scholarly journals A practical approach to lake water density from electrical conductivity and temperature

2016 ◽  
Vol 20 (7) ◽  
pp. 2975-2986 ◽  
Author(s):  
Santiago Moreira ◽  
Martin Schultze ◽  
Karsten Rahn ◽  
Bertram Boehrer
Keyword(s):  
Electrical Conductivity ◽  
Common Procedure ◽  
New Approach ◽  
Circulation Patterns ◽  
Lakes And Reservoirs ◽  
High Concentrations ◽  
Lake Waters ◽  
Very High ◽  
Limited Accuracy ◽  
Better Than

Abstract. Density calculations are essential to study stratification, circulation patterns, internal wave formation and other aspects of hydrodynamics in lakes and reservoirs. Currently, the most common procedure is the use of CTD (conductivity, temperature and depth) profilers and the conversion of measurements of temperature and electrical conductivity into density. In limnic waters, such approaches are of limited accuracy if they do not consider lake-specific composition of solutes, as we show. A new approach is presented to correlate density and electrical conductivity, using only two specific coefficients based on the composition of solutes. First, it is necessary to evaluate the lake-specific coefficients connecting electrical conductivity with density. Once these coefficients have been obtained, density can easily be calculated based on CTD data. The new method has been tested against measured values and the most common equations used in the calculation of density in limnic and ocean conditions. The results show that our new approach can reproduce the density contribution of solutes with a relative error of less than 10 % in lake waters from very low to very high concentrations as well as in lakes of very particular water chemistry, which is better than all commonly implemented density calculations in lakes. Finally, a web link is provided for downloading the corresponding density calculator.

scholarly journals A practical approach to lake water density from electrical conductivity and temperature

2016 ◽  
Author(s):  
Santiago Moreira ◽  
Martin Schultze ◽  
Karsten Rahn ◽  
Bertram Boehrer
Keyword(s):  
Electrical Conductivity ◽  
Common Procedure ◽  
New Approach ◽  
Specific Composition ◽  
Circulation Patterns ◽  
Lakes And Reservoirs ◽  
High Concentrations ◽  
Lake Waters ◽  
Very High ◽  
Limited Accuracy

Abstract. Density calculations are essential to study stratification, circulation patterns, internal wave formation and other aspects of hydrodynamics in lakes and reservoirs. Currently, the most common procedure is the use of CTD profilers and convert measurements of temperature and electrical conductivity into density. In limnic waters, such approaches are of limited accuracy, if they do not consider lake specific composition of solutes, as we show. A new approach is presented to correlate density and electrical conductivity, using only two specific coefficients based on the composition of solutes. First, it is necessary to evaluate the lake-specific coefficients connecting electrical conductivity with density. Once these coefficients have been obtained, density can easily be calculated based on CTD data. The new method has been tested against measured values and the most common equations used in the calculation of density in limnic and ocean conditions. The results show that our new approach can reproduce the density contribution of solutes with a relative accuracy of 10 % in lake waters from very low to very high concentrations as well as in lakes of very particular water chemistry, which surmounts all commonly implemented density calculations in lakes by far. Finally, we provide a web link for downloading the corresponding density calculator.

scholarly journals Early Window Tailoring: A New Approach to Increase the Number of TCP Connections Served

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Marcos Talau ◽  
Mauro Fonseca ◽  
Emilio C. G. Wille
Keyword(s):  
Congestion Control ◽  
Loss Rate ◽  
New Approach ◽  
Window Management ◽  
Multiple Devices ◽  
Congestion Control Mechanism ◽  
Tcp Connections ◽  
Multiple Scenarios ◽  
Very High ◽  
Better Than

In the absence of losses, TCP constantly increases the amount of data sent per instant of time. This behavior leads to problems that affect its performance, especially when multiple devices share the same gateway. Several studies have been done to mitigate such problems, but many of them require TCP side changes or a meticulous configuration. Some studies have shown promise, such as the use of gateway techniques to change the receiver’s advertised window of ACK segments based on the amount of memory in the gateway; in this work, we use the term “network-return” to refer to these techniques. In this paper, we present a new network-return technique called early window tailoring (EWT). For its use, it does not require any modification in the TCP implementations at the sides and does not require that all routers in the path use the same congestion control mechanism, and the use in the gateway is sufficient. With the use of the simulator ns-3 and following the recommendations of RFC 7928, the new approach was tested in multiple scenarios. The EWT was compared to drop-tail, RED, ARED, and the two network-return techniques—explicit window adaptation (EWA) and active window management (AWM). In the results, it was observed that EWT was shown to be efficient in congestion control. Its use avoided losses of segments, bringing expressive gains in the transfer latency and goodput and maintaining fairness between the flows. However, unlike other approaches, the most prominent feature of EWT is its ability to maintain a very high number of active flows at a given level of segment loss rate. The EWT allowed the existence of a number of flows, which is on average 49.3% better than its best competitor and 75.8% better when no AQM scheme was used.

scholarly journals Physical and Chemical Characteristics of a Mediterranean Coastal Microenvironment: The "Salty Lake" of Aghios Nikolaos (Crete, Greece)

2013 ◽  
Vol 2 (2) ◽  
pp. 167-178
Keyword(s):  
Coastal Waters ◽  
Marine Ecosystem ◽  
Anthropogenic Pollutants ◽  
High Concentrations ◽  
Lake Waters ◽  
Physical And Chemical ◽  
The Impact ◽  
Very High ◽  
Production Of Ammonia

The present paper examines a small and deep (53 m) salty lake, as well as the adjacent harbor of Aghios Nikolaos (Crete). The survey was carried out in 1996. Physicochemical parameters indicated that the main characteristics of the system are the inflow of karstic water from underwater springs inside the lake and the permanent anoxic conditions prevailing in its deeper part, below the thermocline. Nutrient concentrations are very high throughout the water column of the lake. Ammonia is the main source of nitrogen in the summer, particularly below the thermocline, whereas nitrates have high concentrations during spring and autumn. The high levels of these nutrients in the adjacent to the lake harbor and coastal waters indicate clearly the impact of the lake to the marine ecosystem. Anthropogenic pollutants, such as aromatic hydrocarbons, show high concentrations above thermocline, at 5-10 m depths during all samplings. However no particular point source was identified. The presence of hydrocarbons contributes to ineffective oxygenation of the lake waters and facilitates the development of anoxia and the production of ammonia. The PAH concentrations at the sampling stations outside the lake are typical of marine environments, with relatively small oil-derived inputs, indicating the complex role of the system as a source and/or as a trap of PAHs.

scholarly journals Effect of Shatt Al-Arab Salinity on the Groundwater of Al-Fao and Al-Siba in Southern Iraq

2021 ◽  
Vol 54 (1E) ◽  
pp. 114-122
Author(s):  
Shahad Abdul-Hameed ◽  
Amal Jabbar Hatem
Keyword(s):  
Electrical Conductivity ◽  
High Salinity ◽  
Saline Water ◽  
Arabian Gulf ◽  
Karun River ◽  
Ph Values ◽  
High Concentrations ◽  
Extent Of Damage ◽  
Southern Iraq ◽  
Very High

This study was conducted to estimate the extent of damage to the population in Basra, southern Iraq, specifically the areas adjacent to the Shatt al-Arab and the Arabian Gulf, which are the Al-Fao district and the Al-Siba region. They are affected by the progression of saline water resulting from the lack of water imports and the Karun River interruption, which led to high concentrations of salts in the Shatt Al-Arabs. Consequently, its effect on lands and all life types in these areas requires correcting a map of the study area to drop the groundwater sites as well as calculate the total dissolved salts, electrical conductivity and pH. This study concluded that the groundwater contains very high percentages of total dissolved solids (2880–10415 mg/l) and electrical conductivity (4450–14190 µs/cm). As it has very high salinity, so it is not suitable for drinking, irrigation, or industry. The values of the pH values (7.1-7.5) indicate that it is a light alkaline.

A new approach for dealing with depressions in digital elevation models when calculating flow accumulation values

2010 ◽  
Vol 34 (6) ◽  
pp. 781-809 ◽  
Author(s):  
Neil Arnold
Keyword(s):  
Digital Elevation Models ◽  
Physical Geography ◽  
Main Flow ◽  
High Quality ◽  
Common Procedure ◽  
New Approach ◽  
Flow Accumulation ◽  
Digital Elevation ◽  
Fine Spatial Resolution ◽  
Very High

Calculation of flow accumulation (also known as upstream area) matrices from digital elevation models (DEMs) is a very common procedure in hydrological studies, and also has been used in other disciplines within physical geography, such as glaciology. A problem with such calculations has always been the presence of closed depressions in DEMs; flow is directed towards such areas, but then cannot ‘escape’. In many implementations of flow accumulation algorithms such depressions have been removed from the DEM with some form of pre-processing algorithm which typically transform depressions into flat areas, across which area can then be routed. This approach effectively assumes that all depressions in a DEM are therefore artifacts, and not true features within the landscape. The proliferation of very high quality, high precision, and fine spatial resolution DEMs in recent years means that such an assumption is increasingly difficult to support. In this paper, some of the main flow accumulation algorithms and some existing techniques for dealing with closed depressions in DEMs are reviewed. A new algorithm is presented which assumes that such depressions are real features in the landscape, and which allows them to ‘fill’ and then ‘overflow’ into downstream areas within the DEM. Examples with a synthetic and two real DEMs suggest that, at least in these cases, the assumption that depressions are real is justified. These results also suggest that determining the size distribution for depressions within a DEM could form the basis for identifying whether artifact depressions are a problem in individual DEMs.

Treatment of Malignant Gliomas: A New Approach

1998 ◽  
Vol 84 (5) ◽  
pp. 529-533 ◽  
Author(s):  
Alessandro Paccapelo ◽  
Claudio Piana ◽  
Franco Rychlicki ◽  
Maria Antonietta Recchioni ◽  
Ugo Salvolini ◽  
...  
Keyword(s):  
Histological Grade ◽  
Objective Response ◽  
Malignant Gliomas ◽  
Intraarterial Infusion ◽  
New Approach ◽  
Antimitotic Effect ◽  
High Concentrations ◽  
Better Than

The aim of this study is to describe the authors’ experience with intra-arterial ACNU chemotherapy of malignant gliomas. The prognosis of cerebral malignant gliomas remains poor, whatever traditional therapy is applied. ACNU is a well tolerated nitrosourea with a strong antimitotic effect on neurogenic cells both in vitro and in vivo; this drug has enhanced efficacy when used at high concentrations, particularly as an intraarterial infusion. Seventy-six patients have been studied to date, 68 of whom are evaluable; these patients were treated by intraarterial infusion of ACNU (100 mg/m2) every 6 weeks, with a mean of 2.5 courses per patient. The objective response (OR) was 28% and analysis of pretreatment factors revealed that survival was influenced by histological grade, other types of therapy applied, and age. In general IAC is well tolerated and the response and survival appear to be better than with systemic chemotherapy.

Time and Latitude in South Africa

1972 ◽  
Vol 1 ◽  
pp. 27-38
Author(s):  
J. Hers
Keyword(s):  
South Africa ◽  
Cape Town ◽  
Astronomical Observations ◽  
Royal Observatory ◽  
The Republic ◽  
Astronomical Determination ◽  
Limited Accuracy ◽  
Better Than

In South Africa the modern outlook towards time may be said to have started in 1948. Both the two major observatories, The Royal Observatory in Cape Town and the Union Observatory (now known as the Republic Observatory) in Johannesburg had, of course, been involved in the astronomical determination of time almost from their inception, and the Johannesburg Observatory has been responsible for the official time of South Africa since 1908. However the pendulum clocks then in use could not be relied on to provide an accuracy better than about 1/10 second, which was of the same order as that of the astronomical observations. It is doubtful if much use was made of even this limited accuracy outside the two observatories, and although there may – occasionally have been a demand for more accurate time, it was certainly not voiced.

The metachor as a characteristic of the association of electrolytes in aqueous solutions

1984 ◽  
Vol 49 (5) ◽  
pp. 1061-1078 ◽  
Author(s):  
Jiří Čeleda ◽  
Stanislav Škramovský
Keyword(s):  
Aqueous Solutions ◽  
Apparent Volume ◽  
Solutions Of Electrolytes ◽  
Molal Volumes ◽  
The Difference ◽  
High Concentrations ◽  
Experimental Values ◽  
Suitable Characteristic ◽  
Association Of Ions ◽  
Very High

Based on the earlier paper introducing a concept of the apparent parachor of a solute in the solution, we have eliminated in the present work algebraically the effect which is introduced into this quantity by the additivity of the apparent molal volumes. The difference remaining from the apparent parachor after substracting the contribution corresponding to the apparent volume ( for which the present authors suggest the name metachor) was evaluated from the experimental values of the surface tension of aqueous solutions for a set of 1,1-, 1,2- and 2,1-valent electrolytes. This difference showed to be independent of concentration up to the very high values of the order of units mol dm-3 but it was directly proportional to the number of the free charges (with a proportionality factor 5 ± 1 cm3 mol-1 identical for all studied electrolytes). The metachor can be, for this reason, a suitable characteristic for detection of the association of ions and formation of complexes in the solutions of electrolytes, up to high concentrations where other methods are failing.

scholarly journals Nitrification Process in a Nuclear Wastewater with High Load of Nitrogen, Uranium and Organic Matter under ORP Controlled

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1607
Author(s):  
Mariano Venturini ◽  
Ariana Rossen ◽  
Patricia Silva Paulo
Keyword(s):  
Ammonia Oxidation ◽  
High Load ◽  
Nuclear Fuels ◽  
Monod Model ◽  
Nernst Equation ◽  
Nitrification Process ◽  
Real Wastewater ◽  
High Concentrations ◽  
Wastewater Samples ◽  
Very High

To produce nuclear fuels, it is necessary to convert uranium′s ore into UO2-ceramic grade, using several quantities of kerosene, methanol, nitric acid, ammonia, and, in low level, tributyl phosphate (TBP). Thus, the effluent generated by nuclear industries is one of the most toxic since it contains high concentrations of dangerous compounds. This paper explores biological parameters on real nuclear wastewater by the Monod model in an ORP controlled predicting the specific ammonia oxidation. Thermodynamic parameters were established using the Nernst equation to monitor Oxiders/Reductors relationship to obtain a correlation of these parameters to controlling and monitoring; that would allow technical operators to have better control of the nitrification process. The real nuclear effluent is formed by a mixture of two different lines of discharges, one composed of a high load of nitrogen, around 11,000 mg/L (N-NH4+-N-NO3−) and 600 mg/L Uranium, a second one, proceeds from uranium purification, containing TBP and COD that have to be removed. Bioprocesses were operated on real wastewater samples over 120 days under controlled ORP, as described by Nernst equations, which proved to be a robust tool to operate nitrification for larger periods with a very high load of nitrogen, uranium, and COD.

scholarly journals Halogenated Volatile Organic Compounds in Water Samples and Inorganic Elements Levels in Ores for Characterizing a High Anthropogenic Polluted Area in the Northern Latium Region (Italy)

2021 ◽  
Vol 18 (4) ◽  
pp. 1628
Author(s):  
Mario Vincenzo Russo ◽  
Ivan Notardonato ◽  
Alberto Rosada ◽  
Giuseppe Ianiri ◽  
Pasquale Avino
Keyword(s):  
Organic Compounds ◽  
Mean Value ◽  
Greenhouse Crops ◽  
River Waters ◽  
Liquid Liquid Extraction ◽  
Volatile Organic ◽  
High Concentrations ◽  
Very High ◽  
Inorganic Fraction

This paper shows a characterization of the organic and inorganic fraction of river waters (Tiber and Marta) and ores/soil samples collected in the Northern Latium region of Italy for evaluating the anthropogenic/natural source contribution to the environmental pollution of this area. For organic compounds, organochloride volatile compounds in Tiber and Marta rivers were analyzed by two different clean-up methods (i.e., liquid–liquid extraction and static headspace) followed by gas chromatography–electron capture detector (GC-ECD) analysis. The results show very high concentrations of bromoform (up to 1.82 and 3.2 µg L−1 in Tiber and Marta rivers, respectively), due to the presence of greenhouse crops, and of chloroform and tetrachloroethene, due to the presence of handicrafts installations. For the qualitative and quantitative assessment of the inorganic fraction, it is highlighted the use of a nuclear analytical method, instrumental neutron activation analysis, which allows having more information as possible from the sample without performing any chemical-physical pretreatment. The results have evidenced high levels of mercury (mean value 88.6 µg g−1), antimony (77.7 µg g−1), strontium (12,039 µg g−1) and zinc (103 µg g−1), whereas rare earth elements show levels similar to the literature data. Particular consideration is drawn for arsenic (414 µg g−1): the levels found in this paper (ranging between 1 and 5100 µg g−1) explain the high content of such element (as arsenates) in the aquifer, a big issue in this area.

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