• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.13 no.6
• /
• pp.101-108
• /
• 2013

In this paper, we propose a method in which the negative acknowledge (NACK) message is used as command for cooperation and spectrum sharing. This allows for an automatic request for cooperation and sharing when the direct link of the primary user is in outage, and also allows for saving the number of control messages in cooperation-spectrum sharing based paradigm. In the sharing phase, the selected relay shares a power fraction of $1-{\alpha}$ for secondary transmitted signal while the remaining of ${\alpha}$ is for primary retransmitted signal. In the case of no relay collected, primary transmitter uses NACK as a command to retransmit the signal with fully power fraction (${\alpha}=1$). Both systems are assumed to employ BPSK signals. In this scheme, we propose the joint optimal decoding in the secondary user. The frame error rate (FER) performance at both systems is then analyzed. The theoretical and simulation results validate the analysis and confirm the efficiency of the protocol.

• Journal of the Microelectronics and Packaging Society
• /
• v.15 no.2
• /
• pp.7-15
• /
• 2008

In this paper, the Chip-On-Flex (COF) assembly process using anisotropic conductive films (ACFs) was investigated and the reliability of COF assemblies using ACFs was evaluated. Thermo-mechanical properties of ACFs such as coefficient of thermal expansion (CTE), storage modulus (E'), and glass transition temperature $(T_g)$ were measured to investigate the effects of ACF material properties on the reliability of COF assemblies using ACFs. In addition, the bonding conditions for COF assemblies using ACFs such as time, temperature, and pressure were optimized. After the COF assemblies using ACFs were fabricated with optimized bonding conditions, reliability tests were then carried out. According to the reliability test results, COF assemblies using the ACF which had lower CTE and higher $T_g$ showed better thermal cycling reliability. Consequently, thermo-mechanical properties of ACFs, especially $T_g$, should be improved for high thermal cycling reliability of COF assemblies using ACFs for compact camera module (CCM) applications.

• Journal of Korean Foot and Ankle Society
• /
• v.21 no.4
• /
• pp.156-164
• /
• 2017

Purpose: Foot and ankle disease (FAD) is a frequent cause of morbidity among the homeless population. Various conditions, exacerbated by malnutrition, poor lifestyle habits, psychiatric disorders, physical injuries, poor hygiene, and limited access to healthcare, have been described in this population. The purpose of this study was to investigate the cognition and management status of FAD in shelter based homeless people. Materials and Methods: Fifty-two male and twenty-five female volunteer homeless individuals were recruited from two homeless shelters. Each person completed a questionnaire assessing any presence of pain, pain management, as well as foot and ankle care status. A foot and ankle surgeon examined the physical status of the individual's foot and ankle, including tenderness and instability. A radiologic evaluation was done for 18 male and 11 female homeless people who agreed to participate in this test for the existence osteophyte or joint space narrowing representing osteoarthritis and some reference angles for hallux valgus, flatfoot and cavus foot. Results: Homeless people had higher prevalence of body mass index, diabetes, and smoking than the general population. The most prevalent infectious disease was fungal infection (male 78%, female 68%), with a low compliance of management for FAD. Conclusion: Although most of shelter-based homeless people showed an acceptable foot and ankle management status, the potential risk for FAD development and exacerbation of mild FAD was high.

• Physical Therapy Korea
• /
• v.27 no.4
• /
• pp.241-249
• /
• 2020

Background: Prolonged standing during work causes a lower extremity pain and disorders. Patellofemoral pain syndrome (PFPS) is one of the common diagnoses of the knee pain. Although the etiology of PFPS is not completely understood, it is considered to be multifactorial. Objects: The purpose of this study was to investigate difference in strength of knee muscles, quadriceps:hamstring muscles strength ratio (Q:H ratio), asymmetry ratio of knee muscles strength and dorsiflexion range of motion (ROM) between standing workers with and without PFPS. Methods: Twenty-eight standing workers with PFPS and 26 age-, height-, and weight-matched standing workers without PFPS participated in this study. A tension sensor measured knee muscle strength, and motion sensor measured dorsiflexion ROM. The asymmetry ratio of knee muscles was calculated by a specific formula using the knee muscles strength of the dominant side and the sound side. An independent t-test was used to identify significant differences in the strength, ROM, Q:H ratio, and asymmetry ratio between the PFPS and normal groups. Results: The standing worker with PFPS have significantly lower dorsiflexion ROM (p < 0.000) and higher asymmetry ratio of the hamstring muscles strength (p < 0.000) compare to the standing worker without PFPS. No significant differences were seen in the strength of quadriceps muscle and hamstring muscles, Q:H ratio, and asymmetry ratio of quadriceps muscle strength. Conclusion: There was a significant difference in the asymmetry ratio of the isometric hamstring muscle strength. This finding suggests that the asymmetry ratio of isometric hamstring muscle strength may be more important than measuring only the hamstring muscle strength of the PFPS side. Furthermore, the results of this study showed a significant difference in dorsiflexion ROM between the standing industrial workers with and without PFPS. Dorsiflexion ROM and isometric hamstring muscle strength should be considered when evaluating the subjects with PFPS.

• Journal of Broadcast Engineering
• /
• v.20 no.3
• /
• pp.414-420
• /
• 2015

The quality of depth images is important in the 3D video system to represent complete 3D contents. However, the original depth image from a depth camera has a low resolution and a flickering problem which shows vibrating depth values in terms of temporal meaning. This problem causes an uncomfortable feeling when we look 3D contents. In order to solve a low resolution problem, we employ 3D warping and a depth weighted joint bilateral filter. A temporal mean filter can be applied to solve the flickering problem while we encounter a residual spectrum problem in the depth image. Thus, after classifying foreground andbackground regions, we use an upsampled depth image for a foreground region and temporal mean image for background region.Test results shows that the proposed method generates a time consistent depth video with a high resolution.

• Fashion & Textile Research Journal
• /
• v.18 no.4
• /
• pp.520-530
• /
• 2016

This research aims to propose an ergonomic design process for hip protector based on previous studies, existing products, multidisciplinary experts opinion, and wearing test. The elderly are more likely to suffer a hip fracture when they fall due to their physical changes in skeletal form, muscle quantity, bone density, and joint movement. A hip protector is an effective product to prevent hip fractures in the elderly but it also has a problem in that it is uncomfortable. Therefore there is a high chance that it won't be able to prevent hip fractures properly. Since the comfort of a hip protector is one of the most critical elements in preventing a hip fracture, we need to keep improving the hip protector for mobility and usability. Based on the previous studies and limitations of current hip protector products, we need to come up with an optimal design for the Korean elderly. First, knowledge has to be built relating to the ergonomic design of the hip protector considering body shape and size analysis using 3D-scan data, and biomechanical analysis on hip fracture. Second, we need to develop a design process including hip protector pattern design, and wearing evaluation with virtual system. Third, we suggest to reevaluate and verify the design procedure from impact evaluation using testing simulator, virtual evaluation of impact, to wearing comfort and usability evaluation. This design process presented in this study would be expected to contribute to the development of ergonomic hip protector which is suitable for the Korean elderly.

• Laser Solutions
• /
• v.10 no.3
• /
• pp.25-32
• /
• 2007

The effect of welding speed on the weldability, microstructures, hardness, tensile property of Nd:YAG laser welding joint in 600MPa grade precipitation hardening high strength steel was investigated. A shielding gas was not used, and bead-on-plate welding was performed using various welding speeds at a power of 3.5kW. Porosity in the joints occurred at 1.8m/min, but were not observed over the welding speed of 2.1m/min. However, spatter occurred over the welding speed of 6.6m/min. The hardness was the highest at heat affected zone(HAZ) near fusion zone(FZ), and was decreased on approaching to the base metal. The maximum hardness increased with increasing welding speed. The microstructure of FZ was composed of coarse grain boundary ferrite and bainite(upper) but the HAZ near the FZ contained bainite(Lower) and fine ferrite at a low welding speed. With increasing welding speed, ferrite at the FZ and the HAZ became finely and upper binite changed to lower bainite. In a perpendicular tensile test to the weld line, all specimens were fractured at the base metal, and the tensile strength and the yield strength of joints was equal to those of raw material. Elongation was found to be lower than that of the raw material.

• Steel and Composite Structures
• /
• v.27 no.3
• /
• pp.337-353
• /
• 2018

In previous weak-axis moment connection tests, brittle fracture always initiated near the edge of the beam flange groove weld due to force flow towards the stiffer column flanges, which is the opposite pattern as strong-axis moment connections. As part of the China NSFC (51278061) study, this paper tested two full-scale novel weak-axis reduced beam section moment connections, including one exterior frame connection specimen SJ-1 under beam end monotonic loading and one interior frame joint specimen SJ-2 under column top cyclic loading. Test results showed that these two specimens were able to satisfy the demands of FEMA-267 (1995) or ANSI/AISC 341-10 (2010) without experiencing brittle fracture. A parametric analysis using the finite element software ABAQUS was carried out to better understand the cyclic performance of the novel weak-axis reduced beam section moment connections, and the influence of the distance between skin plate and reduced beam section, a, the length of the reduced beam section, b, and the cutting depth of the reduced beam section, c, on the cyclic performance was analyzed. It was found that increasing three parametric values reasonably is beneficial to forming beam plastic hinges, and increasing the parameter a is conducive to reducing stress concentration of beam flange groove welds while increasing the parameters b and c can only reduce the peak stress of beam flange groove welds. The rules recommended by FEMA350 (2000) are suitable for designing the proposed weak-axis RBS moment connection, and a proven calculation formulation is given to determine the thickness of skin plate, the key components in the proposed weak-axis connections. Based on the experimental and numerical results, a design procedure for the proposed weak-axis RBS moment connections was developed.

• Journal of the Microelectronics and Packaging Society
• /
• v.13 no.1 s.38
• /
• pp.63-72
• /
• 2006

Mobile products, such as cellular phones, PDA and notebook, are subjected to many different mechanical loads, which include bending, twisting, impact shock and vibration. In this study, a cyclic bending test of the BGA package was performed to evaluate the fatigue life. Special bending tester, which was suitable for electronic package, was developed using an electromagnetic actuator. A nonlinear finite element model was used to simulate the mechanical bending deformation of solder joint in BGA packages. The fatigue life of lead-free (95.5Sn4.0Ag0.5Cu) solder joints was compared with that of lead-contained (63Sn37Pb). When the applied load to the specimen is small, the lead-free solder has longer fatigue life than lead-contained solder. The fatigue crack is initialized at the exterior solder joints and is propagated into the inner solder joints.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.1
• /
• pp.39-46
• /
• 2017

In this paper, a model updating procedure based on the response surface method combined with the multi-objective optimization was proposed and applied for updating of the FE models representing a low-rise reinforced concrete building before and after the seismic retrofit. The dynamic properties to be matched were obtained from vibration tests using a small shaker system. By varying the structural parameters according to the central composite design, analysis results from the initial FE model using a commercial software were collected and used to produce two regression functions each of which representing the errors in the natural frequencies and mode shapes. The two functions were used as the objective functions for multi-objective optimization. Final solution was determined by examining the Pareto solutions with one iteration. The parameters representing the stiffnesses of existing concrete, masonry, connection stiffness in expansion joint, new concrete, retrofitted members with steel section jacketing were selected and identified.