Search

In this work we study vertical graph surfaces invariant by parabolic screw motions with pitch ℓ > 0 and constant Gaussian curvature or constant extrinsic curvature in the product space H² × R. In particular, we determine flat and extrinsically flat graph surfaces in H² × R. We also obtain complete and non-complete vertical graph surfaces in H² × R with negative constant Gaussian curvature and zero extrinsic curvature. Publisher's Version Q4 WOS:000985795700019

В работе рассмотрены вопросы контроля плоских поверхностей отражателей на основе SiO2 + H2O + ZrO2 экспериментальной установкой, построенной на базе интерферометра Физо. В настоящее время оптическое приборостроение большое внимание уделяется оптической компонентной базе для совершенствования оптических и оптико-электронных приборов, поэтому представленная работа перспективна и актуальна. В работе приведены оптическая схема, внешний вид и технико-эксплуатационные характеристики установки. Получены данные о поверхностях плоских отражателей разных геометрических форм. Проанализированы интерферограммы оптических поверхностей и исследованы представленные образцы в поперечном и продольном направлениях., The work considers the control of flat surfaces of reflectors based on SiO2 + H2O + ZrO2 by experimental setup based on Fizeau interferometer. At present, much attention is paid to optical components for the improvement of optical and optoelectronic devices, so the presented paper is promising and relevant. The article presents an optical scheme, appearance and technical and operational characteristics of the unit. Data on surfaces of flat reflectors of different geometric shapes are obtained. The interferograms of optical surfaces are analysed, and the presented samples are examined in transverse and longitudinal directions., Международный научно-исследовательский журнал, Выпуск 4 (130) 2023

Background Soft tissue balance is important for the success of total knee arthroplasty (TKA). Various types of tensors have been developed for the precise measurement of a gap. We hypothesized that the surface shape of the tensor that contacted the TKA component affected the gap measurement. This study aimed to compare the gaps obtained with flat and insert-shaped surface tensors. Methods Two senior surgeons performed 95 TKAs (Vanguard-PS:55 knees; Persona-PS:40 knees). The joint gap was measured in each static knee flexion status (0°, 30°, 45°, 60°, 90°, 120°, and full flexion). We compared the gaps measured with a flat surface tensor and an insert-shape surface tensor. We defined a significant change as a gap difference of >1 mm with a statistical significance. Results In Vanguard-PS, significant changes were observed at 30° and 45°. In Persona-PS, significant changes were observed at 30°, 45°, and 60°. In both implants, gaps measured with the flat tensor were larger than those measured with the insert tensor at approximately midflexion, and the significant changes disappeared in higher flexion position over midflexion. Conclusions The surface shape of the tensor affected the measurement of midflexion laxity in TKA. When measuring the gap with a flat tensor, the midflexion laxity was overestimated. A tensor with an insert-shaped surface should be used to measure the gap in TKA.

The present paper investigates the static equilibrium of a thin elastic structure with concave sidecut pressed against a flat rigid surface, as an idealization of a ski or snowboard undergoing the conditions of a carved turn. An analytical model is derived to represent the contact behaviour and provide an explanation for concentrated loads occurring at the sidecut extremities. The deformations are prescribed assuming tied contact along the sidecut line and neglecting torsional deformations. The loading conditions leading to this ideal deformed state are then sought, in order to better understand the mechanics of the turn. The results are illustrated with different sidecut geometries and compared with finite element computations for validation purposes. Depending on the function describing the sidecut line, concentrated force and moment are found to take place at the sidecut extremities.

Relief is an expression of feelings and thoughts poured on a flat plane whose flat surface becomes arising and its position is higher than its background. Reliefs have been known since the days of Hindu Buddha with the discovery oftangibleand culturalartifacts. In its development relief is also found in the building of Avalokitesvara Monastery, Serang Banten. This research method uses qualitative methods, where the analysis is more descriptive. Avalokitasvara Monastery building is located in Pamarican Village, Dermayon Village of Serang City, Banten Province. The Avalokitesvara monastery was built as a proof of Sheikh Sheikh Syarif Hidayatullah's love for Princess Ong Tien. The placement of reliefs in the Avalokitesvara Monastery is located on the wall of the main tunnel. Where there are 10 panels placed facing the right and left side walls, each has a different story. The relief also uses visualization of perspective techniques. Visualization on relief describes the situation of the community at the beginning of the initial construction of the monastery until today. The existence of reliefs in the monastery in addition to being an aesthetic element in the interior, but also acts as a medium to ensede the history of the monastery's journey.

Background Droplet impact on a superhydrophobic cylinder differs from that on a flat surface. After bouncing, once re-touch takes place, the contact time τc would increase, which is unfavorable for some applications. The increased τc may strongly depend on the Weber number and radius ratio, R*, of cylinder to droplet. Methods The impact is investigated via lattice Boltzmann method simulations. The particular emphasis is placed on re-touch rebound patterns and τc. Significant findings Rebound patterns and τc both strongly depend on a combined parameter, α=We/R*, characterizing the asymmetry of droplet spreading and retraction. As α increases, upward rebound and stretched breakup take place sequentially for the first bouncing, whereas rebound patterns change as intact re-touch rebound and separate re-touch rebound for the second bouncing. Increasing α enhances the asymmetry, which promotes the first rebound, thereby reducing τc regardless of rebound patterns. The enhanced asymmetry also accelerates rebound and thus reduces τc in the separate re-touch rebound regime, whereas it hinders rebound, leading to a significantly increased τc. The power-law correlations of τc vs α are developed for the first and second bouncing. Besides, a method is proposed to suppress or prevent the re-touch, which is proven to effectively reduce τc.

Humanoid robots, with their overall resemblance to a human body, is modeled for flawless interaction with human-made tools or the environment. In this study, navigation of humanoid robot using hybrid Artificial potential field (APF) and Moth flame optimization (MFO) approach have been performed. The hybrid approach provides the final turning angle (FTA), which is optimum to avoid collision with the hindrances. APF utilizes a negative potential field and a positive potential field to find the location of obstacles and target, respectively. The navigation starts towards the target; when the robot interacts with the obstacle, APF provides an intermediate angle (IA). The IA, along with the position of the obstacle, is fed into MFO as an input. This technique provides the FTA (optimum) to avoid collisions and guide a robot to the target. It is implemented in a single humanoid system and a multi-humanoid system. The presence of multiple humanoids can create the chance of inter-collision. It is dismissed by employing a dining philosopher controller to the proposed technique. Simulations and experiments are accomplished on simulated and real humanoid NAO. The coherency in the behavior of the results evaluated by the simulations and real-time experiments demonstrates the efficiency of the proposed AI technique. Comparisons are performed with a previously used method to validate the robustness of the technique.

The current study aimed to investigate the association between the morphology of the median sacral crest, variation in the angle of the spinous process of the first sacral vertebra, and the occurrence of sacrocaudal fusion in greyhounds. In this study, 167 sacra from cadavers of greyhounds (previously euthanized for reasons unrelated to this study) were collected, classified into standard and fuses sacra (based on the number of fused vertebrae and type of fusion), and then classified based on the morphology of the median sacral crest into three different types: type F (full crest), type N (when the median sacral crest is incomplete, and type R (when the median sacral crest is present but it was short or reduced). Among the 167 sacra, 91 sacra were used to measure the angle of the spinous process of the first sacral vertebrae (1st SPA). Each of the sacra was digitally photographed using a Nikon D3100 digital camera (Tokyo, Japan) in which the camera was positioned laterally with the lens parallel to the central part of the lateral aspect of the sacrum and on a flat surface of the laboratory bench. Image-Pro Express Version 5.0 imaging software (Media Cybernetics, Silver Spring, Maryland) was used to draw and measure the angles. The angle of the 1st SPA was defined as the angle formed dorsally at the intersection of two lines. The first line was drawn to represent the cranial ridge of the spinous process of the 1st SPA, and the second line was drawn across the most dorsal surface points of the spinous processes of the 1st (S1) and 3rd (S3) sacral vertebrae. Significant (p < 0.001) morphological differences (F, R, N) were found in the median sacral crest, and the prevalence of median sacral crest type R in standard sacra was 35.1% compared to 10% in fused sacra, type F was 41.2% in standard sacra and 10% in fused sacra, and type N was 23.7% in standard sacra and 80% in fused sacra. The angle 1st SPA with median sacral type N was statistically significantly less (more upright) than those in sacra with median sacral type F (P < 0.042). Differences have been found in the median sacral crest and angulation of the spinous process of S1 vertebra in sacra with different types of median sacral crest.

The remaining oil distribution in heavy oil reservoir with the unconsolidated sandstone before and after infilling of the inverted nine-spot well pattern was complicated. To better understand the variation of flow field and remaining oil distribution of inverted nine-sport pattern and infill well pattern, the physical experiments were examined using a three-dimensional physical model. The physical simulation experiment of water displacing oil was conducted with the self-developed high pressure–temperature experiment device. For inverted nine-sport pattern, the remaining oil was distributed in the area between injection-production wells and edge region on a flat surface. In vertical, the remaining oil was distributed in the top area of composite reverse and positive rhythm reservoir and in the middle area of composite positive and reverse rhythm reservoir. For infill well pattern, the remaining oil was distributed in the area between production wells on a flat surface. In vertical, the remaining oil was distributed in the area of poor physical property with weak water flooding. Simultaneously, the enhanced recovery efficiency was about 11% by transforming the inverted nine-sport pattern into row injection-production well pattern and the final recovery efficiency was 27.27%. The results can provide reference for tapping the remaining oil and recovery calibration of unconsolidated sand heavy oil reservoir.

The micromechanical methods, among which optical trapping and atomic force microscopy have a special place, are widespread currently in biology to study molecular interactions between different biological objects. Optical trapping is reported to be quite applicable to study the mechanical properties of surface structures onto bacterial (pili and flagella) and eukaryotic (filopodia) cells. The review briefly summarizes the physical basis of optical trapping, as well as the principles of calculating the van der Waals, electrostatic, and donor-acceptor forces when two microparticles or a microparticle and a flat surface are used. Three main types of model systems (abiotic, biotic, and mixed) used in trapping experiments are described, and the peculiarities of manipulation with living (bacteria, fungal spores, etc.) and non-spherical objects (e.g., rod-shaped bacteria) are summarized.

We use the sixth-order linear parabolic equation $$\begin{aligned} \frac{\partial y}{\partial t}=B\left( \alpha \frac{\partial ^{6}y}{\partial x^{6}}-\frac{\partial ^{4}y}{\partial x^{4}}\right) ,\ x\in {\mathbb {R}}_{+},\ t>0, \end{aligned}$$ proposed by Rabkin and describing the evolution of a solid surface covered with a thin, inert and fully elastic passivation layer, to analyze the grain boundary groove formation on initially flat surface. We derive the corresponding boundary conditions and construct an asymptotic representation of the solution to this initial boundary value problem when $$\alpha $$ is small, by applying the theory of singular perturbation. We illustrate the effect of passivation film near and far from a grain boundary groove.

Perkembangan dunia game sekarang ini, lebih cenderung pada permainan bersifat game mobile. Masih sedikit game yang memperkenalkan permainan tradisional kepada generasi muda terutama pada anak-anak sehingga kurangnya pengetahuan anak-anak tentang permainan tradisional contohnya permainan setatak. Setatak adalah permainan tradisional lompat-lompatan pada bidang datar yang digambar di atas tanah dengan membuat gambar kotak-kotak, kemudian melompat dengan satu kaki dari kotak satu ke kotak berikutnya. Seiring dengan kemajuan teknologi, untuk menjaga dan melestarikan permainan tradisional setatak, permainan tradisional setatak dibuat berbasis android dalam bentuk 2D. Metode yang digunakan adalah metode Finite State Machine (FSM). Metode Finite State Machine (FSM), yaitu sebuah perancangan sistem kontrol yang menggambarkan tingkah laku atau prinsip kerja sistem dengan menggunakan tiga hal berikut: State (Keadaan), Event (kejadian) dan action (aksi). Penerapan metode FSM pada game ini adalah untuk mengatur perilaku sistem, yaitu perpindahan kaki pemain dari satu petak ke petak yang lainnya selama game berlangsung. Dengan adanya aplikasi game setatak ini anak-anak dapat memahami dan mampu memainkan permainan game setatak. Hasil pengujian menunjukkan bahwa game setatak dapat dimainkan, disukai dan diminati oleh anak-anak serta menambah pengetahuan anak-anak tentang permainan tradisional setatak.

Mechanical systems are always deal with wear and friction as the liability. The basic principle of the mechanical system is the surface interaction between surfaces which have a frictional force resulting in fatigue and damage to the mechanical components. Lubricant is used to minimize friction in order to solve the problem. A comparative friction characteristic analysis was then conducted to assess the coefficient of friction (COF) between Aluminum Alloy 5083 block and SKD 11 disk using two types of lubricant, that is SAE40 engine oil and RBD palm oil. The thickness of the oil film could be predicted in order to observe the influence of the different lubricants used. Pit pattern surface is required to research the function of the pit as a lubricant reservoir. The experiment was carried out in the laboratory according to the ASTM G99. Load is applied to experiments with loads of 1 kg, 5 kg and 10 kg, in order to find a COF correlation under different application condition. The rotational speed is held constant at 3m/s during the experiment. The results obtained revealed that when using RBD palm oil as a lubricant, the COF between block and disk is lower than when using SAE40 engine oil as a lubricant. The experimental result showed that RBD palm oil can minimize friction much lower than SAE40 engine oil. Based on the results of the comparison analysis on the flat surface and pit pattern surface, the finding revealed that the pit pattern may serve as a lubricant reservoir to retain and store the lubricant for longer than the flat surface that helps to reduce friction.

Objectives Childhood paleodietary reconstruction via dental macrowear analysis is limited in part by available methods to measure dental macrowear. We describe a method to quantify dental macrowear progression (in both deciduous and permanent molars) using a handheld intraoral scanner and two 3D occlusal topographic measurements. We assess the agreement of our macrowear proxies with an established qualitative wear scoring system and their relationship to age. Material and methods We scanned 92 well‐preserved dentitions of immature individuals from the medieval cemetery of St. Pölten in Lower Austria using an intraoral scanner. Two measurements were made on the resulting mesh files—the relative flat surface area in % of the occlusal surface (RFSA%) and the mesial interior slope angle. We estimated the technical error of measurement (TEM). Comparisons were made with the macrowear scoring system—tooth wear index. Results We found that TEM for both measurements was between 1 and 3%, except the interobserver TEM of RFSA% which was above 5%. Both quantitative measurements generally agree with the established qualitative scores and correlate with age; however, RFSA% does not reliably indicate the progression of macrowear for teeth after dentine exposure occurs. Discussion The proposed 3D topographic measurements can be made reliably, and within a certain range of wear provide good quantitative proxies of the progression of dental macrowear. Such measurements constitute a promising approach for improving dental macrowear analysis in contexts such as childhood paleodietary reconstruction, which benefit from additional precision in wear rate estimation and present less dentine exposure.

A conical-shaped Pt nanoelectrode whose tip apex features an effective electrode area was fabricated and used as a probe for scanning electrochemical microscopy (SECM). Nanoelectrodes were prepared by electroplating Pt in porous pyrolyzed polydimethylsiloxane filled into the tip of a quartz nanopipette. The current–distance curves were obtained by acquiring raw (without a low-pass filter) and low-pass-filtered (10 Hz) current simultaneously while a tip approached a flat Pt substrate. The raw-current approach curve showed the transition from faradaic feedback current to electron tunneling between the tip of the probe and the substrate. Alternatively, in the low-pass-filtered approach curve, a faradaic current with an improved signal-to-noise ratio was obtained without a transient increase of the tunneling current. From scanning electron microscopy observations, voltammograms, approach-curve measurements, and digital simulations of the response of a nanoelectrode, we deduced that only the apex of the conical-shaped electrode exhibited electrochemical activity and acted as an effective electrode. The constant-distance SECM imaging of an Au-sputtered polycarbonate membrane with sub-micrometer pores and Pt nanoparticles deposited on a highly oriented pyrolytic graphite (HOPG) was successfully demonstrated using the tunneling-current-based standing approach mode.

It is typical for rock material to be bi-modularity in terms of Young’s modulus and Poisson’s ratio. In other words, these values differ in compression ( $$E_{{\text{c}}} ,\upsilon_{c}$$ ) and in tension ( $$E_{{\text{t}}} {,}\upsilon_{{\text{t}}}$$ ). In this work, four kinds of rock materials (sandstone, marble, granite, basalt) were tested to study such bi-modularity behavior in uniaxial compression and in tension (Brazilian disc test). The compressive elastic constants were determined from uniaxial compression testing, while the tensile elastic constants were determined by an improved methodology using displacement measurement in both horizontal and vertical directions of points on the flat surface of a Brazilian disc. Digital image correlation (DIC) was used to monitor the strain and displacement field on the Brazilian disc surface. Validation of the reliability of the testing method is also carried out, and it is found that tensile cracks initiate at the disc center for all tested specimens. Then, the rationality of the determined tensile elastic constants is validated by comparison with the values obtained from the direct tensile tests. Finally, based on the experimental data, it is found that the values of $${{E_{{\text{t}}} } \mathord{\left/ {\vphantom {{E_{{\text{t}}} } {E_{{\text{c}}} }}} \right. \kern-\nulldelimiterspace} {E_{{\text{c}}} }}$$ and $${{\upsilon_{{\text{t}}} } \mathord{\left/ {\vphantom {{\upsilon_{{\text{t}}} } {\upsilon_{{\text{c}}} }}} \right. \kern-\nulldelimiterspace} {\upsilon_{{\text{c}}} }}$$ of each rock type are similar, except for marble. As the ratio of tensile to compressive strength increases, the value of $${{E_{{\text{t}}} } \mathord{\left/ {\vphantom {{E_{{\text{t}}} } {E_{{\text{c}}} }}} \right. \kern-\nulldelimiterspace} {E_{{\text{c}}} }}$$ also appears to increase slightly. Lastly, the mechanism of bi-modular behavior of rock is discussed.

Selective laser melting (SLM) is a rapidly developing technique in additive manufacturing (AM) that has attracted considerable interests in industry owing to its tremendous advantages. However, the inferior surface quality of SLM components, specifically the partially melted powder attached on the surface, restricts the functionality of the as-printed part and requires further processes to polish their surface. In particular, polishing an internal hole created by SLM becomes more challenging because of poor visibility of the internal surface and consequent complicated manipulation. This study proposed a novel electrochemical mechanical polishing (ECMP) process for SLM internal holes to eliminate the partially melted powders and improve surface quality. This ECMP process could reduce the topographical fluctuation of the internal surface by eliminating the partially melted powders, thus reducing the surface roughness (Sa) values of the straight hole from 14.151 to 3.880 μm. During the electrochemical dissolution, the mechanical effect could minimize surface fluctuation and discharge gas bubbles and electrolytic products, facilitating the continuous polishing process and realizing an even and flat surface. This proposed ECMP process could also sufficiently polish the curving internal hole with eliminating the partially melted powders, which exhibited a rather smooth surface with significantly reduced Sa values from 15.522 to 9.095 μm.

Achieving a highly crystalized perovskite active layer with a dense, flat surface and a large grain size is very significant for constructing efficient perovskite solar cells (PSCs). Regarding this...

PurposeHumanoid robots have complicated dynamics, and they lack dynamic stability. Despite having similarities in kinematic structure, developing a humanoid robot with robust walking is quite difficult. In this paper, an attempt to produce a robust and expected walking gait is made by using an ALO (ant lion optimization) tuned linear inverted pendulum model plus flywheel (LIPM plus flywheel).Design/methodology/approachThe LIPM plus flywheel provides the stabilized dynamic walking, which is further optimized by ALO during interaction with obstacles. It gives an ultimate turning angle, which makes the robot come closer to the obstacle and provide a turning angle that optimizes the travel length. This enhancement releases the constraint on the height of the COM (center of mass) and provides a larger stride. The framework of a sequential locomotion planer has been discussed to get the expected gait. The proposed method has been successfully tested on a simulated model and validated on the real NAO humanoid robot.FindingsThe convergence curve defends the selection of the proposed controller, and the deviation under 5% between simulation and experimental results in regards to travel length and travel time proves its robustness and efficacy. The trajectory of various joints obtained using the proposed controller is compared with the joint trajectory obtained using the default controller. The comparison shows the stable walking behavior generated by the proposed controller.Originality/valueHumanoid robots are preferred over mobile robots because they can easily imitate the behaviors of humans and can result in higher output with higher efficiency for repetitive tasks. A controller has been developed using tuning the parameters of LIPM plus flywheel by the ALO approach and implementing it in a humanoid robot. Simulations and experiments have been performed, and joint angles for various joints are calculated and compared with the default controller. The tuned controller can be implemented in various other humanoid robots