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1

Rapid evaluation method of subgrade performance using Portable Falling Weight Deflectometer

100%

Bu B. , Shang H. , Liu S. , Liu K.

Archives of Civil Engineering

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2023

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tom Vol. 69, nr 4

619--633

EN

The performance evaluation of new and old subgrades is critical for the quality and safety of reconstruction and extension projects. It is necessary to achieve rapid and easy performance testing. In this study, a Portable Falling Weight Deflectometer (PFWD) is chosen to rapid evaluate the performance of subgrade. First, a testing area, the reconstruction and expansion project of the Hefei to Dagudian section of the Shanghai-Shaanxi Expressway, is selected. Then, the PFWD modulus Ep of resilient tested by PFWD and the corresponding water content w and compacting degree K tested by the cutting ring method for old subgrade are obtained. And the correlation relationship between Ep and w and K is established. The performance of old subgrade can be rapid obtained by PFWD. Meanwhile, for the new subgrade, the correlation relationship between Ep and bending value L, w and K is established, and the performance can also be rapid tested by PFWD. Finally, a rapid evaluation method for the reconstruction and expansion of subgrade performance was proposed, which aims to provide technical support for ensuring construction quality and safety and provides a technical reference and a theoretical basis for the prediction of similar subgrade performance.

2

An arbitrary waveform synthesis structure with high sampling rate and low spurious

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Zhao W. , Tian S. , Guo G. , You J. , Wu Q. , Liu K.

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tom Vol. 29, nr 1

159--173

EN

The arbitrary waveform generator is characterised by its flexible signal generation, high frequency resolution and rapid frequency switching speed and is wildly used in fields like communication, radar systems, quantum control, astronautics and biomedicine. With continuous development of technology, higher requirements are placed on to the arbitrary waveform generator. Sampling rate determines the bandwidth of the output signal, spurious-free dynamic range determines the quality of generated signal. Due to above, these two indicators’ improvement is vital. However, the existing waveform generation methods cannot generate signals with quality good enough due to their technical limitations, and in order to realize a high system sampling rate, to accomplish waveform generation process in FPGA, multipath parallel structure is needed. Therefore, we proposed a parallel waveform synthesis structure based on digital resampling, which fixed the problems existing in the current methods effectively and achieved a high sampling rate as well as high quality arbitrary waveform synthesis. We also built up an experimental test bench to validate the proposed structure.

3

The Effect of Green R&D Activities on China’s SO2 Emissions: Evidence from a Panel Threshold Model

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Chen S. , Liu K. , Ding D. , Yue Z. , Bo Z. , Tang Y.

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2021

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tom Vol. 16, nr 2

147--151

EN

Previous studies on the effectiveness of improving sustainable development have acknowledged the importance of domestic research and development (R&D) activities. However, these studies remain general and ambiguous because they assume that all R&D activities are related to energy-saving and sustainable development. The corresponding empirical evidence is scabrous and ambiguous. In this paper, we focus on the effect of green innovation R&D activities on SO2 emission which is an important greenhouse gas affect global climate change and eco-civilization. Considering that there is heterogeneity exists in the innovation activities, the R&D activities are divided into three performers with two purposes. The empirical results based on a Chinese inter-provincial dataset of 2000-2016 suggest that the green innovation R&D activities are crucial for the reduction of the SO2 emission. However, the innovation R&D activities of different purposes and performers show statistically differentiated effects on SO2 emission. The major positive effect of green innovation R&D activities on SO2 emissions reduction is mainly from enterprises and utility-type of R&D activities. A further study based on the panel threshold also indicates that effects of green innovation R&D activities on SO2 emissions are nonlinear, depending on the technology absorptive ability.

PL

Dotychczasowe badania nad zrównoważonym rozwojem potwierdziły znaczenie krajowych działań badawczo-rozwojowych (B + R). Jednak badania te pozostają ogólne i niejednoznaczne, ponieważ zakładają, że wszystkie działania B + R są związane z energooszczędnością i zrównoważonym rozwojem. Odpowiednie dowody empiryczne są niejednoznaczne. W artykule skupiamy się na wpływie działań badawczo-rozwojowych związanych z zielonymi innowacjami na emisję SO2, który jest ważnym gazem cieplarnianym, wpływającym na globalne zmiany klimatyczne. Biorąc pod uwagę, że istnieje heterogeniczność działań innowacyjnych, działalność B + R wskazano 3 aktorów z 2 celami. Wyniki empiryczne oparte na chińskim międzyprowincjalnym zbiorze danych z lat 2000-2016 sugerują, że działania badawczo-rozwojowe związane z zielonymi innowacjami są kluczowe dla redukcji emisji SO2. Jednak innowacyjne działania o różnych celach i różnych wykonawcach wykazują statystycznie zróżnicowany wpływ na emisję SO2. Główny pozytywny wpływ działań B + R w zakresie zielonych innowacji na redukcję emisji SO2 wynika głównie z działalności przedsiębiorstw i działalności B + R o charakterze użytkowym. Dalsze badanie oparte na panelu wskazuje również, że wpływ działań badawczo-rozwojowych związanych z zielonymi innowacjami na emisje SO2 jest nieliniowy, w zależności od zdolności absorpcyjnej technologii.

4

Interfacial enhancement technology in high‑volume fly ash foam concrete: microscopic mechanism and heavy metal safety assessment

63%

Huang D. m. , Liu K. , Wang C.-q. , Shen B.-h. , Zhao H. , Huang Q.-c. , Zhu Y. , Shui Z. h.

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2023

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tom Vol. 23, no. 1

art. no. e17, 2023

EN

Applying a large amount of fly ash to foam concrete can greatly reduce the engineering cost, but the proportion of fly ash is limited due to insufficient pozzolanic activity and heavy metal pollution. Therefore, this study used fly ash, portland cement, fly ash ceramsite, foaming agent, etc. as raw materials to design the mix ratio of large-volume fly ash foam concrete. The micro-interface enhancement mechanism was deeply analyzed, and a multi-method pollution assessment system was finally established for the risk assessment of heavy metals. The dry bulk density of the fly ash foam concrete prepared in this study was 894.5 kg/m3, the compressive strength was 4.22 MPa, and the thermal conductivity is 0.2213 W/(m K). These parameters all met the requirements of the Chinese standard “Foam Concrete” (JG/T 266-2011). The microscopic analysis results showed that, compared with the fly ash content of 60%, the foam concrete with 40% fly ash content had more rodlike ettringite at the interface of the pore wall, and its hydration products were distributed more uniformly. Similarly, the interface between the ceramsite mixed with 40% fly ash and the cement stone was more closely combined, the distribution of hydration products between the interfaces was more uniform, and the interface quality was higher. After adding thickener, the pore distribution of fly ash foam concrete was tight, and there were a lot of small pores between the pores, and the pore structure had better connectivity than when no thickener was added. The evaluation results of foamed concrete with 40% fly ash content with the aid of the multi-method pollution assessment system showed that the harmful heavy metals in fly ash were stably solidified in the silicate structure, resulting in low leaching efficiency. Finally, the performance of the high-volume fly ash foamed concrete slab produced according to the mix ratio designed in this study met the requirements of “Light weight panels for partition wall used in buildings” (GB/T 23,451-2009). Therefore, it is a safe and environmentally friendly high-performance building product.