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[en] This paper presents the process evaluation of the relationship model between the gap and overlap in the design of the bunker lead door. the reference model was successfully developed using Particle and Heavy IonTransport code System (PHITS) simulation software. This study is to prove the accuracy of the relationship model with an optimised correction factor.the introduction to the optimum relationship model is a cost and time-saving approach for determining the permissible ratio of gap and overlap in radiation facility design. (author)

[en] Shielding protocols such as NCRP 151, IAEA SRS 47 and IPEM 47 are commonly used for the design of radiotherapy facilities. Some work has been accomplished in updating the basic formula with the advent of IMRT but little consideration has been made for unflattened beams and stereotactic techniques apart from for facilities housing devices like the CyberKnife.

The inevitable scenario of a stereotactic-only linear accelerator was considered in this study. The necessary shielding requirements were determined based on stereotactic data from a year’s worth treatments from one clinic as well as further measurements of leakage, scatter and use factors. These values were compared to recommendations in the literature.

While tenth value layer amounts, workload and barrier widths could be kept at the status quo, major changes could be made to the parameters of leakage, scatter and use factors while still maintaining safety. Some differences could also be seen for the use of IMRT factors.

Current shielding protocols were found to inadequately describe methodology for the shielding of a stereotactic-only radiotherapy linac bunker, producing overly-conservative wall thicknesses which is in disagreement with the principles of ICRP. (note)

[en] This paper presents the process of developing the relationship model between gap and overlap in the design of the bunker lead door. This involves studies of the relationship between gap and overlap design ratio and the dose rate angular effect based on source position. The model was developed by using Particle and Heavy Ion Transport Code System (PHITS) simulation software. The developed relationship model is an accelerated assist tool to determine the acceptable ratio of gap and overlap in the design of radiation facility based on the attenuation method. (author)

[en] The need to produce high-quality seedlings with adequate quantity has placed a burden on nursery operators, who often require substantial capital and labour with limited daily production capability. The goal of this project was to develop a seedling polybag soil filling machine and evaluate its performance in a simulated oil palm nursery, emphasising small polybag production. The 51 kW diesel engine of a universal, multipurpose 4WD (four-wheel drive) prime mover was utilised to transmit the power to the mixer and auger of the machine system. The recorded average production capacity was 198 bags man hr°C1, which was 24.24% higher than the conventional practice of 150 bags man hr°C1. The final weight was within the limit (<5%) for both small and large polybags. The production capacity of the machine was moderately improved, despite an increase of approximately 53% in total costs per polybag over the conventional practice. Generally, the machine can be deployed in seedling production of the oil palm nursery stage to fill the polybags with suitable planting media selection. (author)

[en] In this study the flow rate in a quasi-2D hopper with two symmetric outlets was investigated numerically. When two outlets merge into one, the flow rate is obviously bigger than that with a large enough distance between them. To explain the influence of the interaction between these two outlets, it was found that the velocity field above one outlet will be affected by the neighboring outlet by reducing the stagnant zone. With increasing distance, this interaction becomes weaker. Finally the formula of flow rate considering various outlet sizes and distances is fitted to the simulation data. - Highlights: • The flow rate in a quasi-2D hopper with two outlets is investigated. • The formula of flow rate is fitted. • The flow field in the hopper is plotted.

[en] The K-130 cyclotron is in operation at VECC, Kolkata. Recently modernization of the cyclotron has taken place. Central region modification has increased reasonable internal beam current. During the tuning of the projectiles, loss of beam is unavoidable and projectiles hitting different parts of the machine inside the vacuum chamber . These interactions produce prompt radiation comprising neutron and gamma. However machine bunker is not accessible during the operation of the machine. The induced activity produced because of interactions of the primary and secondary radiation a radiation hazardous environment during the shut down for the related maintenance work. Area radiation monitors placed at machine bunker room have the interlock with massive shield door of the bunker. Area radiation monitors are set to specified limiting value, lower than that will allow to open the shield door in normal condition. As, the internal beam current being increased and the probability of beam spread being more. Consequently generation of induced activity is also high leading to delay in machine bunker door opening because of the interlock settings. Radiation dose mapping after a long operation of the machine was done for the different strategic points (The locations mainly people access immediate after shut down). Different consequences and remedial measures being presented in paper to raise the dose rate limit level for the interlocks between the area radiation monitors with machine bunker door, keeping in mind of the regulatory requirements. Raising the limit of dose rate limiting value will minimize the waiting time to access the machine bunker which will increase the duty factor of the machine. (author)

[en] Assembly of components with a size in the order of tens of micrometers or less is difficult because the gravitational forces become smaller than weak forces such as capillary, electrostatic and van der Waals forces. As such, the picked-up components commonly adhere to the manipulator, making the release operation troublesome, and the repeatable supply of components cannot be guaranteed because the magazining and bunkering scheme available in conventional scale assembly cannot be extended to these small objects. Moreover, there are also no effective ways known to deliver the finalized assembly externally. In this paper, we present the manipulation and assembly of microparts using optical tweezers, which by nature do not have stiction problems. Techniques allowing bunkering and finalizing the assembly for exporting are also presented. Finally, we demonstrate an exemplary microassembly formed by assembling two microparts: a movable microring and a microrod fixed on a glass substrate. We believe this traceable microassembly to be an important step forward for micro- and nano-manufacturing. (paper)

[en] Two-dimensional (2D) hopper flow of disks has been extensively studied. Here, we investigate hopper flow of ellipses with aspect ratio $\mathrm{\alpha <!--\; ??\; -->}=2$, and we contrast that behavior to the flow of disks. We use a quasi-2D hopper containing photoelastic particles to obtain stress/force information. We simultaneously measure the particle motion and stress. We determine several properties, including discharge rates, clogging probabilities, and the number of particles in clogging arches. For both particle types, the size of the opening, D, relative to the size of particles, ℓ, is an important dimensionless measure. The orientation of the ellipses plays an important role in flow rheology and clogging. The alignment of contacting ellipses enhances the probability of forming stable arches. This study offers insights into applications involving the flow of granular materials consisting of ellipsoidal shapes, and possibly other non-spherical shapes. (letter)

[en] A bunker for the containment and medical use of 10 MV and 6 MV X-rays from a linear accelerator was designed to be added on to four existing bunkers. Space was limited and the walls of the bunker were built using Magnadense, a high density aggregate mined in Sweden and imported into the UK by Minelco Minerals Ltd. The density was specified by the user to be a minimum of 3800 kg/m³. This reduced the thickness of primary and secondary shielding over that required using standard concrete. Standard concrete (density 2350 kg/m³) was used for the roof of the bunker. No published data for the tenth value layer (T.V.L.) of the high density concrete were available and values of T.V.L. were derived from those for standard concrete using the ratio of density. Calculations of wall thickness along established principles using normal assumptions and dose constraints resulted in a design with minimum primary wall barriers of 1500 mm and secondary barriers of between 800 mm and 1000 mm of high density concrete. Following construction, measurements were made of the dose rates outside the shielding thereby allowing estimates of the T.V.L. of the material for 6 and 10 MV X-rays. The instantaneous dose rates outside the primary barrier walls were calculated to be less than 6 x 10^-6 Sv/hr but on measurement were found to be more than a factor of 4 times lower than this. Calculations were reviewed and the T.V.L. was found to be 12% greater than that required to achieve the measured dose rate. On the roof, the instantaneous dose rate at the primary barrier was measured to be within 3% of that predicted using the published values of T.V.L. for standard concrete. Sample cubes of standard and high density concrete poured during construction showed that the density of the standard concrete in the roof was close to that used in the design whereas the physical density of Magnadense concrete was on average 5% higher than that specified. In conclusion, values of T.V.L. for the high density concrete derived from those for ordinary concrete and correcting only for physical density were found to be conservative and resulted in more material being used than necessary in the primary and secondary barriers. The measured values of T.V.L. for the high density concrete could be used in the future. (authors)