62 research outputs found
Surface roughness modeling of CBN hard steel turning
Study in the paper investigate the influence of the cutting conditions parameters on surface roughness parameters during turning of hard steel with cubic boron nitrite cutting tool insert. For the modeling of surface roughness parameters was used central compositional design of experiment and artificial neural network as well. The values of surface roughness parameters Average mean arithmetic surface roughness (Ra) and Maximal surface roughness (Rmax) were predicted by this two-modeling methodology and determined models were then compared. The results showed that the proposed systems can significantly increase the accuracy of the product profile when compared to the conventional approaches. The results indicate that the design of experiments modeling technique and artificial neural network can be effectively used for the prediction of the surface roughness parameters of hard steel and determined significantly influential cutting conditions parameters
DETERMINATION OF CHANGE IN CONTENT OF HEAVY AND RADIOACTIVE METALS IN DRINKING WATER BY AN INDIRECT ANALYSIS METHOD BASED ON SCALE TESTS
In this paper the content of metal in drinking water was determined in two samples, one from 2008 and other from 2010, by the indirect method based on the analysis of scale, which had originally been suggested by Rajkovic and associates. Received results confirmed that drinking water according to the metal content was of constant level (metals are lower than MAC values), but with increased content of U. By the method of fraction extraction it was proved that increased content of U regarded mainly to natural U, and less to U of anthropogenic origin. The increased content of isotope 90Sr was also noticed, probably as the effect of increased presence of alkaline earth metals. The analysis structure of scale by the usage of SEM determined that the dominant form was calcium carbonate of crystal structure of hexagonal shape which corresponded to calcite. By Röentgen diffraction analysis of dust it was determined the content of calcite which contained CaO; MgO; FeO; MnO and CO2 and it belongs to medium manganese calcites. All the analyses done in this paper, confirmed that indirect method of determination of metal content had been reliable and applicable for determination of low concentrations of metals in drinking water
Stanje površinskog sloja materijala obratka kod visokoučinskog brušenja
This paper focuses on the development of high temperatures in the cutting zone during high performance grinding. In order to identify the influence of grinding temperature on surface integrity, temperatures were measured in the workpiece surface layer under different machining conditions. Beside this, under the same conditions, the surface layer properties of the workpiece material were determined through metallographic examination. Microstructureand microhardness of the workpiece surface layer, as well as the burned surfaces and microcracks phenomena were investigated. The conducted experimental investigations allow the surface layer properties of the workpiece material in high performance grinding to be defined.U članku se ukazuje na pojavu visokih temperatura u zoni rezanja pri visokoučinskom brušenju. Da bi se ustanovio utjecaj temperature brušenja na kvalitet obrađene površine, izmjerene su temperature u površinskom sloju materijala obratka pri različitim uvjetima obrade. Ujedno je pri istim uvjetima obrade određeno stanje površinskog sloja materijala obratka metalografskim ispitivanjima. Ispitane su mikrostruktura i mikrotvrdoća površinskog sloja obratka i pojava nagorjelih površina i mikropukotina. Izvedena eksperimentalna istraživanja defi niraju stanje površinskog sloja materijala obratka kod visokoučinskog brušenja
Friction stir welding (FSW) process of copper alloys
The present paper analyzes the structure of the weld joint of technically pure copper, which is realized using friction stir welding (FSW). The mechanism of thermo-mechanical processes of the FSW method has been identified and a correlation between the weld zone and its microstructure established. Parameters of the FSW welding technology influencing the zone of the seam material and the mechanical properties of the resulting joint were analyzed. The physical joining consists of intense mixing the base material along the joint line in the “doughy” phase. Substantial plastic deformations immediately beneath the frontal surface of tool provide fine-grained structure and a good quality joint. The optimum shape of the tool and the optimum welding regime (pressure force, rotation speed and the traverse speed of the tool) in the heat affected zone enable the achievement of the same mechanical properties as those of the basic material, which justifies its use in welding reliable structures
Design optimization of the box section of the single-girder bridge crane by generalized reduced gradient algorithm
Abstract
The paper considers the problem of design optimization of the box section of the single-girder bridge crane. Reduction of the girder mass is set as the objective function. The algorithm of generalized reduced gradient (GRG2 algorithm) was used as the methodology for determination of optimum geometrical parameters of the box section. The criteria of permissible stresses, local stability of plates, lateral stability of the girder, static deflection, dynamic stiffness and production feasibility (distance between the webs) were applied as the constraint functions. The optimization of the box section geometrical parameters was conducted for payloads and spans typical for single-girder bridge cranes
Uloga vaspitača i učitelja u prevazilaženju diskontinuiteta između predškolske ustanove i škole
At school, children spend the most beautiful period of their childhood and youth, and the moment they start school is always festive and exciting. However, it is known that school brings also the first concerns and problems. Problems and difficulties, which can occur at the beginning of schooling may, have long-term effects on the adaption and success of children, even on later adult life. The causes that lead to this situation are many and varied, and one of the most important is the educational gap in the educational system, whose essence lies in the disconnection between the various degrees of education. Taking into account the above findings, we discuss in this paper the most common causes that lead to the discontinuity between preschool and primary levels of education and areas in which the discontinuity is usually expressed. Also, the operation is determined and focused attention on certain assumptions and conditions that need to be accomplished in order to eliminate the effects of discontinuity abd achieve the necessary continuity between the pre-school and primary school children and facilitate the transition from lower to higher levels of education.Opšte je poznato da deca u školi provedu najveći i najlepši period svog detinjstva i deo mladosti. Sam trenutak polaska u školu uvek je svečan i uzbudljiv, ali on, pored radosti i ushićenja, nosi sa sobom i prve brige i probleme. Različiti oblici institucionalnog predškolskog vaspitanja i obrazovanja podstiču razvoj dečjih potencijala i sposobnosti u predškolskom periodu, što značajno doprinosi njihovoj adaptaciji na školske uslove života i rada. Međutim, i pored toga, u praksi se pojavljuju brojni problemi, koji za posledicu imaju lošu adaptaciju i slab uspeh u savladavanju programa predviđenih obaveza. Brojni su razlozi koji doprinose takvom stanju, a jedan od njih je diskontinuitet između predškolskog i osnovnoškolskog stupnja vaspitanja i obrazovanja. U radu se razmatraju najčešći uzroci koji dovode do diskontinuiteta između predškolskog i osnovnoškolskog stupnja vaspitanja i obrazovanja i mogućnosti za njegovo prevazilaženje, u čemu vaspitač i učitelj, imaju posebno važnu ulogu i značaj
Development of Modular and Adaptive Laboratory Set-Up for Neuroergonomic and Human-Robot Interaction Research
The industry increasingly insists on academic cooperation to solve the identified problems such as workers' performance, wellbeing, job satisfaction, and injuries. It causes an unsafe and unpleasant working environment that directly impacts the quality of the product, workers' productivity, and effectiveness. This study aimed to give a specialized solution for tests and explore possible solutions to the given problem in neuroergonomics and human–robot interaction. The designed modular and adaptive laboratory model of the industrial assembly workstation represents the laboratory infrastructure for conducting advanced research in the field of ergonomics, neuroergonomics, and human–robot interaction. It meets the operator's anatomical, anthropometric, physiological, and biomechanical characteristics. Comparing standard, ergonomic, guided, and collaborative work will be possible based on workstation construction and integrated elements. These possibilities allow the industry to try, analyze, and get answers for an identified problem, the condition, habits, and behavior of operators in the workplace. The set-up includes a workstation with an industry work chair, a Poka–Yoke system, adequate lighting, an audio 5.0 system, containers with parts and tools, EEG devices (a cap and smartfones), an EMG device, touchscreen PC screen, and collaborative robot. The first phase of the neuroergonomic study was performed according to the most common industry tasks defined as manual, monotonous, and repetitive activities. Participants have a task to assemble the developed prototype model of an industrial product using prepared parts and elements, and instructed by the installed touchscreen PC. In the beginning, the participant gets all the necessary information about the experiment and gets 15 min of practice. After the introductory part, the EEG device is mounted and prepared for recording. The experiment starts with relaxing music for 5 min. The whole experiment lasts two sessions per 60 min each, with a 15 min break between the sessions. Based on the first experiments, it is possible to develop, construct, and conduct complex experiments for industrial purposes to improve the physical, cognitive, and organizational aspects and increase workers' productivity, efficiency, and effectiveness. It has highlighted the possibility of applying modular and adaptive ergonomic research laboratory experimental set-up to transform standard workplaces into the workplaces of the future
Chemical reaction and diffusion dynamics
In this paper diffusion with chemical reaction was investigated. The concomitant advances in theory, measuring systems and computer simulation bring the new perspectives to the chemical reaction with diffusion studying. The chemical rate and diffusion rate parameters were considered. The obtained results shows effects the chemical reaction rate and diffusion rate. The obtained results demonstrate characterization of the dynamic and steady state conditions, transition between them and how it can be used to predict the stability of the system
The compliance of head-mounted industrial PPE by using deep learning object detectors
The compliance of industrial personal protective equipment (PPE) still represents a challenging problem considering size of industrial halls and number of employees that operate within them. Since there is a high variability of PPE types/designs that could be used for protecting various body parts and physiological functions, this study was focused on assessing the use of computer vision algorithms to automate the compliance of head-mounted PPE. As a solution, we propose a pipeline that couples the head ROI estimation with the PPE detection. Compared to alternative approaches, it excludes false positive cases while it largely speeds up data collection and labeling. A comprehensive dataset was created by merging public datasets PictorPPE and Roboflow with author’s collected images, containing twelve different types of PPE was used for the development and assessment of three deep learning architectures (Faster R-CNN, MobileNetV2-SSD and YOLOv5)—which in literature were studied only separately. The obtained results indicated that various deep learning architectures reached different performances for the compliance of various PPE types—while the YOLOv5 slightly outperformed considered alternatives (precision 0.920 ± 0.147, and recall 0.611 ± 0.287). It is concluded that further studies on the topic should invest more effort into assessing various deep learning architectures in order to objectively find the optimal ones for the compliance of a particular PPE type. Considering the present technological and data privacy barriers, the proposed solution may be applicable for the PPE compliance at certain checkpoints where employees can confirm their identity
- …