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Search Results: 1 - 10 of 152 matches for " Junjiro Onoda "
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Comparison of Analog and Digital Self-Powered Systems in Multimodal Vibration Suppression
Shigeru Shimose,Kanjuro Makihara,Junjiro Onoda
Smart Materials Research , 2012, DOI: 10.1155/2012/287128
Abstract: This paper compares our analog and digital self-powered systems for vibration suppression, and shows experimental results of multimodal vibration suppression for both self-powered systems. The experimental results are evaluated in light of the damping performance and adaptability under various vibrational conditions. We demonstrate various examples of our innovative vibration suppression method, called “digital self-powered.” Proper status switching of an electric circuit made up of an inductor and a selective switch connected to a piezoelectric transducer attenuates the vibrations. The control logic calculation and the switching events are performed with a digital microprocessor that is driven by the electrical energy converted from the mechanical vibration energy. Therefore, this vibration suppression system runs without any external power supply. The self-powering feature makes this suppression method useful in various applications. To realize an ideal vibration suppression system that is both self-powered and effective in suppressing multimode vibration, sophisticated control logic is implemented in the digital microprocessor. We demonstrate that our digital self-powered system can reduce the vibrational displacements of a randomly excited multimodal structure, by as much as 35.5%. 1. Introduction Vibration control methods are roughly categorized into two groups, that is, active and passive methods [1–4]. Active vibration control methods usually yield high-performance vibration suppression [1, 2]. However, active control systems may become unstable if the control is improperly designed. In addition, active vibration control systems need an external energy supply to suppress vibrations. On the other hand, passive vibration control methods use energy dissipative mechanisms such as dampers, frictional devices, and electric resistors [3, 4]. Because passive approaches do not need an energy supply they are always stable. Passive methods are easier to implement in actual systems than are the more complicated active methods, because they do not need controllers, sensors, or filters. However, in most cases, passive systems do not provide a satisfactory vibration suppression performance. In general, the majority of passive systems suppress vibrations well only in expected situations such as those regarding natural frequency and temperature. Typical examples of less robustness of frequency alternation are mechanically tuned mass dampers and electrical dynamic vibration absorbers. There are research papers that compare the performance of semiactive and passive
Energy Harvesting Using an Analog Circuit under Multimodal Vibration
Shigeru Shimose,Kanjuro Makihara,Junjiro Onoda
Smart Materials Research , 2013, DOI: 10.1155/2013/736487
Abstract:
Energy Harvesting Using an Analog Circuit under Multimodal Vibration
Shigeru Shimose,Kanjuro Makihara,Junjiro Onoda
Smart Materials Research , 2013, DOI: 10.1155/2013/736487
Abstract: The efficiency of harvesting energy from a vibrating structure using a piezoelectric transducer and a simple analog circuit is investigated experimentally. This analog circuit was originally invented for a synchronized switch damping on inductor (SSDI) technique, which enhances the damping of mechanical vibration. In this study, the circuit is used to implement a synchronized switch harvesting on inductor (SSHI) technique. A multiple degree of freedom (MDOF) structure is excited by single sinusoidal forces at its resonant frequencies and by random forces. The piezoelectric transducer converts this mechanical energy into electrical energy which is harvested using a standard rectifier bridge circuit with and without our analog circuit. Experimental results show that our analog circuit makes it possible to harvest twice as much energy under both single sinusoidal and random vibration excitations. 1. Introduction Energy harvesting techniques have been studied extensively in recent years. Energy harvesting is a process by which energy is captured and stored. Energy can be harvested from various power sources, including wind power, solar power, ocean tides, heart, magnetic fields, and structural vibrations. We focused on the vibration energy of a structure, using the piezoelectric effect to convert structural vibration energy into electrical energy. There is substantial research on this technique, as reviewed by Sodano et al. [1]. Lesieutre et al. [2] addressed the damping associated with energy harvesting from structural vibrations. Badel et al. [3–5] proposed a synchronized switch harvesting on inductor (SSHI) technique to improve energy harvesting. SSHI is based on vibration suppression technique named synchronized switch damping on inductor (SSDI). Both SSHI and SSDI use a piezoelectric transducer attached to the structure and connected to an inductive circuit having an on-off switch [6–10]. The switch in the circuit is flipped at each extremum of displacement of the structure. A displacement sensor and a controller are needed to synchronize the switching commands with the mechanical vibration. In a self-powered system, these sensors and controllers need to be driven using a fraction of the harvested energy. We previously invented an analog circuit that automatically performs switching without an external energy source [11]. We describe in this paper how this analog circuit enhances the energy harvesting performance when used with SSHI. Although many studies [12–14] have been conducted on SSHI, most of them are limited to the sinusoidal vibration of a
Assessment of Electrical Influence of Multiple Piezoelectric Transducers' Connection on Actual Satellite Vibration Suppression
Shigeru Shimose,Kanjuro Makihara,Kenji Minesugi,Junjiro Onoda
Smart Materials Research , 2011, DOI: 10.1155/2011/686289
Abstract: We conduct comprehensive investigation of a semiactive vibration suppression method using piezoelectric transducers attached to structures. In our system, piezoelectric transducers are connected to an electric circuit composed of the diodes, an inductance, and a selective switch. Our method (SSDI) makes better use of counterelectromotive force to suppress the vibration, instead of simple dissipation of vibration energy. We use an actual artificial satellite to verify their high performance compared to conventional semi-active methods. As a consequence, we demonstrate that our semi-active switching method can suppress the vibration of the real artificial satellite to as much as 50% amplitude reduction. In our experiment, we reveal that the suppression performance depends on how multiple piezoelectric transducers are connected, namely, their series or parallel connection. We draw two major conclusions from theoretical analysis and experiment, for constructing effective semi-active controller using piezoelectric transducers. This paper clearly proves that the performance of the method is the connection (series or parallel) of multiple piezoelectric transducers and the their resistances dependent on frequency. 1. Introduction Space structures, such as the space station or artificial satellites, are built for the purpose of highly demanding space missions. Large solar paddles and bulky antennas are necessary for the space missions. However, since the launch ability of rockets strictly limits the payload weight, space structures have to extremely minimize their weight, which results in the use of flexible structures and spindly members. Therefore, they are more prone to vibrations compared with structures on earth with less weight restriction. Moreover, space structures and artificial satellites are exposed to severe vibration environment at the launch stage. The relaxation of such a severe condition is an important issue in order to improve their reliability and to reduce their development costs. Many methods of vibration suppression have been studied and proposed [1–6]. There is currently a large effort underway to effectively suppress the vibration of structures. Vibration control methods are roughly categorized into two groups, that is, active and passive methods [1–6]. Active vibration control methods usually have high performance in vibration suppression [1–3]. In the space field, the active rack isolation system (ARIS) [1] of the International Space Station is famous as the active vibration control system composed of eight voice-coil actuators in order
Connections and the Second Main Theorem for Holomorphic Curves
Junjiro Noguchi
Mathematics , 2011,
Abstract: By means of $C^\infty$-connections we will prove a general second main theorem and some special ones for holomorphic curves. The method gives a geometric proof of H. Cartan's second main theorem in 1933. By applying the same method, we will prove some second main theorems in the case of the product space $(\pone)^2$ of the Riemann sphere.
Another Direct Proof of Oka's Theorem (Oka IX)
Junjiro Noguchi
Mathematics , 2011,
Abstract: In 1953 K. Oka IX solved in first and in a final form Levi's problem (Hartogs' inverse problem) for domains or Riemann domains over $\C^n$ of arbitrary dimension. Later on a number of the proofs were given; cf.\ e.g., Docquier-Grauert's paper in 1960, R. Narasimhan's paper in 1961/62, Gunning-Rossi's book, and H\"ormander's book (in which the holomorphic separability is pre-assumed in the definition of Riemann domains and thus the assumption is stronger than the one in the present paper). Here we will give another direct elementary proof of Oka's Theorem, relying only on Grauert's finiteness theorem by the {\it induction on the dimension} and the {\it jets over Riemann domains}; hopefully, the proof is most comprehensive.
On Holomorphic Curves in Semi-Abelian Varieties
Junjiro Noguchi
Mathematics , 1996,
Abstract: The algebraic degeneracy of holomorphic curves in a semi-Abelian variety omitting a divisor is proved (Lang's conjecture generalized to semi-Abelian varieties) by making use of the {\it jet-projection method} and the logarithmic Wronskian jet differential after Siu-Yeung. We also prove a structure theorem for the locus which contains all possible image of non-constant entire holomorphic curves in a semi-Abelian variety omitting a divisor.
Nevanlinna Theory and Rational Points
Junjiro Noguchi
Mathematics , 1996,
Abstract: S. Lang conjectured in 1974 that a hyperbolic algebraic variety defined over a number field has only finitely many rational points, and its analogue over function fields. We discuss the Nevanlinna-Cartan theory over function fields of arbitrary dimension and apply it for Diophantine property of hyperbolic projective hypersurfaces (homogeneous Diophantine equations) constructed by Masuda-Noguchi. We also deal with the finiteness property of $S$-units points of those Diophantine equations over number fields.
A Scalar Associated with the Inverse of Some Abelian Integrals and a Ramified Riemann Domain
Junjiro Noguchi
Mathematics , 2015,
Abstract: We introduce a positive scalar function $\rho(a, \Omega)$ for a domain $\Omega$ of a complex manifold $X$ with a global holomorphic frame of the cotangent bundle by closed Abelian differentials, which heuristically measure the distance from $a \in \Omega$ to the boundary $\del\Omega$. We prove an {\em estimate of Cartan--Thullen type with $\rho(a, \Omega)$} for holomorphically convex hulls of compact subsets. In one dimensional case, we apply the obtained estimate of $\rho(a, \Omega)$ to give a new proof of Behnke-Stein's Theorem for the Steiness of open Riemann surfaces. We then use the same idea to deal with the Levi problem for ramified Riemann domains over $\C^n$. We obtain some geometric conditions in terms of $\rho(a, X)$ which imply the validity of the Levi problem for a finitely sheeted Riemann domain over $\C^n$.
Synthesis, Acid and Base Resistance of Various Copper Phosphate Pigments by the Substitution with Lanthanum  [PDF]
Onoda Hiroaki, Okumoto Kenichi
Materials Sciences and Applications (MSA) , 2011, DOI: 10.4236/msa.2011.23026
Abstract: Transition metal phosphates are used as inorganic pigments, however these materials have a weak point for acid or base resistance. Because lanthanum phosphate is insoluble in acidic or basic solution, the addition of lanthanum was tried to improve the acid or base resistance of copper phosphate pigment. Various cooper – lanthanum phosphates were synthesized in wet (H3PO4, Cu(NO3)2, La(NO3)3) or dry (H3PO4, CuCO3●Cu(OH)2●H2O, La2O3) processes. The additional effects of lanthanum were studied on the chemical composition, particle shape and size distribution, specific surface area, color, acid and base resistance of the precipitates and their thermal products.
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