Koji Fujita

Dr. Koji Fujita

Institute of Fluid Science, Tohoku University
orcid

Research Focus & Metrics

Academic Career Length

23Years (2004-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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16 January 2017 in The Aeronautical Journal
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Journal Article
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KFKoji Fujita
Koji Fujita
HNHiroki Nagai
Hiroki Nagai
This paper investigates the effects of the design variables of an aerial deployment mechanism on the robustness of the aerial deployment through a multibody dynamics simulation. The aircraft is modelled as three joined rigid bodies: a right wing, a left wing and a centre body. A spring-loaded hinge is adopted as an actuator for deployment. The design variables are the hinge torque and the deployment timing. The robustness is evaluated using a sigma level method. The margins for the safe deployment conditions are set for the evaluation functions. The dispersive input variables are the initial drop velocity, the surrounding gust velocity, the initial pitch angle and the initial height. The design point with a deployment torque scale valueFof 0.7 and a right-wing deployment delay timeTSRof 1.0 s can safely deploy in the low-torque deployment condition. This design point is able to accomplish both a safe deployment and a lightweight deployment mechanism.

15 September 2018
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Conference Paper
Closed access
RARisako Aoki
Risako Aoki
AOAkira Oyama
Akira Oyama
KFKoji Fujita
Koji Fujita
HNHiroki Nagai
Hiroki Nagai
MKMasahiro Kanazaki
Masahiro Kanazaki
KUKazufumi Uwatoko
Kazufumi Uwatoko

25 January 2022 in Sensors
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Journal Article
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TITsubasa Ikami
Tsubasa Ikami
KFKoji Fujita
Koji Fujita
HNHiroki Nagai
Hiroki Nagai
Temperature-sensitive paint (TSP) can optically measure a global temperature distribution using a thermal quenching of dye molecules. The TSP measurement is often used in wind tunnel tests to measure the temperature and flow fields in the aerodynamic field. The measurement accuracy is affected by the characteristics of TSP, such as temperature sensitivity, pressure dependency, luminescent intensity, photostability, and surface condition. The characteristics depend on the formulation of TSP. This study investigates the characteristics of the TSP using dichlorotris (1,10-phenanthroline) ruthenium(II) hydrate (Ru-phen). We compare the characteristics of TSPs using different polymers, solvents, and dye concentrations. The TSPs using polyacrylic acid as a polymer shows linear calibration curves, high luminescent intensity, high photostability, and smooth surface. On the other hand, the TSPs using polymethyl methacrylate have nonlinear calibration curves, low luminescent intensity, strong photodegradation, and a rough surface.

9 January 2012
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Conference Paper
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KFKoji Fujita
Koji Fujita
HNHiroki Nagai
Hiroki Nagai
KAKeisuke Asai
Keisuke Asai

11 June 2022 in Sensors
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Journal Article
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KYKazuma Yomo
Kazuma Yomo
TITsubasa Ikami
Tsubasa Ikami
KFKoji Fujita
Koji Fujita
HNHiroki Nagai
Hiroki Nagai
Pressure-sensitive paint (PSP) is an optical sensor that can measure global pressure distribution by using the oxygen quenching of dye molecules. In particular, anodized aluminum pressure-sensitive paint (AA-PSP) exhibits a fast time response. AA-PSP has been used in unsteady measurements at supersonic and transonic speeds, such as on the surface of a transonic free-flying sphere or the wall of a shock tube when the shock wave passes. To capture such ultrafast phenomena, the frame rate of the camera must be sufficiently fast, and the exposure time must be sufficiently short. Therefore, it is desirable that the AA-PSP exhibits bright luminescence, high-pressure sensitivity, and fast response time. This study focused on pyrene-based AA-PSPs and investigated their characteristics, such as luminescence intensity and pressure sensitivity, at different anodization times, dipping solvents, and dipping concentrations. Furthermore, a time-response test using a shock tube was conducted on the brightest AA-PSP. Consequently, the time for a 90% rise in pressure was 2.2 μs.

10 January 2014
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Conference Paper
Closed access
KFKoji Fujita
Koji Fujita
TMToshikazu Motoda
Toshikazu Motoda
HNHiroki Nagai
Hiroki Nagai