Flow Tracing Research Articles

A Novel Real-Time Searching Method for Power System Splitting Boundary

It is possible to prevent collapse of the whole post-fault power system, which is in unstable condition, by determining the splitting boundary so as to calm down the system oscillation. A fast method of searching for the splitting boundary of power system controlled islanding is presented in this paper, the aim of which is to minimize the load-generation imbalance in each island. The method contains three phases, namely, defining the domain of each generator according to power flow tracing algorithm, determining an initial splitting boundary based on the grouping information of generators, and refining the initial one to get the final splitting boundary. A real-time searching program for power system splitting boundary was developed based on the method. Simulations on the IEEE 118-bus power system and a practical power system show that the proposed method is effective and fast.

Briefing: Spreadsheet analysis of complex masonry structures

When dealing with complex masonry structures, exploration of the potential flow of forces can sometimes be more useful than rigorous analysis. Exploration requires division of the structure into elements, computation of volumes and weights, summation of forces and then the tracing and visualisation of force flow. This briefing note describes how vector algebra and spreadsheets can be used to develop simple interactive spreadsheet models.

Fluid migration directions inferred from gradient of time surfaces of the sub seabed

The role of sub seabed topographically controlled fluid migration is assessed to improve our understanding of distributions of acoustic chimneys at the Nyegga pockmark field on the mid-Norwegian continental margin. 3D seismic data interpretations resulted in topographic gradients of seismic time surfaces and RMS amplitude maps. Topographical gradient maps and flow tracing allowed identifying migration pathways and trapping locations for free gas within the shallow sub seabed. The occurrence of acoustic chimneys, pockmarks and mounds correlate with identified fluid migration pathways and gas trapping locations. An important factor that controls the trapping locations and the lateral distribution of seeps on the seabed at Nyegga is the variation through time of the depth of the base of the gas hydrate stability zone (BGHSZ). Fluids can derive from gas hydrate systems that are suspected of being a biogenic source and/or Tertiary domes that are considered to show leakage of thermogenic fluids to the shallow geosphere.

Min-Max Fair Power Flow Tracing for Transmission System Usage Cost Allocation: A Large System Perspective

Power flow tracing has been suggested as an approach for evaluating 1) transmission system usage (TSU) cost and 2) loss (MW) cost for generator and load entities in the system. Recently, optimal power flow tracing methods have been proposed to “explicitly” model fairness constraints in the tracing framework. This paper, further, strengthens the tracing-compliant min-max fair cost allocation approach. The min-max model proposed in this paper is robust. It addresses concerns like scalability, numerical stability and termination in a finite number of steps while searching the optimal solution. We also propose a methodology to model DISCOMs and GENCOs as coalition within min-max framework. Case studies on an all India network of 1699 nodes and comparison with average participation and marginal participation methods bring out the better conflict resolution feature of the proposed approach. A method to model HVDC lines within the marginal participation scheme is also proposed. Quantitative and qualitative comparison of various TSU cost allocation methods on such a large system is another noteworthy contribution of the paper.

Gold Nanoparticle Flow Sensors Designed for Dynamic X-ray Imaging in Biofluids

X-ray-based imaging is one of the most powerful and convenient methods in terms of versatility in applicable energy and high performance in use. Different from conventional nuclear medicine imaging, contrast agents are required in X-ray imaging especially for effectively targeted and molecularly specific functions. Here, in contrast to much reported static accumulation of the contrast agents in targeted organs, dynamic visualization in a living organism is successfully accomplished by the particle-traced X-ray imaging for the first time. Flow phenomena across perforated end walls of xylem vessels in rice are monitored by a gold nanoparticle (AuNP) (approximately 20 nm in diameter) as a flow tracing sensor working in nontransparent biofluids. AuNPs are surface-modified to control the hydrodynamic properties such as hydrodynamic size (DH), zeta-potential, and surface plasmonic properties in aqueous conditions. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray nanoscopy (XN), and X-ray microscopy (XM) are used to correlate the interparticle interactions with X-ray absorption ability. Cluster formation and X-ray contrast ability of the AuNPs are successfully modulated by controlling the interparticle interactions evaluated as flow-tracing sensors.

Groundwater recharge areas of a volcanic aquifer system inferred from hydraulic, hydrogeochemical and stable isotope data: Mount Vulture, southern Italy

Environmental isotope techniques, hydrogeochemical analysis and hydraulic data are employed to identify the main recharge areas of the Mt. Vulture hydrogeological basin, one of the most important aquifers of southern Italy. The groundwaters are derived from seepage of rainwater, flowing from the highest to the lowest elevations through the shallow volcanic weathered host-rock fracture zones. Samples of shallow and deep groundwater were collected at 48 locations with elevations ranging from 352 to 1,100 m above sea level (a.s.l.), for stable isotope (δ18O, δD) and major ion analyses. A complete dataset of available hydraulic information has been integrated with measurements carried out in the present study. Inferred recharge elevations, estimated on the basis of the local vertical isotopic gradient of δ18O, range between 550 and 1,200 m a.s.l. The isotope pattern of the Quaternary aquifer reflects the spatial separation of different recharge sources. Knowledge of the local hydrogeological setting was the starting point for a detailed hydrogeochemical and isotopic study to define the recharge and discharge patterns identifying the groundwater flow pathways of the Mt. Vulture basin. The integration of all the data allowed for the tracing of the groundwater flows of the Mt. Vulture basin.

A probabilistic transmission pricing methodology considering transmission reliability margins

This paper posits on a reasonable quantification of the intrinsic reliability offered by an existing transmission network structure for a given set of power transactions. We rely on the concept of transmission reliability margins in the lines, which act as safety nets to protect system security in the face of aleatory uncertainties in the availability of transmission lines and epistemic uncertainty in accounting for the load demand patterns. This is proposed to be used as an equitable basis to charge the users of transmission network, generation and load consumption entities alike, over and above the usage charges levied according to the ‘extent-of-use’ normative. Using the tandem combination of deterministic and probabilistic load flow studies in conjunction with power flow tracing procedures, we propose a step-by-step procedure to arrive at a novel transmission pricing methodology. A six-bus Roy Billinton Test System (RBTS) is employed to illustrate the conceptual feasibility and the computational procedure.

Reliability of electric power systems: challenges in the deregulated environment — a research perspective

Electric power industry deregulation has brought about the unbundling of generation, transmission and distribution services and as such, new techniques for reliability assessment are being developed to account for the consequent structural changes in the restructured environment. The transition towards deregulation imposes several unique challenges for establishing reliability modeling paradigms. Addressing these concerns requires a comprehensive knowledge of the technical and economic issues involved and the identification of relevant research gaps. This paper presents a broader framework for the research perspectives to holistically address the significant issues that can profoundly impact the reliability studies in the liberalized environment. Starting from the improvisations in the reliability network equivalent techniques in vogue, this paper advocates the use of power flow tracing as a potential tool for reliability and well-being studies of power systems, and expands upon their practical implications.

Preform design for forging and extrusion processes based on geometrical resemblance

Preform design in multi-stage forging processes is critical to ensure the production of defect-free parts. Moreover, owing to the geometry and material-flow complexities in forging processes, finding the optimal preform shapes could be difficult and time consuming. This paper proposes an efficient preform design methodology based on geometrical resemblance, which requires several finite element analysis simulation iterations to obtain a good preform shape. The initial and subsequent simulations are carried out by constructing a slightly larger part that geometrically resembles the desired part. Initial finite element analysis simulation of the larger part is performed with a reasonably guessed preform shape, whose forming defects or flash formation would be corrected in subsequent steps. Then a series of intermediate parts of similar shape and between the largest part and the desired part in size are constructed. The undeformed shape corresponding to an intermediate part can be obtained by backwards tracing of material flow from the simulation results of the larger part. This undeformed shape is then taken as the preform shape of the intermediate part. The procedure is repeated until the intermediate part is geometrically close to the desired part, which leads to the preform shape. In order to verify this preform-design methodology, several case studies on forging and extrusion processes have been carried out. The methodology has been shown to be computationally efficient, requiring as few as three finite element iterations to obtain a good preform shape.

Glaciological advances made with interferometric synthetic aperture radar

AbstractSpaceborne interferometric synthetic aperture radar (InSAR) techniques for measuring ice flow velocity and topography have developed rapidly over the last decade and a half, revolutionizing the study of ice dynamics. Spaceborne interferometry has contributed to major progress in many areas of glaciological study by: providing the first comprehensive measurements of ice-stream flow velocity over the major outlets of Greenland and Antarctica; revealing that ice-stream and outlet-glacier flow can change rapidly (months to years); improving understanding of several ice-sheet and ice-shelf processes; providing velocity for flux-gate based mass-balance assessment; mapping flow of mountain glaciers; and capturing the geomorphic traces of past ice flow. We review the basic technique development, the measurement characteristics, and the extensive set of results yielded by these measurements.

A Noninvasive Method to Identify Ineffective Triggering in Patients with Noninvasive Pressure Support Ventilation

Background: Ineffective inspiratory triggering efforts are a major cause of poor patient-ventilator interactions during mechanical ventilation, but their routine identification requires the insertion of an esophageal catheter. Objectives: We developed a mathematical analysis of ventilatory tracings recorded under noninvasive pressure ventilation in order to identify ineffective triggering efforts and their consequences without recording esophageal pressure. Methods: We assessed 2,183 cycles from 44 pressure support tracings in 14 children with cystic fibrosis treated by noninvasive home ventilation. Airway pressure, flow and esophageal pressure time series were visually analyzed and manually counted. Airway pressure versus time and flow versus time were then analyzed using a dedicated algorithm written by us. Esophageal pressure was only used for validation. Results: A mathematical treatment of flow time series allowed us to draw phase portraits that had specific periodic trajectories for triggered ventilatory cycles and ineffective triggering efforts. From flow and pressure tracings, our algorithm correctly identified 100% of triggered cycles and 53/56 (94.6%) of ineffective triggering efforts. Ineffective triggering was associated with a significant reduction in minute ventilation, inspiratory flows and a significant increase in inspiratory efforts. Conclusions: A noninvasive analysis of flow and airway pressure can reliably identify ineffective triggering efforts during noninvasive pressure support ventilation. This approach may be a valuable tool for evaluating patient-ventilator interactions and their consequences during long-term recordings.

A New Pulsatile Volumetric Device With Biomorphic Valves for the In Vitro Study of the Cardiovascular System

A pulsatile mock loop system was designed and tested. This prototype represents a versatile, adjustable, and controllable experimental apparatus for in vitro studies of devices meant to interface with the human circulatory system. The pumping system consisted of a ventricular chamber featuring two biomorphic silicone valves as the inlet and outlet valves. The chamber volume is forced by a piston pump moved by a computer-controlled, low-inertia motor. Fluid dynamic tests with the device were performed to simulate physiological conditions in terms of cardiac output (mean flow of 5 and 6 L/min, with beat rates from 60 to 80 bpm), of rheological properties of the processed fluid, and of systemic circulation impedance. The pulsating actuator performed a good replication of the physiological ventricular behavior and was able to guarantee easy control of the waveform parameters. Experimental pressure and flow tracings reliably simulated the physiological profiles, and no hemolytic subatmospheric pressures were revealed. The performance of the prototype valves was also studied in terms of dynamic and static backflow, effective orifice area, and pressure loss, resulting in their applicability for this device. Mechanical reliability was also tested over 8 h. The device proved to be a reliable lab apparatus for in vitro tests; the pumping system also represents a first step toward a possible future application of pulsating perfusion in the clinic arena, such as in short-term cardiac assist and pulsatile cardiopulmonary bypass.

Flow tracing microparticle sensors designed for enhanced X-ray contrast

In applying the X-ray particle image velocimetry (PIV) technique to biofluid flows, the most pivotal prerequisite is suitable flow tracing sensors which should be detected effectively by the X-ray imaging system. In this study, to design those flow tracing sensors, X-ray contrast agent Iopamidol was encapsulated into the poly(vinyl alcohol) (PVA) microparticles crosslinked by glutaraldehyde (GA). The characteristics of the fabricated particle sensors were determined by optical microscopy, scanning electron microscopy, dynamic light scattering, laser Doppler electrophoresis and nuclear magnetic resonance spectroscopy (1H NMR). The amount of Iopamidol in the microparticles was measured using the energy dispersive X-ray spectroscopy (EDS) and 1H NMR. The physical properties of the PVA microparticles are effectively controlled in terms of the average particle size, degree of crosslinking, degree of swelling and encapsulation efficiency of Iopamidol. By changing the amount of crosslinker, the degree of crosslinking and the efficiency of the Iopamidol encapsulation reached to the optimal. To some extent, the zeta-potential of the PVA microparticles is increased in less ionic media where the particles can effectively repel each other prohibiting aggregation. The X-ray absorption ability of the designed tracing sensors was examined by a synchrotron X-ray imaging technique. The X-ray absorption coefficients of the particle sensors were expressed by an exponential law assuming the spherical shape of the microparticles. The X-ray contrast agent, Iopamidol, was successfully encapsulated into the bio-compatible and bio-degradable PVA. With the controlled physical properties of the flow tracing sensors designed in this study, the particle sensors exhibit excellent X-ray absorption contrast fairly applicable in biological systems.

Full-Field Streamline Tracing in Complex Faulted Systems with Nonneighbor Connections

SummaryFull-field flow simulators use a variety of cell geometries, rang-ing from simple rectangles to complex corner-point systems. One of the benefits of corner-point cells is the ease with which we may represent faulted reservoirs. Each face of a cell may be juxtaposed to two or more cells, depending on the fault throw and the lateral displacements of adjacent cells. Conventional finite-dif-ference approaches routinely include the flux between these cells as "nonneighbor" connections. Other examples of nonneighbor or nonstandard connections occur at the boundary of local grid refinement (LGR) or local grid coarsening (LGC) regions where two computational grids come into juxtaposition. In each of these instances, the velocity across the nonstandard faces of a cell will be unevenly distributed according to the nonneighbor fluxes. In contrast, the standard streamline velocity interpolation model (Pol-lock's scheme) used within a cell assumes that the flux is evenly distributed on each cell face, inconsistent with the nonneighbor connection fluxes. Streamlines traced with such an approach do not have sufficient degrees of freedom to be consistent with the finite-difference fluxes and, consequently, will not follow a physical flow path.We propose a strategy that provides a consistent representation for streamlines and velocities near faults and nonneighbor connec-tions. Our approach is based on a simple local (boundary layer) refinement construction that can be used to honor the fluxes at each face, without affecting the representation of flow within the cell or on any other cell face. The local refinement construction is the simplest extension to 3D for faulted reservoir cells that provides consistency with the finite difference flux calculation. Several examples will be presented for a single pair of cells juxtaposed across a fault and at LGR boundaries to illustrate the difficulties in conventional tracing algorithms and the benefits of our approach. The practical utility of our algorithm is demonstrated in a structurally complex and heavily faulted full-field model. The reservoir geometry includes multiple cells with complex fault juxtaposition and several nonneighbor con-figurations in different faces. This treatment is contrasted with the usual approach, and the implications for reservoir scale fluid flow tracing by streamlines is examined.

Metrology in Gas Analysis at the Federal Office of Metrology METAS

Gas analysis as a metrological discipline has a history of about 25 years in Switzerland. Starting with the requirement of reliable reference gas mixtures for legal applications the Swiss Federal Office of Metrology (METAS) had to increasingly find also calibration solutions for the ambient air level. Thereby the metrological principles of traceability, uncertainty evaluation and verification as well as the use of unambiguous terminology for quantities and units were in the focus of the activities. Using three examples different ways of implementing these principles are explained. For the emission range, traceability is mainly achieved by gravimetrically prepared certified gas mixtures in pressurised cylinders using high purity gases and a highly reproducible comparison method. The reactivity and limited stability of the important analytes in the ambient range ask for dynamic methods to secure traceability to the international system of units (SI). The dynamic methods requiring additionally high accuracy gas flow measurement techniques and trace gas analysis will be the focus for further developments at METAS.

Tracing the History of Goat Pastoralism: New Clues from Mitochondrial and Y Chromosome DNA in North Africa

Valuable insights into the history of human populations have been obtained by studying the genetic composition of their domesticated species. Here we address some of the long-standing questions about the origin and subsequent movements of goat pastoralism in Northern Africa. We present the first study combining results from mitochondrial DNA (mtDNA) and Y chromosome loci for the genetic characterization of a domestic goat population. Our analyses indicate a remarkably high diversity of maternal and paternal lineages in a sample of indigenous goats from the northwestern fringe of the African continent. Median-joining networks and a multidimensional scaling of ours and almost 2000 published mtDNA sequences revealed a considerable genetic affinity between goat populations from the Maghreb (Northwest Africa) and the Near East. It has been previously shown that goats have a weak phylogeographic structure compatible with high levels of gene flow, as demonstrated by the worldwide dispersal of the predominant mtDNA haplogroup A. In contrast, our results revealed a strong correlation between genetic and geographical distances in 20 populations from different regions of the world. The distribution of Y chromosome haplotypes in Maghrebi goats indicates a common origin for goat patrilines in both Mediterranean coastal regions. Taken together, these results suggest that the colonization and subsequent dispersal of domestic goats in Northern Africa was influenced by the maritime diffusion throughout the Mediterranean Sea and its coastal regions of pastoralist societies whose economy included goat herding. Finally, we also detected traces of gene flow between goat populations from the Maghreb and the Iberian Peninsula corroborating evidence of past cultural and commercial contacts across the Strait of Gibraltar.

Validation of a protocol for the assessment of skin temperature and blood flow in childhood localised scleroderma

Localised scleroderma (LS) is the most common form of scleroderma seen in children, and usually presents unilaterally. Infrared thermography (IRT) and laser Doppler (LD) have both been reported to be useful in assessing the active, inflammatory stage of LS. We developed and validated a protocol using these techniques for the assessment of unilateral LS activity in children. We investigated the spatial variability and repeatability of LD measurements from adult control forearm skin, and the inter- and intra-operator reproducibility of both LD blood flow trace analysis and IRT skin temperature analysis. Software was developed to produce overlay images of thermograms onto digital photographs of skin sites. In a group of seven adult control subjects, we established the normal range for skin temperature and LD blood flow at six standardised sites (forehead, cheek, abdomen, back, arm and leg), and measured contralateral differences in readings. In a group of 34 children with LS, we investigated the skin temperature and LD blood flow in unaffected skin at the same six sites. In adults, physiological variability in LD blood flow and skin temperature between the two sides of the body was found to be greater than the uncertainty introduced into the measurements by (inter alia) limited intra- or inter-operator reproducibility. The cheek displayed the highest mean asymmetry in both skin temperature (0.5 degrees C) and LD blood flow (40%). Our protocol combines IRT, LD and photography for LS assessment in children, and establishes a normal range of readings in line with other authors.

Integrating hardware and software information flow analyses

Security-critical communications devices must be evaluated to the highest possible standards before they can be deployed. This process includes tracing potential information flow through the device's electronic circuitry, for each of the device's operating modes. Increasingly, however, security functionality is being entrusted to embedded software running on microprocessors within such devices, so new strategies are needed for integrating information flow analyses of embedded program code with hardware analyses. Here we show how standard compiler principles can augment high-integrity security evaluations to allow seamless tracing of information flow through both the hardware and software of embedded systems. This is done by unifying input/output statements in embedded program execution paths with the hardware pins they access, and by associating significant software states with corresponding operating modes of the surrounding electronic circuitry.

Influence of uncinate process on aerodynamic characteristics of nasal cavity and maxillary sinus

This study aimed to investigate the influence of uncinate process on air flow velocity, trace, distribution, air pressure, as well as the air flow exchange of nasal cavity and paranasal sinuses. Fluent software was used to simulate two nasal cavity and paranasal sinus structures following CT scanning, one had normal nasal cavity, the another had the nasal cavity with uncinate process removed. Air flow velocity, pressure, distribution and trace lines were calculated and compared by Navier-Stokes equation and numerically visualized between two models. Air flow of two models in the common and middle meatus accounted for more than 50% and 30% of total nasal cavity flow. Flow velocity of two models were maximal in the common meatus, followed by the middle meatus. The maximal velocity existed on the left nasal district between limen nasi and head of inferior turbinate. The flow traces of two models were similar. In the normal model, the air flow velocity of the district around uncinate process was almost the same in inhale and exhale. In the model with the uncinate process removed, the air flow velocity of the district around uncinate process was faster, the air flow velocity in expiratory phase was quicker. Compared with the normal nasal cavity, there was more exchange of maxillary sinus in the model with cut uncinate process. In the view of flow dynamics, the uncinate process effects the air flow velocity of the district around uncinate process and the exchange of maxillary sinus, the contribution of nasal flow is connected with the morphosis of the uncinate process.

Cosmic Implications of NXY-059

The SAINT studies on NXY-0591,2 have reinvigorated debate over the momentous issues of neuroprotection and the development of novel stroke therapeutics. Some may argue there is little new ground that NXY-059 has unearthed and, in fact, the clinical trials merely confirm that as a strategy, neuroprotection has not been shown to be effective. Editorials in high-profile journals have sent out the clarion call to terminate research on neuroprotection given decades of work, which has uniformly led to failure after failure in clinical studies.3 These sentiments are premature and ignore studies showing that hypothermia improves outcome in patients after cardiac arrest, a major cause of global cerebral ischemia.4,5 Proof for the neuroprotection concept has therefore already been established. Despite decades of neutral clinical trials, there still remains optimism among the stroke academic community. A majority of university-affiliated stroke neurologists in the United States in a recent survey still believe neuroprotection is a viable therapeutic strategy, although admittedly, that survey was conducted between the SAINT I and SAINT II publications.6 However, the question whether neuroprotection will ever work in stroke has been overshadowed by the larger issue of whether animal studies, which serve as the foundation for the development of stroke therapeutics, are even relevant to our patients with acute stroke. In the discussion section of the SAINT II article, the authors write, “it is possible that the animal models of acute focal infarction are not relevant to the patient population; they certainly are insufficient to guarantee a positive clinical-trial result.” Have all prior neuroprotective agents failed in clinical studies because rodent stroke is not relevant to human stroke? This is a key question. Substantial reductions in infarct size in rodents with stroke treated with various types of purported neuroprotective agents would seem to support this view. There …