Research on Tracking the Behavior of the Ciobanus Forest Road over a Season Time through Specific Tests and Analysis

Forest roads are of great economic importance as they ensure the transport of logs and forest biomass toward collection and processing centers, which is why they should be evaluated periodically, in order to establish the degree of degradation and periodicity and rehabilitation methodology and procedures. The main purpose of the paper is to follow the behavior of the Ciobanus forest road through specific tests over a difficult season of 5 months, in order to diagnose the degree of surface wear and structure degradation. Regarding the traffic on this forest road, an exhaustive study was made during the 2013–2017 period, and for in situ or in laboratory tests a more complex study during the year 2018, in the March-June period was also made. Out of the total of 20 tests that evaluated the Ciobanus forest road, 5 of them were classified as appropriate and 15 unsuitable for traffic, meaning the forest road had to be completely rehabilitated. Moreover, it has been shown that this forest road is part of the category of secondary forest roads and needs a total overhaul to cope with the increasing traffic or tonnage of trucks. Through the methodology and the obtained results, the paper supports the specialists in the field of forest roads to be able to diagnose or evaluate such a road, and to realize a program and its timing for maintenance.

Undrained Elastoplastic Solution for Cylindrical Cavity Expansion in Structured Cam Clay Soil Considering the Destructuration Effects

Soil structure has significant influences on the mechanical behaviors of natural soils, although it is rarely considered in previous cavity expansion analyses. This paper presents an undrained elastoplastic solution for cylindrical cavity expansion in structured soils, considering the destructuration effects. Firstly, a structural ratio was defined to denote the degree of the initial structure, and the Structured Cam Clay (SCC) model was employed to describe the subsequent stress-induced destructuration, including the structure degradation and crushing. Secondly, combined with the large strain theory, the considered problem was formulated as a system of first-order differential equations, which can be solved in a simplified procedure with the introduced auxiliary variable. Finally, the significance and efficiency of the present solution was demonstrated by comparing with the previous solutions, and parametric studies were also conducted to investigate the effects of soil structure and destructuration on the cavity expansion process. The results show that the soil structure has pronounced effects on the mechanical behavior of structured soils around the cavity. For structured soils, a cavity pressure that is larger than the corresponding reconstituted soils when the cavity expands to the same radius is required, and the effective stresses first increase to a peak value before decreasing rapidly with soil structure degradation and crushing. The same final critical state is reached for soils with different degrees of the initial structure, which indicates that the soil structure is completely destroyed during the cavity expansion. With the increase of the destructuring index, the soil structure was destroyed more rapidly, and the stress release during the plastic deformation became more significant. Moreover, the present solution was applied in the jacking of a casing during the sand compact pile installation and in situ self-boring pressuremeter (SBPM) tests, which indicates that the present solution provides an effective theoretical tool for predicting the behavior of natural structured soils around the cavity.

Application of a finite deformation multiplicative plasticity model with non-local hardening to the simulation of CPTu tests in a structured soil

In this paper an isotropic hardening elastoplastic constitutive model for structured soils is applied to the simulation of a standard CPTu test in a saturated soft structured clay. To allow for the extreme deformations experienced by the soil during the penetration process, the model is formulated in a fully geometric non-linear setting, based on: i) the multiplicative decomposition of the deformation gradient into an elastic and a plastic part; and, ii) on the existence of a free energy function to define the elastic behaviour of the soil. The model is equipped with two bonding-related internal variables which provide a macroscopic description of the effects of clay structure. Suitable hardening laws are employed to describe the structure degradation associated to plastic deformations. The strain-softening associated to bond degradation usually leads to strain localization and consequent formation of shear bands, whose thickness is dependent on the characteristics of the microstructure (e.g, the average grain size). Standard local constitutive models are incapable of correctly capturing this phenomenon due to the lack of an internal length scale. To overcome this limitation, the model is framed using a non-local approach by adopting volume averaged values for the internal state variables. The size of the neighbourhood over which the averaging is performed (characteristic length) is a material constant related to the microstructure which controls the shear band thickness. This extension of the model has proven effective in regularizing the pathological mesh dependence of classical finite element solutions in the post-localization regime. The results of numerical simulations, conducted for different soil permeabilities and bond strengths, show that the model captures the development of plastic deformations induced by the advancement of the cone tip; the destructuration of the clay associated with such plastic deformations; the space and time evolution of pore water pressure as the cone tip advances. The possibility of modelling the CPTu tests in a rational and computationally efficient way opens a promising new perspective for their interpretation in geotechnical site investigations.

Degradation of lignin by Bacillus altitudinis SL7 isolated from pulp and paper mill effluent

Lignin is a major by-product of pulp and paper industries, which is resistant to depolymerization due to its heterogeneous structure. Degradation of lignin can be achieved by the use of potential lignin-degrading bacteria. The current study was designed to evaluate the degradation efficiency of newly isolated Bacillus altitudinis SL7 from pulp and paper mill effluent. The degradation efficiency of B. altitudinis SL7 was determined by color reduction, r lignin contents, and ligninolytic activity from degradation medium supplemented with alkali lignin (3 g/L). B. altitudinis SL7 reduced color and lignin contents by 26 and 44%, respectively, on 5th day of the incubation, as evident from the maximum laccase activity. Optimum degradation was observed at 40 °C and pH 8.0. FT-IR spectroscopy and GC-MS analysis confirmed lignin degradation by emergence of the new peaks and identification of low molecular weight compounds in treated samples. The identified compounds such as vanillin, 2-methyoxyhenol, 3-methyl phenol, oxalic acid and ferulic acid suggested the degradation of coniferyl and sinapyl groups of lignin. Degradation efficiency of B. altitudinis SL7 towards high lignin concentration under alkaline pH indicated the potential application of this isolate in biological treatment of the lignin-containing effluents.

An extended super/subloading surface model for soft rock considering structure degradation

The strain-softening and dilatancy behavior of soft rock is affected by the loading history and the development of structure. This study regards soft rock as a structured and overconsolidated soil and develops a new elastoplastic model based on the classical super yield surface Cam-clay model. The proposed model is capable of capturing the effect of yield surface shape on the mechanical behavior of soft rock by introducing a new yield function. The proposed model is validated against the triaxial test results on different types of soft rocks under drained condition. The comparison results indicate that the proposed model is suitable for describing the constitutive behavior of soft rock.

EMBEDDED SYSTEM FOR SUPPLY VOLTAGE CONVERTER OF ORGANIC LIGHT-EMITTING DIODE

The work is dealing with the problem of developing an embedded system for supply voltage converter of Organic Light-Emitting Diode (OLED) with advanced built-in ability to measure the volt-ampere (I – V) characteristics of structures directly during their operation. This feature is crucial in the development of a new generation of intelligent OLED controllers, which in relation to known solutions, are characterized by reduced power consumption and increased speed of periodic or continuous measurement of the I – V characteristics of OLED structures. On the basis of such measurement the drift of characteristics of OLED structures in the course of their operation is carried out, and therefore, the possibility of operative correction of their power modes is provided. The measurement of I – V characteristics of OLED structures is performed on the transients of voltage generation in the boost circuits of the drivers. To meet the requirements for such measurements, the parameters of the transient pulses must meet certain criteria. The pulse amplitude should be sufficient to scan the I – V characteristics of OLED structures in the whole range of their possible operation, and the shape and rise time should be optimal from the point of view of further detection of these I – V patterns, in particular, regarding their drift in temperature modulation or OLED structure degradation. In a number of tasks scanning and measurement of I – V characteristics should be fast enough to prevent heating, but acceptable for high-precision analog-to-digital conversion. The parameters of the pulses provide the ability to measure the thermal parameters of thermal resistance and its dependence on the duration of heating. The controller is implemented on the basis of programmable systems on the chip, namely on the PSoC 5LP.

Enhanced Reversible Zinc Ion Intercalation in Deficient Ammonium Vanadate for High-Performance Aqueous Zinc-Ion Battery

Ammonium vanadate with bronze structure (NH4V4O10) is a promising cathode material for zinc-ion batteries due to its high specific capacity and low cost. However, the extraction of $${\text{NH}}_{{4}}^{ + }$$ NH 4 + at a high voltage during charge/discharge processes leads to irreversible reaction and structure degradation. In this work, partial $${\text{NH}}_{{4}}^{ + }$$ NH 4 + ions were pre-removed from NH4V4O10 through heat treatment; NH4V4O10 nanosheets were directly grown on carbon cloth through hydrothermal method. Deficient NH4V4O10 (denoted as NVO), with enlarged interlayer spacing, facilitated fast zinc ions transport and high storage capacity and ensured the highly reversible electrochemical reaction and the good stability of layered structure. The NVO nanosheets delivered a high specific capacity of 457 mAh g−1 at a current density of 100 mA g−1 and a capacity retention of 81% over 1000 cycles at 2 A g−1. The initial Coulombic efficiency of NVO could reach up to 97% compared to 85% of NH4V4O10 and maintain almost 100% during cycling, indicating the high reaction reversibility in NVO electrode.