title: Evaporation from a raised peat bog

authors: Campbell, David I.

subjects: hydrology

abstract: Evaporation rates were measured for an oligotrophic raised peat bog dominated by the restionaceous rush Empodisma minus (Hook. f.) Johnson and Cutler in northern New Zealand.
Evaporation rates were smaller than those found for other wetlands, ranging between 0.06-0.16 mm h−1 during the daytime, and the average latent heat flux accounted for only 23% of net radiation. Daily average evaporation was only 34% of the Penman potential open water rate, yet the soil was permanently close to saturation.
Bowen ratios in the range 3-5 indicate that available energy is primarily partitioned into sensible heat by the dense plant canopy. Bowen ratios in this range are normally associated with semi-arid zone climates rather than with a permanently moist raised peat bog.
According to the Penman-Monteith model, the conservative evaporation regime at this site is due to a very large canopy resistance, with daily averages in the range 150-608 s m−1 when the canopy is dry. This large canopy resistance is probably the result of plant responses to a nutrient-poor environment, combined with the effect of an extremely dense canopy preventing the diffusion of water vapour from the moist peat substrate. 
Variations in canopy resistance behaviour are caused by variable degrees of canopy wetness for several days following rain. This behaviour poses difficulties for modelling evaporation in water balance studies, hence a simple scheme utilising the Penman potential open water evaporation is favoured.

text: Evaporation from a raised peat bog Evaporation rates were measured for an oligotrophic raised peat bog dominated by the restionaceous rush Empodisma minus (Hook. f.) Johnson and Cutler in northern New Zealand.
Evaporation rates were smaller than those found for other wetlands, ranging between 0.06-0.16 mm h−1 during the daytime, and the average latent heat flux accounted for only 23% of net radiation. Daily average evaporation was only 34% of the Penman potential open water rate, yet the soil was permanently close to saturation.
Bowen ratios in the range 3-5 indicate that available energy is primarily partitioned into sensible heat by the dense plant canopy. Bowen ratios in this range are normally associated with semi-arid zone climates rather than with a permanently moist raised peat bog.
According to the Penman-Monteith model, the conservative evaporation regime at this site is due to a very large canopy resistance, with daily averages in the range 150-608 s m−1 when the canopy is dry. This large canopy resistance is probably the result of plant responses to a nutrient-poor environment, combined with the effect of an extremely dense canopy preventing the diffusion of water vapour from the moist peat substrate. 
Variations in canopy resistance behaviour are caused by variable degrees of canopy wetness for several days following rain. This behaviour poses difficulties for modelling evaporation in water balance studies, hence a simple scheme utilising the Penman potential open water evaporation is favoured.

year: 1997-06-01

title: Mechanical behaviour of ultrafine grained Cu and Cu-(2.5 and 5) vol.%Al₂O₃ composites produced by powder compact forging

authors: Mukhtar, Aamir

subjects: high energy mechanical milling

abstract: Nanostructured Cu-(2.5 and 5) vol.%Al₂O₃ composite powders were produced from a mixture of Cu powder and Al₂O₃  nanopowder using high energy mechanical milling, and then compacted by hot pressing. The Cu and Cu- Al₂O₃  composite powder compacts were then forged into disks at temperatures in the range of 500-800°C to consolidate the Cu and Cu- Al₂O₃ composite powders. Tensile testing of the specimens cut from the forged disks showed that the Cu forged disk had a good ductility (plastic strain to fracture: ~15%) and high yield strength of 320 MPa, and the Cu-(2.5 and 5)vol.%Al₂O₃ composite forged disks had a high fracture strength in range of 530-600 MPa, but low ductility.

text: Mechanical behaviour of ultrafine grained Cu and Cu-(2.5 and 5) vol.%Al₂O₃ composites produced by powder compact forging Nanostructured Cu-(2.5 and 5) vol.%Al₂O₃ composite powders were produced from a mixture of Cu powder and Al₂O₃  nanopowder using high energy mechanical milling, and then compacted by hot pressing. The Cu and Cu- Al₂O₃  composite powder compacts were then forged into disks at temperatures in the range of 500-800°C to consolidate the Cu and Cu- Al₂O₃ composite powders. Tensile testing of the specimens cut from the forged disks showed that the Cu forged disk had a good ductility (plastic strain to fracture: ~15%) and high yield strength of 320 MPa, and the Cu-(2.5 and 5)vol.%Al₂O₃ composite forged disks had a high fracture strength in range of 530-600 MPa, but low ductility.

year: 2011

title: The chronology of Waikato pā: A spatio-temporal investigation of pā in the middle Waikato basin

authors: McBride, Rowan

subjects: pā

abstract: This study considers the chronology of pā construction, proliferation, and development within the 
Middle Waikato Basin through a spatio-temporal investigation of palisade construction activity as 
identified at six pā (fortified places). The chronological approach applied in this thesis uses 14C 
wiggle-match dating to provide an accurate and precise calendar date for the felling of a tree 
(Felling Date) used to construct a palisade defence at a pā. These Felling Dates are interpreted using 
the theory of time perspectivism, focusing on three distinct scales of analysis: Event, Local, and 
Regional. The event scale of analysis successfully produced twenty high-precision felling dates on 
posts recovered from Lake Mangakaware 1 (MA1), Lake Mangakaware 2 (MA2), Lake Mangahia 
(MGA), Taraheke Pā (TAR), Te Uapata Pā (TEU) and Lake Rotokauri (ROT). The local scale 
analysis utilised these felling dates to track the development of the identified palisade defences 
over time, identifying multiple palisade construction phases, representing construction, repair and 
redevelopment episodes at MA1, MA2, MGA, TAR and TEU. Finally, the regional scale analysis 
integrated this evidence into a broader chronological framework, identifying shared episodes of 
palisade construction activity within the Middle Waikato Basin. This analysis highlights three 
critical periods of proposed socio-political stress and stability between the late fifteenth and early 
nineteenth centuries, related to hypothesised influential variables from the broader cultural and 
archaeological landscape that are proposed to be responsible for the emergence, proliferation and 
development of pā over time.

text: The chronology of Waikato pā: A spatio-temporal investigation of pā in the middle Waikato basin This study considers the chronology of pā construction, proliferation, and development within the 
Middle Waikato Basin through a spatio-temporal investigation of palisade construction activity as 
identified at six pā (fortified places). The chronological approach applied in this thesis uses 14C 
wiggle-match dating to provide an accurate and precise calendar date for the felling of a tree 
(Felling Date) used to construct a palisade defence at a pā. These Felling Dates are interpreted using 
the theory of time perspectivism, focusing on three distinct scales of analysis: Event, Local, and 
Regional. The event scale of analysis successfully produced twenty high-precision felling dates on 
posts recovered from Lake Mangakaware 1 (MA1), Lake Mangakaware 2 (MA2), Lake Mangahia 
(MGA), Taraheke Pā (TAR), Te Uapata Pā (TEU) and Lake Rotokauri (ROT). The local scale 
analysis utilised these felling dates to track the development of the identified palisade defences 
over time, identifying multiple palisade construction phases, representing construction, repair and 
redevelopment episodes at MA1, MA2, MGA, TAR and TEU. Finally, the regional scale analysis 
integrated this evidence into a broader chronological framework, identifying shared episodes of 
palisade construction activity within the Middle Waikato Basin. This analysis highlights three 
critical periods of proposed socio-political stress and stability between the late fifteenth and early 
nineteenth centuries, related to hypothesised influential variables from the broader cultural and 
archaeological landscape that are proposed to be responsible for the emergence, proliferation and 
development of pā over time.

year: 2024