Modal analysis and nonlinear characterization of an airborne power ultrasonic transducer with rectangular plate radiator

Some industrial processes like particle agglomeration or food dehydration among others can be enhanced by the use of power ultrasonic technologies. These technologies are based on an airborne power ultrasonic transducer (APUT) constituted by a pre-stressed Langevin-type transducer, a mechanical amplifier and an extensive plate radiator. In order to produce the desired effects in industrial processing, the transducer has to vibrate in an extensional mode driving an extensive radiator in the desired flexural mode with high amplitude displacements. Due to the generation of these high amplitude displacements in the radiator surfaces, non-linear effects like frequency shifts, hysteresis or modal interactions, among others, may be produced in the transducer behavior. When any nonlinear effect appears, when applying power, the stability and efficiency of this ultrasonic technology decreases, and the transducer may be damaged depending on the excitation power level and the nature of the nonlinearity. In this paper, an APUT with flat rectangular radiator is presented, as the active part of an innovative system with stepped reflectors. The nonlinear behavior of the APUT has been characterized numerically and experimentally in case of the modal analysis and experimentally in the case of dynamic analysis. According to the results obtained after the experiments, no modal interactions are expected, nor do other nonlinear effects

Matrix tree theorem for Schrödinger operators on networks

Postprint (published version

Exercise-induced left septal fascicular block: an expression of severe myocardial ischemia

The electrocardiogram (ECG) criteria for the left septal fascicular block (LSFB) are not universally accepted and many other denominations can be seen in literature: focal septal block, septal focal block, left septal fascicular block, left anterior septal block, septal fascicular conduction disorder of the left branch, left septal Purkinje network block, left septal subdivision block of the left bundle branch, anterior conduction delay, left median hemiblock, left medial subdivision block of the left bundle branch, middle fascicle block, block of the anteromedial division of the left bundle branch of His, and anteromedial divisional block. During exercise stress test, fascicular blocks (left anterior and posterior) seem to indicate severe coronary artery narrowing of left main coronary or proximal left anterior descending artery disease1 and transient exercise-induced left septal fascicular block has been reported a few times2,3. 54-year-old male, with a history of essential arterial systemic hypertension, primary hyperlipidemia and six-month typical chest pain during exercise (Class II – Canadian Cardiovascular Society) underwent an exercise stress test. During the exercise stress test, ECG demonstrated abrupt prominent anterior forces, an increase in R wave amplitude from V1 to V4, extreme left axis deviation and minor ST segment depression in DII, DIII and aVF (Figure 1). The post-exercise period showed progressive return of the QRS axis in both frontal and horizontal planes and the ST depression worsened by 1 mm. Coronary angiogram (Figure 2A) showed a critical proximal left anterior descending artery lesion. An exercise stress test done three months after coronary artery bypass surgery grafting was normal (Figure 2B)

Topological analysis of powertrains for refusecollecting vehicles based on real routes – Part II: Hybrid electric powertrain

In this two-part paper, a topological analysis of powertrains for refuse-collecting vehicles (RCVs) based on simulation of different architectures (internal combustion engine, hybrid electric, and hybrid hydraulic) on real routes is proposed. In this second part, three different hybrid electric powertrain architectures are proposed and modeled. These architectures are based on the use of fuel cells, ultracapacitors, and batteries. A calculation engine, which is specifically designed to estimate energy consumption, respecting the original performance as the original internal combustion engine (ICE), is presented and used for simulations and component sizing. Finally, the overall performance of the different architectures (hybrid hydraulic, taken from the first paper part, and hybrid electric, estimated in this second part) and control strategies are summarized in a fuel and energy consumption table. Based on this table, an analysis of the different architecture performance results is carried out. From this analysis, a technological evolution of these vehicles in the medium- and long terms is proposed.Postprint (author's final draft

FOULING MONITORING AND CLEANING OPTIMISATION IN A HEAT EXCHANGER NETWORK OF A CRUDE DISTILLATION UNIT

Fouling in preheat networks of crude distillation units (CDU) plays an important role in energy consumption. In this work a procedure to monitor the performance of the heat exchanger network (HEN) and to optimize the cleaning strategies is presented. The procedure is based on a rigorous simulation of the HEN using Hysys (from Aspen Technology). The simulation is used to estimate the service overall heat transfer coefficient with real operational data acquired from the unit’s Plant Information System (PI). The clean overall heat transfer coefficient is calculated for each one of the individual heat exchangers with a rigorous simulation using TASC (rigorous heat exchanger simulator also from Aspen Technology), embedded into Hysys. A comparison between the service and clean overall heat transfer coefficients provides the actual performance for each individual heat exchanger and for the complete HEN. The first step is to collect the HEN operative data from the Plant Information System and to perform an ad-hoc preprocessing of each individual exchanger data (i.e., feed and product inlet and outlet temperatures and flow rates) in order to identify stable periods from which the mentioned calculations will be performed. As the feed/products flow rates and unit operating conditions are constantly changing, the steady intervals detection is a very important task because calculations performed with data of unstable operation time intervals could be erroneous and produce non-sense results. The overall procedure is managed from an Excel environment, which performs the needed calls to PI and Hysys/TASC simulators in order to calculate each exchanger fouling and HEN overall performance under the actual fouling situation. Excel also commands the evaluation of the cleaning policies economics, searching between several pre-defined cleaning alternatives. Results of the above mentioned methodology applied to a complex feed preheat HEN of the Topping IV CDU of REPSOL YPF Luján de Cuyo Refinery, Argentina, are presented

Topological analysis of powertrains for refusecollecting vehicles based on real routes – Part I: Hybrid hydraulic powertrain

In this two-part paper, a topological analysis of powertrains for refuse-collecting vehicles (RCVs) based on the simulation of different architectures (internal combustion engine, hybrid electric, and hybrid hydraulic) on real routes is proposed. In this first part, a characterization of a standard route is performed, analyzing the average power consumption and the most frequent working points of an internal combustion engine (ICE) in real routes. This information is used to define alternative powertrain architectures. A hybrid hydraulic powertrain architecture is proposed and modelled. The proposed powertrain model is executed using two different control algorithms, with and without predictive strategies, with data obtained from real routes. A calculation engine (an algorithm which runs the vehicle models on real routes), is presented and used for simulations. This calculation engine has been specifically designed to analyze if the different alternative powertrain delivers the same performance of the original ICE. Finally, the overall performance of the different architectures and control strategies are summarized into a fuel and energy consumption table, which will be used in the second part of this paper to compare with the different architectures based on hybrid electric powertrain. The overall performance of the different architectures indicates that the use of a hybrid hydraulic powertrain with simple control laws can reduce the fuel consumption up to a 14 %.Postprint (author's final draft