核桃隔膜总黄酮和微量元素的测定

本实验采用分光光度法测定了核桃隔膜中总黄酮的含量,黄酮总含量为6.259%(62.59mg/g),微量元素的测定采用了火焰原子吸收法,10种微量元素含量分别为Na5.69×102μg/g、K6.95×103μg/g、Ca6.22×102μg/g、Mg6.10×102μg/g、Zn6.10μg/g、Fe1.20×102μg/g、Cu2.03μg/g、Co<0.05μg/g、Ni6.10μg/g、Mn16.27μg/g。总黄酮是最新发现的一种激发脑潜能的物质,它能有效地激发脑活力,对提高青少年智力产生积极作用,并且能有效抑制成人及老年人脑功能衰退。     

天山花楸全株化学成分定性研究

本实验采用水提取法、醇提取法和石油醚提取法对天山花楸全株的化学成分进行了比较全面的定性研究。结果表明：天山花楸根、茎、叶和果实中均含有多种化学成分,包括：氨基酸、蛋白质、糖类、酚类、有机酸、黄酮、生物碱、强心苷、挥发油、甾类。     

One-step fabrication of superhydrophobic P(VDF-co-HFP) nanofibre membranes using electrospinning technique

In this study, superhydrophobic electrospun P(VDF-co-HFP) membranes were fabricated in a one-step electrospinning process. The effects of the key parameters of electrospinning (solution concentration, electrical potential, flow rate, and solvent) on the surface roughness, fiber formation, and hydrophobicity of the membranes were evaluated using Taguchi method. A 4 × 3 orthogonal array was utilized, and the results indicated that the solvent played the critical role in producing the superhydrophobic nanofibre membranes. It was demonstrated that it is possible to produce superhydrophobic membranes with P(VDF-co-HFP) without additional functionalisation and fillers. The highest water contact angle and the lowest contact angle hysteresis obtained were 156° and 5°, respectively, and the roughness values varied from 0.15 to 5.74 μm for the produced P(VDF-co-HFP) nanofibre membranes. The surface superhydrophobicity of the membranes was attributed to the specific structures consisting of a combination of beads and nanofibres. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48817.     

Process parameters for hydrocooling apricots, plums, and peaches

Freshly harvested apricots, plums, and peaches in crates containing 5–20kg were hydrocooled in flowing water at 1°C and 50mms^-1. The cooling parameters: lag factor, cooling coefficient, and time to half-cool, determined from the exponential decline in the dimensionless ratio of temperature differences between fruit centre and coolant temperature at time t and at zero time, varied somewhat with crate load. Increasing the load from 5 to 20kg increased the time to half-cool apricots by 17% and plums and peaches by 39%.     

Effective methods for increasing aggregate diversity in recommender systems

In order to make a recommendation, a recommender system typically first predicts a user’s ratings for items and then recommends a list of items to the user which have high predicted ratings. Quality of predictions is measured by accuracy, that is, how close the predicted ratings are to actual ratings. On the other hand, quality of recommendation lists is evaluated from more than one perspective. Since accuracy of predicted ratings is not enough for customer satisfaction, metrics such as novelty, serendipity, and diversity are also used to measure the quality of the recommendation lists. Aggregate diversity is one of these metrics which measures the diversity of items across the recommendation lists of all users. Increasing aggregate diversity is important because it leads a more even distribution of items in the recommendation lists which prevents the long-tail problem. In this study, we propose two novel methods to increase aggregate diversity of a recommender system. The first method is a reranking approach which takes a ranked list of recommendations of a user and reranks it to increase aggregate diversity. While the reranking approach is applied after model generation as a wrapper the second method is applied in model generation phase which has the advantage of being more efficient in the generation of recommendation lists. We compare our methods with the well-known methods in the field and show the superiority of our methods using real-world datasets.     

Quaternion-based Robust Trajectory Tracking Control of a Quadrotor Hover System

This paper presents a robust nonlinear output feedback control method that achieves three degree of freedom (3-DOF) attitude trajectory tracking of a hover system test bed. The proposed control method formally incorporates dynamic model uncertainty in addition to test bed voltage constraints. To reduce the computational requirement in the closed-loop system, constant feedforward estimates of the input-multiplicative parametric uncertainty are utilized in lieu of adaptive parameter estimates. To eliminate the need for angular rate measurements, the control design employs a bank of dynamic filters, which operates as a velocity estimator in the closed-loop system. A rigorous error system development and Lyapunov-based stability analysis are presented to prove asymptotic 3-DOF attitude trajectory tracking control. Computer simulation and experimental results are also included to illustrate the performance of the attitude control method using the Quanser 3-DOF hover system test bed.     

Clustering-based diversity improvement in top-N recommendation

The major aim of recommender algorithms has been to predict accurately the rating value of items. However, it has been recognized that accurate prediction of rating values is not the only requirement for achieving user satisfaction. One other requirement, which has gained importance recently, is the diversity of recommendation lists. Being able to recommend a diverse set of items is important for user satisfaction since it gives the user a richer set of items to choose from and increases the chance of discovering new items. In this study, we propose a novel method which can be used to give each user an option to adjust the diversity levels of their own recommendation lists. Experiments show that the method effectively increases the diversity levels of recommendation lists with little decrease in accuracy. Compared to the existing methods, the proposed method, while achieving similar diversification performance, has a very low computational time complexity, which makes it highly scalable and allows it to be used in the online phase of the recommendation process.     

Phosphate adsorption characteristics of alunite to be used as a cement additive

The adsorption of phosphate from aqueous solution by alunite has been investigated as a function of calcination temperature, particle size, pH, agitation time and initial phosphate concentration. Phosphate adsorption was seen to increase with increasing calcination temperature, decreasing adsorbent particle size and pH. The adsorption isotherm data were fitted to the Langmuir isotherm. The alunite exhibited the highest phosphate uptake capacity at 1073 K calcination temperature, at a particle size of 90-150 μm, at the initial pH of 5.0, at an equilibrium time of 60 min and at the initial phosphate concentration of 20×10⁻⁴ mol/l. The adsorption capacity, Q, was 4.697×10⁻³ mol/g at initial pH 5.0.     

Improved cache utilization and preconditioner efficiency through use of a space-filling curve mesh element- and vertex-reordering technique

Solving partial differential equations using finite element (FE) methods for unstructured meshes that contain billions of elements is computationally a very challenging task. While parallel implementations can deliver a solution in a reasonable amount of time, they suffer from low cache utilization due to unstructured data access patterns. In this work, we reorder the way the mesh vertices and elements are stored in memory using Hilbert space-filling curves to improve cache utilization in FE methods for unstructured meshes. This reordering technique enumerates the mesh elements such that parallel threads access shared vertices at different time intervals, reducing the time wasted waiting to acquire locks guarding atomic regions. Further, when the linear system resulting from the FE analysis is solved using the preconditioned conjugate gradient method, the performance of the block-Jacobi preconditioner also improves, as more nonzeros are present near the stiffness matrix diagonal. Our results show that our reordering reduces the L1 and L2 cache miss-rates in the stiffness matrix assembly step by about 50 and 10 %, respectively, on a single-core processor. We also reduce the number of iterations required to solve the linear system by about 5 %. Overall, our reordering reduces the time to assemble the stiffness matrix and to solve the linear system on a 4-socket, 48-core multi-processor by about 20 %.