Marian Popescu

Technological advancements in the cloud field are becoming widely used on a large scale in increasing activity sectors. Agriculture is an important domain in everyday life, central to human existence. This research comparatively analyzes two proposed types of infrastructures that optimize the growth flow of plants in a hydroponic system for continuous monitoring, one full-cloud and one full-local. The study’s main objective is to determine which of the two infrastructures is more suitable for the hydroponic scenario by conducting seven types of tests. This research aims to fill a gap in the specialized literature through a detailed analysis of the configuration, implementation methods, and all implications of the two approaches from the perspective of the seven indicators. The seven indicators are response time, operational reliability, implementation costs, operational costs, configuration scalability, data accessibility, and data security. The cloud infrastructure uses Microsoft Azure technologies, while the local variant uses custom-made scripts and locally installed services. For both software infrastructures, the hardware components are identical, including an M5Stack module with sensors for monitoring temperature, humidity, electrical conductivity, and liquid level in the hydroponic container. The test results highlight that the local infrastructure offers a shorter response time (200 ms compared to 300 ms for the cloud infrastructure). The results also showed lower operational costs for the local infrastructure, making it more suitable for autonomous hydroponic systems. On the other hand, the results showed that cloud infrastructure has greater data accessibility than local infrastructure, and the security measures are advanced. These advantages of cloud infrastructure involve recurring costs of USD 82.57/month. The limitations of this research are associated with the exclusion of human errors and cybernetics simulations from the analysis. Another limitation concerns the real analysis of short-term costs. Future research will explore the real fluctuations of long-term costs. Additionally, infrastructure studies on different plant species and hydroponic farms will also be considered.

Refinery processes are characterized by high energy consumption and extremely long operating regimes. Increasing the profitability of refinery installations can be achieved by implementing optimal control systems. Due to the particularity of the processes, the steady-state regimes are particularly important and implicitly the optimal control in steady-state is often used. The paper presents the results of research carried out between 1990 and 2022 in the Petroleum-Gas University of Ploiesti, Romania.

Simulation is an efficient and inexpensive tool for testing automatic systems. The paper presents the authors' research in the field of simulation of automatic systems for quality control of the separated products in a distillation column. The used simulation environment is Unisim Design, the features of this environment allowing the implementation of a wide range of computational relationships. The proposed automatic system is designed to feedforward control the quality of the products. The control algorithm is based on the Fenske-Gilliland-Underwood relations, being adapted for multicomponent mixtures. The authors' efforts were oriented towards the substantiation of the programming actions, in the Unisim Design environment, of the computational relations associated with the controller.

Gasification is the thermal process that converts biomass into useful combustible and advantageous gaseous fuels or into chemical raw material that can be burned or used to produce chemicals with added value. The combustible gas contains carbon monoxide, hydrogen, carbon dioxide, methane, water, nitrogen. The aim of the paper is to develop a simulation model of biomass gasification process using UniSim Design environment. A steady-state model was elaborated for hardwood biomass to study the effect of variable process parameters on the products syngas composition. Results show that CO yield decrease with enhancement of water content, leading to a higher CO2 yield, due to the reforming reaction. The mole fraction of CO shows a decrease from 0.13 to 0.02 mole fraction, as the air flow rate increases from 1 to 15 kg/h, meanwhile the hydrogen content rises.

The development of the natural gas exploitation and transport industry involves both research in the field of compressor mechanics and their automatic control. The paper contains four parts and presents the state of research regarding the automation of centrifugal compressors built with recirculation pipes. In the first part the theoretical and industrial achievements presented in literature are analyzed. The second part deals with the steady-state modelling and simulation of a natural gas compression station. The third part presents the configuration features of the Unisim Design simulator used for dynamic simulation. The fourth part contains the results obtained in the dynamic simulation of the natural gas compression station and conclusions.

Natural gas is an important energy resource in the current international context. Natural gas processing plants are complex, depending on the gas composition and the separation technology. The research objective of the article is the demethanizer column in the gas treatment system. The paper is structured in three parts. The first part presents the structure of the natural gas treatment plant. The second part deals with the demethanizer steady-state simulation. The results highlighted the sensitivity of the outputs of the column to variations of the inputs, thus orienting the development of a new control structure. The third part presents the authors' contributions to the Basic Control Structure, Basic Control Structure Dynamic Simulation and Advanced Control Structure Design. The dynamic response validates the proposed advanced control structure.