scholarly journals Distributed multi-robot sweep coverage for a region with unknown workload distribution

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Muqing Cao ◽  
Kun Cao ◽  
Xiuxian Li ◽  
Shenghai Yuan ◽  
Yang Lyu ◽  
...  
Keyword(s):  
Unit Area ◽  
Operation Time ◽  
Exact Distribution ◽  
Simulation Studies ◽  
Multiple Robots ◽  
Target Region ◽  
Workload Distribution ◽  
Time Required ◽  
Time Update ◽  
Theoretical Results

AbstractThis paper considers the scenario where multiple robots collaboratively cover a region in which the exact distribution of workload is unknown prior to the operation. The workload distribution is not uniform in the region, meaning that the time required to cover a unit area varies at different locations of the region. In our approach, we divide the target region into multiple horizontal stripes, and the robots sweep the current stripe while partitioning the next stripe concurrently. We propose a distributed workload partition algorithm and prove that the operation time on each stripe converges to the minimum under the discrete-time update law. We conduct comprehensive simulation studies and compare our method with the existing methods to verify the theoretical results and the advantage of the proposed method. Flight experiments on mini drones are also conducted to demonstrate the practicality of the proposed algorithm.

scholarly journals Different characteristics of infants diagnosed with congenital choledochal malformation prenatally or postnatally

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wei Chen ◽  
Jia Geng ◽  
Ya-lan Tan ◽  
Lian Zhao ◽  
Hui-hui Jia ◽  
...  
Keyword(s):  
Histopathological Examination ◽  
Fibrous Tissue ◽  
Operation Time ◽  
Normal Diet ◽  
Treatment Regimens ◽  
Total Length ◽  
Time Required ◽  
Different Characteristics ◽  
Length Of Hospitalization ◽  
Choledochal Malformation

AbstractThe general condition, clinical and pathological characteristics, and treatment regimens of patients prenatally and postnatally diagnosed with congenital choledochal malformation (CM) were analyzed in order to investigate the clinical significance of early diagnosis, treatment, and intervention in CM. We retrospectively analyzed 33 children who were admitted to the Children’s Hospital of Soochow University between 1 March 2010 and 31 May 2019, and their diagnosis of CM was confirmed by radiological, surgical and pathological findings. All the patients were under 36 months of age. The patients were divided into prenatally diagnosed and postnatally diagnosed groups. There were 16 and 17 CM patients in the prenatally and postnatally diagnosed groups, respectively, with a preponderance of females in both groups. Compared with the prenatally diagnosed group, the postnatally diagnosed group had a higher incidence of abdominal pain and vomiting (p < 0.05) and higher AST, GGT, and TB levels (p < 0.05). Although postoperative histopathological examination showed inflammation in both groups, congestion in the cyst walls and fibrous tissue hyperplasia were more significant in the postnatally diagnosed group (p < 0.05). In addition, operation time, length of time required to resume a normal diet after surgery, and total length of hospitalization differed between the 2 groups (p < 0.05), with the prenatally diagnosed group having a relatively longer operation time and taking longer to resume a normal diet after surgery. However, the total length of hospitalization in the prenatally diagnosed group was shorter than that in the postnatally diagnosed group. Compared with prenatally diagnosed CM patients, more symptoms, greater severity of symptoms, and more time to recovery after surgery were observed in postnatally diagnosed CM patients.

scholarly journals A steering model for articulated tracked vehicle considering soil deformation on track–soil interaction

2018 ◽  
Vol 10 (10) ◽  
pp. 168781401880270 ◽  
Author(s):  
Yu Yao ◽  
Kai Cheng ◽  
Bangcheng Zhang ◽  
Jinhua Lin ◽  
Dawei Jiang ◽  
...  
Keyword(s):  
Experimental Results ◽  
Simulation Studies ◽  
Soil Deformation ◽  
Tracked Vehicle ◽  
Tracked Vehicles ◽  
Model Based ◽  
Theoretical Results ◽  
Strong Agreement

With the advantage of steering performance, articulated tracked vehicles have excellent mobility in off-road application. However, in current models for steering performance, soil deformation on the interaction between track and soil cannot always be taken into account. Therefore, steering performance cannot always be calculated accurately. In order to solve the problem, it is essential to propose a steering model which can take the effect of soil deformation on track–soil interaction into consideration. In this article, a steering model of articulated tracked vehicle is proposed on track–soil interaction. Moreover, in order to improve steering performance, a track–soil sub-model is developed that can consider soil deformation on track–soil interaction. Using this steering model based on track–soil sub-model, steering performance can be calculated more accurately. Simulation studies and experimental results are in strong agreement with the theoretical results in this article. The results show that equipped with the track–soil sub-model, the proposed steering model can be used to accurately predict steering performance. The steering model of articulated tracked vehicle proposed in this article can provide a basis for other similar vehicles.

Rotordynamic Performance Measurements and Predictions of a Rotor Supported on Multilayer Gas Foil Journal Bearings for Microturbomachinery

2016 ◽  
Author(s):  
Jongsung Lee ◽  
Young Min Kim ◽  
Moon Sung Park ◽  
Tae Ho Kim ◽  
Kyoung Ku Ha ◽  
...  
Keyword(s):  
Damping Ratio ◽  
Operation Time ◽  
Journal Bearings ◽  
Displacement Sensor ◽  
Radial Clearance ◽  
Performance Measurements ◽  
Displacement Sensors ◽  
Model Predictions ◽  
Type C ◽  
Time Required

This paper presents rotordynamic performance measurements of multilayer gas foil journal bearings (GFJBs) supporting the rotor of oil-free microturbomachinery, and a comparison with the model predictions. A series of rotor coast-down tests from 60 krpm were conducted to compare the rotordynamic performances of three previously developed multilayer GFJBs: types A, B, and C. During the tests, two sets of orthogonally positioned displacement sensors recorded the horizontal and vertical rotor motions, and an axially positioned displacement sensor measured the thrust of the runner axial motion. The test results revealed that the type C GFJBs have a superior rotordynamic capability over the other types. The additional coast-down tests from 100 krpm for the type C showed that the synchronous motions of the rotor are dominant at up to ∼50 krpm, but that large amplitudes of subsynchronous motion associated with the natural frequency of a rotor-GFJB system occur above this speed. Thermal transient response measurements were conducted using four k-type thermocouples at increasing rotor speeds of 20 to 100 krpm with increments of 10 krpm. The operation time required to establish steady-state temperatures was approximately 25 min for each speed. For most of the speeds tested, the front GFJB near the rotor impeller end showed the lowest temperatures, and both the rear GFJB near the thrust runner end and the permanent magnet (PM) motor showed the highest temperatures. The GFTB showed the lowest temperature at low speeds of below 50 krpm, and the highest temperature at the top speed of 100 krpm owing to the increasing axial load caused by the impeller force. The measured impeller pressure and motor output power increased nonlinearly with the increasing rotor speed and fits best with the second-order and third-order polynomial equations, respectively. The measured axial displacement revealed that the rotor moved axially up to ∼ 270 μm toward the impeller side as the speed increased to 100 krpm. Further experiments using a decrease in radial clearance of 30 μm demonstrated a suppression of the large amplitude of the subsynchronous rotor motion to a certain degree. In addition, the onset speed of the subsynchronous motions increased to 80 krpm for the type C GFJBs with the decrease in the radial clearance. Rotordynamic model predictions with the predicted GFJB stiffness and damping coefficients were benchmarked against the test data. The predicted natural frequencies, onset speed of instability (OSI) where the damping ratio became negative, and synchronous rotor response versus speed agreed reasonably with the measured whirl frequencies of the subsynchronous motions, the onset speed of subsynchronous motions (OSS), and the filtered synchronous rotor motion versus speed, respectively. The predictions also showed that the OSI increased from 50 krpm to 80 krpm with a decrease in the radial clearance, thus validating the present rotordynamic model.

Optimization of the Operation Time Required for Data Gathering Requirement in Extended-Reach Drilling Well by the Use of Open Hole Tractor in the United Arab Emirates

2017 ◽  
Author(s):  
Takahiro Toki ◽  
Mhammed Benygzer ◽  
Khalid Ahmed Al Wahedi ◽  
Atul Kumar Anurag ◽  
Rudrap Pratap Narayan Singh ◽  
...  
Keyword(s):  
United Arab Emirates ◽  
Data Gathering ◽  
Operation Time ◽  
Open Hole ◽  
Time Required ◽  
Extended Reach Drilling

TRAPS FOR MONITORING POPULATIONS OF THE CITRUS THRIPS, SCIRTOTHRIPS CITRI (THYSANOPTERA: THRIPIDAE)

1981 ◽  
Vol 113 (1) ◽  
pp. 9-12 ◽  
Author(s):  
L. K. Tanigoshi ◽  
D. S. Moreno
Keyword(s):  
Unit Area ◽  
Trapping Efficiency ◽  
Field Laboratory ◽  
Scirtothrips Citri ◽  
Time Required

AbstractModified versions of the standard Reed-Rich citrus thrips trap were compared for trapping efficiency and labor required. The number of migrant Scirtothrips citri (Moulton) captured per unit trapping area of a PVC-acetate trap was comparable to the number captured per unit area of the Reed-Rich trap, though the PVC-acetate trapping surface was about 35% that of the 929 cm2 standard trap. The reduced counting surface and the use of disposable acetate sheets reduced to one-quarter the time required for field-laboratory handling, preparing, and processing. The PVC-acetate trap is recommended as a new standard trap for monitoring S. citri population levels in California and Arizona citriculture.

scholarly journals Empirical Likelihood-Based Inference in Regressive Model with Moment Restrictions

2020 ◽  
Vol 2020 ◽  
pp. 1-7
Author(s):  
Zhao Zhiwen ◽  
He Jinghua
Keyword(s):  
Empirical Likelihood ◽  
Least Squares Method ◽  
Weighted Least Squares ◽  
Auxiliary Information ◽  
Likelihood Method ◽  
Model Parameters ◽  
Simulation Studies ◽  
Weighted Least Squares Method ◽  
Moment Restrictions ◽  
Theoretical Results

In this paper, we consider the parameter estimation problem of linear regression model when the auxiliary information can be denoted by moment restrictions. We use the weighted least squares method to estimate the model parameters and to obtain the weights based on the auxiliary information by using the empirical likelihood method. The limiting distribution of the estimator is established, and the simulation studies are carried out to demonstrate the feasibility of our theoretical results.

scholarly journals Reaching a Group-Agreement in Finite Time Under Acyclic Interaction Topology

2021 ◽  
Author(s):  
Xinru Ma ◽  
Hengyu Li ◽  
Tiehui Zhang ◽  
Jun Liu ◽  
Shaorong Xie ◽  
...  
Keyword(s):  
Finite Time ◽  
Multiagent System ◽  
Matrix Theory ◽  
Structural Characteristics ◽  
Mathematical Induction ◽  
Time Required ◽  
Interaction Topology ◽  
Theoretical Results ◽  
Group Agreement ◽  
Agreement Problem

Abstract This paper discusses the finite time agreement problem of networks with acyclic partition topology. In view of the structural characteristics of such network topology, mathematical induction is particularly suitable to prove the main conclusions in the paper. In addition, for the consideration of the finite time consensus problem, in addition to using basic matrix theory to verify the solution of the problem, this brief also has a more detailed analysis of the time required to reach consensus. Based on these two points, it is observed that the solution of this problem is due to the features of acyclic partition interactions and the continuity of the related finite time protocol and contributes to the research on the grouping consensus of multiagent system. Furthermore, simulation examples are presented to verify the theoretical results.

Mechanism Design for Correlated Valuations: Efficient Methods for Revenue Maximization

2021 ◽  
Author(s):  
Michael Albert ◽  
Vincent Conitzer ◽  
Giuseppe Lopomo ◽  
Peter Stone
Keyword(s):  
Mechanism Design ◽  
Good Reason ◽  
Exact Distribution ◽  
Revenue Maximization ◽  
Computationally Efficient ◽  
Auction Design ◽  
Efficient Procedure ◽  
Underlying Distribution ◽  
Theoretical Results

Traditionally, much of the focus of the mechanism/auction design community has been on revenue optimal mechanisms for settings where bidders’ private valuations over outcomes can be reasonably thought of as independent of each other. This has been the case even though there is good reason to believe that valuations are often correlated and there are theoretical results suggesting that mechanisms designed with this correlation in mind can generate much higher revenue. In “Mechanism Design for Correlated Valuations: Efficient Methods for Revenue Maximization,” we look at the setting where there is correlation, but the exact distribution is unknown and must be estimated from samples. We show that in this setting, the previous extremely strong theoretical results around the usefulness of correlation are now very sensitive to the degree of correlation in the underlying distribution and the number of samples that the mechanism designer has access to. However, we also show that if correlation is sufficient, we can construct mechanisms, using a computationally efficient procedure, that significantly outperform traditional mechanism design paradigms.

Helicopter Landing Ship: Undercarriage Strength and the Role of the Human Factor

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
E. Suhir
Keyword(s):  
Human Factor ◽  
Operation Time ◽  
Extreme Value Distribution ◽  
Mean Value ◽  
Helicopter Landing ◽  
The Times ◽  
The Moment ◽  
Normal Law ◽  
Time Required

We address, using probabilistic modeling and the extreme-value-distribution technique, the helicopter undercarriage strength in a helicopter-landing-ship situation. Our analysis contains an attempt to quantify, on the probabilistic basis, the role of the human factor in the situation in question. This factor is important from the standpoint of the operation time that affects the likelihood of safe landing during the lull period in the sea condition. The operation time includes (1) the time required for the officer-on-ship-board and the helicopter pilot to make their go-ahead decisions and (2) the time of actual landing. It is assumed, for the sake of simplicity, that both these times could be approximated by Rayleigh’s law, while the lull duration follows the normal law with a high enough ratio of the mean value to the standard deviation. Safe landing could be expected if the probability that it occurs during the lull time is sufficiently high. The probability that the helicopter undercarriage strength is not compromised can be evaluated as a product of the probability that landing indeed occurs during the lull time and the probability that the relative velocity of the helicopter undercarriage with respect to the ship’s deck at the moment of encounter does not exceed the allowable level. This level is supposed to be determined for the helicopter-landing-ground situation. The developed model can be used when developing specifications for the undercarriage strength, as well as guidelines for personnel training. Particularly, the model can be of help when establishing the times to be met by the two humans involved to make their go-ahead decisions for landing and to actually land the helicopter. Plenty of additional risk analyses (associated with the need to quantify various underlying uncertainties) and human psychology related efforts will be needed, of course, to make such guidelines practical.

Helicopter Landing Ship (HLS): Undercarriage Strength and the Role of the Human Factor

2009 ◽  
Author(s):  
Ephraim Suhir
Keyword(s):  
Human Factor ◽  
Probabilistic Approach ◽  
Operation Time ◽  
Extreme Value Distribution ◽  
Helicopter Landing ◽  
To Come ◽  
The Times ◽  
The Moment ◽  
Time Required

Based on the probabilistic approach and using the extreme value distribution (EVD) technique, we address the helicopter undercarriage strength in a helicopter-landing-ship (HLS) situation. Our analysis contains an attempt to quantify, also on the probabilistic basis, the role of the human factor in the situation in question. This factor is important from the standpoint of the operation time and, hence, from the standpoint of the likelihood of safe landing during the lull period in the sea condition. The operation time includes the time required for the officer-on-ship-board and the helicopter pilot to come up with their go-ahead decisions, and the time of actual landing. It is assumed, for the sake of simplicity, that both these times could be approximated by Rayleigh’s law, while the lull duration follows the normal law. Safe landing can be expected if the probability that it takes place during the lull time is sufficiently high. The probability that the helicopter undercarriage strength is not compromised can be evaluated as the product of the probability that landing occurs during the lull time and the probability that the relative velocity of the helicopter with respect the ship’s deck at the moment of the encounter of the undercarriage with the deck does not exceed the allowable level. The developed model can be used when establishing the requirements for the undercarriage strength, as well as when developing guidelines for personnel training. Particularly, it can be employed for establishing the times that need to be met by the two humans involved to make their decisions for landing and to actually land the helicopter in a timely fashion. It goes without saying that plenty of additional risk analyses (associated with the need to quantify various underlying uncertainties) and human psychology related effort will be needed to make such guidelines practical.

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