• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권11호
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• pp.2597-2615
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• 2013

This paper proposes a dynamic downlink load control scheme that jointly employs dynamic load threshold management and virtual coverage management schemes to reduce the degree of performance degradation due to traffic overload in two-tier femtocell networks. With the proposed scheme, the downlink load in a serving macrocell is controlled with a load threshold which is adjusted dynamically depending on the varying downlink load conditions of neighboring macrocells. In addition, traffic overloading is alleviated by virtually adjusting the coverage of the overloaded serving macrocell, based on the adjusted load threshold of the serving macrocell. Simulation results show that the proposed scheme improves the performance of two-tier femtocell networks in terms of the outage probability and sum throughput. This improvement is significantly increased with appropriate values of load thresholds and with an intermediate-level adjustment of the virtual coverage area (i.e., handover hysteresis margin: HOM). Furthermore, the proposed scheme outperforms both a previously proposed load control scheme with a static load threshold and the LTE system without a HOM adjustment.

• Journal of Information Processing Systems
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• 제9권3호
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• pp.379-394
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• 2013

Cloud computing is an evolving computing paradigm that has influenced every other entity in the globalized industry, whether it is in the public sector or the private sector. Considering the growing importance of cloud, finding new ways to improve cloud services is an area of concern and research focus. The limitation of the available Virtual Machine Load balancing policies for cloud is that they do not save the state of the previous allocation of a virtual machine to a request from a Userbase and the algorithm requires execution each time a new request for Virtual Machine allocation is received from the Userbase. This problem can be resolved by developing an efficient virtual machine load balancing algorithm for the cloud and by doing a comparative analysis of the proposed algorithm with the existing algorithms.

• ETRI Journal
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• 제30권4호
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• pp.618-620
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• 2008

A distributed virtual environment (DVE) allows multiple geographically distributed objects to interact concurrently in a shared virtual space. Most DVE applications use a non-replicated server architecture, which dynamically partitions a virtual space. An important issue in this system is effective scalability as the number of users increases. However, it is hard to provide suitable load balancing because of the unpredictable movements of users and hot-spot locations. Therefore, we propose a mechanism for sharing roles and separating service regions. The proposed mechanism reduces unnecessary partitions of short duration and supports efficient load balancing.

• Journal of Korea Multimedia Society
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• 제7권8호
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• pp.1097-1106
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• 2004

The typical web cluster architecture consists of replicated real servers and a virtual server that routes client requests among the real servers. In this paper, we proposed an efficient dynamic load distribution method with load prediction for the web cluster systems. The virtual server transmit status request message to real servers in other to get load states. However the load states dose not accurate during load distribution, thus the virtual server predict the load status of real servers and assign a request of the client to the minimum loaded real server. The proposed distribution methods works not related to partial breakdown of real servers, thus the system works with high availability. We also show that the proposed distribution method preserve scalable property and improve the throughput through a set of simulations.

• The Journal of the Korean dental association
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• 제58권11호
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• pp.670-682
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• 2020

This research examined the difference in cognitive load and the virtual presence depending on auditory feedback and task difficulty in haptic-based dental simulation. In the field of dental education, practice-centered training using handpiece has been crucial because a practitioner's psychomotor experience has a significant impact on the mastery of treatment skills. For the novice, it is necessary to reduce errors in dental treatment to enhancing skill acquisition in the haptic practice. In the training process, the force-feedback is crucial to elaborate subtle movement to guide what to do and how it should be hard or soft. However, It is not easy to add force-feedback to generate kinetic experience training. As an alternative method, we examined that auditory feedback can help learners' skill training. In this study, we analyzed how the presence/absence of auditory feedback at the different levels of task difficulty impacts learners' psychological demand and virtual presence in the virtual reality simulation. For this study, 29 dental college students participated in a dental simulation. The participants were grouped into two conditions that are with and without auditory feedback. Additionally, two consecutive tooth preparation tasks with different levels of difficulty were used in the simulation. The auditory feedback condition gives alarms to a learner when he treats a non-targeted tooth with a virtual handpiece. The user's cognitive load and virtual presence were measured to examine the effects of auditory feedback. The results revealed that the main effect was found in cognitive loads. Also, a significant interaction effect was shown in the virtual presence. We discussed the effective design methods for the virtual reality-based dental simulation through the result of this study.

• The Transactions of The Korean Institute of Electrical Engineers
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• 제59권10호
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• pp.1712-1717
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• 2010

To analyze the load of distribution line, real LPs (Load Profile) of AMR (Automatic Meter Reading) customers and VLPs (Virtual Load Profile) of non-AMR customers are required. Accuracy of VLP is an important factor to improve the analysis performance. There are 2 kinds of methods to generate the VLP; one is using ALP (Average Load Profile) per each industrial code and PNN (Probability neural networks) algorithm; the other is using LSI (Load Shape Index) and C5.0 algorithm. In this paper, existing researches are studied, and new method is suggested. Each methods are compared the performance with same LP data of real high voltage customers.

• Journal of the Korea Society of Computer and Information
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• 제13권1호
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• pp.55-64
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• 2008

Recently virtualization becomes one of the most popular research topics. and a lot of software products which is related to virtualization have been released accordingly. Server virtualization, which virtualize physical servers to supply many virtual servers, provides very efficient way to build network-based servers. In this paper, we design and implement virtual desktop service which is based on server virtualization. We also propose load balancing scheme for the virtual desktop service. The proposed virtual desktop service and its load balancing scheme provides a cost-effective way to build high-performance remote desktop service.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 한국정보통신학회 2012년도 추계학술대회
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• pp.793-796
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• 2012

Recently adoption of the Green IT is regarded as an essential element in order to decrease server heat and save energy in data center because of continuous increase of energy consumption and energy price. Consequently the conventional IT infrastructure is replaced with cloud computing platform. In this paper, we have implemented a Linux virtual server load balancing in open source-based cloud platform and the performance of the LVS load balancing is analyzed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권9호
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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.

• Journal of the Korea Fashion and Costume Design Association
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• 제23권3호
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• pp.11-21
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• 2021

Virtual reality is currently mainly used in games, but is starting to be applied as a variety of media fields, such as broadcasting and film. Virtual reality provides more fun than reality, and can provide new experiences in areas that cannot be experienced in reality due to the constraints of time, space, and environment. In particular, as the social non-contact arena has increased due to COVID-19, it is being applied to education, health, and medical industries. The contents are further expanding into design and military fields. Therefore, the purpose of this study was to observe the change in distribution of load and pressure felt by the body in the flying state while wearing a short pants harness, which are mainly used in the game and entertainment industry. In the experiment, the average pressure in the flying state was measured by attaching a pressure sensor to the back and front of a human mannequin. As a result, it was confirmed that the load concentrated on the waist in the flying state was 44 N, with a pressure of 1353 kPa. The pressure distribution was concentrated in front of the center of gravity, and was measured was at 98% by the pressure sensors, with an average pressure value of approximately 15 kPa, and a pressure value of approximately 12 kPa at the back, which was measured at 67% by the pressure sensor. The results of the load and pressure distribution measurement are presented as fundamental data to improve the wearability and comfort of harnesses in the future, and are compared to actual measured pressure values by analyzing the clothing pressure in flight through virtual wear of harnesses through the CLO 3D program.