Leak Test Research Articles

A novel instrumentation approach for achieving in-situ temperature sensing of a Li-ion cylindrical cell under immersion cooling

Battery thermal management systems are critical for high-performance electric vehicles, where the ability to remove heat and homogenize temperature distributions in single cells and packs are key considerations. Immersion cooling, which immerses the battery in a dielectric fluid, can improve cooling efficiency compared to air cooling. However, stringent instrumentation standards make in-situ monitoring under immersion cooling a difficult challenge. This study proposes a novel cell instrumentation method based on the integrated combination of three O-rings, which for the first time achieves in-situ temperature sensing of batteries under oil-immersed cooling conditions. Reliability of the sealing system and instrumentation methodology is ensured by leakage tests and oil corrosion assessment. Data such as cell impedance and discharge capacity also support the success and reliability of the instrumentation process without affecting the battery performance. Compared with natural air cooling, immersion cooling can reduce the temperature rise during battery operation by >10 °C under high C-rate discharge conditions. However, this is accompanied by an increase in radial temperature gradient. The temperature gradient of the cell with oil immersed reaches a maximum of >7 °C, while the temperature gradient under natural cooling under the same test conditions is only 3 to 4 °C. This leads to intensified temperature inhomogeneity of the cell, which may accelerate the local ageing and degradation. Our instrumentation approach contributes to a deeper understanding of the thermal behaviour of batteries under direct immersion cooling, aiding the development of more advanced cooling strategies and associated battery thermal management models.

Feasibility of triple assessment of the anastomosis using an anastomotic checklist.

Colorectal cancer is the third most common cancer and the second highest cause of cancer mortality in Australia. Despite advances in colorectal surgery, anastomotic leak still occurs in low-risk patients and is a substantial cause of morbidity and mortality. Many operative strategies are used to assess anastomotic integrity such as an air leak test or intraoperative flexible sigmoidoscopy, however an objective anastomotic checklist is yet to be developed and studied. This study aims to develop a photodocumentary anastomotic specific checklist and determine its feasibility for implementation. Patients undergoing left sided colorectal resections with primary anastomosis without a de-functioning ileostomy were prospectively included between May 2021 and December 2022. A photographic checklist assessing anastomotic perfusion, integrity via either air test or endoscopic image, evidence of complete operative doughnut specimens and the assessment of tension was implemented. The feasibility of an anastomotic checklist was externally validated by four independent colorectal surgeons from Australia, New Zealand and United States of America. The anastomotic checklist was completed in 44 patients. Mean age was 62 years, with 43% male and mean BMI 28. Operations included high anterior resection (45%), low anterior resection (18%), ultra-low anterior resection (20%), reversal of Hartmann's (11%). Median length of stay was 4 days. Complications post operatively were documented in six patients with anastomotic leak in 2% and wound infection in 6.8%. Intraclass correlation coefficients were poor amongst all reviewers with air leak and tension having no inter-reviewer correlation. The introduction of an anastomotic checklist was a feasible tool to systematically assess and document anastomotic integrity. Unfortunately, with the small sample size there was significant discrepancy in inter-observer variability, and this led to poor correlation regarding which patients were typically high risk requiring a temporary ileostomy. Larger studies on the implementation of an anastomotic checklist will be needed to evaluate if it is an inherently feasible approach and if there is an effect on anastomotic leak.

Parametric design methodology for yoke-magnetization in magnetic flux leakage detection systems

Magnetic flux leakage (MFL) testing is a widely employed non-destructive testing (NDT) method, particularly for ferromagnetic materials. This paper proposes a systematic design procedure for the yoke-magnetization component in MFL systems utilizing permanent magnets. The dimensions of the yoke-magnetization are parameterized, and the design methodology is formulated in the form of analytical equations based on fundamental engineering principles and optimization techniques. The proposed design procedure outlines all the required parameters and metrics to establish a yoke-magnetization configuration tailored for a specified application, thereby facilitating scalability. The theoretical framework identifies the optimal operating point that maximizes leakage flux while minimizing the magnetic field amplitude. A genetic algorithm is employed to minimize the dimensions of the permanent magnets while maintaining a sufficient magnetic field strength for specimen magnetization. An experimental setup is constructed to validate the accuracy of the proposed design procedure. The experimental results exhibit consistency with finite element method (FEM) simulations conducted using a case study. Specifically, the findings reveal that the thickness of the magnetic bridge significantly impacts the leakage fluxes at defect sites within the specimen. When the thickness of the magnetic bridge is 10 mm, slightly smaller than the optimal thickness of approximately 11 mm, the leakage flux at the defect site leaks out towards the surrounding air insignificantly. In contrast, a thickness of 15 mm is observed to strongly improve the leakage flux at the defect site.

Fabrication of Porous Collagen Scaffolds Containing Embedded Channels with Collagen Membrane Linings.

Tissues and organs contain an extracellular matrix (ECM). In the case of blood vessels, endothelium cells are anchored to a specialized basement membrane (BM) embedded inside the interstitial matrix (IM). We introduce a multi-structural collagen-based scaffold with embedded microchannels that mimics in vivo structures within vessels. Our scaffold consists of two parts, each containing two collagen layers, i.e., a 3D porous collagen layer analogous to IM lined with a thin 2D collagen film resembling the BM. Enclosed microchannels were fabricated using contact microprinting. Microchannel test structures with different sizes ranging from 300 to 800 µm were examined for their fabrication reproducibility. The heights and perimeters of the fabricated microchannels were ~20% less than their corresponding values in the replication PDMS mold; however, microchannel widths were significantly closer to their replica dimensions. The stiffness, permeability, and pore size properties of the 2D and 3D collagen layers were measured. The permeability of the 2D collagen film was negligible, making it suitable for mimicking the BM of large blood vessels. A leakage test at various volumetric flow rates applied to the microchannels showed no discharge, thereby verifying the reliability of the proposed integrated 2D/3D collagen parts and the contact printing method used for bonding them in the scaffold. In the future, multi-cell culturing will be performed within the 3D porous collagen and against the 2D membrane inside the microchannel, hence preparing this scaffold for studying a variety of blood vessel-tissue interfaces. Also, thicker collagen scaffold tissues will be fabricated by stacking several layers of the proposed scaffold.

Leaks after laparoscopic sleeve gastrectomy: 2024 update on risk factors.

Leaks after sleeve gastrectomy remain a deadly complication significantly affecting outcomes and medical costs. The aim of the present review is to provide an updated decalogue on leak prevention. Risk factors of leakage after LSG were examined based on an extensive review of literature (in period time 2016-2024) and summary of evidence was provided using Oxford levels of evidence scale. Pathogenesis of leakage after LSG still remain related to ischemic and mechanical factors and, therefore, no new evidence has been reported. Conversely, some technical aspect of the procedure has changed: bougie size, antrum resection, staple line reinforcement, and intraoperative leak testing. Bougie size 36F is effective and safe achieving similar leakage rate compared to larger bougie sizes (EL:2) 2024 UPDATE; There is no significant difference in the leak rate between restrictive (< 6cm) and conservative (6cm) antrum resection (EL: 1) 2024 UPDATE; Surgical experience and case volume affect the leak rate more consistently than every kind of SLR (EL: 2) 2024 UPDATE; Intraoperative leak test after LSG represents a decision based on surgeon preference in absence of standardization (endoscopy, bubble test, methylene blue, indocyanine green.) and strong detection/prevention rate (EL: 3) 2024 UPDATE.

Capric-lauric & capric-palmitic/modified bentonite composite as phase change materials for thermal energy storage

This paper proposes a new double layer structure shape-stabilized thermal energy storage wallboard (TESW), by employing microwave radiation modified bentonite (Bm) to stabilize capric acid-lauric acid (CA-LA) and capric acid-palmitic acid (CA-PA) as major components of internal and external wallboard. Leakage test showed that CA-LA/Bm and CA-PA/Bm had good morphological stability. The chemical compatibility, phase change behaviors, and microstructure of CA-LA/Bm and CA-PA/Bm were analyzed. The maximal loading capacities of CA-LA/Bm and CA-PA/Bm can be reached 45 % and 50 %, respectively. In addition, the mechanical and thermal performance of CA-LA/Bm and CA-PA/Bm-based thermal energy storage concrete (CL&CP/Bm-TESC) was systematically studied. The Digital Image Correlation (DIC) technology was used to collect and analyze the speckle images of CL&CP/Bm-TESC20 before and after 100 cycles of phase change, determining the evolution of principal strains during the deformation and failure processes. It is worth noting that the numerical simulation results of the designed double layer structure shape-stabilized CA-LA&CA-PA/Bm-based thermal energy storage wallboard (CL&CP/Bm-TESW) show better temperature adjusting performance. These results demonstrate that the prepared composite of CA-LA/Bm and CA-PA/Bm has potential application in the field of thermal energy storage.

(Invited) Detection, Location and Quantification of H2 Gas Leaks Based on Data Collected with Electrochemical Sensors in a Specifically Designed Test Chamber

Hydrogen is one of the most important energy gases as it is carbon free and therefore can result in the emission reduction of the greenhouse gas CO2. However, hydrogen itself is a secondary greenhouse gas. As a secondary greenhouse gas, hydrogen does not directly add to global warming by entrapping heat. Instead, it reacts with molecules in the atmosphere that are needed to remove the greenhouse gas CH4. CH4 is comparably short-lived in the atmosphere with approximately 10 years compared to CO2 which can last in the atmosphere for centuries. However, CH4 traps at least 100 times as much heat as CO2. Considering the difference in heat capacities of CH4 and CO2, combined with the difference in lifetime, if the same amount of CH4 and CO2 were to be released into the atmosphere at the same time, the global warming effect of CH4 would be approximately 28 times higher than the warming effect of CO2. This means, by releasing hydrogen in the atmosphere, the global warming effect is indirectly enhanced by increasing the lifetime of CH4. Therefore, it is essential to be able to detect, locate and quantify hydrogen leaks right away.Due to the ever-growing hydrogen infrastructure including production facilities, transportation systems like pipelines, as well as storage facilities and user end stations, it is essential to create low-cost, low-power sensors that can be deployed in high numbers. Electrochemical sensors have the potential to fulfill all the needed criteria and are already used for the detection of hydrogen. However, in order to use these sensors to not only detect the leak, but also to locate and quantify the amount of hydrogen that leaked into the atmosphere, additional models and algorithms are needed. To our knowledge, no system currently exists on the market that can be used to fulfill all three tasks.We built a test chamber that enabled us to evaluate H2 leaks and to collect data with electrochemical sensors in a controlled room and environment. The chamber has the size of 800 x 400 x 450 mm3 with a total volume of 144 L. We placed seven of our commercial electrochemical sensors that can detect 0 – 250 ppm hydrogen at different positions inside the box. The box was equipped with one gas inlet and one gas outlet to ensure pressure stability inside the box during our leak test. The inlet was connected to a gas tube which was connected to two mass flow controllers as well as to an outlet tube via a three-way valve. This way, it could be ensured that the gas stream had a stable volume and a constant speed. We released controlled amounts of hydrogen into the box and collected the data with our seven sensors. We were able to see a location-dependent sensor response over time for a 1 second leak of H2 which indicates the capability of such a sensor system to be used for the location of a leak.Quantifying hydrogen is a very complex issue. It requires extremely accurate readings and an intelligent algorithm that is capable to use the reading from multiple sensors and turn that into a mass of hydrogen leaked or leaking. The extremely accurate reading is difficult because the zero and span readouts from the electrochemical sensor is dependent on temperature as well as humidity. This means that the readout zero and span will have to be compensated for both temperature and humidity. While we currently use algorithms to compensate for temperature, we found that these algorithms are not good enough when the sensors are used to measure concentrations in the low-ppm or ppb range. We are researching AI and other computational means to include both temperature and humidity in the compensation algorithms and how including both variables in the compensation process can improve the sensors performance at low concentrations. Both the H2 sensor and its deployment capabilities are technologically and economically significant to the rapidly expanding H2 market for protecting human health, the environment, stemming expensive product losses and promoting efficient use.

Enhancing thermal energy storage properties of blend phase change materials using beeswax.

This study aims to use beeswax, a readily available and cost-effective organic material, as a novel phase change material (PCM) within blends of low-density polyethylene (LDPE) and styrene-b-(ethylene-co-butylene)-b-styrene (SEBS). LDPE and SEBS act as support materials to prevent beeswax leakage. The physicochemical properties of new blended phase change materials (B-PCM) were determined using an X-ray diffractometer and an infrared spectrometer, confirming the absence of a chemical reaction within the materials. A scanning electron microscope was used for microstructural analysis, indicating that the interconnection of the structure allowed better thermal conductivity. Thermal gravimetric analysis revealed enhanced thermal stability for the B-PCM when combined with SEBS, especially within its operating temperature range. Analysis of phase change temperature and latent heat with differential scanning calorimetry showed no major difference in the melting point of the various PCM blends created. During the melting/solidification process, the B-PCMs possess excellent performance as characterized by W70/P30 (112.45J.g-1) > W70/P20/S10 (94.28J.g-1) > W70/P10/S20 (96.21J.g-1) of latent heat storage. Additionally, the blends tend to reduce supercooling compared to pure beeswax. During heating and cooling cycles, the B-PCM exhibited minimal leakage and degradation, especially in blends containing SEBS. In comparison to the rapid temperature drop observed during the cooling process of W70/P30, the temperature decline of W70/P30 was slower and longer, as demonstrated by infrared thermography. The addition of LDPE to the PCM reduced melting time, indicating an improvement in the thermal energy storage reaction time to the demand. According to the obtained findings, increasing the SEBS concentration in the composite increased the thermal stability of the resulting PCM blends significantly. Despite the challenges mentioned earlier, SEBS proved to be an effective encapsulating material for beeswax, whereas LDPE served well as a supporting material. Leak tests were performed to find the ideal mass ratio, and weight loss was analyzed after multiple cycles of cooling and heating at 70°C. The morphology, thermal characteristics, and chemical composition of the beeswax/LDPE/SEBS composite were all examined. Beeswax proves to be a highly effective phase change material for storing thermal energy within LDPE/SEBS blends.

Enhancing non-metallic gasket performance with shape memory fibers

This study aims to enhance the sealing performance of non-metallic gaskets by incorporating shape memory fibers. The analytical exploration focuses on analyzing the thermomechanical behavior of Nitinol fibers in their woven state within the gasket. Specifically, the investigation examines the variation of phase transformation zones across the wire cross-section with changes in temperature. Subsequently, a series of SMA fiber-reinforced gasket samples were fabricated, and experimental investigations were conducted to assess the impact of Nitinol fibers on composite gaskets using a helium gas leak test. The results demonstrate that the integration of shape memory alloy wires into the composition of gaskets can significantly improve their sealing performance. Moreover, this study examines a number of pivotal factors such as fiber volume fraction, temperature application, woven fiber arrangement, leakage rates, gasket deformation, contact stress, and structural bending. These comprehensive investigations may provide valuable insights into the efficacy of Nitinol fibers in enhancing gasket sealing performance.

Multi-modality hierarchical attention networks for defect identification in pipeline MFL detection

Abstract Magnetic flux leakage (MFL) testing is widely used for acquiring MFL signals to detect pipeline defects, and data-driven approaches have been effectively investigated for MFL defect identification. However, with the increasing complexity of pipeline defects, current methods are constrained by the incomplete information from single modal data, which fail to meet detection requirements. Moreover, the incorporation of multimodal MFL data results in feature redundancy. Therefore, the multi-modality hierarchical attention networks (MMHAN) are proposed for defect identification. Firstly, stacked residual blocks with cross-level attention module (CLAM) and multiscale 1D-CNNs with multiscale attention module are utilized to extract multiscale defect features. Secondly, the multi-modality feature enhancement attention module (MMFEAM) is developed to enhance critical defect features by leveraging correlations among multimodal features. Lastly, the multi-modality feature fusion attention module (MMFFAM) is designed to dynamically integrate multimodal features deeply, utilizing the consistency and complementarity of multimodal information. Extensive experiments were conducted on multimodal pipeline datasets to assess the proposed MMHAN. The experimental results demonstrate that MMHAN achieves a higher identification accuracy, validating its exceptional performance.

Endobronchial Closure for Peripheral Pulmonary Air Leakage

Introduction: A minimally invasive alternative to surgery for treating pneumothorax has been developed, aiming to reduce risks while maintaining efficacy. This study conducted basic experiments using ex vivo and in vivo pig lung employing a super-thin catheter for treatment. This new device injects fibrin glue directly into the responsible lesion to close the air leak, which has two features: thin design and double-lumen. Methods: The experimental setup involved utilizing trachea and both lung specimens from pigs under positive pressure ventilation. To simulate pneumothorax, artificial fistulas were created on the lung surfaces. The super-thin catheter, guided through a bronchoscope near the fistula, was used to embolize the peripheral bronchus by injecting a fibrin preparation. Then, an air leak test was conducted afterward to assess the efficacy of the treatment. Additionally, a similar pneumothorax model was induced in alive pig under general anesthesia to evaluate its curability. Results: In the extracted pig lungs, embolization was performed in 21 cases, resulting in the cessation of air leaks in 19 cases, corresponding to a 90.5% cure rate. Notably, no major adverse events occurred with the treatment devices. Similarly, in living pigs, pneumothorax was successfully treated, with no recurrence observed up to the seventh postoperative day. Conclusion: The novel treatment device utilizing a super-thin catheter offers a minimally invasive and highly curative option for pneumothorax. These promising results suggest the potential for further development and human clinical trials, which could revolutionize the treatment of pneumothorax, reducing risks and improving outcomes.

A Non-Metallic pipeline leak size recognition method based on CWT acoustic image transformation and CNN

Accurately identifying the pipeline leak size is crucial for risk assessment and timely rescue. In this study, a Convolutional Neural Network (CNN) based on Continuous Wavelet Transform (CWT) acoustic image transformation is proposed to identify small-sized leak in non-metallic pipes. Firstly, one-dimensional acoustic signals are filtered using the Piecewise Aggregate Approximation (PAA) algorithm to reduce noise and storage resource consumption. Then, the filtered signals are transformed into two-dimensional images by CWT to enrich signal feature information, serving as the input for the CNN. Further, a leak size recognition model based on CWT-CNN is established. The effectiveness of this model is verified using experimental data from a non-metallic pipeline leak test. A comparative analysis is conducted on diverse acoustic image transformation methods, including CWT, Gramian Angular Summation Field (GASF), and Relative Position Matrix (RPM). The results demonstrate the superiority of the CWT-CNN model in pipeline leak size recognition. Finally, the impact of the signal length in an acoustic image on recognition accuracy is also examined. The results demonstrate that when the signal length in an acoustic image is 0.75 s, the accuracy obtained by CWT-CNN can reach 95 %.

Comparing Container Closure Integrity Test Methods - Performance of Headspace Carbon Dioxide Analysis versus Helium Leakage Using Positive Controls.

As described in USP Chapter <1207>, the deterministic leak test methods using laser-based gas headspace analysis and helium leakage are those with the highest sensitivities. As stated in the chapter, ″no single package leak test or package seal quality test method is applicable to all product-package systems″; therefore, knowing the advantages and disadvantages of both of these techniques, and the extent to which they can be substituted for each other, is valuable. In an effort to begin addressing this issue, a systematic study using these two techniques has been performed. This study used the same well-defined positive controls prepared with microcapillaries for both measurement techniques. For the headspace gas analysis technique, the headspace carbon dioxide content was measured at multiple timepoints during three separate conditioning cycles using either a 0.5, 1.0, or 2.0 bar CO2 overpressure; the observed change in headspace carbon dioxide was then used to determine an ingress rate for each positive control. For the helium leakage technique, the positive controls were measured with a standard helium leak detector with 100% helium atmosphere on the atmospheric pressure side of the artificial defects. The resulting leakage rates from both techniques were compared for ingress into both ISO 2R and ISO 10R vials. The obtained correlation between helium and carbon dioxide leakage rates resulted in a minimum R2 coefficient of 0.98 across all 12 runs. Additionally, both setups met the acceptance criteria for accuracy with their respective calibrated standards.

Evaluation of Intraoperative Saline Injection Leak Test Without Transesophageal Echocardiography as a Reliable Method During Heart Valve Repair

Evaluation of Intraoperative Saline Injection Leak Test Without Transesophageal Echocardiography as a Reliable Method During Heart Valve Repair

Tips and tricks for transluminal specimen extraction and extra-abdominal sigmoid colon resection.

The purpose of this video is to demonstrate how to achieve adequate length and blood supply of the proximal colon for a perineal pull-through procedure, without splenic flexure mobilization during natural orifice specimen extraction. Key steps of the procedure include lateral mobilization of the colon, D3 lymph node dissection, preservation of the left colic artery, low ligation of the inferior mesenteric vein, ligation and washout of the distal bowel lumen, extra-abdominally proximal resection of sigmoid colon, purse-string sutures on the distal sigmoid colon, and an air leak test. Transluminal specimen extraction with extra-abdominal resection was found to be a cost-effective procedure with good cosmetic effects. Tension-free anastomosis was achieved by preservation of the left colic artery and low ligation of the inferior mesenteric vein. The purse-string sutures were placed on the proximal and distal bowel to avoid crossing the staples line. Transluminal specimen extraction with extra-abdominal resection required minimal manipulation intra-abdominally in comparison with other natural orifice specimen extraction techniques.

Nerve-sparing deep endometriosis surgery with rectal discoid resection using da Vinci SP

ObjectiveTo demonstrate the anatomical and technical highlights of nerve-sparing deep endometriosis (DE) surgery with rectal discoid resection using a newer single-port robotic system. DesignStep-by-step demonstration of this method with narrated video footage. SettingAn urban general hospital. Single-port laparoscopic surgery is a useful surgical approach in gynecology because of the excellent cosmetic results, but shows challenges including reduced intracorporeal triangulation and conflict with non-articulating instruments. The range of indications has thus been limited. PatientA 46-year-old woman was referred with severe pelvic pain, dysmenorrhea and pain on defecation. Magnetic resonance imaging revealed uterine adenomyosis, bilateral ovarian endometriomas, and 3 cm of rectal endometriosis. CT colonography confirmed 38% stenosis of the rectum. InterventionA newer single-port robotic system. Main Outcome MeasuresThe technical safety and feasibility of intrapelvic complex DE surgery using a newer single-port robotic platform. ResultsThe procedure was performed using 9 steps with a da Vinci SP surgical system (Intuitive Surgical, Sunnyvale, California). Importantly, the surgical steps were completely identical to conventional multiport laparoscopic or robotic surgery. This suggests that conventional laparoscopic or robotic skills are highly transferrable to the newer system: Step 1, adhesiolysis and adnexal surgery; Step 2, separation of the nerve plane; Step 3, dissection of the ureter; Step 4, reopening of the pouch of Douglas; Step 5, complete removal of DE lesions while avoiding injury to the nerve plane; Step 6, hysterectomy (if the patient desires non-fertility-sparing surgery); Step 7, rectal discoid resection with circular stapler; Step 8, checking for rectal injury using an air leakage test and tissue perfusion; and Step 9, application of barrier agents for adhesion prevention. The newer single-port system offered several advantages, including high-resolution three-dimensional visualization, articulating instruments (intracorporeal instrument triangulation), and improved dexterity and range of motion. These advantages allow precise dissection even in difficult situations such as deep endometriosis. ConclusionsThis appears to be the first reported use of the da Vinci SP for nerve-sparing DE surgery or rectal discoid resection. The newer single-port robotic system can provide the same quality of surgery as conventional multi-port laparoscopic and robotic platforms with cosmetic advantages for the treatment of complex pelvic pathologies.

Measurement of CO2 leakage from pipelines under CCS conditions through acoustic emission detection and data driven modeling

CO2 leakage from carbon capture and storage (CCS) networks may lead to ecological hazards, bodily injury and economic losses. In addition, captured CO2 often contains impurities which affect the leakage behavior of CO2. This paper presents a method for continuous and quantitative measurements of CO2 leakage flowrate and the volume fraction of impurities by combining data-driven models with acoustic emission (AE) and temperature sensors. Three data-driven models based on artificial neural network (ANN), random forest (RF), and least squares support vector machine (LS-SVM) algorithms are established. The outputs from the three data-driven models are then integrated to give improved results. Experimental work was conducted on a purpose-built CO2 leakage test rig under a range of conditions. N2 was injected to the CO2 gas stream as an impurity medium. Results show that the integrated model yields a relative error within ±4.0 % for leakage flowrate and ±3.4 % for volume fraction of N2.

Research on internal leakage detection of the ball valves based on stacking ensemble learning

Abstract Natural gas is an important clean energy source that is mainly transported through pipelines. The ball valve is a crucial piece of control equipment for the pipeline transportation system for natural gas, and the failure of internal leakage of the ball valve will seriously affect the natural gas transmission and increase the risk of sudden safety accidents. In response to the problems of the limitations of a single machine learning model in the traditional ball valve internal leakage rate prediction methods and failure to qualitatively analyze unilateral and bilateral internal leakage recognition of ball valve, a study of ball valve internal leakage detection based on Stacking ensemble learning is proposed. A total of 15 time and frequency domain feature parameters were obtained by feature extraction of 125 and 96 sets of raw acoustic emission signals from the ball valve; the parameters of a single machine learning model were adjusted by Bayesian optimization grid search. An internal leakage rate prediction model and an internal leakage recognition model are constructed, and the proposed model is compared and analyzed with a single model through a field ball valve internal leakage test. The results indicate that the Stacking ensemble learning model outperforms each single machine learning model in terms of SMAPE (17.2583), RMSE (1.1009), and MAE (0.9375) for internal leakage rate prediction. The Stacking ensemble learning model outperformed the single machine learning model in terms of accuracy (1), recall (1), precision (1), FAR(0), and F1-score (1) for internal leakage recognition. Stacking ensemble learning significantly enhances the model's ability to detect internal ball valve leaks.&amp;#xD;

Application of biodegradable poly(lactide-co-glycolide) (PLGA) for efficient & stable perovskite solar cells

Since numerous defects can deteriorate the efficiency as well as long-term stability of perovskite solar cells (PSCs), it is important to control the defects for the industrialization of PSCs. Among various defects, interest is mainly focused on treating the uncoordinated Pb2+, which not only causes the lower performance of PSCs, but also is considered as a risk to the environment and human. Herein, we investigate a FDA (Food and Drug Administration) approved biodegradable poly(lactide-co-glycolide) (PLGA) as a polymer additive to passivate uncoordinated Pb2+. PLGA contains carbonyl groups (CO), which can strongly form a coordination bonding with Pb2+, resulting in the reduction of non-radiative charge recombination and improvement of charge carrier movement. Therefore, the power conversion efficiency (PCE) of air-processed PSCs enhances from 15.87 % to 17.09 %, especially the fill factor enhances from 77.19 % to 81.33 %. The PLGA passivated devices exhibit superior thermal stability maintaining 70 % of the initial PCE for ∼100 h in the air conditions without any encapsulation, moreover, in the test of Pb leakage from perovskite, restricted dissolving of Pb in water was confirmed as a result of immobilization of uncoordinated Pb2+ ion by PLGA.

Application of Distributed Acoustic Sensing Technology in Pipeline Leakage Monitoring

Pipeline leak monitoring is an important industrial safety measure designed to ensure the safety of liquids or gases during transportation. Distributed acoustic sensing (DAS) technology is based on the reverse Rayleigh scattering inside the fiber to reflect the change of the measured physical quantity, and has great advantages in monitoring range, environmental adaptability, transmission loss control and system stability. In this paper, the pipeline leakage monitoring technology based on distributed acoustic sensing fiber is used to study the leakage signal of small leak aperture. In order to improve the sensitivity of leakage monitoring, the optical fiber is spiral wound on the pipe section. The identification method of pipeline leakage signal based on fast Fourier transform is proposed. By analyzing the vibration of the optical fiber in the time domain and the frequency domain, the leakage signal can be accurately monitored. Pipeline leakage tests with different leak apertures were carried out, and the leakage locations were studied by energy attenuation and cross-correlation techniques. The experimental results show that the time-domain signal fluctuates obviously and the full-band energy of the frequency-domain signal increases after pipeline leakage. The increase of leakage diameter will gradually increase the signal energy, and the leakage energy will gradually move from high frequency to low frequency. The energy attenuation positioning technique can locate the leakage within the range of a single sensing unit, and determine the leakage location through cross-correlation analysis with an error of less than 3 m.