桩土复合路基静载试验改进方法研究

静载试验作为复合路基的一种重要检测手段而广泛应用,然而,在工程质量检测中,常出现检测结果与实际情况不符的情况,除人为操作因素外,垫层模拟过于简单是主要原因。借助引入弹性垫层,提出一种桩土复合路基静载试验改进方法。首先,基于数值模拟计算,建立复合路基桩土应力比n和桩土相对位移Δs、弹性垫层厚度h和弹性垫层模量E的函数关系;其次,通过模拟结果和路堤荷载结果对比,确定不同桩型复合路基静载试验中弹性垫层参数选择范围,最后,利用现场对比试验和实测结果,论证桩土复合路基静载试验改进方法的正确性和可靠性。     

煤与天然气气流床共气化制合成气试验研究

为提高煤、天然气资源综合利用效率,优化合成气成分,进行了煤与天然气气流床共气化技术研究。介绍了煤与天然气气流床共气化的试验装置及工艺流程,考察了气化温度、压力、水煤浆浓度、CH4与煤比对共气化反应的影响。结果表明,气化温度和CH4与煤比是共气化反应的主要影响因素,较高的气化温度对共气化反应有利,气化温度为1 350℃时,共气化指标较好,有效气体积分数大于90%;随着CH4与煤比的增大,合成气n(H2)/n(CO)增高。CH4与煤比为0.9 m3/kg时,合成气中n(H2)/n(CO)约1.2。根据后续合成工艺要求,通过调节气化温度和CH4与煤比,可获得n(H2)/n(CO)在0.8~2.0的合成气。     

部分传输序列的遗传模拟退火搜索方法

在正交频分复用(OFDM)系统中,基于遗传算法的部分传输序列(GA-PTS)技术有效地降低了 PTS 的计算复杂度,但在 改进峰值-平均功率比(PAPR)性能方面却并不理想。 为此,提出在遗传算法中嵌入模拟退火(SA)算子从而构造一种混合的遗 传模拟退火(GSA)算法,并把它应用于对 PTS 的最优相位因子进行搜索。 首先,通过对 PTS 相位因子编码形成染色体,采用随 机元素组成的染色体作为遗传算法的初始群体,并评估每个染色体的适应度值。 然后,根据适应度值选择染色体,建立染色体 的变异规则和交叉规则,对群体进行迭代进化。 最后,群体中的染色体利用退火温度进行更新,从而产生出新的下一代种群。 仿真结果说明,与 GA-PTS 方案相比,该方法不仅能降低计算负担,而且能够有效地降低 OFDM 系统 PAPR 值。     

A modified two-dimensional numerical method for prediction of outer wall temperature distribution of rectangular micro-combustors

Two-dimensional (2D) numerical models are frequently adopted to investigate combustion and thermal performances in rectangular micro-channels for micro-thermophotovoltaic and thermoelectric devices. However, large error may exist by applying a simple 2D model. In the present work, the outer wall temperature distributions predicted by 3D model and simple 2D model were compared. The results showed that the maximum relative error of the simple 2D model depends significantly on the aspect ratio (α) of the micro-channel. To be specific, the maximum relative error was >30% for α = 1 and > 10% for 2≤α ≤ 4. However, it was <5% for α ≥ 9. A new 2D model was proposed to modify the underestimated heat loss ratio. The new computational results demonstrated that the maximum relative error of α = 1 decreased to 8.07% and for micro-channels with α ≥ 2, all the maximum relative errors are <5%. In summary, the modified 2D numerical model can achieve a satisfactory prediction with low computation cost.     

Improvement of biohythane production from Chlorella sp. TISTR 8411 biomass by co-digestion with organic wastes in a two-stage fermentation

The suitability of molasses, Napier grass (Pennisetum purpureum), empty fruit bunches (EFB), palm oil mill effluent (POME), and glycerol waste as a co-substrate with Chlorella sp. TISTR 8411 biomass for biohythane production was investigated. Mono-digestion of Chlorella biomass had hydrogen and methane yield of 23–35 and 164–177 mL gVS⁻¹, respectively. Co-digestion of Chlorella biomass with 2–6% TS of organic wastes was optimized for biohythane production with hydrogen and methane yield of 17–75 and 214–577 mL gVS⁻¹, respectively. The hydrogen and methane yield from co-digestion of Chlorella biomass with molasses, POME, and glycerol waste was increased by 8–100% and 80–264%, respectively. The biohythane production of co-digestion of Chlorella was 6–11 L L-mixed waste⁻¹ with an optimal C/N ratio range of 19–41 and H₂/CH₄ ratio range of 0.06–0.3. Co-digestion of Chlorella biomass was significantly improved biohythane production in term of yield, production rate, and kinetics.     

Screening various Yarrowia lipolytica strains for citric acid production

Citric acid (CA) productivity by Yarrowia lipolytica dependents on strain type, carbon source, carbon to nitrogen (C/N) molar ratio as well as physicochemical conditions (pH, temperature, oxygen transfer rate, etc.). In the current study, 10 different Y. lipolytica strains were first challenged in shake-flask culture for CA production in a glucose-based media under nitrogen-limited conditions. For the most promising one, strain K57, CA productivity was monitored during culture in batch bioreactor for three initial C/N molar ratio (167, 367, and 567 Cmol/Nmol). The highest CA yield (0.77 g/g glucose), titre (72.3 g/L CA), and productivity (0.04 g/g.h) were found for C/N ratio of 367. However, the highest growth rate was obtained for an initial C/N ratio of 167. From these results, Y. lipolytica strain K57 could be considered to produce CA at higher titre on glucose-based medium in batch bioreactor than others Y. lipolytica strain reported in the literature.     

基于城区场景的5G SA网络时长驻留比提升策略研究

5G驻留能力是反映5G用户感知非常重要的一个指标。本文重点对影响5G SA网络时长驻留比的因素进行了分析，其次从规划、建设、优化、市场营销4个方面提出了具体的提升思路，并从市场、终端、网络三个维度制定了不同的应对策略。从目前的策略实施和应用效果来看，5G SA时长驻留比提升比较明显，对打造5G 精品网、促进5G业务分流、助力公司数智化转型发展起到了重要作用。     

A novel constitutive stress-strain law for compressive deformation of the gas diffusion layer

Substantial compressive deformation occurs in the gas diffusion layer (GDL) under the pressure applied during the fuel cell assembly. The GDL deformation has a direct impact on the efficiency and performance of the fuel cell since it leads to the alteration of the GDL microstructure and porosity. This makes the accurate characterization of the GDL compressive behavior crucial for analyzing the fuel cell performance and its optimal design. In this paper, analytical, experimental, and numerical methods have been employed to comprehensively study the constitutive law of the GDL under compression. Starting from the recently developed stress-density relations, the constitutive stress-strain equations are derived for the GDL and the relation between the stress-density and stress-strain laws are revealed. Experimental compression tests have been performed on GDL samples and the capability of the proposed constitutive law in capturing the real behavior of the material has been proved. It has been observed that the simplifying assumption of constant zero Poisson's ratio in the through-plane direction made in many previous studies cannot accurately represent the GDL material behavior and a modification is proposed. The developed constitutive law has been successfully implemented in a finite element model of the GDL-bipolar plate assembly in the fuel cell structure and the variations of the GDL porosity, density, and through-plane Young's modulus and Poisson's ratio have been investigated for different vertical displacements of the bipolar plate.     

石油降解菌ZS1对典型抗生素毒害作用的应激响应机制

为了解抗生素对石油降解菌的生态效应及微生物对典型抗生素毒害作用的应激响应机制，通过开展不同浓度典型抗生素对高效石油降解菌铜绿假单胞菌（ZS1）的毒性试验，研究了菌体细胞在3种不同种类抗生素（土霉素、红霉素、磺胺嘧啶）作用下的生长及毒理指标。结果表明，3种抗生素对ZS1有不同的抑菌效果，其中土霉素对ZS1活性的抑制程度最强，抑制率随着土霉素浓度的增大而明显上升，有显著的浓度-效应关系。研究了ZS1抗氧化酶（过氧化氢酶、过氧化物酶、超氧化物歧化酶）对抗生素的响应机制，结果表明ZS1受到污染时会通过产生抗氧化酶抵抗外界污染并维持细胞功能。