• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.3 no.3
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• pp.176-185
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• 1991

Pressure drop and flow characteristics through a filter medium have been investigated numerically. A basic model similar to the filter employed in a hard disk drive was established so that the inflow velocity was 0.1 m/s and the box size was $40mm{\times}50mm{\times}30mm$. The filter medium specifications were 0.38mm of thickness, $1{\mu}m$ of fiber diameter, 0.05 of packing density. And the filter medium was pleated by 10 within the filter box. Twenty-one sets of calculation were performed with different inlet velocities, pleated numbers, and packing densities from the basic model. As the result, it was found that the velocity after filter medium had maximum value at the rear of the upstream pleated line, but had minimum value at the rear of the downstream pleated line. This made the velocity distribution have sinusoidal form immediately after the filter medium. As the inlet velocity increased, the pressure drop increased linearly. But as the packing density increased the pressure drop increased quadratically.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.25 no.3
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• pp.585-594
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• 2015

As the storage market has been expanded due to growing data size, the research on various kinds of storages such as cloud, USB, and external HDD(Hard Disk Drive) has been conducted in digital forensic aspects. NAS(Network-Attached Storage) can store the data over one TB(Tera Byte) and it is well used for private storage as well as for enterprise, but there is almost no research on NAS. This paper selects three NAS products that has the highest market share in domestic and foreign market, and suggests the process and method for data acquisition in live NAS System.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.129-130
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• 2007

Self servo track writing(SSTW)은 servo track writer(STW)를 이용하지 않고 hard disk drive의 내부 VCM을 이용하여 servo track을 기록하는 방식이다. SSTW는 이전 servo track을 상대적인 reference로 하여 기록하게 되므로 초기에 발생된 error와 외부의 disturbance의 영향으로 error는 급속하게 증가된다. 이것을 radial error propagation 이라 한다. 본 논문에서는 radial error propagation을 억제하기 위한 correction signal을 설계하고 servo writing 과정에서 발생하는 disturbance의 영향을 제거하기 위하여 disturbance observer(DOB)를 add-on type으로 구성하여 tracking 제어기를 설계하였다. 또한 DOB를 적용한 경우와 유사한 gain margin, phase margin과 sensitivity function을 갖는 제어기를 설계하여 그 성능을 비교하였다. 제안된 방식은 radial error propagation을 억제 하였을 뿐만 아니라 disturbance의 최소화하여 쓰여진 track의 DC track spacing과 AC track Squeeze가 개선된 것을 모의실험을 통하여 검증하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1319-1324
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• 2007

Accurately controlling the shape of the read/write head structure is critical in the performance of a modem hard disk drive. The sliders investigated are composed of alumina and titanium carbide(AITiC) and act as an air bearing when passing over the disks. Controlling the curvature of the slider is of primary importance. A laser scribing system that produces curvature by inducing residual stress into the slider can be utilized. Predicting the curvature created by a pattern of scribes is of great importance to increase the control over the sliders' shape. The force system that produces stresses similar to the laser scribing is applied to the finite element analysis model. The curvatures created by the force system are calibrated to experimental measurements.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.318-323
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• 2005

This paper introduces the mechanism of the ESD (Electrostatic discharge) in the HDD spindle system using FDBs (Fluid Dynamic Bearings). When a HDD (Hard Disk Drive) spindle system is rotating, triboelectric charging occurs in the FDBs through the friction of the lubricant between the rotating shaft and stationary sleeve. And this electrostatic charge is accumulated in the rotating part of the HDD spindle system because it is insulated from the ground by the lubricant. This research shows experimentally that the behavior of electric charge and discharge in the FDB spindle system is the same as that of a capacitor. It also measures the electrostatic charge and discharge of the FDB spindle system due to the chanse of humidity, supporting load and motor speed. This research shows that the control of ESD is required in the HDD spindle system using FDBs, because the electrostatic charge accumulated in the FDB spindle system may cause the breakdown damage of the GMR head and data loss consequently.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.403-406
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• 2004

In this paper, the design of damped structures associated with the piezoelectric shunt circuits is undertaken and it is applied to optical disk drive (O.D.D) main base in order to reduce unwanted vibration. In order to design effective piezoelectric structure, the admittance of the structure is introduced as the performance index of the piezoelectric shunt system. And the admittance offset of the shunt performance is theoretically investigated. It is also presented that the admittance can be calculated by commercial finite elements program. To verify the admittance calculated by F.E.M, admittance measurement is performed by impedance analyzer. In this verifying process, the validity of the finite element admittance analysis is found. As a practical approach, to reduce the vibration of the O.D.D. main base, piezoelectric shunt system is designed using the proposed admittance analysis and shunt effect is evaluated at all prescribed frequencies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.759-764
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• 2000

The accurate prediction of aeroacoustic analysis is necessary for designers to control and reduce airflow-induced sound pressure levels in high speed rotating DVD drives. This paper focuses on the numerical prediction of airflow-induced sound in DVD drives. Computational fluid dynamics(CFD) is first conducted to evaluate flow field characteristics due to the high-speed disk rotation, and to support the acoustic analysis. The acoustic analogy based on Ffowcs Williams-Hawkings(FW-H) equation is adopted to predict aeroacoustic noise patterns. The integral solution for quadrupole volume source is included to identify the turbulence noise generated inside the DVD tray. The strength of sound pressure level with respect to rotating speed is discussed to meet upfront demand on the high fidelity product development. The present study also focuses on the noise directivity and examines how much the sound noise is sensitive to change in rotating speed. Near-field noise is strongly affected by the flow field characteristic, which is caused by the complex shape of the tray. For a mid-field, the quadrupole noise play as a counterpart of thickness noise or loading noise, so it generates different sound noise patterns compared with those in the near field.

• The Journal of Korea Robotics Society
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• v.14 no.1
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• pp.50-57
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• 2019

This work presents a design and control method for a flexible robot arm operated by a wire drive that follows human gestures. When moving the robot arm to a desired position, the necessary wire moving length is calculated and the motors are rotated accordingly to the length. A robotic arm is composed of a total of two module-formed mechanism similar to real human motion. Two wires are used as a closed loop in one module, and universal joints are attached to each disk to create up, down, left, and right movements. In order to control the motor, the anti-windup PID was applied to limit the sudden change usually caused by accumulated error in the integral control term. In addition, master/slave communication protocol and operation program for linking 6 motors to MYO sensor and IMU sensor output were developed at the same time. This makes it possible to receive the image information of the camera attached to the robot arm and simultaneously send the control command to the robot at high speed.

• Journal of information and communication convergence engineering
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• v.21 no.3
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• pp.208-215
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• 2023

Deep learning techniques provide powerful solutions to several pattern-recognition problems, including Raman spectral classification. However, these networks require large amounts of labeled data to perform well. Labeled data, which are typically obtained in a laboratory, can potentially be alleviated by data augmentation. This study investigated various data augmentation techniques and applied multiple deep learning methods to Raman spectral classification. Raman spectra yield fingerprint-like information about chemical compositions, but are prone to noise when the particles of the material are small. Five augmentation models were investigated to build robust deep learning classifiers: weighted sums of spectral signals, imitated chemical backgrounds, extended multiplicative signal augmentation, and generated Gaussian and Poisson-distributed noise. We compared the performance of nine state-of-the-art convolutional neural networks with all the augmentation techniques. The LeNet5 models with background noise augmentation yielded the highest accuracy when tested on real-world Raman spectral classification at 88.33% accuracy. A class activation map of the model was generated to provide a qualitative observation of the results.

• Journal of Digital Contents Society
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• v.15 no.1
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• pp.19-27
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• 2014

In order to estimate the life of 2,5 inch HDD which is adopted by PC environment, make the test plan which reflect the failure mode of market, make the test model of accelerated life test which reflect the stress of temperature. after an analysis of the environment of PC using, test procedure was decided that operation was write 50 % and read 50 %, and then access method was sequential 50 % and random 50%. The acceleration life test was executed on condition that temperature was $50^{\circ}C$ and $60^{\circ}C$, performance was 95 % in max performance, test time was 1000 hours. by the test of goodness of fit of anderson-darling of the failure data during test, it was confirmed that the distribution of failure fellow weibull. test for shape and scale was equal, and shape parameter was 0.7177, characteristic life was 429434 hours at normal user condition($30^{\circ}C$) by the analysis of weibull-arrhenius modeling. It made no difference about the statistics when equality test was executed. The activation energy was 0.2775eV. In analyzing between the failure samples of acceleration test and the samples of market return even though there is detail difference about the share of failure mode, the rank of share was almost same. This study suggest the test procedure of acceleration test of 2.5 inch HDD in PC using environment, and help the life estimation at manufacture and user.