Seyed Arman Hashemi Monfared

The study presents the development of the Meshless Local Petrov–Galerkin (MLPG) method to model and predict contaminant transport in porous media which is known as an important issue to prevent the pollution propagation in groundwater. The research focuses on the Rafsanjan Plain in southeastern Iran as a real case study, where no studies of meshles...

Groundwater modeling is often associated with uncertainties due to incomplete knowledge of the subsurface system or uncertainties arising from variability in model system processes and field conditions. So far, not much research has been conducted to investigate the uncertainty of the groundwater flow model. Studies in this field focus on statistic...

This study investigates the optimal and safe operation of pumping stations in water distribution systems (WDSs) with the aim of reducing the environmental footprint of water conveyance processes. We introduced the nonlinear chaotic honey badger algorithm (NCHBA), a novel and robust optimization method. The proposed method utilizes chaotic maps to e...

This study aims to assess the change of drought characteristics (intensity, duration, and frequency) under the effect of climate change in Iran using the modified standardized precipitation index (MSPI) and theory of runs on annual and seasonal scales for three near-future, mid-future (MF), and far-future climates. Hence, regional climate models ex...

Multi-model Ensembles (MMEs) are widely used to reduce uncertainties associated with simulations and projections of GCM/RCM.MMEs combine the results of multiple climate models to produce a more robust and reliable prediction. By considering the range of outputs from different models, MMEs can improve the overall accuracy of climate projections. The...

Global warming significantly affects the hydrological cycle that influences hydrological systems worldwide. Knowledge of precipitation variation under a changing climate can provide effective ways to deal with its impacts on water resource management. Hence, in this study, spatiotemporal variability of precipitation under future climatic scenarios...

Floods are one of the natural events that cause significant morphological changes in riverbeds and adjacent lands, which result in financial, human, and other losses. When a flood occurs, the interference of the flow in the main channel and the flood plain causes the transfer of movement and complexity in the flow pattern from the main channel to t...

In Iran, Behesht Abad Water Transfer from the headwaters of Karoon to the central plateau is one of the most critical inter-basin water transfer projects. This study aims to evaluate the impacts of the Water Transfer (WT) on the water level and flow of Farsan Aquifer in the origin basin. To achieve this goal, WEAP-GMS was used. Some defined scenari...

The accuracy of water quality predictions is essential, especially in countries affected by climate change and ecological water diversity. Water quality modelling in rivers is a valuable tool for enabling decision-making in surface water management because water quality prediction using sampling methods is expensive and time-consuming. The collecti...

Introduction One of the ways to increase rainfall and water production is cloud seeding technology. In this regard, the purpose of this study is to investigate the effect of cloud seeding technology on increasing the water of Khash Basin, as the most prone area for climate change projects in Sistan Province as documented in several national and int...

Protecting water resources from pollution is one of the most important challenges facing water management researchers. The governing equation for river pollution is mostly the advection–dispersion equation, with considering the longitudinal dispersion coefficient as its most important effective parameter. The purpose of this paper is to develop a n...

Most parts of Iran have arid and semi-arid climates. Therefore, many deserts and playas have been formed in these areas. In the present study, the return of saline water due to the groundwater head increase in the aquifers with the usage of SUTRA numerical model, was investigated. In order to assess the wedge behavior of saline water in transient s...

Estimations of sediment transport rate is the prerequisite of coastal development and management studies, as accretion and erosion are among main controlling considerations for port planning. The Iranian coastline of the Oman Sea, which is so-called Makran Coastline, has a complex morpho-dynamic behavior and should be considered from both scientifi...

This study investigates the effects of climate change on the water requirement of saffron in 13 regions of South Khorasan and Khorasan Razavi for three periods of 2030-2050, 2055-2075 and 2080-2100 using the Hybrid algorithms ANN-NSGA-II and ANN-ICA. For the first time, this research has obtained the water requirement of saffron based on climate ch...

The most challenging issue of the Sistan region in Southeastern Iran, at least in the recent decades, has been dust propagation. The two main factors responsible for sand and dust storms, i.e., wind and land erosion, are extremely high in this region. The closest part of Hamoun wetland to Zabol, named Saberi, has been assumed as the primary source...

Pollution of surface water especially rivers has created serious problems for both human health and environment. Due to the severe shortage of surface water resources and their pollution, it is very important than ever to plan wisely how to use water resources, especially in areas that consume more water, like drinking water, agriculture, and indus...

The complicated behavior of groundwater system in an arid aquifer is generally studied by solving the governing equations using either analytical or numerical methods. In this regard, analytical methods are just for some aquifers with regular boundaries. Numerical methods used for this aim are finite difference (FDM) and finite element methods (FEM...

Introduction: Utilization of aqueducts and excavations is one of the most common methods of using groundwater. Every year, level of groundwater is lowered too much and its flow rate decreases. In the study area (Khash), the water deficit is negative and the annual water level decreases and it is considered as the main source of water supply in the...

In recent decades, due to the population growth and low precipitation, the overexploitation of ground water resources has become an important issue. To ensure a sustainable scheme for these resources, understanding the behavior of the aquifers is a key step. This study takes a numerical modeling approach to investigate the behavior of an unconfined...

Across the world, rivers are the main supply arches for drinking, industry and agriculture. Hence, in recent years, the identification and study of the processes of transport of pollution in rivers has become very important. Longitudinal dispersion coefficient is the most important parameter in the transport equation, and various methods for its es...

Probability estimation of rare events is a challenging task in the reliability theory. Subset simulation (SS) is a robust simulation technique that transforms a rare event into a sequence of multiple intermediate failure events with large probabilities and efficiently approximates the mentioned probability. Proper handling of a reliability problem...

The water shortage is a challenge in many countries around the world. Today, the latest scientific and practical technologies are used to solve the problem of water shortage in arid and semi-arid regions. The optimal use of water resources as well as the use of novel methods of water extraction plays a significant role in alleviating the effects of...

The longitudinal dispersion coefficient (LDC) of river pollutants is considered as one of the prominent water quality parameters. In this regard, numerous research studies have been conducted in recent years, and various equations have been extracted based on hydrodynamic and geometric elements. LDC’s estimated values obtained using different equat...

Introduction One of the ways to increase rainfall and water production is cloud seeding technology. In this regard, the purpose of this study is to investigate the effect of cloud seeding technology on increasing the water of Khash Basin, as the most prone area for climate change projects in Sistan Province as documented in several national and int...

1. Introduction One of the ways to increase rainfall and water production is cloud seeding technology. In this regard, the purpose of this study is to investigate the effect of cloud seeding technology on increasing the water of Khash Basin, the most prone area for climate change projects in Sistan Province as documented in several national and int...

The present study employs a mathematical method, i.e., Particle Filter (PF), to accurately estimate the parameters of three standard aquifers. The method is linked to a new developed numerical method, i.e., meshless local Petrov-Galerkin based on the moving kriging method (PF-MLPG-MK), to determine the aquifer parameters such as hydraulic conductiv...

inter-basin water transfer is the transfer of water from one basin to another. The basin which water is transferred to that is called the destination basin and the basin which water is transferred from that is called the origin basin. Inter-basin water transfer despite the supply of water in the destination basin, could possibly be the cause of cha...

Entry of various substances like phosphate and nitrate to a reservoir along with the factors such as scarcity of dissolved oxygen leads to water quality reduction. Despite these factors and lack of constant water flow into a reservoir with a long detention time, thermal stratification and eutrophication occur. This research investigates the capabil...

With the continual growth of population and shortage of energy resources, the optimal consumption of these resources is of particular importance. One of these energy sources is electricity, with a significant amount being used in pumping stations for water distribution systems (WDS). Determining the proper pumping schedule can make significant savi...

The environment of the international three-sibling Hamoun wetlands has been posed to serious natural risks due to the recent drought periods in the Sistan region and the watershed of Hirmand River. The problem of dust propagation has endangered the local life. On the other hand, it seriously threatens the flora–fauna ecosystem of the region. The pr...

Abstract Background and objectives Agriculture is the largest water-using sector and water management for agriculture is complex. Balancing between water resources and demand in arid and semi-arid regions will be a major challenge over the coming decades. Because the 21st century is facing a global challenge called climate change, it is becoming mo...

Nowadays, with increasing energy consumption costs, the optimization of energy efficient processes is being more considered than before. The essential part of the operational cost of water conveyance systems is energy consumption and maintenance costs of pumping stations. Therefore, it is necessary to develop an efficient method for optimal operati...

Having the exact values of boundary conditions is one of the effective way to develop precise groundwater models. In the present study, the exact value of constant head boundaries in Birjand aquifer is specified with the usage of particle filter linked to meshless groundwater model. Particle filter known as one of the common data assimilation metho...

Having a pervasive knowledge about the groundwater balance conducts the engineers and managers to have an optimal management about these resources. In the present study, with using meshless local Petrov-Galerkin, one of the meshless methods in the field of fluid dynamic, groundwater balance is computed for a real field aquifer. The independency of...

The reliability analysis of an engineering system with a small failure probability (Pf) and a complex-geometry performance function is a major challenge in the probabilistic engineering mechanics for which the subset simulation (SS) is a promising addressing algorithm. However, SS is potentially problematic when solving complex problems. This has t...

The present study aimed to assess the performance of CMIP6 and CMIP5 projects in projecting mean precipitation at annual, summer, autumn, winter, and spring timescales in the north and northeast of Iran over the period 1987-2005 using relative bias, correlation coefficient, root mean square error, relative error, and the Taylor diagram. This is the...

Protection of water quality from the hazards of industrial, agricultural, urban, and other sources of pollutants has been a big concern for water resources managers in recent decades. Sources of pollutants are often classified into different large categories, which can be predicted by modeling. In this investigation, a river-reservoir system with t...

Inter-basin water transfer is the transfer of water from one basin to another. The basin which water is transferred to that is called the destination basin and the basin which water is transferred from is called the origin basin. Inter-basin water transfer despite the supply of water in the destination basin, could possibly be the cause of changes...

Pollution of water resources particularly surface water and rivers may affect human health and the environment seriously. So it is essential to find an efficient solution to control the pollution at rivers in order to reduce damages for consumers and protect the environment. At this research, a mathematical model is proposed to manage pollutant ent...

Severe water scarcity in recent years has magnified the economic, social, and environmental significance of water stress globally, making optimal planning in water resources necessary for sustainable socioeconomic development. One of the regions that is most affected by this is the Sistan region and its Hamoun wetland, located in southeast Iran. Wa...

Occurrence of factors such as decreasing atmospheric precipitation, population growth and industry progress has increased the importance of paying attention to the proper quality management of water resources. Pollution sources are categorized in different aspects. In this research, controllable and uncontrollable pollutant management is considered...

In this research, a simulation-optimization model is utilized to determine the optimum location of wells on two unconfined aquifers (steady condition and transient state) with different boundary conditions. Meshless local Petrov-Galerkin (MLPG) and particle swarm optimization (PSO) are employed for the simulation model and optimization algorithm, r...

The dominant currents in Caspian Sea, a constituent of which is wind-induced waves, the disconnectedness of Caspian Sea from oceans, complex topography, shoreline configuration, and considerable temperature and density differences, which make it complicated to examine ocean current patterns, are of great importance. This study investigated bottom f...

Every year, significant amounts of freshwater are disappeared from watersheds by evaporation. Many regions of the world have been struggling with arid and semi-arid climates in recent decades. The problem of water shortage that is induced by water evaporation from lakes and water reservoirs or water use for irrigation and domestic consumption has t...

Surface water is one of the most important water resources available to mankind, is used for various purposes, such as drinking and agriculture. Recently, with the growing urban population, there are many problems associated with the pollution and quality of water resources. Therefore, recognizing and studying the process of mixing and conveying ma...

It is imperative to develop and assess approaches to adapt to climate change in order to manage its impacts. The objective of the present study was to explore the impact of the changes in climatic parameters on water resources management and to assess the efficiency of changing water uses as a strategy to mitigate the impacts of water shortage in S...

The purpose of this research is to simulate and optimize the utilization of water resources of Zahedan in the next 20 years under various management scenarios. In order to reach the definitive optimal point in this issue, minimization of non-supply demands and minimization of withdrawal from groundwater resources in a single target was studied usin...

In this study capture zones of wells for the first time is determined and depicted with using a numerical method. Meshless local Petrov-Galerkin is one of the meshless methods which is not used in this field. In this article groundwater flow is simulated by using MLPG method in confined aquifer which has four extraction wells in transient state and...

The prediction of groundwater level fluctuations is one of the most remarkable issues in water resources management, especially in arid and semiarid regions. The present study uses a numerical meshless method, named meshless local Petrov-Galerkin, to predict the groundwater level over a ten-year period. This method makes up for the shortcomings of...

Due to the frequent drought periods, water consumption increase, and competition of different water-using sectors, the Hirmand catchment is in a critical water status in the Sistan region. This threat has been intensified in recent years. To cope with this problem, we must pay more attention to different types of water use such as virtual water as...

The lack of water resources as a critical substance and the increase of water demands and also the complexity of water resources management issues are made the integrated water resource management as an essential tool. In this study considering different water demands, planning and policy analysis in the Sistan region, with the water evaluation and...

Evaporation from reservoirs is an important issue frequently occurring in dry, hot regions like Iran. Since the laboratory and field studies of evaporation control are difficult, time-consuming, and costly, and the investigation of various possible modes is not possible, numerical models with high capabilities are widely used to analyze the hydrolo...

Evaporation is a process that changes fluid from liquid to gas. Evaporation rates from free surfaces depend on factors such as temperature, wind speed, water depth and vapor pressure.A detailed study of the information received from the Meteorological Office of the Zahak concluded that the factors of temperature and wind speed in this region were t...

Water is a basic demand of sustainable development in every region of the world. Hirmand catchment is one of the most important cross-border of Iran basins affected by the recent drought periods from water scarcity and caused severe crisis in the Sistan region. Fuzzy theory is able to convert most incorrect and enigmatic concepts, variables and sys...

Understanding of the fate of temporal and spatial distribution of pollutionis an essential subject for prediction of damages, caused by pollution, on the ecology of rivers and coastal areas. It is also necessary to provide efficient solutions for both pollution control and environmental protection. In this study, shallow water equations have been u...

In this paper, Crude Monte Carlo method and importance sampling are utilized to determine the reliability of long-term changes in groundwater level. Furthermore, different data analysis methods are used to determine the abnormal patterns and to investigate the cause of spatial variations of failure probability. For this purpose, three methods inclu...

One of the most important Pishin dams dam catchment area in south-eastern Iranian province of Sistan-Baluchistan. This area has very low rainfall and evaporation is very high on the one hand and on the other hand with the increasing demand for urban, agricultural and industrial, faces a severe water stress. According to the reference scenario resul...

Indiscriminate Excavation of deep wells has led to a drop of groundwater levels and the resulting problems. The most important of which is the destruction of the vegetation cover of the plains, which absorbed their needed water from the moisture of the ground. The purpose of this research is to analyze the decrease of surface moisture and source of...

Water is a basic demand of sustainable development in most regions of the world. The non-uniform temporal and spatial distribution of water resources will lead to water shortage in arid and semi-arid areas. Pishin catchment is one of the most important catchments in SouthEast Iran. The basin had been faced with consecutive droughts in recent years....

In this study, a probabilistic analysis using first-order reliability method is conducted to predict the reoccurrence of drought conditions. The implementation of the model involves the collection of the long-term average data during 1994–2015 from 609 study areas of Iran. The reliability criterion is defined as the changes in groundwater resource...

Selecting an appropriate crisis management plans during uncontrollable loading of pollution to water systems is crucial. In this research the quality of water resources against uncontrollable pollution is protected by use of suitable tools. Case study which was chosen in this investigation was a river-reservoir system. Analytical and numerical solu...

Drought of Groundwater happens when aquifers as an important source of supplying water, are effected by long-term drought. Groundwater resource index (GRI) have been used for long-term change of piezometric and observational data depth of aquifers. In this research, the results of calculations about drought happens with regard to spatial distributi...

Background: The level of groundwater resources is changing rapidly and this requires the discovery of newer groundwater resources. Drought is one of the most significant natural phenomena affecting different aspects of human life and environment. During the last decades, the application of artificial intelligent techniques has been recognized as e...

Today, with increasing urbanization and changing land border cities such as gardens, agricultural land, Barren land into residential areas, causing damage morphology and physical properties and hydrological basinsare, This will redirect the natural flow of the water from rainfall and reduced infiltration basin is a result of problems such as flo...

In this study, fuzzy AHP method is used for extracting the water quality indicators based on the Schuler standard and World Health Organization (WHO) guidelines during a 20-year period. For this purpose, the best fit of the zoning model was performed. Furthermore, by comparing the standard errors, the continuous Raster layer was extracted from the...

Evaporation depends on various factors including temperature, wind speed, humidity, water salinity, water depth, etc. The study of data on evaporation, temperature, wind speed and humidity in the study area shows that the main factor of evaporation is wind speed. Using windbreaks is a method to control the wind speed, which contributes to reduced e...

The present article explores the impacts of climate change on precipitation at station scale in the Minab basin, Iran. The data used for evaluation were large-scale input (predictor) parameters extracted from the reanalysis data set of the National Center for Environmental Prediction and National Center for Atmospheric Research to downscale monthly...

Population growth, urbanization and industrial expansion are consequentially linked to increasing pollution around the world. The sources of pollution are so vast and also include point and nonpoint sources, with intrinsic challenge for control and abatement. This paper focuses on pollutant concentrations and also the distance that the pollution is...

12 ‫ﺷﻤﺎره‬ ، 2 ، ‫ﺗﺎﺑﺴﺘﺎن‬ 1396 59 » ‫ﺗﺤﻘﯿﻘﺎﺗﯽ‬ ‫ﯾﺎدداﺷﺖ‬ « ‫ﺑﻬﯿﻨﻪ‬ ‫در‬ ‫اﺳﺘﻌﻤﺎري‬ ‫رﻗﺎﺑﺖ‬ ‫اﻟﮕﻮرﯾﺘﻢ‬ ‫ﮐﺎرﺑﺮد‬ ‫ﺳﺎزي‬ ‫ﺑﻬﺮه‬ ‫ﺑﺮداري‬ ‫ﺣﺪاﮐﺜﺮ‬ ‫ﻫﺪف‬ ‫ﺑﺎ‬ ‫ﻣﺨﺰن‬ ‫ﺳﺎزي‬ ‫ﺗﺄﻣﯿﻦ‬ ‫ﻧﯿﺎز‬) ‫ﻣﻮردي‬ ‫ﻣﻄﺎﻟﻌﻪ‬ : ‫ﭘﯿﺸﯿﻦ‬ ‫ﺳﺪ‬ (‫ﻣﻨﻔﺮد‬ ‫ﻫﺎﺷﻤﯽ‬ ‫آرﻣﺎن‬ ‫ﺳﯿﺪ‬ 1 * ‫ﺣﺴﯿﻦ‬ ‫ﻓﻬﯿﻤﻪ‬ ، ‫زاده‬ 2 ‫ﺑﻬﺎره‬ ، ‫ﭘﯿﺮزاده‬ 3 1 ‫و‬ 3-‫زاﻫﺪان‬ ،‫ﺑﻠﻮﭼﺴﺘﺎن‬ ‫و‬ ‫ﺳﯿﺴﺘﺎن‬ ‫داﻧﺸﮕﺎه...

Today, with increasing urbanization and changing land border cities such as gardens, agricultural land, Barren land into residential areas, causing damage morphology and physical properties and hydrological basins are, This will redirect the natural flow of the water from rainfall and reduced infiltration basin is a result of problems such as flood...

Water is the main demand of people settled in the arid areas of large watersheds. This demand is more necessary and critical in the areas with the potential of dust sources and fine sediments entering into the watershed in a long-time period. Sistan watershed to the southeast of Iran is a region with the specific hydrological conditions. The 120-da...

Background: Prediction of future climate change is based on output of global climate models (GCMs). However, because of coarse spatial resolution of GCMs (tens to hundreds of kilometers), there is a need to convert GCM outputs into local meteorological and hydrological variables using a downscaling approach. Downscaling technique is a method of con...

Assessment of the impacts of climate change on water resources has been obtained significant attentions in the past decade. This paper assesses the climate change impacts on precipitation in the Minab basin, in the Hormozgan province in Iran. Two monthly precipitation downscaling methods were proposed based on multi-layer perceptron (MLP) and radia...

The population and settlement growth, amortized water transmission networks, agricultural development with flood irrigation and the rapid growth of industry are increased water demands. The limited controlled surface water and groundwater and continuous increasing of the various and amount of water demands need of correct planning for water managem...

In shallow river, regardless of the vertical acceleration against gravity acceleration, great simplifying will be created in equations that the result of them are shallow water equations. In this study shallow water equation has been used to simulate transport of pollution in 2D limited volumes method. In this method it is possible to turn differen...

In shallow river, regardless of the vertical acceleration against gravity acceleration, great simplifying will be created in equations that the result of them are shallow water equations. In this study shallow water equation has been used to simulate transport of pollution in 2D limited volumes method. In this method it is possible to turn differen...

Background and Objectives: According to the low rainfall and the water resources in the country, investigation of the pollution behavior in water is very important. To Study on this phenomena, advection-diffusion equation in one-dimensional flow is used. Analytical solution and numerical solutions can be used to solve this equation. The residual of...

In this paper a hypothetical case study in the real range is selected and is solved with different numerical solution like Lax, Fromm, Quick and etc. The analytical solution is chosen for the verification. The MAPLE and MATLAB soft wares were used to do the computation of the new proposed advective transport function.

Sistan region is one of the most important agricultural areas in the province of Sistan and Baluchistan. Therefore, given the heterogeneity in agriculture and recognizing these differences, the aim of this study was to obtain the level of development of agriculture in the Sistan region. To obtain this purpose Fuzzy Analytical Hierarchy Process (FAH...

Hirmand catchment is one of the important trans boundary catchment in Iran. Sistan people living in south east Iran related to this catchment. Meanwhile drought of the last two decades, due to dust storms jeopardized the Human health. Also, causing destroyed vegetation cover and animal habitat in region. The first objective of the present study is...

Water quality prediction is a valuable tool for pollutant control in aquatic environments. A river system is selected and one-dimensional flow is assumed for the simulation of pollutant transport in this paper. Advective and diffusive terms of transport equation are considered separately. Different functions of advective transport are proposed and...

Development of industry in Sistan and Baluchestan (SB) province in Iran, has increased the amount of Cadmium (Cd) in industrial wastewater, which is used as a secondary water supply in this area. The present study aimed to investigate the variation of Cd concentration in soil column and cultivated cucumber plant in greenhouse under short-term simul...

Development of industry in Sistan and Baluchestan (SB) province in Iran, has increased the amount of Cadmium (Cd) in industrial wastewater, which is used as a secondary water supply in this area. The present study aimed to investigate the variation of Cd concentration in soil column and cultivated cucumber plant in greenhouse under short-term simul...

Seasonal rivers are the main sources of discharge for many lakes and reservoirs. These rivers can deliver pollutants into these water bodies, especially during large events. The fate and distribution of these pollutants within lakes is difficult to predict. Here, a three-dimensional, finite-volume model for predicting lake water quality is used to...

The increase of phytoplankton and zooplankton in the lakes and reservoirs that supply water to downstream regions is an important environmental issue. In this paper, concentrations of phytoplankton and zooplankton in Chahnimeh reservoir are predicted using an Integrated Seasonal Separate Advection- Diffusion Model (ISSADM). Chahnimeh reservoir is a...

Phytoplankton and zooplankton concentrations in Pishin reservoir are predicted employing a three-dimensional numerical model in this paper. Modeling is performed using a numerical model based on mass transport equation. Advection, diffusion and source/sink processes are considered as separate subroutines for predicting the concentrations of phytopl...

A one-dimensional mathematical model based on convection–dispersion equation in unsaturated porous media is presented to compute inorganic total solid concentration in the soil column under the Shiraz landfill. In addition, a dynamic mathematical model is formulated to simulate concentrations of ions such as Ca2+ , Mg2+, Fe2+, K+, Na+, Cl−, SO4 2−...

Pesticide transport and transformation were modeled in soil column from the soil surface to groundwater zone. A one dimensional dynamic mathematical and computer model is formulated to simulate two types of pesticides namely 2,4-dichlorophenoxy acetic acid and 1,2-dibromo 3-chloro propane in soil column. This model predicts the behavior and persist...

A Model for predicting nutrient transport to CHAHNIMEH reservoir is developec in this paper. Nitrogen and phosphorous have been simulated as the important parameters in evaluating water quality in the reservoir. Solar radiation and wind flow are considered in the model. Model uses mass balance equation to predict a one year period of changing conce...

A Model for predicting nutrient transport to CHAHNIMEH reservoir is developed in this paper. Nitrogen and phosphorous have been simulated as the important parameters in evaluating water quality in the reservoir. Solar radiation and wind flow are considered in the model. Model uses mass balance equation to predict a one year period of changing conce...