Development Engineering最新文献

Two-wheel tractors (2WTs) are widely used by resource-poor farmers to prepare land in the Eastern Indo-Gangetic Plains (EIGP). This paper demonstrates that improved tillage blade design can enhance maize crop establishment under strip tillage, which falls under the rubric of conservation agriculture (CA). In order to achieve this aim, it is necessary to identify appropriate blade design and rotational speed for power tiller operated seeders, or PTOS, which can be attached to 2WTs and that are increasingly popular in the EIGP. We conducted experiments over two years in two locations in the EIGP within Bangladesh with loam and clay loam soils, respectively. Four blades designed with varying tip angles and five levels of rotational speed were compared with commercially available C-shaped blades sold with 2WTs. Torque and power requirements for strip tillage decreased with decreasing blade tip angle and rotational speed. The best combination of blade design and rotational speed was found with a 15° blade tip angle at 320 RPM. This combination resulted in higher furrow cross sectional area, more soil backfill with appropriately sized soil aggregates, and better seeding depth than C-shaped and 45° tip angle blades. These characteristics also facilitated improved crop establishment on both soil types. Our results indicate that strip-till maize establishment can be improved in Bangladesh by substituting commercially-available C-shaped blades with a 15° blade tip angle at appropriate 320 RPM, though machinery operators will require educational efforts to learn how to fine-tune RPM to improve crop establishment and achieve more sustainable crop establishment systems.

Access to electricity is typically the main benefit associated with solar panels, but in economically less developed countries, where access to electricity is still very limited, solar panel systems can also serve as means to generate additional income and to diversify income sources. We analyze high-frequency electricity usage and repayment data of around 70,000 households in Tanzania that purchased a solar panel system on credit, in order to (1) determine the extent to which solar panel systems are used for income generation, and (2) explore the link between the usage of the solar system for business purposes and the repayment of the customer credit that finances its purchase. Based on individual patterns of energy consumption within each day, we use XGBoost as a supervised machine learning model combined with labels from a customer survey on business usage to generate out-of-sample predictions of the daily likelihood that customers operate a business. We find a low average predicted business probability; yet there is considerable variation across households and over time. While the majority of households are predicted to use their system primarily for private consumption, our findings suggest that a substantial proportion uses it for income generation purposes occasionally. Our subsequent statistical analysis regresses the occurrence of individual credit delinquency within each month on the monthly average predicted probability of business-like electricity usage, relying on a time-dependent proportional hazards model. Our results show that customers with more business-like electricity usage patterns are significantly less likely to face repayment difficulties, suggesting that using the system to generate additional income can help to alleviate cash constraints and prevent default.

The informal settlements in the Global South, mostly comprising of inadequate building solutions, are growing rapidly, therefore calling for more sustainable construction interventions and upgrading strategies. Within this context, this study considers that appropriate construction strategies are capable of engaging with the local economy, affected by endemic poverty, therefore contributing to the improvement of the settlement's socio-economic and physical conditions at once.

A deeper understanding of the settlements construction process, actors, and key factors influencing material use, acceptance, and distribution, is therefore needed, and is here presented for the case of Mathare, in Nairobi. The study is based on field-based qualitative and quantitative data collection through semi-structured interviews and mapping, and through the adoption of methods as stakeholders analysis and supply chain mapping.

The following insights have emerged from the study:

1) different client groups have access to different building materials;

2) the distribution of materials inside the settlement is strictly related to stores and building sites accessibility;

3) the local adoption of materials is highly impacted by the availability of space both at the supplier store and on the building site;

4) contextual cultural factors can have a major role in the construction organization. as for the case of ethnicity influencing roles distributions in the construction sector.

The study insights are of relevance for the practice, specifically to inform project managers and policymakers involved in construction projects in the informal settlements about local material supply and demand constraints. Specifically, the study highlights the need to consider the availability of stocking space alongside the supply as well as on-site.

Finally, it shows the validity of adopting a mixed-methods approach, looking at the settlements through a socio-technical approach.

Accessing clean water is a persistent and life-threatening challenge for millions of people in the world. Each hour, 400 children under the age of five die because of the lack of clean water. To help people get access to clean ground water, mechanical hand pumps are often used. Among the most ubiquitous is the India Mark II/III hand pump system, of which there are more than 4 million installed across the world. These are estimated to serve between 600 million and 1 billion people. But as with most mechanical systems, they degrade over time–leading to pumps becoming dysfunctional due to lack of required service. The pump's nitrile cup seals are the most common cause of dysfunctionality. The purpose of this paper is to analyze the robustness of the cup seals in the India Mark II/III hand pump system. In this paper, 110 off-the-shelf nitrile cup seals purchased by the authors in Uganda were tested and characterized. Leak and pump performance tests were performed in both static and dynamic settings and the correlations between performance and geometry and material properties of the cup seals were determined. This important baseline evaluation for the seals supports our future work to improve the longevity and robustness of the India Mark II/III hand pump system, with a focus on the cup seals. We believe that by finding the baseline of a product, engineers and designers will be able to improve its performance.

Social impact indicators provide one effective way to measure the social impacts of products in developing countries and ensure that engineering design is producing positive impacts on individuals. Remote data collection devices enable the use of sensors to collect user data required to calculate social impact indicators remotely, continuously, and potentially less expensively than other methods that require direct interaction with users. However, many key decisions and questions must be considered during the development and use of such devices to avoid risk of failure. To provide a systematic way for researchers and engineers to consider critical device development questions, the parts of device development and use can be decomposed into Data Identification, Device Design, and Device Deployment. This paper discusses the key decisions within each part of development along with critical questions, common options, and considerations that should be addressed during each part of device development, thus increasing the likelihood of success. A sensor development canvas outlining the key decisions is also provided as a design tool to easily identify deficiencies in the device during development. Considering these critical questions while developing and deploying data collection devices can help researchers and engineers successfully collect social impact indicator data that may be used to ensure engineered products are producing desired positive impacts on individuals.

The world is facing an increasingly dire plastic waste crisis that affects people in developing countries disproportionately more than those in industrialized nations. To compare the environmental effects of end of life disposal and recycling options for plastic/sand roof tiles in Uganda, we use an extended exergy analysis (EEA) to quantify the resources used in the disposal process, the resources saved from replaced virgin materials by recycling, and any additional resources needed to bring the tiles, byproducts, and pollutants to an environmentally acceptable end state. We evaluated disposing of waste plastic/sand roof tiles through open burning, burying, landfilling, pyrolyzing, incinerating in cement kilns, mixing into asphalt to pave roads, and recycling into plastic pavers. With a net exergy avoided of 16,462 MJ/tonne of tiles, mixing the waste plastic/sand tiles into asphalt roads proved to be the best option followed by pyrolysis with 11,303 MJ/tonne of net exergy avoided (including remediation). Recycling the tiles into pavers also saved net exergy while burying, landfilling, and incinerating all had negative net exergy values showing that inputting some thermal energy to recycle waste can add value and save net resources. We determined it is not practically feasible to bring all of the pollutants from open burning to an environmentally acceptable end state with the limited technology available in Uganda. However, the method we recommend for remediating CO₂ by planting trees requires only 0.7% of the exergy used in CO₂ scrubbers currently used in developed countries. Such an empirical study focusing specifically on plastic products and disposal options feasible in developing countries has not been done before, so our paper can be useful to policy makers, multilateral organizations, and NGOs making decisions about solid waste management practices in less-industrialized nations. The results from this paper are valid for HDPE, LDPE, and PP plastics but not for PET or PVC.