Column solid‐phase extraction of sunset yellow and spectrophotometric determination of its use in powdered beverage and confectionery products

A new and simple solid‐phase extraction method for the determination of trace levels of sunset yellow has been developed on Diaion HP 2MG column system. The adsorbed sunset yellow on the resin was eluted with 3 mL of methanol and determined by UV–Vis spectrophotometry at 484 nm. Various experimental parameters such as pH, amount of sunset yellow, flow rates of sample and eluent solutions, resin amount, sample volumes, etc. were investigated. The influences of some alkali, alkali earth and transition metals on the recoveries of sunset yellow were investigated. The recovery values for sunset yellow were higher than 95%. Preconcentration factor was found as 150. The detection limit (three sigma) of the reagent blank for sunset yellow was 5.2 μg L^?1. The relative standard deviations (RSD) of the procedure were found as 3.9%. The validation of the presented procedure was performed by the method of standard addition. The procedure was successfully applied to the determination of trace levels of sunset yellow in powdered beverage and confectionery products.     

AZ91HP镁合金化学镀镍磷及镀层性能研究

目的提高AZ91HP镁合金的耐蚀及耐磨性,扩大其应用范围。方法采用H_3PO_4+Na_3PO_4酸洗液+NH_4HF_2活化的无铬前处理工艺,再直接化学镀,获得镍磷合金镀层,随后对镀层进行了热处理。对施镀前后基体和镀层的形貌、显微硬度和耐蚀性等进行了表征分析。结果 AZ91HP镁合金经H_3PO_4+Na_3PO_4酸洗+NH_4HF_2活化的无铬处理后施镀,形成的细小胞状组织均匀致密,结合力良好,镀层结构以非晶态相为主,耐腐蚀性比基体显著增高。经热处理后,镀层的硬度明显增高且在400℃时获得的镀层硬度最高,但耐蚀性有所下降。结论 H_3PO_4+Na_3PO_4酸洗体系+NH_4HF_2活化为镁合金提供了一种环保而有效的化学镀前处理方法,获得了以非晶态相为主的Ni-P镀层,提高了基体的耐腐蚀性,镀后热处理可进一步提高镀层的硬度。     

HP700型圆锥破碎机在调军台选厂的初步实践

ＨＰ７００型圆锥破碎机具有优良的性能，增大了偏心距，加快了轴转速，采用曲线型（非阻塞型）破碎腔，从而在破碎腔内只需较低破碎力，在调军台选厂的初步实践达到了较好的效果。     

362MW汽轮机高压缸上下缸负温差分析与处理

针对某汽轮机组高压外缸上下缸负温差的问题,通过收集运行工况数据,探讨设备内部结构,对进汽管滑环式密封环卡涩这一问题进行了分析和处理,对缸体及轴封套变形进行全面检查处理,彻底解决了负温差过大的问题.     

块三对角线性方程组的一种有效并行算法

提出了求解系数矩阵为块三对角的线性方程组的一种适合于MIMD分布式存储的并行算法,该算法以系数矩阵分解为基础,充分利用了系数矩阵结构的特殊性,进行了近似处理,使整个计算过程只在相邻处理机间通信两次,具有很高的并行效率,并在理论上给出了该算法成立的充分条件。最后,在HPrx2600集群上进行数值试验,结果表明,加速比呈线性增加,并行效率达到90％以上。     

高压氨泵干气密封泄漏的故障分析与处理对策

分析多级离心式高压氨泵干气密封损坏泄漏的原因,是机封紧定套失效使机封内侧动环传动轴套和定位轴套外移,动、静环比压加大,磨损加剧,密封面损伤而泄漏.采取在车床上单边进刀量为0.25 mm的整形光刀措施,可继续使用.     

HP800破碎机常见故障原因分析及对策

HP800破碎机是鞍矿齐大山选矿厂破碎系统中的主体设备,具有破碎比大、运转效率高及产品粒度均匀等优点,它能否稳定运行对选厂的生产起着至关重要的作用.因此,对该破碎机常见故障产生的原因进行分析与处理,确保设备稳定运行.     

Combined effect of high pressure treatment and anti-microbial bio-sourced materials on microorganisms' growth in model food during storage

Antimicrobial bio-sourced films based on poly(lactic acid) containing either carvacrol or allyl isothiocyanate (AITC) were prepared and their antimicrobial properties were assessed on Botrytis cinerea during storage and after a high pressure (HP) “pasteurisation-like” treatment (up to 800 MPa at ambient temperature). A dry process (extrusion + thermomoulding) was used to shape the material. The high temperature encountered during film processing dramatically decreased the carvacrol and AITC content in the film, leading to a less efficient antimicrobial activity. The use of β-cyclodextrin (β-CD) to encapsulate the active compounds before film processing proved to be efficient to protect the AITC against thermal degradation and to control its release from the films during its use. PLA-based films containing either AITC or β-CD encapsulated AITC showed a significant activity against B. cinerea. An effective combination between the antimicrobial activity of AITC-based films and the high pressure treatment was observed on a model food system (PDA) inoculated with N × 10⁴ (N ~ 1–9) conidia of B. cinerea. An HP treatment of only 300 MPa associated with an antimicrobial PLA/β-CD system providing an initial quantity of active agents equivalent to 4 mg of AITC/L of air (i.e. almost 2 folds lower than the minimal inhibition concentration of the active packaging used alone, which was determined to be equal to 10 mg/L of air in the same conditions) was found more efficient (total inhibition of B. cinerea growth during 10 days) than an 800 MPa HP treatment used alone (increase of the lag phase growth of 3.3 days).

Industrial relevance

The consumer demand for “fresh like” product containing reduced amount of preservatives without compromising human and environmental safety needs the development of new preservation strategies. As a consequence, the concept of “hurdle technologies” has risen up. The combined effect of HP treatment and volatile antimicrobial packaging allowed the use of lower individual treatment intensities to inhibit B. cinerea growth. Combining such “hurdles” is of relevance in the context of development of low-cost and eco-friendly food technologies.     

基于矩阵分解的周期块三对角线性方程组的并行直接解法

提出了分布式环境下求解周期块三对角线性方程组的一种并行算法．该算法充分利用系数矩阵结构的特殊性,通过对系数矩阵进行适当分解及近似处理,使算法只在相邻处理机间通信2次,并从理论上给出了算法有效的一个充分条件．最后,在HP rx2600集群上进行了数值试验,结果表明,实算与理论是一致的,并行性也很好．