Modeling and Observation of Compressive Behaviors of Closed Celullar Structures using Central Voronoi Tessellation Concepts

박상윤,이정섭,최병호,Il Hyuk Ahn,문승기 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

Numerous numerical models of mimicking cellular structures have been proposed, but, in many cases, those models were not able to describe the random cell geometry which is common for most cellular products. The concept of Voronoi tessellation has recently applied to construct the random characteristics of cell structures, but the structure generated by classical Voronoi tessellation method is too ideal by comparing with the actual cell structures. Moreover, the verification of physical and mechanical behaviors of random cell structures is scarcely researched due to the complexity of fabricating the cell structures which are numerically generated. In this study, Central Voronoi Tessellation (CVT) theory which considers the center of mass of each cell for further iteration of cell structure modification is adopted to generate realistic shape of cell structures. Some key parameters such as relative density, anisotropy, and number of iteration are considered. Mechanical behaviors of samples with numerically generated cell structures are investigated using elasto-plastic finite element analysis considering instability conditions. In addition, test samples in some cases considered in FEA are fabricated by aluminum alloy using 3-D printer based on the selective laser melting (SLM) technique, and the test results are compared with the numerical simulation results.

온라인 여행상품 고객이탈 분석 연구: 데이터마이닝 로지스틱 회귀분석 활용

박상윤 한국해양관광학회 2023 해양관광학연구 Vol.16 No.4

Data mining has been steadily developed with the development of information technology, and in particular, the development of database technologies such as data storage technology, artificial intelligence, and deep learning and big data analysis technology has provided a major factor in the development of data mining. This spread of data mining is being used not only in database-based marketing such as target marketing, customer segmentation, related analysis, and shopping cart analysis, but also in various industries such as credit rating, quality control, and fraud detection. As the application of data mining expands, the use of data mining as a tool to analyze customer information in customer relationship management (CRM), which manages interactions between companies and customers, is becoming more common. In particular, in terms of customer relationship management, the interest of all companies is 'customer departure', which is important for corporate management because the cost of securing new customers is much higher than the cost of maintaining existing customers. Therefore, this paper attempted to implement online travel customer churn prediction/classification modeling with logistic regression analysis, a data mining technique mainly used for customer CRM, based on travel agency online reservation data, and to present an efficient online travel customer marketing strategy through the results.

A Comparative Study on Bonded Repair Techniques for Aging Aircraft

박상윤,최원종,권혁,최흥섭,이상철 한국항공우주학회 2008 한국항공우주학회 학술발표회 논문집 Vol.- No.-

Correlation between the Oxide Impedance and Corrosion Behavior of Zr-Nb-Sn-Fe-Cu Alloys

박상윤,이명호,정용환,정연호 대한금속·재료학회 2004 METALS AND MATERIALS International Vol.10 No.6

The correlation between the oxide impedance and corrosion behavior of two series of Zr-Nb-Sn-Fe-Cu alloys was evaluated. Corrosion tests were performed in a 70 ppm LiOH aqueous solution at 360 oC for 300 days. The results of the corrosion tests revealed that the corrosion behavior of the alloys depended on the Nb and Sn content. The impedance characteristics for the pre- and post-transition oxide layers formed on the surface of the alloys were investigated in sulfuric acid at room temperature. From the results, a pertinent equivalent circuit model was preferably established, explaining the properties of double oxide layers. The impedance of the oxide layers correlated with the corrosion behavior; better corrosion resistance always showed higher electric resistance for the inner layers. It is thus concluded that a pertinent equivalent circuit model would be useful for evaluating the long-term corrosion behavior of Zr-Nb-Sn-Fe-Cu alloys.

Hand Gesture Recognition using Optical Flow Field Segmentation and Boundary Complexity Comparison based on Hidden Markov Models

박상윤,이응주 한국멀티미디어학회 2011 멀티미디어학회논문지 Vol.14 No.4

In this paper, we will present a method to detect human hand and recognize hand gesture. For detecting the hand region, we use the feature of human skin color and hand feature (with boundary complexity) to detect the hand region from the input image; and use algorithm of optical flow to track the hand movement. Hand gesture recognition is composed of two parts: 1. Posture recognition and 2. Motion recognition, for describing the hand posture feature, we employ the Fourier descriptor method because it’s rotation invariant. And we employ PCA method to extract the feature among gesture frames sequences. The HMM method will finally be used to recognize these feature to make a final decision of a hand gesture. Through the experiment, we can see that our proposed method can achieve 99% recognition rate at environment with simple background and no face region together, and reduce to 89.5% at the environment with complex background and with face region. These results can illustrate that the proposed algorithm can be applied as a production.

A Study on the Machining of Compressor Rotors Using Formed Tools

박상윤,Hi-Koan Lee,양균의,문상돈 한국정밀공학회 2010 International Journal of Precision Engineering and Vol. No.

In this paper it was suggested the machining method that can improve machining accuracy and reduce the machining time applying the formed tools based on the rotor shape feature to finishing machining for efficient machining of asymmetric rotors. For machining the complicated asymmetric rotor profile, machining area is divided and formed tools are manufactured based on the rotor feature., and the efficient machining method of screw motor was proposed using the formed tools and four axis machining devices. With the suggested machining method, machining time could be reduced compared to the general end mill machining method, and the machining errors of the proposed method could be within the allowable tolerance of the product so as to carry out the precise machining.

A study of dependence of dislocation density and magnetic properties on substrate temperature for laser - ablated Y₁Ba₂Cu₃O7-δ films

박상윤,박정수,V. G. Prokhorov,이영백 한국진공학회 2001 한국진공학회 학술발표회초록집 Vol.- No.-

침윤성 외음부암 및 질환

박상윤 약업신문사 2001 의약정보 Vol.2001 No.6

Effects of three - dimensional strain on the magnetic and the transport properties of epitaxial CMR bilayered films

박상윤,홍범수,조광환,이영백,V. G. Prokhorov 한국진공학회 2004 한국진공학회 학술발표회초록집 Vol.- No.-

한국산 감자바이러스병에 관하여

박상윤,소인영 한국미생물학회 1965 미생물학회지 Vol.3 No.2

The potato viruses, as possible potato virus X(PVX), potato virus Y(PVY), potato virus S(PVS) are isolated from potato tuber, which collected from eleven areas (Table 1) in Korea. These viruses are isolated by single lesion isolation, Aphid transmission and inoculating methods through the many species of the different plants. The PVX is identified by host range, symptoms, physical properties, serological reaction and electron micrography. The other two viruses are identified by the first two methods mentioned above. The results of the above experiments are as follows. The total value of these viruses infection is 81%. The value of PVX infection is higher than the other two viruses. The properties of PVX are marked as local lesions on Comphrena globosa. The dilution end point is $10^{-6}$, the thermal inactivation point is $70^{\circ}C$ and the size of virus particles is around 13 x 60 $m\mu$.