Research activities on next-generation mobile communications and services in Korea

In this article we present a perspective on next-generation mobile communications and services. As a preliminary research work on next-generation mobile communications, we exploit what next-generation mobile services will be (S. Ryu et al., May 2003). We define next-generation mobile services as a hierarchy of services consisting of three different service levels: the service areas, the service functionalities, and the service technologies. We derive these service levels by means of scenario-based analysis. Next we propose conceptual reference network architecture, focusing on the realization of the service technologies. We divide the network into four different parts: a user equipments and access part, a network service provisioning layer part, a network control layer part, and non-mobile network operator service pan, according to characteristics of information and service flows within a network. In this reference network architecture, service elements such as servers, processors, and gateways are placed in each network part to support the derived next-generation mobile services. Finally, we give a brief introduction of research and development activities for next-generation mobile communication systems and services in Korea.     

Advances in internet congestion control

In this survey, we first review the concept of congestion control with a focus on the Transmission Control Protocol⁄Internet Protocol (TCP⁄IP). We describe many recently proposed algorithms to combat congestion and improve performance, particularly active queue management (AQM) algorithms such as random early detection (RED) and its variants. We then survey control-theoretic analysis and design of TCP congestion control with an AQM scheme. In addition, we discuss three problems associated with AQM proposals: parameter setting, the insensitivity to the input traffic load variation, and the mismatch between macroscopic and microscopic behavior of queue length dynamics. As alternatives to AQM algorithms, we also survey architectural approaches such as modification of source or network algorithms, and economic approaches including pricing or optimization of allocated resources. Finally, we list many open issues that persist in the design, operation, and control of the Internet.     

Comparison of Macrophage Immune Responses and Metabolic Reprogramming in Smooth and Rough Variant Infections of Mycobacterium mucogenicum

Mycobacterium mucogenicum (Mmuc), a rapidly growing nontuberculous mycobacterium (NTM), can infect humans (posttraumatic wound infections and catheter-related sepsis). Similar to other NTM species, Mmuc exhibits colony morphologies of rough (Mmuc-R) and smooth (Mmuc-S) types. Although there are several case reports on Mmuc infection, no experimental evidence supports that the R-type is more virulent. In addition, the immune response and metabolic reprogramming of Mmuc have not been studied on the basis of morphological characteristics. Thus, a standard ATCC Mmuc strain and two clinical strains were analyzed, and macrophages were generated from mouse bone marrow. Cytokines and cell death were measured by ELISA and FACS, respectively. Mitochondrial respiration and glycolytic changes were measured by XF seahorse. Higher numbers of intracellular bacteria were found in Mmuc-R-infected macrophages than in Mmuc-S-infected macrophages. Additionally, Mmuc-R induced higher levels of the cytokines TNF-α, IL-6, IL-12p40, and IL-10 and induced more BMDM necrotic death. Furthermore, our metabolic data showed marked glycolytic and respiratory differences between the control and each type of Mmuc infection, and changes in these parameters significantly promoted glucose metabolism, extracellular acidification, and oxygen consumption in BMDMs. In conclusion, at least in the strains we tested, Mmuc-R is more virulent, induces a stronger immune response, and shifts bioenergetic metabolism more extensively than the S-type. This study is the first to report differential immune responses and metabolic reprogramming after Mmuc infection and might provide a fundamental basis for additional studies on Mmuc pathogenesis.     

Soft robot review

Soft robots are often inspired from biological systems which consist of soft materials or are actuated by electrically activated materials. There are several advantages of soft robots compared to the conventional robots; safe human-machine interaction, adaptability to wearable devices, simple gripping system, and so on. Due to the unique features and advantages, soft robots have a considerable range of applications. This article reviews state-of-the-art researches on soft robots and application areas. Actuation systems for soft robots can be categorized and analyzed into three types: variable length tendon, fluidic actuation, and electro-active polymer (EAP). The deformable property of soft robots restricts the use of many conventional rigid sensors such as encoders, strain gauges, or inertial measurement units. Thus, contactless approaches for sensing and/or sensors with low modulus are preferable for soft robots. Sensors include low modulus (< 1 MPa) elastomers with liquid-phase material filled channels and are appropriate for proprioception which is determined by the degree of curvature. In control perspective, novel control idea should be developed because the conventional control techniques may be inadequate to handle soft robots. Several innovative techniques and diverse materials & fabrication methods are described in this review article. In addition, a wide range of soft robots are characterized and analyzed based on the following sub-categories; actuation, sensing, structure, control and electronics, materials, fabrication and system, and applications.     

I-Portrait: An Interactive Photograph System for Enhancing Social Presence

ABSTRACT

People often strive to “externalize” memories for long-term saving or sharing with others using different forms of media. We devised a new interactive photograph system, I-Portrait, which enables interactive experiences with figures in a photograph. I-Portrait comprises short video clips that are recorded and played upon user interactions such as touch, voice, gestures, and facial expressions, providing users with the virtual experience of interaction with the figure. We evaluated the system by surveying 40 university students (age 20–29 years) on the level of social presence of the photograph (mutual awareness, emotional connectedness, and awareness of co-location) and users’ satisfaction, and comparing these measures between the I-Portrait system and traditional portraits. We found significant differences in all aspects of social presence suggesting that the interactivity of the I-Portrait system may significantly increase the social presence of physically distant others.     

Relay Performance Analysis of TTR and STR Relay Modes in IEEE 802.16j MMR System

The IEEE802.16j standard uses non‐transparent relay stations to extend coverage. There are two types of non‐transparent relay modes, that is, the time‐division transmit and receive (TTR) relay mode which can operate with one of two types of frame structures, a single‐frame and multiframe structure, and the simultaneous transmit and receive (STR) relay mode. In this paper, we analyze the relay performance of TTR and STR relay modes in IEEE 802.16j MMR system. We also propose a fair resource allocation scheme for the downlink relay frame. Numerical results show that relay performance of the TTR with a single‐frame or a multiframe structure and that of the STR relay modes are almost the same in a two‐hop system. However, in a three‐hop system, the TTR mode with a single‐frame structure outperforms other relay modes.     

Detection of DNA-hybridization using a near-field scanning microwave microscope

A near-field scanning microwave microscope (NSMM) is used to detect sequence-specific hybridization between surface-immobilized and free DNA single strands. Hybridization between target (free) and capture (immobilized) sequences leads to changes in the reflection coefficient (S11) which are measured by the NSMM. These changes are caused by hybridization-induced modification of the dielectric constant profile of the DNA film. NSMM instrumentation does not require labeling of target sequences with fluorophores or other tagging groups. The physical basis of reflection coefficient changes underpinning the NSMM approach is discussed.     

Advances in Active Queue Management (AQM) Based TCP Congestion Control

Current end-to-end Internet congestion control under tail-drop (TD) queue management experiences performance degradations such as multiple packet losses, high queueing delay and low link utilization. In this paper, we review recently proposed active queue management (AQM) algorithms for supporting end-to-end transmission control protocol (TCP) congestion control. We focus recently developed control theoretic design and analysis method for the AQM based TCP congestion control dynamics. In this context, we analyze the problems of existing AQM proposals in which congestion is detected and controlled reactively based on current and/or past congestion. Then we argue that AQM based TCP congestion control should be adaptive to the dynamically changing traffic situation in order to detect, control and avoid the current and the incipient congestion proactively. Finally, we survey two adaptive and proactive AQM algorithms, PID-controller and Pro-Active Queue Management (PAQM), designed using classical proportional-integral–derivative (PID) feedback control to overcome the reactive congestion control dynamics of existing AQM algorithms. A comparative study of these AQM algorithms with existing AQM algorithms is given. A simulation study under a wide range of realistic traffic conditions suggests that PID-controller and PAQM outperform other AQM algorithms such as random early detection (RED) [Floyd and Jacobson, 18] and proportional-integral (PI) controller [Hollot et al., 24].     

Visualization of magnetic domains by near-field scanning microwave microscope

A near-field scanning microwave microscope (NSMM) system was used for the investigation of magnetic properties of a hard disk (HD) under an external magnetic field. To demonstrate local microwave characterization of magnetic domains by NSMM, we scanned the HD surface by measuring the microwave reflection coefficient S₁₁ of the NSMM at an operating frequency near 4.4 GHz. The NSMM offers a reliable means for quantitative measurement of magnetic domains with high spatial resolution and sensitivity.     

Investigation of photoconductivity of silicon solar cells by a near-field scanning microwave microscope

The photovoltaic effect in silicon solar cells were investigated by using a near-field scanning microwave microscope (NSMM) technique by measuring the microwave reflection coefficient at an operating frequency near 4 GHz. As the photoconductivity in the solar cells was varied due to the incident light intensities and the wavelength, we could observe the photoconductivity changes at heterojunction interfaces inside the solar cells by measuring the change of reflection coefficient S₁₁ of the NSMM. By measuring the change of reflection coefficient, we also directly imaged the photoconductivity changes at heterojunction interfaces inside the solar cells.