Stress Meter Research Articles

Interpreting seismic velocity changes observed with ambient seismic noise correlations

Recent results have shown that crosscorrelating ambient seismic noise recorded in underground mines can successfully extract the seismic Green’s function between sensors. We have revisited an earlier experiment that showed that these virtual seismic sources can be used to measure changes in seismic velocity accurately enough to monitor the short- and long-term influences of a blast in an underground mine. To use this method routinely, it is important to determine the cause of velocity variations in the absence of large dynamic stress perturbations (such as blasts). It also is important to calibrate the seismic velocity changes in terms of known stress changes so the effect of mining activities can be quantified in units that can be used by geotechnical engineers. To this end, we used coda-wave interferometry to measure relative velocity variations during times where no significant blasting or microseismic activity occurred and compared it to atmospheric air pressure changes, temperature variations, and modeled tidal strain. The results indicate that atmospheric air pressure changes have a measurable influence on the long-term seismic velocity variations at depth in the absence of large dynamic stress perturbations. This influence enabled us to determine the sensitivity of the relative velocity changes to stress, where a value of [Formula: see text] was found. This calibration essentially enables us to turn each sensor pair in an underground mine into a stress meter, paving the way for geotechnical engineers to use ambient seismic noise correlations to monitor the evolution of stress and to assess seismic hazard in conjunction with conventional microseismic methods.

Assessment of the phytoremediation potential and an adaptive response of Festuca rubra L. sown on fly ash deposits: Native grass has a pivotal role in ecorestoration management

Fly ash (FA) is a coal combustion by-product of thermal power plants, and has been recognized as a great environmental and health hazard worldwide. The establisment of a permanent green cover on fly ash deposits is essential and can be achieved by sowing the native plant species that should be crucial for stability and resilience of an ecosystem. Improved understanding of species’ response to unfavorable properties of fly ash provides key insight into the decision about ecorestoration practice and management. Therefore, long-term research based on the assessment of the phytoremediation potential and adaptive response of Festuca rubra L. (red fescue) sown on the fly ash deposits at the thermoelectric power plant ‘Nikola Tesla-A’ in Obrenovac (Serbia) was the main concern. Field research was carried out on the passive FA lagoons (L3—the lagoons 3 years old and L2—the lagoons 11 years old) and in the Botanical Garden ́́Jevremovać́ in Belgrade (CS—control site). The physico-chemical properties of soil and fly ash were determined by using standard soil analyses. The element concentrations in soils, fly ash and plants were determined by using ICP-OES. Chlorophyll a fluorescence parameters were measured by using the Plant Stress Meter. Pigments, phenolics and malonyldialdehide contents (MDA) in leaves were measured spectrophotometrically and the total antioxidant capacity in plant leaves was determined by using DPPH free radical. Site-dependent variations were observed for all the parameters examined. FA contains alkaline pH, high electrical conductivity (EC) and low total nitrogen (N) coupled with toxic elements i.e. As and B as well as deficiency of Mn and Zn. Improvement of the physico-chemical characteristics of FA over time is reflected in the increased values of higroscopic water (HW), silt, clay, the amount of adsorbed bases (S), total adsorption capacity (T) and the reduced concentrations of total and available As, B, Cu, Zn and Mn (except available As content) indicating favorable fly ash conditions. F. rubra is an excluder plant, it retains a larger content of As, Cu, Mn and Zn in roots than in leaves and with extensive root system it can provide good fly ash stabilization, i.e. this species has a great potential in phytoremediation of FA. Furthermore, results show that F. rubra sown on the FA deposits has a high amount of MDA and reduced values of chlorophyll a fluorescence parameters (Fm, Fv, Fv/Fm, Fm/Fo), chlorophylls (Chl a, Chl a+b) and total carotenoids (Tot Carot) indicating high oxidative stress and lower efficiency of photosynthesis. However, in spite of toxic concentrations of As and B and low content of Cu, Mn and Zn in the leaves, this species has high potential to activate adaptive mechanisms, such as increased biosynthesis of anthocyanins, phenolics, ascorbic acid and total radical scavenging activity. Taken together, F. rubra possesses high adaptive capacity to perform functional ecorestoration on fly ash deposits. These findings indicate that F. rubra can be identified as a vital element for large-scale reclamation purpose.

Case Analysis of the Monitoring Data for a Roller Compacted Concrete Dam at Impoundment

Based on the Nabi hydropower plant, the layout of the safety monitoring device for the roller compacted concrete (RCC) dam is introduced. The variations of some monitoring index during impoundment are analyzed and their evolution rules according to the variation of the water level are presented. The conclusions are made as follows: the osmotic pressure of the dam foundation and the uplift pressure of the upstream curtain are related to the water level; the stability of the dam can be affected by the heat of hydration due to concrete pouring; the water cooling system can effetely inhibit the crack; The impoundment has little effect on the bolt stress meter equipped at the bottom plate of the stilling basin and the reinforcement bar meter located on the surface; there is a negative correlation between their stress state and the temperature.

An Evaluation of Coulomb Stress Changes from Earthquake Productivity Variations in the Western Gulf of Corinth, Greece

Spatial and temporal evolution of the stress field in the seismically active and well-monitored area of the western Gulf of Corinth, Greece, is investigated. The highly accurate and vast regional catalogues were used for inverting seismicity rate changes into stress variation using a rate/state-dependent friction model. After explicitly determining the physical quantities incorporated in the model (characteristic relaxation time, fault constitutive parameters, and reference seismicity rates), we looked for stress changes across space and over time and their possible association with earthquake clustering and fault interactions. We focused our attention on the Efpalio doublet of January 2010 (M = 5.5 and M = 5.4), with a high aftershock productivity, and attempted to reproduce and interpret stress changes prior to and after the initiation of this seismicity burst. The spatial distribution of stress changes was evaluated after smoothing the seismological data by means of a probability density function (PDF). The inverted stress calculations were compared with the calculations derived from an independent approach (elastic dislocation model) and this comparison was quantified. The results of the two methods are in good agreement (up to 80 %) in the far field, with the inversion technique providing more robust results in the near field, where they are more sensitive to the uncertainties of coseismic slip distribution. It is worth mentioning that the stress inversion model proved to be a very sensitive stress meter, able to detect even small stress changes correlated with spatio–temporal earthquake clustering. Data analysis was attempted from 1975 onwards to simulate the stress changes associated with stronger earthquakes over a longer time span. This approach revealed that only M > 5.5 events induce considerable stress variations, although in some cases there was no evidence for such stress changes even after an M > 5.5 earthquake.

Development of a borehole stress meter for studying earthquake predictions and rock mechanics, and stress seismograms of the 2011 Tohoku earthquake (M 9.0)

Although precursory signs of an earthquake can occur before the event, it is difficult to observe such signs with precision, especially on earth’s surface where artificial noise and other factors complicate signal detection. One possible solution to this problem is to install monitoring instruments into the deep bedrock where earthquakes are likely to begin. When evaluating earthquake occurrence, it is necessary to elucidate the processes of stress accumulation in a medium and then release as a fault (crack) is generated, and to do so, the stress must be observed continuously. However, continuous observations of stress have not been implemented yet for earthquake monitoring programs. Strain is a secondary physical quantity whose variation varies depending on the elastic coefficient of the medium, and it can yield potentially valuable information as well. This article describes the development of a borehole stress meter that is capable of recording both continuous stress and strain at a depth of about 1 km. Specifically, this paper introduces the design principles of the stress meter as well as its actual structure. It also describes a newly developed calibration procedure and the results obtained to date for stress and strain studies of deep boreholes at three locations in Japan. To show examples of the observations, records of stress seismic waveforms generated by the 2011 Tohoku earthquake (M 9.0) are presented. The results demonstrate that the stress meter data have sufficient precision and reliability.

In-situ measure to internal stress of shotcrete layer in soft-rock roadway

In order to solve the difficult conditions of soft rock, water-trickling and hard-maintain of main air-return roadway in Tarangaole Colliery, high pretensioned stress and intensive bolt-shotcrete support program was designed and mechanical property of shotcrete layer was specially monitored through utilizing a type of concrete stress meter with oscillating chord after the program was carried out. It was indicated that, due to rock pressure and support resistance, the interior of shotcrete layer would emerge diverse stresses in axial, radial and tangential directions. With time passing internal stresses in three directions, whose average values were −0.061, 0.043 and 0.517 MPa respectively, fluctuated first and then tended to stability slowly. The axial and radial stresses were relatively smaller than tangential stress which was 11, 12 times the two formers respectively. Along the section of roadway, axial and tangential stresses distributed symmetrically and increased gradually from the top of arch to the waist of wall, but reduced at the foot of wall. Radial stresses reduced from the top of arch to the waist of arch first, and then increased in the waist of wall. Axial stresses were tensile substantially, except for stresses in arch vault tending to compressive, but all the radial stresses were compressive. Nevertheless, tangential stresses in the wall were compressive and tangential stresses in the arch were tensile. During the period of roadway excavating, the stress of shotcrete layer was less than its ultimate bearing capacity, with no significant stress concentration. At the end of this article, some suggests are given to shotcrete support design.

Size distribution of Parkfield's microearthquakes reflects changes in surface creep rate

AbstractThe nucleation area of the series of M6 events in Parkfield has been shown to be characterized by low b-values throughout the seismic cycle. Since low b-values represent high differential stresses, the asperity structure seems to be always stably stressed and even unaffected by the latest main shock in 2004. However, because fault loading rates and applied shear stress vary with time, some degree of temporal variability of the b-value within stable blocks is to be expected. We discuss in this study adequate techniques and uncertainty treatment for a detailed analysis of the temporal evolution of b-values. We show that the derived signal for the Parkfield asperity correlates with changes in surface creep, suggesting a sensitive time resolution of the b-value stress meter, and confirming near-critical loading conditions within the Parkfield asperity.

Analysis of Displacement in Guandi Underground Powerhouse Based on the Influence of Dislocation Surfaces

The monitoring data suggests that the overall displacement in Guandi underground powerhouse is a little less, 87% of which is less than 30 mm, while the maximum deformation can be reached as big as 65.77mm. Combined with the study on excavated geological data, the bigger displacement part of Guandi underground powerhouse is mainly affected by the dislocation interfaces, the excavation disturbance causes an opening displacement on the rock mass near the dislocation interfaces and a much bigger displacement partially. Due to the structural surface cut rock mass, deformation coordination between the surrounding rock and the structure surface after stress applied, the stress concentration appears nearby, measuring range of bolt stress meter is excessed in large displacement cases.

Stress management: How the unfolded protein response impacts fatty liver disease

Induction of the unfolded protein response (UPR) is recognized as central to fatty liver disease (FLD) pathophysiology. This pathway may be a potential therapeutic target for FLD, as well as other diseases. However, fundamental questions as to how UPR contributes to FLD remain unanswered. Conflicting data suggest that this pathway can both protect against and augment this disease. Here, we review the relationship between protein secretion, endoplasmic reticulum function (ER), and UPR activation. The UPR serves to maintain secretory pathway homeostasis by enhancing the protein folding environment in the ER, and we review data investigating the role for individual UPR players in fatty liver (steatosis). We explore a novel concept in the field that all cases of UPR activation do not equal "ER stress". Rather, different types of UPRs that can either protect against or cause FLD are discussed. Refining our current understanding of this complex pathway is particularly important, as drugs that affect the protein folding environment in the ER and affect UPR activation are being successful in clinical trials for FLD.

Stress meter for people with Autism Spectrum Disorder (ASD) to visualize and anticipate on their stress level

Stress meter for people with Autism Spectrum Disorder (ASD) to visualize and anticipate on their stress level

Occupational exposure to uncomfortable temperatures in two university presses of Costa Rica

Muchos procesos industriales se llevan a cabo en condiciones de temperatura excesiva, creando en la mayoría de los casos malestar y, con menor frecuencia, un riesgo para la salud, especialmente cuando se añaden al calor una ventilación inadecuada y la falta de supervisión médica. Este problema ha sido estudiado pocas veces en América Latina, por lo que evaluamos la exposición laboral a temperaturas elevadas de los trabajadores en las imprentas de dos editoriales universitarias de San José, Costa Rica. Medimos el nivel de calor en 55 estaciones de trabajo, usando un termo-anemómetro y un medidor de estrés térmico, ambos calibrados y certificados. Aunque no hallamos peligro de estrés térmico, 50% a 80% de los trabajadores indicaron insatisfacción con la temperatura de sus estaciones de trabajo, por lo que recomendamos que a los nuevos trabajadores se les permita un período de aclimatación previa y mejorar la ventilación de las instalaciones. Se necesitan estudios similares en otros países de América Latina para que los datos obtenidos puedan ser comparados.

Unusual Structure and Fabrication Process of Japanese Matchlock Gun (Hinawajuu), Made at the Late EDO Period

The metallurgical macro- and micro-structure, and the residualstress of the Japanese matchlock gun, fabricated at the late Edo period, have been investigated with an optical microscope, an SEM, an EPMA and an X-ray residual stress meter for estimating the fabricating process and their materials. This gun was fabricated by Udonbari (in Japanese) process, which is similar to that of the Russell's method, tubes was created by the joining together opposite edges of a flat iron strip with an iron core bar. The joining line was wavy. Their residual stress was mainly compressive and the values were from 180 to 280 MPa in the longitudinal direction and from 240 to 380 MPa at the transverse direction.The gun was made of low carbon steel with equiaxed ferrite grains; their grain size was mainly 10 μm partly with 100 μm and exceptionally more than 1000 μm grains. Moreover, we find the special banded structure, consisted of fine ferrite grains bands and large ferrite grains bands.The firing part was fabricated by the joining of five parts for getting the L-shape hole. The female screw was made by forging; therefore the shape was tapered screw and the male screw was cut from a low grade steel bar, confirmed by their macro-structure.

EEG Correlates of Song Prosody: A New Look at the Relationship between Linguistic and Musical Rhythm

Song composers incorporate linguistic prosody into their music when setting words to melody, a process called “textsetting.” Composers tend to align the expected stress of the lyrics with strong metrical positions in the music. The present study was designed to explore the idea that temporal alignment helps listeners to better understand song lyrics by directing listeners’ attention to instances where strong syllables occur on strong beats. Three types of textsettings were created by aligning metronome clicks with all, some or none of the strong syllables in sung sentences. Electroencephalographic recordings were taken while participants listened to the sung sentences (primes) and performed a lexical decision task on subsequent words and pseudowords (targets, presented visually). Comparison of misaligned and well-aligned sentences showed that temporal alignment between strong/weak syllables and strong/weak musical beats were associated with modulations of induced beta and evoked gamma power, which have been shown to fluctuate with rhythmic expectancies. Furthermore, targets that followed well-aligned primes elicited greater induced alpha and beta activity, and better lexical decision task performance, compared with targets that followed misaligned and varied sentences. Overall, these findings suggest that alignment of linguistic stress and musical meter in song enhances musical beat tracking and comprehension of lyrics by synchronizing neural activity with strong syllables. This approach may begin to explain the mechanisms underlying the relationship between linguistic and musical rhythm in songs, and how rhythmic attending facilitates learning and recall of song lyrics. Moreover, the observations reported here coincide with a growing number of studies reporting interactions between the linguistic and musical dimensions of song, which likely stem from shared neural resources for processing music and speech.

Heat exposure in sugarcane workers in Costa Rica during the non-harvest season

This observational pilot study was carried out at three sugarcane companies in Costa Rica. Its main objective was to determine the potential for heat stress conditions for workers in one sugarcane-growing region in Costa Rica during the maintenance (non-harvest) period.Wet bulb globe temperature (WBGT) variables were measured with a heat stress meter and threshold value limits and the Sweat Rate Indexes were calculated for each workplace. It was determined that workers in this study were in heat stress conditions. Costa Rica is likely to experience warmer temperatures and increased heat waves in the coming decades. It is therefore important to take action to decrease current and future heat-related risks for sugarcane workers in both harvest and non-harvest conditions and in all sugarcane growing regions in Costa Rica. It is also necessary to improve guidelines and occupational health standards for protecting worker health and productivity in the tropics.

Instrumental measurement of the degree of relaxation with meditation

An experiment evaluating the degree of relaxation by means of a 'coherence meter' was conducted in Hangzhou, China. Chinese Qigong, a form of meditation, was used to induce the state of relaxation in this experiment. The results of the experiment show that many subjects were able to reach deep levels of relaxation through meditation. But, the subjects using Qigong training were able to reach deeper levels of relaxation than those using non-Qigong techniques. However, when the inducement language of experienced Qigong masters was used with the non-Qigong subjects, they were able to reach deeper levels of relaxation. The results also show that the degree of relaxation in meditation can be objectively assessed and monitored by the 'stress meter' technique employed in this study.

Characterization of nanoindentation-induced residual stresses in human enamel by Raman microspectroscopy

The objective of this research was to investigate nanoindentation-induced residual stresses in human enamel using Raman microspectroscopy and establish if this approach can be used as a stress meter. Healthy human premolars and sintered hydroxyapatite samples were embedded, cut, and the surfaces were polished finely with a 0.05 microm polishing paste before Berkovich and spherical indentations were made with a force of 100 mN. Spectra were collected using a Renishaw Raman InVia reflex microscope equipped with an air-cooled charge-coupled device (CCD) camera. Sample excitation was achieved using either an argon ion laser emitting at 514.5-nm or a NIR diode laser emitting at 830-nm. The residual micro stresses within and surrounding the indentation impressions were monitored by mapping the position of the nu(1)(PO(4)) band of (crystalline) hydroxyapatite. The Raman maps coincided well with the optical micrographs of the samples. Despite the presence of a fluorescence background from the organic component of human enamel, spectra collected using 514.5-nm excitation exhibited more significant shifts in the position of the nu(1)(PO(4)) band than spectra collected using 830-nm excitation. This implies that the former excitation may be a more appropriate excitation for stress detection. It was concluded that Raman microspectroscopy provides a novel high-resolution and non-destructive method for exploring the role of microstructure on the residual stress distribution within natural biocomposites.

Characterization of Residual Stress and Pore Distribution in Sealed Area of Large PDP Panel

Residual stress of front and rear glass substrates and remained pore in sealed areas of AC-PDP panel were measured to see the trend of the characteristics of sealed area as the panel size of PDP increased. For this, we compared these characteristics of 6″, 42″ and 80″ panels, between the corner side & straight line, the vertical & horizontal sides, and the around area of ventilation port & area far from that each. Residual stress was measured by the automatic stress meter and the remained pore was analyzed by non destructive X-ray detector and optical microscope. As a result, we showed the trend of sealed area characteristics according to the magnification of PDP panel.

Variations in earthquake-size distribution across different stress regimes

The earthquake size distribution follows, in most instances, a power law, with the slope of this power law, the 'b value', commonly used to describe the relative occurrence of large and small events (a high b value indicates a larger proportion of small earthquakes, and vice versa). Statistically significant variations of b values have been measured in laboratory experiments, mines and various tectonic regimes such as subducting slabs, near magma chambers, along fault zones and in aftershock zones. However, it has remained uncertain whether these differences are due to differing stress regimes, as it was questionable that samples in small volumes (such as in laboratory specimens, mines and the shallow Earth's crust) are representative of earthquakes in general. Given the lack of physical understanding of these differences, the observation that b values approach the constant 1 if large volumes are sampled was interpreted to indicate that b = 1 is a universal constant for earthquakes in general. Here we show that the b value varies systematically for different styles of faulting. We find that normal faulting events have the highest b values, thrust events the lowest and strike-slip events intermediate values. Given that thrust faults tend to be under higher stress than normal faults we infer that the b value acts as a stress meter that depends inversely on differential stress.

Sustainable structural health monitoring system

Structural health monitoring based maintenance (SHMBM) is a basic engineering effort to collect maintenance information, forming a database system to open to the public or citizens for making decision on a suitable solution strategy to extend a structure's life. Sustainability of the infrastructure structural performance can be assessed by performing continuous structural health monitoring system (SHMS) on the structural deformational properties. The essence of SHMS can be considered to involve measurement, inspection, and assessment of in-service structures on a continuous basis with minimum labor requirement. However, human memory limitation, job changes, imperfections and inability to provide a reliable monitoring system can lead to overly optimistic reports on structural health. Therefore, a sustainable SHMS which fulfill ‘AtoE’ characteristics, i.e. accuracy, benefit, comprehensiveness, durability and ease of operation, is necessary to be consider in designing a reliable long-term SHMS. Generally, those characteristics are difficult to compare quantitatively. Specifically, some qualitatively compared sensory technologies will be reviewed in this paper by comparing the application of load cell, stress meter, strain gauge and EM (elastomagnetic) sensory technology. Furthermore, some innovative sensory technologies such as GPS-based MMS (movement monitoring systems), PDMD (peak displacement memory devices) and FOS (fiber optic sensors), are introduced to monitor global structural movement, partial structural movement and local structural deformational properties at different scales of monitored objects. Copyright © 2005 John Wiley & Sons, Ltd.

The Waiouru, New Zealand, earthquake swarm: Persistent mid crustal activity near an active volcano

A persistent swarm of earthquakes occurs 25 km southeast of the summit of Mt Ruapehu, an active volcano in the central North Island of New Zealand. 319 swarm events recorded during a six‐month seismograph deployment in 2001 have been relocated using the double‐difference technique. The relocated events define a vertical sheet in the mid crust, with most activity 11–21 km deep. Both focal mechanisms and a stress inversion indicate strike‐slip motion for the swarm events, in contrast to the normal faulting seen on a parallel active fault mapped at the surface. Various lines of evidence suggest the swarm is of tectonic origin and due to fluid movement. It currently reflects the regional stress field rather than local stresses related to volcanic activity at Mt Ruapehu. Nevertheless, changes in the activity of the swarm appear to correlate with eruptions, and the swarm appears to have potential as a stress meter for monitoring nearby volcanic activity.