Computer simulation of the human leg subjected to impact loading

One of the most important tasks in clinical practice is to determine accurately the forces and displacements of the various anatomical structural components of the human leg, especially when subjected to impact loading. This paper therefore develops a computer simulation which describes the biodynamic response of the human lower extremity for realistic activities such as kicking by foot etc. Firstly, the paper derives the nonlinear equations of motion and nonlinear constraint equation governing the sagittal plane response of the human leg subjected to impact loading. The equations are then solved using numerical techniques and the results are presented. Special attention is given to the ligament, contact and muscle group forces, the location of contact points, anterior-posterior displacements and the motion trajectories of the femur and the tibia.     

Experimental and Simulation Results of Wien Bridge Oscillator Circuıt Realized wıth Op-Amp Designed Using a Memristor

Journal of Electronic Testing - In this study, a new op-amp model was created by re-designing the internal structure of the traditional operational amplifier (741 family) circuit element with a...     

A Study of Boronizing Kinetics and Its Effect on the Structure and Mechanical Properties of Steel 16MnCr5

Metal Science and Heat Treatment - The kinetics of boronizing of low-alloy steel 16MnCr5 at 1123, 1173 and 1223 K for 2, 4 and 6 h in powder mixtures using the Ekabor-II agent is studied for...     

Comparison of electrolyte effects for poly(3,4-ethylenedioxythiophene) and poly(3-octylthiophene) by electrochemical impedance spectroscopy and polymerization parameters with morphological analyses on coated films

3,4-Ethylenedioxythiophene and 3-octylthiophene were electropolymerized on glassy carbon electrodes (GCE) to compare with four different electrolytes [lithium perchlorate (LiClO₄), sodium perchlorate, tetraethylammonium tetrafluoroborate, and tetrabutylammonium tetrafluoroborate] in a solvent of acetonitrile (CH₃CN). Modified electrodes were characterized by cyclic voltammetry, attenuated total reflectance–Fourier transform IR spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, atomic force microscopy, and electrochemical impedance spectroscopy (EIS). Nyquist and Bode plots for magnitude, phase, admittance, and capacitance on both polymer-modified electrodes were comparatively investigated in detail. The highest low-frequency capacitance (C _LF) and double-layer capacitance (C _dl) were obtained in 0.1 M LiClO₄/CH₃CN for poly(3,4-ethylenedioxythiophene) and poly(octylthiophene)/GCE. EIS data were fitted to the equivalent circuit model of R(Q(R(C(R(C(RW))))))(CR), which is used to investigate circuit parameters.     

Wear Characteristics of Traditional Manganese Phosphate and Composite hBN Coatings

In this study, the tribological properties of traditional manganese phosphate coatings and composite hBN coatings

composed of nano-hexagonal boron nitride (hBN) in layered manganese phosphate crystals on AISI 1040 steel were investigated. Wear tests were carried out under controlled temperature and humidity using ball-on-disc tribometers for samples that were either submerged in oil or retaining oil on their surfaces at a sliding speed of 2.5 cm/s with loads of 1, 3, 5, and 10 N and sliding distances of 40, 80, 100, and 120 m. The surface profiles before and after the tests were used to characterize the wear. The surfaces of the coated samples were examined using scanning electron microscopy (SEM). The coefficients of friction and wear rates of the coated samples were also measured. The average wear rates of the composite hBN-coated samples were significantly lower than those of the traditional manganese phosphate–coated samples for each of the loading conditions for the oil submersion and retained oil tests. The coefficient of friction (COF) values for the traditional manganese phosphate–coated samples did not change significantly with increasing load. The COF values for the composite hBN coated–samples decreased with increasing load in the oil submersion test.     

Characterization of the amino acids essential for the photo- and radioprotective effects of a Bowman-Birk protease inhibitor-derived nonapeptide

The Bowman–Birk protease inhibitor has been reported toexert photo- and radioprotective activity. This effect was assignedto a cyclic nonapeptide sequence which is known to contain theamino acids responsible for the anti-chymotryptic activity ofthe BBI. The present study indicated that linearization of thenonapeptide resulted in a significant loss of anti-proteolyticactivity, whereas the photo- and radioprotective capacity persisted.Substitution of the amino acids Leu or Ser of the nonapeptide,essential for the anti-proteolytic activity, with differentamino acids, indicated that rather the hydrophobic featuresof the amino acids in this position than charge are criticalto retain the photo- and radioprotective effect. These resultssuggest the existence of a bifunctional peptide sequence withanti-proteolytic and photo-/radioprotective capacity. However,the lack of correlation between the photo-/radioprotective activityand the anti-proteolytic activity within the peptides generatedby modification of the linear nonapeptide argues for the existenceof two closely colocalized domains within the nonapeptide responsiblefor photo-/radioprotection and protease inhibition.     

Production and characterization of boron carbide and silicon carbide reinforced copper-nickel composites by powder metallurgy method

In this study, composite samples were produced by reinforcing boron carbide and silicon carbide particles in different rates by weight into copper-nickel powder mixture using powder metallurgy method. The prepared powder mixtures were cold pressed under 600 MPa pressure and pelletized. The pelletized samples were then sintered in an atmosphere-controlled furnace. Scanning electron microscopy to determine the microstructure of the produced samples and x-ray diffraction method analysis to determine the phases forming in the structure of the produced samples were used and microhardness was taken to determine the effect of boron carbide and silicon carbide on hardness. In addition to that, the mechanical properties the transverse rupture strength were investigated using three-point bending tests. The corrosion tests were performed potentiodynamic polarization curves of the samples in 3.5 % sodium chloride solution. The highest hardness value was measured as 162 HV 0.05 in the sample reinforced with 10 % boron carbide. As the amount of silicon carbide increased, the corrosion resistance of the composite increased. Moreover, as the amount of boron carbide increased, the corrosion resistance of the composite decreased. Load-contact depth values were examined, copper-nickel+10 % silicon carbide has the highest peak depth of 48.12.     

Sublinear Fully Distributed Partition with Applications

We present new efficient deterministic and randomized distributed algorithms for decomposing a graph with n nodes into a disjoint set of connected clusters with radius at most k−1 and having O(n ^1+1/k ) intercluster edges. We show how to implement our algorithms in the distributed CONGEST\mathcal{CONGEST} model of computation, i.e., limited message size, which improves the time complexity of previous algorithms (Moran and Snir in Theor. Comput. Sci. 243(1–2):217–241, 2000; Awerbuch in J. ACM 32:804–823, 1985; Peleg in Distributed Computing: A Locality-Sensitive Approach, 2000) from O(n) to O(n ^1−1/k ). We apply our algorithms for constructing low stretch graph spanners and network synchronizers in sublinear deterministic time in the CONGEST\mathcal{CONGEST} model.     

Flavonoid content and antioxidant activity of vegetables from Indonesia

Extracts from 11 vegetables of Indonesian origin were screened for flavonoid content, total phenolics, and antioxidant activity. The flavonols myricetin, quercetin, and kaempferol and flavones luteolin and apigenin were quantified by HPLC. Flavonoid content in mg/100 g fresh weight (fw) was apparently initially reported for Cosmos caudatus H.B.K. (52.19), Polyscias pinnata (52.19), Pluchea indica Less. (6.39), Nothopanax scutellarius (Burm.f.) Merr (5.43), Talinum triangulare (Jacq.) Willd. (3.93), Pilea melastomoides (Poir.) Bl. (2.27), and Etlingera elatior (Jack) R.M.Sm (1.18). The flavonoid content of the vegetables studied were mainly quercetin and kaempferol and ranged from 0.3 to 143 mg/100 g fw, with the highest level found in Sauropus androgynus (L) Merr. C. caudatus H.B.K. had the greatest total phenols among the vegetables analysed, with 1.52 mg GAE/100 g fw. P. indica Less. and C. caudatus H.B.K. had the highest antioxidant activity as measured by ferric cyanide reducing power, DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulphonic acid) scavenging, and inhibition of linoleic acid oxidation. Therefore, S. androgynus (L) Merr, C. caudatus H.B.K., and P. pinnata were identified as potentially rich sources of dietary flavonoids and antioxidants.