Improving fermentative hydrogen and methane production from an algal bloom through hydrothermal/steam acid pretreatment

Algal blooms can be harvested as renewable biomass waste for gaseous biofuel production. However, the rigid cell structure of raw algae may hinder efficient microbial conversion for production of biohydrogen and biomethane. To improve the energy conversion efficiency, biomass from an algal bloom in Dianchi Lake was subjected to a hydrothermal/steam acid pretreatment prior to sequential dark hydrogen fermentation and anaerobic digestion. Results from X-ray diffraction and Fourier transform infrared spectroscopy suggest that hydrothermal acid pretreatment leads to stronger damage of the amorphous structure (including hemicellulose and amorphous cellulose) due to the acid pretreatment, as evidenced by the higher crystallinity index. Scanning electron microscopy analysis showed that smaller fragments (∼5 mm) and wider cell gaps (∼1 μm) on algal cell surfaces occurred after pretreatment. In comparison to steam acid pretreatment, hydrothermal acid pretreatment resulted in a maximum energy conversion efficiency of 44.1% as well as production of 24.96 mL H2/g total volatile solids (TVS) and 299.88 mL CH4/g TVS

5 V Compatible Two-Axis PZT Driven MEMS Scanning Mirror with Mechanical Leverage Structure for Miniature LiDAR Application

The MEMS (Micro-Electronical Mechanical System) scanning mirror is an optical MEMS device that can scan laser beams across one or two dimensions. MEMS scanning mirrors can be applied in a variety of applications, such as laser display, bio-medical imaging and Light Detection and Ranging (LiDAR). These commercial applications have recently created a great demand for low-driving-voltage and low-power MEMS mirrors. However, no reported two-axis MEMS scanning mirror is available for usage in a universal supplying voltage such as 5 V. In this paper, we present an ultra-low voltage driven two-axis MEMS scanning mirror which is 5 V compatible. In order to realize low voltage and low power, a two-axis MEMS scanning mirror with mechanical leverage driven by PZT (Lead zirconate titanate) ceramic is designed, modeled, fabricated and characterized. To further decrease the power of the MEMS scanning mirror, a new method of impedance matching for PZT ceramic driven by a two-frequency mixed signal is established. As experimental results show, this MEMS scanning mirror reaches a two-axis scanning angle of 41.9° × 40.3° at a total driving voltage of 4.2 Vpp and total power of 16 mW. The effective diameter of reflection of the mirror is 2 mm and the operating frequencies of two-axis scanning are 947.51 Hz and 1464.66 Hz, respectively

Design of the Supporting Structures for Large and Unusually Shaped Foundation Pit near the Yangtze River

A large underground transportation hub is located on the west side of the Nanjing Youth Olympic Center, which is close to the embankment of the Yangtze River. The near-surface primarily comprises newly deposited soft soil of considerable thickness; the lower part is a riverbed-phase sandy soil containing two confined aquifers. The foundation pit requires deep excavation and has unusual shapes of “pit in pit” and “pit leaning pit.” For the convenience and safety of excavation, the piezometric head of the upper confined aquifer, where the pit bottom is located, reached 1 m below the bottom plane through precipitation, while that of the lower confined aquifer also dewatered down to a safe water level to avoid an uplift problem. After considering the engineering geological conditions, the function and shape of the foundation pits, we divided the soil layers of the foundation pits into two areas (the NW area and the SE area) and proposed the support scheme correspondingly. The numerical simulation results and completed construction safely verified the feasibility of the support scheme

Glycopolymer vesicles with an asymmetric membrane

Direct dissolution of glycosylated polybutadiene–poly(ethylene oxide) block copolymers can lead to the spontaneous formation of vesicles or membranes, which on the outside are coated with glucose and on the inside with poly(ethylene oxide)

A Self-Powered Insole for Human Motion Recognition

Biomechanical energy harvesting is a feasible solution for powering wearable sensors by directly driving electronics or acting as wearable self-powered sensors. A wearable insole that not only can harvest energy from foot pressure during walking but also can serve as a self-powered human motion recognition sensor is reported. The insole is designed as a sandwich structure consisting of two wavy silica gel film separated by a flexible piezoelectric foil stave, which has higher performance compared with conventional piezoelectric harvesters with cantilever structure. The energy harvesting insole is capable of driving some common electronics by scavenging energy from human walking. Moreover, it can be used to recognize human motion as the waveforms it generates change when people are in different locomotion modes. It is demonstrated that different types of human motion such as walking and running are clearly classified by the insole without any external power source. This work not only expands the applications of piezoelectric energy harvesters for wearable power supplies and self-powered sensors, but also provides possible approaches for wearable self-powered human motion monitoring that is of great importance in many fields such as rehabilitation and sports science