Contingent sourcing under supply disruption and competition

With the increasing awareness of the serious consequences of supply disruption risk, firms adopt various kinds of strategies to mitigate it. We consider a supply chain in which two suppliers sell components to two competing manufacturers producing and selling substitutable products. Supplier U is unreliable and cheap, while Supplier R is reliable and expensive. Firm C uses a contingent dual-sourcing strategy and Firm S uses a single-sourcing strategy. We study the implications of the contingent sourcing strategy under competition and in the presence of a possible supply disruption. The time of the occurrence of the supply disruption is uncertain and exogenous, but the procurement time of components is in the control of the firms. We show that supply disruption and procurement times jointly impact the firms’ buying decisions. We characterise the firms’ optimal order quantities and their expected profits under different cases. Subsequently, through numerical computations, we obtain additional managerial insights. Finally, as extensions, we study the impact endogenizing equilibrium sourcing strategies of asymmetric and symmetric firms, and of capacity reservation by Firm C with Supplier R to mitigate disruption.     

Simulation of air-to-refrigerant fin-and-tube heat exchanger with CFD-based air propagation

A new model for simulating air-to-refrigerant fin-and-tube heat exchangers with computational fluid dynamics (CFD)-based air propagation is introduced. This model is based on a segment-by-segment approach and is developed to be a general purpose and flexible simulation tool. The model superimposes a CFD mesh on the heat exchanger model’s geometric grid, interprets the CFD results, and processes them to generate the air propagation path through the heat exchanger. The model is capable of accounting for air flow maldistribution and other complex flow patterns including recirculation zones within the heat exchanger, as well as, entrainment of exit flow into the heat exchanger, using both two-dimensional (2D) and three-dimensional (3D) CFD results. The modeling results show that the overall predicted heat load using 3D-CFD simulation results agrees within ±4% of the experimental data, without employing any multipliers on air side correlations.     

Friction and wear properties of MoAlB against Al2O3 and 100Cr6 steel counterparts

The present work investigates, for the first time, the dry sliding friction and wear behaviour of fully dense, predominantly single-phase MoAlB ceramics against alumina (Al₂O₃) and 100Cr6 steel counterparts. Against Al₂O₃, the friction coefficient (μ) increased with increasing load and the wear was highly dependent on the load applied. A transition from mild wear under 1 N and 4 N to severe wear at 10 N occurred. Scanning electron microscopy revealed that abrasion is the dominant wear mechanism. Against steel, μ decreased with increasing load and the wear rates were low, under all applied loads. The morphologies of the worn surfaces against steel were characterized by the appearance of a rippled layers. Atomic force microscopy and Raman spectroscopy were used to propose a possible formation mechanism of such patterns. X-ray photoelectron spectroscopy revealed the rippled surfaces to be composed of Fe₂O₃ and a mixture of MoO_x.     

Advancing operations management theory using exploratory structural equation modelling techniques

The structural equation modelling (SEM) technique has been touted as a useful tool for tightening links between theoretical and empirical operations management (OM) research. Despite SEM's increasing prominence in the field, leading scholars continue to call for a deeper infusion of theory into empirical OM research. To strengthen ties between theory and analysis in OM research, this study evaluates previous OM applications of SEM and identifies specific ways we can use SEM to advance operations management theory. Through judicious use of SEM techniques, we believe that OM researchers have the opportunity to confirm and extend existing theoretical frameworks. Further, we offer guidance on how to operationalise measurement models such that researchers accurately depict the causality of a construct. To demonstrate how to advance theory, we use an illustrative example of SEM in an OM context based upon data gathered from a survey of over 200 respondents.     

Growth of phases in the solid-state from room temperature to an elevated temperature in the Pd–Sn and the Pt–Sn systems

The solid-state growth of the product phases in bulk and electroplated diffusion couples of the Pd–Sn and the Pt–Sn systems is reported at various temperatures, ranging from room temperature to 215 °C. The growth rate of the product phase in the Pt–Sn system is found to be much lower compared to the Pd–Sn system and the Au–Sn system also, which is currently used in the microelectronics industry. The time dependent experiments indicate that the growth rate in the Pd–Sn system is parabolic in nature, i.e., it is controlled by the diffusion rates of components through the product phases. However, the growth rate is linear and hence reaction-controlled in the Pt–Sn system, which indicates that the formation of the compound is the rate-limiting step rather than the diffusion rates of components. The PdSn₄ phase covers almost whole interdiffusion zone in the Pd/Sn couple, while PtSn₄ is the only phase found in the Pt/Sn couple. The marker experiments indicate that both PdSn₄ and PtSn₄ grow mainly by the diffusion of Sn, with negligible diffusion of Pd and Pt, respectively. Furthermore, the analysis considering the same crystal structure (i.e., oC20) of these phases along with the concept of sublattice diffusion mechanism indicates that the diffusion rates of both Pd and Pt are negligible via both the lattice and the grain boundaries.     

When risks need attention: adoption of green supply chain initiatives in the pharmaceutical industry

The pharmaceutical industry is very important in delivering life-saving products/services to society. There are many ways for materials/products/services concerned with pharmaceuticals to influence the environment; these include improper disposal of pills/tablets by patients, expired and unused medications, improper release of drugs by pharmacies or household sewage mixed with surplus drugs. In view of this, the present work seeks to integrate green supply chain (GSC) concepts in the pharmaceutical sector in a developing economy Indian context. In so doing, managers need to determine the potential risks in adopting GSC initiatives to achieve sustainability in operational perspectives. In this sense, this work seeks to distinguish the potential risks in adopting GSC initiatives within the pharmaceutical industry. This work uses a literature review and fuzzy Delphi approach in finalising the risks. This research also uses fuzzy Analytical Hierarchy Process (AHP) for prioritisation of the risks under vague and unclear surroundings. According to the findings, cold chain technology and supply risks categories are highly prioritised. This work can assist practising managers and government authorities in effectively developing and managing GSC initiatives in line with sustainable development goals in the context of the pharmaceutical industry. Finally, a sensitivity test is applied to evaluate the stability of ranking of risks.     

Epitaxial growth of three-dimensionally architectured optoelectronic devices

Optoelectronic devices have long benefited from structuring in multiple dimensions on microscopic length scales. However, preserving crystal epitaxy, a general necessity for good optoelectronic properties, while imparting a complex three-dimensional structure remains a significant challenge. Three-dimensional (3D) photonic crystals are one class of materials where epitaxy of 3D structures would enable new functionalities. Many 3D photonic crystal devices have been proposed, including zero-threshold lasers, low-loss waveguides, high-efficiency light-emitting diodes (LEDs) and solar cells, but have generally not been realized because of material limitations. Exciting concepts in metamaterials, including negative refraction and cloaking, could be made practical using 3D structures that incorporate electrically pumped gain elements to balance the inherent optical loss of such devices. Here we demonstrate the 3D-template-directed epitaxy of group III-V materials, which enables formation of 3D structured optoelectronic devices. We illustrate the power of this technique by fabricating an electrically driven 3D photonic crystal LED.     

Squeezing flow of Casson hybrid nanofluid between parallel plates with a heat source or sink and thermophoretic particle deposition

The investigations on the flow of non-Newtonian fluids are becoming one of the major topics in the research field. These liquids have substantial applications in industrial and engineering fields such as drilling rigs, food processing, paint and adhesives, nuclear reactors and cooling systems. On the other hand, hybrid nanofluids play a major role in the heat transfer process. Keeping this in mind, the motion of Casson hybrid nanofluid squeezing flow between two parallel plates with the effect of heat source and thermophoretic particle deposition is examined here. The partial differential equations that govern fluid flow are converted into ordinary differential equations using appropriate similarity variables and those equations are numerically solved using the Runge–Kutta–Fehlberg fourth–fifth-order method by implementing the shooting scheme. The graphs depict the effects of a number of key parameters on fluid profiles in the absence and presence of the Casson parameter. These graphs show that fluid velocity enhances with the augmentation of the local porosity parameter. Thermal dispersal upsurges for enhancement of heat source/sink parameter and the concentration profile escalates for an upsurge of the thermophoretic parameter. Skin friction enhances with enhancement in the local porosity parameter.     

An attempt to develop surface plasmon resonance based immunosensor for Karnal bunt (Tilletia indica) diagnosis based on the experience of nano-gold based lateral flow immuno-dipstick test

Karnal bunt (KB) of wheat incited by Tilletia indica is an economically important quarantined fungal pathogen. Similarity in teliospore configuration makes it difficult to differentiate KB teliospores from the teliospores of other bunt fungi using conventional approaches. In order to determine the correct identity of KB teliospore— an infectious entity, it is essential to develop specific diagnostic probes and high quality of immunological reagents against infectious entities. The immuno-dipstick assay developed in our lab is quite sensitive to detect the antigens of even five teliospores. For on-site testing of KB, a nano-gold based lateral flow immuno-dipstick assay (LFID) was also developed in our lab using anti-teliospore antibodies. For development of LFID, colloidal gold was prepared and conjugated with anti-teliospore antibodies which were further characterized. However, species specific detection is yet to be achieved by generation of monoclonal antibodies against diagnostic antigens (34 and 66 kD teliospore's proteins). Based on the experience of nano-gold based LFID, we are proposing to develop surface plasmon resonance (SPR) based label-free detection system. The same may be employed not only for determination of the quality of immunological reagents in terms of sensitivity, specificity and precision but also development of suitable design of immunosensor for differential diagnosis of KB (T. indica). The approach involves the use of a mouse monoclonal antibody against diagnostic antigens and a suitable design of SPR sensor by the preparation of immuno-affinity layer over self assembled monolayer surfaces. The signal to noise ratio can further be enhanced using nano-gold particles. This will be first attempt for real-time monitoring of KB teliospores in wheat lots by SPR sensor and in a fully automated manner for establishing seed certification and plant quarantine standards.     

Towards Virtual Testing of Textile Composites: Calibration of Thermoelastic Tow Properties

We present a methodology for calibrating the thermoelastic properties of constituent tows in a woven C/SiC composite using a combination of experimental measurements and finite element simulations of strain distributions that arise upon heating. Because of the nonuniform distribution of the matrix phase and the presence of matrix microcracks, tow properties cannot be reliably predicted a priori using micromechanical models alone; instead, some can only be inferred from coupled experimental/numerical studies of the kind presented here. A small number of iterations of finite element simulations is required to achieve satisfactory agreement in all thermal strain components. The number of iterations is minimized by first performing simulations using model‐based estimates of the effective tow properties, followed by judicious adjustments to select property values. Comparisons between measurements and simulations are performed on the basis of strains averaged over a characteristic area dictated by tow dimensions. The study reveals that, although each segment of a particular tow genus is nominally equivalent to all others, the strains within each population exhibit considerable variation. This is attributable to variations in both tow geometry and connectivity between adjacent tows. The virtual tests predict strain variations of comparable magnitude.