Workplace environmental demands and energizers at two Kuwait oil companies     

A. Al-Hemoud  W. Behbehani 《International Journal of Environmental Science and Technology》2017,14(5):983-992

The Work Compatibility Improvement Framework was developed and used to assess the environmental and ergonomic work conditions at two oil companies in Kuwait: One is a government-owned company, while the other is a private subcontractor of the government-owned company. The work compatibility presents demand–energizer environmental factors that act upon the individuals in the workplace. The reliability coefficients were tested and considered good (0.752) and excellent (0.855) for two domain conditions environment and ergonomics, respectively. Results reveal that in all of the three regions of the government-owned company (north, southwest, east) the ‘overall’ compatibility data for the ‘environment’ is perceived to be poor. The ‘ergonomics’ compatibility data seem to be average in the southeast and west, while it is considered to be poor in the north. As for the private subcontractor, the perceived ‘environment’ is considered to be poor for two departments out of four (slickline and wellhead maintenance), while considered moderate for the remaining two (maintenance and crude/chemical handling). The ‘ergonomics’ compatibility is reported to be poor for crude/chemical handling and wellhead maintenance jobs; while the conditions seem to be moderate for the maintenance and slickline jobs. The major conclusion extracted from this study is that the oil sector organizations in Kuwait are not managed as ergo-environmental enterprises where there is disharmony in the ergonomics system, environmental system, and the ergo-environmental interface interaction. These gaps in the enterprise-wide systems have a significant impact on work productivity and the environment conditions.  相似文献   

A new bounding surface model for thermal cyclic behaviour          下载免费PDF全文

C. Zhou  K.Y. Fong  C.W.W. Ng 《国际地质力学数值与分析法杂志》2017,41(16):1656-1666

To accurately predict soil volume changes under thermal cycles is of great importance for analysing the performance of many earth structures such as the energy pile and energy storage system. Most of the existing thermo‐mechanical models focus on soil behaviour under monotonic thermal loading only, and they are not able to capture soil volume changes under thermal cycles. In this study, a constitutive model is proposed to simulate volume changes of saturated soil subjected to cyclic heating and cooling. Two surfaces are defined and used: a bounding surface and a memory surface. The bounding surface and memory surface are mainly controlled by the preconsolidation pressure (a function of plastic volumetric strain) and the maximum stress experienced by the soil, respectively. Under thermal cycles, the distance of the two surfaces and plastic modulus increase with an accumulation of plastic strain. By adopting the double surface concept, a new elastoplastic model is derived from an existing single bounding surface thermo‐mechanical model. Comparisons between model predictions and experimental results reveal that the proposed model is able to capture soil volume changes under thermal cycles well. The plastic strain accumulates under thermal cycles, but at a decreasing rate, until stabilization. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Plio-Pleistocene mammals from Mille-Logya,Ethiopia, and the post-Hadar faunal change     

Denis Geraads  Denne Reed  W. Andrew Barr  René Bobe  Peter Stamos  Zeresenay Alemseged 《第四纪科学杂志》2021,36(6):1073-1089

We describe the non-primate mammalian fauna from the late Pliocene to earliest Pleistocene deposits of Mille-Logya in the Lower Awash Valley, Ethiopia, dated to c. 2.9–2.4 Ma, and divided into three successive units: Gafura, Seraitu, and Uraitele. We identify 41 mammalian taxa (including rodents), the most diverse group being the Bovidae, with 17 taxa. While the Gafura assemblage still resembles those from the earlier Hadar Formation, the younger Seraitu assemblage documents a major turnover. While there is little change in the species present across this interval, the relative abundances of various taxa change dramatically, with suids being largely replaced by open-country bovids (Alcelaphini and Antilopini). We interpret this faunal change as reflective of an environmental shift, contemporaneous with the replacement of Australopithecus afarensis by Homo in the area.  相似文献   

Importance of climate,forest fires and human population size in the Holocene boreal forest composition change in northern Europe          下载免费PDF全文

Niina Kuosmanen  Heikki Seppä  Teija Alenius  Richard H. W. Bradshaw  Jennifer l. Clear  Ludmila Filimonova  Maija Heikkilä  Hans Renssen  Miikka Tallavaara  Triin Reitalu 《Boreas: An International Journal of Quaternary Research》2016,45(4):688-702

The relative importance of climate, forest fires and human population size on long‐term boreal forest composition were statistically investigated at regional and local scales in Fennoscandia. We employ pollen data from lakes, reflecting regional vegetation, and small forest hollows, reflecting local vegetation, from Russia, Finland and Sweden to reconstruct the long‐term forest composition. As potential drivers of the Holocene forest dynamics we consider climate, generated from a climate model and oxygen isotope data, past forest fires generated from sedimentary charcoal data and human population size derived from radiocarbon dated archaeological findings. We apply the statistical method of variation partitioning to assess the relative importance of these environmental variables on long‐term boreal forest composition. The results show that climate is the main driver of the changes in Holocene boreal forest composition at the regional scale. However, at the local scale the role of climate is relatively small. In general, the importance of forest fires is low both at regional and local scales. The fact that both climate and forest fires explain relatively small proportions of variation in long‐term boreal vegetation in small forest hollow records demonstrates the complexity of factors affecting stand‐scale forest dynamics. The relative importance of human population size was low in both the prehistorical and the historical time periods. However, this is the first time that this type of data has been used to statistically assess the importance of human population size on boreal vegetation and the spatial representativeness of the data may cause bias to the analysis.  相似文献   

A new structural interpretation relating NW Libya to the Hun Graben,western Sirt Basin based on a new paleostress inversion     

K M Abdunaser  K J W McCaffrey 《Journal of Earth System Science》2015,124(8):1745-1763

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Elastic models for nonlinear response of rigid passive piles     

W. D. Guo 《国际地质力学数值与分析法杂志》2014,38(18):1969-1989

Recent study indicates that the response of rigid passive piles is dominated by elastic pile–soil interaction and may be estimated using theory for lateral piles. The difference lies in that passive piles normally are associated with a large scatter of the ratio of maximum bending moment over maximum shear force and induce a limiting pressure that is ~1/3 that on laterally loaded piles. This disparity prompts this study. This paper proposes pressure‐based pile–soil models and develops their associated solutions to capture response of rigid piles subjected to soil movement. The impact of soil movement was encapsulated into a power‐law distributed loading over a sliding depth, and load transfer model was adopted to mimic the pile–soil interaction. The solutions are presented in explicit expressions and can be readily obtained. They are capable of capturing responses of model piles in a sliding soil owing to the impact of sliding depth and relative strength between sliding and stable layer on limiting force prior to ultimate state. In comparison with available solutions for ultimate state, this study reveals the 1/3 limiting pressure (of the active piles) on passive piles was induced by elastic interaction. The current models employing distributed pressure for moving soil are more pertinent to passive piles (rather than plastic soil flow). An example calculation against instrumented model piles is provided, which demonstrates the accuracy of the current solutions for design slope stabilising piles. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Polygonal grain‐based distinct element modeling for mechanical behavior of brittle rock          下载免费PDF全文

J.‐W. Park  C. Park  J.‐W. Song  E.‐S. Park  J.‐J. Song 《国际地质力学数值与分析法杂志》2017,41(6):880-898

The microstructure of rock was numerically reproduced by a polygonal grain‐based model, and its mechanical behavior was examined by performing the uniaxial compression test and Brazilian tests via the Universal Distinct Element Code. The numerical results of the model demonstrated good agreement with the experimental results obtained with rock specimens in terms of the stress–strain behavior, strength characteristics, and brittle fracture phenomenon. An encouraging result is that the grain‐based model‐Universal Distinct Element Code model can reproduce a low ratio of tensile to compressive strength of 1/20 to 1/10 without the need for an additional process. This finding is ascribed to the fact that the geometrical features of polygons can effectively capture the effects of angularity, finite rotation, and interlocking of grains that exist in reality. A numerical methodology to monitor the evolution of micro‐cracks was developed, which enabled us to examine the progressive process of the failure and distinguish the contribution of tensile cracking to the process from that of shear cracking. From the observations of the micro‐cracking process in reference to the stress–strain relation, crack initiation stress, and crack damage stress, it can be concluded that the failure process of the model closely resembles the microscopic observations of rock. We also carried out a parametric study to examine the relationships between the microscopic properties and the macroscopic behavior of the model. Depending on the micro‐properties, the model exhibited a variety of responses to the external load in terms of the strength and deformation characteristics, the evolution of micro‐cracks, and the post‐peak behavior. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Quantifying flows along hydrological pathways by applying a new filtering algorithm in conjunction with master recession curve analysis          下载免费PDF全文

Ronan J. O'Brien  Bruce D. Misstear  Laurence W. Gill  Paul M. Johnston  Raymond Flynn 《水文研究》2014,28(26):6211-6221

Quantifying the proportion of the river hydrograph derived from the different hydrological pathways is essential for understanding the behaviour of a catchment. This paper describes a new approach using the output from master recession curve analysis to inform a new algorithm based on the Lyne and Hollick ‘one‐parameter’ signal analysis filtering algorithm. This approach was applied to six catchments (including two subcatchments of these) in Ireland. The conceptual model for each catchment consists of four main flow pathways: overland flow, interflow, shallow groundwater and deep groundwater. The results were compared with those of the master recession curve analysis, a recharge coefficient approach developed in Ireland and the semi‐distributed, lumped and deterministic hydrological model Nedbør‐Afstrømings‐Model. The new algorithm removes the ‘free variable’ aspect that is typically associated with filtering algorithms and provides a means of estimating the contribution of each pathway that is consistent with the results of hydrograph separation in catchments that are dominated by quick response pathways. These types of catchments are underlain by poorly productive aquifers that are not capable of providing large baseflows in the river. Such aquifers underlie over 73% of Ireland, ensuring that this new algorithm is applicable in the majority of catchments in Ireland and potentially in those catchments internationally that are strongly influenced by the quick‐responding hydrological pathways. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

What is the source of baseflow in agriculturally fragmented catchments? Complex groundwater/surface‐water interactions in three tributary catchments of the Wabash River,Indiana, USA          下载免费PDF全文

Marty D. Frisbee  Zachary P. Meyers  Noah S. Stewart‐Maddox  Marc W. Caffee  Philine Bogeholz  Madison N. Hughes 《水文研究》2017,31(22):4019-4038

Some conceptual models suggest that baseflow in agriculturally fragmented watersheds may contain little, if any, groundwater. This has critical implications for stream quality and ecosystem functioning. Here, we (a) identify the sources and flowpaths contributing to baseflow using ²²²Rn and ⁸⁷Sr/⁸⁶Sr and (b) quantify mean apparent ages of groundwater and baseflow using multiple isotopic tracers (CFC, SF₆, ³⁶Cl, and ³H) in 4 small (0.08 to 0.64 km²) tributary catchments to the Wabash River in Indiana, USA. ²²²Rn activities and ⁸⁷Sr/⁸⁶Sr ratios indicate that baseflow in 3 catchments is sourced primarily from groundwater; baseflow in the fourth is dominated by a source similar to agricultural run‐off. CFC‐12 data indicate that springs in 1 catchment are discharging significant proportions of water that recharged between 1974 (42 ± 2 years) and 1961 (55 ± 2 years). Those same springs have ³⁶Cl/Cl ratios between 1,381.08 ± 29.37 (×10^?15) and 1,530.64 ± 27.65 (×10^?15) indicating that a substantial proportion of the discharge likely recharged between 1975 (41 years) and 1950 (66 years). Groundwater samples collected from streambed mini‐piezometers in a separate catchment have CFC‐12 concentrations indicating that a large proportion of the recharge occurred between 1948 (68 ± 2 years) and 1950 (66 ± 2 years). Repeat sampling conducted in September 2015 after above‐average summer rainfall did not show significant decreases in mean apparent age. The relatively old ages observed in 3 of the catchments can be explained by geological complexities that are likely present in all 4 catchments, but overwhelmed by flow from the shallow phreatic aquifer in the fourth catchment.  相似文献   

Experimental determination of REE partition coefficients between zircon,garnet and melt: a key to understanding high‐T crustal processes          下载免费PDF全文

R. J. M. Taylor  S. L. Harley  R. W. Hinton  S. Elphick  C. Clark  N. M. Kelly 《Journal of Metamorphic Geology》2015,33(3):231-248

The partitioning of rare earth elements (REE) between zircon, garnet and silicate melt was determined using synthetic compositions designed to represent partial melts formed in the lower crust during anatexis. The experiments, performed using internally heated gas pressure vessels at 7 kbar and 900–1000 °C, represent equilibrium partitioning of the middle to heavy REE between zircon and garnet during high‐grade metamorphism in the mid to lower crust. The D_REE (zircon/garnet) values show a clear partitioning signature close to unity from Gd to Lu. Because the light REE have low concentrations in both minerals, values are calculated from strain modelling of the middle to heavy REE experimental data; these results show that zircon is favoured over garnet by up to two orders of magnitude. The resulting general concave‐up shape to the partitioning pattern across the REE reflects the preferential incorporation of middle REE into garnet, with D_Gd (zircon/garnet) ranging from 0.7 to 1.1, D_Ho (zircon/garnet) from 0.4 to 0.7 and D_Lu (zircon/garnet) from 0.6 to 1.3. There is no significant temperature dependence in the zircon–garnet REE partitioning at 7 kbar and 900–1000 °C, suggesting that these values can be applied to the interpretation of zircon–garnet equilibrium and timing relationships in the ultrahigh‐T metamorphism of low‐Ca pelitic and aluminous granulites.  相似文献