http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
박기석,이덕호 한국학교수학회 1998 韓國學校數學會論文集 Vol.1 No.1
We proposed the teaching method about the logical inference in highschool using Logic Network. This method that we proposed is better than Vendiagram method because that is able to represent the more conditions in plane. The contents of this paper explained the method that conclusion is drived from given conditions using Logic Network. And we gave some examples of the process of logical inference.
3차원 분자 모델을 사용한 재료내의 저장 에너지 계산에 관한 연구
최덕기,유한규 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.5
This paper addresses a theoretical approach to calculate the amount of the stored energy during a deformation using atomistic level simulation. During a deformation, only a small percent of the energy input is stored in the material, and most of input energy is converted into heat. The cause of the temperature rise within materials is traditionally credited to dislocations, vacancies and other defects. An atomistic material model for fcc such as copper is used to calculated the stored elastic energy. The potential energy is obtained by a molecular dynamics (MD) simulation. Two different states are considered for comparison: one is a perfect state and the other is a state with dislocations. The calculated potential energies in these two states are compared. The difference in the potential energies is considered the amount of the stored elastic energy of dislocations. The conversion factor, i.e., the fraction of the input energy that is stored as elastic energy within a material is then calculated. (Received December 22, 2003)
변형률 에너지 밀도 이론을 사용한 3차원 균열 진전각 계산에 관한 연구
최덕기,이상진 단국대학교 2001 산업기술연구 Vol.2 No.-
It is not uncommon to see a fracture of material by loading, force, or natural environment. Scholars have paid a good attention to fracture mechanics to predict the fracture of materials, and researched a number of fracture theories. These theories, however, can not predict where crack propagation angles extendunder mixed mode.
서미자,안수정,박덕기,윤영남 충남대학교 농업과학연구소 1997 농업과학연구 Vol.24 No.1
For the investigation of occurrence of insect pests and their natural enemies, total number of 353 controlled agricultural farms were visited and surveyed. In the 73% of total controlled agricultural farms, 52 species insect pests were occurred. Among these pests, the western flower thrip (Frankliniella occidentalis), the two spotted spider mite (Tetranychus urticae), the greenhouse whitefly (Trialeurodes vaporariorum), the cotton aphid (Aphis gossypii) and the green peach aphid (Myzus persicae) were mainly occurred. On the other hand, small numbers of natural enemies were sustained in 40 controlled agricultural farms, which was 11% and 17% of visited farms and pest occurred farms, respectively. For the most part of collected natural enemies, there were included in Braconid, Coccinellid and Anthocorid, as 63, 20 and 8% of them, respectively.
( Deok Kee Choi ),( Han Kyu Ryu ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 METALS AND MATERIALS International Vol.12 No.4
Materials generate heat due to plastic work. The resultant temperature rise can be significant, changing the properties of the material in many aspects during high-strain-rate deformation. The deformation process can be assumed to be adiabatic, and hence the heat generated remains within the material. It is well known from experiments that only a small percent of the energy input is stored in the material, and most of the input energy is converted into heat. The temperature rise within materials is traditionally credited to dislocations, vacancies, and other defects. It is, however, difficult to explain the phenomenon using macroscopic material models. In the present study, an fcc crystal structure is used for atomistic material simulations. The energy calculation is performed by a molecular dynamics (MD) simulation, using the Lennard-Jones potential. The main purpose of the paper is to evaluate the role of dislocations in the temperature rise during high-strain-rate deformation. To this end, two different atomistic models are used: a perfect model that has no dislocations, and another model that includes the dislocations` movements. Comparison of the potential energy calculated from the two models confirms that dislocations play an important role in raising the heat during high-strain-rate deformation.
Motion Tracking of Four-Wheeled Mobile Robots in Outdoor Environments Using Bayes’ Filters
Deok-Kee Choi 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.5
The demand for outdoor wheeled mobile robots (WMRs) is rapidly growing to assist humans in outdoor environments such as transportation, exploration, rescue, security, agriculture, military, etc. To effectively control outdoor WMRs, we need motion models applicable in such unknown environments. Conventional modeling mainly concerns physics laws or equations of motion, such as kinematics, dynamics, terrains, and wheel-ground interactions. Modeling WMRs on unstructured ground is more complicated than in a well-developed indoor environment. To alleviate such difficulties, we looked at a data-driven approach instead. We built a four-wheeled mobile robot with wheel encoders installed, with which the forward and inverse differential kinematic solutions were derived. Then, we performed more than a thousand test runs in outdoor environments, having the robot run on normal, icy, and sandy roads, including test runs under constraints partially blocked by brick and grid-type holes. We employed Bayes’ filter because the robot’s tri-variate states (two linear velocities and the rotation) are not directly measurable through wheel encoders. With such uncertainty, Bayes’ filtering technique of the Kalman filter and a newly developed unscented Kalman filter were applied to infer how each wheel’s speed affects the robot’s velocity. We established a probabilistic motion model, where the differential kinematic solutions are combined with uncertainty from outdoor environments. Consequently, we could closely track the robot’s motion. This modeling technique can be used to develop better outdoor WMRs.
PC Cluster를 사용한 나노 재료 모사에 관한 연구
최덕기(Deok-Kee Choi),류한규(Han-Kyu Ryu) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Not a few scientists have paid attention to application of molecular dynamics to chemistry, biology and physics. With recent popularity of nano technology, nano-scale analysis has become a major subject in various engineering fields. A underlying nano scale analysis is based on classical molecular theories representing molecular dynamics. Based on Newton's law of motions of particles, the movement of each particles is to be determined by numerical integrations. As the size of computation is closely related with the number of molecules, materials simulation takes up huge amount of computer resources so that it is not until recent days that the application of molecular dynamics to materials simulations draw some attention from many researchers. Thanks to high-performance computers, materials simulation via molecular dynamics looks promising. In this study, a PC cluster consisting of multiple commodity PCs is established and nano scale materials simulations are carried out. Micro-sized crack propagation inside a nano material is displayed by the simulation.