Post-launch analysis of the deployment dynamics of a space web sounding rocket experiment

Lightweight deployable space webs have been proposed as platforms or frames for a construction of structures in space where centrifugal forces enable deployment and stabilization. The Suaineadh project was aimed to deploy a 2×2m2 space web by centrifugal forces in milli-gravity conditions and act as a test bed for the space web technology. Data from former sounding rocket experiments, ground tests and simulations were used to design the structure, the folding pattern and control parameters. A developed control law and a reaction wheel were used to control the deployment. After ejection from the rocket, the web was deployed but entanglements occurred since the web did not start to deploy at the specified angular velocity. The deployment dynamics was reconstructed from the information recorded in inertial measurement units and cameras. The nonlinear torque of the motor used to drive the reaction wheel was calculated from the results. Simulations show that if the Suaineadh started to deploy at the specified angular velocity, the web would most likely have been deployed and stabilized in space by the motor, reaction wheel and controller used in the experiment

Happiness is assortative in online social networks

Social networks tend to disproportionally favor connections between individuals with either similar or dissimilar characteristics. This propensity, referred to as assortative mixing or homophily, is expressed as the correlation between attribute values of nearest neighbour vertices in a graph. Recent results indicate that beyond demographic features such as age, sex and race, even psychological states such as "loneliness" can be assortative in a social network. In spite of the increasing societal importance of online social networks it is unknown whether assortative mixing of psychological states takes place in situations where social ties are mediated solely by online networking services in the absence of physical contact. Here, we show that general happiness or Subjective Well-Being (SWB) of Twitter users, as measured from a 6 month record of their individual tweets, is indeed assortative across the Twitter social network. To our knowledge this is the first result that shows assortative mixing in online networks at the level of SWB. Our results imply that online social networks may be equally subject to the social mechanisms that cause assortative mixing in real social networks and that such assortative mixing takes place at the level of SWB. Given the increasing prevalence of online social networks, their propensity to connect users with similar levels of SWB may be an important instrument in better understanding how both positive and negative sentiments spread through online social ties. Future research may focus on how event-specific mood states can propagate and influence user behavior in "real life".Comment: 17 pages, 9 figure

Tracing evolutionary footprints to identify novel gene functional linkages.

Systematic determination of gene function is an essential step in fully understanding the precise contribution of each gene for the proper execution of molecular functions in the cell. Gene functional linkage is defined as to describe the relationship of a group of genes with similar functions. With thousands of genomes sequenced, there arises a great opportunity to utilize gene evolutionary information to identify gene functional linkages. To this end, we established a computational method (called TRACE) to trace gene footprints through a gene functional network constructed from 341 prokaryotic genomes. TRACE performance was validated and successfully tested to predict enzyme functions as well as components of pathway. A so far undescribed chromosome partitioning-like protein ro03654 of an oleaginous bacteria Rhodococcus sp. RHA1 (RHA1) was predicted and verified experimentally with its deletion mutant showing growth inhibition compared to RHA1 wild type. In addition, four proteins were predicted to act as prokaryotic SNARE-like proteins, and two of them were shown to be localized at the plasma membrane. Thus, we believe that TRACE is an effective new method to infer prokaryotic gene functional linkages by tracing evolutionary events

Numerical and Experimental Studies of Deployment Dynamics of Space Webs and CubeSat Booms

In this thesis, experiments and simulations are performed to study the deployment dynamics of space webs and space booms, focusing on the deployment and stabilization phases of the space web and the behavior of the bi-stable tape spring booms after long-term stowage. The space web, Suaineadh, was launched onboard the sounding rocket REXUS-12 from the Swedish launch base Esrange in Kiruna on 19 March 2012. It served as a technology demonstrator for a space web. A reaction wheel was used to actively control the deployment and stabilization states of the 2×2 m2 space web. After ejection from the rocket, the web was deployed but entanglements occurred since the web did not start to deploy at the specified angular velocity. The deployment dynamics was reconstructed by simulations from the information recorded by inertial measurement units and cameras. Simulations show that if the web would have started to deploy at the specified angular velocity, the web would most likely have been deployed and stabilized in space by the motor, reaction wheel and controller used in the experiment. A modified control method was developed to stabilize the out-of-plane motions before or during deployment. New web arms with tape springs were proposed to avoid entanglements. A deployable booms assembly composed of four 1-m long bi-stable glass fiber tape springs was designed for the electromagnetically clean 3U CubeSat Small Explorer for Advanced Missions (SEAM). The deployment dynamics and reliability of the SEAM boom design after long-term stowage were tested by on-ground experiments. A simple analytical model was developed to predict the deployment dynamics and to assess the effects of the GOLS and the combined effects of friction, viscoelastic strain energy relaxation, and other factors that act to decrease the deployment force. In order to mitigate the viscoelastic effects and thus ensure self-deployment, different tape springs were designed, manufactured and tested. A numerical model was used to assess the long-term stowage effects on the deployment capability of bi-stable tape springs including the friction, nonlinear-elastic and viscoelastic effects. A finite element method was used to model a meter-class fully coiled bi-stable tape spring boom and verified by analytical models.QC 20170508SEA

3D tunable anisotropic metamaterial for low-frequency vibration absorption

In the well-known conflict between design space and performance requirements e.g. in termsof noise and vibration insulation, the emergence of new materials exhibiting exceptional insula-tion properties for a reduced weight or volume increase has received much attention in the lastdecade. Metamaterials with artificially designed architectures are increasingly considered as newfunctional materials with unusual properties. This paper presents a group of novel 3D latticemetamaterials for low-frequency vibration absorption. The novel lightweight cellular microstruc-tures for vibro-acoustic metamaterials are designed by modification of the Kelvin cell. Interestinganisotropic material properties are generated by controlling the geometries, e.g., high-stiffness,auxetic, and strong compression-torsional coupling properties. The interesting meta-propertiesenable to tune the cellular resonators of the structures at a low-frequency range. Previous researchis mostly focused on metamaterials for vibration absorption along only one or two directions. Inthis paper, wide-band high sound absorption properties of energy transfer coupling in all threedirections are achieved by tunning the frequency-dependent meta-structures in controlling the ge-ometry and material properties. Additive manufacturing technologies are used for making the 3Dcomplex tunable metamaterials.QC 20220309</p

Modeling Public Mood and Emotion: Twitter Sentiment and Socio-Economic Phenomena

We perform a sentiment analysis of all tweets published on the microblogging platform Twitter in the second half of 2008. We use a psychometric instrument to extract six mood states (tension, depression, anger, vigor, fatigue, confusion) from the aggregated Twitter content and compute a six-dimensional mood vector for each day in the timeline. We compare our results to a record of popular events gathered from media and sources. We find that events in the social, political, cultural and economic sphere do have a significant, immediate and highly specific effect on the various dimensions of public mood. We speculate that large scale analyses of mood can provide a solid platform to model collective emotive trends in terms of their predictive value with regards to existing social as well as economic indicators

An inverse method for design and characterisation of acoustic materials

This paper presents applications of an inverse method for the design and characterisation of anisotropic elastic material properties of acoustic porous materials. Full field 3D displacements under static surface loads are used as targets in the inverse estimation to fit a material model of an equivalent solid to the measurement data. Test cases of artificial open-cell foams are used, and the accuracy of the results are verified. The method is shown to be able to successfully characterise both isotropic and anisotropic elastic material properties. The paper demonstrates a way to reduce costs by characterising material properties based on the design model without a need for manufacturing and additional experimental tests.QC 20200217</p

3D tunable anisotropic metamaterial for low-frequency vibration absorption

In the well-known conflict between design space and performance requirements e.g. in termsof noise and vibration insulation, the emergence of new materials exhibiting exceptional insula-tion properties for a reduced weight or volume increase has received much attention in the lastdecade. Metamaterials with artificially designed architectures are increasingly considered as newfunctional materials with unusual properties. This paper presents a group of novel 3D latticemetamaterials for low-frequency vibration absorption. The novel lightweight cellular microstruc-tures for vibro-acoustic metamaterials are designed by modification of the Kelvin cell. Interestinganisotropic material properties are generated by controlling the geometries, e.g., high-stiffness,auxetic, and strong compression-torsional coupling properties. The interesting meta-propertiesenable to tune the cellular resonators of the structures at a low-frequency range. Previous researchis mostly focused on metamaterials for vibration absorption along only one or two directions. Inthis paper, wide-band high sound absorption properties of energy transfer coupling in all threedirections are achieved by tunning the frequency-dependent meta-structures in controlling the ge-ometry and material properties. Additive manufacturing technologies are used for making the 3Dcomplex tunable metamaterials.QC 20220309</p