Ship Longitudinal Strength Modelling

The aims of the research work presented in this thesis are to assess the effects of weld-induced residual stresses and initial imperfections on the collapse behaviour of a ship's hull girder, and to demonstrate the close correlation that exists between the hull's ultimate longitudinal strength and the maximum load-carrying capacity of its components under compressive loads. A theoretical method for evaluating the ultimate longitudinal strength of a ship's hull girder under vertical bending is described. The hull's midship cross-section is discretised into structural elements such as stiffened panels, plate elements and hard corners. Effects of buckling of compressive components are allowed for by incorporating the load-end shortening curves of unstiffened and stiffened plates into the hull strength analysis. An incremental approach is employed to derive the moment-curvature relationship and hence the peak moment for the hull girder. Curvature, rather than bending moment, increments are imposed on the hull girder to enable the post-collapse behaviour to be followed. Comparisons with tests on welded steel box girder models and other analytical methods show that the agreement is satisfactory. Prior to determining the vertical moment-curvature relationship for a hull, the load-end shortening curves need to be established for each stiffened panel forming the hull's mid-ship cross-section. An analytical method is developed to examine the large deflection elasto-plastic behaviour of stiffened panels under uniaxial compression. The method is based on a beam-column approach in which the longitudinally stiffened plating is treated as a series of beam-columns formed by the stiffeners and an associated width of plates. The beam-column model is continuous over three supports provided by transverse frames to take effect of interaction between adjacent spans into account. Dynamic Relaxation is employed to numerically solve the non-linear equilibrium equations. The strength contribution from the plating, allowing for buckling effects, is accounted for by using the plate average stress-strain curves. The load is applied through end displacements such that both the pre- and postcollapse behaviour can be traced. It is shown by comparisons with test results and other analytical methods that the present one satisfactorily predicts the behaviour of stiffened compression panels. A numerical method to generate the plate average stress-strain curves for the stiffened panel analysis is proposed. The results from an existing parametric study on the large deflection elasto-plastic behaviour of practical plates in compression with constrained edges are used as basic data. A simplified procedure is followed to interpolate the average stress-strain curve for the plate with parameters different from the standard cases. An analytical study on the ultimate strength behaviour of longitudinally framed frigate-type hulls is presented. Five naval frigates designed in the 1950's and 1960's are analysed by the present incremental approach. The derived load-end shortening curves for the stiffened panels and moment-curvature curves for the hull girders are presented. It is shown that the ultimate strength of longitudinally framed hulls is strongly influenced by the full-range behaviour of components under compressive loads in association with bending. In particular, the ultimate hull strengths are closely correlated with the maximum load-carrying capacities of the critical stiffened panels which are located in deck structures in the sagging condition and in bottom structures in the hogging condition. Two simple expressions for predicting the ultimate moment capacity of longitudinally stiffened hulls in the sagging and hogging conditions are proposed. They are based on the results of the numerical analysis for appropriate initial imperfections in the plate and stiffened panels. The ultimate bending moments of a variety of hull and box girders predicted by the strength formulae are compared with the numerical and experimental results. Satisfactory agreement is obtained which suggests that the proposed formulations could form the basis of an improved design method

Biological Activity of Trimethylselenonium-selenium and Influence of Vitamin E on its In Vivo Formation in Rats Using a Torula Yeast Diet

During recent times, many efforts have been extended to investigate the metabolism of selenium compounds-in microorganisms, animals and plants. Several investigators (1-3) have proposed some hypothetical metabolic pathways for selenium. However, the role of selenium in the life function of animals remains unknown. Liver necrosis, as induced by the feeding of a Torula yeast diet which is unsupplemented with vitamin E and selenium, is known to be a fatal symptom in rats (4-6). The addition of either vitamin E or selenium to the diet is associated with the prevention of this condition. Schwarz (7) has suggested that vitamin E and selenium play their effect on the same syndrome by acting on alternate pathways of one stage in energy metabolism, thus enabling either substance to promote the over-all reaction. Tappel (8) has proposed that either substance acts to stabilize unsaturated lipids in the intact animal, i.e. as antioxidant in preventing lipid peroxidation and accompanying cellular damage. The report that the necrogenic syndrome may occur when rats are fed a diet low in polyunsaturated fat (9) does not appear to support the explanation offered by Tappel

A Packing-Line Productivity Assessment of Particleboard Furniture

Malaysia, with its abundance of wood resources, is one of the traditional powerhouses of Asia's wood industry. In recent years, this sector has lost some of its edge simply because other countries have caught up, or have surpassed it in terms of competitiveness. Local manufacturers have no choice but to improve the production efficiency as well as the quality of their products if they want to remain competitive in the globalize market. In the production of panel particleboard furniture, the operations of packing department is more complicated and complex. The continuous packing process is affected by various factors, known and unknown, tangible and intangible. The objective of this paper is to study and analyze various factors contributing to the productivity of the packing line of particleboard furniture. The productivity and the frequency of the factors affecting the packing lines were measured and analyzed. The result showed that production planning, packing flow chart and work design (55%), insufficient of raw and supporting materials (21%), and the problems related to quality (14%) are the three most influencing factors to the productivity of packing lines, followed by insufficient of manpower arrangement (6%) and machinery breakdown (4%)

An Innovative Direct-Interaction-Enabled Augmented-Reality 3D System

Previous augmented-reality (AR) applications have required users to observe the integration of real and virtual images on a display. This study proposes a novel concept regarding AR applications. By integrating AR techniques with marker identification, virtual-image output, imaging, and image-interaction processes, this study rendered virtual images that can interact with predefined markers in a real three-dimensional (3D) environment

Design and Analysis of a Novel 25 GHz Interleaver for DWDM Applications with Two Ring Configurations

We present a novel scheme of an excellent flat-top 25 GHz optical interleaver based on two ring configurations. And the Advanced Systems Analysis Program (ASAP) optical modeling software has been utilized for the interleaver design. The optical path difference for interference and the phase shift are provided by the interferometer with two birefringent crystals and dual-ring arrangement. The proposed structure exhibits the passband utilization of more than 90% and the channel isolation greater than 95 dB within the C-band. Furthermore, we improve the dispersion performance by employing λ/6 wave plates as birefringent compensators for interleavers. The research results illustrate that our proposed scheme with compensator can improve the dispersion of more than 85.8%. Comparing the performance with the previous studies of optical interleavers with birefringent crystal and ring structure, the proposed system can achieve an excellent 25 GHz multichannel filter for dense wavelength division multiplexing (DWDM) transmission systems

A mini review of plan quality and secondary cancer risk in CyberKnife M6 radiosurgery for benign intracranial tumors

With advancements in medical technology, stereotactic radiosurgery (SRS) has become an essential option for treating benign intracranial tumors. Due to its minimal side effects and high local control rate, SRS is widely applied. This paper evaluates the plan quality and secondary cancer risk (SCR) in patients with benign intracranial tumors treated with the CyberKnife M6 system. The CyberKnife M6 robotic radiosurgery system features both multileaf collimator (MLC) and IRIS variable aperture collimator systems, providing different treatment options. The study included 15 patients treated with the CyberKnife M6 system, examining the differences in plan quality and SCR between MLC and IRIS systems. Results showed that MLC and IRIS plans had equal PTV (planning target volume) coverage (98.57% vs. 98.75%). However, MLC plans demonstrated better dose falloff and conformity index (CI: 1.81 ± 0.26 vs. 1.92 ± 0.27, P = 0.025). SCR assessment indicated that MLC plans had lower cancer risk estimates, with IRIS plans having average LAR (lifetime attributable risk) and EAR (excess absolute risk) values approximately 25% higher for cancer induction and 15% higher for sarcoma induction compared to MLC plans. The study showed that increasing tumor volume increases SCR probability, but there was no significant difference between different plans in PTV and brainstem analyses

Discussions of Effects of Surface Tension on Water Vapor Absorbed by Triethylene Glycol Solution Films

The surface tension gradient can result from releasing a surfactant from the liquid film or feeding a vapor into the liquid film, and the interfacial disturbance will be induced by them. The flowing phenomena were termed “Marangoni effect,” and the mass transfer performance was enhanced by the effect. The objective of this study was to apply the Marangoni effect, such as water vapors absorbed by the liquid film of triethylene glycol (TEG) solution, and to analysze mass transfer behaviors with and without surfactants’ addition in the liquid film. The interfacial disturbance resulted from the surface tension gradient was considered in this study, and the mass transfer behaviors for packed-bed absorbers were discussed to elucidate the influence of the Marangoni effect on the absorbers. It was observed that the trends of mass transfer rates could be increased significantly as the surfactant is added into the absorption system. Experimental results showed that feeding a vapor or adding a surfactant with lower surface tension and/or higher volatility in the liquid will result in the surface tension gradient on the gas-liquid interface. The induced flowing disturbance will lead to an increment of mass transfer rate for a gas-liquid contact system