Maintenance Status and Availability of Public Automated External Defibrillators: Results of On-Site Inspection

Objective This study aimed to assess the maintenance status and availability of publicly installed automated external defibrillators (AEDs). Methods Public AEDs installed in Seoul 2013 to 2017 were included. An inspector checked the maintenance status and availability of AEDs annually using a checklist. Results A total of 23,619 AEDs were inspected for 5 years. Access to AEDs was improved, including reduced obstacles around AEDs (from 9.3% in 2013 to 0.8% in 2017) and increased AED signs (from 34.3% in 2013 to 91.2% in 2017). The number of AEDs in normal operation (from 94.0% in 2013 to 97.5% in 2017), with normal battery charge (from 95.6% in 2013 to 96.8% in 2018), and electrode availability increased (from 97.1% in 2013 to 99.0% in 2017). However, the rate of electrode validity decreased (from 90.0% in 2013 to 87.2% in 2017). Non-ready-to-use AEDs and AEDs with limited 24-h availability accounted for 15.4% and 44.1% of the total number of AEDs, respectively. Conclusions Although most AEDs had a relatively good maintenance status, a significant proportion of public AEDs was not available for 24-h use. Invalid electrodes and limited 24-h accessibility were the main reasons that limited the 24-h availability of public AEDs.

Forecasting Methods of Battery Charge and Discharge Current Profile for LEO Satellites

The orbital characteristics of low Earth orbit (LEO) satellite systems prevent continuous monitoring because ground access time is limited. For this reason, the development of simulators for predicting satellite states for the entire orbit is required. Power-related prediction is one of the important LEO satellite simulations because it is directly related to the lifespan and mission of the satellite. Accurate predictions of the charge and discharge current of a power system’s battery are essential for fault management design, mission design, and expansion of LEO satellites. However, it is difficult to accurately predict the battery power demand and charging of LEO satellites because they have nonlinear characteristics that depend on the satellite’s attitude, season, orbit, mission, and operating period. Therefore, this paper proposes a novel battery charge and discharge current prediction technique using the bidirectional long short-term memory (Bi-LSTM) model for the development of a LEO satellite power simulator. The prediction performance is demonstrated by applying the proposed technique to the KOM-SAT-3A and KOMSAT-5 satellites operating in real orbits. As a result, the prediction accuracy of the proposed Bi-LSTM shows root mean square error (RMSE) within 2.3 A, and the prediction error well outperforms the most recent the probability-based SARIMA model.

Flight Planning Optimization of Multiple UAVs for Internet of Things

This article presents an approach to autonomous flight planning of Unmanned Aerial Vehicles (UAVs)-Drones as data collectors to the Internet of Things (IoT). We have proposed a model for only one aircraft, as well as for multiple ones. A clustering technique that extends the scope of the number of IoT devices (e.g., sensors) visited by UAVs is also addressed. The flight plan generated from the model focuses on preventing breakdowns due to a lack of battery charge to maximize the number of nodes visited. In addition to the drone autonomous flight planning, a data storage limitation aspect is also considered. We have presented the energy consumption of drones based on the aerodynamic characteristics of the type of aircraft. Simulations show the algorithm’s behavior in generating routes, and the model is evaluated using a reliability metric.

Optimizing Regenerative Braking: A Variational Calculus Approach

We begin by analyzing, using basic physics considerations, under what conditions it becomes energetically favorable to use aggressive regenerative braking to reach a lower speed over “coasting” where one relies solely on air drag to slow down. We then proceed to reformulate the question as an optimization problem to find the velocity profile that maximizes battery charge. Making a simplifying assumption on battery-charging efficiency, we express the recovered energy as an integral quantity, and we solve the associated Euler–Lagrange equation to find the optimal braking curves that maximize this quantity in the framework of variational calculus. Using Lagrange multipliers, we also explore the effect of adding a fixed-displacement constraint.

The Cyber Crime of Juice Jacking in Developing Economies: Susceptibilities, Consequences and Control Measures

It is convenient and the norm to have both data and power cables (battery charge) integrated as a single Universal Serial Bus (USB) cable for today’s mobile devices. While the data component of the cables serves as the channels for data communication, the power channel charges the mobile devices through an adapter connected to an Alternating Current (A/C) socket or directly to a USB port. This convenient and seemingly harmless design could also serve as a medium through which malicious hacks are carried out on the connected mobile devices as studies and recent experimentations has shown. This hacking variant called Juice Jacking now serve as a potential avenue for mobile device exploitation, especially in developing economies where poor power grid infrastructures has allowed for indiscretions in charging devices from any available. This paper formulates a simple architecture for Juice Jacking cyber-crime, review prove-of-concept experimentation for Juice Jacking from available literatures, identifies significant threats and levels of impact of this cyber-crime on the community. It also highlights strategies that could mitigate juice jacking in developing economies.

Applying the Heaviside step function to simulate the changes of temperature in automotive batteries

Discharged batteries do not provide the specified voltage in the car’s power supply system during parking, which can cause malfunctions of electrical equipment and an increase in the quiescent current in the on-board network, due to incorrect operation of electronic control units responsible for the operation of self-diagnosis systems, anti-theft alarm, multi-media, maintaining a thermal state, etc. Therefore, to ensure a reliable start of the ICE and the proper operation of the electrical equipment of a car at low temperatures, it is required to maintain the battery in a charged state. Vehicle generator is selected taking into account the nominal capacity of the battery, power and operating modes of electrical consumers, which excludes the battery operation with a low level of charge. However, when operating cars in large cities in winter, the battery charge level decreases. Deterioration of the battery charging characteristics, increased power consumption of additional equipment and low speed of movement of cars in the city with frequent stops at intersections are the reasons for the decrease in the efficiency of the battery charge. In such conditions, the battery can be discharged not only by starting the ICE and turning on consumers in the parking lot, but also when the ICE is idling and at low crankshaft speeds while driving on city routes and during rush hours. Considering that the operational characteristics of the battery change significantly with decreasing temperature, studies aimed at establishing and predicting the battery temperature during operation are relevant.