• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.1479-1482
• /
• 2003

The shock absorber is a part having a direct influence on the ride comfort, stability and dynamic load prediction of a vehicle. Thus, a rationally modeled shock absorber should be required in the dynamic analysis of vehicles. This thesis presents a modified model, based on Worden's hyperbolic tangent function, in order to fit experimental data on the velocity-damping force of a shock absorber. The hyperbolic tangent function correctly indicates the characteristics of a shock absorber. and has the advantage of containing physical causality. To evaluate the method, comparative evaluations of the linear model. the 5th polynomial model and Worden's model were carried out. The function presented in this paper is not only simple but also makes it possible to estimate the function coefficients easily and visually. In addition, it has the advantage of containing physical causality. Lastly, it effectively models the damping force of a shock absorber.

• Journal of Power Electronics
• /
• 제17권4호
• /
• pp.991-1003
• /
• 2017

The conventional sliding mode control (CSMC) has a number of problems. It may cause dc output voltage ripple and it cannot guarantee the robustness of the whole system for a matrix rectifier (MR). Furthermore, the existence of a filter can decrease the input power factor (IPF). Therefore, a novel global sliding mode control (GSMC) based on a hyperbolic tangent function with IPF compensation for MRs is proposed in this paper. Firstly, due to the reachability and existence of the sliding mode, the condition of the matrix rectifier's robustness and chattering elimination is derived. Secondly, a global switching function is designed and the determination of the transient operation status is given. Then a SMC compensation strategy based on a DQ transformation model is applied to compensate the decreasing IPF. Finally, simulations and experiments are carried out to verify the correctness and effectiveness of the control algorithm. The obtained results show that compared with CSMC, applying the proposed GSMC based on a hyperbolic tangent function for matrix rectifiers can achieve a ripple-free output voltage with a unity IPF. In addition, the rectifier has an excellent robust performance at all times.

• 대한수학회지
• /
• 제46권6호
• /
• pp.1267-1276
• /
• 2009

This paper presents a method for approximation of the standard normal distribution by using hyperbolic tangent based functions. The presented approximate formula for the cumulative distribution depends on one numerical coefficient only, and its accuracy is admissible. Furthermore, in some particular cases, closed forms of inverse formulas are derived. Numerical results of the present method are compared with those of an existing method.

• 대한수학회지
• /
• 제48권1호
• /
• pp.133-146
• /
• 2011

We employ a hyperbolic tangent function to construct nonlinear transformations which are useful in numerical evaluation of weakly singular integrals and Cauchy principal value integrals. Results of numerical implementation based on the standard Gauss quadrature rule show that the present transformations are available for the singular integrals and, in some cases, give much better approximations compared with those of existing non-linear transformation methods.

• 한국자동차공학회논문집
• /
• 제11권5호
• /
• pp.156-162
• /
• 2003

The shock absorber is a part having a direct influence on the ride comfort, stability and dynamic load prediction of a vehicle. Thus, a rationally modeled shock absorber should be required in the dynamic analysis of vehicles. This thesis presents a modified model, based on Worden's hyperbolic tangent function, in order to fit experimental data on the velocity-damping force of a shock absorber. The hyperbolic tangent function correctly indicates the characteristics of a shock absorber, and has the advantage of containing physical causality. To evaluate the method, comparative evaluations of the linear model, the 5th polynomial model and Worden's model were carried out. The function presented in this paper is not only simple but also makes it possible to estimate the function coefficients easily and visually. In addition, it has the advantage of containing physical causality. Lastly, it effectively models the damping force of a shock absorber.

• 전자공학회논문지D
• /
• 제35D권8호
• /
• pp.82-88
• /
• 1998

We propose and design a new type of anrrow band-pass optical filter based on two fiber gratings with different reflection wavelength. The ripples occur in the spectra of the filter with two uniform fiber gratings. Our simulation results also show that the ripples disappear with the fiber gratings apodized to both gaussian and hyperbolic tangent function. The hyperbolic tangent function seems to be a better apodization function for improving the filter's performance in terms of narrow pass bandwidth and high transmission.

• 한국추진공학회지
• /
• 제25권6호
• /
• pp.1-11
• /
• 2021

층류화염편 라이브러리에 대한 효율적인 계산과정을 개발하기 위하여 초임계 압력조건의 기체수소/액체산소 연소기에 대해 인공신경망을 이용한 기계학습과정이 적용되었다. 학습성능과 계산효율성에 근거한 최적의 계산과정을 찾기 위하여 은닉층에 대한 ReLU와 쌍곡탄젠트 함수의 25가지 조합이 선택되었다. 정확성이 우수한 높은 학습성능을 얻는데 쌍곡탄젠트 활성화함수가 적절하였다. 인공신경망의 학습성능을 개선하기 위해서 학습데이터 변환이 제안되었다. 4개의 은닉층에 최적의 노드를 배치할 때 학습성능 및 계산비용 관점에서 모두 효율적인 것으로 나타났다. 층류화염편 라이브러리의 보간법보다 인공신경망을 사용하는 경우 전체 계산시간은 37%, 시스템 메모리는 99.98% 감소되었다.

• Communications for Statistical Applications and Methods
• /
• 제8권3호
• /
• pp.625-632
• /
• 2001

Principal component analysis(PCA) is a multivariate technique falling under the general title of factor analysis. The purpose of PCA is to Identify the dependence structure behind a multivariate stochastic observation In order to obtain a compact description of it. In engineering field PCA is utilized mainly (or data compression and restoration. In this paper we propose a new robust Hebbian algorithm for robust PCA. This algorithm is based on a hyperbolic tangent function due to Hampel ef al.(1989) which is known to be robust in Statistics. We do two experiments to investigate the performance of the new robust Hebbian learning algorithm for robust PCA.

• 천문학회보
• /
• 제37권1호
• /
• pp.85.1-85.1
• /
• 2012

In this study we use three-dimensional magnetohydrodynamic simulations of flux emergence from solar subsurface layer to corona. In order to study the twist parameter of magnetic field we compare the simulations for strongly twisted and weakly twisted cases. Based on the results, we derive a flux expansion factor of selected flux tubes which is a ratio of expanded cross section to the one measured at the footpoint of the flux tube. To understand the effect of flux expansion factor, we make a comparison between magnetic field configuration and the expansion factor. By using a fitting function of hyperbolic tangent we derive noticeable correlations among the strength of the vertical magnetic field, current density and expansion factor. We discuss what these results tell about the relationship between the twist of emerging field and the mechanism for the solar wind.

• Journal of electromagnetic engineering and science
• /
• 제12권4호
• /
• pp.290-292
• /
• 2012

This paper proposes a setup for a best multisine design method that uses a time-domain optimization. The method is based on minimization of the time-domain error, so its resulting multisine has a very accurate ACLR estimation. This is because its probability distribution and sample-to-sample correlation are close to those of the original signal, which are crucial for the testing of nonlinear power amplifiers. In addition, a hyperbolic-tangent function is introduced to control the ripple of tone magnitudes within signal bandwidth. For the verification, multisines were generated and compared for many aspects such as normalized error, in-band ripple, and ACLR estimation. Test results with different numbers of tones provide supporting evidence that the suggested multisine design has better ripple suppression, by up to 7 dB, and better accuracy, by up to 0.2 dB, when compared to the conventional method. The accuracy of the ACLR was improved by about 5 dB when the number of tones was 4. The suggested method improves the ACLR estimation performance of multisine testing due to its closer resemblance to the target modulation signal.