Fiber formation model for electrospinning. III. Critical fiber formation

The major concern on this study is the possibilities of polymer solution being continuous fiber form or separate small polymer bid form under the high electric field. Former case is the electrospinning and latter is the electrospraying. A formability model for electrospinning is suggested considering physical properties of the polymer solution and process parameters. This formability model is developed to predict onset of electrospinning. Formability is based on spinnability theories of C. D. Han and Ziabicki’s works. The results show that formability is determined by surface tension, viscosity of solution and radius of nozzle. The fiber diameters calculated through this newly developed formability model is presented and compared with the experimental data using electrospun PVP polymer solution.     

Fiber formation model for electrospinning. II. Stable jet voltage

The major concern in electrospinning process is the occurrence of jet formation. In order to study physical properties of the solution and process parameters, stable jet voltage model is developed to predict the stabilized jet in electrospinning. Break-up frequency model, that predicts behavior of drop breaking, is the theoretical background for stable jet voltage model. This newly developed model based on the previous work gives a clue to produce stable nano thickness fibers and the results are compared with the experimental data by PVP electrospinning. The result of stable jet voltage modeling shows that surface tension is the most important factor and molecular weight and concentration are both negligible for surface tension of solutions. Surface tension of the solution depends on the types of solvent. Therefore, surface tension of solution has different values of stable jet voltage. The stable jet voltage model that predicts the most similar experimental value is SIC hemispherical model under force mode.     

Preparation and dielectric properties of polyvinyl alcohol (Co,Zn Acetate) Fiber/n-Si and polyvinyl alcohol (Ni,Zn Acetate)/n-Si Schottky diodes

Dielectric properties and ac electrical conductivity (σ _ac ) of Au/PVA(Co, Zn acetate)/n-Si and Au/PVA(Ni, Zn acetate)/n-Si Schottky diodes (SDs) have been investigated in dark and under illumination by using experimental capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements at 1 MHz and room temperature. Experimental results indicate that the change in dielectric constant (ɛ′), dielectric loss (ɛ″), loss tangent (tanδ), the real (M′) and imaginary (M″) parts of electric modulus and ac electrical conductivity (σ _ac ) with illumination were found to change linearly with illumination level (P). On the other hand, the ɛ′, ɛ″, tanδ and σ _ac vs P have positive slope while the M′ and M″ vs P have negative slope. Such behavior of dielectric properties and σ _ac can be attributed to illumination induced electron-hole pairs under illumination effect in the depletion region of SDs. The obtained results under illumination suggest that these devices can be used as a sensor in optical applications.     

南非红麻产量基因型与环境互作的效应分析

本实验分析了9个红麻品种在南非地区的产量稳定性.结果显示,在南非纳塔尔地区,红麻产量的基因型和环境相互作用显著.在不同的参试地区和年份中,红麻鲜重,鲜茎产量以及干茎产量均为极显著差异.灌溉条件下各产量指标明显高于干旱地区.本实验还应用了3个不同的参数和方案,评估了这9个品种的稳定性.结果表明,综合三个参数,EI Salvador是在不同环境条件下具有丰产潜力的品种.     

Poly(vinylidene fluoride)/poly(ethylene-co-vinyl acetate) (20/80) blend. I. Miscibility and crystallization behavior

The miscibility and crystallization behavior of the blends of poly(vinylidene fluoride) (PVDF) and ethylene/vinyl acetate(20/80) copolymer (EVAc80) have been studied using a differential scanning calorimeter and a polarizing microscope equipped with a heating stage. From the melting point depression, the values of interaction energy densityB were calculated to be −1.3004 (cal/cm³) and the Flory-Huggins interaction parameterχ ₁₂ was found to be −0.0818 at 445.6 K. With increasing concentration of EVAc80, the radial growth rate of spherulite was reduced drastically. The FT-IR analysis of samples quenched from the melt to various temperatures showed increasing content ofβ-phase with increasing amount of blended EVA80 along with lower quenching temperature.     

乌龙茶加工环境工程技术研究(一)

茶叶加工环境工程是一项系统工程 ,它研究的重点是综合利用茶叶加工工艺学和环境工程学的各种成果 ,改善和控制茶叶加工过程中的环境条件 ,达到优质、高效、低耗目的。茶叶加工环境控制措施与程度 ,主要取决于茶叶加工工艺所要求的环境条件和外界自然条件。实践证明 ,最佳加工环境条件确定后 ,实际生产中还要根据环境调控设备是否经济合理 ,以及工艺和管理等具体条件 ,来修改环境控制的程度。因为茶叶加工环境工程研究的最终目的不是为了创造最佳的环境条件 ,而是为茶叶生产创造实实在在的经济效益。乌龙茶加工中萎凋和做青工序是决定乌龙茶…     

老茶园换种新技术讲座第一讲我国茶树良种繁育现状与老茶园换种新技术

[编者按] 自本刊21卷4期(1995)发表周汉忠等"老茶园换种新途径--短穗嫁接改种成园技术"一文之后,已引起人们关注.1999年9月本刊报道了浙江省茶叶学会和浙江大学茶学系联合举办"茶园良种化与无性繁殖新技术培训班"的信息后,更受到茶区广大专业户的欢迎.     

A simulation model of cereal–legume intercropping systems for semi-arid regions: I. Model development

Cereal–legume intercropping plays an important role in subsistence food production in developing countries, especially in situations of limited water resources. Crop simulation can be used to assess risk for intercrop productivity over time and space. In this study, a simple model for intercropping was developed for cereal and legume growth and yield, under semi-arid conditions. The model is based on radiation interception and use, and incorporates a water stress factor. Total dry matter and yield are functions of photosynthetically active radiation (PAR), the fraction of radiation intercepted and radiation use efficiency (RUE). One of two PAR sub-models was used to estimate PAR from solar radiation; either PAR is 50% of solar radiation or the ratio of PAR to solar radiation (PAR/SR) is a function of the clearness index (K_T). The fraction of radiation intercepted was calculated either based on Beer's Law with crop extinction coefficients (K) from field experiments or from previous reports. RUE was calculated as a function of available soil water to a depth of 900 mm (ASW). Either the soil water balance method or the decay curve approach was used to determine ASW. Thus, two alternatives for each of three factors, i.e., PAR/SR, K and ASW, were considered, giving eight possible models (2 methods × 3 factors). The model calibration and validation were carried out with maize–bean intercropping systems using data collected in a semi-arid region (Bloemfontein, Free State, South Africa) during seven growing seasons (1996/1997–2002/2003). The combination of PAR estimated from the clearness index, a crop extinction coefficient from the field experiment and the decay curve model gave the most reasonable and acceptable result. The intercrop model developed in this study is simple, so this modelling approach can be employed to develop other cereal–legume intercrop models for semi-arid regions.     

A mechanical model for felt in impulse drying: A cellular materials approach. I. Model development and simulation

This paper presents a physically based model of the densification of a felt in the press nip of a paper machine, running at operating conditions similar to those used in impulse drying. The model incorporates the observed features of wet felts compression such as non-linear elasticity and non-recoverable strains that are rate-dependent. A viscoelastoplastic model, based on the cellular solids theory, was developed to describe this behavior. The governing differential equations of the model were established bearing in mind an assembly of modified Maxwell elements combined in series and then arranged in parallel. This approach resulted in a three-dimensional unsteady-state problem, solved by means of an integrator based in the Gear method. The model was used to predict the evolution of thickness, elastic and viscous moduli and apparent density of the material.     

温度对短额负蝗生长发育及种群趋势的影响

为明确温度对短额负蝗Atractomorpha sinensis（I.Bolivar）种群生长发育、生殖力及种群趋势的影响。本试 验设置16℃、20℃、24℃、28℃和32℃等5个恒温梯度,在实验室条件下（H:D = 16:8,RH 70%±5%）,以大豆叶片为食 物饲养,系统观测短额负蝗实验种群各虫态发育历期、发育速率及繁殖等情况,测算其发育起点温度和有效积温, 并利用生命表技术分析各温度条件下的种群趋势。结果表明,短额负蝗各虫态的发育历期均随温度的升高而缩 短,其发育速率与温度呈显著正相关。短额负蝗卵、若虫和成虫的发育起点温度分别为9.58℃、10.55℃、11.40℃,有 效积温依次为449.80、540.03、430.94日·度。在试验条件下,短额负蝗单雌产卵量28℃时最高,为66.12粒,24℃时次 之,为 60.30粒,16℃时最低,为 28粒;各试验温度条件下实验种群趋势指数均>1,其中 24℃时最大,为 18.97。该结 果为短额负蝗的田间预测及综合防控提供了科学依据。      

Performance diagnosis of Mae Lao Irrigation Scheme in Thailand (I) Development of Unsteady Irrigation Water Distribution and Consumption model

The Mae Lao Irrigation Scheme is one of the largest irrigation projects in Northern Thailand. According to the field reconnaissance, water shortage usually occurs during the dry season. And it is very difficult to equally distribute available water to the paddy fields from the upstream to the downstream parts of the system. To understand and identify the causes of the problems, the measurement of water level and flow rate along all canals may be effective. However, it is not easy to achieve this in such a large-scale irrigation system. Thus, the numerical simulation becomes the second option. The objective of this study is to identify and quantify the real water shortage causes by developing an Unsteady Irrigation Water Distribution and Consumption model which can simulate the water movement and consumption in the whole irrigation system. The beneficial area of the right main canal is modeled based on the physical aspect of the system. The components of the model consist of canal networks, control structures, and paddy fields. A canal is divided into several portions called reach. The Saint-Venant equations are applied to describe the unsteady water movement in each reach. Flow movement at the control structure is expressed by the boundary condition. The paddy fields are modeled to make paddy block and connected to each reach. The water consumption in each paddy block is estimated by Paddy Tank model. The numerical model is successfully developed showing the ability to simulate the water movement and consumption properties in this irrigation system.     

Applicability of Industrial Sisal Fiber Waste Derived Activated Carbon for the Adsorption of Volatile Organic Compounds (VOCs)

Agricultural waste produced by the industry is a huge threat for the global environment. Utilization of agricultural waste is necessary and there is an urgent need to develop new techniques to solve this important problem. The main objective of this research was to evaluate the applicability of the activated carbon (AC) derived from industrial sisal fiber waste as passive samplers in monitoring toluene by comparing them to industry standard wafer and granular activated carbon (GAC). Carbonization time and ball milling effect on sisal fiber derived AC sample adsorption properties were investigated. Toluene adsorption isotherms were used to predict toluene adsorption capacities. Surface characteristics including surface area and pore volume were used to determine the relationships between them and adsorption capacity. Even though prepared AC samples have mesoporous structure, commercial samples have microporous structure. Surface area from 1245 m²/g to 1297 m²/g and toluene adsorption capacity from 21.4 % to 26.6 % was improved by increasing carbonization time from 1 h to 3 h at 650 °C carbonization temperature and 94.4 ml/min flow rate. Conversely, ball milling technique had negative effect by decreasing the surface area (674 m²/g) and the adsorption capacity of toluene (12.27 %). It is concluded that industrial sisal fiber waste have great potential as a precursor of AC for application in passive monitoring against toluene, particularly the produced mesoporous AC with 3 h carbonization time performs higher adsorption capacity (26.6 %) than commercially available microporous passive sampler (24.1 %) and GAC (22.8 %).     

一种提取悬铃叶苎麻(B.tricuspis (Hance) Marino)花序 RNA的方法

应用改良CTAB法提取苎麻属野生种悬铃叶苎麻(Boehmeri.tricuspis(Hance) Marino)的花序RNA,通过1.2%琼脂糖凝胶电泳,测定分析260nm和280nm处的吸光值发现,应用该法提得的RNA完整性好,得率高;对其反转录产物进行AFLP分析表明,每一特定引物组合均能产生稳定清晰的条带,且在各引物间有差异.认为所提 RNA符合分子生物学实验要求.另外,本文还对提取RNA过程中应注意的一些事项进行了讨论.     

一种提取悬铃叶苎麻（ B. tricuspis （Hance） Marino）花序RNA的方法

应用改良CTAB法提取苎麻属野生种悬铃叶苎麻（Boehmeri．tricuspis（Hance）Marino）的花序RNA，通过1．2％琼脂糖凝胶电泳，测定分析260nm和280nm处的吸光值发现，应用该法提得的RNA完整性好，得率高；对其反转录产物进行AFLP分析表明，每一特定引物组合均能产生稳定清晰的条带，且在各引物间有差异。认为所提RNA符合分子生物学实验要求。另外，本文还对提取RNA过程中应注意的一些事项进行了讨论。     

Terraclor (PCNB) for control ofRhizoctonia solani. II. PCNB residues in tubers

Terraclor (PCNB) applied to soils by broadcast and row slightly reduced the incidence ofRhizoctonia solani but did not increase yield or per cent of U. S. No. 1 tubers either by weight or numbers. Residues of PCNB in tubers grown in treated soils increased as the rate per acre of PCNB increased. Almost all of the residues were in the tuber peel.     

甘蓝型油菜雄性不育的遗传研究——Ⅰ.NCa甘蓝型油菜异核型雄性不育材料选育初报

用甘蓝型油菜(Brassica napus L.)同埃塞俄比亚芥(Brassica carinata Br)进行正反交,从核基因充分重组后的F_3开始,在选择甘蓝型油菜形态的同时,从正交组合(N×Ca)中选择雄性不育株,用反交组合(CaxN)中的正常可育株成对测交筛选,获得了具有遗传能力的NCa甘蓝型油菜雄性不育及其保持材料。     

Foliar insect pest management on cowpea (Vigna unguiculata Walpers) in simulated varietal mixtures.: I. The suitability of partial insecticide applications

This research described in this paper examined the impact of varietal mixtures on pest management utilising a model system of partial insecticide applications. In six field experiments conducted in 1995 and 1996 in Igalaland, Kogi State, Nigeria varietal mixtures were simulated through the application of systemic insecticide (carbofuran or furathiocarb) to a pre-determined percentage of a cowpea (Vigna unguiculata) crop. The objective was to examine and compare the pest damage on untreated cowpea plants grown in plots in which varying percentages of the cowpea plants were treated with insecticide. A secondary objective was to determine whether action of the foliage pests influenced flower production. The results showed that the presence of insecticide-treated plants reduced the level of leaf damage by Ootheca mutabilis Sahlberg and the densities of Aphis craccivora Koch populations on untreated plants. The greater the percentage of insecticide-treated plants the greater this reduction on the untreated plants. Meanwhile, the number of flowers found on the untreated plants increased suggesting the foliage pest damage reduced flower production.     

A new model for predicting the flight activity of Lobesia botrana (Lepidoptera: Tortricidae)

The grape vine moth, Lobesia botrana (Denis and Schiffermüller) (Lepidoptera: Tortricidae), attacks vineyards mostly in Southern Europe and Northern Africa. The efficiency of most control methods depends on the treatment of pest populations at their most susceptible stages, therefore the prediction of the moth’s development cycle would help greatly in determining an optimal treatment schedule. One strategy for protecting against this pest is based on the day of maximum flight of males per generation (peak flight), when the mating between males and females and the laying of eggs reaches its maximum. The knowledge of these times would enable us to decide the kind of insecticide and the best time to target it. The time of maximum flight can be predicted by the Touzeau model of accumulated average daily temperature exceeding the development threshold. As shown, the fit of this model on data from the Ribera del Duero region in Spain is not accurate enough. Therefore, we propose an empirical and biologically plausible model based on logistic transformation of daily temperatures, which proves a better fit and permits simple inclusion of additional variables such as relative humidity.     

辣木种子苗繁育技术操作规程

种苗繁育是规范化种植的基础环节,为进一步规范辣木种苗繁育技术,于2013～2015年对辣木种苗繁育过程中的种子采收、种苗繁育、田间管理、采收运输及分级标准进行了总结,并制定了辣木种苗繁育技术操作规程(SOP),以期为辣木标准化的种苗生产提供依据。