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Experimental Study of Non-Destructive Approach on PEMFC Stack Using Tri-Axis Magnetic Sensor Probe

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Journal of Power and Energy Engineering 2015年第3期3卷 1-8页

作者： Yutaro Akimoto keiichi okajima Graduate School of Systems and Information Engineering University of Tsukuba Tsukuba Japan

In this paper, the current distribution in a 300-W-class PEMFC stack was investigated in order to determine the operating state of the stack. Measurements of the magnetic field were performed on several cells in the stack. The vector of the magnetic field expressed the direction of the macroscopic current, which was from the anode side to the cathode side. This direction matched the polarity of the stack. In the measurement results, current distributions differed among cells;each cell had a different performance. Furthermore, we have tried to evaluate faults, such as flooding, by measuring the magnetic field and variations in the voltage.

关键词： PEMFC In-Situ Diagnosis Current Distribution Flooding Magnetic Sensor

Evaluation of Heat and Current Characteristics of Bypass Diodes for Fault Detection in Photovoltaic Module

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Journal of Energy and Power Engineering 2017年第3期11卷 179-186页

作者： keiichi okajima Mizuki Hakura Department of Risk Engineering University of Tsukuba Tsukuba 3058573 Japan

A Method for the Detection of Decrease in Power in PV Systems Using Satellite Data

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Smart Grid and Renewable Energy 2019年第1期10卷 1-15页

作者： Kota Kawasaki keiichi okajima Department of Risk Engineering System and Information Engineering University of Tsukuba Ibaraki Japan

In this paper, a method to detect a decrease in the output power of photovoltaic systems is proposed. This method is based on using satellite irradiance data. In addition, fault detection is carried out with only one day’s data in this method. Thus, the time elapses since the decrease in output is shorter than with the other methods. In order to mitigate the error in satellite data and improve the accuracy of fault detection, data extraction is carried out, which consists of two steps. In the first step, effective data are extracted by setting a lower irradiance limit. In the second step, “Calculation day” is determined depending on the number of effective data in one day. Fault detection, which is only conducted on the Calculation day, is conducted by comparing the expected power and the measured power. The parameters used in this study were optimized by testing 45 systems that appear normal. Subsequently, 340 systems were analyzed with the proposed method, using optimized parameters. The results showed the effectiveness of our method from the viewpoints of both accuracy and time required. In addition, three data extraction methods were considered to distinguish between the permanent decrease caused by failure, and the temporary decrease caused by partial shade. Fuzzy cluster analysis showed the best result among the three methods used.

关键词： PV System Fault Detection Fault Classification Satellite Data

Photovoltaic Power Potential Analysis in Equator Territorial: Case Study of Makassar City, Indonesia

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Journal of Power and Energy Engineering 2017年第1期5卷 15-29页

作者： Muhammad Akbar Sihotang keiichi okajima Graduate School of System and Information Engineering University of Tsukuba Tsukuba Japan Faculty of Engineering Information and Systems University of Tsukuba Tsukuba Japan

Solar power energy in some countries can be the most potential renewable energy to overcome lack of energy and environmental problems. Indonesia is one of the examples. One of the promising cities to install photovoltaic (PV) systems is Makassar, which has average 5.83 kWh/m2/day of solar irradiance (Meyta, 2011). However, until 2016, there is still no solar panel installation in Makassar (PLN, 2015). In addition, general lack of research in assessing potential of PV systems in Makassar makes PV system difficult to develop. This study therefore set out to assess PV system potential in Makassar which its objectives are to determine 1) total available area for rooftop and large-scale PV systems in Makassar, 2) economy feasibility and 3) environmental impact due to PV installation. Three cases have been analyzed in this study, first, PV systems for residential rooftop, second, PV systems for large-scale (mega solar) in Makassar, and third, PV systems for large scale in outside Makassar and radius 20 km from center of Makassar. ArcGIS10.3 software is carried out to estimate available area for PV installation. Furthermore, RetScreen 4 software was used to conduct PV system capacity and its energy yield and to evaluate economy analysis such as internal rate of return and cost of energy. As the result, the total available area for residential rooftop PV system is evaluated to be 13.8 km2, which potential installed capacity is estimated to be 2044 MW. Total available area for large-scale PV system in Makassar and outside Makassar are 19.3 km2 and 231.3 km2, which estimated 851 MW and 10,179 MW of installed capacity, respectively.

关键词： GIS Rooftop PV System Large-Scale PV System Internal Rate of Return (IRR)

Surgical strategies for challenging common bile duct stones in the endoscopic era: A comprehensive review of current evidence

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World Journal of Gastrointestinal Endoscopy 2024年第6期16卷 305-317页

作者： Tharathorn Suwatthanarak Vitoon Chinswangwatanakul Asada Methasate Chainarong Phalanusitthepha Minoru Tanabe keiichi Akita Thawatchai Akaraviputh Minimally Invasive Surgery Unit Department of SurgeryFaculty of Medicine Siriraj HospitalMahidol UniversityBangkok Noi 10700BangkokThailand Graduate School of Medical and Dental Sciences Tokyo Medical and Dental UniversityBunkyo 113-8519TokyoJapan Department of Hepatobiliary and Pancreatic Surgery Tokyo Medical and Dental UniversityBunkyo 113-8519TokyoJapan Department of Clinical Anatomy Tokyo Medical and Dental UniversityBunkyo 113-8519TokyoJapan

While endoscopic retrograde cholangiopancreatography(ERCP)remains the primary treatment modality for common bile duct stones(CBDS)or choledocho-lithiasis due to advancements in instruments,surgical intervention,known as common bile duct exploration(CBDE),is still necessary in cases of difficult CBDS,failed endoscopic treatment,or altered anatomy.Recent evidence also supports CBDE in patients requesting single-step cholecystectomy and bile duct stone removal with comparable outcomes.This review elucidates relevant clinical anatomy,selection indications,and outcomes to enhance surgical understanding.The selection between trans-cystic(TC)vs trans-choledochal(TD)approaches is described,along with stone removal techniques and ductal closure.Detailed surgical techniques and strategies for both the TC and TD approaches,including instrument selection,is also provided.Additionally,this review comprehensively addresses operation-specific complications such as bile leakage,stricture,and entrapment,and focuses on preventive measures and treatment strategies.This review aims to optimize the management of CBDS through laparoscopic CBDE,with the goal of improving patient outcomes and minimizing risks.

关键词： Choledocholithiasis Common bile duct stone Difficult common bile duct stone Common bile duct exploration Laparoscopic common bile duct exploration

CO2 Emission from Electricity Generation in Malaysia： A Decomposition Analysis

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Journal of Energy and Power Engineering 2017年第12期11卷 779-788页

作者： Maryam Huda keiichi okajima Kengo Suzuki Risk Engineering Department System and lnformation Engineering University of Tsukuba Ibaraki 305-8577 Japan

In tenth Malaysian Plan, Malaysian government had voluntarily targeted to reduce its emission intensity to 40% compared to the 2005 level by the year 2020 and recently re-pledge to reduce more and declared for 45% emission reduction by 2030. Looking at the country"s high dependency to the fossil fuel generation it is a high concern on the increasing CO2 emission in Malaysia. This paper intends to analyze the current status of CO2 emissions from electricity generation in Malaysia during the period 1992-2014 by applying the LMDI (logarithmic mean Divisia index) technique to find the nature of the factors influencing the changes in CO2 emissions. The decomposition analysis observed three biggest factors contributed to the reduction of CO2 emission throughout the period which is thermal generation effect, electricity generation efficiency effect and electricity structure effect.

关键词： Decomposition analysis LMDI CO2 emission electricity generation

Tapping the Potential of Large Scale Solar PV System in Sabah: The Feasibility Analysis

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Energy and Power Engineering 2017年第2期9卷 108-118页

作者： Maryam Huda keiichi okajima Kengo Suzuki Risk Engineering Department System and Information Engineering University of Tsukuba Ibaraki Japan

As a developing country with the rapid growth of economic and population like Malaysia, energy and electricity play a critical role towards sustaining and supporting the development of the nation. However, like many countries across the world, Malaysia is facing challenges in reducing the carbon footprint while attending the expanding growth. In the Eleventh Malaysia Plan, Malaysia has pledged to renew and increase its commitment to the environment and long-term sustainability by adopting green growth initiatives. According to the plan, one of the approaches towards pursuing green growth is by undertaking the sustainable consumption and production concept that promotes economic growth without compromising the environment. One of the strategies is to focus on promoting renewable energy sources as well as boosting up the development of the systems. The last decade has seen a growing trend towards renewable energy in Malaysia, particular in solar photovoltaic applications in recent years. This paper will investigate the potentials of installing 5 MW solar PV plants in the state of Sabah according to feed in tariff incentives and its financial and environmental assessment in order to promote large scale solar PV in Malaysia. This paper calculates the economic viability through IRR and simple payback indicators and the environmental impact through CO2 emission reduction indicator for the proposed 5 MW plant.

关键词： Large Scale Solar PV Feed in Tariff Renewable Energy CO2 Emission Sabah Malaysia

Life Cycle Input-Output Analysis Extended to Use, Disposal, and Recycling Stages Applied to Embodied CO2 Emissions of a Refrigerator

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Journal of Energy and Power Engineering 2013年第4期7卷 695-704页

作者： Yuki Mizumoto Yohji Uchiyama keiichi okajima Department of Risk Engineering Graduate School of System and Information Engineering University of Tsukuba lbaraki305-8537 Japan Department of Risk Engineering Faculty of System and Information Engineering University of Tsukuba Ibaraki 305-8537 Japan

Input-output analysis is widely employed to analyze inventories of a product"s embodied energy and environmental burdens. However, input-output analysis focuses only on the production stage and ignores other life cycle phases. Input-output analysis is not exactly a LCA (life cycle assessment) method in the strict sense of ISO 14040 standards, which must cover all stages of a product"s life cycle, "from the cradle to the grave", so to speak. A tiered hybrid LCA is a useful tool that covers all life cycle stages by combining a process analysis with the input-output analysis method. This study aims to extend input-output analysis to the use, disposal, and recycling stages by using matrix-based method. The new method is applied to the analysis of the embodied CO2 emissions of a refrigerator as a case study. The entire life cycle CO2 emissions are estimated to be 2.9 tons, including indirect emissions, and the reduction in CO2 emissions due to recycling steel scrap is calculated as 48.5 kg. The authors conclude that the new method enables a consistent inventory analysis for all life cycle stages by combining process and input-output methods.

关键词：二氧化碳排放量生命周期评估投入产出分析扩展使用回收冰箱应用处置

Including Co-benefits in the CDM of the Power Sector： A Case Study for India

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Journal of Energy and Power Engineering 2012年第12期6卷 1925-1934页

作者： Ryo Eto Akinobu Murata Yohji Uchiyama keiichi okajima Department of Risk Engineering Faculty of Systems and Information Engineering University ofTsukuba Ibaraki 305-8573 Japan National Institute of Advanced Industrial Science and Technology (AIST) Ibaraki 305-8564 Japan

This study examines the effects of the inclusion of co-benefits on the potential capacity of advanced thermal plants with a linear programming model in the CDM (clean development mechanism) in India"s power sector. It investigates how different marginal damage costs of air pollutants affect the potential capacity of NGCC (natural gas combined cycle) and IGCC (integrated gasification combined cycle) by CDM projects with a scenario analysis. Three results are found from this analysis. First, IGCC and NGCC are installed at lower CER (certified emission reductions) prices when the marginal damage costs of air pollutants are added to the CER prices. Second, the CER prices of $1/tCO2 correspond with the sum of marginal damage costs of air pollutants of $150/t for NGCC and $30/t for IGCC in India"s power sector. Thus, including the co-benefits into CDM attracts developing countries such as India where coal resource is redundant. Third, the SOx and NOx reduction benefits attained from the CDM projects become large in a grid where IGCC is installed.

关键词： CDM项目电力部门印度利益清洁发展机制项目联合循环发电系统空气污染物 IGCC