• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.972-975
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• 2004

In order to reduce the noise of BLDC motor, a systematic optimization procedure for rotor structure is presented. The noise index is defined as the sum of volume velocity of FE-model that are calculated at the dominant frequencies during dehydration process, which is based on the principle of radiation simple volume source. Then, the five design variables are selected to represent the shape and layout or rotor structure. This discrete design optimization problem for minimizing the noise index is solved by 3-level orthogonal array based effect analysis. Finally, the response surface method (RSM) combined optimization approach is employed for more refining the approximate optimum.

• Journal of Korean Society of Forest Science
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• v.111 no.2
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• pp.311-318
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• 2022

We conducted this study to derive the site index, which is a criterion for the planting of Robinia pseudoacacia, a honey plant, and to investigate the diameter distribution change by derived site index. We applied the Chapman-Richards equation model to estimate the site index of the Robinia pseudoacacia stand. The site index was distributed within the range of 16-22 when the base age was 30 years. The fitness index of the site index estimation model was low, but we judged that there was no problem in the application because the residual distribution of the equation had not shifted to one side. We used the Weibull diameter distribution function to determine the diameter distribution of the Robinia pseudoacacia stand by site index. We used the mean diameter and the dominant tree height as independent variables to present the diameter distribution, and our analysis procedure was to estimate and recover the parameters of the Weibull diameter distribution function. We used the mean diameter and the dominant tree height of the Robinia pseudoacacia stand to show distribution by diameter class, and the fitness index for dbh distribution estimation was about 80.5%. As a result of schematizing the diameter distribution by site indices as a 30-year-old, we found that the higher the site index, the more the curve of the diameter distribution moved to the right. This suggests that if the plantation were to be established in a high site index stand, considering the suitable trees on the site, the growth of Robinia pseudoacacia woul d become active, and not onl y the production of wood but al so the production of honey would increase. We therefore anticipate that the site index classification table and curve of this Robinia pseudoacacia stand will become the standard for decision making in the plantation and management of this tree.

• Journal of Forest and Environmental Science
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• v.22 no.1
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• pp.58-65
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• 2006

This study investigated to distribution of Lepidoptera on the forest stands of cental Gangwon area from July to August in 2005. Collected Lepidoptera in the study area were total 462 individuals 123 genus 15 family and were collected 166 individuals, 66 genus, 15 family in Jumbong Mt., 159 individuals 65 genus 15 family in Eungbok Mt. and 137 individuals 40 genus 9 family in Odae Mt.. Dominant species in study area were Ampelophaga rubiginosa 54 individuals, Antheraea yamamai 35 individuals, Dendrolimus superans 27 individuals, Triphaenopsis jezoensis 14 individuals, Lymantria monacha 13 individuals. Shannon species diversity index(H') and Evenness index (J') were 1.52, 0.84 in Jumbong Mt., 1.69, 0.91 in Eungbok Mt., 1.87, 0.83 in Odae Mt. respectively. Community similarity index showed the lowest value in Jumbong Mt. and Odae Mt. as 0.11, the highest value in Jumbong Mt. and Odae Mt. as 0.28.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.49 no.3
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• pp.385-392
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• 2016

Seasonal variability in the algal community structure of intertidal zones was examined at six study sites in Marine National Parks, on the western and southern coasts of Korea from March to November 2015. A total of 193 species of algae, comprising 27 green, 40 brown and 126 red algae, were identified. Algal biomass averaged 101.50 g dry wt./m² with a maximal at Tonggae (168.12 g dry wt./m²) and minimum at Haseom (54.49 g dry wt./m²). The dominant seaweeds by biomass were Sargassum thunbergii at five sites (Tonggae, Haseom, Namdongri, Ando amd Sinjeonri), and S. fusiforme at Soando. Community indices measured as follows: dominance index (DI), 0.31–0.69; richness index (R), 7.30–11.43; evenness index (J'), 0.33–0.49; and diversity index (H'), 1.15–1.86. As evaluated using community indices and environmental states, the EEI (Ecological Evaluation Index) of the Marine National Park was “normal”. The present results indicate that seaweed community structures and indices could be used to evaluate the environmental status of coastal ecosystems.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.7
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• pp.1234-1242
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• 2003

In this paper we present a simple and efficient robust optimal design formulation for MEMS structures and its application to a resonant-type micro probe. The basic idea is to use the gradient index (GI) to improve robustness of the objective and constraint functions. In the robust optimal design procedure, a deterministic optimization for performance of MEMS structures is followed by design sensitivity analysis with respect to uncertainties such as fabrication errors and change of operating conditions. During the process of deterministic optimization and sensitivity analysis, dominant performance and uncertain variables are identified to define GI. The GI is incorporated as a term of objective and constraint functions in the robust optimal design formulation to make both performance and robustness improved. While most previous approaches for robust optimal design require statistical information on design variations, the proposed GI based method needs no such information and therefore is cost-effective and easily applicable to early design stages. For the micro probe example, robust optimums are obtained to satisfy the targets for the measurement sensitivity and they are compared in terms of robustness and production yield with the deterministic optimums through the Monte Carlo simulation. This method, although shown for MEMS structures, may as well be easily applied to conventional mechanical structures where information on uncertainties is lacking but robustness is highly important.

• Journal of the Korean association of regional geographers
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• v.20 no.1
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• pp.30-48
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• 2014

Relying on the interaction indices - dominance index, relative strength index and entropy index, this paper analyzes the structural features of urban network in the Seoul metropolitan area with the flows of commuting, business, and freight. Analytical results show that the Seoul metropolitan urban system is vertical, size-dependent, one-way, and the highest city-dominant network rather than horizontal, size-neutral, two-way, complementary one. The network of freight flow is a little bit more symmetrical than the networks of commuting and business. However, the interaction with Seoul is still determinant in all aspects of hierarchical structure, relative strength, and symmetry of flow.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.50 no.5
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• pp.553-560
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• 2017

Fluctuations in the abundance and species composition of fishes in the coastal waters of Geumo-do, Yeosu, Jeollanam-do, Korea were investigated from 2002 to 2005. A gill net with entrances on both sides was used to collect a total of 469 individuals (55,180 g) of 3 orders, 18 families, and 28 species. The dominant species was Sebastes inermis (60 individuals, 5,670 g), followed by Neoditrema ransonneti (46 individuals, 2,290 g), and Pseudaesopia japonica (38 individuals, 3,080 g). The highest number of individuals was found in 2004, while the biomass was highest in 2005. The diversity index was highest in 2004 (H'=2.703) and lowest in 2002 (H'=2.580). The dominance index was highest in 2004 (D=3.983) and lowest in 2002 (D=3.404). The richness index was highest in 2003 (RI=0.337) and lowest in 2002 (RI=0.261). Changes in temperature and salinity affected the community structure and the location of spawning grounds. The number of individuals and total biomass increased with changes in temperature and salinity each year.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1254-1261
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• 2003

In this paper we present a simple and efficient robust optimal design formulation and its application to a resonant-type micro probe. The basic idea is to use the Gradient Index (GI) to improve robustness of the objective and constraint functions. In the robust optimal design procedure, a deterministic optimization for performance of MEMS structures is followed by design sensitivity analysis with respect to uncertainties such as fabrication errors and change of operating conditions. During the process of deterministic optimization and sensitivity analysis, dominant performance and uncertain variables are identified to define GI. The GI is incorporated as a term of objective and constraint functions in the robust optimal design formulation to make both performance and robustness improved. While most previous approaches for robust optimal design require statistical information on design variations, the proposed GI based method needs no such information and therefore is cost-efficient and easily applicable to early design stages. For the micro probe example, robust optimums are obtained to satisfy the targets for the measurement sensitivity and they are compared in terms of robustness and production yield with the deterministic optimums through the Monte Carlo simulation.

• Smart Structures and Systems
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• v.12 no.3_4
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• pp.427-440
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• 2013

A growing need has developed in the United States to obtain more specific knowledge on the structural integrity of infrastructure due to aging service lives, heavier and more frequent loading conditions, and durability issues. This need has spurred extensive research in the area of structural health monitoring over the past few decades. Several structural health monitoring techniques have been developed that are capable of locating damage in structures using modal strain energy of mode shapes. Typically in the past, bending strain energy has been used in these methods since it is a dominant vibrational mode in many structures and is easily measured. Additionally, there may be cases, such as pipes, shafts, or certain bridges, where structures exhibit significant torsional behavior as well. In this research, torsional strain energy is used to locate damage. The damage index method is used on two numerical models; a cantilevered steel pipe and a simply-supported steel plate girder bridge. Torsion damage indices are compared to bending damage indices to assess their effectiveness at locating damage. The torsion strain energy method is capable of accurately locating damage and providing additional valuable information to both of the structures' behaviors.

• Geomechanics and Engineering
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• v.13 no.6
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• pp.1045-1055
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• 2017

Tensile strength is considered key properties for characterizing rock material in engineering project. It is determined by direct and indirect methods. Point load test is a useful testing method to estimate the tensile strengths of rocks. In this paper, the effects of rock shape on the point load index of gypsum are investigated by PFC2D simulation. For PFC simulating, initially calibration of PFC was performed with respect to the Brazilian experimental data to ensure the conformity of the simulated numerical models response. In second step, nineteen models with different shape were prepared and tested under point load test. According to the obtained results, as the size of the models increases, the point load strength index increases. It is also found that the shape of particles has no major effect on its tensile strength. Our findings show that the dominant failure pattern for numerical models is breaking the model into two pieces. Also a criterion was rendered numerically for determination of tensile strength of gypsum. The proposed criteria were cross checked with the results of experimental point load test.