• Structural Engineering and Mechanics
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• v.75 no.4
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• pp.435-444
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• 2020

Ultrasonic guided wave testing is a very promising non-destructive testing method for rails, which is of great significance for ensuring the safe operation of railways. On the basis of the semi-analytical finite element (SAFE) method, a analytical model of 59R2 grooved rail was proposed, which is commonly used in the ballastless track of modern tram. The dispersion curves of ultrasonic guided waves in free rail and supported rail were obtained. Sensitivity analysis was then undertaken to evaluate the effect of rail elastic modulus on the phase velocity and group velocity dispersion curves of ultrasonic guided waves. The optimal guided wave mode, optimal excitation point and excitation direction suitable for detecting rail integrity were identified by analyzing the frequency, number of modes, and mode shapes. A sinusoidal signal modulated by a Hanning window with a center frequency of 25 kHz was used as the excitation source, and the propagation characteristics of high-frequency ultrasonic guided waves in the rail were obtained. The results show that the rail pad has a relatively little influence on the dispersion curves of ultrasonic guided waves in the high frequency band, and has a relatively large influence on the dispersion curves of ultrasonic guided waves in the low frequency band below 4 kHz. The rail elastic modulus has significant influence on the phase velocity in the high frequency band, while the group velocity is greatly affected by the rail elastic modulus in the low frequency band.

• The Journal of Advanced Prosthodontics
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• v.6 no.5
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• pp.395-405
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• 2014

PURPOSE. This study aims to investigate the degree of subjective pain and the satisfaction of patients who have undergone an implant treatment using a computer-guided template. MATERIALS AND METHODS. A survey was conducted for 135 patients who have undergone implant surgery with and without the use of the computerguided template during the period of 2012 and 2013 in university hospitals, dental hospitals and dental clinics that practiced implant surgery using the computer-guided template. Likert scale and VAS score were used in the survey questions, and the independent t-test and One-Way ANOVA were performed (${\alpha}=.05$). RESULTS. The route that the subjects were introduced to the computer-guided implant surgery using a surgical template was mostly advices by dentists, and the most common reason for which they chose to undergo such surgery was that it was accurate and safe. Most of them gave an answer that they were willing to recommend it to others. The patients who have undergone the computer-guided implant surgery felt less pain during the operation and showed higher satisfaction than those who have undergone conventional implant surgery. Among the patients who have undergone computer-guided implant surgery, those who also had prior experience of surgery without a computer-guided template expressed higher satisfaction with the former (P<.05). CONCLUSION. In this study, it could be seen that the patients who have undergone computer-guided implant surgery employing a surgical template felt less pain and had higher satisfaction than those with the conventional one, and the dentist's description could provide the confidence about the safety of surgery.

• Smart Structures and Systems
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• v.22 no.4
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• pp.481-493
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• 2018

Ultrasonic guided waves have attracted increasing attention for non-destructive testing (NDT) and structural health monitoring (SHM) of bridge cables. They offer advantages like single measurement, wide coverage of acoustical field, and long-range propagation capability. To design defect detection systems, it is essential to understand how guided waves propagate in cables and how to select the optimal excitation frequency and mode. However, certain cable characteristics such as multiple wires, anchorage, and polyethylene (PE) sheath increase the complexity in analyzing the guided wave propagation. In this study, guided wave modes for multi-wire bridge cables are identified by using a semi-analytical finite element (SAFE) technique to obtain relevant dispersion curves. Numerical results indicated that the number of guided wave modes increases, the length of the flat region with a low frequency of L(0,1) mode becomes shorter, and the cutoff frequency for high order longitudinal wave modes becomes lower, as the number of steel wires in a cable increases. These findings were used in design of transducers for defect detection and selection of the optimal wave mode and frequency for subsequent experiments. A magnetostrictive transducer system was used to excite and detect the guided waves. The applicability of the proposed approach for detecting and locating wire breakages was demonstrated for a cable with 37 wires. The present ultrasonic guided wave method has been found to be very responsive to the number of brokenwires and is thus capable of detecting defects with varying sizes.

• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.75-86
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• 2023

The guided missiles and decoy systems that have been developed have been likened to a spear and shield. When a new attack system appears, another defense system is developed, and the attack system is once again upgraded to neutralize it. Now, due to the limitations of the decoy system, guided weapons have become the main force of both the defense and attack systems. Also, these systems have been expanded to use Space systems as a means of defending against a guided weapon system that is too fast for terrestrial-based systems. Induced weapon systems started at the sub-sonic level, and have become so important that their speeds have become super-sonic and hyper-sonic. The concept of Space has been included in the range of guided missiles, and satellite systems have become essential elements of guided missiles. Focusing on the correlation between the guided missile system and the satellite system, we analyze the characteristics of modern guided munitions and the direction of development of the guided weapons system.

• Proceedings of the Korean Society of Computer Information Conference
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• 2023.07a
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• pp.541-544
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• 2023

LLM(Largescale Language Model)의 성능 향상을 위한 비용 효율적인 방법으로 ChatGPT, GPT-4와 같은 초거대 모델의 output에 대해 SLM(Small Language Model)을 finetune하는 방법이 주목받고 있다. 그러나, 이러한 접근법은 주로 범용적인 지시사항 모델을 위한 학습 방법으로 사용되며, 제한된 특정 도메인에서는 추가적인 성능 개선의 여지가 있다. 본 연구는 특정 도메인(Writing Assistant)에서의 성능 향상을 위한 새로운 방법인 Self-Guided Approach를 제안한다. Self-Guided Approach는 (1) LLM을 활용해 시드 데이터에 대해 도메인 특화된 metric(유용성, 관련성, 정확성, 세부사항의 수준별) 점수를 매기고, (2) 점수가 매겨진 데이터와 점수가 매겨지지 않은 데이터를 모두 활용하여 supervised 방식으로 SLM을 미세 조정한다. Vicuna에서 제안된 평가 방법인, GPT-4를 활용한 자동평가 프레임워크를 사용하여 Self-Guided Approach로 학습된 SLM의 성능을 평가하였다. 평가 결과 Self-Guided Approach가 Self-instruct, alpaca와 같이, 생성된 instruction 데이터에 튜닝하는 기존의 훈련 방법에 비해 성능이 향상됨을 확인했다. 다양한 스케일의 한국어 오픈 소스 LLM(Polyglot1.3B, PolyGlot3.8B, PolyGlot5.8B)에 대해서 Self-Guided Approach를 활용한 성능 개선을 확인했다. 평가는 GPT-4를 활용한 자동 평가를 진행했으며, Korean Novel Generation 도메인의 경우, 테스트 셋에서 4.547점에서 6.286점의 성능 향상이 발생했으며, Korean scenario Genration 도메인의 경우, 테스트 셋에서 4.038점에서 5.795 점의 성능 향상이 발생했으며, 다른 유사 도메인들에서도 비슷한 점수 향상을 확인했다. Self-Guided Approach의 활용을 통해 특정 도메인(Writing Assistant)에서의 SLM의 성능 개선 가능성을 확인했으며 이는 LLM에 비용부담을 크게 줄이면서도 제한된 도메인에서 성능을 유지하며, LLM을 활용한 응용 서비스에 있어 실질적인 도움을 제공할 수 있을 것으로 기대된다.

• Journal of Applied Reliability
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• v.16 no.3
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• pp.208-215
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• 2016

Purpose: ASRP for the domestic development guided missiles requires not only for the reliability evaluation of the products in storage but also for the life cycle management of the products including development prototypes and initial production items. Methods: For this purpose, it should be performed to build a performance database before and after the accelerated aging test with shelf life items including development prototypes and initial production items, based on which the lifetime prediction should also be carried out. In addition, HILS must be applied for the acceptance test with the initial and follow-up production items, and also for ASRP for the long-term storage products in order to secure systematic quality assurance. Results: The results for the life cycle reliability Improving of domestic development of guided missiles are DB building of prescription Item performance, active application of HILS, Management associated with guided missiles life cycle and to Secure technology data about the introduction of foreign guided missiles. Conclusion: Furthermore, it is demanded that DTaQ, the managing agency of ASRP, actively take part in the process to maintain reliability engagement consistency over the life cycle of guided missiles.

• The Journal of Korean Academic Society of Nursing Education
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• v.26 no.1
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• pp.16-24
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• 2020

Purpose: This study examined the effects of guided imagery on stress, state anxiety, test anxiety and core basic nursing skill performance score of undergraduate nursing student. Methods: An equivalent control group pretest-posttest design was utilized. A total of 45 senior nursing students were randomly assigned to either an intervention group to receive guided imagery, or a control group (experimental group=23 students, control group=22 students). The guided imagery was provided via audio files to the intervention group for eight minutes, once a day for five days. The pretest was given before the intervention to measure variables for both groups, and the posttest was performed immediately afterward and three days after the intervention. Results: Significant differences were found between the two groups in stress ((F=4.94, p=.012), state anxiety (F=5.99, p=.005), and basic core nursing skill performance scores (Z=-2.45, p=.015). Conclusion: Guided imagery for nursing students has been identified as effective for stress, state anxiety, and basic core nursing skill performance scores. Guided imagery can be used as an effective intervention before performance tests. These study results can provide useful data for nursing education.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.1912-1921
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• 1999

The equipments mounted on guided-missile undertake heavy vibrational disturbance. Sometimes the equipments mounted on guided-missile go wrong so that the guided-missile flies over unintended place. For the vibration isolation of the equipments mounted on guided-missile, active vibration control was performed. In the case of active vibration technique, the stiffness matrix and the mass matrix are derived based on FEM (ANSYS5.0). Model reduction was carried out and, as a result, we got 7 DOF mass and stiffness matrix. For the sake of FEM model identification, modal experiment was carried out. With the help of Sensitivity Analysis, the natural frequencies of FEM were tuned to those of Experiment. In this work, the Sky Hook and the LQG control theory were adopted for v iteration control using stacked piezoactuator. Experiments were performed with changing excitation frequency from 10 Hz upto 200 Hz and we got frequency response function of guided-missile equipments. The magnitude of 3rd mode of guided-missile equipments is 8.6 % that of Uncontrolled in Skyhook controller and is 3.4 % that of uncontrolled in LQG controller.

• Convergence Security Journal
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• v.8 no.2
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• pp.103-109
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• 2008

In this paper, a study on the seeker technology in guided weapon system development. Seeker is guided weapons mounted on the device that is targeted for implementation homing guided looking for confirmation of the target after picking up, tracking, command, induce calculations necessary to induce the target's direction or control device to provide location information to perform a series of features. Therefore, the Seeker is guided weapons systems and important device that determines the performance of one guided control. Explorer is a tactical and strategy guided weapons from different goals and specifications of weapons systems development and encourage economic efficiency, Interoperability, designed to improve the reliability and hit requirements and the more numerous. Therefore, this research through the Explorer's attributes and weapons systems encourage the development direction of the technical details of the offer.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.5
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• pp.94-100
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• 2003

One of unique characteristics of guided waves is a dispersive behavior that guided wave velocity changes with an excitation frequency and mode. In practical applications of guided wave techniques, it is very important to identify propagating modes in a time-domain waveform for determination of detect location and size. Mode identification can be done by measurement of group velocity in a time-domain waveform. Thus, it is preferred to generate a single or less dispersive mode But, in many cases, it is difficult to distinguish a mode clearly in a time-domain waveform because of superposition of multi modes and mode conversion phenomena. Time-frequency analysis is used as efficient methods to identify modes by presenting wave energy distribution in a time-frequency. In this study, experimental guided wave mode identification is carried out in a steel plate using time-frequency analysis methods such as wavelet transform. The results are compared with theoretically calculated group velocity dispersion own. The results are in good agreement with analytical predictions and show the effectiveness of using the wavelet transform method to identify and measure the amplitudes of individual guided wave modes.