Loading Period Research Articles

Influence of pH on the anaerobic fluidised bed reactor performance for palm oil mill effluent treatment

The effect of pH on the performance of a pilot-scale anaerobic fluidised bed reactor (AnFBR) was studied using palm oil mill effluent (POME) as the substrate. The performance of the 2000-litre reactor at different operating conditions, such as organic loading rates and retention times was studied. This acidic agro-industrial wastewater (pH 4.0–5.0) was neutralised by adding slacked lime. It was observed that, within 12 hr of hydraulic retention time (HRT), the AnFBR removes as high as 85% of the substrate chemical oxygen demand (COD) at a loading rate of 4 kg/m3 day. High pre-treatment cost is needed to neutralise the bulk volume of wastewater that was generated from the palm oil industries. Thus, an attempt was made to study the performance of the AnFBR under pH shock load. The influent pH was increased to 9.2 and then dropped around 5.0 to intensify the effect of the pH shock load. At shock load, the reactor performance for COD removal dropped by about 25% lower than the optimum condition. The maximum and minimum COD removal rates during the short period of continuous shock load were 60% and 56.5%, respectively. The average effluent pH remained steady at around 6.1. From the analysis, it was revealed that the anaerobic fluidised bed had the buffering ability and was capable of treating POME with moderate removal efficiency at an influent pH of 5.0.

Squishy oscillations

The dynamics of soft porous media involves complex interactions between fluid flow and elasticity. The recent paper by Fiori et al. (J. Fluid Mech., vol. 974, 2023, A2) highlights phenomena relating to the periodic loading of such poro-elastic media, including hysteresis and the localisation of deformation at high frequencies. These effects could result in rectification and steady streaming in many important applications.

Emicizumab prophylaxis in infants: Single-centre experience.

The hallmark of haemophilia A (HA) therapy is prophylaxis, aimed at spontaneous bleeding prevention. Emicizumab provides a viable alternative to intravenous factor replacement therapy. However, data on its use in infants are limited. This single-centre open arm prospective study reports on emicizumab prophylaxis in infants. We included severe HA patients under 1 year who started emicizumab prophylaxis since 2018, with longitudinal follow-up. The study collected data on demographics, clinical and laboratory variables, the occurrence of bleeding events, surgeries and treatment outcomes. Of the 27 enrolled infants, whose median age at prophylaxis initiation was 7 months, 24 primarily choose to start emicizumab therapy (3/27 switched from FVIII prophylaxis due to development of FVIII inhibitors). The median age for prophylaxis initiation decreased to 3 months in 2023. Following emicizumab initiation, the median calculated ABR decreased, and no intracranial haemorrhages were observed. Thrombin generation showed a significant improvement in peak height and endogenous thrombin potential at steady state after a loading period. Our study highlights a shift towards early prophylaxis in the era of non-replacement therapies. It underscores the need for continuous evaluation and refinement of treatment approaches, emphasizing personalized care and diligent monitoring in the evolving field of paediatric haemophilia care.

Voltage Regulation through Wide Area Voltage Control of HV/MV Transformers and Inverters’ Reactive Power Support

This paper presents a technical evaluation of two different methods to avoid the excessive voltage deviations caused by dispersed generation in distribution grids. Two voltage regulation methods, wide area voltage control of HV/MV transformer and inverters’ reactive power support, are simulated in several real rural grids with different topologies located in Northern Germany. In all these analysed grids the high penetration of dispersed generation produces big power flow reversals during low load periods. The objective of implementing both voltage regulation methods is to reduce voltage deviations in such an extent that voltage band violations no longer act as the principal obstacle to host more dispersed generation in the distribution grid. We evaluate the effectiveness of these two methods through a power system analysis program and analyse the reciprocal effects caused by simultaneous use of both methods. Moreover, the concept of “voltage inhomogeneity” is introduced.

Integration of digital services in the work of accreditation and simulation center of medical educational organization: experience, problems and prospects

The experience of using universal digital services in the accreditation and simulation center of Yaroslavl State Medical University for the period from 2016 to 2023 was studied. More than 1,000 specialists are trained at the center per year. Over the entire period, 4,684 people underwent the accreditation procedure. The introduction of simulation technologies into medical education requires a high level of automation and digitalization of basic processes. Implemented tools and services of a modular object-oriented dynamic learning environment, a designer of online courses and training simulators, an electronic schedule, cloud technologies and online services, including those based on artificial intelligence. This allowed the training center to provide effective management both within the current educational process and during periods of peak load during the accreditation procedure for specialists.

Contagious order as a risk factor for liver fibrosis progression in co-infection with human immunodeficiency virus, hepatitis B and C viruses

In triple co-infection with HIV/HCV/HBV, the prognosis is significantly poorer and life expectancy is lower because of the rapid progression of liver fibrosis or development of hepatocellular carcinoma. The aim of this study was to test the hypothesis that one of the risk factors for the unfavorable course of HIV/HCV/HBV co-infection is contagious order and the interval between coinfections. The study analyzed anamnestic data and the results of direct follow-up of 97 patients co-infected with HIV/HCV/HBV for 1-2 years. Patients were divided into three study groups: (1) HIV as the first pathogen, (2) HCV as the first pathogen, and (3) HBV as the first pathogen. For each patient, the period (in years) between the acquisition of the first and subsequent pathogens was considered. During the fol-low-up period, viral HIV, HCV, and HBV load was assessed by PCR, and annual transient liver fibro-elastometry was performed to determine the fibrosis stage using the METAVIR scoring system. The risk of progressive liver fibrosis in HIV/HCV/HBV co-infection is higher when HIV or HBV is the first pathogen, but the interval between the acquisition of HBV and other viruses is 10 years. Meanwhile, a stable course of liver fibrosis is associated with an HBV viral load of >7,200 copies/ml. In the risk group, the most effective antiretroviral therapy was a combination of reverse transcriptase inhibitors, HIV protease inhibitors, and direct antiviral (anti-HCV) drugs. Therefore, the order of infection and intervals between pathogen acquisition in triple co-infection with HIV/HCV/HBV have a significant effect on liver fibrosis progression, which requires specific approaches to the organization of diagnostic tests and the control of antiretroviral therapy.

An extrapolation approach within the Wiener path integral technique for efficient stochastic response determination of nonlinear systems

An extrapolation approach within the Wiener path integral (WPI) technique is developed for determining the stochastic response of diverse nonlinear dynamical systems. Specifically, the WPI technique treats the system response joint transition probability density function (PDF) as a functional integral over the space of all possible paths connecting the initial and the final states of the response vector. Further, the functional integral is evaluated, ordinarily, by considering the contribution only of the most probable path. This corresponds to an extremum of the functional integrand, and is determined by solving a functional minimization problem that takes the form of a deterministic boundary value problem (BVP). This BVP corresponds to a specific grid point of the response PDF domain. Remarkably, the BVPs corresponding to two neighboring grid points not only share the same equations, but also the boundary conditions differ only slightly. This unique aspect of the technique is exploited herein. Specifically, it is shown that solution of a BVP and determination of the response PDF value at a specific grid point can be used for extrapolating and estimating efficiently the PDF values at neighboring points without the need for considering additional BVPs. Notably, the herein developed approach enhances significantly the computational efficiency of the WPI technique without, practically, affecting the associated degree of accuracy. Two numerical examples relating to a Duffing nonlinear oscillator subjected to combined stochastic and deterministic periodic loading, and to an oscillator with asymmetric nonlinearities and fractional derivative elements are considered to demonstrate the reliability of the extrapolation approach. Juxtapositions with pertinent Monte Carlo simulation data are included as well.

Effects of dynamical spanwise retraction and stretch on flapping-wing forward flights

Birds and bats retract and stretch their wings dynamically during each flap in level flights, implying intriguing mechanisms for the aerodynamic performance improvement of flapping wings. A numerical investigation into the aerodynamic effects of such bio-inspired concept in forward flights has been performed based on a three-dimensional wing in plunging motion and a two-section wing in flapping motion. The currently considered Reynolds number and Strouhal number are Re=1.5×105 and St=0.3, respectively. During the research, the mean angle of attack is varied in relatively wide ranges to achieve lift-thrust interconversion for the wings. The conclusive results show that dynamical spanwise retraction and stretch has induced three absolutely desirable scenarios for the oscillating wings in forward flights, namely producing more lift and consuming less power for a given thrust generation, producing more thrust and consuming less power for a given lift generation, and producing more lift and more thrust while consuming less power. Furthermore, the morphing wings have alleviated periodical aerodynamic load fluctuations compared with the non-morphing baseline. The mechanism of the aerodynamic effects of the bionic morphing mode is analyzed with the aid of field visualization. The current article is the first to reveal the absolute advantages of the bionic spanwise morphing. Hopefully, it may help comprehend the behaviors of natural fliers and provide inspirations for performance enhancement of micro artificial flapping-wing vehicles.

Biodesulfurization of landfill biogas by a pilot-scale bioscrubber: Operational limits and microbial analysis.

Biogas serves as a crucial renewable energy vector to ensure a more sustainable energy future. However, the presence of hydrogen sulfide (H2S) limits its application in various sectors, emphasizing the importance of effective H2S removal techniques for maximizing its potential. In the present study, the limits of a pilot-scale bioscrubber for biogas desulfurization was study in a real scenario. An increase in the superficial liquid velocity resulted in significant improvements in the H2S removal efficiency, increasing from 76 ± 8% (elimination capacity of 6.2 ± 0.5 gS-H2S m−3 h−1) to 97.7 ± 0.5% (elimination capacity of 8 ± 1 gS-H2S m−3 h−1) as the superficial liquid velocity increased from 50 ± 3 m h−1 to 200 ± 8 m h−1. A USL of 161.4 ± 0.5 m h−1 was able to achieve outlet H2S concentrations as low as 3 ± 1 ppmv (H2S removal efficiency of 97 ± 1%) for 7 days. High superficial liquid velocity favoured the aerobic H2S oxidation reducing the nitrate demand. The maximum EC reached throughout the operation was 50.8 ± 0.6 gS-H2S m−3 h−1 (H2S removal efficiency of 96 ± 1%) and a sulfur production of 60%. Studies in batch flocculation experiments showed sulfur removal rates up to 97.6 ± 0.9% with a cationic flocculant dose of 75 mg L−1. Microbial analysis revealed that the predominant genus with sulfo-oxidant capacity during periods of low H2S inlet load was Thioalkalispira-sulfurivermis (61–69%), while in periods of higher H2S inlet load, family Arcobacteraceae was the most prevalent (11%).

Fatigue Crack Propagation in 5754 Aluminum Alloy under Four-Point Bending

The aluminum 5754 alloy is one of the widely used engineering materials in shipping, rivet making, tread plates and automotive industries. These engineering structures envisage variable loading conditions during their service. In addition to it, it is also experiencing seismic vibrations. Hence, the engineering components made from such aluminum alloy are susceptible to fatigue fracture. In the current study, the prediction of fatigue crack growth (FCG) in 5754 aluminum alloy was made using the exponential function. The beam specimen comes up with a cross-section of 25X25 mm2, a span length of 300 mm with a mechanical notch length of 2.70 mm at the centre was subjected to four-point bending (FPB) employing hydraulic INSTRON 8800 tensile testing apparatus. The periodic loading condition deformed the material up to large plastic deformation. The applied load was further down the elasticity of the material. The experimental data provided the relation between crack length (a) to the number of cycles (N) to failure. The response surface methodology (RSM) and modified exponential equation were used to predict the FCG. In RSM, when “stress intensity factor (K)” and “number of the cycle (N)" were considered independent variables, the response (a) was optimum (maximum) as compared to when “stress intensity factor range (del K)” and “fatigue crack growth rate (da/dN)” were considered independent variables. Hence, for designing the aluminum 5754 alloys as engineering structures, it was the number of cycles which provides a safe design as compared to da/dN. The modified exponential equation using an exponential function predicted the FCG for aluminum 5754 alloy in the form of a beam specimen. The anticipated results agreed with experimental data as the prediction ratio was 1.20 and the % deviation was 3.7.

Effect of periodic loading on mechanical properties of sintered nano-silver components

The sintered nano-silver has been widely concerned by the industry in the field of electronic packing. Researches on sintered nano-silver have mostly focused on individual tensile or compressive loading conditions. In the paper, the mechanical properties of sintered nano-silver components were investigated under the periodic tensile and compressive loads by molecular dynamics method. The influence of periodic load on it was studied, and the difference between sintered and unsintered nano-silver under the same condition was analyzed and compared. Under different periodic loads, the different number of periods do not affect the initial potential energy, and their maximum potential energy peaks are not different. Under the periodic load of different tensile rates, the maximum potential energy increases with the increase of the tensile rate. The yield stress of sintered nano-silver is higher than that of unsintered nano-silver under different periodic loads and different tensile rates. The results show that the sintering process improves the mechanical properties of nano-silver components.

ЕКОНОМІКО-МАТЕМАТИЧНЕ МОДЕЛЮВАННЯ ДИНАМІКИ ЕНЕРГОСПОЖИВАННЯ ЗБАГАЧУВАЛЬНОЇ ФАБРИКИ

The purpose of the work is to establish the dependence of electricity costs on the dynamics of energy consumption from the dynamics of ore supply to the beneficiation plant bunker, namely from the loading period and its duration, and to develop, on the basis of the identified patterns of organizational, technical and economic measures to reduce the energy component of the cost of production of iron ore concentrate at the mining enrichment enterprises. Economic-mathematical methods were used to develop models of the formation of electricity costs on the dynamics of energy consumption, namely: the theory of impulse processes for the development of a model of ore supply to the bunker of the beneficiation factory; operational calculation methods, ore beneficiation theory and power supply theory for the development of a dynamic beneficiation process line model and power consumption model; methods of spectral analysis to identify the dynamic component of active power and electrical energy consumed by the ore beneficiation process; Cost analysis methods were used to calculate electricity costs; economic-mathematical modeling of energy consumption dynamics was performed by computer modeling using the Mathcad software package. An economic-mathematical model of the energy consumption dynamics of the enrichment factory was developed. The regularities of influence of ore loading parameters of beneficiation factory bunkers on the dynamics of the formation of electricity costs during the production of iron ore concentrate have been revealed. Mathematical dependencies of costs for the dynamic component of electrical energy on the time parameters of the process of loading ore into the hopper of the beneficiation factory, namely on the period and time of loading, were obtained. Organizational and economic measures have been developed to load the bunkers of the beneficiation factory, which ensure the saving of electricity. The regularities of influence of ore loading parameters of beneficiation factory bunkers on the dynamics of the formation of electricity costs during the production of iron ore concentrate have been revealed. The principles of building a system of financial incentives for operational and dispatching personnel for saving electricity based on the results of economic and mathematical modeling have been developed. For the first time, it wa s established that the energy component of the production cost of iron ore concentrate depends not only on the quantity and quality of ore, but also on the dynamic parameters of the process of loading ore into the bunkers of the beneficiation factory, while this established dependence has a non-linear nature on the period and time of loading. The proposed measures to save electricity due to the implementation of rational modes of loading bunkers of the beneficia-tion factory with ore can be used in the development of energy saving plans and programs and the development of job instructions for the dispatching staff of the ore beneficiation factory, which will allow to reduce the energy component of the production cost of iron ore concentrate. A system of financial incentives for operational dispatching staff of the beneficiation factory has been developed, which takes into account the saving of electrical energy due to the management of the ore loading of the bunkers of the beneficiation factory and the intensity of the staff’s work.

Two-stage stochastic robust optimization scheduling of electric–thermal microgrid with solid electric thermal storage

During the periods of high heat load (HL) demand in winter, the increased heat output of combined heat and power units (CHPs) can significantly compress the electric power regulation range, thereby posing a threat to the safety of the power system. The solid electric thermal storage (SETS) can be employed as the regulating resource for both electric and thermal systems, expanding the dispatch space of microgrids to promote renewable energy consumption. In this paper, a two-stage stochastic robust optimization scheduling model of an electric–thermal microgrid with SETS is proposed, and the electric–thermal bi-directional regulation characteristics of SETS are considered. First, a SETS operation model based on the heat transfer characteristics of the homogeneous material-type thermal storage unit is established. Second, a regional thermal inertia model under a constant-flow variable-temperature system is established, which integrates HL at different locations to the heat source, avoiding the calculation of variation in water temperature, thus reducing the calculation difficulty. Finally, the two-stage stochastic robust optimization scheduling model of an electric–thermal microgrid with SETS is established. The model decouples the power and heat generation of CHP through the bi-directional regulation function of SETS. Case studies demonstrate the validity and effectiveness of the proposed scheduling model.

RESPOSTAS FISIOLÓGICAS E PSICOAFETIVAS DE ADULTOS TREINADOS EM PROTOCOLOS AGUDOS DE HIIT

ABSTRACT High Intensity Interval Training (HIIT) promotes similar adaptations and in some cases, superior to continuous aerobic training of moderate intensity, even when performed at all-out intensities. In this condition, it tends to have the greatest physiological disturbance and accumulation of metabolites compared to submaximal intensities, being one of the main factors associated with the negative response of pleasure in training. Objective: To verify the relationship between physiological and psychophysiological responses in order to repeat the training of two HIIT protocols of mesm volume load and different periods of work in trained adults of both sexes. Methods: In a randomized experiment, the sample consisted of 9 individuals aged 28±5 years, body mass 69.6±14.2 kg, height 169±0.1cm, BMI 24.1±2.3 kg/m2 and body fat percentage 20.2±7.9% practitioners of structured aerobic physical exercises for at least six months. Two different HIIT protocols were performed on an exercise bike, being (I) protocol 1:0.5, with prescribed intensity (80-90% of MAX HR), (II) protocol 1:2 with prescribed intensity (all-out) with total duration of effort of 20 minutes and interval of at least 48 hours between each session. Heart rate (HR), systemic blood pressure (SBP), subjective perception of exertion (SPE), visual analog scale (VAS), affective response (AR), fun (PACES) and intention to repeat the session were analyzed. The statistical analysis used was ANOVA with Tukey's post-hoc (p<0.05). Results: The analyses of HR, SBP, VAS, PACES and SPE showed no significant difference between the training protocols. The affective response (AR and intention to repeat) showed a decline in the protocol 1:0.5, but without significance (p>0.05). Conclusion: The data allow us to conclude that the 1:2 protocol caused greater physiological disturbances during exertion and presented greater positive affective response and intention to repeat the exercise session, variables that may contribute to adherence to regular physical exercise. Level of Evidence I; Therapeutic studies - Investigation of treatment results.

MODELING AND INVESTIGATION OF THE INFLUENCE OF LOADINGMODE ON THE DEFORMATION PROCESS OF ASPHALT CONCRETEMATERIALS

The article considers a problem of calculating the deformations of forward and reversed creep tension of rheonomic materials. The hereditary theory of creep by Yu.N. Rabotnov is used to describe the nonlinear deformation process. Proposed a method for determining the necessary material characteristics from forward and reversed creep data. During the experiments, there were tested two batches of asphalt concrete samples. Also, was shown behavior of asphalt concrete at cyclic increasing and constant loading modes. At a temperature T = 24 °C were tested 10 samples at cyclic increasing loading mode. Cyclic stresses were equal to 0.041; 0.074; 0.111; 0.148; 0.183 MPa and duration period between loading and relax period were chosen to be 570 seconds. At cyclic constant loading were investigated individual samples for the parameters of forward and reversed creep at stresses of 0.041; 0.117. Then, investigated the affect of reloading two reversed creep process of asphalt concrete samples. From first batch of samples were tested 9 samples before destruction with a period 65 seconds: forward creep of samples at for the following 5 seconds; reversed creep at for the following 60 seconds. From the second batch of samples were tested 11 samples of asphalt concrete before destruction with period 70 seconds: forward creep for the following 10 seconds and reversed creep at for the following 60 seconds. Test results showed that the level of return of second batch increased than the first batch of samples. In the work were tested 5 samples of asphalt concrete according to the direct tensile scheme until a complete failure. Test temperature was T=22-24 °C. For each level of loading with constant rate: 0,6519; 0,4678; 0,0580; 0,0489; 0,0055 MPas-1.Using experimental data, were found parameters of the deformation at different constant rate of loading. As a result, all samples fractured brittle at small deformations.

EFFECTS OF POROSITY ON THE STRENGTH AND MECHANICAL BEHAVIOUR OF POROUS GEO-MATERIALS UNDER CYCLIC LOADING

Most rocks in nature are porous and usually saturated with different fluids such as water, oil, and gas. The conventional and unconventional hydrocarbon reservoirs are mainly associated with sedimentary formations. The main rocks of these reservoirs are sandstone (porous rock), limestone and oil shale (tight rock), which are associated with varying porosity. Hence, porosity serves as a fundamental parameter for most reservoir rocks. In this research, the effect of porosity on the mechanical behaviour of geo-materials and its fatigue behaviour was investigated. For this purpose, a total of five geo-material sample groups with varying porosities were prepared and designated, i.e. groups A, B, C, D, and E. Group A exhibited the highest porosity 20-21.5%, while group E had the lowest porosity 2-3%, respectively. The conventional quasi-static strength tests and cycle loading tests with constant frequency and amplitude were performed on the samples and different results were obtained. The samples belonging to group E, with the lowest porosity (2-3%), exhibited the highest mechanical strength, elastic modulus and fracture toughness values and the lowest Poisson's ratio compared to those of higher porosity samples. During the cyclic loading period, the fatigue stress-life graph of the E group has the lowest slope compared to the other groups. It means that the slope of the graph increases as the porosity increases in all groups. Therefore, the E group has the lowest porosity and the longest fatigue life time, i.e. porosity and fatigue resistance have an inverse correlation.

Elastoplastic Behavior of 316L Stainless Steel (SS) and the Analysis of the Ratcheting Phenomenon Under Cyclic Loading

The present work is concerned with the evaluation of the nonlinear behaviour of 316L steel used in several fields, industry, automotive, aeronautics, medicine .... subjected to cyclic movements. This investigation allowed us to analyze the different responses of steel in low cycle fatigue, and to perceive the phenomenon of Ratcheting leading, to the damage of the structure by an excess of plastic strain, under loading cycles. The prediction of the behaviour of the steel studied, reveals that the Ratcheting increases according to the average stress when the stress amplitude is constant, and decreases according to the attenuation of the stress amplitude when the average stress is constant. The simulation campaign allowed us to present an assessment, of the conditions favoring the acceleration of the Ratcheting, includes several scenarios of periodic loadings, with strain and stress imposed under uniaxial tension/compression. The predictions of this model are evaluated by subjected to cyclic loading within the software ZébuLon.

Topological Optimization of Bi-Directional Progressive Structures with Dynamic Stress Constraints under Aperiodic Load

The topology optimization of dynamic stress constraints is highly nonlinear and singular and has been little studied. Dynamic stress based on progressive structural optimization is only available by applying the modal iteration method, but due to the nonlinear limitations of the modal superposition method, there is an urgent need to develop a progressive structural optimization method based on dynamic stress sensitivity under direct integration. This method is for the dynamic stresses under non-periodic loading with iterative cycle updating variations. This article proposes a topological optimization method of continuum structures with stress constraints under an aperiodic load based on the Bi-directional Evolutionary Structural Optimization Method (BESO). First, the P-norm condensation function was used to obtain the global stress to approximate maximum stress. By introducing the Lagrange multiplier, the design goal was to increase the P-norm stress on the basis of the smallest volume. After that, based on the dynamic finite element theory, the sensitivity of each cell formula of the objective function and the constraint conditions of the design variables were strictly derived. Then, the performance evaluation index was put forward based on volume and stress, and the convergence criterion based on the performance evaluation index was defined. This method solves the topology optimization problem of stress constraints under a non-periodic load and the topology optimization problem of stress constraints under a periodic load, such as a simple harmonic load.

Rat bone responses to hindlimb unloading-reloading: Composition, BMD and mechanical properties

IntroductionBone loss in lower limbs under space microgravity condition can persist even after the astronauts return to Earth's gravitational environment. It is crucial to determine the extent and timing of bone recovery after spaceflight, especially for long-term flights. However, there is a lack of comprehensive descriptions of the recovery of various aspects of bone quality, particularly in terms of compositional characteristics that reflect changes in bone quality. Therefore, the objective of this study is to investigate the alterations in bone mineral density, composition characteristics, and mechanical properties of rat lower limbs during unloading (tail suspension) and the subsequent recovery loading period. MethodsRats were subjected to tail suspension for four weeks (TS4) followed by reloading for an additional four weeks. Bone mineral density (BMD) was measured by μ-CT and analyzed. The mechanical properties of the tibia were assessed by a three-point bending test, and the composition characteristics of bone tissue were evaluated using Raman spectroscopy. Regression analysis was performed to identify main component related to mechanical property. ResultsIn the metaphysis, BMD of the tibia significant decreased, particularly in trabecular bone. Upon reloading, only the cortical bone showed recovery. In the diaphysis, cortical bone remained unchanged during unloading but demonstrated delayed bone loss during the reloading period. Simultaneously, the mechanical properties of tibia experienced a substantial reduction after four weeks of unloading, The stiffness and maximum strength did not fully recover, though the elastic modulus and the ultimate strength were restored following the reloading process. Raman spectroscopy characterization found an increase in the carbonate substitution and crystal crystallinity of the diaphysis after 4 weeks of unloading. There was an intriguing alteration in the mineralized collagen ratio, that an increase was observed in the diaphysis while a decrease was observed in the metaphysis. During 4 weeks of reloading, the compositional characteristics of the diaphysis recovered earlier than those of the metaphysis, with the exception of crystallinity which remained unrecovered. Regression analysis indicated that carbonate replacement has a strong correlation to bone mechanical properties during the 4 weeks of unloading and subsequent 4 weeks of reloading. ConclusionsThe data obtained in this study highlight the incomplete recovery of bone mineral density, mechanical properties, and compositional characteristics during reloading in tail-suspended rats. These findings deepen our understanding of microgravity-induced bone loss and provide valuable information to develop interventions not only for astronauts but also for persons on earth during and after prolonged periods of unloading.

Analysis of Adaptive Individual Pitch Control Schemes for Blade Fatigue Load Reduction on a 15 MW Wind Turbine

Individual pitch control (IPC) is a method to mitigate periodic blade loads in wind turbines, and it is typically implemented using the multi-blade coordinate (MBC) transform, which converts the blade load measurements from a rotating frame into the non-rotating tilt axis and yaw axis. Previous studies have shown that by including an additional tuning parameter in the MBC, the azimuth offset reduces the coupling between non-rotating axes, allowing for higher performance levels for diagonal controller structures. In these studies, the decentralized control of IPC was composed of two identical integral controllers. This work analyzes and compares the improvement that the azimuth offset can provide in different adaptive gain scheduling IPCs where the diagonal controllers can have integral or proportional action with different gains. They are applied to a 15 MW wind turbine simulated with OpenFAST v3.5 software. The controller parameter tuning is addressed as an optimization that reduces blade fatigue load based on the damage equivalent load (DEL) and is resolved through genetic algorithms. Simulations show that only using different controller gains in IPC does not provide significant improvements; however, including azimuth offset in the optimal IPC schemes with integral controllers allows for the greatest DEL reduction with a lower actuator effort.