Experiments on the practical I/O efficiency of geometric algorithms: Distribution sweep versus plane sweep

We present an extensive experimental study comparing the performance of four algorithms for the following orthogonal segment intersection problem: given a set of horizontal and vertical line segments in the plane, report all intersecting horizontal-vertical pairs. The problem has important applications in VLSI layout and graphics, which are large-scale in nature. The algorithms under evaluation are our implementations of distribution sweep and three variations of plane sweep. Distribution sweep is specifically designed for the situations in which the problem is too large to be solved in internal memory, and theoretically has optimal I/O cost. Plane sweep is a well-known and powerful technique in computational geometry, and is optimal for this particular problem in terms of internal computation. The three variations of plane sweep differ by the sorting methods (external versus internal sorting) used in the preprocessing phase and the dynamic data structures (B-tree versus 2-3-4-tree) used in the sweeping phase. We generate the test data by three programs that use a random number generator while producing some interesting properties that are predicted by our theoretical analysis. The sizes of the test data range from 250 thousand segments to 2.5 million segments. The experiments provide detailed quantitative evaluation of the performance of the four algorithms, and the observed behavior of the algorithms is consistent with their theoretical properties. This is, to the best of our knowledge, the first experimental algorithmic study comparing the practical performance between external-memory algorithms and conventional algorithms with large-scale test data.     

Systematic approaches to experimentation: The case of Pick's theorem

In this paper two 10th graders having an accumulated experience on problem-solving ancillary to the concept of area confronted the task to find Pick's formula for a lattice polygon's area. The formula was omitted from the theorem in order for the students to read the theorem as a problem to be solved. Their working is examined and emphasis is given to highlighting the students’ range of systematic approaches to experimentation in the context of problem solving and aspects of control that are reflected in these approaches.     

Experimental study of whistle noise generated by insert edge and oil separator model of refrigeration cycle

The compressed air experiments are conducted to investigate the whistle noise radiated from the oil separator component of refrigerant cycle system. Two types of insert edge and a height-adjustable oil separator model are adopted. The acoustic characteristic of flow through plain top insert edge is more likely to be broadband. Flow through ramp top insert edge would induce whistle peaks at Mach number higher than 0.1197 and the oil separator model works like an acoustic amplifier. Moreover, the Strouhal number jumps are captured inside oil separator model and two mechanisms are presented to clarify the phenomena. First, the whistle noise at Modes A1, A3, B1 and B3 is regarded as coupling of shear layer instability with resonance acoustic modes of oil separator model. Second, the whistle noise at Modes A2 and B2 is regarded to be the feedback loop of flow-acoustic interaction in fluctuated shear layer and defined as jet-cavity interaction tones.     

Development of a finite element model of metal powder compaction process at elevated temperature

This paper presents the finite element modelling of metal powder compaction process at elevated temperature. In the modelling, the behaviour of powder is assumed to be rate independent thermo-elastoplastic material where the material constitutive laws are derived based on a continuum mechanics approach. The deformation process of metal powder has been described by a large displacement based finite element formulation. The Elliptical Cap yield model has been used to represent the deformation behaviour of the powder mass during the compaction process. This yield model was tested and found to be appropriate to represent the compaction process. The staggered-incremental-iterative solution strategy has been established to solve the non-linearity in the systems of equations. Some numerical simulation results were validated through experimentation, where a good agreement was found between the numerical simulation results and the experimental data.     

热电制冷摄像机制冷系统研究

介绍了摄像机热电制冷设计必须考虑的问题 ,研制了性能与同类进口产品相当的摄像机的热电制冷降温、恒温系统。实验结果表明 :该系统对 2 0 0 m W的热负载可以提供 - 40℃以内的稳定恒温 ,温度的控制精度达 0 .1度 ,可作为高性能摄像机及其它成像系统的配套设备。     

Phenoxythiazoline (FTz)-Cobalt(II) Precatalysts Enable C(sp2)–C(sp3) Bond-Formation for Key Intermediates in the Synthesis of Toll-like Receptor 7/8 Antagonists**

Evaluation of the relative rates of the cobalt-catalyzed C(sp²)–C(sp³) Suzuki–Miyaura cross-coupling between the neopentylglycol ester of 4-fluorophenylboronic acid and N-Boc-4-bromopiperidine established that smaller N-alkyl substituents on the phenoxyimine (FI) supporting ligand accelerated the overall rate of the reaction. This trend inspired the design of optimal cobalt catalysts with phenoxyoxazoline (FOx) and phenoxythiazoline (FTz) ligands. An air-stable cobalt(II) precatalyst, (FTz)CoBr(py)₃ was synthesized and applied to the cross-coupling of an indole-5-boronic ester nucleophile with a piperidine-4-bromide electrophile that is relevant to the synthesis of reported toll-like receptor (TLR) 7/8 antagonist molecules including afimetoran. Addition of excess KOMe⋅B(OⁱPr)₃ improved catalyst lifetime due to attenuation of alkoxide basicity that otherwise resulted in demetallation of the FI chelate. A first-order dependence on the cobalt precatalyst and a saturation regime in nucleophile were observed, supporting turnover-limiting transmetalation and the origin of the observed trends in N-imine substitution.     

Reporting computational experiments in mathematical programming

This paper presents a set of recommended standards for the presentation of computational experiments in mathematical programming.The authors are members of the Committee on Algorithms of the Mathematical Programming Society.     

亚纳秒前沿有界波模拟器传输线设计的理论分析与实验

 介绍了亚纳秒前沿有界波模拟器的组成、主要技术指标和传输线结构。用时域有限差分法对模拟器的场传播和场分布进行了数值模拟,并实测了工作区域的电场分布。测量结果表明:不同位置处场的上升时间基本不变,约为800 ps,1 m×1 m×1 m工作区域内的电场两侧不均匀性约为10%,前后位置约为±50%,满足技术指标要求,场的分布与数值模拟结果相一致。     

AEGIS—attribute experimentation guiding improvement searches

The development of a quality heuristic is a challenging undertaking. While some work has been done to link solution quality and problem inputs, relatively little has been done to methodically address that linkage. This research, a meta-heuristic framework called AEGIS, is an initial attempt to integrate problem characteristics into the solution process itself. As the name implies, the goal is to provide guidance to the solution process, through a well-defined learning process. By utilizing statistical techniques and concepts, this study will demonstrate how such knowledge may be used to drive the function of the algorithm.     

The effect of the geometric parameters of the corrugation shape on the vibration analysis of 3D structured beams

This paper deals with the vibration analysis of 3D structured beams with double sinusoidal pattern. The corrugation depends on different parameters such as orientation, amplitude and wave length of the double sinusoid shape. First, a numerical modeling was built using the Finite Element method. Then, experimental tests of bending vibration were conducted on planar and corrugated beams. These data validated our model and proved that the resonant frequencies generally increase due to corrugated shape. A parametric study demonstrated that the optimal values of the corrugation shape can be found to increase the resonant frequencies.