• Journal of Korean Society of Transportation
• /
• v.16 no.1
• /
• pp.129-150
• /
• 1998

신호교차로에서의 효율적인 교통운영을 위해서는 비보호좌회전의 활성화가 필요하며 이를 위해서는 비보호좌회전이 허용되는 신호교차로에서의 교통운영의 정확한 분석이 가능해야한다. 본연구에서는 국내신호교차로에서의 운전자의 행태에 기초하여 USHCM의 비보호 좌회전 분석에서 요구되는 $g_f$, $g_q$, $P_L$, 의 현실적인 값을 산정하기 위한 모형이 제안되었으며 이에 기초하여 비보호좌회전 보정계수 및 용량분석 기법을 제시하였다. 본 연구의 결과는 다음과 같다. 첫째, 공용차로를 가진 비보호좌회전 신호교차로에서 주기당 좌회전교통량(LTC)이 5대까지의 범위에서 G(녹색신호시간)와 LTC를 변수로 한 $g_f$모형이 개발되었다. 둘째, $v_{olc}$와 $qr_o$를 변수로 한 $g_q$모형이 개발되었으며 제안된 모형에 의한 $g_q$값이 진주 및 광주에서의 현장관측치와 거의 일치함을 볼 수 있었다. 셋째, 1994 USHCM의 $P_L$모형이 LTC가 증가할수록 $P_L$값이 감소하는 비현실적인 모형의 구조를 가지므로 현실적인 모형의 구축을 위해 국내 현장자료에 기초하여 LTC를 변수로하여 $P_L$산정을 위한 단순화된 모형이 개발되었다. 넷째, 대향교통류를 통해 좌회전할 수 있는 유효녹색시간의 부분의 $g_u$를 산정하여 비보호좌회전 포화교통류율($S_{LT}$)에 주기 대 $g_u$의 비를 곱한 비보호좌회전 용량산정식이 제안되었다.

• Aerospace Engineering and Technology
• /
• v.10 no.1
• /
• pp.39-44
• /
• 2011

A system of measurement for the thermal diffusivity of porous materials was developed. Although there are several measurement systems for thermal diffusivity, it is typically difficult to measure the thermal diffusivity of porous materials. This paper presents a measurement system for thermal diffusivity that utilizes a cyclic heating method along with the verification of the measured device. To verify the cyclic heating method, the available reference data of aceramic specimen was utilized. To apply the system to an actual porous material, polystyrene foam was tested. The thermal diffusivity of the polystyrene foam under vacuum was reduced by 63%. The measured values from both tests were in good agreement with the reference values, as they were within 10% of these values.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.23 no.9A
• /
• pp.2305-2312
• /
• 1998

This paper analyzed the delay characteristics of speech packets in virtual cellular network(VCN). The probability distribution of packet delay is obtained using the markov chain model when periodic speech packets are transmitted by slotted-ALOHA protocol. The effects of probility of capture and retransmission policy on the performance were also analyzed. At first, the probability cumulative function of packet delay is calculated from the probability of capture as a function of location of mobile terminal. In order to investigate the effects of backoff delay, we defined a parameter NPr, where N is the period (frame size) of the speech packets and Pr is the retransmission probability for each speech packet. We also obtained the 1% outage delay for various frame size N.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.48 no.4
• /
• pp.17-24
• /
• 2011

This paper presents a control scheme to cancel periodic disturbance with unknown frequency for optical disc drives. The control scheme consists of an output regulator and a frequency adaptive algorithm. Here, the frequency adaptive algorithm based on IMP plays a role in obtaining a frequency of periodic disturbance. The stability analysis of whole system and disturbance rejection performance are proven by the singular perturbation theory. The contribution of this paper are as follows. (1) There is no design constraints of the frequency range. (2) Ability for perfect disturbance rejection is preserved even with uncertain plant model.

• The Bulletin of The Korean Astronomical Society
• /
• v.37 no.2
• /
• pp.231.1-231.1
• /
• 2012

한국해양과학기술원 해양위성센터에서 주관운영을 수행하고 있는 천리안 위성의 해양탑재체인 천리안 해양관측위성(이하 GOCI)은 정지궤도위성용 해색센서로서, 태양을 광원으로 지구상의 해수 표면 부근에서 반사되어 대기를 통과한 가시광 및 근적외 대역을 8개 밴드로 분광하여 관측하는 센서이다. 해색센서의 경우, 일반적으로 센서에 입사되는 광신호의 약 90%가 대기에 의한 신호이며, 약 10%에 해당되는 신호만 원래 관측목적인 해수에 의한 신호이기 때문에, 5% 이내의 높은 복사보정 정확도가 요구된다. 이러한 높은 복사보정 정확도를 만족시키기 위해서는, 지상에서의 현장관측을 통한 위성자료 검보정 뿐만 아니라, 발사 후 위성 궤도상에서 센서의 복사보정을 수행하는 궤도상 복사보정이 체계적으로 수행되어야 한다. GOCI는 태양을 기준광원으로 하는 태양광 복사보정을 채택하여, 센서의 셔터부에 태양광 복사보정을 위한 2개의 태양광확산기(Solar Diffuser)를 장비하고 있다. 본 발표에서는 궤도상 시험 후 약 16개월에 걸친 궤도상 복사보정 운영결과와 관련하여, 발사 후 일별, 월별, 계절별 등 각 기간별 센서의 이득변화를 관찰하였으며, 그 결과 1년을 기준으로 약 3% 범위로 주기적인 이득 변화가 있음을 확인하였다. 지상시험결과와의 비교에 의해, 태양광확산기에 대한 태양입사각이 이러한 주기적인 이득 변화의 주 원인임을 궤도상 복사보정 운영결과를 통해 밝히고자 한다.

• The Transactions of the Korea Information Processing Society
• /
• v.4 no.11
• /
• pp.2891-2902
• /
• 1997

This paper presents an analysis on the optimal partitioning configuration of cache (memory) for meeting deadlines of periodic and aperiodic real-time task set. Our goal is not only to decrease the deadline missing ratio of each task by minimizing the task utilization, but also to allocate another tasks to idle spaces of cache. For this reason, we suggest an algorithm so that tasks could be allocated to cache segments. Here, the set of cache segments allocated tasks is called a cache partitioning configuration. Based on how tasks allocate to cache segments, we can get various cache partitioning configurations. From these configurations, we obtain the boundary of task utilization that tasks are possible to schedule, and analyze the cache optimal partitioning configuration that can be executed to minimize the task utilization.

• International Journal of Highway Engineering
• /
• v.9 no.4
• /
• pp.159-169
• /
• 2007

In this paper, a PMS(Pavement Management System) is presented for the public agency who wish to execute rational repair by referring to asset management information regarding road pavement. The aim of the paper is to provide the decision makers with the planning information regarding maintenance strategies for efficient road pavement management. We found that life cycle cost can be minimized and repair cost in each year fluctuates when repeating repair at the IRI management level. The validity of PMS application presented in this paper is investigated through case studies for conducted for 22 national highway road sections in Korea.

• The Journal of the Korea Contents Association
• /
• v.22 no.3
• /
• pp.442-452
• /
• 2022

This study was conducted to understand research trends of HR Analytics (HRA) in Korea and to suggest future research directions. First, a comparative analysis was conducted by classifying six areas of recruitment on-board, work environment, performance evaluation, retention, and exit/retirement building on the employee life cycle framework. The results indicate that first, the distribution of detailed research topics in Korean HRA research has similar to that of international research. Second, Korean HRA studies related to employee training and development function are insufficient. Third, the scope and the method of machine learning are becoming enriched. Finally Korean HRA studies are still in the technical domain and toward entering the predictive analysis domain.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.5C
• /
• pp.548-554
• /
• 2009

OFDM systems are very sensitive to the frequency offset. Therefore, frequency offset estimation is one of the most important procedures in OFDM systems. Ren's periodogram-based frequency offset estimation scheme consists of three steps which estimates the frequency offset accurately. However, there are the drawbacks of the limited frequency offset estimation ranges in the second and third estimation steps of the Ren's scheme. This ranges are insufficient compared with the overall signal bandwidth, making the high complexity of the first estimation step. In this paper, we propose a novel lower complexity frequency offset estimation scheme for OFDM systems which extends the frequency offset estimation range. The simulation results show that the proposed scheme has a wider frequency offset estimation range and lower complexity than those of the Ren's scheme.

• Radiation Oncology Journal
• /
• v.16 no.4
• /
• pp.455-467
• /
• 1998

Purpose : To evaluate influences associated with radiation treatment planning obtained with the patient breathing freely. Materials and Methods : We compared reduction or elimination of planning target volume (PTV) margins with 2-D conventional plan with inclusion of PTV margins associated with breathing with 3-D conformal therapy. The respiratory non gated 3-D conformal treatment plans were compared with respiratory gated conventional 2-D plans in 4 patients with hepatocellular carcinomas. Isodose distribution, dose statistics, and dose volume histogram (DVH) of PTVs were used to evaluate differences between respiratory gated conventional 2-D plans and respiratory non gated 3-D conformal treatment plans. In addition. the risk of radiation exposure of surrounding normal liver and organs are evaluated by means of DVH and normal tissue complication probabilities (NTCPs). Results : The vertical movement of liver ranged 2-3 cm in all patients. We found no difference between respiratory gated 2-D plans and 3-D conformal treatment plans with the patients breathing freely. Treatment planning using DVH analysis of PTV and the normal liver was used for all patients. DVH and calculated NTCP showed no difference in respiratory gated 2-D plans and respiratory non gated 3-D conformal treatment plans. Conclusion : Respiratory gated radiation therapy was very important in hepatic tumors because radiation induced hepatitis was dependent on remaining normal liver volume. Further investigational studies for respiratory gated radiation.