• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.428-428
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• 2016

Copper indium sulfide (selenide) (CuIn(S,Se)2,CISSe)는 1.0~1.5 eV의 Direct band gap과 105 cm-1이 넘는 큰 광 흡수 계수를 가지고 있어 박막 태양전지의 흡수층으로써 연구되어 왔다. 최근 대량생산 및 저가 공정에 용이하다는 측면에서 용액 공정 기반 CISSe 태양전지 연구가 크게 주목 받고 있다. 용액공정 기반 중 하이드라진을 사용 한 경우 매우 높은 효율을 기록하였으나, 하이드라진 자체의 유독성과 폭발성 때문에 분위기 제어가 필요하고 여전히 저가화 및 대면적 제작에 한계가 있다. 따라서 알코올 솔젤 기반 CISSe 태양전지 제작 연구가 많이 진행되었으나, 결정립 성장 및 칼코겐 원자를 공급하기 위해 불가피하게 황화/셀렌화 후속 열처리 공정을 요구한다. 후속 열처리 공정은 폭발성의 황화수소/황화셀레늄 기체 분위기 제어와 고가의 장비를 필요로 한다. 본 연구에서는 매우 안정적이며 저가 용매인 물과 아민계 첨가제를 이용하여 Cu, In 전구체와 S, Se 이 포함된 Cu-In-S 잉크와 Se잉크를 제작하였다. 잉크 내에 S, Se을 첨가 함으로써 추가적인 후속공정 없이 비활성 가스 분위기에서 고품질의 CISSe 박막 제작을 가능케 하였다. 또한 Se 잉크 증착 횟수에 따른 결정 구조, 광학적 성질의 차이에 주목하였다. 따라서 수계 잉크를 대기 중에서 스핀코팅으로 박막을 제작한 후, Hot plate에서 건조하여 균일한 박막을 제조하고, 제작된 박막을 tube furnace에서 환원 분위기 및 비활성 가스 분위기에서 열처리 진행하여 $1.3{\mu}m$ 두께의 고품질의 CISSe 흡수층을 제작하였다. 이러한 흡수층에 대해 XRD, SEM, EDS 분석을 진행하여, 결정성, 미세구조, 및 조성을 확인하였으며, 제작된 흡수층 위에 버퍼층/투명전극층을 차례로 증착하여 CISSe 태양전지를 제작하여 셀 성능 및 양자 효율 특성을 파악하였다. 또한 액상 Raman 분석을 통해 결정립 성장 과정 메커니즘을 제시하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.4
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• pp.786-792
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• 2016

Camellia was jointly developed by Nippon Telegraph and Telephone Corporation and Mitsubishi Electric Corporation in 2000. Camellia specifies the 128-bit message block size and 128-, 192-, and 256-bit key sizes. In this paper, a modified round operation block which unifies a register setting for key schedule and a conventional round operation block is proposed. 16 ROMs needed for key generation and round operation are implemented using only 4 dual-port ROMs. Due to the use of a message buffer, encryption/decryption can be executed without a waiting time immediately after KA and KB are calculated. The suggested block cipher Camellia algorithm is designed using Verilog-HDL, implemented on Virtex4 device and operates at 184.898MHz. The designed cryptographic core has a maximum throughput of 1.183Gbps in 128-bit key mode and that of 876.5Mbps in 192 and 256-bit key modes. The cryptographic core of this paper is applicable to security module of the areas such as smart card, internet banking, e-commerce and satellite broadcasting.

• The Journal of the Acoustical Society of Korea
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• v.19 no.8
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• pp.3-11
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• 2000

This paper considers the performance of a dynamic priority control function (DPCF) of a threshold-based Bernoulli priority jump (TBPJ) scheme. Loss-sensitive and delay-sensitive traffics are applied to a system with a TBPJ scheme that is a general state-dependent Bernoulli scheduling scheme. Loss-sensitive and delay-sensitive traffics represent sound and data, respectively. Under the TBPJ scheme, the first packet of the loss-sensitive traffic buffer goes into the delay-sensitive traffic buffer with Bernoulli probability p according to system states which represent the buffer thresholds and the number of packets waiting for scheduling. Performance analysis shows that TBPJ scheme obtains large performance build-up for the delay-sensitive traffic without performance degradation for the loss-sensitive traffic. TBPJ scheme shows also better performance than that of HOL scheme.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.8
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• pp.75-84
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• 2004

In this paper, we proposed an efficient hardware architecture of line-based lifting algorithm for Motion JPEG2000. We proposed a new architecture of a lifting-based filtering cell which has an optimized and simplified structure. It was implemented in a hardware accommodating both (9,7) and (5,4) filter. Since the output rate is linearly proportional to the input rate, one can obtain the high throughput through parallel operation simply by adding the hardware units. It was implemented into both of ASIC and FPGA The 0.35${\mu}{\textrm}{m}$ CMOS library from Samsung was used for ASIC and Altera was the target for FRGA. In ASIC, the proposed architecture used 41,592 gates for the lifting arithmetic and 128 Kbit memory. For FPGA it used 6,520 LEs(Logic Elements) and 128 ESBs(Embedded System Blocks). The implementations were stably operated in the clock frequency of 128MHz and 52MHz, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.4
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• pp.750-760
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• 1994

In this paper we proposed a multiplexing scheme of real time and non-real traffics in which a congestion control is embedded. Real time traffics are assumed to be nonqueuable and have preemptive priority over non-real time traffics in seizing the common output link, whereas the non-real time traffics wait in the common buffer if the output link is not available for transmission. Real time traffics are encoded according to the bandwidth reduction strategy, paticularly when congestion occurs among non-real time traffics. This scheme provides us an efficient way for utilizing the costly bandwidth resources, by accommodation as many real time traffics as possible with gauranteeing its mimimum bandwidth requirements, and also resloving the congestion encountered among non-real time traffics. We describe the system as a Markov queueing system, provide the analysis by exploiting the matrix geometric method, and present the performance for various performance measures of interest. Some numerical results are also provided.

• Journal of Environmental Impact Assessment
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• v.28 no.6
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• pp.568-579
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• 2019

The present study aims to identify the effect of land cover categories on particulate matter (PM) concentrations by analyzing the correlation between monthly PM concentrations in Seoul's air quality monitoring network and the percentages of land cover categories by buffers around air quality monitoring stations. According to a monthly correlation analysis between land cover categories and PM concentrations, in the buffer 3km, PM₁₀ showed a better correlation than PM_2.5, there was a clear negative correlation with the forest area, the grassland and the urbanized area had some positive correlation with PM₁₀, and the barren land and the urbanized area had some positive correlation with PM_2.5. According to a monthly correlation analysis of dominant land cover sub-categories and sub-sub-categories within the buffer 3km, PM₁₀ showed a clear negative correlation with the broad-leaved forest, and some positive correlation with the road was dominant. PM_2.5 showed partly negative correlation with the broad-leaved forest and partly positive correlation with the commercial area. There was a very low or no correlation with other grassland and bare land subcategories. A monthly stepwise regression analysis on noticeable land cover sub-categories and sub-sub-categories with positive or negative correlations revealed that an increasing percentage of the broad-leaved forest had a clear effect on reducing PM₁₀ concentrations, and the road was excluded from the selected variables. Although an increasing percentage of the commercial area had some effect on increasing monthly PM_2.5 concentrations and an increasing percentage of the broad-leaved forest had an effect on decreasing the PM_2.5 concentrations, their effect size was smaller than that on PM₁₀. The forest area around the city center had the largest and clearest effect on reducing PM concentrations. The urbanized area's sub-categories and sub-sub-categories were also confirmed to have some effect on increasing PM concentrations.

• The KIPS Transactions:PartB
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• v.9B no.6
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• pp.835-844
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• 2002

The number of channels available to a video server is limited since the number of channels a video server can support is determined by its communication bandwidth. Several approaches such as batching, piggybacking and patching have been proposed to reduce I/O demand on the video server by sharing multicast data. Patching has been shown to be efficient in the matter of the cost for VOD systems. Unlike conventional multicast techniques, patching is a dynamic multicast scheme which enables a new request to join an ongoing multicast. In addition, true VOD can be achieved since a new request can be served immediately without having to wait for the next multicast. In this paper. we propose two types of channel reservation patching algorithm : a fixed channel reservation patching and a variable channel reservation patching. To immediately schedule the requests for popular videos, these algorithms reserve the channels of video server for the fixed number of popular videos or for the variable number of popular videos which is determined dynamically according to the load of video server. The performance of the proposed algorithms is evaluated through simulations, and compared with that of simple patching. Our performance measures are average defection rate, average latency, service fairness and the amount of buffered data according to video server loads. Simulation results show that the proposed channel reservation patching algorithms provide better performance compared to simple patching algorithm.

• The KIPS Transactions:PartC
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• v.9C no.4
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• pp.605-614
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• 2002

Amount of the web traffic web server handles are explosively increasing, which requires that the performance of the web server should be improved for the various web services. Although the analysis for the HTTP traffic with the proper tuning for the web server is essential, the research relevant to the subject are insignificant. In particular, although most of applications are implemented over HTTP 1.1 protocol, the researches mostly deal with the performance evaluation of the HTTP 1.0 protocol. Consequently, the modeling approach and the performance evaluation over HTTP 1.1 protocol have not been well formed. Therefore, basing on the HTTP 1.1 protocol supporting persistent connection, we present an analytical end-to-end tandem queueing model for web server to consider the specific hardware configuration inside web server beginning at accepting the user request until completing the service. we compare various performances between HTTP 1.0 and HTTP 1.1 under the overloading condition, and then analyze the characteristics of the HTTP traffic that include file size requested to web server, the OFF time between file transfers, the frequency of requests, and the temporal locality of requests. Presented model is verified through the comparing the server throughput according to varying requests rate with the real web server. Thereafter, we analyze the performance evaluation of the web server, according to the interrelation between TCP Listen queue size, the number of HTTP threads and the size of the network buffers.