Homing Strategy for a 4RRR Parallel Kinematic Machine

Returning home is the most important process of a parallel kinematic machine （PKM） with incremental encoders.Currently,most corresponding articles focus on the accuracy of homing process,and there lacks the investigation of the operation＇s safety.For a 4RRR PKM,all servoaxes would be independently driven to their zero positions at the same time based on the traditional homing mode,and that can bring serious interfere of the kinematic chains.This paper systemically investigates this 4RRR PKM＇s safety of homing process.A homing strategy usually contains three parts which are the home switches＇ locations,the platform＇s initial moving space,and each links＇ homing direction,and all of them can influence the safety of homing operation.For the purpose of evaluating and describing the safety of the homing strategy,some important parameters are introduced as follows：Safely homing ratio （SHR） is used to evaluate the probability of a machine＇s successfully returning home from an initial moving space;Synchronal rotational angle （SRA） is the four links＇ largest synchronal rotational angle with given directions from a given pose.Whether a machine can safely return home from a given pose can be judged by comparing the SRA with all four home switches＇ mounting angles.By meshing the initial moving space and checking the safeties of returning home from all the initial poses on the nodes,the SHR of this initial moving space can be calculate.For the sake of convenience,the platform＇s initial moving space should be as large as possible,and in this 4RRR PKM,a square zone in the center of the workspace with a giving initial rotation range is selected as the platform＇s initial moving space.The forward direction is selected as each link＇s homing direction according to custom,and the platform＇s initial rotational angle is selected as larger than 0° based on this 4RRR PKM＇s kinematic characteristics.The platform＇s initial moving space can be defined only by the side length of the initial moving square.By setting a probable searching step and calculating the SHR of the initial moving square,an optimal procedure of searching for the largest side length of the platform＇s initial moving square is proposed.The homing strategy proposed is based on a systemic research on the safety of homing process for PKM,and the two new indexes SHR and SRA can clearly describe the safety of homing operation.The homing operation based on this strategy is fast and safe,and the method can also be used in other PKMs with the situation of serious components＇ interference.

Variable Structure Proportional Navigation for Homing Missile

The purpose of this paper is to design control loop and guidance loop for the homing missile, to prove that the modified variable structure proportional navigation (VSPN) can be used in passive homing guidance system, and to compare the VSPN with the proportional navigation (PN). Angular rate and linear acceleration are fed back to improve the stability and robust of autopilot, VSPN and PN are compared in mathematics simulation of homing missile in attacking tanks and helicopters. The damp and the stability of the missile body are increased. The VSPN cuts down the overload of guidance phase dramatically, makes the ballistic trajectory straighter than PN and leads to smaller missdistance. The VSPN can be used for passive homing guidance system, and is especially suitable for attacking helicopter.

Homing and migration of mesenchymal stromal cells: How to improve the efficacy of cell therapy?

Mesenchymal stromal cells(MSCs) are currently being investigated for use in a wide variety of clinical applications. For most of these applications, systemic delivery of the cells is preferred. However, this requires the homing and migration of MSCs to a target tissue. Although MSC hominghas been described, this process does not appear to be highly efficacious because only a few cells reach the target tissue and remain there after systemic administration. This has been ascribed to low expression levels of homing molecules, the loss of expression of such molecules during expansion, and the heterogeneity of MSCs in cultures and MSC culture protocols. To overcome these limitations, different methods to improve the homing capacity of MSCs have been examined. Here, we review the current understanding of MSC homing, with a particular focus on homing to bone marrow. In addition, we summarize the strategies that have been developed to improve this process. A better understanding of MSC biology, MSC migration and homing mechanisms will allow us to prepare MSCs with optimal homing capacities. The efficacy of therapeutic applications is dependent on efficient delivery of the cells and can, therefore, only benefit from better insights into the homing mechanisms.

TMTP1, a Novel Tumor-homing Peptide, Specifically Targets Hematological Malignancies and Their Metastases

TMTP1, a 5-amino acid peptide NVVRQ, obtained by using the flagella peptide library screening in our previous studies, can be used for the labeling of malignant in situ and metastatic lesions, and even micro-metastases. In this study, TMTP1 was assessed for its ability to specifically target the malignant hematopoietic cells and metastatic lesions of hematological malignancies. FITC-TMTP1 was chemically synthesized. Immunofluorescence assay and competitive test were carried out to determine the specific binding capacity of TMTPl to hematological malignant cell lines, including HL60, k562, SHI-1, Jurkat, Raji, El-4 and umbilical cord blood mononuclear cells. Mononuclear cells were isolated from the bone marrow of healthy subjects and patients with chronic myeloid leukemia. Then the cells were co-clutured with TMTP1 or scrambled peptides and the binding and affinity of TMTP1 peptide to the primary cells of hematological malignancies were flow cytometrically analyzed. The binding speci-ficity of TMTP1 to target hematological malignancies was measured in vivo by intravenous injection of FITC-conjugated TMTP1 into El-4 lymphoma-bearing mice. The results showed that TMTP1 specifi-cally bound to the cells of a series of hematological malignancies, including HL60, k562, Jurkat, Raji , El-4 and chronic myeloid leukemia primary cells but not to bone marrow mononuclear cells from healthy subjects. By contrast, TMTP1 could bind to the metastatic foci of lymphoma originating from the EL-4 cell line while the scrambled peptide failed to do so. Moreover, the occult metastases could be identified, with high specificity, by detecting FITC-TMTP1. We are led to conclude that TMTP1, as a novel tumor-homing peptide, can serve as a marker for primary malignant and metastatic lesions for the early diagnosis of hematological malignances and a carrier of anticancer drugs for cancer treatment.

Design and simulation for large parafoil fix line object homing algorithm

Traditional parafoil homing usually uses a point as object. As the mobility of parafoil is limited by its glide ratio and wind, in some cases when the parafoil scatter area is large, or the glide ratio of parafoil is small, the deviation of its landing point to object point will be arduous to control. Accordingly, during these situations, when parafoil is used in recovery of spacecraft or satellite, the landing area of parafoil can be set as a rectangle, and the object of parafoil can be set as a line segment. The thesis of this work is designing an algorithm for parafoil homing using line segment as object. The algorithm of wind velocity and direction calculation in different flying segments was also investigated. The algorithm designed navigates the parafoil to land into the predestined area and largely reduce the probability of recovery loads falling to unwanted area to damage houses and people.

Endothelial Progenitor Cells Homing to the Orthotopic Implanted Liver Tumor of Nude Mice

This study investigated the 'homing' phenomenon in hepatocellular carcinoma (HCC).The 'homing' specificity of endothelial progenitor cells (EPC) by establishing an orthotopic implantation model in nude mice.EPCs harvested from the marrow cells were separated by density gradient centrifugation.Fluorescence microscope,flow cytometry (FCM) and double fluorescence staining with FITC-UEA-I and DiI-ac-LDL,were employed to identify the cells.4',6-diamidino-2-phenylindole (DAPI) labelling and real-time PCR were used for detecting the expression of CD133 and chemokines to trace and observe the distribution of EPCs.Our results showed that the distribution rate of EPCs was obviously higher than that in other important organs and the negative control group.Detection of CD133 and chemokines yielded similar results in difference tissues.Our experiment confirmed that the chemotaxis of EPCs does exist in HCC.Moreover,HIF-1α,SDF-1 and VEGF might play important roles in the 'homing' of EPCs in HCC.EPCs might be a potential candidate for targeting vector of HCC for gene therapy.

Research on Attitude Pursuit Guidance Law for Strapdown Homing System

This paper comprehensively analyzes the attitude pursuit guidance law whichis one of the simple guidance methods for strapdown homing guidance system. Via the analyticalsolution of attitude pursuit, limitations on the velocities of missile and target are presented. Theinfluence of damping, lagging and transfer parameter from rudder deviation to angle of attack onthe attitude pursuit guidance law is discussed by using Automatic Control Theory. It is concludedthat the velocities of missile and target should not be too large, and the stable loop of missilebody should have some damping when the missile guidance system has inherent lagging, and thetransfer parameter mentioned above should not be too large when the attitude pursuit guidance law isused.

Smart homing guidance strategy with control saturation against a cooperative target-defender team

A smart homing guidance strategy with control saturation against a target-defender team is derived. It is noteworthy that a cooperative strategy of the target-defender team is applied,which has been proved more challenging for the homing guidance.The defender missile is launched by the target and guided by a cooperative augmented proportional navigation(APN). At the same time, the target performs a one-switch maneuver to cooperate and minimize the defender's acceleration requirement. The problem is analyzed for arbitrary-order linear dynamics of the agents in the linearized form but validated by the mathematical simulations by using nonlinear kinematics. The perfect information of three agents' states is assumed. Then, a method to deal with the target-defender team is proposed. It contains a combined performance index penalizing the miss distance relative to the target and energy consumption in the whole duration. Besides, the specific miss distance related to the defender is regarded as an inequality constraint. An analytical solution for the smart guidance strategy against the APN guided defender is derived. Meanwhile, the control saturations are introduced to get more realistic and reasonable insights to this practical target-missile-defender problem. A simple but effective iterative searching technique is proposed to determine the saturation time points. The solution provides an optimal homing strategy to evade the defender with a specific miss distance and intercept the target with the minimum miss distance in the minimum energy manner. Nonlinear two-dimensional simulation results are used to validate the theoretical analysis. By comparison with the optimal differential game guidance(ODGG) and the combined minimum effort guidance(CMEG), the superiority of this smart guidance strategy is concluded.

Homing Guidance Law with Falling Angle and Flying Time Control

In this paper,a new homing guidance method is used to control the flying time and falling angle for guided missiles. Through this approach,it finds the approximate solution to the quadratic equation of time-togo,which is used for the formula derivation of the flying time control command. In this guidance law design,the acceleration rate control command is adopted. The guidance law is composed of a PN guidance command and a flying time control command. Firstly,it obtains a desired falling angle with accurate guidance. Secondly,it introduces to satisfy the constraint of flying time. The flying time control requires an assumption on the future evolution of missile,which is called time-to-go. To cope with the time-varying speed of missiles,a method of compensating the estimation of time-to-go is presented. The new guidance law is evaluated by using a simulation of typical terminal guidance for rocket-propelled torpedo. The simulation results show that the guidance achieves excellent control performance and exhibits insensitivity to initial trajectory parameter over a widen flight envelope.

Design and optimization in multiphase homing trajectory of parafoil system

In order to realize safe and accurate homing of parafoil system,a multiphase homing trajectory planning scheme is proposed according to the maneuverability and basic flight characteristics of the vehicle.In this scenario,on the basis of geometric relationship of each phase trajectory,the problem of trajectory planning is transformed to parameter optimizing,and then auxiliary population-based quantum differential evolution algorithm(AP-QDEA)is applied as a tool to optimize the objective function,and the design parameters of the whole homing trajectory are obtained.The proposed AP-QDEA combines the strengths of differential evolution algorithm(DEA)and quantum evolution algorithm(QEA),and the notion of auxiliary population is introduced into the proposed algorithm to improve the searching precision and speed.The simulation results show that the proposed AP-QDEA is proven its superior in both effectiveness and efficiency by solving a set of benchmark problems,and the multiphase homing scheme can fulfill the requirement of fixed-points and upwind landing in the process of homing which is simple in control and facile in practice as well.

Stem cell homing, tracking and therapeutic efficiency evaluation for stroke treatment using nanoparticles: A systematic review

BACKGROUND Stroke is the second leading cause of death worldwide.There is a real need to develop treatment strategies for reducing neurological deficits in stroke survivors,and stem cell(SC)therapeutics appear to be a promising alternative for stroke therapy that can be used in combination with approved thrombolytic or thrombectomy approaches.However,the efficacy of SC therapy depends on the SC homing ability and engraftment into the injury site over a long period of time.Nonetheless,tracking SCs from their niche to the target tissues is a complex process.AIM To evaluate SC migration homing,tracking and therapeutic efficacy in the treatment of stroke using nanoparticles METHODS A systematic literature search was performed to identify articles published prior to November 2019 that were indexed in PubMed and Scopus.The following inclusion criteria were used:(1)Studies that used in vivo models of stroke or ischemic brain lesions;(2)Studies of SCs labeled with some type of contrast agent for cell migration detection;and(3)Studies that involved in vivo cellular homing and tracking analysis.RESULTS A total of 82 articles were identified by indexing in Scopus and Pub Med.Afterthe inclusion criteria were applied,35 studies were selected,and the articles were assessed for eligibility;ultimately,only 25 studies were included.Most of the selected studies used SCs from human and mouse bone marrow labeled with magnetic nanoparticles alone or combined with fluorophore dyes.These cells were administered in the stroke model(to treat middle cerebral artery occlusion in 74%of studies and for photothrombotic induction in 26%of studies).Fiftythree percent of studies used xenogeneic grafts for cell therapy,and the migration homing and tracking evaluation was performed by magnetic resonance imaging as well as other techniques,such as near-infrared fluorescence imaging(12%)or bioluminescence assays(12%).CONCLUSION Our systematic review provided an up-to-date evaluation of SC migration homing and the efficacy of cellular therapy for stroke treatment in terms of functional and structural improvements in the late stage.

NSGA Ⅱ based multi-objective homing trajectory planning of parafoil system

Homing trajectory planning is a core task of autonomous homing of parafoil system.This work analyzes and establishes a simplified kinematic mathematical model,and regards the homing trajectory planning problem as a kind of multi-objective optimization problem.Being different from traditional ways of transforming the multi-objective optimization into a single objective optimization by weighting factors,this work applies an improved non-dominated sorting genetic algorithm Ⅱ(NSGA Ⅱ) to solve it directly by means of optimizing multi-objective functions simultaneously.In the improved NSGA Ⅱ,the chaos initialization and a crowding distance based population trimming method were introduced to overcome the prematurity of population,the penalty function was used in handling constraints,and the optimal solution was selected according to the method of fuzzy set theory.Simulation results of three different schemes designed according to various practical engineering requirements show that the improved NSGA Ⅱ can effectively obtain the Pareto optimal solution set under different weighting with outstanding convergence and stability,and provide a new train of thoughts to design homing trajectory of parafoil system.

Strapdown Homing Guidance System Design for Some Ammunition

The strapdown homing guidance system for some ammunition was mainly studied. A strong tracking Kalman filter was designed for the strapdown homing guidance system using the information measured by the strapdown homing seeker to estimate relative movement variables between the ammunition and target. Then the optimal proportional law, which using the estimated information, guided the ammunition. Simulation results show that the designed strapdown homing guidance system with strong tracking Kalman filter can attack the maneuvering target effectively, and satisfy the performance index for the guided ammunition system.

Homeward bound:canopy cover and species identity influence non-breeding season homing success and speed in forest birds

Background:Efficient and safe movement is fundamental for wild birds to thrive in their environments.For arboreal forest animals,especially birds,canopy cover has a large impact on birds’daily movements and is a crucial component of conservation strategies seeking to retain avian population in disturbed or urban habitats.Methods:We translocated woodland bird species utilizing different forest strata during two non-breeding seasons in Gainesville,FL,USA.We used linear model and generalized linear model to examine the effects of canopy cover and species identity on homing success and speed.Results:Among our study species of Tufted Titmouse(Baeolophus bicolor),Carolina Chickadee(Poecile carolinensis),and Northern Cardinal(Cardinalis cardinalis),we found that Carolina Chickadees and Tufted Titmice were more likely to return than Northern Cardinals.Among birds that successfully returned,homing speed is significantly affected by forest canopy cover and species identity(titmice had higher homing speed than cardinals).Birds return much faster in landscape with higher canopy cover.Conclusions:This study presented evidence of species identity’s effect on homing success and speed in common feeder bird species in Southeast US and provided further evidence that bird movements in the suburban land cover are constrained by low canopy cover.

Modeling and simulation of torpedo acoustic homing trajectory with multiple targets

The characteristics of a torpedo＇s acoustic homing trajectory with multiple targets were studied. The differential equations of torpedo motion were presented based on hydrodynamics. The Fourth order Runge-Kutta method was used to solve these equations. Derived from sonar equations and Snell＇ s law, a simple virtual underwater acoustic environment was established for simulating the torpedo homing process. The Newton iteration method was used to calculate homing range and ray tracing was approximated by pieccwise line, which takes into consideration distortions cause by temperature, pressure, and salinity in a given sea area. The influence of some acoustic warfare equipment disturb the torpedo homing process in certain circumstances, including decoys and jammers, was alsotaken into account in simulations. Relative target identification logic and homing control laws were presented. Equal consideration during research was given to the requirements of rcal-timeactivity as well as accuracy. Finally, a practical torpedo homing trajectory simulation program was developed and applied to certain projects.

An unusual homing behavior found in the Sichuan Partridge during the early brooding period

In this study,we report an unusual homing behavior of the Sichuan Partridge(Arborophila rufipectus)at the Laojunshan National Nature Reserve,Sichuan Province,China.Hen Sichuan Partridges led the chicks back to the nests where they hatched in the evening and roosted there over night.This behavior lasted 6.7±4.3 nights(range=1–15;n=13)after the chicks hatched.At this stage,the hens became very vigilant to predators and human disturbance.If disturbed,they often abandoned the nests immediately and no longer returned thereafter.The ambient temperature at night during the early brooding period of Sichuan Partridge at our study site was^12.4°C.Our findings suggest that hen Sichuan Partridges may make trade-offs between nest predation risks versus the thermoregulatory needs of their young.

Monocyte chemotactic protein 1 increases homing of mesenchymal stem cell to injured myocardium and neovascularization following myocardial infarction

Objective：To investigate the effect of MCP-1 on mesenchymal stem cells（MSCs） homing to injured myocardium in a rat myocardial infarction（MI） model. Methods：Rat myocardial infarction model was established by permanent left anterior descending branch ligation. Mesenchymal stem cells from donor rats were cultured in IMDM and labeled with BrdU. The Rats were divided into two groups. Monocyte chemotactic protein I（MCP-1） expression were measured by in situ hybridization and immunohistochemistry in the sham operated or infarcted hearts at 1, 2, 4, 7, 14 and 28 days post operation in MCP-1 detection group. The rats were injected with MCP-1, anti-MCP-1 antibody or saline 4 days after myocardial infarction in intervention group. Then, a total of 5 × 10^6 cells in 2.5 ml of PBS were injected through the tail vein. The number of the labeled MSCs in the infarcted hearts was counted 3 days post injection. Cardiac function and blood vessel density were assessed 28 days post injection. Results：Self-generating MCP-1 expression was increased at the first day, peaked at the 7^th day and decreased thereafter post MI and remained unchanged in sham operated hearts. The MSCs enrichment in the host hearts were more abundant in the MI groups than that in the non-MI group（P= 0.000）, the MSCs enrichment in the host hearts were more abundant in the MCP-1 injected group than that in the anti-MCP-1 antibody and saline injected groups （P = 0.000）. Cardiac function was improved more in MCP-1 injected group than anti-MCP-1 antibody and saline injected groups（P= 0.000）. Neovascularization in MCP-1 injected group significantly increased compared with that of other groups（P = 0.000）. Conclusion： Myocardial MCP-1 expression was increased only in the early phase post MI. MCP-1 may enhance MSCs homing to the injured heart and improve cardiac function by promoting neovascularization.

Induced Monocytes-Derived HSCs (CD34+) with LPS Accelerated Homing Rat Bone Marrow-Mesenchymal Stem Cell (BM-MSCs, CD105) in Injured Pancreas

Investigating the function of combining induced rat monocytes-derived bone marrow-haemopoietic stem cell (rat BM-HSCs) with LPS and rat bone marrow-mesenchymal stem cell (rat BM-MSCs) was to analyze the acceleration of homing process mechanism in injured pancreas. Mononucleated stem cells were isolated from aspirated whole rat BM using ficoll and cultured in α-MEM complete growth medium in 10 cm petridish. After two days, adherent cells after washing twice in petridish were added α-MEM growth medium and then mesenchymal cells were characterized using CD105 marker in third passage and labeled PKH26. Then haemopoietic stem cells (HSCs) were isolated with magnetic beads CD34+ and differentiated in vitro, and then induced monocytes with LPS. Animal experiment used 28 male Wistar rats, and divided them into 4 groups. After transplantation combined, both cells between monocyte derived HSc (mHSCs) and rat BM-MSC were analyzed expression of pair box gen 4 (Pax4), pancreatic and duodenal homeobox (Pdx1), C-peptide using immunohistochemistry, then secretion of insulin and C-peptide analyzed using indirect ELISA. Results showed that the expressions of Pax4, Pdx1, C-peptide found in the surface membrane cell of pancreatic cell, and secreted C-peptide and insulin were shown significant (P < 0.05) in transplanted group 2, 3 and 4, but in group 3 were transplanted with combined cells more dominant than non-combined cells. Conclusions suggested that combining of induced monocytes-derived HSCs and rat BM-MSCs has accelerated homing MSCs into injured pancreatic tissue.

A homing rescue gene drive with multiplexed gRNAs reaches high frequency in cage populations but generates functional resistance

CRISPR homing gene drives have considerable potential for managing populations of medically and agriculturally significant insects.They operate by Cas9 cleavage followed by homology-directed repair,copying the drive allele to the wild-type chromosome and thus increasing in frequency and spreading throughout a population.However,resistance alleles formed by end-joining repair pose a significant obstacle.To address this,we create a homing drive targeting the essential hairy gene in Drosophila melanogaster.Nonfunctional resistance alleles are recessive lethal,while drive carriers have a recoded“rescue”version of hairy.The drive inheritance rate is moderate,and multigenerational cage studies show drive spread to 96%–97%of the population.However,the drive does not reach 100%due to the formation of functional resistance alleles despite using four gRNAs.These alleles have a large deletion but likely utilize an alternate start codon.Thus,revised designs targeting more essential regions of a gene may be necessary to avoid such functional resistance.Replacement of the rescue element’s native 3'UTR with a homolog from another species increases drive inheritance by 13%–24%.This was possibly because of reduced homology between the rescue element and surrounding genomic DNA,which could also be an important design consideration for rescue gene drives.

Enhanced homing of mesenchymal stem cells for in situ niche remodeling and bone regeneration

Mesenchymal stem cells(MSCs)transplantation is a promising strategy for osteoporosis treatment.However,limited sources and poor tissue-homing efficiency limit their clinical capabilities.In this study,we isolated a kind of MSCs from women’s menstrual blood(MenSCs)noninvasively and established a novel MSCs bone marrow-targeted delivery system by utilizing waterin-oil-in-water droplet microfluidics.MenSCs were encapsulated withinβ-cyclodextrin-functionalized alginate microcapsules loaded with zoledronates,which has a high affinity for bone.With this delivery system,MenSCs could be preferentially delivered to the bone marrow tissues via intravenous infusion,and restored bone mass by remodeling the bone marrow niche in situ in ovariectomized mouse models.Moreover,scRNA-seq analysis demonstrated that those MenSCs homed to the bone marrow recruited CD4^(+)FOXP3^(+)natural regulatory T(nT_(reg))cells by secreting CCL28.The recruited nTreg promoted CD8^(+)T cells to secret Wnt family member 10B(WNT10B),activating the Wnt signaling in osteoblasts and thus promoting bone formation in situ in the bone marrow.This study reveals a promising application of MenSCs in postmenopausal osteoporosis treatment and highlights the clinical value of MenSCs by encouraging women to reserve autologous MenSCs before menopause to prevent and alleviate postmenopausal osteoporosis.