Abrupt Point Research Articles

Surface water area dynamics of the major lakes of Ethiopia (1985–2023): A spatio-temporal analysis

Ethiopian lakes face multiple ecosystem threats from human and natural factors, including climate change. The long-term dynamics of water surface area in many lakes remain unknown. This study presents the first comprehensive account of major Ethiopian lakes’ long-term water surface area dynamics, providing essential information for prioritizing hydrological conservation strategies. We extracted the time-series water surface area of the lakes from Landsat images in the Google Earth Engine (GEE), using the Modified Normalized Water Index (MNDWI) and machine learning (Random Forest) methods. Random Forest (RF) outperformed MNDWI across many lakes, especially when water body spectral characteristics became complex. A comparison of the results with the Joint Research Center (JRC) Global Surface Water Mapping Layers showed a good agreement. Long-term water surface area dynamics showed both common and distinct trends. Common trends included: (a) similar recession and expansion periodicities despite lakes being in different climatic zones, (b) an increase in the inter-annual variability of water area after 2000, and (c) a common abrupt point in time (2000/2001). Distinct trends included: (i) long-term decline in five lakes (Abiyata, Langano, Shalla, Chamo, and Hayq), (ii) expansion in three lakes (Ziway, Hawassa, and Abaya), and (iii) non-homogeneous long-term trends in two lakes (Tana and Hardibo). These common and distinct trends show the interplay of climate phenomena and lake-specific factors. Climate factors govern inter-annual lake area change (decreasing/increasing) and recession and expansion cycle periods. The magnitudes of changes and recovery rates after each change cycle vary based on lake-specific factors. We recommend prioritizing conservation efforts for lakes with high water storage degradation risks, as indicated by significant water loss over the historical period and persistent long-term declining trends. This includes Abiyata, Chamo, Shalla, Langano, Hayq, and Hardibo, in order of priority.

Angular dispersion and diffraction imaging analysis in a light wave oblique incident two-dimensional crossed grating

Based on the vector diffraction theory, the angular dispersion and diffraction imaging are analyzed in parallel light oblique incident two-dimensional crossed gratings. The results show that the angular dispersion presents a kind of increase-decrease-increase oscillatory change, and the maximum value of diffractive polar angle dispersion and total dispersion present an abrupt point. The angular dispersion is limited by the light wave incidence angle and two-dimensional gratings crossed angle. In addition, some obvious pincushion distortion has been formed in some cases. The angular dispersion increases with the increase of grating crossed angle in the permissible range, leading to enhancement of the diffraction imaging distortion. The results imply that there is an inherent relationship between the angular dispersion and the diffraction imaging in parallel light oblique incident crossed gratings.

Warming surface and Lake heatwaves as key drivers to harmful algal Blooms: A case study of Lake Dianchi, China

Extreme heat events such as marine and atmospheric heatwaves, have catastrophic impacts on marine and terrestrial ecosystems. Recent studies have shown that the continuous warming of lake surfaces and enhancement of lake heatwaves (LHWs) have generated great research interest globally. However, the effects of LHWs on lake ecosystems, especially cyanobacterial harmful blooms (cHABs), remain unclear. This study reconstructed the daily Lake surface water temperature (LSWT) time series in Lake Dianchi from 1951 to 2020 using random forest. Trends and characteristics of LSWT and LHWs were identified, and their critical driving effects on cHABs were analyzed. Results showed that the LSWT in Lake Dianchi significantly increased with a rate of 0.26 °C/10a and with an abrupt changing point in 1992, coinciding with the first report of severe cHABs in Lake Dianchi. From 1951 to 2020, 141 LHWs were detected, of which 94.3 % occurred after 1992. Among all the potential climatic and water quality driving factors on Chlorophyll-a (Chla) variation, LSWT is the most important. Chla concentration and the intensity of LHWs were significantly correlated. The complex and strong interactions between LHWs and cHABs enable the suppression of cHABs only when both remain low. A case study in Lake Dianchi highlighted the critical driving effects of LSWT and LHWs on cHABs, suggesting that continuously warming surface and enhancing LHWs in the future will further challenge more specific and effective lake management strategies to suppress cHABs.

Time point and scale measurement of carbon sink trading market risk based on catastrophe entropy and potential function

According to the principle of total entropy change of dissipative structure, the carbon trading market is defined as a nonlinear complex system that follows the law of entropy increase in this paper. Based on the potential function of sudden change theory, this paper studies the risk point and scale of the carbon trading market. The results show that (1) the theory of dissipative structure and catastrophe theory can be used as the theoretical basis of carbon financial market risk research, and its core technology can be used to measure and predict risks. (2) The risk mutation point measurement model based on the total entropy change principle and potential function technology effectively detected 16 major risk mutation points in the financial crisis, the European debt crisis, and the European new energy efficiency plan. The empirical test shows that the model has a good ability to capture abrupt changes and prediction accuracy. The fitting effect is very good. (3) The risk index value of the risk abrupt point can be calculated effectively by the risk scale measurement technique based on information entropy and the potential function surface equation. Furthermore, we judge the degree and grade of risk. From 2008 to 2021, amongst the 16 risk mutation points in the EU carbon trading market, there are three extremely high risk mutation points, seven high-risk mutation points, two medium-risk mutation points, two low-risk mutation points, and two very low risk mutation points. High risk or above grade accounted for 62.5%. Empirical analysis supports this conclusion.

Impacts of climate change and anthropogenic stressors on runoff variations in major river basins in China since 1950

Runoff is one of the main components of hydrological cycle and an important index for water resources evaluation, understanding the runoff change and their causes is vital to water resource management. In the study, we analyzed the runoff change and the impacts of climate change and land use alteration on runoff variation based on natural runoff and previous studies in China. The results showed that there was a significant increasing trend in the annual runoff during 1961–2018 (p < 0.05), with change rate of 0.4 mm/a and abrupt point at 1999 across China, climate change dominated the runoff variation with a contribution of 54 %. In previous studies, the runoff of the major basins in China had a downward trend on the whole (−0.99 mm/a) except Continental River Basin (CRB) showed an increasing trend (0.25 mm/a), the abrupt points were mainly concentrated in 1991–2000, and human activity was the leading factor of runoff change with the contribution of 54 % across China. Human activity was the dominant factor of runoff change in Songhua and Liao River Basin (SLRB), Yellow River Basin (YRB), Hai River Basin (HRB) and Pearl River Basin (PRB), the contribution was >56 %, while climate change was the dominant factor of runoff change in Huai River Basin (HuRB), CRB, and Yangtze River Basin (YZRB). Overall, there was a significant correlation between runoff and precipitation, unused land, urban and grassland in China. We concluded that runoff change and the contribution of climate change and human activities varies greatly among different basins. The findings in this work can shed light on the quantitative understanding of runoff changes in national scale and offer a scientific basis for sustainable water management.

Spatiotemporal variability in extreme precipitation and associated large-scale climate mechanisms in Central Asia from 1950 to 2019

Increased sea surface temperature, evaporation, air temperature, and moisture holding capacity associated with climate change may the enhance transport of moisture to Central Asia (CA), resulting in increased extreme precipitation events (EPEs). Changes in EPEs may affect the socioeconomic and ecological environment in typical arid and semi-arid regions of CA. Therefore, based on meteorological station data and four reanalyzed precipitation datasets, we used the Taylor diagram, Geo-Detector method, and other methods to examine 10 EPE indices in CA from 1950 to 2019, analyzed their spatial-temporal trends, and quantified the influence of large-scale climate factors on EPEs. The results showed that GSWP3_W5E5 was the optimal option with better performance in terms of monthly and annual precipitation in CA. Overall, EPEs in CA showed an increasing trend, but an abrupt point was found in 1986, when very wet day precipitation (R95p) increased from 36.64 to 47.84 mm; the increasing rate also changed from 0.8 to 5.06 mm/10a. The changes in the Northern Hemisphere Subtropical High Intensity Index (NSI), NINO B Area Sea Surface Temperature Anomaly Index (NINOB), Asian Zonal Circulation Index, and Atlantic Multidecadal Oscillation Index are the main reasons for the increase in EPEs; the NSI and NINOB had the largest contributions to EPEs, with at 44.32 % and 43.80 %, respectively. Additionally, two-factor interactions had a more significant influence. Further analysis revealed that the abnormal warming of sea surface temperature and others led to the strengthen of water vapor transport in CA caused by a series of cyclones and anticyclonic anomalies in the westerly circulation zone, leading to the increase of EPEs. The results obtained in this study can contribute to a more comprehensive understanding of the changes in EPEs and provide a reference for water resource management and disaster prevention in CA.

Robot-Assisted Laparoscopic Ureteroureterostomy of an Obstructive Retrocaval Ureter

Clinical History: A 32-year-old woman without significant medical history presented with incidentally found right severe hydronephrosis from a computed tomography scan after car accident. Her symptoms include only intermittent right flank pain. She has no dysuria or hematuria. Physical Examination: Examination was notable for right-sided costovertebral angle tenderness. Diagnosis: A computed tomography urogram scan was performed, which revealed severe right hydronephrosis with abrupt transition point at proximal ureter. The transition point was located posterior to the inferior vena cava, consistent with retrocaval ureter anatomy. Renal nucleotide scan showed 40% right kidney split function as well as a t1/2 of 35 minutes in right kidney, suggesting obstruction. Intervention: Given symptomatic pain, radiologic evidence of ureteral obstruction, good residual right renal function, and performance status, decision was made to perform a right robot-assisted laparoscopic ureteroureterostomy. Follow-up/Outcomes: Patient tolerated the procedure well and was discharged home the morning after surgery with drain removed. She had prompt return of daily activities and complete resolution of flank pain. Her ureteral stent was removed in clinic 6 weeks after the surgery. Repeat renal nucleotide scan 3 months after the surgery demonstrated resolution of obstruction with new t1/2 of 8.7 minutes. Patient Consent Statement: The author(s) have received and archived patient consent for video recording/publication in advance of video recording of procedure. The authors have no conflicts of interest that may alter the results of this study. Runtime of video: 4 mins 28 secs

NT-Com: A combined machine learning model for picking up first arrival

We present a combined model named NT-Com that could predict the noise of observation site in China and effectively pick up first arrivals with very high accuracy. Based on a nonlinear autoregressive exogenous model (NARX) known as a variant of recurrent neural network and classification-regression trees (CART), NT-Com picks first arrivals by detecting abrupt points in time series. Several experiments were performed to check the fitting degree and prediction accuracy of NARX on noise signals, and experiments on CART were made to measure the accuracy of first break picking. The experimental results of NT-Com are close to those of experts and better than the traditional automatic detection algorithms. Moreover, the accuracy of NT-Com can reach 96%. The time error of the P-wave first arrival pickup can be shortened to 0.5 s. Because various first arrival patterns are learned during the training process, they can be effectively identified, which leads to a much lower probability of false triggers than traditional automatic detection algorithms. Trained and tested by all seismic data in China Earthquake networks from 2009–2019, the research work finds out a solution for picking up first arrivals by combining a simple structure of the neural networks and trees, which can be applied in China with its strong generalization ability and robustness.

Effects of cascading reservoirs on streamflow and sediment load with machine learning reconstructed time series in the upper Yellow River basin

Large reservoirs are widely built along rivers for flood control, hydropower generation, water supply for industry and agricultural production, and recreation. Many large reservoirs/dams built to provide multiple functions for local people are strongly influenced by the downstream flow and sediment discharge in the upstream of the Yellow River, China. In this study, we assessed the changes in the river flow and sediment discharge in responses to the construction of cascade reservoirs/dams by using continuously hydrological time series observed at six stations during 1956–2018. The temporal change in the streamflow was insignificant, but the sediment load decreased dramatically due to the trapping effects of the cascade reservoirs. The change points were detected in 1969 and 1986, which were consistent with the timing of the construction of gigantic reservoirs. We then applied the abrupt changing points to divide the whole time series into a reference period (1956–1968) and two changing periods (1969–1986 and 1987–2018). The linear regression and three machine learning models were employed to reconstruct the natural streamflow and sediment load at the downstream station, before quantifying their responses to cascade reservoirs. The annual mean streamflow and sediment load decreased by 21% and 84%, respectively, after constructing the Longyangxia and Liujiaxia reservoirs. Cascade reservoirs contributed 85.39% and 94.91% to the decreases in the streamflow and sediment discharge, respectively. Hydrological regimes have been greatly altered by the 13 cascade reservoirs, with seasonal redistribution of the streamflow and flood peak reduction because their high trapping efficiencies exceed 95%. These findings indicate that large and medium sized reservoirs have drastically altered the streamflow and sediment load, thereby intensely influencing the fluvial processes in the upstream of the Yellow River.

Assessing hydrological performance for optimized integrated grey-green infrastructure in response to climate change based on shared socio-economic pathways

Integrated grey-green infrastructure (IGGI) is considered as a promising facility for mitigating urban flooding during extreme rainfall events. However, most IGGI strategies rely heavily on historical precipitation data, while ignoring the long-term effects of dynamic and non-stationary climate change. This study explored a novel approach to assess the hydrological performance under Shared Socio-economic Pathways (SSPs) based on long-term rainfall time series, facilitating the exploration of the optimal solution to urban runoff alleviation in response to climate change. A case study of Guangzhou, China, was applied for model validation. The results indicated that through non-stationarity analysis and stage division, the future time series of the three SSPs were identified with an abrupt point and divided into two stages. By assessing the hydrological performance of the optimal solutions at various historical and future stages, both fully centralized IGGI and decentralized IGGI are found vulnerable to long-term climate change. Based on a certain extent of trade-off between centralization and decentralization, an appropriate degree of decentralization was observed to significantly enhance the hydrological performance of the whole IGGI system, particularly for reducing peak flow following extreme rainfall events. The authors believe that the findings could provide a novel perspective on hydrological performance assessment for IGGI in response to non-stationary and multi-scenario climate change in urban catchments with high built-up density.

Separating seismic diffractions by an improved Cook-distance singular value decomposition method

When seismic waves encounter abrupt points of stratum or lithology in the process of propagation, such as fault edges, pinch-out points, or the protrusion of unconformity surfaces, the Snell law will break down and many diffractions will be generated. However, the diffraction information is typically masked by strong reflections; thus, separating diffractions is one key issue for diffraction imaging. The traditional singular value decomposition (SVD) method with the ability for wavefield decomposition and reconstruction is useful in removing strong reflections of large singular values. However, the continuously changing characteristics of the singular value of steep-slope reflections make it difficult to choose a suitable parameter for separating diffractions. To solve the problem of singular value selection in diffractions reconstruction by the SVD method, we have developed a Cook-distance SVD method by mathematically least-squares measuring the contribution of every singular value. The Cook-distance SVD can amplify the difference between continuously changing singular values and easily find the singular values representing diffractions. Synthetic examples and field data applications demonstrate that our Cook-distance SVD method can avoid parameter testing and has good performance in diffraction separation and can highlight reservoir-involved small-scale geologic edges and scatterers.

Variation Characteristics of Rainstorms and Floods in Southwest China and Their Relationships with Atmospheric Circulation in the Summer Half-Year

Local climates are responding to global warming differently, and the changes in rainstorms in mountainous areas of Southwest China are of particular interest. This study, using monthly NCEP/NCAR reanalysis and daily precipitation observation of 90 meteorological stations from 1961 to 2021, analyzed the temporal and spatial variation characteristics of rainstorms and floods in Southwest China and their relationship with atmospheric circulations. The results led us to the following five conclusions: (1) Rainstorms and floods in southwest China mainly occur from June to August, during which time July has the most weather events, followed by August. (2) The southwest of Guizhou province, the southern edge of Yunnan province, and regions from the east of the Sichuan Basin to the north of Guizhou have experienced more rainstorms and floods, while the northwest regions of Southwest China have had fewer. (3) Over the last 61 years, rainstorms and floods have exhibited an overall rising trend, especially in the last 10 years. The year 2012 was an abrupt inflection point in rainstorms and floods in Southwest China, from low to high frequency, while the correlation coefficient between rainstorms and floods and the global surface temperature is above the 95% significance level. (4) Rainstorms and floods exhibit changes at periods of 8 years, 16 years, and 31 years. (5) Rainstorms and floods show a good correlation with multiple variables, such as South Asian high-pressure systems west of 90°E, the upper trough front, the northwest side of the western Pacific subtropical high, and the convergence of warm and wet air in the middle and lower layers with cold air on the ground.

Concept drift detection in toxicology datasets using discriminative subgraph-based drift detector.

Due to the increasing importance of graphs and graph streams in data representation in today's era, concept drift detection in graph streaming scenarios is more important than ever. Contributions to concept drift detection in graph streams are minimal and practically non-existent in the field of toxicology. This paper applied the discriminative subgraph-based drift detector (DSDD) to graph streams generated from real-world toxicology datasets. We used four toxicology datasets, each of which yielded two graph streams - one with abrupt drift points and one with gradual drift points. We used DSDD both with the standard minimum description length (MDL) heuristic and after replacing MDL with a much simpler heuristic SIZE (number of vertices + number of edges), and applied it to all generated graph streams containing abrupt drift points and gradual drift points for varying window sizes. Following that, we compared and analyzed the results. Finally, we applied a long short-term memory based graph stream classification model to all the generated streams and compared the difference in the performances obtained with and without detecting drift using DSDD. We believe that the results and analysis presented in this paper will provide insight into the task of concept drift detection in the toxicology domain and aid in the application of DSDD in a variety of scenarios.

Permeability evolution of methane and water vapor when simultaneously transporting in shale

Methane and water vapor transport in shale (mud rocks) is important in many resource and environmental issues, e.g., effectively exploiting shale gas and clearly understanding water and methane global cycles. To investigate methane and water vapor permeability in shale, a new permeability determination method was proposed using a linearization approach based on previous studies. The experimental samples are crushed Carboniferous shale from the eastern Qaidam Basin in China. Simultaneous methane and water vapor transport experiments in shale were performed. Water vapor was derived through deionized water evaporation under different methane pressures. The relative humidity dynamically changed during the experiment. The methane and water vapor transport processes were observed and recorded, and the methane and water vapor permeability in the shale matrix was calculated. Both the methane and water vapor permeabilities temporally varied, and a critical abrupt point occurred in the decreasing process over time. After the abrupt point, the permeability rapidly decreased, which was mainly due to capillary condensation plugging at high relative humidities. Pore throat closure could dramatically affect permeability. The relationship between permeability and water saturation (Sw) conformed to an exponential equation. Methane permeability was sensitive to water saturation variation at very low or high levels (Sw <20 % or Sw >50 %, respectively) and relatively insensitive at a moderate water content. Water vapor permeability variation with water saturation was similar to that in methane but basically remained stable at a moderate water saturation (10 % <Sw < 50%). At high water saturations, water vapor permeability reduction was more sensitive than that in methane.

S3531 A Rare Cause of Obstructive Jaundice: Afferent Limb Syndrome

Introduction: Afferent limb syndrome (ALS) is a rare but potentially life-threatening complication of upper gastrointestinal (GI) surgery and reconstruction causing distal obstruction of the biliopancreatic limb with subsequent accumulation of bile, pancreatic fluid, and other small bowel secretions upstream afferent limb dilation. It is imperative to recognize this complication postoperatively as buildup in the small bowel can result in bowel perforation requiring emergency surgery. We present a patient who developed ALS after upper gastrointestinal reconstruction with esophagojejunostomy for the treatment of gastric adenocarcinoma. Case Description/Methods: An 84 year-old female with a past medical history of gastric adenocarcinoma with total gastrectomy and esophagojejunostomy presented to the emergency department with a subacute history of upper abdominal pain and new-onset jaundice. Initial labs were notable for elevated liver chemistries including alkaline phosphate level of 435 U/L (normal 39-117 U/L), alanine transaminase of 62 U/L (normal 6-45 U/L), and aspartate transaminase of 36 U/L (normal 10-25 U/L). Abdominal ultrasound demonstrated markedly dilated common bile and intrahepatic ducts and gallbladder distention without stones. CT scan of the abdomen confirmed the ultrasound findings, but also identified a dilated duodenum with an abrupt transition point in the proximal jejunum suggestive of ALS shown in Figure A. The patient underwent open laparotomy which demonstrated multiple tumor implants. A large implant at the site of the previous jejunojejunostomy was identified as the cause of afferent limb obstruction. A palliative bypass was performed. The patient had a complicated post-operative course. Ultimately, due to the extensive disease burden and ongoing patient discomfort, the patient and their family decided to pursue hospice care. Discussion: ALS is a post-operative complication of upper GI tract surgery that involves mechanical obstruction of the biliopancreatic limb. Patients often present with jaundice. CT scan is the preferred diagnostic modality. First-line treatment involves surgery to relieve the obstruction with revision of the prior anastomosis. Although rare, this diagnosis should be considered in appropriate patients.Figure 1.: A: CT scan with markedly dilated intrahepatic and extrahepatic biliary ductal dilation, distended gallbladder, and markedly dilated duodenum with abrupt transition point in proximal jejunum.

Trajectory Planning and Optimization for Robotic Machining Based On Measured Point Cloud

Industrial robots are characterized by good flexibility and a large working space, and offer a new approach for the machining of large and complex parts with small machining allowances (extra material allowed for subsequent machining). Parts of this type (such as aircraft skin parts, wind turbine blades, etc.) are easily deformed due to their large scale and low stiffness. Therefore, these parts cannot be directly machined according to the designed model. A feasible method is to plan a robotic machining path by using the point clouds of parts after clamping from onsite measurement which contains inherent defects of measurement such as noise points and abrupt points. In this article, a novel method is proposed to plan and optimize a robotic machining path that meets the requirements of smoothness, dexterity, and stiffness based on the point cloud from onsite measurement. The dual nonuniform rational B-spline curves of the machining path points and tool axis points are generated at first. Next, an objective function of smoothness optimization is established to filter out the local mutation of the path by considering the constraints of both the deformation energy and the deviation. Then, the objective function of robot postures optimization is established to optimize dexterity and Cartesian stiffness of a robot during the machining process. To show the feasibility of the proposed method, simulation and experiments are carried out. It is proved that the proposed method can generate a smooth machining trajectory. The stability of joint rotation and the rigidity and dexterity of the robot are improved during the machining process.

Effects of climate variability and anthropogenic factors on sediment load reduction in the Weihe River basin, China

AbstractSediment load of China's Yellow River has dramatically decreased due to the interplay of climate variability and human activities in the past decades. However, the contribution of individual driving factors and the detailed spatial distribution of sediment load at a catchment scale were not well understood. In the study, we quantitatively assessed the relative contributions of individual climatic (i.e. precipitation) and anthropogenic (i.e. vegetation restoration, terrace construction) driving factors to sediment load variations in the largest tributary of the Yellow River, Weihe River. The employed annual sediment load measurements and rainfall data for 1961–2015 were collected at 15 hydrological and 60 meteorological stations that were widely distributed in the basin. Changing trends, periodicity, and abrupt changes of hydro‐climatic variables were detected using the non‐parametric Mann–Kendall test, the empirical mode decomposition method, and Pettitt's test. Results showed that annual sediment load presented significantly decreasing trends at 12 hydrological stations. Annual rainfall erosivity showed a mixed tendency, with the changing trends varying among different regions. A 3‐year periodicity was identified in the annual sediment load at three main stream gauging stations. Abrupt changing points in sediment load primarily occurred in the 1990s and early 2000s at all of the 15 hydrological stations, which were largely attributed to human activities. The increase in vegetation cover was responsible for approximately 40.6%, 37.4%, and 54.7% of the sediment load reduction in the main stream of the Weihe River, the Jinghe River, and the Beiluohe River, respectively. Meanwhile, terrace construction accounted for 19.7%, 43.8%, and 9.9% of the sediment variation, respectively. Conversely, precipitation change accounted for 5.7%, 12.4%, and 8.3% of sediment load reduction, respectively. Overall, vegetation restoration and terrace construction were found to be the two dominating factors for sediment load reduction in the study area.

Two Cases of “Drained and Retained” Inflatable Penile Prosthesis and Artificial Urinary Sphincter Reservoirs causing Small Bowel Obstruction

ABSTRACT Introduction Inflatable penile prosthesis (IPP) and artificial urinary sphincter (AUS) are the most common surgical implants in the field of men's health. Infected or defective implants can be removed or replaced. The “drain and retain” strategy has been described as generally safe when prosthetic reservoirs are not easily retrieved. However, case reports of complications related to retained balloons have been described including erosion into the bowel and bladder, intraperitoneal migration and vascular compression. Here we describe two rare cases of reservoir-induced small bowel obstruction (SBO) from IPP and AUS reservoirs. Objective Describe two rare cases of retained IPP and AUS reservoirs causing SBO. Methods Single institutional retrospective case series. Results Case 1: 75 year old male who underwent IPP placement in 2001. Due to device malfunction, IPP cylinders were removed and replaced with 2-piece device in 2017, and the reservoir was “drained and retained.” The patient presented 4 years later with abdominal pain, nausea/vomiting, and right lower quadrant (RLQ) feculent cutaneous drainage. CT scan showed SBO with a transition within the terminal ileum due and an endoluminal foreign body in the cecum (consistent with the retained reservoir) (Figure 1A). Additionally, a contained bowel perforation with entero-cutaneous fistula tract to the skin was identified. Diagnostic laparoscopy revealed a thickened terminal ileum, walled-off perforation in the RLQ (Figure 1B) thought to be due to reservoir entry into the bowel, and a fistula to the right abdominal wall. The bowel was resected, thorough investigation including right-sided colonoscopy was unable to identify the reservoir, and primary anastomosis was performed. Follow up CT scan 3 days later showed passage of reservoir, presumably in the patient's bowel movements. Case 2: 81 year old male with a history of AUS placement in 2016. The device was removed for infection 5 years later. The reservoir was “drained and retained” given difficult access and no sign of reservoir infection. One month later, he presented with abdominal distention, nausea and vomiting. A CT scan revealed dilated loops of small bowel with an abrupt transition point in the RLQ adjacent to the retained reservoir (Figure 1C). Exploratory laparotomy showed SBO with the reservoir and tubing embedded into the small bowel wall (Figure 1D). The foreign bodies were successfully retrieved and the affected bowel was resected and repaired with a primary anastomosis. Conclusions These two cases of SBO due to IPP and AUS reservoirs show a potential danger of the “drain and retain” strategy, especially when reservoirs are placed intraperitoneal. These cases may be helpful to inform patient counseling on the rare risks of implant revision surgery. Innovative means of reservoir retrieval at explantation are needed to mitigate these risks. Disclosure No

Uncertainty Quantification of Self-Breakdown Switches in a Circuit Model Using Wiener–Haar Expansion

Since many electromagnetic compatibility tests are resourcelimited, it is important to quantify the uncertainties of instruments beforehand. One of the common instruments is the trigger pulse generator with self-breakdown switches. Due to the abrupt changing caused by self-breakdown switches, stochastic methods based on the generalized polynomial chaos suffer from Gibbs-type phenomena and become erroneous around abrupt transition point. This article proposes an effective technique based on the Haar wavelets for quantifying the time delay of self-breakdown switches in stochastic simulations. Wiener–Haar wavelet expansion method is suitable for dealing with abrupt-changing problems and is applied to the nodal-analysis-based circuit model. The stochastic circuit model is expanded to an augmented model with deterministic coefficients by exploiting wavelets’ orthogonality. Furthermore, the distribution of time delay is represented as the mean value of a Heaviside function, which is implemented by an auxiliary circuit in the model. The statistical mean can be directly obtained from the 0th coefficient of Wiener–Haar expansion. A case study of a trigger generator for electromagnetic pulse generators is provided to validate the effectiveness of the proposed method. It is shown that, compared with Monte Carlo methods, Wiener–Haar representation provides robust results with less computational time and a faster convergence rate.

De-Noising of Magnetotelluric Signals by Discrete Wavelet Transform and SVD Decomposition

Magnetotelluric (MT) sounding data can easily be damaged by various types of noise, especially in industrial areas, where the quality of measured data is poor. Most traditional de-noising methods are ineffective to the low signal-to-noise ratio of data. To solve the above problem, we propose the use of a de-noising method for the detection of noise in MT data based on discrete wavelet transform and singular value decomposition (SVD), with multiscale dispersion entropy and phase space reconstruction carried out for pretreatment. No “over processing” takes place in the proposed method. Compared with wavelet transform and SVD decomposition in synthetic tests, the proposed method removes the profile of noise more completely, including large-scale noise and impulse noise. For high levels or low levels of noise, the proposed method can increase the signal-to-noise ratio of data more obviously. Moreover, application to the field MT data can prove the performance of the proposed method. The proposed method is a feasible method for the elimination of various noise types and can improve MT data with high noise levels, obtaining a recovery in the response. It can improve abrupt points and distortion in MT response curves more effectively than the robust method can.