Poly(lactide)/cellulose nanocrystal nanocomposites by high-shear mixing

There is currently considerable interest in developing stiff, strong, tough, and heat resistant poly(lactide) (PLA) based materials with improved melt elasticity in response to the increasing demand for sustainable plastics. However, simultaneous optimization of stiffness, strength, and toughness is a challenge for any material, and commercial PLA is well-known to be inherently brittle and temperature-sensitive and to show poor melt elasticity. In this study, we report that high-shear mixing with cellulose nanocrystals (CNC) leads to significant improvements in the toughness, heat resistance, and melt elasticity of PLA while further enhancing its already outstanding room temperature stiffness and strength. This is evidenced by (i) one-fold increase in the elastic modulus (6.48 GPa), (ii) 43% increase in the tensile strength (87.1 MPa), (iii) one-fold increase in the strain at break (∼6%), (iv) two-fold increase in the impact strength (44.2 kJ/m²), (v) 113-fold increase in the storage modulus at 90°C (787.8 MPa), and (vi) 10³-fold increase in the melt elasticity at 190°C and 1 rad/s (∼10⁵ Pa) via the addition of 30 wt% CNC. It is hence possible to produce industrially viable, stiff, strong, tough, and heat resistant green materials with improved melt elasticity through high-shear mixing.     

Magnetic field enhancement of electrochemical hydrogen evolution reaction probed by magneto-optics

External magnetic fields affect various electrochemical processes and can be used to enhance the efficiency of the electrochemical water splitting reaction. However, the driving forces behind this effect are poorly understood due to the analytical challenges of the available interface-sensitive techniques. Here, we present a set-up based on magneto- and electro-optical probing, which allows to juxtapose the magnetic properties of the electrode with the electrochemical current densities in situ at various applied potentials and magnetic fields. On the example of an archetypal hydrogen evolution catalyst, Pt (in a form of Co/Pt superlattice), we provide evidence that a magnetic field acts on the electrochemical double layer affecting the local concentration gradient of hydroxide ions, which simultaneously affects the magneto-optical and magnetocurrent response.     

Determination of optimum parameters for multi-performance characteristics in drilling by using grey relational analysis

The theory of grey systems is a new technique for performing prediction, relational analysis and decision making in many areas. In this paper, the use of grey relational analysis for optimising the drilling process parameters for the work piece surface roughness and the burr height is introduced. Various drilling parameters, such as feed rate, cutting speed, drill and point angles of drill were considered. An orthogonal array was used for the experimental design. Optimal machining parameters were determined by the grey relational grade obtained from the grey relational analysis for multi-performance characteristics (the surface roughness and the burr height). Experimental results have shown that the surface roughness and the burr height in the drilling process can be improved effectively through the new approach .     

DESIGN OF A LOW-COST MICROCONTROLLER-BASED FUNCTIONAL ELECTRONIC STIMULATION DEVICE FOR DROP FOOT CORRECTION

Correction of drop foot is normally achieved by electrical stimulation of the common peroneal nerve by sending a series of pulses at a given frequency and duration. This article presents the design of a low-cost, programmable, portable, and high performance stimulator, designed at the Near East University. The stimulator, called the NEU-Stim, has been designed to correct the drop foot problems. For this purpose, a foot sensor, microcontroller, and electrodes are used in the design of the stimulator. The frequency, duty cycle, and the amplitude of the output waveform can easily be controlled using switches. The device is currently in experimental stage, and because of its low-cost it should find applications in developing countries after it has been completely assessed. Preliminary results on patients have shown that the device can correct the drop foot, and help patients to walk faster and more comfortably.     

Note: design and characterization of an optical light source based on mixture of white and near-ultraviolet light emitting diode spectra

An optical light source based on a solid-state lighting technology is designed. Main components of the light source are a phosphor-converted white and a near-ultraviolet (near-UV) light emitting diodes (LEDs), the spectral power distributions (SPDs) of which are mixed using a fiber optic combiner. The near-UV LED is used for improving insufficient SPDs of the white LED at shorter wavelengths of the visible radiation. Stable direct current power supplies are also designed and used to operate each of the LED separately. Three steps of the driving current can be selected by means of serial resistors altered with a commutator at nominal current values of ～40%, ～50%, and ～69%. The light source can be used for many characteristic measurements within the scope of photometry and colorimetry.     

The effect of cement alkali content on ASR susceptibility of mortars incorporating admixtures

In this study, the effects of three types of plasticizing chemical admixtures (modified lignosulfonate, sulfonated naphthalene formaldehyde and polycarboxylate based) on deleterious expansion due to alkali–silica reaction (ASR) have been investigated. Two different types of cements with low (0.53 Na₂O eq.) and high (0.98 Na₂O eq.) alkali contents, a non-reactive crushed limestone as fine aggregate and a reactive river sand were used within the scope of the experimental program. ASR tests were conducted according to accelerated mortar bar method (ASTM C 1260). Additionally the flow value, dry unit weight, capillary water absorption and compressive strength tests were performed. Test results indicated that mortars prepared with inert fine aggregate caused no significant expansion, regardless of cement type, admixture type and dosage. However, for mixes containing reactive sand, admixtures increased or decreased the expansion values (compared to plain mortars) depending on the alkali content of cement used. The magnitude of change of expansion also depended on the type and amount of admixture incorporation which have a dominant effect on stability and compactability of mortars. The high-alkali cement usually revealed the ASR expansion augmentation behaviour of admixtures. In contrast, low alkali cement decreased the expansion values compared to the control specimens.     

Technoeconomic analysis of electricity generation from wind energy in Kutahya,Turkey

Conventional energy usage has various environmental effects that cause global warming. Renewable energy sources are thus more favorable because they have nearly zero emission. Wind energy, among the various renewable sources, finds increasing usage, concurrent with developing technology. In addition, wind is an infinite energy source. In this study, the electricity-generation ability of Kutahya has been investigated. With this aim, wind data, from the measurement station located on Bunelek Hill, Kutahya, have been collected for a period of 36 months (July 2001–June 2004). From the collected data, the electricity generated has been calculated for different types of wind turbines. The calculations have been based on the electricity requirement of the main campus of the Dumlupinar University. Finally, the economic evaluation has been analyzed using life-cycle cost analysis. For the analysis of the economical aspects, the social and CO₂ costs have also been taken into account.     

Glass Forming Ability and Magnetic Properties of Fe36Ni36B19.2Si4.8Nb4−x M x (M=Cu, Zr, Ti, Y, Pt) Bulk Glassy Alloys Fabricated by Suction Casting

In this study, the effects of Cu, Zr, Ti, Y, Pt substitution for Nb additions on the stability and magnetic properties of Fe-Ni-based bulk metallic glass (BMG) alloys fabricated by the suction casting method are investigated. The saturation magnetization (J _s) and coercivity (H _c) for as-cast Fe₃₆Ni₃₆B_19.2Si_4.8Nb_4?x M _x (M=Cu, Ti) BMG alloys were in the range of 0.51 T–0.55 T and 76–779 A/m, respectively. Differential scanning calorimetry curves show that the Fe₃₆Ni₃₆B_19.2Si_4.8Nb_4?x M _x (M=Cu, Ti) bulk metallic glasses have a supercooled liquid region for Cu at 44 K and for Ti at 39 K.