Search results for: control surface

Authors: Wenqian Zhang, Xuelin Wang, Yujin Hu, Siyang Wang

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The subsurface layer of a component plays a significant role in its service performance. Any surface mechanical process during fabrication can introduce a deformed layer near the surface, which can be related to the microstructure alteration and strain hardening, and affects the mechanical properties and corrosion resistance of the material. However, there exists a great difficulty in determining the subsurface deformation induced by surface machining. In this study, electron backscatter diffraction (EBSD) was used to study the deformed layer of surface milled 316 stainless steel. The microstructure change was displayed by the EBSD maps and characterized by misorientation variation. The results revealed that the surface milling resulted in heavily nonuniform deformations in the subsurface layer and even in individual grains. The direction of the predominant grain deformation was about 30-60 deg to the machined surface. Moreover, a local deformation rate (LDR) was proposed to quantitatively evaluate the local deformation degree. Both of the average and maximum LDRs were utilized to characterize the deformation trend along the depth direction. It was revealed that the LDR had a strong correlation with the development of grain and sub-grain boundaries. In this work, a scan step size of 1.2 μm was chosen for the EBSD measurement. A LDR higher than 18 deg/μm indicated a newly developed grain boundary, while a LDR ranged from 2.4 to 18 deg/μm implied the generation of a sub-grain boundary. And a lower LDR than 2.4 deg/μm could only introduce a slighter deformation and no sub-grain boundary was produced. According to the LDR analysis with the evolution of grain or sub grain boundaries, the deformed layer could be classified into four zones: grain broken layer, seriously deformed layer, slightly deformed layer and non-deformed layer.

Keywords: surface machining, EBSD, subsurface layer, local deformation

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Authors: M. Doumi, K. Tahir, A. Miloudi, A. G. Aissaoui, C. Belfedal, S. Tahir

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This paper presents a three-phase grid-connected photovoltaic generation system with unity power factor for any situation of solar radiation based on voltage-oriented control (VOC). An input voltage clamping technique is proposed to control the power between the grid and photovoltaic system, where it is intended to achieve the maximum power point operation. This method uses a Perturb and Observe (P&O) controller. The main objective of this work is to compare the energy production unit performances by the use of two types of controllers (namely, classical PI and Sliding Mode (SM) Controllers) for the grid inverter control. The proposed control has a hierarchical structure with a grid side control level to regulate the power (PQ) and the current injected to the grid and to obtain a common DC voltage constant. To show the effectiveness of both control methods performances analysis of the system are analyzed and compared by simulation and results included in this paper.

Keywords: grid connected photovoltaic, MPPT, inverter control, classical PI, sliding mode, DC voltage constant, voltage-oriented control, VOC

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Authors: Martina Kaufmann, Thomas Goetz, Anastasiya A. Lipnevich, Reinhard Pekrun

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Positive emotions have been shown to benefit from optimistic perceptions, even if these perceptions are illusory. The current research investigated the impact of illusions of control on positive emotions. There is empirical evidence showing that people are more emotionally attentive to losses than to gains. Hence, we expected that, compared to gains, losses in illusory control would have a stronger impact on positive emotions. The results of two experimental studies support this assumption: Participants who experienced gains in illusory control showed no substantial change in positive emotions. However, positive emotions decreased when they perceived a loss in illusory control. These results suggest that a loss of illusory control (but not a gain thereof) mediates the impact of the situation on individuals’ positive emotions. Implications for emotion theory and practice are discussed.

Keywords: cognitive appraisal, control, illusions, optimism, positive emotions

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Authors: Ibrahim Tiryakioglu, Mehmet Ali Ugur, Caglar Ozkaymak

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The development of GNSS technology has led to increasingly widespread and successful applications of GNSS surveys for monitoring crustal movements. However, multi-period GPS survey solutions have not been applied in monitoring vertical surface deformation. This study uses long-term GNSS time series that are required to determine vertical deformations. In recent years, the surface deformations that are parallel and semi-parallel to Bolvadin fault have occurred in Western Anatolia. These surface deformations have continued to occur in Bolvadin settlement area that is located mostly on alluvium ground. Due to these surface deformations, a number of cracks in the buildings located in the residential areas and breaks in underground water and sewage systems have been observed. In order to determine the amount of vertical surface deformations, two continuous GNSS stations have been established in the region. The stations have been operating since 2015 and 2017, respectively. In this study, GNSS observations from the mentioned two GNSS stations were processed with GAMIT/GLOBK (GNSS Analysis Massachusetts Institute of Technology/GLOBal Kalman) program package to create a coordinate time series. With the time series analyses, the GNSS stations’ behavior models (linear, periodical, etc.), the causes of these behaviors, and mathematical models were determined. The study results from the time series analysis of these two 2 GNSS stations shows approximately 50-80 mm/yr vertical movement.

Keywords: Bolvadin fault, GAMIT, GNSS time series, surface deformations

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Authors: Solmaz Eskandarion, Haniyeh Eftekhar, Amin Fallahi

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Introduction: Nowadays cosmetic dentistry has gained greater attention because of the changing demands of dentistry patients. Composite resin restorations play an important role in the field of esthetic restorations. Due to the variation between the resin composites, it is important to be aware of their mechanical properties and surface roughness. So, the aim of this study was to compare the mechanical properties (surface hardness, compressive strength, diametral tensile strength) and surface roughness of four kinds of resin composites after thermal aging process. Materials and Method: 10 samples of each composite resins (Gradia-direct (GC), Filtek Z250 (3M), G-ænial (GC), Filtek Z350 (3M- filtek supreme) prepared for evaluation of each properties (totally 120 samples). Thermocycling (with temperature 5 and 55 degree of centigrade and 10000 cycles) were applied. Then, the samples were tested about their compressive strength and diametral tensile strength using UTM. And surface hardness was evaluated with Microhardness testing machine. Either surface roughness was evaluated with Scanning electron microscope after surface polishing. Result: About compressive strength (CS), Filtek Z250 showed the highest value. But there were not any significant differences between 4 groups about CS. Either Filtek Z250 detected as a composite with highest value of diametral tensile strength (DTS) and after that highest to lowest DTS was related to: Filtek Z350, G-ænial and Gradia-direct. And about DTS all of the groups showed significant differences (P<0.05). Vickers Hardness Number (VHN) of Filtek Z250 was the greatest. After that Filtek Z350, G-ænial and Gradia-direct followed it. The surface roughness of nano-filled composites was less than Microhybrid composites. Either the surface roughness of GC Ganial was a little greater than Filtek Z250. Conclusion: This study indicates that there is not any evident significant difference between the groups amoung their mechanical properties. But it seems that Filtek Z250 showed slightly better mechanical properties. About surface roughness, nanofilled composites were better that Microhybrid.

Keywords: mechanical properties, surface roughness, resin composite, compressive strength, thermal aging

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Authors: Sun Lim, Kyun Jung

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In this paper, we describe the control strategy of high speed parallel robot system with EtherCAT network. This work deals the parallel robot system with centralized control on the real-time operating system such as window TwinCAT3. Most control scheme and algorithm is implemented master platform on the PC, the input and output interface is ported on the slave side. The data is transferred by maximum 20usecond with 1000byte. EtherCAT is very high speed and stable industrial network. The control strategy with EtherCAT is very useful and robust on Ethernet network environment. The developed parallel robot is controlled pre-design nonlinear controller for 6G/0.43 cycle time of pick and place motion tracking. The experiment shows the good design and validation of the controller.

Keywords: parallel robot control, etherCAT, nonlinear control, parallel robot inverse kinematic

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Authors: Sanjeev Kumar, Vikas Kumar

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Inconel 718 (IN718) is a high strength nickel-based superalloy designed for high-temperature applications up to 650 °C. It is widely used in gas turbines of jet engines and related aerospace applications because of its good mechanical properties and structural stability at elevated temperatures. Because of good performance ratio and excellent process capability, this alloy has been used predominantly for aeronautic engine components like compressor disc and compressor blade. The main precipitates that contribute to high-temperature strength of IN718 are γʹ Ni₃(Al, Ti) and mainly γʹʹ (Ni₃ Nb). Various processes have been used for modification of the surface of components, such as Laser Shock Peening (LSP), Conventional Shot Peening (SP) and Ultrasonic Shot Peening (USP) to induce compressive residual stress (CRS) and development of fine-grained structure in the surface region. Surface nanostructure by ultrasonic shot peening is a novel methodology of surface modification to improve the overall performance of structural components. Surface nanostructure was developed on the peak aged IN718 superalloy using USP and its effect was studied on low cycle fatigue (LCF) life. Nanostructure of ~ 49 to 73 nm was developed in the surface region of the alloy by USP. The gage section of LCF samples was USPed for 5 minutes at a constant frequency of 20 kHz using StressVoyager to modify the surface. Strain controlled cyclic tests were performed for non-USPed and USPed samples at ±Δεt/2 from ±0.50% to ±1.0% at strain rate (ė) 1×10⁻³ s⁻¹ under reversal loading (R=‒1) at room temperature. The fatigue life of the USPed specimens was found to be more than that of the non-USPed ones. LCF life of the USPed specimen at Δεt/2=±0.50% was enhanced by more than twice of the non-USPed specimen.

Keywords: IN718 superalloy, nanostructure, USP, LCF life

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Authors: Ilham Priadythama, Pringgo Widyo Laksono, Agung Pamungkas

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Myoelectric is prosthetic, flexible, and offered industrial application has been highly developed and widely used. Myoelectric hand use myoelectric signal from muscle to activate and control the membrane part of hand. Commonly myoelectric signal is detected on human arm from skin surface. So that it only small magnitude signal captured. Detecting myoelectric signal on the skin surface takes proper and consistent procedure. This paper provides preliminary study of electrodes position which gives best signal strength for five basic grasping. Two-position scenario used to place three channel electrodes set. A bi-potential amplifier based on AD620 used to amplify the signal. Finally, the signal was analyzed using DSSF3 software. From this study, we found that grasp type was stronger using first scenario electrode placement while the rest type better with another scenario.

Keywords: myoelectric signal, basic grasp, DSSF3, electrode, bi-potential amplifier

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Authors: Punit Kumar, Niraj Kumar

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The traction behavior of lubricants with the linear pressure-viscosity response in EHL line contacts is investigated numerically for smooth as well as rough surfaces. The analysis involves the simultaneous solution of Reynolds, elasticity and energy equations along with the computation of lubricant properties and surface temperatures. The temperature modified Doolittle-Tait equations are used to calculate viscosity and density as functions of fluid pressure and temperature, while Carreau model is used to describe the lubricant rheology. The surface roughness is assumed to be sinusoidal and it is present on the nearly stationary surface in near-pure sliding EHL conjunction. The linear P-V oil is found to yield much lower traction coefficients and slightly thicker EHL films as compared to the synthetic oil for a given set of dimensionless speed and load parameters. Besides, the increase in traction coefficient attributed to surface roughness is much lower for the former case. The present analysis emphasizes the importance of employing realistic pressure-viscosity response for accurate prediction of EHL traction.

Keywords: EHL, linear pressure-viscosity, surface roughness, traction, water/glycol

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Authors: Mohamad Abdelfattah Ibrahim Elghrbawy

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This work deals to evaluate barium sulfate (BS) before and after its surface modification as reinforcing filler for rubber. Barium sulfate was surface-modified using polymethacrylic acid (PMAA), the monolayer surface coverage of barium sulfate by polymethacrylic acid molecules occurred at 5.4x10-6 mol/g adsorbed amount. This amount was sufficient to reduce the sediment volume from 2.65 to 2.55 cm3/gm. Natural rubber (NR) was compounded with different concentrations of barium sulfate. The rheological characteristics of NR mixes were measured using a Monsanto Oscillating Disk Rheometer. The compounded NR was vulcanized at 142°C, and the physico-mechanical properties were tested according to the standard methods. The rheological data show that the minimum torque decreases while the maximum torque increases as the barium sulfate content increase. The physico-mechanical properties of NR vulcanizates were improved up to 50 phr/ barium sulfate loading. On the other hand, styrene–butadiene rubber (SBR) and nitrile–butadiene rubber (NBR) rubbers compounded with 50 phr/barium sulfate had good rheological and mechanical properties. Scanning electron microscope studies show surface homogeneity of rubber samples as a result of good dispersion of surface modified barium sulfate in the rubber matrix. The NR, SBR and NBR vulcanizates keep their values of mechanical properties after subjected to thermal oxidative aging at 90°C for 7 days.

Keywords: barium sulfate, natural rubber (nr), nitrile–butadiene rubber (nbr), polymethacrylic acid (pmaa), styrene–butadiene rubber (sbr), surface modification

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Authors: Ekaterina S. Marchenko, Gulsharat A. Baigonakova, Kirill M. Dubovikov, Igor A. Khlusov

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NiTi alloys combine biomechanical and biochemical properties. This makes them a perfect candidate for medical applications. However, there is a serious problem with these alloys, such as the release of Ni from the matrix. Ni ions are known to be toxic to living tissues and leach from the matrix into the surrounding implant tissues due to corrosion after prolonged use. To prevent the release of Ni ions, corrosive strong coatings are usually used. Titanium nitride-based coatings are perfect corrosion inhibitors and also have good bioactive properties. However, there is an opportunity to improve the biochemical compatibility of the surface by depositing another layer. This layer can consist of elements such as calcium and phosphorus. The Ca and P ions form different calcium phosphate phases, which are present in the mineral part of human bones. We therefore believe that these elements must promote osteogenesis and osteointegration. In view of the above, the aim of this study is to investigate the effect of crystallinity on the biocompatibility of a two-layer coating deposited on NiTi substrate by sputtering. The first step of the research, apart from the NiTi polishing, is the layer-by-layer deposition of Ti-Ni-Ti by magnetron sputtering and the subsequent synthesis of this composite in an N atmosphere at 900 °C. The total thickness of the corrosion resistant layer is 150 nm. Plasma assisted RF sputtering was then used to deposit a bioactive film on the titanium nitride layer. A Ca-P powder target was used to obtain such a film. We deposited three types of Ca-P layers with different crystallinity and compared them in terms of cytotoxicity. One group of samples had no Ca-P coating and was used as a control. We obtained different crystallinity by varying the sputtering parameters such as bias voltage, plasma source current and pressure. XRD analysis showed that all coatings are calcium phosphate, but the sample obtained at maximum bias and plasma source current and minimum pressure has the most intense peaks from the coating phase. SEM and EDS showed that all three coatings have a homogeneous and dense structure without cracks and consist of calcium, phosphorus and oxygen. Cytotoxic tests carried out on three types of samples with Ca-P coatings and a control group showed that the control sample and the sample with Ca-P coating obtained at maximum bias voltage and plasma source current and minimum pressure had the lowest number of dead cells on the surface, around 11 ± 4%. Two other types of samples with Ca-P coating have 40 ± 9% and 21 ± 7% dead cells on the surface. It can therefore be concluded that these two sputtering modes have a negative effect on the corrosion resistance of the whole samples. The third sputtering mode does not affect the corrosion resistance and has the same level of cytotoxicity as the control. It can be concluded that the most suitable sputtering mode is the third with maximum bias voltage and plasma source current and minimum pressure.

Keywords: calcium phosphate coating, cytotoxicity, NiTi alloy, two-layer coating

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Authors: Tukundane Hillary

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This research paper analytically evaluates the project control practice levels used by the building construction companies within Kampala, Uganda. The research also assesses the outcome of project control practices on the productivity of the companies. The research was performed to ascertain the current control practices among 160 respondents from various construction companies registered with the Uganda Registration Services Bureau. This research used amalgamation from multiple literature to obtain the variables. The research adopts 34 standard control practices from four vital project control duties: planning, monitoring, analyzing, and reporting. These project control tasks were organized using mean response ratings grounded on their relevance to the construction companies. Results showed that evaluating performance with the use of curves (4.32), timely access to information and encouragement (4.55), report representation using quantitative tools 4.75, and cost value comparison application during analysis (4.76) were rated least among the control practices. On the other hand, the top project control practices included formulation of the project schedule (8.88), Project feasibility validation (8.86), Budgeting for each activity (8.84), Key project route definition (8.81), Team awareness of the budget (8.77), Setting realistic targets for projects (8.50) and Consultation from subcontractors (8.74). From the results obtained by the sample respondents specified, it can be concluded that planning is the most vital project control task practiced in the building construction industry in Uganda. In addition, this research ascertained a substantial relationship between project control practices and the performance of building construction companies. Accordingly, this research recommends that project control practices be effectively observed by both contracting and consulting companies to enhance their overall performance and governance.

Keywords: cost value, project control, cost control, time control, project performance, control practices

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Authors: Lazhar Belkhiri, Ammar Tiri, Lotfi Mouni

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Water resources present to the public order of the world a very important problem for the protection and management of water quality given the complexity of water quality data sets. In this study, the water quality index (WQI) and irrigation water quality index (IWQI) were calculated in order to evaluate the surface water quality for drinking and irrigation purposes based on nine hydrochemical parameters. In order to separate the variables that are the most responsible for the spatial differentiation, the discriminant analysis (DA) was applied. The results show that the surface water quality for drinking is poor quality and very poor quality based on WQI values, however, the values of IWQI reflect that this water is acceptable for irrigation with a restriction for sensitive plants. Consequently, the discriminant analysis DA method has shown that the following parameters pH, potassium, chloride, sulfate, and bicarbonate are significant discrimination between the different stations with the spatial variation of the surface water quality, therefore, the results obtained in this study provide very useful information to decision-makers

Keywords: surface water quality, drinking and irrigation purposes, water quality index, discriminant analysis

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Authors: Y. Kobayashi, T. Kurosaka, K. Yamamura, T. Yonezawa, K. Yamasaki

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The present work reports an effect of surface- modification of indium tin oxide (ITO) particles with chemicals on their electronic conductivity properties. Examined chemicals were polyvinyl alcohol (nonionic polymer), poly(diallyl dimethyl ammonium chloride) (cationic polymer), poly(sodium 4-styrene-sulfonate) (anionic polymer), (2-aminopropyl) trimethoxy silane (APMS) (silane coupling agent with amino group), and (3-mercaptopropyl) trimethoxy silane (MPS) (silane coupling agent with thiol group). For all the examined chemicals, volume resistivities of surface-modified ITO particles did not increase much when they were aged in air at 80 ^oC, compared to a volume resistivity of un-surface-modified ITO particles. Increases in volume resistivities of ITO particles surface-modified with the silane coupling agents were smaller than those with the polymers, since hydrolysis of the silane coupling agents and condensation of generated silanol and OH groups on ITO particles took place to provide efficient immobilization of them on particles. The APMS gave an increase in volume resistivity smaller than the MPS, since a larger solubility in water of APMS providing a larger amount of APMS immobilized on particles.

Keywords: indium tin oxide, particles, surface-modification, volume resistivity

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Authors: T. Mohammed Chikouche, K. Hartani

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In order to solve the instantaneous power ripple and achieve better performance of direct power control (DPC) for a three-phase PWM rectifier, a control method is proposed in this paper. This control method is applied to overcome the instantaneous power ripple, to eliminate line current harmonics and therefore reduce the total harmonic distortion and to improve the power factor. A switching table is based on the analysis on the change of instantaneous active and reactive power, to select the optimum switching state of the three-phase PWM rectifier. The simulation result shows feasibility of this control method.

Keywords: power quality, direct power control, power ripple, switching table, unity power factor

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Authors: David Lindström

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We evaluate the performance of a numerical method for global optimization of expensive functions. The method is using a response surface to guide the search for the global optimum. This metamodel could be based on radial basis functions, kriging, or a combination of different models. We discuss how to set the cycling parameters of the optimization method to get a balance between local and global search. We also discuss the eventual problem with Runge oscillations in the response surface.

Keywords: expensive function, infill sampling criterion, kriging, global optimization, response surface, Runge phenomenon

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Authors: Mohsen Farahat, Tsuyoshi Hirajima

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Surface characteristics of Bacillus megaterium strain were investigated; zeta potential, FTIR and contact angle were measured. Surface energy components including Lifshitz-van der Waals, Hamaker constant, and acid/base components (Lewis acid/Lewis base) were calculated from the contact angle data. The results showed that the microbial cells were negatively charged over all pH regions with high values at alkaline region. A hydrophilic nature for the strain was confirmed by contact angle and free energy of adhesion between microbial cells. Adsorption affinity of the strain toward dolomite was studied at different pH values. The results showed that the cells had a high affinity to dolomite at acid pH comparing to neutral and alkaline pH. Extended DLVO theory was applied to calculate interaction energy between B. megaterium cells and dolomite particles. The adsorption results were in agreement with the results of Extended DLVO approach. Surface changes occurred on dolomite surface after the bio-treatment were monitored; contact angle decreased from 69° to 38° and the mineral’s floatability decreased from 95% to 25% after the treatment.

Keywords: Bacillus megaterium, surface modification, flotation, dolomite, adhesion energy

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Authors: Fadwa Alaskar, Fang-Chieh Chou, Carlos Flores, Xiao-Yun Lu, Alexandre M. Bayen

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This article proposes a perception model for enhancing the accuracy and stability of car-following control of a longitudinally automated truck. We applied a fusion-based tracking algorithm on measurements of a single preceding vehicle needed for car-following control. This algorithm fuses two types of data, radar and LiDAR data, to obtain more accurate and robust longitudinal perception of the subject vehicle in various weather conditions. The filter’s resulting signals are fed to the gap control algorithm at every tracking loop composed by a high-level gap control and lower acceleration tracking system. Several highway tests have been performed with two trucks. The tests show accurate and fast tracking of the target, which impacts on the gap control loop positively. The experiments also show the fulfilment of control design requirements, such as fast speed variations tracking and robust time gap following.

Keywords: object tracking, perception, sensor fusion, adaptive cruise control, cooperative adaptive cruise control

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Authors: Ji Sun Kim, Jae Ho Baek, Kyeong Ho Kim, Ji Hae Ha, Seong Soo Hong, Jung-Wook Park, Man Sig Lee

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Carbon supported palladium catalysts have been used in many industrial reactions, especially for hydrogenation in the fine chemical industry. Porous carbons had been widely used as catalyst supports due to its higher surface area and larger pore volume. The specific surface area, pore structure and surface chemical functional groups of porous carbon affects metal dispersion and particle size. In this paper, we confirm the effect of support texture on the dispersion of Pd. Pd catalyst supported on activated carbon having various specific surface area were characterized by BET, XRD and FE-TEM. Catalyst activity and dispersion of prepared catalyst were evaluated on the basis of the CO adsorption capacity by CO-chemisorption. As concluding remark to this part of our study, let us note that specific area of carbon play important role on the synthesis of Pd/C catalyst/.

Keywords: carbon, dispersion, Pd/C, specific are, support

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Authors: A. Pesin, D. Pustovoytov, M. Sverdlik

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During production of rolled steel strips the quality of the surface of finished strips influences steel consumption considerably. The most critical areas for crack formation during rolling are lateral sides of slabs. Deformation behaviors of the slab edge in roughing rolling process were analyzed by the finite element method with Deform-3D. In this study our focus is the analysis of the influence of edger’s form on the possibility to decrease surface cracking during roughing hot rolling.

Keywords: roughing hot rolling, FEM, crack, bulging

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Authors: Ying-Chang Yu, Yuan-Lung Lo

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Building envelope design is one of the most popular design fields of architectural profession in nowadays. The main design trend of such system is to highlight the designer's aesthetic intention from the outlook of building project. Due to the trend of current façade design, the building envelope contains more and more layers of components, such as double skin façade, photovoltaic panels, solar control system, or even ornamental components. These exterior components are designed for various functional purposes. Most researchers focus on how these exterior elements should be structurally sound secured. However, not many researchers consider these elements would help to improve the performance of façade system. When the exterior elements are deployed in large scale, it creates an additional layer outside of original façade system and acts like a porous interface which would interfere with the aerodynamic of façade surface in micro-scale. A standard façade performance consists with 'water penetration, air infiltration rate, operation force, and component deflection ratio', and these key performances are majorly driven by the 'Design Wind Load' coded in local regulation. A design wind load is usually determined by the maximum wind pressure which occurs on the surface due to the geometry or location of building in extreme conditions. This research was designed to identify the air damping phenomenon of micro turbulence caused by porous exterior layer leading to surface wind load reduction for improvement of façade system performance. A series of wind tunnel test on dynamic pressure sensor array covered by various scale of porous exterior skin was conducted to verify the effect of wind pressure reduction. The testing specimens were designed to simulate the typical building with two-meter extension offsetting from building surface. Multiple porous exterior skins were prepared to replicate various opening ratio of surface which may cause different level of damping effect. This research adopted 'Pitot static tube', 'Thermal anemometers', and 'Hot film probe' to collect the data of surface dynamic pressure behind porous skin. Turbulence and distributed resistance are the two main factors of aerodynamic which would reduce the actual wind pressure. From initiative observation, the reading of surface wind pressure was effectively reduced behind porous media. In such case, an actual building envelope system may be benefited by porous skin from the reduction of surface wind pressure, which may improve the performance of envelope system consequently.

Keywords: multi-layer facade, porous media, facade performance, turbulence and distributed resistance, wind tunnel test

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Authors: Mohamed El Hachimi, Abdelhakim Ballouk, Ilyas Khelafa, Abdelaziz Mouhou

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Introduction: Type 1 diabetes occurs when beta cells are destroyed by the body's own immune system. Treatment of type 1 diabetes mellitus could be greatly improved by applying a closed-loop control strategy to insulin delivery, also known as an Artificial Pancreas (AP). Method: In this paper, we present a new formulation of the cost function for a Model Predictive Control (MPC) utilizing a technic which accelerates the speed of control of the AP and tackles the nonlinearity of the control problem via asymmetric objective functions. Finding: The finding of this work consists in a new Model Predictive Control algorithm that leads to good performances like decreasing the time of hyperglycaemia and avoiding hypoglycaemia. Conclusion: These performances are validated under in silico trials.

Keywords: artificial pancreas, control algorithm, biomedical control, MPC, objective function, nonlinearity

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Authors: Yaxin Tang, Mingao Hou, Qian He, Guangfu Luo

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Bimetallic nanoparticles serve as a promising class of catalysts with tunable properties suitable for diverse catalytic reactions, yet a comprehensive understanding of their actual structures under operating conditions and the optimal design principles remains largely elusive. In this study, we unveil a prevalent surface segregation phenomenon in nearly 100 platinum-group-element-based bimetallic nanoparticles through first principles-based molecular dynamics simulations. Our findings highlight that two components in a nanoparticle with relatively lower surface energy tend to segregate to the surface. Motivated by this discovery, we propose a deliberate exploitation of surface segregation in designing bimetallic nanoparticle catalysts, aiming for heightened stability and reduced consumption of precious metals. To validate this strategy, we further investigate 36 platinum-based bimetallic nanoparticles for propane dehydrogenation catalysis. Through a systematic examination of catalytic sites on nanoparticles, we identify several systems as top candidates with Pt-enriched surfaces, remarkable thermal stability, and superior catalytic activity for propane dehydrogenation. The insights gained garnered from this study are anticipated to provide a valuable framework for the optimal design of other bimetallic nanoparticles.

Keywords: bimetallic nanoparticles, platinum-group element, catalysis, surface segregation, first-principles calculations

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Authors: Labane Chrif

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A nonlinear approach to the automatic pitch attitude control problem for aircraft transportation is presented. A nonlinear model describing the longitudinal equations of motion in strict feedback form is derived. Backstepping is utilized for the construction of a globally stabilizing controller with a number of free design parameters. The controller is evaluated using the aircraft transportation. The adaptation scheme proposed allowed us to design an explicit controller with a minimal knowledge of the aircraft aerodynamics. Finally, the simulation results will show that backstepping controller have better dynamic performance, simpler design, higher precision, easier implement, etc. At the same time, the control effect will be significantly improved. In addition, backstepping control is superior in short transition, good stability, anti-disturbance and good control.

Keywords: nonlinear control, backstepping, aircraft control, Lyapunov function, longitudinal model

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Authors: Min-Hae Park, Ju-Na Hwang, Cheong-won Seo, Ji-Ho Kim, Kee-Joe Lim

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Polymeric insulators are high hardness, corrosion resistant, lightweight and also good dielectric strength in electric equipment. For such reasons, the amount of polymeric insulators is increased consistently abroad. The current outdoor insulators are replaced by polymeric insulators. Silicone rubber of polymeric insulators is widely used in insulation materials for outdoor application since it has excellent electrical characteristics and high surface hydrophobic. However, it can be evade exposure to pollutant on surface using at outdoor. It also improve the pollution for dust and smoke due to the large are increasing, because most of the industrial area in which the electric power loads are concentrated are located at the coastal area with salt attack. Thus it is important to detect the main cause of the deterioration for outdoor insulation materials. But there has no standards for valuation to apply reliably and determine accurately deterioration under DC, still lacks DC characteristic researches in proportion to AC. In addition, a lot of ATH was added to improve tracking resistivity of silicone rubber, although the problem has been brought up about falling sharply mechanical properties. Therefore, we might compare surface resistivities of silicone rubber compounding of three kinds of filler. In this paper, specimens of silicone rubber composite usable as outdoor insulators were prepared. Micro-silica (SiO2), nano- alumina (Al2O3) and nano-ATH (Al(OH)3) were used in additives. The study aims to investigate properties of DC surface insulation on silicone rubber composite which were filled with various fillers from surface resistivity measurement and salt-fog test.

Keywords: composite, silicone rubber, surface insulation, HVDC

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Authors: Sanjay Singh, Parameswara Rao Vuddanda

Abstract:

The aim of the present study is study the factual benefit of nano size and surface coating of p-gp efflux inhibitor on enhancement of bioavailability of Berberine chloride (BBR); a p-gp substrate. In addition, 28 days sub acute oral toxicity study was also conducted to assess the toxicity of the formulation on chronic administration. BBR loaded polymeric nanoparticles (BBR-NP) were prepared by nanoprecipitation method. BBR NP were surface coated (BBR-SCNP) with the 1 % w/v of vitamin E TPGS. For bioavailability study, total five groups (n=6) of rat were treated as follows first; pure BBR, second; physical mixture of BBR, carrier and vitamin E TPGS, third; BBR-NP, fourth; BBR-SCNP and fifth; BBR and verapamil (widely used p-gp inhibitor). Blood was withdrawn at pre-set timing points in 24 hrs study and drug was quantified by HPLC method. In oral chronic toxicity study, total four groups (n=6) were treated as follows first (control); water, second; pure BBR, third; BBR surface coated nanoparticles and fourth; placebo BBR surface coated nanoparticles. Biochemical levels of liver (AST, ALP and ALT) and kidney (serum urea and creatinine) along with their histopathological studies were also examined (0-28 days). The AUC of BBR-SCNP was significantly 3.5 folds higher compared to all other groups. The AUC of BBR-NP was 3.23 and 1.52 folds higher compared to BBR solution and BBR with verapamil group, respectively. The physical mixture treated group showed slightly higher AUC than BBR solution treated group but significantly low compared to other groups. It indicates that encapsulation of BBR in nanosize form can circumvent P-gp efflux effect. BBR-NP showed pharmacokinetic parameters (Cmax and AUC) which are near to BBR-SCNP. However, the difference in values of T1/2 and clearance indicate that surface coating with vitamin E TPGS not only avoids the P-gp efflux at its absorption site (intestine) but also at organs which are responsible for metabolism and excretion (kidney and liver). It may be the reason for observed decrease in clearance of BBR-SCNP. No toxicity signs were observed either in biochemical or histopathological examination of liver and kidney during toxicity studies. The results indicate that administration of BBR in surface coated nanoformulation would be beneficial for enhancement of its bioavailability and longer retention in systemic circulation. Further, sub acute oral dose toxicity studies for 28 days such as evaluation of intestine, liver and kidney histopathology and biochemical estimations indicated that BBR-SCNP developed were safe for long use.

Keywords: bioavailability, berberine nanoparticles, p-gp efflux inhibitor, nanoprecipitation method

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Authors: Luther Ollier, Sylvie Thiria, Anastase Charantonis, Carlos E. Mejia, Michel Crépon

Abstract:

Sea Surface Height Anomaly (SLA) is a signature of the sub-mesoscale dynamics of the upper ocean. Sea Surface Temperature (SST) is driven by these dynamics and can be used to improve the spatial interpolation of SLA fields. In this study, we focused on the temporal evolution of SLA fields. We explored the capacity of deep learning (DL) methods to predict short-term SLA fields using SST fields. We used simulated daily SLA and SST data from the Mercator Global Analysis and Forecasting System, with a resolution of (1/12)◦ in the North Atlantic Ocean (26.5-44.42◦N, -64.25–41.83◦E), covering the period from 1993 to 2019. Using a slightly modified image-to-image convolutional DL architecture, we demonstrated that SST is a relevant variable for controlling the SLA prediction. With a learning process inspired by the teaching-forcing method, we managed to improve the SLA forecast at five days by using the SST fields as additional information. We obtained predictions of a 12 cm (20 cm) error of SLA evolution for scales smaller than mesoscales and at time scales of 5 days (20 days), respectively. Moreover, the information provided by the SST allows us to limit the SLA error to 16 cm at 20 days when learning the trajectory.

Keywords: deep-learning, altimetry, sea surface temperature, forecast

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Authors: Kai Liu

Abstract:

Remote sensing-derived land surface temperature (LST) can provide an indication of the temporal and spatial patterns of surface evapotranspiration (ET). However, the spatial resolution achieved by existing commonly satellite products is ~1 km, which remains too coarse for ET estimations. This paper proposed a model that can disaggregate coarse resolution MODIS LST at 1 km scale to fine spatial resolutions at the scale of 250 m. Our approach attempted to weaken the impacts of soil moisture and growing statues on LST variations. The proposed model spatially disaggregates the coarse thermal data by using a non-linear model involving Bowen ratio, normalized difference vegetation index (NDVI) and photochemical reflectance index (PRI). This LST disaggregation model was tested on two heterogeneous landscapes in central Iowa, USA and Heihe River, China, during the growing seasons. Statistical results demonstrated that our model achieved better than the two classical methods (DisTrad and TsHARP). Furthermore, using the surface energy balance model, it was observed that the estimated ETs using the disaggregated LST from our model were more accurate than those using the disaggregated LST from DisTrad and TsHARP.

Keywords: Bowen ration, downscaling, evapotranspiration, land surface temperature

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Authors: Ambrish Singh

Abstract:

The corrosion inhibition performance of pyran (AP) and benzimidazole (BI) derivatives on J55 steel in 3.5% NaCl solution saturated with CO₂ was investigated by electrochemical, weight loss, surface characterization, and theoretical studies. The electrochemical studies included electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), electrochemical frequency modulation (EFM), and electrochemical frequency modulation trend (EFMT). Surface characterization was done using contact angle, scanning electron microscopy (SEM), and atomic force microscopy (AFM) techniques. DFT and molecular dynamics (MD) studies were done using Gaussian and Materials Studio softwares. All the studies suggested the good inhibition by the synthesized inhibitors on J55 steel in 3.5% NaCl solution saturated with CO₂ due to the formation of a protective film on the surface. Molecular dynamic simulation was applied to search for the most stable configuration and adsorption energies for the interaction of the inhibitors with Fe (110) surface.

Keywords: corrosion, inhibitor, EFM, AFM, DFT, MD

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Authors: Maamar Yahiaoui, Abdelrrahmene Kechich, Ismail Elkhallile Bousserhene

Abstract:

This article presents a study in simulation by means of MATLAB/Simulink software of the nonlinear control in positioning of a linear synchronous machine with the esteemed force of load, to have effective control in the estimator in all tests the wished trajectory follows and the disturbance of load start. The results of simulation prove clearly that the control proposed can detect the reference of positioning the value estimates of load force equal to the actual value.

Keywords: mathematical model, Matlab, PMLSM, control, linearization, estimator, force, load, current

Procedia PDF Downloads 571