title: Validation of simulated real world TCP stacks

authors: Jansen, Samuel Thomas

subjects: computer science

abstract: The TCP models in ns-2 have been validated and are widely used in network research. They are however not aimed at producing results consistent with a TCP implementation, they are rather designed to be a general model for TCP congestion control. The Network Simulation Cradle makes real world TCP implementations available to ns-2: Linux, FreeBSD and OpenBSD can all be simulated as easily as using the original simplified models. These simulated TCP implementations can be validated by directly comparing packet traces from simulations to traces measured from a real network. We describe the Network Simulation Cradle, present packet trace comparison results showing the high degree of accuracy possible when simulating with real TCP implementations and briefly show how this is reflected in a simulation study of TCP throughput.

text: Validation of simulated real world TCP stacks The TCP models in ns-2 have been validated and are widely used in network research. They are however not aimed at producing results consistent with a TCP implementation, they are rather designed to be a general model for TCP congestion control. The Network Simulation Cradle makes real world TCP implementations available to ns-2: Linux, FreeBSD and OpenBSD can all be simulated as easily as using the original simplified models. These simulated TCP implementations can be validated by directly comparing packet traces from simulations to traces measured from a real network. We describe the Network Simulation Cradle, present packet trace comparison results showing the high degree of accuracy possible when simulating with real TCP implementations and briefly show how this is reflected in a simulation study of TCP throughput.

year: 2007

title: Superintegrability on the two-dimensional hyperboloid

authors: Kalnins, Ernie G.

subjects: Mathematics

abstract: In this work we examine the basis functions for classical and quantum mechanical systems on the two-dimensional hyperboloid that admit separation of variables in at least two coordinate systems. We present all of these cases from a unified point of view. In particular, all of the special functions that arise via variable separation have their essential features expressed in terms of their zeros. The principal new results are the details of the polynomial bases for each of the nonsubgroup bases, not just the subgroup spherical coordinate cases, and the details of the structure of the quadratic symmetry algebras.

text: Superintegrability on the two-dimensional hyperboloid In this work we examine the basis functions for classical and quantum mechanical systems on the two-dimensional hyperboloid that admit separation of variables in at least two coordinate systems. We present all of these cases from a unified point of view. In particular, all of the special functions that arise via variable separation have their essential features expressed in terms of their zeros. The principal new results are the details of the polynomial bases for each of the nonsubgroup bases, not just the subgroup spherical coordinate cases, and the details of the structure of the quadratic symmetry algebras.

year: 1997-10

title: Monitoring and hydrodynamic modelling of groundwater inflows into Lake Rotokakahi, New Zealand

authors: Noakes, Katie

subjects: Groundwater

abstract: Lake Rotokakahi is located 10 km south of Rotorua and is of immense cultural importance to the local iwi. The lake also has significant historical and recreational values, which prompted iwi to make the lake private in 1996. Lake Rotokakahi is one of several Rotorua/ Te Arawa lakes. Several of these lakes have become eutrophic and some have declining water quality. This study was prompted by declining water quality of Lake Rotokakahi and the need to identify potential sources of nutrients to the lake, particularly groundwater inflows.

The interaction between groundwater and surface water has a major influence on the trophic status of lakes, particularly those that are predominantly or solely groundwater fed systems. Lake Rotokakahi has one small spring-fed surface water inflow and one outflow, the Te Wairoa stream. Thus the lake is predominantly groundwater fed. The main objective of this thesis was to quantify the contribution of groundwater and surface water to Lake Rotokakahi and to examine interactions of the groundwater system with the lake, in order to provide a basis to improve lake management practices. Multiple monitoring sites were established around the perimeter of the lake to determine the spatial and temporal variation of groundwater inputs, as well as the groundwater nutrient dynamics. A three-dimensional hydrodynamic lake model was set up and simulations were used to examine how groundwater and surface water inflows were dispersed within the lake upon entry.

Monitoring of the shallow groundwater system took place from 1 January to 1 July 2016. Three separate storm events were monitored at high frequency within this monitoring period. The monitoring results showed the groundwater system varied significantly both spatially and temporally and also contributed a high proportion of the total nutrient load to the lake. Groundwater discharge and nutrient concentrations generally increased in association with or immediately following high rainfall events.
 
The three-dimensional model ELCOM was set up using hydrological data for the catchment, meteorological data from a nearby station and bathymetry of the lake. Simulations were based upon different methods of calculating groundwater inflows. Simulation 1 was based upon the common water balance equation method. Simulation 2 used constant groundwater inflow and outflow volumes as determined by a groundwater flow model, MODFLOW, which had been applied to the catchment by White et al., (2015). Simulation 3 combined MODLFOW values and measured groundwater levels to create a varying inflow volume based on water level. The three simulations accurately captured surface and bottom temperatures and had varying lake water levels. Only simulation 3 accurately captured the presence of the groundwater spring near the lake shore and was concluded the more accurate method of groundwater inflow calculation.

text: Monitoring and hydrodynamic modelling of groundwater inflows into Lake Rotokakahi, New Zealand Lake Rotokakahi is located 10 km south of Rotorua and is of immense cultural importance to the local iwi. The lake also has significant historical and recreational values, which prompted iwi to make the lake private in 1996. Lake Rotokakahi is one of several Rotorua/ Te Arawa lakes. Several of these lakes have become eutrophic and some have declining water quality. This study was prompted by declining water quality of Lake Rotokakahi and the need to identify potential sources of nutrients to the lake, particularly groundwater inflows.

The interaction between groundwater and surface water has a major influence on the trophic status of lakes, particularly those that are predominantly or solely groundwater fed systems. Lake Rotokakahi has one small spring-fed surface water inflow and one outflow, the Te Wairoa stream. Thus the lake is predominantly groundwater fed. The main objective of this thesis was to quantify the contribution of groundwater and surface water to Lake Rotokakahi and to examine interactions of the groundwater system with the lake, in order to provide a basis to improve lake management practices. Multiple monitoring sites were established around the perimeter of the lake to determine the spatial and temporal variation of groundwater inputs, as well as the groundwater nutrient dynamics. A three-dimensional hydrodynamic lake model was set up and simulations were used to examine how groundwater and surface water inflows were dispersed within the lake upon entry.

Monitoring of the shallow groundwater system took place from 1 January to 1 July 2016. Three separate storm events were monitored at high frequency within this monitoring period. The monitoring results showed the groundwater system varied significantly both spatially and temporally and also contributed a high proportion of the total nutrient load to the lake. Groundwater discharge and nutrient concentrations generally increased in association with or immediately following high rainfall events.
 
The three-dimensional model ELCOM was set up using hydrological data for the catchment, meteorological data from a nearby station and bathymetry of the lake. Simulations were based upon different methods of calculating groundwater inflows. Simulation 1 was based upon the common water balance equation method. Simulation 2 used constant groundwater inflow and outflow volumes as determined by a groundwater flow model, MODFLOW, which had been applied to the catchment by White et al., (2015). Simulation 3 combined MODLFOW values and measured groundwater levels to create a varying inflow volume based on water level. The three simulations accurately captured surface and bottom temperatures and had varying lake water levels. Only simulation 3 accurately captured the presence of the groundwater spring near the lake shore and was concluded the more accurate method of groundwater inflow calculation.

year: 2016