Search

Studies and research carried out on seed meters of precision planters whose operating principle is based on the depression / suction of the air created during the work by the exhauster (vacuum generator) in the vacuum chamber have the role of helping to improve their performance. With the advancement of sowing technology, the emphasis on the ability of seed meters to accurately and consistently distribute seeds in the soil increases. The singularization of the seeds by means of the seed meters and their distance along the channels opened by the coulter is essential to ensure the achievement of the maximum yield of the crop sown on a certain area of land. The paper presents the numerical simulation of the working process for a pneumatic seed meter by means of a mathematical model, analysing the movement of the seeds according to the angle of detachment, the height of detachment of the seed, as well as the speed of the seed in its trajectory towards the channel opened by the coulter.

The paper presents the experimental validation of two mathematical models describing biomass powders compaction (a model that expresses the final density of pellets as determined by the final pressure applied during the process, the initial material moisture and the initial density of the material, but also a mathematical model obtained through dimensional analysis, using Π theorem, expressing the density of pellets as determined by pressure, heat, the initial density of the material, the pelleting speed of and the initial volume of the material), through experimental researches using a ring die pelleting equipment. The results showed a strong correlation between the data estimated theoretically and the experimental data, but also a strong influence of biomass material initial moisture on the density of the pellets obtained.

Due to electrical energy reduction need, in the recent years, alternative light sources like Compact Fluorescent Lamps (CFL) and Light Emitting Diode lamps (LED) are replacing the classical incandescent light bulbs. Although they consume less power, these lamps have the disadvantages of being a significant source of harmonics. This means that the lightning network should be redesigned taking into account the magnitude of the current harmonic components and of the null current. To this aim, an accurate model easy to build and a fast analysis are very useful. This paper presents three models for different types of energy saving light bulbs, two existing ones and a new implementation, a procedure for model parameters identification and a comparison of the models. Some errors criteria are considered, both qualitative and quantitative. The periodic steady state response is computed using a frequency domain analysis.

Pole/zero expressions as a function of circuit parameters are essential for circuit designers. Because the exact symbolic expressions become complex even for small circuits, a number of programs designed to compute the numerical or the poles and zeros approximate symbolic expressions have been developed. In this paper a procedure able to compute both the numerical and the approximate symbolic poles and zeros expressions of a circuit is used for a band-stop filter. The numerical values obtained with this procedure are compared with those computed by Hspice and SapWin. The approximate symbolic pole/zero expressions are used to generate the transfer function of the filter and its frequency characteristic is compared with the result of an a.c. analysis. Several design solutions starting from the computed pole/zero approximate symbolic expressions are discussed.

Power systems may be simulated in the time domain or in the frequency domain. The most efficient simulation methods are the harmonic balance (HB) analysis of ADS and the periodic steady state (PSS HB) implemented in Cadence. Recently new frequency domain (FD) models of nonlinear loads have been proposed and implemented in ADS. Their performance has been compared only with transient analysis using time domain (TD) models of ADS. This paper compares the CPU times employing TD and FD models, using the following analyses: transient analysis and HB analysis of ADS, and PSS analysis (TD shooting) and PSS HB of Cadence. Using a test circuit with 100 rectifiers, the ADS HB with FD models proves to be much more efficient than the other methods.

The equipment for burying in the ground the drip irrigation lines was designed and built at INMA Bucharest, within a complex research project carried out in partnership with other institutes, universities and research stations in Romania. The equipment is intended for drip irrigation technology for field crops. Subsurface crop irrigation technology is a variant of the classic drip irrigation technology, in which the drip lines are buried below the soil surface, providing water directly to the root zone of the plants. The depth of burial and the distance between the drip lines depends on the type of soil and the structure of the roots of the crop. The activities prior to the experimental research consisted in determining the characteristics of the test field (soil compactness, soil moisture, geographical coordinates of location). Experimental research of the equipment aimed at determining the energy indices (working speed, traction force, traction power, working capacity and fuel consumption).

Accurate information about fluid distribution in different compartments of the human body is very important in various areas of medicine like drug dosage, renal replacement therapy, nutritional support, coronary artery disease, colorectal cancer and HIV infection. The body impedance analysis method being simple, inexpensive, accurate and noninvasive is largely used to this end. Several models of the body impedance are presented in this chapter. The first is the Cole model, a linear, first-order RC circuit valid for a frequency range of two decades. Another model, developed by De Lorenzo, employs a fractional-order impedance whose parameters are identified using the frequency characteristics of the impedance module and can be used for a frequency range of three decades. In addition, two other models are presented, a ladder RC model valid for a frequency range of two decades and its extension to three decades, as well as a circuit containing multiple RC branches connected in parallel. These two models are obtained by approximating the measured body admittance modulus with a physically realizable circuit function followed by the circuit synthesis. The last model can be simplified, its simplest form being the Cole model. Allowing a better prediction of the intracellular and extracellular water volumes, this model can be viewed as an extension of the Cole model.

due to electrical energy reduction need, in the recent years, alternative light sources like Compact Fluorescent Lamps (CFL) and Light Emitting Diode lamps (LED) are replacing the classical incandescent light bulbs. Although they consume less power, these lamps are a significant source of harmonics. This means that the lightning network should be redesigned taking into account the magnitude of the current harmonic components and of the null current. An accurate model easy to build and a fast analysis are very useful to this aim. This paper presents three models for a CFL, two existing ones and a new implementation, and a comparison from the viewpoint of validity range and simulation time. A frequency domain analysis is used to compute the periodic steady state response.

It is important to know all phenomena that occur during compression of grape seeds because are very complex. Studying these phenomena can help us in increasing the performance of the equipment. Also for the pressing of oilseed materials, it is helpful to understand the compression behavior of grape seeds. The purpose of this study is to find how the stress and deformation propagate in grape seeds during the compression process. Therefore, we used an advanced engineering method named finite element method that shows the propagations of stress and strain fields in grape seeds. In this paper, we made a two dimensional model of grape seed and we analyzing the dispersion of stress and strain with a dedicated software FEM. In the end, to validate the FEM model we made a compression test on grape seeds using a Hounsfield unit. This study is for highlighting the importance of the orientation of the grape seeds during the pressing process to reduce the energy consumed.

Functional ingredients have gained a large-scale development determined by the increased interest shown by consumers worldwide. Functional ingredients are bioactive compounds that can be used in the manufacture of functional food products. These bioactive compounds can be obtained from accessible materials. The use of these materials aims to transform affordable raw materials at low prices into functional ingredients concentrated in proteins, amino acids, minerals and fibres, which can be used to obtain foods with a beneficial role in health. The paper presents a series of experimental researches for obtaining and characterizing functional materials obtained from Jerusalem artichoke and hemp seeds. The samples obtained had low moisture content, between 5.11 – 5.43 % for Jerusalem artichoke and 4.8 – 5.13 % for hemp, ideal for storage and use as powder. Jerusalem artichoke registered high sugar contents (between 21.2 – 27.2 %), while hemp flour had high fat content (between 18.56 – 23.52 %), making both products suitable to be used as functional ingredients in the food industry.

A new approach in the frequency domain analysis of the home appliances networks, previously developed by the authors, is compared with two recent approaches. It follows that our approach is simpler and allows a faster computation of the periodic steady state for home appliances networks. New frequency domain models for some home appliances are presented.

New frequency domain models for nonlinear home appliances as air conditioning systems, vacuum cleaners, microwave ovens and compact fluorescent lamps are proposed. These models employ measured amplitudes and phases of the current fundamental and harmonic components. The harmonic balance simulation using these models is very fast.

Settling time (ST) and phase margin (PM) of an op-amp with an arbitrary number of poles/zeros are estimated using the approximate pole/zero symbolic expressions. The method is illustrated by finding the symbolic expressions of ST and PM for a fully differential two-stage op-amp in terms of load, feedback, and Miller capacities. In this case the closed loop voltage gain has 8 poles and 7 zeros.

Mountain tourism is one of the traditional forms of tourism in affirming tourism in North Oltenia, both nationally through natural potential available by the low degree of degradation of the landscape and the investment efforts that were made in the offer specific. However maintaining and expanding national and international tourist market offer mountain in this area in the context of trends of competing countries require new efforts offer guidance on several important strands. The paper highlights a number of proposals to design and sports facilities that are designed to highlight the promising potential of resorts in the mountains are in the north of Oltenia that have the best ski area in Central and Eastern Europe ski.

All vehicles produced today must be fitted with an On-Board Diagnostic (OBD) interface. With the help of the OBD a data connection through the Controller Area Network (CAN) is realized with the Engine Control Unit (ECU). This control unit is instrumental in optimizing the engine performance. There are many OBD adapters on the market today, ranging from the cheap Do-It-Yourself kind to expensive, professional ones that can be used for telemetry data on racing cars. There is also a wide choice of software to interpret the data provided by the OBD, depending on platform and cost. A small review, which by no means is exhaustive, of available hardware and software needed to access this data is presented. Test results performed with compatible software using an ELM327 OBD II interface with WiFi capabilities on a Skoda Rapid model 2015 are given.

Measurements of the intermodulation products with frequency 2ƒ 1 −ƒ 2 (ƒ 1 - transmitter frequency, ƒ 2 - antenna frequency) for a W-CDMA professional duplexer filter are presented. It is proved that the 2ƒ 1 signal and the intermodulation product are generated in this power BAW filter, despite its careful design.

New frequency domain models for nonlinear loads as one diode and two diodes rectifiers are proposed in this paper. Using these models in the harmonic balance analysis, the simulation time is shortened with about one order of magnitude than that corresponding to the employment of the classical nonlinear models described in the time domain.

This paper compares three possibilities for determining the flicker level generated by industrial customer with arc furnaces: by calculating the electromagnetic perturbations, by experimental measurements, and by simulation using specialized software. The influence of the fault level on the propagation of perturbation in the power system represents a challenging issue studied within the existing context. Several mitigation measures of voltage fluctuations have been considered in this paper. A solution is using a STATCOM, which avoids the exceeding of admissible perturbation levels stipulated by the standards.

The article will present a static analysis of the equipment in order to calculate the vector field distribution of the relative resulting displacement in the structure, the Cauchy stress tensor and tensor fields distribution of the specific deformation in the same structure. This is done in order to improve the structure and highlight the most vulnerable points within an equipment depending on the way of working. After performing the static analysis, tensometric marks were mounted in the most vulnerable points to calculate the displacement of the material and to calculate the major forces that appeared in the structure during the field experiments. At the same time, the idea of the equipment prototype was to improve the equipment with vibrating elements on the working bodies of the body type in order to increase the degree of crushing and to reduce the advancing forces, respectively to reduce the fuel consumption. Therefore, a modal analysis was performed to calculate the vibrations that appeared in the structure in order not to resonate with the frequency of the motor mounted on the working member.

This paper presents results of power quality monitoring collected from transmission system operator (TSO) and several distribution system operators (DSOs) from Romania. The power quality monitoring system is realized in accordance with actual technologies, economic criteria, performance standards and technical codes issued by the Romanian Energy Regulation Authority (ANRE). The implementation of power quality policies in Romania based on the monitoring and corrective actions determined the improvement of quality of transmission and distribution services in power system. The challenges represented by the connection to the grid of new renewable sources have determined ANRE to issue dedicated regulations. The use of the power quality monitoring systems at the interface between TSO and DSO (Distribution Management System, Fault Recording System, Outage Management System) provides better solutions and leads toan increase in the quality of services. The influence of the short-circuit in the propagation of perturbation in power system represents a challenge within the existing context when many renewable sources are connected to the grid.