The general theory of three-phase motors is often built based on the
assumption that the three phases voltage is symmetrical. However, in
practice, this operation mode of the motor cannot be achieved due to a
number of reasons such as the structure of the motor is not symmetrical,
the load in the electrical system is not balanced. The asymmetry of threephase
voltage greatly affects the operation mode of a three-phase
asynchronous motor. The most serious affections are: decrease the
starting torque, increase stator current and rotor current, vibration inside
the motor. This affection will reduce the effective operation of the motor.
The paper investigates the effect of asymmetry voltage on the normal
operation mode of a three-phase asynchronous motor based on the
electromagnetic transforming method of electric machines and
simulating on Matlab-Simulink.
Fire-retardants (FRs) are additives used to improve the fire-resistance of combustible materials. New generations of FRs must be effective and eco-friendly. Traditional inorganic FRs are non-hazardous but have limited fire-retardancy. Here, we aim to develop an innovative way to enhance the fire-retardancy of inorganic FRs. We synthesized a new type of FRs, called mATH, whose compositions are similar to soda-silicate glass (xNa2O.yK2O.zSiO2.tAl2O3). When applied to unsaturated polyester resin, mATH showed a much better performance than traditional aluminum trihydroxide (ATH). The better performance of mATH originated from its new working mechanism. Dehydrated mATH, as a soda-silicate glass, melts under the heat of the fire, which causes heat sink and produces a molten glass. The molten glass forms a charred insulating layer that prevents oxygen from contacting the interior combustible materials. This phenomenon significantly contributes to the fire-retarding behavior of mATH. Our findings open a new method for developing effective eco-friendly FRs.
The dose distribution calculation is one of the major steps in radiotherapy. In this paper the Monte Carlo code MCNP5 has been applied for simulation 15MV photon beams emitted from linear accelerator in a case of lung cancer of the General Hospital of Kien Giang. The settings for beam directions, field sizes and isocenter position used in MCNP5 must be the same as those in treatment plan at the hospital to ensure the results from MCNP5 are accurate. We also built a program CODIM by using MATLAB® programming software. This program was used to construct patient model from lung CT images obtained from cancer treatment cases at the General Hospital of Kien Giang and then MCNP5 code was used to simulate the delivered dose in the patient. The results from MCNP5 show that there is a difference of 5% in comparison with Prowess Panther program – a semi-empirical simulation program which is being used for treatment planning in the General Hospital of Kien Giang. The success of the work will help the planners to verify the patient dose distribution calculated from the treatment planning program being used at the hospital.
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