铝灰渣与废盐酸制备聚合氯化铝的试验研究

以铝灰渣和废盐酸为原料,通过酸溶法制备聚合氯化铝,考察了原料配比、反应温度、反应时间、熟化温度、熟化时间等因素对聚合氯化铝性能的影响,并对最佳工艺参数条件下制备的聚合氯化铝进行红外光谱分析。结果表明,铝灰渣和废盐酸制备聚合氯化铝的最佳工艺参数为:原料配比为m∶V1∶V2=20∶55∶80,反应温度为85℃,反应时间为3.5 h,熟化温度为80℃,熟化时间为42 h;在此条件下,制备的聚合氯化铝中氧化铝质量分数为8.15%,盐基度为35.6%;红外光谱分析表明合成的聚合氯化铝中存在聚合态铝和羟基结构。     

液化气体汽车槽罐缺陷评估及修复

液化气体在工业生产和民用等方面应用广泛,其运输工具为液化气体汽车槽罐。槽罐与＂V＂型支撑连接焊缝受运输振动等因素影响,易出现裂纹缺陷,且易过渡到罐体母材上。对一实例缺陷进行了原因分析,对槽罐的使用寿命进行了评估,给出了缺陷修复工艺和预防措施。     

Effect of Mn-Bearing Dispersoids on Tensile Properties and Recrystallization Resistance of Al-3Mg-0.8Mn Rolled Alloy

Herein, the precipitation behavior of Mn-bearing dispersoids in Al-3Mg-0.8Mn (AA5454) alloy subjected to different heat treatments is investigated. The effects of Mn-bearing dispersoids on the tensile properties and recrystallization resistance of the abovementioned alloy during hot/cold rolling and postrolling annealing are evaluated. The results show that a low-temperature three-step heat treatment (275 °C/12 h + 375 °C/48 h + 425 °C/12 h) generates a higher number density of Mn-bearing dispersoids with finer sizes compared with the typical high-temperature heat treatment (430 °C/2 h + 480 °C/2 h + 525 °C/2 h), thus resulting in significantly improved tensile strengths of hot/cold-rolled sheets. After annealing at 300 °C, the yield strength (YS) of the alloy reached 196 MPa after hot rolling and 237 MPa after cold rolling, showing an improvement of 30%–32% over samples subjected to high-temperature heat treatment. In addition, the low-temperature heat treatment provides a higher recrystallization resistance after hot and cold rolling owing to the higher number density of Mn-bearing dispersoids and the lower fraction of dispersoid-free zones. The YS contributions of various strengthening components after hot and cold rolling are discussed based on constitutive models. The predicted yield strengths agree well with the experimental values.     

Impermeable Graphene Skin Increases the Heating Efficiency and Stability of an MXene Heating Element

A Joule heater made of emerging 2D nanosheets, i.e., MXene, has the advantage of low-voltage operation with stable heat generation owing to its highly conductive and uniformly layered structure. However, the self-heated MXene sheets easily get oxidized in warm and moist environments, which limits their intrinsic heating efficiencies. Herein, an ultrathin graphene skin is introduced as a surface-regulative coating on MXene to enhance its oxidative stability and Joule heating efficiency. The skin layer is deposited on MXene using a scalable solution-phased layer-by-layer assembly process without deteriorating the excellent electrical conductivity of the MXene. The graphene skin comprises narrow and hydrophobic channels, which results in ≈70 times higher water impermeability of the hybrid film of graphene and MXene (GMX) than that of the pristine MXene. A complementary electrochemical analysis confirms that the graphene skin facilitates longer-lasting protection than conventional polymer coatings owing to its tortuous pathways. In addition, the sp² planar carbon surface with a low heat loss coefficient improves the heating efficiency of the GMX, indicating that this strategy is promising for developing adaptive heating materials with a tractable voltage range and high Joule heating efficiency.     

Heat stability of reconstituted, protein-standardized skim milk powders

We determined the effects of standardization material, protein content, and pH on the heat stability of reconstituted milk made from low-heat (LH) and medium-heat (MH) nonfat dry milk (NDM). Low-heat and MH NDM were standardized downward from 35.5% to 34, 32, and 30% protein by adding either edible lactose powder (ELP) or permeate powder (PP) from skim milk ultrafiltration. These powders were called standardized skim milk powders (SSMP). The LH and MH NDM and SSMP were reconstituted to 9% total solids. Furthermore, subsamples of reconstituted NDM and SSMP samples were set aside to measure heat stability at native (unadjusted) pH, and the rest were adjusted to pH 6.3 to 7.0. Heat stability is defined as heat coagulation time at 140°C of the reconstituted LH or MH NDM and SSMP samples. The entire experiment was replicated 3 times at unadjusted pH values and 2 times at adjusted pH values. At an unadjusted pH, powder type, standardization material, and protein content influenced the heat stability of the samples. Heat stability for reconstituted LH NDM and SSMP was higher than reconstituted MH NDM and SSMP. Generally, decreased heat stability was observed in reconstituted LH or MH SSMP as protein content was decreased by standardization. However, adding ELP to MH SSMP did not significantly change its heat stability. When pH was adjusted to values between 6.3 and 7.0, powder type, standardization material, and pH had a significant effect on heat stability, whereas protein content did not. Maximum heat stability was noted at pH 6.7 for both reconstituted LH NDM and SSMP samples, and at pH 6.6 for both reconstituted MH NDM and SSMP samples. Furthermore, for samples with adjusted pH, higher heat stability was observed for reconstituted LH SSMP containing PP compared with reconstituted milk from LH SSMP containing ELP. However, no statistical difference was observed in the heat stability of reconstituted milk from MH NDM and MH SSMP samples. We conclude that powder type (LH or MH) and effect of standardization material (ELP or PP) can help explain differences in heat stability. The difference in the heat stability of powder type may be associated with the difference in the pH of maximum heat stability and compositional differences in the standardization material (ELP or PP).     

Equilibrium moisture content and heat of desorption of saffron

The equilibrium moisture contents of saffron (Crocus sativus L.) stigmas were determined experimentally using the standard gravimetric method at temperatures 30, 45 and 60 °C and water activity ranging from 11% to 83%. The sorption isotherm curves of saffron were sigmoidal in shape and decreased with increased temperature at constant relative humidity. Five selected isotherm models GAB, modified Henderson, modified Chung‐Pfost, modified Halsaey and modified Oswin were tested to fit the experimental isotherm data. Modified Oswin and modified Henderson models were found acceptable for predicting desorption moisture isotherms and fitting to the experimental data, respectively. The isosteric heats of desorption, determined from equilibrium data using the Clausius‐Clapeyron equation, were found to be a function of moisture content. The net isosteric heat of desorption of saffron varied between 1.38 and 5.38 kJ mol^?1 at moisture content varying between 2% and 20% (d.b).     

Partial biochemical characterization of tetrazolium red‐reactive Lactobacillus plantarum mutants

One thousand colonies derived from Lactobacillus plantarum ATCC 8014 cells that survived 34–43 × 10³ ergs cm^‐2 ultraviolet irradiation were screened on media containing tetrazolium red to detect fermentative mutants. Fermentation end‐products formed from pyruvate, glucose, or lactose catabolism were determined. All 37 stable tetrazolium red‐reactive mutants had increased pyruvate utilization compared to the wild‐type strain. Only two did not produce lactate from exogenous pyruvate. When glucose or lactose were substrates, these two mutants and six other representative mutants produced lactate at levels similar to the parent strain. Although the average lactate and acetoin production from pyruvate by the mutants and wild‐type strains were similar, 25% of the mutants had increased acetoin production.     

低损耗纬编成形女士背心的结构设计与建模

为降低纬编成形背心织造工序的原料损耗和生产能耗,以女士紧身短背心为开发对象,进行结构建模与工艺实践。首先将传统纬编成形背心纵向织造的宽肩带转化为横向织造的矩形肩带,其次对背心进行功能分区,设计不同性能的无缝组织。然后通过虚拟仿真,参数可视化建模调整分区结构与数值,实际织造后对比结构转化前后的损耗。结果表明：通过对纬编成形背心的结构转化并进行功能分区、可视化建模,进行工艺参数的调节,实现了低损耗与高效率兼顾的纬编成形女士紧身短背心的生产,为纬编成形服装结构转化与节能产品开发提供参考。     

生活垃圾分类直运模式探究

随着社会的不断发展,人们的生活水平也在不断提升,而生活中产生的垃圾也越来越多,对垃圾的运输成为当前社会考虑的重要内容.在提倡垃圾分类过程中,生活垃圾的直运模式成为当前的一种新型垃圾收运模式,该模式具有成本低、环保等特点,能够更好地满足城市垃圾分类的需求.本文了解了转运模式的现状和问题,说明垃圾直运模式的意义,提出生活垃圾直运模式策略,为生活垃圾分类直运模式的发展提供参考.