• Journal of Genetic Medicine
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• v.4 no.2
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• pp.196-199
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• 2007

Coffin-Lowry syndrome (CLS) is a rare X-linked hereditary disorder characterized by moderate to severe mental retardation, facial dysmorphism, tapering fingers, and skeletal deformity. A 12-month-old boy was referred to our pediatric clinic for his developmental delay and seizure with fever. The boy exhibited a coarse facial appearance characterized by prominent, high-arched eyebrow, broad nose, downward palpebral fissure, high arched palate, hypodontia. The boy also showed finger tapering and puffy hand. Hypotonia, hyperextensible fingers and hypermobility of the joint were seen. Based on these findings, he was diagnosed as having Coffin-Lowry syndrome. We report a case of Coffin-Lowry syndrome with reference.

• The Journal of the Korean bone and joint tumor society
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• v.5 no.1
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• pp.63-69
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• 1999

Recently we experienced four cases of soft tissue Ewing sarcoma, developed in the calf muscles in two cases, and one case each in the foot and suprascapular region. We also found that the clinical course in all cases was rather rapid, because of local recurrence and metastatic lesions developing within a few months, followed by the patients' death in about 2 years after the primary tumor was excised. These cases were improperly treated initially as some kind of benign soft tissue tumor. The delay led to missed early accurate diagnosis and was thought to be one of the main causes for the rapid local recurrence and metastasis after tumor excision. The pulmonary metastasis was the most common cause of death.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.1
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• pp.9-16
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• 2016

Since most of devices in the IEEE 802.15.4 LR-WPAN are expected to operate on batteries, they must be designed to consume energy in a very conservative way. Two energy conservation algorithms are proposed for the LR-WPAN: DDC (Dynamic Duty Cycle) and DBT (Dynamic Beacon Tracking). The DDC algorithm adjusts duty cycle dynamically depending on channel conditions. The DBT algorithm switches beacon tracking mode on and off adaptively depending on traffic conditions. Combining the two algorithms reduces energy consumption more efficiently for a wide range of input loads, while maintaining frame delivery ratio and average delay at satisfactory levels.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.8-12
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• 2009

We propose BMPA(balanced multimedia packet allocation) scheme. This scheme considers the issue of optimal sub-carrier allocation in OFDMA multicast system. When RT(real time) packets and NRT(non-real time) packets arrive at the same time, BMPA scheme gives higher weight to RT packets than NRT packets and then, it allocates sub-carriers according to the total weight sum of packets in each user. This process acts as both packet scheduler and sub-carrier allocation. Therefore, each user receives multimedia packets with reliability. With simulation results, it shows that BMPA scheme ensures long-term system throughput and, in average RT packet delay, BMPA scheme greatly outperforms multi-user water-filling algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.3
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• pp.1313-1336
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• 2020

Cognitive radio (CR) is regarded as an effective approach to avoid the inefficient use of spectrum. However, CRNs have more special security problems compared with the traditional wireless communication systems due to its open and dynamic characteristics. Primary user emulation attack (PUEA) is a common method which can hinder secondary users (SUs) from accessing the spectrum by transmitting signals who has the similar characteristics of the primary users' (PUs) signals, and then the SUs' quality of service (QoS) cannot be guaranteed. To handle this issue, we first design a multiple-phase energy detection scheme based on the cooperation of multiple SUs to detect the PUEA more precisely. Second, a joint SUs scheduling and power allocation scheme is proposed to maximize the weighted effective capacity of multiple SUs with a constraint of the average interference to the PU. The simulation results show that the proposed method can effectively improve the effective capacity of the secondary users compared with the traditional overlay scheme which cannot be aware of the existence of PUEA. Also the good delay QoS guarantee for the secondary users is provided.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.9
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• pp.4144-4165
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• 2018

Software-defined networking (SDN) has emerged as a promising technology for network programmability and experiments. In this work, we focus on virtual network embedding in multiple controllers SDN network. In SDN virtualization environment, virtual SDN networks (vSDNs) operate on the shared substrate network and managed by their each controller, the placement and load of controllers affect vSDN embedding process. We consider controller placement, vSDN embedding, controller adjustment as a joint problem, together considering different quality of service (QoS) requirement for users, formulate the problem into mathematical models to minimize the average time delay of control paths, the load imbalance degree of controllers and embedding cost. We propose a heuristic method which places controllers and partitions control domains according to substrate SDN network, embeds different QoS constraint vSDN requests by corresponding algorithms, and migrates switches between control domains to realize load balance of controllers. The simulation results show that the proposed method can satisfy different QoS requirement of tenants, keep load balance between controllers, and work well in the acceptance ratio and revenue to cost ratio for vSDN embedding.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.1-7
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• 2013

In the next generation of mobile communication systems, high data rates and high capacity will be possible if multiple antennas are used at new frequencies. This paper presents the correlations between channel parameter path loss (PL), delay spread (DS), angular spread (AS) and K-factor established based on channel measurements. To avoid interference from Korean DTV broadcasting, we measured the channel characteristics in urban/rural/suburban areas on Jeju Island using a channel sounder and $4{\times}4$ antennas. The correlations between channel parameter show that the wireless channel characteristics can be determined and effective communication system design can be produced for use in similar environments.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.12
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• pp.4081-4098
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• 2022

With the aim of tackling the contradiction between computation intensive industrial applications and resource-weak Edge Devices (EDs) in Industrial Internet of Things (IIoT), a novel computation task offloading scheme in SDIN-enabled MEC based IIoT is proposed in this paper. With the aim of reducing the task accomplished latency and energy consumption of EDs, a joint optimization method is proposed for optimizing the local CPU-cycle frequency, offloading decision, and wireless and computation resources allocation jointly. Based on the optimization, the task offloading problem is formulated into a Mixed Integer Nonlinear Programming (MINLP) problem which is a large-scale NP-hard problem. In order to solve this problem in an accessible time complexity, a sub-optimal algorithm GPCOA, which is based on hybrid evolutionary computation, is proposed. Outcomes of emulation revel that the proposed method outperforms other baseline methods, and the optimization result shows that the latency-related weight is efficient for reducing the task execution delay and improving the energy efficiency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.1
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• pp.146-170
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• 2017

Joint channel assignment and routing is a well-known problem in multi-radio wireless mesh networks for which optimal configurations is required to optimize the overall throughput and fairness. However, other objectives need to be considered in order to provide a high quality service to network users when it deployed with high traffic dynamic. In this paper, we propose a re-configuration optimization model that optimizes the network throughput in addition to reducing the disruption to the mesh clients' traffic due to the re-configuration process. In this multi-objective optimization model, four objective functions are proposed to be minimized namely maximum link-channel utilization, network average contention, channel re-assignment cost, and re-routing cost. The latter two objectives focus on reducing the re-configuration overhead. This is to reduce the amount of disrupted traffic due to the channel switching and path re-routing resulted from applying the new configuration. In order to adapt to traffic dynamics in the network which might be caused by many factors i.e. users' mobility, a centralized heuristic re-configuration algorithm called State-Aware Joint Routing and Channel Assignment (SA-JRCA) is proposed in this research based on our re-configuration model. The proposed algorithm re-assigns channels to radios and re-configures flows' routes with aim of achieving a tradeoff between maximizing the network throughput and minimizing the re-configuration overhead. The ns-2 simulator is used as simulation tool and various metrics are evaluated. These metrics include channel-link utilization, channel re-assignment cost, re-routing cost, throughput, and delay. Simulation results show the good performance of SA-JRCA in term of packet delivery ratio, aggregated throughput and re-configuration overhead. It also shows higher stability to the traffic variation in comparison with other compared algorithms which suffer from performance degradation when high traffic dynamics is applied.

• The Journal of the Convergence on Culture Technology
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• v.6 no.2
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• pp.191-197
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• 2020

As an effective means of price discrimination, some suppliers offer trade credit to the distributors for the purpose of increasing the demand of the product they produce. The availability of the delay in payments from the supplier enables discount of the distributor's selling price from a wider range of the price option in anticipation of increased customer's demand. In this regard, we consider the problem of determining the distributor's optimal price and lot size simultaneously when the supplier permits delay in payments for an order of a product whose demand rate is represented by a constant price elasticity function. It is assumed that the distributor pays the shipping cost for the order and hence, the distributor's ordering cost consists of a fixed ordering cost and the shipping cost that depend on the order quantity. For the analysis, it is also assumed that inventory is depleted not only by customer's demand but also by decay. We are able to develop a solution algorithm from the properties of the mathematical model. A numerical example is presented to illustrate the algorithm developed.