Front Boundaries Research Articles

Probabilistic analysis of seepage and temperature fields in geothermal extraction process based on discrete fracture network (DFN) model

Enhanced geothermal system is currently the most efficient technology of exploiting geothermal energy from high-temperature rock reservior in deep earth. However, due to the uncertainty of geological structural discontinuities, such as natural or artificial fractures, great challenges are encountered in conducting the precise evaluation of heat extraction within enhanced geothermal system. In this paper, a probability analysis is carried out to incorporate the uncertainty of the fracture network into the analysis of the spatial-time evolution on the seepage and temperature fields, based on a discrete fracture network based modeling scheme developed by the authors. The developed finite element model of the fractured reservior exhibits two-phase structure consisting of rock matrix and fractures, which are practically discretized into triangular elements and zero-thickness elements, respectively. The approach demonstrates a favorable comparison with the results obtained from the thereotical and other numerical solution. Monte Carlo simulation technique is then employed to probabilistically analyze the evolution of coupled thermal–hydraulic behavior, which involves 1000 different realizations considering the uncertainty of fracture structure. The results illustrate that the coefficient of variation of the seepage field decreases from 0 to 0.29 at 1 a to 0.06 to 0.15 at 50 a, averaging at 0.07, and the peak coefficient of variation of the temperature field decreases from 0.61 to 0.52, averaging at 0.27. The uncertainty of the temperature field is varying against time and prominent around the proximity to the advancing cold front, upper and lower boundaries, primarily associated with variations in fractures and constraint of boundary conditions. The existence of highly permeable fractures leads to a pronounced heterogeneity in the seepage and temperature fields within enhanced geothermal system. Furthermore, the importance of taking the uncertainty of the fracture structure into account for geothermal reservoir evaluation is highlighted, to enhance the reliability of numerical modeling for geothermal process prediction.

Dinoflagellate cyst distribution over the past 9 kyrs BP from offshore east Tasmania, southeast Australia

Southeastern Australia’s marine waters are notably warming, surpassing global averages. This region has emerged as a strategic location for researching planktic microfossils, particularly dinoflagellate cysts, in modern and Late Quaternary sediments, offering crucial insights into the biophysical properties of mid-latitude waters. This study examined cyst distribution in marine sediment cores near Maria Island, Tasmania, southeastern Australia, up to 9000 years before present (kyrs BP). Dominant cysts included Protoceratium reticulatum, Protoperidinium spp. (P. avellana, P. conicum, P. oblongum, P. subinerme, P. shanghaiense), and Spiniferites spp. (S. bulloideus, S. hyperacanthus, S. membranaceus, S. mirabilis, S. pachydermus, and S. ramosus). Inshore, Spiniferites spp. constituted a higher proportion (up to 61%), while offshore was dominated by P. reticulatum (up to 80%). Impagidinium spp. and Nematosphaeropsis labyrinthus were exclusively found offshore and displayed increased abundance from ∼6 kyrs BP, suggesting a shift from a shallow to a deep-water habitat. Alexandrium tamarense species complex cysts were present over 140 years inshore and approaching 9 kyrs BP offshore, indicating a longstanding endemic presence. Gymnodinium catenatum cysts were detected exclusively inshore from ∼50 years ago, indicating a relatively recent bloom phenomenon. The East Australian Current’s limited southward reach is suggested by the absence of the warm-water cyst-producing taxon Lingulodinium polyedra. Similarly, the non-detection of the cold-water species Spiniferites antarctica and Impagidinium pallidum reflects Subtropical Front boundaries against subantarctic incursions from the south. In contrast to coccolithophores in the same core, no noticeable shift from cold to warm-water dinoflagellate cyst species was observed. This documentation of dinoflagellate cysts aids in predicting environmental impacts on local communities and beyond.

Lyman-α polarization from cosmological ionization fronts. Part II. Implications for intensity mapping

This is the second paper in a series whose aim is to predict the power spectrum of intensity and polarized intensity from cosmic reionization fronts. After building the analytic models for intensity and polarized intensity calculations in paper I, here we apply these models to simulations of reionization. We construct a geometric model for identifying front boundaries, calculate the intensity and polarized intensity for each front, and compute a power spectrum of these results. This method was applied to different simulation sizes and resolutions, so we ensure that our results are convergent.We find that the power spectrum of fluctuations at z = 8 in a bin of width Δz = 0.5 (λ/Δλ = 18) is Δℓ ≡ [ℓ(ℓ + 1)C ℓ/2π]1/2 is 3.2 × 10-11 erg s-1 cm-2 sr-1 for the intensity I, 7.6 × 10-13 erg s-1 cm-2 sr-1 for the E-mode polarization, and 5.8 × 10-13 erg s-1 cm-2 sr-1 for the B-mode polarization at ℓ = 1.5 × 104.After computing the power spectrum, we compare results to detectable scales and discuss implications for observing this signal based on a proposed experiment. We find that, while fundamental physics does not exclude this kind of mapping from being attainable, an experiment would need to be highly ambitious and require significant advances to make mapping Lyman-α polarization from cosmic reionization fronts a feasible goal.

A parallel technique for multi-objective Bayesian global optimization: Using a batch selection of probability of improvement

Bayesian global optimization (BGO) is an efficient surrogate-assisted technique for problems involving expensive evaluations. A parallel technique can be used to parallelly evaluate the true-expensive objective functions in one iteration to boost the execution time. An effective and straightforward approach is to design an acquisition function that can evaluate the performance of a bath of multiple solutions, instead of a single point/solution, in one iteration. This paper proposes five alternatives of Probability of Improvement (PoI) with multiple points in a batch (q-PoI) for multi-objective Bayesian global optimization (MOBGO), taking the covariance among multiple points into account. Both exact computational formulas and the Monte Carlo approximation algorithms for all proposed q-PoIs are provided. Based on the distribution of the multiple points relevant to the Pareto-front, the position-dependent behavior of the five q-PoIs is investigated. Moreover, the five q-PoIs are compared with the other nine state-of-the-art and recently proposed batch MOBGO algorithms on twenty bio-objective benchmarks. The empirical experiments on different variety of benchmarks are conducted to demonstrate the effectiveness of two greedy q-PoIs ( q-PoI best and q-PoI all ) on low-dimensional problems and the effectiveness of two explorative q-PoIs ( q-PoI one and q-PoI worst ) on high-dimensional problems with difficult-to-approximate Pareto front boundaries.

Features of Carbon and Silicon Thin Films Reflection Spectra in the Visible Region

The article is devoted to the reflection of visible light from a thin absorbing film. For a number of reasons, thin films have recently been the subject of close study. As part of the work, several non-metal films were fabricated on a glass substrate: silicon films (by resistive evaporation) and carbon films (using laser evaporation). The resulting films have an optical thickness in the range of 1 μm (that is, the actual layer thickness is in the range of 0.2-0.4 μm) and at the same time noticeably absorb the light flux. The films were processed according to the standard method in the visible region using a USB4000 spectrometer. Reflection spectra for each of the films were plotted for several different points on the surface. The spectra look similar when differences in numerical values are not considered. The contribution of the interference of rays reflected from the front and rear boundaries is significant at long wavelengths (in the red region), whereas the interference practically disappears against the background of instrument noise in the short wavelength region (violet part of the spectrum). The reason for this is that absorption during propagation of the short-wavelength part inside the film significantly reduces the intensity of the beam reflected from the rear surface of the film.

Toward a clinical optoretinogram: a review of noninvasive, optical tests of retinal neural function.

The past few years have witnessed rapid development of the optoretinogram—a noninvasive, optical measurement of neural function in the retina, and especially the photoreceptors (Ph). While its recent development has been rapid, it represents the culmination of hundreds of experiments spanning decades. Early work showed measurable and reproducible changes in the optical properties of retinal explants and suspensions of Ph, and uncovered some of the biophysical and biochemical mechanisms underlying them. That work thus provided critical motivation for more recent work based on clinical imaging platforms, whose eventual goal is the improvement of ophthalmic care and streamlining the discovery of novel therapeutics. The first part of this review consists of a selective summary of the early work, and identifies four kinds of stimulus-evoked optical signals that have emerged from it: changes in light scattered from the membranous discs of the Ph’s outer segment (OS), changes in light scattered by the front and back boundaries of the OS, rearrangement of scattering material in and near the OS, and changes in the OS length. In the past decade, all four of these signals have continued to be investigated using imaging systems already used in the clinic or intended for clinical and translational use. The second part of this review discusses these imaging modalities, their potential to detect and quantify the signals of interest, and other factors influencing their translational promise. Particular attention is paid to phase-sensitive optical coherence tomography (OCT) with adaptive optics (AO), a method in which both the amplitude and the phase of light reflected from individual Ph is monitored as visible stimuli are delivered to them. The record of the light’s phase is decoded to reveal a reproducible pattern of deformation in the OS, while the amplitude reveals changes in scattering and structural rearrangements. The method has been demonstrated in a few labs and has been used to measure responses from both rods and cones. With the ability to detect responses to stimuli isomerizing less than 0.01% of photopigment, this technique may prove to be a quick, noninvasive, and objective way to measure subtle disease-related dysfunction at the cellular level, and thus to provide an entirely new and complementary biomarker for retinal disease and recovery.

A 2D SWE meshless model with fictitious water level at dry nodes

In this study, a two-dimensional shallow-water-equation numerical model is developed for simulating free surface water flows with internal moving wet/dry front boundaries. It is based on the Eulerian aspect and meshless approach. The predictor-corrector process is used for the time marching. The spatial derivatives of physical quantities are computed using the local polynomial approximation with the weighted-least-squares approach. A formula for specifying the fictitious water level, which does not exist physically, at dry nodes is proposed. This is the main novelty of the present study and it significantly reduces computation time compared with the authors’ previous work. Four dam break test cases are employed to validate the capability of the present model.

Mapping water-abundant zones using transient electromagnetic and seismic methods when tunneling through fractured granite in the Qinling Mountains, China

Severe water inrush currently halts the excavation of the Qinling Water Transportation Tunnel and has even stopped tunneling. Based on the geologic conditions of the construction area, the source of water inrush is abundant groundwater in fractured granite. To accurately predict water inrush, we must know the location, geometry, and boundary information of water-abundant zones before excavation. We have developed a field study of integrated seismic and transient electromagnetic (TEM) applications to map the water-abundant zones ahead of the tunnel face. Before the in-tunnel survey, numerical experiments based on excavation and drilling records verified the feasibility of our scheme. To reveal the fractured zones that may be filled with groundwater, an equitraveltime plane algorithm was used in the seismic data processing. Then, the TEM apparent resistivity was calculated to investigate the water-bearing condition of the fractured zones. To detect the water-abundant zone boundaries, we conducted migration imaging of the TEM pseudowavefield that was extracted from the measured TEM signals. A correlation stacking process to extract the TEM pseudowavefield was used to mitigate the ill-posed effect in the inverse wavefield transformation and obtain boundary information of the water-abundant zones. As expected, the results revealed the depth and geometry of the front and rear boundaries of two water-abundant zones 30 m ahead of the tunnel face, which is consistent with drilling and excavation records after the survey. The results of our case study indicate that the integration of seismic imaging, apparent resistivity imaging, and TEM pseudowavefield migration is an efficient and cost-effective method to provide the location, geometry, and boundary information of water-abundant zones.

Selective laser melting of stainless steel and silicon nitride fibre metal matrix composites

Metal matrix composites are formed by adding certain filler particles to selected base metals to combine the good properties of both in the resulting composite and were proved to be quite promising in numerous applications. The main bottleneck lies in the processing methods, as the traditional solutions often lead to a loss of control on the dispersion of the filler material. The point-by-point consolidation mechanisms typical of additive manufacturing are proposed here as a possible means of enhancing this control over the composition of the metal matrix composites. Selective laser-melted composites with stainless steel 316L as the base metal and Si3 N4 as the filler phase are evaluated in the current study. The results clearly indicated that the dispersion of the filler particles is more controlled, as they are pushed and segregated around the solid front boundaries. The tensile strength of the composites is better than the pure 316L when laser-melted under appropriate process conditions. The surface quality is also substantially enhanced with the metal matrix composites.

Tracking the Gust Fronts of Convective Cold Pools

AbstractIt is increasingly acknowledged that cold pools can influence the initiation of new convective cells. Yet the full complexity of convective organization through cold pool interaction is poorly understood. This lack of understanding may partially be due to the intricacy of the dynamical pattern formed by precipitation cells and their cold pools. Additionally, how exactly cold pools interact is insufficiently known. To better understand this dynamics, we develop a tracking algorithm for cold pool gust fronts. Rather than tracking thermodynamic anomalies, which do not generally coincide with the gust front boundaries, our approach tracks the dynamical cold pool outflow. Our algorithm first determines the locus of the precipitation event. Second, relative to this origin and for each azimuthal bin, the steepest gradient in the near‐surface horizontal radial velocity vr is employed to determine the respective locus of the cold pool gust front edge. Steepest vr gradients imply largest updraft velocities, hence strongest dynamical triggering. Results are compared to a previous algorithm based on the steepest gradient in temperature—highlighting the benefit of the method described here in determining dynamically active gust front regions. Applying the method to a range of numerical experiments, the algorithm successfully tracks an ensemble of cold pools. A linear relation emerges between the peak rain intensity of a given event and maximal vr for its associated cold pool gust front—a relation found to be nearly independent of the specific sensitivity experiment.

A Generator for Multiobjective Test Problems With Difficult-to-Approximate Pareto Front Boundaries

In some real-world applications, it has been found that the performance of multiobjective optimization evolutionary algorithms (MOEAs) may deteriorate when boundary solutions in the Pareto front (PF) are more difficult to approximate than others. Such a problem feature, referred to as difficult-to-approximate (DtA) PF boundaries, is seldom considered in existing multiobjective optimization test problems. To fill this gap and facilitate possible systematic studies, we introduce a new test problem generator. The proposed generator enables the design of test problems with controllable difficulties regarding the feature of DtA PF boundaries. Three representative MOEAs, NSGA-II, SMS-EMOA, and MOEA/D-DRA, are performed on a series of test problems created using the proposed generator. Experimental results indicate that all the three algorithms perform poorly on the new test problems. Meanwhile, a modified variant of MOEA/D-DRA, denoted as MOEA/D-DRA-UT, is validated to be more effective in dealing with these problems. Subsequently, it is concluded that the rational allocation of computational resources between different PF parts is crucial for MOEAs to handle the problems with DtA PF boundaries.

Granite strength and toughness from small notched three-point-bend specimens of geometry dissimilarity

Maximum fracture loads (Pmax) of small notched granite specimens under three-point-bending (3-p-b) conditions can be easily measured with any notch/size ratio. In this study, we report a simple closed-form solution of a non-Linear Elastic Fracture Mechanics (non-LEFM) model emphasizing the influence of average grain size G on quasi-brittle fracture of granite. This simple analytical solution containing the grain size G can be conveniently used to determine granite tensile strength ft and fracture toughness KIC from Pmax measurements of small notched 3-p-b specimens of geometry dissimilarity. The span/width (S/W) ratios of small 3-p-b specimens can vary, e.g. 2.5 or 4. The notch/width (a0/W) can also vary, e.g. the notch a0 can be as short as the average grain size (G), or close to width W. However, specimens with α-ratio (=a0/W) around 0.2 are recommended to minimize the boundary influence/effect from both the front and back specimen boundaries as proven by the Boundary Effect Model (BEM). Blue granite with the average grain size around 2 (mm) was selected to test the new method. Total 64 granite samples from four different groups (different 3-p-b sample designs) were tested, with W = 27, 40 and 70 (mm), S/W = 2.5, 4.0 and a0 = 4, 6 and 8 (mm). The tensile strength ft and fracture toughness KIC estimated from every group is fairly close to the values determined from the entire population of 64 tests. Therefore, tests from any specimen group of given geometry and size are sufficient. Estimations for G = 1.5 and 2.5 (mm) were also provided and compared with those for G = 2 (mm) to show the grain size influence. Advantages and disadvantages of BEM and well-known SEL (size effect law) are also discussed using the granite results.

Reconstruction of glacier area on Citlaltépetl volcano, 1958 and implications for Mexico's deglaciation rates

In this study, a detailed analysis of the measurements made on Glaciar Norte of Citlaltépetl volcano in 1958 by Lorenzo (1964) is conducted. A series of inconsistencies are evident when comparing the dimensions of Citlaltépetl volcano's glaciers and those of the glaciers on Popocatépetl and Iztaccíhuatl volcanoes. From these inconsistencies it was concluded that the delimitation of Citlaltépetl's glaciers was wrong and the values exaggerated the true conditions of these ice bodies for 1958. In this paper we explain the methodology applied for the reconstruction of Glaciar Norte in 1958. From this reconstruction, a new more realistic value for the glaciated area on Citlaltépetl was obtained. The reconstruction respects the glacier front boundaries reported by Lorenzo (1964), which are precisely detailed at the narrative of his fieldwork. Finally, this paper discusses the glacial shrinkage on Citlaltépetl volcano based on the new value obtained for the area of Glaciar Norte (2.04 km2). This value is of a magnitude comparable to the glacial areas of Iztaccíhuatl and Popocatepetl volcanoes that were also measured and reported by Lorenzo (1964) and confirmed in the literature.

The magnetic hole as plasma inhomogeneity in the solar wind and related interplanetary medium perturbations

We considered magnetic hole-type plasma structures with a constant total pressure, which are often observed in the flux of the solar wind. The interaction between a linear magnetic hole and the front of the primary or bow shock wave before the Earth’s magnetosphere was studied, and the appearance of a fast shock wave in the magnetosheath and displacement of the bow shock front in the direction of the Earth’s magnetosphere is described. The magnetic hole in the scope of the MHD theory is considered a plasma inhomogeneity bounded by two tangential discontinuities: the front and rear boundaries. Based on the MHD theory of nonlinear interactions of solar wind discontinuity structures with a magnetic hole, the appearance of new automodel and MHD shock waves inside the magnetic hole is shown. The obtained results, which provide evidence of a change in the configuration of the magnetic hole and a displacement of the bow shock front due to the perturbation from the solar wind, are qualitatively verified in many aspects by observations performed earlier by the Cluster and ACE spacecrafts.

Statistical study of magnetic cloud erosion by magnetic reconnection

AbstractSeveral recent studies suggest that magnetic reconnection is able to erode substantial amounts of the outer magnetic flux of interplanetary magnetic clouds (MCs) as they propagate in the heliosphere. We quantify and provide a broader context to this process, starting from 263 tabulated interplanetary coronal mass ejections, including MCs, observed over a time period covering 17 years and at a distance of 1 AU from the Sun with Wind (1995–2008) and the two STEREO (2009–2012) spacecraft. Based on several quality factors, including careful determination of the MC boundaries and main magnetic flux rope axes, an analysis of the azimuthal flux imbalance expected from erosion by magnetic reconnection was performed on a subset of 50 MCs. The results suggest that MCs may be eroded at the front or at rear and in similar proportions, with a significant average erosion of about 40% of the total azimuthal magnetic flux. We also searched for in situ signatures of magnetic reconnection causing erosion at the front and rear boundaries of these MCs. Nearly ~30% of the selected MC boundaries show reconnection signatures. Given that observations were acquired only at 1 AU and that MCs are large‐scale structures, this finding is also consistent with the idea that erosion is a common process. Finally, we studied potential correlations between the amount of eroded azimuthal magnetic flux and various parameters such as local magnetic shear, Alfvén speed, and leading and trailing ambient solar wind speeds. However, no significant correlations were found, suggesting that the locally observed parameters at 1 AU are not likely to be representative of the conditions that prevailed during the erosion which occurred during propagation from the Sun to 1 AU. Future heliospheric missions, and in particular Solar Orbiter or Solar Probe Plus, will be fully geared to answer such questions.

Stationary strong magnetohydrodynamic discontinuities and pressure balanced structures in the solar wind stream

Strong disturbances of magnetic clouds in the solar wind stream are considered when solar MHD shock waves from the surrounding plasma collide with these inhomogeneities. The boundaries of the considered plasma inhomogeneities are presented as stationary tangential discontinuities. The collision of solar fast shock waves with the back and front boundaries is studied as a decomposition of an arbitrary discontinuity. It is asserted that secondary waves of rarefaction and reverse shock waves arise depending on the initial conditions. It is pointed out that a change occurs in the configuration of the plasma inhomogeneity under study, which is caused by the incoming perturbation repeatedly observed by spacecrafts.

Heredity or traditional knowledge: Fishing tactics and dynamics of artisanal mangrove crab (Scylla serrata) fishery

Globally, artisanal fisheries are challenged by the combined impacts of overfishing, ecosystem degradation, climate change and lack of management intervention. Little is known of how traditional knowledge/skills held by fishers influence ability to exploit marine resources and whether such information could be incorporated into management practices. Failure to understand fishers' traditional knowledge/skills and behaviour may undermine the success of fisheries management measures. Use of traditional knowledge in exploitation of mangrove crabs (Scylla serrata) on local fishing grounds is assessed. The study used complementary approaches (field experiments and fisher-based surveys) to investigate fishing tactics employed by artisanal crab fishers. Also time series data from the ministry of fisheries was used to assess annual trends in production and value of the fishery. Fishers with calibrated GPS fished in different areas and catch per unit effort (CPUE), fishing time, distance and efficiency were assessed. Key informant and semi-structured interviews and direct observation were conducted among mud crab fishers to establish knowledge/skill requirement, fishing tactics and entry into the fishery. The results indicate that mud crab fishing is a male dominated activity. Fishing is done at spring low tide by foot fishers in burrows mainly with rare use of baited traps and lift nets at ankle height water along the intertidal mangrove front boundaries or channels. Fisher's follow specific tracks that are strongly guarded by individual fishers. Fishing for adult crabs showed deeper and further movement in the mangrove forest unlike juvenile crab collection. Fisher's in new areas collected few crabs due to low efficiency compared to well known areas. Entry into the fishery is minimal and skills are inherited from parents or grand parents with limited transfer being obtained from colleagues. The average size of marketable crabs has declined over the years while season and tide have remained major challenges for production and market determination in the fishery. Fisher-based surveys overestimated CPUE and sizes of smallest crabs caught while it underestimated fishing time and distance moved. A weak management system was observed with most fishers operating without a license and lacking a synchronized landing system. Inability of fishers to shift to new areas, “natural closures” and limited distance covered by foot fisher's support site-specific management for the fishery.

A Statistical Study on the Reconnection in Boundary Layers of Small-scale Magnetic Flux Tubes in Solar Winds

With the data from WIND satellite in 1995—2005, the small-scale magnetic flux tubes determined with two methods, i.e., the artificial recognition and program selection respectively, are compared. It is found that there are magnetic reconnections in the boundary layers of 41% small-scale magnetic flux tubes determined with the program selection method, which is similar to the re- sult of small-scale magnetic flux tubes determined with the method of artificial recognition. The features of magnetic reconnections, such as the magnetic shear angle, magnetic field strength, and duration of the dissipation region of recon- nection at the small-scale flux tubes’ boundaries determined from both methods have the same statistical tendency. This shows that there is no essential differ- ence in the properties of reconnections in the boundary layers of the small-scale magnetic flux tubes determined with the two methods. Hence the data yielded by both methods can be used as the samples for statistically studying the events of reconnection in the front and back boundary layers of small-scale flux ropes. There are totally 71 magnetic reconnection events selected in this paper. Our statistical result shows that in 50 events (70%) the decrease of magnetic field strength in the dissipation region of reconnection is larger than 20%, and in 47 events (66%) the magnetic shear angle is larger than 90 degrees. These indicate that the magnetic reconnections in boundaries of the small-scale magnetic flux tubes are more likely to be anti-parallel. The statistics has been performed sep- arately in the reconnections of the front and back boundary layers of small-scale magnetic flux tubes. The results show that the features of reconnections in the front and back boundaries are similar to each other, which is different from the various properties in the front and back boundaries of the magnetic clouds, and this means that the expansion in the large-scale magnetic flux tubes, such as magnetic clouds, does not happen in the small-scale magnetic flux tubes.

A tool to increase information-processing capacity for consumer water meter data

Background: Water service providers invoice most South African urban consumers for the water they use every month. A secure treasury system generates water invoices at municipalities’ financial departments. Information about the water usage of customers initially comes from reading the water meters, usually located in gardens near the front boundaries of properties. Until as recently as 1990, the main purpose of the water meter readings was to generate invoices for water usage. There are various treasury systems for this purpose.Objective: The objective of this research article was to describe the development of Swift, a locally developed software tool for analysing water meter data from an information management perspective, which engineers in the water field generally use, and to assess critically the influence of Swift on published research and industry. This article focuses on water usage and the challenge of data interchange and extraction as issues that various industries face.Method: This article presents the first detailed report on Swift. It uses a detailed knowledge review and presents and summarises the findings chronologically.Results: The water meter data flow path used to be quite simple. The risk of breaches in confidentiality was limited. Technological advances over the years have led to additional knowledge coming from the same water meter readings with subsequent research outputs. However, there are also complicated data flow paths and increased risks. Users have used Swift to analyse more than two million consumers’ water meter readings to date. Studies have culminated in 10 peer-reviewed journal articles using the data. Seven of them were in the last five years.Conclusion: Swift-based data was the basis of various research studies in the past decade. Practical guidelines in the civil engineering fraternity for estimating water use in South Africa have incorporated knowledge from these studies. Developments after 1995 have increased the information processing capacity for water meter data.

Intraoperative fluoroscopy in percutaneous sacroiliac screw fixation based on anatomic measurement and digital reconstructed CT data

Objective To explore the intraoperative fluoroscopy in percutaneous sacroiliac screw fixation based on anatomic measurement and digital reconstructed CT data. Methods The CT data of the pelvis at prostration were collected for 3D reconstruction of the pelvic models from 30 patients with injury to the pelvis or acetabulum.Then the anatomical boundaries of the safe zone of sacroiliac screw insertion were marked on the 3D models,including the upper,front and back cortex boundaries of S1 vertebra,the front and bottom cortex boundaries of sacral foramen area,and the sacral alar slope. The angles between these anatomical boundaries and the pelvic baseline were measured on the sagittal plane.The digital reconstructed radiology (DRR) was applied to form the inlet,outlet and lateral images of fluoroscopy.The standard protocol to acquire accurate intraoperative images was analyzed by characterization of important anatomic landmarks.Results The angles between the upper,front and back cortex boundaries of S1 vertebra and the baseline (αl,α2,α3) were respectively 37.7°± 8.6°(from 23.2°to 50.8°),22.9° ± 6.7° (from 13.1° to 32.0°),41.9°± 6.8° (from 33.0°to 54.8°).The angles between the front and bottom cortex boundaries of sacral foramen area and the baseline (α4,α5) were 37.0°± 12.0° (from 19.9° to 63.1°) and 38.8°± 8.0° (from 25.7°to 54.6°).The angle between the alar slope and the baseline (α6) was 82.4°± 13.0°(from 70.3°to117.3°).The characteristic manifestations of important anatomic landmarks were observed in the simulated fluoroscopy images. Conclusions It is recommended that the projecting angles in the inlet and outlet views should be decided according to the specific data of each patient.Because the alar slope can not be clearly identified in the outlet view due to its large inclination,the position of screw insertion should be verified in the lateral view to prevent the screw from penetrating the slope to hurt the L5 nerve and iliac vessels. Key words: Bone nails; Pelvis; Tomography, X-ray computed; Image processing, computer-assisted; Sacroiliac joint