A study of the dynamic compressive behavior of Elk antler

Large mammalian antler is extremely tough and fracture resistant compared to other more brittle forms of skeletal bone. The ability of antler to resist fracture is associated with a decrease in material stiffness and yield strength and increased non-linear response, due in part to antler being fast growing, since they are typically shed and regrown annually. Since male Elk commonly engage in antler sparring as a means of making dominance displays, the ability to withstand large impacts suggest that antler may exhibit strain-rate dependent behavior even greater than skeletal bone. To evaluate this hypothesis, specimens of antler were tested in compression over a range of strain rates. Specimens were loaded either along or transversely to the osteonal growth direction, in wet and dry conditions. Results showed that antler exhibits higher compressive strengths at increased strain rates, and that strain rate and hydration are greater determinants of compressive strength than osteonal orientation. In addition, antler can sustain compressive strains a full order-of-magnitude greater than in mammalian long bone. Failed specimens showed that a hierarchical chain of deformation mechanisms sustains the large bulk strains supported by antler. These mechanisms appear to be less brittle and more fibrous than those seen previously in skeletal bone.     

Simulation and analysis of metamorphic high electron mobility transistors

In this paper, the metamorphic high electron mobility transistors (mHEMTs) are investigated numerically and compared with pseudo-morphic high electron mobility transistors (pHEMTs). The two-dimensional device simulator, MEDICI, is used to solve the Poisson's equation and the electron/hole current continuity equations. The influences of δ-doping concentration and position, gate width, spacer thickness, etc. on the performances of HEMTs are explored. It shows clearly that mHEMTs have higher transconductances, drain currents and DC voltage swings than pHEMTs.     

Kinetic characterization of the deproteinization of trabecular and cortical bovine femur bones

The present study proposes an interpretation of the mechanism of bone deproteinization. Cortical and trabecular bovine femur bones were deproteinized using 6% NaOCl (37, 50, 60 °C). The kinetic parameters (rate constant and activation energy) were calculated, and the surface area of each type of bone was considered. A statistical analysis of the rate constants shows that cortical bone deproteinizes at a lower rate than trabecular. The activation energy is higher for trabecular than cortical bone, and no significant differences are found in the protein concentration values for both bones. Therefore, although trabecular bone deproteinizes at a higher rate than cortical, trabecular bone requires more energy for the deproteinization reaction to take place. Considering that both types of bones are constituted by mineral, protein, and water; the present work shows that the individual inner matrix architecture of trabecular and cortical bones, along with characteristics such as the mineral concentration and its bonding with collagen fibers, may be the responsible factors that control protein depletion.     

K-band HBT and HEMT monolithic active phase shifters using vector sum method

Two monolithic 3-bit active phase shifters using the vector sum method to K-band frequencies are reported in this paper. They are separately implemented using commercial 6-in GaAs HBT and high electron-mobility transistor (HEMT) monolithic-microwave integrated-circuit (MMIC) foundry processes. The MMIC HBT active phase shifter demonstrates an average gain of 8.87 dB and a maximum phase error of 11/spl deg/ at 18 GHz, while the HEMT phase shifter has 3.85-dB average measured gain with 11/spl deg/ maximum phase error at 20 GHz. The 20-GHz operation frequency of this HEMT MMIC is the highest among all the reported active phase shifters. The analysis for gain deviation and phase error of the active phase shifter using the vector sum method due to the individual variable gain amplifiers is also presented. The theoretical analysis can predict the measured minimum root-mean-square phase error 4.7/spl deg/ within 1/spl deg/ accuracy.     

The pH sensing characteristics of the extended-gate field-effect transistors of multi-walled carbon-nanotube thin film using low-temperature ultrasonic spray method

A novel, simple and low-temperature ultrasonic spray method was developed to fabricate the multi-walled carbon-nanotubes (MWCNTs) based extended-gate field-effect transistors (EGFETs) as the pH sensor. With an acid-treated process, the chemically functionalized two-dimensional MWCNT network could provide plenty of functional groups which exhibit hydrophilic property and serve as hydrogen sensing sites. For the first time, the EGFET using a MWCNT structure could achieve a wide sensing rage from pH = 1 to pH = 13. Furthermore, the pH sensitivity and linearity values of the CNT pH-EGFET devices were enhanced to 51.74 mV/pH and 0.9948 from pH = 1 to pH = 13 while the sprayed deposition reached 50 times. The sensing properties of hydrogen and hydroxyl ions show significantly dependent on the sprayed deposition times, morphologies, crystalline and chemical bonding of acid-treated MWCNT. These results demonstrate that the MWCNT-EGFETs are very promising for the applications in the pH and biomedical sensors.     

A fully integrated multi-band ED-mode pHEMT VCO using variable transformer and switched resonator

A systematic approach to the design of a reconfigurable LC-coupled voltage-controlled oscillator (VCO) is proposed in this article. The focus is on the choice of the reactive elements of the resonance tank which are most suitable to switch to the desired oscillation frequencies. The optimum Q of the tank will be determined by the selected component. We report a 0.5-µm enhancement–depletion (ED) mode pHEMT (HEMT, high-electron mobility transistor) multiple-frequency VCO, and the generation of multiple frequencies are achieved using switched resonator topology. LC-tank circuit is built by square transformers. By careful selection of the reactive elements, evenly distributed results showed at each designed band. The multi-band ED-mode pHEMT VCO showed the output power of ?4.7?dBm for 2?GHz band, ?6.67?dBm for 3.86?GHz band and ?5.9?dBm for 4.5?GHz band, respectively. The phase noises at 1?MHz offset frequency from carrier were ?112.8?dBc/Hz for 2?GHz, ?105?dBc/Hz for 3.86?GHz and ?103.3?dBc/Hz for 4.5?GHz, respectively. The total chip size is only 1.17?×?0.83?mm².     

VIPER: an adaptive guidance and notification service system in internet of vehicles

In recent years, Internet of Vehicles has attracted increasing research attention, especially from the viewpoint of establishing effective information transmission methods to aid drivers and road users. Drivers can currently receive numerous types of assisted information. However, too much and cluttered information may affect their driving performance. Thus, effective guidance and notification services should be provided to drivers according to time, location, and events. For this purpose, we propose a Message Queue Telemetry Transport-based adaptive guide and notification service system called VIPER to provide driving assistance information. VIPER adaptively provides information to drivers and road users based on five conditions: Vehicle, points of Interest, People, Environment, and Roads. First, we establish a hierarchical grid architecture that is used to provide location-based services. Second, we collect information from the vehicles, roads, and environmental sensors to produce a weighted road network. Then, guide and notification services are provided based on this network. Thus, we can provide real-time driving assistance and help drivers to increase their safety and avoid traffic jams. We also analyze historical traffic data collected from vehicle detectors and accident data to estimate the safety and accident risk degrees of roads. To verify the feasibility of the proposed system, a system prototype is implemented to provide guidance and notification services. The experimental results show that our system can effectively assist drivers and road users and that it has a low system response time.

     

Electrochemistry of ionophore-coordinated Cs and Sr ions in the tri-1-butylmethylammonium bis((trifluoromethyl)sulfonyl)imide ionic liquid

The selective extraction of Cs⁺ and Sr²⁺ from aqueous solutions by using the ionophores calix[4]arene-bis(tert-octylbenzo-crown-6) (BOBCalixC6) and dicyclohexano-18-crown-6 (DCH18C6), respectively, was demonstrated in the hydrophobic, room-temperature ionic liquid (RTIL), tri-1-butylmethylammonium bis((trifluoromethyl)sulfonyl)imide (Tf₂N⁻). The electrochemistry of Cs⁺ coordinated by BOBCalixC6 and Sr²⁺ coordinated by DCH18C6 was examined at a mercury film electrode (MFE) in this ionic liquid by using cyclic staircase voltammetry, sampled current voltammetry at a rotating electrode, and chronoamperometry. Both BOBCalixC6·2Cs⁺ and DCH18C6·Sr²⁺ exhibit well-defined reduction waves at approximately −2.4 and −2.9 V versus the ferrocene/ferrocenium (Fc/Fc⁺) couple, respectively, in which the coordinated ions are reduced to their respective amalgams, permitting the recycling of the ionophores. The diffusion coefficients of BOBCalixC6·2Cs⁺ and DCH18C6·Sr²⁺ are (2.7 ± 0.1) × 10⁻⁹ and (2.1 ± 0.1) × 10⁻⁹ cm² s⁻¹, respectively, at 30 °C. The coulometric efficiency for the reduction and stripping of Cs at mercury pool electrodes was about 90% and was independent of the deposition time, whereas the efficiency for Sr was slightly less than 90% at short times and decreased with the deposition time, probably due to the formation of a passive layer of Sr(Tf₂N)₂.     

Effect of the annealing ambient on the electrical characteristics of the amorphous InGaZnO thin film transistors

The influence of the thermal annealing on the amorphous indium gallium zinc oxide (a-IGZO) thin-film transistors (TFTs) under different ambient gases has been systematically addressed. The chemical bonding states and transfer characteristics of a-IGZO TFTs show evident dependence on the annealing ambient gas. For the a-IGZO TFTs in the oxygen ambient annealing at 250 degrees C for 30 mins exhibited a maximum field effect mobility (max muFE) of 9.36 cm2/V x s, on/off current ratio of 6.12 x 10(10), and a subthreshold slope (SS) of 0.21 V/decade. Respectively, the as-deposited ones without annealing possess a max muFE of 6.61 cm2/V x s, on/off current ratio of 4.58 x 10(8), and a SS of 0.46 V/decade. In contrast, the a-IGZO TFTs annealed at 250 degrees C for 30 mins in the nitrogen ambient would be degraded to have a max muFE of 0.18 cm2/V x s, on/off current ratio of 2.22 x 10(4), and a SS of 7.37 V/decade, corresponding. It is attributed to the content of the oxygen vacancies, according the x-ray photoelectron spectroscopy (XPS) analyze of the three different samples.