Dense Placement Research Articles

Visualizing Wireless Network Performance Metrics in Space–Time

To evaluate the performance of emerging mobile wireless networks with multihop coverage extensions, spatiotemporal network models are required. These models should include the directional characteristics of network information flows to exploit the spatial domain due to the deployment of advanced antenna systems. Furthermore, the models should be capable of handling nonstationary scenarios with dynamic evolution of mobile nodes. In an attempt to solve these two problems, which have not been fully addressed in the existing literature, and motivated by the useful analogy between classical propagation channels and wireless networks, we propose a novel network modeling framework where the relevant figure of merit (FOM) may be the received signal power, the event detection error exponent, the channel capacity, etc., depending on the network's type. We first formulate the general description methods of the framework, including the double-directional FOM impulse response, the angular spectrum, and the angular dispersion. Subsequently, we propose the ray approaches, including the geometry-based stochastic channel models (GSCMs) and the deterministic ray-tracing techniques, to support and enrich the description methods. The given analytical tools facilitate visualization of wireless network performance metrics in space–time. Due to their stochastic nature, the proposed methodology would be most useful for the design and analysis of networks featured by decentralized, randomized, and dense placement of nodes.

Research on Preparation Technique of C100 Ultra-High Performance Self-Compaction Concrete

Self-compaction concrete is a new green concrete featuring self-leveling, self-compaction, low noise and low consumption of labor force. Nowadays, a large number of super high-rise buildings (h>400m) are under construction around the world, the complicated structures and dense reinforcement placement has brought numerous inconveniences to construction of concrete. Research on high strength / ultra-high strength self-compaction concrete thus becomes a hotspot. The porous structure of zeolite powder can help absorb the water reducing agent and then release it slowly in concrete mixture. With the low slump loss it produces, the prepared C100UHP-SCC can resist slump loss for over 3 hours. Test of super-high pumping at a height of 411m is carried out in the West Tower program at Pearl River New Town of Guangzhou (the building height is 441m). Drilled core test for L-shaped component indicates a dense internal structure, so it has a desirable self-compaction and capacity to pass through dense reinforcement.

Multi-objective optimal path planning using elitist non-dominated sorting genetic algorithms

A multi-objective vehicle path planning method has been proposed to optimize path length, path safety, and path smoothness using the elitist non-dominated sorting genetic algorithm--a well-known soft computing approach. Four different path representation schemes that begin their coding from the start point and move one grid at a time towards the destination point are proposed. Minimization of traveled distance and maximization of path safety are considered as objectives of this study while path smoothness is considered as a secondary objective. This study makes an extensive analysis of a number of issues related to the optimization of path planning task-handling of constraints associated with the problem, identifying an efficient path representation scheme, handling single versus multiple objectives, and evaluating the proposed algorithm on large-sized grids and having a dense set of obstacles. The study also compares the performance of the proposed algorithm with an existing GA-based approach. The evaluation of the proposed procedure against extreme conditions having a dense (as high as 91 %) placement of obstacles indicates its robustness and efficiency in solving complex path planning problems. The paper demonstrates the flexibility of evolutionary computing approaches in dealing with large-scale and multi-objective optimization problems.

The Research of Emergency Rescue Sites Layout During the Highway Reconstruction

To determine the service distance L in limited rescue time of emergency rescue site，main factors influence the speed of emergency rescue vehicle during the time of highway reconstruction is analyzed，and using multi-level fuzzy evaluation method to obtain comprehensive speed. Based on the considering of arriving accident field in the minimum time first，emergency rescue sites are arranged on black-spot. Then the distance between adjacent emergency rescue sites are compared with service distance L，Amend the possible situation of the spares or dense placement, and take the service facility such us service area and toll station into consideration, then optimize the layout scheme. Finally take the layout of emergency rescue sites of the Jingla Expressway reconstruction project as an example to analyze.

A Tractable Approach to Coverage and Rate in Cellular Networks

Cellular networks are usually modeled by placing the base stations on a grid, with mobile users either randomly scattered or placed deterministically. These models have been used extensively but suffer from being both highly idealized and not very tractable, so complex system-level simulations are used to evaluate coverage/outage probability and rate. More tractable models have long been desirable. We develop new general models for the multi-cell signal-to-interference-plus-noise ratio (SINR) using stochastic geometry. Under very general assumptions, the resulting expressions for the downlink SINR CCDF (equivalent to the coverage probability) involve quickly computable integrals, and in some practical special cases can be simplified to common integrals (e.g., the Q-function) or even to simple closed-form expressions. We also derive the mean rate, and then the coverage gain (and mean rate loss) from static frequency reuse. We compare our coverage predictions to the grid model and an actual base station deployment, and observe that the proposed model is pessimistic (a lower bound on coverage) whereas the grid model is optimistic, and that both are about equally accurate. In addition to being more tractable, the proposed model may better capture the increasingly opportunistic and dense placement of base stations in future networks.

On Optimal Channel Configurations for SMR-based Brain–Computer Interfaces

One crucial question in the design of electroencephalogram (EEG)-based brain-computer interface (BCI) experiments is the selection of EEG channels. While a setup with few channels is more convenient and requires less preparation time, a dense placement of electrodes provides more detailed information and henceforth could lead to a better classification performance. Here, we investigate this question for a specific setting: a BCI that uses the popular CSP algorithm in order to classify voluntary modulations of sensorimotor rhythms (SMR). In a first approach 13 different fixed channel configurations are compared to the full one consisting of 119 channels. The configuration with 48 channels results to be the best one, while configurations with less channels, from 32 to 8, performed not significantly worse than the best configuration in cases where only few training trials are available. In a second approach an optimal channel configuration is obtained by an iterative procedure in the spirit of stepwise variable selection with nonparametric multiple comparisons. As a surprising result, in the second approach a setting with 22 channels centered over the motor areas was selected. Thanks to the acquisition of a large data set recorded from 80 novice participants using 119 EEG channels, the results of this study can be expected to have a high degree of generalizability.

Coding Methods for Automatic Placement of Parts on Printed Circuit Boards.

There have been growing demands for automatic placement of parts on printed circuit boards (PCBs). Since the parts have wide variety in size and these parts should be placed under various constraints, the automatization of parts placement is a very difficult task. The authors proposed a method using the genetic algorithm (GA) for the automatic placement on highly dense PCBs. The study was, however, done on an imaginary board. Many factors, such as gaps between parts, lining up of parts of same type, etc. were not considered.This paper presents three new coding methods for the automatic placement on the PCBs. The three proposed methods incorporate rotating angle of parts, gaps between parts, forming of parts of same type in lines as well as dense placement of parts. Actual PCBs are used for showing and comparing the effects of the new coding methods. The results show that the proposed methods are feasible for the automatic placement of parts on highly dense PCBs.

Re-formation of the channel of the enisei river in the lower pool of the Krasnoyarsk hydroelectric power station

1. At first the main re-formation of the channel occurred in the immediate vicinity of the structures, with its subsequent extension downstream. 2. The asymmetric distribution of discharges over the dam front in 1964 caused scouring of the river bottom in the direct neighborhood of the apron, which encompassed the fractured bedrock. Deposition of the erosion products, which were of large size, occurred near the erosion zone where a bar formed. 3. During flood periods the volume of accumulated sediments greatly exceeded the volume of bottom erosion, which is explained by the erosion of the cofferdams and the channel bottom near the apron, removal, of soil from the banks, and to some extent, by the less dense placement of the accumulating deposits.

2 梁形断面に対するコンクリートの充てん性に関する実験的研究

The composite type anti-seismic structure developed in Japan for multistory construction generally entails structural members with an exceedingly high relative quantity of steel cast in concrete. This dense placement of steel sections and rainforcement bars in concrete results in a high resistance to the flow or plastic deformation of fresh concrete when poured into forms, and eventually leads to appearances of honeycomb or voide defects especially at soffit portions directly under lower corde flange plates of girders. In this report the term "Fill-up-ability" is used for expressing a property pertaining to fresh concrete which is basically the accumulative result of the following three conditions: (1) Material properties of concrete mixture itself comming from its flowability or plastic deformability. (2) Suppressive conditions within forms which hinder the flow or plastic deformation of concrete mixture when it is placed. (3) External forces which are applied to facilitate the flow or plastic deformation of concrete mixture within forms, such as impulses caused by dropping or falling at the time of placement, and vibration applied by mecanical vibrators. Test girder sections were made imitating actual sections of concrete structures. They were given varied suppressive conditions against the flow of concret mix, i.e., with different arrangement of steel sections and reinforcement bars within the test forms. Keeping external force conditions the same, concrete mix with differing material properties was placed in those test forms. The fill-up-ability of concret mix with various properties when poured into the forms of gider type sections of varied suppressive conditions was observed both quantitativly and qualitatively. An index termed "Degree of Fill-up-ability" was created by the author to measure quantitatively the fill-up-ability. Summary Conclusion 1. It was observed that, under same external force conditions and same suppresive conditions, though concrete mix may have idential slumps, its degree of fill-up-ability will differ considerably due to other material properties, and that the existance of a broad range of difference is evident. 2. The fill-up-ability becomes more favorable as the slump is increased, but there are different allowable limit value of slump corresponding to the different strength of suppresive condition and the different material propertie of fresh concrete. 3. The fill-up-ability becomes more favorable as the sand ratio is increased (experiments were performed from 27% up to 41.5%) and the unit cement content is increased, air-entrained concrete shows better fill-up-ability than plain concrete, 4. Concrete with light sand and light gravel show instable qualities of separating easily, and its fill-up-ability was unfavorable in contrast with concrete with river sand and light gravel which shows stable qualities and favorable fill-up-ability. 5. Among the sample girder section of the three structural type, namely, reinforced concret structur, concret convered steel frame structure and composite structure, fill-up of concrete was most difficult for composite structure. Fill-up-ability for girder section types generally used in practice for composite structures was proved poor. The exissance of reinforcement bars in addition to steel sections makes it very difficult for concrete mix to reach portions under the flanges of steel sections. 6. The degree of difference of fill-up-ability of concrete mix, as stated herinabove under item 1,2 and 3, decrease considerably when the strength of suppressive conditions are increased like as the case of the composit structures. 7. It was recognised that the detail design of sections or connections of structural members is very important as well as the serection of material properties of concrete mix is very important to expect favorable fill-up ability, and slump shall be serect relatively