Fuel-oxidizer mixtures: a lab and field study

ABSTRACT

Improvised explosive may be as primitive as a fuel and oxidizer mixture; yet not all fuel-oxidizer mixtures are explosive. Predicting explosive potential from laboratory-scale tests is desirable to screen a large matrix of potential threats in varying concentrations. Herein the properties of various fuel/oxidizer mixtures were measured at small scale (2 g) with bomb calorimetry and on large scale (5 kg) with high speed photography for detonation velocity and with piezoelectric pressure probes for TNT air blast equivalence. Potassium nitrate (KN), potassium chlorate (KC), potassium permanganate (KMnO₄), potassium iodate (KIO₃), ammonium nitrate (AN), and ammonium perchlorate (AP) were prepared with sucrose (Su) and aluminum (Al) fuel. Results were compared to each other as well as predictions from Cheetah thermochemical code.     

Effect of low-pressure carburizing and plasma nitriding on mechanical properties and fatigue endurance limits of low alloy sintered steels

ABSTRACT

Thermochemical treatments like plasma nitriding or surface carburizing are commonly used to enhance surface hardness of steel components. An important difference between these treatments is the temperature at which they are carried out. In the present paper, the surface carburizing was carried out following a recently reported non-isothermal low pressure carburizing (LPC) treatment. In order to gain a comparative view of the effect of different treatments on the microstructure, microhardness, fatigue and impact properties, materials with distinct hardenability and widely used in the industrial production were evaluated. Tests were also carried out using industrially processed components aimed to an application demanding high wear resistance. The microstructural evolution during case hardening was studied by optical and electron microscopy.     

Micro-irrigation development in India: an analysis of distributional pattern and potential correlates

ABSTRACT

In India, of late, micro-irrigation has received considerable policy focus. However, as of 2017, only about 10% of the potential area is under micro-irrigation. The present study analyzes the pattern and equity issues of distribution of micro-irrigation in India and identifies the potential correlates. The regression analysis reveals that the stage of groundwater development and agro-climatic differences significantly influence the spread of micro-irrigation. The relatively low spread of micro-irrigation in states with over-exploited groundwater needs attention. Overall, the study points to the need to revamp the current micro-irrigation development programmes, which focus excessively on subsidy.     

Developing English domestic occupancy profiles

ABSTRACT

Occupancy patterns are necessary to estimate energy demand and evaluate thermal comfort in households. Because of this, many European countries are developing representative domestic schedules to replace outdated criteria. This paper evaluates the state of knowledge of UK domestic occupancy patterns and develops new domestic occupancy profiles for England. The presented research (1) characterizes methods for collecting occupancy data and inferring patterns; (2) identifies and assesses the quality of categories of occupancy patterns used in building simulation; and (3) develops updated occupancy profiles. A systematic scoping review identified social and monitoring surveys as the most deployed data-collection methods. A systematic literature review also established that the occupancy categories most frequently used in UK building simulation are (a) a family with dependent children where the parents work full time; and (b) a retired elderly couple who spend most of their time indoors. The interview sample from the English Housing Survey 2014–15 was used to map household typologies. Results show that categories (a) and (b) combined amount to only 19% of England’s households, which suggest models are over-reliant on these groups. Considering this result, the paper develops occupancy patterns for England derived from 2015 UK Time Use Survey diaries for each household typology previously identified.     

Overview of Physical and Chemical,Operational Properties of Nitrous Oxide Used as a Propellant for Low-thrust Rocket Engines

The results of a system analysis of the efficiency of nitrous oxide(N_2O) as a propellant component for small space vehicles(SSV) were presented. A criterion for mass efficiency of the SSV propulsion system(PS) is determined. The current global state-of-the-art of SSV PSs is shown. The application field of nitrous oxide in SSV PSs is calculated and mass efficiency of N_2O application is quantitatively determined. An overview of physical and chemical as well as operational properties of nitrous oxide as a promising, non-toxic component of rocket propellant is provided. Main physical and chemical constants of gaseous and liquid nitrous oxide; chemical properties of N_2O, thermal stability of N_2O, catalytic decomposition of N_2O, a mechanism of decomposition of N_2O, catalysts for decomposition of N_2O, ballast additives to N_2O, application of nitrous oxide, nitrous oxide as a rocket propellant, production of nitrous oxide, toxicity of nitrous oxide, fire hazard of N_2O, requirements to equipment when handling N_2O; storage and transportation of N_2O are considered. It is demonstrated that nitrous oxide is a chemical compound meeting the requirements to rocket propellants, including those related to the environmental friendliness of propellants. With 75 references.     

A new cladding technology to bond aluminium on magnesium

ABSTRACT

An in situ hot press bonding technology has been developed to clad aluminium on magnesium. Followed by regular hot rolling, magnesium sheets, covered by ductile and corrosion-resistant aluminium without detectable oxides in the interface, are produced. The new technology requires no welding, vacuum, protective atmosphere or barrier layer, and it makes good interfacial strength and rollability. Aluminium–magnesium intermetallic phases are formed along the clad–core interface at elevated temperatures. They are not detrimental under compression but may cause clad-core delamination in tensile strain. However, the tensile failure is more dependent on the formability of magnesium core than on the strength of interface.     

On monitoring the process mean of autocorrelated observations with measurement errors using the w-of-w runs-rules scheme

Runs-rules have been widely used since the 1950s in industrial and nonindustrial process monitoring applications to improve the performance of basic and other traditional monitoring schemes. However, none of the studies on runs-rules have accounted for a process with a combined effect of measurement errors and autocorrelation. Hence, in this paper, the use of the w-of-w runs-rules to improve the performance of the Shewhart $\overline{X}$ scheme using an additive model with a constant variance and a first-order autoregressive model is proposed. To reduce the combined negative effect of measurement errors and autocorrelation, we implement a sampling strategy based on rational subgroups in which (a) multiple measurements per item are taken (instead of a standard single measurement) and (b) non-neighboring observations are gathered. Moreover, the latter sampling strategy is incorporated into the values of probability elements of a Markov chain matrix which is used to derive some closed-form expressions for the zero- and steady-state run-length distribution. The main finding of this study is that, with respect to some overall performance measures, the proposed scheme outperforms the existing Shewhart $\overline{X}$ scheme by a significant margin. A real-life example is used to illustrate the practical implementation of the proposed scheme.     

Tunable passively Q-switched thulium doped fluoride fibre (TDFF) laser using reduced graphene oxide-silver (rGO-Ag) as saturable absorber

A tunable, passively Q-switched thulium doped fluoride fibre (TDFF) laser using a reduced-graphene oxide-silver (rGO-Ag) thin film as a saturable absorber (SA) for S band operation is proposed and its efficacy demonstrated. Over a pump power range of 91.4?mW up to 158.6?mW, passively generated Q-switched pulses are observed with repetition rates from 20 to 34.5?kHz and pulse widths from 3.1 to 7.1?µs. The highest pulse energy observed is 101.2?nJ with a signal to noise ratio of ～42?dB. The proposed laser has a tuning range ～52?nm from 1458 to 1510?nm with a tunable bandpass filter (TBPF) introduced into the cavity.     

Robust adaptive passivity-based PIλD control

In this article, we develop proportional, fractional-integral, and derivative () controllers for the regulation and tracking problems of nonlinear systems. The analytic results are obtained by extending the passivity-based approach to include fractional operators. Robustness under parametric uncertainty is dealt with by a combination with an adaptive scheme. It is also shown their robustness under additive noise and their robustness under uncertainty in the derivation order. The advantages in the controlled system performance and in the control energy consumption in comparison to classic PI and proportional integral derivative controllers are illustrated for the quadratic boost converter and a benchmark system in the literature.     

Modification of structure and conductivity of nanohorns by toluene addition in carbon arc

Abstract

In the present work, we compare the structure and transport properties of carbon nanohorns (CNHs) synthesized by arc evaporation of graphite alone and with the addition of some portion of toluene. The materials have been investigated using transmission electron microscopy, Raman and infrared spectroscopies, thermogravimetric and BET analyses. The addition of a small amount of toluene during the evaporation of graphitic rod increases the length of CNHs, affects their hierarchical arrangement in aggregates and results in surface functionalization. All these features significantly enhance the conductivity of CNHs obtained with toluene additive in comparison with the pristine CNHs.