• 인터넷정보학회논문지
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• 제15권2호
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• pp.1-7
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• 2014

본 논문은 MANET망에서 최적의 통달거리를 구하는 분석 수단을 제공한다. 본 연구의 결과는 특히 전술망에서 유용하게 사용 가능하며, 이는 최적 통달거리가 전송용량 및 지연시간, 배터리 소모 등에 영향을 끼치기 때문이다. 더불어, 제안된 분석 수단을 통해 MANET 단말을 휴대한 병사들을 배치하기 위해 사전에 최적 통달거리를 결정하는 것이 가능하도록 한다. 또한, Hata 전파 모델을 기반으로 다양한 전파 환경하에서 배터리 운용시간과 최적 통달거리를 비교/분석한다. 제안된 방안을 통해 MANET망의 운용 환경에 따라 MANET에서 최적 통달거리를 얻는다.

• 자원ㆍ환경경제연구
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• 제11권2호
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• pp.211-231
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• 2002

This paper summarizes the results of a study that assess how a demand side management (DSM) system addresses key economic and environmental challenges facing in the Korean natural gas sector considering; ${\bullet}$ high discrepancies of seasonal consumption volume and of load factor in unmatured domestic LNG market, ${\bullet}$ unfavorable and volatile international LNG market, imposing with the contestable "take-or-pay" contract terms, ${\bullet}$ low profile of LNG and existence of market barriers against an optimal fuel mix status in the industrial energy sector. A particular focus of this study is to establish an 'extended' DSM system in the unmatured gas market, especially in industry sector, that could play a key role to assure an optimum fuel mix scheme. Under the concept of 'extended' DSM, a system dynamics modeling approach has been introduced to explore the option to maximize economic benefits in terms of the national energy system optimization, entailing different ways of commitments accounting for different DSM measures and time delay scenarios. The study concludes that policy options exist that can reduce inefficiencies in gas industry and end-use system at no net costs to national economy. The most scenarios find that, by the year 2015, it is possible to develop a substantial potential of increased industrial gas end-uses under more reliable and stable load patterns. Assessment of sensitivity analysis suggests that time delay factor, in formulating DSM scenarios, plays a key role to overcome various market barriers in domestic LNG market and provides a strong justification for the policy portfolios 'just in time' (time accurateness), which eventually contribute to establish an optimum fuel mix strategy. The study indicates also the needs of advanced studies based on SD approach to articulate uncertainty in unmatured energy market analysis, including gas.

• 농업과학연구
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• 제45권4호
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• pp.615-622
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• 2018

This study was done to determine the optimum sowing time for spring sowing wheat in the southern region of the entire Korean peninsula. Jokyoung and Keumkangmil were sown four times at one-week intervals starting from Feb. 14, 2013. The thousand grain weights of the two wheat varieties were the highest on February 14 with the seed weights ranging from 36.6 to 40 g and significantly decreasing as the seeding time was delayed. The unmatured grain percentage increased sharply when both cultivars were sown starting on March 7. The grain yields were the highest for Keumkangmil with 3.07 MT/ha when sowed on February 21 and 3.37 MT/ha for Jokyoung when sowed on February 14. In both cultivars, the grain yield decreased drastically when they were sown on March 7. Ash content did increase when the sowing date was delayed. The flour gluten index was the highest at 96.2 in Keumkangmil with a February 28 sowing, and the sodium dodecyl sulphate (SDS) segmentation was the lowest ranging from 63.8 to 65.3 mL with the February 28 sowing. The falling number tended to increase with the delay of the sowing period. The flour milling rate was gradually decreased with the delay of sowing, and the bran gradually decreased. When both cultivars were sown after February 28, the grain and flour yields sharply decreased. In the southern region, the optimum time for the spring sowing of wheat is from February 14 to February 21.

• 대한교통학회지
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• 제24권5호
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• pp.123-133
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• 2006

서울시를 포함한 수도권 각 도시는 중앙버스전용차로의 적극적인 도입으로 버스속도 및 정시성 향상을 통해 대중교통우선 처리 전략을 적극 추진 중에 있다. 그러나 이로 인해 중앙부 $1{\sim}2$개 차로를 버스전용차로가 차지함으로써 기존 신호운영체계에 큰 변화를 가져오게 되었다 좌회전 차량과 중앙버스전용차로를 이용해 직진하는 버스간에 새로운 상충이 발생하게 되어 동시신호 기법 등 교차로 신호운영대안이 줄어들게 된 것이다 이 해결방안으로서 버스전용신호를 도입하여 중첩현시 및 동시신호 등 Dual-Ring방식의 다양한 신호 운영을 가능케 하는 방안이 모색되고 있다. 본 연구에서는 이러한 버스전용신호 도입 시 교차로 정체를 최소화할 수 있는 신호설계방법을 제시하였고, 중앙버스전용차로가 운영 중인 양재역사거리에 동 기법을 이용한 최적신호 설계를 적용, 시뮬레이션을 통해 그 효과를 검증하였다.

• Journal of Communications and Networks
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• 제15권5호
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• pp.496-503
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• 2013

In an orthogonal frequency division multiplexing system, conventional interpolation techniques cannot correctly balance performance and overhead when estimating dynamic long-delay channels in single frequency networks (SFNs). In this study, classical filter analysis and design methods are employed to derive a complex interpolator for maximizing the resistible echo delay in a channel estimator on the basis of the correlation between frequency domain interpolating and time domain windowing. The coefficient computation of the complex interpolator requires a key parameter, i.e., channel length, which is obtained in the frequency domain with a tentative estimation scheme having low implementation complexity. The proposed complex adaptive interpolator is verified in a simulated digital video broadcasting for terrestrial/handheld receiver. The simulation results indicate that the designed channel estimator can not only handle SFN echoes with more than $200{\mu}s$ delay but also achieve a bit-error rate performance close to the optimum minimum mean square error method, which significantly outperforms conventional channel estimation methods, while preserving a low implementation cost in a short-delay channel.

• 산업경영시스템학회지
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• 제6권8호
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• pp.63-71
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• 1983

Aggregate planning coordinate the control variable over long-term to apply a demand variable and forcasting. In order to necessary the goal that doesn't make an inter-contradiction and explicitly defined. We made a considerable point of system approach for scheduling establishment. It include the control variables of aggregate planning : 1) employment 2) over time working and idle time 3) inventory 4) delivery delay S) subcontract 61 long - term facility capacity. Each variables composed of pure strategy as like a decision of inventory level, a change of employment level, etc. md alternative costs make a computation on the economic foundation. But the optimum alternative costs represent the mixed pure strategy. The faults of this method doesn't optimum guarantee a special scheduling as well as increasing a number of alternative combination. Theoretical, Linear Decision Rule make an including all variables, but it is almost impossible for this model to develope actually And also make use of the aggregate planning problem for developing system approach : LDR, heuristic model, Search Decision Rule, all kind of computers, simulation. But these models are very complex, each variables get an extremely inter-dependence. So this study be remained by theory level, some approach methods has not been brought the optimum solution to apply in every cases.

• Journal of Information Technology Applications and Management
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• 제18권1호
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• pp.125-141
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• 2011

As the sales volume of online shops increases, the job burden in the back-offices of the online shops also increases. Order picking is the most labor-intensive operation among the jobs in a back-office and mid-size pure click online shops are experiencing the time delay and complexity in order picking nowadays while fulfilling their customers' orders. Those warehouses of the mid-size shops are based on manual systems, and as order pickings are repeated, the warehouses get a mess and lots of products in those warehouses are getting missing, which results in severe delay in order picking. To overcome this kind of problem in online clothing shops, we research a methodology to locate warehousing products. When products arrive at a warehouse, they are packed into a box and located on a rack in the warehouse. At this point, the operator should determine the box to be put in and the location on the rack for the box to be put on. This problem could be formulated as an Integer Programming model, but the branch-and bound algorithm to solve the IP model requires enormous computation, and sometimes it is even impossible to get a solution in a proper time. So, we relaxed the problem, developed a set of heuristics as a methodology to get a semi-optimum in an acceptable time, and proved by an experiment that the solutions by our methodology are satisfactory and acceptable by field managers.

• 한국컴퓨터정보학회논문지
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• 제20권9호
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• pp.61-66
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• 2015

We investigate rate scheduling and power allocation problem for a delay constrained CDMA systems. Specifically, we determine an energy efficient scheduling policy, while each user maintains the short term (n time slots) average throughput. More importantly, it is shown that the optimal transmission strategy for the uplink is same as that of the downlink, called uplink and downlink duality. We then examine the performance of the optimum transmission strategy for the uplink and the downlink for various system environments.

• 한국통신학회:학술대회논문집
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• 한국통신학회 1984년도 추계학술발표회논문집
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• pp.43-47
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• 1984

This paper describes the mean time delay and its variance before transition from search to lock mode by means of signal flow graph and its transfer function. A relation between hit probability and search stage number is presented with the comparison of the open loop and closed loop. From these results optimum transition probability which we must hold can be obtained.

• 디지털콘텐츠학회 논문지
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• 제15권2호
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• pp.137-145
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• 2014

본 논문에서는 전송시간의 변화가 큰 네트워크 환경에서 이레이저 코딩을 이용한 종단간, M개의 패킷으로 구성된 긴급 메시지의 전달 지연 단축 기법을 제안한다. 제안된 기법에서는 전송할 M개의 긴급 패킷들을 g개의 패킷으로 구성된 b개의 그룹으로 분할하고, 각 그룹에 대하여 r개의 리던던시 패킷이 추가된 이레이저 코딩을 수행한 후 전송한다. 각 그룹은 g+r개의 패킷 중에서 g개의 패킷이 도착하면 복구가 되며, 모든 그룹이 목적지에 도착하면, 전체의 긴급 메시지가 전달된다. 이레이저 코딩을 적용하게 되면 전달 지연은 단축이 되나, 추가적인 패킷 전송 및 코딩과 디코딩과정으로 인한 비용이 발생하게 되므로, 이러한 추가적인 전송비용을 고려하여 제안 기법의 최적 그룹 수 및 리던던시 패킷의 수에 대한 분석을 수행한다. 분석 결과로부터 제안된 기법은 전송시간의 변화가 큰 네트워크에서 큰 효과를 내며, 특히 긴급한 메시지의 전송이 필요할 때 유용함을 알 수 있다.