Alignment Control Research Articles

Collective gradient perception with a flying robot swarm

In this paper, we study the problem of collective and emergent sensing with a flying robot swarm in which social interactions among individuals lead to following the gradient of a scalar field in the environment without the need of any gradient sensing capability. We proposed two methods—desired distance modulation and speed modulation—with and without alignment control. In the former, individuals modulate their desired distance to their neighbors and in the latter, they modulate their speed depending on the social interactions with their neighbors and measurements from the environment. Methods are systematically tested using two metrics with different scalar field models, swarm sizes and swarm densities. Experiments are conducted using: (1) a kinematic simulator, (2) a physics-based simulator, and (3) real nano-drone swarm. Results show that using the proposed methods, a swarm—composed of individuals lacking gradient sensing ability—is able to follow the gradient in a scalar field successfully. Results show that when individuals modulate their desired distances, alignment control is not needed but it still increases the performance. However, when individuals modulate their speed, alignment control is needed for collective motion. Real nano-drone experiments reveal that the proposed methods are applicable in real-life scenarios.

Alignment Control of Smectic Layer Structures in Liquid-Crystalline Polymers by Photopolymerization with Scanned Slit Light.

Photoalignment control of hierarchical structures is a key process to enhance the properties of optical and mechanical materials. We developed an in situ molecular alignment method, where photopolymerization with the scanned slit light causes molecular flow, leading to two-dimensional precise alignment of molecules over large areas; however, the alignment control has been explored only on a molecular scale. In this study, we demonstrate this photopolymerization-induced molecular flow, enabling mesoscopic alignment of smectic layer structures composed of anisotropic molecules. Side-chain liquid-crystalline polymers were obtained from two different monomers with or without alkyl spacers by photopolymerization with one-dimensionally scanned slit light. The polymer with an alkyl spacer displayed mesogens aligned parallel to the scanning direction, while the polymer with no alkyl spacer resulted in perpendicular alignment of mesogens to the scanning direction, regulated by the alignment of the polymer main chain along the light scanning direction. Moreover, the polymerization with the scanned light aligned not only the mesogens but also mesoscopic smectic layer structures over large areas, depending on the structure and scanning pattern of light. We envision that such a simple polymerization technique could become a powerful and versatile alignment platform of anisotropic materials in a wide range of scales.

54.3: Invited Paper: Surface Control of LC Alignment for Creation of Liquid Crystal Lenses Arrays

New photosensitive alignment materials, capable to obtain pretilt angle from 90 to 0 degree in single technological process of UV exposure, are developed. The novel technological method for fabrication LC lens and LC lenses arrays has been developed based on new pretilt angle gradient alignment materials. Laboratory samples of voltage tunable LC lens and LC lenses arrays are obtained and characterized. The developed low cost fabrication technology of tunable micro‐lenses arrays based on photosensitive alignment materials has low complexity and is perspective for light field technology applications.

Pancreatitis-Associated PRSS1-PRSS2 Haplotype Alters T-Cell Receptor Beta (TRB) Repertoire More Strongly Than PRSS1 Expression

Pancreatitis-Associated PRSS1-PRSS2 Haplotype Alters T-Cell Receptor Beta (TRB) Repertoire More Strongly Than PRSS1 Expression

A Bidirectional Active-Alignment Control System for LED Communication

LED-based free-space optical communication is becoming a promising alternative to the traditional acoustics mode of underwater communication because of its low cost, high data rate, and low power consumption. However, a fundamental challenge associated with the free space optical communication systems is to establish and maintain line-of-sight (LOS) between the two communicating agents. It becomes even more challenging when the agents are in motion, requiring an alignment system that enables each agent to point itself towards the LOS direction continuously. This paper presents a bi-directional active alignment control approach for the LED-based communication system of two robots, where the robots navigate in a three-dimensional (3D) space. We propose an extended Kalman filter (EKF) based alignment approach, where the estimates of azimuthal and elevation components of heading bias with the LOS are used to correct the alignment. We introduce and implement a new circular scanning technique on a two-degree-of-freedom (2DOF) rotational system mounted on each robot that enables consecutive independent measurements from a single photo-diode to satisfy the observability constraints of the EKF. Furthermore, we explore a synchronized alternating scheme to address the bidirectional nature of the problem. The scanning amplitude is further adjusted based on the EKF estimation covariance, to balance the trade-off between estimation accuracy and actuation effort. The presented results support the efficacy of the proposed method in the presence of slow relative motion between two robots, and demonstrate its superiority over an extremum-seeking (ES) based approach across a wide range of distances between the robots.

Double-crowned 2D semiconductor nanoplatelets with bicolor power-tunable emission

Nanocrystals (NCs) are now established building blocks for optoelectronics and their use as down converters for large gamut displays has been their first mass market. NC integration relies on a combination of green and red NCs into a blend, which rises post-growth formulation issues. A careful engineering of the NCs may enable dual emissions from a single NC population which violates Kasha’s rule, which stipulates that emission should occur at the band edge. Thus, in addition to an attentive control of band alignment to obtain green and red signals, non-radiative decay paths also have to be carefully slowed down to enable emission away from the ground state. Here, we demonstrate that core/crown/crown 2D nanoplatelets (NPLs), made of CdSe/CdTe/CdSe, can combine a large volume and a type-II band alignment enabling simultaneously red and narrow green emissions. Moreover, we demonstrate that the ratio of the two emissions can be tuned by the incident power, which results in a saturation of the red emission due to non-radiative Auger recombination that affects this emission much stronger than the green one. Finally, we also show that dual-color, power tunable, emission can be obtained through an electrical excitation.

Alignment Control Reconfigurability Analysis and Autonomous Control Methods of Air Spring Vibration Isolation System for High Power Density Main Engine (HPDME-ASVIS)

The alignment stability and controllability deteriorate considerably when the air spring vibration isolation system for the high power density main engine (HPDME-ASVIS) is in a special running state of high power and high output torque. The coupling characteristics among the alignment components are obtained by analyzing the mechanical characteristics of HPDME-ASVIS. A control response model is established, which can predict the alignment state and the vertical displacement of air springs after k times of inflation/deflation. By solving the linear programming problem, the alignment controllability judgment models are constructed for two conditions, which are under hard constraints and soft constraints, respectively. Furthermore, alignment reconfigurability is described and an autonomous control method is established. The experimental results confirm that high output torque will cause large and serious coupling of horizontal offset, self-rotation angle, and vertical deformation of air springs. Meanwhile, hey cannot reach the given control precision range. The traditional control method under hard constraints will result in a state of oscillation and may bring many reliability problems to HPDME-ASVIS. The alignment reconfigurability analysis can judge the alignment control influence degree based on different torque accurately. The autonomous control can use the control parameters autonomous adjustment and the spatial configuration to realize the alignment control reconfigurability for two different alignment control fault states. The stability of the alignment control system in HPDME-ASVIS can be improved observably, which is of great significance to the engineering application of the high power density main engine (HPDME) in the field of marine propulsion technology.

Ferroelectric control of band alignments and magnetic properties in the two-dimensional multiferroic VSe2/In2Se3

Our first-principles evidence shows that the two-dimensional (2D) multiferroic VSe2/In2Se3 experiences continuous change of electronic structures, i.e. with the change of the ferroelectric (FE) polarization of In2Se3, the heterostructure can possess type-I, -II, and -III band alignments. When the FE polarization points from In2Se3 to VSe2, the heterostructure has a type-III band alignment, and the charge transfer from In2Se3 into VSe2 induces half-metallicity. With reversal of the FE polarization, the heterostructure enters the type-I band alignment, and the spin-polarized current is turned off. When the In2Se3 is depolarized, the heterostructure has a type-II band alignment. In addition, influence of the FE polarization on magnetism and magnetic anisotropy energy of VSe2 was also analyzed, through which we reveal the interfacial magnetoelectric coupling effects. Our investigation about VSe2/In2Se3 predicts its wide applications in the fields of both 2D spintronics and multiferroics.

Alignment control of clay and its effect on properties of polymer nanocomposites

Polymer nanocomposites are well known to show high performances by the addition of a small amount of nanofiller. However, the brittleness has often been reported as a general issue of the nanocomposites. In this study, we revealed the excellent toughening effect of poly (vinyl alcohol) (PVA)/montmorillonite (MMT) nanocomposites by controlling the alignment of MMT by drawing. The PVA/MMT nanocomposites with 5 wt% MMT loading was prepared and then drawn by uniaxial drawing, roll drawing and simultaneous-biaxial drawing. The drawn nanocomposites, where MMT was highly aligned parallel to the film surface, showed excellent enhancement in the mechanical properties and barrier properties. It is noteworthy that not only the Young's modulus and the tensile strength, but also the elongation at break and the toughness remarkably increased for the drawn nanocomposites. For example, the simultaneously-biaxially-drawn nanocomposite showed the toughness of 17 times higher than that of the as-cast nanocomposite. Furthermore, the swelling ratio was comparable to that of surface fluorinated PVA film.

Control of alignment of h-BN in polyetherimide composite by magnetic field and enhancement of its thermal conductivity

In this study, hexagonal boron nitride (h-BN) - polyetherimide (PEI) composites were prepared by a simple solution casting method, where the h-BN particles were aligned by an external magnetic field. Prior to the preparation of the composite samples, the h-BN platelets were firstly decorated by iron oxide nanoparticles (Fe 3 O 4 ) to achieve the desired magnetic properties. Due to the alignment of h-BN particles, the composite exhibited greatly enhanced thermal conductivity along that direction. At a filler loading of 20 wt%, an enhancement of 166% was obtained, compared to that of the unaligned composite. Furthermore, the composite samples showed a low dielectric loss (~ 0.01) with the filling ratio below 20 wt% and a tensile modulus of up to 2.34 GPa. Bearing such thermal conductivity, electrical insulation properties, and mechanical properties, these composites with magnetically aligned h-BN particles show potentials for microelectronic packaging applications. • h-BN were added into polyether imide (PEI) to prepare flexible composite films. • h-BN micro-platelets were aligned by an external magnetic field. • h-BN micro-platelets were firstly decorated by iron oxide nanoparticles to achieve magnetic properties. • The vertically aligned h-BN/PEI composite is promising for high-performance electronic packaging applications.

Analysis of the mutation dynamics of SARS-CoV-2 genome in the samples from Georgia State of the United States

BackgroundThe COVID-19 is caused by a novel coronavirus SARS-CoV-2, which started from China. It spread rapidly throughout the world and was later declared a pandemic by the WHO. Over the course of time, SARS-CoV-2 has mutated for survival advantages, and this led to multiple variants. Multiple studies on mutations identification in SARS-CoV2 have been published covering extensive sample areas. The purpose of this study was to limit the sample area to the Georgia state in the U.S. and to analyze the genome sequences for mutation profiling across the genome and origin of variants. MethodsThe genome sequences (n = 3,970) were obtained from the NCBI database as of June 12, 2021, with the filter of being complete sequenced genomes, homo-sapiens host, and only from Georgia State of the U.S. NextClade, an online tool was used for the analysis of the sequences using Wuhan-Hu-1/2019 as a reference genome. The algorithm was sequence alignment, translation, mutation calling, phylogenetic placement, clade assignment, and quality control (QC). Thirty-six samples with bad QC were removed from the mutational analysis. ResultsA total 117,743 mutations in the nucleotides were identified (averaging 31.5 mutations per sample). The mutations A23403G, C3037T, C241T, and C14408T were detected in 98% of the samples. Also, a total of 75,517 mutations in the amino acid were identified (averaging 20.2 mutations per sample). The mutations D614G and P314L were identified in >97% samples whereas R203K, G204R, P681H, and N501Y were detected in >50% samples. Analysis also revealed 16 different clades with 20I (49.6%). Clades 20G (24.2%) and 20A (5.5%) being the most abundant, showed that SARS-CoV-2 in the Georgia State originated mainly from Southeast England, other parts of the U.S., and several countries in Western Europe. ConclusionLooking at the three most common variants in Georgia State of the U.S., we could determine the primary locations of transmission or origin for the virus, and our analyses indicates that majority of the cases originated from Southeast England (Clade 20I), the U.S. itself (Clade 20G), and from Western Europe (Clade 20C).

Joint Communication and Control for mmWave/THz Beam Alignment in V2X Networks

As promising candidate frequency bands, millimeter wave (mmWave) and terahertz (THz) communications can provide ultrahigh transmission rate to enable vehicle-to-everything (V2X) networks for connected autonomous vehicles (CAVs). However, beam alignment is extremely challenging in mmWave/THz communications due to its narrow beam width and fast mobility of CAV. In this article, we propose a new joint communication and control algorithm for beam alignment, where the mutual positive effect of communications and motion control of CAV on each other is discussed. Specifically, we first provide a framework to show the interaction between motion control of CAV and beam alignment of transmission from base station (BS) to CAV. Then, we analyze the effect of CAV control on beam alignment in communications, where a theorem is obtained to show the closed-form expression of their relationship. Finally, we discuss the CAV control design affected by beam alignment. Simulation results show remarkable performance of the proposed method.

Ultrafast X-ray photoelectron diffraction from free molecules: Simulations of diffraction profiles from transient intermediates in the elimination reaction of C2H4I2

We have performed the simulations of C 1 s X-ray photoelectron diffraction (XPD) profiles from C2H4I2, bridged and classical anti-forms of C2H4I intermediates and C2H4 products to capture structures of transient intermediates in the elimination reaction of C2H4I2, under our ultrafast X-ray photoelectron diffraction (UXPD) scheme for free molecules using soft X-ray free-electron laser (SXFEL). In the UXPD scheme, the sample molecules are aligned in advance by near-infrared (NIR) laser with ns pulse duration before applying a pump probe method. Then, we have considered alignment control of C2H4I2 by using the elliptically polarized NIR laser to realize the UXPD experiments for the free molecules. As the results of simulations of XPD profiles from the laser-aligned C2H4I2 molecules, we have demonstrated the two-dimensional (2D) color maps of the C 1 s XPD profiles from C2H4I2, C2H4I, and C2H4. The 2D color maps have revealed that the transient C 1 s XPD profiles from the bridged-form and classical anti-form C2H4I intermediates exhibit remarkable differences, reflecting different intra-molecular scattering pathways of C 1 s photoelectrons within the intermediates. Thus, the present result has proved that UXPD for the free molecules has an advantage, compared with other traditional diffraction methods.

Direct Ink Writing for High-Efficiency Microwave Attenuation with Nanofibers Alignment.

One-dimensional (1D) fibers have been widely used in composites reinforcement for microwave attenuation due to their outstanding mechanical and electromagnetic properties, especially in the axial direction. However, the precise control of fiber alignment in a polymer matrix remains a challenge. In this work, we successfully demonstrated the well-controlled alignment of silicon carbide nanowires (SiCNW) in a silicone matrix by using direct ink writing (DIW)-based 3D printing. It is proven that the printed multilayer material with fiber alignment could show a dramatic improvement in both reflection loss (RL) and effective attenuation bandwidth (EAB, RL < -10 dB). In particular, a uniaxial in-plane orientation is found to be the optimal alignment among other planar and also out-of-plane orientations. Benefiting from the optimized alignment, the 3D-printed SiC composite could show an EAB (∼6.4 GHz)1.6 times broader than that of the randomly mixed composite at the same thickness without alignment, associated with a minimum RL of -48 dB at 14.3 GHz. In addition, it is demonstrated that DIW could print different materials, such as SiCNW and multiwall carbon nanotube (MWCNT), in alternating layers for multiple-frequency-band attenuation benefiting from the distinct property of each material. Considering the one-step control of fiber alignment and material selectivity, DIW could play an important role in materials design for high-efficiency microwave attenuation.

Aligning Liquid Crystal Materials through Nanoparticles: A Review of Recent Progress

Liquid crystals (LCs) have become indispensable materials in everyday life, with their applications ranging from high-resolution television displays to being a part of sophisticated and modern equipment for telecommunications and sensing purposes. Various important features of LC-based devices such as their response time, driving voltage, contrast ratio and brightness are controlled by the uniform alignment of the constituting molecules along the substrate surface. This alignment control can be achieved through various mechanical and non-mechanical techniques. Nanoparticles (NPs), which have become an underbelly of the latest technological developments, can also be incorporated into these tunable materials in order to achieve the desired alignment in them. The present review highlights the advantages of NPs -induced alignment technique over the other contemporary techniques available for aligning LCs. The NPs-induced alignment process is found to be cost-effective and reliable, and it does not require extreme physical conditions such as a low pressure for its operation. This alignment process enables manufacturers to effectively control the pretilt angle of the LC molecules by simply varying the concentration of the doped NPs in the host LC matrix. Furthermore, the alignment behavior in LCs is found to be a function of shape, size, concentration and solubility of the doped NPs in these materials. At the end, this review focuses on the methodology of developing new innovative devices based on this alignment process. With the fabrication of new NPs of different morphologies in recent times, the horizon of the LC nanoscience field is continuously increasing, thus paving way for new devices capitalizing on this alignment technique.

Accurate Cycle Aligned Repetitive Control for the Rejection of Spatially Cyclic Disturbances

The spatial disturbance, which depends on position rather than time, is widespread in rotary machines. In this article, an improved control method named accurate cycle aligned repetitive control (ACARC) is proposed to deal with its suppression. In the ACARC, the data-storage technique is used to realize the spatial internal model and a design requirement is presented for the rejection of spatial disturbance with a better response. Further, the cycle offset, caused by the auxiliary stabilizing compensator, is significantly reduced by the combination of a spatial low-pass compensator and a time-advance element. Moreover, a cascaded structure of ACARCs is presented together with a detailed design procedure for disturbance with multiple components occurring in actual rotary systems. The effectiveness and superiority of the proposed control method are verified and compared with other methods by the simulations and experiments.

Effects of CuInS2 nanoparticles on the alignment control of liquid crystals

Effects of CuInS2 nanoparticles on the alignment control of liquid crystals

Thermal Straightening Control System for Variable-Section Automotive Leaf Springs Rolling Based on IoT Edge Computing

With the rapid development of social economy in recent years, people’s living standards are also improving. The use of automobiles is becoming increasingly frequent, and people’s requirements for the safety, comfort, and energy saving of automobiles are also getting higher. This paper mainly studies the thermal straightening control system after the rolling of variable-section automotive leaf springs through edge computing based on the Internet of Things. This paper presents the basic concepts of IoT edge computing and the role they play in various aspects. The percentage of IoT development trends in 2011 was 6.7%. By 2020, the development trend percentage of IoT reached 68%, an increase of 61.3%. It can be seen that the development of the Internet of Things is very rapid. It can be seen that the straightening accuracy of the thermal straightening control system based on edge computing after the rolling of variable-section automotive leaf springs reaches 78%, and it is 29% higher than the traditional system straightening accuracy, which is only 49%. The safety of the thermal straightening control system of the variable-section automotive leaf spring after rolling based on edge computing reaches 95%, which is 33% higher than the safety of the traditional system. The thermal alignment control system for variable-section automotive leaf springs after rolling based on the edge computing of the Internet of Things is not only safer than the traditional system but also much higher in comfort and alignment accuracy than the traditional system. It can be seen that the thermal straightening control system for variable cross section automotive leaf springs after rolling based on IoT edge computing is more conducive to the development of the automotive industry.

Polarization of Femtosecond Laser for Titanium Alloy Nanopatterning Influences Osteoblastic Differentiation.

Ultrashort pulse lasers have significant advantages over conventional continuous wave and long pulse lasers for the texturing of metallic surfaces, especially for nanoscale surface structure patterning. Furthermore, ultrafast laser beam polarization allows for the precise control of the spatial alignment of nanotextures imprinted on titanium-based implant surfaces. In this article, we report the biological effect of beam polarization on human mesenchymal stem cell differentiation. We created, on polished titanium-6aluminum-4vanadium (Ti-6Al-4V) plates, a laser-induced periodic surface structure (LIPSS) using linear or azimuthal polarization of infrared beams to generate linear or radial LIPSS, respectively. The main difference between the two surfaces was the microstructural anisotropy of the linear LIPSS and the isotropy of the radial LIPSS. At 7 d post seeding, cells on the radial LIPSS surface showed the highest extracellular fibronectin production. At 14 days, qRT-PCR showed on the same surface an increase in osteogenesis-related genes, such as alkaline phosphatase and osterix. At 21 d, mineralization clusters indicative of final osteoinduction were more abundant on the radial LIPSS. Taken together, we identified that creating more isotropic than linear surfaces enhances cell differentiation, resulting in an improved osseointegration. Thus, the fine tuning of ultrashort pulse lasers may be a promising new route for the functionalization of medical implants.

Improving the stability of frequency-dependent squeezing with bichromatic control of filter cavity length, alignment, and incident beam pointing

Frequency dependent squeezing is the main upgrade for achieving broadband quantum noise reduction in upcoming observation runs of gravitational wave detectors. The proper frequency dependence of the squeezed quadrature is obtained by reflecting squeezed vacuum from a Fabry-Perot filter cavity detuned by half of its linewidth. However, since the squeezed vacuum contains no classical amplitude, co-propagating auxiliary control beams are required to achieve the filter cavity's length, alignment, and incident beam pointing stability. In our frequency dependent squeezing experiment at the National Astronomical Observatory of Japan, we used a control beam at a harmonic of squeezed vacuum wavelength and found visible detuning variation related to the suspended mirrors angular drift. These variations can degrade interferometer quantum noise reduction. We investigated various mechanisms that can cause the filter cavity detuning variation. The detuning drift is found to be mitigated sufficiently by fixing the incident beam pointing and applying filter cavity automatic alignment. It was also found that there is an optimal position of the beam on the filter cavity mirror that helps to reduce the detuning fluctuations. Here we report a stabilized filter cavity detuning variation of less than 10$\,$Hz compared to the 113$\,$Hz cavity linewidth. Compared to previously published results [Phys. Rev. Lett. 124, 171101 (2020)], such detuning stability would be sufficient to make filter cavity detuning drift induced gravitational wave detector detection range fluctuation reduce from $11\%$ to within $2\%$.