title: Efficient three-dimensional reconstruction of aquatic vegetation geometry: Estimating morphological parameters influencing hydrodynamic drag

authors: Liénard, Jean

subjects: drag coefficient

abstract: Aquatic vegetation can shelter coastlines from energetic waves and tidal currents, sometimes enabling accretion of fine sediments. Simulation of flow and sediment transport within submerged canopies requires quantification of vegetation geometry. However, field surveys used to determine vegetation geometry can be limited by the time required to obtain conventional caliper and ruler measurements. Building on recent progress in photogrammetry and computer vision, we present a method for reconstructing three-dimensional canopy geometry. The method was used to survey a dense canopy of aerial mangrove roots, called pneumatophores, in Vietnam’s Mekong River Delta. Photogrammetric estimation of geometry required 1) taking numerous photographs at low tide from multiple viewpoints around 1 m2 quadrats, 2) computing relative camera locations and orientations by triangulation of key features present in multiple images and reconstructing a dense 3D point cloud, and 3) extracting pneumatophore locations and diameters from the point cloud data. Step 3) was accomplished by a new ‘sector-slice’ algorithm, yielding geometric parameters every 5 mm along a vertical profile. Photogrammetric analysis was compared with manual caliper measurements. In all 5 quadrats considered, agreement was found between manual and photogrammetric estimates of stem number, and of number × mean diameter, which is a key parameter appearing in hydrodynamic models. In two quadrats, pneumatophores were encrusted with numerous barnacles, generating a complex geometry not resolved by hand measurements. In remaining cases, moderate agreement between manual and photogrammetric estimates of stem diameter and solid volume fraction was found. By substantially reducing measurement time in the field while capturing in greater detail the 3D structure, photogrammetry has potential to improve input to hydrodynamic models, particularly for simulations of flow through large-scale, heterogenous canopies.

text: Efficient three-dimensional reconstruction of aquatic vegetation geometry: Estimating morphological parameters influencing hydrodynamic drag Aquatic vegetation can shelter coastlines from energetic waves and tidal currents, sometimes enabling accretion of fine sediments. Simulation of flow and sediment transport within submerged canopies requires quantification of vegetation geometry. However, field surveys used to determine vegetation geometry can be limited by the time required to obtain conventional caliper and ruler measurements. Building on recent progress in photogrammetry and computer vision, we present a method for reconstructing three-dimensional canopy geometry. The method was used to survey a dense canopy of aerial mangrove roots, called pneumatophores, in Vietnam’s Mekong River Delta. Photogrammetric estimation of geometry required 1) taking numerous photographs at low tide from multiple viewpoints around 1 m2 quadrats, 2) computing relative camera locations and orientations by triangulation of key features present in multiple images and reconstructing a dense 3D point cloud, and 3) extracting pneumatophore locations and diameters from the point cloud data. Step 3) was accomplished by a new ‘sector-slice’ algorithm, yielding geometric parameters every 5 mm along a vertical profile. Photogrammetric analysis was compared with manual caliper measurements. In all 5 quadrats considered, agreement was found between manual and photogrammetric estimates of stem number, and of number × mean diameter, which is a key parameter appearing in hydrodynamic models. In two quadrats, pneumatophores were encrusted with numerous barnacles, generating a complex geometry not resolved by hand measurements. In remaining cases, moderate agreement between manual and photogrammetric estimates of stem diameter and solid volume fraction was found. By substantially reducing measurement time in the field while capturing in greater detail the 3D structure, photogrammetry has potential to improve input to hydrodynamic models, particularly for simulations of flow through large-scale, heterogenous canopies.

year: 2016

title: Improvement of Elite Female Athletes' Physical Performance With a 3-Week Unexpected Disturbance Program

authors: Teichmann, Jorg

subjects: Science & Technology

abstract: Context: Sensorimotor training is commonly used in a rehabilitative setting; however, the effectiveness of an unexpected disturbance program (UDP) to enhance performance measures in uninjured elite athletes is unknown. 
Objective: To assess the impact of a three-week UDP program on strength, power, and proprioceptive measures. 
Design: Matched-group, pre- post design. Setting: National Sports Institute. Participants: Twenty-one international-level female field hockey athletes. Interventions: Two 45 min UDP sessions were incorporated into each week of a three week training program (total 6 sessions). 
Main Outcome Measures: One-repetition maximum strength, lower limb power, 20 m running speed, and proprioception tests were performed before and after the experimental period. 
Results: Substantial improvements in running sprint speed at 5- (4.4 ±2.6%; Effect Size [ES]: 0.88), 10- (2.1 ±1.9%; ES: 0.51), and 20-m (1.0 ±1.6%; ES: 0.23) were observed in the UDP group. Squat jump performance was also clearly enhanced when compared to the control group (3.1 ±6.1%; ES: 0.23). Small but clear improvements in maximal strength were observed in both groups. 
Conclusion: A three week UDP can elicit clear enhancements in running sprint speed and concentric-only jump performance. These improvements are suggestive of enhanced explosive strength and are particularly notable given the elite training status of the cohort and relatively short duration of the intervention. Thus, we would reiterate the statement by Gruber and colleagues (2004) that sensorimotor training is a “highly efficient” modality for improving explosive strength.

text: Improvement of Elite Female Athletes' Physical Performance With a 3-Week Unexpected Disturbance Program Context: Sensorimotor training is commonly used in a rehabilitative setting; however, the effectiveness of an unexpected disturbance program (UDP) to enhance performance measures in uninjured elite athletes is unknown. 
Objective: To assess the impact of a three-week UDP program on strength, power, and proprioceptive measures. 
Design: Matched-group, pre- post design. Setting: National Sports Institute. Participants: Twenty-one international-level female field hockey athletes. Interventions: Two 45 min UDP sessions were incorporated into each week of a three week training program (total 6 sessions). 
Main Outcome Measures: One-repetition maximum strength, lower limb power, 20 m running speed, and proprioception tests were performed before and after the experimental period. 
Results: Substantial improvements in running sprint speed at 5- (4.4 ±2.6%; Effect Size [ES]: 0.88), 10- (2.1 ±1.9%; ES: 0.51), and 20-m (1.0 ±1.6%; ES: 0.23) were observed in the UDP group. Squat jump performance was also clearly enhanced when compared to the control group (3.1 ±6.1%; ES: 0.23). Small but clear improvements in maximal strength were observed in both groups. 
Conclusion: A three week UDP can elicit clear enhancements in running sprint speed and concentric-only jump performance. These improvements are suggestive of enhanced explosive strength and are particularly notable given the elite training status of the cohort and relatively short duration of the intervention. Thus, we would reiterate the statement by Gruber and colleagues (2004) that sensorimotor training is a “highly efficient” modality for improving explosive strength.

year: 2018-01-01

title: Te kākahu whakataratara o Ngāi Tūhoe: Ko te reo ōkawa, ko te reo o te marae

authors: McFarland, Agnes

subjects: Reo Māori

abstract: Ko te reo ōkawa ara ko te reo o te marae, he reo hōhonu. Ka mutu, he tapu katoa ōna āhuatanga katoa. E rua ngā kōrero whakatau o runga i te marae. Ko te karanga me te whaikōrero. Kai roto i wēneki reo e rua, ka ahu mai te kupu nei te poroporoaki. Ka āta tirohia te poroporoaki i roto i ngā whakaaro e pā ana ki ngā tikanga o te karanga. Whai muri ka titiro ki te wāhanga o te poroporoaki i roto i te whaikōrero. Mā wēneki tikanga e rua, ka whakaputaina ngā whakaaro me te hōhonutanga o te mamae o te ngākau pōuri ka ea hoki te mamae. Ka tiro ake tātau ki ngā take i whakaputaina, ngā tohutohu ā rātau mā me ngā rongo o te wairua o te kupu kōrero. Tae atu hoki ki te tohungatanga ki te whakatakoto i te rerenga kupu mai i ngā whatumanawa o ngā kuia me ngā kaumātua ō Ngāi Tūhoe. Nō reira, ka titiro ake tātau ki ngā momo āhuatanga katoa o te karanga. Whai muri ko ngā tikanga e pā ana ki te whaikōrero. Whai muri, ko wētahi atu tūmomo tauira mō te poroporoaki.

text: Te kākahu whakataratara o Ngāi Tūhoe: Ko te reo ōkawa, ko te reo o te marae Ko te reo ōkawa ara ko te reo o te marae, he reo hōhonu. Ka mutu, he tapu katoa ōna āhuatanga katoa. E rua ngā kōrero whakatau o runga i te marae. Ko te karanga me te whaikōrero. Kai roto i wēneki reo e rua, ka ahu mai te kupu nei te poroporoaki. Ka āta tirohia te poroporoaki i roto i ngā whakaaro e pā ana ki ngā tikanga o te karanga. Whai muri ka titiro ki te wāhanga o te poroporoaki i roto i te whaikōrero. Mā wēneki tikanga e rua, ka whakaputaina ngā whakaaro me te hōhonutanga o te mamae o te ngākau pōuri ka ea hoki te mamae. Ka tiro ake tātau ki ngā take i whakaputaina, ngā tohutohu ā rātau mā me ngā rongo o te wairua o te kupu kōrero. Tae atu hoki ki te tohungatanga ki te whakatakoto i te rerenga kupu mai i ngā whatumanawa o ngā kuia me ngā kaumātua ō Ngāi Tūhoe. Nō reira, ka titiro ake tātau ki ngā momo āhuatanga katoa o te karanga. Whai muri ko ngā tikanga e pā ana ki te whaikōrero. Whai muri, ko wētahi atu tūmomo tauira mō te poroporoaki.

year: 2012-05