• Journal of the Korean Society for Precision Engineering
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• v.33 no.1
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• pp.77-83
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• 2016

Intricate deflection requires many conventional actuators (motors, pistons etc.), which can be financially and spatially wasteful. Novel smart soft composite (SSC) actuators have been suggested, but fabrication complexity restricts their widespread use as general-purpose actuators. In this study, a hybrid manufacturing process comprising 3-D printing and casting was developed for automated fabrication of SSC actuators with $200{\mu}m$ precision, using a 3-D printer (3DISON, ROKIT), a simple polymer mixer, and a compressor controller. A method to improve precision is suggested, and the design compensates for deposition and backlash errors (maximum, $170{\mu}m$). A suitable flow rate and tool path are suggested for the polymer casting process. The equipment and process costs proposed here are lower than those of existing 3D printers for a multi-material deposition system and the technique has $200{\mu}m$ precision, which is suitable for fabrication of SSC actuators.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.1
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• pp.523-549
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• 2018

The increasing number of subscribers and demand of multiplicity of services has turned Multi-Server Authentication (MSA) into an integral part of remote authentication paradigm. MSA not only offers an efficient mode to register the users by engaging a trusted third party (Registration Centre), but also a cost-effective architecture for service procurement, onwards. Recently, Lu et al.'s scheme demonstrated that Mishra et al.'s scheme is unguarded to perfect forward secrecy compromise, server masquerading, and forgery attacks, and presented a better scheme. However, we discovered that Lu et al.'s scheme is still susceptible to malicious insider attack and non-compliant to perfect forward secrecy. This study presents a critical review on Lu et al.'s scheme and then proposes a secure multi-server authentication scheme. The security properties of contributed work are validated with automated Proverif tool and proved under formal security analysis.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.4
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• pp.5-11
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• 2001

Vibration and noise of gears is doc to the transmission error and the vibration exciting force caused by the periodically alternating tooth stiffness. Transmission error is the rotation delay between driving and driven gear caused by manufacturing error, alignment error in assembly and so on. Tooth stiffness changes with the proceeding mesh of teeth. The purpose of this study is to develop how to calculate simultaneously the optimum amounts of tooth profile modification. end relief and crowning by minimizing the vibration exciting force of helical gears. We estimate the vibration exciting force by the meshing analysis of gears. Formulated constraints of this problem consist of contact ratio and strengths of gear teeth such as tooth bending strength, surface durability, and scoring. ADS(Automated Design Synthesis) is used as an optimization tool. We also investigate the relation between the aspect ratio and the optimum values of tooth modification. The proposed method can calculate the optimum amount of tooth modification automatically and is expected to be practically useful to resolve the problem of vibration of helical gears.

• Journal of Industrial Technology
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• v.19
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• pp.155-162
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• 1999

In the last few years the automatic classification of morpholgical landforms using GSIS and DEM was investigated. Particular emphasis has been put on the morphological point attribute approaches and the extraction of drainage basin variables from digital elevation models. The automated derivation of landforms has become a neccessity for quantitative analysis in geomorphology. Furthermore, the application of GSIS technologies has become an important tool for data management and numerical data analysis for purpose of geomorphological mapping. A process developed by Dikau et al, which automates Hanmond's manual process, was applied to the pyoung chang of the kangwon. Although it produced a classification that has good resemblance to the landforms in the area, it had some problems. For example, it produced a progressive zonation when landform changes from plains to mountains, it does not distinguish open valleys from a plains mountain interface, and it was affected by micro relief. Although automating existing quantitative manual processes is an important step in the evolution automation, definition may need to be calibrated since the attributes are oftem measured differently. A new process is presented that partly solves these problems.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.12
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• pp.2247-2250
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• 2007

This paper presents an automated API translator for embedded software development based on a model-driven approach. Since MDA(Model Driven Architecture) provides little support for the development of embedded software, we propose a new approach containing its advantages. First, we define #generic APIs# which do not depend on any RTOS#s but provide most of typical RTOS services. We can describe RTOS-related behaviors of target application using these generic APIs in a CIC(Common Intermediate Code). Then, we propose a transformation tool for translating between a CIC using generic APIs and a C-code for specific RTOS. The proposed API translator converts them using XML transformation rule which is defined outside. It indicates that an API translator extends to other RTOS#s by modifying or adding the transformation rule. From the experiment. we validate the proposed method.

• Structural Monitoring and Maintenance
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• v.1 no.1
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• pp.111-130
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• 2014

The increased use of carbon fiber reinforced polymer (CFRP) in retrofitting reinforced concrete (RC) members has led to the need to develop non-destructive techniques that can monitor and characterize the unique damage mechanisms exhibited by such structural systems. This paper presented the damage characterization results of six CFRP retrofitted RC beam specimens tested in the laboratory and monitored using acoustic emission (AE). The focus of this study was to continuously monitor the change in AE parameters and analyze them both qualitatively and quantitatively, when brittle failure modes such as debonding occur in these beams. Although deterioration of structural integrity was traceable and can be quantified by monitoring the AE data, individual failure mode characteristics could not be identified due to the complexity of the system failure modes. In all, AE was an effective non-destructive monitoring tool that can trace the failure progression in RC beams retrofitted with CFRP. It would be advantageous to isolate signals originating from the CFRP and concrete, leading to a more clear understanding of the progression of the brittle damage mechanism involved in such a structural system. For practical applications, future studies should focus on spectral analysis of AE data from broadband sensors and automated pattern recognition tools to classify and better correlate AE parameters to failure modes observed.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.139-142
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• 2003

As composite materials are gaining wide acceptance in aircraft structure, repair of damaged composite is becoming an important issue. The issues in composite repair include high cost, material interchangeability, water ingression, and structural integrity. To address these problems, researchers have studied on the composite repair in various aspects. In this paper, an Internet-based advisory service (called Repair Advisory Service, RAS) for composite repair is proposed to increase efficiency for repair process. In the RAS system the web browser is used as its user interface, which provides easy access to the service. The RAS server provides web-based tools for failure prediction, Structural Repair Manual (SRM), automated prepreg cutting process, material properties, inventory and knowledge base. The computer codes implemented for repair design estimate the tensile failure and shear failure of repaired structures. The prediction of failure is based on the maximum strain criterion for tensile failure while elastic-perfect plastic shear failure model is applied for interfacial failure. The OEM's SRM is provided in the PDF format for viewing and searching by web browsers instead of looking up paper version SRM. The knowledge base in this site offers a room to share and distribute ideas, memos, publications, or suggestions from the repair engineers. The fabrication tool of RAS reads repair geometry from engineers then generates a CNC toolpath to cut prepreg patches. The RAS service is open to public and available at http://nano.gsnu.ac.kr/. Broad feedback from field technicians and engineers is welcome to improve the usefulness of RAS.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.63-69
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• 2017

The golden section search method is widely used to optimize a single design variable in many fields due to its superior advantages of search. In this paper, a new direct search method is proposed by modifying the search structure of the golden section search method; thus, it can be adapted in the optimization of a single design variable for the injection molding process. This proposed method is applied to determine an optimal gate position for the injection molding of a bezel of an automated teller machine for minimizing the injection pressure. Thus, an optimal gate position where the injection pressure is decreased by 4.5 MPa to that of the initial position was obtained with a small number of simulations. It is anticipated that the current proposed search method can be utilized as a practical tool for optimizing single variables for injection molding design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.5
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• pp.514-520
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• 2009

In configuring an automated polishing system, a monitoring scheme to estimate the surface roughness is necessary. In this study, a precision polishing process, magnetic abrasive finishing (MAF), along with an in-process monitoring setup was investigated. A magnetic tooling is connected to a CNC machining to polish the surface of stavax(S136) die steel workpieces. During finishing experiments, both AE signals and force signals were sampled and analysed. The finishing results show that MAF has nano scale finishing capability (upto 8nm in surface roughness) and the sensor signals have strong correlations with the parameters such as gap between the tool and workpiece, feed rate and abrasive size. In addition, the signals were utilized as the input parameters of artificial neural networks to predict generated surface roughness. Among the three networks constructed -AE rms input, force input, AE+force input- the ANN with sensor fusion (AE+force) produced most stable results. From above, it has been shown that the proposed sensor fusion scheme is appropriate for the monitoring and prediction of the nano scale precision finishing process.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3371-3396
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• 2016

Authentication protocols for multi-server architectures have gained momentum in recent times due to advancements in computing technologies and associated constraints. Lu et al. recently proposed a biometrics and smartcards-based authentication scheme for multi-server environment. The careful analysis of this paper demonstrates Lu et al.'s protocol is susceptible to user impersonation attacks and comprises insufficient data. In addition, this paper proposes an improved authentication with key-agreement protocol for multi-server architecture based on biometrics and smartcards. The formal security of the proposed protocol is verified using the widely accepted AVISPA (Automated Validation of Internet Security Protocols and Applications) tool to ensure that our protocol can withstand active and passive attacks. The formal and informal security analysis, and performance analysis sections determines that our protocol is robust and efficient compared to Lu et al.'s protocol and existing similar protocols.