Effects of Long-Term Fertilizer Practices on Rhizosphere Soil Autotrophic CO₂-Fixing Bacteria under Double Rice Ecosystem in Southern China

( Haiming Tang ),( Li Wen ),( Lihong Shi ),( Chao Li ),( Kaikai Cheng ),( Weiyan Li ),( Xiaoping Xiao ) 한국미생물생명공학회 2022 Journal of microbiology and biotechnology Vol.32 No.10

Soil autotrophic bacterial communities play a significant role in the soil carbon (C) cycle in paddy fields, but little is known about how rhizosphere soil microorganisms respond to different long-term (35 years) fertilization practices under double rice cropping ecosystems in southern China. Here, we investigated the variation characteristics of rhizosphere soil RubisCO gene cbbL in the double rice ecosystems of in southern China where such fertilization practices are used. For this experiment we set up the following fertilizer regime: without any fertilizer input as a control (CK), inorganic fertilizer (MF), straw returning (RF), and organic and inorganic fertilizer (OM). We found that abundances of cbbL, 16S rRNA genes and RubisCO activity in rhizosphere soil with OM, RF and MF treatments were significantly higher than that of CK treatment. The abundances of cbbL and 16S rRNA genes in rhizosphere soil with OM treatment were 5.46 and 3.64 times higher than that of CK treatment, respectively. Rhizosphere soil RubisCO activity with OM and RF treatments increased by 50.56 and 45.22%, compared to CK treatment. Shannon and Chao1 indices for rhizosphere soil cbbL libraries with RF and OM treatments increased by 44.28, 28.56, 29.60, and 23.13% compared to CK treatment. Rhizosphere soil cbbL sequences with MF, RF and OM treatments mainly belonged to Variovorax paradoxus, uncultured proteobacterium, Ralstonia pickettii, Thermononospora curvata, and Azoarcus sp.KH33C. Meanwhile, cbbL-carrying bacterial composition was obviously influenced by soil bulk density, rhizosphere soil dissolved organic C, soil organic C, and microbial biomass C contents. Fertilizer practices were the principal factor influencing rhizosphere soil cbbL-carrying bacterial communities. These results showed that rhizosphere soil autotrophic bacterial communities were significantly changed under conditions of different long-term fertilization practices Therefore, increasing rhizosphere soil autotrophic bacteria community with crop residue and organic manure practices was found to be beneficial for management of double rice ecosystems in southern China.

A CYCLIC AND SIMULTANEOUS ITERATIVE ALGORITHM FOR THE MULTIPLE SPLIT COMMON FIXED POINT PROBLEM OF DEMICONTRACTIVE MAPPINGS

Tang, Yu-Chao,Peng, Ji-Gen,Liu, Li-Wei Korean Mathematical Society 2014 대한수학회보 Vol.51 No.5

The purpose of this paper is to address the multiple split common fixed point problem. We present two different methods to approximate a solution of the problem. One is cyclic iteration method; the other is simultaneous iteration method. Under appropriate assumptions on the operators and iterative parameters, we prove both the proposed algorithms converge to the solution of the multiple split common fixed point problem. Our results generalize and improve some known results in the literatures.

Investigation on correlation between pulse velocity and compressive strength of concrete using ANNs

Chao-Wei Tang,Yiching Lin,Shih-Fang Kuo 한국계산역학회 2007 Computers and Concrete, An International Journal Vol.4 No.6

The ultrasonic pulse velocity method has been widely used to evaluate the quality of concrete and assess the structural integrity of concrete structures. But its use for predicting strength is still limited since there are many variables affecting the relationship between strength and pulse velocity of concrete. This study is focused on establishing a complicated correlation between known input data, such as pulse velocity and mixture proportions of concrete, and a certain output (compressive strength of concrete) using artificial neural networks (ANN). In addition, the results predicted by the developed multilayer perceptrons (MLP) networks are compared with those by conventional regression analysis. The result shows that the correlation between pulse velocity and compressive strength of concrete at various ages can be well established by using ANN and the accuracy of the estimates depends on the quality of the information used to train the network. Moreover, compared with the conventional approach, the proposed method gives a better prediction, both in terms of coefficients of determination and root-mean-square error.

Residual properties of high-strength fiber reinforced concrete after exposure to high temperatures

Chao-Wei Tang 사단법인 한국계산역학회 2019 Computers and Concrete, An International Journal Vol.24 No.1

Thermal energy from high temperatures can cause concrete damage, including mechanical and chemical degradation. In view of this, the residual mechanical properties of high-strength fiber reinforced concrete with a design strength of 75 MPa exposed to 400-800°C were investigated in this study. The test results show that the average residual compressive strength of high-strength fiber reinforced concrete after being exposed to 400-800°C was 88%, 69%, and 23% of roomtemperature strength, respectively. In addition, the benefit of steel fibers on the residual compressive strength of concrete was limited, but polypropylene fibers can help to maintain the residual compressive strength and flexural strength of concrete after exposure to 400-600°C. Further, the load-deflection curve of specimen containing steel fibers exposed to 400-800°C had a better fracture toughness.

Fire resistance of high strength concrete filled steel tubular columns under combined temperature and loading

Chao-Wei Tang 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.2

In recent years, concrete-filled box or tubular columns have been commonly used in high-rise buildings. However, a number of fire test results show that there are significant differences between high strength concrete (HSC) and normal strength concrete (NSC) after being subjected to high temperatures. Therefore, this paper presents an investigation on the fire resistance of HSC filled steel tubular columns (CFTCs) under combined temperature and loading. Two groups of full-size specimens were fabricated to consider the effect of type of concrete infilling (plain and reinforced) and the load level on the fire resistance of CFTCs. Prior to fire test, a constant compressive load (i.e., load level for fire design) was applied to the column specimens. Thermal load was then applied on the column specimens in form of ISO 834 standard fire curve in a large-scale laboratory furnace until the set experiment termination condition was reached. The results demonstrate that the higher the axial load level, the worse the fire resistance. Moreover, in the bar-reinforced concrete-filled steel tubular columns, the presence of rebars not only decreased the spread of cracks and the sudden loss of strength, but also contributed to the load-carrying capacity of the concrete core.

Local bond-slip behavior of medium and high strength fiber reinforced concrete after exposure to high temperatures

Chao-Wei Tang 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.4

This study aims to investigate the influence of individual and hybrid fiber on the local bond–slip behavior of medium and high strength concrete after exposure to different high temperatures. Tests were conducted on local pullout specimens (150 mm cubes) with a reinforcing bar embedded in the center section. The embedment lengths in the pullout specimens were three times the bar diameter. The parameters investigated include concrete type (control group: ordinary concrete; experimental group: fiber concrete), concrete strength, fiber type and targeted temperature. The test results showed that the ultimate bond stress in the local bond stress versus slip curve of the high strength fiber reinforced concrete was higher than that of the medium strength fiber reinforced concrete. In addition, the use of hybrid combinations of steel fiber and polypropylene fiber can enhance the residual bond strength ratio of high strength concrete.

Hydration properties of cement pastes containing high-volume mineral admixtures

Chao-Wei Tang 사단법인 한국계산역학회 2010 Computers and Concrete, An International Journal Vol.7 No.1

This research aimed to investigate the influence of high-volume mineral admixtures (MAs), i.e., fly ash and slag, on the hydration characteristics and microstructures of cement pastes. Degree of cement hydration was quantified by the loss-on-ignition technique and degree of pozzolanic reaction was determined by a selective dissolution method. The influence of MAs on the pore structure of paste was measured by mercury intrusion porosimetry. The results showed that the hydration properties of the blended pastes were a function of water to binder ratio, cement replacement level by MAs, and curing age. Pastes containing fly ash exhibited strongly reduced early strength, especially for mix with 45% fly ash. Moreover, at a similar cement replacement level, slag incorporated cement paste showed higher degrees of cement hydration and pozzolanic reaction than that of fly ash incorporated cement paste. Thus, the present study demonstrates that high substitution rates of slag for cement result in better effects on the short- and long-term hydration properties of cement pastes.

Effect of presoaking degree of lightweight aggregate on the properties of lightweight aggregate concrete

Chao-Wei Tang 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.1

This study aimed at exploring the effect of presoaking degree of lightweight aggregate (LWA) on the fresh and hardened properties of concrete. Two series (i.e., Series A and Series B) of concrete mixes that were made of LWA with different moisture states were prepared. The presoaking degree of LWA was divided into three types: oven dry state, 1 hour prewetted and 24 hours prewetted. For the Series A, the water content of the lightweight aggregate concrete (LWAC) mixes was adjusted in accordance with the moisture condition of the LWA. Whereas the amount of water added in the Series B mixes was deliberately not adjusted for the moisture condition of the LWA. Slump test, mechanical tests, interfacial transition zone microscopical tests and thermal conductivity test were carried out on the specimens of different concretes and compared with control normal-weight aggregate concretes. The test results showed that the effect of mixing water absorption by LWA with different moisture states was reflected in the fresh concrete as the loss of mixture workability, while in the hardened concrete as the increase of its strength. With the use of oven-dried LWA, the effect of reduction of water-cement ratio was more significant, and thus the microstructure of the ITZ was more compact.

Mix design and early-age mechanical properties of ultra-high performance concrete

Tang, Chao-Wei Techno-Press 2021 Advances in concrete construction Vol.11 No.4

It is known from the literature that there are relatively few studies on the engineering properties of ultra-high performance concrete (UHPC) in early age. In fact, in order to ensure the safety of UHPC during construction and sufficient durability and long-term performance, it is necessary to explore the early behavior of UHPC. The test parameters (test control factors) investigated included the percentage of cement replaced by silica fume (SF), the percentage of cement replaced by ultra-fine silica powder (SFP), the amount of steel fiber (volume percent), and the amount of polypropylene fiber (volume percentage). The engineering properties of UHPC in the fresh mixing stage and at the age of 7 days were investigated. These properties include freshly mixed properties (slump, slump flow, and unit weight) and hardened mechanical properties (compressive strength, elastic modulus, flexural strength, and splitting tensile strength). Moreover, the effects of the experimental factors on the performance of the tested UHPC were evaluated by range analysis and variance analysis. The experiment results showed that the compressive strength of the C8 mix at the age of 7 days was highest of 111.5 MPa, and the compressive strength of the C1 mix at the age of 28 days was the highest of 128.1 MPa. In addition, the 28-day compressive strength in each experimental group increased by 13%-34% compared to the 7-day compressive strength. In terms of hardened mechanical properties, the performance of each experimental group was superior to that of the control group (without fiber and without additional binder materials), with considerable improvement, and the experimental group did not produce explosive or brittle damage after the test. Further, the flexural test process found that all test specimens exhibited deflection-hardening behavior, resulting in continued to increase carrying capacity after the first crack.

Alkyl-substituted carbazole/pyridine hybrid host materials for efficient solution-processable blue- and green-emitting phosphorescent OLEDs

Chao Tang,Jianmei Chen,Yuxin Li,Xinchao Liu,Lili Zhang,Fangfang Wang,Jia Hu,Xudong Cao,Tao Jiang 대한금속·재료학회 2021 ELECTRONIC MATERIALS LETTERS Vol.17 No.2

Three new pyridine-cored alkyl-substituted carbazole derivatives of 2,6-bis(2,7-dimethyl-9H-carbazol-9-yl)pyridine(2,7-MeCzPy), 2,6-bis(3,6-dimethyl-9H-carbazol-9-yl) pyridine (3,6-MeCzPy) and 2,6-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)pyridine (3,6-tBuCzPy) were synthesized by means of connecting methyl or tert-butyl substituents on the3,6 or 2,7 positions of carbazole with pyridine ring as the core. The influence of different alkyl and linkages modeon the thermal, photophysical, electrochemical properties and devices electrolumiescent (EL) performances of thecompounds were comprehensively studied. In solution-processed blue or green phosphorescent organic light-emittingdiodes (PHOLEDs) with bis[2-(4,6-difluorophenyl)-pyridinato-N,C2] picolinate iridium(III) (FIrpic) or fac-tris(2-phenylpyridine)iridium (Ir(ppy)3) as phosphorescent dopants, EL performances follow the same sequence of 2,7-MeCzPy> 3,6-tBuCzPy > 3,6-MeCzPy, the trend is consistent with the value of triplet energies (ET). Devices hosted by2,7-MeCzPy achieving the best EL performance, exhibited maxima 13.6 cd A−1 and 7.0 lm W−1 for current efficiency(CE) and power efficiency (PE) in blue PHOLEDs, maxima 26.2 cd A−1 and 16.2 lm W−1 for CE and PE in greenPHOLEDs.