Jaw Functional Orthopedics and Cranoficial Growth
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Experimental study on the effect of particle gradation on dewatering performance of geotubes
No full textTo clarify the effect of particle gradation of filling soil on the dewatering and consolidation performance of geotubes, the content of four-particle size classes (powder, fine, medium, and coarse) which are commonly used in engineering as the research object was taken. The dewatering rate, soil infiltration and solid-liquid mixing pressure in the bag with time when filling soil with different particles were studied, and the soil loss of the hanging bag was analyzed from the perspective of seepage soil gradation. The research results show that the dewatering process could be divided into the quick dewatering stage, silting stage, and stable stage according to the dewatering rate. According to the performance of soil conservation, it could be divided into the loss stage and reverse filtration stage. Further, based on the effects of powder content, non-uniformity coefficient, and curvature coefficient of soil on the dewatering rate of the hanging bag, a formula for calculating the dewatering rate of geotubes is summarized
The vibration of a thermoelastic nanobeam due to thermo-electrical effect of graphene nano-strip under Green-Naghdi type-II model
No full textIn this paper, a new analysis of thermoelastic, homogeneous, and isotropic nanobeams has been constructed in the context of the Green-Naghdi type-II heat conduction law. The first end of the nanobeam is based on a graphene strip, which contains an electrical current with a small voltage which is a novel application. Under simply supported boundary conditions with fixed side ratios, the nanobeam has been thermally loaded with a heat source due to the thermal effect of the electrical current. On the time variable, the Laplace transform technique was utilized to solve the governing differential equations. The solutions were computed in the Laplace transform’s domain. Tzou’s approximation technique based on an iteration formula was used to calculate the Laplace transform inversions numerically. The numerical findings for various values of the electrical voltage and electrical resistivity of the graphene nano-strip have been displayed using graphs illustrating distinct scenarios. All the nanobeam’s researched functionalities have been reported to be influenced by electrical voltage and electrical resistivity. The electrical voltage and resistivity of a graphene nano-strip might be utilized as a tuner to regulate the nanobeam's vibration and energy
Structural mechanics analysis of bolt joint of rigid flexible coupling manipulator
No full textAs the key connecting part of the rigid flexible coupling manipulator, the structural dynamic characteristics of the bolted joint are analyzed by using the joint simulation technology of pro/e and ANSYS. Based on the spring equivalent principle, the finite element equivalent model of bolt joint is established, the relationship equation between contact surface pressure and bolt preload is derived, and its stress state is analyzed; Based on the micro convex deformation model and Hertz contact theory, the tangential stiffness equation and normal stiffness equation of the bolted joint are derived respectively. The three-dimensional model of the bolted joint is established by using pro/e and imported into ANSYS for joint simulation. The simulation experiments reveal the influence of bolt joint vibration characteristics under different conditions from the aspects of bolt diameter, pre tightening force, bolt group number and bolt distribution. The conclusions have important engineering value for the structural optimization of rigid flexible coupling manipulator
Study of torque pulsation control of switched reluctance motor by auto-disturbance rejection control
Get PDFThe switched reluctance motor drives the rotor based on the principle of minimum reluctance, which is structurally simpler, but the doubly salient structure of the stator and rotor leads to severe torque pulsation. This paper briefly introduces the switched reluctance motor and the auto-disturbance rejection controller for suppressing the torque pulsation of the switched reluctance motor. Then, the auto-disturbance rejection controller was simulated in the MATLAB software, and it was compared with the direct torque control strategy. The results showed that the switched reluctance motor installed with the self-reluctance controller reached the set rotational speed faster, with a smoother torque change; when the set speed changed abruptly, it was adjusted to the new rotational speed faster, with a smooth and stable torque change; when the load torque changed abruptly, it was adjusted to the new torque smoother and faster, and the adjustment to the rotational speed was also faster
Using vibration data to classify conditions in disk stack separators
Get PDFMounting sensors in disk stack separators is often a major challenge due to the operating conditions. However, a process cannot be optimally monitored without sensors. Virtual sensors can be a solution to calculate the sought parameters from measurable values. We measured the vibrations of disk stack separators and applied machine learning (ML) to detect whether the separator contains only water or whether particles are also present. We combined seven ML classification algorithms with three feature engineering strategies and evaluated our model successfully on vibration data of an experimental disk stack separator. Our experimental results demonstrate that random forest in combination with manual feature engineering using domain specific knowledge about suitable features outperforms all other models with an accuracy of 91.27 %
The influence of the truss bar on the dynamic behavior of a Warren truss by changing the modulus of elasticity
Get PDFThe paper presents the natural frequencies shift of a Warren truss with seven elements in the case that members of the structure are weakened by considering that the modulus of elasticity with a lower value. Taking into consideration that the slenderness ratio has a constant value and the transverse section of the truss bars is changed, the relative frequency shift for the first seven vibration mode were calculated by using the values obtained from numerical modal analysis. The conclusions reveal the fact from the dynamic behavior of the structure it can be obtained templates to identify the weakened truss bar of the structure
Optimization on the jet characteristics of the main nozzle of hot-blowing snow removal device
Get PDFThe exhaust devices used by snow removal vehicles are mainly based on hot-blowing snow removal. Due to the inherent characteristics of the turbojet engine such as low flow rate and high exhaust temperature, the modified hot-blowing snow removal device has problems of low snow removal efficiency and the possibility of ablation and damage to the road surface. In order to solve the problem, transforming the turbofan engine with a high flow rate and a low exhaust temperature into a hot-blowing snow removal device is an important improvement to achieve efficient and safe snow removal operations. In order to convert a medium bypass ratio turbofan engine into a hot-blowing snow removal device, the computational fluid dynamics (CFD) software CFX was used to analyze the internal and external flow field characteristics of the main nozzle of an exhaust device under the 60 % rated condition of the engine. The effective area sizes of the jet velocity and temperature predicted by the external flow field were used to optimize the layout of the main nozzle
Railway foreign body vibration signal detection based on wavelet analysis
Get PDFBased on the wavelet packet analysis method with time-frequency analysis characteristics, the measurement signal of the vibration system is processed for noise reduction, the soft-hard threshold compromise wavelet denoising method used has the advantages of soft threshold and hard threshold denoising, and through the introduction of compromise factors, signal processing can be performed more flexibly in signal analysis. For the denoised signal, the fundamental wavelet time-energy spectrum analysis, the main components of the signal can be clearly displayed, and according to the distribution of its energy in each frequency band, the signal characteristics can be displayed intuitively. Experimental results show: It can be determined that there is a foreign body intrusion incident at a position 520 m away from the monitoring point, rather than a normal train travel incident. In fact, we are walking back and forth at a distance of about 520 m from the monitoring point, simulating the intrusion of illegal foreign objects such as pedestrians and livestock beside the railroad tracks prove that analysis and judgment can be known, the wavelet analysis proposed by the author can realize the monitoring and judgment of some illegal foreign body intrusion incidents such as pedestrians and livestock
New CO2 and Hydrogen storage site marketing: How to make your storage site unique and attractive?
Get PDFToday we met the situation, when our knowledge and expertise are far away from marketing – an ability to sell our knowledge to the end-user (public, policymakers, governments, and small and big enterprises). This study aimed to attract stakeholders by proposing new techno-ecological synergy concept of geological storage of CO2 (CGS) and hydrogen (UHS) in a cost-competitive, self-supporting storage site. The “story of success” of the offshore geological structure E6 in Latvia has started from an invisible point on the European map, oil-bearing but not very promising geological structure to the unique and one of the best cost-competitive, self-supporting, conceptual techno-ecological examples of a possible synergy of storage concepts with renewables energies. Using detailed petrophysical, mineralogical and geochemical analyses of the Cambrian Series 3 Deimena Formation reservoir sandstones in this structure, the CO2 storage capacity was estimated with different levels of reliability from a conservative 158 Mt (106-252 Mt) up to an average optimistic average of 396 Mt (264-631 Mt). The theoretical CO2 storage capacity in the oil-bearing limestones of the Upper Ordovician Saldus Formation was estimated at the end of the Enhanced Oil Recovery cycle using the CO2 (CO2-EOR) as an average of 110 Mt (65-144 Mt). The E6 structure was estimated as the most prospective and the largest for CO2 geological storage in the Baltic Region with a total average CO2 storage capacity of about 500 Mt. Time-lapse numerical seismic modelling was applied to analyze the feasibility of CO2 storage monitoring in the E6. The novelty of this approach was the coupling of the chemically induced petrophysical alteration effect of CO2-hosting rocks, measured in the laboratory during the CO2 injection-like experiment, with time-lapse numerical seismic modelling. According to changes in the amplitude and two-way travel times in the presence of CO2, reflection seismic could detect CO2 injected into the deep aquifer formations even with low CO2 saturation values. Our results showed the effectiveness of the implemented time-lapse rock physics and seismic methods in the monitoring of the CO2 plume evolution and migration in the E6. The new concept of techno-ecological synergy of the CCUS project with different eco-friendly renewable energy recovery technologies, which support circular economy targets, is presented. The concept of the CCUS project includes six innovative elements of techno-ecological synergy: (1) CGS, (2) Geothermal energy recovery during CO2 geological storage (CPG), (3) CO2-EOR, (4) underground hydrogen storage (UHS), (5) solar energy and (6) wind energy recovery. This concept should maximise efficiency, minimize the carbon footprint of the full-chain CCUS process and demonstrate the “winx” situation (where “x” is a number of additional benefits of the project). We demonstrated an example of the project supporting also a win5 global situation (that is, a win-win scenario with a minimum of five potential global outcomes): greenhouse gas emissions (GHGE) reduction, (2) economic profitability, (3) increased CO2 storage capacity, (4) public acceptance and (5) retargeting of oil and gas businesses. Small wind offshore floating plant installed around the rig and solar panels covering free surfaces of the rig and a compact geothermal plant using CO2 (20 times smaller than a conventional plant) will produce renewable energy added to the project electricity net to cover the energy needs of the project. The excess energy will be used by compact hydrogen production plant established directly on the rig. The produced hydrogen could be stored underground and when needed, transported by ship to the port. For the first time, we estimated hydrogen storage capacity in the E6-B, the smaller compartment of the E6 offshore structure as 30 Kt. This scenario is a basis for the new concept of CO2 and hydrogen storage site marketing: how to retarget fossil fuel business (the depleted oil and gas fields) into the storage-targeted and renewable energy business, permitted to achieve the carbon-free energy transition using principles of circular economy and sustainable use of resources and environment
Damage localization in beams based on the analysis of modal parameters
Get PDFThis paper presents a two-step method for damage localization in beams by combining natural frequencies and mode shapes. The general locations of the damage are first identified from an indicator developed using relative natural frequency change (RNFC) curves and the values of RNFCs. A curvature-mode-shape-based method is then utilized to determine the specific location of the damage in the second step. The proposed two-step method is verified by detecting damage in a simulated simply-supported beam. The identified damage location agrees well with the actual damage location. A strategy for fast and accurate damage localization based on general localization using natural frequencies and specific localization using mode shapes is the main novelty of the paper