Simplified LDPC-assisted CNC algorithm for entropy-loaded discrete multi-tone in a 100G flexible-rate PON.

Passive optical networks (PONs) have been widely used in optical access networks to meet the requirement of the rapidly growing data traffic. However, the optical power budget of the worst optical network unit certainly limits the maximum capacity of PON. In this paper, we demonstrate a flexible-rate PON based on entropy-loaded clipping discrete multi-tone (DMT) for increasing the capacity. Meanwhile, clipping operation and simplified low-density parity-check (LDPC) assisted clipping-noise-cancellation (CNC) algorithm are proposed to improve the performance of DMT in peak-power constrained PON. In the simplified LDPC-assisted CNC algorithm, the iteration number of the sum-product algorithm in the LDPC decoding can be reduced to decrease the computational complexity almost without performance loss. The experimental results show that the simplified CNC algorithm can achieve approximately 1.8dB improvement of the optical receiver sensitivity at the 20% soft-decision forward-error-correction limit. The proposed flexible-rate PON has a wide-range data-rate adjustment from 12.5Gb/s to 100Gb/s under the optical power budget from 40dB to 26dB.

Elucidating the hornification mechanism of cellulosic fibers during the process of thermal drying.

Drying-induced hornification is an inevitable phenomenon of cellulosic fibers, which is used to describe internal aggregation structure changes of cellulosic fibers upon drying or water removal. To investigate the hornification process, never-dried cellulosic fibers with different components were thermally dried to different moisture contents. The results indicated that the hornification process could be divided into four stages, including the first crystallization period (>70% moisture), the cocrystallization period (70-31% moisture), the hemicellulose control period (31-11% moisture), and the second crystallization period (11-0% moisture). The decrease of water retention value (WRV) occurred in the cocrystallization period and the second crystallization period, which meant hornification happened in these two periods. Besides, hemicellulose and lignin inhibited hornification by reducing cellulose cocrystallization. The work elucidates the hornification process and mechanism of cellulosic fibers,which will be helpful to control the properties of cellulosic materials for extended utilization.

The influence of "thermal drying pretreatment" on enzymatic hydrolysis of cellulose and xylan in poplar fibers with high lignin content.

Thermal drying for lignocellulosic fibers is a common procedure in laboratories and factories, which isn't a pretreatment traditionally used to enhance cellulose conversion but inevitably occurs. This study investigated the effects of thermal drying conditions on the characteristics and enzymatic hydrolysis of lignocellulosic fiber granules with high lignin content. The results showed that fiber characteristics decreased linearly with the increase of temperature, which caused the linear reduction of enzymatic digestibility. Then, the increase of time caused the exponential decrease of fiber characteristics and enzymatic digestibility. Moreover, the reduction of initial water content obtained by centrifugation resulted in almost the same porosity and slightly increased water retention value (WRV) of fibers, which caused slight changes of lignocellulose digestibility. Finally, repeated drying and swelling led to complex changes in fiber characteristics, which caused fluctuations in enzymatic hydrolysis with a downward trend. This article will provide a reference for lignocellulose enzymatic hydrolysis.

Impact of centrifugation treatment on enzymatic hydrolysis of cellulose and xylan in poplar fibers with high lignin content.

Centrifugation is very common in the production and treatment of lignocellulose for applications like pretreatment for enzymatic hydrolysis, but it is not certain whether it affects applications of lignocellulose and almost no one realizes this problem. This study investigated the effects of centrifugation on the characteristics and enzymatic hydrolysis of poplar fibers with high lignin content. The results showed that centrifugation inhibited the enzymatic hydrolysis of fiber, but fiber characteristics and enzymatic digestibility fluctuated with increasing centrifugation time. Centrifugation for about 15 min had the least effect on fiber properties while centrifugation for 30 min had the least effect on enzymatic hydrolysis. The water retention value was closely related to the enzymatic digestibility, but the pore characteristics and crystallinity index could not reflect the enzymatic accessibility of the fiber. This article will provide useful references for the enzymatic hydrolysis of lignocellulose and other high-value applications to improve production efficiency furtherly.