Numerical analysis of the effects induced by normal faults and dip angles on rock bursts

Science.gov (United States)

Jiang, Lishuai; Wang, Pu; Zhang, Peipeng; Zheng, Pengqiang; Xu, Bin

2017-10-01

The study of mining effects under the influences of a normal fault and its dip angle is significant for the prediction and prevention of rock bursts. Based on the geological conditions of panel 2301N in a coalmine, the evolution laws of the strata behaviors of the working face affected by a fault and the instability of the fault induced by mining operations with the working face of the footwall and hanging wall advancing towards a normal fault are studied using UDEC numerical simulation. The mechanism that induces rock burst is revealed, and the influence characteristics of the fault dip angle are analyzed. The results of the numerical simulation are verified by conducting a case study regarding the microseismic events. The results of this study serve as a reference for the prediction of rock bursts and their classification into hazardous areas under similar conditions.

Principles of safe mechanization of operations in seams with hazards of rock and gas outbursts

Energy Technology Data Exchange (ETDEWEB)

Kozlowski, B; Siarkiewicz, R

1976-10-01

Rock burst hazards in Lower Silesia, Poland, and methods for rock burst forecasting are discussed. From 1894 to 1974, 1403 rock bursts occurred in the basin; five were accompanied by emission of methane, the rest with emission of carbon dioxide. Use of the GMA-030 sensor system (type GfG) for detecting increasing emission of carbon dioxide at longwall faces mined by coal plows is analyzed. Site selection for sensors at longwall faces (retreat or advance) in mines with ascending or descending ventilation, with blowing or exhaust ventilation systems and in mine drivage is analyzed. Examples of sensor installation at face ends are evaluated. Recommendations for sensor installation are made. 2 references.

Multi-Index Monitoring and Evaluation on Rock Burst in Yangcheng Mine

OpenAIRE

Tan, Yunliang; Yin, Yanchun; Gu, Shitan; Tian, Zhiwei

2015-01-01

Based on the foreboding information monitoring of the energy released in the developing process of rock burst, prediction system for rock burst can be established. By using microseismic method, electromagnetic radiation method, and drilling bits method, rock burst in Yangcheng Mine was monitored, and a system of multi-index monitoring and evaluation on rock burst was established. Microseismic monitoring and electromagnetic radiation monitoring were early warning method, and drilling bits moni...

Study on Monitoring Rock Burst through Drill Pipe Torque

Directory of Open Access Journals (Sweden)

Zhonghua Li

2015-01-01

Full Text Available This paper presents a new method to identify the danger of rock burst from the response of drill pipe torque during drilling process to overcome many defects of the conventional volume of drilled coal rubble method. It is based on the relationship of rock burst with coal stress and coal strength. Through theoretic analysis, the change mechanism of drill pipe torque and the relationship of drill pipe torque with coal stress, coal strength, and drilling speed are investigated. In light of the analysis, a new device for testing drill pipe torque is developed and a series of experiments is performed under different conditions; the results show that drill pipe torque linearly increases with the increase of coal stress and coal strength; the faster the drilling speed, the larger the drill pipe torque, and vice versa. When monitoring rock burst by drill pipe torque method, the index of rock burst is regarded as a function in which coal stress index and coal strength index are principal variables. The results are important for the forecast of rock burst in coal mine.

Radon and rock bursts in deep mines

International Nuclear Information System (INIS)

Bulashevich, Yu.P.; Utkin, V.I.; Yurkov, A.K.; Nikolaev, V.V.

1996-01-01

Variation fields of radon concentration in time to ascertain stress-strain state of the North Ural bauxite mines have been studied. It is shown that dynamic changes in the stress-strain state of the rocks prior to the rock burst bring about variations in radon concentration in the observation wells. Depending on mutual positioning of the observation points and the rock burst epicenter, the above-mentioned variations differ in principle, reduction of radon concentration in the near zone and its increase in the far zone are observed [ru

Multi-Index Monitoring and Evaluation on Rock Burst in Yangcheng Mine

Directory of Open Access Journals (Sweden)

Yunliang Tan

2015-01-01

Full Text Available Based on the foreboding information monitoring of the energy released in the developing process of rock burst, prediction system for rock burst can be established. By using microseismic method, electromagnetic radiation method, and drilling bits method, rock burst in Yangcheng Mine was monitored, and a system of multi-index monitoring and evaluation on rock burst was established. Microseismic monitoring and electromagnetic radiation monitoring were early warning method, and drilling bits monitoring was burst region identification method. There were three identifying indexes: silence period in microseismic monitoring, rising period of the intensity, and rising period of pulse count in electromagnetic radiation monitoring. If there is identified burst risk in the workface, drilling bits method was used to ascertain the burst region, and then pressure releasing methods were carried out to eliminate the disaster.

Seismic activity and environment protection in rock burst areas

International Nuclear Information System (INIS)

Travnicek, L.; Holecko, J.; Knotek, S.

1993-01-01

The significance is pointed out of seismic activity caused by mining activities in rock burst areas of the Ostrava-Karvinna district. The need is emphasized of the monitoring of the seismic activity at the Czech-Poland border as needed by the Two-party international committee for exploitation of coal supplies on the common border. The adverse effect of rock burst on the surface is documented by examples provided by the Polish party. The technique is described of investigating the DPB seismic polygon, allowing to evaluate the adverse impact of rock burst on the environment. (author) 1 fig., 8 refs

Theoretical Calculation and Analysis on the Composite Rock-Bolt Bearing Structure in Burst-Prone Ground

Directory of Open Access Journals (Sweden)

Liang Cheng

2015-01-01

Full Text Available Given the increase in mining depth and intensity, tunnel failure as a result of rock burst has become an important issue in the field of mining engineering in China. Based on the Composite Rock-Bolt Bearing Structure, which is formed due to the interaction of the bolts driven into the surrounding rock, this paper analyzes a rock burst prevention mechanism, establishes a mechanical model in burst-prone ground, deduces the strength calculation formula of the Composite Rock-Bolt Bearing Structure in burst-prone ground, and confirms the rock burst prevention criterion of the Composite Rock-Bolt Bearing Structure. According to the rock burst prevention criterion, the amount of the influence on rock burst prevention ability from the surrounding rock parameters and bolt support parameters is discussed.

76 FR 28460 - Agency Information Collection Activities; Submission for OMB Review; Comment Request; Rock Burst...

Science.gov (United States)

2011-05-17

... for OMB Review; Comment Request; Rock Burst Control Plan--Pertains to Underground Metal and Nonmetal... develop a rock burst plan within 90 days after a rock burst has been experienced. Stress data are normally... Administration (MSHA) sponsored information collection request (ICR) titled, ``Burst Control Plan--Pertains to...

Study on Monitoring Rock Burst through Drill Pipe Torque

OpenAIRE

Zhonghua Li; Liyuan Zhu; Wanlei Yin; Yanfang Song

2015-01-01

This paper presents a new method to identify the danger of rock burst from the response of drill pipe torque during drilling process to overcome many defects of the conventional volume of drilled coal rubble method. It is based on the relationship of rock burst with coal stress and coal strength. Through theoretic analysis, the change mechanism of drill pipe torque and the relationship of drill pipe torque with coal stress, coal strength, and drilling speed are investigated. In light of the a...

Structural bursts produced by high energy muons in the rock

International Nuclear Information System (INIS)

Honda, K.; Takahashi, T.; Teramoto, Y.; Higashi, S.; Ozaki, S.

1975-01-01

Lateral structures of bursts produced by high energy muons in the rock have been observed at a depth 30 mw. e. underground by use of two layers of proportional counters. The running times were 7940 hr. The number of structural bursts observed, which have two cores in the both layers ( 1 >= 200, N 2 >= 20 particles) is 110, 1.6% of total events. These structural bursts have two types; 1) incident directions of two cores are parallel, 2) two cores intersect in the rock within 2 m above the roof of the tunnel. The events of this 2) type have large transverse momentum. (orig.) [de

Theoretical Calculation and Analysis on the Composite Rock-Bolt Bearing Structure in Burst-Prone Ground

OpenAIRE

Cheng, Liang; Zhang, Yidong; Ji, Ming; Cui, Mantang; Zhang, Kai; Zhang, Minglei

2015-01-01

Given the increase in mining depth and intensity, tunnel failure as a result of rock burst has become an important issue in the field of mining engineering in China. Based on the Composite Rock-Bolt Bearing Structure, which is formed due to the interaction of the bolts driven into the surrounding rock, this paper analyzes a rock burst prevention mechanism, establishes a mechanical model in burst-prone ground, deduces the strength calculation formula of the Composite Rock-Bolt Bearing Structur...

Pattern Recognition of Signals for the Fault-Slip Type of Rock Burst in Coal Mines

Directory of Open Access Journals (Sweden)

X. S. Liu

2015-01-01

Full Text Available The fault-slip type of rock burst is a major threat to the safety of coal mining, and effectively recognizing its signals patterns is the foundation for the early warning and prevention. At first, a mechanical model of the fault-slip was established and the mechanism of the rock burst induced by the fault-slip was revealed. Then, the patterns of the electromagnetic radiation, acoustic emission (AE, and microseismic signals in the fault-slip type of rock burst were proposed, in that before the rock burst occurs, the electromagnetic radiation intensity near the sliding surface increases rapidly, the AE energy rises exponentially, and the energy released by microseismic events experiences at least one peak and is close to the next peak. At last, in situ investigations were performed at number 1412 coal face in the Huafeng Mine, China. Results showed that the signals patterns proposed are in good agreement with the process of the fault-slip type of rock burst. The pattern recognition can provide a basis for the early warning and the implementation of relief measures of the fault-slip type of rock burst.

Assessment of the rock burst potential in basalt at the Hanford Site

International Nuclear Information System (INIS)

Blake, W.

1984-01-01

The phenomenon of rock bursting has been reviewed and specific case histories have been presented, along with the measures most commonly taken to minimize their occurrence and effects. A combination of high stresses and brittle rock types is necessary to initiate bursting but is not sufficient to do so unless other parameters are present (i.e. an extensive mined-out area, a high extraction ratio, and geologic structures, or discontinuities). Since none of these parameters will result from the construction of a deep underground nuclear waste repository in basalt at the Hanford Site in Southeastern Washington, rock bursting should not occur either during or after this construction. 75 refs., 35 figs., 2 tabs

Comparative Assessment to Danger of Rock Bursts Origin in Different Conditions of Mining in OKR

Directory of Open Access Journals (Sweden)

Bukovanský Stanislav

1998-03-01

Full Text Available For this comparative assessment to factual possibilities of balance failure it is necessary to investigate a character and possible changes in individual elements of the system "rock - time", as well as their mutual interaction with rock burst origin and their course. Research observations after burst show that the influence of strong energy after rock burst, into the overlying impact click is present in a coal seam due to its higher pressure to a face (when compared with a relevant pressure answerring a final deformation after such burst. Certain "avalanche" in failures after burst could be characterized as a certain rank of individual particular phenomena.

Review on the prevailing methods for the prediction of potential rock burst / rock spalling in tunnels

OpenAIRE

Panthi, Krishna Kanta

2017-01-01

Rock burst / rock spalling is among the prevailing stability challenges, which can be met while tunneling through hard rock mass. Especially, this is very relevant for the mountainous country like Norway where hard rock is dominating and many road, railway and hydropower tunnels have to be aligned deep into the mountain with steep valley slope topography. Tunnels passing beneath deep rock cover (overburden), in general, are subjected to high in-situ stresses. If the rock mass is relatively un...

76 FR 3178 - Proposed Extension of Existing Information Collection; Rock Burst Control Plan, Metal and...

Science.gov (United States)

2011-01-19

... Extension of Existing Information Collection; Rock Burst Control Plan, Metal and Nonmetal Mines AGENCY: Mine... extension of the information collection for 30 CFR 57.3461 Rock Bursts. DATES: All comments must be received... contains the request for an extension of the existing collection of information in 30 CFR 57.3461 Rock...

Comparative Assessment to Danger of Rock Bursts Origin in Different Conditions of Mining in OKR

OpenAIRE

Bukovanský Stanislav

1998-01-01

For this comparative assessment to factual possibilities of balance failure it is necessary to investigate a character and possible changes in individual elements of the system "rock - time", as well as their mutual interaction with rock burst origin and their course. Research observations after burst show that the influence of strong energy after rock burst, into the overlying impact click is present in a coal seam due to its higher pressure to a face (when compared with a relevant pressure...

Extraction of microseismic waveforms characteristics prior to rock burst using Hilbert-Huang transform

Science.gov (United States)

Li, Xuelong; Li, Zhonghui; Wang, Enyuan; Feng, Junjun; Chen, Liang; Li, Nan; Kong, Xiangguo

2016-09-01

This study provides a new research idea concerning rock burst prediction. The characteristics of microseismic (MS) waveforms prior to and during the rock burst were studied through the Hilbert-Huang transform (HHT). In order to demonstrate the advantage of the MS features extraction based on HHT, the conventional analysis method (Fourier transform) was also used to make a comparison. The results show that HHT is simple and reliable, and could extract in-depth information about the characteristics of MS waveforms. About 10 days prior to the rock burst, the main frequency of MS waveforms transforms from the high-frequency to low-frequency. What's more, the waveforms energy also presents accumulation characteristic. Based on our study results, it can be concluded that the MS signals analysis through HHT could provide valuable information about the coal or rock deformation and fracture.

Case Studies of Rock Bursts Under Complicated Geological Conditions During Multi-seam Mining at a Depth of 800 m

Science.gov (United States)

Zhao, Tong-bin; Guo, Wei-yao; Tan, Yun-liang; Yin, Yan-chun; Cai, Lai-sheng; Pan, Jun-feng

2018-05-01

A serious rock burst ("4.19" event) occurred on 19 April 2016 in the No. 4 working face of the No. 10 coal seam in Da'anshan Coal Mine, Jingxi Coalfield. According to the China National Seismological Network, a 2.7 magnitude earthquake was simultaneously recorded in this area. The "4.19" event resulted in damage to the entire longwall face and two gateways that were 105 m in long. In addition, several precursor bursts and mine earthquakes had occurred between October 2014 and April 2016 in the two uphill roadways and the No. 4 working face. In this paper, the engineering geological characteristics and in situ stress field are provided, and then the rock burst distributions are introduced. Next, the temporal and spatial characteristics, geological and mining conditions, and other related essential information are reviewed in detail. The available evidence and possible explanations for the rock burst mechanisms are also presented and discussed. Based on the description and analysis of these bursts, a detailed classification system of rock burst mechanisms is established. According to the main causes and different disturbance stresses (i.e., high/low disturbance stresses and far-field/near-field high disturbance stresses), there are a total of nine types of rock bursts. Thus, some guidelines for controlling or mitigating different types of rock bursts are provided. These experiences and strategies not only provide an essential reference for understanding the different rock burst mechanisms, but also build a critical foundation for selecting mitigation measures and optimizing the related technical parameters during mining or tunnelling under similar conditions.

Investigation on the Vibration Effect of Shock Wave in Rock Burst by In Situ Microseismic Monitoring

Directory of Open Access Journals (Sweden)

Mingshi Gao

2018-01-01

Full Text Available Rock burst is a physical explosion associated with enormous damage at a short time. Due to the complicity of mechanics of rock burst in coal mine roadway, the direct use of traditional investigation method applied in tunnel is inappropriate since the components of surrounding rock are much more complex in underground than that of tunnel. In addition, the reliability of the results obtained through these methods (i.e., physical simulation, theoretical analysis, and monitoring in filed application is still not certain with complex geological conditions. Against this background, present experimental study was first ever conducted at initial site to evaluate the effect of shock wave during the rock burst. TDS-6 microseismic monitoring system was set up in situ to evaluate the propagation of shock wave resulting in microexplosions of roadway surrounding rock. Various parameters including the distance of epicentre and the characteristic of response have been investigated. Detailed test results revealed that (1 the shock wave attenuated exponentially with the increase of the distance to seismic source according to the equation of E=E0e-ηl; particularly, the amplitude decreased significantly after being 20 m apart from explosive resource and then became very weak after being 30 m apart from the seismic source; (2 the response mechanics are characteristic with large scatter based on the real location of surrounding rock despite being at the same section. That is, the surrounding rock of floor experienced serious damage, followed by ribs, the roof, and the humeral angles. This in situ experimental study also demonstrated that microseismic monitoring system can be effectively used in rock burst through careful setup and data investigation. The proposed in situ monitoring method has provided a new way to predict rock burst due to its simple instalment procedure associated with direct and reasonable experimental results.

An ARMA prediction model for electromagnetic radiation data preceeding a rock burst

Energy Technology Data Exchange (ETDEWEB)

Liu Zhen-tang; Liu Xiao-fei; Wang En-yuan [China University of Mining & Technology, Xuzhou (China). School of Safety Engineering

2009-03-15

SAS statistical analysis software was used to test the randomness of electromagnetic radiation (EMR) observed during the '1.12 rock burst' of the number 237 working face in the Nanshan coal mine. An auto-regressive-moving-average (ARMA) model was fitted to the EMR data and used to forecast twelve observations into the future. The results show that the rock burst EMR data are non-white noise, stationary and can be fitted with an AR(3) model. Comparing the model EMR values to the real data, the similarity degree is about 66%. An ARMA model can use data preceding an event to describe changes in the EMR trends quantitatively. 10 refs., 4 figs., 4 tabs.

Control Mechanism of Rock Burst in the Floor of Roadway Driven along Next Goaf in Thick Coal Seam with Large Obliquity Angle in Deep Well

Directory of Open Access Journals (Sweden)

Yunhai Cheng

2015-01-01

Full Text Available This paper deals with the theoretical aspects combined with stress analysis over the floor strata of coal seam and the calculation model for the stress on the coal floor. Basically, this research presents the relevant results obtained for the rock burst prevention in the floor of roadway driven along next goaf in the exploitation of thick coal seam with large obliquity in deep well and rock burst tendency. The control mechanism of rock burst in the roadway driven along next goaf is revealed in the present work. That is, the danger of rock burst can be removed by changing the stress environment for the energy accumulation of the floor and by reducing the impact on the roadway floor from the strong dynamic pressure. This result can be profitable being used at the design stage of appropriate position of roadway undergoing rock burst tendency in similar conditions. Based on the analysis regarding the control mechanism, this paper presents a novel approach to the prevention of rock burst in roadway floor under the above conditions. That is, the return airway is placed within the goaf of the upper working face that can prevent the rock burst effectively. And in this way, mining without coal pillar in the thick coal seam with large obliquity and large burial depth (over a thousand meters is realized. Practice also proves that the rock burst in the floor of roadway driven along next goaf is controlled and solved.

Rock slope instabilities in Norway: First systematic hazard and risk classification of 22 unstable rock slopes

Science.gov (United States)

Böhme, Martina; Hermanns, Reginald L.; Oppikofer, Thierry; Penna, Ivanna

2016-04-01

Unstable rock slopes that can cause large failures of the rock-avalanche type have been mapped in Norway for almost two decades. Four sites have earlier been characterized as high-risk objects based on expertise of few researchers. This resulted in installing continuous monitoring systems and set-up of an early-warning system for those four sites. Other unstable rock slopes have not been ranked related to their hazard or risk. There are ca. 300 other sites known of which 70 sites were installed for periodic deformation measurements using multiple techniques (Global Navigation Satellite Systems, extensometers, measurement bolts, and others). In 2012 a systematic hazard and risk classification system for unstable rock slopes was established in Norway and the mapping approach adapted to that in 2013. Now, the first 22 sites were classified for hazard, consequences and risk using this classification system. The selection of the first group of sites to be classified was based on an assumed high hazard or risk and importance given to the sites by Norwegian media and the public. Nine of the classified 22 unstable rock slopes are large sites that deform inhomogeneously or are strongly broken up in individual blocks. This suggests that different failure scenarios are possible that need to be analyzed individually. A total of 35 failure scenarios for those nine unstable rock slopes were considered. The hazard analyses were based on 9 geological parameters defined in the classification system. The classification system will be presented based on the Gamanjunni unstable rock slope. This slope has a well developed back scarp that exposes 150 m preceding displacement. The lateral limits of the unstable slope are clearly visible in the morphology and InSAR displacement data. There have been no single structures observed that allow sliding kinematically. The lower extend of the displacing rock mass is clearly defined in InSAR data and by a zone of higher rock fall activity. Yearly

Determining air distribution during outbursts of gases and rocks

Energy Technology Data Exchange (ETDEWEB)

Struminski, A; Sikora, M; Urbanski, J [Politechnika Wroclawska (Poland). Instytut Gornictwa

1989-01-01

Discusses use of the KPW-1 iterative and autocorrelation method developed by A. Struminski for forecasting effects of rock bursts on ventilation systems of underground coal mines with increased content of methane or carbon dioxide in coal seams and adjacent rock strata. The method is used for prediction of air flow changes caused by a rock burst accompanied by violent outburst of gases. Directions of air flow, flow rate and concentration of gases emitted from surrounding strata to mine workings are predicted. On the basis of this prediction concentration of gases from a coal outburst is determined for any point in a ventilation network. The prediction method is used for assessing hazards for coal mines during and after a rock burst. Use of the method is explained on the example of the Thorez and Walbrzych coal mines. Computer programs developed for ODRA and IBM/XT computers are discussed. 6 refs.

Quantitative rock-fall hazard and risk assessment for Yosemite Valley, California

Science.gov (United States)

Stock, G. M.; Luco, N.; Collins, B. D.; Harp, E.; Reichenbach, P.; Frankel, K. L.

2011-12-01

Rock falls are a considerable hazard in Yosemite Valley, California with more than 835 rock falls and other slope movements documented since 1857. Thus, rock falls pose potentially significant risk to the nearly four million annual visitors to Yosemite National Park. Building on earlier hazard assessment work by the U.S. Geological Survey, we performed a quantitative rock-fall hazard and risk assessment for Yosemite Valley. This work was aided by several new data sets, including precise Geographic Information System (GIS) maps of rock-fall deposits, airborne and terrestrial LiDAR-based point cloud data and digital elevation models, and numerical ages of talus deposits. Using Global Position Systems (GPS), we mapped the positions of over 500 boulders on the valley floor and measured their distance relative to the mapped base of talus. Statistical analyses of these data yielded an initial hazard zone that is based on the 90th percentile distance of rock-fall boulders beyond the talus edge. This distance was subsequently scaled (either inward or outward from the 90th percentile line) based on rock-fall frequency information derived from a combination of cosmogenic beryllium-10 exposure dating of boulders beyond the edge of the talus, and computer model simulations of rock-fall runout. The scaled distances provide the basis for a new hazard zone on the floor of Yosemite Valley. Once this zone was delineated, we assembled visitor, employee, and resident use data for each structure within the hazard zone to quantitatively assess risk exposure. Our results identify areas within the new hazard zone that may warrant more detailed study, for example rock-fall susceptibility, which can be assessed through examination of high-resolution photographs, structural measurements on the cliffs, and empirical calculations derived from LiDAR point cloud data. This hazard and risk information is used to inform placement of existing and potential future infrastructure in Yosemite Valley.

An investigation of fine structure of the bursts produced by muons in the rock

International Nuclear Information System (INIS)

Higashi, S.; Kajino, F.; Nakashita, M.; Osaki, S.; Takahashi, T.; Yamamoto, S.

1981-01-01

Two dimensional lateral structures of the shower particles in the bursts, produced by high energy muons in the rock, have been studied by using the four layers of proportional counters. The mean lateral distributions measured fit well to those of Monte Carlo simulation of electromagnetic cascade showers. The distributions of reduced chi 2 which correspond to the fluctuations of each lateral distribution from the mean value show that the rates of the events giving high chi 2 for the data are somewhat greater than those expected from the simulation. The rates of these excesses to the total events are about 10% in the burst size range 578 - 8277 particles which are induced by the muons in the energy range 714 - 9900 GeV. These excesses could be explained by the contributions from the muon nuclear interactions in the rock

Rock-fall Hazard In The Yosemite Valley, California

Science.gov (United States)

Guzzetti, F.; Reichenbach, P.; Wieczorek, G. F.

Rock slides and rock falls are the most frequent slope movements in Yosemite Na- tional Park, California. In historical time (1851-2001), more than 400 rock falls and rock slides have been documented in the valley, and some of them have been mapped in detail. We present the preliminary results of an attempt to assess rockfall hazard in the Yosemite Valley using STONE, a 3-dimensional rock-fall simulation computer program. The software computes 3-dimensional rock-fall trajectories starting from a digital terrain model (DTM), the location of rock-fall release points (source areas), and maps of the dynamic rolling coefficient and of the coefficients of normal and tan- gential energy restitution. For each DTM cell the software also calculates the number of rock falls passing through the cell, the maximum rock-fall velocity and the maxi- mum flying height. For the Yosemite Valley, a DTM with a ground resolution of 10 x 10 m was prepared using topographic contour lines from USGS 1:24,000-scale maps. Rock-fall release points were identified as DTM cells having a slope steeper than 60 degrees, an assumption based on the location of historical rock falls. Maps of the nor- mal and tangential energy restitution coefficients and of the rolling friction coefficient were produced from a surficial geologic map. The availability of historical rock falls mapped in detail allowed us to check the computer program performance and to cali- brate the model parameters. Visual and statistical comparison of the model results with the mapped rock falls confirmed the accuracy of the model. The model results are also compared with a geomorphic assessment of rock-fall hazard based on potential energy referred to as a "shadow angle" approach, recently completed for the Yosemite Valley.

Molecular cloning of rock bream (Oplegnathus fasciatus) tumor necrosis factor-alpha and its effect on the respiratory burst activity of phagocytes.

Science.gov (United States)

Kim, Min Sun; Hwang, Yoon Jung; Yoon, Ki Joon; Zenke, Kosuke; Nam, Yoon Kwon; Kim, Sung Koo; Kim, Ki Hong

2009-11-01

Rock bream (Oplegnathus fasciatus) tumor necrosis factor-alpha (rbTNF-alpha) gene was cloned, recombinantly produced, and the effect of the recombinant rbTNF-alpha on the respiratory burst activity of rock bream phagocytes was analyzed. Structurally, genomic DNA of rbTNF-alpha was comprised with four exons and three introns, and deduced amino acid sequence of its cDNA possessed the TNF family signature, a transmembrane domain, a protease cleavage site, and two cysteine residues, which are the typical characteristics of TNF-alpha gene in mammals and fish. The chemiluminescent (CL) response of rock bream phagocytes was significantly enhanced by pre-incubation with recombinant rbTNF-alpha, when opsonized zymosan was used as a stimulant of the respiratory burst. However, CL enhancing effect of the recombinant rbTNF-alpha was very weak when the respiratory burst activity of phagocytes was triggered with phorbol-12-myristate-13-acetate (PMA) instead of zymosan. These results suggest that rock bream TNF-alpha might have an ability to prime the respiratory burst activity of phagocytes against receptor-mediated phagocytosis inducing stimulants, such as zymosan, but have little ability against stimulants not accompanying receptor-mediated phagocytosis.

Quantitative rock-fall hazard and risk assessment for Yosemite Valley, Yosemite National Park, California

Science.gov (United States)

Stock, Greg M.; Luco, Nicolas; Collins, Brian D.; Harp, Edwin L.; Reichenbach, Paola; Frankel, Kurt L.

2014-01-01

Rock falls are common in Yosemite Valley, California, posing substantial hazard and risk to the approximately four million annual visitors to Yosemite National Park. Rock falls in Yosemite Valley over the past few decades have damaged structures and caused injuries within developed regions located on or adjacent to talus slopes highlighting the need for additional investigations into rock-fall hazard and risk. This assessment builds upon previous investigations of rock-fall hazard and risk in Yosemite Valley and focuses on hazard and risk to structures posed by relatively frequent fragmental-type rock falls as large as approximately 100,000 (cubic meters) in volume.

Methodology of reducing rock bump hazard during room and rillar mining of North Ural deep bauxite deposits

Directory of Open Access Journals (Sweden)

Д. В. Сидоров

2017-03-01

Full Text Available The article describes practical experience of using room and pillar mining (RAPM under conditions of deep horizons and dynamic overburden pressure. It was identified that methods of rock pressure control efficient at high horizons do not meet safety requirements when working at existing depths, that is explained by changes in geodynamic processes during mining. With deeper depth, the geodynamic processes become more intensive and number of pillar and roof failures increase. When working at 800 m the breakage of mine structures became massive and unpredictable, which paused a question of development and implementation of tools for compliance assessment of used elements of RAPM and mining, geological, technical and geodynamic conditions of North Ural bauxite deposits and further development of guidelines for safe mining under conditions of deep horizons and dynamic rock pressure.It describes reasons of mine structure failures in workings depending on natural and man-caused factors, determines possible hazards and objects of geomechanic support. It also includes compliance assessment of tools used for calculations of RAPM structures, forecast and measures for rock tectonic bursts at mines of OAO “Sevuralboksitruda” (SUBR. It describes modernization and development of new geomechanic support of RAPM considering natural and technogenic hazards. The article presents results of experimental testing of new parameters of RAPM construction elements of SUBR mines. It has data on industrial implementation of developed regulatory and guideline documents at these mines for identification of valid parameters of RAPM elements at deep depths.

Lined rock caverns for the storage of hazardous waste

International Nuclear Information System (INIS)

Semprich, S.; Speidel, S.R.; Schneider, H.J.

1987-01-01

For reasons of environmental protection the storage of hazardous waste in unlined rock caverns is possible to a very limited extent only. Therefore, the authors have recently developed technologies for the lining and sealing of rock caverns. In the process, sealing systems of synthetic materials or metals have proved suitable. Synthetic materials can be used in the form of either sheets or coatings with various materials such as epoxy resins, polyethylenes etc. being used. Metal sealings consist of thin sheets or foils which are either welded or bonded. In either case, the structural design must provide for a leakage control possibility. The article describes the design principles, the structural and operational aspects as well as the control measures with regard to the planning and execution of lined rock caverns for the storage of hazardous waste

Prevention and forecasting of coal, rock and gas bursts in mines of Donets Coal Basin in USSR

Energy Technology Data Exchange (ETDEWEB)

Swidzinski, A

1977-11-01

Coal and methane bursts as well as sandstone and methane bursts are typical for the Donets Coal Basin. The most effective way of forecasting coal and methane bursts is drilling holes (3.5 m long, 45 mm diameter) and measuring the initial speed of gas outflow (5 litres/min gas outflow is a critical value). Additional parameters in this method are: coal firmness and porosity as well as thickness of coal bed. Forecasting sandstone and gas bursts is based on taking rock samples while drilling. When a sample 1 meter long consists of 30 to 40 so called discs, the danger of outburst is substantial, with the decreasing number of discs the probability of bursts also decreases. The following methods of prevention are used in the Donets Coal Basin: preparatory extraction of a layer protecting another layer below or above, where there is a danger of gas burst. This method is effective in 50% of all cases. Other methods include: filling coal beds with water under high pressure (average norm 25 1 water per 1 m

Methods for the risk assessment of rock bursts under the condition of the Upper Silesian coal basin; Methoden zur Bewertung des Risikos von Gebirgsschlaegen unter Bedingungen des oberschlesischen Kohlebeckens

Energy Technology Data Exchange (ETDEWEB)

Myszkowski, Jacek [Forschungsanstalt fuer Gebirgsschlaege und Gebirgsmechanik BT, Katowice (Poland). Hauptinst. fuer Bergbau

2013-06-15

The assessment of the risk of rock burst in underground coal mines is associated with the forecasting, assessment and management of risks. The contribution under consideration presents methods for the risk assessment and prevention of rock bursts.

Lidar-Based Rock-Fall Hazard Characterization of Cliffs

Science.gov (United States)

Collins, Brian D.; Greg M.Stock,

2017-01-01

Rock falls from cliffs and other steep slopes present numerous challenges for detailed geological characterization. In steep terrain, rock-fall source areas are both dangerous and difficult to access, severely limiting the ability to make detailed structural and volumetric measurements necessary for hazard assessment. Airborne and terrestrial lidar survey methods can provide high-resolution data needed for volumetric, structural, and deformation analyses of rock falls, potentially making these analyses straightforward and routine. However, specific methods to collect, process, and analyze lidar data of steep cliffs are needed to maximize analytical accuracy and efficiency. This paper presents observations showing how lidar data sets should be collected, filtered, registered, and georeferenced to tailor their use in rock fall characterization. Additional observations concerning surface model construction, volumetric calculations, and deformation analysis are also provided.

Analysis of Precursors Prior to Rock Burst in Granite Tunnel Using Acoustic Emission and Far Infrared Monitoring

OpenAIRE

Liang, Zhengzhao; Liu, Xiangxin; Zhang, Yanbo; Tang, Chunan

2013-01-01

To understand the physical mechanism of the anomalous behaviors observed prior to rock burst, the acoustic emission (AE) and far infrared (FIR) techniques were applied to monitor the progressive failure of a rock tunnel model subjected to biaxial stresses. Images of fracturing process, temperature changes of the tunnel, and spatiotemporal serials of acoustic emission were simultaneously recorded during deformation of the model. The b-value derived from the amplitude distribution data of AE wa...

Quantitative assessment of diffuse rock fall hazard along a cliff foot

Directory of Open Access Journals (Sweden)

D. Hantz

2011-05-01

Full Text Available Many works have shown that the relation between rock fall frequency and volume is well fitted by a power law. Based on this relation, a new method is presented which allows estimating the fall frequency and probability for a wall section in a homogenous cliff, considering all possible rock fall volumes. The hazard for an element located at the foot of the cliff, with a minimal energy, is also estimated. The method has been applied to an itinerary, for which the human risk has also been estimated. Rock fall inventories featuring the location, date, and volume of the falls and the dimensions of the fallen compartments (width, length, and thickness are needed for better estimating of hazard and risk.

Prospect of shale gas recovery enhancement by oxidation-induced rock burst

Directory of Open Access Journals (Sweden)

Lijun You

2017-11-01

Full Text Available By horizontal well multi-staged fracturing technology, shale rocks can be broken to form fracture networks via hydraulic force and increase the production rate of shale gas wells. Nonetheless, the fracturing stimulation effect may be offset by the water phase trapping damage caused by water retention. In this paper, a technique in transferring the negative factor of fracturing fluid retention into a positive factor of changing the gas existence state and facilitating shale cracking was discussed using the easy oxidation characteristics of organic matter, pyrite and other minerals in shale rocks. Furthermore, the prospect of this technique in tackling the challenges of large retention volume of hydraulic fracturing fluid in shale gas reservoirs, high reservoir damage risks, sharp production decline rate of gas wells and low gas recovery, was analyzed. The organic matter and pyrite in shale rocks can produce a large number of dissolved pores and seams to improve the gas deliverability of the matrix pore throats to the fracture systems. Meanwhile, in the oxidation process, released heat and increased pore pressure will make shale rock burst, inducing expansion and extension of shale micro-fractures, increasing the drainage area and shortening the gas flowing path in matrix, and ultimately, removing reservoir damage and improving gas recovery. To sum up, the technique discussed in the paper can be used to “break” shale rocks via hydraulic force and to “burst” shale rocks via chemical oxidation by adding oxidizing fluid to the hydraulic fracturing fluid. It can thus be concluded that this method can be a favorable supplementation for the conventional hydraulic fracturing of shale gas reservoirs. It has a broad application future in terms of reducing costs and increasing profits, maintaining plateau shale gas production and improving shale gas recovery.

CORRELATIONS ON THE MINING WORKINGS DRIVE BY BLASTING UNDER THE IMPACT OF ROCK BURSTS

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Vladimir Abramović

1989-12-01

Full Text Available Comprehensive testing blastings on ihe development faces in the areas with bursts have been performed in the coal mine of Labin. The obtained results prove d isti ne t relations in exp!osive consumption (kg/m3 and in the dimension of faces' cross-section (m2, The impact of the work face structure (coal: stone bas been distinguished for each blasting, too. Chaoges depending on the brand of esplosive as well as those ones considering the advance of mining activitv have also been observed. It has been proved in the pro-duction process of the mine, that the results with increased work productivity are obtained in spite of the fact that miners are exposed to danger of rock bursts (the paper is published in Croatian.

The influence of normal fault on initial state of stress in rock mass

Directory of Open Access Journals (Sweden)

Tajduś Antoni

2016-03-01

Full Text Available Determination of original state of stress in rock mass is a very difficult task for rock mechanics. Yet, original state of stress in rock mass has fundamental influence on secondary state of stress, which occurs in the vicinity of mining headings. This, in turn, is the cause of the occurrence of a number of mining hazards, i.e., seismic events, rock bursts, gas and rock outbursts, falls of roof. From experience, it is known that original state of stress depends a lot on tectonic disturbances, i.e., faults and folds. In the area of faults, a great number of seismic events occur, often of high energies. These seismic events, in many cases, are the cause of rock bursts and damage to the constructions located inside the rock mass and on the surface of the ground. To estimate the influence of fault existence on the disturbance of original state of stress in rock mass, numerical calculations were done by means of Finite Element Method. In the calculations, it was tried to determine the influence of different factors on state of stress, which occurs in the vicinity of a normal fault, i.e., the influence of normal fault inclination, deformability of rock mass, values of friction coefficient on the fault contact. Critical value of friction coefficient was also determined, when mutual dislocation of rock mass part separated by a fault is impossible. The obtained results enabled formulation of a number of conclusions, which are important in the context of seismic events and rock bursts in the area of faults.

The influence of normal fault on initial state of stress in rock mass

Science.gov (United States)

Tajduś, Antoni; Cała, Marek; Tajduś, Krzysztof

2016-03-01

Determination of original state of stress in rock mass is a very difficult task for rock mechanics. Yet, original state of stress in rock mass has fundamental influence on secondary state of stress, which occurs in the vicinity of mining headings. This, in turn, is the cause of the occurrence of a number of mining hazards, i.e., seismic events, rock bursts, gas and rock outbursts, falls of roof. From experience, it is known that original state of stress depends a lot on tectonic disturbances, i.e., faults and folds. In the area of faults, a great number of seismic events occur, often of high energies. These seismic events, in many cases, are the cause of rock bursts and damage to the constructions located inside the rock mass and on the surface of the ground. To estimate the influence of fault existence on the disturbance of original state of stress in rock mass, numerical calculations were done by means of Finite Element Method. In the calculations, it was tried to determine the influence of different factors on state of stress, which occurs in the vicinity of a normal fault, i.e., the influence of normal fault inclination, deformability of rock mass, values of friction coefficient on the fault contact. Critical value of friction coefficient was also determined, when mutual dislocation of rock mass part separated by a fault is impossible. The obtained results enabled formulation of a number of conclusions, which are important in the context of seismic events and rock bursts in the area of faults.

Develop and implement preconditioning techniques to control face ejection rockbursts for safer mining in seismically hazardous areas

CSIR Research Space (South Africa)

Toper, AZ

1998-01-01

Full Text Available This research report discusses the development of preconditioning techniques to control face bursts, for safer mining in seismically hazardous areas. Preconditioning involves regularly setting off carefully tailored blasts in the fractured rock...

Application of in-situ stress measurement on bursts disasters of rock and CO{sub 2} in coal mine

Energy Technology Data Exchange (ETDEWEB)

Lian-Jie Wang; Dong-Sheng Sun; Li-Rong Zhang; Guan-Wu Zhou [Ministry of Land and Resources, Beijing (China)

2009-01-15

For the purpose of reduction and prevention of rock burst disasters and CO{sub 2}, measurements were made of in-situ stress and mechanical parameters of rock in Yingcheng mine. Geological structure and gas measurements were studied and the stress field was simulated and distribution of stress field was obtained in this area. On the basis of the study, the danger areas of rockbursts and CO{sub 2} were predicted. Preventive measures were suggested to decrease gas pressure and in-situ stress in front of the working face with advance boreholes relieving blasting. 12 refs., 5 figs., 1 tab.

A hazard and risk classification system for catastrophic rock slope failures in Norway

Science.gov (United States)

Hermanns, R.; Oppikofer, T.; Anda, E.; Blikra, L. H.; Böhme, M.; Bunkholt, H.; Dahle, H.; Devoli, G.; Eikenæs, O.; Fischer, L.; Harbitz, C. B.; Jaboyedoff, M.; Loew, S.; Yugsi Molina, F. X.

2012-04-01

The Geological Survey of Norway carries out systematic geologic mapping of potentially unstable rock slopes in Norway that can cause a catastrophic failure. As catastrophic failure we describe failures that involve substantial fragmentation of the rock mass during run-out and that impact an area larger than that of a rock fall (shadow angle of ca. 28-32° for rock falls). This includes therefore rock slope failures that lead to secondary effects, such as a displacement wave when impacting a water body or damming of a narrow valley. Our systematic mapping revealed more than 280 rock slopes with significant postglacial deformation, which might represent localities of large future rock slope failures. This large number necessitates prioritization of follow-up activities, such as more detailed investigations, periodic monitoring and permanent monitoring and early-warning. In the past hazard and risk were assessed qualitatively for some sites, however, in order to compare sites so that political and financial decisions can be taken, it was necessary to develop a quantitative hazard and risk classification system. A preliminary classification system was presented and discussed with an expert group of Norwegian and international experts and afterwards adapted following their recommendations. This contribution presents the concept of this final hazard and risk classification that should be used in Norway in the upcoming years. Historical experience and possible future rockslide scenarios in Norway indicate that hazard assessment of large rock slope failures must be scenario-based, because intensity of deformation and present displacement rates, as well as the geological structures activated by the sliding rock mass can vary significantly on a given slope. In addition, for each scenario the run-out of the rock mass has to be evaluated. This includes the secondary effects such as generation of displacement waves or landslide damming of valleys with the potential of later

Tunnel Design by Rock Mass Classifications

Science.gov (United States)

1990-01-01

Engineering," revised second edition, Institution of Mining and Metallurgy, London, 1977, pp 113-115 and 150-192. 42. Selmer - Olsen , R., and Broch, E...to wall when a)/03 > 10, re- stability) ................ 10-5 0.66-0.33 0.5-2.0 duce oc and ot to L. Mild rock burst (massive 0.6 cc and 0.6 on rock ...5-2.5 0.33-0.16 5-10 where: 0 c = uncon-fined compression M. Heavy rock burst (massive strength, at = rock

Specific activity and hazards of Archeozoic-Cambrian rock samples collected from the Weibei area of Shaanxi (China))

International Nuclear Information System (INIS)

Xinwei, L.; Lingqing, W.; Xiaodan, J.; Leipeng, Y.; Gelian, D.

2006-01-01

The present work deals with the radioactivity of the Archeozoic-Cambrian rocks of the Weibei area, Shaanxi (China)). A total of 45 rock samples of Archeozoic-Cambrian strata were investigated. The radionuclides of the samples, in Bq kg -1 , have been measured using Na(I)Tl gamma-ray spectrometer. The concentration of 226 Ra, 232 Th and 40 K in the Archeozoic-Cambrian rock samples range from 12.3 to 55.4, from 2.4 to 98.7 and from 58.6 to 1613.3 Bq kg -1 , respectively. The measured activity concentrations for these radionuclides were compared with the typical world average values. To assess the radiological hazard of the natural radioactivity in the samples, the radium equivalent activity, the external hazard index, internal hazard index and the annual gonadal dose equivalent associated with the radionuclides were calculated and compared with the international recommended values. (authors)

Investigation and hazard assessment of the 2003 and 2007 Staircase Falls rock falls, Yosemite National Park, California, USA

Directory of Open Access Journals (Sweden)

G. F. Wieczorek

2008-05-01

Full Text Available Since 1857 more than 600 rock falls, rock slides, debris slides, and debris flows have been documented in Yosemite National Park, with rock falls in Yosemite Valley representing the majority of the events. On 26 December 2003, a rock fall originating from west of Glacier Point sent approximately 200 m³ of rock debris down a series of joint-controlled ledges to the floor of Yosemite Valley. The debris impacted talus near the base of Staircase Falls, producing fragments of flying rock that struck occupied cabins in Curry Village. Several years later on 9 June 2007, and again on 26 July 2007, smaller rock falls originated from the same source area. The 26 December 2003 event coincided with a severe winter storm and was likely triggered by precipitation and/or frost wedging, but the 9 June and 26 July 2007 events lack recognizable triggering mechanisms. We investigated the geologic and hydrologic factors contributing to the Staircase Falls rock falls, including bedrock lithology, weathering, joint spacing and orientations, and hydrologic processes affecting slope stability. We improved upon previous geomorphic assessment of rock-fall hazards, based on a shadow angle approach, by using STONE, a three-dimensional rock-fall simulation computer program. STONE produced simulated rock-fall runout patterns similar to the mapped extent of the 2003 and 2007 events, allowing us to simulate potential future rock falls from the Staircase Falls detachment area. Observations of recent rock falls, mapping of rock debris, and simulations of rock fall runouts beneath the Staircase Falls detachment area suggest that rock-fall hazard zones extend farther downslope than the extent previously defined by mapped surface talus deposits.

Investigation and hazard assessment of the 2003 and 2007 Staircase Falls rock falls, Yosemite National Park, California, USA

Science.gov (United States)

Wieczorek, G. F.; Stock, G. M.; Reichenbach, P.; Snyder, J. B.; Borchers, J. W.; Godt, J. W.

2008-05-01

Since 1857 more than 600 rock falls, rock slides, debris slides, and debris flows have been documented in Yosemite National Park, with rock falls in Yosemite Valley representing the majority of the events. On 26 December 2003, a rock fall originating from west of Glacier Point sent approximately 200 m3 of rock debris down a series of joint-controlled ledges to the floor of Yosemite Valley. The debris impacted talus near the base of Staircase Falls, producing fragments of flying rock that struck occupied cabins in Curry Village. Several years later on 9 June 2007, and again on 26 July 2007, smaller rock falls originated from the same source area. The 26 December 2003 event coincided with a severe winter storm and was likely triggered by precipitation and/or frost wedging, but the 9 June and 26 July 2007 events lack recognizable triggering mechanisms. We investigated the geologic and hydrologic factors contributing to the Staircase Falls rock falls, including bedrock lithology, weathering, joint spacing and orientations, and hydrologic processes affecting slope stability. We improved upon previous geomorphic assessment of rock-fall hazards, based on a shadow angle approach, by using STONE, a three-dimensional rock-fall simulation computer program. STONE produced simulated rock-fall runout patterns similar to the mapped extent of the 2003 and 2007 events, allowing us to simulate potential future rock falls from the Staircase Falls detachment area. Observations of recent rock falls, mapping of rock debris, and simulations of rock fall runouts beneath the Staircase Falls detachment area suggest that rock-fall hazard zones extend farther downslope than the extent previously defined by mapped surface talus deposits.

The Spatial Assessment of the Current Seismic Hazard State for Hard Rock Underground Mines

Science.gov (United States)

Wesseloo, Johan

2018-06-01

Mining-induced seismic hazard assessment is an important component in the management of safety and financial risk in mines. As the seismic hazard is a response to the mining activity, it is non-stationary and variable both in space and time. This paper presents an approach for implementing a probabilistic seismic hazard assessment to assess the current hazard state of a mine. Each of the components of the probabilistic seismic hazard assessment is considered within the context of hard rock underground mines. The focus of this paper is the assessment of the in-mine hazard distribution and does not consider the hazard to nearby public or structures. A rating system and methodologies to present hazard maps, for the purpose of communicating to different stakeholders in the mine, i.e. mine managers, technical personnel and the work force, are developed. The approach allows one to update the assessment with relative ease and within short time periods as new data become available, enabling the monitoring of the spatial and temporal change in the seismic hazard.

Review of induced seismic hazard for Hot Dry Rock Project, Rosemanowes, Cornwall

International Nuclear Information System (INIS)

Skipp, B.O.; Woo, G.; Eldred, P.J.L.

1991-01-01

Geothermal energy installations perturb the earth's crust and so may provoke earthquakes. The 21st Dry Rock (HDR) Geothermal Project at Rosemanowes Quarry in Cornwall has given rise to low level unfelt acoustic emission and possibly small, felt earthquakes. This review of induced seismic hazard study examines the effects that the HDR Project could have on seismic events. Events which are modified by the project, in magnitude and time of occurrence, as well as those which might not have occurred at all were studied. From an examination of the literature and relevant seismicity models, a broad estimate of induced seismic hazard was established. (U.K)

Some Open Issues on Rockfall Hazard Analysis in Fractured Rock Mass: Problems and Prospects

Science.gov (United States)

Ferrero, Anna Maria; Migliazza, Maria Rita; Pirulli, Marina; Umili, Gessica

2016-09-01

Risk is part of every sector of engineering design. It is a consequence of the uncertainties connected with the cognitive boundaries and with the natural variability of the relevant variables. In soil and rock engineering, in particular, uncertainties are linked to geometrical and mechanical aspects and the model used for the problem schematization. While the uncertainties due to the cognitive gaps could be filled by improving the quality of numerical codes and measuring instruments, nothing can be done to remove the randomness of natural variables, except defining their variability with stochastic approaches. Probabilistic analyses represent a useful tool to run parametric analyses and to identify the more significant aspects of a given phenomenon: They can be used for a rational quantification and mitigation of risk. The connection between the cognitive level and the probability of failure is at the base of the determination of hazard, which is often quantified through the assignment of safety factors. But these factors suffer from conceptual limits, which can be only overcome by adopting mathematical techniques with sound bases, not so used up to now (Einstein et al. in rock mechanics in civil and environmental engineering, CRC Press, London, 3-13, 2010; Brown in J Rock Mech Geotech Eng 4(3):193-204, 2012). The present paper describes the problems and the more reliable techniques used to quantify the uncertainties that characterize the large number of parameters that are involved in rock slope hazard assessment through a real case specifically related to rockfall. Limits of the existing approaches and future developments of the research are also provided.

Relationship between the rock mass deformation and places of occurrence of seismological events

Energy Technology Data Exchange (ETDEWEB)

Janusz Makowka; Jozef Kabiesz; Lin-ming Ddou [Central Mining Institute, Katowice (Poland)

2009-09-15

Static effort of rock mass very rarely causes of rock burst in Polish coal mines. Rock bursts with source in the seismic tremor within the roof rock layers are prevailing. A seismic tremor is an effect of rupture or sliding in roof layers above the exploited panel in coal seam, sometime in a distance from actual exploitation. Sliding, as a rule occurs in fault zone and tremors in it are expected, but monolithic layer rupture is very hard to predict. In a past few years a practice of analyzing state of deformation in high energy seismic tremors zones has been employed. It let gathering experience thanks to witch determination of dangerous shape of reformatted roof is possible. In the paper some typical forms of roof rocks deformations leading to seismic tremor occurrence will be presented. In general these are various types of multidirectional rock layers bending. Real examples of seismic events and rock bursts in the Czech Republic will be shown. 5 refs., 6 figs.

Probabilistic approach to rock fall hazard assessment: potential of historical data analysis

Directory of Open Access Journals (Sweden)

C. Dussauge-Peisser

2002-01-01

Full Text Available We study the rock fall volume distribution for three rock fall inventories and we fit the observed data by a power-law distribution, which has recently been proposed to describe landslide and rock fall volume distributions, and is also observed for many other natural phenomena, such as volcanic eruptions or earthquakes. We use these statistical distributions of past events to estimate rock fall occurrence rates on the studied areas. It is an alternative to deterministic approaches, which have not proved successful in predicting individual rock falls. The first one concerns calcareous cliffs around Grenoble, French Alps, from 1935 to 1995. The second data set is gathered during the 1912–1992 time window in Yosemite Valley, USA, in granite cliffs. The third one covers the 1954–1976 period in the Arly gorges, French Alps, with metamorphic and sedimentary rocks. For the three data sets, we find a good agreement between the observed volume distributions and a fit by a power-law distribution for volumes larger than 50 m3 , or 20 m3 for the Arly gorges. We obtain similar values of the b exponent close to 0.45 for the 3 data sets. In agreement with previous studies, this suggests, that the b value is not dependant on the geological settings. Regarding the rate of rock fall activity, determined as the number of rock fall events with volume larger than 1 m3 per year, we find a large variability from one site to the other. The rock fall activity, as part of a local erosion rate, is thus spatially dependent. We discuss the implications of these observations for the rock fall hazard evaluation. First, assuming that the volume distributions are temporally stable, a complete rock fall inventory allows for the prediction of recurrence rates for future events of a given volume in the range of the observed historical data. Second, assuming that the observed volume distribution follows a power-law distribution without cutoff at small or large scales, we can

Probabilistic approach to rock fall hazard assessment: potential of historical data analysis

Science.gov (United States)

Dussauge-Peisser, C.; Helmstetter, A.; Grasso, J.-R.; Hantz, D.; Desvarreux, P.; Jeannin, M.; Giraud, A.

We study the rock fall volume distribution for three rock fall inventories and we fit the observed data by a power-law distribution, which has recently been proposed to describe landslide and rock fall volume distributions, and is also observed for many other natural phenomena, such as volcanic eruptions or earthquakes. We use these statistical distributions of past events to estimate rock fall occurrence rates on the studied areas. It is an alternative to deterministic approaches, which have not proved successful in predicting individual rock falls. The first one concerns calcareous cliffs around Grenoble, French Alps, from 1935 to 1995. The second data set is gathered during the 1912-1992 time window in Yosemite Valley, USA, in granite cliffs. The third one covers the 1954-1976 period in the Arly gorges, French Alps, with metamorphic and sedimentary rocks. For the three data sets, we find a good agreement between the observed volume distributions and a fit by a power-law distribution for volumes larger than 50 m3 , or 20 m3 for the Arly gorges. We obtain similar values of the b exponent close to 0.45 for the 3 data sets. In agreement with previous studies, this suggests, that the b value is not dependant on the geological settings. Regarding the rate of rock fall activity, determined as the number of rock fall events with volume larger than 1 m3 per year, we find a large variability from one site to the other. The rock fall activity, as part of a local erosion rate, is thus spatially dependent. We discuss the implications of these observations for the rock fall hazard evaluation. First, assuming that the volume distributions are temporally stable, a complete rock fall inventory allows for the prediction of recurrence rates for future events of a given volume in the range of the observed historical data. Second, assuming that the observed volume distribution follows a power-law distribution without cutoff at small or large scales, we can extrapolate these

Rock cliffs hazard analysis based on remote geostructural surveys: The Campione del Garda case study (Lake Garda, Northern Italy)

Science.gov (United States)

Ferrero, A. M.; Migliazza, M.; Roncella, R.; Segalini, A.

2011-02-01

The town of Campione del Garda (located on the west coast of Lake Garda) and its access road have been historically subject to rockfall phenomena with risk for public security in several areas of the coast. This paper presents a study devoted to the determination of risk for coastal cliffs and the design of mitigation measures. Our study was based on statistical rockfall analysis performed with a commercial code and on stability analysis of rock slopes based on the key block method. Hazard from block kinematics and rock-slope failure are coupled by applying the Rockfall Hazard Assessment Procedure (RHAP). Because of the huge dimensions of the slope, its morphology and the geostructural survey were particularly complicated and demanding. For these reasons, noncontact measurement methods, based on aerial photogrammetry by helicopter, were adopted. A special software program, developed by the authors, was applied for discontinuity identification and for their orientation measurements. The potentially of aerial photogrammetic survey in rock mechanic application and its improvement in the rock mass knowledge is analysed in the article.

Radiological hazard indices and elemental composition of Brazilian and Swiss ornamental rocks

Energy Technology Data Exchange (ETDEWEB)

El Hajj, T.M. [Universidade Federal de Alfenas (UNIFAL), Pocos de Caldas, MG (Brazil); Silva, P.S.C.; Santos, A., E-mail: pscsilva@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Gandolla, M.P.A. [Universita della Svizzera Italiana (USI), Lugano (Switzerland); Dantas, G.A.S.A.; Delboni Junior, H. [Universidade de Sao Paulo (USP), SP (Brazil)

2017-09-01

The objective of this paper was to evaluate the radiological risk index of ornamental rocks sold both in Brazil and Europe and to correlate their radioactive content with their chemical composition. The {sup 238}U, {sup 232}Th and {sup 40}K mean values were 62 ± 65, 122 ± 111, 1126 ± 516 Bq kg{sup -1} for Brazilian and 93 ± 59, 70 ± 67 and 1005 ± 780 Bq kg{sup -1} for Swiss samples, respectively. The radiological index: radium equivalent, external hazard index, absorbed dose rate in air, annual gonadal equivalent dose, annual effective dose equivalent, and excess lifetime cancer risk for Brazilian and Swiss samples were calculated. The main contribution for the radiological indices observed was the radionuclide {sup 232}Th, which is associated with REE, Br, Hf, Na, Rb, Sb and Zr in the rock matrix. (author)

Rock mechanics research in the Coeur d'Alene mining district

Energy Technology Data Exchange (ETDEWEB)

Corp, E. L.

1980-05-15

Over the past 20 years, the Bureau of Mines and mining companies of the Coeur d'Alene district have conducted cooperative research on problems of ground control. For the past six years emphasis has been placed on research to improve deep shaft design and to control rock bursts during cut-and-fill stoping. Finite-element modeling and construction of small-scale circular and rectangular test shafts have shown that circular openings are stable only when stresses are hydrostatic or weakly biaxial. Under a strongly-biaxial horizontal stress field, a rectangular shaft has a greater depth capability if its long axis can be oriented parallel to the major stress and normal to the bedding and joint system. Steel sets appear preferable to wood sets or concrete lining. Based on underground tests at Hecla's Star mine, destressing or preconditioning of the vein rock prior to mining was shown to be an effective means of controlling rock bursts. Drilling and shooting a radial pattern of longholes before stope mining starts has preconditioned or softened the vein material to the extent that seismic energy release during mining is reduced and no bursting occurred. Increased burst and seismic activity while mining about the preconditioned zone points out the need to precondition an entire stope block before mining.

Study on Dynamic Disaster in Steeply Deep Rock Mass Condition in Urumchi Coalfield

Directory of Open Access Journals (Sweden)

Xing-Ping Lai

2015-01-01

Full Text Available The possible mining seismicity (MS and its prediction are important for safety and recovery optimization of mining in steep-heavy-thick rock mass condition. The stress-lever-rotation-effect (SLRE model of fault-like mobilization was proposed preliminarily. Some innovation monitoring technique approaches for mining seismicity assessment were successfully fulfilled at Wudong Mine of Urumchi Coalfield, China. The characteristics on acoustic-seismic-wave index indicated the spatial-temporal-strength and stress redistribution of steeply deeper-heavy thick coal and rock masses. Applications in field investigations showed that the innovation monitoring (in time and space of these instruments could provide important information about the performance of mining disturbed structures (heading and steep pillar during caving of competent overlying roof strata. The prediction and evaluation for mining seismicity were applicable and valid. Operating practice showed that mining efficiency was raised and conspicuous economic benefit was obtained. This approach provides essential data for assessing mining seismicity, coal burst, dynamic hazard prevention, and deep mining potential.

Study of Coal Burst Source Locations in the Velenje Colliery

Directory of Open Access Journals (Sweden)

Goran Vižintin

2016-06-01

Full Text Available The Velenje coal mine (VCM is situated on the largest Slovenian coal deposit and in one of the thickest layers of coal known in the world. The thickness of the coal layer causes problems for the efficiency of extraction, since the majority of mining operations is within the coal layer. The selected longwall coal mining method with specific geometry, increasing depth of excavations, changes in stress state and naturally given geomechanical properties of rocks induce seismic events. Induced seismic events can be caused by caving processes, blasting or bursts of coal or the surrounding rock. For 2.5D visualization, data of excavations, ash content and calorific value of coal samples, hanging wall and footwall occurrence, subsidence of the surface and coal burst source locations were collected. Data and interpolation methods available in software package Surfer®12 were statistically analyzed and a Kriging (KRG interpolation method was chosen. As a result 2.5D visualizations of coal bursts source locations with geomechanical properties of coal samples taken at different depth in the coal seam in the VCM were made with data-visualization packages Surfer®12 and Voxler®3.

Development of uniform hazard response spectra from accelerograms recorded on rock sites

International Nuclear Information System (INIS)

Ghosh, A.K.; Kushwaha, H.S.

2000-05-01

Traditionally, the seismic design basis ground motion has been specified by response spectral shapes and the peak ground acceleration (PGA). The mean recurrence interval (MRI) is evaluated for PGA only. The present work has developed response spectra having the same MRI at all frequencies. This report extends the work of Cornell (on PGA) to consider an aerial source model and a general form of the spectral acceleration at various frequencies. The latter has been derived from a number of strong motion earthquake recorded on rock sites. Sensitivity of the results to the changes in various parameters has also been presented. These results will help to determine the seismic hazard at a given site and the associated uncertainties. (author)

Size Effect on Acoustic Emission Characteristics of Coal-Rock Damage Evolution

OpenAIRE

Wen, Zhijie; Wang, Xiao; Chen, Lianjun; Lin, Guan; Zhang, Hualei

2017-01-01

Coal-gas outburst, rock burst, and other mine dynamic disasters are closely related to the instability and failure of coal-rock. Coal-rock is the assemblies of mineral particles of varying sizes and shapes bonded together by cementing materials. The damage and rupture process of coal-rock is accompanied by acoustic emission (AE), which can be used as an effective means to monitor and predict the instability of coal-rock body. In this manuscript, considering the size effect of coal-rock, the i...

Burst-Mode Asynchronous Controllers on FPGA

Directory of Open Access Journals (Sweden)

Duarte L. Oliveira

2008-01-01

Full Text Available FPGAs have been mainly used to design synchronous circuits. Asynchronous design on FPGAs is difficult because the resulting circuit may suffer from hazard problems. We propose a method that implements a popular class of asynchronous circuits, known as burst mode, on FPGAs based on look-up table architectures. We present two conditions that, if satisfied, guarantee essential hazard-free implementation on any LUT-based FPGA. By doing that, besides all the intrinsic advantages of asynchronous over synchronous circuits, they also take advantage of the shorter design time and lower cost associated with FPGA designs.

Rock mechanics research in the Coeur d'Alene mining district

Energy Technology Data Exchange (ETDEWEB)

Corp, E. L.

1980-05-15

Over the past 20 years, the Bureau of Mines and mining companies of the Coeur d'Alene district have conducted cooperative research on problems of ground control. For the past six years emphasis has been placed on research to improve deep shaft design and to control rock bursts during cut-and-fill stoping. Factors contributing to ground control problems include: depth of mining ranging to 8000 feet; local tectonic activity that in many instances has produced horizontal stresses exceeding the vertical; unequal horizontal stresses at ratios ranging between 1.25 and 2.73; major faults, joints, and bedding planes; and hard, brittle quartzite rock capable of concentrating high levels of stress. Finite-element modeling and construction of small-scale circular and rectangular test shafts have shown that circular openings are stable only when stresses are hydrostatic or weakly biaxial. Under a strongly-biaxial horizontal stress field, a rectangular shaft has a greater depth capabiity if its long axis can be oriented parallel to the major stress and normal to the bedding and joint system. Steel sets appear preferable to wood sets or concrete lining. Based on underground tests at Hecla's Star mine, destressing or preconditioning of the vein rock prior to mining was shown to be an effective means of controlling rock bursts. Drilling and shooting a radial pattern of longholes before stope mining starts has preconditioned or softened the vein material to the extent that seismic energy release during mining is reduced and no bursting occurred. Increased burst and seismic activity while mining above the preconditioned zone points out the need to precondition an entire stope block before mining.

Correlation of electromagnetic radiation emitted from coal or rock to supporting resistance

Energy Technology Data Exchange (ETDEWEB)

Jia, Hui-lin; Wang, En-yuan; Song, Xiao-yan; Zhang, Hong-jie; Li, Zhong-hui [China University of Mining & Technology, Xuzhou (China). School of Safety Engineering

2009-05-15

More accurate forecasting of rock burst might be possible from observations of electromagnetic radiation emitted in the mine. We analyzed experimental observations and field data from the Muchengjian coal mine to study the relationship between electromagnetic radiation signal intensity and stress during the fracturing of coal, or rock, and samples under load. The results show that the signal intensity is positively correlated with stress. In addition, we investigated the change in the electromagnetic radiation intensity, the supporting resistance in a real coal mine environment, and the coal or rock stress in the mining area. The data analysis indicates that: (1) electromagnetic radiation intensity can accurately reflect the distribution of stress in the mining area; and, (2) there is a correlation between electromagnetic radiation intensity and supporting resistance. The research has some practical guiding significance for rock burst forecasting and for the prevention of accidents in coal mines. 9 refs., 6 figs.

Experimental Investigation of the Influence of Confining Stress on Hard Rock Fragmentation Using a Conical Pick

Science.gov (United States)

Li, Xibing; Wang, Shaofeng; Wang, Shanyong

2018-01-01

High geostress is a prominent condition in deep excavations and affects the cuttability of deep hard rock. This study aims to determine the influence of confining stress on hard rock fragmentation as applied by a conical pick. Using a true triaxial test apparatus, static and coupled static and dynamic loadings from pick forces were applied to end faces of cubic rock specimens to break them under biaxial, uniaxial and stress-free confining stress conditions. The cuttability indices (peak pick force, insertion depth and disturbance duration), failure patterns and fragment sizes were measured and compared to estimate the effects of confining stress. The results show that the rock cuttabilities decreased in order from rock breakages under stress-free conditions to uniaxial confining stress and then to biaxial confining stress. Under biaxial confining stress, only flake-shaped fragments were stripped from the rock surfaces under the requirements of large pick forces or disturbance durations. As the level of uniaxial confining stress increased, the peak pick force and the insertion depth initially increased and then decreased, and the failure patterns varied from splitting to partial splitting and then to rock bursts with decreasing average fragment sizes. Rock bursts will occur under elastic compression via ultra-high uniaxial confining stresses. There are two critical uniaxial confining stress levels, namely stress values at which peak pick forces begin to decrease and improve rock cuttability, and those at which rock bursts initially occur and cutting safety decreases. In particular, hard rock is easiest to split safely and efficiently under stress-free conditions. Moreover, coupled static preloading and dynamic disturbance can increase the efficiency of rock fragmentation with increasing preloading levels and disturbance amplitudes. The concluding remarks confirm hard rock cuttability using conical pick, which can improve the applicability of mechanical excavation in

Rockfall hazard and risk assessment in the Yosemite Valley, California, USA

Science.gov (United States)

Guzzetti, F.; Reichenbach, P.; Wieczorek, G. F.

Rock slides and rock falls are the most frequent types of slope movements in Yosemite National Park, California. In historical time (1857-2002) 392 rock falls and rock slides have been documented in the valley, and some of them have been mapped in detail. We present the results of an attempt to assess rock fall hazards in the Yosemite Valley. Spatial and temporal aspects of rock falls hazard are considered. A detailed inventory of slope movements covering the 145-year period from 1857 to 2002 is used to determine the frequency-volume statistics of rock falls and to estimate the annual frequency of rock falls, providing the temporal component of rock fall hazard. The extent of the areas potentially subject to rock fall hazards in the Yosemite Valley were obtained using STONE, a physically-based rock fall simulation computer program. The software computes 3-dimensional rock fall trajectories starting from a digital elevation model (DEM), the location of rock fall release points, and maps of the dynamic rolling friction coefficient and of the coefficients of normal and tangential energy restitution. For each DEM cell the software calculates the number of rock falls passing through the cell, the maximum rock fall velocity and the maximum flying height. For the Yosemite Valley, a DEM with a ground resolution of 10 × 10 m was prepared using topographic contour lines from the U.S. Geological Survey 1:24 000-scale maps. Rock fall release points were identified as DEM cells having a slope steeper than 60°, an assumption based on the location of historical rock falls. Maps of the normal and tangential energy restitution coefficients and of the rolling friction coefficient were produced from a surficial geologic map. The availability of historical rock falls mapped in detail allowed us to check the computer program performance and to calibrate the model parameters. Visual and statistical comparison of the model results with the mapped rock falls confirmed the accuracy of

Rockfall hazard and risk assessment in the Yosemite Valley, California, USA

Directory of Open Access Journals (Sweden)

F. Guzzetti

2003-01-01

Full Text Available Rock slides and rock falls are the most frequent types of slope movements in Yosemite National Park, California. In historical time (1857–2002 392 rock falls and rock slides have been documented in the valley, and some of them have been mapped in detail. We present the results of an attempt to assess rock fall hazards in the Yosemite Valley. Spatial and temporal aspects of rock falls hazard are considered. A detailed inventory of slope movements covering the 145-year period from 1857 to 2002 is used to determine the frequency-volume statistics of rock falls and to estimate the annual frequency of rock falls, providing the temporal component of rock fall hazard. The extent of the areas potentially subject to rock fall hazards in the Yosemite Valley were obtained using STONE, a physically-based rock fall simulation computer program. The software computes 3-dimensional rock fall trajectories starting from a digital elevation model (DEM, the location of rock fall release points, and maps of the dynamic rolling friction coefficient and of the coefficients of normal and tangential energy restitution. For each DEM cell the software calculates the number of rock falls passing through the cell, the maximum rock fall velocity and the maximum flying height. For the Yosemite Valley, a DEM with a ground resolution of 10 × 10 m was prepared using topographic contour lines from the U.S. Geological Survey 1:24 000-scale maps. Rock fall release points were identified as DEM cells having a slope steeper than 60°, an assumption based on the location of historical rock falls. Maps of the normal and tangential energy restitution coefficients and of the rolling friction coefficient were produced from a surficial geologic map. The availability of historical rock falls mapped in detail allowed us to check the computer program performance and to calibrate the model parameters. Visual and statistical comparison of the model results with the mapped rock falls

Development of uniform hazard response spectra for rock sites considering line and point sources of earthquakes

International Nuclear Information System (INIS)

Ghosh, A.K.; Kushwaha, H.S.

2001-12-01

Traditionally, the seismic design basis ground motion has been specified by normalised response spectral shapes and peak ground acceleration (PGA). The mean recurrence interval (MRI) used to computed for PGA only. It is shown that the MRI associated with such response spectra are not the same at all frequencies. The present work develops uniform hazard response spectra i.e. spectra having the same MRI at all frequencies for line and point sources of earthquakes by using a large number of strong motion accelerograms recorded on rock sites. Sensitivity of the number of the results to the changes in various parameters has also been presented. This work is an extension of an earlier work for aerial sources of earthquakes. These results will help to determine the seismic hazard at a given site and the associated uncertainities. (author)

Dynamic Mechanical Behavior of Dry and Water Saturated Igneous Rock with Acoustic Emission Monitoring

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Jun Guo

2018-01-01

Full Text Available The uniaxial cyclic loading tests have been conducted to study the mechanical behavior of dry and water saturated igneous rock with acoustic emission (AE monitoring. The igneous rock samples are dried, naturally immersed, and boiled to get specimens with different water contents for the testing. The mineral compositions and the microstructures of the dry and water saturated igneous rock are also presented. The dry specimens present higher strength, fewer strains, and rapid increase of AE count subjected to the cyclic loading, which reflects the hard and brittle behavior and strong burst proneness of igneous rock. The water saturated specimens have lower peak strength, more accumulated strains, and increase of AE count during the cyclic loading. The damage of the igneous rocks with different water contents has been identified by the Felicity Ratio Analysis. The cyclic loading and unloading increase the dislocation between the mineral aggregates and the water-rock interactions further break the adhesion of the clay minerals, which jointly promote the inner damage of the igneous rock. The results suggest that the groundwater can reduce the burst proneness of the igneous rock but increase the potential support failure of the surrounding rock in igneous invading area. In addition, the results inspire the fact that the water injection method is feasible for softening the igneous rock and for preventing the dynamic disasters within the roadways and working faces located in the igneous intrusion area.

Bursting-protection configuration for cylindrical steam generators of pressurized water reactors

International Nuclear Information System (INIS)

Mutzl, J.

1979-01-01

The bursting-protection jacket consists of cylinder courses, being joined together in axial direction, and of a bottom and a cover, being connected by means of axial prestressing tendons. For absorption and transmission of the steam generator weight and the bursting forces the bottom consists of a conical shell, tapered towards the side of the steam generator, and a support ring supporting the bottom circle of the cone. This support ring is built in sandwich construction and is connected with the axial tendons. The conical shell may be reinforced by radial ribs. If a primary coolant pump is built in there is provided for a rocking bearing between its pump casing flange and the bottom. (DG) [de

Neutron stars as X-ray burst sources. II. Burst energy histograms and why they burst

International Nuclear Information System (INIS)

Baan, W.A.

1979-01-01

In this work we explore some of the implications of a model for X-ray burst sources where bursts are caused by Kruskal-Schwarzschild instabilities at the magnetopause of an accreting and rotating neutron star. A number of simplifying assumptions are made in order to test the model using observed burst-energy histograms for the rapid burster MXB 1730--335. The predicted histograms have a correct general shape, but it appears that other effects are important as well, and that mode competition, for instance, may suppress the histograms at high burst energies. An explanation is ventured for the enhancement in the histogram at the highest burst energies, which produces the bimodal shape in high accretion rate histograms. Quantitative criteria are given for deciding when accreting neutron stars are steady sources or burst sources, and these criteria are tested using the X-ray pulsars

Terrestrial gamma dose rate, radioactivity and radiological hazards in the rocks of an elevated radiation background in Juban District, Ad Dali' Governorate, Yemen.

Science.gov (United States)

Abdurabu, Wedad Ali; Ramli, Ahmad Termizi; Saleh, Muneer Aziz; Heryansyah, Arien; Alnhary, Anees; Fadhl, Shadi

2016-03-01

This study aims to evaluate natural radiation and radioactivity in the rock and to assess the corresponding health risk in a region of elevated background radiation in Juban District, Ad Dali' Governorate, Yemen. The mean external gamma dose rate was 374 nGy h(-1) which is approximately six times the world average. The measured results were used to compute annual effective dose equivalent, collective effective dose and excess lifetime cancer risk, which are 2.298 mSv, 61.95 man Sv y(-1) and 8.043  ×  10(-3), respectively. Rocks samples from different geological formations were analyzed for quantitative determination of (226)Ra, (232)Th and (40)K. The specific activity of the rocks samples ranges from 7  ±  1 Bq Kg(-1) to 12 513  ±  329 Bq Kg(-1) for (232)Th, from 6  ±  1 Bq kg(-1) to 3089  ±  74 Bq kg(-1) for (226)Ra and 702  ±  69 Bq kg(-1) to 2954  ±  285 Bq kg(-1) for (40)K. (232)Th is the main contributor to gamma dose rate from the rock samples. Indicators of radiological health impact, radium equivalent activity and external hazard index are 3738 Bq kg(-1) and 10.10, respectively. The mean external hazard index was ten times unity in the studied locations in Juban District, which is higher than the recommended value.

A Review of Rock Bolt Monitoring Using Smart Sensors

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Gangbing Song

2017-04-01

Full Text Available Rock bolts have been widely used as rock reinforcing members in underground coal mine roadways and tunnels. Failures of rock bolts occur as a result of overloading, corrosion, seismic burst and bad grouting, leading to catastrophic economic and personnel losses. Monitoring the health condition of the rock bolts plays an important role in ensuring the safe operation of underground mines. This work presents a brief introduction on the types of rock bolts followed by a comprehensive review of rock bolt monitoring using smart sensors. Smart sensors that are used to assess rock bolt integrity are reviewed to provide a firm perception of the application of smart sensors for enhanced performance and reliability of rock bolts. The most widely used smart sensors for rock bolt monitoring are the piezoelectric sensors and the fiber optic sensors. The methodologies and principles of these smart sensors are reviewed from the point of view of rock bolt integrity monitoring. The applications of smart sensors in monitoring the critical status of rock bolts, such as the axial force, corrosion occurrence, grout quality and resin delamination, are highlighted. In addition, several prototypes or commercially available smart rock bolt devices are also introduced.

A Review of Rock Bolt Monitoring Using Smart Sensors.

Science.gov (United States)

Song, Gangbing; Li, Weijie; Wang, Bo; Ho, Siu Chun Michael

2017-04-05

Rock bolts have been widely used as rock reinforcing members in underground coal mine roadways and tunnels. Failures of rock bolts occur as a result of overloading, corrosion, seismic burst and bad grouting, leading to catastrophic economic and personnel losses. Monitoring the health condition of the rock bolts plays an important role in ensuring the safe operation of underground mines. This work presents a brief introduction on the types of rock bolts followed by a comprehensive review of rock bolt monitoring using smart sensors. Smart sensors that are used to assess rock bolt integrity are reviewed to provide a firm perception of the application of smart sensors for enhanced performance and reliability of rock bolts. The most widely used smart sensors for rock bolt monitoring are the piezoelectric sensors and the fiber optic sensors. The methodologies and principles of these smart sensors are reviewed from the point of view of rock bolt integrity monitoring. The applications of smart sensors in monitoring the critical status of rock bolts, such as the axial force, corrosion occurrence, grout quality and resin delamination, are highlighted. In addition, several prototypes or commercially available smart rock bolt devices are also introduced.

Rockfall Hazard Process Assessment : [Project Summary

Science.gov (United States)

2017-10-01

The Montana Department of Transportation (MDT) implemented its Rockfall Hazard Rating System (RHRS) between 2003 and 2005, obtaining information on the state's rock slopes and their associated hazards. The RHRS data facilitated decision-making in an ...

Geomorphological hazards in Swat valley, Pakistan

International Nuclear Information System (INIS)

Usman, A.

1999-01-01

This study attempts to describe, interpret and analyze, in depth, the varied geomorphological hazards and their impacts prevailing in the swat valley locate in the northern hilly and mountainous regions of Pakistan. The hills and mountains re zones of high geomorphological activity with rapid rates of weathering, active tectonic activities, abundant precipitation, rapid runoff and heavy sediment transport. Due to the varied topography, lithology, steep slope, erodible soil, heavy winter snowfall and intensive rainfall in the spring and summer seasons, several kinds of geomorphological hazards, such as geomorphic gravitational hazards, Fluvial hazards, Glacial hazards, Geo tectonic hazards, are occurring frequently in swat valley. Amongst them, geomorphic gravitational hazards, such as rock fall rock slide, debris slide mud flow avalanches, are major hazards in mountains and hills while fluvial hazards and sedimentation are mainly confined to the alluvial plain and lowlands of the valley. The Getechtonic hazards, on the other hand, have wide spread distribution in the valley the magnitude and occurrence of each king of hazard is thus, varied according to intensity of process and physical geographic environment. This paper discusses the type distribution and damage due to the various geomorphological hazards and their reduction treatments. The study would to be of particular importance and interest to both natural and social scientists, as well as planner, environmentalists and decision-makers for successful developmental interventions in the region. (author)

RhoA/ROCK downregulates FPR2-mediated NADPH oxidase activation in mouse bone marrow granulocytes.

Science.gov (United States)

Filina, Julia V; Gabdoulkhakova, Aida G; Safronova, Valentina G

2014-10-01

Polymorphonuclear neutrophils (PMNs) express the high and low affinity receptors to formylated peptides (mFPR1 and mFPR2 in mice, accordingly). RhoA/ROCK (Rho activated kinase) pathway is crucial for cell motility and oxidase activity regulated via FPRs. There are contradictory data on RhoA-mediated regulation of NADPH oxidase activity in phagocytes. We have shown divergent Rho GTPases signaling via mFPR1 and mFPR2 to NADPH oxidase in PMNs from inflammatory site. The present study was aimed to find out the role of RhoA/ROCK in the respiratory burst activated via mFPR1 and mFPR2 in the bone marrow PMNs. Different kinetics of RhoA activation were detected with 0.1μM fMLF and 1μM WKYMVM operating via mFPR1 and mFPR2, accordingly. RhoA was translocated in fMLF-activated cells towards the cell center and juxtamembrane space versus uniform allocation in the resting cells. Specific inhibition of RhoA by CT04, Rho inhibitor I, weakly depressed the respiratory burst induced via mFPR1, but significantly increased the one induced via mFPR2. Inhibition of ROCK, the main effector of RhoA, by Y27632 led to the same effect on the respiratory burst. Regulation of mFPR2-induced respiratory response by ROCK was impossible under the cytoskeleton disruption by cytochalasin D, whereas it persisted in the case of mFPR1 activation. Thus we suggest RhoA to be one of the regulatory and signal transduction components in the respiratory burst through FPRs in the mouse bone marrow PMNs. Both mFPR1 and mFPR2 binding with a ligand trigger the activation of RhoA. FPR1 signaling through RhoA/ROCK increases NADPH-oxidase activity. But in FPR2 action RhoA/ROCK together with cytoskeleton-linked systems down-regulates NADPH-oxidase. This mechanism could restrain the reactive oxygen species dependent damage of own tissues during the chemotaxis of PMNs and in the resting cells. Copyright © 2014 Elsevier Inc. All rights reserved.

Numerical Assessment of the Influences of Gas Pressure on Coal Burst Liability

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Haochen Zhao

2018-01-01

Full Text Available When coal mines exploit deep seams with high-gas content, risks are encountered due to the additional high likelihood of rock bursting potential problems. The bursts of coal pillars usually lead to severe fatalities, injuries, and destruction of property, including impeding access to active mine workings underground. The danger exists given that conditions in the already highly brittle coal material can be exacerbated by high stress and high gas pressure conditions. It is thus critical to develop methods that improve current understanding about bursting liability, and techniques to forecast or prevent coal bursting in underground coal mines. This study uses field data from a deep coal mine, and numerical modeling to investigate the effects of gas pressure and mechanical compressive stresses on coal bursting liability in high gas content coal seams. The bursting energy index is adopted to determine the coal bursting liability under high gas pressure conditions. The adopted methodology uses a two-staged approach comprising investigating the influence of gas pressure on the bursting liability of coal pillar, and the influence of the gas pressure on the resulting pillar failure mode. Based on numerical simulations of coal pillars, correlations are observed between the magnitudes of gas pressures and the bursting energy index. Irrespective of pillar size, failure time is shortest when the gas pressure achieves a threshold value between 50 kPa to 70 kPa. At 50 kPa, the value of the BEI increases by 50% going from the 4 m pillar to the 6 m pillar. The value of the BEI increases by 43% going from the 6 m high pillar to the 8 m high pillar at 50 kPa. When pillars fail there is a degree of stress relief leading to a reduction in bursting liability. The results suggest that before 50 kPa, pillar failure is largely due to mechanical loading. After 50 kPa, pillar failure is largely due to excessive gas pressures.

Cosmic gamma-ray burst

International Nuclear Information System (INIS)

Yamagami, Takamasa

1985-01-01

Ballon experiments for searching gamma-ray burst were carried out by employing rotating-cross modulation collimators. From a very long observation of total 315 hours during 1975 to 1979, three gamma-ray intensity anomalies were observed which were speculated as a gamma-ray burst. As for the first gamma-ray intensity anomaly observed in 1975, the burst source could be located precisely but the source, heavenly body, could not be specified. Gamma-ray burst source estimation was made by analyzing distribution of burst source in the celestial sphere, burst size distribution, and burst peak. Using the above-mentioned data together with previously published ones, apparent inconsistency was found between the observed results and the adopted theory that the source was in the Galaxy, and this inconsistency was found due to the different time profiles of the burst observed with instruments of different efficiency. It was concluded by these analysis results that employment of logN - logP (relation between burst frequency and burst count) was better than that of logN - logS (burst size) in the examination of gamma-ray burst because the former was less uncertain than the latter. Analyzing the author's observed gamma-ray burst data and the related published data, it was clarified that the burst distribution was almost P -312 for the burst peak value larger than 10 -6 erg/cm 2 .sec. The author could indicate that the calculated celestial distribution of burst source was consistent with the observed results by the derivation using the logN - logP relationship and that the burst larger than 10 -6 erg/cm 2 .sec happens about one thousand times a year, about ten times of the previous value. (Takagi, S.)

Hazard assessment due to falling stones on a reach of the regional road in the Trenta valley, Slovenia

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Urška Petje

2005-12-01

Full Text Available In the framework of the new Slovenian methodology for determining hazard areas and the classification of land parcels into hazard classes due to land slides and rock falls, a pilot project was carried out on the regional road between Bovec and Vr{i~ pass in theTrenta valley. For this around 20 km long road in a typical alpine environment, a hazard assessment of falling rocks was carried out, even tough the road also passes through snow avalanches hazard areas. The performed hazard assessment of falling rocks is based onan expert knowledge taking into account the field mapping, and classifies the road into three hazard classes: 9811 m is classified into the low hazard class, 7233 m is classifiedinto the medium hazard class, and 1301 m is classified into high hazard class of falling rocks.

Swift pointing and gravitational-wave bursts from gamma-ray burst events

International Nuclear Information System (INIS)

Sutton, Patrick J; Finn, Lee Samuel; Krishnan, Badri

2003-01-01

The currently accepted model for gamma-ray burst phenomena involves the violent formation of a rapidly rotating solar-mass black hole. Gravitational waves should be associated with the black-hole formation, and their detection would permit this model to be tested. Even upper limits on the gravitational-wave strength associated with gamma-ray bursts could constrain the gamma-ray burst model. This requires joint observations of gamma-ray burst events with gravitational and gamma-ray detectors. Here we examine how the quality of an upper limit on the gravitational-wave strength associated with gamma-ray bursts depends on the relative orientation of the gamma-ray-burst and gravitational-wave detectors, and apply our results to the particular case of the Swift Burst-Alert Telescope (BAT) and the LIGO gravitational-wave detectors. A result of this investigation is a science-based 'figure of merit' that can be used, together with other mission constraints, to optimize the pointing of the Swift telescope for the detection of gravitational waves associated with gamma-ray bursts

Historical rock falls in Yosemite National Park, California (1857-2011)

Science.gov (United States)

Stock, Greg M.; Collins, Brian D.; Santaniello, David J.; Zimmer, Valerie L.; Wieczorek, Gerald F.; Snyder, James B.

2013-01-01

Inventories of rock falls and other types of landslides are valuable tools for improving understanding of these events. For example, detailed information on rock falls is critical for identifying mechanisms that trigger rock falls, for quantifying the susceptibility of different cliffs to rock falls, and for developing magnitude-frequency relations. Further, inventories can assist in quantifying the relative hazard and risk posed by these events over both short and long time scales. This report describes and presents the accompanying rock fall inventory database for Yosemite National Park, California. The inventory database documents 925 events spanning the period 1857–2011. Rock falls, rock slides, and other forms of slope movement represent a serious natural hazard in Yosemite National Park. Rock-fall hazard and risk are particularly relevant in Yosemite Valley, where glacially steepened granitic cliffs approach 1 km in height and where the majority of the approximately 4 million yearly visitors to the park congregate. In addition to damaging roads, trails, and other facilities, rock falls and other slope movement events have killed 15 people and injured at least 85 people in the park since the first documented rock fall in 1857. The accompanying report describes each of the organizational categories in the database, including event location, type of slope movement, date, volume, relative size, probable trigger, impact to humans, narrative description, references, and environmental conditions. The inventory database itself is contained in a Microsoft Excel spreadsheet (Yosemite_rock_fall_database_1857-2011.xlsx). Narrative descriptions of events are contained in the database, but are also provided in a more readable Adobe portable document format (pdf) file (Yosemite_rock_fall_database_narratives_1857-2011.pdf) available for download separate from the database.

Quantum key based burst confidentiality in optical burst switched networks.

Science.gov (United States)

Balamurugan, A M; Sivasubramanian, A

2014-01-01

The optical burst switching (OBS) is an emergent result to the technology concern that could achieve a feasible network in future. They are endowed with the ability to meet the bandwidth requirement of those applications that require intensive bandwidth. There are more domains opening up in the OBS that evidently shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution, and quality of service (QoS). This paper deals with employing RC4 (stream cipher) to encrypt and decrypt bursts thereby ensuring the confidentiality of the burst. Although the use of AES algorithm has already been proposed for the same issue, by contrasting the two algorithms under the parameters of burst encryption and decryption time, end-to-end delay, it was found that RC4 provided better results. This paper looks to provide a better solution for the confidentiality of the burst in OBS networks.

Quantum Key Based Burst Confidentiality in Optical Burst Switched Networks

Directory of Open Access Journals (Sweden)

A. M. Balamurugan

2014-01-01

Full Text Available The optical burst switching (OBS is an emergent result to the technology concern that could achieve a feasible network in future. They are endowed with the ability to meet the bandwidth requirement of those applications that require intensive bandwidth. There are more domains opening up in the OBS that evidently shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution, and quality of service (QoS. This paper deals with employing RC4 (stream cipher to encrypt and decrypt bursts thereby ensuring the confidentiality of the burst. Although the use of AES algorithm has already been proposed for the same issue, by contrasting the two algorithms under the parameters of burst encryption and decryption time, end-to-end delay, it was found that RC4 provided better results. This paper looks to provide a better solution for the confidentiality of the burst in OBS networks.

Geologic hazards in the region of the Hurricane fault

Science.gov (United States)

Lund, W.R.

1997-01-01

Complex geology and variable topography along the 250-kilometer-long Hurricane fault in northwestern Arizona and southwestern Utah combine to create natural conditions that can present a potential danger to life and property. Geologic hazards are of particular concern in southwestern Utah, where the St. George Basin and Interstate-15 corridor north to Cedar City are one of Utah's fastest growing areas. Lying directly west of the Hurricane fault and within the Basin and Range - Colorado Plateau transition zone, this region exhibits geologic characteristics of both physiographic provinces. Long, potentially active, normal-slip faults displace a generally continuous stratigraphic section of mostly east-dipping late Paleozoic to Cretaceous sedimentary rocks unconformably overlain by Tertiary to Holocene sedimentary and igneous rocks and unconsolidated basin-fill deposits. Geologic hazards (exclusive of earthquake hazards) of principal concern in the region include problem soil and rock, landslides, shallow ground water, and flooding. Geologic materials susceptible to volumetric change, collapse, and subsidence in southwestern Utah include; expansive soil and rock, collapse-prone soil, gypsum and gypsiferous soil, soluble carbonate rocks, and soil and rock subject to piping and other ground collapse. Expansive soil and rock are widespread throughout the region. The Petrified Forest Member of the Chinle Formation is especially prone to large volume changes with variations in moisture content. Collapse-prone soils are common in areas of Cedar City underlain by alluvial-fan material derived from the Moenkopi and Chinle Formations in the nearby Hurricane Cliffs. Gypsiferous soil and rock are subject to dissolution which can damage foundations and create sinkholes. The principal formations in the region affected by dissolution of carbonate are the Kaibab and Toroweap Formations; both formations have developed sinkholes where crossed by perennial streams. Soil piping is

Burst suppression probability algorithms: state-space methods for tracking EEG burst suppression

Science.gov (United States)

Chemali, Jessica; Ching, ShiNung; Purdon, Patrick L.; Solt, Ken; Brown, Emery N.

2013-10-01

Objective. Burst suppression is an electroencephalogram pattern in which bursts of electrical activity alternate with an isoelectric state. This pattern is commonly seen in states of severely reduced brain activity such as profound general anesthesia, anoxic brain injuries, hypothermia and certain developmental disorders. Devising accurate, reliable ways to quantify burst suppression is an important clinical and research problem. Although thresholding and segmentation algorithms readily identify burst suppression periods, analysis algorithms require long intervals of data to characterize burst suppression at a given time and provide no framework for statistical inference. Approach. We introduce the concept of the burst suppression probability (BSP) to define the brain's instantaneous propensity of being in the suppressed state. To conduct dynamic analyses of burst suppression we propose a state-space model in which the observation process is a binomial model and the state equation is a Gaussian random walk. We estimate the model using an approximate expectation maximization algorithm and illustrate its application in the analysis of rodent burst suppression recordings under general anesthesia and a patient during induction of controlled hypothermia. Main result. The BSP algorithms track burst suppression on a second-to-second time scale, and make possible formal statistical comparisons of burst suppression at different times. Significance. The state-space approach suggests a principled and informative way to analyze burst suppression that can be used to monitor, and eventually to control, the brain states of patients in the operating room and in the intensive care unit.

The forecasting method of rock-burst and the application based on overlying multi-strata spatial structure theory

Energy Technology Data Exchange (ETDEWEB)

Cun-Wen Wang; Fu-Xing Jiang; Qing-Guo Sun; Chun-Jiang Sun; Ming Zhang; Zhen-Wen Ji; Xiu-Feng Zhang [University of Science and Technology, Beijing, Beijing (China). Civil & Environmental Engineering School

2009-02-15

Based on the overlying multi-strata spatial structure theory and mechanical analysis, the paper discusses the relationship between 'S' shape spatial strata structure movement and mining stress distribution. Coal out-burst forecasting based on 'S' shape spatial strata structure movement was studied. Microseismic monitoring in Huafeng Coal Mine in Shandong Province showed that coal out-burst will ocur when the advancing distance of the longwall face is equal to one, two or three times the length of the longwall face respectively. During these periods, the mined areas approach to square shape while the 'S' shape spatial strata structure acts strongly. Based on this, the time and position of coal out-burst in No. 1410 longwall face of Huafeng Coal Mine was predicted. By using large diameter and deep drill holes in the coal seam and deep drill holes with blasting in the roof at those danger areas, the No. 1410 longwall face safely advanced through those danger areas. During those periods the microseismic monitoring system detected very strong mine quakes. 15 refs., 1 fig., 2 tabs.

THE FERMI-GBM X-RAY BURST MONITOR: THERMONUCLEAR BURSTS FROM 4U 0614+09

International Nuclear Information System (INIS)

Linares, M.; Chakrabarty, D.; Connaughton, V.; Bhat, P. N.; Briggs, M. S.; Preece, R.; Jenke, P.; Kouveliotou, C.; Wilson-Hodge, C. A.; Van der Horst, A. J.; Camero-Arranz, A.; Finger, M.; Paciesas, W. S.; Beklen, E.; Von Kienlin, A.

2012-01-01

Thermonuclear bursts from slowly accreting neutron stars (NSs) have proven difficult to detect, yet they are potential probes of the thermal properties of the NS interior. During the first year of a systematic all-sky search for X-ray bursts using the Gamma-ray Burst Monitor aboard the Fermi Gamma-ray Space Telescope we have detected 15 thermonuclear bursts from the NS low-mass X-ray binary 4U 0614+09 when it was accreting at nearly 1% of the Eddington limit. We measured an average burst recurrence time of 12 ± 3 days (68% confidence interval) between 2010 March and 2011 March, classified all bursts as normal duration bursts and placed a lower limit on the recurrence time of long/intermediate bursts of 62 days (95% confidence level). We discuss how observations of thermonuclear bursts in the hard X-ray band compare to pointed soft X-ray observations and quantify such bandpass effects on measurements of burst radiated energy and duration. We put our results for 4U 0614+09 in the context of other bursters and briefly discuss the constraints on ignition models. Interestingly, we find that the burst energies in 4U 0614+09 are on average between those of normal duration bursts and those measured in long/intermediate bursts. Such a continuous distribution in burst energy provides a new observational link between normal and long/intermediate bursts. We suggest that the apparent bimodal distribution that defined normal and long/intermediate duration bursts during the last decade could be due to an observational bias toward detecting only the longest and most energetic bursts from slowly accreting NSs.

Fuzzy-Based Adaptive Hybrid Burst Assembly Technique for Optical Burst Switched Networks

Directory of Open Access Journals (Sweden)

Abubakar Muhammad Umaru

2014-01-01

Full Text Available The optical burst switching (OBS paradigm is perceived as an intermediate switching technology for future all-optical networks. Burst assembly that is the first process in OBS is the focus of this paper. In this paper, an intelligent hybrid burst assembly algorithm that is based on fuzzy logic is proposed. The new algorithm is evaluated against the traditional hybrid burst assembly algorithm and the fuzzy adaptive threshold (FAT burst assembly algorithm via simulation. Simulation results show that the proposed algorithm outperforms the hybrid and the FAT algorithms in terms of burst end-to-end delay, packet end-to-end delay, and packet loss ratio.

Cracking and Failure in Rock Specimen Containing Combined Flaw and Hole under Uniaxial Compression

Directory of Open Access Journals (Sweden)

Xiang Fan

2018-01-01

Full Text Available Flaw is a key factor influencing failure behavior of a fractured specimen. In the present study, rectangular-flawed specimens were prepared using sandstone to investigate the effect of flaw on failure behavior of rock. Open flaw and cylindrical hole were simultaneously precut within rock specimens using high-pressure water jet cutting technology. Five series of specimens including intact, single-hole-alone, two-hole-alone, single-hole and two-flaw, and two-hole and single-flaw blocks were prepared. Uniaxial compressive tests using a rigid servo control instrument were carried out to investigate the fracture processes of these flawed specimens. It is observed that during loading, internal stress always intensively distributed at both sidewalls of open hole, especially at midpoint of sidewalls, so rock crumb flaking was firstly observed among all sandstone specimens containing single hole or two holes. Cracking around open hole is associated with the flaw inclination angle which was observed in Series III and V. Crack easily initiated at the tips of flaw with inclination angles of 0°, 30°, and 60° but hard for 90° in Series III and V. Rock burst was the major failure mode among most tested specimens, which generally induced new cracks and finally created crater shape. Additionally, due to extrusion between blocks, new shear or tensile cracks were generated and the rock specimen surface spalled. Eventually, four typical failure processes including rock crumb flaking, crack initiation and propagation, rock burst, and second rupture, were summarized.

Dynamic Behavior of Fault Slip Induced by Stress Waves

Directory of Open Access Journals (Sweden)

Guang-an Zhu

2016-01-01

Full Text Available Fault slip burst is a serious dynamic hazard in coal mining. A static and dynamic analysis for fault slip was performed to assess the risk of rock burst. A numerical model FLAC3D was established to understand the stress state and mechanical responses of fault rock system. The results obtained from the analysis show that the dynamic behavior of fault slip induced by stress waves is significantly affected by mining depth, as well as dynamic disturbance intensity and the distance between the stope and the fault. The isolation effect of the fault is also discussed based on the numerical results with the fault angle appearing to have the strongest influence on peak vertical stress and velocity induced by dynamic disturbance. By taking these risks into account, a stress-relief technology using break-tip blast was used for fault slip burst control. This technique is able to reduce the stress concentration and increase the attenuation of dynamic load by fracturing the structure of coal and rock. The adoption of this stress-relief method leads to an effective reduction of fault slip induced rock burst (FSIRB occurrence.

Burst Suppression on Processed Electroencephalography as a Predictor of Post-Coma Delirium in Mechanically Ventilated ICU Patients

Science.gov (United States)

Andresen, Jennifer M.; Girard, Timothy D.; Pandharipande, Pratik P.; Davidson, Mario A.; Ely, E. Wesley; Watson, Paula L.

2015-01-01

Objectives Many patients, due to a combination of illness and sedatives, spend a considerable amount of time in a comatose state that can include time in burst suppression. We sought to determine if burst suppression measured by processed electroencephalography (pEEG) during coma in sedative-exposed patients is a predictor of post-coma delirium during critical illness. Design Observational convenience sample cohort Setting Medical and surgical ICUs in a tertiary care medical center Patients Cohort of 124 mechanically ventilated ICU patients Measurements and Main Results Depth of sedation was monitored twice daily using the Richmond Agitation-Sedation Scale and continuously monitored by pEEG. When non-comatose, patients were assessed for delirium twice daily using Confusion Assessment Method for the ICU (CAM-ICU). Multiple logistic regression and Cox proportional hazards regression were used to assess associations between time in burst suppression and both incidence and time to resolution of delirium, respectively, adjusting for time in deep sedation and a principal component score consisting of APACHE II score and cumulative doses of sedatives while comatose. Of the 124 patients enrolled and monitored, 55 patients either never had coma or never emerged from coma yielding 69 patients for whom we performed these analyses; 42 of these 69 (61%) had post-coma delirium. Most patients had burst-suppression during coma, though often short-lived [ median (intraquartile range) time in burst suppression, 6.4 (1-58) minutes]. After adjusting for covariates, even this short time in burst suppression independently predicted a higher incidence of post-coma delirium [odds ratio 4.16; 95% confidence interval (CI) 1.27-13.62; p=0.02] and a lower likelihood (delayed) resolution of delirium (hazard ratio 0.78; 95% CI 0.53-0.98; p=0.04). Conclusions Time in burst suppression during coma, as measured by processed EEG, was an independent predictor of incidence and time to resolution of

Impact of type of the roof rocks on location and range of endogenous fires particular hazard zone by in goaf with caving

Science.gov (United States)

Tutak, Magdalena; Brodny, Jarosław

2018-01-01

Hazard of endogenous fires is one of the basic and common presented occupational safety hazards in coal mine in Poland and in the world. This hazard means possibility of coal self-ignition as the result of its self-heating process in mining heading or its surrounding. In underground coal-mining during ventilating of operating longwalls takes place migration of parts of airflow to goaf with caving. In a case when in these goaf a coal susceptible to self-ignition occurs, then the airflow through these goaf may influence on formation of favorable conditions for coal oxidation and subsequently to its self-heating and self-ignition. Endogenous fire formed in such conditions can pose a serious hazards for the crew and for continuity of operation of mining plant. From the practical point of view a very significant meaning has determination of the zone in the goaf with caving, in which necessary conditions for occurence of endogenous fire are fulfilled. In the real conditions determination of such a zone is practically impossible. The main aim of the analysis was to determine the impact of type of the roof rocks forming the goaf on the location and range of endogenous fires particular hazard zone by in these goaf. For determined mining-geological conditions, the critical value of velocity of airflow and oxygen concentration in goaf, conditioning initiation of coal oxidation process were determined.

QKD-Based Secured Burst Integrity Design for Optical Burst Switched Networks

Science.gov (United States)

Balamurugan, A. M.; Sivasubramanian, A.; Parvathavarthini, B.

2016-03-01

The field of optical transmission has undergone numerous advancements and is still being researched mainly due to the fact that optical data transmission can be done at enormous speeds. It is quite evident that people prefer optical communication when it comes to large amount of data involving its transmission. The concept of switching in networks has matured enormously with several researches, architecture to implement and methods starting with Optical circuit switching to Optical Burst Switching. Optical burst switching is regarded as viable solution for switching bursts over networks but has several security vulnerabilities. However, this work exploited the security issues associated with Optical Burst Switching with respect to integrity of burst. This proposed Quantum Key based Secure Hash Algorithm (QKBSHA-512) with enhanced compression function design provides better avalanche effect over the conventional integrity algorithms.

The genesis of period-adding bursting without bursting-chaos in the Chay model

International Nuclear Information System (INIS)

Yang Zhuoqin; Lu Qishao; Li Li

2006-01-01

According to the period-adding firing patterns without chaos observed in neuronal experiments, the genesis of the period-adding 'fold/homoclinic' bursting sequence without bursting-chaos is explored by numerical simulation, fast/slow dynamics and bifurcation analysis of limit cycle in the neuronal Chay model. It is found that each periodic bursting, from period-1 to 7, is separately generated by the corresponding periodic spiking pattern through two period-doubling bifurcations, except for the period-1 bursting occurring via a Hopf bifurcation. Consequently, it can be revealed that this period-adding bursting bifurcation without chaos has a compound bifurcation structure with transitions from spiking to bursting, which is closely related to period-doubling bifurcations of periodic spiking in essence

Size Effect on Acoustic Emission Characteristics of Coal-Rock Damage Evolution

Directory of Open Access Journals (Sweden)

Zhijie Wen

2017-01-01

Full Text Available Coal-gas outburst, rock burst, and other mine dynamic disasters are closely related to the instability and failure of coal-rock. Coal-rock is the assemblies of mineral particles of varying sizes and shapes bonded together by cementing materials. The damage and rupture process of coal-rock is accompanied by acoustic emission (AE, which can be used as an effective means to monitor and predict the instability of coal-rock body. In this manuscript, considering the size effect of coal-rock, the influence of different height to diameter ratio on the acoustic emission characteristics of coal-rock damage evolution was discussed by microparticle flow PFC2D software platform. The results show that coal-rock size influences the uniaxial compressive strength, peak strain, and elastic modulus of itself; the size effect has little effect on the acoustic emission law of coal-rock damage and the effects of the size of coal-rock samples on acoustic emission characteristics are mainly reflected in three aspects: the triggering time of acoustic emission, the strain range of strong acoustic emission, and the intensity of acoustic emission; the damage evolution of coal-rock specimen can be divided into 4 stages: initial damage, stable development, accelerated development, and damage.

A repeating fast radio burst.

Science.gov (United States)

Spitler, L G; Scholz, P; Hessels, J W T; Bogdanov, S; Brazier, A; Camilo, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J; Ferdman, R D; Freire, P C C; Kaspi, V M; Lazarus, P; Lynch, R; Madsen, E C; McLaughlin, M A; Patel, C; Ransom, S M; Seymour, A; Stairs, I H; Stappers, B W; van Leeuwen, J; Zhu, W W

2016-03-10

Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

The genesis of period-adding bursting without bursting-chaos in the Chay model

International Nuclear Information System (INIS)

Yang Zhuoqin; Lu Qishao; Li Li

2006-01-01

According to the period-adding firing patterns without chaos observed in neuronal experiments, the genesis of the period-adding 'fold/homoclinic' bursting sequence without bursting-chaos is explored by numerical simulation, fast/slow dynamics and bifurcation analysis of limit cycle in the neuronal Chay model. It is found that each periodic bursting, from period-1 to period-7, is separately generated by the corresponding periodic spiking pattern through two period-doubling bifurcations, except for the period-1 bursting occurring via a Hopf bifurcation. Consequently, it can be revealed that this period-adding bursting bifurcation without chaos has a compound bifurcation structure with transitions from spiking to bursting, which is closely related to period-doubling bifurcations of periodic spiking in essence

INVESTIGATION OF PRIMORDIAL BLACK HOLE BURSTS USING INTERPLANETARY NETWORK GAMMA-RAY BURSTS

Energy Technology Data Exchange (ETDEWEB)

Ukwatta, T. N. [Director' s Postdoctoral Fellow, Space and Remote Sensing (ISR-2), Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Hurley, K. [University of California, Berkeley, Space Sciences Laboratory, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); MacGibbon, J. H. [Department of Physics, University of North Florida, Jacksonville, FL 32224 (United States); Svinkin, D. S.; Aptekar, R. L.; Golenetskii, S. V.; Frederiks, D. D.; Pal' shin, V. D. [Ioffe Physical Technical Institute, St. Petersburg, 194021 (Russian Federation); Goldsten, J. [Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723 (United States); Boynton, W. [Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721 (United States); Kozyrev, A. S. [Space Research Institute, 84/32, Profsoyuznaya, Moscow 117997 (Russian Federation); Rau, A.; Kienlin, A. von; Zhang, X. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, Postfach 1312, Garching, D-85748 (Germany); Connaughton, V. [University of Alabama in Huntsville, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Yamaoka, K. [Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 229-8558 (Japan); Ohno, M. [Department of Physics, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Ohmori, N. [Department of Applied Physics, University of Miyazaki, 1-1 Gakuen kibanadai-nishi, Miyazaki-shi, Miyazaki 889-2192 (Japan); Feroci, M. [INAF/IAPS-Roma, via Fosso del Cavaliere 100, I-00133, Roma (Italy); Frontera, F., E-mail: tilan@lanl.gov [Department of Physics and Earth Science, University of Ferrara, via Saragat 1, I-44122 Ferrara (Italy); and others

2016-07-20

The detection of a gamma-ray burst (GRB) in the solar neighborhood would have very important implications for GRB phenomenology. The leading theories for cosmological GRBs would not be able to explain such events. The final bursts of evaporating primordial black holes (PBHs), however, would be a natural explanation for local GRBs. We present a novel technique that can constrain the distance to GRBs using detections from widely separated, non-imaging spacecraft. This method can determine the actual distance to the burst if it is local. We applied this method to constrain distances to a sample of 36 short-duration GRBs detected by the Interplanetary Network (IPN) that show observational properties that are expected from PBH evaporations. These bursts have minimum possible distances in the 10{sup 13}–10{sup 18} cm (7–10{sup 5} au) range, which are consistent with the expected PBH energetics and with a possible origin in the solar neighborhood, although none of the bursts can be unambiguously demonstrated to be local. Assuming that these bursts are real PBH events, we estimate lower limits on the PBH burst evaporation rate in the solar neighborhood.

Hazards associated with stage one-mining

International Nuclear Information System (INIS)

Anon.

1975-01-01

Radiation hazards in uranium mining arise from the presence of radon-222, a gas which can escape from exposed rock surfaces into the air. Radon daughter products have been associated with an increased incidence of respiratory lung cancer. Other hazards include the tailings which arise from the extraction of uranium ores. The tailings still contain most of the original radium and emit gamma rays and radon gas. The hazards associated with uranium enrichment and fuel manufacture are also discussed. (R.L.)

Gamma Ray Bursts - Observations

Science.gov (United States)

Gehrels, N.; Cannizzo, J. K.

2010-01-01

We are in an exciting period of discovery for gamma-ray bursts. The Swift observatory is detecting 100 bursts per year, providing arcsecond localizations and sensitive observations of the prompt and afterglow emission. The Fermi observatory is observing 250 bursts per year with its medium-energy GRB instrument and about 10 bursts per year with its high-energy LAT instrument. In addition, rapid-response telescopes on the ground are providing new capabilities to study optical emission during the prompt phase and spectral signatures of the host galaxies. The combined data set is enabling great advances in our understanding of GRBs including afterglow physics, short burst origin, and high energy emission.

Heterogeneity in Short Gamma-Ray Bursts

Science.gov (United States)

Norris, Jay P.; Gehrels Neil; Scargle, Jeffrey D.

2011-01-01

We analyze the Swift/BAT sample of short gamma-ray bursts, using an objective Bayesian Block procedure to extract temporal descriptors of the bursts' initial pulse complexes (IPCs). The sample comprises 12 and 41 bursts with and without extended emission (EE) components, respectively. IPCs of non-EE bursts are dominated by single pulse structures, while EE bursts tend to have two or more pulse structures. The medians of characteristic timescales - durations, pulse structure widths, and peak intervals - for EE bursts are factors of approx 2-3 longer than for non-EE bursts. A trend previously reported by Hakkila and colleagues unifying long and short bursts - the anti-correlation of pulse intensity and width - continues in the two short burst groups, with non-EE bursts extending to more intense, narrower pulses. In addition we find that preceding and succeeding pulse intensities are anti-correlated with pulse interval. We also examine the short burst X-ray afterglows as observed by the Swift/XRT. The median flux of the initial XRT detections for EE bursts (approx 6 X 10(exp -10) erg / sq cm/ s) is approx > 20 x brighter than for non-EE bursts, and the median X-ray afterglow duration for EE bursts (approx 60,000 s) is approx 30 x longer than for non-EE bursts. The tendency for EE bursts toward longer prompt-emission timescales and higher initial X-ray afterglow fluxes implies larger energy injections powering the afterglows. The longer-lasting X-ray afterglows of EE bursts may suggest that a significant fraction explode into more dense environments than non-EE bursts, or that the sometimes-dominant EE component efficiently p()wers the afterglow. Combined, these results favor different progenitors for EE and non-EE short bursts.

HETEROGENEITY IN SHORT GAMMA-RAY BURSTS

International Nuclear Information System (INIS)

Norris, Jay P.; Gehrels, Neil; Scargle, Jeffrey D.

2011-01-01

We analyze the Swift/BAT sample of short gamma-ray bursts, using an objective Bayesian Block procedure to extract temporal descriptors of the bursts' initial pulse complexes (IPCs). The sample is comprised of 12 and 41 bursts with and without extended emission (EE) components, respectively. IPCs of non-EE bursts are dominated by single pulse structures, while EE bursts tend to have two or more pulse structures. The medians of characteristic timescales-durations, pulse structure widths, and peak intervals-for EE bursts are factors of ∼2-3 longer than for non-EE bursts. A trend previously reported by Hakkila and colleagues unifying long and short bursts-the anti-correlation of pulse intensity and width-continues in the two short burst groups, with non-EE bursts extending to more intense, narrower pulses. In addition, we find that preceding and succeeding pulse intensities are anti-correlated with pulse interval. We also examine the short burst X-ray afterglows as observed by the Swift/X-Ray Telescope (XRT). The median flux of the initial XRT detections for EE bursts (∼6x10 -10 erg cm -2 s -1 ) is ∼>20x brighter than for non-EE bursts, and the median X-ray afterglow duration for EE bursts (∼60,000 s) is ∼30x longer than for non-EE bursts. The tendency for EE bursts toward longer prompt-emission timescales and higher initial X-ray afterglow fluxes implies larger energy injections powering the afterglows. The longer-lasting X-ray afterglows of EE bursts may suggest that a significant fraction explode into denser environments than non-EE bursts, or that the sometimes-dominant EE component efficiently powers the afterglow. Combined, these results favor different progenitors for EE and non-EE short bursts.

Time-dependent behaviour of deep level tabular excavations in hard rock

CSIR Research Space (South Africa)

Malan, DF

1999-04-01

Full Text Available . It appears that the closure data may provide useful diagnostic information of the stress conditions in the fracture zone ahead of the face. This may possibly be used to identify hazardous conditions such as areas prone to face bursting. The effect...

Hard-rock tunneling using pulsed electron beams

International Nuclear Information System (INIS)

Avery, R.T.; Keefe, D.; Brekke, T.L.; Finnie, I.

1975-01-01

Intense sub-microsecond bursts of energetic electrons cause significant pulverization and surface spalling of a variety of rock types. The spall debris generally consists of sand, dust, and small flakes. If carried out at rapid repetition rate, this technique appears promising for increasing the speed and reducing the cost of underground excavation of tunnels, mines, and storage spaces. The conceptual design features of a pulsed electron tunnel excavator, capable of tunneling approximately ten times faster than conventional drill/blast methods, is presented. (auth)

Seismic hazard maps for Haiti

Science.gov (United States)

Frankel, Arthur; Harmsen, Stephen; Mueller, Charles; Calais, Eric; Haase, Jennifer

2011-01-01

We have produced probabilistic seismic hazard maps of Haiti for peak ground acceleration and response spectral accelerations that include the hazard from the major crustal faults, subduction zones, and background earthquakes. The hazard from the Enriquillo-Plantain Garden, Septentrional, and Matheux-Neiba fault zones was estimated using fault slip rates determined from GPS measurements. The hazard from the subduction zones along the northern and southeastern coasts of Hispaniola was calculated from slip rates derived from GPS data and the overall plate motion. Hazard maps were made for a firm-rock site condition and for a grid of shallow shear-wave velocities estimated from topographic slope. The maps show substantial hazard throughout Haiti, with the highest hazard in Haiti along the Enriquillo-Plantain Garden and Septentrional fault zones. The Matheux-Neiba Fault exhibits high hazard in the maps for 2% probability of exceedance in 50 years, although its slip rate is poorly constrained.

BurstMem: A High-Performance Burst Buffer System for Scientific Applications

Energy Technology Data Exchange (ETDEWEB)

Wang, Teng [Auburn University, Auburn, Alabama; Oral, H Sarp [ORNL; Wang, Yandong [Auburn University, Auburn, Alabama; Settlemyer, Bradley W [ORNL; Atchley, Scott [ORNL; Yu, Weikuan [Auburn University, Auburn, Alabama

2014-01-01

The growth of computing power on large-scale sys- tems requires commensurate high-bandwidth I/O system. Many parallel file systems are designed to provide fast sustainable I/O in response to applications soaring requirements. To meet this need, a novel system is imperative to temporarily buffer the bursty I/O and gradually flush datasets to long-term parallel file systems. In this paper, we introduce the design of BurstMem, a high- performance burst buffer system. BurstMem provides a storage framework with efficient storage and communication manage- ment strategies. Our experiments demonstrate that BurstMem is able to speed up the I/O performance of scientific applications by up to 8.5 on leadership computer systems.

Nonlinear Dynamics Mechanism of Rock Burst Induced by the Instability of the Layer-Crack Plate Structure in the Coal Wall in Deep Coal Mining

Directory of Open Access Journals (Sweden)

Yanlong Chen

2017-01-01

Full Text Available The instability of layer-crack plate structure in coal wall is one of the causes of rock burst. In the present paper, we investigate the formation and instability processes of layer-crack plate structure in coal wall by experiments and theoretical analysis. The results reveal that layer-crack plate structure formed near the free surface of the coal wall during the loading. During the formation of the layer-crack plate structure, the lateral displacement curve of the coal wall experiences a jagged variation, which suggests the nonlinear instability failure of the coal wall with a sudden release of the elastic energy. Then, a dynamic model for the stability analysis of the layer-crack plate structure was proposed, which takes consideration of the dynamic disturbance factor. Based on the dynamic model, the criterion for dynamic instability of the layer-crack plate structure was determined and demonstrated by an example. According to the analytical results, some control methods of dynamic stability of the layer-crack plate structure was put forward.

Bursting Bubbles from Combustion of Thermoplastic Materials in Microgravity

Science.gov (United States)

Butler, K. B.

1999-01-01

Many thermoplastic materials in common use for a wide range of applications, including spacecraft, develop bubbles internally as they burn due to chemical reactions taking place within the bulk. These bubbles grow and migrate until they burst at the surface, forceably ejecting volatile gases and, occasionally, molten fuel. In experiments in normal gravity, Kashiwagi and Ohlemiller observed vapor jets extending a few centimeters from the surface of a radiatively heated polymethylmethacrylate (PMMA) sample, with some molten material ejected into the gas phase. These physical phenomena complicated the combustion process considerably. In addition to the non-steady release of volatiles, the depth of the surface layer affected by oxygen was increased, attributed to the roughening of the surface by bursting events. The ejection of burning droplets in random directions presents a potential fire hazard unique to microgravity. In microgravity combustion experiments on nylon Velcro fasteners and on polyethylene wire insulation, the presence of bursting fuel vapor bubbles was associated with the ejection of small particles of molten fuel as well as pulsations of the flame. For the nylon fasteners, particle velocities were higher than 30 cm/sec. The droplets burned robustly until all fuel was consumed, demonstrating the potential for the spread of fire in random directions over an extended distance. The sequence of events for a bursting bubble has been photographed by Newitt et al.. As the bubble reaches the fluid surface, the outer surface forms a dome while the internal bubble pressure maintains a depression at the inner interface. Liquid drains from the dome until it breaks into a cloud of droplets on the order of a few microns in size. The bubble gases are released rapidly, generating vortices in the quiescent surroundings and transporting the tiny droplets. The depression left by the escaping gases collapses into a central jet, which rises with a high velocity and may

A search for optical bursts from the repeating fast radio burst FRB 121102

Science.gov (United States)

Hardy, L. K.; Dhillon, V. S.; Spitler, L. G.; Littlefair, S. P.; Ashley, R. P.; De Cia, A.; Green, M. J.; Jaroenjittichai, P.; Keane, E. F.; Kerry, P.; Kramer, M.; Malesani, D.; Marsh, T. R.; Parsons, S. G.; Possenti, A.; Rattanasoon, S.; Sahman, D. I.

2017-12-01

We present a search for optical bursts from the repeating fast radio burst FRB 121102 using simultaneous observations with the high-speed optical camera ULTRASPEC on the 2.4-m Thai National Telescope and radio observations with the 100-m Effelsberg Radio Telescope. A total of 13 radio bursts were detected, but we found no evidence for corresponding optical bursts in our 70.7-ms frames. The 5σ upper limit to the optical flux density during our observations is 0.33 mJy at 767 nm. This gives an upper limit for the optical burst fluence of 0.046 Jy ms, which constrains the broad-band spectral index of the burst emission to α ≤ -0.2. Two of the radio pulses are separated by just 34 ms, which may represent an upper limit on a possible underlying periodicity (a rotation period typical of pulsars), or these pulses may have come from a single emission window that is a small fraction of a possible period.

Cosmic gamma bursts

International Nuclear Information System (INIS)

Ehstulin, I.V.

1980-01-01

A brief consideration is being given to the history of cosmic gamma burst discovery and modern knowledge of their properties. The time dependence of gamma bursts is described and their possible sources are discussed

Detection circuit for gamma-ray burst

International Nuclear Information System (INIS)

Murakami, Hiroyuki; Yamagami, Takamasa; Mori, Kunishiro; Uchiyama, Sadayuki.

1982-01-01

A new gamma-ray burst detection system is described. The system was developed as an environmental monitor of an accelerator, and can be used as the burst detection system. The system detects the arrival time of burst. The difference between the arrival times detected at different places will give information on the burst source. The frequency of detecting false burst was estimated, and the detection limit under the estimated frequency of false burst was also calculated. Decision whether the signal is false or true burst was made by the statistical treatment. (Kato, T.)

Hard rock tunneling using pulsed electron beams

International Nuclear Information System (INIS)

Avery, R.T.; Brekke, T.L.; Finnie, I.

1974-01-01

Intense submicrosecond bursts of energetic electrons cause significant pulverization and surface spalling of a variety of rock types, the spall debris generally consisting of sand, dust, and small flakes. If carried out at rapid repetition rate this can lead to a promising technique for increasing the speed and reducing the cost of underground excavation of tunnels, mines, and storage spaces. The conceptual design features of a Pulsed Electron Tunnel Excavator capable of tunneling approximately ten times faster than conventional drill/blast methods were studied. (auth)

The influence of regional geological settings on the seismic hazard level in copper mines in the Legnica-Głogów Copper Belt Area (Poland

Directory of Open Access Journals (Sweden)

Burtan Zbigniew

2017-01-01

Full Text Available The current level of rockburst hazard in copper mines of the (LGOM Legnica- Głogów Copper Belt Area is mostly the consequence of mining-induced seismicity, whilst the majority of rockbursting events registered to date were caused by high-energy tremors. The analysis of seismic readings in recent years reveals that the highest seismic activity among the copper mines in the LGOM is registered in the mine Rudna. This study investigates the seismic activity in the rock strata in the Rudna mine fields over the years 2006-2015. Of particular interest are the key seismicity parameters: the number of registered seismic events, the total energy emissions, the energy index. It appears that varied seismic activity in the area may be the function of several variables: effective mining thickness, the thickness of burst-prone strata and tectonic intensity. The results support and corroborate the view that principal factors influencing the actual seismic hazard level are regional geological conditions in the copper mines within the Legnica-Głogów Copper Belt Area.

The influence of regional geological settings on the seismic hazard level in copper mines in the Legnica-Głogów Copper Belt Area (Poland)

Science.gov (United States)

Burtan, Zbigniew

2017-11-01

The current level of rockburst hazard in copper mines of the (LGOM) Legnica- Głogów Copper Belt Area is mostly the consequence of mining-induced seismicity, whilst the majority of rockbursting events registered to date were caused by high-energy tremors. The analysis of seismic readings in recent years reveals that the highest seismic activity among the copper mines in the LGOM is registered in the mine Rudna. This study investigates the seismic activity in the rock strata in the Rudna mine fields over the years 2006-2015. Of particular interest are the key seismicity parameters: the number of registered seismic events, the total energy emissions, the energy index. It appears that varied seismic activity in the area may be the function of several variables: effective mining thickness, the thickness of burst-prone strata and tectonic intensity. The results support and corroborate the view that principal factors influencing the actual seismic hazard level are regional geological conditions in the copper mines within the Legnica-Głogów Copper Belt Area.

Gamma-ray burst models.

Science.gov (United States)

King, Andrew

2007-05-15

I consider various possibilities for making gamma-ray bursts, particularly from close binaries. In addition to the much-studied neutron star+neutron star and black hole+neutron star cases usually considered good candidates for short-duration bursts, there are also other possibilities. In particular, neutron star+massive white dwarf has several desirable features. These systems are likely to produce long-duration gamma-ray bursts (GRBs), in some cases definitely without an accompanying supernova, as observed recently. This class of burst would have a strong correlation with star formation and occur close to the host galaxy. However, rare members of the class need not be near star-forming regions and could have any type of host galaxy. Thus, a long-duration burst far from any star-forming region would also be a signature of this class. Estimates based on the existence of a known progenitor suggest that this type of GRB may be quite common, in agreement with the fact that the absence of a supernova can only be established in nearby bursts.

Solar microwave bursts - A review

Science.gov (United States)

Kundu, M. R.; Vlahos, L.

1982-01-01

Observational and theoretical results on the physics of microwave bursts that occur in the solar atmosphere are reviewed. Special attention is given to the advances made in burst physics over the last few years with the great improvement in spatial and time resolution, especially with instruments like the NRAO three-element interferometer, the Westerbork Synthesis Radio Telescope, and more recently the Very Large Array. Observations made on the preflare build-up of an active region at centimeter wavelengths are reviewed. Three distinct phases in the evolution of cm bursts, namely the impulsive phase, the post-burst phase, and the gradual rise and fall, are discussed. Attention is also given to the flux density spectra of centimeter bursts. Descriptions are given of observations of fine structures with temporal resolution of 10-100 ms in the intensity profiles of cm-wavelength bursts. High spatial resolution observations are analyzed, with special reference to the one- and two-dimensional maps of cm burst sources.

Neutron activation analysis of alternative phosphate rocks used in animal nutrition

International Nuclear Information System (INIS)

Canella, Artur A.; Ferreira, Walter M.

2005-01-01

Since 1980's, Bovine Sponghiform Encephalophaty has insidiously created a fierce battleground between farmers, scientists, environmentalists and consumers. The use of meat and bone meals is currently prohibited in ruminant feeds throughout the world. Some inorganic sources offer the combination of high phosphorus content and acceptable animal digestibility make them options as supplemental phosphorus, for instance phosphate rocks, general term applied to minerals valued chiefly for their phosphorus content. However, phosphate rocks are long been known containing hazardous elements, make them sometimes unsuitable for animal nutrition. Neutron Activation Analysis has been supportive to the mineral evaluation of alternative phosphate rocks. This evaluation is subject of on-going doctoral thesis which has been carried-out by the main author. The NAA method has been very efficient due to its highly sensitive and multi-elemental nature. In this paper results of Vanadium content from three different phosphate rocks are presented. Their values have been pointed out that Brazilian phosphate rocks present hazardous elements at the same levels of phosphate rocks from some countries of Africa, North America and Middle East, data from our study (Brazilian data) and FAO - Food and Agriculture Organization (others countries). (author)

Optical observations of Gamma-Ray Bursts

International Nuclear Information System (INIS)

Hjorth, J.; Pian, E.; Fynbo, J.P.U.

2004-01-01

We briefly review the status and recent progress in the field of optical observations of gamma-ray burst afterglows. We will focus on the fundamental observational evidence for the relationship between gamma-ray bursts and the final evolutionary phases of massive stars. In particular, we will address (i) gamma-ray burst host galaxies, (ii) optically dark gamma-ray burst afterglows, (iii) the gamma-ray burst-supernova connection, and (iv) the relation between X-ray flashes, gamma-ray bursts, and supernovae

Solar Radio Bursts and Space Weather

Science.gov (United States)

Gopalswamy, Natchimuthuk,

2012-01-01

Radio bursts from the Sun are produced by electron accelerated to relativistic energies by physical processes on the Sun such as solar flares and coronal mass ejections (CMEs). The radio bursts are thus good indicators of solar eruptions. Three types of nonthermal radio bursts are generally associated with CMEs. Type III bursts due to accelerated electrons propagating along open magnetic field lines. The electrons are thought to be accelerated at the reconnection region beneath the erupting CME, although there is another view that the electrons may be accelerated at the CME-driven shock. Type II bursts are due to electrons accelerated at the shock front. Type II bursts are also excellent indicators of solar energetic particle (SEP) events because the same shock is supposed accelerate electrons and ions. There is a hierarchical relationship between the wavelength range of type /I bursts and the CME kinetic energy. Finally, Type IV bursts are due to electrons trapped in moving or stationary structures. The low frequency stationary type IV bursts are observed occasionally in association with very fast CMEs. These bursts originate from flare loops behind the erupting CME and hence indicate tall loops. This paper presents a summary of radio bursts and their relation to CMEs and how they can be useful for space weather predictions.

Electromagnetic emission graded warning model and its applications against coal rock dynamic collapses

Energy Technology Data Exchange (ETDEWEB)

Wang, E.Y.; He, X.Q.; Wei, J.P.; Nie, B.S.; Song, D.Z. [China University of Mining & Technology, Xuzhou (China)

2011-06-15

Dynamic collapses of deeply mined coal rocks are severe threats to miners. In order to predict the collapses more accurately using electromagnetic emission (EME), we established a loaded coal rock EME electromechanical coupling model based on statistical damage mechanics. By using it, we numerically simulated both the accumulative pulse and strain ratios. We further improved the model with the Weibull pattern parameter, which has important effects on simulated results and can be applied to judge coal's homogeneity, and determined the pattern parameter and its value domain. Based on the revised model and the characteristics of coal rock deformation and fracture, we setup EME graded warning criteria against coal rock dynamic collapses by determining static critical coefficient and dynamic trend coefficient. We have applied this model to predict and deal with coal and gas outburst and rock burst occurring at Xie I and Taoshan Mines, respectively. All these verifications show that the model has many advantages and provides more sensitive and accurate warning for dynamic collapses.

Seismic hazard studies in Egypt

Directory of Open Access Journals (Sweden)

Abuo El-Ela A. Mohamed

2012-12-01

Full Text Available The study of earthquake activity and seismic hazard assessment of Egypt is very important due to the great and rapid spreading of large investments in national projects, especially the nuclear power plant that will be held in the northern part of Egypt. Although Egypt is characterized by low seismicity, it has experienced occurring of damaging earthquake effect through its history. The seismotectonic sitting of Egypt suggests that large earthquakes are possible particularly along the Gulf of Aqaba–Dead Sea transform, the Subduction zone along the Hellenic and Cyprean Arcs, and the Northern Red Sea triple junction point. In addition some inland significant sources at Aswan, Dahshour, and Cairo-Suez District should be considered. The seismic hazard for Egypt is calculated utilizing a probabilistic approach (for a grid of 0.5° × 0.5° within a logic-tree framework. Alternative seismogenic models and ground motion scaling relationships are selected to account for the epistemic uncertainty. Seismic hazard values on rock were calculated to create contour maps for four ground motion spectral periods and for different return periods. In addition, the uniform hazard spectra for rock sites for different 25 periods, and the probabilistic hazard curves for Cairo, and Alexandria cities are graphed. The peak ground acceleration (PGA values were found close to the Gulf of Aqaba and it was about 220 gal for 475 year return period. While the lowest (PGA values were detected in the western part of the western desert and it is less than 25 gal.

Complex transitions between spike, burst or chaos synchronization states in coupled neurons with coexisting bursting patterns

International Nuclear Information System (INIS)

Gu Hua-Guang; Chen Sheng-Gen; Li Yu-Ye

2015-01-01

We investigated the synchronization dynamics of a coupled neuronal system composed of two identical Chay model neurons. The Chay model showed coexisting period-1 and period-2 bursting patterns as a parameter and initial values are varied. We simulated multiple periodic and chaotic bursting patterns with non-(NS), burst phase (BS), spike phase (SS), complete (CS), and lag synchronization states. When the coexisting behavior is near period-2 bursting, the transitions of synchronization states of the coupled system follows very complex transitions that begins with transitions between BS and SS, moves to transitions between CS and SS, and to CS. Most initial values lead to the CS state of period-2 bursting while only a few lead to the CS state of period-1 bursting. When the coexisting behavior is near period-1 bursting, the transitions begin with NS, move to transitions between SS and BS, to transitions between SS and CS, and then to CS. Most initial values lead to the CS state of period-1 bursting but a few lead to the CS state of period-2 bursting. The BS was identified as chaos synchronization. The patterns for NS and transitions between BS and SS are insensitive to initial values. The patterns for transitions between CS and SS and the CS state are sensitive to them. The number of spikes per burst of non-CS bursting increases with increasing coupling strength. These results not only reveal the initial value- and parameter-dependent synchronization transitions of coupled systems with coexisting behaviors, but also facilitate interpretation of various bursting patterns and synchronization transitions generated in the nervous system with weak coupling strength. (paper)

Gamma-ray burst spectra

International Nuclear Information System (INIS)

Teegarden, B.J.

1982-01-01

A review of recent results in gamma-ray burst spectroscopy is given. Particular attention is paid to the recent discovery of emission and absorption features in the burst spectra. These lines represent the strongest evidence to date that gamma-ray bursts originate on or near neutron stars. Line parameters give information on the temperature, magnetic field and possibly the gravitational potential of the neutron star. The behavior of the continuum spectrum is also discussed. A remarkably good fit to nearly all bursts is obtained with a thermal-bremsstrahlung-like continuum. Significant evolution is observed of both the continuum and line features within most events

Evaluation of the instability problems in rock slopes surrounding historical Safranbolu by kinematic analysis

Directory of Open Access Journals (Sweden)

İnan Keskin

2017-10-01

Full Text Available Safranbolu which has high probability for slope-induced disasters is a very worthwhile settlement for our country and also for the world with its historical and cultural heritage. Finding out potential hazards that may affect the wealth of this world heritage city is very crucial. The historic Safranbolu is surrounded by very steep rock slopes, and occasionally instability occurs in the rock mass that forms these slopes. The rock blocks that are relaesed in various causes and shapes can damage the historic town living spaces by creating a source for the rock fallings and moving down the slope in these very steep slopes. The rock slopes were evaluated by kinematic analysis in order to reduce the mentioned damages and to reveal potential hazards. In the study, characteristics of mass that causes rock fallings are analysed, kinematic controlled instability types are determined considering the obtained data and characteristic of slopes.

Analysis of historic bursts and burst detection in water supply areas of different size

NARCIS (Netherlands)

Bakker, M.; Trietsch, E.A.; Vreeburg, J.H.G.; Rietveld, L.C.

2014-01-01

Pipe bursts in water distribution networks lead to water losses and a risk of damaging the urban environment. We studied hydraulic data and customer contact records of 44 real bursts for a better understanding of the phenomena. We found that most bursts were reported to the water company shortly

Influence of Fissure Number on the Mechanical Properties of Layer-Crack Rock Models under Uniaxial Compression

Directory of Open Access Journals (Sweden)

Yun-liang Tan

2018-01-01

Full Text Available Many case studies have revealed that rock bursts generally occur in the high stress concentration area where layer-crack structures often exist, especially for brittle coal or rock masses. Understanding the mechanical properties of layer-crack rock models is beneficial for rational design and stability analysis of rock engineering project and rock burst prevention. This study experimentally investigated the influence of fissure number on the mechanical properties of layer-crack rock models through uniaxial compression tests. The digital speckle correlation method (DSCM and acoustic emission (AE techniques were applied to record and analyze the information of deformation and failure processes. Test results show the following: the bearing capacity of layer-crack specimen decreases compared with intact specimen, but their failure modes are similar, which are the splitting failure accompanied with local shear failure; the nonuniform deformation phenomenon begins to appear at the elastic deformation stage for layer-crack specimens; the AE behavior of intact specimens consists of three stages, that is, active stage, quiet stage, and major active stage, but for layer-crack specimens, it is characteristic by three peaks without quiet stage. In addition, as the fissure number of layer-crack specimens increases, the bearing capacity of specimens decreases, the appearing time of nonuniform deformation phenomenon in the specimen surface decreases, the AE events are denser and denser in each peak stage, and the risk of dynamic instability of layer-crack structure increases. At last, the failure mechanism of layer-crack structure and the related mitigation advices were discussed based on the test results. In general, the novelty is that this paper focuses on the failure mechanism of layer-crack structure directly.

Rockfall Hazard Process Assessment : Implementation Report

Science.gov (United States)

2017-10-01

The Montana Department of Transportation (MDT) commissioned a new research program to improve assessment and management of its rock slope assets. The Department implemented a Rockfall Hazard Rating System (RHRS) program in 2005 and wished to add valu...

Acoustic Emission Behavior of Rock-Like Material Containing Two Flaws in the Process of Deformation Failure

Directory of Open Access Journals (Sweden)

Quan-Sheng Liu

2015-01-01

Full Text Available Many sudden disasters (such as rock burst by mining extraction originate in crack initiation and propagation. Meanwhile a large number of shock waves are produced by rock deformation and failure. With the purpose of investigating crack coalescence and failure mechanism in rock, experimental research of rock-like materials with two preexisting flaws was performed. Moreover, the AE technique and photographic monitoring were adopted to clarify further the procedure of the crack coalescence and failure. It reveals that AE location technique can record the moments of crack occurrences and follow the crack growth until final failure. Finally, the influence of different flaw geometries on crack initiation strength is analyzed in detail. This research provides increased understanding of the fracture mechanism of mining-induced disasters.

Fermi/GAMMA-RAY BURST MONITOR OBSERVATIONS OF SGR J0501+4516 BURSTS

International Nuclear Information System (INIS)

Lin Lin; Zhang Shuangnan; Kouveliotou, Chryssa; Baring, Matthew G.; Van der Horst, Alexander J.; Finger, Mark H.; Guiriec, Sylvain; Preece, Robert; Chaplin, Vandiver; Bhat, Narayan; Woods, Peter M.; Goegues, Ersin; Kaneko, Yuki; Scargle, Jeffrey; Granot, Jonathan; Von Kienlin, Andreas; Watts, Anna L.; Wijers, Ralph A. M. J.; Gehrels, Neil; Harding, Alice

2011-01-01

We present our temporal and spectral analyses of 29 bursts from SGR J0501+4516, detected with the gamma-ray burst monitor on board the Fermi Gamma-ray Space Telescope during 13 days of the source's activation in 2008 (August 22- September 3). We find that the T 90 durations of the bursts can be fit with a log-normal distribution with a mean value of ∼123 ms. We also estimate for the first time event durations of soft gamma repeater (SGR) bursts in photon space (i.e., using their deconvolved spectra) and find that these are very similar to the T 90 values estimated in count space (following a log-normal distribution with a mean value of ∼124 ms). We fit the time-integrated spectra for each burst and the time-resolved spectra of the five brightest bursts with several models. We find that a single power law with an exponential cutoff model fits all 29 bursts well, while 18 of the events can also be fit with two blackbody functions. We expand on the physical interpretation of these two models and we compare their parameters and discuss their evolution. We show that the time-integrated and time-resolved spectra reveal that E peak decreases with energy flux (and fluence) to a minimum of ∼30 keV at F = 8.7 x 10 -6 erg cm -2 s -1 , increasing steadily afterward. Two more sources exhibit a similar trend: SGRs J1550-5418 and 1806-20. The isotropic luminosity, L iso , corresponding to these flux values is roughly similar for all sources (0.4-1.5 x 10 40 erg s -1 ).

PWR clad ballooning: The effect of circumferential clad temperature variations on the burst strain/burst temperature relationship

International Nuclear Information System (INIS)

Barlow, P.

1983-01-01

By experiment, it has been shown by other workers that there is a reduction in the creep ductility of Zircaloy 4 in the α+β phase transition region. Results from single rod burst tests also show a reduction in burst strain in the α+β phase region. In this report it is shown theoretically that for single rod burst tests in the presence of circumferential temperature gradients, the temperature dependence of the mean burst strain is not determined by temperature variations in creep ductility, but is governed by the temperature sensitivity of the creep strain rate, which is shown to be a maximum in the α+β phase transition region. To demonstrate this effect, the mean clad strain at burst was calculated for creep straining at different temperature levels in the α, α+β and β phase regions. Cross-pin temperature gradients were applied which produced strain variations around the clad which were greatest in the α+β phase region. The mean strain at burst was determined using a maximum local burst strain (i.e. a creep ductility) which is independent of temperature. By assuming cross-pin temperature gradients which are typical of those observed during burst tests, then the calculated mean burst strain/burst temperature relationship gave good agreement with experiment. The calculations also show that when circumferential temperature differences are present, the calculated mean strain at burst is not sensitive to variations in the magnitude of the assumed creep ductility. This reduces the importance of the assumed burst criterion in the calculations. Hence a temperature independent creep ductility (e.g. 100% local strain) is adequate as a burst criterion for calculations under PWR LOCA conditions. (author)

Observations of short gamma-ray bursts.

Science.gov (United States)

Fox, Derek B; Roming, Peter W A

2007-05-15

We review recent observations of short-hard gamma-ray bursts and their afterglows. The launch and successful ongoing operations of the Swift satellite, along with several localizations from the High-Energy Transient Explorer mission, have provoked a revolution in short-burst studies: first, by quickly providing high-quality positions to observers; and second, via rapid and sustained observations from the Swift satellite itself. We make a complete accounting of Swift-era short-burst localizations and proposed host galaxies, and discuss the implications of these observations for the distances, energetics and environments of short bursts, and the nature of their progenitors. We then review the physical modelling of short-burst afterglows: while the simplest afterglow models are inadequate to explain the observations, there have been several notable successes. Finally, we address the case of an unusual burst that threatens to upset the simple picture in which long bursts are due to the deaths of massive stars, and short bursts to compact-object merger events.

X-ray bursts: Observation versus theory

Science.gov (United States)

Lewin, W. H. G.

1981-01-01

Results of various observations of common type I X-ray bursts are discussed with respect to the theory of thermonuclear flashes in the surface layers of accreting neutron stars. Topics covered include burst profiles; irregular burst intervals; rise and decay times and the role of hydrogen; the accuracy of source distances; accuracy in radii determination; radius increase early in the burst; the super Eddington limit; temperatures at burst maximum; and the role of the magnetic field.

Secured Hash Based Burst Header Authentication Design for Optical Burst Switched Networks

Science.gov (United States)

Balamurugan, A. M.; Sivasubramanian, A.; Parvathavarthini, B.

2017-12-01

The optical burst switching (OBS) is a promising technology that could meet the fast growing network demand. They are featured with the ability to meet the bandwidth requirement of applications that demand intensive bandwidth. OBS proves to be a satisfactory technology to tackle the huge bandwidth constraints, but suffers from security vulnerabilities. The objective of this proposed work is to design a faster and efficient burst header authentication algorithm for core nodes. There are two important key features in this work, viz., header encryption and authentication. Since the burst header is an important in optical burst switched network, it has to be encrypted; otherwise it is be prone to attack. The proposed MD5&RC4-4S based burst header authentication algorithm runs 20.75 ns faster than the conventional algorithms. The modification suggested in the proposed RC4-4S algorithm gives a better security and solves the correlation problems between the publicly known outputs during key generation phase. The modified MD5 recommended in this work provides 7.81 % better avalanche effect than the conventional algorithm. The device utilization result also shows the suitability of the proposed algorithm for header authentication in real time applications.

Looking before we leap: an ongoing, quantative investigation of asteroid and comet impact hazard mitigation

Energy Technology Data Exchange (ETDEWEB)

Plesko, Catherine S [Los Alamos National Laboratory; Weaver, Robert P [Los Alamos National Laboratory; Bradley, Paul A [Los Alamos National Laboratory; Huebner, Walter F [Los Alamos National Laboratory

2010-01-01

There are many outstanding questions about the correct response to an asteroid or comet impact threat on Earth. Nuclear munitions are currently thought to be the most efficient method of delivering an impact-preventing impulse to a potentially hazardous object (PHO). However, there are major uncertainties about the response of PHOs to a nuclear burst, and the most appropriate ways to use nuclear munitions for hazard mitigation.

Geomechanical rock properties of a basaltic volcano

Directory of Open Access Journals (Sweden)

Lauren N Schaefer

2015-06-01

Full Text Available In volcanic regions, reliable estimates of mechanical properties for specific volcanic events such as cyclic inflation-deflation cycles by magmatic intrusions, thermal stressing, and high temperatures are crucial for building accurate models of volcanic phenomena. This study focuses on the challenge of characterizing volcanic materials for the numerical analyses of such events. To do this, we evaluated the physical (porosity, permeability and mechanical (strength properties of basaltic rocks at Pacaya Volcano (Guatemala through a variety of laboratory experiments, including: room temperature, high temperature (935 °C, and cyclically-loaded uniaxial compressive strength tests on as-collected and thermally-treated rock samples. Knowledge of the material response to such varied stressing conditions is necessary to analyze potential hazards at Pacaya, whose persistent activity has led to 13 evacuations of towns near the volcano since 1987. The rocks show a non-linear relationship between permeability and porosity, which relates to the importance of the crack network connecting the vesicles in these rocks. Here we show that strength not only decreases with porosity and permeability, but also with prolonged stressing (i.e., at lower strain rates and upon cooling. Complimentary tests in which cyclic episodes of thermal or load stressing showed no systematic weakening of the material on the scale of our experiments. Most importantly, we show the extremely heterogeneous nature of volcanic edifices that arise from differences in porosity and permeability of the local lithologies, the limited lateral extent of lava flows, and the scars of previous collapse events. Input of these process-specific rock behaviors into slope stability and deformation models can change the resultant hazard analysis. We anticipate that an increased parameterization of rock properties will improve mitigation power.

Chaotic characteristic of electromagnetic radiation time series of coal or rock under different scales

Energy Technology Data Exchange (ETDEWEB)

Zhen-Tang Liu; En-Lai Zhao; En-Yuan Wang; Jing Wang [China University of Mining and Technology, Xuzhou (China). School of Safety Engineering

2009-02-15

Based on chaos theory, the chaotic characteristics of electromagnetic radiation time series of coal or rock under different loads was studied. The results show that the correlation of electromagnetic radiation time series of small-scale coal or rock and coal mine converges to a stable saturation value, which shows that these electromagnetic radiation time series have chaos characteristics. When there is danger of coal seam burst, the value of the saturation correlation dimension D{sub 2} of the electromagnetic radiation time series is bigger and it changes greatly; when there is no danger, its value is smaller and changes smoothly. The change of saturation correlation of electromagnetic radiation time series can be used to forecast coal or rock dynamic disasters. 11 refs., 4 figs.

Solar Drift-Pair Bursts

Science.gov (United States)

Stanislavsky, A.; Volvach, Ya.; Konovalenko, A.; Koval, A.

2017-08-01

In this paper a new sight on the study of solar bursts historically called drift pairs (DPs) is presented. Having a simple morphology on dynamic spectra of radio records (two short components separated in time, and often they are very similar) and discovered at the dawn of radio astronomy, their features remain unexplained totally up to now. Generally, the DPs are observed during the solar storms of type III bursts, but not every storm of type III bursts is linked with DPs. Detected by ground-based instruments at decameter and meter wavelengths, the DP bursts are limited in frequency bandwidth. They can drift from high frequencies to low ones and vice versa. Their frequency drift rate may be both lower and higher than typical rates of type III bursts at the same frequency range. The development of low-frequency radio telescopes and data processing provide additional possibilities in the research. In this context the fresh analysis of DPs, made from recent observations in the summer campaign of 2015, are just considered. Their study was implemented by updated tools of the UTR-2 radio telescope at 9-33 MHz. During 10-12 July of 2015, DPs forming the longest patterns on dynamic spectra are about 7% of the total number of recorded DPs. Their marvelous resemblance in frequency drift rates with the solar S-bursts is discussed.

A new energy-absorbing bolt for rock support in high stress rock masses

Energy Technology Data Exchange (ETDEWEB)

Charlie Chunlin Li [Norwegian University of Science and Technology (NTNU) (Norway)

2010-04-15

An energy-absorbing rock support device, called a D bolt, has been recently developed to counteract both burst-prone and squeezing rock conditions that occur during underground excavation. The bolt is a smooth steel bar with a number of anchors along its length. The anchors are firmly fixed within a borehole using either cement grout or resin, while the smooth sections of the bolt between the anchors may freely deform in response to rock dilation. Failure of one section does not affect the reinforcement performance of the other sections. The bolt is designed to fully use both the strength and the deformation capacity of the bolt material along the entire length. The bolt has large load-bearing and deformation capacities. Static pull tests and dynamic drop tests show that the bolt length elongates by 14-20% at a load level equal to the strength of the bolt material, thereby absorbing a large amount of energy. The impact average load of a 20 mm D bolt is 200-230 kN, with only a small portion of the load transferred to the bolt plate. The cumulative dynamic energy absorption of the bolt is measured to be 47 kJ/m. D bolts were tested in three deep mines. Filed measurements show that D bolts are loaded less than rebar bolts. This paper presents the layout and principle of the D bolt, and corresponding results from static, dynamic, and field tests.

Mountain permafrost, glacier thinning, and slope stability - a perspective from British Columbia (and Alaska)

Science.gov (United States)

Geertsema, Marten

2016-04-01

The association of landslides with thinning glaciers and mapped, or measured, mountain permafrost is increasing. Glacier thinning debuttresses slopes and promotes joint expansion. It is relatively easy to map. Permafrost, a thermal condition, is generally not visually detectible, and is difficult to map. Much mountain permafrost may have been overlooked in hazard analysis. Identifying, and characterizing mountain permafrost, and its influence on slope instability is crucial for hazard and risk analysis in mountainous terrain. Rock falls in mountains can be the initial event in process chains. They can transform into rock avalanches, debris flows or dam burst floods, travelling many kilometres, placing infrastructure and settlements at risk.

The Drift Burst Hypothesis

OpenAIRE

Christensen, Kim; Oomen, Roel; Renò, Roberto

2016-01-01

The Drift Burst Hypothesis postulates the existence of short-lived locally explosive trends in the price paths of financial assets. The recent US equity and Treasury flash crashes can be viewed as two high profile manifestations of such dynamics, but we argue that drift bursts of varying magnitude are an expected and regular occurrence in financial markets that can arise through established mechanisms such as feedback trading. At a theoretical level, we show how to build drift bursts into the...

Rock-fall potential in the Yosemite Valley, California

Science.gov (United States)

Wieczorek, G.F.; Morrissey, M.M.; Iovine, Giulio; Godt, Jonathan

1999-01-01

We used two methods of estimating rock-fall potential in the Yosemite Valley, California based on (1) physical evidence of previous rock-fall travel, in which the potential extends to the base of the talus, and (2) theoretical potential energy considerations, in which the potential can extend beyond the base of the talus, herein referred to as the rock-fall shadow. Rock falls in the valley commonly range in size from individual boulders of less than 1 m3 to moderate-sized falls with volumes of about 100,000 m3. Larger rock falls exceeding 100,000 m3, referred to as rock avalanches, are considered to be much less likely to occur based on the relatively few prehistoric rock-fall avalanche deposits in the Yosemite Valley. Because the valley has steep walls and is relatively narrow, there are no areas that are absolutely safe from large rock avalanches. The map shows areas of rock-fall potential, but does not predict when or how frequently a rock fall will occur. Consequently, neither the hazard in terms of probability of a rock fall at any specific location, nor the risk to people or facilities to such events can be assessed from this map.

Ionization and Corona Discharges from Stressed Rocks

Science.gov (United States)

Winnick, M. J.; Kulahci, I.; Cyr, G.; Tregloan-Reed, J.; Freund, F. T.

2008-12-01

Pre-earthquake signals have long been observed and documented, though they have not been adequately explained scientifically. These signals include air ionization, occasional flashes of light from the ground, radio frequency emissions, and effects on the ionosphere that occur hours or even days before large earthquakes. The theory that rocks function as p-type semiconductors when deviatoric stresses are applied offers a mechanism for this group of earthquake precursors. When an igneous or high-grade metamorphic rock is subjected to deviatoric stresses, peroxy bonds that exist in the rock's minerals as point defects dissociate, releasing positive hole charge carriers. The positive holes travel by phonon-assisted electron hopping from the stressed into and through the unstressed rock volume and build up a positive surface charge. At sufficiently large electric fields, especially along edges and sharp points of the rock, air molecules become field-ionized, loosing an electron to the rock surface and turning into airborne positive ions. This in turn can lead to corona discharges, which manifest themselves by flashes of light and radio frequency emissions. We applied concentrated stresses to one end of a block of gabbro, 30 x 15 x 10 cm3, inside a shielded Faraday cage and observed positive ion currents through an air gap about 25 cm from the place where the stresses were applied, punctuated by short bursts, accompanied by flashes of light and radio frequency emissions characteristic of a corona discharge. These observations may serve to explain a range of pre-earthquake signals, in particular changes in air conductivity, luminous phenomena, radio frequency noise, and ionospheric perturbations.

X-ray bursts observed with JEM-X

DEFF Research Database (Denmark)

Brandt, Søren Kristian; Chenevez, Jérôme; Lund, Niels

2006-01-01

We report on the search for X-ray bursts in the JEM-X X-ray monitor on INTEGRAL during the first two years of operations. More than 350 bursts from 25 different type-I X-ray burst sources were found.......We report on the search for X-ray bursts in the JEM-X X-ray monitor on INTEGRAL during the first two years of operations. More than 350 bursts from 25 different type-I X-ray burst sources were found....

黏性防冲锚索支护技术及其在冲击地压矿井中的应用%Application of impact-constant resistance anchor support theory in rock burst mine

Institute of Scientific and Technical Information of China (English)

黄自伟; 韩雪峰; 连小勇; 时晓东; 周辰辰

2016-01-01

为解决现行的支护方法及材料(金属支架、锚网等)在冲击性高应力巷道支护中出现的支护材料破断、支护体失效等问题,提出了黏性支护方法,即在支护系统中加入黏弹性材料,利用附加在锚索尾端的阻尼器增加支护系统黏性,将冲击地压产生的机械能转化为热能,减弱冲击破坏程度;研发了一种新的黏性支护材料——抗冲击恒阻锚索,该支护材料具有高恒阻力让压和抗冲击特性,以阻尼器型号为skp18-1/500的抗冲击恒阻锚索为例,其恒阻力保持在220 kN左右、抗冲击能量大于50 kJ,并通过力学性能实验得以验证;论述了新型支护方法及材料的理论依据及实施措施,通过力学特性检验及现场应用,证实了新型支护体能够通过可控变形吸收转化冲击能量,使围岩从一种稳定状态过渡到另一种稳定状态.%The theory of viscous support was put forward to solve the problems with current support methods and materials (metal stent,bolting-wire mesh) which were extremely prone to failure and fracture when they were used in impact roadway with high stress.The core of viscous support theory required the support system to add viscoelastic materials.The damper was installed on the one end of the anchor cable to increase the viscosity of support system because viscoelastic materials could absorb and consume energy.Thus,it could be used to transfer energy to achieve the purpose of reducing damage,in other words,the mechanical energy caused by rock burst was converted into internal energy.Based on the theory above,the authors had developed a new viscous support product which was named as an impact-constant resistance anchor cable.The cable could have a large deformation when it was pulled to a certain forced state and absorbed the impact energy caused by rock burst.Using skpl8-1/500 damper as an example,when it was pulled up to 220 kN,it would yield a large deformation,when the rock burst occurred

UWB dual burst transmit driver

Science.gov (United States)

Dallum, Gregory E [Livermore, CA; Pratt, Garth C [Discovery Bay, CA; Haugen, Peter C [Livermore, CA; Zumstein, James M [Livermore, CA; Vigars, Mark L [Livermore, CA; Romero, Carlos E [Livermore, CA

2012-04-17

A dual burst transmitter for ultra-wideband (UWB) communication systems generates a pair of precisely spaced RF bursts from a single trigger event. An input trigger pulse produces two oscillator trigger pulses, an initial pulse and a delayed pulse, in a dual trigger generator. The two oscillator trigger pulses drive a gated RF burst (power output) oscillator. A bias driver circuit gates the RF output oscillator on and off and sets the RF burst packet width. The bias driver also level shifts the drive signal to the level that is required for the RF output device.

Solar X-ray bursts

International Nuclear Information System (INIS)

Urnov, A.M.

1980-01-01

In the popular form the consideration is given to the modern state tasks and results of X-ray spectrometry of solar bursts. The operation of X-ray spectroheliograph is described. Results of spectral and polarization measurings of X-ray radiation of one powerful solar burst are presented. The conclusion has been drawn that in the process of burst development three characteristic stages may be distingwished: 1) the initial phase; just in this period processes which lead to observed consequences-electromagnetic and corpuscular radiation are born; 2) the impulse phase, or the phase of maximum, is characterised by sharp increase of radiation flux. During this phase the main energy content emanates and some volumes of plasma warm up to high temperatures; 3) the phase of burst damping, during which plasma cools and reverts to the initial condition

SRS BEDROCK PROBABILISTIC SEISMIC HAZARD ANALYSIS (PSHA) DESIGN BASIS JUSTIFICATION (U)

Energy Technology Data Exchange (ETDEWEB)

(NOEMAIL), R

2005-12-14

This represents an assessment of the available Savannah River Site (SRS) hard-rock probabilistic seismic hazard assessments (PSHAs), including PSHAs recently completed, for incorporation in the SRS seismic hazard update. The prior assessment of the SRS seismic design basis (WSRC, 1997) incorporated the results from two PSHAs that were published in 1988 and 1993. Because of the vintage of these studies, an assessment is necessary to establish the value of these PSHAs considering more recently collected data affecting seismic hazards and the availability of more recent PSHAs. This task is consistent with the Department of Energy (DOE) order, DOE O 420.1B and DOE guidance document DOE G 420.1-2. Following DOE guidance, the National Map Hazard was reviewed and incorporated in this assessment. In addition to the National Map hazard, alternative ground motion attenuation models (GMAMs) are used with the National Map source model to produce alternate hazard assessments for the SRS. These hazard assessments are the basis for the updated hard-rock hazard recommendation made in this report. The development and comparison of hazard based on the National Map models and PSHAs completed using alternate GMAMs provides increased confidence in this hazard recommendation. The alternate GMAMs are the EPRI (2004), USGS (2002) and a regional specific model (Silva et al., 2004). Weights of 0.6, 0.3 and 0.1 are recommended for EPRI (2004), USGS (2002) and Silva et al. (2004) respectively. This weighting gives cluster weights of .39, .29, .15, .17 for the 1-corner, 2-corner, hybrid, and Greens-function models, respectively. This assessment is judged to be conservative as compared to WSRC (1997) and incorporates the range of prevailing expert opinion pertinent to the development of seismic hazard at the SRS. The corresponding SRS hard-rock uniform hazard spectra are greater than the design spectra developed in WSRC (1997) that were based on the LLNL (1993) and EPRI (1988) PSHAs. The

Monitoring burst (M-burst) — A novel framework of failure localization in all-optical mesh networks

KAUST Repository

Ali, Mohammed L.; Ho, Pin-Han; Wu, Bin; Tapolcai, Janos; Shihada, Basem

2011-01-01

Achieving instantaneous and precise failure localization in all-optical wavelength division multiplexing (WDM) networks has been an attractive feature of network fault management systems, and is particularly important when failure-dependent protection is employed. The paper introduces a novel framework of real-time failure localization in all-optical WDM mesh networks, called monitoring-burst (m-burst), which aims to initiate a graceful compromise between consumed monitoring resources and monitoring delay. Different from any previously reported solution, the proposed m-burst framework has a single monitoring node (MN) which launches optical bursts along a set of pre-defined close-loop routes, called monitoring cycles (m-cycles), to probe the links along the m-cycles. Bursts along different m-cycles are kept non-overlapping through any link of the network. By identifying the lost bursts due to single link failure events only, the MN can unambiguously localize the failed link in at least 3-connected networks. We will justify the feasibility and applicability of the proposed m-burst framework in the scenario of interest. To avoid possible collision among optical bursts launched by the MN, we define the problem of collision-free scheduling and formulate it into an integer linear program (ILP) in order to minimize the monitoring delay. Numerical results demonstrate the effectiveness of the proposed framework and the proposed solution.

Monitoring burst (M-burst) — A novel framework of failure localization in all-optical mesh networks

KAUST Repository

Ali, Mohammed L.

2011-10-10

Achieving instantaneous and precise failure localization in all-optical wavelength division multiplexing (WDM) networks has been an attractive feature of network fault management systems, and is particularly important when failure-dependent protection is employed. The paper introduces a novel framework of real-time failure localization in all-optical WDM mesh networks, called monitoring-burst (m-burst), which aims to initiate a graceful compromise between consumed monitoring resources and monitoring delay. Different from any previously reported solution, the proposed m-burst framework has a single monitoring node (MN) which launches optical bursts along a set of pre-defined close-loop routes, called monitoring cycles (m-cycles), to probe the links along the m-cycles. Bursts along different m-cycles are kept non-overlapping through any link of the network. By identifying the lost bursts due to single link failure events only, the MN can unambiguously localize the failed link in at least 3-connected networks. We will justify the feasibility and applicability of the proposed m-burst framework in the scenario of interest. To avoid possible collision among optical bursts launched by the MN, we define the problem of collision-free scheduling and formulate it into an integer linear program (ILP) in order to minimize the monitoring delay. Numerical results demonstrate the effectiveness of the proposed framework and the proposed solution.

Using CTX Image Features to Predict HiRISE-Equivalent Rock Density

Science.gov (United States)

Serrano, Navid; Huertas, Andres; McGuire, Patrick; Mayer, David; Ardvidson, Raymond

2010-01-01

Methods have been developed to quantitatively assess rock hazards at candidate landing sites with the aid of images from the HiRISE camera onboard NASA s Mars Reconnaissance Orbiter. HiRISE is able to resolve rocks as small as 1-m in diameter. Some sites of interest do not have adequate coverage with the highest resolution sensors and there is a need to infer relevant information (like site safety or underlying geomorphology). The proposed approach would make it possible to obtain rock density estimates at a level close to or equal to those obtained from high-resolution sensors where individual rocks are discernable.

Localization of Gamma-Ray Bursts Using the Fermi Gamma-Ray Burst Monitor

NARCIS (Netherlands)

Connaughton, V.; Briggs, M.S.; Goldstein, A.; Meegan, C.A.; Paciesas, W.S.; Preece, R.D.; Wilson-Hodge, C.A.; Gibby, M.H.; Greiner, J.; Gruber, D.; Jenke, P.; Kippen, R.M.; Pelassa, V.; Xiong, S.; Yu, H-F.; Bhat, P.N.; Burgess, J.M.; Byrne, D.; Fitzpatrick, G.; Foley, S.; Giles, M.M.; Guiriec, S.; van der Horst, A.J.; von Kienlin, A.; McBreen, S.; McGlynn, S.; Tierney, D.; Zhang, B..B.

2015-01-01

The Fermi Gamma-ray Burst Monitor (GBM) has detected over 1400 gamma-ray bursts (GRBs) since it began science operations in 2008 July. We use a subset of over 300 GRBs localized by instruments such as Swift, the Fermi Large Area Telescope, INTEGRAL, and MAXI, or through triangulations from the

Geologic mapping as a prerequisite to hazardous waste facility siting

International Nuclear Information System (INIS)

LaMoreaux, P.E.

1993-01-01

The nation's welfare is based on its capability to develop the mineral, water, and energy resources of the land. In addition, these resources must be developed with adequate consideration of environmental impact and the future welfare of the country. Geologic maps are an absolute necessity in the discovery and development of natural resources; for managing radioactive, toxic, and hazardous wastes; and for the assessment of hazards and risks such as those associated with volcanic action, earthquakes, landslides, and subsidence. Geologic maps are the basis for depicting rocks and rock materials, minerals, coal, oil, and water at or near the earth's surface. Hazardous waste facility projects require the preparation of detailed geologic maps. Throughout most of the USA, this type of mapping detail is not available. If these maps were available, it is estimated that the duration of an individual project could be reduced by at least one-fourth (1/4). Therefore, adequate site-specific mapping is required if one is to eliminate environmental problems associated with hazardous, toxic, radioactive, and municipal waste sites

Beam On Target (BOT) Produces Gamma Ray Burst (GRB) Fireballs and Afterglows

Science.gov (United States)

Greyber, H. D.

1997-12-01

Unlike the myriads of ad hoc models that have been offered to explain GRB, the BOT process is simply the very common process used worldwide in accelerator laboratories to produce gamma rays. The Strong Magnetic Field (SMF) model postulates an extremely intense, highly relativistic current ring formed during the original gravitational collapse of a distant galaxy when the plasma cloud was permeated by a primordial magnetic field. GRB occur when solid matter (asteroid, white dwarf, neutron star, planet) falls rapidly through the Storage Ring beam producing a very strongly collimated electromagnetic shower, and a huge amount of matter from the target, in the form of a giant, hot, expanding plasma cloud, or ``Fireball,'' is blown off. BOT satisfies all the ``severe constraints imposed on the source of this burst --'' concluded by the CGRO team (Sommer et al, Astrophys. J. 422 L63 (1994)) for the huge intense burst GRB930131, whereas neutron star merger models are ``difficult to reconcile.'' BOT expects the lowest energy gamma photons to arrive very slightly later than higher energy photons due to the time for the shower to penetrate the target. The millisecond spikes in bursts are due to the slender filaments of current that make up the Storage Ring beam. Delayed photons can be explained by a broken target ``rock.'' See H. Greyber in the book ``Compton Gamma Ray Observatory,'' AIP Conf. Proc. 280, 569 (1993).

Dynamic response of underground openings in discontinuous rock

International Nuclear Information System (INIS)

Asmis, H.W.

1984-02-01

This report examines the behaviour of underground openings in discontinuous rock in response to seismic waves associated with either earthquakes or rock bursts. A literature search revealed that well-constructed underground structures, such as would be expected for nuclear fuel waste disposal vaults, underground pumped-storage or nuclear plants, have an extremely high resistance to damage from seismic motion. To complement these qualitative results, it was necessary to examine the basic mechanisms of the entire progression of seismic motion, from wave generation and propagation, to wave interaction with the underground opening. From these investigations, it was found that unless a seismic event occurs very close to the installation, the stresses generated will be low with respect to the excavation stresses, because high stress waves are rapidly attenuated in travelling through rock. As well, an earthquake may generate extremely high accelerations, but is limited in the maximum amount of stress that it can create. The question, however, of the actual specific nature of underground seismic motions still remains essentially unanswered, although it is expected that there is a reduction in peak motions with depth due to the effect of the free surface of the earth

Geomorphological analysis, monitoring and modeling of large rock avalanches in northern Chile (Iquique area) for regional hazard assessment.

Science.gov (United States)

Yugsi Molina, F. X.; Hermanns, R. L.; Crosta, G. B.; Dehls, J.; Sosio, R.; Sepúlveda, S. A.

2012-04-01

mapped characterized by well defined lateral levees and clear internal morphological features (ridges and furrows, hummocks). Rock avalanche run out simulations have been carried out to back analyze the sites using DAN 3D and a 3 m pixel resolution digital elevation model (DEM) obtained from stereoscopic Geoeye-1 images to assess parameters that controlled propagation mechanism and impact area extent of the events. The older lobes were dated by radiocarbon methods. Results indicate ages higher than 40,000 yr BP for the northern site. The second site could only be dated relatively with an underlying terrace that resulted older than the age limit of radiocarbon dating (43.500 yr BP). All the deposits are positioned well above (40-70 m) the present sea level rise, and at the reported uplift rates for the area, they could be associated to events older than some hundreds of thousand years. A more complete record of the failure history of the sites will be obtained when results of cosmogenic nuclides (CN) and luminescence dating will become available later this year. Several other smaller rock avalanches have been mapped in the study area. Satellite-based radar interferometry (InSAR) was performed using ERS-1 and ERS-2 scenes from 1995-2000 as well as ENVISAT ASAR scenes from 2004-2010. Both datasets show only small deformation in the area. This deformation includes sliding of small surficial slope deposits and subsidence apparently due to local groundwater withdrawal. No deformation of bedrock along the escarpment edge is observed. Results show that only major rock avalanches could reach the main access roads to Iquique and currently no large slope segments show signs of large displacement rates. Moreover, there is no strong correlation between M > 8 earthquakes return periods and age of the dated deposits, which implies that large rock avalanches could have been triggered by other factors. Hence, from a hazard and risk perspective, it is unlikely that large rock avalanches

Analysis on the Dynamics of Burst Debris Flood at the Inclined Pressure-Shaft of Svandalsflona Hydropower Project, Norway

Science.gov (United States)

Panthi, K. K.

2014-05-01

Long-term stability of the waterway system of the hydropower plants is crucial and should not be underestimated. The compromise may result in severe economic consequences related to revenue loss caused by the plant closedown for needed repair, extra resources and time required for repair work, and third party loss related to industries and societies at large. In addition, possible contractual disputes between the clients and the contractors may arise in some occasions. Serious accidents may happen during repair and construction work with loss of life, since engineering geological environment (conditions) in the rock mass changed once under water for long period. This article focuses on one of the recent shaft collapse that happened in Norway in 2008. The article discusses and analyses the dynamics of burst debris flood that took place on 9 May 2009, while removing the slide rock mass deposited in the 45° inclined shaft of the Svandalsflona hydropower plant located at the Southern Norway. Careful review on the geological conditions inside the shaft, evaluation on the course of events, investigations on the inspections and inspections reports, assessment on the temperature and precipitation conditions have been carried out to come to the conclusion on what might have triggered the sudden burst flood.

Determination of specific activity of 226Ra, 232Th and 40K for assessment of environmental hazards

International Nuclear Information System (INIS)

Al-Haydari, A.; Al Sharabi, E. S. A.; Al Buhairi, M. H.

2012-01-01

Studies have been carried out using gamma-spectrometric techniques to determine the natural radioactivity in some rocks that are used as building materials in Yemen. The concentrations of the natural radionuclides namely 226 Ra, 232 Th and 40 K in the rock samples collected from different rock markets in Yemen have been determined using an NaI(Tl) detector. The concentrations of 226 Ra, 232 Th and 40 K in the studied rock samples range from 22.2 to 88.8 Bq kg -1 , 8.12 to 113.68 Bq kg -1 and 31.3 to 2222.3 Bq kg -1 , respectively. The concentrations of these radionuclides are compared with the typical world values. To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the air absorbed dose rate, the annual effective dose rate, the representative level index and the values of both external and internal hazard indices were evaluated and compared with the internationally approved values. The radium equivalent activity values of all rock samples are lower than the limit of 370 Bq kg -1 except for one sample which is about 413.386. The values of external hazard index (H ex ) and internal hazard index (H in ), absorbed doses in indoor air and the corresponding effective dose equivalents in a typical dwelling are presented. The need for further studies is also discussed. (authors)

X-Ray Bursts from NGC 6652

Science.gov (United States)

Morgan, Edward

The possibly transient X-ray Source in the globular cluster NGC 6652 has been seen by BeppoSax and the ASM on RXTE to undergo X-ray bursts, possibly Type I. Very little is known about this X-ray source, and confirmation of its bursts type-I nature would identify it as a neutron star binary. Type I bursts in 6 other sources have been shown to exhibit intervals of millisecond ocsillation that most likely indicate the neutron star spin period. Radius-expansion bursts can reveal information about the mass and size of the neutron star. We propose to use the ASM to trigger an observation of this source to maximize the probability of catching a burst in the PCA.

Transitions to Synchrony in Coupled Bursting Neurons

Science.gov (United States)

Dhamala, Mukeshwar; Jirsa, Viktor K.; Ding, Mingzhou

2004-01-01

Certain cells in the brain, for example, thalamic neurons during sleep, show spike-burst activity. We study such spike-burst neural activity and the transitions to a synchronized state using a model of coupled bursting neurons. In an electrically coupled network, we show that the increase of coupling strength increases incoherence first and then induces two different transitions to synchronized states, one associated with bursts and the other with spikes. These sequential transitions to synchronized states are determined by the zero crossings of the maximum transverse Lyapunov exponents. These results suggest that synchronization of spike-burst activity is a multi-time-scale phenomenon and burst synchrony is a precursor to spike synchrony.

Transitions to synchrony in coupled bursting neurons

International Nuclear Information System (INIS)

Dhamala, Mukeshwar; Jirsa, Viktor K.; Ding Mingzhou

2004-01-01

Certain cells in the brain, for example, thalamic neurons during sleep, show spike-burst activity. We study such spike-burst neural activity and the transitions to a synchronized state using a model of coupled bursting neurons. In an electrically coupled network, we show that the increase of coupling strength increases incoherence first and then induces two different transitions to synchronized states, one associated with bursts and the other with spikes. These sequential transitions to synchronized states are determined by the zero crossings of the maximum transverse Lyapunov exponents. These results suggest that synchronization of spike-burst activity is a multi-time-scale phenomenon and burst synchrony is a precursor to spike synchrony

A perspective multidisciplinary geological approach for mitigation of effects due to the asbestos hazard

Science.gov (United States)

Vignaroli, Gianluca; Rossetti, Federico; Belardi, Girolamo; Billi, Andrea

2010-05-01

Asbestos-bearing rock sequences constitute a remarkable natural hazard that poses important threat to human health and may be at the origin of diseases such as asbestosis, mesothelioma and lung cancer). Presently, asbestos is classified as Category 1 carcinogen by world health authorities. Although regulatory agencies in many countries prohibit or restrict the use of asbestos, and discipline the environmental asbestos exposure, the impact of asbestos on human life still constitutes a major problem. Naturally occurring asbestos includes serpentine and amphibole minerals characterised by fibrous morphology and it is a constituent of mineralogical associations typical of mafic and ultramafic rocks within the ophiolitic sequences. Release of fibres can occur both through natural processes (erosion) and through human activities requiring fragmentation of ophiolite rocks (quarrying, tunnelling, railways construction, etc.). As a consequence, vulnerability is increasing in sites where workers and living people are involved by dispersion of fibres during mining and milling of ophiolitic rocks. By analysing in the field different exposures of ophiolitic sequences from the Italian peninsula and after an extensive review of the existing literature, we remark the importance of the geological context (origin, tectonic and deformation history) of ophiolites as a first-order parameter in evaluating the asbestos hazard. Integrated structural, textural, mineralogical and petrological studies significantly improve our understanding of the mechanisms governing the nucleation/growth of fibrous minerals in deformation structures (both ductile and brittle) within the ophiolitic rocks. A primary role is recognised in the structural processes favouring the fibrous mineralization, with correlation existing between the fibrous parameters (such as mineralogical composition, texture, mechanics characteristics) and the particles released in the air (such as shape, size, and amount liberated

The Second SWIFT Burst Alert Telescope (BAT) Gamma-Ray Burst Catalog

Science.gov (United States)

Sakamoto, T.; Barthelmy, S. D.; Baumgartner, W. H.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Krimm, H. A.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.;

Stimulus induced bursts in severe postanoxic encephalopathy.

Science.gov (United States)

Tjepkema-Cloostermans, Marleen C; Wijers, Elisabeth T; van Putten, Michel J A M

2016-11-01

To report on a distinct effect of auditory and sensory stimuli on the EEG in comatose patients with severe postanoxic encephalopathy. In two comatose patients admitted to the Intensive Care Unit (ICU) with severe postanoxic encephalopathy and burst-suppression EEG, we studied the effect of external stimuli (sound and touch) on the occurrence of bursts. In patient A bursts could be induced by either auditory or sensory stimuli. In patient B bursts could only be induced by touching different facial regions (forehead, nose and chin). When stimuli were presented with relatively long intervals, bursts persistently followed the stimuli, while stimuli with short intervals (encephalopathy can be induced by external stimuli, resulting in stimulus-dependent burst-suppression. Stimulus induced bursts should not be interpreted as prognostic favourable EEG reactivity. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Stellar Sources of Gamma-ray Bursts

OpenAIRE

Luchkov, B. I.

2011-01-01

Correlation analysis of Swift gamma-ray burst coordinates and nearby star locations (catalog Gliese) reveals 4 coincidences with good angular accuracy. The random probability is 4\\times 10^{-5}, so evidencing that coincident stars are indeed gamma-ray burst sources. Some additional search of stellar gamma-ray bursts is discussed.

Neutrino burst identification in underground detectors

International Nuclear Information System (INIS)

Fulgione, W.; Mengotti-Silva, N.; Panaro, L.

1996-01-01

We discuss the problem of neutrino burst identification in underground ν-telescopes. First the usual statistical analysis based on the time structure of the events is reviewed, with special attention to the statistical significance of burst candidates. Next, we propose a second level analysis that can provide independent confirmation of burst detection. This exploits the spatial distribution of the single events of a burst candidate, and uses the formalism of the entropy of information. Examples of both techniques are shown, based on the LVD experiment at Gran Sasso. (orig.)

Swift: A gamma ray burst MIDEX

International Nuclear Information System (INIS)

Barthelmy, Scott

2001-01-01

Swift is a first of its kind multiwavelength transient observatory for gamma-ray burst astronomy. It has the optimum capabilities for the next breakthroughs in determining the origin of gamma-ray bursts and their afterglows as well as using bursts to probe the early Universe. Swift will also perform the first sensitive hard X-ray survey of the sky. The mission is being developed by an international collaboration and consists of three instruments, the Burst Alert Telescope (BAT), the X-ray Telescope (XRT), and the Ultraviolet and Optical Telescope (UVOT). The BAT, a wide-field gamma-ray detector, will detect ∼1 gamma-ray burst per day with a sensitivity 5 times that of BATSE. The sensitive narrow-field XRT and UVOT will be autonomously slewed to the burst location in 20 to 70 seconds to determine 0.3-5.0 arcsec positions and perform optical, UV, and X-ray spectrophotometry. On-board measurements of redshift will also be done for hundreds of bursts. Swift will incorporate superb, low-cost instruments using existing flight-spare hardware and designs. Strong education/public outreach and follow-up programs will help to engage the public and astronomical community. Swift has been selected by NASA for development and launch in late 2003

SGR J1550-5418 Bursts Detected with the Fermi Gamma-Ray Burst Monitor during Its Most Prolific Activity

Science.gov (United States)

vanderHorst, A. J.; Kouveliotou, C.; Gorgone, N. M.; Kaneko, Y.; Baring, M. G.; Guiriec, S.; Gogus, E,; Granot, J.; Watts, A. L.; Lin, L.;

INTEGRAL monitoring of unusually long X-ray bursts

DEFF Research Database (Denmark)

of the accreted material, these bursts may be explained by either the unstable burning of a large pile of mixed hydrogen and helium, or the ignition of a thick pure helium layer. Long duration bursts are particularly expected at very low accretion rates and make possible to study the transition from a hydrogen......Thermonuclear bursts on the surface of accreting neutron stars in low mass X-ray binaries have been studied for many years and have in a few cases confirmed theoretical models of nuclear ignition and burning mechanisms. The large majority of X-ray bursts last less than 100s. A good number......-rich bursting regime to a pure helium regime. Moreover, a handful of long bursts have shown, before the extended decay phase, an initial spike similar to a normal short X-ray burst. Such twofold bursts might be a sort of link between short and super-bursts, where the premature ignition of a carbon layer could...

Bursting synchronization in scale-free networks

International Nuclear Information System (INIS)

Batista, C.A.S.; Batista, A.M.; Pontes, J.C.A. de; Lopes, S.R.; Viana, R.L.

2009-01-01

Neuronal networks in some areas of the brain cortex present the scale-free property, i.e., the neuron connectivity is distributed according to a power-law, such that neurons are more likely to couple with other already well-connected ones. Neuron activity presents two timescales, a fast one related to action-potential spiking, and a slow timescale in which bursting takes place. Some pathological conditions are related with the synchronization of the bursting activity in a weak sense, meaning the adjustment of the bursting phase due to coupling. Hence it has been proposed that an externally applied time-periodic signal be applied in order to control undesirable synchronized bursting rhythms. We investigated this kind of intervention using a two-dimensional map to describe neurons with spiking-bursting activity in a scale-free network.

BATSE/OSSE Rapid Burst Response

National Research Council Canada - National Science Library

Matz, S. M; Grove, J. E; Johnson, W. N; Kurfess, J. D; Share, G. H; Fishman, G. J; Meegan, Charles A

1995-01-01

...) slew the OSSE detectors to burst locations determined on-board by BATSE. This enables OSSE to make sensitive searches for prompt and delayed post-burst line and continuum emission above 50 keV...

Some polarization features of solar microwave bursts

Energy Technology Data Exchange (ETDEWEB)

Uralov, A M; Nefed' ev, V P [AN SSSR, Irkutsk. Sibirskij Inst. Zemnogo Magnetizma Ionosfery i Rasprostraneniya Radiovoln

1977-01-01

Consequences of the thermal microwave burst model proposed earlier have been considered. According to the model the centimeter burst is generated at the heat propagation to the upper atmosphere. The polarization features of the burst are explained: a change of the polarization sign in a frequency range, a rapid change of the polarization sign in the development of a burst at a fixed frequency, a lack of time coincidence of the moments of the burst maximum of the polarization and of the total flux. From the model the consequences are obtained, which are still not confirmed by experiment. An ordinary-type wave prevails in the burst radiation, in the course of which the polarization degree falls on the ascending branch of bursts development. At the change of the polarization sign at the fixed frequency prior to the sign change an ordinary-type wave should be present in excess and later an extreordinary type wave.

Gamma Ray Bursts-Afterglows and Counterparts

Science.gov (United States)

Fishman, Gerald J

1998-01-01

Several breakthrough discoveries were made last year of x-ray, optical and radio afterglows and counterparts to gamma-ray bursts, and a redshift has been associated with at least one of these. These discoveries were made possible by the fast, accurate gamma-ray burst locations of the BeppoSAX satellite. It is now generally believed that the burst sources are at cosmological distances and that they represent the most powerful explosions in the Universe. These observations also open new possibilities for the study of early star formation, the physics of extreme conditions and perhaps even cosmology. This session will concentrate on recent x-ray, optical and radio afterglow observations of gamma-ray bursts, associated redshift measurements, and counterpart observations. Several review and theory talks will also be presented, along with a summary of the astrophysical implications of the observations. There will be additional poster contributions on observations of gamma-ray burst source locations at wavelengths other than gamma rays. Posters are also solicited that describe new observational capabilities for rapid follow-up observations of gamma-ray bursts.

Natural radioactivity in some rocks employed as dimension and decorative stones in the Nigerian building industry.

Science.gov (United States)

Tubosun, I A; Tchokossa, P; Balogun, F A; Fasasi, M K; Ocan, O; Adesanmi, C A

2013-12-01

The natural radioactivity in some selected granites and allied rocks from the Basement Complex of Nigeria for use as dimension/decorative stones was measured by gamma-ray spectrometry. The average activity concentrations observed for the selected rock samples range from 9 to 124 Bq kg⁻¹; 13 to 60 Bq kg⁻¹ and 1360 to 2326 Bq kg⁻¹ for ²²⁶Ra, ²³²Th and ⁴⁰K, respectively. The mean radiological hazard indices were 121.62 nGy h⁻¹; 239.73 Bq kg⁻¹; 0.65 Bq kg⁻¹ and 0.77 Bq kg⁻¹ for the absorbed dose rate, radium equivalent, external hazard and internal hazard, respectively. The results obtained were examined on the basis of existing International recommended limits and compared with data on similar rocks from other parts of the world. The values obtained for the rocks, except one, were found to be lower than the values recommended for building materials, and the rocks are considered safe for use as decorative stones as defined by OECD criteria (NEA-OCED Nuclear Energy Agency Dose Constraints in Optimisation of Occupational Radiological Protection Report by NEA Group Experts, OCED, France (2011)). Results highlight the fact that, despite meeting certain suitability criteria such as colour, texture, etc., the radioactivity content of the rocks is another factor of importance for their continued application in the human environment/building industry.

Ozone generation by rock fracture: Earthquake early warning?

Energy Technology Data Exchange (ETDEWEB)

Baragiola, Raul A.; Dukes, Catherine A.; Hedges, Dawn [Engineering Physics, University of Virginia, Charlottesville, Virginia 22904 (United States)

2011-11-14

We report the production of up to 10 ppm ozone during crushing and grinding of typical terrestrial crust rocks in air, O{sub 2} and CO{sub 2} at atmospheric pressure, but not in helium or nitrogen. Ozone is formed by exoelectrons emitted by high electric fields, resulting from charge separation during fracture. The results suggest that ground level ozone produced by rock fracture, besides its potential health hazard, can be used for early warning in earthquakes and other catastrophes, such as landslides or land shifts in excavation tunnels and underground mines.

Rock shape, restitution coefficients and rockfall trajectory modelling

Science.gov (United States)

Glover, James; Christen, Marc; Bühler, Yves; Bartelt, Perry

2014-05-01

Restitution coefficients are used in rockfall trajectory modelling to describe the ratio between incident and rebound velocities during ground impact. They are central to the problem of rockfall hazard analysis as they link rock mass characteristics to terrain properties. Using laboratory experiments as a guide, we first show that restitution coefficients exhibit a wide range of scatter, although the material properties of the rock and ground are constant. This leads us to the conclusion that restitution coefficients are poor descriptors of rock-ground interaction. The primary problem is that "apparent" restitution coefficients are applied at the rock's centre-of-mass and do not account for rock shape. An accurate description of the rock-ground interaction requires the contact forces to be applied at the rock surface with consideration of the momentary rock position and spin. This leads to a variety of rock motions including bouncing, sliding, skipping and rolling. Depending on the impact configuration a wide range of motions is possible. This explains the large scatter of apparent restitution coefficients. We present a rockfall model based on newly developed hard-contact algorithms which includes the effects of rock shape and therefore is able to reproduce the results of different impact configurations. We simulate the laboratory experiments to show that it is possible to reproduce run-out and dispersion of different rock shapes using parameters obtained from independent tests. Although this is a step forward in rockfall trajectory modelling, the problem of parametersing real terrain remains.

Radon monitoring for the prediction of mine outbursts

International Nuclear Information System (INIS)

Lebecka, J.; Wysocka, M.; Chalupnik, S.

1993-01-01

Observations of changes of concentrations of radon in gases occurring in coal seams prone to instantaneous outbursts of coal and gas have been performed. Gas samples have been taken from specially drilled boreholes. In coal seams prone to outbursts strong variations of radon concentration have been found, while in seams where no outbursts occurred radon concentration was much more stable. In all cases outbursts were always preceded by very low concentrations of radon, which raised again afterwards. Similar observations are performed in coal mines where a strong hazard of shocks accompanied by rock bursts occur which is caused by mining activity. Obtained results indicate the possibility of using radon as supporting indicator for prediction of instantaneous outbursts and rock bursts and may be worth-while for prevention of these catastrophes. (author). 9 refs, 2 figs

SGR J1550-5418 BURSTS DETECTED WITH THE FERMI GAMMA-RAY BURST MONITOR DURING ITS MOST PROLIFIC ACTIVITY

Energy Technology Data Exchange (ETDEWEB)

Van der Horst, A. J.; Finger, M. H. [Universities Space Research Association, NSSTC, Huntsville, AL 35805 (United States); Kouveliotou, C. [Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Gorgone, N. M. [Connecticut College, New London, CT 06320 (United States); Kaneko, Y.; Goegues, E.; Lin, L. [Sabanc Latin-Small-Letter-Dotless-I University, Orhanl Latin-Small-Letter-Dotless-I -Tuzla, Istanbul 34956 (Turkey); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Guiriec, S.; Bhat, P. N.; Chaplin, V. L.; Goldstein, A. [University of Alabama, Huntsville, CSPAR, Huntsville, AL 35805 (United States); Granot, J. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Watts, A. L. [Astronomical Institute ' Anton Pannekoek' , University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Bissaldi, E.; Gruber, D. [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, Postfach 1312, 85748 Garching (Germany); Gehrels, N.; Harding, A. K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Gibby, M. H.; Giles, M. M., E-mail: A.J.VanDerHorst@uva.nl [Jacobs Technology, Inc., Huntsville, AL (United States); and others

2012-04-20

We have performed detailed temporal and time-integrated spectral analysis of 286 bursts from SGR J1550-5418 detected with the Fermi Gamma-ray Burst Monitor (GBM) in 2009 January, resulting in the largest uniform sample of temporal and spectral properties of SGR J1550-5418 bursts. We have used the combination of broadband and high time-resolution data provided with GBM to perform statistical studies for the source properties. We determine the durations, emission times, duty cycles, and rise times for all bursts, and find that they are typical of SGR bursts. We explore various models in our spectral analysis, and conclude that the spectra of SGR J1550-5418 bursts in the 8-200 keV band are equally well described by optically thin thermal bremsstrahlung (OTTB), a power law (PL) with an exponential cutoff (Comptonized model), and two blackbody (BB) functions (BB+BB). In the spectral fits with the Comptonized model, we find a mean PL index of -0.92, close to the OTTB index of -1. We show that there is an anti-correlation between the Comptonized E{sub peak} and the burst fluence and average flux. For the BB+BB fits, we find that the fluences and emission areas of the two BB functions are correlated. The low-temperature BB has an emission area comparable to the neutron star surface area, independent of the temperature, while the high-temperature BB has a much smaller area and shows an anti-correlation between emission area and temperature. We compare the properties of these bursts with bursts observed from other SGR sources during extreme activations, and discuss the implications of our results in the context of magnetar burst models.

Precarious Rock Methodology for Seismic Hazard: Physical Testing, Numerical Modeling and Coherence Studies

Energy Technology Data Exchange (ETDEWEB)

Anooshehpoor, Rasool; Purvance, Matthew D.; Brune, James N.; Preston, Leiph A.; Anderson, John G.; Smith, Kenneth D.

2006-09-29

This report covers the following projects: Shake table tests of precarious rock methodology, field tests of precarious rocks at Yucca Mountain and comparison of the results with PSHA predictions, study of the coherence of the wave field in the ESF, and a limited survey of precarious rocks south of the proposed repository footprint. A series of shake table experiments have been carried out at the University of Nevada, Reno Large Scale Structures Laboratory. The bulk of the experiments involved scaling acceleration time histories (uniaxial forcing) from 0.1g to the point where the objects on the shake table overturned a specified number of times. The results of these experiments have been compared with numerical overturning predictions. Numerical predictions for toppling of large objects with simple contact conditions (e.g., I-beams with sharp basal edges) agree well with shake-table results. The numerical model slightly underpredicts the overturning of small rectangular blocks. It overpredicts the overturning PGA for asymmetric granite boulders with complex basal contact conditions. In general the results confirm the approximate predictions of previous studies. Field testing of several rocks at Yucca Mountain has approximately confirmed the preliminary results from previous studies, suggesting that he PSHA predictions are too high, possibly because the uncertainty in the mean of the attenuation relations. Study of the coherence of wavefields in the ESF has provided results which will be very important in design of the canisters distribution, in particular a preliminary estimate of the wavelengths at which the wavefields become incoherent. No evidence was found for extreme focusing by lens-like inhomogeneities. A limited survey for precarious rocks confirmed that they extend south of the repository, and one of these has been field tested.

Laboratory testing of a long expansion rock bolt support for energy-absorbing applications

Directory of Open Access Journals (Sweden)

Skrzypkowski Krzysztof

2018-01-01

Full Text Available The main purpose of rock support and reinforcement in underground mining is to maintain excavations safe and open for their intended lifespan. The basic type of rock mass reinforcement method both in ore and hard coal mining is rock bolt support. Very often, existing bolt support systems are not always capable of providing a reliable controlled performance. Therefore, in recent years energy-absorbing bolts which are exposed to dynamic loading, for example from rock burst caused by high rock stresses, earthquakes, or blasting have appeared. In this article particular attention was paid to short and long expansion bolts. Quasi-static tests of expansion bolts were carried out at the laboratory test facility in simulated mining conditions, especially for the KGHM Polska Miedź S.A. mines. In the underground mines of the Legnica-Głogów Copper District (LGOM the main way to protect the room excavation is rock bolt support with a length from 1.2 m to 2.6 m. Rock bolt support longer than 2.6 m is considered as additional support of excavations and is increasingly being used to reinforce the roofs. The comparisons of energy-absorbing short and long expansion bolts with a length of 1.8m, 3.6m and 5.2m were presented. In addition, for elastic and plastic range of each bolts were determined.

Laboratory testing of a long expansion rock bolt support for energy-absorbing applications

Science.gov (United States)

Skrzypkowski, Krzysztof

2018-01-01

The main purpose of rock support and reinforcement in underground mining is to maintain excavations safe and open for their intended lifespan. The basic type of rock mass reinforcement method both in ore and hard coal mining is rock bolt support. Very often, existing bolt support systems are not always capable of providing a reliable controlled performance. Therefore, in recent years energy-absorbing bolts which are exposed to dynamic loading, for example from rock burst caused by high rock stresses, earthquakes, or blasting have appeared. In this article particular attention was paid to short and long expansion bolts. Quasi-static tests of expansion bolts were carried out at the laboratory test facility in simulated mining conditions, especially for the KGHM Polska Miedź S.A. mines. In the underground mines of the Legnica-Głogów Copper District (LGOM) the main way to protect the room excavation is rock bolt support with a length from 1.2 m to 2.6 m. Rock bolt support longer than 2.6 m is considered as additional support of excavations and is increasingly being used to reinforce the roofs. The comparisons of energy-absorbing short and long expansion bolts with a length of 1.8m, 3.6m and 5.2m were presented. In addition, for elastic and plastic range of each bolts were determined.

THE FIVE YEAR FERMI/GBM MAGNETAR BURST CATALOG

Energy Technology Data Exchange (ETDEWEB)

Collazzi, A. C. [SciTec, Inc., 100 Wall Street, Princeton, NJ 08540 (United States); Kouveliotou, C.; Horst, A. J. van der; Younes, G. A. [Department of Physics, The George Washington University, 725 21st Street NW, Washington, DC 20052 (United States); Kaneko, Y.; Göğüş, E. [Sabancı University, Orhanlı-Tuzla, İstanbul 34956 (Turkey); Lin, L. [François Arago Centre, APC, 10 rue Alice Domon et Léonie Duquet, F-75205 Paris (France); Granot, J. [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Raanana 43537 (Israel); Finger, M. H. [Universities Space Research Association, NSSTC, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Chaplin, V. L. [School of Medicine, Vanderbilt University, 1161 21st Avenue S, Nashville, TN 37232 (United States); Huppenkothen, D. [Center for Data Science, New York University, 726 Broadway, 7th Floor, New York, NY 10003 (United States); Watts, A. L. [Anton Pannekoek Institute, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Kienlin, A. von [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Baring, M. G. [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Gruber, D. [Planetarium Südtirol, Gummer 5, I-39053 Karneid (Italy); Bhat, P. N. [CSPAR, University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35899 (United States); Gibby, M. H., E-mail: acollazzi@scitec.com [Jacobs Technology, Inc., Huntsville, AL (United States); and others

2015-05-15

Since launch in 2008, the Fermi Gamma-ray Burst Monitor (GBM) has detected many hundreds of bursts from magnetar sources. While the vast majority of these bursts have been attributed to several known magnetars, there is also a small sample of magnetar-like bursts of unknown origin. Here, we present the Fermi/GBM magnetar catalog, providing the results of the temporal and spectral analyses of 440 magnetar bursts with high temporal and spectral resolution. This catalog covers the first five years of GBM magnetar observations, from 2008 July to 2013 June. We provide durations, spectral parameters for various models, fluences, and peak fluxes for all the bursts, as well as a detailed temporal analysis for SGR J1550–5418 bursts. Finally, we suggest that some of the bursts of unknown origin are associated with the newly discovered magnetar 3XMM J185246.6+0033.7.

Modeling the Rock Glacier Cycle

Science.gov (United States)

Anderson, R. S.; Anderson, L. S.

2016-12-01

Rock glaciers are common in many mountain ranges in which the ELA lies above the peaks. They represent some of the most identifiable components of today's cryosphere in these settings. Their oversteepened snouts pose often-overlooked hazards to travel in alpine terrain. Rock glaciers are supported by avalanches and by rockfall from steep headwalls. The winter's avalanche cone must be sufficiently thick not to melt entirely in the summer. The spatial distribution of rock glaciers reflects this dependence on avalanche sources; they are most common on lee sides of ridges where wind-blown snow augments the avalanche source. In the absence of rockfall, this would support a short, cirque glacier. Depending on the relationship between rockfall and avalanche patterns, "talus-derived" and "glacier-derived" rock glaciers are possible. Talus-derived: If the spatial distribution of rock delivery is similar to the avalanche pattern, the rock-ice mixture will travel an englacial path that is downward through the short accumulation zone before turning upward in the ablation zone. Advected debris is then delivered to the base of a growing surface debris layer that reduces the ice melt rate. The physics is identical to the debris-covered glacier case. Glacier-derived: If on the other hand rockfall from the headwall rolls beyond the avalanche cone, it is added directly to the ablation zone of the glacier. The avalanche accumulation zone then supports a pure ice core to the rock glacier. We have developed numerical models designed to capture the full range of glacier to debris-covered glacier to rock glacier behavior. The hundreds of meter lengths, tens of meters thicknesses, and meter per year speeds of rock glaciers are well described by the models. The model can capture both "talus-derived" and "glacier-derived" rock glaciers. We explore the dependence of glacier behavior on climate histories. As climate warms, a pure ice debris-covered glacier can transform to a much shorter rock

Observation of gamma-ray bursts with GINGA

International Nuclear Information System (INIS)

Murakami, Toshio; Fujii, Masami; Nishimura, Jun

1989-01-01

Gamma-ray Burst Detector System (GBD) on board the scientific satellite 'GINGA' which was launched on Feb. 5, 1987, was realized as an international cooperation between ISAS and LANL. It has recorded more than 40 Gamma-Ray Burst candidates during 20 months observation. Although many observational evidences were accumulated in past 20 years after the discovery of gamma-ray burst by LANL scientists, there are not enough evidence to determine the origin and the production mechanism of the gamma-ray burst. GBD consists of a proportional counter and a NaI scintillation counter so that it became possible to observe energy spectrum of the gamma-ray burst with high energy resolution over wide range of energy (1.5-380 keV) together with high time resolution. As the result of observation, the following facts are obtained: (1) A large fraction of observed gamma-ray bursts has a long X-ray tail after the harder part of gamma-ray emission has terminated. (2) Clear spectral absorption features with harmonic in energy was observed in some of the energy spectrum of gamma-ray bursts. These evidences support the hypothesis that the strongly magnetized neutron star is the origin of gamma-ray burst. (author)

Swift Burst Alert Telescope (BAT) Instrument Response

International Nuclear Information System (INIS)

Parsons, A.; Barthelmy, S.; Cummings, J.; Gehrels, N.; Hullinger, D.; Krimm, H.; Markwardt, C.; Tueller, J.; Fenimore, E.; Palmer, D.; Sato, G.; Takahashi, T.; Nakazawa, K.; Okada, Y.; Takahashi, H.; Suzuki, M.; Tashiro, M.

2004-01-01

The Burst Alert Telescope (BAT), a large coded aperture instrument with a wide field-of-view (FOV), provides the gamma-ray burst triggers and locations for the Swift Gamma-Ray Burst Explorer. In addition to providing this imaging information, BAT will perform a 15 keV - 150 keV all-sky hard x-ray survey based on the serendipitous pointings resulting from the study of gamma-ray bursts, and will also monitor the sky for transient hard x-ray sources. For BAT to provide spectral and photometric information for the gamma-ray bursts, the transient sources and the all-sky survey, the BAT instrument response must be determined to an increasingly greater accuracy. This paper describes the spectral models and the ground calibration experiments used to determine the BAT response to an accuracy suitable for gamma-ray burst studies

Practical example of the infrastructure protection against rock fall

Science.gov (United States)

Jirásko, Daniel; Vaníček, Ivan

2017-09-01

The protection of transport infrastructures against rock falls represents for the Czech Republic one of the sensitive questions. Rock falls, similarly as other typical geo-hazards for the Czech Republic, as landslides and floods, can have negative impact on safety and security of these infrastructures. One practical example how to reduce risk of rock fall is described in the paper. Great care is devoted to the visual inspection enabling to indicate places with high potential to failure. With the help of numerical modelling the range of rock fall negative impact is estimated. Protection measures are dealing with two basic ways. The first one utilize the results of numerical modelling for the optimal design of protection measures and the second one is focused on the monitoring of the rock blocks with high potential of instability together with wire-less transfer of measured results. After quick evaluation, e.g. comparison with warning values, some protection measures, mostly connected with closure of the potential sector, can be recommended.

assessment of radiological hazard indices from surface soil to ...

African Journals Online (AJOL)

samples in Eagle, Atlas and rock cement companies in Port Harcourt was carried out by ... and external hazard indices in order to assess the radiological implication to the people .... Sciences & Environmental Management, Vol. 9, No. 3, pp.

Dark gamma-ray bursts

Science.gov (United States)

Brdar, Vedran; Kopp, Joachim; Liu, Jia

2017-03-01

Many theories of dark matter (DM) predict that DM particles can be captured by stars via scattering on ordinary matter. They subsequently condense into a DM core close to the center of the star and eventually annihilate. In this work, we trace DM capture and annihilation rates throughout the life of a massive star and show that this evolution culminates in an intense annihilation burst coincident with the death of the star in a core collapse supernova. The reason is that, along with the stellar interior, also its DM core heats up and contracts, so that the DM density increases rapidly during the final stages of stellar evolution. We argue that, counterintuitively, the annihilation burst is more intense if DM annihilation is a p -wave process than for s -wave annihilation because in the former case, more DM particles survive until the supernova. If among the DM annihilation products are particles like dark photons that can escape the exploding star and decay to standard model particles later, the annihilation burst results in a flash of gamma rays accompanying the supernova. For a galactic supernova, this "dark gamma-ray burst" may be observable in the Čerenkov Telescope Array.

BURST AND OUTBURST CHARACTERISTICS OF MAGNETAR 4U 0142+61

Energy Technology Data Exchange (ETDEWEB)

Göğüş, Ersin; Chakraborty, Manoneeta; Kaneko, Yuki [Sabancı University, Orhanlı-Tuzla, İstanbul 34956 (Turkey); Lin, Lin [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Roberts, Oliver J. [School of Physics, University College Dublin, Stillorgan Road, Belfield, Dublin 4 (Ireland); Gill, Ramandeep; Granot, Jonathan [Department of Natural Sciences, The Open University of Israel, 1 University Road, P.O. Box 808, Ranana 43537 (Israel); Horst, Alexander J. van der; Kouveliotou, Chryssa; Younes, George [Department of Physics, The George Washington University, Washington, DC 20052 (United States); Watts, Anna L. [Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam (Netherlands); Baring, Matthew [Department of Physics and Astronomy, Rice University, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Huppenkothen, Daniela [Center for Data Science, New York University, 726 Broadway, 7th Floor, NY 10003 (United States)

2017-01-20

We have compiled the most comprehensive burst sample from magnetar 4U 0142+61, comprising 27 bursts from its three burst-active episodes in 2011, 2012 and the latest one in 2015 observed with Swift /Burst Alert Telescope and Fermi /Gamma-ray Burst Monitor. Bursts from 4U 0142+61 morphologically resemble typical short bursts from other magnetars. However, 4U 0142+61 bursts are less energetic compared to the bulk of magnetar bursts. We uncovered an extended tail emission following a burst on 2015 February 28, with a thermal nature, cooling over a timescale of several minutes. During this tail emission, we also uncovered pulse peak phase aligned X-ray bursts, which could originate from the same underlying mechanism as that of the extended burst tail, or an associated and spatially coincident but different mechanism.

The influence of microwave irradiation on thermal properties of main rock-forming minerals

International Nuclear Information System (INIS)

Lu, Gao-ming; Li, Yuan-hui; Hassani, Ferri; Zhang, Xiwei

2017-01-01

Highlights: • Different rock-forming minerals present very different microwave absorption capacity to microwave energy. • The test results can be used to estimate the heating behaviors of rocks to microwave irradiation. • SEM-EDX technique was used to determine the elemental distribution and mineralogical composition. • Ferrum may influence the interacting mechanisms between rock-forming minerals and microwaves. - Abstract: The sample will burst into fragment when the thermal stress induced by thermal expansion greater than the ultimate strength of the rock after microwave irradiation. Microwave-assisted rock fragmentation has been illustrated to be potentially beneficial for mineral processing, mining and geotechnical engineering. In order to have a comprehensive understanding on the influence of microwave on thermo-mechanical properties of rocks, it is necessary to investigate the interaction effect between microwaves and the main rock-forming minerals. In this work, eleven rock-forming minerals were tested in a multimode cavity at 2.45G Hz with a power of 2 kW, subsequently, the Scanning Electron Microscopy–Energy Dispersive X-ray (SEM-EDX) was used to determine the elemental distribution and mineralogical composition of the tested samples. It was observed that different rock-forming minerals present very different susceptibility induced by microwave treatment. Enstatite presents the strongest microwave absorption capacity by a large margin and most of the rock-forming minerals are weak microwave absorbers. It is significant that the results can be used to predict the heating behaviors of rocks subjected to microwave energy. Furthermore, the SEM-EDX elemental analysis demonstrates that the microwave absorption capacity of rock-forming minerals could link to the contribution of the ferrum, which may influence the interacting mechanisms between microwaves and the rock-forming minerals.

A Coal Burst Mitigation Strategy for Tailgate during Deep Mining of Inclined Longwall Top Coal Caving Panels at Huafeng Coal Mine

Directory of Open Access Journals (Sweden)

Guorui Feng

2018-01-01

Full Text Available A coal burst mitigation strategy for tailgate in mining of deep inclined longwall panels with top coal caving at Huafeng Coal Mine is presented in this paper. Field data showed that coal bursts, rib sloughing or slabbing, large convergence, and so forth frequently occurred within the tailgate entries during development and panel retreating employing standard longwall top coal caving (LTCC layout which resulted in fatal injuries and tremendous profit loss. The contributing factors leading to coal bursts were analyzed. Laboratory tests, in situ measurement, and field observation demonstrate that the intrinsic bursting proneness of the coal seam and immediate roof stratum, deep cover, overlying ultrathick (500–800 m conglomerate strata, faults, and, most importantly, improper panel layout led to coal bursts. By employing a new strategy, that is, longwall mining with split-level gateroads (LMSG, gateroads on either end of a LMSG panel are located at different levels within a coal seam, adjacent LMSG panels overlap end to end, and the tailgate of the adjacent new LMSG panel can be located below the headgate entry of the previous LMSG panel or may be offset horizontally with respect to it. Numerical modeling was carried out to investigate the stress distribution and yield zone development within surrounding rock mass which was validated by field investigation. The results indicate that standard LTCC system gave rise to high ground pressure around tailgate entries next to the gob, while LMSG tailgate entry below the gob edge was in a destressed environment. Therefore, coal bursts are significantly mitigated. Field practice of LMSG at Huafeng Coal Mine demonstrates how the new strategy effectively dealt with coal burst problems in mining of deep inclined longwall panels with a reduced incidence of ground control problems. The new strategy can potentially be applied in similar settings.

Bursting synchronization in clustered neuronal networks

International Nuclear Information System (INIS)

Yu Hai-Tao; Wang Jiang; Deng Bin; Wei Xi-Le

2013-01-01

Neuronal networks in the brain exhibit the modular (clustered) property, i.e., they are composed of certain subnetworks with differential internal and external connectivity. We investigate bursting synchronization in a clustered neuronal network. A transition to mutual-phase synchronization takes place on the bursting time scale of coupled neurons, while on the spiking time scale, they behave asynchronously. This synchronization transition can be induced by the variations of inter- and intracoupling strengths, as well as the probability of random links between different subnetworks. Considering that some pathological conditions are related with the synchronization of bursting neurons in the brain, we analyze the control of bursting synchronization by using a time-periodic external signal in the clustered neuronal network. Simulation results show a frequency locking tongue in the driving parameter plane, where bursting synchronization is maintained, even in the presence of external driving. Hence, effective synchronization suppression can be realized with the driving parameters outside the frequency locking region. (interdisciplinary physics and related areas of science and technology)

Self-regulation of turbulence bursts and transport barriers

International Nuclear Information System (INIS)

Floriani, E; Ciraolo, G; Ghendrih, Ph; Sarazin, Y; Lima, R

2013-01-01

The interplay between turbulent bursts and transport barriers is analyzed with a simplified model of interchange turbulence in magnetically confined plasmas. The turbulent bursts spread into the transport barriers and, depending on the competing magnitude of the burst and stopping capability of the barrier, can burn through. Simulations of two models of transport barriers are presented: a hard barrier where interchange turbulence modes are stable in a prescribed region and a soft barrier with external plasma biasing. The response of the transport barriers to the non-linear perturbations of the turbulent bursts, addressed in a predator–prey approach, indicates that the barriers monitor an amplification factor of the turbulent bursts, with amplification smaller than one for most bursts and, in some cases, amplification factors that can significantly exceed unity. The weak barriers in corrugated profiles and magnetic structures, as well as the standard barriers, are characterized by these transmission properties, which then regulate the turbulent burst transport properties. The interplays of barriers and turbulent bursts are modeled as competing stochastic processes. For different classes of the probability density function (PDF) of these processes, one can predict the heavy tail properties of the bursts downstream from the barrier, either exponential for a leaky barrier, or with power laws for a tight barrier. The intrinsic probing of the transport barriers by the turbulent bursts thus gives access to the properties of the barriers. The main stochastic variables are the barrier width and the spreading distance of the turbulent bursts within the barrier, together with their level of correlation. One finds that in the case of a barrier with volumetric losses, such as radiation or particle losses as addressed in our present simulations, the stochastic model predicts a leaky behavior with an exponential PDF of escaping turbulent bursts in agreement with the simulation

The γ-ray burst-detection system of SPI

International Nuclear Information System (INIS)

Lichti, G.G.; Georgii, R.; Kienlin, A. von; Schoenfelder, V.; Wunderer, C.; Jung, H.-J.; Hurley, K.

2000-01-01

The determination of precise locations of γ-ray bursts is a crucial task of γ-ray astronomy. Although γ-ray burst locations can be obtained nowadays from single experiments (BATSE, COMPTEL, BeppoSax) the location of bursts via triangulation using the interplanetary network is still important because not all bursts will be located precisely enough by these single instruments. In order to get location accuracies down to arcseconds via triangulation one needs long baselines. At the beginning of the next decade several spacecrafts which explore the outer planetary system (the Mars-Surveyor-2001 Orbiter and probably Ulysses) will carry γ-ray burst instruments. INTEGRAL as a near-earth spacecraft is the ideal counterpart for these satellites. The massive anticoincidence shield of the INTEGRAL-spectrometer SPI allows the measurement of γ-ray bursts with a high sensitivity. Estimations have shown that with SPI some hundred γ-ray bursts per year on the 5σ level can be measured. This is equivalent to the BATSE sensitivity. We describe the γ-ray burst-detection system of SPI, present its technical features and assess the scientific capabilities

Balloon observation of gamma-ray burst

International Nuclear Information System (INIS)

Nishimura, Jun; Fujii, Masami; Yamagami, Takamasa; Oda, Minoru; Ogawara, Yoshiaki

1978-01-01

Cosmic gamma-ray burst is an interesting high energy astrophysical phenomenon, but the burst mechanism has not been well understood. Since 1975, long duration balloon flight has been conducted to search for gamma-ray bursts and to determine the source locations. A rotating cross-modulation collimator was employed to determine the locations of sources, and four NaI(Tl) scintillation counters were employed to detect hard X-ray with energy from 20 to 200 keV. The balloon light was performed at altitude of 8.3 mb from September 28, 1977, and the observation time of 79 hours was achieved. In this experiment, the monitor counter was not mounted. The count increase was observed at 16 h 22 m 31 s JST on October 1, 1977. The event disappeared after 1 sec. The total flux is estimated to be 1.6 x 10 -6 erg/cm 2 sec at the top of the atmosphere. When this event was observed, the solar-terrestrial environment was also quiet. Thus, this event was attributed to a small gamma-ray burst. Unfortunately, the duration of the burst was so short that the position of the burst source was not able to be determined. (Yoshimori, M.)

Frequency of fast, narrow γ-ray bursts

International Nuclear Information System (INIS)

Norris, J.P.; Maryland Univ., College Park; Cline, T.L.; Desai, U.D.; Teegarden, B.J.

1984-01-01

The paper describes the existence of two γ-ray burst populations detected by the ISEE-3 experiment. Data from the distribution of 123 Venera 13 and 14 events (60 detected by both spacecraft) also suggests two γ-ray burst populations in each experiment sample, the domains separated with a minimum near 1 or 2 s. The authors point out that the results of the Goddard ISEE-3 γ-ray burst spectrometer actually enhance the appearance of two burst populations suggested in the Venera data. (author)

Effect of Micro-Structure on Fatigue Behavior of Intact Rocks under Completely Reversed Loading

Directory of Open Access Journals (Sweden)

Saeed Jamali Zavareh

2017-01-01

Full Text Available Rock formations and structures can be subjected to both static and dynamic loadings. Static loadings resulting from different sources such as gravity and tectonic forces and dynamic forces are intermittently transmitted via vibrations of the earth’s crust, through major earthquakes, rock bursts, rock blasting and drilling and also, traffic. Reaction of rocks to cyclic and repetitive stresses resulting from dynamic loads has been generally neglected with the exception of a few rather limited studies. In this study, , two crystalline quarry stones in Iran; (Natanz gabbro and Green onyx and one non-crystalline rock (Asmari limestone are used to evaluate the effect of micro-structure of intact rock on fatigue behavior. These rocks have different mineral compositions and formation conditions. A new apparatus based on rotating beam fatigue testing machine (R.R.Moore, which is commonly used for laboratory fatigue test in metals, is developed and fatigue behavior and existence of the endurance limit were evaluated for the mentioned rocks based on stress-life method. The obtained results in the variation of applied amplitude stress versus loading cycle number (S-N diagram followed common relationship in other materials. In addition, the endurance limit is perceived for all tested rocks. The results also illustrated that the endurance limits for all types of tested rocks in this study are ranged between 0.4 and 0.6 of their tensile strengths. The endurance limit to tensile strength fraction of green onyx and Natanz gabbro were approximated in a higher value compared to the Asmari limestone with non-crystalline micro-structure.

Assess the toxycity and hazard class moldboard rocks Western Donbass

Directory of Open Access Journals (Sweden)

Kroyik H.A. О. М. , Т. D.

2011-11-01

Full Text Available Researches of the contents of water-soluble forms of heavy metals in different types of dumping mine rocks of the Western Donbass are executed. According to existing state sanitary rules and norms two methods calculate indexes of toxicity for lead, cadmium, zinc, cobalt, nickel, copper. The estimation of an opportunity of application of existing norms and rules at definition of a class of danger of firm waste of the coal-mining industry. ,,

Possible galactic origin of. gamma. -ray bursts

Energy Technology Data Exchange (ETDEWEB)

Manchanda, R K; Ramsden, D [Southampton Univ. (UK). Dept. of Physics

1977-03-31

It is stated that extragalactic models for the origin of non-solar ..gamma..-ray bursts include supernova bursts in remote galaxies, and the collapse of the cores of active stars, whilst galactic models are based on flare stars, thermonuclear explosions in neutron stars and the sudden accretion of cometary gas on to neutron stars. The acceptability of any of these models may be tested by the observed size spectrum of the ..gamma..-ray bursts. The extragalactic models predict a power law spectrum with number index -1.5, whilst for the galactic models the number index will be -1. Experimental data on ..gamma..-ray bursts is, however, still meagre, and so far only 44 confirmed events have been recorded by satellite-borne instruments. The number spectrum of the observed ..gamma..-ray bursts indicates that the observed distribution for events with an energy < 10/sup -4/ erg/cm/sup 2/ is flat; this makes the choice of any model completely arbitrary. An analysis of the observed ..gamma..-ray events is here presented that suggests very interesting possibilities for their origin. There appears to be a preferred mean energy for ..gamma..-ray bursts; some 90% of the recorded events show a mean energy between 5 x 10/sup -5/ and 5 x 10/sup -4/ erg/cm/sup 2/, contrary to the predicted characteristics of the number spectrum of various models. A remarkable similarity is found between the distribution of ..gamma..-ray bursts and that of supernova remnants, suggesting a genetic relationship between the two and the galactic origin of the ..gamma..-ray bursts, and the burst source could be identified with completely run down neutron stars, formed during supernova explosions.

Reassessment of probabilistic seismic hazard in the Marmara region

Science.gov (United States)

Kalkan, Erol; Gulkan, Polat; Yilmaz, Nazan; Çelebi, Mehmet

2009-01-01

In 1999, the eastern coastline of the Marmara region (Turkey) witnessed increased seismic activity on the North Anatolian fault (NAF) system with two damaging earthquakes (M 7.4 Kocaeli and M 7.2 D??zce) that occurred almost three months apart. These events have reduced stress on the western segment of the NAF where it continues under the Marmara Sea. The undersea fault segments have been recently explored using bathymetric and reflection surveys. These recent findings helped scientists to understand the seismotectonic environment of the Marmara basin, which has remained a perplexing tectonic domain. On the basis of collected new data, seismic hazard of the Marmara region is reassessed using a probabilistic approach. Two different earthquake source models: (1) the smoothed-gridded seismicity model and (2) fault model and alternate magnitude-frequency relations, Gutenberg-Richter and characteristic, were used with local and imported ground-motion-prediction equations. Regional exposure is computed and quantified on a set of hazard maps that provide peak horizontal ground acceleration (PGA) and spectral acceleration at 0.2 and 1.0 sec on uniform firm-rock site condition (760 m=sec average shear wave velocity in the upper 30 m). These acceleration levels were computed for ground motions having 2% and 10% probabilities of exceedance in 50 yr, corresponding to return periods of about 2475 and 475 yr, respectively. The maximum PGA computed (at rock site) is 1.5g along the fault segments of the NAF zone extending into the Marmara Sea. The new maps generally show 10% to 15% increase for PGA, 0.2 and 1.0 sec spectral acceleration values across much of Marmara compared to previous regional hazard maps. Hazard curves and smooth design spectra for three site conditions: rock, soil, and soft-soil are provided for the Istanbul metropolitan area as possible tools in future risk estimates.

Throughput Estimation Method in Burst ACK Scheme for Optimizing Frame Size and Burst Frame Number Appropriate to SNR-Related Error Rate

Science.gov (United States)

Ohteru, Shoko; Kishine, Keiji

The Burst ACK scheme enhances effective throughput by reducing ACK overhead when a transmitter sends sequentially multiple data frames to a destination. IEEE 802.11e is one such example. The size of the data frame body and the number of burst data frames are important burst transmission parameters that affect throughput. The larger the burst transmission parameters are, the better the throughput under error-free conditions becomes. However, large data frame could reduce throughput under error-prone conditions caused by signal-to-noise ratio (SNR) deterioration. If the throughput can be calculated from the burst transmission parameters and error rate, the appropriate ranges of the burst transmission parameters could be narrowed down, and the necessary buffer size for storing transmit data or received data temporarily could be estimated. In this paper, we present a method that features a simple algorithm for estimating the effective throughput from the burst transmission parameters and error rate. The calculated throughput values agree well with the measured ones for actual wireless boards based on the IEEE 802.11-based original MAC protocol. We also calculate throughput values for larger values of the burst transmission parameters outside the assignable values of the wireless boards and find the appropriate values of the burst transmission parameters.

Optimal Codes for the Burst Erasure Channel

Science.gov (United States)

Hamkins, Jon

2010-01-01

Deep space communications over noisy channels lead to certain packets that are not decodable. These packets leave gaps, or bursts of erasures, in the data stream. Burst erasure correcting codes overcome this problem. These are forward erasure correcting codes that allow one to recover the missing gaps of data. Much of the recent work on this topic concentrated on Low-Density Parity-Check (LDPC) codes. These are more complicated to encode and decode than Single Parity Check (SPC) codes or Reed-Solomon (RS) codes, and so far have not been able to achieve the theoretical limit for burst erasure protection. A block interleaved maximum distance separable (MDS) code (e.g., an SPC or RS code) offers near-optimal burst erasure protection, in the sense that no other scheme of equal total transmission length and code rate could improve the guaranteed correctible burst erasure length by more than one symbol. The optimality does not depend on the length of the code, i.e., a short MDS code block interleaved to a given length would perform as well as a longer MDS code interleaved to the same overall length. As a result, this approach offers lower decoding complexity with better burst erasure protection compared to other recent designs for the burst erasure channel (e.g., LDPC codes). A limitation of the design is its lack of robustness to channels that have impairments other than burst erasures (e.g., additive white Gaussian noise), making its application best suited for correcting data erasures in layers above the physical layer. The efficiency of a burst erasure code is the length of its burst erasure correction capability divided by the theoretical upper limit on this length. The inefficiency is one minus the efficiency. The illustration compares the inefficiency of interleaved RS codes to Quasi-Cyclic (QC) LDPC codes, Euclidean Geometry (EG) LDPC codes, extended Irregular Repeat Accumulate (eIRA) codes, array codes, and random LDPC codes previously proposed for burst erasure

Gamma-Ray Bursts: 4th Huntsville Symposium. Proceedings

International Nuclear Information System (INIS)

Meegan, C.A.; Preece, R.D.; Koshut, T.M.

1998-01-01

These proceedings represent papers presented at the Fourth Huntsville Gamma-Ray Bursts Symposium held in September, 1997 in Huntsville, Alabama, USA. This conference occurred at a crucial time in the history of the gamma-ray burst research. In early 1997, 30 years after the detection of the first gamma-ray burst by the Vela satellites, counterparts to bursts were finally detected at optical and radio wavelengths. The symposium attracted about 200 scientists from 16 countries. Some of the topics discussed include gamma-ray burst spectra, x-ray observations, optical observations, radio observations, host galaxies, shocks and afterglows and models of gamma-ray bursts. There were 183 papers presented, out of these, 16 have been abstracted for the Energy Science and Technology database

Influence of porosity and groundmass crystallinity on dome rock strength: a case study from Mt. Taranaki, New Zealand

Science.gov (United States)

Zorn, Edgar U.; Rowe, Michael C.; Cronin, Shane J.; Ryan, Amy G.; Kennedy, Lori A.; Russell, James K.

2018-04-01

Lava domes pose a significant hazard to infrastructure, human lives and the environment when they collapse. Their stability is partly dictated by internal mechanical properties. Here, we present a detailed investigation into the lithology and composition of a Rocks with variable porosity and groundmass crystallinity were compared using measured compressive and tensile strength, derived from deformation experiments performed at room temperature and low (3 MPa) confining pressures. Based on data obtained, porosity exerts the main control on rock strength and mode of failure. High porosity (> 23%) rocks show low rock strength (rocks (5-23%) exhibit higher measured rock strengths (up to 278 MPa) and brittle failure. Groundmass crystallinity, porosity and rock strength are intercorrelated. High groundmass crystal content is inversely related to low porosity, implying crystallisation and degassing of a slowly undercooled magma that experienced rheological stiffening under high pressures deeper within the conduit. This is linked to a slow magma ascent rate and results in a lava dome with higher rock strength. Samples with low groundmass crystallinity are associated with higher porosity and lower rock strength, and represent magma that ascended more rapidly, with faster undercooling, and solidification in the upper conduit at low pressures. Our experimental results show that the inherent strength of rocks within a growing dome may vary considerably depending on ascent/emplacement rates, thus significantly affecting dome stability and collapse hazards.

X-ray echoes from gamma-ray bursts

International Nuclear Information System (INIS)

Dermer, C.D.; Hurley, K.C.; Hartmann, D.H.

1991-01-01

The identification of an echo of reflected radiation in time histories of gamma-ray burst spectra can provide important information about the existence of binary companions or accretion disks in gamma-ray burst systems. Because of the nature of Compton scattering, the spectrum of the echo will be attenuated at gamma-ray energies compared with the spectrum of the primary burst emission. The expected temporal and spectral signatures of the echo and a search for such echoes are described, and implications for gamma-ray burst models are discussed. 35 refs

Gamma-ray burst observations: the present situation

International Nuclear Information System (INIS)

Vedrenne, G.

1984-01-01

Recent results in gamma ray burst investigations concerning the spectral variability on a short time scale, precise locations, and the discovery of optical flashes in gamma ray burst positions on archival plates are presented. The implications of optical and X-ray observations of gamma ray burst error boxes are also discussed. 72 references

Detecting pipe bursts by monitoring water demand

NARCIS (Netherlands)

Bakker, M.; Vreeburg, J.H.G.; Van der Roer, M.; Sperber, V.

2012-01-01

An algorithm which compares measured and predicted water demands to detect pipe bursts was developed and tested on three data sets of water demand and reported pipe bursts of three years. The algorithm proved to be able to detect bursts where the water loss exceeds 30% of the average water demand in

Fine structure in fast drift storm bursts

International Nuclear Information System (INIS)

McConnell, D.; Ellis, G.R.A.

1981-01-01

Recent observations with high time resolution of fast drift storm (FDS) solar bursts are described. A new variety of FDS bursts characterised by intensity maxima regularly placed in the frequency domain is reported. Possible interpretations of this are mentioned and the implications of the short duration of FDS bursts are discussed. (orig.)

Bursting neurons and ultrasound avoidance in crickets

Directory of Open Access Journals (Sweden)

Gary eMarsat

2012-07-01

Full Text Available Decision making in invertebrates often relies on simple neural circuits composed of only a few identified neurons. The relative simplicity of these circuits makes it possible to identify the key computation and neural properties underlying decisions. In this review, we summarize recent research on the neural basis of ultrasound avoidance in crickets, a response that allows escape from echolocating bats. The key neural property shaping behavioral output is high-frequency bursting of an identified interneuron, AN2, which carries information about ultrasound stimuli from receptor neurons to the brain. AN2's spike train consists of clusters of spikes –bursts– that may be interspersed with isolated, non-burst spikes. AN2 firing is necessary and sufficient to trigger avoidance steering but only high-rate firing, such as occurs in bursts, evokes this response. AN2 bursts are therefore at the core of the computation involved in deciding whether or not to steer away from ultrasound. Bursts in AN2 are triggered by synaptic input from nearly synchronous bursts in ultrasound receptors. Thus the population response at the very first stage of sensory processing –the auditory receptor- already differentiates the features of the stimulus that will trigger a behavioral response from those that will not. Adaptation, both intrinsic to AN2 and within ultrasound receptors, scales the burst-generating features according to the stimulus statistics, thus filtering out background noise and ensuring that bursts occur selectively in response to salient peaks in ultrasound intensity. Furthermore AN2’s sensitivity to ultrasound varies adaptively with predation pressure, through both developmental and evolutionary mechanisms. We discuss how this key relationship between bursting and the triggering of avoidance behavior is also observed in other invertebrate systems such as the avoidance of looming visual stimuli in locusts or heat avoidance in beetles.

AUTOMATIC RECOGNITION OF CORONAL TYPE II RADIO BURSTS: THE AUTOMATED RADIO BURST IDENTIFICATION SYSTEM METHOD AND FIRST OBSERVATIONS

International Nuclear Information System (INIS)

Lobzin, Vasili V.; Cairns, Iver H.; Robinson, Peter A.; Steward, Graham; Patterson, Garth

2010-01-01

Major space weather events such as solar flares and coronal mass ejections are usually accompanied by solar radio bursts, which can potentially be used for real-time space weather forecasts. Type II radio bursts are produced near the local plasma frequency and its harmonic by fast electrons accelerated by a shock wave moving through the corona and solar wind with a typical speed of ∼1000 km s -1 . The coronal bursts have dynamic spectra with frequency gradually falling with time and durations of several minutes. This Letter presents a new method developed to detect type II coronal radio bursts automatically and describes its implementation in an extended Automated Radio Burst Identification System (ARBIS 2). Preliminary tests of the method with spectra obtained in 2002 show that the performance of the current implementation is quite high, ∼80%, while the probability of false positives is reasonably low, with one false positive per 100-200 hr for high solar activity and less than one false event per 10000 hr for low solar activity periods. The first automatically detected coronal type II radio burst is also presented.

NICER Eyes on Bursting Stars

Science.gov (United States)

Kohler, Susanna

2018-03-01

What happens to a neutron stars accretion disk when its surface briefly explodes? A new instrument recently deployed at the International Space Station (ISS) is now watching bursts from neutron stars and reporting back.Deploying a New X-Ray MissionLaunch of NICER aboard a Falcon 9 rocket in June 2017. [NASA/Tony Gray]In early June of 2017, a SpaceX Dragon capsule on a Falcon 9 rocket launched on a resupply mission to the ISS. The pressurized interior of the Dragon contained the usual manifest of crew supplies, spacewalk equipment, and vehicle hardware. But the unpressurized trunk of the capsule held something a little different: the Neutron star Interior Composition Explorer (NICER).In the two weeks following launch, NICER was extracted from the SpaceX Dragon capsule and installed on the ISS. And by the end of the month, the instrument was already collecting its first data set: observations of a bright X-ray burst from Aql X-1, a neutron star accreting matter from a low-mass binary companion.Impact of BurstsNICERs goal is to provide a new view of neutron-star physics at X-ray energies of 0.212 keV a window that allows us to explore bursts of energy that neutron stars sometimes emit from their surfaces.Artists impression of an X-ray binary, in which a compact object accretes material from a companion star. [ESA/NASA/Felix Mirabel]In X-ray burster systems, hydrogen- and helium-rich material from a low-mass companion star piles up in an accretion disk around the neutron star. This material slowly funnels onto the neutron stars surface, forming a layer that gravitationally compresses and eventually becomes so dense and hot that runaway nuclear fusion ignites.Within seconds, the layer of material is burned up, producing a burst of emission from the neutron star that outshines even the inner regions of the hot accretion disk. Then more material funnels onto the neutron star and the process begins again.Though we have a good picture of the physics that causes these bursts

INTEGRAL monitoring of unusually long X-ray bursts

DEFF Research Database (Denmark)

Chenevez, Jérôme; Falanga, M.; Kuulkers, E.

2008-01-01

of exceptional burst events lasting more than ~10 minutes. Half of the dozen so-called intermediate long bursts registered so far have been observed by INTEGRAL. The goal is to derive a comprehensive picture of the relationship between the nuclear ignition processes and the accretion states of the system leading...... up to such long bursts. Depending on the composition of the accreted material, these bursts may be explained by either the unstable burning of a large pile of mixed hydrogen and helium, or the ignition of a thick pure helium layer. Intermediate long bursts are particularly expected to occur at very...

Geological hazard zonation in a marble exploitation area (Apuan Alps, Italy)

Science.gov (United States)

Francioni, M.; Salvini, R.; Riccucci, S.

2011-12-01

The present paper describes the hazard mapping of an exploitation area sited in the Apuan Alps marble district (Italy) carried out by the integration of various survey and analysis methodologies. The research, supported by the Massa and Carrara Local Sanitary Agency responsible for workplace health and safety activities, aimed to reduce the high degree hazard of rock fall caused by the presence of potentially unstable blocks located on slopes overhanging the marble quarries. The study of rocky fronts bases on the knowledge of both the structural setting and the physical-mechanical properties of intact material and its discontinuities. In this work the main difficulty in obtaining this information was the inaccessibility of the slope overhanging the area (up to 500 meters high). For this reason, the structural and geological-engineering surveys were integrated by outcomes from digital photogrammetry carried out through terrestrial stereoscopic photos acquired from an aerostatic balloon and a helicopter. In this way, it was possible to derive the geometrical characteristics of joints (such as discontinuities dip, dip direction, spacing and persistence), blocks volumes and slopes morphology also in inaccessible areas. This information, combined with data coming from the geological-engineering survey, was used to perform the stability analysis of the slope. Subsequently, using the topographic map at the scale of 1:2,000, the Digital Terrain Model (DTM) of the slopes and several topographic profiles along it were produced. Assuming that there is a good correspondence between travelling paths and maximum down slope angle, probable trajectories of rock fall along the slope were calculated on the DTM by means of a GIS procedure which utilizes the ArcHydro module of EsriTM ArcMap software. When performing such a 2D numerical modelling of rock falls, lateral dispersion of trajectories has often been hampered by the "a priori" choice of the travelling path. Such a choice can

Observation of cosmic gamma ray burst by Hinotori

International Nuclear Information System (INIS)

Okudaira, Kiyoaki; Yoshimori, Masato; Hirashima, Yo; Kondo, Ichiro.

1982-01-01

The solar gamma ray detecor (SGR) on Hinotori has no collimator, and the collimator of a hard X-ray monitor is not effective for gamma ray with energy more than 100 KeV. Accordingly, the detection system can detect cosmic gamma ray burst, and two bursts were observed. The first burst was detected on February 28, 1981, and the source of the burst was in the direction of 81 degree from Venus. The time profile and the spectrum were observed. In July 21, 1981, the second burst was detected. The time profile obtained with the SGR was compared with those of PVO (Pioneer Venus Orbiter) and LASL-ISEE. The time difference among the data of time profiles indicated that the source of the burst was not the sun. The spectrum was also measured. (Kato, T.)

Advances in gamma-ray burst astronomy

International Nuclear Information System (INIS)

Cline, T.L.; Desai, U.D.

1976-01-01

Work at Goddard is presently being carried out in three major areas of gamma-ray burst research: (1) A pair of simultaneously operating 0.8-m 2 burst detectors were successfully balloon-borne at locations 800 miles apart on 9 May, 1975, each to atmospheric depths of 3 to 4 g cm -2 , for a 20-h period of coincident data coverage. This experiment investigates the size spectrum of bursts in the 10 -7 to 10 -6 erg cm -2 size region where dozens of events per day are expected on a -1.5 index integral power-law extrapolation. Considerable separation in latitude was used to avoid possible atmospheric and auroral secondary effects. Its results are not yet available. (2) A deep-space burst detector, the first spacecraft instrument built specifically for gamma-ray burst studies, was recently successfully integrated into the Helios-B space probe. Its use at distances of up to 2 AU will make possible the first high-resolution directional study of gamma-ray burst source locations. Similar modifications to several other space vehicles are also being prepared. (3) The gamma-ray instrument on the IMP-7 satellite is presently the most sensitive burst detector still operating in orbit. Its results have shown that all measured event-average energy spectra are consistent with being alike. Using this characteristic spectrum to select IMP-7 candidate events of smaller size than those detected using other spacecraft in coincidence, a size spectrum is constructed which fits the -1.5 index power law down to 2.5 x 10 -5 erg cm -2 per event, at an occurrence rate of about once per month. (Auth.)

Study on cosmic gamma bursts in the ''KONUS'' experiment

International Nuclear Information System (INIS)

Mazets, E.P.; Golenetskij, S.V.; Il'inskij, V.N.; Panov, V.N.; Aptekar', R.L.; Gur'yan, Yu.A.; Sokolov, I.A.; Sokolova, Z.Ya.; Kharitonova, T.V.

1979-01-01

Made are the investigations of cosmic gamma bursts with the help of the ''Konus'' apparatus, positioned on the ''Venera 11'' and ''Venera 12'' automatic interplanetary stations. 37 gamma bursts have been recorded in the energy range from 50 to 150 keV during the observation period from September to December 1978. Time profiles of bursts on 4, 9 and 24.11.1978 are presented. For the most events the time of burst increase and decrease constitute parts and units of seconds. Differential energy spectra are measured for all recorded bursts. In many cases the spectrum shape is similar to the grade one with the 1.5-2.3 index. In a graphical form built up are the integral distributions of gamma bursts appearence frequency in dependence on their intensity and maximum capacity in the burst peak. Galaxy coordinates of the 17-teen bursts, for which a simple localization is possible, are put on the celestial sphere map. The type of the integral distributions and the source distribution about the celestial sphere show that the gamma burst sources are whithin the Galaxy

A Novel QKD-based Secure Edge Router Architecture Design for Burst Confidentiality in Optical Burst Switched Networks

Science.gov (United States)

Balamurugan, A. M.; Sivasubramanian, A.

2014-06-01

The Optical Burst Switching (OBS) is an emergent result to the technology issue that could achieve a viable network in future. They have the ability to meet the bandwidth requisite of those applications that call for intensive bandwidth. The field of optical transmission has undergone numerous advancements and is still being researched mainly due to the fact that optical data transmission can be done at enormous speeds. The concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of burst aggregation, routing, authentication, dispute resolution and quality of service (QoS). This paper proposes a framework based on QKD based secure edge router architecture design to provide burst confidentiality. The QKD protocol offers high level of confidentiality as it is indestructible. The design architecture was implemented in FPGA using diverse models and the results were taken. The results show that the proposed model is suitable for real time secure routing applications of the Optical burst switched networks.

3rd Interplanetary Network Gamma-Ray Burst Website

Science.gov (United States)

Hurley, Kevin

1998-05-01

We announce the opening of the 3rd Interplanetary Network web site at http://ssl.berkeley.edu/ipn3/index.html This site presently has four parts: 1. A bibliography of over 3000 publications on gamma-ray bursts, 2. IPN data on all bursts triangulated up to February 1998, 3. A master list showing which spacecraft observed which bursts, 4. Preliminary IPN data on the latest bursts observed.

THE INTERPLANETARY NETWORK SUPPLEMENT TO THE BURST AND TRANSIENT SOURCE EXPERIMENT 5B CATALOG OF COSMIC GAMMA-RAY BURSTS

International Nuclear Information System (INIS)

Hurley, K.; Briggs, M. S.; Kippen, R. M.; Kouveliotou, C.; Fishman, G.; Meegan, C.; Cline, T.; Trombka, J.; McClanahan, T.; Boynton, W.; Starr, R.; McNutt, R.; Boer, M.

2011-01-01

We present Interplanetary Network localization information for 343 gamma-ray bursts observed by the Burst and Transient Source Experiment (BATSE) between the end of the 4th BATSE catalog and the end of the Compton Gamma-Ray Observatory (CGRO) mission, obtained by analyzing the arrival times of these bursts at the Ulysses, Near Earth Asteroid Rendezvous (NEAR), and CGRO spacecraft. For any given burst observed by CGRO and one other spacecraft, arrival time analysis (or t riangulation ) results in an annulus of possible arrival directions whose half-width varies between 11 arcsec and 21 0 , depending on the intensity, time history, and arrival direction of the burst, as well as the distance between the spacecraft. This annulus generally intersects the BATSE error circle, resulting in an average reduction of the area of a factor of 20. When all three spacecraft observe a burst, the result is an error box whose area varies between 1 and 48,000 arcmin 2 , resulting in an average reduction of the BATSE error circle area of a factor of 87.

High-voltage pulsed generator for dynamic fragmentation of rocks.

Science.gov (United States)

Kovalchuk, B M; Kharlov, A V; Vizir, V A; Kumpyak, V V; Zorin, V B; Kiselev, V N

2010-10-01

A portable high-voltage (HV) pulsed generator has been designed for rock fragmentation experiments. The generator can be used also for other technological applications. The installation consists of low voltage block, HV block, coaxial transmission line, fragmentation chamber, and control system block. Low voltage block of the generator, consisting of a primary capacitor bank (300 μF) and a thyristor switch, stores pulse energy and transfers it to the HV block. The primary capacitor bank stores energy of 600 J at the maximum charging voltage of 2 kV. HV block includes HV pulsed step up transformer, HV capacitive storage, and two electrode gas switch. The following technical parameters of the generator were achieved: output voltage up to 300 kV, voltage rise time of ∼50 ns, current amplitude of ∼6 kA with the 40 Ω active load, and ∼20 kA in a rock fragmentation regime (with discharge in a rock-water mixture). Typical operation regime is a burst of 1000 pulses with a frequency of 10 Hz. The operation process can be controlled within a wide range of parameters. The entire installation (generator, transmission line, treatment chamber, and measuring probes) is designed like a continuous Faraday's cage (complete shielding) to exclude external electromagnetic perturbations.

High-voltage pulsed generator for dynamic fragmentation of rocks

Science.gov (United States)

Kovalchuk, B. M.; Kharlov, A. V.; Vizir, V. A.; Kumpyak, V. V.; Zorin, V. B.; Kiselev, V. N.

2010-10-01

A portable high-voltage (HV) pulsed generator has been designed for rock fragmentation experiments. The generator can be used also for other technological applications. The installation consists of low voltage block, HV block, coaxial transmission line, fragmentation chamber, and control system block. Low voltage block of the generator, consisting of a primary capacitor bank (300 μF) and a thyristor switch, stores pulse energy and transfers it to the HV block. The primary capacitor bank stores energy of 600 J at the maximum charging voltage of 2 kV. HV block includes HV pulsed step up transformer, HV capacitive storage, and two electrode gas switch. The following technical parameters of the generator were achieved: output voltage up to 300 kV, voltage rise time of ˜50 ns, current amplitude of ˜6 kA with the 40 Ω active load, and ˜20 kA in a rock fragmentation regime (with discharge in a rock-water mixture). Typical operation regime is a burst of 1000 pulses with a frequency of 10 Hz. The operation process can be controlled within a wide range of parameters. The entire installation (generator, transmission line, treatment chamber, and measuring probes) is designed like a continuous Faraday's cage (complete shielding) to exclude external electromagnetic perturbations.

Dynamic encoding of natural luminance sequences by LGN bursts.

Directory of Open Access Journals (Sweden)

Nicholas A Lesica

2006-07-01

Full Text Available In the lateral geniculate nucleus (LGN of the thalamus, visual stimulation produces two distinct types of responses known as tonic and burst. Due to the dynamics of the T-type Ca(2+ channels involved in burst generation, the type of response evoked by a particular stimulus depends on the resting membrane potential, which is controlled by a network of modulatory connections from other brain areas. In this study, we use simulated responses to natural scene movies to describe how modulatory and stimulus-driven changes in LGN membrane potential interact to determine the luminance sequences that trigger burst responses. We find that at low resting potentials, when the T channels are de-inactivated and bursts are relatively frequent, an excitatory stimulus transient alone is sufficient to evoke a burst. However, to evoke a burst at high resting potentials, when the T channels are inactivated and bursts are relatively rare, prolonged inhibitory stimulation followed by an excitatory transient is required. We also observe evidence of these effects in vivo, where analysis of experimental recordings demonstrates that the luminance sequences that trigger bursts can vary dramatically with the overall burst percentage of the response. To characterize the functional consequences of the effects of resting potential on burst generation, we simulate LGN responses to different luminance sequences at a range of resting potentials with and without a mechanism for generating bursts. Using analysis based on signal detection theory, we show that bursts enhance detection of specific luminance sequences, ranging from the onset of excitatory sequences at low resting potentials to the offset of inhibitory sequences at high resting potentials. These results suggest a dynamic role for burst responses during visual processing that may change according to behavioral state.

Low-Frequency Type III Bursts and Solar Energetic Particle Events

Science.gov (United States)

Gopalswamy, Nat; Makela, Pertti

2010-01-01

We analyzed the coronal mass ejections (CMEs), flares, and type 11 radio bursts associated with a set of six low frequency (15 min) normally used to define these bursts. All but one of the type III bursts was not associated with a type 11 burst in the metric or longer wavelength domains. The burst without type 11 burst also lacked a solar energetic particle (SEP) event at energies >25 MeV. The 1-MHz duration of the type III burst (28 min) is near the median value of type III durations found for gradual SEP events and ground level enhancement (GLE) events. Yet, there was no sign of SEP events. On the other hand, two other type III bursts from the same active region had similar duration but accompanied by WAVES type 11 bursts; these bursts were also accompanied by SEP events detected by SOHO/ERNE. The CMEs were of similar speeds and the flares are also of similar size and duration. This study suggests that the type III burst duration may not be a good indicator of an SEP event.

New decoding methods of interleaved burst error-correcting codes

Science.gov (United States)

Nakano, Y.; Kasahara, M.; Namekawa, T.

1983-04-01

A probabilistic method of single burst error correction, using the syndrome correlation of subcodes which constitute the interleaved code, is presented. This method makes it possible to realize a high capability of burst error correction with less decoding delay. By generalizing this method it is possible to obtain probabilistic method of multiple (m-fold) burst error correction. After estimating the burst error positions using syndrome correlation of subcodes which are interleaved m-fold burst error detecting codes, this second method corrects erasure errors in each subcode and m-fold burst errors. The performance of these two methods is analyzed via computer simulation, and their effectiveness is demonstrated.

Flash photoionization of gamma-ray burst environments

Science.gov (United States)

Band, David L.; Hartmann, Dieter H.

1992-01-01

The H-alpha line emission that a flash-photoionized region emits is calculated. Archival transients, as well as various theoretical predictions, suggest that there may be significant ionizing flux. The limits on the line flux which might be observable indicate that the density must be fairly high for the recombination radiation to be observable. The intense burst radiation is insufficient to melt the dust which will be present in such a dense medium. This dust may attenuate the observable line emission, but does not attenuate the ionizing radiation before it ionizes the neutral medium surrounding the burst source. The dust can also produce a light echo. If there are indeed gamma-ray bursts in dense clouds, then it is possible that the burst was triggered by Bondi-Hoyle accretion from the dense medium, although it is unlikely on statistical grounds that all bursts occur in clouds.

The supernova-gamma-ray burst-jet connection.

Science.gov (United States)

Hjorth, Jens

2013-06-13

The observed association between supernovae and gamma-ray bursts represents a cornerstone in our understanding of the nature of gamma-ray bursts. The collapsar model provides a theoretical framework for this connection. A key element is the launch of a bipolar jet (seen as a gamma-ray burst). The resulting hot cocoon disrupts the star, whereas the (56)Ni produced gives rise to radioactive heating of the ejecta, seen as a supernova. In this discussion paper, I summarize the observational status of the supernova-gamma-ray burst connection in the context of the 'engine' picture of jet-driven supernovae and highlight SN 2012bz/GRB 120422A--with its luminous supernova but intermediate high-energy luminosity--as a possible transition object between low-luminosity and jet gamma-ray bursts. The jet channel for supernova explosions may provide new insights into supernova explosions in general.

Long X-ray burst monitoring with INTEGRAL

DEFF Research Database (Denmark)

X-ray bursts are thermonuclear explosions on the surface of accreting neutron stars in low mass X-ray binary systems. In the frame of the INTEGRAL observational Key Programme over the Galactic Center a good number of the known X-ray bursters are frequently being monitored. An international...... collaboration lead by the JEM-X team at the Danish National Space Center has proposed to exploit the improved sensitivity of the INTEGRAL instruments to investigate the observational properties and physics up to high energies of exceptional burst events lasting between a few tens of minutes and several hours....... Of special interest are low luminosity bursting sources that exhibit X-ray bursts of very different durations allowing to study the transition from a hydrogen-rich bursting regime to a pure helium regime and from helium burning to carbon burning. I will present results obtained from INTEGRAL archive data...

Frequency chirping during a fishbone burst

International Nuclear Information System (INIS)

Marchenko, V.S.; Reznik, S.N.

2011-01-01

It is shown that frequency chirping during fishbone activity can be attributed to the reactive torque exerted on the plasma during the instability burst, which slows down plasma rotation inside the q = 1 surface and reduces the mode frequency in the lab frame. Estimates show that the peak value of this torque can exceed the neutral beam torque in modern tokamaks. The simple line-broadened quasilinear burst model (Berk et al 1995 Nucl. Fusion 35 1661), properly adapted for the fishbone case, is capable of reproducing the key features of the bursting mode. (letter)

Simulating X-ray bursts during a transient accretion event

Science.gov (United States)

Johnston, Zac; Heger, Alexander; Galloway, Duncan K.

2018-06-01

Modelling of thermonuclear X-ray bursts on accreting neutron stars has to date focused on stable accretion rates. However, bursts are also observed during episodes of transient accretion. During such events, the accretion rate can evolve significantly between bursts, and this regime provides a unique test for burst models. The accretion-powered millisecond pulsar SAX J1808.4-3658 exhibits accretion outbursts every 2-3 yr. During the well-sampled month-long outburst of 2002 October, four helium-rich X-ray bursts were observed. Using this event as a test case, we present the first multizone simulations of X-ray bursts under a time-dependent accretion rate. We investigate the effect of using a time-dependent accretion rate in comparison to constant, averaged rates. Initial results suggest that using a constant, average accretion rate between bursts may underestimate the recurrence time when the accretion rate is decreasing, and overestimate it when the accretion rate is increasing. Our model, with an accreted hydrogen fraction of X = 0.44 and a CNO metallicity of ZCNO = 0.02, reproduces the observed burst arrival times and fluences with root mean square (rms) errors of 2.8 h, and 0.11× 10^{-6} erg cm^{-2}, respectively. Our results support previous modelling that predicted two unobserved bursts and indicate that additional bursts were also missed by observations.

Review of GRANAT observations of gamma-ray bursts

DEFF Research Database (Denmark)

Terekhov, O.; Denissenko, D.; Sunyaev, R.

1995-01-01

The GRANAT observatory was launched into a high apogee orbit on 1 December, 1989. Three instruments onboard GRANAT - PHEBUS, WATCH and SIGMA are able to detect gamma-ray bursts in a very broad energy range from 6 keV up to 100 MeV. Over 250 gamma-ray bursts were detected. We discuss the results...... of the observations of the time histories and spectral evolution of the detected events provided by the different instruments in different energy ranges. Short Gamma-Ray Bursts ( 2 s) events. Evidence of the existence...... of four differently behaving componenents in gamma-ray burst spectra is discussed. Statistical properties of the gamma-ray burst sources based on the 5 years of observations with (∼ 10−6 erg/cm2) sensitivity as well as the results of high sensitivity (∼ 10−8 erg/cm2) search for Gamma-Ray Bursts within...

Near stellar sources of gamma-ray bursts

OpenAIRE

Luchkov, B. I.; Markin, P. D.

2012-01-01

Correlation analysis of gamma-ray burst coordinates and nearby stars, registered on 2008-2011, revealed 5 coincidences with angular accuracy better than 0.1 degree. The random probability is $7\\times 10^{-7}$, so evidencing that coincident stars are indeed gamma-ray burst sources. The proposed method should be continued in order to provide their share in common balance of cosmic gamma-ray bursts.

Research on preventive technologies for bed-separation water hazard in China coal mines

Science.gov (United States)

Gui, Herong; Tong, Shijie; Qiu, Weizhong; Lin, Manli

2018-03-01

Bed-separation water is one of the major water hazards in coal mines. Targeted researches on the preventive technologies are of paramount importance to safe mining. This article studied the restrictive effect of geological and mining factors, such as lithological properties of roof strata, coal seam inclination, water source to bed separations, roof management method, dimensions of mining working face, and mining progress, on the formation of bed-separation water hazard. The key techniques to prevent bed-separation water-related accidents include interception, diversion, destructing the buffer layer, grouting and backfilling, etc. The operation and efficiency of each technique are corroborated in field engineering cases. The results of this study will offer reference to countries with similar mining conditions in the researches on bed-separation water burst and hazard control in coal mines.

Gamma-Ray Burst Host Galaxies Have "Normal" Luminosities.

Science.gov (United States)

Schaefer

2000-04-10

The galactic environment of gamma-ray bursts can provide good evidence about the nature of the progenitor system, with two old arguments implying that the burst host galaxies are significantly subluminous. New data and new analysis have now reversed this picture: (1) Even though the first two known host galaxies are indeed greatly subluminous, the next eight hosts have absolute magnitudes typical for a population of field galaxies. A detailed analysis of the 16 known hosts (10 with redshifts) shows them to be consistent with a Schechter luminosity function with R*=-21.8+/-1.0, as expected for normal galaxies. (2) Bright bursts from the Interplanetary Network are typically 18 times brighter than the faint bursts with redshifts; however, the bright bursts do not have galaxies inside their error boxes to limits deeper than expected based on the luminosities for the two samples being identical. A new solution to this dilemma is that a broad burst luminosity function along with a burst number density varying as the star formation rate will require the average luminosity of the bright sample (>6x1058 photons s-1 or>1.7x1052 ergs s-1) to be much greater than the average luminosity of the faint sample ( approximately 1058 photons s-1 or approximately 3x1051 ergs s-1). This places the bright bursts at distances for which host galaxies with a normal luminosity will not violate the observed limits. In conclusion, all current evidence points to gamma-ray burst host galaxies being normal in luminosity.

Cosmology and the Subgroups of Gamma-ray Bursts

Directory of Open Access Journals (Sweden)

A. Mészáros

2011-01-01

Full Text Available Both short and intermediate gamma-ray bursts are distributed anisotropically in the sky (Mészáros, A. et al. ApJ, 539, 98 (2000, Vavrek, R. et al. MNRAS, 391, 1 741 (2008. Hence, in the redshift range, where these bursts take place, the cosmological principle is in doubt. It has already been noted that short bursts should be mainly at redshifts smaller than one (Mészáros, A. et al. Gamma-ray burst: Sixth Huntsville Symp., AIP, Vol. 1 133, 483 (2009; Mészáros, A. et al. Baltic Astron., 18, 293 (2009. Here we show that intermediate bursts should be at redshifts up to three.

Type III Radio Burst Duration and SEP Events

Science.gov (United States)

Gopalswamy, N.; Makela, P.; Xie, H.

2010-01-01

Long-duration (>15 min), low-frequency (25 MeV. The 1-MHz duration of the type III burst (28 rein) is near the median value of type III durations found for gradual SEP events and ground level enhancement (GLE) events. Yet, there was no sign of SEP events. On the other hand, two other type III bursts from the same active region had similar duration but accompanied by WAVES type 11 bursts; these bursts were also accompanied by SEP events detected by SOHO/ERNE. This study suggests that the type III burst duration may not be a good indicator of an SEP event, consistent with the statistical study of Cliver and Ling (2009, ApJ ).

High-resolution three-dimensional imaging and analysis of rock falls in Yosemite valley, California

Science.gov (United States)

Stock, Gregory M.; Bawden, G.W.; Green, J.K.; Hanson, E.; Downing, G.; Collins, B.D.; Bond, S.; Leslar, M.

2011-01-01

We present quantitative analyses of recent large rock falls in Yosemite Valley, California, using integrated high-resolution imaging techniques. Rock falls commonly occur from the glacially sculpted granitic walls of Yosemite Valley, modifying this iconic landscape but also posing signifi cant potential hazards and risks. Two large rock falls occurred from the cliff beneath Glacier Point in eastern Yosemite Valley on 7 and 8 October 2008, causing minor injuries and damaging structures in a developed area. We used a combination of gigapixel photography, airborne laser scanning (ALS) data, and ground-based terrestrial laser scanning (TLS) data to characterize the rock-fall detachment surface and adjacent cliff area, quantify the rock-fall volume, evaluate the geologic structure that contributed to failure, and assess the likely failure mode. We merged the ALS and TLS data to resolve the complex, vertical to overhanging topography of the Glacier Point area in three dimensions, and integrated these data with gigapixel photographs to fully image the cliff face in high resolution. Three-dimensional analysis of repeat TLS data reveals that the cumulative failure consisted of a near-planar rock slab with a maximum length of 69.0 m, a mean thickness of 2.1 m, a detachment surface area of 2750 m2, and a volume of 5663 ?? 36 m3. Failure occurred along a surfaceparallel, vertically oriented sheeting joint in a clear example of granitic exfoliation. Stress concentration at crack tips likely propagated fractures through the partially attached slab, leading to failure. Our results demonstrate the utility of high-resolution imaging techniques for quantifying far-range (>1 km) rock falls occurring from the largely inaccessible, vertical rock faces of Yosemite Valley, and for providing highly accurate and precise data needed for rock-fall hazard assessment. ?? 2011 Geological Society of America.

Eddington-limited X-Ray Bursts as Distance Indicators. I. Systematic Trends and Spherical Symmetry in Bursts from 4U 1728-34

Science.gov (United States)

Galloway, Duncan K.; Psaltis, Dimitrios; Chakrabarty, Deepto; Muno, Michael P.

2003-06-01

We investigate the limitations of thermonuclear X-ray bursts as a distance indicator for the weakly magnetized accreting neutron star 4U 1728-34. We measured the unabsorbed peak flux of 81 bursts in public data from the Rossi X-Ray Timing Explorer (RXTE). The distribution of peak fluxes was bimodal: 66 bursts exhibited photospheric radius expansion (presumably reaching the local Eddington limit) and were distributed about a mean bolometric flux of 9.2×10-8ergscm-2s-1, while the remaining (non-radius expansion) bursts reached 4.5×10-8ergscm-2s-1, on average. The peak fluxes of the radius expansion bursts were not constant, exhibiting a standard deviation of 9.4% and a total variation of 46%. These bursts showed significant correlations between their peak flux and the X-ray colors of the persistent emission immediately prior to the burst. We also found evidence for quasi-periodic variation of the peak fluxes of radius expansion bursts, with a timescale of ~=40 days. The persistent flux observed with RXTE/ASM over 5.8 yr exhibited quasi-periodic variability on a similar timescale. We suggest that these variations may have a common origin in reflection from a warped accretion disk. Once the systematic variation of the peak burst fluxes is subtracted, the residual scatter is only ~=3%, roughly consistent with the measurement uncertainties. The narrowness of this distribution strongly suggests that (1) the radiation from the neutron star atmosphere during radius expansion episodes is nearly spherically symmetric and (2) the radius expansion bursts reach a common peak flux that may be interpreted as a standard candle intensity. Adopting the minimum peak flux for the radius expansion bursts as the Eddington flux limit, we derive a distance for the source of 4.4-4.8 kpc (assuming RNS=10 km), with the uncertainty arising from the probable range of the neutron star mass MNS=1.4-2 Msolar.

Bursts from the very early universe

International Nuclear Information System (INIS)

Silk, J.; Stodolsky, L.

2006-01-01

Bursts of weakly interacting particles such as neutrinos or even more weakly interacting particles such as wimps and gravitons from the very early universe would offer a much deeper 'look back time' to early epochs than is possible with photons. We consider some of the issues related to the existence of such bursts and their detectability. Characterizing the burst rate by a probability P per Hubble four-volume we find, for events in the radiation-dominated era, that the natural unit of description is the present intensity of the CMB times P. The existence of such bursts would make the observation of phenomena associated with very early times in cosmology at least conceptually possible. One might even hope to probe the transplanckian epoch if complexes more weakly interacting than the graviton can exist. Other conceivable applications include the potential detectability of the formation of 'pocket universes' in a multiverse

Light Dawns on Dark Gamma-ray Bursts

Science.gov (United States)

2010-12-01

Gamma-ray bursts are among the most energetic events in the Universe, but some appear curiously faint in visible light. The biggest study to date of these so-called dark gamma-ray bursts, using the GROND instrument on the 2.2-metre MPG/ESO telescope at La Silla in Chile, has found that these gigantic explosions don't require exotic explanations. Their faintness is now fully explained by a combination of causes, the most important of which is the presence of dust between the Earth and the explosion. Gamma-ray bursts (GRBs), fleeting events that last from less than a second to several minutes, are detected by orbiting observatories that can pick up their high energy radiation. Thirteen years ago, however, astronomers discovered a longer-lasting stream of less energetic radiation coming from these violent outbursts, which can last for weeks or even years after the initial explosion. Astronomers call this the burst's afterglow. While all gamma-ray bursts [1] have afterglows that give off X-rays, only about half of them were found to give off visible light, with the rest remaining mysteriously dark. Some astronomers suspected that these dark afterglows could be examples of a whole new class of gamma-ray bursts, while others thought that they might all be at very great distances. Previous studies had suggested that obscuring dust between the burst and us might also explain why they were so dim. "Studying afterglows is vital to further our understanding of the objects that become gamma-ray bursts and what they tell us about star formation in the early Universe," says the study's lead author Jochen Greiner from the Max-Planck Institute for Extraterrestrial Physics in Garching bei München, Germany. NASA launched the Swift satellite at the end of 2004. From its orbit above the Earth's atmosphere it can detect gamma-ray bursts and immediately relay their positions to other observatories so that the afterglows could be studied. In the new study, astronomers combined Swift

Analytical Technique of Gravel Propensity in Coal pit

OpenAIRE

Kovačič, Blaž; Zupančič, Borislav; Potočnik, Damir

2011-01-01

In terms of surrounding rock with rock burst tendency in coal mine, the rock burst occur when elastic energy accumulation of rock mass system for rock mass deformation reached the limit of rock mass energy storage, and the condition that the factors effected elastic energy accumulation needed to meet can be laid out. The rock burst tendency analysis can be defined as a progress as following: making sure the stress condition of surrounding rock and the. For the purpose of forecasting rock burs...

Relativistic motion in gamma-ray bursts

International Nuclear Information System (INIS)

Krolik, J.H.; Pier, E.A.

1991-01-01

Three fundamental problems affect models of gamma-ray bursts, i.e., the energy source, the ability of high-energy photons to escape the radiation region, and the comparative weakness of X-ray emission. It is indicated that relativistic bulk motion of the gamma-ray-emitting plasma generically provides a solution to all three of these problems. Results show that, if the plasma that produces gamma-ray bursts has a bulk relativistic velocity with Lorentz factor gamma of about 10, several of the most troubling problems having to do with gamma-ray bursts are solved. 42 refs

A new design concept of fully grouted rock bolts in underground construction

Science.gov (United States)

Phich Nguyen, Quang; Nguyen, Van Manh; Tuong Nguyen, Ke

2018-04-01

The main problem after excavating an underground excavation is to maintain the stability of the excavation for a certain period of time. Failure in meeting this demand is a threat to safety of men and equipment. Support and reinforcement are different instruments with different mechanisms. Among the common support systems in tunnelling and mining, rock bolts have been widely used to reinforce rock mass and also to reduce geological hazards. Furthermore rock bolts can be applied under varying different geological conditions with cost-effectiveness. Although different methods are developed for grouted rock bolts design until now, the interaction mechanism of the rock bolts and rock mass is still very complicated issue. The paper addresses an analytical model for the analysis and design of fully grouted rock bolts based on the reinforcement principle. According to this concept the jointed rock mass reinforced by grouted rock bolts is considered as composite material which includes rock mass, the grout material and the bolt shank. The mechanical properties of this composite material depend on the ratio of the components. The closed-form solution was developed based on the assumption that the rock mass arround a circular tunnel remained elastic after installing fully grouted rock bolts. The main parameters of the rock-bolt system (the diameter and length of bolt shank, the space between the bolts) are then easily estimated from the obtained solution.

THE FERMI –GBM THREE-YEAR X-RAY BURST CATALOG

Energy Technology Data Exchange (ETDEWEB)

Jenke, P. A. [CSPAR, SPA University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Linares, M. [Instituto de Astrofísica de Canarias, c/Vía Láctea s/n, E-38205 La Laguna, Tenerife (Spain); Connaughton, V.; Camero-Arranz, A.; Finger, M. H. [Universities Space Research Association, Huntsville, AL 35805 (United States); Beklen, E. [Department of Physics, Suleyman Demirel University, 32260, Isparta (Turkey); Wilson-Hodge, C. A. [Marshall Space Flight Center, Huntsville, AL 35812 (United States)

2016-08-01

The Fermi Gamma-ray Burst Monitor (GBM) is an all-sky gamma-ray monitor well known in the gamma-ray burst (GRB) community. Although GBM excels in detecting the hard, bright extragalactic GRBs, its sensitivity above 8 keV and its all-sky view make it an excellent instrument for the detection of rare, short-lived Galactic transients. In 2010 March, we initiated a systematic search for transients using GBM data. We conclude this phase of the search by presenting a three-year catalog of 1084 X-ray bursts. Using spectral analysis, location, and spatial distributions we classified the 1084 events into 752 thermonuclear X-ray bursts, 267 transient events from accretion flares and X-ray pulses, and 65 untriggered gamma-ray bursts. All thermonuclear bursts have peak blackbody temperatures broadly consistent with photospheric radius expansion (PRE) bursts. We find an average rate of 1.4 PRE bursts per day, integrated over all Galactic bursters within about 10 kpc. These include 33 and 10 bursts from the ultra-compact X-ray binaries 4U 0614+09 and 2S 0918-549, respectively. We discuss these recurrence times and estimate the total mass ejected by PRE bursts in our Galaxy.

Research of explosives in an environment of high pressure and temperature using a new test stand

Directory of Open Access Journals (Sweden)

Jan Drzewiecki

2015-01-01

Full Text Available In this article the test stand for determining the blast abilities of explosives in high pressure and temperature conditions as well as the initial results of the research are presented. Explosives are used in rock burst and methane prevention to destroy precisely defined fragments of the rock mass where energy and methane are accumulated. Using this preventive method for fracturing the structure of the rocks which accumulate the energy or coal of the methane seam very often does not bring the anticipated results. It is because of the short range of destructive action of the post-blast gases around the blast hole. Evaluation of the blast dynamics of explosives in a test chamber, i.e. in the pressure and temperature conditions comparable to those found “in situ”, will enable evaluation of their real usefulness in commonly used mining hazard preventive methods. At the same time, it will enable the development of new designs of the explosive charges used for precisely determined mining hazards. In order to test the explosives for their use in difficult environmental conditions and to determine the characteristics of their explosion, a test chamber has been built. It is equipped with a system of sensors and a high-frequency recording system of pressure and temperature during a controlled explosion of an explosive charge. The results of the research will enable the development of new technologies for rock burst and methane prevention which will significantly increase workplace health and safety level. This paper presented results constitute the initial phase of research started in the middle of 2014.

Discovery of the short gamma-ray burst GRB 050709.

Science.gov (United States)

Villasenor, J S; Lamb, D Q; Ricker, G R; Atteia, J-L; Kawai, N; Butler, N; Nakagawa, Y; Jernigan, J G; Boer, M; Crew, G B; Donaghy, T Q; Doty, J; Fenimore, E E; Galassi, M; Graziani, C; Hurley, K; Levine, A; Martel, F; Matsuoka, M; Olive, J-F; Prigozhin, G; Sakamoto, T; Shirasaki, Y; Suzuki, M; Tamagawa, T; Vanderspek, R; Woosley, S E; Yoshida, A; Braga, J; Manchanda, R; Pizzichini, G; Takagishi, K; Yamauchi, M

2005-10-06

Gamma-ray bursts (GRBs) fall into two classes: short-hard and long-soft bursts. The latter are now known to have X-ray and optical afterglows, to occur at cosmological distances in star-forming galaxies, and to be associated with the explosion of massive stars. In contrast, the distance scale, the energy scale and the progenitors of the short bursts have remained a mystery. Here we report the discovery of a short-hard burst whose accurate localization has led to follow-up observations that have identified the X-ray afterglow and (for the first time) the optical afterglow of a short-hard burst; this in turn led to the identification of the host galaxy of the burst as a late-type galaxy at z = 0.16 (ref. 10). These results show that at least some short-hard bursts occur at cosmological distances in the outskirts of galaxies, and are likely to be caused by the merging of compact binaries.

The Drift Burst Hypothesis

DEFF Research Database (Denmark)

Christensen, Kim; Oomen, Roel; Renò, Roberto

are an expected and regular occurrence in financial markets that can arise through established mechanisms such as feedback trading. At a theoretical level, we show how to build drift bursts into the continuous-time Itô semi-martingale model in such a way that the fundamental arbitrage-free property is preserved......, currencies and commodities. We find that the majority of identified drift bursts are accompanied by strong price reversals and these can therefore be regarded as “flash crashes” that span brief periods of severe market disruption without any material longer term price impacts....

Hazard-consistent response spectra in the Region of Murcia (Southeast Spain): comparison to earthquake-resistant provisions

OpenAIRE

Gaspar Escribano, Jorge M.; Benito Oterino, Belen; Garcia Mayordomo, Julian

2008-01-01

Hazard-consistent ground-motion characterisations of three representative sites located in the Region of Murcia (southeast Spain) are presented. This is the area where the last three damaging events in Spain occurred and there is a significant amount of data for comparing them with seismic hazard estimates and earthquake-resistant provisions. Results of a probabilistic seismic hazard analysis are used to derive uniform hazard spectra (UHS) for the 475-year return period, on rock and soil cond...

Limits of the memory coefficient in measuring correlated bursts

Science.gov (United States)

Jo, Hang-Hyun; Hiraoka, Takayuki

2018-03-01

Temporal inhomogeneities in event sequences of natural and social phenomena have been characterized in terms of interevent times and correlations between interevent times. The inhomogeneities of interevent times have been extensively studied, while the correlations between interevent times, often called correlated bursts, are far from being fully understood. For measuring the correlated bursts, two relevant approaches were suggested, i.e., memory coefficient and burst size distribution. Here a burst size denotes the number of events in a bursty train detected for a given time window. Empirical analyses have revealed that the larger memory coefficient tends to be associated with the heavier tail of the burst size distribution. In particular, empirical findings in human activities appear inconsistent, such that the memory coefficient is close to 0, while burst size distributions follow a power law. In order to comprehend these observations, by assuming the conditional independence between consecutive interevent times, we derive the analytical form of the memory coefficient as a function of parameters describing interevent time and burst size distributions. Our analytical result can explain the general tendency of the larger memory coefficient being associated with the heavier tail of burst size distribution. We also find that the apparently inconsistent observations in human activities are compatible with each other, indicating that the memory coefficient has limits to measure the correlated bursts.

Relativistic effects in gamma-ray bursts

International Nuclear Information System (INIS)

Eriksen, Erik; Groen, Oeyvind

1999-01-01

According to recent models of the sources of gamma-ray bursts the extremely energetic emission is caused by shells expanding with ultrarelativistic velocity. With the recent identification of optical sources at the positions of some gamma-ray bursts these ''fireball'' models have acquired an actuality that invites to use them as a motivating application when teaching special relativity. We demonstrate several relativistic effects associated with these models which are very pronounced due to the great velocity of the shell. For example a burst lasting for a month in the rest frame of an element of the shell lasts for a few seconds only, in the rest frame of our detector. It is shown how the observed properties of a burst are modified by aberration and the Doppler effect. The apparent luminosity as a function of time is calculated. Modifications due to the motion of the star away from the observer are calculated. (Author)

Bursts from the very early universe

Energy Technology Data Exchange (ETDEWEB)

Silk, J. [Department of Physics, University of Oxford, Oxford OX1 3RH (United Kingdom); Stodolsky, L. [Max-Planck-Institut fuer Physik, Foehringer Ring 6, 80805 Munich (Germany)]. E-mail: les@mppmu.mpg.de

2006-07-27

Bursts of weakly interacting particles such as neutrinos or even more weakly interacting particles such as wimps and gravitons from the very early universe would offer a much deeper 'look back time' to early epochs than is possible with photons. We consider some of the issues related to the existence of such bursts and their detectability. Characterizing the burst rate by a probability P per Hubble four-volume we find, for events in the radiation-dominated era, that the natural unit of description is the present intensity of the CMB times P. The existence of such bursts would make the observation of pheno associated with very early times in cosmology at least conceptually possible. One might even hope to probe the transplanckian epoch if complexes more weakly interacting than the graviton can exist. Other conceivable applications include the potential detectability of the formation of 'pocket universes' in a multiverse.

Different types of bursting calcium oscillations in non-excitable cells

International Nuclear Information System (INIS)

Perc, Matjaz; Marhl, Marko

2003-01-01

In the paper different types of bursting Ca 2+ oscillations are presented. We analyse bursting behaviour in four recent mathematical models for Ca 2+ oscillations in non-excitable cells. Separately, regular, quasi-periodic, and chaotic bursting Ca 2+ oscillations are classified into several subtypes. The classification is based on the dynamics of separated fast and slow subsystems, the so-called fast-slow burster analysis. For regular bursting Ca 2+ oscillations two types of bursting are specified: Point-Point and Point-Cycle bursting. In particular, the slow passage effect, important for the Hopf-Hopf and SubHopf-SubHopf bursting subtypes, is explained by local divergence calculated for the fast subsystem. Quasi-periodic bursting Ca 2+ oscillations can be found in only one of the four studied mathematical models and appear via a homoclinic bifurcation with a homoclinic torus structure. For chaotic bursting Ca 2+ oscillations, we found that bursting patterns resulting from the period doubling root to chaos considerably differ from those appearing via intermittency and have to be treated separately. The analysis and classification of different types of bursting Ca 2+ oscillations provides better insight into mechanisms of complex intra- and intercellular Ca 2+ signalling. This improves our understanding of several important biological phenomena in cellular signalling like complex frequency-amplitude signal encoding and synchronisation of intercellular signal transduction between coupled cells in tissue

Solar energetic particles and radio burst emission

Directory of Open Access Journals (Sweden)

Miteva Rositsa

2017-01-01

Full Text Available We present a statistical study on the observed solar radio burst emission associated with the origin of in situ detected solar energetic particles. Several proton event catalogs in the period 1996–2016 are used. At the time of appearance of the particle origin (flare and coronal mass ejection we identified radio burst signatures of types II, III and IV by inspecting dynamic radio spectral plots. The information from observatory reports is also accounted for during the analysis. The occurrence of solar radio burst signatures is evaluated within selected wavelength ranges during the solar cycle 23 and the ongoing 24. Finally, we present the burst occurrence trends with respect to the intensity of the proton events and the location of their solar origin.

Bright x-ray flares in gamma-ray burst afterglows.

Science.gov (United States)

Burrows, D N; Romano, P; Falcone, A; Kobayashi, S; Zhang, B; Moretti, A; O'brien, P T; Goad, M R; Campana, S; Page, K L; Angelini, L; Barthelmy, S; Beardmore, A P; Capalbi, M; Chincarini, G; Cummings, J; Cusumano, G; Fox, D; Giommi, P; Hill, J E; Kennea, J A; Krimm, H; Mangano, V; Marshall, F; Mészáros, P; Morris, D C; Nousek, J A; Osborne, J P; Pagani, C; Perri, M; Tagliaferri, G; Wells, A A; Woosley, S; Gehrels, N

2005-09-16

Gamma-ray burst (GRB) afterglows have provided important clues to the nature of these massive explosive events, providing direct information on the nearby environment and indirect information on the central engine that powers the burst. We report the discovery of two bright x-ray flares in GRB afterglows, including a giant flare comparable in total energy to the burst itself, each peaking minutes after the burst. These strong, rapid x-ray flares imply that the central engines of the bursts have long periods of activity, with strong internal shocks continuing for hundreds of seconds after the gamma-ray emission has ended.

Implications of fast radio bursts for superconducting cosmic strings

Energy Technology Data Exchange (ETDEWEB)

Yu, Yun-Wei [Institute of Astrophysics, Central China Normal University, 152 Luoyu Road, Wuhan 430079 (China); Cheng, Kwong-Sang [Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Shiu, Gary; Tye, Henry, E-mail: yuyw@phy.ccnu.edu.cn, E-mail: hrspksc@hku.hk, E-mail: shiu@ust.hk, E-mail: iastye@ust.hk [Department of Physics and Institute for Advanced Study, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong (China)

2014-11-01

Highly beamed, short-duration electromagnetic bursts could be produced by superconducting cosmic string (SCS) loops oscillating in cosmic magnetic fields. We demonstrated that the basic characteristics of SCS bursts such as the electromagnetic frequency and the energy release could be consistently exhibited in the recently discovered fast radio bursts (FRBs). Moreover, it is first showed that the redshift distribution of the FRBs can also be well accounted for by the SCS burst model. Such agreements between the FRBs and SCS bursts suggest that the FRBs could originate from SCS bursts and thus they could provide an effective probe to study SCSs. The obtained values of model parameters indicate that the loops generating the FRBs have a small length scale and they are mostly formed in the radiation-dominated cosmological epoch.

Implications of fast radio bursts for superconducting cosmic strings

International Nuclear Information System (INIS)

Yu, Yun-Wei; Cheng, Kwong-Sang; Shiu, Gary; Tye, Henry

2014-01-01

Highly beamed, short-duration electromagnetic bursts could be produced by superconducting cosmic string (SCS) loops oscillating in cosmic magnetic fields. We demonstrated that the basic characteristics of SCS bursts such as the electromagnetic frequency and the energy release could be consistently exhibited in the recently discovered fast radio bursts (FRBs). Moreover, it is first showed that the redshift distribution of the FRBs can also be well accounted for by the SCS burst model. Such agreements between the FRBs and SCS bursts suggest that the FRBs could originate from SCS bursts and thus they could provide an effective probe to study SCSs. The obtained values of model parameters indicate that the loops generating the FRBs have a small length scale and they are mostly formed in the radiation-dominated cosmological epoch

Neutrino bursts and gravitational waves experiments

Energy Technology Data Exchange (ETDEWEB)

Castagnoli, C; Galeotti, P; Saavedra, O [Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica

1978-05-01

Several experiments have been performed in many countries to observe gravitational waves or neutrino bursts. Since their simultaneous emission may occur in stellar collapse, the authors evaluate the effect of neutrino bursts on gravitational wave antennas and suggest the usefulness of a time correlation among the different detectors.

Broadband Spectral Investigations of Magnetar Bursts

Science.gov (United States)

Kırmızıbayrak, Demet; Şaşmaz Muş, Sinem; Kaneko, Yuki; Göğüş, Ersin

2017-09-01

We present our broadband (2-250 keV) time-averaged spectral analysis of 388 bursts from SGR J1550-5418, SGR 1900+14, and SGR 1806-20 detected with the Rossi X-ray Timing Explorer (RXTE) here and as a database in a companion web-catalog. We find that two blackbody functions (BB+BB), the sum of two modified blackbody functions (LB+LB), the sum of a blackbody function and a power-law function (BB+PO), and a power law with a high-energy exponential cutoff (COMPT) all provide acceptable fits at similar levels. We performed numerical simulations to constrain the best fitting model for each burst spectrum and found that 67.6% of burst spectra with well-constrained parameters are better described by the Comptonized model. We also found that 64.7% of these burst spectra are better described with the LB+LB model, which is employed in the spectral analysis of a soft gamma repeater (SGR) for the first time here, than with the BB+BB and BB+PO models. We found a significant positive lower bound trend on photon index, suggesting a decreasing upper bound on hardness, with respect to total flux and fluence. We compare this result with bursts observed from SGR and AXP (anomalous X-ray pulsar) sources and suggest that the relationship is a distinctive characteristic between the two. We confirm a significant anticorrelation between burst emission area and blackbody temperature, and find that it varies between the hot and cool blackbody temperatures differently than previously discussed. We expand on the interpretation of our results in the framework of a strongly magnetized neutron star.

Broadband Spectral Investigations of Magnetar Bursts

Energy Technology Data Exchange (ETDEWEB)

Kırmızıbayrak, Demet; Şaşmaz Muş, Sinem; Kaneko, Yuki; Göğüş, Ersin, E-mail: demetk@sabanciuniv.edu [Faculty of Engineering and Natural Sciences, Sabancı University, Orhanlı Tuzla, Istanbul 34956 (Turkey)

2017-09-01

We present our broadband (2–250 keV) time-averaged spectral analysis of 388 bursts from SGR J1550−5418, SGR 1900+14, and SGR 1806−20 detected with the Rossi X-ray Timing Explorer ( RXTE ) here and as a database in a companion web-catalog. We find that two blackbody functions (BB+BB), the sum of two modified blackbody functions (LB+LB), the sum of a blackbody function and a power-law function (BB+PO), and a power law with a high-energy exponential cutoff (COMPT) all provide acceptable fits at similar levels. We performed numerical simulations to constrain the best fitting model for each burst spectrum and found that 67.6% of burst spectra with well-constrained parameters are better described by the Comptonized model. We also found that 64.7% of these burst spectra are better described with the LB+LB model, which is employed in the spectral analysis of a soft gamma repeater (SGR) for the first time here, than with the BB+BB and BB+PO models. We found a significant positive lower bound trend on photon index, suggesting a decreasing upper bound on hardness, with respect to total flux and fluence. We compare this result with bursts observed from SGR and AXP (anomalous X-ray pulsar) sources and suggest that the relationship is a distinctive characteristic between the two. We confirm a significant anticorrelation between burst emission area and blackbody temperature, and find that it varies between the hot and cool blackbody temperatures differently than previously discussed. We expand on the interpretation of our results in the framework of a strongly magnetized neutron star.

Sources of type III solar microwave bursts

Directory of Open Access Journals (Sweden)

Zhdanov D.A.

2016-06-01

Full Text Available Microwave fine structures allow us to study plasma evolution in an energy release region. The Siberian Solar Radio Telescope (SSRT is a unique instrument designed to examine fine structures at 5.7 GHz. A complex analysis of data from RATAN-600, 4–8 GHz spectropolarimeter, and SSRT, simultaneously with EUV data, made it possible to localize sources of III type microwave bursts in August 10, 2011 event within the entire frequency band of burst occurrence, as well as to determine the most probable region of primary energy release. To localize sources of III type bursts from RATAN-600 data, an original method for data processing has been worked out. At 5.7 GHz, the source of bursts was determined along two coordinates, whereas at 4.5, 4.7, 4.9, 5.1, 5.3, 5.5, and 6.0 GHz, their locations were identified along one coordinate. The size of the burst source at 5.1 GHz was found to be maximum as compared to those at other frequencies.

Spectra of gamma-ray bursts at high energies

International Nuclear Information System (INIS)

Matz, S.M.

1986-01-01

Between 1980 February and 1983 August the Gamma-Ray Spectrometer (GRS) on the Solar Maximum Mission satellite (SMM) observed 71 gamma-ray bursts. These events form a representative subset of the class of classical gamma-ray bursts. Since their discovery more than 15 years ago, hundreds of gamma-ray bursts have been detected; however, most observations have been limited to an energy range of roughly 30 keV-1 MeV. The large sensitive area and spectral range of the GRS allow, for the first time, an investigation of the high energy (>1 MeV) behavior of a substantial number of gamma-ray bursts. It is found that high-energy emission is seen in a large fraction of all events and that the data are consistent with all bursts emitting to at least 5 MeV with no cut-offs. Further, no burst spectrum measured by GRS has a clear high-energy cut-off. The high-energy emission can be a significant part of the total burst energy on the average about 30% of the observed energy above 30 keV is contained in the >1 MeV photons. The fact that the observations are consistent with the presence of high-energy emission in all events implies a limit on the preferential beaming of high-energy photons, from any mechanism. Single-photon pair-production in a strong magnetic field produces such beaming; assuming that the low-energy emission is isotropic, the data imply an upper limit of 1 x 10 12 G on the typical magnetic field at burst radiation sites

Powerful Radio Burst Indicates New Astronomical Phenomenon

Science.gov (United States)

2007-09-01

Astronomers studying archival data from an Australian radio telescope have discovered a powerful, short-lived burst of radio waves that they say indicates an entirely new type of astronomical phenomenon. Region of Strong Radio Burst Visible-light (negative greyscale) and radio (contours) image of Small Magellanic Cloud and area where burst originated. CREDIT: Lorimer et al., NRAO/AUI/NSF Click on image for high-resolution file ( 114 KB) "This burst appears to have originated from the distant Universe and may have been produced by an exotic event such as the collision of two neutron stars or the death throes of an evaporating black hole," said Duncan Lorimer, Assistant Professor of Physics at West Virginia University (WVU) and the National Radio Astronomy Observatory (NRAO). The research team led by Lorimer consists of Matthew Bailes of Swinburne University in Australia, Maura McLaughlin of WVU and NRAO, David Narkevic of WVU, and Fronefield Crawford of Franklin and Marshall College in Lancaster, Pennsylvania. The astronomers announced their findings in the September 27 issue of the online journal Science Express. The startling discovery came as WVU undergraduate student David Narkevic re-analyzed data from observations of the Small Magellanic Cloud made by the 210-foot Parkes radio telescope in Australia. The data came from a survey of the Magellanic Clouds that included 480 hours of observations. "This survey had sought to discover new pulsars, and the data already had been searched for the type of pulsating signals they produce," Lorimer said. "We re-examined the data, looking for bursts that, unlike the usual ones from pulsars, are not periodic," he added. The survey had covered the Magellanic Clouds, a pair of small galaxies in orbit around our own Milky Way Galaxy. Some 200,000 light-years from Earth, the Magellanic Clouds are prominent features in the Southern sky. Ironically, the new discovery is not part of these galaxies, but rather is much more distant

Ballerina - pirouettes in search of gamma bursts

DEFF Research Database (Denmark)

Brandt, Søren Kristian; Lund, Niels; Pedersen, Henrik

1999-01-01

The cosmological origin of gamma ray bursts has now been established with reasonable certainty, Many more bursts will need to be studied to establish the typical distance scale, and to map out the large diversity in properties which have been indicated by the first handful of events. We are propo...... are proposing Ballerina, a small satellite to provide accurate positions and new data on the gamma-ray bursts. We anticipate a detection rate an order of magnitude larger than obtained from Beppo-SAX....

Derivation of muon range spectrum under rock from the recent primary spectrum

International Nuclear Information System (INIS)

Pal, P.; Bhattacharyya, D.P.

1985-01-01

The muon range spectra under Mont Blanc Tunnel and Kolar Gold Field rocks have been calculated from the recently measured primary cosmic ray spectrum. The scaling hypothesis of Feynman has been used for the calculation of pion and kaon spectra in the atmosphere. The meson atmospheric diffusion equation has been solved by following the method of Bugaev et al. The derived muon energy spectrum has been found to be in good agreement with the measured data of the Kiel, Durham, DEIS, and Moscow University groups. The calculated muon energy spectra at large polar angles have been compared with the different experimental results. The integral muon spectrum up to 20 TeV supports the MARS burst data favourably. Using the procedure of Kobayakawa, the muon energy loss in rock due to ionization, pair production, and bremsstrahlung and nuclear interactions from Bezrukov and Bugaev, we have constructed the range-energy relation in Mont Blanc and Kolar Gold Field rocks. The estimated range spectra have been corrected for range fluctuations and have been compared with the Mont Blanc Tunnel data of Castagnoli et al., Bergamasco et al., and Sheldon et al. and the Kolar Gold Field data compilation by Krishnaswamy et al

Beta burst dynamics in Parkinson's disease OFF and ON dopaminergic medication.

Science.gov (United States)

Tinkhauser, Gerd; Pogosyan, Alek; Tan, Huiling; Herz, Damian M; Kühn, Andrea A; Brown, Peter

2017-11-01

Exaggerated basal ganglia beta activity (13-35 Hz) is commonly found in patients with Parkinson's disease and can be suppressed by dopaminergic medication, with the degree of suppression being correlated with the improvement in motor symptoms. Importantly, beta activity is not continuously elevated, but fluctuates to give beta bursts. The percentage number of longer beta bursts in a given interval is positively correlated with clinical impairment in Parkinson's disease patients. Here we determine whether the characteristics of beta bursts are dependent on dopaminergic state. Local field potentials were recorded from the subthalamic nucleus of eight Parkinson's disease patients during temporary lead externalization during surgery for deep brain stimulation. The recordings took place with the patient quietly seated following overnight withdrawal of levodopa and after administration of levodopa. Beta bursts were defined by applying a common amplitude threshold and burst characteristics were compared between the two drug conditions. The amplitude of beta bursts, indicative of the degree of local neural synchronization, progressively increased with burst duration. Treatment with levodopa limited this evolution leading to a relative increase of shorter, lower amplitude bursts. Synchronization, however, was not limited to local neural populations during bursts, but also, when such bursts were cotemporaneous across the hemispheres, was evidenced by bilateral phase synchronization. The probability of beta bursts and the proportion of cotemporaneous bursts were reduced by levodopa. The percentage number of longer beta bursts in a given interval was positively related to motor impairment, while the opposite was true for the percentage number of short duration beta bursts. Importantly, the decrease in burst duration was also correlated with the motor improvement. In conclusion, we demonstrate that long duration beta bursts are associated with an increase in local and

Chimera states in bursting neurons

OpenAIRE

Bera, Bidesh K.; Ghosh, Dibakar; Lakshmanan, M.

2015-01-01

We study the existence of chimera states in pulse-coupled networks of bursting Hindmarsh-Rose neurons with nonlocal, global and local (nearest neighbor) couplings. Through a linear stability analysis, we discuss the behavior of stability function in the incoherent (i.e. disorder), coherent, chimera and multi-chimera states. Surprisingly, we find that chimera and multi-chimera states occur even using local nearest neighbor interaction in a network of identical bursting neurons alone. This is i...

US Army Nuclear Burst Detection System (NBDS)

International Nuclear Information System (INIS)

Glaser, R.F.

1980-07-01

The Nuclear Burst Detection System (NBDS) was developed to meet the Army requirements of an unattended, automatic nuclear burst reporting system. It provides pertinent data for battlefield commanders on a timely basis with high reliability

X-ray bursts from GX 17+2: a new approach

International Nuclear Information System (INIS)

Sztajno, M.; Langmeier, A.; Truemper, J.; Pietsch, W.; Paradijs, J. van; Lewin, W.H.G.; Massachusetts Inst. of Tech., Cambridge

1986-01-01

The detection of two X-ray bursts from GX 17+2 is reported; a short one (lasting about 10s), and a long one (which lasted about 5 min). These bursts reached a maximum intensity of only about 40 per cent above the persistent flux level. Like previous long bursts observed from GX 17+2 the long burst showed little softening during its decay, and it is difficult at first glance to classify it as either a type 1 or a type 2 burst. Following the recent results of two of the authors a time-dependent spectral analysis of these bursts has been made. (author)

Cosmic gamma-ray bursts

International Nuclear Information System (INIS)

Hurley, K.

1989-01-01

This paper reviews the essential aspects of the gamma-ray burst (GRB) phenomenon, with emphasis on the more recent results. GRBs are introduced by their time histories, which provide some evidence for a compact object origin. The energy spectra of bursts are presented and they are seen to demonstrate practically unambiguously that the origin of some GRBs involves neutron stars. Counterpart searches are reviewed briefly and the statistical properties of bursters treated. This paper presents a review of the three known repeating bursters (the Soft Gamma Repeaters). Extragalactic and galactic models are discussed and future prospects are assessed

PNN-based Rockburst Prediction Model and Its Applications

Directory of Open Access Journals (Sweden)

Yu Zhou

2017-07-01

Full Text Available Rock burst is one of main engineering geological problems significantly threatening the safety of construction. Prediction of rock burst is always an important issue concerning the safety of workers and equipment in tunnels. In this paper, a novel PNN-based rock burst prediction model is proposed to determine whether rock burst will happen in the underground rock projects and how much the intensity of rock burst is. The probabilistic neural network (PNN is developed based on Bayesian criteria of multivariate pattern classification. Because PNN has the advantages of low training complexity, high stability, quick convergence, and simple construction, it can be well applied in the prediction of rock burst. Some main control factors, such as rocks’ maximum tangential stress, rocks’ uniaxial compressive strength, rocks’ uniaxial tensile strength, and elastic energy index of rock are chosen as the characteristic vector of PNN. PNN model is obtained through training data sets of rock burst samples which come from underground rock project in domestic and abroad. Other samples are tested with the model. The testing results agree with the practical records. At the same time, two real-world applications are used to verify the proposed method. The results of prediction are same as the results of existing methods, just same as what happened in the scene, which verifies the effectiveness and applicability of our proposed work.

Rheological characteristics of waste rock materials in abandoned mine deposit and debris flow hazards

Science.gov (United States)

Jeong, Sueng-Won; Lee, Choonoh; Cho, Yong-Chan; Wu, Ying-Hsin

2015-04-01

In Korea, approximately 5,000 metal mines are spread, but 50% of them are still abandoned without any proper remediation and cleanup. Summer heavy rainfall can result in the physicochemical modification of waste rock materials in the mountainous. From the geotechnical monitoring and field investigation, there are visible traces of mass movements every year. Soil erosion is one of severe phenomena in the study area. In particular, study area is located in the upper part of the Busan Metropolitan City and near the city's water supply. With respect to the supply of drinking water and maintenance of ecological balance, proper disposal of waste rock materials is required. For this reason, we examine the rheological properties of waste rock materials as a function of solid content using a ball- and vane-penetrated rheometer. In the flow curves, which are the relationship between the shear stress and shear rate of waste rock materials, we found that the soil samples exhibited a shear thinning beahivor regardless of solid content. The Bingham, Herschel-Bulkley, Power-law, and Papanastasiou models are used to determine the rheological properties. Assuming that the soil samples behaved as the viscoplastic behavior, the yield stress and viscosity are determined for different water contents. As a result, there are clear relationships between the solid content and rheological values (i.e., Bingham yield stress and plastic viscosity). From these relationships, the maximum and minimum of Bingham yield stresses are ranged from 100 to 2000 Pa. The debris flow mobilization is analysed using a 1D BING and 2D Debris flow models. In addition, the effect of wall slip and test apparatus are discussed.

Rock mechanics in the National Waste Terminal Storage Program

International Nuclear Information System (INIS)

Monsees, J.E.; Wigley, M.R.

1982-01-01

The overall objective of the rock mechanics program of the Office of Nuclear Waste Isolation is to predict the response of a rock mass hosting a waste repository during its construction, operation, and postoperational phases. The operational phase is expected to be 50 to 100 yr; the postoperational phase will last until the repository no longer poses any potential hazard to the biosphere, a period that may last several thousand years. The rock mechanics program is concerned with near-field effects on mine stability, as well as far-field effects relative to the overall integrity of the geologic waste isolation system. To accomplish these objectives, the rock mechanics program has established interactive studies in numerical simulation, laboratory testing, and field testing. The laboratory and field investigations provide input to the numerical simulations and give an opportunity for verification and validation of the predictive capabilities of the computer codes. Ultimately the computer codes will be used to predict the response of the geologic system to the development of a repository. 3 references, 5 figures

Leader neurons in population bursts of 2D living neural networks

International Nuclear Information System (INIS)

Eckmann, J-P; Zbinden, Cyrille; Jacobi, Shimshon; Moses, Elisha; Marom, Shimon

2008-01-01

Eytan and Marom (2006 J. Neurosci. 26 8465-76) recently showed that the spontaneous bursting activity of rat neuron cultures includes 'first-to-fire' cells that consistently fire earlier than others. Here, we analyze the behavior of these neurons in long-term recordings of spontaneous activity of rat hippocampal and rat cortical neuron cultures from three different laboratories. We identify precursor events that may either subside ('aborted bursts') or can lead to a full-blown burst ('pre-bursts'). We find that the activation in the pre-burst typically has a first neuron ('leader'), followed by a localized response in its neighborhood. Locality is diminished in the bursts themselves. The long-term dynamics of the leaders is relatively robust, evolving with a half-life of 23-34 h. Stimulation of the culture alters the leader distribution, but the distribution stabilizes within about 1 h. We show that the leaders carry information about the identity of the burst, as measured by the signature of the number of spikes per neuron in a burst. The number of spikes from leaders in the first few spikes of a precursor event is furthermore shown to be predictive with regard to the transition into a burst (pre-burst versus aborted burst). We conclude that the leaders play a role in the development of the bursts and conjecture that they are part of an underlying sub-network that is excited first and then acts as a nucleation center for the burst

Impulsive EUV bursts observed in C IV with OSO-8

International Nuclear Information System (INIS)

Grant Athay, R.; White, O.R.; Lites, B.W.

1980-01-01

Time sequences of profiles of the lambda 1548 line of C IV containing 51 EUV bursts observed in or near active regions are analyzed to determine the brightness. Doppler shift and line broadening characteristics of the bursts. The bursts have mean lifetimes of approximately 150s, and mean increases in brightness at burst maximum of four-fold as observed with a field of view of 2'' x 20''. Mean burst diameters are estimated to be 3'', or smaller. All but three of the bursts show Doppler shift with velocities sometimes exceeding 75 km s -1 ; 31 are dominated by red shifts and 17 are dominated by blue shifts. Approximately half of the latter group have red-shifted precursors. We interpret the bursts as prominence material, such as surges and coronal rain, moving through the field of view of the spectrometer. (orig.)

PHYSICAL CONSTRAINTS ON FAST RADIO BURSTS

Energy Technology Data Exchange (ETDEWEB)

Luan, Jing; Goldreich, Peter, E-mail: jingluan@caltech.edu [California Institute of Technology, Pasadena, CA 91125 (United States)

2014-04-20

Fast radio bursts (FRBs) are isolated, ms radio pulses with dispersion measure (DM) of order 10{sup 3} pc cm{sup –3}. Galactic candidates for the DM of high latitude bursts detected at GHz frequencies are easily dismissed. DM from bursts emitted in stellar coronas are limited by free-free absorption and those from H II regions are bounded by the nondetection of associated free-free emission at radio wavelengths. Thus, if astronomical, FRBs are probably extragalactic. FRB 110220 has a scattering tail of ∼5.6 ± 0.1 ms. If the electron density fluctuations arise from a turbulent cascade, the scattering is unlikely to be due to propagation through the diffuse intergalactic plasma. A more plausible explanation is that this burst sits in the central region of its host galaxy. Pulse durations of order ms constrain the sizes of FRB sources implying high brightness temperatures that indicates coherent emission. Electric fields near FRBs at cosmological distances would be so strong that they could accelerate free electrons from rest to relativistic energies in a single wave period.

PHYSICAL CONSTRAINTS ON FAST RADIO BURSTS

International Nuclear Information System (INIS)

Luan, Jing; Goldreich, Peter

2014-01-01

Fast radio bursts (FRBs) are isolated, ms radio pulses with dispersion measure (DM) of order 10 3 pc cm –3 . Galactic candidates for the DM of high latitude bursts detected at GHz frequencies are easily dismissed. DM from bursts emitted in stellar coronas are limited by free-free absorption and those from H II regions are bounded by the nondetection of associated free-free emission at radio wavelengths. Thus, if astronomical, FRBs are probably extragalactic. FRB 110220 has a scattering tail of ∼5.6 ± 0.1 ms. If the electron density fluctuations arise from a turbulent cascade, the scattering is unlikely to be due to propagation through the diffuse intergalactic plasma. A more plausible explanation is that this burst sits in the central region of its host galaxy. Pulse durations of order ms constrain the sizes of FRB sources implying high brightness temperatures that indicates coherent emission. Electric fields near FRBs at cosmological distances would be so strong that they could accelerate free electrons from rest to relativistic energies in a single wave period

IDENTIFICATION OF BURSTING WATER MASER FEATURES IN ORION KL

International Nuclear Information System (INIS)

Hirota, Tomoya; Honma, Mareki; Kim, Mi Kyoung; Kobayashi, Hideyuki; Shibata, Katsunori M.; Tsuboi, Masato; Fujisawa, Kenta; Kawaguchi, Noriyuki; Imai, Hiroshi; Omodaka, Toshihiro; Shimoikura, Tomomi; Yonekura, Yoshinori

2011-01-01

In 2011 February, a burst event of the H 2 O maser in Orion KL (Kleinmann-Low object) has started after a 13 year silence. This is the third time such phenomena has been detected in Orion KL, followed by the events in 1979-1985 and 1998. We have carried out astrometric observations of the bursting H 2 O maser features in Orion KL with the VLBI Exploration of Radio Astrometry (VERA), a Japanese very long baseline interferometry network dedicated for astrometry. The total flux of the bursting feature at the local standard of rest (LSR) velocity of 7.58 km s -1 reaches 4.4 x 10 4 Jy in 2011 March. The intensity of the bursting feature is three orders of magnitude larger than that of the same velocity feature in the quiescent phase in 2006. Two months later, another new feature appears at the LSR velocity of 6.95 km s -1 in 2011 May, separated by 12 mas north of the 7.58 km s -1 feature. Thus, the current burst occurs at two spatially different features. The bursting masers are elongated along the northwest-southeast direction as reported in the previous burst in 1998. We determine the absolute positions of the bursting features for the first time ever with a submilliarcsecond (mas) accuracy. Their positions are coincident with the shocked molecular gas called the Orion Compact Ridge. We tentatively detect the absolute proper motions of the bursting features toward the southwest direction. It is most likely that the outflow from the radio source I or another young stellar object interacting with the Compact Ridge is a possible origin of the H 2 O maser burst.

Thalamic neuron models encode stimulus information by burst-size modulation

Directory of Open Access Journals (Sweden)

Daniel Henry Elijah

2015-09-01

Full Text Available Thalamic neurons have been long assumed to fire in tonic mode during perceptive states, and in burst mode during sleep and unconsciousness. However, recent evidence suggests that bursts may also be relevant in the encoding of sensory information. Here we explore the neural code of such thalamic bursts. In order to assess whether the burst code is generic or whether it depends on the detailed properties of each bursting neuron, we analyzed two neuron models incorporating different levels of biological detail. One of the models contained no information of the biophysical processes entailed in spike generation, and described neuron activity at a phenomenological level. The second model represented the evolution of the individual ionic conductances involved in spiking and bursting, and required a large number of parameters. We analyzed the models' input selectivity using reverse correlation methods and information theory. We found that n-spike bursts from both models transmit information by modulating their spike count in response to changes to instantaneous input features, such as slope, phase, amplitude, etc. The stimulus feature that is most efficiently encoded by bursts, however, need not coincide with one of such classical features. We therefore searched for the optimal feature among all those that could be expressed as a linear transformation of the time-dependent input current. We found that bursting neurons transmitted 6 times more information about such more general features. The relevant events in the stimulus were located in a time window spanning ~100 ms before and ~20 ms after burst onset. Most importantly, the neural code employed by the simple and the biologically realistic models was largely the same, implying that the simple thalamic neuron model contains the essential ingredients that account for the computational properties of the thalamic burst code. Thus, our results suggest the n-spike burst code is a general property of

Thalamic neuron models encode stimulus information by burst-size modulation.

Science.gov (United States)

Elijah, Daniel H; Samengo, Inés; Montemurro, Marcelo A

2015-01-01

Thalamic neurons have been long assumed to fire in tonic mode during perceptive states, and in burst mode during sleep and unconsciousness. However, recent evidence suggests that bursts may also be relevant in the encoding of sensory information. Here, we explore the neural code of such thalamic bursts. In order to assess whether the burst code is generic or whether it depends on the detailed properties of each bursting neuron, we analyzed two neuron models incorporating different levels of biological detail. One of the models contained no information of the biophysical processes entailed in spike generation, and described neuron activity at a phenomenological level. The second model represented the evolution of the individual ionic conductances involved in spiking and bursting, and required a large number of parameters. We analyzed the models' input selectivity using reverse correlation methods and information theory. We found that n-spike bursts from both models transmit information by modulating their spike count in response to changes to instantaneous input features, such as slope, phase, amplitude, etc. The stimulus feature that is most efficiently encoded by bursts, however, need not coincide with one of such classical features. We therefore searched for the optimal feature among all those that could be expressed as a linear transformation of the time-dependent input current. We found that bursting neurons transmitted 6 times more information about such more general features. The relevant events in the stimulus were located in a time window spanning ~100 ms before and ~20 ms after burst onset. Most importantly, the neural code employed by the simple and the biologically realistic models was largely the same, implying that the simple thalamic neuron model contains the essential ingredients that account for the computational properties of the thalamic burst code. Thus, our results suggest the n-spike burst code is a general property of thalamic neurons.

Coronal mass ejections and solar radio bursts

International Nuclear Information System (INIS)

Kundu, M.R.

1990-01-01

The properties of coronal mass ejection (CME) events and their radio signatures are discussed. These signatures are mostly in the form of type II and type IV burst emissions. Although type II bursts are temporally associated with CMEs, it is shown that there is no spatial relationship between them. Type II's associated with CMEs have in most cases a different origin, and they are not piston-driven by CMEs. Moving type IV and type II bursts can be associated with slow CMEs with speeds as low as 200 km/s, contrary to the earlier belief that only CMEs with speeds >400 km/s are associated with radio bursts. A specific event has been discussed in which the CME and type IV burst has nearly the same speed and direction, but the type II burst location was behind the CME and its motion was transverse. The speed and motion of the type II burst strongly suggest that the type II shock was decoupled from the CME and was probably due to a flare behind the limb. Therefore only the type IV source could be directly associated with the slow CME. The electrons responsble for the type IV emission could be produced in the flare or in the type II and then become trapped in a plasmoid associated with the CME. The reconnected loop could then move outwards as in the usual palsmoid model. Alternatively, the type IV emission could be interpreted as due to electrons produced by acceleration in wave turbulence driven by currents in the shock front driven by the CME. The lower-hybrid model Lampe and Papadopoulos (1982), which operates at both fast and slow mode shocks, could be applied to this situation. (author). 31 refs., 12 figs

An in-situ stimulation experiment in crystalline rock - assessment of induced seismicity levels during stimulation and related hazard for nearby infrastructure

Science.gov (United States)

Gischig, Valentin; Broccardo, Marco; Amann, Florian; Jalali, Mohammadreza; Esposito, Simona; Krietsch, Hannes; Doetsch, Joseph; Madonna, Claudio; Wiemer, Stefan; Loew, Simon; Giardini, Domenico

2016-04-01

A decameter in-situ stimulation experiment is currently being performed at the Grimsel Test Site in Switzerland by the Swiss Competence Center for Energy Research - Supply of Electricity (SCCER-SoE). The underground research laboratory lies in crystalline rock at a depth of 480 m, and exhibits well-documented geology that is presenting some analogies with the crystalline basement targeted for the exploitation of deep geothermal energy resources in Switzerland. The goal is to perform a series of stimulation experiments spanning from hydraulic fracturing to controlled fault-slip experiments in an experimental volume approximately 30 m in diameter. The experiments will contribute to a better understanding of hydro-mechanical phenomena and induced seismicity associated with high-pressure fluid injections. Comprehensive monitoring during stimulation will include observation of injection rate and pressure, pressure propagation in the reservoir, permeability enhancement, 3D dislocation along the faults, rock mass deformation near the fault zone, as well as micro-seismicity. The experimental volume is surrounded by other in-situ experiments (at 50 to 500 m distance) and by infrastructure of the local hydropower company (at ~100 m to several kilometres distance). Although it is generally agreed among stakeholders related to the experiments that levels of induced seismicity may be low given the small total injection volumes of less than 1 m3, detailed analysis of the potential impact of the stimulation on other experiments and surrounding infrastructure is essential to ensure operational safety. In this contribution, we present a procedure how induced seismic hazard can be estimated for an experimental situation that is untypical for injection-induced seismicity in terms of injection volumes, injection depths and proximity to affected objects. Both, deterministic and probabilistic methods are employed to estimate that maximum possible and the maximum expected induced

ARE ULTRA-LONG GAMMA-RAY BURSTS DIFFERENT?

Energy Technology Data Exchange (ETDEWEB)

Boër, M.; Gendre, B. [CNRS-ARTEMIS, Boulevard de l' Observatoire, CS 34229, 06304 Nice Cedex 4 (France); Stratta, G., E-mail: michel.boer@unice.fr [Università degli Studi di Urbino Carlo Bo, I-61029 Urbino (Italy)

2015-02-10

The discovery of a number of gamma-ray bursts (GRBs) with duration exceeding 1000 s has opened the debate on whether these bursts form a new class of sources, the so-called ultra-long GRBs, or if they are rather the tail of the distribution of the standard long GRB duration. Using the long GRB sample detected by Swift, we investigate the statistical properties of long GRBs and compare them with the ultra-long burst properties. We compute the burst duration of long GRBs using the start epoch of the so-called ''steep decay'' phase detected with Swift/XRT. We discuss also the differences observed in their spectral properties. We find that ultra-long GRBs are statistically different from the standard long GRBs with typical burst duration less than 100-500 s, for which a Wolf-Rayet star progenitor is usually invoked. Together with the presence of a thermal emission component we interpret this result as indication that the usual long GRB progenitor scenario cannot explain the extreme duration of ultra-long GRBs, their energetics, as well as the mass reservoir and size that can feed the central engine for such a long time.

Galactic distribution of X-ray burst sources

International Nuclear Information System (INIS)

Lewin, W.H.G.; Hoffman, J.A.; Doty, J.; Clark, G.W.; Swank, J.H.; Becker, R.H.; Pravdo, S.H.; Serlemitsos, P.J.

1977-01-01

It is stated that 18 X-ray burst sources have been observed to date, applying the following definition for these bursts - rise times of less than a few seconds, durations of seconds to minutes, and recurrence in some regular pattern. If single burst events that meet the criteria of rise time and duration, but not recurrence are included, an additional seven sources can be added. A sky map is shown indicating their positions. The sources are spread along the galactic equator and cluster near low galactic longitudes, and their distribution is different from that of the observed globular clusters. Observations based on the SAS-3 X-ray observatory studies and the Goddard X-ray Spectroscopy Experiment on OSO-9 are described. The distribution of the sources is examined and the effect of uneven sky exposure on the observed distribution is evaluated. It has been suggested that the bursts are perhaps produced by remnants of disrupted globular clusters and specifically supermassive black holes. This would imply the existence of a new class of unknown objects, and at present is merely an ad hoc method of relating the burst sources to globular clusters. (U.K.)

On Burst Detection and Prediction in Retweeting Sequence

Science.gov (United States)

2015-05-22

We conduct a comprehensive empirical analysis of a large microblogging dataset collected from the Sina Weibo and report our observations of burst...whether and how accurate we can predict bursts using classifiers based on the extracted features. Our empirical study of the Sina Weibo data shows the...feasibility of burst prediction using appropriately extracted features and classic classifiers. 1 Introduction Microblogging, such as Twitter and Sina

LAT Onboard Science: Gamma-Ray Burst Identification

International Nuclear Information System (INIS)

Kuehn, Frederick; Hughes, Richard; Smith, Patrick; Winer, Brian; Bonnell, Jerry; Norris, Jay; Ritz, Steven; Russell, James

2007-01-01

The main goal of the Large Area Telescope (LAT) onboard science program is to provide quick identification and localization of Gamma Ray Bursts (GRB) onboard the LAT for follow-up observations by other observatories. The GRB identification and localization algorithm will provide celestial coordinates with an error region that will be distributed via the Gamma ray burst Coordinate Network (GCN). We present results that show our sensitivity to bursts as characterized using Monte Carlo simulations of the GLAST observatory. We describe and characterize the method of onboard track determination and the GRB identification and localization algorithm. Onboard track determination is considerably different than in the on-ground case, resulting in a substantially altered point spread function. The algorithm contains tunable parameters which may be adjusted after launch when real bursts characteristics at very high energies have been identified

Methane bursts as a trigger for intermittent lake-forming climates on post-Noachian Mars

Science.gov (United States)

Kite, Edwin S.; Gao, Peter; Goldblatt, Colin; Mischna, Michael A.; Mayer, David P.; Yung, Yuk L.

2017-10-01

Lakes existed on Mars later than 3.6 billion years ago, according to sedimentary evidence for deltaic deposition. The observed fluviolacustrine deposits suggest that individual lake-forming climates persisted for at least several thousand years (assuming dilute flow). But the lake watersheds’ little-weathered soils indicate a largely dry climate history, with intermittent runoff events. Here we show that these observational constraints, although inconsistent with many previously proposed triggers for lake-forming climates, are consistent with a methane burst scenario. In this scenario, chaotic transitions in mean obliquity drive latitudinal shifts in temperature and ice loading that destabilize methane clathrate. Using numerical simulations, we find that outgassed methane can build up to atmospheric levels sufficient for lake-forming climates, if methane clathrate initially occupies more than 4% of the total volume in which it is thermodynamically stable. Such occupancy fractions are consistent with methane production by water-rock reactions due to hydrothermal circulation on early Mars. We further estimate that photochemical destruction of atmospheric methane curtails the duration of individual lake-forming climates to less than a million years, consistent with observations. We conclude that methane bursts represent a potential pathway for intermittent excursions to a warm, wet climate state on early Mars.

Gamma-ray burst polarimeter (GAP)

International Nuclear Information System (INIS)

Mihara, Tatehiro; Murakami, Toshio; Yonetoku, Daisuke; Gunji, Shuichi; Kubo, Shin

2013-01-01

The gamma-ray burst polarimeter (GAP: GAmma-ray burst Polarimeter), which had been almost handcrafted by scientists, has succeeded in working normally in interplanetary space, and in detecting the polarization of the gamma-ray from a mysterious astronomical object 'gamma-ray burst'. It is the first result of the detectors in the world exclusively aiming at detecting gamma-ray polarization. We mainly describe the hardware of our GAP equipment and show the method of preparing equipment to work in the cosmic space with a tight budget. The mechanical structure, the electronic circuits, the software on the equipment, the data analysis on the earth, and the scientific results gained by the observation just over one year, are presented after explaining the principle of gamma-ray polarization detection. Our design to protect equipment against mechanical shock and cosmic radiation may provide useful information for future preparation of compact satellite. (J.P.N.)

Multifrequency Observations of Gamma-Ray Burst

OpenAIRE

Greiner, J.

1995-01-01

Neither a flaring nor a quiescent counterpart to a gamma-ray burst has yet been convincingly identified at any wavelength region. The present status of the search for counterparts of classical gamma-ray bursts is given. Particular emphasis is put on the search for flaring counterparts, i.e. emission during or shortly after the gamma-ray emission.

Gamma Ray Bursts and the Birth of Black Holes

Science.gov (United States)

Gehrels, Neil

2009-01-01

Black holes have been predicted since the 1940's from solutions of Einstein's general relativity field equation. There is strong evidence of their existence from astronomical observations, but their origin has remained an open question of great interest. Gamma-ray bursts may the clue. They are powerful explosions, visible to high redshift, and appear to be the birth cries of black holes. The Swift and Fermi missions are two powerful NASA observatories currently in orbit that are discovering how gamma-ray bursts work. Evidence is building that the long and short duration subcategories of GRBs have very different origins: massive star core collapse to a black hole for long bursts and binary neutron star coalescence to a black hole for short bursts. The similarity to Type II and Ia supernovae originating from young and old stellar progenitors is striking. Bursts are tremendously luminous and are providing a new tool to study the high redshift universe. One Swift burst at z=8.3 is the most distant object known in the universe. The talk will present the latest gamma-ray burst results from Swift and Fermi and will highlight what they are teaching us about black holes and jet outflows.

Observational properties of cosmic gamma-ray bursts

International Nuclear Information System (INIS)

Mazets, E.P.

1986-01-01

A brief overview of the major observational results obtained in gamma-ray burst studies is presented. Also discussed is to what extent the thermonuclear model, which appears at present to be the most plausible, can account for the observed properties of the bursts. The investigation of gamma-ray bursts should cover observations of the time histories of events, energy spectra, and their variablility, source localization, and inspection of the localization regions during the active and quiescent phases of the source in other wavelengths, as well as, evaluation of the statistical distributions of the data obtained

Heuristic burst detection method using flow and pressure measurements

NARCIS (Netherlands)

Bakker, M.; Vreeburg, J.H.G.; Roer, Van de M.; Rietveld, L.C.

2014-01-01

Pipe bursts in a drinking water distribution system lead to water losses, interruption of supply, and damage to streets and houses due to the uncontrolled water flow. To minimize the negative consequences of pipe bursts, an early detection is necessary. This paper describes a heuristic burst

IGR J17254-3257, a new bursting neutron star

DEFF Research Database (Denmark)

Chenevez, Jérôme; Falanga, M.; Kuulkers, E.

2007-01-01

Aims. The study of the observational properties of uncommonly long bursts from low luminosity sources is important when investigating the transition from a hydrogen - rich bursting regime to a pure helium regime and from helium burning to carbon burning as predicted by current burst theories. On ...

Introduction to numerical modeling of thermohydrologic flow in fractured rock masses

International Nuclear Information System (INIS)

Wang, J.S.Y.

1980-01-01

More attention is being given to the possibility of nuclear waste isolation in hard rock formations. The waste will generate heat which raises the temperature of the surrounding fractured rock masses and induces buoyancy flow and pressure change in the fluid. These effects introduce the potential hazard of radionuclides being carried to the biosphere, and affect the structure of a repository by stress changes in the rock formation. The thermohydrological and thermomechanical responses are determined by the fractures as well as the intact rock blocks. The capability of modeling fractured rock masses is essential to site characterization and repository evaluation. The fractures can be modeled either as a discrete system, taking into account the detailed fracture distributions, or as a continuum representing the spatial average of the fractures. A numerical model is characterized by the governing equations, the numerical methods, the computer codes, the validations, and the applications. These elements of the thermohydrological models are discussed. Along with the general review, some of the considerations in modeling fractures are also discussed. Some remarks on the research needs in modeling fractured rock mass conclude the paper

The development of a burst criterion for zircaloy fuel cladding under LOCA conditions

International Nuclear Information System (INIS)

Neitzel, H.J.; Rossinger, H.E.

1980-02-01

A burst criterion model, which assumes that deformation is controlled by steady-state creep, has been developed for a thin-walled cladding, in this case Zircaloy-4, subjected to a differential pressure and high temperature. The creep equation is integrated to obtain a burst time at the singularity of the strain. Once the burst time is known, the burst temperature and burst pressure can be calculated from the known temperature and pressure histories. A further relationship between burst stress and burst temperature is used to calculate the burst strain. Comparison with measured burst data shows good agreement between theory and experiment was found that, if the heating rate is constant, the burst temperature increases with decreasing stress, and that, if the stress level is constant, the burst temperature increases with increasing heating rate. It was also found that anisotropy alters the burst temperature and burst strain, and that test conditions in the α-Zr temperature range have no influence on the burst data. (auth)

Bursts generate a non-reducible spike-pattern code

Directory of Open Access Journals (Sweden)

Hugo G Eyherabide

2009-05-01

Full Text Available On the single-neuron level, precisely timed spikes can either constitute firing-rate codes or spike-pattern codes that utilize the relative timing between consecutive spikes. There has been little experimental support for the hypothesis that such temporal patterns contribute substantially to information transmission. Using grasshopper auditory receptors as a model system, we show that correlations between spikes can be used to represent behaviorally relevant stimuli. The correlations reflect the inner structure of the spike train: a succession of burst-like patterns. We demonstrate that bursts with different spike counts encode different stimulus features, such that about 20% of the transmitted information corresponds to discriminating between different features, and the remaining 80% is used to allocate these features in time. In this spike-pattern code, the "what" and the "when" of the stimuli are encoded in the duration of each burst and the time of burst onset, respectively. Given the ubiquity of burst firing, we expect similar findings also for other neural systems.

Internally consistent gamma ray burst time history phenomenology

International Nuclear Information System (INIS)

Cline, T.L.

1985-01-01

A phenomenology for gamma ray burst time histories is outlined. Order of their generally chaotic appearance is attempted, based on the speculation that any one burst event can be represented above 150 keV as a superposition of similarly shaped increases of varying intensity. The increases can generally overlap, however, confusing the picture, but a given event must at least exhibit its own limiting characteristic rise and decay times if the measurements are made with instruments having adequate temporal resolution. Most catalogued observations may be of doubtful or marginal utility to test this hypothesis, but some time histories from Helios-2, Pioneer Venus Orbiter and other instruments having one-to several-millisecond capabilities appear to provide consistency. Also, recent studies of temporally resolved Solar Maximum Mission burst energy spectra are entirely compatible with this picture. The phenomenology suggested here, if correct, may assist as an analytic tool for modelling of burst processes and possibly in the definition of burst source populations

Directions of the US Geological Survey Landslide Hazards Reduction Program

Science.gov (United States)

Wieczorek, G.F.

1993-01-01

The US Geological Survey (USGS) Landslide Hazards Reduction Program includes studies of landslide process and prediction, landslide susceptibility and risk mapping, landslide recurrence and slope evolution, and research application and technology transfer. Studies of landslide processes have been recently conducted in Virginia, Utah, California, Alaska, and Hawaii, Landslide susceptibility maps provide a very important tool for landslide hazard reduction. The effects of engineering-geologic characteristics of rocks, seismic activity, short and long-term climatic change on landslide recurrence are under study. Detailed measurement of movement and deformation has begun on some active landslides. -from Author

What can NuSTAR do for X-ray bursts?

DEFF Research Database (Denmark)

Chenevez, Jérôme; Tomsick, John; Chakrabarty, Deepto

2012-01-01

burning are ejected in the burst expansion wind. We have investigated the possibility of observing with NuSTAR some X-ray bursters selected for their high burst rate and trend to exhibit so-called superexpansion bursts. Our main ambition is to detect the photoionization edges associated with the ejected...

Prediction of Brittle Failure for TBM Tunnels in Anisotropic Rock: A Case Study from Northern Norway

Science.gov (United States)

Dammyr, Øyvind

2016-06-01

Prediction of spalling and rock burst is especially important for hard rock TBM tunneling, because failure can have larger impact than in a drill and blast tunnel and ultimately threaten excavation feasibility. The majority of research on brittle failure has focused on rock types with isotropic behavior. This paper gives a review of existing theory and its application before a 3.5-m-diameter TBM tunnel in foliated granitic gneiss is used as a case to study brittle failure characteristics of anisotropic rock. Important aspects that should be considered in order to predict brittle failure in anisotropic rock are highlighted. Foliation is responsible for considerable strength anisotropy and is believed to influence the preferred side of v-shaped notch development in the investigated tunnel. Prediction methods such as the semi- empirical criterion, the Hoek- Brown brittle parameters, and the non-linear damage initiation and spalling limit method give reliable results; but only as long as the angle between compression axis and foliation in uniaxial compressive tests is relevant, dependent on the relation between tunnel trend/plunge, strike/dip of foliation, and tunnel boundary stresses. It is further demonstrated that local in situ stress variations, for example, due to the presence of discontinuities, can have profound impact on failure predictions. Other carefully documented case studies into the brittle failure nature of rock, in particular anisotropic rock, are encouraged in order to expand the existing and relatively small database. This will be valuable for future TBM planning and construction stages in highly stressed brittle anisotropic rock.

Rockfall hazard assessment integrating probabilistic physically based rockfall source detection (Norddal municipality, Norway).

Science.gov (United States)

Yugsi Molina, F. X.; Oppikofer, T.; Fischer, L.; Hermanns, R. L.; Taurisano, A.

2012-04-01

Traditional techniques to assess rockfall hazard are partially based on probabilistic analysis. Stochastic methods has been used for run-out analysis of rock blocks to estimate the trajectories that a detached block will follow during its fall until it stops due to kinetic energy loss. However, the selection of rockfall source areas is usually defined either by multivariate analysis or by field observations. For either case, a physically based approach is not used for the source area detection. We present an example of rockfall hazard assessment that integrates a probabilistic rockfall run-out analysis with a stochastic assessment of the rockfall source areas using kinematic stability analysis in a GIS environment. The method has been tested for a steep more than 200 m high rock wall, located in the municipality of Norddal (Møre og Romsdal county, Norway), where a large number of people are either exposed to snow avalanches, rockfalls, or debris flows. The area was selected following the recently published hazard mapping plan of Norway. The cliff is formed by medium to coarse-grained quartz-dioritic to granitic gneisses of Proterozoic age. Scree deposits product of recent rockfall activity are found at the bottom of the rock wall. Large blocks can be found several tens of meters away from the cliff in Sylte, the main locality in the Norddal municipality. Structural characterization of the rock wall was done using terrestrial laser scanning (TLS) point clouds in the software Coltop3D (www.terranum.ch), and results were validated with field data. Orientation data sets from the structural characterization were analyzed separately to assess best-fit probability density functions (PDF) for both dip angle and dip direction angle of each discontinuity set. A GIS-based stochastic kinematic analysis was then carried out using the discontinuity set orientations and the friction angle as random variables. An airborne laser scanning digital elevation model (ALS-DEM) with 1 m

Effect of wear on the burst strength of l-80 steel casing

International Nuclear Information System (INIS)

Irawan, S; Bharadwaj, A M; Temesgen, B; Karuppanan, S; Abdullah, M Z B

2015-01-01

Casing wear has recently become one of the areas of research interest in the oil and gas industry especially in extended reach well drilling. The burst strength of a worn out casing is one of the significantly affected mechanical properties and is yet an area where less research is done The most commonly used equations to calculate the resulting burst strength after wear are Barlow, the initial yield burst, the full yield burst and the rupture burst equations. The objective of this study was to estimate casing burst strength after wear through Finite Element Analysis (FEA). It included calculation and comparison of the different theoretical bursts pressures with the simulation results along with effect of different wear shapes on L-80 casing material. The von Misses stress was used in the estimation of the burst pressure. The result obtained shows that the casing burst strength decreases as the wear percentage increases. Moreover, the burst strength value of the casing obtained from the FEA has a higher value compared to the theoretical burst strength values. Casing with crescent shaped wear give the highest burst strength value when simulated under nonlinear analysis. (paper)

Bubble bursting at an interface

Science.gov (United States)

Kulkarni, Varun; Sajjad, Kumayl; Anand, Sushant; Fezzaa, Kamel

2017-11-01

Bubble bursting is crucial to understanding the life span of bubbles at an interface and more importantly the nature of interaction between the bulk liquid and the outside environment from the point of view of chemical and biological material transport. The dynamics of the bubble as it rises from inside the liquid bulk to its disappearance on the interface after bursting is an intriguing process, many aspects of which are still being explored. In our study, we make detailed high speed imaging measurements to examine carefully the hole initiation and growth in bursting bubbles that unearth some interesting features of the process. Previous analyses available in literature are revisited based on our novel experimental visualizations. Using a combination of experiments and theory we investigate the role of various forces during the rupturing process. This work aims to further our current knowledge of bubble dynamics at an interface with an aim of predicting better the bubble evolution from its growth to its eventual integration with the liquid bulk.

Size-Frequency Distributions of Rocks on Mars and Earth Analog Sites: Implications for Future Landed Missions

Science.gov (United States)

Golombeck, M.; Rapp, D.

1996-01-01

The size-frequency distribution of rocks and the Vicking landing sites and a variety of rocky locations on the Earth that formed from a number of geologic processes all have the general shape of simple exponential curves, which have been combined with remote sensing data and models on rock abundance to predict the frequency of boulders potentially hazardous to future Mars landers and rovers.

The development of a burst criterion for Zircaloy fuel cladding under LOCA conditions

International Nuclear Information System (INIS)

Neitzel, H.J.; Rosinger, H.E.

1980-10-01

A burst criterion model, which assumes that deformation is controlled by steady-state creep, has been developed for a thin-walled cladding, in this case Zircaloy-4, subjected to a differential pressure and high temperature. The creep equation is integrated to obtain a burst time at the singularity of the strain. Once that urst time is known, the burst temperature and burst pressure can be calculated from the known temperature and pressure histories. A further relationship between burst stress and burst temperature is used to calculate the burst strain. Comparison with measured burst data shows good agreement between theory and experiment. It was found that, if the heating rate is constant, the burst temperature increases with decreasing stress, and that, if the stress level is constant, the burst temperature increases with increasing heating rate. It was also found that anisotropy alters the burst temperature and burst strain, and that thest conditions in the α-Zr temperature range have no influence on the burst data. (orig.) [de

Stimulus-dependent modulation of spike burst length in cat striate cortical cells.

Science.gov (United States)

DeBusk, B C; DeBruyn, E J; Snider, R K; Kabara, J F; Bonds, A B

1997-07-01

Burst activity, defined by groups of two or more spikes with intervals of cats. Bursting varied broadly across a population of 507 simple and complex cells. Half of this population had > or = 42% of their spikes contained in bursts. The fraction of spikes in bursts did not vary as a function of average firing rate and was stationary over time. Peaks in the interspike interval histograms were found at both 3-5 ms and 10-30 ms. In many cells the locations of these peaks were independent of firing rate, indicating a quantized control of firing behavior at two different time scales. The activity at the shorter time scale most likely results from intrinsic properties of the cell membrane, and that at the longer scale from recurrent network excitation. Burst frequency (bursts per s) and burst length (spikes per burst) both depended on firing rate. Burst frequency was essentially linear with firing rate, whereas burst length was a nonlinear function of firing rate and was also governed by stimulus orientation. At a given firing rate, burst length was greater for optimal orientations than for nonoptimal orientations. No organized orientation dependence was seen in bursts from lateral geniculate nucleus cells. Activation of cortical contrast gain control at low response amplitudes resulted in no burst length modulation, but burst shortening at optimal orientations was found in responses characterized by supersaturation. At a given firing rate, cortical burst length was shortened by microinjection of gamma-aminobutyric acid (GABA), and bursts became longer in the presence of N-methyl-bicuculline, a GABA(A) receptor blocker. These results are consistent with a model in which responses are reduced at nonoptimal orientations, at least in part, by burst shortening that is mediated by GABA. A similar mechanism contributes to response supersaturation at high contrasts via recruitment of inhibitory responses that are tuned to adjacent orientations. Burst length modulation can serve

Voltage interval mappings for an elliptic bursting model

OpenAIRE

Wojcik, Jeremy; Shilnikov, Andrey

2013-01-01

We employed Poincar\\'e return mappings for a parameter interval to an exemplary elliptic bursting model, the FitzHugh-Nagumo-Rinzel model. Using the interval mappings, we were able to examine in detail the bifurcations that underlie the complex activity transitions between: tonic spiking and bursting, bursting and mixed-mode oscillations, and finally, mixed-mode oscillations and quiescence in the FitzHugh-Nagumo-Rinzel model. We illustrate the wealth of information, qualitative and quantitati...

Supernova sheds light on gamma-ray bursts

CERN Multimedia

2003-01-01

On 29 March the HETE-II satellite detected the most violent explosion in the universe to date - an enormous burst of gamma rays. Observers across the world recorded and studied the event. It appears to prove that gamma ray bursts originate in supernovae (1 page)

Observation of L-bursts of Jupiter decameter waves

International Nuclear Information System (INIS)

Imai, Kazumasa; Tomisawa, Ichiro

1978-01-01

The Jupiter decameter waves are the only information source which can be obtained on the earth for the investigation of dynamics concerning the generation of plasma waves in the magnetosphere of Jupiter. The emission of Jupiter decameter waves is modulated by the satellite Io considerably. It is observed that the emission of decameter waves fluctuated much in course of time. The duration time of bursts is 1 to 10 sec and 1 to 50 msec for L-bursts and S-bursts, respectively. The simultaneous observations were conducted at two locations from August, 1977, and at three locations from December, 1977, for searching the source of L-bursts. The relation between the appearance frequency of L-bursts and S-bursts and Io phase and system 3 longitude is explained. The observation points were Sugadaira, Chofu and Toyokawa, The minimum detectable flux density by the wave receiving network is 10 -21 W/m 2 .Hz. Concerning the observed results, the locations of observed events on the Io phase and the system 3 longitude are shown. The analytical results on the L-bursts of the main source and the early source are explained, taking ten events. The analysed dynamic cross-correlation and the spectrum analysis of the decameter intensity are shown. The relation between the origin and the emission mechanism was investigated, considering the observed data and the evaluation mentioned above for the main source and early source, and the clue was obtained to solve the riddle of emission mechanism. (Nakai, Y.)

Detection of gamma-ray bursts from Andromeda

International Nuclear Information System (INIS)

Bulik, Tomasz; Coppi, Paolo S.; Lamb, Donald Q.

1996-01-01

If gamma-ray bursts originate in a corona around the Milky Way, it should also be possible to detect them from a similar corona around Andromeda. Adopting a simple model of high velocity neutron star corona, we evaluate the ability of instruments on existing missions to detect an excess of bursts toward Andromeda. We also calculate the optimal properties of an instrument designed to detect such an excess. We find that if the bursts radiate isotropically, an experiment with a sampling distance d max > or approx. 500 kpc could detect a significant excess of bursts in the direction of Andromeda in a few years of observation. If the radiation is beamed along the neutron star's direction of motion, an experiment with d max > or approx. 800 kpc would detect such an excess in a similar amount of time, provided that the width of the beam is greater than 10 deg. Lack of an excess toward Andromeda would therefore be compelling evidence that the bursts are cosmological in origin if made by an instrument at least 50 times more sensitive than BATSE, given current constraints on Galactic corona models. Comparisons with detailed dynamical calculations of the spatial distribution of high velocity neutron stars in the coronae around the Milky Way and Andromeda confirm these conclusions

Scientific Applications Performance Evaluation on Burst Buffer

KAUST Repository

Markomanolis, George S.

2017-10-19

Parallel I/O is an integral component of modern high performance computing, especially in storing and processing very large datasets, such as the case of seismic imaging, CFD, combustion and weather modeling. The storage hierarchy includes nowadays additional layers, the latest being the usage of SSD-based storage as a Burst Buffer for I/O acceleration. We present an in-depth analysis on how to use Burst Buffer for specific cases and how the internal MPI I/O aggregators operate according to the options that the user provides during his job submission. We analyze the performance of a range of I/O intensive scientific applications, at various scales on a large installation of Lustre parallel file system compared to an SSD-based Burst Buffer. Our results show a performance improvement over Lustre when using Burst Buffer. Moreover, we show results from a data hierarchy library which indicate that the standard I/O approaches are not enough to get the expected performance from this technology. The performance gain on the total execution time of the studied applications is between 1.16 and 3 times compared to Lustre. One of the test cases achieved an impressive I/O throughput of 900 GB/s on Burst Buffer.

Multi scenario seismic hazard assessment for Egypt

Science.gov (United States)

Mostafa, Shaimaa Ismail; Abd el-aal, Abd el-aziz Khairy; El-Eraki, Mohamed Ahmed

2018-05-01

Egypt is located in the northeastern corner of Africa within a sensitive seismotectonic location. Earthquakes are concentrated along the active tectonic boundaries of African, Eurasian, and Arabian plates. The study area is characterized by northward increasing sediment thickness leading to more damage to structures in the north due to multiple reflections of seismic waves. Unfortunately, man-made constructions in Egypt were not designed to resist earthquake ground motions. So, it is important to evaluate the seismic hazard to reduce social and economic losses and preserve lives. The probabilistic seismic hazard assessment is used to evaluate the hazard using alternative seismotectonic models within a logic tree framework. Alternate seismotectonic models, magnitude-frequency relations, and various indigenous attenuation relationships were amended within a logic tree formulation to compute and develop the regional exposure on a set of hazard maps. Hazard contour maps are constructed for peak ground acceleration as well as 0.1-, 0.2-, 0.5-, 1-, and 2-s spectral periods for 100 and 475 years return periods for ground motion on rock. The results illustrate that Egypt is characterized by very low to high seismic activity grading from the west to the eastern part of the country. The uniform hazard spectra are estimated at some important cities distributed allover Egypt. The deaggregation of seismic hazard is estimated at some cities to identify the scenario events that contribute to a selected seismic hazard level. The results of this study can be used in seismic microzonation, risk mitigation, and earthquake engineering purposes.

Physical characterization of the Skua fast burst assembly

International Nuclear Information System (INIS)

Paternoster, R.; Bounds, J.; Sanchez, R.; Miko, D.

1994-01-01

In this paper we discuss the system design and ongoing efforts to characterize the machine physics and operating properties of the Skua fast burst assembly. The machine is currently operating up to prompt critical while we await approval for super-prompt burst operations. Efforts have centered on characterizing neutron kinetic properties, comparing calculated and measured temperature coefficients and power distributions, improving the burst reproducibility, examining the site-wide dose characteristics, and fitting the machine with cooling and filtration systems

DO THE FERMI GAMMA-RAY BURST MONITOR AND SWIFT BURST ALERT TELESCOPE SEE THE SAME SHORT GAMMA-RAY BURSTS?

International Nuclear Information System (INIS)

Burns, Eric; Briggs, Michael S.; Connaughton, Valerie; Zhang, Bin-Bin; Lien, Amy; Goldstein, Adam; Pelassa, Veronique; Troja, Eleonora

2016-01-01

Compact binary system mergers are expected to generate gravitational radiation detectable by ground-based interferometers. A subset of these, the merger of a neutron star with another neutron star or a black hole, are also the most popular model for the production of short gamma-ray bursts (GRBs). The Swift Burst Alert Telescope (BAT) and the Fermi Gamma-ray Burst Monitor (GBM) trigger on short GRBs (SGRBs) at rates that reflect their relative sky exposures, with the BAT detecting 10 per year compared to about 45 for GBM. We examine the SGRB populations detected by Swift BAT and Fermi GBM. We find that the Swift BAT triggers on weaker SGRBs than Fermi GBM, providing they occur close to the center of the BAT field of view, and that the Fermi GBM SGRB detection threshold remains flatter across its field of view. Overall, these effects combine to give the instruments the same average sensitivity, and account for the SGRBs that trigger one instrument but not the other. We do not find any evidence that the BAT and GBM are detecting significantly different populations of SGRBs. Both instruments can detect untriggered SGRBs using ground searches seeded with time and position. The detection of SGRBs below the on-board triggering sensitivities of Swift BAT and Fermi GBM increases the possibility of detecting and localizing the electromagnetic counterparts of gravitational wave (GW) events seen by the new generation of GW detectors

DO THE FERMI GAMMA-RAY BURST MONITOR AND SWIFT BURST ALERT TELESCOPE SEE THE SAME SHORT GAMMA-RAY BURSTS?

Energy Technology Data Exchange (ETDEWEB)

Burns, Eric; Briggs, Michael S. [University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Connaughton, Valerie [Universities Space Research Association, Science and Technology Institute, 320 Sparkman Drive, Huntsville, AL 35805 (United States); Zhang, Bin-Bin [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Lien, Amy [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Goldstein, Adam [NASA Postdoctoral Program, Space Science Office, VP62, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Pelassa, Veronique [Smithsonian Astrophysical Observatory, P.O. Box 97, Amado, AZ 85645 (United States); Troja, Eleonora, E-mail: eb0016@uah.edu [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2016-02-20

Compact binary system mergers are expected to generate gravitational radiation detectable by ground-based interferometers. A subset of these, the merger of a neutron star with another neutron star or a black hole, are also the most popular model for the production of short gamma-ray bursts (GRBs). The Swift Burst Alert Telescope (BAT) and the Fermi Gamma-ray Burst Monitor (GBM) trigger on short GRBs (SGRBs) at rates that reflect their relative sky exposures, with the BAT detecting 10 per year compared to about 45 for GBM. We examine the SGRB populations detected by Swift BAT and Fermi GBM. We find that the Swift BAT triggers on weaker SGRBs than Fermi GBM, providing they occur close to the center of the BAT field of view, and that the Fermi GBM SGRB detection threshold remains flatter across its field of view. Overall, these effects combine to give the instruments the same average sensitivity, and account for the SGRBs that trigger one instrument but not the other. We do not find any evidence that the BAT and GBM are detecting significantly different populations of SGRBs. Both instruments can detect untriggered SGRBs using ground searches seeded with time and position. The detection of SGRBs below the on-board triggering sensitivities of Swift BAT and Fermi GBM increases the possibility of detecting and localizing the electromagnetic counterparts of gravitational wave (GW) events seen by the new generation of GW detectors.

Swift-BAT: The First Year of Gamma-Ray Burst Detections

Science.gov (United States)

Krimm, Hans A.

2006-01-01

The Burst Alert Telescope (BAT) on the Swift has been detecting gamma-ray bursts (GRBs) since Dec. 17,2004 and automated burst alerts have been distributed since Feb. 14,2005. Since commissioning the BAT has triggered on more than 100 GRBs, nearly all of which have been followed up by the narrow-field instruments on Swift through automatic repointing, and by ground and other satellite telescopes after rapid notification. Within seconds of a trigger the BAT produces and relays to the ground a position good to three arc minutes and a four channel light curve. A full ten minutes of event data follows on subsequent ground station passes. The burst archive has allowed us to determine ensemble burst parameters such as fluence, peak flux and duration. An overview of the properties of BAT bursts and BAT'S performance as a burst monitor will be presented in this talk. BAT is a coded aperture imaging system with a wide (approx.2 sr) field of view consisting of a large coded mask located 1 m above a 5200 cm2 array of 32.768 CdZnTe detectors. All electronics and other hardware systems on the BAT have been operating well since commissioning and there is no sign of any degradation on orbit. The flight and ground software have proven similarly robust and allow the real time localization of all bursts and the rapid derivation of burst light curves, spectra and spectral fits on the ground.

Frequency dependent characteristics of solar impulsive radio bursts

International Nuclear Information System (INIS)

Das, T.K.; Das Gupta, M.K.

1983-01-01

An investigation was made of the impulsive radio bursts observed in the frequency range 0.245 to 35 GHz. Important results obtained are: (i) Simple type 1 bursts with intensities 0 to 10 f.u. and simple type 2 bursts with intensities 10 to 500 f.u. are predominant in the frequency ranges 1.415 to 4.995 GHz and 4.995 to 8.8 GHz, respectively; (ii) With maxima around 2.7 GHz and 4 GHz for the first and second types respectively, the durations of the radio bursts decrease gradually both towards lower and higher frequencies; (iii) As regards occurrences, the first type dominates in the southern solar hemisphere peaking around 8.8 GHz, whereas the second type favours the north with no well-defined maximum in any frequency; (iv) Both types prefer the eastern hemisphere, the peak occurrences being around 8.8 GHz and 5 GHz for the two successive types, respectively; (c) The spectra of impulsive radio bursts are generally of the inverted U-type with the maximum emission intensity between 5 and 15 GHz. (author)

Ion burst event in the earth's dayside magnetosheath

International Nuclear Information System (INIS)

Paschalidis, N.P.; Krimigis, S.M.; Sibeck, D.G.; McEntire, R.W.; Zanetti, L.J.; Sarris, E.T.; Christon, S.P.

1991-01-01

The MEPA instrument on the AMPTE/CCE Spacecraft provided ion angular distributions as rapidly as every 6 sec for H, He, and O at energies of 10 keV to 2 MeV in the dayside magnetosheath within 8.75 R E , the CCE apogee. In this report the authors discuss a burst of energetic particles in the subsolar magnetosheath and its association with rapid changes in the local magnetic field direction in such a way that the magnetic field connected the spacecraft to the magnetopause during the enhancement. They find that magnetosheath angular distributions outside the burst peaked at 90 degree pitch angles, whereas during the burst they exhibited field aligned streaming either parallel or antiparallel to the magnetic field combined with a clear earthward gradient. The clear earthward gradients at E ≥ 10 KeV, the streaming, and the slope change in the burst-time magnetosheath spectrum at ∼10 KeV suggest magnetospheric source for the burst-time ≥ 10 KeV ions and heated solar wind for E < 10 KeV

Geohazard reconnaissance mapping for potential rock boulder fall using low altitude UAV photogrammetry

Science.gov (United States)

Sharan Kumar, N.; Ashraf Mohamad Ismail, Mohd; Sukor, Nur Sabahiah Abdul; Cheang, William

2018-05-01

This paper discusses potential applications of unmanned aerial vehicles (UAVs) for evaluation of risk immediately with photos and 3-dimensional digital element. Aerial photography using UAV ready to give a powerful technique for potential rock boulder fall recognition. High-resolution outputs from this method give the chance to evaluate the site for potential rock boulder falls spatially. The utilization of UAV to capture the aerial photos is a quick, reliable, and cost-effective technique contrasted with terrestrial laser scanning method. Reconnaissance of potential rock boulder susceptible to fall is very crucial during the geotechnical investigation. This process is essential in the view of the rock fall hazards nearby site before the beginning of any preliminary work. Photogrammetric applications have empowered the automated way to deal with identification of rock boulder susceptible to fall by recognizing the location, size, and position. A developing examination of the utilization of digital photogrammetry gives numerous many benefits for civil engineering application. These advancements have made important contributions to our capabilities to create the geohazard map on potential rock boulder fall.

Fuzzy correlations of gamma-ray bursts

International Nuclear Information System (INIS)

Hartmann, D.H.; Linder, E.V.; Blumenthal, G.R.

1991-01-01

The origin of gamma-ray bursts is not known, both in the sense of the nature of the source emitting the radiation and literally, the position of the burst on the sky. Lacking unambiguously identified counterparts in any wavelength band studied to date, statistical approaches are required to determine the burster distance scale. Angular correlation analysis is one of the most powerful tools in this regard. However, poor detector resolution gives large localization errors, effectively beam smearing the positions. The resulting fuzzy angular correlation function is investigated and the generic isotropization that smearing induces on any intrinsic clustering is discussed. In particular, the extent to which gamma-ray burst observations by the BATSE detector aboard the Gamma-Ray Observatory might recover an intrinsic source correlation is investigated. 16 refs

Accelerating Science with the NERSC Burst Buffer Early User Program

Energy Technology Data Exchange (ETDEWEB)

Bhimji, Wahid [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bard, Debbie [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Romanus, Melissa [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Rutgers Univ., New Brunswick, NJ (United States); Paul, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Ovsyannikov, Andrey [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Friesen, Brian [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bryson, Matt [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Correa, Joaquin [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Lockwood, Glenn K. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Tsulaia, Vakho [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Byna, Suren [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Farrell, Steve [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Gursoy, Doga [Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS); Daley, Chris [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Beckner, Vince [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Van Straalen, Brian [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Trebotich, David [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Tull, Craig [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Weber, Gunther H. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Wright, Nicholas J. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Antypas, Katie [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Prabhat, none [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

2016-01-01

NVRAM-based Burst Buffers are an important part of the emerging HPC storage landscape. The National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory recently installed one of the first Burst Buffer systems as part of its new Cori supercomputer, collaborating with Cray on the development of the DataWarp software. NERSC has a diverse user base comprised of over 6500 users in 700 different projects spanning a wide variety of scientific computing applications. The use-cases of the Burst Buffer at NERSC are therefore also considerable and diverse. We describe here performance measurements and lessons learned from the Burst Buffer Early User Program at NERSC, which selected a number of research projects to gain early access to the Burst Buffer and exercise its capability to enable new scientific advancements. To the best of our knowledge this is the first time a Burst Buffer has been stressed at scale by diverse, real user workloads and therefore these lessons will be of considerable benefit to shaping the developing use of Burst Buffers at HPC centers.

Beyond initiation-limited translational bursting: the effects of burst size distributions on the stability of gene expression

KAUST Repository

Kuwahara, Hiroyuki

2015-11-04

A main source of gene expression noise in prokaryotes is translational bursting. It arises from efficient translation of mRNAs with low copy numbers, which makes the production of protein copies highly variable and pulsatile. To obtain analytical solutions, previous models to capture this noise source had to assume translation to be initiation-limited, representing the burst size by a specific type of a long-tail distribution. However, there is increasing evidence suggesting that the initiation is not the rate-limiting step in certain settings, for example, under stress conditions. Here, to overcome the limitations imposed by the initiation-limited assumption, we present a new analytical approach that can evaluate biological consequences of the protein burst size with a general distribution. Since our new model can capture the contribution of other factors to the translational noise, it can be used to analyze the effects of gene expression noise in more general settings. We used this new model to analytically analyze the connection between the burst size and the stability of gene expression processes in various settings. We found that the burst size with different distributions can lead to quantitatively and qualitatively different stability characteristics of protein abundance and can have non-intuitive effects. By allowing analysis of how the stability of gene expression processes changes based on various distributions of translational noise, our analytical approach is expected to enable deeper insights into the control of cell fate decision-making, the evolution of cryptic genetic variations, and fine-tuning of gene circuits.

The sample of INTEGRAL SPI-ACS gamma-ray bursts

International Nuclear Information System (INIS)

Rau, A.; Kienlin, A. von; Licht, G.G.; Hurley, K.

2005-01-01

The anti-coincidence system of the spectrometer on board INTEGRAL is operated as a nearly omni directional gamma-ray burst detector above ∼ 75 KeV. During the elapsed mission time 324 burst candidates were detected. As part of the 3rd Interplanetary Network of gamma-ray detectors the cosmic origin of 115 burst was confirmed. Here we present a preliminary analysis of the SPI-ACS gamma-ray burst sample. In particular we discuss the origin of a significant population of short events (duration < 0.2 s) and a possible method for a flux calibration of the data

Coupled hydro-neutronic calculations for fast burst reactor accidents

International Nuclear Information System (INIS)

Paternoster, R.; Kimpland, R.; Jaegers, P.; McGhee, J.

1994-01-01

Methods are described for determining the fully coupled neutronic/hydrodynamic response of fast burst reactors (FBR) under disruptive accident conditions. Two code systems, PAD (1 -D Lagrangian) and NIKE-PAGOSA (3-D Eulerian) were used to accomplish this. This is in contrast to the typical methodology that computes these responses by either single point kinetics or in a decoupled manner. This methodology is enabled by the use of modem supercomputers (CM-200). Two examples of this capability are presented: an unreflected metal fast burst assembly, and a reflected fast burst assembly typical of the Skua or SPR-III class of fast burst reactor

Gamma Ray Burst Discoveries by the Swift Mission

Science.gov (United States)

Gehrels, Neil

2006-01-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. The NASA swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit since November 20, 2004 and all hardware is performing well. A new-technology wide-field gamma-ray camera is detecting a hundred bursts per year. sensitive narrow-field X-ray and uv/optical telescopes, built in collaboration with UK and Italian partners, are pointed at the burst location in 50-100 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. The first year of findings from the mission will be presented. There has been a break-through in the longstanding mystery of short GRBs; they appear to be caused by merging neutron stars. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow.

Gamma Ray Burst Discoveries by the Swift Mission

Science.gov (United States)

Gehrels, Neil

2006-04-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. The NASA Swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit since November 20, 2004 and all hardware is performing well. A new-technology wide-field gamma-ray camera is detecting a hundred bursts per year. Sensitive narrow-field X-ray and UV/optical telescopes, built in collaboration with UK and Italian partners, are pointed at the burst location in 50-100 sec by an autonomously controlled ``swift'' spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. The first year of findings from the mission will be presented. There has been a break-through in the long-standing mystery of short GRBs; they appear to be caused by merging neutron stars. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow.

The Vaigat Rock Avalanche Laboratory, west-central Greenland

Science.gov (United States)

Dunning, S.; Rosser, N. J.; Szczucinski, W.; Norman, E. C.; Benjamin, J.; Strzelecki, M.; Long, A. J.; Drewniak, M.

2013-12-01

Rock avalanches have unusually high mobility and pose both an immediate hazard, but also produce far-field impacts associated with dam breach, glacier collapse and where they run-out into water, tsunami. Such secondary hazards can often pose higher risks than the original landslide. The prediction of future threats posed by potential rock avalanches is heavily reliant upon understanding of the physics derived from an interpretation of deposits left by previous events, yet drawing comparisons between multiple events is normally challenging as interactions with complex mountainous terrain makes deposits from each event unique. As such numerical models and the interpretation of the underlying physics which govern landslide mobility is commonly case-specific and poorly suited to extrapolation beyond the single events the model is tuned to. Here we present a high-resolution LiDAR and hyperspectral dataset captured across a unique cluster of large rock avalanche source areas and deposits in the Vaigat straight, west central Greenland. Vaigat offers the unprecedented opportunity to model a sample of > 15 rock avalanches of various age sourced from an 80 km coastal escarpment. At Vaigat many of the key variables (topography, geology, post-glacial history) are held constant across all landslides providing the chance to investigate the variations in dynamics and emplacement style related to variable landslide volume, drop-heights, and thinning/spreading over relatively simple, unrestricted run-out zones both onto land and into water. Our data suggest that this region represents excellent preservation of landslide deposits, and hence is well suited to calibrate numerical models of run out dynamics. We use this data to aid the interpretation of deposit morphology, structure lithology and run-out characteristics in more complex settings. Uniquely, we are also able to calibrate our models using a far-field dataset of well-preserved tsunami run-up deposits, resulting from the 21

Recent achievements in the field of gamma-ray bursts

International Nuclear Information System (INIS)

Lu Tan; Dai Zigao

2001-01-01

Recent progresses in the field of gamma-ray bursts is briefly introduced. Gamma-ray bursts are the most energetic explosion since the Big Bang of the universe. Within a few tens of seconds, the energy released in gamma-ray bursts could be several hundred times larger than that released form the sun in its whole life (about 10 billion years). The authors will first briefly discuss the observational facts, based on which the authors will discuss the standard fireball model, the dynamical behavior and evolution of gamma-ray bursts and their afterglows. Then, various observational phenomena that contradict the standard model are given and the importance of these post-standard effects are pointed out. The questions related to the energy source of gamma-ray bursts are still unanswered, and other important questions also remain to be solved

Probing Intrinsic Properties of Short Gamma-Ray Bursts with Gravitational Waves.

Science.gov (United States)

Fan, Xilong; Messenger, Christopher; Heng, Ik Siong

2017-11-03

Progenitors of short gamma-ray bursts are thought to be neutron stars coalescing with their companion black hole or neutron star, which are one of the main gravitational wave sources. We have devised a Bayesian framework for combining gamma-ray burst and gravitational wave information that allows us to probe short gamma-ray burst luminosities. We show that combined short gamma-ray burst and gravitational wave observations not only improve progenitor distance and inclination angle estimates, they also allow the isotropic luminosities of short gamma-ray bursts to be determined without the need for host galaxy or light-curve information. We characterize our approach by simulating 1000 joint short gamma-ray burst and gravitational wave detections by Advanced LIGO and Advanced Virgo. We show that ∼90% of the simulations have uncertainties on short gamma-ray burst isotropic luminosity estimates that are within a factor of two of the ideal scenario, where the distance is known exactly. Therefore, isotropic luminosities can be confidently determined for short gamma-ray bursts observed jointly with gravitational waves detected by Advanced LIGO and Advanced Virgo. Planned enhancements to Advanced LIGO will extend its range and likely produce several joint detections of short gamma-ray bursts and gravitational waves. Third-generation gravitational wave detectors will allow for isotropic luminosity estimates for the majority of the short gamma-ray burst population within a redshift of z∼1.

Spatial-temporal variation of low-frequency earthquake bursts near Parkfield, California

Science.gov (United States)

Wu, Chunquan; Guyer, Robert; Shelly, David R.; Trugman, D.; Frank, William; Gomberg, Joan S.; Johnson, P.

2015-01-01

Tectonic tremor (TT) and low-frequency earthquakes (LFEs) have been found in the deeper crust of various tectonic environments globally in the last decade. The spatial-temporal behaviour of LFEs provides insight into deep fault zone processes. In this study, we examine recurrence times from a 12-yr catalogue of 88 LFE families with ∼730 000 LFEs in the vicinity of the Parkfield section of the San Andreas Fault (SAF) in central California. We apply an automatic burst detection algorithm to the LFE recurrence times to identify the clustering behaviour of LFEs (LFE bursts) in each family. We find that the burst behaviours in the northern and southern LFE groups differ. Generally, the northern group has longer burst duration but fewer LFEs per burst, while the southern group has shorter burst duration but more LFEs per burst. The southern group LFE bursts are generally more correlated than the northern group, suggesting more coherent deep fault slip and relatively simpler deep fault structure beneath the locked section of SAF. We also found that the 2004 Parkfield earthquake clearly increased the number of LFEs per burst and average burst duration for both the northern and the southern groups, with a relatively larger effect on the northern group. This could be due to the weakness of northern part of the fault, or the northwesterly rupture direction of the Parkfield earthquake.

Arachidonic acid triggers an oxidative burst in leukocytes

Directory of Open Access Journals (Sweden)

Pompeia C.

2003-01-01

Full Text Available The change in cellular reducing potential, most likely reflecting an oxidative burst, was investigated in arachidonic acid- (AA stimulated leukocytes. The cells studied included the human leukemia cell lines HL-60 (undifferentiated and differentiated into macrophage-like and polymorphonuclear-like cells, Jurkat and Raji, and thymocytes and macrophages from rat primary cultures. The oxidative burst was assessed by nitroblue tetrazolium reduction. AA increased the oxidative burst until an optimum AA concentration was reached and the burst decreased thereafter. In the leukemia cell lines, optimum concentration ranged from 200 to 400 µM (up to 16-fold, whereas in rat cells it varied from 10 to 20 µM. Initial rates of superoxide generation were high, decreasing steadily and ceasing about 2 h post-treatment. The continuous presence of AA was not needed to stimulate superoxide generation. It seems that the NADPH oxidase system participates in AA-stimulated superoxide production in these cells since the oxidative burst was stimulated by NADPH and inhibited by N-ethylmaleimide, diphenyleneiodonium and superoxide dismutase. Some of the effects of AA on the oxidative burst may be due to its detergent action. There apparently was no contribution of other superoxide-generating systems such as xanthine-xanthine oxidase, cytochromes P-450 and mitochondrial electron transport chain, as assessed by the use of inhibitors. Eicosanoids and nitric oxide also do not seem to interfere with the AA-stimulated oxidative burst since there was no systematic effect of cyclooxygenase, lipoxygenase or nitric oxide synthase inhibitors, but lipid peroxides may play a role, as indicated by the inhibition of nitroblue tetrazolium reduction promoted by tocopherol.

Establishment of the effective modes of the slowdown explosion by rocks destruction at quarries

Directory of Open Access Journals (Sweden)

О.О. Frolov

2017-12-01

Full Text Available Existing for today theoretical modeling tools of the mass explosion do not fully consider the sequence and intensity of destruction of the rock mass. This leads to significant energy losses in the explosion. Therefore, the control of the sequence and modes of micro- and millisecond delayed blasting of systems of borehole charges of explosives in quarries will allow achieving better mass explosion indices. Interaction of the stress waves generated by the individual charges explosion is considered in this work as a way to control the effect of an explosion in a rock mass. It is established that the maximum value of the amount of rocks destruction in the presence of a single plane of exposure depends on the interval of delay between the explosion of the adjacent borehole charges in a group, which, in turn, is determined by the ratio of the distance between charges to the velocity of propagation of longitudinal stress waves in the rock mass. A formula for determining the rational delay interval between bursts of charge groups, which takes into account both the physical and mechanical properties of the rock mass and the main technological parameters of the explosion is proposed. Based on the results of research, the blasting scheme is recommended to be formed taking into account the deceleration intervals between the groups of borehole charges and for adjacent charges placed in one group.

The velocities of type II solar radio bursts

International Nuclear Information System (INIS)

Tlamicha, A.; Karlicky, M.

1976-01-01

A list is presented of type II radio bursts identified at Ondrejov between January 1973 and December 1974 in the frequency range of the dynamic spectrum 70 to 810 MHz. The velocities of shock waves in the individual cases of type II bursts are given using the fourfold Newkirk model. Some problems associated with type II radio bursts and with the propagation of the shock wave into the interplanetary space and into the region of the Earth are also discussed. (author)

The LASL gamma-ray burst astronomy program

International Nuclear Information System (INIS)

Klebesadel, R.W.; Evans, W.D.; Laros, J.G.

1981-01-01

Gamma-ray burst observations performed by LASL began with the identification and initial report of the phenomenon from data acquired by the Vela satellites. The Vela instruments have recorded responses to 73 gamma-ray bursts over a ten-year interval, and are continuing to contribute toward these observations. Similar instrumentation was included aboard the NRL SOLRAD 11 spacecraft. These performed well but suffered an early demise. Recently, the LASL gamma-ray burst astronomy program has been enhanced through the implementation of experiments aboard the Pioneer Venus Orbiter and ISEF-C spacecraft. Both of these experiments are continuing to contribute data vital to trigonometric directional analyses. (orig.)

Gamma ray bursts observed with WATCH‐EURECA

DEFF Research Database (Denmark)

Brandt, Søren; Lund, Niels; Castro-Tirado, A. J.

1994-01-01

The WATCH wide field x‐ray monitor has the capability of independently locating bright Gamma Ray Bursts to 1° accuracy. We report the preliminary positions of 12 Gamma Ray Bursts observed with the WATCH monitor flown on the ES spacecraft EURECA during its 11 month mission. Also the recurrence...

Gamma ray bursts: Current status of observations and theory

International Nuclear Information System (INIS)

Meegan, C.A.

1990-04-01

Gamma ray bursts display a wide range of temporal and spectral characteristics, but typically last several seconds and emit most of their energy in a low energy, gamma ray region. The burst sources appear to be isotropically distributed on the sky. Several lines of evidence suggest magnetic neutron stars as sources for bursts. A variety of energy sources and emission mechanisms are proposed

Infrared and X-ray bursts from the rapid burster

International Nuclear Information System (INIS)

Apparao, K.M.V.; Chitre, S.M.

1979-01-01

Studies on sudden bursts from the cosmic X-ray sources are reported. The processes occuring from the rise in luminosity of an x-ray source to its collapse are described. Records of the x-ray burst from the globular cluster NGC 6624 and the 'Rapid Burster' are shown. The Infra-red bursts from the Rapid Burster are also explained. (A.K.)

Hazard Detection Software for Lunar Landing

Science.gov (United States)

Huertas, Andres; Johnson, Andrew E.; Werner, Robert A.; Montgomery, James F.

2011-01-01

The Autonomous Landing and Hazard Avoidance Technology (ALHAT) Project is developing a system for safe and precise manned lunar landing that involves novel sensors, but also specific algorithms. ALHAT has selected imaging LIDAR (light detection and ranging) as the sensing modality for onboard hazard detection because imaging LIDARs can rapidly generate direct measurements of the lunar surface elevation from high altitude. Then, starting with the LIDAR-based Hazard Detection and Avoidance (HDA) algorithm developed for Mars Landing, JPL has developed a mature set of HDA software for the manned lunar landing problem. Landing hazards exist everywhere on the Moon, and many of the more desirable landing sites are near the most hazardous terrain, so HDA is needed to autonomously and safely land payloads over much of the lunar surface. The HDA requirements used in the ALHAT project are to detect hazards that are 0.3 m tall or higher and slopes that are 5 or greater. Steep slopes, rocks, cliffs, and gullies are all hazards for landing and, by computing the local slope and roughness in an elevation map, all of these hazards can be detected. The algorithm in this innovation is used to measure slope and roughness hazards. In addition to detecting these hazards, the HDA capability also is able to find a safe landing site free of these hazards for a lunar lander with diameter .15 m over most of the lunar surface. This software includes an implementation of the HDA algorithm, software for generating simulated lunar terrain maps for testing, hazard detection performance analysis tools, and associated documentation. The HDA software has been deployed to Langley Research Center and integrated into the POST II Monte Carlo simulation environment. The high-fidelity Monte Carlo simulations determine the required ground spacing between LIDAR samples (ground sample distances) and the noise on the LIDAR range measurement. This simulation has also been used to determine the effect of

THE SECOND SWIFT BURST ALERT TELESCOPE GAMMA-RAY BURST CATALOG

International Nuclear Information System (INIS)

Sakamoto, T.; Baumgartner, W. H.; Cummings, J. R.; Krimm, H. A.; Barthelmy, S. D.; Gehrels, N.; Markwardt, C. B.; Parsons, A. M.; Tueller, J.; Fenimore, E. E.; Palmer, D. M.; Sato, G.; Stamatikos, M.; Ukwatta, T. N.; Zhang, B.

2011-01-01

We present the second Swift Burst Alert Telescope (BAT) catalog of gamma-ray bursts (GRBs), which contains 476 bursts detected by the BAT between 2004 December 19 and 2009 December 21. This catalog (hereafter the BAT2 catalog) presents burst trigger time, location, 90% error radius, duration, fluence, peak flux, time-averaged spectral parameters, and time-resolved spectral parameters measured by the BAT. In the correlation study of various observed parameters extracted from the BAT prompt emission data, we distinguish among long-duration GRBs (L-GRBs), short-duration GRBs (S-GRBs), and short-duration GRBs with extended emission (S-GRBs with E.E.) to investigate differences in the prompt emission properties. The fraction of L-GRBs, S-GRBs, and S-GRBs with E.E. in the catalog are 89%, 8%, and 2%, respectively. We compare the BAT prompt emission properties with the BATSE, BeppoSAX, and HETE-2 GRB samples. We also correlate the observed prompt emission properties with the redshifts for the GRBs with known redshift. The BAT T 90 and T 50 durations peak at 70 s and 30 s, respectively. We confirm that the spectra of the BAT S-GRBs are generally harder than those of the L-GRBs. The time-averaged spectra of the BAT S-GRBs with E.E. are similar to those of the L-GRBs. Whereas, the spectra of the initial short spikes of the S-GRBs with E.E. are similar to those of the S-GRBs. We show that the BAT GRB samples are significantly softer than the BATSE bright GRBs and that the time-averaged E obs peak of the BAT GRBs peaks at 80 keV, which is significantly lower energy than those of the BATSE sample, which peak at 320 keV. The time-averaged spectral properties of the BAT GRB sample are similar to those of the HETE-2 GRB samples. By time-resolved spectral analysis, we find that only 10% of the BAT observed photon indices are outside the allowed region of the synchrotron shock model. We see no obvious observed trend in the BAT T 90 and the observed spectra with redshifts. The T 90

On the Nature of the Gamma-ray Bursts

Directory of Open Access Journals (Sweden)

Kyung-Ai Hong

1987-12-01

Full Text Available Review of the γ-ray burst phenomena are presented. History of the γ-ray bursts, characteristics, and three radiation mechanisms of thermal bremsstrahlung, thermal synchrotron, and inverse Compton scattering processes are considered.

Unusual X-ray burst profiles from 4U/MXB 1636-53

Science.gov (United States)

Sztajno, M.; Truemper, J.; Pietsch, W.; Van Paradijs, J.; Stollman, G.

1985-01-01

During a one day Exosat observation eight X-ray bursts from 4U/MXB 1636-53 are observed. Four of these were very unusual. Their peak fluxes were relatively low, and they showed a distinct double peak in their bolometric flux profiles. These new double-peaked bursts are unexplained by presently available models of X-ray bursts. It is possible that the energy release in these bursts proceeds in two 'steps'. The burst profiles are not the result of an expansion and subsequent contraction of the photosphere of the neutron star. Thus, they are very different from previously observed bursts which do show a double peak in certain energy ranges but not in their bolometric flux profiles; these are satisfactorily explained in terms of photospheric radius expansion and contraction. The anticorrelation between the apparent blackbody radius and blackbody temperature is discussed in terms of the nonPlanckian character of burst spectra and it is concluded that the model calculations reported by London, Taam, and Howard in 1984 give a reasonable first-order description of the observed apparent radius changes in X-ray bursts.

DETECTING THE SUPERNOVA BREAKOUT BURST IN TERRESTRIAL NEUTRINO DETECTORS

International Nuclear Information System (INIS)

Wallace, Joshua; Burrows, Adam; Dolence, Joshua C.

2016-01-01

We calculate the distance-dependent performance of a few representative terrestrial neutrino detectors in detecting and measuring the properties of the ν e breakout burst light curve in a Galactic core-collapse supernova. The breakout burst is a signature phenomenon of core collapse and offers a probe into the stellar core through collapse and bounce. We examine cases of no neutrino oscillations and oscillations due to normal and inverted neutrino-mass hierarchies. For the normal hierarchy, other neutrino flavors emitted by the supernova overwhelm the ν e signal, making a detection of the breakout burst difficult. For the inverted hierarchy (IH), some detectors at some distances should be able to see the ν e breakout burst peak and measure its properties. For the IH, the maximum luminosity of the breakout burst can be measured at 10 kpc to accuracies of ∼30% for Hyper-Kamiokande (Hyper-K) and ∼60% for the Deep Underground Neutrino Experiment (DUNE). Super-Kamiokande (Super-K) and Jiangmen Underground Neutrino Observatory (JUNO) lack the mass needed to make an accurate measurement. For the IH, the time of the maximum luminosity of the breakout burst can be measured in Hyper-K to an accuracy of ∼3 ms at 7 kpc, in DUNE to ∼2 ms at 4 kpc, and JUNO and Super-K can measure the time of maximum luminosity to an accuracy of ∼2 ms at 1 kpc. Detector backgrounds in IceCube render a measurement of the ν e breakout burst unlikely. For the IH, a measurement of the maximum luminosity of the breakout burst could be used to differentiate between nuclear equations of state

On burst-and-coast swimming performance in fish-like locomotion

International Nuclear Information System (INIS)

Chung, M-H

2009-01-01

Burst-and-coast swimming performance in fish-like locomotion is studied via two-dimensional numerical simulation. The numerical method used is the collocated finite-volume adaptive Cartesian cut-cell method developed previously. The NACA00xx airfoil shape is used as an equilibrium fish-body form. Swimming in a burst-and-coast style is computed assuming that the burst phase is composed of a single tail-beat. Swimming efficiency is evaluated in terms of the mass-specific cost of transport instead of the Froude efficiency. The effects of the Reynolds number (based on the body length and burst time), duty cycle and fineness ratio (the body length over the largest thickness) on swimming performance (momentum capacity and the mass-specific cost of transport) are studied quantitatively. The results lead to a conclusion consistent with previous findings that a larval fish seldom swims in a burst-and-coast style. Given mass and swimming speed, a fish needs the least cost if it swims in a burst-and-coast style with a fineness ratio of 8.33. This energetically optimal fineness ratio is larger than that derived from the simple hydromechanical model proposed in literature. The calculated amount of energy saving in burst-and-coast swimming is comparable with the real-fish estimation in the literature. Finally, the predicted wake-vortex structures of both continuous and burst-and-coast swimming are biologically relevant.

On burst-and-coast swimming performance in fish-like locomotion.

Science.gov (United States)

Chung, M-H

2009-09-01

Burst-and-coast swimming performance in fish-like locomotion is studied via two-dimensional numerical simulation. The numerical method used is the collocated finite-volume adaptive Cartesian cut-cell method developed previously. The NACA00xx airfoil shape is used as an equilibrium fish-body form. Swimming in a burst-and-coast style is computed assuming that the burst phase is composed of a single tail-beat. Swimming efficiency is evaluated in terms of the mass-specific cost of transport instead of the Froude efficiency. The effects of the Reynolds number (based on the body length and burst time), duty cycle and fineness ratio (the body length over the largest thickness) on swimming performance (momentum capacity and the mass-specific cost of transport) are studied quantitatively. The results lead to a conclusion consistent with previous findings that a larval fish seldom swims in a burst-and-coast style. Given mass and swimming speed, a fish needs the least cost if it swims in a burst-and-coast style with a fineness ratio of 8.33. This energetically optimal fineness ratio is larger than that derived from the simple hydromechanical model proposed in literature. The calculated amount of energy saving in burst-and-coast swimming is comparable with the real-fish estimation in the literature. Finally, the predicted wake-vortex structures of both continuous and burst-and-coast swimming are biologically relevant.

Characteristics of shock-associated fast-drift kilometric radio bursts

Science.gov (United States)

Macdowall, R. J.; Kundu, M. R.; Stone, R. G.

1987-01-01

The existence of a class of fast-drift, shock-associated (SA), kilometric radio bursts which occur at the time of metric type II emission and which are not entirely the kilometric continuation of metric type III bursts has been reported previously (Cane et al., 1981). In this paper unambiguous SA event criteria are established for the purpose of statistically comparing SA events with conventional kilometric type III bursts. Applying these criteria to all long-duration, fast-drift bursts observed by the ISEE-3 spacecraft during a 28-month interval, it is found that more than 70 percent of the events satisfying the criteria are associated with the radio signatures of coronal shocks. If a given event is associated with a metric type II or type IV burst, it is 13 times more likely to satisfy the SA criteria than an event associated only with metric type III activity.

Gamma-ray bursts observed by the watch experiment

DEFF Research Database (Denmark)

Lund, Niels; Brandt, Søren; Castro-Tirado, A. J.

1991-01-01

After two years in orbit the WATCH instruments on the GRANAT space observatory have localized seven gamma burst sources with better than 1° accuracy. In several cases, follow‐up observations with Schmidt telescopes have been made within a few days. Some of the bursts have also been detected...... by the distant space probes PVO and ULYSSES and there are, therefore, good prospects for obtaining much improved positions using the burst arrival times. The existence of the almost concurrent Schmidt plates could then become particularly interesting....

Debris flows: behavior and hazard assessment

Science.gov (United States)

Iverson, Richard M.

2014-01-01

Debris flows are water-laden masses of soil and fragmented rock that rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form lobate deposits when they spill onto valley floors. Because they have volumetric sediment concentrations that exceed 40 percent, maximum speeds that surpass 10 m/s, and sizes that can range up to ~109 m3, debris flows can denude slopes, bury floodplains, and devastate people and property. Computational models can accurately represent the physics of debris-flow initiation, motion and deposition by simulating evolution of flow mass and momentum while accounting for interactions of debris' solid and fluid constituents. The use of physically based models for hazard forecasting can be limited by imprecise knowledge of initial and boundary conditions and material properties, however. Therefore, empirical methods continue to play an important role in debris-flow hazard assessment.

NEESROCK: A Physical and Numerical Modeling Investigation of Seismically Induced Rock-Slope Failure

Science.gov (United States)

Applegate, K. N.; Wartman, J.; Keefer, D. K.; Maclaughlin, M.; Adams, S.; Arnold, L.; Gibson, M.; Smith, S.

2013-12-01

Worldwide, seismically induced rock-slope failures have been responsible for approximately 30% of the most significant landslide catastrophes of the past century. They are among the most common, dangerous, and still today, least understood of all seismic hazards. Seismically Induced Rock-Slope Failure: Mechanisms and Prediction (NEESROCK) is a major research initiative that fully integrates physical modeling (geotechnical centrifuge) and advanced numerical simulations (discrete element modeling) to investigate the fundamental mechanisms governing the stability of rock slopes during earthquakes. The research is part of the National Science Foundation-supported Network for Earthquake Engineering Simulation Research (NEES) program. With its focus on fractures and rock materials, the project represents a significant departure from the traditional use of the geotechnical centrifuge for studying soil, and pushes the boundaries of physical modeling in new directions. In addition to advancing the fundamental understanding of the rock-slope failure process under seismic conditions, the project is developing improved rock-slope failure assessment guidelines, analysis procedures, and predictive tools. Here, we provide an overview of the project, present experimental and numerical modeling results, discuss special considerations for the use of synthetic rock materials in physical modeling, and address the suitability of discrete element modeling for simulating the dynamic rock-slope failure process.

Gamma-ray burst theory after Swift.

Science.gov (United States)

Piran, Tsvi; Fan, Yi-Zhong

2007-05-15

Afterglow observations in the pre-Swift era confirmed to a large extend the relativistic blast wave model for gamma-ray bursts (GRBs). Together with the observations of properties of host galaxies and the association with (type Ic) SNe, this has led to the generally accepted collapsar origin of long GRBs. However, most of the afterglow data was collected hours after the burst. The X-ray telescope and the UV/optical telescope onboard Swift are able to slew to the direction of a burst in real time and record the early broadband afterglow light curves. These observations, and in particular the X-ray observations, resulted in many surprises. While we have anticipated a smooth transition from the prompt emission to the afterglow, many observed that early light curves are drastically different. We review here how these observations are changing our understanding of GRBs.

Interaction function of coupled bursting neurons

International Nuclear Information System (INIS)

Shi Xia; Zhang Jiadong

2016-01-01

The interaction functions of electrically coupled Hindmarsh–Rose (HR) neurons for different firing patterns are investigated in this paper. By applying the phase reduction technique, the phase response curve (PRC) of the spiking neuron and burst phase response curve (BPRC) of the bursting neuron are derived. Then the interaction function of two coupled neurons can be calculated numerically according to the PRC (or BPRC) and the voltage time course of the neurons. Results show that the BPRC is more and more complicated with the increase of the spike number within a burst, and the curve of the interaction function oscillates more and more frequently with it. However, two certain things are unchanged: ϕ = 0, which corresponds to the in-phase synchronization state, is always the stable equilibrium, while the anti-phase synchronization state with ϕ = 0.5 is an unstable equilibrium. (paper)

Type III bursts in interplanetary space - Fundamental or harmonic?

Science.gov (United States)

Dulk, G. A.; Steinberg, J. L.; Hoang, S.

1984-01-01

ISEE-3 spacecraft observation of 120 relatively simple, isolated bursts in the 30-1980 kHz range are the basis of the present study of Type III bursts in the solar wind. Several characteristics are identified for many of these bursts which imply that the mode of emission changes from predominantly fundamental plasma radiation during the rise phase to predominantly second harmonic during decay. The fundamental emission begins in time coincidence with the start of Langmuir waves, confirming the conventional belief in these waves' causation of Type III bursts. Attention is given to the characteristics of fundamental components, by comparison to harmonics, at km-wavelengths.

A polarized fast radio burst at low Galactic latitude

OpenAIRE

Petroff, E.; Kasliwal, M.; Ravi, V.

2017-01-01

We report on the discovery of a new fast radio burst (FRB), FRB 150215, with the Parkes radio telescope on 2015 February 15. The burst was detected in real time with a dispersion measure (DM) of 1105.6 ± 0.8 pc cm^(−3), a pulse duration of 2.8 ^(+1.2)_(−0.5)ms, and a measured peak flux density assuming that the burst was at beam centre of 0.7 ^(+0.2)_(−0.1) Jy. The FRB originated at a Galactic longitude and latitude of 24.66°, 5.28° and 25° away from the Galactic Center. The burst was found t...

Frequency-volume Statistics of Rock Falls: Examples From France, Italy and California

Science.gov (United States)

Dussauge-Peisser, C.; Guzzetti, F.; Wieczorek, G. F.

There is accumulating evidence that the distribution of rock-fall volume exhibits power law (fractal) statistics in different physiographic and geologic environments. We have studied the frequency-volume statistics of rock falls in three areas: Grenoble, France; Umbria, Italy; and Yosemite Valley, California, USA. We present a compari- son of the datasets currently available. For the Grenoble area a catalogue of rock falls between 1248 and 1995 occurred along a 120 km long limestone cliff. The dataset contains information on 105 rock-fall events ranging in size from 3xE-2 to 5xE8 m3. Only the time window 1935-1995 is considered in the study, involving 87 events from 1E-2 to 1E6 m3. The cumulative frequency-volume statistics follow a power-law (frac- tal) relationship with exponent b = -0.4 over the range 50 m3 Yosemite Valley the database contains information on historical (1851-2001) rock falls (122), rock slides (251) and prehistoric rock avalanches (5). For Yosemite, the non-cumulative frequency-volume statistics of rock falls and rock slides are very sim- ilar and correlate well with a power-law (fractal) relation with exponent beta = -1.4, over the range 30 m3 rock avalanches. We discuss the implications of such a power law fitting the data for rock-fall hazard assessment. We also discuss the variation of the b and beta exponents for natural events and earthquake triggered events.

Phase-locking of bursting neuronal firing to dominant LFP frequency components.

Science.gov (United States)

Constantinou, Maria; Elijah, Daniel H; Squirrell, Daniel; Gigg, John; Montemurro, Marcelo A

2015-10-01

Neuronal firing in the hippocampal formation relative to the phase of local field potentials (LFP) has a key role in memory processing and spatial navigation. Firing can be in either tonic or burst mode. Although bursting neurons are common in the hippocampal formation, the characteristics of their locking to LFP phase are not completely understood. We investigated phase-locking properties of bursting neurons using simulations generated by a dual compartmental model of a pyramidal neuron adapted to match the bursting activity in the subiculum of a rat. The model was driven with stochastic input signals containing a power spectral profile consistent with physiologically relevant frequencies observed in LFP. The single spikes and spike bursts fired by the model were locked to a preferred phase of the predominant frequency band where there was a peak in the power of the driving signal. Moreover, the preferred phase of locking shifted with increasing burst size, providing evidence that LFP phase can be encoded by burst size. We also provide initial support for the model results by analysing example data of spontaneous LFP and spiking activity recorded from the subiculum of a single urethane-anaesthetised rat. Subicular neurons fired single spikes, two-spike bursts and larger bursts that locked to a preferred phase of either dominant slow oscillations or theta rhythms within the LFP, according to the model prediction. Both power-modulated phase-locking and gradual shift in the preferred phase of locking as a function of burst size suggest that neurons can use bursts to encode timing information contained in LFP phase into a spike-count code. Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.. All rights reserved.

Observations of the highest energy gamma-rays from gamma-ray bursts

International Nuclear Information System (INIS)

Dingus, Brenda L.

2001-01-01

EGRET has extended the highest energy observations of gamma-ray bursts to GeV gamma rays. Such high energies imply the fireball that is radiating the gamma-rays has a bulk Lorentz factor of several hundred. However, EGRET only detected a few gamma-ray bursts. GLAST will likely detect several hundred bursts and may extend the maximum energy to a few 100 GeV. Meanwhile new ground based detectors with sensitivity to gamma-ray bursts are beginning operation, and one recently reported evidence for TeV emission from a burst

Stress Effects on Stop Bursts in Five Languages

Directory of Open Access Journals (Sweden)

Marija Tabain

2016-11-01

Full Text Available This study examines the effects of stress on the stop burst in five languages differing in number of places of articulation, as reflected in burst duration, spectral centre of gravity, and ­spectral standard deviation. The languages studied are English (three places of articulation /p t k/, the Indonesian language Makasar (four places /p t c k/, and the Central Australian languages ­Pitjantjatjara, Warlpiri (both five places /p t ʈ c k/, and Arrernte (six places /p t̪ t ʈ c k/. We find that languages differ in how they manifest stress on the consonant, with Makasar not ­showing any effect of stress at all, and Warlpiri showing an effect on burst duration, but not on the ­spectral measures. For the other languages, the velar /k/ has a “darker” quality (i.e., lower spectral centre of gravity, and/or a less diffuse spectrum (i.e., lower standard deviation under stress; while the alveolar /t/ has a “lighter” quality under stress. In addition, the dental /t̪/ has a more diffuse spectrum under stress. We suggest that this involves enhancement of the features [grave] and [diffuse] under stress, with velars being [+grave] and [–diffuse], alveolars being [–grave], and dentals being [+diffuse]. We discuss the various possible spectral effects of enhancement of these features. Finally, in the languages with five or six places of articulation, the stop burst is longer only for the palatal /c/ and the velar /k/, which have intrinsically long burst durations, and not for the anterior coronals /t̪ t ʈ/, which have intrinsically short burst durations. We suggest that in these systems, [burst duration] is a feature that separates these two groups of consonants.

Fermi/GBM Observations of SGRJ0501 + 4516 Bursts

Science.gov (United States)

Lin, Lin; Kouveliotou, Chryssa; Baring, Matthew G.; van der Horst, Alexander J.; Guiriec, Sylvain; Woods, Peter M.; Goegues, Ersin; Kaneko, Yuki; Scargle, Jeffrey; Granot, Jonathan;

Polarization of a periodic solar microwave burst

Energy Technology Data Exchange (ETDEWEB)

Kaufmann, P [Universidade Mackenzie, Sao Paulo (Brazil). Centro de Radio-Astronomia e Astrofisica

1976-09-01

No fluctuations in polarization have been found during a 7 GHz solar burst showing 17s periodic pulses in intensity. Polarization effects can be produced by the propagation media in the active centre, which are not affected directly by the burst source, but situated more deeply than the observed heights at that microwave frequency.

The host galaxy of a fast radio burst.

Science.gov (United States)

Keane, E F; Johnston, S; Bhandari, S; Barr, E; Bhat, N D R; Burgay, M; Caleb, M; Flynn, C; Jameson, A; Kramer, M; Petroff, E; Possenti, A; van Straten, W; Bailes, M; Burke-Spolaor, S; Eatough, R P; Stappers, B W; Totani, T; Honma, M; Furusawa, H; Hattori, T; Morokuma, T; Niino, Y; Sugai, H; Terai, T; Tominaga, N; Yamasaki, S; Yasuda, N; Allen, R; Cooke, J; Jencson, J; Kasliwal, M M; Kaplan, D L; Tingay, S J; Williams, A; Wayth, R; Chandra, P; Perrodin, D; Berezina, M; Mickaliger, M; Bassa, C

2016-02-25

In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy; we measure the galaxy's redshift to be z = 0.492 ± 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of ΩIGM = 4.9 ± 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called 'missing baryons'. The ~6-day radio transient is largely consistent with the radio afterglow of a short γ-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts.

Burst Test Qualification Analysis of DWPF Canister-Plug Weld

International Nuclear Information System (INIS)

Gupta, N.K.; Gong, Chung.

1995-02-01

The DWPF canister closure system uses resistance welding for sealing the canister nozzle and plug to ensure leak tightness. The welding group at SRTC is using the burst test to qualify this seal weld in lieu of the shear test in ASME B ampersand PV Code, Section IX, paragraph QW-196. The burst test is considered simpler and more appropriate than the shear test for this application. Although the geometry, loading and boundary conditions are quite different in the two tests, structural analyses show similarity in the failure mode of the shear test in paragraph QW-196 and the burst test on the DWPF canister nozzle Non-linear structural analyses are performed using finite element techniques to study the failure mode of the two tests. Actual test geometry and realistic stress strain data for the 304L stainless steel and the weld material are used in the analyses. The finite element models are loaded until failure strains are reached. The failure modes in both tests are shear at the failure points. Based on these observations, it is concluded that the use of a burst test in lieu of the shear test for qualifying the canister-plug weld is acceptable. The burst test analysis for the canister-plug also yields the burst pressures which compare favorably with the actual pressure found during burst tests. Thus, the analysis also provides an estimate of the safety margins in the design of these vessels

X-Ray Spectral Characteristics of Ginga Gamma-Ray Bursts

International Nuclear Information System (INIS)

Strohmayer, T.E.; Fenimore, E.E.; Murakami, T.; Yoshida, A.

1998-01-01

We have investigated the spectral characteristics of a sample of bright gamma-ray bursts detected with the gamma-ray burst sensors aboard the satellite Ginga. This instrument employed a proportional and scintillation counter to provide sensitivity to photons in the 2 endash 400 keV region and as such provided a unique opportunity to characterize the largely unexplored X-ray properties of gamma-ray bursts. The photon spectra of the Ginga bursts are well described by a low-energy slope, a bend energy, and a high-energy slope. In the energy range where they can be compared, this result is consistent with burst spectral analyses obtained from the BATSE experiment aboard the Compton Gamma-Ray Observatory. However, below 20 keV we find evidence for a positive spectral number index in approximately 40% of our burst sample, with some evidence for a strong rolloff at lower energies in a few events. There is a correlation (Pearson's r = -0.62) between the low-energy slope and the bend energy. We find that the distribution of spectral bend energies extends below 10 keV. There has been some concern in cosmological models of gamma-ray bursts (GRBs) that the bend energy covers only a small dynamic range. Our result extends the observed dynamic range, and, since we observe bend energies down to the limit of our instrument, perhaps observations have not yet limited the range. The Ginga trigger range was virtually the same as that of BATSE, yet we find a different range of fit parameters. One possible explanation might be that GRBs have two break energies, one often in the 50 endash 500 keV range and the other near 5 keV. Both BATSE and Ginga fit with only a single break energy, so BATSE tends to find breaks near the center of its energy range, and we tend to find breaks in our energy range. The observed ratio of energy emitted in the X-rays relative to the gamma rays can be much larger than a few percent and, in fact, is sometimes larger than unity. The average for our 22 bursts

BACODINE/3rd Interplanetary Network burst localization

International Nuclear Information System (INIS)

Hurley, K.; Barthelmy, S.; Butterworth, P.; Cline, T.; Sommer, M.; Boer, M.; Niel, M.; Kouveliotou, C.; Fishman, G.; Meegan, C.

1996-01-01

Even with only two widely separated spacecraft (Ulysses and GRO), 3rd Interplanetary Network (IPN) localizations can reduce the areas of BATSE error circles by two orders of magnitude. Therefore it is useful to disseminate them as quickly as possible following BATSE bursts. We have implemented a system which transmits the light curves of BACODINE/BATSE bursts directly by e-mail to UC Berkeley immediately after detection. An automatic e-mail parser at Berkeley watches for these notices, determines the Ulysses crossing time window, and initiates a search for the burst data on the JPL computer as they are received. In ideal cases, it is possible to retrieve the Ulysses data within a few hours of a burst, generate an annulus of arrival directions, and e-mail it out to the astronomical community by local nightfall. Human operators remain in this loop, but we are developing a fully automated routine which should remove them, at least for intense events, and reduce turn-around times to an absolute minimum. We explain the current operations, the data types used, and the speed/accuracy tradeoffs

Water - rock interaction in different rock environments

International Nuclear Information System (INIS)

Lamminen, S.

1995-01-01

The study assesses the groundwater geochemistry and geological environment of 44 study sites for radioactive waste disposal. Initially, the study sites were divided by rock type into 5 groups: (1) acid - intermediate rocks, (2) mafic - ultramafic rocks, (3) gabbros, amphibolites and gneisses that contain calc-silicate (skarn) rocks, (4) carbonates and (5) sandstones. Separate assessments are made of acid - intermediate plutonic rocks and of a subgroup that comprises migmatites, granite and mica gneiss. These all belong to the group of acid - intermediate rocks. Within the mafic -ultramafic rock group, a subgroup that comprises mafic - ultramafic plutonic rocks, serpentinites, mafic - ultramafic volcanic rocks and volcanic - sedimentary schists is also evaluated separately. Bedrock groundwaters are classified by their concentration of total dissolved solids as fresh, brackish, saline, strongly saline and brine-class groundwaters. (75 refs., 24 figs., 3 tabs.)

Gamma-ray bursts from black hole accretion disks

International Nuclear Information System (INIS)

Strong, I.B.

1975-01-01

The suggestion was first made more than a year ago that gamma-ray bursts might originate in the neighborhood of black holes, based on some rather circumstantial evidence linking Cygnus X-1, the prime black-hole candidate, with two of the then-known gamma-ray bursts. Since then additional evidence makes the idea still more plausible. The evidence is summarized briefly, a physical model for production of gamma-ray bursts is given, and several of the more interesting consequences of such an origin are pointed out. (orig.) [de

Gamma-ray bursts

CERN Document Server

Wijers, Ralph A M J; Woosley, Stan

2012-01-01

Cosmic gamma ray bursts (GRBs) have fascinated scientists and the public alike since their discovery in the late 1960s. Their story is told here by some of the scientists who participated in their discovery and, after many decades of false starts, solved the problem of their origin. Fourteen chapters by active researchers in the field present a detailed history of the discovery, a comprehensive theoretical description of GRB central engine and emission models, a discussion of GRB host galaxies and a guide to how GRBs can be used as cosmological tools. Observations are grouped into three sets from the satellites CGRO, BeppoSAX and Swift, and followed by a discussion of multi-wavelength observations. This is the first edited volume on GRB astrophysics that presents a fully comprehensive review of the subject. Utilizing the latest research, Gamma-ray Bursts is an essential desktop companion for graduate students and researchers in astrophysics.

V/V(max) test applied to SMM gamma-ray bursts

Science.gov (United States)

Matz, S. M.; Higdon, J. C.; Share, G. H.; Messina, D. C.; Iadicicco, A.

1992-01-01

We have applied the V/V(max) test to candidate gamma-ray bursts detected by the Gamma-Ray Spectrometer (GRS) aboard the SMM satellite to examine quantitatively the uniformity of the burst source population. For a sample of 132 candidate bursts identified in the GRS data by an automated search using a single uniform trigger criterion we find average V/V(max) = 0.40 +/- 0.025. This value is significantly different from 0.5, the average for a uniform distribution in space of the parent population of burst sources; however, the shape of the observed distribution of V/V(max) is unusual and our result conflicts with previous measurements. For these reasons we can currently draw no firm conclusion about the distribution of burst sources.

Ablation of silicon with bursts of femtosecond laser pulses

Science.gov (United States)

Gaudiuso, Caterina; Kämmer, Helena; Dreisow, Felix; Ancona, Antonio; Tünnermann, Andreas; Nolte, Stefan

2016-03-01

We report on an experimental investigation of ultrafast laser ablation of silicon with bursts of pulses. The pristine 1030nm-wavelength 200-fs pulses were split into bursts of up to 16 sub-pulses with time separation ranging from 0.5ps to 4080ps. The total ablation threshold fluence was measured depending on the burst features, finding that it strongly increases with the number of sub-pulses for longer sub-pulse delays, while a slowly increasing trend is observed for shorter separation time. The ablation depth per burst follows two different trends according to the time separation between the sub-pulses, as well as the total threshold fluence. For delays shorter than 4ps it decreases with the number of pulses, while for time separations longer than 510ps, deeper craters were achieved by increasing the number of subpulses in the burst, probably due to a change of the effective penetration depth.

A polarized fast radio burst at low Galactic latitude

Science.gov (United States)

Petroff, E.; Burke-Spolaor, S.; Keane, E. F.; McLaughlin, M. A.; Miller, R.; Andreoni, I.; Bailes, M.; Barr, E. D.; Bernard, S. R.; Bhandari, S.; Bhat, N. D. R.; Burgay, M.; Caleb, M.; Champion, D.; Chandra, P.; Cooke, J.; Dhillon, V. S.; Farnes, J. S.; Hardy, L. K.; Jaroenjittichai, P.; Johnston, S.; Kasliwal, M.; Kramer, M.; Littlefair, S. P.; Macquart, J. P.; Mickaliger, M.; Possenti, A.; Pritchard, T.; Ravi, V.; Rest, A.; Rowlinson, A.; Sawangwit, U.; Stappers, B.; Sullivan, M.; Tiburzi, C.; van Straten, W.; ANTARES Collaboration; Albert, A.; André, M.; Anghinolfi, M.; Anton, G.; Ardid, M.; Aubert, J.-J.; Avgitas, T.; Baret, B.; Barrios-Martí, J.; Basa, S.; Bertin, V.; Biagi, S.; Bormuth, R.; Bourret, S.; Bouwhuis, M. C.; Bruijn, R.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carr, J.; Celli, S.; Chiarusi, T.; Circella, M.; Coelho, J. A. B.; Coleiro, A.; Coniglione, R.; Costantini, H.; Coyle, P.; Creusot, A.; Deschamps, A.; de Bonis, G.; Distefano, C.; di Palma, I.; Donzaud, C.; Dornic, D.; Drouhin, D.; Eberl, T.; El Bojaddaini, I.; Elsässer, D.; Enzenhöfer, A.; Felis, I.; Fusco, L. A.; Galatà, S.; Gay, P.; Geißelsöder, S.; Geyer, K.; Giordano, V.; Gleixner, A.; Glotin, H.; Grégoire, T.; Gracia-Ruiz, R.; Graf, K.; Hallmann, S.; van Haren, H.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Hößl, J.; Hofestädt, J.; Hugon, C.; Illuminati, G.; James, C. W.; de Jong, M.; Jongen, M.; Kadler, M.; Kalekin, O.; Katz, U.; Kießling, D.; Kouchner, A.; Kreter, M.; Kreykenbohm, I.; Kulikovskiy, V.; Lachaud, C.; Lahmann, R.; Lefèvre, D.; Leonora, E.; Lotze, M.; Loucatos, S.; Marcelin, M.; Margiotta, A.; Marinelli, A.; Martínez-Mora, J. A.; Mathieu, A.; Mele, R.; Melis, K.; Michael, T.; Migliozzi, P.; Moussa, A.; Mueller, C.; Nezri, E.; Pǎvǎlaş, G. E.; Pellegrino, C.; Perrina, C.; Piattelli, P.; Popa, V.; Pradier, T.; Quinn, L.; Racca, C.; Riccobene, G.; Roensch, K.; Sánchez-Losa, A.; Saldaña, M.; Salvadori, I.; Samtleben, D. F. E.; Sanguineti, M.; Sapienza, P.; Schnabel, J.; Seitz, T.; Sieger, C.; Spurio, M.; Stolarczyk, Th.; Taiuti, M.; Tayalati, Y.; Trovato, A.; Tselengidou, M.; Turpin, D.; Tönnis, C.; Vallage, B.; Vallée, C.; van Elewyck, V.; Vivolo, D.; Vizzoca, A.; Wagner, S.; Wilms, J.; Zornoza, J. D.; Zúñiga, J.; H.E.S.S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Tjus, J. Becker; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Bulik, T.; Capasso, M.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Cui, Y.; Davids, I. D.; Decock, J.; Degrange, B.; Deil, C.; Devin, J.; Dewilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O'c.; Dubus, G.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hadasch, D.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holler, M.; Horns, D.; Ivascenko, A.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Kerszberg, D.; Khélifi, B.; Kieffer, M.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morâ, K.; Moulin, E.; Murach, T.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Öttl, S.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Piel, Q.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reimer, A.; Reimer, O.; Renaud, M.; Reyes, R. De Los; Rieger, F.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schulz, A.; Schüssler, F.; Schwanke, U.; Schwemmer, S.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tuffs, R.; Uchiyama, Y.; Walt, D. J. Van Der; van Eldik, C.; van Rensburg, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zanin, R.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.

2017-08-01

We report on the discovery of a new fast radio burst (FRB), FRB 150215, with the Parkes radio telescope on 2015 February 15. The burst was detected in real time with a dispersion measure (DM) of 1105.6 ± 0.8 pc cm-3, a pulse duration of 2.8^{+1.2}_{-0.5} ms, and a measured peak flux density assuming that the burst was at beam centre of 0.7^{+0.2}_{-0.1} Jy. The FRB originated at a Galactic longitude and latitude of 24.66°, 5.28° and 25° away from the Galactic Center. The burst was found to be 43 ± 5 per cent linearly polarized with a rotation measure (RM) in the range -9 < RM < 12 rad m-2 (95 per cent confidence level), consistent with zero. The burst was followed up with 11 telescopes to search for radio, optical, X-ray, γ-ray and neutrino emission. Neither transient nor variable emission was found to be associated with the burst and no repeat pulses have been observed in 17.25 h of observing. The sightline to the burst is close to the Galactic plane and the observed physical properties of FRB 150215 demonstrate the existence of sight lines of anomalously low RM for a given electron column density. The Galactic RM foreground may approach a null value due to magnetic field reversals along the line of sight, a decreased total electron column density from the Milky Way, or some combination of these effects. A lower Galactic DM contribution might explain why this burst was detectable whereas previous searches at low latitude have had lower detection rates than those out of the plane.

Natural radioactivity measurements in rock samples of Cuihua Mountain National Geological Park (China))

International Nuclear Information System (INIS)

Lu, X.; Zhang, X.

2008-01-01

The concentrations of the natural radionuclides namely 40 K, 232 Th and 226 Ra in rock samples collected from Cuihua Mountain National Geological Park of China have been determined using a NaI(Tl) detector. The concentrations of 226 Ra, 232 Th and 40 K in the studied rock samples range from 10.7 to 34.8, 19.9 to 53.6 and 642.7 to 1609.9 Bq kg -1 with an average of 20.4, 30.1 and 1009.5 Bq kg -1 , respectively. The concentrations of these radionuclides are compared with the typical world values. To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the air absorbed dose rate, the annual effective dose rate, the representative level index and the values of both external and internal hazard indices were evaluated and compared with the internationally approved values. The radium equivalent activity values of all rock samples are lower than the limit of 370 Bq kg -1 . The values of H ex and H in are less than unity. The mean outdoor air absorbed dose rate is 69.7 nGy h -1 , and the corresponding outdoor effective dose rate is 0.086 mSv y -1 . (authors)

Diagnostics from three rising submillimeter bursts

International Nuclear Information System (INIS)

Zhou, Ai-Hua; Li, Jian-Ping; Wang, Xin-Dong

2016-01-01

In this paper we investigate three novel rising submillimeter (THz) bursts that occurred sequentially in Super Active Region NOAA 10486. The average rising rate of the flux density above 200 GHz is only 20 sfu GHz −1 (corresponding to spectral index α of 1.6) for the THz spectral components of the 2003 October 28 and November 4 bursts, but it attained values of 235 sfu GHz −1 (α = 4.8) in the 2003 November 2 burst. The steeply rising THz spectrum can be produced by a population of highly relativistic electrons with a low-energy cutoff of 1 MeV, but it only requires a low-energy cutoff of 30 keV for the two slowly rising THz bursts, via gyrosynchrotron (GS) radiation based on our numerical simulations of burst spectra in the magnetic dipole field case. The electron density variation is much larger in the THz source than in the microwave (MW) source. It is interesting that the THz source radius decreased by 20%–50% during the decay phase for the three events, but the MW source increased by 28% for the 2003 November 2 event. In the paper we will present a formula that can be used to calculate the energy released by ultrarelativistic electrons, taking the relativistic correction into account for the first time. We find that the energy released by energetic electrons in the THz source exceeds that in the MW source due to the strong GS radiation loss in the THz range, although the modeled THz source area is 3–4 orders smaller than the modeled MW source one. The total energies released by energetic electrons via the GS radiation in radio sources are estimated, respectively, to be 5.2 × 10 33 , 3.9 × 10 33 and 3.7 × 10 32 erg for the October 28, November 2 and 4 bursts, which are 131, 76 and 4 times as large as the thermal energies of 2.9 × 10 31 , 2.1 × 10 31 and 5.2 × 10 31 erg estimated from soft X-ray GOES observations. (paper)

Properties of gamma-ray burst time profiles using pulse decomposition analysis

Energy Technology Data Exchange (ETDEWEB)

Lee, A.

2000-02-08

The time profiles of many gamma-ray bursts consist of distinct pulses, which offers the possibility of characterizing the temporal structure of these bursts using a relatively small set of pulse shape parameters. This pulse decomposition analysis has previously been performed on a small sample of bright long bursts using binned data from BATSE, which comes in several data types, and on a sample of short bursts using the BATSE Time-Tagged Event (TTE) data type. The authors have developed an interactive pulse-fitting program using the phenomenological pulse model of Norris, et. al. and a maximum-likelihood fitting routine. They have used this program to analyze the Time-to-Spill (TTS) data for all bursts observed by BATSE up through trigger number 2000, in all energy channels for which TTS data is available. They present statistical information on the attributes of pulses comprising these bursts, including relations between pulse characteristics through the course of a burst. They carry out simulations to determine the biases that their procedures may introduce. They find that pulses tend to have shorter rise times than decay times, and tend to be narrower and peak earlier at higher energies. They also find that pulse brightness, pulse width, and pulse hardness ratios do not evolve monotonically within bursts, but that the ratios of pulse rise times to decay times tends to decrease with time within bursts.

Intrinsic and cosmological signatures in gamma-ray burst time profiles: Time dilation

Energy Technology Data Exchange (ETDEWEB)

Lee, A.

2000-02-08

The time profiles of many gamma-ray bursts consist of distinct pulses, which offers the possibility of characterizing the temporal structure of these bursts using a relatively small set of pulse shape parameters. The authors have used a pulse decomposition procedure to analyze the Time-to-Spill (TTS) data for all bursts observed by BATSE up through trigger number 2000, in all energy channels for which TTS data is available. The authors obtain amplitude, rise and decay timescales, a pulse shape parameter, and the fluencies of individual pulses in all of the bursts. The authors investigate the correlations between brightness measures (amplitude and fluence) and timescale measures (pulse width and separation) which may result from cosmological time dilation of bursts, or from intrinsic properties of burst sources or from selection effects. The effects of selection biases are evaluated through simulations. The correlations between these parameters among pulses within individual bursts give a measure of the intrinsic effects while the correlations among bursts could result both from intrinsic and cosmological effects. The authors find that timescales tend to be shorter in bursts with higher peak fluxes, as expected from cosmological time dilation effects, but also find that there are non-cosmological effects contributing to this inverse correlation. The authors find that timescales tend to be longer in bursts with higher total fluences, contrary to what is expected from cosmological effects. The authors also find that peak fluxes and total fluences of bursts are uncorrelated, indicating that they cannot both be good distance indicators for bursts.

Fast Radio Burst/Gamma-Ray Burst Cosmography

Science.gov (United States)

Gao, He; Li, Zhuo; Zhang, Bing

2014-06-01

Recently, both theoretical arguments and observational evidence suggested that a small fraction of fast radio bursts (FRBs) could be associated with gamma-ray bursts (GRBs). If such FRB/GRB association systems are commonly detected in the future, the combination of dispersion measures (DM) derived from FRBs and redshifts derived from GRBs makes these systems a plausible tool to conduct cosmography. We quantify uncertainties in deriving the redshift-dependent DM_{IGM} as a function of z and test how well dark energy models can be constrained with Monte Carlo simulations. We show that with several tens of FRB/GRB systems potentially detected in a decade or so, one may reach reasonable constraints on wCDM models. When combined with Type Ia supernova (SN Ia) data, unprecedented constraints on the dark energy equation of state may be achieved, thanks to the prospects of detecting FRB/GRB systems at relatively high redshifts. The ratio between the mean value \\lt {DM_IGM} (z)\\gt and luminosity distance (D L(z)) is insensitive to dark energy models. This gives the prospect of applying SN Ia data to calibrate \\lt {DM_IGM} (z)\\gt using a relatively small sample of FRB/GRB systems, allowing a reliable constraint on the baryon inhomogeneity distribution as a function of redshift. The methodology developed in this paper can also be applied if the FRB redshifts can be measured by other means. Some caveats of putting this method into practice are also discussed.

Fast radio burst/gamma-ray burst cosmography

International Nuclear Information System (INIS)

Gao, He; Zhang, Bing; Li, Zhuo

2014-01-01

Recently, both theoretical arguments and observational evidence suggested that a small fraction of fast radio bursts (FRBs) could be associated with gamma-ray bursts (GRBs). If such FRB/GRB association systems are commonly detected in the future, the combination of dispersion measures (DM) derived from FRBs and redshifts derived from GRBs makes these systems a plausible tool to conduct cosmography. We quantify uncertainties in deriving the redshift-dependent DM IGM as a function of z and test how well dark energy models can be constrained with Monte Carlo simulations. We show that with several tens of FRB/GRB systems potentially detected in a decade or so, one may reach reasonable constraints on wCDM models. When combined with Type Ia supernova (SN Ia) data, unprecedented constraints on the dark energy equation of state may be achieved, thanks to the prospects of detecting FRB/GRB systems at relatively high redshifts. The ratio between the mean value and luminosity distance (D L (z)) is insensitive to dark energy models. This gives the prospect of applying SN Ia data to calibrate using a relatively small sample of FRB/GRB systems, allowing a reliable constraint on the baryon inhomogeneity distribution as a function of redshift. The methodology developed in this paper can also be applied if the FRB redshifts can be measured by other means. Some caveats of putting this method into practice are also discussed.

Fast radio burst/gamma-ray burst cosmography

Energy Technology Data Exchange (ETDEWEB)

Gao, He; Zhang, Bing [Department of Physics and Astronomy, University of Nevada Las Vegas, NV 89154 (United States); Li, Zhuo, E-mail: gaohe@physics.unlv.edu, E-mail: zhang@physics.unlv.edu, E-mail: zhuo.li@pku.edu.cn [Department of Astronomy, School of Physics, Peking University, Beijing 100871 (China)

2014-06-20

Recently, both theoretical arguments and observational evidence suggested that a small fraction of fast radio bursts (FRBs) could be associated with gamma-ray bursts (GRBs). If such FRB/GRB association systems are commonly detected in the future, the combination of dispersion measures (DM) derived from FRBs and redshifts derived from GRBs makes these systems a plausible tool to conduct cosmography. We quantify uncertainties in deriving the redshift-dependent DM{sub IGM} as a function of z and test how well dark energy models can be constrained with Monte Carlo simulations. We show that with several tens of FRB/GRB systems potentially detected in a decade or so, one may reach reasonable constraints on wCDM models. When combined with Type Ia supernova (SN Ia) data, unprecedented constraints on the dark energy equation of state may be achieved, thanks to the prospects of detecting FRB/GRB systems at relatively high redshifts. The ratio between the mean value and luminosity distance (D {sub L}(z)) is insensitive to dark energy models. This gives the prospect of applying SN Ia data to calibrate using a relatively small sample of FRB/GRB systems, allowing a reliable constraint on the baryon inhomogeneity distribution as a function of redshift. The methodology developed in this paper can also be applied if the FRB redshifts can be measured by other means. Some caveats of putting this method into practice are also discussed.

Detection of pseudo gamma-ray bursts of long duration

International Nuclear Information System (INIS)

Frontera, F.; Fuligni, F.; Morelli, E.; Pizzichini, G.; Ventura, G.

1981-01-01

It is known that the counting rate of both Na I and Cs I hard X-ray detectors can have intense enhancements of brief (< 1 s) duration, which appear like very short cosmic gamma-ray bursts but probably are due to phosphorescence in the detector itself. Unfortunately, this problem is not limited to short bursts. We present here three much longer (up to 80 s) pseudo-gamma-ray bursts observed during a transatlantic balloon flight. We conclude that detections of gamma-ray bursts (and probably also of hard X-ray source flares) based only on a rate increase by a single scintillator should always be confirmed by at least one other instrument. (orig.)

A Fast Radio Burst Host Galaxy

OpenAIRE

Keane, E. F.; Johnston, S.; Bhandari, S.; Barr, E.; Bhat, N. D. R.; Burgay, M.; Caleb, M.; Flynn, C.; Jameson, A.; Kramer, M.; Petroff, E.; Possenti, A.; van Straten, W.; Bailes, M.; Burke-Spolaor, S.

2016-01-01

In recent years, millisecond duration radio signals originating from distant galaxies appear to have been discovered in the so-called Fast Radio Bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity which, in tandem with a redshift measurement, can be used for fundamental physical investigations. While every fast radio burst has a dispersion measurement, none before now have had a redshift measurement, due to the difficulty in...

Physical properties and strength of cohesive strata from a hazardous area at the Western long-term slope of the Turow surface mine

Energy Technology Data Exchange (ETDEWEB)

Konderla, H; Suchnicka, H [Politechnika Wroclawska (Poland)

1991-01-01

Evaluates landslide hazards in the Turow brown coal mine in the area of a safety pillar of the Neisse river. Physical and mechanical properties of the following types of rocks from the pillar were investigated under laboratory conditions: cohesive Quaternary strata, clay layers adjacent to the coal seams and separating the seams, weathered and disintegrated granite, basalt and tuff (detritus). Rock samples were tested under conditions of tri-axial stresses, with natural water pore pressure, samples with a natural structure without artificial consolidation. The tests showed intensive fluctuations of rock properties. Nonhomogeneity of the samples and structural disturbances were determined. The tests showed the existence of landslide hazards in the Neisse river area. Recommendations for further investigations are made. 3 refs.

COSMOLOGICAL IMPLICATIONS OF FAST RADIO BURST/GAMMA-RAY BURST ASSOCIATIONS

Energy Technology Data Exchange (ETDEWEB)

Deng, Wei; Zhang, Bing, E-mail: deng@physics.unlv.edu, E-mail: zhang@physics.unlv.edu [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States)

2014-03-10

If a small fraction of fast radio bursts (FRBs) are associated with gamma-ray bursts (GRBs), as recently suggested by Zhang, the combination of redshift measurements of GRBs and dispersion measure (DM) measurements of FRBs opens a new window to study cosmology. At z < 2 where the universe is essentially fully ionized, detections of FRB/GRB pairs can give an independent measurement of the intergalactic medium portion of the baryon mass fraction, Ω {sub b} f {sub IGM}, of the universe. If a good sample of FRB/GRB associations are discovered at higher redshifts, the free electron column density history can be mapped, which can be used to probe the reionization history of both hydrogen and helium in the universe. We apply our formulation to GRBs 101011A and 100704A that each might have an associated FRB, and constrained Ω {sub b} f {sub IGM} to be consistent with the value derived from other methods. The methodology developed here is also applicable, if the redshifts of FRBs not associated with GRBs can be measured by other means.

COSMOLOGICAL IMPLICATIONS OF FAST RADIO BURST/GAMMA-RAY BURST ASSOCIATIONS

International Nuclear Information System (INIS)

Deng, Wei; Zhang, Bing

2014-01-01

If a small fraction of fast radio bursts (FRBs) are associated with gamma-ray bursts (GRBs), as recently suggested by Zhang, the combination of redshift measurements of GRBs and dispersion measure (DM) measurements of FRBs opens a new window to study cosmology. At z < 2 where the universe is essentially fully ionized, detections of FRB/GRB pairs can give an independent measurement of the intergalactic medium portion of the baryon mass fraction, Ω b f IGM , of the universe. If a good sample of FRB/GRB associations are discovered at higher redshifts, the free electron column density history can be mapped, which can be used to probe the reionization history of both hydrogen and helium in the universe. We apply our formulation to GRBs 101011A and 100704A that each might have an associated FRB, and constrained Ω b f IGM to be consistent with the value derived from other methods. The methodology developed here is also applicable, if the redshifts of FRBs not associated with GRBs can be measured by other means

Frequency Chirping during a Fishbone Burst

Energy Technology Data Exchange (ETDEWEB)

Marchenko, V.; Reznik, S., E-mail: march@kinr.kiev.ua [Institute for Nuclear Research, Kyiv (Ukraine)

2012-09-15

Full text: It is shown that gradual (more than a factor of two, in some cases - down to zero in the lab frame) reduction of the mode frequency (the so called frequency chirping) can be attributed to the reactive torque exerted on the plasma during the fishbone instability burst, which slows down the plasma rotation inside the q = 1 surface and reduces the mode frequency in the lab frame, while frequency in the plasma frame remains constant. This torque arises due to imbalance between the power transfered to the mode by energeric ions and the power of the mode dissipation by thermal species. Estimates show that the peak value of this torque exceeds the neutral beam torque in modern tokamaks and in ITER. The line-broadened quasilinear burst model, properly adapted for the fishbone case, is capable of reproducing the key features of the bursting mode. (author)

Gamma-Ray Bursts: A Radio Perspective

Directory of Open Access Journals (Sweden)

Poonam Chandra

2016-01-01

Full Text Available Gamma-ray bursts (GRBs are extremely energetic events at cosmological distances. They provide unique laboratory to investigate fundamental physical processes under extreme conditions. Due to extreme luminosities, GRBs are detectable at very high redshifts and potential tracers of cosmic star formation rate at early epoch. While the launch of Swift and Fermi has increased our understanding of GRBs tremendously, many new questions have opened up. Radio observations of GRBs uniquely probe the energetics and environments of the explosion. However, currently only 30% of the bursts are detected in radio bands. Radio observations with upcoming sensitive telescopes will potentially increase the sample size significantly and allow one to follow the individual bursts for a much longer duration and be able to answer some of the important issues related to true calorimetry, reverse shock emission, and environments around the massive stars exploding as GRBs in the early Universe.

Investigation of Non-Linear Dynamics of the Rock Massive,Using Seismological Catalogue data and Induction Electromagnetic Monitoring Data in a Rock Burst Mine.

Science.gov (United States)

Hachay, O. A.; Khachay, O. Y.; Klimko, V. K.; Shipeev, O. V.

2012-04-01

Geological medium is an open dynamical system, which is influenced on different scales by natural and man-made impacts, which change the medium state and lead as a result to a complicated many ranked hierarchic evolution. That is the subject of geo synergetics. Paradigm of physical mesomechanics, which was advanced by academician Panin V.E. and his scientific school, which includes the synergetic approach is a constructive method for research and changing the state of heterogenic materials [1]. That result had been obtained on specimens of different materials. In our results of research of no stationary geological medium in a frame of natural experiments in real rock massifs, which are under high man-made influence it was shown, that the state dynamics can be revealed with use synergetics in hierarchic medium. Active and passive geophysical monitoring plays a very important role for research of the state of dynamical geological systems. It can be achieved by use electromagnetic and seismic fields. Our experience of that research showed the changing of the system state reveals on the space scales and times in the parameters, which are linked with the peculiarities of the medium of the second or higher ranks [2-5]. Results of seismological and electromagnetic information showed the mutual additional information on different space-time levels of rock massive state, which are energetic influenced by explosions, used in mining technology. It is revealed a change of nonlinearity degree in time of the massive state by active influence on it. The description of massive movement in a frame of linear dynamical system does not satisfy the practical situation. The received results are of great significance because for the first time we could find the coincidences with the mathematical theory of open systems and experimental natural results with very complicated structure. On that base we developed a new processing method for the seismological information which can be used in

Imaging assessment of vertebral burst fracture

International Nuclear Information System (INIS)

Ding Jianlin; Liang Lihua; Wang Yujia

2006-01-01

Objective: To investigate the diagnostic value of radiography, CT and MRI in diagnosis of vertebral burst fracture. Methods: 51 patients with vertebral burst fracture were evaluated with X-ray, CT and MRI, including 3 cases in cervical vertebra, 18 cases in thoracic vertebra, and 30 cases in lumbar vertebra. The imaging features were comparatively studied. Results: Radiography showed decreased height of the vertebral body, increased antero-posterior diameter and the transverse diameter, and/or the widened interpedicle distance, the inter-spinous distance, as well as the bony fragment inserted into the vertebral canal in 28 cases(54.90%). X-ray findings similar to the compression fracture were revealed in 20 cases(39.21%). And missed diagnosis was made in 3 cases (5.88%). CT clearly demon-strated the vertebral body vertically or transversely burst crack in 49 cases (96.07%); bony fragment inserted into the vertebral canal and narrowed vertebral canal in 35 cases(68. 62% ); fracture of spinal appendix in 22 cases(43.14%). Meanwhile MRI showed abnormal signals within the spinal cord in 35 cases (68.62%),injured intervertebral disk in 29 cases(56.86% ), extradural hematoma in 12 cases(23.52% ) and torn posterior longitudinal ligament in 6 cases (11.76%). Conclusions: Radiography is the routine examination, while with limited diagnostic value in vertebral burst fracture. These patients who have nervous symptoms with simple compression fracture or unremarkable on X-ray should receive the CT or MRI examination. CT is better than MRI in demonstrating the fracture and the displaced bony fragment, while MRI is superior to CT in showing nervous injuries. CT and MRI will provide comprehensive information guiding clinical treatment of vertebral burst fracture. (authors)

Bursting of a bubble confined in between two plates

Science.gov (United States)

Murano, Mayuko; Kimono, Natsuki; Okumura, Ko

2015-11-01

Rupture of liquid thin films, driven by surface tension, has attracted interests of scientists for many years. It is also a daily phenomenon familiar to everyone in the form of the bursting of soap films. In recent years, many studies in confined geometries (e.g. in a Hele-Shaw cell) have revealed physical mechanisms of the dynamics of bubbles and drops. As for a liquid film sandwiched in between another liquid immiscible to the film liquid in the Hele-Shaw cell, it is reported that the thin film bursts at a constant speed and the speed depends on the viscosity of the surrounding liquid when the film is less viscous, although a rim is not formed at the bursting tip; this is because the circular symmetry of the hole in the bursting film is lost. Here, we study the bursting speed of a thin film sandwiched between air instead of the surrounding liquid in the Hele-Shaw cell to seek different scaling regimes. By measuring the bursting velocity and the film thickness of an air bubble with a high speed camera, we have found a new scaling law in viscous regime. This research was partly supported by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).

A POSSIBLE CONNECTION BETWEEN FAST RADIO BURSTS AND GAMMA-RAY BURSTS

International Nuclear Information System (INIS)

Zhang, Bing

2014-01-01

The physical nature of fast radio bursts (FRBs), a new type of cosmological transient discovered recently, is not known. It has been suggested that FRBs can be produced when a spinning supra-massive neutron star loses centrifugal support and collapses to a black hole. Here, we suggest that such implosions can happen in supra-massive neutron stars shortly (hundreds to thousands of seconds) after their births, and an observational signature of such implosions may have been observed in the X-ray afterglows of some long and short gamma-ray bursts (GRBs). Within this picture, a small fraction of FRBs would be physically connected to GRBs. We discuss possible multi-wavelength electromagnetic signals and gravitational wave signals that might be associated with FRBs, and propose an observational campaign to unveil the physical nature of FRBs. In particular, we strongly encourage a rapid radio follow-up observation of GRBs starting from 100 s after a GRB trigger

DEPENDENCE OF X-RAY BURST MODELS ON NUCLEAR REACTION RATES

Energy Technology Data Exchange (ETDEWEB)

Cyburt, R. H.; Keek, L.; Schatz, H. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI 48824 (United States); Amthor, A. M. [Department of Physics and Astronomy, Bucknell University, Lewisburg, PA 17837 (United States); Heger, A.; Meisel, Z.; Smith, K. [Joint Institute for Nuclear Astrophysics (JINA), Michigan State University, East Lansing, MI 48824 (United States); Johnson, E. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States)

2016-10-20

X-ray bursts are thermonuclear flashes on the surface of accreting neutron stars, and reliable burst models are needed to interpret observations in terms of properties of the neutron star and the binary system. We investigate the dependence of X-ray burst models on uncertainties in (p, γ ), ( α , γ ), and ( α , p) nuclear reaction rates using fully self-consistent burst models that account for the feedbacks between changes in nuclear energy generation and changes in astrophysical conditions. A two-step approach first identified sensitive nuclear reaction rates in a single-zone model with ignition conditions chosen to match calculations with a state-of-the-art 1D multi-zone model based on the Kepler stellar evolution code. All relevant reaction rates on neutron-deficient isotopes up to mass 106 were individually varied by a factor of 100 up and down. Calculations of the 84 changes in reaction rate with the highest impact were then repeated in the 1D multi-zone model. We find a number of uncertain reaction rates that affect predictions of light curves and burst ashes significantly. The results provide insights into the nuclear processes that shape observables from X-ray bursts, and guidance for future nuclear physics work to reduce nuclear uncertainties in X-ray burst models.

Postillumination burst of carbon dioxide in crassalacean Acid metabolism plants.

Science.gov (United States)

Crews, C E; Vines, H M; Black, C C

1975-04-01

Immediately following exposure to light, a postillumination burst of CO(2) has been detected in Crassulacean acid metabolism plants. A detailed study with pineapple (Ananas comosus) leaves indicates that the postillumination burst changes its amplitude and kinetics during the course of a day. In air, the postillumination burst in pineapple leaves generally is exhibited as two peaks. The postillumination burst is sensitive to atmospheric CO(2) and O(2) concentrations as well as to the light intensity under which plants are grown. We propose that the CO(2) released in the first postillumination burst peak is indicative of photorespiration since it is sensitive to either O(2) or CO(2) concentration while the second CO(2) evolution peak is likely due to decarboxylation of organic acids involved in Crassulacean acid metabolism.In marked contrast to other higher plants, the postillumination burst in Crassulacean acid metabolism plants can be equal to or greater than the rate of photosynthesis. Photosynthesis in pineapple leaves also varies throughout a day. Both photosynthesis and the postillumination burst have a daily variation which apparently is a complex function of degree of leaf acidity, growth light intensity, ambient gas phase, and the time a plant has been exposed to a given gas.

Burst mode trigger of STEREO in situ measurements

Science.gov (United States)

Jian, L. K.; Russell, C. T.; Luhmann, J. G.; Curtis, D.; Schroeder, P.

2013-06-01

Since the launch of the STEREO spacecraft, the in situ instrument suites have continued to modify their burst mode trigger in order to optimize the collection of high-cadence magnetic field, solar wind, and suprathermal electron data. This report reviews the criteria used for the burst mode trigger and their evolution with time. From 2007 to 2011, the twin STEREO spacecraft observed 236 interplanetary shocks, and 54% of them were captured by the burst mode trigger. The capture rate increased remarkably with time, from 30% in 2007 to 69% in 2011. We evaluate the performance of multiple trigger criteria and investigate why some of the shocks were missed by the trigger. Lessons learned from STEREO are useful for future missions, because the telemetry bandwidth needed to capture the waveforms of high frequency but infrequent events would be unaffordable without an effective burst mode trigger.

A Bayesian inversion framework for yield and height-of-burst/depth-of-burial for near-surface explosions

Energy Technology Data Exchange (ETDEWEB)

Johannesson, Gardar [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bulaevskaya, Vera [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ramirez, Abe [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ford, Sean [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rodgers, Artie [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2015-09-07

A Bayesian inversion framework is presented to estimate the yield of an explosion and height-of-burst/depth-of-burial (HOB/DOB) using seismic and air pressure data. This is accomplished by first calibrating the parameters in the forward models that relate the observations to the yield and HOB/DOB and then using the calibrated model to estimate yield and HOB/DOB associated with a new set of seismic and air pressure observations. The MCMC algorithms required to perform these steps are outlined, and the results with real data are shown. Finally, an extension is proposed for a case when clustering in the seismic displacement occurs as a function of different types of rock and other factors.

Gas nad mud volcanism formation as a result of geodynamic development of the Black sea region

International Nuclear Information System (INIS)

Dmitrievsky, A.N.; Karakin, A.V.; Kazmin, V.G.

2002-01-01

Full text : Fluidodynamic model of moving of gas-mud mixture accompanied by eruptions of mud volcanoes and gas bursts is firstly demonstrated by the example of the Black sea basin. The entire spectrum of gas bursts can be divided into gas and mud-fluid volcanoes. Emanation of hydrocarbon gases during the eruptions accompanied by powerful exploison, bursts of gas, water and fragments of rocks as well as by issue of breccia are typical for the first type of volcanoes. It was suggested that the eastern part of the Black sea forms block or subplate moving to the northeast. This conclusion is important for estimation of seismic and connected geological hazard in the studied region. It was established that deformations and seismicity were mainly confined to the edges of the East Black sea subplate while in its inner part the level of seismic activity is considerably lower.

Radon-hazard potential the Beaver basin, Utah

International Nuclear Information System (INIS)

Bishop, C.E.

1995-01-01

Indoor-radon levels in the Beaver basin of southwestern Utah are the highest recorded to date in Utah, ranging from 17.5 to 495 picocuries per liter (pCi/L). Because the U.S. Environment Protection Agency considers indoor-radon levels above 4 pCi/L to represent a risk of lung cancer from long-term exposure, the Utah Geological Survey is preparing a radon-hazard-potential map for the area to help prioritize indoor testing and evaluate the need for radon-resistant construction. Radon is a chemically inert radioactive gas derived from the decay of uranium-238, which is commonly found in rocks and soils. Soil permeability, depth to ground water, and uranium/thorium content of source materials control the mobility and concentration of radon in the soil. Once formed, radon diffuses into the pore space of the soil and then to the atmosphere or into buildings by pressure-driven flow of air or additional diffusion. The Beaver basin has been a topographic and structural depression since late Miocene time. Paleocene to Miocene volcanic and igneous rocks border the basin. Uraniferous alluvial-fan, piedmont-slope, flood-plain, and lacustrine sediments derived from the surrounding volcanic rocks fill the basin. A soil-gas radon and ground radioactivity survey in the Beaver basin shows that soils have high levels of radon gas. In this survey, uranium concentrations range from 3 to 13 parts per million (ppm) and thorium concentrations range from 10 to 48 ppm. Radon concentrations in the soil gas ranged from 85 to 3,500 pCi/L. The highest concentrations of uranium, thorium, and radon gas and the highest radon-hazard-potential are in the well-drained permeable soils in the lower flood- plain deposits that underlie the city of Beaver

An origin for short gamma-ray bursts unassociated with current star formation.

Science.gov (United States)

Barthelmy, S D; Chincarini, G; Burrows, D N; Gehrels, N; Covino, S; Moretti, A; Romano, P; O'Brien, P T; Sarazin, C L; Kouveliotou, C; Goad, M; Vaughan, S; Tagliaferri, G; Zhang, B; Antonelli, L A; Campana, S; Cummings, J R; D'Avanzo, P; Davies, M B; Giommi, P; Grupe, D; Kaneko, Y; Kennea, J A; King, A; Kobayashi, S; Melandri, A; Meszaros, P; Nousek, J A; Patel, S; Sakamoto, T; Wijers, R A M J

2005-12-15

Two short (gamma-ray bursts (GRBs) have recently been localized and fading afterglow counterparts detected. The combination of these two results left unclear the nature of the host galaxies of the bursts, because one was a star-forming dwarf, while the other was probably an elliptical galaxy. Here we report the X-ray localization of a short burst (GRB 050724) with unusual gamma-ray and X-ray properties. The X-ray afterglow lies off the centre of an elliptical galaxy at a redshift of z = 0.258 (ref. 5), coincident with the position determined by ground-based optical and radio observations. The low level of star formation typical for elliptical galaxies makes it unlikely that the burst originated in a supernova explosion. A supernova origin was also ruled out for GRB 050709 (refs 3, 31), even though that burst took place in a galaxy with current star formation. The isotropic energy for the short bursts is 2-3 orders of magnitude lower than that for the long bursts. Our results therefore suggest that an alternative source of bursts--the coalescence of binary systems of neutron stars or a neutron star-black hole pair--are the progenitors of short bursts.

CLIFF COLLAPSE HAZARD FROM REPEATED MULTICOPTER UAV ACQUISITIONS: RETURN ON EXPERIENCE