Skew-Dependent Performance Evaluation of Array-Reader-Based Magnetic Recording With Dual-Reader

Euiseok Hwang,Oenning, Travis,Mathew, George,Rahgozar, Parviz,Tedja, Suharli,Han Fang,Garfunkel, Glen,Yan Wu,Hu, David,Duquette, Paul,Fitch, Ken,Rabbitt, Chad,Petrizzi, Joseph,Wilson, Bruce,Rauschmaye IEEE 2015 IEEE transactions on magnetics Vol.51 No.4

<P>Array-reader-based magnetic recording (ARMR) shows potential to achieve areal density capability (ADC) beyond 1 Tb/in<SUP>2</SUP> by jointly processing multiple readback streams. Dual-reader ARMR with two read sensors and associated read channel signal processing algorithms are currently being actively investigated. In this paper, dual-reader ARMR performance is evaluated focusing on skew-induced variation in cross-track separation (CTS) between the two read sensors. Spin-stand captured waveforms based evaluation is presented for the cases where a dual-reader with certain CTS and skew is emulated using captures from a single-reader at different cross-track locations as well as for the case of actual dual-reader-based captures, where the latter also accounts for head rotation. Based on bit error rate scan along cross-track under various squeezed recording and skew conditions, squeeze-to-death margin-based ADC gain of ARMR is predicted. Dual-reader ARMR shows 5%-10% ADC gain over single-reader for CTS less than 0.6 track pitch, while showing limited gains for larger CTS. Also presented is the performance evaluation of dual-reader ARMR on spin-stand using a hardware accelerated ARMR performance evaluation platform, called Stingray, which uses four Avago read channel silicon chips and a customized field programmable gate array to enable high-speed joint equalization and detection using dual-reader readback streams.</P>

표면활성화법에 의한 이종재료의 저온접합에 관한 연구

국중민,임언택,권택용,최병기 朝鮮大學校 機械技術硏究所 1998 機械技術硏究 Vol.1 No.1

본 논문은 서로 다른 재료를 표면활성화법을 이용하여 저온에서 접합할 목적으로 이들 재료의 접합 가능성을 검토하고 이들 접합계면에서의 접합 메카니즘을 검토할 목적으로 연구하였으며 연구 결과는 다음과 같다. 1) 10-7 Torr대의 진공도에서도 알루미늄은 알루미나, 질화 알루미늄, 질화규소, 지르코늄 등의 세라믹스와 양호한 접합이 가능하였다. 2) 알루미늄, 동, 은은 같은 금속끼리의 접합이 가능하고, 또 알루미늄과 동의 이종재료의 접합도 가능하였다. 3) 실리콘은 알루미늄, 동, 은, 금 등의 실험결과 모든 금속과 접합이 가능하였다. In this paper considered it possible to bone different materials in low temperature using surface activated method. To do so, It was examined the possibility of bonding different materials and applied the bonding mechanism on the bonding surface. The followings are the result. 1) It was possible that Aluminum could be bonded well with ceramics such as alumina, nitrification aluminum, nitrification silicon, and zirconium at the vaccum level of 10-7 Torr. 2) It was possible that aluminum, copper, and copper could be bonded with each other and aluminum and copper could be bonded with other metals. 3) Silicon was bonded with aluminum copper silver, and gold which were tested before.

Quantifying the Precision of Single-Molecule Torque and Twist Measurements Using Allan Variance

van Oene, Maarten M.,Ha, Seungkyu,Jager, Tessa,Lee, Mina,Pedaci, Francesco,Lipfert, Jan,Dekker, Nynke H. Elsevier 2018 Biophysical journal Vol.114 No.8

<P><B>Abstract</B></P> <P>Single-molecule manipulation techniques have provided unprecedented insights into the structure, function, interactions, and mechanical properties of biological macromolecules. Recently, the single-molecule toolbox has been expanded by techniques that enable measurements of rotation and torque, such as the optical torque wrench (OTW) and several different implementations of magnetic (torque) tweezers. Although systematic analyses of the position and force precision of single-molecule techniques have attracted considerable attention, their angle and torque precision have been treated in much less detail. Here, we propose Allan deviation as a tool to systematically quantitate angle and torque precision in single-molecule measurements. We apply the Allan variance method to experimental data from our implementations of (electro)magnetic torque tweezers and an OTW and find that both approaches can achieve a torque precision better than 1 pN · nm. The OTW, capable of measuring torque on (sub)millisecond timescales, provides the best torque precision for measurement times</P> <P> ≲ 10 s, after which drift becomes a limiting factor. For longer measurement times, magnetic torque tweezers with their superior stability provide the best torque precision. Use of the Allan deviation enables critical assessments of the torque precision as a function of measurement time across different measurement modalities and provides a tool to optimize measurement protocols for a given instrument and application.</P>

Shock Response Prediction of a Low Altitude Earth Observation Satellite During Launch Vehicle Separation

Dae-Oen Lee,Jae-Hung Han,Hae-Won Jang,Sung-Hyun Woo,Kyung-Won Kim 한국항공우주학회 2010 International Journal of Aeronautical and Space Sc Vol.11 No.1

Several pyrotechnic devices are employed over the course of satellite's missions, generally for the separation of structural subsystems and deployment of appendages. Firing of pyrotechnic devices results in impulsive loads characterized by high peak acceleration and high frequency content which can cause failures of various flight hardware elements and small components. Thus, accurate prediction of acceleration level in various components of spacecraft due to pyrotechnic devices is important. In this paper, two methods for pyroshock prediction, an empirical model and statistical energy analysis in conjunction with virtual mode synthesis, are applied to predict shock response of a low altitude earth observation satellite during launch vehicle separation. The predicted results are then evaluated through comparison with the shock test results.

A Comparison of Vibration Isolation Characteristics of Various Forms of Passive Vibration Isolator

Dae-Oen Lee(이대은),Jae-Hung Han(한재흥) 한국소음진동공학회 2012 한국소음진동공학회 학술대회논문집 Vol.2012 No.4

정밀 시스템에 전달되는 진동은 시스템의 성능 저하 및 오작동을 초래할 수 있기 때문에 저감되어야 한다. 진동을 저감시키는 가장 일반적인 방법은 진동이 전달되는 경로에 수동 진동절연 장치를 도입함으로 전달되는 진동을 절연시키는 방법이다. 탄성소자와 점성 감쇠기로 구성된 일반적인 수동 진동 절연 장치는 공진에서의 전달율을 낮추기 위해서 고주파수 대역에서 진동 절연 성능을 희생해야 하는 단점을 지니고 있다. 본 논문에서는 공진에서 낮은 전달율과 고주파수 대역에서 높은 진동 절연 성능을 동시에 가진 수동 진동 절연 장치들의 특성을 비교분석하였다. Transmission of unwanted vibration to sensitive systems can cause various problems including performance degradation and system malfunction. The most common approach to limit the transmission of harmful vibration disturbances to the sensitive system is adapting passive vibration isolator. The classical passive vibration isolator comprising a viscous damper and spring element in parallel, however, exhibits conflicting performance characteristics in that low amplification at the resonance, which is desirable, can only be achieved at the sacrifice of vibration isolation performance in high frequency region, which is undesirable. In this paper, vibration isolation characteristics of various passive isolator schemes in literature to circumvent this conflict are introduced and compared.

Development of Active Micro-Vibration Isolator using Electromagnet

Dae-Oen Lee(이대은),Gee-Yong Park(박지용),Jae-Hung Han(한재흥) 한국소음진동공학회 2013 한국소음진동공학회 학술대회논문집 Vol.2013 No.4

고정밀 광학계를 탑재한 관측 위성은 매우 높은 지향 안정성을 요구하지만 인공위성의 자세 제어를 위해 사용하는 반작용 휠, 극저온 냉각을 위한 cooler 등 다양한 진동원에 의해 미소 진동이 발행할 수 있다. 고정밀 탑재체를 외부 진동으로부터 보호하기 위한 가장 일반적인 방법은 진동이 전달되는 경로에 진동 절연장치를 도입하는 것이다. 본 논문에서는 미소진동 절연을 위한 1 축 능동 진동 절연장치의 개발 및 진동 절연 성능 시험을 기술하였다. 개발한 절연장치의 고유진동수를 조절하기 위해 원하는 강성을 갖는 membrane 구조를 설계하였으며 능동 제어를 위해 전자석을 사용하였다. 절연장치의 성능 시험 결과를 통해 능동 제어 시 고주파수 대역에서 절연성능의 저하 없이 공진의 크기를 줄일 수 있는 것과 개발된 진동 절연 장치가 미소 진동을 효과적으로 절연 할 수 있는 것을 확인하였다. Observation satellites carrying high precision optical payload require extremely stringent pointing stability that may be violated in the presence of the disturbances coming from reaction wheels, cryocoolers or other actuating components onboard the satellite. The most common method to protect the sensitive payloads from external disturbances is implementation of vibration isolator. In this paper development of a single axis active vibration isolator using electromagnet and its performance in isolating micro-vibration is presented. The main components of the developed isolator are membrane structure providing the isolator with the required stiffness and an electromagnet for active control. The performance test results show that additional damping can be achieved by active control without degrading isolation performance in high frequency region and that the developed isolator can effectively isolate micro-vibration.

Development of Integrated Simulation Tool for Jitter Analysis

Dae-Oen Lee,Jae-San Yoon,Jae-Hung Han 한국항공우주학회 2012 International Journal of Aeronautical and Space Sc Vol.13 No.1

Pointing stability of high precision observation satellites must satisfy the stringent requirements to perform at a designed level. As even a small vibrational disturbance can result in severe degradation of the optical performance, the effects of inorbit vibrational environment on the performance of optical payload must be predicted and analyzed in the design phase in order to ensure that the requirements imposed on the payload are fully met. In this paper, an integrated framework for the evaluation of the performance of optical payloads is developed. The developed simulation tool comprises of the reaction wheel induced disturbance model, state space model of a structure in modal form and Cassegrain reflector model. The performance degradation of the optical system due to jitter is expressed by using modulation transfer function (MTF) and image simulation. Moreover, vibration isolator model is also added to show the effectiveness of using a vibration isolator for the elimination of the effects of jitter in the acquisition of an image.

大學附設統一問題硏究所의 運營現況과 改善方向

李元達 영남대학교 통일문제연구소 1988 統一問題硏究 Vol.13 No.-

Shock Response Prediction of a Low Altitude Earth Observation Satellite During Launch Vehicle Separation

Lee, Dae-Oen,Han, Jae-Hung,Jang, Hae-Won,Woo, Sung-Hyun,Kim, Kyung-Won The Korean Society for Aeronautical and Space Scie 2010 International Journal of Aeronautical and Space Sc Vol.11 No.1

Several pyrotechnic devices are employed over the course of satellite's missions, generally for the separation of structural subsystems and deployment of appendages. Firing of pyrotechnic devices results in impulsive loads characterized by high peak acceleration and high frequency content which can cause failures of various flight hardware elements and small components. Thus, accurate prediction of acceleration level in various components of spacecraft due to pyrotechnic devices is important. In this paper, two methods for pyroshock prediction, an empirical model and statistical energy analysis in conjunction with virtual mode synthesis, are applied to predict shock response of a low altitude earth observation satellite during launch vehicle separation. The predicted results are then evaluated through comparison with the shock test results.

A sub-1-volt nanoelectromechanical switching device.

Lee, Jeong Oen,Song, Yong-Ha,Kim, Min-Wu,Kang, Min-Ho,Oh, Jae-Sub,Yang, Hyun-Ho,Yoon, Jun-Bo Nature Pub. Group 2013 Nature nanotechnology Vol.8 No.1

<P>Nanoelectromechanical (NEM) switches have received widespread attention as promising candidates in the drive to surmount the physical limitations currently faced by complementary metal oxide semiconductor technology. The NEM switch has demonstrated superior characteristics including quasi-zero leakage behaviour, excellent density capability and operation in harsh environments. However, an unacceptably high operating voltage (4-20 V) has posed a major obstacle in the practical use of the NEM switch in low-power integrated circuits. To utilize the NEM switch widely as a core device component in ultralow power applications, the operation voltage needs to be reduced to 1 V or below. However, sub-1 V actuation has not yet been demonstrated because of fabrication difficulties and irreversible switching failure caused by surface adhesion. Here, we report the sub-1 V operation of a NEM switch through the introduction of a novel pipe clip device structure and an effective air gap fabrication technique. This achievement is primarily attributed to the incorporation of a 4-nm-thick air gap, which is the smallest reported so far for a NEM switch generated using a 'top-down' approach. Our structure and process can potentially be utilized in various nanogap-related applications, including NEM switch-based ultralow-power integrated circuits, NEM resonators, nanogap electrodes for scientific research and sensors.</P>