Overlay Model Research Articles

An assessment of groundwater potential and vulnerability in the Upper Manyame Sub-Catchment of Zimbabwe

Severe depletion and pollution of groundwater resources are of rising concern in the Upper Manyame Sub-Catchment (UMSC); Zimbabwe's most urbanised sub-catchment. Despite groundwater playing a pivotal role in the provision of potable water in the sub-catchment, it is under serious threat from anthropogenic stressors which include sewage effluents and leachates from landfills, among others. Inadequate scientific knowledge pertaining to the spatio-temporal variability of groundwater storage and vulnerability in the UMSC is further compromising its sustainability. Therefore, comprehensive assessments of UMSC's Groundwater Potential (GP) and vulnerability are crucial for its effective management. This study assessed GP and vulnerability in the UMSC using Geographic Information Systems and Remote Sensing techniques. Groundwater conditioning factors: geology, slope, land-use, drainage density, topographic index, altitude, recharge and rainfall were used to develop GP zones. Validation of the GP map was done by correlating estimated GP with historical borehole yields. An assessment of groundwater vulnerability was done at micro-catchment level (Marimba) using the GOD model; a three parameter Index Overlay Model. Marimba is the most urbanised and has the second highest borehole density. It also exhibits similar landuse characteristics as the UMSC. Furthermore, groundwater quality in Marimba was assessed from 15 sampling sites. Fifteen drinking water parameters were analysed based on the standard methods for Water and Wastewater Examination. The potability of groundwater was then assessed by comparing the measured water quality parameters with the Standards Association of Zimbabwe (SAZ) drinking water standards and/or WHO guidelines for drinking water. Repeated Measures ANOVA and Principal Component Analysis (PCA) were used to assess the spatio-temporal variations in groundwater quality and to identify key parameters, respectively. About 72% (2725.9 km2) of the UMSC was found to be of moderate GP, while 19% and 9% accounted for high and low GP, respectively. Marimba vulnerability status was dominantly moderate (77.3%). Parameters: EC, pH, coliforms, TDS, total hardness, Fe, NH4+ and turbidity exceeded SAZ and/or WHO drinking water limits on most sampling sites with DO, total and faecal coliforms showing significant variations (p < 0.05). Four Principal Components representing 84% of the cumulative variance were extracted; with PC1, PC2, PC3 and PC4 contributing 38%, 19.1%, 14.3% and 12.85%, respectively. PC1 was characterized by pH, TDS, EC and total hardness. PC2's variance was associated with elevated levels of Cl−, Zn and Cu. PC3 had high loadings of total and faecal coliforms, Fl− and turbidity while PC4 was characterized by high loadings of Pb, Fe, ammonia and turbidity. The variation in the nature of the parameters across PCs explains the complexity of pollutants within the micro-catchment. PC2 and PC4 were largely characterized by metallic compounds, suggesting pollution from mineral dissolution into the aquifers e.g. from industrial areas and dumpsites. PC3 indicate the contribution of domestic waste e.g. faecal waste from waste pipe leakages and poorly constructed pit latrines. The findings of this study are useful decision-making tools on groundwater utilisation and groundwater protection.

Joint UE Location Energy-Efficient Resource Management in Integrated Satellite and Terrestrial Networks

Integrated satellite and terrestrial networks can be used to solve communication problems in natural disasters, forestry monitoring and control, and military communication. Unlike traditional communication methods, integrated networks are effective solutions because of their advantages in communication, remote sensing, monitoring, navigation, and all-weather seamless coverage. Monitoring, urban management, and other aspects will also have a wide range of applications. This study first builds an integrated network overlay model, and divides the satellite network into two categories: terrestrial network end users and satellite network end users. The energy efficiency, throughput, and signal-to-noise ratio (SINR) are deduced and analyzed. In this paper, we discuss the influence of various factors, such as transmit power, number of users, size of the protected area, and terminal position, on energy efficiency and SINR. A satellite-sharing scheme with a combination of the user location and an exclusion zone with high energy efficiency and anti-jamming capability is proposed to provide better communication quality for end users in integrated satellite and terrestrial networks.

Application of remote sensing, GIS and MCA techniques for delineating groundwater prospect zones in Kashipur block, Purulia district, West Bengal

Demand of groundwater resources has increased manifold with population expansion as well as with the advent of modern civilization. Assessment, planning and management of groundwater resource are becoming crucial and extremely urgent in recent time. The study area belongs to Kashipur block, Purulia district, West Bengal. The area is characterized with dry climate and hard rock terrain. The objective of this study is to delineate groundwater potential zone for the assessment of groundwater availability using remote sensing, GIS and MCA techniques. Different thematic layers such as hydrogeomorphology, slope and lineament density maps have been transformed to raster data in TNT mips pro2012. To assign weights and ranks to different input factor maps, multi-influencing factor (MIF) technique has been used. The weights assigned to each factor have been computed statistically. Weighted index overlay modeling technique was used to develop a groundwater potential zone map with three weighted and scored parameters. Finally, the study area has been categorized into four distinct groundwater potential zones—excellent 1.5% (6.45 sq. km), good 53% (227.9 sq. km), moderate 45% (193.5 sq. km.) and poor ~ 0.5% (2.15 sq. km). The outcome of the present study will help local authorities, researchers, decision makers and planners in formulating proper planning and management of groundwater resources in different hydrogeological situations.

Intelligent tutoring system model based on fuzzy logic and constraint-based student model

A model for an intelligent tutoring system (ITS) that uses fuzzy logic and a constraint-based student model (CBM) is proposed. The goal of the ITS is to teach the use of punctuation in Turkish. The proposed ITS includes two student models, i.e., an overlay student model and a CBM. The student modeler in the CBM records each mistake a student make when answering questions in the system. Immediate feedback and hints are provided based on the recorded mistakes. In addition, moreover the level of students’ learning of the usage of punctuation marks is determined and overlay student model is updated according to the mistakes. If the student cannot provide the correct answer relative to the desired learning level after a specified number of attempts, this information is recorded by the overlay student model. Students can study the pages and attempt to answer the questions again. For determining the level of learning MYCIN certainty factor, the number of times the student takes for answering the question and fuzzy logic decision system are used. Crowded classes make it difficult for teachers to evaluate all student answers and provide individual feedback. The proposed ITS identifies student mistakes and provides feedback immediately. In addition, the ITS analyzes mistakes to determine the student’s learning gaps relative to specific topics and concepts. Learning to use punctuation correctly is valuable; thus, the proposed ITS model is important and worthwhile.

Energy Balance-Based Steerable Arguments Coverage Method in WSNs

Coverage is one of the important performance indexes in wireless sensor networks. When the target is covered by $k$ degrees by the sensor, more redundant data are generated, which may lead to network congestion, thus reducing the communication and coverage of the network and leading to a rapid depletion of energy. Therefore, this paper presents an energy balance and coverage control algorithm for the overlay network model based on node position relations. Areas are given by the analysis of the overlay network model. In terms of energy consumption, nodes with low energy consumption are scheduled by a given proportion of expected functions between the working nodes and the neighboring nodes, which balances the energy consumption of the entire network and optimizes network resources. Finally, the simulation results show that the proposed $k$ -degree coverage algorithm not only improves the coverage quality of the network but also reduces the rapid energy consumption and prolongs the service life of the network.

Risk of seawater intrusion on coastal community of Bentota river basin Sri Lanka

Abstract Land degradation in coastal area is one of the major critical problems affecting the future economic development of Sri Lanka. Eighty percent of land in Bentota river basin has been abandoned and 25km distance along the Bentota river has already been affected by the seawater intrusion. Temporal and spatial variation of physicochemical parameters of selected dug wells, all surface water bodies and soil parameters were measured to detect the magnitude of the salinity due to seawater intrusion during August 2016 to March 2017 by using a systematic sampling method. Surface water, groundwater and soil salinity levels were comparatively very high in the river basin with respect to the WHO standards. With reference to the developed GIS salinity risk assessment weighted overlay model the highly saline, moderately saline, slightly saline and non-saline land extent with respect to the total land extent were 10.16%, 19.47%, 40.18% and 29.79% respectively. The highest economic loss was occurred due to the reduction of agricultural productions in the area (2279ha abandoned) and it was about 3,624,000 USD per year. Therefore, 52% from the total population was economically not active with the reduction of agricultural sector in the area. The total annual economic loss in the coastal community was 7,529,698.50 USD per year and it was directly happened due to the seawater intrusion.

Aquifer Vulnerability Assessment for Sustainable Groundwater Management Using DRASTIC

Groundwater management and protection has been facilitated by computational modeling of aquifer vulnerability and monitoring aquifers using groundwater sampling. The DRASTIC (Depth to water, Recharge, Aquifer media, Soil media, Topography, Impact of vadose zone media, and hydraulic Conductivity) model, an overlay and index GIS model, has been used for groundwater quality assessment because it relies on simple, straightforward methods. Aquifer vulnerability mapping identifies areas with high pollution potential that can be areas for priority management and monitoring. The objectives of this study are to demonstrate how aquifer vulnerability assessment can be achieved using DRASTIC with high resolution data. This includes calibrating DRASTIC weights using a binary classifier calibration method with a genetic algorithm (Bi-GA), identifying areas of high potential aquifer vulnerability, and selecting potential aquifer monitoring sites using spatial statistics. The aquifer vulnerability results from DRASTIC using Bi-GA were validated with a well database of observed nitrate concentrations for a study area in Indiana. The DRASTIC results using Bi-GA showed that approximately 42.2% of nitrate detections &gt;2 ppm are within “High” and “Very high” vulnerability areas (representing 3.4% of study area) as simulated by DRASTIC. Moreover, 53.4% of the nitrate detections were within the “Moderate” vulnerability class (26.9% of study area), and only 4.3% of the nitrate detections were within the “Low” vulnerability class (60.1% of study area). Nitrates &gt;2 ppm were not detected at all within the “Very low” vulnerability class (9.6% of area). “High” and “Very high” vulnerability areas should be regarded as priority areas for groundwater monitoring and efforts to prevent groundwater contamination. This case study suggests that the approach may be applicable to other areas as part of efforts to target groundwater management efforts.

Study on the clinical and imaging features of solitary pulmonary glass nodule

Objective To investigate the imaging features of the elderly patients with GGN and to guide the follow-up. Methods Thirty-four cases of elderly patients with pulmonary GGN were enrolled in this study, including 14 cases of adenocarcinoma in situ (AIS) and 20 cases of invasive adenocarcinoma (IAC). The clinical characteristics of these patients were analyzed and compared.The CT imaging features of burr sign, lobulated sign, pleural retraction sign, vacuole sign and solid component were analyzed by two doctors via blind method.The average diameter, volume, mass, volume doubling time (VDT) and mass doubling time (MDT) of GGN were measured and calculated by software layer by layer overlay model. Results There were no statistically significant differences between the group AIS and group IAC in age, gender, smoking history (P>0.05); The burr sign, lobulated sign, vacuole sign, pleural retraction sign and the average diameter had no significant difference (P>0.05). There were statistically significant difference between the group AIS and group IAC in the solid component incidence (14.3%, 65%, P=0.003), volume ( (714.4+ 261.8) mm3, (927.2±259.7) mm3, t=2.344, P=0.025), mass ( (376.4±144.0) mg, (586.8±182.0) mg, t=3.600, P=0.001), volume doubling time ( (1511.1±1098.2) d, (654.1±229.0) d, t=-2.876, P=0.012), quality doubling time ( (1427.4±989.3) d, (540.4±190.7) d, t=-3.312, P=0.005). Conclusion The signs of solid components, volume, mass, VDT, MDT can be used as an important basis for identification of AIS and GGN in the elderly patients.The treatment of the elderly patients with GGN should be based on the basic diseases, life expectancy, surgical risk and imaging features of the elderly patients, so as to give more appropriate treatment strategies for the elderly patients. Key words: Lung cancer; Ground-glass nodule; Elderly; Volume; Mass; Doubling time

Geospatial landslide hazard zonation for district pauri garhwal, Uttarakhand, India, Using quantitative methods

Introduction: Landslides are one of the critical natural processes, which cause enormous damage to life and property..Uttarakhand Himalaya is vital to sustainity of region. This region is very fragile due to topographic and climatic condition. Landslides in the mountainous terrains are natural derivational processes and one of the most. There is a need for Landslide Hazard Zonation for identification of potential landslide areas. Keeping this in mind one hilly district, Pauri district of Uttarakhand, India was selected. Materials and Methods: The present study is an attempt towards development of a landslide model by using multi-criteria decision analysis in GIS and remote sensing techniques for landslide hazard zonation. The IRS LISS-4 satellite imageries, Survey of India topographical maps, and ancillary data were used as inputs to the study. The data layers of land use–land cover and geology were interpreted from satellite image and available ancillary data. Other raster thematic layers, i.e., slope, aspect, elevation, and drainage density, have been generated in Arc info three-dimensional analyst tool using ASTER DEM of 30 m resolution. A numerical rating scheme for the factors was developed for spatial data analysis in GIS. Results and Decision: Using high-resolution LISS-IV and Cartosat-2A, merged data of 2011–2012 landslides were mapped by visual interpretation of satellite image. A total of 167 landslides have been identified. Elevation map of Pauri district was prepared by classifying digital elevation model into 5 elevation categories. Distribution of landslides in different elevation categories is also done. Maximum landslides have occurred in elevation category (710–1134 m) and (185–709 m). Slope map has been generated and classifi ed into 6 slope classes, i.e. 0°–5°, 5°–10°, 10°–20°, 20°–30°, 30°–40°, and more than 40°. Distribution of landslides in different slope categories is also done. Maximum landslides have occurred in slopecategories (10°–20°), (20°–30°), and (30°–40°). Aspect map has been generated and classified into 8 aspect classes. Maximum landslides have occurred in aspect categories South-West (14.37%), South (35.97%), and South East (15.57%) directions. The Southern aspect (SW-S-SE) contributes to 65.91% of total landslides. Drainage density map has been generated from ASTER DEM using three-dimensional Analyst tool and classified into 6 classes, namely 0–2, 2–4, 4–6, 6–8, and more than 8 (km/sq.km). Geological map of Pauri district has been adopted from Geological map from Geological SOI. Rock types such as phyllites, quartzites, slates, siltstone, sandstones, graywacks, granitoids, alluvium, crystallines and metamorphics, and limestones are present in the district. Distribution of landslides in different drainage density categories is also done. Maximum landslides have occurred in drainage density category 2–4, 4–6, and 6–8 (km/sq.km). LULC map of Pauri was classified into various classes such as water body, forest scrub, wasteland/scrub, tree-clad, forest evergreen, agriculture land, built up, forest deciduous open, and forest deciduous dense/close. Maximum landslides have occurred in forest deciduous open category (84) followed by agriculture land (22), forest scrub (14), forest evergreen and forest deciduous dense/close (13 each), and water body. Conclusion: The above-mentioned 6 layers were integrated in the weighted overlay model of Arc Info and weights were assigned corresponding to landslide occurrence in these layers. The influence of the layer in causing landslide has also assigned. The final LHZ map generated after processing 6 themes. The final map has been classified into 3 categories, namely high, moderate, and low hazard categories. Of a total of 167 landslides, 110Landslides fall in the high HZ and 43 landslides fall in moderate HZ category while only 14 landslides fall in the low HZ category. 34.01% of the district falls under low HZ category and 40.73% falls under moderate HZ category while 25.26 under high HZ category. More layers need to be added in the model to obtain more precision. This map is not checked in the fi eld ground truth.

Integrated Weighted Overlay Model Using Inverse Distance Weightage for Assessing Groundwater Quality

Groundwater management is a potential solution to the global water crisis. This study assessed the groundwater quality at Mettupalayam, Tamil Nadu, India in order to determine its suitability for drinking. Groundwater samples were collected and their physicochemical parameters such as pH, electrical conductivity (EC), total hardness (TH), total dissolved solids (TDS), Ca2+, Mg2+, SO42- and Cl- were determined and benchmarked with standard drinking water requirements. The variations of these parameters were presented spatially. The groundwater is generally brackish and hard; and of low alkalinity and high salinity. Consequently, the groundwater in most parts of the study area is unsuitable for drinking without treatment. It is recommended that point and nonpoint sources of groundwater pollution at Mettupalayam should be identified, monitored and managed in order to protect the groundwater resource.

Cooperative Hybrid Spectrum Sharing: A NOMA-based Approach

Non-orthogonal multiple (NOMA) access using successive interference cancellation and cognitive radio are two promising techniques for enhancing the spectrum efficiency and utilization for future wireless communication systems. This paper presents a NOMA-based cooperative hybrid spectrum sharing protocol for cognitive radio networks. A two phase decode-and- forward (DF) relaying scheme in a multi-relay scenario is considered. Each secondary transmitter is grouped into one of the two clusters: a non-cooperative cluster (NCC) and a cooperative cluster (CC). The cluster head (CH) of the CC working as the best DF relay for the primary system is permitted to transmit its own signal superimposed on the primary signal using a NOMA approach in exchange for cooperation. On the other hand, the CH of the NCC transmits in parallel with the primary system satisfying a predefined peak transmit power and peak interference power constraints that guarantee a given primary quality of the service requirement. It is demonstrated that the performances of both the primary and secondary systems increase with the increasing number of secondary nodes. The simulation and theoretical results affirm the efficacy of the proposed protocol compared to the traditional overlay and underlay models in terms of the outage probability and the ergodic capacity.

International portfolio optimisation with integrated currency overlay costs and constraints

International financial portfolios can be exposed to substantial risk from variations of the exchange rates between the countries in which they hold investments. Nonetheless, foreign exchange can both generate extra return as well as loss to a portfolio, hence rather than just being avoided, there are potential advantages to well-managed international portfolios. This paper introduces an optimisation model that manages currency exposure of a portfolio through a combination of foreign exchange forward contracts, thereby creating a “currency overlay” on top of asset allocation. Crucially, the hedging and transaction costs associated with holding forward contracts are taken into account in the portfolio risk and return calculations. This novel extension of previous overlay models improves the accuracy of the risk and return calculations of portfolios. Consequently, more accurate investment decisions are obtained through optimal asset allocation and hedging positions. Our experimental results show that inclusion of such costs significantly changes the optimal decisions. Furthermore, effects of constraints related to currency hedging are examined. It is shown that tighter constraints weaken the benefit of a currency overlay and that forward positions vary significantly across return targets. A larger currency overlay is advantageous at low and high return targets, whereas small overlay positions are observed at medium return targets. The resulting system can hence enhance intelligent expert decision support for financial managers.

Dynamic performance of a multi-ribbed belt based on an overlay constitutive model of carbon-black-filled rubber and experimental validation

The focus of this work is the accurate prediction of dynamic mechanical performances of a multi-ribbed belt span. An overlay constitutive model, which consists of hyperelastic, viscoelastic and elastoplastic parts coupled in parallel, is established to describe mechanical properties of carbon-black-filled rubber material used in the belt. A uniaxial tensile test and a uniaxial compressional test are conducted to obtain the hyperelastic material parameters of the constitutive model, and a simple dynamic shear test is used to identify the viscoplastic material parameters via a standard genetic algorithm. Finite element (FE) simulations with the constitutive model are performed to simulate static and hysteretic dynamic characteristics of rubber specimens in these tests. By comparing the simulation results with experiments, the accuracy of the constitutive model and its material parameters is validated. A three-dimensional FE model based on the constitutive model is established to predict both longitudinal and transverse dynamic performances of the multi-ribbed belt span and its good agreements with experimental results are achieved.

Measuring and Advancing Experimental Design Ability in an Introductory Course without Altering Existing Lab Curriculum.

Introductory biology courses provide an important opportunity to prepare students for future courses, yet existing cookbook labs, although important in their own way, fail to provide many of the advantages of semester-long research experiences. Engaging, authentic research experiences aid biology students in meeting many learning goals. Therefore, overlaying a research experience onto the existing lab structure allows faculty to overcome barriers involving curricular change. Here we propose a working model for this overlay design in an introductory biology course and detail a means to conduct this lab with minimal increases in student and faculty workloads. Furthermore, we conducted exploratory factor analysis of the Experimental Design Ability Test (EDAT) and uncovered two latent factors which provide valid means to assess this overlay model’s ability to increase advanced experimental design abilities. In a pre-test/post-test design, we demonstrate significant increases in both basic and advanced experimental design abilities in an experimental and comparison group. We measured significantly higher gains in advanced experimental design understanding in students in the experimental group. We believe this overlay model and EDAT factor analysis contribute a novel means to conduct and assess the effectiveness of authentic research experiences in an introductory course without major changes to the course curriculum and with minimal increases in faculty and student workloads.

Optical constants of electroplated gold from spectroscopic ellipsometry

The optical constants of an opaque electroplated gold film (Laser Gold from Epner Technology Inc.), were determined by spectroscopic ellipsometry at room temperature over the spectral range from 0.142μm in the vacuum ultraviolet to 36μm in the infrared (photon energy range 0.034–8.75eV). Data from two separate ellipsometer instruments covering different spectral ranges were analyzed simultaneously. The optical constants n&k or ε1&ε2 were determined by fitting an oscillator dispersion model combining Drude, Gaussian, and Sellmeier dispersion functions to the experimental Ψ and Δ data.The data were analyzed using both an ideal bulk substrate model and a simple overlayer model to account for surface roughness. Including the optical surface roughness layer improved ellipsometric data fits in the UV, and using a separate Drude function for the surface layer improved fits in the infrared. The surface roughness was also characterized using an Atomic Force Microscope.Using an oscillator dispersion model for the optical constants determined in this work allows for more realistic extrapolation to longer infrared wavelengths. Extending optical constants out to 50μm and beyond is important for calibrating far-infrared reflectance measurements. Applications include understanding the thermal performance of cryogenic space-based instruments, such as the James Webb Space Telescope (JWST).

Land suitability assessment for urban green space using AHP and GIS: A case study of Ahvaz parks, Iran

Soil is a vital parameter for planting design in urban green spaces especially in adverse climate conditions. In this study, the utilization of analytic hierarchy process (AHP) in surveying land suitability for urban green space from measured criteria like suitability indices, including physical (i.e. clay, silt, sand, bulk density, penetration resistance), chemical (i.e. electrical conductivity, sodium absorption ratio, organic matter, Olsen phosphorus, water soluble potassium and DTPA-extractable of Fe, Zn, Cu, Mn) and heavy metal (i.e. total Ni, Cd and Pb) properties of soil and topography attributes (i.e. slope degree) data were investigated. The subjective value judgment, in light of questionnaire survey was utilized for pair-wise comparison after standard AHP method in a structure of four criteria (suitability indices) alongside related sub-criteria (19 factors). AHP method and GIS techniques were combined to create suitability map. The outcomes demonstrated that less than 8.86% of the all study region has no restriction and 34.54% has extreme restrictions for green space land use. The southern part of the riverside parks had higher suitability, whereas the northern area had lower suitability. The real limiting variables include soil compaction, soil salinity, and Zn deficiency; albeit direct mild accumulations were for lead in Ahvaz riverside parks. This study delineates the efficacy of AHP and weighted overlay model for the soil suitability investigation of green space in the study territory. In light of the outcomes, bulk density and organic matter are the most vital indices of soil in urban green space.

APPLYING IO AND AHP TO LOCATE COASTAL TOURISM SITES USING GIS: A CASE STUDY OF MAZANDARAN PROVINCE, IRAN

Increase in tourism demand in the coastal areas of Mazandaran Province, Iran, as one of the major tourist attractions near Tehran, has led to tourism development and consequently adverse environmental impacts. However, given the tourism potential within the region, tourism managers and planners seek to follow sustainable development principles. In this regard, determining sites capable of tourism development and finding an optimal site among the alternatives are two main challenges that they are facing. Therefore, this study aims to both identify and prioritize the suitable sites for coastal tourism. For this purpose, the methodology was employed in two stages. In the first stage, by integrating Index Overlay (IO) model and analytic hierarchy process (AHP), suitable sites for coastal tourism development were determined using geographical information system (GIS). In this regard, the ecological and socio-economic criteria, with 10 sub-criteria, were considered as the main criteria to identify the intended sites. The factor maps were integrated according to IO model in GIS. Meanwhile, based on the relative importance, the criteria, sub-criteria and classes were weighted using AHP. In the second stage, the selected sites were prioritized based on AHP and the most suitable alternative was identified accordingly. The results of this study indicate that combining IO with AHP in GIS can be employed as a suitable tool by decision-makers to determine appropriate sites for coastal tourism development. This study also demonstrates that a well-structured spatial decision support system (SDSS) can provide a comprehensive framework to assist decision-makers in sustainable tourism development.

Topology-aware overlay network in mobile IP environment

An overlay network is a computer network which is built on the top of an underlying physical network. With the mobile internet access becoming the leading tool, overlay must be changing with different IP addresses, which may incur a large number of unnecessary update messages to overlay network. In recent years, mobile IP is being spread widely as one of fundamental protocols of mobile internet, which can guarantee overlay network unchangeable. However, the overlay efficiency may be affected negatively due to the mismatch between overlay and mobile IP network. In this paper, we present a topology-aware overlay network model. In the model, we proposed near-home principle applied in the joining procedure in mobile IPv4 environment and near-ROSP principle in mobile IPv6 environment. In our simulation, our proposed near-home principle and near-ROSP principle could do better to alleviate the mismatch between overlay and mobile IP network.

GIS-based surface irrigation suitability analysis: a case study of Walga sub-basin, Oromia Region, Ethiopia

Irrigation development could improve agricultural productivity and enhance socioeconomic development of the community. Though agriculture is the leading economic development sector of Ethiopia, most of the country's cultivated land is under rain-fed farming. Assessment of GIS-based irrigation suitability analysis with regard to the prevailing slope, soil, land use/land cover and surface water resources has been carried out. Geo-referenced irrigation suitability map of the watershed area for the intended irrigation method was produced using ArcGIS weighted overlay model. Results of the suitability analysis revealed that about 45.72% (135,519.2 ha) of the watershed area is categorised in the range of highly suitable to marginally suitable for surface irrigation development as a result of combined effect of slope, soil and land use land cover suitability. Potentially suitable sites for surface irrigation development were evaluated for the selected dominant crops (maize, soybean and sesame) in the sub-watershed. Accordingly, Amanya, Rebu, Kulit, Nano, Walga and Darge river catchments have a total potentially irrigable area of 41.32% (122,488.2 ha). The analysis results from the present study might be providing a useful information for decision makers.

Groundwater Vulnerability Assessment of the Pingtung Plain in Southern Taiwan.

In the Pingtung Plain of southern Taiwan, elevated levels of NO3−-N in groundwater have been reported. Therefore, efforts for assessing groundwater vulnerability are required as part of the critical steps to prevent and control groundwater pollution. This study makes a groundwater vulnerability assessment for the Pingtung Plain using an improved overlay and index-based DRASTIC model. The improvement of the DRASTIC model is achieved by reassigning the weighting coefficients of the factors in this model with the help of a discriminant analysis statistical method. The analytical results obtained from the improved DRASTIC model provide a reliable prediction for use in groundwater vulnerability assessment to nitrate pollution and can correctly identify the groundwater protection zones in the Pingtung Plain. Moreover, the results of the sensitivity analysis conducted for the seven parameters in the improved DRASTIC model demonstrate that the aquifer media (A) is the most sensitive factor when the nitrate-N concentration is below 2.5 mg/L. For the cases where the nitrate-N concentration is above 2.5 mg/L, the aquifer media (A) and net recharge (R) are the two most important factors.