Numerical study of the hydraulic excavator overturning stability during performing lifting operations

This article presents a numerical study of the stability of a hydraulic excavator during performing lifting operations. A planar dynamic model is developed with six degrees of freedom, which considers the base body elastic connection with the terrain, the front digging manipulator links, and the presence of the freely suspended payload. Differential equations describing the excavator dynamic behavior are obtained by using the Lagrange formalism. Numerical experiments are carried out to study the excavator dynamic stability under different operating conditions during the motion along a vertical straight-line trajectory. It is shown that the arising inertial loads during the movement of the links along the vertical trajectory, combined with the payload swinging and the motion of the base body, decreases the excavator stability. It was found that the excavator stability during following vertical straight-line trajectory decreases considerably in the lower part of the vertical trajectory. If the stability coefficient is close to 1, the payload swinging can cause the separation of a support from the terrain; nevertheless, the excavator stability can be restored. A method for tire stiffness and damping coefficients estimation is presented. The validation of the dynamical model is performed by the use of a small-scale elastically mounted manipulator.DFG, 414044773, Open Access Publizieren 2019 - 2020 / Technische Universität Berli

Optimization of the Parameters of a Hydraulic Excavator Swinging Mechanism

The presented paper is focused to the optimization of the parameters of a hydraulic excavator swinging mechanism. A trapezoidal velocity profile is considered for rotation of the excavator platform to the predefined angle. Equations for the torque and power, needed to rotate the platform according to the prescribed trapezoidal trajectory are derived. The maximum values of the driving torque and power are optimized

Dynamical modelling of hydraulic excavator considered as a multibody system

This paper considers the development of a plane multibody mechanical model of a hydraulic excavator simultaneously containing an open kinematic chain and closed loops. The Lagrange multiplier technique is used for modelling of the constrained mechanical systems. This approach is used for working out the dynamic equations of excavator motion in the case of performing transportation and digging operations. The excavator is considered as a rigid body system and detailed governing equations of the mechanical and hydraulic systems are presented. The performed verification and a typical digging task simulation show the applicability of the model for study of the excavator motion simulation. Simulation results of the machine’s response are provided. It is shown that the digging process considerably influences the mechanical and hydraulic system parameters. Such models can be used for training simulators, sizing components and system design.DFG, 325093850, Open Access Publizieren 2017 - 2018 / Technische Universität Berli

Theoretical aspects of several successive two-step redox mechanisms in protein-film cyclic staircase voltammetry

Protein-film voltammetry (PFV) is a versatile tool designed to provide insight into the enzymes physiological functions by studying the redox properties of various oxido-reductases with suitable voltammetric technique. The determination of the thermodynamic and kinetic parameters relevant to protein’s physiological properties is achieved via methodologies established from theoretical considerations of various mechanisms in PFV. So far, the majority of the mathematical models in PFV have been developed for redox proteins undergoing a single-step electron transfer reactions. However, there are many oxido-reductases containing quinone moieties or polyvalent ions of transition metals like Mo, Mn, W, Fe or Co as redox centers, whose redox chemistry can be described only via mathematical models considering successive two-step electron transformation. In this work we consider theoretically the protein-film redox mechanisms of the EE (Electrochemical–Electrochemical), ECE (Electrochemical–Chemical–Electrochemical), and EECat (Electrochemical–Electrochemical–Catalytic) systems under conditions of cyclic staircase voltammetry. We also propose methodologies to determine the kinetics of electron transfer steps by all considered mechanisms. The experimentalists working with PFV can get large benefits from the simulated voltammograms given in this work

Surgical treatment of aortic aneurysms in a patient with Ehlers-Danlos syndrome

Ehlers-Danlos syndrome IS a rare inherited disorder of the connective tissue that has been divided Into 10 types according to the clinical course and Inheritance In type IV Ehlers-Danlos syndrome extreme fragility of the arteries Is associated with multiple aneurysm formation, spontaneous rupture, and dissection

Distribution of the disease Bois noir (stolbur) in some vineyards in Macedonia

Bois noir (BN) has been present in Macedonia for a long time, but its first scientific report dating back to 2003 (Šeruga et al. 2003). BN is caused by phytoplasmas from stolbur group (16SrXII-A). This group of phytoplasma infects a wide range of wild and cultivated plants in Europe. Three phytoplasma isolates associated with BN were identified in grapevine in the world: VKI VKII and VKIII (Langer & Maixner, 2004). In this study, the spreading of the phytoplasma isolates associated with Bois noir (BN) was investigated on grapevine in the biggest vineyards in Macedonia (Central Vardar region), in the season 2006/07. Used of molecular methods show the presence of Bois noir phytoplasma, type II, VKII, spreader in all investigated regions

Body mass index and health-related quality of life in patients preparing for coronary angiography

There is evidence that body mass index (BMI) is related to some extent to the health related quality of life (HRQoL) in different populations. The purpose of our study was to investigate the relationship between the BMI and the HRQoL in patients awaiting coronary angiography. The sample consisted of 100 patients (68 males and 32 females) with symptomatology indicated for coronary angiography. For all of them BMI was calculated. They were also administered Duke Health profile questionnaire which measures adult self-reported functional health status. The findings reveal that BMI is related to some aspects of HRQoL. Considering this, health counseling directed at regulating body weight as part of the positive health behavior can benefit and improve some domains of the HRQoL and the QoL per se of the individuals having health problems

SEM analyses of minerals from Allchar deposite - Republic of Macedonia

The Allchar Sb-As-Tl-Au volcanogenic hydrothermal deposit is situated at the northwestern margins of Kožuf Mts. (Republic of Macedonia), close to the border between Republic of Macedonia and Greece. From the geotectonic point of view, ore mineralization is related to a Pliocene volcano-intrusive complex located between the rigid Pellagonian block in the west, and the labile Vardar zone in the east. From the metallogenic point of view, the Allchar deposit belongs to the Kožuf ore district as part of the Serbo-Macedonian metallogenetic province.The locality is one of the Unique deposits in the world not because of its size but because of its mineral composition and diversity, including an abundance of particularly rare thallium sulfosalts

Bacterial Crown of Grapes with Particular Devote on the Seedling Material

The production of healthy bedding material of grapes are extremely complex and responsible work, which needs high qualifications and knowledge from different aspects. Bedding material can transmit many diseases and pests, and has a bad influence in susceptibility, developing and fruitfulness in grapes. The some problem makes bacterial crown gall indicated by Agrobacterium tumefaciens. The bacterium with its products, affect the meristem tissues and develop tumor tissues. So, the bacterium has an indirect influence perturbing leaf vein and root system. Diseased grafts have got a slow advancement and soon they decay

Транскатетер перкутано затворање на ductus arteriosus

Ductus arteriosus persistens (DAP) е честа аномалија со 9%- 15% од сите адулти со вродени срцеви маани (VSM) и во 25% кај други VSM. Новородени со коплексни VSM може да имаат DAP зависна циркулација (прекинат аортен лак, пулм. атрезија без VSD). Протокот зависи од ширината и пулмоналната васкуларна рестенција