Slope Of Line Research Articles

Multi-centre data harmonisation applied to heart-to-mediastinum quantification in parkinsonism (ITA-MIBG): a cross-calibration phantom study with tube and bottle

Abstract Purpose Planar cardiac scintigraphy with [123I]I-mIBG is widely used to image myocardial sympathetic activity. In multicentre studies, different γ-cameras can cause variability in quantitative parameters. This study aimed to harmonise multicentre [123I]I-mIBG data using a custom-designed phantom and to assess its feasibility and acceptability. Methods A ‘tube and bottle’ phantom was designed to standardise the heart-to-mediastinum (H/M) ratio across 15 centres. Each centre prepared three versions of the phantom (A, B, and C) with varying pertechnetate ([99mTc]Tc-O4-) activities, acquired static images using their own γ-camera, and uploaded DICOM data to a shared platform. In the phantom, the tube and bottle represent the heart and mediastinum, respectively, with the tube-to-bottle (T/B) ratio simulating the H/M ratio. The reference centre analysed the images and calculated the T/B ratios, applying linear regression for data harmonisation. A survey was conducted to assess the phantom’s usability. Results The harmonised T/B ratios for versions A and B were 20.46 ± 0.78 and 6.19 ± 0.39, respectively. The average slope and intercept of the regression line across the participating centres resulted in 1.07 ± 0.38 and − 0.82 ± 4.95. Survey feedback indicated high feasibility and acceptability, with all centres recommending the phantom for multicentre harmonisation. Conclusions The custom-made phantom effectively harmonised experimental data across different centres, supporting its use in multicentre studies to improve data consistency.

Behavior of water at lipid/water interfaces upon phase transition of the lipid bilayer: Insights from 1D- and 2D-vibrational sum frequency generation spectral calculations from molecular dynamics simulations.

We have investigated the structural and dynamical changes of the interfacial water near [1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine] (DMPC) lipid bilayer across various temperatures, ranging from 285K (gel phase of lipid) to 320K (liquid phase of lipid), through calculations of one-dimensional (1D) and two-dimensional (2D) vibrational sum frequency generation (VSFG) spectra from molecular dynamics simulations. The 1D-VSFG spectra show a broad positive peak in the hydrogen-bonded region, which means that water molecules are oriented upward toward the lipid bilayer. Although DMPC is a zwitterionic lipid, the negatively charged phosphate group primarily influences the orientation of the water molecules. The absence of a dangling peak in the 1D- and 2D-VSFG spectra shows that the water molecules form hydrogen bonds with the lipid headgroup atoms. The spectral diffusion timescales obtained from the 2D-VSFG metrics of the slope of the nodal line clearly reveal a dynamical crossover and exhibit Arrhenius behavior with different activation energies before and after the melting of the lipid bilayer. Apart from 2D-VSFG, the frequency fluctuation time correlation function also exhibits a dynamical crossover upon melting of the lipid bilayer.

Some Statistical Estimations for Voting in Hough Transform

Transform The Hough Transform (HT) is an essential method in detecting geometric shapes in images. In this work, we concentrate on enhancing the accuracy and efficiency of the HT through the statistical estimation for the voting process in lines detection. We propose a statistical pattern detection method, which aims to introduce a new estimation of the polar angle θ of a detected line in an image and its radial distance r after estimating the slope and intercept of line of detection.

Integration of item response theory in the development of PhET-based graphing lines worksheets for optimizing student algebra competence

This study develops and evaluates a graphing line worksheet based on PhET Interactive Simulation integrated with Item Response Theory (IRT) methods to enhance student algebra competence. Involving 120 students, the worksheet comprises 12 items measuring four key indicators: understanding the geometric significance of line slopes, constructing line equations, graphing from line equations, and predicting the effects of variable changes. The 2-Parameter Logistic (2PL) model of IRT was employed to analyze item difficulty and student ability in logit form. The results indicate that the worksheet is effective in improving student algebra competence, with Items 1 and 11 demonstrating a good balance between difficulty and discrimination. Item 2 requires further review because of its high difficulty, whereas Item 12 is considered too easy. Heatmap analysis and Item Characteristic Curves (ICC) revealed variations in student response patterns, confirming the test's ability to evaluate diverse levels of student ability. The integration of interactive simulation and IRT has proven to be an effective strategy in instructional design, supporting adaptive and personalized learning.

Aluminum Reservoir Welding Surface Defect Detection Method Based on Three-Dimensional Vision

Welding is an important process in the production of aluminum reservoirs for motor vehicles. The welding quality affects product performance. However, rapid and accurate detection of weld surface defects remains a huge challenge in the field of industrial automation. To address this problem, we proposed a 3D vision-based aluminum reservoir welding surface defect detection method. First of all, a scanning system based on laser line scanning camera was constructed to acquire the point cloud data of weld seams on the aluminum reservoir surface. Next, a planar correction algorithm was used to adjust the slope of the contour line according to the slope of the contour line in order to minimize the effect of systematic disturbances when acquiring weld data. Then, the surface features of the weld, including curvature and normal vector direction, were extracted to extract holes, craters, and undercut defects. For better extraction of the defect, a double-aligned template matching method was used to ensure comprehensive extraction and measurement of defect areas. Finally, the detected defects were categorized according to their morphology. Experimental results show that the proposed method using 3D laser scanning data can detect and classify typical welding defects with an accuracy of more than 97.1%. Furthermore, different types of defects, including holes, undercuts, and craters, can also be accurately detected with precision 98.9%.

Using the Regression Slope of Training Loss to Optimize Chest X-ray Generation in Deep Convolutional Generative Adversarial Networks.

Diffusion models, variational autoencoders, and generative adversarial networks (GANs) are three common types of generative artificial intelligence models for image generation. Among these, GANs are the most frequently used for medical image generation and are often employed for data augmentation in various studies. However, due to the adversarial nature of GANs, where the generator and discriminator compete against each other, the training process can sometimes end with the model unable to generate meaningful images or even producing noise. This phenomenon is rarely discussed in the literature, and no studies have proposed solutions to address this issue. Such outcomes can introduce significant bias when GANs are used for data augmentation in medical image training. Moreover, GANs often require substantial computational power and storage, adding to the challenges. In this study, we used deep convolutional GANs for chest X-raygeneration, and three typical training outcomes were found. Two scenarios generated meaningful medical images and one failed to produce usable images. By analyzing the loss history during training, we observed that the regression line of the overall losses tends to diverge slowly. After excluding outlier losses, we found that the slope of the regression line within the stable loss segment indicates the optimal point to terminate training, ensuring the generation of meaningful medical images.

Estimating Hourly Solar Irradiations On A Tilted Surface In Rabat, Morocco: Performance of Different Transposition Models

Objective: The objective of this study is to find the most appropriate model that estimate the global solar irradiation on an inclined plane from horizontal data, by using hourly measurements of global solar irradiation on this plane, for Rabat city capital of Morocco. Theoretical Framework: Morocco is interested in developing renewable energy strategies to produce clean electricity, reducing thereby CO2 emissions. Solar systems are installed on inclined surfaces. Method: Transposition models with complete formulation are evaluated by comparison with two years of measured data in Rabat city. NIP pyrheliometer and Kipp & Zonen SP-Lite pyranometers are used to provide our “Solar Energy and Environment Laboratory” with measured data. Results and Discussion: There is no great discrepancy between selected models regarding the performance for the same sky type condition. For Perez the most suitable model, the slope of the best fit regression line between estimated and measured values, the coefficient of determination, MBE% and RMSE%, regarding the “All” sky type condition, are subsequently 0.9716, 0.9849, -4.16 and 9.29 respectively. Research Implications: .An accurate evaluation of solar radiation arriving on an inclined surface is required and very important to engineers for solar energy collecting devices, to architects for buildings and to agronomists for studies on mountain slopes. Originality/Value: This work contributes to the literature by providing useful information about the influence of different sky type condition on the performance of a model that could help future similar studies.

Hydrogen bonding blues: Vibrational spectroscopy of the TIP3P water model.

The computational spectroscopy of water has proven to be a powerful tool for probing the structure and dynamics of chemical systems and for providing atomistic insight into experimental vibrational spectroscopic results. However, such calculations have been limited for biochemical systems due to the lack of empirical vibrational frequency maps for the TIP3P water model, which is used in many popular biomolecular force fields. Here, we develop an empirical map for the TIP3P model and evaluate its efficacy for reproducing the experimental vibrational spectroscopy of water. We observe that the calculated infrared and Raman spectra are blueshifted and narrowed compared to the experimental spectra. Further analysis finds that the blueshift originates from a shifted distribution of frequencies, rather than other dynamical effects, suggesting that the TIP3P model forms a significantly different electrostatic environment than other three-point water models. This is explored further by examining the two-dimensional infrared spectra, which demonstrates that the blueshift is significant for the first two vibrational transitions. Similarly, spectral diffusion timescales, evaluated through both the center line slope and the frequency-frequency time correlation function demonstrate that TIP3P exhibits significantly faster spectral dynamics than other three-point models. Finally, sum-frequency generation spectroscopy calculations suggest that despite these challenges, the TIP3P empirical map can provide phenomenological, qualitative, insight into the behavior of water at the air-water and lipid-water interfaces. As these interfaces are models for hydrophobic and hydrophilic environments observed in biochemical systems, the presently developed empirical map will be useful for future studies of biochemical systems.

Experimental Characterization of Contact Stiffness for Fixture Design

When cutting flexible metal workpieces, the mechanical characteristics of the fixture play a crucial role in suppressing deformation and vibration. Previously, the influence of fixture design elements on workpiece vibration has been studied with the aim of gaining a fundamental understanding of the phenomenon. Meanwhile, there has been limited research on the contact area between the fixture and workpiece, and there is a need for further research to understand the phenomenon and establish design guidelines for fixtures. In this paper, an experimental approach is proposed to characterize the relationship between stress on the contact surface and the resulting displacement. The main goal is to analyze the influence of contact surface shape and material on the deformation (or vibration) of the fixture and the workpiece. To this end, an on-machine measurement device was introduced. This device was used to obtain displacement-load curves without setup errors for materials such as PTFE, MC nylon, and aluminum alloy, as well as contact surface shapes such as flat or conical. From the obtained curves, the repeatability stability of the fixture was qualitatively evaluated. When using MC nylon, the plastic deformation was minimal even when loads were applied multiple times under flat conditions or conical conditions with a tip angle of 170° or more. This indicates that these contact conditions are stable as fixtures. On the other hand, when using PTFE, buckling occurred due to its low Young’s modulus, and the workpiece was damaged when using aluminum alloy. This suggests that these materials are not suitable for use as fixtures in this paper. For a more quantitative evaluation, an assessment based on contact stiffness was conducted. The displacement-load curves were modeled using a power-law function, following existing elastoplastic models. The contact stiffness was calculated from the slope of the tangent line to the displacement-load curve at maximum load. When using MC nylon as the material, the contact stiffness was found to be a maximum of 6×106 N/m. Furthermore, the rate of change of contact stiffness during loading and unloading was used to quantitatively evaluate the fixture stability.

Undrained behaviour of fibre reinforced cemented toyoura sand in triaxial compression and extension loading

ABSTRACT This study examines the effects of fibre (0–3%) and cement (0–3%) additives on poorly graded Toyoura sand under consolidated undrained (CIU) compression and extension conditions. Compression tests revealed that dense sands exhibit increased peak strength, stiffness, and a steady decline from peak to post-peak strength. Cemented and fibre-cemented specimens demonstrated stiffer responses and strain-hardening post-peak behavior compared to pure sand. Adding fibres and cement significantly enhanced peak deviatoric stresses, while their impact under extension loading was less pronounced. Fibre and cement combinations, particularly at higher percentages, improved the strength of pure sand under extension conditions. Randomly oriented fibres increased friction angle, cohesion, and compressive strength, while cemented and fibre-cemented specimens exhibited higher secant moduli. The additives enhanced strength parameters, the slope of the critical state line, and the state parameter, with the stress ratio (q/p’) rising for both peak and critical states.

Deciphering surface water-groundwater connectivity using chemical and stable isotope tracers (H and O) in the headwaters of São Francisco River, Brazil.

This study assessed the chemical composition of major elements and stable isotopes (H and O) in precipitation, groundwater, and surface water in São Francisco 1 (SF1) sub-basin (approximately 14,000km2), located at the São Francisco River headwater region, fractured aquifer system region with a complex geologic framework. Both groundwater and surface water exhibited low mineral content, with average electrical conductivity of 147.2±99.4 μS.cm-1 and 65.7±78.7 μS.cm-1, respectively. The ionic abundance (mEq.L-1) followed Ca2+>Na+>Mg2+>K+ for cations and HCO₃->SO₄2->Cl->NO₃->F->PO₄3- for anions, with most samples being calcic and/or magnesian bicarbonates. Chemical composition was primarily influenced by rock-water interactions and wet-season precipitation in surface water. The isotopic composition of precipitation showed a seasonal pattern, with lower values in the wet season (-63.87‰ for δ2H and-9.86‰ for δ18O) and higher values in the dry season (-5.12‰ for δ2H and-2.12‰ for δ18O). Groundwater remained constant (-43.71‰ for δ2H and-6.70‰ for δ18O), while surface water varied seasonally (-44.95‰ for δ2H and-7.07‰ for δ18O in the wet season, and-38.12‰ for δ2H and-6.14‰ for δ18O in the dry season), reflecting wet-season precipitation inputs. Consistent groundwater Evaporation Line (EL) slopes across seasons suggest that the recharge was gradual and slow. The Mann-Whitney test for chemical and isotopes tracers pointed out that surface water-groundwater connectivity was present in both seasons, although enhanced in the wet season. In Lower SF1, identical distributions (p=1) of NO₃-, δ2H and δ18O underscore the stronger connectivity and mixing within this compartment. Groundwater was the primary source of streamflow, contributing from 60% to 85%, and wet-season precipitation was another source of surface water.

The Cardiac Output-Cerebral Blood Flow Relationship Is Abnormal in Most Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients with a Normal Heart Rate and Blood Pressure Response During a Tilt Test.

Orthostatic intolerance is highly prevalent in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and is caused by an abnormal reduction in cerebral blood flow (CBF). In healthy controls (HCs), the regulation of CBF is complex and cardiac output (CO) is an important determinant of CBF: a review showed that a 30% reduction in CO results in a 10% reduction in CBF. In previous and separate ME/CFS studies, we showed that CO and CBF decreased to a similar extent during tilt testing. to test the relationship between CBF and CO, which seems to be abnormal in ME/CFS patients and is different from that in HCs. In this retrospective study we analyzed this relationship in a large group of patients. To compare the patient data with those of HCs, we focused on patients with a normal heart rate (HR) and blood pressure (BP) response to upright tilt. Also, the influence of clinical data was analyzed. A total of 534 ME/CFS patients and 49 HCs underwent tilt testing with measurements of HR, BP, CBF, CO, and end-tidal PCO2. To measure CBF, extracranial Doppler flow velocity and vessel diameters were obtained using a GE echo system. The same device was used to measure suprasternal aortic flow velocities. End-tidal PCO2 was recorded using a Nonin Lifesense device. In 46 (9%) patients, CO and CBF changes were in the normal range for HCs, and in 488 (91%) an abnormal CO and CBF reduction was found. In patients with abnormal CO and CBF reductions, the slope of the regression line of CO versus CBF reduction was almost 1. The multiple regression analysis of the latter group showed that the CO reduction for the most part predicted the CBF reduction, with a limited role for the PETCO2 reduction. Two different patient groups with a normal HR and BP response during the tilt were identified: those with a CO and CBF in the normal range for HCs and those with an abnormal CO and CBF reduction during the tilt (91% of patients). In the latter group of patients, an almost 1:1 relationship between the CO and CBF reduction suggests the absence of compensatory vasodilation in the cerebral vasculature. This might indicate endothelial dysfunction in most ME/CFS patients and may have clinical and therapeutic implications.

ПРОСТРАНСТВЕННАЯ ВАРИАБЕЛЬНОСТЬ ИНТЕНСИВНОСТИ НАКОПЛЕНИЯ РТУТИ В МЫШЦАХ РАЗНОРАЗМЕРНОГО ОКУНЯ РЫБИНСКОГО ВОДОХРАНИЛИЩА

The study investigates the relationship between the mercury (Hg) content in the muscles of the perch Perca fluviatilis L., 1758 from different areas of the Rybinsk Reservoir including tail-water of the Uglich hydroelectric power plant, which differ in their physico-chemical characteristics, and the length of the fish. The measurement of Hg was carried out using the atomic absorption method on a RA-915+ mercury analyzer with the PYRO prefix (Lumex), without any preliminary sample preparation. The detection limits for Hg concentrations in biological samples on this device range from 0.0005 to 2.0000 mg/kg. Average metal concentrations ranged from 0.04 to 0.87 mg/kg of wet weight for fish with an average length of 2.2–45.0 cm, and differed by reservoir sections. The magnitude of effect of the fish length on the metal content in fish muscles was determined by the slope of the regression line, which indicates the rate of Hg accumulation, and the intercept of the line on the Y-axis representing the baseline level of Hg in organisms at the beginning of the food chain for each specified group. It was found that the maximum intensity of Hg accumulation is attained in the perch of up to 10 cm long and then significantly decreased in larger fishes, variably depending on the sampling area within the Rybinsk Reservoir.

Relationships Among Capillary Refill Time, Peripheral Blood Flow Rate, and Fingertip Temperature: Advances in Peripheral Artery Contractility Diagnosis.

Capillary refill time (CRT) is a widely used noninvasive measure of cardiovascular health. Despite its widespread diagnostic utility, it has several limitations, particularly its low sensitivity for certain conditions, because factors such as the contraction and relaxation of distal blood vessels can influence CRT readings. This study was performed to explore the relationships between CRT and distal blood flow. The right hand of each of ten healthy adult volunteers was cooled to induce blood vessel contraction. CRT, fingertip temperature, and blood flowrate were measured using a custom device, a thermometer, and a laser Doppler blood flowmeter, respectively, before and after cooling. Hand cooling significantly decreased blood flowrate and increased CRT. A robust inverse correlation was observed between blood flowrate and CRT, supporting a model where CRT is the time required for blood to flow through a cylindrical pipe. Furthermore, CRT showed a significant negative correlation with fingertip temperature. Most participants had high correlation coefficients, although two showed lower values. However, all data points exhibited a linear relationship, with the slopes of the regression lines between CRT and temperature varying among participants. These results suggested that the slope between CRT and fingertip temperature indicates individual differences in arterial contractility. These findings could improve the diagnostic utility of CRT in assessing vascular health, including arterial age and Raynaud's phenomenon, based on the contractility of peripheral arteries.

A Yoga Pose Difficulty Level Estimation Method Using OpenPose for Self-Practice System to Yoga Beginners

Yoga is an exercise preferable for various users at different ages to enhance physical and mental health. To help beginner yoga self-practitioners avoid getting injured by selecting difficult yoga poses, the information of the difficulty level of yoga poses is very important to provide an objective metric to assist yoga self-practitioners in selecting appropriate exercises on the basis of their skill level by using the yoga self-practice system. To enhance the developed yoga self-practice system, the yoga difficulty level estimation function will enable users to clearly understand whether the selected yoga poses are suitable for them. In this paper, the newest difficulty level estimation method of yoga poses is proposed by using and analyzing OpenPose two-dimensional (2D) human body keypoints. The proposed method effectively uses the selected six keypoints areas of the upper and lower body, body support types, center of gravity calculations, and body tilt angles and slopes to produce estimations. Firstly, the method calculates the weighted centers of the upper and lower human body for each pose by using keypoints. Secondly, it refers the slope of the centroid line between the two centers and infers the body’s balance state. Lastly, the system estimates the difficulty level by additionally considering the keypoints of the body to contact the ground. For evaluations of the proposal, more than one hundred yoga poses are collected from the Internet and applied to classify them into five difficulty levels. Through comparisons with subjective levels from one instructor and 10 users, the validity of the estimation results is confirmed, a comparison is performed with existing designs, and it is implemented in embedded systems.

Effect of the Cross-Sectional Geometry of the Mixed Particle Zone on the Spiral Separation Process and Its Structural Optimization

Cross-sectional geometry is of significance in determining the flow characteristics and the particles separation in spiral concentrators. The effects of the cross-sectional geometry within the mixed particle zone on the secondary flow and the separation process of hematite and quartz particles with a size of 89.5 μm were investigated via a computational fluid dynamics (CFD) approach. The optimization of the line segment slopes was conducted using response surface methodology (RSM). The results indicate that the peak radial fluxes and average radial velocities of the secondary flow are positively correlated with the corresponding line segment slope. The independent adjustment of line slopes in regions I and II, and the interaction of line slopes in regions I and III, influence the separation efficiency of hematite and quartz particles significantly. The separation performance of the experimental spiral concentrator with a cross-sectional profile of the optimized line segments for a feed of hematite and quartz with a size range of −100 + 75 μm is remarkably improved by nearly 5%. This study provides insights for the cross-section design of spiral concentrators for the effective separation of coarse-grained hematite and quartz.

Silicon Isotopic Composition of Mainstream Presolar SiC Grains Revisited: The Impact of Nuclear Reaction Rate Uncertainties

Abstract Presolar grains are stardust particles that condensed in the ejecta or in the outflows of dying stars and can today be extracted from meteorites. They recorded the nucleosynthetic fingerprint of their parent stars and thus serve as valuable probes of these astrophysical sites. The most common types of presolar silicon carbide grains (called mainstream SiC grains) condensed in the outflows of asymptotic giant branch stars. Their measured silicon isotopic abundances are not significantly influenced by nucleosynthesis within the parent star but rather represent the pristine stellar composition. Silicon isotopes can thus be used as a proxy for galactic chemical evolution (GCE). However, the measured correlation of 29Si/28Si versus 30Si/28Si does not agree with any current chemical evolution model. Here, we use a Monte Carlo model to vary nuclear reaction rates within their theoretical or experimental uncertainties and process them through stellar nucleosynthesis and GCE models to study the variation of silicon isotope abundances based on these nuclear reaction rate uncertainties. We find that these uncertainties can indeed be responsible for the discrepancy between measurements and models and that the slope of the silicon isotope correlation line measured in mainstream SiC grains agrees with chemical evolution models within the nuclear reaction rate uncertainties. Our result highlights the importance of future precision reaction rate measurements for resolving the apparent data–model discrepancy.

Assessing the Accuracy of Cardiovascular Disease Prediction Using Female-Specific Risk Factors in Women Aged 45 to 69 Years in the UK Biobank Study.

Cardiovascular disease (CVD) is the leading cause of mortality in women. We aimed to assess whether adding female-specific risk factors to traditional factors could improve CVD risk prediction. We used a cohort of women from the UK Biobank Study aged 45 to 69 years, free of CVD at baseline (2006-2010) followed until the end of 2019. We developed Cox proportional hazards models using the risk factors included in 3 contemporary CVD risk calculators: Pooled Cohort Equation - Atherosclerotic Cardiovascular Disease, Qrisk2, and PREDICT. We added each of the following female-specific risk factors, individually and all together, to determine if these improved measures of discrimination and calibration for predicting CVD: early menarche (<11 years), endometriosis, excessive, frequent or irregular menstruation, miscarriage, number of miscarriages, number of stillbirths, infertility, preeclampsia or eclampsia, gestational diabetes (without subsequent type 2 diabetes), premature menopause (<40 years), early menopause (<45 years), and natural or surgical early menopause (menopause <45 years or timing of menopause reported as unknown and oophorectomy reported at age <45). In the model of 135 142 women (mean age, 57.5 years; SD, 6.8) using risk factors from Pooled Cohort Equation - Atherosclerotic Cardiovascular Disease, CVD incidence was 5.3 per 1000 person-years. The c-indices for the Pooled Cohort Equation - Atherosclerotic Cardiovascular Disease, Qrisk2, and PREDICT models were 0.710, 0.713, and 0.718, respectively. Adding each of the female-specific risk factors did not improve the c-index, the net reclassification index, the integrated discrimination index, the slope of the regression line for predicted versus observed events, and the Brier score or plots of calibration. Adding all female-specific risk factors simultaneously increased the c-index for the Pooled Cohort Equation - Atherosclerotic Cardiovascular Disease, Qrisk2, and PREDICT models to 0.712, 0.715, and 0.720, respectively. Although several female-specific factors have been shown to be early indicators of CVD risk, these factors should not be used to reclassify risk in women aged 45 to 69 years when considering whether to commence a blood pressure or lipid-lowering medication.

Evaluation of the Seismicity Index for Nigerian Nuclear Installations

Seismic Hazard Assessment (SHA) is a quantitative measure of assessing the seismic hazard or risk involved for a given site. The parameter computed for such an assessment is needed for building engineers or national decision makers especially when it concerns nuclear installations. Even though the International Atomic Energy Agency (IAEA) currently makes it mandatory to provide such an index before undertaking any form of development or construction of a nuclear installation, this computation has not been done for Nigeria. Data over long period of time is usually necessary for a quantitative seismic hazard assessment, but because such information is scarce in Nigeria a fractal approach is therefore used in this research. A SHA index called the b-value is evaluated by determining the fractal dimension of the network of locations of recorded past tremor events within Nigeria. In this work a b-value of 0.43 which quantitatively measures the seismic hazard or risk of a given region is computed for Nigeria. Aeromagnetic data was used in producing analytic signal maps that accurately mapped faults that could have been responsible for causing the earth tremors, and the coordinates of these faults or lineament were used in calculating the fractal dimension of the system of faults. The fractal dimension of 0.8568 was obtained by determining the slope of line of best-fit of the plot of the log of the average number of tremor locations &lt;N(R)&gt; within radius R of each location against log of radius R, which was in turn used to determine the b-value. A b-value of 0.43 obtained indicates that Nigeria is in a less seismically active region and this can be used in the IAEA safety guidelines for nuclear installations.

A hysteretic water retention model incorporating the soil deformability and its application to rainfall-induced landslides

A hysteretic water retention model incorporating the soil deformability and its application to rainfall-induced landslides