Signal Threshold Research Articles

Effect of time-delayed feedback in a bistable system inferred by logic operation

• The effect of time delay in bistable system can be inferred by logic operation. • Time-delayed negative feedback can reduce the width of bistable region. • There is an unstable limit cycle on the directly connected boundary between the oscillatory and suprathreshold region. • In the alternate region, the system is sensitive to parameters and can enter two potential wells alternately with the slight variation in sensitive parameters. The effect of time delay is inferred by studying the influence of time-delayed feedback on the signal threshold of logic input signal, which reflects the width of the bistable region. Time-delayed positive feedback does not alter the width of the bistable region but increases the switching time. Time-delayed negative feedback leads to decreases in the depth of two potential wells and the width of the bistable region of the system, resulting in instability and oscillation of the system. Then, the parameter plane of the system can be divided into suprathreshold, subthreshold, oscillatory and alternate regions. With increasing time delay and negative feedback intensity, the suprathreshold and oscillatory regions continuously squeeze the middle subthreshold region until they are connected. One part of the oscillatory region is directly connected with the suprathreshold region, while the other part is transiently connected with the alternate region. There is an unstable limit cycle on the directly connected boundary. In the alternate region, the system is sensitive to initial values and system parameters and can enter two potential wells alternately with slight variations in sensitive parameters.

A prespecified interim analysis of the PATHFINDER study: Performance of a multicancer early detection test in support of clinical implementation.

3070 Background: A multi-cancer early detection (MCED) test that uses targeted methylation-based cfDNA technology to detect cancer and predict cancer signal origin (CSO) has potential to efficiently identify malignancies for which effective screening modalities do not exist. A previous version of a blood-based MCED test demonstrated favorable classification and test characteristics. Samples from the ongoing PATHFINDER study were reanalyzed in a prespecified interim analysis to evaluate performance of a more recent version of the test with an updated classifier (eg, updated CSO localization, hematological signal threshold) that is planned for clinical implementation as a general multi-cancer screening tool. Methods: PATHFINDER (NCT04241796) is an interventional, prospective study in which results (cancer signal detected/not detected and predicted CSO) using a previous version of the MCED test are returned to investigators, and those with a signal detected undergo further diagnostic testing. In this prespecified interim analysis, samples from those enrolled as of October 6, 2020 were reanalyzed with the more recent version of the MCED test (these results were not returned to investigators). The positive predictive value (PPV) for cancer detection, overall CSO accuracy, and concordance between the two test versions were assessed. Results: A total of 4011/4047 (99%) participants (pts) were analyzable (mean [SD] age 63.9 [8.7] years, 62% female, 92% white, 24% with prior cancer history, 39% ever smoker [4% current], 6% with genetic cancer predisposition). Cancer signal was detected in 0.95% (38/4011). A total of 27/38 also had signal detected by the previous version of the MCED test, including 19 who reached diagnostic resolution (13 with cancer diagnosis and 6 without); 11/38 were discordant positives. Nine different cancer types were detected in the 13 pts (2 stage I, 3 stage II, 2 stage III, and 3 stage IV); 1 had no AJCC stage expected, 1 metastatic recurrence and 1 stage evaluation underway. A conservative minimal PPV assuming all discordant positives are false positives, was 43.3% (13/30, 95% CI 27.4-60.8%) based on 19 pts with diagnostic resolution and 11 discordant positives. High negative percent agreement (PA) 99.7% (99.5-99.8%) between the two test versions was observed. Positive PA of 43.5% (95% CI, 31.9-55.9%) was consistent with the more stringent threshold for hematologic signal in the recent MCED version, as most discrepant cases had hematologic CSO with the previous MCED test. Among 13 detected cancers, accuracy of the top CSO prediction was 92.3% (12/13, 95% CI 66.7-99.6%). Conclusions: In this prespecified interim analysis, the more recent version of the MCED test detected cancers with high PPV and high accuracy of CSO prediction, supporting readiness for use in clinical practice. Full enrollment cohort data will be available at the meeting. Clinical trial information: NCT04241796.

TIM-3 drives temporal differences in restimulation-induced cell death sensitivity in effector CD8+ T cells in conjunction with CEACAM1

Abstract Immune homeostasis depends upon effective clearance of pathogens while simultaneously preventing immunopathology in the host. Restimulation-induced cell death (RICD) is one such mechanism where by activated T cells receive subsequent antigenic stimulation, reach a critical signal threshold through the T cell receptor (TCR), and commit to apoptosis. Many details of this process remain unclear, including the role of proteins that influence the TCR signaling cascade. Here we characterize the role of T cell immunoglobulin and mucin domain containing 3 (TIM-3) in RICD regulation. TIM-3 protected newly activated CD8+ effector T cells from premature RICD during clonal expansion. Surprisingly, however, we found that TIM-3 potentiated RICD in late-stage effector T cells. The presence of TIM-3 increased proximal TCR signaling and pro-apoptotic protein expression in late-stage effector T cells, with no consistent signaling effects in newly activated cells. We found that TIM-3 was expressed on the surface of newly activated effector T cells, but remained largely intracellular in late-stage effector cells. Consistent with this, TIM-3 required a ligand to prevent early RICD only immediately after activation. We found that CEACAM1, a known ligand of TIM-3, protected newly activated cells from premature RICD, with no measurable effects in late-stage effectors. Indeed, CEACAM1 enabled TIM-3 surface expression on T cells, implying a co-dependency for these proteins in protecting expanding T cells from premature RICD. Our findings suggest that co-signaling proteins like TIM-3 and CEACAM1 can alter RICD sensitivity at different stages of the effector T cell response, with important implications for checkpoint blockade therapy.

Novel approach for quantification of multiple immunofluorescent signals using histograms and 2D plot profiling of whole-section panoramic images

We describe a novel approach for quantification and colocalization of immunofluorescence (IF) signals of multiple markers on high-resolution panoramic images of serial histological sections utilizing standard staining techniques and readily available software for image processing and analysis. Human gingiva samples stained with primary antibodies against the common leukocyte antigen CD45 and factors related to heparan sulfate glycosaminoglycans (HS GAG) were used. Expression domains and spatial gradients of IF signals were quantified by histograms and 2D plot profiles, respectively. The importance of histomorphometric profiling of tissue samples and IF signal thresholding is elaborated. This approach to quantification of IF staining utilizes pixel (px) counts and comparison of px grey value (GV) or luminance. No cell counting is applied either to determine the cellular content of a given histological section nor the number of cells positive to the primary antibody of interest. There is no selection of multiple Regions-Of-Interest (ROIs) since the entire histological section is quantified. Although the standard IF staining protocol is applied, the data output enables colocalization of multiple markers (up to 30) from a given histological sample. This can serve as an alternative for colocalization of IF staining of multiple primary antibodies based on repeating cycles of staining of the same histological section since those techniques require non standard staining protocols and sophisticated equipment that can be out of reach for small laboratories in academic settings. Combined with the data from ontological bases, this approach to quantification of IF enables creation of in silico virtual disease models.

Frequency selectivity in the modulation domain estimated using forward masking: Effects of masker modulation depth and masker-signal delay

The threshold for detecting amplitude modulation (AM) of a sinusoidal or noise carrier is elevated when the signal AM is preceded by masker AM applied to the same carrier. This effect, called AM forward masking, shows selectivity in the AM domain, consistent with the existence of a modulation filter bank (MFB). In this paper we explore the effect of two factors that can influence AM forward masking, using an 8-kHz sinusoidal carrier and a range of masker AM frequencies, fm, both below and above the signal AM frequency, fs, of 40 Hz. The first factor was the time delay, td, between the end of the masker AM and the start of the signal AM. The second was the AM depth, m, of the masker, which was either 1 or 0.25. The AM forward masking patterns in all conditions showed tuning in the AM domain; signal thresholds were highest when fm was close to fs. The amount of AM forward masking decreased with increasing td in a similar way for all fm, so the shapes of the masking patterns did not change markedly with td. Remarkably, the amount of AM forward masking decreased by only about 3 dB (a non-significant effect) when the masker m was decreased from 1 to 0.25. This result appears to be inconsistent with an explanation of AM forward masking in terms of adaptation in a MFB or in terms of a sliding temporal integrator.

A summary of behavioral measures of cochlear gain and gain reduction in listeners with normal hearing or minimal cochlear hearing loss

This study examined the relationship between cochlear hearing loss and psychoacoustic measures related to cochlear function. Listeners’ audiometric thresholds for long tones ranged from well within the clinically normal range to just above this range. Where thresholds were elevated, other clinical tests were consistent with a cochlear origin. Because the medial olivocochlear reflex decreases cochlear gain in response to sound, measures were made with short stimuli. Signal frequencies were from 1 to 8 kHz. One point on the lower leg of the input/output function was measured by finding threshold masker level for a masker almost one octave below the signal frequency needed to mask a signal at 5 dB SL. Gain reduction was estimated by presenting a pink broadband noise precursor before the signal and masker and measuring the change in signal threshold as a function of precursor level. Previous studies with listeners with normal hearing have shown that gain reduction begins at a low precursor level and grows compressively as the precursor level is increased. In the present study, the estimate of gain reduction decreased as quiet threshold increased, but was not solely determined by the amount of gain. [Work supported by NIH(NIDCD)R01 DC008327 (EAS) and NIH(NIDCD) T32 DC016853 (WBS).]

TIM-3 drives temporal differences in restimulation-induced cell death sensitivity in effector CD8+ T cells in conjunction with CEACAM1

Immune homeostasis depends upon effective clearance of pathogens while simultaneously preventing autoimmunity and immunopathology in the host. Restimulation-induced cell death (RICD) is one such mechanism where by activated T cells receive subsequent antigenic stimulation, reach a critical signal threshold through the T cell receptor (TCR), and commit to apoptosis. Many details of this process remain unclear, including the role of co-stimulatory and co-inhibitory proteins that influence the TCR signaling cascade. Here we characterize the role of T cell immunoglobulin and mucin domain containing 3 (TIM-3) in RICD regulation. TIM-3 protected newly activated CD8+ effector T cells from premature RICD during clonal expansion. Surprisingly, however, we found that TIM-3 potentiated RICD in late-stage effector T cells. The presence of TIM-3 increased proximal TCR signaling and proapoptotic protein expression in late-stage effector T cells, with no consistent signaling effects noted in newly activated cells with or without TIM-3. To better explain these differences in TIM-3 function as T cells aged, we characterized the temporal pattern of TIM-3 expression in effector T cells. We found that TIM-3 was expressed on the surface of newly activated effector T cells, but remained largely intracellular in late-stage effector cells. Consistent with this, TIM-3 required a ligand to prevent early RICD, whereas ligand manipulation had no effects at later stages. Of the known TIM-3 ligands, carcinoembryonic antigen‐related cell adhesion molecule (CEACAM1) showed the greatest difference in surface expression over time and also protected newly activated cells from premature RICD, with no measurable effects in late-stage effectors. Indeed, CEACAM1 enabled TIM-3 surface expression on T cells, implying a co-dependency for these proteins in protecting expanding T cells from premature RICD. Our findings suggest that co-signaling proteins like TIM-3 and CEACAM1 can alter RICD sensitivity at different stages of the effector T cell response, with important implications for checkpoint blockade therapy.

Comparing the use of individual and composite terms to evaluate adverse drug event disproportionality: a focus on glucagon-like peptide-1 receptor agonists and diabetic retinopathy

ABSTRACT Background: The SUSTAIN-6 trial showed significantly higher rates of retinopathy complications in the semaglutide group compared to placebo. Observational studies have not consistently corroborated this finding, raising questions about the appropriateness of composite variables and whether the relationship exists across the entire drug class or is limited to individual glucagon-like peptide 1 agonists (GLP-1RAs). The study objective was to evaluate the difference between using individual and composite terms to assess associations between GLP-1RAs and diabetic retinopathy events. Research Design and Methods: Reports from the US Food and Drug Administration Adverse Event Reporting System were utilized to examine relationships between GLP-1RAs and diabetic retinopathy events. A disproportionality analysis was conducted using the proportional reporting ratio. Results: Four GLP-1RAs demonstrated signals for diabetic retinopathy events. The GLP-1RA drug class had four diabetic retinopathy signals. Only semaglutide had a signal for the composite diabetic retinopathy outcome. The GLP-1RA drug class and the composite diabetic retinopathy outcome did not meet the PRR signal thresholds. Conclusions: The use of drug class level and composite outcome variables may mask diabetic retinopathy signals in comparison to individual drug assessments. Our results support the SUSTAIN-6 trial findings and suggest an association between four GLP-1RAs and diabetic retinopathy events.

A Tale of Two Domains Pushing Lateral Roots.

Successful plant organ development depends on well-coordinated intercellular communication between the cells of the organ itself, as well as with surrounding cells. Intercellular signals often move via the symplasmic pathway using plasmodesmata. Intriguingly, brief periods of symplasmic isolation may also be necessary to promote organ differentiation and functionality. Recent findings suggest that symplasmic isolation of a subset of parental root cells and newly forming lateral root primordia (LRPs) plays a vital role in modulating lateral root development and emergence. In this opinion article we discuss how two symplasmic domains may be simultaneously established within an LRP and its overlying cells, and the significance of plasmodesmata in this process.

Research on Cooling Characteristics of Power Battery Fast-charging of Refrigerant-based Direct Cooling System

In this paper, the temperature variation characteristics and control methods of power battery during rapid charging are studied. For the problem of large heat production in power battery fast-charging process, a refrigerant-based direct cooling battery thermal management system were built based on the AMEsim one-dimensional simulation platform. The change law of the battery temperature and the influence of different types of control thresholds on the cooling effect and the thermal management boundary of the cooling process in the constant current charging method of were studied. The results show that in the cooling process with the temperature as the threshold value, the cooling response is good under the condition of lower C-rate. With the increase of the C-rate, the temperature threshold cooling can not meet the cooling response requirements. Based on the consequence, the battery’s SOC(state of charge) was proposed as the control threshold signal for the advance cooling. The simulation results show that the SOC threshold cooling can control the highest temperature of the battery below 40°C, meeting the requirements of battery operation request. Through the full cooling of the maximum power, it is obtained that the thermal management boundary C-rate decreases linearly with the initial temperature change, and the final temperature in different initial temperatures increases linearly with the increase of the C-rate.

Design of Time-to-Digital Converters for Time-Over-Threshold Measurement in Picosecond Timing Detectors

In picosecond timing detectors, the time over threshold (TOT) of detector signals is normally required to be measured to enhance the front-edge timing precision. The extremely narrow pulsewidth of these detector signals has posed challenges to the design of time-to-digital converters (TDCs) based on field programmable gate arrays (FPGAs) for TOT measurement. In this article, an FPGA-based tapped-delay-line (TDL)-type TDC is proposed to simultaneously measure the arrival time and TOT time of nuclear pulses. By propagating the hit signal along a single TDL, the proposed bubble-proof encoding scheme can extract the time information of two transitions of hit signal in one measurement. The minimum measurable TOT time is proved to be limited only by the electrical characteristics of low-voltage differential signaling (LVDS) receivers of FPGAs. Through the performance evaluation on the prototype with a Virtex Ultrascale + FPGA, where the minimum measurable TOT time can be as low as 370 ps, the rms precision reaches 3.0 ps for TOT time measurement. Given the pulsewidths ranging from 0.4 to 1.5 ns, the measured TOT time is highly consistent with the direct readout values from the oscilloscope in a wide temperature range. To apply the TDC into a microchannel plate photomultiplier tube (MCP-PMT)-based timing detector, the front-end electronics board with a dual-threshold TOT measurement is constructed. The joint beam test results show that the coincidence time resolution of two identical detector channels can be improved from 36.5 to 10.3 ps, which demonstrates the significance of TOT measurement to modern picosecond timing detectors.

Validation of Heat-Level Vapor Phase Soldering Process and Workspace Leakage Detection with Applied Pressure Sensors

Electronic manufacturing principles are continuously developing, further improving assembly quality and productivity. There is a continuous need to apply novel and improved methods of process monitoring to provide accurate measurement and control during assembling. In this paper, a new principle for monitoring filmwise condensation-based heat-level—vapour phase soldering (HL-VPS) is presented to improve the process control. The experiment is based on thermocouple sensors in fusion with a sensitive gauge type pressure sensor. The aim is to precisely identify the steps of condensation-based reflow heat transfer process with commercially available components and the mindset of possible retrofitting in the generally used HL-VPS soldering ovens. It was found that the gauge sensor can follow the state of the workspace more precisely as the thermocouples, by monitoring the hydrostatic state of the vapour. The pressure (time) function gives information about the build-up of the vapour column, highlighting four characteristic steps (phases) of the process, meaning: immersion of the sample to be soldered, condensation-based heat transfer, solder-break, and cooling. Combined application with thermocouples enables more precise control, improving soldering quality and can reduce idle time of the oven. In addition, it was showed that the gauge type sensors could highlight any failure in the oven sealing by a sensor signal threshold detection. The original concept of workspace identification also fits the present and future industry 4.0 directives.

Cytoneme delivery of Sonic Hedgehog from ligand-producing cells requires Myosin 10 and a Dispatched-BOC/CDON co-receptor complex.

Morphogens function in concentration-dependent manners to instruct cell fate during tissue patterning. The cytoneme morphogen transport model posits that specialized filopodia extend between morphogen-sending and responding cells to ensure that appropriate signaling thresholds are achieved. How morphogens are transported along and deployed from cytonemes, how quickly a cytoneme-delivered, receptor-dependent signal is initiated, and whether these processes are conserved across phyla are not known. Herein, we reveal that the actin motor Myosin 10 promotes vesicular transport of Sonic Hedgehog (SHH) morphogen in mouse cell cytonemes, and that SHH morphogen gradient organization is altered in neural tubes of Myo10-/- mice. We demonstrate that cytoneme-mediated deposition of SHH onto receiving cells induces a rapid, receptor-dependent signal response that occurs within seconds of ligand delivery. This activity is dependent upon a novel Dispatched (DISP)-BOC/CDON co-receptor complex that functions in ligand-producing cells to promote cytoneme occurrence and facilitate ligand delivery for signal activation.

Expression of the ace operon in Escherichia coli is triggered in response to growth rate-dependent flux-signal of ATP.

The signal that triggers the expression of the ace operon and, in turn, the transition of central metabolism's architecture from acetogenic to gluconeogenic in Escherichia coli remains elusive despite extensive research both in vivo and in vitro. Here, with the aid of flux analysis together with measurements of the enzymic activity of isocitrate lyase (ICL) and its aceA-messenger ribonucleuc acid (mRNA) transcripts, we provide credible evidence suggesting that the expression of the ace operon in E. coli is triggered in response to growth rate-dependent threshold flux-signal of adenosine triphosphate (ATP). Flux analysis revealed that the shortfall in ATP supply observed as the growth rate ($\mu $) diminishes from µmax to≤0.43h-1 ($ \pm 0.02;n4)\ $is partially redressed by up-regulating flux through succinyl CoA synthetase. Unlike glycerol and glucose, pyruvate cannot feed directly into the two glycolytic ATP-generating reactions catalyzed by phosphoglycerokinase and pyruvate kinase. On the other hand, glycerol, which upon its conversion to D-glyceraldehyde, feeds into the phosphorylation and dephosphorylation parts of glycolysis including the substrate-level phosphorylation-ATP generating reactions, thus preventing ATP flux from dropping to the critical threshold signal required to trigger the acetate-diauxic switch until glycerol is fully consumed. The mRNA transcriptional patterns of key gluconeogenic enzymes, namely, ackA, acetate kinase; pta, phosphotransacetylase; acs, acetyl CoA synthetase and aceA, ICL, suggest that the pyruvate phenotype is better equipped than the glycerol phenotype for the switch from acetogenic to gluconeogenic metabolism.

Integration of multiple response signals into the probability of detection modelling in eddy current NDE of flaws

A new method of modelling the probability of detection (PoD) of a flaw parameter (flaw length) for the case of multiple correlated flaw response signals is proposed in this work. The PoD modelling is assisted by boundary element method in order to compute the required flaw features, the maximum change in the impedance of a coil, at two different frequencies. Experiments were performed using a LCR meter to verify the predictions of the boundary element model. The modelling was performed on a finite thickness aluminum-1050 plate with a narrow opening surface flaw. The features were computed for various flaw lengths and fit with a bi-variate Gaussian distribution, thus evading the problem of heteroscedasticity. On knowing the signal thresholds, the PoD of a flaw length can be computed from the Gaussian density. The obtained discrete PoD is then regressed by a generalized logistic function (GLF) in order to attain a continuous function for the PoD of the flaw length. The parameters of the GLF are estimated via non-linear least squares minimization by Levenberg-Marquardt algorithm.

Adaptive Thresholds of EEG Brain Signals for IoT Devices Authentication

In this paper, a new authentication method has been proposed for the Internet of Things (IoT) devices. This method is based on electroencephalography EEG signals, and hand gestures. The proposed EEG signals authentication method used a low price NeuroSky MindWave headset. This was based on choosing the adaptive thresholds of attention and meditation mode for the authentication key. Hand gestures to control authentication processes by using a general camera. To verify that a new authentication method is widely accepted, it must meet two main conditions, security and usability. The evaluation of the prototype usability was based on ISO 9241-11:2018 standards usability model. Results revealed that the proposed method demonstrated the usability of authentication by using EEG signals with the accuracy of 92%, the efficiency of 93%, and user satisfaction is acceptable and satisfying. To evaluate the security of the prototype, we consider the most important three threats related to IoT devices which they are guessing, physical observation, and targeted impersonation. The results showed that the password strength, using the proposed system is stronger than the traditional keyboard. The proposed authentication method also is resistant to target impersonation and physical observation.

A SVD-Based Signal De-Noising Method With Fitting Threshold for EMAT

The electromagnetic acoustic transducer (EMAT) is a powerful and useful non-destructive testing technology for structural health monitoring. However, EMAT has an issue of low efficiency in conversion and its signal is easily affected by noise, which make it difficult to accurately identify and evaluate structural defects. Thereby, signal de-noising preprocessing is essential for the evaluation of defects. In this paper, we proposed an improved singular value decomposition (SVD) de-noising method based on the fitting threshold for EMAT signal. For SVD de-noising method, the key point is to determine the singular value threshold for reconstructing the signal. We applied a segmented regression model to find the appropriate threshold in this approach. To investigate the efficacy of the proposed method, simulation signals and experimental signals are used for verification respectively. A comparative analysis has been under-taken to confirm that the proposed signal de-noising has advantages over other methods in EMAT signal noise reduction, and it is useful for more accurate evaluation of defects.

StimulEye: An intelligent tool for feature extraction and event detection from raw eye gaze data

Extraction of eye gaze events is highly dependent on automated powerful software that charges exorbitant prices. The proposed open-source intelligent tool StimulEye helps to detect and classify eye gaze events and analyse various metrics related to these events. The algorithms for eye event detection in use today heavily depend on hand-crafted signal features and thresholding, which are computed from the stream of raw gaze data. These algorithms leave most of their parametric decisions on the end user which might result in ambiguity and inaccuracy. StimulEye uses deep learning techniques to automate eye gaze event detection which neither requires manual decision making nor parametric definitions. StimulEye provides an end to end solution which takes raw streams of data from an eye tracker in text form, analyses these to classify the inputs into the events, namely saccades, fixations, and blinks. It provides the user with insights such as scanpath, fixation duration, radii, etc.

Assessment of Slope-Adaptive Metrics of GEDI Waveforms for Estimations of Forest Aboveground Biomass over Mountainous Areas

Waveform broadening effects of large-footprint lidar caused by terrain slopes are still a great challenge limiting the estimation accuracy of forest aboveground biomass (AGB) over mountainous areas. Slope-adaptive metrics of waveforms were proposed in our previous studies. However, its validation was limited by the unavailability of enough reference data. This study made full validation of slope-adaptive metrics using data acquired by the Global Ecosystem Dynamics Investigation (GEDI) mission, meanwhile exploring GEDI waveforms on estimations of forest AGB. Three types of waveform metrics were employed, including slope-adaptive metrics (RHT), typical height metrics relative to ground peaks (RH), and waveform parameters (WP). In addition to terrain slopes, two other factors were also explored including the geolocation issue and signal start and ending points of waveforms. Results showed that footprint geolocations in the first version GEDI data products were shifted to the left forward of nominal geolocations with a distance of about 24 m~30 m and were substantially corrected in the second version; the fourth and fifth groups of signal start and ending points of waveforms had worse performance than the rest of the four groups because they used the maximum and minimum signal thresholds, respectively. Taking airborne laser scanner (ALS) data as reference, the root mean square error (RMSE) of terrain slopes extracted from the digital elevation model of the shuttle radar topography mission (SRTM DEM) was about 3°. The coefficients of determination ( R 2 ) of estimation models of forest AGB based on RH metrics were improved from 0.48 to 0.68 with RMSE decreased from 19.7 Mg/ha to 15.4 Mg/ha by the second version geolocations. The RHT and WP metrics gave the best and the worst estimation accuracy, respectively. RHT further improved R 2 to 0.77 and decreased RMSE to 13.0 Mg/ha using terrain slopes extracted from SRTM DEM with a resolution of 1 arc second. R 2 of estimation models based on RHT was finally improved to 0.8 with RMSE decreased to 11.7 Mg/ha using exact terrain slopes from ALS data. This study demonstrated the great potential of slope-adaptive metrics of GEDI waveforms on estimations of forest aboveground biomass over mountainous areas.

Evaluation of ultrasonic cleaning process

Purpose. To establish relationship between intensity of ultrasonic cleaning and an ultrasonic response fixed at a set point. To determine the influence of liquid contamination on this signal. To specify parameters of an ultrasonic signal to evaluate the course of cleaning a preset section of a body. To define limiting values indicating efficiency of ceasing the cleaning process. Methodology. The research is based on simulation of ultrasonic wave propagation in the heterogeneous environment and subsequent analysis of the signals by using software. Findings. Dependences are established to form evaluation of the course of the cleaning process by parameters of the ultrasonic response. It is found that both the bodys state and that of the liquid affect the ultrasonic response obtained by the sensor at the set point during ultrasonic cleaning. With high contamination (>30%) the state of the liquid becomes a critical factor for forming the signal of the ultrasonic response. With that, there is an abrupt reduction of threshold signal arrival time and increase in the main amplitude, which is to be one of indicators of ceasing the cleaning process in case of its inefficiency. With lower contamination, suspended contaminant particles only correct the signal to some extent without distorting it. There is a relationship between reduction of contamination, the arrival time of threshold signal, on the one hand, and the value of the main amplitude and the 2nd and 3rd-order nonlinearity coefficients, on the other hand. The arrival of the threshold value of the signal is the major parameter determining intensity of cleaning, i.e. reduction of contaminant thickness, which is determined by the value of the main amplitude of the signal and the 2nd and 3rd-order nonlinearity coefficients. Originality. For the first time, methods for evaluating the course of the ultrasonic cleaning process by analyzing ultrasonic responses at a specified point have been developed. Practical value. To consider spatial distribution of the ultrasonic cleaning process, its control is to be based on evaluating the bodys contamination in several preset points. To implement this, the character of dependences between changes in contamination of the body section and parameters of the fixed ultrasonic response is determined. Impacts are considered of suspended contaminant particles in the liquid on the signal analyzed. The observed relationship will provide the basis for building the spatially distributed control over ultrasonic cleaning considering the cleaned bodys state.