Load Relief Research Articles

Rolling active load relief technology for launch vehicle bundled with common booster core in face

The aerodynamic interference forces and moments of different windward surfaces of a launch vehicle bundled with a common booster core in the face vary considerably. The servo mechanism is laid out to maximize the control capability of the rocket at a certain angle. The dominant surface of the rocket is determined by aerodynamic interference and control capability. For the problem of large interference and asymmetry during the flight of a nominal rocket, a rolling active load relief control law based on the optimization of the spatial interference vector is proposed. The direction with the largest spatial interference vector is obtained online by visual acceleration information. By adjusting the rolling program angle, the rocket will align the dominant face with the direction of the largest interference when flying through the windy area. And then, the rocket obtains a good control effect. The simulation results show that the control law proposed in this paper can effectively improve the adaptability of the rocket control in the case of sudden changes in wind direction. It achieves the purpose of reducing the static load of the rocket body structure during the flight.

A Case Study of Transient and Dynamic Performance of Saturated Core Reactor Static Var Compensator

This paper presents results related to transient, dynamic and steady state response of a Saturated Core Reactor Static VAr Compensator (SCR-SVC) at regulating a real radial 230 kV transmission line supplying a low density and highly distributed load in a developing area of Brazil. The studies are carried out using a time domain computational simulator in which a comprehensive model for a given twin-triple saturated reactor compensator model was implemented to cope with the receiving end load requirements for voltage regulation. Investigations are then performed to highlight the overall system and reactive compensator behavior at the occurrence of the reactor switch on conditions, final load relief and harmonic distortions.

Compensated acceleration feedback based active disturbance rejection control for launch vehicles

In this paper, the attitude tracking and load relief control problems against wind disturbances and uncertain aerodynamics as well as the engine thrust of launch vehicles are studied. Firstly, a framework of Compensated Acceleration Feedback based Active Disturbance Rejection Control (CAF-ADRC) is established to achieve both desired attitude tracking and load relief performances. In particular, the total disturbance that includes the effects caused by both aero-coefficient perturbations and disturbances is estimated by constructing an Extended State Observer (ESO) to achieve attitude tracking. Furthermore, combined with the normal acceleration due to the engine thrust, the accelerometer measurement is also compensated to enhance the load relief effect. Secondly, the quantitative analysis of ESO and the entire closed-loop system are studied. It can be concluded that the desired attitude tracking and load relief performances can be achieved simultaneously under the proposed approach. Besides, tuning laws of the proposed approach are systematically given, which are divided into ESO, Proportional Derivative (PD) and Compensated Acceleration Feedback (CAF) modules. Moreover, the performances under CAF-ADRC approach can be better than those under CAF based PD (CAF-PD) approach by tuning load relief gain. Finally, the approach presented is applied to a typical control problem of launch vehicles with wind disturbances and parameter uncertainties.

Research of the Performance of a Hydraulic Actuator Based on an Acoustic Power Analysis

The powered roof support in a mining complex protects machines and people from the harmful effects of the rockmass. The design of the powered roof support should be strictly prepared for adverse working conditions. This especially applies to the construction of the hydraulic actuator, which is designed to transfer uncontrolled load relief. The hydraulic actuators and an adequately selected safety valve determine the requirements for safe work. The study analyses the hydraulic actuators based on the signal obtained from the dynamic impact. The signal obtained from the load of the powered roof support in the bench tests allowed us to determine the opening time of the safety valve, which is not much different than the time of the pressure increase. Until now, the valve’s operation has been primarily analysed regarding pressure increase. This research was intended to determine whether introducing the sound power method for developing powered roof support research in the near future would be helpful. The sub-piston pressure increased during bench testing, generating a dynamic impact signal. The analysed results of the sound power tests in terms of their suitability for the development of standards related to powered roof support. This paper describes a new approach to research on powered roof support. Determining the acoustic power based on bench tests for the hydraulic actuator of a powered longwall support is ground-breaking research. The research results pave the way for new technologies based on acoustic information.

Study on field applicability of a cleaning machine for marine growth removal in seawater pipelines

In a seawater intake facility, the proliferation and inflow of marine life impede the flow of seawater, thereby hindering the normal operation of offshore plants. To address this issue, it is necessary to use appropriate device for cleaning the fouled intake pipe, and particularly devices that are suited to dealing with polymer pipes over 2000 mm in diameter. This study aimed to improve the field applicability of a winch jig cleaning device designed for deep seawater pipes for which existing commercial devices and services were not economically feasible. The forward movement and rotation of brushes effectively remove attached marine life without causing damage to the pipe material and recover the water level of the intake structure from the trip level of 4600 mm to design level of 6000 mm in intake tank. 3D modeling using SolidWorks was used to assess the load distribution within the device and allowed for the calculation of individual loads on device elements based on their physical properties, thus resulting in the determination of the total load of 1450 kg in a manner similar to field weight measurements. The potential fatigue load relief in the brush body installation section on the shaft was calculated to be the maximum stress of 5.979e-03 N/mm2 ·MPa, that was lower than the maximum stress of 2.390e+01 N/mm2 ·MPa and the yield stress of 2.05e+02 N/mm2 ·MPa. It was achieved by reducing the weight of brushes and brush frames. The installation of brushes and brush frames resulted in maximum stress becoming concentrated, but the stress levels decreased after installation of the floater due to its effective load-lightening capability.

Bilateral bone marrow edema syndrome of the humeral head mimicking avascular necrosis: a case report

BackgroundBone marrow edema syndrome (BMES), previously referred to as transient osteoporosis, is an uncommon and underdiagnosed self-limiting condition typically affecting the weight-bearing joints of the hip and lower limb. Its occurrence in upper limb or non-weight bearing joints is particularly rare.Case presentationWe report the case of an otherwise healthy 42-year-old man who gradually developed severe and disabling left shoulder pain over the course of 6 months. Nine months after onset, he presented clinically with bilateral involvement and radiologically (magnetic resonance imaging, MRI) with diffuse BME associated with a subchondral insufficiency fracture, suggestive of proximal humeral avascular necrosis. Clinical evidence of subacromial shoulder impingement and MRI findings of bilateral subchondral bursitis and tenosynovitis with effusion of the biceps tendons likely resulted from primary BME, as musculoskeletal sonography confirmed the absence of rotator cuff tears. Repeated MRI findings at 2, 12, and 18 months documented near complete resolution of both edema and fracture, consistent with BMES of the proximal humerus. During this time, the patient reported a gradual improvement in both pain symptoms and range of motion. The clinical picture of insidious shoulder pain, exacerbated by activity and improved by load relief, in the absence of predisposing factors for osteonecrosis or antecedent trauma in patients of middle age, should indicate the possibility of the diagnosis of BMES.ConclusionsThis unprecedented report documents a rare case of bilateral BMES of the humeral head mimicking avascular necrosis. The correct diagnosis of BMES within an atypical anatomical location avoids invasive measures in the affected bone. The misdiagnosis of secondary BME and idiopathic osteonecrosis can be avoided by recognizing the characteristics of BME and subchondral fractures of the humeral head in the absence of rotator cuff tears, as well as their evolution on serial MRI.

Early Detection of Risk of Neo-Sinus Blood Stasis Post-Transcatheter Aortic Valve Replacement Using Personalized Hemodynamic Analysis

BackgroundDespite the demonstrated benefits of transcatheter aortic valve replacement (TAVR), subclinical leaflet thrombosis and hypoattenuated leaflet thickening are commonly seen as initial indications of decreased valve durability and augmented risk of transient ischemic attack. MethodsWe developed a multiscale patient-specific computational framework to quantify metrics of global circulatory function, metrics of global cardiac function, and local cardiac fluid dynamics of the aortic root and coronary arteries. ResultsBased on our findings, TAVR might be associated with a high risk of blood stagnation in the neo-sinus region due to the lack of sufficient blood flow washout during the diastole phase (e.g., maximum blood stasis volume increased by 13, 8, and 2.7 fold in the left coronary cusp, right coronary cusp, and noncoronary cusp, respectively [N = 26]). Moreover, in some patients, TAVR might not be associated with left ventricle load relief (e.g., left ventricle load reduced only by 1.2 % [N = 26]) and diastolic coronary flow improvement (e.g., maximum coronary flow reduced by 4.94%, 15.05%, and 23.59% in the left anterior descending, left circumflex coronary artery, and right coronary artery, respectively, [N = 26]). ConclusionsThe transvalvular pressure gradient amelioration after TAVR might not translate into adequate sinus blood washout, optimal coronary flow, and reduced cardiac stress. Noninvasive personalized computational modeling can facilitate the determination of the most effective revascularization strategy pre-TAVR and monitor leaflet thrombosis and coronary plaque progression post-TAVR.

Reversal of right ventricular pressure loading improves biventricular function independent of fibrosis in a rabbit model of pulmonary artery banding.

Right ventricular (RV) pressure loading leads to RV and left ventricular (LV) dysfunction through RV hypertrophy, dilatation and fibrosis. Relief of RV pressure load improves RV function. However, the impact and mechanisms on biventricular reverse-remodelling and function are only partially characterized. We evaluated the impact of RV pressure overload relief on biventricular remodelling and function in a rabbit model of reversible pulmonary artery banding (PAB). Rabbits were randomized to three groups: (1) Sham-operated controls (n=7); (2) PAB (NDef, n=7); (3) PAB followed by band deflation (Def, n=5). Sham and NDef animals were sacrificed at 6weeks after PAB surgery. Def animals underwent PAB deflation at 6weeks and sacrifice at 9weeks. Biventricular geometry, function, haemodynamics, hypertrophy and fibrosis were compared between groups using echocardiography, magnetic resonance imaging, high-fidelity pressure-tipped catheters and histology. RV pressure loading caused RV dilatation, systolic dysfunction, myocyte hypertrophy and LV compression which improved after PAB deflation. RV end-diastolic pressure (RVEDP) decreased after PAB deflation, although remaining elevated vs. Sham. LV end-diastolic pressure (LVEDP) was unchanged following PAB deflation. RV and LV collagen volumes in the NDef and Def group were increased vs. Sham, whereas RV and LV collagen volumes were similar between NDef and Def groups. RV myocyte hypertrophy (r=0.75, P<0.001) but not collagen volume was related to RVEDP. LV myocyte hypertrophy (r=0.58, P=0.016) and collagen volume (r=0.56, P=0.031) correlated with LVEDP. In conclusion, relief of RV pressure overload improves RV and LV geometry, hypertrophy and function independent of fibrosis. The long-term implications of persistent fibrosis and increased biventricular filling pressures, even after pressure load relief, need further study. KEY POINTS: Right ventricular (RV) pressure loading in a pulmonary artery banding rabbit model is associated with RV dilatation, left ventricular (LV) compression; biventricular myocyte hypertrophy, fibrosis and dysfunction. The mechanisms and impact of RV pressure load relief on biventricular remodelling and function has not been extensively studied. Relief of RV pressure overload improves biventricular geometry in conjunction with improved RV myocyte hypertrophy and function independent of reduced fibrosis. These findings raise questions as to the importance of fibrosis as a therapeutic target.

Comprehensive Load Relief of Launch Vehicle with the Constraints of Legacy Stages

Facing diversified launch needs, it is uneconomical to redevelop new rockets from scratch. The concept of combining legacy modules into a new launcher has become attractive. However, these mature modules may not adapt to new flight profiles due to differences in factors such as the propulsion system configuration, payloads, and trajectories. Thus, structural load relief measures play a key role in module integration. A comprehensive load relief strategy applied in the Long March 8 (LM-8) rocket is introduced, including the inflight load reduction by engine throttling, wind biasing trajectory, and onboard load relief control techniques. A unified analysis process for the elastic loads caused by gusts and fluctuating pressures was proposed, and an integral optimization problem for simultaneous planning with complicated constraints (such as the maximum dynamic pressure, wind biasing, and throttling level and time) is discussed. A real-time load relief technology based on an extended state observer, which predicts the angular acceleration caused by the wind, is proposed. Its efficiency, adaptability, influence on the stability and control accuracy, and application in the LM-8 maiden flight are studied. The proposed scheme expands the launch probability of LM-8 and provides a systematic solution for the load relief design and control of in-service rockets.

이승 보조 돌봄 작업의 수동 돌봄(Manual Care)과 로봇 돌봄(Robot-aided Care)의 작업부하 비교를 위한 작업부담 평가체계 개발

Objective: The aim of this study was to develop an assessment system for quantitatively comparing the workloads of manual care (MC) and robot-aid care (RC) of the care jobs.<BR>Background: Due to the rapid aging of Korea, the demand for human resources for elderly care tasks has been rapidly increased. Caregivers taking care of the elderly have been under high physical and mental stress due to various types of care work. Recently, many care robots using the technology of the 4th Industrial Revolution have been proposed as a solution to reduce caregiver’s load. However, there is still insufficient research to evaluate the physical and mental load relief effects of caregivers through comprehensive assessment.<BR>Method: The upper index (physical and mental loads) and the lower indexes of each upper index were determined through the literature survey and 42 ergonomic experts’ opinions. Ergonomics experts and caregivers also conducted the Analytic Hierarchy Process (AHP) to determine weights of the upper and lower indexes. Two task types (Bed to Chair and Chair to Bed) and two care types (Manual care and Robot-aid care) were performed to estimate the final work load scores based on the task types and care types in this study.<BR>Results: The results of the AHP analysis showed that the physical load was higher than the mental load for elderly caring tasks. Muscle load was the highest work stress in the physical load, followed by subjective body and posture loads. Safety stress was the most in the mental load, followed by task-difficulty stress and emotional stress, respectively. Robot-aided care showed a lower final workload score, including physical and mental load scores, than manual care in both types of tasks (Bed to Chair, Chair to Bed).<BR>Conclusion: A workload assessment system was developed by selecting assessment indexes of physical and mental loads that reflect the characteristics of transfer assistive care. It was noted that the physical and mental loads might be reduced in robot-aided care compared to manual care based on this study.<BR>Application: The workload assessment system can be used to quantitatively evaluate the reduction of workloads for applying different types of manual care and robot-aided care systems in elderly care work.

Launcher flight control design using robust wind disturbance observation

The development of effective load relief strategies is key to the improvement of launcher flight performance as it enables a joint increase of wind resilience and decrease of mass. This is particularly relevant for reusable launchers, which are aimed at maximising operational availability and payload capacity. Yet, despite various load relief advances in the aeronautics and wind energy sectors, classical feedback-only techniques remain the state-of-practice for launchers. In this article, an improved load relief functionality for reusable vehicles is proposed based on the use of a disturbance observer for on-board wind anticipation and a load relief compensator driven by the estimate of the wind for its amelioration.Two space systems are used to demonstrate the capabilities of the proposed approach. First, it is applied to a 3 degrees-of-freedom nonlinear simulation model of DLR’s EAGLE vertical-flight demonstrator. Then, it is applied to a 6 degrees-of-freedom nonlinear simulation model of a generic lightweight, reusable launch vehicle. For both cases, the results highlight the benefits of using this type of wind-estimation/load-relief compensation schemes. Further, for the second case, which uses thrust vector control and planar fins for ascent and descent attitude control, it is also shown that the use of fins during ascent (which is not common practice), can further improve launcher performance.

A flexibility product for electric water heater aggregators on electricity markets

Electric thermal loads, such as those for space heaters, water heaters and air conditioners, due to their association with energy storage, are deferrable. Thus, they can become an effective tool to compensate for the mismatches between power generation and power demand induced by renewable sources. Load reduction and load increase may appear to be equivalent to generation increase and generation withdrawal, but there is a significant difference in the associated post-load-control energy rebound phenomena. These phenomena can provoke undesirable post-load-control changes in the demand dynamics. The contribution of this paper is twofold. First, we define a flexibility product that load aggregators could propose that would involve a mean energy increase or decrease offer for a price and also guarantee bounds on the post-load-control deviations from normal. Second, we provide aggregators with the mathematical tools to specify the maximum load relief or increase possible under specific constraints on post-control recovery dynamics. The analysis rests on successive solutions of a linear program and exploits recent results on load control based on mean field game theory. We consider the case of aggregate electric water heater loads.

Randomized controlled clinical trial evaluating the efficacy of hyperbaric oxygen therapy in facilitating the healing of chronic foot ulcers in diabetic patients: the study protocol

BackgroundDiabetic limb ulcers are highly prevalent and contribute to a significant increase in cost for the treatment of these patients in health services. However, healing of these wounds is a major health problem and may even lead to amputation. The primary aim of the current study is to evaluate the efficacy of hyperbaric oxygen therapy (HBOT) in facilitating the healing of diabetic foot ulcers, in addition to secondarily evaluating whether it reduces the number of amputations and improves the quality of life in these patients.MethodsA non-blind randomized clinical study will be conducted in the city of Imperatriz, Maranhão state, Brazil, from 2019 to 2020, in diabetic patients with chronic foot ulcers (classified as Wagner grades 2, 3 and 4, persisting for more than 1 month). The outpatient follow-up for diabetic foot patients will be done at the Unified Health System, with a sample size of 120 patients (the randomization allocation will be 1:1, being 60 patients for each arm). Half of the patients will receive standard treatment, i.e. dressings, debridement, antibiotics and load relief, along with HBOT (HBOT group), and the other half will receive only standard treatment (control group). The patients of the HBOT group will be evaluated upon admission, after 10, 20, 30 and 35 HBOT sessions, and after 6 months and 1 year. The patients of the control group will also be evaluated at equivalent periods (upon admission, after 2, 4, 6 and 7 weeks, 6 months and 1 year). The SF-36 quality of life questionnaire will be filled upon admission and after 3 months of follow-up in both groups. The primary and secondary endpoints will be assessed with 1 year of follow-up.DiscussionDiabetic foot ulcers are a highly prevalent complication of diabetes with serious consequences. A study to assess the efficacy of HBOT in healing the ulcers and reducing the rate of amputations in diabetic patients is justified, which will eventually aid in the development of guidelines for treating these ulcers.Trial registrationRegistration number RBR-7bd3xy. Registered on 17 July 2019—Retrospectively registered.

The effect of a knee brace in dynamic motion-An instrumented gait analysis.

BackgroundOsteoarthritis (OA) is a common problem in the older population. To reduce pain and stress in the affected knee joint compartment, a functional knee brace is often prescribed by physicians to protect it from high loads.ObjectivesAn instrumented gait analysis should evaluate how the 4-point knee orthosis for varus or valgus load relief (M.4s OA) changes the kinematics of the knee, especially in the frontal plane.Methods17 healthy participants took part and were analyzed with an inertial sensor system (MyoMotion) giving continuous, objective information on the anatomical angles. The measurements were made both without wearing a knee brace and with the brace in different settings.ResultsThe results show a significant reduction in the maximum knee abduction and raised knee adduction. The knee brace, with a strong adjustment in varus or valgus orientation, caused a shift of maximum ab-/adduction in the proposed direction in 69% and 75% of the dynamic tests, respectively. The knee motion in the frontal plane shows individual movement patterns.ConclusionThe use of the brace leads to significant changes in the knee’s movement. Patient-specific movement patterns may explain different effects of functional knee braces on individual persons. Inertial sensors have been shown to be a low-cost, easy-to-use option for individual movement analysis and further personalized therapy.

A novel ischemia reperfusion injury hereditary tissue model for pressure ulcers progression.

Ischemia reperfusion injury (IRI) involvement in pressure ulcers (PU) progression via a surge of oxidative stress and inflammatory responses is well documented. IRI strongly depends on the mechanical loading history. We present a generalized IRI model considering external loading, dynamic tissue healing capacity, accumulating mechanical and reperfusion-mediated damages and competing repair processes of saturating nature. Reperfusion depends on strain and strain rate to enhance loading history sensitivity. Tissue-specific ulceration susceptibility is assumed dependent on variable accumulated damage. We study damage evolution under cyclic loading having several strain expulsion profiles and demonstrate load relief history has critical impact on PU progression. Abrupt load removal generally follows existing models representing extreme repair/damage. We show (first time in silico) that under certain conditions (previously experimentally identified), IRI becomes repairing rather than damaging. In particular, we recapitulate the preconditioning and postconditioning IRI hallmarks. Finally, it is customary among physicians and nurses to promptly alleviate mechanical load applied to patients lying in bed for extended periods and in risk of developing PUs. We demonstrate this practice can be harmful. If load removal is performed early while reperfusion is still beneficial, then this conduct is suitable. However, if critical tissue damage has been crossed, then abrupt expulsion can constitute the worst-case scenario for patient outcome. If no preliminary patient documentation is available, we recommend gradual load removal since risks of accelerated damage eventually leading to ulceration supersede the improved repair potential benefit.

Load relief rupture mechanism based on particle flow rocklike material

Load relief rupture mechanism based on particle flow rocklike material

Improved aerostructural performance via aeroservoelastic tailoring of a composite wing

ABSTRACTThis paper investigates the synergies and trade-offs between passive aeroelastic tailoring and adaptive aeroelastic deformation of a transport composite wing for fuel burn minimisation. This goal is achieved by optimising thickness and stiffness distributions of constitutive laminates, jig-twist shape and distributed control surface deflections through different segments of a nominal “cruise-climb” mission. Enhanced aerostructural efficiency is sought both passively and adaptively as a means of aerodynamic load redistribution, which, in turn, is used for manoeuvre load relief and minimum drag dissipation. Passive shape adaptation is obtained by embedding shear-extension and bend-twist couplings in the laminated wing skins. Adaptive camber changes are provided via full-span trailing-edge flaps. Optimised design solutions are found using a bi-level approach that integrates gradient-based and particle swarm optimisations in order to tailor structural properties at rib-bay level and retrieve blended stacking sequences. Performance benefits from the combination of passive aeroelastic tailoring with adaptive control devices are benchmarked in terms of fuel burn and a payload-range efficiency. It is shown that the aeroservoelastically tailored composite design allows for significant weight and fuel burn improvements when compared to a similar all-metallic wing. Additionally, the trailing-edge flap augmentation can extend the aircraft performance envelope and improve the overall cruise span efficiency to nearly optimal lift distributions.

Hardware Implementation and Real-Time Evaluation of an ANN-Based Algorithm for Anti-Islanding Protection of Distributed Generators

Recently, it has been verified by simulation results that the ability of recognizing and classifying patterns by artificial neural network can be successfully used for anti-islanding protection of distributed synchronous generators. However, since this type of protection differs from the available commercial relays, it is important to test the algorithm performance implemented in hardware. So, this paper presents a performance evaluation of the hardware implementation of an ANN-based algorithm for anti-islanding protection of distributed generators. For the evaluation process, a complete digital relay architecture is developed in LabVIEW, thus allowing its implementation in the commercial real-time platform cRIO-9025/cRIO-9018. The proposed scheme is tested under real conditions by means of the CMC-256-plus test set, as performed for conventional intelligent electronic devices. The proposed algorithm implemented in hardware shows high effectiveness, detecting all islanding conditions within 1 s, sharing the same good performance verified by computational simulations. The algorithm implementation shows robustness, as it remains blocked for other power grid disturbances, such as frequency variation in the grid utility, massive connection or load relief.

A Demand Response Scheme for Wind Integrated Power System Based on Mechanism Design Theory

The increasing integration of high penetration of wind power into power systems have created great challenges for stable operation of the power system. It is important to design a reasonable demand response scheme (DRS) to make decision the optimal load relief, specially, for the wind power suppliers (WPS) and their customers (WPSC). Therefore, this paper proposes a demand response scheme for wind integrated power system based on mechanism design theory. Firstly, we derive the outage cost function and incentive function modeled by the two variables: the customers’ type parameter and the location value. Secondly, incorporate customers’ type parameter and locational flexibility into the DRS, and based on game theory, a demand response scheme with incentive compatible constraint and participation constraint is designed to maximize the benefit both the wind power suppliers and their customers. The implication of demand response scheme is to design an incentive structure that encourages customers to sign up for the right scheme and reveal their true value of load reduction. Finally, the eight-bus system example can demonstrate the effectiveness of the proposed method.

Development of a self-centering tension-only brace for seismic protection of frame structures

This study develops and numerically verifies an innovative seismically resilient bracing system. The proposed selfcentering tension-only brace (SC-TOB) is composed of a tensioning system to provide a self-centering response, a frictional device for energy dissipation, and a high-strength steel cable as a bracing element. It is considered to be an improvement over the traditional self-centering braces in terms of lightness, high bearing capacity, load relief, and double-elongation capacity. In this paper, the mechanics of the system are first described. Governing equations deduced from the developed analytical model to predict the behavior of the system are then provided. The results from a finite element validation confirm that the SC-TOB performs as analytically predicted. Key parameters including the activation displacement and load, the self-centering parameter, and equivalent viscous damping are investigated, and their influences on the system behavior are discussed. Finally, a design procedure considering controlled softening behavior is developed and illustrated through a design example.