• 한국도로학회논문집
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• 제14권5호
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• pp.75-83
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• 2012

PURPOSES: Suggestion of asphalt binder constitutive model based on time-temperature superposition principle and overstress concept in order to describe behavior of asphalt binders. METHODS: A series of temperature sweep tests and multiple stress creep and recovery(MSCR) tests are performed to verify the applicability of time-temperature superposition principle(t-Ts) and to develop viscoelastoplastic constitutive equation based on overstress concept. For the tests, temperature sweep tests at various high temperature and various frequency and MSCR test at $58^{\circ}C$, $64^{\circ}C$ $70^{\circ}C$, $76^{\circ}C$, and $82^{\circ}C$ are performed. From the temperature sweep tests, dynamic shear modulus mastercurve and time-temperature shift function are built and the shift function and MSCR at $58^{\circ}C$ are utilized to determine model coefficients of VBO model. RESULTS: It is observed that the time-temperature shift function built at low strain level of 0.1% is applicable not only to 1.0% strain level temperature sweep test but also maximum 500,00% strain level of MSCR test. As well, the modified VBO model shows perfect prediction on MSCR measured strain at the other temperatures. CONCLUSIONS: The Time-temperature superposition principle stands hold from very low strain level to very high strain level and that the modified VBO model can be applicable for various range of strain and temperature region to predict elastic, viscoelastic, and viscoplastic strain of asphalt binders.

• 한국도로학회논문집
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• 제15권2호
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• pp.65-71
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• 2013

PURPOSES : The objective of this study is to evaluate the effect of physical characteristics of emulsion asphalt and aggregate on performance of chip seal pavements. METHODS : In order to evaluate the performance of chip seal materials, the sweep tests and Vialit Plate Shock tests were conducted on the mixtures with five emulsion asphalt binders and three aggregate types. The sweep tests was intended to investigate the change of bonding properties between emulsion asphalt and aggregate with curing time. The Vialit Plate Shock test was used to evaluate the bonding properties of chip seal materials at low temperatures. RESULTS : Results from sweep tests showed that polymer modified emulsion asphalt can reduce the curing time by 1.5 hour comparing with typical emulsion asphalt. It is also found that the Flakiness Index of aggregates and absorption rate of binder are the major factors affecting the bonding properties of chip seal materials. The Vialit Plate Shock test results showed that the average aggregate loss of CRS-2 is ten times higher than CRS-2P No.2 indicating that the use of polymer additives in emulsion asphalt can improve the performance of chip seal materials in low temperature region. CONCLUSIONS : The use of polymer in emulsion asphalt can decrease the curing time of chip seal materials and increase the bonding properties between aggregates and asphalt binder. It is also concluded that the lower Flakiness Index and absorption rate of aggregates can improve the performance of chip seal pavement.

• 센서학회지
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• 제26권1호
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• pp.44-49
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• 2017

In this paper, the automatic sweep flattening for wavelength swept laser of SS-OCT has implemented. Through its performance test applied to the laser, 50 nm flat sweeping range, ${\pm}0.5dB$ fluctuation range, 22 sec the time required, and 10 mW average optical power were obtained. This shows that the realized automatic process can replace the inconvenient manual operation used for polarization control of current sweeping laser. Additionally it cuts costs for optical spectrum analyzer necessary to sweep monitoring.

• 대한전기학회논문지:전력기술부문A
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• 제51권1호
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• pp.15-22
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• 2002

This paper proposes a new power flow method for distribution system analysis by modifying the conventional back/forward sweep method using symmetrical components. Since the proposed method backward and forward sweeps with the variables expressed by symmetrical components, this method reduces computation time for matrix calculations; therefore, it is able to reduce the computational burden for real-time distribution network analysis. The proposed method was also developed to effectively analyze the unbalanced distribution system installing AVR(Auto Voltage Regulator), shunt capacitors. The proposed algorithm was compared with the conventional Back/forward Sweep method by applying both methods to three phase unbalanced distribution system of IEEE 123-bus model, and the test results showed that the proposed method would outperformed the conventional method in real-time distribution system analysis.

• 한국인쇄학회지
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• 제23권2호
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• pp.1-14
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• 2005

Generally, printing inks are composed of pigment, vehicle and additive. Among others, the vehicle transfers the pigment to substrate and then binds it on the surface. So, rheological properties of the vehicle are an important factor which has influence on printability. Thus, in this study, rheology of the vehicle was investigated by using rotational rheometer according to molecular weight of resin. Also, emlusion rheology of water in oil type and its microstructure were examined with increasing the shear rate. Consequently, the following results were obtained: (1) By viscometric flow test, zero shear viscosity and shear thinning index of vehicle increased with increasing the molecular weight of resin. (2) By relaxation and creep test, relaxation time and retardation time of vehicle increased with increasing the molecular weight of resin. (3) By frequency sweep test, crossover point of vehicle increased with increasing the molecular weight of resin. (4) G' and G" of emlusions increased with increasing the molecular weight by amplitude sweep test. (5) The shape of water drop in emlusions was changed to the capillary tube.

• Elastomers and Composites
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• 제51권1호
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• pp.24-30
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• 2016

Sole in the footwear usually modified with foaming agent on the polymer resin to improve the lightweightness and crush-cushion effect. In this study, we investigated rheological properties for polymer resin filled with the different type and concentration of foaming agent, capsule type foaming agent and organo-chemical foaming agent, under the time sweep test. Curing times of each polymer resin with different kind of foaming agent are delayed than reference material (epoxy resin with curing agent). In case of adding capsule type foaming agent, however, there is appropriate concentration to reduce the curing time, relatively. When foaming agent is activated, foaming force inflates the sample in contrast to condensation force of curing and then axial normal force develop to the (+) direction. Interestingly, by increase concentration of foaming agent, there is a specific point to break down the axial normal force development. The reason for this phenomenon is that coalescence of foams induce the blocking of axial normal force development.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1384-1387
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• 1996

SCPI(Standard Commands for Programmable Instrument) is a standard command sets designed for controlling various types of instruments. In order to control FFT(Fast Fourier Transform) analyzing device using SCPI it is required to support sweep measurement function. We defined SCPI command set for FFT analysis and developed parser of defined command set using lex(Lexical Analyzer Generator) and yacc(Yet Another Compiler Compiler). After developing FFT analyzing test was performed with that parser. Up to audible signal frequency the result of FFT analysis was accurate and that result was agree with that of conventional FFT analyzer. As a result it is proved that various types of instruments including sweep measurement instrument can be controlled with appropriate SCPI command sets. Also when developing new instruments the method used in this experiment will contribute to reducing the time required to develop the SCPI parser and increasing reliability.

• Journal of Biosystems Engineering
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• 제36권6호
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• pp.476-483
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• 2011

The aerial application using an unmanned helicopter has been already utilized and an attitude controller would be developed to enhance the operational convenience and safety of the operator. For a preliminary study of designing flight controller, a state space model for an RC helicopter would be identified. Frequency sweep flight tests were performed and time history data were acquired in the previous study. In this study, frequency response of the flight test data of a small unmanned helicopter was analyzed by using the CIFER software. The time history flight data consisted of three replications each for collective pitch, aileron, elevator and rudder sweep inputs. A total of 36 frequency responses were obtained for the four control stick inputs and nine outputs including linear velocities and accelerations and angular velocities in 3-axis. The results showed coherence values higher than 0.6 for every primary control inputs and corresponding on-axis outputs for the frequency range from 0.07 to 4 Hz. Also the analysis of conditioned frequency response showed its effectiveness in evaluating cross coupling effects. Based on the results, the dynamic characteristics of the model helicopter can further be analyzed in terms of transfer functions and the undamped natural frequency and damping ratio of each critical mode.

• Elastomers and Composites
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• 제49권4호
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• pp.323-329
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• 2014

MIF (Molded-In Foaming) 공법의 발포 거동에 적합한 고분자 기재를 선정하기 위해 SBC (K-resin KK38)와 SBS (KTR 101와 KTR 301)의 유변물성을 측정하였다. SBS의 유변물성 ($G^{\prime}$, $G^{{\prime}{\prime}}$, ${\eta}^*$)은 $155^{\circ}C$와 $170^{\circ}C$의 경우 시간에 따라 유변물성 값의 변화가 거의 없으나, $185^{\circ}C$와 $200^{\circ}C$의 경우에는 시간에 따라 증가하는 것을 볼 수 있었다. 특히, KTR 301의 유변물성 값이 시간에 따라 큰 폭으로 증가하였다. 시간에 따른 유변물성 상승의 정확한 원인을 확인하기 위해 $155^{\circ}C$와 $200^{\circ}C$에서 1800 s 이후의 KTR 301의 비선형 유변물성을 진폭에 대해 측정하였다. $155^{\circ}C$에서는 일반적인 수지와 같은 한 번의 박화(thinning)현상이 관찰되나 $200^{\circ}C$에서는 두 번의 박화현상이 관찰되었고 (Payne effect), 이는 고온에서 SBS가 겔화에 의한 경화가 일어난다고 볼 수 있다. 따라서 이러한 유변물성으로부터 MIF 공법에 요구되는 특성(발포 초기 낮은 점도와 발포 완료 이후 높은 점도)에 적합한 고분자 기재는 SBS KTR 301임을 확인할 수 있었다.

• 한국항공운항학회지
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• 제23권4호
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• pp.22-29
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• 2015

Quadrotor is widely used in variable application nowadays. Due to its inherent unstable characteristics, control system to augment the stability is essential for quadrotor operation. To design control system and verify its performance through simulation, accurate dynamic model is required. Quadrotor dynamic model is simply compared with conventional rotorcraft such as helicopter. However, the accurate dynamic model of quadrotor is not easy to develop because of the highly correlated aerodynamic effect of each rotor. In this paper, quadrotor dynamic model is identified from the flight data using frequency domain approach. Flight test of quadrotor is performed in closed loop configuration with stability augmentation system included. Frequency sweep input is applied in each of lateral, longitudinal, yaw and heave axis separately. The bare dynamic model is identified from the flight data of quadrotor responses and thrust measurement through Pulse Width Modulation(PWM) data. The frequency responses of identified model match well with those of flight data, and time responses of identified model for doublet input in each axis are also shown to agree with flight data.