Academic literature on the topic 'Atypical Time Series'
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Journal articles on the topic "Atypical Time Series"
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Tkachenko, Anastasiia Yevhenivna, Liudmyla Olehivna Kyrychenko, and Tamara Anatoliivna Radyvylova. "Clustering Noisy Time Series." System technologies 3, no. 122 (October 10, 2019): 133–39. http://dx.doi.org/10.34185/1562-9945-3-122-2019-15.
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One of the urgent tasks of machine learning is the problem of clustering objects. Clustering time series is used as an independent research technique, as well as part of more complex data mining methods, such as rule detection, classification, anomaly detection, etc.A comparative analysis of clustering noisy time series is carried out. The clustering sample contained time series of various types, among which there were atypical objects. Clustering was performed by k-means and DBSCAN methods using various distance functions for time series.A numerical experiment was conducted to investigate the application of the k-means and DBSCAN methods to model time series with additive white noise. The sample on which clustering was carried out consisted of m time series of various types: harmonic realizations, parabolic realizations, and “bursts”.The work was carried out clustering noisy time series of various types.DBSCAN and k-means methods with different distance functions were used. The best results were shown by the DBSCAN method with the Euclidean metric and the CID function.Analysis of the results of the clustering of time series allows determining the key differences between the methods: if you can determine the number of clusters and you do not need to separate atypical time series, the k-means method shows fairly good results; if there is no information on the number of clusters and there is a problem of isolating non-typical rows, it is advisable to use the DBSCAN method.
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Oesterreich, Maciej. "On the method of identification of atypical observations in time series." Econometrics 24, no. 2 (2020): 1–16. http://dx.doi.org/10.15611/eada.2020.2.01.
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Shahid, SMA, MN Ali, M. Ahmed, SS Islam, and SB Hossain. "Diaphragmatic Hernia with Atypical Presentation - A Case Series." Journal of Bangladesh College of Physicians and Surgeons 32, no. 1 (November 30, 2014): 45–50. http://dx.doi.org/10.3329/jbcps.v32i1.21050.
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Congenital Diaphragmatic Hernia is one of the most challenging diagnosis faced by pediatric surgeons. From the time of its first anatomic description more than 300 years ago, CDH has carried a high mortality rate. We aimed to review patients who presented with hernia of diaphragm during the last six months. In this retrospective study, the medical records of three patients treated for diaphragmatic hernias who were admitted to Rajshahi Medical College Hospital between July 2012 and December 2012 were analyzed. Three patients with age of 45 days to 7 years were included in the study. Male to female ratio was 1:2. All patients had left-sided diaphragmatic hernia. Chest X-ray was obtained from all patients which was diagnostic. One patient needed thoracotomy incision. No patient required mesh repair. The mean hospitalization time was 14 days. There was no postoperative death. Diaphragmatic hernia is an uncommon and challenging situation for the surgeon. Prompt diagnosis and treatment prevent serious morbidity and mortality associated with complications such as gangrene and perforation of herniated organ. DOI: http://dx.doi.org/10.3329/jbcps.v32i1.21050 J Bangladesh Coll Phys Surg 2014; 32: 45-50
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Rutkowski, Martin J., Ryan M. Alward, Rebecca Chen, Jeffrey Wagner, Arman Jahangiri, Derek G. Southwell, Sandeep Kunwar, Lewis Blevins, Han Lee, and Manish K. Aghi. "Atypical pituitary adenoma: a clinicopathologic case series." Journal of Neurosurgery 128, no. 4 (April 2018): 1058–65. http://dx.doi.org/10.3171/2016.12.jns162126.
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OBJECTIVEIn 2004, the WHO classified atypical pituitary adenoma as a distinct adenoma subtype. However, the clinical significance of this distinction remains undetermined. The authors sought to define patient characteristics, tumor features, and treatment outcomes associated with atypical pituitary adenoma.METHODSThe authors reviewed records of patients who underwent resection of pituitary adenoma at the University of California, San Francisco, between 2007 and 2014. Per institutional protocol, adenomas exhibiting mitotic activity underwent evaluation for all 3 markers of atypicality (mitotic index, extensive p53 staining, and MIB-1 index ≥ 3%). Statistical analyses were performed using χ2, Fisher’s exact test, t-test, log-rank, and logistic regression.RESULTSBetween 2007 and 2014, 701 patients underwent resection for pituitary adenoma. Among these patients, 122 adenomas exhibited mitotic activity and therefore were evaluated for all 3 markers of atypicality, with 36 tumors (5%) proving to be atypical. There were 21 female patients (58%) and 15 male patients (42%) in the atypical cohort, and 313 female patients (47%) and 352 male patients (53%) in the nonatypical cohort (p = 0.231). The mean age of patients in the atypical cohort was 37 years (range 10–65 years), which was significantly lower than the mean age of 49 years (range 10–93 years) for patients in the nonatypical cohort (p < 0.001). The most common presenting symptoms for patients with atypical adenomas were headaches (42%) and visual changes (33%). Atypical adenomas were more likely to be functional (78%) than nonatypical adenomas (42%; p < 0.001). Functional atypical adenomas were significantly larger than functional nonatypical adenomas (mean diameter 2.2 vs 1.4 cm; p = 0.009), as were nonfunctional atypical adenomas compared with nonfunctional nonatypical adenomas (mean diameter 3.3 vs 2.3 cm; p = 0.01). Among the entire adenoma cohort, larger presenting tumor size was associated with cavernous sinus invasion (p < 0.001), and subtotal resection was associated with cavernous sinus invasion (p < 0.001) and larger size (p < 0.001) on binomial multivariate regression. The median time until recurrence was 56 months for atypical adenomas, 129 months for functional nonatypical adenomas, and 204 months for nonfunctional nonatypical adenomas (p < 0.001). Functional atypical adenomas recurred more frequently and significantly earlier than functional nonatypical adenomas (p < 0.001). When accounting for extent of resection, cavernous sinus invasion, size, age, sex, and functional subtype, atypicality remained a significant predictor of earlier recurrence among functional adenomas (p = 0.002).CONCLUSIONSWhen compared with nonatypical pituitary adenomas, atypical adenomas are more likely to present in younger patients at a larger size, are more often hormonally hypersecretory, and are associated with earlier recurrence. These features lend credence to atypical pituitary adenomas being a distinct clinical entity in addition to a discrete pathological diagnosis.
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Bedard, Thomas, Mujtaba Mohammed, Serenella Serinelli, and Timothy A. Damron. "Atypical Enostoses—Series of Ten Cases and Literature Review." Medicina 56, no. 10 (October 13, 2020): 534. http://dx.doi.org/10.3390/medicina56100534.
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Bone islands (BI; enostoses) may be solitary or occur in the setting of osteopoikilosis (multiple bone islands) and are sometimes associated with Gardner’s Syndrome (osteopoikilosis and colonic polyposis). Characteristic features of bone islands are (1) absence of pain or local tenderness, (2) typical radio dense central appearance with peripheral radiating spicules (rose thorn), (3) Mean CT (computerized tomography) attenuation values above 885 Hounsfield units (HU) (4) absence of uptake on bone scan and (5) radiographic stability over time. However, when enostoses display atypical features of pain, unusual radiographic appearance, aberrant HU, increased radiotracer uptake, and/or enlargement, they can be difficult to differentiate from more sinister bony lesions such as osteoblastic metastasis, low grade central osteosarcoma, osteoid osteoma and osteoblastoma. In this retrospective case series, the demographic, clinical, radiographic, treatment and outcome for ten patients with eleven atypical bone islands (ABI) are presented, some showing associated pain (5), some with atypical radiographic appearance (3), some with increased activity on BS (4), some with documented enlargement over time (7), one with abnormal CT attenuation value, some in the setting of osteopoikilosis (2), one in the setting of Gardner’s Syndrome and one osteoid osteoma simulating a bone island. This series represents the spectrum of presentations of ABI. Comprehensive review of the literature reveals that the previous largest series of ABI showing enlargement as the atypical feature was in younger patients with jaw BI. Hence, this represents one of the largest series reported of ABI of all types in adults.
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Ghosh, Arindam, Subhankar Chakravorty, Somak Krishna Biswas, and Sumitra Kumar Biswas. "Series of rare diagnosis and presentations of abdominal mass in children: a great learning experience." International Journal of Contemporary Pediatrics 7, no. 5 (April 24, 2020): 1184. http://dx.doi.org/10.18203/2349-3291.ijcp20201658.
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Abdominal mass is a common finding in children, either palpable or radiologically evident surprisingly. Some of them are rare tumors. Functional active tumors are rarely palpable but present with varied arrays of symptoms. In this series authors are discussing few rare cases with atypical presentations such as- teratoma arising from adrenal gland, teratoma presenting with hypertension, fetus in fetu (Girl and Boy child), adrenocortical tumor presenting as precocious puberty and adrenal pheochromocytoma with features of cushing’s syndrome. These atypical presentations may have pose a challenge in diagnosis and management for the treating team with first time occurrence specifically if they are handling them for first time.
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Marucci, G., M. Faustini-Fustini, A. Righi, E. Pasquini, G. Frank, R. Agati, and M. P. Foschini. "Thyrotropin-secreting pituitary tumours: significance of “atypical adenomas” in a series of 10 patients and association with Hashimoto thyroiditis as a cause of delay in diagnosis." Journal of Clinical Pathology 62, no. 5 (December 19, 2008): 455–59. http://dx.doi.org/10.1136/jcp.2008.061523.
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Background:Thyrotropin-secreting adenomas (TSH-As) are rare and, according to the World Health Organization criteria (WHO 2004), a significant proportion of them present features of atypical adenomas at the time of diagnosis.Aims:To determine the frequency of “atypical adenomas” and the significance of this definition as regards follow-up. To investigate their possible association with Hashimoto thyroiditis, leading to a delay in diagnosis.Methods:Case notes for patients who underwent trans-sphenoidal surgery between 1992 and 2006 were retrieved. Follow-up ranged from 6 to 180 months.Results:Ten cases of TSH-As out of 908 pituitary adenomas were selected. Before surgery, eight patients had hyperthyroidism, one was euthyroid and another one showed hypothyroidism associated with Hashimoto thyroiditis. All cases were macroadenomas; six of them were invasive. Three cases met the criteria for classification as atypical. In none of the cases, including the three “atypical adenomas”, were clinical or radiological signs of recurrence observed.Conclusions:The three cases with features of atypical adenoma did not recur or metastasise, suggesting that, at least in the present series, a strict relationship between the morphological criteria for diagnosing atypical adenomas and biological behaviour may be sometimes lacking. Furthermore, the casual association of TSH-As with Hashimoto thyroiditis may led to an adjunctive delay in diagnosis, because of low thyroid hormone levels.
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Komotar, Ricardo J., J. Bryan Iorgulescu, Daniel M. S. Raper, Eric C. Holland, Kathryn Beal, Mark H. Bilsky, Cameron W. Brennan, et al. "The role of radiotherapy following gross-total resection of atypical meningiomas." Journal of Neurosurgery 117, no. 4 (October 2012): 679–86. http://dx.doi.org/10.3171/2012.7.jns112113.
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Object Atypical (WHO Grade II) meningiomas comprise a heterogeneous group of tumors, with histopathology delineated under the guidance of the WHO and a spectrum of clinical outcomes. The role of postoperative radiotherapy for patients with atypical meningiomas who have undergone gross-total resection (GTR) remains unclear. In this paper, the authors sought to clarify this role by reviewing their experience over the past 2 decades. Methods The authors retrospectively analyzed all patients at their institution who underwent GTR between 1992 and 2011 with a final histology demonstrating atypical meningioma. Information regarding patients, tumor characteristics, and postoperative adjuvant therapy was gleaned from medical records. Time to recurrence and overall survival were analyzed using univariate, multivariate, and Kaplan-Meier survival analyses. Results Forty-five patients who met the inclusion criteria underwent GTR for atypical meningiomas. By a median follow-up of 44.1 months, 22% of atypical meningiomas had recurred. There was no recurrence in 12 (92%) of 13 patients who received postoperative radiotherapy or in 19 (59%) of 32 patients who did not undergo postoperative radiotherapy (p = 0.085), demonstrating a strong trend toward improved local control with postoperative radiotherapy. No other factors were significantly associated with recurrence in univariate or multivariate analyses. Conclusions This retrospective series supports the observation that postoperative radiotherapy likely results in lower recurrence rates of gross totally resected atypical meningiomas. Although a multicenter prospective trial will ultimately be needed to fully define the role of radiotherapy in managing gross totally resected atypical meningiomas, the authors' results contribute to a growing number of series that support routine postoperative radiotherapy as an adjuvant treatment for these lesions.
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Bogdan, Yelena, and Juan de Dios Robinson. "Healing time and complications in operatively treated atypical femur fractures associated with bisphosphonate use: A multicentre series." Injury 46, no. 8 (August 2015): 1430. http://dx.doi.org/10.1016/j.injury.2015.06.011.
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Morokoff, Andrew P., Jacob Zauberman, and Peter M. Black. "SURGERY FOR CONVEXITY MENINGIOMAS." Neurosurgery 63, no. 3 (September 1, 2008): 427–34. http://dx.doi.org/10.1227/01.neu.0000310692.80289.28.
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ABSTRACT OBJECTIVE Meningiomas that occur over the convexity of the brain are the most common meningiomas, but little has been published about their contemporary management. We aimed to analyze a large series of convexity meningiomas with respect to surgical technique, complication rates, and pathological factors leading to recurrence. METHODS We retrospectively reviewed 163 cases of convexity meningiomas operated on in our institution by the senior author (PMB) between 1986 and 2005. The median follow-up time was 2.3 years (range, 1–13 yr). RESULTS Convexity tumors represented 22% of all meningiomas operated on. There was a female:male ratio of 2.7:1. Median age was 57 years (range, 20–89 yr). Image-guided surgery was used on all cases in the last 5 years. The 30-day mortality rate was 0%. The incidence of new neurological deficits was 1.7%, and the overall complication rate was 9.4%. The pathology of the tumors was benign in 144 (88.3%), atypical in 16 (9.8%), and anaplastic/malignant in 3 (1.8%). In six of the cases designated “benign,” there were borderline atypical features. The 5-year recurrence rate for benign meningiomas was 1.8%, atypical meningiomas 27.2%, and anaplastic meningiomas 50%. The two cases of benign tumor recurrences involved tumors with borderline atypia and high MIB-1 indices. The borderline atypical cases had a 5-year recurrence-free survival rate of only 55.9%, more closely approximating that of tumors designated “atypical.” CONCLUSION Convexity meningiomas can be safely removed using modern image-guided minimally invasive surgical techniques with a very low operative mortality. Benign convexity meningiomas having a Simpson Grade I complete excision have a very low recurrence rate. The recurrence rates of atypical and malignant tumors are significantly higher, and borderline atypical tumors should be considered to behave more like atypical rather than benign lesions. Longer-term follow-up data are needed to more accurately determine the recurrence rates of benign meningiomas.
Dissertations / Theses on the topic "Atypical Time Series"
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Кіріченко, Л. О., Т. А. Радівілова, and А. Є. Ткаченко. "Comparative Analysis of Noisy Time Series Clustering." Thesis, 2019. http://openarchive.nure.ua/handle/document/9456.
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A comparative analysis of the clustering of sample time series was
performed. The clustering sample contained time series of various types, among
which atypical objects were present. In the numerical experiment, white noise
with different variance was added to the time series. Clustering was performed
by k-means and DBSCAN methods using various similarity functions of time
series. The values of the quality functionals were quantitative measures of the
quality of clustering. The best results were shown by the DBSCAN method using the Euclidean metric with a Complexity Invariant Distance. The method allows to separate a cluster with atypical series at different levels of additive
noise. The results of the clustering of real time series confirmed the applicability of the DBSCAN method for detecting anomaly.
Books on the topic "Atypical Time Series"
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Shaibani, Aziz. Pseudoneurologic Syndromes. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780190661304.003.0022.
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The term functional has almost replaced psychogenic in the neuromuscular literature for two reasons. It implies a disturbance of function, not structural damage; therefore, it defies laboratory testing such as MRIS, electromyography (EMG), and nerve conduction study (NCS). It is convenient to draw a parallel to the patients between migraine and brain tumors, as both cause headache, but brain MRI is negative in the former without minimizing the suffering of the patient. It is a “software” and not a “hardware” problem. It avoids irritating the patient by misunderstanding the word psychogenic which to many means “madness.”The cause of this functional impairment may fall into one of the following categories:• Conversion reaction: conversion of psychological stress to physical symptoms. This may include paralysis, hemisensory or distal sensory loss, or conversion spasms. It affects younger age groups.• Somatization: chronic multiple physical and cognitive symptoms due to chronic stress. It affects older age groups.• Factions disorder: induced real physical symptoms due to the need to be cared for, such as injecting oneself with insulin to produce hypoglycemia.• Hypochondriasis: overconcern about body functions such as suspicion of ALS due to the presence of rare fasciclutations that are normal during stress and after ingestion of a large amount of coffee. Medical students in particular are targets for this disorder.The following points are to be made on this topic. FNMD should be diagnosed by neuromuscular specialists who are trained to recognize actual syndrome whether typical or atypical. Presentations that fall out of the recognition pattern of a neuromuscular specialist, after the investigations are negative, they should be considered as FNMDs. Sometimes serial examinations are useful to confirm this suspicion. Psychatrists or psychologists are to be consulted to formulate a plan to discover the underlying stress and to treat any associated psychiatric disorder or psychological aberration. Most patients think that they are stressed due to the illness and they fail to connect the neuromuscular manifestations and the underlying stress. They offer shop around due to lack of satisfaction, especially those with somatization disorders. Some patients learn how to imitate certain conditions well, and they can deceive health care professionals. EMG and NCS are invaluable in revealing FNMD. A normal needle EMG of a weak muscles mostly indicates a central etiology (organic or functional). Normal sensory responses of a severely numb limb mean that a lesion is preganglionic (like roots avulsion, CISP, etc.) or the cause is central (a doral column lesion or functional). Management of FNMD is difficult, and many patients end up being chronic cases that wander into clinics and hospitals seeking solutions and exhausting the health care system with unnecessary expenses.It is time for these disorders to be studied in detail and be classified and have criteria set for their diagnosis so that they will not remain diagnosed only by exclusion. This chapter will describe some examples of these disorders. A video clip can tell the story better than many pages of writing. Improvement of digital cameras and electronic media has improved the diagnosis of these conditions, and it is advisable that patients record some of their symptoms when they happen. It is not uncommon for some Neuromuscular disorders (NMDs), such as myasthenia gravis (MG), small fiber neuropathy, and CISP, to be diagnosed as functional due to the lack of solid physical findings during the time of the examination. Therefore, a neuromuscular evaluation is important before these disorders are labeled as such. Some patients have genuine NMDs, but the majority of their symptoms are related to what Joseph Marsden called “sickness behavior.” A patient with carpal tunnel syndrome (CTS) may unconsciously develop numbness of the entire side of the body because he thinks that he may have a stroke.
Book chapters on the topic "Atypical Time Series"
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Haddow, Scott D., Joshua W. Sadvari, Christopher J. Knüsel, Sophie V. Moore, Selin E. Nugent, and Clark Spencer Larsen. "Out of Range?" In The Odd, the Unusual, and the Strange, 323–46. University Press of Florida, 2020. http://dx.doi.org/10.5744/florida/9781683401032.003.0017.
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Çatalhöyük is most well known for its Neolithic settlement, but the site also served as a cemetery during the Bronze Age, as well as the Roman, Byzantine, and Islamic periods. During the Neolithic, Çatalhöyük is distinctive as a place for both the living and the dead, but thereafter the site becomes more closely associated with the dead. This chapter discusses four examples of non-normative burials from different time periods at the site, including two Neolithic burials: one of a mature male buried with a sheep and another of a young male with a congenital deformity; a Roman period double burial with an atypical grave orientation; and an isolated twentieth-century burial of a woman from the local village, which represents the last known burial on the mound. Osteobiographical information and sociocultural context are used to assess the significance of each burial. We also question how normative and non-normative burials are typically defined in the archaeological record.
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Harding, Dennis. "Dead among the living landscape." In Death and Burial in Iron Age Britain. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780199687565.003.0009.
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The discovery of human remains in both hillforts and settlements has a long archaeological history, whether whole or partial skeletons or simply individual bones and fragments, though the former were often dismissed as the atypical disposal of social outcasts or malefactors, and the latter were never satisfactorily explained as casual discards. The fact that complete or near-complete skeletons were found in pits that evidently had been designed for another purpose, together with the absence of grave-goods, militated against their interpretation as formal burials, and set these apart from those grouped burials in pits that we have treated as small cemeteries. As regards fragmentary remains, the idea that the dead were exposed for excarnation, possibly over a protracted period of time, is now well established in Iron Age studies. What happened after excarnation is less clear, whether the skeleton was reassembled and buried, either in a formal cemetery or in a settlement context, or distributed as body parts or individual bones in pits, ditches, entrances, or other locations around settlements. Alternatively, in ethnographic contexts it is not unknown for the dead to be interred in a temporary burial ground for a period of months or even years, whilst the process of decomposition took place, before exhumation and re-burial following a final funerary feast. That final stage of re-interment in the British Iron Age likewise could have involved complete or near-complete re-burial, or separation of body parts and their distribution into liminal locations, as a means of incorporating the benign dead into the living community. And hillforts might well have served as the location, not only for excarnation platforms, but for temporary burial as well. We should not, however, exclude other possible interpretations. As Duday (2006: 30) warned, ‘one must not presuppose a funerary context of all such deposits because certain intentional deposits of human remains have nothing to do with burial’. Necessarily, of course, researchers are dependent upon the quantity as well as the quality of the excavated data-base, particularly in terms of statistical assessments, and for this reason Danebury has tended to dominate recent studies.
Conference papers on the topic "Atypical Time Series"
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Ziegler, Hartmut, Tilo Nietzschmann, and Daniel A. Keim. "Visual Exploration and Discovery of Atypical Behavior in Financial Time Series Data using Two-Dimensional Colormaps." In 2007 11th International Conference Information Visualization (IV '07). IEEE, 2007. http://dx.doi.org/10.1109/iv.2007.124.
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Chávez, Manuel, Israel Chávez, Eduardo Torres, Sandro Atoche, Stefano Palacios, Luis Trelles, Cristhian Aldana, Yesenia Saavedra, Gustavo Mendoza, and Nelson Chuquihuanca. "Detection of Outliers in The Peruvian Fruit Production Time Series Using Arima Models." In Intelligent Human Systems Integration (IHSI 2022) Integrating People and Intelligent Systems. AHFE International, 2022. http://dx.doi.org/10.54941/ahfe1001008.
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The present applied, non-experimental, descriptive and prognostic research; was aimed at detecting outliers in the agricultural production of Mangifera indica (mango), Persea americana (avocado) and Citrus x aurantifolia (lemon) at the national level, was performed by applying an ARIMA Model. To fulfill it purposes, documentary analysis was used at the National Institute of Statistics and Informatics (In Spanish, INEI). The study sample consisted of the mango, avocado and lemon production indices 2000-2020. As a result, the models were obtained arima mango (1,0,0) (2,1,2) (AIC=5448.99, BIC=5473.35 and RMSE=19067.93), arima avocado (0,1,3) (2,1,0) (AIC=4687.05, BIC=4707.91 and RMSE=4114.35) and arima lemon (1,0,1) (0,1,1) (AIC=4484.36, BIC=4501.76 and RMSE=2551.96) with a 12 months period, the diagram of boxes and whiskers was also made with which it was identified that atypical data (Outliers) abound in the periods of greatest production.
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Discenzo, Fred M., Steven A. Kania, Chung-Chin Liu, Laurie Dudik, Aleksandr Vasser, and Benjamin Ward. "Dissolved Wear Metal Monitoring in Lubricating Fluids." In ASME/STLE 2007 International Joint Tribology Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ijtc2007-44102.
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Lubricating fluids play a critical role in the operation of many machines in commerce, industry, and the military. Failure of a lubricant often results in accelerated metal wear and the release of wear debris in the lubricant. Early detection of abnormal metal wear is important for fault detection and failure prevention. An electrochemical cell can be operated in a lubricating fluid in such a way that the operating characteristics of the cell can provide an indication of the chemistry of the fluid. For example, certain ions in the fluid, such as wear metal ions, will react to particular potential values applied to electrodes in the electrochemical cell. By applying a changing potential across the electrodes in an electrochemical cell and observing the resulting current it is possible to detect and identify the ionic species present in the lubricating fluid. The objective is to provide real-time monitoring of lubricating fluids using an in situ sensor to detect and diagnose conditions leading to machinery failure. A series of experiments have been conducted to confirm the ability of an electrochemical cell to detect wear metal ions in lubricating fluids extracted from machinery. Additional tests have been conducted to test the hypothesis that the presence and amount of wear metal ions corresponds to the type and amount of wear particles in the fluid. Initial laboratory tests have established a positive correlation with wear particles detected in used lubricating oil with ion presence determined using ion chromatography. The results reported indicate that a small, real-time multielement sensor with an electrochemical cell will be able to detect wear metal ions and provide an early indication of unusual material wear. This capability may provide an early warning of atypical wear patterns and provide a cue to an operator or service engineer indicating the type of fault occurring and the specific component experiencing wear or early failure.
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Nijhawan, Sunil. "Importance of Reactor Heat Transport System Overpressure Protection System Under Severe Accident Conditions With Special Reference to CANDU Reactors." In 2012 20th International Conference on Nuclear Engineering and the ASME 2012 Power Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/icone20-power2012-54301.
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After Fukushima, any Station Blackout capability reviews must be carried out with diligence and integrity beyond any reasonable doubt. This is especially true for nuclear reactors that did not consider a sustained loss of AC power and severe accidents in their original design basis. Integrity of the engineered barriers to release of activity must be demonstrated to showcase the extension of defense in depth to a Station Blackout and reasonable provisions for effective interventions. An important aspect of nuclear reactor heat transport system pressure boundary integrity is the ability of its over-pressure protection system to meet the challenges upon a sustained loss of AC power. The primary heat transport systems in water cooled nuclear power reactors have at least two passive safety relief valves so that at least one is available to act with the generally mandated consideration of a single failure. Design criteria for these relief valves vary but their steam relief capacity, reliability and performance must conform to the relevant ASME code or equivalent requirements. A typical PWR of about 3000 MW thermal power may usually have 3–5 such valves able to relieve upto ∼200 kg/s of steam, which may be about an order of magnitude higher than required. A typical single unit CANDU reactor, on the other hand, has about 30% less thermal power but only 2 such safety relief valves with a combined steam relief capacity of about 4 kg/s or about 4 MW of thermal power equivalent at the relief set-point and a time when the decay power is ∼20 MW. Installation of these valves in a CANDU reactor is also atypical; as they do not provide a direct and unobstructed path from the heat transport system but are installed downstream of another series of isolating Liquid Relief Valves emptying into an unpressurized and small degasser condenser vessel downstream of which they are mounted. These valves become critical when there is a sustained loss/depletion of engineered heat removal systems following multiple failures as in Fukushima. An unmitigated increase in heat transport pressure and a consequential breech in pressure boundary become inevitable if the core decay heat exceeds the safety valve steam relief capacity. If the ensuing failure is in the boiler tubes, a containment bypass and release of activity into atmosphere is possible. The present design of CANDU reactor Primary Heat Transport system does not seem to allow the anticipated energy relief through the safety relief valves following a sustained loss of all engineered heat sinks. This may result in uncontrolled primary heat transport system pressurization and a potential for boiler tube ruptures such that activity releases bypass the containment and expose the population to dangerously high radiation well before any evacuation. If the valves are to conform to requirements of the ASME codes under early stages of a loss of heat sinks scenario just as they must for design basis accidents (energy relief capacity greater than the heat load), it may seem that many clauses of the applicable ASME code sections for the subject valves are violated in abundance and with impunity. A containment bypass resulting from boiler tube failure caused by the faulty overpressure protection can cause fatalities that can be high with astronomical economic consequences, especially after the fuel begins to overheat. Such a containment bypass is considered to present the highest risk to public. The probability of a sustained loss of heat sinks is not insignificant and the overall risk is yet to be quantified for all instigators for any CANDU power plant. The national regulators have not required that utilities do so in a timely manner and as a condition of operating license. The paper examines the CANDU safety relief valve design criteria, lists design challenges and potential consequences during a station blackout severe accident scenario that could be well mitigated by an otherwise robust design.