Patient-specific computational flow analysis of coronary arteries with time-dependent medical-image data can provide valuable information to doctors making treatment decisions. Reliable computational ...analysis requires a good core method, high-fidelity space and time discretizations, and an anatomically realistic representation of the lumen motion. The space–time variational multiscale (ST-VMS) method has a good track record as a core method. The ST framework, in a general context, provides higher-order accuracy. The VMS feature of the ST-VMS addresses the computational challenges associated with the multiscale nature of the unsteady flow in the artery. The moving-mesh feature of the ST framework enables high-resolution flow computation near the moving fluid–solid interfaces. The ST isogeometric analysis is a superior discretization method. With IGA basis functions in space, it enables more accurate representation of the lumen geometry and increased accuracy in the flow solution. With IGA basis functions in time, it enables a smoother representation of the lumen motion and a mesh motion consistent with that. With cubic NURBS in time, we obtain a continuous acceleration from the lumen-motion representation. Here we focus on making the lumen-motion representation anatomically realistic. We present a method to obtain from medical-image data in discrete form an anatomically realistic NURBS representation of the lumen motion, without sudden, unrealistic changes introduced by the higher-order representation. In the discrete projection from the medical-image data to the NURBS representation, we supplement the least-squares terms with two penalty terms, corresponding to the first and second time derivatives of the control-point trajectories. The penalty terms help us avoid the sudden unrealistic changes. The computation we present demonstrates the effectiveness of the method.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Four-dimensional (4D) printing, a new technology emerged from additive manufacturing (3D printing), is widely known for its capability of programming post-fabrication shape-changing into artifacts. ...Fused deposition modeling (FDM)-based 4D printing, in particular, uses thermoplastics to produce artifacts and requires computational analysis to assist the design processes of complex geometries. However, these artifacts are weak against structural loads, and the design quality can be limited by less accurate material models and numerical simulations. To address these issues, this paper propounds a composite structure design made of two materials – polylactic acid (PLA) and carbon fiber reinforced PLA (CFPLA) – to increase the structural strength of 4D printed artifacts and a workflow composed of several physical experiments and series of dynamic mechanical analysis (DMA) to characterize materials. We apply this workflow to 3D printed samples fabricated with different printed parameters to accurately characterize the materials and implement a sequential finite element analysis (FEA) to achieve accurate simulations. The accuracy of deformation induced by the triggering process is both computationally and experimentally verified with several creative design examples and is measured to be at least 95%, with a confidence interval of (0.972,0.985). We believe the presented workflow is essential to the combination of geometry, material mechanism and design, and has various potential applications.
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•A novel workflow is proposed for forward design, with accurate material property characterization and precise FEA simulation. This workflow supports robust and accurate fabrication of the designed object through an iterative optimization process and accurate control of the final configuration.•The material properties of 3D printing polymers, including both PLA and CFPLA, are characterized in a precise way based on the DMA experiments. The characterization results are effectively incorporated into FEA with accurate mathematical models.•A sequential FEA is developed to achieve accurate simulation results, considering both the residual stress releasing and the body force creeping. We simulate these two processes in a sequence to precisely derive the final deformation of the fabricated product.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Magnetoelectric (ME) sensors cannot effectively detect broadband magnetic field signals due to their narrow bandwidth, and existing readout circuits are unable to vary the bandwidth of the sensors. ...To expand the bandwidth, this paper introduces a negative-feedback readout circuit, fabricated by introducing a negative-feedback compensation circuit based on the direct readout circuit of the ME sensor. The negative-feedback compensation circuit contains a current amplifier, a feedback resistor, and a feedback coil. For this purpose, a Metglas/PVDF/Metglas ME sensor was prepared. Experimental measurements show that there is a six-fold difference between the maximum and minimum values of the ME voltage coefficients in the 6-39 kHz frequency band for the ME sensor without the negative-feedback compensation circuit when the sensor operates at the optimal bias magnetic field. However, the ME voltage coefficient in this band remains stable, at 900 V/T, after the charge amplification of the direct-reading circuit and the negative-feedback circuit. In addition, experimental results show that this negative-feedback readout circuit does not increase the equivalent magnetic noise of the sensor, with a noise level of 240 pT/√Hz in the frequency band lower than 25 kHz, 63 pT/√Hz around the resonance frequency of 30 kHz, and 620 pT/√Hz at 39 kHz. This paper proposes a negative-feedback readout circuit based on the direct readout circuit, which greatly increases the bandwidth of ME sensors and promotes the widespread application of ME sensors in the fields of broadband weak magnetic signal detection and DBS electrode positioning.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
This paper proposes a model predictive control method based on dynamic multi-objective optimization algorithms (MPC_CPDMO-NSGA-II) for reducing freeway congestion and relieving environment impact ...simultaneously. A new dynamic multi-objective optimization algorithm based on clustering and prediction with NSGA-II (CPDMO-NSGA-II) is proposed. The proposed CPDMO-NSGA-II algorithm is used to realize on-line optimization at each control step in model predictive control. The performance indicators considered in model predictive control consists of total time spent, total travel distance, total emissions and total fuel consumption. Then TOPSIS method is adopted to select an optimal solution from Pareto front obtained from MPC_CPDMO-NSGA-II algorithm and is applied to the VISSIM environment. The control strategies are variable speed limit (VSL) and ramp metering (RM). In order to verify the performance of the proposed algorithm, the proposed algorithm is tested under the simulation environment originated from a real freeway network in Shanghai with one on-ramp. The result is compared with fixed speed limit strategy and single optimization method respectively. Simulation results show that it can effectively alleviate traffic congestion, reduce emissions and fuel consumption, as compared with fixed speed limit strategy and classical model predictive control method based on single optimization method.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
We use continuous night light data and LandScan population data to construct a monocentric index to measure whether a city tends to be a monocentric or polycentric spatial structure, and estimate the ...impact of such structure on energy efficiency by using a two-way fixed effects model. In order to solve the endogeneity of urban structure, the historical census data and topographic relief data at the city level are used to construct the instrumental variables. We find that an increase in the urban monocentricity index would significantly reduce the level of the urban energy intensity. Meanwhile, the relationship between monocentricity and urban energy intensity is U-shaped. When the degree of monocentricity is at relatively low level, its impact on energy efficiency is positive, implying the dominance of agglomeration effect. When economic agglomeration is greater than a certain degree, the impact of monocentricity becomes negative which results from the dominance of congestion effect. Moreover, impact of urban structure on energy intensity varies with urban population density. An increase in population density would weaken the negative impact of monocentricity on energy intensity, that is, in sparsely populated cities, the monocentricity is more conducive to energy saving. In terms of city form, monocentric structure may improve energy efficiency in the cities with poor transportation infrastructure more than in the cities with good transportation infrastructure. Monocentricity facilitates energy efficiency primarily by increasing corporate innovation and saving commuting time and distance. We perform a series of robustness tests and the findings are basically consistent with the baseline result. Our findings suggest that the cities at this stage should continue to strengthen the development of monocentricity, pay attention to compactness of urban spatial structure, and develop the polycentric structure cautiously. Meanwhile, in the development process, the local population density and the carrying capacity of the transportation infrastructure should be taken into consideration to avoid the negative effects caused by the congestion in main center.
•A monocentric index to measure whether cities tend to be a monocentric or polycentric spatial structure is constructed using continuous night light and LandScan population data.•The monocentric structure is associated with a lower level of energy intensity, and the relationship between monocentricity degree and energy intensity is U-shaped.•The historical census data and topographic relief data is used to construct the IVs in 2SLS, and the system-GMM and spatial correlation models is employed to address the time and space lag effects of energy intensity, making the empirical evidence more reliable.•Population density plays an important moderating role in this relationship: the increase of urban population density significantly weakens the negative effect of monocentricity on energy intensity.•Compared with polycentric structure, the promotion of innovation and saving commuting time and distance among centers are effective ways for a monocentric structure to affect energy efficiency.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The development of renewable, hydrophobic, and biodegradable intelligent packaging materials as an alternative to petroleum-based plastic products has become a new research focus in recent years, but ...remains a challenge. Herein, regenerated cellulose/curcumin composite films were fabricated by dispersing hydrophobic curcumin uniformly in a hydrophilic cellulose matrix using an aqueous alkali/urea solvent based on the pH-driven principle of curcumin. In addition, a unilateral hydrophobic modification was carried out using chemical vapor deposition of methyltrichlorosilane to obtain Janus structure. The composite films exhibited high transparency in the visible light spectrum, excellent antioxidation, thermal stability, mechanical strength, gas barrier properties, and antibacterial activity. Furthermore, the films demonstrated the capability to lower the overall levels of volatile basic nitrogen in stored fish. The color of the films shifted from a pale yellow to a reddish-brown over time during storage. The composite films can be completely degraded after approximately 98 days in soil with an average environmental temperature of 29 °C. This work provided a facile strategy to prepare biodegradable cellulose/curcumin films with Janus structure as packaging materials which could preserve the freshness of food products while offering visual monitor of their freshness in real-time.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Fused deposition modeling (FDM)-based 4D printing uses thermoplastics to produce artifacts and requires computational analysis to assist its design processes of complex geometries. Previously, finite ...element analysis (FEA) has been used to simulate 4D printing deformations, and its accuracy has been computationally and experimentally verified. However, using FEA also leads to several limitations, such as geometric approximation error and the computational time-cost due to the high degrees of freedom. To address these issues, this paper introduces isogeometric analysis (IGA) into the deformation simulations and propounds a composite design by hybridizing FEA and IGA elements to reduce the number of degrees of freedom while maintaining the simulation accuracy. Moreover, since the hybrid IGA-FEA method used for modeling 4D printing structure deformation excludes real-time interactivity, we develop a polycube-based random forest regressor machine learning (ML) model to learn the IGA-FEA-based structural mechanics simulations and provide fast deformation predictions. Given the input actuator block distribution and geometry configurations, our well-trained model can predict the residual stress-induced deformation behaviors of mesh-like thermoplastic composite structures. With an error less than 0.11% and computation speed 20 times faster than hybrid IGA-FEA simulations, our model can create real-time (0.93 s) and truthful (99.89% accuracy) results. The effectiveness of the proposed model is demonstrated with several complex design examples. We believe the presented workflow effectively combines IGA, FEA, ML, and 4D printing to provide a powerful computational tool that enriches the 4D printing design tool box, and brings huge application potentials.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The prevalence of plastics in the oceans has significantly intensified microplastic pollution, contributing to broader marine secondary pollution issues. This paper examines how plastic structure ...affects the aging characteristics of plastics and the release of metal ions, to better understand this secondary source of marine pollution. This study simulate the photoaging of plastics in natural environments, focusing on aliphatic and aromatic polymers. The results showed that the photodegradation degree was higher for aliphatic than aromatic polymers. All polymers contained thirteen detectable metals, with their release increasing over time due to photoaging, The release dynamics of these metal ions correlated more strongly with the level of polymer degradation rather than with the polymer structure itself, adhering to a second-order kinetic model driven by surface and intraparticle diffusion processes. The results will help control and treat marine plastic pollution.
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•The photodegradation degree of the aliphatic polymer is higher than the aromatic.•The release of metal additives increases with the photoaging process.•The degree of degradation of polymer affects the release of metal.•The metal ion release kinetics conform to the second-order kinetic model.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Natural bacteria have been utilized to directly maintain the human body’s homeostasis for directly or indirectly relieving diseases throughout history. With the rapid development of genetic ...engineering and synthetic materials modification, the recent era has witnessed numerous hybrid bacteria designed to meet the clinical requirements with expanded functionality in treating dozens of diseases, including obesity, gastrointestinal disorders, and even cancers. This review outlined the characteristics and applications of natural bacteria-based drugs in treating different disease conditions and summarized different conjugation methods of hybrid bacteria and their fate in vivo through multiple administration routes. Moreover, therapeutic bacteria-based complex disease treatments were also discussed to reveal the importance and feasibility of these biotherapeutics. Finally, the challenges in the clinical applications of bacterial drugs were discussed. The current review further highlighted the forward-looking solution strategies for bacterial bio-therapy to accelerate its clinical usage.
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•Emphasizing the characteristics and applications of natural bacteria-based drugs in treatment.•Summarizing different conjugations of hybrid bacteria and their in vivo fate via multiple administration routes.•Comprehensively reviewing the clinical applications of bacterial drugs and discussing the challenges of bacterial drugs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The target of this study is to gain a deeper understanding of the micro-dissolution process of cellulose in alkaline aqueous solutions and to develop a novel method for extracting cellulose ...nanofibrils (CNFs). Herein, the dissolution process of cellulose in alkaline aqueous solutions will be controlled by varying the temperature, and the undissolved cellulose will be analyzed to reveal the microscopic dissolution process of cellulose, and a novel process for extracting cellulose nanofibrils (CNFs) will be developed based on the findings. The crystalline structure of cellulose was gradually disrupted as the dissolution progressed, and the crystal form of cellulose changed gradually from cellulose I to cellulose II during the dissolution process, while all undissolved cellulose crystals remained as cellulose I. Cellulose, after its structure is disrupted during the dissolution process, will inevitably decompose into CNFs, and the microscopic dissolution process of cellulose follows a “top-down” dissolution sequence. The CNFs extraction method developed in this study can extract CNFs with high yield (>60 %) in a stable manner, as well as narrow particle size distribution, high crystallinity (>77 %), and good thermal stability. This study enhances the comprehension of the dissolution process of cellulose and paves a possible way for industrialization of CNFs production.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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