True Thickness Research Articles

Mapping soil thickness by accounting for right‐censored data with survival probabilities and machine learning

AbstractIn digital soil mapping, modelling soil thickness poses a challenge due to the prevalent issue of right‐censored data. This means that the true soil thickness exceeds the depth of sampling, and neglecting to account for the censored nature of the data can lead to poor model performance and underestimation of the true soil thickness. Survival analysis is a well‐established domain of statistical modelling that can deal with censored data. The random survival forest is a notable example of a survival‐related machine learning approach used to address right‐censored soil property data in digital soil mapping. Previous studies that employed this model either focused on mapping the probability of soil thickness exceeding certain depths, and thereby not mapping soil thickness itself, or dismissed it due to perceived poor performance. In this study, we propose an alternative survival model to map soil thickness that is based on the inverse probability of censoring weighting. In this approach, calibration data are weighted by the inverse of the probability that soil thickness exceeds a certain depth, that is, a survival probability. These weights can then be used with most machine learning models. We used the weights with a regular random forest, and compared it with a random survival forest, and other strategies for handling right‐censored data, through a comprehensive synthetic simulation study and two real‐world case studies. The results suggest that the weighted random forest model produces competitive predictions, establishing it as a viable option for mapping right‐censored soil property data.

Ultra-Fine Bainite in Medium-Carbon High-Silicon Bainitic Steel.

The effects of austenitizing and austempering temperatures on the bainite transformation kinetics and the microstructural and mechanical properties of a medium-carbon high-silicon ultra-fine bainitic steel were investigated via dilatometric measurements, microstructural characterization and mechanical tests. It is demonstrated that the optimum austenitizing temperature exists for 0.3 wt.%C ultra-fine bainitic steel. Although the finer austenite grain at 950 °C provides more bainite nuclei site and form finer bainitic ferrite plates, the lower dislocation density in plates and the higher volume fraction of the retained austenite reduces the strength and impact toughness of ultra-fine steel. When the austenitizing temperature exceeds 1000 °C, the true thickness of bainitic ferrite plates and the volume fraction of blocky retained austenite in the bainite microstructure increase significantly with the increases in austenitizing temperature, which do harm to the plasticity and impact toughness. The effect of austempering temperature on the transformation behavior and microstructural morphology of ultra-fine bainite is greater than that of austenitizing temperature. The prior martensite, formed when the austempering temperature below Ms, can refine the bainitic ferrite plates and improve the strength and impact toughness. However, the presence of prior martensite divides the untransformed austenite and inhibits the growth of bainite sheaves, thus prolonging the finishing time of bainite transformation. In addition, prior martensite also strengthens the stability of untransformed austenite though carbon partition and enhances the volume fraction of blocky retained austenite, which reduces the plasticity of ultra-fine bainitic steel. According to the experimental results, the optimum austempering process for 0.3 wt. %C ultra-fine bainitic steel is through austenitization at 1000 °C and austempering at 340 °C.

Uncertainty Study Aids Development-Plan Optimization in Deepwater Gulf of Mexico

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 32622, “Development-Plan Optimization and Uncertainty Study in a Major Deepwater Field in the US Gulf of Mexico,” by Mohsen Rezaveisi, SPE, Jennifer L. Campbell, and Paula L. Wigley, Woodside Energy Group, et al. The paper has not been peer reviewed. Copyright 2023 Offshore Technology Conference. _ This paper describes development-plan optimization and a probabilistic uncertainty study using Latin hypercube experimental design constrained to production performance in Lower Miocene (LM) reservoirs of the deepwater Gulf of Mexico Shenzi Field. The purpose of the development-plan optimization was to identify, rank, and characterize future development opportunities (i.e., infills and injectors) in the LM reservoirs to arrest field decline. The study uses history-matched dynamic simulation models. Introduction The Shenzi discovery is approximately 122 miles off the coast of Louisiana in a water column approximately 4,400 ft deep (Fig. 1). This part of the field is a partially filled three-way closure against a salt-cored anticline. The discovery includes four main sand units (A, B, C, and D) that exhibit various degrees of hydraulic connectivity based on pressure data and production history. The area of interest in the current study is the Eastern part of the field. Static Model Build The geomodel covering the area of interest was built from two seismically interpreted horizons and approximately 180 faults. The model is subdivided into 13 zones using well-based true stratigraphic thickness maps. The average cell height is 2–3.5 ft thick with heterolithics driving the lower end of the range. Sequential indicator simulation was used to populate facies using well-based net sand trend maps by zone. In zones with evidence of channelization, a second nested facies model was used to build channels into the model. Shenzi East reservoir properties are good because of the high-quality sand deposited in the field. Lower reservoirs (C and D) have slightly more depositional complexity because of the varying paleotopography and a lower average net-to-gross (NTG) of approximately 53%. Upper reservoirs (A and B) had a larger sediment supply and were more continuously deposited, which resulted in a larger average NTG of approximately 67%. Dynamic Model History Matching The Shenzi East reservoir has been on production since March 2009, providing abundant production data for history matching. Of seven producers, six are still active, and the reservoir also features three water injectors. Producers and injectors are identified with letters P and I, respectively, followed by well numbers. Well P7 was drilled after 6 months of production from other producers; formation pressure data showing reservoir depletion are available for history matching. The water injectors were drilled in 2012–2013, but only two have formation pressure testing data available. Well P1 was completed in all sands; Wells P2, P3, and P6 were completed in three sands (D, C, and B); and the rest of the producers were completed in two sands (D and C). Production is commingled in all producers, resulting in allocation uncertainties between sands. Water production has been observed in five wells, with the current water cut in the range of 35–65%. The two most updip wells, P1 and P7, are still producing at zero water cut.

Effect of plate orientation on apparent thickness of mineral plates by transmission electron microscopy.

Transmission electron microscopy (TEM) is widely used to study the ultrastructure of bone. The mineral of bone occurs as polycrystalline mineral plates about 3 to 6 nm in thickness. A problem in using TEM to make quantitative analyses of bone is that the orientation of the plates with respect to the plane of the section being imaged is expected to affect their apparent thickness. The purpose of this study was to test if this was true, if the apparent thickness of plates changed substantially as a result of tilt of the section. We prepared TEM sections of samples of cortical human bone by ion beam milling, orienting one section parallel to the collagen fibril axes and one perpendicular to them. We obtained TEM bright field and HAADF images of these sections, tilting the sections up to ± 20° at 2° intervals and measuring the apparent thickness of individual mineral platelets at each angle of tilt. Thickness appears to double as section is tilted ± 20°. True thickness of plates is determined by tilting the section along an axis parallel to the plate orientation and determining the minimum apparent thickness. However, as plates are tilted away from minimum-thickness orientation, they become less well-resolved, disappearing when tilted more than 20°. We therefore also measured apparent thickness of only the darkest (most electron scattering) plate images in an untilted section and obtained the same average thickness as that obtained by tilting. We conclude that tilting of the section is not necessary to obtain an accurate measurement of the thickness of mineral plates.

On the critical role of martensite hardening behavior in the paradox of local and global ductility in dual-phase steels

The ductility of sheet metal is typically limited by either localized necking or by damage and fracture. A recent ductility classification refers to these failure modes respectively as “global” and “local” formability. The forming limit curve (FLC) and the uniaxial tensile test assess global formability, whereas the fracture forming limit (FFL), the true thickness fracture strain, hole expansion ratios (HER), etc. are indicators of local formability. Experimental hole expansion data in the literature for different dual-phase (DP) steel grades of similar strength and composition presents a paradox: grades which are found to be ductile in a tensile test and/or FLC show a low ductility in hole expansion, whereas other grades with a low ductility in conventional tests perform surprisingly well at cut edges. In this work, an in-depth systematic statistical analysis of idealized artificial two-phase microstructures is carried out to unravel the underlying mechanisms of the observed paradoxical trends. This is done by scaling the hardness of martensite and its volume fraction to generate virtual DP steels of the same strength but different strain hardening and mechanical phase contrast (hardness difference). The proposed micromechanical model adequately reproduces the experimentally observed trends. The results show that in DP steels, a higher global (necking-driven) ductility is obtained upon delaying martensite plasticity by increasing the mechanical contrast of the two phases. Consequently, the stress–strain distributions becomes more heterogeneous, resulting in a lower fracture limit of one of the phases or interfaces in shear loading, thereby, reducing the local ductility. Global ductility is improved by higher mechanical phase contrast and lower martensite volume fraction, whereas local ductility is improved by low phase contrast and higher martensite volume fraction. The hardening behavior of martensite is the key to avoiding the above trade-off between local and global ductility. It is shown that if the strain hardening capacity of martensite in the later stages of deformation (in high strains) can be increased, this would result in removing the observed paradoxical trends of local and global ductility in DP steels.

One-dimensional magnetotelluric (MT) data inversion modeling using convolutional neural network

The magnetotelluric method is a geophysical method commonly used to map subsurface resistivity. The subsurface’s true resistivity is generated by inversion of the magnetotelluric data. Inversions carried out using conventional methods such as linear and global approaches have several limitations including the need for an initial model, models trapped in local minima, a large number of iterations and long computation time. To overcome the drawbacks, this paper proposes to invert one-dimensional magnetotelluric data using one of the deep learning methods, the convolutional neural network, which is heavily inspired by the human nervous system. This method starts by training the network with large amounts of data. The trained network is then used for inversion by receiving input in the form of apparent resistivity data and generating true resistivity and thickness values instantly. This method has been tested on synthetic data with curves of type A, H, K, and Q. The inversion results show that the convolutional neural network could approach the true resistivity and thickness values with a fairly small error and extremely fast computation time without initial model guess and iteration.

Reliability Analysis of Pipe Wall Thinning based on Quantification of Ultrasonic Testing

Piping in nuclear power plants is subject to corrosion and erosion caused by the interaction with fluids it carries. In order to prevent accidents such as pipe rupture, it is necessary to non-destructively inspect the thickness of the pipe wall and predict the remaining pipe life. In contrast, signals obtained by non-destructive inspection are affected by various uncontrollable and unknown factors, which will result in uncertainty in evaluating pipe wall thickness. Ignoring the uncertainty would lead to a large error in the pipe reliability assessment. Therefore, it is important to develop a reasonable pipe wall thinning management that can takes the uncertainty of non-destructive testing into consideration. Based on this background, this study aimed to develop a piping wall thinning prediction model that accounts for the uncertainty in evaluating pipe wall thickness and to evaluate its applicability to ultrasonic testing. At first, ultrasonic tests were performed to measure the thickness of specimens simulating flow accelerated corrosion. The results of the measurements were statistically analysed to obtain a mathematical model correlating the evaluated and true thickness. A numerical model to predict the reduction of wall thinning with its uncertainty is developed. Compared to the conventional method, the proposed method is able to predict wall thickness with high accuracy.

Investigation of Wall Thickness, Corrosion, and Deposits in Industrial Pipelines Using Radiographic Technique

In this study, radiographic techniques were used to inspect large-diameter pipes that are used for transporting fluids in some industries in Ghana. Radiographic approaches such as the double wall technique (DWT) and tangential radiographic technique (TRT) were used to evaluate the remaining wall thickness, deposits, and corrosion in the pipes. Two steel pipes with known varying wall thicknesses ranging from 4.00 mm to 13.00 mm with a diameter of 150.00 mm were examined to authenticate the accuracy and reliability of the tangential method that was used to measure the remaining wall thickness. The tangential configuration resulted in a higher material thickness, which therefore required more time of exposure compared to the DWT method. The exposure angle of the source to the tangential part of the specimen was approximately 87°. The film generated was compared with a normal pipe piece that was not machined to serve as a control. From the radiograph obtained, an average of 6 and 7 rounded indications depicting pitting corrosion were revealed on the radiograph of the internally and externally fabricated pipe, respectively. Radiographs after the TRT revealed that the recorded wall thickness obtained from the film is about twice the value of the calculated true wall thickness.

Polarimetric airborne scientific instrument, mark 2, an ice‐sounding airborne synthetic aperture radar for subglacial 3D imagery

AbstractPolarimetric Airborne Scientific INstrument, mark 2 (PASIN2) is a 150 MHz coherent pulsed radar with the purpose of deep ice sounding for bedrock, subglacial channels and ice‐water interface detection in Antarctica. It is designed and operated by the British Antarctic Survey from 2014. With multiple antennas, oriented along and across‐track, for transmission and reception, it enables polarimetric 3D estimation of the ice base with a single pass, reducing the gridding density of the survey paths. The off‐line data processing stream consists of channel calibration; 2D synthetic aperture radar (SAR) imaging based on back‐projection, for along‐track and range dimensions; and finally, a direction of arrival estimation (DoA) of the remaining across‐track angle, by modifying the non‐linear MUSIC algorithm. Calibration flights, during the Antarctic Summer campaigns in 16/17 and 19/20 seasons, assessed and validated the instrument and processing performances. Imaging flights over ice streams and ice shelves close to grounding lines demonstrate the 3D sensing capabilities. By resolving directional ambiguities and accounting for reflector across‐track location, the true ice thickness and bed elevation are obtained, thereby removing the error of the usual assumption of vertical DoA, that greatly influence the output of flow models of ice dynamics.

Evaluation of hole expansion ratio of ultra-high strength martensitic steels produced with various processing routes

Hole expansion ratio of hot rolled ultra-high strength martensitic steels with tensile strength around 1000 MPa was evaluated. Steels were produced with direct quenching and traditional reheat and quenching processes with final thickness of 3 mm. Achieved yield strength values (Rp0.2) varied between 918 – 1068 MPa depending on the processing route. Mean hole expansion ratios (HER) in direct-quenched (DQ) and direct-quenched and tempered (DQT) conditions were between 22 – 36 %, and no clear improvement was seen after tempering treatment compared to quenched variant. HER values for reheat and quenched (RQ) and reheat, quenched and tempered (RQT) variants were between 31 – 49 %, and the highest values were achieved with RQT steels, which were tempered at 600 °C. Based on the field emission scanning electron microscope with electron backscatter scanning diffraction (FESEM-EBSD) analysis/characterization of martensite grain size, more uniform grain structure was discovered in RQ steels, which could be the reason for improved HER properties. HER values were also compared to tensile test results (uniform elongation, true thickness strain), and formability maps were constructed. However, only minor correlation was found between HER and true thickness strain values.

2D Electrical Resistivity Imaging to delineate the exact boundary and true thickness of granular aquifers

Electrical resistivity imaging (ERI) is one of the best geophysical techniques for studying subsurface and groundwater aquifer investigations. In clastic sediments, determining the exact boundary between different layers on the inverse section of ERI is not an easy task due to gradual changes in resistivity between surrounding layers and the granular aquifers. Therefore, the main aim of the study is to indicate a more precise boundary of the granular aquifers (true thickness of aquifers) on the inverse section. Two different models were used: the field model and the laboratory model, in the field model, four different locations were selected. They are located in (Kalar, Chamchamal, Bazyan, and Piramagroon), within the Sulaymaniyah Governorate, NE Iraq. Two-dimensional (2D) electrical resistivity imaging was carried out along four profiles of 355 m length with a five-meter electrode spacing. The Wenner-Schlumberger array was used for recording the data. For the lab model, a laboratory geological model was constructed has length, height, and width equal to 192, 65, and 45 cm, respectively. Two synthetic profiles were carried out on this model, they have lengths of 190 cm with electrode spacing of 10 cm. The field results indicated that aquifers in clastic sediments on inverse sections always showed anomalies with apparent thicknesses larger than their true thicknesses, which were obtained from the geological column of the wells. In the four studied locations, aquifers' average true thickness is approximately 68.2% of the apparent thicknesses on the inverse sections. The result of the laboratory geological model also showed that the true thickness of the unsaturated gravel is approximately equal to 59.7% of the apparent thickness of the anomaly, which is formed by the dry gravel layer. Also, the true thickness of the saturated gravel is about 57.1% of the apparent thickness of the anomaly, which is formed by the saturated gravel layer. Moreover, the geological model showed that the higher resistivity layer (dry gravel) creates a narrower transitional resistivity zone between clay and gravel than saturated gravel of lower resistivity.

Influence of the Graft Length on Nanocomposite Structure and Interfacial Dynamics.

Both the dispersion state of nanoparticles (NPs) within polymer nanocomposites (PNCs) and the dynamical state of the polymer altered by the presence of the NP/polymer interfaces have a strong impact on the macroscopic properties of PNCs. In particular, mechanical properties are strongly affected by percolation of hard phases, which may be NP networks, dynamically modified polymer regions, or combinations of both. In this article, the impact on dispersion and dynamics of surface modification of the NPs by short monomethoxysilanes with eight carbons in the alkyl part (C8) is studied. As a function of grafting density and particle content, polymer dynamics is followed by broadband dielectric spectroscopy and analyzed by an interfacial layer model, whereas the particle dispersion is investigated by small-angle X-ray scattering and analyzed by reverse Monte Carlo simulations. NP dispersions are found to be destabilized only at the highest grafting. The interfacial layer formalism allows the clear identification of the volume fraction of interfacial polymer, with its characteristic time. The strongest dynamical slow-down in the polymer is found for unmodified NPs, while grafting weakens this effect progressively. The combination of all three techniques enables a unique measurement of the true thickness of the interfacial layer, which is ca. 5 nm. Finally, the comparison between longer (C18) and shorter (C8) grafts provides unprecedented insight into the efficacy and tunability of surface modification. It is shown that C8-grafting allows for a more progressive tuning, which goes beyond a pure mass effect.

Исследование основных свойств пушных шкурок, полученных от самок норки с различной степенью интенсивности инвазии эймериями

The article analyzes the obtained results of the study of indicators of some commodity properties and evaluation of quality of female female mink of cellular breeding, obtained from animals with different intensity of invasion of eumeriosis. Infection of the female mink by eumeriosis is a significant reason for stopping the growth of young mink, as well as increasing its waste and changing the quality of the hair. The material for the study was the skins of female mink cellular breeding of the standard dark brown (STK) color type with various degrees of invasion from the animal husbandry of the Kaliningrad region of the North-Western region of the Russian Federation, divided into four experienced groups: the first group of pelts – from clinically healthy animals, the second group of pelts – from patients of mink with a low degree of invasion intensity, the third group of pelts – from patients with eumeriosis of mink with a medium degree of invasion, the fourth group of pelts are from highly invasive Mink eumeriosis patients. The analysis of the results of the study of indicators of natural and true length and thickness of hair, height and thickness of hair, area of female mink skins with different degrees of invasion is presented.

Lithology Interpretation Based on Drilling and Geophysical Well Logging Data at Pit G Roto North PT Kideco Jaya Agung, Paser District, East Kalimantan Province.

Coal is a non-renewable energy source and has a role that almost competes with petroleum. In this connection, it is necessary to explore and inventory coal resources. One of the exploration stages is drilling where data from drilling results can be used for coal resources and reserves estimation. PT Kideco Jaya Agung is one of the biggest coal mining companies in Indonesia, located in Paser District, East Kalimantan Province. In carrying out its drilling, PT Kideco uses the open hole, touch coring, and full coring drilling methods then compares it with the results of geophysical logging to obtain accurate coal thickness and depth data. Drilling data was obtained in the form of rock samples. The logging process is carried out after the drilling stage is complete. Logging methods used are gamma-ray logs, density logs, HRD logs, and BRD logs. Lithology interpretation is done by comparing rock sample data and log curves. The results of the interpretation of coal seams in drill hole ZA04 were found at a depth of 102.5 – 128.5 m with a true thickness of 10.78 m and in drill hole ZA05 coal was found at a depth of 106.2 – 121.7 m with a true thickness of 3.63 m.

Exploring hydrogeological parameters by integration of geophysical and hydrogeological methods in northern Khartoum state, Sudan

The recent study aims to detect the spatial distribution of the hydraulic parameters and evaluate the protective capacity of the groundwater aquifers in northern Khartoum state using geophysical and hydrogeological methods. The study area is located in the transition zone between the sedimentary basin and the area dominated by crystalline basement rocks. Vertical electrical sounding (VES) measurements, using Schlumberger configuration, were taken along three profiles to delineate the thicknesses of the sediments and groundwater aquifers. The VES measurements were combined with the lithology logs to reduce the uncertainty of the resulting models. VES findings denoted that the study area comprises two hydraulically connected aquifers. The upper aquifer is composed of fine sandstone with an average thickness of 50 m, and the lower aquifer has a thickness of up to 150 m. These two aquifers are confined to semi-confined, separated by relatively thick aquitards. To evaluate the aquifer quantitively, pumping test analysis using Cooper-Jacob method was applied to estimate the aquifer's hydraulic parameters, including transmissivity and hydraulic conductivity. The pumping test approach is costly and time-consuming, and extrapolation of the results is restricted to homogeneous boundary conditions. Since groundwater aquifers are mostly heterogeneous, a geophysical-based method called Dar Zarrouk parameters was applied to give a continuous estimate for the hydraulic parameters. Dar Zarrouk parameters include longitudinal conductance and transverse resistance, combining the true resistivity and thickness obtained from the inverted VES data to determine the hydraulic parameters. The calculated hydraulic parameters from the pumping test and Dar Zarrouk parameters showed high compatibility. Furthermore, longitudinal conductance was used to predict the protective capacity of the aquifers. Generally, it ranged from good to very good protective capacity suggesting potable water quality. The findings of this research indicated that the groundwater aquifer in the study area is ideal for groundwater exploitation. However, this study recommends applying a detailed geophysical survey to reduce the uncertainty of the resulting geological and hydrogeological models.

Nondestructive testing and imaging of corrosion thickness of steel plates using THz-TDS

The corrosion of steel plates is one of the main reasons for the decrease of bearing capacity and structural durability. The existing nondestructive testing (NDT) approaches is difficult to accurately detect steel plate corrosion, including the location and degree of corrosion. Therefore, a non-contact nondestructive terahertz time-domain spectroscopy (THz-TDS) is utilized to evaluate the corrosion based on the properties of THz waves. The experimental results show that in the effective frequency range of 0.2–1.2 THz, the refractive index of corrosion products is around 2.8, and Fe3O4 has a significant impact on the optical parameters of the corrosion products mixture. The relative amplitude of the first signal from reflection THz-TDS exhibits a logarithmic relationship with the corrosion time of the steel plates and a linear relationship with the reciprocal of the corrosion time. By the method of extracting the delay time difference in the reflected THz signal, the THz-TDS can accurately measure the corrosion layer with a thickness larger than 40 μm, and the measurement accuracy is over 90 %. Meanwhile, the 3-dimensional (3D) visualization based on the THz method directly describes the true thickness and geographical distribution of the corrosion layer while removing the influence of coating materials. It provides a novel way to quantify corrosion degree of steel plate through NDT of corrosion under coating and extraction of corrosion thickness. The applicability and accuracy of non-contact THz-TDS for corrosion detection are therefore proved.

Miranda's Thick Regolith Indicates a Major Mantling Event from an Unknown Source

We investigated “muted” craters and scarps across Miranda’s cratered terrain. The morphologies of the muted craters are most consistent with modification by regolith deposition instead of erosion or viscous relaxation. We used three techniques to estimate regolith thickness. (1) Analysis of muted crater depth–Diameter (d-D) ratios near the South Polar Terrain Chasma indicates that regolith mantling their floors ranges from 0.3 to 1.2 km thick. Because older craters may have collected more regolith than younger craters, the true thickness may be similar to the highest estimate. (2) Analysis of crater size–frequency distributions across the cratered terrain indicates a thickness of 1.0 ± 0.2 km. (3) Analysis of a central mound within Alonso Crater indicates a thickness of km near Verona Rupes and may represent an upper limit. These results indicate that Miranda has one of the thickest regoliths in the solar system, which has important implications for Miranda’s interior thermal properties. Regolith appears to mantle some scarps within Arden but not Elsinore or Inverness, indicating that Arden may be the oldest corona, contrary to previous relative age estimates. In this scenario, the mantling event was ongoing during Arden’s formation but before Elsinore or Inverness formed. We propose three possible sources for Miranda’s thick regolith: (1) giant impact ejecta, (2) plume deposits, and (3) Uranian ring deposits. We favor the ring deposit hypothesis, which is consistent with the regolith’s large spatial extent, substantial thickness, and Miranda’s slightly spectrally blue color. Follow-up studies that rigorously investigate these scenarios are required.

A single extensional, diffuse, ductile fault zone in the Goriganga section, western Himalaya: Part of the upper South Tibetan Detachment System?

The Trans-Himadri Detachment Fault (T-HDF) of the Kumaon region of western Himalaya, a north-easterly steeply dipping discrete brittle/semi-brittle fault, had previously been regarded as a strand of the South Tibetan Detachment System (STDS). Yet, elsewhere in the Himalaya, the STDS is defined as a diffuse, ductile low-angle normal-sense shear zone. This aspect of the STDS remained conjectural and was even refuted by various workers in the Goriganga valley in the Kumaon. We have systematically documented the STDS as a low-angle, northerly dipping, ductile, diffuse shear zone, with a true thickness of >5 km in this transect. In the present scenario, the shear zone is located only within the psammo-pelitic basal part of the Tethyan Sedimentary Sequence (TSS), and bypassed the rock units of the Greater Himalayan Sequence (GHS). Multiple grain-statistical parameters of mylonitized micaceous quartzites point to an anastomosing architecture which displays a single precursory damage zone and a wider core for the entire STDS shear zone. The 40Ar*/39Ar geochronology and oxygen isotope analysis of the micas in mylonites demonstrated that the STDS evolved in weak lithologies, between c.14–11 Ma, at ∼300–350 °C ambient temperature, at or immediately below the brittle-plastic transition depth in the quartzo-feldspathic continental crust.Consideration of similar range of optimum ages of cessation of the extensional activity and already published timings of the end of brittle motion of the STDS in adjacent regions suggests that this wide diffuse shear zone is a deeper counterpart of the brittle upper STDS. This is in sharp contrast to the exposures of the detachment elsewhere in the Himalaya, where diffuse zone demonstrably constitutes the lower branch of this detachment. This finding has potential implications on overall understanding of the deformation related to the STDS and late Miocene geodynamic evolution of the GHS in this region.

Thickness measurement optimisation for permanently installed inductively coupled ultrasonic transducer systems

An inductively coupled ultrasonic transducer system (ICTS) is a lightweight, wireless, battery-free, and low-profile (0.5 mm thick) permanently installed sensor system for measuring remaining wall thickness at fixed locations for structural health monitoring. In an ICTS, a slight variation in measured thickness has been observed that is dependent on the misalignment between the handheld probing unit and the permanently attached sensor. A correction algorithm has been developed to improve the ultimate thickness measurement performance of ICTS even with misalignment. The algorithm eliminates a system delay from the measured first arrival time based on the measured bandwidth of the cross-talk signal. Crucially, the algorithm does not require identification of the second back-wall echo as this is not always possible if the back surface of the structure is badly corroded. The correction algorithm has successfully improved the thickness measurement precision from 0.19 mm to 0.07 mm. A higher accuracy of thickness measurement is also achieved, with the mean of the corrected thicknesses equals to the true thickness to ±0.01 mm. The algorithm also enabled the detection of a thickness loss of 0.09 mm. The improvement on thickness measurement performance is important for manual inspection, and future robotic interrogation which will become more viable as up to 20 mm lateral misalignment and 10 mm vertical misalignment can be accommodated.

The effect of transverse ocular magnification adjustment on macular thickness profile in different refractive errors in community-based adults.

PurposeChanges in retinal thickness are common in various ocular diseases. Transverse magnification due to differing ocular biometrics, in particular axial length, affects measurement of retinal thickness in different regions. This study evaluated the effect of axial length and refractive error on measured macular thickness in two community-based cohorts of healthy young adults.MethodsA total of 2160 eyes of 1247 community-based participants (18–30 years; 23.4% myopes, mean axial length = 23.6mm) were included in this analysis. Macular thickness measurements were obtained using a spectral-domain optical coherence tomography (which assumes an axial length of 24.385mm). Using a custom program, retinal thickness data were extracted at the 9 Early Treatment of Diabetic Retinopathy Study (ETDRS) regions with and without correction for transverse magnificent effects, with the corrected measurements adjusting according to the participant’s axial length. Linear mixed models were used to analyse the effect of correction and its interaction with axial length or refractive group on retinal thickness.ResultsThe raw measures (uncorrected for axial length) underestimated the true retinal thickness at the central macula, while overestimating at most non-central macular regions. There was an axial length by correction interaction effect in all but the nasal regions (all p<0.05). For each 1mm increase in axial length, the central macular thickness is overestimated by 2.7–2.9μm while thicknesses at other regions were underestimated by 0.2–4.1μm. Based on the raw thickness measurements, myopes have thinner retinas than non-myopes at most non-central macular. However, this difference was no longer significant when the corrected data was used.ConclusionIn a community-based sample, the raw measurements underestimate the retinal thickness at the central macula and overestimate the retinal thickness at non-central regions of the ETDRS grid. The effect of axial length and refractive error on retinal thickness is reduced after correcting for transverse magnification effects resulting from axial length differences.