• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2008.11a
• /
• pp.190-191
• /
• 2008

• The KSFM Journal of Fluid Machinery
• /
• v.10 no.5
• /
• pp.64-73
• /
• 2007

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.48 no.1
• /
• pp.56-61
• /
• 2011

This paper describes design of a programmable frequency synthesizer for RF PLL with $0.18{\mu}m$ silicon CMOS technology being used as an application of the UWB system like MBOA. To get good performance of speed and noise super dynamic circuits was used, and to get programmable division ratio switching circuits was used. Especially to solve narrow bandwidth problem of the dynamic circuits load resistance value of unit divider block was varied. Simulation results of the designed circuit shows very fast and wide operation characteristics as 1~14GHz frequency range.

• Tribology and Lubricants
• /
• v.30 no.1
• /
• pp.9-14
• /
• 2014

In this Part II study, rotordynamic stability analyses were carried out to confirm improvements to the stability of a process high-speed lightweight centrifugal compressor, depending on the effects of tilting pad journal bearing designs. The bearing design variables considered were the clearances, LBPs, LOPs, and preloads. The results showed that the rotordynamic stability of the subject compressor rotor-bearing system improves exactly in accordance with the effects of the bearing design variables, which were determined in the preceding Part I study, owing to reduced bearing stiffnesses. Specifically, it was confirmed that the stability of the rotor system can be greatly improved by increasing both the machined and assembled bearing clearances, but there were no stability improvements by simply changing from an LBP to an LOP design. In addition, it was confirmed that for given fixed machined bearing clearances, the stability can be additionally improved by decreasing the preloads, i.e., by increasing the assembled clearances. In conclusion, it may be necessary to improve the designs of the original tilting pad bearings to obtain a sufficient margin of rotordynamic stability against a possible aerodynamic cross-coupled stiffness in a process high-speed centrifugal compressor. Thus, increasing the machined and assembled bearing clearances and decreasing the preload could be effective solutions.

• Journal of Korean Library and Information Science Society
• /
• v.53 no.2
• /
• pp.265-284
• /
• 2022

This study applied dynamic topic modeling on titles and abstracts of 55,442 academic papers in 85 SSCI journals from 2001 to 2020 in order to analyze research topic trend in library and information science. The analysis revealed four major themes of library management, informatics, library service, and library system in 10 major topics. The results also showed subtopics in information science and library management topic areas to change over time, while library service remained stable over 20 years to establish itself as a robust topic. In addition, medical information emerged as a significant sub-topic of informatics, thus exemplifying the interdisciplinary characteristics of library and information science field.

• Journal of the Korea Society for Simulation
• /
• v.28 no.2
• /
• pp.1-14
• /
• 2019

A full scale hydrodynamic simulation that requires an accurate reproduction of shock-induced detonation was conducted for design of an energetic component system. A detailed hydrodynamic analysis SW was developed to validate the reactive flow model for predicting the shock propagation in a train configuration and to quantify the shock sensitivity of the energetic materials. The pyrotechnic device is composed of four main components, namely a donor unit (HNS+HMX), a bulkhead (STS), an acceptor explosive (RDX), and a propellant (BPN) for gas generation. The pressurized gases generated from the burning propellant were purged into a 10 cc release chamber for study of the inherent oscillatory flow induced by the interferences between shock and rarefaction waves. The pressure fluctuations measured from experiment and calculation were investigated to further validate the peculiar peak at specific characteristic frequency (${\omega}_c=8.3kHz$). In this paper, a step-by-step numerical description of detonation of high explosive components, deflagration of propellant component, and deformation of metal component is given in order to facilitate the proper implementation of the outlined formulation into a shock physics code for a full scale hydrodynamic simulation of the energetic component system.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.25 no.5
• /
• pp.391-399
• /
• 2005

Laser-generated ultrasonic inspection system is a non-contact scanning inspection device with high spatial resolution and wide bandwidth. The amplitude of laser-generated ultrasound is varied according to the energy of pulse laser and the surface conditions of an object where the CW measuring laser beam is pointing. In this paper, we correct the generating errors by measuring the energy of pulse laser beam and correct the measuring errors by extracting the gain information of laser interferometer at each time. h dynamic stabilizer is developed to stably scan on the surface of an object for an laser-generated ultrasonic inspection system. The developed system generates ultrasound after adaptively finding the maximum gain time of an laser interferometer and processes the signal in real time after digitization with high speed. In this paper, we describe hardware configuration and control algorithm to build a stable laser-generated ultrasonic inspection system. Also, we confirmed through experiments that the proposed correction method for the generating errors and measuring errors is effective to improve the performance of a system.

• The KIPS Transactions:PartA
• /
• v.14A no.2
• /
• pp.77-84
• /
• 2007

The intima media thickness(IMT) of the carotid artery from B mode ultrasound images has recently been proposed as the most useful index of individual atherosclerosis and can be used to predict major cardiovascular events. Ultrasonic measurements of the IMT are conventionally obtained by manually tracing interfaces between tissue layers. The drawbacks of this method are the inter and intra observer variability and its inefficiency. In this paper, we present a multiresolution snake method combined with the dynamic programming, which overcomes the various noises and sensitivity to initialization of conventional snake. First, an image pyramid is constructed using the Gaussian pyramid that maintains global edge information with smoothing in the images, and then the boundaries are automatically detected in the lowest resolution level by minimizing a cost function based on dynamic programming. The cost function includes cost terms which are representing image features and geometrical continuity of the vessel interfaces. Since the detected boundaries are selected as initial contour of the snake for the next level, this automated approach solves the problem of the initialization. Moreover, the proposed snake improves the problem of converging th the local minima by defining the external energy based on multiple image features. In this paper, our method has been validated by computing the correlation between manual and automatic measurements. This automated detection method has obtained more accurate and reproducible results than conventional edge detection by considering multiple image features.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.14 no.1
• /
• pp.22-28
• /
• 2021

Multivariate processes, such as chemical and mechanical process, power plants are operated in a state where several facilities are complexly connected, the fault of a particular system can also have fatal consequences for the entire process. In addition, since process data is measured in an unstable environment, outlier is likely to be include in the data. Therefore, monitoring technology is essential, which can remove outlier from measured data and detect failures in advance. In this paper, data obtained from dynamic and multivariate process models was used to detect fault in various type of processes. The dynamic process is a simulation of a process with autoregressive property, and the multivariate process is a model that describes a situation when a specific sensor fault. Mahalanobis distance was used to remove outlier contained in the data generated by dynamic process model and multivariate process model, and fault detection was performed using ICA. For comparison, we compared performance with and a conventional single ICA method. The proposed fault detection method improves performance by 0.84%p for bias data and 6.82%p for drift data in the dynamic process. In the case of the multivariate process, the performance was improves by 3.78%p, therefore, the proposed method showed better fault detection performance.

• Korean Architects
• /
• no.10 s.258
• /
• pp.30-39
• /
• 1990

"주제와 대상장소에 의해 그 실험은 다양하게 전개된다.예를들면 1900년대 초에 시작되었던 일부 근대주의가 내포했던 역사성에 대한 인식, 유리, 금속, 콘크리트, 플라스틱등 근대의 소산인 재료의 재질감에 대한 보다 다양한 가능성의 탐구, 구조와 표현사이의 관계모색, 추상도형에 있어 디테일이 갖는 에너지에 대한 신뢰와 발굴 다이나믹한 부분과 전체의 균형에 대한 연구, 이 결과로 생성된 과거와 미래라는 시간의 양의적 관계에서 부상되는 현재의 표현, 그것들은 각각 중요한 주제가 되는 동시에 놀랄만한 상징기능도 내포하는 보다 넓은 의미의 기능주의의 근본이 되고 있다. 그렇기 때문에 한사람의 건축가 그리고 한사무소에서 이룬 결과로서의 건축도 다양하게 전개되는 것이다."