Dynamic Leak Research Articles

A machine learning-based model for real-time leak pinpointing in buildings using accelerometers

Modern water networks from municipal network to building networks are plagued with the threat of leaks. Leaks create a significant amount of loss of resources. Pressurized water pipelines are more susceptible due to the high pressure at which water travels. Multiple researchers have tried to utilize a variety of static (devices that are left in the network) and dynamic (devices that are mobilized to the suspected location) leak detection techniques to ensure the early detection and pinpointing of leaks in water transportation networks. The main goal is to provide quick and efficient tools that can identify and pinpoint leaks in buildings while being cost-effective. This article proposes a small-scale experimental static real-time monitoring system that can identify leaks and their location with high accuracy by measuring vibration signals via wireless accelerometers. The experiment utilizes one-inch and two-inch Polyvinyl Chloride (PVC) and iron pipelines, which are commonly used in residential buildings. Since the proposed system is static, the wireless accelerometers are placed on the exterior walls of the pipelines. The vibration signals, derived from each accelerometer, were calculated and analyzed. A leak is identified when a spike in the signal is detected. Once a leak was identified, the model would move to determine the source of the signal, that is, the leak location. The developed models proved to be capable of accurately pinpointing leaks within an accuracy of 25 cm. The main techniques that were used in model development were regression analysis and backpropagation of artificial neural networks models.

A Non-spiking Neuron Model With Dynamic Leak to Avoid Instability in Recurrent Networks.

Recurrent circuitry components are distributed widely within the brain, including both excitatory and inhibitory synaptic connections. Recurrent neuronal networks have potential stability problems, perhaps a predisposition to epilepsy. More generally, instability risks making internal representations of information unreliable. To assess the inherent stability properties of such recurrent networks, we tested a linear summation, non-spiking neuron model with and without a “dynamic leak”, corresponding to the low-pass filtering of synaptic input current by the RC circuit of the biological membrane. We first show that the output of this neuron model, in either of its two forms, follows its input at a higher fidelity than a wide range of spiking neuron models across a range of input frequencies. Then we constructed fully connected recurrent networks with equal numbers of excitatory and inhibitory neurons and randomly distributed weights across all synapses. When the networks were driven by pseudorandom sensory inputs with varying frequency, the recurrent network activity tended to induce high frequency self-amplifying components, sometimes evident as distinct transients, which were not present in the input data. The addition of a dynamic leak based on known membrane properties consistently removed such spurious high frequency noise across all networks. Furthermore, we found that the neuron model with dynamic leak imparts a network stability that seamlessly scales with the size of the network, conduction delays, the input density of the sensory signal and a wide range of synaptic weight distributions. Our findings suggest that neuronal dynamic leak serves the beneficial function of protecting recurrent neuronal circuitry from the self-induction of spurious high frequency signals, thereby permitting the brain to utilize this architectural circuitry component regardless of network size or recurrency.

Technical Performance of Continuous Pressure Insufflators Versus Traditional Insufflators in the Presence of Leaks During Laparoscopic Surgery.

Background. New insufflators have been developed to manage leaks emanating from the working cavity during laparoscopic surgery. Little data have been published to show the performance of these insufflators. This study evaluates the performance of 2 modern continuous pressure insufflators in various leak conditions. Methods. Performance of a new continuous pressure insufflator, EVA15 (Palliare, Galway, Ireland), was compared with that of a continuous pressure insufflator, Airseal intelligent Flow System (iFS) (CONMED, Utica, NY), and a traditional intermittent pressure insufflator, Endoflator 40 (KARL STORZ, Tuttlingen, Germany). Six different leak scenarios were created in a swine model to create different dynamic leak profiles of between 5 and 15L/min. Pressure deviation from setting was measured for each insufflator tested. The following were calculated: (a) mean absolute difference of measured insufflation pressure vs. the insufflator pressure setting for the 50second measurement period (MAD) and (b) standard deviation of the absolute differences (SD). Results. The average mean absolute pressure difference between the EVA15 and Airseal is .27mmHg. However, the average mean absolute pressure difference between the EVA15 and Endoflator 40 is 2.62mmHg. Conclusions. Continuous pressure insufflators provide superior pressure delivery performance in leak situations when compared against a traditional intermittent pressure insufflator. No clinically significant performance difference was observed when comparing the EVA15 and Airseal iFS insufflators in the tested leak situations.

Precise memory leak detection for java software using container profiling

A memory leak in a Java program occurs when object references that are no longer needed are unnecessarily maintained. Such leaks are difficult to detect because static analysis typically cannot precisely identify these redundant references, and existing dynamic leak detection tools track and report fine-grained information about individual objects, producing results that are usually hard to interpret and lack precision. In this article we introduce a novel container-based heap-tracking technique, based on the fact that many memory leaks in Java programs occur due to incorrect uses of containers, leading to containers that keep references to unused data entries. The novelty of the described work is twofold: (1) instead of tracking arbitrary objects and finding leaks by analyzing references to unused objects, the technique tracks only containers and directly identifies the source of the leak, and (2) the technique computes a confidence value for each container based on a combination of its memory consumption and its elements' staleness (time since last retrieval), while previous approaches do not consider such combined metrics. Our experimental results show that the reports generated by the proposed technique can be very precise: for two bugs reported by Sun, a known bug in SPECjbb 2000, and an example bug from IBM developerWorks, the top containers in the reports include the containers that leak memory.

Applying monitoring, verification, and accounting techniques to a real-world, enhanced oil recovery operational CO2 leak

Abstract The use of carbon dioxide (CO2) for enhanced oil recovery (EOR) is being tested for oil fields in the Illinois Basin, USA. While this technology has shown promise for improving oil production, it has raised some issues about the safety of CO2 injection and storage. The Midwest Geological Sequestration Consortium (MGSC) organized a Monitoring, Verification, and Accounting (MVA) team to develop and deploy monitoring programs at three EOR sites in Illinois, Indiana, and Kentucky, USA. MVA goals include establishing baseline conditions to evaluate potential impacts from CO2 injection, demonstrating that project activities are protective of human health and the environment, and providing an accurate accounting of stored CO2. This paper focuses on the use of MVA techniques in monitoring a small CO2 leak from a supply line at an EOR facility under real-world conditions. The ability of shallow monitoring techniques to detect and quantify a CO2 leak under real-world conditions has been largely unproven. In July of 2009, a leak in the pipe supplying pressurized CO2 to an injection well was observed at an MGSC EOR site located in west-central Kentucky. Carbon dioxide was escaping from the supply pipe located approximately 1 m underground. The leak was discovered visually by site personnel and injection was halted immediately. At its largest extent, the hole created by the leak was approximately 1.9 m long by 1.7 m wide and 0.7 m deep in the land surface. This circumstance provided an excellent opportunity to evaluate the performance of several monitoring techniques including soil CO2 flux measurements, portable infrared gas analysis, thermal infrared imagery, and aerial hyperspectral imagery. Valuable experience was gained during this effort. Lessons learned included determining (1) hyperspectral imagery was not effective in detecting this relatively small, short-term CO2 leak, (2) even though injection was halted, the leak remained dynamic and presented a safety risk concern during monitoring activities and, (3) the atmospheric and soil monitoring techniques used were relatively cost-effective, easily and rapidly deployable, and required minimal manpower to set up and maintain for short-term assessments. However, characterization of CO2 distribution near the land surface resulting from a dynamic leak with widely variable concentrations and fluxes was challenging.

Hydrodynamics of a liquid–solid circulating fluidized bed: Effect of dynamic leak

Abstract Experiments were conducted in a liquid–solid circulating fluidized bed (LSCFB) of 80 mm i.d. and 2.8 m high to study the macroscopic flow structure over a wide range of liquid velocity and solids inventory in the storage vessel. The results indicate that the valve configuration (i.e. lift pot and the angle made by the solids feed pipe with the riser), solids inventory in the storage vessel and location of the primary liquid distributor were found to play an important role on the macroscopic properties of LSCFB. Dynamic leak, flow of solids from the return leg into the riser in the absence of auxiliary liquid flow, has been noticed at very high liquid velocities when the primary liquid distributor inlet (positioned at the bottom of the riser) is near to the solids feed pipe from the storage vessel. The dynamic leak was prevented by changing the position of the primary distributor inlet and the macroscopic flow behavior with and without dynamic leak was compared. The transitional liquid velocity that demarcates the conventional fluidization from the circulating fluidization was determined by three different methods and was found to be independent of solids inventory and dynamic leak.

A closed xenon anesthesia delivery system.

A closed xenon anesthesia delivery system.

Leak Detection Implementation: Modeling and Tuning Methods

This paper contains an overview of the Williams Pipe Line computerized dynamic leak detection system, including the basic calculation methods used in the system, instrumentation support requirements, and various operational situations encountered during the implementation process. Special emphasis is given to enhanced modeling techniques required for complex pipeline configurations. Sample performance test results are also presented with a discussion focused primarily on the system response time.

A dynamic leak testing method for radioactive sources used in chromatography

A dynamic leak testing method for radioactive sources used in chromatography

The solid solubility of nitrogen in Nb and Nbrich NbHf, NbMo and NbW alloys: Part I: The binary system NbN

Using a dynamic leak method, a Sieverts apparatus and a combination of X-ray diffraction and microscopical techniques, a study has been made of the interstitial solid-solubility of nitrogen in niobium as a function of pressure and temperature. It has been found that Nb can accommodate 9.48 at.% N interstitially at 2200°C and 3 × 10 −1torr N 2, but the amount which can be retained in solution at room temperature is very much smaller, being about 1.0 at.% depending on the quenching rate. The results are fully in accord with those of Gebhardt, Fromm and Jakob, and of Cost and Wert who obtain a relationship x = 6.2 × 10 −4 (p N 2 ) 1 2 exp( 46,000 RT ) for the amount x, in at.% of nitrogen in solid solution, p N 2 being the nitrogen pressure in torr, R the gas constant and T in degrees Kelvin. The lattice parameter of Nb is increased from a =3.2986 A ̊ to 3.3060 Å with 1.05 at.% N retained in the lattice.

The solid-solubility of oxygen in Nb and Nb-rich Nb-Hf, Nb-Mo and Nb-W alloys: Part I: the Nb-O system

The interstitial solid-solubility of oxygen in niobium has been studied by means of X-ray diffraction, micrographic and thermal techniques using both a dynamic leak method and a Sieverts apparatus. The lattice parameter of degassed, zone-refined niobium was found to be 3.2986 Å, which is much lower than hitherto published values. At pressures above 10 −11 torr O 2, Nb is in thermodynamic equilibrium with oxide vapor and can take up to 6 at.% O 2 into solid solution at 1775°C. Above this temperature oxidation is “catastrophic” and the volatile oxides Nb 2O, NbO and Nb 2O 5 form on the surface. The “degassing” of Nb at 2200°C and above at a pressure of 10 −6 torr O 2 is, in effect, brought about by the volatilization of the oxide and not by the de-adsorption of gaseous oxygen.

A hydrogen Pirani leak detector using a charcoal trap

A simple robust dynamic leak detector suitable for vacuum proving large numbers of components down to 10-3 1μ/s is described. The property of charcoal at low temperatures to absorb a large percentage of atmospheric gases and little hydrogen is used to eliminate irregular pressure pulses caused by impurities in the component and to increase the response of a Pirani gauge when a leak is probed with hydrogen. A charcoal trap is placed between the component and a Pirani gauge on a vacuum unit.