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Concept drift detection in delayed and partially labeled data streams: An experimental survey
(Elsevier, 2026) Alencar, Brenno; Cassales, Guilherme; Gomes, Heitor Murilo; Prazeres, Cássio; Rios, Tatiane N.; Bifet, Albert; Rios, Ricardo A.
Fully labeled data is the ideal scenario for supervised model training. However, labels might be scarce in many situations, specially when large data is produced as an open-ended stream. Moreover, in dynamic streams, it is assumed that the underlying process generating the data is non-stationary, changing its behavior over time. Therefore, concepts learned by the classification model are likely to change, and non-adaptive models will suffer performance degradation, a phenomenon known as concept drift. The challenge of recognizing and reacting to such changes is even more complex by facing streams with partial or delayed labels. This refers to realistic scenarios where the true label of an incoming point is not immediately available (delay) or might never be available (partial). In this work, we focus on investigating the performance of concept drift detectors in handling delayed and partially labeled data streams. We categorize the main methods from the literature, providing a taxonomy of concept drift detectors and an overview of the most influential approaches for evaluating these detectors under conditions of delayed or partial labeling. Finally, we conduct a series of experiments to analyze the performance of these detectors in scenarios with label scarcity. Concluding, the survey discusses its main limitations and offers insights into potential avenues for future research in the field.
Organometallic chemistry of arsenic, phosphorus and other systems
(The University of Waikato, 1992) Arnold, Leslie John; Nicholson, Brian K.; Main, Lyndsay
Arsenic hydride and antimony hydride reactions with iron carbonyls were investigated and compared to analogous reactions using germanium hydrides. The reaction between arsane and Fe(CO)₅ is a new, higher yielding synthesis of [(μ₃-As)₂Fe₃(CO)₉]. The reaction between arsane and Fe₂(CO)₉ led to the new cluster [Fe₂(CO)₈(μ₄-As)]₂[Fe₂(CO)₆]. Characterisation was by an X-ray crystal structure determination. [Fe₂(CO)₈(μ₄-As)]₂[Fe₂(CO)₆] crystallises in the orthorhombic space group Pbca, with unit cell parameters a = 22.908(7), b = 17.521(9), c = 16.071(7) Å and Z = 8. This cluster consists of four AsFe₂ triangles linked by arsenic vertices and an iron-iron edge. In an attempt to prepare similar antimony clusters, stibane was reacted with Fe(CO)₅, Fe₂(CO)₉ and Fe₃(CO)₁₂, but no analogues were isolated. The β-ketophosphane (2-acetylphenyl)diphenylphosphane, Ph₂P[C₆H₄COMe], was prepared in a multi-step synthesis that involved; (i) coupling chlorodiphenylphosphane and 2-bromoethylbenzene, (ii) oxidation of the phosphorus with H₂O₂, (iii) oxidation of the ethyl group with CrO₃, and (iv) reduction at the phosphorus atom. Attempts to prepare the similar disubstituted phosphane PhP[C₆H₄COMe]₂, by an analogous route, instead afforded PhP[C₆H₄C(O)O]₂ at the CrO₃ oxidation step. The potential use of Ph₂P[C₆H₄COMe] as a ligand on metal centres was demonstrated by its electron-transfer catalysed reaction with Ru₃(CO)₁₂, which gave the expected product Ru₃(CO)₁₁[PPh₂(C₆H₄COMe)]. Gentle heating of Ru₃(CO)₁₁[PPh₂(C₆H₄COMe)] in heptane led to the cyclo-metallated cluster Ru₃(CO)₉(μ-PPh₂)(η²-C₆H₄COMe) through P-C bond cleavage. A single crystal X-ray diffraction study on Ru₃(CO)₉(μ-PPh₂)(η²-C₆H₄COMe) showed that it crystallises in the triclinic space group Pī with a = 10.200(11), b = 12.084(12) and c = 14.422(13) Å, a= 81.06(7), β = 77.18(8) and γ = 76.98(8)° and Z = 2. The cluster is derived from Ru₃(CO)₁₂ with three carbonyl ligands replaced by a μ-PPh₂ moiety and an η²-2-acetylphenyl group. The reactions between ortho-manganated acetophenone derivatives and various halides were investigated and compared to the analogous aryl-transfer reactions using mercury chloride. From the reaction between RC(O) C₆H₃R"Mn(CO)₄, ( R=Me, OMe, Ph; R"=H, OMe ), R'OH ( R'=Me, Et and Ph ) and CuCl₂ the following products were isolated [Figures x 4] These can be explained in terms of competition between Mn-Cₐᵣᵧₗ bond cleavage ( the first two products ), or in terms of CO insertion into the Mn-Cₐᵣᵧₗ bond, with subsequent attack by the solvent ( the last two products). The reaction between 2-MeC(O) C₆H₄Mn(CO)₄, and PPh₂Cl involves CO replacement to give fac-[2-MeC(O)C₆H₄Mn(CO)₃(PPh₂Cl)] in essentially quantitative yield. Prolonged refluxing of fac-[2-MeC(O)C₆H₄Mn(CO)₃(PPh₂Cl)] yields Mn₂(μ-η¹-η¹-PhPPPh)-(μ-Cl)₂(CO)₆ in which the newly formed diphosphane ligand bridges two non-bonded manganese atoms; this compound was characterised by an X-ray structure analysis; Pī with a = 10.980(4), b = 11.756(3) and c = 12.186(3) Å, α = 96.20(2), β = 99.51(2) and γ = 96.56(2)° and Z = 2. The probable products from the reaction between SnCl₂ and 2-RC(O)C₆H₄HgCl ( R = Ph, Me) and from the reaction between RₙSnCl₄₋ₙ and 2-MeC(O)C₆H₄HgX ( R = Buⁿ, n = 1, X = Cl; R = Ph, n = 2, X = I) are the acylaryltin derivatives 2-RC(O)C₆H₄SnX₂Cl ( R = Ph, X = Cl; R = Me, X = Cl, Ph) and [2-MeC(O)C₆H₄]₂Sn(Buⁿ)Cl shown below [Figures x 2] These assignments were based on ¹¹⁹Sn and ¹³C nmr spectroscopy.
A parallel lisp and multivariate polynomial GCD implementation
(The University of Waikato, 1991) Willcock, Diane K.; Broughan, Kevin A.
This thesis is concerned with the intersection of two fields of study - computer algebra and parallel processing. The operation of multivariate polynomial greatest common divisor (gcd), an important and fundamental computer algebra operation, is investigated for amenability to parallelisation following the investigation of a suitable environment for implementation of a parallel computer algebra algorithm. After researching the requirements of a parallel computer algebra system, these were matched as closely as possible to available hardware. The choice of an array of transputers as the hardware system lead to the development of a parallel lisp for such a system as there was none readily available. The result was a useful, experimental, coarse-grained, message-passing parallel lisp (Tlisp) based on the eval-server model where each processor in the array (configured in a tree) executes its own lisp process, reading, evaluating and printing s-expressions independently of the others, but with facilities for passing s-expressions to and from its neighbours. Following an appraisal of algorithms available for calculating multivariate polynomial gcds, Zippel’s sparse modular gcd algorithm was selected as the most suitable candidate for parallelisation and implementation in Tlisp. Evaluation of the performance of both Tlisp and the parallel gcd algorithm was achieved by detailed examination of how they performed during execution for a range of test data. The results of the performance experiments and the practical experience gained from a working parallel lisp system and its implementation of an important computer algebra algorithm clearly show that there is much potential for a medium- to coarse-grained message-passing parallel system in the quest for a suitable system for parallel computer algebra.
Transition metal carbonyl clusters incorporating silicon
(The University of Waikato, 1991) Van Tiel, Martin L.; Mackay, Kenneth M.; Nicholson, Brian K.
This thesis reports the reactions of silicon hydrides with the following metal carbonyls; Fe(CO)₅, Fe₂(CO)₉, Co₂(CO)₈ and Co₄(CO)₁₂. The silicon hydrides investigated include SiH₄, Si₂H₆, PhSiH₃, BrSiH₃, ISiH₃, H₃SiOSiH₃ and H₃SiSSiH₃. The reaction of Si₂H₆ with Co₂(CO)₈ at low reactant ratios (1 : 2.5) gave the cluster H₂Si₃Co₆(CO)₂₀ (3.7). This is a rare example of a silicon-transition metal cluster with Si-H bonds. The structure can be regarded as Si[Co₂(CO)₆(μ-CO)]₂ with both bridging carbonyls replaced by μ-Si(H)Co(CO)₄ groups. Further infrared evidence for the previously postulated cluster Si₂Co₆(CO)₂₀ was also obtained. [Figure 3.7] In attempts to crystallise an unknown product from the reaction of SiH₄ with Fe(CO)₅ and Co₂(CO)₈ using THF, ionic products were formed. [FeCo₃(CO)₁₂]⁻ was isolated with [Fe(THF)₄(H₂O)₂]²⁺ as the counter ion. The structure adopted by [FeCo₃(CO)₁₂]⁻ is very similar to that found for the neutral carbonyl, (Co₄CO)₁₂. [Cp(CO)₂FeGe]₂Fe₃(CO)₉ (3.19) was prepared for NMR and crystallographic studies for comparison with the previously reported silicon and tin analogues. The reaction of PhSiH₃ with Co₄(CO)₁₂ resulted in the formation of the square-bipyramidal cluster (PhSi)₂Co₄(CO)₁₁ (4.6) in high yield. This is compared with the wide range of known (RP)₂M₄Lₓ (R = phenyl or p-tolyl) clusters. [Figure 3.19] [Figure 4.6] Initial investigation of BrSiH₃ with Co₄(CO)₁₂ tentatively identified a similar cluster (BrSi)₂Co₄CO)₁₁, which retains a functional halogen group. The reaction of BrSiH₃ or ISiH₃ with Co₂(CO)₈ shows evidence for the formation of the orange clusters (CO)₄CoXSiCo₂(CO)₇ (X = Br, I). These clusters also retain the halogen group via which further substitution could occur. The reaction of H₃SiOSiH₃ with Co₂(CO)₈ proved to be very unpredictable. Tentatively identified products include two clusters which retain the Si-O-Si linkage, O{[Si[Co(CO)₄]Co₂(CO)₇}₂ and O[SiCo₃(CO)₉]₂. Reaction of the sulphur analogue H₃SiSSiH₃ with Co₂(CO)₈ forms the unique cluster SSi₂Co₄(CO)₁₄ (5.9). This cluster consists of a Co₂(CO)₆ unit doubly bridged by SiCo(CO)₄ groups. Both silicon atoms are further linked together with a sulphur atom giving rise to a very acute Si-S-Si angle of 70.3(1)°. The reaction of the analogous hydride H₃GeSGeH₃, with Co₂(CO)₈ shows no formation of a similar product. At higher temperatures the reaction of H₃SiSSiH₃ with Co₂(CO)₈ forms the previously reported cluster S₂Co₄(CO)₁₀ (5.16) which consists of a rectangular cobalt plane with sulphur atoms quadruply bridging both faces. An accurate structural determination of this cluster allows for a detailed discussion. [Figure 5.9] [Figure 5.16] The reactions of various silicon chlorides (SiCl₄, Si₂Cl₆ and Cl₃SiOSiCl₃) with [Co(CO)₄]⁻ were investigated. With SiCl₄, initial formation of the siloxy cluster Cl₃Si-O-CCo₃(CO)₉ was observed and further substitution resulted in the formation of (CO)₄Co(Cl)₂SiOCCo₃(CO)₉ (6.4, characterised crystallographically). In attempts to further substitute the remaining chlorine atoms the carbido cluster [Co₆C(CO)₁₅]²⁻ (6.9) was formed and the structure of the [Et₄N]⁺ salt was determined. [Figure 6.9] [Figure 6.4]
Life history strategies of New Zealand Ceriodaphnia (Crustacea: Cladocera): a comparative study
(The University of Waikato, 1993) Greenwood, Tracey; Green, John D.; Chapman, M. Ann
The seasonal changes in the plankton communities, and the dynamics and life histories of the Cladocera of Lake Mangakaware, were studied over a period of 19 months, during which time populations were sampled at weekly or two weekly intervals. Lake Mangakaware, a small, polymictic lake in the North Island of New Zealand, is characterised by a high nutrient status, low Secchi transparencies, and an unstable thermal regime. In the algal community, small euchlorophycean genera and diatoms predominated. Peak abundances occurred in autumn and late spring and were due almost exclusively to Tetrastrum triangulare and Aulacosira distans respectively. The frequent mixing events precluded the prolonged abundance of any one species and species replacements were rapid. Small species (< 30 μm) predominated amongst the dominant class (Euchlorophyceae), but there were frequent occurrences of large, unpalatable and/or nutritionally poor genera (Aulacosira, Closterium, Trachelomonas). Amongst the zooplankton, the Copepoda and Rotifera predominated. The rotifer community exhibited a pattern of sharp sequential peaks in the abundance of different species. Maximum density occurred in summer (1989) due almost entirely to Keratella cochlearis. The Copepoda were generally low in abundance in winter, but increased in summer and autumn periods. The four cladoceran species: Bosmina meridionalis; Ceriodaphnia pulchella; C. dubia; and B. longirostris; exhibited disjunct population maxima, with peak abundances occurring in mid summer (1987), autumn (1988), spring (1988), and summer (1989). Only B. longirostris was perennially present. The Cladocera of Lake Mangakaware have life histories which predispose them to success at particular times of the year. All species exhibited low fecundities and lipid scores, indicating that resource availability was low and competitive interactions and starvation resistance were probably important in determining species success. Increases in body size in cooler seasons were correlated with higher egg volumes, but not with higher clutch sizes, giving further support for the view that available food was limited. B. longirostris appears to be the most successful planktonic cladoceran in Lake Mangakaware. It is a small species, but produces relatively large neonates which mature quickly. It appears able to maintain populations for prolonged periods with low fecundity, produces ephippia as a means of persistence, and is not particularly vulnerable to predation from Mesocyclops leuckarti. Its selective feeding mode is probably favoured in Lake Mangakaware, where palatable algal species are in low density or difficult to obtain. B. meridionalis is a less able competitor than its congener and is apparently disadvantaged by long development times at low temperatures. The seasonal success of each of the two species of Ceriodaphnia appears to be partly determined by temperature. C. pulchella was the more abundant species but was restricted to warmer seasons and, like B. meridionalis, has a prolonged development time at low temperature. In contrast C. dubia grows quickly at low temperature. The life history responses of C. pulchella and C. dubia to different food and temperature regimes were examined using two way ANOVA for the treatments: 23°C-high food; 23°C-low food; 13°C-high food; 13°C-low food. Growth, fecundity, and resource allocation were examined and the two species found to be different in critical aspects of their life history. At high resource levels, C. dubia had a higher fecundity than C. pulchella and increased its reproductive effort with age while maintaining a high growth rate. However, at low food levels, C. dubia lost most of this advantage and development times were also considerably prolonged. C. dubia neonates were larger than those of C. pulchella, yet possessed the same amount of lipid for any given regime. C. pulchella, although the smaller of the two species, with generally lower fecundity and longer development times, produced relatively larger neonates than C. dubia. C. pulchella was less responsive to low food level, curtailed growth after maturity, and maintained a rather constant clutch size regardless of food availability. Offspring were quite resistant to starvation and were able to reproduce without provided food, regardless of maternal history. The results suggest that subtle differences in life history can determine seasonal success and competitive outcome between similar species. Very large differences in life history strategy or selection pressure need not be invoked.