bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of ryanodine receptor 2 and FK506-binding protein 12.6 dissociation in pulmonary hypertension
Authors: Wang Yong-Xiao , Reyes-García Jorge , Di Mise Annarita , Zheng Yun-Min
Published: January 2023

Pulmonary hypertension (PH) is a devastating disease characterized by a progressive increase in pulmonary arterial pressure leading to right ventricular failure and death. A major cellular response in this disease is the contraction of smooth muscle cells (SMCs) of the pulmonary vasculature. Cell contraction is determined by the increase in intracellular Ca2+ concentration ([Ca2+]i), which is generated and regulated by various ion channels. Several studies by us and others have shown that ryanodine receptor 2 (RyR2), a Ca2+-releasing channel in the sarcoplasmic reticulum (SR), is an essential ion channel for the control of [Ca2+]i in pulmonary artery SMCs (PASMCs), thereby mediating the sustained vasoconstriction seen in PH. FK506-binding protein 12.6 (FKBP12.6) strongly associates with RyR2 to stabilize its functional activity. FKBP12.6 can be dissociated from RyR2 by a hypoxic stimulus to increase channel function and Ca2+ release, leading to pulmonary vasoconstriction and PH. More specifically, dissociation of the RyR2–FKBP12.6 complex is a consequence of increased mitochondrial ROS generation mediated by the Rieske iron-sulfur protein (RISP) at the mitochondrial complex III after hypoxia. Overall, RyR2/FKBP12.6 dissociation and the corresponding signaling pathway may be an important factor in the development of PH. Novel drugs and biologics targeting RyR2, FKBP12.6, and related molecules may become unique effective therapeutics for PH.
Characterizing Superradiant Phase of the Quantum Rabi Model
Authors: Yang Yun-Tong , Luo Hong-Gang
Published: January 2023

Recently, a superradiant phase transition first predicted theoretically in the quantum Rabi model (QRM) has been verified experimentally. This further stimulates the interest in the study of the process of phase transition and the nature of the superradiant phase since the fundamental role of the QRM in describing the interaction of light and matter, and more importantly, the QRM contains rich physics deserving further exploration despite its simplicity. Here we propose a scheme consisting of two successive diagonalizations to accurately obtain the ground-state and excited states wavefunctions of the QRM in full parameter regime ranging from weak to deep-strong couplings. Thus, one is able to see how the phase transition occurs and how the photons populate in Fock space of the superradiant phase. We characterize the photon populations by borrowing the distribution concept in random matrix theory and find that the photon population follows a Poissonian-like distribution once the phase transition takes place and further exhibits the statistics of Gaussian unitary ensemble with increasing coupling strength. More interestingly, the photons in the excited states behave even like the statistics of Gaussian orthogonal ensemble. Our results not only deepen understanding on the superradiant phase transition but also provide an insight on the nature of the superradiant phase of the QRM and related models.
UV/blue/green converted efficient red-NIR photoluminescence in Cr incorporated MgAl2O4 nanocrystals: Site selective emission tailored through cation inversion and intrinsic defects
Authors: Savita  , Vashishtha Pargam , Gupta Govind , Vij Ankush , Thakur Anup
Published: January 2023

The UV/visible activated near-infrared (NIR) phosphors have many applications in solid state lighting, night vision devices and bio-imaging. The early research reported the red-NIR emitting phosphors doped with Cr3+ centers upon visible light excitation. Here, in this work the intense red-NIR emission and color tuning is achieved for broad excitation range (UV/blue/green) through Cr dopant induced defect centers and cation inversion in Mg

1
−
x

Cr

x

Al2O4 (

x

= 0.5, 1, 3, 5 and 10 mol%) nanocrystals. The Cr3+ doped MgAl2O4 nanocrystals were synthesized by combustion method through stoichiometric substitution of Mg by Cr, while most of the Cr3+ ions occupied the octahedral sites of spinel host with the formation of antisite defects, Cr3+ clusters, magnesium and oxygen vacancies. These defect centers were probed through Rietveld refinement, photoluminescence (PL), x-ray photoelectron and nuclear magnetic resonance spectra analyses. At UV excitation, the intrinsic defects played an interesting role in exhibiting the blue-violet emission attributed to host lattice defects and red-NIR emission attributed to strong/weak ligand field octahedral Cr3+ sites, via charge transfer to Cr3+ ions. The PL spectra evinced the enhanced red-NIR emission intensity upon 266 nm excitation than upon blue and green light excitation. Further, the weak ligand field site emission is found to be dominating with increase in doping concentration. Thus, Cr doped MgAl2O4 nanocrystals showed their potency of exhibiting the intense red-NIR emission and color tuning (from red purple to bluish purple and then to red color) upon UV/blue/green excitation.
Force and stability mechanism analysis of two types of nonlinear mono-stable and multi-stable piezoelectric energy harvesters using cantilever structure and magnetic interaction
Authors: Sun Shuailing , Leng Yonggang , Hur Sunghoon , Sun Fei , Chen Xiaoyu , Song Hyun-Cheol , Kang Chong-Yun
Published: January 2023

Nonlinear mono-stable and multi-stable piezoelectric energy harvesters have attracted a lot of attention owing to their broadband frequency spectra and excellent energy harvesting performance. Herein, two types of nonlinear mono-stable, bi-stable, tri-stable, and quad-stable piezoelectric energy harvesters using cantilever structure and magnetic interaction are compared and analyzed. Based on the magnetizing current method, the magnetic force equations are obtained. Calculation results demonstrate that the stability of these harvesters is dependent on the equivalent linear elastic force and the vertical magnetic force. The equilibrium point occurs when the equivalent linear elastic force equals to the vertical magnetic force. The relationship between the number of stable equilibrium points E
S and the number of the intersections of the two force curves N
I is that E
S= (N
I + 1)/2. Experiments are carried out to verify the equivalent linear elastic force, vertical magnetic force, and the number of stable equilibrium points of the fabricated prototypes. The experimental results are consistent with the calculated results, which verifies the correctness of the stability mechanism. Moreover, it is found that the stability mechanism is also applicable to the harvesters with more stable equilibrium points, such as penta-stable and hexa-stable harvesters. This work reveals the stability mechanism of nonlinear mono-stable and multi-stable energy harvesters using cantilever structure and magnetic interaction, and provides technical methods for the design of multi-stable energy harvesters.
Effects of static magnetic field, driving laser strength and polarization on the coherent properties of a microwave mediated four-level tripod-type atomic system
Authors: Das Aparajita , Hossain Md Mabud
Published: January 2023

In this theoretical work, we study the optical behaviour of a microwave driven four-level tripod-type atomic system, configured by Zeeman sub-levels in D
1 line of 87
Rb atom. The non-optical microwave field (L) reasonably assists the optical pumping by a linearly polarized (π) laser field (P1) and a right-handed circularly polarized (σ
+) laser field (P2), in presence as well as absence of a static magnetic field (MF). The optical responses of the system to the left-handed circularly polarized (σ
−) optical probe laser field (Pr) under three specific P1-P2 strength conditions depict substantial variations in the Doppler-free and Doppler-broadened absorption peaks, accompanied with single EIT or double EIT windows. The origin of Doppler-free Pr absorption peaks are explained by analyzing the resonant poles for the scanning Pr which attribute to the decaying-dressed-states. Perceptible changes of resonant pole positions on the complex planes of the poles w. r. t. the applied MF and L signify that one can externally alter the optical responses of the medium. The related Pr dispersion and its controllability are discussed as well. It is found that the interaction length of the Doppler-free medium has a prominent effect on the Pr absorption and transmission when both MF and L are present in the medium. Furthermore, we have shown the modifications in the Doppler-free Pr absorption profiles in presence of MF and L by considering P2 as an elliptically polarized laser field. Interestingly, Pr absorption turns into Pr gain at suitable polarization rotation angles of the elliptically polarized P2 field for different P1-P2 strength ratios.
Optimization of phase prediction for brain-state dependent stimulation: a grid-search approach
Authors: Bigoni Claudia , Cadic-Melchior Andéol , Morishita Takuya , Hummel Friedhelm C
Published: January 2023

Objective. Sources of heterogeneity in non-invasive brain stimulation literature can be numerous, with underlying brain states and protocol differences at the top of the list. Yet, incoherent results from brain-state-dependent stimulation experiments suggest that there are further factors adding to the variance. Hypothesizing that different signal processing pipelines might be partly responsible for heterogeneity; we investigated their effects on brain-state forecasting approaches. Approach. A grid-search was used to determine the fastest and most-accurate combination of preprocessing parameters and phase-forecasting algorithms. The grid-search was applied on a synthetic dataset and validated on electroencephalographic (EEG) data from a healthy (n = 18) and stroke (n = 31) cohort. Main results. Differences in processing pipelines led to different results; the grid-search chosen pipelines significantly increased the accuracy of published forecasting methods. The accuracy achieved in healthy was comparably high in stroke patients. Significance. This systematic offline analysis highlights the importance of the specific EEG processing and forecasting pipelines used for online state-dependent setups where precision in phase prediction is critical. Moreover, successful results in the stroke cohort pave the way to test state-dependent interventional treatment approaches.
Design optimization of backscatter X-ray security scanner based on pencil-beam scanning
Authors: An G. , Park J. , Seo H.
Published: January 2023

At national borders and high-security facilities, security screening is conducted to block the entrance of illicit goods such as weapons, explosives, and drugs. In the Republic of Korea, the Korea Customs Service currently conducts transmission X-ray security screening using fixed energy. However, the detection efficiency of this system for drugs or explosives composed of organic substances is rather low. Alternatively, the backscatter X-ray detection system is sensitive to materials of low atomic number; therefore, it can play an essential, complementary role in security screening. In the present study, the design of a pencil-beam-based backscatter X-ray security scanner was optimized and, subsequently, its performance was evaluated under various conditions using the Monte Carlo (MC) simulation technique. As for the X-ray generator, we optimized the tube voltage and the geometry of the chopper wheel collimator. Detector parameters including length, distance between detectors, and thickness also were optimized for detection efficiency. Finally, the performance of the optimized system was evaluated for various object conditions and postal phantoms.
An analytical model for fluorescent and scattering X-ray beam monitor designing
Authors: Sacchetti E. , Desjardins K. , Medjoubi K.
Published: January 2023

All the beamlines at modern synchrotron facilities are equipped with X-ray Beam Intensity or Position Monitors. Among those monitors, a relatively simple device is aiming at measuring the X-ray fluorescence and the X-ray scattering (elastic and inelastic) signal emitted from a thin foil with a punctual detector, a combination of several punctual detectors or a 2D detector. To improve the design of this kind of monitor, an analytical simulation has been developed to estimate the recording signal intensity according to the foil, the detector and the beam parameters. The mains X-ray interaction with matter processes involved in these monitors are simulated and several parameters of the incident X-ray beam are taken into account such as its intensity, energy, size and polarization. Furthermore, in contrast to the complex and time-consuming Monte-Carlo method, this analytical simulation is performed in few seconds and is implemented in a user-friendly interface. In order to validate our tool, the simulated results were compared to a series of measurements performed on the METROLOGIE beamline of the SOLEIL synchrotron. The differences with the experimental results are less than 30% by using a metallic foil and less than 50% with a Kapton® foil. The performances of our tool in term of accuracy, computation time and ease of use are perfectly adapted for the design of X-ray monitors based on an X-ray fluorescence and scattering foil.
TDC with uncontrolled delay lines: calibration approaches and precision improvement methods
Authors: Zhang W. , Edwards C. , Gong D. , Huang X. , Liu C. , Liu T. , Liu T. , Olsen J. , Sun H. , Sun Q. , Wu J. , Ye J. , Zhang L.
Published: January 2023

The time-to-digital-converter (TDC) using uncontrolled delay lines has a simple structure and finer measurement precision since the delay cells are pure digital gates that operate at maximum speed. For every incoming hit, two “snapshots” of the delay line are taken by the register array with two strobes separated with a known time interval. With two measurements, propagation delays of each cell in the delay line can be calibrated for the operating temperature and voltage. The two measurements can also be averaged to improve the TDC measurement precision. We will discuss various calibration approaches and present test results in this work.
Influence of high-frequency magnetic fields on the noise behavior of CMS 2S module prototypes
Authors: Dziwok C. , Feld L. , Klein K. , Lipinski M. , Pauls A. , Pooth O. , Röwert N.
Published: January 2023

For the CMS tracker Phase-2 upgrade new modules with silicon strip sensors are being developed.Each module features a Service Hybrid (SEH), which is responsible for the distribution of low voltages to the module components using a two-stage DC-DC conversion scheme.For modules equipped with the latest generation of SEHs an increase in module noise has been observed.A setup for inducing radiative noise with external magnetic fields that are frequency- and location-dependent is presented.Measurements carried out on modules from different prototyping phases show that the sensitivity is similar across generations, which indicates that radiative coupling into the sensor or readout electronics is not responsible for the observed noise increase.
A novel wave-like crawling robot has excellent swimming capabilities
Authors: Guetta Omer , Shachaf Dan , Katz Rotem , Zarrouk David
Published: January 2023

Multiple animals ranging from micro-meter scale bacteria to meter scale vertebrates rely on undulatory motion to propel themselves on land and in the water. This type of locomotion also appears in amphibious animals such as sea snakes and salamanders. While undulatory motion can be used for both crawling and swimming, it requires the coordination of multiple joints so that only a few robots have the ability to mimic this motion. Here, we report a new minimalistic method for both crawling and swimming based on producing a wave motion in the sagittal (vertical) plane. A robotic prototype AmphiSAW was developed to demonstrate this methodology in a variety of scenarios. AmphiSAW (using its wave mechanism only) crawled at 1.5 B s−1 and swam at 0.74 B s−1. The robot can be fitted with legs or wheels at the front, which can further increase its performance especially when crawling on uneven terrains. In addition to its high speeds, the robot has the lowest cost of transport among all amphibious robots reported in literature.
Labor markets: A critical link between global-local shocks and their impact on agriculture
Authors: Ray Srabashi , Haqiqi Iman , Hill Alexandra E , Taylor J Edward , Hertel Thomas W
Published: January 2023

Labor markets can shape the impacts of global market developments and local sustainability policies on agricultural outcomes, including changes in production and land use. Yet local labor market outcomes, including agricultural employment, migration and wages, are often overlooked in integrated assessment models (IAMs). The relevance of labor markets has become more important in recent decades, with evidence of diminished labor mobility in the United States (US) and other developed countries. We use the SIMPLE-G (Simplified International Model of agricultural Prices, Land use, and the Environment) modeling framework to investigate the impacts of a global commodity price shock and a local sustainable groundwater use policy in the US. SIMPLE-G is a multi-scale framework designed to allow for integration of economic and biophysical determinants of sustainability, using fine-scale geospatial data and parameters. We use this framework to compare the impacts of the two sets of shocks under two contrasting assumptions: perfect mobility of agricultural labor, as generally implicit in global IAMs, and relatively inelastic labor mobility (‘sticky’ agricultural labor supply response). We supplement the numerical simulations with analytical results from a stylized two-input model to provide further insights into the impacts of local and global shocks on agricultural labor, crop production and resource use. Findings illustrate the key role that labor mobility plays in shaping both local and global agricultural and environmental outcomes. In the perfect labor mobility scenario, the impact of a commodity price boom on crop production, employment and land-use is overestimated compared with the restricted labor mobility case. In the case of the groundwater sustainability policy, the perfect labor mobility scenario overestimates the reduction in crop production and employment in directly targeted grids as well as spillover effects that increase employment in other grids. For both shocks, impacts on agricultural wages are completely overlooked if we ignore rigidities in agricultural labor markets.
Counterdiabatic driving for pseudo- and antipseudo- Hermitian systems
Authors: Song Y H , Wang Xin , Liu H D , Yi X X
Published: January 2023

In this work, we study the counterdiabatic (CD) driving scheme and population transfer in pseudo- and antipseudo-Hermitian systems. By discussing the adiabatic condition for non-Hermitian system and the relation between the adiabatic evolution and the real energy spectrum, we derive the CD driving scheme for pseudo- and antipseudo-Hermitian systems. Based on these, we derive the condition that an eigenstate of a non-Hermitian Hamiltonian is self-normalized to guarantee the normalized populations of the bare states in non-Hermitian systems. Our results are illustrated by studying the CD driving for a non-Hermitian three-level system. A scheme to realize the perfect population transfer between the bare states is proposed in the antipseudo-Hermitian case.
A generalised diffusion equation corresponding to continuous time random walks with coupling between the waiting time and jump length distributions
Authors: Cleland J D , Williams M A K
Published: January 2023

This work outlines a transiently coupled continuous time random walk framework. The coupling is between the displacement probability density function (PDF) and the elapsed waiting time, and is of the form

1
−
exp

(

−
α
t

)

. Coupling of this kind generates larger displacements for longer waiting times, however, decouples on longer timescales. Such coupling is proposed to be physically relevant to systems in which diffusion is driven by the development of internal stresses which release and develop cyclically. This article outlines the associated generalised diffusion equation (GDE), which describes the time evolution of the position PDF,

P
(
x
,
t
)

. The solution for

P
(
x
,
t
)

is obtained using the properties of the Fox H function, both in terms of its transform properties but also its expansion theorems. The second moment and the asymptotic features of the solution are extracted. The relaxation of

P
(
x
,
t
)

back to the solution of a decoupled-type GDE is highlighted.
Analysis and determination of the stress field at the Olkiluoto site
Authors: Figueiredo B , Sjöberg J , Mattila J , Hakala M , Suikkanen J
Published: January 2023

Hydraulic, overcoring and LVDT stress measurements have been conducted for characterizing the in situ stress state at the spent nuclear fuel repository at Olkiluoto site, located in Western Finland. The effect of foliation on the stress measurement data was investigated. The analysis of the hydraulic data conducted in foliated rock types shows that the hydraulically-induced fracture propagates along a foliation plane rather than developing along the true maximum horizontal stress direction as dictated by the theory of hydraulic fracturing. An integration of the stress measurement data considered to be reliable was conducted for establishing the most likely stress field and confidence intervals for the large (site) and small scales. At the depth of the planned repository, the stress magnitudes obtained for the two scales were found to be similar, thus concluding that the confidence in the derived stresses is high. The mean magnitudes of the major, intermediate and minor principal stresses are 22, 18, and 11 MPa, respectively. The estimated orientation of the major principal stress (WNW-ESE) agrees with the regional stress state.
Potential applications of deep learning in automatic rock joint trace mapping in a rock mass
Authors: Chiu J K , Li C C , Mengshoel O J
Published: January 2023

In blasted rock slopes and underground openings, rock joints are visible in different forms. Rock joints are often exposed as planes confining rock blocks and visible as traces on a well-blasted, smooth rock mass surface. A realistic rock joint model should include both visual forms of joints in a rock mass: i.e., both joint traces and joint planes. Imaged-based 2D semantic segmentation using deep learning via the Convolutional Neural Network (CNN) has shown promising results in extracting joint traces in a rock mass. In 3D analysis, research studies using deep learning have demonstrated outperforming results in automatically extracting joint planes from an unstructured 3D point cloud compared to state-of-the-art methods. We discuss a pilot study using 3D true colour point cloud and their source and derived 2D images in this paper. In the study, we aim to implement and compare various CNN-based networks found in the literature for automatic extraction of joint traces from laser scanning and photogrammetry data. Extracted joint traces can then be clustered and connected to potential joint planes as joint objects in a discrete joint model. This can contribute to a more accurate estimation of rock joint persistence. The goal of the study is to compare the efficiency and accuracy between using 2D images and 3D point cloud as input data. Data are collected from two infrastructure projects with blasted rock slopes and tunnels in Norway.
Predicting the geological condition beyond the tunnel excavation face using MSP monitoring data and LSTM algorithm
Authors: Lee Je-Kyum , Lee Sean Seungwon
Published: January 2023

The ground conditions beyond an excavation face, especially discontinuities in rock masses, have a significant influence on tunnel construction. However, the actual ground conditions observed during tunnel construction are often different from the ground conditions predicted in the geotechnical site explorations carried out in the design stage. Changes in ground conditions may require alterations in tunnel design, leading to substantial disruptions in the construction schedule and budget. In this regard, accurate ground evaluation prior to the design and construction stages are essential for successful tunnel construction projects. Machine learning models have been developed in order to evaluate the condition of rock discontinuities within 50 m of the tunnel face. Machine data (rotational pressure, feed pressure, and drilling (advance) speed) obtained from a large boring hole machine, called MSP, at an NATM construction site in a granite formation located in South Korea were logged, and the actual ground Discontinuity Score (DS) was appraised by analysing internal bore hole images taken after drilling. Then, the LSTM algorithm was applied to develop the machine learning model to determine DS based on the logged machine data. DS was most accurately predicted when the drilling speed was included in the input data, whereas those cases using only the rotational and feed pressure in the input data showed low prediction accuracy. Therefore, the drilling speed seems to have a higher correlation than hydraulic pressure with regard to ground conditions, including discontinuities. Once additional data is collected from various tunnel sites, the machine learning model could be further enhanced to become more robust and provide solutions to various engineering problems.
A geotechnical evaluation of the Cumba Pit Slope Failure, Dominican Republic
Authors: Bar N , McQuillan A , Ma T , Wai D , Hammah R , Corkum B , Yacoub T , Cobián JC , Mojica B
Published: January 2023

The combined availability of topographical, geological, structural, hydrogeological and monitoring data is rapidly increasing. Technology and software advances allow the real time incorporation of this data across various software platforms. This paper describes the back-analysis of a 70 m high, pit slope failure of an open pit gold mine in the Dominican Republic, using data from aerial photogrammetry, ground-based synthetic aperture radar and 3D limit equilibrium and finite element modelling. This back-analysis process is considered leading practice with the latest technology. The (northern) side of the Cumba pit slumped along a non-daylighting plane that was identified after the failure event. Remedial investigations included review of geological data, major structures, rock mass constitutive models and groundwater conditions. Topographical and structural data acquired from aerial photogrammetry, pre- and post-failure event, was input into 3D models to replicate observed ground movement. 3D models of pit progression were compared with displacements recorded by ground-based synthetic aperture radar to calibrate model inputs and increase reliability of forward predictions. Such a technical review was completed in less than one week, and the review process implemented for the Cumba pit slope failure now forms the baseline approach for all future geotechnical analysis at the operating mine.
Mechanical and physical characterization mapping of evaporitic rocks from Abu Dhabi city and its surroundings
Authors: Arman Hasan , Paramban Safwan , Saima Mahmoud Abu , Abdelghany Osman , Aldahan Ala
Published: January 2023

Safe and sustainable engineering structure designs always require carefully and detailed mechanical and physical characterization of rocks. Abu Dhabi city, which is the capital of the United Arab Emirates (UAE), have been fast developing and industrializing region in the country and it is located on evaporitic rocks. Construction companies in this city often face some technical problems associated with evaporite bedrocks. Mechanical and physical characterization of rocks in either in-situ or laboratory is relatively expensive, takes significant time, efforts and adequate rock specimens must be tested to achieve reliable and representative values. In this study, extensive field and laboratory studies were carried out and 152 evaporitic rock blocks, which represent the study area, were collected from 27 locations. Large number test samples were prepared, tested and the mechanical and physical characterization maps, which are prepared by interpretation of the obtained data sets from 27 locations, for each considered parameters like Unconfined Compressive Strength (USC), Indirect Tensile Strength (ITS), P Wave Velocity (Vp), Porosity (n), Water Content (wc) etc. Availability of such characterization maps for evaporitic rocks in the Abu Dhabi city vicinity will be practical, useful, economical and certainly provides vital information for the construction businesses, engineers, and decision makers.
Geotechnical assessment of rock masses in metallic mineral deposits, a view on the “hidden” issues in open-pit design
Authors: Peshevski I , Jovanovski M , Angelova E , Jovanovska T
Published: January 2023

Defining rock mass geotechnical properties is a critical step in the process of open-pit slope design. Geotechnical engineers assess the frequently highly altered rocks of metallic mineral deposits by applying standardized geotechnical classifications primarily developed for underground mining operations or design of civil structures such as tunnels and cut slopes. In some cases, the projects do not consider additional aspects of the rock masses, such as: zoning according to rock mass alteration schemes, prediction of blasting disturbance and weathering depth, rock strength loss over time, swelling effects, etc. Unfortunately, in some mineral deposits, many of these aspects appear to overlap, leading to difficulties in the process of open-pit design. In the case of neglecting such complex issues, there can be serious consequences in regard to future safe mine operation or even failure of slope/s. The paper presents findings from Macedonian legislation and literature overview on these aspects, regulations from other countries where available, as well as personal experiences of the authors. Some suggestions on the scope of geotechnical investigation works are briefly presented. It is considered that a more serious approach is needed in order to achieve a better understanding of the “long term” geotechnical behaviour of rock masses in such high risk environments.
Evaluation of the Performance of the ISRM Suggested Methods for Measuring Density and Porosity when Applied to Low-Porosity Rocks
Authors: Kiuru R , Nieman P , Rinne M
Published: January 2023

Recent studies conducted in the context of geological disposal of spent nuclear fuel in low-porosity crystalline bedrock have found density and porosity values obtained following the ISRM Suggested Method (ISRM 1977) to occasionally be sporadic. To investigate this behaviour, 137 core specimens of 5 different rock types (granite, granitic pegmatoid, veined gneiss, mica gneiss and sandstone) were submerged in water under NTP conditions and measured repeatedly until the observed saturated mass was constant within the accuracy of the measurement system. These specimens were then fully dried and subsequently saturated again, this time following the Suggested Method (1 hour in water at <800 Pa vacuum) and measured again for density and porosity. Density and porosity values observed following the ISRM Suggested Method were found to be systematically lower than values observed using immersion saturation. Specimens saturated following the ISRM Suggested Method reached on average 40 – 60 % of the level of saturation reached with the immersion method. This resulted in significant differences in observed density and porosity values when compared to values observed after immersion saturation. Performance of the saturation method proposed in the ISRM Suggested Method should thus be studied in more detail and possibly re-evaluated.
Fluid flow of various configurations in a rock-proppant-system
Authors: Witte L C , Backers T
Published: January 2023

A high rock mass permeability is essential for developing an enhanced geothermal system and commonly achieved through the fracture conductivity. Hydraulic stimulation of fractures in combination with the use of proppants can significantly increase and maintain rock mass permeability. To investigate and quantify the effect of proppants, which are so far not commonly used to enhance deep geothermal reservoirs, on the rock mass hydraulic conductivity we performed various sets of laboratory experiments. We performed long-term creep deformation tests on a stack of rock samples with simultaneous a) fluid flow and b) acidification and fluid flow, in both cases with and without a proppant-filled fracture between the stacked rock samples. A central borehole served as fluid inlet into the lower sample of the stack. Two more boreholes in the lower sample allowed fluid flow. Sample stacks were placed in a Hoek cell at elevated confining pressures to prevent fluid flow along the sidewalls of the cylindrical sample setup. We compared the axial deformation and injection pressures between the experimental setups. The laboratory tests are part of the ZoKrateS Project, which aims at showing the feasibility of enhancing fractured carbonate rock mass by proppant placement for geothermal applications.
Hybrid InSARTrac for monitoring interglacial movement patterns
Authors: Zambanini C , Kieffer D S
Published: January 2023

InSARTrac is a hybrid 3D monitoring method, for which controlled field measurements have indicated significant potential for geotechnical applications. Various approaches can be taken to derive 3D displacements from InSAR measurements, such as combining multiple InSAR ascending and descending satellite passes or combining multi-geometrical radar datasets from ground and satellite based radars. InSARTrac is a cost-effective solution requiring only one terrestrial InSAR device and a camera used for feature tracking. This study summarizes the results of glacial displacement measurements that were conducted to test the InSARTrac methodology. The InSARTrac 3D displacement vectors show details concerning glacial retreat dynamics related to a combination of ice flow and volume loss. By extrapolating prior results obtained from controlled field measurements, the resultant displacement vector orientations have an estimated angular error of approximately 5 degrees. With a fixed camera mount and longer monitoring times this error can be further reduced. Current studies are focused on deploying InSARTrac to investigate its potential for landslide and geostructure monitoring.
An approach to estimate influence region of field investigation sampling points, investigation zone in civil infrastructure projects and brief review of existing field investigation process
Authors: Singh Naval
Published: January 2023

Geotechnical investigation is a cyclic process. The interdependency between different steps involved in whole process, i.e., from planning, performing investigation, transporting samples and analysis of data obtained from field or lab, present opportunities for improvements and further discussion.

For estimating number of investigation sampling points required for a particular site and selection of investigation methods, today we mostly relay on information from previously conducted site investigations, local experience from that area or site. In geotechnical investigation getting field samples which represents actual ground conditions for the whole site is well known challenge and has been highlighted in many research papers.

In this paper we are presenting concept of influence region of geotechnical investigation points and an approach for estimation of the same. We believe the influence region concept; its estimation approach will provide a mathematical model and will help in deciding number of sampling points at the geotechnical investigation sites. In author’s opinion the presented concept will further improve the quality of geotechnical ground investigation process and will provide help in getting representative, quality field samples for laboratory analysis.

The presented concept and estimation approach in this paper is based on author’s field experience and exposure gained from working in Swedish infrastructure projects. We think the influence region concept will further improve the existing geotechnical ground investigation process and will open opportunities for its validation through focused scientific research.

A brief overview of the existing ground investigation processes has been covered in the paper, along with examples from geotechnical site investigations from Trafikverket (The Swedish Transport Administration) projects in Sweden.
Tensile strength of anisotropic rocks from enhanced Brazilian laboratory testing and data analysis protocols
Authors: Packulak T R M , Day J J , Diederichs M S
Published: January 2023

The tensile strength of rock and rock-like materials is a critical material property in rock engineering design and the prediction of rockmass behaviour to mitigate any potential failure that may affect personnel safety or damage property. This study presents new instrumentation guidelines to the Brazilian Tensile Strength (splitting tensile strength) test to enhance the data processing techniques to determine true tensile strength. For this study a total of eighteen (18) specimens of two lithologies (Pointe Du Bois tonalite gneiss and Key Anacon metabasalt) were instrumented, tested, and reviewed to determine the true tensile strength of the material. This paper also identifies three potential failure modes and presents a failure envelope based on the identified potential failure modes.
An example of digital field training for a diversity-friendly (and pandemic-proof) field education in geoengineering disciplines
Authors: Godlewska J C , Ogan M S , Duda M , Backers T
Published: January 2023

Geological field training and site inspections are important components of the education in geological and civil engineering and associated disciplines. However, field training is not inclusive, does not consider students’ family situations, for example associated with care work, places high demands on students’ financial resilience, and therefore does not address family educational backgrounds. Also, it is not pandemic proof. Through the implementation of digital field training, students can get access to important aspects of field work in a barrier-reduced and location-independent way. Knowledge associated with geological field training therefore becomes more accessible and inclusive. Moreover, outcrops or specific rock structures that are difficult or unsafe to access in the field can be explored digitally. In this project, parts of a geological mapping course physically held in southern Germany and taught at the Faculty of Geosciences at Ruhr-Universität Bochum were turned into a digital field course. A virtual 360° tour with 3D models of outcrops and rock samples was complemented by photo, video and audio material with information on the geological setting. The digital field training was integrated via Moodle as a full lecture with H5P elements. Additionally, individual components were combined in a game engine, so that students can immerse themselves into the project settings via virtual reality experiences or on-screen. The learning outcome includes the creation of a geological map in the study area in QGIS that is complemented by a field report. The choice of equipment, procedure and results are presented. While acknowledging that a digital experience cannot fully replace the learning experience of physical field trips, it can be a valuable complement to physical field work, provide access to inaccessible geological regions, support interdisciplinary teaching projects, and provide an alternative to marginalised students who would otherwise not be able to complete a geoengineering curriculum.
Measuring the hydraulic transmissivity of a rock joint under varying normal load
Authors: Jacobsson L , Godio M
Published: January 2023

The water flow rate through a rectangular granite specimen with a tight unopened natural induced joint of dimensions 200×200 mm was measured in two perpendicular directions. The measurements were conducted at five different levels of stress corresponding to loading from 0 to 8 MPa and unloading back to 0 MPa. The flow was measured at different hydraulic gradients in the range of 10 to 25. The results showed a joint transmissivity between 0.002–0.03 mm2/s and a hydraulic aperture of 8–32 μm. It was shown that the measurements performed in the second orientation displayed smaller transmissivity and hydraulic aperture as compared to those in the first orientation, showing a residual compaction after the first load cycle. The Reynolds number was less than one in all the measurements yielding laminar flow conditions. Deviations from the linear regime relationship were observed for the lowest flow rates (Re < 0.1). A transitory regime was observed when varying the hydraulic gradient. This regime was observed to be longer at the lowest flow rates.
Experimental assessment of dynamic loading response of grouted non-persistent jointed rock
Authors: Kumar Sachin , Tiwari Gaurav , Das Arghya
Published: January 2023

Grouting is a well-established engineering practice for stabilizing the jointed and/or fractured rock mass. This process may lead to the enhancement of the mechanical properties of fractured rocks. In the majority of the studies, the efficiency of grouting is determined under static loading conditions. Nonetheless, the grouted rock may be subjected to different dynamic loading from blasts or earthquakes. The present study explored the dynamic loading response, in terms of strength and fracture propagation, of a rock mass having a diagonal non-persistent joint (45° to the loading direction) subjected to impact loading to determine the efficiency of grout material. The focus of the study is to present a comparative assessment of different grout materials under dynamic loading. Split Hopkinson Pressure Bar (SHPB) was used to conduct the compressive impact tests on the synthetic rock mass with varying infill conditions (unfilled, cement-filled and epoxy-filled). The progressive fractures within the specimens were monitored by Photron fastcam analysis (PFA, a high-speed image analysis) and digital image correlation (DIC). The experiments highlighted that the strength of rock mass has an increasing trend with the dynamic strain rate. Epoxy resin provided a better strength enhancement than cement paste as the grout material. Due to the higher strength of epoxy resin than cement paste, the epoxy-grouted jointed rock demonstrates a similar response as the intact rock. In the case of both unfilled and cement-filled specimens, the nature of the primary crack was the coplanar shear crack. In contrast, with the injection of epoxy grout, the nature of the initial crack became the tensile or far-field tensile crack, which is often noticed in intact rocks.
Explicit numerical models for the prediction of plastic and weakening rockmass behaviour around a circular tunnel in isotropic and anisotropic stress conditions
Authors: Fischer C P , Diederichs M S
Published: January 2023

The Geological Strength Index, GSI, is an assessment system for rockmass structure conditions (blockiness and discontinuity condition) based on the visual examination of exposed rockmass surfaces. The Generalized Hoek-Brown failure criterion is widely used with GSI to estimate the strength and stiffness of jointed rockmasses in traditional continuum numerical modelling. Modern numerical analysis tools allow networks of discrete structure to be represented with assigned properties based on site investigation data. In this paper, models with defined explicit structure are shown to yield similar results to implicit GSI-based models and provide more detailed information on the spatial variability of tunnel response when reasonable rockmass input parameters are estimated and calibrated. Once plastic explicit models are calibrated to give similar response to plastic implicit GSI-based models, explicit models using weakening joint and intact rock elements are used to determine appropriate post-yield strength and dilation parameters for use in implicit GSI-based modelling.
Evaluation of surface roughness of rock-like joints using close range photogrammetry method
Authors: Momeni A , Torkan M , Azhari A , Uotinen L , Baghbanan A
Published: January 2023

The surface roughness of the joints affects their hydraulic and mechanical behavior. There are various methods for assessing the surface roughness of discontinuities. With the development of photography technology and the release of powerful software, a photogrammetric analyzer has been introduced as a non-contact surface evaluation method. In this research, a three-dimensional model of the fracture surface was constructed using the close-range photogrammetric procedure and the joint roughness coefficient (JRC) is derived from the surface profiles. Also, the surface profiles were surveyed using the Profilometers (Barton Comb) and the JRC values were obtained using the Z2 method. Calculations were performed in two sampling steps of 0.42 and 1.27 mm. Ultimately, the results of the two methods were compared. A Sony Cybershot HX1 digital camera was used to capture the images. To process the images and build the 3D model, they were loaded in the “Agisoft metashape” software. A point cloud data was obtained with very high accuracy with a distance of 0.13 mm between points in the 3D model. The results show that the JRC values obtained from the photogrammetry method, for the upper surface of the joint, recorded 8% and 11% difference from the joint surface for sampling intervals of 1.27 and 0.42 mm, respectively. While for the bottom surface of the joint, these differences were 6.1% and 10% for sampling intervals of 1.27 and 0.42 mm, respectively.
A New Explanation of loading Rate Effect on Rock Compressive Strength
Authors: Zhu Jun , Deng Jianhui
Published: January 2023

Apart from several qualitative descriptions, such as the delay crack propagation and the difference in energy absorption, the involved mechanism of loading rate effect (rate-dependence) on unconfined compressive strength (UCS) of rock is not clear. According to the statistical analysis of the dominant frequency of acoustic emission (AE) waveforms, this work proposed a new explanation of rate-dependence on rock UCS from a micro failure perspective. The uniaxial compression tests, coupling with AE signals monitoring, of five types of hard rocks under different loading rates were conducted. The rate-dependence on compressive strength of various rocks was investigated comprehensively. By using batch processing and Fast Fourier Transform methods, the dominant frequencies of AE waveforms associated with rock failures were extracted and analyzed to explain the rate-dependence of rock UCS. The results show that, as the loading rates increase, the UCS of most of the rocks increase, while the AE waveforms with low dominant frequency released during the entire loading process significantly decrease. Moreover, the percentage of AE waveforms with low dominant frequency has a negative correlation with the rock UCS. The micro-tensile failures can be characterized by AE waveforms with low dominant frequency and its reduction can be responsible for the increase in the UCS with increasing loading rates. The proposed explanation provides a new and reasonable perspective on the rate-dependence of rock UCS based on its intrinsic property.