Internal Contours Research Articles

Fabrication and properties of PLA/nano-HA composite scaffolds with balanced mechanical properties and biological functions for bone tissue engineering application

Abstract Repair of critical bone defects is a challenge in the orthopedic clinic. 3D printing is an advanced personalized manufacturing technology that can accurately shape internal structures and external contours. In this study, the composite scaffolds of polylactic acid (PLA) and nano-hydroxyapatite (n-HA) were manufactured by the fused deposition modeling (FDM) technique. Equal mass PLA and n-HA were uniformly mixed to simulate the organic and inorganic phases of natural bone. The suitability of the composite scaffolds was evaluated by material characterization, mechanical property, and in vitro biocompatibility, and the osteogenesis induction in vitro was further tested. Finally, the printed scaffold was implanted into the rabbit femoral defect model to evaluate the osteogenic ability in vivo. The results showed that the composite scaffold had sufficient mechanical strength, appropriate pore size, and biocompatibility. Most importantly, the osteogenic induction performance of the composite scaffold was significantly better than that of the pure PLA scaffold. In conclusion, the PLA/n-HA scaffold is a promising composite biomaterial for bone defect repair and has excellent clinical transformation potential.

DOES THICKNESS REALLY MATTER? DIAGNOSTIC DILEMMAS IN CAVITARY LESIONS

TOPIC: Lung Cancer TYPE: Medical Student/Resident Case Reports INTRODUCTION: A pulmonary cavity is a gas-filled space seen as a lucency within a pulmonary consolidation, a mass, or a nodule. The differential for a solitary cavity of the lung includes anaerobic lung abscess, fungal infections, tuberculosis and malignancy. Wall thickness <4 mm has been shown to be caused by benign processes while thickness >15 mm are usually malignant. We describe the case of a former smoker in whom an infection was masking a cavitary squamous cell carcinoma of the lung. CASE PRESENTATION: A 75 year-old former smoker presented to the ER with hemoptysis for 1 week. He was afebrile with BP 90/50 and HR 124. WBC count was 17.8K/L. CT Chest revealed a 9.7 cm irregular cavitary mass in the right upper lobe of the lung with thick walls measuring 29 mm and evidence of invasion into the right hilum and chest wall causing rib fractures. Exam was significant for foul-smelling breath and poor dentition with gross aspiration while lying flat. Bronchoscopy demonstrated thick purulent secretions in the RUL and advancement into RUL takeoff with the bronchoscope led directly inside the cavity, revealing thick, friable walls. BAL and endobronchial brushings were obtained. Given patient's risk factors for aspiration and imaging findings, there was concern for possible anaerobic lung abscess. BAL cultures were polymicrobial. He received antibiotics and improved. However, BAL cytology and endobronchial brushing demonstrated malignant cells. Pathology from a CT-guided biopsy of the lesion confirmed squamous cell carcinoma of the lung. DISCUSSION: Several features of our patient's clinical presentation were suggestive of anaerobic lung abscess including aspiration, poor dentition, halitosis and leukocytosis. However, primary lung cancer remains the most frequent cause of a solitary cavitary lung lesion. Squamous cell carcinoma is the most common subtype to cavitate due to tumoral necrosis, in up-to 82% of patients. Features that can raise suspicion for malignancy as an etiology of a lung cavity include thickness of cavity wall >15 mm with irregular internal contours, upper lobe location and chest wall invasion, all of which were present in our patient. Our case highlights the importance of maintaining a high index of suspicion for underlying malignancy in smokers with cavitary lesions, despite an overwhelming clinical picture of infection. CONCLUSIONS: Cavitary lung lesions with high-risk radiological features such as wall thickness>15 mm should prompt accelerated work-up for malignancy to minimize high morbidity and mortality. REFERENCE #1: Gafoor K, Patel S, Girvin F, Gupta N, Naidich D, Machnicki S, Brown KK, Mehta A, Husta B, Ryu JH, Sarosi GA, Franquet T, Verschakelen J, Johkoh T, Travis W, Raoof S. Cavitary Lung Diseases: A Clinical-Radiologic Algorithmic Approach. Chest. 2018 Jun;153(6):1443-1465. doi: 10.1016/j.chest.2018.02.026. Epub 2018 Mar 6. PMID: 29518379. DISCLOSURES: No relevant relationships by Roxanne GarciaOrr, source=Web Response No relevant relationships by Sumit Patel, source=Web Response No relevant relationships by Nehan Sher, source=Web Response

Nests of Eufriesea aff. auriceps (Hymenoptera, Apidae, Euglossini) in remnants of Atlantic Forest and reforested areas

In recent decades, the use of the trap-nest technique has helped to increase knowledge on the nest architecture of many orchid bee species. This study describes the nest architecture of Eufriesea aff. auriceps constructed in trap-nests made of dried bamboo internodes (canes). The nests were placed in remnants of Atlantic forest and in reforested areas next to forest remnants and monitored monthly from August 2015 to August 2016 and from August 2018 to August 2019 in southern Brazil. The bamboo internodes occupied by bees varied in internal diameter from 1.0cm to 2.0 cm (`X = 1.7; SD = 0.3; N = 12) and in length from 11.0 cm to 28.0 cm (`X = 19.5; SD = 4.8; N = 12). The total size of the nests inside the bamboo internodes ranged from 9.0 cm to 19.9 cm (`X = 14.3; SD= 3.9; N = 12). The number of brood cells constructed per nest varied from 1 to 10 (`X = 4.0; SD = 2.3; N = 15). The cells were built with small pieces of bark cemented with resin, linearly arranged along the bamboo tube. Internally, the cell wall was lined with resin. The cells measured 1.5-3.0 cm (`X = 2.3 ± 0.5; N = 48) in length and 1.4-1.7 (`X = 1.5 ± 0.1; N = 17) cm in width. The internal contour of the cells was elliptical. Females of Eufriesea aff. auriceps occupied trap-nests in both the forest remnants and in areas undergoing restoration.

Communication aspects of cooperation in the forestry waste processing cluster

The article is devoted to the study of communications in the cluster for forest waste processing as a factor and indicator of cooperation development. The article provides an overview of 4 groups of clusters with ecological, forestry, biotechnological and agricultural specialization; in total 21 clusters are studied. The cluster communication field is considered through a number of general scientific approaches. An algorithm for systematizing and replicating the experience of successful communication building in a cluster is proposed. The communication field of clusters using renewable natural resources is reviewed. From the perspective of an outside researcher, the conditions for effective and free interaction in the considered cases have not been created. The used communication practices are summarized. The target characteristics of the cluster communication model as an open network with an external and internal contour, with public involvement are formulated. The dependence of the functional content of communications on the stage of evolution in the cluster, on the ratio of the goals of innovation and efficiency is shown. The achievement of innovative cluster-specific effects is determined by the nature of relationships between participants and largely depends on the organization of the cluster’s communication field.

THE CASE OF THE ACUTE MYOCARDIAL INFARCTION AT THE CONGENITAL ANOMALY OF THE HEART – THE MYOCARDIAL BRIDGE

Muscle bridges in the human heart are benign developmental abnormalities that can lead to acute myocardial ischemia. Muscular myocardial bridges are often found in the region of the anterior interventricular artery, while the diameter of the coronary artery before the bridge is larger than after it. The gold standard for detecting this pathology is coronary angiography, which allows visualizing the internal contours of the coronary artery. The study makes it possible to give a qualitative assessment of the site of stenosis with the determination of the cause of its occurrence. Angiographic signs of this pathology can include curvature of the segment of the affected coronary artery, uniform narrowing of the vessel lumen by more than 40% in systole and restoration of the diameter in diastole, clear signs of narrowing in at least two angiographic views, absence of vasoconstriction caused by pharmacological agents or a catheter. The aim of the study was to conduct a clinical and anatomical analysis of a case of acute myocardial infarction of type 2 caused by an anomaly in the development of the anterior interventricular artery. The analysis used data from the medical history, the results of intravital laboratory and instrumental studies, qualitative and quantitative morphological studies of the heart obtained during autopsy. The results of the study describe in detail at the macroscopic and microscopic levels the analyzed case of myocardial infarction against the background of an anomaly in the development of the anterior interventricular artery. The deceased patient has a history of comorbid pathology - myeloma. The authors suggest that an anomaly in the development of one of the branches of the left coronary artery in the form of a myocardial bridge and myeloma were pathogenic factors in the development of type 2 myocardial infarction of the anterior wall of the left ventricle. The immediate cause of death of the patient was acute left ventricular failure with pulmonary edema.

Influence of inertial links on the distribution of vibration amplitudes of points of the working body of a technological vibrating

Features of problems of dynamics and formation of dynamic states of working bodies of vibrating technological machines are considered. The purpose of the work is to develop a method for constructing mathematical models of vibration machines that provide the ability to evaluate, control and adjust the forms of movement of working bodies by introducing additional links into the structure of the system, forming a closed internal contour. Methods of structural mathematical modeling are used in the construction of original structural formations of their typical elements. The direction of constructive and technical solutions in the implementation of approaches to configure and adjust the structure of the vibration field of the working body is proposed. The method is implemented using the analytical apparatus of the automatic control theory. The features of dynamic states formation based on the application of transfer functions of structural mathematical models of mechanical oscillatory systems are studied. The use of transfer functions of interpartial connections for the formation of vibration fields of working bodies is proposed. Analytical relations are obtained that determine the possibility of implementing specific dynamic modes, including the decoupling of movements by individual coordinates, taking into account the features of the connectivity of movements by characteristic points of the working body, the manifestation of oscillation nodes or modes of dynamic damping. Features of using structural mathematical modeling methods in problems of dynamics of mechanical oscillatory systems with additional connections are discussed. The work is aimed at specialists in the field of theoretical and applied mechanics, machine science and mechanical engineering.

Ways to improve the efficiency of regulation of biomass concentration using modern control systems

The paper presents an option for solving the task of controlling the process of growing yeast in order to bring their concentration X closer to the desired one by deliberately changing the parameters of the process conditions within acceptable limits. The relationships between the main parameters of the process of cultivation of microorganisms are revealed. It is shown that these relationships are of a complex cross character, and the control object is multidimensional. Based on the analysis of the interaction of the main parameters, a diagram of their relationship is drawn up. At optimal values of the parameters of the process conditions, the change in yeast concentration is far from the required. It is proposed to change the parameters of the process conditions in accordance with a given value of the concentration of yeast Xgiv, which can be determined with constant periodicity during the cultivation process. To solve assigned task, the principle of cascade control of yeast concentration X is used, where the internal contour includes the systems of controlling the temperature, acidity, formal value, and respiratory coefficient. The analysis of transients in cascade systems showed that the most effective systemsunder consideration are concentration control systems that use the temperature and the acidity of the medium control in the internal circuits.

THE MODEL OF THE INTERCULTURAL ADAPTATION ECOSYSTEM OF UNIVERSITIES AS AN ELEMENT OF STRATEGIC DEVELOPMENT

The tasks of increasing the international competitiveness and export of Russian education within the framework of national development priorities are inextricably linked with the need to create a favorable environment for the adaptation of international students based on ecosystem and stakeholder approaches. The development of an integral and multidimensional model of the Russian intercultural adaptation ecosystem for universities and other educational organizations should take place with full recognition of the values of external and internal internationalization in all activities in order to form long-term key competencies. The model of the intercultural adaptation ecosystem should become a matrix and, in a way, a framework solution from the point of view of the strategic development of universities in the global world, taking into account rethinking and sophistication of their mission as a social institution in global partnership.The article offers a comprehensive vision of a model of an intercultural adaptation ecosystem of the educational organization with two contours – internal and external. The internal contour includes four components: values, practices, processes and structures. The external contour of the intercultural adaptation ecosystem of an educational organization also includes four components: inner Russian educational collaborations, international cooperation, interaction with national and cultural communities, and recommendations for authorities.The authors offer a detailed analysis of the factors and priorities of the necessary organizational changes in Russian universities in the context of the tasks of intercultural literacy skills’ strategic development for all participants and stakeholders of the educational process with further transformation into the competence of cultural intelligence.

Enhanced Surface Quality of Internal Machined Contours

Based on integrated concepts in the aspects of product design, choice of materials and manufacturing technologies, companies in the mechanical engineering as well as oil and gas industries are striving to increase energy efficiency through weight-optimized components and manufacturing processes. With regard to the design of e.g. functional components for hydraulic systems or aircraft structures, customized manufacturing concepts are crucial in order to combine the highest product quality with the economical use of energy and resources. The use of a flexible tooling system for combined internal contouring and mechanical post-processing of boreholes developed within the framework of a ZIM project, founded by the Federal Ministry for Economic Affairs and Energy and in collaboration with BGTB GmbH makes it possible to achieve highest surface qualities of high-performance components. In order to realize a further optimization of the machined surface, the influences of increased operating pressures during roller burnishing on surface smoothing are investigated in analogy tests. In this regard, different steel types are considered as typical application materials. Based on reference tests, the surface integrity as a result of increased working pressures was analyzed as well. Besides the variation of the mechanically applied force, the adjustment of the process strategy is a central issue of the experimental investigations. On the one hand, the influences of varying roll feeds are analyzed with reference to the surface finishing quality and the process efficiency. On the other hand, different strategies for surface improvements increase by varying holding pressures are assessed comparatively.

Investigations on the surface quality of grinded inner contours using different manufacturing strategies on fused silica

In the field of optical manufacturing, fused silica has a high and constantly growing application potential. Its material advantages, such as low thermal expansion and high thermal shock resistance, as well as its high transparency from the ultraviolet to the infrared spectral range, result in a large number of application fields. For example, manufacturing processes in semiconductor technology require high-quality quartz materials throughout the wafer handling process to avoid non-permissible contamination and to withstand the high process temperatures. Another example are monolithic components for fiber preform manufacturing, where internal contours with high aspect ratios (e.g. component length to component diameter) and high surface qualities are required to draw fiber types with special properties. The demands on the complexity and accuracy of these components are constantly increasing, which is accompanied by the need to analyse and optimize modern CNC manufacturing techniques more and more. In the following, investigations on the grinding of internal contours with a high aspect ratio are presented, in which the influence of an ultrasonic assistance as well as different machining strategies are considered.

Contextual loss based artifact removal method on CBCT image.

PurposeCone beam computed tomography (CBCT) offers advantages such as high ray utilization rate, the same spatial resolution within and between slices, and high precision. It is one of the most actively studied topics in international computed tomography (CT) research. However, its application is hindered owing to scatter artifacts. This paper proposes a novel scatter artifact removal algorithm that is based on a convolutional neural network (CNN), where contextual loss is employed as the loss function.MethodsIn the proposed method, contextual loss is added to a simple CNN network to correct the CBCT artifacts in the pelvic region. The algorithm aims to learn the mapping from CBCT images to planning CT images. The 627 CBCT‐CT pairs of 11 patients were used to train the network, and the proposed algorithm was evaluated in terms of the mean absolute error (MAE), average peak signal‐to‐noise ratio (PSNR) and so on. The proposed method was compared with other methods to illustrate its effectiveness.ResultsThe proposed method can remove artifacts (including streaking, shadowing, and cupping) in the CBCT image. Furthermore, key details such as the internal contours and texture information of the pelvic region are well preserved. Analysis of the average CT number, average MAE, and average PSNR indicated that the proposed method improved the image quality. The test results obtained with the chest data also indicated that the proposed method could be applied to other anatomies.ConclusionsAlthough the CBCT‐CT image pairs are not completely matched at the pixel level, the method proposed in this paper can effectively correct the artifacts in the CBCT slices and improve the image quality. The average CT number of the regions of interest (including bones, skin) also exhibited a significant improvement. Furthermore, the proposed method can be applied to enhance the performance on such applications as dose estimation and segmentation.

The research of thermoelastic deformation models with thin elliptic boundary contours plates and accounting uncertainty factors

Consider thin plates with external or internal boundary elliptical contours. It is necessary to take into account the scattering errors of the values of the initial physical, mechanical and geometric parameters based on the use of the heuristic principle of generalization. Known research methods for such systems based on the methodology of accounting for plate deformation under the influence of thermometric factors. Of particular interest is the assessment of the endogenous characteristics of the process using a hybrid technology for accounting for displaying the variability of inputs to these characteristics. Significant relationships of low-variant versions of the model are created for the base component, which is a homogeneous orthorhombic area of nonzero thickness and nonzero area in given coordinates. Axes passing through the middle of the element are defined. Half shafts define an elliptical contour. Stresses in the element are generated by the heat flux, which is symmetric and axial with respect to the coordinate system in the heat flux part.

A new approach to the design of suspension roof systems

Over the last century, the suspension roofs design has progressed until the advent of the shells theory in the first half of the 20th century, due to a rapid pace in technological advancement. A paradigm shift emerged with the new trend in structural design towards a new design process that cooperatively integrated economy, efficiency, and elegance. Different approaches in computation, design and reliability assessment of roof structures are discussed in this work to identify the key conditions that have significantly contributed to modern suspension roof design principles. A new algorithm to assess the reliability of suspension roofs at the design stage is proposed and a novel method for computational design and reliability evaluation of suspension roofs is presented in this paper. The proposed method provides solutions for the following problems: obtaining rational geometric parameters of a structure; finding appropriate rigidity characteristics of basic supporting elements; determining the elements failure trajectory for typical roof diagram with the following evaluation of stress - strain state of a structure; calculating numerical safety indices of a structure (determining the lower and upper safety limits). The method enables to find the zones, where failure will be initiated. It offers an opportunity to create additional strength and reliability of structures, located in dangerous places, such as bearing joints of the connecting trusses to external contour and internal contour, the braces to the lower chord of the trusses, intermediate joints of upper and lower chords of supporting trusses etc., at the stage of design and construction. Large-span roofs have increased liability level, since their failure can lead to severe economic and social consequences. In this case, the design of these unique structures should be based on complex approach for selecting the rational structural concept related to the structure’s function, architectural concept, manufacturing methods, construction, etc. Reliability requirements, adaptability to manufacture, economic efficiency, ecological and social factors should be also fulfilled. Young engineers should be inspired by the great structural forms of the past and be encouraged to study more works from our generation to spark improved designs in the future. Based on the above, we can recommend to young researchers the universal algorithm, based on: - preliminary computation; - analysis of survivability; - design according to the limit states requirements; - design based on the numerical reliability indicators. It will allow improvement of computation methods quality and more accurate analysis of roof structures. Using this approach also leads to increasing of reliability and durability of such types of structures and minimizes mistakes in designin and computation.

Аналіз сучасного стану та тенденцій інноваційного лідерства в публічному управлінні

У статті досліджуються актуальні питання інноваційного лідерства в публічному управлінні, аналізуються сучасний стан та тенденції розвитку його потенціалу в умовах глобальних трансформацій та кризових явищ в суспільстві. Визначено сутність, зміст, поняття інноваційного лідерства в публічному управлінні в історичній ретроспективі та контексті нових концептуальних підходів до дослідження лідерства. Встановлено, що інноваційне лідерство становить собою підхід до організаційного розвитку та організаційних змін. Наголошується, що у внутрішньому контурі системи публічного управління інноваційне лідерство детерміновано соціально-психологічними процесами в організації, управлінням діяльністю команди, впливом на працівників, який супроводжується зміною уявлень і цінностей останніх, активізацією вищих потреб у новаторстві, досягненні, творчості, самоактуалізації. &#x0D; До понятійного апарату інноваційного лідерства віднесено роль інноваційного лідерства в умовах глобальних трансформацій, особистість інноваційного лідера, реалізацію інноваційного лідерства в публічному управлінні, забезпечення ефективної та результативної роботи. &#x0D; Сучасний стан інноваційного лідерства в публічному управлінні характеризується усвідомленням ролі культури управління, необхідності опанування механізмів самоорганізації, які вивільняють енергію людської ініціативи, дозволять ефективно реагувати на невизначеність та швидкі зміни навколишнього світу при вирішенні необмежених завдань. &#x0D; Тенденції розвитку інноваційного лідерства розглядаються відносно умов глобальних трансформацій та кризових явищ в контексті невідворотних та варіативних трендів. &#x0D; Проаналізовано основні функції інноваційної організаційної культури органів публічної влади для реалізації цілей регіонального та місцевого інноваційного розвитку.&#x0D; В основі методів дослідження використано загальні та спеціальні наукові методи для вивчення та оцінки підґрунтя щодо формування реалізації інноваційного лідерства в історичному і сучасному контексті.

Multiple Morphological Constraints-Based Complex Gland Segmentation in Colorectal Cancer Pathology Image Analysis

Histological assessment of glands is one of the major concerns in colon cancer grading. Considering that poorly differentiated colorectal glands cannot be accurately segmented, we propose an approach for segmentation of glands in colon cancer images, based on the characteristics of lumens and rough gland boundaries. First, we use a U-net for stain separation to obtain H-stain, E-stain, and background stain intensity maps. Subsequently, epithelial nucleus is identified on the histopathology images, and the lumen segmentation is performed on the background intensity map. Then, we use the axis of least inertia-based similar triangles as the spatial characteristics of lumens and epithelial nucleus, and a triangle membership is used to select glandular contour candidates from epithelial nucleus. By connecting lumens and epithelial nucleus, more accurate gland segmentation is performed based on the rough gland boundary. The proposed stain separation approach is unsupervised, and the stain separation makes the category information contained in the H&amp;E image easy to identify and deal with the uneven stain intensity and the inconspicuous stain difference. In this project, we use deep learning to achieve stain separation by predicting the stain coefficient. Under the deep learning framework, we design a stain coefficient interval model to improve the stain generalization performance. Another innovation is that we propose the combination of the internal lumen contour of adenoma and the outer contour of epithelial cells to obtain a precise gland contour. We compare the performance of the proposed algorithm against that of several state-of-the-art technologies on publicly available datasets. The results show that the segmentation approach combining the characteristics of lumens and rough gland boundary has better segmentation accuracy.

SEARCH AND ELIMINATION OF REPEATED CONNECTIONS IN THE SCHEME OF GUIDING SLIDE-CRANK MECHANISM OF THE GRIPPING DEVICE

Purpose. The article is aimed to carry out a structural analysis of the coupled straight-guiding crank-slide mechanism of variable structure gripping devices with external unilateral constraints. It is also necessary to determine the number of internal and external repeating connections in the contours of the mechanism at different stages of its functioning, to assess their possible perniciousness and to suggest ways to reduce them. Methodology. Achieving this goal is carried out based on the universal structural theory of Ozols mechanisms for analyzing the gripping device as a mechanism with geometric, internal and frictional holonomic external constraints. Ozols internal and external structural formulas are used. Findings. The eleven-link gripping device is built on the basis of coupled central parallelogram crank-slider mechanism with a driving cranks. Synchronous driving cranks act on elongated connecting rods connected to sliders and gripping clamp elements. Gripping clamp elements carry out plane-parallel movement. Structural analysis was performed using structural schemes for two states of the mechanism: before clamping the object and in the state of the clamped object. In the first state of the mechanism with kinematic pairs of class V, the one-movable scheme contains thirteen internal redundant constraints. In the second state of the mechanism, external constraints act and in the scheme another five additional external repeating constraints are formed. Their contour arrangement and possible consequences of their action are shown. Originality. Structural analysis of the coupled crank-slider mechanism of the gripping device as a mechanism of a variable structure with internal and external connections is carried out for the first time. It is performed contour analysis, search and elimination, as well as reduction of pernicious repeated connections in the internal and external contour of the mechanism. Practical value. Practical recommendations have been developed on changing the mobilities of sliding pairs to eliminate all repeated connections in the internal contours of the mechanism. To reduce the number of pernicious repeated connections, the introduction of a self-centering unloading coupling into the external contour of the mechanism is proposed.

Improvement of Traction Indicators of a Track-Chain Tractor

The aim of this research was to conduct the comparative traction tests for T-170M1.03-55 tractor with a flat and elliptical rim. Structurally rational geometry of the crawler's support surface for tractors with semi-rigid suspension is realized by placing the support rollers at different heights relative to the cart. The results of traction tests showed that elliptical track rim has increased the maximum traction power by 10.4%, conditional traction propulsive efficiency coefficient to 7.43% and the specific traction effort by 8%. The increase in indicators is provided by a lower rolling resistance of a tractor with an elliptical rim. Reduction of the resistance power to rolling of the tractor with an ellipse track rim occurs due to alignment of support rollers vertical load and reduction of resistance to rollers movement on internal contours of tracks and in hinges of track chain links. The results of the research indicate a significant improvement in traction performance of T-170M1.03.55 tractors with elliptical track-chain rim.

Surface finishing of additively manufactured Inconel 625 complex internal channels: A case study using a multi-jet hydrodynamic approach

The surface roughness of components built using the laser powder bed fusion (L-PBF) process is poor. Surface finishing the internal channels of L-PBF components is a challenge. We propose a multi-jet hydrodynamic approach to enhance the surface finish quality of the internal channels. We investigate the hydrodynamic finishing on L-PBF Inconel 625 linear, stepped, and non-linear internal channels with diameters 5 to 1 mm and length up to 100 mm (replicating the geometries in rocket injectors, fuel nozzles, and cooling channels). The multi-jet hydrodynamic finishing approach improved the surface quality by 60–90 % (final Ra, Sa ≤ 1 μm and Rz, Sz ≤ 20 μm), using an abrasive concentration of ≤1 % in 15 min. of processing time. Areal surface texture parameters Sdr and roughness ratio r ≈1, evidenced the uniformity of the surface finish with dominant abrasive microcuts, regardless of the initial non-uniform additive manufactured surface. Most of the surface finished channels had excellent dimensional integrity and internal contour circularity. We then discussed the advancements required in metal additive manufacturing and internal surface finishing—to safely deploy L-PBF components with micro internal channels in fuel injection and fluid transfer applications.

Analysis of free oscillations of round thin plates of variable thickness with a point support

This paper reports the derived general analytical solution to the IV-order differential equation with variable coefficients for the problem on free axisymmetric oscillations of a circular plate of variable thickness. The plate thickness changes along the radius ρ in line with the parabolic law h=H0(1–µρ)2. When building a solution, the synthesis of the factorization method and the symmetry method was used. The factorization method has enabled us to represent the solution to the original IV-order equation as the sum of the solutions to the two respectively constructed II-order equations. The method of symmetry has produced precise solutions to these two equations.The problem on a point fixation of the plate has been considered as a boundary case of the problem on the rigid fixation of the inner contour of a circular plate whose ρ→0. To this end, the general solution has been transformed into the form that pre-meets the conditions on a rigid point support. The result of such a transformation is a simpler solution, with only two permanent integration variables instead of four. As a result, the frequency equation for a plate under any conditions on the outer contour is significantly simplified because it is derived from the second-order determinant. The frequency equation for a plate with a point support and with a free edge at µ=1.39127, which corresponds to the ratio of the limit thicknesses equal to 10.8, yielded the first five eigenvalues λi (i=1÷5). The oscillation shapes have been constructed as a graphic illustration for λi (i=1÷3). The numerical values of amplitude ratios have been given, as well as coordinates (relative radii) of the oscillation antinodes and nodal circles for each of the five oscillation shapes (i=1÷5). The derived numerical values of the oscillation parameters could in practice be used to initially identify the type of an oscillatory system and its possible characteristics for the case when a plate is fixed inside the inner contour of the small diameter. The criterial ratio of the fastening contour diameter to the plate diameter could serve the same purpose. If this ratio is equal to or less than 0.2, then it is permissible to assume that it is a point-type fastening. In this case, it is possible to calculate the circular plate oscillations with its internal contour fixed using the algorithm set out for a plate with a point support

Ukrainian science in the time of "military communism" (on domestic books printed in 1920)

The article presents the problem of spiritual achievements of the Ukrainian National-Democratic Revolution of 1917. With the legitimation of their own power institutions, Ukrainian studies became widespread, as a generalized complex of knowledge about the modern Ukrainian nation. The process of uniting Ukrainians into a political nation needed to educate and educate the society on the basis of Ukrainian values. Recognizing this important component of its development activities, the national governments of Ukraine (General Secretariat of the Ukrainian People's Republic, State Secretariat of the Western Ukrainian People's Republic, Council of Ministers of Hetmanat Paul Skoropadsky, the Council of People's Ministers during the Development of the Directory of Ukraine). Having been defeated in the struggle for the preservation of Ukrainian statehood, national forces, meanwhile, were able to preserve and show to the society the potential of Ukrainian studies as a factor in the education of ethnic identity. Even the regime of the dictatorship of the proletariat, intensified by the policy of "war communism", did not become a hindrance. Moreover, the Bolsheviks, in their own way, accepted from the national forces the "baton" of public dissemination of Ukrainian studies. Considering the latter as an effective mechanism for gaining authority among the masses, the leaders of the Communist Party and the Soviet government treated Ukrainian economics with economic prudence. Not only did the Soviet authorities retain the achievements of their opponents in the civil war, but also transformed them into their own political "indigenization" campaign, which began in 1923 and brought numerous bonuses to the Bolsheviks, both on the internal and external contours of life. The author made the aforementioned analysis and his conclusions in this article on the basis of the study of the national books in 1920, kept in the State Archives of the Book of Ukraine named after Ivan Fedorov.