There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The path of chemical reactions - the IRC approach

Since the 3rd century for more than a thousand years chemistry has been thought of as a complicated, hard-to-predict science. Efforts to improve even a part of its unpredictable character are said to have born fruit first of all in the success of the \" electronic theory \". This was founded mainly by organic chemists , such as Fry, Stieglitz, Lucas, Lapworth and Sidgwick, brought to a completed form by Robinson and Ingold, and developed later by many other chemists. 1 In the electronic theory, the mode of migration of electrons in molecules is noted and is considered under various judgements. For that purpose, a criterion is necessary with respect to the number of electrons which should originally exist in an atom or a bond in a molecule. Therefore, it can be said to be the concept by Lewis of the sharing of electrons that has given a firm basis to the electronic theory. 2 In the organic electronic theory, the chemical concepts such as acid and base, oxidation and reduction and so on, have been conveniently utilized from a long time ago. Furthermore, there are terms centring closer around the electron concept, such as electrophilicity and nucleophilicity, and electron donor and acceptor both being pairs of relative concepts. One may be aware that these concepts can be connected qualitatively to the scale of electron density or electric charge. In the electronic theory, the static and dynamic behaviours of molecules are explained by the electronic effects which are based on nothing but the distribution of electrons in a molecule. The mode of charge distribution in a molecule can be sketched to some extent by the use of the electronegativity concept of atoms through organic chemical experience. At the same time, it is given foundation, made quantitative , and supported by physical measurements of electron distribution and theoretical calculations based on quantum theory. The distribution of electrons or electric charge-with either use the result is unchanged-in a molecule is usually represented by the total numbers (generally not integer) of electrons in each atom and each bond, and it was a concept easily acceptable even to empirical chemists as having a tolerably realistic meaning. Therefore, chemists employed the electron density as a fundamental concept to explain or to comprehend various phenomena. In particular, for the purpose of promoting chemical investigations, researchers usually rely upon the analogy through experience, and the electron density …

https://science.sciencemag.org/content/sci/218/4574/747.full.pdf

Role of Frontier Orbitals in Chemical Reactions

The ability of platinum and gold catalysts to effect powerful atom-economic transformations has led to a marked increase in their utilization. The quite remarkable correlation of their catalytic behavior with the available structural data, coordination chemistry, and organometallic reactivity patterns, including relativistic effects, allows the underlying principles of catalytic carbophilic activation by π acids to be formulated. The spectrum of reactivity extends beyond their utility as catalytic and benign alternatives to conventional stoichiometric π acids. The resulting reactivity profile allows this entire field of catalysis to be rationalized, and brings together the apparently disparate electrophilic metal carbene and nonclassical carbocation explanations. The advances in coupling, cycloisomerization, and structural reorganization—from the design of new transformations to the improvement to known reactions—are highlighted in this Review. The application of platinum- and gold-catalyzed transformations in natural product synthesis is also discussed.

Catalytic Carbophilic Activation: Catalysis by Platinum and Gold π Acids

In-wheel-motor type electric vehicles (IWM-EVs), which have independent motors inside each of the four wheels, are expected to be the next power-trains because they have quite good motion-control performance. From the viewpoint of commercial use, a reduction gear must be inserted between the motor and the wheels to increase the driving torque of the wheels, but doing so drastically declines the control performance because of gear elasticity and backlash. Moreover, the reduction gear not only obstructs the smooth transmission of the driving torque but also leads to unpleasant noise or ride-comfort deterioration. Here, we propose the gear-collision-free backlash-compensation and the joint-torque-control method for geared IWM-EVs by using a double encoder. Currently, the concepts of the double-encoder system are prevailing as an effective control method for the two-inertia systems in the motion-control societies. We have introduced these schemes skillfully and constructed a simple and practical control strategy. The suitable mechanical system of IWM and angular sensor resolution are also discussed, and its effectiveness is demonstrated via some simulations and experiments. We anticipate this research to solve the critical problem of the gear noise and facilitate the practical realization of IWM-EVs.

Acceleration Noise Suppression for Geared In-Wheel-Motor Vehicles Using Double Encoder

Requirement of large motor torque with limited mounting space for In-wheel-motors (IWMs) expects a geared drivetrain, but the vibration and noise caused by gear collision deteriorates ride comfort. In our previous study, our research group proposed to apply joint torque control using motor-side encoders and additional load-side encoders to geared IWMs and the effectiveness is validated. However, in point of space and costs, the effect of mounting load-side encoders should be investigated carefully. In this paper, joint torque control using both motor-side and load-side encoders is compared with joint torque control using only motor-side encoders. Simulations and experiments demonstrate that load-side encoders make it possible to design controller without vehicle parameters and to reduce the impact of collision sufficiently.

Gear Collision Reduction of Geared In-Wheel-Motor by Effective Use of Load-Side Encoder

Rro compensation of hard disk drives with multirate repetitive ptc

Interior permanent magnet motors (IPMSMs) are employed for the drive motors of electric and hybrid vehicles. Therefore, control method to be used in the overmodulation range of the inverter is important to achieve fast torque response and expand the operating range of the IPMSMs. In general, an IPMSM is controlled in the overmodulation range by using current vector control and voltage phase control. However, the mode of the controller should be switched from current vector control to voltage phase control. This switch deteriorates the torque response. Therefore, it is desirable to control the IPMSMs using only one mode of the controller over the full operating range. In this paper, a control method over the full operating range based on perfect tracking control and PWM hold model is proposed; the method does not require a switching structure of controllers. In addition, the torque response is affected by harmonic current which is generated when the IPMSM is used in the overmodulation range. Solutions to this problem were proposed, based on removing harmonic currents from real currents with estimating harmonic currents. However, the discrete-time model for estimating harmonic current has not been discussed. In this paper, the PWM hold model of IPMSM is used for estimating the nominal output which takes harmonic currents into consideration. Moreover, the windup phenomenon is simultaneously prevented by estimating the nominal output which takes saturated fundamental component of inverter output voltage into consideration. Fig. 1 show the block diagram of proposed method 2. The NOE is the nominal output estimator. The NOE estimates the nominal output which takes harmonic current and saturated fundamental component into consideration. In the overmodulation range, the estimated nominal output î0 is used as the nominal output i0. In linear range, i0 which is the target tracking trajectory delayed one sample is used as i0. In proposed method 1, î0 is used as i ∗ 0 over the full operating range. Fig. 2 shows experimental results. T̂ is the estimated torque calculated using the real current i. T0 is the torque calculated using i0. In the conventional method, current vector control and voltage phase control are employed. The experimental results show the advantages of proposed method 2.

Control Method for IPMSM Based on Perfect Tracking Control Method and PWM Hold Model in Overmodulation Range

Wireless power transfer (WPT) via magnetic resonant coupling has been widely studied for many applications. In the control of WPT systems with variable power load such as motor, achieving high efficiency and desired power corresponding to the load at any time is important. Some methods which increases efficiency by secondary side power converters has been proposed. In these research, however margin between possible transmission power which is determined by the primary and secondary side voltage and received power is necessary because WPT systems with variable power load is unstable. This paper proposes a method for maximum efficiency operation by dynamic voltage control of the primary and secondary side DC-link. Margin in the transmission power is unnecessary in the system configuration which has supercapacitor and DC/DC converter on the secondary-side because supercapacitor compensates power fluctuation. Simulations and experiments demonstrated feasibility of the proposed method and effectiveness of the controllers.

Hiroshi Fujimoto

Papers

Acceleration Noise Suppression for Geared In-Wheel-Motor Vehicles Using Double Encoder

Gear Collision Reduction of Geared In-Wheel-Motor by Effective Use of Load-Side Encoder

Rro compensation of hard disk drives with multirate repetitive ptc

Control Method for IPMSM Based on Perfect Tracking Control Method and PWM Hold Model in Overmodulation Range

Maximum Efficiency Operation in Wider Output Power Range of Wireless In-Wheel Motor with Wheel-Side Supercapacitor