Effect of surface treatment of recycled concrete aggregate by cement -silica fume slurry on compressive strength of concrete

Recycled concrete aggregate (RCA) used as an alternative to natural aggregate (NA) contains weak adhered mortar. The adhered mortar adversely affects the properties of RCA, and compressive strength of concrete with RCA. Therefore, a treatment method by coating surface of RCA with cement-silica fume slurry (CSS) at concentrations of 20, 40, and 60% was done to evaluate its effects on crushing value and water absorption of RCA, and compressive strength of concrete with treated RCA. The replacements of natural coarse aggregate by RCA for concrete production were 0, 25, and 50% by volume. Compressive strength of the concrete having a constant water-to-cement ratio of 0.35 was tested at ages of 3, 7, 28, and 56 days. Results showed that crushing value and water absorption of the treated RCA were more improved when compared with those of the untreated RCA due to new products formed from cement hydration and pozzolanic reactions on its surface detected by using scanning electron microscope. The surface treatment with CSS at concentration of 60% was the most effective method when compared with that with CSS at concentrations of 20 and 40%. The higher the concentration of CSS, the higher the compressive strength of concrete with the treated RCA. The treatment of RCA led to a significant improvement of compressive strength of the concrete at later ages (i.e., at 28 and 56 days) when compared with the concrete using untreated RCA

Effect of surface treatment of recycled concrete aggregate by cement -silica fume slurry on compressive strength of concrete

Recycled concrete aggregate (RCA) used as an alternative to natural aggregate (NA) contains weak adhered mortar. The adhered mortar adversely affects the properties of RCA, and compressive strength of concrete with RCA. Therefore, a treatment method by coating surface of RCA with cement-silica fume slurry (CSS) at concentrations of 20, 40, and 60% was done to evaluate its effects on crushing value and water absorption of RCA, and compressive strength of concrete with treated RCA. The replacements of natural coarse aggregate by RCA for concrete production were 0, 25, and 50% by volume. Compressive strength of the concrete having a constant water-to-cement ratio of 0.35 was tested at ages of 3, 7, 28, and 56 days. Results showed that crushing value and water absorption of the treated RCA were more improved when compared with those of the untreated RCA due to new products formed from cement hydration and pozzolanic reactions on its surface detected by using scanning electron microscope. The surface treatment with CSS at concentration of 60% was the most effective method when compared with that with CSS at concentrations of 20 and 40%. The higher the concentration of CSS, the higher the compressive strength of concrete with the treated RCA. The treatment of RCA led to a significant improvement of compressive strength of the concrete at later ages (i.e., at 28 and 56 days) when compared with the concrete using untreated RCA

Innovation and Productivity of Vietnamese Small and Medium Enterprises: Firm level panel data evidence

Innovation is considered as a driver of productivity at both country and firm level. However, the researches on the relationship between innovation and firm productivity in Vietnam are rare. Using Vietnam's SMEs survey in 2007 and 2009, this paper examines this relationship for the small and medium enterprises (SMEs). Cobb-Douglas production function and the fixed effect model are employed throughout the paper. We find that the presence of innovation has positive effects on firm productivity. In addition, this study also looks at the impact of firm size, firm location and manufacturing sector on the relationship between innovation and SMEs' productivity. Keywords: innovation, productivity, SMEs Vietnam JEL Classifications: D24; L60; O3

Soft Robotic Link with Controllable Transparency for Vision-based Tactile and Proximity Sensing

Robots have been brought to work close to humans in many scenarios. For coexistence and collaboration, robots should be safe and pleasant for humans to interact with. To this end, the robots could be both physically soft with multimodal sensing/perception, so that the robots could have better awareness of the surrounding environment, as well as to respond properly to humans' action/intention. This paper introduces a novel soft robotic link, named ProTac, that possesses multiple sensing modes: tactile and proximity sensing, based on computer vision and a functional material. These modalities come from a layered structure of a soft transparent silicon skin, a polymer dispersed liquid crystal (PDLC) film, and reflective markers. Here, the PDLC film can switch actively between the opaque and the transparent state, from which the tactile sensing and proximity sensing can be obtained by using cameras solely built inside the ProTac link. In this paper, inference algorithms for tactile proximity perception are introduced. Evaluation results of two sensing modalities demonstrated that, with a simple activation strategy, ProTac link could effectively perceive useful information from both approaching and in-contact obstacles. The proposed sensing device is expected to bring in ultimate solutions for design of robots with softness, whole-body and multimodal sensing, and safety control strategies.Comment: Submitted to RoboSoft 2023 for review. Final content subjected to chang

Improving Generative Flow Networks with Path Regularization

Generative Flow Networks (GFlowNets) are recently proposed models for learning stochastic policies that generate compositional objects by sequences of actions with the probability proportional to a given reward function. The central problem of GFlowNets is to improve their exploration and generalization. In this work, we propose a novel path regularization method based on optimal transport theory that places prior constraints on the underlying structure of the GFlowNets. The prior is designed to help the GFlowNets better discover the latent structure of the target distribution or enhance its ability to explore the environment in the context of active learning. The path regularization controls the flow in GFlowNets to generate more diverse and novel candidates via maximizing the optimal transport distances between two forward policies or to improve the generalization via minimizing the optimal transport distances. In addition, we derive an efficient implementation of the regularization by finding its closed form solutions in specific cases and a meaningful upper bound that can be used as an approximation to minimize the regularization term. We empirically demonstrate the advantage of our path regularization on a wide range of tasks, including synthetic hypergrid environment modeling, discrete probabilistic modeling, and biological sequence design.Comment: 28 pages, 2 figures, 5 tables. Anh Do, Duy Dinh, and Tan Nguyen contributed equally to this wor

Application of industrial enzymes in the traditional technology of alcohol from cooked sticky rice in Nam Dinh province, Vietnam

Based on the traditional technology of alcohol from cooked sticky rice in Nam Dinh province, Vietnam, the experiments were conducted by the way to kept the technological process as well as the proportion of ingredients. The quantity of the sticky rice for every experiments was 10 kg. The obtained results showed that the addition of 0.05% enzyme SEBflo-TL compared to the dry matter of sticky rice leads to an increase of the absolute anhydrous alcohol by 10%. Combined application of 0.05% enzyme SEBflo-TL and 0.08% SEBrew-GL for hydrolysing starch and β -glucan, the amount of obtained anhydrous alcohol is 4.6 liters compared to 4.0 liters in the sample control without enzyme application, yield increased by 15% and could provide significant economic benefits to wine producer. In other hand, after the first distillation, the fractional distillation reduced concentration of metanol, acetaldehyde and improved volatile compounds of producted alcohol. The finished alcohol met the Vietnam National technical regulation for alcoholic beverages and are unlikely to cause toxicity to consumers

Three-Dimensional Self-Standing and Conductive MnCO3@Graphene/CNT Networks for Flexible Asymmetric Supercapacitors

The practical applications of flexible supercapacitor depend strongly on the successful fabrication of advanced electrode materials with high electrochemical performance. Herein, three-dimensional conductive network-based self-standing MnCO3@graphene/CNT hybrid film fabricated through a combination of a hydrothermal method and vacuum filtration for flexible solid-state supercapacitors is reported. The MnCO3@graphene structure is embedded in a CNT network, in which monodispersed MnCO3 nanorod is well confined in graphene nanosheets. This hierarchical structure provides rapid electron/electrolyte ion transport pathways and exhibits excellent structural stability, resulting in rapid kinetics and a long life cycle. The MnCO3@graphene/CNT electrode delivers high specific capacity (467.2 F g–1 at 1 A g–1). Asymmetric supercapacitor (ASC) devices are assembled with the MnCO3@graphene/CNT film as positive electrode and activated carbon/carbon cloth as negative electrode, which exhibits a high energy density of 27 W h kg–1. Remarkably, 93% capacitance retention is obtained for the ASC devices after 6000 cycles