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Shuhei Yamaguchi,Nobuhiro Yamaguchi,Masaki Mito,Hiroyuki Deguchi,Peter. J. Baker,Stephen. J. Blundell,Michael. J. Pitcher,Dinah. R. Parker,Simon. J. Clarke 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
The pressure effects on the 111-type Fe-based superconductor LiFeAs were investigated throughAC susceptibility measurements and X-ray diffraction experiments, and revealed a correlation betweenthe superconducting transition temperature (Tc) and the As-Fe-As bond angle (α) ratherthan the height of As from the Fe layers (hAs). As the pressure was increased, Tc of 17 K at P =0 GPa decreased down to 10 K at P = 5.2 GPa. According to a previous report from an X-raydiffraction experiment, α changes from 101.5˚ at 0 GPa to 97.8˚ at 17 GPa. The obtained changein Tc is consistent with Lee et al.’s plot of Tc as a function of α, and from this result, we concludethat Tc will fall to zero at around α = 98˚.
Collision Avoidance of the Aircraft in the 3 Dimensional Space
Yoshihiro Yamaguchi,Hiroyuki Takano,Takeshi Yamasaki,Isao Yamaguchi 제어로봇시스템학회 2011 제어로봇시스템학회 국제학술대회 논문집 Vol.2011 No.10
Recently, domestic and overseas LCC’s (Low Cost Carriers) increase air-traffic in Japan. However, we have narrow domain and many airports. Large training areas of USAF or JSDF also exist in the airspace. In the present circumstances, the flight safety is kept by separating airways from training areas. In the near future, increasing number of flights will make severe situation. In this paper, we try to optimize the evasive courses of aircraft in the narrow airspace. We formulate collision avoidance as a nonlinear programming problem and analyzed numerically. The optimal solution we obtained show courses in narrower spaces than ordinary ones. The assumption of limited airspaces is useful in severe situation like bad weather. Thus, this study might be a good proposal to decide direction for collision avoidance.
A Soundness Verification Tool Based on the SPIN Model Checker for Acyclic Workflow Nets
Shingo YAMAGUCHI,Munenori YAMAGUCHI,Minoru TANAKA 대한전자공학회 2008 ITC-CSCC :International Technical Conference on Ci Vol.2008 No.7
Workflow nets (WF-nets) are Petri nets for modeling workflows, and are utilized to verification and performance evaluation of workflows. A WF-net should have a property, called soundeness, which guarantees a logical correctness of the modeled workflow. If a given WF-net is free choice then its soundness can be verified in polynomial time. Otherwise there is no polynomial time method to verify soundness for general WF-nets. Unfortunately, some workflows cannot be represented as free choice WF-nets. For example, the WF-net representing an inter-organizational workflow may become asymmetric choice. Thus an efficient method is required. In this paper, we propose a tool to verify soundness using the SPIN model checker. We also show efficiency of our tool by comparing it with an existing WF-nets analysis tool, Woflan, on verification time for asymmetric choice WF-nets.
A Study on the Deep-Surge Frequencies in Various Conditions of Axial Flow Compressors and Flow-paths
Yamaguchi, Nobuyuki Korean Society for Fluid machinery 2017 International journal of fluid machinery and syste Vol.10 No.4
Frequencies of deep surges and their behaviors in axial flow compressors were surveyed numerically. Relative surge frequencies, normalized by the basic acoustical resonance frequencies, are seen to tend to lower together with increases in the stalling pressure ratios, i.e. increases in the number of stages and the compressor tip speed, and also together with increases in the flow-path sectional area ratios. However, it appears difficult to express simply the general behaviors of the relative frequencies affected by the various factors. In order to know the essential behaviors, a modified reduced surge frequency is proposed, which is a dimensionless number comparing the mass flow filling and emptying the plenum volume in surge and the mass flow provided by the compressor. The modified reduced surge frequencies are found to have or approach a definite and nearly constant value in conditions of deep surges. The parameter suggests the fundamental mechanism of deep surges and could be used to determine approximate frequencies of deep-surges in various conditions of compressors and flow-paths.
A Study on the Fundamental Surge Frequencies in Multi-Stage Axial Flow Compressor Systems
Yamaguchi, Nobuyuki Korean Society for Fluid machinery 2014 International journal of fluid machinery and syste Vol.7 No.4
Surge phenomena in multi-stage axial flow compressors were studied with attention to the frequency behaviors. A new parameter "volume-modified reduced surge frequency" was introduced, which took into consideration the essential surge process, i.e., emptying and filling of the working gas in the delivery plenum. The behaviors of the relative surge frequencies at the stall stagnation boundaries, compared with the corresponding duct resonance frequencies, have demonstrated the existence of two types of surges; i.e., a near-resonant surge and a subharmonic surge. The former, which has fundamentally a near-resonance frequency, occurs predominantly at the stall stagnation boundary for the short -and-fat plenum delivery flow-path and the long-and-narrow delivery duct flow-path, and possibly in the intermediate conditions. The latter, which has a subharmonic frequency of the fundamental near-resonant one and occurs mainly in the intermediate zone, is considered to be caused by the reduced frequency restricted to a limited range. In relation with those dimensionless frequencies at the stall stagnation boundary, the surge frequency behaviors in more general situations away from the boundaries could be estimated, though very roughly.
Three-dimensional simplified slope stability analysis by hybrid-type penalty method
Yamaguchi, Kiyomichi,Takeuchi, Norio,Hamasaki, Eisaku Techno-Press 2018 Geomechanics & engineering Vol.15 No.4
In this study, we propose a three-dimensional simplified slope stability analysis using a hybrid-type penalty method (HPM). In this method, a solid element obtained by the HPM is applied to a column that divides the slope into a lattice. Therefore, it can obtain a safety factor in the same way as simplified methods on the slip surface. Furthermore, it can obtain results (displacement and strain) that cannot be obtained by conventional limit equilibrium methods such as the Hovland method. The continuity condition of displacement between adjacent columns and between elements for each depth is considered to incorporate a penalty function and the relative displacement. For a slip surface between the bottom surface and the boundary condition to express the slip of slope, we introduce a penalty function based on the Mohr-Coulomb failure criterion. To compute the state of the slip surface, an r-min method is used in the load incremental method. Using the result of the simple three-dimensional slope stability analysis, we obtain a safety factor that is the same as the conventional method. Furthermore, the movement of the slope was calculated quantitatively and qualitatively because the displacement and strain of each element are obtained.