• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.997-1010
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• 2014

Today, as the hierarchical cellular system is getting more attention than before, some recent studies introduce delay based admission control (AC) scheme which delays the admission to the macro-embedded small cell for a relatively short time to prevent unnecessary handover caused by the short-term visitors of the small cell area. In such delay based ACs, when we use improper delay parameter, the system frequently makes incorrect handover decisions such as where unnecessary handover is allowed due to too short delaying, or where necessary handover is denied due to too long delaying. In order to avoid these undesirable situations as much as possible, we develop a new delay parameter decision method based on probabilistic cell residence time approximations. By the extensive numerical and analytical evaluations, we determine the proper delay parameter which prevents the incorrect handover decision as much as possible. We expect our delay parameter decision method can be useful system administration tips in hierarchical cellular system where delay based AC is adopted.

• ETRI Journal
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• v.23 no.4
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• pp.168-176
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• 2001

This paper discusses two important issues of corpus-based synthesis: synthesis unit generation based on phrase break strength information and pruning redundant synthesis unit instances. First, the new sentence set for recording was designed to make an efficient synthesis database, reflecting the characteristics of the Korean language. To obtain prosodic context sensitive units, we graded major prosodic phrases into 5 distinctive levels according to pause length and then discriminated intra-word triphones using the levels. Using the synthesis unit with phrase break strength information, synthetic speech was generated and evaluated subjectively. Second, a new pruning method based on weighted vector quantization (WVQ) was proposed to eliminate redundant synthesis unit instances from the synthesis database. WVQ takes the relative importance of each instance into account when clustering similar instances using vector quantization (VQ) technique. The proposed method was compared with two conventional pruning methods through objective and subjective evaluations of synthetic speech quality: one to simply limit the maximum number of instances, and the other based on normal VQ-based clustering. For the same reduction rate of instance number, the proposed method showed the best performance. The synthetic speech with reduction rate 45% had almost no perceptible degradation as compared to the synthetic speech without instance reduction.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.1
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• pp.54-60
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• 2011

The flight control law designed for prototype aircraft often leads to degraded stability and performance, although developed control law verify by non-real time simulation and pilot based evaluations. Therefore, the proper evaluation methods should be applied such that flight control law designed can be verified in real flight environment. The one proposed in this paper is IFS (In-Flight Simulator). Currently, this system has been implemented into the F-18 HARV (High Angle of Attack Research Vehicle), SU-27 and F-16 VISTA (Variable stability In flight Simulation Test Aircraft) programs. The IFS necessary switching control law such as fader logic and integrator stand-by mode to reduce abrupt transient and minimize the integrator effect for each flight control laws switching. This paper addresses the concept of switching mechanism with fader logic of "TFS (Transient Free Switch)" and stand-by mode of "feedback type" based on SSWM (Software Switching Mechanism). And the result of real-time pilot evaluation reveals that the aircraft is stable for inter-conversion of flight control laws and transient response is minimized.

• Advances in aircraft and spacecraft science
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• v.7 no.5
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• pp.405-423
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• 2020

Non-linear energy sink (NES) is an emerging passive absorber able to mitigate the dynamic response of structures without any external energy supply, resonating with all the modes of the primary structure to control. However, its inherent non-linearities hinder its large-scale use and leads to complicated design procedures. For this purpose, an approximate design approach is herein proposed in a stochastic framework. Since loads are random in nature, the stochastic analysis of non-linear systems may be performed by means of computational intensive techniques such as Monte Carlo simulations (MCS). Alternatively, the Stochastic Linearisation (SL) technique has proven to be an effective tool to investigate the performance of different passive control systems under random loads. Since controlled systems are generally non-classically damped and most of SL algorithms operate recursively, the computational burden required is still large for those problems that make intensive use of SL technique, as optimal design procedures. Herein, a procedure to speed up the Stochastic Linearisation technique is proposed by avoiding or strongly reducing numerical evaluations of response statistics. The ability of the proposed procedure to effectively reduce the computational effort and to reliably design the NES is showed through an application on a well-known case study related to the vibrations mitigation of an aircraft wing.

• Journal of the Korea Society for Simulation
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• v.16 no.4
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• pp.67-75
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• 2007

Radio Frequency IDentification(RFID) is in the limelight of fields of military, delivery and library management as an alternative or barcode system. However, it is restricted within product manufacturing, sales and delivery. In this paper, we apply RFID technology into process, especially packing process management to gauge RFID applicability. To verify beneficial features of RFID, we simulate RFID-adopted packing process. As a result, we demonstrate the effectiveness of a RFID-based Process Improvement In manufacturing process. The results of performance evaluations demonstrate that the proposed RFID-based Process Improvement reduces the labour time, labour cost and material cost. Furthermore, we analyze the validity of RFID-based Process Improvement by RFID cost.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.4
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• pp.123-131
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• 2006

The majority of pedestrian fatalities and injuries are caused by vehicle-pedestrian accidents. Recently, it has been recognized as a serious problem. Injuries of occupants in a vehicle have been decreased considerably. However, efforts for protection of pedestrians are still insufficient. These days, many advanced industries are striving for a better protection of pedestrians by using an active hood lift system, rather than reforming the existing structure. In this research, the active hood lift system is designed to enhance the performance for protection. The active hood lift system is analyzed by using the nonlinear finite element method. An optimization problem is formulated by incorporation of the analysis results. Orthogonal arrays are utilized to solve the formulated problem. An iterative optimization algothrithm using orthogonal arrays is utilized for design in the discrete space. It is found that the method can remarkably decrease the number of function evaluations.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.247-250
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• 2001

This paper presents a simple and cost effective circuit topology of single-ended type high frequency quasi-resonant PWM inverter using IGBTs, which can operate under wide soft switching operation range based on ZCS for main power switch as compared with a conventional active voltage-clamped ZVS-PWM high frequency quasi-resonant inverter developed previously. In principle, this new circuit topology can efficiently operate under a constant frequency PWM control-based power regulation scheme. In particular, it is noted that the zero current soft switching (ZCS) commutation can achieve for the main active power switch. On the other hand, the zero voltage soft switching (ZVS) commutation can also achieve for the auxiliary active power switch. The operating principle of this high-frequency Inverter treated here and its power regulation characteristics are illustrated on the basis of the simulation and feasible experimental results.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.223-226
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• 2003

This paper presents a high-frequency ZVS-PWM boost chopper-fed DC-DC converter with a single active auxiliary edge-resonant snubber which is used for power conditioner such as solar photovoltaic generation and fuel cell generation. The experimental results of boost chopper fed ZVS-PWM DC-DC converter are evaluated. In audition to its switching voltage and current waveforms, and the switching v-i trajectory of the power devices are discussed and compared with the conventional hard switching DC-DC converter treated here. The temperature performance of IGBT module,, efficiency, and EMI noise characteristics of this ZVS-PWM DC-DC converter using IGBTs are measured and evaluated from an experimental point of view.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.8
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• pp.861-866
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• 2014

This study evaluates the modeling accuracy of the existing three phase shift models on which the time domain oscillator phase noise theories are based. For the evaluation, this study investigates how accurately the three models can model the phase shift impulse train response of a simple planar oscillator. Evaluation result reveals that Kaertner model most accurately reflects the oscillator's phase shift impulse train responses for five different impulse train inputs, whereas PP model exhibited the worst performance in modeling the phase shift impulse train responses.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.1
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• pp.1-7
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• 2016

In the dentistry field, an ultrasonic surgery unit is widely used in bone cutting and scaling to reduce operation time and minimize hemorrhage. The purpose of this study was to evaluate bone cutting and the effect of a specimen's temperature on the two-type ultrasonic surgery unit using a handpiece moving system(HMS). A HMS, which can cut the bone, was developed to perform the experimental procedure with precision of motion control. Bone specimens were prepared from a combination of epoxy-hardener and cortical bone of bovine leg. Through the bone-cutting experiment, the cutting depth was evaluated by not only scanning electron microscopy, but also Vernier calipers. Also, the temperature distribution was measured by a thermo-graphic camera. This study may be applied methodically in various experimental evaluations on a performance test by a HMS.