Innovations in metal-organic frameworks (MOFs): Pioneering adsorption approaches for persistent organic pollutant (POP) removal.

Adsorption is a promising way to remove persistent organic pollutants (POPs), a major environmental issue. With their high porosity and vast surface areas, MOFs are suited for POP removal due to their excellent adsorption capabilities. This review addresses the intricate principles of MOF-mediated adsorption and helps to future attempts to mitigate organic water pollution. This review examines the complicated concepts of MOF-mediated adsorption, including MOF synthesis methodologies, adsorption mechanisms, and material tunability and adaptability. MOFs' ability to adsorb POPs via electrostatic forces, acid-base interactions, hydrogen bonds, and pi-pi interactions is elaborated. This review demonstrates its versatility in eliminating many types of contaminants. Functionalizing, adding metal nanoparticles, or changing MOFs after they are created can improve their performance and remove contaminants. This paper also discusses MOF-based pollutant removal issues and future prospects, including adsorption capacity, selectivity, scale-up for practical application, stability, and recovery. These obstacles can be overcome by rationally designing MOFs, developing composite materials, and improving material production and characterization. Overall, MOF technology research and innovation hold considerable promise for environmental pollution solutions and sustainable remediation. Desorption and regeneration in MOFs are also included in the review, along with methods for improving pollutant removal efficiency and sustainability. Case studies of effective MOF regeneration and scaling up for practical deployment are discussed, along with future ideas for addressing these hurdles.

Real-Time Structural Health Monitoring and Damage Identification Using Frequency Response Functions along with Finite Element Model Updating Technique.

Throughout service, damage can arise in the structure of buildings; hence, their dynamic testing becomes essential to verify that such buildings possess sufficient strength to withstand disturbances, particularly in the event of an earthquake. Dynamic testing, being uneconomical, requires proof of concept; for this, a model of a structure can be dynamically tested, and the results are used to update its finite element model. This can be used for damage detection in the prototype and aids in predicting its behavior during an earthquake. In this instance, a wireless MEMS accelerometer was used, which can measure the vibration signals emanating from the building and transfer these signals to a remote workstation. The base of the structure is excited using a shaking table to induce an earthquake-like situation. Four natural frequencies have been considered and six different types of damage conditions have been identified in this work. For each damage condition, the experimental responses are measured and the finite element model is updated using the Berman and Nagy method. It is seen that the updated models can predict the dynamic responses of the building accurately. Thus, depending on these responses, the damage condition can be identified by using the updated finite element models.

A Low-Cost Multi-Sensor Data Acquisition System for Fault Detection in Fused Deposition Modelling.

Fused deposition modelling (FDM)-based 3D printing is a trending technology in the era of Industry 4.0 that manufactures products in layer-by-layer form. It shows remarkable benefits such as rapid prototyping, cost-effectiveness, flexibility, and a sustainable manufacturing approach. Along with such advantages, a few defects occur in FDM products during the printing stage. Diagnosing defects occurring during 3D printing is a challenging task. Proper data acquisition and monitoring systems need to be developed for effective fault diagnosis. In this paper, the authors proposed a low-cost multi-sensor data acquisition system (DAQ) for detecting various faults in 3D printed products. The data acquisition system was developed using an Arduino micro-controller that collects real-time multi-sensor signals using vibration, current, and sound sensors. The different types of fault conditions are referred to introduce various defects in 3D products to analyze the effect of the fault conditions on the captured sensor data. Time and frequency domain analyses were performed on captured data to create feature vectors by selecting the chi-square method, and the most significant features were selected to train the CNN model. The K-means cluster algorithm was used for data clustering purposes, and the bell curve or normal distribution curve was used to define individual sensor threshold values under normal conditions. The CNN model was used to classify the normal and fault condition data, which gave an accuracy of around 94%, by evaluating the model performance based on recall, precision, and F1 score.

Application of remodeled water quality indices for the appraisal of water quality in a Himalayan lake.

Natural and anthropogenic pollution influence the general hydrochemistry of freshwater sources. Effective management strategies need an accurate evaluation of the water quality parameters, and inferences extracted from the data should be based on the most appropriate statistical methods. Conventional water quality indices (WQI) being related to a large number of water quality parameters results in significant variability and analytical costs. The focus of this study was to develop a remodeled water quality index (WQImin) based on the localized trends in water quality and demonstrate it to understand water quality variations of Dal Lake (a freshwater lake in the Himalayan region). Spatio-temporal changes and trends of 14 water quality parameters were investigated that were arbitrated from the samples collected at 11 sampling locations during the water quality monitoring across the Dal Lake from September 2017 to August 2020. The results signify that the general mean WQI value was 81.9, and seasonal average WQI values ranges from 79.44 to 84.55. The water quality showed seasonal variance, with lowest values in summer, succeeded by autumn and winter, and highest in spring. Moreover, the results from stepwise multiple regression analysis indicated that the WQImin significantly correlates with six water quality parameters (ammonia, dissolved oxygen, chemical oxygen demand, temperature, turbidity, and nitrate) in Dal Lake. The WQImin model predicted the water quality of the Dal Lake with a coefficient of determination (R2) value of 0.96, root mean square error (RMSE) value of 4.1, and percentage error (PE) of 5.3%. The developed WQImin model can be applied as a cost-effective and efficacious approach to determine the water quality of fresh surface water bodies.

Investigating the efficiency of α-Bismuth zinc oxide heterostructure composite/UV-LED in methylene blue dye removal and evaluation of its antimicrobial activity.

Heterostructured α-Bismuth zinc oxide (α-Bi2O3-ZnO) photocatalyst was fabricated by a facile and cost-effective, ultrasound assisted chemical precipitation method followed by hydrothermal growth technique. As synthesized α-Bi2O3-ZnO photocatalyst showed enhanced photocatalytic performance for the MB dye degradation in contrast to pure ZnO and α-Bi2O3. Light emitting diodes (UV-LED) were used in the experimental setup, which has several advantages over conventional lamps like wavelength selectivity, high efficacy, less power consumption, long lifespan, no disposal problem, no warming-up time, compactness, easy and economic installation. XRD study confirmed the presence of both the lattice phases i.e. monoclinic and hexagonal wurtzite phase corresponding to α-Bi2O3 and ZnO in the α-Bi2O3-ZnO composite photocatalyst. FESEM images showed that α-Bi2O3-ZnO photocatalyst is composed of dumbbell like structures of ZnO with breadth ranging 4-5 µm and length ranging from 10 to 11 µm respectively. It was observed that α-Bi2O3 nanoparticles were attached on the ZnO surface and were in contact with each other. Low recombination rate of photo-induced electron-hole pairs, due to the migration of electrons and holes between the photocatalyst could be responsible for the 100% photocatalytic efficiency of α-Bi2O3-ZnO composite. In addition, photocatalyst was also observed to show the excellent antimicrobial activity with 1.5 cm zone of inhibition for 1 mg L-1 dose, against the human pathogenic bacteria (S. aureus).

Three-dimensional printing in the fight against novel virus COVID-19: Technology helping society during an infectious disease pandemic.

Indeed, the scientific milestones set by the ever-emerging three-dimensional printing (3DP) technologies are tremendous. Till now, the innovative 3DP technologies have benefitted the aerospace, automobile, textile, pharmaceutical, and biomedical sectors by developing pre-requisite designed and customized performance standards of the end-user products. As the scientific world, at this moment, is expediting efforts to fight against the highly damaging novel coronavirus (COVID-19) pandemic, the 3DP technologies are facilitating creative solutions in terms of personal protective equipment (PPE), medical equipment (such as ventilators and other respiratory devices), and other health and welfare tools to aid the personal hygiene as well as safe environment for humans by restricting the communication of risks. Various sources (including journal articles, news articles, white papers of the government and other non-profit organizations, commercial enterprises, as well as academic institutions have been reviewed for the collection of the information relevant to COVID-19 and 3DP. This communication presents the recent applications of the 3DP technologies aiding in developing innovative products designed to save the lives of millions of people around the world. Moreover, the potential of 3DP technologies in developing test swabs and controlled medicines has been highlighted. The literature reviewed in the present study indicated that the fused filament fabrication (FFF) is one of the most preferred technologies and contribute about 62% in the overall production of the protective gears developed through overall class of 3DP.

Neuroprotective role of dexmedetomidine in epilepsy surgery: A preliminary study.

PURPOSE: Long standing temporal lobe epilepsy (TLE) causes cerebral insult and results in elevated brain injury biomarkers, S100b and neuron specific enolase (NSE). Surgery for TLE, has the potential to cause additional cerebral insult. Dexmedetomidine is postulated to have neuroprotective effects. The aim of this study was to assess the effect of intraoperative dexmedetomidine on S100b and NSE during TLE surgery. MATERIALS AND METHODS: 19 consenting adult patients with TLE undergoing anteromedial temporal lobectomy were enrolled and divided into two groups. Patients in Group D (n = 9) received dexmedetomidine whereas patients in Group C (n = 10) received saline as placebo in addition to the standard anaesthesia technique. Blood samples of these patients were drawn, before induction of anaesthesia, at the end of surgery, as well at 24 hours and 48 hours postoperatively, and analysed for serum S100b and NSE. RESULTS: The demographic and clinical profile was comparable in both the groups. The baseline S100b in group C and group D was 66.7 ± 26.5 pg/ml and 34.3 ± 21.7 pg/ml (P = 0.013) respectively. After adjustment for the baseline, the overall value of S100b was 71.0 ± 39.8 pg/ml and 40.5 ± 22.5 pg/ml (P = 0.002) in the control and study group, respectively. The values of S100b (79.3 ± 53.6 pg/ml) [P = 0.017] were highest at 24 hours postoperatively. The mean value of NSE in the control and study group was 32.8 ± 43.4 ng/ml (log 3.0 ± 0.1) and 13.51 ± 9.12 ng/ml (log 2.42 ± 0.60), respectively. The value of NSE in both the groups was comparable at different time points. CONCLUSIONS: Lower perioperative values of S100b were observed in patients who received intraoperative dexmedetomidine. Dexmedetomidine may play a role in cerebroprotection during epilepsy surgery.

Assessment of pulmonary function and respiratory symptoms among INDIAN textile sizing mill workers.

BACKGROUND: Textile-sizing mill workers are exposed to various hazards in the sizing units during their working hours and are at risk of acquiring lung impairments due to the usage of sizing chemicals in the sizing process. OBJECTIVE: The main aim of this study is to assess the influence of cotton dust and sizing agents on lung function and breathing difficulties among Indian textile sizing mill workers. METHODS: This cross-sectional study was carried out at a textile-sizing mill from August 2022 to September 2022. A modified questionnaire based American Thoracic Society's standard was used to assess respiratory symptoms among sizing mill workers and the pulmonary function test was conducted Spirometry. The chi-square test was used to find the difference between respiratory symptoms and the t-test was used to find the difference between spirometric parameters. RESULTS: Textile sizing mill workers showed significant (P <  0.0001) decline in peak expiratory flow rate, forced vital capacity (FVC), ratio of FEV1 and forced vital capacity, and forced expiratory volume in 1 s (FEV1). There was an association between symptoms and duration of exposure to pulmonary abnormality. Sizing mill workers showed a significant decline in lung functions and an increase in pulmonary symptoms. As the service duration of exposure in terms of years increased, respiratory symptoms increased and spirometric abnormality also increased. CONCLUSION: This study confirms that sizing agents such as polyvinyl alcohol (PVA), emulsifier, wax, carboxymethyl cellulose (CMC), and starch used in sizing mills are also responsible for respiratory illness and lung impairment among textile workers.

Effect of Elevated Acetabular Cup on Contact and Failure Analysis in Hip Implants for Different Microseparations and Cup Inclinations Under Routine Gait Activities Using In Silico Approach.

Objectives: The acetabular cup design plays a critical role in reducing contact stress between femur head acetabular cup. Many studies used ellipsoidal and spheroidal geometry in acetabular cup design to effectively reduce contact stress. The present study focuses on elevated acetabular cup rim with round corner design to reduce contact stress with round corner geometry. Methods: The cobalt chromium femur head and cup are considered for finite element (FE) model of hip resurfacing. The gait loads of routine activities of humans like normal walking, stair ascending and descending and sitting down and getting up gait activities are applied to the developed 3D FE model. Five microseparations of 0.5, 1, 1.5, 2 and 2.5 mm are considered in the present study. The acetabular cup inclination angle considered for this study are 35°, 45°, 55°, 65° and 75°. The contact stress and von Mises stress plot for each gait activities under these microseparations are analyzed for betterment of longevity of implants. Results: Overall elevated cup rim design helped in reducing contact stress to a greater extent than conventional cup with different geometries. Also, the predicted von Mises stress for all the parameters considered in the current study are well within the yield strength of CoCr material. Therefore, elevated cup rim could be used as a better alternative to spline and, ellipsoidal and circular geometries of cup.

Nano-Sized Al2O3-Gr Reinforced Al7075 Hybrid Composite: Impact of Cooling Agents on Mechanical, Wear, and Fracture Behavior.

Aluminum metal cast composites (AMCCs) are frequently used in high-tech sectors such as automobiles, aerospace, biomedical, electronics, and others to fabricate precise and especially responsible parts. The mechanical and wear behavior of the metal matrix composites (MMCs) is anticipated to be influenced by the cooling agent's action and the cooling temperature. This research paper presents the findings of a series of tests to investigate the mechanical, wear, and fracture behavior of hybrid MMCs made of Al7075 reinforced by varying wt % of nano-sized Al2O3 and Gr and quenched with water and ice cubes. The heat-treated Al7075 alloy hybrid composites were evaluated for their hardness, tensile, and wear behavior, showcasing a significant process innovation. The heat treatment process greatly improved the hybrid composites' mechanical and wear performance. The samples quenched in ice attained the highest hardness of 119 VHN. There is a 45.37% improvement in the hardness of base alloy with the addition of 3% of Al2O3 and 1% of graphite particles. Further, the highest tensile and compression strengths were found in the ice-quenched 3% Al2O3 and 1% graphite hybrid composites with improvements of 34.2 and 48.83%, respectively, compared to the water-quenched base alloy. Under the samples quenched in ice, the mechanical and wear behavior improved. The tensile fractured surface showed voids, particle pullouts, and dimples. The worn-out surface of wear test samples of the created hybrid composite had micro pits, delamination layers, and microcracks.

Synergy of silica sand and waste plastics as thermoplastic composites on abrasive wear characteristics under conditions of different loads and sliding speeds.

The diverse nature of polymers with attractive properties has replaced the conventional materials with polymeric composites. The present study was sought to evaluate the wear performance of thermoplastic-based composites under the conditions of different loads and sliding speeds. In the present study, nine different composites were developed by using low-density polyethylene (LDPE), high-density polyethylene (HDPE) and polyethylene terephthalate (PET) with partial sand replacements i.e., 0, 30, 40, and 50 wt%. The abrasive wear was evaluated as per the ASTM G65 standard test for abrasive wear through a dry-sand rubber wheel apparatus under the applied loads of 34.335, 56.898, 68.719, 79.461 and 90.742 (N) and sliding speeds of 0.5388, 0.7184, 0.8980, 1.0776 and 1.4369 (m/s). The optimum density and compressive strength were obtained to be 2.0555 g/cm3 and 46.20 N/mm2, respectively for the composites HDPE60 and HDPE50 respectively. The minimum value of abrasive wear were found to 0.02498, 0.03430, 0.03095, 0.09020 and 0.03267 (cm3) under the considered loads of 34.335, 56.898, 68.719, 79.461 and 90.742 (N), respectively. Moreover, the composites LDPE50, LDPE100, LDPE100, LDPE50PET20 and LDPE60 showed a minimum abrasive wear of 0.03267, 0.05949, 0.05949, 0.03095 and 0.10292 at the sliding speeds of 0.5388, 0.7184, 0.8980, 1.0776 and 1.4369 (m/s), respectively. The wear response varied non-linearly with the conditions of loads and sliding speeds. Micro-cutting, plastic deformations, fiber peelings, etc. were included as the possible wear mechanism. The possible correlations between wear and mechanical properties, and throughout discussions for wear behaviors through the morphological analyses of the worn-out surfaces were provided.

Approaches for Memristive Structures Using Scratching Probe Nanolithography: Towards Neuromorphic Applications.

This paper proposes two different approaches to studying resistive switching of oxide thin films using scratching probe nanolithography of atomic force microscopy (AFM). These approaches allow us to assess the effects of memristor size and top-contact thickness on resistive switching. For that purpose, we investigated scratching probe nanolithography regimes using the Taguchi method, which is known as a reliable method for improving the reliability of the result. The AFM parameters, including normal load, scratch distance, probe speed, and probe direction, are optimized on the photoresist thin film by the Taguchi method. As a result, the pinholes with diameter ranged from 25.4 ± 2.2 nm to 85.1 ± 6.3 nm, and the groove array with a depth of 40.5 ± 3.7 nm and a roughness at the bottom of less than a few nanometers was formed. Then, based on the Si/TiN/ZnO/photoresist structures, we fabricated and investigated memristors with different spot sizes and TiN top contact thickness. As a result, the HRS/LRS ratio, USET, and ILRS are well controlled for a memristor size from 27 nm to 83 nm and ranged from ~8 to ~128, from 1.4 ± 0.1 V to 1.8 ± 0.2 V, and from (1.7 ± 0.2) × 10-10 A to (4.2 ± 0.6) × 10-9 A, respectively. Furthermore, the HRS/LRS ratio and USET are well controlled at a TiN top contact thickness from 8.3 ± 1.1 nm to 32.4 ± 4.2 nm and ranged from ~22 to ~188 and from 1.15 ± 0.05 V to 1.62 ± 0.06 V, respectively. The results can be used in the engineering and manufacturing of memristive structures for neuromorphic applications of brain-inspired artificial intelligence systems.

A rare case report of pleomorphic adenoma of the upper lip: An unusual clinical presentation.

Pleomorphic adenoma is the most common salivary gland tumor which accounts for about 60% of all salivary neoplasms. It is also known as "mixed tumor because of its wide cytomorphologic diversity". Pleomorphic adenoma salivary glands mostly occurs on the palate, but the involvement of the upper lip is rare. The present report describes a case of a 62-year-old male with asymptomatic firm nodular swelling attached with upper lip which was later diagnosed as pleomorphic adenoma in the excisional biopsy.

Advanced Characterization of Adhesive Joints and Adhesives.

Structural adhesives have shown significant improvements in their behavior over the past few decades [...].

Microstructure and Mechanical Properties Analysis of Al/Cu Dissimilar Alloys Joining by Using Conventional and Bobbin Tool Friction Stir Welding.

The feasibility of producing welding joints between 6061-T6 aluminum and pure copper sheets of 6 mm thickness by conventional friction stir welding (CFSW) and bobbin tool friction stir welding (BTFSW) by using a slot-groove configuration at the joining surface was investigated. The microstructure of the welded samples was examined by using an optical microscope and X-ray diffraction. Furthermore, the mechanical properties of the weld samples are compared based on the results of the tensile test, hardness measurement, and fractography test. The slot-groove configuration resulted in the presence of a bulk-sized Al block on the Cu side. The microscopic observations revealed the dispersion of fine Cu particles in the stir zone. The presence of intermetallic compounds (IMCs) CuAl2, which are hard and brittle, lowered the strength of the weld joints. The strength of the weld joints produced with BTFSW was superior to that of the C-FSW. The maximum hardness values of 214 HV and 211 HV are reported at the stir zone for BTFSW and CFSW, respectively. The fracture location of all the joints was at the intersection of the stir zone and the thermomechanically affected zone was on the Cu side.

Corrosion Behavior of Friction Stir Welded AA8090-T87 Aluminum Alloy.

Aerospace alloys with reduced wall thickness but possessing higher hardness, good tensile strength and reasonable corrosion resistance are essential in manufacturing of structures such as fuselage. In this work, friction stir welding has been carried out on such an aerospace aluminum alloy AA8090 T87 which contains 2.3% lithium. Tool rotational speed of 900 rpm and traverse speeds of 90 mm/min., 110 mm/min. are the welding parameters. Hardness analysis, surface roughness analysis and corrosion analysis are conducted to analyze the suitability of the joint for the intended application. The samples were corrosion tested in acid alkali solution and they resulted in the formation of pits of varying levels which indicate the extent of surface degradation. Hardness of the samples was measured after corrosion analysis to observe the changes. The analysis suggests that the change in tool traverse speed transformed the corrosion behavior of the joint and affected both the hardness and surface roughness which mitigated the quality of the joint.

Al-Mg-MoS2 Reinforced Metal Matrix Composites: Machinability Characteristics.

Several components are made from Al-Mg-based composites. MoS2 is used to increase the composite's machinability. Different weight percent (3, 4, and 5) of MoS2 are added as reinforcement to explore the machinability properties of Al-Mg-reinforced composites. The wire cut electrical discharge machining (WEDM) process is used to study the machinability characteristics of the fabricated Al-Mg-MoS2 composite. The machined surface's roughness and overcut under different process conditions are discussed. The evaluation-based distance from average solution (EDAS) method is used to identify the optimal setting to get the desired surface roughness and overcut. The following WEDM process parameters are taken to determine the impact of peak current, pulse on time, and gap voltage on surface roughness, and overcut. The WEDM tests were carried out on three different reinforced samples to determine the impact of reinforcement on surface roughness and overcut. The surface roughness and overcut increase as the reinforcement level increases, but the optimal parameters for all three composites are the same. According to EDAS analysis, I3, Ton2, and V1 are the best conditions. Furthermore, peak current and pulse on-time significantly influence surface roughness and overcut.

Optimization of Selective Laser Melting Parameter for Invar Material by Using JAYA Algorithm: Comparison with TLBO, GA and JAYA.

In this study, the hardness and surface roughness of selective laser-melted parts have been evaluated by considering a wide variety of input parameters. The Invar-36 has been considered a workpiece material that is mainly used in the aerospace industry for making parts as well as widely used in bimetallic thermostats. It is the mechanical properties and metallurgical properties of parts that drive the final product's quality in today's competitive marketplace. The study aims to examine how laser power, scanning speed, and orientation influence fabricated specimens. Using ANOVA, the established models were tested and the parameters were evaluated for their significance in predicting response. In the next step, the fuzzy-based JAYA algorithm has been implemented to determine which parameter is optimal in the proposed study. In addition, the optimal parametric combination obtained by the JAYA algorithm was compared with the optimal parametric combination obtained by TLBO and genetic algorithm (GA) to establish the effectiveness of the JAYA algorithm. Based on the results, an orientation of 90°, 136 KW of laser power, and 650 mm/s scanning speed were found to be the best combination of process parameters for generating the desired hardness and roughness for the Invar-36 material.

Effect of Mass on the Dynamic Characteristics of Single- and Double-Layered Graphene-Based Nano Resonators.

Graphene has been widely and extensively used in mass sensing applications. The present study focused on exploring the use of single-layer graphene (SLG) and double-layer graphene (DLG) as sensing devices. The dynamic analysis of SLG and DLG with different boundary conditions (BDs) and length was executed using the atomistic finite element method (AFEM). SLG and DLG sheets were modelled and considered as a space-frame structure similar to a 3D beam. Spring elements (Combin14) were used to identify the interlayer interactions between two graphene layers in the DLG sheet due to the van der Waals forces. Simulations were carried out to visualize the behavior of the SLG and DLG subjected to different BDs and when used as mass sensing devices. The variation in frequency was noted by changing the length and applied mass of the SLGs and DLGs. The quantity of the frequency was found to be highest in the armchair SLG (6, 6) for a 50 nm sheet length and lowest in the chiral SLG (16, 4) for a 20 nm sheet length in the bridged condition. When the mass was 0.1 Zg, the frequency for the zigzag SLG (20, 0) was higher in both cases. The results show that the length of the sheet and the various mass values have a significant impact on the dynamic properties. The present research will contribute to the ultra-high frequency nano-resonance applications.

Influence of Fiber Angle on Steady-State Response of Laminated Composite Rectangular Plates.

Significant advances in the field of composite structures continue to be made on a variety of fronts, including theoretical studies based on advances in structural theory kinematics and computer models of structural elements employing advanced theories and unique formulations. Plate vibration is a persistently interesting subject owing to its wider usage as a structural component in the industry. The current study was carried out using the Co continuous eight-noded quadrilateral shear-flexible element having five nodal degrees of freedom, which is ground on first-order shear deformation theory (FSDT). For small strain and sufficiently large deformation, the geometric nonlinearity is integrated using the Von Kármán assumption. The governing equations in the time domain are solved employing the modified shooting technique along with an arc-length and pseudo-arc-length continuation strategy. This work explored the effect of fiber angle on the steady-state nonlinear forced vibration response. To explain hardening nonlinearity, the strain and stress fluctuation throughout the thickness for a rectangular laminated composite plate is determined. The cyclic fluctuation of the steady-state nonlinear normal stress during a time period at the centre of the top/bottom surfaces is also provided at the forcing frequency ratio of peak amplitude in a nonlinear response. Because of the variation in restoring forces, the frequency spectra for all fiber angle orientations show significantly enhanced harmonic participation in addition to the fundamental harmonic.