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The impact of data aggregation: Advocating for individualized analysis in wearable sensor research
(ACM, 2025) König, Jemma; Penaredondo, Jascha; Lim, Nick Jin Sean; Hinze, Annika; Bowen, Judy; Viller, Stephen; Paay, Jeni; Fredericks, Joel; Turner, Jane; Vickery, Nicole; Wadley, Greg; Muñoz, Diego; Capel, Tara; Atiq, Arzoo; Davis, Hilary; Boden, Marie; Harman, Joel; Ploderer, Bernd
The use of wearable sensors to record physiological data is becoming increasingly common, both in research and in daily life. User studies collect data using wrist bands, chest straps, and headbands to measure heart rate, skin conductance, and brain activity, to name a few. These readings can then be used to classify a range of physical and cognitive functions, such as cognitive and physical workload, cognitive and physical fatigue, stress, and attention. However, while physiological data is highly individualized, many researchers use machine learning classification methods that combine the participants' data into one dataset. In this paper, we demonstrate the negative impact this has on results and show that the individualized nature of physiological data requires individualized analysis and classification.
Studies of the structures and redox chemistries of chromate zeolites
(The University of Waikato, 1994) Brown, Mark Langtry; Langdon, Alan G.; Cartner, Tony
Solid-state reactions of sodium chromate, sodium molybdate, and sodium tungstate and zeolites of the types A, X, Y, mordenite, and silicalite at temperatures between 465°C and 655°C resulted in substantial uptakes of the salts. The occluded oxyanions could not be removed by boiling water indicating either a strong interaction with the zeolite lattice or occlusion in β-cages. Factors found to influence the amount of oxyanion occluded were temperature, time, and zeolite to oxyanion mole ratio. Under certain conditions maximum loading was achieved within 24 hours in the absence of significant zeolite framework degradation. In the chromate system, solid-state reactions performed near 800°C resulted in collapse of the zeolite framework and crystallisation of chromate nosean. The kinetics of chromate uptake by 13X followed a √t dependence over the initial stages of reaction indicating a diffusion controlled rate determining step. An apparent activation energy of 124 ± 10 kJ mol⁻¹ was calculated. Occluded sodium chromate was removed from X and Y type zeolites upon heating in strong alkali or salt solutions. A salt-exchange mechanism for chromate removal is proposed. The physiochemical nature of chromate loaded zeolites was examined using a variety of experimental techniques including PXRD, EPR, XRF, DTA, SEM, XPS, FTIR and Raman spectroscopies, and BET surface area determination. All results were consistent with the occlusion of chromate within the α-cages of X, Y, and A type zeolites. No evidence for β-cage occlusion was observed. Maximum chromate uptakes per unit cell were 13.6 for 13X, 13.4 for Y52, and 32.3 for 5A. These uptakes correlated with half the number of S6R facing α-cages of these zeolites suggesting coordination across two S6R. A model consisting of the oxyanion coordinated across its two sodium cations located near the Sɪɪ sites is proposed. Coordination across S5R of mordenite and silicalite was proposed. The Si/ Al ratio had no effect on the maximum chromate uptake. Redox reactions of sodium chromate salt were investigated. Reduction by H₂₍g₎ formed NaCrO₂ and NaOH. Reoxidations were incomplete ceasing at an average oxidation state of Cr(+4.67) through the formation of Na₂CrO₄ and Na₂CrO₃ in a 1:2 ratio. The addition of NaOH to the partially oxidised product allowed full oxidation indicating a dependence of oxidation product on NaOH concentration. A mechanism consistent with the degree of reoxidation was deduced. Chromate occluded in zeolites was reduced by H₂₍g₎ and reoxidised by O₂₍g₎ The degree of loading affected the product of reduction. Reductions of chromates in lowly-loaded zeolites ceased at Cr(IV), chromates in moderately-loaded zeolites (MLZ) were reduced to Cr(III), while chromates in highly-loaded zeolites (HLZ) were reduced to an average oxidation state of Cr(+3.5) containing equimolar amounts of Cr(III) and Cr(IV). The formation of occluded Cr(III)-Cr(IV) “dimers” was postulated. Chromates in chromate nosean reacted with H₂₍g₎ to give a reduction product similar to that of HLZ, i.e. with an average oxidation state of Cr(+3.5). A unit cell edge contraction from 9.107(2) Å for chromate nosean to 8.916(6) Å upon reduction was shown to be consistent with the formation of [Na₄.CrO₂]³⁺, [Na₄.CrO₃]²⁺, [Na₄.OH]³⁺, and [Na₄]⁴⁺ clusters per two unit cells. Changes to the X-ray pattern upon reduction to an average oxidation state of Cr(+3.5) indicated transformation of chromate noselite to a reduced chromate sodalite. The movement of the reduced chromate species off the anion site and coordination to the lattice was envisaged. Reaction with O2(g) at 600°C formed chromate sodalite. Retention of the sodalite framework was attributed to the anion lying off the anion site. Heating the chromate sodalite in air at 1000°C for 2 hours reformed chromate noselite through movement of the chromate oxyanions back to anion sites. The effect of temperature, zeolite type, and degree of loading on the kinetics of redox reactions were investigated. Unlike the reactions in nosean, transport control was not a feature of the reactions and zeolite structure had no significant effect on the redox kinetics. Reductions generally followed second-order kinetics and were highly activated processes with apparent activation energies between 86 ± 2 kJ mol⁻¹ and 97 ± 10 kJ mol⁻¹. In contrast, reoxidations were usually described by chemisorption kinetics. Preliminary investigations indicated a lack of activity of chromate zeolites in ethylene polymerisation and oxidation of methanol reactions. Chromate zeolites were also unable to oxidise CO(g) and CHi(g).
Using technological contexts for teaching school physics a study based in two cultures
(The University of Waikato, 1994) Mohamed, Abdul Muhsin; Carr, Malcolm; Jones, Alister
The study reported in this thesis explored the process and outcomes of using technological contexts that are relevant to students for the teaching of senior secondary school physics in the Maldives and in New Zealand. Recent research findings indicate that the use of contexts that are relevant to the learner in the teaching of science enhances the affective and cognitive outcomes (e.g. Rodrigues 1993, Yager and Tamir 1993, The Cognition and Technology Group at Vanderbilt 1990, Cosgrove 1989, Jones 1988). These research studies were conducted in western countries, using a strategy referred to in this thesis as contextual teaching. Although these studies indicated that teachers and students may face difficulties in using the contextual approach, very little information about the nature of these difficulties was provided. This study explored the possibility of using the contextual teaching strategy in a non-western country, the Maldives, and further clarified the process by using the same strategy in a western country, New Zealand. Particular attention was given to the difficulties teachers faced in using the strategy for the first time. The research was conducted in four iterative phases. The first phase explored technological contexts students in the targeted populations considered relevant. Students in a sample of boys and girls from Grade 10 and Grade 11 physics classes in the Maldives (n=32) and the corresponding Form 5 science and Form 6 physics classes in New Zealand (n=32) were individually interviewed to clarify their interest and ideas about applications used in an area of technology common to the two countries - telecommunications. The reasons for student interest in the applications were very similar in the two samples. The similarity in student interest in the two samples indicated that similar contextual teaching strategies may be successfully used in physics classrooms in the two countries. During the second, third, and fourth phases of the study classroom interventions, based on the ideas of social constructivism, were conducted in physics classrooms in New Zealand and the Maldives. The interventions were designed to teach secondary school electromagnetism in the two countries. While the second and third phases of the study clarified the process and outcomes of contextual teaching, the last phase of the research concentrated on the difficulties faced by teachers in using the strategy for the first time. The contextual teaching strategies used in this study had similar success with students from the two cultures. The cognitive and affective outcomes for the majority of the students, particularly the weaker students, were enhanced. In spite of the socio-political and economic differences between the Maldives and New Zealand, students responded in a similar manner in the two countries. Teachers, particularly those who were used to organising their lessons along conceptual hierarchies, faced difficulties in using the approach. These difficulties were mainly related to structuring and managing classroom activities during contextual teaching. The difficulties were partially addressed during the study. The outcomes of the study has implications for learning, teaching, teacher development, and curriculum development.
Reliable distributed computing in parallel processing systems
(The University of Waikato, 1994) Tian, Yong Qian; Graham, Ian
This thesis presents a software approach which uses efficient diagnosis along with a recovery strategy to achieve fault tolerance in a multiprocessor system. It proposes two algorithms: a hybrid diagnosis algorithm, and an adjacent checkpointing and recovery synchronisation algorithm for multiprocessor systems. The hybrid diagnosis algorithm is t diagnosable, and is able to identify hardware faults or errors correctly, given t processor failures in a k-regular connected network (where t= ᵏ/₂). It requires only one broadcast message to determine the global state in the absence of failures, and 2k+2 messages to detect a failure in the worst case. The number of messages required is constant as the size of the network varies. Compared to other algorithms that require at least O(n) messages for deciding the global state, this algorithm offers a significant improvement. The adjacent checkpointing and recovery synchronisation algorithm is designed for dynamic partial failure recovery in an array parallel processing system. This algorithm can be incorporated into a parallel operating system, and be independent of the application. It provides continuing operation in the presence of multiple processor failures, or failed inter-processor links, without the requirement for spare hardware modules. The algorithm is constructed by combining a process replication strategy and a process migration technique. The discussion is centered on two issues: efficient checkpointing, and network synchronisation for failure recovery. The algorithm uses neighbouring nodes to store recovery points, and checkpointing is executed in parallel. In the thesis, we estimate the performance penalty imposed by the fault-tolerant algorithm in the fault-free situation and judge the performance degradation when the system suffers one or more processor failures. The thesis also presents a fault tolerant numerical weather prediction system designed for the New Zealand Meterological Service.
Synthesis and reactions of some orthomanganated complexes
(The University of Waikato, 1995) Depree, Gary J.; Main, Lyndsay; Nicholson, Brian K.
New orthomanganated indoles of the types shown in Figure 1 have been prepared, including two new examples of orthomanganated aldehydes which are relatively rare. The first crystal structure determination of an orthomanganated aldehyde was carried out on η²-(1-methyl-3-formyl-2-indolyl)tetracarbonylmanganese (11). Figure 1 Solvent effects on the thermally induced coupling reactions of η²-(2- acetylphenyl)tetracarbonylmanganese (9) and η²-(1-acetyl-2 indolyl)tetracarbonylmanganese (4) with a range of alkynes were shown to influence the course of reaction markedly but unpredictably. Of special interest was the reactions of (4) with dimethyl acetylenedicarboxylate which afforded the tricyclic carbinolamine (17) (Figure 2). Reactions of other orthomanganated indole derivatives with various alkynes are also reported. For example, a complex (21) (Figure 2) arising from the triple-insertion of ethyne was characterised by a single X-ray crystal structure determination, as a η³-allyl species that could be converted to a η⁵-C₅H₅ complex on heating. Figure 2 A new class of orthomanganated compound (Figure 3) has been prepared from the reaction of PhCH₂Mn(CO)₅ with triphenylphosphine chalcogens (Figure 3). These are the first reported examples of orthometalated tertiary phosphine chalcogenide metal complexes. Single crystal X-ray structure determinations of the examples with X=S (31) and Se (32) were determined. Figure 3 Cis-PhCH₂Mn(CO)₄PPh₃ (34) and [Mn(CO)₄(μ-SeCH₂Ph)]₂ (33) were also isolated from the orthomanganation reaction of Ph₃P=Se, with the latter being identified by a crystal structure determination. The thermally induced coupling reactions of orthomanganated Ph₃P=S (31) with the alkenes methyl vinyl ketone, methyl acrylate and acrylonitrile gave mainly arylalkane products (Figure 4) in moderate yields. Similar alkyne-coupling reactions of orthomanganated Ph₃P=S (31) were explored. Reaction with dimethyl acetylenedicarboxylate yielded (39) (whose crystal structure is reported) (Figure 4), and a doubly inserted alkyne complex was tentatively identified. Figure 4 However, the insertion of alkynes into the Mn-Cₐᵣᵧₗ bond of (31) was not general, as methyl propiolate was the only other alkyne to undergo insertion. Sulfur dioxide inserts efficiently into the Mn-C ₐᵣᵧₗ bond of orthomanganated Ph₃P=S (31) and Ph₃P=Se (32), to give the corresponding S-sulfinato complexes which contain novel metallocyclic rings (Figure 5). Figure 5 The X-ray crystal structure of the example with X=Se (45) was determined: it has a six-membered metallocycle ring incorporating five different elements. Reactions of other cyclomanganated species with SO₂ were found to be less straightforward. Preliminary investigations into the reactions Ph-N=S=O and Ph-N=C=O with orthomanganated Ph₃P=S are also described. The crystal structure of the phosphite substituted complex (40) (Figure 6) was determined, and its reactivity towards SO₂ and an alkyne was compared with that of the unsubstituted precursor. Figure 6