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"Kim, Yongjae"
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The Impact of Dual-Channel Investments and Contract Mechanisms on Telecommunications Supply Chains
2025
This study examines how contract structures influence coordination and innovation incentives in dual-channel telecommunications supply chains. We consider a setting where a mobile network operator (MNO) supplies services both directly to consumers and indirectly through a mobile virtual network operator (MVNO), which competes in the retail market. Using a game-theoretic framework, we evaluate how different contracts—single wholesale pricing, revenue sharing, and quantity discounts—shape strategic decisions, particularly in the presence of investment spillovers between parties. A key coordination problem emerges from the externalized gains of innovation, where one party’s investment generates value for both participants. Our results show that single wholesale and revenue sharing contracts often lead to suboptimal investment and profit outcomes. In contrast, quantity discount contracts, especially when combined with appropriate transfer payments, improve coordination and enhance the total performance of the supply chain. We also find that innovation led by the MVNO, while generally less impactful, can still yield reciprocal benefits for the MNO, reinforcing the value of cooperative arrangements. These findings emphasize the importance of contract design in managing interdependence and improving efficiency in decentralized supply chains. This study offers theoretical and practical implications for telecommunications providers and policymakers aiming to promote innovation and mutually beneficial outcomes through well-aligned contractual mechanisms.
Journal Article
Optimal Timing Strategies in the Evolutionary Dynamics of Competitive Supply Chains
2024
This study investigates the dynamics of endogenous order placement timing among competing retailers within a single period, driven by the evolution of demand-forecast information. Despite the critical role of accurate market trends and demand forecasts in determining firm success during selling seasons, the existing literature lacks a comprehensive understanding of how firms strategically adjust their order timing with imperfect and evolving information landscapes. By leveraging resources such as predictive analytics systems operated by big data and social media, firms tend to enhance their market demand precision as the selling season approaches, aligning with market practices. With this background, we aim to address the strategic behaviors of competing retailers in timing their orders, filling the aforementioned research gap. We construct a non-cooperative game-theoretical model to analyze the strategic behaviors of competing retailers in timing their orders. The model incorporates factors such as imperfect and evolving information landscapes, considering how firms leverage resources to enhance their market demand precision as the selling season approaches. Our analysis shows two primary equilibria, each shedding light on distinct strategic choices and their implications. First, the better-informed firm decides to execute early orders, capitalizing on the first mover’s advantage, particularly when initial information imprecision exceeds a specific threshold. Conversely, a second equilibrium emerges when the better-informed firm delays its orders, yielding the first mover’s advantage to the less-informed competitor. These equilibria highlight the correlation between order timing strategies and the trajectory of information evolution within the competitive landscape. Additionally, our study extends beyond equilibrium analysis to investigate these strategic choices on supply-chain performance.
Journal Article
EMPhone: Electromagnetic Covert Channel via Silent Audio Playback on Smartphones
2025
Covert channels enable hidden communication that poses significant security risks, particularly when smartphones are used as transmitters. This paper presents the first end-to-end implementation and evaluation of an electromagnetic (EM) covert channel on modern Samsung Galaxy S21, S22, and S23 smartphones (Samsung Electronics Co., Ltd., Suwon, Republic of Korea). We first demonstrate that a previously proposed method relying on zero-volume playback is no longer effective on these devices. Through a detailed analysis of EM emissions in the 0.1–2.5 MHz range, we discovered that consistent, volume-independent signals can be generated by exploiting the hardware’s recovery delay after silent audio playback. Based on these findings, we developed a complete system comprising a stealthy Android application for transmission, a time-based modulation scheme, and a demodulation technique designed around the characteristics of the generated signals to ensure reliable reception. The channel’s reliability and robustness were validated through evaluations of modulation time, probe distance, and message length. Experimental results show that the maximum error-free bit rate (bits per second, bps) reached 0.558 bps on Galaxy S21 and 0.772 bps on Galaxy S22 and Galaxy S23. Reliable communication was feasible up to 0.5 cm with a near-field probe, and a low alignment-aware bit error rate (BER) was maintained even for 100-byte messages. This work establishes a practical threat, and we conclude by proposing countermeasures to mitigate this vulnerability.
Journal Article
Major Quantitative Trait Loci and Putative Candidate Genes for Powdery Mildew Resistance and Fruit-Related Traits Revealed by an Intraspecific Genetic Map for Watermelon (Citrullus lanatus var. lanatus)
by
Hwang, Ji-Hyun
,
Park, Young-Hoon
,
Kim, Sun-Tae
in
Airborne microorganisms
,
Amplification
,
Binding sites
2015
An intraspecific genetic map for watermelon was constructed using an F2 population derived from 'Arka Manik' × 'TS34' and transcript sequence variants and quantitative trait loci (QTL) for resistance to powdery mildew (PMR), seed size (SS), and fruit shape (FS) were analyzed. The map consists of 14 linkage groups (LGs) defined by 174 cleaved amplified polymorphic sequences (CAPS), 2 derived-cleaved amplified polymorphic sequence markers, 20 sequence-characterized amplified regions, and 8 expressed sequence tag-simple sequence repeat markers spanning 1,404.3 cM, with a mean marker interval of 6.9 cM and an average of 14.6 markers per LG. Genetic inheritance and QTL analyses indicated that each of the PMR, SS, and FS traits is controlled by an incompletely dominant effect of major QTLs designated as pmr2.1, ss2.1, and fsi3.1, respectively. The pmr2.1, detected on chromosome 2 (Chr02), explained 80.0% of the phenotypic variation (LOD = 30.76). This QTL was flanked by two CAPS markers, wsb2-24 (4.00 cM) and wsb2-39 (13.97 cM). The ss2.1, located close to pmr2.1 and CAPS marker wsb2-13 (1.00 cM) on Chr02, explained 92.3% of the phenotypic variation (LOD = 68.78). The fsi3.1, detected on Chr03, explained 79.7% of the phenotypic variation (LOD = 31.37) and was flanked by two CAPS, wsb3-24 (1.91 cM) and wsb3-9 (7.00 cM). Candidate gene-based CAPS markers were developed from the disease resistance and fruit shape gene homologs located on Chr.02 and Chr03 and were mapped on the intraspecific map. Colocalization of these markers with the major QTLs indicated that watermelon orthologs of a nucleotide-binding site-leucine-rich repeat class gene containing an RPW8 domain and a member of SUN containing the IQ67 domain are candidate genes for pmr2.1 and fsi3.1, respectively. The results presented herein provide useful information for marker-assisted breeding and gene cloning for PMR and fruit-related traits.
Journal Article
An evolutionarily conserved non-synonymous SNP in a leucine-rich repeat domain determines anthracnose resistance in watermelon
2019
Key messageA non-synonymous SNP of CC–NBS–LRR was firstly mapped to confer resistance to anthracnose in watermelon. Newly proposed LRR domain harboring the SNP is evolutionary conserved in the Cucurbitaceae and Fabaceae.Anthracnose disease caused by Colletotrichum devastates many plants. Despite the importance of the disease, the mechanisms of resistance against it are poorly understood. Here, we identified a non-synonymous single-nucleotide polymorphism (SNP) located in a leucine-rich repeat domain as a marker for resistance to anthracnose race 1 in watermelon, using a combination of genetic analyses. We validated this SNP in segregating populations and 59 watermelon accessions using high-resolution melting assays and Sanger sequencing. We demonstrated that the resulting arginine-to-lysine substitution is particularly conserved among the Cucurbitaceae and Fabaceae. We identified a conserved motif, IxxLPxSxxxLYNLQTLxL, found in 1007 orthologues/paralogues from 89 plant species, and discovered that residue 18 of this motif could determine resistance to disease caused by external invaders. This study provides a step forward in understanding anthracnose resistance in watermelon, as well as functional and evolutionary insight into leucine-rich repeat proteins.
Journal Article
Distributed Learning for Dynamic Channel Access in Underwater Sensor Networks
by
Baek, Seungjae
,
Song, Yujae
,
Kim, Yongjae
in
Access control
,
acoustic communication
,
Acoustics
2020
In this study, the problem of dynamic channel access in distributed underwater acoustic sensor networks (UASNs) is considered. First, we formulate the dynamic channel access problem in UASNs as a multi-agent Markov decision process, wherein each underwater sensor is considered an agent whose objective is to maximize the total network throughput without coordinating with or exchanging messages among different underwater sensors. We then propose a distributed deep Q-learning-based algorithm that enables each underwater sensor to learn not only the behaviors (i.e., actions) of other sensors, but also the physical features (e.g., channel error probability) of its available acoustic channels, in order to maximize the network throughput. We conduct extensive numerical evaluations and verify that the performance of the proposed algorithm is similar to or even better than the performance of baseline algorithms, even when implemented in a distributed manner.
Journal Article
Effect of SIFRCCs with Varying Steel Fiber Volume Fractions on Flexural Behavior
2020
Conventional concrete is a brittle material with a very low tensile strength as a result of compressive strength and tensile strain. In this study, the flexural behavior characteristics of slurry-infiltrated fiber-reinforced cementitious composites (SIFRCCs) based on slurry-infiltrated fiber concrete (SIFCON), such as high-performance fiber-reinforced cementitious composites (HPFRCCs), were analyzed to maximize the fiber volume fraction and increase resistance to loads with very short working times (such as explosions or impacts). For extensive experimental variables, one fiber aspect ratio and three fiber volume fractions (6%, 5%, and 4%) were designed, and the flexural toughness and strength were figured out with respect to variables. A maximum flexural strength of 45 MPa was presented for a fiber volume fraction of 6%, and it was found that by increasing the fiber volume fraction the flexural strength and toughness increased. The test results with respect to fiber volume fraction revealed that after the initial crack, the load of SIFRCCs frequently increased because of the high fiber volume fraction. In addition to maximum strength, acceptable strength was found, which could have a positive effect on brittle fractures in structures where an accidental load is applied (such as an impact or explosion).
Journal Article
Exploring the Impact of Message Framing on Donation Behavior Through Emotions in Sport CSR: The Moderating Roles of Perceived CSR Motives and Team Identification Through Biometric Facial Expression Analysis
by
Kim, Yongjae
,
Kim, Soojin
2025
Despite extensive research on corporate social responsibility (CSR), the effects of message framing within sport CSR remain unexplored. This study bridges this gap by examining how message framing impacts donation behavior through emotions, using advanced biometric facial expression analysis. Results indicate that negatively framed messages, which evoke sadness, lead to higher donation amounts than that of positive emotions. Additionally, perceived CSR motives and team identification moderated these effects. CSR motives perceived as public-serving were more effective, especially when they evoked sadness. In contrast, when CSR motives were perceived as self-serving, a significant positive relationship between negative emotions and donation was found only among individuals with high team identification. By understanding the emotional mechanisms at play and considering factors such as perceived CSR motives and team identification, charitable organizations can design more effective fundraising campaigns that resonate with donors and inspire greater generosity within sport context.
Journal Article
The moderating role of consumers' ad perception in athlete endorsement effectiveness
2021
PurposeThis paper aims to examine the structural relationships among the variables of social cause involvement, attitudes toward the endorser, attitudes toward advertising, attitudes toward the brand and social cause behavioral intentions. Additionally, by using the persuasion knowledge model (PKM) as the guiding framework, the moderating effects of ad perception on the proposed relationship were investigated.Design/methodology/approachBy using Amazon Mechanical Turk, a total of 291 usable surveys were retained for analysis. Following the participants' exposure to the Nike commercial, they completed a survey containing questions about advertising perception and their consequent responses to the advertisement. Structural equation modeling was used to test the conceptual model. Multigroup analysis was also performed to discover any moderating effects of consumers' advertising perception in endorsement effectiveness.FindingsThis study highlights the extensive impact of social cause involvement in the domain of celebrity endorsements, while attitudes toward the endorser are not a significant antecedent of celebrity endorsement effectiveness in the sport contexts. Additionally, this study demonstrates and confirms the presence of the moderating effects of advertisement perception on the proposed relationship. This supports the general premise of the PKM that consumers' attitudes and thoughts are influenced based on consumers' judgment of persuasion attempts.Originality/valueThe current study extends the line of research on the role of advertising perception in the domain of celebrity endorsement. In particular, this study found that the PKM is a theoretically sound model that can be used to predict sports fans' attitudinal and behavioral responses.
Journal Article
Guided Self-Organization in a Dynamic Embodied System Based on Attractor Selection Mechanism
by
Iida, Fumiya
,
Yu, Xiaoxiang
,
Kim, Yongjae
in
attractor selection mechanism
,
Control systems
,
curved beam hopping robot
2014
Guided self-organization can be regarded as a paradigm proposed to understand how to guide a self-organizing system towards desirable behaviors, while maintaining its non-deterministic dynamics with emergent features. It is, however, not a trivial problem to guide the self-organizing behavior of physically embodied systems like robots, as the behavioral dynamics are results of interactions among their controller, mechanical dynamics of the body, and the environment. This paper presents a guided self-organization approach for dynamic robots based on a coupling between the system mechanical dynamics with an internal control structure known as the attractor selection mechanism. The mechanism enables the robot to gracefully shift between random and deterministic behaviors, represented by a number of attractors, depending on internally generated stochastic perturbation and sensory input. The robot used in this paper is a simulated curved beam hopping robot: a system with a variety of mechanical dynamics which depends on its actuation frequencies. Despite the simplicity of the approach, it will be shown how the approach regulates the probability of the robot to reach a goal through the interplay among the sensory input, the level of inherent stochastic perturbation, i.e., noise, and the mechanical dynamics.
Journal Article