طراحی پایدار، به فلسفه طراحی اشیا فیزیکی و محیط ساخته شدهای گفته می شود که با اصول پایداری در محیط زیست، اقتصاد و اجتماع تطابق داشته باشند.
اهداف اصلی :
Metallic implants are known to generate bright and dark streaking artifacts in x-ray computed
tomography (CT) images, which in turn propagate to corresponding functional positron emission
tomography (PET) images during the CT-based attenuation correction procedure commonly
used on hybrid clinical PET/CT scanners. Therefore, visual artifacts and overestimation and/or
underestimation of the tracer uptake in regions adjacent to metallic implants are likely to occur and
as such, inaccurate quantification of the tracer uptake and potential erroneous clinical interpretation
of PET images is expected. Accurate quantification of PET data requires metal artifact reduction
(MAR) of the CT images prior to the application of the CT-based attenuation correction procedure.
In this review, the origins of metallic artifacts and their impact on clinical PET/CT imaging are
discussed. Moreover, a brief overview of proposed MAR methods and their advantages and
drawbacks is presented. Although most of the presented MAR methods are mainly developed for
diagnostic CT imaging, their potential application in PET/CT imaging is highlighted. The
challenges associated with comparative evaluation of these methods in a clinical environment in
the absence of a gold standard are also discussed. V
C 2012 American Association of Physicists in
Medicine.
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مقدمه
انسان ها همواره از بدو خلقت، فطرتاً در جستجوی ترفیع نیازهای خود بوده اند.برای میل به مقصود،بسیار از طبیعت و عناصر چهارگانۀ آن بهره جسته اند.مهارتی که انسان بواسطۀ آن عظیم ترین و سرکش ترین انرژی نهفته در طبیعت یعنی باد را رام و مسخر خود ساخته و به انواع گوناگون ،با دگرگونی در چهرۀ آن ،مظهر یک نوع رابطه بین انسان و طبیعت را به زیبا ترین شکل نمایان ساخته است .از دیر باز برای مقابله با گرمای سخت تابستان مردم این دیار به زیر زمین پناه می بردند. بادگیرها با هدایت هوا به سطح حوض آبی که در وسط زیر زمین قرارداشت ، موجب ایجاد هوایی خنک و فرح بخش می شدند. بادگیر، یک روش ابداعی ایرانی برای ایجاد فضای خنک در داخل منازل گرم کویری است
...
Neutron multiplicity measurements are a useful technique for the characterization of special nuclear
material. This technique relies on the detection of correlated neutrons from fission events. As correlated
events are detected it is possible to determine the neutron multiplicity distribution for the sample. This
distribution is useful for identifying the material and estimating the mass. This work focuses on the
ability of the Monte Carlo code MCNP-PoliMi to simulate measured distributions. The experiment used
as the basis of comparison consisted of a 4.5 kg plutonium metal sphere surrounded by up to 6 in. of
polyethylene. A bank of 15 (3 He) detectors was used to detect the correlated neutron events. MCNP-
PoliMi was used to simulate the particle transport and a post-processing algorithm was developed to
apply detector deadtime effects and to determine the neutron multiplicity distributions. These
simulated distributions were then compared to the measured results. The simulation provided an
adequate estimation of the measured data. However, we observed a systematic over-prediction in both
the mean and the variance of the measured distribution.
قالب خم ورق در نرم افزار سالید ورکز (solid works) مدل سازی شده و تمامی قطعات به همراه فایل مونتاژ در آن تعبیه شده است.
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