• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.12
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• pp.44-55
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• 2001

MAC(Multiply and ACcumulate) is the core operation of multimedia data processing. Because MAC units implemented on traditional DSP units or embedded processors have latency of three cycles and cannot operate on multiple data simultaneously, then, performances are seriously limited. Many high end general purpose microprocessors have SIMD MAC unit as a functional unit. But these high end MAC units must support pipeline structure for various operation modes and high clock frequency, which makes control logic complex and increases chip area. In this paper, a 64bit SIMD MAC unit for embedded processors is designed. It is implemented to have a latency of one clock cycle to remove pipeline control logics and a minimal area overhead for SIMD support is added to existing Booth multipliers.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.213-213
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• 2016

현재 반도체 산업에서는 디바이스의 고 집적화, 고 수율을 목적으로 패턴의 미세화 및 웨이퍼의 대면적화와 같은 이슈가 크게 부각되고 있다. 다중 패터닝(multiple patterning) 기술을 통하여 고 집적 패턴을 구현이 가능해졌으며, 이와 같은 상황에서 각 패턴의 임계치수(critical dimension) 변화는 패턴의 위치 및 품질에 큰 영향을 끼치기 때문에 포토마스크의 임계치수 균일도(critical dimension uniformity, CDU)가 제작 공정에서 주요 파라미터로 인식되고 있다. 반도체 광 리소그래피 공정에서 크롬(Cr) 박막은 사용되는 포토 마스크의 재료로 널리 사용되고 있으며, 이러한 포토마스크는 fused silica, chrome, PR의 박막 층으로 이루어져 있다. 포토마스크의 패턴은 플라즈마 식각 장비를 이용하여 형성하게 되므로, 식각 공정의 플라즈마 균일도를 계측하고 관리 하는 것은 공정 결과물 관리에 필수적이며 전체 반도체 공정 수율에도 큰 영향을 미친다. 흔히, 포토마스크 임계치수는 플라즈마 공정에서의 라디칼 농도 및 식각 선택비에 의해 크게 영향을 받는 것으로 알려져 왔다. 본 연구에서는 Cr 포토마스크 에칭 공정에서의 Cl2/O2 공정 플라즈마에 대해 O2 가스 주입량에 따른 식각 선택비(etch selectivity) 변화를 계측하여 선택비 제어를 통한 Cr 포토마스크 임계치수 균일도 향상을 실험적으로 입증하였다. 연구에서 사용한 플라즈마 계측 방법인 발광분광법(OES)과 optical actinometry의 적합성을 확인하기 위해서 Cl2 가스 주입량에 따른 actinometer 기체(Ar)에 대한 atomic Cl 농도비를 계측하였고, actinometry 이론에 근거하여 linear regression error 1.9%을 보였다. 다음으로, O2 가스 주입비에 따른 Cr 및 PR의 식각률(etch rate)을 계측함으로써 식각 선택비(etch selectivity)의 변화율이 적은 O2 가스 농도 범위(8-14%)를 확인하였고, 이 구간에서 임계치수 균일도가 가장 좋을 것으로 예상할 수 있었다. (그림 1) 또한, spatially resolvable optical emission spectrometer(SROES)를 사용하여 플라즈마 챔버 내부의 O atom 및 Cl radical의 공간 농도 분포를 확인하였다. 포토마스크의 임계치수 균일도(CDU)는 챔버 내부의 식각 선택비의 변화율에 강하게 영향을 받을 것으로 예상하였고, 이를 입증하기 위해 각각 다른 O2 농도 환경에서 포토마스크 임계치수 값을 확인하였다. (표1) O2 11%에서 측정된 임계치수 균일도는 1.3nm, 그 외의 O2 가스 주입량에 대해서는 임계치수 균일도 ~1.7nm의 범위를 보이며, 이는 25% 임계치수 균일도 향상을 의미함을 보인다.

• Journal of Energy Engineering
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• v.11 no.1
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• pp.10-17
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• 2002

The objective of performing this study is to develop low emission condensing gas boiler. To reduce NOx and CO, three reasonable distances between burner and heat exchanger were decided through the experiments of model plane burner. Three burners with different diameter were made and then emission characteristics were examined. The optimum burner geometry was determined from flame stability, pollutant emission characteristics and applicability to the practical boiler system. In the domain of equivalence ratio 0.68~0.85, turn-down ratio of the burner designed by this research was extended to a wider range of 5 : 1. Thermal efficiency of the boiler developed by this study reached to 97% (LHV basis) of heating water efficiency at heating load of 20,000 kcal/hr when fueled by both of LNG or LPG. Emission ($O_2$=0%, wet basis) of NOx and CO concentration was 26 ppm and 85 ppm when fueled by LNG, 41 ppm and 113 ppm when fueled by LPG respectively.

• The KIPS Transactions:PartC
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• v.12C no.5 s.101
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• pp.741-748
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• 2005

SyncML is an open standard data synchronization protocol proposed by OMA(Open Mobile Alliance). In this paper, a Session Handler module, one of major modules for developing SyncML data synchronization clients, and a client User Setup program are designed and implemented. The Session Handier Module controls communication sessions, generates header parts of messages exchanged, and determines the legitimacy of incoming messages. In order to justify normal operations of the Session Handler module and the client User Setup program implemented In this paper, they are ported to a Zaurus PDA, which runs on LINUX operating system. In addition, data synchronization operations are performed between the PDA and a Synthesis sever, whose SyncML data synchronization operation is certificated by OMA, Wireless Internet International Standard Forum.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.62-71
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• 2008

Swirl injector with adjustable backhole length was analyzed to suppress high-frequency combustion instability in Liquid Rocket Engines. In order to analyze the effect of swirl injector as an acoustic absorber, swirl injector was regarded as a quarter-wave resonator and its damping capacity is verified in atmospheric temperature. Experiments were carried out with copied tubes on air core because the interior air core volume of injector has a direct effect on damping. From the experimental data, it is proved that increasing the number of injectors mounted at each anti-node point can increase acoustic damping effect. Also, when tuned injectors at 1L, 1T, 1L1T modes simultaneously are installed at each anti-node point of model chamber, the damping effect of tuned injectors with multi modes agree well with it of tuned injectors with single mode.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.10
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• pp.71-79
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• 2006

Swirl injector with multi-stage tangential entry was analyzed to suppress high-frequency combustion instability in Liquid Rocket Engines. In order to analyze the effect of swirl injector as an acoustic absorber, swirl injector was regarded as a quarter-wave resonator and it's damping capacity is verified in atmospheric temperature. It has a finite mode of vibration and natural frequencies which can be tuned to the natural frequencies of a model combustion chamber. The interior air core shape of injector is more stable in the case of using the swirl injector with multi-stage entry than with single-stage entry. Also, when the swirl injector with multi-stage entry is used, tuned-injector length for unstable mode is well agreed with the calculated length. From the experimental data, it is proved that if the interior air core shape of swirl injector is stable, the fine tuned swirl injector can decrease the unstable mode of model chamber effectively and increase the damping rate.

• The Journal of Korean Association of Computer Education
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• v.23 no.4
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• pp.61-68
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• 2020

The purpose of this study is to develop a debugging task to support process-centered assessment on software(SW) education and to develop a service site. Achievement criteria for programming in elementary and middle school SW curriculum consists of control structures such as repetition and condition, and elements such as variables and input/output. In order to apply the process-centered assessment presented by the Ministry of Education, it is necessary to present tasks that can be used in the actual classroom environment and to consider connection with achievement levels. Therefore, in this study, 12 tasks for elementary school and 15 tasks for middle school were developed as debugging tasks and their validity was verified. As a result of conducting Delphi verification for validity, it was found that the level and content of the debugging task are appropriate. In addition, as a result of verifying the usability of the debugging challenge site by applying a heuristic evaluation method, it was found that it is suitable for use in the real educational field.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.11
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• pp.1125-1132
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• 2011

The purpose of this study is to suggest installation methods of a mobile-communication repeater into a lift system with consideration of EMC. Two approaches, one(Solution 1) is realized with a repeater installed in a lift hoistway and another(Solution 2) installed inside a lift, were proposed. It is confirmed that the Solution 1 is more effective than the Solution 2. And it is suggested that the EIRP of a repeater must be limited to be ${\leq}$-5 dBm by considering electromagnetic immunity level for a lift and safety margin of 20 dB. This limit can provide suitable electromagnetic environment inside a lift with precise power-control mechanism of mobile communication systems. This study could be a good example of Green ICT by improving electromagnetic environment in spite of radio use.

• Journal of the Korea Society of Computer and Information
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• v.15 no.11
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• pp.135-142
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• 2010

QoS in the proxy system are under heavy influence from interferences such as congestion, latency, and retransmission. Also, multi-level streaming services affects from temporal synchronization, which lead to degrade the service quality. This paper proposes a new segment-based buffer management mechanism which reduces performance degradation of streaming services and enhances throughput of streaming due to drawbacks of the proxy system. The proposed paper optimizes streaming services by: 1) Use of segment-based buffer management mechanism, 2) Minimization of overhead due to congestion and interference, and 3) Minimization of retransmission due to disconnection and delay. This paper utilizes fuzzy value $\mu$ and cost weight $\omega$ to process the result. The simulation result shows that the proposed mechanism has better performance in buffer cache control rate, average packet loss rate, and delay saving rate with stream relevance metric than the other existing methods of fixed segmentation method, pyramid segmentation method, and skyscraper segmentation method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37B no.12
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• pp.1113-1118
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• 2012

Smart grid and intelligent transportation system draw significant interest since they are considered as one of the green technologies. These systems require a large number of sensors, actuators, and controllers. Also, machine-to-machine (M2M) communications is important because of the automatic control. The LTE-Advanced networks is preparing a set of functions that facilitate the M2M communications, and particularly the development of an efficient call admission control mechanism is critical. A method that groups MTC devices according to QoS constraints and determines the admission depending on the QoS satisfaction is limitedly applied only if the data transmission period and the maximum delay are identical. This paper proposed a call admission control that is free from such limitation and also optimizes the admission process under the certain condition of the transmission period and maximum delay. The theorems regarding the proposed method are presented with the proofs. The simulations confirms its validity and shows it is better in call admission probability than existing works.