Refrigerated transport by sea

Sea transport of refrigerated goods is a vital link in the cold chain conveying perishables from producer to consumer. Despite the unprecedented crisis at present afflicting marine transportation and shipyards, sea refrigerated transport has experimented with important advances in the last few years. A ‘reefer’ ship is today a complex structure, with a great deal of computer technology and automation installed onboard. Ships are always ships, they may have lost some of the fascinating allure of the past, only to become sophisticated, specialized and efficient tools, up to the expectations of today's way of life. This Paper will concentrate on cargo ships and fishing vessels and will omit references to the specialized vessels required for liquefied gases.     

Strength of carbon/epoxy laminates with countersunk hole

The aim of this study is to predict the static strength of carbon/epoxy laminates with countersunk hole. Also, three-point bend (TPB) specimens with the same lay-up were analysed. For this purpose, the notched strength of the laminates was analysed by a damage zone model (DZM), where damage around the notch is represented by an ‘equivalent crack’ with cohesive forces acting between the crack surfaces. The DZM requiring only basic properties of the laminate such as unnotched tensile strength, δ₀, fracture energy, G_c^*, and stiffnesses of the laminate. However, the complex geometry around the countersunk hole implies that both δ₀ and G_c^* will vary in this area, and in order to avoid this problem an approximate geometry of the countersunk hole is used in the DZM-calculations. With this approximation, good agreement between experimental and calculated strength was observed for the laminates with countersunk hole. This was also the case for the TPB specimens.     

About the use of rank transformation in sensitivity analysis of model output

Rank transformations are frequently employed in numerical experiments involving a computational model, especially in the context of sensitivity and uncertainty analyses. Response surface replacement and parameter screening are tasks which may benefit from a rank transformation. Ranks can cope with nonlinear (albeit monotonic) input-output distributions, allowing the use of linear regression techniques. Rank transformed statistics are more robust, and provide a useful solution in the presence of long tailed input and output distributions.

As is known to practitioners, care must be employed when interpreting the results of such analyses, as any conclusion drawn using ranks does not translate easily to the original model. In the present note an heuristic approach is taken, to explore, by way of practical examples, the effect of a rank transformation on the outcome of a sensitivity analysis. An attempt is made to identify trends, and to correlate these effects to a model taxonomy.

Employing sensitivity indices, whereby the total variance of the model output is decomposed into a sum of terms of increasing dimensionality, we show that the main effect of the rank transformation is to increase the relative weight of the first order terms (the ‘main effects’), at the expense of the ‘interactions’ and ‘higher order interactions’.

As a result the influence of those parameters which influence the output mostly by way of interactions may be overlooked in an analysis based on the ranks. This difficulty increases with the dimensionality of the problem, and may lead to the failure of a rank based sensitivity analysis.

We suggest that the models can be ranked, with respect to the complexity of their input-output relationship, by mean of an ‘Association’ index I_y. I_y may complement the usual model coefficient of determination R_y² as a measure of model complexity for the purpose of uncertainty and sensitivity analysis.     

Knowledge-based support for event tree construction

A prototype system called EventMAP has been developed to provide knowledge-based support for event tree construction. It comprehends an event tree model of a physical system, which represents the possible event sequences following an initial incident. This model can be used to identify potentially hazardous accident or failure scenarios, to help in assessing the possible outcomes of an observed incident, and to support decisions about appropriate actions. It can also be used during modification to provide insights into the needs for specific safety features.

EventMAP incorporates explicit knowledge about safety engineering and good event tree construction practice. This assures that model building will be more systematic, and will produce more complete and correct event trees. Assumptions underlying the model are tracked explicitly, allowing ‘what-if’ exploration. Moreover, the safety-related design rationale will be preserved despite personnel changes over time. EventMAP incorporates knowledge about: plant structure in terms of subsystems, components, and interconnections; cause/effect relationships and other interactions among subsystems; and failure modes, including human errors. The role of EventMAP is to act as an ‘intelligent assistant’ for the event tree developer; it monitors the evolving model and issues suggestions and warnings to the user as appropriate.     

Treatment of nondetects in multivariate analysis of groundwater geochemistry data

Principal components analysis (PCA) is used to evaluate similarities in the trace element chemistry of groundwaters. Many of the trace elements, however, occur at concentrations below the detection limits (DL), which presents problems for statistical analyses. Since the optimal methods for dealing with the ‘

In this study, a new approach was developed to determine the best substitution methods when dealing with the ‘DL’ values for a given data set. Monte Carlo simulation experiments, using a mixture multivariate model, were performed to test the effects of substitution of the ‘

When ‘相似文献   

Development of a cryogenic detection concept for GNO

The Gallium-Neutrino-Experiment at GNO measures solar neutrinos radiochemically via the reaction ⁷¹Ga(ν,e)⁷¹Ge. In order to reduce statistical and systematic uncertainties in detecting the decay of ⁷¹Ge to ⁷¹Ga, a favourable way could be the use of high-resolution cryogenic detectors instead of the presently integrated miniaturized proportional counters. After the successful development of a highly efficient 4π-detector, optimization of thermal Ge-deposition and decoupling of deposition and detection, present activity concentrates on low background considerations, enhancement of external and internal shielding of the cryostat and a long-term run with artificially activated ⁷¹Ge to prove the feasibility of ‘cryoGNO’ in our Underground Laboratory in Garching.     

Interface structure at the large misfit, still common epitaxy β-FeSi2(101) or (110)//Si(111)

In this paper we compare the elastic energies obtained by tight-binding molecular dynamics simulations for several strained structures of β-FeSi₂, corresponding to the most frequent epitaxial relationships ‘on’ and ‘in’ silicon. Our results confirm that, for coherent interfaces, the very common β-FeSi₂(101) or (110)//Si(111) orientation generates a very large contribution to the elastic energy, due to the large misfit. Therefore, we suggest that the frequent nucleation of such epitaxial relationships in precipitates is provided by the correspondence of the two-dimensional crystal structure for the Si sites between Si(111) and β-FeSi₂(101) or (110). We show it to be maintained even after misfit relaxation in the silicon matrix, as simulated by a large-scale molecular dynamics run.     

Cost effectiveness and the choice of ‘best environmental options’

‘Best’ environmental options can be identified by standard techniques of economic analysis. However, the concept of ‘best’ will depend on the nature of the damage avoided by the use of different control types, the secondary cross-media effects of using environmental control, and the costs of control.

Control cost estimation does present problems but these can be largely overcome. However, damage estimates have been notoriously difficult to generate. To overcome some of the intractible problems, an alternative approach is suggested which is less powerful but more operational.     

Structural integrity analysis of embedded optical fibres in composite structures

The virtues of having sensors in manufactured goods for increased functionality purposes have been well documented. Benefits include sophisticated structures requiring less maintenance and repair, increased safety and reliability, and avoidance of ‘over design’. Though many schemes of sensing are available, these so-called ‘smart’ products in the near future, will increasingly rely on the optical fibres (OF) principles because of numerous inherent advantages. Optical fibres are small, lightweight, possess geometrical flexibility, Electromagnetic interference (EMI) immunity, operate over a wide range of environmental conditions, and can be configured to respond to many physical parameters.

This paper will report on the suitability of embedding OF in commonly used carbon-fibre composites. These panels will be designed, manufactured and tested for the effects of typical fibre-optic geometrical and physical parameters such as types of fibre coating polymers, fibre diameter and fibre distribution. Corroboration of these test results with finite element (FE) results will be shown. Based on tensile and compression tests on OF-embedded composites, it is shown that significant deterioration on strength is observed beyond a certain OF density level. This paper will focus on the macroscopic effect of having optical fibres in composites from a structural integrity point of view. To this end, an exposition on the theoretical considerations using continuum mechanics and energy principles is provided.     

Residual stress fields in surface-treated silicon carbide for space industry—comparison of biaxial and triaxial analysis using different X-ray methods

Any mechanical surface treatment and machining leaves ‘footprints’ in the form of residual stress fields in the surface region of technical parts or components, which are detectable by X-ray diffraction. In the present paper, we applied different X-ray methods to investigate the residual stress state in the near-surface zone of sintered silicon carbide after mechanical surface processing. Using the sin² ψ-based ‘universal plot’ method, we found steep gradients for the in-plane components σ₁₁ and σ₂₂ in the form of high compressive stresses at the surface, which change into tensile stresses within a few microns. To gain information on the triaxial residual stress state, we applied the scattering vector method, which is based on strain depth profiling by sample rotation around the diffraction vector. For the in-plane stresses, we observed gradients similar to those obtained by the ‘universal plot’ method, but they were shifted on the absolute scale towards tensile stress. We explain this difference by ‘pseudo-macroscopic’ tensile residual stress fields σ₃₃, which act normal to the surface and therefore pretend higher in-plane compressive stresses σ_ii (i = 1, 2), if they are not regarded in the evaluation procedure.     

Young’s modulus and interlaminar fracture toughness of SU-8 film on silicon wafer

SU-8 cantilever beams deposited on the polished sides or unpolished sides of silicon wafers were fabricated by MEMS and bulk micro-machining techniques. Bending tests were conducted to measure the Young’s modulus and interface fracture toughness. The results indicate that the Young’s modulus is increasing as the width of specimens is increasing because the specimen quality becomes better. When the width of SU-8 cantilever beam is 400 μm, the Young’s modulus is about 3.5 GPa. On the other hand, since the interface between SU-8 and silicon wafer does not suffer the attack of etchant, the measured interface fracture toughness has no clear dependence on the specimen width. The averaged interface fracture toughness is about 25–30 J/m² for the polished interface and 15–20 J/m² for the unpolished interface.     

NiN4/Cr修饰的石墨烯电化学固氮电极

工业上应用哈伯工艺法合成氨过程要求严苛, 需要消耗大量能源且二氧化碳排放量大。因此, 开发在常规环境条件下通过电催化氮还原反应的清洁技术, 对未来可持续的能源转化进程具有重要意义。本研究采用密度泛函理论计算方法, 对TM₁N₄/TM₂嵌入石墨烯的氮还原反应进行了全面研究。在充分考虑活性和稳定性的情况下, 研究结果表明, NiN₄/Cr锚定石墨烯通过酶促反应途径表现出最佳的催化活性, 其中第一次加氢为电位决定步骤, 起始电位为0.57 V, 优于商业Ru基材料。此外, 与单一的Cr原子修饰的石墨烯相比, 引入NiN₄官能团降低了ΔG_max并提高了电催化性能。根据Mulliken电荷分析, 催化剂的催化活性主要来源于载体和反应中间体之间的电子转移。上述结果为高效合成氨提供了电极候选材料, 进一步深化了相应的电催化机理。     

Overdispersion in modelling accidents on road sections and in empirical bayes estimation

In multivariate statistical models of road safety one usually finds that the accident counts are ‘overdispersed’. The extent of the overdispersion is itself subject to estimation. It is shown that the assumption one makes about the nature of overdispersion will affect the maximum likelihood estimates of model parameters. If one assumes that the same overdispersion parameter applies to all road sections in the data base, then, the maximum likelihood estimate of parameters will be unduly influenced by very short road sections and insufficiently influenced by long road sections. The same assumption about the overdispersion parameter also leads to an inconsistency when one estimates the safety of a road section by the Empirical Bayes method. A way to avoid both problems is to estimate an overdispersion parameter (φ) that applies to a unit length of road, and to set the overdispersion parameter for a road section of length L to φL. How this would change the estimates of regression parameters for road section models now in use requires examination. Safety estimation by the Empirical Bayes method is altered substantially.     

Partition, luminescence and energy transfer of Er/Yb ions in oxyfluoride glass ceramic containing CaF2 nano-crystals

A complete spectroscopic investigation of energy transfer processes in oxyfluoride glass ceramics containing CaF₂ nano-crystals doped with various amounts of Er³⁺ and Yb³⁺ was reported. An enhancement of the 1.53 μm emission and infrared to visible up-conversion fluorescence was confirmed experimentally due to efficient non-radiative energy transfer from Yb³⁺ to Er³⁺ ions concentrated in CaF₂ nano-crystals. The efficiency of Yb³⁺ to Er³⁺ energy transfer in excess of 85% was obtained for 0.5 mol% Er³⁺/2.0 mol% Yb³⁺ co-doped glass ceramic. Using rate equation formulism, the coefficient of Yb³⁺ to Er³⁺ energy transfer was determined to be about 3.5 times higher than that of Er³⁺ to Yb³⁺ energy back transfer, which is sufficient to provide high ⁴I_11/2 population of Er³⁺ to improve the fluorescence of the co-doped glass ceramics.     

Ion irradiation hardening of C60 thin films

The nanoindentation technique is used to measure the hardness and the Young’s modulus of ion irradiated C₆₀ films, 70 nm thick, deposited on a Silicon substrate. An increase of hardness from 1.3 GPa for the pristine sample to 10 GPa after irradiation with 800 keV Bi⁺ and N²⁺ ions was observed. The Young’s modulus also increases from 60–150 GPa after the irradiation. The results are discussed in terms of the damage and amorphization produced as consequences of the electronic and nuclear energy transference due to the irradiation.     

Practical use of the ‘equivalent’ measured stress intensity factor to control fatigue crack propagation rates in aircraft full-scale fatigue tests—First assessment of the method in testing of a pressurized aircraft fuselage

In the case of circumferential cracks in a cylindrical fuselage, the comparison of some analysis and test results shows that the theoretical stress intensity factor is a suitable correlation parameter of fatigue crack propagation rates, both in aircraft fuselages and in plane panels. Values of the ‘equivalent’ stress intensity factor, computed by applying the Barrois-Bhandari method to slot-opening measurements performed under decreasing loading levels, agree well with the values computed from two dimensional Theory of Elasticity, using the method of finite elements.

In the case of longitudinal cracks, the experimental values of the ‘equivalent’ stress intensity factor, i.e. the stress intensity factor of the infinite plane sheet containing a centre crack with the same elastic strain and stress distributions near the boundary of the plastically strained region around the crack tip, yield a good correlation of fatigue crack propagation rates of the cracked fuselage and of cracked plane structures. The values of the ‘equivalent’ stress intensity factor are lower than those of the theoretical stress intensity factor, the interest of which disappears, but are also far higher than the bidimensionally computed values, which are no longer to be considered.

Some meant of safety provided to limit crack openings will make it possible, in the near future, to investigate test conditions reaching the ultimate residual static strength of cracked structures, while avoiding, however, catastrophic failures.     

Analysis of Pu, Cm and Am alpha spectra using the unfolding code Colégram without prior use of a nuclear data library

This paper shows the unfolding capabilities of a code developed in our laboratory when applied to alpha spectrometry. The code, called ‘Colégram’, uses the Levenberg–Marquardt algorithm. Colégram has some particularly interesting features when compared to other codes using χ² as the convergence criterion. Low statistics peaks are treated more successfully. No nuclear data library is needed. The emission probabilities obtained with Colégram from ²³⁹Pu, ²⁴⁴Cm and ²⁴³Am alpha spectra characterized by high statistics and good energy resolution are presented. These emission probabilities and the alpha-particle energies deduced from them are compared to those obtained in the most recent works. We show that Colégram also offers the possibility of identifying and quantifying contaminants present in the spectra. Finally, with Colégram, it is necessary to identify electron conversion lines and include them in the unfolding process to increase the quality of the fits.     

Extensive air shower experiment at Kolar Gold Fields

An experiment to determine the nature of primary cosmic rays of energy > 10¹⁴ eV by studying high energy (> 220 GeV) muons and their correlations with other parameters of extensive air showers generated by them, was carried out at Kolar Gold Fields, India (atmospheric depth of 920 g cm⁻²). An accurate estimate of shower parameters in showers as small as 10⁴ particles was achieved by means of a closely packed array of large area detectors and by employing special methods of analysis. In this paper, the details of the array, the data recording system, the procedure of data analysis and error estimates are described.     

A novel technique for fabrication of metallic structures on polyimide by selective electroless copper plating using ion implantation

The successful use of palladium ion implantation into polyimide to seed an electroless plated film of copper on the polyimide surface is reported. Polyimide (Hitachi PIX 3400) was implanted with palladium ions to doses of 1.5 × 10¹⁵ − 1.2 × 10¹⁷ ions cm⁻² using a MEVVA ion implanter. The implanted ions acted as sites for nucleation of copper film. A copper film was then deposited on implanted polyimide using a commercial electroless plating solution. The ion energy was kept low enough to facilitate a low critical ‘seed’ threshold dose that was measured to be 3.6× 10¹⁶ Pd ions cm⁻². Test patterns were made using polyimide to study the adaptability of this technique to form thick structures. Plated films were studied with optical microscopy, Rutherford Backscattering Spectrometry (RBS) and Profilometry. The adhesion of films was qualitatively assessed by a ‘scotch tape test’. The film growth (thickness) was observed to be linear with plating time. A higher implantation dose led to greater plating rates. The adhesion was found to improve with increasing dose.     

The single-filament-composite test: a new statistical theory for estimating the interfacial shear strength and Weibull parameters for fiber strength

For over two decades the single-filament-composite (SFC) test has been an important tool in the study of the failure of fibrous composites. The SFC test itself involves a single brittle fiber embedded along the center-line of a matrix specimen of both large cross-sectional area and strain to failure. With increasing strain, the fiber fractures progressively, breaking into an increasing number of shorter and shorter fragments. Surrounding each break a shielded or exclusion zone develops within which no further breaks typically occur. At some strain level ‘saturation’ occurs abruptly as the shielded zones finally occupy the whole fiber, thus leaving a final distribution of fiber fragments end-to-end. Two uses for the SFC test have emerged: one has been to estimate the interfacial shear stress, τ, in the exclusion zone, sometimes called the interfacial shear strength and usually idealized as a constant over this zone. The other has been to estimate the fiber strength distribution and in particular the Weibull shape and scale parameters, ρ and σ_l, for fiber strength appropriate to some characteristic ‘gage’ length, l, such as the mean fragmentation length. In the past, theoretical bases for these estimates have handled the statistics of shielding in ways that have led to quite large biases. The purpose of the present paper is to use some recent theoretical advances to develop more sophisticated estimation procedures for τ and the Weibull fiber strength parameters ‘ in situ’, and thus to eliminate various errors in previous methods. Straightforward computer programs (written in release 3 of Maple), which calculate the various quantities in the paper, will be provided by the first or second author on request.