LS Technique Research Articles

Experimental dynamic identification and model feed-forward control of Novint Falcon haptic device

This paper addresses the dynamic identification and model feed-forward control implementation of a Novint Falcon haptic device. Firstly, inverse and forward kinematic problem of the device is obtained. Subsequently, equations describing the robot’s dynamics is derived using Newton–Euler approach which includes friction of active joints. The unknown dynamic parameters including mass and moment of inertia of constituting parts along with dry and viscous friction coefficients is identified practically by a white-box identification approach using LS technique. Furthermore, the torque digital scale coefficient which Novint Falcon’s firmware uses is identified. To the end of obtaining some of regressors a novel numerical-based differentiation approach is presented. Having an experimentally verified dynamic model in hand, the model is used in a model feed-forward impedance controller in order to omit the effect of natural dynamics of the robot, including active joints frictions from displayed impedance. Experimental tests reveal that the implemented force sensor-less controller performs 26% more accurate in terms of output force comparing device’s official controller.

Channel Estimation in MIMO-OFDM System using LS, LMMSE and STBC Technique

Channel Estimation in MIMO-OFDM System using LS, LMMSE and STBC Technique

Bleeding after circumcision is more likely in children with lichen sclerosus (balanitis xerotica obliterans)

Over 27,000 circumcisions were performed in England in 2012-13. The complication rate is generally perceived to be low, although published figures vary widely. Balanitis xerotica obliterans, more correctly termed Lichen Sclerosus et atrophicus (LS), is one of the commonest indications for medical circumcision. To test the hypothesis that children undergoing circumcision for LS have a higher rate of postoperative bleeding than those undergoing the procedure for other reasons, we retrospectively reviewed records for patients undergoing circumcision. The disease and procedure coding system was used to identify patients who underwent circumcision (ICD10 code N303) between 2000-2010. Cases with a diagnosis unrelated to circumcision and children circumcised during hypospadias repair were excluded. Bleeding which required return to theatre for surgical arrest was considered significant. Cases were identified by review of medical records if there was: a second procedure during the same admission, or readmission coded for circumcision within 2 weeks. Only cases with histologically confirmed LS were included in the LS cohort. GraphPad online calculator was used for statistical analysis (two tailed Fisher's exact test. 2385 boys with a median age of 4 years (range 0-16) were included in the study. Indication for circumcision included religious (1305, 54.7%), phimosis or redundant prepuce (512, 21.5%), suspected LS (366, 15.4%) and balanoposthitis (202, 8.5%). LS was histologically confirmed in 262 (10.9%) boys. Fourteen (0.6%) patients returned to theatre for surgical arrest of bleeding following circumcision; 6 had LS and 8 did not (Table 1). The bleeding rate was higher in those with LS (2.3%) than in those without (0.3%), P=0.0003 with a relative risk of 6.08. Post-operative complications are distressing, especially if further surgery is required. Published figures for complications following circumcision vary widely making counseling regarding risk difficult. Since LS includes an inflammatory element and circumcision in widespread LS can be challenging, the observation of more post-operative bleeding in patients with histologically confirmed LS during a previous audit prompted the hypothesis that this may be a significant finding. Thus we reviewed all patients requiring return to theatre within 2 weeks of circumcision, finding that whilst the overall bleeding rate was low, circumcision for LS significantly increased the risk. Although factors such as the severity of LS and surgical technique were not assessed, this is still a notable finding which should be reflected during pre-operative counseling.

Power System Frequency Estimation by Using a Newton-Type Technique for Smart Meters

This paper proposes a single-phase grid voltage fundamental frequency estimation technique for smart meters. The technique relies on a nonlinear Newton-type algorithm and a recursive differentiation filter (NTA–DF). It can reject the negative effects caused by dc offset, harmonics, notches, and spikes. When compared with a NTA technique based on least-squares (NTA–LS), the proposed one reduces matrix dimensions, avoids matrix inversion, and is computationally efficient, thus requiring less hardware and associated cost for real-time implementation. Moreover, unlike the NTA–LS technique, the NTA–DF shows less sensitivity to the presence of harmonics. Simulation and experimental results are presented to verify the performance of the proposed technique.

Modélisation par éléments finis de l’ostéosynthèse rachidienne cervicale postérieure

Background contextDespite largely, used in the past, biomechanical test, to investigate the fixation techniques of subaxial cervical spine, information is lacking about the internal structural response to external loading. It is not yet clear which technique represents the best choice and whether stabilization devices can be efficient and beneficial for three-column injuries (TCI). HypothesisThe different posterior cervical fixation techniques (pedicle screw PS, lateral mass screw LS, and transarticular screw TS) have respective indications. Materials and methodsA detailed, geometrically accurate, nonlinear C3–C7 finite element model FEM had been successfully developed and validated. Then three FEMs were reconstructed from different fixation techniques after C4–C6 TCI. A compressive preload of 74N combined with a pure moment of 1.8 Nm in flexion, extension, left–right lateral bending, and left–right axial rotation was applied to the FEMs. ResultsThe ROM results showed that there were obvious significant differences when comparing the different fixation techniques. PS and TS techniques can provide better immediate stabilization, compared to LS technique. The stress results showed that the variability of von Mises stress in the TS fixation device was minimum and LS fixation device was maximum. Furthermore, the screws inserted by TS technique had high stress concentration at the middle part of the screws. Screw inserted by PS and LS techniques had higher stress concentration at the actual cap–rod–screw interface. ConclusionsThe research considers that spinal surgeon should first consider using the TS technique to treat cervical TCI. If PS technique is used, we should eventually prolong the need for external bracing in order to reduce the higher risk of fracture on fixation devices. If LS technique is used, we should add anterior cervical operation for acquire a better immediate stabilization.

Finite element analysis of posterior cervical fixation

Background contextDespite largely, used in the past, biomechanical test, to investigate the fixation techniques of subaxial cervical spine, information is lacking about the internal structural response to external loading. It is not yet clear which technique represents the best choice and whether stabilization devices can be efficient and beneficial for three-column injuries (TCI). HypothesisThe different posterior cervical fixation techniques (pedicle screw PS, lateral mass screw LS, and transarticular screw TS) have respective indications. Materials and methodsA detailed, geometrically accurate, nonlinear C3–C7 finite element model (FEM) had been successfully developed and validated. Then three FEMs were reconstructed from different fixation techniques after C4–C6 TCI. A compressive preload of 74N combined with a pure moment of 1.8 Nm in flexion, extension, left–right lateral bending, and left–right axial rotation was applied to the FEMs. ResultsThe ROM results showed that there were obvious significant differences when comparing the different fixation techniques. PS and TS techniques can provide better immediate stabilization, compared to LS technique. The stress results showed that the variability of von Mises stress in the TS fixation device was minimum and LS fixation device was maximum. Furthermore, the screws inserted by TS technique had high stress concentration at the middle part of the screws. Screw inserted by PS and LS techniques had higher stress concentration at the actual cap–rod–screw interface. ConclusionsThe research considers that spinal surgeon should first consider using the TS technique to treat cervical TCI. If PS technique is used, we should eventually prolong the need for external bracing in order to reduce the higher risk of fracture on fixation devices. If LS technique is used, we should add anterior cervical operation for acquire a better immediate stabilization.

An intelligent framework for activity led learning in network planning and management

Monitoring students' activity and performance is vital to enable educators to provide effective teaching and learning to engage students with the subject and improve their understanding of the material. We describe the use of a fuzzy linguistic summarisation LS technique for extracting linguistically interpretable rules from student data describing prominent relationships between activity/engagement characteristics and achieved performance. We propose an intelligent framework for monitoring individual or group performance during activity and problem-based learning tasks. The proposed system is developed as a set of services to cater for data heterogeneity and deployable on a cloud computing platform. We present a case study and experiments in which we apply the fuzzy LS technique for analysing the effectiveness of using a group performance model GPM to deploy activity led learning ALL in a master-level module. Results show that the fuzzy rules can identify useful relationships between student engagement and performance.

Modeling and Identification of High Speed High Accuracy Lightweight Stages with Flexible Arms

Light-weight structures operating at high speeds may suffer from significant vibration problems, thus degrading positioning accuracy and exhibiting large settling time. High-performance vibration and motion controllers are usually designed based on precise dynamic model. This paper addresses the problem of modeling and identification of a high speed high accuracy lightweight positioning stage with flexible arm. A simplified state space model for vibration motion control purpose is given. A separated identification method is proposed. The parameters related to rigid body part and flexible body part are identified, separately. Rigid body dynamics is firstly identified by employing unbiased Least Squares technique. Subsequently, flexible body dynamics is identified by impact test and nonlinear LS technique. The experiment results show that applying proposed identification strategy can get more precise low frequency rigid body dynamic parameters without loss the identification precision of high frequency parameters.

The Effects of Extra‐Articular Suture Tension on Contact Mechanics of the Lateral Compartment of Cadaveric Stifles Treated with the TightRope CCL®or Lateral Suture Technique

To determine the effect of suture tension on contact pressures in the lateral compartment of the stifle for the TightRope CCL((R)) (TR) and circumfabellar-tibial suture (LS) techniques. Ex vivo biomechanical study. Pelvic limbs (n=12) from dogs weighing 21-24 kg. A pressure sensor was used to record peak contact pressure (PCP) and mean contact pressure (MCP) and contact area (CA) in limbs mounted in a materials testing machine. Stifles were stabilized using either a TR or LS technique and the prosthesis was tensioned increasingly from 25 to 70 N. PCP, MCP, and CA were collected at each applied tension before and after applying an axial load of 150 N. In the unloaded condition, LS stabilization resulted in a significant increase (P=.034) in PCP at >or=40 N tensions, whereas TR stabilization resulted in a significant increase (P=.047) in PCP at 70 N tension. There was a significant increase in CA at tensions >or=60 N in the LS group. No effect on MCP was noted. No significant differences in contact pressures were observed in the loaded condition. There were no significant differences in normalized PCP and CA between stabilization groups at any of the tension increment. The application of high tension to the extra-articular prosthesis alters lateral compartment contact pressures in the unloaded stifle in this ex vivo model. Over tightening of an extra-articular prosthesis may increase lateral compartment pressure at the time of surgery. The clinical implications of this finding are unknown, as weight bearing may negate any detrimental effect of high prosthesis tension.

Forecasting sea level anomalies from TOPEX/Poseidon and Jason-1 satellite altimetry

This paper aims at the prediction of both global mean sea level anomalies (SLAs) and gridded SLA data in the east equatorial Pacific obtained from TOPEX/Poseidon and Jason-1 altimetric measurements. The first prediction technique (denoted as LS) is based on the extrapolation of a polynomial-harmonic deterministic least-squares model describing a linear trend, annual and semi-annual oscillations. The second prediction method (denoted as LS + AR) is a combination of the extrapolation of a polynomial-harmonic model with the autoregressive forecast of LS residuals. In the case of forecasting global mean SLA data, both techniques allow one to compute the predictions of comparable accuracy (root mean square error for 1-month in the future is of 0.5 cm). In the case of predicting gridded SLA data, the LS + AR prediction method gains significantly better prediction accuracy than the accuracy obtained by the LS technique during El Nino 1997/1998, La Nina 1998/1999 and during normal conditions.

Another form for LAMBDA method

The LAMBDA method that was proposed by Teunissen is introduced. Then, on the basis of both the back-sequential conditional LS technique and the upper-triangular Cholesky decomposition, another form for LAMBDA method is proposed. This new form for LAMBDA method has the same principle and calculation speed as the traditional LAMBDA method.

The 'Lightspeed' preparation technique evaluated by Swiss clinicians after attending continuing education courses.

This survey evaluated acceptance of the Lightspeed canal preparation (LS) technique by Swiss practitioners. The technique was introduced to Switzerland in June 1994 and 10 other continuing education (CE) courses were held at the Zurich Dental School by July 1995. Acceptance was assessed by posting questionnaires to the CE course attendees. Of the 305 questionnaires posted, 177 (58%) were returned. Of the CE participants 80% had used the technique with 60% finding the method easier and 43% finding it quicker than their usual preparation techniques. Of the respondents 58% used the technique on all tooth types and 76% of the LS users had fractured an instrument at least once. Amongst others, fractures were caused by too much pressure (25%), incorrect insertion angles (17%) and by a complicated root morphology (15%). Fractures occurred high up on the instrument shaft (74%) and near the tip (7%). Working lengths were claimed by 62% to be easier to maintain by LS than their usual preparation techniques. Among the respondents 52% obturated LS prepared canals more easily and quickly compared with their usual preparation techniques. Only 10% of LS users would not recommend the technique, but those who would suggested that proper tuition was necessary to minimize the risk of instrument fracture. The LS technique was positively assessed by clinicians who attended the CE courses in Switzerland where endodontics is not accepted as a specialty.

A NUMERICAL ALGORITHM FOR DIRECT REAL-TIME ESTIMATION OF VOLTAGE PHASOR, FREQUENCY AND ITS RATE OF CHANGE

ABSTRACT A new algorithm for direct estimation of voltage phasor, frequency and its rate of change, of a voltage signal distorted by a DC component and contaminated by random noise is presented. The method is based on the non-recursive Least Error Squares Technique (LS Technique). Using digitized samples of voltage at the relay location, the estimation of the voltage signal unknown parameters is improved by means of an update procedure. The algorithm is adapted to the actually estimated frequency iteratively, which improved the measurement accuracy, increased the measurement range and reduced sensitivity to the noise. To demonstrate the performance of the algorithm developed, computer simulated data record tests are presented. The proposed method seems to be particularly useful in the field of frequency relaying.

Robust time-varying parametric modelling of voiced speech

Although time-varying parametric models have been proposed in the speech literature, few, if any, have had success when applied to speech. Since most employ the LS technique for parameter extraction, these do not perform very well in the presence of large errors (called outliers), which is a distinct possibility when dealing with voiced speech of short-pitch period in particular. In this paper, a robust time-varying LP algorithm is proposed, based on Huber's robust statistics. Testing on both synthetic and natural speech demonstrates that the robust time-varying LP algorithm can eliminate the effect of the glottal excitation on the parameter estimates.

Adaptive algorithm for estimation of voltage phasor, frequency and rate of change of frequency

AbstractThis paper presents results in the design of an adaptive algorithm for real‐time estimation of voltage phasor, frequency and its rate of change. The new algorithm, separated in two stages, is based on the non‐recursive “Least Error Squares Technique” (LS Technique). The estimation of the unknown parameters of the voltage signal is improved by means of an update procedure in the first stage. The update procedure is iteratively provided by the algorithm adaptation to the actual estimated frequency so that the frequency measurement range and accuracy are significantly improved and sensibility to the noise is reduced. The rate of change of frequency, estimated in the second stage using a common LS Technique, is represented by the linearly time‐dependent observation model. To demonstrate the performance of the algorithm developed, computer simulated, experimentally obtained and real‐life data records tests are presented.