The interaction of oblique flexural gravity waves with a small bottom deformation on a porous ocean-bed: Green’s function approach

The interaction of oblique incident water waves with a small bottom deformation on a porous ocean-bed is examined analytically here within the framework of linear water wave theory. The upper surface of the ocean is assumed to be covered by an infinitely extended thin uniform elastic plate, while the lower surface is bounded by a porous bottom surface having a small deformation. By employing a simplified perturbation analysis, involving a small parameter δ(=1), which measures the smallness of the deformation, the governing Boundary Value Problem (BVP) is reduced to a simpler BVP for the first-order correction of the potential function. This BVP is solved using a method based on Green’s integral theorem with the introduction of suitable Green’s function to obtain the first-order potential, and this potential function is then utilized to calculate the first-order reflection and transmission coefficients in terms of integrals involving the shape function c(x) representing the bottom deformation. Consideration of a patch of sinusoidal ripples shows that when the quotient of twice the component of the incident field wave number propagating just below the elastic plate and the ripple wave number approaches one, the theory predicts a resonant interaction between the bed and the surface below the elastic plate. Again, for small angles of incidence, the reflected wave energy is more as compared to the other angles of incidence. It is also observed that the reflected wave energy is somewhat sensitive to the changes in the flexural rigidity of the elastic plate, the porosity of the bed and the ripple wave numbers. The main advantage of the present study is that the results for the values of reflection and transmission coefficients obtained are found to satisfy the energy-balance relation almost accurately.     

Authentic assessment in seafarer education: using literature review to investigate its validity and reliability through rubrics

With the Standards of Training, Certification and Watchkeeping Convention 1995 (STCW’95) moving seafarer training towards outcome-based education (OBE), emphasis has shifted to assessment practices that will allow seafarer students to demonstrate their ability to perform workplace tasks at standards described in the STCW Code. This paper argues that authentic assessment comprising of performance-based tasks applied in real-world and meaningful contexts can provide a holistic approach to competence assessment for seafarers. But, authentic assessment can capture essential aspects of workplace tasks and result in consistency of student performance in different contexts only if they are valid and reliable. Rubrics as assessment tools are known to increase validity and reliability of assessments; however, it can do so only if different aspects of its own validity and reliability have been addressed. A literature review undertaken for this paper has uncovered an absence of academic investigation and empirical study on the different aspects of validity and reliability of authentic assessment through assessment rubrics. Moreover, there exists an even greater absence of global research on authentic assessment in the area of seafarer training. Through an investigation of authentic assessment, this research has uncovered the importance of using valid and reliable rubrics in order to improve not only the assessment process but also the tools and methods used to support the valid, reliable, and authentic assessment of outcomes achieved in the learning process. Future research aims to offer insights into improving the validity and reliability of rubrics and to empirically investigate how they can be used in authentic assessment within the confines of the STCW Code, in particular, to improve seafarer training practices, student engagement, resulting learning outcomes, and employer and regulator satisfaction with the attainment of the standards stipulated in the STCW Code to produce an evidence of competence.     

The impact of transportation alternatives on the decision to cease driving by older adults in Japan

This study investigated whether the availability of transportation alternatives for older drivers is a determinant of the decision to cease driving. We recruited participants from a total of 7827 drivers aged 69 years or older living in Ibaraki Prefecture, Japan who were scheduled to renew their driving license between February and April 2011. In November 2010, we distributed questionnaires to collect data on predictors of driving cessation, and again in December 2012 to determine who had actually ceased driving. The relative impacts of factors related to driving cessation were then estimated. Of the 3089 respondents, 157 did not renew their license. The strongest determinants of this decision were having been advised to stop driving and if they had developed less confidence in their ability to drive safely. Even so, respondents were far more likely to have actually stopped driving if they were sure that someone else was available to provide a ride when they needed one. The final decision to stop driving is strongly influenced by personal convenience based on private transport, especially amongst drivers who have been advised to stop. The availability of public transport alternatives is not as important a factor in this decision.     

Establishing value of time for the inter-island passenger transport of the Western Visayas region,Philippines

Transportation infrastructure planning process requires cost–benefit analysis in the evaluation of project proposals. Value of time (VOT) facilitates the conversion of travel time savings, which is a significant proportion of benefits in monetary terms. In cases where VOT has not been established, planners resort to crude estimates that often results in erroneous or biased measurements of benefits. This is the case of the Western Visayas region in the Philippines where transportation studies are rare. Secondary cities and its peripheral regions have often been overlooked subjects of transportation studies. In this study, multinomial logit models using revealed preference data were estimated to facilitate the calculation of the VOT. The total cost, square of the total cost, and total time were identified as significant explanatory variables affecting mode choice. The square of the total cost term was introduced in the models in order to account for income effect. Results indicate that VOT estimates for the inter-island passenger transportation between Iloilo and Negros Occidental generally range from 78.15PHP to 179.15PHP (1.91USD to 4.37USD) depending on trip and traveller characteristics.     

An optimization approach to resolve activity scheduling conflicts in ADAPTS activity-based model

Activity conflict resolution as the core of scheduling process in activity-based modeling is a challenging step because the activity diary databases mostly report the outcome of the scheduling decisions and often fail to capture key factors influencing the resolution process itself. Consequently, most activity-based frameworks ignore modeling this process by using either predefined set of activity patterns or priority-based assumptions to schedule daily activities and prevent conflict occasions. ADAPTS is one of the few activity-based models that attempts to simulate the process of activity scheduling and resolve the conflicts as they occur. This paper advances the current rule-based conflict resolution model of ADAPTS by implementing an advanced and flexible non-linear optimization model. A set of linear optimization sub-models is then proposed that together perform the same task as the non-linear model, however they are much easier to implement and maintain, while fast to run and flexible to extend. The proposed approach defines an objective function, which aims to minimize the extent of changes in timing and duration of conflicting activities, while fitting them in the schedule. Comparing performance of the proposed model with TASHA scheduler and former resolution module of ADAPTS using CHASE scheduling process data reveals significant improvement in fitting the newly planned activities in the schedules with the minimal modifications in the timing and duration of activities.     

A reference-dependent user equilibrium model for activity-travel scheduling

Existing user equilibrium models of activity-travel scheduling generally fall short in representing travelers’ decision-making processes. The majority have either implicitly or explicitly assumed that travelers follow the principle of utility maximization. This assumption ignores the fact that individuals may be loss–averse when making activity-travel decisions. Allowing for the situation that travelers possess accurate information of the urban-transportation system due to modern technologies, studies on reference-dependent decision-making under near-perfect information are receiving increasing attention. In view of traveler heterogeneity, individuals can be divided into multiple classes according to their reference points. In this paper, we propose a reference-dependent multi-class user equilibrium model for activity-travel scheduling, which can be reformulated as a variational inequality problem. Moreover, comparative analyses are conducted on the equilibrium states between utility-maximization (no reference) and reference-dependency of exogenous and endogenous references. A numerical example regarding combined departure-time and mode choice for commuting is conducted to illustrate the proposed model. The simulated results indicate that reference points and loss aversion attitudes have significant effects on the choice of departure time and mode.     

Calculation on the solid solution forming enthalpies of Re-Mo-Ti gradient alloy in thermodynamics

The idea about preparation of Re-Mo-Ti alloy is put forward because of applications of Re and Mo-Re alloys in aerospace. Basing on the thermodynamics theory, the feasibility of developing a new high temperature alloy Re-Mo-Ti is investigated. The solid solution forming enthalpies of binary alloys Re-Ti, Mo-Ti and Mo-Re are calculated with the Miedema thermodynamics theory. The Miedema theory of binary alloy can be used in ternary alloy through Kohler model or Toop model. The calculated results show that the forming enthalpies of binary alloys Re-Ti, Ti-Mo and Re-Mo are negative, which indicates that binary alloys Re-Ti, Ti-Mo and Re-Mo can form solid solution in wider component area. The forming enthalpies of Re-Mo-Ti ternary alloy are still negative and smaller than those of binary alloys Re-Ti, Ti-Mo or Re-Mo, which indicates it is possible to form large solid solution graph area among ternary alloys of Ti, Mo, Re elements. It is feasible to develop a new high temperature material in thermodynamics, in this material Re-Mo-Ti solid solution as base phase, and the Ti₅Re₂₄ intermetallic compounds or interphase ω (Ti₄Mo₃) as strengthening phase.     

A new model for soil consolidation based on microstructure

This paper introduces a new means to predict consolidation deformation of soil from its microstructure. Based on a kind of pore-size distribution density function, a fractal model for soil consolidation is established. Through this model, the relation between macroscopic deformation and microcosmic pore property of soil is founded. In order to justify this proposed model for soil consolidation, consolidation experiments of soft clay are performed. Afterward, the microstructure of soft clay unconsolidated and consolidated under every pressure is studied by a scanning electron microscope (SEM). The results show that the proposed model for soil consolidation is valid in predicting consolidation deformation.     

Chosen ciphertext secure identity-based broadcast encryption in the standard model

To give concurrent consideration both the efficiency and the security (intensity of intractable problem) in the standard model, a chosen ciphertext secure identity-based broadcast encryption is proposed. Against the chosen ciphertext security model, by using identity (ID) sequence and adding additional information in ciphertext, the self-adaptive chosen identity security (the full security) and the chosen ciphertext security are gained simultaneously. The reduction of scheme’s security is the decisional bilinear Diffie-Hellman (BDH) intractable assumption, and the proof of security shows that the proposed scheme is indistinguishable against adaptive chosen ciphertext attacks in the standard model under the decisional BDH intractable assumption. So the security level is improved, and it is suitable for higher security environment.     

Aero-optical characteristics of supersonic flow over blunt wedge with cavity window

The optical rays that form the image of an object and propagate a supersonic flow over a vehicle are refracted by the density variations. A numerical analysis of the aero-optical characteristics of supersonic flow over blunt wedge with a cavity window is carried out. A hybrid method of Reynold averaged Navier-Stokes and direct simulation Monte Carlo (RANS/DSMC) is employed to simulate the flowfield. Refraction factor is introduced to evaluate the flowfield’s aero-optical characteristic. The results show that mean flow’s aero-optical effects are mainly caused by the shock wave, the expansion wave and the turbulent boundary layer. Fluctuation flow’s aero-optical effects are mainly caused by the turbulent boundary layer and the shock wave induced by the cavity window. The aero-optical effects at the leading side of window are caused by the mean density variations, while the effects at the trailing side are caused by the density fluctuations. Different draft angles of the cavity window are investigated. The airborne optical devices of supersonic vehicle should be mounted in the middle of the cavity window with a large draft angle.