• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.1
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• pp.1-10
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• 2005

This paper proposes a new and simple input prediction method for robust servo system. A robust tracking control system for optical disk drives was proposed recently based on both Coprime Factorization (CF) and Zero Phase Error Tracking (ZPET) control. The CF control system can be designed simply and systematically. Moreover, this system has not only stability but also robustness to parameter uncertainties and disturbance rejection capability. Since optical disk tracking servo system can detect only tracking error, it was proposed that the reference input signal for ZPET could be estimated from tracking errors. In this paper, we propose a new control structure for the ZPET controller. It requires less memory than the previously proposed method for the reference signal generation. Numerical simulation results show that the proposed method is effective.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.2
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• pp.185-192
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• 2000

Cam mechanism is one of the common devices used in many automatic machinery. Since the motion of the cam mechanism depends on the shape of the cam and the type of the follower, the shape design procedure must be well defined in order to determine the accurate shape of the cam corresponding to the prescribed motion of the follower. This paper proposes a new approach for designing the shape of disk cams. The proposed relative velocity method uses the relative velocity at center of the follower roller or at contact point between the cam and the follower for 4 different types of the disk cam systems. Also, the relative velocity method for determining the cam profile uses the geometric relationships of the cam and the follower.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.19 no.37
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• pp.241-249
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• 1996

In this paper, a 0-1 integer programming model for solving vertical partitioning problem minimizing the number of disk accesses is formulated and a branch-and-bound method is used to solve the binary vertical partitioning problem. In relational databases, the number of disk accesses depends on the amount of data transferred from disk to main memory for processing the transactions. Vertical partitioning of the relation can often result in a decrease in the number of disk accesses, since not all attributes in a tuple are required by each transactions. The algorithm is illustrated with numerical examples and is shown to be computationally efficient. Numerical experiments reveal that the proposed method is more effective in reducing access costs than the existing algorithms.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.3 s.108
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• pp.247-254
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• 2006

This paper (Part II) provides the application results of the method presented in a companion paper (Part I) where the dynamic equation for rotating polar orthotropic disk is formulated and its solution method is considered. The natural frequencies and critical speed of polycarbonate CD are calculated to validate the present method and are shown to by very accurate. The critical speeds of typical GFRP and CFRP CD's are computed by aligning the fibers in radial and circumferential directions. The radially reinforced CFRP CD is shown to have the five times higher critical speed than that of the polycarbonate CD. The natural frequencies and critical speeds of disks with various elastic modulus ratios are obtained. The results show that the radially reinforced disk is more effective in increasing critical speed than the circumferentially reinforced disk.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.571-577
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• 2003

This research proposes a finite element method to determine the natural vibration characteristics of the spinning disk-spindle system in a HDD including the flexibility of supporting structure. Finite element equations of each substructure are derived with the introduction of consistent variables to satisfy the geometric compatibility at the internal boundaries. The natural frequencies and modes from the global asymmetric matrix equations of motion are determined by using the implicit restarted Arnoldi iteration method. The validity of the proposed method is verified by the experimental modal testing. It also shows that the flexibility of base plate plays an important role to determine the natural frequencies of the spinning disk-spindle system in a HDD.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.482-487
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• 2001

Time responses of a flexible spinning disk of which axis of symmetry is misaligned with the axis of rotation are analyzed in a numerical manner. Equations of motions are derived by Hamilton's principle based on Kirchhoff plate theory and von-Karman strain theory, and the equations are discretized by finite element method. In obtaining the time responses, Generalized-$\alpha$ method is used to solve the equations. Based on the result, the effects of the misalignment are analyzed on the vibration characteristics of a spinning disk.

• Journal of Korean Institute of Industrial Engineers
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• v.22 no.4
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• pp.567-578
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• 1996

In relational databases the number of disk accesses depends on the amount of data transferred from disk to main memory for processing the transactions. N-ary vertical partitioning of the relation can often result in a decrease in the number of disk accesses, since not all attributes in a tuple are required by each transactions. In this paper, a 0-1 integer programming model for solving n-ary vertical partitioning problem minimizing the number of disk accesses is formulated and a branch-and-bound method is used to solve it. A preprocessing procedure reducing the number of variables is presented. The algorithm is illustrated with numerical examples and is shown to be computationally efficient. Numerical experiments reveal that the proposed method is more effective in reducing access costs than the existing algorithms.

• YAKHAK HOEJI
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• v.35 no.4
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• pp.348-351
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• 1991

A new agar-disk method was developed from the fast selection and characterization of antibiotic producing organisms.

• Structural Engineering and Mechanics
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• v.47 no.4
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• pp.455-470
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• 2013

This paper presents a theory concerning the beam element subjected to an eccentric rolling disk (or simply called the eccentric-disk-loaded beam element) such that the dynamic responses of a beam subjected to an eccentric rolling disk with its inertia force, Coriolis force and centrifugal force considered can be easily determined. To this end, the property matrices of an eccentric-disk-loaded beam element are firstly derived by means of the Lagrange's equations. Then, the overall property matrices of the entire vibrating system are determined by directly adding the property matrices of the eccentric-disk-loaded beam element to the overall ones of the entire beam itself. Finally, the Newmark direct integration method is used to solve the equations of motion for the dynamic responses of a beam subjected to an eccentric rolling disk. Some factors relating to the title problem, such as the eccentricity, radius and rotating speed of the rolling disk, and the Coriolis force and centrifugal force induced by the rolling disk are investigated. Numerical results reveal that the influence of last factors on the dynamic responses of the pinned-pinned beam is significant except the centrifugal force.

• Journal of KSNVE
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• v.9 no.4
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• pp.643-651
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• 1999

A brief description of the current technology (contact-start-stop) employed in most of today's hard disk drive is presented. The dynamics and head/disk interactions during a start/stop process are very complicated and no one has been able to accurately model the interactions. Thus, the head/disk interface that meets the start/stop durability and stiction requirements are always developed statistically. In arriving at a solution. many sets of statistical tests are run by varying several parameters. such as, the carbon overcoat thickness. lubricant thickness. disk surface roughness, etc. Consequently, the cost associated III developing an interface could be significant since the outcome is difficult to predict. An alternative method known as Load/Unload technology alters the problem set. such that. the start/stop performance can be designed in a predictable manner. Although this techno¬logy offers superior performance and significantly reduces statistical testing time, it also has some potential problems. However. contrary to the CSS technology. most of the problems can be solved by design and not by trial and error. One critical problem is that of head/disk contacts during the loading and unloading processes. These contact can cause disk and slider damage because the contacts are likely to occur at high disk speeds resulting in large friction forces. Use of glass substrate disks also may present problems if not managed correctly. Due to the low thermal conductivity of glass substrates. any head/disk contacts may result in erasure due to frictional heating of the head/disk interface. In spite of these and other potential problems. the advantage with L/UL system is that these events can be understood. analyzed. and solved in a deterministic manner.