Unlike proton therapy, conventional radiation therapy directs X-rays not only at the tumor but also unavoidably at nearby healthy tissue. Protons deliver radiation to tumor tissue while the healthy structures will be spared during proton therapy. When protons travel through matter, secondary particles like neutrons and photons are produced. It is believed that the secondary dose can lead to secondary cancer. It is not generally possible to measure directly the absorbed dose in a Human body. Therefore, Monte Carlo simulations and phantoms are useful for estimating the absorbed dose in organs. In this study, the MCNPX and Analytical phantom of the human body, ORNL-female phantom were used for breast proton therapy. We considered a characteristic tumor with the same composition of breast tissue. Measurement was performed with the energy range of 60-70 MeV proton beams accelerated. secondary productions generated in the body of the patient can affect the organs surrounding the target region, so the equivalent dose of these secondary radiations was calculated in vital organs including Right-Lung and Left-Lung. For all energies, the equivalent dose of photons in vital organs is lower than neutrons. Our Monte Carlo results show that the equivalent dose of the Neutrons and Photons in the left lung is 0. 1051 mSV and 0. 0178 mSV in the right lung per 1mSV of 70 MeV energy incident proton beam. It is shown that for high-energy proton beams, most of the absorbed dose by organs is due to secondary neutrons but those are low enough to be neglected. Breast proton therapy provides satisfactory target coverage and enhances normal tissue sparing that can limit unnecessary doses delivered to the lung, though there has been a significant development in Radiation therapy technology, there still remain concerns on treatment related to long-term side effects. This problem is more pronounced in pediatric cases.

Introduction Use of hadron therapy as an advanced radiotherapy technique is increasing. In this method, secondary particles are produced through primary beam interactions with the beam-transport system and the patient’ s body. In this study, Monte Carlo simulations were employed to determine the dose of produced secondary particles, particularly neutrons during treatment. Materials and Methods In this study, secondary particles, produced by proton and ion beams, were simulated for a cancer treatment plan. In particular, we evaluated the distribution of secondary neutrons, produced by a 400 MeV/u carbon beam on an electronic crate, which was exposed to radiation field under radioactive conditions. The level of major secondary particles, particularly neutrons, irradiating the target, was evaluated, using FLUKA Monte Carlo code. Results The fluences and radiation doses were applied to determine the shielding efficiency of devices and the probability of radiation damage to nearby electronic systems. According to the results, by using maximum-energy carbon ions (400 MeV/u), electronic devices are exposed to a dose rate of 0. 05 μ Sv/s and an integrated dose of about 34 mSv, each year. Conclusion The simulation results could provide significant information about radiation assessment; they could also be a major help for clinical facilities to meet shielding requirements. Moreover, such simulations are essential for determining the radiation level, which is responsible for radiation-induced damages.

Flat reflectors which have lower price compared with parabolic ones are used in Fresnel concentrator. Each Fresnel collector is comprised of a few flat reflectors which are placed parallel to each other near the ground. If effective width of flat reflectors is more than absorber tube diameter, reflected rays will be partly lost, hence low optical efficiency. By installing a secondary reflector above the absorber tube, lost rays are mostly redirected towards the absorber tube. This leads to a more uniform Flux and a higher optical efficiency. In this research, effects of three geometries for the secondary reflector are investigated and the results are presented. One of these designs produces very uniform Flux on the absorber tube whereas the second design leads to higher optical efficiency. A computer program has been employed to evaluate these effects.

In this research, the effect of bubble surface area Flux, Sb, and particle size on flotation rate constant, k, of pyrite (FeS2) particles was studied using bubble-particle interactions. The bubble-particle collision, attachment and detachment efficiencies were calculated under different flow regimes. The k increased with increase in the collision efficiency and decrease in the detachment efficiency. Also the bubble-particle collection efficiency increased with increase in the Sb. Thus difficulty in the floating of fine particles was attributed to low efficiency of the bubble-particle collision efficiency while difficulty in the floating of coarse particles was due to high efficiency of bubble-particle detachment. Maximum collision, attachment and detachment efficiencies were obtained as 81.57%, 50.60% and 51.89%, respectively.

In this paper, using simulation code CRPropa3. 0, the propagation of 104 primary cosmic rays of proton and iron with energy range of 1018 to 1021 eV was simulated. The spectra of the secondary photons and electron-positrons generated in the interactions of ultra-high energy cosmic rays (UHECRs) with cosmic background photons were investigated. The photon and electron spectra considered here are generated in photopion production, beta decay, and pair production. The minimum energy of primaries and the spectral index of source injection is changed separately and the effect of these changes on the spectra is investigated. Also, the total primary energy percent which transfers to secondaries, is calculated. It is found that for both primaries, lowering the minimum energy of the primaries leads to the decrease of the Flux of secondaries. This also results in the decrease of the total energy percent carried by beta and photopion products and the increase of the energy percent of pair production. Finally, in is shown that by increasing the spectral index, the Flux and the energy percent of all secondaries decreases for proton and iron primaries.

In recent years, inertial microfluidics (the use of inertial forces in microchannels) have attracted much attention aiming particle separation. The advantage of this method over other methods of separation and enrichment is its high-throughput performance and inexpensiveness. In the present study, the purpose of enriching the fluid with particles greater than 15 microns in diameter accomplished by designing a rectangular microchannel with an array of contraction-expansion regions in which expansion regions (reservoirs) had the task of trapping larger particles. By using the finite element method and by solving the Navier-Stokes equations, streamlines and vortex shapes are obtained. It was observed that for inlet flow rates in the range of 0. 25 to 0. 5 milliliters per minute, the highest capture efficiency for particles larger than 10 microns in diameter occurred near 0. 35 milliliters per minute. The effect of parameters such as channel height, number of reservoirs and the initial length of the contraction region on the capture efficiency was also measured. Finally, in order to approach the practical applications, the effect of viscosity change due to replacement of blood (Non-Newtonian fluid) instead of water was also investigated, which resulted in the formation of vortices at higher flow rates. In general, vortices created in the expansion region, whose intensity depends on the parameters mentioned above, play a dominant role in particle separation, while inertial lift forces appear as an initial guide.

This paper presents a sensorless system drive on primary Flux oriented control (PFOC) and secondary Flux oriented control (SFOC) for the linear induction motor (LIM) with taking into account end effect. Extended kalman filter (EKF) is applied to estimate LIM speed by measuring motor voltages and currents. In order to achieve desirable dynamic and robustness motor performance instead of traditional PI controller, a fuzzy PI controller is used for speed regulation in LIM vector control. The accuracy and validity of fuzzy PI controller operation are investigated and evaluated and its results are compared with traditional PI controller. Transient and steady state responses of proposed controller under load thrust variations and speed command are studied. Also characteristics and performances of primary Flux oriented control (PFOC) and secondary Flux oriented control (SFOC) for the linear induction motor are compared with each other. In order to evaluate the proposed method, simulations are performed in MATLAB/SIMULINK. Results show that the fuzzy PI controller has more excellent performance than the traditional PI controller and also PFOC has better performance than SFOC, because SFOC depend on rotor resistance. EKF properly estimate motor speed by measuring motor voltages and currents and therefore speed sensor can be eliminated.

Background: The present study aimed to investigate the equivalent dose in vital organs, including heart and lung, due to secondary particles produced during breast proton therapy. Materials and Methods: The numerical ORNL female-phantom was improved and simulated using the Monte Carlo MCNPX code. The depth-dose profile of proton beams with different energies was simulated. The proper energy range of incident proton beams has been estimated in order to have the Bragg peaks inside the breast tissue. The equivalent dose of secondary particles, including neutron and photon in vital organs, were evaluated. The TALYS code was used to investigate the neutron and photon particles’ production cross-sections. Results: The results showed that for the proton energy range of 60-70 MeV, the Bragg peaks positioned inside the breast. The maximum dose of 0. 65 mSv/nA-p was in Heart-Left Ventricle due to neutrons production by incident 70 MeV protons. However, the maximum absorbed dose, due to the secondary particles, was less than 0. 0004% of proton equivalent dose at the Bragg peak. The maximum photons dose and the protons dose into the Heart-Left Ventricle were 8. 42 μ Sv/nA-p and 68. 08 μ Sv/nA-p, respectively, which were negligible compared to the proton equivalent dose at the Bragg peak. Conclusion: The results confirmed a noticeable lower dose in the heart and lungs for breast proton therapy, compared with the previously reported dose for breast radiotherapy using photon. Most of the dose absorbed by the organs is due to the secondary neutrons, but those are low enough to be neglected.

Sedimentation tanks are designed for removal of floating solids in water flowing through the water treatment plants. These tanks are one of the most important parts of water treatment plants and their performance directly affects the functionality of these systems. Flow pattern has an important role in the design and performance improvement of sedimentation tanks. In this work, an experimental study of particle-laden flow in a rectangular sedimentation tank has been performed. Kaolin was used as solid particles in these experiments. Also, a numerical simulation was developed using the finite volume method with a k-e turbulent model. The results of the numerical model agree well with the experimental data. Hydrodynamic parameters and flow patterns of the fresh water flow and particle-laden flow are also compared in this study. The results show that the existence of particles completely changes the flow structures. It seems that the main reason for this phenomenon is the particles settling. Our experimental observations and numerical results show that parameters such as the maximum stream wise velocity, fully developed location, shear stress coefficient at the bottom of the tank and so on are different in water-containing particles compared to pure water and the inlet concentration strongly intensifies the differences.

Linear Flux switching motors with simple passive segmented secondary, referred as Segmented secondary Linear Flux Switching Motors (SSLFSMs), have low cost secondary and therefore are applicable to transportation systems like Maglev. However, it is shown that the SSLFSMs suffer from high thrust ripples. In this paper, minimizing SSLFSM thrust ripples besides maximizing its developed thrust are performed by considering the motor dimensions as design variables. Since the optimization of the motor is a high dimensional problem, a multi-level optimization method is employed to improve the machine performances and efficiency. According to the effects of the design variables on the optimization objectives, a sensitivity analysis is carried out to divide the design variables into two levels: mild-sensitive level and strong-sensitive level. Then, the two levels of design variables are optimized based on a mathematical model. Two different optimization methods as the Design of Experiment (DOE) and the Response Surface Method (RSM) are used in mild-sensitive level and the Genetic Algorithm (GA) is also used in strong-sensitive level. Based on FEM analysis, electromagnetic performance of the original motor and the optimal one are compared and the validity of the proposed optimization method is verified. Also, the effectiveness of the mathematical model used in thrust and thrust ripples calculations is evaluated and verified.