Detection and quantification of the insect pest Rhyzopertha dominica (F.) (Coleoptera: Bostrichidae) in rice by qPCR

The early detection of insects during grain storage and processing remains a major issue for the cereal industry, especially when immature stages are hidden inside the grain kernels. For this reason, we developed a qPCR method to detect and quantify one of the main pests of stored products in rice: the coleopteran internal feeder Rhyzopertha dominica. For that purpose, a specific primer set was designed to amplify artificial infestations of this pest in rice. Then, using a regression model, a standard curve was generated that correlated individuals to adult equivalent DNA quantity (inverse of the C_t value). Results revealed that the designed primer set was specific for R. dominica when tested against the other 4 common internal feeders in grain. The technique showed to be accurated (DNA was detected in more than 73% of the samples) and sensitive to insect presence (i.e. from 0.02 adults, 0.1 3rd instar to pupae or 13 egg to 2nd instar detectable per kg of rice). Moreover, the detection of R. dominica was strongly associated with a given infestation size: DNA quantity increased along with the size of the population. The use of the described qPCR protocol in grain and milling factories may enhace the critical detection and quantification of R. dominica populations in raw materials and processed food.     

Microstructure and tribological properties of cubic boron nitride films on Si3N4 inserts via boron-doped diamond buffer layers

Cubic boron nitride (cBN) coatings were deposited on silicon nitride (Si₃N₄) cutting inserts through conductive boron-doped diamond (BDD) buffer layers in an electron cyclotron resonance microwave plasma chemical vapor deposition (ECR MPCVD) system. The adhesion and crystallinity of cBN coatings were systematically characterized, and the influence of doping level of BDD on the phase composition and microstructure of the cBN coatings were studied. The nano-indentation tests showed that the hardness and elastic modulus of the obtained cBN coatings were 78 GPa and 732 GPa, respectively. The tribological properties of the cBN coatings were evaluated by using a ball-on-disc tribometer with Si₃N₄ as the counterpart. The coefficient of the friction and the wear rate of the cBN coatings were estimated to be about 0.17 and 4.1 × 10^− 7 mm³/N m, respectively, which are remarkably lower than those of titanium aluminum nitride (TiAlN) coatings widely used in machining ferrous metal. The results suggest that cBN/BDD coated Si₃N₄ inserts may have great potentials for advanced materials machining.     

Double-parallel-junction hybrid solar cells based on silicon nanocrystals

A novel type silicon nanocrystal-based hybrid solar cell is demonstrated here, where two individual junctions are designed carefully and arranged in parallel with each other. It is found that complementary absorption can be realized by double parallel junctions, and more photons in a wide energy range can be absorbed. As a result, device efficiency has been enhanced more than twice compared to single junction reference device. In addition, its working principles are also studied extensively.     

A multi-case study of agile requirements engineering and the use of test cases as requirements

ContextIt is an enigma that agile projects can succeed ‘without requirements’ when weak requirements engineering is a known cause for project failures. While agile development projects often manage well without extensive requirements test cases are commonly viewed as requirements and detailed requirements are documented as test cases.ObjectiveWe have investigated this agile practice of using test cases as requirements to understand how test cases can support the main requirements activities, and how this practice varies.MethodWe performed an iterative case study at three companies and collected data through 14 interviews and two focus groups.ResultsThe use of test cases as requirements poses both benefits and challenges when eliciting, validating, verifying, and managing requirements, and when used as a documented agreement. We have identified five variants of the test-cases-as-requirements practice, namely de facto, behaviour-driven, story-test driven, stand-alone strict and stand-alone manual for which the application of the practice varies concerning the time frame of requirements documentation, the requirements format, the extent to which the test cases are a machine executable specification and the use of tools which provide specific support for the practice of using test cases as requirements.ConclusionsThe findings provide empirical insight into how agile development projects manage and communicate requirements. The identified variants of the practice of using test cases as requirements can be used to perform in-depth investigations into agile requirements engineering. Practitioners can use the provided recommendations as a guide in designing and improving their agile requirements practices based on project characteristics such as number of stakeholders and rate of change.     

A FPGA-based digital synchronous methodology for IEC 61850-9-2 process bus

In this paper, a network synchronization proposal for digital substation process bus in the process layer was designed. It appears differences of timing grouping queuing delay in the forward and backward on the channel due to the switch/routing device, thus introducing queue-induced asymmetry, which is a major contributor to time offset and time delay between master and subordinate clocks. The sampled value of the transmission time error caused by the electronic transformer (ECT) signal processing channel and Ethernet communication channel is analyzed. An FPGA-based (field-programmable gate array, FPGA) digital synchronization approach for merging unit (MU) was proposed, which included oversampling, linear phase-shifting, dynamic interpolation resampling technique. It solved the sampled value message precise synchronization problems on the IEC61850-9-2 process bus. Time offset and delay were reduced more than 70 μs between the master and subordinate clocks based on IEEE 1588v2, and he test results were well in 0.2 S level of IEC 60044 standard. Numerical examples are presented to demonstrate the effectiveness of the theoretical results.     

Performance evaluation of cup-anemometers and wind speed characteristics analysis

The objective of the present work is to study the performance of cup-anemometers installed at different heights on a 40 m tall wind mast over an approximate period of 55 months between September 13, 2005 and May 09, 2010. The performance of co-located cup anemometers has been analyzed by calculating the annual mean, median, standard deviation, tower distortion factor (TDF), scatter factor (SCF), and developing linear correlations between the co-located sensors. The study showed that the performance of sensors did not deteriorate much with time but slightly higher values of TDF were obtained with passage of time. The annual mean wind speeds, the median values and the standard deviations were almost the same during different years and were comparable with co-located sensors at each height. The SCF values were found to be increasing with decreasing height of wind speed measurements. Finally, a total of 16 wind turbines of 2 MW rated capacity each were used to find the most suitable wind turbine for the location under investigation.     

Influence of TiO2 compact layer precursor on the performance of perovskite solar cells

The optimization of the hole-blocking layer in perovskite solar cells (PSC), typically based on TiO₂, is crucial, as it strongly affects the device performance. In this work, we thoroughly characterize the thickness, roughness, and crystal structure of a set of TiO₂ compact layers produced by spin coating of different precursor sols and correlate the choice of the TiO₂ precursor to the photovoltaic performance of the PSC. By replacing the commonly used titanium isopropoxide (TTIP) blocking layer precursor with titanium tetrachloride (TiCl₄), a clear enhancement in the PSC performance was observed, particularly in the hysteresis behavior and stability. The results from the morphological/structural analysis and transient photoluminescence studies clarify the different behavior of the compact layers in PSCs.     

Hybrid carbon source for single-walled carbon nanotube synthesis by aerosol CVD method

The conductivity enhancement of single-walled carbon nanotube (SWCNT) films was achieved by increasing the bundle length in an aerosol CVD synthesis method with the help of two carbon sources. Carbon monoxide provides carbon at temperatures below 900 °C, while ethylene takes over at higher temperatures. The significant decrease in the sheet resistance at the 90% transmittance was observed from 3500 to 7500 Ω/sq. for pure CO system via 1909 and 1709 Ω/sq. for CO–H₂ system to 291 and 358 Ω/sq. in the presence of C₂H₄ at 900 and 1100 °C, respectively. Doping the film with a gold chloride solution in acetonitrile allowed us to create the transparent conductive films with the sheet resistance as low as 73 Ω/sq. at a transmittance of 90%.     

Performance of Secondary Wireless Networks with Contention Control in TV White Spaces

In this paper we study the spectrum coexistence of secondary wireless networks with contention control and TV services. We propose to use the carrier sensing threshold as a parameter to control the density of secondary transmitters and through that the generated secondary interference to the TV system. For the calculated threshold we propose a simple method to assess the data rate of the secondary system. Using this method one can study whether the secondary performance is limited due to the TV protection requirements or not. Also, the method can be used to study the trade-off between the secondary performance and the TV protection requirement.