title: Corrosion segmentation on steel structures via illumination-aware preprocessing and Bayesian U²-Net

authors: Zheng, Yangxiao

subjects: corrosion detection

abstract: Steel corrosion poses a major threat to infrastructure safety and longevity, demanding reliable and accurate automated inspection systems. This study presents a semantic segmentation framework that integrates an illumination-adaptive preprocessing pipeline with a Bayesian enhanced U²-Net to address two core challenges in UAV-based corrosion inspection: performance degradation under uneven lighting and lack of predictive uncertainty estimation.
Variational Bayesian convolutional layers are embedded in the U²-Net encoder to enhance robustness and regularization in small-sample scenarios without relying on full probabilistic inference. A high-resolution, pixel-level annotated dataset was developed for evaluation.
Experimental results across 45 independent training runs show that BU²-Net achieves an F1-score of 75.088%, an IoU of 60.350%, and a recall of 71.537%, while maintaining the lowest standard deviation across all metrics. The results confirm the method’s ability to improve training stability and predictive consistency under visually complex conditions. This practical integration of adaptive preprocessing and lightweight uncertainty modeling supports real world deployment in multimodal sensing systems for intelligent structural health monitoring.

text: Corrosion segmentation on steel structures via illumination-aware preprocessing and Bayesian U²-Net Steel corrosion poses a major threat to infrastructure safety and longevity, demanding reliable and accurate automated inspection systems. This study presents a semantic segmentation framework that integrates an illumination-adaptive preprocessing pipeline with a Bayesian enhanced U²-Net to address two core challenges in UAV-based corrosion inspection: performance degradation under uneven lighting and lack of predictive uncertainty estimation.
Variational Bayesian convolutional layers are embedded in the U²-Net encoder to enhance robustness and regularization in small-sample scenarios without relying on full probabilistic inference. A high-resolution, pixel-level annotated dataset was developed for evaluation.
Experimental results across 45 independent training runs show that BU²-Net achieves an F1-score of 75.088%, an IoU of 60.350%, and a recall of 71.537%, while maintaining the lowest standard deviation across all metrics. The results confirm the method’s ability to improve training stability and predictive consistency under visually complex conditions. This practical integration of adaptive preprocessing and lightweight uncertainty modeling supports real world deployment in multimodal sensing systems for intelligent structural health monitoring.

year: 2024

title: Organophosphorus chemistry of camphene

authors: Leach, Meto T.

abstract: Chapter one reviews the literature relating to terpene-phosphorus chemistry. Topics include a summary of the phosphorus chemistry of the monoterpenes and terpenoids camphor, menthol, camphene and pinene. A general discussion on terpene-phosphines and terpene-phosphonates is also included.
 
Chapter two of this thesis describes the chemistry of the camphene-derived phosphinic acids, 8-camphanylphosphinic acid [C₁₀H₁₇P(O)(H)(OH) 1] (2,2-dimethylbicyclo[2.2.1] hept-3-ylmethylphosphinic acid) and 8-camphanyl-(phenyl)phosphinic acid [C₁₀H₁₇P(O)(Ph)(OH) 3], which are formed by the radical-catalysed addition of hypophosphorous acid [H₃PO₂] and phenylphosphinic acid [PhPO₂H₂] to camphene. Reaction conditions which optimise the yield of 1 have been investigated along with the detailed characterisation by single crystal X-ray studies, ESMS and one- and two-dimensional NMR studies. The attempted preparation of chiral 1 starting from (R)-(+)-camphene yields only racemic material, the result of the acid-catalysed racemisation of camphene prior to the reaction with H₃PO₂. Methylation of the phosphinic acids 1 and 3 with diazomethane yields the methyl esters 6 [C₁₀H₁₇P(O)(H)(OMe)] and 7 [C₁₀H₁₇P(O)(Ph)(OMe)]. These methyl esters have been fully characterised by NMR and GCMS. 1 reacts with paraformaldehyde to form the hydroxymethylphosphinic acid 9 [C₁₀H₁₇P(O)(OH)(CH₂OH)] and with a formaldehyde/dimethylamine mixture to form 10 [(C₁₀H₁₇P(O)(OH)-(CH₂NHMe₂))Cl]. The oxidative chlorination of 1 and 3 with thionyl chloride [using a pyridine catalyst] yields the acid chlorides 11 [C₁₀H₁₇P(O)Cl₂] and 12 [C₁₀H₁₇P(O)(Ph)Cl]. 

The reaction of 1 with calcium nitrate and excess urea (for pH control) for 5 days yields polymeric calcium salt 13 [(Ca(C₁₀H₁₇PO₂H)₂(C₁₀H₁₇PO₂H₂)-(H₂O))ₙ] on the basis of a single crystal X-ray study. The dominance of the bulky camphanyl groups, which form a coherent, essentially ‘close-packed’ hydrocarbon sheath around the central hydrophilic inorganic Ca/O/P core give the appearance of individual chains resembling ‘insulated wire’. 

Chapter three describes the synthesis and subsequent derivatisation of the camphene-derived phosphonic acid 14 [C₁₀H₁₇P(O)(OH)₂]. The formation of 14 via both the oxidation of 1 and the hydrolysis of 11 [C₁₀H₁₇P(O)Cl₂] (in mild conditions), are investigated. 14 is characterised in detail by single crystal X-ray studies and one- and two-dimensional NMR studies. The treatment of 14 with diazomethane yields the methyl ester 15 [C₁₀H₁₇P(O)(OMe)₂]. 

Also included in Chapter 3 is the reaction of an excess of silver oxide with equimolar quantities of the platinum dichloride complexes cis-[PtCl₂L₂] [L=PPh₃, PPhMe₂; L₂=DPPE] {DPPE=1,2-bis(diphenylphosphane)ethane} and 14. The Pt(II) complexes 16, 17 and 18, [Pt{OP(O)(C₁₀H₁₇)O(L)₂} L=PPh₃, PPhMe₂; L₂=DPPE], which are formed in moderate yields, are characterised in detail by ³¹P, ¹H and ¹³C NMR spectroscopy. The analogous palladium chemistry of 14 is non-selective, forming a large number of unidentifiable products. 

Chapter four describes the formation of the phosphines 20 [C₁₀H₁₇PH₂], 23 [C₁₀H₁₇P(CH₂OH)₂] and their derivatives. The reaction of phosphonic dichloride 11 [C₁₀H₁₇P(O)Cl₂] with lithium aluminium hydride does not afford the free phosphine but a metal-phosphine adduct of 8- camphanylphosphine. However when 1 is heated to 140°C under vacuum [0.5 mm Hg] 1 disproportionates to yield 8-camphanylphosphine 20 [C₁₀H₁₇PH₂] which, when treated with aqueous hydrochloric acid/formaldehyde, affords an air-stable tris(hydroxymethyl)phosphonium chloride 22 [(C₁₀H₁₇P(CH₂OH)₃)Cl]. 22 is the first tris(hydroxymethyl)phosphonium salt to date to be subjected to a crystallographic study.

The treatment of 22 with equimolar amounts of either potassium hydroxide or triethylamine affords the bis(hydroxymethyl)phosphine 23 [C₁₀H₁₇P(CH₂OH)₂]. The subsequent addition of an excess of sulfur or selenium yields the phosphine sulfide 24 [C₁₀H₁₇P(S)(CH₂OH)₂] and the phosphine selenide 25 [C₁₀H₁₇P(Se)(CH₂OH)₂]. The controlled oxidation of 23 with hydrogen peroxide gives the bis(hydroxymethyl)phosphine oxide 26 [C₁₀H₁₇P(O)(CH₂OH)₂]. 

The treatment of 23 with CODPtCl₂ {COD = 1, 5 cyclooctadiene} directly precipitates the platinum dichloride complex 27 [(C₁₀H₁₇P(CH₂OH)₂)₂PtCl₂) while the gold(I) chloride complex 28 [C₁₀H₁₇P(CH₂OH)₂AuCl] is precipitated by the action of tetrahydrothiophene gold(I) chloride upon 23. Hydroxymethylphosphine 23 and its derivatives [24-28] have been fully characterised by NMR spectroscopy and ESMS.

Included in Chapter four is an investigation of the gas phase decomposition of 20 by Berrigan and Russell at Auckland University. Aided by the use of I.R. Laser Powered Homogeneous Pyrolysis, results indicate that phosphine is firstly eliminated followed by the rearrangement and decomposition of camphene through two distinct pathways.

Chapter five describes the formation of uranyl nitrate complexes of the camphene-derived phosphorylic ligands 15, 7 and 29 [the synthesis of 29 [C₁₀H₁₇P(O)Ph₂] is also described therein]. The spontaneous evaporation of methanolic solutions containing uranyl(VI) nitrate and these monodentate ligands yield the uranyl(VI) nitrate complexes UO₂(NO₃)₂L₂ [30 L= C₁₀H₁₇P(O)(OMe)₂], [31 L= C₁₀H₁₇P(O)(Ph)(OMe)] and [32 L= C₁₀H₁₇P(O)Ph₂]. The uranyl(VI) nitrate complex [UO₂(NO₃)₂{C₁₀H₁₇P(O)(OMe)₂}₂] (30) has been subjected to a single crystal X-ray study. The structure determination was not straightforward, largely as a result of the combination of a dominant scattering atom (uranium) and substantial disorder of the camphanyl groups.

text: Organophosphorus chemistry of camphene Chapter one reviews the literature relating to terpene-phosphorus chemistry. Topics include a summary of the phosphorus chemistry of the monoterpenes and terpenoids camphor, menthol, camphene and pinene. A general discussion on terpene-phosphines and terpene-phosphonates is also included.
 
Chapter two of this thesis describes the chemistry of the camphene-derived phosphinic acids, 8-camphanylphosphinic acid [C₁₀H₁₇P(O)(H)(OH) 1] (2,2-dimethylbicyclo[2.2.1] hept-3-ylmethylphosphinic acid) and 8-camphanyl-(phenyl)phosphinic acid [C₁₀H₁₇P(O)(Ph)(OH) 3], which are formed by the radical-catalysed addition of hypophosphorous acid [H₃PO₂] and phenylphosphinic acid [PhPO₂H₂] to camphene. Reaction conditions which optimise the yield of 1 have been investigated along with the detailed characterisation by single crystal X-ray studies, ESMS and one- and two-dimensional NMR studies. The attempted preparation of chiral 1 starting from (R)-(+)-camphene yields only racemic material, the result of the acid-catalysed racemisation of camphene prior to the reaction with H₃PO₂. Methylation of the phosphinic acids 1 and 3 with diazomethane yields the methyl esters 6 [C₁₀H₁₇P(O)(H)(OMe)] and 7 [C₁₀H₁₇P(O)(Ph)(OMe)]. These methyl esters have been fully characterised by NMR and GCMS. 1 reacts with paraformaldehyde to form the hydroxymethylphosphinic acid 9 [C₁₀H₁₇P(O)(OH)(CH₂OH)] and with a formaldehyde/dimethylamine mixture to form 10 [(C₁₀H₁₇P(O)(OH)-(CH₂NHMe₂))Cl]. The oxidative chlorination of 1 and 3 with thionyl chloride [using a pyridine catalyst] yields the acid chlorides 11 [C₁₀H₁₇P(O)Cl₂] and 12 [C₁₀H₁₇P(O)(Ph)Cl]. 

The reaction of 1 with calcium nitrate and excess urea (for pH control) for 5 days yields polymeric calcium salt 13 [(Ca(C₁₀H₁₇PO₂H)₂(C₁₀H₁₇PO₂H₂)-(H₂O))ₙ] on the basis of a single crystal X-ray study. The dominance of the bulky camphanyl groups, which form a coherent, essentially ‘close-packed’ hydrocarbon sheath around the central hydrophilic inorganic Ca/O/P core give the appearance of individual chains resembling ‘insulated wire’. 

Chapter three describes the synthesis and subsequent derivatisation of the camphene-derived phosphonic acid 14 [C₁₀H₁₇P(O)(OH)₂]. The formation of 14 via both the oxidation of 1 and the hydrolysis of 11 [C₁₀H₁₇P(O)Cl₂] (in mild conditions), are investigated. 14 is characterised in detail by single crystal X-ray studies and one- and two-dimensional NMR studies. The treatment of 14 with diazomethane yields the methyl ester 15 [C₁₀H₁₇P(O)(OMe)₂]. 

Also included in Chapter 3 is the reaction of an excess of silver oxide with equimolar quantities of the platinum dichloride complexes cis-[PtCl₂L₂] [L=PPh₃, PPhMe₂; L₂=DPPE] {DPPE=1,2-bis(diphenylphosphane)ethane} and 14. The Pt(II) complexes 16, 17 and 18, [Pt{OP(O)(C₁₀H₁₇)O(L)₂} L=PPh₃, PPhMe₂; L₂=DPPE], which are formed in moderate yields, are characterised in detail by ³¹P, ¹H and ¹³C NMR spectroscopy. The analogous palladium chemistry of 14 is non-selective, forming a large number of unidentifiable products. 

Chapter four describes the formation of the phosphines 20 [C₁₀H₁₇PH₂], 23 [C₁₀H₁₇P(CH₂OH)₂] and their derivatives. The reaction of phosphonic dichloride 11 [C₁₀H₁₇P(O)Cl₂] with lithium aluminium hydride does not afford the free phosphine but a metal-phosphine adduct of 8- camphanylphosphine. However when 1 is heated to 140°C under vacuum [0.5 mm Hg] 1 disproportionates to yield 8-camphanylphosphine 20 [C₁₀H₁₇PH₂] which, when treated with aqueous hydrochloric acid/formaldehyde, affords an air-stable tris(hydroxymethyl)phosphonium chloride 22 [(C₁₀H₁₇P(CH₂OH)₃)Cl]. 22 is the first tris(hydroxymethyl)phosphonium salt to date to be subjected to a crystallographic study.

The treatment of 22 with equimolar amounts of either potassium hydroxide or triethylamine affords the bis(hydroxymethyl)phosphine 23 [C₁₀H₁₇P(CH₂OH)₂]. The subsequent addition of an excess of sulfur or selenium yields the phosphine sulfide 24 [C₁₀H₁₇P(S)(CH₂OH)₂] and the phosphine selenide 25 [C₁₀H₁₇P(Se)(CH₂OH)₂]. The controlled oxidation of 23 with hydrogen peroxide gives the bis(hydroxymethyl)phosphine oxide 26 [C₁₀H₁₇P(O)(CH₂OH)₂]. 

The treatment of 23 with CODPtCl₂ {COD = 1, 5 cyclooctadiene} directly precipitates the platinum dichloride complex 27 [(C₁₀H₁₇P(CH₂OH)₂)₂PtCl₂) while the gold(I) chloride complex 28 [C₁₀H₁₇P(CH₂OH)₂AuCl] is precipitated by the action of tetrahydrothiophene gold(I) chloride upon 23. Hydroxymethylphosphine 23 and its derivatives [24-28] have been fully characterised by NMR spectroscopy and ESMS.

Included in Chapter four is an investigation of the gas phase decomposition of 20 by Berrigan and Russell at Auckland University. Aided by the use of I.R. Laser Powered Homogeneous Pyrolysis, results indicate that phosphine is firstly eliminated followed by the rearrangement and decomposition of camphene through two distinct pathways.

Chapter five describes the formation of uranyl nitrate complexes of the camphene-derived phosphorylic ligands 15, 7 and 29 [the synthesis of 29 [C₁₀H₁₇P(O)Ph₂] is also described therein]. The spontaneous evaporation of methanolic solutions containing uranyl(VI) nitrate and these monodentate ligands yield the uranyl(VI) nitrate complexes UO₂(NO₃)₂L₂ [30 L= C₁₀H₁₇P(O)(OMe)₂], [31 L= C₁₀H₁₇P(O)(Ph)(OMe)] and [32 L= C₁₀H₁₇P(O)Ph₂]. The uranyl(VI) nitrate complex [UO₂(NO₃)₂{C₁₀H₁₇P(O)(OMe)₂}₂] (30) has been subjected to a single crystal X-ray study. The structure determination was not straightforward, largely as a result of the combination of a dominant scattering atom (uranium) and substantial disorder of the camphanyl groups.

year: 1999

title: Puna

authors: Apiata, Hāwea

abstract: Bilingual poem for issue 11 of Mayhem Literary Journal.

text: Puna Bilingual poem for issue 11 of Mayhem Literary Journal.

year: 2024-09-26