• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.218-225
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• 2021

The purpose of this study is to present a rational analytical method for predicting the behavioral characteristics from crack occurrence to fracture for a one-way CFRP grid reinforced concrete slab specimen. A total of four specimens were selected by Zhang et al.(2004) as the main experimental variables for CFRP grid amount, material properties and loading method. Analysis was performed through the Nonlinear Finite Element analysis program(RCAHEST), which applied the newly modified constitutive relational equations by the author. The mean and coefficient of variation for maximum moment from the experiment and analysis results was predicted 1.38 and 7 %. The mean and coefficient of variation for displacement corresponding maximum moment from the experiment and analysis results was predicted 1.41and 9.8 %. The prediction results for the behavioral characteristics from crack occurrence to fracture were verified and evaluated. It is judged that additional research is needed to secure various experimental results and to develop a more reliable analytical method.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.6
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• pp.7-15
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• 2018

We propose a method for evaluating sound quality quantitatively to develop high-level home appliances (HA). Generally, a refrigerator has diverse movable parts such as slider, drawer, and folding shelf. Therefore, an engineering treatment to control the noise quality is considered as one of key technologies for a higher level refrigerator. Among the movable parts, we have selected a folding shelf as an example, which is commonly setup inside of a home refrigerator for increasing space convenience, to control the noise quality. However, it is known that its noise level is very high comparing to other movable parts when folding or unfolding actions. In order to evaluate and compare the noise quality, we have tested different eighteen models, and have suggested an impact sound quality index (ISQI) based on subjective evaluation data obtained experimentally by thirty two evaluators. The ISQI was formulated using three sound quality elements (noise peak, raising time, impact duration) to determine psycho-acoustic properties. Through this work, we developed an evaluating process and ISQI that was verified the usefulness by comparing the test results of personal perceptions given by evaluators with the prediction value of ISQI. We showed a good relations between them, so we believe that the proposed method and ISQI can be utilized to control of the noise quality of HA effectively.

• Design & Manufacturing
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• v.13 no.2
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• pp.54-59
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• 2019

CNC(Computer Numerical Control) machine tools are being used in various industrial fields such as aircraft and automobiles. The machining conditions used in the mold industry are used, and the simulation and the experiment are compared. The tool used in the experiment was carried out to increase the reliability of the simulation of the cutting machining. The program used in the 3D-FEM (finite element method) was the AdvantEdge and predicted by down-milling. The tool model is used 3D-FEM simulation by using the cutting force, temperature prediction. In this study, we carried out the verification of cutting force by using a 3-axis tool dynamometer (Kistler 9257B) system when machining the plastic mold Steel machining of NAK-80. The cutting force experiment data using on the charge amplifier (5070A) is amplified, and the 3-axis cutting force data are saved as a TDMS file using the Lab-View based program using on NI-PXIe-1062Q. The machining condition 7 was the most similar to the simulation and the experimental results. The material properties of the NAK-80 material and the simulation trends reflected in the reverse design of the tool were derived similarly to the experimental results.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.2
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• pp.111-117
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• 2019

An experimental study on the welding part of a heat transfer plate that constitutes the lightweight and high efficiency recuperator is presented in this paper. In particular, to find out the service life of the welded part, fatigue characteristics were determined through experiments. Experiments were carried out on two materials (STS347, AL20-25 + nb), which are selected as the material of the recuperator; further, the specimens were manufactured through the methods used for actual fabrication and the standards recommended by ASTM. To evaluate the mechanical properties of the specimens at room and high temperature, MTS-810 was used in a high-temperature furnace. The tensile test was carried out at room and high temperatures for each specimen. The fatigue test was carried out by setting the load ratio corresponding to 50%, 40%, 30%, 20%, and 10% of the tensile strength at the stress ratio of 0.1. Finally, the fatigue life characteristics obtained by the experiment were compared with the stresses owing to the load generated in the operating conditions of the recuperator, and the lifetime of the welds was evaluated to prepare for the operation time required by the UAV.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.1
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• pp.1-8
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• 2019

Developing reliable soil moisture prediction techniques at agricultural regions is a pivotal issue for sustaining stable crop productions. In this study, a physically-based SWAP(Soil-Water-Atmosphere-Plant) model was suggested to estimate soil moisture dynamics at the study sites. ROSETTA was also integrated to derive the soil hydraulic properties(${\alpha}$, n, ${\Theta}_r$, ${\Theta}_s$, $K_s$) as the input variables to SWAP based on the soil information(Sand, Silt and Clay-SSC, %). In order to predict the soil moisture dynamics in future, the mid-term TIGGIE(THORPEX Interactive Grand Global Ensemble) and long-term S2S(Subseasonal to Seasonal) weather forecasts were used, respectively. Our proposed approach was tested at the six study sites of RDA(Rural Development Administration). The estimated soil moisture values based on the SWAP model matched the measured data with the statistics of Root Mean Square Error(RMSE: 0.034~0.069) and Temporal Correlation Coefficient(TCC: 0.735~0.869) for validation. When we predicted the mid-/long-term soil moisture values using the TIGGE(0~15 days)/S2S(16~46 days) weather forecasts, the soil moisture estimates showed less variations during the TIGGE period while uncertainties were increased for the S2S period. Although uncertainties were relatively increased based on the increased leading time of S2S compared to those of TIGGE, these results supported the potential use of TIGGE/S2S forecasts in evaluating agricultural drought. Our proposed approach can be useful for efficient water resources management plans in hydrology, agriculture, etc.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.10
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• pp.3729-3749
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• 2021

At present, deep convolution network-based salient object detection (SOD) has achieved impressive performance. However, it is still a challenging problem to make full use of the multi-scale information of the extracted features and which appropriate feature fusion method is adopted to process feature mapping. In this paper, we propose a new adjacency auxiliary network (AANet) based on multi-scale feature fusion for SOD. Firstly, we design the parallel connection feature enhancement module (PFEM) for each layer of feature extraction, which improves the feature density by connecting different dilated convolution branches in parallel, and add channel attention flow to fully extract the context information of features. Then the adjacent layer features with close degree of abstraction but different characteristic properties are fused through the adjacent auxiliary module (AAM) to eliminate the ambiguity and noise of the features. Besides, in order to refine the features effectively to get more accurate object boundaries, we design adjacency decoder (AAM_D) based on adjacency auxiliary module (AAM), which concatenates the features of adjacent layers, extracts their spatial attention, and then combines them with the output of AAM. The outputs of AAM_D features with semantic information and spatial detail obtained from each feature are used as salient prediction maps for multi-level feature joint supervising. Experiment results on six benchmark SOD datasets demonstrate that the proposed method outperforms similar previous methods.

• Journal of Digital Convergence
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• v.19 no.5
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• pp.307-313
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• 2021

In this paper, a lightweight network with fewer parameters compared to the existing object detection method is proposed. In the case of the currently used detection model, the network complexity has been greatly increased to improve accuracy. Therefore, the proposed network uses EfficientNet as a feature extraction network, and the subsequent layers are formed in a pyramid structure to utilize low-level detailed features and high-level semantic features. An attention process was applied between pyramid structures to suppress unnecessary noise for prediction. All computational processes of the network are replaced by depth-wise and point-wise convolutions to minimize the amount of computation. The proposed network was trained and evaluated using the PASCAL VOC dataset. The features fused through the experiment showed robust properties for various objects through a refinement process. Compared with the CNN-based detection model, detection accuracy is improved with a small amount of computation. It is considered necessary to adjust the anchor ratio according to the size of the object as a future study.

• Journal of the Korea Convergence Society
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• v.12 no.1
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• pp.105-110
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• 2021

Radiation shielding of affinity material, which is widely used in medical institutions, is made in sheet form and is mainly applied to apron. Shielding performance is presented based on lead equivalent, and is presented as 0.25-0.50mmPb. In the case of shielding materials where lead is used as the main material, the shielding performance can be adjusted by thickness due to the excellent machinability of lead. However, eco-friendly shielding sheets are difficult to control shielding performance based on thickness criteria as shielding performance varies depending on the content of shielding materials, the properties of polymeric materials that are base materials, and the technical differences in the process. In this study, shielding sheets were manufactured based on thickness to solve these problems and the shielding performance was compared in this study. As a result, it was shown that the laminated structure shielding sheet was more effective.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.4
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• pp.161-167
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• 2020

In the process of cutting large aircraft parts, the tool may be abnormally worn or damaged due to various factors such as mechanical vibration, disturbances such as chips, and physical properties of the workpiece, which may result in deterioration of the surface quality of the workpiece. Because workpieces used for large aircrafts parts are expensive and require strict processing quality, a maintenance plan is required to minimize the deterioration of the workpiece quality that can be caused by unexpected abnormalities of the tool and take maintenance measures at an earlier stage that does not adversely affect the machining. In this paper, we propose a method to indirectly monitor the tool condition that can affect the machining quality of large aircraft parts through real-time monitoring of the current signal applied to the spindle motor during machining by comparing whether the monitored current shows an abnormal pattern during actual machining by using this as a reference pattern. First, 30 types of tools are used for machining large aircraft parts, and three tools with relatively frequent breakages among these tools were selected as monitoring targets by reflecting the opinions of processing experts in the field. Second, when creating the CNC machining program, the M code, which is a CNC auxiliary function, is inserted at the starting and ending positions of the tool to be monitored using the editing tool, so that monitoring start and end times can be notified. Third, the monitoring program was run with the M code signal notified from the CNC controller by using the DAQ (Data Acquisition) device, and the machine learning algorithms for detecting abnormality of the current signal received in real time could be used to determine whether there was an abnormality. Fourth, through the implementation of the prototype system, the feasibility of the method proposed in this paper was shown and verified through an actual example.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.6
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• pp.146-152
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• 2020

This study was initiated to develop an effective inspection method to detect defects such as corrosion in closed-cell steel members in steel-box girder bridges. The ultrasonic velocity method among various non-destructive method was selected as a rapid and effective method to derive the average propagation velocity in the medium by using the ultrasonic wave velocity method for specimens of different thickness. The regression analysis was performed based on the experimental results, and the results was interpolated to evaluate the prediction accuracy. If the material properties are identical, this ultrasonic velocity method can predict the thickness using the averaged transmitted velocity. In addition, a continuous scanning method moving at 200 mm/s was tested for scanning a wide area of a bridge. The results exhibited that the continuous scanning method was able to effectively scan the different thickness of a bridge.