in the present study, the kinetics of biodiesel production through transesterification of brassica carinata oil with methanol in the presence of potassium hydroxide is investigated by kinetic monte carlo simulation. the obtained results from simulation agree qualitatively with the existing experimental data. the kinetics data for each step of suggested mechanism are confirmed by simulation. by ...

introduction: monte carlo (mc) is the most common method for simulating virtual spect projections. it is useful for optimizing procedures, evaluating correction algorithms and more recently image reconstruction as a forward projector in iterative algorithms; however, the main drawback of mc is its long run time. we introduced a model based method considering the effect of body attenuation and i...

background: most preclinical studies are carried out on mice. for internal dose  assessment of a mouse, specific absorbed fraction (saf) values play an important role.  in most studies, saf values are estimated using older standard human organ compositions  and values for limited source target pairs. objective: saf values for monoenergetic photons of energies 15, 50, 100, 500,  1000 and 4000 ke...

aims: the aim of the present work is (1) to evaluate dose calculation accuracy of two commonly used algorithms for 15 mv small photon fields in a medium encompassing heterogeneity and (2) compare these results with measured results obtained using gafchromic film ebt2. materials and methods: authors employed kailwood (pinus wallichiana) to mimic lung. briefly, seven kailwood plates, each measuri...

in this paper we focus on a continuously deteriorating two units series equipment which its failure can not be measured by cost criterion. for these types of systems avoiding failure during the actual operation of the system is extremely important. in this paper we determine inspection periods and maintenance policy in such a way that failure probability is limited to a pre-specified value and ...

we calculate the stopping power for heavy-ion diclusters moving in a strongly coupled two-dimensional electron gas system by using the local field corrected dielectric function at finite temperature. we obtain a parameterized local field correction factor based on a relation between the thermal compressibility and exchange-correlation energy in two-dimension. the interpolated parameter is deriv...

background: accurate small radiation field dosimetry is essential in modern radiotherapy techniques such as stereotactic radiosurgery (srs) and intensity modulated radiotherapy (imrt). precise measurement of dosimetric parameters such as beam profile, percentage depth doses and output factor of these beams are complicated due to the electron disequilibrium and the steep dose gradients. in the p...

background: high density concrete is extensively used for efficient radiation attenuation in radiotherapy rooms and nuclear reactors. over the past eight years, some efficient galena-based concrete samples for shielding x or gamma rays was produced. the goal of this study was to produce a novel high density concrete against neutron and photon radiations using tourmaline and galena. materials an...

background: the characteristics of secondary neutrons in a high energy radiation therapy room were studied using the mcnpx monte carlo (mc) code. materials and methods: two mc models including a model with full description of head components and a simplified model used in previous studies were implemented for mc simulations. results: results showed 4-53% difference between full and with the sim...

deregulation policy has caused some changes in the concepts of power systems reliability assessment and enhancement. in this paper, generation reliability is considered, and a method for its assessment using intelligent systems is proposed. also, because of power market and generators’ forced outages stochastic behavior, monte carlo simulation is used for reliability evaluation. generation reli...