Synthesis and structure study of copolymers from thiadiazole fused indolocarbazole and dithienosilole

We report synthesis and characterization of two D-A polymers (PSDT-C12 and PSDT-EH) with different side chains. Both polymers are based on alternate 12,13-dioctyl-indolo[2,3-a][1,2,5]thiadiazolo[3,4-c]carbazole (TDZIC) and dithienosilole derivative units in polymer main chain. We used TDZIC to enlarge the 2D conjugated plane of acceptor monomers by fusing benzothiadiazole (BT) unit with an indole unit having alkyl groups. PSDT-C12 exhibited 10 nm redshift compared to PSDT-EH in solid films, while their absorption spectra were almost identical in solutions. Since the backbone and side chains on the indolocarbazole group are the same, the redshift on PSDT-C12 could be resulted from the dodecyl (C12) side chain on the dithienosilole unit and different molecular weight between these two polymers. PSDT-C12 has a larger molecular weight than PSDT-EH. Therefore possibly both side chains and molecular weight contributed to the difference in the absorption spectra in solid films. The straight C-12 side chain has less steric hindrance than the branched EH side chain in solid films. PSDT-C12 has a longer main chain (larger molecule weight) than PSDT-EH, which can favour a more extended main chain interaction. The vibronic peak at 519 nm and shoulder at 563 nm in the PSDT-C12 film further confirmed stronger main chain interaction. Geometry optimization showed that head–tail (HT)-PSDT had a more twisting conjugated backbone with larger dihedral angle between dithienosilole unit and thiadiazole-fused ring compared to head–head/tail–tail (HH/TT)-PSDT.     

A probabilistic model for assessing the reliability of wind farms in a power system

Modeling the generation of a wind farm and its effect on power system reliability is a challenging task, largely due to the random behavior of the output power. In this paper, we propose a new probabilistic model for assessing the reliability of wind farms in a power system at hierarchical level II (HLII), using a Monte Carlo simulation. The proposed model shows the effect of correlation between wind and load on reliability calculation. It can also be used for identifying the priority of various points of the network for installing new wind farms, to promote the reliability of the whole system. A simple grid at hierarchical level I (HLI) and a network in the north-eastern region of Iran are studied. Simulation results showed that the correlation between wind and load significantly affects the reliability.     

A decision-process model of relational risk and governance and their impact on performance

The purpose of this paper is to investigate the link among risk, governance, and performance. In order to achieve this objective, the paper examines the impact of relational risk on governance decision options (trust, bilateral control, and unilateral control) and performance (design time). Survey research was conducted to collect data from 221 new product development (NPD) relationships and structural equation modeling was conducted to test the hypotheses. The results suggest that relational risk influences trust and bilateral control negatively and unilateral control positively. Results also indicated that trust and bilateral control are positively related to shortened design time while unilateral control and shortened design time are negatively related. We also found that there are threshold effects for modes of governance decision as they influence shortened design time. This study enhances the understanding of NPD relationships by examining the key mechanisms through which governance decision modes are influenced and how they influence NPD performance. In summary, this study shows how relational risk perception through affecting governance decision modes influence shortened design time.     

Synthesis Gas and Zinc Production in a Noncatalytic Packed‐Bed Reactor

A noncatalytic packed‐bed reactor has been constructed for management of the reduction of ZnO by methane, which leads to co‐production of synthesis gas and zinc. The reactor consisted of a simple vertical pipe filled with ZnO pellets. These pellets underwent reaction with a pure methane flow. Experimental tests were conducted in the temperature range 860–995 °C at atmospheric pressure in an electrically heated reactor. The results showed complete chemical conversion of methane to synthesis gas in the aforementioned temperature range. In addition, analysis of the product solids indicated that the collected solids in the outlet of the reactor were entirely zinc. The maximum methane flow rates (149–744 mL min^–1) were adjusted to ensure complete chemical conversion of methane. These adjustments were performed for different bed heights at various operating temperatures. Analysis of the product gases revealed high quality synthesis gas production without the influence of methane cracking or other undesired side reactions in the experimental tests. Finally, the governing partial differential equations of the reactor modeling were solved by the finite element method. Consequently, the gaseous profiles along the reactor and the breakthrough curves were predicted and compared with the experimental tests.     

Impact of Freezing Process on Salt Diffusivity of Seafood: Application to Salmon (Salmo salar) Using Conventional and Pressure Shift Freezing

The depression of the melting temperature of ice under pressure permits to obtain a rapid freezing of foods. The expected benefit lies in reduced water diffusion from the intra- toward the extracellular media, resulting in a reduced drip loss during thawing. Beside, the modification of the cellular structure induced by ice formation may affect the mass diffusivity of the flesh. In the present study, salmon was used as a model food. Slabs of salmon (1-cm thick) were frozen using blast air and pressure shift freezing at 200 MPa. The impact of the freezing process on the mass diffusivity of salt was evaluated using an aqueous solution (NaCl, 3% w/w). Results indicate that the effective mass diffusivity was slightly increased in comparison to non-frozen flesh when a rapid freezing process was used. This may be attributed to a change in the permeability of cell membranes caused by freezing and high pressure.     

Robust nonlinear controller based on control Lyapunov function and terminal sliding mode for buck converter

This paper studies the sliding mode control (SMC) and terminal SMC (TSMC) techniques of output voltage regulation in dc–dc buck converters. In this paper, the conventional terminal sliding manifold (TSM), fast terminal sliding manifold, and adaptive terminal sliding manifold are investigated by using hysteresis‐modulated control. In addition, proportional‐integral‐derivative‐shaped TSM, PI‐shaped TSM, and proportional‐integral‐derivative‐integral‐shaped TSM are proposed in order to overcome the problems of conventional TSMs. Furthermore, a new continuous controller based on control Lyapunov function (CLF), with pre‐settable‐fixed switching frequency, is suggested. CLF‐based controller (CLF‐bC) is also adapted to the discontinuous digital input of the buck converter. In the proposed CLF‐bC, the switching frequency is completely independent and pre‐settable. Stabilization, reference tracking, high performance dynamic response, robustness against parameter uncertainties, and rejection of disturbances (e.g., input voltage changes and load variations) are some advantages of the proposed controllers. Impact of the controllers' parameters on the performance of the system is also summarized. Finite‐time stability of TSMs and proposed CLF‐bC, and the robustness of CLF‐bC against parameter variations and disturbances are mathematically proved. Performance of the proposed Adaptive TSMC (ATSMC), proportional‐integral‐derivative‐TSMC, and CLF‐bC has been verified through matlab simulations and compared with the conventional SMC and TSMC strategies. Copyright © 2016 John Wiley & Sons, Ltd.     

3D experimental and numerical analysis of wind flow around domed-roof buildings with open and closed apertures

This paper presents experimental and numerical study of airflow distribution around a reduced-scale model of a common type of domed-roof building. Measurements are performed in an open loop wind tunnel. A new modified Counihan scheme is developed for constructing a part-depth atmospheric boundary layer (ABL). Measured quantities include: wind velocity profile, turbulence intensity and airflow pattern around the building. To conduct the experiments, a 1:54 scale model of a real domed-roof building with six windows and an aperture on the roof is fabricated and placed in the test section of the wind tunnel. In addition, using a numerical modeling, turbulent airflow around such scale model in the wind tunnel is simulated and airflow field inside and outside the model as well as ventilating discharge coefficient are computed. It is illustrated that, airflow around this type of building contains complex adjacent recirculation flows. The building with open apertures has acceptable discharge coefficient for ventilation, which can be a factor to ensure comfort condition for residents as well as complying with energy-saving considerations.     

Characterization and Investigation of Magnetic and Microwave Properties of Multiwalled Carbon Nanotube/SrFe10MnSn0.5Ti0.5O19 Nanocomposites

SrFe₁₀MnSn_0.5Ti_0.5O₁₉/multiwalled carbon nanotube (MWCNT) nanocomposites with different volume percentages of MWCNT content were synthesized by a sol–gel method. The results of x-ray diffraction, field-emission scanning electron microscopy, and Fourier-transform infrared spectrometry analyses demonstrated that the SrFe₁₀MnSn_0.5Ti_0.5O₁₉ nanoparticles were attached on the external surfaces of the MWCNTs. Mössbauer spectroscopy indicates that the substituted cations preferentially occupy the 12k sites. Magnetic properties were measured using a vibrating-sample magnetometer, and microwave absorption properties were investigated using a vector network analyzer. It was found that, with increasing volume percentage of MWCNT content, the saturation magnetization as well as the coercivity decrease, but the reflection loss widely increases. To investigate the effect of sample thickness on the absorption properties, different values of thickness (1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, and 2 mm) were selected. The results showed that, with increasing thickness of the absorber, the reflection loss and bandwidth broadly increase.     

Analysis of the Mechanical Stability of Boreholes Drilled in Sedimentary Rocks

This article presents the method and results of wellbore stability analysis for three common reservoir lithologies consisting of a consolidated sandstone, a shaly sandstone, and a limestone formation. The effect of stress anisotropy on the mechanical stability of wellbores is evaluated while varying the inclination angle from 0 to 90°, for both the Mohr-Coulomb and the Drucker-Prager failure criteria. The selected failure criterion, and the in-situ rock stress regime are found to have significant effects on the safe drilling fluid density required to maintain wellbore integrity. According to some field examples, the Drucker-Prager failure criterion appears to systematically mimic rock conditions more realistically than the Mohr-Coulomb failure criterion. The simulated consolidated sandstone formation is found more stable with lesser drilling fluid density, at any inclination angle, than the simulated shaly sandstone formation. The simulated limestone formation is even more stable than the consolidated sandstone at all inclination angles since it requires lighter fluid density to prevent wellbore collapse. For all these rock types, the higher the deviation angle (from vertical), the higher the drilling fluid density needed for maintaining wellbore integrity. For the depth and rock conditions simulated, both consolidated and shaly sands are unstable in a strike-slip stress regime, but stable in an extensional stress regime. The simulated limestone formation was found stable in both stress regimes. However, in an extensional stress regime, the limestone formation required lighter fluid density to maintain wellbore integrity than in a strike-slip stress regime. This article introduces the theory of using a practically-oriented model to assess the mechanical stability of a wellbore in a linearly-elastic stress field. The model can be used to determine the range of mechanically stable well inclinations for a given formation, and to suggest drilling-fluid density programs tailored to efficient and safe drilling.