• 한국산업융합학회 논문집
• /
• 제23권5호
• /
• pp.817-823
• /
• 2020

In recent, the machining of difficult-to-cut materials such as titanium alloys, stainless steel, Inconel, ceramic, glass, and carbon fiber reinforced plastics (CFRP) used in aerospace, automobile, medical industry is actively researched. Abrasive waterjet is a non-traditional processing method in which ultra-high pressure water and abrasive particles are mixed in a mixing chamber and shoot out jet through a nozzle, and removed by erosion due to collision with a material. In particular, the nozzle of the abrasive waterjet is one of the most important parts that affect the machining quality as with a cutting tool in general machining. It is very important to monitor the condition of the nozzle because the workpiece is uncut or the surface quality deteriorates due to wear, expanding of the bore, damage of the nozzle and clogging of the abrasive, etc. Therefore, in this paper, we propose a monitoring system based on Acoustic Emission(AE) sensor that can detect nozzle condition in real time during AWJ processing.

• 설비공학논문집
• /
• 제23권8호
• /
• pp.549-555
• /
• 2011

For a $CO_2$ one-stage twin rotary compressor, a T-shaped suction port was used to effectively supply the suction gas stream into two individual suction chambers of the twin cylinders. Suction gas pulsations were observed in the pressure sensor signals and these were simulated by using the acoustic modeling of Helmholz resonators in parallel. The module of acoustic modeling was combined to a computer simulation program for the compressor performance. Validation of the simulation program has been carried out for a bench model compressor in a compressor calorimeter. Cooling capacity and the compressor input power were reasonably well compared between the simulation and the calorimeter test. Particularly, good agreement on P-V diagram between the simulation and the test was obtained.

• 센서학회지
• /
• 제32권6호
• /
• pp.418-424
• /
• 2023

Natural killer (NK) cells play a crucial role in combating infections and tumors. However, their therapeutic application in solid tumors is hindered by challenges, such as limited lifespan, tumor penetration, and delivery precision. Our research introduces a novel ultrasonic actuation technique to navigate NK cells more effectively in the vascular system, particularly at vessel bifurcations where targeted delivery is most problematic. We use a hemispherical ultrasonic transducer array that generates phase-modulated traveling waves, focusing on an ultrasound beam to steer NK cells using blood-flow dynamics and a focused acoustic field. This method enables the precise obstruction of non-target vessels and efficiently directs NK cells toward the tumor site. The simulation results offer insights into the behavior of NK cells under various conditions of cell size, radiation pressure, and fluid velocity, which inform the optimization of their trajectories and increase targeting efficiency. The experimental results demonstrate the feasibility of this ultrasonic approach for enhancing NK cell targeting, suggesting a potential leap forward in solid tumor immunotherapy. This study represents a significant step in NK cell therapeutic strategies, offering a viable solution to the existing limitations and promising enhancement of the efficacy of cancer treatments.

• 한국압력기기공학회 논문집
• /
• 제12권1호
• /
• pp.93-100
• /
• 2016

Since the sodium-cooled fast reactor is operated in a hostile environment due to the use of liquid sodium as its coolant, advanced techniques for in-service inspection are required to periodically verify the integrity of the reactor. This paper presents the development of in-service inspection techniques for Proto-type Generation IV Sodium-cooled Fast Reactor. First, the 10 m long plate-type ultrasonic waveguide sensor has been developed for in-service inspection of reactor internals, and its feasibility was verified through several under-water and under-sodium experiments. Second, the combined inspection system for in-service inspection of ferromagnetic steam generator tubes has been developed. The remote field eddy current testing and magnetic flux leakage testing can be conducted simultaneously by using the developed inspection system, and the detectability was demonstrated through several damage detection experiments. Finally, the electro-magnetic acoustic transducer which can withstand high temperature and be installable in the remote operated vehicle has been developed for in-service inspection of the reactor vessel, and its detectability was investigated through damage detection experiments.

• 대한기계학회논문집
• /
• 제17권5호
• /
• pp.1054-1065
• /
• 1993

본 연구에서는 정상상태의 단일 주파수에서의 임의의 음압분포로 조화가진되 는 3차원 정방형 밀폐계 음장의 경우에 대한 능동제어를 시도함으로써 사무실과 같은 실내 공간에 대한 능동적 소음저감의 응용 가능성을 검토하고자 하였다. 또한 변환기 의 위치선정을 위하여 상태공간 모드 모델의 모드 근사화에 따른 계수행렬의 요소를 평가함으로써 가제어성과 가광측성을 만족하는 최적한 변환기 (부가음원, 마이크로폰) 의 위치를 선정하였다. 밀폐계 내부의 음압을 저감시키는 목적함수로는 전체 시간평 균 음향 포텐셜에너지를 사용하였으며 폐공간의 음압변동을 이론적으로 규명함으로써 부가적인 음원의 복소세기를 적절히 선정하여 이 음향 포텐셜 에너지의 양을 최소화 시킬 수 있음을 보였다.

• 융합신호처리학회논문지
• /
• 제9권1호
• /
• pp.10-17
• /
• 2008

본 논문은 설비진단에 있어 크랙 성장부터 누설에 이르기까지 결함으로 발생하는 AE 신호를 통하여 위치를 표정하여 진단 시스템의 오차를 줄이는 것이다. wavelet을 이용한 잡음 제거로서 위치표정의 개선을 제안하였고, 실험을 위한 신호원으로 알루미늄 평판에 샤프심 파단음을, 공기압축기의 누설음을 사용하였다. 신호원에 대하여 웨이블릿 Shrinkage방법과 Soft Threshold을 이용한 신호의 잡음제거 및 시간 도달차 법과 물성치를 적용한 속도 값으로 시뮬레이션을 통하여 위치표정 결과를 확인하였다. 그 결과 웨이블릿 변환을 이용한 잡음제거는 크랙실험의 경우 평균거리 10.46mm이하로 30% 이상과 누설 실험의 경우 평균필터에 비해 2%의 개선된 위치표정을 확인하였다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2000년도 추계학술대회 논문집
• /
• pp.97-101
• /
• 2000

The AE measurement is one of the most convenient methods for detecting contacts between slider disk. The AE method has been widely used in the investigation of the tribology of sliding interfaces due to the convenience of using AE sensor. In this study, we examined the relationship between the AE signal and the flying height of a slider. We tried to know the influence of the disk velocity on the AE rms signal by using the AE measurement system. The experiment also gives the relationship between the take-off velocity and the disk surface state. To investigate the behavior of the slider further, the variances of the AE signal are analyzed. The results about a subambient pressure slider indicate that the increase in the magnitude of AE rms signal does not necessarily mean the slider/disk contacts.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 춘계학술대회논문집
• /
• pp.1197-1202
• /
• 2001

Near-field acoustic holography is a powerful tool to visualize sound sources. This method requires pressure measurement at many points for a good hologram. Thus one has to measure carefully so that errors due to the uncertainty of position, sensor mismatch, and so on are reduced. A method to solve this problem is to use a well-designed measurement system. This paper introduces a sound visualization system at center for noise and vibration control (NOVIC), KAIST, and addresses the advantages in terms of the error reduction. The system consists of array microphones, array jigs, a system to control the position and the velocity of the jigs, a data acquisition system, and a monitoring system. This paper also shows some sound visualization results when the system is applied to a speaker and a computer. The results verifies that the sound visualization system is useful for identifying sound sources.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.1667-1674
• /
• 2000

A new method is proposed to measure the flow rate in a pipe by multiple measurements of acoustic pressure using a microphone array. It is based on the realization that variation in flow velocity affects the change in wave number. The method minimizes measurement random errors and sensor mismatch errors thereby providing practically realizable flow rate measurement. One of the advantages of the method is that it does not obstruct the flow field and can provide the time-spatial mean flow rate. Numerical simulations and experiments were conducted to verify the utility of this method.

• 비파괴검사학회지
• /
• 제8권1호
• /
• pp.12-21
• /
• 1988

The behaviour of pressure vessel made of SS41 steel was investigated during hydrotest. AE tests were carried out for the vessels in as-manufactured, V-notched and weld-cracked state using microcomputer-based AE instrumentation. The following results were obtained: 1) In the case of source location using cylindrical program, to minimize the error of source location, the difference of max. Delta T values measured from each sensor should be kept as small as possible. 2) When crack grew, AE event rate increased continuously but AE event from the inclusions occurred intermittently, so by analyzing event rate, the source of AE could be derived. 3) From the spot welding part of supporter, many events with low energy occurred independent of Kaiser effect, which could be confirmed by analyzing energy parameter. 4) The b-value from the tensile specimen of was lower than that from normal specimen and the b-value from crack propagation was lower than that from deformation, so by analyzing peak amplitude distribution, the source mechanism could be derived from the b-value.