Presence Of Blockages Research Articles

IDENTIFICATION OF RISK FACTORS FOR URINARY TRACT INFECTION IN PATIENTS WITH UROLITHIASIS

Urinary tract infections (UTIs) are common among patients with urolithiasis, making treatment complicated and even dangerous. This study aimed to identify risk factors associated with UTIs in urolithiasis patients. A retrospective study was conducted at Mayo Hospital Lahore, which included 300 patients with kidney stones. The patients were separated into two groups: those with UTIs and those without. Various factors were examined, including age, gender, smoking history, stone structure, alcohol use, stone location, and presence of blockages in the urinary tract. Out of the 300 patients, 73 (24.33%) had UTIs. The most common pathogens found in the urine cultures were gram-negative bacteria, followed by gram-positive bacteria and fungi. The study concluded that gender, age, blockages in the urinary tract, stone structure, and multiple stone locations could be considered independent risk factors for UTIs in urolithiasis patients. However, no statistically significant relationship was found between drinking and smoking and the incidence of UTIs. The most common organism found in UTIs among urolithiasis patients was a gram-negative bacillus.

Validation of RANS simulations on a 61-pin wire-wrapped fast-reactor fuel assembly under the presence of localized blockages

One of the fuel assembly designs considered for liquid metal-cooled fast reactors (LMFR) uses wires helically wrapped around fuel pins as spacers. The understanding of the coolant behavior in LMFR fuels under the influence of a partially blocked flow area is required for a correct safety assessment of the Nuclear Power Plant. Accumulation of debris or cladding deformation may generate a partial or total flow blockage of coolant channels at different locations. In this paper, Unsteady Reynolds-Averaged Navier-Stokes (URANS) is applied using different turbulence models to predict the axial friction factor under the presence of blockages, placed at different positions on the bundle cross section. The simulated Reynolds number was 17,000. Results are compared with experimental friction factor data produced at the Texas A&M experimental facility. The sensitivity analysis of the RANS turbulence models concluded that the k-∊ Realizable model is the recommended one for this Reynolds number because it presented the minimum relative error with respect to the experimental data that was found below 5%.

Adaptacyjny algorytm regulacji strumienia powietrza

The paper presents an adaptive air stream control algorithm for use in a bioreactor for waste composting. The system controls the streams of air supplied to the six ducts of the bireactor. Bioreactors of this type are characterized by the fact that the porosity of the charge is very heterogeneous throughout the volume. In addition, during the process, the charge is compacted and blockages for the gas flow often occur. The control algorithm should take into account the formation of blockages and attempt to clear them. In situations where unblocking is impossible, it should ensure proper distribution of air flow in other ducts despite the presence of blockages. The overriding goal of this algorithm is to ensure equal air flow streams in all channels, regardless of differences in flow resistance. Since the air circulation in bioreactors is forced by fans with constant capacity, the algorithm should adaptively determine the maximum average value of air streams that is possible to obtain under given conditions and adjust the control system to achieve it. The paper proposes a solution to meet these requirements.

Reconfigurable Intelligent Surface aided Indoor and Outdoor User Distribution in Heterogeneous Network

Millimeter wave communication suffers from static blockages such as trees, buildings and so on. Reconfigurable Intelligent Surfaces (RISs) has been adapted to solve this blockage problem and enable the urban environment user to choose mmW enabled small cells as their source transmitter or to choose macro cells in case of non-line of sight exists. RIS is a promising network technology to improve the quality of service parameters such as spectral efficiency and energy efficiency by artificially reconfiguring the propagation environment of electromagnetic waves. An indoor user can be connected with mmW band if the line of sight (LOS) link exists. Otherwise, the system utilizes RIS transmission model to have reliable and low-latency communication. It reflects the capability of RISs to enable enhanced communications in challenging environments. An optimization problem is formulated to maximize the sum data rate of an indoor user by phase shift optimization at the RIS. The outage probability of the proposed scheme is analyzed under Rician fading channel. The proposed RIS enabled method targets to enhance the overall performance in terms of average spectral efficiency and achievable data rate in the presence of blockages and system imperfections. The data rate is increased by three fold times than that of the transmission without RIS. The utility of this framework is discussed for both indoor and outdoor environments.

Correlation between Head Computed Tomography Scan Examination and Cranial Index Measurement in Pediatric Hydrocephalus

Hydrocephalus in children can inhibit child growth. However, if treated immediately, the patient will develop normal intelligence. In radiology, the most important problem is to detect hydrocephalus early. Currently, radiology examinations can detect hydrocephalus accurately with a CT scan to identify the presence of blockages and assess the degree. Skull radiography is used to assess the presence of advanced hydrocephalus. A comparison is carried out and assesses the relationship between hydrocephalus measurement on the ventricular and cranial index by scanogram. The study used a cross-sectional analytics design, using Picture Archiving and Communication System (PACS) data. There were 68 samples taken using consecutive sampling, obtaining ventricular index measurement results above 0.30, and patients under 12 years old. Spearman rank test showed a correlation between the ventricular index measurements and cranial index, with Spearman’s Rho (r) = 0.856 and p0.001 with linear equation Y= 2.973 + 0.005X. It revealed that the constant 2.973 indicated that if there is no B coefficient value, the participation value will be 2.973. Furthermore, regression coefficient X of 0.005 indicated that the participation value grows by 0.005 for every 1 addition of the B coefficient value with R2= 0.340.

Pressure drop and flow characteristics in partially blocked wire wrapped rod bundles

One of the fuel assembly designs considered for liquid metal-cooled fast reactors (LMFR) uses wires helically wrapped around fuel pins as spacers. The understanding of the coolant behavior in LMFR fuels under the influence of a partially blocked flow area is required for a correct safety assessment. Accumulation of debris or cladding deformation may generate a partial or total flow blockage of coolant channels at different locations. Unsteady Reynolds-Averaged Navier-Stokes (URANS) is applied using different turbulence models to predict the axial friction factor under the presence of blockages. Results are compared with experiments. The different turbulence models presented a variable performance for the blockage scenarios under study, finding k-∊ Realizable the recommended model for turbulent regime and k-ω SST the recommended model at transition regime. A Large Eddy Simulation was also implemented to simulate the case with the largest blocked area finding its results in reasonable agreement with the experiments.

Experimental and Numerical Studies of Enhanced Interdigitated Flow Field for PEM Fuel Cells

AbstractThe presence of blockages in the flow field (FF) of proton exchange membrane fuel cells (PEMFCs) increases the mass transport of reactants toward the catalyst layer regions and improves cel...

On the Placement of Intelligent Surfaces for RSSI-Based Ranging in Mm-Wave Networks

We study the received signal strength indicator (RSSI)-based ranging performance of a cellular user in a millimeter-wave (mm-wave) network aided by reconfigurable intelligent surfaces (RISs). First, we propose an optimal RIS deployment strategy that minimizes the joint blockage probability of the user to the base station (BS) link and the user to the RIS link. Then, we provide a bound-based characterization of a ranging strategy in which the BS estimates the distance the user in the direct link in case it is in the line of sight (LOS) state, whereas in case the direct link is blocked, the BS estimates the user distance via the reflected, i.e., RIS-aided link. In literature, for maximizing the path-gain the RIS deployment is recommended to be in close proximity to the BS. In contrast, our study shows that in the presence of blockages, close locations of the RIS and the BS is sub-optimal.

MinDFul: Using double links for stabilizing mmWave wireless channels for application to autonomous vehicles and augmented reality

Abstract Applications that require short-range ultra-high bitrate communication, such as cable removal in virtual reality games and communication between autonomous vehicles, are examining solutions such as millimetre wave wireless (mmWave). When using mmWave, steerable directional antennas are used to mitigate the severe signal power attenuation common with high frequencies. Nonetheless, even small movements in the user device can cause a sudden drop in data-rate down (even to 0 bits/s) making mmWave channels unstable and unusable. To make the channel more stable for the aforementioned applications, which are vulnerable due to frequent blockages and fast movement, we designed and developed a robust solution based on a double link mmWave system. We duplicate the radio transceivers (RT) of a user device (UD) to increase the probability of finding line of sight to an access point (AP) representing the other side of the communication channel. The AP selects one RT of the UD for communication, based on continuous measurement of quality compared to the channel of the other RT. This concept was implemented in a laboratory environment and evaluated using a series of controlled experiments. The experiments serve to validate that using double links is feasible, and is considerably more robust and it can double the link utilization, compared to only using one mmWave link. These results show great promise for the concept, by demonstrating that using multiple mmWave links yields ultra-high bit-rate wireless communication with no disruption, even in the presence of blockages and mobility.

Thermal-hydraulics analysis of flow blockage events for fuel assembly in a sodium-cooled fast reactor

The subchannel code ATHAS-LMR has been improved for analyzing thermal-hydraulics characteristics of flow blockage events in the fuel assembly of a sodium-cooled fast reactor (SFR). Based on the in-depth study of the phenomenon of flow blockage and combined with the characteristics of fast reactor assembly, enhanced models for the wire-wrap spacer and convective heat transfer have been added to account for changes in transverse flow in the presence of blockages. And appropriate transverse mixing and local resistance model are also implemented in ATHAS-LMR-FB. The improved code has been assessed against experimental data obtained at adiabatic and diabatic conditions in SFR assemblies with simulated flow blockages. Good agreement between predictions and experimental data on velocity and temperature distributions downstream of the blockage has been observed. Comparison of predictions of various analytical tools have also been performed. Predictions of the improved ATHAS-LMR code are shown to be compatible with those of other analytical tools. An in-depth analysis of effects of location and size of blockage has been carried out for the fuel assembly of the China Experimental Fast Reactor. Boiling has been predicted to occur for blockage ratios greater than 55.61% at the central location of the fuel assembly. Peak cladding and coolant temperatures are predicted at the axial location 70% of the rod length (just downstream of the maximum local power position of the non-uniform axial power profile).

Eigenfrequency Shift Mechanism due to an Interior Blockage in a Pipe

AbstractThe presence of blockages in water supply systems wastes energy, decreases system performance, and may pose safety concerns. Previous research showing that blockages induce a shift in the r...

Coverage and Rate Analysis for Millimeter-Wave Cellular Networks

Millimeter wave (mmWave) holds promise as a carrier frequency for fifth generation cellular networks. Because mmWave signals are sensitive to blockage, prior models for cellular networks operated in the ultra high frequency (UHF) band do not apply to analyze mmWave cellular networks directly. Leveraging concepts from stochastic geometry, this paper proposes a general framework to evaluate the coverage and rate performance in mmWave cellular networks. Using a distance-dependent line-of-site (LOS) probability function, the locations of the LOS and non-LOS base stations are modeled as two independent non-homogeneous Poisson point processes, to which different path loss laws are applied. Based on the proposed framework, expressions for the signal-to-noise-and-interference ratio (SINR) and rate coverage probability are derived. The mmWave coverage and rate performance are examined as a function of the antenna geometry and base station density. The case of dense networks is further analyzed by applying a simplified system model, in which the LOS region of a user is approximated as a fixed LOS ball. The results show that dense mmWave networks can achieve comparable coverage and much higher data rates than conventional UHF cellular systems, despite the presence of blockages. The results suggest that the cell size to achieve the optimal SINR scales with the average size of the area that is LOS to a user.

Rapid detection of sewer defects and blockages using acoustic-based instrumentation

Sewer flooding incidents in the UK are being increasingly associated with the presence of blockages. Blockages are difficult to deal with as although there are locations where they are more likely to occur, they do occur intermittently. In order to manage sewer blockage pro-actively sewer managers need to be able to identify the location of blockages promptly. Traditional closed-circuit television (CCTV) inspection technologies are slow and relatively expensive so are not well suited to the rapid inspection of a network. This is needed if managers are to be able to address sewer blockages proactively. This paper reports on the development of an acoustic-based sensor. The sensor was tested in a full scale sewer pipe in the laboratory and it was shown that it is able to find blockages and identify structural aspects of a sewer pipe such as a manhole and lateral connection. Analysis of the received signal will locate a blockage and also provide information on its character. The measurement is very rapid and objective and so inspections can be carried out at much faster rates than using existing CCTV technologies.

Maze Routing Steiner Trees With Delay Versus Wire Length Tradeoff

In this paper, we address the problem of generating good topologies of rectilinear Steiner trees using path search algorithms. Various techniques have been applied in order to achieve acceptable run times on a maze router that builds Steiner trees. A biasing technique proposed for wire length improvement, produces trees that are within 2% from optimal topologies in average. By introducing a sharing factor and a path-length factor we show how to trade-off wire length for delay. Experimental results show that our algorithm generates topologies with better delay compared to state of the art heuristics for Steiner trees, such as AHHK (from 26% to 40%) and P-Trees (from 1% to 30% and from 6% to 21% in the presence of blockages) while keeping the properties of a routing algorithm. An important motivation for this work lies in the fact that it can be used for estimation in the early stages as well as for actual routing, thereby improving the convergence and timing closure of the design significantly. We also provide some valuable theoretical background and insights on delay optimization and on how it relates to our maze router implementation.

Large Eddy Simulation and PIV Measurements of Unsteady Premixed Flames Accelerated by Obstacles

In gas explosions, the unsteady coupling of the propagating flame and the flow field induced by the presence of blockages along the flame path produces vortices of different scales ahead of the flame front. The resulting flame–vortex interaction intensifies the rate of flame propagation and the pressure rise. In this paper, a joint numerical and experimental study of unsteady premixed flame propagation around three sequential obstacles in a small-scale vented explosion chamber is presented. The modeling work is carried out utilizing large eddy simulation (LES). In the experimental work, previous results (Patel et al., Proc Combust Inst 29:1849–1854, 2002) are extended to include simultaneous flame and particle image velocimetry (PIV) measurements of the flow field within the wake of each obstacle. Comparisons between LES predictions and experimental data show a satisfactory agreement in terms of shape of the propagating flame, flame arrival times, spatial profile of the flame speed, pressure time history, and velocity vector fields. Computations through the validated model are also performed to evaluate the effects of both large-scale and sub-grid scale (SGS) vortices on the flame propagation. The results obtained demonstrate that the large vortical structures dictate the evolution of the flame in qualitative terms (shape and structure of the flame, succession of the combustion regimes along the path, acceleration-deceleration step around each obstacle, and pressure time trend). Conversely, the SGS vortices do not affect the qualitative trends. However, it is essential to model their effects on the combustion rate to achieve quantitative predictions for the flame speed and the pressure peak.

Blocking of capillaries as fouling mechanism for dead-end ultrafiltration

In this paper plugging of capillaries in the potting is investigated. A lot of research has been done on fouling of the membrane surface (pore blocking, cake filtration) but research on other types of membrane fouling like plugging of capillaries is not so common. Experiments were performed with a lab-scale test installation under constant flux conditions with synthetic feed water containing ferric hydroxide flocks as a fouling component. The experiments showed that during operation capillaries became blocked by fouling plugs. The presence of blockages, especially in the potting at the concentrate side of the capillaries, could not be detected by measuring the clean water resistance. However such blockages did result in an increased forward flush pressure. A combination of the clean water resistance and the forward flush pressure is suitable for determining the fouling of a membrane and the effectiveness of a cleaning procedure. The part of the capillaries in the potting is not backwashed and therefore the hydraulic as well as the chemical cleaning is not efficient at this place.

Numerical Simulation of the Urine Flow in a Stented Ureter

When a stent is implanted in a blocked ureter, the urine passing from the kidney to the bladder must traverse a very complicated flow path. That path consists of two parallel passages, one of which is the bore of the stent and the other is the annular space between the external surface of the stent and the inner wall of the ureter. The flow path is further complicated by the presence of numerous pass-through holes that are deployed along the length of the stent. These holes allow urine to pass between the annulus and the bore. Further complexity in the pattern of the urine flow occurs because the coiled "pig tails," which hold the stent in place, contain multiple ports for fluid ingress and egress. The fluid flow in a stented ureter has been quantitatively analyzed here for the first time using numerical simulation. The numerical solutions obtained here fully reveal the details of the urine flow throughout the entire stented ureter. It was found that in the absence of blockages, most of the pass-through holes are inactive. Furthermore, only the port in each coiled pig tail that is nearest the stent proper is actively involved in the urine flow. Only in the presence of blockages, which may occur due to encrustation or biofouling, are the numerous pass-through holes activated. The numerical simulations are able to track the urine flow through the pass-through holes as well as adjacent to the blockages. The simulations are also able to provide highly accurate results for the kidney-to-bladder urine flow rate. The simulation method presented here constitutes a powerful new tool for rational design of ureteral stents in the future.

Heat transfer coefficients and other performance parameters for variously positioned and supported thermal loads in ovens with/without water-filled or empty blockages

An in-depth experimental study of heat transfer in ovens has provided basic data that is directly applicable to design. Heat transfer coefficients were measured for thermal loads having either black or highly reflective surface finishes. Approximately 100 different data runs were carried out. These heat transfer coefficients enabled the separation of the heat transfer into convective and radiative components, with radiation being the dominant transfer mechanism for blackened loads. The thermal response of the load to the presence of blockages situated either below or above the load was quantified. This response was only slightly affected by the blockages when they were empty of water, but major effects were observed when the blockages were water filled. Major effects were also encountered when the load was supported from below by cookie sheets. On the other hand, extensive investigation of various positions throughout the oven indicated a very weak effect of load position on the thermal response.