Determination Of Threshold Research Articles

Bearing Fault Diagnosis under Time-Varying Speed and Load Conditions via Observer-Based Load Torque Analysis

Bearing fault is the most common failure in rotating machines, and bearing fault diagnosis (BFD) has been investigated using vibration, current, or acoustic signals. However, there are still challenges in some existing approaches. This study proposes a novel BFD method based on natural observer. Based on the analysis of the effects on the load torque signal caused by bearing faults in the permanent magnetic synchronous machine (PMSM), a modified natural observer was designed to reconstruct the load torque signal from electrical signals, acquiring a novel indicator without the additional sensor installed. Angular resampling was implemented to convert the non-stationary load torque signal into a stationary one to reduce the computational complexity. For full-auto diagnosis without human involvement, a threshold determination algorithm was also modified. Experimental validations were carried out under speed-varying and torque-varying conditions and were compared with phase current and q-axis current signals. The average signal-to-noise ratio (SNR) of the estimated load torque is about 8.65 times compared with the SNR of the traditional q-axis current. The effectiveness of the proposed method prior to the traditional PMSM bearing fault indicators is demonstrated by the order spectrum results.

Effects of Organic Acids on the Release of Fruity Esters in Water: An Insight at the Molecular Level

It is well known that organic acids (OAs) could affect the flavour of fruit juices and beverages. However, the molecular mechanism of aroma release is still unclear. In this study, the effects of citric acid (CA), L-(-)-malic acid (MA) and L-lactic acid (LA) on the release of six selected esters and their sensory perception were investigated by means of HS-GC-MS analyses and odour detection threshold determination, respectively. Meanwhile, the density functional theory (DFT) calculation was employed to explore the interaction modes between esters and OAs. HS-GC-MS analyses showed that the concentration and the type of OAs regulated the release of esters. The results were basically consistent with the detection threshold change of those esters. The DFT calculation suggested that the main intermolecular interaction was hydrogen bonds, and several esters could form a ternary ring structure with OAs through hydrogen bonds. The interactions can induce the different release behaviours of esters in OAs water solution. The number of carboxyl functional groups in OAs and the spatial conformation of esters appeared to influence the magnitude of the interaction. The above results demonstrated the mechanism of OAs affecting the release of esters and indicated a possible flavour control way by using different OAs and OA concentrations.

MO604: Determinants of an Aerobic Threshold in Chronic Kidney Disease

Abstract BACKGROUND AND AIMS Anaerobic threshold (AT) is a widely used cardiopulmonary exercise test (CPX) parameter in the field of preoperative assessment in general population where it is used as a surrogate marker of cardiovascular fitness. There is growing interest in the application of AT in the evaluation of fitness for kidney transplantation. However, the determinants of anaerobic threshold in CKD have not been well studied. In the present study, we evaluated the hemodynamic, biochemical and anthropometric determinants of AT in CKD. Furthermore, we evaluated the association between AT and objectively measured index of cardiac functional reserve in CKD. METHOD In this cross-sectional study, 70 male CKD patients (stages 2–5) without any cardiac diseases or diabetes underwent a specialised CPX to measure exercise capacity, AT, peak cardiac hemodynamics and cardiac power output (CPO).1 Cardiac functional reserve was calculated as ∆CPOpeak—CPOrest. Blood samples were assayed for standard renal biochemistry. Univariate and multivariate regression were employed. Results were presented as mean ± SD. P < 0.05 is considered significant. RESULTS The study subjects had a mean age of 48.4 ± 12.6 years and a mean eGFR of 33.9 ± 23.5 mL/min. All subjects performed high intensity CPX to volitional exhaustion with a mean RER of 1.16 ± 0.09 and a mean peak aerobic capacity (VO2peak) of 2.51 ± 0.53 L/min. Table 1 shows the univariate and multivariate predictors of AT in CKD. Figure 1 shows the association between AT and objectively measured cardiac functional reserve. CONCLUSION The results demonstrate that AT only has a modest association with cardiac functional reserve in CKD. Noncardiac factors such as haemoglobin and peripheral O2 extraction are also significant determinants of AT in addition to cardiac factors. Therefore, AT should be interpreted with caution if employed as a surrogate marker of cardiovascular fitness in CKD. 1Chinnappa S et al. JASN July 2021, 32 (7): 1813–1822

Comparison between determination of second anaerobic threshold by respiratory compensating point and X-method in rowers

Background and Study Aim. The aim of this study is to verify the X-method for determining the second anaerobic threshold in rowers.Material and Methods. Twelve male athletes from the national rowing team of Bulgaria were tested. Participants performed a one-time graded incremental exercise test to exhaustion on a rowing ergometer. The workload were conducted on rowing ergometer system Concept 2, and spirometry system Clark C5. We obtained ventilatory indices, intensity and heart rate bred-by-bred for each participant, for each test stage. The anaerobic threshold was determined by two methods: 1) by the localization of the respiratory compensation point visually, after polynomial regression analysis of the trends for the dynamics of the ventilatory variables related to time and 2) by the X-method using the change in the ratio between heart rate and pulmonary ventilation. We compared the heart rate corresponding to the anaerobic threshold determined by both methods.Results. We found similar values for heart rate at the respiratory compensation point and the anaerobic threshold determined by the X-method for each of the investigated. The Shapiro-Wilk test showed a normal distribution of the two samples with a significance level of α = 0.05. Thus, the t-test for two paired samples showed a p-value of 0.202 at α = 0.05. We found a correlation coefficient r = 0.973 between the heart rate at the anaerobic threshold (determined by X-method) and the heart rate at the anaerobic threshold (detected at the respiratory compensation point). The Blant-Altman analysis showed that 95% of the points in the scatter plot lie within the confidence interval.Conclusions. The two methods give similar results and can be applied alternatively in the investigation of rowers in the age group 18.3 ± 1.07 years. The X-method always gives a reliable intersection point, which in our studies is close to the second anaerobic threshold. Comparative studies are also needed in other contingents for the wider use of the X-method.

Determiningoptimal donor heart ischemic times in adult cardiac transplantation.

ObjectivesUnsupervised statistical determination of optimal allograft ischemic time (IT) on heart transplant outcomes among ABO donor heart types.MethodsWe identified 36,145 heart transplants (2000–2018) from the United Network for Organ Sharing database. Continuous and categorical variables were analyzed with parametric and nonparametric testing. Determination of IT cutoffs for survival analysis was performed using Contal and O'Quigley univariable method and Vito Muggeo multivariable segmented modeling.ResultsUnivariable and multivariable IT threshold determination revealed a cutoff at about 3 h. The hourly increase in survival risk with ≥3 h IT is asymmetrically experienced at the early 90 days (hazard ratio [HR] = 1.29, p < .001) and up to 1‐year time point (HR = 1.16, p < .001). Beyond 1 year the risk of prolonged IT is less impactful (HR = 1.04, p = .022). Longer IT was associated with more postoperative complications such as stroke (2.7% vs. 2.3, p = .042), dialysis (11.6% vs. 9.1%, p < .001) and death from primary graft dysfunction (1.8% vs. 1.2%, p < .001). O blood type donor hearts with IT ≥ 3 h has significantly increased hourly mortality risk at 90 days (HR = 1.27, p < .001), 90 days to 1 year (HR = 1.22, p < .001) and >1 year (HR = 1.05, p = .041). For non‐O blood types with ≥3 h IT hourly mortality risk was increased at 90 days (HR = 1.33, p < .001), but not at 90 days to 1 year (HR = 1.09, p = .146) nor ≥1 year (HR = 1.08, p = .237).ConclusionsThe donor heart IT threshold for survival determined from unbiased statistical modeling occurs at 3 h. With longer preservation times, transplantation with O donor hearts was associated with worse survival.

Critical Rainfall Thresholds as a Tool for Urban Flood Identification in Attica Region, Greece

Rainfall intensity–duration thresholds are commonly used to assess flood potential in both urban and rural environments. Derivation of these thresholds is one of the approaches commonly used for the development of flash flood warning systems that are mainly based on rainfall predictions. This research work presents a detailed analysis on these threshold estimations, implemented for the Attica region, Greece, as prior work in parts of the study area is limited and previous estimations regarding rainfall intensity–duration thresholds are based on a short period of available data. The analysis considers a large number of stations and takes into account all flood events occurred during the period between 2005 and 2017 in order to define two maximum intensity limits for various durations that denote three areas; conditions of flood occurrence, mixed conditions, and conditions linked to solely flood occurrence, respectively. Finally, limitations regarding the determination of specific spatiotemporal thresholds as observed through this analysis are also discussed. The application of this methodology as a tool to assess flood occurrence may contribute to minimize possible situations of pre-crisis or immediate crisis by reducing the flood consequences and the resources involved in emergency response to flood events.

A Fast Quality Control of 0.5 Hz Temperature Data in China

Fast quality control (FQC) is important to deal with high-frequency observation records at meteorological station networks in time, and may check whether the records fall within a range of acceptable values. Threshold tests in the previous quality control methods for monthly, daily, or hourly observation data do not work well for 0.5 Hz data at a single station. In this study, we develop an algorithm for the automatic determination of maximum and minimum minute thresholds for 0.5 Hz temperature data in the data collection phase of the newly built stations. The fast threshold test based on the percentile threshold (0.1–99.9%) and standard deviation scheme is able to efficiently identify the incorrect data in the current minute. A visual graph is generated every minute, and the time series of the data records and the thresholds are displayed by the automated graphical procedures. The observations falling outside the thresholds are flagged and then a manual check is performed. This algorithm has the higher efficiency and lower computational requirement in identifying out the obvious outliers of 0.5 Hz data in real or near-real time observation. Meanwhile, this algorithm can also find problems in observation instruments. This method is applied to the quality control of 0.5 Hz data at two Tianjin experiment stations and hourly data at one Shenyang experiment station. The results show that this fast threshold test may be a viable option in the data collection phase. The advantage of this method is that the computation requires less memory and the computational burden is reduced for real or near-real time observations, so it may be extended to test other meteorological variables measured by high-frequency measurement systems.

Speech Understanding in Manic and Depressive Episodes of Mood Disorders.

The aim of this study was to assess the perception of speech in adverse acoustic conditions during manic and depressive episodes of mood disorders. Forty-three patients with bipolar disorder (mania, N=20; depression, N=23) and 32 patients with unipolar depression were included for analyses. Thirty-five participants served as the control group. The study of speech understanding was carried out using the Polish Sentence Matrix Test, allowing for the determination of the speech reception threshold (SRT). The test was performed in the clinical groups both during an acute episode and remission; during remission, patients underwent audiometric evaluation. Compared with control subjects, patients with mood disorders had worse speech understanding (higher SRT), regardless of the episode or remission. A manic episode in the course of bipolar disorder was not associated with worse speech understanding compared with remission of mania. However, an episode of depression in the course of both bipolar disorder and unipolar depression was associated with worse speech understanding compared with remission of depression. In bipolar depression, this correlated with age, duration of the disorder, number of episodes, and number of hospitalizations, as well as in remission with age and duration of illness. In unipolar depression, poor speech understanding was more severe in individuals with hearing impairment. These findings revealed that patients with mood disorders had impaired speech understanding, even while in remission, and manic episodes in the course of bipolar disorder were not associated with impaired speech understanding compared with mania remission.

Maximum acceptable level for the determination of ECAP and ESRT in a paediatric population

Objectives Two of the most used objective measures are electrically evoked action potentials (ECAPs) and electrically evoked stapedius reflex thresholds (ESRTs). Although stimuli used for these measures differ considerably, both measures are influenced by subjective loudness percept. We focus on the subjective maximum acceptable loudness (MAL) to investigate if loudness sensitivity varied along the electrode array during ECAP recordings. In addition, we explored how the MAL reached during an ECAP recording related to the postoperative ESRT. Methods Uni- and bilaterally implanted young CI users (n = 15, average age = 9 y, age range 3–18 y) underwent ECAP and ESR recordings using the clinical software MAESTRO (MED-EL, Innsbruck, Austria) and a commercially available immittance instrument (PATH MEDICAL GmbH, Germering, Germany). Results Loudness tolerance during ECAP recordings was lowest at the two apical-most electrode contacts (number 1 and 2). There was a moderate correlation between the MAL achieved during ECAP recordings and ESR maximum stimulation amplitudes. (r: 0.44344). Conclusions ECAP recordings should commence at basal or medial contacts to increase the users’ comfort and loudness tolerance, especially in young CI users. A higher maximum stimulation appears to increase the chance of the automatic determination of ECAP thresholds for all electrode contacts.

Prediction-Based Resource Deployment and Task Scheduling in Edge-Cloud Collaborative Computing

Edge computing is becoming increasingly commonplace, as consumer devices become more computationally capable and network connectivity improves (e.g., due to 5G). With the rapid development of edge computing and Internet of Things (IoT), the use of edge-cloud collaborative computing to provide service-oriented network application (i.e., task) in edge-cloud IoT has become an important research topic. In this paper, we present an edge-cloud collaborative computing framework and our resource deployment algorithm with task prediction (RDAP). Based on our paradigm, tasks in the cloud service center are predicted using the two-dimensional time series, and task classification aggregation and delay threshold determination are combined to optimize task resource deployment of edge servers. A task scheduling algorithm with Pareto improvement (TSAP) is also proposed. At the edge servers, the Pareto progressive comparison is conducted in two stages to obtain the tangent point or any intersection point of the two objective curves of user’s quality of service and effect of system service to optimize task scheduling. The experimental results show that for varying user task scales and different Zipf distribution α parameters, combining RDAP and TSAP (RDAP-TSAP) can improve the average user task hit rate. In addition, the average task completion time of users, the overall system service effect, and the total task delay rate of RDAP-TSAP are better than TSAP and the benchmark algorithms for task scheduling.

A multilayer soil approach for seepage process analysis in earthen levees

The analysis of seepage through earthen levees is fundamental to investigate the levee safety condition, since that the seepage phenomenon can often lead to piping causing the collapse of the levee (Saghaee et al., 2012). This work proposes a new approach for identifying the location of the saturation line through the earthen levee by using a multilayer soil approach that assumes the levee body and the levee foundation as two different layers, characterized by using a different hydraulic conductivity parameter. The main purpose is to investigate the difference in the predicted saturation line identified through the proposed method and the one based on the single layer analytical solution of the seepage flow suggested by Marchi (1961). On comparison of the saturation lines provided by two different approaches, the ratio between the river water head and the groundwater thickness or depth increases; allowing the determination of a ratio threshold above which the Marchi equation should no longer be applied. The proposed multilayer (levee and foundation) soil approach is also used to assess the seepage vulnerability of the methodology proposed by Barbetta et al. (2017). The results show that the differences between the seepage vulnerabilities evaluated using the multilayer approach and the single layer method are quite low. Although notably, significant modifications of the seepage probability are observed when the distance between the ground level and the groundwater table changes.

Rethinking our chemical legacy and reclaiming our planet

Rethinking our chemical legacy and reclaiming our planet

Influence of trends on subseasonal temperature prediction skill

AbstractSubseasonal‐to‐seasonal (S2S) predictions have a wide range of applications. Improving forecasts on this time‐scale has therefore become a major effort. To evaluate their performance, these forecasts are routinely compared to a reference that forecasts the climatological distribution at any given time. This distribution is commonly assumed to be stationary over the verification period on time‐scales longer than the seasonal cycle. However, there are prominent deviations from this assumption, especially considering trends associated with climate change. By employing synthetic forecast‐verification pairs, we show that estimates of the probabilistic skill of both continuous and categorical forecasts increase as a function of the variance explained by the trend over the verification period, even when there are errors in the trends simulated by the forecasts. We also show this skill enhancement due to the trend in the ECMWF extended‐range ensemble prediction system. We demonstrate that the effects on the skill in an operational forecast setting are currently strongest in the Tropics. Our results show that care needs to be taken when evaluating forecasts that are subject to non‐stationarity on time‐scales much longer than the forecast verification window. This is especially important for determining the skill of categorical forecasts, where assumptions on the stationarity of the climatology enter both in the reference forecast and in the determination of the category thresholds. The results presented in this study are not exclusive to the S2S time‐scale but have wider implications for forecast verification on seasonal to decadal time‐scales, where the existence of trends can further impact forecast skill.

Determination of Second Lactate Threshold Using Near-infrared Spectroscopy in Elite Cyclists.

The use of near-infrared spectroscopy could be an interesting alternative to other invasive or expensive methods to estimate the second lactate threshold. Our objective was to compare the intensities of the muscle oxygen saturation breakpoint obtained with the Humon Hex and the second lactate threshold in elite cyclists. Ninety cyclists performed a maximal graded exercise test. Blood capillary lactate was obtained at the end of steps and muscle oxygenation was continuously monitored. There were no differences (p>0.05) between muscle oxygen oxygenation breakpoint and second lactate threshold neither in power nor in heart rate, nor when these values were relativized as a percentage of maximal aerobic power or maximum heart rate. There were also no differences when men and women were studied separately. Both methods showed a highly correlation in power (r=0.914), percentage of maximal aerobic power (r=0.752), heart rate (r=0.955), and percentage of maximum heart rate (r=0.903). Bland-Altman resulted in a mean difference of 0.05±0.27 W·kg-1, 0.91±4.93%, 0.63±3.25 bpm, and 0.32±1.69% for power, percentage of maximal aerobic power, heart rate and percentage of maximum heart rate respectively. These findings suggest that Humon may be a non-invasive and low-cost alternative to estimate the second lactate threshold intensity in elite cyclists.

Determination of diagnostic threshold in harmonization and comparison of clinical utility for five major antiphospholipid antibody assays used in Japan.

Anticardiolipin antibodies (aCL) and anti-β2 -glycoprotein I antibodies (aβ2 GPI) are essential in diagnosing antiphospholipid syndrome (APS) according to the international APS guideline. Five commercial assays for aCL and aβ2 GPI are available in Japan, but their test results are quite discordant. For harmonization of diagnosing APS, upper reference limit (URL) and diagnostic accuracy of each assay were evaluated and compared by testing common sets of specimens across all assays. We evaluated two manual and three automated assays for aCL and aβ2 GPI of IgG- and IgM classes. 99%URL (the upper limit of reference interval: as per guideline) together with 97.5%URL were determined by testing sera from 198 to 400 well-defined healthy subjects. Both URLs were compared with the cutoff values, which were determined based on ROC analysis by testing 50 each of plasma specimens from patients with/without APS. Diagnostic accuracy was evaluated as area under curve (AUC) of the ROC curve. A variable degree of discrepancy between URLs and the cutoff values was observed, which was partly attributable to between-year assay variability. 97.5%URLs were set lower and closer to the cutoff values than 99%URLs. For all assays, diagnostic accuracies of both aβ2 GPI-IgG and aCL-IgG were generally high (AUC: 0.84-0.93); whereas those for IgM-class assays were low (AUC: 0.57-0.67), implicating its utility is limited to rare IgG negative APS cases. To ensure harmonized APS diagnosis, the diagnostic thresholds of the five assays were evaluated by common procedures. Contrary to the guideline, 97.5%URL is rather recommended for diagnosing APS, which showed a closer match to the cutoff value.

Effect of washing on quality, breathability performance and reusability of disposable face masks

Disposable face masks are among the personal protective equipment (PPE) that highly contribute to protecting people in the context of the current COVID-19 pandemic. Health authorities recommend wearing a mask as a barrier measure to limit the spread of viral respiratory diseases. During the first waves of the pandemic, besides professional high-quality PPE, decontaminated disposable mask reuse and homemade cloth masks were allowed due to scarcities. This work introduces a simple method based on-time history of the differential pressure, and an easy to use the setup for the testing of different kinds of respiratory protective masks for the purposes of quality control and evaluation of air permeability performance. The standard mask testing method and the new proposed approach were then used to evaluate the effect of machine washing on the widely used type of disposable masks; namely the surgical (medical) face masks. The objective is to determine the number of acceptable washing cycles that this kind of mask can withstand before losing its performance in terms of breathability and airflow resistance. Other quality characteristics such as material (fibres) degradation and hydrophobicity are investigated. Degradation mechanisms due to washing cycles for the different mask constituent layers were studied by scanning electron microscopy (SEM) imaging. This work is an attempt to contribute to the determination of the reusability threshold of general-purpose disposable surgical type face masks thereby contributing to the reduction of environmental concerns. Results in terms of the studied above parameters suggest limiting the reuse of standard type surgical masks to only one machine washing cycle.

Validity of detrended fluctuation analysis of heart rate variability to determine intensity thresholds in elite cyclists

ABSTRACT Background: The evaluation of performance in endurance athletes and the subsequent individualisation of training is based on the determination of individual physiological thresholds during incremental tests. Gas exchange or blood lactate analysis are usually implemented for this purpose, but these methodologies are expensive and invasive. The short-term scaling exponent alpha 1 of detrended Fluctuation Analysis (DFA-α1) of the Heart Rate Variability (HRV) has been proposed as a non-invasive methodology to detect intensity thresholds. Purpose: The aim of this study is to analyse the validity of DFA-α1 HRV analysis to determine the individual training thresholds in elite cyclists and to compare them against the lactate thresholds. Methodology: 38 male elite cyclists performed a graded exercise test to determine their individual thresholds. HRV and blood lactate were monitored during the test. The first (LT1 and DFA-α1-0.75, for lactate and HRV, respectively) and second (LT2 and DFA-α1-0.5, for lactate and HRV, respectively) training intensity thresholds were calculated. Then, these points were matched to their respective power output (PO) and heart rate (HR). Results: There were no significant differences (p > 0.05) between the DFA-α1-0.75 and LT1 with significant positive correlations in PO (r = 0.85) and HR (r = 0.66). The DFA-α1-0.5 was different against LT2 in PO (p = 0.04) and HR (p = 0.02), but it showed significant positive correlation in PO (r = 0.93) and HR (r = 0.71). Conclusions: The DFA1-a-0.75 can be used to estimate LT1 non-invasively in elite cyclists. Further research should explore the validity of DFA-α1-0.5. Highlights The power and heart rate values derived from the DFA-α1-0.75 threshold showed high levels of validity and agreement when they were compared against the first lactate threshold. The second lactate threshold and the DFA-α1-0.5 were different (p < 0.05) but showed high levels of correlation. The detrended fluctuation analysis is a valid method to estimate the first lactate threshold and more studies are needed to verify its validity with the second lactate threshold.

Comparison of Mitral Regurgitant Volume Assessment between Proximal Flow Convergence and Volumetric Methods in Patients with Significant Primary Mitral Regurgitation: An Echocardiographic and Cardiac Magnetic Resonance Imaging Study

Discrepancies have been observed between transthoracic echocardiography (TTE) and cardiac magnetic resonance imaging (CMR) severity grading in primary mitral regurgitation (MR). We sought to compare mitral regurgitant volume (RVol) determined by the TTE proximal flow convergence (proximal isovelocity surface area [PISA]) method and by volumetric methods (TTE and CMR) and to study the relationship between left ventricle (LV) size and RVol obtained by either the PISA or volumetric methods. Two centers prospectively recruited 188 patients with at least moderate to severe primary MR due to prolapse in sinus rhythm who underwent TTE and CMR examinations. Regurgitant volume was estimated by either PISA (PISA-RVol) or volumetric methods (LV total stroke volume-systolic aortic forward outflow volume) using either CMR (CMR-RVol) or TTE (TTE-RVol). The PISA-RVol was weakly correlated with CMR-RVol and TTE-RVol (r=0.29 and 0.30, respectively; P<.001 for both). On multivariable analysis, smaller CMR-left ventricular end-diastolic volume (LVEDV) and absence of mitral annular disjunction independently correlated with increased magnitude of RVol difference between PISA and volumetric methods. While PISA-RVol and LVEDV were unrelated, CMR-RVol and TTE-RVol moderately correlated with LVEDV (r=0.66 and 0.68, respectively; P<.001 for both). In contrast, LVEDV and regurgitant fraction (RVol/LVtotal stroke volume), assessed with either TTE or CMR, were poorly correlated (r=0.17, P=.02; and r=0.12, P=.10, respectively). Mitral RVol values estimated by PISA and volumetric methods are not directly comparable. The expected proportional relationship between volumetric RVol and LV size, which was not observed with PISA-RVol, suggests that PISA-RVol would be inaccurate. Given that RVol assessed with volumetric methods depends on LV size, determination of a unique RVol threshold for severe MR is challenging. In contrast to RVol, calculating regurgitant fraction by volumetric methods allows the quantification of MR severity independently from LV size.

An improved quantification method for characterisation of clay microstructure using SEM

Clay is a material widely used in environmental geotechnics. Quantification of clay microstructure properties using scanning electron microscopy (SEM) images is intuitively the simplest way, but the challenges remain in extracting more credible quantified micro-parameters that can represent the holistic macroscopic properties of clay from SEM images and with higher efficiency. In this paper, an improved quantification method is proposed to deal with this issue. The influence of different milling and drying methods on quantification results was analysed to improve reliability and efficiency. The A–K threshold determination method (A–K method) was proposed to calculate the optimal threshold in image processing. Also, the interval estimation method was introduced to obtain the optimal magnification and number of images. Then, this quantification method was applied to Hangzhou clay. The results show that anisotropy in the clay microstructure should be considered when choosing the observed surface. Moreover, there is no significant difference in micro-parameters between liquid nitrogen frozen-vacuum drying and critical point drying. A comparison among the A–K method, artificial method and theoretical methods that can determine thresholds shows that the proposed A–K method combines the advantages of all methods. The optimal magnification and number of images can be determined by mathematical theory, which also improves reliability and efficiency.

Evaluation and Determination of the Salt Tolerance Threshold of Some Fenugreek (Trigonella foenum-graecum) Ecotypes at Seedling emergence Stage

Evaluation and Determination of the Salt Tolerance Threshold of Some Fenugreek (Trigonella foenum-graecum) Ecotypes at Seedling emergence Stage