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R&D Spillovers and Foreign Market Entry: Acquisition versus Greenfield Investment
Kazuhiko Yokota,KUNG-MING CHEN 한국국제경제학회 2012 International Economic Journal Vol.26 No.2
This paper presents a three-stage game to model the entry behavior of a multinational firm in the presence of R&D spillovers. The multinational firm's entry mode choice – that is, to invest to set up a new plant or merge with a local firm – is a function of the magnitude of spillovers, as well as the relative cost of greenfield investment, and mergers and acquisitions (M&A). Our model shows that if there exist relatively high R&D leakages and relatively small difference in cost between M&A and greenfield investment, an R&D-intensive foreign firm tends to choose greenfield investment rather than M&A, while if there exist relatively low R&D leakages, the foreign firm is more likely to choose M&A rather than greenfield investment. It is also shown that the size of social welfare of the host country depends on the degree of R&D spillovers. These results produce strong implications for antitrust policy for particularly developing countries.
Ayumu Yokota,Kazuhiro Sekita,Tomiharu Hirano,Kazuhiko Noda 한국표면공학회 2010 한국표면공학회 학술발표회 초록집 Vol.2010 No.11
The corrosion prevention mechanism and end corrosion of the galvanized steels have been investigated. The atmospheric exposure tests were carried out for the observation of corrosion process on the specimen surface under the seashore environment for one and half years. From the results of the exposure tests, it was indicated that the galvanized steel was protected by the corrosion product of Zn under the atmospheric environment. The anodic polarization curve measurements were carried out for the exploration of the anodic polarization behavior under the neutral solution. According to the results in the anodic polarization curves of the galvanized steels, the anodic current density of the edge part was larger than that of the surface part.
Initial Corrosion Behavior of Galvanized Steels in Atmospheric Environment
Ayumu Yokota,Youhei Hirohata,Kazuhiko Noda,Hideki Katayama,Hiroyuki Masuda 한국표면공학회 2010 한국표면공학회 학술발표회 초록집 Vol.2010 No.11
The corrosion prevention mechanism of Zn/Fe galvanic couple changes with time and have been investigated by atmospheric exposure tests and surface potential distribution measurement. The samples used in experiment were non-chromate treated galvanized steel and chromate treated galvanized steel. Corrosion products were observed on the surface of non-chromate treated galvanized steel after atmospheric exposure tests. On the other hand, the corrosion products were not observed on the surface of chromate treated galvanized steels. The experimental results show that chromate conversion treatments increase corrosion resistance of the galvanized steel. The sacrificial anodic reaction in non-chromate treated galvanized steels was seen at the Zn/Fe boundary. However, the effect of corrosion prevention by the sacrificial anodic reaction was less seen on chromate treated galvanized steels. From these results, chromate conversion treatments increase the corrosion resistance of the coatings, while decreasing the effect of sacrificial anodic reaction at the Zn/Fe boundary. The expansion of sacrificial anodic reaction was confirmed by surface potential distribution measurement due to the corrosion product at the Zn/Fe boundary.
Reaction Evaluation of Metal Surface Using Surface Potential Distribution Measurement
Youhei Hirohata,Ayumu Yokota,Kazuhiko Noda,Hideki Katayama,Hiroyuki Masuda 한국표면공학회 2010 한국표면공학회 학술발표회 초록집 Vol.2010 No.11
A surface potential measurement device with non-contact probe is applied to measure the potential of the passive metals. The surface potential distribution of high corrosion resistance materials shows difference behavior between titanium and type 304 stainless steel. From these results, the measurement of the surface potential using a surface potential measurement device is quite suitable to investigate the atmospheric corrosion behavior of high corrosion resistance materials.
Atmospheric Corrosion Behavior of the Pure Zirconium
Ayami Kameda,Yuki Kagawa,Ayumu Yokota,Youhei Hirohata,Kazuhiko Noda 한국표면공학회 2010 한국표면공학회 학술발표회 초록집 Vol.2010 No.11
The zircalloy improved the corrosion resistance and the materials strength, largely is used for a fuel aggregate member, a pressure pipe, and the fuel coating pipes of the nuclear reactor. The estimation of the reaction characteristics of pure zirconium is important in order to investigate the application in actual using. The pure zirconium was examined by the polarization curves measurement in solution environment and the surface potential distribution measurement to evaluate the stability of the passive film on zirconium as the fundamental data. A surface potential measurement device with non-contact probe is applied to measure the potential of the pure zirconium. The corrosion behavior of the pure zirconium surface is also investigated by using the surface potential date. The surface potential distribution of pure zirconium shows a good corrosion resistance in the atmospheric condition.
Proposal of Design Method for Viscous Micropumps with a Rotating-Disk Using Theory and Simulation
Wakana Tsuru,Donghyuk Kang,Kotaro Sato,Kazuhiko Yokota 한국유체기계학회 2022 International journal of fluid machinery and syste Vol.15 No.1
The aim of the present study is to treat circular- and spiral-shaped viscous micropumps unitarily and provide guidelines for determining the appropriate micropump for performance requirements. Three-dimensional theoretical equations applicable to circular- and spiral-shaped micropumps were derived. Numerical simulations were also performed, and the results were compared with the theoretical results. The results were qualitatively consistent. By comparing the performances of the two micropumps, the spiral- and the circular-shaped micropumps are suitable in the ratio of outermost diameter to channel width c* < 0.2, and c* > 0.2, respectively. The theoretical performance for rotating disk-type micropumps was expressed in a unified manner. Furthermore, the design guideline was provided based on the theoretical method.
Unified Performance Model for S-Shaped Characteristics of Pump–Turbines Considering Reverse Flow
Donghyuk Kang,Wakana Tsuru,Ono Koudai,Kazuhiko Yokota 한국유체기계학회 2023 International journal of fluid machinery and syste Vol.16 No.1
This study proposes a new unified performance model for the S-shaped characteristics of pump–turbines considering reverse flow. The turbine and reverse pump characteristic equations were unified using a sigmoid function considering the reverse flow. In the analysis, the torque coefficient is larger for small guide vane angles than for large guide vane angles due to an increase in the turbine Euler head. In the turbine mode, the runner shock loss and the circumferential discharge loss are directly proportional to the shock dynamic pressure and the circumferential dynamic pressure in the discharge section, respectively. In the reverse pump mode, the guide vane shock and friction losses are directly proportional to the shock dynamic pressure and the absolute dynamic pressure, respectively. The S-shaped characteristics of pump–turbines can be completely simulated using the proposed theoretical model
Two-Dimensional Theoretical Study on Flow Characteristics of a Spiral-Channel Viscous Micropump
Donghyuk Kang,Koichi Nishibe,Kotaro Sato,Kazuhiko Yokota 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.4
This study investigates the flow characteristics of a spiral-channel viscous micropump using two-dimensional theoretical analysis. The obtained results are compared to the results obtained from experiments, numerical simulations, and the theoretical analysis of Kilani et al., and the similarities and differences between these approaches are discussed. The present two-dimensional theoretical approach is validated. Its accuracy is improved as compared to previous work by setting the spiral-channel axis as the spiral-channel length from the pump inlet to the outlet and by considering the moving wall as a component in the spiral-channel direction of the circumferential velocity of the rotating disk. Furthermore, the present two-dimensional analysis can accurately predict pump performance, even though the actual flow in the micropump is three dimensional.
Three-Dimensional Theoretical Study on Flow Characteristics of a Spiral-Channel Viscous Micropump
Donghyuk Kang,Koichi Nishibe,Kotaro Sato,Kazuhiko Yokota 한국유체기계학회 2019 International journal of fluid machinery and syste Vol.12 No.2
Technological developments have led to micropumps playing an ever-greater role at the heart of micro total analysis systems. Spiral-channel viscous micropumps have been studied theoretically, numerically, and experimentally. However, high-accuracy performance predictions have not been achieved over a wide range of operating conditions. The present study proposes three-dimensional and quasi-three-dimensional theoretical expressions for predicting the pressure performance of spiral-channel viscous micropumps in low-Reynolds-number environments. The theoretical analysis is validated through a series of comparisons with numerical simulation results for the pressure performance curves, velocity distributions, velocity gradient distributions, and channel internal pressure distributions. Furthermore, the influence of the channel aspect ratio on the performance characteristics is investigated.
Behavior of Plane Synthetic Jets Generated by an Asymmetric Stepped Slot
Ryota Kobayashi,Hiroaki Terakado,Kotaro Sato,Junya Taniguchi,Koichi Nishibe,Kazuhiko Yokota 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.1
This paper presents a fundamental study of jet directional control, i.e., thrust vectoring, using a synthetic jet generated by an asymmetric stepped slot. We present and discuss the results for a synthetic jet generated by a one-sided asymmetric stepped slot and focus on the relationship between the traveling direction of the formed jet and the offset ratio of the stepped slot and/or dimensionless frequency of the synthetic jet, within a jet deflection angle range of 0–90°. We demonstrate that there is an optimum offset ratio for jet deflection under the same dimensionless frequency because the traveling direction of the synthetic jet is dependent on the offset ratio of the stepped slot and the dimensionless stroke length (dimensionless frequency).