• Journal of Information Processing Systems
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• 제18권4호
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• pp.587-598
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• 2022

To increase building change recognition accuracy, we present a deep learning-based building change detection using remote sensing images. In the proposed approach, by merging pixel-level and object-level information of multitemporal remote sensing images, we create the difference image (DI), and the frequency-domain significance technique is used to generate the DI saliency map. The fuzzy C-means clustering technique pre-classifies the coarse change detection map by defining the DI saliency map threshold. We then extract the neighborhood features of the unchanged pixels and the changed (buildings) from pixel-level and object-level feature images, which are then used as valid deep neural network (DNN) training samples. The trained DNNs are then utilized to identify changes in DI. The suggested strategy was evaluated and compared to current detection methods using two datasets. The results suggest that our proposed technique can detect more building change information and improve change detection accuracy.

• 대한치과보철학회지
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• 제38권6호
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• pp.765-781
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• 2000

The purpose of this study was to compare the screw loosening characteristics of three avail-able cementation type abutments: one-piece cementation type abutment; two-piece cementation type abutment using titanium abutment screw; two-piece cementation type abutment using gold abutment screw. Two implant supported three-unit superstructures were fabricated using a pair of 3 kinds of abutments for each experimental model. Cyclic loading was applied on the specimen, and made to stop when the superstructure showed movement over threshold range. The loaded cycle was counted until the machine stopped. Frequency analysis was done to measure the change of natural frequency before and after the application of cyclic load and to find the effect of screw loosening on the change of natural frequency. The specimen assembly was modeled to perform the finite element analysis to see the distribution of the stress induced by the application of preload over the screw joint and to compare the pattern of the distribution of stress induced by the external force with the change of the preload condition. The following results were obtained: 1. The failure loading cycle of two-piece cementation type abutment using gold screw was significantly greater than those of the other groups. 2. One-piece cementation type abutment applied to multi-unit restoration case did not show greater resistance to screw loosening compared to two-piece cementation type abutments. 3. Frequency analysis showed decrease in natural frequency when screw loosening occured.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.184-186
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• 2003

Power systems must be operated within limits that will ensure adequate generation and transmission capacity to avoid cascading. In developing a set of operations limits, it is important to do so within a general framework in order to ensure that the operating objectives are met. In the this regard, when the system experiences a generation-load imbalance, the principles of sound operation will be maintained by bringing under control an unscheduled power flow condition as quickly as possible. This paper presents load shedding application which responds both to frequency and to rate of change of frequency. Its application is in the operating situation of load suddenly in excess of generation, either because of generator or other equipment failure. A scheme which is able to utilize rate of change of frequency as well as frequency itself is an improvement over existing scheme.

• 전기학회논문지
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• 제62권7호
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• pp.918-924
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• 2013

In a conventional power system, the frequency is recovered to the nominal value by the inertial, primary, and secondary responses of the synchronous generators (SGs) after a large disturbance such as a generator tripping. For a power system with high wind penetration, the system inertia is significantly reduced due to the maximum power point tracking control based operation of the variable speed wind generators (WGs). This paper proposes a virtual inertial control for a wind power plant (WPP) based on the maximum rate of change of frequency to release more kinetic energy stored in the WGs. The performance of the proposed algorithm is investigated in a model system, which consists of a doubly fed induction generator-based WPP and SGs using an EMTP-RV simulator. The results indicate that the proposed algorithm can improve the frequency nadir after a generator tripping. In addition, the algorithm can lead the instant of a frequency rebound and help frequency recovery after the frequency rebound.

• 한국인터넷방송통신학회논문지
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• 제20권6호
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• pp.129-135
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• 2020

본 연구는 10MHz SC-CUT 크리스탈을 이용한 오븐제어수정발진기(이하 OCXO)의 온도센서 위치에 의한 특성 변화와 주파수 보정방법에 관한 것이다. 기존의 고정밀 10MHz OCXO의 제작 방법은 여러 가지가 있지만, 본 연구에서는 온도센서의 위치를 조정하는 것만으로도 외부 온도 변화에 대한 주파수 안정도 특성이 향상될 수 있다는 것을 보여준다. OCXO의 주파수 특성에 영향을 주는 인자로는 크리스탈에 전달되는 온도, 크리스탈에 인가되는 전압, 발진회로를 구성하는 캐패시턴트 등이 있다. 이러한 인자들에 의한 주파수 변화량을 측정하고 온도 변곡점 측정과 캐패시터 값의 변화를 통하여 OCXO 출력주파수의 보정값 변화를 알아보았다.

• 한국가구학회지
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• 제22권3호
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• pp.230-238
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• 2011

Consumers' expenditure is getting larger on children due to their parents' compensation for increase of double-income family life and decrease of birth rate caused by high economic growth. Increase of demand on children items in the market leads the necessity of development of furniture for children. This study is aimed to design children chairs that meet the environment for children. In this study, the age of children is defined to be 5~7 years old. In order to investigate what causes environment change, this study covers roughly change of environment, change of learning program and use of environment-friendly material. In such scope, we drew out the factors that the chairs for children shall be equipped with. Case studies were done through such drawn factors. The scope of the furniture for children is limited to the chairs for children among the ones made in either Korea or overseas. As a result, we could draw out such keyword of the furniture as storage, mobility, environment-friendly, object style image, preferred color, functionality and safety, based on which we could plan the design and make the final result through high frequency round molding manufacturing process.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.127-130
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• 2005

In this paper, we investigated the change of recognition distance according to the resonance frequency of the transponder for the ISO 14443 Type A 13.56MHz RFID(Radio Frequency IDentification) system. We made thirteen transponders of the same size. The dimension of the transponder is $84.65mm{\times}53.00mm{\times}0.45mm$. We measured the resonance frequency by means of an inductive coupling. The measured resonance frequencies were between 12.9MHz and 17.3MHz. We measured the maximum distances where the transponder's USN(Unique Serial Number) was recognized and the subcarrier was observed. The measurement results show that we can obtain good performance when the Type A transponder has the resonance frequency around 14.2MHz for the given case.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.146-149
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• 2003

To control the position, velocity and torque of the ultrasonic motor, a great variety of method are proposed such as the amplitude, phase difference, frequency and so on. In the case of phase difference method, it has some advantages: it can control the direction and velocity of rotation only adjusting the phase difference and it has wide control-band. During the USM driving on adjusting phase difference, its characteristic was transformed by the change of resonance-frequency of stator, which means that the resonance frequency is different according to the phase difference. Consequently, we need to set up the most suitable driving frequency according to each phase difference.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.963-968
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• 2004

Free vibration analysis of helical spring with crack was studied. Natural frequency changes due to the crack was analyzed with respect to crack locations. The effect of crack on natural frequency was decreased as crack location is further from the fixed end of a spring. The frequency change was larger in rectangular-shaped spring than that in circular-shaped spring. It was found that experiment may not be appropriate to determine the presence of crack because no significant natural frequency change can be shown by experiment.

• 한국전기전자재료학회논문지
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• 제13권1호
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• pp.47-51
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• 2000

To make a practical application of a micro-strain sensors with ultrahigh sensitivity, a strain on electrical properties of micro-patterned amorphous (Fe\ulcornerco\ulcorner)\ulcornerSi\ulcornerB\ulcorner films had influenced on the impedance over frequency range from 1 MHz to 1 GHz. Reflecting excellent magnetomachanical couping properties of films, high frequency impedance was subject to change sensitively by a strain : a change in impe-dance of 39% was observed at 200 MHz applied a strain of 224$\times$10\ulcorner. To determine a optimum shape of micro-patterned films, film impedance was analyzed by virtue of its constitutive components of resis-tance and reactance. Result was shown that reduction of the resistance term(hence increase of resultant reactance term) of impedance is more effective for enhancing the strain sensitivity of films at relatively low frequency range.