The theory of vibrational wave movement in drying grain mixture

This paper outlines a theory that involves the vibrational wave transportation of bulk grain during the course of passing that grain under an infrared radiation source, in a working thermal radiation drying chamber, and using a vibrational wave transporter belt that has been developed by the authors of this paper. The main outstanding feature of the proposed design is the presence of mechanical off-centre vibration drives which generate the vibration in the working rollers at a preset amplitude and frequency, thereby generating a mechanical wave on the surface of the flexible transporter belt which ensures the movement of bulk grain along the processing zone which itself is being subjected to infrared radiation. A calculation method was developed for the oscillation system that is used in conjunction with the vibrational transportation of the grain mass, in order to be able to determine the forces that may be present in the vibrational system and to prepare the differential calculations for the movement of the vibrational drive’s actuators, utilising for this purpose Type II Lagrange equations. The solving of the aforementioned integral equations on a PC yielded a number of graphical dependencies in terms of kinetic and dynamic parameters for the vibrational system described above; the analysis of those dependencies provided a rational structural, along with kinetic and dynamic indicators. According to the results that were taken from theoretical and experimental studies on the functioning of the developed infrared grain dryer combined with a vibrational exciter, stable movement for its working roller takes place if the angular velocity of a drive shaft is changed within the range of between 50–80 rads-1, whereas the amplitude of the indicated oscillations falls within the range of 3.0–4.0 mm. It has been discovered that a rational speed when transporting soy seeds during infrared drying falls between the range of between 0.15–0.60 cm·s-1, whereas the amplitude of the indicated oscillations falls within the range of 3.0–4.0 mm. An increase of this parameter within the stated limits increases the time that it takes to achieve the stage in which a constant drying soy speed is reached by more than 2.5 times (from 205 seconds to 520 seconds), stabilising the figure at a level of 520 seconds, which makes it possible to recommend a range of transport speeds of between 0.15–0.40 cm·s-1 under infrared radiation for the seeds in order to achieve the required moisture content with a single pass of the produce on the wave transporter. With that in mind, the power consumption levels for the vibrational exciter do not exceed 50W, while the angular velocity of the drive shaft’s rotation falls within the range of between 100– 120 rads-1 . The results of the experimental study that has been conducted indicated that a rational transportation speed for the soy seeds on the wave transporter under infrared radiation is between 0.15–0.40 cm·s-1

Un élément fini de poutre fissurée application à la dynamique des arbres tournants

International audienceDans ce travail on présente une méthode originale de construction d'un élément fini de poutre affectée de fissurations. La souplesse additionnelle due à la présence des fissures est identifiée à partir de calculs éléments finis tridimensionnels tenant compte des conditions de contact unilatéral entre les lèvres. Cette souplesse est répartie sur toute la longueur de l'élément dont on se propose de construire la matrice de rigidité. La démarche permet un gain considérable en temps de calcul par rapport à la représentation nodale de la section fissurée lors de l'intégration temporelle de systèmes différentiels en dynamique des structures

Automated office blood pressure measurements in primary care are misleading in more than one third of treated hypertensives: The VALENTINE-Greece Home Blood Pressure Monitoring study

Abstract Background This study assessed the diagnostic reliability of automated office blood pressure (OBP) measurements in treated hypertensive patients in primary care by evaluating the prevalence of white coat hypertension (WCH) and masked uncontrolled hypertension (MUCH) phenomena. Methods Primary care physicians, nationwide in Greece, assessed consecutive hypertensive patients on stable treatment using OBP (1 visit, triplicate measurements) and home blood pressure (HBP) measurements (7 days, duplicate morning and evening measurements). All measurements were performed using validated automated devices with bluetooth capacity (Omron M7 Intelli-IT). Uncontrolled OBP was defined as ≥140/90 mmHg, and uncontrolled HBP was defined as ≥135/85 mmHg. Results A total of 790 patients recruited by 135 doctors were analyzed (age: 64.5 ± 14.4 years, diabetics: 21.4%, smokers: 20.6%, and average number of antihypertensive drugs: 1.6 ± 0.8). OBP (137.5 ± 9.4/84.3 ± 7.7 mmHg, systolic/diastolic) was higher than HBP (130.6 ± 11.2/79.9 ± 8 mmHg; difference 6.9 ± 11.6/4.4 ± 7.6 mmHg, p Conclusions In primary care, automated OBP measurements are misleading in approximately 40% of treated hypertensive patients. HBP monitoring is mandatory to avoid overtreatment of subjects with WCH phenomenon and prevent undertreatment and subsequent excess cardiovascular disease in MUCH

Thermomechanical Response of Fullerene-Reinforced Polymers by Coupling MD and FEM

The aim of the present study is to provide a computationally efficient and reliable hybrid numerical formulation capable of characterizing the thermomechanical behavior of nanocomposites, which is based on the combination of molecular dynamics (MD) and the finite element method (FEM). A polymeric material is selected as the matrix—specifically, the poly(methyl methacrylate) (PMMA) commonly known as Plexiglas due to its expanded applications. On the other hand, the fullerene C240 is adopted as a reinforcement because of its high symmetry and suitable size. The numerical approach is performed at two scales. First, an analysis is conducted at the nanoscale by utilizing an appropriate nanocomposite unit cell containing the C240 at a high mass fraction. A MD-only method is applied to accurately capture all the internal interfacial effects and accordingly its thermoelastic response. Then, a micromechanical, temperature-dependent finite element analysis takes place using a representative volume element (RVE), which incorporates the first-stage MD output, to study nanocomposites with small mass fractions, whose atomistic-only simulation would require a substantial computational effort. To demonstrate the effectiveness of the proposed scheme, numerous numerical results are presented while the investigation is performed in a temperature range that includes the PMMA glass transition temperature, Tg

The Effect of Atom Vacancy Defect on the Vibrational Behavior of Single-Walled Carbon Nanotubes: A Structural Mechanics Approach

An atomistic structural mechanics method, which is based on the exclusive use of spring elements, is developed in order to study the effect of imperfections due to atom vacancy on the vibrational characteristics of single-walled carbon nanotubes (SWCNTs). The developed elements simulate the relative translations and rotations between atoms as well as the mass of the atoms. In this way, molecular mechanics theory can be applied directly because the atomic bonds are modeled by using exclusively physical variables such as bond stretching. The method is validated for its predictability comparing with vibration results found in the open literature for pristine nanotubes. Then, it is used for the vibration analysis of defective nanotubes. Imperfections such as one-atom vacancy, two-atom vacancy, and one carbon hexagonal cell vacancy are investigated. Their effect on vibrational behavior is explored for different defect positions, nanotube diameters, and support conditions. According to the obtained results, the fundamental frequency is decreased as the size of imperfection increases, and the percentage reduction in fundamental frequency due to the atomic vacancy defect is more affected for a single-clamped SWCNT than for a double-clamped one

Electrolyzer performance analysis of an integrated hydrogen power system for greenhouse heating a case study

A greenhouse containing an integrated system of photovoltaic panels, a water electrolyzer, fuel cells and a geothermal heat pump was set up to investigate suitable solutions for a power system based on solar energy and hydrogen, feeding a self-sufficient, geothermal-heated greenhouse. The electricity produced by the photovoltaic source supplies the electrolyzer; the manufactured hydrogen gas is held in a pressure tank. In these systems, the electrolyzer is a crucial component; the technical challenge is to make it work regularly despite the irregularity of the solar source. The focus of this paper is to study the performance and the real energy efficiency of the electrolyzer, analyzing its operational data collected under different operating conditions affected by the changeable solar radiant energy characterizing the site where the experimental plant was located. The analysis of the measured values allowed evaluation of its suitability for the agricultural requirements such as greenhouse heating. On the strength of the obtained result, a new layout of the battery bank has been designed and exemplified to improve the performance of the electrolyzer. The evaluations resulting from this case study may have a genuine value, therefore assisting in further studies to better understand these devices and their associated technologies

Risks linked to the management of pressured hydrogen within a photovoltaic-electrolyzer-fuel cell power system located on a rural land

A power system formed by photovoltaic panels, alkaline electrolyzer and fuel cell stacks was designed and realized to supply the heating system of an experimental greenhouse. The barometric alkaline electrolyzer produces pressured hydrogen (3 MPa), which is stored inside iron tanks. The aim of this paper is to emphasize the main safety aspects of the power system connected to the management of the pressured hydrogen. From the safety point of view the electrolyzer unit has been equipped with devices able to highlight the malfunctions before they cause damages to the operators and break off the process of hydrogen production. The system can be reactivated after the repair just if the cause of malfunctioning has been removed effectively. Nevertheless the management of the products of the electrolysis process involves forethought and trained operators. Starting from the study of international directives and through the Hazard and Operability (HAZOP) Study method, the standards of safety systems for the hydrogen equipment located on a rural land have been estimated

Hazards assessment and technical actions due to the production of pressured hydrogen within a pilot photovoltaic-electrolyser-fuel cell power system for agricultural equipment

A pilot power system formed by photovoltaic panels, alkaline electrolyser and fuel cell stacks was designed and set up to supply the heating system of an experimental greenhouse. The aim of this paper is to analyse the main safety aspects of this power system connected to the management of the pressured hydrogen, such as the explosion limits of the mixture hydrogen-oxygen, the extension of the danger zone, the protection pressure vessels and the system to make unreactive the plant. The electrolyser unit is the core of this plant and from the safety point of view has been equipped with devices able to highlight the malfunctions before they cause damages. Alarm situations are highlighted and the production process is cut off in safe conditions in the event that the operational parameters have an abnormal deviation from the design values. Also the entire power system has been designed so that any failure to its components does not compromise the workers’ safety even if the risk analysis is in progress because technical operations are being carried out for enhancing the plant functionality, making it more suitable to the designed task of supplying electrically the greenhouse heating system during cold periods. Some experimental data pertinent to the solar radiation and the corresponding hydrogen production rate are also reported. At present it does not exist a well-established safety reference protocol to design the reliability of these types of power plants and then the assumed safety measures even if related to the achieved pilot installation, can represent an original base of reference to set up guidelines for designing the safety of power plants in the future available for agricultural purposes

Study of a pilot photovoltaic-electrolyzer-fuel cell power system for a geothermal heat pump heated greenhouse and evaluation of the electrolyzer efficiency and operational mode

The intrinsic factor of variability of renewable energy sources often limits their broader use. The photovoltaic solar systems can be provided with a power back up based on a combination of an electrolyzer and a fuel cell stack. The integration of solar hydrogen power systems with greenhouse heating equipment can provide a possible option for powering stand-alone greenhouses. The aim of the research under development at the experimental farm of Department of Agro-Environmental Sciences of the University of Bari “Aldo Moro” is to investigate on the suitable solutions of a power system based on photovoltaic energy and on the use of hydrogen as energy vector, integrated with a ground source heat pump for greenhouse heating in a self sustained way. The excess energy produced by a purpose-built array of solar photovoltaic modules supplies an alkaline electrolyzer; the produced hydrogen gas is stored in pressured storage tank. When the solar radiation level is insufficient to meet the heat pump power demand, the fuel cell starts converting the chemical energy stored by the hydrogen fuel into electricity. This paper reports on the description of the realized system. Furthermore the efficiency and the operational mode of the electrolyzer were evaluated during a trial period characterized by mutable solar radiant energy. Anyway the electrolyzer worked continuously in a transient state producing fluctuations of the hydrogen production and without ever reaching the steady–state conditions. The Faradic efficiency, evaluated by means of an empirical mathematic model, highlights that the suitable working range of the electrolyzer was 1.5÷2.5 kW and then for hydrogen production more than 0.21 Nm^3h^-1