Spray Drying Performance of a Laboratory Spray Dryer for Tomato Powder Preparation

This work investigates the performance of a spray dryer for tomato powder preparation by spray drying of tomato pulp. Samples of tomato pulp with a 14% constant total solids concentration were used, and a pilot scale spray dryer (Buchi, B-191) with cocurrent operation and a two-fluid nozzle atomizer was employed for the spray drying process. Twenty-four different experiments were conducted keeping constant the feed rate, the feed temperature, and the atomizer pressure, and varying the compressed air flow rate, the flow rate of drying rate, and the air inlet temperature. In each experiment the air outlet temperature was recorded. Data for the residue remaining in the chamber and cyclone walls was gathered and two types of efficiencies were calculated as an indication of the spray dryer performance. Analysis of experimental data yielded correlations between residue accumulation and the variable operating conditions. The same operating parameters had a great influence on the air outlet temperature whereas temperature deviations were observed comparing measured air outlet temperatures with corresponding outlet adiabatic saturation temperatures.     

Moisture adsorption characteristics of a thin bed of polycrystalline potash pellets: Part I. Experimental study

This study is an experimental investigation of heat and moisture transfer within a packed bed of polycrystalline, porous potash pellets. Experiments were first performed to determine the moisture uptake characteristics on individual pellets subject to a step-change in relative humidity. Then a bed of pellets was subjected to flows of humid air on the upper boundary and a cold impermeable surface on the lower boundary resulting in a temperature gradient across the bed. Temperature and moisture content were measured within the bed. It was found that moisture uptake is less for potash pellets and they are less likely to cake than granular and standard potash when subjected to the same ambient air conditions. This is due to the porous nature of the pellet and its nearly uniform size and spherical shape.     

Crop yield, nitrogen uptake and nitrate-nitrogen accumulation in soil as affected by 23 annual applications of fertilizer and manure in the rainfed region of Northwestern China

Application of chemical fertilizers and farmyard manure affects crop productivity and improves nutrient cycling within soil–plant systems, but the magnitude varies with soil-climatic conditions. A long-term (1982–2004) field experiment was conducted to investigate the effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizers and farmyard swine manure (M) on seed and straw yield, protein concentration, and N uptake in the seed and straw of 19-year winter wheat (Triticum aestivum L.) and four-year oilseed (three-year canola, Brassica napus L. in 1987, 2000 and 2003; one-year flax, Linum usitatisimum L. in 1991), accumulation of nitrate-N (NO₃-N) in the soil profile (0–210 cm), and N balance sheet on a Huangmian soil (calcaric cambisols, FAO) near Tianshui, Gansu, China. The two main plot treatments were without and with farmyard swine manure (M); sub-plot treatments were control (Ck), N, NP, and NPK.␣The average seed yield decreased in the order MNPK ≥ MNP > MN ≥ NPK ≥ NP > M > N > Ck. The average effect of manure and fertilizers on seed yield was in the order M > N > P > K. The seed yield increase was 20.5% for M, 17.8% for N, 14.2% for P, and 2.9 % for K treatment. Seed yield response to fertilizers was much greater for N and P than for K, and it was much greater for no manure than for manure treatment. The response of straw yield to fertilization treatments was usually similar to that of seed yield. The N fertilizer and manure significantly increased protein concentration and N uptake plant. From the standpoint of increasing crop yield and seed quality, MNPK was the best fertilization strategy. Annual applications of N fertilizer and manure for 23 successive years had a marked effect on NO₃-N accumulation in the 0–210 cm soil profile. Accumulation of NO₃-N in the deeper soil layers with application of N fertilizer and manure is regarded as a potential danger, because of pollution of the soil environment and of groundwater. Application of N fertilizer in combination with P and/or K fertilizers reduced residual soil NO₃-N significantly compared with N fertilizer alone in both no manure and manure plots. The findings suggest that integrated and balanced application of N, P, and K fertilizers and␣manure at proper rates is important for protecting soil and groundwater from potential NO₃-N pollution and for maintaining high crop productivity in the rainfed region of Northwestern China.     

叠合盆地油气成藏体系研究方法探讨

应用三维模拟技术,强化油气成藏体系动态演化过程,采用正反演结合的思路,探讨叠合盆地油气成藏体系的研究思路和方法。研究过程分五步:通过成藏要素研究构建地质模型;通过正演烃源岩生烃过程与时空演化,分阶段计算生烃量;通过输导体系研究来调整油气最终的分布;应用油气组分追踪技术分析不同烃源岩层贡献比例;根据三维模拟结果动态分析资源空间分布及变化过程。     

论金融衍生产品的风险积聚效应

从美国次贷危机出发,探讨了金融衍生产品的风险积聚功能。认为:由于金融衍生产品的价格受相关基础金融工具价格决定,具有财务杠杆效应、复杂的性质和设计的灵活性等特性,使其具有风险积聚能力;而金融自由化、管理层认识的滞后、激励机制的过度使用以及先进的交易技术是风险积聚的客观条件;建议通过严格的监管、完善的制度、合理的激励机制以及风险教育来化解金融衍生产品的风险积聚效应。     

S-P混杂纤维对混凝土长期性能与耐久性影响

采用对比的试验方法,研究并讨论了钢纤维、聚丙烯纤维及其混杂对混凝土长期性能及耐久性的影响.研究结果表明,用不同尺度、不同性质的钢纤维与聚丙烯纤维按二元混杂以总体积率0.9%掺入高性能混凝土中,明显改善了水泥混凝土的长期性能,90d干缩值减少36.6%,200d徐变度降低45.4%,并可显著提高混凝土的耐久性能,相对渗透系数降低79.03%,氯离子渗透系数降低30.5%.     

Shut-cut nitrification characteristics of aerobic granule in a sequencing batch airlift reactor at low temperature

To investigate the shut-cut nitrification characteristics of aerobic granule,an aerobic granular sequencing batch airlift reactor(AG-SBAR) was carried out with mixed carbon sources of sodium acetate and glucose at 10±1 ℃.Results indicated that ammonia oxidizing bacteria was accumulated inside the aerobic granules and the reactor performed stably with shut-cut nitrification for a long term at low temperature.During the stable operation period,the effluent ammonia nitrogen concentration was maintained at 13.6 mg/L without nitrate and nitrite when the COD/N ratio was 20:1.However,the effluent concentration of ammonia nitrogen was below 0.5 mg/L with effluent nitrosation ratio of 96.7% on average when the COD/N ratio was reduced to 15:1 and 10:1.And the effluent phosphorus concentration was less than 0.4 mg/L during the stable period with the sludge retention time of 30 d.The phosphorus removal efficiency was not strongly influenced by the adjustment of COD/N ratio in this experiment.The removal efficiencies for COD,NH4+-N and PO43--P were 91.3%-94.6%,97.9%-99.7% and 97.1%-99.5%,respectively.     

Robust and Low-Complexity Synchronization for Energy Detection UWB Receiver

A simple method using aided sliding rectangular windows for synchronization in e nergy detector (ED) receiver is proposed for impulse-based ultra wideband radio s (IR-UWB) under binary pulse position modulation (PPM), therefore grants an at tractive solution for gaining low complexity while the accompanying performance loss in terms of UWB signal reception is comparatively low. Also, a method is de veloped to suppress noise through accumulation of integrated results before sync hronization point is reached....     

菱镁防火板改性的实验研究

研究了菱镁制品防止返卤泛霜的工艺和结构改性问题,采用正交试验优化菱镁水泥配比,同时加入微硅粉和粉煤灰及乳白胶等构成的复合改性剂,通过实验找出复合改性剂的最佳配方.复合改性剂中的高分子聚合物包覆在晶体外壁形成良好的防水保护层,提高了耐水性;扫描电子显微镜(SEM)观察微观结构表明,改性剂中的硅酸根在晶体间的空隙中自行交联一方面堵塞毛细孔道,抑制氯离子渗出而返卤泛霜,另一方面又能与Mg2+形成抗水性较强的胶凝结晶化合物,使菱镁制品返卤泛霜的现象得到了明显的抑制,同时也增加了制品强度和减小了翘曲变形性.     

循环动载作用下层状介质长期沉降计算方法

针对循环动载作用下交通基础设施长期沉降,研究解决在移动条形荷载作用下层状介质动应力和循环加卸载条件下层状介质残余应力、永久应变与残余沉降计算2个基本问题.采用Fourier积分变换与递推矩阵方法,依据平面问题动力微分方程、边界条件与层间连续条件,推导得到移动条形荷载作用下的层状介质动应力解析解.考虑应力水平和应力路径的影响,提出新的永久应变经验公式,通过卸载条件下附加永久应变的弹性边值问题求解,获得循环动载作用下层状介质残余应力与长期沉降的表达式.针对3种不同路基半刚性基层沥青路面环道试验,研究路表残余长期沉降变化规律;通过实测值和预测值对比分析验证了本文方法的合理性和可靠性.