• 한국정밀공학회지
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• 제31권11호
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• pp.1015-1021
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• 2014

This paper proposes the center distributed embroidery machine structure with 1,500 RPM, 52 heads for productivity and large sized embroidery goods. The synchronous velocity controller is adopted for control of the 2-axis distributed embroidery machine and the DOB(Disturbance Observer) is also adopted for minimizing disturbances caused by needle cams. For driving experiments of 2-axis center distributed driving structure, two conventional 26 heads 1,500RPM embroidery machines are used. It was shown that the center distributed driving structure with 2-axis synchronous control can be one way for implementing a large embroidery machine.

• Nuclear Engineering and Technology
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• 제56권8호
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• pp.3199-3209
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• 2024

During the decommissioning of nuclear and particle accelerator facilities, a considerable amount of large-scale radioactive waste may be generated. Accurately defining the activation level of the waste is crucial for proper disposal. However, directly measuring the internal radioactivity distribution poses challenges. This study introduced a novel technology employing machine learning to assess the internal radioactivity distribution based on external measurements. Random radioactivity distribution within a structure were established, and the photon spectrum measured by detectors from outside the structure was simulated using the FLUKA Monte-Carlo code. Through training with spectrum data corresponding to various radioactivity distributions, an evaluation model for radioactivity using simulated data was developed by above Monte-Carlo simulation. Convolutional Neural Network and Transformer methods were utilized to establish the evaluation model. The machine learning construction involves 5425 simulation datasets, and 603 datasets, which were used to obtain the evaluated results. Preprocessing was applied to the datasets, but the evaluation model using raw spectrum data showed the best evaluation results. The estimation of the intensity and shape of the radioactivity distribution inside the structure was achieved with a relative error of 10%. Additionally, the evaluation based on the constructed model takes only a few seconds to complete the process.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1993년도 Proceedings of International Conference for Agricultural Machinery and Process Engineering
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• pp.119-128
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• 1993

Effective machine capacity is affected by the physical and geometrical conditions of the fields. In the small and scattered farmland structure field efficiency is greatly influenced by plot geometry. In this paper, a method for estimating field efficiency and effective machine capacity was developed . The developed method was applied to Korean paddy cultivation. Various time elements related to farm operations for small and scattered plots are discussed in this paper . Available working time is divided into two parts, viz. the preparation time for machine operation and actual working time. Two kinds of machine efficiencies, namely , Machine Efficiency 1, applicable on a single large plot or set of well consolidated plots ; and Machine Efficiency 2, applicable on small and scattered multiple plots, are considered. Based assumptions made and steps followed to construct the model are discussed. Effective capacity of each machine based on different plot geometries are calculated y the model. Machine efficiency on a single plot increases with increase in the dimension of longer side of the plot . Low speed, low theoretical capacity machines have higher machine efficiency which is only slightly influenced by plot geometry. As plot geometry is improved , the machine efficiency of high speed, high capacity machines increases rapidly. The effects of short side length and plot size on machine efficiency on a single plot depend on the type of farm operation. For a particular plot shape, as plot size increases, machine efficiency on multiple plots increases rapidly. The effects of consolidation on machine efficiency is highly significant if the plot size is small and/or machine size is large.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.286-292
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• 2008

Transverse flux machine (TFM) has been developed to drive a machine of large input power at low-speed. However, it has complicated structure and large torque ripple due to its inherent structure In this paper the characteristics of torque of a rotatory two-phase TFM are analyzed by using the 3-dimensional finite to element method and optimal design. This research shows that one of the effective design variables is the skew angle of permanent magnet. The skew angles of permanent magnet are optimized by using a Progressive Quadratic Response Surface Method (PQRSM). It also shows that the proposed optimal skew magnet not only increases average torque but also decreases torque ripple of a rotatory two-phase TFM.

• 한국소음진동공학회논문집
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• 제19권10호
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• pp.1003-1011
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• 2009

Transverse flux machine(TFM) has been developed to drive a machine of large input power at low-speed. However, it has complicated structure and large torque ripple due to its inherent structure. In this paper the characteristics of torque of a rotatory two-phase TFM are analyzed by using the 3-dimensional finite element method and optimal design. This research shows that one of the effective design variables is the skew angle of permanent magnet. The skew angles of permanent magnet are optimized by using a genetic algorithm. It also shows that the proposed optimal skew magnet not only increases average torque but also decreases torque ripple of a rotatory two-phase TFM.

• 한국생산제조학회지
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• 제25권5호
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• pp.313-320
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• 2016

The need for high-strength, multi-axis, and multi-functional machine tools has recently increased because of part complexity and workpiece strength. However, most of the machine tool manufacturers rely on experience for a detailed design because of the shortcomings in the existing design technology. This study uses a topology optimization method to more effectively design a large multi-functional machine tool considering static stiffness. The ram, saddle, and column parts are important structures in a machine tool. Hence, they are selected for the finite element method analysis. Based on this analysis, the optimized internal rib structure for those parts is designed for desirable rigidity and weight. This structure could possibly provide the required design technology for machine tool manufacturers.

• 한국공작기계학회논문집
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• 제11권5호
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• pp.58-64
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• 2002

Mirror surface finish of Si-wafers has been achieved by rotary in-feed machining with cup-type wheels in ELID grinding. But the diameter of the workpiece is limited with the diameter of the grinding wheel in the in-feed machining method. In this study, some finding experiments by the rotary surface grinding machine with straight type wheels were conducted, by which the possible grinding area of the workpiece is independent of the diameter of the wheels. For the purpose of investigating the grinding characteristics of large scale diametrical silicon wafer, grinding conditions such as rotation speed of grinding wheels and revolution of workpieces are varied, and grinding machine used in this experiment is rotary type surface grinding m/c equipment with an ELID unit. The surface ground using the SD8000 wheels showed that mirror like surface roughness can be attained near 2~6 nm in Ra.

• 대한원격탐사학회지
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• 제40권2호
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• pp.123-139
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• 2024

Forest vertical structure is vital for comprehending ecosystems and biodiversity, in addition to fundamental forest information. Currently, the forest vertical structure is predominantly assessed via an in-situ method, which is not only difficult to apply to inaccessible locations or large areas but also costly and requires substantial human resources. Therefore, mapping systems based on remote sensing data have been actively explored. Recently, research on analyzing and classifying images using machine learning techniques has been actively conducted and applied to map the vertical structure of forests accurately. In this study, Sentinel-2 and digital surface model images were obtained on two different dates separated by approximately one month, and the spectral index and tree height maps were generated separately. Furthermore, according to the acquisition time, the input data were separated into cases 1 and 2, which were then combined to generate case 3. Using these data, forest vetical structure mapping models based on random forest, support vector machine, and extreme gradient boost(XGBoost)were generated. Consequently, nine models were generated, with the XGBoost model in Case 3 performing the best, with an average precision of 0.99 and an F1 score of 0.91. We confirmed that generating a forest vertical structure mapping model utilizing bi-seasonal data and an appropriate model can result in an accuracy of 90% or higher.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.223-226
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• 2002

To maximize the productivity in machining molds and dies, machine tools should operate at high speeds. However, the productivity of mold manufacturing has not increased significantly because CNC milling machines have massive slides, which do not allow rapid acceleration and deceleration during the frequent starts/stops encountered in machining molds and dies. This paper presents the use of composites for these slides to overcome this limitation. The vertical and horizontal slides of a large CNC machine were constructed by bonding high-modulus carbon-fiber epoxy composite sandwiches to welded steel structures using adhesives. These composite structures reduced the weight of the vertical and horizontal slides by 34% and 26%, respectively, and increased damping by 1.5 to 5.7 times without sacrificing the stiffness. Without much tuning, this machine had a positional accuracy of $\pm5\mu\textrm{m}$ per 300 m of the slide displacement.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1233-1240
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• 2005

As the geotechnical technologies have grown, the size of civil structures has become bigger than before, thereby requiring large-scale geotechnical testing equipments which can evaluate the mechanical behavior of large size testing materials such as gravel, crushed rock and so on. These kind of large testing equipments are usually used to evaluate the mechanical characteristics of large size material which are applied in the large infra structures like dam, seashore structure, coastal landfill, soil-structure interaction and seismic response of large-scale structure. In this research, state-of-the-art information in the field of geotechnical engineering was collected and summarized for such large-scale experimental equipments as large-scale geo-centrifuge, large-scale triaxial testing machine, large-scale direct shear testing apparatus and large-scale oedometer.