title: Undue influence: Mitigating range-intensity coupling in AMCW ‘flash’ lidar using scene texture

authors: Godbaz, John Peter

subjects: AMCW flass lidar

abstract: We present a new algorithm for mitigating range-intensity coupling caused by scattered light in full-field amplitude modulated continuous wave lidar systems using scene texture. Full-field Lidar works using the time-of-flight principle to measure the range to thousands of points in a scene simultaneously. Mixed pixel are erroneous range measurements caused by pixels integrating light from more than one object at a time. Conventional optics suffer from internal reflections and light scattering which can result in every pixel being mixed with scattered light. This causes erroneous range measurements and range-intensity coupling. By measuring how range changes with intensity over local regions it is possible to determine the phase and intensity of the scattered light without the complex calibration inherent in deconvolution based restoration. The new method is shown to produce a substantial improvement in range image quality. An additional range from texture method is demonstrated which is resistant to scattered light. Variations of the algorithms are tested with and without segmentation - the variant without segmentation is faster, but causes erroneous ranges around the edges of objects which are not present in the segmented algorithm.

text: Undue influence: Mitigating range-intensity coupling in AMCW ‘flash’ lidar using scene texture We present a new algorithm for mitigating range-intensity coupling caused by scattered light in full-field amplitude modulated continuous wave lidar systems using scene texture. Full-field Lidar works using the time-of-flight principle to measure the range to thousands of points in a scene simultaneously. Mixed pixel are erroneous range measurements caused by pixels integrating light from more than one object at a time. Conventional optics suffer from internal reflections and light scattering which can result in every pixel being mixed with scattered light. This causes erroneous range measurements and range-intensity coupling. By measuring how range changes with intensity over local regions it is possible to determine the phase and intensity of the scattered light without the complex calibration inherent in deconvolution based restoration. The new method is shown to produce a substantial improvement in range image quality. An additional range from texture method is demonstrated which is resistant to scattered light. Variations of the algorithms are tested with and without segmentation - the variant without segmentation is faster, but causes erroneous ranges around the edges of objects which are not present in the segmented algorithm.

year: 2009

title: The hydrodynamics of the southern basin of Tauranga Harbour

authors: Tay, H.W.

subjects: hydrodynamic model

abstract: The circulation of the southern basin of Tauranga Harbour was simulated using a 3-D hydrodynamic model ELCOM. A 9-day field campaign in 1999 provided data on current velocity, temperature and salinity profiles at three stations within the main basin. The tidal wave changed most in amplitude and speed in the constricted entrances to channels, for example the M2 tide attenuated by 10% over 500 m at the main entrance, and only an additional 17% over the 15 km to the top of the southern basin. The modelled temperature was sensitive to wind mixing, particularly in tidal flat regions. Residence times ranged from 3 to 8 days, with higher residence times occurring in sub-estuaries with constricted mouths. The typical annual storm events were predicted to reduce the residence times by 24%–39% depending on season. Model scenarios of storm discharge events in the Wairoa River varying from 41.69 m3/s to 175.9 m3/s show that these events can cause salinity gradients across the harbour of up to 4 PSU.

text: The hydrodynamics of the southern basin of Tauranga Harbour The circulation of the southern basin of Tauranga Harbour was simulated using a 3-D hydrodynamic model ELCOM. A 9-day field campaign in 1999 provided data on current velocity, temperature and salinity profiles at three stations within the main basin. The tidal wave changed most in amplitude and speed in the constricted entrances to channels, for example the M2 tide attenuated by 10% over 500 m at the main entrance, and only an additional 17% over the 15 km to the top of the southern basin. The modelled temperature was sensitive to wind mixing, particularly in tidal flat regions. Residence times ranged from 3 to 8 days, with higher residence times occurring in sub-estuaries with constricted mouths. The typical annual storm events were predicted to reduce the residence times by 24%–39% depending on season. Model scenarios of storm discharge events in the Wairoa River varying from 41.69 m3/s to 175.9 m3/s show that these events can cause salinity gradients across the harbour of up to 4 PSU.

year: 2013

title: Microbiological quality of Toroi:  A Māori food delicacy

authors: Dixon, Lorraine Louise

subjects: Maori

abstract: A study was undertaken to determine the food safety of the fermented Māori delicacy, Toroi.  Ten batches of Toroi were prepared by a commonly used traditional method that consisted of boiling the vegetable component, either watercress or puha, and combining it with chopped mussel flesh.  The mixture was cooled and then stored in a refrigerator for up to eight months to allow natural fermentation to take place.  All ingredients were sourced from retail outlets.  The Toroi was examined at intervals over eight months for a range of pathogens (seven in all) that have been related to incidents of food poisoning in ready-to-eat foods in New Zealand.  The survival of a faecal contamination indicator, the laboratory grown strain Escherichia coli NZRM 916, was mapped over eight months.  Two strategies to prevent the growth of Listeria monocytogenes in Toroi were also investigated.  

Only one of the seven pathogens sought was recovered from any sample.  This pathogen was Bacillus cereus, a spore-former known to be associated with vegetables.  All batches contained B. cereus on the day of preparation but after two weeks refrigerated storage there was no further recovery from any sample.  There was a very low incidence of natural E. coli in the Toroi, consistent with levels permitted in mussels sold in retail outlets.  The laboratory grown strain, E. coli declined substantially over two months and was not recovered from any samples at eight months.  
A laboratory grown strain of Listeria monocytogenes, (L70) was added to Toroi and grew well with an increase in concentration of about seven-fold, over 19 days storage in a refrigerator.  A bacteriocin producing lactic acid bacterium, Lactobacillus sake Lb706, was added in combined culture with L. monocytogenes to Toroi.  It was found that at least 5 x108 L. sake cells were required as an inoculum to ensure elimination of L. monocytogenes from the Toroi.  When a purified bacteriocin; nisin, was added, a concentration of 10 mg g-1 in the Toroi was required to eliminate L. monocytogenes.  The inhibition study results suggest that unacceptably high inocula or purified bacteriocin would be required to prevent the growth of L. monocytogenes in Toroi.

The results of this suggest that Toroi be prepared from mussels either purchased from a retail outlet or harvested from sites known to be free from contamination.  Toroi should be safe to eat if prepared carefully, chilled promptly and thoroughly and allowed to ferment for at least two weeks.  In addition, care should be taken to maintain Toroi at refrigerated temperatures until it is eaten.

text: Microbiological quality of Toroi:  A Māori food delicacy A study was undertaken to determine the food safety of the fermented Māori delicacy, Toroi.  Ten batches of Toroi were prepared by a commonly used traditional method that consisted of boiling the vegetable component, either watercress or puha, and combining it with chopped mussel flesh.  The mixture was cooled and then stored in a refrigerator for up to eight months to allow natural fermentation to take place.  All ingredients were sourced from retail outlets.  The Toroi was examined at intervals over eight months for a range of pathogens (seven in all) that have been related to incidents of food poisoning in ready-to-eat foods in New Zealand.  The survival of a faecal contamination indicator, the laboratory grown strain Escherichia coli NZRM 916, was mapped over eight months.  Two strategies to prevent the growth of Listeria monocytogenes in Toroi were also investigated.  

Only one of the seven pathogens sought was recovered from any sample.  This pathogen was Bacillus cereus, a spore-former known to be associated with vegetables.  All batches contained B. cereus on the day of preparation but after two weeks refrigerated storage there was no further recovery from any sample.  There was a very low incidence of natural E. coli in the Toroi, consistent with levels permitted in mussels sold in retail outlets.  The laboratory grown strain, E. coli declined substantially over two months and was not recovered from any samples at eight months.  
A laboratory grown strain of Listeria monocytogenes, (L70) was added to Toroi and grew well with an increase in concentration of about seven-fold, over 19 days storage in a refrigerator.  A bacteriocin producing lactic acid bacterium, Lactobacillus sake Lb706, was added in combined culture with L. monocytogenes to Toroi.  It was found that at least 5 x108 L. sake cells were required as an inoculum to ensure elimination of L. monocytogenes from the Toroi.  When a purified bacteriocin; nisin, was added, a concentration of 10 mg g-1 in the Toroi was required to eliminate L. monocytogenes.  The inhibition study results suggest that unacceptably high inocula or purified bacteriocin would be required to prevent the growth of L. monocytogenes in Toroi.

The results of this suggest that Toroi be prepared from mussels either purchased from a retail outlet or harvested from sites known to be free from contamination.  Toroi should be safe to eat if prepared carefully, chilled promptly and thoroughly and allowed to ferment for at least two weeks.  In addition, care should be taken to maintain Toroi at refrigerated temperatures until it is eaten.

year: 2007