Nonstationary frequency analysis of extreme daily precipitation amounts in Southeastern Canada using a peaks-over-threshold approach

Theoretical and Applied Climatology - In this paper, a statistical inference of Southeastern Canada extreme daily precipitation amounts is proposed using a classical nonstationary...     

Development tendencies and future prospects of recreation geography in Russia

It is pointed out that the conceptual basis for the shaping of Soviet recreation geography was provided by the logical-graphical model of a territorial recreation system as developed in the early 1970s. We emphasize that the fundamentally novel concepts of the functioning and development of the territorial recreation system built upon the adaptive and synergic research approaches began emerging and evolving in the Soviet Union during the 1980s. At a later time, this greatly enhanced the understanding of the mechanisms of market competition in the sphere of tourism business evolving in the country. The findings obtained in this study are in good agreement with internationally recognized achievements of other countries in the realm of tourism geography, more specifically in the study of cross-cultural interactions in terms of the home–destination and guest–host models. It is confirmed that the increasing current importance of economic synergy is attendant by a growth of research interest in the ethnopsychological aspects of tourism. A rationale is given to the sustainability criteria of recreation-geographical processes from the perspective of the problems of preserving the uniqueness of tourist destinations and ensuring the progressive dynamics of their main components: natural environment, population, economy, culture, and self-management bodies.     

Micromechanical aspects of the shear strength of wet granular soils

This paper presents a micromechanical model for the analysis of wet granular soils at low saturation (below 30%). The discrete element method is employed to model the solid particles. The capillary water is assumed to be in a pendular state and thus exists in the form of liquid bridges at the particle‐to‐particle contacts. The resulting inter‐particle adhesion is accounted for using the toroidal approximation of the bridge. Hydraulic hysteresis is accounted for based on the possible mechanism of the formation and breakage of the liquid bridges during wetting and drying phases. Shear test computational simulations were conducted at different water contents under relatively low net normal stresses. The results of these simulations suggest that capillary‐induced attractive forces and hydraulic hysteresis play an important role in affecting the shear strength of the soil. These attractive forces produce a tensile stress that contributes to the apparent cohesion of the soil and increases its stiffness. During a drying phase, capillary‐induced tensile stresses, and hence shear strength, tend to be larger than those during a wetting phase. The proposed model appears to capture the macroscopic response of wet granular materials and revealed a number of salient micromechanical mechanisms and response patterns consistent with theoretical considerations. Copyright © 2008 John Wiley & Sons, Ltd.     

Design and Application of Underground Mine Paste Backfill Technology

This paper reviews the design and application of paste backfill in underground hard rock mines used as ground support for pillars and walls, to help prevent caving and roof falls, and to enhance pillar recovery for improved productivity. Arching after stope filling reduces vertical stress and increases horizontal stress distribution within the fill mass. It is therefore important to determine horizontal stress on stope sidewalls using various predictive models in the design of paste backfill. Required uniaxial compressive strength (UCS) for paste backfill depends on the intended function, such as vertical roof support, development opening within the backfill, pillar recovery, ground or pillar support, and working platform. UCS design models for these functions are given. Laboratory and backfill plant scale designs for paste backfill mix design and optimization are presented, with emphasis on initial tailings density control to prevent under-proportioning of binder content. Once prepared, paste backfill is transported (or pumped) and placed underground by pipeline reticulation. The governing elements of paste backfill transport are rheological factors such as shear yield stress, viscosity, and slump height (consistency). Different models (analytical, semi-empirical, and empirical) are given to predict the rheological factors of paste backfill (shear yield stress and viscosity). Following backfill placement underground, self-weight consolidation settlement, internal pressure build-up, the arching effect, shrinkage, stope volume, and wall convergence against backfill affect mechanical integrity. An erratum to this article can be found at     

Production optimization and quality assessment of biodiesel from waste vegetable oil

Biodiesel production is worthy of continued study and optimization of production procedures because of its environmentally beneficial attributes and its renewable nature. In Egypt, millions L. of oil used for frying foods are discarded each year into sewage systems. Thus, it adds to the cost of treating effluent or pollutes waterways. This study is intended to consider aspects related to the feasibility of the production of biodiesel from waste/recycled oils in an attempt to help reduce the cost of biodiesel and reduce waste and pollution coming from waste oils. The variables affecting the yield and characteristics of the biodiesel produced from used frying oil were studied, the achieved results were analyzed and a set of recommendations was proposed. From the obtained results, the best yield percentage was obtained using a methanol/oil molar ratio of 6:1, potassium hydroxide as catalyst (1%) and 65 °C temperature for one hour. The yield percentage obtained from waste vegetable oil was comparable to that obtained from neat vegetable oil which reached 96.15% under optimum conditions. From the results it was clear that the produced biodiesel fuel, whether from neat vegetable oil or waste vegetable oil, was within the recommended standards of biodiesel fuel.     

Cross-Wavelet Analysis: a Tool for Detection of Relationships between Paleoclimate Proxy Records

Cross-wavelet transform (XWT) is proposed as a data analysis technique for geological time-series. XWT permits the detection of cross-magnitude, phase differences (= lag time), nonstationarity, and coherency between signals from different paleoclimate records that may exhibit large stratigraphic uncertainties and noise levels. The approach presented herein utilizes a continuous XWT technique with Morlet wavelet as the mother function, allows for variable scaling factors for time and scale sampling, and the automatic extraction of the most significant periodic signals. XWT and cross-spectral analysis is applied on computer generated time-series as well as two independently sampled proxy records (CO₂ content approximated from plant cuticles and paleotemperature derived from δ ¹⁸O from marine fossil carbonate) of the last 290 Ma. The influence of nonstationarities in the paleoclimate records that are introduced by stratigraphic uncertainties were a particular focus of this study. The XWT outputs of the computer-models indicate that a potential causal relationship can be distorted if different geological time-scale and/or large stratigraphic uncertainties have been used. XWT detect strong cross-amplitudes (∼200 ppm ‰) between the CO₂ and δ ¹⁸O record in the 20–50 Myr waveband, however, fluctuating phase differences prevent a statistical conclusion on causal relationship at this waveband.     

Tidal asymmetry in a tidal creek with mixed mainly semidiurnal tide,Bushehr Port,Persian Gulf

This study investigated the tidal asymmetry imposed by both the interaction of principal tides and the higher harmonics generated by distortions within a tidal creek network with mixed mainly semidiurnal tide in the Bushehr Port, Persian Gulf. Since velocity and water-level imposed by principal triad tides K₁-O₁-M₂ are in quadrature, duration asymmetries during a tidal period in this short, shallow inverse estuary should be manifest as skewed velocities. The principal tides produce periodic asymmetries including a strong ebb-dominance and a weak flood-dominance condition during spring and neap tides respectively. The higher harmonics induced by nonlinearities engender a flood-dominance condition where the convergence effects are higher than frictional effects, and an ebbdominance condition where intertidal storage are extended. Since the triad K₁-O₁-M₂ driven asymmetry is not overcome by higher harmonics close to the mouth, the periodic asymmetry dominates within the creek in which higher harmonics reinforce the weak flood-dominance (strong ebb-dominance) condition in the convergent channel (divergent area). Also, the maximum flood and the maximum ebb from all harmonic constituents occurred close to high water slack time during both spring and neap tides in this short creek. Since occational wetting of intertidal areas happened close to the high water (HW) time during spring tide, the water level flooded slowly close to the HW time of the spring tide.     

Microfacies analysis and cyclostratigraphy of the upper cretaceous- lower paleogene succession of Bir Dakhl section,north eastern desert,Egypt

The Bir Dakhl section which is located in the southern Galala plateau, north eastern desert was sampled for microfacies analysis of the upper Cretaceous–lower Paleogene succession. Microfacies analysis led to the recognition of eight mixed clastic-carbonate facies types (black shale lithofacies MF-1, pure shale lithofacies MF-2, sandy shale lithofacies MF-3, marly shale lithofacies MF-4, mudstone microfacies MF-5, foraminiferal wackestone microfacies MF-6, bioclastic wackestone microfacies MF-7, and bioclastic packstone microfacies MF-8) of the studied interval. These microfacies can be grouped into three depositional environments: inner, middle and outer ramp. The interpreted depositional environments have been suggested to range from neritic to middle bathyal (~ 700 m). Based on cyclostratigraphy, five deepening upward cycles and three shallowing upward cycles have been differentiated in Bir Dakhl section.     

A pan-sharpening method based on NSCT and formulated as compressive sensing problem

In this paper, a pan-sharpening method, using non-subsampled contourlet transform (NSCT) and the theory of compressive sensing (CS), is proposed. The NSCT is used for sparse image representation to perform a multiscale and directional decomposition of source images in order to express their detail and express the sparsity of their high frequency. The CS is used to merge the multispectral (MS) and panchromatic (pan) images from partial random measurements. Two different fusion rules are then applied. The final pan-sharpened image is obtained by inverse NSCT. Experimental results show the efficiency of the proposed method, compared with pan sharpening based on standard NSCT, in terms of visual quality and objective assessment. Moreover, the proposed technique is very effective when the storage and transmission bandwidth are limited.     

Source mechanism and parameters of the 19 October 2012 earthquake,northern Egyptian continental margin

The 19 October 2012 earthquake (M _L = 5.1) occurred in the northern continental margin of Egypt within the Nile Cone at latitude 32.35° N and longitude 31.27° E. The quake was felt over a wide area in north Egypt and East Mediterranean countries, but no casualties have been reported. This area had experienced the large earthquake (Ms = 6.7) of 12 September 1955. The fault plane solution of the 19 October 2012 earthquake is here presented based on the digital seismograms recorded by the Egyptian National Seismological Network (ENSN) and other regional seismic stations. The analysis is carried out using the well-known techniques of first motion polarities of P-wave and the amplitude ratios of P-, SH-, and SV-waves with lower hemisphere projection. The fault plane solution based on the first P-wave onset demonstrates a left lateral strike-slip faulting mechanism, while the solution based on both P-wave polarities and amplitude ratios of P-, SH-, and SV-waves reveals a reverse fault with strike-slip component trending NW–SE to NE–SW, in conformity with the N–S compression along the Hellenic Arc convergence zone. Following the Brune’s model, the source dynamic parameters for the 19 October 2012 earthquake are estimated as corner frequency = 1.47 Hz, fault radius = 0.7 km, stress drop = 22.1 MPa, seismic moment = 2.80E + 16 Nm, and moment magnitude M _w = 4.9. These parameters may provide important quantitative information for the seismic hazard assessment studies.