bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Testing and Evaluation of Neat Biodiesel and Heptanol Blends in Diesel Engine
Authors: Devarajan Yuvarajan , Munuswamy Dinesh Babu , Radhakrishnan Santhanakrishnan , Mahalingam Arulprakasajothi , Nagappan Beemkumar 
Published: May 2018

Abstract
Alcohol will be an exceptional alternative fuel for existing diesel engines because of its built-in fuel-improving properties (high cetane number and high energy content). Biosynthesis of N-heptanol by means of engineered microbes, such as the Clostridium species and Escherichia coli, is an active area of research. Hence, extensive investigation on the compatibility of N-heptanol in existing diesel engines is necessary. This study examined the effect of heptanol mustard oil biodiesel blends of varying proportions on the emission and performance patterns in a 1,800 r/min constant-speed immobile diesel engine. The main objective of this investigation was to investigate the reduction in all the emissions and increase the performance characteristics associated with neat mustard oil biodiesel when deploying three different fuels. Base catalyzed transesterification process was employed to convert the mustard oil into mustard oil biodiesel. Heptanol with 98.4 % purity was used as an oxygenated additive. The experimental results revealed that converting heptanol to mustard oil biodiesel caused a significant reduction in hydrocarbons, carbon monoxide, nitrogen oxides, and smoke emissions when compared to mustard oil biodiesel in naturally aspirated conditions.
Reliability and Sensitivity Analysis of the Controllable Repair System with Warm Standbys under the Recovery Threshold Policy
Authors: Chen Wu-Lin 
Published: May 2018

Abstract
This article performs reliability and sensitivity analyses of a controllable repair system with M operating units, S warm standby units, and an unreliable repair server under the recovery threshold policy. Failure times and service times of an operating unit or a standby unit are assumed to follow exponential distributions. When the repair server normally operates, it is subject to breakdowns; while a breakdown occurs, the repair server requires repair at another repair facility, and the repair of the breakdown server cannot be initiated until there are more than or equal to q failed units. The times to breakdown and repair times of the server are also assumed to be exponentially distributed. A server during a breakdown period can provide partial service with lower service rates. This article derives expressions for system reliability as well as the mean time to failure. The sensitivity analyses of both system performance measures are performed. Finally, some numerical experiments are designed and performed to demonstrate how the system performance measures are affected by the change of each system parameter.
On definitions
Authors: Abbott Michael B. 
Published: May 2018

Originating from a concern about the use of terms in hydroinformatics, this paper takes up the question of the nature of a definition and its consequences in a technical, and increasingly sociotechnical field like hydroinformatics. It is explained that the way things are defined is not so simple and so obvious as might at first appear, but is in fact an essentially ideological matter, having consequences not only within an individual discipline, but also for the applications of that discipline within a wider context. A mode of definition that satisfies the needs and expectations of hydroinformatics is then advanced.
The notion of a defining self is introduced in order to explain how the influences of the mode of definition attains to a greater influence in social and ecological applications. This influence is exerted through communication, which is necessarily realised through the use of tokens. The four classes of tokens necessary for all processes of communication are introduced, delineated and defined.
The way in which such broad concepts as ‘reality’ and ‘truth’ are defined is then seen to influence the definition of a model in the widest sense. Further definitions that are of central concern in hydroinformatics are developed accordingly. The paper concludes with a description of a phenomenon known only by its German name, as Gerede, that is at the root of much current confusion of terms in hydroinformatics, as in so many other places, and how its malign influences can be opposed.
Sensitivity and uncertainty analysis for river quality modelling
Authors: Radwan Mona , Willems Patrick , Berlamont Jean 
Published: May 2018

Uncertainty analysis for model simulation is of growing importance in the field of water quality management. The importance of this concern is provided by recent public awareness over health risks from improper disposal of toxic wastes as well as by the continuing emphasis on risk assessment. The first step in the chain of risk assessment is the quantification of the error in predicting water quality.
In each mathematical modelling application, different uncertainties are involved. The uncertainty sources can be classified into different categories (in this study, as model-input uncertainty, model-structure uncertainty, model-parameter uncertainty and measurement errors). These different types of uncertainty sources determine collectively the total uncertainty in the model results. In this paper, the relative contributions of uncertainties associated with each source are studied for the physico-chemical water quality modelling of a river in Belgium. This provides information as to where available modelling resources should be focused.
MECHANISM OF GROUND WATER RESERVOIRS
Authors: ELIASSON JONAS 
Published: May 2018

The article deals with unsteady ground water flow in an aquifer of limited horizontal extent. The changes in storage are taken to be dependent on a storage coefficient S, and flow rates are taken to be dependent on the coefficient of transmissibility T. Here the relation to Darcy's constant k is that T ≿ kD, where D is the aquifer thickness. The equilibrium ground water surface is found and further calculations are based on the departure of the ground water level from this equilibrium value.
An expression of the impulse response function (the instantaneous unit hydrograph or IUH) is found, and its use demonstrated.
Finally, it is shown how such calculations have been used to analyse the inflow into a water reservoir in Iceland, serving as guidelines in the planning of field investigations of a major ground water reservoir in a nearby lava field.
NUMERICAL SIMULATION OF THE RAINFALL-RUNOFF PROCESS ON A DAILY BASIS
Authors: NIELSEN STEEN ASGER , HANSEN EGGERT 
Published: May 2018

A digital model has been developed for the simulation of the rainfall-runoff process of rural watersheds. Input data are daily values of precipitation and temperature together with mean monthly potential evapotranspiration. The model produces daily values of streamflow as well as information on the time variation of the soil moisture content. In all, ten model parameters have to be identified, seven of which have a major influence on the performance of the model.
The model operates by accounting continuously for the moisture content in four different and mutually interrelated storages representing physical elements in the watershed.
It has been applied to three different Danish watersheds. Several statistical measures of accuracy have been utilized for a quantitative evaluation of the simulation results. The simulations demonstrate that the main shortcomings of the model are due to the lack of a procedure accounting for frozen ground during extended periods of frost, which could improve some of the simulation results during winter and spring.
GROUND WATER COMPUTATIONS IN NEW JERSEY, U.S.A.
Authors: HALASI-KUN GEORGE J. 
Published: May 2018

In rural areas the 100-year flood of smaller watersheds has a strong dependence on the permeability of the geologic subsurface of the watershed and on the point rainfall intensity.
Based on 70 000 well record files in the state of New Jersey, U.S.A. the ground water availability in the rock formations have been estimated.
Chemical Budgets and Chemical Quality of Snow and Runoff During Spring Snowmelt
Authors: Skartveit Arvid , Gjessing Yngvar T. 
Published: May 2018

In connection with water acidification and the subsequent disappearance of fish populations and also massive fish kills during spring floods, particular interest has been focused upon the fate and effects of ions released from the snowpack during melting.
Meltwater, enriched in ions, leaves the snowpack during melting episodes in winter. These (often small) amounts of water may via the ground-water reservoir have a long term influence upon the quality of winter runoff.
Data from catchments ranging from 0.04 to 232 km2 indicate that, during spring snowmelt in Tovdal, South Norway, the equivalent sum of ions in runoff is mainly governed by the release from the snowpack of sulphate and chloride, which move more or less directly into the watercourses, carrying with them cations directly from the snowpack or from biological and geological material within the catchment.
The concentrations in bulk snow decrease during melting and, therefore, during early snowmelt, the concentrations of sulphate and chloride are 2–5 times higher in the runoff than in the snowpack, well in accordance with polyethylene lysimeter experiments. The composition of the cationic counterparts of these anions in the runoff varies with the runoff rate, with high runoff rate yielding the most acid water.
Evaluation of a Precipitation Map Using a Smoothed Elevation-Precipitation Relationship and Optimal Estimates (Kriging)
Authors: de Montmollin F.A. , Olivier R.J. , Simard R. G. , Zwahlen F. 
Published: May 2018

Using 45 rain gauges, located in the center of French-speaking Switzerland (approx. 1,600 sq. km), we evaluate an annual mean precipitation map for the years 1974, 1975 and 1976. This estimate is based mainly on the anomaly method. For the index elevation, we selected an average altitude over an area of optimized size. This was evaluated from the best linear regression between index elevation of different areas and the precipitations.
An anomaly map was estimated using universal kriging: the structural analysis of the anomaly values permitted the adjustment of a variogram which made it possible to evaluate the spatial dependence of the anomaly variable. In order to obtain the precipitation map, not only was an anomaly map used but also a smoothed altitude map. This was calculated with the aid of an altimetric data bank covering the west part of Switzerland
Acid Groundwater
Authors: Hultberg Hans , Johansson Sivert 
Published: May 2018

Studies of the groundwater flow and quality around the lakes Bredvatten and Lysevatten have shown, that the increased concentrations of aluminum in acid lake water is caused by acid groundwater, and hence of leaching of aluminum into the groundwater. The increased aluminum concentration was later shown to be a major factor in the widespread ecosystem changes occurring in lakes and water systems.
When a similar, but even more pronounced soil- and groundwater acidification occurred via oxidation of accumulated sulfur to sulfuric acid and thereby releasing several soil minerals to the groundwater, a number of regional investigations were carried out on wells and groundwater systems in different provinces in southern Sweden.
The widespread problem with acid groundwater and thus acid tap water, made clear in these studies, shows that several thousand individual households have already acute problems with their drinking water and corroding metalpiping.
The acidification of the groundwater has caused health problems by elevated metal concentrations and economic problems for house owners in an even more pronounced way than acidification of the surface water systems (lakes and rivers). These effects also show how severely affected the lime poor natural ecosystem has become through our own and other countries' airborne acid pollutants.
The Step-Drawdown Test and Non-Darcian Flow: A Critical Review of Theory, Methods and Practice
Authors: Kærgaard Henrik 
Published: May 2018

Step-drawdown tests are usually carried out with succeeding steps of increased pumping yield, each step of equal duration of 1 hour. The background for this procedure is reviewed, and it is shown, that very often much shorter duration of steps is adequate.
The analysis of step-tests is usually based on the formulas of Jacob or Rorabaugh. The physical background for these formulas is reviewed, and the latter is shown to be unsatisfactory. However, the formula is used in cases where the data do not fit the Jacob formula, some typical deviations are shown. Reasons for these problems, trivial and non-trivial, are discussed, and some reasonably sound pshysical explanations for the various systematic deviations from the Jacob formula are given.
Trends in Nitrate Pollution of Groundwater in Denmark
Authors: Overgaard Kurt 
Published: May 2018

A nation-wide investigation of nitrate concentrations in groundwater in Denmark has been carried out. The investigation is based on analyses of groundwater samples from app. 11,000 wells and drinking water from 2,800 groundwaterworks spread equally all over the country, 43,000 km2. Furthermore the trends in nitrate concentrations have been investigated on the basis of time-series of nitrate concentrations for 184 waterworks.
The investigation shows that:
- the overall mean level of nitrate concentrations in the groundwaters has trebled within the last 20-30 years,
- there are pronounced regional differences in the nitrate concentrations of the groundwaters and in the trends of the nitrate concentrations,
- in the western parts of the country the groundwaters are more seriously affected than in the eastern parts and rising trends are significantly more pronounced,
- 36% of the investigated time-series of nitrate concentrations in drinking water from 184 groundwaterworks show a rising trend of 1 to 6 mg NO3/1 per year with a mean value of 3.3, and there is no sign of levelling off,
- drinking water from 8% of the waterworks exceed the EEC maximum admissible concentration for nitrate of 50 mg/1 and 18% EEC guide level of 25 mg/1.
The causes of the general rising trends in the nitrate concentrations in the groundwaters and the regional differences of the trends are discussed. In particular, the impact of agricultural activities and the role of the geological conditions are considered.
Experience with Field Testings of SHE on Research Catchments
Authors: Storm Børge , Høgh Jensen K. 
Published: May 2018

The development of the European Hydrologic System (SHE) has now reached such a stage, that it is ready for practical applications. Extensive field testings and associated developments have been carried out in recent years. The testings have included the complete system as well as the individual components. Particular emphasis has been given to the development and testing of the soil water flow model.
The paper demonstrates results from a field testing of SHE on the Wye Catchment in Britain, as well as examples of applications on small experimental catchments in Germany and New Zealand.
An Automatic Precipitation Gauge Based on Vibrating-Wire Strain Gauges
Authors: Bakkehøi S. , Øien K. , Førland E. J. 
Published: May 2018

The Norwegian Geotechnical Institute, NGI, has recently developed and tested a new automatic precipitation gauge for rain and snow which can measure accumulated precipitation with a resolution better than 0.1 mm. The gauge, which is a direct weighing device, is based on the use of vibrating-wire strain gauges. NGI's prototype instrument has a capacity of up to 300 mm precipitation before the gauge must be emptied. A new improved version designed by Geonor has a capacity of 600 mm precipitation. A diagram showing the relationship between the automatic observations and the manual measurements is included.
In the NGI prototype the precipitation container is suspended from three small steel wires, each of which is in effect the sensing element in a vibrating-wire type strain gauge. When these gauge wires are set into vibration by an electromagnetic exciter, their resonant frequency of vibration is proportional to the square of the tension in the wire. Thus change in the frequency signals is a measure of the change in tension in the wires and correspondingly a measure of the accumulative weight of precipiation in the container.
The distance between the precipitaion gauge and the monitoring station can be up to one kilometre without any loss in performance.
A Review of Chemical Solute Transport Models
Authors: Engesgaard P. , Christensen Th. H. 
Published: May 2018

This paper presents a review of groundwater models capable of simulating solute transport (i.e. advection-dispersion) and equilibrium chemistry processes.
Introductory, basic model components are discussed including a physical and a chemical model component and the coupling between the two components. However, emphasis is placed on the chemical model component, since this represents the recent addition to solute transport modeling.
Several ways exist of formulating either model component. For the physical model component this may include a continous description based on the governing mass balance equations or a discontinous description by a mixing cell approach. For the chemical model component, i.e. processes such as ion exchange, adsorption, complexation, precipitation/dissolution and open/closed carbonate system reactions, local equilibrium is usually assumed. The assumption of local equilibrium is investigated. The relation between the continuous formulation and a coupling/decoupling of the physical and chemical components and the resulting nature of the mathematical problem and its numerical strategy is briefly discussed.
In all, 27 models have been surveyed in terms of their physical and chemical model components, their verification and applicability to field scale problems. Due to a lack of actual field applications it has not been possible to evaluate all models in natural settings and hence, each model will, in theory, be valid when the constraints given by the assumptions and limitations taken in developing the model are met.
The models show great diversity with respect to complexity and general applicability to field scale problems. Most of the models were developed for specific purposes and it is difficult to point out one or more »general« models. However, it may be concluded that there exist many ways of formulating a model both with respect to transport and chemical calculations, but also to numerical techniques.
Many of the models are very complex and future research should be directed towards validation studies of these models on a field scale, rather than developing still more complex models.
Simulation of Soil Frost Depth and Effect on Runoff
Authors: Vehviläinen Bertel , Motovilov Yuri 
Published: May 2018

A physically based soil frost depth model usable with air temperature data and precipitation data, is presented. Snow depth is calculated from precipitation data using a physical snow cover model. The soil frost depth model is tested in one small basin, with a five-year calibration and verification period. Results from snow depth and soil frost depth simulation were satisfactory also in the verification period.
In the second stage simulated frost depth information was used to develop an HBV-runoff model version, attempting to simulate the possible effect of soil frost on runoff. The simulation results are presented. These results suggest that soil frost does not have a very important effect on runoff in this forested basin.
Rain-Runoff Parameters for Six Small Gauged Urban Catchments
Authors: Jensen Mogens 
Published: May 2018

The interpretation of rain-runoff measurements from 6 small (less than 17 ha) urban catchments is described. The recording period covers mostly 1979-1983. Relations between rain- and runoff depths were developed using the traditional linear regression model as well as a new continuous model. Both models compute runoff from impervious surfaces in the same way. Calculation of runoff from semipervious surfaces accounts for infiltration through cracks, percolation from a sublayer and evaporation during dry weather. These phenomena are related to water content of the sublayer. The 10 parameters in the continuous model are calibrated and show values in good agreement with data from the literature. The continuous model fits the measured runoff depths somewhat better for the largest runoff events. For more frequent events, however, the two models are equally good.
Rain intensity – duration – frequency curves have been computed. Variations of up to 20 %, for return periods 1/5 and 1/2 yr., are seen for catchments with distances approximately 5 km from each other.
Peak flow statistics are compared with rain intensity. The peak runoff coefficient (cf. rational method) is mostly constant or slightly increasing with the return period.
The Solubility and Hydrolysis of Aqueous Aluminium Hydroxides in Dilute Fresh Waters at Different Temperatures
Authors: Lydersen Espen 
Published: May 2018

This study is mainly focusing on the effect of temperature and pH on the chemistry of Al(OH)3(s) using available thermodynamic data.
The calculations show that a doubling of the [H+] or a decrease in temperature by 15°C, approximately yields the same solubility increase of the various Al(OH)3(s) presented.
The relative concentration of aqueous aluminium hydrolysis complexes is also highly temperature dependent. At 25°C and pH 5, the calculated distribution of dissolved, inorganic aluminium hydroxides corresponds to about 36% of Al3+, 37 % of Al(OH)2+, 26 % of Al(OH)2+ and 1 % of Al(OH)30. At the same pH but at 0°C, about 84%, 13%, 2% and 0% are present as Al3+, Al(OH)2+, Al(OH)2+ and Al(OH)30, respectively. This temperature effect is of major importance as the hydroxide species are supposed to be the most toxic species to aquatic biota.
Literature reports on the equilibrium constants Al(OH)3(s), log*Ks, vary from about 8 to 11, a variation in the product by a factor of 1000. In natural soil/water systems the solubility products of crystalline and amorphous solid aluminium sources are unknown and the solubility may also be coupled to combined weathering/ion exchange processes. In addition substantial amount of aluminium may be present as organic complexes where aluminium by cation exchange reactions may enter the solution as monomeric inorganic species. Thus, if a low value for the equilibrium constants of Al(OH)3(s) is used as reference when calculating the degree of aluminium saturation, an apparent oversaturation will often be demonstrated. To estimate the degree of aluminium saturation in natural waters whould therefore only be of theoretical interest.
Electromagnetic Profiling for Groundwater in Precambrian Basement Complex Areas of Nigeria
Authors: Olayinka A. Idowu 
Published: May 2018

Ground electromagnetic profiling, using a Geonics EM34-3 instrument, has been employed to identify areas of high conductivity in a Precambrian basement complex terrain of Nigeria.
Field examples, conducted as part of a rural water supply programme, are presented. They indicate that the apparent conductivities are generally lower than about 60 mmho m−1. Subsequent borehole drilling suggests a good correlation between high EM34 anomalies, deep weathering and high well yield (&gt; 1 1 s−1). On the other hand, boreholes sited on conductivity lows penetrated a thinner regolith with relatively lower yields.