Underwater Spectral Imaging System Based on Liquid Crystal Tunable Filter

In the past decade, underwater spectral imaging (USI) has shown great potential in underwater exploration for its high spectral and spatial resolution. This proposal presents a stare-type USI system combined with the liquid crystal tunable filter (LCTF) spectral splitting device. Considering the working features of LCTF and the theoretical model of USI, the core structure containing “imaging lens-LCTF-imaging sensor” is designed and developed. The system is compact, and the optical geometry is constructed minimally. The spectral calibration test analysis proved that the spectral response range of the system covers a full band of 400 nm to 700 nm with the highest spectral resolution between 6.7 nm and 18.5 nm. The experiments show that the system can quickly collect high-quality spectral image data by switching between different spectral bands arbitrarily. The designed prototype provides a feasible and reliable spectral imaging solution for in situ underwater targets observation with high spectrum collecting efficiency.

Finite Element Modeling and Performance Evaluation of Piezoelectric Energy Harvesters with Various Piezoelectric Unit Distributions

The piezoelectric energy harvester (PEH) is a device for recycling wasted mechanical energy from pavements. To evaluate energy collecting efficiency of PEHs with various piezoelectric unit distributions, finite element (FE) models of the PEHs were developed in this study. The PEH was a square of 30 cm × 30 cm with 7 cm in thickness, which was designed according to the contact area between tire and pavement. Within the PEHs, piezoelectric ceramics (PZT-5H) were used as the core piezoelectric units in the PEHs. A total of three distributions of the piezoelectric units were considered, which were 3 × 3, 3 × 4, and 4 × 4, respectively. For each distribution, two diameters of the piezoelectric units were considered to investigate the influence of the cross section area. The electrical potential, total electrical energy and maximum von Mises stress were compared based on the computational results. Due to the non-uniformity of the stress distribution in PEHs, more electrical energy can be generated by more distributions and smaller diameters of the piezoelectric units; meanwhile, more piezoelectric unit distributions cause a higher electrical potential difference between the edge and center positions. For the same distribution, the piezoelectric units with smaller diameter produce higher electrical potential and energy, but also induce higher stress concentration in the piezoelectric units near the edge.

Enhancing the generating and collecting efficiency of single particle upconverting luminescence at low power excitation

Upconverting luminescent nanoparticles are photostable, nonblinking, and low chemically toxic fluorophores that are emerging as promising fluorescent probes at the single molecule level. High luminescence intensity upconversion nanoparticles (UCNPs) have previously been achieved by doping with high amounts of rare-earth ions using high excitation power (>2.5 MW/cm2). However, such particles are inadequate for in vitro live-cell imaging and single-particle tracking, as high excitation power can cause photodamage. Here, we compared UCNP luminescence intensities with different dopant concentrations and presented more efficient (about seven times) UCNPs at low excitation power by increasing the concentrations of Yb3+ and Tm3+ dopants (NaYF4: 60% Yb3+, 8% Tm3+) and adding a core-shell structure.

Enhancing generating and collecting efficiency of single particle upconverting luminescence at low-level power excitation

Upconverting luminescent nanoparticles are photostable, non-blinking, and low chemically toxic fluorophores that are emerging as promising fluorescent probe at single-molecule level. High luminescence intensity upconversion nanoparticles (UCNPs) is achieved with highly doped rare-earth ions co-doped (20% Yb3+) using high excitation power (>2.5 MW/cm2). However, such particles are inadequate for in-vitro live-cell imaging and single-particle tracking since high excitation power can cause photodamage. Here, we compared UCNPs luminescence intensities with different dopants concentrations and presented a more efficient (∼7x) UCNPs at low excitation power by increasing the concentrations of Yb3+ and Tm3+ dopants (NaYF4: 60% Yb3+, 8% Tm3+) and adding a core-shell structure.

Analysis of solar seasonal storage in rural residences with Zhongyuan region as an example

A combined system of refrigeration and heating unit with seasonal solar thermal storage was presented in this paper. Based on the climate character of the Zhongyuan region, China, the system?s performance in rural residences was studied. A computational program was established based on the DEST software, the solar heat collecting capacity, heat collecting efficiency, and other parameters were analyzed. The results showed that the system can supply 76.28% heating load and 40.14% cooling load, when the total collector surface area equals to 40 m2 and heat collecting temperature is 80?C. The results will provide theoretical support for the system?s optimization.