A Novel Passive Quasi-Zero Stiffness Isolator for Ultra-Precision Measurement Systems

김장헌,전영준,엄상우,Usung Park,김경수,Soohyun Kim 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.9

In the paper, a novel passive vibration isolator is proposed for an ultra-precision sensing system, utilizing a quasi-zero stiffness (QZS) mechanism. The QZS mechanism implements the high static low dynamic stiffness, which effectively reduces the dynamic force transmission while minimizing the static deflection under the natural frequency of conventional passive isolator. Furthermore, it does not need any electric components; the mechanism is suitable for the ultra-precision sensing systems measuring extremely weak electromagnetic fields. However, nonlinear stiffness and hysteresis caused from the negative stiffness elements degrade the system performance. A vertical spring with a pre-tension and eight horizontal plate springs with nonlinear buckling characteristics constitute the proposed system to solve these problems. The mathematical model compares the negative stiffness design with previous QZS research. The buckled plate spring with ball joint design reduces stiffness variation. Transmissibility of the proposed system for low frequency range is investigated experimentally.

회전형 다면 석재 재단기 개발에 관한 연구

김장헌,이현우,조상환,조현,정원석 한국기계기술학회 2016 한국기계기술학회지 Vol.18 No.5

This study presents the stone cutter design that can rotate and change the cutting side of the stone automatically by the combination structures of the rotatable and foldable plates. Foldable plates are consisted with the iron plate and the hydraulic cylinders system(1500W pump power) which can generate high pressure to raise the plates and the stone. Additionally, rotatable plates are designed by gear system which has high gear ratio(1:8) for rotating heavy stone(5ton) easily. We analyzed the movement of the stone and investigated the total system of the stone cutter including a rotator and a tilter. Moreover, we constructed a control board to control the system accurately. This system can induce high quality cutting process controlled within errors of 5% and also reduce the process time from about 20 min to 90 sec by the automatic system.

Bluff Body 확산화염의 안정성에 관한 연구

김장헌,안진근,송규근 전북대학교 공업기술연구소 1992 工學硏究 Vol.23 No.-

The stability of diffusion flame formed behind a bulff-body with fuel injection was investigated experimentally in various injection angle and injection ratio of two-dimensionalized cylinders. The bluff-body was located in the range of air stream velocity 10-60m/s. Especially, flame stability problem was risen at the high speed flow because such a high flow condition flame was nonsteady and nonstable. Therefore, we measured the flame stability limits, distributions of temperrature, and take photographs of flame. The results from this study clearly show that the recirculation zone serves as a steady ignition source of combutible stream and governs the stabilization mechanism, the direction of injection is important factor for determinig the flame stability.

방산업체 연구개발 효율성 평가에 관한 연구

김장헌,이선헌,최형묵 한국방위산업학회 2011 韓國防衛産業學會誌 Vol.18 No.2

Nowadays, the performance evaluation of R&D activities to yield fundamental information for the effectiveness of decision-making on R&D investment has become important since the government budget is limited. This article suggests a hybrid type of evaluation model (i.e. qualitatively weighted quantified model) that makes up assessment of both quantitative and qualitative R&D performances in the Korean defense industry. The model tries to combine a DEA (Data Envelopment Analysis) methodology that uses a well-known quantitative measure for technical and cost efficiency of a number of DMUs (Decision Making Units) and an AHP (Analysis Hierarchical Process) method that helps discopose the qualitative evaluation problem into a hierarchical or more easily comprehensible sub-problems. Weight is measured for each qualitatively evaluating hierarchy by a survey targeting defense industry experts, researchers, military specialists, and planners. Technical and cost efficiency of a DMU are relatively calculated by comparing differences in efficiency across all DMUs while the importance of each quantitative measure is weighted. We verified the suggested model by practically evaluating 7 major companies in the Korean defense industry.

Selective atomic layer deposition of AL2O3 onto monolayer graphene

김장헌,김수현,정원석 대한기계학회 2016 대한기계학회 춘추학술대회 Vol.2016 No.5

생체 이온채널 모사용 나노채널의 유동 제어에 관한 연구

김장헌,정원석 한국기계기술학회 2015 한국기계기술학회지 Vol.17 No.6

This study presents the possibility of control of nano-fluidics in the bio-inspired nano- sized ion channel using a field effect transistor (FET) structure. We analyzed effects from main dominant factors to control the ion flow in nano-sized channel such as electro-osmosis, Diffusion effect, Coulomb force between ions and pressure force. Additionally, we suggest a strategy to control the ion flow accurately at the specific position in the nano channel by handling the viscosity, ion molecular density, pressure, gate and trans-cis voltages of FET structure.

M-추정을 사용한 국방과학기술 수준조사 기술성장모형의 이상치 제거

김장헌,Kim, Jangheon 한국군사과학기술학회 2020 한국군사과학기술학회지 Vol.23 No.1

Technology growth curve methodology is commonly used in technology forecasting. A technology growth curve represents the paths of product performance in relation to time or investment in R&D. It is a useful tool to compare the technological performances between Korea and advanced nations and to describe the inflection points, the limit of improvement of a technology and their technology innovation strategies, etc. However, the curve fitting to a set of survey data often leads to model mis-specification, biased parameter estimation and incorrect result since data through survey with experts frequently contain outlier in process of curve fitting due to the subjective response characteristics. This paper propose a method to eliminate of outlier from a technology growth curve using M-estimator. The experimental results prove the overall improvement in technology growth curves by several pilot tests using real-data in Defense Science and Technology Survey reports.

나노 다공성 멤브레인의 통과 기체 압력 패턴 및 압력 변화 패턴 분석을 통한 물질 특성 판별에 관한 연구

김장헌(Jangheon Kim),김경수(Kyung-soo Kim),김수현(Soohyun Kim) 대한기계학회 2020 大韓機械學會論文集B Vol.44 No.7

최근 배터리 분리막, 가스 분리, 항균 필터 등의 기술을 필요로 하는 산업들이 크게 발전함에 따라 우수한 관련 특성을 지닌 나노 다공성 물질이 주목을 받고 있다. 소재의 독특한 특성과 높은 산업적 활용도 덕분에 나노 다공성 물질과 관련된 많은 논문들이 발표되고 있다. 그러나 다뤄지는 나노 다공성 물질들의 특성을 비파괴적으로 빠르게 분석할 수 있는 방법은 거의 없다. 본 논문에서는 나노 다공성 멤브레인을 대기가 통과했을 시 형성되는 압력 변화 패턴을 분석하여 소재의 특성을 비파괴적이면서 고속으로 분석할 수 있는 방법을 제시한다. 대기가 나노 다공성 멤브레인을 통과할 시, 멤브레인 고유의 구조와 요소들로 인해 기체 분자의 에너지 손실이 멤브레인별로 다르게 발생한다. 이러한 기체의 에너지 손실은 압력 강하, 낮은 압력 변화치 등의 현상의 원인이 되어 결과적으로 고유의 압력 패턴을 만들어낸다. 본 논문의 결과는 대기가 멤브레인을 통과할 시 만들어지는 고유 압력 패턴을 통해 다공성 나노 소재의 특성 파악 및 물질 판별이 가능하다는 점을 제시하고 있다. Recent developments in battery membranes, gas separations, and antibacterial filters have resulted in increased attention on nanoporous materials because of their excellent related properties. Owing to their unique properties and industrial applications, numerous articles on nanoporous materials have been published. However, few methods are available to analyze nanoporous materials in a fast and nondestructive manner. In this paper, the method for the fast and nondestructive analysis of nanoporous materials is proposed using the pressure patterns generated by air passing through the membrane. When air passes through the membrane, different amounts of energy are lost per membrane because of their unique structure and properties. This energy loss causes phenomena such as pressure drops and low-pressure variations, resulting in unique pressure patterns. The results show the possibility of nanoporous membrane characterization and recognition using air pressure patterns generated by passing through the membrane.

다채널 움직임 정보를 사용한 전자광학/적외선 영상융합에 관한 연구

김장헌(Jang Heon Kim) 한국통신학회 2011 한국통신학회 학술대회논문집 Vol.2011 No.6

다시점 혼합현실 시스템을 위한 강인한 3차원 정합영역 추적기법

김장헌(Jang-heon Kim),손광훈(Kwang-hoon Sohn) 한국정보과학회 2002 한국정보과학회 학술발표논문집 Vol.29 No.2Ⅱ

다시점 영상 부호화와 함께, 가상물체를 지능형으로 합성하기 위해서는 정합할 위치를 강인하게 추적(tracking)하여야 한다. 기존의 특징추적기법은 시점이 확장된 시스템에서, 광원의 영향과 가려진 영역의 발생으로 인하여, 추적 할 수 없게 되거나 시각적 혼동 발생하는 등의 많은 문제점을 유발한다. 뿐만 아니라 다시점에 의한 정보의 급격한 증가는 시점간 움직임을 추적하여 정합하는 연산량의 추가적 발생을 초래한다. 이에 본 논문은 광원이나 가려진 영역(occlusion)의 영향이 적은 형상과 정보량이 많은 텍스쳐를 동시에 고려하여 영역의 변형에 따라 발생하는 최적 움직임을 예측하는 파라미터 모델을 결정함으로써 시각영역을 추적한다. 이 때 미리 연산된 카메라 파라미터와 투영관계를 사용해 시점간에 가성 객체를 지속적으로 3차원 정합한다. 결과적으로, 제안된 알고리즘은 기존의 특징추적 알고리즘에 비해 광원의 영향과 가려진 영역에 강인하며 정합의 오류가 적고 추적 할 때 시점간의 대응을 위한 연산을 줄이기 때문에 실감 혼합현실 시스템의 구현에 매우 효율적임을 실험을 통해 증명하였다.