• Journal of Korean Association for Spatial Structures
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• v.8 no.3
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• pp.45-51
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• 2008

A single layer-latticed dome is advantageous for large span structures because it is very stiff despite the light weight of the structure itself. However, this structure becomes easily unstable during erection due to its large size. The Block method is popular with the large span structures. A partial block of the dome is fabricated on the ground and lifted by crane to a designated location of structures. The lifting point selection is very important to create a stable erection and to avoid buckling of members during the erection. The purpose of this study is to analyze the structural behaviors and buckling characteristics according to the lifting point of single-layer latticed domes with triangle network in order to take materials about the safe and economic erection. The conclusions are obtained as follow. 1) The buckling strength of the block part varies with the location of lifting points when it is erected. In case, the height of the dome is lower, the effort of buckling strength of the structure is higher. 2) In buckling strength, the effect of the lifting rope length is smaller than it of the lifting points change.

• Korean Journal of Construction Engineering and Management
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• v.16 no.6
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• pp.101-111
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• 2015

The modular construction method has been getting more attention followed by global eco-friendly trend as the domestic construction industry has focused more on remodeling and extension work. The modular construction method is an industrialized construction system which is not likely as the existing construction method it manufactures more than 70% modules at the factory then assembling can be completed in a short amount of time on site. The modular construction method has various strengths; shortening of construction period by on-site work decrease, weight pressure reduction by usage of light steel frames and cost saving by repetitive manufacturing. However, it is currently not expanded due to the existing commercialized construction method. Therefore, this research is in order to help the related authorities make decisions to select the construction method and motivate expansion of modular construction method which can be utilized effectively in the extension works. The intention of this research is to stress differentiation from other construction methods in construction period, construction expenses, labor and forces by comparing and analyzing actual cases, to inform competitiveness of modular construction method by concrete effect analysis and to support adoption of the modular construction method into the domestic industry.

• Journal of the Society of Disaster Information
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• v.15 no.4
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• pp.524-530
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• 2019

Purpose: In this paper, we construct a detailed three-dimensional interface element using a three-dimensional analysis program, and evaluate the composite behavior stability of the connector by applying physical properties such as the characteristics of general members and those of reinforced members Method: The analytical model uses solid elements, including non-linear material behavior, to complete the modeling of beam structures, circular flanges, bolting systems, etc. to the same dimensions as the design drawing, with each member assembled into one composite behavior linkage. In order to more effectively control the uniformity and mesh generation of other element type contact surfaces, the partitioning was performed. Modeled with 50 carbon steel materials. Results: It shows the displacement, deformation, and stress state of each load stage by the contact adjoining part, load loading part, fixed end part, and vulnerable anticipated part by member, and after displacement, deformation, The effect of the stress distribution was verified and the validity of the design was verified. Conclusion: Therefore, if the design support of the micro pile is determined based on this result, it is possible to identify the Vulnerable Parts of the composite behavior connector and the degree of reinforcement.

• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.287-293
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• 2008

The collimator which makes a collimated beam, is an essential instrument for assembly and evaluation of telescopes. Recently, the Cassegrain type collimator has been widely used for its compact size as the focal length of high resolution cameras becomes longer. However, this kind of collimator has a disadvantage in that the secondary mirror is a heat source which can degrade the evaluation accuracy for an IR camera system. In this paper, we present the fabrication and measurement process for an off-axis parabolic mirror with the physical diameter pf 1 m, effective diameter 930 mm, and the focal length 6 m. After four months of works we obtained the final surface wave-front error of 30.4 nm rms ($\lambda$/138, ${\lambda}=4.2\;{\mu}m$), which is capable of evaluation of an IR camera as well as a visible camera.

• Journal of the Korea Society for Simulation
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• v.28 no.2
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• pp.107-117
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• 2019

Because shipbuilding is single-product production with limited resources, production management technology is essential to manage the resources effectively and maximize the productivity of ship-process. Therefore, many shipbuilding companies are conducting research on ship production plan and process considering various constraints in the field by applying modeling and simulation. However, it is difficult to provide accurate production plan on sudden schedule and process changes, and to understand the interconnectivity between the processes that produce blocks in existing research. In addition, there are many differences between the production planning and field planning because detailed processes and quantity of blocks can not be considered. In this research, we propose the integrated process-based modeling method considering process-operation sequences, BOM(Bill of materials) and resource constraints of all the scheduled blocks in the indoor system. Through the integrated process-based model, it is easy for the user to grasp the assembly relationship, workspace and preliminary relationship of assembly process between the blocks in indoor system. Also, it is possible to obtain the overall production plan that maximizes resource efficiency without the separate simulation and resource modeling procedures because resource balancing that considers the amount of resource quantity shared in the indoor system is carried out.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.4
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• pp.35-42
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• 2019

Nut fasteners that require ultra-precise control are required in the overall manufacturing industry including electronic products that are currently developing with the automobile industry. Important performance factors when tightening nuts include loosening due to insufficient fastening force, breakage due to excessive fastening, Tightening torque and angle are required to maintain and improve the assembling quality and ensure the life of the product. Nut fasteners, which are now marketed under the name Nut Runner, require high torque and precision torque control, precision angle control, and high speed operation for increased production, and are required for sophisticated torque control dedicated to high output BLDC motors and nut fasteners. It is demanded to develop a high-precision torque control driver and a high-speed, low-speed, high-response precision speed control system, but it does not satisfy the high precision, high torque and high speed operation characteristics required by customers. Therefore, in this paper, we propose a control technique of BLDC motor variable speed control and nut runner based on vector control and torque control based on coordinate transformation of d axis and q axis that can realize low vibration and low noise even at accurate tightening torque and high speed rotation. The performance results were analyzed to confirm that the proposed control satisfies the nut runner performance. In addition, it is confirmed that the pattern is programmed by One-Stage operation clamping method and it is tightened to the target torque exactly after 10,000 [rpm] high speed operation. The problem of tightening torque detection by torque ripple is also solved by using disturbance observer Respectively.

• Journal of Marine Life Science
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• v.6 no.1
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• pp.38-46
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• 2021

The blood clam, Tegillarca granosa, is economically important in marine bivalve and is used in fisheries industry among western Pacific Ocean Coasts especially in Korea, China, and Japan. The number of chromosomes in the blood clam is known as 2n=38, but the genome size and genetic information of the genome are not still clear. In order to predict the genomic size of the T. granosa, the in-silico analysis analysed the genomic size using short DNA sequence information obtained using the NGS Illumina HiSeq platform. As a result, the genomic size of T. granosa was estimated to be 770.61 Mb. Subsequently, a draft genome assembly was performed through the MaSuRCA assembler, and a simple sequence repeat (SSR) analysis was done by using the QDD pipeline. 43,944 SSRs were detected from the genome of T. granosa and 69.51% di-nucleotide, 16.68% trinucleotide, 12.96% tetra-nucleotide, 0.82% penta-nucleotide, and 0.03% hexa-nucleotide were consisted. 100 primer sets that could be used for genetic diversity studies were selected. In the future, this study will help identify the genetic diversity of T. granosa and population genetic studies, and further identify the classification of origin between homogenous groups.

• Journal of the Korean Geosynthetics Society
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• v.22 no.2
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• pp.63-70
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• 2023

Most of the industrial complexes and housing complexes in Busan and Gyeongnam were constructed by developing mountainous areas, except for some landfill areas. During the development process, the surplus soil for site development was mainly used as the embankment material. In the field, however, even if the material of the material changes during the embankment work for site development, for convenience reasons such as construction period and site conditions, the material property test and compaction test are not additionally conducted for the embankment material, and quality control is conducted. In this study, physical property tests and compaction tests were conducted on surplus soils in mountainous areas in Busan, GyungNam Province and then regression analysis was performed on the data. In addition, a comparative analysis was conducted along with existing studies in Korea. The surplus soils at the sites in Busan and Gyeongnam were mainly weathered soils of granites, and were classified into clayey sand (SC) and silty sand (SM). As a result of regression analysis of the compaction characteristics according to the content of coarse and fine soils, the correlation between them was very high. Using the relational formula as a result of this study, it will be very useful for compaction management of the surplus soils in the field.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.2
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• pp.103-114
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• 2023

Objectives: This study was conducted to evaluate hand-arm vibration (HAV) exposure levels due to the use of power hand tools and to evaluate the determinants in the automobile assembly process. Methods: The exposure level to HAV was evaluated for 30 work lines in five assembly processes (body, engine, chassis, door, and design) that use air-powered tools and battery-powered tools and operate in circulation for two hours. The 2-hr equivalent energy vibration acceleration, A (2), of the task was measured. The 8-hr equivalent energy vibration acceleration, A (8), was estimated in consideration of the number of tasks that can be performed per day by each process. In addition, a survey on the working environment was conducted with workers exposed to vibration. Results: The geometric mean of the HAV exposure level, A (2), for a total of 30 tasks was 2.51 m/s², and one case was 10.30 m/s², exceeding TLV (2hr). The HAV exposure level of A (8) was evaluated from 1.03 m/s² to 5.36 m/s². A (2) showed a statistically significant difference (P<0.01) for each process, and the chassis process (GM=3.90 m/s²) was the highest. The larger the tool size and the longer the tool length, the higher was the vibration acceleration when using a battery-powered tool than an air-powered tool (P<0.01). Battery-powered tool users showed higher dissatisfaction on all items than did air-powered tool users. Conclusions: As a result of this study, it is necessary to implement a program to reduce the HAV exposure levels.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.4
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• pp.270-282
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• 2012

This study was conducted to investigate the impact of sand addition to an intertidal for the development of the Manila clam habitat on benthic community structure. For this, we focused on the spatio-temporal changes in the surface sediment condition and benthic community structure before and after the event. Study site was an sandbank in Gonam-myeon, Taean-gun where sand added to on July 2010. We set three stations at each of sand adding area (experimental plot) and non sand-adding area (control plot) and did sampling works ten times from June 2010 to October 2011. Directly after the event, surface sediments changed to very coarse sand, but the state was not maintained over four months because of seasonal sedimentation and finally got back to very fine sand in eight months. The number of species and density were temporarily reduced right after the event and crustacean species such as Apocorophium acutum, Photis sp. were most negatively affected by the event. However, the number of species recovered from the reduction in three months and density did in four months due to the recolonization by the existing species and species in the vicinity of the plot. During the study period, dominant species continuously changed from the species such as A. acutum, Photis sp. at the time before the event, through the species such as Heteromastus filiformis, Macrophthalmus japonicus at the time right after the event, to the species such as Musculista senhousia, Ruditapes philippinarum, Mediomastus californiensis in the latter part of the study period. Although surface sediment properties and ecological indices recovered within a certain period after the event, the recovery of community structure has never been observed up to the end of the study.