Sub-nH Inductor Modeling and Design in 90-nm CMOS Technology for Millimeter-Wave Applications

Inductor design is an important issue in millimeter-wave CMOS circuits. In these frequencies the required inductance is very small and hence special structure is required for inductors. The quality factor is the most important design parameter for these inductors, especially in CMOS process. To incorporate these inductors in circuit simulation, a simple lumped model is necessary. This work proposes a simple and accurate model, developed for design and optimization of such inductors. This model is based on quasi-transverse-electromagnetic-mode assumption. To increase the model accuracy we have separately modeled the short-end section of the inductor. Model parameters are calculated using reported analytic equations and some new empirical equations. Using this model we have designed and optimized a 250-pH inductor with different shield layers, for STMicroelectronics 90-nm digital CMOS process. The accuracy of the model parameters and the evaluation of the model has been carried out using 2-D and method-of-momentss electromagnetic solvers in Advanced Design System, with the substrate modeled using foundry design kit data.     

Mechanobiological Mimicry of Helper T Lymphocytes to Evaluate Cell–Biomaterials Crosstalk

The unique properties of immune cells have inspired many efforts in engineering advanced biomaterials capable of mimicking their behaviors. However, an inclusive model capable of mimicking immune cells in different situations remains lacking. Such models can provide invaluable data for understanding immune–biomaterial crosstalk. Inspired by CD4+ T cells, polymeric microparticles with physicochemical properties similar to naïve and active T cells are engineered. A lipid coating is applied to enhance their resemblance and provide a platform for conjugation of desired antibodies. A novel dual gelation approach is used to tune the elastic modulus and flexibility of particles, which also leads to elongated circulation times. Furthermore, the model is enriched with magnetic particles so that magnetotaxis resembles the chemotaxis of cells. Also, interleukin‐2, a proliferation booster, and interferon‐γ cytokines are loaded into the particles to manipulate the fates of killer T cells and mesenchymal stem cells, respectively. The penetration of these particles into 3D environments is studied to provide in vitro models of immune‐biomaterials crosstalk. This biomimicry model enables optimization of design parameters required for engineering more efficient drug carriers and serves as a potent replica for understanding the mechanical behavior of immune cells.     

Design and optimization of fully differential capacitive MEMS accelerometer based on surface micromachining

In this paper, design and simulation of a single-axial, capacitive, fully differential MEMS accelerometer based on surface micromachining with two proof masses is presented. So far, most surface micromachined capacitive accelerometers offered, employed differential interface circuits to measure capacitor variations. However, in the presented structure, the possibility of fully differential design is realized by dividing the proof mass to two electrically isolated parts that are located on a silicon nitride layer. By utilizing two proof masses and altering outputs and stimulation voltage, parasitic capacitor is reduced and the sensitivity is increased. Moreover, some sensor capacitors are embedded inside the proof mass, so that sensitivity could be increased in the limited area and electrode length could be reduced. Furthermore, analytic equations are derived to calculate the sensitivity, as well to optimize the sensor structure. The designed sensor has been simulated and optimized using COMSOL Multiphysics, where the simulation results show the mechanical and capacitive sensitivity of 29.8 nm/g and 15.8 fF/g, respectively. The sensor size is 1 mm × 1 mm that leads to excellent performance, regarding to the defined figure of merit.

     

Flexible High-Performance Photovoltaic Devices based on 2D MoS2 Diodes with Geometrically Asymmetric Contact Areas

Optoelectronic performance of 2D transition metal dichalcogenides (TMDs)-based solar cells and self-powered photodetectors remain limited due to fabrication challenges, such as difficulty in doping TMDs to form p–n junctions. Herein, MoS₂ diodes based on geometrically asymmetric contact areas are shown to achieve a high current rectification ratio of ≈10⁵, facilitating efficient photovoltaic charge collection. Under solar illumination, the device demonstrates a high open-circuit voltage (V_oc) of 430 mV and a short-circuit current density (J_sc) of −13.42 mA cm⁻², resulting in a high photovoltaic power conversion efficiency (PCE) of 3.16%, the highest reported for a lateral 2D solar cell. The diodes also show a high photoresponsivity of 490.3 mA W⁻¹, and a large photo detectivity of 4.05 × 10¹⁰ Jones, along with a fast response time of 0.8 ms under 450 nm wavelength at zero bias for self-powered photodetection applications. The device transferred on a flexible substrate shows a high photocurrent and PCE retentions of 94.4%, and 88.2% after 5000 bending cycles at a bending radius of 1.5 cm, respectively, demonstrating robustness for flexible optoelectronic applications. The simple fabrication process, superior photovoltaic properties, and high flexibility suggests that the geometrically asymmetric MoS₂ device architecture is an excellent candidate for flexible photovoltaic and optoelectronic applications.     

Correlation Between Magnetic Properties and Allotropic Phase Transition of Fe–Co–V Alloy

In this study, the allotropic phase transition and its effect on the magnetic behavior of Fe Co–7 wt%V alloy were investigated. It was found that c phase is observed in the microstructure in the as-cast condition, and it diminishes after severe cold rolling(90% reduction). After annealing at temperatures higher than 500 up to 750 ℃, the c phase is observed in the structure, again. But, this phase is disappeared by annealing at temperatures above 750 ℃ due to the formation of vanadium-rich precipitates. Thermocalc software was used in order to elucidate the influence of vanadium percent on the stability of c phase in Fe–Co alloys. Also, magnetic studies showed that the saturation induction is reduced by annealing at temperatures from 500 up to 750 ℃, which is related to the formation of residual non-magnetic γ phase.     

Three-dimensional numerical analysis of the natural convection and entropy generation of MWCNTs-H2O and air as two immiscible fluids in a rectangular cuboid with fillet corners

A numerical investigation has been carried out to study the natural convection and entropy generation within the three-dimensional enclosure with fillets. There are two immiscible fluids of Multi-Walled Carbon Nano-Tubes (MWCNTs)-water and air in the enclosure, which is simulated as two discrete phases. There are two heaters with constant heat flux at the sides, and the top and bottom walls are kept at cold constant temperature. The finite volume approach is applied to solve the governing equations. Moreover, a numerical method is developed based on the three-dimensional solution of Navier–Stokes equations. The fluid flow, heat transfer, and total volumetric entropy generation due to natural convection are studied carefully in a three-dimensional enclosure. The effects of the corner radius of fillets (r?=?0, 0.15, 0.2, and 0.25), Rayleigh number (10³?Ra?6), and solid volume fraction (φ?=?0.002 and 0.01) of the nanofluid have been investigated on both natural convection characteristic and volumetric entropy generation.* The results show that the curved corner can be an effective method to control fluid flow and energy consumption, and three dimensional solutions render more accurate results.     

Accurate solution for free vibration analysis of functionally graded thick rectangular plates resting on elastic foundation

Vibration analysis of a functionally graded rectangular plate resting on two parameter elastic foundation is presented here. The displacement filed based on the third order shear deformation plate theory is used. By considering the in-plane displacement components of an arbitrary material point on the mid-plane of the plate and using Hamilton’s principle, the governing equations of motion are obtained which are five highly coupled partial differential equations. An analytical approach is employed to decouple these partial differential equations. The decoupled equations of functionally graded rectangular plate resting on elastic foundation are solved analytically for levy type of boundary conditions. The numerical results are presented and discussed for a wide range of plate and foundation parameters. The results show that the Pasternak (shear) elastic foundation drastically changes the natural frequency. It is also observed that in some boundary conditions, the in-plane displacements have significant effects on natural frequency of thick functionally graded plates and they cannot be ignored.     

Investigating the antecedents to the adoption of SCRM technologies by start-up companies

Despite their fairly recent emergence, start-up companies now play an important role in the economic development of countries around the globe. These companies have fewer tangible assets and capital, and therefore, the efficient delivery of services and products is a key business priority for them. Customer relationship management (CRM) technologies, which are designed to facilitate customer engagement during the design, development and delivery of services and products may play a significant role in the success or failure of start-up companies. Developments in new communication technologies have transformed traditional CRM into electronic CRM (eCRM), mobile CRM (mCRM); and more recently, social CRM (SCRM). However, there remains very little understanding of the factors affecting SCRM adoption in start-up businesses. The relative newness of SCRM technologies, coupled with the swiftly evolving nature of start-up companies: which has made them difficult cases to study – has limited the amount of research undertaken in this area. This paper aims to close this gap by proposing a framework that depicts the factors affecting start-up companies’ intention to adopt SCRM applications, and explores the relative importance of these factors. Inspired by an extended Technological, Organisational and Environmental (TOE) framework, this paper investigates effects of technological characteristics (TC), organisational characteristics (OC), environmental characteristics (EC) and managerial characteristics (MC) on start-up companies’ intentions to adopt SCRM applications.The results outlined in this research indicate that the observability, compatibility and trialability of SCRM solutions positively affect SCRM adoption in start-up businesses. Moreover, the availability of internal financial resources has a similarly positive effect. When considering environmental characteristics, it was found that support from venture capitalists, crowd funding support, governmental support, business angels support and external pressure all positively affect the intention to adopt SCRM applications within start-up businesses.     

Phase transitions and transport properties of Cu<Subscript>3</Subscript>Co<Subscript>0.5</Subscript>Se<Subscript>2</Subscript> crystals

We have synthesized a solid solution with the composition Cu₃Co_0.5Se₂ and investigated its structural phase transitions by high-temperature X-ray diffraction on a D8 Advance diffractometer. The results demonstrate that, in the range 100–773 K, the solid solution undergoes two phase transitions: at 560 K, the low-temperature, orthorhombic phase (α) transforms into an intermediate, primitive cubic phase (β); at 765 K, the β-phase transforms into a high-temperature phase (γ, sp. gr. Fm3m). The thermoelectric power, electrical conductivity, and Hall coefficient of the solid solution were measured in the temperature range 80–350 K. The observed temperature variation of its thermoelectric power and conductivity can be accounted for under the assumption that its conduction band has an additional subband due to the cobalt atoms.     

A Tension Analysis During Oxidation of Pure Aluminum Powder Particles: Non-isothermal Condition

In this research the role of stress acting on the rupture of the oxide film on aluminum powder particles during oxidation under non-isothermal conditions was studied. For this purpose, aluminum particles went under TG-DTA heat analysis tests at different heating rates up to 1,300 °C. The results obtained from these tests showed that the major part of the oxidation took place at non-isothermal conditions close to 1,000 °C. The scanning electron microscope also provided information about the rupture behavior of the oxide film under the effect of the stresses resulting during this intense oxidation. The finite element method was employed to study the intensity of the factors generating stress on the oxide film. The results of this simulation regarding the analysis of the imposed stresses showed that the expansion of the melt inside the film and also the shrinkage resulting from the transformation of the oxide structure from γ to α could impose a high rate of stress on this crust during the heating of aluminum powder particles in a non-thermal manner close to the above temperature. Also, with regard to the results obtained from this stress analysis, it was specified that although the rate of the stress resulting from the expansion of the melt inside the oxide film relative to the stress resulting from its shrinkage was much higher quantitatively, this shrinkage was also an important factor in the direction of activating the defects present in the structure of the oxide film played a determining role in the occurrence of its rupture.