Thin Film Chip Resistors with High Resistance and Low Temperature Coefficient of Resistance

High resistance thin film chip resistors(0603 type) were studied,and the specifications are as follows:1 k? with tolerance about ±0.1% after laser trimming and temperature coefficient of resistance(TCR) less than ±15×10-6/℃.Cr-Si-Ta-Al films were prepared with Ar flow rate and sputtering power fixed at 20 standard-state cubic centimeter per minute(sccm) and 100 W,respectively.The experiment shows that the electrical properties of Cr-SiTa-Al deposition films can meet the specification requirements of 0603 ty...

Variety Test on Low Temperature-resistant Pleurotus ostreatus Strains in Beijing Area

With 7 familiar Pleurotus ostreatus strains in Beijing region as the test materials,the randomized block design method was adopted to analyze the antagonistic effects,mycelial growth rate,yield of mushroom at low temperature season,total biological efficiency and agronomic characteristics of fruit bodies.The results showed that there were antagonistic effects and differences in all the tested items between all the tested strains,of which the strain PL5 had the shortest spawn age,the strain PL3 showed the highest total biological efficiency,and the fructification of the strain PL7 tasted crisp and tender.

Abnormality of Magnetic Behavior and Resistivity of La_(0.7-x)Dy_x Sr_(0.3)MnO_3 (0.00≤x≤0.30)System at Low Temperature

By measuring M-T curves, ρ-T curves and MR-T curves of the samples under different temperatures, the influence of Dy doping （0.00 ≤ x ≤0.30） on the magnetic and electric properties of La0.7-xDyxSr0.3MnO3 has been studied. The experimental results show that, with the increase of the Dy content, the system undergoes a transition from long range ferromagnetic order to the cluster-spin glass state and further to antiferromagnetic order. For the samples with x=0.20 and 0.30, their magnetic behaviors are abnormal at low temperature, and their resistivities at low temperature have a minimum value. These peculiar phenomena not only come from the lattice effect induced by doping, but also from extra magnetic coupling induced by doping.

Comparison of Genetic Diversity and Growth Performance between the Selected Population and Hybridized Population of Litopenaeus vannamei at Low Temperature

[Objective] This study was conducted to compare the genetic diversity and growth performance of two Litopenaeus vannamei populations at low temperature. [Method] One population（selected population, SP） was produced through inbreeding and 3 years of selection from seven popula- tions of L. vannamei introduced from the United States and Singapore. The other population （hybridized population, HP） was the F1 generation of the crosses between Population SP and some excellent populations introduced from South Korea and Singapore. The growth performance of the two populations at low temperature was compared, and the genetic diversity and genetic differentiation between the two populations were assessed using 13 microsatellite loci. [Result] The shrimps of population HP had better growth performance than those of population SP. The average body weight （BW） for population HP, which was （13.18±3.65） g/ind., was significantly higher than that of population SP, which was （12.20±3.14） g/ind. The coefficient of variation in body weight for population SP was 25.74%, and that for population HP was 27.69%. The other growth indices of popula- tion HP were all higher than those of population SP. One-way analysis of variance （ANOVA） indicated that there were highly significant differences in both BW and width of third abdominal segment （WTAS） between HP and SP（P〈0.001）. The specific growth rate （SGR） and absolute growth rate （AGR） for population HP were （5.09±0.61） %/d and （0.26±0.60） g/d, respectively, while the SGR and AGR for population SP were （4.94±0.57） %/d and （0.24±0.63） g/d., both significantly lower than those of population HP （P〈0.001）. Genetic diversity analysis revealed that the number of alleles （Na） of population HP （Na=7.9） was slightly higher than that of population SP （Na=7.6）. The average polymorphic information content （PIC） of HP and SP populations was similar 0.63 and 0.62, both indicating high level of genetic diversity. The average observed heterozygosity （HQ） of HP and SP was 0.492 and 0.483, and the expected heterozygosity（He） was 0.675 and 0.663, respectively. Both Ho and He of population HP were higher than those of population SP, suggesting that HP had higher genetic diversity than population SP. Moreover, the mean of FsT values at the 13 microsatellite loci between HP and SP was 0.155 6, suggesting there was a significant genetic differentiation between the two populations. [Conclusion] Our results provide a theoretical basis for the breeding of new L. vannamei strains that are resistant to low temperature.

Low-molecular-weight supramolecular adhesive with resistance to low temperatures

The design of adhesive materials with strong adhesion capacity at low temperatures is a great challenge.Herein,we report a low-molecular-weight supramolecular adhesive that exhibits good adhesion performance to various surfaces at low temperatures(from-18℃ to-80℃).Moreover,this supramolecular adhesive has good adhesion ability in the presence of water.

Surface metallization of PTFE and PTFE composites by ion implantation for low-background electronic substrates in rare-event detection experiments

Polytetrafluoroethylene(PTFE)is a low-background polymer that is applied to several applications in rare-event detection and underground low-background experiments.PTFE-based electronic substrates are important for reducing the detection limit of high-purity germanium detectors and scintillator calorimeters,which are widely applied in dark matter and 0υββdetection experiments.The traditional adhesive bonding method between PTFE and copper is not conducive to working in liquid nitrogen and extremely low-temperature environments.To avoid adhesive bonding,PTFE must be processed for surface metallization owing to the mismatch between the PTFE and copper conductive layer.Low-background PTFE matrix composites(m-PTFE)were selected to improve the electrical and mechanical properties of PTFE by introducing SiO_(2)/TiO_(2) particles.The microstructures,surface elements,and electrical properties of PTFE and m-PTFE were characterized and analyzed following ion implantation.PTFE and m-PTFE surfaces were found to be broken,degraded,and cross-linked by ion implantation,resulting in C=C conjugated double bonds,increased surface energy,and increased surface roughness.Comparably,the surface roughness,bond strength,and conjugated double bonds of m-PTFE were significantly more intense than those of PTFE.Moreover,the interface bonding theory between PTFE and the metal copper foil was analyzed using the direct metallization principle.Therefore,the peel strength of the optimized electronic substrates was higher than that of the industrial standard at extremely low temperatures,while maintaining excellent electrical properties.

Resistivity response to the porosity and permeability of low rank coal

Laojunmiao coal samples from the eastern Junggar basin were studied to understand the relationship between coal resistivity and the physical parameters of coal reservoirs under high temperatures and pressures.Specifically,we analysed the relationship of coal resistivity to porosity and permeability via heating and pressurization experiments.The results indicated that coal resistivity decreases exponentially with increasing pressure.Increasing the temperature decreases the resistivity.The sensitivity of coal resistivity to the confining pressure is worse when the temperature is higher.The resistivity of dry coal samples was linearly related to φ~m.Increasing the temperature decreased the cementation exponent(m).Increasing the confining pressure exponentially decreases the porosity.Decreasing the pressure increases the resistivity and porosity for a constant temperature.Increasing the temperature yields a quadratic relationship between the resistivity and permeability for a constant confining pressure.Based on the Archie formula,we obtained the coupling relationship between coal resistivity and permeability for Laojunmiao coal samples at different temperatures and confining pressures.

Hyperelastic Graphene Aerogels Reinforced by In‑suit Welding Polyimide Nano Fiber with Leaf Skeleton Structure and Adjustable Thermal Conductivity for Morphology and Temperature Sensing

Graphene-aerogel-based flexible sensors have heat tolerances and electric-resistance sensitivities superior to those of polymer-based sensors.However,graphene sheets are prone to slips under repeated compression due to inadequate chemical con-nections.In addition,the heat-transfer performance of existing compression strain sensors under stress is unclear and lacks research,making it difficult to perform real-temperature detections.To address these issues,a hyperelastic polyimide fiber/graphene aerogel(PINF/GA)with a three-dimensional interconnected structure was fabricated by simple one-pot compound-ing and in-situ welding methods.The welding of fiber lap joints promotes in-suit formation of three-dimensional crosslinked networks of polyimide fibers,which can effectively avoid slidings between fibers to form reinforced ribs,preventing graphene from damage during compression.In particular,the inner core of the fiber maintains its macromolecular chain structure and toughness during welding.Thus,PINF/GA has good structural stabilities under a large strain compression(99%).Moreover,the thermal and electrical conductivities of PINF/GA could not only change with various stresses and strains but also keep the change steady at specific stresses and strains,with its thermal-conductivity change ratio reaching up to 9.8.Hyperelastic PINF/GA,with dynamically stable thermal and electrical conductivity,as well as high heat tolerance,shows broad applica-tion prospects as sensors in detecting the shapes and temperatures of unknown objects in extreme environments.

Effects of SO2 on the low temperature selective catalytic reduction of NO by NH3 over CeO2-V2O5-WO3/TiO2 catalysts

The CeO2-V2O5-WO3/TiO2 （CeO2-VWT） catalysts were prepared by one-step and two-step impregnation methods. The effects of different loading of CeO2 and different preparation methods on De-NOx activity of catalysts had been investigated. CeO2 helped to improve the De-NOx activity and sulfur resistance. The optimal loading of CeO2 was 3% with the De-NOx efficiency reached 89.9% at 140℃. The results showed that the De-NOx activity of 3% CeO2-VWT catalysts by one-step method was the same as two-step method basically and reached the level of industrial applications, the N2 selectivity of catalysts was more than 99.2% between 110℃ and 320℃. In addition, CeO2 promoted the oxidation of NO to NO2, which adsorbed on the Lewis acid site （V5＋-O） to form V5＋-NO3 and inspired the fast SCR reaction. Not only the thermal stability but also the De-NOx activity of catalysts decreased with excess CeO2 competed with V2O5. Characterizations of catalysts were carried out by XRF, BET, XRD, TG and FT-IR. BET showed that the specific surface area of catalysts decreased with the loading of CeO2 increased, the active components content and specific surface area of catalysts decreased slightly after entering SO2. Ammonium sulfate species were formed in poisoned catalyst which had been investigated by XRF, BET, TG and FT-IR. The largest loss rate of weight fraction was 0.024%.℃-1 at 380℃ 390℃, which was in accordance with the decomposition temperature of NH4HSO4 and （NH4）2SO4,

Effect of Polydimethylsilxoane Molecular of Soft Segment on Novel Urethane-Siloxane Copolymers

Novel segmented urethane-siloxane copolymers were synthesized by a two-step bulk polymerization procedure using 4,4'-methylenediphenyl diisocyanate( MDI) and 1,4-butanediol( BDO)as the hard segment components and novel polypropyleneoxide polyether( PPO) blocked polydimethylsilxoane( PDMS) α,ω-dihydroxy-( PPO-PDMS-PPO) as the soft segment component,where the hard segment content was 30% by weight,and the molar ratio of NCO / OH was 1. 02. A series of urethane-siloxane copolymers were prepared from different molecular weights of α,ω-dihydroxy-( PPO-PDMS-PPO). The soft segments were different in the molecular of PDMS block segment. Chemical structure,morphology,mechanical properties,surface properties and thermal properties of thermoplastic polyurethane( TPU) were investigated by Fourier transform infrared spectroscopy( FT-IR),scanning electron microscopy and energy dispersive X-ray spectroscopy( SEM-EDX),mechanical properties( MP) test,water contact angle( WCA) test,differential scanning calorimetry( DSC),thermogravimetric analysis( TGA), respectively. According to the obtained results, the hydrophobicity of silicone modified TPU promoted,surface WCA increased from 73° to 120°. Low temperature resistant performance was improved,and the glass transition temperature decreased from- 44. 2℃ to- 120. 8℃. Thermal stability was also improved,the beginning temperature of thermal degradation increased from 281 ℃to 299 ℃.