Vertical Stability Research Articles

Angular stability measurement of a cryocooled double-crystal monochromator at SSRF

Precisely measuring the angular stability is essential to evaluate and improve the performance of the double-crystal monochromator (DCM). Herein, we apply a non-contact high-precision angular measurement method by utilization of the interferometers instead of conventional capacitive sensors, realizing a high resolution of picometer scale; particularly, a large working range of tens of millimeters can be simultaneously achieved, superior to previous method. By this means, we systematically investigate a homemade cryo-cooled DCM at Shanghai Synchrotron Radiation Facility (SSRF). The temporal stability as well as main eigen-frequencies of the DCM mechanics are measured at ambient temperature (25°C) and under liquid nitrogen (LN2) cooling condition, respectively. Fast Fourier Transform (FFT) analysis of these data hints possible vibration sources. Accordingly, flexible tube with an alumina fiber textile inner is adopted and the support of the cooling lines is optimized. Furthermore, relative vibrations with different cryo-cooler settings are compared, revealing a slightly enhanced amplitude with increasing flow rate. Through these optimizations, the DCM achieves a vertical stability of 125 nrad RMS in 1∼100 Hz and 180 nrad RMS in 1∼1000 Hz over the full photon energy, which meets the requirement of the Fast X-ray Imaging beamline at SSRF.

Modeling Marsh‐Forest Boundary Transgression in Response to Storms and Sea‐Level Rise

AbstractThe lateral extent and vertical stability of salt marshes experiencing rising sea levels depend on interacting drivers and feedbacks with potential for nonlinear behaviors. A two‐dimensional transect model was developed to examine changes in marsh and upland forest lateral extent and to explore controls on marsh inland transgression. Model behavior demonstrates limited and abrupt forest retreat with long‐term upland boundary migration rates controlled by slope, sea‐level rise (SLR), high water events, and biotic‐abiotic interactions. For low to moderate upland slopes the landward marsh edge is controlled by the interaction of these inundation events and forest recovery resulting in punctuated transgressive events. As SLR rates increase, the importance of the timing and frequency of water‐level deviations diminishes, and migration rates revert back to a slope‐SLR‐dominated process.

Avaliação da esteira de turbulência gerada por um parque eólico teórico na região do Pampa Gaúcho utilizando o modelo WRF

The main objective of this study is to analyze the influence of a wind farm on the variables that control the flow in the atmospheric boundary layer. The simulated period was the whole year of 2008, using a control simulation performed with the Weather Research and Forecasting model (WRF), and the wind farm model (the WRF model with the module Fitch, which parameters the influence of wind turbines on atmospheric flow). Both simulations using the Yonsei-University (YSU) boundary layer parameterization. From the control simulation is made the validation of the model, using observational data collected in two automatic stations of the National Institute of Meteorology (INMET) in the cities of Alegrete-RS and Quaraí-RS. The wind farm idealized in this work has 100 wind generators of 3 MW of power with 120 m in height and with rotor measuring 125 m in diameter. Although the wind speed responds adequately, the temperature and turbulence of near-surface runoff decrease. Analysis of the dependence of near-surface turbulence with vertical stability indicates that the turbulence being generated by the turbines is not reaching the surface. This problem may be related to the chosen boundary layer parameterization.

Avaliação da previsão de estabilidade na camada atmosférica de superfície do modelo WRF e efeitos na previsão de geração eólica no Uruguai

This work evaluates forecasts of vertical stability of the surface atmospheric layer obtained with the WRF regional model in Uruguay, for different times of the day and seasons of the year. The temperature and humidity values obtained from the model outputs and from field measurements at different heights in an anemometric tower allow to calculate the vertical gradient of virtual static stability both for predictions and field measurements. With the results obtained, it was possible to know the behavior of the WRF model in relation to the stability of the surface layer, which is closely related to the wind potential that may exist at different times of the day. In this way, a possible relationship between the systematic errors of forecasts of wind power and surface layer stability in Uruguay can be proposed.

Wave Induced Effects on the Hydrodynamic Coefficients of an Oscillating Heave Plate in Offshore Wind Turbines

The research problem discussed in this paper is of relevance to floating offshore wind turbine design, where heave plates are attached to the columns of a semi-submersible in order to improve vertical plane stability and the power output. Because of the shallow draft of these structures, the heave plates are proximal to the water surface. When subject to vertical plane motions the flow around a plate is altered by the presence of the free surface, resulting in changes in added mass and damping forces. In this paper, we present the experimental results for the added mass and damping coefficients for circular heave plates attached to a column, when oscillating in heave in the presence of oncoming waves. The results tend to indicate that applying the hydrodynamic coefficients obtained from still water experiments for a structure moving in waves may only be an approximation. For different relative phases of the wave and the motion, large variations could occur. We define a modified Keulegan—Carpenter (KC) number that depends on the relative amplitude of motion with respect to the wave. With this definition, the added mass and damping values are seen to be closer to the still water trends. However, at lower KC values, the added mass coefficients could differ by 30%, which can affect natural frequency estimates. Thus, caution needs to be exerted in the selection of hydrodynamic coefficients for heave plates oscillating in proximity to the free surface.

Noise limits on ITER plasma vertical stabilization system imposed by tungsten divertor monoblock thermal fatigue

Abstract Tokamak plasmas with vertically elongated cross-sections are unstable due to vertical displacements. Feedback stabilization of the ITER plasma current centre will be performed using the speed of its vertical displacements, dZ/dt, as input. Inevitable noise in the diagnostic signal for dZ/dt leads to “noisy” components in the feedback voltage and current in the stabilizing coils. This leads to noisy components in the vertical position of the plasma current centre and the divertor strike points. For burning plasma conditions on ITER, these strike point displacements may be a concern for thermal fatigue at the water cooling interface of the tungsten monoblocks constituting the divertor targets. A study is presented here in which this concern is examined for the first time. The baseline 15 MA scenario (fusion power of 500 MW with a 500 s flattop and fusion power gain, QDT = 10) is simulated with the DINA code, assuming low frequency noise in the dZ/dt diagnostic signal. The noise has uniform spectrum with a given root mean square (RMS) value ( =0.6 ms−1 or 0.2 ms−1) in the frequency band (0, 1 kHz). The results of these DINA simulations are combined with dissipative divertor plasma solutions obtained with the SOLPS-ITER plasma boundary code to provide a time dependent divertor target heat flux density profile. The latter is then imposed on a finite element model of the target monoblocks to assess the temporal evolution of the 3D temperature field in the block, including the Cu-W and Cu-CuCrZr joints at the cooling interface. These joints represent the points of the Cu and CuCrZr materials that see the largest temperature changes and are thus at greatest risk of failure. To evaluate an acceptance criterion on the non-cyclic and non-uniform thermal loads at the joints, an approach is developed which combines a Rainflow counting technique with Palmgren-Miner’s rule for fatigue accumulation. Analysis of the temperature evolution at the Cu-W joint shows that the RMS value of noise ∼0.6 ms−1 is unacceptable from the point of view of thermal fatigue for the expected total exposure time under burning plasma conditions that the first ITER divertor must survive. The lower value ( ∼0.2 ms−1) is found to be acceptable. A subsequent parametric study concludes that ≲ 0.44 ms−1 is just consistent with fatigue lifetime for the prescribed divertor power flux density profile, but should be kept lower than this to allow for some margin. Regarding the monoblock surface temperature, the natural power spreading caused by the separatrix movements is found to be beneficial from the point of view of recrystallization. For the level of noise in the dZ/dt diagnostic required to stay below joint fatigue limits, the average surface temperature on the most loaded monoblocks is reduced by ∼100 °C compared to the case with stationary strike points and the amount of time spent at this temperature at any one block by over 80 %.

Imaging of the Acromioclavicular Joint: Anatomy, Function, Pathologic Features, and Treatment.

The acromioclavicular joint is an important component of the shoulder girdle; it links the axial skeleton with the upper limb. This joint, a planar diarthrodial articulation between the clavicle and the acromion, contains a meniscus-like fibrous disk that is prone to degeneration. The acromioclavicular capsule and ligaments stabilize the joint in the horizontal direction, while the coracoclavicular ligament complex provides vertical stability. Dynamic stability is afforded by the deltoid and trapezius muscles during clavicular and scapular motion. The acromioclavicular joint is susceptible to a broad spectrum of pathologic entities, traumatic and degenerative disorders being the most common. Acromioclavicular joint injury typically affects young adult males and can be categorized by using the Rockwood classification system as one of six types on the basis of the direction and degree of osseous displacement seen on conventional radiographs. MRI enables the radiologist to more accurately assess the regional soft-tissue structures in the setting of high-grade acromioclavicular separation, helping to guide the surgeon's selection of the appropriate management. Involvement of the acromioclavicular joint and its stabilizing ligaments is also important for understanding and classifying distal clavicle fractures. Other pathologic processes encountered at this joint include degenerative disorders; overuse syndromes; and, less commonly, inflammatory arthritides, infection, metabolic disorders, and developmental malformations. Treatment options for acromioclavicular dysfunction include conservative measures, resection arthroplasty for recalcitrant symptoms, and surgical reconstruction techniques for stabilization after major trauma.

Hydrogen storage using liquid organic carriers: Equilibrium simulation and dehydrogenation reactor design

Liquid organic hydrogen carriers (LOHC) are unsaturated organic compounds used for chemical hydrogen storage. Using an equilibrium model of the LOHC N-ethylcarbazole, we discuss potential efficiency increases of hydrogen storage systems based on N-ethylcarbazole by the integration of low-temperature waste heat. N-ethylcarbazole is well suited for pressure swing operation with heat exchange between hydrogenation and dehydrogenation. We present and discuss kinetic data of the dehydrogenation reaction gathered in a tubular reactor that was mounted in different orientations and flow configurations. Similar maximum values of power density are reached in vertical and in horizontal orientation. Vertical orientation allows the favorable operation with counter-flow of the liquid carrier and the evolved hydrogen gas and radial heat transfer is significantly better than in horizontal orientation. In vertical reactor configurations, catalyst efficiency and operational stability are impaired at high void fractions. This issue can be reduced by dehydrogenation at elevated pressure and intermediate gas separation from the catalyst bed.

The Thermal and Structural Analysis of Vertical Stability Coil

The vertical stability coil is a new set of saddle shaped non-superconducting coil designed for the purpose of improving the control capability of plasma vertical movement. To avoid the electromagnetic shielding and en-hance the response performance, the vertical stability coil is installed in the inner wall of vacuum vessel. The subsequent disadvantage accompanying the benefit is that the coil is under severe neutron radiation. Besides the neutron radiation the coil will also encounter the ohmic heat once it is energized. The temperature rising of vertical stability coil is not allowed to beyond the specific threshold to guarantee the reliability of the coil com-ponents. Thus, the ohmic heat and nuclear heat calculation methods are presented and the detail temperature field is analysed by using ANSYS to check whether or not the coil can bear the thermal load. In addition, the thermal load will result in the thermal stress. To verify whether the thermal stress will lead to the structural damage, the thermal-structural coupling analysis is launched and the stress is evaluated based on ASME ana-lytical design. The analysis results will provide guidance for the local structural optimization of vertical stabil-ity coil.

Exploiting periodic orbits as dynamical clues for Kepler and K2 systems

Aims. Many extrasolar systems possessing planets in mean-motion resonance or resonant chain have been discovered to date. The transit method coupled with transit timing variation analysis provides an insight into the physical and orbital parameters of the systems, but suffers from observational limitations. When a (near-)resonant planetary system resides in the dynamical neighbourhood of a stable periodic orbit, its long-term stability, and thus survival, can be guaranteed. We use the intrinsic property of the periodic orbits, namely their linear horizontal and vertical stability, to validate or further constrain the orbital elements of detected two-planet systems. Methods. We computed the families of periodic orbits in the general three-body problem for several two-planet Kepler and K2 systems. The dynamical neighbourhood of the systems is unveiled with maps of dynamical stability. Results. Additional validations or constraints on the orbital elements of K2-21, K2-24, Kepler-9, and (non-coplanar) Kepler-108 near-resonant systems were achieved. While a mean-motion resonance locking protects the long-term evolution of the systems K2-21 and K2-24, such a resonant evolution is not possible for the Kepler-9 system, whose stability is maintained through an apsidal anti-alignment. For the Kepler-108 system, we find that the stability of its mutually inclined planets could be justified either solely by a mean-motion resonance, or in tandem with an inclination-type resonance. Going forward, dynamical analyses based on periodic orbits could yield better constrained orbital elements of near-resonant extrasolar systems when performed in parallel to the fitting of the observational data.

RAPID ASSESSMENT OF CHEMICAL CONTAMINATION PARAMETERS

The article describes a chemical hazard that can adversely affect the environment and humans in the event of accidents at high-risk facilities, lead to man-made pollution, large casualties and deaths. The existing methods of assessment of the effects of chemical contamination were analysed. The toxic properties of poisonous substances (PSs) have been revealed. The calculation algorithm has been presented and the technique for the prediction of the chemical situation after the release of explosive or emergency spills, highly toxic substances (HTS) into the environments has been disclosed. The sequence of solution calculation of the estimation of chemical parameters problem using conditional initial data has been shown. A computer program has been developed to handle the parameters of chemical contamination and to calculate losses among working personnel and residents who may end up in the accident zone of chemical industry facilities or into the environment (PS, HTS). The analysis of the calculations without the use of a computer program for processing chemical parameters of contamination and using it confirms the reliability of its design based on the Microsoft Visual Studio software (Visual C#). The method of calculation and estimation of a chemical situation after accidents and destruction at chemical industry facilities has been offered. The practical application of the developed computer program has been described, which enables the specialists in the field of civil protection (CP) to make calculations more quickly to determine the degree of vertical stability of air, depth and area of distribution of chemical cloud, time of reaching the settlement, losses of both working personnel and population, more promptly to make decisions both in peacetime and in a special period. Conclusions were made regarding the calculations performed and the results obtained when solving the problems of chemical situation estimation using modern technologies.

Different precipitation response over land and ocean to orbital and greenhouse gas forcing

Various proxies suggest a nearly in-phase variation of monsoons with local summer insolation. Oceanic proxies of monsoons document a more complex response. Climate model simulations also indicate that the response is different over land and ocean. Here using a transient simulation by a climate model over the last 22,000 years we have unraveled the factors that lead to these differences within the Indian subcontinent. We show that during the deglacial (22–12 ka) precipitation over India and the Bay of Bengal (BoB) are in phase, whereas they are out of phase across the Holocene (sim 12 ka to 0 ka). During the deglacial, water vapor amplifies the effect of solar forcing on precipitation over both the regions, whereas contributions from surface latent heat fluxes over the BoB drive an opposite response across the Holocene. We find that greenhouse gas forcing drives similar precipitation response over land and ocean, whereas orbital forcing produces a different response over land and ocean. We have further demonstrated that during periods of abrupt climate change [such as the Bølling–Allerød (sim 14 ka)], water vapor affects precipitation mainly through its influence on the vertical stability of the atmosphere. These results highlight the complex nature of precipitation over the BoB and thus has implications for the interpretation of monsoon proxies.

The Fast Algorithm of Running Stability in Mechanical Analysis of High Speed Railway

The running stability of high-speed railway is the goal of operators and vehicle manufacturers, so the running stability of high-speed railway is an important part of vehicle dynamics analysis. The stability analysis involves a lot of working conditions and suspension parameters, and the analysis workload is huge. Therefore, in this paper, the random vibration and running stability of high-speed trains are taken as the research object, and the relevant fast algorithm of responding to the power spectrum of high-speed railway vehicles is derived through the virtual excitation method, so as to realize the running stability research of high-speed railway vehicles. In this paper, the vertical and horizontal response power spectrum and stability index of a high-speed train are analyzed. Finally, the stability index is used to analyze the dynamic performance of the train at the same time, and the line test results of the dynamic performance of the train are evaluated. The research results show that the simple and efficient analysis algorithm is helpful to improve the analysis efficiency and reduce the simulation calculation time.

Plasma Control in Tokamaks

The plasma magnetic control systems for ITER (International Thermonuclear Experimental Reactor) are presented. The systems comprise original engineering solutions for plasma position, current and shape control for the two versions of ITER: ITER-1 and ITER-2, including those designed in V. A. Trapeznikov Institute of Control Sciences of the RAS. It is noted that in ITER-1 the plasma position and shape were controlled by all PF-coils and robust H∞-controllers, while to decrease peaks of control power for suppressing minor disruptions the additional nonlinear circuit was used without significant changes in displacements of the gaps between the plasma separatrix and the first wall. In ITER-2 the special circuit with a fast voltage rectifier was used for plasma vertical speed stabilization about zero, while for plasma current and shape control the special cascade control systems were designed with and without the control channels decoupling, with robust H∞-controllers and predictive model, and with adaptive stabilization of the plasma vertical position as well. To increase the plasma controllability region in the vertical direction the additional horizontal field coils were introduced into the ITER-2 vacuum vessel and the capabilities of the system with the new circuits to control the plasma vertical position at the noise presence were investigated.

Optimización del proceso de barrenado del área del estabilizador vertical para disminuir defectos en una empresa del sector aeroespacial mediante la implementación de la metodología DMAIC

Currently for organizations it is very important to comply with the satisfaction of both external and internal customers, in the same way it must comply with the established quality protocols, because the products that can be obtained can come to undermine the consumer's well-being final. The present work deals with this subject, however, it is necessary to specify that the company where the project was carried out will be determined as "Company A", due to a confidentiality contract. In which there is a process where holes are made in the skin of the vertical stabilizer with a semi-automated machine. At the end it is inspected, and it is noted that the countersink has marks which are visible or can be felt when the nail is passed over it. This problem causes operators to have to carry out this process again, but by hand so as not to exceed the established countersink measurement and leave it with a mirror polished aesthetic. The objective of this project is to minimize these defects that appear in the skin of the vertical stabilizer in the drilling process of "Company A", which have been generating rework in the production line. In this context, the importance of complying with quality problems would continue to contend in an increasingly strict market, seeking continuous improvement, standardization and control of processes, and customer satisfaction. The present identification work reduces and controls the sources of variation that are affecting the outputs of the vertical stabilizer barrier process, through the application of the DMAIC methodology (Define, Measure, Analyze, Improve, and Control. generated were favorable to the process and that in addition to the reduction of defects, other areas of improvement were found so that the affected process became standardized and controlled. Taking this into account, it is recommended that the methods and production department continue to work together, so that these defects do not continue to appear. Additional research can be done to identify other factors that indirectly affect the drilling process and this could be a great opportunity for the station.

Motor control of landing in an unsteady environment

BackgroundWhen landing from a jump or a drop, muscles contract before touchdown to anticipate imminent collision with the ground, soften ground contact and allow to return to a stable standing position without stepping or rebounding. Research questionThis study assesses the effect of the unsteadiness of the environment on the motor control of landing. The ‘unsteady environment’ was induced by asking participants to perform drop landings inside an aircraft that underwent trajectories parallel to Earth’s surface. The participants also performed the same task in a ‘steady environment’ in our laboratory. MethodsGround reaction forces, lower limb joints’ movements and the activity of lower limb muscles were recorded. The stability of the landing was assessed by the vertical and anterior-posterior stability indexes, center of pressure measures and by the coefficient of variation of kinetic and kinematic parameters. ResultsOn one hand, participants slowdown their joint movements and reduce the knee joint excursion during landing, probably to avoid excessive movements that may induce imbalance. On the other hand, the stability of the landing is reduced while the variability of the movement is increased, illustrating a less stable and less consistent landing. In addition, whatever the environment, landing parameters associated with increased stiffness (i.e., increased impact forces and decreased joint range of motion) are correlated with decreased landing stability. SignificanceOverall, landings in the‘unsteady environment’ appear to be more cautious but less stable and less finely tuned. Since the stability of the landing is not directly influenced by the steadiness of the environment, this more cautious behavior could be, at least in part, related to the fear/apprehension induced by sudden acceleration variations of the frame of the aircraft.

Modelling of RFX-mod2 tokamak equilibria with DEMO-like shape conditions and negative triangularity

In this paper, DEMO-like shaped plasma equilibria are defined for RFX-mod2 tokamak operations by using the Inverse Equilibrium Tool (IET code). IET allows for the computation of the coil currents needed to obtain a predetermined plasma shape with well defined plasma global parameters (i.e. total plasma current and total poloidal magnetic flux at the boundary) by solving a constrained minimization problem. The new shape conditions would allow achieving higher plasma current and plasma density values at the same toroidal magnetic field and safety factor limits of previous RFX-mod tokamak operations. The feasibility of these new equilibria is explored in terms of coil current requirements and vertical stability analysis. This study shows that RFX-mod2 is a flexible device, able to perform DEMO-like shaped tokamak operations with low requirements on both magnitude and distribution of active coil currents.

The Effect of Divided Attention with Bounce Drop Jump on Dynamic Postural Stability.

This study determined the effect of divided attention on controlling postural stability during a drop vertical jump task. In total, 30 participants were tested for drop vertical jumps from a 30-cm high platform and landing on a single leg with or without divided attention tasks. Three-dimensional marker trajectories and ground reaction forces were collected simultaneously. Vertical ground reaction force, loading rate, and dynamic postural stability index were analyzed with or without divided attention tasks. The paired sample t test indicated a significantly low knee flexion angle, high vertical ground reaction force, and increased loading rate in the divided attention task. Moreover, participants showed an increased vertical stability index and dynamic postural stability index in the divided attention task than in the nondivided attention task. Thus, results demonstrated that the divided attention task could affect posture control, leading to poor dynamic posture stability and possibly increasing lower extremity injury risk. The influence of the divided attention task on movement quality likely indicates that an athlete can no longer focus his attention on the bounce drop jump maneuver. Therefore, the bounce drop jump combined with dynamic postural stability index could be used in posture stability screening.

Developments of NDE method of jacket welds for ITER In-Vessel coil joints

The ITER facility currently incorporates two types of In Vessel Coils (IVC) as a method of stabilizing “Edge Localized Modes” (ELM) and providing “Vertical Stabilization” (VS). To withstand the severe conditions, the IVCs are made of stainless steel mineral insulated conductor (SSMIC). The jacket of the SSMIC is modified stainless steel 316LN. The diameter is 59mm and thickness is only 2.5mm. In order to join the IVC coils, it is necessary to develop the joints manufacturing. Jacket welding is an important process of the joints manufacturing. Based on the structural analysis, the maximum acceptable defect sizes inside the jacket weld were defined. This paper presents the non-destructive examination (NDE) development of the jacket weld NDE is the thin thickness which will cause the scattering of sound waves and lead the difficulty of effective identification of defects. Phased Array Ultrasonic Test (PAUT) and eddy current test (ECT) were developed for the jacket welds inspection. The results indicated the feasibility of the PAUT and ECT method could solve the problem of the thin thickness tube weld inspection.

Resorbable Versus Titanium Fixation of Le Fort I Osteotomy.

Resorbable and titanium systems have been used in maxillary fixation. The aim of this review was to evaluate stability and morbidity of Le Fort I osteotomy by comparing both systems. It was performed in 11 databases, and reported according to preferred reporting items for systematic reviews and meta-analysis. Randomized and nonrandomized clinical trials, and retrospective comparative studies with patients who underwent nonsegmented Le Fort I osteotomy were included. Eleven articles were selected, with a total of 262 patients treated with resorbable and 252 with titanium fixation. The meta-analysis showed that when measured at point A, horizontal stability was 0.06 mm (95% confidence interval [CI] -0.19, 0.30), vertical stability for impaction was -0.43 mm (95% CI -0.94, 0.07), and for inferior repositioning was -1.29 mm (95% CI -2.62, 0.04). Morbidity was similar in the groups. Regarding infection, resorbable presented an absolute risk (AR) = 0.032, and titanium an AR = 0.025 (P = 1.0). For soft tissue reaction, an AR = 0.120 was shown for resorbable, and an AR = 0.132 for titanium (P = 0.85). Removal of fixation showed an AR = 0.024 for resorbable, and an AR = 0.025 for titanium (P = 1.0). Based on these results, resorbable and metal fixation systems seem to be equivalent with respect to stability and morbidity. This review was limited by the quality of the studies. Future studies should address these quality limitations to improve comparison between these 2 fixation approaches.