• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.9
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• pp.44-51
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• 2019

Three types of samples with defects were measured by lock-in med-IR (infrared) thermography with various lock-in frequencies for different materials. The lock-in method can be used to detect defects when an external energy source is applied to the object, the non-uniformity of the incident thermal energy distribution is eliminated, and the camera's measurement cycle is synchronized with the load cycle of the incident energy source. For inspecting samples with defects, results of thermal images are analyzed when three types of materials, i.e., SM45C, STS316L, and AL6061 are tested and three lock-in frequencies, i.e., 0.08, 0.1, and 0.12 Hz are applied. In this study, the optimal lock-in frequencies were determined by comparing the results of each material and lock-in frequency measured using the mid-IR camera.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.173-176
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• 2007

The characteristics of the tool system give many effects into the costs and qualities for the finished components. This study proposes a new method for manufacturing of high manufacturing productivity, production process reduction and low cost through back pressure forming. The Lock-up hub is manufactured through many processes, such as upsetting($1^{st}$ Forming), piercing, direct extrusion($2^{nd}$ Forming), final sizing process($3^{rd}$ Forming). In this study, process design for closed-die forging of a Lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of Lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

• 전기의세계
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• v.22 no.1
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• pp.42-51
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• 1973

The contriving equivalent circuit of single phase induction motor which does not separate the primary leakage reactance and the secondary leakage reactance by the revolving field theory, and the graphically calculating method of the characteristics with T-type circle diagram of three phase induction motor which does not suppose the primary leakage reactance can be drawn up only by the no load test, the lock test, and measuring the resistance of stator winding are suggested in this paper. The method which can calculate the parameters of the equivalent circuit and the characteristics with no load test, lock test and measuring resistance of stator windings is suggested in this paper. Considered the exciting current in lock test, we could calculate very accurate characteristics of the single phase induction motor.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.560-563
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• 2015

Door lock system is used for the conventional method by using a key or a card, a pad Replication, loss, and the risk of damage, and has a problem that exposure to others. In this paper, Bluetooth communication and OTP built into smartphones in order to complement the existing door lock system problems OTP(One-Time-Password), Hide-Key utilizing the authentication method and the Arduino smartphone-based design of wireless OTP door lock system by enabling users it allows for more convenient and safe life free from the risk of theft and robbery.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.331-332
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• 2022

The previously used locking device is a PIN method and has a problem in that the password is exposed by malicious users. In other words, if attackers looks at lock passwords from the side, correct passwords are known. In this paper, we aim to solve these security problems in lock devices resistant to shoulder surfing attacks. The proposed encryption approach is designed so that attackers cannot know lock passwords. To this end, we use a hidden password method instead of directly entering a PIN-type password to prevent the correct password from being exposed to an attacker even if someone steals the lock password.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.4
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• pp.1865-1870
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• 2014

Torque converter is a complex turbomachine used to transfer power smoothly from an engine to a transmission by lock-up clutch. A torque converter consists of the hydrodynamic clutch device and the lock-up clutch device. The retaining plate and driven plate are part of the lock-up clutch. The lock-up clutch connects directly to achieve the improvement of efficiency and fuel consumption. In this paper, using structure analysis of stress distribution on the shape of the mechanical stopper on retaining plate. The shape of mechanical stopper has effect on the stress distribution of lock-up clutch.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.133-134
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• 2023

In general, all buildings are equipped with various types of handles for opening and closing the door, and unlike wooden doors, steel doors such as fire doors are equipped with a box-shaped door lock box frame surrounding the outside of the door lock to protect the door lock, which is called a cylinder protection cover. These cylinder protection covers have various types and types of fastening structures, and the cylinder protection covers on the market are molded in factories and standardized according to the size and shape of the door lock, requiring various types of cylinder protection covers. Accordingly, a variable cylinder protection cover with a simple prefabricated structure that can fundamentally solve these problems can be used as one cylinder protection cover regardless of the type, shape, and size of the door lock.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.6
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• pp.539-544
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• 2020

The research is on progressing to operate digital door lock with the method to guarantee the security and safety in the meantime to use digital door lock conveniently using Internet of Things (IoT) standardizing various service providing technology using IoT in home network currently. In this study, compose home network interconnecting Raspberry-PI and web server reflection this trend and composed the system to control the door lock after connect Arduino substituting converter function. Making Raspberry-PI using dynamic IP address using existing open source easily maintain DNS information and possible to connect internet network in home network ethernet and finally, making the smartphone can control door lock remotely entering designated address after connect the internet. The connection between home network and Arduino is executed by Raspberry-PI and bluetooth pairing as 1:1 and make random user's access to be impossible. Especially, to make open/close the door lock with smartphone not by using password on the keypad or using RFID card is judged as the method increasing the security make random user's access to be impossible and also increased the usefulness making remote control to be possible.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.2
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• pp.91-97
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• 2010

This paper proposes method to evaluate the location and size of the internal defects of metallic specimens by the shearing phase lock-in infrared thermography. Until now, infrared thermography test for metal specimen of STS304 and Cu-Zn were conducted to find the best test conditions. However, In unspecified situation of the form and existence of defects, there was a disadvantage to takes a long time for finding the optimal experimental conditions. The defect detection and evaluation was performed at 60 MHz signal using lock-in and shearing-phase method under limited heating conditions. By shearing-phase distribution method, Defects for the maximum, minimum and zero points were quantitatively detected at the size and location of the subsurface. As results, application of the proposed technique was verified for STS304 and Cu7-Zn3 with artificial defect and factors affected defect evaluation were searched and analyzed.

• International Journal of Automotive Technology
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• v.8 no.5
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• pp.599-603
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• 2007

An efficient optimum design process has been developed and applied to systematically design a lock-up clutch system for a torque converter used in an automatic transmission. A simulated annealing algorithm was applied to determine the parameters of the compressive helical damper springs in the clutch. The determination of the number, location, a number of turns, and deflection of damper springs plays an important role in reducing vibration and noise in the lock-up system. Next, FE-based shape optimization was coded to find the shape of the clutch disk that would satisfy the strength, noise and vibration requirements. Using the optimum code, parametric studies were performed to see how spring diameters and frequencies of clutch systems changed as the damper spring traveling angles and the torques were varied. Based on the optimum results, five different designs for clutches with different springs were fabricated and vibration analyses and tests were conducted to validate the accuracy of the proposed method. Results from the two methods show a good correlation.