• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.09a
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• pp.35-40
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• 2005

The demand for small and high-capacity optical data storage devices has rapidly increased. The areal density of optical disk is increased using higher numerical aperture objective lens and shorter wavelength source. A wafer-scale stacked micro objective lens with a numerical aperture of 0.85 and a focal length of 0.467mm for the 405nm blue- violet laser was designed and fabricated. A diffractive optical element (DOE) was used to compensate the spherical aberration of the objective lens. Among the various fabrication methods for micro DOE, the UV-replication process is more suitable for mass-production. In this study, an 8-stepped DOE pattern as a master was fabricated by photolithography and reactive ion etching process. A flexible mold was fabricated for improving the releasing properties and shape accuracy in UV-molding process. In the replication process, the effects of exposing time and applied pressure on the replication quality were analyzed. Finally, the shapes of master, mold and molded pattern were measured by optical scanning profiler. The deviation between the master and the molded DOE was less than 0.1um. The efficiency of the molded DOE was measured by DOE efficiency measurement system which consists of laser source, sample holder, aperture and optical power meter, and the measured value was $84.5\%$.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.3
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• pp.427-438
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• 2012

The SCADA(Supervisory Control and Data Acquisition) systems are used to control some critical national infrastructures such as electricity, gas, and water distribution systems. Recently, there are many researches on key management scheme for secure communication due to change to the open network environment. We propose a new key management method which is established on ID-based cryptosystem using pairing on MTU(Master Terminal Unit), Sub-MTU, and RTU(Remote Terminal Unit). Furthermore, we present a redistribution protocol of private key of each device and a system recovery protocol as a countermeasure of exposure of KMS(Key Management System) master key which is occurred by some unexpected accidents or malicious attacks.

• The Journal of Advanced Prosthodontics
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• v.4 no.4
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• pp.227-234
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• 2012

PURPOSE. The aims of this pilot study were to introduce implant loading devices designed for animal study and to evaluate the validity of the load transmission ability of the loading devices. MATERIALS AND METHODS. Implant loading devices were specially designed and fabricated with two implant abutments and cast metal bars, and orthodontic expansion screw. In six Beagles, all premolars were extracted and two implants were placed in each side of the mandibles. The loading device was inserted two weeks after the implant placement. According to the loading protocol, the load was applied to the implants with different time and method, simulating early, progressive, and delayed loading. The implants were clinically evaluated and the loading devices were removed and replaced to the master cast, followed by stress-strain analysis. Descriptive statistics of remained strain (${\mu}{\varepsilon}$) was evaluated after repeating three cycles of the loading device activation. Statistic analysis was performed using nonparametric, independent t-test with 5% significance level and Friedman's test was also used for verification. RESULTS. The loading devices were in good action. However, four implants in three Beagles showed loss of osseointegration. In stress-strain analysis, loading devices showed similar amount of increase in the remained strain after applying 1-unit load for three times. CONCLUSION. Specialized design of the implant loading device was introduced. The loading device applied similar amount of loads near the implant after each 1-unit loading. However, the direction of the loads was not parallel to the long axis of the implants as predicted before the study.

• Journal of dental hygiene science
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• v.23 no.2
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• pp.176-184
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• 2023

Background: Recently, a piezoelectric ultrasonic scaler based on a feedback control mechanism was introduced for pain relief. This study aimed to investigate the effects of a new ultrasonic scaler in reducing pain and discomfort in adults. Methods: A newly introduced ultrasonic scaler (Master 700^®) was used as the test device and a conventional ultrasonic scaler device (PIEZON^®) was used as the control device. Forty-one healthy adults visited the dental clinic for dental scaling but did not undergo scaling or periodontal treatment within 6 months. Intraoral examinations were performed before scaling and 3 months later; before scaling, both devices were randomly assigned on the left or right side of each dentition (split-mouth model) and scaling was performed by a registered dental hygienist. The levels of pain and discomfort during scaling were evaluated subjectively and objectively using the visual analog scale (VAS) and physiological monitoring of the heart rate (HR), respectively. Time was measured for each device. Results: All clinical indicators, except bleeding on probing, significantly improved with both devices. The treatment times were 7 minutes, 13 minutes (control) and 6 minutes, 59 minutes (test). VAS scores for pain were 4.89±2.12 (control) and 4.58±2.77 (test) points out of 10; for noise, these were 4.68±2.33 (control) and 4.55±2.55 (test), and for vibration, the values were 4.26±2.0 (control) and 4.18±2.48 (test). HR averages were 72.34±3.39 (control) and 75.97±9.78 (test) beats/min. No statistically significant differences were observed between the devices. Conclusion:The pain, discomfort levels, and scaling time of the new piezoelectric ultrasonic scaler did not differ from those of the conventional device. Further research and development are necessary for more prominent pain-relief effects of scaling devices.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.28 no.5
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• pp.1047-1057
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• 2018

As the number of services offered on the Internet exponentially increases, password managers are increasing popular applications that store several passwords in an encrypted database (or password vault). Browser-integrated password managers or locally-installed password managers store the password vault on the user's device. Although a web-based password manager stores the password vault on the cloud server, a user can store the master password used to sign in the cloud server on her device. An attacker that steals a user's encrypted vault stored in the victim's device can make an offline attack and, if successful, all the passwords in the vault will be exposed to the attacker. This paper investigates the vulnerability of the password vault stored in the device and develops attack programs to verify the vulnerability of the password vault.

• Tunnel and Underground Space
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• v.32 no.3
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• pp.194-202
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• 2022

An increased number of cases have occurred in applying ICT technology in the resource development field due to factors such as safety, eco-friendliness, and low cost since the 2000s. In Korea, the 2nd mining master plan specified the significance of converging the full cycle of mining and ICT, while the 3rd mining master plan highlighted ICT and smart mining such as supporting the supply of an ICT mining device and introducing demonstrational smart mining. This study introduces the application of an ICT device and safety system operation in the Jangseong underground mine of Korea Cement Co., Ltd. Currently, Jangseong mine combines two different kinds of 3D equipment including the handheld 3D scanner and multi-station that provides both the measurement and 3D scanning to perform a 3D measurement of the mine. Taken from the 3D measurement of the mine, it is now possible to identify any hazardous areas and abnormalities in different directions and analyze the safety of the crown pillar between two stopes in different level. Besides, the real-time location tracking and communications system have established highly efficient rescue and evacuation plans to effectively deal with any accidents in the mine.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.1
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• pp.111-118
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• 1999

Throughout this thesis, I describe the design, fabrication, and evaluation of the 3 DOF farce-reflecting haptic interface using USMs(ultrasonic motors). This haptic interface allows a htmlaIl "observer" to explore and interact with a virtual environrrent for the sense of touch. To effectively display the mechanical impedance of the htmlaIl hand we need a haptic device with specific characteristics, such as low inertia, alrmst zero friction and very high stiffness. USMs have attracted considerable attention as the actuator satisfied these conditions. An observer may grasp the end effector of revice and interact with surfaces and objects created within a virtual environment The revice provires force feedback, allowing users to "feel" objects within the environment. The device works very well, as users are able to detect the edge of the wall, the stiffness of the button and the puncture. TIle force-reflecting haptic interface could be suitable as a master for micro-surgery or as an interface to virtual reality training systems.

• Journal of Biomedical Engineering Research
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• v.29 no.3
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• pp.179-186
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• 2008

This paper presents a portable tele-assessment system designed for remote evaluation of the hypertonic elbow joint of neurologically impaired patients. A patient's upper limb was securely strapped to a portable limb-stretching device which is connected through Internet to a portable haptic device by which a clinician remotely moved the patient's elbow joint and felt the resistance from the patient. Elbow flexion angle and joint torques were measured from both master and slave devices and bilaterally fed back to their counterparts. In order to overcome problems associated with the network latency, two different tele-operation schemes were proposed depending on relative speed of tasks compared to the amount of time delay. For slow movement tasks, the bilateral tele-operation was achieved in real-time by designing control architectures after causality analysis. For fast movement tasks, we used a semi-real-time tele-operation scheme which provided the clinicians with stable and transparent feeling. The tele-assessment system was verified experimentally on patients with stroke. The devices were made portable and low cost, which makes it potentially more accessible to patients in remote areas.

• Genomics & Informatics
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• v.19 no.1
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• pp.2.1-2.10
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• 2021

BRAF inhibitors (e.g., vemurafenib) are widely used to treat metastatic melanoma with the BRAF V600E mutation. The initial response is often dramatic, but treatment resistance leads to disease progression in the majority of cases. Although secondary mutations in the mitogen-activated protein kinase signaling pathway are known to be responsible for this phenomenon, the molecular mechanisms governing acquired resistance are not known in more than half of patients. Here we report a genome- and transcriptome-wide study investigating the molecular mechanisms of acquired resistance to BRAF inhibitors. A microfluidic chip with a concentration gradient of vemurafenib was utilized to rapidly obtain therapy-resistant clones from two melanoma cell lines with the BRAF V600E mutation (A375 and SK-MEL-28). Exome and transcriptome data were produced from 13 resistant clones and analyzed to identify secondary mutations and gene expression changes. Various mechanisms, including phenotype switching and metabolic reprogramming, have been determined to contribute to resistance development differently for each clone. The roles of microphthalmia-associated transcription factor, the master transcription factor in melanocyte differentiation/dedifferentiation, were highlighted in terms of phenotype switching. Our study provides an omics-based comprehensive overview of the molecular mechanisms governing acquired resistance to BRAF inhibitor therapy.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1621-1623
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• 1997

Use of teaching pendant is the most widespread and economical way to teach desired motion to robots. It is also very primitive,time consuming and ineffective way of teaching which has not changed since the early days of robot. In order to reduce the teaching effor, a new efficient form of teaching is needed. Also, the recent robotics research trend into service robots such as home robot, nurse robot and medical robot calls for a new teaching method which is both easy and inexpensive. In this paper, the design and operation principle of a low cost force/moment sensor is presented. The proposed sensor architecture is so simple and inexpensive that it opens the prospect for a new paradigm of robot teaching which is easy and efficinet. Other prospective areas of application are tele-manipulation of robots wher it can be used in master arm, and virtual environment where it can be used as an user input device.