Intermittent Contact Research Articles

The Potential of E-Health in Patients after Allogeneic Stem Cell Transplantation

Introduction Modern information and communication technologies (ICT) have become increasingly important in daily life as well as in patient-physician interaction, health monitoring and health related information (E-Health). Progress in allogeneic stem cell transplantation (allo-SCT) has led to improved survival and increasing numbers of patients. However, with a multitude of potential complications, follow-up of allo-SCT patients remains complex requiring close monitoring, support and treatment with a plethora of medical fields involved. Early studies have shown that E-Health can benefit caretaking of these patients. So far, only little information is known about the patients’ current use of E-Health and their perspective on its potential. Yet, this knowledge is of particular importance for re-structurization of follow-up after allo-SCT including the standardized use of E-Health and its comprehensive acceptance. This multicenter study aims to close this knowledge gap by investigating the patients’ view towards E-Health and use of telemedicine after allo-SCT. The results will help to facilitate the implementation of E-Health in standard follow-up after allo-SCT and other cellular therapies with a focus on patients’ perspective. Methods and Results Between May 2021 and June 2022, 237 patients after allo-SCT were asked to answer a structured questionnaire at the university hospitals Aachen, Bonn, Cologne and Duesseldorf (Center for Integrated Oncology, CIO ABCD) in Germany. Overall, 219 patients returned the questionnaire leading to a response rate of 92%. Of these, 34% were female and 66% were male with a median age of 59 years (range 18-81). In our patient cohort, the current distribution of internet-enabled computers/smartphones is over 90% and the electronic devices are mainly used for daily life activities. Nevertheless, the use of ICT in medical monitoring and patient-physician interaction is still limited. Only a minority of patients have digitized medication plans, use digital monitoring of health data/fitness-apps or own wearables for health monitoring such as smartwatches. In contrast, the majority of patients favors additional online patient-physician interaction such as scheduling and transmission of medical reports and 65% of the patients support real-time transmission of health data through wearables to the physician for a limited time period. Of note, 40-50% of patients have concerns regarding data safety, even more when using messenger services (67%). The majority of patients considers online chats or video calls with their physician to be beneficial and expects an improvement of the treatment quality through increased use of E-Health. Additionally, most patients favor local treatment with online correspondence between their local practitioner and a specialized center, especially if the patients are present during the online communication or with intermittent personal patient contact to the center. Subgroup analyses revealed that in most areas there is no gender difference in use and perspective on E-Health. However, male patients consider online chats more beneficial and expect an improved patient-physician interaction through increased use of ICT compared to females. Age and educational attainment are very significant factors in patients’ view on E-Health. Younger (<60 years) as well as higher educated patients favor increased use of online communication, applications and devices in almost all regards and expect benefits of patient-physician interaction and treatment quality, which is in significant contrast to the views of older or less educated patients. Hometown size or distance to a specialized center does not show a relevant impact on the view on E-Health. This is also true for time after allo-SCT or frequency of outpatient visits at the time of questioning. Conclusions Dissemination of internet-enabled devices is wide and the potential of E-Health is high in patients after allo-SCT. The majority of patients favors further standardized implementation of E-Health technologies and telemedically supported caretaking post allo-SCT and potentially other cellular therapies to improve patient-physician interaction and cross-sectoral care. Future research should focus on patients’ needs in the context of data safety and exchange of medical information in interdisciplinary care processes to successfully integrate new E-Health technologies.

Personalized vascular healthcare: insights from a large international survey.

Fragmentation of healthcare systems through limited cross-speciality communication and intermittent, intervention-based care, without insight into follow-up and compliance, results in poor patient experiences and potentially contributes to suboptimal outcomes. Data-driven tools and novel technologies have the capability to address these shortcomings, but insights from all stakeholders in the care continuum remain lacking. A structured online questionnaire was given to respondents (n = 1432) in nine global geographies to investigate attitudes to the use of data and novel technologies in the management of vascular disease. Patients with coronary or peripheral artery disease (n = 961), physicians responsible for their care (n = 345), and administrators/healthcare leaders with responsibility for commissioning/procuring cardiovascular services (n = 126) were included. Narrative themes arising from the survey included patients' desire for more personalized healthcare, shared decision-making, and improved communication. Patients, administrators, and physicians perceived and experienced deficiencies in continuity of care, and all acknowledged the potential for data-driven techniques and novel technologies to address some of these shortcomings. Further, physicians and administrators saw the 'upstream' segment of the care journey-before diagnosis, at point of diagnosis, and when determining treatment-as key to enabling tangible improvements in patient experience and outcomes. Finally, despite acceptance that data sharing is critical to the success of such interventions, there remains persistent issues related to trust and transparency. The current fragmented care continuum could be improved and streamlined through the adoption of advanced data analytics and novel technologies, including diagnostic and monitoring techniques. Such an approach could enable the refocusing of healthcare from intermittent contacts and intervention-only focus to a more holistic patient view.

Robust triboelectric-electromagnetic hybrid nanogenerator with maglev-enabled automatic mode transition for exploiting breeze energy

Exploiting the pervasive breeze energy is normally difficult due to the high start-up wind speed of the conventional electromagnetic generator (EMG) and the material abrasion of the emerging triboelectric nanogenerator (TENG). We report herein an automatic-mode-transition (AMT) strategy, which enables the TENG to work in intermittent-contact (IC) mode under a low wind speed of 2.4 m/s and automatically transition to noncontact (NC) mode with the increasing wind speed. Realized with a rationally designed maglev mechanism, the AMT-TENG can replenish the dissipated charges with very small friction drag and minute material abrasion, contributing to a low start-up speed, high mechanical durability, and enhanced electrical stability. During a 10-day durability test, the AMT-TENG can maintain 82 % of its incipient voltage; by contrast, the NC-TENG and C-TENG only retain 36 % and 10 % output voltage, respectively. The AMT-TENG can be upgraded easily to an AMT triboelectric-electromagnetic hybrid nanogenerator (AMT-TEHG) by simply adding pick-up coils, allowing the device to generate complementary electric outputs. By exploiting the breeze energy, the AMT-TEHG can serve not only as a self-sufficient wind speed sensor but also as a green energy source for some electronics. This work demonstrates a promising strategy for realizing robust TEHGs, which has great potential in breeze energy exploitation and self-sufficient sensing.

Influences of the Contact State between Friction Pairs on the Thermodynamic Characteristics of a Multi-Disc Clutch.

The relationship between clutch thermodynamic characteristics and contact states of friction components is explored numerically and experimentally. The clutch thermodynamic numerical model is developed with consideration of the contact state and oil film between friction pairs. The clutch bench test is conducted to verify the variation of the clutch thermodynamic characteristics from the uniform contact (UCS) to the intermittent contact (ICS). The results show that the oil film decreases gradually with increasing temperature; the lubrication state finally changes from hydrodynamic lubrication to dry friction, where the friction coefficient shows an increasing trend before a decrease. Thus, the friction torque in UCS gradually increases after the applied pressure stabilizes. When the contact state changes to ICS, the contact pressure increases suddenly and the oil film decreases rapidly in the local contact area, bringing about a sharp increase in friction torque; subsequently, the circumferential and radial temperature differences of friction components expand dramatically. However, if the contact zone is already in the dry friction state, friction torque declines directly, resulting in clutch failure. The conclusions can potentially be used for online monitoring and fault diagnosis of the clutch.

Finger-STS: Combined Proximity and Tactile Sensing for Robotic Manipulation

This paper introduces and develops novel touch sensing technologies that enable robots to better sense and react to to intermittent contact interactions. We present Finger-STS, a robotic finger embodiment of the See-Through-your-Skin (STS) sensor that can capture 1) an “in the hand” visual perspective of an object that is being manipulated and 2) a high resolution tactile imprint of the contact geometry. We demonstrate the value of the sensor on a Bead Maze task. Here the multimodal feedback provided by the Finger-STS is leveraged by a robot to locate a bead visually and to guide it across a wire in response to tactile cues, with no additional sensing or planning required. To achieve this, we introduce a set of relevant visuotactile operations using computer vision-based algorithms. In particular, we sense the proximity of the object relative to the sensor as well as the nature of contact as a high resolution stick/slip vector field tracking the object motion in the finger.

Transient dynamic analysis and experimental verification on lubrication regime transition during startup period of non-contacting mechanical seal in liquid oxygen turbopump

The transition process of lubrication regime during startup period of liquid oxygen lubricated seal is investigated. A comprehensive numerical model is proposed, which includes asperity contact, transient micro-clearance flow as well as dynamic motion with axial vibration and angular misalignment. The influence of structural and operational parameters on separation capacity is compared. Meanwhile, the transient response under a strong vibration environment is analyzed. An experimental verification combined with various sensors is designed to monitor film formation. Results show that leakage has obvious oscillation with high-frequency and low-amplitude when face separation. Excessive frequency or amplitude in a vibration environment may cause intermittent contact. Evidently different characteristics of acoustic emission signals are observed corresponding to various lubrication regimes during startup and shutdown.

The split-belt rimless wheel

Split-belt treadmill walking, in which the two belts move at different speeds, reveals a mechanism through which energy can be extracted from the environment. When a person walks with positive step length asymmetry on a split-belt treadmill, the treadmill can perform net positive work on the person. Here we use a split-belt rimless wheel model to explore how people could take advantage of the treadmill. We show that a split-belt rimless wheel can passively walk steadily by capturing energy from the treadmill to overcome collision losses, whereas it loses energy on each step with no way to recover the losses when walking on tied belts. Our simulated split-belt rimless wheel can walk steadily for a variety of leg angle and belt speed combinations, tolerating both speed disturbances and ground height variability. The wheel can even capture enough energy to walk uphill. We also built a physical split-belt rimless wheel robot and demonstrated that it can walk continuously without additional energy input. In comparing the wheel solutions to human split-belt gait, we found that humans do not maximize positive work performed by the treadmill. Other aspects of walking, such as costs associated with swing, balance, and free vertical moments, likely limit people’s ability to benefit from the treadmill. This study uses a simple walking model to characterize the mechanics and energetics of split-belt walking, demonstrating that energy capture through intermittent contact with two belts is possible and providing a simple model framework for understanding human adaptation during split-belt walking.

The Hidden Flower in WS2 Flakes: A Combined Nanomechanical and Tip-Enhanced Raman Exploration.

We report on tungsten disulfide (WS2) flakes grown by chemical vapor deposition (CVD), which exhibit a flower-like surface structure above the primary few-layer flake with a triangular shape. The fine structure is only revealed in the mechanical, chemical, and electronic properties of the flake but not in the topography. The origin of this structure is the peculiar one-step growth during the CVD process that permits to control the sulfur concentration at any time. A high concentration of S at the onset of the deposition process leads to a rapid growth of the flake, resulting in tungsten vacancies. Reducing the sulfur concentration toward the end of the growth slows down the reaction and leads to sulfur vacancies. These microscale domains were studied by confocal- and tip-enhanced Raman spectroscopy revealing their chemical composition with high spatial resolution. A strong quenching of the photoluminescence in the tungsten-vacancy domains is observed. Atomic force microscope measurements, performed in intermittent contact mode, force modulation mode (including lateral force mode), and PeakForce quantitative nanomechanics mode, show that the mechanical properties of these domains differ. Within the tungsten-vacancy domains, the adhesion force is reduced, while the friction force increased. Kelvin probe force microscopy measurements show that the electronic properties of the flakes are modulated by these domains. The combined nanomechanical and nanospectroscopy measurements provide detailed insights on the inhomogeneous surface properties of the single WS2 flake, further highlighting how its multidomain properties can be finely tuned using CVD.

Socializing Models During Lactation Alter Colonic Mucosal Gene Expression and Fecal Microbiota of Growing Piglets.

The enrichment of the social environment during lactation alleviates the stress of weaned piglets. It is significant to understand how the enriched social environment improves the weaning stress of piglets. RNA sequencing (RNA-seq) of colonic mucosa, 16S rRNA sequencing of feces, and short-chain fatty acids (SCFAs) of colonic content were used to determine the effects of social contact during lactation. In this study, thirty litter lactating piglets were divided into intermittent social contact (ISC) group that contacted with neighbors intermittently, continuous social contact (CSC) group that contacted with neighbors starting at day (D) 14 after birth, and control (CON) group in which piglets were kept in their original litter. The piglets were weaned at D35 and regrouped at D36. The colonic mucosal RNA-seq, fecal microbes, and SCFAs of colonic contents of 63-day-old piglets were analyzed. The results of RNA-seq showed that compared with the CON group, the pathways of digestion and absorption of minerals, protein, and vitamins of piglets were changed in the ISC group, whereas the pathways of retinol metabolism and nitrogen metabolism in the colonic mucosal were affected and stimulated the immune response in the CSC group. Compared with the CON group, the abundances of pernicious microorganisms (Desulfovibrio, Pseudomonas, Brevundimonas, etc.) in the CSC group and pernicious microorganisms (Desulfovibrio, Neisseria, Sutterella, etc.) and beneficial bacteria (Bifidobacterium, Megamonas, and Prevotella_9) in the ISC group were significantly higher (p < 0.05). The abundances of proinflammatory bacteria (Coriobacteriaceae_unclassified, Coprococcus_3, and Ruminococcus_2) in the CSC group were significantly increased (p < 0.05), but the abundances of SCFAs producing bacteria (Lachnospiraceae_UCG-010, Parabacteroides, Anaerotruncus, etc.) and those of anti-inflammatory bacteria (Eubacterium, Parabacteroides, Ruminiclostridium_9, and Alloprevotella) were significantly reduced (p < 0.05) in the CSC group. Compared with the CON group, the concentrations of microbial metabolites, acetate, and propionate in the colonic contents were reduced (p < 0.05) in the ISC group, whereas the concentration of acetate was reduced (p < 0.05) in the CSC group. Therefore, both ISC and CSC during lactation affected the composition of fecal microbes and changed the expression of intestinal mucosal genes related to nutrient metabolism and absorption of piglets.

Patterning SS304 Surface at Microscale to Reduce Wettability and Corrosion in Saline Water

Stainless steel 304 (SS304) experiences corrosion when it is exposed to a saline atmosphere, which attains severity due to its high surface wettability. Topographical modification of metallic surfaces is an effective route to reduce wettability and thereby mitigate liquid-mediated corrosion. In this work, topographical modification of stainless steel 304 flat surface in the form of micropillars was done (pillar width: 100 μm, inter-pillar distance: 100 μm and height: 80 μm). Micropillars were fabricated by a chemical etching process. Wetting and corrosion of the micropillars was studied over long-time duration in comparison with flat surface, before and after intermittent and continuous exposures to saline water for 168 h. Wetting was characterized by measuring the static water contact angle on the test surfaces and their corrosion by electrochemical polarization tests (electrolyte: 3.5 wt.% sodium chloride solution). The relationship between the nature of wetting of the test surfaces and their corrosion was examined. Micropillars showed predominantly composite wetting over a long time, which imparted an effective resistance against corrosion over a long time to the SS304 surface. When compared to the flat surface, the corrosion rates of the micropillars were lower by two orders of magnitude, prior to and also upon long-time contact with the NaCl solution. Micropillars lowered corrosion due to composite wetting, i.e., solid-liquid-air interface that reduced the area that was in contact with the NaCl solution. The efficiency of corrosion inhibition (η) of micropillars was 88% before long-time contact, 84% after intermittent contact, and 77% after continuous contact with NaCl solution. Topographical modification in the form of micropillars that can impart composite wetting is an effective route to induce long-term anticorrosion ability to the SS304 surface.

Use of current imaging tools for the study of odontogenic myxoma. A review of the literature

Odontogenic myxoma (OM) is currently classified as a benign tumor of ectomesenchymal origin, observed between the second and fourth decade of age, with a predilection in women and predominance in the mandibular region, composed of rounded and angular cells embedded in an abundant myxoid stroma, of aggressive biological behavior, having the characteristic of being locally infiltrative. Tumor cells spread in the intratrabecular space beyond the bone limit, making it difficult to determine the edge of the tumor, even without cortical continuity, presenting intermittent direct contact with soft tissue; the appearance can be unilocular (small lesions), or commonly the typical image is that of a destructive lesion with poorly defined borders with a multilocular growth pattern, for which the use of advanced medical images such as Cone Beam Computed Tomography (CTHC), Computed Tomography (CT), Magnetic Resonance Imaging (MRI), are useful to establish an adequate diagnosis with the ability to point out the characteristics of OM with precision and three-dimensional perspective. This review presents a systematic analysis of the types of imaging tools currently used for the study of OM.

Motion Strategies for a Cobot in a Context of Intermittent Haptic Interface

Abstract From the list of interfaces used in virtual reality systems, haptic interfaces allow users to touch a virtual world with their hands. Traditionally, the user’s hand moves the end-effector of a robotic arm. When there is no contact in the virtual world, the robotic arm is passive; when there is contact, the arm suppresses mobility to the user’s hand in certain directions. Unfortunately, the passive mode is never completely seamless to the user. Haptic interfaces with intermittent contacts are interfaces using industrial robots that move towards the user when contact needs to be made. As the user is immersed in the virtual world via a virtual reality head mounted display (HMD), he cannot perceive the danger of a collision when he changes his area of interest in the virtual environment. The objective of this article is to describe four movement strategies for the robot to be as fast as possible on the contact zone while guaranteeing safety. This work uses the concept of predicting the user’s intention through his gaze direction and the position of his dominant hand (the one touching the object) and safe-points outside the human workspace. Experiments are done and analyzed with a Pareto front with a UR5 robot, an HTC vive tracker system for an industrial application involving the analysis of materials in the interior of a car.

Ultrastructural characterisation of young and aged dental enamel by atomic force microscopy.

Recent advances in atomic force microscopy (AFM) have allowed the characterisation of dental-associated biomaterials and biological surfaces with high resolution. In this context, the topography of dental enamel - the hardest mineralised tissue in the body - has been explored with AFM-based approaches at the microscale. With age, teeth are known to suffer changes that can impact their structural stability and function; however, changes in enamel structure because of ageing have not yet been explored with nanoscale resolution. Therefore, the aim of this exploratory work was to optimise an approach to characterise the ultrastructure of dental enamel and determine potential differences in topography, hydroxyapatite (HA) crystal size, and surface roughness at the nanoscale associated to ageing. For this, a total of six teeth were collected from human donors from which enamel specimens were prepared. By employing intermittent contact (AC mode) imaging, HA crystals were characterised in both transversal and longitudinal orientation (respect to surface plane) with high resolution in environmental conditions. The external enamel surface displayed the presence of a pellicle-like coating on its surface that was not observable on cleaned specimens. Acid-etching exposed crystals that were imaged and morphologically characterised in high resolution at the nanoscale in both the external and internal regions of enamel in older and younger specimens. Our results demonstrated important individual variations in HA crystal width and roughness parameters across the analysed specimens; however, an increase in surface roughness and decrease in HA width was observed for the pooled older external enamel group compared to younger specimens. Overall, high-resolution AFM was an effective approach for the qualitative and quantitative characterisation of human dental enamel ultrastructure. Future work should focus on exploring the ageing of dental enamel with increased sample sizes to compensate for individual differences as well as other potential confounding factors such as behavioural habits and mechanical forces.

Atomic Force Microscope with an Adjustable Probe Direction and Integrated Sensing and Actuation

This article presents the application and evaluation of a cantilever with integrated sensing and actuation as part of an atomic force microscope (AFM) with an adjustable probe direction, which is integrated into a nano measuring machine (NMM-1). The AFM, which is operated in closed-loop intermittent contact mode, is based on two rotational axes that enable the adjustment of the probe direction to cover a complete hemisphere. The axes greatly enlarge the metrology frame of the measuring system by materials with a comparatively high coefficient of thermal expansion, which ultimately limits the achievable measurement uncertainty of the measuring system. Thus, to reduce the thermal sensitivity of the system, the redesign of the rotational kinematics is mandatory. However, in this article, some preliminary investigations on the application of a self-sensing cantilever with an integrated micro heater for its stimulation will be presented. In previous investigations, a piezoelectric actuator has been applied to stimulate the cantilever. However, the removal of the piezoelectric actuator, which is enabled by the application of a cantilever with an integrated micro heater, promises an essential simplification of the sensor holder. Thus, in the future it might be possible to use materials with a low coefficient of thermal expansion, which are often difficult to machine and therefore only allow for rather simple geometries. Furthermore, because of the creepage of piezoelectric actuators, their removal from the metrology frame might lead to improved metrological characteristics. As will be shown, there are no significant differences between the two modes of actuation. Therefore, the redesigned rotational system will be based on the cantilever with integrated sensing and actuation.

Optimum coating thickness for the fastest chilldown of Teflon-coated stainless steel flat plate in liquid nitrogen pool

In this study, a novel model was developed to accurately determine the optimum thickness of a low-thermal-conductivity coating layer applied on a stainless steel flat plate resulting in the fastest chilldown of the plate in a cryogenic liquid pool. A low-thermal-conductivity layer coated on a metal surface is known to significantly reduce the cryogenic chilldown time of the metal by facilitating the early transition from film to nucleate boiling. However, there is still a lack of models to estimate the optimum coating thickness. An attempt has been made to address this issue. To do so, the authors first investigated the transient pool boiling of liquid nitrogen on Teflon-coated stainless-steel plates with various coating thicknesses ranging from 0 to 300 μm. Both the pool mass and plate temperature over time were measured and used to determine the heat flux into the liquid pool. A coating layer that results in a lower thermal resistance during film boiling would lead to a higher thermal resistance in nucleate boiling. As the thickness of the coating layer increases, the thermal resistance in film boiling decreases and the transition from film to nucleate boiling occurs earlier. The early transition of the boiling regimes was successfully explained by the assumption of intermittent liquid-solid contact during the film-boiling regime. The coating thickness in the range of 100–150 μm was observed to be the optimum thickness that resulted in both the smallest thermal resistance and earliest transition of boiling regimes. Subsequently, a new model to estimate the optimum coating thickness was derived based on experimental observations and the assumption of intermittent liquid-solid contact. The findings of this study are expected to be beneficial in enhancing the chilldown efficiency of cryogenic systems.

Atrial Embolization after a Transcatheter Mitral Valve Replacement

Atrial Embolization after a Transcatheter Mitral Valve Replacement

Effect of gravity conditions on heat transfer and flow fluctuations of liquid hydrogen in a non-isothermal horizontal circular tube

Liquid hydrogen phase transition is a common phenomenon in space missions for space vehicles using low temperature liquid hydrogen as propellant. In this study, a numerical model with coupled RANS solver and VOF/Level-set method was used to simulate the liquid hydrogen phase transition in a non-isothermal horizontal circular tube under different gravity conditions (1g-10−4 g). The gas phase hydrogen produced by evaporation of liquid hydrogen was calculated by Lee model. The statistics of the overall volume, heat flux, mass flow rate, mean velocity of gas phase hydrogen was carried out. The data results shown that the flow fluctuations were strongest under the gravity acceleration of 10−1 g relative to other gravity conditions. The average bubble volume at 10−1 g was the smallest, which was 11.58% smaller than that at 10−3 g condition. The intermittent contact with the tube wall, which leaded to intermittent long bubble and flow resistance, was the main reason.

Boxcar Averaging Scanning Nonlinear Dielectric Microscopy.

Scanning nonlinear dielectric microscopy (SNDM) is a near-field microwave-based scanning probe microscopy method with a wide variety of applications, especially in the fields of dielectrics and semiconductors. This microscopy method has often been combined with contact-mode atomic force microscopy (AFM) for simultaneous topography imaging and contact force regulation. The combination SNDM with intermittent contact AFM is also beneficial for imaging a sample prone to damage and using a sharp microscopy tip for improving spatial resolution. However, SNDM with intermittent contact AFM can suffer from a lower signal-to-noise (S/N) ratio than that with contact-mode AFM because of the shorter contact time for a given measurement time. In order to improve the S/N ratio, we apply boxcar averaging based signal acquisition suitable for SNDM with intermittent contact AFM. We develop a theory for the S/N ratio of SNDM and experimentally demonstrate the enhancement of the S/N ratio in SNDM combined with peak-force tapping (a trademark of Bruker) AFM. In addition, we apply the proposed method to the carrier concentration distribution imaging of atomically thin van der Waals semiconductors. The proposed method clearly visualizes an anomalous electron doping effect on few-layer Nb-doped MoS2. The proposed method is also applicable to other scanning near-field microwave microscopes combined with peak-force tapping AFM such as scanning microwave impedance microscopy. Our results indicate the possibility of simultaneous nanoscale topographic, electrical, and mechanical imaging even on delicate samples.

Evaluation of two collocated federal equivalent method PM2.5 instruments over a wide range of concentrations in Sarajevo, Bosnia and Herzegovina

Two widely used PM2.5 monitors in the United States (U.S.) designated as federal equivalent methods (FEMs) by the U.S. Environmental Protection Agency were collocated for 15 months in Sarajevo, Bosnia and Herzegovina (BiH) to evaluate their comparability. With differing measurement principles, the FEMs (Met One BAM-1020 and Teledyne API T640) exhibited unique responses to the significant range in PM2.5 over the study period. During the winter months when concentrations greatly increased (e.g., daily PM2.5 > 100 μg m−3), the BAM-1020 had intermittent malfunctioning nozzle contact to the collection tape, resulting in periods of data invalidation. Increased operator observation and doubling the cleaning frequency were required to maintain proper operation. The hourly data from the BAM-1020, which detects PM2.5 via beta-attenuation of particles loaded to the collection tape, indicated higher noise at concentrations below 40 μg m−3 relative to the T640, which detects PM2.5 via an optical method. Above this concentration threshold, the two instruments appear to have comparable hourly fluctuations in the data. Relative to the BAM-1020, the T640 reported higher concentrations when PM2.5 is above 80 μg m−3. A linear regression equation was developed and applied to adjust T640 PM2.5 high concentration values, resulting in 24-hr average T640adj PM2.5 values closely matching that from the BAM-1020 for the full concentration range. Based on the T640adj values, the annual average for Sarajevo was calculated at the site to be 42 μg m−3, with significant seasonality resulting in over 7-fold higher concentrations in the months of December–January compared to June–July.

Influence of wheel flat on railway vehicle helical gear system under Traction/Braking conditions

The gear system is an essential component of railway vehicles. However, wheel flat often affects the gear system's fault diagnosis and fatigue life and further jeopardizes vehicle operation safety. This paper develops a railway vehicle model equipped with a helical gear system. The model validation uses the experimental data under various operating conditions. The discussion of the simulation results involves the time-domain and time–frequency domain responses of the gear system of a vehicle with the wheel flat under variable speed conditions. Simultaneously, the analysis of its regularity uses the peak-to-peak value as characteristic vibration indicators. The results show that the wheel-rail contact status has two regions: the continuous contact region and the intermittent contact region. The vibration of the gear system is relatively stable in the continuous contact region. However, it fluctuates sharply in the intermittent contact region. In the time–frequency domain results, the fundamental frequency of the wheel flat and its multiplier gradually replaces the healthy gear meshing frequency and its multiplier as the primary contributor to energy. Furthermore, the peak-to-peak value shows that the gear system vibrates significantly under critical conditions. The above results can help improve the gear system's stability and thus the running stability and safety of railway vehicles.