Loading Period Research Articles

Experimental study on damage characteristics of Beishan granite under single loading and multiple loading with AE techniques

An insight into the damage characteristics of host rock is important for permanent disposal of high-level radioactive waste (HLW). Single loading and multiple loading tests for Beishan granite were carried out. The acoustic emission (AE) monitoring system was utilized simultaneously to measure the damage evolution in the specimens. The results show that, during single loading the AE signal has been maintained at a very high level after dilatancy. But a decreasing trend of AE signals can be observed when the axial stress approaches the peak stress. While during multiple loading, AE signals are mainly generated in the loading period in the elastic stage. However, in the failure and residual stages, AE signals generated in the unloading period are considerable. Most of the AE waveforms have a dominant frequency of less than 200 kHz and amplitude of less than 80 dB, and three frequency bands are obtained. In addition, the amplitude increases with the increase of loading stress. Furthermore, the obtained AE b-values indicate that the relative proportion of micro- to macro-cracks increases first and then decreases with increasing confining pressure. And the AE a-values and b-values confirms that micro cracks develop rapidly in the damage stage and lead to the formation of macro cracks in the residual stage for the specimens experienced multiple loading.

Dynamic Changes Of Physiological And Psychological Parameters Of Young Persons As Asthenia Risk Factors

Asthenic syndrome is the most important problem of the modern stage of development of human society, which is the most important component of many pathological conditions or risk factors for diseases. The purpose of the study is to determine some physiological and psychological parameters in young people in dynamics at different levels of intellectual load and evaluate their role in the formation of asthenic syndrome. Materials and Methods: The study involved 160 3rd year students of the Medical Institute of Moscow State University. N.P. Ogarev, divided into four groups according to the type of higher nervous activity (HNA), based on the indicators "Extraversion / Introversion" and "Neuroticism", determined by the Eysenck scale. We assessed the characteristics of emotional balance, functional parameters of autonomic regulation, features of cognitive functions in young people in different periods of training load. Results: the indicator of neuroticism correlated with the severity of asthenic syndrome in young people. Persons with a high level of neuroticism more often revealed maladjustment of mental processes, a decrease in cognitive functions, and an increase in emotional instability during the period of intense intellectual loads. After a period of increased intellectual load, asthenia occurs significantly more often in females. Features of autonomic regulation have little effect on the development of asthenia. The exceptions were individuals with a high level of neuroticism. In these groups, the stress of hemodynamic mechanisms was occurred frequently.

Periodic surface loading using GRACE data for a layered viscoelastic earth model based on a direct relationship between geoid and displacement

SUMMARY Loading theory is fundamental in explaining deformation resulting from surface mass changes. Although various theoretical methods, including the classical elastic loading theory by W. E. Farrell and I. M. Longman, have been proposed, a viscoelasticity-based theory may be required to address long timescale loading problems, such as annual and interannual deformation, as well as longer timescale loading effects. In this study, we use a semi-analytical approach to simulate the continuous periodic loading deformation of a viscoelastic, spherical, layered earth model with linear rheology profiles. We provide a series of formulas in the spectral domain for the spatiotemporal displacement, which establish connections between mass, geoid and displacement solely through the utilization of complex Love numbers and Stokes coefficients, thereby circumventing the need for viscoelastic Green's function. Using our newly proposed method, we investigate the viscoelastic loading deformation caused by annual cyclic mass loading, considering both steady-state creep and additional transient creep with a wide range of viscosities. The results indicate that when utilizing steady-state viscosity values constrained by GIA data, the viscoelastic effect is not evident in the annual cyclic load deformation. However, incorporating the Burgers model with transient creep mainly constrained by post-seismic deformation influences the amplitude and phase of the annual cyclic loading, highlighting the role of rheology. Furthermore, we observe that the horizontal displacement in periodic load deformation exhibits a higher sensitivity to the viscosity of the model compared to the geoid and vertical displacement, regardless of the rheological model used.

Influence of high temperatures on the behavior, productivity and bioenergetic characteristics of goats

Abstract. The research was carried out in IE «Babyni kozy» of Kyiv region at a goat farm where a stable-pasture system of goats is used. In winter, goats are kept at free-stall housing on a deep litter and during the grazing period, on a forage area. Goats are milked on a milking parlor into the milk line. The article presents the results of researches of the influence of ambient temperature during the thermo neutral period and during the period of high temperatures on the productivity, daily behavior and bioenergetic characteristics of Saanen goats. A group of goats of the Saanen breed of the 3rd lactation was formed during the period of the milk yield increasing. The research was performed in thermo neutral period (average daily air temperature was up to + 22.3 °C) and during the period of temperature load at an average daily air temperature of + 27.6 °C. Each period lasted 12 days. It has been found that goats responded to the change in temperature by reducing of productivity by 10.70 % (0.35 kg). Hereby, the mass fraction of fat in goat's milk during this period increased by 0.09 %. During the period of high temperatures, goats spent a little less time eating food, watering and walking, but rested more in a supine position compared to the thermo neutral period. In general, in both temperature periods, the duration of the main acts of behavior in goats corresponded to physiological norms. The decrease in the duration of feed consumption during the temperature load caused a decrease in the number of feed reactions and the duration of chewing the cuddy in goats. The energy index, i.e. the amount of net energy consumption of feed, which transfers into milk energy during the temperature load decreased by 1.42 MJ %. Net energy consumption per 1 MJ of milk energy during the period of high temperatures has increased by 0.62 MJ. Key words: goats, temperature, productivity, metabolic energy, behavior, bio-energy.

V2 vasopressin receptor mutations: future personalized therapy based on individual molecular biology.

The diluting and concentrating function of the kidney plays a crucial role in regulating the water homeostasis of the body. This function is regulated by the antidiuretic hormone, arginine vasopressin through the type 2 vasopressin receptor (V2R), allowing the body to adapt to periods of water load or water restriction. Loss-of-function mutations of the V2R cause X-linked nephrogenic diabetes insipidus (XNDI), which is characterized by polyuria, polydipsia, and hyposthenuria. Gain-of-function mutations of the V2R lead to nephrogenic syndrome of inappropriate antidiuresis disease (NSIAD), which results in hyponatremia. Various mechanisms may be responsible for the impaired receptor functions, and this review provides an overview of recent findings about the potential therapeutic interventions in the light of the current experimental data.

Fault resonance process and its implications on seismicity modulation on the active fault system

Various periodic external loading processes (e.g., snow, hydrological and atmospheric, earth tide and surface reservoir load, etc.) affect tectonic deformation and sometimes modulate seismicity in diverse tectonic settings. Small stress variations induced by external loads may influence the fault dynamics and destabilize fault zones. In this article, we report five cases of earthquake occurrence in the plate boundary and plate interior regions where such a destabilization seems to be operating. We test the possibility of resonance amplification assuming rate-and-state friction and look for the model parameters that could justify resonance destabilization. We find that frictional resonance destabilization is possible in regions that are near the stability boundary (velocity neutral areas). The critical slip distance for the evolution of friction is similar to laboratory estimates. In some cases, effective normal stress lower than the lithostatic stress have to be assumed for the model to be consistent with the observations, implying high pore pressure. We propose that crustal faults of conditionally stable frictional domains with anomalous pore pressure are sensitive to periodic stress perturbations by the external loading process.

Effect of cyclic load on mechanical properties and failure mechanisms of different rank coals

Underground coal is often subjected to periodic loads caused by mining stress. To determine the effect of cyclic load on mechanical properties of coal of different ranks and failure mechanisms, nanoindentation experiments and molecular dynamics (MD) simulations were used to study different rank coals. The results indicated that cyclic hardening occurred in all the coal matrices under cyclic loading. With the increase in coal rank, the change of the elastic modulus and the hardness, the energy dissipation rate, and the damage layer decreased, the cyclic hardening weakened, and the resistance of the six-membered ring structure increased. The plastic failure of the coal matrix was mainly connected with the bending and stretching of the bond, the dihedral angle twisting, and the out-of-plane bending vibration. The elastic deformation was correlated with the variation of the Coulomb force and the van der Waals force, the twisting and recuperation of the dihedral angle, and the out-of-plane bending vibration. With increasing coal rank, the effect of the elastic deformation of the Coulomb force weakened. When the coal rank exceeded a certain range, the influence of the plastic failure of the out-of-plane bending vibration was transformed into the elastic deformation, and the effect of the elastic deformation of the van der Waals force was transformed into the plastic failure.

An Analytic Solution for the Dynamic Behavior of a Cantilever Beam with a Time-Dependent Spring-like Actuator

The purpose of this study is to derive an analytical solution for a cantilever beam with a novel spring-like actuator that behaves like a time-dependent spring and to study the dynamic behavior of the system. A time-dependent spring was set at the free end of the cantilever beam to model the novel spring-like actuator. First, the boundary conditions were transformed from being nonhomogeneous to being homogeneous using the shifting function method. The solution of the analytic series was then obtained by using the expansion theorem method. The correctness of the proposed analytical solution was verified by comparing the results with those obtained via the separation of variables in the special extreme case of a constant spring coefficient. We took the free end of a cantilever beam with harmonic spring stiffness and an external periodic unit load as an example. The influence of the actuator parameters, such as the effect of the magnitude and the frequency of the time-dependent spring stiffness on the resonance frequency, was investigated. An important new result was found, i.e., that the resonance frequency is clearly dependent on the magnitude and the frequency of the spring-like actuator in the first two modes, but not in the third and fourth modes. In practical engineering applications, system resonance can be avoided by adjusting the magnitude and frequency of the actuator.

Evaluation of the Horizontal Transmission of White Spot Syndrome Virus for Whiteleg Shrimp (Litopenaeus vannamei) Based on the Disease Severity Grade and Viral Shedding Rate.

White spot syndrome virus (WSSV) is the most problematic pathogen in crustaceans. In this study, we investigated the horizontal transmission model of WSSV based on the correlation between the disease severity grade and viral shedding rate and determined the minimum infective dose of WSSV via the waterborne route. Intramuscular injection challenges at different doses and water temperatures revealed that the thresholds of viral shedding and mortality were G1 (3.1 × 103 copies/mg) and G2 (8.5 × 104 copies/mg), respectively. Furthermore, a positive linear correlation was observed between viral copies of pleopods and viral shedding rate (y = 0.7076x + 1.414; p < 0.001). Minimum infective doses of WSSV were determined via an immersion challenge. Infection was observed within 1, 3, and 7 d in 105-, 103-, and 101 copies/mL of seawater, respectively. In the cohabitation challenge, infection was observed within six days with viral loads of 101 to 102 copies/mL of seawater, which further increased in the recipient group. Our results indicate a positive correlation between disease severity grade and viral shedding rate of infected shrimp and suggest that the waterborne transmission of WSSV depends on the viral load and exposure period.

Power Compensation Strategy and Experiment of Large Seedling Tree Planter Based on Energy Storage Flywheel

The intermittent hole-digging tree-planting machine shows a periodic short-time peak load law in planting operation, and the operation process is “idling” for small loads most of the time, leading to large torque fluctuations in the transmission system, unscientific power matching, and high energy consumption. To solve the above problems, this article proposes to use a series of energy-saving flywheels in the transmission system of the tree planting machine. On the premise of obtaining holes that meet the target young tree planting requirements, the optimal power compensation strategy for the flywheel system of the tree planting machine is studied to reduce torque fluctuations in the power transmission system, use smaller power drive units, and save energy. Firstly, the nonlinear multi-body dynamics simulation model of soil cutting by the hole-digging component is established. The boundary and contact conditions are set to simulate the power consumption of the hole-digging component at three rotating speeds. Based on the simulation results, the flywheel power compensation strategy is discussed, and the torque fluctuation of the flywheel balance system is analyzed. The results showed that the higher the speed, the greater the power consumption. The power value suddenly increased from 17.82 kW (1.28 s) to 27.93 kW (1.43 s) when the speed was 220 r/min. Then, the power value rapidly decreased, and the power consumption presented a short-term peak feature. The transmission system’s maximum input power is determined as 17.82 kW according to the various simulated power consumption characteristics. The part exceeding the power consumption is compensated by the energy storage flywheel. The total compensation energy was 2382.5 J. After the flywheel system was involved, the maximum output power of the tractor power output shaft decreased by 36.2%, and the peak torque decreased from 445.7 N·m to 285.1 N·m. The power consumption obtained from the field test and simulation was similar, but the energy required to overcome peak load was jointly provided by the flywheel and the engine. The actual input power of the power output shaft during the energy release period of the flywheel system was 18.51 kW when the rotating speed of the hole-digging component was 220 r/min, and the relative error with the simulation value was 2.43%. The measured actual speed reduction of the flywheel system was 8.9%. After installing an energy storage flywheel in the transmission system of the tree planting machine, the output power of the power unit can be stabilized. Tree planting machines can be equipped with smaller power units, which can reduce energy consumption and exhaust emissions.

Understanding the performance of bridge decks through full-scale accelerated testing

Understanding the long-term performance of bridges plays a major role in the selection of appropriate asset-management strategies, which eventually reduce life-cycle costs and extend the service life of a bridge. To understand bridge performance better, the Federal Highway Administration initiated a research project utilising accelerated testing of full-scale bridge superstructure systems subjected to cyclic moving wheel loads and freeze–thaw environmental conditions. As part of the research project, complementary non-destructive evaluation (NDE) techniques were used to assess the performance of a full-scale bridge deck during the curing and loading period. NDE results, shortly after construction, revealed a smaller cover depth of rebars in the middle section of the deck. This has likely created a preferential path for the subsequent deterioration of the deck. It was suggested to use a scaled version of the electrical resistivity (ER) values to improve the consistency between temporal ER measurements of the deck, and it was shown that combining construction information with NDE results can improve the interpretation of results. Overall, the results showed the importance of NDE for quality assurance of new construction and provided a better understating of the long-term bridge deck performance.

Observation of the Coupling Current During Stress Corrosion Cracking of Aluminum Alloy 5083

A unique fracture mechanics device was created to allow for simultaneously measuring the load and localized electrochemical potential gradients in AA5083 bend bars. For the first time, periodic Scanning Vibrating Probe (SVP) maps were collected in order to obtain a full view of the coupling current, (which can be deduced from measured potential gradients) that emanates from an anodic crack tip. As a result of mapping the current density over a wide surface area compared to the area of the notch and crack tip, clarification is given on whether or not the external surfaces of an alloy or any other metal that experiences Stress Corrosion Cracking (SCC) play a role in crack growth. The SVP maps clearly show the anodic and cathodic potential gradients of a growing crack (resulting from SCC) in an AA5083 fracture mechanics specimen while the stress intensity increases. The notch and crack-tip remained anodic throughout most of the obtained scans for sensitized and as-received specimens. Furthermore, a coupling effect is observed on sensitized specimens even at low fracture toughness values in sensitized specimens under load for longer periods of time (&gt; 1 week). These higher resolution maps captured during the crack growth process give more insight to the SCC phenomenon and the electrochemical mechanisms of crack growth in AA5083 and other alloys.

Creep strain recovery of an in situ spinel-forming refractory castable under loading/unloading compressive creep conditions

Creep strain recovery after unloading has been well studied for metals and certain ceramic composites; however, it has not yet been investigated for ordinary ceramic refractories applied in industrial furnaces. The present study explores the question whether creep strain recovery can be observed in ordinary ceramic refractories to justify its consideration in the design of such refractories and refractory linings. To this end, the dependence of creep strain recovery on different loading conditions was investigated for a high-alumina in situ spinel-forming castable, commonly used as refractory lining of steel ladles in secondary steel metallurgy. Several loading/unloading compressive creep tests were performed at 1300 °C for different loading histories. Creep strain recovery was observed to occur and it was significantly affected by the holding time and degree of unloading. A longer holding time for the loading period was found to increase the internal stress, which is the driving force for creep strain recovery. In addition, the findings indicate that a higher excess of internal stress over external stress after unloading induces higher strain recovery.

Performance optimization of the air-cooling system in a coal-fired power unit based on intelligent algorithms

Air-cooled condensing technology is considered a preferred technology for thermal power generation due to the advantages of water savings. The performance of air-cooled condenser (ACC) is mainly influenced by external weather conditions and unit operation. In this paper, an artificial intelligence algorithm model is developed to predict and optimize the performance of the air-cooled condenser in advance based on long-term operational data of coal-fired power plants. A back propagation neural network algorithm is used to establish a net power output-back pressure model, and the optimal back pressure search is completed based on the established model. Finally, the average power savings of a single sample over a 30-second period was used as an indicator to evaluate the energy saving effect of optimized back pressure. The artificial intelligence analysis method not only enables the use of a large amount of operational data, but also allows effective prediction, analysis, and optimization of the performance of the air-cooled condenser, ultimately improving the overall performance of this equipment. The results indicate that: (1) when the back pressure of the unit reaches 9.25 kPa, the net power output of the unit is the highest, thus achieving the optimal back pressure; (2) by calculating the average energy savings, it can be concluded that, for a single sample over a 30-second period, the average power savings of the unit are above 7.0 kWh during the medium load period, and 5.0 kWh during the low and high load periods. Therefore, the proposed optimization method is beneficial for energy saving of the air-cooled condenser.

Intravenous Immunoglobulin Treatment Patterns and Outcomes in Patients with Chronic Inflammatory Demyelinating Polyradiculoneuropathy: A US Claims Database Analysis.

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a rare progressive or relapsing inflammatory disease. Intravenous immunoglobulin (IVIG) is recommended as a first-line therapy. The aim of this study was to describe real-world treatment patterns and outcomes of patients with CIDP in the Define initiating IVIG treatment. This cohort study used health insurance claims data from the Merative MarketScan Research Databases (2008-2018). Adult patients (≥ 18years old) with CIDP without prior immunoglobulin treatment were identified using International Statistical Classification of Diseases and Related Health Problems (ICD) codes, and patients subsequently initiating IVIG were included in the analysis. Real-world IVIG treatment patterns and treatment and safety outcomes (assessed via ICD codes) were described. In total, 3975 patients (median age 58years) with CIDP who initiated IVIG were identified. After the initial IVIG loading period, patients received IVIG at a median dosing interval of 21days (quartile [Q]1, Q3: 7, 28), and continued treatment for a median of 129days (Q1, Q3: 85, 271). After the 2-year follow-up period, 55% of patients had discontinued all IVIG treatment; more than one-half of these discontinuations occurred within 4months. Diagnoses of impaired functional status were evident in more than 30% of patients at baseline, but at lower rates during follow-up. Rates of new-onset safety outcomes after IVIG treatment were low. This real-world analysis of IVIG treatment patterns and treatment and safety outcomes of patients with CIDP who initiated IVIG highlights the unmet need for improved long-term management. Further research is needed to evaluate the use of functional status measures as endpoints for immunoglobulin treatment effectiveness.

Pachychoroid neovasculopathy has clinical properties that differ from conventional neovascular age-related macular degeneration

To determine the clinical properties of pachychoroid neovasculopathy (PNV) that differ from conventional neovascular age-related macular degeneration (nAMD) and suggest that they are different clinical entities. To accomplish this, we reviewed the medical records of 100 consecutive patients diagnosed with nAMD. All of the patients were Japanese, and their mean age was 75.5 years. There were 72 men and 28 women. For the bilateral cases, only the right eye was analyzed. An eye was diagnosed with PNV when a macular neovascularization (MNV) was detected just above the dilated choroidal vessels. The Indocyanine green angiographic (ICGA) and en face optical coherence tomographic (OCT) images were used to assess the vertical symmetry of the medium and large choroidal vessels. The subfoveal choroidal thickness (SCT) was also measured manually in the OCT images. After reclassification, there were 29 (29%) patients with typical nAMD (25 with type 1 MNV, 4 with type 2 MNV), 43 (43%) with PNV, 21 (21%) with polypoidal choroidal vasculopathy, and 7 (7%) with retinal angiomatous proliferation. Of the 43 PNV, 17 (39.5%) had polypoidal lesions and 26 (60.5%) had no polypoidal lesions. The percentage of eyes with vertical asymmetry of the medium and large choroidal vessels was significantly greater in the 35 PNV (81.4%) than in the 16 non-PNV (28.1%; P < 0.01) cases. The mean SCT was significantly thicker in the PNV eyes than in the non-PNV eyes (298 ± 96 μm vs. 228 ± 82 μm; P < 0.01). The response of PNV to anti-vascular endothelial growth factor treatments was better than that of non-PNV eyes [higher dry macula rate after the loading period (90.9% vs. 59.1%), fewer total number of injections (11.0 ± 2.9 vs. 13.4 ± 3.2), and longer treatment intervals for the anti-VEGF therapy (8.4 ± 3.1 vs. 13.4 ± 3.2 weeks) at 2 years (all P < 0.01)]. These differences in the morphology and response to anti-VEGF treatments suggest that PNV is a separate clinical entity to conventional nAMD.

Influence of water content on clay deformation characteristics subjected to periodic intermittent loading

The influence of clay's drainage and reconsolidation behavior during the intermittent period on clay's deformation needs to be further studied. Dynamic loads, such as traffic and earthquake, etc., have a certain intermittent period during the loading process. This study examined the deformation behavior of the clay obtained from Nanchang under various cyclic stress ratios (CSR) and water content conditions. The results demonstrated that minor strain rebound occurs in all intermittent periods. Aside from that, drainage reconsolidation during intermittent periods alters the pattern of strain accumulation during subsequent loading periods, and cyclic stress levels and water content conditions can impact the intermittent effects. In contrast, the development of strain in the samples under intermittent loading is more negatively impacted by high CSR and low water content (deviation from optimal water content). The hysteresis curve continued to change throughout the test, the accumulation and dissipation of excess pore water pressure changed, and it was found that the samples' resilient modulus had increased, indicating an improvement in the samples' resistance to deformation.

An Axially Compressed Moving Nanobeam Based on the Nonlocal Couple Stress Theory and the Thermoelastic DPL Model

This article introduces a new model that can be used to describe elastic thermal vibrations caused by changes in temperature in elastic nanobeams in response to transverse external excitations. Using the idea of nonlocal elasticity and the dual-phase lagging thermoelastic model (DPL), the coupled equations of motion and heat transfer were derived to explain small-scale effects. Additionally, modified couple stress theory (MCST) and Euler–Bernoulli (EB) beam assumptions were considered. The proposed theory was verified by considering the thermodynamic response of nanobeams moving horizontally at a constant speed while one end is subjected to a periodic thermal load. The system of governing equations has been solved numerically with the help of Laplace transforms and one of the tested evolutionary algorithms. The effects of changing the nonlocal modulus, the magnitude of the external force, and the length scale parameter on the system fields were investigated. It is also shown how the behavior of the thermal nanobeam changes depending on the phase delay factors in addition to the horizontal velocity of the beam. To determine this model’s accuracy, its results were compared with the results of the classical continuity model and thermoelastic concepts. The numerical results show that when the nanobeam moves, the length scale can change the studied thermal and mechanical vibration wave patterns and physical fields. Additionally, during thermally stimulated vibrations, thermodynamic effects that have implications for the dynamic design and performance improvement of nanostructures must be considered.

The impact of periodic axial loads on nonlinear dynamic instability behavior of Inconel 625 pipes

In various engineering fields like aerospace and aircraft structures or marine and offshore platforms, constitutive material of critical components should be made of specific materials that can work properly in the required workspace. Such materials must have excellent properties such as high mechanical strength as well as great resistance to corrosion, oxidation, and creep. Inconel 625 is a superalloy that is chosen as constitutive material of critical components due to its great abilities. On the other hand, since investigating Inconel 625 pipe has not been done yet, different mechanical characteristics of using structures made of Inconel 625 should be assessed. Additionally, doing so would be necessary to gather information for current industrial affairs and also future investigations. Therefore, the nonlinear dynamic instability response of axially loaded Inconel 625 pipes is investigated in the current article. The pipe structure is modeled via the Donnell shell theory and nonlinear von Kármán theory. The motion equations of pipes are established by applying the Hamiltonian approach. Then, in order to alter the nonlinear derived partial differential equations into the Mathieu-Hill equation, both Navier's solution and Airy stress function are implemented. Additionally, the amplitudes of steady-state oscillation of the Inconel 625 pipe are determined by employing Bolotin's method. Eventually, the impacts of various effective parameters on the nonlinear dynamic behaviors of Inconel 625 pipes are evaluated. The results indicate static and dynamic load factors possess a remarkable effect on instability exciting areas and steady-state vibration amplitudes of pipe. Moreover, the dynamic instability response of the pipe is dependent on the radius-to-thickness and length-to-radius ratios, and also how the ratios are affected depends on the wave number.

Sensorless Control Based on the Uncertainty and Disturbance Estimator for IPMSMs With Periodic Loads

The research object in this paper is a single rotor compressor based on the interior permanent magnet synchronous motors (IPMSM) with sensorless control, whose load fluctuates periodically with the mechanical angle. The periodically fluctuating loads can cause obvious periodic fluctuations of motor speed. Meanwhile, the traditional phase-locked loop (PLL) can lead to obvious phase shift and amplitude attenuation. Therefore, the controller is designed from two aspects to make the motor run stably at low speed under the periodic load. Firstly, a speed control based on the uncertainty and disturbance estimator (UDE) is proposed to suppress speed fluctuations caused by the periodic load. Secondly, the phase-locked loop based on the resonance control (R-PLL) is proposed to compensate for the periodic angle and speed errors caused by the phase shift coming from the PLL under the periodic load. The experimental results show that the sensorless control based on the R-PLL and UDE can effectively improve the estimated angle accuracy and suppress the speed fluctuations, making the motor run stably at low speed under periodic loads.