Vibration-based methods for structural and machinery fault diagnosis based on nonlinear dynamics tools

This study explains and demonstrates the utilisation of different nonlinear-dynamics-based procedures for the purposes of structural health monitoring as well as for monitoring of robot joints

Vibration-based damage detection in plates by using time series analysis

This paper deals with the problem for vibration health monitoring (VHM) in structures with nonlinear dynamic behaviour. It aims to introduce two viable VHM methods that use large amplitude vibrations and are based on nonlinear time series analysis. The methods suggested explore some changes in the state space geometry/distribution of structural dynamic response with damage and their use for damage detection purposes. One of the methods uses the statistical distribution of state space points on the attractor of a vibrating structure, while the other one is based on the Poincaré map of the state space projected dynamic response. In this paper both methods are developed and demonstrated for a thin vibrating plate. The investigation is based on finite element modelling of the plate vibration response. The results obtained demonstrate the influence of damage on the local dynamic attractor of the plate state space and the applicability of the proposed strategies for damage assessment. The approach taken in this study and the suggested VHM methods are rather generic and permit development and applications for other more complex nonlinear structures

Large amplitude vibrations and damage detection of rectangular plates

In this work, geometrically nonlinear vibrations of fully clamped rectangular plates are used to study the sensitivity of some nonlinear vibration response parameters to the presence of damage. The geometrically nonlinear version of the Mindlin plate theory is used to model the plate behaviour. Damage is represented as a stiffness reduction in a small area of the plate. The plate is subjected to harmonic loading with a frequency of excitation close to the first natural frequency leading to large amplitude vibrations. The plate vibration response is obtained by a pseudo-load mode superposition method. The main results are focussed on establishing the influence of damage on the vibration response of the plate and the change in the time-history diagrams and the Poincaré maps caused by the damage. Finally, a criterion and a damage index for detecting the presence and the location of the damage is proposed. The criterion is based on analyzing the points in the Poincaré sections of the damaged and healthy plate. Numerical results for large amplitude vibrations of damaged and healthy rectangular and square plates are presented and the proposed damage index for the considered cases is calculated. The criterion demonstrates quite good abilities to detect and localise damage

Does Abnormal Sleep Impair Memory Consolidation in Schizophrenia?

Although disturbed sleep is a prominent feature of schizophrenia, its relation to the pathophysiology, signs, and symptoms of schizophrenia remains poorly understood. Sleep disturbances are well known to impair cognition in healthy individuals. Yet, in spite of its ubiquity in schizophrenia, abnormal sleep has generally been overlooked as a potential contributor to cognitive deficits. Amelioration of cognitive deficits is a current priority of the schizophrenia research community, but most efforts to define, characterize, and quantify cognitive deficits focus on cross-sectional measures. While this approach provides a valid snapshot of function, there is now overwhelming evidence that critical aspects of learning and memory consolidation happen offline, both over time and with sleep. Initial memory encoding is followed by a prolonged period of consolidation, integration, and reorganization, that continues over days or even years. Much of this evolution of memories is mediated by sleep. This article briefly reviews (i) what is known about abnormal sleep in schizophrenia, (ii) sleep-dependent memory consolidation in healthy individuals, (iii) recent findings of impaired sleep-dependent memory consolidation in schizophrenia, and (iv) implications of impaired sleep-dependent memory consolidation in schizophrenia. This literature suggests that abnormal sleep in schizophrenia disrupts attention and impairs sleep-dependent memory consolidation and task automation. We conclude that these sleep-dependent impairments may contribute substantially to generalized cognitive deficits in schizophrenia. Understanding this contribution may open new avenues to ameliorating cognitive dysfunction and thereby improve outcome in schizophrenia

Damage detections in nonlinear vibrating thermally loaded plates

In this work, geometrically nonlinear vibrations of fully clamped rectangular plates subjected to thermal changesare used to study the sensitivity of some vibration response parameters to the presence of damage and elevated temperature. The geometrically nonlinear version of the Mindlin plate theory is used to model the plate behaviour.Damage is represented as a stiffness reduction in a small area of the plate. The plates are subjected to harmonicloading leading to large amplitude vibrations and temperature changes. The plate vibration response is obtained by a pseudo-load mode superposition method. The main results are focussed on establishing the influence of damage on the vibration response of the heated and the unheated plates and the change in the time-history diagrams and the Poincaré maps caused by damage and elevated temperature. The damage criterion formulated earlier for nonheated plates, based on analyzing the points in the Poincaré sections of the damaged and healthy plate, is modified and tested for the case of plates additionally subjected to elevated temperatures. The importance of taking into account the actual temperature in the process of damage detection is shown

An investigation on vibration-based damage detection in circular plates

This study aims at the development of vibration-based health monitoring (VHM) methodology for thin circular plates. The possibility of using the first several natural frequencies of a circular plate for damage detection purposes is investigated first. The study then suggests a damage detection method, which considers a vibrating plate as a dynamic system and uses its time domain response represented in a new phase (state) space to extract damage sensitive characteristics. The paper introduces the idea of using large amplitude vibrations and nonlinear time series analysis for damage detection purposes. The suggested damage detection approach explores the possibility to use certain characteristics of the distribution of phase space points on the attractor of the system. It studies the histograms of this distribution and attempts to extract damage sensitive features. Three damage features are suggested and they are shown to detect damage at a rather low level using a finite element model of the plate. The method suggested is rather generic and permits development and application to more complex structures and real data

Grit dan Religiositas terhadap Work Engagement pada Pengurus Ormawa yang Beragama Kristiani di Surabaya

Pengurus Ormawa membutuhkan work engagement untuk mendukung proses kerjanya. Work Engagement merupakan kondisi pikiran yang positif dan adanya pemenuhan diri pada pekerjaan dengan timbulnya rasa puas sehingga melibatkan afeksi dan perasaan termotivasi untuk mencapai kesejahteraan individu melawan timbulnya burnout saat bekerja. Dalam JD-R model, individu dengan job demands dan job resources memerlukan personal resources untuk dapat menunjukkan work engagement dan salah satu bentuknya adalah konsistensi minat dan daya tahan individu dalam melaksanakan tugas dalam organisasi yang disebut juga dengan grit. Faktor personal resources juga berkaitan dengan konstruk religiositas pada individu yang merupakan tata cara individu dalam menjalankan ajaran keagamaannya. Tujuan penelitian ini adalah peneliti ingin menguji pengaruh antara grit dan religiositas terhadap work engagement pada pengurus Ormawa beragama Kristiani di Surabaya. Penelitian ini menggunakan metode penelitian kuantitatif dengan teknik purposive sampling. Pengumpulan data dilakukan dengan menggunakan kuesioner Google form dengan menyebarkan skala Utrecht Work Engagement Scale–9 (UWES-9), 12-Item Grit Scale, dan skala Religiositas dengan menurunkan berdasarkan aspek-aspek. Partisipan penelitian ini merupakan pengurus Ormawa beragama Kristiani (Kristen Protestan & Katolik) di periode 2022/2023. Penelitian ini memperoleh hasil adanya pengaruh yang signifikan antara Grit & Religiositas terhadap Work Engagement pada pengurus Ormawa beragama Kristiani di kota Surabaya. Sumbangan efektif yang diberikan pada penelitian ini sebesar 11,5% dan nilai sig. 0,002 (p<0,05) dengan persamaan garis linier y= 18,267 + 0,298x1 +0,083x2. Arti dari persamaan garis linier tersebut adalah setiap penambahan 1 poin Grit dan Religiositas akan menambah pula poin Work Engagement sebesar 0,38

SURVEI EPIDEMIOLOGI CEDERA OLAHRAGA PADA ATLET BULUTANGKIS DI INDONESIA

Dalam penelitian ini, penulis bertujuan untuk memetakan atau mengevaluasi tentang penyebaran cedera yang sering terjadi pada atlet bulutangkis dengan melakukan metode penelitian deskriptif kuantitatif menggunakan metode survei. Populasi dari penelitian adalah atlet bulutangkis berusia 17-22 tahun yang pernah mengalami cedera. Teknik pengumpulan data dilakukan dengan memberikan kuesioner kepada atlet bulutangkis yang pernah mengalami cedera. Dalam penelitian ini, peneliti mengumpulkan data kuesioner melalui google form yang dilakukan secara daring. Setelah data kuisoner terkumpul, kemudian data diproses dan dianalisis menggunakan SPSS. Hasil dari data kuesioner tersebut menunjukkan bahwa : (1) tubuh bagian bawah (lower body) sebagai bagian yang paling sering mengalami cedera. (2) cedera otot (strain) adalah yang cedera yang paling sering dialami atlet. (3) dari banyak faktor penyebab cedera, kelelahan menjadi penyebab terbesar terjadinya cedera

Can primary health care staff be trained in basic life-saving surgery?

The following article by Leet et al advocates training rural PHC staff in basic emergency surgery in those areas of South Sudan where there is no access to secondary or tertiary level facilities (i.e. surgical task-shifting). Based on their experience, the authors describe and recommend the type of on-the-job training that they feel is most suitable for this level of staff.Task-shifting at this time in South Sudan is a controversial topic and is not presently government policy. Please send us your views and tell us if you agree with the authors of this article. For example: Can rural middle level non-medical health staff be trained to safely carry out basic emergency surgical procedures? If so, what type of training is best? Should there be a recognized curriculum and accreditation? What further information would you like the authors to provide? Is your organisation training non-medical health staff in surgery (or other medical procedures)? If so, what are the results? Write to the editor at: [email protected]