Modeling,numerical optimization,and irreversibility reduction of a dual-pressure reheat combined-cycle

Optimizing the gas-turbine combined-cycle is an important method for improving its efficiency. In this paper, a dual-pressure reheat combined-cycle was modeled and optimized for 80 cases. Constraints were set on the minimum temperature-difference for pinch points (PP_m), superheat approach temperature-difference, steam-turbine inlet temperature and pressure, stack temperature, and dryness fraction at the steam-turbine’s outlet. The dual-pressure reheat combined-cycle was optimized using two different methods; the direct search and the variable metric. A technique to reduce the irreversibility of the steam generator of the combined cycle was introduced. The optimized and the reduced-irreversibility dual-pressure reheat combined-cycles were compared with the regularly-designed dual-pressure reheat combined-cycle, which is the typical design for a commercial combined-cycle. The effects of varying the inlet temperature of the gas turbine (TIT) and PP_m on the performance of all cycles were presented and discussed. The results indicated that the optimized combined-cycle is up to 1% higher in efficiency than the reduced-irreversibility combined-cycle, which is 2–2.5% higher in efficiency than the regularly-designed combined-cycle when compared for the same values of TIT and PP_m. The advantages of the optimized and reduced-irreversibility combined-cycles were manifested when compared with the most efficient commercially-available combined cycle at the same value of TIT.     

The effect of Acetobacter sp. and a sulfate-reducing bacterial consortium from ethanol fuel environments on fatigue crack propagation in pipeline and storage tank steels

This paper evaluates the effects of microbiologically influenced corrosion (MIC) on fatigue-crack growth of candidate materials useful in expanding bio-ethanol usage, including a storage-tank steel (ASTM A36) and two pipeline steels (API 5L X52 and X70). The microbiological species sampled and cultivated from an ethanol fuel production stream are responsible for both acetic acid and hydrogen sulfide production that lead to significant increases in fatigue-crack growth rate across a wide range of stress-intensity-factor amplitudes (ΔK). The mechanism for increased fatigue damage is hydrogen uptake through adsorption into the steel, which embrittles material ahead of the growing fatigue crack.     

Addition of phytochemical-rich plant extracts mitigate the antimicrobial activity of essential oil/wine mixtures against Escherichia coli O157:H7 but not against Salmonella enterica

Marinades for preparing raw meats for cooking are frequently made of wine and herbs. We simulated several formulations of potential antimicrobial marinades with these components and other food compatible/food derived extracts. Red wine formulations containing essential oils from oregano or thyme, or their primary active components carvacrol and thymol, respectively, and a mixture of plant extract powders from phytochemical-rich apple skin, green tea, and olive, were evaluated for inhibitory activity against the foodborne pathogens Escherichia coli O157:H7 and Salmonella enterica. Red wine alone exhibited low activity, as did the plant extract suspended in the wine. Surprisingly, the high activity of oregano or thyme essential oils in red wine was reduced in E. coli, but not in Salmonella, by addition of the plant extract. This study shows that essential oils in red wine can be an effective antimicrobial in food, however the possibility exists that phytochemicals, added to the treatment solution or natively present in the food itself, could adversely impact the antimicrobial activity and should be addressed with future studies.     

Mechanical properties and thermal conductivity of Si3N4 ceramics with YF3 and MgO as sintering additives

Si₃N₄ ceramic was densified by hot pressing sintering at 1750 °C for 1 h under the uniaxial pressure of 20 MPa in N₂ atmosphere with YF₃ and MgO as sintering additives. The thermal conductivities of SN-YF specimen were both higher than that of Si₃N₄ ceramic sintered with Y₂O₃ and MgO before and after annealing treatment. The grain size and aspect ratio in SN-YF specimen were both bigger than those in the SN-YO specimen, which was beneficial for the creation of high thermal conductive path. On the other hand, the improvement of thermal conductivity by the addition of YF₃ might be attributed to the reduction of the grain boundary phase due to the evaporation of SiF₄, and the resultant reduction of the lattice oxygen due to the reduction of SiO₂ in the grain boundary phase. The {0001} direction of grains had the probability of growing along the hot pressing direction in the SN-YF specimen, which was beneficial for the improvement of thermal conductivity while the {0001} direction grew along the X₀-Y₀ plane in the SN-YO specimen. The mechanical properties of SN-YF specimen were comparable to those of SN-YO specimen.     

Structural characteristics and microwave dielectric properties of Zn1−xBixVxW1−xO4-based ceramics for LTCC applications

Herein, the improvement of the microwave dielectric properties and sintering characteristics of Zn_1?xBi_xV_xW_1?xO₄(x = 0–0.15)-based ceramics is reported. The results showed that an appropriate amount of doping could not only reduce the optimum sintering temperature from 1100° to 900°C, but also enhance the densification of the microstructures and increase the Q×f value from 5351 to 42525 GHz. Additionally, various structural parameters including the phase composition, crystal structure, vibrational and chemical bond characteristics that are correlated with the dielectric properties were systematically investigated. By considering the chemical bond characteristics, the first-principles calculations and the acquired Raman spectra, the interaction between W-O is stronger than Zn-O in the ZnWO₄ structure, while the interaction between V-O is stronger than Bi-O in BiVO₄. Interestingly, when the Zn_0.97Bi_0.03V_0.03W_0.97O₄-based ceramics were sintered at 900 °C, improved microwave dielectric properties were acquired (ε_r =18.32, Q×f=42525 GHz, τ_f=?67.51 ppm/°C), which provides a promising candidate in low-temperature co-fired ceramics technology.     

DMC质量对110甲基乙烯基硅橡胶生产的影响

统计分析了含不同未知物数量的DMC对110甲基乙烯基硅橡胶生产一次聚合得率、目标分子量生产控制的影响,结果表明随着未知物数量的增加,一次聚合得率逐步下降,实际分子量偏离目标分子量越远。DMC中未知物总量控制在200 ppm以内,最有利于生产控制。     

沉淀白炭黑在脱酸型硅酮密封胶中的应用研究

以α,ω-二羟基聚二甲基硅氧烷为主粘料、气相白炭黑和沉淀白炭黑为补强填料、配合醋酸型交联剂、催化剂制备出单组分脱酸型硅酮密封胶。考查了不同规格的沉淀法白炭黑及其加入量对密封胶综合性能的影响。结果表明,随沉淀白炭黑比表面积的增大,密封胶的性能提高、应力发白现象减弱,在配方中的质量分数可增加。     

Increase the current density and reduce the defects of ZnO by modification of the band gap edges with Cu ions implantation for efficient,flexible dye-sensitized solar cells (FDSSCs)

Flexible dye-sensitized solar cells (FDSSCs) have good potential in future photovoltaic technology. The spin coating method deposited the ZnO films on indium-tin-oxide-coated polyethylene terephthalate (ITO-PET) flexible plastic substrates. These films are implanted with Cu-ions with 1 × 10¹³ ions/cm², 1 × 10¹⁴ ions/cm², and 1 × 10¹⁵ ions/cm². All the films have a hexagonal structure. The film irradiated with 1 × 10¹⁴ ions/cm² showed high crystallinity and crystallite size. Important optical properties like bandgap energy (E_g), band edges, refractive index, extinction coefficient, and dielectric constants are measured by UV–Vis spectroscopy. Bandgap energy decreases, and the refractive index increases at the fluence of Cu ions. The maximum decrease in E_g is observed at the 1 × 10¹⁴ ions/cm² dose. Photoluminescence spectra suggest that defects-related emission peaks are decreased at 1 × 10¹⁴ ions/cm² Cu ions fluency. J-V measurements have significantly improved photovoltaic performance compared to pristine ZnO-based solar cells. The highest efficiency (2.30%) is observed at a 1 × 10¹⁴ ions/cm² dose. The efficiency increase is related to improving the charge transfer ratio and shifting the fermi level toward the conduction band.     

Study on the role of niobium in corrosion mechanism of low-alloy pipeline steel in H2S-saturated solution

In this study, the role of Nb addition on the corrosion behavior of low-alloy steel exposed to H₂S solution is studied by means of microstructure, macro/microsurface morphology characteristics, type of corrosion product, cross-sectional structure and elemental distribution. The addition of Nb is a route to refine grains and improve corrosion resistance. The surface formation process of iron sulfides changes from homogeneity to dispersion at the initial corrosion stage when Nb is added to steel. However, the transformation process and crystal structure of iron sulfides are not affected by the addition of Nb. The elemental distribution of corrosion products is not affected by Nb addition although thick and compact corrosion products are formed on the specimen surface of Nb steel. A schematic model is proposed to clarify the difference of the corrosion mechanism in atomic and molecular level.     

A Study on Characteristic Flavor Compounds in Traditional Chinese Rice Wine — Guyue Longshan Rice Wine

The objective of the study was to systematically investigate flavor compounds in Chinese rice wine (CRW) using chromatography technology. In twelve CRW samples, 93 different flavor compounds were detected and identified including 16 alcohols in addition to ethanol, 29 esters, 9 aldehydes, 9 organic acids, 19 amino acids and 11 fatty acids. Statistical analysis by principal component analysis (PCA) indicated that seventeen flavor compounds in Guyue Longshan rice wine made a large contribution to its special flavor. These compounds were benzaldehyde, acetaldehyde, ethyl 2‐hydroxy‐4‐methylvalerate, ethyl butyrate, phenyl ethyl isobutyrate, ethyl benzoate, ethyl phenyl‐acetate, methyl dodecanoate, methyl oleate, ethyl dedecanoate, 1‐butanol, 3‐ethoxyl‐1‐propanol, 1‐enanthol, dodecanol, lactic acid, fumaric acid and lauric acid.