Finite Element Simulation Analysis of a Novel 3D-FRSPA for Crawling Locomotion

A novel three-dimensional-fiber reinforced soft pneumatic actuator(3D-FRSPA)inspired by crab claw and human hand structure that can bend and deform independently in each segment is proposed.It has an omni-directional bending configuration,and the fibers twined symmetrically on both sides to improve the bending performance of FRSPA.In this paper,the static and kinematic analysis of 3D-FRSPA are carried out in detail.The effects of fiber,pneumatic chamber and segment length,and circular air chamber radius of 3D-FRSPA on the mechanical performance of the actuator are discussed,respectively.The soft mobile robot composed of 3D-FRSPA has the ability to crawl.Finally,the crawling processes of the soft mobile robot on different road conditions are studied,respectively,and the motion mechanism of the mobile actuator is shown.The numerical results show that the soft mobile robots have a good comprehensive performance,which verifies the correctness of the proposedmodel.This work shows that the proposed structures have great potential in complex road conditions,unknown space detection and other operations.

A Survey about Algorithms Utilized by Focused Web Crawler

Abstract—Focused crawlers （also known as subjectoriented crawlers）, as the core part of vertical search engine, collect topic-specific web pages as many as they can to form a subject-oriented corpus for the latter data analyzing or user querying. This paper demonstrates that the popular algorithms utilized at the process of focused web crawling, basically refer to webpage analyzing algorithms and crawling strategies （prioritize the uniform resource locator （URLs） in the queue）. Advantages and disadvantages of three crawling strategies are shown in the first experiment, which indicates that the best-first search with an appropriate heuristics is a smart choice for topic-oriented crawlingwhile the depth-first search is helpless in focused crawling. Besides, another experiment on comparison of improved ones （with a webpage analyzing algorithm added） is carried out to verify that crawling strategies alone are not quite efficient for focused crawling and in most cases their mutual efforts are taken into consideration. In light of the experiment results and recent researches, some points on the research tendency of focused crawler algorithms are suggested.

分布式Web Crawler的研究:结构、算法和策略

本文介绍了一个大型分布式Web Crawler系统——Igloo 1.2版。它采用分布式的系统结构,通过我们设计的二级哈希映射算法使系统可以进行高效的任务分割,并且系统的规模动态可扩展.爬行网页的质量是评价Crawler的一个重要指标,Igloo以PageRank值作为网页质量评价的标准,从而提高了爬行质量.加快爬行速度的关键是如何解除Crawler系统中的性能瓶颈,本文对此也作了详细的讨论,并提出了一种基于“滞后合并”策略的UBL数据库存取方法.实验表明,Igloo在保持高性能的同时能快速爬行到高质量的网页.

Strategy to control crawling vehicles with automated mechanical transmission

In order to move vehicles with automated mechanical transmission （AMT） a little bit of distance, such as reversing into or moving in a garage, a control strategy for crawling vehicles was proposed. Based on the dynamic analysis of vehicle starting process and requirements of crawl driv- ing for the vehicle, a control strategy of the clutch was designed. The strategy increased the.slipping friction torque first and then decreased it, in order to realize the crawl driving. The speed increased by the engagement of the clutch, and then the clutch turned to disengage to the half disengage point, when the speed met the requirements. Based on the control strategy, a control software was de- signed. In the end, the software was tested on a vehicle with AMT. The lowest steady vehicle speed was reduced to 40% of the original value, which was set in the control strategy.

New focused crawling algorithm

Focused carawling is a new research approach of search engine. It restricts information retrieval and provides search service in specific topic area. Focused crawling search algorithm is a key technique of focused crawler which directly affects the search quality. This paper first introduces several traditional topic-specific crawling algorithms, then an inverse link based topic-specific crawling algorithm is put forward. Comparison experiment proves that this algorithm has a good performance in recall, obviously better than traditional Breadth-First and Shark-Search algorithms. The experiment also proves that this algorithm has a good precision.

SmartCrawler:A Three-Stage Ranking Based Web Crawler for Harvesting Hidden Web Sources

Web crawlers have evolved from performing a meagre task of collecting statistics,security testing,web indexing and numerous other examples.The size and dynamism of the web are making crawling an interesting and challenging task.Researchers have tackled various issues and challenges related to web crawling.One such issue is efficiently discovering hidden web data.Web crawler’s inability to work with form-based data,lack of benchmarks and standards for both performance measures and datasets for evaluation of the web crawlers make it still an immature research domain.The applications like vertical portals and data integration require hidden web crawling.Most of the existing methods are based on returning top k matches that makes exhaustive crawling difficult.The documents which are ranked high will be returned multiple times.The low ranked documents have slim chances of being retrieved.Discovering the hidden web sources and ranking them based on relevance is a core component of hidden web crawlers.The problem of ranking bias,heuristic approach and saturation of ranking algorithm led to low coverage.This research represents an enhanced ranking algorithm based on the triplet formula for prioritizing hidden websites to increase the coverage of the hidden web crawler.

Manipulation of Crawling Growth for the Formation of Sub-millimeter Long ZnO Nanowalls

Vapor-phase growth of ZnO nanowires based on gold catalyst is usually accompanied with lateral crawling growth on the substrate surface. We present results from our systematic experiments where the growth temperature and catalyst size are controlled. The data corroborate that it is possible to obtain clean vertical nanowire arrays while avoiding the crawling growth. 0% the other hand, crawling growth can be manipulated to obtain root-interconnected nanowire arrays, which could be useful for certain applications. Our results also imply that the previously suggested growth mechanism for the wire-on-wall hybridstructure might be incorrect. Finally, we show the formation of sub-millimeter long, straight ZnO nanowalls by combining a gold-catalyzed epitaxial growth of vertical nanowires and their mergence due to a confined crawling growth. These unconventional nanostructures might have unique electric or optical transport properties.

Infiltration of Mould from Crawl Space under the Prefabricated Bathroom

The indoor mould concentration depends not only on the outdoor mould source but also on the indoor mould source. The mould source is not only on the interior surface but also in the concealed spaces: a crawl space, a beam space, a wall cavity etc. Most detached houses in Japan have crawl spaces under the first floor. The humidity is high from spring to autumn in crawl spaces. Therefore the concentration of mould spore is very high in most crawl spaces. Prefabricated bathrooms called “bath-units” are installed in most Japanese houses. The authors showed in the previous studies that there are infiltration routes between bath-units and walls that the routes may lead chemical compounds from crawl space to indoor space. In this study, the influence of mould infiltration from crawl space upon indoor mould concentration is investigated using a test house which consists of a lavatory and a bathroom. The structure of the house is wooden post-and-beam. The house is airtight and insulated according to the latest building code for save energy. The mould concentrations were measured in the crawl space and the indoor spaces continuously using a mould multi-sampling system with a pump, valves and impingers. Before the measurements, the indoor mould concentration was made low using an air cleaner. The air flow rates were measured using tracer gases. After the exhaust fan was switched on, the mould concentration increased. The number of infiltrated mould was calculated using air flow rates and mould concentrations. The results showed that mould infiltration ratio may be one of the important indicators of indoor air quality.

Lower-body strength,power and sprint front crawl performance

Purpose To determine the association between lower-body strength and lower-body power capacities with sprint swimming performance in adolescent competitive swimmers.Methods A total of 44 front crawl swimmers(27 males and 17 females)performed anthropometric assessments,lower-body strength tests(half squat maximum isometric strength,dynamic half squat with 20,30 and 40%of the maximum isometric strength,and knee extension maximum isometric strength)and lower-body power tests(squat jump[SJ],countermovement jump[CMJ]and Abalakov jump).Further front crawl swimming best times in 50 and 100 m were recorded from official swimming competitions and front crawl technique was assessed by an experienced coach using a visual analogue scale.Results Swimming performance was correlated with lower-body power variables(SJ[r=−0.573 for 50 m and−0.642 for 100 m],CMJ[r=−0.497 for 50 m and−0.544 for 100 m],and Abalakov jump[r=−0.452 for 50 m and−0.415 for 100 m];p≤0.05)and lower-body strength(half squat maximum isometric strength[r=−0.430 for 50 m and−0.443 for 100 m];p≤0.05)in males but not in females.Further linear regression models showed that only lower-body power predicted both 50 m(Abalakov jump;r^(2)=0.58;change in r^(2)=0.18)and 100 m(SJ;r^(2)=0.66;change in r^(2)=0.15)performance in male swimmers.Conclusions This study emphasizes the greater association between lower-body power and sprint front crawl performance in adolescent males compared to females.Practical tests(i.e.,SJ and Abalakov jump)are shown to predict front crawl swimming performance,which may facilitate the performance control by coaches and trainers.

A Miniaturized Crawler Design Based on an Origami-inspired and Geometrically Constrained Spherical Six-bar Linkage

This paper focuses on a newly developed transmission for a milli-scale eight-legged crawling robot called OriSCO.The transmission allows intuitive steering by directly changing the direction of the propulsion force.The transmission is based on the constrained spherical six-bar linkage.The constrained spherical six-bar linkage passes only reciprocating motion out of the motor’s rotating motion,allowing the crawling legs to kick the ground and obtain propulsion.Steering is achieved by adjusting the geometric constraints of the spherical six-bar using a servomotor,allowing the direction of propulsion to be changed.As a result,the OriSCO can move along the ground at a speed of 2.15 body lengths/s,and the robot is 60 mm long.

An Inchworm-inspired Robot Based on Modular Body, Electronics and Passive Friction Pads Performing the Two-anchor Crawl Gait

We have created an inchworm robot capable of the two-anchor crawl gait on level ground and inclined plane. The main novelty is in the design of the inchworm： （1） three-part body that is 3D printed and actuated by two servo motors to allow a looping and lengthening action, （2） passive friction pads to anchor the feet, each of which may be disengaged using a servo motor actuated lever arm, and （3） modular body and electronics. The robot is about 2 feet （61 cm） in length, has a mass of about 4 kg, and uses an open-loop controller to achieve steady crawling gait. The inchworm robot achieved a speed of 2.54 em.sI on level ground as well as on an incline plane of 19~. The energy usage as measured by the Mechanical Cost of Transport （a non-dimensional number defined as the energy used per unit weight per unit distance moved） is 3.34. Our results indicate that simple robotic designs that copy the basic features of natural organisms provide a promising alternative over conventional wheeled robots.

Clustering-based topical Web crawling using CFu-tree guided by link-context

Topical Web crawling is an established technique for domain-specific information retrieval. However, almost all the conventional topical Web crawlers focus on building crawlers using different classifiers, which needs a lot of labeled training data that is very difficult to label manually. This paper presents a novel approach called clustering-based topical Web crawling which is utilized to retrieve information on a specific domain based on link-context and does not require any labeled training data. In order to collect domain-specific content units, a novel hierarchical clustering method called bottom-up approach is used to illustrate the process of clustering where a new data structure, a linked list in combination with CFu-tree, is implemented to store cluster label, feature vector and content unit. During clustering, four metrics are presented. First, comparison variation （CV） is defined to judge whether the closest pair of clusters can be merged. Second, cluster impurity （CIP） evaluates the cluster error. Then, the precision and recall of clustering are also presented to evaluate the accuracy and comprehensive degree of the whole clustering process. Link-context extraction technique is used to expand the feature vector of anchor text which improves the clustering accuracy greatly. Experimental results show that the performance of our proposed method overcomes conventional focused Web crawlers both in Harvest rate and Target recall.

Modular crawling robots using soft pneumatic actuators

Crawling robots have elicited much attention in recent years due to their stable and efficient locomotion.In this work,several crawling robots are developed using two types of soft pneumatic actuators(SPAs),namely,an axial elongation SPA and a dual bending SPA.By constraining the deformation of the elastomeric chamber,the SPAs realize their prescribed motions,and the deformations subjected to pressures are characterized with numerical models.Experiments are performed for verification,and the results show good agreement.The SPAs are fabricated by casting and developed into crawling robots with 3D-printing connectors.Control schemes are presented,and crawling tests are performed.The speeds predicted by the numerical models agree well with the speeds in the experiments.

Impact of weather conditions and building design on contaminant infiltration from crawl spaces in Swedish schools-Numerical modeling using Monte Carlo method

Some Swedish school buildings built in the 1960s and 1970s experience indoor air quality problems,where the contaminants are suspected to come from the crawl space underneath the building.The poor indoor air quality causes discomfort among pupils and teachers.Installing an exhaust fan to maintain a negative pressure difference in the crawl space relative to indoors or increasing the ventilation in the classroom are two examples of common measures taken to improve the indoor air quality.However,these measures are not always effective,and sometimes the school building has to be demolished.The relation between pressure distribution,contaminant concentration in the classroom,outdoor temperature,wind,mechanical ventilation,and air leakage distribution is complex.A better understanding of these relations is crucial for making decisions on the most efficient measure to improve the indoor air quality.In this paper,a model for contaminant infiltration from the crawl space is used together with the Monte Carlo method to study these relations.Simulations are performed for several cases where different building shapes,building orientations,shielding conditions,and geographical locations are simulated.Results show,for example,that for a building with an imbalanced ventilation system,air is leaking from the crawl space to the classroom for the majority of cases and that concentration levels in the classroom are usually the highest during mild and calm days.

Research on Piezoelectric Driving Microminiature Three-Legged Crawling Robot

Micro-robots have the characteristics of small size,light weight and flexible movement.To design a micro three-legged crawling robot with multiple motion directions,a novel driving scheme based on the inverse piezoelectric effect of piezoelectric ceramics was proposed.The three legs of the robot were equipped with piezoelectric bimorphs as drivers,respectively.The motion principles were analyzed and the overall force analysis was carried out with the theoretical mechanics method.The natural frequency,mode shape and amplitude were analyzed with simulation software COMSOL Multiphysics,the optimal size was determined through parametric analysis,and then the micro three-legged crawling robot was manufactured.The effects of different driving voltages,different driving frequencies,different motion bases and different loads on the motion speed of the robot were tested.It is shown that the maximum speed of single-leg driving was 35.41 cm/s,the switching ability between different motion directions was measured,and the movements in six different directions were achieved.It is demonstrated the feasibility of multi-directional motion of the structure.The research may provide a reference for the design and development of miniature piezoelectric three-legged crawling robots.

A Musculoskeletal Modeling of Hand-foot Crawling with Different Heights

As a bionic therapy,hand-foot crawling has been reported to be used for the rehabilitation of low back pain.However,there have been few relevant biomechanical studies about this type of exercise.The purpose of this study was to calculate muscle activation and lumbar spinal load based on the examined limb kinematics and kinetics,which associated with hand-foot crawling at the different Centre of Mass(CoM)heights.A total of 14 men performed hand-foot crawling at three CoM heights.The kinematics and kinetics data were collected.One-way repeated measure analysis of variance was used to analyze the efFect of the CoM height on crawling parameters.The crawling data from one subject at the three heights were used to calculate the muscle activation and compressive lumbar load with an OpenSim musculoskeletal model.The CoM heights had no significant effect on kinematics,kinetics or muscle activation.The spinal load was larger at higher heights.Hand-foot crawling was associated with lower trunk muscle activity.This study helps us to understand hand-foot crawling from the perspective of biomechanics.The findings from this study may help physical therapists choose hand-foot crawling as an appropriate exercise for patients with low back pain during early rehabilitation.

曲线梁桥横向爬移影响因素分析及对策研究

随着城市交通的发展,曲线梁桥成为不同道路互联互通的首选桥型。曲线梁桥独特的受力特点易造成桥梁出现支座脱空、伸缩缝破坏、墩柱开裂等横向爬移引起的病害。文章在总结分析常见病害及原因的基础上,从主动与被动影响因素两个方面分析了不同因素的影响原因及程度,并对新桥的设计和运营桥梁的加固设计提出了相应的预防与加固对策,可为后续曲线梁桥设计与加固提供一定的指导。

论数据爬取的反不正当竞争法规制

数字经济时代,数据爬取具有市场效果两面性、侵犯利益多元性及行为实施隐蔽性等特点。为充分发挥数据爬取积极作用,理论界和实务界选择通过反不正当竞争法对其进行规制。然而,侵权式判断思维错误适用、数据爬取违法性认定规则不统一及数据爬取监管机制不健全等问题影响反不正当竞争法有效适用。对此,我国应明确反不正当竞争法规制范式、统一数据违法性认定规则,并健全数据爬取监管制度,以促进数据要素自由流动,同时保证市场公平竞争。

Between Swimming and Crawling

动物从水生到陆地的演变并非像攀登阶梯一样简单,其间有各种各样的变化和波折。而人类对“过去的过去”的探索也从未停止过。最近在美国宾夕法尼亚州发现了一种nearly a meter long,weighing 20 kilograms or more的两栖动物化石。这一发现或许能让研究人员对这一过程有更深入的了解。

爬行真的可有可无吗?——婴幼儿动作发展的国际论证与经验启示

动作发展是指个体在成长过程中逐渐掌握并发展出的各种动作技能。爬行在婴幼儿动作发展中扮演着重要角色,对认知神经系统、肌肉骨骼系统、动作能力和社交能力等方面的成长发育有着积极意义。然而,我国学术界对于动作发展,尤其是爬行的重视程度相对较低,且公众对于爬行在个体成长中的重要性认知不足。以爬行这一婴幼儿时期关键的动作发展里程碑为例,运用文献资料法和逻辑分析法,系统梳理了国际上关于婴儿爬行的相关研究,包括其发展变化、多元作用、影响因素和干预措施等方面的理论研究与实践探索。对实现我国“幼有优育”的婴幼儿健康成长的研究启示主要有:开展大样本的婴儿爬行队列研究;采用婴儿爬行经历作为临床筛查的参考指标;改善婴儿家庭养育的爬行支持环境;完善特殊婴儿的爬行活动干预。