• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.893-896
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• 1998

A new evolutionary programming technique using multiple subpopulations with completely differnt evolution mechanisms is propsed to solve the optimization problems. Three subpopulations, each has different evolution charcteristics and uses different EP algorithms such as SAEP, AEP and FEP, are cooperating with synergy effect in which it increases the possibility to quickly find the global optimum of continuous optimization problems. Subpopulations evolve in differnt manner and the interaction among these leads to global minimum quickly.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.811-814
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• 1997

In this paper, the torque optimization of a kinematically redundant manipulator for minimizing the torque demands is discussed. The minimum torque solution based on a local optimization has been known to encounter the instability problem and then the global torque optimization was suggested as one of the alternatives. Herein, by adopting the infinity-norm rather than the 2-norm for the magnitude of torques, we are to propose a new cost function more advantageous to the avoidance of torque limits. By the way, a solution to the global torque optimization formulated with the new cost function can not be obtained by the previous methods due to their difficulties such as inability to treat discontinuous cost functions and various constraints on the joint variables. Thus, to overcome those deficiencies, we are developing a new approach using the dynamic programming. The effectiveness of the proposed method is shown through simulation examples for a 3-link planar redundant manipulator.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.176-183
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• 2008

This paper highlights the importance of carrying out global slope stability analysis as part of design calculations for geosynethetic walls in tiered configuration. Four design case histories were selected to examine the appropriateness of their design by performing additional slope stability analyses using the shear strength reduction method with in the frame work of finite element analysis. The results indicated that all of the walls examined, which were designed to meet the current design guide lines, did not satisfy the global slope stability requirement, and that longer reinforcements are required in the upper tiers to achieve the minimum factor of safety. Practical implications of the findings are discussed.

• Journal of Positioning, Navigation, and Timing
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• v.7 no.4
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• pp.285-294
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• 2018

In this study, we implemented the data quality monitoring algorithm which is the previous step for real-time Global Navigation Satellite System (GNSS) correction generation and compared Global Positioning System (GPS) and BeiDou System (BDS). Signal Quality Monitoring (SQM), Data QM, and Measurement QM (MQM) that are well known in Ground Based Augmentation System (GBAS) were used for quality monitoring. SQM and Carrier Acceleration Ramp Step Test (CARST) of MQM result were divided by satellite elevation angle and analyzed. The data which are judged as abnormal are removed and presented as Root Mean Square (RMS), standard deviation, average, maximum, and minimum value.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.2
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• pp.208-213
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• 2011

This paper analyzes potential interference effects of Ultra Wide Band(UWB) on Global Positioning System(GPS) which is providing safety service. For the interference analysis, positioning error method is used to determine the minimum protection distance to meet positioning error of 2.5 m below and Minimum Coupling Loss(MCL) method is used to determine the required protection ratio(I/N) from the protection distance of UWB transmitter and GPS receiver to meet positioning error of 2.5 m below. In a result, the minimum protection distance to meet positioning error of 2.5 m below was about 10 m and the protection ratio to meet positioning error 2.5 m below was -20 dB. The protection ratio proposed in this paper is the same value of the protection ratio of safety service proposed by ITU-R. The obtained protection ratio can be used for the protection standard of domestic GPS system for the safe of life service.

• Journal of Climate Change Research
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• v.8 no.2
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• pp.109-123
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• 2017

The effects of recent climate change on hydrological systems could affect the Winter Olympic Games (WOG) because the event is dependent on suitable snow and ice conditions to support elite-level competitions. We investigate the long-term variability and change in winter total precipitation (P), snowfall water equivalent (SFE), and ratios of SFE to P during the period 1973/74~2015/16 in Gangwon province. The climatological percentages of SFE relative to winter total precipitation were 71%, 28%, and 44% in Daegwallyeong, Chuncheon, and Gangneung, respectively. The winter total P, SFE, and SFE/P has decreased (but not significantly), although significant increases of winter maximum and minimum temperature were detected at a 95% confidence level. Notably, a significant negative trend of SFE/P at Daegwallyeong in February, the month of the WOG, was attributable to a larger decrease in SFE related to the increases in maximum and minimum temperature. Winter wet-day minimum temperatures were warmer than climatological minimum temperatures averaged over the study period. The 20-year return values of daily maximum P and SFE decreased in Yongdong area. Since the SFE/P decrease with increasing temperature, the probability of rainfall rather than snowfall can increase if global warming continues.

• Water for future
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• v.28 no.2
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• pp.169-180
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• 1995

The cost of a looped pipe network is affected by a set of loop flows. The mathematical model for optimizing the looped pipe network is expressed in the optimal set of loop flows to apply to a stochastic optimization method. Because the feasible region of the looped pipe network problem is nonconvex with multiple local optima, the Modified Stochastic Probing Method is suggested to efficiently search the feasible region. The method consists of two phase: i) a global search phase(the stochastic probing method) and ii) a local search phase(the nearest neighbor method). While the global search sequentially improves a local minimum, the local search escapes out of a local minimum trapped in the global search phase and also refines a final solution. In order to test the method, a standard test problem from the literature is considered for the optimal design of the paralled expansion of an existing network. The optimal solutions thus found have significantly smaller costs than the ones reported previously by other researchers.

• International Journal of Concrete Structures and Materials
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• v.2 no.2
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• pp.161-167
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• 2008

Optimization of concrete mixing system is very important for the production of quality mixture of concrete and requires very complicated, specialized knowledge as there are a variety of variables that influence the result. One of the methods of optimizing the concrete mixing system is to minimize the volume of cement paste which, in turn, means maximizing the volume of aggregate. The purpose of this study is to determine the minimum volume of cement paste used in the design of concrete mixture and to design the optimum concrete mixing system based on the fluidity of mortar and concrete. In determining the minimum volume of cement paste, experiments of mortar and concrete were performed based on their workability, material segregation and bleeding. Type of aggregate, granularity distribution and sand percentage were used as test parameters and measurements were taken of the distribution of granularity, usage of HRWRA, minimum volume of paste and drying shrinkage and compressive strength of concrete.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.6
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• pp.557-563
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• 2010

This paper addresses the issue of adaptive global optimization using Kriging metamodel known as EGO(Efficient Global Optimization). The algorithm adaptively chooses where to generate subsequent samples based on an explicit trade-off between reduction of global uncertainty and exploration of the region of the interest. A strategy that saves the computational cost by using expectations derived from probabilistic nature of approximate model is proposed. At every iteration, a candidate test point that seems to be feasible/inactive or has little possibility to improve for minimum is identified and excluded from updating approximate models. By doing that the computational cost is saved without loss of accuracy.

• Journal of Photoscience
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• v.9 no.2
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• pp.154-157
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• 2002

Direct, continuous, and accurate measurements of solar ultraviolet irradiance (290-400 nm: UVR) have been carried out since 1990, by using both band-spectral ultraviolet-B (290-320 nm: UV-B) and ultraviolet-A (320-400 nm: UV-A) radiometers at Tokai University in Hiratsuka, Japan (35$^{\circ}$N, 139$^{\circ}$E). From our observations, the following findings are provided: 1) an increasing trend in solar UV -B from Oct. 1990 to Sept. 2000; 2) a regional comparison of solar UVR in Japan; 3) the distinct characteristics of UV-B and UV-A irradiance, such as diffuse property, daily and seasonal variation; and 4) human body protection against solar UVR. An increasing 10-year trend in global solar UV - B in Hiratsuka corresponded to a decrease in the total ozone amount measured at Tsukuba (36$^{\circ}$N, 140$^{\circ}$E), giving supportive evidence for a direct link between these two parameters. Furthermore, a strong correlation was found between solar UV-B and total ozone amount from results of UVR measurements at four Tokai University monitoring stations dispersed throughout Japan. Additional results revealed different diffuse properties in global solar UV and in global solar total (300-3000 nm: Total) irradiances. For example, in the global UVR, the diffuse component was dominant: about 80 % independent of weather, with more than 60 % of global UV-B, and more than 50% of global UV-A with even a cloudless clear sky. On the other hand, the portion of the diffuse in the global total irradiance was very low, less than 10 % on a cloudless clear day. Daily and seasonal variations of UV -B and UV -A irradiances were found to be quite different, because of the marked dependence of UV -B irradiance on the atmospheric ozone amount. Moreover, UV -B irradiance showed large daily and seasonal variations: the ratio between maximum and minimum irradiances was more than 5. In contrast, the variation in UV-A was small: the ratio between maximum and minimum was less than 2. Three important facts are proposed concerning solar UVR protection of the human body: 1) the personal minimal erythema dose (MED); 2) gender based difference in MED values; and 3) proper colors for UVR protective clothing.