Injury Failure Research Articles

Commonly Used Wind Generator Systems: A Comparison Note

<p>Amongst all renewable energy generation sources, wind power exhibits fastest growth rate. The increasing number of wind farm installations worldwide demand low maintenance, cost and failure rates with high efficiency. Determining the optimal drive train configuration amongst various configurations available for wind turbines is a challenge. In this paper commonly used, doubly fed induction generator with single stage gear box (GDFIG), doubly fed induction generator with multi stage gear box (DFIG) and the direct-drive permanent-magnet generator (DDPMG) are compared. Modelling of wind turbine with efficiency computations is presented. Considering common wind turbine parameters, performance of GDFIG, DFIG and DDPMG is compared through an experimental study. Considering a reference 5 MW variable speed wind turbine, efficiency of DDPMG is 96% when compared to 93.58%, 93.12% for DFIG and GDFIG. The experimental results presented prove that the DDPMG is a preferable solution considering low cost and high efficiency.</p>

Quantification of Storage Necessary to Firm Up Wind Generation

This paper proposes a method to quantitatively determine the sizes of energy storage systems that are intended to mitigate negative impacts of integrating wind energy into power systems. Although the integration of wind power has several advantages, it poses several technical challenges such as variability and uncertainty of wind speed and failures of wind turbine generators (WTGs), which may deteriorate the reliability of power systems. One of the most practical solutions to mitigate these drawbacks is the use of energy storage systems. The method proposed in this paper determines the sizes of the energy storage systems considering the effect of wind power uncertainty and variability, failures of WTGs, wind speed temporal resolution, and correlation with system load. Sizes of energy storage systems are determined based on composite system reliability analysis under operational and technical constraints using the ac power flow model. Monte Carlo simulation is used to emulate the behavior of the system. The proposed method is demonstrated on the IEEE reliability test system and the results are provided. The results show that the size of an energy storage system is dependent on wind farm characteristics, as well as the connectivity with the rest of the system.

Effects of topical negative pressure therapy on tissue oxygenation and wound healing in vascular foot wounds

ObjectiveTopical negative pressure (TNP) therapy is widely used in the treatment of acute wounds in vascular patients on the basis of proposed multifactorial benefits. However, numerous recent systematic reviews have concluded that there is inadequate evidence to support its benefits at a scientific level. This study evaluated the changes in wound volume, surface area, depth, collagen deposition, and tissue oxygenation when using TNP therapy compared with traditional dressings in patients with acute high-risk foot wounds. MethodsThis study was performed with hospitalized vascular patients. Forty-eight patients were selected with an acute lower extremity wound after surgical débridement or minor amputation that had an adequate blood supply without requiring further surgical revascularization and were deemed suitable for TNP therapy. The 22 patients who completed the study were randomly allocated to a treatment group receiving TNP or to a control group receiving regular topical dressings. Wound volume and wound oxygenation were analyzed using a modern stereophotographic wound measurement system and a hyperspectral transcutaneous oxygenation measurement system, respectively. Laboratory analysis was conducted on wound biopsy samples to determine hydroxyproline levels, a surrogate marker to collagen. ResultsDifferences in clinical or demographic characteristics or in the location of the foot wounds were not significant between the two groups. All patients, with the exception of two, had diabetes. The two patients who did not have diabetes had end-stage renal failure. There was no significance in the primary outcome of wound volume reduction between TNP and control patients on day 14 (44.2% and 20.9%, respectively; P = .15). Analyses of secondary outcomes showed a significant result of better healing rates in the TNP group by demonstrating a reduction in maximum wound depth at day 14 (36.0% TNP vs 17.6% control; P = .03). No significant findings were found for the other outcomes of changes in hydroxyproline levels (58.0% TNP vs 94.5% control; P = .32) or tissue perfusion by tissue oxyhemoglobin saturation (19.4% TNP vs 12.0% control; P = .07) at day 14. At 1 year of follow-up, there were no significant outcomes in the analysis of wound failure, major amputation, and overall survival rates between the two groups. ConclusionsIn this pilot study, applying TNP to acute high-risk foot wounds in patients with diabetes or end-stage renal failure improved the wound healing rate in reference to wound depth. This suggests that TNP may play a role in enhancing wound healing. This study sets the foundation for larger studies to evaluate the superiority of TNP over traditional dressings in high-risk foot wounds.

Study on locating transformer internal faults using sweep frequency response analysis

As an extensive network of resistances, capacitances, and inductances, a transformer has inherent characteristic parameters that are functions of frequency. The form of these functions is predicated on the geometric design of the transformer and materials that comprise it. Any change in the structure of a transformer will be reflected in its frequency response characteristics. Of the possible changes that can take place in a transformer structure, an internal short circuit is one of the far-reaching incidents that has been recently reported for many wind-farm transformers. Detecting the location of an internal short circuit that has occurred in a transformer winding is therefore beneficial in the repair process and also in improving future designs. In an effort to identify trends with inter-turn fault locations and frequency responses, this research investigates the effect of the location of deliberately initiated internal faults on parameters such as transfer voltages and input impedances by means of sweep frequency response analysis (SFRA). The analysis of three different model transformers with different core and winding designs shows several trends in frequency response patterns, depending on the location of the internal short circuits. The paper discusses such trends as a potential use of SFRA in locating inter-turn winding failures that may result in noticeable short circuits.

Refinement of Tissue-Engineering Chamber Implantation in the Rat

ABSTRACTPurpose: Rodent in vivo models that successfully generate new adipose, muscle, or vascular tissue in a tissue-engineering chamber (TEC) has advanced in the last decade. In this article, technical refinements in these operative foreign body implantations have been described to improve the execution of animal models in a way so that they can reduce wastage of time and resources. Materials & Methods: Male Sprague–Dawley rats were studied and randomly divided into two equal sized groups. In each group, a different operative procedure was used for implanting the TEC. Twenty animals were operated with diagonal incisions in the groin region, followed by staples for wound closure after TEC implantation. The remaining 20 animals received longitudinal incisions in the abdominal region followed by wound closure with ongoing intradermal nonresorbable sutures and skin glue. The outcome of both procedures with regard to complications, animal growth, and experimental failure was compared. Statistical analysis was performed using the nonparametric chi-squared (χ2) test. Results: Significant difference in wound dehiscence was recorded in Group I as compared to Group II (p = 0.0001). Consequently, 55% of the experiments had to be aborted in Group I and the animals were removed from the experiment. On the contrary, in Group II, all the animals could be kept. Conclusion: Median longitudinal incisions and thorough wound closure with ongoing intradermal nonresorbable sutures, followed by application of skin glue, are strongly recommended to prevent surgical site complications, such as wound dehiscence, animal harm, and failure of the individual experiment.

Update on Severe Burn Management for the Intensivist.

Thermal injury of humans causes arguably the most severe perturbations in physiology that can be experienced. These physiologic derangements start immediately and can persist in some form until months or even years after the burn wounds are healed. Burn shock, marked activation of the systemic inflammatory response, multiple-organ failure, infection, and wound failure are just a few of the insults that may require management by the intensivist. The purpose of this article is to review recent advances in the critical care management of thermally injured patients.

A Singular Value Decomposition based Space Vector Modulation to Reduce the Output Common-Mode Voltage of Direct Matrix Converters

Large magnitude common-mode voltage (CMV) and its variation dv/dt have an adverse effect on motor drives that leads to early winding failure and bearing deterioration. For matrix converters, the switch states that connect each output line to a different input phase result in the lowest CMV among all of the valid switch states. To reduce the output CMV for matrix converters, this paper presents a new space vector modulation (SVM) strategy by utilizing these switch states. By this mean, the peak value and the root mean square of the CMV are dramatically decreased. In comparison with the conventional SVM methods this strategy has a similar computation overhead. Experiment results are shown to validate the effectiveness of the proposed modulation method.

Modelling short‐ and open‐circuit faults in permanent magnet synchronous machines using Modelica

Electrical machine models are indispensable for describing and predicting the machine behaviour in several operating conditions. Modelling fault conditions are an attractive research area, since fault simulations allow to figure the behaviour of the electric drive and prevent damages to its components. In this study, winding failures in permanent magnet synchronous machines (PMSMs) are considered. In particular, short-circuits and open-circuits failures have been taken into account via two simple PMSM models. These models have been created using Modelica as modelling language. Feasibility of the proposed models is investigated in simulation (using Dymola environment) under the following fault conditions: single-phase open-circuit, single- and three-phase short-circuits. Moreover, models validation has been carried out through experimental tests, injecting windings failures into a fault-tolerant PMSM.

Effects of Recombinant Human Bone Morphogenetic Protein-2 Dose and Ceramic Composition on New Bone Formation and Space Maintenance in a Canine Mandibular Ridge Saddle Defect Model.

Treatment of mandibular osseous defects is a significant clinical challenge. Maintenance of the height and width of the mandibular ridge is essential for placement of dental implants and restoration of normal dentition. While guided bone regeneration using protective membranes is an effective strategy for maintaining the anatomic contour of the ridge and promoting new bone formation, complications have been reported, including wound failure, seroma, and graft exposure leading to infection. In this study, we investigated injectable low-viscosity (LV) polyurethane/ceramic composites augmented with 100 μg/mL (low) or 400 μg/mL (high) recombinant human bone morphogenetic protein-2 (rhBMP-2) as space-maintaining bone grafts in a canine mandibular ridge saddle defect model. LV grafts were injected as a reactive paste that set in 5-10 min to form a solid porous composite with bulk modulus exceeding 1 MPa. We hypothesized that compression-resistant LV grafts would enhance new bone formation and maintain the anatomic contour of the mandibular ridge without the use of protective membranes. At the rhBMP-2 dose recommended for the absorbable collagen sponge carrier in dogs (400 μg/mL), LV grafts maintained the width and height of the host mandibular ridge and supported new bone formation, while at suboptimal (100 μg/mL) doses, the anatomic contour of the ridge was not maintained. These findings indicate that compression-resistant bone grafts with bulk moduli exceeding 1 MPa and rhBMP-2 doses comparable to that recommended for the collagen sponge carrier support new bone formation and maintain ridge height and width in mandibular ridge defects without protective membranes.

Probabilistic analysis of climate change impacts on timber power pole networks

The IPCC, a collection of 800 of the world’s leading climate change scientists, state that future climate related risks to society and infrastructure are likely to change. It is therefore important for the power industry to consider the possible impacts of future climate change on infrastructure performance. However, very few studies have been published to date examining the potential impacts of climate change on power distribution poles networks, which constitute large and valuable infrastructure assets worldwide. The work presented in this paper builds on the limited research in this area by developing a framework for examination of the possible impacts of climate change on timber power pole networks. The time-dependent event-based model developed herein allows network maintenance and predicted climate change effects to be considered, while also incorporating uncertainty associated with both climate change predictions, and structural reliability modelling of infrastructure networks over time. The results of a case study which examined notional power pole networks for five Australian cities revealed that the effects of climate change on predicted power pole performance can be significant. Wind failures for the Brisbane location were predicted to increase by approximately 60% when considering a period from 2015 to 2070, under the severe climate change scenario. However, the predicted impacts are also highly regionally variable, with one location considered experiencing positive climate change impacts for a medium climate change scenario.

Assessment of Extreme Wind Risk for Window Systems in Apartment Buildings Based on Probabilistic Model

본 연구에서는 강풍 위험과 강풍 취약도의 합성곱을 통하여 강풍 위험도를 평가할 수 있는 확률적 체계를 수립하였으며, 수치적으로 개발한 모형으로 아파트 창호 시스템의 강풍 위험도를 평가하였다. 강풍 위험 모형은 1951년부터 2013년까지에 한반도에 영향을 준 태풍의 기후학적 자료를 몬테카를로 모사기법에 적용하여 개발되었다. 또한 몬테카를로 모사기법으로 창호 시스템의 저항성능과 풍하중의 확률 분포를 비교하여 강풍에 대한 4가지 피해단계의 구조적 파괴확률을 평가할 수 있는 취약도 모형이 개발되었다. 개발된 몬테카를로 모사기법으로 평가한 강풍 위험과 강풍 취약도는 각각 웨이블 분포와 로그정규분포로 곡선맞춤 되었으며, 합성곱을 통한 강풍 위험도 평가에 사용되었다. 본 연구에서 개발한 확률적 위험도 평가 체계를 통하여 평가지역, 지표조도, 지형, 지붕 경사각, 건물 높이 등이 아파트 창호 시스템의 강풍 위험도에 미치는 영향성을 정량적으로 평가할 수 있었다. 향후 본 연구를 통하여 개발된 강풍 위험도 평가 모델은 평가지역의 존재하는 건축물에 대한 데이터베이스와 결합하여 손실추정 및 피해 저감대책 수립 등의 분야에서 활용이 가능할 것으로 판단된다.In this study, a coupled probabilistic framework is developed to assess wind risk on apartment buildings by using the convolution of wind hazard and fragility functions. In this framework, typhoon induced extreme wind is estimated by applying the developed Monte Carlo simulation model to the climatological data of typhoons affecting Korean peninsular from 1951 to 2013. The Monte Carlo simulation technique is also used to assess wind fragility function for 4 different damage states by comparing the probability distributions of the window system’s resistance performance and wind load. Wind hazard and fragility functions are modeled by the Weibull and lognormal probability distributions based on simulated wind speeds and failure probabilities. The modeled functions are convoluted to obtain the wind risk for the different damage levels. The developed probabilistic framework clearly shows that wind risk are influenced by various important characteristics of terrain and apartment building such as location of building, exposure category, topographic condition, roof angle, height of building, etc. The risk model presented in this paper can be used as tools to predict economic loss estimation and to establish wind risk mitigation plan for the existing building inventory.

Bivariate dependent rate analyses for fault identification in transformer windings during impulse test

Identification of winding insulation failure during lightning impulse testing of transformer has been an important issue over a long period of time. It requires a significant human expertise and knowledge for proper judgment of transformer insulation. In this paper, the bivariate dependent rate analyses are proposed to identify the failure in transformer windings. The proposed analyses enable the calculation of winding response due to any impulse voltage excitation of full wave (FW) and chopped wave impulse (CW) for typical transformers. Initially, the line of best-fit on the scatter diagram is utilized to visualize the similarities between the measured winding responses and also to identify the type of relationship with potential outliers. Further, ellipse analysis is utilized to calculate the diversification (size, shape and orientation) between the responses. The actual interdependency between winding responses is established through nonlinear interpretation coefficients. To prove the feasibility of the analyses, 66.7 MVA, 90 MVA, 150 MVA, 250 MVA transformers, 80 MVAr reactor and 22 kV interleaved winding are used.

Multi-objective design optimization strategies for small-scale vertical-axis wind turbines

Extracting energy from wind has been an interesting and serious topic over the last few decades and a lot of work has been done on the subject. This paper discusses in detail possible approaches to optimization of a somewhat less known type of wind turbines, particularly suitable for small consumers. In order to perform full aerodynamic and structural shape optimization of a small-scale vertical-axis wind turbine, a Double-multiple streamtube model code, known to provide good results in stationary working regimes, was complemented by a finite element analysis and implemented into a multi-objective particle swarm algorithm. For the purpose of shortening the total time needed for aerodynamic computation, the performed numerical simulations were two-dimensional and experimentally measured static airfoil data were used. The used aerodynamic model was validated against the available experimental data of similar wind turbines. The subsequent structural analyses of the composite turbine blades were performed by applying computed maximal aerodynamic forces together with gravitational and inertial loads. By employing various input and output parameters different multi-objective optimization strategies were analyzed and compared and their applicability was demonstrated. Investigated input parameters included: wind turbine rotor diameter, blade length, chord and airfoil, composite shell thickness, laminate lay-up and ply orientations, while optimization goal functions and constraints comprised rated power, cut-in and optimal wind speed, blade mass, tip deflection, failure index and blade natural frequencies. The fidelity and accuracy of proposed methodologies can be increased by employing more complex numerical models which can easily be implemented into the code.

Extending analyzed frequency range in interpretation of frequency responses measured on a distribution transformer

In the field of diagnosis of mechanical failures in power transformer’s active part, i.e., windings, leads and the core, the technique of Frequency Response Analysis (FRA) has been recently approved as the main application tool. Mechanical failures in transformer windings reflect changes on measured terminal frequency responses normally in medium frequency range, from several to hundreds of kHz, which is in fact not easy to interpret for diagnosis. The authors proposed a new method based on simulation of a lumped three-phase equivalent circuit of power transformers to interpret frequency responses effectively, but only within low frequency range. This limitation is due to the fact that, the circuit cannot reflect well physical phenomena at medium and higher frequencies. To improve the FRA performance of the proposed method at medium frequencies for transformer failure diagnosis purpose, the paper introduces an investigation on a distributed three-phase equivalent circuit of a 200 kVA 10.4/0.46 kV Yy6 distribution transformer. Result of the investigation is a simplified procedure in determination of electrical parameters associated with the distributed circuit for better simulation based FRA interpretation at medium frequencies.

Lessons of War: Turning Data Into Decisions

BackgroundRecent conflicts in Afghanistan and Iraq produced a substantial number of critically wounded service-members. We collected biomarker and clinical information from 73 patients who sustained 116 life-threatening combat wounds, and sought to determine if the data could be used to predict the likelihood of wound failure. MethodsFrom each patient, we collected clinical information, serum, wound effluent, and tissue prior to and at each surgical débridement. Inflammatory cytokines were quantified in both the serum and effluent, as were gene expression targets. The primary outcome was successful wound healing. Computer intensive methods were used to derive prognostic models that were internally validated using target shuffling and cross-validation methods. A second cohort of eighteen critically injured civilian patients was evaluated to determine if similar inflammatory responses were observed. FindingsThe best-performing models enhanced clinical observation with biomarker data from the serum and wound effluent, an indicator that systemic inflammatory conditions contribute to local wound failure. A Random Forest model containing ten variables demonstrated the highest accuracy (AUC 0.79). Decision Curve Analysis indicated that the use of this model would improve clinical outcomes and reduce unnecessary surgical procedures. Civilian trauma patients demonstrated similar inflammatory responses and an equivalent wound failure rate, indicating that the model may be generalizable to civilian settings. InterpretationUsing advanced analytics, we successfully codified clinical and biomarker data from combat patients into a potentially generalizable decision support tool. Analysis of inflammatory data from critically ill patients with acute injury may inform decision-making to improve clinical outcomes and reduce healthcare costs. FundingUnited States Department of Defense Health Programs.

An Electro-Thermal Analysis of a Variable-Speed Doubly-Fed Induction Generator in a Wind Turbine

This paper focuses on the electro-thermal analysis of a doubly-fed induction generator (DFIG) in a wind turbine (WT) with gear transmission configuration. The study of the thermal mechanism plays an important role in the development of cost-effective fault diagnostic techniques, design for reliability and premature failure prevention. Starting from an analysis of the DFIG system control and its power losses mechanism, a model that synthesizes the thermal mechanism of the DFIG and a WT system principle is developed to study the thermodynamics of generator stator winding. The transient-state and steady-state temperature characteristics of stator winding under constant and step-cycle patterns of wind speed are studied to show an intrinsic thermal process within a variable-speed WT generator. Thermal behaviors of two failure modes, i.e., generator ventilation system failure and generator stator winding under electric voltage unbalance, are examined in details and validated by both simulation and data analysis. The effective approach presented in this paper for generator fault diagnosis using the acquired SCADA data shows the importance of simulation models in providing guidance for post-data analysis and interpretation. WT generator winding lifetime is finally estimated based on a thermal ageing model to investigate the impacts of wind speed and failure mode.

Evolution and advances in laparoscopic ventral and incisional hernia repair.

Primary ventral hernias and ventral incisional hernias have been a challenge for surgeons throughout the ages. In the current era, incisional hernias have increased in prevalence due to the very high number of laparotomies performed in the 20(th) century. Even though minimally invasive surgery and hernia repair have evolved rapidly, general surgeons have yet to develop the ideal, standardized method that adequately decreases common postoperative complications, such as wound failure, hernia recurrence and pain. The evolution of laparoscopy and ventral hernia repair will be reviewed, from the rectoscopy of the 4(th) century to the advent of laparoscopy, from suture repair to the evolution of mesh reinforcement. The nuances of minimally invasive ventral and incisional hernia repair will be summarized, from preoperative considerations to variations in intraoperative practice. New techniques have become increasingly popular, such as primary defect closure, retrorectus mesh placement, and concomitant component separation. The advent of robotics has made some of these repairs more feasible, but only time and well-designed clinical studies will tell if this will be a durable modality for ventral and incisional hernia repair.

Effective Factors on the Generated Transient Voltage in the Wind Farm due to Lightning

According to reports that had been published in many papers, wind turbines (WTs) fault due to lightning is one of the most difficult challenges. Lightning overvoltage lead to malfunction in the wind farm equipments. These improper functioning contain of malfunction electronic equipments and deformation of transformer winding and Surge arrester failures. The travelling waves which are generated due to high ground potential rise under lightning struck turbine cause these problems. To evaluate these cases, it must be performed an accurate analysis on the wave shape and level of the Lightning overvoltage and ground potential rise. This paper investigates the effective factors on the wave shape and level of the overvoltage, GPR and surge arrester burnout. These factors are included impulse Current-second characteristics, position of lightning, inception angle, multiple lightning strokes and chopped current. ATP-EMTP simulation program is applied to analyze the lightning over-voltage of onshore wind farm. This paper provides a practical procedure of lightning protection. DOI: http://dx.doi.org/10.11591/telkomnika.v13i1.6844

Unrecognized Arteriosclerosis Is Associated with Wound Complications after Below-Knee Amputation

Guillotine below-knee amputation (BKA) for wet gangrene is an unfortunate complication of poorly controlled diabetes. We examined risk factors associated with wound complications after amputation formalization in this patient population. Retrospective data over a 4-year period were collected for patients undergoing guillotine BKA for wet gangrene followed by staged formalization. Patients with abnormal distal pulses underwent evaluation before formalization to stratify for peripheral arterial disease (PAD). Those patients with palpable pulses and no known PAD went to formalization without further investigation. Poor operative candidates underwent delayed formalization to allow for preoperative optimization. Patient history, interval between surgeries, pathology, and preformalization laboratories were tested for significance. Primary outcome was postformalization wound complication. Fifty-six amputations in 55 patients met inclusion criteria. Wound complications after formalization occurred in 18 cases, all BKAs (32%). A history of PAD was present in 19 patients (34.5%). On pathology, 23 patients (41%) had small-vessel atherosclerosis or arteriosclerosis. There was no association between wound complications and history of PAD (P = 0.4), preformalization albumin (P = 0.09), glucose (P = 0.9), white blood cell count (P = 0.4), or delayed versus expedited formalization (P = 0.8). Only the presence of microvascular disease on formal pathology was predictive of wound complications (P = 0.03). There was no association between microvascular disease on pathology and a history of PAD (P = 0.07). After formalization of lower extremity amputation for wet gangrene, traditional markers of PAD were not predictive of wound complications. Although formalization of guillotine BKA can safely be performed without significant delay, more thorough assessment of microvascular disease in the perioperative period may be useful in identifying patients at risk for wound failure.

Risk factors for wound complications in patients undergoing primary closure of the perineal defect after total proctectomy.

Perineal wounds after complete proctectomy are at risk for failure, with dramatic consequences on patients' health and quality of life. This study is aimed at identifying risk factors for wound complications in patients undergoing primary closure of the perineal defect after total proctectomy. Data from 284 patients undergoing total proctectomy from 2002 to 2012 either at the University of Chicago Medical Center or the Catholic University of Rome Hospital were collected and analyzed. Overall, the perineal wound complication rate was 21.8%. Successful conservative management was accomplished in 45.2% of cases. Complications occurred significantly more often in patients with a higher Charlson score index, with the diagnosis of rectal cancer, who had received preoperative radiation and who had a surgical drain placed at the time of initial surgery. Neoadjuvant radiation was the only significant risk factor at multivariate analysis (OR 4.40). In the rectal cancer subgroup, younger age, female gender, and preoperative radiation were predictors of wound complications. Based on that, a 3-point score (radiation, age, and gender (RAG)) was developed. Patients with a score of 3 had a 50% risk of developing a perineal wound complication. Perineal wound complications are a common and burdensome problem after total proctectomy. Preoperative radiation is the single most significant and controllable risk factor predicting perineal wound failure. In the presence of multiple, non-modifiable risk factors, alternative approaches to primary closure should be considered in managing complex perineal defects.