Preparation of a Nickel Layer with Bell-Mouthed Macropores via the Dual-Template Method

A relatively static and unique bubble template is successfully realized on a microporous substrate by controlling the surface tensions of the electrodeposit solution, and a nickel layer containing macropores is prepared using this bubble template. When the surface tension of the solution is 50.2 mN/m, the desired bubble template can be formed, there are fewer bubbles attached to other areas on the substrate, and a good nickel layer is obtained. In the analysis of the macropore formation process, it is found that the size of the bell-mouthed macropores can be tailored by changing the solution stirring speed or the current density to adjust the growth rate of the bubble template. The size change of a macropore is measured by the profile angle of the longitudinal macropore, section. As the solution stirring speed increases from 160 to 480 r/min, the angle range of the bell-mouthed macropores cross-sectional profile is increased from 21.0° to 44.3°. In addition, the angle range of the bell-mouthed macropore cross-sectional profile is increased from 39.3° to 46.3° with the current density increasing from 1 to 2.5 A/dm2. Different from the dynamic hydrogen bubble template, the bubble template implemented in this paper stays attached on the deposition and grows slowly, which is novel and interesting, and the nickel layer containing macropores prepared using this bubble template is applied in completely different fields.

A generalized meshing analysis method and its application to toroidal surface enveloping conical worm drive

A generalized method for the meshing analysis of conical worm drive is proposed, whose mathematical model is more general and whose application scope is expanded. A universal mathematical model, which can be conveniently applied to left-handed and right-handed conical worm pairs and their tooth flanks on different sides, is established by introducing the helical spin coefficient and tooth side coefficient of the conical worm. The pressure angle at the reference point, which is a key parameter for calculating the curvature parameters and lubrication angle, is determined based on the unit normal vector of the worm helical surface and is no longer determined by the tooth profile angle in the worm shaft section. The above improvement breaks away from the limitation of the classic meshing analysis method based on the reference-point-based meshing theory and thus expands its application scope. The toroidal surface enveloping conical worm drive is taken as an instance to illustrate the proposed method and the numerical example studies are conducted. The approaches to determine the reference point, the normal unit vector, and the curvature parameters at the reference point are all demonstrated in detail. The numerical results all manifest that the method presented in the current work is correct and practicable.

Aerodynamic improvement of an aircraft gas-turbine engine fan

This work is concerned with the development of approaches to the aerodynamic improvement of axial-flow compressors for gas-turbine engines. The aim of this work is the aerodynamic improvement of an aircraft gas-turbine engine two-stage fan by numerical simulation of 3D turbulent gas flows. The approach used in this study features: varying the spatial shape of the fan blades for the first- and the second-stage impeller by varying the profile angle along the blade height; formulating quality criteria as the mean integral values of the power characteristics of each impeller of the fan over the operating range of the air flow rate through the impeller; and searching for advisable values of the impeller blade parameters by scanning the independent variable range at points that form a uniformly distributed sequence of small length. The basic tool is a numerical method developed at the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine, which simulates 3D turbulent gas flows using the complete averaged Navier¬–Stokes equations and a two-parameter turbulence model. It is shown that varying the profile angle along the blade height for the fan second-stage impeller allows one to increase the air compression ratio in the fan by about 2 percent throughout the operating range of the fan air flow rate without affecting the adiabatic efficiency of the fan. On the whole, by the example of the fan under study, the paper considers the assumption that the aerodynamic improvement of compressors at the initial stage can be made on an impeller by impeller basis. It is shown that in further analysis providing the gas-dynamic stability of the compressor should be accounted for. The results obtained are intended to be used in the aerodynamic improvement of multistage compressors for aircraft gas-turbine engines and various power plant.

A Device to Measure Profile Angle Clinically: Profilometer

In orthodontic diagnosis and treatment planning, soft tissue profile assessment is of prime importance. Due to the emerging soft tissue paradigm, greater emphasis has been given to the clinical examination of soft tissue function and esthetics. Various cephalometric and photographic methods were introduced in the past to assess and measure profile angle and other facial angles. Our new device, that is, profilometer, helps to measure profile angle clinically.

An evaluation of three-dimensional facial changes after surgically assisted rapid maxillary expansion (SARME)

Background: The purpose of the study was to evaluate the three-dimensional (3D) facial changes following surgically assisted rapid maxillary expansion (SARME). In 15 skeletally mature patients with maxillary transverse deficiency the planned maxillary expansion (on average 8.8 mm ± 2.3 mm) was achieved with bone-borne palatal distractor. The 3D optical scans of the facial surface were obtained before and 6 months after SARME and compared with cephalometric and regional analysis to evaluate the soft-tissue changes. Findings. The largest differences between the pre- and post-operation scans were observed for the paranasal and cheek area (1.4 ± 1.0 mm) in the lateral direction with a soft-to-hard tissue ratio of 0.22. Significant differences occurred for an increased nasal width, a decreased upper-face height with an unchanged lower height, an increased vertical philtrum height and an increased nasolabial angle. A significant increase in the facial profile angle was also observed, resulting in an increased facial convexity and anterior displacement of the upper-lip area. Conclusions. We have confirmed the widening of the nose and increased projection in the cheek and paranasal area in the lateral direction after maxillary expansion, while we found facial convexity increases, reflecting the underlying advancement of the maxilla.

Study on Clamping Mechanism of Internal and External Variable Diameter Lifting Tool for Offshore Foundation Pile

Large marine foundation piles are an important part of offshore structural pile foundations, and their lifting operations have always been a major problem in the construction and construction of marine structures. Based on IHC’s bilateral marine foundation pile spreader, this paper proposes a structural scheme of “internal and external clamping type variable diameter marine foundation pile spreader”. It solves the problem of poor adaptability of spreaders to foundation piles of the same specification and different pipe diameters. At the same time, this article has conducted in-depth research on the two clamping methods of friction clamping and wedge tooth embedded clamping. Through experiments, it is found that under the same lateral load, the load capacity of the wedge teeth tightening is three times that of the friction clamping. Aiming at the embedding and clamping method of the wedge teeth of the spreader, first of all, the influence of the tooth profile angle of the wedge teeth on their embedding performance was studied by the plastic mechanics slip line field theory and Abaqus simulation analysis. Subsequently, the elastic mechanics theory and Abaqus simulation analysis were used to study the stress characteristics of the wedge teeth during the lifting process, and the internal stress distribution was obtained. The article aims to provide a reference for the design of spreaders in actual projects.

IMPACT OF MALOCCLUSION OF CLASS ІІ1 ACCORDING TO ANGLE’S CLASSIFICATION METHOD ON FACIAL ESTHETICS

The aim: There is no information on the esthetic features of the face, which are typical of the patients with late mixed occlusion with maxillodental anomalies of Angle’s class II1 depending on the types of mandible growth in domestic and foreign literature. To study the esthetic peculiarities in the face profile, which are typical of the patients aged 10-13 with maxillodental anomalies of Angle’s class II1 with different types of mandible growth. Materials and methods: 55 patients aged 10-13 with maxillodental anomalies of Angle’s class II1 were examined. Teenagers were divided into five groups depending on the type of mandible growth. 82 photostatic images in profile were analyzed. Soft tissue analysis was performed using the Viasis method. Results: Face profile was studied based on the following indicators: convexity angle of the face profile Viazis (<V), profile angle by Schwarz (<T), the angle of the face profile shape (<gl-UL -pg), Th-me / NoV angle, nasolabial angle, labial angle (<L), mentolabial angle. Conclusions: Photometric study in 55 patients aged 10-13 with maxillodental anomalies of Angle’s class I and analysis of the results depending on the types of mandible growth prove the presence of a retrogenic type of the lower third of the face, convex shape of the profile, the development of posterior bite of varying severity. All patients were reported to have changes in the indicators of the lips position and non-harmonious development of their faces. The greatest esthetic changes were reported in the group of patients with a component of horizontal type of mandible growth.

Dolphin software accuracy in soft tissue facial profile prediction of Class II patients in orthognathic surgery

ABSTRACT Objective: The present study aimed to analyze the accuracy of the Dolphin Imaging 11.9® computer program in the surgical prediction of the soft tissue facial profile. Methods: The investigators designed and implemented a retrospective study. It was used a sample of 55 patients, being 14 males and 41 females, aged from 19 to 55 years old. All patients were subjected to surgery orthognathic bimaxillary combined with mentoplasty, in Class II facial profile – Angle. Patients’ actual results were compared to the obtained up to a year and a half after the surgery procedure. The study was delineated in three phases. In the first phase, cephalometric preoperative radiographs were performed; in the second phase the postoperative cephalometries were made; in the third phase, the measurements of the soft profile of the virtual analysis were compared with the real post-surgical profile. The data was collected and subjected to statistical analysis in the “R” program, using the t test and ANOVA. Results: The results demonstrated that measures A’ and Eis were underestimated in -0.15 ± 0. 52 mm and -0.47 ± 1.05 mm, respectively, while measures Pg’ and ANL were overestimated at 0.76 ± 1.98 mm and 3.31 ± 3.60° respectively. There was no evidence of measures, Ls, Li and B’, being different between real and virtual. Conclusions: The results of this study suggest that Dolphin 11.9® computer program complies with the function of preserving with reliability virtual surgical planning.

TEETH AND GEAR WHEELS DESIGN DEVELOPMENT FOR AIRCRAFT REDUCTION TRAINS

The development of designs of teeth, gear wheels and gears, which have found application in gearboxes of aircraft and helicopters, is presented. Parameters of different types of initial generating circuits, their modifications and examples of application corresponding gear wheels in gearboxes of airplanes and helicopters are considered. The main attention is paid to GOST 13755-2015, developed by CIAMD (Central Institute of Aviation Motor Development) and having a number of advantages over the old GOST 13755-81. The main advantage is achieved by replacing the standard tooth head height with a standard tooth tip thickness. When the teeth work along the entire active part of the gearing line with a profile angle of 250, high contact and bending strength is provided, as well as resistance against galling of the surfaces of the teeth of highly stressed gears. A further increase in contact strength and resource is ensured by using the initial generating circuit with a profile angle of 280. Gear trains with a guaranteed overlap ratio of 2.0 have a vibration level five times lower and, in general, their bearing capacity is approximately 1.5 times higher than that of highly stressed reduction trains with an overlap ratio less than 2.0. The asymmetrical teeth parameters were chosen to increase the density of the transmitted power, as well as to reduce the dynamic loads and vibration of the gear wheels. The strength of gear trains according to GOST 13755-2015 significantly exceeds the strength of gear trains according to GOST 13755-81, but the most significant advantage (more than twice) is obtained in terms of noise level. The highest strength of gears with a main circuit angle of 330 occurs at a guide circuit angle of 20 °. The highest stiffness of arched teeth of all designs provides arched gear trains with high durability and load capacity, which makes it possible to design reduction trains with smaller weight and size specifications.

SUBSTANTIATION OF CHIPPING FRACTURE MECHANICS DURING DRAWING OF CYLINDRICAL SURFACES WITH ALLOWANCE

The mechanics of chip fracture when cutting the allowance of pre-divisible technological grooves was studied for the first time, and the relationship between the profile and depth of the latter and the characteristics of the stress-strain state in the chip formation zone (relative shear, chip shrinkage, shear angle, front angle, contact processes . This article discusses a more complex problem - the longitudinal division of chips or allowance. Most researchers are inclined to believe that this problem should be solved by pre-dividing the allowance by a network of special chip-splitting ring or screw grooves. The depth of these grooves should be 0.6… 0.95 of the amount of rise on a single tooth of the broach. The results of the study of the mechanics of chip destruction are described when the tool meets the process groove in the drawing process. The connection between the structure of the pipe and the intensively deformed state in the zone of chip formation is shown. From the obtained results the following follows. Preliminary deformation hardening by means of deforming drawing allows to increase hardness of OM twice (steel 10), to 60% (steel 35), to 50% (steel 45) and to 25% (aluminum alloy AK6). This significantly reduces the shrinkage coefficient of chips (respectively 2; 1.4; 1.4 and 1.3 times) and the actual previous angle (at a sharpening angle γ = 15⁰, respectively: from 36⁰ to 18⁰; from 25⁰ to 17⁰; from 21⁰ to 16⁰ and from 22⁰ to 17⁰). All this indicates a decrease in the intensity of the cutting process with increasing intensity of the previous HPD The following minimum values of the groove profile angle for the investigated materials 2φmin were determined: 80⁰ (steel10); 60⁰ (steel 35); 50⁰ (steel 45 and alloy AK6). It is established that the minimum depth of the chip-splitting groove hC is determined from the condition of chip destruction when the tangential stresses in the shear zone are exceeded above the shear resistance of the processed material. The following values of the minimum depth of the chip-splitting groove for the studied materials were obtained: hCmin = (0.4… 0.55) Sz - steels 35 and 45; hCmin = (0.55 (0.6) Sz - AK6 alloy.