Experimental Studies of Structural and Technological Parameters of a Downdraft Gasifier Based on Plant Biomass

The relevance of the study is conditioned upon the need to develop and implement structural and technological solutions to improve the efficiency of the chemical and thermal conversion of biomass into combustible gas. Within the framework of the above, the authors of this paper have designed a downdraft gasifier running on plant biomass. The presented research links the heat quantity received from the utilisation of syngas produced during the gasifier operation cycle with the parameters of the gas blow regime and the physico-chemical properties of biomass. For an in-depth study of the influence of the gas blow regime on the yield and calorific value of syngas produced from biomass, the authors introduce the concept of the blow coverage quality coefficient. This coefficient describes the quality of the cross-section coverage of the gasification chamber neck with gas currents of the tuyere zone. The purpose of this study is to establish the influence of the blow coverage quality coefficient, the volume of blow gases and the void ratio of the bulk biomass layer on the heat quantity received from syngas produced during the gasifier operation cycle. A multi-factor experiment was planned and performed, which relates the dependent factor to variables, and the corresponding response surfaces were constructed. The research findings are that the maximum value of the heat quantity received from the utilisation of syngas produced during the one-hour gasifier operation cycle was 519 MJ. This value is achieved with 0.8 blow coverage quality coefficient and a blow gas volume of 47.4 m3/h and 46.75% void ratio of the bulk biomass layer. The measurement results are highly consistent with the calculated data. The coefficient of determination was R2=0.983. The practical value of this study is to substantiate the rational design and technological parameters of the downdraft biomass gasifier operation, which will increase the efficiency of biomass energy production. The findings presented in this study can be used both to design new gasifiers and to improve the efficiency of the available ones

Joint Deployment Strategy of Battery-Free Sensor Networks with Coverage Guarantee

The energy limitation of wireless sensors limits the lifetime of the traditional wireless sensor networks. The <b>Battery-Free Sensor Network (BF-WSN)</b> is a new network architecture proposed in recent years to address the limitation of wireless sensor networks. In a BF-WSN, the battery-free node can harvest energy from the ambient environment, and thus the lifetime of a BF-WSN is unlimited in terms of energy. The coverage quality is an important measurement of BF-WSNs. Considering the specific features of BF-WSNs, we propose a new deployment concept for BF-WSNs, named <i>Joint Deployment</i>. It aims to determine the locations and working schedules of sensor nodes to maximize network coverage quality. Based on the joint deployment concept, we propose a new deployment problem of battery-free sensor nodes. We prove that this problem is at least NP-Hard. We also analyze the upper bound of this problem. Furthermore, we propose an approximated algorithm to solve this problem and analyze the time complexity and the ratio bound of the algorithm. Extensive simulations are carried out to examine the performance of the proposed algorithm. The simulation results show that the algorithm is efficient and effective.

Using Household Surveys to Assess Missed Opportunities for Simultaneous Vaccination: Longitudinal Examples from Colombia and Nigeria

One important strategy to increase vaccination coverage is to minimize missed opportunities for vaccination. Missed opportunities for simultaneous vaccination (MOSV) occur when a child receives one or more vaccines but not all those for which they are eligible at a given visit. Household surveys that record children’s vaccination dates can be used to quantify occurrence of MOSVs and their impact on achievable vaccination coverage. We recently automated some MOSV analyses in the World Health Organization’s freely available software: Vaccination Coverage Quality Indicators (VCQI) making it straightforward to study MOSVs for any Demographic & Health Survey (DHS), Multi-Indicator Cluster Survey (MICS), or Expanded Programme on Immunization (EPI) survey. This paper uses VCQI to analyze MOSVs for basic vaccine doses among children aged 12–23 months in four rounds of DHS in Colombia (1995, 2000, 2005, and 2010) and five rounds of DHS in Nigeria (1999, 2003, 2008, 2013, and 2018). Outcomes include percent of vaccination visits MOSVs occurred, percent of children who experienced MOSVs, percent of MOSVs that remained uncorrected (that is, the missed vaccine had still not been received at the time of the survey), and the distribution of time-to-correction for children who received the MOSV dose at a later visit.

UAV Path Planning for Reconnaissance and Look-Ahead Coverage Support for Mobile Ground Vehicles

Path planning of unmanned aerial vehicles (UAVs) for reconnaissance and look-ahead coverage support for mobile ground vehicles (MGVs) is a challenging task due to many unknowns being imposed by the MGVs’ variable velocity profiles, change in heading, and structural differences between the ground and air environments. Few path planning techniques have been reported in the literature for multirotor UAVs that autonomously follow and support MGVs in reconnaissance missions. These techniques formulate the path planning problem as a tracking problem utilizing gimbal sensors to overcome the coverage and reconnaissance complexities. Despite their lack of considering additional objectives such as reconnaissance coverage and dynamic environments, they retain several drawbacks, including high computational requirements, hardware dependency, and low performance when the MGV has varying velocities. In this study, a novel 3D path planning technique for multirotor UAVs is presented, the enhanced dynamic artificial potential field (ED-APF), where path planning is formulated as both a follow and cover problem with nongimbal sensors. The proposed technique adopts a vertical sinusoidal path for the UAV that adapts relative to the MGV’s position and velocity, guided by the MGV’s heading for reconnaissance and exploration of areas and routes ahead beyond the MGV sensors’ range, thus extending the MGV’s reconnaissance capabilities. The amplitude and frequency of the sinusoidal path are determined to maximize the required look-ahead visual coverage quality in terms of pixel density and quantity pertaining to the area covered. The ED-APF was tested and validated against the general artificial potential field techniques for various simulation scenarios using Robot Operating System (ROS) and Gazebo-supported PX4-SITL. It demonstrated superior performance and showed its suitability for reconnaissance and look-ahead support to MGVs in dynamic and obstacle-populated environments.

Coverage Area of a Localization Fixed Sensors Network System with the process of Triangulation

This paper presents a novel work on localization of transmitters using triangulation with sensors at fixed positions. This is achieved when three or more sensors cover the whole area, a factor which enables the system to perform localization via triangulation. The network needs to keep a high detection rate which, in most cases, is achieved by adequate sensor coverage. Various tests using various grids of sensors have been carried out to investigate the way the system operates in different cases using a lot of transmitters. Detection complexity is tackled by finding the optimal detecting sensor radius in order the network to continue operate normally. The coverage quality changes in the area of interest and the network is able to detect new transmitters that might enter it's area. It is also shown that as the number of transmitters increases the network keeps its high performance by using additional groups of sensors in a sub-region area of that of interest. This way, even when the network is saturated by many transmitters in one region, new transmitters can still be detected.

Customer’s Satisfaction toward Robi Axiata Limited: Study on Rajshahi University Area

The beginning of the telecommunication business has been appealing not on time in Bangladesh when to compare Asian countries. The mobile telecommunication of serving is repetition on a yearly basis over the last two or three years. Now in our country four mobile phone operators, one is Robi. Most of the companies are offering diverse innovative packages and offer charge added services for satisfying the customer’s needs &demands. This research is the main objective to find out Customer’s satisfaction with Robi Axiata Limited in the Rajshahi University area. There are different ways which have an effect on the performance. The aim of this paper is to search crucial issues which regularly control the more level of performance of mobile users in the Rajshahi University area. Network of coverage, quality of the network, quality of internet, taxes, customer services, value-added services, payment system; encouraging offers are the utmost valuable issues that feelings customer fulfillment. Robi carries their work till now because of their different 4.5 packages.

A Robust Fault-Tolerance Scheme with Coverage Preservation for Planar Topology based WSN

Maintaining prolonged service lifetime and adequate quality of sensing coverage are the key challenges in constructing Wireless Sensor Network (WSN) based applications. As such networks usually operate in inhospitable and hostile environment, failures are ineludible and providing resilience is a necessity. However, it is challenging to satisfy the conflicting problems of enhancing energy efficiency and fault tolerance simultaneously. Fault-tolerance is a significant requirement while designing WSN. It is crucial to detect the failures in advance and take necessary measures to maintain durable and efficient functioning of the network. Generally, in the existing face structured WSNs, node faults and failures can induce the formation of coverage holes, disrupt the face structure and consequently curtail the application performance. The coverage quality will affect the monitoring effectiveness of tracking applications, e.g., a moving target tracking. Moreover, node failures can cause the network to be partitioned, further reducing the accuracy in tracking. In this paper, we propose a robust fault-tolerance scheme with coverage preservation using a face structured WSN topology (FCAFT ). The key objective of the proposed FCAFT scheme is to sustain the performance of the network by timely healing the faults in the network, to enhance the durability and reliability of the WSN. The results of simulation and comparison with existing methods reveal that FCAFT is efficacious in sustaining the coverage and enhancing the service lifetime of WSN, which is a necessity for critical monitoring and tracking applications of WSNs.