New empirical relation for MOSFET noise unified over linear and saturation regions

This paper proposes an empirical relation, which represents noise bias condition dependence for a silicon N-channel MOSFET. No matter whether the MOSFET is operated in linear or saturation region, bias condition dependence is found to be well described by a power function of voltage gain. By introducing a device's intrinsic noise emf v_nc(ƒ), which is independent from bias condition, and empirical parameter β, input-referred noise voltage v_ni(ƒ) is clarified to be a function of v_nc(ƒ), β, and voltage gain , i.e. . This relation implies that noise voltage depends implicitly on bias condition through voltage gain, because transconductance g_m and drain-source differential conductance g_DS depend on bias condition. If β − 1 value is negligible, v_ni(ƒ) = v_nc(ƒ) is almost independent from bias condition, whereas, if β − 1 value is not negligible, bias condition dependence for v_ni(ƒ) appears to be observed. The β deviation from unity, which characterizes bias condition dependence, measures the difference between signal amplification and noise amplification.     

Flow dynamics in Taylor–Couette flow reactor with axial distribution of temperature

In this study, the flow dynamics of a Taylor–Couette flow with an axial distribution of temperature was experimentally investigated. The flow can be classified into three patterns based on the balance between the centrifugal force and the buoyancy. If the buoyancy is dominant, global heat convection is observed instead of Taylor vortices (Case I). When the buoyancy is comparable to the centrifugal force, the Taylor vortices and global heat convection appear alternately (Case II). If the centrifugal force is sufficiently high to suppress the buoyancy, stable Taylor vortices are observed (Case III). The characteristics of the mixing/diffusion are investigated by conducting a decolorization experiment on a passive tracer. In Case II, the tracer is rapidly decolorized in the presence of the global heat convection instead of the Taylor vortices. This result implies that the interaction between the centrifugal force and the buoyancy would induce an anomalous transport. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1075–1082, 2018     

Solubility of Nitrogen Gas in Aqueous Solution of Tetra-<Emphasis Type="Italic">n</Emphasis>-Butylammonium Bromide

Semiclathrate hydrates are water-based host-guest compounds formed from aqueous solutions of ionic guest substances. These materials can greatly moderate formation pressures and temperatures from canonical gas hydrates. This is a significant advantage for industrial applications such as gas separation and storage. \(\hbox {N}_{2}\) gas is a major component contained in various flue gases and is usually mixed with \(\hbox {CO}_{2}\). Semiclathrate hydrates can separate these gases under moderate thermodynamic conditions. Tetra-n-butylammonium bromide (TBAB) is a widely used ionic guest substance. To develop the application technologies and their theoretical models, solubility data of \(\hbox {N}_{2}\) gas in TBAB aqueous solutions are required. In this study, we report \(\hbox {N}_{2}\) gas solubility measured by an absolute gravimetric method for the semiclathrate hydrate formation system of \(\hbox {TBAB} + \hbox {H}_{2}\hbox {O} + \hbox {N}_{2}\). The measurement pressures, temperatures and TBAB mass fractions were 3 MPa, 5 MPa and 7 MPa, 292.15 K, 302.15 K and 307.15 K, and 0 (pure water), 0.10, 0.20, 0.32 and 0.40, respectively. The uncertainties were 0.056 MPa, 0.44 K and 0.00012 in mole fraction. Although the technical difficulty lays on measurements of small \(\hbox {N}_{2}\) gas solubility by the absolute gravimetric method, our data implied the unique gas dissolution property of aqueous TBAB solution depending on the TBAB concentration. The aqueous TBAB solutions with mass fractions of 0.10 and 0.20 had similar \(\hbox {N}_{2}\) gas solubility as that in pure water. With higher mass fractions, 0.32 and 0.40, the \(\hbox {N}_{2}\) gas solubility slightly increased from that in pure water, which implies the salting-in effect of TBAB.     

Enhancement of Thermoelectric Properties in Surface Nanostructures

The thermoelectric properties of TiN/MgO surface nanostructures have been determined using first-principles calculations based on the nonequilibrium Green’s function (NEGF) method. Through structural modification of the surfaces at the atomistic level, we find that the metallic TiN thin-film layer becomes semiconducting with a small bandgap, which enhances the Seebeck coefficient, while the electrical conductivity remains high at room temperature. Hence, a much larger thermoelectric figure of merit is obtained compared with bulk. These findings indicate the possibility of designing thermoelectric devices with surface nanostructures.     

Effect of Surface Condition on Oxygen Self-Diffusion Coefficients for Single-Crystal Al2O3

Oxygen self-diffusion coefficients were determined for two Al₂O₃ single crystals by the isotope-exchange technique, using chemically polished and Ar -ion-milled samples. Results represented by D=562 exp[–665(kJ/mol)/RT] cm²/s are lower than those for diamond-paste-finished samples and near Reed and Wuensch's results. The oxygen diffusion coefficient determined using crushed particles and the microscopically measured ratio of surface area to volume agreed with these values     

Emulsion of polyurethane having thermosetting properties. I. Preparation

A method of preparation of an urethane emulsion which provides thermosetting film is described here. By reacting a urethane prepolymer containing terminal isocyanate groups with diethylenetriamine in the presence of ketones, poly(urethane-urea-amine) was prepared. In other organic solvents, however, gelation occurred immediately and preparation of polyurethane-urea-amine was not successful. The function of ketone was ascribed to the tentative formation of a Schiff base between the primary amino group of diethylenetriamine and ketone in situ, and the reaction of primary amine with isocyanate was partly masked to prevent gelation. Then the free amino group is generated when the polymer is treated with epichlorohydrin and the reaction occurs between them. After the solution was neutralized with an aqueous acid, the solvent was removed in vacuo to give a stable self-emulsifiable thermosetting urethane emulsion. Typical mechanical properties of film from this urethane emulsion are also given here.     

Dynamic study of intramembranous particles in human fresh erythrocytes using an "in vitro cryotechnique"

For analyses of dynamic ultrastructures of erythrocyte intramembranous particles (IMPs) in situ, a quick-freezing method was used to stabilize the flow behavior of erythrocytes embedded in vitreous ice. Fresh human blood was jetted at various pressures through artificial tubes, in which the flowing erythrocytes were elongated from biconcave discoid shapes to elliptical ones, and quickly frozen in liquid isopentane-propane cryogen (-193 degrees C). They were freeze-fractured using a scalpel in liquid nitrogen, and routinely prepared for replica membranes. Many IMPs were observed on the protoplasmic freeze-fracture face (P-face) of the erythrocyte membranes. Some control erythrocytes under nonflowing or stationary conditions showed IMPs with their random distribution. However, other jetted erythrocytes under flowing conditions showed variously sized IMPs with much closer distribution. They were also arranged into parallel rows in some parts, and aggregated together. This quick-freezing method enabled for the first time the visualization of time-dependent topology and the molecular alteration of IMPs in dynamically flowing erythrocytes.     

紫外Ce3+:LuLiF4晶体激光光谱特性的研究

Ce³⁺:LuLiF₄晶体被证明在紫外区域具有较大的增益光谱宽度,这点对于短脉冲激光应用非常有吸引力.我们获得了较大的小信号增益,大于6dB/厘米.而且,在共焦四程放大结构中,对连续的氦镉激光的增益达到20dB.     

Multilayer Mg-Stainless Steel Sheets,Microstructure, and Mechanical Properties

Different multilayer Mg AZ31 and SS304L steel sheet combinations were prepared with different volume fractions of Mg. Isolated stress–strain curves of the Mg layers showed significant improvements in the strength and elongation of multilayer samples. Results indicated that in the most extreme situation with the lowest Mg volume fraction (V _f  = 0.39), the ultimate strength was increased by 25 pct to 370 MPa and the elongation was improved by 70 pct to 0.34. Investigation of the fracture surface showed that failure occurs by the coalescence of cracks close to the interface region. The improved strength of the multilayer samples was due to the combined effect of surface crack prevention by the steel layer and the higher work-hardening rate caused by the possible increased activity of non-basal systems. It is suggested that the stronger work-hardening behavior and the enhanced activity of non-basal systems in the multilayer samples were due to the formation of new stress components in the transverse direction. The larger the volume fraction of steel in the multilayer, the longer the distance remaining unstrained before the UTS.