• Structural Engineering and Mechanics
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• v.10 no.2
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• pp.93-110
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• 2000

An alternative interpretation of the completeness requirements for the higher order elements is presented. Apart from the familiar condition, $\sum_iN_i=1$, some additional conditions to be satisfied by the shape functions of higher order elements are identified. Elements with their geometry in the natural form, i.e., without any geometrical distortion, satisfy most of these additional conditions inherently. However, the geometrically distorted elements satisfy only fewer conditions. The practical implications of the satisfaction or non-satisfaction of these additional conditions are investigated with respect to a 3-node bar element, and 8- and 9-node quadrilateral elements. The results suggest that non-satisfaction of these additional conditions results in poorer performance of the element when the element is geometrically distorted. Based on the new interpretation of completeness requirements, a 3-node element and an 8-node rectangular element that are insensitive to mid-node distortion under a quadratic displacement field have been developed.

• Smart Structures and Systems
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• v.24 no.2
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• pp.257-266
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• 2019

The benefit of data fusion in improving the performance of Higher Order Sliding Mode (HOSM) observer is brought out in this paper. This improvement in the performance of HOSM observer, resulted in the improvement of active vibration control of a piezo actuated structure, when controlled by a Discrete Sliding Mode Controller (DSMC). The structure is embedded with two piezo sensors for measuring the first two vibrating modes. The fused output of sensors is applied to the HOSM observer for generating state estimates, these states generated are applied to the DSMC, designed for the fourth order linear time invariant model of the structure. In the simulation study, the structure is excited at the first and second mode resonance. It is found that better vibration suppression is obtained, when the states generated by the fused output of sensors is applied as controller input, than the vibration suppression obtained by applying the states generated by using individual sensor output. The closed loop performance of DSMC obtained with HOSM observer is compared with the closed loop performance obtained with the conventional observer. Results obtained shows that better vibration suppression is obtained when the states generated by HOSM observer is applied as controller input.

• Journal of computational fluids engineering
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• v.11 no.1 s.32
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• pp.36-42
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• 2006

The existing numerical approximations of convection flux, especially the spatial higher-order difference schemes, in unstructured cell-centered finite volume methods are examined in detail with each other and evaluated with respect to the accuracy through their application to a 2-D benchmark problem. Six higher-order schemes are examined, which include two second-order upwind schemes, two central difference schemes and two hybrid schemes. It is found that the 2nd-order upwind scheme by Mathur and Murthy(1997) and the central difference scheme by Demirdzic and Muzaferija(1995) have more accurate prediction performance than the other higher-order schemes used in unstructured cell-centered finite volume methods.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.5
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• pp.268-277
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• 1999

Impulsive acoustic and vibration signals within gear are often induced by impacting of fault tooths in gear. Thus the detection of these impulses can be useful for fault diagnosis. Recently there is an increasing trend towards the use of higher order statistics for fault detection within mechanical systems based on the observation that impulsive signals then to increase the kurtosis values. We show that the fourth order Wigner Moment Spectrum, called the Wigner Trispectrum, has found superior detection performance to second order Wigner distribution for typical impulsive signals in a condition monitoring application. These methods are also applied to data sets measured within an industrial gear box.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.6
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• pp.2446-2462
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• 2016

In this paper, a frequency domain Expectation-Maximization (EM)-based channel estimation algorithm for Space Time Block Coded-Orthogonal Frequency Division Multiplexing (STBC-OFDM) systems is investigated to support higher data rate applications in wireless communications. The computational complexity of the frequency domain EM-based channel estimation is increased when higher order constellations are used because of the ascending size of the search set space. Thus, a search set reduction algorithm is proposed to decrease the complexity without sacrificing the system performance. The performance results of the proposed algorithm is obtained in terms of Bit Error Rate (BER) and Mean Square Error (MSE) for 16QAM and 64QAM modulation schemes.

• Health Policy and Management
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• v.11 no.3
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• pp.1-30
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• 2001

This study was conducted to evaluate the effectiveness of team system at university hospitals in Korea. Data were collected from administrative and medical support workers at 4 university hospitals through the self-administered questionnaires and analyzed using frequency analysis, t-test, and oneway ANOVA. The results of this study are as follows. First, teams with higher team management characteristics show higher level of quality of work life and performance effectiveness. Second, teams which consist of members with variety background and skills show higher level of quality of work life and performance effectiveness. Third, team which have the higher autonomy, technology variety, job significance, and feedback show higher team effectiveness. Fourth, team which have team leaders with higher leadership score show higher level of quality of work life and performance effectiveness. Fifth, there are differences in team effectiveness in terms of sicio- demographic variables such as average age, position, and tenure of team members, length of team system, and team size. Sixth, the job autonomy of team members and the leadership of team managers have significant effects on the quality of work life variables. Seventh, the leadership of team leaders, job autonomy of members, and individual contact between team managers and members have significant effects on the team performance variables. In conclusion, in order to increase the effectiveness of team system in university hospitals, it is required to consider the characteristics of team management, diversity of team members, the autonomy of team members, the leadership of team manager, and the socio-demographic factors of team members.

• Journal of Power Electronics
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• v.12 no.5
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• pp.689-698
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• 2012

This paper investigates the effects of applying different input current waveshapes on the performance of a continuous-conduction-mode (CCM) power-factor-correction (PFC) boost pre-regulator. It is found that the output voltage ripple of the pre-regulator can be reduced if the input current is modified to include controlled amount of higher order harmonics. This finding allows us to balance the performance of output regulation and the harmonic current emission when coming to the design of the pre-regulator. An experimental PFC boost pre-regulator prototype is constructed to verify the analysis and show the benefit of the pre-regulator operating with input current containing higher order harmonics.

• Journal of Korean society of Dental Hygiene
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• v.10 no.3
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• pp.503-512
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• 2010

Objectives : In this study, in order to provide basic data for more efficient and systematic clinical practice training by recognizing the need of effective and standardized operation of clinical practice accomplished in clinical fields belonging to the curriculum of dental hygiene department, grasping, investigating, and analyzing satisfaction degree of the clinical practice through student's frequency of observation practice and performance practice. Methods : A survey was conducted against 208 students in the 3rd grade of 4 dental hygiene departments located in Jeonbuk province. Results : As results, it was found that for the observation practice frequency according to clinical practice term by universities, the basic clinical practice was higher in A, B, and D university and that the correction and practice was higher in D university. For the performance practice frequency, it was found that basic care practice was higher in B and D university, oral medicine practice, preventive dentistry practice, and periodontal practice were higher in A and C university, pediatric dentistry practice was higher in B and C university, prosthetic dentistry practice was higher in A, B, and C university, and oral surgery practice was higher in B university. It was identified that satisfaction was higher in the basic care practice, the preventive dentistry practice, and the periodontal practice in the range of clinical practice, and the A and C university receiving higher score in the performance practice frequency got higher score in the oral medicine practice, the preventive dentistry practice, and the periodontal practice. Conclusions : As the basic care practice items in the clinical practice area which got relatively higher score in observation practice, performance practice, and satisfaction degree of the dental hygiene trainee are basic and essential works that they will perform the most frequently, it is considered that integrated clinical practice training including the intramural practice course is required.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.3
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• pp.629-631
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• 2007

In hands-free full-duplex communication systems, acoustic signals picked up by the microphones can be mixed with echo signals as well as noises, which may result in poor performance of the corresponding communication system. Also, the system performance may decrease further if the reverberation occurs since it is harder to estimate the impulse response of the demixing system. For blind source separation (BSS) in such cases, a time-frequency masking approach can be employed to separate undesired echo signals and noises, but, permutation ambiguities also should be solved for the echo cancellation. In this paper, we propose a new acoustic echo cancellation (AEC) approach utilizing the time-frequency masking and higher-order statistics, whereby a desired signal selection, based on coherence and third-order statistics (i.e., kurtosis), is introduced along with output signal normalization. Simulation results demonstrate that the proposed approach yields better echo and noise cancellation performances than the conventional AEC approaches.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.5
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• pp.630-635
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• 1998

The objective of this paper is to propose a new efficient technique for the estimation of time-delay parameters using wavelet theory and third-order cumulants, yielding good performance even in the case of low SNR. In particular, band-limited non-Gaussian signals with non-zero skewness and spatially correlated Gaussian noises are considered here. The approach is based on the fact that the effects of spatially correlated Gaussian noises on time-delay estimation can be reduced by using the projection sequences (based on the redundant wavelet decomposition) of given measurements in the higher-order cumulant domain. Finally, the performance of the proposed approach is demonstrated using simulations.