Modeling of Calcium Chloride and Pectin Methylesterase Prefreezing Treatments of Strawberries and Jams

ABSTRACT: :
Different calcium chloride (CaCl₂) and pectin methylesterase (PME) prefreezing treatments in a vacuum were used to clarify the most effective prefreezing factors for strawberries and traditional jams. Fractional factorial design and modeling were used. CaCl₂ had the greatest effect on the majority of the 15 studied responses ( p < 0.001). The pretreatment time should be short (about 5 to 10 min), the temperature low (less than 20 °C), the vacuum level high (pressure less than 10 kPa), the CaCl₂ concentration moderate (about 1%) and the dosage of PME comparatively low (about 50 to 100 nkat/g) in order to yield high quality frozen strawberries for jam making.     

Wind energy resource assessment for five locations in Saudi Arabia

The analysis of recently collected wind data at five sites in Saudi Arabia namely, Dhulum, Arar, Yanbu, Gassim and Dhahran is presented. The five sites represent different geographically and climatologically conditions. The data collected over a period spanned between 1995 and 2002 with different collection periods for each site. Daily, monthly and frequency profiles of the wind speed at the sites showed that Dhulum and Arar sites have higher wind energy potential with annual wind speed average of 5.7 and 5.4 m/s and speeds higher than 5 m/s for 60 and 47% of the time, respectively. The two sites are candidates for remote area wind energy applications. The costal site's, i.e. Yanbu and Dhahran wind speed data indicated that the two sites have lower annual wind speed averages and wind blows at speed higher than 5 m/s during afternoon hours. That makes the two sites candidates for grid connected wind systems for electrical load peak shaving. The data of Gassim site showed that the site has the lowest wind energy potential compared to the others. The annual energy produced by a Nordex N43 wind machine is estimated to be 1080, 990, 730, 454 and 833 MWh for Dhulum, Arar, Yanbu, Gassim and Dhahran, respectively. The analysis showed that the estimated annual energy produced by the machine based on 10 min averaged data is 2.5% higher than the estimated energy based on 30 min averaged data.     

油气输送管线冰堵定位检测技术的开发与应用

冬季油气输送管线的冰堵时刻威胁着高寒地区石油化工装置的安全运行，带式传感器动态应变定位检测技术的研制与开发解决了这一难题，它能迅速而准确地查找冰堵点，从而保证炼化装置的冬季正常运行。     

20CrMnTiH钢水口堵塞机理研究与解决措施

研究了转炉生产20CrMnTiH钢时连铸水口堵塞的机理，主要通过精炼造CaO—Al2O3-SiO2-CaF2系渣，保持熔渣良好的流动性和高碱度、低熔点、低氧化铁，提高吸附夹杂能力并针对引起水口堵塞的物质，对钙处理、软吹及进站S含量进行严格的要求，成功解决了水口堵塞问题。     

Simulation of smoke from a burning vehicle and pollution levels caused by traffic jam in a road tunnel

Detailed analyses of smoke movement from a burning vehicle in a road tunnel have been carried out for the westbound Melbourne City Link tunnel. The time-averaged equations for velocity, pressure, temperature, and mass fraction of emissions were solved for transient condition using the CFD software FLUENT 6.0. For the analysis, a burning bus was assumed to release an equivalent energy of burning 500 l of diesel in 6 min, with vehicles upstream of the fire at a standstill. On the other hand, the vehicles downstream of the fire had enough time to escape from the tunnel through the exit portal. Due to the action of jet fans, most of the smoke was pushed downstream of the fire. The smoke had also dispersed about 55 m upstream of the fire, putting the passengers in this region at great risk. The emissions released from the vehicles in the jam, with their engines running, also posed a threat to human health. Within 8 min after the fire had started, the mass concentrations of O₂, CO₂ and CO were in the ranges of 0.12–0.15, 0.08–0.11 and 0.0006–0.0014, respectively. Therefore, quick evacuation of the passengers is essential in the event of a fire in the tunnel.     

磨削加工中磨削液对砂轮堵塞影响的试验分析

砂轮堵塞是影响砂轮耐用度的重要指标，磨削液在磨削加工中起到润滑、冷却、清洗等作用，对砂轮的堵塞有着较大影响．文章通过试验，分析了磨削液对砂轮堵塞的原因．     

应用分子蒸馏技术分离提纯玫瑰精油

应用刮膜式分子蒸馏装置对玫瑰精油的提纯进行了研究。考察了进料速率、进料温度、蒸发温度和刮膜器转速等因素对玫瑰精油分离效果的影响。通过试验,初步得到了工艺参数的范围:进料速率为50~70 mL/h,进料温度为53~60℃,蒸发温度Ⅰ为100~108℃,蒸发温度Ⅱ为120~130℃,操作压力1.5 Pa,刮膜器转速150~160r/m in,得到的玫瑰精油产品的纯度在86%以上,分离过程总收率大于60%,并为今后工艺参数优化奠定了基础。     

玫瑰香精油化学成分分析

应用气相色谱-质谱联用(GC/MS)方法,定性定量地分析了山东平阴玫瑰精油、新疆玫瑰精油、北京妙峰山玫瑰精油和保加利亚玫瑰精油的化学成分,各鉴定了29、37、23和24个成分.它们的主要成分均为香茅醇及其脂类、香叶醇、芳樟醇、玫瑰醚和丁香酚,其中北京妙峰山玫瑰油与其他油品有较大差异.各种香精物质含量上的差异使得这几种玫瑰油的香气产生了微妙的出入.详细地讨论了这4种玫瑰油的化学成分与香气间的关系,指出国内玫瑰油的不足之处,为提升我国玫瑰精油的品质提供借鉴和依据.     

牡丹江长江屯站2009年1月冰坝特征及其成因分析

对牡丹江长江屯站2009年1月5~7日形成的冰坝的概况、河道特性、冰坝特征及成因进行分析,以期为冰坝预测及凌汛分析等相关研究提供参考。     

北太平洋海温异常对黑龙江上游冰坝的影响及其预报的研究

在研究北太平洋海温异常对黑龙江冰坝的影响中,从预测黑龙江上游冰坝需要出发,利用反映北太平洋海域表面温度变化的分布型指数（该指数较好地表征出海温的年际变化特征及厄尔尼诺和拉尼娜事件）,以及黑龙江上游水文站的封江水位距平构建了该站的冰坝预报模型,该模型可以较好地预测出黑龙江上游冰坝,实际预测结果表明,该方法是可行的,在冰坝预报中可以发挥重要作用。