• Bulletin of the Korean Chemical Society
• /
• 제7권1호
• /
• pp.59-62
• /
• 1986

Folded Box coherent anti-Stokes Raman spectroscopy (FBCARS) spectra of the fundamental symmetric stretch(213 $cm^{-1}$) and the first overtone(421 $cm^{-1}$) of $I_2$ have been recorded over the pump wavelength range from 495 nm to 580 nm. The lineshapes were fitted using the least squares method and the A and C term of CARS were calculated. From the fitting of A and C terms, the real(R) and imaginary(I) term intensity of CARS were calculated using harmonic oscillator program. The calculated CARS excitation profile of $I_2$ with R and I term data was about 270 $cm^{-1}$ red shifted from the absorption spectrum.

• International Journal of Automotive Technology
• /
• 제8권1호
• /
• pp.59-66
• /
• 2007

High frequency excitation terms in a cam profile can excite vibration of a cam follower system. In this paper, modified smoothing spline curves are used to reduce the high frequency terms. The essential difference between the proposed method and other existing approaches is its ability to make the principal cam motions smooth while still exactly satisfying boundary conditions of follower displacement, velocity and acceleration. The boundary values usually depend on the ramp properties of a cam. Our method, thus, allows designers to smooth the existing cam motion without any damages on its ramp areas. Because the ramp height, velocity and acceleration are maintained exactly, more radical smoothing is possible. An example shows that the proposed method can be a powerful tool of cam profile smoothing, which removes high frequency components in the cam profile excitations without any changes in ramp properties.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1997년도 춘계학술대회
• /
• pp.471-474
• /
• 1997

Several selective excitation pulses are used in MRI. Because of the nonlinearity of the Block equation, the pulse problem is nonlinear generally. Recently, Shinnar & Le Roux have proposed a direct solution of this problem. In this paper, we introduce the SLR algorithm and design pulses using SLR algorithm. This SLR pulse produces a specified slice profile. For example, we demonstrate the sinc function pulse with piece wise constant duration ${\Delta}t$. Further, we will design $\pi/2$ pulse and slice profile.

• International Journal of Automotive Technology
• /
• 제8권2호
• /
• pp.225-232
• /
• 2007

A tooth profile modification for loaded gears is used to avoid a tooth impact. Since a tooth profile error causes amplification of the cumbersome whine noise in automotive gear transmissions, an optimal quantity of tooth profile modifications must be obtained for good performance in the vibration sense. In this paper, a tooth profile modification curve considering profile manufacturing errors and elastic deformation of the gear tooth is formulated; in addition, transmission errors of the gear system with modified teeth are verified. The equivalent excitation due to transmission errors is formulated. For experimental evaluation of the transmission error, the transmission error for a simple gear system was measured by two rotational laser vibrometers. Finally, we perform a comparative analysis between the calculated and measured responses to the excitations due to the transmission error to verify the practicability of the application to automotive transmissions.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2014년도 추계학술대회 논문집
• /
• pp.791-795
• /
• 2014

In this paper, in order to impart the aging condition of the parts, by configuring the cycle of temperature from low temperature was performed by applying the aging conditions for vehicle cockpit module. The reason for the selected modules of the cockpit vehicle parts, because the joint occurrence typical components of the room component is a first module and ceiling cockpit module. After setting the excitation profile using the BSR exciter only that this is for the module degradation after the initial and grasp the change in the dynamic characteristics of the modules based on the before and after deterioration may be made in the module, grasp the noise generating position I measured the noise and proximity. Was also visualized on the position of the joint is generated using a sound camera to objective results occurring where the joint is selected through subjective evaluation.

• 한국기계가공학회지
• /
• 제11권5호
• /
• pp.42-47
• /
• 2012

Construction equipment is heavily loaded during normal operation. In recent years, there is a trend that lower gear noise levels are demanded for drivers to avoid annoyance and fatigue during operation. For articulated hauler's final drive, meshing transmission error(T.E.) is the excitation that leads the tonal noise known as gear whine, and radiated gear whine is also the dominant source of noise in the whole gearbox. This paper presents a method for the analysis of the tooth profile modification, and the prediction of transmission error under the loaded torques for the spur gear pair of the articulated hauler's final drive. And the transmission error, transmission error harmonics and contact stress are also calculated and compared before and after tooth modification under one torque. The simulation result shows that the transmission error and contact stress under the loads can be minimized by the appropriate tooth profile modification.

• 대한기계학회논문집
• /
• 제17권1호
• /
• pp.1-10
• /
• 1993

본 연구에서는 치차의 소음은 근본적으로 치형에 관계된 것으로 생각하여 치 차소음을 감소시키기 위해 제시한 방법에 적합한 치형, 즉 물림률을 증가시킬 수 있고 동시에 치형수정의 효과를 나타내며, 미끄럼률.치면접촉응력.이뿌리응력이 작은 인벌 류트-사이클로이드 하벙치형을 유효치형으로 하여 저소음 치차의 치형을 치차의 소음 을 감소시키기에 적절한 치형설계조건을 설정하여 설계한다. 설계한 합성치형치차의 소음저감성능을 확인하기 위해 치형을 생성시키는 컴퓨터프로그램의 치형데이터를 이 용하여 합성치형치차, 인벌류트치차, 그리고 사이클로이드치차를 NC Wire Cutting Ma- chine으로 가공하고 각 치차에 대해 소음측정실험을 하여 소음레벨을 비교검토한다.

• Investigative Magnetic Resonance Imaging
• /
• 제20권1호
• /
• pp.27-35
• /
• 2016

Purpose: Among RF pulses, a sinc pulse is typically used for slice selection due to its frequency-selective feature. When a sinc pulse is implemented in practice, it needs to be apodized to avoid truncation artifacts at the expense of broadening the transition region of the excited-band profile. Here a sinc pulse tailored by a new apodization function is proposed that produces a sharper transition region with well suppression of truncation artifacts in comparison with conventional tailored sinc pulses. A multiband pulse designed using this newly apodized sinc pulse is also suggested inheriting the better performance of the newly apodized sinc pulse. Materials and Methods: A new apodization function is introduced to taper a sinc pulse, playing a role to slightly shift the first zero-crossing of a tailored sinc pulse from the peak of the main lobe and thereby producing a narrower bandwidth as well as a sharper pass-band in the excitation profile. The newly apodized sinc pulse was also utilized to design a multiband pulse which inherits the performance of its constituent. Performances of the proposed sinc pulse and the multiband pulse generated with it were demonstrated by Bloch simulation and phantom imaging. Results: In both simulations and experiments, the newly apodized sinc pulse yielded a narrower bandwidth and a sharper transition of the pass-band profile with a desirable degree of side-lobe suppression than the commonly used Hanning-windowed sinc pulse. The multiband pulse designed using the newly apodized sinc pulse also showed the better performance in multi-slice excitation than the one designed with the Hanning-windowed sinc pulse. Conclusion: The new tailored sinc pulse proposed here provides a better performance in slice (or slab) selection than conventional tailored sinc pulses. Thanks to the availability of analytical expression, it can also be utilized for multiband pulse design with great flexibility and readiness in implementation, transferring its better performance.

• 대한조선학회논문집
• /
• 제40권5호
• /
• pp.26-35
• /
• 2003

Propellers operating in a given nonuniform ship wake generate unsteady loads leading to undesirable stern vibration problems. The skew is known to be the most proper and effective geometric parameter to control or reduce the fluctuating forces on the shaft. This paper assumes the skew profile as either a quadratic or a cubic function of the radius and determines the coefficients of the polynomial function by applying the simplex method. The method uses the converted unconstrained algorithm to solve the constrained minimization problem of 6-component shaft excitation forces. The propeller excitation was computed either by applying the two-dimensional gust theory for quick estimation or by the fully three-dimensional unsteady lifting surface theory in time domain for an accurate solution. A sample result demonstrates that the shaft forces can be further reduced through optimization from the original design.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 하계학술대회 논문집 B
• /
• pp.1191-1193
• /
• 2001

In switched reluctance motor(SRM) drive, it is necessary to synchronize the stator phase excitation with the rotor position. Therefore, the rotor position information is essential. Usually, optical encoders or resolvers are used to provide the rotor position information. These sensors are expensive and are not suitable for high speed operation. This paper proposes a new encoder for high performance excitation control of SRM. The proposed encoder has complex structures of incremental and absolute encoder. An each phase inductance profile can be synchronized with 4-bit absolute position signal and incremental pulses are used for speed detection. Low cost and simple structure are possible.