The large signal modulation response of a 1.3 μm InGaAsP 4‐well laser of the Fabry–Perot type is investigated. The current density is assumed to take the form J = JO+JM sin(ωt…
Abstract
The large signal modulation response of a 1.3 μm InGaAsP 4‐well laser of the Fabry–Perot type is investigated. The current density is assumed to take the form J = JO+JM sin(ωt) where JO is the steady state current density above threshold and JM is allowed to take values such that the modulation depth, m, may not satisfy the condition m<< 1. The time evolution of the photon density shows that the output power may be sinusoidal when m<< 1, i.e. small signal modulation, low and very high frequencies. At intermediate frequencies, in the gigahertz range, the output power is far from sinusoidal and may show the characteristic oscillations due to the large‐signal transients. The resonance frequency is seen to decrease as the modulation depth increases, the worst case being when the nonlinear saturation effects are not included.
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This paper seeks to present a numerical model which is used to obtain the transit time limited frequency response of p‐i‐n photodiodes with an arbitrary electric field profile…
Abstract
Purpose
This paper seeks to present a numerical model which is used to obtain the transit time limited frequency response of p‐i‐n photodiodes with an arbitrary electric field profile. The effect of the absorption layer width and bias voltage on the frequency response is also investigated.
Design/methodology/approach
The absorption region is divided into any desired number of layers and the continuity equations are solved, for each layer, assuming that within the layer the carriers' drift velocities are constant. The frequency response of the multilayer structure is calculated from the response of each layer using matrix algebra.
Findings
The numerical results agree well with those from the experiment. It is seen that the results, assuming the saturation drift velocities, are usually overestimated especially for low values of the bias voltage or high values of the absorption region width.
Research limitations/implications
The numerical method under study neglects the capacitive effects which may determine the frequency response of very short devices. In this case a more complete treatment, including also the displacement current, should be carried out.
Practical implications
Software development for the design of multilayer photodiodes with optimized frequency response.
Originality/value
To the best of one's knowledge this is an original report of the application of this numerical method to the calculation of the frequency response of p‐i‐n photodiodes. The numerical method, being able to treat in a simple way multilayer structures with any electric field profile, is a very powerful tool in the development of software for the design of efficient photodiodes of various types.
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Diversified trading networks have recently drawn a great deal of attention. In the process, the importance of diversity has perhaps been overemphasized. Using the trade in port…
Abstract
Diversified trading networks have recently drawn a great deal of attention. In the process, the importance of diversity has perhaps been overemphasized. Using the trade in port wine from Portugal to Britain as an example, this essay attempts to show how a market once dominated by general, diversified traders was taken over by dedicated specialists whose success might almost be measured by the degree to which they rejected diversification to form a dedicated “commodity chain.” The essay suggests that this strategy was better able to handle matters of quality and the specialized knowledge that port wine required. The essay also highlights the question of power in such a chain. Endemic commodity-chain struggles are clearest in the vertical brand war that broke out in the nineteenth century, which, by concentrating power, marked the final stage in the transformation of the trade from network to vertical integration.
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Cristian Camilo Fernández Lopera, José Manuel Mendes and Eduardo Jorge Barata
Climate-related disasters are the most representative in terms of recurrence and impacts. To reduce them, risk transfer is a key strategy for climate risk management. However…
Abstract
Purpose
Climate-related disasters are the most representative in terms of recurrence and impacts. To reduce them, risk transfer is a key strategy for climate risk management. However, this approach does not consider the socioeconomic vulnerability of each population group, limiting its effectiveness. The objective of this paper is to improve and increase the usefulness of risk transfer through the Differential Risk Transfer (DRT) approach.
Design/methodology/approach
A comprehensive and systematic review of the state of the art on Differential Approach (DA) is presented, and its connection with existing models of vulnerability to disasters is analysed. Through epistemic deliberations, an operational definition of Differential Risk Transfer (DRT), as well as its advantages are discussed. Finally, general guidelines are presented for the implementation of the DRT in a specific context.
Findings
The results confirm that DA presents a clear relation with the models for the study of disaster vulnerability. The small group discussions agree with the usefulness of DRT for improving climate-related risk management.
Practical implications
This paper argues for the inclusion of the DRT approach in the climate risk management strategies aiming to fill the disaggregated data gaps that limit the potentiality and accuracy of risk transfer schemes worldwide.
Originality/value
This innovative approach improves the accuracy of the risk transfer mechanisms through the recognition of the differences of ethnicity, gender and life cycle that increase socioeconomic vulnerability to climate-related disasters.
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Cuba’s 1959 Revolution brought about dramatic changes not only in that island‐nation but also in the USA. Cubans, and later Cuban‐Americans, have changed the face of Miami and…
Abstract
Cuba’s 1959 Revolution brought about dramatic changes not only in that island‐nation but also in the USA. Cubans, and later Cuban‐Americans, have changed the face of Miami and south Florida. The economic and social successes of Cuban‐Americans, the third largest Latino group in the USA, are prevalent in scholarly and popular literature. In this annotated bibliography, the author presents journal articles, chapters in books, books, and human rights reports, published between 1990 and 1998, as well as World Wide Web sites, that discuss the Cuban‐American experience. Articles from the popular literature are not included, nor are materials that deal primarily with Cuba or Cuba‐USA relations.
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Cristian Armando Yepes-Lugo, Robert Ojeda-Pérez and Luz Dinora Vera-Acevedo
This paper aims to evaluate the evolution of the organizational field in the Colombian coffee industry between 1960 and 2020 and explain how peripheral actors influenced…
Abstract
Purpose
This paper aims to evaluate the evolution of the organizational field in the Colombian coffee industry between 1960 and 2020 and explain how peripheral actors influenced institutional change.
Design/methodology/approach
The methods analyze historical processes from a hermeneutical and interpretative perspective. The authors used data collection techniques through interviews, archive data, publications and media reports, embracing an interdisciplinary and qualitative documentary approach. This approach helps the authors unravel the temporal dimensions of the historical discourse related to coffee and the involvement of various actors within organizational structures.
Findings
The authors found that, unlike the literature regarding the change in organizational fields, recently, within the coffee sector in Colombia, the institutional work of peripheral actors (small producers, local associative groups and coffee women, among others) is changing the field as follows: (1) women are changing traditional behaviors moving from hierarchical family structures and lack of gender awareness, to empowered, horizontal and sustained relationships, (2) indigenous people include rituals and other traditional practices in coffee production and (3) ex-guerrilla members are helping to strengthen the peace process implementation in Colombia through coffee production.
Research limitations/implications
The authors did not conduct statistical or computational analysis to simulate the emergence of new organizational forms. Instead, the authors attempted to elucidate narratives and discourses that reflect the tensions between central and peripheral actors from a historical perspective.
Practical implications
This study seeks to help leaders and managers overcome processes or organizational change in which peripheral actors are crucial. From that perspective, allocating resources and capabilities can become more effective.
Originality/value
This paper offers a new perspective of change within organizational fields from the roles of peripheral actors, which are fundamental in change processes within organizational fields, especially in the global south, where tensions between elites and vulnerable people are familiar.