Critical Analysis of Different Hilbert-Huang Algorithms for Pavement Profile Evaluation

Pavement profile analysis is a major component in pavement infrastructure management decision making for maintenance and rehabilitation. This paper takes an in-depth look at pavement profile characterization and evaluation, taking into account the inherent nature of road profile data, i.e., nonstationary and non-Gaussian. Although there have been several studies aimed at the analysis and characterization of pavement profile, the bulk have been limited to applying relatively conventional signal processing techniques, such as the Fourier analysis. Using this approach, only the average condition of the local conditions can be represented. Most transient and changing signals will not be handled well due to the averaging effect of the technique. The Hilbert-Huang transform operates at the scale of every oscillation, an extremely important property for obtaining localized profile information. In this paper, the different algorithms of the Hilbert-Huang transform: empirical mode decomposition (EMD), ensemble EMD, and complex EMD (CEMD) have been discussed and implemented to extract useful information from road profile data. The robustness of the algorithms is compared based on its ability to produce physically meaningful intrinsic mode functions (IMFs) which truly characterize the underlying process. The results show that although all the methodologies yielded similar residual trends, the CEMD produced physically meaningful and trusted IMFs whose information at the various levels of decomposition could be used to extract profile information such as the extent of deterioration and localized roughness information.     

Anonymising group data sharing in opportunistic mobile social networks

Wireless Networks - The security and privacy risks of group users are major concerns in opportunistic mobile social network (OMSN) platforms, especially when the users share data publicly in a...     

Why do maize farmers in Ghana have a limited choice of improved seed varieties? An assessment of the governance challenges in seed supply

The liberalisation of commercial seed systems has largely been seen as an essential means of improving agricultural productivity in Sub-Saharan Africa. Yet, access to improved seed varieties has remained a major constraint in many countries in spite of liberalisation and other reform efforts. This paper analyses the governance challenges involved in seed systems from a theoretical and an empirical perspective. The paper applies theoretical concepts of New Institutional Economics to identify potential governance challenges involved at the different stages of the seed supply system. The commercial maize seed sector in Ghana is used for an empirical case study. Ghana has passed a seed law that aims to increase the availability of improved seed varieties to farmers by providing more opportunities to the private sector. However, there is still a chronic lack of varietal diversity, indicating that governance challenges in the seed system remain despite the reform efforts. For data collection, a participatory mapping technique known as Process Net-Map was applied, together with expert interviews involving a diverse set of stakeholders. The empirical evidence reveals that, in line with the theoretical considerations, governance challenges indeed affect all stages of the seed supply system. These challenges include limited involvement of smallholders in setting breeding priorities, restricted private sector participation in source seed production, limited ability of an under-resourced public regulatory body to ensure high seed quality through mandatory seed certification and overdependence on a weak public extension system to promote improved varieties. The paper discusses the policy implications of the findings.     

Timing of N fertilization on N2 fixation, N recovery and soil profile nitrate dynamics on sorghum/pigeonpea intercrops on Alfisols on the semi-arid tropics

Cropping systems and fertilizer management strategies that effectively use applied nitrogen (N) are important in reducing costs of N inputs. We examined the effect of time of N application on dry matter (DM) and grain yield (GY), N accumulation, the N budget in crop from soil, fertilizer and atmosphere, and the fertilizer N use efficiency (estimated by the conventional difference method, and the direct ¹⁵N recovery by the crops), in a sorghum/pigeonpea intercropping system on an Alfisol (Ferric Luvisols (FAO); or Udic Rhodustalf (USDA) in India. Fertilizer N was applied at planting (basal) and at 40 days after sowing (delayed). Nitrogen was applied only to the sorghum rows in the intercropping treatment. Nitrogen derived from air (N_dfa) was estimated by the¹⁵ N natural abundance method, and N derived from fertilizer (N_dff) was estimated by the ¹⁵N isotope dilution method. Delaying N fertilization till 40 days after sowing (DAS), rather than applying at sowing increased DM and GY of the sorghum, but not of pigeonpea. Delaying N fertilization to sorghum for 40 days significantly (p<0.001) increased ¹⁵N recovery in shoot from 15 to 32% in sole crop, and from 10 to 32% in intercrop. Similarly, there was a significant (p<0.001) increase in N recovery (by the difference method) from 43 to 59% in sole crop and from 28 to 71 % in intercrop sorghum. Fertilizer N recovery by sole crop pigeonpea (14%) was higher than intercrop pigeonpea (2–4%). Pigeonpea fixed between 120–170 kg ha-¹ of atmospheric N throughout the cropping season. Although there was a marked difference in nitrate-N (N0₃-N) concentrations between basal and delayed treatments at planting, no difference was observed in N0₃-N concentrations in soil solution between the treatments at 40 DAS. Our data on N accumulation by plants showed that the rate of N depletion or disappearance from the soil solution was 2–3 times faster than N accumulation by plants, suggesting that an appreciable amount of N0₃-N would disappear from soil solution in the top soil without being utilized by crops during the initial growth stage. This revised version was published online in August 2006 with corrections to the Cover Date.     

Agronomic effectiveness of urea deep placement technology for upland maize production

Nutrient Cycling in Agroecosystems - Effective fertilizer management is critical for sustainable maize production. Field trials were conducted in six locations in northern Ghana during the 2016 and...