Multistage Test Research Articles

The Effect of Low-Impact Aerobic Dance Exercise Video on Cardiovascular Endurance, Flexibility, and Concentration in Females With Sedentary Lifestyle

The study purpose was to prove the effectiveness of a low-impact aerobic dance exercise video on cardiovascular endurance, flexibility, and concentration in women with a sedentary lifestyle.
 Materials and methods. This study used the Pre-Experimental method with a One-Group Pretest-Posttest Design research design. Total of 18 females aged 18–20 y.o., body mass index (BMI) 19 kg/m2 – 24 kg/m2, normal systolic and diastolic blood pressure, normal resting heart rate, oxygen saturation (SpO2) 96% – 100% participated in the research. Low-impact aerobic dance exercise was done using video for 30 minutes/exercise session with an intensity of 75% – 85% HRmax with a frequency of 3 times/week for 6 weeks. Measurement of cardiovascular endurance was done using the Multi-Stage 20-m Shuttle Run Fitness Test, flexibility was measured with the Sit and Reach Test, and concentration was meassured with the Grid Concentration Test. The statistical analysis technique used the Paired Sample T-Test with a significance level of 5%.
 Results. The results showed the average cardiovascular endurance of the pretest vs. posttest (28.13 ± 4.80 vs. 30.52 ± 0.88 mL/kg/min (p ≤ 0.001)), mean flexibility of pretest vs. posttest (17.79 ± 4.72 vs. 18.75 ± 5.02 cm (p ≤ 0.001)), mean concentration of pretest vs. posttest (7.39 ± 2.38 vs. 9.11 ± 2.45 score (p ≤ 0.001)).
 Conclusions. Based on the results of the study, it was concluded that a low-impact aerobic exercise dance video performed with a frequency of 3 times/week for 6 weeks increased cardiovascular endurance, flexibility, and concentration in adolescent girls with a sedentary lifestyle.

Study on Soil Leaching Risk of Reuse of Reclaimed Fertilizer from Micro-Flush Sanitary Wastewater

In view of the potential soil leaching risk of the reuse of fertilizer reclaimed from micro-flush sanitary wastewater, the batch tests of soil adsorption and degradation, soil column percolation test and multi-stage soil box percolation test were adopted. The characteristics of leachate after the interaction between reclaimed fertilizer and soil, as well as the changes of soil attributes in the soil box system, were analyzed. After obtaining the correlation coefficients of solute transport in soil through the above experiments, the HYDRUS-1D model was constructed to simulate the solute migration and transformation in the soil with a duration of 1 year and a soil thickness of 5 m. The impacts of leachate on groundwater and soil were analyzed. The results showed that the adsorption intensity of total ammonia nitrogen (TAN) (1n=0.8009) in the tested soil was lower than that of chemical oxygen demand (COD) (1n=1.1830). The HYDRUS prediction showed that concentrations of TAN and COD at the soil depth of 5 m were 0, while total nitrogen (TN) still had a concentration of 0.11 mg/L. However, the TN leaching into the deep soil mainly came from the soil itself. The TAN at 3.4 m soil showed an upward trend in the prediction period. In addition, the reuse of reclaimed fertilizer can expand the soil nutrient inventory, which is conducive to the improvement of soil fertility. It can be concluded that the soil leaching risk of reuse of reclaimed fertilizer is not significant in the short term (one year). However, the risk of fertilization on soil with high-nitrogen background value should be paid attention to in the long term.

Functional Performance Tests, On-Ice Testing and Game Performance in Elite Junior Ice Hockey Players.

This study aimed to explore relationships between fitness, on-ice physical abilities and game performance among elite junior male ice hockey players. Twenty-one major junior ice hockey players (18.9 ± 1.4 years old) participated in the study. Measures including five fitness tests (anthropometric measures, pull up test, bench press test, broad jump, vertical jump) and three on-ice skating tests (multi-stage aerobic skating test, 44-m sprint test, and backward skating test) were assessed during their pre-season training camp. Game performance metrics (collected during the regular season) were collected using InStat software. Results of the (on-ice and off-ice) functional performance test protocol and on-ice tests were analyzed by evaluating correlation coefficients in multiple areas of game performance: 1) physical implication (body checks), 2) offensive contribution (expected goals for, types of zone entries), and 3) defensive actions (blocked shots, expected goals against). They revealed that performance in the broad jump test was associated with skating speed. Some significant correlations were also observed between on-ice test performance indicators such as received body checks, expected goals and blocked shots. In summary, results indicate that on-ice test protocols were associated with players’ performance in multiple aspects of the game. Partial correlation analyses revealed that some of these relationships were specific to the player's position. Forward skating was associated with forwards’ offensive play, and backward skating was specifically related with defensemen’s performance (offense and defense). The addition of on-ice physical tests appears essential for interpreting the results of ice hockey players' physical tests and integrating these results into players’ physical preparation and the in-season follow-up.

Mechanical Characterization of Anchor under Uniaxial Compression Loading Conditions

Bolt reinforcement technology plays an important role in supporting the construction of many engineering fields, and the uniaxial loading characteristics and behavior tests of anchors have great significance to the research and application of anchors. Therefore, four anchor specimens GA ∼ GD were fabricated and tested to explore the macro and microbehavior characteristics of anchors under uniaxial compression. The stress-strain curves for GA ∼ GC specimens under uniaxial compression were analyzed. The stress-strain curve, elastic strain and creep strain, the failure results, and electrochemical impedance spectroscopy of specimen GD under multistage loading were investigated. The results showed a series of behavior characteristics of anchor under uniaxial compression. Under uniaxial compression, the shapes of stress-strain curves of three specimens GA ∼ GC were similar, and they had experienced four different stages from stage I to stage IV, respectively. After calculating the uniaxial compressive strength of the three specimens, the average uniaxial compressive strength of these specimens was σ c ¯ = 8.31 MPa. The stress-strain curve of the specimen GD was obtained by a multi-stage loading test. The total strain of the specimen consisted of elastic strain and creep strain. In the whole process of loading, the proportion of elastic strain was greater than that of creep strain, and the proportion range of elastic strain was 51.90% ∼ 55.82%. Seven electrochemical impedance spectrum curves of the specimen GD under multi-stage compression load were obtained. The dispersion and concentration of Nyquist curves were affected by different loading levels; the higher the loading level, the more dispersed the Nyquist curve is. In the measured Bode diagram, compared with the previous six measurements, the variation laws of impedance value and phase angle measured at the seventh time in the failure stage of the specimen were quite different. The above research and conclusions can provide some reference for the test theory and engineering application of anchors.

Experimental investigation into the cyclic behaviour of geogrid enhanced base layer aggregate through large-diameter triaxial tests

The base layer is constructed of coarse-grain soils, usually reinforced by geogrid. In the study, a large-diameter cyclic triaxial testing system was employed to study the cyclic behaviour of geogrid enhanced soil, especially the long-term deformation behaviour. The multi-stage cyclic loading test was performed to determine the shakedown behaviour of soil enhanced by different geogrid layers under different cyclic loading amplitudes. Then, single-stage tests with one cyclic loading amplitude in plastic creep range and the other in the incremental range were performed on soils enhanced by different geogrid layers. Test results indicated that the effect of geogrid on the long-term deformation of soil is dependent on the shakedown response of soil: the enhancement effect was observed to be much more significant for specimens that exhibit the incremental collapse response than those that exhibit the plastic creep response. Besides, the resilient modulus was found limited affected by the geogrid layer, irrespectively the specimen that exhibits plastic creep or incremental collapse. Furthermore, the reinforcement mechanism was discussed in detail from the consistent/inconsistent deformation of soil and geogrid, which benefits geogrid design and construction.

Physical Activity, Physical Fitness And Adiposity; Associations With Cardiometabolic Health And Cognitive Function Across Adolescence.

The cross-sectional associations between physical activity, fitness, and adiposity with risk factors for cardiometabolic disease (particularly novel ones such as inflammatory cytokines) and cognitive function across the period of adolescence are not well understood. Additionally, novel physical activity metrics that summarise activity volume and intensity in a continuous manner have not been investigated in this context. PURPOSE: This study investigated the cross-sectional associations between physical activity, fitness, and adiposity with risk factors for cardiometabolic disease and cognitive function. These associations were compared between younger and older adolescents. METHODS: Seventy younger (11-12y, 35 girls) and 43 older (14-15y, 27 girls) adolescents volunteered to take part in the study. Fitness (multi-stage fitness test, MSFT) and adiposity (waist circumference) were determined; followed 7d later by resting blood pressure, a fasted blood sample (glucose, plasma insulin, IL6, IL10, IL15 and IL-1β concentrations) and a cognitive function test battery. Habitual physical activity was monitored via hip-worn accelerometers over this 7-d period and the average acceleration (activity volume), and intensity gradient (intensity distribution of activity) were determined. RESULTS: Average acceleration and intensity gradient were negatively associated with mean arterial blood pressure (β = -0.75 mmHg, p = 0.021; β = -10 mmHg, p = 0.006), and waist circumference was positively associated with IL-6 concentration (β = 0.03%, p = 0.026), with stronger associations observed in older adolescents. Higher fitness (MSFT distance) was positively associated with anti-inflammatory IL-15 concentration (β = 0.03%, p = 0.038) and faster response times on the incongruent Stroop task (β = -1.43 ms, p = 0.025), one-item Sternberg paradigm (β = -0.66 ms, p = 0.026) and the simple (β = 0.43 ms, p = 0.032) and complex (β = -2.43 ms, p = 0.020) levels of the visual search test, in the sample overall. CONCLUSIONS: The present study highlights the important role of physical activity (both the volume and intensity distribution) and fitness for cardio-metabolic health. Furthermore, the present study highlights the importance of fitness for a variety of cognitive function domains in adolescents, irrespective of age.

Regulatory Considerations for the Potential Use of a Multi-Stage Validation Testing Approach to Support Human Factors Engineering Technical Reviews for Proposed Nuclear Power Plant Control Room Design Modifications

Traditionally, integrated system validation (ISV) testing for proposed nuclear power plant control room design changes has been completed prior to the U.S. Nuclear Regulatory Commission (NRC) approving the proposed change. This, however, can pose scheduling challenges for proposed changes to operating facilities. The NRC is therefore considering possible alternatives for licensees to provide the human factors engineering validation information necessary to demonstrate reasonable assurance of safety for proposed design changes. One such alternative could be the use of early-stage testing results from a multi-stage validation (MSV) program. If early-stage results, along with other design considerations, can provide sufficient supporting information, the NRC may be able to make a safety determination for a proposed design change prior to the completion of ISV testing. Licensees proposing such an approach should consider available industry standards discussing MSV, in conjunction with existing NRC guidance where applicable, when developing their validation program and establishing success criteria. The NRC intends to engage in future discussions with stakeholders regarding the potential development of additional NRC-endorsed guidance on the use of MSV to support proposed changes to existing facilities, as well as designs for new reactor control facilities.

Cluster randomised controlled trial to determine the impact of an activity enabling uniform on primary school student’s fitness and physical activity: study protocol for the Active WeAR Everyday (AWARE) study

IntroductionMulticomponent school-based physical activity (PA) interventions can improve students’ cardiorespiratory fitness (CRF) and PA. Due to the complex nature of such interventions when delivered at scale their effect sizes markedly...

Item Selection With Collaborative Filtering in On-The-Fly Multistage Adaptive Testing

An important design feature in the implementation of both computerized adaptive testing and multistage adaptive testing is the use of an appropriate method for item selection. The item selection method is expected to select the most optimal items depending on the examinees’ ability level while considering other design features (e.g., item exposure and item bank utilization). This study introduced collaborative filtering (CF) as a new method for item selection in the on-the-fly assembled multistage adaptive testing framework. The user-based CF (UBCF) and item-based CF (IBCF) methods were compared to the maximum Fisher information method based on the accuracy of ability estimation, item exposure rates, and item bank utilization under different test conditions (e.g., item bank size, test length, and the sparseness of training data). The simulation results indicated that the UBCF method outperformed the traditional item selection methods regarding measurement accuracy. Also, the IBCF method showed the most superior performance in terms of item bank utilization. Limitations of the current study and the directions for future research are discussed.

Longitudinal Changes in Health and Fitness Measures Among State Patrol Officers by Sex.

Dawes, JJ, Lopes dos Santos, M, Kornhauser, C, Holmes, RJ, Alvar, BA, Lockie, RG, and Orr, RM. Longitudinal changes in health and fitness measures among state patrol officers by sex. J Strength Cond Res 37(4): 881-886, 2023-Research suggests that police officers lose fitness as a result of their policing vocation with occupational factors like stress, shift work, poor sleep, and poor diet all contributors to this loss The purpose of this research was to measure changes in fitness test scores of qualified police officers over a 5-year period. Archived fitness data for 523 state patrol officers ( n = 494 men; 29 women) from one agency were used for this analysis. These tests included 60-second sit-up [SU] and push-up [PU] scores (muscular endurance), vertical jump height [VJ] (lower-body power), and 20-m multistage fitness test (aerobic capacity). A series of paired-samples t-tests and effect size calculations were used to investigate mean differences in fitness tests score at the beginning and end of a 5-year period. The paired-samples t test showed significant tests score decreases among male officers over the 5-year period in VJ, PU, and V̇ o2 max , , with no differences observed in SU performance. Small effect sizes were observed in both VJ ( g = -0.20) and PU ( g = -0.27) with a trivial effect size observed in changes to V̇ o2 max ( g = -0.14). In contrast, significant improvements in performance were observed in SU performance among female officers, with a small effect size ( g = 0.38). No other significant differences were found in female measures. Whether at an organizational or individual level, annual fitness assessments for police officers can serve to educate and motivate officers regarding their personal fitness and potentially slow the negative impact of aging on health, fitness, and performance in these populations.

Associations of Self-Control with Physical Activity, Physical Fitness, and Adiposity in Adolescents

The associations between self-control and objective measures of physical activity, physical fitness, and adiposity are yet to be explored in young people; this is a gap in the literature that the present study aimed to address. The study employed a cross-sectional design. A total of 101 young people participated in the study. Participants completed the Brief Self-Control Scale as a measure of trait self-control. Free-living physical activity was assessed using an ActiGraph GT3X + triaxial accelerometer, which was worn for 7 days. Participants also completed the 15-meter version of the multistage fitness test as a measure of physical fitness. For the assessment of adiposity, three criterion measures were used: body mass index (BMI), sum of skinfolds, and waist circumference. Data were analyzed using the glm function in the open access software R. Higher levels of trait self-control were associated with higher levels of physical fitness (measured by distance run on the multistage fitness test) and lower adiposity (BMI, waist circumference, and sum of skinfolds) in adolescents. There was a tendency for a positive association between self-control and time spent in vigorous physical activity, although this did not reach statistical significance. In a combined model, self-control was also associated with both physical fitness and waist circumference, with these effects independent of each other. These findings suggest that self-control is associated with healthy behaviors and characteristics in adolescents and is thus potentially an attractive target for future interventions aimed at increasing physical activity and physical fitness and reducing adiposity in this population.

Effect of 5-weeks participation in The Daily Mile on cognitive function, physical fitness, and body composition in children

The aim of the present study was to determine the effect of 5-weeks participation in The Daily Mile on cognitive function, physical fitness, and adiposity in primary school children. In a quasi-experimental study, one class from each school completed The Daily Mile (n = 44) or acted as a control group (n = 35). Baseline measures included cognitive function tests (Stroop test, Sternberg paradigm, Flanker task), physical fitness (multi-stage fitness test) and body composition (BMI percentile, waist:hip circumference, sum of skinfolds). The intervention group completed 5-weeks of The Daily Mile. Follow-up measurements were completed within 48-h of the last training session. Data were analysed via ANCOVA, examining between group differences at follow-up, controlling for baseline values. Response times on the complex Stroop test were faster at follow-up in the intervention group (Intervention: 1357 ms [1280–1400 ms]; Control: 1463 ms, [1410–1523 ms], d = 0.31, p = 0.048). There was no effect of The Daily Mile on the Sternberg paradigm or Flanker test. Physical fitness was greater at follow-up in the intervention group (Intervention: 880 m, [820–940 m]; Control: 740 m, [680–800 m], d = 0.39, p = 0.002). There was no effect of the intervention on adiposity. In conclusion, five-weeks of The Daily Mile enhanced inhibitory control and physical fitness in children, but did not affect working memory, attention, or adiposity.

Estimating three- and four-parameter MIRT models with importance-weighted sampling enhanced variational auto-encoder.

Multidimensional Item Response Theory (MIRT) is widely used in educational and psychological assessment and evaluation. With the increasing size of modern assessment data, many existing estimation methods become computationally demanding and hence they are not scalable to big data, especially for the multidimensional three-parameter and four-parameter logistic models (i.e., M3PL and M4PL). To address this issue, we propose an importance-weighted sampling enhanced Variational Autoencoder (VAE) approach for the estimation of M3PL and M4PL. The key idea is to adopt a variational inference procedure in machine learning literature to approximate the intractable marginal likelihood, and further use importance-weighted samples to boost the trained VAE with a better log-likelihood approximation. Simulation studies are conducted to demonstrate the computational efficiency and scalability of the new algorithm in comparison to the popular alternative algorithms, i.e., Monte Carlo EM and Metropolis-Hastings Robbins-Monro methods. The good performance of the proposed method is also illustrated by a NAEP multistage testing data set.

Influence of loading history on creep behavior of rock salt

Creep is a vital factor that affects the long-term stability of gas storage salt caverns. When we conduct a laboratory creep test of rock salt, compared with the single-stage loading method, the multi-stage loading method is used more frequently as it eliminates the discreteness of the sample. However, the early loading history affects the later creep behavior when the multi-stage loading method is used. To study the influence of loading history on the creep behavior of rock salt, the multi-stage loading triaxial creep test of rock salt and synchronous acoustic emission test were performed. Then, the numerical sample is established based on the laboratory test results and the discrete element numerical simulation is carried out. Single-stage loading and multi-stage loading creep tests were carried out on the initial numerical samples, respectively. Finally, the multi-stage loading data processing methods were compared using numerical simulation data. The results indicate that: (1) the improved multi-stage loading data processing method works well and it is recommended to use this method to process the multi-stage loading creep data. (2) Cracks are more developed in multi-stage loading sample, which experienced an early loading history, than in samples under single-stage loading. The damage accumulation in rock salt leads to its mechanical properties deterioration, which makes the creep deformation more prone to occur in the later stage. (3) The steady-state creep rate of rock salt is independent of loading history, only related to stress and temperature. The effect of damage accumulation in the loading history is mainly reflected in the transient strain and the strain in the transient creep phase. The study is helpful to further understanding the influence of loading history of rock salt on its creep, and provides an important basis for the design, construction, and operation of gas storage salt caverns.

Continuous and competitive circuit training: Methods to increase vo2max on young badminton player

The characteristic of badminton game is a sport with high intensity and intermitten actions. It takes the ability of a high level of physical condition, especially the level of VO2max to reach peak performance. There are many kinds of training method to increase VO2max, one of them is continuous circuit training and competitive circuit training. The purpose of this study is to discover the effect of continuous circuit training and competitive circuit training and to determine a more effective method to increase VO2max. This study is pre-experimental study with pre-test and post-test group design. The sample consisted of 60 badminton athletes in range of 9 – 12 years old and all of them were male. The instrument used to measure VO2max level was Multistage Fitness Test (MFT). VO2max data before and after treatement were analyzed with descriptive statistic and t-test on 5% significancy standard. Based on the data analysis, the following results were obtained: (1) There was a significant effect on the level of VO2max in the continuous circuit training group with sig 0.000 values; (2) There was a significant effect on the level of VO2max in the competitive circuit training group with values sig 0.000; and (3) There was no significant difference between the continuous circuit training group and the competitive circuit training group. So it can be concluded that continuous and competitive circuit training can increase the VO2max of young badminton players.

Effect of two-weeks of school-based sprint training on physical fitness, risk factors for cardiometabolic diseases and cognitive function in adolescent girls: A randomized controlled pilot trial

BackgroundSchool-based physical activity interventions are accessible to most adolescents and could enhance adolescent cardiometabolic health and cognition; yet the feasibility and success of school-based physical activity interventions is understudied.MethodsSixteen adolescent girls (age: 11.7 ± 0.3 y; height: 1.58 ± 0.07 m; body mass: 45.5 ± 9.2 kg) were randomized to either an intervention (2-weeks sprint training; n = 8) or control group (continuation of regular physical activity levels; n = 8). Following familiarization, all participants completed baseline measurements including fasted and postprandial capillary blood samples, a battery of cognitive function tests (Stroop Test, Sternberg Paradigm and Flanker Task), and an assessment of physical fitness (20 m sprint and multi-stage fitness test). The intervention group completed 2-weeks progressive sprint training (3 sessions per week: week one 6 × 10 s sprints, week two 8 × 10 s sprints). Follow-up measurements were completed 48 h after the final sprint training session. Data were analyzed via ANCOVA to examine between group differences at follow-up whilst controlling for baseline score.ResultsAccuracy in the intervention group during the three-item Sternberg paradigm was greater when compared with the control group (Intervention: 99.6 ± 1.1%; Control: 97.7 ± 2.2%, p = 0.046). BDNF concentration was also higher in the intervention group at follow-up than control group (Intervention: 39.12 ± 9.88 ng.ml−1; Control: 22.95 ± 9.13 ng.ml−1, p < 0.001). There were no differences at follow-up between the intervention and control group for measures of cardiometabolic health (fasted cytokine concentrations or postprandial glycaemic and insulinaemic responses) or on the Stroop Test or Flanker Task (all p > 0.05). However, the intervention group reported enjoying the sprint training and that they found the sessions valuable.ConclusionTwo-weeks sprint interval training in a school-setting enhanced working memory and increased concentrations of BDNF in adolescent girls. The intervention was deemed enjoyable and worthwhile by the adolescent girls and thus the longer-term implementation of such an intervention should be examined.

The Impacts of Plyometric Circuit Training before and after Technical Training on Cardiorespiratory and Power Abilities of Junior Male Volleyball Athletes

This study aimed to determine the effect of plyometric circuit training on cardiorespiratory and power abilities in male volleyball athletes. This study was experimental research with a Quasi-Experimental Design that involved male volleyball athletes from the Yuso Sleman Club as the population. The sample included 20 athletes determined by ordinal pairing, which were then divided into two groups. Using the multistage test, the first group was utilized to measure cardiorespiratory ability (VO_2max). Meanwhile, the other group used the vertical jump test to measure the power ability. The data analysis applied the t-test to comprehend the data structure in high dimensions because it involved more than one variable. The research analysis showed that the VO_2max variable in group I increased cardiorespiratory ability by 5.21% or 2.24 ml/kg BW/minute, and group II showed an increase by 2.64 or 1.15 ml/kg BW/minute. The power variable or vertical jump in group I showed 66.20, increased by 0.8 cm or 1.2% to 67.00; group II showed 69.50 cm, increased by 3.60 cm or 5.18% to 73.10 cm. The smash variable in group I showed 27.50 times, increased by 0.20 or 0.73% to 27.70 times, group II showed 27.20 times, increased by 5.8 or 31.32% to 33 times. Based on the results, plyometric circuit training before technical training had a more positive and significant effect on the cardiorespiratory and power of volleyball players, and to improve cardiorespiratory ability and power using plyometric circuit training, it is better to give it after technical training.

Model test study on static performance of rib-patterned small rise-span ratio suspend-dome structure

To investigate the distribution characteristics of prestressing force and static characteristics of the rib-patterned small rise-span ratio suspend-dome structure, a 1:20 scaled model of the Lanzhou Olympic Gymnasium roof structure was established. During to the small-scale ratio model with dense nodes, according to the principle of constant structural stiffness, a multi-node synchronous loading device was designed. The construction tensile loading test and multi-stage static loading test were carried out. The axial force of rods, vertical displacement of nodes, and radial displacement of supports for the model with initial geometric imperfection under 11 load cases were tested. Test results were used to validate and then refine the numerical simulation using ABAQUS. The study shows that a multi-node synchronous loading device dramatically improved the loading efficiency and satisfied the accuracy requirement of the test. The test results were in good agreement with the simulated results, which verified the correctness of the finite element modelling method, the accuracy of the test method, and the rationality of the measuring point arrangement. The small rise-span ratio suspend-dome structure with a rib-patterned has good elasticity at a low load level. The full-span arrangement of the live load is the most unfavorable load case of the structure. The outer loop cable bearing capacity exhibited a higher proportion. The third ring rod was found to sustain the highest load, the outer ring rod is more sensitive to load, and the fourth circle node was found to have the largest vertical displacement in the model. The change of support displacement in practical engineering should not be neglected.

Prediction of Rotating Instabilities in Low Pressure Steam Turbines Operating at Low Load

Abstract Due to the increasing need for operational flexibility nowadays, the low-pressure (LP) steam turbine might face widely variable operation conditions up to extreme low volume flow situations. Hereby, rotating instabilities (RIS), well known from compressor aerodynamics, can initiate nonsynchronous blade excitations, which can lead to increased vibrations of the last stage moving blade (L-0R). This paper describes a numerical method able to be used in an applicable way for blade designing. To judge the onset and the shape of RIS, a numerical approach based on a transient three-dimensional unsteady Reynolds averaged Navier–Stokes flow computation of the single passage L-1 stage, a full row L-0 stage, and an axis-symmetric diffuser was established. Mesh size, solver settings, etc., were optimized to reduce the computational effort without losing prediction accuracy. The dominant harmonic compound of a spatial Fourier transform of all monitored L-0R blade forces over the blade row's circumference reveals the stall cell count and excitation amplitude for each time-step. The transient change of the corresponding phase lag provided the stall cell speed and, multiplied with the stall cell count, the excitation frequency. Their distribution over decreasing flow rates finally displays the likely onset of RIS. The approach is capable to run the analyses of several load conditions within a couple of days and was successfully validated using measured blade tip deflections and unsteady pressure probes in multistage test turbines. Furthermore, it is shown that the approach can be used to find LP blade designs, where the effects of RIS can be significantly suppressed.

Study on Creep Mechanical Properties of Non-Water Reacting Polyurethane Grouting Material

Non-water reacting polyurethane is a new type of grouting material for support reinforcement and emergency rescue, whose creep mechanical behavior is directly related to the stability and safety of the reinforcement project. To investigate the creep properties of non-water reacting polyurethane grouting material, a series of multistage loading creep tests were performed under uniaxial compression conditions. Then, the creep curves, creep strain rate, and creep failure modes of non-water reacting polyurethane grouting material were obtained. In addition, the effects of temperature and density on the creep properties of non-water reacting polyurethane grouting material were also analyzed. Finally, based on the finite difference program, the numerical simulation of the uniaxial compression creep test of non-water reacting polyurethane grouting material was conducted by employing the Burgers–Mohr creep model. The simulated creep curve was in good agreement with the test curve, which verified the feasibility of the model to describe the creep characteristics of non-water reacting polyurethane grouting material. The research results can provide a reference for studying the creep behavior of polyurethane grouting material and also contribute to the development and application of polyurethane material grouting technology.