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This paper is a summary of many of the key findings on the application of geosynthetics in tailings storage facilities. Topics include the compressibility and permeability of tailings, the equations predicting leakage through circular and non-circular geomembrane holes, the effect of the subgrade permeability, and the effect of a lateral drainage system within tailings on leakage predictions. Two commonly encountered engineering problems relating to the piping through circular geomembrane holes and the opening width of non-circular defective geomembrane seams are given to demonstrate the potential application of leakage prediction equations. Meanwhile, issues related to the subgrade imperfection and the long-term performance of both high-density polyethylene (HDPE) and bituminous geomembranes in tailings storage applications are addressed. The research highlights that an appropriate HDPE geomembrane liner can be expected to perform very well for an extremely long time, limiting leakage and contaminant migration from the facility into the surrounding environment if the liner is well constructed on a suitable subgrade.

Dimensional measurements are fundamental in microfluidic device manufacturing and performance. The main focus of this study is the measurement of the connection port sizes in microfluidic devices and components and, accordingly, the possible existence of fluid leaks determined using the flow rate error. The sizes associated with three different microfluidic systems were determined using laser interferometry and through an optical measuring instrument, with metrological traceability to national length standards. It was possible to infer the method with the greatest accuracy and lowest measurement uncertainty for characterizing this kind of system. In conclusion, the results of this work directly address the current lack of dimensions measuring methods of microfluidic components by providing a comprehensive comparison of different protocols, ultimately suggesting a preferred option for immediate application within the microfluidic industry.

To improve the performance of valves in relation to the leakage rate, a comprehensive evaluation of the valve characteristics and behavior during pressure exposure is important. Often, these low gas flow rates below 0.1 cm3/min cannot be accurately measured with conventional flow sensors. This paper presents a small and low-cost test rig for measuring gas leakage rates accurately, even far below 0.1 cm3/min, with the pressure decay method. These leakage flows are substantiated with a flow model, where we demonstrate the feasibility of modeling those gas flows with an extended Navier–Stokes framework to obtain more accurate theoretical predictions. As expected, the comparison to the experimental results proves that the classical Navier–Stokes system is unsuitable for modeling Knudsen flows. Hence, self-diffusion of gas, a wall-slip boundary condition, and an effective mean free path model were introduced in a physically evident manner. In terms of the calculated mass flow, while self-diffusion and slip boundary conditions explain deviations from the classical Navier–Stokes equation for Knudsen numbers already smaller than 1, the effective mean free path model has an effect, especially when Kn > 1. For simplified conditions, an analytical solution was presented and compared to the results of an OpenFOAM CFD-solver for flow rates through more complex gap-flow geometries of the flap valve. Hereby, acceptable deviations between 10% and 20% were observed. A comparison with measurement results was carried out. The reproducibility of the measurement method was verified by comparing multiple measurements of one silicon microvalve sample to a state-of-the-art flow sensor. Three geometrically similar passive silicon microvalves were measured with air overpressure decreasing from 15 kPa relative to atmospheric pressure. Maximum gas volume flowing in a blocking direction of 1–26 µL/min with high reproducibility and marginal noise were observed.

This paper presents the application of the Comparison of Flow Pattern Distribution (CFPD) method for detecting water leakage and understanding consumption behaviors at both microscale and macroscale. Implemented at Lille University’s Scientific Campus, this research utilizes Automated Meter Reading (AMR) to collect real-time water supply and consumption data. The research successfully identified several significant leak events by analyzing this data with the CFPD method on weekly and daily scales. The analysis of the data resulted in identifying the seasonal and operational consumption patterns across different periods of the year. The findings highlight the effectiveness of the CFPD method in achieving water conservation and operational efficiency, consequently contributing to the UN Sustainable Development Goal (SDG) 6 concerning clean water and sanitation.

As a paradigm of clean energy, hydrogen is gradually attracting global attention. However, its unique characteristics of leakage and autoignition pose significant challenges to the development of high-pressure hydrogen storage technologies. In recent years, numerous scholars have made significant progress in the field of high-pressure hydrogen leakage autoignition. This paper, based on diffusion ignition theory, thoroughly explores the mechanism of high-pressure hydrogen leakage autoignition. It reviews the effects of various factors such as gas properties, burst disc rupture conditions, tube geometric structure, obstacles, etc., on shock wave growth patterns and autoignition characteristics. Additionally, the development of internal flames and propagation characteristics of external flames after ignition kernels generation are summarized. Finally, to promote future development in the field of high-pressure hydrogen energy storage and transportation, this paper identifies deficiencies in the current research and proposes key directions for future research.

Accurate segmentation of the pulmonary airway tree is crucial for diagnosing lung diseases. To tackle the issues of low segmentation accuracy and frequent leaks in existing methods, this paper proposes a precise segmentation method using quasi-spherical region-constrained wavefront propagation with tracheal wall gap sealing. Based on the characteristic that the surface formed by seed points approximates the airway cross-section, the width of the unsegmented airway is calculated, determining the initial quasi-spherical constraint region. Using the wavefront propagation method, seed points are continuously propagated and segmented along the tracheal wall within the quasi-spherical constraint region, thus overcoming the need to determine complex segmentation directions. To seal tracheal wall gaps, a morphological closing operation is utilized to extract the characteristics of small holes and locate low-brightness tracheal wall gaps. By filling the CT values at these gaps, the method seals the tracheal wall gaps. Extensive experiments on the EXACT09 dataset demonstrate that our algorithm ranks third in segmentation completeness. Moreover, its performance in preventing airway leaks is significantly better than the top-two algorithms, effectively preventing large-scale leak-induced spread.

In a rail transit system, there is a constant leakage of current from the subway rails to the earth, and these stray currents have complex propagation paths and a wide range of influence. Since no stray current collection devices are installed at subway depots, some of the stray current leaking from the mainline will converge at the depot, seriously corroding the structural reinforcement and buried metal of the station, thereby jeopardizing the normal operation of subway trains and passenger safety. In this paper, a field-circuit coupling method is proposed to analyze the current leakage and distribution law of the subway mainline and depot. It is found that the failure of the gauge block at the mainline will trigger the maximum leakage of rail current. Additionally, it is observed that the stray current distribution at the depot is mainly influenced by the operating status of the one-way conduction device (OWCD) and the change of rail potential. These results validate the applicability and effectiveness of the field-circuit coupling method proposed in this paper and provide new technical support for the study of stray current leakage distribution in subways.

Leakage is a high-incidence disease of embankment dams, and efficiently addressing this disease guarantees the safe operation of dams. Underwater leakage self-priming plugging technology is a new technology that utilizes the melting and solidifying characteristics of phase-change materials and the negative pressure in the leakage entry area to accurately plug the leakage. However, little is yet known about the underwater melting process of phase-change materials and how their characteristics influence the plugging effect. In this study, three kinds of phase-change materials, namely, paraffin, rosin, and stearic acid, were used to conduct underwater leakage self-priming plugging tests, observe and analyze the underwater melting process, and compare the plugging effects. The results showed that the underwater melting process of phase-change materials exhibited different plugging window periods depending on their melting points, specific heat capacities, and mobilities, which were the main factors affecting their plugging effects. In the final plugging stage, paraffin had the best plugging effect, but the material strength was low; rosin had good plugging compactness, but the fluidity performance was poor, and the material effective utilization was low; stearic acid had a low melting point but dispersed easily. Therefore, a blocking material with a suitable blocking window period can be produced by adjusting the material properties accordingly for an improved blocking effect.

While only a minimal fraction of global water resources is accessible for drinking water production, their uneven distribution combined with the climate crisis impacts leads to challenges in water availability. Leakage in water distribution networks compounds these issues, resulting in significant economic losses and environmental risks. A coherent review of (a) the most widely applied water loss estimation techniques, (b) factors influencing them, and (c) strategies for their resilient reduction provides a comprehensive understanding of the current state of knowledge and practices in leakage management. This work aims towards covering the most important leakage estimation methodologies, while also unveiling the factors that critically affect them, both internally and externally. Finally, a thorough discussion is provided regarding the current state-of-the-art technics for leakage reduction at the municipal-wide level.

Sulfur hexafluoride (SF6) is a typical fluorine gas with excellent insulation and arc extinguishing properties that has been widely used in large-scale power equipment. The detection of SF6 gas in high-power electrical equipment is a necessary measure to ensure the reliability and safety of power grid operation. A failure of SF6 insulated electrical equipment, such as discharging or overheating conditions, can cause SF6 gas decomposition, resulting in various decomposition products. The decomposed gases inside the equipment decrease the insulating properties and are toxic. The leakage of SF6 can also decrease the insulating properties. Therefore, it is crucial to monitor the leakage of SF6 decomposed gases from electrical equipment. Quantitative testing of decomposition products allows us to assess the insulation state of the equipment, identify internal faults, and maintain the equipment. This review comprehensively introduces the decomposition formation mechanism of SF6 gas and the current detection technology of decomposition products from the aspects of principle and structure, materials, test effect, and practicability. Finally, the development trends of SF6 and decomposition gas detection technology for the reliability and safety of power grid operation are prospected.

In this paper, the possibility of using monofractal and multifractal analysis of acoustic signals of pipelines to detect leaks is considered. An experimental stand has been created to study the fractal characteristics of acoustic signals of pipelines with “slit” type defects. During the experiments, defects of the “slit” type pipeline with dimensions of 2 mm, 8 mm, and 20 mm were modeled. Detrended fluctuation analysis (DFA) and the multifractal detrended fluctuation analysis (MF-DFA) were used. As a result of the experimental studies, it was found that the occurrence of leakage leads to the occurrence of anticorrelated vibrations in a pipeline with multifractal properties. The analyses of acoustic signals by DFA and MF-DFA methods make it possible to reliably determine the leakage. The Hurst exponent and the width of the multifractal spectrum can serve as indicators of the occurrence of leaks in pipelines.

Ferroelectric scandium-doped aluminum nitride (Al1-xScxN) is of considerable research interest because of its superior ferroelectricity. Studies indicate that Al1-xScxN may suffer from a high leakage current, which can hinder further thickness scaling and long-term reliability. In this work, we systematically investigate the origin of the leakage current in Al0.7Sc0.3N films via experiments and theoretical calculations. The results reveal that the leakage may originate from the nitrogen vacancies with positively charged states and fits well with the trap-assisted Poole-Frenkel (P-F) emission. Moreover, we examine the cycling behavior of ferroelectric Al0.7Sc0.3N-based FeRAM devices. We observe that the leakage current substantially increases when the device undergoes bipolar cycling with a pulse amplitude larger than the coercive electric field. Our analysis shows that the increased leakage current in bipolar cycling is caused by the monotonously reduced trap energy level by monitoring the direct current (DC) leakage under different temperatures and the P-F emission fitting.

Due to the hydrodynamic pressure effect, the bearing capacity of the oil film on the surface of a textured friction pair is greater than that of a smooth surface. In this paper, the effects of PTFE surface texture parameters (shape, depth, width, and area ratio) on the oil film bearing capacity and leakage of the sealing system under lubrication are studied using the FLURNT simulation. It is found in this present study that greater texture depths do not necessarily lead to better sealing performance. When the texture depth exceeds a certain level, a reverse flow occurs at the bottom of the texture, thereby weakening the hydrodynamic pressure effect. An optimal texture depth of 5–10 μm maximizes the oil film bearing capacity. Within a certain range, the oil film bearing capacity increases along with texture widths. In addition, leakage of the rectangular texture rises significantly with growing texture widths. Larger texture area ratios result in higher leakage, but the bearing capacity first rises and then falls with an increase in the area ratio, with a maximum value of 70–80%. Considering the influence of texture parameters on oil film bearing capacity and leakage, selecting the most appropriate texture parameters for surface texture treatment optimizes the performance of the sealing system. The findings of this paper provide a theoretical basis for improving the sealing performance of high-end aviation equipment using texture treatment, thereby enabling the application of surface texture technology to improve the tribological properties of materials.

Flexible capacity applications demand a large energy storage density and high breakdown electric field strength of flexible films. Here, P(VDF-HFP) with ultra-thin Al2O3 nanosheet composite films were designed and fabricated through an electrospinning process followed by hot-pressing into a sandwich structure. The results show that the insulating ultra-thin Al2O3 nanosheets and the sandwich structure can enhance the composites’ breakdown strength (by 24.8%) and energy density (by 30.6%) compared to the P(VDF-HFP) polymer matrix. An energy storage density of 23.5 J/cm3 at the ultrahigh breakdown strength of 740 kV/mm can be therefore realized. The insulating test and phase-field simulation results reveal that ultra-thin nanosheets insulating buffer layers can reduce the leakage current in composites; thus, it affects the electric field spatial distribution to enhance breakdown strength. Our research provides a feasible method to increase the breakdown strength of ferroelectric polymers, which is comparable to those of non-ferroelectric polymers.

An increasingly significant area of research with several applications in numerous disciplines is that of multi-neck Helmholtz resonators. This research is set to explore the accuracy and applicability of the finite element method (FEM) for the calculation of the resonance frequency of multi-neck Helmholtz resonators. The FEM is employed for the estimation of the resonance frequency in various cases of multi-neck Helmholtz resonators: with cylindrical or spherical bodies, with unflanged or flanged necks of various dimensions and with various combinations of the above. Also, single neck resonators are examined. The FEM results are compared with the results of a recently proposed theoretical model available in the literature and with the outcome of the lumped element approximation (multi-neck) accounting for the added neck surface area. Comparisons revealed little deviation between the FEM and theoretical model (less than 1.1% error of calculation for every case). On the contrary, in comparison with the lumped element approximation (multi-neck), the error of calculation is significant (up to 40.3% for the cases examined). The FEM will prove useful in expanding our understanding of how multi-neck Helmholtz resonators perform under various conditions and configurations. The present research, which highlights the applicability of the FEM for the calculations of the resonance frequency of multi-neck Helmholtz resonators, goes a step further; this approach can be applied in special cases where it is not trivial to apply an analytical formula. The method can be used for applications of multi-neck Helmholtz resonators for various fields such as acoustic metamaterials, musical acoustics and noise mitigation.

Plastic waste poses a significant threat to the environment, impacting both aquatic ecosystems and human health. This study aimed to quantify the leakage of plastic waste from urban and rural areas into the Tam Giang–Cau Hai lagoon system area in Vietnam. The research involved conducting surveys and sampling plastic waste in wards and communes surrounding the Tam Giang–Cau Hai lagoon system, as well as utilizing a waste flow diagram to calculate the amount of plastic waste leakage into the environment. The findings of the study reveal that the annual plastic leakage in this study area is approximately 479 tons. The majority of this waste enters the water body system, accounting for 74.1% of the total leakage, followed by land areas at 23.4% and land burning at 2.5%. Among the sources contributing to the wastewater flow in the area, households and markets were found to be the two primary contributors. Household waste accounted for 70.4% (2806 tons year−1) of the total, while the market sources accounted for 16.9% (675 tons year−1). This study marks the inaugural effort to assess the extent of plastic waste released from Hue City into the Tam Giang–Cau Hai lagoon system. It plays a pivotal role in examining the makeup, source of plastic waste and path of plastic waste leakage.

An acoustic emission (AE) is caused by the sudden release of energy by a material as a result of material degradation related to deformations, cracks, or faults within a solid. The same situation also occurs in leaks caused by turbulence in the fluid around the leak. In this study, analytical modeling for an AE due to leakage through a circular pinhole in a gas storage cylinder was performed. The displacement fields responsible for AEs, excited by the concentrated force (CF) associated with the turbulent flow though the pinhole, were derived by solving the Navier–Lamé equation. The CF as an excitation source was formulated in terms of a fluctuating Reynolds stress (FRS) and spatial Green’s function. In particular, a series of experiments were conducted under different operating conditions to explore the characteristics of the AE signals due to leak in a gas cylinder. Finally, the simulation and experimental results were compared to verify the accuracy of the simulation results.

As an advanced flexible dynamic sealing technology, the leakage characteristics of a finger seal (FS) is one of the key research areas in this technology field. Based on the fractal theory, this paper establishes a mathematical model of the FS main leakage rate considering the fractal wear effect by taking into account the influence of the wear height on the basis of the eccentric annular gap flow equation. Based on the Hagen-Poiseuille law and the fractal geometry theory of porous media, a mathematical model of the FS side leakage rate considering the fractal porous media seepage effect is developed. Then, a mathematical model of the FS total leakage rate is established. The results show that the mathematical model of the FS total leakage rate is verified with the test results, the maximum error rate is less than 5%, and the mathematical model of the FS total leakage rate is feasible. With the gradual increase in working conditions and eccentricity, the FS main leakage rate gradually increases. In addition, the effects of the fractal dimension, fractal roughness parameters and porosity after loading on the FS main leakage rate are negligible. As the fractal dimension of tortuosity after loading gradually decreases, the fractal dimension of porosity after loading gradually increases, and the FS side leakage rate gradually increases. As the porosity after loading gradually increases, the FS side leakage rate gradually increases. Under different working conditions, different fractal characteristic parameters and different porosities after loading, the weight of the FS main leakage rate is much greater than that of the FS side leakage rate by more than 95%.

Simple analytical models can be employed to estimate the leakage mass flow rate from labyrinth seals, resulting in a quick procedure, well suited for the early design process. Different formulas were proposed by many authors during the past decades and most of them employ a carry-over factor and a flow coefficient to predict the mass flow rate across the clearance area. The present work aims to compare the analytical prediction with the results of an experimental campaign. The experimental results were retrieved from a dedicated test rig for both a straight-through and a stepped labyrinth seal. Hence, for each seal, the effect of the clearance size, the Reynolds number and the pressure ratio has been investigated. Starting from the experimental required inputs, six different correlations are considered, with both direct and indirect methods. The results are shown as a function of pressure ratio and clearance gap. Despite some differences in the comparison, and most of the used correlation underestimate the measured mass flow rate, some general trends and guidelines can be highlighted.

The reverse inter-shaft gas film seal is a gas path seal used in the intermediate bearing cavity of an aero-engine, which is challenging to implement due to its special installation and usage conditions. This paper proposes a C/C (Carbon/Carbon) composite cylindrical reverse inter-shaft seal structure and carries out a performance simulation analysis based on bidirectional fluid–solid coupling technology. The results show that the cylindrical reverse inter-shaft gas film seal with double-layer C/C composite sealing rings with different material mesoscopic parameters can balance seal leakage and friction power consumption and is beneficial to improving the comprehensive performance of the seal. As the mesoscopic parameters of the inner sealing ring material increase in warp and weft density, the sealing leakage rate decreases, and the gas film force and gas friction power consumption all increase. As the pressure difference increases, the sealing leakage rate and gas film force increase. As the rotation speed of the inner and outer rotors increases, the seal leakage rate increases, and the gas film force decreases. A C/C composite sealing ring cylindrical reverse inter-shaft gas film seal has a lower leakage rate and larger gas film force than a graphite sealing ring cylindrical reverse inter-shaft seal, which confers certain performance advantages. The work in this paper can provide a reference for the design of reverse inter-shaft seals.

Leakage is one of the abnormal conditions in water distribution systems (WDSs). Real-time monitoring can be used to prevent or recover quickly from leakage. However, this is not enough: for improved leakage detection, a status diagnosis of the WDS must be performed together with this real-time monitoring, and numerous studies have been conducted on this. Furthermore, the existing proposed methodology only provides optimal sensor location and fast recognition. This paper proposes a technique that can quantitatively evaluate the volume of leakage along with leakage detection using deep learning technology. The hydraulic data (e.g., pressure, velocity, and flow) from the calibrated hydraulic model were used as training data and deep learning techniques were applied to conduct a simultaneous detection of leakage volume and location. We examined various scenarios regarding leakage volume and location for the data configuration of a simulated leakage accident. Furthermore, for optimal leakage detection performance, the detection performance according to the size of the network, the meter types of meters, the number of meters, and the locations of the meters were analyzed. This study is expected to be helpful in various aspects such as recovery and restoration decision making after leakage, because it simultaneously identifies the amount and location of the leakage.

The profile of sealing land is a sensitive factor affecting the thermo-hydrodynamic lubrication characteristics of the slipper pair. In this paper, the non-uniform wear of the running surface under the slipper was presented and defined as the boundary condition. Based on the finite volume method and the successive over-relaxation iteration method, a discrete numerical model coupled with the temperature, pressure, and thickness of the oil film was constructed. The Newton and sequential circulation methods were used to solve the coupling equations. The influence of the wear profile on the film thickness, sliding attitude, and leakage were discussed. The analyzed results show that the control of the wear on the outer side of sealing land and the contour vertex position, and the avoidance of the wear on the inner side of sealing land could improve the thermo-hydrodynamic lubrication performance of the slipper pair.

Optimizing the interface between biomaterials and dental hard tissues can prevent leakage of bacteria or inflammatory mediators into periapical tissues and thus avoid alveolar bone inflammation. In this study, an analysis system for testing the periodontal–endodontic interface using gas leakage and subsequent mass spectrometry was developed and validated using the roots of 15 single-rooted teeth in four groups: (I) roots without root canal filling, (II) roots with an inserted gutta-percha post without sealer, (III) roots with gutta-percha post and sealer, (IV) roots filled with sealer only, and (V) adhesively covered roots. Helium was used as the test gas, and its leakage rate was found by measuring the rising ion current using mass spectrometry. This system made it possible to differentiate between the leakage rates of tooth specimens with different fillings. Roots without filling showed the highest leakage values (p < 0.05). Specimens with a gutta-percha post without sealer showed statistically significantly higher leakage values than groups with a filling of gutta-percha and sealer or sealer alone (p < 0.05). This study shows that a standardized analysis system can be developed for periodontal–endodontic interfaces to prevent biomaterials and tissue degradation products from affecting the surrounding alveolar bone tissue.

In mobile devices such as aircraft and electric vehicles, due to limited space, there are strict requirements on the volume and weight of the compressor mounted on the vehicle. Therefore, high-speed scroll compressors have attracted more and more attention because of their small size and light weight. In this paper, the numerical calculations and analysis of the three-dimensional (3D) transient flows in a high-speed scroll refrigeration compressor were established and validated. Circumferential gas intake was used in the simulation. According to the actual compressor size, the mesh generation accurately considers clearances. The radial and the axial clearances were both set as 0.01 mm. A dynamic and high-quality hexahedral structured mesh was generated for the working chamber, and the problem of insufficient grid density in radial clearance was solved. When the rotational speed was set as 3000 rpm, 6000 rpm, and 9000 rpm alternatively, the difference in the volume efficiency of the simulation and the experiment results was below 6.3%. The results show that the higher rotational speed contributed to the greater pressure fluctuation in the compression chamber and the discharge process, and the over-compression phenomenon was more obvious. The maximum leakage velocity was 160 m/s, and the tangential leakage velocity was higher than the radial leakage velocity. Meanwhile, radial leakage velocity will increase significantly in high-speed operation mode. With the increasing rotational speed, the position of the maximum axial and tangential leakage velocity was closer to the start of the scroll. Therefore, the seal of the scroll starting part is very important in the design of a high-speed scroll compressor.

Intelligent polymers have become the focus of attention worldwide. Intelligent polymer materials through organic synthesis methods are used to make inanimate organic materials become “feeling” and “sentient”. Intelligent polymer materials have been applied in actual engineering production, and they are becoming a new research topic for scientists in various fields and countries, especially in the areas of drilling and plugging. The development of intelligent polymer materials can provide new solutions and technical means for drilling and plugging. Unlike traditional plugging materials, intelligent polymer plugging materials can cope with environmental changes. They have the characteristics of a strong target, good plugging effect, and no damage to the reservoir. However, there are currently no reviews on intelligent polymer plugging materials in the drilling field, so this paper fills that gap by reviewing the research progress of intelligent polymer plugging materials. In addition, this paper describes the mechanism and application status of intelligent polymer shape-memory polymers, intelligent polymer gels, intelligent polymer membranes, and intelligent polymer bionic materials in drilling and plugging. It is also pointed out that some intelligent polymer plugging materials still have problems, such as insufficient toughness and a poor resistance to salt and high temperature. At the same time, some suggestions for future research directions are also presented for reference.

Quantum state processing is one of the main tools of quantum technologies. While real systems are complicated and/or may be driven by non-ideal control, they may nevertheless exhibit simple dynamics approximately confined to a low-energy Hilbert subspace. Adiabatic elimination is the simplest approximation scheme allowing us to derive in certain cases an effective Hamiltonian operating in a low-dimensional Hilbert subspace. However, these approximations may present ambiguities and difficulties, hindering a systematic improvement of their accuracy in larger and larger systems. Here, we use the Magnus expansion as a systematic tool to derive ambiguity-free effective Hamiltonians. We show that the validity of the approximations ultimately leverages only on a proper coarse-graining in time of the exact dynamics. We validate the accuracy of the obtained effective Hamiltonians with suitably tailored fidelities of quantum operations.

During underground space exploitation in the urbanization process, numerous foundation pits were constructed where a diaphragm wall was often used as a retaining structure and waterproof curtain. Due to complicated engineering geological conditions or improper construction, diaphragm walls and wall joints often exhibit quality defects. Groundwater leaked from these quality defects to foundation pits during excavation, endangering the safety of the pit and surrounding facilities. The current leakage identification of the underground retaining structure was performed by artificial visual detection, which cannot satisfy the engineering requirement. The temperature field in the leakage area of the diaphragm wall was different from other areas. The leakage wall imaging system using a thermal imager was efficient in visualizing leaking, which was not visible to the naked eye. In this study, infrared thermal imaging technology was introduced in potential leakage detection for the diaphragm wall of a foundation pit. The infrared radiation characteristics of the diaphragm wall leakage and the potential leakage parts were studied through laboratory simulation tests and on-site detection methods. The maximum temperature appeared at the water outlet and the surface of the defect with hidden defect, and the temperature field was symmetrically distributed along the cross-section direction. In the potential leakage area, the temperature difference at the penetration point was 23.4 °C when the initial water pressure was 10 kPa. The temperature difference at the penetration point was 21.8 °C when the initial water pressure was 30 kPa. In the field test, the maximum temperature difference between the leakage area and the surrounding wall was 4.5 °C. The study can provide a reference for similar engineering.

Thermal energy storage (TES) is vital to the absorption and release of plenty of external heat for various applications. For such storage, phase change material (PCM) has been considered as a sustainable energy material that can be integrated into a power generator. However, pure PCM has a leakage problem during the phase transition process, and we should fabricate a form stable PCM composite using some supporting materials. To prevent the leakage problem during the phase transition process, two different methods, microencapsulation and 3D porous infiltration, were used to fabricate PCM composites in this work. It was found that both microsphere and 3D porous aerogel supported PCM composites maintained their initial solid state without any leakage during the melting process. Compared with the microencapsulated PCM composite, the 3D porous aerogel supported PCM exhibited a relatively high weight fraction of working material due to its high porosity. In addition, the cross-linked graphene aerogel (GCA) could reduce volume shrinkage effectively during the infiltration process, and the GCA supported PCM composite kept a high latent heat (∆H) and form stability.

Leakage in the diaphragm wall is difficult to detect in deep foundation pits. In this study, the conceptual model of active and passive thermal leak detection methods was proposed according to the occurrence of temperature field anomalies caused by seepage. Experiments were performed using a heating system and an optical fiber temperature measurement system to verify the thermal leakage detection systems. Numerical simulations were performed to understand the mechanism of the detecting method. Results indicated that the optical cable could detect the low-temperature anomaly in the active temperature field leak detection. The arrangement method of the leakage detection system was also presented in actual engineering.

The rotary seal is a key component of the aero engine. Under actual working conditions, most rotary seals always operate in an eccentric state (caused by installation errors), and when a large eccentricity occurs, it may lead to a large amount of gas leakage, resulting in a decrease in aero engine efficiency, which ultimately affects the reliability and life of the aero engine. Therefore, the effect of installation error on the rotary seal of the aero engine was studied in this research. The flow field numerical models of the honeycomb seal, labyrinth seal, and hybrid labyrinth–honeycomb seal were established, the effects of the honeycomb seal, labyrinth seal, and hybrid labyrinth–honeycomb seal on leakage were numerically analyzed, the sealing mechanisms of three types of seals were revealed, and the effect of radial eccentricity on the leakage of three types of seals was also studied. Additionally, the high-pressure and high-speed rotary seal experiment bench was improved, the effect of eccentricity on the leakage characteristics of the honeycomb seal, labyrinth seal, and hybrid labyrinth–honeycomb seal was studied using the improved experiment bench, and the leakage characteristics of the three types of seals were compared under the same condition. The experimental results are consistent with the numerical simulation results; the honeycomb seal is the least sensitive to eccentricity, and its sealing performance is the best. The research results in this paper reveal the seal mechanisms of the honeycomb seal, labyrinth seal, and hybrid labyrinth–honeycomb seal and demonstrate the effect law of eccentricity regarding the leakage characteristics of these three types of seals. The results of this research can provide theoretical support for aero engine efficiency improvement.

Urban areas exercise numerous and strong pressures on water bodies, implying that different external anthropogenic factors also stress groundwater. Sewerage networks play an important role, being the place of wastewater flow. When sewerage deterioration conditions occur, aquifers can be contaminated by contaminants contained within wastewater. The study aims to verify the impact of sewerage leaks in urban semi-confined aquifers through a multidisciplinary approach. Geological, hydrogeological, hydrochemical, microbiological, and biomolecular investigations are carried out in a test site close to a sewer pipe, from February to October 2022. Microbiological analyses are carried out on a monthly basis, contextually to hydraulic head measurements in purpose-drilled piezometers. The presence of sandy intercalations and the prevalence of silt within the outcropping (about 10 m thick) aquitard makes the aquifer vulnerable to percolation from leaky sewers, therefore causing persistent microbial contamination in groundwater. The presence of fecal indicators (including pathogenic genera), corrosive and human-associated bacteria markers, is detected. The magnitude of microbiological impact varies over time, depending on hydrogeological factors such as dilution, hydrodynamic dispersion, and variation of the groundwater flow pathway at the site scale. As for personal care products, only Disodium EDTA is detected in wastewater, while in groundwater the concentrations of all the analyzed substances are lower than the instrumental detection limit.

This study investigates how operating conditions such as ambient temperature and sealing pressure affect sealing performance for a typical U-cup seal. The developed analysis method combines inverse fluid lubrication (IHL) theory and the Greenwood–Williamson contact model (G–W model), and the effect of increasing surface temperature due to frictional heat generated between two surfaces is considered. Commercial FE software (ABAQUS) was used to simulate the interference fit analysis of rubber seals and the pressurized process. Through this model, the film distribution, working fluid leakage, and friction force in the sealing area were discussed according to the operating parameters, such as sealed pressure, rod velocity, and ambient temperature. The simulation results demonstrate the effect of fluid viscosity on oil film formation (which varies with ambient temperature), the effect of increasing the surface temperature, and the effect of surface roughness at a very small film thickness.

This article presents an energy-efficient BJT-based temperature sensor. The output of sensing front-ends is modulated by employing an incremental Δ-Σ ADC as a readout interface. The cascoded floating-inverter-based dynamic amplifier (FIA) is used as the integrator instead of the conventional operational transconductance amplifier (OTA) to achieve a low power consumption. To enhance the accuracy, chopping and dynamic element matching (DEM) are applied to eliminate the component mismatch error while β-compensation resistor and optimized bias current are used to minimize the effect of β variation. Fabricated in a standard 180-nm CMOS process, this sensor has an active area of 0.13 mm2. While dissipating only 45.7 μW in total, the sensor achieves an inaccuracy of ±0.8 °C (3σ) from −50 °C to 150 °C after one-point calibration.

A fully penetrating cut-off wall is a vertical seepage barrier that fully penetrates an aquifer and is embedded in an underlying aquitard to a certain depth. Groundwater seepage with this type of wall occurs through three paths: leakage through the body of the wall in the aquifer, leakage through the body of the wall embedded in the aquitard, and seepage under the wall. Seepage through the first path can be simply treated as one-dimensional flow. However, due to the mutual influence of seepage through the latter two paths, the seepage problem is complicated and still needs to be studied. An analytical method is proposed to solve this problem in this study. Mathematic expressions for flow rate and head value are obtained by superposition of drawdowns of two exact models, namely, the model with only leakage through the wall body and the model with only seepage under the wall, respectively. Exact solutions are quoted or derived for the exact models, but they involve Legendre’s elliptic integrals of the first and third kinds. To facilitate an engineering application, approximate models of the exact models are introduced and their solutions are applied to the analytical formulas. The accuracy and applicability of the proposed method are verified compared with the numerical method. The proposed method provides a simple but effective method for quickly estimating the quantity of seepage in the aquitard (including leakage through the wall body and seepage under the wall) when simultaneously considering the effects of wall permeability and thickness.

Currently, acoustic methods are widely used as a way to detect pipeline leaks. This is due to the fact that the acoustic signal has sufficiently capacious information about the state of the pipeline. The effectiveness of acoustic monitoring depends on the correct extraction of this information from the diagnostic signal. Currently, there is a search for new, more effective methods for analyzing acoustic signals. The article proposes to apply the theory of fractals to determine pipeline leaks. One of the most accurate methods for determining the fractal dimension of time series is R/S analysis using the Hurst exponent. An experimental stand has been developed and created, which includes a steel pipeline with water circulating in it. Water leakage from the pipeline was simulated by installing discs with holes of different diameters. The discs were placed in a special fitting on the surface of the pipeline. Acoustic signals recorded from the pipeline surface at different leakages and water pressure were analyzed. A relationship has been established between the size of the leak and the Hurst exponent of acoustic signals. The proposed method is compared with spectral analysis. Empirical experience has proven that R/S analysis can be used to determine pipeline leaks, as well as their classification by size.

China–Myanmar oil and gas pipelines in Southwest China guarantee the energy security of China. Due to poor geographical circumstances, the safety of pipelines is seriously threatened by natural disasters. Therefore, there is a crucial, practical significance to establishing a model of leakage and diffusion of crude oil in the mountainous terrain and to conduct related applied studies. In the present study, computational fluid dynamic simulations of the dynamic diffusion process of leaking contaminants on the mountain surface was performed; the influence of the pipe pressure, landform, surface environment and leakage location on diffusion speed and range were discussed carefully. The results indicate that the variation of topographic altitude determines the path of leaking contaminants. Accordingly, an improved algorithm based on the SFD8 algorithm to predict the path of leaking contaminants at a low leakage rate was proposed; this would be instructive for an emergency response to ensure the safety of pipelines.

Care for the natural environment, which can be observed in the tightening of emission standards, has enforced the search for new fuels, especially renewable sources of natural origin. The article presents the results of theoretical and experimental considerations on the impact of aviation biofuels on the materials used for sealing flange joints. The fuel type selected for the test is compatible with aviation fuels. Fuels have been enriched with a bio-additive that changes the technical and physical properties of the fuel. The tested gaskets were made of soft, aramid-elastomeric materials that were flat in shape and without reinforcement. Their commercial names are AFO and AFM. Tests were carried out with the use of a simple flange joint with a fuel reservoir at 373 K. Both fuel loss and the pressure drop on the gasket were measured during a 1000 h period of time. The experiments showed that the seals preserved the technical parameters in the presence of the tested fuels. The fuel loss did not exceed the accepted limits, which demonstrates the suitability of the tested materials for utilization with new types of fuel. However, no unequivocal conclusions can be drawn about the positive or negative impact of bio-additives on the sealing material due to the fact that both an improvement and deterioration in tightness under certain circumstances were observed. Based on the experimental data, a mathematical model was proposed that makes it possible to predict the service life of the gaskets in flange joints in contact with the investigated types of fuel. The potential application of the research results is practical information about the impact of biofuel on the gasket, and hence the information about the possibility of using traditional sealing materials in a new application—for sealing installations for the production, transmission and storage of biofuels.

This study determines the effects of leakage attributed to conduit defects on the failure behavior on the downstream slope of a homogeneous reservoir. To analyze the failure mechanism, model experiments and a three-dimensional deformation–seepage analysis were conducted based on the failure shape, pore-water pressure, hydraulic gradient, and settlement, and the results were compared with the changes in the water storage capacity of the failed reservoir owing to conduit defects. The comparison showed that failure estimation based on settlement gauges and water storage capacity is limited in its ability to detect rapid changes compared with monitoring methods. An area of potential failure owing to internal erosion was formed at a location that is 1.4–2.4 times the conduit height on the downstream slope. The findings of this study can provide insights for determining the pre-reinforcement required to prevent or minimize reservoir failure due to the fact of leakage.

Gas-fire-suppression systems are currently applied to some specific buildings in Norway, as sprinkler systems may not provide sufficient protection in some cases. The application of inert-gas-fire-suppression systems for hazard class 6 buildings needs further intensive validation by experimental and numerical study. Due to the presence of cracks and ventilation systems, it becomes doubtful whether inert-gas agents can extinguish a deep-seated fire located in a leaky enclosure. In this study, tests and numerical simulations were both conducted to investigate the extinguishing effectiveness of inert-gas agents for a closet fire in a leaky apartment. The results show that the location of cracks plays a nonnegligible role in determining the oxygen level in the leaky apartment. The tests and simulations demonstrated that the gas-fire-suppression system successfully extinguished the closet fire even if the activation of the gas-fire-suppression system was postponed or the path available for the inert-gas agent to reach the fire source was narrowed. However, the sprinkler system failed to achieve this. The experimental data also demonstrated that the calculation method proposed in our previous work can be used to estimate the oxygen level in a leaky enclosure.

Objectives: Epidural blood patching (EBP) is the mainstay therapy for spontaneous intracranial hypotension (SIH). MRI is used for evaluating spinal CSF leakage. Post-EBP MRI has been. shown to be effective in predicting the efficacy of EBP. However, there are few reports on how post-EBP MRI findings may change with time. The aim of this study was to evaluate the relationship between post-EBP MRI findings at different time points and the corresponding effectiveness of EBP. Methods: We retrospectively reviewed 63 SIH patients who had received target EBP. All patients received an MRI follow-up within 10 days (post-EBP MRI) and at 3 months after EBP (3-month MRI). A sub-group analysis was performed at different post-EBP MRI time points (0–2, 3–6, and 7–10 days). The relationships between the post-EBP MRI findings and the EBP effectiveness were evaluated. Results: Thirty-five (55.56%) patients were assigned to the EBP-effective group, and 28 (44.44%) were assigned to the EBP non-effective group according to the 3-month MRI. Compared to the EBP non-effective group, the EBP-effective group had significantly lower numbers of spinal CSF leakage in the post-EBP MRI (4.49 vs. 11.71; p = 0.000) and greater numbers of leakage improvement (7.66 vs. 2.96; p = 0.003). For patients who received post-EBP MRI during periods of 0–10, 0–2, 3–6, and 7–10 days, the cutoff values of numbers of spinal CSF leakage for predicting EBP failure were 4, 6, 4, and 5, respectively, with an AUC above 0.77. Conclusion: By using post-EBP MRI, which only takes approximately 20 min, predicting EBP efficacy became possible in SIH patients. This study provides cutoff values of numbers of spinal CSF leakage at different follow-up times to serve as clues of if further EBP is needed, which provides the novelty of the current study.

This paper studies the groundwater logging problem in the Quaternary aquifer in Aswan city, Upper Egypt. Groundwater levels are already very high in Aswan city, but this has not been exploited, and it causes damage to the environment and infrastructure for roads, building, and templets. Rising groundwater leads to the deterioration and poor quality of agricultural lands. The main objective of this study is to assess and investigate the main reasons for the groundwater logging in the tourist city of Aswan using field investigation during different periods and gain a better understanding of the water dynamics in the study area. This study investigated the surface water levels in the High Dam Lake (HDL), the Kima Lake water levels, the recharge in the fish hatchery, the abstraction well rates in Kima and El-Shalal, and the leakage from the drinking water and wastewater network in Aswan city within the study area using field investigation. The results of this study show that the HDL is one of the most important sources feeding the aquifer in the study area, and it affects the rise and fall of the groundwater levels, but it is not the only factor that affects this problem. Moreover, the rise in the groundwater levels was due to the infiltration from the unlinking fish hatchery, the reduction in abstraction well rates from Kima Lake, the lack of abstraction from El shallal region, the increase in the leakage from drinking water pipelines, sewage networks and septic underground wastewater tanks; these factors are affecting groundwater logging in Aswan city. Potential groundwater level maps for the study area were generated using field data and ArcGIS technique for the years 2010, 2012, 2014, 2017, 2018, and 2020. Based on the results of the potential groundwater maps, the maximum and minimum difference for the groundwater levels in the study area between 2017 and 2012 reached 12.56 m and 0.83 m, respectively; also, between 2018 and 2017, the levels were 4.34 m and 0.25 m, respectively. Moreover, between 2020 and 2018, they were 8 m and 0.38 m, respectively.

Groundwater is of great importance in our daily life, and its importance is due to its multiple uses, whether in agriculture, industry or other uses. Increasing the Groundwater Levels (GWL) in any area is a great benefit for its importance and multiplicity of uses, but in the city of Aswan, it is different, as the increase in the GWL causes severe damage to buildings and leads to poor quality of agricultural land and the destruction of infrastructure due to the lack of good management. The main objective of this study is to develop a conceptual model of the groundwater system to gain better understanding of water dynamics in the study area and to investigate different management scenarios of the use of groundwater. The model was developed using MODFLOW code to achieve the objective of the study, where the necessary field data were collected to feed the model from the study area, such as Surface Water Levels (SWL) in the Aswan Dam lake and the Nile River, GWL in the Aswan Aquifer and the different characteristics of the layers constituting the aquifer, such as porosity and recharge for different periods to ensure obtaining the most accurate and best results from the model. The model was calibrated with mean residual and absolute mean residual which reached −0.08 and 0.629 m, respectively, with a Root Mean Square Error (RMSE) of 0.737m and a normalized RMSE of 4.319%. Two future scenarios have been developed to arrive at a future vision of GWL in the Aswan aquifer. The first scenario investigated GWL in the study area by changing the values of recharge to the aquifer resulting from an increase in the drinking water and sewage networks’ leakage values, which were predicted in the future for years 2025, 2030, 2035 and 2040. The GWL in the study area are increasing as a result of the increase in the amount of leakage in the years 2025, 2030, 2035 and 2040 compared to the GWL in the study area for the year 2020 by 0.29%, 1.31%, 2.01% and 3.16%, respectively. The second scenario investigated GWL by changing the water levels in El hebs (the lake between the High Dam and the Aswan Dam) as follows (108 m, 110 m, 112 m, 114 m, 116 m and 118 m), where the groundwater levels were calculated in the Aswan Aquifer corresponding to each level. The percentage of increase in groundwater levels corresponding to the levels 108 m, 110 m, 112 m, 114 m, 116 m and 118 m compared to the groundwater levels at the level of 106 m was found as follows: 0.92%, 2%, 2.87%, 4.05%, 4.91% and 5.67%, respectively. The simulation results are intended to support integrated groundwater modeling for the components of the hydrological water budget in the city of Aswan. Furthermore, the model provides us with a better understanding of long-term scenarios for the waterlogging in the city. The results are useful for managing the water logging problems and planning the future infrastructure in the city of Aswan.

The need for water supply companies to exercise control over the operating conditions of water supply networks has contributed to the development of a number of methods for their diagnosis. The diagnostics of technical infrastructure is a constantly developing field, and therefore, over the years, we have observed the development of various methods of diagnosing network operating conditions and their classification. The article presents, in a synthetic way, the division and review of the previously used methods of diagnosing the operating conditions of water supply networks. The authors also classified and assessed the usefulness of the methods of diagnosis in specific operating conditions. The review carried out by the authors shows that there is a need for research on the detection of operating conditions of water supply networks under the operating conditions of real systems. The results of our deep analysis allow for the understanding of the most important areas of research, as well as the existing worldwide trends in the development of methods for leak diagnosis and detection in water distribution networks. This review is a compendium of knowledge on the detection and diagnosis of water supply networks.

The issues of leakage with respect to the clearance between the pump plunger outer surface and the pump barrel inner surface and other operational conditions have been revisited in this paper. Both Poiseuille flow rate due to the pressure difference and Couette flow rate due to the plunger motion have been considered. The purpose of this study is to explore the possibility of representing the entire downhole pump system with a simple viscoelastic model. We have explored both Kelvin and Maxwell viscoelastic models along with the dynamic behaviors of a mass point attached to the viscoelastic model. By using the time-dependent polished rod force measured with a dynamometer as the input to the viscoelastic models, we have obtained the displacement responses, which match closely with the actual measurements in experiments and operations. Further study and experiments have been planned and partially implemented in the McCoy School of Engineering at Midwestern State University, a member of the Texas Tech University System.

The characteristics of transmitted acoustic field have important significance to the leakage detection and the acoustic metasurface technology. When the additional leak holes are present, the conventional single neck Helmholtz resonator will naturally become the one with multiple necks. Based on such a background, in this paper, the effects of leakages on the transmission properties of a Duct Helmholtz Resonator (DHR) device is investigated both analytically and numerically. A set of closed-form formulas are derived to analytically predict the transmission spectra of the DHR device with leakages. The theoretical results are compared with COMSOL predictions. The simulation results show that the number and width of leak holes have significant influences on the amplitude, phase shift of the transmitted wave, and resonance frequency of the DHR system.

Quantification of water losses (WL) in water distribution networks (WDNs) is a crucial task towards the development of proper strategies to reduce them. Currently, WL estimation methods rely on semi-empirical assumptions and different implementation strategies that increase the uncertainty of the obtained estimates. In this work, we compare the effectiveness and robustness of two widely applied WL estimation approaches found in the international literature: (a) the water balance, or top-down, approach introduced by the International Water Association (IWA), and (b) the bottom-up or minimum night flow (MNF) approach, based on a recently proposed probabilistic MNF estimation method. In doing so, we use users’ consumption and flow-pressure data from the 4 largest pressure management areas (PMAs) of the WDN of the city of Patras (the third largest city in Greece), which consist of more than 200 km of pipeline, cover the entire city center of Patras, and serve approximately 58,000 consumers. The obtained results show that: (a) when MNF estimation is done in a rigorous statistical setting from high resolution flow-pressure timeseries, and (b) there is sufficient understanding of the consumption types and patterns during day and night hours, the two approaches effectively converge, allowing for more reliable estimation of the individual WL components. In addition, when high resolution flow-pressure timeseries are available at the inlets of PMAs, the suggested version of the bottom-up approach with probabilistic estimation of MNF should be preferred as less sensitive, while allowing for confidence interval estimation of the individual components of water losses and development of proper strategies to reduce them.

Based on the geological and hydrogeological conditions of the Jurong Pumped Storage Hydroelectric Power Station (JPSHP), a 3D groundwater flow model was developed in the power station area, which took into account the heterogeneity and anisotropy of fractured rocks. A control inversion method for fractured rock structural planes was proposed, where larger-scale fractures were used as water-conducting media and the relatively intact rock matrix was used as water-storage media. A statistical method was used to obtain the geometric parameter values of the structural planes, so as to obtain the hydraulic conductivity tensor of the fractured rocks. Combining the impermeable drainage systems of the upper storage reservoir, underground powerhouse and lower storage reservoir, the 3D groundwater seepage field in the study area was predicted using the calibrated model. The leakage amounts of the upper storage reservoir, powerhouse and lower storage reservoir were 710.48 m3/d, 969.95 m3/d and 1657.55 m3/d, respectively. The leakage changes of the upper storage reservoir, powerhouse and lower storage reservoir were discussed under the partial and full failure of the anti-seepage system. The research results provide a scientific basis for the seepage control of the power station, and it is recommended to strengthen the seepage control of the upper and lower storage reservoirs and the underground powerhouse to avoid excessive leakage and affect the efficiency of the reservoir operation.

Newly developed transrenal ureteral occlusion self-expanding metallic stents (SEMSs) are applied in patients with inoperable fistulas. In this study, the occlusive properties of M- and D-type occlusion SEMSs were investigated in 3D-printed phantom and ex vivo porcine urinary tracts. In the former, the mean bursting pressure causing leakage of contrast medium through the occlusion SEMS was relatively higher in M-types (42.8 ± 3.8 mmHg) than in D-types (38.8 ± 3.8 mmHg), without a statistical difference (p = 0.075). In the latter, the bursting pressure causing leakage through the M-type occlusion SEMS (110.7 ± 8.6 mmHg) was significantly higher than that of the D-type occlusion SEMS (93.8 ± 11.2 mmHg, p = 0.015); however, the mean bursting pressures causing contrast blowout did not differ between the two types (178.7 ± 11.2 mmHg vs. 176.2 ± 11.8 mmHg, p = 0.715). In conclusion, M- and D-type occlusion SEMSs showed similar efficacy in occlusive properties in the 3D phantom study; however, the M-type was superior in the ex vivo porcine urinary tract model. Further in vivo experimental studies are required to confirm these experimental results.

The seal is designed to reduce leakage and improve the efficiency of gas turbine machines, and is an important technology that needs to be studied in gas turbine design. A series of seals were proposed to try to achieve this goal. However, due to the complex fluid dynamic performance of the seal-rotor system, the seal structure can obtain both the best leakage performance and best rotordynamic performance. This paper presents a detailed flow analysis of the hole diaphragm labyrinth seal (HDLS) at several whirl frequencies and several rotation speeds. The pressure drop, velocity, turbulence kinetic energy and leakage performance of the HDLS were discussed by simulations. An interesting exponential–type relationship between rotation speeds and leakage flow at different whirl frequencies was observed by curve fitting technology. A reverse flow rate was proposed to describe such an unusual phenomenon. Such a relationship can be used to further establish the leakage model of the HDLS and other similar seals.

Optical fiber communications are essential for all types of long- and short-distance transmissions. The aim of this paper is to analyze the previously presented security risks and, based on measurements, provide the risk level evaluation. The major risk is the possibility of inserting a splitter into the optical distribution network and capturing a portion of the entire spectrum, i.e., all channels in the optical fiber. Another significant security risk is crosstalk on multiplexers in networks with wavelength division multiplexing. The paper covers the macrobend attenuation evaluation of fiber and back-reflection measurements. Based on the measurements, risks were evaluated for both point-to-point and point-to-multipoint networks and, lastly, the paper covers crosstalk measurements of an optomechanical switch. Finally, all individual risks are evaluated according to the severity, and a proposal for risk minimization is provided.