scholarly journals Approximation algorithms for tours of orientation-varying view cones

2020 ◽  
Vol 39 (4) ◽  
pp. 389-401
Author(s):  
Nikolaos Stefas ◽  
Patrick A Plonski ◽  
Volkan Isler
Keyword(s):  
Approximation Algorithm ◽  
Ground Plane ◽  
Orientation Angle ◽  
Apex Angle ◽  
Field Of View ◽  
Plane Normal ◽  
Polynomial Time Approximation Algorithm ◽  
New Variant ◽  
Angle Difference ◽  
Novel Variant

This article considers the problem of finding a shortest tour to visit viewing sets of points on a plane. Each viewing set is represented as an inverted view cone with apex angle [Formula: see text] and height [Formula: see text]. The apex of each cone is restricted to lie on the ground plane. Its orientation angle (tilt) [Formula: see text] is the angle difference between the cone bisector and the ground plane normal. This is a novel variant of the 3D Traveling Salesman Problem with Neighborhoods (TSPN) called Cone-TSPN. One application of Cone-TSPN is to compute a trajectory to observe a given set of locations with a camera: for each location, we can generate a set of cones whose apex and orientation angles [Formula: see text] and [Formula: see text] correspond to the camera’s field of view and tilt. The height of each cone [Formula: see text] corresponds to the desired resolution. Recently, Plonski and Isler presented an approximation algorithm for Cone-TSPN for the case where all cones have a uniform orientation angle of [Formula: see text]. We study a new variant of Cone-TSPN where we relax this constraint and allow the cones to have non-uniform orientations. We call this problem Tilted Cone-TSPN and present a polynomial-time approximation algorithm with ratio [Formula: see text], where [Formula: see text] is the set of all cone heights. We demonstrate through simulations that our algorithm can be implemented in a practical way and that by exploiting the structure of the cones we can achieve shorter tours. Finally, we present experimental results from various agriculture applications that show the benefit of considering view angles for path planning.

scholarly journals Approximation algorithms for tours of height-varying view cones

2018 ◽  
Vol 38 (2-3) ◽  
pp. 224-235 ◽  
Author(s):  
Patrick A Plonski ◽  
Volkan Isler
Keyword(s):  
Precision Agriculture ◽  
Ground Plane ◽  
Optimal Solution ◽  
Field Of View ◽  
Coverage Problem ◽  
Polynomial Time Approximation Algorithm ◽  
Novel Variant ◽  
The Common ◽  
The Traveling Salesman Problem ◽  
Theoretical Performance

We introduce a novel coverage problem that arises in aerial surveying applications. The goal is to compute a shortest path that visits a given set of cones. The apex of each cone is restricted to lie on the ground plane. The common angle [Formula: see text] of the cones represent the field of view of the onboard camera. The cone heights, which can be varying, correspond with the desired observation quality (e.g. resolution). This problem is a novel variant of the traveling salesman problem with neighborhoods (TSPN). We name it Cone-TSPN. Our main contribution is a polynomial time approximation algorithm for Cone-TPSN. We analyze its theoretical performance and show that it returns a solution whose length is at most [Formula: see text] times the length of the optimal solution where [Formula: see text] and [Formula: see text] are the heights of the tallest and shortest input cones, respectively.We demonstrate the use of our algorithm in a representative precision agriculture application. We further study its performance in simulation using randomly generated cone sets. Our results indicate that the performance of our algorithm is superior to standard solutions.

scholarly journals Inapproximability and Polynomial-Time Approximation Algorithm for UET Tasks on Structured Processor Networks

2011 ◽  
Vol 2011 ◽  
pp. 1-20 ◽  
Author(s):  
M. Bouznif ◽  
R. Giroudeau
Keyword(s):  
Approximation Algorithm ◽  
Large Class ◽  
Bipartite Graph ◽  
Polynomial Time ◽  
Performance Guarantee ◽  
Makespan Minimization ◽  
Time Approximation ◽  
Polynomial Time Approximation Algorithm ◽  
Precedence Graph ◽  
Polynomial Time Approximation

We investigate complexity and approximation results on a processor networks where the communication delay depends on the distance between the processors performing tasks. We then prove that there is no heuristic with a performance guarantee smaller than 4/3 for makespan minimization for precedence graph on a large class of processor networks like hypercube, grid, torus, and so forth, with a fixed diameter . We extend complexity results when the precedence graph is a bipartite graph. We also design an efficient polynomial-time -approximation algorithm for the makespan minimization on processor networks with diameter .

scholarly journals The experiment of four-point bending behaviours of helicoidally laminated CFRPs

2019 ◽  
Vol 258 ◽  
pp. 04012
Author(s):  
Ikuma Ishizawa ◽  
Takashi Matsumoto ◽  
Kenta Kondo
Keyword(s):  
Orientation Angle ◽  
Video Camera ◽  
Metallic Materials ◽  
Characteristic Structure ◽  
Corrosion Resistant ◽  
Mantis Shrimp ◽  
Specific Strength ◽  
Four Point Bending ◽  
Angle Difference ◽  
Laminated Structures

The purpose of this study is to mitigate the brittle behaviour of CFRP. CFRP is a composite material of carbon fibre and a thermosetting resin. As a feature, it has a low density than metallic materials such as steel and aluminium, and it is excellent in specific strength, specific stiffness, and is corrosion resistant. In the civil engineering field, CFRP is expected to be utilized for durability improvement and long life achievement. However, it is necessary to be careful when using it as a primary member, because the behaviour at the time of fracture is very brittle, thereby it is necessary to set a large safety factor at the time of design. One way to achieve the purpose of the current study is to follow a biological structure, so-called biomimetics. In this study, mantis shrimp is selected. The characteristic structure of its forefoot is that chitin fibres are stacked while changing helicoidally their angles. It is said that the forefoot can withstand a thousand times the force of its own weight because of its structure. Helicoidally laminated CFRP is fabricated by processing prepreg sheets of unidirectional carbon fibres. Four laminated structures were examined in which four-point bending experiments were carried out under displacement control of 2 mm/min, and load and displacement were recorded. During the experiments, the specimens were observed until fracture with a video camera. As a result, the brittle behaviour was improved significantly as the orientation angle difference of the fibre sheets decreased.

Molecular cloning and characterization of a novel human variant of RIC-3, a putative chaperone of nicotinic acetylcholine receptors

2008 ◽  
Vol 28 (6) ◽  
pp. 299-306 ◽  
Author(s):  
Tamara Seredenina ◽  
Teresa Ferraro ◽  
Georg C. Terstappen ◽  
Andrea Caricasole ◽  
Renza Roncarati
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Coiled Coil ◽  
Surface Expression ◽  
Protein Product ◽  
Nicotinic Acetylcholine ◽  
Α7 Nachr ◽  
New Variant ◽  
Novel Variant

Recent reports demonstrate that the RIC-3 (resistant to inhibitors of cholinesterase-3) protein is important for the maturation of nAChRs (nicotinic acetylcholine receptors). In the present study RIC-3e, a novel variant of RIC-3, is described. This variant contains a deletion of exons 4 and 5 of RIC-3, resulting in a protein product lacking a conserved coiled-coil domain. Like RIC-3, the new variant is predominantly, but not exclusively, expressed in the brain. The analysis of expression of variant RIC-3 mRNA and of α7-nAChR mRNA in a set of human tissues shows a similar profile. The RIC-3e protein is functionally active and enables surface expression of mature α7-nAChRs in cell lines not otherwise permissive for the expression of this receptor.

Force and Stability Measurements on Models of Submerged Pipelines

1971 ◽  
Vol 93 (4) ◽  
pp. 1290-1298 ◽  
Author(s):  
J. F. Wilson ◽  
H. M. Caldwell
Keyword(s):  
Free Stream ◽  
Ground Plane ◽  
Orientation Angle ◽  
Reynolds Numbers ◽  
Ocean Floor ◽  
Stream Velocity ◽  
Piping System ◽  
Lift And Drag ◽  
Vertical Spacing ◽  
Fixed End

The effect of currents on pipes anchored just above the ocean floor is the subject of this study. Lift, drag, and stability of two parallel pipes, parallel to a flat plane (the sea floor) were measured for simulated ocean currents up to two knots at several subcritical, free stream Reynolds numbers. First, a wind tunnel was utilized to find the lift and drag coefficients on two parallel, rigid, cylindrical models. The effects of horizontal spacing, vertical spacing from the ground plane, and orientation angle of the horizontal free stream velocity were observed. These results were compared to date available for the single and double cylinder cases where the ground plane was absent. Second, a water tow tank was utilized to observe conditions for vortex-shedding induced vibrations for fixed end, flexible, parallel cylinders. The natural frequencies and buoyancies of these models simulated pipelines of reasonable span clamped to evenly spaced anchor blocks. A numerical example illustrates the use of these data in the design of a dynamically stable piping system close to the ocean floor.

scholarly journals A Novel RHCE*ce Variant Allele Is Highly Frequent in Chinese D-Negative Individuals and Results in C-Expression

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2892-2892
Author(s):  
Tamara C Stegmann ◽  
Y L Ji ◽  
Lonneke Haer-Wigman ◽  
L Wei ◽  
Y Zhao ◽  
...  
Keyword(s):  
Conflicts Of Interest ◽  
Lentiviral Vector ◽  
Variant Allele ◽  
The Novel ◽  
Facs Analysis ◽  
Exon 2 ◽  
Chinese Populations ◽  
New Variant ◽  
Novel Variant ◽  
Dependent Probe

Abstract Background: The RHCE allele is highly polymorphic and many variants have been described, especially in individuals of African origin. Donors carrying these variants can be falsely typed and elicit transfusion reactions, and patients carrying such a variant may be at risk to develop allo-antibodies in response to mismatched transfusions. Not much is known about the frequency of RHCE variants in Chinese populations, whereas in China genotyping assays are increasingly applied for typing of blood donors and patients. Methods: Standard column agglutination was used to serologically type for C/c and E/e expression in 200 serologically D-negative and 200 serologically D-positive Chinese donors. The RH Multiplex Ligation-dependent Probe Amplification (MLPA) genotyping assay was used for genotyping the RHCE status (Transfusion 2013;53:1559). In donors with discrepant results of genotyping and phenotyping all 10 exons of RHCE were amplified and directly sequenced. A lentivirus containing the novel RHce variant was created to transduce human erythroblasts cultured from peripheral blood from 3 ccDee and 3 CCDee donors as previously described (Haematologica 2010;95:1594). FACS analysis was used to assess the c- and C-expression caused by the variant. Results: In 6 out of 200 Chinese D-negative donors the results of the RH-MLPA indicated the presence of only one copy of exon 2 of the CE*c-allele, and no copy of exon 2 of the CE*C-allele, whereas these donors were serologically typed as Cc. Sequencing of all 10 RHCE exons revealed a novel RHCE*ce allele defined by 308C>T (p.103Pro>Leu) mutation next to a normal RHCE*ce allele. The variant allele was not found in the 200 Chinese D-positive donors, indicating the linkage of this new variant RHCE*ce allele with the D-negative haplotype. Wild type Rhce cDNA was mutated to create the RHce*308C>T mutation and subsequently cloned into a lentiviral vector. Transduction of human ccDee erythroblasts with this vector resulted in C expression, whereas virtually no c-expression was induced by transduction of human CCDee erythroblasts as assessed by FACS analysis with the monoclonals MS33, MS35 and MS42 to detect c expression and monoclonals MS24 and MS273 to detect C. Discussion: A new RHCE variant (RHCE*ce308T) is identified, which is present in 3% of D-negative Chinese individuals. The 308C>T mutation in the triplet encoding the 103Pro results in the expression of 103Leu. Position 103 is one of the 4 aminoacid differences between the c- and C-carrying polypeptides (Pro and Ser, respectively). The Pro>Leu mutation in the novel variant leads to C-expression and loss or strongly diminished c-expression. Most Rhc-genotyping assays target the c-specific-307C nucleotide and most RhC-genotyping assays target the C-specific-intron 2, which are respectively present and absent in this variant allele. Therefore, when individuals carrying this allele are genotyped, the predictive phenotype will be falsely C-negative. Conclusion: RHC-genotyping assays applied in Chinese populations, should be adapted to recognize the presence of this new RHCE*ce308T allele to prevent C-mismatched transfusions. Disclosures No relevant conflicts of interest to declare.

scholarly journals Chamberlin--Courant Rule with Approval Ballots: Approximating the MaxCover Problem with Bounded Frequencies in FPT Time

2017 ◽  
Vol 60 ◽  
pp. 687-716 ◽  
Author(s):  
Piotr Skowron ◽  
Piotr Faliszewski
Keyword(s):  
Approximation Algorithm ◽  
Exact Algorithms ◽  
The Other ◽  
Winner Determination ◽  
Exponential Time ◽  
Time Approximation ◽  
Polynomial Time Approximation Algorithm ◽  
Voting Rule ◽  
Np Complete ◽  
Better Than

We consider the problem of winner determination under Chamberlin--Courant's multiwinner voting rule with approval utilities. This problem is equivalent to the well-known NP-complete MaxCover problem and, so, the best polynomial-time approximation algorithm for it has approximation ratio 1 - 1/e. We show exponential-time/FPT approximation algorithms that, on one hand, achieve arbitrarily good approximation ratios and, on the other hand, have running times much better than known exact algorithms. We focus on the cases where the voters have to approve of at most/at least a given number of candidates.

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