Deep Trench Isolation and Inverted Pyramid Array Structures Used to Enhance Optical Efficiency of Photodiode in CMOS Image Sensor via Simulations.

The photodiode in the backside-illuminated CMOS sensor is modeled to analyze the optical performances in a range of wavelengths (300-1100 nm). The effects of changing in the deep trench isolation depth (DTI) and pitch size (d) of the inverted pyramid array (IPA) on the peak value (OEmax.) of optical efficiency (OE) and its wavelength region are identified first. Then, the growth ratio (GR) is defined for the OE change in these wavelength ranges to highlight the effectiveness of various DTI and d combinations on the OEs and evaluate the OE difference between the pixel arrays with and without the DTI + IPA structures. Increasing DTI can bring in monotonous OEmax. increases in the entire wavelength region. For a fixed DTI, the maximum OEmax. is formed as the flat plane (d = 0 nm) is chosen for the top surface of Si photodiode in the RGB pixels operating at the visible light wavelengths; whereas different nonzero value is needed to obtain the maximum OEmax. for the RGB pixels operating in the near-infrared (NIR) region. The optimum choice in d for each color pixel and DTI depth can elevate the maximum GR value in the NIR region up to 82.2%.

Control and Entropy Analysis of Tip Leakage Flow for Compressor Cascade under Different Clearance Sizes with Endwall Suction.

To investigate the influence of the change of tip clearance size on the control effect of the endwall suction, the effects of endwall suction on the aerodynamic performance of the axial compressor cascade were studied numerically. Three tip clearance sizes of 0.5% h, 1.0% h, and 2.0% h (h is the blade height) were mainly considered. The results show that the endwall suction scheme whose coverage range was 8-33% axial chord can reduce the leakage flow and improve the aerodynamic performance by directly influencing the structure of tip leakage vortex. The overall total pressure loss coefficients of the three clearance size schemes at 0° angle of incidence with 0.4 inlet Mach number are reduced by about 10.3%, 10.8%, and 6.0%, respectively, at the suction flow rate of 0.7%. Under the same suction flow rate, the onset position of the tip leakage vortex of the cascade with small clearance is shifted from the 15% of the axial chord length of original to the 48% of the axial chord length, which with large clearance is nearly no changed. The leakage flow rate and the distance from the leakage vortex to the suction slot are the main reasons for the different control effect of the endwall suction under different tip clearance sizes. The difference of the spanwise distribution of flow field parameters may also cause the difference of flow control effect.

An innovative integrated system utilizing solar energy as power for the treatment of decentralized wastewater.

This article reports an innovative integrated system utilizing solar energy as power for decentralized wastewater treatment, which consists of an oxidation ditch with double channels and a photovoltaic (PV) system without a storage battery. Because the system operates without a storage battery, which can reduce the cost of the PV system, the solar radiation intensity affects the amount of power output from the PV system. To ensure that the power output is sufficient in all different weather conditions, the solar radiation intensity of 78 W/m2 with 95% confidence interval was defined as a threshold of power output for the PV system according to the monitoring results in this study, and a step power output mode was used to utilize the solar energy as well as possible. The oxidation ditch driven by the PV system without storage battery ran during the day and stopped at night. Therefore, anaerobic, anoxic and aerobic conditions could periodically appear in the oxidation ditch, which was favorable to nitrogen and phosphate removal from the wastewater. The experimental results showed that the system was efficient, achieving average removal efficiencies of 88% COD, 98% NH4+-N, 70% TN and 83% TP, under the loading rates of 140 mg COD/(g MLSS x day), 32 mg NH4+-N/(g MLSS x day), 44 mg TN/(g MLSS x day) and 5 mg TP/(g MLSS x day).

Characterization of the elastic and viscoelastic properties of dentin by a nanoindentation creep test.

Dentin is the main supporting structure of teeth, but its mechanical properties may be adversely affected by pathological demineralization. The purposes of this study were to develop a quantitative approach to characterize the viscoelastic properties of dentin after de- and re-mineralization, and to examine the elastic properties using a nanoindentation creep test. Dentin specimens were prepared to receive both micro- and nano-indentation tests at wet and dry states. These tests were repeatedly performed after demineralization (1% citric acid for 3 days) and remineralization (artificial saliva immersion for 28 days). The nanoindentation test was executed in a creep mode, and the resulting displacement-time responses were disintegrated into primary (transient) and secondary (viscous) creep. The structural changes and mineral densities of dentin were also examined under SEM and microCT, respectively. The results showed that demineralization removed superficial minerals of dentin to the depth of 400 µm, and affected its micro- and nano-hardness, especially in the hydrate state. Remineralization only repaired the minerals at the surface layer, and partially recovered the nanohardness. Both the primary the secondary creep increased in the demineralized dentin, while the hydration further enhanced creep deformation of untreated and remineralized dentin. Remineralization reduced the primary creep of dentin, but did not effectively increase the viscosity. In conclusion, water plasticization increases the transient and viscous creep strains of demineralized dentin and reduces load sustainability. The nanoindentation creep test is capable of analyzing the elastic and viscoelastic properties of dentin, and reveals crucial information about creep responses.

Riboflavin-ultraviolet-A-induced collagen cross-linking treatments in improving dentin bonding.

OBJECTIVES: To evaluate the collagen cross-linkers, riboflavin-ultraviolet-A (RF/UVA) and glutaraldehyde, with regard to their efficacy in cross-linking the dentinal collagen and improving dentin bonding. METHODS: Glutaraldehyde and different RF/UVA protocols (0.1%RF/1-minUV, 0.1%RF/2-minUV, and 1%RF/1-minUV) were first evaluated by gel electrophoresis to determine their abilities of collagen cross-linking. The mechanical properties of acid-etched dentin receiving these cross-linking treatments were examined in either dry or wet condition by a nanoindentation test. Fifteen teeth with exposed occlusal dentin received the microtensile bond strength (µTBS) test. The teeth were primed either with RF/UVA or glutaraldehyde, followed by adhesive treatment and composite restorations, and then cut into resin-dentin microbeams. Half of the microbeams received the µTBS test after 24h, and the other half received test after 5000 thermocycles. Nanoleakage at the bond interface was examined under TEM. The alignments of collagen fibrils in the hybrid layers were also defined by an image analysis. RESULTS: Gel electrophoresis showed that glutaraldehyde induced strong collagen gelation, while RF/UVA generated milder collagen cross-linking. Glutaraldehyde, 0.1%RF/2-min-UVA, and 1%RF/1-minUV showed higher stiffness compared to untreated and 0.1%RF/1-minUV in wet condition. All the crosslinking treatments improved early µTBS, but 0.1%RF/2-minUVA treatment maintained high µTBS after theromocycles. Under TEM, glutaraldehyde-treated dentin showed dense and enclosed collagen network on the adhesive interface. 0.1%RF/2-minUVA showed the least nanoleakage, and this could be associated with the suspended collagen fibrils in the hybrid layer. SIGNIFICANCE: 0.1%RF/2-minUVA treatment enhanced resin-dentin bond possibly through enhancing the stiffness and maintaining the expanding collagen matrix in the hybrid layer.

Stress-strain analysis for evaluating the effect of the orientation of dentin tubules on their mechanical properties and deformation behavior.

A model whose porosity does not vary with compression depth is developed for evaluating the mechanical properties of dentin tubules with various orientation angles from micro-pillar nanocompression tests. Experimental results for a range of loading rates indicate that the yielding parameters and the elastic modulus are little affected by the creep behavior. For a given compression depth, the hardness, elastic modulus, and yielding strength decrease with increasing orientation angle of dentin. The mechanical properties obtained using the proposed model are consistent with the reported data, and are actually more precise since they consider the orientation angle. The proposed testing method can be applied to materials that yield a negative value of the elastic modulus due to creep behavior.

Theoretical modeling developed to evaluate the hardness and reduced modulus for the C/a-Si composite film using nanoindentation tests.

A general mechanical model, which is composed of the mechanical models employed to describe the contact behaviors and deformations arising in all layers (including the substrate), is successfully developed in the present study for multilayer specimens in order to evaluate the contact projected area by a theoretical model, and thus the hardness and reduced modulus, using nanoindentation tests. The governing differential equations for the depth solutions of the indenter tip formed at all layers of the specimen under their contact load are developed individually. The influence of the material properties of the substrate on a multilayer specimen's hardness and reduced modulus at various indentation depths can thus be evaluated. Transition and pop-in occurred at depths near, but still before, the C (top layer)/a-Si (buffer layer) interface and the a-Si/Si (substrate) interface, respectively. Using the present analysis, the depths corresponding to the transition and pop-in behaviors can be predicted effectively.

[Study on biodegradation of polyacrylamide].

Phanerochaete chrysosporium was introduced into biodegradation of polyacrylamide(PAM), and effects of glucose amount, pH, N concentration, Mn2+ concentration and biodegradation time on biodegradation of PAM were studied. Results show that Phanerochaete chrysosporium has special abilities of enzyme catalysis biodegradation of PAM. And the removal rate of PAM is 50%. Nitrogen limitation (NH4+ = 0.2 g/L) and Mn2+ concentration (Mn2+ = 0.017 5 g/L) are optima of producing PAM biodegradation enzyme.