• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.253-255
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• 2003

Electricity is the prime commodity in mobile device, e.g. smart phone, PDA, MP3 player and etc. This strict restriction on power consumption requirement of the mobile device puts unique demand in designing hardware and software components of the device. In this paper, we address the issue of minimizing the power consumption in retrieving the continuous media data from the disk drive for real-time playback purpose. Different from the legacy text based data, real-time multimedia playback requires that the storage supplies the data block continuous fashion. This may put immense burden on the power scarce environment since the disk Is required to be active for the entire playback duration. We develop elaborate algorithm which carefully analyzes the power consumption profile of the disk drive and which establishes the data retrieval schedule for the given playback. It computes the amount of data blocks to read, the length of active and standby period. According to our simulation result, the ARM algorithm exhibits superior performance in continuous media retrieval from the aspect of power consumption to legacy playback scheme.

• Proceedings of the Korean Society of Computer Information Conference
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• 2016.07a
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• pp.33-36
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• 2016

발사통제시스템의 주요 구성장치인 카운트다운 타임 생성 시스템은 카운트다운 신호를 생성하여 타 시스템에 제공하는 임무를 수행한다. 발사 관련 주요 장비들은 카운트다운 타임 생성 장치로부터 수신한 카운트다운 타임 정보에 따라 기능 수행을 하므로 안정적인 카운트다운 타임의 제공이 필수적이다. 따라서 카운트다운 타임 생성 시스템은 신뢰성과 고장 감내성을 보장하기 위한 설계가 요구된다. 이를 위해서는 시스템의 신뢰성을 보장하기 위한 방안으로 구성 장치들을 이중화하고 고장을 실시간 감시하여 고장 발생시 Active 장치에서 Standby 장치로의 절체 운용에 대한 설계가 필요하다. 본 논문에서는 카운트다운 타임 생성 장치의 이중화 설계에 따른 실시간 고장 감지 및 절체 운용 방법과 기능 시험 결과에 대하여 기술하였다.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.2
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• pp.36-47
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• 1998

Low power circuit techniques have been developed to realize the highest possible performance of embedded SRAM at 1V power supply with$0.5\mu\textrm{m}$ single threshold CMOS technology in which the unbalance between NMOS and PMOS threshold voltages is utilized to optimize the low power CMOS IC design. To achieve the best trade-off between the transistor drivability and the subthreshold current increase, the ground potential of memory array is raised to suppressthe subthreshold current. The problems of lower cellstability and bit-line dealy increase due to the enhanced array ground potential are evaluated to be controlled within the allowable range by careful circuit design. 160MHz, 128kb embedded SRAM with 3.4ns access time is demonstrated with the power consumption of 14.8mW in active $21.4{mu}W$ in standby mode at 1V power supply.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.8
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• pp.1291-1298
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• 2004

In development of monitoring and control systems, one of the most important points is to consider a redundancy so that the system can be operated normally although hardware faults are partly occurred. The purpose of this paper is to introduce a monitoring and control system with a redundancy function for I/O servers and communication networks. I/O servers composed with an active server and a standby server. Each server also has 3 communication ports, 2 ports of them were connected to field units and the other 1 port was connected to the other server. Field units have to be constructed to 2 communication ports connected I/O servers through communication lines. Also, server communication module was implemented for analyzing and handling fault elements. and was submodularized for linking easily with a monitoring and control module. An experiment with 2 servers and 2 field units was constructed to demonstrate its effectiveness.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1348-1357
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• 2015

Under traditional unified power quality conditioner (UPQC) control, a UPQC series converter (SC) is mainly used to handle grid-side power quality problems while its parallel converter (PC) is mainly used to handle load-side power quality problems. The SC and PC are relatively independent. The SC is usually in standby mode and it only runs when the grid voltage abruptly changes. In this paper, novel UPQC coordinated control strategies are proposed which use the SC to share the reactive power compensation function of the PC especially without grid-side power quality problems. However, in some cases, there will be a circulating current between the SC and the PC, which will probably influence the compensation fashion, the compensation capacity, or the normal work of the UPQC. Through an active power circulation analysis, strategies with and without a circulating current are presented which fuses the reactive power allocation strategy of the SC and the PC, the composite control strategy of the SC and the compensation strategy of the DC storage unit. Both of the strategies effectively solve the SC long term idle problem, limit the influence of the circulating current, optimize all of the UPQC units and reduce the production cost. An analysis, along with simulation andexperimental results, is presented to verify the feasibility and effectiveness of the proposed control strategies.

• Journal of the Korea Society of Computer and Information
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• v.21 no.10
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• pp.125-133
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• 2016

In this paper, we propose a real-time fault monitoring and dual system design of the countdown time-generating system, which is the main component of the mission control system. The countdown time-generating system produces a countdown signal that is distributed to mission control system devices. The stability of the countdown signal is essential for the main launch-related devices because they perform reserved functions based on the countdown time information received from the countdown time-generating system. Therefore, a reliable and fault-tolerant design is required for the countdown time-generating system. To ensure system reliability, component devices should be redundant and faults should be monitored in real time to manage the device changeover from Active mode to Standby mode upon fault detection. In addition, designing different methods for mode changeover based on fault classification is necessary for appropriate changeover. This study presents a real-time fault monitoring and changeover system, which is based on the dual system design of countdown time-generating devices, as well as experiment on real-time fault monitoring and changeover based on fault inputs.

• Journal of IKEEE
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• v.20 no.3
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• pp.314-317
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• 2016

Recently, efforts to maximize battery life in progress with an increase in the demand for portable devices. In this paper, we propose multi-phase buck converter with fast transient response. Multi-phase buck converter may be used for the output capacitor of small size because the ripple cancellation effect, it is possible to use an inductor having an inductance less. The portable device for quick change from standby mode to active 4-phase design structure was given a fast transient response. The proposed multi-phase buck converter was fabricated using a 0.18 um CMOS process and the supply voltage ranges from 2.7V to 3.3V, the maximum load current is 500mA and settling time is 10us.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.11
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• pp.2634-2639
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• 2014

The idea of redundancy is used in order to improve the availability of networks and systems and there are various methods for implementing redundancy. To perform the availability analysis various stochastic models have been used. In this paper, 2N redundancy with one active service unit and one standby service unit is considered. To evaluate the expected availability, we model 2N redundancy using Stochastic Reward Nets. This model can be solved using the SPNP package.

• Journal of Fashion Business
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• v.12 no.3
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• pp.167-174
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• 2008

The purpose of this study was to categorize customers types in accordance with current shop masters' perception of difficult customers and to identify their responding techniques and know-hows in dealing with those customers in detail, a qualitative study is carried out by conducting thorough interviews with the shop masters. The interview contained questions on occupational hold-ups of shop masters, types of hard-to-handle customers, techniques in handling difficult customers, their know-hows in customer managements and what they perceived as the qualities of a shop master. T The results were as follows: 1) Customers who are perceived as difficult by shop masters are categorized into six types, making unreasonable demands, pointing out product defects, disregarding salespersons, making no purchase after testing products, having no personality and having no response. 2) Responding techniques for difficult customers were categorized into three types, 'active response', 'standby' and 'polite refusal'. 3)The result from the question on know-hows of shop masters in customer management can be divided into 4 groups, providing special treatment or information, building one-to-one relationship with the customer, suggesting garments in accordance with the customer's taste and providing friendly customer service. 4) For the question on perceived qualities as a shop master, individual quality, customer management capacity, work experience and occupational knowledge were answered.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.12
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• pp.4725-4747
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• 2020

Software defined networking (SDN) is considered to be one of the most promising paradigms in the future. To solve the scalability and performance problem that a single and centralized controller suffers from, the distributed multi-controller architecture is adopted, thus forms multi-domain SDN. In a multi-domain SDN network, it is of great importance to ensure a reliable control plane. In this paper, we focus on the reliability problem of multi-domain SDN against controller failure from perspectives of backup controller deployment and controller replication. We firstly propose a placement algorithm for backup controllers, which considers both the reliability and the cost factors. Then a controller replication mechanism based on shared data storage is proposed to solve the inconsistency between the active and standby controllers. We also propose a shared data storage layout method that considers both reliability and performance. Besides, a fault recovery and repair process is designed based on the controller backup and shared data storage mechanism. Simulations show that our approach can recover and repair controller failure. Evaluation results also show that the proposed backup controller placement approach is more effective than other methods.