A Comparative Study on Fatigue Damage using a Wave Load Sequence Model

Despite that ships get the approval of classification societies and structural members are designed to survive random environmental conditions for twenty or twenty-five years, fatigue crack damage still occurs. Nowadays, the operation based on weather routing programs has become important, not only to avoid adverse sea conditions that can cause damage, time loss or significant speed reduction but also to improve the crew safety. In this paper, S-N based fatigue assessment of a welded joint in an ocean going is performed. It is assumed that the ship sails following a planned route and a route based on weather conditions. Short sea sequences are generated by a storm model called “4G Storm Model”, proposed by one of the co-authors (De Gracia et al., 2017). Stress histories are generated considering the stochastical nature of the wave direction variation. Cumulative fatigue damage is performed following a classification society rule. Based on these results, the effect of ship routing and headings model on the S-N fatigue assessment is discussed. Keywords: Weather routing, fatigue, cumulative damage, storm model, wave sequence model

Facilitation of management plan development via spatial classification of areas invaded by alien invasive plant

Propagule supply and habitat suitability strongly influence the success of invasive alien plants. Thus, an invaded area is likely to have an adequate propagule supply, a suitable habitat, or both for species persistence. Based on this idea, we classified invaded areas into four categories as follows but with establishment still occurring in some cases: Class 1, adequate propagule supply and habitat suitability; Class 2, adequate propagule supply but limited habitat suitability; Class 3, limited propagule supply and adequate habitat suitability; and Class 4, mid- to low-level propagule supply and habitat suitability. We propose a framework for the classification of invaded areas into these four classes and present a case study in which this framework was applied. Classifying target areas in this manner could facilitate more efficient and practical management planning, thereby saving time and resources. We selected the alien shrub Leucaena leucocephala L. (Fabaceae) as a model species, which has invaded the Nakodo-jima Island in the Ogasawara Archipelago of Japan. We developed a species distribution model by incorporating proxy variables for propagule supply and habitat suitability as well as submodels for propagule supply or habitat suitability. Using these submodels, we estimated the levels of propagule supply and habitat suitability in each, and classified the current distribution range appropriately. Using these classifications, land managers could set priorities to concentrate their efforts to efficiently control target species

Development of a Practical Straightening Simulation for Welded Structures Using Inherent Strain Method

Welding is the most widely used assembly method available to industries in the construction of metal structures, ships, and offshore platforms. However, this method always produces a certain amount of distortion that will not only degrade the performance but also increase the building cost of the structure, and it should be straightened. Murakawa [1] developed a thermal elastic plastic based and inherent strain based welding simulation FE code JWRIAN. Coarse shell FE models are usually used in the inherent strain based JWRIAN elastic analyses. This drastically reduces the manpower needed for modeling and computer resources needed for the calculation. However, it is not easy to perform straightening analysis using JWRIAN because gas heating’s inherent strain distributes over a range much smaller than element sizes of the shell model.RUIZ [2] modified JWRIAN’s code so that the inherent strain equivalent nodal forces along the heating line are calculated and applied in the elastic shell analysis. However, a discrepancy between 3-dimensional thermal-elastic-plastic analysis and elastic analysis was observed. This is mainly because of the nature of solid and shell elements. RUIZ [3] proposed a linearized inherent strain and applied it to both 3-d and 2d analysis, getting matching results between solid and shell element models. In this study, as a working example, a thin plate panel with an opening is considered utilizing the developed system at the same time a friendly user interface for staffs and workers on a production site is developed.  Keywords: Inherent strain, straightening, finite element method, Gauss-Legendre quadratur

Impact of ship operations aided by voyage optimization on a ship’s fatigue assessment

In this study, different operation factors affecting a ship’s wave statistics are studied, such as the slow steaming and voyage optimizations. Especially, the impact of various voyage optimization methods on the long-term wave statistics and corresponding fatigue damage during ship operations is investigated by comparing the encountered waves with the design wave scatter diagram. Three years of full-scale measurements from a container ship sailing in the North Atlantic are employed to study the impact, in addition to noon reports from two fleets of container ships and VLCCs. Furthermore, the benefits of using voyage optimizations for minimum fatigue damage accumulation during operation are discussed. The large difference of wave statistics is found when the ship follows routes generated by various optimization methods and the design diagram. For some westbound voyages, the voyage optimization methods can significantly decrease the ship’s fatigue damage accumulations, leading to longer fatigue life

DEVELOPMENT OF A NEW FATIGUE TESTING MACHINE FOR HIGH FREQUENCY FATIGUE DAMAGE ASSESSMENT

ABSTRACT A new simple fatigue testing machine, which can carry out fast and low-cost fatigue tests of welded joints subject to wave with high frequency vibration, has been developed. This machine is designed for plate bending type fatigue tests, and wave load is applied by using motors with eccentric mass. Springing vibration is superimposed by attaching an additional vibrator to the test specimen, and whipping vibration is superimposed by an intermittent hammering. Fatigue tests which simulate springing and whipping by a conventional servo-type fatigue testing machines are very expensive and use a large amount of electricity. If one uses these conventional machines, it is difficult to simulate superimposed stress wave forms at high speed, and it takes long hours of testing to examine the high frequency effect. In contrast, it is found that fatigue tests can be carried out in fast, i.e. waves with 10Hz or higher frequency for out-of-plane gusset welded joint specimens with 12mm plate thickness by using the developed machine. The electricity to be used for fatigue tests could be minimal, for example one thousandth of that needed for conventional machines. These results demonstrate the superiority of the developed machine

Characterization of surface dielectric barrier discharge influenced by intermediate frequency for ozone production

The aim of this study is to investigate the effect of the intermediate frequency (1–10 kHz) of the sinusoidal driving voltage on the characteristics of a developed surface dielectric barrier discharge (SDBD)-based reactor having spikes on its discharge electrode. Moreover, its influence on the production of ozone and nitrogen oxide byproducts is evaluated. The results show that SDBD is operated in the filamentary mode at all the frequencies. Nevertheless, the pulses of the discharge current at high frequencies are much denser and have higher amplitudes than those at low frequencies. The analysis of the power consumed in the reactor shows that a small portion of the input power is dissipated in the dielectric material of SDBD source, whereas the major part of the power is consumed in the plasma discharge. The results of the ozone production show that higher frequencies have a slightly adverse effect on the ozone production at relatively high energy density values, where the ozone concentration is slightly decreased when the frequency is increased at the same energy density. The temperature of the discharge channels and gas is not a crucial factor for the decomposition of ozone in this reactor, while the results of the measurements of nitrogen oxides characteristics indicate that the formation of NO and NO2 has a significant adverse effect on the production efficiency of ozone due to their oxidation to another nitrogen oxides and their catalytic effect

Idiopathic Normal-Pressure Hydrocephalus: Temporal Changes in ADC during Cardiac Cycle

Normal-pressure hydrocephalus (NPH) is characterized by a clinical triad of ataxia, incontinence, and dementia, as well as dilated ventricles but normal cerebrospinal fluid (CSF) pressures. In patients with NPH, CSF shunt placement is effective for improving these symptoms (1). NPH has attracted attention as one of the few treatable causes of dementia. Diagnosis of idiopathic NPH (INPH) without a known cause of communicating hydrocephalus, including subarachnoid hemorrhage or meningitis, is particularly difficult (2). Moreover, to clarify the cause of NPH, accurately diagnose NPH, and identify appropriate patients for shunt surgery, several tests have been proposed, including cisternography, the CSF tap test, resistance measures, external lumbar drainage, and intracranial pressure recording, in addition to clinical findings and conventional imaging diagnosis with x-ray computed tomography or magnetic resonance (MR) imaging (3–6). It has also been reported (7) that a single standard for the prognostic evaluation of patients with INPH was lacking and that supplemental tests could increase the predictive accuracy of the prognosis. The CSF tap test is a particularly reliable examination, but it is invasive and has low sensitivity. It has been proposed that MR imaging CSF flow studies can be used to noninvasively obtain information about intracranial mechanical properties in INPH (eg, intracranial compliance) (2,8–12). However, the diagnostic utility of this latter method is still not established.Arterial inflow into the cranium induces venous and CSF outflow and displacement of the intracranial spinal cord during the cardiac cycle, resulting in pulsatile brain motion (12–14). Brain pulsation (ie, bulk motion) reportedly can give rise to artifactual phase dispersion and may lead to overestimation of the apparent diffusion coefficient (ADC) (15,16). Brockstedt et al (17) reported that ADC was not changed significantly during the cardiac cycle with the single-shot echo-planar imaging (EPI) sequence widely used in diffusion MR imaging. However, they analyzed only two delay times (100 and 400 msec) between the R peaks in the cardiac cycle. To more completely analyze ADC changes during the cardiac cycle, our own group has previously evaluated the temporal change in ADC during the entire cardiac cycle by using an electrocardiographically (ECG)-triggered single-shot diffusion EPI sequence to minimize bulk motion effect. As a result, we revealed in a previous study that white matter ADC changed significantly over the cardiac cycle and that such changes were synchronized with the arterial inflow (volume loading) at systole (18). We further hypothesize that changes in ADC during the cardiac cycle are related to the biomechanical properties of intracranial tissues; hence, observed temporal changes in ADC in diseases such as INPH that are characterized by low intracranial compliance (12) may well be different than those in other diseases. Therefore, the purpose of our study was to determine whether temporal changes in ADC over the cardiac cycle were different in patients with INPH as compared with patients with ex vacuo ventricular dilatation and healthy control subjects

Psychiatric disorders and clinical correlates of suicidal patients admitted to a psychiatric hospital in Tokyo

<p>Abstract</p> <p>Background</p> <p>Patients admitted to a psychiatric hospital with suicidal behavior (SB) are considered to be especially at high risk of suicide. However, the number of studies that have addressed this patient population remains insufficient compared to that of studies on suicidal patients in emergency or medical settings. The purpose of this study is to seek features of a sample of newly admitted suicidal psychiatric patients in a metropolitan area of Japan.</p> <p>Method</p> <p>155 suicidal patients consecutively admitted to a large psychiatric center during a 20-month period, admission styles of whom were mostly involuntary, were assessed using Structured Clinical Interviews for DSM-IV Axis I and II Disorders (SCID-I CV and SCID-II) and SB-related psychiatric measures. Associations of the psychiatric diagnoses and SB-related characteristics with gender and age were examined.</p> <p>Results</p> <p>The common DSM-IV axis I diagnoses were affective disorders 62%, anxiety disorders 56% and substance-related disorders 38%. 56% of the subjects were diagnosed as having borderline PD, and 87% of them, at least one type of personality disorder (PD). SB methods used prior to admission were self-cutting 41%, overdosing 32%, self-strangulation 15%, jumping from a height 12% and attempting traffic death 10%, the first two of which were frequent among young females. The median (range) of the total number of SBs in the lifetime history was 7 (1-141). Severity of depressive symptomatology, suicidal intent and other symptoms, proportions of the subjects who reported SB-preceding life events and life problems, and childhood and adolescent abuse were comparable to those of the previous studies conducted in medical or emergency service settings. Gender and age-relevant life-problems and life events were identified.</p> <p>Conclusions</p> <p>Features of the studied sample were the high prevalence of affective disorders, anxiety disorders and borderline PD, a variety of SB methods used prior to admission and frequent SB repetition in the lifetime history. Gender and age appeared to have an influence on SB method selection and SB-preceding processes. The findings have important implications for assessment and treatment of psychiatric suicidal patients.</p

Three cases of Asymptomatic Gastric Anisakiasis during health check-ups

　本邦での胃アニサキス症の報告例は多く，健康診断（以下：健診）や人間ドック診療において偶然発見される無症候性の胃アニサキス症の報告例も散見される．我々は，当施設の人間ドックで発見された胃アニサキス症３例を経験したので報告する．症例は58歳女性，66歳男性，73歳男性．自覚症状は全例で無症状であった．診断時期は12月から２月の冬季で，全例で検査数日前に鯖，イカ等の魚介類の生ものの摂食歴があった．血液検査所見では，白血球数は全例で正常範囲であり， CRP は２例で軽度の上昇を認めた（0.02 mg/dl，0.41 mg/dl，0.91 mg/dl）．好酸球数は２例で前回値より軽度の上昇を認めた（181/μl から322/μl，379/μl から540/μl）．胃内視鏡所見については，穿入部の発赤，浮腫，びらんを全例で認め，２例で非萎縮粘膜領域に虫体が穿入していた．背景胃粘膜所見は「胃炎の京都分類」で評価すると１例が萎縮やびまん性発赤等の所見のないH. pylori未感染胃相当であり，２例は除菌後の症例（木村・竹本分類：C2 type）であった．過去の報告例と同様，当院で診断した３症例は，全例が無症状で発見され，２例で好酸球数の上昇が認められた．健診・人間ドック診療において胃アニサキス症を検査前に強く疑うことは困難であるが，この疾患を念頭に入れ，無症状であっても十分な問診や内視鏡観察を行うことが重要である．　There are several reports of gastric anisakiasis, and some reports of asymptomatic gastric anisakiasis observed during health check-ups in Japan. We are reporting three cases of gastric anisakis found in health check-up in our hospital. These cases presented in a 58-year-old woman, a 66-year-old man, and a 73-year-old man. All the three cases were asymptomatic in nature. All the cases were observed during the winter season from December to February. The patients consumed fish such as mackerel, tuna, and squid before the examination. White Blood Cell (WBC) counts on blood tests was stable in all cases, whereas two cases exhibited a slight increase in C-reactive Protein (CRP) levels (0.41 mg/dl, 0.91 mg/ dl). Eosinophil count were slightly higher than the previous values in two cases (from 181/μl to 322/μl, and 379/μl to 540/μl). Endoscopic findings in the area invaded by the parasite showed redness, edema, and swelling. In addition to this, parasites penetrated the non-atrophic mucosal area in two cases. According to evaluation by the“Kyoto classification of gastritis”, one case was non-H. pylori infected stomach and 2 cases were post-eradication. All cases depicted asymptomatic gastric anisakiasis in our institutions and two cases indicated an increase in the eosinophil count. Even if it is asymptomatic, the eosinophil count may increase due to the effects of gastric anisakiasis. It is challenging to diagnose gastric anisakiasis before the examination in health check-ups. However, it is imperative to pay attention to this disease and to opt for endoscopic evaluations despite the absence of symptoms