Due to the wide use of gearmotor systems in industry, many diagnostic techniques have been developed/employed to prevent their failures. An insufficient lubrication of gearboxes of these machines could shorten their life and lead to catastrophic failures and losses, making it important to ensure a required lubrication level. For the first time in worldwide terms, this paper proposed to diagnose a lack of gearbox oil lubrication using motor current signature analysis (MCSA). This study proposed, investigated, and experimentally validated two new technologies to diagnose a lack of lubrication of gear motor systems based on MCSA. Two new diagnostic features were extracted from the current signals of a three-phase induction motor. The effectiveness of the proposed technologies was evaluated for different gear lubrication levels and was compared for three phases of motor current signals and for a case of averaging the proposed diagnostic features over three phases. The results confirmed a high effectiveness of the proposed technologies for diagnosing a lack of oil lubrication in gearmotor systems. Other contributions were as follows: (i) it was shown for the first time in worldwide terms, that the motor current nonlinearity level increases with the reduction of the sgearbox oil level; (ii) novel experimental validations of the proposed two diagnostic technologies via comprehensive experimental trials (iii) novel experimental comparisons of the diagnosis effectiveness of the proposed two diagnostic technologies. Gearboxes are a key mechanical component widely used in various industries, such as energy (wind turbines), automotive and aerospace, etc. Lubrication is a crucial factor in the efficiency and operating lifetime of rotating components and improper lubrication could cause their faults/failures. Therefore, it is important to have proper levels of lubricants in gearboxes to insure the higher productivity, uptime, and efficiency of machines.In most typical applications, gearmotor systems are exposed to high mechanical loads and wide temperature ranges which make the decrease of their lubrication oil levels common, either due to transformation in the oil composition  or due to sudden oil leaks that can be caused by loose plugs or crankcase perforation. Thus, it is important to have an on-line technique which can monitor the oil levels inside gearmotor systems.On-line sensors that are directly installed in systems and continuously monitor oil conditions may offer a solution to these kinds of problems. Different approaches have been performed for this purpose, including impedance spectroscopy , oil debMotor current signature analysis (MCSA), which is a relatively new approach in condition-based maintenance (CBM), has been proven to be a reliable condition monitoring technique and has been the focus of many researchers in past years. The main reason is that induction motors (IM) are used in many types of machinery as they are easy to manufacture, cost-effective, reliable, and efficient. In addition, collecting stator current data is much simpler than other diagnostic techniques because no sensor should be mounted directly on the machinery and the price of the required equipment is lower.MCSA is becoming a commonly used approach since it can be used to detect different types of faults in various components such as air-gap irregularities ,6, brokeThe first category is the Park’s Vector Approach (PVA), which is a traditional method of MCSA ,17. ThisThe second category analyses the spectral components in the frequency domain representation of stator current signals. Ref.  is one oRef.  proposesThere are no works in the literature which have taken advantage of motor current signals analysis to diagnose a lack of oil lubrication in gearboxes. Ref.  detects Despite all the promotive results for MCSA in machinery defect diagnosis, there are no technologies in the existing literature and on the market for diagnosing a lack of gear oil lubrication via MCSA.This paper proposed and investigated, for the first time in worldwide terms, two novel powerful diagnostic technologies for oil level diagnosis in gearmotor systems based on MCSA. Two diagnostic features were proposed and applied for the first time in this study to diagnose oil level in a gearmotor, based on MCSA. The effectiveness of the proposed technologies was evaluated using the current signals, recorded for different oil levels in a three-phase induction gearmotor used to drive a conveyor belt system for a baggage handling at airports. To investigate the effect of grid fluctuations, two sets of data, corresponding to two different measurement days (Day 1 and Day 2), were considered as a reference for the standard oil level condition. The study separately used three phases of motor current signals and diagnostic features, which were then averaged over three phases.The main difference between the approaches/technologies proposed in this paper, and the technology in Ref.  is that The main novelty of the paper is a novel proposition (by L. Gelman) for the first time in worldwide terms, for performing the diagnosis, via MCSA, of a lack of oil lubrication of gearboxes coupled to induction motors.The proposed novel diagnostic technology/feature, which employs the power in a frequency range around the fundamental harmonic and the higher harmonics of the supply frequency;It was shown for the first time in worldwide terms, that the energy consumption of a motor changes with the reduction of the gearbox oil level;The proposed novel diagnostic technology/feature, which employed spectral magnitudes of the fundamental harmonic of the supply frequency, normalized by the average value of the spectral magnitudes of higher harmonics of the supply frequency in the spectrum of the current signal;It was shown for the first time in worldwide terms, that motor current non-linearity level increases with the reduction of gearbox oil levels;Novel experimental validations of the proposed two diagnostic technologies were presented via comprehensive experimental trials;Novel experimental comparisons of the diagnosis effectiveness of the proposed two diagnostic technologies were presented.Other novelties presented in this paper included:develop and investigate for the first time in worldwide terms two motor current-based diagnosis technologies for a lack of oil lubrication diagnosis in gearboxes, connected to induction motors;perform an experimental validation of the proposed technologies in diagnosing a lack of oil lubrication in gearboxes via comprehensive experimental trials;perform a comparison between the proposed diagnostic technologies;develop a strategy for diagnosing the lack of oil lubrication in gearboxes based on the obtained results.The objectives of this paper were to:This paper is structured as follows. In The objective of this section is to propose two novel diagnostic technologies for a lack of oil lubrication in gearmotor systems based on motor current signature analysis. The proposition of using the motor current signals for such diagnosis is based on the assumption that a lack of oil lubrication of a gearbox converts into changes of the electrical energy consumption of the motor coupled to it.A lack of gearbox oil lubrication has an influence on motor mechanical load. Electrical motors, subjected to a load variation, tend to adapt their produced electrical torque to compensate for the variation of the mechanical load, which results in a variation of their electrical energy consumption. Therefore, a method of diagnosing a lack of gear oil lubrication based on the power spectral density of supply harmonics in the gearmotor current signals was proposed.The main idea of the proposed technology 1 is that a lack of gear oil lubrication at an initial oil reduction stage creates less motor load, and therefore reduces motor electrical energy consumption: i.e., less motor power is r0equired to circulate a reduced oil level inside a gearbox. This idea is justifiable provided that there is still enough oil to lubricate gear teeth and, therefore, there is still a liquid friction between gear teeth. If a solid–solid friction between gear teeth occurs as a result of removing more oil , a motor energy consumption starts increasing.If other factors will be affecting motor energy consumption, then more diagnostic features should be employed that will effectively differentiate a lack of gear oil lubrication from other factors.The proposed technology 1 is based on Feature 1, which is the power in a frequency bandwidth around the harmonics of the supply frequency, as follows:The main idea of the proposed technology 2 is the same as for technology 1: i.e,. a lack of gear oil lubrication creates less motor load, and, therefore, reduces motor electrical energy consumption. However, taking into account possible intensity fluctuations of the fundamental supply harmonic, it is proposed for technology 2 to essentially reduce the influence of these fluctuations by normalizing the intensity of the fundamental supply harmonic by the intensities of the higher supply harmonics. The proposed normalized feature characterizes a motor current level of non-linearity. Therefore, diagnostic technology 2, based on Feature 2 and characterizing the motor current non-linearity level, is proposed for the first time worldwide to diagnose a lack of gear oil lubrication in gearmotor systems.th harmonic of the supply frequency The proposed Feature 2 is the magnitude of the fundamental harmonic of the supply frequency, normalized by the average magnitude of the higher harmonics of the supply frequency in the spectrum of the current signal, as follows:ransform ,30 of thThe instantaneous frequency (IF) of the supply grid is estimated from the current signals, based on the Hilbert transform phase demodulation approach, Ref. ;The magnitudes of the fundamental harmonic and the higher harmonics of the supply frequency are estimated based on the short time Chirp Fourier transform, Refs. ,30, of tThe feature is estimated based on the magnitudes of the supply frequency harmonics.The following steps are needed for estimation of Feature 2:The time-frequency technique, the short time chirp-Fourier transform , is usedFeature 2 can be physically interpreted as a factor of non-linearity of the motor current signal. An increase of the magnitudes of the higher harmonics of the supply frequency at a constant or decreased magnitude of the fundamental harmonic of the supply frequency  will result in a decrease in the value of the feature.The machinery under investigation is a conveyor belt system for a baggage handling at airports. A conveyor is driven by a gearmotor type Simens-JKE2104, consisting in a two stages gearbox, coupled to a three-phase AC induction motor a. The fiThe experiments are carried out under no-load and under 20 kg load on the conveyor. The load consists of a series of rollers contained within a frame placed on the conveyor belt, as shown in The data acquisition system and a schematic of that system are shown in The captured analogue current signals from each phase are passed through anti-aliasing filters of the KEMO DR 1600 type to avoid frequency aliasing during data sampling. The KEMO filter series is a small compact signal filter unit with switchable pre-filter input gain, wide range power input , and a configurable input stage. The nominal attenuation rate of these KEMO filters in the transition band is 100 dB per octave, their bandwidth is 500 kHz, and their total harmonic distortion (THD) is lower than 0.003%. The KEMO filter also offers adjustable input gain in 1, 2, 5 steps to ×1000 (+60 dB), allowing the adjustment of the amplitude of the measured current signals to meet the input voltage range of the utilized data acquisition card. In the present study, the cut-off frequency, and the gain of the KEMO filters, are set to 8 kHz and ×20, respectively. The choice of 8 kHz cut-off frequency for the KEMO filters is because the frequency bandwidth of the selected current sensors is 1.5 kHz at level −1 dB, but 8 kHz at level −6 dB; therefore, 8 kHz cut-off frequency is selected in order not to miss an important current information. The gain is chosen considering the input voltage range of the acquisition card.After limiting their bandwidth and choosing their appropriate gain, the motor current signals (output of the KEMO filters) are sampled at 51,200 Hz and recorded using a WebDAQ 504 data acquisition card. The sampling rate of 51,200 Hz is chosen since it is the maximum sampling rate for the WebDAQ 504 card. This maximum sampling rate ensures a more accurate estimation of the instantaneous frequency (IF) of the supply frequency, since at a higher sampling rate accuracy of frequency estimation is higher . The WebThe current signals of the motor are measured for different levels of oil in the gearbox. The first measurements are carried out under no-load conditions, where 10 signals of 20 min duration each are acquired using a brand new gearmotor containing 1600 mL of oil . Then, the load is set to 20 kg and signals are acquired for the standard oil level and when 120 mL, 260 mL, 280 mL and 490 mL of oil are removed from the gearbox. For each oil level (including the standard oil level), 10 signals of 20 min duration, acquired at the same acquisition date, are considered. For the case of the standard level of oil, 6 additional signals of 20 min duration, corresponding to a different acquisition date, are also considered. From now on, the standard oil level data acquired at two different measurement dates (under a 20 kg load) will be called Day 1 data and Day 2 data respectively.In this section, the proposed diagnostic technologies, based on Feature 1 and Feature 2, are experimentally validated for diagnosis of a lack of gearbox oil lubrication. Results will be presented separately for diagnostic technology, based on Feature 1 and diagnostic technology, based on Feature 2 and comparisons will be made between the results of the two proposed technologies.Feature 1 is estimated for a 1 Hz frequency band B, Equation (1), around the first and the third harmonics of the supply frequency. The selected frequency band is large enough to include the small variations of the supply frequency over time; however, it is not too large in order to isolate the supply harmonics from other characteristic spectral components in current spectrum.For the multiple continuously acquired signals for 20 min and the different oil levels, every signal is divided into 50 s time segments with an overlap of 75% and then Feature 1 is estimated for each segment, while the power spectral density is estimated via a frequency resolution of 0.1 Hz. This process is repeated for three phases of current data. Frequency approach .After estimating Feature 1 for the standard oil level (Day 1), 120 mL, 260 mL, 280 mL, and 490 mL of removed oil cases, the estimates of the probability density functions of feature values for each case are evaluated via the histograms. To consider the influence of an oil removal on three phases simultaneously, it is proposed here to employ average of Feature 1 for three phases. The results are similar to the other phases and there is a clear distinction between the 4 oil removal cases and the case in which the gearbox is working with the standard level of oil. The results show that a motor energy consumption reduces when oil is removed. The highest level of Feature 1 occurs when the gearbox is working with the standard oil level (Day 1) and for all other cases of oil removal, lower quantities are achieved for Feature 1. Hence, the energy level of the first harmonic of the supply frequency has the potential for monitoring/diagnosis of the oil level in gearboxes.These histograms clearly highlight the main idea of technology 1, that a lack of gear oil lubrication at initial oil removal stage creates less motor load, and therefore reduces motor electrical energy consumption: i.e., less motor power is required to circulate reduced oil inside the gearbox, and therefore less average power is in a frequency range around the fundamental harmonic of the supply frequency .To estimate the total probability of correct diagnosis (TPOCD), which is the ratio of correctly diagnosed cases to the total number of cases for each two data sets presented in the histograms, firstly, a threshold should be defined. Afterwards, if the value of Feature 1 for an oil-removed case is lower than the defined threshold, then this oil-removed case is correctly diagnosed. Conversely, the standard oil case is correctly diagnosed once its Feature 1 value is higher than the defined threshold.For one-dimensional Feature 1, the estimates of the probability density functions of this feature  are unimTo estimate a threshold for each pair of histograms of Feature 1, assuming, that Feature 1 has the normal distribution, the normal  probability density functions (PDF) of the Feature 1 are estimated for every oil level. Next, an intersection point of two PDFs is utilized as the threshold value. The histograms, PDFs and the decision-making thresholds are depicted in The TPOCDs, using the above-mentioned decision-making procedure, are given in The Fisher Criterion (FC) is defined as:The FC is an indicator of the level of separation between two classes of one-dimensional data. Thus, it is employed to quantify a separation between histograms of the standard oil level and of the removed oil cases.The FC are given in The TPOCD and the FC results reveal that at the early stage of oil removal, namely in the 120 mL and 260 mL cases, the separation between the standard oil level and the removed oil cases are higher, as a higher TPOCD and the FC are obtained. While the level of removed oil increases to 280 mL and 490 mL, the values of Feature 1 for these cases get closer to the standard oil level case, as a result, the TPOCD and the FC decreases. This is explained by the fact that, when a small amount of oil is removed at the beginning of the test, resisting force against the flow of the oil decreases; therefore, less motor power is required to circulate oil inside the gearbox resulting in reduction of Feature 1 values.Further increase in the power usage of the electric motor by removing more oil, which leads to a lower TPOCD and the FC, is due to an improper lubrication of the gears. This is because by removing more oil, part of the liquid friction is transferred to a solid–solid friction between gear teeth; thus, more motor power is required due to solid–solid gear tooth friction.To further investigate the effect of oil removal on the first harmonic of the supply frequency, standard oil level data is considered for a different day of the experiment (Day 2). Similar to the previous standard oil level data (Day 1), the values of Feature 1 for 120 mL, 260 mL, 280 mL and 490 mL are compared to the standard oil case (Day 2) for three phases. The histograms are depicted in the The TPOCD decreases in comparison to the ones. obtained for Day 1, though, in most cases, the two distributions are still separable. The highest TPOCD is achieved by using current signals of phase 3 among the three phases; the average of Feature 1 for all phases also provides a high TPOCD. The FC is given in Overall, while the average of Feature 1 over three phases does not always offer the highest TPOCD for each condition, it is the most reliable indicator as it integrates all information of three phases, related to oil removal, and, therefore, high TPOCDs are achieved even when one of the phases does not provide enough information to properly distinguish between the standard oil level case and the removed oil cases. For instance, for Day 2 and 260 mL of the removed oil case, the TPOCD of 99% is obtained for the average feature, which is higher, than the 52% and 79% of the TPOCD, achieved for phases 1 and 2, respectively. Considering the average feature, the highest TPOCD is obtained for the 260 mL case and, after that, 120 mL, 280 mL, and 490 mL cases provide less level of the TPOCD.The results show that, while the energy level of the first harmonic of the supply frequency has some potential to diagnose different levels of oil inside the gearbox, it could also vary for reasons other than the oil level; as it is shown, Feature 1 values change while considering standard oil level data acquired in two different days. To show this variation, Feature 1 for the standard oil level data (Day 1 + Day 2) are compared to the removed oil cases. The histograms are depicted in The first harmonic of the supply frequency is by far the strongest harmonic. The recorded current signals also include other harmonics of the supply frequency, but the magnitudes of the even harmonics are negligible. As was mentioned, Feature 1, estimated for the first harmonic, shows some variations when the data recorded for different days are used. In the following section, the TPOCD and the FC will be estimated for the third harmonic of the supply frequency to investigate diagnosis information it contains regarding the removed oil levels.Considering Day 1 and Day 2 data, the TPOCDs for different levels of the removed oil and three phases for the third harmonic of the supply frequency are displayed in To validate the diagnosis effectiveness of technology 2, effectiveness is estimated from the current signals, acquired for the different oil level cases. The acquired 20-min current signals are divided into 100 s non-overlapping segments and Feature 2 is estimated for each segment following the steps explained in Following estimation of Feature 2 from the current signals corresponding respectively to the standard oil level (Day 1) and the 120 mL, 260 mL, 280 mL, and 490 mL of oil removal cases, estimates of the probability density functions of feature values are evaluated and compared, using histograms. From the histograms, it can be noticed that Feature 2 values are decreasing  as oil is removed. However, at 120 mL level of removal, overlaps are observed between histograms for all phases. The overlaps become less frequent in the case of 260 mL of the removed oil for histograms of Feature 2 for phase 1 and phase 2 and no overlap is seen for the histograms of phase 3. For the cases of 280 mL and 490 mL of the removed oil, a complete separation is observed with respect to the standard oil level (Day 1) in all appropriate histograms. It means, that for 280 mL and 490 mL of the removed oil, the estimates of the TPOCD are 100% for all phases. Overall, Feature 2 for phase 3 shows better separation compared to Feature 2 for phase 1 and phase 2.To make technology 2 more stable (robust) in conditions of possible variations of phase currents, it is proposed here to average values of Feature 2 over three phases.decreasing magnitude of the fundamental supply frequency harmonic;increasing magnitudes of the higher supply frequency harmonics;increasing motor current level of non-linearity .These histograms clearly highlight the main idea of technology 2, that a lack of gear oil lubrication at initial oil removal stage creates less motor load, and, therefore, reduces motor electrical energy consumption: i.e., less motor power is required to circulate reduced oil inside the gearbox and, therefore, it is:For one-dimensional Feature 2, the estimates of the probability density functions of this feature  are alsoFor the case of 260 mL of the removed oil, Feature 2 of phase 3 offers a better TPOCD than those of phase 1 and phase 2. In contrast, for the case of 120 mL of the removed oil, Feature 2 of phases 1 and 2 offers better TPOCD than those of phase 3 . Thus, Feature 2, estimated from phases 1 and 2, is more effective in the diagnosis of early stage of oil removal and Feature 2 estimated from phase 3, is becoming more effective as the amount of the removed oil increases. Averaging of Feature 2 across the three phases provides reasonable TPOCD for all levels of oil removal, but the TPOCD of phase 3 are still the best.Altogether, feature averaging over the three phases could be a useful indicator since it provides good results even if Feature 2 for one of the phases  provides not sufficient level of diagnosis effectiveness, which can be explained by a high correlation between features corresponding to the different phases.To examine the effect of the current grid fluctuation on the performance of technology 2, the current signals, related to the standard oil level and collected on a different day of measurement (Day 2), are considered. It can be noticed from all histograms, that for Day 2, Feature 2 values are also decreasing  as oil is removed. The TPOCD and the FC for the considered oil removals for Day 2 are presented in When using signals of Day 2 as a reference, an overlap is observed with data, corresponding to 120 mL oil removal, and a low TPOCD and the FC are obtained. Feature values tend to increase as 260 mL of oil is removed, but with an overlap for the data of Day 2. The feature overlap is greater for phase 1, and less for phase 3, making Feature 2 of phase 3 the most sensitive in the case of 260 mL of the removed oil. For the cases of 280 mL and 490 mL of the removed oil, a complete separation is observed with respect to data of Day 2 for all phases (meaning a 100% TPOCD), and Feature 2 of phase 3 offers the best separation between distributions .The results, obtained by averaging the three phases (averaged TPOCD and averaged FC), are better than those obtained when using Feature 2 for phase 1 and phase 2 separately, except for the case of 120 mL of the removed oil, where Feature 2 of phase 2 offers a slightly better TPOCD and the FC. On the contrary, Feature 2 for phase 3 shows better TPOCD and the FC than Feature 1, averaged over three phases for the 260 mL, 280 mL and 490 mL of the removed oil cases and lower performance in the case of 120 mL of the removed oil.To evaluate the overall performance of technology 2 in diagnosis of a lack of gearbox oil lubrication, diagnosis is also performed using data of (Day1 + Day 2) as a reference for the standard oil level condition. When using signals of (Day 1 + Day 2) as a reference, a low TPOCD and the FC are obtained in the case of 120 mL of removed oil for three phases and when averaging over all phases. This is reflected for the histograms by a complete overlap between features for the standard oil condition (Day 1 + Day 2) and features for 120 mL of the removed oil. When 260 mL of oil is removed, Feature 2 of phase 3 offers the best TPOCD (98%), followed by Feature 2 of phase 2 (85%), then Feature 2 of phase 1 offers a poor diagnosis (68%), and the TPOCD of 92% is obtained for averaging Feature 2 across the three phases. Furthermore, a very good match is observed between the FC values and the degree of overlap  between the histograms, corresponding to the different phases, i.e., the lower the FC values, the higher the overlap, observed between histograms.When 280 mL and 490 mL of oil is removed, Feature 2 for all phases and average of Feature 2 for all phases offer a high diagnosis effectiveness, i.e., all TPOCDs are 100%, except for phase 1, 490 mL; however, the TPOCD is also high, at 97%, for the last case.Using Day 1 or Day 2 data separately, a 100% TPOCD is achieved for 280 mL and 490 mL of the removed oil from those of Day 1 and Day 2 signals for all phases. Feature 2 of phase 3 proved to be the most sensitive in the case 280 mL and 490 mL of the removed oil as it offers a better separation between the distributions compared to Feature 2 of phase 1 and phase 2.While results of feature averaging across the three phases are better than results for Feature 2 for phase 1 and phase 2 for 260 mL, 280 mL and 490 mL the removed oil cases, results for Feature 2 for phase 3 are better, than results for average feature over three phases for most of oil removal cases, except for the case of 120 mL of the removed oil.As explained in From Based on the performed experimental tests, technologies 1 and 2 have proven to be effective in diagnosing a lack of oil lubrication in gearboxes, but with a varying performance depending on the amounts of the removed oil. To obtain a clear understanding of which technology offers better diagnostic performance on which amount of the removed oil, a comparison between their TPOCDs and their FCs in diagnosis of all the considered oil removals is performed for signals from the three phases.When the amount of the removed oil reached 280 mL, the TPOCD of technology 1 still exhibits a high effectiveness. Technology 2 provides a 100% TPOCD for all cases. Technology 2 provides better TPOCD, compared to technology 1, in the case of 490 mL of the removed oil; Overall, technology 2 provides better diagnosis results, than technology 1, for the case of 490 mL of the removed oil, making technology 2 the most sensitive in the case of essential oil removal.A second comparison between technology 1 and technology 2 is performed using data of Day 2 as a reference for the standard oil level condition. Although the TPOCD of technology 2 is better than of technology 1 when considering signals from phase 1 and phase 2, technology 1 provides a better TPOCD, than technology 2, if considering phase 3 and if averaging features across all phases, making diagnosis results of technology 1 and technology 2 comparable in the case of a 260 mL of the removed oil. In cases of 280 mL and 490 mL of the removed oil, technology 2 provides higher TPOCD and higher FC than technology 1 for all cases. While the TPOCD of technology 2 is almost 100%, technology 1 presents a low TPOCD, especially, in the case of 490 mL of the removed oil, making technology 2 the most sensitive in the case of an essential oil removal.Altogether, technology 1 provided better diagnosis results for the case of 120 mL of the removed oil and technology 2 provided better diagnosis results for 280 mL and 490 mL of the removed oil, with comparable effective diagnosis results for both technologies for 260 mL of the removed oil.Based on these results, technology 1 is suggested for diagnosis of a reduction in gearbox oil level in relative oil reduction range (8–16%) and technology 2 is suggested for diagnosis of reduction in gearbox oil level in relative oil reduction range (16–31%). Relative oil reduction range (20–30%) is detrimental to the gearbox and requires urgent maintenance intervention.It should be also noticed that technology 2 is less affected by the current grid fluctuations for three phases of current signals. In fact, while the overall decrease of Feature 1 for the Day 2 data compared to Day 1 data reached 15.2%, the overall decrease of Feature 2 for Day 2 data compared to Day 1 data did not exceed 6%. This could also be deduced from the diagnostic results (the TPOCD and the FC) which are, referring to The difference between dependencies of technologies 1 and 2 on grid fluctuations could be explained by the fact, that Feature 2 is normalized while Feature 1 is not normalized. Indeed, the fluctuations of the current grid system are likely to influence the fundamental harmonic as well as the higher harmonics of the supply frequency. Thus, the normalization of the fundamental harmonic of the supply frequency by the higher harmonics of the supply frequency, adopted for Feature 2, provides less dependency of Feature 2 on current grid fluctuations, which is not a case for Feature 1, since it is unnormalized and it only considers the power of the harmonics of the supply frequency. Thus, for an application, in which current grid is fluctuating , it is recommended to use technology 2 as a diagnostic technique for a lack of oil lubrication, rather than technology 1, to minimize the effect of current grid fluctuations on diagnostic effectiveness.Another important advantage of the normalization, adopted for Feature 2, compared to Feature 1, is related to the case of a change in operating load of a conveyor for baggage handling, that is driven by a gearmotor. It can be noticed from In contrast, it can be seen from Therefore, technology 1 could not be effectively used for a gear lack of oil lubrication diagnosis in conditions of essential current fluctuations in a grid system and of an essential variation of a conveyor operating load. For instance, Feature 1 for Day 1 and Day 2 of the experiment, which have the same standard level of oil, has different distributions, i.e., Feature 1 of Day 1 has higher values than Feature 1 of Day 2, and based on the approach, proposed in this paper, Day 2 should have a lower level of oil in gearbox compared to Day 1, which is not the case.For the first time in worldwide terms, a method for performing the diagnosis of a lack of oil lubrication in gearboxes coupled to induction motors, via motor current signature analysis (MCSA) was proposed;Two new diagnostic technologies for a lack of oil lubrication in gearboxes, based on MCSA, were proposed, investigated and experimentally validated;Comprehensive experimental trials were performed for validation of the proposed two technologies. Three-phase motor current data of an AC induction motor driving a conveyor belt system (for baggage handling at airports) via a gearbox were recorded, respectively, for the standard oil level in the gearbox and for conditions in which specific amounts of oil are removed from the gearbox;It was proposed that the gearbox oil level has an influence on the energy consumed by a motor. Thus, the power in a frequency bandwidth around harmonics of the supply frequency was proposed as diagnostic feature (Feature 1) for technology 1.the power level of the first harmonic of the supply frequency is the most beneficial diagnostic feature as a higher TPOCD and the FC are obtained for this harmonic compared to the third harmonic of the supply frequency;the power of the supply frequency harmonics changes as type of gear friction varies in the gearbox. When lower levels of oils are removed, there is still enough oil to lubricate gears via a liquid friction between gear teeth; as a result, a lower power is required to circulate oil inside a gearbox and, therefore, Feature 1 value decreases. When the solid–solid friction between gear teeth occurs as a result of removing more oil, a motor energy consumption starts increasing and Feature 1 value starts increasing as well;technology 1 was shown to be sensitive/effective to the following oil removals: 120 mL  and 260 mL ;while using datasets corresponding to different days of experimental trials and different conveyor loads with a standard oil level, Feature 1 was shown to be affected by current fluctuations of the grid system and conveyor load variations.it was shown that technology 1 could provide essentially different TPOCDs of a lack of gearbox oil lubrication for different current phases; therefore, it is recommended to employ three phases for diagnosis by technology 1;Feature 1, averaged over the three phases, was proposed as a useful diagnostic feature, since it provides effective results even if one of the phases does not provide a sufficient level of diagnosis effectiveness.The experimental estimates of the probability density functions of Feature 1 values for the standard oil level and for the removed oil cases are evaluated and compared and the total probabilities of correct diagnosis (TPOCD) and the Fisher criteria (FC), based on these estimates, were also evaluated and compared. The study was carried out separately for the three phases of motor current signals and for the case of averaging Feature 1 over the three phases. The results showed that:It was proposed, for the first time in worldwide terms, that te non-linearity of the motor current changes due to a reduction of oil levels in gearboxes. Therefore, technology 2 was proposed, based on diagnostic Feature 2, for the diagnosis of a lack of gearbox oil lubrication. Feature 2 employs spectral magnitude of the fundamental harmonic of the supply frequency, normalized by the average value of the spectral magnitudes of higher harmonics of the supply frequency in the spectrum of the current signal and characterizes non-linearity of the motor current.non-linearity of the motor current increases with increase of an amount of the removed oil;technology 2 was shown to be sensitive/effective to the following oil removals: 260 mL , 280 mL  and 490 mL .while using datasets corresponding to different days of experimental trials and to different conveyor loads with standard oil levels, Feature 2 was shown to be almost unaffected by current fluctuations of the grid system and conveyor load variations.it was shown that technology 2 could provide essentially different TPOCDs of a lack of gearbox oil lubrication for different current phases; therefore, it is recommended to employ three phases for diagnosis by technology 2.Feature 2, averaged over the three phases, was proposed as a useful diagnostic feature, since it provided effective results even if one of the phases does not provide a sufficient level of diagnosis effectiveness.It was shown that the increase in non-linearity of the motor current signals due to increase of oil removal results from both increase the magnitudes of the higher harmonics of the supply frequency and decrease of the magnitude of the fundamental harmonic of the supply frequency due to increase of oil removal.The experimental estimates of the probability density functions of Feature 2 values for the standard oil level and for the removed oil cases were evaluated and compared and the TPOCDs and the FCs, based on these estimates, were also evaluated and compared. The study was carried out separately for the three phases of motor current signals and for the case of averaging Feature 2 over the three phases. The results showed that:diagnostic Feature 1 of technology 1 is more affected by current fluctuations in a grid system and by variation of gearbox operating load compared to Feature 2 of technology 2, because Feature 1 is unnormalized. Therefore, technology 1 is recommended for use in conditions of no- to low-current fluctuations of a grid system and of no- to low-variations of a gearbox load to ensure a reliable diagnosis and to avoid false alarms;diagnostic Feature 2 is less affected by current fluctuations in a grid system and by variation of gearbox operating load compared to Feature 1, because Feature 2 is normalized. Therefore, technology 2 is recommended to use in conditions of medium to high current fluctuations of a grid system and of medium to high variations of a gearbox load to ensure a reliable diagnosis and to avoid false alarms;technology 1 has shown its ability for diagnosing a lack of gear oil lubrication with more sensitivity to training data, compared to technology 2.Novel comparisons are made between the two proposed technologies. The following statements were concluded:


To investigate the correlation between the volume of the radical cystectomy and the U-shaped ileal neobladder The clinical data of patients undergoing in orthotopic U-shaped neobladder in our hospital were retrospectively analyzed. They were divided into two groups according to the length of the retained ileum. Group 1: The length of the ileum was 25-35cm (including 35cm), and the second group: the length of the ileum was 35-45cm. The basic information, cushion usage, urodynamic examination and complications of the two groups were obtained.A total of 88 patients were included in the study, including 33 in the first group and 55 in the second group. There was no statistical difference in general data, lymph node collection, lymph node positive rate, positive margin rate, postoperative pathological stage, pathological grade, pathological type, intraoperative blood loss, blood transfusion, postoperative hospital stay, and complications between the two groups of patients. significance. Although the usage of urine pads in group 1 was more than that in group 2 in the short term after operation (P<0.05), it started from the third year after operation. Patients in group 1 used less cushion than group 2 (P<0.05). Urodynamic examination was performed on the patients, and the bladder function of group 1 maintained satisfactory time longer than that of group 2. The total number of deaths in the two groups was 12 and 23, respectively. The 5-year overall survival (OS) rate of group 1 was 53.60%, and the 5-year overall survival rate of group 2 was 52.9%.A new bladder formed by cutting the ileum with a length of 25-35 cm (including 35cm) has a longer time to maintain good bladder function than cutting the ileum with a length of 35-45 cm to produce a new bladder. Currently, urinary reconstruction is divided into two categories: incontinence diversions, including ileal conduit (Bricker) diversion, and continental diversions, such as skin reservoirs and orthotopic neobladder connected to the urethra . In orthThis study reviewed 88 cases of locally advanced bladder cancer (cT2-3) admitted in our hospital from May 2014 to May 2019. The inclusion criteria included patients with better urinary control through preoperative urodynamic examination. Patients complete a follow-up for 2-7 years after surgery. The patients were divided into two parallel observation groups according to the length of the ileum intercepted during the operation. Observation group one: 33 cases, 30 males and 3 females; age from 48 to 77 years old with an average age of 60 years; Observation group 2: A total of 55 cases, 50 males and 5 females; aged 46-82 years old, with an average age of 64 years old; the two groups of patients have different ileum interception lengths. Observation group one: the length of the ileum cut was 25-35cm; the observation group two: the length of the cut ileum was 35-45cm.The operations were performed by the same team of experienced doctors. Both groups of patients were under general anesthesia, and the patients were in a supine position. After entering the pelvic cavity through an abdominal incision, they underwent lymph node dissection and cystectomy. Separate a section of ileum from the ileocecal area, and perform a U-fold folding with the extremities facing the patient’s head. A mechanical stapler is used for lateral intestinal-intestinal anastomosis to establish intestinal continuity. The separated intestinal segment is folded in a U-shape, and the jaws of the mechanical stapler are placed into the intestinal segment opening for cutting and anastomosis. In order to complete the pouch to the tube, an opening is made at the lowest point of the U-shaped ileum, and the jaws of the mechanical stapler pass through the opening to complete the U-bag.We use the cutting closure device to make the U-shaped neobladder of the ileum. This method reduces the length of the intestine required and reduces the tension between the urethra and the anastomosis of the neobladder. The neurovascular bundle is preserved during the operation. After the operation, a new bladder is flushed through a catheter to dilute the ileal mucus and prevent the catheter from being blocked. Postoperative angiography was performed to evaluate reflux and leakage.We collected and evaluated the basic data of the two groups of patients, the clinical stage of the tumor, the volume of the new bladder, the residual urine volume, the maximum urine flow rate, the recovery of postoperative urinary control, and postoperative complications. The standard for good urinary control after surgery: the number of urine pads used is less than or equal to 1 piece , and thePostoperative follow-up was conducted in the form of telephone contact and outpatient follow-up, with an interval of 3 months in the first year, 6 months in the second year, and annual follow-up. The bladder function training after the operation is carried out about 1 week after the operation, and the urinary catheter is clamped and opened regularly. The time starts from every half hour and gradually opens once every 2 to 3 hours. The urine output varies from low to high, until about 250 mL of urine is excreted from the catheter each time. The urination habit training is carried out after the catheter is removed. According to the patient’s living habits and activity requirements, a urination plan is formulated. Generally, the patient is instructed to urinate 6 to 8 times during the day and 2 to 3 times at night. Voiding pattern training: They are taught to empty the neobladder by increasing intra-abdominal pressure and relaxing the pelvic floor. Urinary continence training: by repeatedly contracting and relaxing the pelvic floor muscles, to restore urinary continence as soon as possible and eliminate urinary incontinence.The SPSS 25.0 software was used to statistically process the data, and the Kruskal-Wallis, T test and X2 test were used to analyze the data. The difference was statistically significant with P<0.05.We evaluated 88 patients who underwent surgery. The median follow-up time of 33 patients in observation group 1 was 44 months (27-65 months), and the median follow-up time of 55 patients in observation group 2 was 65 months (42-82 months). There was no significant difference in the follow-up time between the two groups (P>0.05). The BMI of most patients was within the normal range, and the difference between the two groups was not statistically significant. There was no significant difference in the clinical staging of tumors between the two groups. There was also no significant difference in diabetes and postoperative pathological lymph node positive between the two groups Table S1VS 359 ± 163.1 P=0.629). The number of intraoperative or postoperative blood transfusions in group 2 was more than that in group 1, but there was no significant difference in blood transfusion between the two groups. The postoperative hospital stay was 16.0 ± 3.3 VS 17.8 ± 4.4 in the two groups respectively, and the difference was not statistically significant. There was no significant difference in early postoperative complications and late complications  between the two groups. The operation time of group 1 was slightly shorter than that of group 2, but the difference was not statistically significant. There was no significant difference in estimated intraoperative blood loss between the two groups , and the incidence of hydronephrosis in group 2 was significantly higher than that in group 1. The time of exhaust and defecation in group 1 was significantly earlier than that in group 2, and there was no significant difference in other complications between the two groups. Table 1.The usage of the changing pad reflects the bladder function of the patient. One year after the operation, the daily usage of urine pad in observation group 2 was less than that in observation group 1. At the same time, more than half of the patients have good urinary control ability during the day and only need to use the urine pad at night. With the prolongation of monitoring time, the use of urine pads in both groups improved significantly. By the second year after surgery, there was no statistically significant difference in the use of changing pads and the use of changing pads during the day and night between the two groups (P>0.05). Further follow-up, regardless of the comparison of the usage of the urine pad and the usage, the observation group 1 was significantly better than the observation group 2 Table 2.The use of changing pads reflects the patient’s ability to control urine. At 1 year after surgery, the daily usage of changing pads in group 2 was less than that in observation group 1. At the same time, more than half of the patients had good urination control during the day, and only needed to use a urine pad at night. With the extension of follow-up time, the use of urine pads in both groups was significantly improved. By the 2nd year after operation, the patients in the two groups were better than the patients in the first group in terms of the number of urine pads used and the use of the white night pads. With the extension of follow-up time, the number of patients in group 1 gradually decreased, while the use of pads in group 2 increased gradually after the third year of follow-up Table 3.The size and wetness of the pad are important indicators of urinary incontinence. In our study, the size of day and night pad use in group 1 was significantly smaller than that in group 2. It was found that there was no significant difference between group 1 and group 2 in the degree of pad wetting during the day (P =0.073). However, the pads were significantly wetter at night in group 2 than in group 1 Table 4.Within 1 year after the completion of radical bladder resection and orthotopic U-shaped neobladder, there was no significant difference in residual urine between the two groups (P>0.05). Subsequently, the bladder residual urine in observation group 1 was significantly less than that in observation group 2, and the difference in average residual urine volume between the two groups gradually increased. The residual urine volume of observation group 2 first showed a downward trend, and gradually increased in the 4th year after surgery. The maximum urine flow rate can reflect bladder function. The average maximum urine flow rate of observation group 1 after operation showed an upward trend. By the fifth year after operation, the average maximum urine flow rate was 19.0 ± 2.3 mL/s. However, the peak of the maximum urine flow rate in observation group 2 was in the 4th year after surgery. Too large or too small a new bladder will affect the function of the bladder. The longer it stays within a certain range, the more beneficial it will be to the patient’s postoperative urine control. Due to the different length of the intercepted ileum between the two groups of patients, the maximum bladder volume after the operation of the two groups has always been different Table 5.The follow-up time of the patients in the two groups was 43.8 ± 13.0 and 47.5 ± 15.7 months, respectively, and the overall deaths were 12 and 23, respectively. The 5-year overall survival (OS)in group 1 was 53.60%, and the 5-year OS in group 2 was 52.90% Figure 1Among urinary system tumors, the incidence or mortality of bladder cancer is extremely high. Radical cystectomy (RC) + urinary diversion (UD) is the gold standard for the treatment of muscular invasive bladder cancer and high-risk non-muscular invasive bladder cancer . As the There are some technical difficulties in the operation of RARC combined with urinary diversion. Previous experience shows that RARC is feasible to combine with urinary diversion, and is superior to LRC and ORC in many aspects (including Urinary function) –8. The tInitially, we used a 35-45 cm ileum for neobladder preparation during laparoscopic in orthotopic U-shaped ileal neobladder surgery. During the postoperative follow-up of the patient, it was found that the bladder function did not meet our ideal expectations. After analysis, it was found that the new bladder capacity expanded too quickly with time, and the time to maintain good bladder function was too short. To this end, we actively explored a shorter ileum for neobladder preparation, and finally decided to use a 25-35cm length of ileum for neobladder preparation.After orthotopic bladder replacement, the most noteworthy issues include urinary tract changes and urinary dysfunction. As urine fills the new bladder, it acts as a low-pressure reservoir. During urination, the pressure on the abdomen, renal pelvis, and bladder increase at the same time, and the use of Valsalva will promote the emptying of urine without reflux , 11. In VS 23.6%); by the second year after operation, the difference in the rate of day incontinence between the two groups decreased (24.2% VS 16.4%); from the third year after the operation, the day incontinence rate of observation group 1 was always lower than that of observation group 2 during the follow-up period: ;. The nocturnal incontinence rate of the two groups also showed the above trend, . According to reports, the urinary control rate after Intracorporeal orthotopic neobladder is 80-100% during the day and 45-90% at night . The patients/participants provided their written informed consent to participate in this study.Study conception and design: BZ and ZL. Acquisition of data; JW and HW. Analysis and interpretation of data: BZ and ZL. Drafting of manuscript: BZ and ZL. Critical revision of manuscript: PZ and DZ. All authors contributed to the article and approved the submitted version.This study was funded by Medical Technology Plan of Zhejiang Province (grant number: 2021421701), Medical Technology Plan of Zhejiang Province (grant number: 2022497314), the Natural Science Foundation of Zhejiang Province (grant number: LQ21H160041), the Natural Science Foundation of Zhejiang Province (grant number: LBQ20H050001).The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Cavia porcellus), are crucial for scientific development, as they play an important role in the development and quality control chain of vaccines and drugs distributed by the Brazilian public health system. Investigating their biological and physiological parameters is fundamental to raise and keep these animals, so the handling of the facilities that hold them can be updated whenever new information comes up, with the well-being of the animals and alignment with the 3 Rs in mind. In the search for understanding reproductive aspects of Guinea pigs, the present study had the main goal of studying puberty by means of estrous cycle analysis in short-haired Guinea pigs. Guinea pigs have a vaginal occlusive membrane that covers the vaginal orifice. Its rupture takes place gradually and naturally, moments before labor and during estrus. The present study followed 42 females as for the presentation of the vaginal occlusive membrane. Once the membranes ruptured spontaneously, a swab was collected to study vaginal cytology. Membrane rupture was observed in 39 females; six females showed membrane rupture with less than 21 days of age (17 to 21 days). Twenty-three females were characterized as being in estrus due to cytology showing a prevalence of anucleated superficial cells. One of these females was younger than 21 days old. The opening of the vaginal occlusive membrane took place most frequently in intervals between 17 and 18 days, and the membrane remained open between one and three consecutive days. It was possible to follow three cycles of membrane opening on six females. The present study showed the need to adapt handling guidelines for C. porcellus kept in research animal facilities. The early age of puberty imposes the need of separate the female daughters from their fathers at 16 days old.Lab animals, such as Guinea pigs ( Cavia porcellus) are very important in the field of science, especially to the quality control of vaccines and drugs distributed via the Brazilian public health service .The animal facilities in which the Guinea pigs were held into autoclavable polypropylene cages measuring 90 x 60 x 30 (length x width x height), in family groups with 6 animals .The environment was kept at temperatures between 19 and 21 °C, relative air humidity between 40 and 60%, and light-dark cycles of 12:12 hours. All food and materials offered to the animals were submitted to chemical and/or physical decontamination processes. Nutritional handling consisted of specific Guinea pig feed (Quimtia®), supplemented with vitamin C (Vetec Quimica Fina LTDA), a multivitamin (Organnact®), and autoclaved water.At 14 days old the puppies received microchips in the dorsal scapular region for identification.Observation of vaginal membranes began when the animals turned 15 days old. Every day, between 9 and 10 a.m., the animals were physically restrained, weighed, and had their genital area observed, with a macroscopic evaluation of the vaginal occlusive membrane classified in three stages: Partially open (VMPO) – when had opening of the membrane but not enough for a swab to be introduced; Closed (VMC) - when had vaginal canal completely covered by the membrane. From 30 to 60 days of age, the membrane was inspected every two days. When it was seen opened, cytological samples were collected daily, until observed closed. The macroscopic aspects of the genitalia  were also recorded daily.The vaginal material was collected with an extra-fine cylinder-shaped interdental brush, 3 mm of diameter, soft bristles, damp with saline solution and introduced in the vaginal canal, then rotated to gently exfoliate the vaginal epithelium.Following the collection, the material was smeared on two microscopy slides, which were identified (sample ID) with a combination of a random number and a letter corresponding to the staining technique to be used (A for rapid panoptic and B for Papanicolaou).The Romanowsky staining technique (panoptic staining) was made by a commercial kit (LABORCLIN). The The quantitative evaluation considered the counting of cell types in absolute numbers, for a total of 200 cells, which was performed by optical microscopy (100 and 400 x zoom). After the counting, the percentage of cell types contained in the vaginal epithelium was calculated. According to the classification used by For the description of the results, the following criteria were considered: opening of the occlusive membrane, age, time the membrane remained open and phase of the cycle during which the membrane opened. For the vaginal cytology figures, descriptive statistic, average and standard deviation, standard error, and variation of original data were considered. Variance analysis (ANOVA) was used to compare the number of cell types present in the three cycles observed and the T Test used to compare the averages obtained in the first and second cycles, using the Bioestat free software (version 5.0).0 (hypothesis of nullity) was 5%, that is, lower than 0.05.The level of significance used to reject HThis study was approved by the Ethics Committee for Use of Animals - CEUA Fiocruz, under licence number LW-12/15 and the additive term P39/14.4 for the inclusion of the activity “sampling for vaginal cytology”.Observation was finished when the animals turned 61 days old. The animals’ management general routine was not modified, except for the observations and sample collections.Evaluation of estrous cycle between 15 and 60 days of age.The macroscopic evaluation of the vaginal membrane was carried out in all 42 animals of the study . We observed that in 73% of evaluations, the status found was that of closed vaginal membrane 1B, whileThe vaginal occlusive membrane broke at least once in 39 of the 42 females (92.85%) under evaluation. Of the total number of females with open vaginal membrane, 23 (58.97%) had a second opening, with an interval between openings from 7 to 21 days, while six females (15.38%) had a third opening, at intervals between 15 to 18 days. We observed a variation in the period during which the vaginal membrane remained open, from 1 to 12 days. The duration of the interval in between membrane openings varied between 7 and 21 days, with a higher frequency at 17 and 18 days, totalling 44.81% of the intervals observed .Overall, 164 slides were prepared and evaluated, to analyze the average distribution of the cell types found. The average distribution of cell types of the vaginal epithelium shows a predominance of enucleated and intermediate superficial cells, according to the description .When characterizing the phases of the estrous cycle in Guinea pigs (n = 39), we observed that during proestrus intermediate cells were in higher number  and a light presence (+) of mucus and leukocytes. During estrus, superficial cells were predominant, mainly enucleated (113 ± 32.8), in addition to the absence of leukocytes and mucus. During metaestrus, intermediate cells were those most frequent, corresponding to about 95 ± 26 cells, with moderate presence of leukocytes (++) and no mucus. During diestrus we observed a more uniform distribution between nucleated, enucleated, and intermediate superficial cells and a very high number of leukocytes (+++). We observed an increase in the number of parabasal cells during metaestrus and diestrus, when compared with the other phases. No statistic difference was observed in the quantity of each cell type on the different phases of the estrous cycle (P < 0.05) .In 39 females that presented vaginal occlusive membrane opening, six were younger than 21 days (17 to 21 days) corresponding to 15.38% of females in the first opening of the membrane. For the females of this age group, the time membrane remained open varied between 1 and 5 days.As for the distribution of total superficial cells in vaginal smears, in animals younger than 21 days (n = 6). One 21 days old female showed a counting above 140 superficial cells (nucleated and enucleated), low presence of intermediate, parabasal and basal cells, as observed in The study observed a significant difference (p=0.02) between average body weight values between the six females with vaginal membrane opening before 21 days of age (299 ± 45.42 g) and the 33 females whose vaginal membrane opened at more than 21 days of age (264 ± 32.03 g) .C. porcellus. Of the 42 females under study, six had vaginal occlusive membrane opening before 21 days of age. In this study it was possible to prove, via vaginal cytology analysis and observation of vaginal occlusive membrane, the occurrence of early puberty in It should be highlighted that the fact that evidence of estrus was observed on the vaginal smear in only one female younger than 21 days does not rule out the possibility of occurrance in the other five females that presented early opening of the vaginal occlusive membrane. A revision of literature showed a duration of the estrous phase between 8 and 24 hours, according to The significant difference observed in the average values of body weight at 20 days of age between females with vaginal occlusive membrane rupture before and after 21 days of age corroborates the study developed by The results, in the conditions reported herein, showed a wide range in the age of spontaneously opening of vaginal occlusive membrane, between 15 and 60 days old.The time during which the vaginal membrane remained opened for the first time varied greatly (1-12 successive days) and was higher than that reported by other authors , who desThe duration of the interval in openings showed a variation between 7 and 21 days, occurring with a higher frequency to 17 and 18 days, higher than those presented in literature, which describe cycles between 15 and 17 days , or betwVaginal cytology proved to be reliable for the characterization of the estrous cycle. There was distribution of cell types of the vaginal epithelium in each phase, as in the study by Thus, observation of the rupture of vaginal occlusive membrane, together with the characterization and incidence of cell types through vaginal cytology, made it possible to detect estrous in Guinea pigs, supporting previous reports in studies by C. porcellus females with the evidence of early estrous (before 21 days) and the characterization of at least three estrous cycles before 60 days old.This study provides important and novel information on the reproductive biology of young The Guinea pig females kept in laboratory animal facilities conditions showed that the rupture of the occlusive membrane occurs gradually, in some cases, with a partially open phase that makes cytological sampling impossible. Differences in body development (weight) of the females with early puberty is one of the possible factors in the distribution of age in the opening of the vaginal membrane.In the conditions in which the study was carried out, Guinea pigs showed vaginal occlusive membrane rupture and vaginal cytology characteristic of estrous at an age below 21 days, pointing to puberty before the standard weaning period. Because of this observation, in laboratory animal facilities is necessary to modify the Guinea pigs management practices aiming to adapt the separation of female daughters from their fathers at 16 days old.


The corrosion rate was the fastest during the acidic copper acceleration experiments from 4 h to 16 h, and the corrosion products of WCo3 and Co3O4 were generated on the corrosion surface. The maximum erosion rate of 0.00104 in the erosion experiment corresponds to a corrosion sample with a corrosion time of 36 h. (4) Therefore, the coercive magnetic force and magnetic saturation strength could be derived from the prepared carbide hard phase grains and carbon content in the appropriate range. The corrosion product in the corrosion process slowed the corrosion rate, and a large amount of cobalt and a small amount of tungsten was lost by oxidation during the corrosion process. The corrosion time had the greatest effect on the erosion performance of the carbide, and the long corrosion time led to surface sparseness, which reduced the erosion resistance.(1) Mud pulser carbide rotors, as a core component of ground communication in crude oil exploration, are often subjected to mud erosion and acid corrosion, resulting in pitting pits on the surface, which affects the accuracy. The purpose of this study was to investigate the acid corrosion and erosion behavior of cemented carbide materials and provide a reference for the wider application of cemented carbide materials in the petrochemical industry. (2) Experimental samples of tungsten–cobalt carbide were sintered at a low pressure by powder metallurgy. The petrochemical application environment was simulated by accelerated salt spray corrosion and solid slurry erosion with the aid of acidic copper, and the experimental phenomena were analyzed by SEM (scanning electron microscope), EDS (Energy Dispersive Spectroscopy), and XRD (X-ray diffraction). (3) The experimental results show that the coercivity of the pitted cobalt-cemented tungsten carbide prepared in this study was 17.89 KA/m, and the magnetic saturation strength was 14.42 G·cm Crude oil is called the “blood of industry” and is the raw material for many chemical products, such as petroleum, fertilizers, pesticides, lubricants, etc. . The keyIn summary, the research on cemented carbide materials has focused on the material preparation and microscopic characterization of cemented carbide and the investigation of corrosion and erosion properties. Crude oil is rich in C, H, and small amounts of S and N, which easily form an acidic environment. It also contains solid phase particles of mud fluid, which is liable to produce the erosion phenomenon. The existing cemented carbide materials for petrochemical environments only consider the effect of solid phase particles on the erosion and lack the influence of acidic corrosion on erosion performance. Therefore, this study used alcohol ball mill powder and low-pressure sintering to prepare WC-Co cemented carbide for petrochemical environments, which is rich in rare earth elements. We used an acidic copper-accelerated salt spray corrosion test and ablation test to simulate the environment with both acidic corrosion and solid phase particle ablation and investigate the acidic corrosion and high-pressure slurry erosion behavior of WC-Co cemented carbide material for MWD rotors in a petrochemical environment. We performed a comprehensive simulation of the environment of the cemented carbide materials so as to study the corrosion mechanism of cemented carbide and corrosion mechanism of cemented carbide and explore the comprehensive performance of corrosion resistance and erosion resistance of the prepared cemented carbide. The comprehensive properties of the cemented carbide were tested using magnetic saturation and coercive force. The magnetic saturation strength was affected by the chemical composition of the cemented carbide, but not by the microstructure. The coercive magnetic force was sensitive to the chemical composition and microstructure of the cemented carbide. It is of great significance to control the comprehensive properties of cemented carbide by the constraint of coercive force and magnetic saturation value.WC-Co cemented carbide samples were prepared using the powder metallurgy method; the specific preparations were as follows: WC and Co powders with particle sizes of 3.5 μm and 1 μm, respectively, were used. A carbide spherical grinding body with high hardness was placed in the horizontal rolling ball mill cavity, while the prepared powder and additives, including paraffin and industrial alcohol, were loaded into the ball mill cavity. The ratio of the ball to material was 4:1, the speed of the ball mill was 36 r/min, and the slurry was ground for 72 h. The carbide was ground to the required particle size and mixed with Co powder to achieve good material uniformity and density. The role of the paraffin wax was to increase the plasticity, staining, and lubrication of the mixture and prevent oxidation and easy granulation. The alcohol, as the wet grinding medium, reduced the oxygen content in the mixture, thus reducing the oxygen content in the sintering process and obtaining better sintering performance.Then, the ground mixed slurry was pumped into a drying tower, atomized, and dried at an inlet temperature of 180 °C and an outlet temperature of 95 °C. The cyclone was recycled into a mixed dry fine powder. The chemical composition of the mixed powder is shown in The mixed powder was pressed into round bars using a 25-ton cantilever hydraulic press, as shown in 2+. Cathode: The remaining e− in the metal was depolarized by oxygen and reached the surface of the cathode by diffusion or convection, absorbing electrons and becoming hydroxide ions (OH−). Then, the Co2+ and WC chemical reaction generated corrosion products Co3O4, WCo3, and CO2, resulting in the loss of Co in the carbide surface crater formation, as shown in Before the experiment, the sample needed to be ground and polished to achieve a mirror effect, with a maximum surface roughness of 0.12 μm, and ultrasonic cleaning to remove surface stains. The bottom of the cylindrical test piece was dipped in a plastic plane, and then the whole piece was placed in the equipment to ensure that each polished experimental end face was exposed to salt spray at 20° to the vertical direction, as shown in According to the information about the deep well environment, it is known that the solid phase component of the mud is mainly quartz sand ,23. The Before and after the experiments, the samples were observed by scanning electron microscopy  with energy dispersive X-ray spectroscopy (EDS) to observe the microscopic morphology as well as the energy spectrum and analyze the elemental composition of the corrosion products and the XRD crystallographic corrosion products.The quality of the powder mixture determines the quality of the cemented carbide, and a stable and homogeneous mixture is required to prepare a cemented carbide with excellent properties. The properties of cemented carbide depend on its composition and structure, and once the composition is determined, it is necessary to consider its structure. In this paper, the structure of this cemented carbide sample was studied in terms of the alloy phase composition, grain size, and tissue defects. The relative magnetic saturation value of the alloy was used to measure the carbon content of the alloy and the coercivity magnetism to measure the grain size of the alloy.3/g < 15.98 G·cm3/g as measured by the Changsha Zhongda ZDMA6535 specific saturation magnetization strength measuring precision instrument , which indicates that the magnetic saturation requirement of this YG type cemented carbide was met, and the alloy properties were also within the specified range. S. Sundin’s formula is as follows:The elemental content of the uncorroded sample was analyzed using scanning electron microscopy  with energy dispersive X-ray spectroscopy (EDS) on the surface of the sample, and c: the coercive magnetic force of the alloy;Hs: the saturation magnetization strength of the alloy;MCo: the interface area between the Co and the WC in the alloy, i.e., the surface area of WC grains in the alloy.SWC/SAccording to Equation (1), the coarser the WC grains and the smaller the surface area of the WC grains, the thicker the Co layer that can be analyzed for the same Co content. The coercive magnetism is related to the Co content, sintering time and process, added elements, and impurities. The measured coercive magnetism value was 17.89 kA/m < 20 kA/m.3O4 [3O4 ) appeare−2·h−1;V: metal corrosion rate, mg·m0: weight of metal before corrosion;m1: weight of metal after corrosion, as shown in ms: area of the corrosion surface of the metal sample;t: corrosion time.Through the weighing determination method in accordance with Formula (1), the corrosion rate of the salt spray corrosion process of cemented carbide samples can be calculated, and the change curve is shown in 0 represents the weight of sample Y33 before corrosion, that is, the corrosion time of the third group of samples was up to 36 h. m1 is the real-time weight of the samples every 4 h, representing the weight change during the corrosion process. The reason there was only one Y33 is because it was the one that corroded the longest so the weight data are adequate. mThe surface SEM morphology of cemented carbide under different corrosion cases is shown in 3O4 (PDF#98-000-0166), which corresponds to the Co oxides formed after the enrichment of the large amount of Co and O that appeared in the EDS analysis. The rest of the peaks were not retrieved with matching phases and were considered to be a small amount of adulterated material or error-induced spurious peaks. The XRD analysis results show that the main material components of the sample proved to be WC, WCo3, and Co3O4. The results indicate that a large amount of Co was lost during the corrosion to form corrosion products with O and W, resulting in a large loss of Co and a small amount of W.XRD analysis was performed on the carbide surface after salt spray corrosion for 0 h, 12 h, 24 h, and 36 h, and the results are shown in During the erosion process, a well-mixed abrasive fluid (a mixture of abrasive and water) was delivered to the gun by the abrasive pump. In addition, compressed air was used as an additional acceleration power for the abrasive fluid, which passed into the gun through the air delivery pipe. Inside the gun, the compressed air accelerated the abrasive fluid entering the gun and ejected it at a high speed through the nozzle, spraying the sample surface according to the set angle for the analysis of the erosion resistance of the sample. In ΔM: the rate of change of mass during metal erosion;b: metal weight before erosion;ma: metal weight after erosion, see mIn 2 particles hit the surface of the corroded sample at an oblique high speed, forming irregular pits and scratches. For the uncorroded carbide surface after erosion morphology, as shown in 2 particles across the surface. In addition, the surface properties of the uncorroded carbide were more uniform, thus forming uniform scratches. The right side shows the magnified surface morphology, and it can be seen that the uncorroded surface was relatively smooth during the erosion process and there were few erosion pits and surface flaking marks. However, after slight corrosion 3/g, respectively, meeting the carbide production standards.The research and quality control of the mixed powder used for the sintering enabled the sintering of the carbide samples with a carbon content and grain size that met the requirements, and the measured coercive magnetic force and magnetic saturation strength were 17.89 KA/m and 14.42 G·cm(2)3 and Co3O4, which caused a large amount of cobalt and a small amount of tungsten oxidation loss.The acidic copper-accelerated salt spray corrosion experiments on cemented carbide showed that the corrosion rate was different with different corrosion time periods. The corrosion rate was fast at the 4–16 h stage, and the generation of corrosion in the corrosion process slowed down the corrosion rate. A large number of rust spots and corrosion holes appeared on the surface during the corrosion process and generated corrosion products of WCo(3)After corrosion, the erosion experiments show that the corrosion of the carbide had a great impact on the anti-corrosion performance. The longer the corrosion time was, the greater the erosion rate was, reaching 0.00104. The long corrosion time led to surface loosening, which reduced the erosion resistance. Erosion occurred after a large number of erosion pits formed, and surface flaking seriously affected the durability and accuracy of the material.


Using waste clay brick powder (RBP) to partially replace cement in the preparation of concrete, is one way to recycle construction waste. In order to investigate the physical and mechanical properties and volume stability of recycled micropowder ultra-high-performance concrete (UHPC), the basic mechanical and shrinkage properties of recycled micropowder UHPC were studied at replacement rates of 10%, 20%, 30%, 40% and 50%. The results show that: (1) When the activated recycled brick powder is used to replace the cement, the compressive strength, flexural strength and splitting tensile strength of the UHPC initially increase and then decrease with the increase in the substitution rate. When the substitution rate is 10%, the 28 d compressive strength, flexural strength and splitting tensile strength of the UHPC are the highest; (2) Replacing cement with recycled brick powder can reduce the autogenous shrinkage of the UHPC, and the autogenous shrinkage rate of the UHPC decreases with the increase in the brick powder replacement rate. The drying shrinkage of the UHPC can be reduced by replacing cement with recycled brick powder. The drying shrinkage of the UHPC initially decreases, and then increases, with the increase in the replacement rate of brick powder. When the replacement rate of the brick powder was 30%, the drying shrinkage of the UHPC was the least, and this was 49.7% lower than that in the benchmark group. The prediction models of autogenous shrinkage and drying shrinkage are in good agreement with the experimental results, which can be used to predict the shrinkage development of recycled brick powder UHPC. The continuous social and economic development of the construction industry has meant that a large amount of construction waste is generated globally, and this is expected to remain high over the next decades ,2,3,4. T2O3 and SiO2 contents, C-A-S-H and C-S-H gels were formed with 5% brick powder, which improved the bending and compressive strength of the materials, while the use of a higher percentage of brick powder resulted in a decrease in the strength of the materials. Rovnanik et al. [It is well known that physical and mechanical properties and volume stability are important aspects of concrete performance ,24,25,26k et al.  examinedk et al.  preparedExisting studies show that the mechanical and shrinkage properties of cement-based materials can be improved by replacing cement partially with an appropriate amount of clay brick powder. Based on the above research reports, this paper reports a study of the compressive, flexural, and splitting tensile properties, and the autogenous and drying shrinkage properties of recycled brick powder UHPC, with the replacement rate of recycled brick powder as the main variable. Based on the experimental results, a shrinkage prediction model of recycled brick powder UHPC is proposed, which provides an experimental basis and theoretical guidance for the application of recycled brick powder UHPC.3. The admixture was first-class fly ash from the Yuanheng Environmental Protection Engineering Co., Ltd., Zhengzhou City, Henan Province, China.—the apparent density of first-class fly ash is 2363 kg/m3, and silica ash with a SiO2 content equal to 96.76%—the apparent density of silica ash is 2200 kg/m3. The recycled brick powder came from the sintered waste clay bricks resulting from demolition in Zhengzhou City. The compressive strength of the waste bricks was MU20~MU25, and the brick powder used in the test was obtained by jaw crushing, screening, and ball milling . The preparation process is shown in −3, and tensile strength of more than 2000 MPa. Using a CQJ-JSS type polycarboxylic acid high-efficiency water-reducing agent produced by Shanghai Chenqi Chemical Technology Co., Ltd., China. the water reduction rate was 32%. The water for test mixing and curing was the ordinary tap water of Zhengzhou City.This test used the Mengdian Group Cement Co., Ltd., Xinxiang City, Henan Province, China. P.O 52.5 ordinary Portland cement; its main technical indicators are shown in The recycled brick powder comes from the sintered waste clay bricks produced by demolition in Zhengzhou city; the compressive strength of the waste bricks was MU20~MU25. The influence of the recycled brick powder on the properties of cement-based materials is determined by many factors, which are not only related to the specific surface area of the materials, but also closely related to the morphology of recycled brick powder, the interaction of recycled brick powder with other materials and other factors. The cement and brick powder were placed in a vacuum drying oven, vacuum dried at 50 °C for 1 h, and subsequently, sealed and stored for scanning electron microscopy. 2, Ca(OH)2, CaCO3 and C-S-H. In 3Al2O6 crystal may result because the recycled micropowder was not ball milled and contains some cement mortar. The Ca3Al2O6 crystal may be the product of secondary hydration. The SiO2 in the sample after ball milling is mainly from sand and recycled fine powder in the aggregate, and the Ca(OH)2 is mainly from cement hydration. This indicates that after mechanical ball-milling excitation, the SiO2 in some recycled micropowders is activated and reacts with the hydration product of cement, Ca(OH)2, to form a C-S-H gel, which helps to improve the strength of the materials. The recycled brick powder is prepared from waste clay bricks, with silicon accounting for most of the composition of the clay bricks. A previous investigation reported that the high content of silicon and its oxide contained in RBP contribute to the pozzolanic reaction of cementitious materials [The reclaimed micropowder was milled by a SM500×500 ball mill, after which the mortar specimens were prepared by replacing cement with a 30% content, and an XRD analysis was carried out. aterials . HoweverThe standard UHPC with a designed water–binder ratio of 0.17 is used to replace cement with 10%, 20%, 30%, 40% and 50% mass substitution rates to prepare recycled brick powder UHPC. The details of mixes are listed in The specimens were designed and tested according to T/CCPA 7-2018 (T/CBMF 37)  and (GB/The specimens were designed and tested according to the T/CCPA7-2018T/CBMF37) , , the shrinkage rate of the R1 group was 37.5% lower than that in the benchmark group. When the replacement rate increased from 10% to 30%, the autogenous shrinkage development law of the UHPC was relatively close. After the shrinkage was basically stable, the shrinkage rate of R1, R2 and R3 was not much different. The 168 h shrinkage rate of R2 and R3 was reduced by 36.6% and 37.2%, respectively, compared with the benchmark group. When the replacement rate was 40–50%, the shrinkage rate of the UHPC continued to decrease, and the 168 h-autogenous shrinkage rate of R4 and R5 was 61.2% and 63.7% lower, respectively, than that in the benchmark group. The results show that the autogenous shrinkage of each group of specimens decreased with the increase in the replacement rate of brick powder. This was because the addition of the RBP reduced the cement composition, thereby reducing the autogenous shrinkage value of the UHPC ,43.The drying shrinkage time curve of the recycled brick powder UHPC is shown in According to the above test results, the 28 d drying shrinkage rates of R0~R5 account for 93.1%, 90.9%, 89.0%, 88.4%, 92.6% and 91.5% of the whole test cycle, respectively. It is evident that the drying shrinkage of the reclaimed brick powder UHPC mainly occurs before the age of 28 d. The shrinkage of the UHPC is mainly autogenous shrinkage and drying shrinkage. The drying shrinkage of R1~R5 accounts for 18.5%, 22.1%, 19.6%, 15.4%, 17.2% and 26.4% of the total shrinkage, respectively. When the replacement rate was 30%, the drying shrinkage of the UHPC reached the minimum. The drying shrinkage of the recycled brick powder UHPC accounted for about 15–26% of the total shrinkage.c(t) is the autogenous shrinkage value, 1 × 10−6; δ and a are the influence coefficients of brick powder, which are calculated by Formula (2) and Formula (3), respectively. b is the final strain value of autogenous shrinkage of each specimen; t is the test age, h; r is brick powder replacement rate, %.The research on the shrinkage model at home and abroad mostly focuses on an ordinary UHPC, and the existing model is not fully applicable to the autogenous shrinkage prediction of the recycled brick powder UHPC due to different test conditions, the material mix ratio, specimen size and test methods. Therefore, the autogenous shrinkage model of the recycled brick powder UHPC is established based on the experimental results of this paper, as shown in Formula (1):The calculation results of the prediction model are compared with the experimental data to verify the accuracy of the model. The benchmark group and the 40% substitution rate group are selected for analysis, and the results are shown in ds(t) is drying shrinkage, 1 × 10−6; m is a constant, and its value is the final drying shrinkage value of each group of specimens. t is the test age, d; n is the influence coefficient of the replacement rate of brick powder, which is calculated according to Equation (5). r is the replacement rate of brick powder, %; p is a constant, . Comparing the prediction model calculation results with the drying shrinkage test results, the benchmark group and 40% substitution rate group are still selected for analysis, and the results are shown in The drying shrinkage prediction model of recycled brick powder UHPC was obtained by fitting the drying shrinkage test data, as shown in Equation (4):(1)The compressive strength of the UHPC decreased with the increase in replacement rate after the cement was replaced by activated recycled brick powder, and the decreasing trend was more obvious with the older age. An increase in age resulted in the compressive strength of the recycled brick micropowder UHPC showing an increasing trend. At the age of 28 days, the compressive strength of the UHPC in each group after replacement was lower than that in the benchmark group. When the replacement rate of recycled brick powder was 10%, the 28 d compressive strength was the highest at 141.3 MPa;(2)The flexural strength of the UHPC decreased with the increase in replacement rate after the cement was replaced by activated recycled brick powder, and the decreasing trend was more obvious with age. As age increased, the flexural strength of the recycled micro-brick powder UHPC showed an increasing trend. At the age of 28 days, the flexural strength of the UHPC in each group after replacement was lower than that in the benchmark group. When the replacement rate of the recycled brick powder was 10%, the 28 d flexural strength was the highest at 25.0 MPa;(3)The splitting tensile strength of the UHPC decreased with the increase in replacement rate after the cement was replaced by activated recycled brick powder, and the decreasing trend was more obvious with age. Alternatively, with the increase in age, the splitting tensile strength of the recycled brick micropowder UHPC showed an increasing trend. At the age of 28 days, the splitting tensile strength of the UHPC in each group, after replacement, was lower than that in the benchmark group. When the replacement rate of recycled brick powder was 10%, the 28 d splitting tensile strength was the highest at 13.77 MPa;(4)The autogenous shrinkage of the recycled brick powder UHPC developed most rapidly in the first 0–6 h. After the recycled brick powder replaced the cement, the autogenous shrinkage of the UHPC decreased, and with the increase in the replacement rate, the autogenous shrinkage of the UHPC decreased;(5)The drying shrinkage of the UHPC can be reduced after the recycled brick powder replaces the cement, and with the increase in the replacement rate of recycled brick powder, the drying shrinkage of the UHPC presented a trend of initially decreasing and then increasing. When the replacement rate of the brick powder was 30%, the drying shrinkage of the UHPC was the smallest, which was 49.7% lower than that in the benchmark group. The drying shrinkage of the recycled brick powder UHPC mainly occurred in the first 28 d, and the drying shrinkage at 28 d accounts for about 90% of the drying shrinkage value of the whole test span.(6)e, and the drying shrinkage and age conform to the exponential function relationship. The autogenous shrinkage prediction model and drying shrinkage prediction model of the recycled brick powder UHPC are in good agreement with the test results, which can be used to predict the shrinkage of recycled brick powder UHPC.The autogenous shrinkage and age of the recycled brick powder UHPC conform to the exponential function relationship based on In this paper, the compressive, flexural and splitting tensile properties, and the autogenous and drying shrinkage properties of the recycled brick powder UHPC were studied with the substitution rate of recycled brick powder as a variable. Based on the test results, a shrinkage prediction model of the reclaimed brick powder UHPC was proposed. The results are as follows: