• Journal of Dental Rehabilitation and Applied Science
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• v.38 no.2
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• pp.81-89
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• 2022

Purpose: Wireless endodontic handpieces (WEH) are widely used in dental clinics due to their convenience and portability. This study aimed to compare the vibration magnitudes and patterns generated by five WEH. Materials and Methods: Vibration acceleration of five WEH (X-Smart IQ, E connect S, Endo A Class, ENDOIT, and TRAUS ENDO) in the rotary and reciprocating motion was measured with accelerometer The average vibration acceleration was analyzed using the t-test, Welch's ANOVA test, and Dunnett T3 test at P < 0.05. Results: In all WEH, the average vibration acceleration in reciprocating motion was significantly higher than that in rotary motion (P < 0.001). In rotary motion, repeated vibration graphs of constant amplitude were obtained without sudden changes in the magnitude of vibration, and the average vibration acceleration value was high in the order of X Smart IQ, Endo A Class, ENDOIT, E Connect S, and TRAUS ENDO (P < 0.001), there was no statistically significant difference between X Smart IQ and Endo A Class. In reciprocating motion, a vibration graph was obtained in which large amplitude peaks appear at specific points within one cycle are repeated. The average vibration acceleration value was highest in the order of X Smart IQ, E Connect S, Endo A class, ENDOIT, and TRAUS ENDO (P < 0.001). Conclusion: Regardless of the type of WEH, greater vibration occurred in the reciprocating motion than in the rotary motion (P < 0.001). In the reciprocating motion, there was a difference in vibration for all handpieces (P < 0.001).

• Journal of the Korean Data and Information Science Society
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• v.14 no.4
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• pp.951-963
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• 2003

In this paper, we propose goodness of fit test statistics based on the estimated Kullback-Leibler information functions using the data from three step stress accelerated life test. This acceleration model is assumed to be a tampered random variable model. The power of the proposed test under various alternatives is compared with Kolmogorov-Smirnov statistic, Cramer-von Mises statistic and Anderson-Darling statistic.

• Journal of Biomedical Engineering Research
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• v.32 no.2
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• pp.177-184
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• 2011

In this study, the system for application of the bone stimulation was implemented using high frequency and low strain method. The whole system consists of the high frequency and low strain vibration stimulation system 177 for stimulating bone, LVDT sensor, and wireless sensor based on tri-axial accelerometer. To evaluate the usefulness of the system, the frequencies and accelerations from function generator were applied to the vibration stimulation system. The range of frequency was 17 Hz, 30 Hz, 45 Hz, 50 Hz and the range of acceleration was set 0.3 g, 0.6 g, 1g, and 2 g. The measured frequencies and acceleration using LVDT (linear variable difference transformer) sensor and 3-axial accelerometer were estimated and compared. The range of frequencies average difference was from 0.0 to 0.004 Hz. As the standard deviation of frequencies estimated by LVDT sensor and accelerometer was below 0.03 Hz and the output frequencies of function generator were similar: Also the results of t-test were satisfied with conditions of p > 0.05. And the acquired frequencies and acceleration from vibration measuring device module were estimated and analyzed. As the mean of accelerations was similar to the acceleration applied from function generator. And the standard deviation of acceleration estimated from vibration measuring device module was ranged from 0.019 g to 0.038 g. Also the results of t-test were satisfied with conditions of p > 0.05. Therefore, these results were airy similar to the acceleration applied from function generator. As a result, the usefulness of the system was confirmed. n a further study, clinical experiment will be carried out with the authorization of IRB (institutional review board) so that appropriate frequency and strain would be investigated in clinical field.

• Journal of the Microelectronics and Packaging Society
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• v.17 no.4
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• pp.19-26
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• 2010

We found that saturated water vapor pressure is the most dominant stress factor for the degradation phenomenon in the package for high-power phosphor-converted white light emitting diode (high power LED). Also, we proved that saturated water vapor pressure is effective acceleration stress of LED package degradation from an acceleration life test. Test conditions were $121^{\circ}C$, 100% R.H., and max. 168 h storage with and without 350 mA. The accelerating tests in both conditions cause optical power loss, reduction of spectrum intensity, device leakage current, and thermal resistance in the package. Also, dark brown color and pore induced by hygro-mechanical stress partially contribute to the degradation of LED package. From these results, we have known that the saturated water vapor pressure stress is adequate as the acceleration stress for shortening life test time of LED packages.

• Advances in aircraft and spacecraft science
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• v.2 no.2
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• pp.217-232
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• 2015

To prevent over-testing of the test-item during random vibration testing Scharton proposed and discussed the force limited random vibration testing (FLVT) in a number of publications. Besides the random vibration specification, the total mass and the turn-over frequency of the load (test item), $C^2$ is a very important parameter for FLVT. A number of computational methods to estimate $C^2$ are described in the literature, i.e., the simple and the complex two degrees of freedom system, STDFS and CTDFS, respectively. The motivation of this work is to evaluate the method for the computation of a realistic value of $C^2$ to perform a representative random vibration test based on force limitation, when the adjacent structure (source) description is more or less unknown. Marchand discussed the formal description of getting $C^2$, using the maximum PSD of the acceleration and maximum PSD of the force, both at the interface between load and source. Stevens presented the coupled systems modal approach (CSMA), where simplified asparagus patch models (parallel-oscillator representation) of load and source are connected, consisting of modal effective masses and the spring stiffness's associated with the natural frequencies. When the random acceleration vibration specification is given the CSMA method is suitable to compute the value of the parameter $C^2$. When no mathematical model of the source can be made available, estimations of the value $C^2$ can be find in literature. In this paper a probabilistic mathematical representation of the unknown source is proposed, such that the asparagus patch model of the source can be approximated. The chosen probabilistic design parameters have a uniform distribution. The computation of the value $C^2$ can be done in conjunction with the CSMA method, knowing the apparent mass of the load and the random acceleration specification at the interface between load and source, respectively. Data of two cases available from literature have been analyzed and discussed to get more knowledge about the applicability of the probabilistic method.

• Journal of Biosystems Engineering
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• v.27 no.5
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• pp.391-398
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• 2002

During handling unitized products, they are subjected to a variety of environmental hazards. Shock and vibration hazards are generally considered the most damaging of the environmental hazards on a product and it may encounter while passing through the distribution environment. A major cause of shock damage to products is drops during manual handling. The increasing use of unitization of pallets has been resulted in a reduction of the shock hazards. This has caused an increasing interest in research focused on vibration caused dam age. Damage to the product by the vibration most often occurs when a product or a product component has a natural frequency that falls within the range of the forcing frequencies of the particular mode of transportation being used. Transportation vibration is also a major cause of fruit and vegetable quality loss due to mechanical damage. This study was conducted to determine the vibration characteristics of the corrugated fiberboard bones for packages of pears, and to investigate the degree of vibration injury of the pears in the boxes during the simulated transportation environment. The vibration tests were performed on an electrohydraulic vibration exciter. The input acceleration to exciter was fixed at 0.25 G for a single container resonance test and 0.5 G for the vertical stacked container over the frequency range from 3 to 100 Hz. Function generator (HP-33120A) was connected by wire to the vibration exciter for controlling the input acceleration at a continuous logarithmic sweep rate of 1.0 octave per min. The peak frequency and acceleration on the single box test were 22.02 Hz, 1.5425 G respectively, and these values on the vertical stacked boxes were observed from the bottom box 19.02, 18.14, 16.62 and 15.40 Hz and 2.2987, 3.7654. 5.6087, and 7.9582 G, respectively. The pear in the bottom box had a slightly higher damage level than the fruit packed in the other stacked boxes. It is desirable that the package and transportation system has to be so designed that 15∼20 Hz frequency will not occur during the transportation environment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.129-136
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• 2005

The vehicle loading test under the strict traffic control is generally carried out as a present practice in an evaluation process of the bearing capacity of a bridge. The quasi-static load test is recently proposed to mitigate the traffic condition of test, and analyze the disturbed acceleration time-history data of free vibration due to the ambient traffic on the bridge by Fourier transform to calculate only the natural frequencies of the bridge. The calculated frequencies have some errors due to the analysis technique as well as the influence of ambient traffic loads, and in addition to it is cumbersome to obtain the free vibration data during a quasi-static load test. In this study, the wavelet transform technique using Morlet wavelet is used to analyze the acceleration data recorded during a quasi-static load test on a bridge and calculate the natural frequencies and the modal damping ratios of the bridge. The study results show that the wavelet transform technique is a reliable and reasonable method to analyze test data and obtain the natural frequencies and the modal damping ratios of a bridge regardless of the data types i.e. free or forced vibrations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2048-2055
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• 2001

This paper develops a computational model for estimating the ride quality of a cabover type large-sized truck in a double wheel bumpy ride test. The computational model is developed using ADAMS. To verify the developed model, an actual vehicle double wheel bumpy ride test is performed. In the test, the vehicle maintains a straight course with a constant velocity such that the front two wheels are passed the bump at the same time. The bump has the height of 60mm, and the width of 550mm. In the test, four velocities are used. They are 10kph, 20kph, 30kph and 40kph. Since the large-sized truck's center of gravity location is high, and its weight is heavy, it is a quite severe test condition to perform the test with more than 30kph velocity. In the test, vertical accelerations on the floor of the cab are measured. The measured accelerations are compared to the simulation results. From the comparison, it is shown that the developed model can predict not only the measured acceleration's tendency but also peak accelerations quite well. In this paper, the validated model is utilized to compare the ride quality between a vehicle with a multi-leaf spring and a vehicle with a tapered leaf spring in the front suspension system in a double bumpy ride test.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.2
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• pp.217-225
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• 2007

This paper proposes the real-time hybrid shaking table testing methods to simulate the dynamic behavior of a soil-structure interaction system with dynamic soil stiffness by using only a structure model as the physical specimen and verifies their effectiveness for experimental implementation. Experimental methodologies proposed in this paper adopt such a way that absolute accelerations measured from the superstructure and shaking table are feedback to the shaking table controller, and then the shaking table is driven by the calculated motion of the absolute acceleration (acceleration feedback method) or the absolute velocity (velocity feedback method) of foundation that is required to simulate the dynamic behavior of a whole soil-structure interaction system. The shaking table test is implemented by reflecting the dynamic soil stiffness, which are differently approximated from the theoretical one depending on the feedback methods, on the shaking table controller to calculate soil part. The effectiveness of the proposed experimental methods is verified by comparing the response measured from the test on a foundation-fixed structural model and that obtained from the experiment of a soil-interaction system under the consideration in this paper and by matching the dynamic soil stiffness reflected on the shaking table controller with that identified using the experimentally measured data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.11
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• pp.949-956
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• 2016

There are a number of effects by solar radiation in many aerospace industrial fields, such as degradation of mechanical properties, sealing effect of sealants or decolorization. Because it takes long time to investigate these effects by using the light of natural state, new methods are developed for accelerating this phenomenon. In this paper, we developed an apparatus to simulate accelerated solar radiation phenomenon selecting irradiation intensity $1,120W/m^2$ as the designed environment. Epoxy polymer as the composite material was chosen and processed by ASTM-D638, a reference for tensile test of polymer and plastic. Total color shift was selected as the test category to evaluate acceleration of the test. We obtained acceleration factors and numerical model from test data and concluded it can shorten test periods by accelerated irradiation intensity of $1,120W/m^2$.