Energy Balance Technique Research Articles

Exploration of soliton solution of coupled Drinfel’d–Sokolov–Wilson equation under conformable differential operator

The aim of this paper is to study the nonlinear couple Drinfel’d–Sokolov–Wilson (DSW) equation under conformable differential operator (CDO) that plays an important role in describing the shallow water in fluid mechanics, plasma physics, nonlinear optics and Bose–Einstein condensate (soliton formation). The Tanh–Coth and energy balance techniques are implemented in this work to explore some travelling wave solutions. These analytical methods yield various solutions for the considered DSW equation. The solutions obtained from both method are expressed in the form of hyperbolic and trigonometric function. Furthermore, the dynamic behaviour of the obtained solutions are illustrated, via 2D and 3D curves. Additionally, the effect of the conformable differential operator on dynamics of wave solutions is studied via 2D graphs.

Construction of optical solitary wave solutions and their propagation for Kuralay system using tanh-coth and energy balance method

In this article, we study the complex coupled Kuralay system (CKS), which have many applications in different field such as ferromagnetic material and fiber optics. We implement an analytical method, namely, the tanh–coth method to considered system to formulate a system of algebraic equations. Solving the obtained system, we acquire different traveling wave solutions that are expressed in term of hyperbolic tangent functions and hyperbolic cotangent functions. Also, we employ the energy balance technique to the selected model to sort out the behavior of traveling wave solutions. By this method, we obtain periodic wave solution that are expressed in term of cosine function. In order to show the graphical presentation of the acquired solitary waves solutions, 3D and 2D curve are created by selecting well-suited parametric values via Mathematica.

Estimating Completely Remote Sensing-Based Evapotranspiration for Salt Cedar (Tamarix ramosissima), in the Southwestern United States, Using Machine Learning Algorithms

Accurate estimation of evapotranspiration (ET) is a prerequisite for water management in arid regions. Field based methods estimate point-wise ET accurately, but the challenge is in estimating ET over a region with high accuracies. Machine learning based approaches were taken to estimate ET over a large spatial scale using the Bowen Ratio Energy Balance (BREB) technique. The BREB method depends on terrestrial energy balance equations to estimate ET. Thus, remote sensing-based parameters representing variables in the energy balance equation, and vegetation index representing plant health conditions were used in the model. The study was conducted in the arid areas of the southwestern United States, where dense patches of Salt cedar consume water from the primary water source. The preliminary model used enhanced vegetation index (EVI), global horizontal irradiance (GHI), surface temperature (TS), and relative humidity (RH) as parameters. The k-nearest neighbor method consistently generated poor accuracies. When all the parameters were used, accuracies of the other models varied within 90–94%. When one predictor parameter was dropped, the best model produced accuracies between 90 to 93%, which dropped to 87–92% when a second variable was dropped. Random forest and support vector machine with radial kernel consistently produced the best predictive accuracies.

The RGD region of bone sialoprotein affects metabolic activity in mice

IntroductionBone sialoprotein (BSP) is a key regulator of mineralized tissue formation. Previously, we generated BSP-KAE knock-in mice (KAEKI mice) by substituting a non-function KAE (lysine-alanine-glutamic acid) for the integrin-binding RGD (arginine-glycine-aspartic acid) sequence and reported a vital role of the BSP-RGD motif in modulating the periodontal ligament (PDL). Specifically, histologically a disorganization of the PDL was noted, resulting in a weakened function of the PDL as measured by dynamic mechanical analysis. Intriguingly, also noted was a weight gain as KAEKI mice aged. While several proteins associated with mineralized tissues are reported to affect energy metabolism, the metabolic role of the BSP-RGD region has yet to be elucidated. Here we focus on defining the role of the BSP-RGD region in metabolic activity.MethodsBody weight, body composition, and caloric intake were measured in wild type (WT) and KAEKI mice. Energy expenditure was estimated using energy balance technique. Epididymal fat, interscapular fat, and liver were harvested for histological analysis. Systemic metabolic phenotype was assessed by sera analyses, insulin tolerance and glucose tolerance tests.ResultsThe results showed that KAEKI mice developed mild obesity starting from 13 weeks postnatal (wpn). The increase in body weight correlated with an increase in lean mass and visceral adiposity. Histological examination revealed adipocyte hypertrophy in white epididymal fat and interscapular brown fat in KAEKI vs. WT mice at 17 wpn. Metabolic profiling indicated that KAEKI mice had dyslipidemia and hyperleptinemia but no significant changes in glucose metabolism. Energy balance analyses revealed that hyperphagia preceded weight gain in KAEKI mice.ConclusionThese data suggest that the RGD region of BSP affects energy metabolism by regulating food intake, with further studies warranted to uncover the underlying mechanisms.

Ultraviolet to far infrared self-consistent analysis of the stellar populations of massive starburst galaxies at intermediate redshifts

ABSTRACT We study in detail the properties of the stellar populations of 111 massive [log (M⋆/M⊙) ≥ 10] dusty [far-infrared (FIR)-selected] starburst (SFR/SFRMS > 2) galaxies at 0.7 < z < 1.2. For that purpose, we use self-consistent methods that analyse the UV-to-FIR broad-band observations in terms of the stellar light and dust re-emission with energy-balance techniques. We find that the emission of our starburst galaxies can be interpreted as a recent star formation episode superimposed on a more evolved stellar population. On average, the burst age is ∼80 Myr and its attenuation ∼2.4 mag. Assuming our starburst galaxies at half their lifetimes, we infer a duration of the starburst phase of ∼160 Myr. The median stellar mass and star formation rate (SFR) are log (M⋆/M⊙) ∼ 10.6 and ∼220 M⊙yr−1. Assuming this SFR and the inferred duration of the starburst phase, the stellar mass added during this phase corresponds to ∼40 per cent the median stellar mass of our sample. The young-population age determines the position of our galaxies in the M⋆–SFR plane. Galaxies located at the largest distances of the MS present shorter young-population ages. The properties of the underlying stellar population cannot be constrained accurately with our broad-band data. We also discuss the impact of including the FIR data and energy-balance techniques in the analysis of the properties of the stellar populations in starburst galaxies.

Application of a Heuristic Method to Solve Nonlinear Oscillators with Irrational Forces

This paper applies another amplitude-frequency relationship as of late established by Yazdi and Tehrani (Alexandria Engineering Journal 54 99-103, 2015) to analyze periodical solutions of nonlinear oscillators; such oscillators are considered emphatically nonlinear on the grounds that they contain an irrational force term. Estimation strategy is straightforward yet additionally helpful and its formulation depends on combining the energy balance technique with an uncommon collocation point. At long last, we uncover the convenience and proficiency of the proposed technique resolving three instances of conservative nonlinear oscillators in which the maximum relative error acquired is $2.5\%.$ Exposed models show that the strategy has a high precision to solve mechanical issues of both small and huge estimations of the oscillation amplitude. Finally, the methodology used can be very useful for the study of nonlinear oscillators in basic undergraduate physics and mechanics courses.

A remote sensing and modeling integrated approach for constructing continuous time series of daily actual evapotranspiration

Satellite remote sensing-based surface energy balance (SEB) techniques have emerged as useful tools for quantifying spatialized actual evapotranspiration at various temporal and spatial scales. However, discontinuous data acquisitions and/or gaps in image acquisition due to cloud cover can limit the applicability of satellite remote sensing (RS) in agriculture water management where continuous time series of daily crop actual evapotranspiration (ETc act) are more valued. The aim of the research is to construct continuous time series of daily ETc act starting from temporal estimates of actual evapotranspiration obtained by SEB modelling (ETa eb) on Landsat-TM images. SEBAL model was integrated with the FAO 56 evaporation model, RS-retrieved vegetative biomass dynamics (by NDVI) and on-field measurements of soil moisture and potential evapotranspiration. The procedure was validated by an eddy covariance tower on a vineyard with partial soil coverage in the south of Sardinia Island, Italy. The integrated modeling approach showed a good reproduction of the time series dynamics of observed ETc act (R2 =0.71, MAE=0.54 mm d-1, RMSE=0.73 mm d-1). A daily and a cumulative monthly temporal analysis showed the importance of integrating parameters that capture changes in the soil-plant-atmosphere (SPA) continuum between Landsat acquisitions. The comparison with daily ETc act obtained by the referenced ET fraction (ETrF) method that considers only weather variability (by ETo) confirmed the lead of the proposed procedure in the spring/early summer periods when vegetation biomass changes and soil water evaporation have a significant weight in the ET process. The applied modelling approach was also robust in constructing the missing ETc act data under scenarios of limited cloud-free Landsat acquisitions. The presented integrated approach has a great potential for the near real time monitoring and scheduling of irrigation practices. Further testing of this approach with diverse dataset and the integration with the soil water modeling is to be analyzed in future work.

Feasibility of using an energy balance to measure evapotranspiration in green stormwater infrastructure.

Effective green stormwater infrastructure (GSI) design requires comprehensive quantification of the volume of water that can be treated or removed over a given time period. It is recognized that evapotranspiration (ET) can be a substantial pathway for stormwater volume reduction in bioretention systems. However, measuring ET is often difficult and expensive, such as with lysimeters or a mass balance approach. This research focused on a new technique for quantifying ET in bioretention systems by exploring an approach using thermal imaging to calculate ET by measuring the flux of energy at the canopy surface. This thermal imaging approach was compared to ET measurements given by a traditional mass balance approach. The experimental setup had three benchtop scale vegetated lysimeters planted with Switchgrass. Time lapse thermal images of the Switchgrass plants were taken at 10 second intervals and paired with meteorological data. The data were used in an energy balance to estimate the mass of water lost from the lysimeter plant/soil system. That mass was compared to the change in weight measured by weighing the lysimeter before and after the data collection period. For comparison, reference ET was also calculated for the vegetated systems using three common reference ET equations. The uncalibrated energy balance equation developed here estimated an averaged ET over 12 data collection days within 1 mm of the mass balance measured ET. These findings demonstrate the feasibility of using a thermal image energy balance technique to estimate ET.

Experimental study of heat transfer characteristics of finned-tube and circular-pore heat exchangers in oscillatory flow

This work is concerned with an experimental investigation of the thermal performance of two thermoacoustic heat exchangers characterized by different pore geometries, namely a circular-pore geometry and a finned-tube geometry. A standing wave engine, where the heat exchangers under test play the role of ambient HXs, is used as test-rig. Heat transfer rates measurements by standard energy balance techniques and dynamic pressure measurements are used to assess the impact of the two heat exchangers on the engine performance. The gas-side heat transfer coefficient, expressed as Nusselt number, is also determined for the finned-tube heat exchanger. The resulting values are compared to the heat transfer coefficients estimated in analogous experimental studies and by predictive models. Results show that the circular-pore heat exchanger reduces the performance of the engine compared to the finned-tube heat exchanger by about 23%, being affected by higher thermal and viscous irreversibility. Moreover, the boundary layer conduction model exhibits a better agreement with the measured heat transfer coefficients compared to other models. A new correlation law, based on regression of the experimental data, is also derived.

Comprehensive evaluation and sensitivity analysis of regeneration energy for acid gas removal plant using single and activated-methyl diethanolamine solvents

Abstract The absorption of acid gas using reactive amines is among the most widely used types of capturing technologies. However, the absorption process requires intensive energy expenditure majorly in the solvent regeneration process. This study simultaneously evaluated the regeneration energy of MDEA and PZ/MDEA solvents in terms of heat of absorption, sensible heat, and vaporization heat. Aspen Hysys version 8.8 simulation tool is applied to model the full acid gas removal plant for the chemical absorption process. The new energy balance technique presents around the absorption and desorption columns to bring a new perspective of energy distribution in the capturing of acid gas plants. Sensitivity analysis of regeneration energy and its three contributors is performed at several operation parameters such as absorber and stripper pressures, lean amine circulation rate, solvent concentration, reflux ratio, and CO2 and H2S concentrations. The results show that the heat of absorption of PZ/MDEA system is higher than that for MDEA system for the same operating conditions. The sensible heat is the main contributor in the required regeneration energy of MDEA solvent system. The simulation results have been validated against data taken from real plant and literature. The product specifications of our simulation corroborate with real plant data in an excellent approach; additionally, the profile temperature of the absorber and the stripper columns are in good agreement with literature. The overall results highlight the direction of the effects of each parameter on the heat of absorption, sensible heat, and vaporization heat.

Ionospheric O+ Momentum Balance Through Charge Exchange With Thermospheric O Atoms

AbstractOne of the most notorious uncertainties in ionosphere/thermosphere physics concerns the cross section for resonant charge exchange between neutral atomic and ionized oxygen, O and O+, the principle constituents between ∼200–500 km in the terrestrial atmosphere. O − O+ charge exchange plays a vital role in both momentum and energy exchange between the thermosphere and ionosphere, such that the value of the cross section, , strongly influences calculations of plasma drift speeds, diffusion coefficients, and electron density distributions. We present an analysis of the nighttime O+ momentum budget in the F region ionosphere, using an unprecedented 27‐year baseline of observations from Arecibo Observatory, as a means to assess the agreement between the data, recent theoretical calculations of , and NRLMSISE‐00 model predictions of O density, [O]. We find evidence for local time, seasonal, and solar cycle variation between the derived and modeled O − O+ collision frequency, with the best agreement observed near midnight at solar maximum. The data overall support our conclusion that recent theory regarding the magnitude of is likely accurate. Although biases in the momentum balance technique may account in part or in full for the local time and seasonal dependencies in observed O+ momentum imbalances, the most likely source of the observed solar cycle variation is MSIS model underestimation of [O]. These findings serve to establish the O+ momentum and energy balance techniques as a valuable means of remotely sensing thermospheric [O] in support of future model validation and development.

Analysis of energy demand for natural gas sweetening process using a new energy balance technique

ABSTRACTAbsorption by alkanolamine solvents is widely used for acid gas removal in natural gas sweetening plant. In the present research, one of the Iranian gas treating unit, Ilam Gas Treating Company (IGTC), with 3.27 mole % H2S and 3.76 mole % CO2 in the inlet feed gas was simulated using HYSYS V8.8. Piperazine activated solution of MDEA (PZ-MDEA) at various process operating conditions was examined to yield energy demand of natural gas sweetening process using a new energy balance technique. In this technique, the total required energy demand was related to three sections: 1. heat of vaporization, 2. sensible heat and 3. heat of the absorption. Energy balance of the absorption and regeneration columns brings a perspective of energy distribution in the sweetening plant. The effects of CO2 and H2S concentration at inlet feed, PZ mass fraction in activated solution of MDEA and lean amine temperature on energy distribution of the natural gas sweetening process and reboiler duty were investigated. It was finally elucidated that energy demand in the gas sweetening process or duty of reboiler is greatly influenced by heat of vaporization rate. It was also found that the heat of absorption and sensible heat have minor impacts on the energy demand.

Satellite Psychrometric Formulation of the Operational Simplified Surface Energy Balance (SSEBop) Model for Quantifying and Mapping Evapotranspiration

Abstract.Remote sensing-based evapotranspiration (ET) can be derived using various methods, from soil moisture accounting to vegetation-index based approaches to simple and complex surface energy balance techniques. Due to the complexity of fully representing and parameterizing ET sub-processes, different models tend to diverge in their estimations. However, most models appear to provide reasonable estimations that can meet user requirements for seasonal water use estimation and drought monitoring. One such model is the Operational Simplified Surface Energy Balance (SSEBop). This study presents a formulation of the SSEBop model using the psychrometric principle for vapor pressure/relative humidity measurements where the “dry-bulb” and “wet-bulb” equivalent readings can be obtained from satellite-based land surface temperature estimates. The difference in temperature between the dry (desired location) and wet limit (reference value) is directly correlated to the soil-vegetation composite moisture status (surface humidity) and thus producing a fractional value (0-1) to scale the reference ET. The reference ET is independently calculated using available weather data through the standardized Penman-Monteith equation. Satellite Psychrometric Approach (SPA) explains the SSEBop model more effectively than the energy balance principle because SSEBop does not solve all terms of the surface energy balance such as sensible and ground-heat fluxes. The SPA explanation demonstrates the psychrometric constant for the air can be readily adapted to a comparable constant for the surface, thus allowing the creation of a “surface” psychrometric constant that is unique to a location and day-of-year. This new surface psychrometric constant simplifies the calculation and explanation of satellite-based ET for several applications in agriculture and hydrology. The SPA formulation of SSEBop was found to be an enhancement of the ET equation formulated in 1977 by pioneering researchers. With only two key parameters, improved model results can be obtained using a one-time calibration for any bias correction. The model can be set up quickly for routine monitoring and assessment of ET at landscape scales and beyond. Keywords: Dry-bulb, ET fraction, ET modeling, Remote sensing, Satellite psychrometry, Wet-bulb.

Spatio-temporal patterns of energy consumption-related GHG emissions in China's crop production systems

This paper aims to reveal the spatio-temporal patterns of energy consumption-related greenhouse gas (ECR-GHG) emissions in China's crop production systems (CPSs). The relevant crop production data from 31 provinces during 1997–2014 are utilized. In order to fully reflect the energy consumption and ECR-GHG emissions in CPSs, energy balance techniques are adopted from a consumption perspective. The driving factors behind ECR-GHG emissions are identified by means of a Logarithmic Mean Divisia Index analysis at both national and provincial levels. The results are as follows: (1) The yield of China's CPS is not positively correlated with energy consumption, and China's CPS has the relatively high potential to conserve energy and reduce ECR-GHG emissions; (2) Most of China's provinces have experienced enormous growth in ECR-GHG emissions; however there are relatively significant regional disparities; (3) ECR-GHG emissions from CPSs were mostly derived directly from the consumption of chemical fertilizers and diesel oil; (4) Areal productivity is the determining factor in the growth of ECR-GHG emissions, whereas the emission coefficient and energy mix are the main inhibiting factors; (5) Energy intensity has not achieved its full potential to decrease ECR-GHG emissions. This study provides insights into the potential for sustainable crop production in China.

Selecting Canopy Zones and Thresholding Approaches to Assess Grapevine Water Status by Using Aerial and Ground-Based Thermal Imaging

Aerial and terrestrial thermography has become a practical tool to determine water stress conditions in vineyards. However, for proper use of this technique it is necessary to consider vine architecture (canopy zone analysis) and image thresholding approaches (determination of the upper and lower baseline temperature values). During the 2014–2015 growing season, an experimental study under different water conditions (slight, mild, moderate, and severe water stress) was carried out in a commercial vineyard (Vitis vinifera L., cv. Carménè). In this study thermal images were obtained from different canopy zones by using both aerial (>60 m height) and ground-based (sunlit, shadow and nadir views) thermography. Using customized code that was written specifically for this research, three different thresholding approaches were applied to each image: (i) the standard deviation technique (SDT); (ii) the energy balance technique (EBT); and (iii) the field reference temperature technique (FRT). Results obtained from three different approaches showed that the EBT had the best performance. The EBT was able to discriminate over 95% of the leaf material, while SDT and FRT were able to detect around 70% and 40% of the leaf material, respectively. In the case of canopy zone analysis, ground-based nadir images presented the best correlations with stomatal conductance (gs) and stem water potential (Ψstem), reaching determination coefficients (r2) of 0.73 and 0.82, respectively. The best relationships between thermal indices and plant-based variables were registered during the period of maximum atmospheric demand (near veraison) with significant correlations for all methods.

Simulating concrete cover separation in RC beams strengthened with near-surface mounted reinforcements

The near surface mounted (NSM) technique for strengthening reinforced concrete (RC) beams normally utilizes fibre reinforced polymer (FRP) bars or strips placed within grooves made on the soffit of the beams. For RC beams strengthened with NSM the failure mode would normally be the premature debonding failure by separation of concrete cover. A few methods have been proposed to predict the failure loads. The application of these methods however were found to be limited by the empirical formulations that were used, which severely affects their accuracy when applied to situations outside of the testing regime that formed the empirical formulations. To address this issue, in this paper the moment-rotation technique and the global energy balance technique were combined to predict the failure load. The proposed method is more versatile as it requires significantly less empirical formulations when simulating NSM strengthened RC beams as the mechanics of the beam such as crack formation, crack widening and tension stiffening are simulated directly. The proposed method was validated against published experimental results. Comparison between simulated and experimental load-deflection curves shows that the method is able to give good accuracy.

Satellite-based crop coefficient and regional water use estimates for Hawaiian sugarcane

Water availability is a major limiting factor for sustainable production of potential biofuel crops in Maui, Hawaii, USA. It is essential to improve regional, near-real time estimates of crop water use to facilitate optimal water management. Satellite remote-sensing offers multiple methods to estimate water management, however, most approaches assume a spatially homogeneous regional meteorology, which does not apply in Hawaii due to strong orographically-induced variations in climate. Canopy ground cover (fc) and spectral reflectance were measured over two sugarcane fields on the satellite Landsat 7 overpass dates. A strong linear relationship between satellite-based Normalized Difference Vegetation Index (NDVI) values and fc was found (R2=0.97). Canopy ground cover was also found to be highly correlated to crop coefficient (Kc) which was calculated from reference evapotranspiration (ET0) and sugarcane crop evapotranspiration (ETc) observations from the Eddy Covariance towers. Spatial ET0 for the entire sugarcane plantation was determined from an automated weather station network previously installed by the commercial grower of the plantation. Regressions were used to convert the satellite NDVI to Kc maps, and then the satellite-based ETc maps were created from the satellite-based Kc maps and ET0 values computed and interpolated from the weather station network. To compare with the satellite-based crop coefficient/reference ET method, ETc and Kc were also estimated using a satellite-based surface energy balance technique, the METRIC model. These two satellite-based methods were correlated fairly well (R2=0.84 for Kc and 0.81 for ETc). Compared to the METRIC model, the satellite-based crop coefficient/reference ET method may be more practicable for estimating crop water use in Maui, where ground-based ET0 measurements are available through the on-site automated weather station network with right choice of reference ET equation.

AN ALMA SURVEY OF SUB-MILLIMETER GALAXIES IN THE EXTENDEDCHANDRADEEP FIELD SOUTH: PHYSICAL PROPERTIES DERIVED FROM ULTRAVIOLET-TO-RADIO MODELING

[abridged] The ALESS survey has followed-up a sample of 122 sub-millimeter sources in the Extended Chandra Deep Field South at 870um with ALMA, allowing to pinpoint the positions of sub-millimeter galaxies (SMGs) to 0.3'' and to find their precise counterparts at different wavelengths. This enabled the first compilation of the multi-wavelength spectral energy distributions (SEDs) of a statistically reliable survey of SMGs. In this paper, we present a new calibration of the MAGPHYS modelling code that is optimized to fit these UV-to-radio SEDs of z>1 star-forming galaxies using an energy balance technique to connect the emission from stellar populations, dust attenuation and dust emission in a physically consistent way. We derive statistically and physically robust estimates of the photometric redshifts and physical parameters for the ALESS SMGs. We find that they have a median stellar mass $M_\ast=(8.9\pm0.1)\times10^{10} M_\odot$, SFR$=280\pm70 M_\odot$/yr, overall V-band dust attenuation $A_V=1.9\pm0.2$ mag, dust mass $M_\rm{dust}=(5.6\pm1.0)\times10^8 M_\odot$, and average dust temperature Tdust~40 K. The average intrinsic SED of the ALESS SMGs resembles that of local ULIRGs in the IR range, but the stellar emission of our average SMG is brighter and bluer, indicating lower dust attenuation, possibly because they are more extended. We explore how the average SEDs vary with different parameters, and we provide a new set of SMG templates. To put the ALESS SMGs into context, we compare their stellar masses and SFRs with those of less actively star-forming galaxies at the same redshifts. At z~2, about half of the SMGs lie above the star-forming main sequence, while half are at the high-mass end of the sequence. At higher redshifts (z~3.5), the SMGs tend to have higher SFR and Mstar, but the fraction of SMGs that lie significantly above the main sequence decreases to less than a third.

Nonlinear normal modes, modal interactions and isolated resonance curves

The objective of the present study is to explore the connection between the nonlinear normal modes of an undamped and unforced nonlinear system and the isolated resonance curves that may appear in the damped response of the forced system. To this end, an energy balance technique is used to predict the amplitude of the harmonic forcing that is necessary to excite a specific nonlinear normal mode. A cantilever beam with a nonlinear spring at its tip serves to illustrate the developments. The practical implications of isolated resonance curves are also discussed by computing the beam response to sine sweep excitations of increasing amplitudes.

Bowen Ratio Measurements of Energy Budget Components over Various Ecosystems in Mymensingh, Bangladesh

Surface energy budget components were measured over four different surfaces in the campus of Bangladesh Agricultural University, Mymensingh, Bangladesh (24.75oN, 90.5oE) at the beginning of dry season (August to December 2004) using Bowen Ratio Energy Balance (BREB) technique. Under sufficient soil moisture conditions, surface energy budget during the study period was characterized by dominant latent heat flux (79% to 92% of net radiation) and negligibly small sensible heat flux with small modification by vegetation. DOI: http://dx.doi.org/10.3329/jesnr.v7i1.22139 J. Environ. Sci. & Natural Resources, 7(1): 21-25 2014