• The Journal of Korean Physical Therapy
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• v.22 no.6
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• pp.29-33
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• 2010

Purpose: This study was designed to investigate inter-rater and intra-rater reliability of navicular drop measurements by clinicians in sitting and standing positions. Methods: Fourteen subjects with pronated foot were recruited. Two physical therapists randomly assessed the same patients on different occasions but on the same day. Almost all patients were assessed on more than one day. The intra-rater and inter-rater reliability of navicular dropwas estimated by calculation of the intraclass correlation coefficient (ICC). Results: The intra-rater reliability of navicular drop measurements ranged from 0.93 to 0.87, the inter-rater reliability from 0.98 to 0.70 with the patient in standing and sitting positions. These results showed good reliability for calculated variables. Intra-rater and inter-rater reliability of navicular drop in standing position was higher than those of sitting position. Conclusion: Although inter-rater and intra-rater reliability of navicular drop in the sitting position was lower than in the standing position, measurement of navicular drop in the sitting position showed good reliability and was acceptable for patients who could not stand alone without assistance. We recommend that having the patient in the standing position is appropriate in navicular drop measurement.

• Journal of Korean Physical Therapy Science
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• v.26 no.1
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• pp.9-14
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• 2019

Background: Pes planus, or flat foot, causes lower limb malalignment and foot pain during walking or exercise. Therefore, a highly reliable evaluation method to accurately diagnose flat feet is necessary. This study investigated the intra-and inter-rater reliability of the navicular drop test in different postures. Design: Cross sectional study. Methods: Forty healthy volunteers performed the navicular drop test in three different combinations of non-weight-bearing and weight-bearing postures (standing/standing, sitting/sitting, and sitting/standing). Two examiners alternately performed the measurements five times in each subject, and in each posture. Significant differences in measurements were obtained among the three postures, with the highest navicular drop being observed in the sitting/standing posture. Results: Inter-rater reliability was high in the sitting/standing and sitting/sitting postures. Intra-rater reliability was high in all three postures. In the sitting/sitting and sitting/standing postures, large navicular drop values and high inter- and intra-rater reliability were observed. Conclusion: Therefore, the sitting/standing and sitting/sitting postures are recommended for use in navicular drop tests to diagnose flat feet.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.250-255
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• 2008

This study utilized a high speed lap-shear test to evaluate the mechanical behavior of Sn-37Pb/Cu and Sn-37Pb/Electroless Nickel immersion Gold under bump metallization solder joints under high speed loading and hence the drop reliability. The samples were aged for 120 h at different temperatures ($120^{\circ}C,\;150^{\circ}C,\;170^{\circ}C$) and afterward tested at different displacement rates (0.01 mm/s to 500 mm/s) to examine the effects of aging on the drop life reliability. The combination of the stress-strain graphs captured from the shear tests and identifying a fracture mode dominant in the samples for different strain rates leads us to conclude that the drop reliability of solder joints degrades as the aging temperature increases, possibly due to the role of the IMC layer. This study successfully demonstrates that the analysis based on a high speed lap-shear test could be critically used to evaluate the drop reliability of solder joints.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.1
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• pp.33-38
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• 2009

The use of portable devices has created the need for new reliability criterion of drop impact tests because of the tendency to accidentally drop in the use of these devices. The effects of different PCB surface finishes (organic solderability preservative (OSP) and electroless nickel immersion gold (ENIG)) and high temperature storage (HTS) test on the drop reliability were studied. Various drop test conditions were used to evaluate a drop reliability of assemblies to endure such impact and shock load. In the case of the as-reflowed samples (no HTS test), the SAC/OSP boards exhibited a better drop impact reliability than that of SAC/ENIG. However, the reverse was true if HTS test is performed. In addition, significant decrease of drop reliability was observed for both SAC/ENIG and SAC/OSP assemblies after HTS test. It was also observed that the thickness of intermetallic compound layer do play an important role in the brittle fracture of drop test.

• Transactions of the Society of Information Storage Systems
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• v.9 no.2
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• pp.56-61
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• 2013

The recent increased use of mobile phone has resulted in a technical focusing on reliability issues related to drop performance. Since mobile phone may be dropped several times during their use, it is required to survive common drop accidents. The plastic injection parts such as base stopper and carrier in the encoder type actuator can be broken easily in the actual reliability test of 1.5m free drop. So, we analyzed the shock resistance characteristics of auto focus actuator with variables in the material properties using finite element method. By applying the new resin materials, we can decrease the breakage of plastic injection parts and improve the reliability of mobile phone.

• Journal of the Microelectronics and Packaging Society
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• v.18 no.2
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• pp.35-41
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• 2011

Recently, board level solder joint reliability performance of IC packages during drop impact becomes a great concern to semiconductor and electronic product manufacturers. The handheld electronic products are prone to being dropped during their useful service life because of their size and weight. The IC packages are susceptible to solder joint failures, induced by a combination of printed circuit board (PCB) bending and mechanical shock during impact. The board level drop testing is an effective method to characterize the solder joint reliability performance of miniature handheld products. In this paper, applying the JEDEC (JESD22-B111) standard present a finite element modeling of the FBGA. The simulation results revealed that maximum stress was located at the outermost solder ball in the PCB or IC package side, which consisted well with the location of crack initiation observed in the failure analysis after drop reliability tests.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.365-366
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• 2007

Micro jetting drop inspection system is essential to measuring micro drop volume. Measuring pico-liter drop volume is useful for new LCD color filter product process that is based on inkjet printing technology. To upgrade the reliability in drop measurement system, we use the auto focusing & multi drop reiteration & blurring average algorism. First of all we used standard mark for gage R&R in the vision system. Finding the most suitable threshold for multi blurring drop, is the main key of this research. Sensitivity of vision system is a standard in measuring the upgrade system level. So, suitable threshold can upgrade the performance of jetting drop inspection system.

• Journal of Power System Engineering
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• v.9 no.1
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• pp.64-69
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• 2005

In evaluation of electronic reliability on the PCB(Print Circuit Borad),electrochemical migration is one of main test objects. The phenomenon of electrochemical migration occurs in the environment of the hight humidity and the hight temperature under bias through a continuous aqueous electrolyte. In this paper, the generating mechanism of electrochemical migration is investigated by using water drop acceleration test under various waters. The waters used in the water drop test are city water, distilled water and ionic water. It found that the generated velocity of electrochemical migration depended on electrolyte quantity which included in the various waters.

• Nuclear Engineering and Technology
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• v.52 no.4
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• pp.784-790
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• 2020

The accelerated corrosion by Flow Accelerated Corrosion (FAC) has caused unexpected rupture of piping, hindering the safety of nuclear power plants (NPPs) and sometimes causing personal injury. For the safety, it may be necessary to select some pipes in terms of condition monitoring and to measure the change in thickness of pipes in real time. Direct current potential drop (DCPD) method has advantages in on-line monitoring of pipe wall thinning. However, it has a disadvantage in that it is difficult to quantify thinning due to various thinning shapes and thus there is a limitation in application. The machine learning approach has advantages in that it can be easily applied because the machine can learn the signals of various thinning shapes and can identify the thinning using these. In this paper, finite element analysis (FEA) was performed by applying direct current to a carbon steel pipe and measuring the potential drop. The fundamental machine learning was carried out and the piping thinning model was developed. In this process, the features of DCPD to thinning were proposed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.559-563
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• 2011

Drop impact reliability assessment of solder joints on the flip chip is one of the critical issues for micro system packaging. Our previous researches have been showing that new solder ball compositions of Sn-3.0Ag-0.5Cu has better mechanical reliability than Sn-1.0Ag-0.5Cu. In this paper, dynamic reliability analysis using Finite Element Analysis (FEA) is carried out to assess the factors affecting flip chip in drop simulation. The design parameters are size and thickness of chip, and size, pitch and array of solder ball with composition of Sn1.0Ag0.5Cu. The board systems by JEDEC standard including 15 chips, solder balls and PCB are modeled with various design parameter combinations, and through these simulations, maximum yield stress and strain at each chip are shown at the solder balls. It is found that larger chip size, smaller chip array, smaller ball diameter, larger pitch, and larger chip thickness have bad effect on maximum yield stress and strain at solder ball of each chip.