Showing papers on "NQS published in 2019"

Neural Quantum States of frustrated magnets: generalization and sign structure

Abstract: Neural quantum states (NQS) attract a lot of attention due to their potential to serve as a very expressive variational ansatz for quantum many-body systems. Here we study the main factors governing the applicability of NQS to frustrated magnets by training neural networks to approximate ground states of several moderately-sized Hamiltonians using the corresponding wavefunction structure on a small subset of the Hilbert space basis as training dataset. We notice that generalization quality, i.e. the ability to learn from a limited number of samples and correctly approximate the target state on the rest of the space, drops abruptly when frustration is increased. We also show that learning the sign structure is considerably more difficult than learning amplitudes. Finally, we conclude that the main issue to be addressed at this stage, in order to use the method of NQS for simulating realistic models, is that of generalization rather than expressibility.

Comparing regulatory and non-regulatory indices of early childhood education and care (ECEC) quality in the Australian early childhood sector

Abstract: This study examines associations between Australia’s regulatory ratings of quality in early childhood education and care (ECEC)—the National Quality Standard (NQS)—and two research-based quality rating scales. The analytic sample consisted of 257 ECEC services across three Australian states. Results indicated (1) modest positive associations between NQS ratings and scale scores; (2) some specificity between NQS quality areas (educational programs and practice; relationships with children) and one research scale—the Sustained Shared Thinking and Emotional Wellbeing (SSTEW) scale; (3) variability in quality scales scores within each NQS designation; and (4) mitigation of these associations when the time-gap between ratings exceeded 24 months. Findings suggest NQS and research scales tap some common core of quality, yet capture different aspects of quality, suggesting both could be used to raise standards of quality in Australian preschools, where the research scales potentiate raising quality to even higher levels than NQS.

A Complete Small-Signal MOSFET Model and Parameter Extraction Technique for Millimeter Wave Applications

Abstract: In this paper, we propose a parameter extraction method for a complete MOSFET small signal equivalent circuit model addressing nearly all the parasitic and non-quasi-static (NQS) effects. Extraction and de-embedding of drain/source/gate series resistances and the substrate network are found to be necessary for obtaining the intrinsic elements of the small-signal equivalent circuit. We demonstrate for the first time, a step-by-step procedure for the extraction and de-embedding of the extrinsic model parameters directly from measurements. As a result, a precise intrinsic parameters derivation in the saturation region is presented. Moreover, for the intrinsic small signal equivalent circuit, a gate drain branch is supplemented in parallel to describe parasitic gate-drain coupling under high frequency up to 60 GHz together with the NQS effects. Finally, the presented parameter extraction method is verified by comparing with the corresponding measurement data from the 40-nm RF CMOS process of Shanghai Huali Microelectronics Corporation.

Accurate and Computationally Efficient Modeling of Nonquasi Static Effects in MOSFETs for Millimeter-Wave Applications

Abstract: A lumped-circuit nonquasi-static (NQS) model, that is applicable for both large-signal transient simulations and a small-signal ac analysis, is developed in this paper. An improved physical equivalent circuit, capturing NQS effects in the millimeter waveband, is derived using a transmission line model, by incorporating the high-frequency longitudinal gate electrode and a channel distributed RC network. The proposed model is implemented in a BSIM-BULK MOSFET model and validated with dc and RF data, obtained from technology computer-aided design device simulations and experimental data. The proposed model is in very good agreement with the data up to ${50}{f}_{t}$ . The transient currents, for a gate-voltage switching rate of ${5}\times {10}^{{10}}$ V/s, show excellent match with the data. The dc, transient, and ac simulations using the proposed model are much faster than a 10-segmented MOSFET model. This shows that the proposed model is better than other computationally complex compact models, for most RF applications.

BSIM-BULK: Accurate Compact Model for Analog and RF Circuit Design

Abstract: In this work, we present the recent and upcoming enhancements of the industry standard BSIM-BULK (formerly BSIM6) model. BSIM-BULK is the latest body referenced compact model for bulk MOSFETs having a unified core, which is developed by the BSIM group for accurate design of analog and RF circuits. The model satisfies the symmetry test for DC and AC, correctly predicts harmonic slope, and exhibits accurate results for RF and analog simulations. In order to further improve the model accuracy for transconductance $(g_{m})$ and output conductance $(g_{ds})$, an analytical model for bulk charge effect, in both current and capacitance, is implemented. Several other advanced models are added to capture real device physics. These include: parasitic current at the shallow trench isolation edges; leakage current components in zero threshold voltage native devices; new model for NQS to capture the NQS effects up to the millimeter wave regime; self heating effect; and heavily halo implanted MOSFET’s anomalous g m , flicker noise and I DS mismatch. All these enhancements have been implemented to high standards of computational efficiency and robustness.

Quality and safety of the nurse practice environment: Implications for management commitment to a culture of safety.

Abstract: Background The Philippines experiences several challenges pertaining to the quality of the practice environment (PE) and nursing quality safety (NQS) among nurses. Although there is already considerable empirical data on PE effects on NQS, there is still little overall information on the association between these variables. Aim This survey study examined the contribution of nurses' perceptions of their PE on their perception of their PE's quality of safety among hospital nurses in the Philippines. This survey was conducted in two government hospitals and two private hospitals in the Philippines. Participants A total of 374 nurses selected from two selected government hospitals and two private hospitals in the Philippines using a convenience sample technique. Methods Data were collected using a self-administered questionnaire focusing on the PE and NQS among nurses. Results The overall PE mean score of nurses is 3.07 (SD = 0.159) while the overall mean score of their NQS is 3.97 (SD = 0.702). NQS was higher in female nurses compared with male nurses (M = 2404 vs 4.16). Nurses assigned to emergency departments (F = 1.04, [df = 11], and P = .025) presented higher perceived NQS compared with those in other departments. Conclusion Nurses report moderate PE and higher NQS. Sex and emergency room department are significantly associated with NQS. Health care services have an obligation to ensure strong PE, as an important factor in regard to nursing management and affecting the QNS.

Transadmittance Efficiency Under NQS Operation in Asymmetric Double Gate FDSOI MOSFET

Abstract: The state-of-the-art RF and millimeter-wave circuits design requires accurate prediction of the nonquasi-static (NQS) effects at high frequency for all levels of channel inversion. This paper provides a practical insight to help high-frequency performance assessment of ultrathin body and box fully depleted silicon-on-insulator MOSFETs through a powerful frequency normalization scheme. Frequency dependence of small signal characteristics derived from experimental S-parameters is analyzed and reveals that the transconductance efficiency ( ${g}_{\textsf {m}}/{I}_{\textsf {D}}$ ) concept, already adopted as a low-frequency analog figure-of-merit (FoM), can be generalized to high frequency, including under asymmetric operation. We report that the normalized frequency dependence of the generalized transadmittance efficiency ( ${y}_{\textsf {m}}/{I}_{\textsf {D}}$ ) FoM only depends on the mobility and inversion coefficient. In addition, this approach is also used to extract essential parameters such as the critical NQS frequency ${f}_{\textsf {NQS}}$ .

A Non-Quasi-Static Model for Tunneling FETs Based on the Relaxation Time Approximation

Abstract: The models for tunneling field-effect-transistors (TFETs) reported up to date mainly used a quasi-static (QS) method to simulate the dc current-voltage (I-V) and capacitance-voltage (C-V) characteristics. The ignoring of the finite charging time of channel carriers makes the QS models problematic for the transient and ac simulations. In this paper, the relaxation time approximation (RTA) is adopted for the first time to develop a non-quasi-static (NQS) model for TFETs taking the effects of the carrier charging time into account and good agreements have been obtained between the model results and the numerical simulations. The proposed NQS model can give accurate prediction of not only the transient current under different signal changing range and rate, but also high-frequency capacitance. Moreover, the new NQS model is deduced based on the existing I-V and C-V model. This makes the new model can be easily incorporated with the existing I-V and C-V model for comprehensive description of TFET-based circuits.

Non-quasi-static effects in graphene field-effect transistors under high-frequency operation

Abstract: We have investigated the non-quasi-static (NQS) effects in graphene field-effect transistors (GFETs), which are relevant for GFET operation at high frequencies as a result of significant carrier inertia. A small-signal NQS model is derived from the analytical solution of drift-diffusion equation coupled with the continuity equation, which can be expressed in terms of modified Bessel functions of the first kind. The NQS model can be conveniently simplified to provide an equivalent circuit of lumped elements ready to be used in standard circuit simulators. Taking into account only first-order NQS effects, accurate GFET based circuit simulations up to several times the cut-off frequency (fT) can be performed. Notably, it reduces to the quasi-static (QS) approach when the operation frequency is below ~fT/4. To validate the NQS model, we have compared its outcome against simulations based on a multisegment approach consisting of breaking down the channel length in N equal segments described by the QS model each one.

MOSFET Small-Signal Model Considering Hot-Carrier Effect for Millimeter-Wave Frequencies

Abstract: The hot-carrier effect, which is caused by the generation of interface states, is the main degradation mechanism for MOSFETs. Predicting the degradation of circuit performance due to the hot-carrier effect is important for practical circuit design. In this paper, we propose a small-signal model considering the hot-carrier effect by establishing time-dependent model parameters, which is verified by small-signal simulation and measurement for 40-nm-process MOSFETs at millimeter-wave (mmW) frequencies. In the proposed small-signal model, the shift of relaxation time of the non-quasi-static (NQS) effect is investigated and verified for mmW frequencies for the first time. By comparing simulation and measurement results, it is shown that the shift of relaxation time of the NQS effect should be considered for the prediction of MOSFETs performance degradation at mmW frequencies.