Vibration control of pitch movement using command shaping techniques– Experimental investigation

This paper investigates the development of feedforward control strategies for vibration control of pitch movement (1 DOF) of a twin rotor multi-input multi-output system (TRMS) using command shaping techniques. Command shaping is a feedforward method used to reduce residual vibrations during motion in flexible systems. The TRMS is a laboratory platform designed for control experiments. In certain aspects, its behaviour resembles that of a helicopter. Feedforward controllers are designed for resonance suppression produced by the main rotor, which produces pitch movement around the longitudinal axis, while the lateral axis (yaw movement) is physically constrained. Three feed-forward controllers: input-shaper, low-pass filter and band-stop filter are designed based on the natural frequencies and damping ratios of the system. The three controllers are assessed in terms of level of vibration reduction at the system’s natural frequencies. Their performances are compared with an unshaped input (single-switch bang-bang signal) that is used to determine the dynamic response of the system

Hysteroscopic Endometrial Resection in the Management of Abnormal Uterine Bleeding Among Libyan Women

Background: Abnormal uterine bleeding (AUB) is a major health problem and it is a substantial cause of ill health in women. Medical treatment has a high failure rate and adverse effects. There are few published data on hysteroscopic endometrial resection (HER) in the management of patients with AUB.Objective: To investigate the efficacy and outcomes of hysteroscopic endometrial resection (HER) in patients with AUB.Materials and Methods: A descriptive hospital - based study was carried out at the departments of Obstetrics and Gynecology, Misurata and Sirt, Libya, during the period from January 2009 to December 2013. Women with AUB were recruited in the study. All women had a detailed medical and obstetrical history, physical examination and the hysteroscopic endometrial ablation and were followed-up for success or failure of the procedure which was assessed via symptoms (bleeding).Results: A total of 120 women with mean (SD) of age and parity of 42.3 (6.8) years and 3.8 (2.4), respectively were recruited in the study initially. Thirty (25%) of these women were lost of followup Therefore, only 70 women (50 with DUB, and 20 women with fibroids) were available for the final analysis. All women underwent hysteroscopic endometrial resection and 28 of them had hysteroscopic myomectomy. The success rate was 92.8% (65/70) after 2 years follow up. All the five women with failure of the procedure were younger (<40 years); had bleeding with dysmenorrhea, bigger uterine size, thicker endometrium (> 7 mm) and they had fibroids.Conclusions: Endometrial resection is an effective procedure in the majority of women with AUB, especially in those over age of 40 and without an increase in uterine size and has no fibroids.Keywords: Uterine bleeding, hysteroscopic, endometrial resection, Libya

Hysteroscopy in Libyan women with Recurrent Pregnancy Loss

Background: Hysteroscopy is an efficient procedure of management in many gynecologic conditions. There are few published data on hysteroscopy and recurrent pregnancy loss especially in developing countries.Objectives: To assess hysteroscopic findings in patients with consecutive miscarriages, and to compare the prevalence of uterine abnormalities between women with two and three or more miscarriages.Methods: Three hundred and twenty four women with two or more consecutive miscarriages were enrolled in the study. All participants underwent a diagnostic hysteroscopy. Congenital (arcuate uterus, septate uterus, unicornuate uterus) and acquired uterine abnormalities (intrauterine adhesions, polyp and submucous myoma) were documented. The findings were compared between the groups of women with two miscarriages and women who had three or more miscarriages.Results: Out of a total of 324 women [their mean (SD) of the age and gravidity was 28.3 (6.5) years and 5.1(1.5), respectively] 135 (41.7%) and 189 (58.3%) had two consecutive miscarriages and three or more consecutive miscarriages, respectively. While 194 (59.9%) women had no pathological findings on hysteroscopy, 130 (40.1%) women were found to have uterine anomalies. The congenital anomalies were found in 79 (24.4%) and the acquired were in 51 (15.7%) women. In comparison with women who had three or more miscarriages, women who had two miscarriages had significantly higher number of congenital anomalies, 53/135 (39.2%) vs. 26/189 (13.8%), P < 0.001. However there was no significant difference in the acquired anomalies between women who had two miscarriages and women who had three or more miscarriages.Conclusions: Patients who had two consecutive miscarriages were found to have a higher prevalence of congenital anatomical abnormalities. Diagnostic hysteroscopy should be carried out after two such miscarriages.Keywords: Hysteroscope, Recurrent Pregnancy Loss, miscarriage, Libya

Genetic algorithm optimization and control system design of flexible structures

This paper presents an investigation into the deployment of genetic algorithm (GA)-based controller design and optimization for vibration suppression in flexible structures. The potential of GA is explored in three case studies. In the first case study, the potential of GA is demonstrated in the development and optimization of a hybrid learning control scheme for vibration control of flexible manipulators. In the second case study, an active control mechanism for vibration suppression of flexible beam structures using GA optimization technique is proposed. The third case study presents the development of an effective adaptive command shaping control scheme for vibration control of a twin rotor system, where GA is employed to optimize the amplitudes and time locations of the impulses in the proposed control algorithm. The effectiveness of the proposed control schemes is verified in both an experimental and a simulation environment, and their performances are assessed in both the time and frequency domains

ANN-derived equation and ITS application in the prediction of dielectric properties of pure and impure CO₂

High-performing equation has been step-wisely extracted from artificial neural network (ANN) simulation and subsequently applied for the prediction of the dielectric properties of pure and impure CO2. Data of relative permittivity (εr) for pure and impure CO2 were used in the ANN to train different ANN structures so that the network can recognise and predict CO2 property under different conditions. Analyses of the results from the training showed that single-layer ANN model [3-6-1] outperformed others. From this best-performing ANN structure, a single mathematical equation was extracted that can be employed in predicting εr for pure CO2 and CO2-ethanol mixture, even without access to ANN software. Using this ANN-based mathematical model, predictions of the relative permittivity (εr) for pure CO2 and CO2-ethanol mixture were performed, under different temperatures and pressures and at different ethanol concentrations. Under similar conditions, the output of the model provides good match with the original experimental εr. With increment in ethanol concentration, the model correctly predicted the rise in εr for the mixture. Also, it was shown that the εr rises with an increase in pressure but decreases with a rise in temperature. The work showed the reliability and applicability of the ANN in characterizing and predicting the dielectric property of pure CO2 as well as its mixture or impurities. The model developed and the techniques demonstrated in this work offers immense benefits and guides for researchers, who may want to explore the behaviours of a pure compound and its mixtures/impurities using ANN, as well as those interested in derived mathematical model from statistical computation tool like ANN

Evaluation of weld porosity in laser beam seam welds: optimizing continuous wave and square wave modulated processes.

Nd:YAG laser joining is a high energy density (HED) process that can produce high-speed, low-heat input welds with a high depth-to-width aspect ratio. This is optimized by formation of a ''keyhole'' in the weld pool resulting from high vapor pressures associated with laser interaction with the metallic substrate. It is generally accepted that pores form in HED welds due to the instability and frequent collapse of the keyhole. In order to maintain an open keyhole, weld pool forces must be balanced such that vapor pressure and weld pool inertia forces are in equilibrium. Travel speed and laser beam power largely control the way these forces are balanced, as well as welding mode (Continuous Wave or Square Wave) and shielding gas type. A study into the phenomenon of weld pool porosity in 304L stainless steel was conducted to better understand and predict how welding parameters impact the weld pool dynamics that lead to pore formation. This work is intended to aid in development and verification of a finite element computer model of weld pool fluid flow dynamics being developed in parallel efforts and assist in weld development activities for the W76 and future RRW programs

Ex vivo normothermic perfusion of isolated segmental porcine bowel: a novel functional model of the small intestine.

BACKGROUND: There is an unmet need for suitable ex vivo large animal models in experimental gastroenterology and intestinal transplantation. This study details a reliable and effective technique for ex vivo normothermic perfusion (EVNP) of segmental porcine small intestine. METHODS: Segments of small intestine, 1.5-3.0 m in length, were retrieved from terminally anaesthetized pigs. After a period of cold ischaemia, EVNP was performed for 2 h at 37°C with a mean pressure of 80 mmHg using oxygenated autologous blood diluted with Ringer's solution. The duration of EVNP was extended to 4 h for a second set of experiments in which two segments of proximal to mid-ileum (1.5-3.0 m) were retrieved from each animal and reperfused with whole blood (control) or leucocyte-depleted blood to examine the impact of leucocyte depletion on reperfusion injury. RESULTS: After a mean cold ischaemia time of 5 h and 20 min, EVNP was performed in an initial group of four pigs. In the second set of experiments, five pigs were used in each group. In all experiments bowel segments were well perfused and exhibited peristalsis during EVNP. Venous glucose levels significantly increased following luminal glucose stimulation (mean(s.e.m.) basal level 1.8(0.6) mmol/l versus peak 15.5(5.8) mmol/l; P < 0.001) and glucagon-like peptide 1 (GLP-1) levels increased in all experiments, demonstrating intact absorptive and secretory intestinal functions. There were no significant differences between control and leucocyte-depleted animals regarding blood flow, venous glucose, GLP-1 levels or histopathology at the end of 4 h of EVNP. CONCLUSIONS: This novel model is suitable for the investigation of gastrointestinal physiology, pathology and ischaemia reperfusion injury, along with evaluation of potential therapeutic interventions

Use of Ex Vivo Normothermic Perfusion for Quality Assessment of Discarded Human Donor Pancreases.

A significant number of pancreases procured for transplantation are deemed unsuitable due to concerns about graft quality and the associated risk of complications. However, this decision is subjective and some declined grafts may be suitable for transplantation. Ex vivo normothermic perfusion (EVNP) prior to transplantation may allow a more objective assessment of graft quality and reduce discard rates. We report ex vivo normothermic perfusion of human pancreases procured but declined for transplantation, with ABO-compatible warm oxygenated packed red blood cells for 1-2 h. Five declined human pancreases were assessed using this technique after a median cold ischemia time of 13 h 19 min. One pancreas, with cold ischemia over 30 h, did not appear viable and was excluded. In the remaining pancreases, blood flow and pH were maintained throughout perfusion. Insulin secretion was observed in all four pancreases, but was lowest in an older donation after cardiac death pancreas. Amylase levels were highest in a gland with significant fat infiltration. This is the first study to assess the perfusion, injury, as measured by amylase, and exocrine function of human pancreases using EVNP and demonstrates the feasibility of the approach, although further refinements are required.This study was financially supported by a grant from the Mason Medical Research Foundation.This is the author accepted manuscript. The final version is available via Wiley at http://onlinelibrary.wiley.com/doi/10.1111/ajt.13303/abstract

Lightning arrestor connector lead magnesium niobate qualification pellet test procedures.

Enhanced knowledge preservation for DOE DP technical component activities has recently received much attention. As part of this recent knowledge preservation effort, improved documentation of the sample preparation and electrical testing procedures for lead magnesium niobate--lead titanate (PMN/PT) qualification pellets was completed. The qualification pellets are fabricated from the same parent powders used to produce PMN/PT lightning arrestor connector (LAC) granules at HWF&amp;T. In our report, the procedures for fired pellet surface preparation, electrode deposition, electrical testing and data recording are described. The dielectric measurements described in our report are an information only test. Technical reasons for selecting the electrode material, electrode size and geometry are presented. The electrical testing is based on measuring the dielectric constant and dissipation factor of the pellet during cooling from 280 C to 220 C. The most important data are the temperature for which the peak dielectric constant occurs (Curie Point temperature) and the peak dielectric constant magnitude. We determined that the peak dielectric constant for our procedure would be that measured at 1 kHz at the Curie Point. Both the peak dielectric constant and the Curie point parameters provide semi-quantitative information concerning the chemical and microstructural homogeneity of the parent material used for the production of PMN/PT granules for LACs. Finally, we have proposed flag limits for the dielectric data for the pellets. Specifically, if the temperature of the peak dielectric constant falls outside the range of 250 C {+-} 30 C we propose that a flag limit be imposed that will initiate communication between production agency and design agency personnel. If the peak dielectric constant measured falls outside the range 25,000 {+-} 10,000 we also propose that a flag limit be imposed

A mixed methods approach to evaluating community drug distributor performance in the control of neglected tropical diseases

BACKGROUND: Trusted literate, or semi-literate, community drug distributors (CDDs) are the primary implementers in integrated preventive chemotherapy (IPC) programmes for Neglected Tropical Disease (NTD) control. The CDDs are responsible for safely distributing drugs and for galvanising communities to repeatedly, often over many years, receive annual treatment, create and update treatment registers, monitor for side-effects and compile treatment coverage reports. These individuals are 'volunteers' for the programmes and do not receive remuneration for their annual work commitment. METHODS: A mixed methods approach, which included pictorial diaries to prospectively record CDD use of time, structured interviews and focus group discussions, was used to triangulate data on how 58 CDDs allocated their time towards their routine family activities and to NTD Programme activities in Uganda. The opportunity costs of CDD time were valued, performance assessed by determining the relationship between time and programme coverage, and CDD motivation for participating in the programme was explored. RESULTS: Key findings showed approximately 2.5 working weeks (range 0.6-11.4 working weeks) were spent on NTD Programme activities per year. The amount of time on NTD control activities significantly increased between the one and three deliveries that were required within an IPC campaign. CDD time spent on NTD Programme activities significantly reduced time available for subsistence and income generating engagements. As CDDs took more time to complete NTD Programme activities, their treatment performance, in terms of validated coverage, significantly decreased. Motivation for the programme was reported as low and CDDs felt undervalued. CONCLUSIONS: CDDs contribute a considerable amount of opportunity cost to the overall economic cost of the NTD Programme in Uganda due to the commitment of their time. Nevertheless, programme coverage of at least 75 %, as required by the World Health Organisation, is not being achieved and vulnerable individuals may not have access to treatment as a consequence of sub-optimal performance by the CDDs due to workload and programmatic factors