International Journal of Automation Technology
Online ISSN : 1883-8022
Print ISSN : 1881-7629
ISSN-L : 1881-7629
12 巻 , 6 号
選択された号の論文の20件中1~20を表示しています
Special Issue on Design and Manufacturing for Environmental Sustainability
  • Yasushi Umeda
    原稿種別: Editorial
    2018 年 12 巻 6 号 p. 805
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    This is the fourth special issue on design and manufacturing for environmental sustainability. While Japanese manufacturers are not so active in this field, the trend of integrating sustainability into manufacturing activities and management of companies is becoming dominant. We can point out three epoch-making instances: namely, United Nations’ ‘Sustainable Development Goals (SDGs),’ which consists of 17 goals to be achieved by 2030, covering not only environmental sustainability but also social and human sustainability; EU’s ‘Circular Economy,’ which promotes various routes for resource circulation (e.g., reuse, remanufacturing, maintenance, and recycling) for increasing employment and market competitiveness of EU and resource efficiency; and ‘Paris Agreement’ on climate change, which enforces reduction of the emission of greenhouse gases to zero by the end of this century.

    This special issue includes six well-written papers, all of which are deeply related to these three policies. The first four papers focus on product life cycle or even multiple product life cycles. This aspect is an inherent feature of design and manufacturing for environmental sustainability, which was not considered in traditional design and manufacturing. The keywords of these four papers are life cycle CO2 emission evaluation of electric vehicles, life cycle simulation of reuse among multiple product life cycles, disassembly part selection based on the idea of life expectancy, and personalization design aiming at avoiding mass production and mass disposal. The latter two papers are rather fresh in this journal. The fifth paper deals with customer preferences in Indonesia. Focusing on life styles in developing countries is a very important topic emphasized in SDGs. The last paper deals with food waste, which is emphasized in both SDGs and Circular Economy.

    Most of the papers, revised and extended in response to the editor’s invitations, were originally presented at EcoDesign 2017: the tenth International Symposium on Environmentally Conscious Design and Inverse Manufacturing, held in Tainan, Taiwan.

    The editor sincerely thanks the authors and reviewers for their devoted work in making this special issue possible. We hope that these articles will encourage further research on design and manufacturing for environmental sustainability.

  • Keita Ishizaki, Masaru Nakano
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 806-813
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    This paper presents a comprehensive life-cycle analysis of CO2 (LCCO2) emissions from automobiles using a hybrid life-cycle inventory approach to predict the growth of electrified vehicles in Japan. Herein, the hybrid electric vehicle (HEV), plug-in HEV (PHEV), and battery electric vehicle (BEV) versions of the mass-produced Toyota Prius hatchback are analyzed, considering the automobile-usage environment in Japan. In particular, a breakeven analysis of HEV vs. PHEV vs. BEV is conducted in terms of LCCO2 emissions that are affected by (i) outside air temperature and (ii) CO2 emissions during power generation from the present day up to 2030. Our results show that HEV has the lowest LCCO2 emissions when the current thermal-power-dependent electricity generation mix (average for 2012–2014) is considered, followed in order by PHEV and BEV. However, it is predicted that in 2030, PHEV will have the lowest LCCO2 emissions, followed in order by HEV and BEV, as it is anticipated that nuclear and renewable energy sources will be widely available by 2030. PHEV is expected to gain popularity by 2030. Regarding BEV, large quantities of CO2 emissions are emitted during battery production. Furthermore, due to the domestic electricity generation mix from the present day up to 2030, the LCCO2 emissions of BEV will exceed those of HEV and PHEV.

  • Hidenori Murata, Naoya Yokono, Shinichi Fukushige, Hideki Kobayashi
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 814-821
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    Reuse is an effective method of circulating resources in terms of environmental benefits because it requires fewer resources and less energy than manufacturing new products from virgin materials. In global reuse, a used component or module is reused in a different application. To evaluate a system of multiple product lifecycle systems (PLSs), the lifecycle simulation methodology LCS4SoS has been proposed. LCS4SoS comprises three elements, namely, individual PLSs, interactions among them, and their evolution over time. This paper proposes a lifecycle simulation method for global reuse based on the LCS4SoS framework. Flow control rules are developed for global reuse to control the directions and quantities of material flow among the PLSs. The usefulness of this method is verified by a case study of automobile and stationary battery PLSs.

  • Shota Hasegawa, Yuki Kinoshita, Tetsuo Yamada, Masato Inoue, Stefan Br ...
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 822-832
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    The depletion of natural resources is a critical environmental issue, and the recovery, including reuse and recycling, of end-of-life assembled products is the key to reducing the use of natural resources. However, in order to reuse or recycle an assembled product, it is essential to consider the life expectancy or material type and the weight of the parts in the product. In addition, because the assembled products comprise various parts, manual disassembly is required, which entails high costs. To recover assembled products in an environmentally friendly and economical manner, part selection for disassembly is required. A part selection method is proposed with three selection types: reuse, recycling, and disposal. First, data-set preparation is addressed. Second, the method for selecting the disassembly parts using integer programming and the ϵ constraint method is explained. Finally, numerical experiments are conducted using the proposed part selection method with a computer as a case study. Lifetime changes of the parts/product are then analyzed.

  • Kazuki Kaneko, Yusuke Kishita, Yasushi Umeda
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 833-841
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    The personalization of products and services is expected to become an indispensable feature of manufacturing. Because the concept of personalization ranges over a variety of domains from the manufacturing of a prosthetic foot to a web recommendation, there exist no commonly applicable design methodologies for product personalization. The purpose of this research is to propose methods of personalization. Therefore, this paper is focused on designing procedures of personalization, which include preparation, readout, design, production and provision, use, and feedback. For supporting the design of personalization procedure, we developed ten personalization strategies, a step-flow model, and a design procedure. Finally, the advantages of this method are investigated through a case study.

  • Ihwan Ghazali, Salwa Hanim Abdul Rashid, Siti Zawiah Md Dawal, Hideki ...
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 842-852
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    Nowadays, increasing awareness is directed toward the fulfilment of sustainability demands in production in rapidly developing Southeast Asian countries such as Indonesia. However, producing green products that satisfy customer preferences is still a challenging task for product designers and manufacturers. Cultural values can be a significant factor that influences customer preferences. The aim of this study is to investigate the influence of cultural values on green-product preferences. Data were statistically analyzed based on the fulfilment of critical threshold values for the modeling of a structural equation. According to the results, customer preferences in Indonesia were mostly influenced by uncertainty avoidance and long-term orientation. Further, additional product services were identified as the most important characteristic of green products for Indonesian customers.

  • Jui-Che Tu, Yi-Lin Lee
    原稿種別: Technical Paper
    2018 年 12 巻 6 号 p. 853-860
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    The density of convenience stores in Taiwan is the highest in the world. Among the numerous commodities, the market competition for fresh food products is the fiercest and has become a focus of convenience store operations. Due to the change in Taiwanese lifestyles and consumer acceptance of the dining-out model, the demand and supply of fresh food products in convenience stores continues to increase. To benefit marketing performance, not only do convenience stores carry out promotional activities by reducing the price of products but they constantly innovate the taste and variety of fresh food products. For example, the tide of Taiwanese bento, during which promotions were implemented in the President Chain Store, has changed consumer diet habits; despite the raised price, consumers are still willing to purchase the product. However, convenient, real-time fresh food brought by this convenience store usually causes a massive waste of food. In its manufacturing and production processes, the food production chain ranks among the top three for national greenhouse gases. Whenever a piece of food is wasted, greenhouse gases are produced. Moreover, more resources are consumed to dispose of the wasted foods and garbage, further increasing greenhouse gas emissions and multiplying the carbon footprint. The phenomenon of excessive food waste has become an urgent issue in recent years in Taiwan, which is famous for its convenient food culture and service. In addition, because of Taiwan’s special economic development status, as well as rapid urbanization and family structure change, the ways to jointly affect this special consumption and food culture have become a topic worthy of discussion. Therefore, this research selected cooked food products in convenience stores as the main subject to explore the effect of social status and diet consumption from the perspective of daily social patterns and family structure data. It also examined the dilemma of excessive waste of food, to provide improvement advice as a reference to future relevant social policies and research.

Special Issue on Precision Abrasive Technology of Difficult-to-Machine Materials
  • Hirofumi Suzuki, Kazuhito Ohashi
    原稿種別: Editorial
    2018 年 12 巻 6 号 p. 861
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    The demand for high-precision hard components and their molds/dies have increased in various industries such as in the optical, automotive, and communication industries, as well as in life and medical sciences. Some difficult-to-machine materials can be reliably machined using deterministic precision cutting processes. On the other hand, hard and brittle materials such as ceramics, carbides, hardened steel of molds, glassy materials, or semiconductor materials have to be machined using precision abrasive technologies with super abrasives of diamond or cBN. However, the machining of high-precision components and their molds/dies by abrasive processes, is much more difficult because of their complex and non-deterministic nature and textured surface. Furthermore, high-energy processes such as laser technology can assist abrasive technologies for ensuring higher precision and efficiency. In this sense, precision grinding and polishing process are primarily used to generate high-quality and functional components usually made of difficult-to-machine materials. The surface quality achievable by precision grinding and polishing processes becomes more important for reducing machining time and costs.

    This special issue features five research articles – five papers – related to the most recent advances in precision abrasive technology of difficult-to-machine materials. Their subjects cover various abrasive machining processes of grinding, polishing, abrasive flow machining, tooling technology, and laser technologies.

    We deeply appreciate the careful work of all authors and thank the reviewers for their incisive efforts. We also hope this special issue will trigger further research on abrasive technologies.

  • Xue Sun, Tianbiao Yu, Zixuan Wang, Zhelun Ma, Maoqiang Xu
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 862-867
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    This paper investigates the mechanical property and microstructures of vitrified-bonded Ti-coated cubic boron nitride (CBN) composites under different sintering conditions. Three-point bending tests of the sintered vitrified-bonded Ti-coated CBN composite samples were carried out, and the microstructure, phase composition, and energy spectrum of the sintered composite samples were analyzed using SEM and X-ray diffraction. The test results indicate that the mechanical properties of the vitrified-bonded Ti-coated CBN composites improve with the increased temperature, and then show a declining trend. It was found that the titanium layer has a protective effect on the CBN abrasive. During the course of sintering, as the temperature increases, titanium in the titanium-coated layer is not only present on the CBN abrasive surface but is also diffused into the glass phase. In addition, oxidation reactions occur, which become stronger with the higher sintering temperature. Thus, the sintering temperature of the vitrified-bonded Ti-coated CBN composites should not be too high. It is better to sinter them in a vacuum rather than in air. Ti-coated CBN grains are not suitable for a vitrified bond with low refractoriness.

  • Shuhei Kodama, Shinya Suzuki, Akihiro Shibata, Keita Shimada, Masayosh ...
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 868-875
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    In recent years, nanostructures have been required for industry and medical services, to perform functions such as reduction in friction, control of wettability, and enhancement in biological affinity. Ultrashort pulsed lasers have been applied to meet these demands, and have been actively studied both experimentally and theoretically in terms of phenomena and principles. In this study, to clarify the phenomenon of the fabrication of laser-induced periodic surface structures (LIPSS), and its application to industry, experiments were conducted on SUS304, titanium, and nickel-phosphorus by a short pulsed laser that has a longer pulse duration, higher cost-effectiveness, and higher stability than ultrashort pulsed lasers. The results confirmed that while LIPSS were fabricated on Ti and Ni-P workpieces, a uniform fine periodic structure was not fabricated on the whole irradiated surface of SUS304, and crystal grain boundaries appeared with low energy density and irradiation number because SUS304 is an alloy composed of Fe, Cr, and Ni. Further, the short pulsed laser has a low power and long pulse duration, inducing the thermal effect. We clarified the effect of crystal structure on fabricating fine periodic surface structures with short pulsed laser.

  • Ryo Matsuda, Masatoshi Shindou, Toshiki Hirogaki, Eiichi Aoyama
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 876-882
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    We have developed a novel wireless multifunctional tool holder system to monitor the process vibrations of a rotating machining tool. The primary feature of the developed holder system is its ability to detect vibrations in three directions, two of which lie along the orthogonal axes, with the remaining direction of detection occurring along the rotational axis. This study aims to evaluate the vibrations induced by tapping and end-milling processes. It is demonstrated that the developed holder system enables the stick-slip vibrations induced by tapping and the chatter vibrations of end-milling to be monitored. Consequently, the developed holder system is found to be effective at estimating and improving the machining conditions that use a machining center.

  • Eckart Uhlmann, Simon Roßkamp
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 883-891
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    Trends like lightweight construction and functional integration lead to more and more complex workpieces. Often, these workpieces must be finished after machining. Especially inner contours are difficult to finish. Hence, only a few manufacturing techniques are suitable for deburring, edge rounding and polishing of inner contours. An appropriate solution is abrasive flow machining (AFM), in which a highly viscous fluid with abrasive grains is used. Despite the wide usage of AFM in industry, the knowledge about the fundamentals of abrasive flow machining processes is limited. After elaborated test series new findings concerning the surface integrity are presented in this paper. This is done in terms of the regressive development of the surface roughness on the one hand and in terms of the generated edge rounding on the other hand. In this context, it is found that there is a factor of approximately 16 between the chipped material at the edge and the chipped material at the surface. This factor is nearly constant during the processing time. Finally, using the results of the studies, the correlation between the processing parameters, surface roughness, edge rounding, and material removal rate can be characterized. Moreover, these new findings can be transferred to a comprehensive process model, which is the basis for a reliable process simulation. Owing to this progress, predictions of the processing results of AFM will be possible.

  • Eckart Uhlmann, Christian Sommerfeld
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 892-900
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    Abrasive brushes are often used for surface finishing and deburring and consist of a brush body with fixed, highly flexible abrasive filaments. During the brushing process the highly flexible abrasive filaments deform tangentially and axially and adapt to the shape of the workpiece. The contact behaviour of abrasive brushes in the machining process is very complex and has been insufficiently investigated so far. Abrasive brushes consist of a brush body with fixed, highly flexible abrasive filaments and are often used for surface finishing and deburring. During the brushing process, the highly flexible abrasive filaments deform tangential and axial and adapt to the shape of the workpiece. The mentioned contact behavior of the abrasive brush during the machining process is complex, and has not yet been sufficiently investigated. To better understand the contact behavior and, thus, the brushing process, a model of an abrasive filament is proposed in this study. The model describes the dynamic behavior of a single filament in contact with different workpiece geometries. The filament is discretized into a multi-body system of rigid links connected with rotational springs and rotational dampers, and the workpiece is approximated by using a polynomial. The contact of the multi-body system representing the filament with the surface of the workpiece is described by using Hertz’s theory of elastic contact and Coulomb’s law of friction. Based on this, a system of equations of motion for the multi-body system is obtained by using Lagrangian mechanics. A numerical solution of the equation of motion system was calculated by using experimentally determined material and contact properties of the filament as a composite of a plastic matrix and abrasive grains. A comparison of the calculated results with experimental data yielded satisfactory agreement for the contact between the filament and different workpiece geometries.

Regular Papers
  • Yoshitaka Midorikawa, Hiroshi Masuda
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 901-910
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    In industrial facilities, there are various types of equipment composed of surfaces that have a high degree of freedom. Rotational surfaces and generalized cylinders are often used for equipment handling liquids and gases. In this paper, we propose methods for reconstructing rotational surfaces and generalized cylinders from noisy and incomplete point-clouds captured by a terrestrial laser scanner. In our method, we convert point-clouds into wireframe models and calculate the intersection points with section planes. Then, we extract ellipses from the intersection points on each section plane and reconstruct the rotational surfaces and generalized cylinders using the extracted ellipses. We also propose a method for subdividing a rotational surface into primitive surfaces. We evaluated our method using actual point-clouds of engineering facilities and confirmed that our method could successfully reconstruct rotational surfaces and generalized cylinders.

  • Guillaume Lopez, Takahiro Tokuda, Manami Oshima, Kizito Nkurikiyeyezu, ...
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 911-920
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    Today in Japan, comfortable lifestyle and environment realized by abundant electric power is being questioned by energy consumption reduction policies called “cool biz” in summer, and “warm biz” in winter. One reason of these policies is the bad energy consumption efficiency of current air-conditioning systems that cool or warm indirectly human body. Several researches have been investigating the effect of direct human body cooling and warming. However, most proposed solutions focus on direct head or neck cooling, using ice to cool a water circulating system, such temperature during use cannot be controlled accurately nor adapted to user and environment conditions. Recently, a Japanese research team developed a portable system using Peltier elements that can both cool and warm neck. Though cooling was demonstrated to affect positively both physiological and psychological state in summer heat environment, in cold climate it could be confirmed for only neck warming but not feet and hands. In our objective of developing effective energy saving technology for direct temperature-conditioning of human body, and in order to reduce the discomfort caused by body chillness, we have proposed and developed a Peltier element based wrist-mounted wearable device that directly warms human body. A first experimental study showed how wrist warming rhythm affects hyperthermic sensation. Then, we verified whether the thermal sensation of the body, including the extremities, is improved by changing the position where the wrist is warmed.

  • Masato Okada, Makoto Shinke, Masaaki Otsu, Takuya Miura, Kuniaki Dohda
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 921-929
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    Burnishing characteristics of a newly developed roller burnishing method were developed. The developed method can effectively control the sliding direction between the roller and a cylindrical workpiece by inclining the roller axis with respect to the workpiece axis. The outer surface of a round aluminum alloy bar was targeted. The influence of burnishing conditions on burnished-surface quality was investigated, and surface quality was evaluated based primarily on the surface roughness, surface profile, and external appearance. As observed, the burnished-surface quality was strongly influenced by the pressing force, roller-inclination angle, and number of tool passes. A superior surface quality could be realized by increasing the number of tool passes.

  • Atsushi Motegi, Tomohiro Hishida, Yasuhiko Murata
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 930-939
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    In recent years, long glass fiber reinforced plastic and carbon fiber reinforced plastic have begun to be used for structural components that require high strength. As a result, thick-walled injection molded products are being manufactured. However, defects, known as voids, are generated inside the molded product and decrease the strength of the molded product, posing a significant problem at molding production sites. The partial compression method, which is a type of injection compression molding, is effective in preventing voids in thick-walled injection molding. However, there have been limited studies that comprehensively investigated the effects of the compression conditions on void prevention in thick-walled injection molding products or the shape and dimension of the molded product, or the issues in the molded product produced by applying compression. The authors have previously proposed the in-mold pressing (IMP) method, which allows the application of partial compression without the use of an injection compression molding machine and verified its validity. In this study, we proposed a compression device in which a servomotor-driven hydraulic pump actuator is used to propel a movable rod to apply compression to the melt inside the mold cavity. The IMP method using this device was applied to mold thick-walled products with thicknesses of 10 mm and greater, and the effects of compression on the generation of voids inside the molded product and the shape and dimensions of the product were investigated. The results indicate that the generation of voids can be prevented by application of this method. In addition, it was found that marginal deformations, which can pose issues, occur in the molded product when compressive stresses generated inside the molded product by compression are released after demolding.

  • Kosaku Nomura, Naoya Takeuchi, Hiroyuki Sasahara
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 940-946
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    Delamination or fiber out often occurs when machining carbon fiber reinforced plastics (CFRPs) with conventional cutting tools. Moreover, the tool life is short. As a new machining strategy for peripheral finishing of CFRP plates, an oscillating finish grinding process with a woven metal wire (WMW) tool utilizing plunger pump pulsation is proposed in this study. A WMW tool is a type of core drill, but the tool body is made of woven metal wire. A wire mesh and grinding fluid supplied from the inner side of the wire netting are expected to prevent the clogging of CFRP chips on the tool surface. However, the surface machined by the side face of the WMW tool becomes wavy as the wavy side surface of the WMW tool is copied to the machined surface when the rotating tool moves vertically to the tool axis. To overcome this limitation, a tool oscillation mechanism utilizing plunger pump pulsation action was newly developed and applied for finish grinding. As a result, it was demonstrated that the machined surface roughness of the CFRPs was improved through axial oscillation of the WMW tool.

  • Isamu Nishida, Ryo Tsuyama, Ryuta Sato, Keiichi Shirase
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 947-954
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    A new methodology to generate instruction commands for real-time machine control instead of preparing NC programs is developed under the CAM-CNC integration concept. A machine tool based on this methodology can eliminate NC program preparation, achieve cutting process control, reduce production lead time, and realize an autonomous distributed factory. The special feature of this methodology is the generation of instruction commands in real time for the prompt machine control instead of NC programs. Digital Copy Milling (DCM), which digitalizes copy milling, is realized by referring only to the CAD model of the product. Another special feature of this methodology is the control of the tool motion according to the information predicted by a cutting force simulator. This feature achieves both the improvement in the machining efficiency and the avoidance of machining trouble. In this study, the customized end milling operation of a dental artificial crown is realized as an application using the new methodology mentioned above. In this application, the CAM operation can be eliminated for the NC program generation, and tool breakage can be avoided based on the tool feed speed control from the predicted cutting force. The result shows that the new methodology has good potential to achieve customized manufacturing, and can realize both high productivity and reliable machining operation.

  • Makoto Nikawa, Kengo Usui, Hiroaki Iwahori, Atsushi Sato, Minoru Yamas ...
    原稿種別: Paper
    2018 年 12 巻 6 号 p. 955-963
    発行日: 2018/11/05
    公開日: 2018/11/05
    ジャーナル オープンアクセス

    A method for the estimation of the die release force of die castings of JIS-ADC12 aluminum alloy manufactured through high-pressure die casting was examined. The die release force was evaluated by the strain in the axial direction of the extrusion pin when releasing the die castings. In this research, it was assumed that the factors that influenced the die release force were the thermal deformation of the die and die castings and the reaction layer of Al and Fe generated during the solidification process in the die. These factors in the resistance of the die release were evaluated by the friction coefficient. The die and die castings temperature in the die release process were simulated, and calculation results were mapped onto an FE model, and a coupled analysis of the thermal structure was performed. The calculated value of the mold release force was approximately the same as the actual value, and the friction coefficient was estimated to be approximately 0.5.

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