Applied Sciences

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EISSN : 20763417
Current Publisher: MDPI (10.3390)
Total articles ≅ 6,971
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Philipp Knödler
Published: 25 June 2019
by MDPI
Applied Sciences, Volume 9; doi:10.3390/app9122569

Abstract:Thermal energy storage (TES) systems are central elements for various types of new power plant concepts, whereat packed beds represent a promising storage inventory option. Due to thermal expansion and shrinking of the packed bed’s particles during cyclic thermal charging and discharging operation, high technical risks arise, and possibly lead to material failure. In order to accurately design the heat storage system, suitable tools for calculating induced forces and stresses are mandatory. Continuum models offer time efficient simulation results, but are in need of effective packed bed parameters. This paper introduces a methodology for applying a simplified continuum model and presents first results for an exemplarily large-scale application.
Jing Guo, Bo Xiao, Hongliang Ren
Published: 25 June 2019
by MDPI
Applied Sciences, Volume 9; doi:10.3390/app9122573

Abstract:Force sensing in robotic-assisted minimally invasive surgery (RMIS) is crucial for performing dedicated surgical procedures, such as bilateral teleoperation and palpation. Due to the bio-compatibility and sterilization requirements, a specially designed surgical tool/shaft is normally attached to the sensor while contacting the organ targets. Through this design, the measured force from the sensor usually contains uncertainties, such as noise, inertial force etc., and thus cannot reflect the actual interaction force with the tissue environment. Motivated to provide the authentic contact force between a robotic tool and soft tissue, we proposed a data-driven force compensation scheme without intricate modeling to reduce the effects of force measurement uncertainties. In this paper, a neural-network-based approach is utilized to automatically model the inertial force subject to noise during the robotic palpation procedure, then the exact contact force can be obtained through the force compensation method which cancels the noise and inertial force. Following this approach, the genuine interaction force during the palpation task can be achieved furthermore to improve the appraisal of the tumor surrounded by the soft tissue. Experiments are conducted with robotic-assisted palpation tasks on a silicone-based soft tissue phantom and the results verify the effectiveness of the suggested method.
Jijian Lian, Yan Zheng, Chao Liang, Bin Ma
Published: 25 June 2019
by MDPI
Applied Sciences, Volume 9; doi:10.3390/app9122572

Abstract:During the flood discharge in large-scale hydraulic engineering projects, intense flow-induced vibrations may occur in hydraulic gates, gate piers, spillway guide walls, etc. Furthermore, the vibration mechanism is complicated. For the spillway guide wall, existing studies on the vibration mechanism usually focus on the vibrations caused by flow excitations, without considering the influence of dam vibration. According to prototype tests, the vibrations of the spillway guide wall and the dam show synchronization. Thus, this paper presents a new vibration mechanism of associated-forced coupled vibration (AFCV) for the spillway guide wall to investigate the dynamic responses and reveal coupled vibrational properties and vibrational correlations. Different from conventional flow-induced vibration theory, this paper considers the spillway guide wall as a lightweight accessory structure connected to a large-scale primary structure. A corresponding simplified theoretical model for the AFCV system is established, with theoretical derivations given. Then, several vibrational signals measured in different structures in prototype tests are handled by the cross-wavelet transform (XWS) to reveal the vibrational correlation between the spillway guide wall and the dam. Afterwards, mutual analyses of numeral simulation, theoretical derivation, and prototype data are employed to clarify the vibration mechanism of a spillway guide wall. The proposed mechanism can give more reasonable and accurate results regarding the dynamic response and amplitude coefficient of the guide wall. Moreover, by changing the parameters in the theoretical model through practical measures, the proposed vibration mechanism can provide benefits to vibration control and structural design.
Chang Liu, Binzhen Zhang, Chenyang Xue, Guojun Zhang, Wendong Zhang, Yijun Cheng
Published: 25 June 2019
by MDPI
Applied Sciences, Volume 9; doi:10.3390/app9122574

Abstract:In order to better detect information about a mass in breast tissue, an ultrasound tomography algorithm based on adaptive time gain compensation (TGC) was designed. Field II was utilized to automatically evaluate the phantom attenuation coefficient and compensate for the attenuated image. The image reconstruction algorithm process is presented here. Furthermore, the experimental setup with the cylindrical motion of a piezoelectric micromachined ultrasonic transducer (PMUT) linear array was used to detect the mass in the breast model. The attenuation coefficient was evaluated by using the spectral cross-correlation method. According to the acquired attenuation coefficients, TGC compensates for the pulse-echo signal, and the horizontal slice image was reconstructed using the tomography algorithm. The experimental results show that this algorithm can evaluate the attenuation coefficient of the breast model and improve the ability to detect an internal mass. At the same time, the realization of attenuation compensation with software is beneficial to the development of portable medical equipment.
Yang Zhao, Xudong Liu, Qi Zhang
Published: 25 June 2019
by MDPI
Applied Sciences, Volume 9; doi:10.3390/app9122575

Abstract:To enhance the control performance of permanent-magnet synchronous motor (PMSM) drive systems, achieving high-precision motion control, a generalized predictive control (GPC) method based on a novel extended-state observer (ESO) is investigated for the speed control of PMSM. In this paper, the controller design consists of two steps. Firstly, according to the continuous time model of PMSM, using the Taylor series expansion, the predictive value of motor speed in finite time is derived, and the single-loop speed controller by combining the speed loop and q - axis current loop is obtained through the defined cost function. The structure of the controller is simple compared to other forms. Secondly, considering the uncertainty of the load torque and the model uncertainties, a novel extended-state observer is designed to compute the actual torque, and the observed value is introduced to the GPC controller. The simulation and experimental results show that the proposed GPC+ESO control method has superior dynamic performance and strong robustness.
Boursier Niutta, Tridello, Ciardiello, Belingardi, Paolino, Carlo Boursier Niutta, Andrea Tridello, Raffaele Ciardiello, Giovanni Belingardi, Davide Salvatore Paolino
Published: 25 June 2019
by MDPI
Applied Sciences, Volume 9; doi:10.3390/app9122579

Abstract:In structural component applications the use of composite materials is increasing thanks to their optimal mechanical characteristics. However, the complexity of the damage evolution in composite materials significantly limits their widespread diffusion. Non-destructive tests are thus becoming ever more important. The detecting Damage Index (DId) technique has been recently brought in the realm of the non-destructive characterization tests for components made of composite material. In contrast to other techniques, this methodology allows to quantitatively assess local residual properties. In this paper, the DId technique is adopted in combination with the finite element method. The mechanical response of two composite plates (an 8-layer twill fabric carbon/epoxy) subjected to four-point bending test is firstly used to tune a finite element model of the laminate. Then, an undamaged laminate of the same composite material is progressively damaged through repeated four-point bending tests. Local residual elastic properties are mapped on the plate through the DId technique. A continuous polynomial curve has been considered to account for the variation of the elastic modulus in the finite element model. The resulting force-displacement curve of the numerical analysis is compared to experimental data of damaged plate, resulting in very good agreement. The combination of the experimental activity and the numerical finite element analysis points out the accuracy of the DId methodology in assessing local residual elastic properties of composite materials.
Elena M. Balboa, Rosendo Millán, Herminia Domínguez, Cristina Taboada
Published: 25 June 2019
by MDPI
Applied Sciences, Volume 9; doi:10.3390/app9122570

Abstract:Sargassum muticum was processed by hydrothermal extraction under previously optimized non-isothermal conditions (up to 187 °C). The alginate free crude hydrolysate was further concentrated by ultrafiltration, operating in diafiltration mode to produce an extract (SmE) enriched in the fucoidan and the phlorotannin fractions and with low mineral content and antiradical capacity equivalent to that of Trolox. In order to explore the potential of this concentrated product for food or feed additive, the in vivo antioxidant potential was assessed. Male Sprague–Dawley rats were fed SmE dissolved in distilled water at doses of 0.5, 1.0 or 2.0 g kg−1, administered via an intragastric tube daily for three weeks. The weight and organ gain was not significantly affected in the different groups in relation to the control group fed a standard diet. Serum glucose was significantly lowered in the groups receiving the higher SmE doses, liver GPx levels were reduced and liver TBARS levels decreased in rats administered the extract, but no effect on SOD activity in either liver or erythrocytes was observed.
Steven Lecompte, Erika Ntavou, Bertrand Tchanche, George Kosmadakis, Aditya Pillai, Dimitris Manolakos, Michel De Paepe
Published: 25 June 2019
by MDPI
Applied Sciences, Volume 9; doi:10.3390/app9122571

Abstract:Supercritical operation is considered a main technique to achieve higher cycle efficiency in various thermodynamic systems. The present paper is a review of experimental investigations on supercritical operation considering both heat-to-upgraded heat and heat-to-power systems. Experimental works are reported and subsequently analyzed. Main findings can be summarized as: steam Rankine cycles does not show much studies in the literature, transcritical organic Rankine cycles are intensely investigated and few plants are already online, carbon dioxide is considered as a promising fluid for closed Brayton and Rankine cycles but its unique properties call for a new thinking in designing cycle components. Transcritical heat pumps are extensively used in domestic and industrial applications, but supercritical heat pumps with a working fluid other than CO2 are scarce. To increase the adoption rate of supercritical thermodynamic systems further research is needed on the heat transfer behavior and the optimal design of compressors and expanders with special attention to the mechanical integrity.
Guangpan Zhou, Aiqun Li, Jianhui Li, Maojun Duan, Zhiyuan Xia, Li Zhu
Published: 25 June 2019
by MDPI
Applied Sciences, Volume 9; doi:10.3390/app9122576

Abstract:The present work is aimed at studying the determination method and implementation process of reasonable completion state for the Hunan Road Bridge, which is currently the widest concrete self-anchored suspension bridge in China. The global finite element model and the cable analytic program BNLAS were integrated. The synthesis algorithm of completion state determination was proposed. The contact relationships between the cable and saddles were captured using the refined FE discretization method. The concrete shrinkage and creep effects during the construction and operation periods were predicted using the CEB-FIP 90 model and the age-adjusted effective modulus method. The cable alignments under the free cable state, system transformation condition, and completion state were obtained. Moreover, the multiple-control method for the whole process of system transformation was proposed. The multiple parameters included the hanger tensioning force, exposed amount of hanger anchor cup, and tag line position. A detailed system transformation procedure was formulated and well preformed in the construction site. In addition, the further optimization analysis of final hanger force was conducted based on the actual completion state. The influence on the stress and geometry evolution of girder brought by the final girder alignment was investigated. The measured results of structural alignment and stress show that the target completion state was well implemented. The accuracy and efficiency of the proposed multiple-control method were verified by checking the tag line position of each step. In addition, the optimized final hanger force and girder lifting amount were obtained, which can provide feedback and reference for the construction control and service safety of the similar concrete self-anchored suspension bridges.
Claire L. Wong, Marcus Ang, Anna C. S. Tan
Published: 25 June 2019
by MDPI
Applied Sciences, Volume 9; doi:10.3390/app9122577

Abstract:Optical coherence tomography angiography (OCTA) provides us with a non-invasive and efficient means of imaging anterior and posterior segment vasculature in the eye. OCTA has been shown to be effective in imaging diseases such as diabetic retinopathy; retinal vein occlusions; retinal artery occlusions; ocular ischemic syndrome; and neovascularization of the iris. It is especially useful with depth-resolved imaging of the superficial, intermediate, and deep capillary plexi in the retina, which enables us to study and closely monitor disease progression and response to treatment. With further advances in technology, OCTA has the potential to become a more widely used tool in the clinical setting and may even supersede ocular angiography in some areas.