The polar form of the spherical harmonic spectrum: implications for filtering <Emphasis Type="BoldSmallCaps">grace</Emphasis> data

Representing the spherical harmonic spectrum of a field on the sphere in terms of its amplitude and phase is termed as its polar form. In this study, we look at how the amplitude and phase are affected by linear low-pass filtering. The impact of filtering on amplitude is well understood, but that on phase has not been studied previously. Here, we demonstrate that a certain class of filters only affect the amplitude of the spherical harmonic spectrum and not the phase, but the others affect both the amplitude and phase. Further, we also demonstrate that the filtered phase helps in ascertaining the efficacy of decorrelation filters used in the grace community.     

Effect of surface wave propagation in a four-layered oceanic crust model

Dispersion of Rayleigh type surface wave propagation has been discussed in four-layered oceanic crust. It includes a sandy layer over a crystalline elastic half-space and over it there are two more layers—on the top inhomogeneous liquid layer and under it a liquid-saturated porous layer. Frequency equation is obtained in the form of determinant. The effects of the width of different layers as well as the inhomogeneity of liquid layer, sandiness of sandy layer on surface waves are depicted and shown graphically by considering all possible case of the particular model. Some special cases have been deduced, few special cases give the dispersion equation of Scholte wave and Stoneley wave, some of which have already been discussed elsewhere.     

Spatial and temporal trends of dust storms across desert regions of Iran

Dust storms are among natural and anthropogenic hazards for socioeconomic resources, especially in desert regions. In recent years, dust storms have become a serious problem, especially in desert regions of Iran. This study investigates temporal and spatial variation of dust storm frequency in desert regions of Iran. The number of dusty days (NDD) are collected from 22 stations across the region. The statistical analysis of NDD time series is carried out to show both spatial and seasonal pattern of dust storm occurrence in the region. The regional map of statistical characteristics indicates a north to south increasing dust storm frequency. The spatial map also reveals higher year-to-year variation in south eastern Iran. The seasonality of NDD shows the highest frequency for summer followed by the spring and autumn seasons. The popular Mann–Kendall and the bootstrap MK test to consider serial correlation are then applied for Trend assessment. Results showed both negative (across the north and northwestern regions) and positive trend (across south and south eastern regions) in the annual and seasonal NDD time series. This north-to-south gradient in the spatial and temporal frequency NDD may arise from harsh dry and gusty winds as well as intense land use change in the south eastern territories of Iran. However, more careful and detailed studies are required to connect environmental conditions to change in NDD frequency.     

Effect of heat treatment on dynamic properties of selected rock types taken from the Salt Range in Pakistan

Temperature is one of the variables that influence the elasto-plastic behavior and integrity of rock outcrops. Fluctuations in temperature can trigger alteration of some of the mineral properties and impact the brittle-plastic transition. Initiation and propagation of thermally induced tension cracks tend to weaken most rock types. The principal goal of this study was to anticipate impacts of thermal stress-strain cycles on the dynamic response of representative rock units exposed in the Khewra Gorge of the Salt Range Punjab of Pakistan. Ten types of sedimentary rock units were sampled, including marl, dolomite, three types of limestone, and five different sandstones exhibiting varying characteristics in outcrop. Boulder specimens were collected from the field and transported to the laboratory to prepare 50 drill cores that could be subjected to thermal cycling between 50 and 200 °C in increments of 50 °C. Room temperature core samples were tested using an Erudite resonance frequency meter to measure their Q-factors and the resonance frequency (F_r) at an applied loading frequency of 7 KHz with 0.01 V output voltage. Results suggest that thermal cycling tends to reduce the dynamic Young’s modulus (E_d) and Q-factor. Other parameters, such as damping ratio (ξ), specific damping capacity (Ψ), and loss factor (?) appeared to increase with increasing temperature cycles, likely as a result of developing thermally induced tensile fractures. The resultant values of the null hypothesis (t-critical and t-stats) suggests that the null hypothesis can be discarded because there was no observable difference between the measured and expected values for the cores tested. The observations and data emanating from this study might be useful in designing low-level radioactive waste landfills, nuclear waste repositories, and deep underground excavations where the increased temperature could alter the mechanical behavior of the parent rock mass.     

Assessment of the reliability of supervised classifications of Landsat-7, ASTER,and SPOT-5 multispectral data in rock unit discriminations of Jabal Daf-Wadi Fatima area,Saudi Arabia

Multispectral, multiresolution remotely sensed data were processed to emphasize geological interpretation of Jabal Daf-Wadi Fatima area. The investigated area is situated in the central western part of Saudi Arabia and geologically consists of igneous and metamorphosed rocks overlain by sedimentary sequence belonging to the Arabian-Nubian Shield. Three sets of digital satellite data, Landsat-7 ETM+, ASTER, and SPOT-5, were used in this study. The application of image processing techniques enables to identify and delineate the lithologic units and the structural features of the study area. The results of this study indicate that the confusion matrix of the three maximum likelihood supervised classifications of the three datasets shows that the Landsat ETM+ bands scored the best degree of average and overall accuracy (77 and 78%, respectively). This classification distinguishes most of the rock units for mapping in the investigated area. The supervised classification of ASTER and SPOT bands has lower degrees of accuracy than the classified Landsat data. The supervised classification of SPOT bands has a degree of average and overall accuracy of 66 and 67%, respectively, but it is the best for distinguishing the spectral signatures of the different members of Fatima Formation (lower, middle, and upper members). The statistical analyses of the confusion matrices of classifications and the interpretation of the produced classified thematic maps revealed that the classification accuracy does not necessary depend on the spatial resolution of satellite data. The data of the highest spatial resolution such as SPOT data are also very useful in emphasizing and classifying the rock units of a small outcrop area. The detailed geological map of Jabal Daf-Wadi Fatima area is interpreted in this work from supervised classified images of different resolutions as well as the structure map of this area. This study shows that it is preferable to use the supervised classifications of multiresolution data for rock unit discrimination in detailed field mapping.     

Structural properties of Urfa stone doped with erbium oxide

In this study, we investigated the structural properties of Urfa stone (US) doped with erbium oxide (Er₂O₃). Solid US was powdered by using an agate mortar, and its elemental composition was determined using inductive coupling plasma (ICP) methods. Varying amounts of Er₂O₃ (5, 10, 20, 30, and 40%) were added as a dopant to the US powder using mechanical alloying methods. The resultant samples were sintered at 1000 °C for 1 h. The structural properties of the Er₂O₃-doped US samples were subsequently investigated using X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FTIR), and photoluminescence methods. Results from the XRD analysis of the Er₂O₃-doped US powder indicated two crystalline phases: (1) calcium oxide (CaO) or lime and (2) Er₂O₃. After the samples were sintered at 1000 °C, CaO, Er₂O₃, calcium carbonate (CaCO₃), and mixed crystalline phases were observed. Results from the FTIR analysis of the Er₂O₃-doped US samples indicated absorption bands at 711.91, 872.08, and 1396.87 cm^?1 in the spectra. Finally, photoluminescence analysis results indicated a shift in the emission and excitation bands to longer and shorter wavelengths, respectively, in the solid state (non-aqueous media) US-Er complex.     

Geospatial assessment of soil erosion intensity and sediment yield: a case study of Potohar Region,Pakistan

Estimation of spatial extent of soil erosion, one of the most serious forms of land degradation, is critical because soil erosion has serious implications on soil fertility, water ecosystem, crop productivity and landscape beauty. The primary objective of the current study was to assess and map the soil erosion intensity and sedimentation yield of Potohar region of Pakistan. Potohar is the rainfed region with truncated and complex topography lying at the top of the Indus Basin, the world’s largest irrigation networks of canals and barrages. Spatially explicit Revised Universal Soil Loss Equation (RUSLE) Model integrated with Remote Sensing-GIS techniques was used for detecting/mapping of erosion prone areas and quantification of soil losses. The results show that the Potohar region is highly susceptible to soil erosion with an average annual soil loss of 19 tons ha^?1 year^?1 of which the maximum erosion (70–208 tons ha^?1 year^?1) was near the river channels and hilly areas. The sediment yield due to the erosion is as high as 148 tons ha^?1 year^?1 with an average of 4.3 tons ha^?1 year^?1. It was found that 2.06% of the total area falls under severe soil erosion, 13.34% under high erosion, 15.35% under moderate soil erosion while 69.25% of the area lies in the low (tolerable) soil erosion. Chakwal and Jhelum districts of the region are seriously affected by erosion owing to their topography and soil properties. The information generated in this study is a step forward towards proper planning and implementation of strategies to control the erosion and for protection of natural resources. It is, hence, necessary that suitable water harvesting structures be made to control water to prevent soil erosion and provision of water in the lean season in this region. Tree plantation and other erosion control practices such as strip cropping can also minimize soil erosion in this region.     

Efficacy of laser cleaning in the removal of biological patina on the volcanic scoria of the rock-hewn churches of Lalibela,Ethiopia

The Lalibela rock-hewn churches are one of the most important religious pilgrimage sites in Ethiopia. These churches are carved from the scoriaceous basalt rock substrate, which has been exposed to attack by biological agents with significant loss of surface material. Particularly, the widespread growth of lichens and other microorganisms on the carved surfaces of the churches has proven to represent a substantial threat for the preservation of the site. In this study, laboratory tests have been conducted to assess the feasibility of using laser technology as an efficient cleaning method of biological patina from polymineralic stone substrates. Multi-analytical techniques were applied for the characterization of the stone samples collected from two of the Lalibela churches: Bete Giyorgis and Bete Amanuel. Stone samples artificially inoculated with bacteria, yeast, fungi isolates, and lichen-encrusted samples were laser cleaned using UV and IR laser wavelengths. The high content of Fe and Ti oxides and the high porosity have made the stone surfaces easily susceptible to low-energy laser treatment. Results indicate that laser cleaning can be applied to polymineralic lithotypes and UV irradiation can successfully remove lichen colonies. Further studies need to be conducted to optimize the laser procedure in polymineralic, high porosity stones.     

Chinese overseas industrial parks in Southeast Asia: An examination of policy mobility from the perspective of embeddedness

The development of overseas industrial parks is a key component of the Belt and Road Initiative and an expected experimental way of promoting inclusive globalization by inventing new forms of cooperation between China and local host countries. Policy mobility, a classic theory within international political geography addressing the connection between local and global policies, has implications for overseas industrial parks development. In this paper, we argue that policies are not easily moved directly from one place to another; instead, policies are embedded due to the role of local actors in policy mobility. This article first provides an overview of seven China-Southeast Asia economic and trade cooperation zones identified by the Ministry of Commerce, and analyzes their key participants. It then discusses policy mobility by looking into the roles of revenue, land, and talent in developing these industrial parks. The paper finds that these parks face challenges, such as the complicated geographical environments of host countries, huge pressure from enterprise investment capital, the lack of overseas service platforms, and underdeveloped agglomeration economies. In the light of the current situation, policy suggestions for the future sustainable development of overseas industrial parks are put forward.