Aggregate–disaggregate approach to an airfreight forwarder’s planning under uncertainty: a case study

Resource planning of airfreight forwarders is a complex endeavor, requiring decisions to be made in a dynamic and uncertain environment. Airfreight forwarders acquire airfreight spaces from three sources: allotment from carriers, retail from carriers and subcontracting to partners, all of which differ in terms of cost, flexibility and timing of booking. This real-life problem has many planning decisions (bookings in terms of carriers, route, time, ULDs, etc.). In this case study, we propose an aggregate–disaggregate approach and focus on the most critical decisions. A two-stage stochastic dynamic program first determines, in aggregates, the amount of allotment bookings, retail resources, and subcontracting or surplus co-loading. Then, a heuristic is used to disaggregate resource requirements into specific bookings. An analysis is provided to examine the relevant managerial issues. Based on real-life data, we show several patterns of aggregate resource bookings with respect to different levels of demand uncertainty and cost parameters. We show that resource disaggregation has to balance cost-effectiveness, capacity flexibility and routing flexibility of a resource plan.     

Structural Characteristics and Properties of a New Graphitic‐Based Material

The hydrogenation of commercial graphite using lithium/ammonia as the reducing agent and tert‐butyl alcohol as a proton source was investigated. Characterization of the products after successive reductions of the same material by high‐resolution transmission electron microscopy revealed a new material that was replete with edge and circular dislocations. Analysis by solid‐state ¹³C NMR spectroscopy indicates that after three reductions, the remaining aromatic rings appear to be interior benzene rings. NMR spectroscopy also offers strong evidence for the presence of small amounts of tert‐butyl alcohol and ethanol (workup solvent) that could not be removed in vacuo from the samples. These compounds could be observed to move freely between the layers of the hydrographene.     

On the thermal expansion of molecules: a sequel

In a recent article (Varga Z, Hargittai M, Bartell LS (2011) Struct Chem 22: 111–121), we showed with the example of lanthanide triiodide that contrary to previous claims by others, simple metal trihalide molecules do expand with increasing temperature. This sequel is meant to strengthen our argument and the validity of the method we used besides correcting a numerical error.     

Decoherence,the Density Matrix,the Thermal State and the Classical World

Decoherence has been the basis for understanding the emergence of the classical world from its quantum underpinnings. Unfortunately the calculations establishing decoherence overshoot and, based on assumptions that break down, predict that with the passage of time the off-diagonal elements of the density matrix become arbitrarily small. It has been recognized by some authors that the thermal state, assumed to hold for systems in equilibrium, places a bound on off diagonal terms. In this article we establish—preserving the conservation of energy, as is not the case for previous work—that indeed the thermal state is an attractor under scattering. Moreover, the bound on the off-diagonal terms present in the thermal state does not contradict everyday experience.     

A comparison of Bayesian,Hazard, and Mixed Logit model of bankruptcy prediction

Computational Management Science - The purpose of this study is to examine the impact of the choice of cut-off points, sampling procedures, and business cycles on the forecasting accuracy of...     

Semi-analytic method for slow light photonic crystal waveguide design

We present a semi-analytic method to calculate the dispersion curves and the group velocity of photonic crystal waveguide modes in two-dimensional geometries. We model the waveguide as a homogenous strip, surrounded by photonic crystal acting as diffracting mirrors. Following conventional guided-wave optics, the properties of the photonic crystal waveguide may be calculated from the phase upon propagation over the strip and the phase upon reflection. The cases of interest require a theory including the specular order and one other diffracted reflected order. The computational advantages let us scan a large parameter space, allowing us to find novel types of solutions.     

Interaction of fiber and transformation toughening

B small scale bridging (SSB) assumption, a theoretical study is made of the interaction between the fracture toughening effects of transforming particles and crack bridging fibers which are aligned in the direction perpendicular to the crack surfaces. The fibers bridging the crack are assumed to undergo large amounts of slipping inside the matrix. It is found that the interaction can be synergistic over a parametric range of material properties of the ceramic composite system. The Mode-1 plane-strain fracture toughness of the ceramic composite system is determined in terms of fiber strength, transformation toughening parameters and interaction parameters. The results obtained here are qualitatively similar to those for the interaction between the fracture toughening effects of transforming particles and crack-bridging ductile particles by A and B (1988a, J. Mech. Phys. Solids 36, 581).     

Resonances of a Harmonically Forced Duffing Oscillator with Time Delay State Feedback

The paper presents analytical and numerical studies of the primary resonance and the 1/3 subharmonic resonance of a harmonically forced Duffing oscillator under state feedback control with a time delay. By using the method of multiple scales, the first order approximations of the resonances are derived and the effect of time delay on the resonances is analyzed. The concept of an equivalent damping related to the delay feedback is proposed and the appropriate choice of the feedback gains and the time delay is discussed from the viewpoint of vibration control. In order to numerically solve the problem of history dependence prior to the start of excitation, the concepts of the Poincaré section and fixed points are generalized. Then, a modified shooting scheme associated with the path following technique is proposed to locate the periodic motion of the delayed system. The numerical results show the efficacy of the first order approximations of the resonances.