• Journal of Environmental Impact Assessment
• /
• v.20 no.3
• /
• pp.357-365
• /
• 2011

The QUAL2K has the same basic characteristics as the QUAL2E model, which has been widely used in stream water quality modeling; in QUAL2K, however, various functions are supplemented. The QUAL2Kw model uses a genetic algorithm(GA) for automatic calibration of QUAL2K, and it can search for optimum water quality parameters efficiently using the calculation results of the model. The QUAL2Kw model was applied to the Gangneung Namdaecheon River on the east side of the Korean Peninsula. Because of the effluents from the urban area, the middle and lower parts of the river are more polluted than the upper parts. Moreover, the hydraulic characteristics differ between the lower and upper parts of rivers. Thus, the river reaches were divided into seven parts, auto-calibration for the multiple reaches was performed using the function of the user-defined automatic calibration of the rates worksheets. Because GA parameters affect the optimal solution of the model, the impact of the GA parameters used in QUAL2Kw on the fitness of the model was analyzed. Sensitivity analysis of various factors, such as population size, crossover probability, crossover mode, strategy for mutation and elitism, mutation rate, and reproduction plan, were performed. Using the results of this sensitivity analysis, the optimum GA parameters were selected to achieve the best fitness value.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.3
• /
• pp.22-30
• /
• 2010

This paper proposes a combination system of Adaptive Modulation and Coding (AMC) and Multiple Input Multiple Output (MIMO), which improves the throughput and has a better reliability. In addition, the system includes Precoding, Antenna Subset Selection and MIMO Mode Selection scheme. Finally, we make a performance analysis of the proposed system. The principal environmental parameters for the simulation experiment consist of a frequency non-selective rayleigh fading channel and a Spreading Factor (SF) of 16. Other parameters may be included in order to fulfill the requirements of the HSDP A Standard. The proposed system has a higher throughput and more reliability than the conventional system, which does not include MIMO Mode Selection scheme, Precoding or Antenna Subset Selection. According to the simulation results, the proposed system reaches the maximum throughput at 8dB, presentlng an improvement of 6dB and twice higher throughput, respect to the conventional system. Specifically, at the point of -6dB, the conventional system reaches 2.5Mbps, while the proposed system reaches 6.4Mbps at the same SNR. Also, at the point of 2dB, each system reaches 7.5Mbps (conventional system) and 15.3Mbps (proposed system), with near twice the difference. According to the results exposed above, we can conclude that the system proposed in this paper has, as the greatest contribution, the improvement of the throughput, especially, the average throughput.

• Journal of Korean Institute of Industrial Engineers
• /
• v.25 no.1
• /
• pp.141-149
• /
• 1999

In this paper, we consider multiple-class queueing systems in which the server starts a set-up as soon as the number of customers in the "start-up class" reaches threshold N. After the set-up the server starts his service. We obtain the Laplace-Stieltjes transform and the mean of the waiting times of each class of customers for FCFS and non-preemptive priority disciplines.

• The Journal of the Acoustical Society of Korea
• /
• v.32 no.1
• /
• pp.86-94
• /
• 2013

In this paper, we propose a network coding scheme that is one of the most promising techniques for overcoming transmission errors in underwater acoustic communications. It is assumed that the proposed scheme operates in a Code Division Multiple Access (CDMA) network where multiple sensor nodes share the underwater acoustic channel in both the frequency and the time domains by means of orthogonal codes. The network topology deploys multi-hop transmission with relaying between multiple source nodes and one destination node via multiple relay nodes. The proposed scheme is evaluated in terms of the successful packet delivery ratio of end-to-end transactions under varying packet loss rates. A computer simulation shows that the successful delivery ratio is maintained at over 95% even when the packet loss rate reaches 50%.

• Journal of the Korean Statistical Society
• /
• v.36 no.2
• /
• pp.285-297
• /
• 2007

We consider the $P_{\lambda}^M-service$ policy for an M/G/1 queueing system in which the workload is monitored randomly at discrete points in time. If the level of the workload exceeds a threshold ${\lambda}$ when it is monitored, then the service rate is increased from 1 to M instantaneously and is kept as M until the workload reaches zero. By using level-crossing arguments, we obtain explicit expressions for the stationary distribution of the workload in the system.

• Proceedings of the Korean Information Science Society Conference
• /
• 2007.10b
• /
• pp.22-27
• /
• 2007

Phosphorylation is one of the most important post translational modifications which regulate the activity of proteins. The problem of predicting phosphorylation sites is the first step of understanding various biological processes that initiate the actual function of proteins in each signaling pathway. Although many prediction methods using single or multiple features extracted from protein sequences have been proposed, systematic data integration approach has not been applied in order to improve the accuracy of predicting general phosphorylation sites. In this paper, we propose an optimal way of integrating multiple features in the framework of multiple kernel learning. We optimally combine seven kernels extracted from sequence, physico-chemical properties, pairwise alignment, and structural information. Using the data set of Phospho. ELM, the accuracy evaluated by 5-fold cross-validation reaches 85% for serine, 85% for threonine, and 81% for tyrosine. Our computational experiments show significant improvement in the performance of prediction relative to a single feature, or to the combined feature with equal weights. Moreover, our systematic integration method significantly improves the prediction preformance compared with the previous well-known methods.

• Ecology and Resilient Infrastructure
• /
• v.5 no.4
• /
• pp.229-245
• /
• 2018

This study aims to investigate the changes in the riparian vegetated area in the Naeseong stream, an unregulated river, in order to analyze the main factors leading to these changes. For this purpose, the land surface cover in the channel area of the Naeseong stream was classified into 9 categories using past aerial photographs collected between 1970 and 2016, which recorded the long-term changes of the Naeseong stream. The increase or decrease in the vegetated area was calculated for each category using a pair of before and after images. The changes in the vegetated area were divided into 6 periods: the unvegetated channel period (1970 - 1980), the first rapid increase (1980 - 1986), the period of decrease due to flood (1986 - 1988), the period of repetitive man-induced disturbance and vegetation increase (1988 - 2008), the period of gradual vegetation increase (2008 - 2013), and the period of second rapid increase (2013 - 2016). Multiple regression analysis was performed using independent variables representing hydrology, climate, and geomorphology. The major variables found to be involved in the changes in the vegetated area of the Naeseong stream were the discharge during June - July, channel width, and temperature during April - June. Among the three variables, discharge and temperature were respectively the main independent variables in the downstream and the upstream reaches as per a single variable model. Channel width was the variable that distinguished the upstream and downstream reaches of the stream. The implication of the long-term increase in the vegetated area in the Naeseong stream was discussed based on the result of this study.

• Journal of Biosystems Engineering
• /
• v.14 no.2
• /
• pp.128-136
• /
• 1989

The purpose of this study was to develop a computer operated automatic drip irrigation system for application in vinyl-house cultivation. The results can be summarized as follows: 1) The T-type ice compensation wire was used to measure the temperature. The voltage level measured up to 0.02 volt was used as input to an 8-bit A/D converter. 2) A specially devised tensiometer was used to content the watering system. When the needle of the pressure gauge reaches the lower threshold position it turns on the pumping system and turns off when it reaches higher threshold position. 3) In order to use the multiple gypsum blocks for one transducer, reed relays and a D/O board were used to make the sequential switching possible. 4) It was possible to automate the trickle irrigation system for the whole growth period of vinyl-house crops with the help of microcomputer. 5) In terms of furrow irrigation, the irrigation water consumption was the smallest, 2.8 times less than conventional method of surface trickle irrigation, 3.4 times less than subsurface trickle irrigation method. 6) In terms of productivity of cucumber, there was a drop in productivity when compared to furrow irrigation method, 7.2% for surface trickle irrigation, 27.4% for subsurface irrigation method.

• 연구논문집
• /
• s.27
• /
• pp.175-181
• /
• 1997

Superconducting joints between Bi-2223/Ag tapes are fabricated by a press & reaction anneal and a multiple press & anneal. The silver sheath was mechanically or chemically removed from one side of each tape without altering the superconducting core. The exposed superconducting core of the two tapes were brought into contact and pressed so as to form a lap joint. The joined tapes were then subjected to a series of different thermomechanical treatments to achieve optimum heat treatment condition. The result from transport measurements shows that critical current ($I_c$) transmitting through joined area reaches 9A, approximately 60% of the current capacity of the tapes themselves. The critical current through joined area was improved by repeated press and reaction annealing. Measurements of the current-voltage relationship were made with several configuration of the voltage probes to characterize the critical current variation and I-V curve along the joint. Also discussed are microstructural aspects of the superconducting joint.

• ETRI Journal
• /
• v.31 no.4
• /
• pp.419-428
• /
• 2009

A question answering (QA) system can be built using multiple QA modules that can individually serve as a QA system in and of themselves. This paper proposes a learnable, strategy-driven QA model that aims at enhancing both efficiency and effectiveness. A strategy is learned using a learning-based classification algorithm that determines the sequence of QA modules to be invoked and decides when to stop invoking additional modules. The learned strategy invokes the most suitable QA module for a given question and attempts to verify the answer by consulting other modules until the level of confidence reaches a threshold. In our experiments, our strategy learning approach obtained improvement over a simple routing approach by 10.5% in effectiveness and 27.2% in efficiency.