Okinawa National College of Technology

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Okinawa, Japan
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Teruya M.,Okinawa National College of Technology | Chinen K.,Okinawa National College of Technology
AIP Conference Proceedings | Year: 2017

We have investigated how wavelength spacing and frequency spacing in WDM (Wavelength Division Multiplexing) and FDM (Frequency Division Multiplexing) using direct modulation lasers (DML) and external modulators of Mach-Zehnder Modulator (MZM) affect optical and electrical interferences. Two signals of 4.8GHz-64QAM-5MHzBW WiMAX and 4.7GHz-32MHzBW FM were directly modulated with uncooled 1550nm DFB-LDs, and 5GHz-256QAM-80MHzBW IEEE802.11ac signal was modulated on the combined optical signals of WiMAX and FM at an MZM. Change in RCE of the WiMAX signal and EVM of the IEEE 802.11ac signal were measured when the wavelength spacing between two DFB-LDs was varied. When the wavelength spacing was larger than 0.05 nm and the ratio of peak to bottom of optical power was larger than 30 dB, the RCE of WiMAX signal was decreased to lower than -20dB. The WDM using directly modulated DFB-LDs and MZM was realized, when the wavelength spacing was larger than 0.1 nm and the peak to bottom ratio of optical power was larger than 60 dB, since the EVM of IEEE802.11ac signal was decreased to around -30dB. The FDM with the same configuration as that of the WDM was realized, when the frequency spacing was larger than a half of the sum of the BWs of WiMAX and FM signals, as the RCE of WiMAX signal decreased to lower than -35 dB and the EVM of IEEE802.11ac signal decreased to around -30dB. © 2017 Author(s).


Sano Y.,Toshiba Corporation | Masaki K.,Okinawa National College of Technology | Gushi T.,Okinawa National College of Technology | Sano T.,Osaka University
Materials and Design | Year: 2012

The authors have applied laser peening without coating (LPwC) to fatigue specimens cut out from friction stir welded (FSWed) A6061-T6 aluminum alloy plates with a thickness of 3mm. Both crown and root sides of the specimens were peened by laser pulses with an energy of 60mJ and a peak power density of 2GW/cm2 from a frequency-doubled Nd:YAG laser. The effects on the fatigue properties were studied through plane bending fatigue tests with a stress ratio of R=-1. The results showed that the fatigue strength of unwelded specimens (base material; BM) was 110MPa at 107 cycles and LPwC enhanced the strength by 60MPa in spite of increase in surface roughness due to the direct irradiation of the laser pulses to the bare surface of the specimens. Meanwhile the fatigue strength of FSWed specimens was 90MPa and LPwC enhanced it by 30MPa to 120MPa. This increment is a half compared to that in the BM, however the fatigue strength of the FSWed specimens after LPwC was higher than that of the BM. The surface roughness, hardness and residual stress were assessed and characterized as well. © 2011 Elsevier Ltd.


Makishi O.,Okinawa National College of Technology | Honda H.,Kyushu University
International Journal of Heat and Mass Transfer | Year: 2012

Previously proposed theories of the minimum-heat-flux-point (MHF-point) condition were examined using available experimental data obtained from the immersion cooling of spheres in water. The sphere diameter ranged from 9.5 to 30 mm and the liquid subcooling from 0 to 85 K. The limiting liquid superheat predicted by the Lienhard equation was compared with the liquid-solid interface superheat at the instant of liquid-solid contact at the MHF-point. The results showed that the liquid-solid interface superheat was not limited by the limiting liquid superheat and its value was connected with the collapse mode of vapor film. The collapse mode was a coherent collapse at a low interface superheat and the mode changed to a propagative collapse as the interface superheat increased. The critical vapor film thickness obtained from the linear stability analysis of vapor film was compared with the calculated value of average vapor film thickness at the MHF-point. For all data, the ratio of the average vapor film thickness to the critical vapor film thickness was correlated well as a function of liquid subcooling. The ratio decreased with increasing liquid subcooling and tended to about 0.8 to 1 depending on the experiments. This indicated that the MHF-point at a high liquid subcooling was determined by the critical vapor film thickness. A physical consideration was given to the effect of liquid-solid contact that occurred in the film boiling region on the calculated value of the vapor film thickness and the stability of vapor film. © 2012 Elsevier Ltd. All rights reserved.


Taira J.,Okinawa National College of Technology | Taira K.,Okinawa Prefectural Enterprise Bureau | Ohmine W.,Okinawa National College of Technology | Nagata J.,National Institute of Health and Nutrition
Journal of Food Composition and Analysis | Year: 2013

In this study, the essential minerals Fe, Ca and Mg including the essential trace elements of Cr, Co, Ni, Cu and Zn in 11 species of sweet potato (Ipomoea batatas L.) leaves were determined by ICP-MS. The levels of these elements were similar to those of common green leafy vegetables. The ratio of K and Na for the seven species of sweet potato leaves was higher than that of spinach, indicating that sweet potato leaves may be used in anti-hypertensive diet. The selenium and manganese contents were higher in all the sweet potato leaves than in other green leafy vegetables, such as spinach and water spinach. In addition, the anti-oxidative activity of the sweet potato leaves was examined in a low-density lipoprotein (LDL)-oxidation induction system. All the caffeoylquinic acid (CQA) derivatives indicated an anti-LDL oxidation activity at low concentrations (1-5 μM) and particularly, the activity of 3,4,5-triCQA was remarkably higher than those of 5-CQA and diCQA, such as 4,5-diCQA, 3,5-diCQA and 3,4-diCQA. The antioxidant activity of sweet potato leaves was correlated with the amounts of CQA derivatives in the range of r= 0.69-0.75. These results suggested that sweet potato leaves may prevent that developing atherosclerosis causes the oxidative modification of LDL. This study demonstrated that the sweet potato leaves containing an abundant nutrient mineral and functional polyphenol will be useful as a functional food material. © 2012 Elsevier Inc.


Tansuriyavong S.,Okinawa National College of Technology
ICIIBMS 2015 - International Conference on Intelligent Informatics and Biomedical Sciences | Year: 2015

This paper proposes a new method of learning English for Japanese people, by using English-subbed Japanese-sounded cartoons (anime). In the proposed system, the English subtitles are recognized into text in real time and sent to the text-to-speech system. After that, the sound is generated and can be heard immediately, after Japanese sound. It means that, while the learner is watching anime, learner can hear the sound of English subtitles in immediately after he/she heard the sound of original Japanese. By hearing Japanese and English alternately a lot, finally the learner will be able to understand English. This system is suitable for everyone who wants to learn English while watching anime, including the child. © 2015 IEEE.


Chinen K.,Okinawa National College of Technology
Technical Digest - 2012 17th Opto-Electronics and Communications Conference, OECC 2012 | Year: 2012

The dominant cause of the increase of the Relative Constellation Error (RCE) when the DFB-LD is largely modulated in the WiMAX-RoF is not the current clipping around the threshold current but the optical multi-mode oscillation. © 2012 IEEE.


Zacharie M.,Okinawa National College of Technology
Journal of Computer Science | Year: 2010

Problem statement: Research into robot motion control offers research opportunities that will change scientists and engineers for year to come. Autonomous robots are increasingly evident in many aspects of industry and everyday life and a robust robot motion control can be used for homeland security and many consumer applications. This study discussed the adaptive fuzzy knowledge based controller for robot motion control in indoor and outdoor environment. Approach: The proposed method consisted of two components: the process monitor that detects changes in the process characteristics and the adaptation mechanism that used information passed to it by the process monitor to update the controller parameters. Results: Experimental evaluation had been done in both indoor and outdoor environment where the robot communicates with the base station through its Wireless fidelity antenna and the performance monitor used a set of five performance criteria to access the fuzzy knowledge based controller. Conclusion: The proposed method had been found to be robust. © 2010 Science Publications.


Sugimoto K.,Okinawa National College of Technology
Proceedings - Frontiers in Education Conference, FIE | Year: 2015

In this paper, the effectiveness of our approach for engineering education at an early stage is presented. It is designed for 15 or 16-year-old students who have just begun to take lectures for a specific specialized field of engineering in our college of technology. Here, how to encourage their learning motivation for various fields of engineering becomes important. Therefore, our program was designed by focusing on skills for communication, writing reports and making presentation through an engineering education practice as a project based learning by 4 or 5 students a group. The decision was made through discussion by the group unit. In order to check presence of the difference between generations, the investigation with a program of the same contents has been carried out for three years. By analyzing the answer to the questionnaire and impression in free form answering from 160 students in total every year for inspection of effectiveness, we conclude that our approach is effective not only for the enhancement of student's learning motivation in the engineering education program but their recognition for importance of the skill acquirement was confirmed. © 2014 IEEE.


Ogino T.,Okinawa National College of Technology
Advances in Intelligent Systems and Computing | Year: 2015

The network intrusion is becoming a big threat for a lot of companies, organization and so on. Recent intrusions are becoming more clever and difficult to detect. Many of today's intrusion detection systems are based on signature-based. They have good performance for known attacks, but theoretically they are not able to detect unknown attacks. On the other hand, an anomaly detection system can detect unknown attacks and is getting focus recently. In this paper, we study the effectiveness and the performance experiments of one of the major anomaly detection scales, LOF, on distributed online machine learning framework, Jubatus. © Springer International Publishing Switzerland 2015.


Mbaitiga Z.,Okinawa National College of Technology
2014 International Conference on Computer and Information Sciences, ICCOINS 2014 - A Conference of World Engineering, Science and Technology Congress, ESTCON 2014 - Proceedings | Year: 2014

This paper discusses the multi-color recognition using the min-max color threshold for outdoor robot navigation. All colors used in this project are RGB orthogonal color space in order to see how much of each primary color between min and max that can be observed in the color to be recognized. The white color value in the color space is set as the object for which the target color to be recognized belongs, while the black color value is set as the object background. The recognition process is done by summing up first the values of the red, green and blue in each color to obtain the rgb sum value, which is then divided by the individual color element to obtain the color threshold. This threshold is compared to the originally color threshold for the recognition, where a satisfactory result is expected as the project is not yet finished. © 2014 IEEE.

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