涉外企业的货币经营风险管理

结合涉外企业投入与产出所处市场的分割程度或一体化程度,分析了当地企业、进口企业、出口企业或全球经营企业所面临的货币经营风险;对计量涉外企业货币经营风险的方法进行比较,认为管理层估计法对于计量货币经营风险以及制定相应的竞争对策有着重要作用;分别从金融性套期保值、经营性套期保值和营销策略等视角讨论货币经营风险的管理。笔者认为:金融性套期保值通过锁定涉外企业的外币现金流出或流入,可部分抵消涉外企业的货币经营风险暴露;经营性套期保值通过调整企业的经营业务并尽可能多地增加经营现金流,可从根本上提高涉外企业适应汇率变化的能力;通过影响涉外企业及其竞争对手所处的经营环境,营销策略有助于降低涉外企业的货币经营风险暴露。     

二甲亚砜热稳定性的实验研究

采用先进的绝热加速量热仪为手段,对二甲亚砜的热稳定性进行了系统研究,其内容涉及纯二甲亚砜的热稳定性、加酸碱和硫化物等杂质后二甲亚砜的热稳定性,包括初始放热温度、温升速率、温度-压力等;通过修正试验数据,消除了热惰性因子的影响;得到了二甲亚砜的热稳定性特性。研究表明,在酸、碱存在时,二甲亚砜在室温下即可发生强烈的放热反应,导致二甲亚砜的分解温度提前。该实验研究结果,对二甲亚砜的安全生产工艺过程控制具有重要参考价值。     

硝酸甲胺反应过程的安全性研究

用反应量热仪(RC1e)对硝酸溶液与一甲胺溶液在反应过程中的热安定性进行初步研究,分别测试不同反应温度、加料速度和初始硝酸浓度下反应的放热情况。实验结果表明:该中和过程反应迅速,在室温就能进行;与反应温度、加料速度相比,起始硝酸浓度对反应安全性影响最大,且硝酸浓度越高,反应的速度和反应的完全程度也越高。实验还表明:RC1e是研究反应过程中热安定性情况的有效工具,能通过反应过程的热量变化体现反应速率,所得结果对硝酸甲胺的工业化生产具有重要的参考价值。     

Effects of organic matter on Leymus chinensis germination,growth, and urease activity and available nitrogen in coastal saline soil

ABSTRACT

The present study was carried out to investigate the effect of three organic matters (stalk powder, microbial fertilizer, and manure) on Leymus chinensis germination, growth, and urease activity and available nitrogen (N) in coastal saline soil. The study was conducted in a completely randomized design with eight treatments: J₀V₀Y₀, J₁V₀Y₀, J₀V₁Y₀, J₀V₀Y₁, J₁V₁Y₀, J₁V₀Y₁, J₀V₁Y₁, J₁V₁Y₁. The notations were based on the quantities of each agent added to 1 kg of coastal saline soil: J₀ – no straw powder, J₁ – 0.2 kg straw powder, Y₀ – no manure, Y₁ – 0.3 kg manure, V₀ – no microbial fertilizer, V₁ – 0.2 L microbial fertilizer, each in quantic repeat. L. chinensis was sown as 50 seeds per pot. Results indicated that addition of organic agents exerted a significantly enhanced germination, increase in fresh weight and elevated soil urease activity. Soil available N levels were significantly positively correlated with soil urease activity and fresh weight, but not with germination rate. It is noteworthy that the halophyte L. chinensis showed improved characteristics when grown in coastal saline soil with addition of organic amendments.     

Development of heat transfer and evaporation model of LNG covered by Hi-Ex foam

Natural gas is a kind of clean, efficient green energy source, which is used widely. Liquefied natural gas (LNG) is produced by cooling natural gas to −161 °C, at which it becomes the liquid. Once LNG was released, fire or explosion would happen when ignition source existed nearby. The high expansion foam (Hi-Ex foam) is believed to quickly blanket on the top of LNG spillage pool and warm the LNG vapor to lower the vapor cloud density at the ground level and raising vapor buoyancy. To identify the physical structure after it contacted with LN₂ and to develop heat transfer model, the small-scale field test with liquid nitrogen (LN₂) was designed. In experiment, three layers including frozen ice layer, frozen Hi-Ex layer and soft layer of Hi-Ex foam were observed at the steady state. By characterizing physical structure of the foam, formulas for calculating the surface of single foam bubble and counting foam film thickness were deduced. The micro heat transfer and evaporation model between cryogenic liquid and Hi-Ex foam was established. Indicating the physical structure of the frozen ice layer, there were a certain number of icicles below it. The heat transfer and evaporation mathematical model between the frozen ice layer and LNG was derived. Combining models above with the heat transfer between LNG, ground and cofferdam, the heat transfer and evaporation mathematical model of LNG covered by Hi-Ex foam was developed eventually. Finally, LN₂ evaporation rate calculated by this model was compared with the measured evaporation rate. The calculated results are 1.2–2.1 times of experimental results, which were acceptable in engineering and proved the model was reliable.     

SBR法处理低C/N污水的工程应用——以某基地污水处理站改造工程为例

低C/N污水的生化处理过程中,由于碳源不足,不能满足硝化和反硝化的要求,造成出水NH3-N超标。采用SBR工艺对某基地污水处理站厌氧处理后的低C/N污水进行改造,处理后出水COD去除率达到97%以上,NH3-N去除率达到93%以上。     

复合沸石滤床修复北方景观水体的实验研究

以天然矿物质沸石、细砂及煤渣取代传统滤料构建复合基质生态床,表面种植景观植物,采用下向流-上向流运行方式修复北方景观水体。分别进行静态实验及不同循环速率下的动态实验,考察对水体污染物去除过程。结果表明,2种运行方式下对水体NH⁺₄-N去除率都在85%以上,其中以1 h为循环周期的运行方式去除率达97%,较静态提高12.8%;TN去除率最高为84%;TP去除不稳定,过程缓慢。煤渣层对NH⁺₄-N的去除效果差,硝化作用不彻底与反硝化作用的加强使下层出水NH⁺₄-N 、NO^-₂-N及NO^-₃-N浓度均高于上层。提高循环速率有利于对氮的去除。     

反渗透处理稀土氨氮废水试验研究

根据稀土冶炼厂排放的碳铵沉淀洗涤废水的水质情况,采用NH4Cl和 NaCl模拟废水进行了反渗透可行性对比实验。模拟实验发现,在相同条件下反渗透对NaCl 较NH₄Cl 有着更高的去除率,而NH₄Cl 相对NaCl则有着更高的产水速率。实际废水试验结果表明,在恒定操作压力范围内回收率为65%的条件下,NH₄Cl浓度为2.85 g/L的碳铵沉淀洗涤废水经反渗透处理其NH₄Cl去除率为77.3%,可作为氨氮废水的预处理。对该废水处理成本进行了分析,得出其约为2.7元/m³,比相近浓度氨氮废水的氨吹脱处理成本节省约26%。     

高锰酸钾降解地下水中PCE的研究

以氯代有机污染物中常见的PCE为目标污染物,以自制高锰酸钾溶液为氧化剂,采用批实验方法,探讨了高锰酸钾降解PCE的反应动力学、影响因素以及反应机理。反应结果表明,高锰酸钾降解PCE的反应符合一级动力学方程,反应活化能E为57.119 kJ/mol,在30℃条件下,反应速率常数为0.0076 min^-1,半衰期为91.20 min。在pH在3～10,离子强度在0～0.1030 mol/L之间变化时,反应速率不受明显影响。     

抽穗期低温对杂交晚粳宁67A／K1722结实率的影响

利用人工气候箱研究了抽穗期低温对杂交晚粳新组合宁67A/K1722开花量、包颈率及结实率的影响。结果表明：低温使抽穗速度明显变慢,开花量减少,包颈率呈现上升趋势,不同温度处理对结实率的影响不同,17℃与21℃处理间差异极显著,而19℃与21℃间差异不显著,不同时期处理及不同处理天数（3d,5d,7d和12d）间结实率差异不显著,表明该组合对抽穗期低温的耐受力较强,对抽穗期耐低温的鉴定指标问题进行了讨论。