Minimizing Residual Vibrations for Non-Zero Initial States:Application to an Emergency Stop of a Crane

Joaquim Maria Veciana,Salvador Cardona-Foix,Pau Català 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.

This paper presents an approach to design command inputs for the reduction of residual vibrations in mechanical systems for nonzero initial states. The technique starts with the development of a standard input shaper in a second order oscillator, and adds the initial states of the system to the formulation. However, it is proven that the obtained input shaper does not guarantee a null residual vibration when it is convolved with any unshaped command. To obtain an analytically proven zero-vibration response, it is required to include the parameters that characterize the response of the system to a selected normalized unshaped command in the formulation. By introducing an appropriate processing time delay and by measuring the initial states using a feedback sensor, the proposed method has been applied in a real time scenario where an emergency stop of a crane is required, assuming that initially the payload is swaying. The analyzed systems are those that can be modeled as discrete linear ones and can be described with constant parameter motion equations. Experimental results show the efficacy of the developed method with its application to a scaled crane test platform.

Economic Evaluation of Public Policies Aiming the Reduction of Greenhouse Gas Emissions in Brazil

( Joaquim Bento De Souza Ferreira Filho ),( Marcelo Theoto Rocha ) 세종대학교 경제통합연구소 (구 세종대학교 국제경제연구소) 2008 Journal of Economic Integration Vol.23 No.3

In this paper a static, inter-regional and bottom-up general equilibrium model of greenhouse gas emissions in Brazil is used to analyze the impact of different types of carbon taxes on the economy. The core database is calibrated with Brazilian economic data from 1996, while the emissions module is based on the Brazilian Initial National Communication to the United Nations Convention about Global Climate Change for the 1994 reference year. The gas module in the model comprises all known sources of greenhouse gases emissions except emissions from land use change (deforestation). The simulations comprise scenarios with carbon taxes on emissions, either on fuel use or on the activity level of industries. Results show that taxing activities is more relevant for greenhouse gases emissions reductions in Brazil than just taxing fuel use, due to the importance of activity related emissions in the Brazilian emissions matrix. Livestock is found to be one of the most important emission sectors in Brazil. Carbon tax on activities, however, generates the higher increase in food prices, with negative implications for poverty alleviation. Different carbon tax schemes would also have different regional impacts inside Brazil, with taxation on fuels harming more the Southeast and Northeast regions, and taxation on activity levels affecting negatively more the South and Center west regions.

Residual Vibration Reduction in Mechanical Systems: A Time-domain Approach

Joaquim Maria Veciana,Salvador Cardona 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.

This paper presents a time-domain technique to generate command inputs for the reduction of residual vibrations in mechanical systems. The technique is based on the generation of motion profiles with zero-crossing points in their frequency spectra at the system resonances in the same way as the zero-vibration (ZV) command generation methods. By including an appropriate negative exponential time function, which contains the system natural frequency and the damping ratio, the resultant input can be applied to damped systems with a result of zero residual vibration. The signals synthesized can be used as a generic physical magnitude in vibratory systems. However, they were particularized for mechanical systems and engineering metrics were used. Compared to other ZV methods, for a short duration input range, the signals obtained have better performance in terms of minimum-acceleration-switch shape which is translated to a smoother motion profile. The development includes the application to single-mode and multiple-mode mechanical systems and the possibility of handling two functional requirements or constraints in the desired application. The analyzed systems are those that can be modeled as discrete linear ones with several vibratory degrees of freedom and can be described with constant parameter motion equations. Experimental results show the efficacy of the method developed with its application to a damped pendulum test platform.

Modified Adaptive Input Shaping for Maneuvering Cranes Using a Feedback MEM Gyroscope with Null Drift

Joaquim Maria Veciana,Salvador Cardona-Foix,Pau Català 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

This paper presents an adaptive algorithm to reduce residual vibrations when the feedback sensor used has null drift along the time. The adaptive approaches are useful to deal with large variations of the system parameters at each maneuver, such as it occurs in cranes. For the feedback sensor, the use of inertial measurement units such as Micro-Electro-Mechanical Systems (MEMS) is increasingly extended because of their cost, size, robustness and power consumption. However, the effectiveness of the adaptive input shaping algorithms is compromised because of this drift, which is a commonly raised issue in this kind of devices. The study presented in this manuscript focuses on the development of an automatic compensation of this drift to obviate frequent calibrations. It is based on a non-asymptotic algebraic identification technique, which does not require initial conditions and has a short convergence time. This study uses the Zero-Vibration (ZV) input shaper technique, and the null drift is added to the algorithm as a parameter to be identified. The proposed method is particularized for single maneuvers of cranes with a gyroscope as feedback sensor, in a real time scenario. Experimental results show the efficacy of the method on a scaled crane test platform.

Steel fibre reinforced concrete for elements failing in bending and in shear

Barros, Joaquim A.O.,Lourenco, Lucio A.P.,Soltanzadeh, Fatemeh,Taheri, Mahsa Techno-Press 2013 Advances in concrete construction Vol.1 No.1

Discrete steel fibres can increase significantly the bending and the shear resistance of concrete structural elements when Steel Fibre Reinforced Concrete (SFRC) is designed in such a way that fibre reinforcing mechanisms are optimized. To assess the fibre reinforcement effectiveness in shallow structural elements failing in bending and in shear, experimental and numerical research were performed. Uniaxial compression and bending tests were executed to derive the constitutive laws of the developed SFRC. Using a cross-section layered model and the material constitutive laws, the deformational behaviour of structural elements failing in bending was predicted from the moment-curvature relationship of the representative cross sections. To evaluate the influence of the percentage of fibres on the shear resistance of shallow structures, three point bending tests with shallow beams were performed. The applicability of the formulation proposed by RILEM TC 162-TDF for the prediction of the shear resistance of SFRC elements was evaluated. Inverse analysis was adopted to determine indirectly the values of the fracture mode I parameters of the developed SFRC. With these values, and using a softening diagram for modelling the crack shear softening behaviour, the response of the SFRC beams failing in shear was predicted.

Revision Surgeries at the Index Level After Cervical Disc Arthroplasty – A Systematic Review

Andrei Fernandes Joaquim,Nathan J. Lee,K. Daniel Riew 대한척추신경외과학회 2021 Neurospine Vol.18 No.1

Objective: To perform a systematic literature review on revision surgeries at the index level after cervical disc arthroplasty (CDA) failure. Methods: A systematic literature review was performed according to the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. Prospective studies on patients who required a secondary surgery after CDA failure were included for analysis. The minimum follow-up for these studies was 5 years. Results: Out of 864 studies in the original search group, a total of 20 studies were included. From a total of 4,087 patients, 161 patients required a reoperation at the index level. A total of 170 surgeries were performed, as some patients required multiple surgeries. The most common secondary procedures were anterior cervical discectomy and fusion (ACDF) (68%, N=61) and posterior cervical fusion (15.5%, N=14), followed by other reoperation (13.3%, N=12). The associated outcomes for those who required a revision surgery were rarely mentioned in the included literature. Conclusion: The long-term revision rate at the index level of failed CDA surgery was 3.9%, with a minimum 5-year follow-up. ACDF was the most commonly performed procedure to salvage a failed CDA. Some patients who required a new surgery after CDA failure may require a more extensive salvage procedure and even subsequent surgeries.

Transoral and Endoscopic Endonasal Odontoidectomies – Surgical Techniques, Indications, and Complications

Andrei Fernandes Joaquim,Joseph A. Osorio,K. Daniel Riew 대한척추신경외과학회 2019 Neurospine Vol.16 No.3

Odontoidectomy is indicated for some cases of ventral compression in the upper cervical spine. In this paper, we discuss the indications, surgical steps, and nuances of transoral odondoidectomy (TO) and endoscopic endonasal (EE) odontoidectomy. We compare both approaches and discuss the advantages and disadvantages of each. A broad narrative literature review was performed. We also added tips and surgical pearls of the senior author (KDR) in performing odontoidectomies. Surgical techniques were presented. EE is performed in patients where the dens is located above the nasopalatine line. Although technically more demanding, EE has less soft tissue injury and potentially less risk of dysphonia and dysphagia. The TO approach provides a wider exposure and is not limited by the nasopalatine line. Additionally, the TO approach allows the ability for a more extensive resection of C2; these could include the C2 body and the C2–3 disc space. Ventral reconstructions with cages and plates are also feasible via the TO approach. However, there are additional risks of prolonged intubation and tracheostomy with the TO approach. Surgeons who manage upper cervical spine disease should be comfortable performing both approaches, and selecting the best approach should be determined using patient-specific characteristics.

C1 Stenosis – An Easily Missed Cause for Cervical Myelopathy

Andrei Fernandes Joaquim,Griffin Baum,Lee A. Tan,K. Daniel Riew 대한척추신경외과학회 2019 Neurospine Vol.16 No.3

C1 stenosis is often an easily missed cause for cervical myelopathy. The vast majority of cervical myelopathy occurs in the subaxial cervical spine. The cervical canal is generally largest at C1/2, explaining the relatively rare incidence of neurological deficits in patients with odontoid fractures. However, some subjects have anatomical anomalies of the atlas, which may cause stenosis and result in clinical symptoms similar to subaxial cord compression. Isolated pure atlas hypoplasia leading to stenosis is quite rare and may be associated with other anomalies, such as atlas clefts or transverse ligament calcification. It may also be more commonly associated with syndromic conditions such as Down or Turner syndrome. Although the diagnosis can be easily made with a cervical magnetic resonance imaging, the C3/2 spinolaminar test using a lateral cervical plain radiograph is a useful and sensitive tool for screening. Surgical treatment with a C1 laminectomy is generally necessary and any atlantoaxial or occipito-atlanto instability must be treated with spinal stabilization and fusion.

Circumferential Operations of the Cervical Spine

Andrei Fernandes Joaquim,Nathan J. Lee,K. Daniel Riew 대한척추신경외과학회 2021 Neurospine Vol.18 No.1

Generally, a combined anterior and posterior cervical approach is associated with significant morbidity since it requires an extended operative time, greater intraoperative blood loss, and both anterior- and posterior-related surgical complications. However, there are some instances where a circumferential cervical fusion can be advantageous. Our objective is to discuss the indications for circumferential cervical spine procedures. A narrative review of the literature was performed. We include the indications for circumferential cervical approaches of the senior author (KDR). Indications for circumferential approaches include: (1) high-risk patients for pseudoarthrosis, (2) cervical deformity (e.g., degenerative, posttraumatic, cervicothoracic kyphosis), (3) cervical spine metastases (especially those with multilevel involvement), (4) cervical spine infection, (5) unstable cervical trauma, (6) movement disorders and cerebral palsy, (7) Multiply operated patient (especially postlaminectomy kyphosis and patients with massive ossification of the posterior longitudinal ligament), and when (8) early fusion is desirable. Circumferential procedures may be useful in many different cervical spine conditions requiring surgery. Despite its advantages, particularly with reducing the risk for pseudarthrosis, the benefits of a combined approach must be weighed against the risks associated with a dual approach. With appropriate preoperative planning, intraoperative decision-making, and surgical techniques, excellent clinical outcomes can be achieved.

Dynamic Cord Compression Causing Cervical Myelopathy

Andrei Fernandes Joaquim,Griffin R. Baum,Lee A. Tan,K. Daniel Riew 대한척추신경외과학회 2019 Neurospine Vol.16 No.3

Due to the highly mobile nature of the cervical spine, and the fact that most magnetic resonance imagings (MRIs) and computed tomography scans are obtained only in one single position, dynamic cord compression can be an elusive diagnosis that is often missed and not well-understood. In this context, dynamic MRI (dMRI) has been utilized to improve the diagnostic accuracy of cervical stenosis. We performed a literature review on dynamic cord compression in the context of cervical spondylotic myelopathy (CSM), with particular emphasis on the role of dMRI. Cadaveric studies report that the spinal cord lengthens in flexion and the spinal canal dimension increases, whereas the spinal cord relaxes and shortens in extension and the spinal canal decreases. These changes may lead to biomechanical stress in the spinal cord with movement, especially in patients with critical cervical stenosis. The majority of the studies using dMRI in CSM reported that this imaging modality is more sensitive at detecting cervical cord compression compared to routine MRIs done in a neutral position, especially with the neck in extension. Dynamic MRI was also useful to diagnose dynamic cervical cord compression after laminectomies in patients with clinical deterioration without evident cord compression on neutral static MRI. Finally, dMRI is more sensitive in detecting stenosis in patients with CSM than in those with ossification of the posterior longitudinal ligament (OPLL), likely because OPLL patients often have a more limited range of motion than CSM patients. Thus, dMRI is a promising new tool that can help spine surgeons in diagnosing and treating CSM.