Maintenance Of Joints Research Articles

Prediction of storage lifetime of rubber materials for flexible joint elastomers

To investigate the aging performance and storage lifetime of rubber materials used in flexible joint elastomers for solid rocket engines, a compression permanent deformation was used as the performance evaluation index to conduct aging tests on the elastic specimens of joint rubber materials at different temperatures. The results showed that the compression permanent deformation increased with the aging time and temperature, and the value of compression permanent deformation was greater in the initial stage of aging than in the later stage. Based on the regularity of material aging performance, the storage lifetime of rubber materials at room temperature of 25°C is extrapolated to be approximately 17.35 years through the linear equation of aging kinetics. Given that the aging mechanism remains unchanged, the calculation based on the principle of time-temperature equivalence reveals that as the aging temperature of the rubber material increases, the accelerated aging time to reach the regular storage lifetime becomes faster. Aging for 11.25 days at 140°C is equivalent to storing for this rubber material 15 years at 25°C. This research provides references for the future design, manufacturing, maintenance, and storage reliability of flexible joints.

Investigating the Application of Smart Materials for Enhanced Maintenance of Rubber Expansion Joints in Bridge Expansion Joint Systems

In South Korea, the public infrastructure encompasses 172,111 facilities, with bridges accounting for a significant segment (totaling 34,199). These bridges undergo expansion due to traffic, vehicular loads, and temperature fluctuations. Expansion joint devices are installed to maintain vehicle stability and driving performance across expansion gaps. While these devices effectively ensure vehicular stability and performance, they do not address issues such as leakage and debris fall; therefore, rubber expansion joints should be installed. However, these rubber joints are prone to damage from various factors, resulting in secondary issues such as girder corrosion and accidents under bridges. Because of these inherent vulnerabilities, these joints require frequent replacements, making continuous bridge maintenance challenging. Therefore, this study explores the development of novel expansion joints using superelastic shape memory alloys to overcome the limitations of traditional rubber expansion joints. A comparative finite element analysis was conducted on the developed superelastic shape memory alloy and traditional rubber expansion joints. This study also assessed the long-term usability of these novel joints, particularly their ability to revert to their original shape post load removal. This research presents a promising alternative to conventional expansion joints and holds potential implications for enhancing the durability and safety of bridge infrastructure.

Effects of structure size on post-earthquake fire resistance of CCBCC joints at non-uniform elevated temperatures

The probability of secondary fires caused by earthquakes is very high. Due to the residual stress and deformation caused by earthquakes, the mechanical behavior of cruciform combined beam-CFST column (CCBCC) joints is extremely complex. In view of this, the goal of this study is to investigate the effects of structure size on the post-earthquake fire failure mechanism of CCBCC joints under gradient temperatures. The calculation model in this article was validated using existing experimental results, subsequently 20 computational models were established to conduct parameter analysis, including the width-to-thickness ratio (γ) of the CFST column, the slenderness ratio (λ) of the CFST column, the width-to-thickness ratio (α) of beam flange, the height-to-thickness ratio (β) of beam web and the damage variable (D̃). The results have demonstrated that the post-earthquake fire resistance of CCBCC joints is mostly affected by damage variable. Parameters β, α, λ and γ also have a significant impact on the failure of these joints. An empirical bearing capacity prediction model of CCBCC joints is obtained. The research results can provide reference and data support for the design, maintenance, and reinforcement of CCBCC joints under post-earthquake fire.

Evaluation of Joint Clearance Effects on the Shimmy of Nose Landing Gear

Through the establishment of a three-dimensional joint clearance model, the effects of joint clearances at different positions on shimmy stability are evaluated. In this paper, considering the radial, axial and coupling characteristics of joint clearance, the shimmy multibody dynamics (MBD) model is applied to different joints in the nose landing gear (NLG) transmission system. It is proposed to evaluate the influence of joint clearance on shimmy from two aspects of position factor and wear factor. The study found that different joint clearances have different effects on shimmy: the joint clearance between the NLG and fuselage has little influence on shimmy; the larger axial clearance of upper and lower torque link joint will cause the shimmy of the NLG, but the radial clearance has no effect on shimmy; while the joint clearance between turning sleeve and upper torque link, lower torque link and piston only works in the axial and radial coupling. The reasons for the different influence characteristics of each joint space are analyzed. Consequently, studying and summarizing the influence of different clearance on shimmy is of great significance for the design and maintenance of the NLG joints.

Failure analysis of aviation hydraulic rotary joints

The aviation hydraulic rotary joint is an accessory of the aviation hydraulic system used to connect two pipelines in relative motion. The safety accident caused by the failure of the aviation hydraulic rotary joint occurred in engineering. The analysis of the potential failure causes of aviation hydraulic rotary joints can provide basic technical support for aircraft maintenance activities. In this study, a ground reliability experimental apparatus for an aviation hydraulic rotary joint was built, and a reliability test was conducted. The potential failure mode of an aviation hydraulic rotary joint was analyzed by observing the surface topography of each component. Finally, the failure mechanism was analyzed using the finite element method. To provide a basis for the maintenance and replacement strategy of the joints, the influence of the fit clearance on the reliability of aviation hydraulic rotary joints was analyzed. The results show that the wear of metal components and sealing components and the stress failure of sealing components are the main failure mechanisms of rotary joints; when the fit clearance increases from 0.02 mm to 0.12 mm, the maximum von Mises stress and maximum shear stress of the retaining ring were increased by 44.45% and 43.72%, respectively, and the maximum von Mises stress and maximum shear stress of the O-ring were increased by 131.89% and 123.64%, respectively. With the increase of the fit clearance, the stress damage probability of the retaining ring and O-ring will increase. The maintenance and replacement strategy of rotary joints can be made according to the size of the fit clearance.

Patient Disease Trajectories in Rheumatoid Arthritis Patients Treated with Baricitinib 4-mg in FourPhase 3 Clinical Studies.

We sought to identify and compare treatment response groups based on individual patient responses (rather than group mean response) over time on the Clinical Disease Activity Index (CDAI) for rheumatoid arthritis (RA), in patients treated with baricitinib 4-mg in 4phase 3studies. Trajectory subgroups were identified within each study using growth mixture modeling. Following grouping, baseline characteristics and disease measures were summarized and compared. In each study, three response trajectories were identified. In the three studies of patients naïve to biological disease-modifying anti-rheumatic drugs (bDMARDs) patients had, on average, high disease activity, as measured by CDAI. In these studies, a group of rapid responders (65-71% of patients) had the lowest baseline CDAI scores and achieved mean CDAI ≤ 10 by week 16. Gradual responders (10-17%) had higher baseline CDAI, but generally achieved low disease activity (CDAI ≤ 10) by week 24. A group of partial responders (18-22%) had higher baseline CDAI and did not achieve mean CDAI ≤ 10. In bDMARD-experienced patients, the subgroups were rapid responders, who achieved mean CDAI ≤ 10 (42% of patients); partial responders, with mean CDAI decrease of ~ 15 points from baseline (42% of patients); and limited responders (15% of patients). Changes in modified total sharp score (mTSS; assessed only in biologic-naïve patients) were below the smallest detectable difference at 24/52weeks for > 90% of patients in each group, excepting partial responders in RA-BEGIN (≥ 75% no detectable change). In patients receiving baricitinib 4-mg, lower baseline CDAI was generally associated with rapid response, while higher baseline CDAI scores were generally seen for patients who either reached treatment targets more gradually, or who had a partial or limited response. Maintenance of response was observed with continued baricitinib treatment in all response groups and generally included maintenance of mTSS.

Taxonomy of fibroblasts and progenitors in the synovial joint at single-cell resolution

ObjectivesFibroblasts in synovium include fibroblast-like synoviocytes (FLS) in the lining and Thy1+ connective-tissue fibroblasts in the sublining. We aimed to investigate their developmental origin and relationship with adult progenitors.MethodsTo discriminate...

Research on Operation Management Technology of Cable Joints of Ring Network Cabinet Based on Temperature Sensors

In this paper, aiming at the operation and maintenance of the internal cable joints of the ring main unit, the research on the operation and management technology of the ring main unit cable joints based on temperature sensors is carried out. Starting from the principle of temperature sensing technology for cable joints, an online temperature monitoring system for the cable joints of the ring network cabinet is developed during the operating cycle. Comprehensive consideration of factors such as seasons, ambient temperature and humidity, line load current, etc., to evaluate the operating status of the cable joint temperature data as the main basis. A simple and adjustable bracket suitable for the fixed installation of the non-contact temperature sensor of the ring main unit has been developed. A method of managing the cable joints of the ring main unit during the operating cycle is proposed to realize the effective evaluation of the cable joint status. It can greatly improve the accuracy of condition monitoring, and improve the efficiency and level of operation and maintenance.

Fire resistance of reinforced SHS T-joints considering gradient temperature effect under post-earthquake fire

The earthquake usually causes serious damage on the T-joints in structure, which may reduce its fire resistance. Moreover the gradient temperature distribution for reinforced SHS T-joints appears under a fire. Therefore it is very necessary to evaluate the fire resistance of reinforced SHS T-joint considering gradient temperature effect under post-earthquake fire (PEF). The objective of this paper is to investigate the fire resistance of earthquake-damaged doubler-plate reinforced SHS T-joints considering gradient temperature effect. A computation model was established and validated using the existing experimental results. The gradient-temperature field distribution against reinforced SHS T- joints was conducted by transient-response analysis method, then a parametric study was carried out using 30 established computation models involving following dimensionless parameters such as the width ratio of brace to chord (δ), diameter to thickness ratio of chord (ζ), wall thickness ratio of doubler-plate to chord (α), wall thickness ratio of brace to chord (ε), length ratio of doubler-plate to chord (ξ), ratio of chord length to chord width (φ), welding effect, damage variable (D~) and fire retardant coating thickness. The results demonstrated that damage variable and fire retardant coating thickness had a great influence on the fire resistance of doubler-plate reinforced SHS T-joints, the parameters δ, ζ and α had a major influence on reinforced SHS T-joints. The findings can provide data support and theoretical reference for the design, maintenance and reinforcement of such joints.

Finding Natural Compounds as Potential Inhibitors for Osteoarthritis

Osteoarthritis is the fourth leading cause of disability affecting more than 300 million people around the globe. In this disease, chondrocytes responsible for the growth and maintenance of articular joints start to deplete due to the rogue involvement of phosphoinositide 3-kinase, protein kinase-B and p38 mitogenactivated protein kinases. Presently, there are medications providing symptomatic treatment, however, they cannot thwart the progression of osteoarthritis. Natural compounds can rejuvenate injured tissues, averting inflammation and can be useful for treating osteoarthritis. The present study was conducted to obtain inhibitors using natural compounds for phosphoinositide 3-kinase/protein kinase-B/mitogenactivated protein kinases implicated in the pathogenesis of osteoarthritis. Results revealed that out of 1541 natural compounds, cordycepin and geraniol formed an inhibitory interaction with these kinases. Moreover, these compounds down regulated important inflammatory markers (DNA methyltransferase 1, cluster of differentiation 74 and ETS proto-oncogene 1) and increased the expression of glutamate-cysteine ligase catalytic, FAM111 trypsin like peptidase A, secreted frizzled related protein 1 and ferritin light chain genes implicated in the survival of chondrocytes. The absorption, distribution, metabolism, excretion, toxicity and lethal dose prediction studies showed that cordycepin has appropriate pharmacokinetics and low acute toxicity level, whereas geraniol has high toxicity level and efficient pharmacokinetic profile. Our study provided a preliminary insight that cordycepin and geraniol are capable inhibitors of phosphoinositide 3-kinase/protein kinase-B/mitogen-activated protein kinases and can be lead compounds in osteoarthritis therapy.

Study on seismic performance of welding beam reinforced with symmetrical flange plate to H-shaped column after fire

The objective of this paper is to investigate the seismic performance of welding beam strengthened with symmetrical flange plates to H-type column (WBSFPHC) after fire. The accuracy effectiveness of the calculation model was verified using the existing experimental results. Considering the application of practical engineering parameters, the column width-thickness ratio (α), ratio of beam width to column width (β), height-thickness ratio of beam web (γ), width-thickness ratio of stiffener (ε), length thickness ratio of flange plate (η) and temperature (T) were used to perform a parametric study against the post-fire seismic performance of the WBSFPHC connections. Then, 25 calculation models were established to explore hysteretic behavior, stiffness degradation, ductility and energy dissipation capacity of the WBSFPHC connection under post-fire cyclic load. The results showed that the stiffness and bearing capacity of the WBSFPHC connection were improved with the increase of the parameters β and γ, temperature had great effect on the stiffness, stress distribution, energy dissipation capacity and bearing capacity of the WBSFPHC connection. The findings can provide reference and technical support to the seismic performance design, maintenance and reinforcement of such joints after fire.

Association Analysis of GDF5 and Contributing Factors in Developmental Dysplasia of the Hip in Infants.

Developmental dysplasia of the hip (DDH) is a developmental disorder which is reported to be associated with hip instability. When untreated, it can lead to irreversible joint damage. DDH is known to be a multifactorial disease involving genetic, mechanical and environmental factors. The greatest causative potential is attributed to the genetic component. Growth Differentiation Factor 5 (GDF5) is among the most studied genes associated with processes of regeneration and maintenance of joints. The aim of this work was to analyse the association of SNP rs143383 in the GDF5 gene and the occurrence of DDH, along with association with various contributing factors in the Caucasian population. A total of 118 samples were analysed for the presence of the mutation. DNA was isolated from all individuals from peripheral blood. SNP rs143383 in the GDF5 gene was genotyped using the TaqMan assay. A standard chi-square test was used to compare allele and genotype distributions in patients and healthy controls. The association analysis of genotypes of DDH and rs143383 revealed a significant association. Also, the association of GDF5 and selected contributing factors was statistically significant in female gender (p=0.002), family history (p<0.001), count of pregnancy (p=0.009), laterality of hip involvement and initial US examination. 1. The results indicate an important effect of rs143383 polymorphism in the GDF5 gene on DDH development. 2. However, our results also suggest that rs143383 is not the only contributing factor in the genetic component of DDH.

Life-cycle environmental and economic benefits of jointless bridges considering climate change

The damage of expansion joints is a common problem of bridges, which adversely affects not only driving comfort and safety but also the durability of the structure. Jointless bridges can fundamentally solve this fragile problem. However, how to accurately assess its environmental and economic benefits has not been studied, specifically as climate change intensifies. To address these issues, this study first examines the effects of climate change on design expansion allowance of bridge expansion joints based on climate projections. Subsequently, the life-cycle environmental and economic benefits of two jointless bridges located in Beijing–Hong Kong–Macau Expressway are quantified under climate change scenarios. Moreover, uncertainty and random forest algorithm-based importance analyses are carried out to help decision-makers identify major environmental and economic factors and develop eco-friendly plans to facilitate jointless bridge construction. Results indicate the following: (1) the design expansion allowance of bridge expansion joints tends to increase with the time-dependent temperature and humidity; (2) the avoidance of traffic detours caused by the maintenance and replacement of expansion joints is a major source of life-cycle environmental and economic benefits; (3) traffic detour distance is the most important factor influencing the life-cycle environmental and economic benefits.

The Role of the SOX11 Transcription Factor in Regulating Growth Differentiation Factor‐5 During Joint Formation

Growth differentiation factor 5 (GDF5) is associated with the formation and maintenance of joints. Disruption of GDF5 expression is also linked to accelerated osteoarthritis. We have identified a GDF5 Associated Regulatory Region (GARR) that contains several Sox binding sites. The SOX11 transcription factor has been shown to upregulate GDF5 and we hypothesized that SOX11 is necessary for GARR mediated expression of GDF5 during joint development and maintenance. To test this hypothesis, we compared the expression of SOX11 and GDF5 in chicken limbs during development using in-situ hybridization, using MYOD, TNMD, and Col1A2 as muscle and tendon markers. We also generated a GARR reporter construct and mutated the Sox binding sites. The native and mutated GARR reporters were transfected into developing chick wings. Our results showed that in chicken, SOX11 expression primarily surrounds GDF5 expression in joint spaces at Hamburger-Hamilton stages (HH) 25-27. At HH 29, the expression of SOX11 and GDF5 colocalized in joint spaces. SOX11 expression was not confined to joints, but also found in muscles (MYOD) and tendons (TNMD, Col1A2). Disruption of the Sox binding sites greatly reduced GARR activity within joint spaces. Colocalization of SOX11 and GDF5 in joints shows that SOX11 may play a role in the regulation of GDF5 through GARR. Additionally, it may be a competency factor for the formation and organization of joint-related tissues. Decreased activity with mutant GARR suggests it is required for GARR activity. Further experiments are needed to clarify the role of SOX11 in regulating joints and joint associated tissues.

Evaluating Physical and Fiscal Water Leakage in Water Distribution System

With increasing population, the need for research ideas on the field of reducing wastage of water can save a big amount of water, money, time, and energy. Water leakage (WL) is an essential problem in the field of water supply field. This research is focused on real water loss in the water distribution system located in Ethiopia. Top-down and bursts and background estimates (BABE) methodology is performed to assess the data and the calibration process of the WL variables. The top-down method assists to quantify the water loss by the record and observation throughout the distribution network. In addition, the BABE approach gives a specific water leakage and burst information. The geometrical mean method is used to forecast the population up to 2023 along with their fiscal value by the uniform tariff method. With respect to the revenue lost, 42575 Br and 42664 Br or in 1562$ and 1566$ were lost in 2017 and 2018, respectively. The next five-year population was forecasted to estimate the possible amount of water to be saved, which was about 549627 m3 and revenue 65,111$ to make the system more efficient. The results suggested that the majority of losses were due to several components of the distribution system including pipe-joint failure, relatively older age pipes, poor repairing and maintenance of water taps, pipe joints and shower taps, negligence of the consumer and unreliable water supply. As per the research findings, recommendations were proposed on minimizing water leakage.

PB1843 EFFECT OF ADHERENCE TO PHYSICAL THERPY REGIMEN ON JOINTS OUTCOMES FOR HEMOPHILIAC CHILDREN AT ZAGAZIG UNIVERSITY HOSPITALS

Background:The maintenance of healthy joints and muscles is crucial to the quality of life of patients with hemophilia. Clotting factor replacement may stop or even prevent bleeds but it does not restore joint or muscle function. Only regular movement and exercise and adherence to them can do that. Physiotherapy aims to bring relief from pain, restore muscle power and control, restore range of joint movement and prevent further injury to a target joint. Enhancing adherence, joint function and decreasing pain by using physiotherapy is the major hope for all hemophiliac patients, especially in developing countries with limited access to treatment.Aims:to Identify the effect of adherence to physical therapy regimen on joint outcomes for children with hemophilia.Methods:A quasi–experimental study was conducted on a sample of “35” children were suffering from hemophilia “A” or “B” at the Pediatric Hematology outpatient clinic at Zagazig University Hospitals. The knee joint was selected to perform the physiotherapy regimen Tools was composed of three parts Part I: a structured interview sheet. Part II assessment of adherence using (attendance at clinic appointments, SIRASa and Patient Self‐Report Scale of their Home‐Based Rehbiltation adherence). Part III was the assessment of the musculoskeletal status and joint evaluation using (Gibert score, FISH© and the musculoskeletal data sheet).Results:‐ There was a significant statistical relation and improvement in the mean score of functional ability of the studied group throughout the intermediate and post‐test phases than the pre‐test phase.‐ There was a significant statistical improvement in the studied sample adherence and knee joint outcomes throughout the study phases.Summary/Conclusion:the adherence to physiotherapy have a profound effect on improving joint outcomes. So,we recommend encouraging the awareness of hemophiliac patients about physiotherapy and its beneficial role in decreasing the musculoskeletal complications.

Regulation of a GDF5 Associated Enhancer During Limb Development

Growth differentiation factor 5 (GDF5) is an anabolic growth factor that plays a critical role in the formation, maintenance and repair of bones and joints. Reduced levels of GDF5 are associated with accelerated degradation of joint cartilage, a disease called osteoarthritis (OA). Identification of factors involved in GDF5 regulation may offer therapeutic targets for treating or preventing OA. A GDF5 Associated Regulatory Region (GARR) has been previously identified as a 900 bp enhancer located 78 kb downstream of the GDF5 locus. GARR contains a number of potential transcription factor binding sites, including sites for odd‐skipped related (Osr) zinc‐finger and Sry box (Sox) transcription factors. As Osr1/2 and Sox11 are important for normal Gdf5 expression, and their expression patterns overlap that of Gdf5, we hypothesized that mutation of OSR and SOX binding sites within GARR would disrupt enhancer activity.To identify whether putative OSR and SOX transcription factor binding sites contribute to GARR activity, we performed site‐directed mutagenesis on both potential OSR binding sites (GARRmutOSR), or on both potential SOX binding sites (GARRmutSOX) in the GARR‐tk‐EGFP reporter construct (GARRcontrol). We used targeted regional electroporation (TREP) to introduce control and mutated reporter constructs into Hamburger‐Hamilton stage 23 chicken limb buds near the developing elbow joint. Transfection efficiency was determined by co‐transfection with a β‐actin promoter‐driven RFP construct. We determined GARR activity by fluorescence microscopy, following 48 hours of incubation after TREP.Comparison of GARRcontrol and GARRmutOSR demonstrated similar GFP fluorescence intensity localized to the elbow joint. In contrast, fluorescence of GARRmutSOX was markedly reduced relative to GARRcontrol, although similarly restricted to the elbow. Though Osr transcription factors are associated with Gdf5 expression, mutation of the OSR binding sites in GARR was insufficient to substantially alter the level of GARR activity. Mutation of SOX binding sites, however, dramatically reduced GARR activity, implicating SOX transcription factors as critical regulators of GDF5 expression.Support or Funding InformationThe research was funded in part by a grant from the LLU Pathology Research Endowment.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Tgfbr2 is required in Acan-expressing cells for maintenance of the intervertebral and sternocostal joints.

BackgroundMembers of the transforming growth factor beta (TGF‐β) family are secreted proteins that regulate skeletal development. TGF‐β signaling is critical in embryonic development of the annulus fibrosus (AF) of the intervertebral disc (IVD). To address the question of the role of TGF‐β signaling in postnatal development and maintenance of the skeleton, we generated mice in which Tgfbr2 was deleted at 2‐weeks of age in Aggrecan (Acan)‐expressing cells using inducible Cre/LoxP recombination.MethodsLocalization of Cre recombination was visualized by crossing Acantm1(cre/ERT2)Crm mice to fluorescent mTmG reporter mice. Acantm1(cre/ERT2)Crm mice were mated to Tgfbr2 LoxP/LoxP mice and Cre recombinase was activated by tamoxifen injection at 2‐weeks postnatally. Following tamoxifen injection, mice were aged to 3, 6, and 12‐months and control mice were compared to the experimental (cKO) group. Mice were initially analyzed using X‐ray and skeletal preparations. Sternocostal joints and IVD tissues were further analyzed histologically by hematoxylin and eosin (H&E), Safranin O, and Picrosirius Red staining as well as Col10 immunostaining.ResultsCre recombination was observed in the IVD and sternocostal joints. X‐ray analysis revealed osteophyte formation within the disc space of 12‐month‐old cKO mice. Skeletal preparations confirmed calcification within the IVD and the sternocostal joints in cKO mice. H&E staining of cKO IVD revealed disorganized growth plates, delay in the formation of the bony endplate, and Col10 staining in the AF indicative of ectopic endochondral bone formation. Furthermore, proteoglycan loss was observed and collagen bundles within the inner AF were thinner and less organized. Alterations in the IVD were apparent beginning at 3 months and were progressively more visible at 6 and 12 months. Similarly, histological analysis of cKO sternocostal joints revealed joint calcification, proteoglycan loss, and disorganization of the collagen architecture at 12 months of age.ConclusionsTGF‐β signaling is important for postnatal development and maintenance of fibrocartilaginous IVD and sternocostal joints.

Some research results on the tightness and strength of flange joints

The paper presents recently published literature research on the tightness and strength of flange joints. These could influence both the calculation and the maintenance of flange joints. Some of the research results have been compared to normative stipulations currently used in the calculation of flange joints. The presentation covers: – the influence of sealing gasket design and screw load on sealing; – the influence of creep on screw relaxation, and thereby on gasket sealing; – cracking in flange joints; – the influence of an additional axial force of flange joints on the rotation and on the deformation of flange joint components; – flanges without sealing gasket; – the influence of the method of flange joint bolt tightening on the uniformity of bolts loading and tightness.

Selection, Maintenance and Acoustic Diagnostics of Expansion Joints in Bridges Located in Areas with Ground Deformations

Abstract In the paper are presented general rules of the assortment of expansion joints in bridges located in areas being under the mining impacts. The maintenance problems associated with ground deformations are also mentioned. The special attention is given to the noise emitted by expansion joint devices. A legal status in the protection from noise and factors affecting this noise are discussed.