title: Resolving depth measurement ambiguity with commercially available range imaging cameras

authors: McClure, Shane H.

subjects: range imaging

abstract: Time-of-flight range imaging is typically performed with the amplitude modulated continuous wave method. This involves illuminating a scene with amplitude modulated light. Reflected light from the scene is received by the sensor with the range to the scene encoded as a phase delay of the modulation envelope. Due to the cyclic nature of phase, an ambiguity in the measured range occurs every half wavelength in distance, thereby limiting the maximum useable range of the camera.
This paper proposes a procedure to resolve depth ambiguity using software post processing. First, the range data is processed to segment the scene into separate objects. The average intensity of each object can then be used to determine which pixels are beyond the non-ambiguous range. The results demonstrate that depth ambiguity can be resolved for various scenes using only the available depth and intensity information. This proposed method reduces the sensitivity to objects with very high and very low reflectance, normally a key problem with basic threshold approaches.
This approach is very flexible as it can be used with any range imaging camera. Furthermore, capture time is not extended, keeping the artifacts caused by moving objects at a minimum. This makes it suitable for applications such as robot vision where the camera may be moving during captures.
The key limitation of the method is its inability to distinguish between two overlapping objects that are separated by a distance of exactly one non-ambiguous range. Overall the reliability of this method is higher than the basic threshold approach, but not as high as the multiple frequency method of resolving ambiguity.

text: Resolving depth measurement ambiguity with commercially available range imaging cameras Time-of-flight range imaging is typically performed with the amplitude modulated continuous wave method. This involves illuminating a scene with amplitude modulated light. Reflected light from the scene is received by the sensor with the range to the scene encoded as a phase delay of the modulation envelope. Due to the cyclic nature of phase, an ambiguity in the measured range occurs every half wavelength in distance, thereby limiting the maximum useable range of the camera.
This paper proposes a procedure to resolve depth ambiguity using software post processing. First, the range data is processed to segment the scene into separate objects. The average intensity of each object can then be used to determine which pixels are beyond the non-ambiguous range. The results demonstrate that depth ambiguity can be resolved for various scenes using only the available depth and intensity information. This proposed method reduces the sensitivity to objects with very high and very low reflectance, normally a key problem with basic threshold approaches.
This approach is very flexible as it can be used with any range imaging camera. Furthermore, capture time is not extended, keeping the artifacts caused by moving objects at a minimum. This makes it suitable for applications such as robot vision where the camera may be moving during captures.
The key limitation of the method is its inability to distinguish between two overlapping objects that are separated by a distance of exactly one non-ambiguous range. Overall the reliability of this method is higher than the basic threshold approach, but not as high as the multiple frequency method of resolving ambiguity.

year: 2010

title: Catabolism of naphthalene and phenanthrene by Burkholderia sp. strain RP007

authors: Laurie, Andrew David

abstract: Burkholderia sp. strain RP007 was isolated for its ability to utilise phenanthrene as a sole source of carbon and energy. This strain was identified as a Burkholderia sp. by biochemical tests, fatty acid analysis, and nucleotide sequencing of the 16S rRNA gene. The ability of Burkholderia sp. strain RP007 to mineralise [9-¹⁴C]phenanthrene and [1-¹⁴C]naphthalene was confirmed.

A gene cluster (phn) which represents a new group of upper pathway genes for polycyclic aromatic hydrocarbon (PAH) degradation was cloned from Burkholderia sp. strain RP007. Nucleotide sequencing of an 11.5 kb HindIII fragment cloned from RP007 revealed the presence of nine open reading frames (ORFѕ). Escherichia coli carrying the recombinant phn genes was able to transform naphthalene to salicylic acid. The phn genes are significantly different in sequence and gene order from the previously described nah, ndo, pah and dox genes for PAH degradation. The phn locus encodes iron-sulfur protein α and β subunits of a PAH initial dioxygenase, but not the ferredoxin and reductase components. The dihydrodiol dehydrogenase of the RP007 pathway, PhnB, shows greater similarity to analogous dehydrogenases from described biphenyl pathways than to those characterised from naphthalene/phenanthrene pathways. Furthermore, the RP007 extradiol dioxygenase, PhnC, shows no similarity to other extradiol dioxygenases for naphthalene or biphenyl oxidation, but is a member of the recently proposed Class III extradiol dioxygenases. Upstream of the phn catabolic genes are two putative regulatory genes phnR and phnS. phnR is divergently transcribed with respect to the other genes and is similar to the σ⁵⁴-dependent family of positive transcriptional regulators. phnS is a LysR-type transcriptional activator. Expression experiments suggest the phn operon is under regulatory control which may involve PhnR and PhnS.

Two loci encoding aromatic meta cleavage pathways were also cloned from Burkholderia sp. strain RP007. The nucleotide sequence of the catechol 2,3-dioxygenase genes, and adjacent open reading frames, suggest these are meta pathways of different classes which specify catabolism of different aromatic substrates. One of these may be the lower pathway for phenanthrene and naphthalene degradation.

The presence of catabolic genes homologous to the phnAc gene of Burkholderia sp. strain RP007, relative to the archetypal nahAc gene of Pseudomonas putida G7, was screened for in both culturable and nonculturable microbial communities. Of 77 environmental isolates cultured for their ability to degrade naphthalene or phenanthrene, 28 showed homology to nahAc, whilst none of the strains possessed catabolic genes similar to phnAc. However, using phnAc-specific primers, PCR products homologous to phnAc were amplified from DNA extracts of eight hydrocarbon-contaminated soils, demonstrating the widespread distribution of this genotype. Analysis of these phnAc PCR products by nucleotide sequencing of selected cloned products revealed very high (98.5-100%) homology to the phnAc gene of RP007, suggesting the phn genotype is highly conserved. PCR products were also amplified from soil DNA using nahAc-specific primers, and sequencing of these products revealed a diversity similar to that amongst previously described nah-like genes.

text: Catabolism of naphthalene and phenanthrene by Burkholderia sp. strain RP007 Burkholderia sp. strain RP007 was isolated for its ability to utilise phenanthrene as a sole source of carbon and energy. This strain was identified as a Burkholderia sp. by biochemical tests, fatty acid analysis, and nucleotide sequencing of the 16S rRNA gene. The ability of Burkholderia sp. strain RP007 to mineralise [9-¹⁴C]phenanthrene and [1-¹⁴C]naphthalene was confirmed.

A gene cluster (phn) which represents a new group of upper pathway genes for polycyclic aromatic hydrocarbon (PAH) degradation was cloned from Burkholderia sp. strain RP007. Nucleotide sequencing of an 11.5 kb HindIII fragment cloned from RP007 revealed the presence of nine open reading frames (ORFѕ). Escherichia coli carrying the recombinant phn genes was able to transform naphthalene to salicylic acid. The phn genes are significantly different in sequence and gene order from the previously described nah, ndo, pah and dox genes for PAH degradation. The phn locus encodes iron-sulfur protein α and β subunits of a PAH initial dioxygenase, but not the ferredoxin and reductase components. The dihydrodiol dehydrogenase of the RP007 pathway, PhnB, shows greater similarity to analogous dehydrogenases from described biphenyl pathways than to those characterised from naphthalene/phenanthrene pathways. Furthermore, the RP007 extradiol dioxygenase, PhnC, shows no similarity to other extradiol dioxygenases for naphthalene or biphenyl oxidation, but is a member of the recently proposed Class III extradiol dioxygenases. Upstream of the phn catabolic genes are two putative regulatory genes phnR and phnS. phnR is divergently transcribed with respect to the other genes and is similar to the σ⁵⁴-dependent family of positive transcriptional regulators. phnS is a LysR-type transcriptional activator. Expression experiments suggest the phn operon is under regulatory control which may involve PhnR and PhnS.

Two loci encoding aromatic meta cleavage pathways were also cloned from Burkholderia sp. strain RP007. The nucleotide sequence of the catechol 2,3-dioxygenase genes, and adjacent open reading frames, suggest these are meta pathways of different classes which specify catabolism of different aromatic substrates. One of these may be the lower pathway for phenanthrene and naphthalene degradation.

The presence of catabolic genes homologous to the phnAc gene of Burkholderia sp. strain RP007, relative to the archetypal nahAc gene of Pseudomonas putida G7, was screened for in both culturable and nonculturable microbial communities. Of 77 environmental isolates cultured for their ability to degrade naphthalene or phenanthrene, 28 showed homology to nahAc, whilst none of the strains possessed catabolic genes similar to phnAc. However, using phnAc-specific primers, PCR products homologous to phnAc were amplified from DNA extracts of eight hydrocarbon-contaminated soils, demonstrating the widespread distribution of this genotype. Analysis of these phnAc PCR products by nucleotide sequencing of selected cloned products revealed very high (98.5-100%) homology to the phnAc gene of RP007, suggesting the phn genotype is highly conserved. PCR products were also amplified from soil DNA using nahAc-specific primers, and sequencing of these products revealed a diversity similar to that amongst previously described nah-like genes.

year: 1998

title: Materials for enhancing denitrification performance in partially saturated vertical flow wetlands for marae

authors: Liu, Lucian XiaoRan

abstract: There are upwards of 773 marae in New Zealand which are responsible for many key events for the indigenous people, Māori, many of which are located rurally and have inadequate on-site wastewater treatment mostly comprising of a septic tank followed by land application. Māori have many strong beliefs about water and subsequently criteria surround the treatment of wastewater due to the effects it can have on people and environment. One proposed solution that meets criteria are treatment wetlands, more specifically partially saturated vertical flow wetlands which require a smaller footprint and produce better effluent than traditional wetland designs. NIWA (National Institute of Water and Atmospheric Research) has experimented with mesocosm scale versions of this design and has encountered issues with denitrification in the saturated zone.

This research is therefore directed at enhancing denitrification in the saturated zone with materials that are able to supplement organic carbon for denitrification. Several woodchip materials (Eastern Cottonwood, Mahogany, Manuka, Eucalyptus, Crack Willow, Princess Tree and Pine) along with two industry by-product materials (Brewers Spent Grain and Slum gum) and Coir (Coconut derivative) were examined for denitrification capabilities and to serve in producing a leachate for dosing the proposed system to supplement organic carbon for denitrification.

The research is split into three phases; the first examines the ability of materials to release organic carbon into water over 60 days, the second examines the same but over three 10 day cycles, and the third quantifies denitrification performance of the materials at lab scale.

Results showed that producing a suitable leachate is not possible without the use of fresh material for each batch. By-product materials had great capacity for releasing organic carbon into water and denitrification (up to 85.5% nitrate removal) but had limited lifespans as media. While woodchip materials did not exhibit as great carbon release, they achieved comparable denitrification (74.2-74.5% nitrate removal) with long lifespans. Therefore, a woodchip and industry by-product mix could be the solution. Alternatively, there are many woodchip species, some which could have better denitrification capacity or suitable industry by-products with longer useful lifespans.

text: Materials for enhancing denitrification performance in partially saturated vertical flow wetlands for marae There are upwards of 773 marae in New Zealand which are responsible for many key events for the indigenous people, Māori, many of which are located rurally and have inadequate on-site wastewater treatment mostly comprising of a septic tank followed by land application. Māori have many strong beliefs about water and subsequently criteria surround the treatment of wastewater due to the effects it can have on people and environment. One proposed solution that meets criteria are treatment wetlands, more specifically partially saturated vertical flow wetlands which require a smaller footprint and produce better effluent than traditional wetland designs. NIWA (National Institute of Water and Atmospheric Research) has experimented with mesocosm scale versions of this design and has encountered issues with denitrification in the saturated zone.

This research is therefore directed at enhancing denitrification in the saturated zone with materials that are able to supplement organic carbon for denitrification. Several woodchip materials (Eastern Cottonwood, Mahogany, Manuka, Eucalyptus, Crack Willow, Princess Tree and Pine) along with two industry by-product materials (Brewers Spent Grain and Slum gum) and Coir (Coconut derivative) were examined for denitrification capabilities and to serve in producing a leachate for dosing the proposed system to supplement organic carbon for denitrification.

The research is split into three phases; the first examines the ability of materials to release organic carbon into water over 60 days, the second examines the same but over three 10 day cycles, and the third quantifies denitrification performance of the materials at lab scale.

Results showed that producing a suitable leachate is not possible without the use of fresh material for each batch. By-product materials had great capacity for releasing organic carbon into water and denitrification (up to 85.5% nitrate removal) but had limited lifespans as media. While woodchip materials did not exhibit as great carbon release, they achieved comparable denitrification (74.2-74.5% nitrate removal) with long lifespans. Therefore, a woodchip and industry by-product mix could be the solution. Alternatively, there are many woodchip species, some which could have better denitrification capacity or suitable industry by-products with longer useful lifespans.

year: 2023