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Recently, electrical engineers are paying great attention to develop oceanic wave energy conversion technologies based on the piezoelectric materials because of their excellent conveniences. Piezoelectric oceanic wave energy converters (OWECs) have several benefits over the others such as its small size, lightweight, no requirement of using intermediate device as well as having less negative impacts on the oceanic environment. Various review and research papers focus on the piezoelectric devices, their operation and application for oceanic energy conversion. But, to the best of the authors' knowledge, none of the existing research or review papers present detailed scheme of piezoelectric device based power generation covering all the relevant topics as depicted in this review. This paper focuses different aspects of piezoelectric device based oceanic wave energy conversion technology including prospect, historical development, classification, operating principle, configuration, arrangement, model, processing, post-processing, and their test setups. In addition, technical challenges, future direction of research and critical review are also illustrated. It is assumed that, this paper would play a significant role for the future development of piezoelectric OWECs and the researcher working in this field. INDEX TERMS Energy conversion, oceanic wave energy, piezoelectric material, piezoelectric generator, renewable energy, wave power.

Homestead agroforestry, in the form of homegardens, has a long tradition in many developing countries. These systems are an intimate mix of diversified agricultural crops and multipurpose trees planted, maintained by members of the household. This paper aims to explore the species composition commonly found in the homestead agroforestry systems in the Ganges valley of northern Bangladesh and their contribution to local livelihoods. Three villages i.e., 'Capasia', 'Chak Capasia' and 'Baduria' were selected as the primary study area. Data were collected by (1) rapid rural appraisal, (2) direct observation, (3) informal and structured interviews with a purposive sample of 90 households. A total of 53 plant species under 32 families were identified from the study area and it was found that the relative density were highest for Areca catechu (areca palm), Artocarpus heterophyllus (jackfruit) and Mangifera indica (mango). Financial analysis showed that homestead agroforestry net benefit increases with the increasing landholding classes. However, no significant difference was found between the number of species in different farm sizes, contrasting other studies that accused this relationship. The comparison of Shannon-Wiener index between agroforestry systems and natural forest showed no statistical difference, reinforcing the role of homegardens in biological conservation in Bangladesh. Therefore, increasing agroforestry practices in homesteads, should be the strategy for enhancing tree cover in order to meet basic needs of the local people and for environmental sustainability.

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