Damp Conditions Research Articles

Chilblain-Like Lesions in COVID-19: A Detailed Review

Coronavirus disease (COVID-19) was declared a pandemic in early 2020. Since then, it has continued to spread havoc in the lives of millions of people. The Covid-19 infection can have a spectrum of symptoms, ranging from asymptomatic infection to a fatal multi-organ failure. A number of unusual manifestations have also been reported. Among them are pernio-like lesions, also referred to as Chilblain-like lesions. Previously, these skin lesions were associated with damp conditions and autoimmune diseases. But, their presentation in this pandemic has confused the clinicians. It is very important to understand the clinical picture, pathophysiology, histology, and treatment of these lesions, especially in the COVID era. Hence, in this review, we have made an effort to understand these lesions further. The main aim of our article is to provide physicians with a detailed analysis of chilblains like lesions so that this can help them with diagnosis and treatment.

Research on the influence of humid heat environment on the mechanical properties of multilayer composite structure

For resin-based composite materials, the hot and humid environment has a very obvious impact on its performance. Moisture can penetrate into the composite material through diffusion and capillary action, which causes the resin matrix with plasticization, swelling and hydrolysis, and swelling and infiltration of liquid will lead to micro-stress inside the material. Thus, the polymer macromolecular chain will stretche or even break, and it can lead to the weakening of the interface properties of the resin and the fiber, which in turn leads to fluctuations in the mechanical properties of the composite material. In this paper, we carried out damp and heat tests on multilayer composite structures to study the effects of different temperature and humidity environments on the physical and chemical properties and mechanical properties of composite materials. The law of moisture absorption characteristics of composite materials is clarified, and the moisture absorption in the initial stage of moisture absorption is proportional to the moisture absorption time t1/2. With time increasing, the moisture absorption gradually tends to balance, and the higher are the damp and heat conditions, the greater the moisture absorption of the composite material will be. The moisture absorption is between 0.13% and 0.78% with different damp and heat environments. The chemical structure of the composite material itself has not changed significantly, and the damp-heat effect will induce the destruction of the fiber-matrix interface and the expansion of cracks along the pores, which weakens the bonding strength of the interface. As a result, the moisture makes the transverse performance and shear performance of the composite material greatly reducing, but has little effect on the longitudinal performance.

Parameters optimization of release force under top-excited in stuck pipe

Stuck drilling accident is one of the most frequent accidents in the drilling process. The operation time of release drilling is also one of the most time-consuming operations in workover process. In recent years, the technique of release, by drilling string resonance, has been introduced into the drilling field, greatly reducing working hours and improving efficiency. In this paper, the release force’s sensitivity analysis is introduced to optimize the design parameters of the device and the working parameters of the release process. First, the pipe vibration behavior under the surface vibration agitator’s action is analyzed, and the natural frequencies are obtianed analytically. Second, based on Rayleigh damping and specific boundary conditions, the damping effect equation of drilling fluid is derived under drill string vibration. Finally, the influence of structural parameters, environmental parameters, and working parameters on the clamping force is obtained. This paper casts carry through the theoretical interpretation of the release force’s sensitivity analysis by stuck release mechanism and is of significance to optimize the stuck release operations.

Study of novel high-density panels based on negative space welding technology with cells cut by different techniques

Negative space welding technology (NSWT) is a newly adopted advanced technology for high-density solar panels. The benefit of this technology is its capability to improve the efficiency of panels. However, the introduction of a new technology or material may affect the original reliability. Some unexpected power loss may occur during its operation in different environments. Hence, in this work, damp heat (DH), thermal cycle (TC), UV irradiation and humidity freezing (HF) tests were utilized to evaluate the weatherability of NSWT-based panels fabricated with silicon cells cut by two different techniques. It is suggested by our results that these new panels with negative space between cells have good weatherability both in damp heat, dry heat and UV irradiation condition. The novel low-damage laser-induced cutting technique is beneficial for the improvement of module reliability.

Nonintrusive Inspection of Moisture Damp in Composited Insulation Structure Based on Terahertz Technology

Moisture damp has been identified as one of the most harmful agents of multilayer composited insulation, which can seriously accelerate its degradation, cause unexpected failure, and even lead to catastrophic accidents. This article proposes a nonintrusive method for moisture inspection of multilayer insulation structure based on terahertz (THz) technology with a focus on the cable terminal of the electric multiple units (EMUs). First, a three-layer scattering model is established based on the actual structure of the composite cable terminal, and theoretical analysis is performed to reveal the potential application mechanism. Based on that, an artificial model of a three-layer structure is then built on which the insulation damp test is carried out. Finally, the THz spectrum and THz imaging tests are performed. Results show that the frequency-domain signal can effectively identify the moisture inside the multilayer composited insulation. The imaging results in the frequency domain of the sample can accurately determine the geometric parameters of the damp area. By further analyzing the time-domain spectroscopy, the thickness of insulation affected by moisture can be identified quantitatively. This article verifies the feasibility of THz technology in inspecting the moisture dampness of multilayer composite insulation and its potential application in the damp condition assessment of EMU cable terminals.

Experimental investigation and performance comparison of a 1 single OWC, array and M-OWC

Ocean wave energy continues to develop through innovation and a growing number of collaborations around the world. With the vast resource of wave energy on our doorstep it remains a focal point in ocean energy engineering with great potential. In order for wave energy to become more competitive and a serious player in the renewable energy mix, such innovations should not only benefit the wave energy sector but also other technological applications by providing attractive options for synergies in novel projects. This paper concerns the experimental investigation of Oscillating Water Column (OWC) Wave Energy Converter (WEC) technology and its potential as a Multi-Oscillating Water Column (M-OWC). This research investigation utilises a progressive and pragmatic experimental modelling approach, by cross comparing the models of a single standalone OWC, an OWC array and finally a modular M-OWC under the same environment and test conditions. Performance and characteristic responses are analysed while varying the values of OWC spacing, damping and wave conditions. The results indicate that the spacing of OWC chambers significantly affects the performance of an M-OWC. While performance improves with the increase of spacing, the efficiency of the M-OWC is greater than that of a single OWC or the OWC array at reduced spacing values. In addition, the results indicate that an OWC array is less efficient by having individual power take-off systems operating in isolation as opposed to the modular M-OWC.

Investigation of the generation mechanism of squeal noise under non-negative damping conditions

The traditionally known generation mechanism of squeal noise is generally agreed to be the negative damping theory, which is represented by the negative slope of friction creepage curve. Recently, however, it was found that squeal noise still can be generated when the negative slope is eliminated. To investigate this phenomenon, water-based and oil-based friction modifiers are applied on a test rig to create non-negative damping conditions. The adhesion ratios at various rolling speeds are measured, and it is found that the negative slopes of friction curves can be eliminated when using friction modifiers, but squeal noise still exists. To investigate this phenomenon, a model involving the effect of vertical dynamics on squeal noise is developed in this research. The results show that the involvement of vertical dynamics has negligible effect on wheel vibration velocity when the friction creepage curve has a negative slope. When the friction creepage curve has a zero or positive slope, however, the results show that a stable lateral vibration still can be generated when vertical dynamics is involved. The generation mechanism of wheel squeal involving vertical dynamics is illustrated from the perspective of power input. Furthermore, the sound pressure levels of squeal noise are simulated using this model and the results correlate well with experimental measurements. Therefore, the results indicate that the vertical dynamics may be the reason why squeal noise still exists under non-negative damping conditions.

Practically Viable Approach to Efficient and Reliable Semitransparent Flexible Organic Solar Cells: Face‐Seal Encapsulation Embedded with Tailored Color‐Control Functionality

The success of semitransparent organic solar cells (ST‐OSCs) depends heavily on whether they can achieve high efficiency while meeting the conditions for high transmittance or target apparent color. Herein, a device architecture for ST‐OSCs that achieves both enhanced efficiency and controlled apparent color or high transmittance is proposed, while providing protection from ambient air. In the proposed scheme, cells are encapsulated by a barrier foil embedded with a color‐controlling dielectric mirror (CCDM) structure, which is tailored for selective reflection at the targeted spectral band and transmission in the other spectral band. This approach effectively enhances the photocurrent with little compromise in transmittance, yet it allows control of the color of ST‐OSCs. Preparing these CCDMs independently of cell fabrication, the best material composition is utilized without damaging the underlying layers. With the proposed approach, ST‐OSCs with an efficiency of 8.30% and luminous transmittance over 30.4% are demonstrated. Furthermore, by setting ST‐OSCs in the neutral plane utilizing face‐seal encapsulation geometry, it is shown that these devices can maintain 98% of the initial efficiency even after 2000 cycles of repeated bending at a strain of 0.5%. Moreover, they can maintain initial efficiency very well in a highly damp condition for 120 h.

Towards Autonomous Control of Magnetic Suture Needles.

This paper proposes a magnetic needle steering controller to manipulate mesoscale magnetic suture needles for executing planned suturing motion. This is an initial step towards our research objective: enabling autonomous control of magnetic suture needles for suturing tasks in minimally invasive surgery. To demonstrate the feasibility of accurate motion control, we employ a cardinally-arranged four-coil electromagnetic system setup and control magnetic suture needles in a 2-dimensional environment, i.e., a Petri dish filled with viscous liquid. Different from only using magnetic field gradients to control small magnetic agents under high damping conditions, the dynamics of a magnetic suture needle are investigated and encoded in the controller. Based on mathematical formulations of magnetic force and torque applied on the needle, we develop a kinematically constrained dynamic model that controls the needle to rotate and only translate along its central axis for mimicking the behavior of surgical sutures. A current controller of the electromagnetic system combining with closed-loop control schemes is designed for commanding the magnetic suture needles to achieve desired linear and angular velocities. To evaluate control performance of magnetic suture needles, we conduct experiments including needle rotation control, needle position control by using discretized trajectories, and velocity control by using a time-varying circular trajectory. The experiment results demonstrate our proposed needle steering controller can perform accurate motion control of mesoscale magnetic suture needles.

Nonlinear vibration and chaos of a moving flexible graphene smart electronic web

Flexible graphene smart electronics are a kind of electronic device made of silver or other inorganic material and a flexible graphene web substrate. Because of their flexibility and excellent electronic properties, flexible graphene smart electronics have become a research topic of interest. However, during the mass production process, the high-speed transmission of the continuous tension state is susceptible to external disturbances, which seriously restricts the improvement of the flexible graphene smart electronic printing speed. Therefore, studying the dynamic characteristics of moving flexible graphene electronic materials is of great significance for improving their quality and production efficiency. This paper considers a roll-to-roll smart RFID label graphene web as the research object. Based on the energy functional variational theory, the Bubnov-Galerkin method is used to eliminate the residual value of the dynamic Von Karman partial differential equation, and a discrete forced nonlinear vibration control equation for a moving flexible graphene smart electronic web is established. The Melnikov method is used to obtain the Melnikov function of the orbit parameter for the vibration control equation and solve the conditions of the chaos criterion. Using the fourth-order Runge-Kutta method, the nonlinear vibration phase-plane portraits, Poincare maps, time history diagram, and power spectra of the moving flexible graphene smart electronic web are obtained. The effects of the web moving speed, external damping, and initial system conditions on nonlinear dynamic behaviour are calculated, and the stable and unstable working regions of the moving flexible graphene smart electronic web are obtained. This research provides a theoretical basis for the dynamic stability and vibration control of a moving graphene smart electronic web.

A New Class of History–Dependent Evolutionary Variational–Hemivariational Inequalities with Unilateral Constraints

In this paper we study a new abstract evolutionary variational–hemivariational inequality which involves unilateral constraints and history–dependent operators. First, we prove the existence and uniqueness of solution by using a mixed equilibrium formulation with suitable selected functions together with a fixed-point principle for history–dependent operators. Then, we apply the abstract result to show the unique weak solvability to a dynamic viscoelastic frictional contact problem. The contact law involves a unilateral Signorini-type condition for the normal velocity combined with the nonmonotone normal damped response condition while the friction condition is a version of the Coulomb law of dry friction in which the friction bound depends on the accumulated slip.

From a Pinecone to Design of an Active Textile.

Botanical nastic systems demonstrate non-directional structural responses to stimuli such as pressure, light, chemicals or temperature; hygronasty refers to systems that respond specifically to moisture. Many seed dispersal mechanisms such as wheat awns, legume pods, spruce and pinecones fall within this classification. The variety of behaviours varies greatly from opening and closing to self-digging, but the mechanism is based on differential hygroscopic swelling between two adjacent areas of tissue. We describe the application of hygronastic principles specifically within the framework of textiles via the lens of structural hierarchy. Two novel prototypes are presented. One is designed to increase its permeability to airflow in damp conditions and reduce permeability in the dry by 25–30%, a counterintuitive property compared to conventional cotton, wool and rayon textiles that decrease their permeability to airflow as their moisture content increases. The second prototype describes the design and development of a hygroscopic shape changing fibre capable of reducing its length in damp conditions by 40% when compared with dry.

Thermal and Multispectral Remote Sensing for the Detection and Analysis of Archaeologically Induced Crop Stress at a UK Site

In intensively cultivated landscapes, many archaeological remains are buried under the ploughed soil, and detection depends on crop proxies that express subsurface features. Traditionally these proxies have been documented in visible light as contrasting areas of crop development commonly known as cropmarks. However, it is recognised that reliance on the visible electromagnetic spectrum has inherent limitations on what can be documented, and multispectral and thermal sensors offer the potential to greatly improve our ability to detect buried archaeological features in agricultural fields. The need for this is pressing, as ongoing agricultural practices place many subsurface archaeological features increasingly under threat of destruction. The effective deployment of multispectral and thermal sensors, however, requires a better understanding of when they may be most effective in documenting archaeologically induced responses. This paper presents the first known use of the FLIR Vue Pro-R thermal imager and Red Edge-M for exploring crop response to archaeological features from two UAV surveys flown in May and June 2019 over a known archaeological site. These surveys provided multispectral imagery, which was used to create vegetation index (VI) maps, and thermal maps to assess their effectiveness in detecting crop responses in the temperate Scottish climate. These were visually and statistically analysed using a Mann Whitney test to compare temperature and reflectance values. While the study was compromised by unusually damp conditions which reduced the potential for cropmarking, the VIs (e.g., Normalised Difference Vegetation Index, NDVI) did show potential to detect general crop stress across the study site when they were statistically analysed. This demonstrates the need for further research using multitemporal data collection across case study sites to better understand the interactions of crop responses and sensors, and so define appropriate conditions for large-area data collection. Such a case study-led multitemporal survey approach is an ideal application for UAV-based documentation, especially when “perfect” conditions cannot be guaranteed.

Modelling of lateral forces generated by pedestrians walking across footbridges

The mechanism which results in the synchronization of people walking across footbridges with the bridges fundamental horizontal frequency is studied. The lateral vibration of a bridge subjected to walking pedestrians is modelled by considering the bridge to be a slender beam. The effect of bridge motion on the footfall forces of walking pedestrians is not considered. The contribution of pedestrians varies with their position on the bridge. It is assumed that the walking gait frequency of a pedestrian follows a Gaussian distribution and pedestrians can unconsciously adjust the phase of their walking cycle closer to that of the bridge, based on the theory of coupled oscillators. A time-dependent nonlinear dynamic equation is derived using the modal expansion approach. The model is then applied to the north span of the Millennium Bridge in London, to produce its excessive lateral vibrations. Agreement between the results and the existing observations supports the rationality and reliability of the method. Several parameters, in particular the walking gait frequency of pedestrians, crowd sensitivity to bridge motion, bridge frequency, bridge damping and different load conditions are investigated. The numerical simulation shows that these parameters have different degrees of impact on the critical number of pedestrians triggering excessive vibrations.

Forest typological and phytosozological assessment of forest vegetation of Slobozhansky National Park

Forest typological and phytososological biodiversity of forest vegetation of Slobozhansky National Park is shown. The park covers 5244 hectares and includes the main parts of the run off valleys of the left-bank Merla River tributary, which belongs to the Vorskla River basin in the Kharkiv region. The main forest-forming species of the Slobozhansky National Nature Park are Pinus sylvestris L. (2779.3 hectares, 59.84%), Quercus robur L. (1451.8 hectares, 31.26%). Minor areas are occupied by Betula pendula Roth (138.3 hectares, 2.98%), Alnus glutinosa (L.) P. Gaertn. (122.5 hectares, 2.64%), Populus tremula L. (45.0 hectares, 0.97%) and other species. Areas covered with forest vegetation are represented by 16 edatopes: all trophotope and almost all hygrotopes, except very dry. Among the trophotopes subors (2015.2 hectares, 43.39%), oak wood (1504.4 hectares, 32.39%) and sugruds (1042.2 hectares, 22.44%) predominate, and the part of pine forest is insignificant (82.5 hectares, 1.78%). Among hygrotopes, the majority are with fresh conditions (4060.6 hectares, 87.43%), much smaller areas are dry (268.4 hectares, 5.78%), damp (184.3 hectares, 3.97%), moist (124.4 hectares, 2.68%) and wet (6.6 hectares, 0.14%) conditions. There are 17 types of forests in the Slobozhansky National Park areas covered with forest vegetation. Fresh oak-pine forest (1780.6 hectares, 38.35%), fresh maple-linden forest (1453.6 hectares, 31.30%), fresh linden-oak-pine sugrud (756.8 hectares, 16.30%) are dominated. Pinus sylvestris plantations grow in 10 forest types. The most common types of pine forests are fresh oak-pine and fresh linden-oak-pine sugrud. Quercus robur growth in 7 forest types, the most common of which is fresh maple-linden oak wood. The distribution of forest typological differences on the territory of the park of vascular plants rare species populations, which have different sozological status is analyzed. Annex I to Resolution 6 of the Berne Convention includes the following species: Dracocephalum ruyschiana L., Jurinea cyanoides (L.) Rchb., Iris pineticola Klokov. A number of species have the appropriate conservation status in Ukraine (Diphasiastrum complanatum (L.) Holub, Lycopodium annotinum L., Dracocephalum ruyschiana, Pulsatilla pratensis (L.) Mill. Sl, Allium ursinum L., Iris furcata M. Bieb., Iris pineticola, Fritillaria meleagris L., F. ruthenica Wikstr., Tulipa quercetorum Klokov & Zoz, Epipactis helleborine (L.) Crantz, Listera ovata (L.) R. Br., Neottia nidus-avis (L.) Rich., Platanthera bifolia (L.) Rich., Stipa borysthenica Klokov ex Prokudin) and 22 species at the regional range.

Mediolateral damping of an overhead body weight support system assists stability during treadmill walking

BackgroundBody weight support systems with three or more degrees of freedom (3-DoF) are permissive and safe environments that provide unloading and allow unrestricted movement in any direction. This enables training of walking and balance control at an early stage in rehabilitation. Transparent systems generate a support force vector that is near vertical at all positions in the workspace to only minimally interfere with natural movement patterns. Patients with impaired balance, however, may benefit from additional mediolateral support that can be adjusted according to their capacity. An elegant solution for providing balance support might be by rendering viscous damping along the mediolateral axis via the software controller. Before use with patients, we evaluated if control-rendered mediolateral damping evokes the desired stability enhancement in able-bodied individuals.MethodsA transparent, cable-driven robotic body weight support system (FLOAT) was used to provide transparent body weight support with and without mediolateral damping to 21 able-bodied volunteers while walking at preferred gait velocity on a treadmill. Stability metrics reflecting resistance to small and large perturbations were derived from walking kinematics and compared between conditions and to free walking.ResultsCompared to free walking, the application of body weight support per-se resulted in gait alterations typically associated with body weight support, namely increased step length and swing phase. Frontal plane dynamic stability, measured by kinematic variability and nonlinear dynamics of the center of mass, was increased under body weight support, indicating reduced balance requirements in both damped and undamped support conditions. Adding damping to the body weight support resulted in a greater increase of frontal plane stability.ConclusionAdding mediolateral damping to 3-DoF body weight support systems is an effective method of increasing frontal plane stability during walking in able-bodied participants. Building on these results, adjustable mediolateral damping could enable therapists to select combinations of unloading and stability specifically for each patient and to adapt this in a task specific manner. This could extend the impact of transparent 3-DoF body weight support systems, enabling training of gait and active balance from an early time point onwards in the rehabilitation process for a wide range of mobility activities of daily life.

Calculation of the energy transferred by radiation damping from nuclear spin system to receiver coil in NMR

In nuclear magnetic resonance (NMR) experiments the free induction decay (FID) current is induced by the precession of the excited magnetization, and the FID signal carries energy. This energy must come from the spin system, but has never been investigated quantitatively. This letter finds a way to calculate the energy transformed from the magnetic potential energy in the spin system to the electric kinetic energy associated with the FID current by revisiting the radiation-damping-modified Bloch equations. The result shows that under strong radiation damping conditions, almost all of the energy stored in the excited spin system is transferred to FID with negligible energy loss.

Wood-borers in Historic Ships

ABSTRACT Using evidence of wood-borers in several of the National Museum of the Royal Navy’s historic ships, this article will examine the threat posed to the historic fabric by non-marine species and the reasons that we struggle to eradicate the problem. The relationship between fungal attack and beetle activity will be discussed, and the need for supporting research into this and other aspects of damage due to wood-boring species. HMS Victory, HMS Warrior and HMS Trincomalee all suffer from attack by wood-boring species, though the infestations are in different stages of development on each vessel. By investigating and employing an integrated pest management strategy on Trincomalee, we hope to learn more about the most effective means of combatting the much more widespread infestation of death watch beetle on Victory. Other wood-borers including weevil, furniture beetle and wharfborer are also present across our collection of ships, and all these species are facilitated by the damp conditions which can never be truly resolved as the ships are located in open coastal environments.

Decay rates for semilinear wave equations with vanishing damping and Neumann boundary conditions

The paper is concerned with the semilinear wave equations with time‐dependent damping γ(t)=α/(1+t) (α>0), under the effect of nonlinear source f behaving like a polynomial, and subject to Neumann boundary conditions. Constructing appropriate auxiliary functions, we obtain an explicit uniform decay rate estimate for the solutions of the equation in terms of the exponent of f, when α is large enough. On the other hand, via a new hyperbolic version of Dirichlet quotients, we show that the upper estimate is optimal in some case, which implies the existence of slow solutions.

A novel approach of active control of structures based on the critically damped condition

In this research, the active control of structures based on the critically damped condition was proposed for reducing displacements and drifts of structures under seismic loading. In this approach, the second-order dynamic equation is converted into a first-order dynamic equation and a first-order derivative operator with the same constants, which satisfy critically damped conditions of the system. Based on this concept and using the defined performance index, the feedback gain matrix of the structural velocity is obtained. In the method of active control of structures based on the critically damped condition, the control force, which is the linear definition of the feedback gain matrix and the structural velocity, is exerted on the structure in each time step. Four types of numerical examples are examined to the comparison verification of active control of structures based on the critically damped condition with the classical linear optimal control, standard model predictive control, and other methods proposed in several references. Programming and calculations are done by Mathcad prime mathematical software.