• Journal of Soil and Groundwater Environment
• /
• v.18 no.2
• /
• pp.45-53
• /
• 2013

Many cases of strategically designed groundwater remediation have lack of information of hydraulic conductivity or permeability, which can render remediation methods inefficient. Many studies have been carried out to minimize this shortcoming by determining detailed hydraulic information either through direct or indirect measurements. One popular method for hydraulic characterization is the pilot point method (PPM), where the hydraulic property is estimated at a small number of strategically selected points using secondary measurements such as hydraulic head or tracer concentration. This paper adopted a D-optimality based pilot point method (DBM) developed previously for hydraulic head measurements and extended it to include both hydraulic head and tracer measurements. Based on different combinations of trials, our analysis showed that DBM performs well when hydraulic head is used for pilot point selection and both hydraulic head and tracer measurements are used for determining the conductivity values.

• 한국항공운항학회:학술대회논문집
• /
• 2005.05a
• /
• pp.99-103
• /
• 2005

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.9
• /
• pp.965-970
• /
• 2010

Because of a large number of subcarriers, the high PAPR(Peak-to-Average Power Ratio) is the major drawback of NC-OFDM system used for wireless communication system. Comb type pilot assignment is more efficient and lower computational complexity for the channel estimation than the block type pilot. However, even if the CAZAC(Constant Amplitude Zero Autocorrelation) matrix transform is used for the PAPR reduction of the data symbols, PAPR increases when the pilot is inserted in comb type with the data symbols. Therefore, in this paper, we additionally use a new SLM technique in order to lower the PAPR again even in the comb type pilot. Also, a new SLM technique suggested in this paper does not need any additional bandwidth for sending selection information for SLM. This combined method has good PAPR reduction performance and efficient data transmission.

• Journal of the military operations research society of Korea
• /
• v.11 no.1
• /
• pp.33-46
• /
• 1985

This study develops a scientific method in pilot selection by analysing a divided attention performance between the successful pilots and the failures in a flight training course. To measure the divided attention performance, Dual Task Method is used in which the primary task is a tracking task while the secondary tasks are, 1. short-term memory task 2. choice reaction task 3. judgement task. Result shows that the performance of the pilots is significantly better (p < 0.1) than that of the failures in divided attention performance. In addition, the differences in the divided attention performance between the two groups are increased in proportion to the difficulty of the task and especially in the short term memory, the increment is most dramatic.

• Journal of Korean Institute of Industrial Engineers
• /
• v.10 no.2
• /
• pp.3-16
• /
• 1984

This study develops a scientific method in pilot selection by analysing a divided attention performance between the successful pilots and the failures in a flight training course. To measure the divided attention performance, Dual Task Method is used in which the primary task is a tracking task while the secondary tasks are, 1. short term memory task, 2. choice reaction task and 3. judgement task. Result shows that the performance of the pilots is significantly better (P < 0.1) than that of the failures in dual performance. In addition, the differences in the divided attention performance between the two groups are increased in proportion to the difficulty of the task and especially in the Short Term Memory, the increment is most dramatic.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.4A
• /
• pp.467-472
• /
• 2008

One of the maindisadvantages of Orthogonal Frequency Division Multiplexing (OFDM) is the Peak to Average Power Ratio (PAPR) problem. To reduce PAPR and improve the error performance of the OFDM signal over a fading channel, an OFDM system combining an Adaptive Symbol Selection Scheme (ASSS) and channel estimation can be used. Because of the side information of ASSS, however, the data rate decreases in the conventional ASSS OFDM system. In this letter, to overcome this impairment, we propose a technique to transmit side information by using pilot tones, and demonstrate that the proposed technique can give reasonable bit error rate (BER) performance.

• The Journal of Asian Finance, Economics and Business
• /
• v.6 no.2
• /
• pp.213-221
• /
• 2019

The study aims to investigate some criteria of supplier selection in the textile and apparel (T&A) sector in Vietnam. Most research on supplier selection criteria for T&A sector was mainly conducted based on the review of literature. Therefore, the purpose of this study is to explore these criteria based on a framework in which an integrated approach of qualitative and quantitative was employed. First, an in-depth interview was used to explore what supplier selection criteria T&A companies were utilized after the literature on supplier selection criteria had been reviewed. Next, a prequestionnaire was built and sent to some practitioners and experts for their revision. Then, a pilot survey of 31 T&A companies with numerous statistical tests was conducted to validate the questionnaire. Finally, an official study of 282 respondents was conducted to determine supplier selection criteria which are best suited for T&A companies through exploratory factor analysis. The findings of the study suggest that there are eight supplier selection criteria including Quality, Cost, Delivery, Service, Capability, Company's image, Relationship, and Sourcing country. Each criterion comprises certain sub-criteria to make the supplier selection criteria set more comprehensive. The findings will be a contribution to the selection process of T&A companies as they can utilize these criteria to select capable suppliers.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.14 no.1
• /
• pp.63-69
• /
• 2006

The operational environment of helicopters extends from the civil air traffic control system to remote and hazardous areas and from day operations under visual flight conditions to night operations in adverse weather. Helicopters can move in any direction, remain stationary while airborne, climb and descend vertically, and take off and land almost anywhere. Thus their range of maneuvers and control requirements vary more widely than do those of fixed-wing aircraft. In this study, I analyzed the job of helicopter pilot through methods of observation, and classified the required ability of them into the domain of cognitive, perceptual/spatial, psychomotor. I expect that the result of this study will be used to aid training and selection of helicopter pilot.

• Aerospace Engineering and Technology
• /
• v.6 no.2
• /
• pp.245-249
• /
• 2007

The objective of the UAV removes the life loss of the pilot who is the maximum weak point of the manned reconnaissance aircraft, accomplishes the reconnaissance it is an aircraft for. The camera which will confirm the pilot substitution reconnaissance result which stands is necessary, we should confirm; the target which this camera probably is what. The report which described like this demand condition against the consideration fact which is necessary to the selection of the image sensory device which is a camera which with character will be applied in UAV.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.1
• /
• pp.27-32
• /
• 2016

In this paper, we proposed a soft decision-directed channel estimation based on MMSE estimation for MIMO-OFDM system. While the conventional method employs only pilot signals for channel estimation, the proposed algorithm performs channel estimation using pilot and reliable data signals. We also proposed selection criterion among reliable data signal for channel estimation. From numerical simulations, we show that the proposed channel estimator achieves 1 dB performance gain over conventional channel estimators.