• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.1118-1133
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• 2017

Computer vision-based human activity recognition (HAR) has become very famous these days due to its applications in various fields such as smart home healthcare for elderly people. A video-based activity recognition system basically has many goals such as to react based on people's behavior that allows the systems to proactively assist them with their tasks. A novel approach is proposed in this work for depth video based human activity recognition using joint-based motion features of depth body shapes and Deep Belief Network (DBN). From depth video, different body parts of human activities are segmented first by means of a trained random forest. The motion features representing the magnitude and direction of each joint in next frame are extracted. Finally, the features are applied for training a DBN to be used for recognition later. The proposed HAR approach showed superior performance over conventional approaches on private and public datasets, indicating a prominent approach for practical applications in smartly controlled environments.

• Journal of Ocean Engineering and Technology
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• v.13 no.2 s.32
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• pp.66-73
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• 1999

This paper presents the experimental examinations and statistical quantitative analysis of the correlation between the cumulative counts of acoustic emission(AE) during plastic deformation periods of the welding and the tensile strength and other properties of the tube-to-tube welded joints of O.D. 30mm (I.D 18mm) nozzle steel. This is a new approach which attempts finally to develop real-time quality monitoring system for friction welding. And this study results in practical possiblility of real-time quality control more than 100% joint efficiency showing good weld no micro structural defects.

• Steel and Composite Structures
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• v.24 no.6
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• pp.643-658
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• 2017

High strength preloadable bolt assemblies are commonly adopted in beam-to-column bolted connections. Nowadays, two systems of high strength preloadable grade 10.9 bolt assembly are recommended in Europe for structural applications, namely HR and HV, which are characterized by different failure modes. Recently, experimental tests performed on HR and HV bolt assemblies highlighted that the type of bolt assembly may significantly influence the joint response. Therefore, the accuracy of numerical modelling of bolt assemblies is crucial to simulate effectively the non-linear behaviour of bolted joints with either failure mode 2 or mode 3 of the bolt rows. In light of these considerations, this present paper describes and discusses some modelling criteria for both HR and HV bolts to be implemented in 3D finite element models by finite element analysis and structural designers. The comparison between the calibrated models and experimental results shows the accuracy of the proposed assumptions in simulating all stages of assembly tensile response.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.4
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• pp.314-322
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• 2021

Skeleton-based action recognition has attracted considerable attention in human action recognition. Recent methods for skeleton-based action recognition employ spatiotemporal graph convolutional networks (GCNs) and have remarkable performance. However, most of them have heavy computational complexity for robust action recognition. To solve this problem, we propose a shuffle graph convolutional network (SGCN) which is a lightweight graph convolutional network using pointwise group convolution rather than pointwise convolution to reduce computational cost. Our SGCN is composed of spatial and temporal GCN. The spatial shuffle GCN contains pointwise group convolution and part shuffle module which enhances local and global information between correlated joints. In addition, the temporal shuffle GCN contains depthwise convolution to maintain a large receptive field. Our model achieves comparable performance with lowest computational cost and exceeds the performance of baseline at 0.3% and 1.2% on NTU RGB+D and NTU RGB+D 120 datasets, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.705-713
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• 2018

An automotive ball joint connects the suspension system to the steering system and helps to enable rotational and linear motion between the two elements for steering. This study examines a ball joint used in medium and large-sized pickup trucks. Ball joints consist of a stud, socket, bearing, and plug. The main structural performance metrics of ball joints are the pull-out strength and push-out strength. These structural parameters must meet certain criteria to avoid serious accidents. Test and simulation methods are used to investigate the design requirements, but tests are time-consuming and costly. In this study, we modeled ball joints in SolidWorks and performed a finite element analysis in Abaqus to predict structural performance. The analysis was used to obtain the structural performance required for the static analysis of a 2D axisymmetric model. The uncertainties in the manufacturing of the ball joint were assumed to be the manufacturing tolerances, and the dimensional design variables were identified through case studies. The manufacturing tolerances at each level were defined, and the results were compared with experimental results.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.2
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• pp.25-30
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• 2018

Sn-Pb solder has been used in automotive electronics for decades. However, recently, due to the environmental and health concerns, some international environmental organizations such as the end-of-life vehicle (ELV) enacted legislation banning of the Pb usage in automotive electronics. For this reason, many studies to develop and promote Pb-free soldering have been significantly reported. Meanwhile, because of flexibility and lightweight, flexible printed circuit boards (FPCBs) have been increasingly used in automotive electronics for lightweight to improve fuel efficiency and space utilization. Although the properties of lead-free solders for automotive electronics have been widely studied, there is a lack of research on the reliability performance of the lead-free solder joint on FPCB under user conditions. This study reported the properties of solder joints between Pb-free solders such as Sn3.0Ag0.5Cu, Sn0.7Cu and Sn0.5Cu0.01Al (Si), and various FPCBs finished with organic solderability preservative (OSP) and electroless nickel immersion gold (ENIG). To evaluate on joint properties and reliabilities with different solder compositions and surface-finishing materials, pull strength test, thermal shock test, and bending cycle test were performed and analyzed. After the bending cycle test of solder joint on OSP-finishing, the fractures were occurred in solder and the lifetime of Sn3.0Ag0.5Cu solder joint was the longest.

• The Journal of Engineering Geology
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• v.20 no.3
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• pp.329-338
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• 2010

The foundation area for tram contains biotite gneiss, quartzo-feldspathic gneiss, calc-silicate rock, and porphyroblastic gneiss of the pre-Cambrian Kyeonggi gneiss complex. These rocks record at least three stages of deformation, as indicated by fold sets of contrasting orientations (D1-D3). Joints are generally steeply dipping and strike NW-SE to WNW-ESE. The Gonjiam Fault, which strikes WNW-ESE, follows a river in the area. The fault possesses a 3-m-wide fracture zone, a 10-m-wide damage zone, and is 15 km long. Two tunnels have been constructed through the biotite gneiss. The geometric relationship between discontinuities (e.g., joints and foliation) and tunneling direction reveals that set 3 of the AA tunnel is unstable but that BB tunnel is relatively safe.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.2
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• pp.1-7
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• 2014

Recent experimental observations support the hypothesis that mechanical stimuli play a role in regulating the specialized molecular expression of articular cartilage in vitro and in vivo. Other studies have demonstrated that the continuous passive motion(CPM)bioreactor for whole joints can provide a platform for possible future in vitro studies and applications, including possible interactions of bio-mechanical and biochemical signals. In this study, we have developed acustom-made bioreactor capable of bending and stretching with circular type motion, and a biomimetic knee joint model, using a 3D printer. This system could be used to investigate the effects of rehabilitative joint motion of dynamic culture.

• Fire Science and Engineering
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• v.31 no.4
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• pp.65-70
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• 2017

The seismic performance of press fittings is studied, which is one of the weldless joints of stainless steel pipe used in the water piping of recent fire protection system. The piping of this study was constructed based on the piping connection reference of NFPA 13. The permissible displacement of the piping was set as the allowed amount which is given in the Building Structure Standard, and the measurements were repeated 10 times. The Von-mises stress of the piping was 2.48 and 1.25 times of the allowed amount of stress, which was less than the standard, noted three times on the NPPs Allowable Stress for Level D service loading. Therefore, the press fittings shows enough seismic performance.

• Laser Solutions
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• v.16 no.3
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• pp.1-10
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• 2013

In this study, Al-Si coated boron steel(1.2 mm) were laser welded by $CO_2$ laser and hot-stamping was applied to the laser joints. Tensile properties and microstructures of the joints were investigated before and after hot-stamping. Tensile and yield strengths of the as welded specimen similar with base metal and fracture occurred base metal of boron steel. Although, in case of heat treated specimen, fracture occurred fusion zone that Al segregated zone near the bond line. These could be explained by the existence of ferrite, in the Al segregated zone near the bond line and base metal of boron steel. Before hot-stamping, hardness of base metal is lower than fusion zone and heat affected zone in spite of exist Al segregation zone($Fe_3$(Al,Si)). So fracture occurred base metal. Although, after hot-stamping, microstructure of base metal and welds zone transformed to martensite and bainite except in Al segregation zone near the bond line that $Fe_3$(Al,Si) transformed to a-ferrite. So fracture occurred Al segregation zone near the bond line.