title: Enhancing rainfall measurement using microwave links at three scales

authors: Esmaeil Nia, Saeid

abstract: The application of microwave signals in telecommunication has advanced in recent decades. Hence the CMLs (Commercial Microwave Links) have been spread all over the lands. Meanwhile, the decrease in power of the signal due to rainfall has raised the idea of measuring rainfall with microwave attenuation. This PhD research delves into the challenges of these techniques and investigates potential solutions to enhance the accuracy of measuring rainfall. The objectives of the study set to three levels of raindrops’ impact, signal characteristics, and catchment evaluations.  

In the first stage, the cross-sections of different sizes of raindrops are calculated by solving Maxwell’s differential equations in COMSOL software. Rainfall is calculated from different Drop Size Distribution (DSD) models. Then, the correlation between the resulting attenuation and rainfall provided different coefficients for the power correlation between rainfall and attenuation. Regarding the variability in DSD with rainfall intensity, alterations in extinction cross-section play a role in establishing a fluid relationship between attenuation and rainfall. This necessitates adjusting constants for the correlation across different rainfall intensities. 

The results support the idea of having varying coefficients for different rainfall intensities.  At the second level, the signal characteristics were investigated to find a robust method for extracting attenuation from the received power. The study led to defining a reference signal level through signal denoising methods of moving average, Butterworth, and Chebyshev methods. The study showed the superior performance of the moving average in predicting rainfall, especially in 38 GHz links (H and V) indicated by NSE and KGE. Overall, the moving average also resulted in 2%, 16%, and 14% lower RMSE than the conventional method in microwave links 26H, 38H, and 38V, respectively. Butterworth and Chebyshev filters exhibited higher NSE and lower RMSE in 38 GHz links, with competitive accuracy in the 26 GHz link compared to conventional methods.  The effect of wet antenna also decreased and even vanished in some cases. 

At last, the catchment runoff was used to calibrate the relationship between rainfall and attenuation. In a study in 15 catchments in Melbourne, the suggested method established a relation between attenuation and the quick flow of 15 flow stations. Meanwhile, the coefficients of the rainfall-attenuation formula were calibrated to reach the highest accuracy of runoff prediction. The results indicate a more robust connection between attenuation and quick flow in contrast to conventional rain gauge data. The new suggested method achieved a maximum NSE of 0.78 and KGE of 0.86. Compared to rain gauges, the conventional CML model improved NSE by an average of 197%, while the new model showed an additional 50% enhancement. RMSE optimisation also demonstrated improvement, with a 15% enhancement using the conventional CML model and an additional 4% on average with the new model. Moreover, the revised flow calibration technique reduces the wet antenna effect by an average of 49%.

text: Enhancing rainfall measurement using microwave links at three scales The application of microwave signals in telecommunication has advanced in recent decades. Hence the CMLs (Commercial Microwave Links) have been spread all over the lands. Meanwhile, the decrease in power of the signal due to rainfall has raised the idea of measuring rainfall with microwave attenuation. This PhD research delves into the challenges of these techniques and investigates potential solutions to enhance the accuracy of measuring rainfall. The objectives of the study set to three levels of raindrops’ impact, signal characteristics, and catchment evaluations.  

In the first stage, the cross-sections of different sizes of raindrops are calculated by solving Maxwell’s differential equations in COMSOL software. Rainfall is calculated from different Drop Size Distribution (DSD) models. Then, the correlation between the resulting attenuation and rainfall provided different coefficients for the power correlation between rainfall and attenuation. Regarding the variability in DSD with rainfall intensity, alterations in extinction cross-section play a role in establishing a fluid relationship between attenuation and rainfall. This necessitates adjusting constants for the correlation across different rainfall intensities. 

The results support the idea of having varying coefficients for different rainfall intensities.  At the second level, the signal characteristics were investigated to find a robust method for extracting attenuation from the received power. The study led to defining a reference signal level through signal denoising methods of moving average, Butterworth, and Chebyshev methods. The study showed the superior performance of the moving average in predicting rainfall, especially in 38 GHz links (H and V) indicated by NSE and KGE. Overall, the moving average also resulted in 2%, 16%, and 14% lower RMSE than the conventional method in microwave links 26H, 38H, and 38V, respectively. Butterworth and Chebyshev filters exhibited higher NSE and lower RMSE in 38 GHz links, with competitive accuracy in the 26 GHz link compared to conventional methods.  The effect of wet antenna also decreased and even vanished in some cases. 

At last, the catchment runoff was used to calibrate the relationship between rainfall and attenuation. In a study in 15 catchments in Melbourne, the suggested method established a relation between attenuation and the quick flow of 15 flow stations. Meanwhile, the coefficients of the rainfall-attenuation formula were calibrated to reach the highest accuracy of runoff prediction. The results indicate a more robust connection between attenuation and quick flow in contrast to conventional rain gauge data. The new suggested method achieved a maximum NSE of 0.78 and KGE of 0.86. Compared to rain gauges, the conventional CML model improved NSE by an average of 197%, while the new model showed an additional 50% enhancement. RMSE optimisation also demonstrated improvement, with a 15% enhancement using the conventional CML model and an additional 4% on average with the new model. Moreover, the revised flow calibration technique reduces the wet antenna effect by an average of 49%.

year: 2024

title: Mechanical performance of Kraft fibre reinforced polypropylene composites: Influence of fibre length, fibre beating and hygrothermal ageing

authors: Pickering, Kim L.

subjects: A. Natural fibre composites

abstract: This paper describes the influence of fibre length, fibre beating and hygrothermal ageing on tensile strength (TS), Young’s modulus (YM), failure strain (FS) and impact strength (IS) of Kraft fibre reinforced polypropylene (PP) composites. TS, YM and IS of composites were found to decrease and FS increased with decreasing fibre length. Modest levels of fibre beating increased the TS of composites, which is believed to be due to improved interfacial bonding. During hygrothermal ageing, the diffusion coefficient increased with increased ageing temperature. Composites without coupling agent showed higher water uptake and diffusion coefficient than those with coupling agent. TS and YM were found to decrease for hygrothermal ageing due to fibre damage and reduced fibre matrix interfacial bonding, whilst FS and IS were found to increase due to the plasticizing effect of water.

text: Mechanical performance of Kraft fibre reinforced polypropylene composites: Influence of fibre length, fibre beating and hygrothermal ageing This paper describes the influence of fibre length, fibre beating and hygrothermal ageing on tensile strength (TS), Young’s modulus (YM), failure strain (FS) and impact strength (IS) of Kraft fibre reinforced polypropylene (PP) composites. TS, YM and IS of composites were found to decrease and FS increased with decreasing fibre length. Modest levels of fibre beating increased the TS of composites, which is believed to be due to improved interfacial bonding. During hygrothermal ageing, the diffusion coefficient increased with increased ageing temperature. Composites without coupling agent showed higher water uptake and diffusion coefficient than those with coupling agent. TS and YM were found to decrease for hygrothermal ageing due to fibre damage and reduced fibre matrix interfacial bonding, whilst FS and IS were found to increase due to the plasticizing effect of water.

year: 2008

title: Taonga tuku iho: Intergenerational transfer of raranga and whatu

authors: Te Kanawa, Kahutoi Mere

subjects: Intergenerational Knowledge Transfer through Raranga and Whatu

abstract: The intergenerational transfer of Māori weaving knowledge is based on the succession and continuum of raranga and whatu skills. This study will show how the genesis of inherent know-ledge and skills imbues the nature and continuity of our own cultural practice, especially specific to raranga, whatu and wider areas such as tukutuku. Kaupapa Māori research methodology u-sing the framework of Te Aho tapu provides the methodological approach for this research.  In particular I draw upon the experiences of our whānau and the pedagogical processes used by five generations to define the fundamental underpinnings of a Kaupapa Māori approach to knowledge transfer within, and between, generations of whānau and hapū. Another important driving force behind this work is a need to express the actual practice of intergenerational trans-mission as evidence of the centrality of ako or Māori pedagogy in terms of raranga.
The research questions I pose, are based around the difference between, mōhiotanga, mātauranga, māramatanga and mahi within in a raranga and whatu context.
What is the importance of indigenous intergenerational knowledge transmission through raranga/whatu?
Is it possible to understand the skills and intricacies of an artefact that gives us knew, yet old knowledge from the expertise left by our kairaranga?
The creative component of this research includes as a feature the reproduction of a kete pūkoro, also known as a pututu, especially in the northern tribal dialects (Williams, 2005). The pūkoro is held in the the Otago Museum and the kairaranga has not been identified. The Ngai Tahu dialect emphasise this kete is a pūkoro (Dr J.Williams, personal communication, 2015) which is the term I utilise throughout this research as an acknowledgement to the kairaranga from the southern region of Otakau. A kete pūkoro is a finely woven kete which was used to squeeze the juice from the tutu berries (Beever, 1991). The pūkoro is the only known such taonga that exists and is so fragile that it‘s no longer exhibited. The fragility of the piece is prone to damage through touch, movement and light exposure, so is kept in a temperature controlled draw in the Otago Museum, Dunedin. The uniqueness of this piece of work is the construction, form and the function. The pūkoro sits at the centre of the practice for this research as an example of intergenerational knowledge transfer of the taonga. The raranga technique will be analyzed and the function and form will be replicated to understand more about the kairaranga through the making of the pūkoro. The artefact will be researched and analyzed considering every detail possible, documenting, and reflecting on the processes. Whilst the pūkoro is the centre piece that shows the refinement of knowledge of the kairaranga, it demonstrated the skills and ability to produce a taonga that could be used as a practical kete for sieving out the poisonous kernels of the tutu, only allowing the juice to be strained through it.
Why the pūkoro?
When I first came upon the pūkoro, it was only by osmosis. The pūkoro was stored away in a dark area, and I was attracted to the space where it was stored while viewing kete whakairo that were put out for display for me. I was the kaiako at Otago University for the Toi Onamata classes within Te Tumu, the Māori and Pacific studies Faculty. I arranged with the museum curator to view the kete whakairo in their collection.
I felt drawn to that part of the museum after feeling a strong sense of needing to see what was kept in the dark. I had a strong feeling and attraction to viewing what was kept in the dark, so I asked the curator if I could see what was kept in that space. I was told it was a very fragile kete made of harakeke which they considered was an un-usual shape and it was noted that it was a very old piece. and that the shape of it was unusual, and it was a very old. This made me more curious, as there was something particularly that I was alluring about me to this taonga.
When closely analysing the piece, I realised I could not see the commencement or completion. With closer inspection of the construction, it became more obvious to me, as a kairaranga that the skills and technical detail of horizontal and vertical twills of overlaying patterns used, were woven that way for a purpose.
From that first viewing, I was able to tell the curator, exactly what this artefact was used for, what material it was made out of and that the technical construction of the kete pūkoro was different from others I had viewed before.
It was this moment in time, that I had an epiphany, that this piece of work could tell a story of the unknown kairaranga. I decided right from that point, that I would try my best to bring to light the technical ability of the raranga weave and why it was constructed in such a way.
Like anything, further research needed to be done on the pūkoro, to understand the purpose of this fine piece of work. This was the impetus of my study. The questions I asked myself were:
Why was I attracted to this dark space? For me it was my wairuatanga, alluring me to a space with a deep sense that there was a reason I needed to be there at that time. It was that strong spiritual belief that enabled me to listen to that and to go into the space the pūkoro was being held.
How did I know and understand the construction of the kete pūkoro?. This was about my Mōhiotanga, using my own tacit knowledge, years of observation and passion to engage with a taonga left from a kairaranga of the past century.
What was the purpose of reconstructing this taonga? – This is about the mātauranga imbued in the construction of the Kete Pūkoro. It was to engage in further research to find out more detail beyond what I already knew.
How can I best share this knowledge and practice? – This is about Māramatanga, as I have been always taught, there is no point knowing a skill, and information if it is not shared.

text: Taonga tuku iho: Intergenerational transfer of raranga and whatu The intergenerational transfer of Māori weaving knowledge is based on the succession and continuum of raranga and whatu skills. This study will show how the genesis of inherent know-ledge and skills imbues the nature and continuity of our own cultural practice, especially specific to raranga, whatu and wider areas such as tukutuku. Kaupapa Māori research methodology u-sing the framework of Te Aho tapu provides the methodological approach for this research.  In particular I draw upon the experiences of our whānau and the pedagogical processes used by five generations to define the fundamental underpinnings of a Kaupapa Māori approach to knowledge transfer within, and between, generations of whānau and hapū. Another important driving force behind this work is a need to express the actual practice of intergenerational trans-mission as evidence of the centrality of ako or Māori pedagogy in terms of raranga.
The research questions I pose, are based around the difference between, mōhiotanga, mātauranga, māramatanga and mahi within in a raranga and whatu context.
What is the importance of indigenous intergenerational knowledge transmission through raranga/whatu?
Is it possible to understand the skills and intricacies of an artefact that gives us knew, yet old knowledge from the expertise left by our kairaranga?
The creative component of this research includes as a feature the reproduction of a kete pūkoro, also known as a pututu, especially in the northern tribal dialects (Williams, 2005). The pūkoro is held in the the Otago Museum and the kairaranga has not been identified. The Ngai Tahu dialect emphasise this kete is a pūkoro (Dr J.Williams, personal communication, 2015) which is the term I utilise throughout this research as an acknowledgement to the kairaranga from the southern region of Otakau. A kete pūkoro is a finely woven kete which was used to squeeze the juice from the tutu berries (Beever, 1991). The pūkoro is the only known such taonga that exists and is so fragile that it‘s no longer exhibited. The fragility of the piece is prone to damage through touch, movement and light exposure, so is kept in a temperature controlled draw in the Otago Museum, Dunedin. The uniqueness of this piece of work is the construction, form and the function. The pūkoro sits at the centre of the practice for this research as an example of intergenerational knowledge transfer of the taonga. The raranga technique will be analyzed and the function and form will be replicated to understand more about the kairaranga through the making of the pūkoro. The artefact will be researched and analyzed considering every detail possible, documenting, and reflecting on the processes. Whilst the pūkoro is the centre piece that shows the refinement of knowledge of the kairaranga, it demonstrated the skills and ability to produce a taonga that could be used as a practical kete for sieving out the poisonous kernels of the tutu, only allowing the juice to be strained through it.
Why the pūkoro?
When I first came upon the pūkoro, it was only by osmosis. The pūkoro was stored away in a dark area, and I was attracted to the space where it was stored while viewing kete whakairo that were put out for display for me. I was the kaiako at Otago University for the Toi Onamata classes within Te Tumu, the Māori and Pacific studies Faculty. I arranged with the museum curator to view the kete whakairo in their collection.
I felt drawn to that part of the museum after feeling a strong sense of needing to see what was kept in the dark. I had a strong feeling and attraction to viewing what was kept in the dark, so I asked the curator if I could see what was kept in that space. I was told it was a very fragile kete made of harakeke which they considered was an un-usual shape and it was noted that it was a very old piece. and that the shape of it was unusual, and it was a very old. This made me more curious, as there was something particularly that I was alluring about me to this taonga.
When closely analysing the piece, I realised I could not see the commencement or completion. With closer inspection of the construction, it became more obvious to me, as a kairaranga that the skills and technical detail of horizontal and vertical twills of overlaying patterns used, were woven that way for a purpose.
From that first viewing, I was able to tell the curator, exactly what this artefact was used for, what material it was made out of and that the technical construction of the kete pūkoro was different from others I had viewed before.
It was this moment in time, that I had an epiphany, that this piece of work could tell a story of the unknown kairaranga. I decided right from that point, that I would try my best to bring to light the technical ability of the raranga weave and why it was constructed in such a way.
Like anything, further research needed to be done on the pūkoro, to understand the purpose of this fine piece of work. This was the impetus of my study. The questions I asked myself were:
Why was I attracted to this dark space? For me it was my wairuatanga, alluring me to a space with a deep sense that there was a reason I needed to be there at that time. It was that strong spiritual belief that enabled me to listen to that and to go into the space the pūkoro was being held.
How did I know and understand the construction of the kete pūkoro?. This was about my Mōhiotanga, using my own tacit knowledge, years of observation and passion to engage with a taonga left from a kairaranga of the past century.
What was the purpose of reconstructing this taonga? – This is about the mātauranga imbued in the construction of the Kete Pūkoro. It was to engage in further research to find out more detail beyond what I already knew.
How can I best share this knowledge and practice? – This is about Māramatanga, as I have been always taught, there is no point knowing a skill, and information if it is not shared.

year: 2022