Applications of ground source heat pump systems in different temperature zones in China

An analysis of the application of ground source heat pump (GSHP) systems to different temperature zones in China is presented in this paper. According to the climate characteristics, China is divided into six different temperature zones: the tropical zone, the subtropical zone, the warm temperate zone, the mid temperate zone, the cold temperate zone, and Qinghai-Tibet Plateau vertical temperature zone. Six representative cities corresponding to the six temperature zones are chosen and their different climate and soil characteristics are studied. The results show that a GSHP system can be applied to the first four temperature zones above, but not the cold temperate zone and the Qinghai-Tibet Plateau vertical temperature zone. However, in different temperature zones, different GSHP systems should be designed and built.     

Intercomparison of a portable and two stationary mobility particle sizers for nanoscale aerosol measurements

During occupational exposure studies, the use of conventional scanning mobility particle sizers (SMPS) provides high quality data but may convey transport and application limitations. New instruments aiming to overcome these limitations are being currently developed. The purpose of the present study was to compare the performance of the novel portable NanoScan SMPS TSI 3910 with that of two stationary SMPS instruments and one ultrafine condensation particle counter (UCPC) in a controlled atmosphere and for different particle types and concentrations.

The results show that NanoScan tends to overestimate particle number concentrations with regard to the UCPC, particularly for agglomerated particles (ZnO, spark generated soot and diesel soot particles) with relative differences >20%. The best agreements between the internal reference values and measured number concentrations were obtained when measuring compact and spherical particles (NaCl and DEHS particles). With regard to particle diameter (modal size), results from NanoScan were comparable < [± 20%] to those measured by SMPSs for most of the aerosols measured.

The findings of this study show that mobility particle sizers using unipolar and bipolar charging may be affected differently by particle size, morphologies, particle composition and concentration. While the sizing accuracy of the NanoScan SMPS was mostly within ±25%, it may miscount total particle number concentration by more than 50% (especially for agglomerated particles), thus making it unsuitable for occupational exposure assessments where high degree of accuracy is required (e.g., in tier 3). However, can be a useful instrument to obtain an estimate of the aerosol size distribution in indoor and workplace air, e.g., in tier 2.     

Improving thermo‐oxidative degradation resistance of bamboo fiber reinforced polymer composites with antioxidants. Part II: Effect on other select properties

The first of this two‐article study showed that the addition of antioxidants can significantly improve the thermo‐oxidative resistance of bamboo fiber reinforced polypropylene composites (BFPCs). In this article, the effect of antioxidants on water absorption, thermal stability, crystallinity, and the dynamic mechanical properties of the composites were investigated. The results showed that the addition of antioxidants resulted in a slight increase in water absorption, but this increase can be reduced by controlling the ratio of the primary and secondary antioxidants. The glass transition temperature (T_g) of composites also slightly increased. However, the effects of antioxidants on the crystallinity as well as other thermal properties of BFPCs were small or even insignificant. The different combinations, ratios, and the adding amounts of antioxidants show tiny differences for all these properties. As a whole, the addition of minor antioxidants in the bamboo fiber (BF) polymer composites will not produce obvious negative effects on their overall performances. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44199.     

Improving thermo‐oxidative degradation resistance of bamboo fiber reinforced polypropylene composite with antioxidants. Part I: Screening of antioxidants

In this study, the effect of antioxidant application (applied in different combinations, ratios and contents) on the thermo‐oxidative degradation resistance of bamboo fiber polypropylene composites (BFPCs) were investigated, with oxidative induction time (OIT), weight loss, surface color, and flexural mechanical properties as the main indicators for evaluation. The results showed the addition of antioxidants could greatly increase the OIT and reduce the weight loss and color change of the composites after 900 h of thermal weathering. Meanwhile, the flexural mechanical properties were little affected or even slightly improved. The combination of 1076 and DLTP antioxidants at a ratio of 2:1 and 0.2 wt % content was found to exhibit the best thermal oxidation resistance with respect to the OIT, mechanical properties and cost. Our study indicate that the OIT can serve as a simple and quick indicator for the evaluation of thermo‐oxidative resistance of BFPC. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44198.     

Preparation and performance of PANI–PVA composite film doped with HCl

The polyaniline (PANI)–poly (vinyl alcohol) (PVA) composite film doped with HCl was prepared by adopting PVA as matrix. Effects of PVA content and film drying temperature on properties of HCl–PANI–PVA composite film were studied. A comparison was made for tensile strength, elasticity, conductivity and thermal stability of PVA, HCl–PANI or HCl–PANI–PVA. PVA film presented the highest tensile strength and elasticity (150.8?MPa and 300.0%), but its conductivity was the lowest. The conductivity of HCl–PANI–PVA was the highest (1500?S?m^?1), and tensile strength and elasticity of HCl–PANI–PVA were higher than those of HCl–PANI. The order of their thermal stability is PVA?>?HCl–PANI?>?HCl–PANI–PVA before 260°C, and the order of their thermal stability is HCl–PANI?>?HCl–PANI–PVA?>?PVA after 260°C. At the same time, the structure and conductive mechanism of composite materials were characterised and analysed through infrared and scanning electron microscopy (SEM).     

Interrogating the Tailoring Steps of Pactamycin Biosynthesis and Accessing New Pactamycin Analogues

Pactamycin is a bacteria‐derived aminocyclitol antibiotic with a wide‐range of biological activity. Its chemical structure and potent biological activities have made it an interesting lead compound for drug discovery and development. Despite its unusual chemical structure, many aspects of its formation in nature remain elusive. Using a combination of genetic inactivation and metabolic analysis, we investigated the tailoring processes of pactamycin biosynthesis in Streptomyces pactum. The results provide insights into the sequence of events during the tailoring steps of pactamycin biosynthesis and explain the unusual production of various pactamycin analogues by S. pactum mutants. We also identified two new pactamycin analogues that have better selectivity indexes than pactamycin against malarial parasites.     

Effect of alumina on the structure and properties of polyimide matrix films

To improve the properties of polyimide (PI), different mass fractions of alumina (Al₂O₃) nanoparticles, unmodified or modified by KH550, were incorporated into PI matrix to form PI/Al₂O₃ hybrid films by in situ polymerisation. The effects of Al₂O₃ additives on the structure, dielectric and mechanical properties of the films were studied. Fourier transform infrared spectroscopy confirmed the successful preparation of PI/Al₂O₃ hybrid films, and the microstructures of the samples showed a more uniform dispersion of the modified Al₂O₃ nanoparticles than the unmodified ones in the matrix. The dielectric constant of the films increased with increasing filler content, and the maximum electrical breakdown strength of 311 MV m^?1 was obtained with a filler content of 8.0 wt-% modified Al₂O₃ in the matrix. Both unmodified and modified Al₂O₃-reinforced PI hybrids demonstrated improved mechanical properties compared with the PI matrix. Moreover, the properties of films with Al₂O₃ modified by KH550 were better.     

Corrosion behavior of Ti-35Nb-7Zr-5Ta alloy prepared by spark plasma sintering in Hank’s artificial body fluid北大核心CSCD

Biomedical Ti-35Nb-7Zr-5Ta(Ti-Osteum) alloys was prepared by spark plasma sintering (SPS). Corrosion behavior and mechanism of the alloys was investigated in Hank’s solution by means of open-circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Both commercially pure titanium (TA1) and Ti-6Al-4V (TC4) alloy were also investigated to make a comparison. The results showed that, in comparison with TA1 and TC4 alloy, the Ti-Osteum alloy prepared by SPS exhibited a good corrosion resistance with lower corrosion current, lower passive current density and higher polarization resistance, but more or less the similar corrosion potential. As a result, the corrosion resistance of the three materials may be ranked as follows: Ti-Osteum＞TC4＞TA1. The excellent corrosion resistance of Ti-Osteum alloy prepared by SPS in simulated artificial body fluid may be attributed to its higher sintered density, β-type single phase microstructure, and a stable passive film mainly consisted of titanium oxide, nio bium oxide, zirconium oxide, and tantalum oxide on its surface. © 2016, Corrosion Science and Protection Technology. All rights reserved.     

Inquire into degradation process of Ni-Co coating in 3.5% NaCl solution by EIS北大核心CSCD

The degradation process of Ni-Co coating on plate of Kovar alloy 4J42 in 3.5%NaCl solution was studied by means of electrochemical impedance spectroscope (EIS). Four distinguished electrical equivalent circuits (EEC) were proposed to simulate the degradation process. At the very beginning of immersion, the coating exhibited excellent corrosion resistance, which could be treated as a barrier layer with a high resistance in parallel with a low capacitance. After a short time of immersion, a double-layer capacitance Cdl and a charge-transfer resistance Rct were introduced, indicating that the electrochemical reactions at the metal/coating interface may take place. In the late stage of immersion, Warburg impedance was adopted to characterize the corrosion products. With the accumulation of the corrosion products, the diffusion process of corrosive medium was affected, and the EEC comprising a diffusion capacitance (Cdiff) and a diffusion resistance (Rdiff) was then introduced to fit the impedance spectra. The evolution of coating resistance and coating capacitance were investigated to illuminate the Ni-Co coating degradation process. The results showed that the degradation process of Ni-Co coating could be described by three stages: the permeation of corrosive medium, the corrosion of metal at the interface of coating/substrate and finally the failure of coating. © 2016, Corrosion Science and Protection Technology. All rights reserved.