scholarly journals A Monolithic Compliant Continuum Manipulator: A Proof-of-Concept Study

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Theodosia Lourdes Thomas ◽  
Venkatasubramanian Kalpathy Venkiteswaran ◽  
G. K. Ananthasuresh ◽  
Sarthak Misra
Keyword(s):  
Time Varying ◽  
Magnetic Actuation ◽  
Proof Of Concept ◽  
Invasive Procedures ◽  
Continuum Robots ◽  
Electromagnetic Coils ◽  
The Mean ◽  
Continuum Manipulator ◽  
Tissue Trauma ◽  
Surgical Manipulator

Abstract Continuum robots have the potential to form an effective interface between the patient and surgeon in minimally invasive procedures. Magnetic actuation has the potential for accurate catheter steering, reducing tissue trauma and decreasing radiation exposure. In this paper, a new design of a monolithic metallic compliant continuum manipulator is presented, with flexures for precise motion. Contactless actuation is achieved using time-varying magnetic fields generated by an array of electromagnetic coils. The motion of the manipulator under magnetic actuation for planar deflection is studied. The mean errors of the theoretical model compared to experiments over three designs are found to be 1.9 mm and 5.1 deg in estimating the in-plane position and orientation of the tip of the manipulator, respectively, and 1.2 mm for the whole shape of the manipulator. Maneuverability of the manipulator is demonstrated by steering it along a path of known curvature and also through a gelatin phantom, which is visualized in real time using ultrasound imaging, substantiating its application as a steerable surgical manipulator.

Comparison of Inverse Kinematics Algorithms for Multi-Section Continuum Robots

2021 ◽  
Vol 22 (8) ◽  
pp. 420-424
Author(s):  
D. Yu. Kolpashchikov ◽  
O. M. Gerget
Keyword(s):  
Inverse Kinematics ◽  
Complex Geometry ◽  
Forward Kinematics ◽  
Non Destructive Testing ◽  
Invasive Procedures ◽  
Destructive Testing ◽  
Continuum Robots ◽  
Unique Type ◽  
Non Destructive ◽  
Constant Section

Continuum robots are a unique type of robots that move due to the elastic deformation of their own body. Their flexible design allows them to bend at any point along their body, thus making them usable in workspaces with complex geometry and many obstacles. Continuum robots are used in industry for non-destructive testing and in medicine for minimally invasive procedures and examinations. The kinematics of continuum robots consisting of a single bending section are well known, as is the forward kinematics for multi-section continuum robots. There exist efficient algorithms for them. However, the problem of inverse kinematics for multi-section continuum robots is still relevant. The complexity of the inverse kinematics for multi-section continuum robots is quite high due to the nonlinearities of the robots’ motion. The article discusses in detail the modification of the FABRIK algorithm proposed by the authors, as well as a Jacobian-based iterative algorithm. A comparison of inverse kinematics algorithms for multi-section continuum robots with constant section length is given and the results of the experiment are described.

Profiles of Trauma in Primary and Permanent Teeth of Children and Adolescents

2019 ◽  
Vol 43 (1) ◽  
pp. 5-10
Author(s):  
Jackeline Nogueira de Paula Barros ◽  
Thayssa Augusto Assis de Araújo ◽  
Thais Rodrigues Campos Soares ◽  
Michele Machado Lenzi ◽  
Patrícia de Andrade Risso ◽  
...  
Keyword(s):  
Primary Teeth ◽  
Dental Trauma ◽  
Permanent Teeth ◽  
Therapeutic Approaches ◽  
Tooth Type ◽  
The Mean ◽  
Dental Records ◽  
Gingival Mucosa ◽  
Tissue Trauma ◽  
Type Of Fracture

This retrospective study aimed to evaluate the dental trauma profile in primary and permanent teeth from patients between 0 and 15 years old who attended the Faculty of Dentistry of the Federal University of Rio de Janeiro. Data regarding gender, age, trauma classification, tooth type, and affected tissues were obtained from dental records. The data were analyzed descriptively and by the χ2 test (p < 0.05). Data associated with 333 traumatized teeth (70% primary and 30% permanent teeth) were included. The mean ages of children with affected primary and permanent teeth were 3.35 ± 2.02 and 9.09 ± 2.43 years, respectively. Males presented more permanent teeth with trauma (64.4%) than primary ones (55.6%; p = 0.085). The upper central incisors, both primary (68.9%) and permanent (69.4%), were the teeth most commonly affected. Primary teeth showed a higher frequency (p < 0.001) of supportive tissue trauma (73.3%) and lower frequency (p = 0.001) of hard tissue trauma (40.7%) than those in permanent ones (51.5% and 60.6%, respectively). The most frequent trauma in the supportive tissue was subluxation (27.2%) and permanent lateral luxation (42.0%). In the hard tissues, permanent teeth presented a higher prevalence of trauma than primary ones (p = 0.001), however this difference was not statistical significant when each type of fracture injury was evaluated individually (p > 0.005). With affected primary teeth, there was a greater frequency of trauma in the gingival mucosa (31.0%; p = 0.022); in the permanent ones, traumatic lesions in the chin region were the most prevalent (20.8%; p = 0.009). Trauma was recurrent in 26.3% of primary teeth and in 20.2% permanent teeth. Therefore, primary and permanent teeth showed distinct trauma profiles, suggesting that distinct preventive and therapeutic approaches are needed for these two groups.

scholarly journals Predicting the early depleting transmission dynamics of COVID-19: A time-varying SIR model

2020 ◽  
Author(s):  
Kian Boon Law ◽  
Kalaiarasu M Peariasamy ◽  
Balvinder Singh Gill ◽  
Sarbhan Singh Lakha Singh ◽  
Bala Murali Sundram ◽  
...  
Keyword(s):  
Temporal Trends ◽  
Model Fitting ◽  
Sir Model ◽  
Transmission Dynamics ◽  
Time Varying ◽  
Force Of Infection ◽  
Planning And Control ◽  
The Mean ◽  
And Control ◽  
Absolute Percent Error

Abstract The susceptible-infectious-removed (SIR) model offers the simplest framework to study transmission dynamics of COVID-19, however, it does not factor in its early depleting trend observed during a lockdown. We modified the SIR model to specifically simulate the early depleting transmission dynamics of COVID-19 to better predict its temporal trend in Malaysia. The classical SIR model was fitted to observed total (I total), active (I), and removed (R) cases of COVID-19 before lockdown to estimate the basic reproduction number. Next, the model was modified with a partial time-varying force of infection, given by a proportionally depleting transmission coefficient, βt, and a fractional term, z. The modified SIR model was then fitted to observed data over 6 weeks during the lockdown. Model fitting and projection were validated using the mean absolute percent error (MAPE). The transmission dynamics of COVID-19 was interrupted immediately by the lockdown. The modified SIR model projected the depleting temporal trends with lowest MAPE for I total, followed by I, I daily, and R. During lockdown, the dynamics of COVID-19 depleted at a rate of 4·7% each day with a decreased capacity of 40%. For 7–day and 14–day projections, the modified SIR model accurately predicted I total, I, and R. The depleting transmission dynamics for COVID-19 during lockdown can be accurately captured by time-varying SIR model. Projection generated based on observed data is useful for future planning and control of COVID-19.

Coding of time-varying electric field amplitude modulations in a wave-type electric fish

1996 ◽  
Vol 75 (6) ◽  
pp. 2280-2293 ◽  
Author(s):  
R. Wessel ◽  
C. Koch ◽  
F. Gabbiani
Keyword(s):  
Mutual Information ◽  
Electric Fish ◽  
Signal To Noise Ratio ◽  
Cutoff Frequency ◽  
Spike Trains ◽  
Time Varying ◽  
Signal To Noise ◽  
Single Spike ◽  
The Mean ◽  
P Type

1. The coding of time-varying electric fields in the weakly electric fish, Eigenmannia, was investigated in a quantitative manner. The activity of single P-type electroreceptor afferents was recorded while the amplitude of an externally applied sinusoidal electric field was stochastically modulated. The amplitude modulation waveform (i.e., the stimulus) was reconstructed from the spike trains by mean square estimation. 2. From the stimulus and the reconstructions we calculated the following: 1) the signal-to-noise ratio and thus an effective temporal bandwidth of the units; 2) the coding fraction, i.e., a measure of the fraction of the time-varying stimulus encoded in single spike trains; and 3) the mutual information provided by the reconstructions about the stimulus. 3. Signal-to-noise ratios as high as 7:1 were observed and the bandwidth ranged from 0 up to 200 Hz, consistent with the limit imposed by the sampling theorem. Reducing the cutoff frequency of the stimulus increased the signal-to-noise ratio at low frequencies, indicating a nonlinearity in the receptors' response. 4. The coding fraction and the rate of mutual information transmission increased in parallel with the standard deviation (i.e., the contrast) of the stimulus as well as the mean firing rate of the units. Significant encoding occurred 20-40 Hz above the spontaneous discharge of a unit. 5. When the temporal cutoff frequency of the stimulus was increased between 80 and 400 Hz, 1) the coding fraction decreased, 2) the rate of mutual information transmission remained constant over the same frequency range, and 3) the reconstructed filter changed. This is in agreement with predictions obtained in a simplified neuronal model. 6. Our results suggest that 1) the information transmitted by single spike trains of primary electrosensory afferents to higherorder neurons in the fish brain depends on the contrast and the cutoff frequency of the stimulus as well as on the mean firing rate of the units; and 2) under optimal conditions, more than half of the information about a Gaussian stimulus that can in principle be encoded is carried in single spike trains of P-type afferents at rates up to 200 bits per second.

scholarly journals Increasing adolescent firearm homicides and racial disparities following Florida’s ‘Stand Your Ground’ self-defence law

2019 ◽  
Vol 26 (2) ◽  
pp. 187-190 ◽  
Author(s):  
Michelle Degli Esposti ◽  
Douglas J Wiebe ◽  
Jason Gravel ◽  
David K Humphreys
Keyword(s):  
Racial Disparities ◽  
Black Adolescents ◽  
Interrupted Time Series ◽  
Time Varying ◽  
Series Design ◽  
Firearm Suicide ◽  
The Mean ◽  
The Law ◽  
Negative Controls ◽  
Interrupted Time Series Design

Establishing whether specific laws impact rates of firearm homicide in adolescents is critical for identifying opportunities to reduce preventable adolescent death. We evaluated Florida’s Stand Your Ground law, enacted October 2005, using an interrupted time series design from 1999 to 2017. We used segmented quasi-Poisson regression to model underlying trends in quarterly rates of adolescent (15–19 years) firearm homicide in Florida and disaggregated by race (Black/White). We used synthetic and negative controls (firearm suicide) to address time-varying confounding. Before Florida’s Stand Your Ground law, the mean quarterly rate was 1.53 firearm homicides per 100 000 adolescents. Black adolescents comprised 63.5% of all adolescent firearm homicides before and 71.8% after the law. After adjusting for trends, the law was associated with a 44.6% increase in adolescent firearm homicide. Our analysis indicates that Florida’s Stand Your Ground is associated with a significant increase in firearm homicide and may also exacerbate racial disparities.

The Research on Time-Dependent Reliability Analysis for RC Structures Based on the Theory of Stochastic Processes

2011 ◽  
Vol 243-249 ◽  
pp. 5650-5655
Author(s):  
Cheng Yu Xia ◽  
Qing You Liu ◽  
Li Qin Qian
Keyword(s):  
Reliability Analysis ◽  
Structural Reliability ◽  
Time Dependent ◽  
Time Varying ◽  
Rc Structures ◽  
Calculating Method ◽  
Specific Analysis ◽  
The Mean ◽  
Compression Member ◽  
Strong Ability

This paper proposes a new calculating method for the reliability analysis of the time-varying structure，and applies the calculating method to optimize the design for the concrete structure . The RC compression member was taken as an example in the specific analysis in by the mean of resistance and structural reliability with time t. The results show that, this mode has a strong ability of analyzing adequately all kinds of random variant in procedure of structure failures.

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