In spite of an increasing number of rubber-tracked vehicles, there are no engineering models for predicting and optimizing the energy consumption of vehicles of this type. To formulate those models, ...the models of the phenomena resulting in the internal losses of rubber-track systems need to be developed. This article presents a model describing the losses caused by the transverse vibrations of rubber tracks. The predictions made using the model are discussed against the background of the preliminary experimental tests on a sample rubber track for heavy off-road vehicles. The model predictions and the experimental tests suggest that the losses caused by the 1st mode vibration of rubber tracks are marginal in relation to the total internal resistance of rubber-track systems. However, according to the model predictions, a significant increase in the rubber-tracked undercarriage internal resistance is expected as a result of the high-amplitude track vibrations corresponding to the higher-order modes. To make the model applicable in practice, a method for determining the essential parameters of the model, including the bending stiffness and the decrement of oscillation damping, is demonstrated. The accuracy of the method is confirmed by the computations, where the sag and the frequency of the 1st mode free vibration of a sample track are predicted with an error of 10% and 1.8%, respectively. The parameter values obtained by this method are suitable for modeling a wide variety of off-road vehicles. The method can be applied to many other types of reinforced rubber belts, e.g., conveyor belts.
Reliable assessment of soil mechanical parameters causes many problems due to its random nature, and therefore the literature on the subject provides many techniques in this area. The article ...presents an analysis of the state of the art in the field of process analogues (testers) for identifying soil compaction under external loads that are generated, for example, by the running gear components of off-road machinery and vehicles. A classification of these testers into three main groups is proposed: small-size (penetrometers), medium-size (plate testers), and large-size (chassis components). The cone index approach for small-scale testers is described in detail in the paper. Consequently, the bevameter approach, which is used for medium- and large-scale testers, is described in Part 2 of this pair of articles. The main application of penetrometers in terramechanics, which is to determine the mobility of off-road vehicles, mostly qualitatively, is highlighted, with a description of the most important mobility metrics, also in the context of the NATO Reference Mobility Model, also being presented. An overview of the devices is presented, with the tester area, applied pressure levels, types of soil tested, and field of use also being discussed. The analyses include static and dynamic testers. The pair of articles also presents the main issues with penetrometer testing, and the reasons for which bevameters are the most commonly used tester for determining quantitative soil parameters for the purpose of terramechanics.
•Penetrometers are basic testers for evaluating the mobility of off-road vehicles.•Various tester shapes are used with cone penetrometers being the most common ones.•There are methods for dynamic and impact soil testing incorporating penetrometers.•Taking from already conducted penetration tests can improve research pace.
•Comprehensive review of soil shear strength measurement methods is presented.•Results obtained with different methods differ by up to a few hundred %.•Shear speed affects strength of cohesive soils ...by up to a few hundred %.•C and φ are strongly affected by shear surface up to around 300 cm2.
Soil mechanics as a field of science has been developed for over a century. One of its most important issues is determination of soil strength. Despite passing years, there is still no universal method for determination of soil shear strength. The goal of this paper was to attempt to systematize methods for measurement of soil shear strength and describe the differences between them and where the differences come from. It presents a list of over 20 types of measurement methods, including their basic features such as dimensions or measurement speed. The list contains both standard and prototype methods that can be found in the literature. These methods can be divided into those with forced (direct shear) and with free shear plane (indirect shear), which comprise penetration testing. A comparative review of literature on different measurement methods shows substantial discrepancies, reaching up to few hundred percent, between methods. Cohesion and internal friction angle determined by these methods should not be treated as soil intrinsic properties, as they are affected by a number of factors. These factors—i.e. scale effect, wall effect, strain rate effect, bulldozing effect, shear kinematics, and type of material that the tester is made of—are described in this paper. The most important parameters of the test methods were found to be the geometry, kinematics and speed. The scale effect in soils during shear is discernible up to about 300 cm2 shearing surface; therefore, for most fine-grained soils, it is not necessary to use bigger test devices. Shear speed plays a significant role for cohesive soils, increasing cohesion values threefold or more. The article concludes with guidelines that, according to the authors, should be followed when selecting a method for measurement of shear strength to be applied when determining soil traction properties.
MCORD - MPD Cosmic Ray Detector a new features Bielewicz, M.; Milewicz-Zalewska, M.; Grodzicka-Kobylka, M. ...
EPJ Web of Conferences,
2019, Letnik:
204
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The main detector system at the Nuclotron-based Ion Collider fAcility (NICA) located in Dubna, Russia is the Multi-Purpose Detector (MPD). For better calibration reason, the MPD needs an additional ...trigger system for an off-beam calibration of MPD sub-detectors and for rejection (veto) of cosmic muons. The system should also be useful for practical astrophysics observations of cosmic showers. The consortium NICA-PL group defines goals and basic assumptions for the MPD Cosmic Ray Detector (MCORD). This article describes the conceptual design and simulation plans of the MCORD detector based on plastic scintillators with SiPM photodetectors and electronic digital system based on the MicroTCA crate.
•The internal losses of track systems can be represented by a single coefficient.•More complex models are needed to optimize the energy efficiency of track systems.•The literature describes the ...phenomena leading to internal losses in track systems.•Some of those phenomena are described by at least several alternative models.•Complex models of the internal losses of rubber-track systems need to be developed.
This article summarizes the known methods for calculating the internal resistance of tracked undercarriages. The values of the coefficient of internal resistance for sample tracked vehicles are available in the literature and presented in this paper. Although they are suitable for simple computations, they cannot be used to optimize the energy efficiency of new generation tracked undercarriages. This problem might be solved by the models where every phenomenon leading to energy dissipation during vehicle motion is described by a separate submodel as a function of vehicle speed, track tension, undercarriage layout, design features of the undercarriage components, etc. This kind of model is still missing for vehicles with conventional rubber tracks. The article presents multiple state-of-the-art models describing rolling resistance of road wheels, bending resistance of rubber belts, etc., including the models of belt conveyors resistance. A vast majority of the phenomena discussed herein are described by several incompatible models whose parameters have not yet been determined for conventional rubber tracks. Consequently, in the second and the third part of the article, the authors have undertaken a theoretical and experimental studies on the methods for calculating and optimizing the internal motion resistance of vehicles with conventional rubber tracks.
•Low-friction/low-hysteresis rubber liners reduce the motion resistance of rollers.•Rubber-track systems with oscillating bogie wheels exhibit small internal losses.•The more road wheels, the better ...the efficiency of a rubber-track system.•Uniform distribution of the vehicle weight to the wheels improves the efficiency.
In spite of an increasing number of rubber-tracked crawlers, the literature provides few guidelines and calculation models suitable for minimizing their internal motion resistance. This article presents a model where the internal resistance of double-flanged road wheels for rubber-tracked vehicles is calculated as a sum of the losses resulting from the indentation of the wheels into the track surface and friction of the wheels against the track guide lugs. The model allows for vertical and lateral load of the wheels, the non-uniform distribution of the wheel pressure on the track, and the relationship between the friction coefficient and normal reaction force in the interface between the wheel and track guide lugs. The model has been verified by experiments. According to the results of model computations and experiments discussed in the article, the internal losses of a given rubber-tracked undercarriage might be reduced if: the road wheels are covered with a material that exhibits low friction coefficient and mechanical hysteresis, the vehicle suspension system features oscillating bogie wheels, the undercarriage is fitted with the largest possible number of road wheels, and the vehicle weight is evenly distributed to all of the road wheels.
•Track tension does not significantly affect the bending losses of rubber tracks.•The bending resistance of rubber tracks decreases with increasing pulley diameter.•The bending resistance of rubber ...tracks increases with increasing track speed.•The efficiency of rubber-tracked vehicles increases with increasing drawbar pull.•The efficiency of light-weight rubber-tracked vehicles must be optimized.
Optimizing the efficiency of rubber-tracked undercarriages requires models for calculating external and internal motion resistance, including the resistance resulting from bending of rubber tracks. The experiments on the bending resistance of rubber tracks and a new model of this phenomenon are discussed in this article. An empirical model of friction in bearings typically implemented in driving and idler wheels of rubber-tracked undercarriages is also presented. According to the sample computations carried out on the basis of these models, the efficiency of rubber-tracked undercarriages might be improved by minimizing the number and maximizing the diameter of idler wheels. Furthermore, it has been shown that increase in the initial tension and driving force transmitted by rubber tracks does not significantly affect bending resistance of these tracks; however, it results in increased friction in the driving and idler wheels’ bearings. Nevertheless, the higher the driving force transmitted by the rubber tracks, the higher the efficiency of rubber-tracked undercarriages. Consequently, since track systems of vehicles operating at relatively small drawbar pull will manifest exceptionally low efficiency, there is a serious need for optimizing them in terms of energy consumption.
•New experimental analogue of wheel/track-soil interaction.•Takes into account the process dynamics, eliminates the scale and bulldozer effect.•Important phenomenon of strengthening of cohesive soils ...was confirmed.•Correctness of previously introduced criterion was confirmed.
This publication series describes the phenomenon of dynamic strengthening of soils. This part presents a literature review, based on which a new tester was designed. It allows shearing of soils in a wide range of speeds, it is not susceptible to the scale effect, wall effect and the bulldozing effect, as well as it has shear kinematics adequate to the modelled process. Comparison of the test device with direct shear tester showed a substantial decrease of cohesion and increase of internal friction angle of cohesive soils with the new tester. Four different cohesive and non-cohesive soils have been investigated in this study. Dynamic shearing tests have confirmed that cohesive soils may increase shear strength by up to almost 3 times compared to quasi-static shearing. Non-cohesive soil (quartz sand) did not exhibit distinct increase of shear strength. Validation of the new criterion proved it can be used to describe the shear strength – shear speed relationship of agricultural soils. The proposed model correlated with experimental data at R2 over 0.85 for cohesive soils and over 0.64 for sand.
Numerous studies show that 17β-estradiol (E2) protects against Alzheimer’s disease (AD) induced neurodegeneration. The E2-synthesizing enzyme aromatase is expressed in healthy hippocampi, but ...although the hippocampus is severely affected in AD, little is known about the expression of hippocampal aromatase in AD. To better understand the role of hippocampal aromatase in AD, we studied its expression in postmortem material from patients with AD and in a mouse model for AD (5xFAD mice). In human hippocampi, aromatase-immunoreactivity was observed in the vast majority of principal neurons and signal quantification revealed higher expression of aromatase protein in AD patients compared to age- and sex-matched controls. The tissue-specific first exons of aromatase I.f, PII, I.3, and I.6 were detected in hippocampi of controls and AD patients by RT-PCR. In contrast, 3-month-old, female 5xFAD mice showed lower expression of aromatase mRNA and protein (measured by qRT-PCR and semiquantitative immunohistochemistry) than WT controls; no such differences were observed in male mice. Our findings stress the importance of hippocampal aromatase expression in neurodegenerative diseases.
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