Effective and Low-Maintenance IMTA System as Effluent Treatment Unit for Promoting Sustainability in Coastal Aquaculture

Integrated multitrophic aquaculture (IMTA) is a versatile technology emerging as an ecological and sustainable solution for traditional monoculture aquacultures in terms of effluent treatment. Nevertheless, IMTA is still poorly applied in aquaculture industry due to, among other reasons, the lack of effective, low-investment and low-maintenance solutions. In this study, one has developed a practical and low maintenance IMTA-pilot system, settled in a semi-intensive coastal aquaculture. The optimisation and performance of the system was validated using Ulva spp., a macroalgae that naturally grows in the fishponds of the local aquaculture. Several cultivation experiments were performed at lab-scale and in the IMTA-pilot system, in static mode. The specific growth rate (SGR), yield, nutrient removal, N and C enrichment, protein and pigment content were monitored. Ulva spp. successfully thrived in effluent from the fish species sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) production tanks and significantly reduced inorganic nutrient load in the effluent, particularly, NH4+, PO43− and NO3−. The enrichment of nitrogen in Ulva spp.’s tissues indicated nitrogen assimilation by the algae, though, the cultivated Ulva spp. showed lower amounts of protein and pigments in comparison to the wild type. This study indicates that the designed IMTA-pilot system is an efficient solution for fish effluent treatment and Ulva spp., a suitable effluent remediator.

The output stage of an operational amplifier on GaAs n-channel field-effect and GaAs p-n-p bipolar transistors with nonlinear negative feedback

<p>A new circuit of the output stage of an operational amplifier implemented on GaAs n-channel field-effect transistors with a control p-n junction and GaAs bipolar p-n-p transistors is investigated. Its peculiarity consists in the presence of a nonlinear negative feedback that stabilizes the drain current of the output transistor with an n-channel at a negative input voltage. The basic equations for the static mode of the output stage are given. The results of modeling in the LTspice simulation software of 3 modifications of the proposed circuit solutions are discussed.</p>

The output stage of an operational amplifier on GaAs n-channel field-effect and GaAs p-n-p bipolar transistors with nonlinear negative feedback

<p>A new circuit of the output stage of an operational amplifier implemented on GaAs n-channel field-effect transistors with a control p-n junction and GaAs bipolar p-n-p transistors is investigated. Its peculiarity consists in the presence of a nonlinear negative feedback that stabilizes the drain current of the output transistor with an n-channel at a negative input voltage. The basic equations for the static mode of the output stage are given. The results of modeling in the LTspice simulation software of 3 modifications of the proposed circuit solutions are discussed.</p>

Ergonomic risk factors and musculoskeletal disorders in bank staff: an interventional follow-up study in Iran

Background Long-term use of computer in a static mode may cause musculoskeletal disorders (MSDs) in bank staff. Considering the high number of bank employees in different countries, such as Iran, the risk factors of these disorders should be investigated in order to implement interventions required to reduce the risk factors. This study aimed to examine the risk factors of MSDs using the Rapid Office Strain Assessment (ROSA) method and to perform an ergonomic intervention program with banking staff in Iran. Methods This interventional study was conducted on 277 bank employees in Iran. Subjects were randomly divided into three groups, including a control group (without any intervention), an educational intervention (EI) group, and a group receiving both educational and physical intervention (EPI). Before and after the intervention, the ROSA method and Nordic questionnaire were used to assess the risk factors of MSDs in office jobs and to investigate the prevalence of MSDs. Data were collected 2 weeks before and 9 months following the intervention. Results Before the intervention, the mean score of ROSA at workstations of all groups was above five with high risk. Nine months after the start of the intervention, there was a significant decrease in the mean ROSA score and its components in the two groups that received the intervention, which was statistically significant (P < 0.001). The results of the study of the prevalence of MSDs in the employees—before the intervention—indicate that the highest prevalence of MSDs in the control group was in areas of the neck (67.1%), back (64.4%), and lower back (63%). In the EI group, the highest prevalence of MSDs was in the neck (65.2%), lower back (61.6%), and back (60.7%) areas. In the EPI group, the discomfort areas were the neck (68.5%), shoulders (66.3%), and lower back (60.9%). Nine months after the intervention, there was a significant decrease in the prevalence of MSDs in the neck, shoulders, and lumbar regions of staff who received the intervention (P < 0.05). Conclusion Nine months after performing the interventions, there was a relative improvement in workstations and prevalence of MSDs in various areas within the bodies of the bank staff. This study showed that using the ROSA method is appropriate for assessing the risk factors of office work and that it can identify deficiencies in workstations. These defects can be addressed by designing and implementing an EI program together with physical interventions according to the components of the ROSA method.

On SINS\Star Tracker Geo-localization

This work focuses on the feasibility of a fully autonomous geo-localization system for near-earth applications based on the strap-down inertial navigation system (SINS) and the star tracker. First, each sensor is analyzed individually. Then, the performance of the integrated system in a dynamic situation is investigated. Moreover, a detailed angle error analysis is given to estimate the impact on geo-localization. The navigation solution is proven to be affected by the sensors' errors plus an algorithmic error from the dead reckoning computation. Lastly, simulations are concluded to assess the dynamic movement scenario's performance and navigational possibility using the nonlinear Kalman filter. The results show the continuing divergence of the integrated navigation system affected by the dead reckoning algorithm. However, the continuous initial alignment in static mode reinitializes the position error successfully.

Structural Health Monitoring Issues Using Inclinometers on Prestressed Concrete Girder Bridge Decks

In the last decades, assessment and rehabilitation of the existing built environment constitute one of the major challenges for engineers, practitioners and code-makers all over the world. Aging, deterioration processes, lack of or improper maintenance, and increasing occurrence of extreme events have led to the need of more efficient methods for the safety assessment and retrofitting/rehabilitation of existing concrete structures like bridges. New approaches deriving from research should be able to provide solutions devoted to reduce and/or avoid the necessity of interventions, verifying the safety conditions for human life and performances for serviceability on aged infrastructures. Structural Health Monitoring (SHM) of existing bridges has become a key issue in all western world as most of the infrastructures of each Country are reaching the end of their design life. SHM can be divided classically in two approaches: static and dynamic. Static SHM is based on the measure of displacements and their derivatives like rotations or strains regardless of the dynamic behaviour of the structure. Clinometers are among the most used devices to measure angles on structures; they can provide high accuracy when used in static mode as advanced techniques of signal processing can be used to reduce the noise of the signal working on acquisitions that can last several seconds to provide one single accurate measure of angle. Nevertheless, many issues one the affidability and the correct use of measures done with clinometers have to be addressed to achieve a trustworthy SHM using such devices. In this paper the most relevant issues related to the f.e.m. modelling of a bridge deck in view of the use of clinometers for SHM are presented providing explanation using a test case bridge that has been under continuous investigation for many months. A brief explanation of the process for data cleaning and interpretation is also given, stressing out the limits of the technology and the possible outcomes.

CONTRIBUTION OF BATHYMETRIC MULTI-BEAM SONAR AND LASER SCANNERS IN 3D MODELING AND ESTIMATION OF SILTATION OF DAM BASIN IN MOROCCO

In Morocco, the phenomenon of silting affects all the dams, where more than 75 Mm3 of sediments are deposited every year at the bottom of the reservoirs. The aim of our study is to assess the contribution of the bathymetric multi-beam sonar as well as static and mobile laser scanners in the estimation of siltation of the basin of the Tanger-Med dam in the north of Morocco. The proposed methodology consists of performing and fusion of a bathymetric survey by multi-beam echo-sounder with terrestrial laser scanner surveys in static mode and mobile mode. The result of these surveys is used, for the calculation of the siltation volume and the inspection of the upstream facing of the main structure. Siltation calculation was carried out with comparison to a reference survey obtained by single beam sonar. The comparison between these two instruments showed that the multi-beam presents many advantages: high density of the cloud of points acquired and precision. The density allows providing a better description of the dam's bottom. The comparative study between the two types of scanners showed that static scanner offers a better accuracy. However, mobile scanner gives more accessibility of all parts of the dam. As a conclusion, the multi-beam echo-sounder with additional laser scanner data have many advantages in this study: volume calculation precision, reduction of the acquisition time and the enhancement of the acquired point cloud density. We also obtained a global 3d modelling useful for the monitoring of the infrastructure.

Model of the States of Critical Information Infrastructure Subjects under Destructive Influences in Static Mode

With the introduction of 187-FL "On the security of critical information infrastructure in the Russian Federation", a class of tasks requiring new approaches was determined. This is due to the solution of not only practical problems with the introduction of this law, but also with the development of its scientific and methodological support, which is one of the tasks of regulators. The main regulatory problem in ensuring the security of critical information infrastructure (CII), in our opinion, is associated with the lack of a systematic approach as a methodological basis for developing requirements for the development of CII. This leads to gross errors and errors in the course of making managerial decisions, therefore, to an increase in information security risks. When considering the subject of CII as a system, there is a need to consider inter-object relationships as sources of destructive influences that can lead to the effect of infrastructural "destructivism", i.e. to the self-destruction of infrastructure. To study this issue at the initial stage, it is proposed to build a model of the states of CII subjects in a static mode. In the course of working with this model, it is possible to predict the development of the situation of self-destruction of the infrastructure of the CII subject in a situation of uncertainty.

Investigation of the operation of a ship’s synchronous generator based on a numerical model

The article presents the results of modeling a ship’s synchronous generator. Based on preliminary design calculations, a geometric model of the generator was built. The static and overclocking processes of the generator are investigated. For static modes, the frequency response of the process is obtained. A numerical model was used to identify a mechanical defect. On the example of a simulated defect of an electrical machine - the eccentricity of the generator rotor, the signature of the defect signal is obtained. The study revealed that the presence of rotor eccentricity leads to the appearance of a harmonic component in the spectrum of the force of large amplitude with a maximum value at a low frequency. Transient analysis was carried out using wavelet transformations. The results of the study of dynamics show how the rotor speed increases. The simulation revealed three frequency regions of the signal under study: the region of the increase in speed, the achievement of the critical speed (between the second and third seconds), and the exit to the steady-state. A diagram of a system for diagnosing defects in an electrical machine using a digital twin - a numerical model is proposed. Generator defects (mechanical and electromechanical) can be identified based on model data. Databases of defect signatures in a static mode and a diagnostic model, which contains algorithms for deciding on the presence of a defect, can serve as the basis of information for an operator to decide.

Selection of sorption materials for the extraction of nickel and cobalt from the ore of the Gornostaevskoye deposit

Oxidized nickel ores account for the majority of industrial ores suitable for nickel production. The processing of such ores using traditional pyrometallurgical technology is not economically viable due to the low nickel content. One of the most cost-effective methods of processing oxidized nickel ores is sulfuric acid leaching technology followed by sorption extraction. The aim of this work is to establish the kinetic and thermodynamic parameters of the sorption extraction of nickel and cobalt using iminodiacetate chelating ion-exchange sorbents from various manufacturers, to select a desorbing solution and to determine the degree of desorption. The sorption of nickel and cobalt was carried out in a weakly acidic medium from a model solution containing impurities of other metals in static and dynamic modes. The limiting sorption capacity for the studied sorbents is 18-26 mg/g for nickel and 1-2 mg/g for cobalt in the static mode. The sorption capacity in the dynamic mode for nickel is equal to 25.5 g/L for Purolite S 930, 29.2 g/L for Lewatit TP 207, 1.4 g/L, and 1.8 g/L for cobalt, respectively. The best desorption parameters are achieved when using a 2 M sulfuric acid solution. The degree of desorption for sorbents Purolite S 930 and Lewatit TP 207 exceeds 90%. The use of the Lewatit TP 207 sorbent for the extraction of nickel from the leaching solution of nickel ore of the Gornostaevskoye deposit in 5 cycles made it possible to obtain a commercial desorbate with a nickel content of 18 g/L. The use of a part of the commercial desorbate obtained in the previous cycle, further strengthened to the initial concentration of sulfuric acid, for re-extracting nickel from the saturated sorbent during a cyclic process leads to a deterioration in desorption characteristics. It is recommended to remove the commercial desorbate from the process after several cycles of desorption and supply new solution of sulfuric acid for desorption to restore the sorption parameters.