Estimation of monthly solar radiation distribution for solar energy system analysis

The concept of probability density frequency, which is successfully used for analyses of wind speed and outdoor temperature distributions, is now modified and proposed for estimating solar radiation distributions for design and analysis of solar energy systems. In this study, global solar radiation distribution is comprehensively analyzed for photovoltaic (PV) panel and thermal collector systems. In this regard, a case study is conducted with actual global solar irradiation data of the last 15 years recorded by the Turkish State Meteorological Service. It is found that intensity of global solar irradiance greatly affects energy and exergy efficiencies and hence the performance of collectors.     

A short-term fair MAC protocol for WLANs

Designing a medium access control (MAC) protocol that simultaneously provides high throughput and allows individual users to share limited spectrum resources fairly, especially in the short-term time horizon, is a challenging problem for wireless LANs. In this paper, we propose an efficient cooperative MAC protocol with very simple state information that considers only collisions, like the standard IEEE 802.11 MAC protocol. However, contrary to the IEEE 802.11 MAC, the cooperative MAC gives collided users priority to access the channel by assigning them shorter backoff counters and interframe-spaces than users who did not participate in the collision event. In other words, collided users are the only ones allowed to transmit in the following contention period. For the cooperative MAC protocol, we utilize an analytical throughput model to obtain the optimal parameter settings. Simulation results show that the cooperative MAC provides significant improvement in short-term fairness and access delay, while still providing high network throughput.     

TECTONIC CONTROLS ON THE EVOLUTION OF POROSITY IN THE CRETACEOUS MARDIN GROUP CARBONATES, ADIYAMAN OILFIELDS, SE TURKEY

The mid-Cretaceous Mardin Group carbonates constitute the principal reservoir in a number of oilfields near the city of Adiyaman in SE Turkey (the Adiyaman, G. Adiyaman, Cemberlitas, Cukurtas, Bolukyayla and Karakus oilfields). Porosity development in these carbonates was controlled by two phases of brittle deformation. The first of these accompanied the emplacement of the allochthonous Koçali-Karadut Complex in the Late Cretaceous (Maastrichtian), which principally influenced the development of porosity in the northern oilfields. Subsequently, movement during the Mio-Pliocene on the transcurrent Adiyaman fault affected porosity development in the south.
The topmost unit of the Mardin Group, the Karababa Formation, consists of argillaceous carbonates, whose permeability and porosity were increased as a result of abundant tectonically-induced microfractures and stylolites. The underlying Derdere Formation includes porous limestones and dolomites, which are the principal reservoir units in the Adiyaman fields.
Porosity versus depth and geothermal gradient versus depth curves indicate that porosity trends are controlled principally by the transcurrent Adiyaman fault and its antithetics. The Koçali-Karadut thrusts have had less influence on the evolution of porosity in the Mardin Group carbonates in the study area.     

Art on the Nanoscale and Beyond

Methods of forming and patterning materials at the nano‐ and microscales are finding increased use as a medium of artistic expression, and as a vehicle for communicating scientific advances to a broader audience. While sharing many attributes of other art forms, miniaturized art enables the direct engagement of sensory aspects such as sight and touch for materials and structures that are otherwise invisible to the eye. The historical uses of nano‐/microscale materials and imaging techniques in arts and sciences are presented. The motivations to create artwork at small scales are discussed, and representations in scientific literature and exhibitions are explored. Examples are presented using semiconductors, microfluidics, and nanomaterials as the artistic media; these utilized techniques including micromachining, focused ion beam milling, two‐photon polymerization, and bottom‐up nanostructure growth. Finally, the technological factors that limit the implementation of artwork at miniature scales are identified, and potential future directions are discussed. As research marches toward even smaller length scales, innovative and engaging visualizations and artistic endeavors will have growing implications on education, communication, policy making, media activism, and public perception of science and technology.     

Movement time to edge and non-edge targets

Time to capture a target at the edge of a screen is expected to be less than when the target is slightly away from the screen edge. This is due to the effective target width, in the direction of cursor movement, being large when the target is at the screen edge, allowing a user to control the movement only in a direction perpendicular to the direction of movement. An experiment with 71 participants and a range of Fitts’ Index of Difficulty (ID) showed a strong difference in the capture times of targets at the screen edge and targets placed one pixel from the screen edge. This advantage is typically 100 ms, independent of the ID of the movement.

Practitioner Summary: Movement time to icons placed at the screen edge (no space between icon and screen edge) is faster than when they are placed a short distance from the edge (as in Microsoft Windows).     

A Pyrene–Poly(acrylic acid)–Polyrotaxane Supramolecular Binder Network for High‐Performance Silicon Negative Electrodes

Although being incorporated in commercial lithium‐ion batteries for a while, the weight portion of silicon monoxide (SiO_x, x ≈ 1) is only less than 10 wt% due to the insufficient cycle life. Along this line, polymeric binders that can assist in maintaining the mechanical integrity and interfacial stability of SiO_x electrodes are desired to realize higher contents of SiO_x. Herein, a pyrene–poly(acrylic acid) (PAA)–polyrotaxane (PR) supramolecular network is reported as a polymeric binder for SiO_x with 100 wt%. The noncovalent functionalization of a carbon coating layer on the SiO_x is achieved by using a hydroxylated pyrene derivative via the π–π stacking interaction, which simultaneously enables hydrogen bonding interactions with the PR–PAA network through its hydroxyl moiety. Moreover, the PR's ring sliding while being crosslinked to PAA endows a high elasticity to the entire polymer network, effectively buffering the volume expansion of SiO_x and largely mitigating the electrode swelling. Based on these extraordinary physicochemical properties of the pyrene–PAA–PR supramolecular binder, the robust cycling of SiO_x electrodes is demonstrated at commercial levels of areal loading in both half‐cell and full‐cell configurations.     

A study of some equation‐of‐state parameters of poly(methylhydrosiloxane‐co‐dimethylsiloxane) with some solvents by gas chromatography

Trace amount of methyl acetate, ethyl acetate, tert‐butyl acetate, pentane, hexane, and heptane were passed through the chromatographic column loaded with poly(methylhydrosiloxane‐co‐dimethylsiloxane) coated on Chromosorb W. The retention diagrams of the solvents on the copolymer were plotted by means of specific retention volumes at temperatures between 40 and 80°C by inverse gas chromatography technique. In this study, some thermodynamic interaction parameters such as Flory–Huggins polymer–solvent interaction parameter, equation‐of‐state polymer–solvent interaction parameter, effective exchange energy parameter, and weight fraction activity coefficients at infinite dilution of the solvent were determined. Then, the exchange enthalpy parameter and entropy parameter were determined by using a relation for the enthalpy interaction parameter of the equation‐of‐state theory, which is arranged for the inverse gas chromatography conditions. Later, the partial molar heat of sorption and the partial molar heat of mixing were obtained. The solubility parameter of this copolymer was determined as 6.64 (cal/cm³)^1/2 at room temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1627–1631, 2007     

A Simple Method Producing Shadow Masks Used in Electrical Characterization Techniques

In this paper, a novel technique is introduced to make a shadow mask (SM) that is used in various electrical characterization techniques such as Hall-resistivity, magnetoresistance, and TLM (Transmission Line Method) ohmic contact measurements. By using this technology, a film thickness of about 0.25–0.30 m was obtained after photoprocessing. We reached an SM thickness of 15–20 m by electrodeposition, which is required for a sufficiently high toughness. It was observed that the sharpness of the masks was also fairly good. The SMs obtained using this technology have been successfully used in various applications.     

Degradation of milk proteins by extracellular proteinase from brevibacterium linens flk‐61

The objective of this study was to investigate the specificity of an extracellular proteinase from Brevibacterium linens FLK‐61 on the degradation of milk proteins (α_s1, ß‐casein, sodium caseinate and whey proteins). Each protein and the enzyme solution were incubated at 45° C for “0”;, 15, and 30 min and 1, 2, 3, 4, and 5 h. After that, hydrolysis of the proteins was evaluated by urea‐PAGE electrophoresis and densitometry. It was found that the enzymatic degradation of α_st casein occured much faster and it was more complete (P<0.01) than degradation of β‐casein. No degradation of whey proteins was found during 5 h incubation.     

Evaluation of membrane fouling and flux decline related with mass transport in nanofiltration of tartrazine solution

BACKGROUND: This work was carried out to investigate and analyze the interrelated dynamics of mass transport, membrane fouling and flux decline during nanofiltration of tartrazine. A combined application including pore diffusion transport model and a material balance approach was used to model an experimental flux data obtained from different values of pH (3, 5, 7 and 10), feed‐dye concentration (25, 100 and 400 mg L^?1), and transmembrane pressure (1200, 1800 and 2400 kPa). RESULTS: Almost 100% dye solution removal and a permeate flux of 135 L m^?2 h^?1 were obtained for 25 mg L^?1 and 1200 kPa at pH 10. At pH 10, lower membrane fouling was obtained due to the increase of electrostatic repulsion between anionic dye molecules and the more negatively charged membrane surface. Flux decline and membrane fouling increased together with transmembrane pressure and dye concentration. Fouling was found to be directly related to proportional‐permeation coefficient (k_O′) of dye which was identified as the solute passing into the permeate with respect to the amount transported into the membrane from the feed. CONCLUSIONS: For a decrease of pH (10 to 3) and transmembrane pressure (2400 to 1200 kPa) or an increase of feed‐dye concentration (25 to 400 mg L^?1), fewer dye molecules passed into the permeate with respect to the amount transported into the membrane from the feed. This situation depended mainly on the combined influences of the gel layer and fouling in the membrane. Copyright © 2010 Society of Chemical Industry