Investigation into the variation in airfield pavement strength rating calculation

The Pavement Classification Number (PCN) was an international method developed by the International Civil Aviation Organization (ICAO) to report runway, taxiway as well as apron pavement strength. In the past, the great variation in calculated PCN values obtained through available internationally recognised methods for PCN calculation, allowed pavement engineers to target a specific PCN to the potential detriment of the airfield pavement and its safe operation. Recently, in June 2020, the ACN-PCN system was replaced by the new ACR-PCR (Aircraft Classification Rating ‒ Pavement Classification Rating) system. During this study a series of PCN calculations were performed for a range of typical airport pavement structures with different internationally recognised PCN calculation approaches. The process was repeated using the new PCR approach with the currently available calculation approaches. The variation in PCN was compared to the variation in PCR to confirm if the new rating system results in reduced variation. The analysis confirmed a reduced variation in calculated ratings for flexible pavements, but not for rigid pavements.Papers presented at the 40th International Southern African Transport Conference on 04 -08 July 202

Using multicriteria analysis to select alternative surfacings for low volume roads

A large portion of the road network in developing countries in Africa consist of Low Volume Roads (LVRs). Funding for upgrading and maintenance of these roads pose a challenge for roads authorities as their limited budgets are mainly aimed at highways and major corridors. Isolated communities bear the burden of inaccessibility to markets, education and health facilities. As part of a study that was launched by the Research for Community Access Partnership (ReCAP) an investigation into alternative surfacings to gravel roads was conducted in Ghana, Liberia and Sierra Leone. A stakeholder engagement process, designed around several workshops, was used to gain insight into the needs of the community. The local roads authorities, local engineers and technical pavement experts were involved in the selection of surfacing options which would be most suitable for implementation. Several other aspects of the surfacing types were investigated such as the initial construction cost, anticipated maintenance costs and life cycle cost. An exclusive multicriteria analysis, which used the outputs from the different costing scenarios and the workshops was conducted, and a Monte Carlo simulation was completed to select the most appropriate surfacing solutions.Papers presented at the 40th International Southern African Transport Conference on 04 -08 July 202

Holographic description of Kerr-Bolt-AdS-dS Spacetimes

We show that there exists a holographic 2D CFT description of a Kerr-Bolt-AdS-dS spacetime. We first consider the wave equation of a massless scalar field propagating in extremal Kerr-Bolt-AdS-dS spacetimes and find in the "near region", the wave equation in extremal limit could be written in terms of the $SL(2,R)$ quadratic Casimir. This suggests that there exist dual CFT descriptions of these black holes. In the probe limit, we compute the scattering amplitudes of the scalar off the extremal black holes and find perfect agreement with the CFT prediction. Furthermore we study the holographic description of the generic four dimensional non-extremal Kerr-Bolt-AdS-dS black holes. We find that if focusing on the near-horizon region, for the massless scalar scattering in the low-frequency limit, the radial equation could still be rewritten as the $SL(2,R)$ quadratic Casimir, suggesting the existence of dual 2D description. We read the temperatures of the dual CFT from the conformal coordinates and obtain the central charges by studying the near-horizon geometry of near-extremal black holes. We recover the macroscopic entropy from the microscopic counting. We also show that for the superradiant scattering, the retarded Green's functions and the corresponding absorption cross sections are in perfect match with CFT prediction.Comment: 17 pages, typos corrected, references adde

Kerr/CFT Correspondence in the Low Energy Limit of Heterotic String Theory

We investigate the recently proposed Kerr/CFT correspondence in the context of heterotic string theory. The Kerr/CFT correspondence states that the near-horizon states of an extremal four (or higher) dimensional black hole could be identified with a certain chiral conformal field theory under the conjecture that the central charges from the non-gravitational fields vanish. The corresponding Virasoro algebra is generated by a class of diffeomorphisms which preserves the appropriate boundary conditions on the near-horizon geometry. To understand the chiral conformal field theory, we consider the class of extremal Kerr-Sen black hole (that contains three non-gravitational fields) as a class of solutions in the low energy limit (effective field theory) of heterotic string theory. We derive the expression of the conserved charges for the extremal Kerr-Sen solutions that contain dilaton, abelian gauge filed and antisymmetric tensor filed. We confirm and extend the validity of the conjecture (that the central charges from the non-gravitational fields vanish) for theories including antisymmetric tensor fields. We combine the calculated central charges with the expected form of the temperature using the Cardy formula to obtain the entropy of the extremal black hole microscopically; in agreement with the macroscopic Bekenstein-Hawking entropy of the extremal black hole.Comment: 14 pages, a few sentences added to the introduction, version to appear in JHE

Nonlocal reflection by photonic barriers

The time behaviour of microwaves undergoing partial reflection by photonic barriers was measured in the time and in the frequency domain. It was observed that unlike the duration of partial reflection by dielectric layers, the measured reflection duration of barriers is independent of their length. The experimental results point to a nonlocal behaviour of evanescent modes at least over a distance of some ten wavelengths. Evanescent modes correspond to photonic tunnelling in quantum mechanics.Comment: 8 pages, 5 figure

The minimal important difference of the constant work rate cycle test in severe COPD

Background: The Constant Work Rate Cycle Test (CWRT) is a commonly used and sensitive test to detect treatment success in patients with Chronic Obstructive Pulmonary Disease (COPD). Earlier, the Minimal Important Difference (MID) of the CWRT was estimated at 101 s (or 34%) change from baseline based on one well executed study. However, this study was performed in a population of patients with mild-to-moderate COPD, and we have learned that MIDs might be quite different in patients with severe COPD. Therefore, we aimed to establish the MID of the CWRT in patients with severe COPD.Methods: We included 141 patients with severe COPD, who underwent either pulmonary rehabilitation, bronchoscopic lung volume reduction with endobronchial valves, or a sham bronchoscopy as a control group. CWRT workload was set at 75% of the peak work capacity, as determined by an incremental cycle test. We used the change in 6-min walking test (6-MWT), forced expiratory volume in 1s (FEV1), residual volume (RV), and St. George's Respiratory Questionnaire (SGRQ) total score as anchors to calculate the MID.Results: All anchors had an association of ≥0.41 with change in CWRT. The MID estimates for the different anchors were: 6-MWT 278 s (95%), FEV1 273 s (90%), RV 240 s (84%), and SGRQ 208 s (71%). The average of these four MID estimates resulted in an MID of 250 s (or 85%).Conclusion: We established the MID for CWRT at 250 s (or 85%) change from baseline in patients with severe COPD.</p

The Health Belief Model Applied to Understanding Diabetes Regimen Compliance

Inadequate adherence to prescribed treatment plans is perhaps the most serious obstacle to achieving success ful therapeutic outcomes, and non compliance by diabetic patients is no exception. This is partly based on pa tients' realization that compliance does not necessarily result in lack of illness. A psychosocial framework for under standing patient compliance is the Health Belief Model, which is based upon the value an individual places on the identified goal and the likelihood that compliance will achieve that goal. This Model has been useful to explain noncompliance, to make an "educa tional diagnosis," and for designing compliance-enhancing interventions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68410/2/10.1177_014572178501100108.pd

Hartman effect in presence of Aharanov Bohm flux

The Hartman effect for the tunneling particle implies the independence of group delay time on the opaque barrier width, with superluminal velocities as a consequence. This effect is further examined on a quantum ring geometry in the presence of Aharonov-Bohm flux. We show that while tunneling through an opaque barrier the group delay time for given incident energy becomes independent of the barrier thickness as well as the magnitude of the flux. The Hartman effect is thereby extended beyond one dimension and in the presence of Aharonov-Bohm flux.Comment: 4 pages, 4 figure

Development of a test method to identify erosion characteristics

Paper presented at the 31st Annual Southern African Transport Conference 9-12 July 2012 "Getting Southern Africa to Work", CSIR International Convention Centre, Pretoria, South Africa.Erosion of the sub-base material in concrete pavements leads to a loss in slab support and thus cracking of the concrete slab itself. This occurrence is indicated when pumping occurs at the joints in the concrete slab and needs to be predicted in the design stage. Current test methods used to evaluate erosion and durability properties, such as the wet and dry durability test takes weeks to conclude and are highly influenced by human factors. This paper describes the design and construction of a Rotational Shear Device (RSD) that can be used to identify erosion characteristics of sub base materials. Results from a series of tests are presented that indicate a potential benefit in the characterisation of erosion properties of sub base materials.This paper was transferred from the original CD ROM created for this conference. The material was published using Adobe Acrobat 10.1.0 Technology. The original CD ROM was produced by Document Transformation Technologies Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: nigel@doctech URL: http://www.doctech.co.zadm201

Long-term cognitive correlates of traumatic brain injury across adulthood and interactions with APOE genotype, sex, and age cohorts.

There is continuing debate about long-term effects of brain injury. We examined a range of traumatic brain injury (TBI) variables (TBI history, severity, frequency, and age of injury) as predictors of cognitive outcome over 8 years in an adult population, and interactions with apolipoprotein E (APOE) genotype, sex, and age cohorts. Three randomly sampled age cohorts (20-24, 40-44, 60-64 years at baseline; N = 6333) were each evaluated three times over 8 years. TBI variables, based on self-report, were separately modeled as predictors of cognitive performance using linear mixed effects models. TBI predicted longitudinal cognitive decline in all three age groups. APOE ε4 + genotypes in the young and middle-aged groups predicted lower baseline cognitive performance in the context of TBI. Baseline cognitive performance was better for young females than males but this pattern reversed in middle age and old age. The findings suggest TBI history is associated with long-term cognitive impairment and decline across the adult lifespan. A role for APOE genotype was apparent in the younger cohorts but there was no evidence that it is associated with impairment in early old age. The effect of sex and TBI on cognition varied with age cohort, consistent with a proposed neuroprotective role for estrogen