Wyniki wyszukiwania - BazTech

1

An approximation algorithm for multi-unit auctions: numerical and subject experiments

Takahashi S., Izunaga Y., Watanabe N.

Operations Research and Decisions

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2018

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Vol. 28, No. 1

95--115

EN

In multi-unit auctions for a single item, the Vickrey–Clarke–Groves mechanism (VCG) attains allocative efficiency but suffers from its computational complexity. Takahashi and Shigeno thus proposed a greedy based approximation algorithm (GBA). In a subject experiment there was truly a difference in efficiency rate but no significant difference in seller’s revenue between GBA and VCG. It is not clear in theory whether each bidder will submit his or her true unit valuations in GBA. We show, however, that in a subject experiment there was no significant difference in the number of bids that obey “almost” truth-telling between GBA and VCG. As for individual bidding behavior, GBA and VCG show a sharp contrast when a human bidder competes against machine bidders; underbidding was observed in GBA, while overbidding was observed in VCG. Some results in a numerical experiment are also provided prior to reporting those observations.

2

The analysis of environmental and human impacts of using Strong Alkaline Water for cooling during machining

Da Silva P., Tanabe I., Junior D. C. R., Takahashi S.

Journal of Machine Engineering

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2018

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Vol. 18, No. 1

45--60

EN

An eco-friendly manufacturing approach is important for the environment. Enhancing machining performances is not only required to improve product’s quality, time saving, and reduces costs; it is also contributed to the environmental protection efforts. Cooling is important aspect for obtaining this purpose. Therefore the benefits of Strong Alkaline Water (SAW) cooling method was assessed and compared with conventional wet cutting method. An experiment was performed at Nagaoka University of Technology machining centre. Three machine tools including a milling machine, a drilling machine and a turning machine were used. The study shows that using SAW for cooling is far more efficient than conventional cooling method. It reduces annual global warming potential by 72.95%, acidification potential 98.18%, ozone depletion potential 99.6%, smog formation potential 85.71% and human toxicity potential 42.86% compare with conventional method. The study concludes that besides inhibiting corrosion, prolonging tool life, improving surface roughness of final cutting and reducing energy usage, strong alkaline water cooling is an environmentally friendly approach and has positive impact on human health.

3

Machine tool distortion estimation due to environmental thermal fluctuations – a focus on heat transfer coefficient

Da Silva P., Pena-Gonzalez L. E., Tanabe I., Takahashi S.

Journal of Machine Engineering

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2018

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Vol. 18, No. 2

17--30

EN

Thermally induced errors have been approached in multiple ways due to the influence these have over the positional accuracy of a machine tool. Here, approaches regarding environmental thermal fluctuations surrounding a machine tool remain to be explored in detail. These fluctuations have been explored in terms of the heat transfer coefficient and thermal radiation of the machine shop walls, as well as in terms of seasonality and varying thermal gradients. This paper presents additional considerations regarding environmental temperature perturbations, as heat transfer coefficient fluctuations in the machine shop were thought to play a significant role in machine tool thermal deformation a broader term for these phenomena, environmental thermal fluctuations, was defined and evaluated. Specifically, an environmental thermal data survey of a machine shop was explored. This data was then applied to a NC milling machine and a CNC jig borer FEM analyses and compared to experimental data. FEM simulations were then used to demonstrate that convection regimes and heat transfer coefficient values at a machine shop have a significant influence over machining precision. Here, under maximum and minimum heat transfer coefficient values, the NC milling machine and CNC jig borer simulations results showed an error of cut difference up to 36.5 μm and 18.17 μm, respectively. In addition, as the importance of the heat transfer coefficient was highlighted, considerations regarding machine tool surface color were deemed relevant and were described.

4

Development of Software for Calculation of Best Condition Using Taguchi Methods and Its Evaluation

Sakamoto H., Tanabe I., Takahashi S.

Journal of Machine Engineering

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2015

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Vol. 15, No. 2

44--54

EN

Recently Taguchi methods are used to decide optimum processing conditions with narrow dispersion for robust design. On the other hand, innovative development with short-term, low cost, labor and energy saving is also required in the world. In this study, the software for development of a product with optimum condition using Taguchi methods is developed and evaluated. There are two trials in the software using Taguchi methods. First trial investigates rough functions regarding all levers of all control factors, then important control factors and meaningless control factors were sorted with the several comments for the second trial. At that time, maximum, intermediate and minimum values for each lever of each of the control factors should be used for pursuit of all possibilities. In the first trial, the relationship between each level value of each of the control factor and the desired property is also decided by the function, then the optimum combination using each level of each of the control factors were calculated for the second trial by using the function. The second trial is confirmed for the best combination using the estimated optimum level values. For example of an application, the optimum design for the paper craft “airplane” was investigated for evaluating this software in the experiment. It is concluded from the result that: (1) The proposed software was useful for developing with short-term and lower cost, (2) This tool could quickly and exactly decide the optimum design condition and (3) The paper craft “airplane“ with most long flying length is manufactured by using the developed software.

5

Development for Sound Quality Optimisation by Taguchi Methods

Sakamoto H., Tanabe I., Takahashi S.

Journal of Machine Engineering

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2015

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Vol. 15, No. 2

69--81

EN

Characteristic that is hard to obtain in the calculation in product development. The sensory characteristic is often had such as sound quality, visual sensation and tactile sensation. The evaluation method for visualizing the determination of the customer is being established by applying Taguchi-methods and so on. The fact is still got many corresponds with the method of Try & Error as numbers of cases are small in order to optimize the properties. Therefore, the study was conducted of the method for optimization of sound quality by using the innovative tool using Taguchi-methods that newly developed. The research results are summarized as follows. (1) Sensory characteristic tuning method by using Taguchi-methods was calculated the values to be optimized in a few studies, and the result was equal to or greater than the result of specialists is carried out. (2) Commonly, the sensory characteristic of optimization is conducted with the method of Try & Error; moreover, it could be confirmed that leading to improvement of productivity by using this method even though it takes time to perform so as to optimize under changing in physical condition and environment.

6

On counter measure of vibration for machine using alkaline water with polymer

De Sousa Gama V., Tanabe I., Takahashi S.

Journal of Machine Engineering

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2014

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Vol. 14, No. 3

58--70

EN

In the 21st century, as it is important to produce the products with high accuracy, high quality and eco-friendly, the most of manufacturers need several daring plans, unique ideas and new technologies. For example, in machine tool technology, restraint of vibration on the machine tool was required for high accuracy and quality, and several countermeasures using costly equipment and large quantity of electrical energy were used for the restraint, however those countermeasures are not enough. Therefore a countermeasure of vibration for machine tool using alkaline water with polymer was developed and evaluated. Polyethylene oxide was used for the polymer because of the low cost and the safety for health. Relationship between the mixed polymer in the alkaline water and the damping ratio were firstly investigated. And the optimum percentage of the polymer was decided for restraint of vibration on a machine tool. Then the damper structures using alkaline water with polymer were development, and the three dampers were set for restraint of vibration in the small machine tool; those are the support units, the vise and the head stock. Each damper was evaluated regarding noise and vibration on the machine tool and surface roughness on a work piece in the experiment. It is concluded from the results that; (1) the optimum percentage of the polymer for the damper was 6 wt%, (2) the damper structures using alkaline water with polymer were very effective for restraint of both noise and vibration on the machine tool and smoothly surface on the work piece.

7

Development of polishing technology using heat for mirror-like surface of aluminum

Takahashi S., Tanabe I., Fukuda N.

Journal of Machine Engineering

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2014

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Vol. 14, No. 2

57--68

EN

Recently, high efficient solar power generation is required because eco-awareness is increasing. High efficient generation becomes possible by focusing sunlight on electric generating element, i.e. CPV (Concentrator photovoltaic). Although the concentrator is used for focusing sunlight, it demands large spherical surface with high solar reflectance, fine accuracy and lightweight. Aluminum is considered as suitable material for concentrator. However, mirror-like processing on large spherical surface is very difficult. Therefore, new polishing technology for aluminum was developed and evaluated in this paper.Main objective is to obtain high solar reflectance by improving surface roughness. As a trial study, workpiece was not large spherical but small and flat. Firstly, the polishing tool which attached polishing cloth was developed.Optimum polishing cloth for tool was investigated by trial and error approach. When workpiece was heated before starting polishing, a number of oxides were adhered to polishing cloth and surface roughness was improved efficiently.Then optimum polishing condition was decided by using design of experiments method. Finally, solar reflectance on polished surface was measured and evaluated. It is concluded from these results that (1) the developed polishing technology was effective for processing the mirror-like surface on the surface of aluminum, (2) 82% solar reflectance was obtained with developed polishing technology by improving surface roughness of workpiece.

8

Development of perfectly design system using Taguchi methods

Sakamoto H., Tanabe I., Takahashi S.

Journal of Machine Engineering

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2014

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Vol. 14, No. 2

69--80

EN

As swift development with low cost was required for the manufacturing in industry, CAE simulation was used to predict the result of the design process, and Taguchi methods was used to decide optimum conditions for minimizing the dispersion.In this study, the perfectly design system without trial production using CAE and Taguchi methods was developed and evaluated. Software for original Taguchi methods and software for productivity management were firstly created, these softwares were combined with established CAE, and software package was developed for estimating the optimum combination of design parameters. Then the quality and the functionality were advanced to gain the optimum condition for the maximum profit considering the function of the grading of products, the delinquent charge and the loss function in the quality engineering based on the developed software. The research results are summarized as follows. (1) Perfectly design system without trial production using Taguchi methods was developed for calculations of the grading products, adding the delinquent charge and the loss function. (2) The evaluation with Kami-copter contributes to the profit evaluation of the grading; the delinquent charge and the loss function with high dimensional accuracy and is evaluated effective on industry.

9

Calculation for Reaction Unburned Component in CO(2) Recovering Semi-closed Gas Turbine System

Ebara T., Iki N., Takahashi S.

Prace Naukowe Politechniki Warszawskiej. Mechanika

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2003

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z. 202

45--51

EN

The aim of this research was to propose optimal operation conditions and system configuration for C02 Recovering Semi-closed Gas Thrbine System with CH4-02 firing. To reduce the C02 emission and protect the environment, it is needed to develop a clean and high-efficiency power generation system. Although higher turbine inlet temperature (TIT) derives higher system efficiency, it causes higher NOx emission in open gas turbine systems. The semi-closed gas turbine system with steam recirculation has been noted because of its high efficiency (ni)>60%, HHV ) without any NOx emission. There are many technical challenges in the realization of this system, such as materials and combustion control. We try to clarify the relationship between the emission properties from system (e.g., concentration of CO which is a regulated poison) and the geometry of gas path in a high temperature turbine. The calculation results clarify that the CO concentration is low, but strongly effected by the turbine geometry at a lean combustion surroundings, which is the realistic operating condition. And the necessity of wide and suitable length duct for lower CO emission is also clarified.

10

Observation of flat-ignition of H2-O2-O3 mixtures with excimer laser

Furutani H., Liu F., Iki N., Hama J., Takahashi S.

Archivum Combustionis

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2000

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Vol. 20 nr 1-2

13-18

EN

To develop a new ignition method, authors carrieg out a series of experiments about the ignition process of H2-O2O3/ H2-O2-O3-Ar mixtures with an excimer laser. From laser-focusing ignition experiments, we found that the Minimum Incident Laser Energy for ignition (MILE) decreased drastically with the concentration of ozone, and the plane ignition was possible with a laser sheet, providing the possibility of the bulk ignition with UV light. The schlieren observation of the process of plane ignition with a high-speed framing camera showed that the float part of mixture irradiated with the laser sheet ignited simultaneously. And then, the flame kernel grew extremely rapidly.

11

Future hydrogen technologies in power engineering and semi-closed gas turbine system

Iki N., Hama J., Takahashi S., Miller A., Kiryk S.

Prace Naukowe Politechniki Warszawskiej. Mechanika

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1999

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z. 181

97-106

EN

This paper introduces one of the utilisation of the hydrogen as a power systems` fuel in Japanese program, which has been progressed to establish the global energy network by using hydrogen as a secondary clean energy. And it introduces semi-closed gas turbine systems with steam recirculation. They are not only capable of the high efficiency with hydrogen-oxygen combustion but useful with fuel-oxygen combustion for CO(sub 2) separation. This paper also describes the key technologies to evaluate the possibilities of a semi-closed gas turbine system with higher efficiency.

PL

Niniejszy artykuł przedstawia jedną z możliwych technologii wykorzystania wodoru jako paliwa dla systemów wytwarzania energii, zaproponowaną w japońskim programie badawczym. Program ten ma za zadanie stworzenie globalnej sieci energetycznej z wykorzystaniem wodoru jako wtórnego nośnika czystej energii użytkowej. Przedstawiono także układ z turbiną gazową i recylkulacją pary, który może z dużą sprawnością produkować energię zarówno dla spalania wodór-tlen, jak też dla spalania gaz/olej-tlen przy separacji CO(sub 2). W artykule wymieniono kluczowe technologie, których rozwój ma wpływ na uzyskanie wysokiej sprawności powyższego układu.