Interface Length Research Articles

Mixing driven by transient buoyancy flows.II. Flow dynamics

The chaotic advection of the interface between two miscible liquids inside a closed cavity, generated by a damped oscillatory buoyancy-driven (BD) regular flow field, is investigated experimentally for BD mixing. The Lagrangian history of interface motion, determined using the planar laser-induced fluorescence and the photographic full-field view method, is contrasted against the Eulerian flow field measured from particle image velocimetry. Chaotic advection stretches and folds the interface at an early stage to produce an asymmetric pairwise Rayleigh–Taylor (RT) morphology (RTM) structure from long wavelength RT instability and short-time Richtmyer–Meshkov instability and its fractal interface structure at a high impulsive-Reynolds number. The mechanism of folding, from global bifurcation of the flow field, caused by a hyperbolic point, served as an organizing center for multiple vortex interactions. The intermediate-stage kinematics of the RTM structure exhibits RT mixing and shows unfolding of the lamellar structure from the net effect of stretching, folding, and molecular diffusion prior to its breakdown; and it has a probabilistic outcome of exhibiting topological transitions through a breakup of the RTM structure in phase space from necking singularity and pinch-off, indicating sensitivity to the initial conditions. The effectiveness of mixing determined from mixing efficiency is contrasted against mechanical and lamellar models of mixing. The determination of topological entropy, from an approximate Gaussian distribution of the interface length stretch, yields time scale for information decay comparable to time scale for which a low-order horseshoe map emerges from flow, indicating local chaos of the interface. The late-stage breakdown of the RTM structure from internal and wall collision drives the interaction between advection and diffusion, which indicates that critical mixing time scales as the logarithmic of Peclet number, comparable to time-periodic sine flow and blinking vortex flow chaotic mapping models.

Topological antennas: Aperture radiators, leaky-wave surfaces, and orbital angular momentum beam generation

The emerging field of topological photonics has extended our capability to control and manipulate electromagnetic waves. Thus far, however, research has focused on realizing defect-immune waveguides for on-chip communication. Making similar advancement for antennas, which are an integral component and crucial to the performance of wireless devices, could lead to a parallel impact on wireless communication. In particular, the requirement for impedance matching that is fundamental to current antenna technology constitutes a major limitation to transmitting and receiving free-space signals in terms of bandwidth and power efficiency. Here, we show how reciprocal photonic topological insulator (PTI) metasurfaces can be designed to enable a unique radiation mechanism needless of impedance matching. This relies on the fact that counter-propagating spin states are decoupled from each other; hence, this self-matching characteristic spans the entire bandwidth of the PTI’s bandgap. Specifically, we present two strategies for out-coupling spin-polarized edge modes: (1) in the form of an end-fire antenna at the abrupt termination of the PTI with free space and (2) in the form of a leaky-wave antenna by engineering the dispersion of the edge mode to lie above the light line. In the first approach, we compare our results to conventional rectangular waveguide apertures and planar Vivaldi antennas, which either have a large profile or flared ends to obtain gradual impedance matching. In the second approach, we demonstrate how our structure can emit orbital angular momentum (OAM) beams with various orbital charge numbers by simply varying the length of the PTI interface when made into a circular loop. The reduced device area and complexity due to removing the need for any matching network and the ability to easily multiplex OAMs of any charge, in addition to the wideband and high efficiency performance, make the proposed topological antennas highly attractive for many applications.

Investigations on fracture properties and analytical solutions of fracture parameters at rock-concrete interface

To investigate fracture properties and find analytical solutions of fracture parameters at rock-concrete interface, three-point bending tests were performed on the composite rock-concrete specimens with different degrees of interface roughness. Numerical simulations were conducted to analyse the crack propagation and the fracture process zone evolution at rock-concrete interface. For convenient applications in practice, a series of analytical solutions were derived or curve-fitted to calculate the fracture parameters of rock-concrete interface. The results indicate that the roughness degree has significant effects on the fracture properties of rock-concrete interface. With the increase of the roughness degree, the fracture energy, the critical crack length and the double-K fracture parameters exhibit obvious increasing tendencies. Meanwhile, the ratio of the unstable fracture toughness of rock-concrete interface to concrete is much less than that of the initial fracture toughness, indicating the much weaker cohesive effect of rock-concrete interface compared with concrete. In addition, with the increase of the roughness degree, the length of the fully formed FPZ and the corresponding ratio of the crack propagation length to the ligament length decrease. The characteristic length of rock-concrete interface is proved to decrease with the increase of the roughness degree, indicating larger brittle behaviour with the increase of the roughness degree. Finally, a series of analytical expressions were curve-fitted or derived to calculate the fracture parameters of rock-concrete interface under three-point bending loading, including the mode-I stress intensity factor, the critical crack length and the characteristic length of rock-concrete interface.

Prediction of three-phase relative permeabilities of Berea sandstone using lattice Boltzmann method

Three-phase flows through a pore network of Berea sandstone are studied numerically under critical interfacial tension conditions. Results show that the relative permeability of each fluid increases as its own saturation increases. The specific interfacial length between wetting and nonwetting fluids monotonously decreases with increasing the saturation of intermediate-wetting fluid, while the other two specific interfacial lengths exhibit a nonmonotonous variation. As the wetting (nonwetting) fluid becomes less wetting (nonwetting), the relative permeability of wetting fluid monotonously increases, while the other two relative permeabilities show a nonmonotonous trend. Due to the presence of a spreading layer, the specific interfacial length between wetting and nonwetting fluids always stabilizes at a low level. As the viscosity ratio of wetting (nonwetting) to intermediate-wetting fluids increases, the relative permeability of wetting (nonwetting) fluid increases. With the viscosity ratio deviating from unity, the phase interfaces become increasingly unstable, leading to an increased specific interfacial length.

A fluid-solid coupled modeling on water seepage through gasketed joint of segmented tunnels

The water leakage at segment joints of underwater shield tunnels has always been the major concern and trouble to be dealt with in tunneling practices, not only for its threat to the durability and safe operation of tunnels but also for its difficulty to check the leaking process directly in the joints either on-site or in the laboratory test. In order to explore the water leakage mechanism of the segmented tunnel, a Coupled Eulerian-Lagrangian based model considering water flow and large deformation of rubber gasket was developed to simulate the whole process of water seepage through the gasketed joint. A series of numerical modelings were conducted to investigate the seepage pattern and the stress variation during the seepage process, and the dynamic waterproof performance of gasket was investigated. Then, the numerical modeling results were verified against the laboratory test data to prove the reliability of the proposed numerical method. Finally, a formula quantifying the relationship between the waterproof capacity and joint deformations was established, and the critical joint deformation sets were derived from the formula. It was found that the water has an impact effect on the gasket during seepage, which is up to 4 times the initial contact stress. The pressurized water must overcome a cluster of seepage stress barriers to form a seepage path through the gasketed joint. And therefore, the waterproof performance over the length of the gasket-gasket interface is changing and fluctuating with the seepage process, with higher values at both ends of the interface and lower values in the middle. Based on a comprehensive analysis, the critical joint deformation sets (joint opening, joint offset) are recommended for the design and construction of Qiongzhou Strait Tunnel (a planned deep-water shield tunnel in Hainan Province, China) to meet the long-term waterproof capacity of 2 MPa. It is suggested that the assembly accuracy of the segments and gaskets as well as the adhesion of gaskets to joint groove should be strongly guaranteed during the construction process.

Correlating interfacial fracture toughness to surface roughness in polymer-based interfaces

Statistical fractal characteristics are examined for polymer-based interfaces. Interfacial fracture behavior is modulated via exposure to varying levels of chemical contaminant concentration so as not to affect the initial interface roughness. The results of 1D height–height correlation analysis show a strong correlation between the interfacial fracture toughness and the resulting fracture surface roughness, and a toughness-independent roughness exponent; $$\beta \approx$$ 0.35 ± 0.04, which is the slope of the self-affine domain. The cut-off length scale of the self-affinity is found to scale with interface toughness, and equal the combined length scales of interfacial cohesive length and plastic zone size within the adhesive layer. The reported statistical characteristics of interfacial fracture surfaces is among the first to show the quantitative inter-correlation between interfacial adhesion and the resulting fracture surface roughness. With additional examination of other systems, the observed correlations have the potential to assess the interfacial fracture toughness for a wide range of polymer-based interfaces.

Role of Src‐Dependent Phosphorylation of Mitofusin 2 in Endoplasmic Reticulum‐Mitochondria Tethering

Introduction : Contact sites between the mitochondria and endoplasmic reticulum (ER) are one of the key structures involved in regulating lipid, Ca2+ and reactive oxygen species exchange across the two organelles which is critical for the maintenance of mitochondrial bioenergetics. Recent studies have reported that a major component of the tethering structures between the two organelles is mitofusin 2 (Mfn2), a GTPase associated with fusion of the outer mitochondrial membrane (OMM) as well as the activities of mitophagy and ER stress. While several post-translational modifications (PTMs) that influence the fusion and mitophagy functions of Mfn2 have been identified, it remains unclear whether there are PTMs that can regulate its tethering function. Data from mass spectroscopy reveals that there is basal tyrosine phosphorylation (P-Tyr) of Mfn2, but it is unknown whether Mfn2 is a substrate of mitochondria-localized tyrosine kinases (proline rich tyrosine kinase 2 [Pyk2] and proto-oncogene Src kinase [Src]). Objective : To determine whether P-Tyr of Mfn2 regulates Mfn2 functions. Methods HEK293T cells stably overexpressing shRNA targeted to a specific negative regulator of Src, C-terminal Src kinase (CSK) or a control vector were subjected to several biochemical (Fluorescent western blotting), cell biological (Transmission electron microscopy [TEM], Förster Resonance Energy Transfer [FRET] between cyan-fluorescent protein targeted to the OMM and yellow-fluorescent protein targeted to the ER membrane observed under confocal microscopy) and physiological (mitochondrial calcium [mtCa2+] uptake measurements using a mitochondria-targeted Ca2+ biosensor, mt-RCaMp1h) assays. Results Overexpression of Pyk2 and Src lead to P-Tyr of Mfn2 with Src having greater P-Tyr levels of Mfn2. Generation of a HEK293T cell line with stable knockdown of CSK reveals that CSK knockdown promotes Src activation in the mitochondria and increases P-Tyr of Mfn2 without changing expression levels of Src and Mfn2. CSK knockdown (CSK-KD) cells showed decreased distance between the ER and OMM as assessed by FRET measurement under confocal microscopy. This change was abolished by pretreatment with a Src-specific inhibitor, PP2. TEM images also showed that CSK knockdown decreases the distance between OMM and ER without changing the length of interface. To assess the impact of changes in the physical interaction between ER and mitochondria, mtCa2+ uptake profiles in CSK-KD cells were observed. In CSK-KD cells, mtCa2+ uptake in response to cytosolic Ca2+ elevation induce by Gq-protein coupled receptor stimulation was enhanced with faster kinetics compared to that in control cells. While physical coupling between ER and mitochondria increased, we found that hallmarks of ER stress and mitophagy were not altered in CSK-KD cells compared to control cells. Conclusion : Src-dependent phosphorylation of Mfn2 decreased the distance between the OMM and ER and lead to increased Ca2+ exchange between ER and mitochondria.

Multiscale modeling and validation of the flow around Taylor bubbles surrounded with small dispersed bubbles using a coupled VOF-DBM approach

This work presents a multiscale three-dimensional CFD model for the simulation of two-phase gas-liquid flows with different interface length scales, with focus on slug flow pattern. The model is based on the coupling of the Volume-of-Fluid (VOF) method, used to model the large-scale interface dynamics, and the Discrete Bubble Model (DBM) for modeling the small-scale bubbles, which allows to simulate two-phase flows with different interface length scales. A validation study is conducted independently for the VOF and DBM methods, by comparing the numerical results with experimental data from the literature, showing a very good agreement. A model for the collision between the VOF interface and Lagrangian bubbles is proposed and also independently validated. The coupled VOF-DBM model is used to study a liquid-gas two-phase flow with different interface length scales, where large Taylor bubbles and small dispersed bubbles are present. The results demonstrate that the presence of the small dispersed bubbles alters the flow structure around the Taylor bubble, increases the terminal velocity of the Taylor bubble and affects the flow structure in the wake region, which is directly related to heat and mass transfer rates in slug flow.

Experimental Study on the Bond Performance between Fiber-Reinforced Polymer Bar and Unsaturated Polyester Resin Concrete

Fiber-reinforced polymer (FRP) bar-reinforced unsaturated polyester resin concrete (UPC) can solve the problem of rebar corrosion in ordinary reinforced concrete members. However, it has not been widely used in engineering practice because there have been few studies conducted on the bond behaviors of FRP bar and UPC, and the interaction mechanisms between FRP bar and UPC have not been well understood. A series of pull-out tests are conducted on FRP bar-UPC specimens to study the bond behaviors between these two materials. Parametric studies are also carried out to investigate the effects of FRP bar diameter, fiber type, type of surface treatment, concrete cover thickness, and interfacial bond length between the two. Three failure modes of the specimens are observed from pull-out tests, i.e., FRP bar pull-out, tensile failure of FRP bar, and UPC split. A new constitutive model is, therefore, proposed to predict the bond stress of FRP bar and UPC in the residual stage, and the proposed model is finally verified by test data reported in this study.

Testing method of critical energy release rate for interfacial mode II crack

The energy release rate of an interfacial crack is a basic performance parameter for characterizing interfacial failure, but there is no direct testing method for this. Therefore, a testing method of the critical energy release rate for mode II cracks was proposed in this paper. First, multiple sets of double shear specimens with different precast interfacial crack lengths were prepared, the interface shear experiments were carried out with the improved interface double shear specimens, testing devices and method, and the load–displacement curves of the specimens were obtained. Then, the load–displacement curve of each specimen was normalized, and the corresponding load–displacement curve equation, and the critical displacement or critical load were determined. Finally, the energy release rate of the interfacial mode II crack was calculated based on its definition, and the critical energy release rate was determined. As an example, the results of the double shear tests on fully-bonded fiber reinforced polymer (FRP)-concrete interface showed that the critical energy release rate is 1.10 N/mm. Compared with the experimental results, the simplified theoretical models and the empirical models with the compressive strength of concrete as the main parameter can be acceptable, and the errors are less than 20%, but the errors of the empirical models with the concrete tensile strength as the main parameter are relatively large, which are about 50%.

Limit analysis of lateral earth pressure on geosynthetic-reinforced retaining structures using finite element and second-order cone programming

In this paper, a thorough numerical study is conducted to rigorously evaluate the lateral earth pressures exerted on the retaining walls backfilled with geosynthetic-reinforced soil strata. With this aim, the lower bound theorem of limit analysis is exploited in conjunction with the finite element discretization method. The computational programming adopting second-order cone optimization is employed to model the Mohr-Coulomb yield criterion in its respective nonlinear form. The reinforcement layers are assumed to bear solely axial tension; but not bending moment, which is the common characteristic of all geosynthetic materials. Results show that the horizontal stress field behind retaining structures is heavily disturbed by placing geosynthetic layers, especially in close proximity to the retaining structure. Accordingly, the failure zone shrinks in size and the lateral earth pressure decreases by either adding more reinforcement layers or increasing their relative lengths. Through a comprehensive parametric survey, the influence of several parameters, including internal friction angle, soil-wall and soil-reinforcement interface friction angles, length and number of reinforcements, soil inherent anisotropy and surface loading on the lateral earth pressure is meticulously examined. The employed formulations are rigorously compared with results published in the literature. A design table is also provided so as to effectively estimate the active earth pressure coefficient of geosynthetic-reinforced walls accounting for all contributing parameters.

H2-SCR of NOx on low-SSA CeO2-supported Pd: The effect of Pd particle size

The H2-SCR of NO was investigated in the 130−220 °C range over low-SSA CeO2-supported Pd of varying particle size, dPd (ca. 13−45 nm). Relationships were derived between dPd and the specific integral rate (per gram of Pd or length of metal-support interface), NO conversion, N2-selectivity, TOFNO and the concentration of active NOx-s. The large enhancement in the rate of NO conversion per gram of Pd metal over the small Pd particles was found to be largely related to the increase in the concentration of active NOx formed within a zone around the Pd-ceria interface and the rate of H-spillover. The effect of H2O on the integral rate and N2-selectvity as a function of dp (nm) was also investigated.

Potential importance of malate diffusion in the response of maize photosynthesis to heterogeneous light

It is well known that the photosynthetic performance of a leaf is highly dependent on the systemic regulation from distal parts within a plant under light heterogeneity. However, there are few studies focusing on C4-specific processes. In the present study, two cultivars of maize (Zea mays L.), ‘Rongyu 1210’ (RY) and ‘Zhongdan 808’ (ZD), were treated with heterogeneous light (HL). The net photosynthetic rate (Pn) of newly developed leaves was found to increase in HL-treated RY, while it decreased in HL-treated ZD. Result also showed a negative correlation between the Pn and the content of malate, a key metabolite in C4 photosynthesis, in these two cultivars. In HL-treated ZD, malate content increased with a decline in the abundance of NADP-malic enzyme (EC 1.1.1.40), suggesting that less malate was decarboxylated. Moreover, a restriction of malate diffusion is proposed in HL-treated ZD, since the interface length between mesophyll cells (MC) and bundle sheath cells (BSC) decreased. In contrast, malate diffusion and subsequent decarboxylation in HL-treated RY should be stimulated, due to an increase in the abundance of NADP-malate dehydrogenase (EC 1.1.1.82) and a decline in the content of malate. In this case, malate diffusion from MC to BSC should be systemically stimulated, thereby facilitating C4 photosynthesis of a maize leaf in heterogeneous light. While if it is systemically restricted, C4 photosynthesis would be suppressed.

Effects of pore-size disorder and wettability on forced imbibition in porous media

Imbibition is the process by which the wetting fluid displaces the non-wetting fluid driven by capillary force. It occurs in many natural and industrial processes, such as enhanced oil recovery and geological carbon sequestration. The imbibition process is highly affected by wettability, viscosity ratio and injection flow rate, and the competition between these factors becomes more complicated when pore-size disorder is involved. In this study, we systematically investigate forced imbibition in four two-dimensional (2D) porous media with different disorders over a broad range of wettability conditions and flow rates. We analyze the relationship between the interfacial length and the invading fluid saturation, and the relationship between displacement front and invading fluid saturation. Results show that disorder and wettability have different impacts on the imbibition process under different capillary numbers. At low capillary number, displacement process is not sensitive to disorder due to the contradicting effects and the imbibition process is governed by the wettability. At intermediate capillary number, only the largest disorder has obvious influence on the displacement process due to the highest entry pressure. The transition from capillary fingering to viscous fingering occurs leading to a higher displacement efficiency. At high capillary number, disorder has a great influence on the front morphology and displacement efficiency while the wettability has relatively weak impact. The pattern transition is also observed at strong imbibition because of the competing effects between the capillary force and the viscous force.

Cohesive zone analysis of cylindrical ice adhesion: Determining whether interfacial toughness or strength controls fracture

Ice accretion remains an unsolved challenge in many industrial and residential applications. The iced area can vary from ~1 cm2 to many square meters depending on the situation, and this directly affects the ice debonding mechanism. The fracture of short interfaces is controlled by interfacial shear strength, whereas interfacial toughness dominates the fracture of longer interfaces. The transition from strength-controlled to toughness-controlled fracture occurs at a critical interfacial length. Here we study the fracture mechanics and debonding of ice from several polymeric materials evaluated by the common Zero-Degree Cone Test (ZDCT). Cohesive zone analyses assuming Dugdale-type and linear cohesive laws are performed in cylindrical coordinates. For most materials, the calculated critical length is smaller than the actual interfacial length previously used in the ZDCT, indicating that ice detachment was controlled by interfacial toughness. Good agreement was observed between the values of interfacial toughness calculated in the present study and those reported in the literature. From the data, lower bounds for the ice adhesion strengths are estimated based on the actual length of ice. Our analysis indicates that the prior fracture stresses measured using the ZDCT were not the material's ice adhesion strength, but rather the asymptotic detachment load per interfacial area. Overall, the zero-degree cone test should not be used to measure the ice adhesion strength with its prior or current dimensions, but is an excellent tool for characterizing the interfacial toughness between ice and a material.

Optimisation of aggregate gradation of ultra-high-performance concrete based on the modified compressible packing model

The compressible packing model (CPM), which is a method for designing aggregate gradation, was used to calculate the packing density of quartz aggregate. The aggregate gradation of ultra-high-performance concrete (UHPC) was optimised using the CPM. The number of interfaces between the aggregates and cement was determined using Image-Pro Plus software. The CPM modified using the equation Y = 0·60073X + 0·20551 was found to calculate the packing density of quartz aggregate accurately. The compressive strength of the UHPC was found to be positively correlated with the packing density of the aggregate: an increase in the packing density led to a compressive strength increase from 97·9 MPa to 124·1 MPa, an increase of 26·7%. The flexural strengths of the material was found to be sensitive to the number of interfaces: the smaller the number of interfaces, the greater the flexural strength. The specimen with an interface length of 5·56 mm/mm2 had the smallest flexural strength (21·5 MPa) and the specimen with an interface length of 3·596 mm/mm2 had the largest flexural strength (25·9 MPa). It is recommended that, when designing aggregate gradation, a gradation with high density should be selected and the proportion of small-size aggregates should not be too large.

The Effect of Surface Roughness on Immiscible Displacement Using Pore Scale Simulation

Pore scale immiscible displacement is crucial in oil industry. The surface roughness of throat is an important factor affecting water–oil interface movement. In this paper, the Navier–Stokes (N-S) equation coupled with the phase-field method is adopted to analyze the oil–water flow and interface movement in single channel, considering different surface roughness, diverse wettability and various capillary numbers. The simulation results show that the resistance increases significantly due to the surface roughness. The velocity of interface movement in rough channels is slower than that in smooth channels. The existence of asperities strengthens the interface deformation and promotes the formation of fingering phenomenon. The water flooding process presents different flow patterns in the rough channel with diverse wettability, and the influence of wall roughness on oil–water interface movement is different under various wettability conditions. There is an approximate exponential relationship between the ratio of interface length to channel length and capillary number. When the capillary number exceeds 0.03574, the phenomenon of viscous fingering is obvious, and the influence of capillary number is amplified by roughness.

Diffusion bonding of 304 austenitic stainless-steel using pressure pulses

Abstract The influence of bonding temperature during impulse pressure assisted diffusion bonding on characteristics of AISI 304 austenitic stainless steel has been reported in this paper. Austenitic stainless steel sheets were joined by impulse pressure assisted diffusion bonding in a temperature range of 850–950 °C. The bond interface was analyzed by tensile shear testing, optical microscope, field emission scanning electron microscope. The soundness of the diffusion bond was evaluated by calculating the interface bonding ratio (ratio of void free interface length to the total interface length). The effect of diffusion bonding temperature on tensile properties and interface bonding ratio was investigated. The maximum tensile shear load carrying capacity of the diffusion bond obtained was 34.42 kN at 950 °C. The structural analysis revealed good joint quality of the diffusion bonds and 91.25% bonding interface ratio at 950 °C bonding temperature.

Lattice Boltzmann Simulations of the Interface Dynamics During Two-Phase Flow in Porous Media

This paper systematically investigates the impact of porous media disorder and its coupling with flow rates, favorable and unfavorable viscosity ratios, as well as surface tensions on the dynamics of interfaces development during two-phase drainage flow. A special attention is paid to establishing relationship between the dynamics of fluid–fluid and fluid–solid interfacial lengths, the pore selectivity and the displacement efficiency using imaging of fluids distribution in porous media. As samples of study, we used artificially generated models of porous media with different disorder parameters and with two-types of pore-channels systems "— hexagonal and square. In our methodology, the disorder defines the range of grain size distribution and is applied to control the pore size range. For two-phase flow simulation, the lattice Boltzmann equations and the color-gradient model are applied. It was established the linear relationships between fluid–fluid and fluid–solid interfacial length and saturation of the invaded fluid. During numerical simulations at different disorders, the lack of disorder effect on the fluid–fluid interface dynamics and negative disorder impact on the fluid–solid interface dynamics was found. When varying the flow parameters, it was identified that the increase in the fluid–fluid interface dynamics is accompanied by a decrease in the fluid–solid interface dynamics. For all displacement mechanisms considered in this paper, except capillary fingering, an inverse relationship between pore selectivity and pore number, involved in displacement, was detected. We found a shift of pore selectivity towards higher values with increasing disorder which negatively impacts on the displacement efficiency. In capillary fingering regime, a strong tendency to minimize fluid–fluid interfacial length with surface tension explains the lack of relationship between pore selectivity and pore number which leads to bad predictable displacement efficiency in this regime.

An 8-bit Ring-Amplifier Based Mixed-Signal MAC Circuit With Full Digital Interface and Variable Accumulation Length

An 8-bit switched-capacitor multiply-and-accumulator (MAC) in 65nm CMOS is presented. Based on a cascaded low-power ring-amplifier-based switched-capacitor DACs, the MAC circuit features a programmable accumulation length in MAC computation. Fabricated in 65nm CMOS, the prototype MAC circuit achieves a precision-scaled energy efficiency of 1.32fJ per MAC operation, which is comparable to other state-of-the-art MAC circuits, along with best-in-class linearity. The noise performance has been verified using four real-world convolutional neural networks (CNNs) and 10,000-image data sets with up to 1,000 classes with an accuracy drop of less than 2% compared to the baseline 32-bit floating-point MAC.