• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.21 no.2
• /
• pp.349-353
• /
• 2012

As the world wind energy market grows rapidly, the productions of wind power generation equipment have recently increased, but manufacturers are not able meet this requirement. Particularly offshore wind energy industry is one of the most popular renewable energy sectors. To generalize welding processes, the welding automation is considered for steel structure manufacturing in offshore wind energy to get high quality and productivity. Welding technology in construction of the wind towers is depended on progress productivity. In addition, the life of wind tower structures should be considered by taking account of the natural weathering and the load it endures. The root passes are typically deposited using Gas Tungsten Arc Welding(GTAW) with a specialized backing gas shield. Not only the validation consists of welders experienced in determining the welding productivity of the baseline welding procedure, but also the standard testing required by the ASME section IX and API1104 codes, toughness testing was performed on the completed field welds. This paper presents the welding characteristics of the root-pass welding of high tensile steel in manufacturing of offshore wind tower. Based on the result from welding experiments, optimal welding conditions were selected after analyzing correlation between welding parameters(peak current, background current and wire feed rate) and back-bead geometry such as back-bead width(mm) and back-bead height performing root-pass welding experiment under various conditions. Furthermore, a response surface approach has been applied to provide an algorithm to predict an optimal welding quality.

• The KIPS Transactions:PartC
• /
• v.11C no.5
• /
• pp.595-604
• /
• 2004

By the help of expansion of computer network and rapid growth of Internet, the information infrastructure is now able to provide a wide range of services. Especially open architecture - the inherent nature of Internet - has not only got in the way of offering QoS service, managing networks, but also made the users vulnerable to both the threat of backing and the issue of information leak. Thus, people recognized the importance of both taking active, prompt and real-time action against intrusion threat, and at the same time, analyzing the similar patterns of in-trusion already known. There are now many researches underway on Intrusion Detection System(IDS). The paper carries research on the in-trusion detection system which hired supervised learning algorithm and Fuzzy membership function especially with Neuro-Fuzzy model in order to improve its performance. It modifies tansigmoid transfer function of Neural Networks into fuzzy membership function, so that it can reduce the uncertainty of anomaly intrusion detection. Finally, the fuzzy logic suggested here has been applied to a network-based anomaly intrusion detection system, tested against intrusion data offered by DARPA 2000 Intrusion Data Sets, and proven that it overcomes the shortcomings that Anomaly Intrusion Detection usually has.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2011.01a
• /
• pp.107-108
• /
• 2011

Since the development of railway technology, the current urban Railway the first train line in the country for safe operation control automatic/unattended operation, automatic train operation equipment available (ATO) on time and reliable operation has introduced. ATO Automatic operation controlled by the value (Target velocity) and the feedback value (Actual velocity) by the error between the backing and braking of the train by repeated low energy efficiency. In this paper, given a fixed distance stations between time operation with minimal energy in the driving characteristics and driving trains are modeled. Therefore, in line 5 real route time sectional drive straight sections for experimental data analysis / draft Section / curved and section of the train on that line is selected according to the changing driving patterns to minimize the energy optimal driving patterns were presented.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.28 no.9
• /
• pp.749-755
• /
• 2017

In this paper, a wideband microwave absorber for X-band(8~12 GHz) applications is proposed. The structure of the proposed absorber unit cell consists of a resonator with a slot and slit, a backing ground plate, and a Taconic RF-30(${\varepsilon}_r=3$, $tan{\delta}=0.0014$) substrate with a dimension of $8.5{\times}8.5{\times}0.5mm^3$. The proposed absorber has a dual resonance at 9.83 and 10.37 GHz. To demonstrate the operating principle of the proposed absorber structure at each resonance frequency, the simulated current distributions on the unit cell are analyzed. To verify the performance of the proposed absorber, a prototype absorber was fabricated with a planar array of $20{\times}20$ unit cells. The measured results exhibit two absorptivity peaks stronger than 99 % and full-width at half-maximum(FWHM) bandwidth of 1.1 GHz(9.51~10.61 GHz).

• The KIPS Transactions:PartD
• /
• v.12D no.1 s.97
• /
• pp.91-102
• /
• 2005

In the past it was generally felt that software quality was the same as product quality. But as the software industry is getting bigger and more complex, it has become hard to develop quality software that meets customers' needs just depending on product quality. Therefore, lately many domestic and foreign companies are making efforts to upgrade product quality by implementing Process Improvement. Measurement in Process Improvement activities enhances the effect of Process Improvement, and also identifies and helps the activities. In support of this paper, research on the measurement program was conducted based on the CMMI adopted by many domestic and foreign companies for their process improvement model. MA process area that deals with measurement process setup is one of the CMMI process areas and was the basis of the structure of the measurement program. This study presents differences of the measurement program for each level of CMMI and how to apply it. The results of this study can help a business to apply CMMI-based Process Improvement by backing up the structure of the measurement program. Furthermore, it can offer a roadmap for progress of the measurement program for each level.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.50-53
• /
• 2003

CMP (chemical mechanical polishing) process remained to solve several problems in deep sub-micron integrated circuit manufacturing process. especially consumables (polishing pad, backing film, slurry, pad conditioner), one of the most important components in the CMP system is the slurry. Among the composition of slurries (buffer solution, bulk solution, abrasive particle, oxidizer, inhibitor, suspension, antifoaming agent, dispersion agent), the abrasive particles are important in determining polish rate and planarization ability of a CMP process. However, the cost of abrasives is still very high. So, in order to reduce the high COO (cost of ownership) and COC (cost of consumables) in this paper, we have collected the silica abrasive powders by filtering after subsequent CMP process for the purpose of abrasive particle recycling. And then, we have studied the possibility of recycle of reused silica abrasive through the analysis of particle size and hardness. Also, we annealed the collected abrasive powders to promote the mechanical strength of reduced abrasion force. Finally, we compared the CMP characteristics between self-developed KOH-based silica abrasive slurry and original slurry. As our experimental results, we obtained the comparable removal rate and good planarity with commercial products. Consequently, we can expect the saving of high cost slurry.

• Tribology and Lubricants
• /
• v.33 no.1
• /
• pp.9-14
• /
• 2017

This paper presents a rotordynamic analysis and the operation of a power turbine applied to a 250 kW super-critical $CO_2$ cycle. The power turbine consists of a turbine wheel and a shaft supported by two fluid film bearings. We use a tilting pad bearing for the power turbine owing to the high speed operation, and employ copper backing pads to improve the thermal management of the bearing. We conduct a rotordynamic analysis based on the design parameters of the power turbine. The dynamic coefficients of the tilting pad bearings were calculated based on the iso-thermal lubrication theory and turbine wheel was modeled as equivalent inertia. The predicted Cambell diagram showed that there are two critical speeds, namely the conical and bending critical speeds under the rated speed. However, the unbalance response prediction showed that vibration levels are controlled within 10 mm for all speed ranges owing to the high damping ratio of the modes. Additionally, the predicted logarithmic decrement indicates that there is no unstable mode. The power turbine uses compressed air at a temperature of $250^{\circ}C$ in its operation, and we monitor the shaft vibration and temperature of the lubricant during the test. In the steady state, we record a temperature rise of $40^{\circ}C$ between the inlet and outlet lubricant and the measured shaft vibration shows good agreement with the prediction.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.10
• /
• pp.1514-1519
• /
• 2001

This paper is concerned with design, manufacturing and performance test of LIPCA ( Lightweight Piezo- composite Curved Actuator) using a top carbon fiber composite layer with near -zero CTE(coefficient of thermal expansion), a middle PZT ceramic wafer and a bottom glass/epoxy layer with high CTE. The main point of this design is to replace the heavy metal layers of THUNDER by thigh tweight fiber reinforced plastic layers without losing capabilities to generate high force and large displacement. It is possible to save weight up to about 30% if we replace the metallic backing material by the light fiber composite layer. We can also have design flexibility by selecting the fiber direction and the size of prepreg layers. In addition to the lightweight advantage and design flexibility, the proposed device can be manufactured without adhesive layers when we use epoxy resin prepreg system. Glass/epoxy prepregs, a ceramic wafer with electrode surfaces, and a graphite/epoxy prepreg were simply stacked and cured at an elevated temperature (177 $^{circ}C$ after following an autoclave bagging process. It was found that the manufactured composite laminate device had a sufficient curvature after detached from a flat mold. The analysis method of the cure curvature of LIPCA using the classical lamination theory is presented. The predicted curvatures are fairly in agreement with the experimental ones. In order to investigate the merits of LIPCA, a performance test of both LIPCA and THUNDE$^{TM}$ were conducted under the same boundary conditions. From the experimental actuation tests, it was observed that the developed actuator could generate larger actuation displacement than THUNDERT$^{TM}$.

• School Mathematics
• /
• v.18 no.1
• /
• pp.85-103
• /
• 2016

This study was to find characteristics of argumentation derived from a discourse in a math-gifted 5 grade class, which was held for finding a Pick's formula using Geoboard function of TI-73 calculator. For the analysis, a video record of the class, transcript of its voice record, and activity paper were used as data and Toulmin's argument schemes were applied as analysis standard. As a result of the study, we found that the graphing calculator helped the students to create an experimental environment that graphing a grid-polygon and figuring out its area. Furthermore, it also provided a basic demonstration through 'data->claim' composition and reasoning activities which consisted of guarantee, warrant, backing, qualifier and refutal for justifying. The basic argumentation during the process of deriving the Pick's theorem by the numbers of boundary points and inner points was developed into a 'collective argumentation' while a teacher took a role of a conductor of the argumentation and an authorizer on the knowledge at the same time.

• The Journal of the Korea Contents Association
• /
• v.19 no.12
• /
• pp.313-320
• /
• 2019

One of the causes of many damage cases that occur today by hacking attack is social engineering attack. The attacker is usually a malicious traitor or an ignorant insider. As a solution, we are strengthening security training for all employees in the organization. Nevertheless, there are frequent situations in which computers are shared. In this case, the person in charge of the computer has difficulty in tracking and responding when a specific representative accessed and what a specific representative did. In this paper, we propose the method that the person in charge of the computer tracks in real time through the smartphone when a representative access the computer, when a representative access offline using hacked or shared authentication. Also, we propose a method to prevent the leakage of important information by encrypting and backing up important files of the PC through the smartphone in case of abnormal access.