Joon Yeop Lee

Constructing a reliable and fast recoverable network for drones

In recent years, due to the technological development of various kinds of drones, also known as unmanned aerial vehicles (UAVs), drones have emerged as an effective solution for a wide area of applications. In such applications, employing multiple drones promises a better way to carry out a given mission than employing a single drone. To utilize multiple drones, all drones should establish a network that can provide connectivity among themselves. In this paper, we propose GCS-routing, a routing protocol for multiple drones employed by a ground control system (GCS). GCS-routing utilizes the information of drones that can be obtained from GCS, such as geographic information and per-drone flight schedules. The actual implementation of GCS-routing was applied to a fleet of drones, and evaluated in various aspects.

Devising Mobile Sensing and Actuation Infrastructure with Drones

Vast applications and services have been enabled as the number of mobile or sensing devices with communication capabilities has grown. However, managing the devices, integrating networks or combining services across different networks has become a new problem since each network is not directly connected via back-end core networks or servers. The issue is and has been discussed especially in wireless sensor and actuator networks (WSAN). In such systems, sensors and actuators are tightly coupled, so when an independent WSAN needs to collaborate with other networks, it is difficult to adequately combine them into an integrated infrastructure. In this paper, we propose drone-as-a-gateway (DaaG), which uses drones as mobile gateways to interconnect isolated networks or combine independent services. Our system contains features that focus on the service being provided in the order of importance, different from an adaptive simple mobile sink system or delay-tolerant system. Our simulation results have shown that the proposed system is able to activate actuators in the order of importance of the service, which uses separate sensors’ data, and it consumes almost the same time in comparison with other path-planning algorithms. Moreover, we have implemented DaaG and presented results in a field test to show that it can enable large-scale on-demand deployment of sensing and actuation infrastructure or the Internet of Things (IoT).

Improving quality of multimedia services through network performance isolation in a mobile device

Due to the advancement of hardware and software, today’s mobile devices, such as smartphones, tablet PCs, and laptops, are capable of providing a wide range of services. Among various services, a lot of users use multimedia services on mobile devices, and the size of mobile multimedia traffic is constantly increasing. Especially, the growth of social networking services and content-sharing sites stimulates creating and sharing of multimedia contents. Such environment made it possible for today’s mobile users to frequently download or upload multimedia data. Nowadays, smartphones allow users to multi-task between different services, so the multimedia service often coexists with background services in a mobile device at the same time. In these cases, the performance degradation of a multimedia service happens due to concurrently running background services in the device. In this paper, we propose MuSNet, a scheme for improving QoS and QoE of multimedia services through network performance isolation in a mobile device, which resolves the aforementioned problem by applying the concept of performance isolation to the multimedia services. MuSNet is the mobile device-based scheme without any modification on servers. Furthermore, unlike most performance isolation implemented by virtual machines, we suggest a scheme that does not require virtualization that might be heavy for mobile devices. The proposed scheme was implemented on a smartphone by modifying the kernel, and various experiments were conducted to evaluate the advanced system behavior of MuSNet.

Network Performance Isolation Scheme for QoE in a mobile device

Todays smartphones and tablet PCs are equipped with various sensor units and wireless capabilities along with high performance computing units, which make these mobile devices capable of providing a wide range of services. Because of such characteristics, mobile devices consume more network traffic and frequently use multiple Internet services at the same time. The performance degradation of a foreground service happens frequently due to concurrently running background services in a mobile device. In this paper, we propose NetPIS, Network Performance Isolation Scheme for QoE, which resolves the aforementioned problem by applying the concept of performance isolation to the foreground service. NetPIS is the receiver-based scheme suitable for mobile devices without any modification on senders. Furthermore, unlike most performance isolation implemented by virtual machines, we suggest a scheme that does not require virtualization that might be heavy for mobile devices. The proposed scheme was implemented on a smartphone by modifying the kernel, and various experiments were conducted to evaluate the advanced system behavior of NetPIS.

Estrogen receptor activation contributes to RNF146 expression and neuroprotection in Parkinson's disease models

RNF146 is an E3 ubiquitin ligase that specifically recognizes and polyubiquitinates poly (ADP-ribose) (PAR)-conjugated substrates for proteasomal degradation. RNF146 has been shown to be neuroprotective against PAR polymerase-1 (PARP1)-induced cell death during stroke. Here we report that RNF146 expression and RNF146 inducers can prevent cell death elicited by Parkinson’s disease (PD)-associated and PARP1-activating stimuli. In SH-SY5Y cells, RNF146 expression conferred resistance to toxic stimuli that lead to PARP1 activation. High-throughput screen using a luciferase construct harboring the RNF146 promoter identified liquiritigenin as an RNF146 inducer. We found that RNF146 expression by liquiritigenin was mediated by estrogen receptor activation and contributed to cytoprotective effect of liquiritigenin. Finally, RNF146 expression by liquiritigenin in mouse brains provided dopaminergic neuroprotection in a 6-hydroxydopamine PD mouse model. Given the presence of PARP1 activity and RNF146 deficits in PD, it could be a potential therapeutic strategy to restore RNF146 expression by natural compounds or estrogen receptor activation.

Adaptive Transmission Scheme for TCP in Wireless Multi-Hop Network

Wireless multi-hop networks are scalable in that devices can easily connect to the network. Such scalability is also required in IoT. However, wireless multi-hop network mostly suffers from high probability of transmission failure due to interference, and nodes connected to the network often experience connection loss and subsequent segment loss which node mobility and routing update incur. Due to the fact that the congestion is not a sole reason for segment loss in wireless multi-hop network, the congestion control of TCP should consider momentary link instability, which unnecessarily reduces transmission speed. For this reason, this paper suggests adjustment of slow-start threshold (ssthresh) value which is used for congestion control algorithm. The adjustment algorithm is called adaptive ssthresh decision ASD algorithm that is to reduce unnecessary decrease of transmission speed in wireless multi-hop network.

Warning and detection system for epidemic disease

Epidemic diseases have repeatedly troubled mankind. With the Zika virus threatening societies around the whole world in recent years, the importance of epidemic disease control is greater than ever. We propose a warning and detection system for epidemic diseases. In our work, we designed the system and algorithm using GPS to prevent disease infection at the source and international propagation. The system was divided into 3 parts: the control center of the epidemic disease, the travelers smartphone app, and the GPS log analyzer at airports. The control center distributes epidemic disease information, the app keeps track of the current location (GPS) and presents warning messages if necessary, and the analyzer detects people who are likely to be infected. The validity and performance of the system were examined through experiments. To confirm the accuracy of the system, the experiment was conducted with different scenarios considering practical application.

Sex Differences in Hippocampal Neuronal Sensitization by Nicotine in M. gerbils

We studied the sex different nicotine effect on evoked population spike amplitudes (ePSA) and connexin (Cx) expression in the hippocampus CA1 area of gerbils. Acute doses of nicotine bitartrate (0.5 mg/kg: NT-0.5) slightly reduced ePSA in males but markedly augmented that in females. Acute NT (5.0 mg/kg) markedly increased the ePSA in all gerbils. Unlike acute NT-0.5, repeated NT-0.5 injection (twice a day for 7 days) significantly increased the ePSA in males and slightly affected the NT-0.5 effect in females. The Cx36 and Cx43 expression levels as well as Cx expressing neuronal populations were significantly increased by repeated NT-0.5 in in both male and female gerbils, and particularly, Cx43 expression was somewhat prominent in females. These results demonstrated a sex difference with respect to the nicotine effect on hippocampal bisynaptic excitability, irrelevant to connexin expression.