Experimental and Numerical Investigation of Joints for a Pultruded Fiber-Reinforced Polymer Truss.

Bolted connections usually govern the structural rigidity and load-carrying capacity of pultruded glass fiber-reinforced polymer (GFRP) truss structures. In this study, a novel bolted integrated gusset plate (IGP) connection is proposed to enhance the stiffness and capacity of GFRP truss structures. Nine double-lap shear tests of GFRP joints and numerical simulation were conducted to investigate the influence of variable design parameters of the bolted GFRP joints (number of bolts, width and thickness of GFRP, edge distance of bolts, and the employment of adhesive). Three full-scale GFRP truss joints were tested under static loading to study the response of a typical bolted connection, a bolted gusset plate connection, and the proposed IGP connection. The nine double-lap shear tests showed that the bolted-bonded mixed connection has 50% higher shear stiffness and 27% higher ductility compared with bolted joints, and bearing failure dominated the capacity of most specimens, which agreed well with numerical simulation results. Tests on the three full-scale GFRP truss joints showed that the bolted gusset plate can substantially reduce the number of cracks and improve the initial stiffness, but the maximum bearing capacity of the joints did not increase because the shear fracture of pultruded GFRP webs governs the capacity. The proposed IGP substantially increased the stiffness and capacity compared with the bolted connection and typical bolted gusset plate connection. The full-scale GFRP joint test is suggested to be used together with direct shear tests to study the performance of joints of the GFRP truss.

1.27 kW, 2.2 GHz pseudo-random binary sequence phase modulated fiber amplifier with Brillouin gain-spectrum overlap.

We present a 2.2 GHz modulated, 1.27 kW output power, monolithic fiber amplifier based on pseudo-random binary sequence (PRBS) phase modulation. The spectral line spacing of maximizing the threshold enhancement factor (plateau of trend) was found by theoretical simulation. The spectral line spacing was adjusted to 12.7 MHz by a pattern length of n = 9, which is close to the plateau of trend in the proposed architecture. A 2.2 GHz low-pass radio frequency filter was used to control the FWHM of the seed. A four-stage Yb-doped fiber amplifier chain was established to boost a distributed Bragg reflector (DBR) laser and a distributed feedback (DFB) diode laser to 1.2 kW and 1.27 kW with a backward reflectively of <1‰, which shows a good suppression of SBS effect.

Biosynthesis of L-Erythrose by Assembly of Two Key Enzymes in Gluconobacter oxydans.

L-erythrose, a rare aldotetrose, possesses various pharmacological activities. However, efficient L-erythrose production is challenging. Currently, L-erythrose is produced by a two-step fermentation process from erythritol. Here, we describe a novel strategy for the production of L-erythrose in Gluconobacter oxydans (G. oxydans) by localizing the assembly of L-ribose isomerase (L-RI) to membrane-bound sorbitol dehydrogenase (SDH) via the protein-peptide interactions of the PDZ domain and PDZ ligand. To demonstrate this self-assembly, green fluorescent protein (GFP) replaced L-RI and its movement to membrane-bound SDH was observed by fluorescence microscopy. The final L-erythrose production was improved to 23.5 g/L with the stepwise metabolic engineering of G. oxydans, which was 1.4-fold higher than that obtained using coexpression of SDH and L-RI in G. oxydans. This self-assembly strategy shows remarkable potential for further improvement of L-erythrose production.

[Effect of alkaline treatment on anaerobic digestion of rice straw].

The biogas yields of rice straw during anaerobic digestion can be improved by alkaline pretreatment, while it increased the cost because of large amount of alkaline. In order to decrease the amount, 3 sets of experiments were performed using straw with alkaline treatment (pretreatment), digested straw with alkaline treatment (post-treatment) and straw digested directly (control). The results showed that cell wall of straw was destroyed by 5% NaOH treated for 48h, the COD (chemical oxygen demand), total nitrogen, NO(3-) -N and NH(4+) -N were increased from 2 311.11, 175.40, 5.02 and 117.82 mg/L to 10488.89, 417.84, 248.64 and 141.44 mg/L respectively. It suggested that not only lignocellulose but also some nitrogenous materials were destroyed or broken down by alkaline treatment. The lignin structure was destroyed through alkaline treatment that caused the decreased lignin, but the crystallinity index (C(r)I) of cellulose increased from 0.592 3 to 0.662 2. The results of anaerobic digestion showed that the total solid of straw decreased 50.47% after anaerobic digestion treatment leading to less workload and only 50% alkaline used. However, the biogas yield of post-treatment and pretreatment were 382.32 mL/g of TS(added) and 375.84 mL/g of TS(added). Lignin content of control increased while decreased in pretreatment and post-treatment. After anaerobic digestion, crystalline of cellulose was destroyed significantly, and crystalline and amorphous of post-treatment were destroyed more severely than that of pretreatment. From all those mentioned above, post-treatment of straw with alkaline was economical and feasible for biogas production.

Experimental co-digestion of corn stalk and vermicompost to improve biogas production.

Anaerobic co-digestion of corn stalk and vermicompost (VC) as well as mono-digestion of corn stalk were investigated. Batch mono-digestion experiments were performed at 35+/-1 degrees C and initial total solid loading (TSL) ranged from 1.2% to 6.0%. Batch co-digestion experiments were performed at 35+/-1 degrees C and initial TSL of 6% with VC proportions ranged from 20% to 80% of total solid (TS). For mono-digestion of corn stalk, a maximum methane yield of 217.60+/-13.87 mL/g TS(added) was obtained at initial TSL of 4.8%, and acidification was found at initial TSL of 6.0% with the lowest pH value of 5.10 on day 4. Co-digestion improved the methane yields by 4.42-58.61% via enhancing volatile fatty acids (VFAs) concentration and pH value compared with mono-digestion of corn stalk. The maximum biogas yield of 410.30+/-11.01 mL/g TS(added) and methane yield of 259.35+/-13.85 mL/g TS(added) were obtained for 40% VC addition. Structure analysis by X-ray diffractometry (XRD) showed that the lowest crystallinity of 35.04 of digested corn stalk was obtained from co-digestion with 40% VC, which decreased 29.4% compared to 49.6 obtained from un-treated corn stalk. It is concluded that co-digestion with VC is beneficial for improving biodigestibility and methane yield from corn stalk.

[Anaerobic co-digestion of corn stalk and vermicompost].

The characteristics of corn stalk digested alone at different total solid (TS) loading rates and co-digestion of various proportions of corn stalk and vermicompost were investigated by batch model at 35 degrees C +/- 1 degrees C. The organic loading rates (OLRs) studied were in the range of 1.2%-6.0% TS and increasing proportions of vermicompost from 20% to 80% TS. A maximum methane yield of corn stalk digested alone was 217.60 mL/g obtained at the TS loading rate of 4.8%. However, when the TS loading rate was 6.0%, the anaerobic system was acidified and the lowest pH value was 5.10 obtained on day 4 and the biogas productivity decreased. Furthermore, co-digestion of vermicompost and corn stalk in varying proportions were investigated at constant of 6.0% TS. Co-digestion with vermicompost improved the biodegradability of corn stalk and the methane yield was improved by 4.42%-58.61%, and led to higher pH values, higher volatile fatty acids (VFAs) concentration and lower alkalinity content compared with corn stalk digested alone. The maximum biogas yield and methane yield of 410.30 mL/g and 259. 35 mL/g were obtained for 40% vermicompost and 60% corn stalk respectively. Compared with corn stalk digested alone, co-digested with vermicompost didn' t affect methane content and the fermentation type, but promoted the destruction of crystalline of cellulose and the highest destruction rate was 29.36% for 40% vermicompost and 60% corn stalk. Therefore, adding vermicompost was beneficial for the decomposition and increasing the biotransformation rate of corn stalk.

[Effect of cow feces on anaerobic digestion process of Spartina alterniflora].

Effects of cow feces on anaerobic digestion process of Spartina alterniflora was studied by batch model at 35 degrees C. When Spartina alterniflora was digested alone, the biogas yield was 222.61 mL/g, and it was acidified from 10 d to 15 d. When cow feces was added, the environment where microorganisms lived in was meliorated, pH value was stabilized and biogas production was improved by 38.83%. Volatile fatty acids production was not affected significantly, but the peak was advanced. FTIR and XRD analysis of solid residue substances further proved that co-digestion promoted the removal of carbohydrates and resulted in higher content of lignin than Spartina alterniflora straw digested alone, and promoted the destruction of crystalline of cellulose. The crystallinity index (C(x)I) of Spartina alterniflora, digested Spartina alterniflora and co-digested Spartina alterniflora were 0.617 6, 0.6200 and 0.615 4, respectively. Therefore, adding cow feces was beneficial for the decomposition and increasing the biotransformation rate of Spartina alterniflora straw.