, we were motivated to re-examine both events using consistent data reduction and analysis methods to enable robust, quantitative comparisons. To study the aftermath of the SL9 impacts, we examined infrared (7.8–20.5μm) spectrophotometry of Jupiter measured by the MIRAC (Mid-Infrared Camera) on NASA’s Infrared Telescope Facility on July 20, 21 1994 and low-resolution (R = 100) N-band (7–13μm) spectroscopy measured by SpectroCam-10 on the Palomar Telescope on July 22 1994. To study the aftermath of the Wesley impact, we examined low-resolution (R = 100) N- and Q-band (R = 80, 17–25μm) spectroscopy recorded by Gemini South Telescope’s T-ReCS (Thermal-Region Camera Spectrograph). We analyzed the observations with two independent analyses: (1) a least-squares search over a grid of candidate mineral species to determine the composition of impact residue and (2) a radiative transfer analysis to derive atmospheric information. We observe that the SL9 impact sites are enhanced in stratospheric CH4 emissions at 7.9μm, due to shock heating and adiabatic compression from plume re-entry, and from 8.5–11.5μm due to stratospheric NH3 emission and non-gaseous cometary material, in agreement with previous work. In the G impact site, we derive NH3 concentrations of 5.7−2.8+4.5 ppmv at 30 mbar. In new findings, we find that the SL9 impact sites also exhibit a non-gaseous emission feature at 18–19μm. The non-gaseous emission at 8.5–11.5μm and 18–19μm emission result is best reproduced by predominantly amorphous olivine and (obsidian) silica at similar abundances. The Wesley impact site exhibits enhanced emissions from 8.8–11.5μm and 18–19μm. We found this could be reproduced by predominantly amorphous olivine and stratospheric gaseous NH3 at concentrations of 150−121+338 ppbv retrieved at 30 mbar. Stratospheric abundances of NH3 are a factor of ∼40 higher in the SL9 impacts compared to the Wesley impact, which confirms the former reached deeper, NH3-richer altitudes of Jupiter’s atmosphere compared to the latter. The absence of silicas in the Wesley impact would place an upper limit of 10 km/s on the incident angle and ∼9∘ on the entry angle of the impactor such that shock heating associated with the impact did not reach temperatures required for silicates to be converted.

Effect of the length of truncated nozzle with a tip on its thrust characteristics

Nowadays, for solving new problems, rocket engine nozzle developers are increasingly turning to non- traditional nozzle configurations that differ from the classic Laval one. A relatively new line in the design of supersonic nozzles is the development of the so-called bell-shaped nozzle, which, unlike the classical Laval nozzle, has a larger angle of entry into the supersonic part of the nozzle. In this case, dual bell nozzles, which have two flow expansion sections in their supersonic part, are considered. However, the effect of the length ratio of the two flow expansion sections of a truncated nozzle on its characteristics has not yet been studied. The goal of this work is to determine the effect of the length of the upstream conical supersonic section on the static pressure distribution in the nozzle and its thrust characteristics with the shape of the bell-shaped tip kept unchanged. The nozzle characteristics were studied using the ANSYS Fluent computing package. It was shown that the flow patterns in the nozzle (velocity fields) change with the length of the conical part upstream of the tip and the underexpansion degree. Under terrestrial conditions (Pн = 1 bar), all variants show a developed separation zone that starts from the corner point where the tip is connected to the conical part. In this case, the pressure on the nozzle wall is nearly equal to the ambient pressure. At a large flow underexpansion degree (P0 = 300 bar) and in low-pressure conditions conditions (Pн =0.1 bar), the flow in the tip is adjacent to the wall. At a large flow underexpansion degree, the pressure in the nozzle increases from the corner point to the tip exit, and the pressure at the tip exit increases with decreasing tip length. The nozzle thrust coefficient decreases with increasing flow underexpansion degree, and it reaches a constant value after the flow becomes adjacent to the tip wall downstream of the corner point where the tip is connected to the nozzle. At high flow underexpansion degrees, the nozzle thrust coefficient is higher for a nozzle with a longer conical part. The calculated results are in good agreement with experimental data on nozzles of this type.

Ship bow shape effects on brash ice channel resistance

This study investigated the effects of different bow shapes on channel resistance. In this paper, specifically examined angles: the waterline entrance angle (α), the stem angle at the centerline (φ1), and the stem angle at the waterline at breadth B/4 (φ2). Several ship models with different bow shapes were generated by combining these angles. Using these models, we evaluated the resistance of the brash ice channel numerically. Results were compared to channel resistance in the Finnish–Swedish Ice Class Rules (FSICR). Additionally, we investigated trends of resistance for varied α, φ1, and φ2.Results show that the resistance obtained in our simulation was as small as 1/4 of the resistance in FSICR. However, linear correlation was found between our simulation results and the calculations in FSICR. Our simulations show qualitative agreement. When calculating channel resistance for brash ice without consolidated layers, φ1 is not incorporated in the FSICR resistance equation. Therefore, effects of φ1 cannot be observed in FSICR. Simulation results show that the resistance decreases as φ1 increases. As φ2 increases, channel resistance also increases. The FSICR resistance formula shows this trend irrespective of α. However, our calculation results show that as α decreases, the effect of φ2 also decreases. For FSICR, the channel resistance does not change markedly when α is changed from 15 degrees to 25 degrees. It sometimes decreases. When α is increased from 25 degrees, the resistance increases unconditionally in all cases. In this simulation, the resistance increases constantly when α increases.

Study on Impact Load and Head Cap Load Reduction Performance of Vehicle Entering Water at High Speed

Aiming at the problem of high-speed entry of vehicles with a diameter of 200 mm, a numerical model of high-speed entry of vehicles is established based on the arbitrary Lagrange–Euler (ALE) algorithm, and the numerical simulation of high-speed entry of flat-nosed and round-nosed vehicles is carried out. On this basis, the experimental research on the entry of vehicle with buffer caps is carried out. The following conclusions are obtained through simulation. The peak value of the axial load of the vehicle raises with the increase of the inlet velocity and angle, while the stable value only raises with the increase of the inlet velocity. The impact load on the round-nosed vehicle is obviously smaller than that on the flat-nosed vehicle when the water entry angle is greater than 80°. The peak value of axial load can be reduced by 22% when entering water vertically at 100 m/s. The following conclusions are obtained through experiments. The buffer head cap has a significant load reduction effect. It shows compaction, cracks and breakage under the impact of water. These processes can absorb part of the impact energy, reduce the peak value of axial load and increase the pulse width. The load reduction rate grows from 4.7% to 18.5% when the length of the buffer head cap is increased from 200 mm to 300 mm while the water inlet speed is the same. The damage level of the head cap increases sharply, and the load reduction rate raises when the water entry speed is increased while the length of the buffer head cap is the same.

The Criterion of Access to the Sky View in Residential Environment Architectural Designing

Abstract Standards specifying the requirements for daylight in shaping the interiors of residential buildings do not cover issues related to visual perception and the role of light as a carrier of images of the outside world. The general recommendations in this regard, given in the 2018 European Lighting Standard can hardly be considered an unambiguous, precise normative regulation. According to the author, the inalienable element of the view through the window is the image of the sky, which is the basic reference in human perception of the space of the external environment. The aim of the research is to identify the main determinants for ensuring access to the sky view from apartments in housing estates with high intensity of development. The analyzes are based on the author's simple graphical research methods capable of simulating the visual perception of images of the external environment space through a window. The key parameter in the analyzes is the vertical viewing angle, called the sky view entry angle. Its minimum value set at 7.5°C is of fundamental importance in shaping the geometric relations between neighbouring buildings. The research results oblige, in the context of the paradigm of sustainable housing development, to recognize the criterion of access to the sky view from residential interiors as a mandatory design guideline.

Digital versus radiographic accuracy evaluation of guided implant surgery: an in vitro study

BackgroundCone-beam computed tomography (CBCT) is the most widely used method for postsurgical evaluation of the accuracy of guided implant surgery. However, the disadvantages of CBCT include radiation exposure, artifacts caused by metal implants, and high cost. Few studies have introduced a digital registration method to replace CBCT for evaluating the accuracy of guided surgery. The purpose of this study was to compare digital registration to conventional CBCT in terms of the capacity to evaluate the implant positioning accuracy of guided surgery.Materials and methodsThis in vitro study included 40 acrylic resin models with posterior single mandibular tooth loss. Guided surgery software was used to determine the optimal implant position; 40 tooth-supported fully guided drilling templates were designed and milled accordingly. After the guided surgery, the accuracies of the surgical templates were evaluated by conventional CBCT and digital registration. For evaluation by conventional CBCT, postsurgical CBCT scans of the resin models were performed. The CBCT data were reconstructed and superimposed on the implant planning data. For digital registration, we constructed a virtual registration unit that consisted of an implant replica and a scan body. Next, we obtained postsurgical optical scans of resin models with the scan body. The postsurgical implant position was identified by superimposition of the registration unit and optical scan data. The implant planning data and postsurgical implant position data were superimposed; deviations were reported in terms of distance for implant entry/apex point and in terms of angle for the implant axis. Interclass correlation coefficients (ICCs) and Bland–Altman plots were used to analyze the agreement between the two evaluation methods.ResultsThe ICCs between the two methods were 0.986, 0.993, and 0.968 for the entry point, apex point, and angle, respectively; all were significantly greater than 0.75 (p < 0.001). Bland–Altman plots showed that the 95% limits of agreement of the differences were − 0.144 to + 0.081 mm, − 0.135 to + 0.147 mm, and − 0.451° to + 0.729° for the entry point, apex point, and angle, respectively; all values were within the maximum tolerated difference.ConclusionConventional CBCT and digital registration showed good agreement in terms of evaluating the accuracy of implant positioning using tooth-supported surgical templates.

Prism adaptation response and surgical outcomes of acquired nonaccommodative comitant esotropia

ABSTRACT Purpose To investigate the clinical factors influencing the prism adaptation response of acquired non-accommodative comitant esotropia (ANAET) and evaluate the surgical outcomes. Study design Retrospective observational study. Methods This study assessed patients with ANAET who underwent strabismus surgery based on the results of a short prism adaptation test (PAT). Patients wore Fresnel trial prisms based on alternate prism cover tests in outpatient clinics. The cover test was then performed after 15–20 minutes; if the deviation increased, the power of the prism was increased to neutralize the angle. The test was repeated until the angle was stable. Patients were classified as either prism builders (angle increased by ≥ 10 prism diopters [PD] compared with the entry angle) or prism non-builders (angle increased by < 10 PD). The following clinical characteristics were noted: age at onset, age at surgery, duration of esotropia, refractive error, angle of deviation, presence or absence of intermittent esotropia at near, and pre- and postoperative sensory status. Results A total of 41 patients (median age, 15.4 years) were evaluated. The mean (standard deviation) spherical equivalent refractions were −3.03 (3.33) diopters (D) and −3.05 (3.23) D in the right and left eyes, respectively. Twenty-seven (66%) patients were prism builders. The prism builders had greater myopia (builders vs. non- builders, right eye: −3.97 [2.97] vs. −1.22 [3.33] D, P = .01; left eye: −4.08 [2.78] vs. −1.07 [3.20] D; P = .003), lower angle of deviation at near (median [interquartile range] 30.0 [20.0, 35.0] vs. 42.5 [35.0, 49.4] PD; P = .009), much more preoperative intermittent esotropia or esophoria at near (44% vs. 7%, P = .03) and diplopia (96% vs. 64%, P = .01), and better postoperative stereoacuity (50 [40, 110] vs. 100 [60, 400] arcsec, P = .02) than the prism non-builders. The overall success rate was 83%, without a significant difference between the two groups (builders vs. non-builders, 89% vs. 71%, P = .21). Conclusion In cases of myopic refractive error, a small entry angle with intermittency at near, and good binocularity, it is recommended that surgery is performed based on prism-adapted angle to prevent under-correction.

ОБОСНОВАНИЕ И ОПРЕДЕЛЕНИЕ ПАРАМЕТРОВ БОРОЗДООБРАЗОВАТЕЛЯ КАРТОФЕЛЕСАЖАЛКИ

Furrow formation is one of the most labor-intensive operations in potato cultivation technology. The article discusses the justification and determination of furrower parameters of the potato planter. Analytical dependences of the height of the junction point of the disks and the width of the furrow bottom are obtained, taking into account the technological parameters, its design features and the physical and mechanical properties of the soil. Potatoes are planted in the usual way. The main row spacing in our country is 70 cm. However, in areas of high humidity and in irrigated areas, wide-row planting with a row spacing of 90 cm is used. In some areas of the European part, in arid areas, potatoes are planted with a row spacing of 60 cm. By the time of harvesting, the potato field has a ridged appearance, obtained as a result of hilling, where the height of the ridges is 11…20 cm. The angle of the row seed drills is that the vanishing point of the coulter rises above the bottom of the furrow by 6.3 cm. With an increase in the angle of entry of the coulter into the soil from 2° to 11°, the depth of the coulter travel increases. At angle values from 3° to 8°, the stroke depth approaches the optimum (12…18 cm).

Computational study on the uptake of soft nanoparticles and nanoparticle cluster by cells

Nanoparticles (NPs) and exosomes used to transport therapeutic drug molecules to cells have attracted considerable attention in biopharmaceuticals. However, soft NPs entering cells with different angles are hard to be simulated by traditional theoretical endocytic models, let alone clustering of NPs with varied shapes. Here, the endocytic model based on the co-rotational grid method is implemented. The endocytosis of a single soft NP and a nanoparticle cluster (NPC) are investigated. Both the actin force and the dynamic assembly of the clathrin coat have been considered. The results show that NP size is the main factor affecting the internalization efficiency, followed by the aspect ratio, and finally the entry angle. The increase in NP size, aspect ratio, and entry angle will lead to a decrease in internalization efficiency. However, the final configuration of the endocytic vesicle and the internalization efficiency are both independent of the entry angle for NPs with an equivalent radius greater than 15 nm. Besides, a large entry angle can assist a large soft NP in successfully entering cells. The increase in NP stiffness also reduces the internalization efficiency considering the actin force required during endocytosis. The transformation of the NP from the inclined configuration to the vertical configuration is mainly due to NP deformation. Compared with a single NP, NPC has a lower internalization efficiency. The results provide new mechanistic insights into the endocytosis of soft NPs and NPCs.

Classification of the collapse of a composite fairing during the oblique high-speed water entry

The crushing behaviors of the buffer devices for the projectile in the high-speed oblique water entry process were investigated numerically. The high-speed water entry tests of the aluminum alloy projectile with a sabot were conducted to study the cavity formation, also used to validate the numerical method. Detailed material parameters of three kinds of foams including expanded polystyrene foam (EPS), closed-cell aluminum foam, and rigid polyurethane foam (PU), and the composite material for the fairings were obtained from a series of statics and dynamics mechanics experiments. Twelve collapse modes of the thin-walled fairings were identified during the oblique water impact. The effects of the length of the fairing, foam type, and water entry angle on these failure modes, and the peak impact acceleration of the projectiles were revealed. The results showed that the load reduction efficiency (LRE) is dependent on both entry angle θ and dimensionless length LFA/DPJ. The critical load reduction water entry angle (CLRA) is linearly related to LFA/DPJ. Among the three kinds of foam materials, the closed-cell aluminum foam has the best load reduction performance (up to 72.82%) and the widest range of load reduction water entry angles. Meanwhile, the EPS foam makes the projectile withstand the largest impact overload (up to 11.43%).

A Simple Practical Method to Show the Forces of the Surface Propeller during One Cycle

This paper presents a simple practical method to show the forces of the surface propeller during one cycle and the effect of the immersion depth and blade number on the performance of the surface propeller (SP). During one cycle of the propeller rotation, each blade enters the water and exits from it. The entry and exit angles are determined by the geometrical formulas. Three forces (thrust, horizontal and vertical forces) and torque are calculated by assuming that the thrust and torque are uniformly distributed on the blade. The results are presented at three immersed ratios (IT=0.25, 0.33, 0.5) for three blade numbers (Z=3, 4, 5). Many results of thrust and torque as well as horizontal and vertical forces are presented and discussed.

The pros and cons of multiple puncture in percutaneous balloon compression for treatment of trigeminal neuralgia.

Percutaneous balloon compression (PBC) is an effective and well-established surgery for treating trigeminal neuralgia (TN). However, if the initial attempt fails to produce a distinct pear shape, there is no conventional strategy to follow: repeat a few days later or re-puncture? This study aimed to analyze the risk and gain of re-puncturation in PBC surgery for TN treatment. We reviewed radiographs and medical records from 79 consecutive PBC cases. The complications and surgical outcomes were compared between one-time success pears and multiple re-puncturing pears. Re-puncturing methods included selecting a more appropriate entry point, a more possible entry angle, finding a stretchy spot around the margin of foramen ovale (FO) with a trocar, and exploring the direction with more resistance using a thinner guiding needle. In 50% of cases, satisfactory pears were obtained after the first puncture, and in 35% of cases, satisfactory pears were obtained following re-puncturation. Except for hemihypogeusia, which was significantly more in multiple punctures cases (p < 0.05), no additional adverse effects were statistically different between the two groups. There are very few rare complications associated with re-puncturation. Log-Rank test of pain-free rate revealed no statistically significant differences between the two groups (p = 0.129). This study establishes the safety of re-puncturation in PBC surgery for TN treatment. The operation increases pears and does not cause any serious complications. The surgical outcomes of re-puncturation pears are almost identical to those one-time success pears.

The Traspena meteorite: heliocentric orbit, atmospheric trajectory, strewn field, and petrography of a new L5 ordinary chondrite

ABSTRACTThe Traspena meteorite fell on 2021 January 18 about 20 km south-east of the city of Lugo (Galiza, Spain), shortly after a huge and bright fireball crossed the sky for 4.84 s. Astrometric measurements obtained from the fireball cameras of the Universidade de Santiago de Compostela (USC) as well as from many casual videos were used to determine the atmospheric trajectory of this meteoroid which penetrated the atmosphere and generated sound waves that were detected at three seismic stations. The original meteoroid had a diameter of about 1.15 m and a mass around 2620 kg. It impacted the Earth’s atmosphere with a steep entry angle of about 76${_{.}^{\circ}}$7 from a height of 75.10 km until fading away at 15.75 km with a velocity of 2.38 km s−1. Before the impact, this small asteroid was orbiting the Sun with a semimajor axis of 1.125 au, a moderate eccentricity of 0.386, and a low inclination of 4${_{.}^{\circ}}$55. A weak evidence of dynamic link with the PHA (Potential Hazardous Asteroid) Minos was investigated. During the atmospheric entry, two major fragmentation events occurred between heights of 35 and 29 km at aerodynamic pressures between 1 and 5 MPa. The strewn field was computed after calculating the individual dark flights of the main body along with two smaller fragments. Fortunately, 2 month after the superbolide, a 527-g meteorite was found. It was examined using several geochemical and petrographic analyses which allowed us to classify it as a moderately shocked (S3) L5 ordinary chondrite with a bulk density of 3.25 g cm−3.

Mechanistic force model for double-phased high-feed mills

Being able to predict cutting forces, torque and power in machining applications allows to check their influence on the quality of the product, to assess the feasibility of the process and to compare different operations for sustainability purposes. In this paper, the analytical development of a mechanistic model for cutting forces prediction for high-feed mills is carried out. High-feed cutters are featured by extremely low lead angles, leading to a gradual engagement of the cutter inside the workpiece. This fact prevents the mechanistic literature formulation to accurately compute the undeformed instantaneous chip section of each cutter, and thus to correctly predict the spindle torque and power. A closed analytical formulation for the mechanistic cutting force model, including an improved chip thickness formulation with variable entry and exit angles and double-phased cutter geometry, is presented. Experimental cutting tests using double-phased high-feed mills were carried out on Ti6Al4V with variable feed rate per tooth, cutting speed and axial depth of cut. The model was assessed by comparing the performances of the literature model and the developed high-feed one in the identification of specific force coefficients — SFC. The identified SFC resulted to belong to two statistically different populations. SFC 95% confidence intervals were found to be significantly narrower with respect to the literature ones. Kt,c 95% confidence intervals were equal to (1085; 1426) MPa and (970; 2423) MPa for the proposed and literature model, respectively. The validity of the proposed model was assessed in terms of mean forces, mean spindle torque and mean spindle power prediction capabilities. The Root Mean Squared Prediction Error for the proposed model resulted to be remarkably lower (15 N, 0.33 Nm, 29 W) with respect to literature model (41 N, 1.25 Nm, 120 W).

Experimental Research on the Influences of Head Shape and Surface Properties on the Water Entry Cavity

Addressing the problem of the influence of surface properties on the cavity in the process of a moving body entering water, especially the problems of water entry speed and the cavitation evolution of the round-head, air-delivered projectile that has many practical applications, a self-designed launch platform and high-speed camera were used, and the MK46 was used as a prototype to conduct scaled model experiments with different head form types and different surface properties. This paper describes the general process of the moving body entering the water and the generation of the cavity. The relationship between the re-injection flow, the local cavity number and the cavity stability is discussed. At the same time, the effects of head shape, launch velocity and surface wettability on the cavity evolution and motion characteristics were analyzed, including 0°, 57°, 70°, 90° and 180° hemispherical angle-head projectiles with speeds of 2.2 m/s and 3.95 m/s, so as to observe the cavity development and ballistics. The results show that hydrophobic surfaces are more prone to cavities when entering water vertically at low speeds. The influencing factors of water entry ballistics are often the combined effects of head shape, water entry speed and water entry angle. The speed of the hydrophilic surface models with head hemisphere angles of 57 degrees and 70 degrees entering the water is the fastest. This provides a reference for us to design the shape of the projectile. The internal relationship between the cavity shape and the ballistic characteristics is based on the premise that the cavity will complicate the force on the model. The cavity affects the ballistic characteristics of the model by affecting the forces on the model.

Sagittal imaging study of the lumbar spine with the short rod technique.

The short rod technique (SRT) is a novel method for lumbar pedicle screw placement to reduce surgical trauma and avoid damage to the facet joint and articular surface. The core concept is to change the entry point and angle of the screw on the vertebrae at both ends in the sagittal plane to shorten the length of the longitudinal rods. The purpose of this study is to determine the sagittal screw angle (SSA) and its safe Maximum (MAX) value on each lumbar vertebra for the SRT and to observe the shortening effect on the longitudinal rods. A total of 152 healthy adults were investigated by measuring the lumbar spine lateral view images. The SSA and MAX-SSA were measured with SRT as reference to the conventional placement technique method. The distance between the entry points of the proximal and distal vertebrae was measured to compare the changes in the length of the longitudinal rods using the two screw placement techniques. + SSA increased from L1 to L4, and -SSA increased from L2 to L5, in which the -SSA of L2, L3, and L4 were significantly greater than those of + SSA (P < 0.05). + MAX-SSA at L1-L4 was 23.26 ± 3.54°, 23.68 ± 3.37°, 24.12 ± 3.29°, and 24.26 ± 3.42°, respectively. -MAX-SSA at L2-L5 was 36.25 ± 3.26°, 38.26 ± 3.73°, 38.62 ± 3.63° and 37.33 ± 3.31°, respectively. Theoretical reductions by calculation for the 2-segment lumbar pedicles were: L1-2: 9mm, L2-3: 9.29mm, L3-4: 6.23mm, and L4-5: 7.08mm; And the 3-segment lumbar pedicles were: L1-3: 16.97mm, L2-4: 16.73mm, L3-5, and 18.24mm, respectively. The application of the SRT to lumbar pedicles is a safe screw placement method that can significantly shorten the length of the used longitudinal rods.