Generation of superradiation in quantum dot nanoheterostructures

Conditions for the generation of Dicke supperradiation are studied for two types of quantum dot nanoheterostructures: a planar waveguide and a microdisk. The domain model for the generation of superradiation suggested earlier for quantum wells is generalized to inhomogeneous quantum dot arrays. Different scenarios of the generation of superradiation in a semiconductor microdisk are classified.     

Development of thermophysical calculator for stainless steel casting alloys by using CALPHAD approach

The calculation of thermophysical properties of stainless steel castings and its application to casting simulation is discussed. It is considered that accurate thermophysical properties of the casting alloys are necessary for the valid simulation of the casting processes. Although previous thermophysical calculation software requires a specific knowledge of thermodynamics, the calculation method proposed in the present study does not require any special knowledge of thermodynamics, but only the information of compositions of the alloy. The proposed calculator is based on the CALPHAD approach for modeling of multi-component alloys, especial y in stainless steels. The calculator proposed in the present study can calculate thermophysical properties of eight-component systems on an iron base alloy (Fe-C-Si-Cr-Mn-Ni-Cu-Mo), and several Korean standard stainless steel alloys were calculated and discussed. The calculator can evaluate the thermophysical properties of the alloys such as density, heat capacity, enthalpy, latent heat, etc, based on full Gibbs energy for each phase. It is expected the proposed method can help casting experts to devise the casting design and its process easily in the field of not only stainless steels but also other alloy systems such as aluminum, copper, zinc, etc.     

Features of simultaneous ground- and excited-state lasing in quantum dot lasers

The lasing spectra and light-current (L-I) characteristics of an InAs/InGaAs quantum dot laser emitting in the simultaneous lasing mode at the ground- and excited-state optical transitions are studied. Lasing and spontaneous emission spectra are compared. It is shown that ground-state quenching of lasing is observed even in the absence of active region self-heating or an increase in homogeneous broadening with growth in the current density. It is found that the intensities of both lasing and spontaneous emission at the ground-state transition begin to decrease at a pump intensity that significantly exceeds the two-level lasing threshold. It is also found that different groups of quantum dots are involved in ground- and excited-state lasing.     

Fire Safety at Manufacturing Plants: The Role of Exceptional Technical Specifications

Russian Engineering Research - In the design and construction of industrial buildings, it is often impossibly to comply with current fire regulations, on account of production requirements. For...     

Operation of a pond-cooler: the case of Berezovskaya GRES-1

Pond-coolers at heat and nuclear power stations are natural-technological systems, so the program of their monitoring should include the effect made by the SRPS (state regional power station) on the pond ecosystem, including thermal discharge of cooling water. The objectives of this study were development and implementation of a monitoring program for the cooling pond of Berezovskaya SRPS-1 on the chemical and biological water quality indicators and identification of patterns of the thermal and hydrochemical regime when operating the progressive power plant (from 1996 to 2015). The quality of the cooling water of the pond-cooler BGRES-1 was studied under full-scale conditions by selecting and analyzing the water samples of the pond in accordance with the principles of complexity, systematic observation, and consistency of timing their conduct with the characteristic hydrological phases. Processing of the obtained array of monitoring data by methods of mathematical statistics makes it possible to identify the main factors affecting the water quality of the pond. The data on water quality obtained during their monitoring and mathematical processing over a long time interval are the scientific basis for forecasting the ecological state of the pond, which is necessary to economically ensure the efficient energy production and safety of water use. Recommendations proposed by these authors, including those partially already implemented, have been to prevent the development of eutrophication processes in the pond-cooler: the construction of a dam that cuts off the main peat massif and cleaning the river banks forming the cooling pond.     

Contract law 2.0: ‘Smart’ contracts as the beginning of the end of classic contract law

The paper analyzes legal issues associated with the application of existing contract law provisions to so-called Smart contracts, defined in the paper as ‘agreements existing in the form of software code implemented on the Blockchain platform, which ensures the autonomy and self-executive nature of Smart contract terms based on a predetermined set of factors’. The paper consists of several sections. In the second section, the paper outlines the peculiarities of Blockchain technology, as currently implemented in Bitcoin cryptocurrency, which forms the core of Smart contracts. In the third section, the main characteristic features of Smart contracts are described. Finally, the paper outlines key tensions between classic contract law and Smart contracts. The concluding section sets the core question for analysis of the perspectives of implementation of this technology by governments: ‘How to align the powers of the government with Blockchain if there is no central authority but only distributed technologies’. The author suggests two solutions, neither of which is optimal: (1) providing the state authorities with the status of a Superuser with extra powers; and (2) relying on traditional remedies and enforcement practices, by pursuing specific individuals – parties to a Smart contract – in offline mode.     

Effect of carrier dynamics and temperature on two-state lasing in semiconductor quantum dot lasers

It is analytically shown that the both the charge carrier dynamics in quantum dots and their capture into the quantum dots from the matrix material have a significant effect on two-state lasing phenomenon in quantum dot lasers. In particular, the consideration of desynchronization in electron and hole capture into quantum dots allows one to describe the quenching of ground-state lasing observed at high injection currents both qualitatevely and quantitatively. At the same time, an analysis of the charge carrier dynamics in a single quantum dot allowed us to describe the temperature dependences of the emission power via the ground- and excited-state optical transitions of quantum dots.