Superiority of integrated cervicothoracic immobilization in the setup of lung cancer patients treated with supraclavicular station irradiation

ObjectiveTo investigate the superiority of the integrated cervicothoracic immobilization devices (ICTID) on the mobility of the supraclavicular station in lung cancer patients requiring both primary lung lesion and positive supraclavicular lymph nodes irradiation.MethodsOne hundred patients with lung cancer were prospectively enrolled in the study. The following four different fixation methods are used for CT simulation positioning: thoracoabdominal flat immobilization device fixation with arms lifting (TAFID group), head-neck-shoulder immobilization device fixation with arms on the body sides (HNSID group), ICTID fixation with arms on the body sides (ICTID arms-down group), and n ICTID fixation with arms lifting (ICTID arms-up group). Cone-beam computed tomography (CBCT) images are taken daily or weekly before treatment, to assess anatomical changes during the radiotherapy course.ResultsThe translation errors in X (left-right direction), Y (head-foot direction), and Z (abdomen-back direction) directions of the ICTID arms-up, TAFID, ICTID arms-down and HNSID groups were (0.15 ± 0.18) cm, (0.15 ± 0.16) cm, (0.16 ± 0.16) cm, and (0.15 ± 0.20) cm; (0.15 ± 0.15) cm, (0.21 ± 0.25) cm, (0.28 ± 0.23) cm, and (0.27 ± 0.21) cm; (0.13 ± 0.14) cm, (0.15 ± 0.14) cm, (0.17 ± 0.13) cm, and (0.16 ± 0.14) cm, respectively. Among them, the ICTID arms-up group had the minimal setup errors in X direction than those in ICTID arms-down (p=0.001) and HNSID groups (p=0.001), and in Y direction than those in TAFID (p<0.001), and in Z direction than those in ICTID arms-down (p<0.001) and TAFID groups (p=0.034). For the rotational errors of the four groups in the directions of sagittal plane, transverse plane, and coronal plane, the ICTID arms-up group had the smallest setup errors in the sagittal plane than that of TAFID groups and similar rotation setup errors with those of the other three groups.ConclusionFor patients requiring radiation of primary lung lesion and positive supraclavicular lymph nodes, an integrated frame fixation device is preferred the ICTID arms-up methods provide the smallest set up error and satisfied repeatability of body position, compared with TAFID and HNSID

DEM study of the flow of cohesive particles in a screw feeder

Screw feeders are widely used in various industries to transfer granular materials at relatively precise rates. The performance can be affected by many factors such as the shape and size of particles, and the design of a screw and associated charging container. Some of these factors are difficult to investigate experimentally, including, for example, the cohesion between particles. In this work, a numerical model is developed by means of the discrete element method to study the flow of cohesive particles in screw feeders. In the model, the magnitude of the cohesive force is assumed, but it can be related to the van der Waals attraction for fine particles or the capillary force for wet particles. Based on the simulated results, a correlation for the prediction of solid flowrate is formulated as a function of the magnitude of cohesive force and the rotational speed of a screw. The mechanisms are then depicted in terms of contact forces and their spatial and temporal distributions. Three flow regimes, namely, continuous, intermittent and stable arch, are identified based on the standard deviation of solid flowrate in a screw feeder. Possible methods to reduce the effect of cohesive force on solid flow are discussed, in the study of the effects of the screw length in the associated charging container as well as the container design. The findings should be useful for the design and operation of screw feeders

Linking discrete particle simulation to continuum process modelling for granular matter : theory and application

Two approaches are widely used to describe particle systems: the continuum approach at macroscopic scale and the discrete approach at particle scale. Each has its own advantages and disadvantages in the modelling of particle systems. It is of paramount significance to develop a theory to overcome the disadvantages of the two approaches. Averaging method to link the discrete to continuum approach is a potential technique to develop such a theory. This paper introduces an averaging method, including the theory and its application to the particle flow in a hopper and the particle-fluid flow in an ironmaking blast furnace

Simulation and micromechanical analysis of flow and heat transfer in gas fluidized systems

Fluidization is widely used in industries as a major mode in fluid bed reactors. Understanding its fundamentals is important to structural optimization and temperature control of such a system. Mathematical modelling is a useful tool to investigate particle-fluid flows and heat transfer. The combined approach of computational fluid dynamics and discrete element method is particularly popular due to its reliability and relatively low computational demand. This thesis represents an effort in this area.To establish the connection between macroscopic and microscopic descriptions of complex particle-fluid flows, the micromechanics of different flow regimes, such as the fixed bed, expanded bed and fluidized bed, in gas fluidization is investigated for different powders. Focus is given to two aspects: the formation of a stable expanded bed, and the correlation between contact number and porosity. A new phase diagram in terms of macroscopic variables is established. The findings should be useful in the continuum modelling of particle-fluid flows.To study the effect of material properties and quantify heat transfer process, heat transfer characteristics of different powders in gas fluidization are investigated. Three flow modes of group A powders, namely fixed, expanded and fluidized are first reproduced and their heat transfer characteristics are examined. Then, the effects of the Hamaker constant and particle size are investigated. Finally, the heating process is quantified by an equation with a constant representing the overall heat transfer rate of a bed.To enhance the understanding of heat transfer between immersed surfaces and fluidized beds, studies at a particle scale are carried out. The approach is first validated through the good agreement between the predicted distribution and magnitude of local heat transfer coefficient with those measured. Then, the effects of some operating parameters such as inlet gas superficial velocity, tube temperature, and particle properties such as particle thermal conductivity and particle size are investigated and explained mechanistically. The relative importance of various heat transfer mechanisms is analysed at a wide range of tube temperature

Averaging method of particulate systems and its application to particle-fluid flow in a fluidized bed

A particulate system can be described through the discrete approach at the microscopic level or through the continuum approach at the macroscopic level. It is very significant to develop the method to link the two approaches for the development of models allowing a better understanding of the fundamentals of particulate systems. Several averaging methods have been proposed for this purpose in the past, but they mainly focused on cohesionless particle systems. In this work, a more general averaging method is proposed by extending it for cohesionless particle systems. The application of the method to the particle-fluid flow in a gas fluidized bed is studied. The density, velocity and stress of this flow are examined. A detailed discussion has been conducted to understand the dependence of the averaged variables on sample size

Effect of packing method on packing formation and the correlation between packing density and interparticle force

The packing of cohesive particles is of paramount importance in many industries because the packing structure is closely related to process performance. A general relation between packing density and interparticle force was previously proposed based on packing structures formed without dynamic fluid flows. Its universality is examined here in two different packings, formed in settling and defluidization of static and dynamic fluids, respectively. First, it is shown that the packings of the same particles formed by two different methods have different structures because of different impact-induced pressures. Nevertheless, a one-to-one relationship between packing density and structural properties still holds regardless of the different packing methods, and the force distribution in those packings obeys similar rules. Finally, the packing densities obtained by the different methods are demonstrated to be universally correlated with the ratio of the interparticle force to the effective gravity. These findings indicate that different phenomena of particulate systems at a macro- or meso-scale may share similar microscopic origins, with the interparticle force playing a crucial role

New insights into the molecular structure of kaolinite - methanol intercalation complexes

A series of kaolinite–methanol complexes with different basal spacings were synthesized using guest displacement reactions of the intercalation precursors kaolinite–N-methyformamide (Kaol–NMF), kaolinite–urea (Kaol–U), or kaolinite–dimethylsulfoxide (Kaol–DMSO), with methanol (Me). The interaction of methanol with kaolinite was examined using X-ray diffraction (XRD), infrared spectroscopy (IR), and nuclear magnetic resonance (NMR). Kaolinite (Kaol) initially intercalated with N-methyformamide (NMF), urea (U), or dimethylsulfoxide (DMSO) before subsequent reaction with Me formed final kaolinite–methanol (Kaol–Me) complexes characterized by basal spacing ranging between 8.6 Å and 9.6 Å, depending on the pre-intercalated reagent. Based on a comparative analysis of the three Kaol–Me displacement intercalation complexes, three types of Me intercalation products were suggested to have been present in the interlayer space of Kaol: (1) molecules grafted onto a kaolinite octahedral sheet in the form of a methoxy group (Al-O-C bond); (2) mobile Me and/or water molecules kept in the interlayer space via hydrogen bonds that could be partially removed during drying; and (3) a mixture of types 1 and 2, with the methoxy group (Al-O-C bond) grafted onto the Kaol sheet and mobile Me and/or water molecules coexisted in the system after the displacement reaction by Me. Various structural models that reflected four possible complexes of Kaol–Me were constructed for use in a complimentary computational study. Results from the calculation of the methanol kaolinite interaction indicate that the hydroxyl oxygen atom of methanol plays the dominant role in the stabilization and localization of the molecule intercalated in the interlayer space, and that water existing in the intercalated Kaol layer is inevitable